2 . /////////////////////////////////////////////////////////////////////////////
3 . This is the primary source of the Exim Manual. It is an xfpt document that is
4 . converted into DocBook XML for subsequent conversion into printable and online
5 . formats. The markup used herein is "standard" xfpt markup, with some extras.
6 . The markup is summarized in a file called Markup.txt.
8 . WARNING: When you use the .new macro, make sure it appears *before* any
9 . adjacent index items; otherwise you get an empty "paragraph" which causes
10 . unwanted vertical space.
11 . /////////////////////////////////////////////////////////////////////////////
16 . /////////////////////////////////////////////////////////////////////////////
17 . This outputs the standard DocBook boilerplate.
18 . /////////////////////////////////////////////////////////////////////////////
22 . /////////////////////////////////////////////////////////////////////////////
23 . These lines are processing instructions for the Simple DocBook Processor that
24 . Philip Hazel has developed as a less cumbersome way of making PostScript and
25 . PDFs than using xmlto and fop. They will be ignored by all other XML
27 . /////////////////////////////////////////////////////////////////////////////
31 foot_right_recto="&chaptertitle; (&chapternumber;)"
32 foot_right_verso="&chaptertitle; (&chapternumber;)"
33 toc_chapter_blanks="yes,yes"
34 table_warn_overflow="overprint"
38 . /////////////////////////////////////////////////////////////////////////////
39 . This generates the outermost <book> element that wraps the entire document.
40 . /////////////////////////////////////////////////////////////////////////////
44 . /////////////////////////////////////////////////////////////////////////////
45 . These definitions set some parameters and save some typing.
46 . Update the Copyright year (only) when changing content.
47 . /////////////////////////////////////////////////////////////////////////////
49 .set previousversion "4.96"
50 .include ./local_params
52 .set ACL "access control lists (ACLs)"
53 .set I " "
55 .set drivernamemax "64"
61 . /////////////////////////////////////////////////////////////////////////////
62 . Additional xfpt markup used by this document, over and above the default
63 . provided in the xfpt library.
64 . /////////////////////////////////////////////////////////////////////////////
66 . --- Override the &$ flag to automatically insert a $ with the variable name.
68 .flag &$ $& "<varname>$" "</varname>"
70 . --- Short flags for daggers in option headings. They will always be inside
71 . --- an italic string, but we want the daggers to be in Roman.
73 .flag &!! "</emphasis>†<emphasis>"
74 .flag &!? "</emphasis>‡<emphasis>"
76 . --- A macro for an Exim option definition heading, generating a one-line
77 . --- table with four columns. For cases when the option name is given with
78 . --- a space, so that it can be split, a fifth argument is used for the
88 .itable all 0 0 4 8* left 6* center 6* center 6* right
89 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
93 . --- A macro for the common 2-column tables. The width of the first column
94 . --- is suitable for the many tables at the start of the main options chapter;
95 . --- a small number of other 2-column tables override it.
97 .macro table2 196pt 254pt
98 .itable none 0 0 2 $1 left $2 left
102 . --- A macro for a plain variable, including the .vitem and .vindex
108 . --- A macro for a "tainted" marker, done as a one-element table
110 .itable none 0 0 1 10pt left
115 . --- A macro for a tainted variable, adding a taint-marker
121 . --- A macro for a cmdline option, including a .oindex
122 . --- 1st arg is the option name, undecorated (we do that here).
123 . --- 2nd arg, optional, text (decorated as needed) to be appended to the name
125 .vitem &%$1%&$=2+&~$2+
129 . --- A macro that generates .row, but puts &I; at the start of the first
130 . --- argument, thus indenting it. Assume a minimum of two arguments, and
131 . --- allow up to four arguments, which is as many as we'll ever need.
135 .row "&I;$1" "$2" "$3" "$4"
139 .row "&I;$1" "$2" "$3"
147 . --- Macros for option, variable, and concept index entries. For a "range"
148 . --- style of entry, use .scindex for the start and .ecindex for the end. The
149 . --- first argument of .scindex and the only argument of .ecindex must be the
150 . --- ID that ties them together.
151 . --- The index entry points to the most-recent chapter head, section or subsection
152 . --- head, or list-item.
155 &<indexterm role="concept">&
156 &<primary>&$1&</primary>&
158 &<secondary>&$2&</secondary>&
164 &<indexterm role="concept" id="$1" class="startofrange">&
165 &<primary>&$2&</primary>&
167 &<secondary>&$3&</secondary>&
173 &<indexterm role="concept" startref="$1" class="endofrange"/>&
177 &<indexterm role="option">&
178 &<primary>&$1&</primary>&
180 &<secondary>&$2&</secondary>&
185 . --- The index entry points to the most-recent chapter head, section or subsection
186 . --- head, or varlist item.
189 &<indexterm role="variable">&
190 &<primary>&$1&</primary>&
192 &<secondary>&$2&</secondary>&
198 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
202 . use this for a concept-index entry for a header line
204 .cindex "&'$1'& header line"
205 .cindex "header lines" $1
207 . ////////////////////////////////////////////////////////////////////////////
210 . ////////////////////////////////////////////////////////////////////////////
211 . The <bookinfo> element is removed from the XML before processing for ASCII
213 . ////////////////////////////////////////////////////////////////////////////
217 <title>Specification of the Exim Mail Transfer Agent</title>
218 <titleabbrev>The Exim MTA</titleabbrev>
222 <author><firstname>Exim</firstname><surname>Maintainers</surname></author>
223 <authorinitials>EM</authorinitials>
224 <revhistory><revision>
226 <authorinitials>EM</authorinitials>
227 </revision></revhistory>
230 </year><holder>The Exim Maintainers</holder></copyright>
235 . /////////////////////////////////////////////////////////////////////////////
236 . These implement index entries of the form "x, see y" and "x, see also y".
237 . However, the DocBook DTD doesn't allow <indexterm> entries
238 . at the top level, so we have to put the .chapter directive first.
239 . /////////////////////////////////////////////////////////////////////////////
241 .chapter "Introduction" "CHID1"
245 <indexterm role="$2">
246 <primary>$3</primary>
248 <secondary>$5</secondary>
250 <$1><emphasis>$4</emphasis></$1>
255 . NB: for the 4-arg variant the ordering is awkward
257 .seeother see "$1" "$2" "$3" "$4"
260 .seeother seealso "$1" "$2" "$3" "$4"
263 .see variable "<emphasis>$1</emphasis>, <emphasis>$2</emphasis>, etc." "numerical variables"
264 .see concept address rewriting rewriting
265 .see concept "Bounce Address Tag Validation" BATV
266 .see concept "Client SMTP Authorization" CSA
267 .see concept "CR character" "carriage return"
268 .see concept CRL "certificate revocation list"
269 .seealso concept de-tainting "tainted data"
270 .see concept delivery "bounce message" "failure report"
271 .see concept dialup "intermittently connected hosts"
272 .see concept exiscan "content scanning"
273 .see concept fallover fallback
274 .see concept filter "Sieve filter" Sieve
275 .see concept headers "header lines"
276 .see concept ident "RFC 1413"
277 .see concept "LF character" "linefeed"
278 .seealso concept maximum limit
279 .see concept monitor "Exim monitor"
280 .see concept "no_<emphasis>xxx</emphasis>" "entry for xxx"
281 .see concept NUL "binary zero"
282 .see concept "passwd file" "/etc/passwd"
283 .see concept "process id" pid
284 .see concept RBL "DNS list"
285 .see concept redirection "address redirection"
286 .see concept "return path" "envelope sender"
287 .see concept scanning "content scanning"
289 .see concept string expansion expansion
290 .see concept "top bit" "8-bit characters"
291 .see concept variables "expansion, variables"
292 .see concept "zero, binary" "binary zero"
295 . /////////////////////////////////////////////////////////////////////////////
296 . This is the real start of the first chapter. See the comment above as to why
297 . we can't have the .chapter line here.
298 . chapter "Introduction"
299 . /////////////////////////////////////////////////////////////////////////////
301 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
302 Unix-like operating systems. It was designed on the assumption that it would be
303 run on hosts that are permanently connected to the Internet. However, it can be
304 used on intermittently connected hosts with suitable configuration adjustments.
306 Configuration files currently exist for the following operating systems: AIX,
307 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
308 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
309 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
310 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and UnixWare.
311 Some of these operating systems are no longer current and cannot easily be
312 tested, so the configuration files may no longer work in practice.
314 There are also configuration files for compiling Exim in the Cygwin environment
315 that can be installed on systems running Windows. However, this document does
316 not contain any information about running Exim in the Cygwin environment.
318 The terms and conditions for the use and distribution of Exim are contained in
319 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
320 Public Licence, a copy of which may be found in the file &_LICENCE_&.
322 The use, supply, or promotion of Exim for the purpose of sending bulk,
323 unsolicited electronic mail is incompatible with the basic aims of Exim,
324 which revolve around the free provision of a service that enhances the quality
325 of personal communications. The author of Exim regards indiscriminate
326 mass-mailing as an antisocial, irresponsible abuse of the Internet.
328 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
329 experience of running and working on the Smail 3 code, I could never have
330 contemplated starting to write a new MTA. Many of the ideas and user interfaces
331 were originally taken from Smail 3, though the actual code of Exim is entirely
332 new, and has developed far beyond the initial concept.
334 Many people, both in Cambridge and around the world, have contributed to the
335 development and the testing of Exim, and to porting it to various operating
336 systems. I am grateful to them all. The distribution now contains a file called
337 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
341 .section "Exim documentation" "SECID1"
342 . Keep this example change bar when updating the documentation!
345 .cindex "documentation"
346 This edition of the Exim specification applies to version &version() of Exim.
347 Substantive changes from the &previousversion; edition are marked in some
348 renditions of this document; this paragraph is so marked if the rendition is
349 capable of showing a change indicator.
352 This document is very much a reference manual; it is not a tutorial. The reader
353 is expected to have some familiarity with the SMTP mail transfer protocol and
354 with general Unix system administration. Although there are some discussions
355 and examples in places, the information is mostly organized in a way that makes
356 it easy to look up, rather than in a natural order for sequential reading.
357 Furthermore, this manual aims to cover every aspect of Exim in detail, including
358 a number of rarely-used, special-purpose features that are unlikely to be of
361 .cindex "books about Exim"
362 An &"easier"& discussion of Exim which provides more in-depth explanatory,
363 introductory, and tutorial material can be found in a book entitled &'The Exim
364 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
365 (&url(https://www.uit.co.uk/exim-book/)).
367 The book also contains a chapter that gives a general introduction to SMTP and
368 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
369 with the latest release of Exim. (Note that the earlier book about Exim,
370 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
372 .cindex "Debian" "information sources"
373 If you are using a Debian distribution of Exim, you will find information about
374 Debian-specific features in the file
375 &_/usr/share/doc/exim4-base/README.Debian_&.
376 The command &(man update-exim.conf)& is another source of Debian-specific
379 .cindex "&_doc/NewStuff_&"
380 .cindex "&_doc/ChangeLog_&"
382 As Exim develops, there may be features in newer versions that have not
383 yet made it into this document, which is updated only when the most significant
384 digit of the fractional part of the version number changes. Specifications of
385 new features that are not yet in this manual are placed in the file
386 &_doc/NewStuff_& in the Exim distribution.
388 Some features may be classified as &"experimental"&. These may change
389 incompatibly while they are developing, or even be withdrawn. For this reason,
390 they are not documented in this manual. Information about experimental features
391 can be found in the file &_doc/experimental.txt_&.
393 All changes to Exim (whether new features, bug fixes, or other kinds of
394 change) are noted briefly in the file called &_doc/ChangeLog_&.
396 .cindex "&_doc/spec.txt_&"
397 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
398 that it can easily be searched with a text editor. Other files in the &_doc_&
402 .row &_OptionLists.txt_& "list of all options in alphabetical order"
403 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
404 .row &_exim.8_& "a man page of Exim's command line options"
405 .row &_experimental.txt_& "documentation of experimental features"
406 .row &_filter.txt_& "specification of the filter language"
407 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
408 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
409 .row &_openssl.txt_& "installing a current OpenSSL release"
412 The main specification and the specification of the filtering language are also
413 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
414 &<<SECTavail>>& below tells you how to get hold of these.
418 .section "FTP site and websites" "SECID2"
421 The primary site for Exim source distributions is the &%exim.org%& FTP site,
422 available over HTTPS, HTTP and FTP. These services, and the &%exim.org%&
423 website, are hosted at the University of Cambridge.
427 As well as Exim distribution tar files, the Exim website contains a number of
428 differently formatted versions of the documentation. A recent addition to the
429 online information is the Exim wiki (&url(https://wiki.exim.org)),
430 which contains what used to be a separate FAQ, as well as various other
431 examples, tips, and know-how that have been contributed by Exim users.
432 The wiki site should always redirect to the correct place, which is currently
433 provided by GitHub, and is open to editing by anyone with a GitHub account.
436 An Exim Bugzilla exists at &url(https://bugs.exim.org). You can use
437 this to report bugs, and also to add items to the wish list. Please search
438 first to check that you are not duplicating a previous entry.
439 Please do not ask for configuration help in the bug-tracker.
442 .section "Mailing lists" "SECID3"
443 .cindex "mailing lists" "for Exim users"
444 The following Exim mailing lists exist:
447 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
448 .row &'exim-users@exim.org'& "General discussion list"
449 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
450 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
453 You can subscribe to these lists, change your existing subscriptions, and view
454 or search the archives via the mailing lists link on the Exim home page.
455 .cindex "Debian" "mailing list for"
456 If you are using a Debian distribution of Exim, you may wish to subscribe to
457 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
460 &url(https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-exim4-users)
462 Please ask Debian-specific questions on that list and not on the general Exim
465 .section "Bug reports" "SECID5"
466 .cindex "bug reports"
467 .cindex "reporting bugs"
468 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
469 via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
470 whether some behaviour is a bug or not, the best thing to do is to post a
471 message to the &'exim-dev'& mailing list and have it discussed.
475 .section "Where to find the Exim distribution" "SECTavail"
477 .cindex "HTTPS download site"
478 .cindex "distribution" "FTP site"
479 .cindex "distribution" "https site"
480 The master distribution site for the Exim distribution is
482 &url(https://downloads.exim.org/)
484 The service is available over HTTPS, HTTP and FTP.
485 We encourage people to migrate to HTTPS.
487 The content served at &url(https://downloads.exim.org/) is identical to the
488 content served at &url(https://ftp.exim.org/pub/exim) and
489 &url(ftp://ftp.exim.org/pub/exim).
491 If accessing via a hostname containing &'ftp'&, then the file references that
492 follow are relative to the &_exim_& directories at these sites.
493 If accessing via the hostname &'downloads'& then the subdirectories described
494 here are top-level directories.
496 There are now quite a number of independent mirror sites around
497 the world. Those that I know about are listed in the file called &_Mirrors_&.
499 Within the top exim directory there are subdirectories called &_exim3_& (for
500 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
501 distributions), and &_Testing_& for testing versions. In the &_exim4_&
502 subdirectory, the current release can always be found in files called
506 &_exim-n.nn.tar.bz2_&
508 where &'n.nn'& is the highest such version number in the directory. The three
509 files contain identical data; the only difference is the type of compression.
510 The &_.xz_& file is usually the smallest, while the &_.gz_& file is the
511 most portable to old systems.
513 .cindex "distribution" "signing details"
514 .cindex "distribution" "public key"
515 .cindex "public key for signed distribution"
516 The distributions will be PGP signed by an individual key of the Release
517 Coordinator. This key will have a uid containing an email address in the
518 &'exim.org'& domain and will have signatures from other people, including
519 other Exim maintainers. We expect that the key will be in the "strong set" of
520 PGP keys. There should be a trust path to that key from the Exim Maintainer's
521 PGP keys, a version of which can be found in the release directory in the file
522 &_Exim-Maintainers-Keyring.asc_&. All keys used will be available in public keyserver pools,
523 such as &'pool.sks-keyservers.net'&.
525 At the time of the last update, releases were being made by Jeremy Harris and signed
526 with key &'0xBCE58C8CE41F32DF'&. Other recent keys used for signing are those
527 of Heiko Schlittermann, &'0x26101B62F69376CE'&,
528 and of Phil Pennock, &'0x4D1E900E14C1CC04'&.
530 The signatures for the tar bundles are in:
532 &_exim-n.nn.tar.xz.asc_&
533 &_exim-n.nn.tar.gz.asc_&
534 &_exim-n.nn.tar.bz2.asc_&
536 For each released version, the log of changes is made available in a
537 separate file in the directory &_ChangeLogs_& so that it is possible to
538 find out what has changed without having to download the entire distribution.
540 .cindex "documentation" "available formats"
541 The main distribution contains ASCII versions of this specification and other
542 documentation; other formats of the documents are available in separate files
543 inside the &_exim4_& directory of the FTP site:
545 &_exim-html-n.nn.tar.gz_&
546 &_exim-pdf-n.nn.tar.gz_&
547 &_exim-postscript-n.nn.tar.gz_&
548 &_exim-texinfo-n.nn.tar.gz_&
550 These tar files contain only the &_doc_& directory, not the complete
551 distribution, and are also available in &_.bz2_& and &_.xz_& forms.
554 .section "Limitations" "SECID6"
556 .cindex "limitations of Exim"
557 .cindex "bang paths" "not handled by Exim"
558 Exim is designed for use as an Internet MTA, and therefore handles addresses in
559 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
560 simple two-component bang paths can be converted by a straightforward rewriting
561 configuration. This restriction does not prevent Exim from being interfaced to
562 UUCP as a transport mechanism, provided that domain addresses are used.
564 .cindex "domainless addresses"
565 .cindex "address" "without domain"
566 Exim insists that every address it handles has a domain attached. For incoming
567 local messages, domainless addresses are automatically qualified with a
568 configured domain value. Configuration options specify from which remote
569 systems unqualified addresses are acceptable. These are then qualified on
572 .cindex "transport" "external"
573 .cindex "external transports"
574 The only external transport mechanisms that are currently implemented are SMTP
575 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
576 transport is available, and there are facilities for writing messages to files
577 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
578 to send messages to other transport mechanisms such as UUCP, provided they can
579 handle domain-style addresses. Batched SMTP input is also catered for.
581 Exim is not designed for storing mail for dial-in hosts. When the volumes of
582 such mail are large, it is better to get the messages &"delivered"& into files
583 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
586 Although Exim does have basic facilities for scanning incoming messages, these
587 are not comprehensive enough to do full virus or spam scanning. Such operations
588 are best carried out using additional specialized software packages. If you
589 compile Exim with the content-scanning extension, straightforward interfaces to
590 a number of common scanners are provided.
594 .section "Runtime configuration" "SECID7"
595 Exim's runtime configuration is held in a single text file that is divided
596 into a number of sections. The entries in this file consist of keywords and
597 values, in the style of Smail 3 configuration files. A default configuration
598 file which is suitable for simple online installations is provided in the
599 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
602 .section "Calling interface" "SECID8"
603 .cindex "Sendmail compatibility" "command line interface"
604 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
605 can be a straight replacement for &_/usr/lib/sendmail_& or
606 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
607 about Sendmail in order to run Exim. For actions other than sending messages,
608 Sendmail-compatible options also exist, but those that produce output (for
609 example, &%-bp%&, which lists the messages in the queue) do so in Exim's own
610 format. There are also some additional options that are compatible with Smail
611 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
612 documents all Exim's command line options. This information is automatically
613 made into the man page that forms part of the Exim distribution.
615 Control of messages in the queue can be done via certain privileged command
616 line options. There is also an optional monitor program called &'eximon'&,
617 which displays current information in an X window, and which contains a menu
618 interface to Exim's command line administration options.
622 .section "Terminology" "SECID9"
623 .cindex "terminology definitions"
624 .cindex "body of message" "definition of"
625 The &'body'& of a message is the actual data that the sender wants to transmit.
626 It is the last part of a message and is separated from the &'header'& (see
627 below) by a blank line.
629 .cindex "bounce message" "definition of"
630 When a message cannot be delivered, it is normally returned to the sender in a
631 delivery failure message or a &"non-delivery report"& (NDR). The term
632 &'bounce'& is commonly used for this action, and the error reports are often
633 called &'bounce messages'&. This is a convenient shorthand for &"delivery
634 failure error report"&. Such messages have an empty sender address in the
635 message's &'envelope'& (see below) to ensure that they cannot themselves give
636 rise to further bounce messages.
638 The term &'default'& appears frequently in this manual. It is used to qualify a
639 value which is used in the absence of any setting in the configuration. It may
640 also qualify an action which is taken unless a configuration setting specifies
643 The term &'defer'& is used when the delivery of a message to a specific
644 destination cannot immediately take place for some reason (a remote host may be
645 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
648 The word &'domain'& is sometimes used to mean all but the first component of a
649 host's name. It is &'not'& used in that sense here, where it normally refers to
650 the part of an email address following the @ sign.
652 .cindex "envelope, definition of"
653 .cindex "sender" "definition of"
654 A message in transit has an associated &'envelope'&, as well as a header and a
655 body. The envelope contains a sender address (to which bounce messages should
656 be delivered), and any number of recipient addresses. References to the
657 sender or the recipients of a message usually mean the addresses in the
658 envelope. An MTA uses these addresses for delivery, and for returning bounce
659 messages, not the addresses that appear in the header lines.
661 .cindex "message" "header, definition of"
662 .cindex "header section" "definition of"
663 The &'header'& of a message is the first part of a message's text, consisting
664 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
665 &'Subject:'&, etc. Long header lines can be split over several text lines by
666 indenting the continuations. The header is separated from the body by a blank
669 .cindex "local part" "definition of"
670 .cindex "domain" "definition of"
671 The term &'local part'&, which is taken from RFC 2822, is used to refer to the
672 part of an email address that precedes the @ sign. The part that follows the
673 @ sign is called the &'domain'& or &'mail domain'&.
675 .cindex "local delivery" "definition of"
676 .cindex "remote delivery, definition of"
677 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
678 delivery to a file or a pipe on the local host from delivery by SMTP over
679 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
680 host it is running on are &'remote'&.
682 .cindex "return path" "definition of"
683 &'Return path'& is another name that is used for the sender address in a
686 .cindex "queue" "definition of"
687 The term &'queue'& is used to refer to the set of messages awaiting delivery
688 because this term is in widespread use in the context of MTAs. However, in
689 Exim's case, the reality is more like a pool than a queue, because there is
690 normally no ordering of waiting messages.
692 .cindex "queue runner" "definition of"
693 The term &'queue runner'& is used to describe a process that scans the queue
694 and attempts to deliver those messages whose retry times have come. This term
695 is used by other MTAs and also relates to the command &%runq%&, but in Exim
696 the waiting messages are normally processed in an unpredictable order.
698 .cindex "spool directory" "definition of"
699 The term &'spool directory'& is used for a directory in which Exim keeps the
700 messages in its queue &-- that is, those that it is in the process of
701 delivering. This should not be confused with the directory in which local
702 mailboxes are stored, which is called a &"spool directory"& by some people. In
703 the Exim documentation, &"spool"& is always used in the first sense.
710 . ////////////////////////////////////////////////////////////////////////////
711 . ////////////////////////////////////////////////////////////////////////////
713 .chapter "Incorporated code" "CHID2"
714 .cindex "incorporated code"
715 .cindex "regular expressions" "library"
718 A number of pieces of external code are included in the Exim distribution.
721 Regular expressions are supported in the main Exim program and in the
722 Exim monitor using the freely-distributable PCRE2 library, copyright
723 © University of Cambridge. The source to PCRE2 is not longer shipped with
724 Exim, so you will need to use the version of PCRE2 shipped with your system,
725 or obtain and install the full version of the library from
726 &url(https://github.com/PhilipHazel/pcre2/releases).
728 .cindex "cdb" "acknowledgment"
729 Support for the cdb (Constant DataBase) lookup method is provided by code
730 contributed by Nigel Metheringham of (at the time he contributed it) Planet
731 Online Ltd. The implementation is completely contained within the code of Exim.
732 It does not link against an external cdb library. The code contains the
733 following statements:
736 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
738 This program is free software; you can redistribute it and/or modify it under
739 the terms of the GNU General Public License as published by the Free Software
740 Foundation; either version 2 of the License, or (at your option) any later
742 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
743 the spec and sample code for cdb can be obtained from
744 &url(https://cr.yp.to/cdb.html). This implementation borrows
745 some code from Dan Bernstein's implementation (which has no license
746 restrictions applied to it).
749 .cindex "SPA authentication"
750 .cindex "Samba project"
751 .cindex "Microsoft Secure Password Authentication"
752 Client support for Microsoft's &'Secure Password Authentication'& is provided
753 by code contributed by Marc Prud'hommeaux. Server support was contributed by
754 Tom Kistner. This includes code taken from the Samba project, which is released
758 .cindex "&'pwcheck'& daemon"
759 .cindex "&'pwauthd'& daemon"
760 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
761 by code taken from the Cyrus-SASL library and adapted by Alexander S.
762 Sabourenkov. The permission notice appears below, in accordance with the
763 conditions expressed therein.
766 Copyright © 2001 Carnegie Mellon University. All rights reserved.
768 Redistribution and use in source and binary forms, with or without
769 modification, are permitted provided that the following conditions
773 Redistributions of source code must retain the above copyright
774 notice, this list of conditions and the following disclaimer.
776 Redistributions in binary form must reproduce the above copyright
777 notice, this list of conditions and the following disclaimer in
778 the documentation and/or other materials provided with the
781 The name &"Carnegie Mellon University"& must not be used to
782 endorse or promote products derived from this software without
783 prior written permission. For permission or any other legal
784 details, please contact
786 Office of Technology Transfer
787 Carnegie Mellon University
789 Pittsburgh, PA 15213-3890
790 (412) 268-4387, fax: (412) 268-7395
791 tech-transfer@andrew.cmu.edu
794 Redistributions of any form whatsoever must retain the following
797 &"This product includes software developed by Computing Services
798 at Carnegie Mellon University (&url(https://www.cmu.edu/computing/)."&
800 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
801 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
802 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
803 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
804 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
805 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
806 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
811 .cindex "Exim monitor" "acknowledgment"
814 The Exim Monitor program, which is an X-Window application, includes
815 modified versions of the Athena StripChart and TextPop widgets.
816 This code is copyright by DEC and MIT, and their permission notice appears
817 below, in accordance with the conditions expressed therein.
820 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
821 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
825 Permission to use, copy, modify, and distribute this software and its
826 documentation for any purpose and without fee is hereby granted,
827 provided that the above copyright notice appear in all copies and that
828 both that copyright notice and this permission notice appear in
829 supporting documentation, and that the names of Digital or MIT not be
830 used in advertising or publicity pertaining to distribution of the
831 software without specific, written prior permission.
833 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
834 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
835 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
836 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
837 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
838 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
843 .cindex "opendmarc" "acknowledgment"
844 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
845 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
846 derived code are indicated in the respective source files. The full OpenDMARC
847 license is provided in the LICENSE.opendmarc file contained in the distributed
851 Many people have contributed code fragments, some large, some small, that were
852 not covered by any specific license requirements. It is assumed that the
853 contributors are happy to see their code incorporated into Exim under the GPL.
860 . ////////////////////////////////////////////////////////////////////////////
861 . ////////////////////////////////////////////////////////////////////////////
863 .chapter "How Exim receives and delivers mail" "CHID11" &&&
864 "Receiving and delivering mail"
867 .section "Overall philosophy" "SECID10"
868 .cindex "design philosophy"
869 Exim is designed to work efficiently on systems that are permanently connected
870 to the Internet and are handling a general mix of mail. In such circumstances,
871 most messages can be delivered immediately. Consequently, Exim does not
872 maintain independent queues of messages for specific domains or hosts, though
873 it does try to send several messages in a single SMTP connection after a host
874 has been down, and it also maintains per-host retry information.
877 .section "Policy control" "SECID11"
878 .cindex "policy control" "overview"
879 Policy controls are now an important feature of MTAs that are connected to the
880 Internet. Perhaps their most important job is to stop MTAs from being abused as
881 &"open relays"& by misguided individuals who send out vast amounts of
882 unsolicited junk and want to disguise its source. Exim provides flexible
883 facilities for specifying policy controls on incoming mail:
886 .cindex "&ACL;" "introduction"
887 Exim 4 (unlike previous versions of Exim) implements policy controls on
888 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
889 series of statements that may either grant or deny access. ACLs can be used at
890 several places in the SMTP dialogue while receiving a message from a remote
891 host. However, the most common places are after each RCPT command, and at the
892 very end of the message. The sysadmin can specify conditions for accepting or
893 rejecting individual recipients or the entire message, respectively, at these
894 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
897 An ACL is also available for locally generated, non-SMTP messages. In this
898 case, the only available actions are to accept or deny the entire message.
900 When Exim is compiled with the content-scanning extension, facilities are
901 provided in the ACL mechanism for passing the message to external virus and/or
902 spam scanning software. The result of such a scan is passed back to the ACL,
903 which can then use it to decide what to do with the message.
905 When a message has been received, either from a remote host or from the local
906 host, but before the final acknowledgment has been sent, a locally supplied C
907 function called &[local_scan()]& can be run to inspect the message and decide
908 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
909 is accepted, the list of recipients can be modified by the function.
911 Using the &[local_scan()]& mechanism is another way of calling external scanner
912 software. The &%SA-Exim%& add-on package works this way. It does not require
913 Exim to be compiled with the content-scanning extension.
915 After a message has been accepted, a further checking mechanism is available in
916 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
917 runs at the start of every delivery process.
922 .section "User filters" "SECID12"
923 .cindex "filter" "introduction"
924 .cindex "Sieve filter"
925 In a conventional Exim configuration, users are able to run private filters by
926 setting up appropriate &_.forward_& files in their home directories. See
927 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
928 configuration needed to support this, and the separate document entitled
929 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
930 of filtering are available:
933 Sieve filters are written in the standard filtering language that is defined
936 Exim filters are written in a syntax that is unique to Exim, but which is more
937 powerful than Sieve, which it pre-dates.
940 User filters are run as part of the routing process, described below.
944 .section "Message identification" "SECTmessiden"
945 .cindex "message ids" "details of format"
946 .cindex "format" "of message id"
947 .cindex "id of message"
952 .cindex "exim_msgdate"
953 Every message handled by Exim is given a &'message id'& which is sixteen
954 characters long. It is divided into three parts, separated by hyphens, for
955 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
956 normally encoding numbers in base 62. However, in the Darwin operating
957 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
958 (avoiding the use of lower case letters) is used instead, because the message
959 id is used to construct filenames, and the names of files in those systems are
960 not always case-sensitive.
962 .cindex "pid (process id)" "re-use of"
963 The detail of the contents of the message id have changed as Exim has evolved.
964 Earlier versions relied on the operating system not re-using a process id (pid)
965 within one second. On modern operating systems, this assumption can no longer
966 be made, so the algorithm had to be changed. To retain backward compatibility,
967 the format of the message id was retained, which is why the following rules are
971 The first six characters of the message id are the time at which the message
972 started to be received, to a granularity of one second. That is, this field
973 contains the number of seconds since the start of the epoch (the normal Unix
974 way of representing the date and time of day).
976 After the first hyphen, the next six characters are the id of the process that
977 received the message.
979 There are two different possibilities for the final two characters:
981 .oindex "&%localhost_number%&"
982 If &%localhost_number%& is not set, this value is the fractional part of the
983 time of reception, normally in units of 1/2000 of a second, but for systems
984 that must use base 36 instead of base 62 (because of case-insensitive file
985 systems), the units are 1/1000 of a second.
987 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
988 the fractional part of the time, which in this case is in units of 1/200
993 After a message has been received, Exim waits for the clock to tick at the
994 appropriate resolution before proceeding, so that if another message is
995 received by the same process, or by another process with the same (re-used)
996 pid, it is guaranteed that the time will be different. In most cases, the clock
997 will already have ticked while the message was being received.
999 The exim_msgdate utility (see section &<<SECTexim_msgdate>>&) can be
1000 used to display the date, and optionally the process id, of an Exim
1004 .section "Receiving mail" "SECID13"
1005 .cindex "receiving mail"
1006 .cindex "message" "reception"
1007 The only way Exim can receive mail from another host is using SMTP over
1008 TCP/IP, in which case the sender and recipient addresses are transferred using
1009 SMTP commands. However, from a locally running process (such as a user's MUA),
1010 there are several possibilities:
1013 If the process runs Exim with the &%-bm%& option, the message is read
1014 non-interactively (usually via a pipe), with the recipients taken from the
1015 command line, or from the body of the message if &%-t%& is also used.
1017 If the process runs Exim with the &%-bS%& option, the message is also read
1018 non-interactively, but in this case the recipients are listed at the start of
1019 the message in a series of SMTP RCPT commands, terminated by a DATA
1020 command. This is called &"batch SMTP"& format,
1021 but it isn't really SMTP. The SMTP commands are just another way of passing
1022 envelope addresses in a non-interactive submission.
1024 If the process runs Exim with the &%-bs%& option, the message is read
1025 interactively, using the SMTP protocol. A two-way pipe is normally used for
1026 passing data between the local process and the Exim process.
1027 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1028 example, the ACLs for SMTP commands are used for this form of submission.
1030 A local process may also make a TCP/IP call to the host's loopback address
1031 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1032 does not treat the loopback address specially. It treats all such connections
1033 in the same way as connections from other hosts.
1037 .cindex "message sender, constructed by Exim"
1038 .cindex "sender" "constructed by Exim"
1039 In the three cases that do not involve TCP/IP, the sender address is
1040 constructed from the login name of the user that called Exim and a default
1041 qualification domain (which can be set by the &%qualify_domain%& configuration
1042 option). For local or batch SMTP, a sender address that is passed using the
1043 SMTP MAIL command is ignored. However, the system administrator may allow
1044 certain users (&"trusted users"&) to specify a different sender addresses
1045 unconditionally, or all users to specify certain forms of different sender
1046 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1047 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1048 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1049 users to change sender addresses.
1051 Messages received by either of the non-interactive mechanisms are subject to
1052 checking by the non-SMTP ACL if one is defined. Messages received using SMTP
1053 (either over TCP/IP or interacting with a local process) can be checked by a
1054 number of ACLs that operate at different times during the SMTP session. Either
1055 individual recipients or the entire message can be rejected if local policy
1056 requirements are not met. The &[local_scan()]& function (see chapter
1057 &<<CHAPlocalscan>>&) is run for all incoming messages.
1059 Exim can be configured not to start a delivery process when a message is
1060 received; this can be unconditional, or depend on the number of incoming SMTP
1061 connections or the system load. In these situations, new messages wait on the
1062 queue until a queue runner process picks them up. However, in standard
1063 configurations under normal conditions, delivery is started as soon as a
1064 message is received.
1070 .section "Handling an incoming message" "SECID14"
1071 .cindex "spool directory" "files that hold a message"
1072 .cindex "file" "how a message is held"
1073 When Exim accepts a message, it writes two files in its spool directory. The
1074 first contains the envelope information, the current status of the message, and
1075 the header lines, and the second contains the body of the message. The names of
1076 the two spool files consist of the message id, followed by &`-H`& for the
1077 file containing the envelope and header, and &`-D`& for the data file.
1079 .cindex "spool directory" "&_input_& sub-directory"
1080 By default, all these message files are held in a single directory called
1081 &_input_& inside the general Exim spool directory. Some operating systems do
1082 not perform very well if the number of files in a directory gets large; to
1083 improve performance in such cases, the &%split_spool_directory%& option can be
1084 used. This causes Exim to split up the input files into 62 sub-directories
1085 whose names are single letters or digits. When this is done, the queue is
1086 processed one sub-directory at a time instead of all at once, which can improve
1087 overall performance even when there are not enough files in each directory to
1088 affect file system performance.
1090 The envelope information consists of the address of the message's sender and
1091 the addresses of the recipients. This information is entirely separate from
1092 any addresses contained in the header lines. The status of the message includes
1093 a list of recipients who have already received the message. The format of the
1094 first spool file is described in chapter &<<CHAPspool>>&.
1096 .cindex "rewriting" "addresses"
1097 Address rewriting that is specified in the rewrite section of the configuration
1098 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1099 both in the header lines and the envelope, at the time the message is accepted.
1100 If during the course of delivery additional addresses are generated (for
1101 example, via aliasing), these new addresses are rewritten as soon as they are
1102 generated. At the time a message is actually delivered (transported) further
1103 rewriting can take place; because this is a transport option, it can be
1104 different for different forms of delivery. It is also possible to specify the
1105 addition or removal of certain header lines at the time the message is
1106 delivered (see chapters &<<CHAProutergeneric>>& and
1107 &<<CHAPtransportgeneric>>&).
1111 .section "Life of a message" "SECID15"
1112 .cindex "message" "life of"
1113 .cindex "message" "frozen"
1114 A message remains in the spool directory until it is completely delivered to
1115 its recipients or to an error address, or until it is deleted by an
1116 administrator or by the user who originally created it. In cases when delivery
1117 cannot proceed &-- for example when a message can neither be delivered to its
1118 recipients nor returned to its sender, the message is marked &"frozen"& on the
1119 spool, and no more deliveries are attempted.
1121 .cindex "frozen messages" "thawing"
1122 .cindex "message" "thawing frozen"
1123 An administrator can &"thaw"& such messages when the problem has been
1124 corrected, and can also freeze individual messages by hand if necessary. In
1125 addition, an administrator can force a delivery error, causing a bounce message
1128 .oindex "&%timeout_frozen_after%&"
1129 .oindex "&%ignore_bounce_errors_after%&"
1130 There are options called &%ignore_bounce_errors_after%& and
1131 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1132 The first applies only to frozen bounces, the second to all frozen messages.
1134 .cindex "message" "log file for"
1135 .cindex "log" "file for each message"
1136 While Exim is working on a message, it writes information about each delivery
1137 attempt to its main log file. This includes successful, unsuccessful, and
1138 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1139 lines are also written to a separate &'message log'& file for each message.
1140 These logs are solely for the benefit of the administrator and are normally
1141 deleted along with the spool files when processing of a message is complete.
1142 The use of individual message logs can be disabled by setting
1143 &%no_message_logs%&; this might give an improvement in performance on very busy
1146 .cindex "journal file"
1147 .cindex "file" "journal"
1148 All the information Exim itself needs to set up a delivery is kept in the first
1149 spool file, along with the header lines. When a successful delivery occurs, the
1150 address is immediately written at the end of a journal file, whose name is the
1151 message id followed by &`-J`&. At the end of a delivery run, if there are some
1152 addresses left to be tried again later, the first spool file (the &`-H`& file)
1153 is updated to indicate which these are, and the journal file is then deleted.
1154 Updating the spool file is done by writing a new file and renaming it, to
1155 minimize the possibility of data loss.
1157 Should the system or Exim crash after a successful delivery but before
1158 the spool file has been updated, the journal is left lying around. The next
1159 time Exim attempts to deliver the message, it reads the journal file and
1160 updates the spool file before proceeding. This minimizes the chances of double
1161 deliveries caused by crashes.
1165 .section "Processing an address for delivery" "SECTprocaddress"
1166 .cindex "drivers" "definition of"
1167 .cindex "router" "definition of"
1168 .cindex "transport" "definition of"
1169 The main delivery processing elements of Exim are called &'routers'& and
1170 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1171 number of them is provided in the source distribution, and compile-time options
1172 specify which ones are included in the binary. Runtime options specify which
1173 ones are actually used for delivering messages.
1175 .cindex "drivers" "instance definition"
1176 Each driver that is specified in the runtime configuration is an &'instance'&
1177 of that particular driver type. Multiple instances are allowed; for example,
1178 you can set up several different &(smtp)& transports, each with different
1179 option values that might specify different ports or different timeouts. Each
1180 instance has its own identifying name. In what follows we will normally use the
1181 instance name when discussing one particular instance (that is, one specific
1182 configuration of the driver), and the generic driver name when discussing
1183 the driver's features in general.
1185 A &'router'& is a driver that operates on an address, either determining how
1186 its delivery should happen, by assigning it to a specific transport, or
1187 converting the address into one or more new addresses (for example, via an
1188 alias file). A router may also explicitly choose to fail an address, causing it
1191 A &'transport'& is a driver that transmits a copy of the message from Exim's
1192 spool to some destination. There are two kinds of transport: for a &'local'&
1193 transport, the destination is a file or a pipe on the local host, whereas for a
1194 &'remote'& transport the destination is some other host. A message is passed
1195 to a specific transport as a result of successful routing. If a message has
1196 several recipients, it may be passed to a number of different transports.
1198 .cindex "preconditions" "definition of"
1199 An address is processed by passing it to each configured router instance in
1200 turn, subject to certain preconditions, until a router accepts the address or
1201 specifies that it should be bounced. We will describe this process in more
1202 detail shortly. First, as a simple example, we consider how each recipient
1203 address in a message is processed in a small configuration of three routers.
1205 To make this a more concrete example, it is described in terms of some actual
1206 routers, but remember, this is only an example. You can configure Exim's
1207 routers in many different ways, and there may be any number of routers in a
1210 The first router that is specified in a configuration is often one that handles
1211 addresses in domains that are not recognized specifically by the local host.
1212 Typically these are addresses for arbitrary domains on the Internet. A precondition
1213 is set up which looks for the special domains known to the host (for example,
1214 its own domain name), and the router is run for addresses that do &'not'&
1215 match. Typically, this is a router that looks up domains in the DNS in order to
1216 find the hosts to which this address routes. If it succeeds, the address is
1217 assigned to a suitable SMTP transport; if it does not succeed, the router is
1218 configured to fail the address.
1220 The second router is reached only when the domain is recognized as one that
1221 &"belongs"& to the local host. This router does redirection &-- also known as
1222 aliasing and forwarding. When it generates one or more new addresses from the
1223 original, each of them is routed independently from the start. Otherwise, the
1224 router may cause an address to fail, or it may simply decline to handle the
1225 address, in which case the address is passed to the next router.
1227 The final router in many configurations is one that checks to see if the
1228 address belongs to a local mailbox. The precondition may involve a check to
1229 see if the local part is the name of a login account, or it may look up the
1230 local part in a file or a database. If its preconditions are not met, or if
1231 the router declines, we have reached the end of the routers. When this happens,
1232 the address is bounced.
1236 .section "Processing an address for verification" "SECID16"
1237 .cindex "router" "for verification"
1238 .cindex "verifying address" "overview"
1239 As well as being used to decide how to deliver to an address, Exim's routers
1240 are also used for &'address verification'&. Verification can be requested as
1241 one of the checks to be performed in an ACL for incoming messages, on both
1242 sender and recipient addresses, and it can be tested using the &%-bv%& and
1243 &%-bvs%& command line options.
1245 When an address is being verified, the routers are run in &"verify mode"&. This
1246 does not affect the way the routers work, but it is a state that can be
1247 detected. By this means, a router can be skipped or made to behave differently
1248 when verifying. A common example is a configuration in which the first router
1249 sends all messages to a message-scanning program unless they have been
1250 previously scanned. Thus, the first router accepts all addresses without any
1251 checking, making it useless for verifying. Normally, the &%no_verify%& option
1252 would be set for such a router, causing it to be skipped in verify mode.
1257 .section "Running an individual router" "SECTrunindrou"
1258 .cindex "router" "running details"
1259 .cindex "preconditions" "checking"
1260 .cindex "router" "result of running"
1261 As explained in the example above, a number of preconditions are checked before
1262 running a router. If any are not met, the router is skipped, and the address is
1263 passed to the next router. When all the preconditions on a router &'are'& met,
1264 the router is run. What happens next depends on the outcome, which is one of
1268 &'accept'&: The router accepts the address, and either assigns it to a
1269 transport or generates one or more &"child"& addresses. Processing the
1270 original address ceases
1271 .oindex "&%unseen%&"
1272 unless the &%unseen%& option is set on the router. This option
1273 can be used to set up multiple deliveries with different routing (for example,
1274 for keeping archive copies of messages). When &%unseen%& is set, the address is
1275 passed to the next router. Normally, however, an &'accept'& return marks the
1278 Any child addresses generated by the router are processed independently,
1279 starting with the first router by default. It is possible to change this by
1280 setting the &%redirect_router%& option to specify which router to start at for
1281 child addresses. Unlike &%pass_router%& (see below) the router specified by
1282 &%redirect_router%& may be anywhere in the router configuration.
1284 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1285 requests that the address be passed to another router. By default, the address
1286 is passed to the next router, but this can be changed by setting the
1287 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1288 must be below the current router (to avoid loops).
1290 &'decline'&: The router declines to accept the address because it does not
1291 recognize it at all. By default, the address is passed to the next router, but
1292 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1293 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1294 &'decline'& into &'fail'&.
1296 &'fail'&: The router determines that the address should fail, and queues it for
1297 the generation of a bounce message. There is no further processing of the
1298 original address unless &%unseen%& is set on the router.
1300 &'defer'&: The router cannot handle the address at the present time. (A
1301 database may be offline, or a DNS lookup may have timed out.) No further
1302 processing of the address happens in this delivery attempt. It is tried again
1303 next time the message is considered for delivery.
1305 &'error'&: There is some error in the router (for example, a syntax error in
1306 its configuration). The action is as for defer.
1309 If an address reaches the end of the routers without having been accepted by
1310 any of them, it is bounced as unrouteable. The default error message in this
1311 situation is &"unrouteable address"&, but you can set your own message by
1312 making use of the &%cannot_route_message%& option. This can be set for any
1313 router; the value from the last router that &"saw"& the address is used.
1315 Sometimes while routing you want to fail a delivery when some conditions are
1316 met but others are not, instead of passing the address on for further routing.
1317 You can do this by having a second router that explicitly fails the delivery
1318 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1319 facility for this purpose.
1322 .section "Duplicate addresses" "SECID17"
1323 .cindex "case of local parts"
1324 .cindex "address duplicate, discarding"
1325 .cindex "duplicate addresses"
1326 Once routing is complete, Exim scans the addresses that are assigned to local
1327 and remote transports and discards any duplicates that it finds. During this
1328 check, local parts are treated case-sensitively. This happens only when
1329 actually delivering a message; when testing routers with &%-bt%&, all the
1330 routed addresses are shown.
1334 .section "Router preconditions" "SECTrouprecon"
1335 .cindex "router" "preconditions, order of processing"
1336 .cindex "preconditions" "order of processing"
1337 The preconditions that are tested for each router are listed below, in the
1338 order in which they are tested. The individual configuration options are
1339 described in more detail in chapter &<<CHAProutergeneric>>&.
1342 .cindex affix "router precondition"
1343 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1344 the local parts handled by the router may or must have certain prefixes and/or
1345 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1346 skipped. These conditions are tested first. When an affix is present, it is
1347 removed from the local part before further processing, including the evaluation
1348 of any other conditions.
1350 Routers can be designated for use only when not verifying an address, that is,
1351 only when routing it for delivery (or testing its delivery routing). If the
1352 &%verify%& option is set false, the router is skipped when Exim is verifying an
1354 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1355 &%verify_recipient%&, which independently control the use of the router for
1356 sender and recipient verification. You can set these options directly if
1357 you want a router to be used for only one type of verification.
1358 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1360 If the &%address_test%& option is set false, the router is skipped when Exim is
1361 run with the &%-bt%& option to test an address routing. This can be helpful
1362 when the first router sends all new messages to a scanner of some sort; it
1363 makes it possible to use &%-bt%& to test subsequent delivery routing without
1364 having to simulate the effect of the scanner.
1366 Routers can be designated for use only when verifying an address, as
1367 opposed to routing it for delivery. The &%verify_only%& option controls this.
1368 Again, cutthrough delivery counts as a verification.
1370 Individual routers can be explicitly skipped when running the routers to
1371 check an address given in the SMTP EXPN command (see the &%expn%& option).
1374 If the &%domains%& option is set, the domain of the address must be in the set
1375 of domains that it defines.
1376 .cindex "tainted data" "de-tainting"
1377 .cindex "de-tainting" "using router domains option"
1378 A match verifies the variable &$domain$& (which carries tainted data)
1379 and assigns an untainted value to the &$domain_data$& variable.
1380 Such an untainted value is often needed in the transport.
1381 For specifics of the matching operation and the resulting untainted value,
1382 refer to section &<<SECTdomainlist>>&.
1384 When an untainted value is wanted, use this option
1385 rather than the generic &%condition%& option.
1388 .vindex "&$local_part_prefix$&"
1389 .vindex "&$local_part_prefix_v$&"
1390 .vindex "&$local_part$&"
1391 .vindex "&$local_part_suffix$&"
1392 .vindex "&$local_part_suffix_v$&"
1393 .cindex affix "router precondition"
1394 If the &%local_parts%& option is set, the local part of the address must be in
1395 the set of local parts that it defines.
1396 A match verifies the variable &$local_part$& (which carries tainted data)
1397 and assigns an untainted value to the &$local_part_data$& variable.
1398 Such an untainted value is often needed in the transport.
1399 For specifics of the matching operation and the resulting untainted value,
1400 refer to section &<<SECTlocparlis>>&.
1402 When an untainted value is wanted, use this option
1403 rather than the generic &%condition%& option.
1405 If &%local_part_prefix%& or
1406 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1407 part before this check. If you want to do precondition tests on local parts
1408 that include affixes, you can do so by using a &%condition%& option (see below)
1409 that uses the variables &$local_part$&, &$local_part_prefix$&,
1410 &$local_part_prefix_v$&, &$local_part_suffix$&
1411 and &$local_part_suffix_v$& as necessary.
1414 .vindex "&$local_user_uid$&"
1415 .vindex "&$local_user_gid$&"
1417 If the &%check_local_user%& option is set, the local part must be the name of
1418 an account on the local host. If this check succeeds, the uid and gid of the
1419 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1420 user's home directory is placed in &$home$&; these values can be used in the
1421 remaining preconditions.
1424 If the &%router_home_directory%& option is set, it is expanded at this point,
1425 because it overrides the value of &$home$&. If this expansion were left till
1426 later, the value of &$home$& as set by &%check_local_user%& would be used in
1427 subsequent tests. Having two different values of &$home$& in the same router
1428 could lead to confusion.
1431 If the &%senders%& option is set, the envelope sender address must be in the
1432 set of addresses that it defines.
1435 If the &%require_files%& option is set, the existence or non-existence of
1436 specified files is tested.
1439 .cindex "customizing" "precondition"
1440 If the &%condition%& option is set, it is evaluated and tested. This option
1441 uses an expanded string to allow you to set up your own custom preconditions.
1442 Expanded strings are described in chapter &<<CHAPexpand>>&.
1444 Note that while using
1445 this option for address matching technically works,
1446 it does not set any de-tainted values.
1447 Such values are often needed, either for router-specific options or
1448 for transport options.
1449 Using the &%domains%& and &%local_parts%& options is usually the most
1450 convenient way to obtain them.
1454 Note that &%require_files%& comes near the end of the list, so you cannot use
1455 it to check for the existence of a file in which to lookup up a domain, local
1456 part, or sender. However, as these options are all expanded, you can use the
1457 &%exists%& expansion condition to make such tests within each condition. The
1458 &%require_files%& option is intended for checking files that the router may be
1459 going to use internally, or which are needed by a specific transport (for
1460 example, &_.procmailrc_&).
1464 .section "Delivery in detail" "SECID18"
1465 .cindex "delivery" "in detail"
1466 When a message is to be delivered, the sequence of events is as follows:
1469 If a system-wide filter file is specified, the message is passed to it. The
1470 filter may add recipients to the message, replace the recipients, discard the
1471 message, cause a new message to be generated, or cause the message delivery to
1472 fail. The format of the system filter file is the same as for Exim user filter
1473 files, described in the separate document entitled &'Exim's interfaces to mail
1475 .cindex "Sieve filter" "not available for system filter"
1476 (&*Note*&: Sieve cannot be used for system filter files.)
1478 Some additional features are available in system filters &-- see chapter
1479 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1480 filter only once per delivery attempt, however many recipients it has. However,
1481 if there are several delivery attempts because one or more addresses could not
1482 be immediately delivered, the system filter is run each time. The filter
1483 condition &%first_delivery%& can be used to detect the first run of the system
1486 Each recipient address is offered to each configured router, in turn, subject to
1487 its preconditions, until one is able to handle it. If no router can handle the
1488 address, that is, if they all decline, the address is failed. Because routers
1489 can be targeted at particular domains, several locally handled domains can be
1490 processed entirely independently of each other.
1492 .cindex "routing" "loops in"
1493 .cindex "loop" "while routing"
1494 A router that accepts an address may assign it to a local or a remote
1495 transport. However, the transport is not run at this time. Instead, the address
1496 is placed on a list for the particular transport, which will be run later.
1497 Alternatively, the router may generate one or more new addresses (typically
1498 from alias, forward, or filter files). New addresses are fed back into this
1499 process from the top, but in order to avoid loops, a router ignores any address
1500 which has an identically-named ancestor that was processed by itself.
1502 When all the routing has been done, addresses that have been successfully
1503 handled are passed to their assigned transports. When local transports are
1504 doing real local deliveries, they handle only one address at a time, but if a
1505 local transport is being used as a pseudo-remote transport (for example, to
1506 collect batched SMTP messages for transmission by some other means) multiple
1507 addresses can be handled. Remote transports can always handle more than one
1508 address at a time, but can be configured not to do so, or to restrict multiple
1509 addresses to the same domain.
1511 Each local delivery to a file or a pipe runs in a separate process under a
1512 non-privileged uid, and these deliveries are run one at a time. Remote
1513 deliveries also run in separate processes, normally under a uid that is private
1514 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1515 run in parallel. The maximum number of simultaneous remote deliveries for any
1516 one message is set by the &%remote_max_parallel%& option.
1517 The order in which deliveries are done is not defined, except that all local
1518 deliveries happen before any remote deliveries.
1520 .cindex "queue runner"
1521 When it encounters a local delivery during a queue run, Exim checks its retry
1522 database to see if there has been a previous temporary delivery failure for the
1523 address before running the local transport. If there was a previous failure,
1524 Exim does not attempt a new delivery until the retry time for the address is
1525 reached. However, this happens only for delivery attempts that are part of a
1526 queue run. Local deliveries are always attempted when delivery immediately
1527 follows message reception, even if retry times are set for them. This makes for
1528 better behaviour if one particular message is causing problems (for example,
1529 causing quota overflow, or provoking an error in a filter file).
1531 .cindex "delivery" "retry in remote transports"
1532 Remote transports do their own retry handling, since an address may be
1533 deliverable to one of a number of hosts, each of which may have a different
1534 retry time. If there have been previous temporary failures and no host has
1535 reached its retry time, no delivery is attempted, whether in a queue run or
1536 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1538 If there were any permanent errors, a bounce message is returned to an
1539 appropriate address (the sender in the common case), with details of the error
1540 for each failing address. Exim can be configured to send copies of bounce
1541 messages to other addresses.
1543 .cindex "delivery" "deferral"
1544 If one or more addresses suffered a temporary failure, the message is left on
1545 the queue, to be tried again later. Delivery of these addresses is said to be
1548 When all the recipient addresses have either been delivered or bounced,
1549 handling of the message is complete. The spool files and message log are
1550 deleted, though the message log can optionally be preserved if required.
1556 .section "Retry mechanism" "SECID19"
1557 .cindex "delivery" "retry mechanism"
1558 .cindex "retry" "description of mechanism"
1559 .cindex "queue runner"
1560 Exim's mechanism for retrying messages that fail to get delivered at the first
1561 attempt is the queue runner process. You must either run an Exim daemon that
1562 uses the &%-q%& option with a time interval to start queue runners at regular
1563 intervals or use some other means (such as &'cron'&) to start them. If you do
1564 not arrange for queue runners to be run, messages that fail temporarily at the
1565 first attempt will remain in your queue forever. A queue runner process works
1566 its way through the queue, one message at a time, trying each delivery that has
1567 passed its retry time.
1568 You can run several queue runners at once.
1570 Exim uses a set of configured rules to determine when next to retry the failing
1571 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1572 should give up trying to deliver to the address, at which point it generates a
1573 bounce message. If no retry rules are set for a particular host, address, and
1574 error combination, no retries are attempted, and temporary errors are treated
1579 .subsection "Temporary delivery failure" SECID20
1580 .cindex "delivery" "temporary failure"
1581 There are many reasons why a message may not be immediately deliverable to a
1582 particular address. Failure to connect to a remote machine (because it, or the
1583 connection to it, is down) is one of the most common. Temporary failures may be
1584 detected during routing as well as during the transport stage of delivery.
1585 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1586 is on a file system where the user is over quota. Exim can be configured to
1587 impose its own quotas on local mailboxes; where system quotas are set they will
1590 If a host is unreachable for a period of time, a number of messages may be
1591 waiting for it by the time it recovers, and sending them in a single SMTP
1592 connection is clearly beneficial. Whenever a delivery to a remote host is
1594 .cindex "hints database" "deferred deliveries"
1595 Exim makes a note in its hints database, and whenever a successful
1596 SMTP delivery has happened, it looks to see if any other messages are waiting
1597 for the same host. If any are found, they are sent over the same SMTP
1598 connection, subject to a configuration limit as to the maximum number in any
1603 .subsection "Permanent delivery failure" SECID21
1604 .cindex "delivery" "permanent failure"
1605 .cindex "bounce message" "when generated"
1606 When a message cannot be delivered to some or all of its intended recipients, a
1607 bounce message is generated. Temporary delivery failures turn into permanent
1608 errors when their timeout expires. All the addresses that fail in a given
1609 delivery attempt are listed in a single message. If the original message has
1610 many recipients, it is possible for some addresses to fail in one delivery
1611 attempt and others to fail subsequently, giving rise to more than one bounce
1612 message. The wording of bounce messages can be customized by the administrator.
1613 See chapter &<<CHAPemsgcust>>& for details.
1615 .cindex "&'X-Failed-Recipients:'& header line"
1616 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1617 failed addresses, for the benefit of programs that try to analyse such messages
1620 .cindex "bounce message" "recipient of"
1621 A bounce message is normally sent to the sender of the original message, as
1622 obtained from the message's envelope. For incoming SMTP messages, this is the
1623 address given in the MAIL command. However, when an address is expanded via a
1624 forward or alias file, an alternative address can be specified for delivery
1625 failures of the generated addresses. For a mailing list expansion (see section
1626 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1631 .subsection "Failures to deliver bounce messages" SECID22
1632 .cindex "bounce message" "failure to deliver"
1633 If a bounce message (either locally generated or received from a remote host)
1634 itself suffers a permanent delivery failure, the message is left in the queue,
1635 but it is frozen, awaiting the attention of an administrator. There are options
1636 that can be used to make Exim discard such failed messages, or to keep them
1637 for only a short time (see &%timeout_frozen_after%& and
1638 &%ignore_bounce_errors_after%&).
1644 . ////////////////////////////////////////////////////////////////////////////
1645 . ////////////////////////////////////////////////////////////////////////////
1647 .chapter "Building and installing Exim" "CHID3"
1648 .scindex IIDbuex "building Exim"
1650 .section "Unpacking" "SECID23"
1651 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1652 creates a directory with the name of the current release (for example,
1653 &_exim-&version()_&) into which the following files are placed:
1656 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1657 .irow &_CHANGES_& "contains a reference to where changes are &&&
1659 .irow &_LICENCE_& "the GNU General Public Licence"
1660 .irow &_Makefile_& "top-level make file"
1661 .irow &_NOTICE_& "conditions for the use of Exim"
1662 .irow &_README_& "list of files, directories and simple build &&&
1666 Other files whose names begin with &_README_& may also be present. The
1667 following subdirectories are created:
1670 .irow &_Local_& "an empty directory for local configuration files"
1671 .irow &_OS_& "OS-specific files"
1672 .irow &_doc_& "documentation files"
1673 .irow &_exim_monitor_& "source files for the Exim monitor"
1674 .irow &_scripts_& "scripts used in the build process"
1675 .irow &_src_& "remaining source files"
1676 .irow &_util_& "independent utilities"
1679 The main utility programs are contained in the &_src_& directory and are built
1680 with the Exim binary. The &_util_& directory contains a few optional scripts
1681 that may be useful to some sites.
1684 .section "Multiple machine architectures and operating systems" "SECID24"
1685 .cindex "building Exim" "multiple OS/architectures"
1686 The building process for Exim is arranged to make it easy to build binaries for
1687 a number of different architectures and operating systems from the same set of
1688 source files. Compilation does not take place in the &_src_& directory.
1689 Instead, a &'build directory'& is created for each architecture and operating
1691 .cindex "symbolic link" "to build directory"
1692 Symbolic links to the sources are installed in this directory, which is where
1693 the actual building takes place. In most cases, Exim can discover the machine
1694 architecture and operating system for itself, but the defaults can be
1695 overridden if necessary.
1696 .cindex compiler requirements
1697 .cindex compiler version
1698 A C99-capable compiler will be required for the build.
1701 .section "PCRE2 library" "SECTpcre"
1702 .cindex "PCRE2 library"
1703 Exim no longer has an embedded regular-expression library as the vast majority of
1704 modern systems include PCRE2 as a system library, although you may need to
1705 install the PCRE2 package or the PCRE2 development package for your operating
1706 system. If your system has a normal PCRE2 installation the Exim build
1707 process will need no further configuration. If the library or the
1708 headers are in an unusual location you will need to either set the PCRE2_LIBS
1709 and INCLUDE directives appropriately,
1710 or set PCRE2_CONFIG=yes to use the installed &(pcre-config)& command.
1711 If your operating system has no
1712 PCRE2 support then you will need to obtain and build the current PCRE2
1713 from &url(https://github.com/PhilipHazel/pcre2/releases).
1714 More information on PCRE2 is available at &url(https://www.pcre.org/).
1716 .section "DBM libraries" "SECTdb"
1717 .cindex "DBM libraries" "discussion of"
1718 .cindex "hints database" "DBM files used for"
1719 Even if you do not use any DBM files in your configuration, Exim still needs a
1720 DBM library in order to operate, because it uses indexed files for its hints
1721 databases. Unfortunately, there are a number of DBM libraries in existence, and
1722 different operating systems often have different ones installed.
1724 .cindex "Solaris" "DBM library for"
1725 .cindex "IRIX, DBM library for"
1726 .cindex "BSD, DBM library for"
1727 .cindex "Linux, DBM library for"
1728 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1729 Linux distribution, the DBM configuration should happen automatically, and you
1730 may be able to ignore this section. Otherwise, you may have to learn more than
1731 you would like about DBM libraries from what follows.
1733 .cindex "&'ndbm'& DBM library"
1734 Licensed versions of Unix normally contain a library of DBM functions operating
1735 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1736 versions of Unix seem to vary in what they contain as standard. In particular,
1737 some early versions of Linux have no default DBM library, and different
1738 distributors have chosen to bundle different libraries with their packaged
1739 versions. However, the more recent releases seem to have standardized on the
1740 Berkeley DB library.
1742 Different DBM libraries have different conventions for naming the files they
1743 use. When a program opens a file called &_dbmfile_&, there are several
1747 A traditional &'ndbm'& implementation, such as that supplied as part of
1748 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1750 .cindex "&'gdbm'& DBM library"
1751 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1752 compatibility interface it makes two different hard links to it with names
1753 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1754 filename is used unmodified.
1756 .cindex "Berkeley DB library"
1757 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1758 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1759 programmer exactly the same as the traditional &'ndbm'& implementation.
1761 If the Berkeley package is used in its native mode, it operates on a single
1762 file called &_dbmfile_&; the programmer's interface is somewhat different to
1763 the traditional &'ndbm'& interface.
1765 To complicate things further, there are several very different versions of the
1766 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1767 2.&'x'& and 3.&'x'& were current for a while,
1768 but the latest versions when Exim last revamped support were numbered 5.&'x'&.
1769 Maintenance of some of the earlier releases has ceased,
1770 and Exim no longer supports versions before 3.&'x'&.
1771 All versions of Berkeley DB could be obtained from
1772 &url(http://www.sleepycat.com/), which is now a redirect to their new owner's
1773 page with far newer versions listed.
1774 It is probably wise to plan to move your storage configurations away from
1775 Berkeley DB format, as today there are smaller and simpler alternatives more
1776 suited to Exim's usage model.
1778 .cindex "&'tdb'& DBM library"
1779 Yet another DBM library, called &'tdb'&, is available from
1780 &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
1781 operates on a single file.
1785 .cindex "DBM libraries" "configuration for building"
1786 Exim and its utilities can be compiled to use any of these interfaces. In order
1787 to use any version of the Berkeley DB package in native mode, you must set
1788 USE_DB in an appropriate configuration file (typically
1789 &_Local/Makefile_&). For example:
1793 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1794 error is diagnosed if you set more than one of these.
1795 You can set USE_NDBM if needed to override an operating system default.
1797 At the lowest level, the build-time configuration sets none of these options,
1798 thereby assuming an interface of type (1). However, some operating system
1799 configuration files (for example, those for the BSD operating systems and
1800 Linux) assume type (4) by setting USE_DB as their default, and the
1801 configuration files for Cygwin set USE_GDBM. Anything you set in
1802 &_Local/Makefile_&, however, overrides these system defaults.
1804 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1805 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1806 in one of these lines:
1810 DBMLIB = -lgdbm -lgdbm_compat
1812 The last of those was for a Linux having GDBM provide emulated NDBM facilities.
1813 Settings like that will work if the DBM library is installed in the standard
1814 place. Sometimes it is not, and the library's header file may also not be in
1815 the default path. You may need to set INCLUDE to specify where the header
1816 file is, and to specify the path to the library more fully in DBMLIB, as in
1819 INCLUDE=-I/usr/local/include/db-4.1
1820 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1822 There is further detailed discussion about the various DBM libraries in the
1823 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1827 .section "Pre-building configuration" "SECID25"
1828 .cindex "building Exim" "pre-building configuration"
1829 .cindex "configuration for building Exim"
1830 .cindex "&_Local/Makefile_&"
1831 .cindex "&_src/EDITME_&"
1832 Before building Exim, a local configuration file that specifies options
1833 independent of any operating system has to be created with the name
1834 &_Local/Makefile_&. A template for this file is supplied as the file
1835 &_src/EDITME_&, and it contains full descriptions of all the option settings
1836 therein. These descriptions are therefore not repeated here. If you are
1837 building Exim for the first time, the simplest thing to do is to copy
1838 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1840 There are three settings that you must supply, because Exim will not build
1841 without them. They are the location of the runtime configuration file
1842 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1843 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1844 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1845 a colon-separated list of filenames; Exim uses the first of them that exists.
1847 There are a few other parameters that can be specified either at build time or
1848 at runtime, to enable the same binary to be used on a number of different
1849 machines. However, if the locations of Exim's spool directory and log file
1850 directory (if not within the spool directory) are fixed, it is recommended that
1851 you specify them in &_Local/Makefile_& instead of at runtime, so that errors
1852 detected early in Exim's execution (such as a malformed configuration file) can
1855 .cindex "content scanning" "specifying at build time"
1856 Exim's interfaces for calling virus and spam scanning software directly from
1857 access control lists are not compiled by default. If you want to include these
1858 facilities, you need to set
1860 WITH_CONTENT_SCAN=yes
1862 in your &_Local/Makefile_&. For details of the facilities themselves, see
1863 chapter &<<CHAPexiscan>>&.
1866 .cindex "&_Local/eximon.conf_&"
1867 .cindex "&_exim_monitor/EDITME_&"
1868 If you are going to build the Exim monitor, a similar configuration process is
1869 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1870 your installation and saved under the name &_Local/eximon.conf_&. If you are
1871 happy with the default settings described in &_exim_monitor/EDITME_&,
1872 &_Local/eximon.conf_& can be empty, but it must exist.
1874 This is all the configuration that is needed in straightforward cases for known
1875 operating systems. However, the building process is set up so that it is easy
1876 to override options that are set by default or by operating-system-specific
1877 configuration files, for example, to change the C compiler, which
1878 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1883 .section "Support for iconv()" "SECID26"
1884 .cindex "&[iconv()]& support"
1886 The contents of header lines in messages may be encoded according to the rules
1887 described RFC 2047. This makes it possible to transmit characters that are not
1888 in the ASCII character set, and to label them as being in a particular
1889 character set. When Exim is inspecting header lines by means of the &%$h_%&
1890 mechanism, it decodes them, and translates them into a specified character set
1891 (default is set at build time). The translation is possible only if the operating system
1892 supports the &[iconv()]& function.
1894 However, some of the operating systems that supply &[iconv()]& do not support
1895 very many conversions. The GNU &%libiconv%& library (available from
1896 &url(https://www.gnu.org/software/libiconv/)) can be installed on such
1897 systems to remedy this deficiency, as well as on systems that do not supply
1898 &[iconv()]& at all. After installing &%libiconv%&, you should add
1902 to your &_Local/Makefile_& and rebuild Exim.
1906 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1907 .cindex "TLS" "including support for TLS"
1908 .cindex "encryption" "including support for"
1909 .cindex "OpenSSL" "building Exim with"
1910 .cindex "GnuTLS" "building Exim with"
1911 Exim is usually built to support encrypted SMTP connections, using the STARTTLS
1912 command as per RFC 2487. It can also support clients that expect to
1913 start a TLS session immediately on connection to a non-standard port (see the
1914 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1917 If you want to build Exim with TLS support, you must first install either the
1918 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1921 If you do not want TLS support you should set
1925 in &_Local/Makefile_&.
1927 If OpenSSL is installed, you should set
1930 TLS_LIBS=-lssl -lcrypto
1932 in &_Local/Makefile_&. You may also need to specify the locations of the
1933 OpenSSL library and include files. For example:
1936 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1937 TLS_INCLUDE=-I/usr/local/openssl/include/
1939 .cindex "pkg-config" "OpenSSL"
1940 If you have &'pkg-config'& available, then instead you can just use:
1943 USE_OPENSSL_PC=openssl
1945 .cindex "USE_GNUTLS"
1946 If GnuTLS is installed, you should set
1949 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1951 in &_Local/Makefile_&, and again you may need to specify the locations of the
1952 library and include files. For example:
1955 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1956 TLS_INCLUDE=-I/usr/gnu/include
1958 .cindex "pkg-config" "GnuTLS"
1959 If you have &'pkg-config'& available, then instead you can just use:
1962 USE_GNUTLS_PC=gnutls
1965 You do not need to set TLS_INCLUDE if the relevant directory is already
1966 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1967 given in chapter &<<CHAPTLS>>&.
1972 .section "Use of tcpwrappers" "SECID27"
1974 .cindex "tcpwrappers, building Exim to support"
1975 .cindex "USE_TCP_WRAPPERS"
1976 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1977 .cindex "tcp_wrappers_daemon_name"
1978 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1979 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1980 alternative to Exim's own checking facilities for installations that are
1981 already making use of &'tcpwrappers'& for other purposes. To do this, you
1982 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1983 &_tcpd.h_& to be available at compile time, and also ensure that the library
1984 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1985 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1988 USE_TCP_WRAPPERS=yes
1989 CFLAGS=-O -I/usr/local/include
1990 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1992 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1993 files is &"exim"&. For example, the line
1995 exim : LOCAL 192.168.1. .friendly.domain.example
1997 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1998 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1999 All other connections are denied. The daemon name used by &'tcpwrappers'&
2000 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
2001 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
2002 configure file. Consult the &'tcpwrappers'& documentation for
2006 .section "Including support for IPv6" "SECID28"
2007 .cindex "IPv6" "including support for"
2008 Exim contains code for use on systems that have IPv6 support. Setting
2009 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
2010 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
2011 where the IPv6 support is not fully integrated into the normal include and
2014 Two different types of DNS record for handling IPv6 addresses have been
2015 defined. AAAA records (analogous to A records for IPv4) are in use, and are
2016 currently seen as the mainstream. Another record type called A6 was proposed
2017 as better than AAAA because it had more flexibility. However, it was felt to be
2018 over-complex, and its status was reduced to &"experimental"&.
2020 have a compile option for including A6 record support but this has now been
2025 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
2026 .cindex "lookup modules"
2027 .cindex "dynamic modules"
2028 .cindex ".so building"
2029 On some platforms, Exim supports not compiling all lookup types directly into
2030 the main binary, instead putting some into external modules which can be loaded
2032 This permits packagers to build Exim with support for lookups with extensive
2033 library dependencies without requiring all users to install all of those
2035 Most, but not all, lookup types can be built this way.
2037 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2038 installed; Exim will only load modules from that directory, as a security
2039 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2040 for your OS; see &_OS/Makefile-Linux_& for an example.
2041 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2042 see &_src/EDITME_& for details.
2044 Then, for each module to be loaded dynamically, define the relevant
2045 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2046 For example, this will build in lsearch but load sqlite and mysql support
2055 .section "The building process" "SECID29"
2056 .cindex "build directory"
2057 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2058 created, run &'make'& at the top level. It determines the architecture and
2059 operating system types, and creates a build directory if one does not exist.
2060 For example, on a Sun system running Solaris 8, the directory
2061 &_build-SunOS5-5.8-sparc_& is created.
2062 .cindex "symbolic link" "to source files"
2063 Symbolic links to relevant source files are installed in the build directory.
2065 If this is the first time &'make'& has been run, it calls a script that builds
2066 a make file inside the build directory, using the configuration files from the
2067 &_Local_& directory. The new make file is then passed to another instance of
2068 &'make'&. This does the real work, building a number of utility scripts, and
2069 then compiling and linking the binaries for the Exim monitor (if configured), a
2070 number of utility programs, and finally Exim itself. The command &`make
2071 makefile`& can be used to force a rebuild of the make file in the build
2072 directory, should this ever be necessary.
2074 If you have problems building Exim, check for any comments there may be in the
2075 &_README_& file concerning your operating system, and also take a look at the
2076 FAQ, where some common problems are covered.
2080 .section 'Output from &"make"&' "SECID283"
2081 The output produced by the &'make'& process for compile lines is often very
2082 unreadable, because these lines can be very long. For this reason, the normal
2083 output is suppressed by default, and instead output similar to that which
2084 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2085 each module that is being compiled or linked. However, it is still possible to
2086 get the full output, by calling &'make'& like this:
2090 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2091 command reflection in &'make'&. When you ask for the full output, it is
2092 given in addition to the short output.
2096 .section "Overriding build-time options for Exim" "SECToverride"
2097 .cindex "build-time options, overriding"
2098 The main make file that is created at the beginning of the building process
2099 consists of the concatenation of a number of files which set configuration
2100 values, followed by a fixed set of &'make'& instructions. If a value is set
2101 more than once, the last setting overrides any previous ones. This provides a
2102 convenient way of overriding defaults. The files that are concatenated are, in
2105 &_OS/Makefile-Default_&
2106 &_OS/Makefile-_&<&'ostype'&>
2108 &_Local/Makefile-_&<&'ostype'&>
2109 &_Local/Makefile-_&<&'archtype'&>
2110 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2111 &_OS/Makefile-Base_&
2113 .cindex "&_Local/Makefile_&"
2114 .cindex "building Exim" "operating system type"
2115 .cindex "building Exim" "architecture type"
2116 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2117 architecture type. &_Local/Makefile_& is required to exist, and the building
2118 process fails if it is absent. The other three &_Local_& files are optional,
2119 and are often not needed.
2121 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2122 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2123 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2124 values are used, thereby providing a means of forcing particular settings.
2125 Otherwise, the scripts try to get values from the &%uname%& command. If this
2126 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2127 of &'ad hoc'& transformations are then applied, to produce the standard names
2128 that Exim expects. You can run these scripts directly from the shell in order
2129 to find out what values are being used on your system.
2132 &_OS/Makefile-Default_& contains comments about the variables that are set
2133 therein. Some (but not all) are mentioned below. If there is something that
2134 needs changing, review the contents of this file and the contents of the make
2135 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2139 .cindex "building Exim" "overriding default settings"
2140 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2141 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2142 need to change the original files. Instead, you should make the changes by
2143 putting the new values in an appropriate &_Local_& file. For example,
2144 .cindex "Tru64-Unix build-time settings"
2145 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2146 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2147 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2148 called with the option &%-std1%&, to make it recognize some of the features of
2149 Standard C that Exim uses. (Most other compilers recognize Standard C by
2150 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2151 containing the lines
2156 If you are compiling for just one operating system, it may be easier to put
2157 these lines directly into &_Local/Makefile_&.
2159 Keeping all your local configuration settings separate from the distributed
2160 files makes it easy to transfer them to new versions of Exim simply by copying
2161 the contents of the &_Local_& directory.
2164 .cindex "NIS lookup type" "including support for"
2165 .cindex "NIS+ lookup type" "including support for"
2166 .cindex "LDAP" "including support for"
2167 .cindex "lookup" "inclusion in binary"
2168 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2169 lookup, but not all systems have these components installed, so the default is
2170 not to include the relevant code in the binary. All the different kinds of file
2171 and database lookup that Exim supports are implemented as separate code modules
2172 which are included only if the relevant compile-time options are set. In the
2173 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2179 and similar settings apply to the other lookup types. They are all listed in
2180 &_src/EDITME_&. In many cases the relevant include files and interface
2181 libraries need to be installed before compiling Exim.
2182 .cindex "cdb" "including support for"
2183 However, there are some optional lookup types (such as cdb) for which
2184 the code is entirely contained within Exim, and no external include
2185 files or libraries are required. When a lookup type is not included in the
2186 binary, attempts to configure Exim to use it cause runtime configuration
2189 .cindex "pkg-config" "lookups"
2190 .cindex "pkg-config" "authenticators"
2191 Many systems now use a tool called &'pkg-config'& to encapsulate information
2192 about how to compile against a library; Exim has some initial support for
2193 being able to use pkg-config for lookups and authenticators. For any given
2194 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2195 variable with the &`_PC`& suffix in the name and assign as the value the
2196 name of the package to be queried. The results of querying via the
2197 &'pkg-config'& command will be added to the appropriate Makefile variables
2198 with &`+=`& directives, so your version of &'make'& will need to support that
2199 syntax. For instance:
2202 LOOKUP_SQLITE_PC=sqlite3
2204 AUTH_GSASL_PC=libgsasl
2205 AUTH_HEIMDAL_GSSAPI=yes
2206 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2209 .cindex "Perl" "including support for"
2210 Exim can be linked with an embedded Perl interpreter, allowing Perl
2211 subroutines to be called during string expansion. To enable this facility,
2215 must be defined in &_Local/Makefile_&. Details of this facility are given in
2216 chapter &<<CHAPperl>>&.
2218 .cindex "X11 libraries, location of"
2219 The location of the X11 libraries is something that varies a lot between
2220 operating systems, and there may be different versions of X11 to cope
2221 with. Exim itself makes no use of X11, but if you are compiling the Exim
2222 monitor, the X11 libraries must be available.
2223 The following three variables are set in &_OS/Makefile-Default_&:
2226 XINCLUDE=-I$(X11)/include
2227 XLFLAGS=-L$(X11)/lib
2229 These are overridden in some of the operating-system configuration files. For
2230 example, in &_OS/Makefile-SunOS5_& there is
2233 XINCLUDE=-I$(X11)/include
2234 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2236 If you need to override the default setting for your operating system, place a
2237 definition of all three of these variables into your
2238 &_Local/Makefile-<ostype>_& file.
2241 If you need to add any extra libraries to the link steps, these can be put in a
2242 variable called EXTRALIBS, which appears in all the link commands, but by
2243 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2244 command for linking the main Exim binary, and not for any associated utilities.
2246 .cindex "DBM libraries" "configuration for building"
2247 There is also DBMLIB, which appears in the link commands for binaries that
2248 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2249 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2250 binary, and which can be used, for example, to include additional X11
2253 .cindex "configuration file" "editing"
2254 The make file copes with rebuilding Exim correctly if any of the configuration
2255 files are edited. However, if an optional configuration file is deleted, it is
2256 necessary to touch the associated non-optional file (that is,
2257 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2260 .section "OS-specific header files" "SECID30"
2262 .cindex "building Exim" "OS-specific C header files"
2263 The &_OS_& directory contains a number of files with names of the form
2264 &_os.h-<ostype>_&. These are system-specific C header files that should not
2265 normally need to be changed. There is a list of macro settings that are
2266 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2267 are porting Exim to a new operating system.
2271 .section "Overriding build-time options for the monitor" "SECID31"
2272 .cindex "building Eximon"
2273 A similar process is used for overriding things when building the Exim monitor,
2274 where the files that are involved are
2276 &_OS/eximon.conf-Default_&
2277 &_OS/eximon.conf-_&<&'ostype'&>
2278 &_Local/eximon.conf_&
2279 &_Local/eximon.conf-_&<&'ostype'&>
2280 &_Local/eximon.conf-_&<&'archtype'&>
2281 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2283 .cindex "&_Local/eximon.conf_&"
2284 As with Exim itself, the final three files need not exist, and in this case the
2285 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2286 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2287 variables of the same name, preceded by EXIMON_. For example, setting
2288 EXIMON_LOG_DEPTH in the environment overrides the value of
2289 LOG_DEPTH at runtime.
2293 .section "Installing Exim binaries and scripts" "SECID32"
2294 .cindex "installing Exim"
2295 .cindex "BIN_DIRECTORY"
2296 The command &`make install`& runs the &(exim_install)& script with no
2297 arguments. The script copies binaries and utility scripts into the directory
2298 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2299 .cindex "setuid" "installing Exim with"
2300 The install script copies files only if they are newer than the files they are
2301 going to replace. The Exim binary is required to be owned by root and have the
2302 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2303 install`& as root so that it can set up the Exim binary in this way. However, in
2304 some special situations (for example, if a host is doing no local deliveries)
2305 it may be possible to run Exim without making the binary setuid root (see
2306 chapter &<<CHAPsecurity>>& for details).
2308 .cindex "CONFIGURE_FILE"
2309 Exim's runtime configuration file is named by the CONFIGURE_FILE setting
2310 in &_Local/Makefile_&. If this names a single file, and the file does not
2311 exist, the default configuration file &_src/configure.default_& is copied there
2312 by the installation script. If a runtime configuration file already exists, it
2313 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2314 alternative files, no default is installed.
2316 .cindex "system aliases file"
2317 .cindex "&_/etc/aliases_&"
2318 One change is made to the default configuration file when it is installed: the
2319 default configuration contains a router that references a system aliases file.
2320 The path to this file is set to the value specified by
2321 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2322 If the system aliases file does not exist, the installation script creates it,
2323 and outputs a comment to the user.
2325 The created file contains no aliases, but it does contain comments about the
2326 aliases a site should normally have. Mail aliases have traditionally been
2327 kept in &_/etc/aliases_&. However, some operating systems are now using
2328 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2329 Exim's configuration if necessary.
2331 The default configuration uses the local host's name as the only local domain,
2332 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2333 running as the local user. System aliases and &_.forward_& files in users' home
2334 directories are supported, but no NIS or NIS+ support is configured. Domains
2335 other than the name of the local host are routed using the DNS, with delivery
2338 It is possible to install Exim for special purposes (such as building a binary
2339 distribution) in a private part of the file system. You can do this by a
2342 make DESTDIR=/some/directory/ install
2344 This has the effect of pre-pending the specified directory to all the file
2345 paths, except the name of the system aliases file that appears in the default
2346 configuration. (If a default alias file is created, its name &'is'& modified.)
2347 For backwards compatibility, ROOT is used if DESTDIR is not set,
2348 but this usage is deprecated.
2350 .cindex "installing Exim" "what is not installed"
2351 Running &'make install'& does not copy the Exim 4 conversion script
2352 &'convert4r4'&. You will probably run this only once if you are
2353 upgrading from Exim 3. None of the documentation files in the &_doc_&
2354 directory are copied, except for the info files when you have set
2355 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2357 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2358 to their names. The Exim binary itself, however, is handled differently. It is
2359 installed under a name that includes the version number and the compile number,
2360 for example, &_exim-&version()-1_&. The script then arranges for a symbolic link
2361 called &_exim_& to point to the binary. If you are updating a previous version
2362 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2363 from the directory (as seen by other processes).
2365 .cindex "installing Exim" "testing the script"
2366 If you want to see what the &'make install'& will do before running it for
2367 real, you can pass the &%-n%& option to the installation script by this
2370 make INSTALL_ARG=-n install
2372 The contents of the variable INSTALL_ARG are passed to the installation
2373 script. You do not need to be root to run this test. Alternatively, you can run
2374 the installation script directly, but this must be from within the build
2375 directory. For example, from the top-level Exim directory you could use this
2378 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2380 .cindex "installing Exim" "install script options"
2381 There are two other options that can be supplied to the installation script.
2384 &%-no_chown%& bypasses the call to change the owner of the installed binary
2385 to root, and the call to make it a setuid binary.
2387 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2391 INSTALL_ARG can be used to pass these options to the script. For example:
2393 make INSTALL_ARG=-no_symlink install
2395 The installation script can also be given arguments specifying which files are
2396 to be copied. For example, to install just the Exim binary, and nothing else,
2397 without creating the symbolic link, you could use:
2399 make INSTALL_ARG='-no_symlink exim' install
2404 .section "Installing info documentation" "SECTinsinfdoc"
2405 .cindex "installing Exim" "&'info'& documentation"
2406 Not all systems use the GNU &'info'& system for documentation, and for this
2407 reason, the Texinfo source of Exim's documentation is not included in the main
2408 distribution. Instead it is available separately from the FTP site (see section
2411 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2412 source of the documentation is found in the source tree, running &`make
2413 install`& automatically builds the info files and installs them.
2417 .section "Setting up the spool directory" "SECID33"
2418 .cindex "spool directory" "creating"
2419 When it starts up, Exim tries to create its spool directory if it does not
2420 exist. The Exim uid and gid are used for the owner and group of the spool
2421 directory. Sub-directories are automatically created in the spool directory as
2427 .section "Testing" "SECID34"
2428 .cindex "testing" "installation"
2429 Having installed Exim, you can check that the runtime configuration file is
2430 syntactically valid by running the following command, which assumes that the
2431 Exim binary directory is within your PATH environment variable:
2435 If there are any errors in the configuration file, Exim outputs error messages.
2436 Otherwise it outputs the version number and build date,
2437 the DBM library that is being used, and information about which drivers and
2438 other optional code modules are included in the binary.
2439 Some simple routing tests can be done by using the address testing option. For
2442 &`exim -bt`& <&'local username'&>
2444 should verify that it recognizes a local mailbox, and
2446 &`exim -bt`& <&'remote address'&>
2448 a remote one. Then try getting it to deliver mail, both locally and remotely.
2449 This can be done by passing messages directly to Exim, without going through a
2450 user agent. For example:
2452 exim -v postmaster@your.domain.example
2453 From: user@your.domain.example
2454 To: postmaster@your.domain.example
2455 Subject: Testing Exim
2457 This is a test message.
2460 The &%-v%& option causes Exim to output some verification of what it is doing.
2461 In this case you should see copies of three log lines, one for the message's
2462 arrival, one for its delivery, and one containing &"Completed"&.
2464 .cindex "delivery" "problems with"
2465 If you encounter problems, look at Exim's log files (&'mainlog'& and
2466 &'paniclog'&) to see if there is any relevant information there. Another source
2467 of information is running Exim with debugging turned on, by specifying the
2468 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2469 with debugging turned on by a command of the form
2471 &`exim -d -M`& <&'exim-message-id'&>
2473 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2474 produces rather a lot of output, but you can cut this down to specific areas.
2475 For example, if you use &%-d-all+route%& only the debugging information
2476 relevant to routing is included. (See the &%-d%& option in chapter
2477 &<<CHAPcommandline>>& for more details.)
2479 .cindex '&"sticky"& bit'
2480 .cindex "lock files"
2481 One specific problem that has shown up on some sites is the inability to do
2482 local deliveries into a shared mailbox directory, because it does not have the
2483 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2484 writing to a mailbox file, and if it cannot create the lock file, the delivery
2485 is deferred. You can get round this either by setting the &"sticky bit"& on the
2486 directory, or by setting a specific group for local deliveries and allowing
2487 that group to create files in the directory (see the comments above the
2488 &(local_delivery)& transport in the default configuration file). Another
2489 approach is to configure Exim not to use lock files, but just to rely on
2490 &[fcntl()]& locking instead. However, you should do this only if all user
2491 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2492 see chapter &<<CHAPappendfile>>&.
2494 One thing that cannot be tested on a system that is already running an MTA is
2495 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2496 &%-oX%& option can be used to run an Exim daemon that listens on some other
2497 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2498 &'exim_checkaccess'& utility can be used to check out policy controls on
2501 Testing a new version on a system that is already running Exim can most easily
2502 be done by building a binary with a different CONFIGURE_FILE setting. From
2503 within the runtime configuration, all other file and directory names
2504 that Exim uses can be altered, in order to keep it entirely clear of the
2508 .section "Replacing another MTA with Exim" "SECID35"
2509 .cindex "replacing another MTA"
2510 Building and installing Exim for the first time does not of itself put it in
2511 general use. The name by which the system's MTA is called by mail user agents
2512 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2513 operating system), and it is necessary to make this name point to the &'exim'&
2514 binary in order to get the user agents to pass messages to Exim. This is
2515 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2516 or &_/usr/lib/sendmail_&
2517 .cindex "symbolic link" "to &'exim'& binary"
2518 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2519 privilege and executable status from the old MTA. It is then necessary to stop
2520 and restart the mailer daemon, if one is running.
2522 .cindex "FreeBSD, MTA indirection"
2523 .cindex "&_/etc/mail/mailer.conf_&"
2524 Some operating systems have introduced alternative ways of switching MTAs. For
2525 example, if you are running FreeBSD, you need to edit the file
2526 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2527 described. A typical example of the contents of this file for running Exim is
2530 sendmail /usr/exim/bin/exim
2531 send-mail /usr/exim/bin/exim
2532 mailq /usr/exim/bin/exim -bp
2533 newaliases /usr/bin/true
2535 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2536 your Exim installation is &"live"&. Check it by sending a message from your
2537 favourite user agent.
2539 You should consider what to tell your users about the change of MTA. Exim may
2540 have different capabilities to what was previously running, and there are
2541 various operational differences such as the text of messages produced by
2542 command line options and in bounce messages. If you allow your users to make
2543 use of Exim's filtering capabilities, you should make the document entitled
2544 &'Exim's interface to mail filtering'& available to them.
2548 .section "Running the daemon" SECTdaemonLaunch
2549 The most common command line for launching the Exim daemon looks like
2553 This starts a daemon which
2555 listens for incoming smtp connections, launching handler processes for
2558 starts a queue-runner process every five minutes, to inspect queued messages
2559 and run delivery attempts on any that have arrived at their retry time
2561 Should a queue run take longer than the time between queue-runner starts,
2562 they will run in parallel.
2563 Numbers of jobs of the various types are subject to policy controls
2564 defined in the configuration.
2567 .section "Upgrading Exim" "SECID36"
2568 .cindex "upgrading Exim"
2569 If you are already running Exim on your host, building and installing a new
2570 version automatically makes it available to MUAs, or any other programs that
2571 call the MTA directly. However, if you are running an Exim daemon, you do need
2572 .cindex restart "on HUP signal"
2573 .cindex signal "HUP, to restart"
2574 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2575 new binary. You do not need to stop processing mail in order to install a new
2576 version of Exim. The install script does not modify an existing runtime
2582 .section "Stopping the Exim daemon on Solaris" "SECID37"
2583 .cindex "Solaris" "stopping Exim on"
2584 The standard command for stopping the mailer daemon on Solaris is
2586 /etc/init.d/sendmail stop
2588 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2589 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2590 for the text &"sendmail"&; this is not present because the actual program name
2591 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2592 solution is to replace the line that finds the process id with something like
2594 pid=`cat /var/spool/exim/exim-daemon.pid`
2596 to obtain the daemon's pid directly from the file that Exim saves it in.
2598 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2599 still be received from local processes, and if automatic delivery is configured
2600 (the normal case), deliveries will still occur.
2605 . ////////////////////////////////////////////////////////////////////////////
2606 . ////////////////////////////////////////////////////////////////////////////
2608 .chapter "The Exim command line" "CHAPcommandline"
2609 .scindex IIDclo1 "command line" "options"
2610 .scindex IIDclo2 "options" "command line"
2611 Exim's command line takes the standard Unix form of a sequence of options,
2612 each starting with a hyphen character, followed by a number of arguments. The
2613 options are compatible with the main options of Sendmail, and there are also
2614 some additional options, some of which are compatible with Smail 3. Certain
2615 combinations of options do not make sense, and provoke an error if used.
2616 The form of the arguments depends on which options are set.
2619 .section "Setting options by program name" "SECID38"
2621 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2622 were present before any other options.
2623 The &%-bp%& option requests a listing of the contents of the mail queue on the
2625 This feature is for compatibility with some systems that contain a command of
2626 that name in one of the standard libraries, symbolically linked to
2627 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2630 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2631 were present before any other options, for compatibility with Smail. The
2632 &%-bS%& option is used for reading in a number of messages in batched SMTP
2636 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2637 &%-oee%& options were present before any other options, for compatibility with
2638 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2641 .cindex "queue runner"
2642 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2643 were present before any other options, for compatibility with Smail. The &%-q%&
2644 option causes a single queue runner process to be started.
2646 .cindex "&'newaliases'&"
2647 .cindex "alias file" "building"
2648 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2649 If Exim is called under the name &'newaliases'& it behaves as if the option
2650 &%-bi%& were present before any other options, for compatibility with Sendmail.
2651 This option is used for rebuilding Sendmail's alias file. Exim does not have
2652 the concept of a single alias file, but can be configured to run a given
2653 command if called with the &%-bi%& option.
2656 .section "Trusted and admin users" "SECTtrustedadmin"
2657 Some Exim options are available only to &'trusted users'& and others are
2658 available only to &'admin users'&. In the description below, the phrases &"Exim
2659 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2660 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2661 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2664 .cindex "trusted users" "definition of"
2665 .cindex "user" "trusted definition of"
2666 The trusted users are root, the Exim user, any user listed in the
2667 &%trusted_users%& configuration option, and any user whose current group or any
2668 supplementary group is one of those listed in the &%trusted_groups%&
2669 configuration option. Note that the Exim group is not automatically trusted.
2671 .cindex '&"From"& line'
2672 .cindex "envelope from"
2673 .cindex "envelope sender"
2674 Trusted users are always permitted to use the &%-f%& option or a leading
2675 &"From&~"& line to specify the envelope sender of a message that is passed to
2676 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2677 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2678 users to set envelope senders.
2682 For a trusted user, there is never any check on the contents of the &'From:'&
2683 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2684 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2686 Trusted users may also specify a host name, host address, interface address,
2687 protocol name, ident value, and authentication data when submitting a message
2688 locally. Thus, they are able to insert messages into Exim's queue locally that
2689 have the characteristics of messages received from a remote host. Untrusted
2690 users may in some circumstances use &%-f%&, but can never set the other values
2691 that are available to trusted users.
2693 .cindex "user" "admin definition of"
2694 .cindex "admin user" "definition of"
2695 The admin users are root, the Exim user, and any user that is a member of the
2696 Exim group or of any group listed in the &%admin_groups%& configuration option.
2697 The current group does not have to be one of these groups.
2699 Admin users are permitted to list the queue, and to carry out certain
2700 operations on messages, for example, to force delivery failures. It is also
2701 necessary to be an admin user in order to see the full information provided by
2702 the Exim monitor, and full debugging output.
2704 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2705 Exim to attempt delivery of messages on its queue is restricted to admin users.
2706 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2707 option false (that is, specifying &%no_prod_requires_admin%&).
2709 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2710 is restricted to admin users unless &%queue_list_requires_admin%& is set
2715 &*Warning*&: If you configure your system so that admin users are able to
2716 edit Exim's configuration file, you are giving those users an easy way of
2717 getting root. There is further discussion of this issue at the start of chapter
2723 .section "Command line options" "SECID39"
2724 Exim's command line options are described in alphabetical order below. If none
2725 of the options that specifies a specific action (such as starting the daemon or
2726 a queue runner, or testing an address, or receiving a message in a specific
2727 format, or listing the queue) are present, and there is at least one argument
2728 on the command line, &%-bm%& (accept a local message on the standard input,
2729 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2730 outputs a brief message about itself and exits.
2732 . ////////////////////////////////////////////////////////////////////////////
2733 . Insert a stylized XML comment here, to identify the start of the command line
2734 . options. This is for the benefit of the Perl script that automatically
2735 . creates a man page for the options.
2736 . ////////////////////////////////////////////////////////////////////////////
2739 <!-- === Start of command line options === -->
2745 .cindex "options" "command line; terminating"
2746 This is a pseudo-option whose only purpose is to terminate the options and
2747 therefore to cause subsequent command line items to be treated as arguments
2748 rather than options, even if they begin with hyphens.
2751 This option causes Exim to output a few sentences stating what it is.
2752 The same output is generated if the Exim binary is called with no options and
2756 This option is an alias for &%-bV%& and causes version information to be
2763 These options are used by Sendmail for selecting configuration files and are
2766 .cmdopt -B <&'type'&>
2768 .cindex "8-bit characters"
2769 .cindex "Sendmail compatibility" "8-bit characters"
2770 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2771 clean; it ignores this option.
2775 .cindex "SMTP" "listener"
2776 .cindex "queue runner"
2777 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2778 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2779 that the daemon should also initiate periodic queue runs.
2781 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2782 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2783 disconnect from the controlling terminal. When running this way, it can be
2784 stopped by pressing ctrl-C.
2786 By default, Exim listens for incoming connections to the standard SMTP port on
2787 all the host's running interfaces. However, it is possible to listen on other
2788 ports, on multiple ports, and only on specific interfaces. Chapter
2789 &<<CHAPinterfaces>>& contains a description of the options that control this.
2791 When a listening daemon
2792 .cindex "daemon" "process id (pid)"
2793 .cindex "pid (process id)" "of daemon"
2794 is started without the use of &%-oX%& (that is, without overriding the normal
2795 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2796 in Exim's spool directory. This location can be overridden by setting
2797 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2800 When &%-oX%& is used on the command line to start a listening daemon, the
2801 process id is not written to the normal pid file path. However, &%-oP%& can be
2802 used to specify a path on the command line if a pid file is required.
2806 .cindex restart "on HUP signal"
2807 .cindex signal "HUP, to restart"
2808 .cindex "daemon" "restarting"
2809 .cindex signal "to reload configuration"
2810 .cindex daemon "reload configuration"
2811 .cindex reload configuration
2812 can be used to cause the daemon to re-execute itself. This should be done
2813 whenever Exim's configuration file, or any file that is incorporated into it by
2814 means of the &%.include%& facility, is changed, and also whenever a new version
2815 of Exim is installed. It is not necessary to do this when other files that are
2816 referenced from the configuration (for example, alias files) are changed,
2817 because these are reread each time they are used.
2820 Either a SIGTERM or a SIGINT signal should be used to cause the daemon
2821 to cleanly shut down.
2822 Subprocesses handling recceiving or delivering messages,
2823 or for scanning the queue,
2824 will not be affected by the termination of the daemon process.
2828 This option has the same effect as &%-bd%& except that it never disconnects
2829 from the controlling terminal, even when no debugging is specified.
2832 .cindex "testing" "string expansion"
2833 .cindex "expansion" "testing"
2834 Run Exim in expansion testing mode. Exim discards its root privilege, to
2835 prevent ordinary users from using this mode to read otherwise inaccessible
2836 files. If no arguments are given, Exim runs interactively, prompting for lines
2837 of data. Otherwise, it processes each argument in turn.
2839 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2840 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2841 used without command line arguments. If successful, it uses the &[readline()]&
2842 function, which provides extensive line-editing facilities, for reading the
2843 test data. A line history is supported.
2845 Long expansion expressions can be split over several lines by using backslash
2846 continuations. As in Exim's runtime configuration, white space at the start of
2847 continuation lines is ignored. Each argument or data line is passed through the
2848 string expansion mechanism, and the result is output. Variable values from the
2849 configuration file (for example, &$qualify_domain$&) are available, but no
2850 message-specific values (such as &$message_exim_id$&) are set, because no message
2851 is being processed (but see &%-bem%& and &%-Mset%&).
2853 &*Note*&: If you use this mechanism to test lookups, and you change the data
2854 files or databases you are using, you must exit and restart Exim before trying
2855 the same lookup again. Otherwise, because each Exim process caches the results
2856 of lookups, you will just get the same result as before.
2858 Macro processing is done on lines before string-expansion: new macros can be
2859 defined and macros will be expanded.
2860 Because macros in the config file are often used for secrets, those are only
2861 available to admin users.
2864 The word &"set"& at the start of a line, followed by a single space,
2865 is recognised specially as defining a value for a variable.
2866 The syntax is otherwise the same as the ACL modifier &"set ="&.
2869 .cmdopt -bem <&'filename'&>
2870 .cindex "testing" "string expansion"
2871 .cindex "expansion" "testing"
2872 This option operates like &%-be%& except that it must be followed by the name
2873 of a file. For example:
2875 exim -bem /tmp/testmessage
2877 The file is read as a message (as if receiving a locally-submitted non-SMTP
2878 message) before any of the test expansions are done. Thus, message-specific
2879 variables such as &$message_size$& and &$header_from:$& are available. However,
2880 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2881 recipients are read from the headers in the normal way, and are shown in the
2882 &$recipients$& variable. Note that recipients cannot be given on the command
2883 line, because further arguments are taken as strings to expand (just like
2886 .cmdopt -bF <&'filename'&>
2887 .cindex "system filter" "testing"
2888 .cindex "testing" "system filter"
2889 This option is the same as &%-bf%& except that it assumes that the filter being
2890 tested is a system filter. The additional commands that are available only in
2891 system filters are recognized.
2893 .cmdopt -bf <&'filename'&>
2894 .cindex "filter" "testing"
2895 .cindex "testing" "filter file"
2896 .cindex "forward file" "testing"
2897 .cindex "testing" "forward file"
2898 .cindex "Sieve filter" "testing"
2899 This option runs Exim in user filter testing mode; the file is the filter file
2900 to be tested, and a test message must be supplied on the standard input. If
2901 there are no message-dependent tests in the filter, an empty file can be
2904 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2905 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2906 filter and a user filter in the same run. For example:
2908 exim -bF /system/filter -bf /user/filter </test/message
2910 This is helpful when the system filter adds header lines or sets filter
2911 variables that are used by the user filter.
2913 If the test filter file does not begin with one of the special lines
2918 it is taken to be a normal &_.forward_& file, and is tested for validity under
2919 that interpretation. See sections &<<SECTitenonfilred>>& to
2920 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2923 The result of an Exim command that uses &%-bf%&, provided no errors are
2924 detected, is a list of the actions that Exim would try to take if presented
2925 with the message for real. More details of filter testing are given in the
2926 separate document entitled &'Exim's interfaces to mail filtering'&.
2928 When testing a filter file,
2929 .cindex "&""From""& line"
2930 .cindex "envelope from"
2931 .cindex "envelope sender"
2932 .oindex "&%-f%&" "for filter testing"
2933 the envelope sender can be set by the &%-f%& option,
2934 or by a &"From&~"& line at the start of the test message. Various parameters
2935 that would normally be taken from the envelope recipient address of the message
2936 can be set by means of additional command line options (see the next four
2939 .cmdopt -bfd <&'domain'&>
2940 .vindex "&$qualify_domain$&"
2941 This sets the domain of the recipient address when a filter file is being
2942 tested by means of the &%-bf%& option. The default is the value of
2945 .cmdopt -bfl <&'local&~part'&>
2946 This sets the local part of the recipient address when a filter file is being
2947 tested by means of the &%-bf%& option. The default is the username of the
2948 process that calls Exim. A local part should be specified with any prefix or
2949 suffix stripped, because that is how it appears to the filter when a message is
2950 actually being delivered.
2952 .cmdopt -bfp <&'prefix'&>
2953 .cindex affix "filter testing"
2954 This sets the prefix of the local part of the recipient address when a filter
2955 file is being tested by means of the &%-bf%& option. The default is an empty
2958 .cmdopt -bfs <&'suffix'&>
2959 .cindex affix "filter testing"
2960 This sets the suffix of the local part of the recipient address when a filter
2961 file is being tested by means of the &%-bf%& option. The default is an empty
2964 .cmdopt -bh <&'IP&~address'&>
2965 .cindex "testing" "incoming SMTP"
2966 .cindex "SMTP" "testing incoming"
2967 .cindex "testing" "relay control"
2968 .cindex "relaying" "testing configuration"
2969 .cindex "policy control" "testing"
2970 .cindex "debugging" "&%-bh%& option"
2971 This option runs a fake SMTP session as if from the given IP address, using the
2972 standard input and output. The IP address may include a port number at the end,
2973 after a full stop. For example:
2975 exim -bh 10.9.8.7.1234
2976 exim -bh fe80::a00:20ff:fe86:a061.5678
2978 When an IPv6 address is given, it is converted into canonical form. In the case
2979 of the second example above, the value of &$sender_host_address$& after
2980 conversion to the canonical form is
2981 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2983 Comments as to what is going on are written to the standard error file. These
2984 include lines beginning with &"LOG"& for anything that would have been logged.
2985 This facility is provided for testing configuration options for incoming
2986 messages, to make sure they implement the required policy. For example, you can
2987 test your relay controls using &%-bh%&.
2991 You can test features of the configuration that rely on ident (RFC 1413)
2992 information by using the &%-oMt%& option. However, Exim cannot actually perform
2993 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2996 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2997 are also skipped when testing using &%-bh%&. If you want these callouts to
2998 occur, use &%-bhc%& instead.
3000 Messages supplied during the testing session are discarded, and nothing is
3001 written to any of the real log files. There may be pauses when DNS (and other)
3002 lookups are taking place, and of course these may time out. The &%-oMi%& option
3003 can be used to specify a specific IP interface and port if this is important,
3004 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
3005 session were authenticated.
3007 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
3008 output just states whether a given recipient address from a given host is
3009 acceptable or not. See section &<<SECTcheckaccess>>&.
3011 Features such as authentication and encryption, where the client input is not
3012 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
3013 specialized SMTP test program such as
3014 &url(https://www.jetmore.org/john/code/swaks/,swaks).
3016 .cmdopt -bhc <&'IP&~address'&>
3017 This option operates in the same way as &%-bh%&, except that address
3018 verification callouts are performed if required. This includes consulting and
3019 updating the callout cache database.
3022 .cindex "alias file" "building"
3023 .cindex "building alias file"
3024 .cindex "Sendmail compatibility" "&%-bi%& option"
3025 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
3026 Exim does not have the concept of a single alias file, and so it cannot mimic
3027 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
3028 tend to appear in various scripts such as NIS make files, so the option must be
3031 If &%-bi%& is encountered, the command specified by the &%bi_command%&
3032 configuration option is run, under the uid and gid of the caller of Exim. If
3033 the &%-oA%& option is used, its value is passed to the command as an argument.
3034 The command set by &%bi_command%& may not contain arguments. The command can
3035 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
3036 if this is required. If the &%bi_command%& option is not set, calling Exim with
3039 . // Keep :help first, then the rest in alphabetical order
3041 .cindex "querying exim information"
3042 We shall provide various options starting &`-bI:`& for querying Exim for
3043 information. The output of many of these will be intended for machine
3044 consumption. This one is not. The &%-bI:help%& option asks Exim for a
3045 synopsis of supported options beginning &`-bI:`&. Use of any of these
3046 options shall cause Exim to exit after producing the requested output.
3049 .cindex "DSCP" "values"
3050 This option causes Exim to emit an alphabetically sorted list of all
3051 recognised DSCP names.
3054 .cindex "Sieve filter" "capabilities"
3055 This option causes Exim to emit an alphabetically sorted list of all supported
3056 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3057 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3058 &`SIEVE`& capability response line. As the precise list may depend upon
3059 compile-time build options, which this option will adapt to, this is the only
3060 way to guarantee a correct response.
3063 .cindex "local message reception"
3064 This option runs an Exim receiving process that accepts an incoming,
3065 locally-generated message on the standard input. The recipients are given as the
3066 command arguments (except when &%-t%& is also present &-- see below). Each
3067 argument can be a comma-separated list of RFC 2822 addresses. This is the
3068 default option for selecting the overall action of an Exim call; it is assumed
3069 if no other conflicting option is present.
3071 If any addresses in the message are unqualified (have no domain), they are
3072 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3073 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3074 suppressing this for special cases.
3076 Policy checks on the contents of local messages can be enforced by means of
3077 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3079 .cindex "return code" "for &%-bm%&"
3080 The return code is zero if the message is successfully accepted. Otherwise, the
3081 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3084 .cindex "message" "format"
3085 .cindex "format" "message"
3086 .cindex "&""From""& line"
3087 .cindex "UUCP" "&""From""& line"
3088 .cindex "Sendmail compatibility" "&""From""& line"
3089 of the message must be as defined in RFC 2822, except that, for
3090 compatibility with Sendmail and Smail, a line in one of the forms
3092 From sender Fri Jan 5 12:55 GMT 1997
3093 From sender Fri, 5 Jan 97 12:55:01
3095 (with the weekday optional, and possibly with additional text after the date)
3096 is permitted to appear at the start of the message. There appears to be no
3097 authoritative specification of the format of this line. Exim recognizes it by
3098 matching against the regular expression defined by the &%uucp_from_pattern%&
3099 option, which can be changed if necessary.
3101 .oindex "&%-f%&" "overriding &""From""& line"
3102 The specified sender is treated as if it were given as the argument to the
3103 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3104 preference to the address taken from the message. The caller of Exim must be a
3105 trusted user for the sender of a message to be set in this way.
3107 .cmdopt -bmalware <&'filename'&>
3108 .cindex "testing", "malware"
3109 .cindex "malware scan test"
3110 This debugging option causes Exim to scan the given file or directory
3111 (depending on the used scanner interface),
3112 using the malware scanning framework. The option of &%av_scanner%& influences
3113 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3114 the expansion should have defaults which apply to this invocation. ACLs are
3115 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3116 will never be populated and &%-bmalware%& will fail.
3118 Exim will have changed working directory before resolving the filename, so
3119 using fully qualified pathnames is advisable. Exim will be running as the Exim
3120 user when it tries to open the file, rather than as the invoking user.
3121 This option requires admin privileges.
3123 The &%-bmalware%& option will not be extended to be more generally useful,
3124 there are better tools for file-scanning. This option exists to help
3125 administrators verify their Exim and AV scanner configuration.
3128 .cindex "address qualification, suppressing"
3129 By default, Exim automatically qualifies unqualified addresses (those
3130 without domains) that appear in messages that are submitted locally (that
3131 is, not over TCP/IP). This qualification applies both to addresses in
3132 envelopes, and addresses in header lines. Sender addresses are qualified using
3133 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3134 defaults to the value of &%qualify_domain%&).
3136 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3137 being used to re-submit messages that originally came from remote hosts after
3138 content scanning, you probably do not want to qualify unqualified addresses in
3139 header lines. (Such lines will be present only if you have not enabled a header
3140 syntax check in the appropriate ACL.)
3142 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3143 messages that originate on the local host. When this is used, unqualified
3144 addresses in the envelope provoke errors (causing message rejection) and
3145 unqualified addresses in header lines are left alone.
3149 .cindex "configuration options" "extracting"
3150 .cindex "options" "configuration &-- extracting"
3151 If this option is given with no arguments, it causes the values of all Exim's
3152 main configuration options to be written to the standard output. The values
3153 of one or more specific options can be requested by giving their names as
3154 arguments, for example:
3156 exim -bP qualify_domain hold_domains
3158 .cindex "hiding configuration option values"
3159 .cindex "configuration options" "hiding value of"
3160 .cindex "options" "hiding value of"
3161 However, any option setting that is preceded by the word &"hide"& in the
3162 configuration file is not shown in full, except to an admin user. For other
3163 users, the output is as in this example:
3165 mysql_servers = <value not displayable>
3167 If &%config%& is given as an argument, the config is
3168 output, as it was parsed, any include file resolved, any comment removed.
3170 If &%config_file%& is given as an argument, the name of the runtime
3171 configuration file is output. (&%configure_file%& works too, for
3172 backward compatibility.)
3173 If a list of configuration files was supplied, the value that is output here
3174 is the name of the file that was actually used.
3176 .cindex "options" "hiding name of"
3177 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3178 name will not be output.
3180 .cindex "daemon" "process id (pid)"
3181 .cindex "pid (process id)" "of daemon"
3182 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3183 directories where log files and daemon pid files are written are output,
3184 respectively. If these values are unset, log files are written in a
3185 sub-directory of the spool directory called &%log%&, and the pid file is
3186 written directly into the spool directory.
3188 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3190 exim -bP +local_domains
3192 it searches for a matching named list of any type (domain, host, address, or
3193 local part) and outputs what it finds.
3195 .cindex "options" "router &-- extracting"
3196 .cindex "options" "transport &-- extracting"
3197 .cindex "options" "authenticator &-- extracting"
3198 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3199 followed by the name of an appropriate driver instance, the option settings for
3200 that driver are output. For example:
3202 exim -bP transport local_delivery
3204 The generic driver options are output first, followed by the driver's private
3205 options. A list of the names of drivers of a particular type can be obtained by
3206 using one of the words &%router_list%&, &%transport_list%&, or
3207 &%authenticator_list%&, and a complete list of all drivers with their option
3208 settings can be obtained by using &%routers%&, &%transports%&, or
3211 .cindex "environment"
3212 If &%environment%& is given as an argument, the set of environment
3213 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3216 .cindex "options" "macro &-- extracting"
3217 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3218 are available, similarly to the drivers. Because macros are sometimes used
3219 for storing passwords, this option is restricted.
3220 The output format is one item per line.
3221 For the "-bP macro <name>" form, if no such macro is found
3222 the exit status will be nonzero.
3225 .cindex "queue" "listing messages in"
3226 .cindex "listing" "messages in the queue"
3227 This option requests a listing of the contents of the mail queue on the
3228 standard output. If the &%-bp%& option is followed by a list of message ids,
3229 just those messages are listed. By default, this option can be used only by an
3230 admin user. However, the &%queue_list_requires_admin%& option can be set false
3231 to allow any user to see the queue.
3233 Each message in the queue is displayed as in the following example:
3235 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3236 red.king@looking-glass.fict.example
3239 .cindex "message" "size in queue listing"
3240 .cindex "size" "of message"
3241 The first line contains the length of time the message has been in the queue
3242 (in this case 25 minutes), the size of the message (2.9K), the unique local
3243 identifier for the message, and the message sender, as contained in the
3244 envelope. For bounce messages, the sender address is empty, and appears as
3245 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3246 the default sender address, the user's login name is shown in parentheses
3247 before the sender address.
3249 .cindex "frozen messages" "in queue listing"
3250 If the message is frozen (attempts to deliver it are suspended) then the text
3251 &"*** frozen ***"& is displayed at the end of this line.
3253 The recipients of the message (taken from the envelope, not the headers) are
3254 displayed on subsequent lines. Those addresses to which the message has already
3255 been delivered are marked with the letter D. If an original address gets
3256 expanded into several addresses via an alias or forward file, the original is
3257 displayed with a D only when deliveries for all of its child addresses are
3262 This option operates like &%-bp%&, but in addition it shows delivered addresses
3263 that were generated from the original top level address(es) in each message by
3264 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3269 .cindex "queue" "count of messages on"
3270 This option counts the number of messages in the queue, and writes the total
3271 to the standard output. It is restricted to admin users, unless
3272 &%queue_list_requires_admin%& is set false.
3276 This option operates like &%-bp%&, but the output is not sorted into
3277 chronological order of message arrival. This can speed it up when there are
3278 lots of messages in the queue, and is particularly useful if the output is
3279 going to be post-processed in a way that doesn't need the sorting.
3282 This option is a combination of &%-bpr%& and &%-bpa%&.
3285 This option is a combination of &%-bpr%& and &%-bpu%&.
3289 This option operates like &%-bp%& but shows only undelivered top-level
3290 addresses for each message displayed. Addresses generated by aliasing or
3291 forwarding are not shown, unless the message was deferred after processing by a
3292 router with the &%one_time%& option set.
3296 .cindex "testing" "retry configuration"
3297 .cindex "retry" "configuration testing"
3298 This option is for testing retry rules, and it must be followed by up to three
3299 arguments. It causes Exim to look for a retry rule that matches the values
3300 and to write it to the standard output. For example:
3302 exim -brt bach.comp.mus.example
3303 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3305 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3306 argument, which is required, can be a complete address in the form
3307 &'local_part@domain'&, or it can be just a domain name. If the second argument
3308 contains a dot, it is interpreted as an optional second domain name; if no
3309 retry rule is found for the first argument, the second is tried. This ties in
3310 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3311 rule is found that matches the host, one that matches the mail domain is
3312 sought. Finally, an argument that is the name of a specific delivery error, as
3313 used in setting up retry rules, can be given. For example:
3315 exim -brt haydn.comp.mus.example quota_3d
3316 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3320 .cindex "testing" "rewriting"
3321 .cindex "rewriting" "testing"
3322 This option is for testing address rewriting rules, and it must be followed by
3323 a single argument, consisting of either a local part without a domain, or a
3324 complete address with a fully qualified domain. Exim outputs how this address
3325 would be rewritten for each possible place it might appear. See chapter
3326 &<<CHAPrewrite>>& for further details.
3329 .cindex "SMTP" "batched incoming"
3330 .cindex "batched SMTP input"
3331 This option is used for batched SMTP input, which is an alternative interface
3332 for non-interactive local message submission. A number of messages can be
3333 submitted in a single run. However, despite its name, this is not really SMTP
3334 input. Exim reads each message's envelope from SMTP commands on the standard
3335 input, but generates no responses. If the caller is trusted, or
3336 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3337 believed; otherwise the sender is always the caller of Exim.
3339 The message itself is read from the standard input, in SMTP format (leading
3340 dots doubled), terminated by a line containing just a single dot. An error is
3341 provoked if the terminating dot is missing. A further message may then follow.
3343 As for other local message submissions, the contents of incoming batch SMTP
3344 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3345 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3346 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3348 Some other SMTP commands are recognized in the input. HELO and EHLO act
3349 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3350 QUIT quits, ignoring the rest of the standard input.
3352 .cindex "return code" "for &%-bS%&"
3353 If any error is encountered, reports are written to the standard output and
3354 error streams, and Exim gives up immediately. The return code is 0 if no error
3355 was detected; it is 1 if one or more messages were accepted before the error
3356 was detected; otherwise it is 2.
3358 More details of input using batched SMTP are given in section
3359 &<<SECTincomingbatchedSMTP>>&.
3362 .cindex "SMTP" "local input"
3363 .cindex "local SMTP input"
3364 This option causes Exim to accept one or more messages by reading SMTP commands
3365 on the standard input, and producing SMTP replies on the standard output. SMTP
3366 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3367 Some user agents use this interface as a way of passing locally-generated
3368 messages to the MTA.
3371 .cindex "sender" "source of"
3372 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3373 set, the senders of messages are taken from the SMTP MAIL commands.
3374 Otherwise the content of these commands is ignored and the sender is set up as
3375 the calling user. Unqualified addresses are automatically qualified using
3376 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3377 &%-bnq%& option is used.
3381 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3382 using a listening daemon. Exim can distinguish the two cases by checking
3383 whether the standard input is a TCP/IP socket. When Exim is called from
3384 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3385 above concerning senders and qualification do not apply. In this situation,
3386 Exim behaves in exactly the same way as it does when receiving a message via
3387 the listening daemon.
3390 .cindex "testing" "addresses"
3391 .cindex "address" "testing"
3392 This option runs Exim in address testing mode, in which each argument is taken
3393 as a recipient address to be tested for deliverability. The results are
3394 written to the standard output. If a test fails, and the caller is not an admin
3395 user, no details of the failure are output, because these might contain
3396 sensitive information such as usernames and passwords for database lookups.
3398 If no arguments are given, Exim runs in an interactive manner, prompting with a
3399 right angle bracket for addresses to be tested.
3401 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3402 &[readline()]& function, because it is running as &'root'& and there are
3405 Each address is handled as if it were the recipient address of a message
3406 (compare the &%-bv%& option). It is passed to the routers and the result is
3407 written to the standard output. However, any router that has
3408 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3409 genuine routing tests if your first router passes everything to a scanner
3412 .cindex "return code" "for &%-bt%&"
3413 The return code is 2 if any address failed outright; it is 1 if no address
3414 failed outright but at least one could not be resolved for some reason. Return
3415 code 0 is given only when all addresses succeed.
3417 .cindex "duplicate addresses"
3418 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3419 addresses after routing is complete, so that only one delivery takes place.
3420 This does not happen when testing with &%-bt%&; the full results of routing are
3423 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3424 routers in the configuration makes any tests on the sender address of a
3426 .oindex "&%-f%&" "for address testing"
3427 you can use the &%-f%& option to set an appropriate sender when running
3428 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3429 default qualifying domain. However, if you have set up (for example) routers
3430 whose behaviour depends on the contents of an incoming message, you cannot test
3431 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3435 .cindex "version number of Exim"
3436 This option causes Exim to write the current version number, compilation
3437 number, and compilation date of the &'exim'& binary to the standard output.
3438 It also lists the DBM library that is being used, the optional modules (such as
3439 specific lookup types), the drivers that are included in the binary, and the
3440 name of the runtime configuration file that is in use.
3442 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3443 configuration file. However, this is a static check only. It cannot check
3444 values that are to be expanded. For example, although a misspelt ACL verb is
3445 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3446 alone to discover (for example) all the typos in the configuration; some
3447 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3448 dynamic testing facilities.
3451 .cindex "verifying address" "using &%-bv%&"
3452 .cindex "address" "verification"
3453 This option runs Exim in address verification mode, in which each argument is
3454 taken as a recipient address to be verified by the routers. (This does
3455 not involve any verification callouts). During normal operation, verification
3456 happens mostly as a consequence processing a &%verify%& condition in an ACL
3457 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3458 including callouts, see the &%-bh%& and &%-bhc%& options.
3460 If verification fails, and the caller is not an admin user, no details of the
3461 failure are output, because these might contain sensitive information such as
3462 usernames and passwords for database lookups.
3464 If no arguments are given, Exim runs in an interactive manner, prompting with a
3465 right angle bracket for addresses to be verified.
3467 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3468 &[readline()]& function, because it is running as &'exim'& and there are
3471 Verification differs from address testing (the &%-bt%& option) in that routers
3472 that have &%no_verify%& set are skipped, and if the address is accepted by a
3473 router that has &%fail_verify%& set, verification fails. The address is
3474 verified as a recipient if &%-bv%& is used; to test verification for a sender
3475 address, &%-bvs%& should be used.
3477 If the &%-v%& option is not set, the output consists of a single line for each
3478 address, stating whether it was verified or not, and giving a reason in the
3479 latter case. Without &%-v%&, generating more than one address by redirection
3480 causes verification to end successfully, without considering the generated
3481 addresses. However, if just one address is generated, processing continues,
3482 and the generated address must verify successfully for the overall verification
3485 When &%-v%& is set, more details are given of how the address has been handled,
3486 and in the case of address redirection, all the generated addresses are also
3487 considered. Verification may succeed for some and fail for others.
3490 .cindex "return code" "for &%-bv%&"
3491 return code is 2 if any address failed outright; it is 1 if no address
3492 failed outright but at least one could not be resolved for some reason. Return
3493 code 0 is given only when all addresses succeed.
3495 If any of the routers in the configuration makes any tests on the sender
3496 address of a message, you should use the &%-f%& option to set an appropriate
3497 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3498 calling user at the default qualifying domain.
3501 This option acts like &%-bv%&, but verifies the address as a sender rather
3502 than a recipient address. This affects any rewriting and qualification that
3508 .cindex "inetd" "wait mode"
3509 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3510 similarly to the &%-bd%& option. All port specifications on the command-line
3511 and in the configuration file are ignored. Queue-running may not be specified.
3513 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3514 listening for connections. This permits the system to start up and have
3515 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3516 each port only when the first connection is received.
3518 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3519 which the daemon will exit, which should cause inetd to listen once more.
3521 .cmdopt -C <&'filelist'&>
3522 .cindex "configuration file" "alternate"
3523 .cindex "CONFIGURE_FILE"
3524 .cindex "alternate configuration file"
3525 This option causes Exim to find the runtime configuration file from the given
3526 list instead of from the list specified by the CONFIGURE_FILE
3527 compile-time setting. Usually, the list will consist of just a single filename,
3528 but it can be a colon-separated list of names. In this case, the first
3529 file that exists is used. Failure to open an existing file stops Exim from
3530 proceeding any further along the list, and an error is generated.
3532 When this option is used by a caller other than root, and the list is different
3533 from the compiled-in list, Exim gives up its root privilege immediately, and
3534 runs with the real and effective uid and gid set to those of the caller.
3535 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3536 file contains a list of full pathnames, one per line, for configuration files
3537 which are trusted. Root privilege is retained for any configuration file so
3538 listed, as long as the caller is the Exim user (or the user specified in the
3539 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3540 not writeable by inappropriate users or groups.
3542 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3543 configuration using &%-C%& right through message reception and delivery,
3544 even if the caller is root. The reception works, but by that time, Exim is
3545 running as the Exim user, so when it re-executes to regain privilege for the
3546 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3547 test reception and delivery using two separate commands (one to put a message
3548 in the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3550 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3551 prefix string with which any file named in a &%-C%& command line option
3552 must start. In addition, the filename must not contain the sequence &`/../`&.
3553 However, if the value of the &%-C%& option is identical to the value of
3554 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3555 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3556 unset, any filename can be used with &%-C%&.
3558 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3559 to a directory to which only root has access. This prevents someone who has
3560 broken into the Exim account from running a privileged Exim with an arbitrary
3563 The &%-C%& facility is useful for ensuring that configuration files are
3564 syntactically correct, but cannot be used for test deliveries, unless the
3565 caller is privileged, or unless it is an exotic configuration that does not
3566 require privilege. No check is made on the owner or group of the files
3567 specified by this option.
3570 .vitem &%-D%&<&'macro'&>=<&'value'&>
3572 .cindex "macro" "setting on command line"
3573 This option can be used to override macro definitions in the configuration file
3574 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3575 unprivileged caller, it causes Exim to give up its root privilege.
3576 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3577 completely disabled, and its use causes an immediate error exit.
3579 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3580 colon-separated list of macros which are considered safe and, if &%-D%& only
3581 supplies macros from this list, and the values are acceptable, then Exim will
3582 not give up root privilege if the caller is root, the Exim run-time user, or
3583 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3584 to be removed in the future. Acceptable values for the macros satisfy the
3585 regexp: &`^[A-Za-z0-9_/.-]*$`&
3587 The entire option (including equals sign if present) must all be within one
3588 command line item. &%-D%& can be used to set the value of a macro to the empty
3589 string, in which case the equals sign is optional. These two commands are
3595 To include spaces in a macro definition item, quotes must be used. If you use
3596 quotes, spaces are permitted around the macro name and the equals sign. For
3599 exim '-D ABC = something' ...
3601 &%-D%& may be repeated up to 10 times on a command line.
3602 Only macro names up to 22 letters long can be set.
3605 .vitem &%-d%&<&'debug&~options'&>
3607 .cindex "debugging" "list of selectors"
3608 .cindex "debugging" "&%-d%& option"
3609 This option causes debugging information to be written to the standard
3610 error stream. It is restricted to admin users because debugging output may show
3611 database queries that contain password information. Also, the details of users'
3612 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3613 writes an error message to the standard error stream and exits with a non-zero
3616 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3617 standard debugging data is output. This can be reduced, or increased to include
3618 some more rarely needed information, by directly following &%-d%& with a string
3619 made up of names preceded by plus or minus characters. These add or remove sets
3620 of debugging data, respectively. For example, &%-d+filter%& adds filter
3621 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3622 no spaces are allowed in the debug setting. The available debugging categories
3624 .itable none 0 0 2 20* left 80* left
3625 .irow acl "ACL interpretation"
3626 .irow auth "authenticators"
3627 .irow deliver "general delivery logic"
3628 .irow dns "DNS lookups (see also resolver)"
3629 .irow dnsbl "DNS black list (aka RBL) code"
3630 .irow exec "arguments for &[execv()]& calls"
3631 .irow expand "detailed debugging for string expansions"
3632 .irow filter "filter handling"
3633 .irow hints_lookup "hints data lookups"
3634 .irow host_lookup "all types of name-to-IP address handling"
3635 .irow ident "ident lookup"
3636 .irow interface "lists of local interfaces"
3637 .irow lists "matching things in lists"
3638 .irow load "system load checks"
3639 .irow local_scan "can be used by &[local_scan()]& (see chapter &&&
3640 &<<CHAPlocalscan>>&)"
3641 .irow lookup "general lookup code and all lookups"
3642 .irow memory "memory handling"
3643 .irow noutf8 "modifier: avoid UTF-8 line-drawing"
3644 .irow pid "modifier: add pid to debug output lines"
3645 .irow process_info "setting info for the process log"
3646 .irow queue_run "queue runs"
3647 .irow receive "general message reception logic"
3648 .irow resolver "turn on the DNS resolver's debugging output"
3649 .irow retry "retry handling"
3650 .irow rewrite "address rewriting""
3651 .irow route "address routing"
3652 .irow timestamp "modifier: add timestamp to debug output lines"
3653 .irow tls "TLS logic"
3654 .irow transport "transports"
3655 .irow uid "changes of uid/gid and looking up uid/gid"
3656 .irow verify "address verification logic"
3657 .irow all "almost all of the above (see below), and also &%-v%&"
3659 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3660 for &`-all`&. The reason for this is that &`+all`& is something that people
3661 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3662 is included, an awful lot of output that is very rarely of interest is
3663 generated, so it now has to be explicitly requested. However, &`-all`& does
3664 turn everything off.
3666 .cindex "resolver, debugging output"
3667 .cindex "DNS resolver, debugging output"
3668 The &`resolver`& option produces output only if the DNS resolver was compiled
3669 with DEBUG enabled. This is not the case in some operating systems. Also,
3670 unfortunately, debugging output from the DNS resolver is written to stdout
3673 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3674 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3675 However, the &`pid`& selector is forced when debugging is turned on for a
3676 daemon, which then passes it on to any re-executed Exims. Exim also
3677 automatically adds the pid to debug lines when several remote deliveries are
3680 The &`timestamp`& selector causes the current time to be inserted at the start
3681 of all debug output lines. This can be useful when trying to track down delays
3684 .cindex debugging "UTF-8 in"
3685 .cindex UTF-8 "in debug output"
3686 The &`noutf8`& selector disables the use of
3687 UTF-8 line-drawing characters to group related information.
3688 When disabled. ascii-art is used instead.
3689 Using the &`+all`& option does not set this modifier,
3691 If the &%debug_print%& option is set in any driver, it produces output whenever
3692 any debugging is selected, or if &%-v%& is used.
3694 .vitem &%-dd%&<&'debug&~options'&>
3696 This option behaves exactly like &%-d%& except when used on a command that
3697 starts a daemon process. In that case, debugging is turned off for the
3698 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3699 behaviour of the daemon without creating as much output as full debugging does.
3702 This is an obsolete option that is now a no-op. It used to affect the way Exim
3703 handled CR and LF characters in incoming messages. What happens now is
3704 described in section &<<SECTlineendings>>&.
3707 .cindex "bounce message" "generating"
3708 This option specifies that an incoming message is a locally-generated delivery
3709 failure report. It is used internally by Exim when handling delivery failures
3710 and is not intended for external use. Its only effect is to stop Exim
3711 generating certain messages to the postmaster, as otherwise message cascades
3712 could occur in some situations. As part of the same option, a message id may
3713 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3714 new message contains the id, following &"R="&, as a cross-reference.
3717 .oindex "&%-e%&&'x'&"
3718 There are a number of Sendmail options starting with &%-oe%& which seem to be
3719 called by various programs without the leading &%o%& in the option. For
3720 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3721 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3723 .cmdopt -F <&'string'&>
3724 .cindex "sender" "name"
3725 .cindex "name" "of sender"
3726 This option sets the sender's full name for use when a locally-generated
3727 message is being accepted. In the absence of this option, the user's &'gecos'&
3728 entry from the password data is used. As users are generally permitted to alter
3729 their &'gecos'& entries, no security considerations are involved. White space
3730 between &%-F%& and the <&'string'&> is optional.
3732 .cmdopt -f <&'address'&>
3733 .cindex "sender" "address"
3734 .cindex "address" "sender"
3735 .cindex "trusted users"
3736 .cindex "envelope from"
3737 .cindex "envelope sender"
3738 .cindex "user" "trusted"
3739 This option sets the address of the envelope sender of a locally-generated
3740 message (also known as the return path). The option can normally be used only
3741 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3744 Processes running as root or the Exim user are always trusted. Other
3745 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3746 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3747 of a local message is set to the caller's login name at the default qualify
3750 There is one exception to the restriction on the use of &%-f%&: an empty sender
3751 can be specified by any user, trusted or not, to create a message that can
3752 never provoke a bounce. An empty sender can be specified either as an empty
3753 string, or as a pair of angle brackets with nothing between them, as in these
3754 examples of shell commands:
3756 exim -f '<>' user@domain
3757 exim -f "" user@domain
3759 In addition, the use of &%-f%& is not restricted when testing a filter file
3760 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3763 Allowing untrusted users to change the sender address does not of itself make
3764 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3765 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3766 though this can be overridden by setting &%no_local_from_check%&.
3769 .cindex "&""From""& line"
3770 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3771 given as two arguments or one combined argument). The sender of a
3772 locally-generated message can also be set (when permitted) by an initial
3773 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3774 if &%-f%& is also present, it overrides &"From&~"&.
3777 .cindex "submission fixups, suppressing (command-line)"
3778 This option is equivalent to an ACL applying:
3780 control = suppress_local_fixups
3782 for every message received. Note that Sendmail will complain about such
3783 bad formatting, where Exim silently just does not fix it up. This may change
3786 As this affects audit information, the caller must be a trusted user to use
3789 .cmdopt -h <&'number'&>
3790 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3791 This option is accepted for compatibility with Sendmail, but has no effect. (In
3792 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3796 .cindex "Solaris" "&'mail'& command"
3797 .cindex "dot" "in incoming non-SMTP message"
3798 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3799 line by itself should not terminate an incoming, non-SMTP message.
3800 Solaris 2.4 (SunOS 5.4) Sendmail has a similar &%-i%& processing option
3801 &url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf),
3802 p. 1M-529), and therefore a &%-oi%& command line option, which both are used
3803 by its &'mailx'& command.
3805 .cmdopt -L <&'tag'&>
3806 .cindex "syslog" "process name; set with flag"
3807 This option is equivalent to setting &%syslog_processname%& in the config
3808 file and setting &%log_file_path%& to &`syslog`&.
3809 Its use is restricted to administrators. The configuration file has to be
3810 read and parsed, to determine access rights, before this is set and takes
3811 effect, so early configuration file errors will not honour this flag.
3813 The tag should not be longer than 32 characters.
3815 .cmdopt -M <&'message&~id'&>&~<&'message&~id'&>&~...
3816 .cindex "forcing delivery"
3817 .cindex "delivery" "forcing attempt"
3818 .cindex "frozen messages" "forcing delivery"
3819 This option requests Exim to run a delivery attempt on each message in turn. If
3820 any of the messages are frozen, they are automatically thawed before the
3821 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3822 and &%hold_domains%& are ignored.
3825 .cindex "hints database" "overriding retry hints"
3826 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3827 the normal retry time has not yet been reached. This option requires the caller
3828 to be an admin user. However, there is an option called &%prod_requires_admin%&
3829 which can be set false to relax this restriction (and also the same requirement
3830 for the &%-q%&, &%-R%&, and &%-S%& options).
3832 The deliveries happen synchronously, that is, the original Exim process does
3833 not terminate until all the delivery attempts have finished. No output is
3834 produced unless there is a serious error. If you want to see what is happening,
3835 use the &%-v%& option as well, or inspect Exim's main log.
3837 .cmdopt -Mar <&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3838 .cindex "message" "adding recipients"
3839 .cindex "recipient" "adding"
3840 This option requests Exim to add the addresses to the list of recipients of the
3841 message (&"ar"& for &"add recipients"&). The first argument must be a message
3842 id, and the remaining ones must be email addresses. However, if the message is
3843 active (in the middle of a delivery attempt), it is not altered. This option
3844 can be used only by an admin user.
3846 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&&&
3848 &~<&'sequence&~number'&>&&&
3849 &~<&'message&~id'&>"
3851 .cindex "SMTP" "passed connection"
3852 .cindex "SMTP" "multiple deliveries"
3853 .cindex "multiple SMTP deliveries"
3854 This option is not intended for use by external callers. It is used internally
3855 by Exim to invoke another instance of itself to deliver a waiting message using
3856 an existing SMTP connection, which is passed as the standard input. Details are
3857 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3858 must be root or the Exim user in order to use it.
3861 This option is not intended for use by external callers. It is used internally
3862 by Exim in conjunction with the &%-MC%& option. It signifies that the
3863 connection to the remote host has been authenticated.
3866 This option is not intended for use by external callers. It is used internally
3867 by Exim in conjunction with the &%-MC%& option. It signifies that the
3868 remote host supports the ESMTP &_DSN_& extension.
3871 This option is not intended for use by external callers. It is used internally
3872 by Exim in conjunction with the &%-d%& option
3873 to pass on an information string on the purpose of the process.
3875 .cmdopt -MCG <&'queue&~name'&>
3876 This option is not intended for use by external callers. It is used internally
3877 by Exim in conjunction with the &%-MC%& option. It signifies that an
3878 alternate queue is used, named by the following argument.
3881 This option is not intended for use by external callers. It is used internally
3882 by Exim in conjunction with the &%-MC%& option. It signifies that a
3883 remote host supports the ESMTP &_CHUNKING_& extension.
3886 This option is not intended for use by external callers. It is used internally
3887 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3888 which Exim is connected advertised limits on numbers of mails, recipients or
3890 The limits are given by the following three arguments.
3893 This option is not intended for use by external callers. It is used internally
3894 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3895 which Exim is connected supports pipelining.
3898 This option is not intended for use by external callers. It is used internally
3899 by Exim in conjunction with the &%-MC%& option. It signifies that the connection
3900 t a remote server is via a SOCKS proxy, using addresses and ports given by
3901 the following four arguments.
3903 .cmdopt -MCQ <&'process&~id'&>&~<&'pipe&~fd'&>
3904 This option is not intended for use by external callers. It is used internally
3905 by Exim in conjunction with the &%-MC%& option when the original delivery was
3906 started by a queue runner. It passes on the process id of the queue runner,
3907 together with the file descriptor number of an open pipe. Closure of the pipe
3908 signals the final completion of the sequence of processes that are passing
3909 messages through the same SMTP connection.
3911 .cmdopt -MCq <&'recipient&~address'&>&~<&'size'&>
3912 This option is not intended for use by external callers. It is used internally
3913 by Exim to implement quota checking for local users.
3916 This option is not intended for use by external callers. It is used internally
3917 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3918 ESMTP SIZE option should be used on messages delivered down the existing
3922 This option is not intended for use by external callers. It is used internally
3923 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3924 host to which Exim is connected supports TLS encryption.
3926 .vitem &%-MCr%&&~<&'SNI'&> &&&
3930 These options are not intended for use by external callers. It is used internally
3931 by Exim in conjunction with the &%-MCt%& option, and passes on the fact that
3932 a TLS Server Name Indication was sent as part of the channel establishment.
3933 The argument gives the SNI string.
3934 The "r" variant indicates a DANE-verified connection.
3936 .cmdopt -MCt <&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
3937 This option is not intended for use by external callers. It is used internally
3938 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3939 connection is being proxied by a parent process for handling TLS encryption.
3940 The arguments give the local address and port being proxied, and the TLS cipher.
3942 .cmdopt -Mc <&'message&~id'&>&~<&'message&~id'&>&~...
3943 .cindex "hints database" "not overridden by &%-Mc%&"
3944 .cindex "delivery" "manually started &-- not forced"
3945 This option requests Exim to run a delivery attempt on each message, in turn,
3946 but unlike the &%-M%& option, it does check for retry hints, and respects any
3947 that are found. This option is not very useful to external callers. It is
3948 provided mainly for internal use by Exim when it needs to re-invoke itself in
3949 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3950 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3951 respects retry times and other options such as &%hold_domains%& that are
3952 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3953 If you want to run a specific delivery as if in a queue run, you should use
3954 &%-q%& with a message id argument. A distinction between queue run deliveries
3955 and other deliveries is made in one or two places.
3957 .cmdopt -Mes <&'message&~id'&>&~<&'address'&>
3958 .cindex "message" "changing sender"
3959 .cindex "sender" "changing"
3960 This option requests Exim to change the sender address in the message to the
3961 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3962 &"edit sender"&). There must be exactly two arguments. The first argument must
3963 be a message id, and the second one an email address. However, if the message
3964 is active (in the middle of a delivery attempt), its status is not altered.
3965 This option can be used only by an admin user.
3967 .cmdopt -Mf <&'message&~id'&>&~<&'message&~id'&>&~...
3968 .cindex "freezing messages"
3969 .cindex "message" "manually freezing"
3970 This option requests Exim to mark each listed message as &"frozen"&. This
3971 prevents any delivery attempts taking place until the message is &"thawed"&,
3972 either manually or as a result of the &%auto_thaw%& configuration option.
3973 However, if any of the messages are active (in the middle of a delivery
3974 attempt), their status is not altered. This option can be used only by an admin
3977 .cmdopt -Mg <&'message&~id'&>&~<&'message&~id'&>&~...
3978 .cindex "giving up on messages"
3979 .cindex "message" "abandoning delivery attempts"
3980 .cindex "delivery" "abandoning further attempts"
3981 This option requests Exim to give up trying to deliver the listed messages,
3982 including any that are frozen. However, if any of the messages are active,
3983 their status is not altered. For non-bounce messages, a delivery error message
3984 is sent to the sender, containing the text &"cancelled by administrator"&.
3985 Bounce messages are just discarded. This option can be used only by an admin
3988 .cmdopt -MG <&'queue&~name'&>&~<&'message&~id'&>&~<&'message&~id'&>&~...
3990 .cindex "named queues" "moving messages"
3991 .cindex "queue" "moving messages"
3992 This option requests that each listed message be moved from its current
3993 queue to the given named queue.
3994 The destination queue name argument is required, but can be an empty
3995 string to define the default queue.
3996 If the messages are not currently located in the default queue,
3997 a &%-qG<name>%& option will be required to define the source queue.
3999 .cmdopt -Mmad <&'message&~id'&>&~<&'message&~id'&>&~...
4000 .cindex "delivery" "cancelling all"
4001 This option requests Exim to mark all the recipient addresses in the messages
4002 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
4003 message is active (in the middle of a delivery attempt), its status is not
4004 altered. This option can be used only by an admin user.
4006 .cmdopt -Mmd <&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
4007 .cindex "delivery" "cancelling by address"
4008 .cindex "recipient" "removing"
4009 .cindex "removing recipients"
4010 This option requests Exim to mark the given addresses as already delivered
4011 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
4012 the remaining ones must be email addresses. These are matched to recipient
4013 addresses in the message in a case-sensitive manner. If the message is active
4014 (in the middle of a delivery attempt), its status is not altered. This option
4015 can be used only by an admin user.
4017 .cmdopt -Mrm <&'message&~id'&>&~<&'message&~id'&>&~...
4018 .cindex "removing messages"
4019 .cindex "abandoning mail"
4020 .cindex "message" "manually discarding"
4021 This option requests Exim to remove the given messages from the queue. No
4022 bounce messages are sent; each message is simply forgotten. However, if any of
4023 the messages are active, their status is not altered. This option can be used
4024 only by an admin user or by the user who originally caused the message to be
4025 placed in the queue.
4030 . .cindex REQUIRETLS
4031 . This option is used to request REQUIRETLS processing on the message.
4032 . It is used internally by Exim in conjunction with -E when generating
4036 .cmdopt -Mset <&'message&~id'&>
4037 .cindex "testing" "string expansion"
4038 .cindex "expansion" "testing"
4039 This option is useful only in conjunction with &%-be%& (that is, when testing
4040 string expansions). Exim loads the given message from its spool before doing
4041 the test expansions, thus setting message-specific variables such as
4042 &$message_size$& and the header variables. The &$recipients$& variable is made
4043 available. This feature is provided to make it easier to test expansions that
4044 make use of these variables. However, this option can be used only by an admin
4045 user. See also &%-bem%&.
4047 .cmdopt -Mt <&'message&~id'&>&~<&'message&~id'&>&~...
4048 .cindex "thawing messages"
4049 .cindex "unfreezing messages"
4050 .cindex "frozen messages" "thawing"
4051 .cindex "message" "thawing frozen"
4052 This option requests Exim to &"thaw"& any of the listed messages that are
4053 &"frozen"&, so that delivery attempts can resume. However, if any of the
4054 messages are active, their status is not altered. This option can be used only
4057 .cmdopt -Mvb <&'message&~id'&>
4058 .cindex "listing" "message body"
4059 .cindex "message" "listing body of"
4060 This option causes the contents of the message body (-D) spool file to be
4061 written to the standard output. This option can be used only by an admin user.
4063 .cmdopt -Mvc <&'message&~id'&>
4064 .cindex "message" "listing in RFC 2822 format"
4065 .cindex "listing" "message in RFC 2822 format"
4066 This option causes a copy of the complete message (header lines plus body) to
4067 be written to the standard output in RFC 2822 format. This option can be used
4068 only by an admin user.
4070 .cmdopt -Mvh <&'message&~id'&>
4071 .cindex "listing" "message headers"
4072 .cindex "header lines" "listing"
4073 .cindex "message" "listing header lines"
4074 This option causes the contents of the message headers (-H) spool file to be
4075 written to the standard output. This option can be used only by an admin user.
4077 .cmdopt -Mvl <&'message&~id'&>
4078 .cindex "listing" "message log"
4079 .cindex "message" "listing message log"
4080 This option causes the contents of the message log spool file to be written to
4081 the standard output. This option can be used only by an admin user.
4084 This is a synonym for &%-om%& that is accepted by Sendmail
4085 (&url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf)
4086 p. 1M-258), so Exim treats it that way too.
4089 .cindex "debugging" "&%-N%& option"
4090 .cindex "debugging" "suppressing delivery"
4091 This is a debugging option that inhibits delivery of a message at the transport
4092 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4093 it just doesn't actually transport the message, but instead behaves as if it
4094 had successfully done so. However, it does not make any updates to the retry
4095 database, and the log entries for deliveries are flagged with &"*>"& rather
4098 Because &%-N%& discards any message to which it applies, only root or the Exim
4099 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4100 words, an ordinary user can use it only when supplying an incoming message to
4101 which it will apply. Although transportation never fails when &%-N%& is set, an
4102 address may be deferred because of a configuration problem on a transport, or a
4103 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4104 the message, and applies to any subsequent delivery attempts that may happen
4108 This option is interpreted by Sendmail to mean &"no aliasing"&.
4109 For normal modes of operation, it is ignored by Exim.
4110 When combined with &%-bP%& it makes the output more terse (suppresses
4111 option names, environment values and config pretty printing).
4113 .cmdopt -O <&'data'&>
4114 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4117 .cmdopt -oA <&'file&~name'&>
4118 .cindex "Sendmail compatibility" "&%-oA%& option"
4119 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4120 alternative alias filename. Exim handles &%-bi%& differently; see the
4124 .cindex "SMTP" "passed connection"
4125 .cindex "SMTP" "multiple deliveries"
4126 .cindex "multiple SMTP deliveries"
4127 This is a debugging option which limits the maximum number of messages that can
4128 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4129 transport. If <&'n'&> is omitted, the limit is set to 1.
4132 .cindex "background delivery"
4133 .cindex "delivery" "in the background"
4134 This option applies to all modes in which Exim accepts incoming messages,
4135 including the listening daemon. It requests &"background"& delivery of such
4136 messages, which means that the accepting process automatically starts a
4137 delivery process for each message received, but does not wait for the delivery
4138 processes to finish.
4140 When all the messages have been received, the reception process exits,
4141 leaving the delivery processes to finish in their own time. The standard output
4142 and error streams are closed at the start of each delivery process.
4143 This is the default action if none of the &%-od%& options are present.
4145 If one of the queueing options in the configuration file
4146 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4147 overrides it if &%queue_only_override%& is set true, which is the default
4148 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4151 .cindex "foreground delivery"
4152 .cindex "delivery" "in the foreground"
4153 This option requests &"foreground"& (synchronous) delivery when Exim has
4154 accepted a locally-generated message. (For the daemon it is exactly the same as
4155 &%-odb%&.) A delivery process is automatically started to deliver the message,
4156 and Exim waits for it to complete before proceeding.
4158 The original Exim reception process does not finish until the delivery
4159 process for the final message has ended. The standard error stream is left open
4162 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4163 false and one of the queueing options in the configuration file is in effect.
4165 If there is a temporary delivery error during foreground delivery, the
4166 message is left in the queue for later delivery, and the original reception
4167 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4168 restricted configuration that never queues messages.
4172 This option is synonymous with &%-odf%&. It is provided for compatibility with
4176 .cindex "non-immediate delivery"
4177 .cindex "delivery" "suppressing immediate"
4178 .cindex "queueing incoming messages"
4179 This option applies to all modes in which Exim accepts incoming messages,
4180 including the listening daemon. It specifies that the accepting process should
4181 not automatically start a delivery process for each message received. Messages
4182 are placed in the queue, and remain there until a subsequent queue runner
4183 process encounters them. There are several configuration options (such as
4184 &%queue_only%&) that can be used to queue incoming messages under certain
4185 conditions. This option overrides all of them and also &%-odqs%&. It always
4189 .cindex "SMTP" "delaying delivery"
4190 .cindex "first pass routing"
4191 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4192 However, like &%-odb%& and &%-odi%&, this option has no effect if
4193 &%queue_only_override%& is false and one of the queueing options in the
4194 configuration file is in effect.
4196 When &%-odqs%& does operate, a delivery process is started for each incoming
4197 message, in the background by default, but in the foreground if &%-odi%& is
4198 also present. The recipient addresses are routed, and local deliveries are done
4199 in the normal way. However, if any SMTP deliveries are required, they are not
4200 done at this time, so the message remains in the queue until a subsequent queue
4201 runner process encounters it. Because routing was done, Exim knows which
4202 messages are waiting for which hosts, and so a number of messages for the same
4203 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4204 configuration option has the same effect for specific domains. See also the
4208 .cindex "error" "reporting"
4209 If an error is detected while a non-SMTP message is being received (for
4210 example, a malformed address), the error is reported to the sender in a mail
4213 .cindex "return code" "for &%-oee%&"
4215 this error message is successfully sent, the Exim receiving process
4216 exits with a return code of zero. If not, the return code is 2 if the problem
4217 is that the original message has no recipients, or 1 for any other error.
4218 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4221 .cindex "error" "reporting"
4222 .cindex "return code" "for &%-oem%&"
4223 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4224 return code, whether or not the error message was successfully sent.
4225 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4228 .cindex "error" "reporting"
4229 If an error is detected while a non-SMTP message is being received, the
4230 error is reported by writing a message to the standard error file (stderr).
4231 .cindex "return code" "for &%-oep%&"
4232 The return code is 1 for all errors.
4235 .cindex "error" "reporting"
4236 This option is supported for compatibility with Sendmail, but has the same
4240 .cindex "error" "reporting"
4241 This option is supported for compatibility with Sendmail, but has the same
4245 .cindex "dot" "in incoming non-SMTP message"
4246 This option, which has the same effect as &%-i%&, specifies that a dot on a
4247 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4248 single dot does terminate, though Exim does no special processing for other
4249 lines that start with a dot. This option is set by default if Exim is called as
4250 &'rmail'&. See also &%-ti%&.
4253 This option is treated as synonymous with &%-oi%&.
4255 .cmdopt -oMa <&'host&~address'&>
4256 .cindex "sender" "host address, specifying for local message"
4257 A number of options starting with &%-oM%& can be used to set values associated
4258 with remote hosts on locally-submitted messages (that is, messages not received
4259 over TCP/IP). These options can be used by any caller in conjunction with the
4260 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4261 other circumstances, they are ignored unless the caller is trusted.
4263 The &%-oMa%& option sets the sender host address. This may include a port
4264 number at the end, after a full stop (period). For example:
4266 exim -bs -oMa 10.9.8.7.1234
4268 An alternative syntax is to enclose the IP address in square brackets,
4269 followed by a colon and the port number:
4271 exim -bs -oMa [10.9.8.7]:1234
4273 The IP address is placed in the &$sender_host_address$& variable, and the
4274 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4275 are present on the command line, the sender host IP address is taken from
4276 whichever one is last.
4278 .cmdopt -oMaa <&'name'&>
4279 .cindex "authentication" "name, specifying for local message"
4280 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4281 option sets the value of &$sender_host_authenticated$& (the authenticator
4282 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4283 This option can be used with &%-bh%& and &%-bs%& to set up an
4284 authenticated SMTP session without actually using the SMTP AUTH command.
4286 .cmdopt -oMai <&'string'&>
4287 .cindex "authentication" "id, specifying for local message"
4288 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4289 option sets the value of &$authenticated_id$& (the id that was authenticated).
4290 This overrides the default value (the caller's login id, except with &%-bh%&,
4291 where there is no default) for messages from local sources. See chapter
4292 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4294 .cmdopt -oMas <&'address'&>
4295 .cindex "authentication" "sender, specifying for local message"
4296 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4297 option sets the authenticated sender value in &$authenticated_sender$&. It
4298 overrides the sender address that is created from the caller's login id for
4299 messages from local sources, except when &%-bh%& is used, when there is no
4300 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4301 specified on a MAIL command overrides this value. See chapter
4302 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4304 .cmdopt -oMi <&'interface&~address'&>
4305 .cindex "interface" "address, specifying for local message"
4306 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4307 option sets the IP interface address value. A port number may be included,
4308 using the same syntax as for &%-oMa%&. The interface address is placed in
4309 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4311 .cmdopt -oMm <&'message&~reference'&>
4312 .cindex "message reference" "message reference, specifying for local message"
4313 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4314 option sets the message reference, e.g. message-id, and is logged during
4315 delivery. This is useful when some kind of audit trail is required to tie
4316 messages together. The format of the message reference is checked and will
4317 abort if the format is invalid. The option will only be accepted if exim is
4318 running in trusted mode, not as any regular user.
4320 The best example of a message reference is when Exim sends a bounce message.
4321 The message reference is the message-id of the original message for which Exim
4322 is sending the bounce.
4324 .cmdopt -oMr <&'protocol&~name'&>
4325 .cindex "protocol, specifying for local message"
4326 .vindex "&$received_protocol$&"
4327 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4328 option sets the received protocol value that is stored in
4329 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4330 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4331 SMTP protocol names (see the description of &$received_protocol$& in section
4332 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4333 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4334 be set by &%-oMr%&. Repeated use of this option is not supported.
4336 .cmdopt -oMs <&'host&~name'&>
4337 .cindex "sender" "host name, specifying for local message"
4338 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4339 option sets the sender host name in &$sender_host_name$&. When this option is
4340 present, Exim does not attempt to look up a host name from an IP address; it
4341 uses the name it is given.
4343 .cmdopt -oMt <&'ident&~string'&>
4344 .cindex "sender" "ident string, specifying for local message"
4345 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4346 option sets the sender ident value in &$sender_ident$&. The default setting for
4347 local callers is the login id of the calling process, except when &%-bh%& is
4348 used, when there is no default.
4351 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4352 In Sendmail, this option means &"me too"&, indicating that the sender of a
4353 message should receive a copy of the message if the sender appears in an alias
4354 expansion. Exim always does this, so the option does nothing.
4357 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4358 This option is ignored. In Sendmail it specifies &"old style headers"&,
4359 whatever that means.
4361 .cmdopt -oP <&'path'&>
4362 .cindex "pid (process id)" "of daemon"
4363 .cindex "daemon" "process id (pid)"
4364 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4365 value. The option specifies the file to which the process id of the daemon is
4366 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4367 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4368 because in those cases, the normal pid file is not used.
4371 .cindex "pid (process id)" "of daemon"
4372 .cindex "daemon" "process id (pid)"
4373 This option is not intended for general use.
4374 The daemon uses it when terminating due to a SIGTEM, possibly in
4375 combination with &%-oP%&&~<&'path'&>.
4376 It causes the pid file to be removed.
4378 .cmdopt -or <&'time'&>
4379 .cindex "timeout" "for non-SMTP input"
4380 This option sets a timeout value for incoming non-SMTP messages. If it is not
4381 set, Exim will wait forever for the standard input. The value can also be set
4382 by the &%receive_timeout%& option. The format used for specifying times is
4383 described in section &<<SECTtimeformat>>&.
4385 .cmdopt -os <&'time'&>
4386 .cindex "timeout" "for SMTP input"
4387 .cindex "SMTP" "input timeout"
4388 This option sets a timeout value for incoming SMTP messages. The timeout
4389 applies to each SMTP command and block of data. The value can also be set by
4390 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4391 for specifying times is described in section &<<SECTtimeformat>>&.
4394 This option has exactly the same effect as &%-v%&.
4396 .cmdopt -oX <&'number&~or&~string'&>
4397 .cindex "TCP/IP" "setting listening ports"
4398 .cindex "TCP/IP" "setting listening interfaces"
4399 .cindex "port" "receiving TCP/IP"
4400 This option is relevant only when the &%-bd%& (start listening daemon) option
4401 is also given. It controls which ports and interfaces the daemon uses. Details
4402 of the syntax, and how it interacts with configuration file options, are given
4403 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4404 file is written unless &%-oP%& is also present to specify a pid filename.
4407 .cindex "daemon notifier socket"
4408 This option controls the creation of an inter-process communications endpoint
4410 It is only relevant when the &%-bd%& (start listening daemon) option is also
4412 Normally the daemon creates this socket, unless a &%-oX%& and &*no*& &%-oP%&
4413 option is also present.
4415 If this option is given then the socket will not be created. This is required
4416 if the system is running multiple daemons, in which case it should
4418 The features supported by the socket will not be available in such cases.
4420 The socket is currently used for
4422 fast ramp-up of queue runner processes
4424 caching compiled regexes
4426 obtaining a current queue size
4431 .cindex "Perl" "starting the interpreter"
4432 This option applies when an embedded Perl interpreter is linked with Exim (see
4433 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4434 option, forcing the starting of the interpreter to be delayed until it is
4438 .cindex "Perl" "starting the interpreter"
4439 This option applies when an embedded Perl interpreter is linked with Exim (see
4440 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4441 option, forcing the starting of the interpreter to occur as soon as Exim is
4444 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4446 For compatibility with Sendmail, this option is equivalent to
4448 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4450 It sets the incoming protocol and host name (for trusted callers). The
4451 host name and its colon can be omitted when only the protocol is to be set.
4452 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4453 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4454 or &`s`& using this option (but that does not seem a real limitation).
4455 Repeated use of this option is not supported.
4458 .cindex "queue runner" "starting manually"
4459 This option is normally restricted to admin users. However, there is a
4460 configuration option called &%prod_requires_admin%& which can be set false to
4461 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4462 and &%-S%& options).
4464 .cindex "queue runner" "description of operation"
4465 If other commandline options do not specify an action,
4466 the &%-q%& option starts one queue runner process. This scans the queue of
4467 waiting messages, and runs a delivery process for each one in turn. It waits
4468 for each delivery process to finish before starting the next one. A delivery
4469 process may not actually do any deliveries if the retry times for the addresses
4470 have not been reached. Use &%-qf%& (see below) if you want to override this.
4473 .cindex "SMTP" "passed connection"
4474 .cindex "SMTP" "multiple deliveries"
4475 .cindex "multiple SMTP deliveries"
4476 the delivery process spawns other processes to deliver other messages down
4477 passed SMTP connections, the queue runner waits for these to finish before
4480 When all the queued messages have been considered, the original queue runner
4481 process terminates. In other words, a single pass is made over the waiting
4482 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4483 this to be repeated periodically.
4485 Exim processes the waiting messages in an unpredictable order. It isn't very
4486 random, but it is likely to be different each time, which is all that matters.
4487 If one particular message screws up a remote MTA, other messages to the same
4488 MTA have a chance of getting through if they get tried first.
4490 It is possible to cause the messages to be processed in lexical message id
4491 order, which is essentially the order in which they arrived, by setting the
4492 &%queue_run_in_order%& option, but this is not recommended for normal use.
4494 .vitem &%-q%&<&'qflags'&>
4495 The &%-q%& option may be followed by one or more flag letters that change its
4496 behaviour. They are all optional, but if more than one is present, they must
4497 appear in the correct order. Each flag is described in a separate item below.
4501 .cindex "queue" "double scanning"
4502 .cindex "queue" "routing"
4503 .cindex "routing" "whole queue before delivery"
4504 .cindex "first pass routing"
4505 .cindex "queue runner" "two phase"
4506 An option starting with &%-qq%& requests a two-stage queue run. In the first
4507 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4508 every domain. Addresses are routed, local deliveries happen, but no remote
4511 Performance will be best if the &%queue_run_in_order%& option is false.
4513 the &%queue_fast_ramp%& option is true
4514 and a daemon-notifier socket is available
4515 then in the first phase of the run,
4516 once a threshold number of messages are routed for a given host,
4517 a delivery process is forked in parallel with the rest of the scan.
4519 .cindex "hints database" "remembering routing"
4520 The hints database that remembers which messages are waiting for specific hosts
4521 is updated, as if delivery to those hosts had been deferred.
4523 After the first queue scan complete,
4524 a second, normal queue scan is done, with routing and delivery taking
4526 Messages that are routed to the same host should mostly be
4527 delivered down a single SMTP
4528 .cindex "SMTP" "passed connection"
4529 .cindex "SMTP" "multiple deliveries"
4530 .cindex "multiple SMTP deliveries"
4531 connection because of the hints that were set up during the first queue scan.
4534 Two-phase queue runs should be used on systems which, even intermittently,
4535 have a large queue (such as mailing-list operators).
4536 They may also be useful for hosts that are connected to the Internet
4540 .vitem &%-q[q]i...%&
4542 .cindex "queue" "initial delivery"
4543 If the &'i'& flag is present, the queue runner runs delivery processes only for
4544 those messages that haven't previously been tried. (&'i'& stands for &"initial
4545 delivery"&.) This can be helpful if you are putting messages in the queue using
4546 &%-odq%& and want a queue runner just to process the new messages.
4548 .vitem &%-q[q][i]f...%&
4550 .cindex "queue" "forcing delivery"
4551 .cindex "delivery" "forcing in queue run"
4552 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4553 message, whereas without &'f'& only those non-frozen addresses that have passed
4554 their retry times are tried.
4556 .vitem &%-q[q][i]ff...%&
4558 .cindex "frozen messages" "forcing delivery"
4559 If &'ff'& is present, a delivery attempt is forced for every message, whether
4562 .vitem &%-q[q][i][f[f]]l%&
4564 .cindex "queue" "local deliveries only"
4565 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4566 be done. If a message requires any remote deliveries, it remains in the queue
4569 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4572 .cindex "named queues" "deliver from"
4573 .cindex "queue" "delivering specific messages"
4574 If the &'G'& flag and a name is present, the queue runner operates on the
4575 queue with the given name rather than the default queue.
4576 The name should not contain a &'/'& character.
4577 For a periodic queue run (see below)
4578 append to the name a slash and a time value.
4580 If other commandline options specify an action, a &'-qG<name>'& option
4581 will specify a queue to operate on.
4584 exim -bp -qGquarantine
4586 exim -qGoffpeak -Rf @special.domain.example
4589 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4590 When scanning the queue, Exim can be made to skip over messages whose ids are
4591 lexically less than a given value by following the &%-q%& option with a
4592 starting message id. For example:
4594 exim -q 0t5C6f-0000c8-00
4596 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4597 second message id is given, messages whose ids are lexically greater than it
4598 are also skipped. If the same id is given twice, for example,
4600 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4602 just one delivery process is started, for that message. This differs from
4603 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4604 that it counts as a delivery from a queue run. Note that the selection
4605 mechanism does not affect the order in which the messages are scanned. There
4606 are also other ways of selecting specific sets of messages for delivery in a
4607 queue run &-- see &%-R%& and &%-S%&.
4609 .vitem &%-q%&<&'qflags'&><&'time'&>
4610 .cindex "queue runner" "starting periodically"
4611 .cindex "periodic queue running"
4612 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4613 starting a queue runner process at intervals specified by the given time value
4614 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4615 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4616 single daemon process handles both functions. A common way of starting up a
4617 combined daemon at system boot time is to use a command such as
4619 /usr/exim/bin/exim -bd -q30m
4621 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4622 process every 30 minutes.
4625 .cindex "named queues" "queue runners"
4626 It is possible to set up runners for multiple named queues within one daemon,
4629 exim -qGhipri/2m -q10m -qqGmailinglist/1h
4633 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4634 pid file is written unless one is explicitly requested by the &%-oP%& option.
4636 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4638 This option is synonymous with &%-R%&. It is provided for Sendmail
4641 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4643 This option is synonymous with &%-S%&.
4645 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4647 .cindex "queue runner" "for specific recipients"
4648 .cindex "delivery" "to given domain"
4649 .cindex "domain" "delivery to"
4650 The <&'rsflags'&> may be empty, in which case the white space before the string
4651 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4652 which are the possible values for <&'rsflags'&>. White space is required if
4653 <&'rsflags'&> is not empty.
4655 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4656 perform a single queue run, except that, when scanning the messages on the
4657 queue, Exim processes only those that have at least one undelivered recipient
4658 address containing the given string, which is checked in a case-independent
4659 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4660 regular expression; otherwise it is a literal string.
4662 If you want to do periodic queue runs for messages with specific recipients,
4663 you can combine &%-R%& with &%-q%& and a time value. For example:
4665 exim -q25m -R @special.domain.example
4667 This example does a queue run for messages with recipients in the given domain
4668 every 25 minutes. Any additional flags that are specified with &%-q%& are
4669 applied to each queue run.
4671 Once a message is selected for delivery by this mechanism, all its addresses
4672 are processed. For the first selected message, Exim overrides any retry
4673 information and forces a delivery attempt for each undelivered address. This
4674 means that if delivery of any address in the first message is successful, any
4675 existing retry information is deleted, and so delivery attempts for that
4676 address in subsequently selected messages (which are processed without forcing)
4677 will run. However, if delivery of any address does not succeed, the retry
4678 information is updated, and in subsequently selected messages, the failing
4679 address will be skipped.
4681 .cindex "frozen messages" "forcing delivery"
4682 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4683 all selected messages, not just the first; frozen messages are included when
4686 The &%-R%& option makes it straightforward to initiate delivery of all messages
4687 to a given domain after a host has been down for some time. When the SMTP
4688 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4689 effect is to run Exim with the &%-R%& option, but it can be configured to run
4690 an arbitrary command instead.
4693 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4695 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4697 .cindex "delivery" "from given sender"
4698 .cindex "queue runner" "for specific senders"
4699 This option acts like &%-R%& except that it checks the string against each
4700 message's sender instead of against the recipients. If &%-R%& is also set, both
4701 conditions must be met for a message to be selected. If either of the options
4702 has &'f'& or &'ff'& in its flags, the associated action is taken.
4704 .cmdopt -Tqt <&'times'&>
4705 This is an option that is exclusively for use by the Exim testing suite. It is not
4706 recognized when Exim is run normally. It allows for the setting up of explicit
4707 &"queue times"& so that various warning/retry features can be tested.
4710 .cindex "recipient" "extracting from header lines"
4714 When Exim is receiving a locally-generated, non-SMTP message on its standard
4715 input, the &%-t%& option causes the recipients of the message to be obtained
4716 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4717 from the command arguments. The addresses are extracted before any rewriting
4718 takes place and the &'Bcc:'& header line, if present, is then removed.
4720 .cindex "Sendmail compatibility" "&%-t%& option"
4721 If the command has any arguments, they specify addresses to which the message
4722 is &'not'& to be delivered. That is, the argument addresses are removed from
4723 the recipients list obtained from the headers. This is compatible with Smail 3
4724 and in accordance with the documented behaviour of several versions of
4725 Sendmail, as described in man pages on a number of operating systems (e.g.
4726 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4727 argument addresses to those obtained from the headers, and the O'Reilly
4728 Sendmail book documents it that way. Exim can be made to add argument addresses
4729 instead of subtracting them by setting the option
4730 &%extract_addresses_remove_arguments%& false.
4732 .cindex "&%Resent-%& header lines" "with &%-t%&"
4733 If there are any &%Resent-%& header lines in the message, Exim extracts
4734 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4735 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4736 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4737 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4739 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4740 message is resent several times). The RFC also specifies that they should be
4741 added at the front of the message, and separated by &'Received:'& lines. It is
4742 not at all clear how &%-t%& should operate in the present of multiple sets,
4743 nor indeed exactly what constitutes a &"set"&.
4744 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4745 are often added at the end of the header, and if a message is resent more than
4746 once, it is common for the original set of &%Resent-%& headers to be renamed as
4747 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4750 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4751 compatibility with Sendmail.
4753 .cmdopt -tls-on-connect
4754 .cindex "TLS" "use without STARTTLS"
4755 .cindex "TLS" "automatic start"
4756 This option is available when Exim is compiled with TLS support. It forces all
4757 incoming SMTP connections to behave as if the incoming port is listed in the
4758 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4759 &<<CHAPTLS>>& for further details.
4763 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4764 Sendmail uses this option for &"initial message submission"&, and its
4765 documentation states that in future releases, it may complain about
4766 syntactically invalid messages rather than fixing them when this flag is not
4767 set. Exim ignores this option.
4770 This option causes Exim to write information to the standard error stream,
4771 describing what it is doing. In particular, it shows the log lines for
4772 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4773 dialogue is shown. Some of the log lines shown may not actually be written to
4774 the log if the setting of &%log_selector%& discards them. Any relevant
4775 selectors are shown with each log line. If none are shown, the logging is
4779 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4780 National Language Support extended characters in the body of the mail item"&).
4781 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4784 .cmdopt -X <&'logfile'&>
4785 This option is interpreted by Sendmail to cause debug information to be sent
4786 to the named file. It is ignored by Exim.
4788 .cmdopt -z <&'log-line'&>
4789 This option writes its argument to Exim's logfile.
4790 Use is restricted to administrators; the intent is for operational notes.
4791 Quotes should be used to maintain a multi-word item as a single argument,
4799 . ////////////////////////////////////////////////////////////////////////////
4800 . Insert a stylized DocBook comment here, to identify the end of the command
4801 . line options. This is for the benefit of the Perl script that automatically
4802 . creates a man page for the options.
4803 . ////////////////////////////////////////////////////////////////////////////
4806 <!-- === End of command line options === -->
4813 . ////////////////////////////////////////////////////////////////////////////
4814 . ////////////////////////////////////////////////////////////////////////////
4817 .chapter "The Exim runtime configuration file" "CHAPconf" &&&
4818 "The runtime configuration file"
4820 .cindex "runtime configuration"
4821 .cindex "configuration file" "general description"
4822 .cindex "CONFIGURE_FILE"
4823 .cindex "configuration file" "errors in"
4824 .cindex "error" "in configuration file"
4825 .cindex "return code" "for bad configuration"
4826 Exim uses a single runtime configuration file that is read whenever an Exim
4827 binary is executed. Note that in normal operation, this happens frequently,
4828 because Exim is designed to operate in a distributed manner, without central
4831 If a syntax error is detected while reading the configuration file, Exim
4832 writes a message on the standard error, and exits with a non-zero return code.
4833 The message is also written to the panic log. &*Note*&: Only simple syntax
4834 errors can be detected at this time. The values of any expanded options are
4835 not checked until the expansion happens, even when the expansion does not
4836 actually alter the string.
4838 The name of the configuration file is compiled into the binary for security
4839 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4840 most configurations, this specifies a single file. However, it is permitted to
4841 give a colon-separated list of filenames, in which case Exim uses the first
4842 existing file in the list.
4845 .cindex "EXIM_GROUP"
4846 .cindex "CONFIGURE_OWNER"
4847 .cindex "CONFIGURE_GROUP"
4848 .cindex "configuration file" "ownership"
4849 .cindex "ownership" "configuration file"
4850 The runtime configuration file must be owned by root or by the user that is
4851 specified at compile time by the CONFIGURE_OWNER option (if set). The
4852 configuration file must not be world-writeable, or group-writeable unless its
4853 group is the root group or the one specified at compile time by the
4854 CONFIGURE_GROUP option.
4856 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4857 to root, anybody who is able to edit the runtime configuration file has an
4858 easy way to run commands as root. If you specify a user or group in the
4859 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4860 who are members of that group will trivially be able to obtain root privileges.
4862 Up to Exim version 4.72, the runtime configuration file was also permitted to
4863 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4864 since it offered a simple privilege escalation for any attacker who managed to
4865 compromise the Exim user account.
4867 A default configuration file, which will work correctly in simple situations,
4868 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4869 defines just one filename, the installation process copies the default
4870 configuration to a new file of that name if it did not previously exist. If
4871 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4872 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4877 .section "Using a different configuration file" "SECID40"
4878 .cindex "configuration file" "alternate"
4879 A one-off alternate configuration can be specified by the &%-C%& command line
4880 option, which may specify a single file or a list of files. However, when
4881 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4882 unless the argument for &%-C%& is identical to the built-in value from
4883 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4884 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4885 is useful mainly for checking the syntax of configuration files before
4886 installing them. No owner or group checks are done on a configuration file
4887 specified by &%-C%&, if root privilege has been dropped.
4889 Even the Exim user is not trusted to specify an arbitrary configuration file
4890 with the &%-C%& option to be used with root privileges, unless that file is
4891 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4892 testing a configuration using &%-C%& right through message reception and
4893 delivery, even if the caller is root. The reception works, but by that time,
4894 Exim is running as the Exim user, so when it re-execs to regain privilege for
4895 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4896 can test reception and delivery using two separate commands (one to put a
4897 message in the queue, using &%-odq%&, and another to do the delivery, using
4900 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4901 prefix string with which any file named in a &%-C%& command line option must
4902 start. In addition, the filename must not contain the sequence &"&`/../`&"&.
4903 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any
4904 filename can be used with &%-C%&.
4906 One-off changes to a configuration can be specified by the &%-D%& command line
4907 option, which defines and overrides values for macros used inside the
4908 configuration file. However, like &%-C%&, the use of this option by a
4909 non-privileged user causes Exim to discard its root privilege.
4910 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4911 completely disabled, and its use causes an immediate error exit.
4913 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4914 to declare certain macro names trusted, such that root privilege will not
4915 necessarily be discarded.
4916 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4917 considered safe and, if &%-D%& only supplies macros from this list, and the
4918 values are acceptable, then Exim will not give up root privilege if the caller
4919 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4920 transition mechanism and is expected to be removed in the future. Acceptable
4921 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4923 Some sites may wish to use the same Exim binary on different machines that
4924 share a file system, but to use different configuration files on each machine.
4925 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4926 looks for a file whose name is the configuration filename followed by a dot
4927 and the machine's node name, as obtained from the &[uname()]& function. If this
4928 file does not exist, the standard name is tried. This processing occurs for
4929 each filename in the list given by CONFIGURE_FILE or &%-C%&.
4931 In some esoteric situations different versions of Exim may be run under
4932 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4933 help with this. See the comments in &_src/EDITME_& for details.
4937 .section "Configuration file format" "SECTconffilfor"
4938 .cindex "configuration file" "format of"
4939 .cindex "format" "configuration file"
4940 Exim's configuration file is divided into a number of different parts. General
4941 option settings must always appear at the start of the file. The other parts
4942 are all optional, and may appear in any order. Each part other than the first
4943 is introduced by the word &"begin"& followed by at least one literal
4944 space, and the name of the part. The optional parts are:
4947 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4950 .cindex "AUTH" "configuration"
4951 &'authenticators'&: Configuration settings for the authenticator drivers. These
4952 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4954 &'routers'&: Configuration settings for the router drivers. Routers process
4955 addresses and determine how the message is to be delivered (see chapters
4956 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4958 &'transports'&: Configuration settings for the transport drivers. Transports
4959 define mechanisms for copying messages to destinations (see chapters
4960 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4962 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4963 If there is no retry section, or if it is empty (that is, no retry rules are
4964 defined), Exim will not retry deliveries. In this situation, temporary errors
4965 are treated the same as permanent errors. Retry rules are discussed in chapter
4968 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4969 when new addresses are generated during delivery. Rewriting is discussed in
4970 chapter &<<CHAPrewrite>>&.
4972 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4973 want to use this feature, you must set
4975 LOCAL_SCAN_HAS_OPTIONS=yes
4977 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4978 facility are given in chapter &<<CHAPlocalscan>>&.
4981 .cindex "configuration file" "leading white space in"
4982 .cindex "configuration file" "trailing white space in"
4983 .cindex "white space" "in configuration file"
4984 Leading and trailing white space in configuration lines is always ignored.
4986 Blank lines in the file, and lines starting with a # character (ignoring
4987 leading white space) are treated as comments and are ignored. &*Note*&: A
4988 # character other than at the beginning of a line is not treated specially,
4989 and does not introduce a comment.
4991 Any non-comment line can be continued by ending it with a backslash. Note that
4992 the general rule for white space means that trailing white space after the
4993 backslash and leading white space at the start of continuation
4994 lines is ignored. Comment lines beginning with # (but not empty lines) may
4995 appear in the middle of a sequence of continuation lines.
4997 A convenient way to create a configuration file is to start from the
4998 default, which is supplied in &_src/configure.default_&, and add, delete, or
4999 change settings as required.
5001 The ACLs, retry rules, and rewriting rules have their own syntax which is
5002 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
5003 respectively. The other parts of the configuration file have some syntactic
5004 items in common, and these are described below, from section &<<SECTcos>>&
5005 onwards. Before that, the inclusion, macro, and conditional facilities are
5010 .section "File inclusions in the configuration file" "SECID41"
5011 .cindex "inclusions in configuration file"
5012 .cindex "configuration file" "including other files"
5013 .cindex "&`.include`& in configuration file"
5014 .cindex "&`.include_if_exists`& in configuration file"
5015 You can include other files inside Exim's runtime configuration file by
5018 &`.include`& <&'filename'&>
5019 &`.include_if_exists`& <&'filename'&>
5021 on a line by itself. Double quotes round the filename are optional. If you use
5022 the first form, a configuration error occurs if the file does not exist; the
5023 second form does nothing for non-existent files.
5024 The first form allows a relative name. It is resolved relative to
5025 the directory of the including file. For the second form an absolute filename
5028 Includes may be nested to any depth, but remember that Exim reads its
5029 configuration file often, so it is a good idea to keep them to a minimum.
5030 If you change the contents of an included file, you must HUP the daemon,
5031 because an included file is read only when the configuration itself is read.
5033 The processing of inclusions happens early, at a physical line level, so, like
5034 comment lines, an inclusion can be used in the middle of an option setting,
5037 hosts_lookup = a.b.c \
5040 Include processing happens after macro processing (see below). Its effect is to
5041 process the lines of the included file as if they occurred inline where the
5046 .section "Macros in the configuration file" "SECTmacrodefs"
5047 .cindex "macro" "description of"
5048 .cindex "configuration file" "macros"
5049 If a line in the main part of the configuration (that is, before the first
5050 &"begin"& line) begins with an upper case letter, it is taken as a macro
5051 definition, and must be of the form
5053 <&'name'&> = <&'rest of line'&>
5055 The name must consist of letters, digits, and underscores, and need not all be
5056 in upper case, though that is recommended. The rest of the line, including any
5057 continuations, is the replacement text, and has leading and trailing white
5058 space removed. Quotes are not removed. The replacement text can never end with
5059 a backslash character, but this doesn't seem to be a serious limitation.
5061 Macros may also be defined between router, transport, authenticator, or ACL
5062 definitions. They may not, however, be defined within an individual driver or
5063 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
5065 .section "Macro substitution" "SECID42"
5066 Once a macro is defined, all subsequent lines in the file (and any included
5067 files) are scanned for the macro name; if there are several macros, the line is
5068 scanned for each, in turn, in the order in which the macros are defined. The
5069 replacement text is not re-scanned for the current macro, though it is scanned
5070 for subsequently defined macros. For this reason, a macro name may not contain
5071 the name of a previously defined macro as a substring. You could, for example,
5074 &`ABCD_XYZ = `&<&'something'&>
5075 &`ABCD = `&<&'something else'&>
5077 but putting the definitions in the opposite order would provoke a configuration
5078 error. Macro expansion is applied to individual physical lines from the file,
5079 before checking for line continuation or file inclusion (see above). If a line
5080 consists solely of a macro name, and the expansion of the macro is empty, the
5081 line is ignored. A macro at the start of a line may turn the line into a
5082 comment line or a &`.include`& line.
5085 .section "Redefining macros" "SECID43"
5086 Once defined, the value of a macro can be redefined later in the configuration
5087 (or in an included file). Redefinition is specified by using &'=='& instead of
5092 MAC == updated value
5094 Redefinition does not alter the order in which the macros are applied to the
5095 subsequent lines of the configuration file. It is still the same order in which
5096 the macros were originally defined. All that changes is the macro's value.
5097 Redefinition makes it possible to accumulate values. For example:
5101 MAC == MAC and something added
5103 This can be helpful in situations where the configuration file is built
5104 from a number of other files.
5106 .section "Overriding macro values" "SECID44"
5107 The values set for macros in the configuration file can be overridden by the
5108 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5109 used, unless called by root or the Exim user. A definition on the command line
5110 using the &%-D%& option causes all definitions and redefinitions within the
5115 .section "Example of macro usage" "SECID45"
5116 As an example of macro usage, consider a configuration where aliases are looked
5117 up in a MySQL database. It helps to keep the file less cluttered if long
5118 strings such as SQL statements are defined separately as macros, for example:
5120 ALIAS_QUERY = select mailbox from user where \
5121 login='${quote_mysql:$local_part}';
5123 This can then be used in a &(redirect)& router setting like this:
5125 data = ${lookup mysql{ALIAS_QUERY}}
5127 In earlier versions of Exim macros were sometimes used for domain, host, or
5128 address lists. In Exim 4 these are handled better by named lists &-- see
5129 section &<<SECTnamedlists>>&.
5132 .section "Builtin macros" "SECTbuiltinmacros"
5133 Exim defines some macros depending on facilities available, which may
5134 differ due to build-time definitions and from one release to another.
5135 All of these macros start with an underscore.
5136 They can be used to conditionally include parts of a configuration
5139 The following classes of macros are defined:
5141 &` _HAVE_* `& build-time defines
5142 &` _DRIVER_ROUTER_* `& router drivers
5143 &` _DRIVER_TRANSPORT_* `& transport drivers
5144 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5145 &` _EXP_COND_* `& expansion conditions
5146 &` _EXP_ITEM_* `& expansion items
5147 &` _EXP_OP_* `& expansion operators
5148 &` _EXP_VAR_* `& expansion variables
5149 &` _LOG_* `& log_selector values
5150 &` _OPT_MAIN_* `& main config options
5151 &` _OPT_ROUTERS_* `& generic router options
5152 &` _OPT_TRANSPORTS_* `& generic transport options
5153 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5154 &` _OPT_ROUTER_*_* `& private router options
5155 &` _OPT_TRANSPORT_*_* `& private transport options
5156 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5159 Use an &"exim -bP macros"& command to get the list of macros.
5162 .section "Conditional skips in the configuration file" "SECID46"
5163 .cindex "configuration file" "conditional skips"
5164 .cindex "&`.ifdef`&"
5165 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5166 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5167 portions of the configuration file. The processing happens whenever the file is
5168 read (that is, when an Exim binary starts to run).
5170 The implementation is very simple. Instances of the first four directives must
5171 be followed by text that includes the names of one or macros. The condition
5172 that is tested is whether or not any macro substitution has taken place in the
5176 message_size_limit = 50M
5178 message_size_limit = 100M
5181 sets a message size limit of 50M if the macro &`AAA`& is defined
5182 (or &`A`& or &`AA`&), and 100M
5183 otherwise. If there is more than one macro named on the line, the condition
5184 is true if any of them are defined. That is, it is an &"or"& condition. To
5185 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5187 Although you can use a macro expansion to generate one of these directives,
5188 it is not very useful, because the condition &"there was a macro substitution
5189 in this line"& will always be true.
5191 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5192 to clarify complicated nestings.
5196 .section "Common option syntax" "SECTcos"
5197 .cindex "common option syntax"
5198 .cindex "syntax of common options"
5199 .cindex "configuration file" "common option syntax"
5200 For the main set of options, driver options, and &[local_scan()]& options,
5201 each setting is on a line by itself, and starts with a name consisting of
5202 lower-case letters and underscores. Many options require a data value, and in
5203 these cases the name must be followed by an equals sign (with optional white
5204 space) and then the value. For example:
5206 qualify_domain = mydomain.example.com
5208 .cindex "hiding configuration option values"
5209 .cindex "configuration options" "hiding value of"
5210 .cindex "options" "hiding value of"
5211 Some option settings may contain sensitive data, for example, passwords for
5212 accessing databases. To stop non-admin users from using the &%-bP%& command
5213 line option to read these values, you can precede the option settings with the
5214 word &"hide"&. For example:
5216 hide mysql_servers = localhost/users/admin/secret-password
5218 For non-admin users, such options are displayed like this:
5220 mysql_servers = <value not displayable>
5222 If &"hide"& is used on a driver option, it hides the value of that option on
5223 all instances of the same driver.
5225 The following sections describe the syntax used for the different data types
5226 that are found in option settings.
5229 .section "Boolean options" "SECID47"
5230 .cindex "format" "boolean"
5231 .cindex "boolean configuration values"
5232 .oindex "&%no_%&&'xxx'&"
5233 .oindex "&%not_%&&'xxx'&"
5234 Options whose type is given as boolean are on/off switches. There are two
5235 different ways of specifying such options: with and without a data value. If
5236 the option name is specified on its own without data, the switch is turned on;
5237 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5238 boolean options may be followed by an equals sign and one of the words
5239 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5240 the following two settings have exactly the same effect:
5245 The following two lines also have the same (opposite) effect:
5250 You can use whichever syntax you prefer.
5255 .section "Integer values" "SECID48"
5256 .cindex "integer configuration values"
5257 .cindex "format" "integer"
5258 If an option's type is given as &"integer"&, the value can be given in decimal,
5259 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5260 number is assumed. Otherwise, it is treated as an octal number unless it starts
5261 with the characters &"0x"&, in which case the remainder is interpreted as a
5264 If an integer value is followed by the letter K, it is multiplied by 1024; if
5265 it is followed by the letter M, it is multiplied by 1024x1024;
5266 if by the letter G, 1024x1024x1024.
5268 of integer option settings are output, values which are an exact multiple of
5269 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5270 and M. The printing style is independent of the actual input format that was
5274 .section "Octal integer values" "SECID49"
5275 .cindex "integer format"
5276 .cindex "format" "octal integer"
5277 If an option's type is given as &"octal integer"&, its value is always
5278 interpreted as an octal number, whether or not it starts with the digit zero.
5279 Such options are always output in octal.
5282 .section "Fixed point numbers" "SECID50"
5283 .cindex "fixed point configuration values"
5284 .cindex "format" "fixed point"
5285 If an option's type is given as &"fixed-point"&, its value must be a decimal
5286 integer, optionally followed by a decimal point and up to three further digits.
5290 .section "Time intervals" "SECTtimeformat"
5291 .cindex "time interval" "specifying in configuration"
5292 .cindex "format" "time interval"
5293 A time interval is specified as a sequence of numbers, each followed by one of
5294 the following letters, with no intervening white space:
5304 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5305 intervals are output in the same format. Exim does not restrict the values; it
5306 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5310 .section "String values" "SECTstrings"
5311 .cindex "string" "format of configuration values"
5312 .cindex "format" "string"
5313 If an option's type is specified as &"string"&, the value can be specified with
5314 or without double-quotes. If it does not start with a double-quote, the value
5315 consists of the remainder of the line plus any continuation lines, starting at
5316 the first character after any leading white space, with trailing white space
5317 removed, and with no interpretation of the characters in the string. Because
5318 Exim removes comment lines (those beginning with #) at an early stage, they can
5319 appear in the middle of a multi-line string. The following two settings are
5320 therefore equivalent:
5322 trusted_users = uucp:mail
5323 trusted_users = uucp:\
5324 # This comment line is ignored
5327 .cindex "string" "quoted"
5328 .cindex "escape characters in quoted strings"
5329 If a string does start with a double-quote, it must end with a closing
5330 double-quote, and any backslash characters other than those used for line
5331 continuation are interpreted as escape characters, as follows:
5334 .irow &`\\`& "single backslash"
5335 .irow &`\n`& "newline"
5336 .irow &`\r`& "carriage return"
5338 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5339 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5343 If a backslash is followed by some other character, including a double-quote
5344 character, that character replaces the pair.
5346 Quoting is necessary only if you want to make use of the backslash escapes to
5347 insert special characters, or if you need to specify a value with leading or
5348 trailing spaces. These cases are rare, so quoting is almost never needed in
5349 current versions of Exim. In versions of Exim before 3.14, quoting was required
5350 in order to continue lines, so you may come across older configuration files
5351 and examples that apparently quote unnecessarily.
5354 .section "Expanded strings" "SECID51"
5355 .cindex "expansion" "definition of"
5356 Some strings in the configuration file are subjected to &'string expansion'&,
5357 by which means various parts of the string may be changed according to the
5358 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5359 is as just described; in particular, the handling of backslashes in quoted
5360 strings is done as part of the input process, before expansion takes place.
5361 However, backslash is also an escape character for the expander, so any
5362 backslashes that are required for that reason must be doubled if they are
5363 within a quoted configuration string.
5366 .section "User and group names" "SECID52"
5367 .cindex "user name" "format of"
5368 .cindex "format" "user name"
5369 .cindex "groups" "name format"
5370 .cindex "format" "group name"
5371 User and group names are specified as strings, using the syntax described
5372 above, but the strings are interpreted specially. A user or group name must
5373 either consist entirely of digits, or be a name that can be looked up using the
5374 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5377 .section "List construction" "SECTlistconstruct"
5378 .cindex "list" "syntax of in configuration"
5379 .cindex "format" "list item in configuration"
5380 .cindex "string" "list, definition of"
5381 The data for some configuration options is a list of items, with colon as the
5382 default separator. Many of these options are shown with type &"string list"& in
5383 the descriptions later in this document. Others are listed as &"domain list"&,
5384 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5385 are all the same; however, those other than &"string list"& are subject to
5386 particular kinds of interpretation, as described in chapter
5387 &<<CHAPdomhosaddlists>>&.
5389 In all these cases, the entire list is treated as a single string as far as the
5390 input syntax is concerned. The &%trusted_users%& setting in section
5391 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5392 in a list, it must be entered as two colons. Leading and trailing white space
5393 on each item in a list is ignored. This makes it possible to include items that
5394 start with a colon, and in particular, certain forms of IPv6 address. For
5397 local_interfaces = 127.0.0.1 : ::::1
5399 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5401 &*Note*&: Although leading and trailing white space is ignored in individual
5402 list items, it is not ignored when parsing the list. The spaces around the first
5403 colon in the example above are necessary. If they were not there, the list would
5404 be interpreted as the two items 127.0.0.1:: and 1.
5406 .section "Changing list separators" "SECTlistsepchange"
5407 .cindex "list separator" "changing"
5408 .cindex "IPv6" "addresses in lists"
5409 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5410 introduced to allow the separator character to be changed. If a list begins
5411 with a left angle bracket, followed by any punctuation character, that
5412 character is used instead of colon as the list separator. For example, the list
5413 above can be rewritten to use a semicolon separator like this:
5415 local_interfaces = <; 127.0.0.1 ; ::1
5417 This facility applies to all lists, with the exception of the list in
5418 &%log_file_path%&. It is recommended that the use of non-colon separators be
5419 confined to circumstances where they really are needed.
5421 .cindex "list separator" "newline as"
5422 .cindex "newline" "as list separator"
5423 It is also possible to use newline and other control characters (those with
5424 code values less than 32, plus DEL) as separators in lists. Such separators
5425 must be provided literally at the time the list is processed. For options that
5426 are string-expanded, you can write the separator using a normal escape
5427 sequence. This will be processed by the expander before the string is
5428 interpreted as a list. For example, if a newline-separated list of domains is
5429 generated by a lookup, you can process it directly by a line such as this:
5431 domains = <\n ${lookup mysql{.....}}
5433 This avoids having to change the list separator in such data. You are unlikely
5434 to want to use a control character as a separator in an option that is not
5435 expanded, because the value is literal text. However, it can be done by giving
5436 the value in quotes. For example:
5438 local_interfaces = "<\n 127.0.0.1 \n ::1"
5440 Unlike printing character separators, which can be included in list items by
5441 doubling, it is not possible to include a control character as data when it is
5442 set as the separator. Two such characters in succession are interpreted as
5443 enclosing an empty list item.
5447 .section "Empty items in lists" "SECTempitelis"
5448 .cindex "list" "empty item in"
5449 An empty item at the end of a list is always ignored. In other words, trailing
5450 separator characters are ignored. Thus, the list in
5452 senders = user@domain :
5454 contains only a single item. If you want to include an empty string as one item
5455 in a list, it must not be the last item. For example, this list contains three
5456 items, the second of which is empty:
5458 senders = user1@domain : : user2@domain
5460 &*Note*&: There must be white space between the two colons, as otherwise they
5461 are interpreted as representing a single colon data character (and the list
5462 would then contain just one item). If you want to specify a list that contains
5463 just one, empty item, you can do it as in this example:
5467 In this case, the first item is empty, and the second is discarded because it
5468 is at the end of the list.
5473 .section "Format of driver configurations" "SECTfordricon"
5474 .cindex "drivers" "configuration format"
5475 There are separate parts in the configuration for defining routers, transports,
5476 and authenticators. In each part, you are defining a number of driver
5477 instances, each with its own set of options. Each driver instance is defined by
5478 a sequence of lines like this:
5480 <&'instance name'&>:
5485 In the following example, the instance name is &(localuser)&, and it is
5486 followed by three options settings:
5491 transport = local_delivery
5493 For each driver instance, you specify which Exim code module it uses &-- by the
5494 setting of the &%driver%& option &-- and (optionally) some configuration
5495 settings. For example, in the case of transports, if you want a transport to
5496 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5497 a local file you would use the &(appendfile)& driver. Each of the drivers is
5498 described in detail in its own separate chapter later in this manual.
5500 You can have several routers, transports, or authenticators that are based on
5501 the same underlying driver (each must have a different instance name).
5503 The order in which routers are defined is important, because addresses are
5504 passed to individual routers one by one, in order. The order in which
5505 transports are defined does not matter at all. The order in which
5506 authenticators are defined is used only when Exim, as a client, is searching
5507 them to find one that matches an authentication mechanism offered by the
5510 .cindex "generic options"
5511 .cindex "options" "generic &-- definition of"
5512 Within a driver instance definition, there are two kinds of option: &'generic'&
5513 and &'private'&. The generic options are those that apply to all drivers of the
5514 same type (that is, all routers, all transports or all authenticators). The
5515 &%driver%& option is a generic option that must appear in every definition.
5516 .cindex "private options"
5517 The private options are special for each driver, and none need appear, because
5518 they all have default values.
5520 The options may appear in any order, except that the &%driver%& option must
5521 precede any private options, since these depend on the particular driver. For
5522 this reason, it is recommended that &%driver%& always be the first option.
5524 Driver instance names, which are used for reference in log entries and
5525 elsewhere, can be any sequence of letters, digits, and underscores (starting
5526 with a letter) and must be unique among drivers of the same type. A router and
5527 a transport (for example) can each have the same name, but no two router
5528 instances can have the same name. The name of a driver instance should not be
5529 confused with the name of the underlying driver module. For example, the
5530 configuration lines:
5535 create an instance of the &(smtp)& transport driver whose name is
5536 &(remote_smtp)&. The same driver code can be used more than once, with
5537 different instance names and different option settings each time. A second
5538 instance of the &(smtp)& transport, with different options, might be defined
5544 command_timeout = 10s
5546 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5547 these transport instances from routers, and these names would appear in log
5550 Comment lines may be present in the middle of driver specifications. The full
5551 list of option settings for any particular driver instance, including all the
5552 defaulted values, can be extracted by making use of the &%-bP%& command line
5560 . ////////////////////////////////////////////////////////////////////////////
5561 . ////////////////////////////////////////////////////////////////////////////
5563 .chapter "The default configuration file" "CHAPdefconfil"
5564 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5565 .cindex "default" "configuration file &""walk through""&"
5566 The default configuration file supplied with Exim as &_src/configure.default_&
5567 is sufficient for a host with simple mail requirements. As an introduction to
5568 the way Exim is configured, this chapter &"walks through"& the default
5569 configuration, giving brief explanations of the settings. Detailed descriptions
5570 of the options are given in subsequent chapters. The default configuration file
5571 itself contains extensive comments about ways you might want to modify the
5572 initial settings. However, note that there are many options that are not
5573 mentioned at all in the default configuration.
5577 .section "Macros" "SECTdefconfmacros"
5578 All macros should be defined before any options.
5580 One macro is specified, but commented out, in the default configuration:
5582 # ROUTER_SMARTHOST=MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
5584 If all off-site mail is expected to be delivered to a "smarthost", then set the
5585 hostname here and uncomment the macro. This will affect which router is used
5586 later on. If this is left commented out, then Exim will perform direct-to-MX
5587 deliveries using a &(dnslookup)& router.
5589 In addition to macros defined here, Exim includes a number of built-in macros
5590 to enable configuration to be guarded by a binary built with support for a
5591 given feature. See section &<<SECTbuiltinmacros>>& for more details.
5594 .section "Main configuration settings" "SECTdefconfmain"
5595 The main (global) configuration option settings section must always come first
5596 in the file, after the macros.
5597 The first thing you'll see in the file, after some initial comments, is the line
5599 # primary_hostname =
5601 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5602 to know the official, fully qualified name of your host, and this is where you
5603 can specify it. However, in most cases you do not need to set this option. When
5604 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5606 The first three non-comment configuration lines are as follows:
5608 domainlist local_domains = @
5609 domainlist relay_to_domains =
5610 hostlist relay_from_hosts = 127.0.0.1
5612 These are not, in fact, option settings. They are definitions of two named
5613 domain lists and one named host list. Exim allows you to give names to lists of
5614 domains, hosts, and email addresses, in order to make it easier to manage the
5615 configuration file (see section &<<SECTnamedlists>>&).
5617 The first line defines a domain list called &'local_domains'&; this is used
5618 later in the configuration to identify domains that are to be delivered
5621 .cindex "@ in a domain list"
5622 There is just one item in this list, the string &"@"&. This is a special form
5623 of entry which means &"the name of the local host"&. Thus, if the local host is
5624 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5625 be delivered locally. Because the local host's name is referenced indirectly,
5626 the same configuration file can be used on different hosts.
5628 The second line defines a domain list called &'relay_to_domains'&, but the
5629 list itself is empty. Later in the configuration we will come to the part that
5630 controls mail relaying through the local host; it allows relaying to any
5631 domains in this list. By default, therefore, no relaying on the basis of a mail
5632 domain is permitted.
5634 The third line defines a host list called &'relay_from_hosts'&. This list is
5635 used later in the configuration to permit relaying from any host or IP address
5636 that matches the list. The default contains just the IP address of the IPv4
5637 loopback interface, which means that processes on the local host are able to
5638 submit mail for relaying by sending it over TCP/IP to that interface. No other
5639 hosts are permitted to submit messages for relaying.
5641 Just to be sure there's no misunderstanding: at this point in the configuration
5642 we aren't actually setting up any controls. We are just defining some domains
5643 and hosts that will be used in the controls that are specified later.
5645 The next two configuration lines are genuine option settings:
5647 acl_smtp_rcpt = acl_check_rcpt
5648 acl_smtp_data = acl_check_data
5650 These options specify &'Access Control Lists'& (ACLs) that are to be used
5651 during an incoming SMTP session for every recipient of a message (every RCPT
5652 command), and after the contents of the message have been received,
5653 respectively. The names of the lists are &'acl_check_rcpt'& and
5654 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5655 section of the configuration. The RCPT ACL controls which recipients are
5656 accepted for an incoming message &-- if a configuration does not provide an ACL
5657 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5658 contents of a message to be checked.
5660 Two commented-out option settings are next:
5662 # av_scanner = clamd:/tmp/clamd
5663 # spamd_address = 127.0.0.1 783
5665 These are example settings that can be used when Exim is compiled with the
5666 content-scanning extension. The first specifies the interface to the virus
5667 scanner, and the second specifies the interface to SpamAssassin. Further
5668 details are given in chapter &<<CHAPexiscan>>&.
5670 Three more commented-out option settings follow:
5672 # tls_advertise_hosts = *
5673 # tls_certificate = /etc/ssl/exim.crt
5674 # tls_privatekey = /etc/ssl/exim.pem
5676 These are example settings that can be used when Exim is compiled with
5677 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5678 first one specifies the list of clients that are allowed to use TLS when
5679 connecting to this server; in this case, the wildcard means all clients. The
5680 other options specify where Exim should find its TLS certificate and private
5681 key, which together prove the server's identity to any clients that connect.
5682 More details are given in chapter &<<CHAPTLS>>&.
5684 Another two commented-out option settings follow:
5686 # daemon_smtp_ports = 25 : 465 : 587
5687 # tls_on_connect_ports = 465
5689 .cindex "port" "465 and 587"
5690 .cindex "port" "for message submission"
5691 .cindex "message" "submission, ports for"
5692 .cindex "submissions protocol"
5693 .cindex "smtps protocol"
5694 .cindex "ssmtp protocol"
5695 .cindex "SMTP" "submissions protocol"
5696 .cindex "SMTP" "ssmtp protocol"
5697 .cindex "SMTP" "smtps protocol"
5698 These options provide better support for roaming users who wish to use this
5699 server for message submission. They are not much use unless you have turned on
5700 TLS (as described in the previous paragraph) and authentication (about which
5701 more in section &<<SECTdefconfauth>>&).
5702 Mail submission from mail clients (MUAs) should be separate from inbound mail
5703 to your domain (MX delivery) for various good reasons (eg, ability to impose
5704 much saner TLS protocol and ciphersuite requirements without unintended
5706 RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
5707 which uses STARTTLS, so this is the &"submission"& port.
5708 RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
5709 which should be used in preference to 587.
5710 You should also consider deploying SRV records to help clients find
5712 Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
5714 Two more commented-out options settings follow:
5717 # qualify_recipient =
5719 The first of these specifies a domain that Exim uses when it constructs a
5720 complete email address from a local login name. This is often needed when Exim
5721 receives a message from a local process. If you do not set &%qualify_domain%&,
5722 the value of &%primary_hostname%& is used. If you set both of these options,
5723 you can have different qualification domains for sender and recipient
5724 addresses. If you set only the first one, its value is used in both cases.
5726 .cindex "domain literal" "recognizing format"
5727 The following line must be uncommented if you want Exim to recognize
5728 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5729 (an IP address within square brackets) instead of a named domain.
5731 # allow_domain_literals
5733 The RFCs still require this form, but many people think that in the modern
5734 Internet it makes little sense to permit mail to be sent to specific hosts by
5735 quoting their IP addresses. This ancient format has been used by people who
5736 try to abuse hosts by using them for unwanted relaying. However, some
5737 people believe there are circumstances (for example, messages addressed to
5738 &'postmaster'&) where domain literals are still useful.
5740 The next configuration line is a kind of trigger guard:
5744 It specifies that no delivery must ever be run as the root user. The normal
5745 convention is to set up &'root'& as an alias for the system administrator. This
5746 setting is a guard against slips in the configuration.
5747 The list of users specified by &%never_users%& is not, however, the complete
5748 list; the build-time configuration in &_Local/Makefile_& has an option called
5749 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5750 contents of &%never_users%& are added to this list. By default
5751 FIXED_NEVER_USERS also specifies root.
5753 When a remote host connects to Exim in order to send mail, the only information
5754 Exim has about the host's identity is its IP address. The next configuration
5759 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5760 in order to get a host name. This improves the quality of the logging
5761 information, but if you feel it is too expensive, you can remove it entirely,
5762 or restrict the lookup to hosts on &"nearby"& networks.
5763 Note that it is not always possible to find a host name from an IP address,
5764 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5767 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5768 1413 (hence their names):
5771 rfc1413_query_timeout = 0s
5773 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5774 Few hosts offer RFC1413 service these days; calls have to be
5775 terminated by a timeout and this needlessly delays the startup
5776 of an incoming SMTP connection.
5777 If you have hosts for which you trust RFC1413 and need this
5778 information, you can change this.
5780 This line enables an efficiency SMTP option. It is negotiated by clients
5781 and not expected to cause problems but can be disabled if needed.
5786 When Exim receives messages over SMTP connections, it expects all addresses to
5787 be fully qualified with a domain, as required by the SMTP definition. However,
5788 if you are running a server to which simple clients submit messages, you may
5789 find that they send unqualified addresses. The two commented-out options:
5791 # sender_unqualified_hosts =
5792 # recipient_unqualified_hosts =
5794 show how you can specify hosts that are permitted to send unqualified sender
5795 and recipient addresses, respectively.
5797 The &%log_selector%& option is used to increase the detail of logging
5800 log_selector = +smtp_protocol_error +smtp_syntax_error \
5801 +tls_certificate_verified
5804 The &%percent_hack_domains%& option is also commented out:
5806 # percent_hack_domains =
5808 It provides a list of domains for which the &"percent hack"& is to operate.
5809 This is an almost obsolete form of explicit email routing. If you do not know
5810 anything about it, you can safely ignore this topic.
5812 The next two settings in the main part of the default configuration are
5813 concerned with messages that have been &"frozen"& on Exim's queue. When a
5814 message is frozen, Exim no longer continues to try to deliver it. Freezing
5815 occurs when a bounce message encounters a permanent failure because the sender
5816 address of the original message that caused the bounce is invalid, so the
5817 bounce cannot be delivered. This is probably the most common case, but there
5818 are also other conditions that cause freezing, and frozen messages are not
5819 always bounce messages.
5821 ignore_bounce_errors_after = 2d
5822 timeout_frozen_after = 7d
5824 The first of these options specifies that failing bounce messages are to be
5825 discarded after 2 days in the queue. The second specifies that any frozen
5826 message (whether a bounce message or not) is to be timed out (and discarded)
5827 after a week. In this configuration, the first setting ensures that no failing
5828 bounce message ever lasts a week.
5830 Exim queues it's messages in a spool directory. If you expect to have
5831 large queues, you may consider using this option. It splits the spool
5832 directory into subdirectories to avoid file system degradation from
5833 many files in a single directory, resulting in better performance.
5834 Manual manipulation of queued messages becomes more complex (though fortunately
5837 # split_spool_directory = true
5840 In an ideal world everybody follows the standards. For non-ASCII
5841 messages RFC 2047 is a standard, allowing a maximum line length of 76
5842 characters. Exim adheres that standard and won't process messages which
5843 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5844 In particular, the Exim maintainers have had multiple reports of
5845 problems from Russian administrators of issues until they disable this
5846 check, because of some popular, yet buggy, mail composition software.
5848 # check_rfc2047_length = false
5851 If you need to be strictly RFC compliant you may wish to disable the
5852 8BITMIME advertisement. Use this, if you exchange mails with systems
5853 that are not 8-bit clean.
5855 # accept_8bitmime = false
5858 Libraries you use may depend on specific environment settings. This
5859 imposes a security risk (e.g. PATH). There are two lists:
5860 &%keep_environment%& for the variables to import as they are, and
5861 &%add_environment%& for variables we want to set to a fixed value.
5862 Note that TZ is handled separately, by the &%timezone%& runtime
5863 option and by the TIMEZONE_DEFAULT buildtime option.
5865 # keep_environment = ^LDAP
5866 # add_environment = PATH=/usr/bin::/bin
5870 .section "ACL configuration" "SECID54"
5871 .cindex "default" "ACLs"
5872 .cindex "&ACL;" "default configuration"
5873 In the default configuration, the ACL section follows the main configuration.
5874 It starts with the line
5878 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5879 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5880 and &%acl_smtp_data%& above.
5882 .cindex "RCPT" "ACL for"
5883 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5884 RCPT command specifies one of the message's recipients. The ACL statements
5885 are considered in order, until the recipient address is either accepted or
5886 rejected. The RCPT command is then accepted or rejected, according to the
5887 result of the ACL processing.
5891 This line, consisting of a name terminated by a colon, marks the start of the
5896 This ACL statement accepts the recipient if the sending host matches the list.
5897 But what does that strange list mean? It doesn't actually contain any host
5898 names or IP addresses. The presence of the colon puts an empty item in the
5899 list; Exim matches this only if the incoming message did not come from a remote
5900 host, because in that case, the remote hostname is empty. The colon is
5901 important. Without it, the list itself is empty, and can never match anything.
5903 What this statement is doing is to accept unconditionally all recipients in
5904 messages that are submitted by SMTP from local processes using the standard
5905 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5908 deny domains = +local_domains
5909 local_parts = ^[.] : ^.*[@%!/|]
5910 message = Restricted characters in address
5912 deny domains = !+local_domains
5913 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5914 message = Restricted characters in address
5916 These statements are concerned with local parts that contain any of the
5917 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5918 Although these characters are entirely legal in local parts (in the case of
5919 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5920 in Internet mail addresses.
5922 The first three have in the past been associated with explicitly routed
5923 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5924 option). Addresses containing these characters are regularly tried by spammers
5925 in an attempt to bypass relaying restrictions, and also by open relay testing
5926 programs. Unless you really need them it is safest to reject these characters
5927 at this early stage. This configuration is heavy-handed in rejecting these
5928 characters for all messages it accepts from remote hosts. This is a deliberate
5929 policy of being as safe as possible.
5931 The first rule above is stricter, and is applied to messages that are addressed
5932 to one of the local domains handled by this host. This is implemented by the
5933 first condition, which restricts it to domains that are listed in the
5934 &'local_domains'& domain list. The &"+"& character is used to indicate a
5935 reference to a named list. In this configuration, there is just one domain in
5936 &'local_domains'&, but in general there may be many.
5938 The second condition on the first statement uses two regular expressions to
5939 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5940 or &"|"&. If you have local accounts that include these characters, you will
5941 have to modify this rule.
5943 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5944 allows them because they have been encountered in practice. (Consider the
5945 common convention of local parts constructed as
5946 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5947 the author of Exim, who has no second initial.) However, a local part starting
5948 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5949 filename (for example, for a mailing list). This is also true for local parts
5950 that contain slashes. A pipe symbol can also be troublesome if the local part
5951 is incorporated unthinkingly into a shell command line.
5953 The second rule above applies to all other domains, and is less strict. This
5954 allows your own users to send outgoing messages to sites that use slashes
5955 and vertical bars in their local parts. It blocks local parts that begin
5956 with a dot, slash, or vertical bar, but allows these characters within the
5957 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5958 and &"!"& is blocked, as before. The motivation here is to prevent your users
5959 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5961 accept local_parts = postmaster
5962 domains = +local_domains
5964 This statement, which has two conditions, accepts an incoming address if the
5965 local part is &'postmaster'& and the domain is one of those listed in the
5966 &'local_domains'& domain list. The &"+"& character is used to indicate a
5967 reference to a named list. In this configuration, there is just one domain in
5968 &'local_domains'&, but in general there may be many.
5970 The presence of this statement means that mail to postmaster is never blocked
5971 by any of the subsequent tests. This can be helpful while sorting out problems
5972 in cases where the subsequent tests are incorrectly denying access.
5974 require verify = sender
5976 This statement requires the sender address to be verified before any subsequent
5977 ACL statement can be used. If verification fails, the incoming recipient
5978 address is refused. Verification consists of trying to route the address, to
5979 see if a bounce message could be delivered to it. In the case of remote
5980 addresses, basic verification checks only the domain, but &'callouts'& can be
5981 used for more verification if required. Section &<<SECTaddressverification>>&
5982 discusses the details of address verification.
5984 accept hosts = +relay_from_hosts
5985 control = submission
5987 This statement accepts the address if the message is coming from one of the
5988 hosts that are defined as being allowed to relay through this host. Recipient
5989 verification is omitted here, because in many cases the clients are dumb MUAs
5990 that do not cope well with SMTP error responses. For the same reason, the
5991 second line specifies &"submission mode"& for messages that are accepted. This
5992 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5993 messages that are deficient in some way, for example, because they lack a
5994 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5995 probably add recipient verification here, and disable submission mode.
5997 accept authenticated = *
5998 control = submission
6000 This statement accepts the address if the client host has authenticated itself.
6001 Submission mode is again specified, on the grounds that such messages are most
6002 likely to come from MUAs. The default configuration does not define any
6003 authenticators, though it does include some nearly complete commented-out
6004 examples described in &<<SECTdefconfauth>>&. This means that no client can in
6005 fact authenticate until you complete the authenticator definitions.
6007 require message = relay not permitted
6008 domains = +local_domains : +relay_to_domains
6010 This statement rejects the address if its domain is neither a local domain nor
6011 one of the domains for which this host is a relay.
6013 require verify = recipient
6015 This statement requires the recipient address to be verified; if verification
6016 fails, the address is rejected.
6018 # deny dnslists = black.list.example
6019 # message = rejected because $sender_host_address \
6020 # is in a black list at $dnslist_domain\n\
6023 # warn dnslists = black.list.example
6024 # add_header = X-Warning: $sender_host_address is in \
6025 # a black list at $dnslist_domain
6026 # log_message = found in $dnslist_domain
6028 These commented-out lines are examples of how you could configure Exim to check
6029 sending hosts against a DNS black list. The first statement rejects messages
6030 from blacklisted hosts, whereas the second just inserts a warning header
6033 # require verify = csa
6035 This commented-out line is an example of how you could turn on client SMTP
6036 authorization (CSA) checking. Such checks do DNS lookups for special SRV
6041 The final statement in the first ACL unconditionally accepts any recipient
6042 address that has successfully passed all the previous tests.
6046 This line marks the start of the second ACL, and names it. Most of the contents
6047 of this ACL are commented out:
6050 # message = This message contains a virus \
6053 These lines are examples of how to arrange for messages to be scanned for
6054 viruses when Exim has been compiled with the content-scanning extension, and a
6055 suitable virus scanner is installed. If the message is found to contain a
6056 virus, it is rejected with the given custom error message.
6058 # warn spam = nobody
6059 # message = X-Spam_score: $spam_score\n\
6060 # X-Spam_score_int: $spam_score_int\n\
6061 # X-Spam_bar: $spam_bar\n\
6062 # X-Spam_report: $spam_report
6064 These lines are an example of how to arrange for messages to be scanned by
6065 SpamAssassin when Exim has been compiled with the content-scanning extension,
6066 and SpamAssassin has been installed. The SpamAssassin check is run with
6067 &`nobody`& as its user parameter, and the results are added to the message as a
6068 series of extra header line. In this case, the message is not rejected,
6069 whatever the spam score.
6073 This final line in the DATA ACL accepts the message unconditionally.
6076 .section "Router configuration" "SECID55"
6077 .cindex "default" "routers"
6078 .cindex "routers" "default"
6079 The router configuration comes next in the default configuration, introduced
6084 Routers are the modules in Exim that make decisions about where to send
6085 messages. An address is passed to each router, in turn, until it is either
6086 accepted, or failed. This means that the order in which you define the routers
6087 matters. Each router is fully described in its own chapter later in this
6088 manual. Here we give only brief overviews.
6091 # driver = ipliteral
6092 # domains = !+local_domains
6093 # transport = remote_smtp
6095 .cindex "domain literal" "default router"
6096 This router is commented out because the majority of sites do not want to
6097 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
6098 you uncomment this router, you also need to uncomment the setting of
6099 &%allow_domain_literals%& in the main part of the configuration.
6101 Which router is used next depends upon whether or not the ROUTER_SMARTHOST
6102 macro has been defined, per
6104 .ifdef ROUTER_SMARTHOST
6113 If ROUTER_SMARTHOST has been defined, either at the top of the file or on the
6114 command-line, then we route all non-local mail to that smarthost; otherwise, we'll
6115 perform DNS lookups for direct-to-MX lookup. Any mail which is to a local domain will
6116 skip these routers because of the &%domains%& option.
6120 driver = manualroute
6121 domains = ! +local_domains
6122 transport = smarthost_smtp
6123 route_data = ROUTER_SMARTHOST
6124 ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
6127 This router only handles mail which is not to any local domains; this is
6128 specified by the line
6130 domains = ! +local_domains
6132 The &%domains%& option lists the domains to which this router applies, but the
6133 exclamation mark is a negation sign, so the router is used only for domains
6134 that are not in the domain list called &'local_domains'& (which was defined at
6135 the start of the configuration). The plus sign before &'local_domains'&
6136 indicates that it is referring to a named list. Addresses in other domains are
6137 passed on to the following routers.
6139 The name of the router driver is &(manualroute)& because we are manually
6140 specifying how mail should be routed onwards, instead of using DNS MX.
6141 While the name of this router instance is arbitrary, the &%driver%& option must
6142 be one of the driver modules that is in the Exim binary.
6144 With no pre-conditions other than &%domains%&, all mail for non-local domains
6145 will be handled by this router, and the &%no_more%& setting will ensure that no
6146 other routers will be used for messages matching the pre-conditions. See
6147 &<<SECTrouprecon>>& for more on how the pre-conditions apply. For messages which
6148 are handled by this router, we provide a hostname to deliver to in &%route_data%&
6149 and the macro supplies the value; the address is then queued for the
6150 &(smarthost_smtp)& transport.
6155 domains = ! +local_domains
6156 transport = remote_smtp
6157 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
6160 The &%domains%& option behaves as per smarthost, above.
6162 The name of the router driver is &(dnslookup)&,
6163 and is specified by the &%driver%& option. Do not be confused by the fact that
6164 the name of this router instance is the same as the name of the driver. The
6165 instance name is arbitrary, but the name set in the &%driver%& option must be
6166 one of the driver modules that is in the Exim binary.
6168 The &(dnslookup)& router routes addresses by looking up their domains in the
6169 DNS in order to obtain a list of hosts to which the address is routed. If the
6170 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6171 specified by the &%transport%& option. If the router does not find the domain
6172 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6173 the address fails and is bounced.
6175 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6176 be entirely ignored. This option is present because a number of cases have been
6177 encountered where MX records in the DNS point to host names
6178 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6179 Completely ignoring these IP addresses causes Exim to fail to route the
6180 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6181 continue to try to deliver the message periodically until the address timed
6188 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6190 file_transport = address_file
6191 pipe_transport = address_pipe
6193 Control reaches this and subsequent routers only for addresses in the local
6194 domains. This router checks to see whether the local part is defined as an
6195 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6196 data that it looks up from that file. If no data is found for the local part,
6197 the value of the &%data%& option is empty, causing the address to be passed to
6200 &_/etc/aliases_& is a conventional name for the system aliases file that is
6201 often used. That is why it is referenced by from the default configuration
6202 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6203 &_Local/Makefile_& before building Exim.
6208 # local_part_suffix = +* : -*
6209 # local_part_suffix_optional
6210 file = $home/.forward
6215 file_transport = address_file
6216 pipe_transport = address_pipe
6217 reply_transport = address_reply
6219 This is the most complicated router in the default configuration. It is another
6220 redirection router, but this time it is looking for forwarding data set up by
6221 individual users. The &%check_local_user%& setting specifies a check that the
6222 local part of the address is the login name of a local user. If it is not, the
6223 router is skipped. The two commented options that follow &%check_local_user%&,
6226 # local_part_suffix = +* : -*
6227 # local_part_suffix_optional
6229 .vindex "&$local_part_suffix$&"
6230 show how you can specify the recognition of local part suffixes. If the first
6231 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6232 by any sequence of characters, is removed from the local part and placed in the
6233 variable &$local_part_suffix$&. The second suffix option specifies that the
6234 presence of a suffix in the local part is optional. When a suffix is present,
6235 the check for a local login uses the local part with the suffix removed.
6237 When a local user account is found, the file called &_.forward_& in the user's
6238 home directory is consulted. If it does not exist, or is empty, the router
6239 declines. Otherwise, the contents of &_.forward_& are interpreted as
6240 redirection data (see chapter &<<CHAPredirect>>& for more details).
6242 .cindex "Sieve filter" "enabling in default router"
6243 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6244 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6245 is commented out by default), the contents of the file are interpreted as a set
6246 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6247 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6248 separate document entitled &'Exim's interfaces to mail filtering'&.
6250 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6251 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6252 There are two reasons for doing this:
6255 Whether or not a local user has a &_.forward_& file is not really relevant when
6256 checking an address for validity; it makes sense not to waste resources doing
6259 More importantly, when Exim is verifying addresses or handling an EXPN
6260 command during an SMTP session, it is running as the Exim user, not as root.
6261 The group is the Exim group, and no additional groups are set up.
6262 It may therefore not be possible for Exim to read users' &_.forward_& files at
6266 The setting of &%check_ancestor%& prevents the router from generating a new
6267 address that is the same as any previous address that was redirected. (This
6268 works round a problem concerning a bad interaction between aliasing and
6269 forwarding &-- see section &<<SECTredlocmai>>&).
6271 The final three option settings specify the transports that are to be used when
6272 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6273 auto-reply, respectively. For example, if a &_.forward_& file contains
6275 a.nother@elsewhere.example, /home/spqr/archive
6277 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6283 # local_part_suffix = +* : -*
6284 # local_part_suffix_optional
6285 transport = local_delivery
6287 The final router sets up delivery into local mailboxes, provided that the local
6288 part is the name of a local login, by accepting the address and assigning it to
6289 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6290 routers, so the address is bounced. The commented suffix settings fulfil the
6291 same purpose as they do for the &(userforward)& router.
6294 .section "Transport configuration" "SECID56"
6295 .cindex "default" "transports"
6296 .cindex "transports" "default"
6297 Transports define mechanisms for actually delivering messages. They operate
6298 only when referenced from routers, so the order in which they are defined does
6299 not matter. The transports section of the configuration starts with
6303 Two remote transports and four local transports are defined.
6307 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6312 This transport is used for delivering messages over SMTP connections.
6313 The list of remote hosts comes from the router.
6314 The &%message_size_limit%& usage is a hack to avoid sending on messages
6315 with over-long lines.
6317 The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
6318 negotiated between client and server and not expected to cause problems
6319 but can be disabled if needed. The built-in macro _HAVE_PRDR guards the
6320 use of the &%hosts_try_prdr%& configuration option.
6322 The other remote transport is used when delivering to a specific smarthost
6323 with whom there must be some kind of existing relationship, instead of the
6324 usual federated system.
6329 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6333 # Comment out any of these which you have to, then file a Support
6334 # request with your smarthost provider to get things fixed:
6335 hosts_require_tls = *
6336 tls_verify_hosts = *
6337 # As long as tls_verify_hosts is enabled, this this will have no effect,
6338 # but if you have to comment it out then this will at least log whether
6339 # you succeed or not:
6340 tls_try_verify_hosts = *
6342 # The SNI name should match the name which we'll expect to verify;
6343 # many mail systems don't use SNI and this doesn't matter, but if it does,
6344 # we need to send a name which the remote site will recognize.
6345 # This _should_ be the name which the smarthost operators specified as
6346 # the hostname for sending your mail to.
6347 tls_sni = ROUTER_SMARTHOST
6349 .ifdef _HAVE_OPENSSL
6350 tls_require_ciphers = HIGH:!aNULL:@STRENGTH
6353 tls_require_ciphers = SECURE192:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1
6360 After the same &%message_size_limit%& hack, we then specify that this Transport
6361 can handle messages to multiple domains in one run. The assumption here is
6362 that you're routing all non-local mail to the same place and that place is
6363 happy to take all messages from you as quickly as possible.
6364 All other options depend upon built-in macros; if Exim was built without TLS support
6365 then no other options are defined.
6366 If TLS is available, then we configure "stronger than default" TLS ciphersuites
6367 and versions using the &%tls_require_ciphers%& option, where the value to be
6368 used depends upon the library providing TLS.
6369 Beyond that, the options adopt the stance that you should have TLS support available
6370 from your smarthost on today's Internet, so we turn on requiring TLS for the
6371 mail to be delivered, and requiring that the certificate be valid, and match
6372 the expected hostname. The &%tls_sni%& option can be used by service providers
6373 to select an appropriate certificate to present to you and here we re-use the
6374 ROUTER_SMARTHOST macro, because that is unaffected by CNAMEs present in DNS.
6375 You want to specify the hostname which you'll expect to validate for, and that
6376 should not be subject to insecure tampering via DNS results.
6378 For the &%hosts_try_prdr%& option see the previous transport.
6380 All other options are defaulted.
6384 file = /var/mail/$local_part_data
6391 This &(appendfile)& transport is used for local delivery to user mailboxes in
6392 traditional BSD mailbox format.
6394 We prefer to avoid using &$local_part$& directly to define the mailbox filename,
6395 as it is provided by a potential bad actor.
6396 Instead we use &$local_part_data$&,
6397 the result of looking up &$local_part$& in the user database
6398 (done by using &%check_local_user%& in the the router).
6400 By default &(appendfile)& runs under the uid and gid of the
6401 local user, which requires the sticky bit to be set on the &_/var/mail_&
6402 directory. Some systems use the alternative approach of running mail deliveries
6403 under a particular group instead of using the sticky bit. The commented options
6404 show how this can be done.
6406 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6407 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6408 similarly-named options above.
6414 This transport is used for handling deliveries to pipes that are generated by
6415 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6416 option specifies that any output on stdout or stderr generated by the pipe is to
6417 be returned to the sender.
6425 This transport is used for handling deliveries to files that are generated by
6426 redirection. The name of the file is not specified in this instance of
6427 &(appendfile)&, because it comes from the &(redirect)& router.
6432 This transport is used for handling automatic replies generated by users'
6437 .section "Default retry rule" "SECID57"
6438 .cindex "retry" "default rule"
6439 .cindex "default" "retry rule"
6440 The retry section of the configuration file contains rules which affect the way
6441 Exim retries deliveries that cannot be completed at the first attempt. It is
6442 introduced by the line
6446 In the default configuration, there is just one rule, which applies to all
6449 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6451 This causes any temporarily failing address to be retried every 15 minutes for
6452 2 hours, then at intervals starting at one hour and increasing by a factor of
6453 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6454 is not delivered after 4 days of temporary failure, it is bounced. The time is
6455 measured from first failure, not from the time the message was received.
6457 If the retry section is removed from the configuration, or is empty (that is,
6458 if no retry rules are defined), Exim will not retry deliveries. This turns
6459 temporary errors into permanent errors.
6462 .section "Rewriting configuration" "SECID58"
6463 The rewriting section of the configuration, introduced by
6467 contains rules for rewriting addresses in messages as they arrive. There are no
6468 rewriting rules in the default configuration file.
6472 .section "Authenticators configuration" "SECTdefconfauth"
6473 .cindex "AUTH" "configuration"
6474 The authenticators section of the configuration, introduced by
6476 begin authenticators
6478 defines mechanisms for the use of the SMTP AUTH command. The default
6479 configuration file contains two commented-out example authenticators
6480 which support plaintext username/password authentication using the
6481 standard PLAIN mechanism and the traditional but non-standard LOGIN
6482 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6483 to support most MUA software.
6485 The example PLAIN authenticator looks like this:
6488 # driver = plaintext
6489 # server_set_id = $auth2
6490 # server_prompts = :
6491 # server_condition = Authentication is not yet configured
6492 # server_advertise_condition = ${if def:tls_in_cipher }
6494 And the example LOGIN authenticator looks like this:
6497 # driver = plaintext
6498 # server_set_id = $auth1
6499 # server_prompts = <| Username: | Password:
6500 # server_condition = Authentication is not yet configured
6501 # server_advertise_condition = ${if def:tls_in_cipher }
6504 The &%server_set_id%& option makes Exim remember the authenticated username
6505 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6506 &%server_prompts%& option configures the &(plaintext)& authenticator so
6507 that it implements the details of the specific authentication mechanism,
6508 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6509 when Exim offers authentication to clients; in the examples, this is only
6510 when TLS or SSL has been started, so to enable the authenticators you also
6511 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6513 The &%server_condition%& setting defines how to verify that the username and
6514 password are correct. In the examples it just produces an error message.
6515 To make the authenticators work, you can use a string expansion
6516 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6518 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6519 usercode and password are in different positions.
6520 Chapter &<<CHAPplaintext>>& covers both.
6522 .ecindex IIDconfiwal
6526 . ////////////////////////////////////////////////////////////////////////////
6527 . ////////////////////////////////////////////////////////////////////////////
6529 .chapter "Regular expressions" "CHAPregexp"
6531 .cindex "regular expressions" "library"
6533 Exim supports the use of regular expressions in many of its options. It
6534 uses the PCRE2 regular expression library; this provides regular expression
6535 matching that is compatible with Perl 5. The syntax and semantics of
6536 regular expressions is discussed in
6537 online Perl manpages, in
6538 many Perl reference books, and also in
6539 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6540 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6541 . --- the http: URL here redirects to another page with the ISBN in the URL
6542 . --- where trying to use https: just redirects back to http:, so sticking
6543 . --- to the old URL for now. 2018-09-07.
6545 The documentation for the syntax and semantics of the regular expressions that
6546 are supported by PCRE2 is included in the PCRE2 distribution, and no further
6547 description is included here. The PCRE2 functions are called from Exim using
6548 the default option settings (that is, with no PCRE2 options set), except that
6549 the PCRE2_CASELESS option is set when the matching is required to be
6552 In most cases, when a regular expression is required in an Exim configuration,
6553 it has to start with a circumflex, in order to distinguish it from plain text
6554 or an &"ends with"& wildcard. In this example of a configuration setting, the
6555 second item in the colon-separated list is a regular expression.
6557 domains = a.b.c : ^\\d{3} : *.y.z : ...
6559 The doubling of the backslash is required because of string expansion that
6560 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6561 of this issue, and a way of avoiding the need for doubling backslashes. The
6562 regular expression that is eventually used in this example contains just one
6563 backslash. The circumflex is included in the regular expression, and has the
6564 normal effect of &"anchoring"& it to the start of the string that is being
6567 There are, however, two cases where a circumflex is not required for the
6568 recognition of a regular expression: these are the &%match%& condition in a
6569 string expansion, and the &%matches%& condition in an Exim filter file. In
6570 these cases, the relevant string is always treated as a regular expression; if
6571 it does not start with a circumflex, the expression is not anchored, and can
6572 match anywhere in the subject string.
6574 In all cases, if you want a regular expression to match at the end of a string,
6575 you must code the $ metacharacter to indicate this. For example:
6577 domains = ^\\d{3}\\.example
6579 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6582 domains = ^\\d{3}\\.example\$
6584 if you want &'example'& to be the top-level domain. The backslash before the
6585 $ is needed because string expansion also interprets dollar characters.
6589 . ////////////////////////////////////////////////////////////////////////////
6590 . ////////////////////////////////////////////////////////////////////////////
6592 .chapter "File and database lookups" "CHAPfdlookup"
6593 .scindex IIDfidalo1 "file" "lookups"
6594 .scindex IIDfidalo2 "database" "lookups"
6595 .cindex "lookup" "description of"
6596 Exim can be configured to look up data in files or databases as it processes
6597 messages. Two different kinds of syntax are used:
6600 A string that is to be expanded may contain explicit lookup requests. These
6601 cause parts of the string to be replaced by data that is obtained from the
6602 lookup. Lookups of this type are conditional expansion items. Different results
6603 can be defined for the cases of lookup success and failure. See chapter
6604 &<<CHAPexpand>>&, where string expansions are described in detail.
6605 The key for the lookup is &*specified*& as part of the string to be expanded.
6607 Lists of domains, hosts, and email addresses can contain lookup requests as a
6608 way of avoiding excessively long linear lists. In this case, the data that is
6609 returned by the lookup is often (but not always) discarded; whether the lookup
6610 succeeds or fails is what really counts. These kinds of list are described in
6611 chapter &<<CHAPdomhosaddlists>>&.
6612 Depending on the lookup type (see below)
6613 the key for the lookup may need to be &*specified*& as above
6614 or may be &*implicit*&,
6615 given by the context in which the list is being checked.
6618 String expansions, lists, and lookups interact with each other in such a way
6619 that there is no order in which to describe any one of them that does not
6620 involve references to the others. Each of these three chapters makes more sense
6621 if you have read the other two first. If you are reading this for the first
6622 time, be aware that some of it will make a lot more sense after you have read
6623 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6625 .section "Examples of different lookup syntax" "SECID60"
6626 It is easy to confuse the two different kinds of lookup, especially as the
6627 lists that may contain the second kind are always expanded before being
6628 processed as lists. Therefore, they may also contain lookups of the first kind.
6629 Be careful to distinguish between the following two examples:
6631 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6632 domains = lsearch;/some/file
6635 The first uses a string expansion, the result of which must be a domain list.
6636 The key for an expansion-style lookup must be given explicitly.
6637 No strings have been specified for a successful or a failing lookup; the
6638 defaults in this case are the looked-up data and an empty string, respectively.
6639 The expansion takes place before the string is processed as a list, and the
6640 file that is searched could contain lines like this:
6642 192.168.3.4: domain1:domain2:...
6643 192.168.1.9: domain3:domain4:...
6645 When the lookup succeeds, the result of the expansion is a list of domains (and
6646 possibly other types of item that are allowed in domain lists).
6647 .cindex "tainted data" "de-tainting"
6648 .cindex "de-tainting" "using a lookup expansion"
6649 The result of the expansion is not tainted.
6652 In the second example, the lookup is a single item in a domain list. It causes
6653 Exim to use a lookup to see if the domain that is being processed can be found
6655 The file could contains lines like this:
6660 Any data that follows the keys is not relevant when checking that the domain
6661 matches the list item.
6663 The key for a list-style lookup is implicit, from the lookup context, if
6664 the lookup is a single-key type (see below).
6665 For query-style lookup types the query must be given explicitly.
6668 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6669 Consider a file containing lines like this:
6671 192.168.5.6: lsearch;/another/file
6673 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6674 first &%domains%& setting above generates the second setting, which therefore
6675 causes a second lookup to occur.
6677 The lookup type may optionally be followed by a comma
6678 and a comma-separated list of options.
6679 Each option is a &"name=value"& pair.
6680 Whether an option is meaningful depends on the lookup type.
6682 All lookups support the option &"cache=no_rd"&.
6683 If this is given then the cache that Exim manages for lookup results
6684 is not checked before doing the lookup.
6685 The result of the lookup is still written to the cache.
6687 The rest of this chapter describes the different lookup types that are
6688 available. Any of them can be used in any part of the configuration where a
6689 lookup is permitted.
6692 .section "Lookup types" "SECID61"
6693 .cindex "lookup" "types of"
6694 .cindex "single-key lookup" "definition of"
6695 Two different types of data lookup are implemented:
6698 The &'single-key'& type requires the specification of a file in which to look,
6699 and a single key to search for. The key must be a non-empty string for the
6700 lookup to succeed. The lookup type determines how the file is searched.
6701 .cindex "tainted data" "single-key lookups"
6702 The file string may not be tainted.
6704 .cindex "tainted data" "de-tainting"
6705 .cindex "de-tainting" "using a single-key lookup"
6706 All single-key lookups support the option &"ret=key"&.
6707 If this is given and the lookup
6708 (either underlying implementation or cached value)
6709 returns data, the result is replaced with a non-tainted
6710 version of the lookup key.
6713 .cindex "query-style lookup" "definition of"
6714 The &'query-style'& type accepts a generalized database query. No particular
6715 key value is assumed by Exim for query-style lookups. You can use whichever
6716 Exim variables you need to construct the database query.
6717 .cindex "tainted data" "quoting for lookups"
6718 If tainted data is used in the query then it should be quuted by
6719 using the &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*& expansion operator
6720 appropriate for the lookup.
6723 The code for each lookup type is in a separate source file that is included in
6724 the binary of Exim only if the corresponding compile-time option is set. The
6725 default settings in &_src/EDITME_& are:
6730 which means that only linear searching and DBM lookups are included by default.
6731 For some types of lookup (e.g. SQL databases), you need to install appropriate
6732 libraries and header files before building Exim.
6737 .section "Single-key lookup types" "SECTsinglekeylookups"
6738 .cindex "lookup" "single-key types"
6739 .cindex "single-key lookup" "list of types"
6740 The following single-key lookup types are implemented:
6743 .cindex "cdb" "description of"
6744 .cindex "lookup" "cdb"
6745 .cindex "binary zero" "in lookup key"
6746 The given file is searched as a Constant DataBase file, using the key
6747 string without a terminating binary zero. The cdb format is designed for
6748 indexed files that are read frequently and never updated, except by total
6749 re-creation. As such, it is particularly suitable for large files containing
6750 aliases or other indexed data referenced by an MTA. Information about cdb and
6751 tools for building the files can be found in several places:
6753 &url(https://cr.yp.to/cdb.html)
6754 &url(https://www.corpit.ru/mjt/tinycdb.html)
6755 &url(https://packages.debian.org/stable/utils/freecdb)
6756 &url(https://github.com/philpennock/cdbtools) (in Go)
6758 A cdb distribution is not needed in order to build Exim with cdb support,
6759 because the code for reading cdb files is included directly in Exim itself.
6760 However, no means of building or testing cdb files is provided with Exim, so
6761 you need to obtain a cdb distribution in order to do this.
6764 .cindex "DBM" "lookup type"
6765 .cindex "lookup" "dbm"
6766 .cindex "binary zero" "in lookup key"
6767 Calls to DBM library functions are used to extract data from the given
6768 DBM file by looking up the record with the given key. A terminating binary
6769 zero is included in the key that is passed to the DBM library. See section
6770 &<<SECTdb>>& for a discussion of DBM libraries.
6772 .cindex "Berkeley DB library" "file format"
6773 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6774 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6775 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6776 the DB_UNKNOWN option. This enables it to handle any of the types of database
6777 that the library supports, and can be useful for accessing DBM files created by
6778 other applications. (For earlier DB versions, DB_HASH is always used.)
6781 .cindex "lookup" "dbmjz"
6782 .cindex "lookup" "dbm &-- embedded NULs"
6784 .cindex "dbmjz lookup type"
6785 This is the same as &(dbm)&, except that the lookup key is
6786 interpreted as an Exim list; the elements of the list are joined together with
6787 ASCII NUL characters to form the lookup key. An example usage would be to
6788 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6789 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6790 &(cram_md5)& authenticator.
6793 .cindex "lookup" "dbmnz"
6794 .cindex "lookup" "dbm &-- terminating zero"
6795 .cindex "binary zero" "in lookup key"
6797 .cindex "&_/etc/userdbshadow.dat_&"
6798 .cindex "dbmnz lookup type"
6799 This is the same as &(dbm)&, except that a terminating binary zero
6800 is not included in the key that is passed to the DBM library. You may need this
6801 if you want to look up data in files that are created by or shared with some
6802 other application that does not use terminating zeros. For example, you need to
6803 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6804 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6805 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6806 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6809 .cindex "lookup" "dsearch"
6810 .cindex "dsearch lookup type"
6811 The given file must be an absolute directory path; this is searched for an entry
6812 whose name is the key by calling the &[lstat()]& function.
6813 The key may not contain any forward slash characters.
6814 If &[lstat()]& succeeds then so does the lookup.
6815 .cindex "tainted data" "dsearch result"
6816 The result is regarded as untainted.
6818 Options for the lookup can be given by appending them after the word "dsearch",
6819 separated by a comma. Options, if present, are a comma-separated list having
6820 each element starting with a tag name and an equals.
6822 Two options are supported, for the return value and for filtering match
6824 The "ret" option requests an alternate result value of
6825 the entire path for the entry. Example:
6827 ${lookup {passwd} dsearch,ret=full {/etc}}
6829 The default result is just the requested entry.
6830 The "filter" option requests that only directory entries of a given type
6831 are matched. The match value is one of "file", "dir" or "subdir" (the latter
6832 not matching "." or ".."). Example:
6834 ${lookup {passwd} dsearch,filter=file {/etc}}
6836 The default matching is for any entry type, including directories
6839 An example of how this
6840 lookup can be used to support virtual domains is given in section
6841 &<<SECTvirtualdomains>>&.
6843 .subsection iplsearch
6844 .cindex "lookup" "iplsearch"
6845 .cindex "iplsearch lookup type"
6846 The given file is a text file containing keys and data. A key is
6847 terminated by a colon or white space or the end of the line. The keys in the
6848 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6849 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6850 being interpreted as a key terminator. For example:
6852 1.2.3.4: data for 1.2.3.4
6853 192.168.0.0/16: data for 192.168.0.0/16
6854 "abcd::cdab": data for abcd::cdab
6855 "abcd:abcd::/32" data for abcd:abcd::/32
6857 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6858 file is searched linearly, using the CIDR masks where present, until a matching
6859 key is found. The first key that matches is used; there is no attempt to find a
6860 &"best"& match. Apart from the way the keys are matched, the processing for
6861 &(iplsearch)& is the same as for &(lsearch)&.
6863 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6864 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6865 lookup types support only literal keys.
6867 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6868 the implicit key is the host's IP address rather than its name (see section
6869 &<<SECThoslispatsikey>>&).
6871 &*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
6872 IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
6873 notation before executing the lookup.)
6875 One option is supported, "ret=full", to request the return of the entire line
6876 rather than omitting the key portion.
6877 Note however that the key portion will have been de-quoted.
6881 .cindex json "lookup type"
6882 .cindex JSON expansions
6883 The given file is a text file with a JSON structure.
6884 An element of the structure is extracted, defined by the search key.
6885 The key is a list of subelement selectors
6886 (colon-separated by default but changeable in the usual way)
6887 which are applied in turn to select smaller and smaller portions
6888 of the JSON structure.
6889 If a selector is numeric, it must apply to a JSON array; the (zero-based)
6890 nunbered array element is selected.
6891 Otherwise it must apply to a JSON object; the named element is selected.
6892 The final resulting element can be a simple JSON type or a JSON object
6893 or array; for the latter two a string-representation of the JSON
6895 For elements of type string, the returned value is de-quoted.
6901 .cindex database lmdb
6902 The given file is an LMDB database.
6903 LMDB is a memory-mapped key-value store,
6904 with API modeled loosely on that of BerkeleyDB.
6905 See &url(https://symas.com/products/lightning-memory-mapped-database/)
6906 for the feature set and operation modes.
6908 Exim provides read-only access via the LMDB C library.
6909 The library can be obtained from &url(https://github.com/LMDB/lmdb)
6910 or your operating system package repository.
6911 To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&.
6913 You will need to separately create the LMDB database file,
6914 possibly using the &"mdb_load"& utility.
6918 .cindex "linear search"
6919 .cindex "lookup" "lsearch"
6920 .cindex "lsearch lookup type"
6921 .cindex "case sensitivity" "in lsearch lookup"
6922 The given file is a text file that is searched linearly for a
6923 line beginning with the search key, terminated by a colon or white space or the
6924 end of the line. The search is case-insensitive; that is, upper and lower case
6925 letters are treated as the same. The first occurrence of the key that is found
6926 in the file is used.
6928 White space between the key and the colon is permitted. The remainder of the
6929 line, with leading and trailing white space removed, is the data. This can be
6930 continued onto subsequent lines by starting them with any amount of white
6931 space, but only a single space character is included in the data at such a
6932 junction. If the data begins with a colon, the key must be terminated by a
6937 Empty lines and lines beginning with # are ignored, even if they occur in the
6938 middle of an item. This is the traditional textual format of alias files. Note
6939 that the keys in an &(lsearch)& file are literal strings. There is no
6940 wildcarding of any kind.
6942 .cindex "lookup" "lsearch &-- colons in keys"
6943 .cindex "white space" "in lsearch key"
6944 In most &(lsearch)& files, keys are not required to contain colons or #
6945 characters, or white space. However, if you need this feature, it is available.
6946 If a key begins with a doublequote character, it is terminated only by a
6947 matching quote (or end of line), and the normal escaping rules apply to its
6948 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6949 quoted keys (exactly as for unquoted keys). There is no special handling of
6950 quotes for the data part of an &(lsearch)& line.
6953 .cindex "NIS lookup type"
6954 .cindex "lookup" "NIS"
6955 .cindex "binary zero" "in lookup key"
6956 The given file is the name of a NIS map, and a NIS lookup is done with
6957 the given key, without a terminating binary zero. There is a variant called
6958 &(nis0)& which does include the terminating binary zero in the key. This is
6959 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6960 aliases; the full map names must be used.
6962 .subsection (n)wildlsearch
6963 .cindex "wildlsearch lookup type"
6964 .cindex "lookup" "wildlsearch"
6965 .cindex "nwildlsearch lookup type"
6966 .cindex "lookup" "nwildlsearch"
6967 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6968 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6969 the file may be wildcarded. The difference between these two lookup types is
6970 that for &(wildlsearch)&, each key in the file is string-expanded before being
6971 used, whereas for &(nwildlsearch)&, no expansion takes place.
6973 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6974 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6975 file that are regular expressions can be made case-sensitive by the use of
6976 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6979 The string may begin with an asterisk to mean &"ends with"&. For example:
6981 *.a.b.c data for anything.a.b.c
6982 *fish data for anythingfish
6985 The string may begin with a circumflex to indicate a regular expression. For
6986 example, for &(wildlsearch)&:
6988 ^\N\d+\.a\.b\N data for <digits>.a.b
6990 Note the use of &`\N`& to disable expansion of the contents of the regular
6991 expression. If you are using &(nwildlsearch)&, where the keys are not
6992 string-expanded, the equivalent entry is:
6994 ^\d+\.a\.b data for <digits>.a.b
6996 The case-insensitive flag is set at the start of compiling the regular
6997 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6998 For example, to make the entire pattern case-sensitive:
7000 ^(?-i)\d+\.a\.b data for <digits>.a.b
7003 If the regular expression contains white space or colon characters, you must
7004 either quote it (see &(lsearch)& above), or represent these characters in other
7005 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
7006 colon. This may be easier than quoting, because if you quote, you have to
7007 escape all the backslashes inside the quotes.
7009 &*Note*&: It is not possible to capture substrings in a regular expression
7010 match for later use, because the results of all lookups are cached. If a lookup
7011 is repeated, the result is taken from the cache, and no actual pattern matching
7012 takes place. The values of all the numeric variables are unset after a
7013 &((n)wildlsearch)& match.
7016 Although I cannot see it being of much use, the general matching function that
7017 is used to implement &((n)wildlsearch)& means that the string may begin with a
7018 lookup name terminated by a semicolon, and followed by lookup data. For
7021 cdb;/some/file data for keys that match the file
7023 The data that is obtained from the nested lookup is discarded.
7026 Keys that do not match any of these patterns are interpreted literally. The
7027 continuation rules for the data are the same as for &(lsearch)&, and keys may
7028 be followed by optional colons.
7030 &*Warning*&: Unlike most other single-key lookup types, a file of data for
7031 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
7032 lookup types support only literal keys.
7035 .cindex "spf lookup type"
7036 .cindex "lookup" "spf"
7037 If Exim is built with SPF support, manual lookups can be done
7038 (as opposed to the standard ACL condition method).
7039 For details see section &<<SECSPF>>&.
7042 .section "Query-style lookup types" "SECTquerystylelookups"
7043 .cindex "lookup" "query-style types"
7044 .cindex "query-style lookup" "list of types"
7045 The supported query-style lookup types are listed below. Further details about
7046 many of them are given in later sections.
7049 .cindex "DNS" "as a lookup type"
7050 .cindex "lookup" "DNS"
7051 This does a DNS search for one or more records whose domain names
7052 are given in the supplied query. The resulting data is the contents of the
7053 records. See section &<<SECTdnsdb>>&.
7056 .cindex "InterBase lookup type"
7057 .cindex "lookup" "InterBase"
7058 This does a lookup in an InterBase database.
7061 .cindex "LDAP" "lookup type"
7062 .cindex "lookup" "LDAP"
7063 This does an LDAP lookup using a query in the form of a URL, and
7064 returns attributes from a single entry. There is a variant called &(ldapm)&
7065 that permits values from multiple entries to be returned. A third variant
7066 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
7067 any attribute values. See section &<<SECTldap>>&.
7070 .cindex "MySQL" "lookup type"
7071 .cindex "lookup" "MySQL"
7072 The format of the query is an SQL statement that is passed to a
7073 MySQL database. See section &<<SECTsql>>&.
7076 .cindex "NIS+ lookup type"
7077 .cindex "lookup" "NIS+"
7078 This does a NIS+ lookup using a query that can specify the name of
7079 the field to be returned. See section &<<SECTnisplus>>&.
7082 .cindex "Oracle" "lookup type"
7083 .cindex "lookup" "Oracle"
7084 The format of the query is an SQL statement that is passed to an
7085 Oracle database. See section &<<SECTsql>>&.
7088 .cindex "lookup" "passwd"
7089 .cindex "passwd lookup type"
7090 .cindex "&_/etc/passwd_&"
7091 This is a query-style lookup with queries that are just user names. The
7092 lookup calls &[getpwnam()]& to interrogate the system password data, and on
7093 success, the result string is the same as you would get from an &(lsearch)&
7094 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
7095 password value. For example:
7097 *:42:42:King Rat:/home/kr:/bin/bash
7101 .cindex "PostgreSQL lookup type"
7102 .cindex "lookup" "PostgreSQL"
7103 The format of the query is an SQL statement that is passed to a
7104 PostgreSQL database. See section &<<SECTsql>>&.
7107 .cindex "Redis lookup type"
7108 .cindex lookup Redis
7109 The format of the query is either a simple get or simple set,
7110 passed to a Redis database. See section &<<SECTsql>>&.
7113 .cindex "sqlite lookup type"
7114 .cindex "lookup" "sqlite"
7115 The format of the query is
7116 an SQL statement that is passed to an SQLite database. See section &<<SECTsqlite>>&.
7119 This is a lookup type that is used for testing Exim. It is
7120 not likely to be useful in normal operation.
7123 .cindex "whoson lookup type"
7124 .cindex "lookup" "whoson"
7125 &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
7126 allows a server to check whether a particular (dynamically allocated) IP
7127 address is currently allocated to a known (trusted) user and, optionally, to
7128 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
7129 at one time for &"POP before SMTP"& authentication, but that approach has been
7130 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
7131 &"POP before SMTP"& checking using ACL statements such as
7133 require condition = \
7134 ${lookup whoson {$sender_host_address}{yes}{no}}
7136 The query consists of a single IP address. The value returned is the name of
7137 the authenticated user, which is stored in the variable &$value$&. However, in
7138 this example, the data in &$value$& is not used; the result of the lookup is
7139 one of the fixed strings &"yes"& or &"no"&.
7143 .section "Temporary errors in lookups" "SECID63"
7144 .cindex "lookup" "temporary error in"
7145 Lookup functions can return temporary error codes if the lookup cannot be
7146 completed. For example, an SQL or LDAP database might be unavailable. For this
7147 reason, it is not advisable to use a lookup that might do this for critical
7148 options such as a list of local domains.
7150 When a lookup cannot be completed in a router or transport, delivery
7151 of the message (to the relevant address) is deferred, as for any other
7152 temporary error. In other circumstances Exim may assume the lookup has failed,
7153 or may give up altogether.
7157 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
7158 .cindex "wildcard lookups"
7159 .cindex "lookup" "default values"
7160 .cindex "lookup" "wildcard"
7161 .cindex "lookup" "* added to type"
7162 .cindex "default" "in single-key lookups"
7163 In this context, a &"default value"& is a value specified by the administrator
7164 that is to be used if a lookup fails.
7166 &*Note:*& This section applies only to single-key lookups. For query-style
7167 lookups, the facilities of the query language must be used. An attempt to
7168 specify a default for a query-style lookup provokes an error.
7170 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
7171 and the initial lookup fails, the key &"*"& is looked up in the file to
7172 provide a default value. See also the section on partial matching below.
7174 .cindex "*@ with single-key lookup"
7175 .cindex "lookup" "*@ added to type"
7176 .cindex "alias file" "per-domain default"
7177 Alternatively, if &"*@"& is added to a single-key lookup type (for example
7178 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
7179 character, a second lookup is done with everything before the last @ replaced
7180 by *. This makes it possible to provide per-domain defaults in alias files
7181 that include the domains in the keys. If the second lookup fails (or doesn't
7182 take place because there is no @ in the key), &"*"& is looked up.
7183 For example, a &(redirect)& router might contain:
7185 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
7187 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
7188 looks up these keys, in this order:
7194 The data is taken from whichever key it finds first. &*Note*&: In an
7195 &(lsearch)& file, this does not mean the first of these keys in the file. A
7196 complete scan is done for each key, and only if it is not found at all does
7197 Exim move on to try the next key.
7201 .section "Partial matching in single-key lookups" "SECTpartiallookup"
7202 .cindex "partial matching"
7203 .cindex "wildcard lookups"
7204 .cindex "lookup" "partial matching"
7205 .cindex "lookup" "wildcard"
7206 .cindex "asterisk" "in search type"
7207 The normal operation of a single-key lookup is to search the file for an exact
7208 match with the given key. However, in a number of situations where domains are
7209 being looked up, it is useful to be able to do partial matching. In this case,
7210 information in the file that has a key starting with &"*."& is matched by any
7211 domain that ends with the components that follow the full stop. For example, if
7212 a key in a DBM file is
7214 *.dates.fict.example
7216 then when partial matching is enabled this is matched by (amongst others)
7217 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
7218 by &'dates.fict.example'&, if that does not appear as a separate key in the
7221 &*Note*&: Partial matching is not available for query-style lookups. It is
7222 also not available for any lookup items in address lists (see section
7223 &<<SECTaddresslist>>&).
7225 Partial matching is implemented by doing a series of separate lookups using
7226 keys constructed by modifying the original subject key. This means that it can
7227 be used with any of the single-key lookup types, provided that
7228 partial matching keys
7229 beginning with a special prefix (default &"*."&) are included in the data file.
7230 Keys in the file that do not begin with the prefix are matched only by
7231 unmodified subject keys when partial matching is in use.
7233 Partial matching is requested by adding the string &"partial-"& to the front of
7234 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
7235 is done, the subject key is first looked up unmodified; if that fails, &"*."&
7236 is added at the start of the subject key, and it is looked up again. If that
7237 fails, further lookups are tried with dot-separated components removed from the
7238 start of the subject key, one-by-one, and &"*."& added on the front of what
7241 A minimum number of two non-* components are required. This can be adjusted
7242 by including a number before the hyphen in the search type. For example,
7243 &%partial3-lsearch%& specifies a minimum of three non-* components in the
7244 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
7245 subject key is &'2250.dates.fict.example'& then the following keys are looked
7246 up when the minimum number of non-* components is two:
7248 2250.dates.fict.example
7249 *.2250.dates.fict.example
7250 *.dates.fict.example
7253 As soon as one key in the sequence is successfully looked up, the lookup
7256 .cindex "lookup" "partial matching &-- changing prefix"
7257 .cindex "prefix" "for partial matching"
7258 The use of &"*."& as the partial matching prefix is a default that can be
7259 changed. The motivation for this feature is to allow Exim to operate with file
7260 formats that are used by other MTAs. A different prefix can be supplied in
7261 parentheses instead of the hyphen after &"partial"&. For example:
7263 domains = partial(.)lsearch;/some/file
7265 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
7266 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
7267 components is unchanged). The prefix may consist of any punctuation characters
7268 other than a closing parenthesis. It may be empty, for example:
7270 domains = partial1()cdb;/some/file
7272 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
7273 &`a.b.c`&, &`b.c`&, and &`c`&.
7275 If &"partial0"& is specified, what happens at the end (when the lookup with
7276 just one non-wild component has failed, and the original key is shortened right
7277 down to the null string) depends on the prefix:
7280 If the prefix has zero length, the whole lookup fails.
7282 If the prefix has length 1, a lookup for just the prefix is done. For
7283 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
7285 Otherwise, if the prefix ends in a dot, the dot is removed, and the
7286 remainder is looked up. With the default prefix, therefore, the final lookup is
7287 for &"*"& on its own.
7289 Otherwise, the whole prefix is looked up.
7293 If the search type ends in &"*"& or &"*@"& (see section
7294 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
7295 this implies happens after all partial lookups have failed. If &"partial0"& is
7296 specified, adding &"*"& to the search type has no effect with the default
7297 prefix, because the &"*"& key is already included in the sequence of partial
7298 lookups. However, there might be a use for lookup types such as
7299 &"partial0(.)lsearch*"&.
7301 The use of &"*"& in lookup partial matching differs from its use as a wildcard
7302 in domain lists and the like. Partial matching works only in terms of
7303 dot-separated components; a key such as &`*fict.example`&
7304 in a database file is useless, because the asterisk in a partial matching
7305 subject key is always followed by a dot.
7310 .section "Lookup caching" "SECID64"
7311 .cindex "lookup" "caching"
7312 .cindex "caching" "lookup data"
7313 Exim caches all lookup results in order to avoid needless repetition of
7314 lookups. However, because (apart from the daemon) Exim operates as a collection
7315 of independent, short-lived processes, this caching applies only within a
7316 single Exim process. There is no inter-process lookup caching facility.
7318 If an option &"cache=no_rd"& is used on the lookup then
7319 the cache is only written to, cached data is not used for the operation
7320 and a real lookup is done.
7322 For single-key lookups, Exim keeps the relevant files open in case there is
7323 another lookup that needs them. In some types of configuration this can lead to
7324 many files being kept open for messages with many recipients. To avoid hitting
7325 the operating system limit on the number of simultaneously open files, Exim
7326 closes the least recently used file when it needs to open more files than its
7327 own internal limit, which can be changed via the &%lookup_open_max%& option.
7329 The single-key lookup files are closed and the lookup caches are flushed at
7330 strategic points during delivery &-- for example, after all routing is
7336 .section "Quoting lookup data" "SECID65"
7337 .cindex "lookup" "quoting"
7338 .cindex "quoting" "in lookups"
7339 When data from an incoming message is included in a query-style lookup, there
7340 is the possibility of special characters in the data messing up the syntax of
7341 the query. For example, a NIS+ query that contains
7345 will be broken if the local part happens to contain a closing square bracket.
7346 For NIS+, data can be enclosed in double quotes like this:
7348 [name="$local_part"]
7350 but this still leaves the problem of a double quote in the data. The rule for
7351 NIS+ is that double quotes must be doubled. Other lookup types have different
7352 rules, and to cope with the differing requirements, an expansion operator
7353 of the following form is provided:
7355 ${quote_<lookup-type>:<string>}
7357 For example, the safest way to write the NIS+ query is
7359 [name="${quote_nisplus:$local_part}"]
7361 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
7362 operator can be used for all lookup types, but has no effect for single-key
7363 lookups, since no quoting is ever needed in their key strings.
7368 .section "More about dnsdb" "SECTdnsdb"
7369 .cindex "dnsdb lookup"
7370 .cindex "lookup" "dnsdb"
7371 .cindex "DNS" "as a lookup type"
7372 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7373 of a record type and a domain name, separated by an equals sign. For example,
7374 an expansion string could contain:
7376 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7378 If the lookup succeeds, the result is placed in &$value$&, which in this case
7379 is used on its own as the result. If the lookup does not succeed, the
7380 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7381 &<<SECTforexpfai>>& for an explanation of what this means.
7383 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7384 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7385 If no type is given, TXT is assumed.
7387 For any record type, if multiple records are found, the data is returned as a
7388 concatenation, with newline as the default separator. The order, of course,
7389 depends on the DNS resolver. You can specify a different separator character
7390 between multiple records by putting a right angle-bracket followed immediately
7391 by the new separator at the start of the query. For example:
7393 ${lookup dnsdb{>: a=host1.example}}
7395 It is permitted to specify a space as the separator character. Further
7396 white space is ignored.
7397 For lookup types that return multiple fields per record,
7398 an alternate field separator can be specified using a comma after the main
7399 separator character, followed immediately by the field separator.
7401 .cindex "PTR record" "in &(dnsdb)& lookup"
7402 When the type is PTR,
7403 the data can be an IP address, written as normal; inversion and the addition of
7404 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7406 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7408 If the data for a PTR record is not a syntactically valid IP address, it is not
7409 altered and nothing is added.
7411 .cindex "MX record" "in &(dnsdb)& lookup"
7412 .cindex "SRV record" "in &(dnsdb)& lookup"
7413 For an MX lookup, both the preference value and the host name are returned for
7414 each record, separated by a space. For an SRV lookup, the priority, weight,
7415 port, and host name are returned for each record, separated by spaces.
7416 The field separator can be modified as above.
7418 .cindex "TXT record" "in &(dnsdb)& lookup"
7419 .cindex "SPF record" "in &(dnsdb)& lookup"
7420 For TXT records with multiple items of data, only the first item is returned,
7421 unless a field separator is specified.
7422 To concatenate items without a separator, use a semicolon instead.
7424 default behaviour is to concatenate multiple items without using a separator.
7426 ${lookup dnsdb{>\n,: txt=a.b.example}}
7427 ${lookup dnsdb{>\n; txt=a.b.example}}
7428 ${lookup dnsdb{spf=example.org}}
7430 It is permitted to specify a space as the separator character. Further
7431 white space is ignored.
7433 .cindex "SOA record" "in &(dnsdb)& lookup"
7434 For an SOA lookup, while no result is obtained the lookup is redone with
7435 successively more leading components dropped from the given domain.
7436 Only the primary-nameserver field is returned unless a field separator is
7439 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7442 .subsection "Dnsdb lookup modifiers" SECTdnsdb_mod
7443 .cindex "dnsdb modifiers"
7444 .cindex "modifiers" "dnsdb"
7445 .cindex "options" "dnsdb"
7446 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7447 each followed by a comma,
7448 that may appear before the record type.
7450 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7451 temporary DNS error for any of them, the behaviour is controlled by
7452 a defer-option modifier.
7453 The possible keywords are
7454 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7455 With &"strict"& behaviour, any temporary DNS error causes the
7456 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7457 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7458 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7459 error causes the whole lookup to defer only if none of the other lookups
7460 succeed. The default is &"lax"&, so the following lookups are equivalent:
7462 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7463 ${lookup dnsdb{a=one.host.com:two.host.com}}
7465 Thus, in the default case, as long as at least one of the DNS lookups
7466 yields some data, the lookup succeeds.
7468 .cindex "DNSSEC" "dns lookup"
7469 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7470 The possible keywords are
7471 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7472 With &"strict"& or &"lax"& DNSSEC information is requested
7474 With &"strict"& a response from the DNS resolver that
7475 is not labelled as authenticated data
7476 is treated as equivalent to a temporary DNS error.
7477 The default is &"lax"&.
7479 See also the &$lookup_dnssec_authenticated$& variable.
7481 .cindex timeout "dns lookup"
7482 .cindex "DNS" timeout
7483 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7484 The form is &"retrans_VAL"& where VAL is an Exim time specification
7486 The default value is set by the main configuration option &%dns_retrans%&.
7488 Retries for the dnsdb lookup can be controlled by a retry modifier.
7489 The form if &"retry_VAL"& where VAL is an integer.
7490 The default count is set by the main configuration option &%dns_retry%&.
7492 .cindex caching "of dns lookup"
7493 .cindex TTL "of dns lookup"
7495 Dnsdb lookup results are cached within a single process (and its children).
7496 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7497 value of the set of returned DNS records.
7500 .subsection "Pseudo dnsdb record types" SECID66
7501 .cindex "MX record" "in &(dnsdb)& lookup"
7502 By default, both the preference value and the host name are returned for
7503 each MX record, separated by a space. If you want only host names, you can use
7504 the pseudo-type MXH:
7506 ${lookup dnsdb{mxh=a.b.example}}
7508 In this case, the preference values are omitted, and just the host names are
7511 .cindex "name server for enclosing domain"
7512 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7513 records on the given domain, but if none are found, it removes the first
7514 component of the domain name, and tries again. This process continues until NS
7515 records are found or there are no more components left (or there is a DNS
7516 error). In other words, it may return the name servers for a top-level domain,
7517 but it never returns the root name servers. If there are no NS records for the
7518 top-level domain, the lookup fails. Consider these examples:
7520 ${lookup dnsdb{zns=xxx.quercite.com}}
7521 ${lookup dnsdb{zns=xxx.edu}}
7523 Assuming that in each case there are no NS records for the full domain name,
7524 the first returns the name servers for &%quercite.com%&, and the second returns
7525 the name servers for &%edu%&.
7527 You should be careful about how you use this lookup because, unless the
7528 top-level domain does not exist, the lookup always returns some host names. The
7529 sort of use to which this might be put is for seeing if the name servers for a
7530 given domain are on a blacklist. You can probably assume that the name servers
7531 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7534 .cindex "CSA" "in &(dnsdb)& lookup"
7535 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7536 records according to the CSA rules, which are described in section
7537 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7538 not sufficient because of the extra parent domain search behaviour of CSA. The
7539 result of a successful lookup such as:
7541 ${lookup dnsdb {csa=$sender_helo_name}}
7543 has two space-separated fields: an authorization code and a target host name.
7544 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7545 authorization required but absent, or &"?"& for unknown.
7547 .cindex "A+" "in &(dnsdb)& lookup"
7548 The pseudo-type A+ performs an AAAA
7549 and then an A lookup. All results are returned; defer processing
7550 (see below) is handled separately for each lookup. Example:
7552 ${lookup dnsdb {>; a+=$sender_helo_name}}
7556 .subsection "Multiple dnsdb lookups" SECID67
7557 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7558 However, you can specify a list of domains or IP addresses in a single
7559 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7560 the default separator, but with the ability to change this. For example:
7562 ${lookup dnsdb{one.domain.com:two.domain.com}}
7563 ${lookup dnsdb{a=one.host.com:two.host.com}}
7564 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7566 In order to retain backwards compatibility, there is one special case: if
7567 the lookup type is PTR and no change of separator is specified, Exim looks
7568 to see if the rest of the string is precisely one IPv6 address. In this
7569 case, it does not treat it as a list.
7571 The data from each lookup is concatenated, with newline separators by default,
7572 in the same way that multiple DNS records for a single item are handled. A
7573 different separator can be specified, as described above.
7578 .section "More about LDAP" "SECTldap"
7579 .cindex "LDAP" "lookup, more about"
7580 .cindex "lookup" "LDAP"
7581 .cindex "Solaris" "LDAP"
7582 The original LDAP implementation came from the University of Michigan; this has
7583 become &"Open LDAP"&, and there are now two different releases. Another
7584 implementation comes from Netscape, and Solaris 7 and subsequent releases
7585 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7586 the lookup function level, their error handling is different. For this reason
7587 it is necessary to set a compile-time variable when building Exim with LDAP, to
7588 indicate which LDAP library is in use. One of the following should appear in
7589 your &_Local/Makefile_&:
7591 LDAP_LIB_TYPE=UMICHIGAN
7592 LDAP_LIB_TYPE=OPENLDAP1
7593 LDAP_LIB_TYPE=OPENLDAP2
7594 LDAP_LIB_TYPE=NETSCAPE
7595 LDAP_LIB_TYPE=SOLARIS
7597 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7598 same interface as the University of Michigan version.
7600 There are three LDAP lookup types in Exim. These behave slightly differently in
7601 the way they handle the results of a query:
7604 &(ldap)& requires the result to contain just one entry; if there are more, it
7607 &(ldapdn)& also requires the result to contain just one entry, but it is the
7608 Distinguished Name that is returned rather than any attribute values.
7610 &(ldapm)& permits the result to contain more than one entry; the attributes
7611 from all of them are returned.
7615 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7616 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7617 the data returned by a successful lookup is described in the next section.
7618 First we explain how LDAP queries are coded.
7621 .subsection "Format of LDAP queries" SECTforldaque
7622 .cindex "LDAP" "query format"
7623 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7624 the configuration of a &(redirect)& router one might have this setting:
7626 data = ${lookup ldap \
7627 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7628 c=UK?mailbox?base?}}
7630 .cindex "LDAP" "with TLS"
7631 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7632 secure (encrypted) LDAP connections. The second of these ensures that an
7633 encrypted TLS connection is used.
7635 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7636 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7637 See the &%ldap_start_tls%& option.
7639 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7640 controlled. Every part of the TLS configuration can be configured by settings in
7641 &_exim.conf_&. Depending on the version of the client libraries installed on
7642 your system, some of the initialization may have required setting options in
7643 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7644 certificates. This revealed a nuance where the current UID that exim was
7645 running as could affect which config files it read. With Exim 4.83, these
7646 methods become optional, only taking effect if not specifically set in
7650 .subsection "LDAP quoting" SECID68
7651 .cindex "LDAP" "quoting"
7652 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7653 and the second because the LDAP query is represented as a URL. Furthermore,
7654 within an LDAP query, two different kinds of quoting are required. For this
7655 reason, there are two different LDAP-specific quoting operators.
7657 The &%quote_ldap%& operator is designed for use on strings that are part of
7658 filter specifications. Conceptually, it first does the following conversions on
7666 in accordance with RFC 2254. The resulting string is then quoted according
7667 to the rules for URLs, that is, all non-alphanumeric characters except
7671 are converted to their hex values, preceded by a percent sign. For example:
7673 ${quote_ldap: a(bc)*, a<yz>; }
7677 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7679 Removing the URL quoting, this is (with a leading and a trailing space):
7681 a\28bc\29\2A, a<yz>;
7683 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7684 base DN specifications in queries. Conceptually, it first converts the string
7685 by inserting a backslash in front of any of the following characters:
7689 It also inserts a backslash before any leading spaces or # characters, and
7690 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7691 is then quoted according to the rules for URLs. For example:
7693 ${quote_ldap_dn: a(bc)*, a<yz>; }
7697 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7699 Removing the URL quoting, this is (with a trailing space):
7701 \ a(bc)*\, a\<yz\>\;\
7703 There are some further comments about quoting in the section on LDAP
7704 authentication below.
7707 .subsection "LDAP connections" SECID69
7708 .cindex "LDAP" "connections"
7709 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7710 is in use, via a Unix domain socket. The example given above does not specify
7711 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7714 ldap://<hostname>:<port>/...
7716 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7717 used. When no server is specified in a query, a list of default servers is
7718 taken from the &%ldap_default_servers%& configuration option. This supplies a
7719 colon-separated list of servers which are tried in turn until one successfully
7720 handles a query, or there is a serious error. Successful handling either
7721 returns the requested data, or indicates that it does not exist. Serious errors
7722 are syntactical, or multiple values when only a single value is expected.
7723 Errors which cause the next server to be tried are connection failures, bind
7724 failures, and timeouts.
7726 For each server name in the list, a port number can be given. The standard way
7727 of specifying a host and port is to use a colon separator (RFC 1738). Because
7728 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7729 doubled. For example
7731 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7733 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7734 to the LDAP library with no server name, and the library's default (normally
7735 the local host) is used.
7737 If you are using the OpenLDAP library, you can connect to an LDAP server using
7738 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7739 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7740 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7743 For this type of connection, instead of a host name for the server, a pathname
7744 for the socket is required, and the port number is not relevant. The pathname
7745 can be specified either as an item in &%ldap_default_servers%&, or inline in
7746 the query. In the former case, you can have settings such as
7748 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7750 When the pathname is given in the query, you have to escape the slashes as
7751 &`%2F`& to fit in with the LDAP URL syntax. For example:
7753 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7755 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7756 a pathname, it uses the Unix domain socket code, even if the query actually
7757 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7758 socket connection. This behaviour means that you can use a setting of
7759 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7760 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7761 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7764 If an explicit &`ldapi`& type is given in a query when a host name is
7765 specified, an error is diagnosed. However, if there are more items in
7766 &%ldap_default_servers%&, they are tried. In other words:
7769 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7772 Using &`ldapi`& with a host name causes an error.
7776 Using &`ldapi`& with no host or path in the query, and no setting of
7777 &%ldap_default_servers%&, does whatever the library does by default.
7781 .subsection "LDAP authentication and control information" SECID70
7782 .cindex "LDAP" "authentication"
7783 The LDAP URL syntax provides no way of passing authentication and other control
7784 information to the server. To make this possible, the URL in an LDAP query may
7785 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7786 spaces. If a value contains spaces it must be enclosed in double quotes, and
7787 when double quotes are used, backslash is interpreted in the usual way inside
7788 them. The following names are recognized:
7789 .itable none 0 0 2 20* left 80* left
7790 .irow DEREFERENCE "set the dereferencing parameter"
7791 .irow NETTIME "set a timeout for a network operation"
7792 .irow USER "set the DN, for authenticating the LDAP bind"
7793 .irow PASS "set the password, likewise"
7794 .irow REFERRALS "set the referrals parameter"
7795 .irow SERVERS "set alternate server list for this query only"
7796 .irow SIZE "set the limit for the number of entries returned"
7797 .irow TIME "set the maximum waiting time for a query"
7799 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7800 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7801 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7802 library from trying to follow referrals issued by the LDAP server.
7804 .cindex LDAP timeout
7805 .cindex timeout "LDAP lookup"
7806 The name CONNECT is an obsolete name for NETTIME, retained for
7807 backwards compatibility. This timeout (specified as a number of seconds) is
7808 enforced from the client end for operations that can be carried out over a
7809 network. Specifically, it applies to network connections and calls to the
7810 &'ldap_result()'& function. If the value is greater than zero, it is used if
7811 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7812 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7813 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7814 Netscape SDK; for OpenLDAP no action is taken.
7816 The TIME parameter (also a number of seconds) is passed to the server to
7817 set a server-side limit on the time taken to complete a search.
7819 The SERVERS parameter allows you to specify an alternate list of ldap servers
7820 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7821 default list of ldap servers, and a single lookup can specify a single ldap
7822 server to use. But when you need to do a lookup with a list of servers that is
7823 different than the default list (maybe different order, maybe a completely
7824 different set of servers), the SERVERS parameter allows you to specify this
7825 alternate list (colon-separated).
7827 Here is an example of an LDAP query in an Exim lookup that uses some of these
7828 values. This is a single line, folded to fit on the page:
7831 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7832 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7835 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7836 any of the auxiliary data. Exim configuration settings that include lookups
7837 which contain password information should be preceded by &"hide"& to prevent
7838 non-admin users from using the &%-bP%& option to see their values.
7840 The auxiliary data items may be given in any order. The default is no
7841 connection timeout (the system timeout is used), no user or password, no limit
7842 on the number of entries returned, and no time limit on queries.
7844 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7845 removes any URL quoting that it may contain before passing it to the LDAP library.
7847 some libraries do this for themselves, but some do not. Removing the URL
7848 quoting has two advantages:
7851 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7852 DNs as with DNs inside actual queries.
7854 It permits spaces inside USER= DNs.
7857 For example, a setting such as
7859 USER=cn=${quote_ldap_dn:$1}
7861 should work even if &$1$& contains spaces.
7863 Expanded data for the PASS= value should be quoted using the &%quote%&
7864 expansion operator, rather than the LDAP quote operators. The only reason this
7865 field needs quoting is to ensure that it conforms to the Exim syntax, which
7866 does not allow unquoted spaces. For example:
7870 The LDAP authentication mechanism can be used to check passwords as part of
7871 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7876 .subsection "Format of data returned by LDAP" SECID71
7877 .cindex "LDAP" "returned data formats"
7878 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7879 as a sequence of values, for example
7881 cn=manager,o=University of Cambridge,c=UK
7883 The &(ldap)& lookup type generates an error if more than one entry matches the
7884 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7885 the result between the data from different entries. It is possible for multiple
7886 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7887 you know that whatever values are returned all came from a single entry in the
7890 In the common case where you specify a single attribute in your LDAP query, the
7891 result is not quoted, and does not contain the attribute name. If the attribute
7892 has multiple values, they are separated by commas. Any comma that is
7893 part of an attribute's value is doubled.
7895 If you specify multiple attributes, the result contains space-separated, quoted
7896 strings, each preceded by the attribute name and an equals sign. Within the
7897 quotes, the quote character, backslash, and newline are escaped with
7898 backslashes, and commas are used to separate multiple values for the attribute.
7899 Any commas in attribute values are doubled
7900 (permitting treatment of the values as a comma-separated list).
7901 Apart from the escaping, the string within quotes takes the same form as the
7902 output when a single attribute is requested. Specifying no attributes is the
7903 same as specifying all of an entry's attributes.
7905 Here are some examples of the output format. The first line of each pair is an
7906 LDAP query, and the second is the data that is returned. The attribute called
7907 &%attr1%& has two values, one of them with an embedded comma, whereas
7908 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7909 (they have SUP &%attr%& in their schema definitions).
7912 ldap:///o=base?attr1?sub?(uid=fred)
7915 ldap:///o=base?attr2?sub?(uid=fred)
7918 ldap:///o=base?attr?sub?(uid=fred)
7919 value1.1,value1,,2,value two
7921 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7922 attr1="value1.1,value1,,2" attr2="value two"
7924 ldap:///o=base??sub?(uid=fred)
7925 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7928 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7929 results of LDAP lookups.
7930 The &%extract%& operator in string expansions can be used to pick out
7931 individual fields from data that consists of &'key'&=&'value'& pairs.
7932 The &%listextract%& operator should be used to pick out individual values
7933 of attributes, even when only a single value is expected.
7934 The doubling of embedded commas allows you to use the returned data as a
7935 comma separated list (using the "<," syntax for changing the input list separator).
7940 .section "More about NIS+" "SECTnisplus"
7941 .cindex "NIS+ lookup type"
7942 .cindex "lookup" "NIS+"
7943 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7944 and field name. If this is given, the result of a successful query is the
7945 contents of the named field; otherwise the result consists of a concatenation
7946 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7947 values containing spaces are quoted. For example, the query
7949 [name=mg1456],passwd.org_dir
7951 might return the string
7953 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7954 home=/home/mg1456 shell=/bin/bash shadow=""
7956 (split over two lines here to fit on the page), whereas
7958 [name=mg1456],passwd.org_dir:gcos
7964 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7965 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7966 operator is to double any quote characters within the text.
7970 .section "SQL lookups" "SECTsql"
7971 .cindex "SQL lookup types"
7972 .cindex "MySQL" "lookup type"
7973 .cindex "PostgreSQL lookup type"
7974 .cindex "lookup" "MySQL"
7975 .cindex "lookup" "PostgreSQL"
7976 .cindex "Oracle" "lookup type"
7977 .cindex "lookup" "Oracle"
7978 .cindex "InterBase lookup type"
7979 .cindex "lookup" "InterBase"
7980 .cindex "Redis lookup type"
7981 .cindex lookup Redis
7982 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
7984 databases. Queries for these databases contain SQL statements, so an example
7987 ${lookup mysql{select mailbox from users where id='userx'}\
7990 If the result of the query contains more than one field, the data for each
7991 field in the row is returned, preceded by its name, so the result of
7993 ${lookup pgsql{select home,name from users where id='userx'}\
7998 home=/home/userx name="Mister X"
8000 Empty values and values containing spaces are double quoted, with embedded
8001 quotes escaped by a backslash. If the result of the query contains just one
8002 field, the value is passed back verbatim, without a field name, for example:
8006 If the result of the query yields more than one row, it is all concatenated,
8007 with a newline between the data for each row.
8010 .subsection "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" SECID72
8011 .cindex "MySQL" "lookup type"
8012 .cindex "PostgreSQL lookup type"
8013 .cindex "lookup" "MySQL"
8014 .cindex "lookup" "PostgreSQL"
8015 .cindex "Oracle" "lookup type"
8016 .cindex "lookup" "Oracle"
8017 .cindex "InterBase lookup type"
8018 .cindex "lookup" "InterBase"
8019 .cindex "Redis lookup type"
8020 .cindex lookup Redis
8021 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
8022 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
8023 or &%redis_servers%&
8024 option (as appropriate) must be set to a colon-separated list of server
8026 .oindex &%mysql_servers%&
8027 .oindex &%pgsql_servers%&
8028 .oindex &%oracle_servers%&
8029 .oindex &%ibase_servers%&
8030 .oindex &%redis_servers%&
8031 (For MySQL and PostgreSQL, the global option need not be set if all
8032 queries contain their own server information &-- see section
8033 &<<SECTspeserque>>&.)
8035 each item in the list is a slash-separated list of four
8036 items: host name, database name, user name, and password. In the case of
8037 Oracle, the host name field is used for the &"service name"&, and the database
8038 name field is not used and should be empty. For example:
8040 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
8042 Because password data is sensitive, you should always precede the setting with
8043 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
8044 option. Here is an example where two MySQL servers are listed:
8046 hide mysql_servers = localhost/users/root/secret:\
8047 otherhost/users/root/othersecret
8049 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
8050 because this is a colon-separated list, the colon has to be doubled. For each
8051 query, these parameter groups are tried in order until a connection is made and
8052 a query is successfully processed. The result of a query may be that no data is
8053 found, but that is still a successful query. In other words, the list of
8054 servers provides a backup facility, not a list of different places to look.
8056 For Redis the global option need not be specified if all queries contain their
8057 own server information &-- see section &<<SECTspeserque>>&.
8058 If specified, the option must be set to a colon-separated list of server
8060 Each item in the list is a slash-separated list of three items:
8061 host, database number, and password.
8063 The host is required and may be either an IPv4 address and optional
8064 port number (separated by a colon, which needs doubling due to the
8065 higher-level list), or a Unix socket pathname enclosed in parentheses
8067 The database number is optional; if present that number is selected in the backend
8069 The password is optional; if present it is used to authenticate to the backend
8072 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
8073 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
8074 respectively, and the characters single-quote, double-quote, and backslash
8075 itself are escaped with backslashes.
8077 The &%quote_redis%& expansion operator
8078 escapes whitespace and backslash characters with a backslash.
8080 .subsection "Specifying the server in the query" SECTspeserque
8081 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
8082 it is possible to specify a list of servers with an individual query. This is
8083 done by appending a comma-separated option to the query type:
8085 &`,servers=`&&'server1:server2:server3:...'&
8087 Each item in the list may take one of two forms:
8089 If it contains no slashes it is assumed to be just a host name. The appropriate
8090 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
8091 of the same name, and the remaining parameters (database, user, password) are
8094 If it contains any slashes, it is taken as a complete parameter set.
8096 The list of servers is used in exactly the same way as the global list.
8097 Once a connection to a server has happened and a query has been
8098 successfully executed, processing of the lookup ceases.
8100 This feature is intended for use in master/slave situations where updates
8101 are occurring and you want to update the master rather than a slave. If the
8102 master is in the list as a backup for reading, you might have a global setting
8105 mysql_servers = slave1/db/name/pw:\
8109 In an updating lookup, you could then write:
8111 ${lookup mysql,servers=master {UPDATE ...} }
8113 That query would then be sent only to the master server. If, on the other hand,
8114 the master is not to be used for reading, and so is not present in the global
8115 option, you can still update it by a query of this form:
8117 ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
8120 An older syntax places the servers specification before the query,
8121 semicolon separated:
8123 ${lookup mysql{servers=master; UPDATE ...} }
8125 The new version avoids potential issues with tainted
8126 arguments in the query, for explicit expansion.
8127 &*Note*&: server specifications in list-style lookups are still problematic.
8130 .subsection "Special MySQL features" SECID73
8131 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
8132 causes a connection to the server on the local host by means of a Unix domain
8133 socket. An alternate socket can be specified in parentheses.
8134 An option group name for MySQL option files can be specified in square brackets;
8135 the default value is &"exim"&.
8136 The full syntax of each item in &%mysql_servers%& is:
8138 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
8139 <&'database'&>/<&'user'&>/<&'password'&>
8141 Any of the four sub-parts of the first field can be omitted. For normal use on
8142 the local host it can be left blank or set to just &"localhost"&.
8144 No database need be supplied &-- but if it is absent here, it must be given in
8147 If a MySQL query is issued that does not request any data (an insert, update,
8148 or delete command), the result of the lookup is the number of rows affected.
8150 &*Warning*&: This can be misleading. If an update does not actually change
8151 anything (for example, setting a field to the value it already has), the result
8152 is zero because no rows are affected.
8155 .subsection "Special PostgreSQL features" SECID74
8156 PostgreSQL lookups can also use Unix domain socket connections to the database.
8157 This is usually faster and costs less CPU time than a TCP/IP connection.
8158 However it can be used only if the mail server runs on the same machine as the
8159 database server. A configuration line for PostgreSQL via Unix domain sockets
8162 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
8164 In other words, instead of supplying a host name, a path to the socket is
8165 given. The path name is enclosed in parentheses so that its slashes aren't
8166 visually confused with the delimiters for the other server parameters.
8168 If a PostgreSQL query is issued that does not request any data (an insert,
8169 update, or delete command), the result of the lookup is the number of rows
8172 .subsection "More about SQLite" SECTsqlite
8173 .cindex "lookup" "SQLite"
8174 .cindex "sqlite lookup type"
8175 SQLite is different to the other SQL lookups because a filename is required in
8176 addition to the SQL query. An SQLite database is a single file, and there is no
8177 daemon as in the other SQL databases.
8179 .oindex &%sqlite_dbfile%&
8180 There are two ways of
8181 specifying the file.
8182 The first is is by using the &%sqlite_dbfile%& main option.
8183 The second, which allows separate files for each query,
8184 is to use an option appended, comma-separated, to the &"sqlite"&
8185 lookup type word. The option is the word &"file"&, then an equals,
8187 The filename in this case cannot contain whitespace or open-brace charachters.
8189 A deprecated method is available, prefixing the query with the filename
8190 separated by white space.
8192 .cindex "tainted data" "sqlite file"
8193 the query cannot use any tainted values, as that taints
8194 the entire query including the filename - resulting in a refusal to open
8197 In all the above cases the filename must be an absolute path.
8199 Here is a lookup expansion example:
8201 sqlite_dbfile = /some/thing/sqlitedb
8203 ${lookup sqlite {select name from aliases where id='userx';}}
8205 In a list, the syntax is similar. For example:
8207 domainlist relay_to_domains = sqlite;\
8208 select * from relays where ip='$sender_host_address';
8210 The only character affected by the &%quote_sqlite%& operator is a single
8211 quote, which it doubles.
8213 .cindex timeout SQLite
8214 .cindex sqlite "lookup timeout"
8215 The SQLite library handles multiple simultaneous accesses to the database
8216 internally. Multiple readers are permitted, but only one process can
8217 update at once. Attempts to access the database while it is being updated
8218 are rejected after a timeout period, during which the SQLite library
8219 waits for the lock to be released. In Exim, the default timeout is set
8220 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
8223 .subsection "More about Redis" SECTredis
8224 .cindex "lookup" "Redis"
8225 .cindex "redis lookup type"
8226 Redis is a non-SQL database. Commands are simple get and set.
8229 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
8230 ${lookup redis{get keyname}}
8233 As of release 4.91, "lightweight" support for Redis Cluster is available.
8234 Requires &%redis_servers%& list to contain all the servers in the cluster, all
8235 of which must be reachable from the running exim instance. If the cluster has
8236 master/slave replication, the list must contain all the master and slave
8239 When the Redis Cluster returns a "MOVED" response to a query, Exim does not
8240 immediately follow the redirection but treats the response as a DEFER, moving on
8241 to the next server in the &%redis_servers%& list until the correct server is
8248 . ////////////////////////////////////////////////////////////////////////////
8249 . ////////////////////////////////////////////////////////////////////////////
8251 .chapter "Domain, host, address, and local part lists" &&&
8252 "CHAPdomhosaddlists" &&&
8253 "Domain, host, and address lists"
8254 .scindex IIDdohoadli "lists of domains; hosts; etc."
8255 A number of Exim configuration options contain lists of domains, hosts,
8256 email addresses, or local parts. For example, the &%hold_domains%& option
8257 contains a list of domains whose delivery is currently suspended. These lists
8258 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
8259 arguments to expansion conditions such as &%match_domain%&.
8261 Each item in one of these lists is a pattern to be matched against a domain,
8262 host, email address, or local part, respectively. In the sections below, the
8263 different types of pattern for each case are described, but first we cover some
8264 general facilities that apply to all four kinds of list.
8266 Note that other parts of Exim use a &'string list'& which does not
8267 support all the complexity available in
8268 domain, host, address and local part lists.
8272 .section "Results of list checking" SECTlistresults
8273 The primary result of doing a list check is a truth value.
8274 In some contexts additional information is stored
8275 about the list element that matched:
8278 A &%hosts%& ACL condition
8279 will store a result in the &$host_data$& variable.
8281 A &%local_parts%& router option or &%local_parts%& ACL condition
8282 will store a result in the &$local_part_data$& variable.
8284 A &%domains%& router option or &%domains%& ACL condition
8285 will store a result in the &$domain_data$& variable.
8287 A &%senders%& router option or &%senders%& ACL condition
8288 will store a result in the &$sender_data$& variable.
8290 A &%recipients%& ACL condition
8291 will store a result in the &$recipient_data$& variable.
8294 The detail of the additional information depends on the
8295 type of match and is given below as the &*value*& information.
8300 .section "Expansion of lists" "SECTlistexpand"
8301 .cindex "expansion" "of lists"
8302 Each list is expanded as a single string before it is used.
8304 &'Exception: the router headers_remove option, where list-item
8305 splitting is done before string-expansion.'&
8308 expansion must be a list, possibly containing empty items, which is split up
8309 into separate items for matching. By default, colon is the separator character,
8310 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
8311 &<<SECTempitelis>>& for details of the list syntax; the second of these
8312 discusses the way to specify empty list items.
8315 If the string expansion is forced to fail, Exim behaves as if the item it is
8316 testing (domain, host, address, or local part) is not in the list. Other
8317 expansion failures cause temporary errors.
8319 If an item in a list is a regular expression, backslashes, dollars and possibly
8320 other special characters in the expression must be protected against
8321 misinterpretation by the string expander. The easiest way to do this is to use
8322 the &`\N`& expansion feature to indicate that the contents of the regular
8323 expression should not be expanded. For example, in an ACL you might have:
8325 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
8326 ${lookup{$domain}lsearch{/badsenders/bydomain}}
8328 The first item is a regular expression that is protected from expansion by
8329 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
8330 senders based on the receiving domain.
8335 .subsection "Negated items in lists" SECID76
8336 .cindex "list" "negation"
8337 .cindex "negation" "in lists"
8338 Items in a list may be positive or negative. Negative items are indicated by a
8339 leading exclamation mark, which may be followed by optional white space. A list
8340 defines a set of items (domains, etc). When Exim processes one of these lists,
8341 it is trying to find out whether a domain, host, address, or local part
8342 (respectively) is in the set that is defined by the list. It works like this:
8344 The list is scanned from left to right. If a positive item is matched, the
8345 subject that is being checked is in the set; if a negative item is matched, the
8346 subject is not in the set. If the end of the list is reached without the
8347 subject having matched any of the patterns, it is in the set if the last item
8348 was a negative one, but not if it was a positive one. For example, the list in
8350 domainlist relay_to_domains = !a.b.c : *.b.c
8352 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
8353 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
8354 list is positive. However, if the setting were
8356 domainlist relay_to_domains = !a.b.c
8358 then all domains other than &'a.b.c'& would match because the last item in the
8359 list is negative. In other words, a list that ends with a negative item behaves
8360 as if it had an extra item &`:*`& on the end.
8362 Another way of thinking about positive and negative items in lists is to read
8363 the connector as &"or"& after a positive item and as &"and"& after a negative
8368 .subsection "File names in lists" SECTfilnamlis
8369 .cindex "list" "filename in"
8370 If an item in a domain, host, address, or local part list is an absolute
8371 filename (beginning with a slash character), each line of the file is read and
8372 processed as if it were an independent item in the list, except that further
8373 filenames are not allowed,
8374 and no expansion of the data from the file takes place.
8375 Empty lines in the file are ignored, and the file may also contain comment
8379 For domain and host lists, if a # character appears anywhere in a line of the
8380 file, it and all following characters are ignored.
8382 Because local parts may legitimately contain # characters, a comment in an
8383 address list or local part list file is recognized only if # is preceded by
8384 white space or the start of the line. For example:
8386 not#comment@x.y.z # but this is a comment
8390 Putting a filename in a list has the same effect as inserting each line of the
8391 file as an item in the list (blank lines and comments excepted). However, there
8392 is one important difference: the file is read each time the list is processed,
8393 so if its contents vary over time, Exim's behaviour changes.
8395 If a filename is preceded by an exclamation mark, the sense of any match
8396 within the file is inverted. For example, if
8398 hold_domains = !/etc/nohold-domains
8400 and the file contains the lines
8405 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
8406 any domain matching &`*.b.c`& is not.
8410 .subsection "An lsearch file is not an out-of-line list" SECID77
8411 As will be described in the sections that follow, lookups can be used in lists
8412 to provide indexed methods of checking list membership. There has been some
8413 confusion about the way &(lsearch)& lookups work in lists. Because
8414 an &(lsearch)& file contains plain text and is scanned sequentially, it is
8415 sometimes thought that it is allowed to contain wild cards and other kinds of
8416 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
8417 always fixed strings, just as for any other single-key lookup type.
8419 If you want to use a file to contain wild-card patterns that form part of a
8420 list, just give the filename on its own, without a search type, as described
8421 in the previous section. You could also use the &(wildlsearch)& or
8422 &(nwildlsearch)&, but there is no advantage in doing this.
8427 .subsection "Named lists" SECTnamedlists
8428 .cindex "named lists"
8429 .cindex "list" "named"
8430 A list of domains, hosts, email addresses, or local parts can be given a name
8431 which is then used to refer to the list elsewhere in the configuration. This is
8432 particularly convenient if the same list is required in several different
8433 places. It also allows lists to be given meaningful names, which can improve
8434 the readability of the configuration. For example, it is conventional to define
8435 a domain list called &'local_domains'& for all the domains that are handled
8436 locally on a host, using a configuration line such as
8438 domainlist local_domains = localhost:my.dom.example
8440 Named lists are referenced by giving their name preceded by a plus sign, so,
8441 for example, a router that is intended to handle local domains would be
8442 configured with the line
8444 domains = +local_domains
8446 The first router in a configuration is often one that handles all domains
8447 except the local ones, using a configuration with a negated item like this:
8451 domains = ! +local_domains
8452 transport = remote_smtp
8455 The four kinds of named list are created by configuration lines starting with
8456 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8457 respectively. Then there follows the name that you are defining, followed by an
8458 equals sign and the list itself. For example:
8460 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8461 addresslist bad_senders = cdb;/etc/badsenders
8463 A named list may refer to other named lists:
8465 domainlist dom1 = first.example : second.example
8466 domainlist dom2 = +dom1 : third.example
8467 domainlist dom3 = fourth.example : +dom2 : fifth.example
8469 &*Warning*&: If the last item in a referenced list is a negative one, the
8470 effect may not be what you intended, because the negation does not propagate
8471 out to the higher level. For example, consider:
8473 domainlist dom1 = !a.b
8474 domainlist dom2 = +dom1 : *.b
8476 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8477 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8478 means it matches the second list as well. The effect is not the same as
8480 domainlist dom2 = !a.b : *.b
8482 where &'x.y'& does not match. It's best to avoid negation altogether in
8483 referenced lists if you can.
8485 .cindex "hiding named list values"
8486 .cindex "named lists" "hiding value of"
8487 Some named list definitions may contain sensitive data, for example, passwords for
8488 accessing databases. To stop non-admin users from using the &%-bP%& command
8489 line option to read these values, you can precede the definition with the
8490 word &"hide"&. For example:
8492 hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
8496 Named lists may have a performance advantage. When Exim is routing an
8497 address or checking an incoming message, it caches the result of tests on named
8498 lists. So, if you have a setting such as
8500 domains = +local_domains
8502 on several of your routers
8503 or in several ACL statements,
8504 the actual test is done only for the first one. However, the caching works only
8505 if there are no expansions within the list itself or any sublists that it
8506 references. In other words, caching happens only for lists that are known to be
8507 the same each time they are referenced.
8509 By default, there may be up to 16 named lists of each type. This limit can be
8510 extended by changing a compile-time variable. The use of domain and host lists
8511 is recommended for concepts such as local domains, relay domains, and relay
8512 hosts. The default configuration is set up like this.
8516 .subsection "Named lists compared with macros" SECID78
8517 .cindex "list" "named compared with macro"
8518 .cindex "macro" "compared with named list"
8519 At first sight, named lists might seem to be no different from macros in the
8520 configuration file. However, macros are just textual substitutions. If you
8523 ALIST = host1 : host2
8524 auth_advertise_hosts = !ALIST
8526 it probably won't do what you want, because that is exactly the same as
8528 auth_advertise_hosts = !host1 : host2
8530 Notice that the second host name is not negated. However, if you use a host
8533 hostlist alist = host1 : host2
8534 auth_advertise_hosts = ! +alist
8536 the negation applies to the whole list, and so that is equivalent to
8538 auth_advertise_hosts = !host1 : !host2
8542 .subsection "Named list caching" SECID79
8543 .cindex "list" "caching of named"
8544 .cindex "caching" "named lists"
8545 While processing a message, Exim caches the result of checking a named list if
8546 it is sure that the list is the same each time. In practice, this means that
8547 the cache operates only if the list contains no $ characters, which guarantees
8548 that it will not change when it is expanded. Sometimes, however, you may have
8549 an expanded list that you know will be the same each time within a given
8550 message. For example:
8552 domainlist special_domains = \
8553 ${lookup{$sender_host_address}cdb{/some/file}}
8555 This provides a list of domains that depends only on the sending host's IP
8556 address. If this domain list is referenced a number of times (for example,
8557 in several ACL lines, or in several routers) the result of the check is not
8558 cached by default, because Exim does not know that it is going to be the
8559 same list each time.
8561 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8562 cache the result anyway. For example:
8564 domainlist_cache special_domains = ${lookup{...
8566 If you do this, you should be absolutely sure that caching is going to do
8567 the right thing in all cases. When in doubt, leave it out.
8571 .section "Domain lists" "SECTdomainlist"
8572 .cindex "domain list" "patterns for"
8573 .cindex "list" "domain list"
8574 Domain lists contain patterns that are to be matched against a mail domain.
8575 The following types of item may appear in domain lists:
8578 .cindex "primary host name"
8579 .cindex "host name" "matched in domain list"
8580 .oindex "&%primary_hostname%&"
8581 .cindex "domain list" "matching primary host name"
8582 .cindex "@ in a domain list"
8583 If a pattern consists of a single @ character, it matches the local host name,
8584 as set by the &%primary_hostname%& option (or defaulted). This makes it
8585 possible to use the same configuration file on several different hosts that
8586 differ only in their names.
8588 The value for a match will be the primary host name.
8592 .cindex "@[] in a domain list"
8593 .cindex "domain list" "matching local IP interfaces"
8594 .cindex "domain literal"
8595 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8596 in square brackets (as in an email address that contains a domain literal), but
8597 only if that IP address is recognized as local for email routing purposes. The
8598 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8599 control which of a host's several IP addresses are treated as local.
8600 In today's Internet, the use of domain literals is controversial;
8601 see the &%allow_domain_literals%& main option.
8603 The value for a match will be the string &`@[]`&.
8608 .cindex "@mx_primary"
8609 .cindex "@mx_secondary"
8610 .cindex "domain list" "matching MX pointers to local host"
8611 If a pattern consists of the string &`@mx_any`& it matches any domain that
8612 has an MX record pointing to the local host or to any host that is listed in
8613 .oindex "&%hosts_treat_as_local%&"
8614 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8615 are similar, except that the first matches only when a primary MX target is the
8616 local host, and the second only when no primary MX target is the local host,
8617 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8618 preference value &-- there may of course be more than one of them.
8620 The MX lookup that takes place when matching a pattern of this type is
8621 performed with the resolver options for widening names turned off. Thus, for
8622 example, a single-component domain will &'not'& be expanded by adding the
8623 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8624 options of the &(dnslookup)& router for a discussion of domain widening.
8626 Sometimes you may want to ignore certain IP addresses when using one of these
8627 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8628 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8629 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8630 on a router). For example:
8632 domains = @mx_any/ignore=127.0.0.1
8634 This example matches any domain that has an MX record pointing to one of
8635 the local host's IP addresses other than 127.0.0.1.
8637 The list of IP addresses is in fact processed by the same code that processes
8638 host lists, so it may contain CIDR-coded network specifications and it may also
8639 contain negative items.
8641 Because the list of IP addresses is a sublist within a domain list, you have to
8642 be careful about delimiters if there is more than one address. Like any other
8643 list, the default delimiter can be changed. Thus, you might have:
8645 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8646 an.other.domain : ...
8648 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8649 involved, it is easiest to change the delimiter for the main list as well:
8651 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8652 an.other.domain ? ...
8654 The value for a match will be the list element string (starting &`@mx_`&).
8658 .cindex "asterisk" "in domain list"
8659 .cindex "domain list" "asterisk in"
8660 .cindex "domain list" "matching &""ends with""&"
8661 If a pattern starts with an asterisk, the remaining characters of the pattern
8662 are compared with the terminating characters of the domain. The use of &"*"& in
8663 domain lists differs from its use in partial matching lookups. In a domain
8664 list, the character following the asterisk need not be a dot, whereas partial
8665 matching works only in terms of dot-separated components. For example, a domain
8666 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8669 The value for a match will be the list element string (starting with the asterisk).
8670 Additionally, &$0$& will be set to the matched string
8671 and &$1$& to the variable portion which the asterisk matched.
8674 .cindex "regular expressions" "in domain list"
8675 .cindex "domain list" "matching regular expression"
8676 If a pattern starts with a circumflex character, it is treated as a regular
8677 expression, and matched against the domain using a regular expression matching
8678 function. The circumflex is treated as part of the regular expression.
8679 Email domains are case-independent, so this regular expression match is by
8680 default case-independent, but you can make it case-dependent by starting it
8681 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8682 are given in chapter &<<CHAPregexp>>&.
8684 &*Warning*&: Because domain lists are expanded before being processed, you
8685 must escape any backslash and dollar characters in the regular expression, or
8686 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8687 it is not to be expanded (unless you really do want to build a regular
8688 expression by expansion, of course).
8690 The value for a match will be the list element string (starting with the circumflex).
8691 Additionally, &$0$& will be set to the string matching the regular expression,
8692 and &$1$& (onwards) to any submatches identified by parentheses.
8697 .cindex "lookup" "in domain list"
8698 .cindex "domain list" "matching by lookup"
8699 If a pattern starts with the name of a single-key lookup type followed by a
8700 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8701 must be a filename in a suitable format for the lookup type. For example, for
8702 &"cdb;"& it must be an absolute path:
8704 domains = cdb;/etc/mail/local_domains.cdb
8706 The appropriate type of lookup is done on the file using the domain name as the
8707 key. In most cases, the value resulting from the lookup is not used; Exim is interested
8708 only in whether or not the key is present in the file. However, when a lookup
8709 is used for the &%domains%& option on a router
8710 or a &%domains%& condition in an ACL statement, the value is preserved in the
8711 &$domain_data$& variable and can be referred to in other router options or
8712 other statements in the same ACL.
8713 .cindex "tainted data" "de-tainting"
8714 .cindex "de-tainting" "using ACL domains condition"
8715 The value will be untainted.
8717 &*Note*&: If the data result of the lookup (as opposed to the key)
8718 is empty, then this empty value is stored in &$domain_data$&.
8719 The option to return the key for the lookup, as the value,
8720 may be what is wanted.
8724 Any of the single-key lookup type names may be preceded by
8725 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8727 domains = partial-dbm;/partial/domains
8729 This causes partial matching logic to be invoked; a description of how this
8730 works is given in section &<<SECTpartiallookup>>&.
8733 .cindex "asterisk" "in lookup type"
8734 Any of the single-key lookup types may be followed by an asterisk. This causes
8735 a default lookup for a key consisting of a single asterisk to be done if the
8736 original lookup fails. This is not a useful feature when using a domain list to
8737 select particular domains (because any domain would match), but it might have
8738 value if the result of the lookup is being used via the &$domain_data$&
8742 If the pattern starts with the name of a query-style lookup type followed by a
8743 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8744 pattern must be an appropriate query for the lookup type, as described in
8745 chapter &<<CHAPfdlookup>>&. For example:
8747 hold_domains = mysql;select domain from holdlist \
8748 where domain = '${quote_mysql:$domain}';
8750 In most cases, the value resulting from the lookup is not used (so for an SQL query, for
8751 example, it doesn't matter what field you select). Exim is interested only in
8752 whether or not the query succeeds. However, when a lookup is used for the
8753 &%domains%& option on a router, the value is preserved in the &$domain_data$&
8754 variable and can be referred to in other options.
8755 .cindex "tainted data" "de-tainting"
8756 .cindex "de-tainting" "using router domains option"
8757 The value will be untainted.
8760 If the pattern starts with the name of a lookup type
8761 of either kind (single-key or query-style) it may be
8762 followed by a comma and options,
8763 The options are lookup-type specific and consist of a comma-separated list.
8764 Each item starts with a tag and and equals "=" sign.
8767 .cindex "domain list" "matching literal domain name"
8768 If none of the above cases apply, a caseless textual comparison is made
8769 between the pattern and the domain.
8771 The value for a match will be the list element string.
8772 .cindex "tainted data" "de-tainting"
8773 Note that this is commonly untainted
8774 (depending on the way the list was created).
8775 Specifically, explicit text in the configuration file in not tainted.
8776 This is a useful way of obtaining an untainted equivalent to
8777 the domain, for later operations.
8779 However if the list (including one-element lists)
8780 is created by expanding a variable containing tainted data,
8781 it is tainted and so will the match value be.
8785 Here is an example that uses several different kinds of pattern:
8787 domainlist funny_domains = \
8790 *.foundation.fict.example : \
8791 \N^[1-2]\d{3}\.fict\.example$\N : \
8792 partial-dbm;/opt/data/penguin/book : \
8793 nis;domains.byname : \
8794 nisplus;[name=$domain,status=local],domains.org_dir
8796 There are obvious processing trade-offs among the various matching modes. Using
8797 an asterisk is faster than a regular expression, and listing a few names
8798 explicitly probably is too. The use of a file or database lookup is expensive,
8799 but may be the only option if hundreds of names are required. Because the
8800 patterns are tested in order, it makes sense to put the most commonly matched
8805 .section "Host lists" "SECThostlist"
8806 .cindex "host list" "patterns in"
8807 .cindex "list" "host list"
8808 Host lists are used to control what remote hosts are allowed to do. For
8809 example, some hosts may be allowed to use the local host as a relay, and some
8810 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8811 two different ways, by name or by IP address. In a host list, some types of
8812 pattern are matched to a host name, and some are matched to an IP address.
8813 You need to be particularly careful with this when single-key lookups are
8814 involved, to ensure that the right value is being used as the key.
8817 .subsection "Special host list patterns" SECID80
8818 .cindex "empty item in hosts list"
8819 .cindex "host list" "empty string in"
8820 If a host list item is the empty string, it matches only when no remote host is
8821 involved. This is the case when a message is being received from a local
8822 process using SMTP on the standard input, that is, when a TCP/IP connection is
8825 .cindex "asterisk" "in host list"
8826 The special pattern &"*"& in a host list matches any host or no host. Neither
8827 the IP address nor the name is actually inspected.
8831 .subsection "Host list patterns that match by IP address" SECThoslispatip
8832 .cindex "host list" "matching IP addresses"
8833 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8834 the incoming address actually appears in the IPv6 host as
8835 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8836 list, it is converted into a traditional IPv4 address first. (Not all operating
8837 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8840 The following types of pattern in a host list check the remote host by
8841 inspecting its IP address:
8844 If the pattern is a plain domain name (not a regular expression, not starting
8845 with *, not a lookup of any kind), Exim calls the operating system function
8846 to find the associated IP address(es). Exim uses the newer
8847 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8848 This typically causes a forward DNS lookup of the name. The result is compared
8849 with the IP address of the subject host.
8851 If there is a temporary problem (such as a DNS timeout) with the host name
8852 lookup, a temporary error occurs. For example, if the list is being used in an
8853 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8854 temporary SMTP error code. If no IP address can be found for the host name,
8855 what happens is described in section &<<SECTbehipnot>>& below.
8858 .cindex "@ in a host list"
8859 If the pattern is &"@"&, the primary host name is substituted and used as a
8860 domain name, as just described.
8863 If the pattern is an IP address, it is matched against the IP address of the
8864 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8865 IPv6 addresses can be given in colon-separated format, but the colons have to
8866 be doubled so as not to be taken as item separators when the default list
8867 separator is used. IPv6 addresses are recognized even when Exim is compiled
8868 without IPv6 support. This means that if they appear in a host list on an
8869 IPv4-only host, Exim will not treat them as host names. They are just addresses
8870 that can never match a client host.
8873 .cindex "@[] in a host list"
8874 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8875 the local host. For example, if the local host is an IPv4 host with one
8876 interface address 10.45.23.56, these two ACL statements have the same effect:
8878 accept hosts = 127.0.0.1 : 10.45.23.56
8882 .cindex "CIDR notation"
8883 If the pattern is an IP address followed by a slash and a mask length, for
8888 , it is matched against the IP address of the subject
8889 host under the given mask. This allows an entire network of hosts to be
8890 included (or excluded) by a single item. The mask uses CIDR notation; it
8891 specifies the number of address bits that must match, starting from the most
8892 significant end of the address.
8894 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8895 of a range of addresses. It is the number of bits in the network portion of the
8896 address. The above example specifies a 24-bit netmask, so it matches all 256
8897 addresses in the 10.11.42.0 network. An item such as
8901 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8902 32 for an IPv4 address is the same as no mask at all; just a single address
8905 Here is another example which shows an IPv4 and an IPv6 network:
8907 recipient_unqualified_hosts = 192.168.0.0/16: \
8908 3ffe::ffff::836f::::/48
8910 The doubling of list separator characters applies only when these items
8911 appear inline in a host list. It is not required when indirecting via a file.
8914 recipient_unqualified_hosts = /opt/exim/unqualnets
8916 could make use of a file containing
8921 to have exactly the same effect as the previous example. When listing IPv6
8922 addresses inline, it is usually more convenient to use the facility for
8923 changing separator characters. This list contains the same two networks:
8925 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8928 The separator is changed to semicolon by the leading &"<;"& at the start of the
8934 .subsection "Host list patterns for single-key lookups by host address" &&&
8936 .cindex "host list" "lookup of IP address"
8937 When a host is to be identified by a single-key lookup of its complete IP
8938 address, the pattern takes this form:
8940 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8944 hosts_lookup = net-cdb;/hosts-by-ip.db
8946 The text form of the IP address of the subject host is used as the lookup key.
8947 IPv6 addresses are converted to an unabbreviated form, using lower case
8948 letters, with dots as separators because colon is the key terminator in
8949 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8950 quoting the keys, but this is a facility that was added later.] The data
8951 returned by the lookup is not used.
8953 .cindex "IP address" "masking"
8954 .cindex "host list" "masked IP address"
8955 Single-key lookups can also be performed using masked IP addresses, using
8956 patterns of this form:
8958 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8962 net24-dbm;/networks.db
8964 The IP address of the subject host is masked using <&'number'&> as the mask
8965 length. A textual string is constructed from the masked value, followed by the
8966 mask, and this is used as the lookup key. For example, if the host's IP address
8967 is 192.168.34.6, the key that is looked up for the above example is
8968 &"192.168.34.0/24"&.
8970 When an IPv6 address is converted to a string, dots are normally used instead
8971 of colons, so that keys in &(lsearch)& files need not contain colons (which
8972 terminate &(lsearch)& keys). This was implemented some time before the ability
8973 to quote keys was made available in &(lsearch)& files. However, the more
8974 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8975 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8976 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8977 converted using colons and not dots.
8978 In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
8979 addresses are always used.
8980 The latter are converted to IPv4 addresses, in dotted-quad form.
8982 Ideally, it would be nice to tidy up this anomalous situation by changing to
8983 colons in all cases, given that quoting is now available for &(lsearch)&.
8984 However, this would be an incompatible change that might break some existing
8987 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8988 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8989 the former case the key strings include the mask value, whereas in the latter
8990 case the IP address is used on its own.
8994 .subsection "Host list patterns that match by host name" SECThoslispatnam
8995 .cindex "host" "lookup failures"
8996 .cindex "unknown host name"
8997 .cindex "host list" "matching host name"
8998 There are several types of pattern that require Exim to know the name of the
8999 remote host. These are either wildcard patterns or lookups by name. (If a
9000 complete hostname is given without any wildcarding, it is used to find an IP
9001 address to match against, as described in section &<<SECThoslispatip>>&
9004 If the remote host name is not already known when Exim encounters one of these
9005 patterns, it has to be found from the IP address.
9006 Although many sites on the Internet are conscientious about maintaining reverse
9007 DNS data for their hosts, there are also many that do not do this.
9008 Consequently, a name cannot always be found, and this may lead to unwanted
9009 effects. Take care when configuring host lists with wildcarded name patterns.
9010 Consider what will happen if a name cannot be found.
9012 Because of the problems of determining host names from IP addresses, matching
9013 against host names is not as common as matching against IP addresses.
9015 By default, in order to find a host name, Exim first does a reverse DNS lookup;
9016 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
9017 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
9018 are done can be changed by setting the &%host_lookup_order%& option. For
9019 security, once Exim has found one or more names, it looks up the IP addresses
9020 for these names and compares them with the IP address that it started with.
9021 Only those names whose IP addresses match are accepted. Any other names are
9022 discarded. If no names are left, Exim behaves as if the host name cannot be
9023 found. In the most common case there is only one name and one IP address.
9025 There are some options that control what happens if a host name cannot be
9026 found. These are described in section &<<SECTbehipnot>>& below.
9028 .cindex "host" "alias for"
9029 .cindex "alias for host"
9030 As a result of aliasing, hosts may have more than one name. When processing any
9031 of the following types of pattern, all the host's names are checked:
9034 .cindex "asterisk" "in host list"
9035 If a pattern starts with &"*"& the remainder of the item must match the end of
9036 the host name. For example, &`*.b.c`& matches all hosts whose names end in
9037 &'.b.c'&. This special simple form is provided because this is a very common
9038 requirement. Other kinds of wildcarding require the use of a regular
9041 .cindex "regular expressions" "in host list"
9042 .cindex "host list" "regular expression in"
9043 If the item starts with &"^"& it is taken to be a regular expression which is
9044 matched against the host name. Host names are case-independent, so this regular
9045 expression match is by default case-independent, but you can make it
9046 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
9047 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
9052 is a regular expression that matches either of the two hosts &'a.c.d'& or
9053 &'b.c.d'&. When a regular expression is used in a host list, you must take care
9054 that backslash and dollar characters are not misinterpreted as part of the
9055 string expansion. The simplest way to do this is to use &`\N`& to mark that
9056 part of the string as non-expandable. For example:
9058 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
9060 &*Warning*&: If you want to match a complete host name, you must include the
9061 &`$`& terminating metacharacter in the regular expression, as in the above
9062 example. Without it, a match at the start of the host name is all that is
9069 .subsection "Behaviour when an IP address or name cannot be found" SECTbehipnot
9070 .cindex "host" "lookup failures, permanent"
9071 While processing a host list, Exim may need to look up an IP address from a
9072 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
9073 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
9074 behaviour when it fails to find the information it is seeking is the same.
9076 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
9077 apply to temporary DNS errors, whose handling is described in the next section.
9079 .cindex "&`+include_unknown`&"
9080 .cindex "&`+ignore_unknown`&"
9081 Exim parses a host list from left to right. If it encounters a permanent
9082 lookup failure in any item in the host list before it has found a match,
9083 Exim treats it as a failure and the default behavior is as if the host
9084 does not match the list. This may not always be what you want to happen.
9085 To change Exim's behaviour, the special items &`+include_unknown`& or
9086 &`+ignore_unknown`& may appear in the list (at top level &-- they are
9087 not recognized in an indirected file).
9090 If any item that follows &`+include_unknown`& requires information that
9091 cannot found, Exim behaves as if the host does match the list. For example,
9093 host_reject_connection = +include_unknown:*.enemy.ex
9095 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
9096 any hosts whose name it cannot find.
9099 If any item that follows &`+ignore_unknown`& requires information that cannot
9100 be found, Exim ignores that item and proceeds to the rest of the list. For
9103 accept hosts = +ignore_unknown : friend.example : \
9106 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
9107 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
9108 name can be found for 192.168.4.5, it is rejected.
9111 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
9112 list. The effect of each one lasts until the next, or until the end of the
9115 .subsection "Mixing wildcarded host names and addresses in host lists" &&&
9117 .cindex "host list" "mixing names and addresses in"
9119 This section explains the host/ip processing logic with the same concepts
9120 as the previous section, but specifically addresses what happens when a
9121 wildcarded hostname is one of the items in the hostlist.
9124 If you have name lookups or wildcarded host names and
9125 IP addresses in the same host list, you should normally put the IP
9126 addresses first. For example, in an ACL you could have:
9128 accept hosts = 10.9.8.7 : *.friend.example
9130 The reason you normally would order it this way lies in the
9131 left-to-right way that Exim processes lists. It can test IP addresses
9132 without doing any DNS lookups, but when it reaches an item that requires
9133 a host name, it fails if it cannot find a host name to compare with the
9134 pattern. If the above list is given in the opposite order, the
9135 &%accept%& statement fails for a host whose name cannot be found, even
9136 if its IP address is 10.9.8.7.
9139 If you really do want to do the name check first, and still recognize the IP
9140 address, you can rewrite the ACL like this:
9142 accept hosts = *.friend.example
9143 accept hosts = 10.9.8.7
9145 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
9146 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
9147 &`+ignore_unknown`&, which was discussed in depth in the first example in
9152 .subsection "Temporary DNS errors when looking up host information" &&&
9154 .cindex "host" "lookup failures, temporary"
9155 .cindex "&`+include_defer`&"
9156 .cindex "&`+ignore_defer`&"
9157 A temporary DNS lookup failure normally causes a defer action (except when
9158 &%dns_again_means_nonexist%& converts it into a permanent error). However,
9159 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
9160 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
9161 section. These options should be used with care, probably only in non-critical
9162 host lists such as whitelists.
9166 .subsection "Host list patterns for single-key lookups by host name" &&&
9168 .cindex "unknown host name"
9169 .cindex "host list" "matching host name"
9170 If a pattern is of the form
9172 <&'single-key-search-type'&>;<&'search-data'&>
9176 dbm;/host/accept/list
9178 a single-key lookup is performed, using the host name as its key. If the
9179 lookup succeeds, the host matches the item. The actual data that is looked up
9182 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
9183 keys in the file, not IP addresses. If you want to do lookups based on IP
9184 addresses, you must precede the search type with &"net-"& (see section
9185 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
9186 two items in the same list, one doing an address lookup and one doing a name
9187 lookup, both using the same file.
9191 .subsection "Host list patterns for query-style lookups" SECID81
9192 If a pattern is of the form
9194 <&'query-style-search-type'&>;<&'query'&>
9196 the query is obeyed, and if it succeeds, the host matches the item. The actual
9197 data that is looked up is not used. The variables &$sender_host_address$& and
9198 &$sender_host_name$& can be used in the query. For example:
9200 hosts_lookup = pgsql;\
9201 select ip from hostlist where ip='$sender_host_address'
9203 The value of &$sender_host_address$& for an IPv6 address contains colons. You
9204 can use the &%sg%& expansion item to change this if you need to. If you want to
9205 use masked IP addresses in database queries, you can use the &%mask%& expansion
9208 If the query contains a reference to &$sender_host_name$&, Exim automatically
9209 looks up the host name if it has not already done so. (See section
9210 &<<SECThoslispatnam>>& for comments on finding host names.)
9212 Historical note: prior to release 4.30, Exim would always attempt to find a
9213 host name before running the query, unless the search type was preceded by
9214 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
9215 still recognized for query-style lookups, but its presence or absence has no
9216 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
9217 See section &<<SECThoslispatsikey>>&.)
9223 .section "Address lists" "SECTaddresslist"
9224 .cindex "list" "address list"
9225 .cindex "address list" "empty item"
9226 .cindex "address list" "patterns"
9227 Address lists contain patterns that are matched against mail addresses. There
9228 is one special case to be considered: the sender address of a bounce message is
9229 always empty. You can test for this by providing an empty item in an address
9230 list. For example, you can set up a router to process bounce messages by
9231 using this option setting:
9235 The presence of the colon creates an empty item. If you do not provide any
9236 data, the list is empty and matches nothing. The empty sender can also be
9237 detected by a regular expression that matches an empty string,
9238 and by a query-style lookup that succeeds when &$sender_address$& is empty.
9240 Non-empty items in an address list can be straightforward email addresses. For
9243 senders = jbc@askone.example : hs@anacreon.example
9245 A certain amount of wildcarding is permitted. If a pattern contains an @
9246 character, but is not a regular expression and does not begin with a
9247 semicolon-terminated lookup type (described below), the local part of the
9248 subject address is compared with the local part of the pattern, which may start
9249 with an asterisk. If the local parts match, the domain is checked in exactly
9250 the same way as for a pattern in a domain list. For example, the domain can be
9251 wildcarded, refer to a named list, or be a lookup:
9253 deny senders = *@*.spamming.site:\
9254 *@+hostile_domains:\
9255 bozo@partial-lsearch;/list/of/dodgy/sites:\
9256 *@dbm;/bad/domains.db
9258 .cindex "local part" "starting with !"
9259 .cindex "address list" "local part starting with !"
9260 If a local part that begins with an exclamation mark is required, it has to be
9261 specified using a regular expression, because otherwise the exclamation mark is
9262 treated as a sign of negation, as is standard in lists.
9264 If a non-empty pattern that is not a regular expression or a lookup does not
9265 contain an @ character, it is matched against the domain part of the subject
9266 address. The only two formats that are recognized this way are a literal
9267 domain, or a domain pattern that starts with *. In both these cases, the effect
9268 is the same as if &`*@`& preceded the pattern. For example:
9270 deny senders = enemy.domain : *.enemy.domain
9273 The following kinds of more complicated address list pattern can match any
9274 address, including the empty address that is characteristic of bounce message
9278 .cindex "regular expressions" "in address list"
9279 .cindex "address list" "regular expression in"
9280 If (after expansion) a pattern starts with &"^"&, a regular expression match is
9281 done against the complete address, with the pattern as the regular expression.
9282 You must take care that backslash and dollar characters are not misinterpreted
9283 as part of the string expansion. The simplest way to do this is to use &`\N`&
9284 to mark that part of the string as non-expandable. For example:
9286 deny senders = \N^.*this.*@example\.com$\N : \
9287 \N^\d{8}.+@spamhaus.example$\N : ...
9289 The &`\N`& sequences are removed by the expansion, so these items do indeed
9290 start with &"^"& by the time they are being interpreted as address patterns.
9293 .cindex "address list" "lookup for complete address"
9294 Complete addresses can be looked up by using a pattern that starts with a
9295 lookup type terminated by a semicolon, followed by the data for the lookup. For
9298 deny senders = cdb;/etc/blocked.senders : \
9299 mysql;select address from blocked where \
9300 address='${quote_mysql:$sender_address}'
9302 Both query-style and single-key lookup types can be used. For a single-key
9303 lookup type, Exim uses the complete address as the key. However, empty keys are
9304 not supported for single-key lookups, so a match against the empty address
9305 always fails. This restriction does not apply to query-style lookups.
9307 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
9308 cannot be used, and is ignored if specified, with an entry being written to the
9310 .cindex "*@ with single-key lookup"
9311 However, you can configure lookup defaults, as described in section
9312 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
9313 default. For example, with this lookup:
9315 accept senders = lsearch*@;/some/file
9317 the file could contains lines like this:
9319 user1@domain1.example
9322 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
9325 nimrod@jaeger.example
9329 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
9330 would mean that every address matches, thus rendering the test useless.
9332 &*Warning 2*&: Do not confuse these two kinds of item:
9334 deny recipients = dbm*@;/some/file
9335 deny recipients = *@dbm;/some/file
9337 The first does a whole address lookup, with defaulting, as just described,
9338 because it starts with a lookup type. The second matches the local part and
9339 domain independently, as described in a bullet point below.
9343 The following kinds of address list pattern can match only non-empty addresses.
9344 If the subject address is empty, a match against any of these pattern types
9349 .cindex "@@ with single-key lookup"
9350 .cindex "address list" "@@ lookup type"
9351 .cindex "address list" "split local part and domain"
9352 If a pattern starts with &"@@"& followed by a single-key lookup item
9353 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
9354 split into a local part and a domain. The domain is looked up in the file. If
9355 it is not found, there is no match. If it is found, the data that is looked up
9356 from the file is treated as a colon-separated list of local part patterns, each
9357 of which is matched against the subject local part in turn.
9359 .cindex "asterisk" "in address list"
9360 The lookup may be a partial one, and/or one involving a search for a default
9361 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
9362 patterns that are looked up can be regular expressions or begin with &"*"&, or
9363 even be further lookups. They may also be independently negated. For example,
9366 deny senders = @@dbm;/etc/reject-by-domain
9368 the data from which the DBM file is built could contain lines like
9370 baddomain.com: !postmaster : *
9372 to reject all senders except &%postmaster%& from that domain.
9374 .cindex "local part" "starting with !"
9375 If a local part that actually begins with an exclamation mark is required, it
9376 has to be specified using a regular expression. In &(lsearch)& files, an entry
9377 may be split over several lines by indenting the second and subsequent lines,
9378 but the separating colon must still be included at line breaks. White space
9379 surrounding the colons is ignored. For example:
9381 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
9384 As in all colon-separated lists in Exim, a colon can be included in an item by
9387 If the last item in the list starts with a right angle-bracket, the remainder
9388 of the item is taken as a new key to look up in order to obtain a continuation
9389 list of local parts. The new key can be any sequence of characters. Thus one
9390 might have entries like
9392 aol.com: spammer1 : spammer 2 : >*
9393 xyz.com: spammer3 : >*
9396 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
9397 local parts for all domains, in addition to the specific local parts listed for
9398 each domain. Of course, using this feature costs another lookup each time a
9399 chain is followed, but the effort needed to maintain the data is reduced.
9401 .cindex "loop" "in lookups"
9402 It is possible to construct loops using this facility, and in order to catch
9403 them, the chains may be no more than fifty items long.
9406 The @@<&'lookup'&> style of item can also be used with a query-style
9407 lookup, but in this case, the chaining facility is not available. The lookup
9408 can only return a single list of local parts.
9411 &*Warning*&: There is an important difference between the address list items
9412 in these two examples:
9415 senders = *@+my_list
9417 In the first one, &`my_list`& is a named address list, whereas in the second
9418 example it is a named domain list.
9423 .subsection "Case of letters in address lists" SECTcasletadd
9424 .cindex "case of local parts"
9425 .cindex "address list" "case forcing"
9426 .cindex "case forcing in address lists"
9427 Domains in email addresses are always handled caselessly, but for local parts
9428 case may be significant on some systems (see &%caseful_local_part%& for how
9429 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
9430 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
9431 blocking lists should be done in a case-independent manner. Since most address
9432 lists in Exim are used for this kind of control, Exim attempts to do this by
9435 The domain portion of an address is always lowercased before matching it to an
9436 address list. The local part is lowercased by default, and any string
9437 comparisons that take place are done caselessly. This means that the data in
9438 the address list itself, in files included as plain filenames, and in any file
9439 that is looked up using the &"@@"& mechanism, can be in any case. However, the
9440 keys in files that are looked up by a search type other than &(lsearch)& (which
9441 works caselessly) must be in lower case, because these lookups are not
9444 .cindex "&`+caseful`&"
9445 To allow for the possibility of caseful address list matching, if an item in
9446 an address list is the string &"+caseful"&, the original case of the local
9447 part is restored for any comparisons that follow, and string comparisons are no
9448 longer case-independent. This does not affect the domain, which remains in
9449 lower case. However, although independent matches on the domain alone are still
9450 performed caselessly, regular expressions that match against an entire address
9451 become case-sensitive after &"+caseful"& has been seen.
9455 .section "Local part lists" "SECTlocparlis"
9456 .cindex "list" "local part list"
9457 .cindex "local part" "list"
9458 These behave in the same way as domain and host lists, with the following
9461 Case-sensitivity in local part lists is handled in the same way as for address
9462 lists, as just described. The &"+caseful"& item can be used if required. In a
9463 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
9464 set false, the subject is lowercased and the matching is initially
9465 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
9466 matching in the local part list, but not elsewhere in the router. If
9467 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
9468 option is case-sensitive from the start.
9470 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
9471 comments are handled in the same way as address lists &-- they are recognized
9472 only if the # is preceded by white space or the start of the line.
9473 Otherwise, local part lists are matched in the same way as domain lists, except
9474 that the special items that refer to the local host (&`@`&, &`@[]`&,
9475 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
9476 Refer to section &<<SECTdomainlist>>& for details of the other available item
9478 .ecindex IIDdohoadli
9483 . ////////////////////////////////////////////////////////////////////////////
9484 . ////////////////////////////////////////////////////////////////////////////
9486 .chapter "String expansions" "CHAPexpand"
9487 .scindex IIDstrexp "expansion" "of strings"
9488 Many strings in Exim's runtime configuration are expanded before use. Some of
9489 them are expanded every time they are used; others are expanded only once.
9491 When a string is being expanded it is copied verbatim from left to right except
9492 .cindex expansion "string concatenation"
9493 when a dollar or backslash character is encountered. A dollar specifies the
9494 start of a portion of the string that is interpreted and replaced as described
9495 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
9496 escape character, as described in the following section.
9498 Whether a string is expanded depends upon the context. Usually this is solely
9499 dependent upon the option for which a value is sought; in this documentation,
9500 options for which string expansion is performed are marked with † after
9501 the data type. ACL rules always expand strings. A couple of expansion
9502 conditions do not expand some of the brace-delimited branches, for security
9504 .cindex "tainted data" expansion
9505 .cindex "tainted data" definition
9506 .cindex expansion "tainted data"
9507 and expansion of data deriving from the sender (&"tainted data"&)
9508 is not permitted (including acessing a file using a tainted name).
9510 Common ways of obtaining untainted equivalents of variables with
9512 .cindex "tainted data" "de-tainting"
9513 come down to using the tainted value as a lookup key in a trusted database.
9514 This database could be the filesystem structure,
9515 or the password file,
9516 or accessed via a DBMS.
9517 Specific methods are indexed under &"de-tainting"&.
9521 .section "Literal text in expanded strings" "SECTlittext"
9522 .cindex "expansion" "including literal text"
9523 An uninterpreted dollar can be included in an expanded string by putting a
9524 backslash in front of it. A backslash can be used to prevent any special
9525 character being treated specially in an expansion, including backslash itself.
9526 If the string appears in quotes in the configuration file, two backslashes are
9527 required because the quotes themselves cause interpretation of backslashes when
9528 the string is read in (see section &<<SECTstrings>>&).
9530 .cindex "expansion" "non-expandable substrings"
9531 A portion of the string can specified as non-expandable by placing it between
9532 two occurrences of &`\N`&. This is particularly useful for protecting regular
9533 expressions, which often contain backslashes and dollar signs. For example:
9535 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
9537 On encountering the first &`\N`&, the expander copies subsequent characters
9538 without interpretation until it reaches the next &`\N`& or the end of the
9543 .section "Character escape sequences in expanded strings" "SECID82"
9544 .cindex "expansion" "escape sequences"
9545 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9546 expanded string is recognized as an escape sequence for the character newline,
9547 carriage return, or tab, respectively. A backslash followed by up to three
9548 octal digits is recognized as an octal encoding for a single character, and a
9549 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9552 These escape sequences are also recognized in quoted strings when they are read
9553 in. Their interpretation in expansions as well is useful for unquoted strings,
9554 and for other cases such as looked-up strings that are then expanded.
9557 .section "Testing string expansions" "SECID83"
9558 .cindex "expansion" "testing"
9559 .cindex "testing" "string expansion"
9561 Many expansions can be tested by calling Exim with the &%-be%& option. This
9562 takes the command arguments, or lines from the standard input if there are no
9563 arguments, runs them through the string expansion code, and writes the results
9564 to the standard output. Variables based on configuration values are set up, but
9565 since no message is being processed, variables such as &$local_part$& have no
9566 value. Nevertheless the &%-be%& option can be useful for checking out file and
9567 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9571 When reading lines from the standard input,
9572 macros can be defined and ACL variables can be set.
9576 set acl_m_myvar = bar
9578 Such macros and variables can then be used in later input lines.
9581 Exim gives up its root privilege when it is called with the &%-be%& option, and
9582 instead runs under the uid and gid it was called with, to prevent users from
9583 using &%-be%& for reading files to which they do not have access.
9586 If you want to test expansions that include variables whose values are taken
9587 from a message, there are two other options that can be used. The &%-bem%&
9588 option is like &%-be%& except that it is followed by a filename. The file is
9589 read as a message before doing the test expansions. For example:
9591 exim -bem /tmp/test.message '$h_subject:'
9593 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9594 Exim message identifier. For example:
9596 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9598 This loads the message from Exim's spool before doing the test expansions, and
9599 is therefore restricted to admin users.
9602 .section "Forced expansion failure" "SECTforexpfai"
9603 .cindex "expansion" "forced failure"
9604 A number of expansions that are described in the following section have
9605 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9606 (which are sometimes called &"curly brackets"&). Which of the two strings is
9607 used depends on some condition that is evaluated as part of the expansion. If,
9608 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9609 the entire string expansion fails in a way that can be detected by the code
9610 that requested the expansion. This is called &"forced expansion failure"&, and
9611 its consequences depend on the circumstances. In some cases it is no different
9612 from any other expansion failure, but in others a different action may be
9613 taken. Such variations are mentioned in the documentation of the option that is
9619 .section "Expansion items" "SECTexpansionitems"
9620 The following items are recognized in expanded strings. White space may be used
9621 between sub-items that are keywords or substrings enclosed in braces inside an
9622 outer set of braces, to improve readability. &*Warning*&: Within braces,
9623 white space is significant.
9626 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9627 .cindex "expansion" "variables"
9628 Substitute the contents of the named variable, for example:
9633 The second form can be used to separate the name from subsequent alphanumeric
9634 characters. This form (using braces) is available only for variables; it does
9635 &'not'& apply to message headers. The names of the variables are given in
9636 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9637 given, the expansion fails.
9639 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9640 .cindex "expansion" "operators"
9641 The string is first itself expanded, and then the operation specified by
9642 <&'op'&> is applied to it. For example:
9646 The string starts with the first character after the colon, which may be
9647 leading white space. A list of operators is given in section &<<SECTexpop>>&
9648 below. The operator notation is used for simple expansion items that have just
9649 one argument, because it reduces the number of braces and therefore makes the
9650 string easier to understand.
9652 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9653 This item inserts &"basic"& header lines. It is described with the &%header%&
9654 expansion item below.
9657 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9658 .cindex "expansion" "calling an acl"
9659 .cindex "&%acl%&" "call from expansion"
9660 The name and zero to nine argument strings are first expanded separately. The expanded
9661 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9662 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9663 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9664 and may use the variables; if another acl expansion is used the values
9665 are restored after it returns. If the ACL sets
9666 a value using a "message =" modifier and returns accept or deny, the value becomes
9667 the result of the expansion.
9668 If no message is set and the ACL returns accept or deny
9669 the expansion result is an empty string.
9670 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9673 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
9674 .cindex authentication "results header"
9675 .chindex Authentication-Results:
9676 .cindex authentication "expansion item"
9677 This item returns a string suitable for insertion as an
9678 &'Authentication-Results:'&
9680 The given <&'authserv-id'&> is included in the result; typically this
9681 will be a domain name identifying the system performing the authentications.
9682 Methods that might be present in the result include:
9691 Example use (as an ACL modifier):
9693 add_header = :at_start:${authresults {$primary_hostname}}
9695 This is safe even if no authentication results are available
9697 and would generally be placed in the DATA ACL.
9701 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9702 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9703 .cindex "expansion" "extracting certificate fields"
9704 .cindex "&%certextract%&" "certificate fields"
9705 .cindex "certificate" "extracting fields"
9706 The <&'certificate'&> must be a variable of type certificate.
9707 The field name is expanded and used to retrieve the relevant field from
9708 the certificate. Supported fields are:
9712 &`subject `& RFC4514 DN
9713 &`issuer `& RFC4514 DN
9718 &`subj_altname `& tagged list
9722 If the field is found,
9723 <&'string2'&> is expanded, and replaces the whole item;
9724 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9725 variable &$value$& contains the value that has been extracted. Afterwards, it
9726 is restored to any previous value it might have had.
9728 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9729 key is not found. If {<&'string2'&>} is also omitted, the value that was
9732 Some field names take optional modifiers, appended and separated by commas.
9734 The field selectors marked as "RFC4514" above
9735 output a Distinguished Name string which is
9737 parseable by Exim as a comma-separated tagged list
9738 (the exceptions being elements containing commas).
9739 RDN elements of a single type may be selected by
9740 a modifier of the type label; if so the expansion
9741 result is a list (newline-separated by default).
9742 The separator may be changed by another modifier of
9743 a right angle-bracket followed immediately by the new separator.
9744 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9746 The field selectors marked as "time" above
9747 take an optional modifier of "int"
9748 for which the result is the number of seconds since epoch.
9749 Otherwise the result is a human-readable string
9750 in the timezone selected by the main "timezone" option.
9752 The field selectors marked as "list" above return a list,
9753 newline-separated by default,
9754 (embedded separator characters in elements are doubled).
9755 The separator may be changed by a modifier of
9756 a right angle-bracket followed immediately by the new separator.
9758 The field selectors marked as "tagged" above
9759 prefix each list element with a type string and an equals sign.
9760 Elements of only one type may be selected by a modifier
9761 which is one of "dns", "uri" or "mail";
9762 if so the element tags are omitted.
9764 If not otherwise noted field values are presented in human-readable form.
9766 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9767 {*&<&'arg'&>&*}...}*&"
9769 This expansion dynamically loads and then calls a locally-written C function.
9770 This functionality is available only if Exim is compiled with
9774 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9775 object so that it doesn't reload the same object file in the same Exim process
9776 (but of course Exim does start new processes frequently).
9778 There may be from zero to eight arguments to the function.
9781 a local function that is to be called in this way,
9782 first &_DLFUNC_IMPL_& should be defined,
9783 and second &_local_scan.h_& should be included.
9784 The Exim variables and functions that are defined by that API
9785 are also available for dynamically loaded functions. The function itself
9786 must have the following type:
9788 int dlfunction(uschar **yield, int argc, uschar *argv[])
9790 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9791 function should return one of the following values:
9793 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9794 into the expanded string that is being built.
9796 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9797 from &'yield'&, if it is set.
9799 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9800 taken from &'yield'& if it is set.
9802 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9804 When compiling a function that is to be used in this way with gcc,
9805 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9806 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9809 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9810 .cindex "expansion" "extracting value from environment"
9811 .cindex "environment" "values from"
9812 The key is first expanded separately, and leading and trailing white space
9814 This is then searched for as a name in the environment.
9815 If a variable is found then its value is placed in &$value$&
9816 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9818 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9819 appear, for example:
9821 ${env{USER}{$value} fail }
9823 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9824 {<&'string1'&>} must be present for &"fail"& to be recognized.
9826 If {<&'string2'&>} is omitted an empty string is substituted on
9828 If {<&'string1'&>} is omitted the search result is substituted on
9831 The environment is adjusted by the &%keep_environment%& and
9832 &%add_environment%& main section options.
9835 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9836 {*&<&'string3'&>&*}}*&"
9837 .cindex "expansion" "extracting substrings by key"
9838 .cindex "&%extract%&" "substrings by key"
9839 The key and <&'string1'&> are first expanded separately. Leading and trailing
9840 white space is removed from the key (but not from any of the strings). The key
9841 must not be empty and must not consist entirely of digits.
9842 The expanded <&'string1'&> must be of the form:
9844 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9847 where the equals signs and spaces (but not both) are optional. If any of the
9848 values contain white space, they must be enclosed in double quotes, and any
9849 values that are enclosed in double quotes are subject to escape processing as
9850 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9851 for the value that corresponds to the key. The search is case-insensitive. If
9852 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9853 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9854 variable &$value$& contains the value that has been extracted. Afterwards, it
9855 is restored to any previous value it might have had.
9857 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9858 key is not found. If {<&'string2'&>} is also omitted, the value that was
9859 extracted is used. Thus, for example, these two expansions are identical, and
9862 ${extract{gid}{uid=1984 gid=2001}}
9863 ${extract{gid}{uid=1984 gid=2001}{$value}}
9865 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9866 appear, for example:
9868 ${extract{Z}{A=... B=...}{$value} fail }
9870 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9871 {<&'string2'&>} must be present for &"fail"& to be recognized.
9873 .vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9874 {*&<&'string3'&>&*}}*&" &&&
9875 "&*${extract jsons{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9876 {*&<&'string3'&>&*}}*&"
9877 .cindex "expansion" "extracting from JSON object"
9878 .cindex JSON expansions
9879 The key and <&'string1'&> are first expanded separately. Leading and trailing
9880 white space is removed from the key (but not from any of the strings). The key
9881 must not be empty and must not consist entirely of digits.
9882 The expanded <&'string1'&> must be of the form:
9884 { <&'"key1"'&> : <&'value1'&> , <&'"key2"'&> , <&'value2'&> ... }
9887 The braces, commas and colons, and the quoting of the member name are required;
9888 the spaces are optional.
9889 Matching of the key against the member names is done case-sensitively.
9890 For the &"json"& variant,
9891 if a returned value is a JSON string, it retains its leading and
9893 For the &"jsons"& variant, which is intended for use with JSON strings, the
9894 leading and trailing quotes are removed from the returned value.
9895 . XXX should be a UTF-8 compare
9897 The results of matching are handled as above.
9900 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9901 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9902 .cindex "expansion" "extracting substrings by number"
9903 .cindex "&%extract%&" "substrings by number"
9904 The <&'number'&> argument must consist entirely of decimal digits,
9905 apart from leading and trailing white space, which is ignored.
9906 This is what distinguishes this form of &%extract%& from the previous kind. It
9907 behaves in the same way, except that, instead of extracting a named field, it
9908 extracts from <&'string1'&> the field whose number is given as the first
9909 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9910 <&'string3'&> as before.
9912 The fields in the string are separated by any one of the characters in the
9913 separator string. These may include space or tab characters.
9914 The first field is numbered one. If the number is negative, the fields are
9915 counted from the end of the string, with the rightmost one numbered -1. If the
9916 number given is zero, the entire string is returned. If the modulus of the
9917 number is greater than the number of fields in the string, the result is the
9918 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9919 provided. For example:
9921 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9925 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9927 yields &"99"&. Two successive separators mean that the field between them is
9928 empty (for example, the fifth field above).
9931 .vitem "&*${extract json {*&<&'number'&>&*}}&&&
9932 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" &&&
9933 "&*${extract jsons{*&<&'number'&>&*}}&&&
9934 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9935 .cindex "expansion" "extracting from JSON array"
9936 .cindex JSON expansions
9937 The <&'number'&> argument must consist entirely of decimal digits,
9938 apart from leading and trailing white space, which is ignored.
9940 Field selection and result handling is as above;
9941 there is no choice of field separator.
9942 For the &"json"& variant,
9943 if a returned value is a JSON string, it retains its leading and
9945 For the &"jsons"& variant, which is intended for use with JSON strings, the
9946 leading and trailing quotes are removed from the returned value.
9949 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9950 .cindex "list" "selecting by condition"
9951 .cindex "expansion" "selecting from list by condition"
9953 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9954 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
9956 in this list, its value is place in &$item$&, and then the condition is
9959 Any modification of &$value$& by this evaluation is discarded.
9961 If the condition is true, &$item$& is added to the output as an
9962 item in a new list; if the condition is false, the item is discarded. The
9963 separator used for the output list is the same as the one used for the
9964 input, but a separator setting is not included in the output. For example:
9966 ${filter{a:b:c}{!eq{$item}{b}}}
9968 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9969 to what it was before.
9970 See also the &%map%& and &%reduce%& expansion items.
9973 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9974 .cindex "hash function" "textual"
9975 .cindex "expansion" "textual hash"
9976 This is a textual hashing function, and was the first to be implemented in
9977 early versions of Exim. In current releases, there are other hashing functions
9978 (numeric, MD5, and SHA-1), which are described below.
9980 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9981 <&'n'&>. If you are using fixed values for these numbers, that is, if
9982 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9983 use the simpler operator notation that avoids some of the braces:
9985 ${hash_<n>_<m>:<string>}
9987 The second number is optional (in both notations). If <&'n'&> is greater than
9988 or equal to the length of the string, the expansion item returns the string.
9989 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9990 function to the string. The new string consists of characters taken from the
9991 first <&'m'&> characters of the string
9993 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9995 If <&'m'&> is not present the value 26 is used, so that only lower case
9996 letters appear. For example:
9998 &`$hash{3}{monty}} `& yields &`jmg`&
9999 &`$hash{5}{monty}} `& yields &`monty`&
10000 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
10003 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
10004 &*$h_*&<&'header&~name'&>&*:*&" &&&
10005 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10006 &*$bh_*&<&'header&~name'&>&*:*&" &&&
10007 "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10008 &*$lh_*&<&'header&~name'&>&*:*&" &&&
10009 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10010 &*$rh_*&<&'header&~name'&>&*:*&"
10011 .cindex "expansion" "header insertion"
10012 .vindex "&$header_$&"
10013 .vindex "&$bheader_$&"
10014 .vindex "&$lheader_$&"
10015 .vindex "&$rheader_$&"
10016 .cindex "header lines" "in expansion strings"
10017 .cindex "header lines" "character sets"
10018 .cindex "header lines" "decoding"
10019 Substitute the contents of the named message header line, for example
10023 The newline that terminates a header line is not included in the expansion, but
10024 internal newlines (caused by splitting the header line over several physical
10025 lines) may be present.
10027 The difference between the four pairs of expansions is in the way
10028 the data in the header line is interpreted.
10031 .cindex "white space" "in header lines"
10032 &%rheader%& gives the original &"raw"& content of the header line, with no
10033 processing at all, and without the removal of leading and trailing white space.
10036 .cindex "list" "of header lines"
10037 &%lheader%& gives a colon-separated list, one element per header when there
10038 are multiple headers with a given name.
10039 Any embedded colon characters within an element are doubled, so normal Exim
10040 list-processing facilities can be used.
10041 The terminating newline of each element is removed; in other respects
10042 the content is &"raw"&.
10045 .cindex "base64 encoding" "in header lines"
10046 &%bheader%& removes leading and trailing white space, and then decodes base64
10047 or quoted-printable MIME &"words"& within the header text, but does no
10048 character set translation. If decoding of what looks superficially like a MIME
10049 &"word"& fails, the raw string is returned. If decoding
10050 .cindex "binary zero" "in header line"
10051 produces a binary zero character, it is replaced by a question mark &-- this is
10052 what Exim does for binary zeros that are actually received in header lines.
10055 &%header%& tries to translate the string as decoded by &%bheader%& to a
10056 standard character set. This is an attempt to produce the same string as would
10057 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
10058 returned. Translation is attempted only on operating systems that support the
10059 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
10060 a system Makefile or in &_Local/Makefile_&.
10063 In a filter file, the target character set for &%header%& can be specified by a
10064 command of the following form:
10066 headers charset "UTF-8"
10068 This command affects all references to &$h_$& (or &$header_$&) expansions in
10069 subsequently obeyed filter commands. In the absence of this command, the target
10070 character set in a filter is taken from the setting of the &%headers_charset%&
10071 option in the runtime configuration. The value of this option defaults to the
10072 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
10075 Header names follow the syntax of RFC 2822, which states that they may contain
10076 any printing characters except space and colon. Consequently, curly brackets
10077 &'do not'& terminate header names, and should not be used to enclose them as
10078 if they were variables. Attempting to do so causes a syntax error.
10080 Only header lines that are common to all copies of a message are visible to
10081 this mechanism. These are the original header lines that are received with the
10082 message, and any that are added by an ACL statement or by a system
10083 filter. Header lines that are added to a particular copy of a message by a
10084 router or transport are not accessible.
10086 For incoming SMTP messages, no header lines are visible in
10087 ACLs that are obeyed before the data phase completes,
10088 because the header structure is not set up until the message is received.
10089 They are visible in DKIM, PRDR and DATA ACLs.
10090 Header lines that are added in a RCPT ACL (for example)
10091 are saved until the message's incoming header lines are available, at which
10092 point they are added.
10093 When any of the above ACLs are
10094 running, however, header lines added by earlier ACLs are visible.
10096 Upper case and lower case letters are synonymous in header names. If the
10097 following character is white space, the terminating colon may be omitted, but
10098 this is not recommended, because you may then forget it when it is needed. When
10099 white space terminates the header name, this white space is included in the
10100 expanded string. If the message does not contain the given header, the
10101 expansion item is replaced by an empty string. (See the &%def%& condition in
10102 section &<<SECTexpcond>>& for a means of testing for the existence of a
10105 If there is more than one header with the same name, they are all concatenated
10106 to form the substitution string, up to a maximum length of 64K. Unless
10107 &%rheader%& is being used, leading and trailing white space is removed from
10108 each header before concatenation, and a completely empty header is ignored. A
10109 newline character is then inserted between non-empty headers, but there is no
10110 newline at the very end. For the &%header%& and &%bheader%& expansion, for
10111 those headers that contain lists of addresses, a comma is also inserted at the
10112 junctions between headers. This does not happen for the &%rheader%& expansion.
10114 .cindex "tainted data" "message headers"
10115 When the headers are from an incoming message,
10116 the result of expanding any of these variables is tainted.
10119 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
10120 .cindex "expansion" "hmac hashing"
10122 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
10123 shared secret and some text into a message authentication code, as specified in
10124 RFC 2104. This differs from &`${md5:secret_text...}`& or
10125 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
10126 cryptographic hash, allowing for authentication that is not possible with MD5
10127 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
10128 present. For example:
10130 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
10132 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
10135 dd97e3ba5d1a61b5006108f8c8252953
10137 As an example of how this might be used, you might put in the main part of
10138 an Exim configuration:
10140 SPAMSCAN_SECRET=cohgheeLei2thahw
10142 In a router or a transport you could then have:
10145 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
10146 ${hmac{md5}{SPAMSCAN_SECRET}\
10147 {${primary_hostname},${message_exim_id},$h_message-id:}}
10149 Then given a message, you can check where it was scanned by looking at the
10150 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
10151 this header line is authentic by recomputing the authentication code from the
10152 host name, message ID and the &'Message-id:'& header line. This can be done
10153 using Exim's &%-be%& option, or by other means, for example, by using the
10154 &'hmac_md5_hex()'& function in Perl.
10157 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10158 .cindex "expansion" "conditional"
10159 .cindex "&%if%&, expansion item"
10160 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
10161 item; otherwise <&'string2'&> is used. The available conditions are described
10162 in section &<<SECTexpcond>>& below. For example:
10164 ${if eq {$local_part}{postmaster} {yes}{no} }
10166 The second string need not be present; if it is not and the condition is not
10167 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
10168 be present instead of the second string (without any curly brackets). In this
10169 case, the expansion is forced to fail if the condition is not true (see section
10170 &<<SECTforexpfai>>&).
10172 If both strings are omitted, the result is the string &`true`& if the condition
10173 is true, and the empty string if the condition is false. This makes it less
10174 cumbersome to write custom ACL and router conditions. For example, instead of
10176 condition = ${if >{$acl_m4}{3}{true}{false}}
10180 condition = ${if >{$acl_m4}{3}}
10185 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
10186 .cindex expansion "imap folder"
10187 .cindex "&%imapfolder%& expansion item"
10188 This item converts a (possibly multilevel, or with non-ASCII characters)
10189 folder specification to a Maildir name for filesystem use.
10190 For information on internationalisation support see &<<SECTi18nMDA>>&.
10194 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10195 .cindex "expansion" "string truncation"
10196 .cindex "&%length%& expansion item"
10197 The &%length%& item is used to extract the initial portion of a string. Both
10198 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
10199 you are using a fixed value for the number, that is, if <&'string1'&> does not
10200 change when expanded, you can use the simpler operator notation that avoids
10201 some of the braces:
10203 ${length_<n>:<string>}
10205 The result of this item is either the first <&'n'&> bytes or the whole
10206 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
10207 &%strlen%&, which gives the length of a string.
10208 All measurement is done in bytes and is not UTF-8 aware.
10211 .vitem "&*${listextract{*&<&'number'&>&*}&&&
10212 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10213 .cindex "expansion" "extracting list elements by number"
10214 .cindex "&%listextract%&" "extract list elements by number"
10215 .cindex "list" "extracting elements by number"
10216 The <&'number'&> argument must consist entirely of decimal digits,
10217 apart from an optional leading minus,
10218 and leading and trailing white space (which is ignored).
10220 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10221 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10223 The first field of the list is numbered one.
10224 If the number is negative, the fields are
10225 counted from the end of the list, with the rightmost one numbered -1.
10226 The numbered element of the list is extracted and placed in &$value$&,
10227 then <&'string2'&> is expanded as the result.
10229 If the modulus of the
10230 number is zero or greater than the number of fields in the string,
10231 the result is the expansion of <&'string3'&>.
10235 ${listextract{2}{x:42:99}}
10239 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
10241 yields &"result: 42"&.
10243 If {<&'string3'&>} is omitted, an empty string is used for string3.
10244 If {<&'string2'&>} is also omitted, the value that was
10246 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
10249 .vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*&
10250 .cindex quoting "for list"
10251 .cindex list quoting
10252 This item doubles any occurrence of the separator character
10253 in the given string.
10254 An empty string is replaced with a single space.
10255 This converts the string into a safe form for use as a list element,
10256 in a list using the given separator.
10259 .vitem "&*${lookup&~{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
10260 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" &&&
10261 "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
10262 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
10263 .cindex "expansion" "lookup in"
10264 .cindex "file" "lookups"
10265 .cindex "lookup" "in expanded string"
10266 The two forms of lookup item specify data lookups in files and databases, as
10267 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
10268 lookups, and the second is used for query-style lookups. The <&'key'&>,
10269 <&'file'&>, and <&'query'&> strings are expanded before use.
10271 If there is any white space in a lookup item which is part of a filter command,
10272 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
10273 other place where white space is significant, the lookup item must be enclosed
10274 in double quotes. The use of data lookups in users' filter files may be locked
10275 out by the system administrator.
10277 .vindex "&$value$&"
10278 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
10279 During its expansion, the variable &$value$& contains the data returned by the
10280 lookup. Afterwards it reverts to the value it had previously (at the outer
10281 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
10282 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
10283 string on failure. If <&'string2'&> is provided, it can itself be a nested
10284 lookup, thus providing a mechanism for looking up a default value when the
10285 original lookup fails.
10287 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
10288 data for the outer lookup while the parameters of the second lookup are
10289 expanded, and also while <&'string2'&> of the second lookup is expanded, should
10290 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
10291 appear, and in this case, if the lookup fails, the entire expansion is forced
10292 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
10293 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
10294 successful lookup, and nothing in the case of failure.
10296 For single-key lookups, the string &"partial"& is permitted to precede the
10297 search type in order to do partial matching, and * or *@ may follow a search
10298 type to request default lookups if the key does not match (see sections
10299 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
10301 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
10302 If a partial search is used, the variables &$1$& and &$2$& contain the wild
10303 and non-wild parts of the key during the expansion of the replacement text.
10304 They return to their previous values at the end of the lookup item.
10306 This example looks up the postmaster alias in the conventional alias file:
10308 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
10310 This example uses NIS+ to look up the full name of the user corresponding to
10311 the local part of an address, forcing the expansion to fail if it is not found:
10313 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
10318 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10319 .cindex "expansion" "list creation"
10321 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10322 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10324 in this list, its value is place in &$item$&, and then <&'string2'&> is
10325 expanded and added to the output as an item in a new list. The separator used
10326 for the output list is the same as the one used for the input, but a separator
10327 setting is not included in the output. For example:
10329 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
10331 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
10332 value of &$item$& is restored to what it was before. See also the &%filter%&
10333 and &%reduce%& expansion items.
10335 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10336 .cindex "expansion" "numeric hash"
10337 .cindex "hash function" "numeric"
10338 The three strings are expanded; the first two must yield numbers. Call them
10339 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10340 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10341 can use the simpler operator notation that avoids some of the braces:
10343 ${nhash_<n>_<m>:<string>}
10345 The second number is optional (in both notations). If there is only one number,
10346 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
10347 processed by a div/mod hash function that returns two numbers, separated by a
10348 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
10351 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
10353 returns the string &"6/33"&.
10357 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
10358 .cindex "Perl" "use in expanded string"
10359 .cindex "expansion" "calling Perl from"
10360 This item is available only if Exim has been built to include an embedded Perl
10361 interpreter. The subroutine name and the arguments are first separately
10362 expanded, and then the Perl subroutine is called with those arguments. No
10363 additional arguments need be given; the maximum number permitted, including the
10364 name of the subroutine, is nine.
10366 The return value of the subroutine is inserted into the expanded string, unless
10367 the return value is &%undef%&. In that case, the entire expansion is
10368 forced to fail, in the same way as an explicit &"fail"& on a lookup item
10369 does (see section &<<SECTforexpfai>>&). Whatever you return is evaluated
10370 in a scalar context, thus the return value is a scalar. For example, if you
10371 return a Perl vector, the return value is the size of the vector,
10374 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
10375 with the error message that was passed to &%die%&. More details of the embedded
10376 Perl facility are given in chapter &<<CHAPperl>>&.
10378 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
10379 out the use of this expansion item in filter files.
10382 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
10383 .cindex "&%prvs%& expansion item"
10384 The first argument is a complete email address and the second is secret
10385 keystring. The third argument, specifying a key number, is optional. If absent,
10386 it defaults to 0. The result of the expansion is a prvs-signed email address,
10387 to be typically used with the &%return_path%& option on an &(smtp)& transport
10388 as part of a bounce address tag validation (BATV) scheme. For more discussion
10389 and an example, see section &<<SECTverifyPRVS>>&.
10391 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
10392 {*&<&'string'&>&*}}*&"
10393 .cindex "&%prvscheck%& expansion item"
10394 This expansion item is the complement of the &%prvs%& item. It is used for
10395 checking prvs-signed addresses. If the expansion of the first argument does not
10396 yield a syntactically valid prvs-signed address, the whole item expands to the
10397 empty string. When the first argument does expand to a syntactically valid
10398 prvs-signed address, the second argument is expanded, with the prvs-decoded
10399 version of the address and the key number extracted from the address in the
10400 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
10402 These two variables can be used in the expansion of the second argument to
10403 retrieve the secret. The validity of the prvs-signed address is then checked
10404 against the secret. The result is stored in the variable &$prvscheck_result$&,
10405 which is empty for failure or &"1"& for success.
10407 The third argument is optional; if it is missing, it defaults to an empty
10408 string. This argument is now expanded. If the result is an empty string, the
10409 result of the expansion is the decoded version of the address. This is the case
10410 whether or not the signature was valid. Otherwise, the result of the expansion
10411 is the expansion of the third argument.
10413 All three variables can be used in the expansion of the third argument.
10414 However, once the expansion is complete, only &$prvscheck_result$& remains set.
10415 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
10417 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
10418 .cindex "expansion" "inserting an entire file"
10419 .cindex "file" "inserting into expansion"
10420 .cindex "&%readfile%& expansion item"
10421 The filename and end-of-line (eol) string are first expanded separately. The file is
10422 then read, and its contents replace the entire item. All newline characters in
10423 the file are replaced by the end-of-line string if it is present. Otherwise,
10424 newlines are left in the string.
10425 String expansion is not applied to the contents of the file. If you want this,
10426 you must wrap the item in an &%expand%& operator. If the file cannot be read,
10427 the string expansion fails.
10429 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
10430 locks out the use of this expansion item in filter files.
10434 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
10435 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
10436 .cindex "expansion" "inserting from a socket"
10437 .cindex "socket, use of in expansion"
10438 .cindex "&%readsocket%& expansion item"
10439 This item inserts data from a Unix domain or TCP socket into the expanded
10440 string. The minimal way of using it uses just two arguments, as in these
10443 ${readsocket{/socket/name}{request string}}
10444 ${readsocket{inet:some.host:1234}{request string}}
10446 For a Unix domain socket, the first substring must be the path to the socket.
10447 For an Internet socket, the first substring must contain &`inet:`& followed by
10448 a host name or IP address, followed by a colon and a port, which can be a
10449 number or the name of a TCP port in &_/etc/services_&. An IP address may
10450 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
10453 ${readsocket{inet:[::1]:1234}{request string}}
10455 Only a single host name may be given, but if looking it up yields more than
10456 one IP address, they are each tried in turn until a connection is made. For
10457 both kinds of socket, Exim makes a connection, writes the request string
10458 (unless it is an empty string; no terminating NUL is ever sent)
10459 and reads from the socket until an end-of-file
10460 is read. A timeout of 5 seconds is applied. Additional, optional arguments
10461 extend what can be done. Firstly, you can vary the timeout. For example:
10463 ${readsocket{/socket/name}{request string}{3s}}
10466 The third argument is a list of options, of which the first element is the timeout
10467 and must be present if any options are given.
10468 Further elements are options of form &'name=value'&.
10471 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
10474 The following option names are recognised:
10477 Defines if the result data can be cached for use by a later identical
10478 request in the same process.
10479 Values are &"yes"& or &"no"& (the default).
10480 If not, all cached results for this connection specification
10481 will be invalidated.
10485 Defines whether or not a write-shutdown is done on the connection after
10486 sending the request. Values are &"yes"& (the default) or &"no"&
10487 (preferred, eg. by some webservers).
10491 Controls the use of TLS on the connection.
10492 Values are &"yes"& or &"no"& (the default).
10493 If it is enabled, a shutdown as described above is never done.
10497 A fourth argument allows you to change any newlines that are in the data
10498 that is read, in the same way as for &%readfile%& (see above). This example
10499 turns them into spaces:
10501 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
10503 As with all expansions, the substrings are expanded before the processing
10504 happens. Errors in these sub-expansions cause the expansion to fail. In
10505 addition, the following errors can occur:
10508 Failure to create a socket file descriptor;
10510 Failure to connect the socket;
10512 Failure to write the request string;
10514 Timeout on reading from the socket.
10517 By default, any of these errors causes the expansion to fail. However, if
10518 you supply a fifth substring, it is expanded and used when any of the above
10519 errors occurs. For example:
10521 ${readsocket{/socket/name}{request string}{3s}{\n}\
10524 You can test for the existence of a Unix domain socket by wrapping this
10525 expansion in &`${if exists`&, but there is a race condition between that test
10526 and the actual opening of the socket, so it is safer to use the fifth argument
10527 if you want to be absolutely sure of avoiding an expansion error for a
10528 non-existent Unix domain socket, or a failure to connect to an Internet socket.
10530 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
10531 locks out the use of this expansion item in filter files.
10534 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10535 .cindex "expansion" "reducing a list to a scalar"
10536 .cindex "list" "reducing to a scalar"
10537 .vindex "&$value$&"
10539 This operation reduces a list to a single, scalar string. After expansion,
10540 <&'string1'&> is interpreted as a list, colon-separated by default, but the
10541 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10542 Then <&'string2'&> is expanded and
10543 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
10544 list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
10545 them. The result of that expansion is assigned to &$value$& before the next
10546 iteration. When the end of the list is reached, the final value of &$value$& is
10547 added to the expansion output. The &%reduce%& expansion item can be used in a
10548 number of ways. For example, to add up a list of numbers:
10550 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
10552 The result of that expansion would be &`6`&. The maximum of a list of numbers
10555 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
10557 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
10558 restored to what they were before. See also the &%filter%& and &%map%&
10561 . A bit of a special-case logic error in writing an expansion;
10562 . probably not worth including in the mainline of documentation.
10563 . If only we had footnotes (the html output variant is the problem).
10566 . &*Note*&: if an &'expansion condition'& is used in <&'string3'&>
10567 . and that condition modifies &$value$&,
10568 . then the string expansions dependent on the condition cannot use
10569 . the &$value$& of the reduce iteration.
10572 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
10573 This item inserts &"raw"& header lines. It is described with the &%header%&
10574 expansion item in section &<<SECTexpansionitems>>& above.
10576 .vitem "&*${run <&'options'&> {*&<&'command&~arg&~list'&>&*}{*&<&'string1'&>&*}&&&
10577 {*&<&'string2'&>&*}}*&"
10578 .cindex "expansion" "running a command"
10579 .cindex "&%run%& expansion item"
10580 This item runs an external command, as a subprocess.
10581 One option is supported after the word &'run'&, comma-separated.
10583 If the option &'preexpand'& is not used,
10584 the command string is split into individual arguments by spaces
10585 and then each argument is expanded.
10586 Then the command is run
10587 in a separate process, but under the same uid and gid. As in other command
10588 executions from Exim, a shell is not used by default. If the command requires
10589 a shell, you must explicitly code it.
10590 The command name may not be tainted, but the remaining arguments can be.
10592 &*Note*&: if tainted arguments are used, they are supplied by a
10593 potential attacker;
10594 a careful assessment for security vulnerabilities should be done.
10596 If the option &'preexpand'& is used,
10597 the command and its arguments are first expanded as one string. The result is
10598 split apart into individual arguments by spaces, and then the command is run
10600 Since the arguments are split by spaces, when there is a variable expansion
10601 which has an empty result, it will cause the situation that the argument will
10602 simply be omitted when the program is actually executed by Exim. If the
10603 script/program requires a specific number of arguments and the expanded
10604 variable could possibly result in this empty expansion, the variable must be
10605 quoted. This is more difficult if the expanded variable itself could result
10606 in a string containing quotes, because it would interfere with the quotes
10607 around the command arguments. A possible guard against this is to wrap the
10608 variable in the &%sg%& operator to change any quote marks to some other
10610 Neither the command nor any argument may be tainted.
10612 The standard input for the command exists, but is empty. The standard output
10613 and standard error are set to the same file descriptor.
10614 .cindex "return code" "from &%run%& expansion"
10615 .vindex "&$value$&"
10616 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
10617 and replaces the entire item; during this expansion, the standard output/error
10618 from the command is in the variable &$value$&. If the command fails,
10619 <&'string2'&>, if present, is expanded and used. Once again, during the
10620 expansion, the standard output/error from the command is in the variable
10623 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
10624 can be the word &"fail"& (not in braces) to force expansion failure if the
10625 command does not succeed. If both strings are omitted, the result is contents
10626 of the standard output/error on success, and nothing on failure.
10628 .vindex "&$run_in_acl$&"
10629 The standard output/error of the command is put in the variable &$value$&.
10630 In this ACL example, the output of a command is logged for the admin to
10633 warn condition = ${run{/usr/bin/id}{yes}{no}}
10634 log_message = Output of id: $value
10636 If the command requires shell idioms, such as the > redirect operator, the
10637 shell must be invoked directly, such as with:
10639 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
10642 .vindex "&$runrc$&"
10643 The return code from the command is put in the variable &$runrc$&, and this
10644 remains set afterwards, so in a filter file you can do things like this:
10646 if "${run{x y z}{}}$runrc" is 1 then ...
10647 elif $runrc is 2 then ...
10651 If execution of the command fails (for example, the command does not exist),
10652 the return code is 127 &-- the same code that shells use for non-existent
10655 &*Warning*&: In a router or transport, you cannot assume the order in which
10656 option values are expanded, except for those preconditions whose order of
10657 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
10658 by the expansion of one option, and use it in another.
10660 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
10661 out the use of this expansion item in filter files.
10664 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
10665 .cindex "expansion" "string substitution"
10666 .cindex "&%sg%& expansion item"
10667 This item works like Perl's substitution operator (s) with the global (/g)
10668 option; hence its name. However, unlike the Perl equivalent, Exim does not
10669 modify the subject string; instead it returns the modified string for insertion
10670 into the overall expansion. The item takes three arguments: the subject string,
10671 a regular expression, and a substitution string. For example:
10673 ${sg{abcdefabcdef}{abc}{xyz}}
10675 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
10676 if any $, } or \ characters are required in the regular expression or in the
10677 substitution string, they have to be escaped. For example:
10679 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
10681 yields &"defabc"&, and
10683 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
10685 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
10686 the regular expression from string expansion.
10688 The regular expression is compiled in 8-bit mode, working against bytes
10689 rather than any Unicode-aware character handling.
10692 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
10693 .cindex sorting "a list"
10694 .cindex list sorting
10695 .cindex expansion "list sorting"
10696 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10697 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10698 The <&'comparator'&> argument is interpreted as the operator
10699 of a two-argument expansion condition.
10700 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
10701 The comparison should return true when applied to two values
10702 if the first value should sort before the second value.
10703 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
10704 the element being placed in &$item$&,
10705 to give values for comparison.
10707 The item result is a sorted list,
10708 with the original list separator,
10709 of the list elements (in full) of the original.
10713 ${sort{3:2:1:4}{<}{$item}}
10715 sorts a list of numbers, and
10717 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10719 will sort an MX lookup into priority order.
10723 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
10724 SRS encoding. See SECT &<<SECTSRS>>& for details.
10728 .vitem &*${substr{*&<&'start'&>&*}{*&<&'len'&>&*}{*&<&'subject'&>&*}}*&
10729 .cindex "&%substr%& expansion item"
10730 .cindex "substring extraction"
10731 .cindex "expansion" "substring extraction"
10732 The three strings are expanded; the first two must yield numbers. Call them
10733 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10734 if <&'start'&> and <&'len'&> do not change when they are expanded, you
10735 can use the simpler operator notation that avoids some of the braces:
10737 ${substr_<n>_<m>:<subject>}
10739 The second number is optional (in both notations).
10740 If it is absent in the simpler format, the preceding underscore must also be
10743 The &%substr%& item can be used to extract more general substrings than
10744 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10745 length required. For example
10747 ${substr{3}{2}{$local_part}}
10749 If the starting offset is greater than the string length the result is the
10750 null string; if the length plus starting offset is greater than the string
10751 length, the result is the right-hand part of the string, starting from the
10752 given offset. The first byte (character) in the string has offset zero.
10754 The &%substr%& expansion item can take negative offset values to count
10755 from the right-hand end of its operand. The last byte (character) is offset -1,
10756 the second-last is offset -2, and so on. Thus, for example,
10758 ${substr{-5}{2}{1234567}}
10760 yields &"34"&. If the absolute value of a negative offset is greater than the
10761 length of the string, the substring starts at the beginning of the string, and
10762 the length is reduced by the amount of overshoot. Thus, for example,
10764 ${substr{-5}{2}{12}}
10766 yields an empty string, but
10768 ${substr{-3}{2}{12}}
10772 When the second number is omitted from &%substr%&, the remainder of the string
10773 is taken if the offset is positive. If it is negative, all bytes (characters) in the
10774 string preceding the offset point are taken. For example, an offset of -1 and
10775 no length, as in these semantically identical examples:
10778 ${substr{-1}{abcde}}
10780 yields all but the last character of the string, that is, &"abcd"&.
10782 All measurement is done in bytes and is not UTF-8 aware.
10786 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10787 {*&<&'replacements'&>&*}}*&"
10788 .cindex "expansion" "character translation"
10789 .cindex "&%tr%& expansion item"
10790 This item does single-character (in bytes) translation on its subject string. The second
10791 argument is a list of characters to be translated in the subject string. Each
10792 matching character is replaced by the corresponding character from the
10793 replacement list. For example
10795 ${tr{abcdea}{ac}{13}}
10797 yields &`1b3de1`&. If there are duplicates in the second character string, the
10798 last occurrence is used. If the third string is shorter than the second, its
10799 last character is replicated. However, if it is empty, no translation takes
10802 All character handling is done in bytes and is not UTF-8 aware.
10808 .section "Expansion operators" "SECTexpop"
10809 .cindex "expansion" "operators"
10810 For expansion items that perform transformations on a single argument string,
10811 the &"operator"& notation is used because it is simpler and uses fewer braces.
10812 The substring is first expanded before the operation is applied to it. The
10813 following operations can be performed:
10816 .vitem &*${address:*&<&'string'&>&*}*&
10817 .cindex "expansion" "RFC 2822 address handling"
10818 .cindex "&%address%& expansion item"
10819 The string is interpreted as an RFC 2822 address, as it might appear in a
10820 header line, and the effective address is extracted from it. If the string does
10821 not parse successfully, the result is empty.
10823 The parsing correctly handles SMTPUTF8 Unicode in the string.
10826 .vitem &*${addresses:*&<&'string'&>&*}*&
10827 .cindex "expansion" "RFC 2822 address handling"
10828 .cindex "&%addresses%& expansion item"
10829 The string (after expansion) is interpreted as a list of addresses in RFC
10830 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10831 operative address (&'local-part@domain'&) is extracted from each item, and the
10832 result of the expansion is a colon-separated list, with appropriate
10833 doubling of colons should any happen to be present in the email addresses.
10834 Syntactically invalid RFC2822 address items are omitted from the output.
10836 It is possible to specify a character other than colon for the output
10837 separator by starting the string with > followed by the new separator
10838 character. For example:
10840 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10842 expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
10843 first, so if the expanded string starts with >, it may change the output
10844 separator unintentionally. This can be avoided by setting the output
10845 separator explicitly:
10847 ${addresses:>:$h_from:}
10850 Compare the &%address%& (singular)
10851 expansion item, which extracts the working address from a single RFC2822
10852 address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
10855 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10856 a strict interpretation of header line formatting. Exim parses the bare,
10857 unquoted portion of an email address and if it finds a comma, treats it as an
10858 email address separator. For the example header line:
10860 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10862 The first example below demonstrates that Q-encoded email addresses are parsed
10863 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10864 It does not see the comma because it's still encoded as "=2C". The second
10865 example below is passed the contents of &`$header_from:`&, meaning it gets
10866 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10867 The third example shows that the presence of a comma is skipped when it is
10868 quoted. The fourth example shows SMTPUTF8 handling.
10870 # exim -be '${addresses:From: \
10871 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10873 # exim -be '${addresses:From: Last, First <user@example.com>}'
10874 Last:user@example.com
10875 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10877 # exim -be '${addresses:フィル <フィリップ@example.jp>}'
10881 .vitem &*${base32:*&<&'digits'&>&*}*&
10882 .cindex "&%base32%& expansion item"
10883 .cindex "expansion" "conversion to base 32"
10884 The string must consist entirely of decimal digits. The number is converted to
10885 base 32 and output as a (empty, for zero) string of characters.
10886 Only lowercase letters are used.
10888 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10889 .cindex "&%base32d%& expansion item"
10890 .cindex "expansion" "conversion to base 32"
10891 The string must consist entirely of base-32 digits.
10892 The number is converted to decimal and output as a string.
10894 .vitem &*${base62:*&<&'digits'&>&*}*&
10895 .cindex "&%base62%& expansion item"
10896 .cindex "expansion" "conversion to base 62"
10897 The string must consist entirely of decimal digits. The number is converted to
10898 base 62 and output as a string of six characters, including leading zeros. In
10899 the few operating environments where Exim uses base 36 instead of base 62 for
10900 its message identifiers (because those systems do not have case-sensitive
10901 filenames), base 36 is used by this operator, despite its name. &*Note*&: Just
10902 to be absolutely clear: this is &'not'& base64 encoding.
10904 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10905 .cindex "&%base62d%& expansion item"
10906 .cindex "expansion" "conversion to base 62"
10907 The string must consist entirely of base-62 digits, or, in operating
10908 environments where Exim uses base 36 instead of base 62 for its message
10909 identifiers, base-36 digits. The number is converted to decimal and output as a
10912 .vitem &*${base64:*&<&'string'&>&*}*&
10913 .cindex "expansion" "base64 encoding"
10914 .cindex "base64 encoding" "in string expansion"
10915 .cindex "&%base64%& expansion item"
10916 .cindex certificate "base64 of DER"
10917 This operator converts a string into one that is base64 encoded.
10919 If the string is a single variable of type certificate,
10920 returns the base64 encoding of the DER form of the certificate.
10923 .vitem &*${base64d:*&<&'string'&>&*}*&
10924 .cindex "expansion" "base64 decoding"
10925 .cindex "base64 decoding" "in string expansion"
10926 .cindex "&%base64d%& expansion item"
10927 This operator converts a base64-encoded string into the un-coded form.
10930 .vitem &*${domain:*&<&'string'&>&*}*&
10931 .cindex "domain" "extraction"
10932 .cindex "expansion" "domain extraction"
10933 The string is interpreted as an RFC 2822 address and the domain is extracted
10934 from it. If the string does not parse successfully, the result is empty.
10937 .vitem &*${escape:*&<&'string'&>&*}*&
10938 .cindex "expansion" "escaping non-printing characters"
10939 .cindex "&%escape%& expansion item"
10940 If the string contains any non-printing characters, they are converted to
10941 escape sequences starting with a backslash. Whether characters with the most
10942 significant bit set (so-called &"8-bit characters"&) count as printing or not
10943 is controlled by the &%print_topbitchars%& option.
10945 .vitem &*${escape8bit:*&<&'string'&>&*}*&
10946 .cindex "expansion" "escaping 8-bit characters"
10947 .cindex "&%escape8bit%& expansion item"
10948 If the string contains any characters with the most significant bit set,
10949 they are converted to escape sequences starting with a backslash.
10950 Backslashes and DEL characters are also converted.
10953 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
10954 .cindex "expansion" "expression evaluation"
10955 .cindex "expansion" "arithmetic expression"
10956 .cindex "&%eval%& expansion item"
10957 These items supports simple arithmetic and bitwise logical operations in
10958 expansion strings. The string (after expansion) must be a conventional
10959 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
10960 logical operators, and parentheses. All operations are carried out using
10961 integer arithmetic. The operator priorities are as follows (the same as in the
10962 C programming language):
10964 .irow &'highest:'& "not (~), negate (-)"
10965 .irow "" "multiply (*), divide (/), remainder (%)"
10966 .irow "" "plus (+), minus (-)"
10967 .irow "" "shift-left (<<), shift-right (>>)"
10968 .irow "" "and (&&)"
10970 .irow &'lowest:'& "or (|)"
10972 Binary operators with the same priority are evaluated from left to right. White
10973 space is permitted before or after operators.
10975 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
10976 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
10977 decimal, even if they start with a leading zero; hexadecimal numbers are not
10978 permitted. This can be useful when processing numbers extracted from dates or
10979 times, which often do have leading zeros.
10981 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
10983 respectively. Negative numbers are supported. The result of the computation is
10984 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
10987 &`${eval:1+1} `& yields 2
10988 &`${eval:1+2*3} `& yields 7
10989 &`${eval:(1+2)*3} `& yields 9
10990 &`${eval:2+42%5} `& yields 4
10991 &`${eval:0xc&5} `& yields 4
10992 &`${eval:0xc|5} `& yields 13
10993 &`${eval:0xc^5} `& yields 9
10994 &`${eval:0xc>>1} `& yields 6
10995 &`${eval:0xc<<1} `& yields 24
10996 &`${eval:~255&0x1234} `& yields 4608
10997 &`${eval:-(~255&0x1234)} `& yields -4608
11000 As a more realistic example, in an ACL you might have
11004 {>{$rcpt_count}{10}} \
11007 {$recipients_count} \
11008 {${eval:$rcpt_count/2}} \
11011 message = Too many bad recipients
11013 The condition is true if there have been more than 10 RCPT commands and
11014 fewer than half of them have resulted in a valid recipient.
11017 .vitem &*${expand:*&<&'string'&>&*}*&
11018 .cindex "expansion" "re-expansion of substring"
11019 The &%expand%& operator causes a string to be expanded for a second time. For
11022 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
11024 first looks up a string in a file while expanding the operand for &%expand%&,
11025 and then re-expands what it has found.
11028 .vitem &*${from_utf8:*&<&'string'&>&*}*&
11030 .cindex "UTF-8" "conversion from"
11031 .cindex "expansion" "UTF-8 conversion"
11032 .cindex "&%from_utf8%& expansion item"
11033 The world is slowly moving towards Unicode, although there are no standards for
11034 email yet. However, other applications (including some databases) are starting
11035 to store data in Unicode, using UTF-8 encoding. This operator converts from a
11036 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
11037 converted to underscores. The input must be a valid UTF-8 string. If it is not,
11038 the result is an undefined sequence of bytes.
11040 Unicode code points with values less than 256 are compatible with ASCII and
11041 ISO-8859-1 (also known as Latin-1).
11042 For example, character 169 is the copyright symbol in both cases, though the
11043 way it is encoded is different. In UTF-8, more than one byte is needed for
11044 characters with code values greater than 127, whereas ISO-8859-1 is a
11045 single-byte encoding (but thereby limited to 256 characters). This makes
11046 translation from UTF-8 to ISO-8859-1 straightforward.
11049 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11050 .cindex "hash function" "textual"
11051 .cindex "expansion" "textual hash"
11052 The &%hash%& operator is a simpler interface to the hashing function that can
11053 be used when the two parameters are fixed numbers (as opposed to strings that
11054 change when expanded). The effect is the same as
11056 ${hash{<n>}{<m>}{<string>}}
11058 See the description of the general &%hash%& item above for details. The
11059 abbreviation &%h%& can be used when &%hash%& is used as an operator.
11063 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
11064 .cindex "base64 encoding" "conversion from hex"
11065 .cindex "expansion" "hex to base64"
11066 .cindex "&%hex2b64%& expansion item"
11067 This operator converts a hex string into one that is base64 encoded. This can
11068 be useful for processing the output of the various hashing functions.
11072 .vitem &*${hexquote:*&<&'string'&>&*}*&
11073 .cindex "quoting" "hex-encoded unprintable characters"
11074 .cindex "&%hexquote%& expansion item"
11075 This operator converts non-printable characters in a string into a hex
11076 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
11077 as is, and other byte values are converted to &`\xNN`&, for example, a
11078 byte value 127 is converted to &`\x7f`&.
11081 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
11082 .cindex "&%ipv6denorm%& expansion item"
11083 .cindex "IP address" normalisation
11084 This expands an IPv6 address to a full eight-element colon-separated set
11085 of hex digits including leading zeroes.
11086 A trailing ipv4-style dotted-decimal set is converted to hex.
11087 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11089 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
11090 .cindex "&%ipv6norm%& expansion item"
11091 .cindex "IP address" normalisation
11092 .cindex "IP address" "canonical form"
11093 This converts an IPv6 address to canonical form.
11094 Leading zeroes of groups are omitted, and the longest
11095 set of zero-valued groups is replaced with a double colon.
11096 A trailing ipv4-style dotted-decimal set is converted to hex.
11097 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11100 .vitem &*${lc:*&<&'string'&>&*}*&
11101 .cindex "case forcing in strings"
11102 .cindex "string" "case forcing"
11103 .cindex "lower casing"
11104 .cindex "expansion" "case forcing"
11105 .cindex "&%lc%& expansion item"
11106 This forces the letters in the string into lower-case, for example:
11110 Case is defined per the system C locale.
11112 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
11113 .cindex "expansion" "string truncation"
11114 .cindex "&%length%& expansion item"
11115 The &%length%& operator is a simpler interface to the &%length%& function that
11116 can be used when the parameter is a fixed number (as opposed to a string that
11117 changes when expanded). The effect is the same as
11119 ${length{<number>}{<string>}}
11121 See the description of the general &%length%& item above for details. Note that
11122 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
11123 when &%length%& is used as an operator.
11124 All measurement is done in bytes and is not UTF-8 aware.
11127 .vitem &*${listcount:*&<&'string'&>&*}*&
11128 .cindex "expansion" "list item count"
11129 .cindex "list" "item count"
11130 .cindex "list" "count of items"
11131 .cindex "&%listcount%& expansion item"
11132 The string is interpreted as a list and the number of items is returned.
11135 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
11136 .cindex "expansion" "named list"
11137 .cindex "&%listnamed%& expansion item"
11138 The name is interpreted as a named list and the content of the list is returned,
11139 expanding any referenced lists, re-quoting as needed for colon-separation.
11140 If the optional type is given it must be one of "a", "d", "h" or "l"
11141 and selects address-, domain-, host- or localpart- lists to search among respectively.
11142 Otherwise all types are searched in an undefined order and the first
11143 matching list is returned.
11144 &*Note*&: Neither string-expansion of lists referenced by named-list syntax elements,
11145 nor expansion of lookup elements, is done by the &%listnamed%& operator.
11148 .vitem &*${local_part:*&<&'string'&>&*}*&
11149 .cindex "expansion" "local part extraction"
11150 .cindex "&%local_part%& expansion item"
11151 The string is interpreted as an RFC 2822 address and the local part is
11152 extracted from it. If the string does not parse successfully, the result is
11154 The parsing correctly handles SMTPUTF8 Unicode in the string.
11157 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*& &&&
11158 &*${mask_n:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
11159 .cindex "masked IP address"
11160 .cindex "IP address" "masking"
11161 .cindex "CIDR notation"
11162 .cindex "expansion" "IP address masking"
11163 .cindex "&%mask%& expansion item"
11164 If the form of the string to be operated on is not an IP address followed by a
11165 slash and an integer (that is, a network address in CIDR notation), the
11166 expansion fails. Otherwise, this operator converts the IP address to binary,
11167 masks off the least significant bits according to the bit count, and converts
11168 the result back to text, with mask appended. For example,
11170 ${mask:10.111.131.206/28}
11172 returns the string &"10.111.131.192/28"&.
11174 Since this operation is expected to
11175 be mostly used for looking up masked addresses in files, the
11178 address uses dots to separate components instead of colons, because colon
11179 terminates a key string in lsearch files. So, for example,
11181 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
11185 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
11187 If the optional form &*mask_n*& is used, IPv6 address result are instead
11188 returned in normailsed form, using colons and with zero-compression.
11189 Letters in IPv6 addresses are always output in lower case.
11192 .vitem &*${md5:*&<&'string'&>&*}*&
11194 .cindex "expansion" "MD5 hash"
11195 .cindex certificate fingerprint
11196 .cindex "&%md5%& expansion item"
11197 The &%md5%& operator computes the MD5 hash value of the string, and returns it
11198 as a 32-digit hexadecimal number, in which any letters are in lower case.
11200 If the string is a single variable of type certificate,
11201 returns the MD5 hash fingerprint of the certificate.
11204 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11205 .cindex "expansion" "numeric hash"
11206 .cindex "hash function" "numeric"
11207 The &%nhash%& operator is a simpler interface to the numeric hashing function
11208 that can be used when the two parameters are fixed numbers (as opposed to
11209 strings that change when expanded). The effect is the same as
11211 ${nhash{<n>}{<m>}{<string>}}
11213 See the description of the general &%nhash%& item above for details.
11216 .vitem &*${quote:*&<&'string'&>&*}*&
11217 .cindex "quoting" "in string expansions"
11218 .cindex "expansion" "quoting"
11219 .cindex "&%quote%& expansion item"
11220 The &%quote%& operator puts its argument into double quotes if it
11221 is an empty string or
11222 contains anything other than letters, digits, underscores, dots, and hyphens.
11223 Any occurrences of double quotes and backslashes are escaped with a backslash.
11224 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
11225 respectively For example,
11233 The place where this is useful is when the argument is a substitution from a
11234 variable or a message header.
11236 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
11237 .cindex "&%quote_local_part%& expansion item"
11238 This operator is like &%quote%&, except that it quotes the string only if
11239 required to do so by the rules of RFC 2822 for quoting local parts. For
11240 example, a plus sign would not cause quoting (but it would for &%quote%&).
11241 If you are creating a new email address from the contents of &$local_part$&
11242 (or any other unknown data), you should always use this operator.
11244 This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
11245 will likely use the quoting form.
11246 Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
11249 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
11250 .cindex "quoting" "lookup-specific"
11251 This operator applies lookup-specific quoting rules to the string. Each
11252 query-style lookup type has its own quoting rules which are described with
11253 the lookups in chapter &<<CHAPfdlookup>>&. For example,
11255 ${quote_ldap:two * two}
11261 For single-key lookup types, no quoting is ever necessary and this operator
11262 yields an unchanged string.
11265 .vitem &*${randint:*&<&'n'&>&*}*&
11266 .cindex "random number"
11267 This operator returns a somewhat random number which is less than the
11268 supplied number and is at least 0. The quality of this randomness depends
11269 on how Exim was built; the values are not suitable for keying material.
11270 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
11271 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
11272 for versions of GnuTLS with that function.
11273 Otherwise, the implementation may be arc4random(), random() seeded by
11274 srandomdev() or srandom(), or a custom implementation even weaker than
11278 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
11279 .cindex "expansion" "IP address"
11280 This operator reverses an IP address; for IPv4 addresses, the result is in
11281 dotted-quad decimal form, while for IPv6 addresses the result is in
11282 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
11283 for DNS. For example,
11285 ${reverse_ip:192.0.2.4}
11286 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
11291 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
11295 .vitem &*${rfc2047:*&<&'string'&>&*}*&
11296 .cindex "expansion" "RFC 2047"
11297 .cindex "RFC 2047" "expansion operator"
11298 .cindex "&%rfc2047%& expansion item"
11299 This operator encodes text according to the rules of RFC 2047. This is an
11300 encoding that is used in header lines to encode non-ASCII characters. It is
11301 assumed that the input string is in the encoding specified by the
11302 &%headers_charset%& option, which gets its default at build time. If the string
11303 contains only characters in the range 33&--126, and no instances of the
11306 ? = ( ) < > @ , ; : \ " . [ ] _
11308 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
11309 string, using as many &"encoded words"& as necessary to encode all the
11313 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
11314 .cindex "expansion" "RFC 2047"
11315 .cindex "RFC 2047" "decoding"
11316 .cindex "&%rfc2047d%& expansion item"
11317 This operator decodes strings that are encoded as per RFC 2047. Binary zero
11318 bytes are replaced by question marks. Characters are converted into the
11319 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
11320 not recognized unless &%check_rfc2047_length%& is set false.
11322 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
11323 access a header line, RFC 2047 decoding is done automatically. You do not need
11324 to use this operator as well.
11328 .vitem &*${rxquote:*&<&'string'&>&*}*&
11329 .cindex "quoting" "in regular expressions"
11330 .cindex "regular expressions" "quoting"
11331 .cindex "&%rxquote%& expansion item"
11332 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
11333 characters in its argument. This is useful when substituting the values of
11334 variables or headers inside regular expressions.
11337 .vitem &*${sha1:*&<&'string'&>&*}*&
11338 .cindex "SHA-1 hash"
11339 .cindex "expansion" "SHA-1 hashing"
11340 .cindex certificate fingerprint
11341 .cindex "&%sha1%& expansion item"
11342 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
11343 it as a 40-digit hexadecimal number, in which any letters are in upper case.
11345 If the string is a single variable of type certificate,
11346 returns the SHA-1 hash fingerprint of the certificate.
11349 .vitem &*${sha256:*&<&'string'&>&*}*& &&&
11350 &*${sha2:*&<&'string'&>&*}*& &&&
11351 &*${sha2_<n>:*&<&'string'&>&*}*&
11352 .cindex "SHA-256 hash"
11353 .cindex "SHA-2 hash"
11354 .cindex certificate fingerprint
11355 .cindex "expansion" "SHA-256 hashing"
11356 .cindex "&%sha256%& expansion item"
11357 .cindex "&%sha2%& expansion item"
11358 The &%sha256%& operator computes the SHA-256 hash value of the string
11360 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11362 If the string is a single variable of type certificate,
11363 returns the SHA-256 hash fingerprint of the certificate.
11365 The operator can also be spelled &%sha2%& and does the same as &%sha256%&
11366 (except for certificates, which are not supported).
11367 Finally, if an underbar
11368 and a number is appended it specifies the output length, selecting a
11369 member of the SHA-2 family of hash functions.
11370 Values of 256, 384 and 512 are accepted, with 256 being the default.
11373 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
11374 &*${sha3_<n>:*&<&'string'&>&*}*&
11375 .cindex "SHA3 hash"
11376 .cindex "expansion" "SHA3 hashing"
11377 .cindex "&%sha3%& expansion item"
11378 The &%sha3%& operator computes the SHA3-256 hash value of the string
11380 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11382 If a number is appended, separated by an underbar, it specifies
11383 the output length. Values of 224, 256, 384 and 512 are accepted;
11384 with 256 being the default.
11386 The &%sha3%& expansion item is only supported if Exim has been
11387 compiled with GnuTLS 3.5.0 or later,
11388 or OpenSSL 1.1.1 or later.
11389 The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
11392 .vitem &*${stat:*&<&'string'&>&*}*&
11393 .cindex "expansion" "statting a file"
11394 .cindex "file" "extracting characteristics"
11395 .cindex "&%stat%& expansion item"
11396 The string, after expansion, must be a file path. A call to the &[stat()]&
11397 function is made for this path. If &[stat()]& fails, an error occurs and the
11398 expansion fails. If it succeeds, the data from the stat replaces the item, as a
11399 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
11400 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
11401 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
11402 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
11403 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
11404 can extract individual fields using the &%extract%& expansion item.
11406 The use of the &%stat%& expansion in users' filter files can be locked out by
11407 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
11408 systems for files larger than 2GB.
11410 .vitem &*${str2b64:*&<&'string'&>&*}*&
11411 .cindex "&%str2b64%& expansion item"
11412 Now deprecated, a synonym for the &%base64%& expansion operator.
11416 .vitem &*${strlen:*&<&'string'&>&*}*&
11417 .cindex "expansion" "string length"
11418 .cindex "string" "length in expansion"
11419 .cindex "&%strlen%& expansion item"
11420 The item is replaced by the length of the expanded string, expressed as a
11421 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
11422 All measurement is done in bytes and is not UTF-8 aware.
11425 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
11426 .cindex "&%substr%& expansion item"
11427 .cindex "substring extraction"
11428 .cindex "expansion" "substring expansion"
11429 The &%substr%& operator is a simpler interface to the &%substr%& function that
11430 can be used when the two parameters are fixed numbers (as opposed to strings
11431 that change when expanded). The effect is the same as
11433 ${substr{<start>}{<length>}{<string>}}
11435 See the description of the general &%substr%& item above for details. The
11436 abbreviation &%s%& can be used when &%substr%& is used as an operator.
11437 All measurement is done in bytes and is not UTF-8 aware.
11439 .vitem &*${time_eval:*&<&'string'&>&*}*&
11440 .cindex "&%time_eval%& expansion item"
11441 .cindex "time interval" "decoding"
11442 This item converts an Exim time interval such as &`2d4h5m`& into a number of
11445 .vitem &*${time_interval:*&<&'string'&>&*}*&
11446 .cindex "&%time_interval%& expansion item"
11447 .cindex "time interval" "formatting"
11448 The argument (after sub-expansion) must be a sequence of decimal digits that
11449 represents an interval of time as a number of seconds. It is converted into a
11450 number of larger units and output in Exim's normal time format, for example,
11453 .vitem &*${uc:*&<&'string'&>&*}*&
11454 .cindex "case forcing in strings"
11455 .cindex "string" "case forcing"
11456 .cindex "upper casing"
11457 .cindex "expansion" "case forcing"
11458 .cindex "&%uc%& expansion item"
11459 This forces the letters in the string into upper-case.
11460 Case is defined per the system C locale.
11462 .vitem &*${utf8clean:*&<&'string'&>&*}*&
11463 .cindex "correction of invalid utf-8 sequences in strings"
11464 .cindex "utf-8" "utf-8 sequences"
11465 .cindex "incorrect utf-8"
11466 .cindex "expansion" "utf-8 forcing"
11467 .cindex "&%utf8clean%& expansion item"
11468 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
11469 In versions of Exim before 4.92, this did not correctly do so for a truncated
11470 final codepoint's encoding, and the character would be silently dropped.
11471 If you must handle detection of this scenario across both sets of Exim behavior,
11472 the complexity will depend upon the task.
11473 For instance, to detect if the first character is multibyte and a 1-byte
11474 extraction can be successfully used as a path component (as is common for
11475 dividing up delivery folders), you might use:
11477 condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
11479 (which will false-positive if the first character of the local part is a
11480 literal question mark).
11482 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
11483 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
11484 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
11485 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
11486 .cindex expansion UTF-8
11487 .cindex UTF-8 expansion
11489 .cindex internationalisation
11490 .cindex "&%utf8_domain_to_alabel%& expansion item"
11491 .cindex "&%utf8_domain_from_alabel%& expansion item"
11492 .cindex "&%utf8_localpart_to_alabel%& expansion item"
11493 .cindex "&%utf8_localpart_from_alabel%& expansion item"
11494 These convert EAI mail name components between UTF-8 and a-label forms.
11495 For information on internationalisation support see &<<SECTi18nMTA>>&.
11503 .section "Expansion conditions" "SECTexpcond"
11504 .scindex IIDexpcond "expansion" "conditions"
11505 The following conditions are available for testing by the &%${if%& construct
11506 while expanding strings:
11509 .vitem &*!*&<&'condition'&>
11510 .cindex "expansion" "negating a condition"
11511 .cindex "negation" "in expansion condition"
11512 Preceding any condition with an exclamation mark negates the result of the
11515 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11516 .cindex "numeric comparison"
11517 .cindex "expansion" "numeric comparison"
11518 There are a number of symbolic operators for doing numeric comparisons. They
11520 .itable none 0 0 2 10* left 90* left
11522 .irow "== " "equal"
11523 .irow "> " "greater"
11524 .irow ">= " "greater or equal"
11526 .irow "<= " "less or equal"
11530 ${if >{$message_size}{10M} ...
11532 Note that the general negation operator provides for inequality testing. The
11533 two strings must take the form of optionally signed decimal integers,
11534 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
11535 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
11536 As a special case, the numerical value of an empty string is taken as
11539 In all cases, a relative comparator OP is testing if <&'string1'&> OP
11540 <&'string2'&>; the above example is checking if &$message_size$& is larger than
11541 10M, not if 10M is larger than &$message_size$&.
11544 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
11545 {*&<&'arg2'&>&*}...}*&
11546 .cindex "expansion" "calling an acl"
11547 .cindex "&%acl%&" "expansion condition"
11548 The name and zero to nine argument strings are first expanded separately. The expanded
11549 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
11550 Any unused are made empty. The variable &$acl_narg$& is set to the number of
11551 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
11552 and may use the variables; if another acl expansion is used the values
11553 are restored after it returns. If the ACL sets
11554 a value using a "message =" modifier the variable $value becomes
11555 the result of the expansion, otherwise it is empty.
11556 If the ACL returns accept the condition is true; if deny, false.
11557 If the ACL returns defer the result is a forced-fail.
11559 .vitem &*bool&~{*&<&'string'&>&*}*&
11560 .cindex "expansion" "boolean parsing"
11561 .cindex "&%bool%& expansion condition"
11562 This condition turns a string holding a true or false representation into
11563 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
11564 (case-insensitively); also integer numbers map to true if non-zero,
11566 An empty string is treated as false.
11567 Leading and trailing whitespace is ignored;
11568 thus a string consisting only of whitespace is false.
11569 All other string values will result in expansion failure.
11571 When combined with ACL variables, this expansion condition will let you
11572 make decisions in one place and act on those decisions in another place.
11575 ${if bool{$acl_m_privileged_sender} ...
11579 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
11580 .cindex "expansion" "boolean parsing"
11581 .cindex "&%bool_lax%& expansion condition"
11582 Like &%bool%&, this condition turns a string into a boolean state. But
11583 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
11584 loose definition that the Router &%condition%& option uses. The empty string
11585 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
11586 true. Leading and trailing whitespace is ignored.
11588 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
11590 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11591 .cindex "expansion" "encrypted comparison"
11592 .cindex "encrypted strings, comparing"
11593 .cindex "&%crypteq%& expansion condition"
11594 This condition is included in the Exim binary if it is built to support any
11595 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
11596 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
11597 included in the binary.
11599 The &%crypteq%& condition has two arguments. The first is encrypted and
11600 compared against the second, which is already encrypted. The second string may
11601 be in the LDAP form for storing encrypted strings, which starts with the
11602 encryption type in curly brackets, followed by the data. If the second string
11603 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
11604 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
11605 Typically this will be a field from a password file. An example of an encrypted
11606 string in LDAP form is:
11608 {md5}CY9rzUYh03PK3k6DJie09g==
11610 If such a string appears directly in an expansion, the curly brackets have to
11611 be quoted, because they are part of the expansion syntax. For example:
11613 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
11615 The following encryption types (whose names are matched case-independently) are
11620 .cindex "base64 encoding" "in encrypted password"
11621 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
11622 printable characters to compare with the remainder of the second string. If the
11623 length of the comparison string is 24, Exim assumes that it is base64 encoded
11624 (as in the above example). If the length is 32, Exim assumes that it is a
11625 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
11629 .cindex "SHA-1 hash"
11630 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
11631 printable characters to compare with the remainder of the second string. If the
11632 length of the comparison string is 28, Exim assumes that it is base64 encoded.
11633 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
11634 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
11637 .cindex "&[crypt()]&"
11638 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
11639 only the first eight characters of the password. However, in modern operating
11640 systems this is no longer true, and in many cases the entire password is used,
11641 whatever its length.
11644 .cindex "&[crypt16()]&"
11645 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
11646 use up to 16 characters of the password in some operating systems. Again, in
11647 modern operating systems, more characters may be used.
11649 Exim has its own version of &[crypt16()]&, which is just a double call to
11650 &[crypt()]&. For operating systems that have their own version, setting
11651 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
11652 operating system version instead of its own. This option is set by default in
11653 the OS-dependent &_Makefile_& for those operating systems that are known to
11654 support &[crypt16()]&.
11656 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
11657 it was not using the same algorithm as some operating systems' versions. It
11658 turns out that as well as &[crypt16()]& there is a function called
11659 &[bigcrypt()]& in some operating systems. This may or may not use the same
11660 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
11662 However, since there is now a move away from the traditional &[crypt()]&
11663 functions towards using SHA1 and other algorithms, tidying up this area of
11664 Exim is seen as very low priority.
11666 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
11667 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
11668 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
11669 default is &`{crypt}`&. Whatever the default, you can always use either
11670 function by specifying it explicitly in curly brackets.
11672 .vitem &*def:*&<&'variable&~name'&>
11673 .cindex "expansion" "checking for empty variable"
11674 .cindex "&%def%& expansion condition"
11675 The &%def%& condition must be followed by the name of one of the expansion
11676 variables defined in section &<<SECTexpvar>>&. The condition is true if the
11677 variable does not contain the empty string. For example:
11679 ${if def:sender_ident {from $sender_ident}}
11681 Note that the variable name is given without a leading &%$%& character. If the
11682 variable does not exist, the expansion fails.
11684 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
11685 &~&*def:h_*&<&'header&~name'&>&*:*&"
11686 .cindex "expansion" "checking header line existence"
11687 This condition is true if a message is being processed and the named header
11688 exists in the message. For example,
11690 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
11692 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
11693 the header name must be terminated by a colon if white space does not follow.
11695 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11696 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11697 .cindex "string" "comparison"
11698 .cindex "expansion" "string comparison"
11699 .cindex "&%eq%& expansion condition"
11700 .cindex "&%eqi%& expansion condition"
11701 The two substrings are first expanded. The condition is true if the two
11702 resulting strings are identical. For &%eq%& the comparison includes the case of
11703 letters, whereas for &%eqi%& the comparison is case-independent, where
11704 case is defined per the system C locale.
11706 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
11707 .cindex "expansion" "file existence test"
11708 .cindex "file" "existence test"
11709 .cindex "&%exists%&, expansion condition"
11710 The substring is first expanded and then interpreted as an absolute path. The
11711 condition is true if the named file (or directory) exists. The existence test
11712 is done by calling the &[stat()]& function. The use of the &%exists%& test in
11713 users' filter files may be locked out by the system administrator.
11715 &*Note:*& Testing a path using this condition is not a sufficient way of
11717 Consider using a dsearch lookup.
11719 .vitem &*first_delivery*&
11720 .cindex "delivery" "first"
11721 .cindex "first delivery"
11722 .cindex "expansion" "first delivery test"
11723 .cindex "&%first_delivery%& expansion condition"
11724 .cindex retry condition
11725 This condition, which has no data, is true during a message's first delivery
11726 attempt. It is false during any subsequent delivery attempts.
11729 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
11730 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
11731 .cindex "list" "iterative conditions"
11732 .cindex "expansion" "&*forall*& condition"
11733 .cindex "expansion" "&*forany*& condition"
11735 These conditions iterate over a list. The first argument is expanded to form
11736 the list. By default, the list separator is a colon, but it can be changed by
11737 the normal method (&<<SECTlistsepchange>>&).
11738 The second argument is interpreted as a condition that is to
11739 be applied to each item in the list in turn. During the interpretation of the
11740 condition, the current list item is placed in a variable called &$item$&.
11742 For &*forany*&, interpretation stops if the condition is true for any item, and
11743 the result of the whole condition is true. If the condition is false for all
11744 items in the list, the overall condition is false.
11746 For &*forall*&, interpretation stops if the condition is false for any item,
11747 and the result of the whole condition is false. If the condition is true for
11748 all items in the list, the overall condition is true.
11750 Note that negation of &*forany*& means that the condition must be false for all
11751 items for the overall condition to succeed, and negation of &*forall*& means
11752 that the condition must be false for at least one item. In this example, the
11753 list separator is changed to a comma:
11755 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
11757 The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
11758 being processed, to enable these expansion items to be nested.
11760 To scan a named list, expand it with the &*listnamed*& operator.
11762 .vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11763 "&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11764 "&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11765 "&*forany_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&"
11766 .cindex JSON "iterative conditions"
11767 .cindex JSON expansions
11768 .cindex expansion "&*forall_json*& condition"
11769 .cindex expansion "&*forany_json*& condition"
11770 .cindex expansion "&*forall_jsons*& condition"
11771 .cindex expansion "&*forany_jsons*& condition"
11772 As for the above, except that the first argument must, after expansion,
11774 The array separator is not changeable.
11775 For the &"jsons"& variants the elements are expected to be JSON strings
11776 and have their quotes removed before the evaluation of the condition.
11780 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11781 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11782 .cindex "string" "comparison"
11783 .cindex "expansion" "string comparison"
11784 .cindex "&%ge%& expansion condition"
11785 .cindex "&%gei%& expansion condition"
11786 The two substrings are first expanded. The condition is true if the first
11787 string is lexically greater than or equal to the second string. For &%ge%& the
11788 comparison includes the case of letters, whereas for &%gei%& the comparison is
11790 Case and collation order are defined per the system C locale.
11792 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11793 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11794 .cindex "string" "comparison"
11795 .cindex "expansion" "string comparison"
11796 .cindex "&%gt%& expansion condition"
11797 .cindex "&%gti%& expansion condition"
11798 The two substrings are first expanded. The condition is true if the first
11799 string is lexically greater than the second string. For &%gt%& the comparison
11800 includes the case of letters, whereas for &%gti%& the comparison is
11802 Case and collation order are defined per the system C locale.
11805 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
11806 SRS decode. See SECT &<<SECTSRS>>& for details.
11809 .vitem &*inlist&~{*&<&'subject'&>&*}{*&<&'list'&>&*}*& &&&
11810 &*inlisti&~{*&<&'subject'&>&*}{*&<&'list'&>&*}*&
11811 .cindex "string" "comparison"
11812 .cindex "list" "iterative conditions"
11813 Both strings are expanded; the second string is treated as a list of simple
11814 strings; if the first string is a member of the second, then the condition
11816 For the case-independent &%inlisti%& condition, case is defined per the system C locale.
11818 These are simpler to use versions of the more powerful &*forany*& condition.
11819 Examples, and the &*forany*& equivalents:
11821 ${if inlist{needle}{foo:needle:bar}}
11822 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11823 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11824 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11827 The variable &$value$& will be set for a successful match and can be
11828 used in the success clause of an &%if%& expansion item using the condition.
11829 .cindex "tainted data" "de-tainting"
11830 .cindex "de-tainting" "using an inlist expansion condition"
11831 It will have the same taint status as the list; expansions such as
11833 ${if inlist {$h_mycode:} {0 : 1 : 42} {$value}}
11835 can be used for de-tainting.
11836 Any previous &$value$& is restored after the if.
11839 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11840 &*isip4&~{*&<&'string'&>&*}*& &&&
11841 &*isip6&~{*&<&'string'&>&*}*&
11842 .cindex "IP address" "testing string format"
11843 .cindex "string" "testing for IP address"
11844 .cindex "&%isip%& expansion condition"
11845 .cindex "&%isip4%& expansion condition"
11846 .cindex "&%isip6%& expansion condition"
11847 The substring is first expanded, and then tested to see if it has the form of
11848 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11849 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11851 For an IPv4 address, the test is for four dot-separated components, each of
11852 which consists of from one to three digits. For an IPv6 address, up to eight
11853 colon-separated components are permitted, each containing from one to four
11854 hexadecimal digits. There may be fewer than eight components if an empty
11855 component (adjacent colons) is present. Only one empty component is permitted.
11857 &*Note*&: The checks used to be just on the form of the address; actual numerical
11858 values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
11860 This is no longer the case.
11862 The main use of these tests is to distinguish between IP addresses and
11863 host names, or between IPv4 and IPv6 addresses. For example, you could use
11865 ${if isip4{$sender_host_address}...
11867 to test which IP version an incoming SMTP connection is using.
11869 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11870 .cindex "LDAP" "use for authentication"
11871 .cindex "expansion" "LDAP authentication test"
11872 .cindex "&%ldapauth%& expansion condition"
11873 This condition supports user authentication using LDAP. See section
11874 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11875 queries. For this use, the query must contain a user name and password. The
11876 query itself is not used, and can be empty. The condition is true if the
11877 password is not empty, and the user name and password are accepted by the LDAP
11878 server. An empty password is rejected without calling LDAP because LDAP binds
11879 with an empty password are considered anonymous regardless of the username, and
11880 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11881 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11885 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11886 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11887 .cindex "string" "comparison"
11888 .cindex "expansion" "string comparison"
11889 .cindex "&%le%& expansion condition"
11890 .cindex "&%lei%& expansion condition"
11891 The two substrings are first expanded. The condition is true if the first
11892 string is lexically less than or equal to the second string. For &%le%& the
11893 comparison includes the case of letters, whereas for &%lei%& the comparison is
11895 Case and collation order are defined per the system C locale.
11897 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11898 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11899 .cindex "string" "comparison"
11900 .cindex "expansion" "string comparison"
11901 .cindex "&%lt%& expansion condition"
11902 .cindex "&%lti%& expansion condition"
11903 The two substrings are first expanded. The condition is true if the first
11904 string is lexically less than the second string. For &%lt%& the comparison
11905 includes the case of letters, whereas for &%lti%& the comparison is
11907 Case and collation order are defined per the system C locale.
11910 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11911 .cindex "expansion" "regular expression comparison"
11912 .cindex "regular expressions" "match in expanded string"
11913 .cindex "&%match%& expansion condition"
11914 The two substrings are first expanded. The second is then treated as a regular
11915 expression and applied to the first. Because of the pre-expansion, if the
11916 regular expression contains dollar, or backslash characters, they must be
11917 escaped. Care must also be taken if the regular expression contains braces
11918 (curly brackets). A closing brace must be escaped so that it is not taken as a
11919 premature termination of <&'string2'&>. The easiest approach is to use the
11920 &`\N`& feature to disable expansion of the regular expression.
11923 ${if match {$local_part}{\N^\d{3}\N} ...
11925 If the whole expansion string is in double quotes, further escaping of
11926 backslashes is also required.
11928 The condition is true if the regular expression match succeeds.
11929 The regular expression is not required to begin with a circumflex
11930 metacharacter, but if there is no circumflex, the expression is not anchored,
11931 and it may match anywhere in the subject, not just at the start. If you want
11932 the pattern to match at the end of the subject, you must include the &`$`&
11933 metacharacter at an appropriate point.
11934 All character handling is done in bytes and is not UTF-8 aware,
11935 but we might change this in a future Exim release.
11937 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11938 At the start of an &%if%& expansion the values of the numeric variable
11939 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11940 succeeds causes them to be reset to the substrings of that condition and they
11941 will have these values during the expansion of the success string. At the end
11942 of the &%if%& expansion, the previous values are restored. After testing a
11943 combination of conditions using &%or%&, the subsequent values of the numeric
11944 variables are those of the condition that succeeded.
11946 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11947 .cindex "&%match_address%& expansion condition"
11948 See &*match_local_part*&.
11950 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11951 .cindex "&%match_domain%& expansion condition"
11952 See &*match_local_part*&.
11954 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11955 .cindex "&%match_ip%& expansion condition"
11956 This condition matches an IP address to a list of IP address patterns. It must
11957 be followed by two argument strings. The first (after expansion) must be an IP
11958 address or an empty string. The second (not expanded) is a restricted host
11959 list that can match only an IP address, not a host name. For example:
11961 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
11963 The specific types of host list item that are permitted in the list are:
11966 An IP address, optionally with a CIDR mask.
11968 A single asterisk, which matches any IP address.
11970 An empty item, which matches only if the IP address is empty. This could be
11971 useful for testing for a locally submitted message or one from specific hosts
11972 in a single test such as
11973 . ==== As this is a nested list, any displays it contains must be indented
11974 . ==== as otherwise they are too far to the left. This comment applies to
11975 . ==== the use of xmlto plus fop. There's no problem when formatting with
11976 . ==== sdop, with or without the extra indent.
11978 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
11980 where the first item in the list is the empty string.
11982 The item @[] matches any of the local host's interface addresses.
11984 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
11985 even if &`net-`& is not specified. There is never any attempt to turn the IP
11986 address into a host name. The most common type of linear search for
11987 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
11988 masks. For example:
11990 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
11992 It is of course possible to use other kinds of lookup, and in such a case, you
11993 do need to specify the &`net-`& prefix if you want to specify a specific
11994 address mask, for example:
11996 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
11998 However, unless you are combining a &%match_ip%& condition with others, it is
11999 just as easy to use the fact that a lookup is itself a condition, and write:
12001 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
12005 Note that <&'string2'&> is not itself subject to string expansion, unless
12006 Exim was built with the EXPAND_LISTMATCH_RHS option.
12008 Consult section &<<SECThoslispatip>>& for further details of these patterns.
12010 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12011 .cindex "domain list" "in expansion condition"
12012 .cindex "address list" "in expansion condition"
12013 .cindex "local part" "list, in expansion condition"
12014 .cindex "&%match_local_part%& expansion condition"
12015 This condition, together with &%match_address%& and &%match_domain%&, make it
12016 possible to test domain, address, and local part lists within expansions. Each
12017 condition requires two arguments: an item and a list to match. A trivial
12020 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
12022 In each case, the second argument may contain any of the allowable items for a
12023 list of the appropriate type. Also, because the second argument
12024 is a standard form of list, it is possible to refer to a named list.
12025 Thus, you can use conditions like this:
12027 ${if match_domain{$domain}{+local_domains}{...
12029 .cindex "&`+caseful`&"
12030 For address lists, the matching starts off caselessly, but the &`+caseful`&
12031 item can be used, as in all address lists, to cause subsequent items to
12032 have their local parts matched casefully. Domains are always matched
12035 The variable &$value$& will be set for a successful match and can be
12036 used in the success clause of an &%if%& expansion item using the condition.
12037 .cindex "tainted data" "de-tainting"
12038 .cindex "de-tainting" "using a match_local_part expansion condition"
12039 It will have the same taint status as the list; expansions such as
12041 ${if match_local_part {$local_part} {alice : bill : charlotte : dave} {$value}}
12043 can be used for de-tainting.
12044 Any previous &$value$& is restored after the if.
12046 Note that <&'string2'&> is not itself subject to string expansion, unless
12047 Exim was built with the EXPAND_LISTMATCH_RHS option.
12049 &*Note*&: Host lists are &'not'& supported in this way. This is because
12050 hosts have two identities: a name and an IP address, and it is not clear
12051 how to specify cleanly how such a test would work. However, IP addresses can be
12052 matched using &%match_ip%&.
12054 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
12055 .cindex "PAM authentication"
12056 .cindex "AUTH" "with PAM"
12057 .cindex "Solaris" "PAM support"
12058 .cindex "expansion" "PAM authentication test"
12059 .cindex "&%pam%& expansion condition"
12060 &'Pluggable Authentication Modules'&
12061 (&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
12062 available in Solaris
12063 and in some GNU/Linux distributions.
12064 The Exim support, which is intended for use in conjunction with
12065 the SMTP AUTH command, is available only if Exim is compiled with
12069 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
12070 in some releases of GNU/Linux &%-ldl%& is also needed.
12072 The argument string is first expanded, and the result must be a
12073 colon-separated list of strings. Leading and trailing white space is ignored.
12074 The PAM module is initialized with the service name &"exim"& and the user name
12075 taken from the first item in the colon-separated data string (<&'string1'&>).
12076 The remaining items in the data string are passed over in response to requests
12077 from the authentication function. In the simple case there will only be one
12078 request, for a password, so the data consists of just two strings.
12080 There can be problems if any of the strings are permitted to contain colon
12081 characters. In the usual way, these have to be doubled to avoid being taken as
12083 The &%listquote%& expansion item can be used for this.
12084 For example, the configuration
12085 of a LOGIN authenticator might contain this setting:
12087 server_condition = ${if pam{$auth1:${listquote{:}{$auth2}}}}
12089 In some operating systems, PAM authentication can be done only from a process
12090 running as root. Since Exim is running as the Exim user when receiving
12091 messages, this means that PAM cannot be used directly in those systems.
12092 . --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that
12095 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
12096 .cindex "&'pwcheck'& daemon"
12098 .cindex "expansion" "&'pwcheck'& authentication test"
12099 .cindex "&%pwcheck%& expansion condition"
12100 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
12101 This is one way of making it possible for passwords to be checked by a process
12102 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
12103 deprecated. Its replacement is &'saslauthd'& (see below).
12105 The pwcheck support is not included in Exim by default. You need to specify
12106 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
12107 building Exim. For example:
12109 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
12111 You do not need to install the full Cyrus software suite in order to use
12112 the pwcheck daemon. You can compile and install just the daemon alone
12113 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
12114 access to the &_/var/pwcheck_& directory.
12116 The &%pwcheck%& condition takes one argument, which must be the user name and
12117 password, separated by a colon. For example, in a LOGIN authenticator
12118 configuration, you might have this:
12120 server_condition = ${if pwcheck{$auth1:$auth2}}
12122 Again, for a PLAIN authenticator configuration, this would be:
12124 server_condition = ${if pwcheck{$auth2:$auth3}}
12126 .vitem &*queue_running*&
12127 .cindex "queue runner" "detecting when delivering from"
12128 .cindex "expansion" "queue runner test"
12129 .cindex "&%queue_running%& expansion condition"
12130 This condition, which has no data, is true during delivery attempts that are
12131 initiated by queue runner processes, and false otherwise.
12134 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
12136 .cindex "expansion" "Radius authentication"
12137 .cindex "&%radius%& expansion condition"
12138 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
12139 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
12140 the Radius client configuration file in order to build Exim with Radius
12143 With just that one setting, Exim expects to be linked with the &%radiusclient%&
12144 library, using the original API. If you are using release 0.4.0 or later of
12145 this library, you need to set
12147 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
12149 in &_Local/Makefile_& when building Exim. You can also link Exim with the
12150 &%libradius%& library that comes with FreeBSD. To do this, set
12152 RADIUS_LIB_TYPE=RADLIB
12154 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
12155 You may also have to supply a suitable setting in EXTRALIBS so that the
12156 Radius library can be found when Exim is linked.
12158 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
12159 Radius client library, which calls the Radius server. The condition is true if
12160 the authentication is successful. For example:
12162 server_condition = ${if radius{<arguments>}}
12166 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
12167 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
12168 .cindex "&'saslauthd'& daemon"
12170 .cindex "expansion" "&'saslauthd'& authentication test"
12171 .cindex "&%saslauthd%& expansion condition"
12172 This condition supports user authentication using the Cyrus &'saslauthd'&
12173 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
12174 Using this daemon is one way of making it possible for passwords to be checked
12175 by a process that is not running as root.
12177 The saslauthd support is not included in Exim by default. You need to specify
12178 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
12179 building Exim. For example:
12181 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
12183 You do not need to install the full Cyrus software suite in order to use
12184 the saslauthd daemon. You can compile and install just the daemon alone
12185 from the Cyrus SASL library.
12187 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
12188 two are mandatory. For example:
12190 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
12192 The service and the realm are optional (which is why the arguments are enclosed
12193 in their own set of braces). For details of the meaning of the service and
12194 realm, and how to run the daemon, consult the Cyrus documentation.
12199 .section "Combining expansion conditions" "SECID84"
12200 .cindex "expansion" "combining conditions"
12201 Several conditions can be tested at once by combining them using the &%and%&
12202 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
12203 conditions on their own, and precede their lists of sub-conditions. Each
12204 sub-condition must be enclosed in braces within the overall braces that contain
12205 the list. No repetition of &%if%& is used.
12209 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12210 .cindex "&""or""& expansion condition"
12211 .cindex "expansion" "&""or""& of conditions"
12212 The sub-conditions are evaluated from left to right. The condition is true if
12213 any one of the sub-conditions is true.
12216 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
12218 When a true sub-condition is found, the following ones are parsed but not
12219 evaluated. If there are several &"match"& sub-conditions the values of the
12220 numeric variables afterwards are taken from the first one that succeeds.
12222 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12223 .cindex "&""and""& expansion condition"
12224 .cindex "expansion" "&""and""& of conditions"
12225 The sub-conditions are evaluated from left to right. The condition is true if
12226 all of the sub-conditions are true. If there are several &"match"&
12227 sub-conditions, the values of the numeric variables afterwards are taken from
12228 the last one. When a false sub-condition is found, the following ones are
12229 parsed but not evaluated.
12231 .ecindex IIDexpcond
12236 .section "Expansion variables" "SECTexpvar"
12237 .cindex "expansion" "variables, list of"
12238 This section contains an alphabetical list of all the expansion variables. Some
12239 of them are available only when Exim is compiled with specific options such as
12240 support for TLS or the content scanning extension.
12241 .cindex "tainted data"
12242 Variables marked as &'tainted'& are likely to carry data supplied by
12243 a potential attacker.
12244 Variables without such marking may also, depending on how their
12245 values are created.
12246 Such variables should not be further expanded,
12248 or used as command-line arguments for external commands.
12251 .vitem "&$0$&, &$1$&, etc"
12252 .cindex "numerical variables (&$1$& &$2$& etc)"
12253 When a &%match%& expansion condition succeeds, these variables contain the
12254 captured substrings identified by the regular expression during subsequent
12255 processing of the success string of the containing &%if%& expansion item.
12256 In the expansion condition case
12257 they do not retain their values afterwards; in fact, their previous
12258 values are restored at the end of processing an &%if%& item. The numerical
12259 variables may also be set externally by some other matching process which
12260 precedes the expansion of the string. For example, the commands available in
12261 Exim filter files include an &%if%& command with its own regular expression
12262 matching condition.
12263 If the subject string was tainted then any captured substring will also be.
12265 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
12266 Within an acl condition, expansion condition or expansion item
12267 any arguments are copied to these variables,
12268 any unused variables being made empty.
12270 .vitem "&$acl_c...$&"
12271 Values can be placed in these variables by the &%set%& modifier in an ACL. They
12272 can be given any name that starts with &$acl_c$& and is at least six characters
12273 long, but the sixth character must be either a digit or an underscore. For
12274 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
12275 variables persist throughout the lifetime of an SMTP connection. They can be
12276 used to pass information between ACLs and between different invocations of the
12277 same ACL. When a message is received, the values of these variables are saved
12278 with the message, and can be accessed by filters, routers, and transports
12279 during subsequent delivery.
12281 .vitem "&$acl_m...$&"
12282 These variables are like the &$acl_c...$& variables, except that their values
12283 are reset after a message has been received. Thus, if several messages are
12284 received in one SMTP connection, &$acl_m...$& values are not passed on from one
12285 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
12286 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
12287 message is received, the values of these variables are saved with the message,
12288 and can be accessed by filters, routers, and transports during subsequent
12291 .vitem &$acl_narg$&
12292 Within an acl condition, expansion condition or expansion item
12293 this variable has the number of arguments.
12295 .vitem &$acl_verify_message$&
12296 .vindex "&$acl_verify_message$&"
12297 After an address verification has failed, this variable contains the failure
12298 message. It retains its value for use in subsequent modifiers of the verb.
12299 The message can be preserved by coding like this:
12301 warn !verify = sender
12302 set acl_m0 = $acl_verify_message
12304 You can use &$acl_verify_message$& during the expansion of the &%message%& or
12305 &%log_message%& modifiers, to include information about the verification
12307 &*Note*&: The variable is cleared at the end of processing the ACL verb.
12309 .vitem &$address_data$&
12310 .vindex "&$address_data$&"
12311 This variable is set by means of the &%address_data%& option in routers. The
12312 value then remains with the address while it is processed by subsequent routers
12313 and eventually a transport. If the transport is handling multiple addresses,
12314 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
12315 for more details. &*Note*&: The contents of &$address_data$& are visible in
12318 If &$address_data$& is set when the routers are called from an ACL to verify
12319 a recipient address, the final value is still in the variable for subsequent
12320 conditions and modifiers of the ACL statement. If routing the address caused it
12321 to be redirected to just one address, the child address is also routed as part
12322 of the verification, and in this case the final value of &$address_data$& is
12323 from the child's routing.
12325 If &$address_data$& is set when the routers are called from an ACL to verify a
12326 sender address, the final value is also preserved, but this time in
12327 &$sender_address_data$&, to distinguish it from data from a recipient
12330 In both cases (recipient and sender verification), the value does not persist
12331 after the end of the current ACL statement. If you want to preserve
12332 these values for longer, you can save them in ACL variables.
12334 .vitem &$address_file$&
12335 .vindex "&$address_file$&"
12336 When, as a result of aliasing, forwarding, or filtering, a message is directed
12337 to a specific file, this variable holds the name of the file when the transport
12338 is running. At other times, the variable is empty. For example, using the
12339 default configuration, if user &%r2d2%& has a &_.forward_& file containing
12341 /home/r2d2/savemail
12343 then when the &(address_file)& transport is running, &$address_file$&
12344 contains the text string &`/home/r2d2/savemail`&.
12345 .cindex "Sieve filter" "value of &$address_file$&"
12346 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
12347 then up to the transport configuration to generate an appropriate absolute path
12348 to the relevant file.
12350 .vitem &$address_pipe$&
12351 .vindex "&$address_pipe$&"
12352 When, as a result of aliasing or forwarding, a message is directed to a pipe,
12353 this variable holds the pipe command when the transport is running.
12355 .vitem "&$auth1$& &-- &$auth4$&"
12356 .vindex "&$auth1$&, &$auth2$&, etc"
12357 These variables are used in SMTP authenticators (see chapters
12358 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
12360 .vitem &$authenticated_id$&
12361 .cindex "authentication" "id"
12362 .vindex "&$authenticated_id$&"
12363 When a server successfully authenticates a client it may be configured to
12364 preserve some of the authentication information in the variable
12365 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
12366 user/password authenticator configuration might preserve the user name for use
12367 in the routers. Note that this is not the same information that is saved in
12368 &$sender_host_authenticated$&.
12370 When a message is submitted locally (that is, not over a TCP connection)
12371 the value of &$authenticated_id$& is normally the login name of the calling
12372 process. However, a trusted user can override this by means of the &%-oMai%&
12373 command line option.
12374 This second case also sets up information used by the
12375 &$authresults$& expansion item.
12377 .vitem &$authenticated_fail_id$&
12378 .cindex "authentication" "fail" "id"
12379 .vindex "&$authenticated_fail_id$&"
12380 When an authentication attempt fails, the variable &$authenticated_fail_id$&
12381 will contain the failed authentication id. If more than one authentication
12382 id is attempted, it will contain only the last one. The variable is
12383 available for processing in the ACL's, generally the quit or notquit ACL.
12384 A message to a local recipient could still be accepted without requiring
12385 authentication, which means this variable could also be visible in all of
12389 .tvar &$authenticated_sender$&
12390 .cindex "sender" "authenticated"
12391 .cindex "authentication" "sender"
12392 .cindex "AUTH" "on MAIL command"
12393 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
12394 SMTP MAIL command if it believes the sender is sufficiently trusted, as
12395 described in section &<<SECTauthparamail>>&. Unless the data is the string
12396 &"<>"&, it is set as the authenticated sender of the message, and the value is
12397 available during delivery in the &$authenticated_sender$& variable. If the
12398 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
12400 .vindex "&$qualify_domain$&"
12401 When a message is submitted locally (that is, not over a TCP connection), the
12402 value of &$authenticated_sender$& is an address constructed from the login
12403 name of the calling process and &$qualify_domain$&, except that a trusted user
12404 can override this by means of the &%-oMas%& command line option.
12407 .vitem &$authentication_failed$&
12408 .cindex "authentication" "failure"
12409 .vindex "&$authentication_failed$&"
12410 This variable is set to &"1"& in an Exim server if a client issues an AUTH
12411 command that does not succeed. Otherwise it is set to &"0"&. This makes it
12412 possible to distinguish between &"did not try to authenticate"&
12413 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
12414 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
12415 is empty and &$authentication_failed$& is set to &"1"&).
12416 Failure includes cancellation of a authentication attempt,
12417 and any negative response to an AUTH command,
12418 (including, for example, an attempt to use an undefined mechanism).
12420 .vitem &$av_failed$&
12421 .cindex "content scanning" "AV scanner failure"
12422 This variable is available when Exim is compiled with the content-scanning
12423 extension. It is set to &"0"& by default, but will be set to &"1"& if any
12424 problem occurs with the virus scanner (specified by &%av_scanner%&) during
12425 the ACL malware condition.
12427 .vitem &$body_linecount$&
12428 .cindex "message body" "line count"
12429 .cindex "body of message" "line count"
12430 .vindex "&$body_linecount$&"
12431 When a message is being received or delivered, this variable contains the
12432 number of lines in the message's body. See also &$message_linecount$&.
12434 .vitem &$body_zerocount$&
12435 .cindex "message body" "binary zero count"
12436 .cindex "body of message" "binary zero count"
12437 .cindex "binary zero" "in message body"
12438 .vindex "&$body_zerocount$&"
12439 When a message is being received or delivered, this variable contains the
12440 number of binary zero bytes (ASCII NULs) in the message's body.
12442 .vitem &$bounce_recipient$&
12443 .vindex "&$bounce_recipient$&"
12444 This is set to the recipient address of a bounce message while Exim is creating
12445 it. It is useful if a customized bounce message text file is in use (see
12446 chapter &<<CHAPemsgcust>>&).
12448 .vitem &$bounce_return_size_limit$&
12449 .vindex "&$bounce_return_size_limit$&"
12450 This contains the value set in the &%bounce_return_size_limit%& option, rounded
12451 up to a multiple of 1000. It is useful when a customized error message text
12452 file is in use (see chapter &<<CHAPemsgcust>>&).
12454 .vitem &$caller_gid$&
12455 .cindex "gid (group id)" "caller"
12456 .vindex "&$caller_gid$&"
12457 The real group id under which the process that called Exim was running. This is
12458 not the same as the group id of the originator of a message (see
12459 &$originator_gid$&). If Exim re-execs itself, this variable in the new
12460 incarnation normally contains the Exim gid.
12462 .vitem &$caller_uid$&
12463 .cindex "uid (user id)" "caller"
12464 .vindex "&$caller_uid$&"
12465 The real user id under which the process that called Exim was running. This is
12466 not the same as the user id of the originator of a message (see
12467 &$originator_uid$&). If Exim re-execs itself, this variable in the new
12468 incarnation normally contains the Exim uid.
12470 .vitem &$callout_address$&
12471 .vindex "&$callout_address$&"
12472 After a callout for verification, spamd or malware daemon service, the
12473 address that was connected to.
12475 .vitem &$compile_number$&
12476 .vindex "&$compile_number$&"
12477 The building process for Exim keeps a count of the number
12478 of times it has been compiled. This serves to distinguish different
12479 compilations of the same version of Exim.
12481 .vitem &$config_dir$&
12482 .vindex "&$config_dir$&"
12483 The directory name of the main configuration file. That is, the content of
12484 &$config_file$& with the last component stripped. The value does not
12485 contain the trailing slash. If &$config_file$& does not contain a slash,
12486 &$config_dir$& is ".".
12488 .vitem &$config_file$&
12489 .vindex "&$config_file$&"
12490 The name of the main configuration file Exim is using.
12492 .vitem &$dkim_verify_status$&
12493 Results of DKIM verification.
12494 For details see section &<<SECDKIMVFY>>&.
12496 .vitem &$dkim_cur_signer$& &&&
12497 &$dkim_verify_reason$& &&&
12498 &$dkim_domain$& &&&
12499 &$dkim_identity$& &&&
12500 &$dkim_selector$& &&&
12502 &$dkim_canon_body$& &&&
12503 &$dkim_canon_headers$& &&&
12504 &$dkim_copiedheaders$& &&&
12505 &$dkim_bodylength$& &&&
12506 &$dkim_created$& &&&
12507 &$dkim_expires$& &&&
12508 &$dkim_headernames$& &&&
12509 &$dkim_key_testing$& &&&
12510 &$dkim_key_nosubdomains$& &&&
12511 &$dkim_key_srvtype$& &&&
12512 &$dkim_key_granularity$& &&&
12513 &$dkim_key_notes$& &&&
12514 &$dkim_key_length$&
12515 These variables are only available within the DKIM ACL.
12516 For details see section &<<SECDKIMVFY>>&.
12518 .vitem &$dkim_signers$&
12519 .vindex &$dkim_signers$&
12520 When a message has been received this variable contains
12521 a colon-separated list of signer domains and identities for the message.
12522 For details see section &<<SECDKIMVFY>>&.
12524 .vitem &$dmarc_domain_policy$& &&&
12525 &$dmarc_status$& &&&
12526 &$dmarc_status_text$& &&&
12527 &$dmarc_used_domains$&
12528 Results of DMARC verification.
12529 For details see section &<<SECDMARC>>&.
12531 .vitem &$dnslist_domain$& &&&
12532 &$dnslist_matched$& &&&
12533 &$dnslist_text$& &&&
12535 .vindex "&$dnslist_domain$&"
12536 .vindex "&$dnslist_matched$&"
12537 .vindex "&$dnslist_text$&"
12538 .vindex "&$dnslist_value$&"
12539 .cindex "black list (DNS)"
12540 When a DNS (black) list lookup succeeds, these variables are set to contain
12541 the following data from the lookup: the list's domain name, the key that was
12542 looked up, the contents of any associated TXT record, and the value from the
12543 main A record. See section &<<SECID204>>& for more details.
12546 When an address is being routed, or delivered on its own, this variable
12547 contains the domain. Uppercase letters in the domain are converted into lower
12548 case for &$domain$&.
12550 Global address rewriting happens when a message is received, so the value of
12551 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
12552 is set during user filtering, but not during system filtering, because a
12553 message may have many recipients and the system filter is called just once.
12555 When more than one address is being delivered at once (for example, several
12556 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
12557 have the same domain. Transports can be restricted to handling only one domain
12558 at a time if the value of &$domain$& is required at transport time &-- this is
12559 the default for local transports. For further details of the environment in
12560 which local transports are run, see chapter &<<CHAPenvironment>>&.
12562 .oindex "&%delay_warning_condition%&"
12563 At the end of a delivery, if all deferred addresses have the same domain, it is
12564 set in &$domain$& during the expansion of &%delay_warning_condition%&.
12566 The &$domain$& variable is also used in some other circumstances:
12569 When an ACL is running for a RCPT command, &$domain$& contains the domain of
12570 the recipient address. The domain of the &'sender'& address is in
12571 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
12572 normally set during the running of the MAIL ACL. However, if the sender address
12573 is verified with a callout during the MAIL ACL, the sender domain is placed in
12574 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
12575 the &(smtp)& transport.
12578 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12579 &$domain$& contains the domain portion of the address that is being rewritten;
12580 it can be used in the expansion of the replacement address, for example, to
12581 rewrite domains by file lookup.
12584 With one important exception, whenever a domain list is being scanned,
12585 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
12586 a &%sender_domains%& condition in an ACL is being processed, the subject domain
12587 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
12588 that, in a RCPT ACL, the sender domain list can be dependent on the
12589 recipient domain (which is what is in &$domain$& at this time).
12592 .cindex "ETRN" "value of &$domain$&"
12593 .oindex "&%smtp_etrn_command%&"
12594 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
12595 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
12598 .cindex "tainted data"
12599 If the origin of the data is an incoming message,
12600 the result of expanding this variable is tainted and may not
12601 be further expanded or used as a filename.
12602 When an untainted version is needed, one should be obtained from
12603 looking up the value in a local (therefore trusted) database.
12604 Often &$domain_data$& is usable in this role.
12607 .vitem &$domain_data$&
12608 .vindex "&$domain_data$&"
12609 When the &%domains%& condition on a router
12612 against a list, the match value is copied to &$domain_data$&.
12613 This is an enhancement over previous versions of Exim, when it only
12614 applied to the data read by a lookup.
12615 For details on match values see section &<<SECTlistresults>>& et. al.
12617 If the router routes the
12618 address to a transport, the value is available in that transport. If the
12619 transport is handling multiple addresses, the value from the first address is
12622 &$domain_data$& set in an ACL is available during
12623 the rest of the ACL statement.
12625 .vitem &$exim_gid$&
12626 .vindex "&$exim_gid$&"
12627 This variable contains the numerical value of the Exim group id.
12629 .vitem &$exim_path$&
12630 .vindex "&$exim_path$&"
12631 This variable contains the path to the Exim binary.
12633 .vitem &$exim_uid$&
12634 .vindex "&$exim_uid$&"
12635 This variable contains the numerical value of the Exim user id.
12637 .vitem &$exim_version$&
12638 .vindex "&$exim_version$&"
12639 This variable contains the version string of the Exim build.
12640 The first character is a major version number, currently 4.
12641 Then after a dot, the next group of digits is a minor version number.
12642 There may be other characters following the minor version.
12643 This value may be overridden by the &%exim_version%& main config option.
12645 .vitem &$header_$&<&'name'&>
12647 This is not strictly an expansion variable. It is expansion syntax for
12648 inserting the message header line with the given name. Note that the name must
12649 be terminated by colon or white space, because it may contain a wide variety of
12650 characters. Note also that braces must &'not'& be used.
12651 See the full description in section &<<SECTexpansionitems>>& above.
12653 .vitem &$headers_added$&
12654 .vindex "&$headers_added$&"
12655 Within an ACL this variable contains the headers added so far by
12656 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
12657 The headers are a newline-separated list.
12661 When the &%check_local_user%& option is set for a router, the user's home
12662 directory is placed in &$home$& when the check succeeds. In particular, this
12663 means it is set during the running of users' filter files. A router may also
12664 explicitly set a home directory for use by a transport; this can be overridden
12665 by a setting on the transport itself.
12667 When running a filter test via the &%-bf%& option, &$home$& is set to the value
12668 of the environment variable HOME, which is subject to the
12669 &%keep_environment%& and &%add_environment%& main config options.
12673 If a router assigns an address to a transport (any transport), and passes a
12674 list of hosts with the address, the value of &$host$& when the transport starts
12675 to run is the name of the first host on the list. Note that this applies both
12676 to local and remote transports.
12678 .cindex "transport" "filter"
12679 .cindex "filter" "transport filter"
12680 For the &(smtp)& transport, if there is more than one host, the value of
12681 &$host$& changes as the transport works its way through the list. In
12682 particular, when the &(smtp)& transport is expanding its options for encryption
12683 using TLS, or for specifying a transport filter (see chapter
12684 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
12687 When used in the client part of an authenticator configuration (see chapter
12688 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
12689 client is connected.
12692 .vitem &$host_address$&
12693 .vindex "&$host_address$&"
12694 This variable is set to the remote host's IP address whenever &$host$& is set
12695 for a remote connection. It is also set to the IP address that is being checked
12696 when the &%ignore_target_hosts%& option is being processed.
12698 .vitem &$host_data$&
12699 .vindex "&$host_data$&"
12700 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
12701 result of the lookup is made available in the &$host_data$& variable. This
12702 allows you, for example, to do things like this:
12704 deny hosts = net-lsearch;/some/file
12705 message = $host_data
12708 .vitem &$host_lookup_deferred$&
12709 .cindex "host name" "lookup, failure of"
12710 .vindex "&$host_lookup_deferred$&"
12711 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
12712 message comes from a remote host and there is an attempt to look up the host's
12713 name from its IP address, and the attempt is not successful, one of these
12714 variables is set to &"1"&.
12717 If the lookup receives a definite negative response (for example, a DNS lookup
12718 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
12721 If there is any kind of problem during the lookup, such that Exim cannot
12722 tell whether or not the host name is defined (for example, a timeout for a DNS
12723 lookup), &$host_lookup_deferred$& is set to &"1"&.
12726 Looking up a host's name from its IP address consists of more than just a
12727 single reverse lookup. Exim checks that a forward lookup of at least one of the
12728 names it receives from a reverse lookup yields the original IP address. If this
12729 is not the case, Exim does not accept the looked up name(s), and
12730 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
12731 IP address (for example, the existence of a PTR record in the DNS) is not
12732 sufficient on its own for the success of a host name lookup. If the reverse
12733 lookup succeeds, but there is a lookup problem such as a timeout when checking
12734 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
12735 &"1"&. See also &$sender_host_name$&.
12737 .cindex authentication "expansion item"
12738 Performing these checks sets up information used by the
12739 &%authresults%& expansion item.
12742 .vitem &$host_lookup_failed$&
12743 .vindex "&$host_lookup_failed$&"
12744 See &$host_lookup_deferred$&.
12746 .vitem &$host_port$&
12747 .vindex "&$host_port$&"
12748 This variable is set to the remote host's TCP port whenever &$host$& is set
12749 for an outbound connection.
12751 .vitem &$initial_cwd$&
12752 .vindex "&$initial_cwd$&
12753 This variable contains the full path name of the initial working
12754 directory of the current Exim process. This may differ from the current
12755 working directory, as Exim changes this to "/" during early startup, and
12756 to &$spool_directory$& later.
12759 .vindex "&$inode$&"
12760 The only time this variable is set is while expanding the &%directory_file%&
12761 option in the &(appendfile)& transport. The variable contains the inode number
12762 of the temporary file which is about to be renamed. It can be used to construct
12763 a unique name for the file.
12765 .vitem &$interface_address$& &&&
12767 .vindex "&$interface_address$&"
12768 .vindex "&$interface_port$&"
12769 These are obsolete names for &$received_ip_address$& and &$received_port$&.
12773 This variable is used during the expansion of &*forall*& and &*forany*&
12774 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
12775 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
12779 .vindex "&$ldap_dn$&"
12780 This variable, which is available only when Exim is compiled with LDAP support,
12781 contains the DN from the last entry in the most recently successful LDAP
12784 .vitem &$load_average$&
12785 .vindex "&$load_average$&"
12786 This variable contains the system load average, multiplied by 1000 so that it
12787 is an integer. For example, if the load average is 0.21, the value of the
12788 variable is 210. The value is recomputed every time the variable is referenced.
12790 .tvar &$local_part$&
12791 When an address is being routed, or delivered on its own, this
12792 variable contains the local part. When a number of addresses are being
12793 delivered together (for example, multiple RCPT commands in an SMTP
12794 session), &$local_part$& is not set.
12796 Global address rewriting happens when a message is received, so the value of
12797 &$local_part$& during routing and delivery is the value after rewriting.
12798 &$local_part$& is set during user filtering, but not during system filtering,
12799 because a message may have many recipients and the system filter is called just
12802 .cindex "tainted data"
12803 If the origin of the data is an incoming message,
12804 the result of expanding this variable is tainted and
12805 may not be further expanded or used as a filename.
12807 &*Warning*&: the content of this variable is usually provided by a potential
12809 Consider carefully the implications of using it unvalidated as a name
12811 This presents issues for users' &_.forward_& and filter files.
12812 For traditional full user accounts, use &%check_local_users%& and the
12813 &$local_part_data$& variable rather than this one.
12814 For virtual users, store a suitable pathname component in the database
12815 which is used for account name validation, and use that retrieved value
12816 rather than this variable.
12817 Often &$local_part_data$& is usable in this role.
12818 If needed, use a router &%address_data%& or &%set%& option for
12819 the retrieved data.
12821 When a message is being delivered to a file, pipe, or autoreply transport as a
12822 result of aliasing or forwarding, &$local_part$& is set to the local part of
12823 the parent address, not to the filename or command (see &$address_file$& and
12826 When an ACL is running for a RCPT command, &$local_part$& contains the
12827 local part of the recipient address.
12829 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12830 &$local_part$& contains the local part of the address that is being rewritten;
12831 it can be used in the expansion of the replacement address, for example.
12833 In all cases, all quoting is removed from the local part. For example, for both
12836 "abc:xyz"@test.example
12837 abc\:xyz@test.example
12839 the value of &$local_part$& is
12843 If you use &$local_part$& to create another address, you should always wrap it
12844 inside a quoting operator. For example, in a &(redirect)& router you could
12847 data = ${quote_local_part:$local_part}@new.domain.example
12849 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
12850 to process local parts in a case-dependent manner in a router, you can set the
12851 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
12853 .vitem &$local_part_data$&
12854 .vindex "&$local_part_data$&"
12855 When the &%local_parts%& condition on a router or ACL
12856 matches a local part list
12857 the match value is copied to &$local_part_data$&.
12858 This is an enhancement over previous versions of Exim, when it only
12859 applied to the data read by a lookup.
12860 For details on match values see section &<<SECTlistresults>>& et. al.
12862 The &%check_local_user%& router option also sets this variable.
12864 .vindex &$local_part_prefix$& &&&
12865 &$local_part_prefix_v$& &&&
12866 &$local_part_suffix$& &&&
12867 &$local_part_suffix_v$&
12868 .cindex affix variables
12869 If a local part prefix or suffix has been recognized, it is not included in the
12870 value of &$local_part$& during routing and subsequent delivery. The values of
12871 any prefix or suffix are in &$local_part_prefix$& and
12872 &$local_part_suffix$&, respectively.
12873 .cindex "tainted data"
12874 If the specification did not include a wildcard then
12875 the affix variable value is not tainted.
12877 If the affix specification included a wildcard then the portion of
12878 the affix matched by the wildcard is in
12879 &$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate,
12880 and both the whole and varying values are tainted.
12882 .vitem &$local_scan_data$&
12883 .vindex "&$local_scan_data$&"
12884 This variable contains the text returned by the &[local_scan()]& function when
12885 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
12887 .vitem &$local_user_gid$&
12888 .vindex "&$local_user_gid$&"
12889 See &$local_user_uid$&.
12891 .vitem &$local_user_uid$&
12892 .vindex "&$local_user_uid$&"
12893 This variable and &$local_user_gid$& are set to the uid and gid after the
12894 &%check_local_user%& router precondition succeeds. This means that their values
12895 are available for the remaining preconditions (&%senders%&, &%require_files%&,
12896 and &%condition%&), for the &%address_data%& expansion, and for any
12897 router-specific expansions. At all other times, the values in these variables
12898 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
12900 .vitem &$localhost_number$&
12901 .vindex "&$localhost_number$&"
12902 This contains the expanded value of the
12903 &%localhost_number%& option. The expansion happens after the main options have
12906 .vitem &$log_inodes$&
12907 .vindex "&$log_inodes$&"
12908 The number of free inodes in the disk partition where Exim's
12909 log files are being written. The value is recalculated whenever the variable is
12910 referenced. If the relevant file system does not have the concept of inodes,
12911 the value of is -1. See also the &%check_log_inodes%& option.
12913 .vitem &$log_space$&
12914 .vindex "&$log_space$&"
12915 The amount of free space (as a number of kilobytes) in the disk
12916 partition where Exim's log files are being written. The value is recalculated
12917 whenever the variable is referenced. If the operating system does not have the
12918 ability to find the amount of free space (only true for experimental systems),
12919 the space value is -1. See also the &%check_log_space%& option.
12922 .vitem &$lookup_dnssec_authenticated$&
12923 .vindex "&$lookup_dnssec_authenticated$&"
12924 This variable is set after a DNS lookup done by
12925 a dnsdb lookup expansion, dnslookup router or smtp transport.
12926 .cindex "DNS" "DNSSEC"
12927 It will be empty if &(DNSSEC)& was not requested,
12928 &"no"& if the result was not labelled as authenticated data
12929 and &"yes"& if it was.
12930 Results that are labelled as authoritative answer that match
12931 the &%dns_trust_aa%& configuration variable count also
12932 as authenticated data.
12934 .vitem &$mailstore_basename$&
12935 .vindex "&$mailstore_basename$&"
12936 This variable is set only when doing deliveries in &"mailstore"& format in the
12937 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
12938 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
12939 contains the basename of the files that are being written, that is, the name
12940 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
12943 .vitem &$malware_name$&
12944 .vindex "&$malware_name$&"
12945 This variable is available when Exim is compiled with the
12946 content-scanning extension. It is set to the name of the virus that was found
12947 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12949 .vitem &$max_received_linelength$&
12950 .vindex "&$max_received_linelength$&"
12951 .cindex "maximum" "line length"
12952 .cindex "line length" "maximum"
12953 This variable contains the number of bytes in the longest line that was
12954 received as part of the message, not counting the line termination
12956 It is not valid if the &%spool_wireformat%& option is used.
12958 .vitem &$message_age$&
12959 .cindex "message" "age of"
12960 .vindex "&$message_age$&"
12961 This variable is set at the start of a delivery attempt to contain the number
12962 of seconds since the message was received. It does not change during a single
12965 .tvar &$message_body$&
12966 .cindex "body of message" "expansion variable"
12967 .cindex "message body" "in expansion"
12968 .cindex "binary zero" "in message body"
12969 .oindex "&%message_body_visible%&"
12970 This variable contains the initial portion of a message's body while it is
12971 being delivered, and is intended mainly for use in filter files. The maximum
12972 number of characters of the body that are put into the variable is set by the
12973 &%message_body_visible%& configuration option; the default is 500.
12975 .oindex "&%message_body_newlines%&"
12976 By default, newlines are converted into spaces in &$message_body$&, to make it
12977 easier to search for phrases that might be split over a line break. However,
12978 this can be disabled by setting &%message_body_newlines%& to be true. Binary
12979 zeros are always converted into spaces.
12981 .tvar &$message_body_end$&
12982 .cindex "body of message" "expansion variable"
12983 .cindex "message body" "in expansion"
12984 This variable contains the final portion of a message's
12985 body while it is being delivered. The format and maximum size are as for
12988 .vitem &$message_body_size$&
12989 .cindex "body of message" "size"
12990 .cindex "message body" "size"
12991 .vindex "&$message_body_size$&"
12992 When a message is being delivered, this variable contains the size of the body
12993 in bytes. The count starts from the character after the blank line that
12994 separates the body from the header. Newlines are included in the count. See
12995 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
12997 If the spool file is wireformat
12998 (see the &%spool_wireformat%& main option)
12999 the CRLF line-terminators are included in the count.
13001 .vitem &$message_exim_id$&
13002 .vindex "&$message_exim_id$&"
13003 When a message is being received or delivered, this variable contains the
13004 unique message id that is generated and used by Exim to identify the message.
13005 An id is not created for a message until after its header has been successfully
13006 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
13007 line; it is the local id that Exim assigns to the message, for example:
13008 &`1BXTIK-0001yO-VA`&.
13010 .tvar &$message_headers$&
13011 This variable contains a concatenation of all the header lines when a message
13012 is being processed, except for lines added by routers or transports. The header
13013 lines are separated by newline characters. Their contents are decoded in the
13014 same way as a header line that is inserted by &%bheader%&.
13016 .tvar &$message_headers_raw$&
13017 This variable is like &$message_headers$& except that no processing of the
13018 contents of header lines is done.
13020 .vitem &$message_id$&
13021 This is an old name for &$message_exim_id$&. It is now deprecated.
13023 .vitem &$message_linecount$&
13024 .vindex "&$message_linecount$&"
13025 This variable contains the total number of lines in the header and body of the
13026 message. Compare &$body_linecount$&, which is the count for the body only.
13027 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
13028 number of lines received. Before delivery happens (that is, before filters,
13029 routers, and transports run) the count is increased to include the
13030 &'Received:'& header line that Exim standardly adds, and also any other header
13031 lines that are added by ACLs. The blank line that separates the message header
13032 from the body is not counted.
13034 As with the special case of &$message_size$&, during the expansion of the
13035 appendfile transport's maildir_tag option in maildir format, the value of
13036 &$message_linecount$& is the precise size of the number of newlines in the
13037 file that has been written (minus one for the blank line between the
13038 header and the body).
13040 Here is an example of the use of this variable in a DATA ACL:
13043 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
13044 message = Too many lines in message header
13046 In the MAIL and RCPT ACLs, the value is zero because at that stage the
13047 message has not yet been received.
13049 This variable is not valid if the &%spool_wireformat%& option is used.
13051 .vitem &$message_size$&
13052 .cindex "size" "of message"
13053 .cindex "message" "size"
13054 .vindex "&$message_size$&"
13055 When a message is being processed, this variable contains its size in bytes. In
13056 most cases, the size includes those headers that were received with the
13057 message, but not those (such as &'Envelope-to:'&) that are added to individual
13058 deliveries as they are written. However, there is one special case: during the
13059 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
13060 doing a delivery in maildir format, the value of &$message_size$& is the
13061 precise size of the file that has been written. See also
13062 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
13064 .cindex "RCPT" "value of &$message_size$&"
13065 While running a per message ACL (mail/rcpt/predata), &$message_size$&
13066 contains the size supplied on the MAIL command, or -1 if no size was given. The
13067 value may not, of course, be truthful.
13069 .vitem &$mime_anomaly_level$& &&&
13070 &$mime_anomaly_text$& &&&
13071 &$mime_boundary$& &&&
13072 &$mime_charset$& &&&
13073 &$mime_content_description$& &&&
13074 &$mime_content_disposition$& &&&
13075 &$mime_content_id$& &&&
13076 &$mime_content_size$& &&&
13077 &$mime_content_transfer_encoding$& &&&
13078 &$mime_content_type$& &&&
13079 &$mime_decoded_filename$& &&&
13080 &$mime_filename$& &&&
13081 &$mime_is_coverletter$& &&&
13082 &$mime_is_multipart$& &&&
13083 &$mime_is_rfc822$& &&&
13084 &$mime_part_count$&
13085 A number of variables whose names start with &$mime$& are
13086 available when Exim is compiled with the content-scanning extension. For
13087 details, see section &<<SECTscanmimepart>>&.
13089 .vitem "&$n0$& &-- &$n9$&"
13090 These variables are counters that can be incremented by means
13091 of the &%add%& command in filter files.
13093 .tvar &$original_domain$&
13094 .vindex "&$domain$&"
13095 When a top-level address is being processed for delivery, this contains the
13096 same value as &$domain$&. However, if a &"child"& address (for example,
13097 generated by an alias, forward, or filter file) is being processed, this
13098 variable contains the domain of the original address (lower cased). This
13099 differs from &$parent_domain$& only when there is more than one level of
13100 aliasing or forwarding. When more than one address is being delivered in a
13101 single transport run, &$original_domain$& is not set.
13103 If a new address is created by means of a &%deliver%& command in a system
13104 filter, it is set up with an artificial &"parent"& address. This has the local
13105 part &'system-filter'& and the default qualify domain.
13107 .tvar &$original_local_part$&
13108 .vindex "&$local_part$&"
13109 When a top-level address is being processed for delivery, this contains the
13110 same value as &$local_part$&, unless a prefix or suffix was removed from the
13111 local part, because &$original_local_part$& always contains the full local
13112 part. When a &"child"& address (for example, generated by an alias, forward, or
13113 filter file) is being processed, this variable contains the full local part of
13114 the original address.
13116 If the router that did the redirection processed the local part
13117 case-insensitively, the value in &$original_local_part$& is in lower case.
13118 This variable differs from &$parent_local_part$& only when there is more than
13119 one level of aliasing or forwarding. When more than one address is being
13120 delivered in a single transport run, &$original_local_part$& is not set.
13122 If a new address is created by means of a &%deliver%& command in a system
13123 filter, it is set up with an artificial &"parent"& address. This has the local
13124 part &'system-filter'& and the default qualify domain.
13126 .vitem &$originator_gid$&
13127 .cindex "gid (group id)" "of originating user"
13128 .cindex "sender" "gid"
13129 .vindex "&$caller_gid$&"
13130 .vindex "&$originator_gid$&"
13131 This variable contains the value of &$caller_gid$& that was set when the
13132 message was received. For messages received via the command line, this is the
13133 gid of the sending user. For messages received by SMTP over TCP/IP, this is
13134 normally the gid of the Exim user.
13136 .vitem &$originator_uid$&
13137 .cindex "uid (user id)" "of originating user"
13138 .cindex "sender" "uid"
13139 .vindex "&$caller_uid$&"
13140 .vindex "&$originator_uid$&"
13141 The value of &$caller_uid$& that was set when the message was received. For
13142 messages received via the command line, this is the uid of the sending user.
13143 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
13146 .tvar &$parent_domain$&
13147 This variable is similar to &$original_domain$& (see
13148 above), except that it refers to the immediately preceding parent address.
13150 .tvar &$parent_local_part$&
13151 This variable is similar to &$original_local_part$&
13152 (see above), except that it refers to the immediately preceding parent address.
13155 .cindex "pid (process id)" "of current process"
13157 This variable contains the current process id.
13159 .vitem &$pipe_addresses$&
13160 .cindex "filter" "transport filter"
13161 .cindex "transport" "filter"
13162 .vindex "&$pipe_addresses$&"
13163 This is not an expansion variable, but is mentioned here because the string
13164 &`$pipe_addresses`& is handled specially in the command specification for the
13165 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
13166 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
13167 It cannot be used in general expansion strings, and provokes an &"unknown
13168 variable"& error if encountered.
13169 &*Note*&: This value permits data supplied by a potential attacker to
13170 be used in the command for a &(pipe)& transport.
13171 Such configurations should be carefully assessed for security vulnerbilities.
13173 .vitem &$primary_hostname$&
13174 .vindex "&$primary_hostname$&"
13175 This variable contains the value set by &%primary_hostname%& in the
13176 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
13177 a single-component name, Exim calls &[gethostbyname()]& (or
13178 &[getipnodebyname()]& where available) in an attempt to acquire a fully
13179 qualified host name. See also &$smtp_active_hostname$&.
13182 .vitem &$proxy_external_address$& &&&
13183 &$proxy_external_port$& &&&
13184 &$proxy_local_address$& &&&
13185 &$proxy_local_port$& &&&
13187 These variables are only available when built with Proxy Protocol
13189 For details see chapter &<<SECTproxyInbound>>&.
13191 .vitem &$prdr_requested$&
13192 .cindex "PRDR" "variable for"
13193 This variable is set to &"yes"& if PRDR was requested by the client for the
13194 current message, otherwise &"no"&.
13196 .vitem &$prvscheck_address$& &&&
13197 &$prvscheck_keynum$& &&&
13198 &$prvscheck_result$&
13199 These variables are used in conjunction with the &%prvscheck%& expansion item,
13200 which is described in sections &<<SECTexpansionitems>>& and
13201 &<<SECTverifyPRVS>>&.
13203 .vitem &$qualify_domain$&
13204 .vindex "&$qualify_domain$&"
13205 The value set for the &%qualify_domain%& option in the configuration file.
13207 .vitem &$qualify_recipient$&
13208 .vindex "&$qualify_recipient$&"
13209 The value set for the &%qualify_recipient%& option in the configuration file,
13210 or if not set, the value of &$qualify_domain$&.
13212 .vitem &$queue_name$&
13213 .vindex &$queue_name$&
13214 .cindex "named queues" variable
13215 .cindex queues named
13216 The name of the spool queue in use; empty for the default queue.
13218 .vitem &$queue_size$&
13219 .vindex "&$queue_size$&"
13220 .cindex "queue" "size of"
13221 .cindex "spool" "number of messages"
13222 This variable contains the number of messages queued.
13223 It is evaluated on demand, but no more often than once every minute.
13224 If there is no daemon notifier socket open, the value will be
13229 .cindex router variables
13230 Values can be placed in these variables by the &%set%& option of a router.
13231 They can be given any name that starts with &$r_$&.
13232 The values persist for the address being handled through subsequent routers
13233 and the eventual transport.
13235 .vitem &$rcpt_count$&
13236 .vindex "&$rcpt_count$&"
13237 When a message is being received by SMTP, this variable contains the number of
13238 RCPT commands received for the current message. If this variable is used in a
13239 RCPT ACL, its value includes the current command.
13241 .vitem &$rcpt_defer_count$&
13242 .vindex "&$rcpt_defer_count$&"
13243 .cindex "4&'xx'& responses" "count of"
13244 When a message is being received by SMTP, this variable contains the number of
13245 RCPT commands in the current message that have previously been rejected with a
13246 temporary (4&'xx'&) response.
13248 .vitem &$rcpt_fail_count$&
13249 .vindex "&$rcpt_fail_count$&"
13250 When a message is being received by SMTP, this variable contains the number of
13251 RCPT commands in the current message that have previously been rejected with a
13252 permanent (5&'xx'&) response.
13254 .vitem &$received_count$&
13255 .vindex "&$received_count$&"
13256 This variable contains the number of &'Received:'& header lines in the message,
13257 including the one added by Exim (so its value is always greater than zero). It
13258 is available in the DATA ACL, the non-SMTP ACL, and while routing and
13261 .tvar &$received_for$&
13262 If there is only a single recipient address in an incoming message, this
13263 variable contains that address when the &'Received:'& header line is being
13264 built. The value is copied after recipient rewriting has happened, but before
13265 the &[local_scan()]& function is run.
13267 .vitem &$received_ip_address$& &&&
13269 .vindex "&$received_ip_address$&"
13270 .vindex "&$received_port$&"
13271 As soon as an Exim server starts processing an incoming TCP/IP connection, these
13272 variables are set to the address and port on the local IP interface.
13273 (The remote IP address and port are in
13274 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
13275 the port value is -1 unless it has been set using the &%-oMi%& command line
13278 As well as being useful in ACLs (including the &"connect"& ACL), these variable
13279 could be used, for example, to make the filename for a TLS certificate depend
13280 on which interface and/or port is being used for the incoming connection. The
13281 values of &$received_ip_address$& and &$received_port$& are saved with any
13282 messages that are received, thus making these variables available at delivery
13284 For outbound connections see &$sending_ip_address$&.
13286 .vitem &$received_protocol$&
13287 .vindex "&$received_protocol$&"
13288 When a message is being processed, this variable contains the name of the
13289 protocol by which it was received. Most of the names used by Exim are defined
13290 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
13291 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
13292 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
13293 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
13294 connection and the client was successfully authenticated.
13296 Exim uses the protocol name &"smtps"& for the case when encryption is
13297 automatically set up on connection without the use of STARTTLS (see
13298 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
13299 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
13300 where the client initially uses EHLO, sets up an encrypted connection using
13301 STARTTLS, and then uses HELO afterwards.
13303 The &%-oMr%& option provides a way of specifying a custom protocol name for
13304 messages that are injected locally by trusted callers. This is commonly used to
13305 identify messages that are being re-injected after some kind of scanning.
13307 .vitem &$received_time$&
13308 .vindex "&$received_time$&"
13309 This variable contains the date and time when the current message was received,
13310 as a number of seconds since the start of the Unix epoch.
13312 .vitem &$recipient_data$&
13313 .vindex "&$recipient_data$&"
13314 This variable is set after an indexing lookup success in an ACL &%recipients%&
13315 condition. It contains the data from the lookup, and the value remains set
13316 until the next &%recipients%& test. Thus, you can do things like this:
13318 &`require recipients = cdb*@;/some/file`&
13319 &`deny `&&'some further test involving'& &`$recipient_data`&
13321 &*Warning*&: This variable is set only when a lookup is used as an indexing
13322 method in the address list, using the semicolon syntax as in the example above.
13323 The variable is not set for a lookup that is used as part of the string
13324 expansion that all such lists undergo before being interpreted.
13326 .vitem &$recipient_verify_failure$&
13327 .vindex "&$recipient_verify_failure$&"
13328 In an ACL, when a recipient verification fails, this variable contains
13329 information about the failure. It is set to one of the following words:
13332 &"qualify"&: The address was unqualified (no domain), and the message
13333 was neither local nor came from an exempted host.
13336 &"route"&: Routing failed.
13339 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
13340 or before the MAIL command (that is, on initial connection, HELO, or
13344 &"recipient"&: The RCPT command in a callout was rejected.
13347 &"postmaster"&: The postmaster check in a callout was rejected.
13350 The main use of this variable is expected to be to distinguish between
13351 rejections of MAIL and rejections of RCPT.
13353 .tvar &$recipients$&
13354 This variable contains a list of envelope recipients for a message. A comma and
13355 a space separate the addresses in the replacement text. However, the variable
13356 is not generally available, to prevent exposure of Bcc recipients in
13357 unprivileged users' filter files. You can use &$recipients$& only in these
13361 In a system filter file.
13363 In the ACLs associated with the DATA command and with non-SMTP messages, that
13364 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
13365 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
13366 &%acl_not_smtp_mime%&.
13368 From within a &[local_scan()]& function.
13372 .vitem &$recipients_count$&
13373 .vindex "&$recipients_count$&"
13374 When a message is being processed, this variable contains the number of
13375 envelope recipients that came with the message. Duplicates are not excluded
13376 from the count. While a message is being received over SMTP, the number
13377 increases for each accepted recipient. It can be referenced in an ACL.
13380 .vitem &$regex_match_string$&
13381 .vindex "&$regex_match_string$&"
13382 This variable is set to contain the matching regular expression after a
13383 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
13385 .vitem "&$regex1$&, &$regex2$&, etc"
13386 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
13387 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
13388 these variables contain the
13389 captured substrings identified by the regular expression.
13390 If the subject string was tainted then so will any captured substring.
13393 .tvar &$reply_address$&
13394 When a message is being processed, this variable contains the contents of the
13395 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
13396 contents of the &'From:'& header line. Apart from the removal of leading
13397 white space, the value is not processed in any way. In particular, no RFC 2047
13398 decoding or character code translation takes place.
13400 .vitem &$return_path$&
13401 .vindex "&$return_path$&"
13402 When a message is being delivered, this variable contains the return path &--
13403 the sender field that will be sent as part of the envelope. It is not enclosed
13404 in <> characters. At the start of routing an address, &$return_path$& has the
13405 same value as &$sender_address$&, but if, for example, an incoming message to a
13406 mailing list has been expanded by a router which specifies a different address
13407 for bounce messages, &$return_path$& subsequently contains the new bounce
13408 address, whereas &$sender_address$& always contains the original sender address
13409 that was received with the message. In other words, &$sender_address$& contains
13410 the incoming envelope sender, and &$return_path$& contains the outgoing
13413 .vitem &$return_size_limit$&
13414 .vindex "&$return_size_limit$&"
13415 This is an obsolete name for &$bounce_return_size_limit$&.
13417 .vitem &$router_name$&
13418 .cindex "router" "name"
13419 .cindex "name" "of router"
13420 .vindex "&$router_name$&"
13421 During the running of a router this variable contains its name.
13424 .cindex "return code" "from &%run%& expansion"
13425 .vindex "&$runrc$&"
13426 This variable contains the return code from a command that is run by the
13427 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
13428 assume the order in which option values are expanded, except for those
13429 preconditions whose order of testing is documented. Therefore, you cannot
13430 reliably expect to set &$runrc$& by the expansion of one option, and use it in
13433 .vitem &$self_hostname$&
13434 .oindex "&%self%&" "value of host name"
13435 .vindex "&$self_hostname$&"
13436 When an address is routed to a supposedly remote host that turns out to be the
13437 local host, what happens is controlled by the &%self%& generic router option.
13438 One of its values causes the address to be passed to another router. When this
13439 happens, &$self_hostname$& is set to the name of the local host that the
13440 original router encountered. In other circumstances its contents are null.
13442 .tvar &$sender_address$&
13443 When a message is being processed, this variable contains the sender's address
13444 that was received in the message's envelope. The case of letters in the address
13445 is retained, in both the local part and the domain. For bounce messages, the
13446 value of this variable is the empty string. See also &$return_path$&.
13448 .vitem &$sender_address_data$&
13449 .vindex "&$address_data$&"
13450 .vindex "&$sender_address_data$&"
13451 If &$address_data$& is set when the routers are called from an ACL to verify a
13452 sender address, the final value is preserved in &$sender_address_data$&, to
13453 distinguish it from data from a recipient address. The value does not persist
13454 after the end of the current ACL statement. If you want to preserve it for
13455 longer, you can save it in an ACL variable.
13457 .tvar &$sender_address_domain$&
13458 The domain portion of &$sender_address$&.
13460 .tvar &$sender_address_local_part$&
13461 The local part portion of &$sender_address$&.
13463 .vitem &$sender_data$&
13464 .vindex "&$sender_data$&"
13465 This variable is set after a lookup success in an ACL &%senders%& condition or
13466 in a router &%senders%& option. It contains the data from the lookup, and the
13467 value remains set until the next &%senders%& test. Thus, you can do things like
13470 &`require senders = cdb*@;/some/file`&
13471 &`deny `&&'some further test involving'& &`$sender_data`&
13473 &*Warning*&: This variable is set only when a lookup is used as an indexing
13474 method in the address list, using the semicolon syntax as in the example above.
13475 The variable is not set for a lookup that is used as part of the string
13476 expansion that all such lists undergo before being interpreted.
13478 .vitem &$sender_fullhost$&
13479 .vindex "&$sender_fullhost$&"
13480 When a message is received from a remote host, this variable contains the host
13481 name and IP address in a single string. It ends with the IP address in square
13482 brackets, followed by a colon and a port number if the logging of ports is
13483 enabled. The format of the rest of the string depends on whether the host
13484 issued a HELO or EHLO SMTP command, and whether the host name was verified by
13485 looking up its IP address. (Looking up the IP address can be forced by the
13486 &%host_lookup%& option, independent of verification.) A plain host name at the
13487 start of the string is a verified host name; if this is not present,
13488 verification either failed or was not requested. A host name in parentheses is
13489 the argument of a HELO or EHLO command. This is omitted if it is identical to
13490 the verified host name or to the host's IP address in square brackets.
13492 .vitem &$sender_helo_dnssec$&
13493 .vindex "&$sender_helo_dnssec$&"
13494 This boolean variable is true if a successful HELO verification was
13495 .cindex "DNS" "DNSSEC"
13496 done using DNS information the resolver library stated was authenticated data.
13498 .tvar &$sender_helo_name$&
13499 When a message is received from a remote host that has issued a HELO or EHLO
13500 command, the argument of that command is placed in this variable. It is also
13501 set if HELO or EHLO is used when a message is received using SMTP locally via
13502 the &%-bs%& or &%-bS%& options.
13504 .vitem &$sender_host_address$&
13505 .vindex "&$sender_host_address$&"
13506 When a message is received from a remote host using SMTP,
13507 this variable contains that
13508 host's IP address. For locally non-SMTP submitted messages, it is empty.
13510 .vitem &$sender_host_authenticated$&
13511 .vindex "&$sender_host_authenticated$&"
13512 This variable contains the name (not the public name) of the authenticator
13513 driver that successfully authenticated the client from which the message was
13514 received. It is empty if there was no successful authentication. See also
13515 &$authenticated_id$&.
13517 .vitem &$sender_host_dnssec$&
13518 .vindex "&$sender_host_dnssec$&"
13519 If an attempt to populate &$sender_host_name$& has been made
13520 (by reference, &%hosts_lookup%& or
13521 otherwise) then this boolean will have been set true if, and only if, the
13522 resolver library states that both
13523 the reverse and forward DNS were authenticated data. At all
13524 other times, this variable is false.
13526 .cindex "DNS" "DNSSEC"
13527 It is likely that you will need to coerce DNSSEC support on in the resolver
13528 library, by setting:
13533 In addition, on Linux with glibc 2.31 or newer the resolver library will
13534 default to stripping out a successful validation status.
13535 This will break a previously working Exim installation.
13536 Provided that you do trust the resolver (ie, is on localhost) you can tell
13537 glibc to pass through any successful validation with a new option in
13538 &_/etc/resolv.conf_&:
13543 Exim does not perform DNSSEC validation itself, instead leaving that to a
13544 validating resolver (e.g. unbound, or bind with suitable configuration).
13546 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
13547 mechanism in the list, then this variable will be false.
13549 This requires that your system resolver library support EDNS0 (and that
13550 DNSSEC flags exist in the system headers). If the resolver silently drops
13551 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
13552 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
13555 .tvar &$sender_host_name$&
13556 When a message is received from a remote host, this variable contains the
13557 host's name as obtained by looking up its IP address. For messages received by
13558 other means, this variable is empty.
13560 .vindex "&$host_lookup_failed$&"
13561 If the host name has not previously been looked up, a reference to
13562 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
13563 A looked up name is accepted only if it leads back to the original IP address
13564 via a forward lookup. If either the reverse or the forward lookup fails to find
13565 any data, or if the forward lookup does not yield the original IP address,
13566 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
13568 .vindex "&$host_lookup_deferred$&"
13569 However, if either of the lookups cannot be completed (for example, there is a
13570 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
13571 &$host_lookup_failed$& remains set to &"0"&.
13573 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
13574 host name again if there is a subsequent reference to &$sender_host_name$&
13575 in the same Exim process, but it does try again if &$host_lookup_deferred$&
13578 Exim does not automatically look up every calling host's name. If you want
13579 maximum efficiency, you should arrange your configuration so that it avoids
13580 these lookups altogether. The lookup happens only if one or more of the
13581 following are true:
13584 A string containing &$sender_host_name$& is expanded.
13586 The calling host matches the list in &%host_lookup%&. In the default
13587 configuration, this option is set to *, so it must be changed if lookups are
13588 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
13590 Exim needs the host name in order to test an item in a host list. The items
13591 that require this are described in sections &<<SECThoslispatnam>>& and
13592 &<<SECThoslispatnamsk>>&.
13594 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
13595 In this case, the host name is required to compare with the name quoted in any
13596 EHLO or HELO commands that the client issues.
13598 The remote host issues a EHLO or HELO command that quotes one of the
13599 domains in &%helo_lookup_domains%&. The default value of this option is
13600 . ==== As this is a nested list, any displays it contains must be indented
13601 . ==== as otherwise they are too far to the left.
13603 helo_lookup_domains = @ : @[]
13605 which causes a lookup if a remote host (incorrectly) gives the server's name or
13606 IP address in an EHLO or HELO command.
13610 .vitem &$sender_host_port$&
13611 .vindex "&$sender_host_port$&"
13612 When a message is received from a remote host, this variable contains the port
13613 number that was used on the remote host.
13615 .vitem &$sender_ident$&
13616 .vindex "&$sender_ident$&"
13617 When a message is received from a remote host, this variable contains the
13618 identification received in response to an RFC 1413 request. When a message has
13619 been received locally, this variable contains the login name of the user that
13622 .vitem &$sender_rate_$&&'xxx'&
13623 A number of variables whose names begin &$sender_rate_$& are set as part of the
13624 &%ratelimit%& ACL condition. Details are given in section
13625 &<<SECTratelimiting>>&.
13627 .vitem &$sender_rcvhost$&
13628 .cindex "DNS" "reverse lookup"
13629 .cindex "reverse DNS lookup"
13630 .vindex "&$sender_rcvhost$&"
13631 This is provided specifically for use in &'Received:'& headers. It starts with
13632 either the verified host name (as obtained from a reverse DNS lookup) or, if
13633 there is no verified host name, the IP address in square brackets. After that
13634 there may be text in parentheses. When the first item is a verified host name,
13635 the first thing in the parentheses is the IP address in square brackets,
13636 followed by a colon and a port number if port logging is enabled. When the
13637 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
13640 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
13641 was used and its argument was not identical to the real host name or IP
13642 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
13643 all three items are present in the parentheses, a newline and tab are inserted
13644 into the string, to improve the formatting of the &'Received:'& header.
13646 .vitem &$sender_verify_failure$&
13647 .vindex "&$sender_verify_failure$&"
13648 In an ACL, when a sender verification fails, this variable contains information
13649 about the failure. The details are the same as for
13650 &$recipient_verify_failure$&.
13652 .vitem &$sending_ip_address$&
13653 .vindex "&$sending_ip_address$&"
13654 This variable is set whenever an outgoing SMTP connection to another host has
13655 been set up. It contains the IP address of the local interface that is being
13656 used. This is useful if a host that has more than one IP address wants to take
13657 on different personalities depending on which one is being used. For incoming
13658 connections, see &$received_ip_address$&.
13660 .vitem &$sending_port$&
13661 .vindex "&$sending_port$&"
13662 This variable is set whenever an outgoing SMTP connection to another host has
13663 been set up. It contains the local port that is being used. For incoming
13664 connections, see &$received_port$&.
13666 .vitem &$smtp_active_hostname$&
13667 .vindex "&$smtp_active_hostname$&"
13668 During an incoming SMTP session, this variable contains the value of the active
13669 host name, as specified by the &%smtp_active_hostname%& option. The value of
13670 &$smtp_active_hostname$& is saved with any message that is received, so its
13671 value can be consulted during routing and delivery.
13673 .tvar &$smtp_command$&
13674 During the processing of an incoming SMTP command, this variable contains the
13675 entire command. This makes it possible to distinguish between HELO and EHLO in
13676 the HELO ACL, and also to distinguish between commands such as these:
13681 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
13682 command, the address in &$smtp_command$& is the original address before any
13683 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
13684 the address after SMTP-time rewriting.
13686 .tvar &$smtp_command_argument$&
13687 .cindex "SMTP" "command, argument for"
13688 While an ACL is running to check an SMTP command, this variable contains the
13689 argument, that is, the text that follows the command name, with leading white
13690 space removed. Following the introduction of &$smtp_command$&, this variable is
13691 somewhat redundant, but is retained for backwards compatibility.
13693 .vitem &$smtp_command_history$&
13694 .cindex SMTP "command history"
13695 .vindex "&$smtp_command_history$&"
13696 A comma-separated list (with no whitespace) of the most-recent SMTP commands
13697 received, in time-order left to right. Only a limited number of commands
13700 .vitem &$smtp_count_at_connection_start$&
13701 .vindex "&$smtp_count_at_connection_start$&"
13702 This variable is set greater than zero only in processes spawned by the Exim
13703 daemon for handling incoming SMTP connections. The name is deliberately long,
13704 in order to emphasize what the contents are. When the daemon accepts a new
13705 connection, it increments this variable. A copy of the variable is passed to
13706 the child process that handles the connection, but its value is fixed, and
13707 never changes. It is only an approximation of how many incoming connections
13708 there actually are, because many other connections may come and go while a
13709 single connection is being processed. When a child process terminates, the
13710 daemon decrements its copy of the variable.
13712 .vitem "&$sn0$& &-- &$sn9$&"
13713 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
13714 that were current at the end of the system filter file. This allows a system
13715 filter file to set values that can be tested in users' filter files. For
13716 example, a system filter could set a value indicating how likely it is that a
13717 message is junk mail.
13719 .vitem &$spam_score$& &&&
13720 &$spam_score_int$& &&&
13722 &$spam_report$& &&&
13724 A number of variables whose names start with &$spam$& are available when Exim
13725 is compiled with the content-scanning extension. For details, see section
13726 &<<SECTscanspamass>>&.
13728 .vitem &$spf_header_comment$& &&&
13729 &$spf_received$& &&&
13731 &$spf_result_guessed$& &&&
13732 &$spf_smtp_comment$&
13733 These variables are only available if Exim is built with SPF support.
13734 For details see section &<<SECSPF>>&.
13736 .vitem &$spool_directory$&
13737 .vindex "&$spool_directory$&"
13738 The name of Exim's spool directory.
13740 .vitem &$spool_inodes$&
13741 .vindex "&$spool_inodes$&"
13742 The number of free inodes in the disk partition where Exim's spool files are
13743 being written. The value is recalculated whenever the variable is referenced.
13744 If the relevant file system does not have the concept of inodes, the value of
13745 is -1. See also the &%check_spool_inodes%& option.
13747 .vitem &$spool_space$&
13748 .vindex "&$spool_space$&"
13749 The amount of free space (as a number of kilobytes) in the disk partition where
13750 Exim's spool files are being written. The value is recalculated whenever the
13751 variable is referenced. If the operating system does not have the ability to
13752 find the amount of free space (only true for experimental systems), the space
13753 value is -1. For example, to check in an ACL that there is at least 50
13754 megabytes free on the spool, you could write:
13756 condition = ${if > {$spool_space}{50000}}
13758 See also the &%check_spool_space%& option.
13761 .vitem &$thisaddress$&
13762 .vindex "&$thisaddress$&"
13763 This variable is set only during the processing of the &%foranyaddress%&
13764 command in a filter file. Its use is explained in the description of that
13765 command, which can be found in the separate document entitled &'Exim's
13766 interfaces to mail filtering'&.
13768 .vitem &$tls_in_bits$&
13769 .vindex "&$tls_in_bits$&"
13770 Contains an approximation of the TLS cipher's bit-strength
13771 on the inbound connection; the meaning of
13772 this depends upon the TLS implementation used.
13773 If TLS has not been negotiated, the value will be 0.
13774 The value of this is automatically fed into the Cyrus SASL authenticator
13775 when acting as a server, to specify the "external SSF" (a SASL term).
13777 The deprecated &$tls_bits$& variable refers to the inbound side
13778 except when used in the context of an outbound SMTP delivery, when it refers to
13781 .vitem &$tls_out_bits$&
13782 .vindex "&$tls_out_bits$&"
13783 Contains an approximation of the TLS cipher's bit-strength
13784 on an outbound SMTP connection; the meaning of
13785 this depends upon the TLS implementation used.
13786 If TLS has not been negotiated, the value will be 0.
13788 .vitem &$tls_in_ourcert$&
13789 .vindex "&$tls_in_ourcert$&"
13790 .cindex certificate variables
13791 This variable refers to the certificate presented to the peer of an
13792 inbound connection when the message was received.
13793 It is only useful as the argument of a
13794 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13795 or a &%def%& condition.
13797 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
13798 when a list of more than one
13799 file is used for &%tls_certificate%&, this variable is not reliable.
13800 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
13802 .vitem &$tls_in_peercert$&
13803 .vindex "&$tls_in_peercert$&"
13804 This variable refers to the certificate presented by the peer of an
13805 inbound connection when the message was received.
13806 It is only useful as the argument of a
13807 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13808 or a &%def%& condition.
13809 If certificate verification fails it may refer to a failing chain element
13810 which is not the leaf.
13812 .vitem &$tls_out_ourcert$&
13813 .vindex "&$tls_out_ourcert$&"
13814 This variable refers to the certificate presented to the peer of an
13815 outbound connection. It is only useful as the argument of a
13816 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13817 or a &%def%& condition.
13819 .vitem &$tls_out_peercert$&
13820 .vindex "&$tls_out_peercert$&"
13821 This variable refers to the certificate presented by the peer of an
13822 outbound connection. It is only useful as the argument of a
13823 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13824 or a &%def%& condition.
13825 If certificate verification fails it may refer to a failing chain element
13826 which is not the leaf.
13828 .vitem &$tls_in_certificate_verified$&
13829 .vindex "&$tls_in_certificate_verified$&"
13830 This variable is set to &"1"& if a TLS certificate was verified when the
13831 message was received, and &"0"& otherwise.
13833 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
13834 except when used in the context of an outbound SMTP delivery, when it refers to
13837 .vitem &$tls_out_certificate_verified$&
13838 .vindex "&$tls_out_certificate_verified$&"
13839 This variable is set to &"1"& if a TLS certificate was verified when an
13840 outbound SMTP connection was made,
13841 and &"0"& otherwise.
13843 .vitem &$tls_in_cipher$&
13844 .vindex "&$tls_in_cipher$&"
13845 .vindex "&$tls_cipher$&"
13846 When a message is received from a remote host over an encrypted SMTP
13847 connection, this variable is set to the cipher suite that was negotiated, for
13848 example DES-CBC3-SHA. In other circumstances, in particular, for message
13849 received over unencrypted connections, the variable is empty. Testing
13850 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
13851 non-encrypted connections during ACL processing.
13853 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
13854 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
13855 becomes the same as &$tls_out_cipher$&.
13857 .vitem &$tls_in_cipher_std$&
13858 .vindex "&$tls_in_cipher_std$&"
13859 As above, but returning the RFC standard name for the cipher suite.
13861 .vitem &$tls_out_cipher$&
13862 .vindex "&$tls_out_cipher$&"
13864 cleared before any outgoing SMTP connection is made,
13865 and then set to the outgoing cipher suite if one is negotiated. See chapter
13866 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
13867 details of the &(smtp)& transport.
13869 .vitem &$tls_out_cipher_std$&
13870 .vindex "&$tls_out_cipher_std$&"
13871 As above, but returning the RFC standard name for the cipher suite.
13873 .vitem &$tls_out_dane$&
13874 .vindex &$tls_out_dane$&
13875 DANE active status. See section &<<SECDANE>>&.
13877 .vitem &$tls_in_ocsp$&
13878 .vindex "&$tls_in_ocsp$&"
13879 When a message is received from a remote client connection
13880 the result of any OCSP request from the client is encoded in this variable:
13882 0 OCSP proof was not requested (default value)
13883 1 No response to request
13884 2 Response not verified
13885 3 Verification failed
13886 4 Verification succeeded
13889 .vitem &$tls_out_ocsp$&
13890 .vindex "&$tls_out_ocsp$&"
13891 When a message is sent to a remote host connection
13892 the result of any OCSP request made is encoded in this variable.
13893 See &$tls_in_ocsp$& for values.
13895 .vitem &$tls_in_peerdn$&
13896 .vindex "&$tls_in_peerdn$&"
13897 .vindex "&$tls_peerdn$&"
13898 .cindex certificate "extracting fields"
13899 When a message is received from a remote host over an encrypted SMTP
13900 connection, and Exim is configured to request a certificate from the client,
13901 the value of the Distinguished Name of the certificate is made available in the
13902 &$tls_in_peerdn$& during subsequent processing.
13903 If certificate verification fails it may refer to a failing chain element
13904 which is not the leaf.
13906 The deprecated &$tls_peerdn$& variable refers to the inbound side
13907 except when used in the context of an outbound SMTP delivery, when it refers to
13910 .vitem &$tls_out_peerdn$&
13911 .vindex "&$tls_out_peerdn$&"
13912 When a message is being delivered to a remote host over an encrypted SMTP
13913 connection, and Exim is configured to request a certificate from the server,
13914 the value of the Distinguished Name of the certificate is made available in the
13915 &$tls_out_peerdn$& during subsequent processing.
13916 If certificate verification fails it may refer to a failing chain element
13917 which is not the leaf.
13920 .vitem &$tls_in_resumption$& &&&
13921 &$tls_out_resumption$&
13922 .vindex &$tls_in_resumption$&
13923 .vindex &$tls_out_resumption$&
13924 .cindex TLS resumption
13925 Observability for TLS session resumption. See &<<SECTresumption>>& for details.
13928 .tvar &$tls_in_sni$&
13929 .vindex "&$tls_sni$&"
13930 .cindex "TLS" "Server Name Indication"
13932 .cindex SNI "observability on server"
13933 When a TLS session is being established, if the client sends the Server
13934 Name Indication extension, the value will be placed in this variable.
13935 If the variable appears in &%tls_certificate%& then this option and
13936 some others, described in &<<SECTtlssni>>&,
13937 will be re-expanded early in the TLS session, to permit
13938 a different certificate to be presented (and optionally a different key to be
13939 used) to the client, based upon the value of the SNI extension.
13941 The deprecated &$tls_sni$& variable refers to the inbound side
13942 except when used in the context of an outbound SMTP delivery, when it refers to
13945 .vitem &$tls_out_sni$&
13946 .vindex "&$tls_out_sni$&"
13947 .cindex "TLS" "Server Name Indication"
13949 .cindex SNI "observability in client"
13951 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
13954 .vitem &$tls_out_tlsa_usage$&
13955 .vindex &$tls_out_tlsa_usage$&
13956 Bitfield of TLSA record types found. See section &<<SECDANE>>&.
13958 .vitem &$tls_in_ver$&
13959 .vindex "&$tls_in_ver$&"
13960 When a message is received from a remote host over an encrypted SMTP connection
13961 this variable is set to the protocol version, eg &'TLS1.2'&.
13963 .vitem &$tls_out_ver$&
13964 .vindex "&$tls_out_ver$&"
13965 When a message is being delivered to a remote host over an encrypted SMTP connection
13966 this variable is set to the protocol version.
13969 .vitem &$tod_bsdinbox$&
13970 .vindex "&$tod_bsdinbox$&"
13971 The time of day and the date, in the format required for BSD-style mailbox
13972 files, for example: Thu Oct 17 17:14:09 1995.
13974 .vitem &$tod_epoch$&
13975 .vindex "&$tod_epoch$&"
13976 The time and date as a number of seconds since the start of the Unix epoch.
13978 .vitem &$tod_epoch_l$&
13979 .vindex "&$tod_epoch_l$&"
13980 The time and date as a number of microseconds since the start of the Unix epoch.
13982 .vitem &$tod_full$&
13983 .vindex "&$tod_full$&"
13984 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
13985 +0100. The timezone is always given as a numerical offset from UTC, with
13986 positive values used for timezones that are ahead (east) of UTC, and negative
13987 values for those that are behind (west).
13990 .vindex "&$tod_log$&"
13991 The time and date in the format used for writing Exim's log files, for example:
13992 1995-10-12 15:32:29, but without a timezone.
13994 .vitem &$tod_logfile$&
13995 .vindex "&$tod_logfile$&"
13996 This variable contains the date in the format yyyymmdd. This is the format that
13997 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
14000 .vitem &$tod_zone$&
14001 .vindex "&$tod_zone$&"
14002 This variable contains the numerical value of the local timezone, for example:
14005 .vitem &$tod_zulu$&
14006 .vindex "&$tod_zulu$&"
14007 This variable contains the UTC date and time in &"Zulu"& format, as specified
14008 by ISO 8601, for example: 20030221154023Z.
14010 .vitem &$transport_name$&
14011 .cindex "transport" "name"
14012 .cindex "name" "of transport"
14013 .vindex "&$transport_name$&"
14014 During the running of a transport, this variable contains its name.
14017 .vindex "&$value$&"
14018 This variable contains the result of an expansion lookup, extraction operation,
14019 or external command, as described above. It is also used during a
14020 &*reduce*& expansion.
14022 .vitem &$verify_mode$&
14023 .vindex "&$verify_mode$&"
14024 While a router or transport is being run in verify mode or for cutthrough delivery,
14025 contains "S" for sender-verification or "R" for recipient-verification.
14028 .vitem &$version_number$&
14029 .vindex "&$version_number$&"
14030 The version number of Exim. Same as &$exim_version$&, may be overridden
14031 by the &%exim_version%& main config option.
14033 .vitem &$warn_message_delay$&
14034 .vindex "&$warn_message_delay$&"
14035 This variable is set only during the creation of a message warning about a
14036 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14038 .vitem &$warn_message_recipients$&
14039 .vindex "&$warn_message_recipients$&"
14040 This variable is set only during the creation of a message warning about a
14041 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14047 . ////////////////////////////////////////////////////////////////////////////
14048 . ////////////////////////////////////////////////////////////////////////////
14050 .chapter "Embedded Perl" "CHAPperl"
14051 .scindex IIDperl "Perl" "calling from Exim"
14052 Exim can be built to include an embedded Perl interpreter. When this is done,
14053 Perl subroutines can be called as part of the string expansion process. To make
14054 use of the Perl support, you need version 5.004 or later of Perl installed on
14055 your system. To include the embedded interpreter in the Exim binary, include
14060 in your &_Local/Makefile_& and then build Exim in the normal way.
14063 .section "Setting up so Perl can be used" "SECID85"
14064 .oindex "&%perl_startup%&"
14065 Access to Perl subroutines is via a global configuration option called
14066 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
14067 no &%perl_startup%& option in the Exim configuration file then no Perl
14068 interpreter is started and there is almost no overhead for Exim (since none of
14069 the Perl library will be paged in unless used). If there is a &%perl_startup%&
14070 option then the associated value is taken to be Perl code which is executed in
14071 a newly created Perl interpreter.
14073 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
14074 need backslashes before any characters to escape special meanings. The option
14075 should usually be something like
14077 perl_startup = do '/etc/exim.pl'
14079 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
14080 use from Exim. Exim can be configured either to start up a Perl interpreter as
14081 soon as it is entered, or to wait until the first time it is needed. Starting
14082 the interpreter at the beginning ensures that it is done while Exim still has
14083 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
14084 fact used in a particular run. Also, note that this does not mean that Exim is
14085 necessarily running as root when Perl is called at a later time. By default,
14086 the interpreter is started only when it is needed, but this can be changed in
14090 .oindex "&%perl_at_start%&"
14091 Setting &%perl_at_start%& (a boolean option) in the configuration requests
14092 a startup when Exim is entered.
14094 The command line option &%-ps%& also requests a startup when Exim is entered,
14095 overriding the setting of &%perl_at_start%&.
14098 There is also a command line option &%-pd%& (for delay) which suppresses the
14099 initial startup, even if &%perl_at_start%& is set.
14102 .oindex "&%perl_taintmode%&"
14103 .cindex "Perl" "taintmode"
14104 To provide more security executing Perl code via the embedded Perl
14105 interpreter, the &%perl_taintmode%& option can be set. This enables the
14106 taint mode of the Perl interpreter. You are encouraged to set this
14107 option to a true value. To avoid breaking existing installations, it
14110 &*Note*&: This is entirely separate from Exim's tainted-data tracking.
14113 .section "Calling Perl subroutines" "SECID86"
14114 When the configuration file includes a &%perl_startup%& option you can make use
14115 of the string expansion item to call the Perl subroutines that are defined
14116 by the &%perl_startup%& code. The operator is used in any of the following
14120 ${perl{foo}{argument}}
14121 ${perl{foo}{argument1}{argument2} ... }
14123 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
14124 arguments may be passed. Passing more than this results in an expansion failure
14125 with an error message of the form
14127 Too many arguments passed to Perl subroutine "foo" (max is 8)
14129 The return value of the Perl subroutine is evaluated in a scalar context before
14130 it is passed back to Exim to be inserted into the expanded string. If the
14131 return value is &'undef'&, the expansion is forced to fail in the same way as
14132 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
14133 by obeying Perl's &%die%& function, the expansion fails with the error message
14134 that was passed to &%die%&.
14137 .section "Calling Exim functions from Perl" "SECID87"
14138 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
14139 is available to call back into Exim's string expansion function. For example,
14142 my $lp = Exim::expand_string('$local_part');
14144 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
14145 Note those are single quotes and not double quotes to protect against
14146 &$local_part$& being interpolated as a Perl variable.
14148 If the string expansion is forced to fail by a &"fail"& item, the result of
14149 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
14150 expansion string, the Perl call from the original expansion string fails with
14151 an appropriate error message, in the same way as if &%die%& were used.
14153 .cindex "debugging" "from embedded Perl"
14154 .cindex "log" "writing from embedded Perl"
14155 Two other Exim functions are available for use from within Perl code.
14156 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
14157 debugging is enabled. If you want a newline at the end, you must supply it.
14158 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
14159 timestamp. In this case, you should not supply a terminating newline.
14162 .section "Use of standard output and error by Perl" "SECID88"
14163 .cindex "Perl" "standard output and error"
14164 You should not write to the standard error or output streams from within your
14165 Perl code, as it is not defined how these are set up. In versions of Exim
14166 before 4.50, it is possible for the standard output or error to refer to the
14167 SMTP connection during message reception via the daemon. Writing to this stream
14168 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
14169 error streams are connected to &_/dev/null_& in the daemon. The chaos is
14170 avoided, but the output is lost.
14172 .cindex "Perl" "use of &%warn%&"
14173 The Perl &%warn%& statement writes to the standard error stream by default.
14174 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
14175 you have no control. When Exim starts up the Perl interpreter, it arranges for
14176 output from the &%warn%& statement to be written to the Exim main log. You can
14177 change this by including appropriate Perl magic somewhere in your Perl code.
14178 For example, to discard &%warn%& output completely, you need this:
14180 $SIG{__WARN__} = sub { };
14182 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
14183 example, the code for the subroutine is empty, so it does nothing, but you can
14184 include any Perl code that you like. The text of the &%warn%& message is passed
14185 as the first subroutine argument.
14189 . ////////////////////////////////////////////////////////////////////////////
14190 . ////////////////////////////////////////////////////////////////////////////
14192 .chapter "Starting the daemon and the use of network interfaces" &&&
14193 "CHAPinterfaces" &&&
14194 "Starting the daemon"
14195 .cindex "daemon" "starting"
14196 .cindex "interface" "listening"
14197 .cindex "network interface"
14198 .cindex "interface" "network"
14199 .cindex "IP address" "for listening"
14200 .cindex "daemon" "listening IP addresses"
14201 .cindex "TCP/IP" "setting listening interfaces"
14202 .cindex "TCP/IP" "setting listening ports"
14203 A host that is connected to a TCP/IP network may have one or more physical
14204 hardware network interfaces. Each of these interfaces may be configured as one
14205 or more &"logical"& interfaces, which are the entities that a program actually
14206 works with. Each of these logical interfaces is associated with an IP address.
14207 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
14208 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
14209 knowledge about the host's interfaces for use in three different circumstances:
14212 When a listening daemon is started, Exim needs to know which interfaces
14213 and ports to listen on.
14215 When Exim is routing an address, it needs to know which IP addresses
14216 are associated with local interfaces. This is required for the correct
14217 processing of MX lists by removing the local host and others with the
14218 same or higher priority values. Also, Exim needs to detect cases
14219 when an address is routed to an IP address that in fact belongs to the
14220 local host. Unless the &%self%& router option or the &%allow_localhost%&
14221 option of the smtp transport is set (as appropriate), this is treated
14222 as an error situation.
14224 When Exim connects to a remote host, it may need to know which interface to use
14225 for the outgoing connection.
14229 Exim's default behaviour is likely to be appropriate in the vast majority
14230 of cases. If your host has only one interface, and you want all its IP
14231 addresses to be treated in the same way, and you are using only the
14232 standard SMTP port, you should not need to take any special action. The
14233 rest of this chapter does not apply to you.
14235 In a more complicated situation you may want to listen only on certain
14236 interfaces, or on different ports, and for this reason there are a number of
14237 options that can be used to influence Exim's behaviour. The rest of this
14238 chapter describes how they operate.
14240 When a message is received over TCP/IP, the interface and port that were
14241 actually used are set in &$received_ip_address$& and &$received_port$&.
14245 .section "Starting a listening daemon" "SECID89"
14246 When a listening daemon is started (by means of the &%-bd%& command line
14247 option), the interfaces and ports on which it listens are controlled by the
14251 &%daemon_smtp_ports%& contains a list of default ports
14253 (For backward compatibility, this option can also be specified in the singular.)
14255 &%local_interfaces%& contains list of interface IP addresses on which to
14256 listen. Each item may optionally also specify a port.
14259 The default list separator in both cases is a colon, but this can be changed as
14260 described in section &<<SECTlistsepchange>>&. When IPv6 addresses are involved,
14261 it is usually best to change the separator to avoid having to double all the
14262 colons. For example:
14264 local_interfaces = <; 127.0.0.1 ; \
14267 3ffe:ffff:836f::fe86:a061
14269 There are two different formats for specifying a port along with an IP address
14270 in &%local_interfaces%&:
14273 The port is added onto the address with a dot separator. For example, to listen
14274 on port 1234 on two different IP addresses:
14276 local_interfaces = <; 192.168.23.65.1234 ; \
14277 3ffe:ffff:836f::fe86:a061.1234
14280 The IP address is enclosed in square brackets, and the port is added
14281 with a colon separator, for example:
14283 local_interfaces = <; [192.168.23.65]:1234 ; \
14284 [3ffe:ffff:836f::fe86:a061]:1234
14288 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
14289 default setting contains just one port:
14291 daemon_smtp_ports = smtp
14293 If more than one port is listed, each interface that does not have its own port
14294 specified listens on all of them. Ports that are listed in
14295 &%daemon_smtp_ports%& can be identified either by name (defined in
14296 &_/etc/services_&) or by number. However, when ports are given with individual
14297 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
14301 .section "Special IP listening addresses" "SECID90"
14302 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
14303 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
14304 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
14305 instead of setting up separate listening sockets for each interface. The
14306 default value of &%local_interfaces%& is
14308 local_interfaces = 0.0.0.0
14310 when Exim is built without IPv6 support; otherwise it is:
14312 local_interfaces = <; ::0 ; 0.0.0.0
14314 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
14318 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
14319 The &%-oX%& command line option can be used to override the values of
14320 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
14321 instance. Another way of doing this would be to use macros and the &%-D%&
14322 option. However, &%-oX%& can be used by any admin user, whereas modification of
14323 the runtime configuration by &%-D%& is allowed only when the caller is root or
14326 The value of &%-oX%& is a list of items. The default colon separator can be
14327 changed in the usual way (&<<SECTlistsepchange>>&) if required.
14328 If there are any items that do not
14329 contain dots or colons (that is, are not IP addresses), the value of
14330 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
14331 items that do contain dots or colons, the value of &%local_interfaces%& is
14332 replaced by those items. Thus, for example,
14336 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
14339 -oX 192.168.34.5.1125
14341 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
14342 (However, since &%local_interfaces%& now contains no items without ports, the
14343 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
14347 .section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
14348 .cindex "submissions protocol"
14349 .cindex "ssmtp protocol"
14350 .cindex "smtps protocol"
14351 .cindex "SMTP" "ssmtp protocol"
14352 .cindex "SMTP" "smtps protocol"
14353 Exim supports the use of TLS-on-connect, used by mail clients in the
14354 &"submissions"& protocol, historically also known as SMTPS or SSMTP.
14355 For some years, IETF Standards Track documents only blessed the
14356 STARTTLS-based Submission service (port 587) while common practice was to support
14357 the same feature set on port 465, but using TLS-on-connect.
14358 If your installation needs to provide service to mail clients
14359 (Mail User Agents, MUAs) then you should provide service on both the 587 and
14362 If the &%tls_on_connect_ports%& option is set to a list of port numbers or
14363 service names, connections to those ports must first establish TLS, before
14364 proceeding to the application layer use of the SMTP protocol.
14366 The common use of this option is expected to be
14368 tls_on_connect_ports = 465
14371 There is also a command line option &%-tls-on-connect%&, which forces all ports
14372 to behave in this way when a daemon is started.
14374 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
14375 daemon to listen on those ports. You must still specify them in
14376 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
14377 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
14378 connections via the daemon.)
14383 .section "IPv6 address scopes" "SECID92"
14384 .cindex "IPv6" "address scopes"
14385 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
14386 can, in principle, have the same link-local IPv6 address on different
14387 interfaces. Thus, additional information is needed, over and above the IP
14388 address, to distinguish individual interfaces. A convention of using a
14389 percent sign followed by something (often the interface name) has been
14390 adopted in some cases, leading to addresses like this:
14392 fe80::202:b3ff:fe03:45c1%eth0
14394 To accommodate this usage, a percent sign followed by an arbitrary string is
14395 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
14396 to convert a textual IPv6 address for actual use. This function recognizes the
14397 percent convention in operating systems that support it, and it processes the
14398 address appropriately. Unfortunately, some older libraries have problems with
14399 &[getaddrinfo()]&. If
14401 IPV6_USE_INET_PTON=yes
14403 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
14404 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
14405 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
14406 function.) Of course, this means that the additional functionality of
14407 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
14409 .section "Disabling IPv6" "SECID93"
14410 .cindex "IPv6" "disabling"
14411 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
14412 run on a host whose kernel does not support IPv6. The binary will fall back to
14413 using IPv4, but it may waste resources looking up AAAA records, and trying to
14414 connect to IPv6 addresses, causing delays to mail delivery. If you set the
14415 .oindex "&%disable_ipv6%&"
14416 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
14417 activities take place. AAAA records are never looked up, and any IPv6 addresses
14418 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
14419 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14420 to handle IPv6 literal addresses.
14422 On the other hand, when IPv6 is in use, there may be times when you want to
14423 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
14424 option to globally suppress the lookup of AAAA records for specified domains,
14425 and you can use the &%ignore_target_hosts%& generic router option to ignore
14426 IPv6 addresses in an individual router.
14430 .section "Examples of starting a listening daemon" "SECID94"
14431 The default case in an IPv6 environment is
14433 daemon_smtp_ports = smtp
14434 local_interfaces = <; ::0 ; 0.0.0.0
14436 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
14437 Either one or two sockets may be used, depending on the characteristics of
14438 the TCP/IP stack. (This is complicated and messy; for more information,
14439 read the comments in the &_daemon.c_& source file.)
14441 To specify listening on ports 25 and 26 on all interfaces:
14443 daemon_smtp_ports = 25 : 26
14445 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
14447 local_interfaces = <; ::0.25 ; ::0.26 \
14448 0.0.0.0.25 ; 0.0.0.0.26
14450 To listen on the default port on all IPv4 interfaces, and on port 26 on the
14451 IPv4 loopback address only:
14453 local_interfaces = 0.0.0.0 : 127.0.0.1.26
14455 To specify listening on the default port on specific interfaces only:
14457 local_interfaces = 10.0.0.67 : 192.168.34.67
14459 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
14463 .section "Recognizing the local host" "SECTreclocipadd"
14464 The &%local_interfaces%& option is also used when Exim needs to determine
14465 whether or not an IP address refers to the local host. That is, the IP
14466 addresses of all the interfaces on which a daemon is listening are always
14469 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
14470 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
14471 available interfaces from the operating system, and extracts the relevant
14472 (that is, IPv4 or IPv6) addresses to use for checking.
14474 Some systems set up large numbers of virtual interfaces in order to provide
14475 many virtual web servers. In this situation, you may want to listen for
14476 email on only a few of the available interfaces, but nevertheless treat all
14477 interfaces as local when routing. You can do this by setting
14478 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
14479 &"all"& wildcard values. These addresses are recognized as local, but are not
14480 used for listening. Consider this example:
14482 local_interfaces = <; 127.0.0.1 ; ::1 ; \
14484 3ffe:2101:12:1:a00:20ff:fe86:a061
14486 extra_local_interfaces = <; ::0 ; 0.0.0.0
14488 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
14489 address, but all available interface addresses are treated as local when
14492 In some environments the local host name may be in an MX list, but with an IP
14493 address that is not assigned to any local interface. In other cases it may be
14494 desirable to treat other host names as if they referred to the local host. Both
14495 these cases can be handled by setting the &%hosts_treat_as_local%& option.
14496 This contains host names rather than IP addresses. When a host is referenced
14497 during routing, either via an MX record or directly, it is treated as the local
14498 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
14499 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
14503 .section "Delivering to a remote host" "SECID95"
14504 Delivery to a remote host is handled by the smtp transport. By default, it
14505 allows the system's TCP/IP functions to choose which interface to use (if
14506 there is more than one) when connecting to a remote host. However, the
14507 &%interface%& option can be set to specify which interface is used. See the
14508 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
14514 . ////////////////////////////////////////////////////////////////////////////
14515 . ////////////////////////////////////////////////////////////////////////////
14517 .chapter "Main configuration" "CHAPmainconfig"
14518 .scindex IIDconfima "configuration file" "main section"
14519 .scindex IIDmaiconf "main configuration"
14520 The first part of the runtime configuration file contains three types of item:
14523 Macro definitions: These lines start with an upper case letter. See section
14524 &<<SECTmacrodefs>>& for details of macro processing.
14526 Named list definitions: These lines start with one of the words &"domainlist"&,
14527 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
14528 section &<<SECTnamedlists>>&.
14530 Main configuration settings: Each setting occupies one line of the file
14531 (with possible continuations). If any setting is preceded by the word
14532 &"hide"&, the &%-bP%& command line option displays its value to admin users
14533 only. See section &<<SECTcos>>& for a description of the syntax of these option
14537 This chapter specifies all the main configuration options, along with their
14538 types and default values. For ease of finding a particular option, they appear
14539 in alphabetical order in section &<<SECTalomo>>& below. However, because there
14540 are now so many options, they are first listed briefly in functional groups, as
14541 an aid to finding the name of the option you are looking for. Some options are
14542 listed in more than one group.
14544 .section "Miscellaneous" "SECID96"
14546 .row &%add_environment%& "environment variables"
14547 .row &%bi_command%& "to run for &%-bi%& command line option"
14548 .row &%debug_store%& "do extra internal checks"
14549 .row &%disable_ipv6%& "do no IPv6 processing"
14550 .row &%keep_environment%& "environment variables"
14551 .row &%keep_malformed%& "for broken files &-- should not happen"
14552 .row &%localhost_number%& "for unique message ids in clusters"
14553 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
14554 .row &%message_body_visible%& "how much to show in &$message_body$&"
14555 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
14556 .row &%print_topbitchars%& "top-bit characters are printing"
14557 .row &%spool_wireformat%& "use wire-format spool data files when possible"
14558 .row &%timezone%& "force time zone"
14562 .section "Exim parameters" "SECID97"
14564 .row &%exim_group%& "override compiled-in value"
14565 .row &%exim_path%& "override compiled-in value"
14566 .row &%exim_user%& "override compiled-in value"
14567 .row &%primary_hostname%& "default from &[uname()]&"
14568 .row &%split_spool_directory%& "use multiple directories"
14569 .row &%spool_directory%& "override compiled-in value"
14574 .section "Privilege controls" "SECID98"
14576 .row &%admin_groups%& "groups that are Exim admin users"
14577 .row &%commandline_checks_require_admin%& "require admin for various checks"
14578 .row &%deliver_drop_privilege%& "drop root for delivery processes"
14579 .row &%local_from_check%& "insert &'Sender:'& if necessary"
14580 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
14581 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
14582 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
14583 .row &%never_users%& "do not run deliveries as these"
14584 .row &%prod_requires_admin%& "forced delivery requires admin user"
14585 .row &%queue_list_requires_admin%& "queue listing requires admin user"
14586 .row &%trusted_groups%& "groups that are trusted"
14587 .row &%trusted_users%& "users that are trusted"
14592 .section "Logging" "SECID99"
14594 .row &%event_action%& "custom logging"
14595 .row &%hosts_connection_nolog%& "exemption from connect logging"
14596 .row &%log_file_path%& "override compiled-in value"
14597 .row &%log_selector%& "set/unset optional logging"
14598 .row &%log_timezone%& "add timezone to log lines"
14599 .row &%message_logs%& "create per-message logs"
14600 .row &%preserve_message_logs%& "after message completion"
14601 .row &%panic_coredump%& "request coredump on fatal errors"
14602 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
14603 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
14604 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
14605 .row &%syslog_facility%& "set syslog &""facility""& field"
14606 .row &%syslog_pid%& "pid in syslog lines"
14607 .row &%syslog_processname%& "set syslog &""ident""& field"
14608 .row &%syslog_timestamp%& "timestamp syslog lines"
14609 .row &%write_rejectlog%& "control use of message log"
14614 .section "Frozen messages" "SECID100"
14616 .row &%auto_thaw%& "sets time for retrying frozen messages"
14617 .row &%freeze_tell%& "send message when freezing"
14618 .row &%move_frozen_messages%& "to another directory"
14619 .row &%timeout_frozen_after%& "keep frozen messages only so long"
14624 .section "Data lookups" "SECID101"
14626 .row &%ibase_servers%& "InterBase servers"
14627 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
14628 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
14629 .row &%ldap_cert_file%& "client cert file for LDAP"
14630 .row &%ldap_cert_key%& "client key file for LDAP"
14631 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
14632 .row &%ldap_default_servers%& "used if no server in query"
14633 .row &%ldap_require_cert%& "action to take without LDAP server cert"
14634 .row &%ldap_start_tls%& "require TLS within LDAP"
14635 .row &%ldap_version%& "set protocol version"
14636 .row &%lookup_open_max%& "lookup files held open"
14637 .row &%mysql_servers%& "default MySQL servers"
14638 .row &%oracle_servers%& "Oracle servers"
14639 .row &%pgsql_servers%& "default PostgreSQL servers"
14640 .row &%sqlite_lock_timeout%& "as it says"
14645 .section "Message ids" "SECID102"
14647 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
14648 .row &%message_id_header_text%& "ditto"
14653 .section "Embedded Perl Startup" "SECID103"
14655 .row &%perl_at_start%& "always start the interpreter"
14656 .row &%perl_startup%& "code to obey when starting Perl"
14657 .row &%perl_taintmode%& "enable taint mode in Perl"
14662 .section "Daemon" "SECID104"
14664 .row &%daemon_smtp_ports%& "default ports"
14665 .row &%daemon_startup_retries%& "number of times to retry"
14666 .row &%daemon_startup_sleep%& "time to sleep between tries"
14667 .row &%extra_local_interfaces%& "not necessarily listened on"
14668 .row &%local_interfaces%& "on which to listen, with optional ports"
14669 .row &%notifier_socket%& "override compiled-in value"
14670 .row &%pid_file_path%& "override compiled-in value"
14671 .row &%queue_run_max%& "maximum simultaneous queue runners"
14672 .row &%smtp_backlog_monitor%& "level to log listen backlog"
14677 .section "Resource control" "SECID105"
14679 .row &%check_log_inodes%& "before accepting a message"
14680 .row &%check_log_space%& "before accepting a message"
14681 .row &%check_spool_inodes%& "before accepting a message"
14682 .row &%check_spool_space%& "before accepting a message"
14683 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
14684 .row &%queue_only_load%& "queue incoming if load high"
14685 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14686 .row &%queue_run_max%& "maximum simultaneous queue runners"
14687 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14688 .row &%smtp_accept_max%& "simultaneous incoming connections"
14689 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14690 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14691 .row &%smtp_accept_max_per_connection%& "messages per connection"
14692 .row &%smtp_accept_max_per_host%& "connections from one host"
14693 .row &%smtp_accept_queue%& "queue mail if more connections"
14694 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14696 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14697 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14698 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14699 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
14700 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14705 .section "Policy controls" "SECID106"
14707 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
14708 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
14709 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
14710 .row &%acl_smtp_auth%& "ACL for AUTH"
14711 .row &%acl_smtp_connect%& "ACL for connection"
14712 .row &%acl_smtp_data%& "ACL for DATA"
14713 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
14714 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
14715 .row &%acl_smtp_etrn%& "ACL for ETRN"
14716 .row &%acl_smtp_expn%& "ACL for EXPN"
14717 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
14718 .row &%acl_smtp_mail%& "ACL for MAIL"
14719 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
14720 .row &%acl_smtp_mime%& "ACL for MIME parts"
14721 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
14722 .row &%acl_smtp_predata%& "ACL for start of data"
14723 .row &%acl_smtp_quit%& "ACL for QUIT"
14724 .row &%acl_smtp_rcpt%& "ACL for RCPT"
14725 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
14726 .row &%acl_smtp_vrfy%& "ACL for VRFY"
14727 .row &%av_scanner%& "specify virus scanner"
14728 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14730 .row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
14731 .row &%dns_csa_search_limit%& "control CSA parent search depth"
14732 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
14733 .row &%header_maxsize%& "total size of message header"
14734 .row &%header_line_maxsize%& "individual header line limit"
14735 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
14736 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
14737 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
14738 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
14739 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
14740 .row &%host_lookup%& "host name looked up for these hosts"
14741 .row &%host_lookup_order%& "order of DNS and local name lookups"
14742 .row &%hosts_proxy%& "use proxy protocol for these hosts"
14743 .row &%host_reject_connection%& "reject connection from these hosts"
14744 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
14745 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
14746 .row &%message_size_limit%& "for all messages"
14747 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14748 .row &%proxy_protocol_timeout%& "timeout for proxy protocol negotiation"
14749 .row &%spamd_address%& "set interface to SpamAssassin"
14750 .row &%strict_acl_vars%& "object to unset ACL variables"
14751 .row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&"
14756 .section "Callout cache" "SECID107"
14758 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
14760 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
14762 .row &%callout_negative_expire%& "timeout for negative address cache item"
14763 .row &%callout_positive_expire%& "timeout for positive address cache item"
14764 .row &%callout_random_local_part%& "string to use for &""random""& testing"
14769 .section "TLS" "SECID108"
14771 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
14772 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
14773 .row &%hosts_require_alpn%& "mandatory ALPN"
14774 .row &%hosts_require_helo%& "mandatory HELO/EHLO"
14775 .row &%openssl_options%& "adjust OpenSSL compatibility options"
14776 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14777 .row &%tls_alpn%& "acceptable protocol names"
14778 .row &%tls_certificate%& "location of server certificate"
14779 .row &%tls_crl%& "certificate revocation list"
14780 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
14781 .row &%tls_dhparam%& "DH parameters for server"
14782 .row &%tls_eccurve%& "EC curve selection for server"
14783 .row &%tls_ocsp_file%& "location of server certificate status proof"
14784 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
14785 .row &%tls_privatekey%& "location of server private key"
14786 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
14787 .row &%tls_require_ciphers%& "specify acceptable ciphers"
14788 .row &%tls_try_verify_hosts%& "try to verify client certificate"
14789 .row &%tls_verify_certificates%& "expected client certificates"
14790 .row &%tls_verify_hosts%& "insist on client certificate verify"
14795 .section "Local user handling" "SECID109"
14797 .row &%finduser_retries%& "useful in NIS environments"
14798 .row &%gecos_name%& "used when creating &'Sender:'&"
14799 .row &%gecos_pattern%& "ditto"
14800 .row &%max_username_length%& "for systems that truncate"
14801 .row &%unknown_login%& "used when no login name found"
14802 .row &%unknown_username%& "ditto"
14803 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
14804 .row &%uucp_from_sender%& "ditto"
14809 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
14811 .row &%header_maxsize%& "total size of message header"
14812 .row &%header_line_maxsize%& "individual header line limit"
14813 .row &%message_size_limit%& "applies to all messages"
14814 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14815 .row &%received_header_text%& "expanded to make &'Received:'&"
14816 .row &%received_headers_max%& "for mail loop detection"
14817 .row &%recipients_max%& "limit per message"
14818 .row &%recipients_max_reject%& "permanently reject excess recipients"
14824 .section "Non-SMTP incoming messages" "SECID111"
14826 .row &%receive_timeout%& "for non-SMTP messages"
14833 .section "Incoming SMTP messages" "SECID112"
14834 See also the &'Policy controls'& section above.
14837 .row &%dkim_verify_hashes%& "DKIM hash methods accepted for signatures"
14838 .row &%dkim_verify_keytypes%& "DKIM key types accepted for signatures"
14839 .row &%dkim_verify_min_keysizes%& "DKIM key sizes accepted for signatures"
14840 .row &%dkim_verify_signers%& "DKIM domains for which DKIM ACL is run"
14841 .row &%dmarc_forensic_sender%& "DMARC sender for report messages"
14842 .row &%dmarc_history_file%& "DMARC results log"
14843 .row &%dmarc_tld_file%& "DMARC toplevel domains file"
14844 .row &%host_lookup%& "host name looked up for these hosts"
14845 .row &%host_lookup_order%& "order of DNS and local name lookups"
14846 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
14847 .row &%rfc1413_hosts%& "make ident calls to these hosts"
14848 .row &%rfc1413_query_timeout%& "zero disables ident calls"
14849 .row &%sender_unqualified_hosts%& "may send unqualified senders"
14850 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
14851 .row &%smtp_accept_max%& "simultaneous incoming connections"
14852 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14853 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14854 .row &%smtp_accept_max_per_connection%& "messages per connection"
14855 .row &%smtp_accept_max_per_host%& "connections from one host"
14856 .row &%smtp_accept_queue%& "queue mail if more connections"
14857 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14859 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14860 .row &%smtp_active_hostname%& "host name to use in messages"
14861 .row &%smtp_banner%& "text for welcome banner"
14862 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14863 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14864 .row &%smtp_enforce_sync%& "of SMTP command/responses"
14865 .row &%smtp_etrn_command%& "what to run for ETRN"
14866 .row &%smtp_etrn_serialize%& "only one at once"
14867 .row &%smtp_load_reserve%& "only reserve hosts if this load"
14868 .row &%smtp_max_unknown_commands%& "before dropping connection"
14869 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
14870 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
14871 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
14872 .row &%smtp_receive_timeout%& "per command or data line"
14873 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14874 .row &%smtp_return_error_details%& "give detail on rejections"
14879 .section "SMTP extensions" "SECID113"
14881 .row &%accept_8bitmime%& "advertise 8BITMIME"
14882 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
14883 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
14884 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
14885 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
14886 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
14887 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
14888 .row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts"
14889 .row &%prdr_enable%& "advertise PRDR to all hosts"
14890 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
14891 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14896 .section "Processing messages" "SECID114"
14898 .row &%allow_domain_literals%& "recognize domain literal syntax"
14899 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
14900 .row &%allow_utf8_domains%& "in addresses"
14901 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14903 .row &%delivery_date_remove%& "from incoming messages"
14904 .row &%envelope_to_remove%& "from incoming messages"
14905 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
14906 .row &%headers_charset%& "default for translations"
14907 .row &%qualify_domain%& "default for senders"
14908 .row &%qualify_recipient%& "default for recipients"
14909 .row &%return_path_remove%& "from incoming messages"
14910 .row &%strip_excess_angle_brackets%& "in addresses"
14911 .row &%strip_trailing_dot%& "at end of addresses"
14912 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
14917 .section "System filter" "SECID115"
14919 .row &%system_filter%& "locate system filter"
14920 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
14922 .row &%system_filter_file_transport%& "transport for delivery to a file"
14923 .row &%system_filter_group%& "group for filter running"
14924 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
14925 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
14926 .row &%system_filter_user%& "user for filter running"
14931 .section "Routing and delivery" "SECID116"
14933 .row &%disable_ipv6%& "do no IPv6 processing"
14934 .row &%dns_again_means_nonexist%& "for broken domains"
14935 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
14936 .row &%dns_dnssec_ok%& "parameter for resolver"
14937 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
14938 .row &%dns_retrans%& "parameter for resolver"
14939 .row &%dns_retry%& "parameter for resolver"
14940 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
14941 .row &%dns_use_edns0%& "parameter for resolver"
14942 .row &%hold_domains%& "hold delivery for these domains"
14943 .row &%local_interfaces%& "for routing checks"
14944 .row &%queue_domains%& "no immediate delivery for these"
14945 .row &%queue_fast_ramp%& "parallel delivery with 2-phase queue run"
14946 .row &%queue_only%& "no immediate delivery at all"
14947 .row &%queue_only_file%& "no immediate delivery if file exists"
14948 .row &%queue_only_load%& "no immediate delivery if load is high"
14949 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14950 .row &%queue_only_override%& "allow command line to override"
14951 .row &%queue_run_in_order%& "order of arrival"
14952 .row &%queue_run_max%& "of simultaneous queue runners"
14953 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
14954 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14955 .row &%remote_sort_domains%& "order of remote deliveries"
14956 .row &%retry_data_expire%& "timeout for retry data"
14957 .row &%retry_interval_max%& "safety net for retry rules"
14962 .section "Bounce and warning messages" "SECID117"
14964 .row &%bounce_message_file%& "content of bounce"
14965 .row &%bounce_message_text%& "content of bounce"
14966 .row &%bounce_return_body%& "include body if returning message"
14967 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
14968 .row &%bounce_return_message%& "include original message in bounce"
14969 .row &%bounce_return_size_limit%& "limit on returned message"
14970 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
14971 .row &%dsn_from%& "set &'From:'& contents in bounces"
14972 .row &%errors_copy%& "copy bounce messages"
14973 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
14974 .row &%delay_warning%& "time schedule"
14975 .row &%delay_warning_condition%& "condition for warning messages"
14976 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
14977 .row &%smtp_return_error_details%& "give detail on rejections"
14978 .row &%warn_message_file%& "content of warning message"
14983 .section "Alphabetical list of main options" "SECTalomo"
14984 Those options that undergo string expansion before use are marked with
14987 .option accept_8bitmime main boolean true
14989 .cindex "8-bit characters"
14990 .cindex "log" "selectors"
14991 .cindex "log" "8BITMIME"
14992 .cindex "ESMTP extensions" 8BITMIME
14993 This option causes Exim to send 8BITMIME in its response to an SMTP
14994 EHLO command, and to accept the BODY= parameter on MAIL commands.
14995 However, though Exim is 8-bit clean, it is not a protocol converter, and it
14996 takes no steps to do anything special with messages received by this route.
14998 Historically Exim kept this option off by default, but the maintainers
14999 feel that in today's Internet, this causes more problems than it solves.
15000 It now defaults to true.
15001 A more detailed analysis of the issues is provided by Dan Bernstein:
15003 &url(https://cr.yp.to/smtp/8bitmime.html)
15006 To log received 8BITMIME status use
15008 log_selector = +8bitmime
15011 .option acl_not_smtp main string&!! unset
15012 .cindex "&ACL;" "for non-SMTP messages"
15013 .cindex "non-SMTP messages" "ACLs for"
15014 This option defines the ACL that is run when a non-SMTP message has been
15015 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
15018 .option acl_not_smtp_mime main string&!! unset
15019 This option defines the ACL that is run for individual MIME parts of non-SMTP
15020 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
15023 .option acl_not_smtp_start main string&!! unset
15024 .cindex "&ACL;" "at start of non-SMTP message"
15025 .cindex "non-SMTP messages" "ACLs for"
15026 This option defines the ACL that is run before Exim starts reading a
15027 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
15029 .option acl_smtp_auth main string&!! unset
15030 .cindex "&ACL;" "setting up for SMTP commands"
15031 .cindex "AUTH" "ACL for"
15032 This option defines the ACL that is run when an SMTP AUTH command is
15033 received. See chapter &<<CHAPACL>>& for further details.
15035 .option acl_smtp_connect main string&!! unset
15036 .cindex "&ACL;" "on SMTP connection"
15037 This option defines the ACL that is run when an SMTP connection is received.
15038 See chapter &<<CHAPACL>>& for further details.
15040 .option acl_smtp_data main string&!! unset
15041 .cindex "DATA" "ACL for"
15042 This option defines the ACL that is run after an SMTP DATA command has been
15043 processed and the message itself has been received, but before the final
15044 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15046 .option acl_smtp_data_prdr main string&!! accept
15047 .cindex "PRDR" "ACL for"
15048 .cindex "DATA" "PRDR ACL for"
15049 .cindex "&ACL;" "PRDR-related"
15050 .cindex "&ACL;" "per-user data processing"
15051 This option defines the ACL that,
15052 if the PRDR feature has been negotiated,
15053 is run for each recipient after an SMTP DATA command has been
15054 processed and the message itself has been received, but before the
15055 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15057 .option acl_smtp_dkim main string&!! unset
15058 .cindex DKIM "ACL for"
15059 This option defines the ACL that is run for each DKIM signature
15060 (by default, or as specified in the dkim_verify_signers option)
15061 of a received message.
15062 See section &<<SECDKIMVFY>>& for further details.
15064 .option acl_smtp_etrn main string&!! unset
15065 .cindex "ETRN" "ACL for"
15066 This option defines the ACL that is run when an SMTP ETRN command is
15067 received. See chapter &<<CHAPACL>>& for further details.
15069 .option acl_smtp_expn main string&!! unset
15070 .cindex "EXPN" "ACL for"
15071 This option defines the ACL that is run when an SMTP EXPN command is
15072 received. See chapter &<<CHAPACL>>& for further details.
15074 .option acl_smtp_helo main string&!! unset
15075 .cindex "EHLO" "ACL for"
15076 .cindex "HELO" "ACL for"
15077 This option defines the ACL that is run when an SMTP EHLO or HELO
15078 command is received. See chapter &<<CHAPACL>>& for further details.
15081 .option acl_smtp_mail main string&!! unset
15082 .cindex "MAIL" "ACL for"
15083 This option defines the ACL that is run when an SMTP MAIL command is
15084 received. See chapter &<<CHAPACL>>& for further details.
15086 .option acl_smtp_mailauth main string&!! unset
15087 .cindex "AUTH" "on MAIL command"
15088 This option defines the ACL that is run when there is an AUTH parameter on
15089 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
15090 &<<CHAPSMTPAUTH>>& for details of authentication.
15092 .option acl_smtp_mime main string&!! unset
15093 .cindex "MIME content scanning" "ACL for"
15094 This option is available when Exim is built with the content-scanning
15095 extension. It defines the ACL that is run for each MIME part in a message. See
15096 section &<<SECTscanmimepart>>& for details.
15098 .option acl_smtp_notquit main string&!! unset
15099 .cindex "not-QUIT, ACL for"
15100 This option defines the ACL that is run when an SMTP session
15101 ends without a QUIT command being received.
15102 See chapter &<<CHAPACL>>& for further details.
15104 .option acl_smtp_predata main string&!! unset
15105 This option defines the ACL that is run when an SMTP DATA command is
15106 received, before the message itself is received. See chapter &<<CHAPACL>>& for
15109 .option acl_smtp_quit main string&!! unset
15110 .cindex "QUIT, ACL for"
15111 This option defines the ACL that is run when an SMTP QUIT command is
15112 received. See chapter &<<CHAPACL>>& for further details.
15114 .option acl_smtp_rcpt main string&!! unset
15115 .cindex "RCPT" "ACL for"
15116 This option defines the ACL that is run when an SMTP RCPT command is
15117 received. See chapter &<<CHAPACL>>& for further details.
15119 .option acl_smtp_starttls main string&!! unset
15120 .cindex "STARTTLS, ACL for"
15121 This option defines the ACL that is run when an SMTP STARTTLS command is
15122 received. See chapter &<<CHAPACL>>& for further details.
15124 .option acl_smtp_vrfy main string&!! unset
15125 .cindex "VRFY" "ACL for"
15126 This option defines the ACL that is run when an SMTP VRFY command is
15127 received. See chapter &<<CHAPACL>>& for further details.
15129 .option add_environment main "string list" empty
15130 .cindex "environment" "set values"
15131 This option adds individual environment variables that the
15132 currently linked libraries and programs in child processes may use.
15133 Each list element should be of the form &"name=value"&.
15135 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
15137 .option admin_groups main "string list&!!" unset
15138 .cindex "admin user"
15139 This option is expanded just once, at the start of Exim's processing. If the
15140 current group or any of the supplementary groups of an Exim caller is in this
15141 colon-separated list, the caller has admin privileges. If all your system
15142 programmers are in a specific group, for example, you can give them all Exim
15143 admin privileges by putting that group in &%admin_groups%&. However, this does
15144 not permit them to read Exim's spool files (whose group owner is the Exim gid).
15145 To permit this, you have to add individuals to the Exim group.
15147 .option allow_domain_literals main boolean false
15148 .cindex "domain literal"
15149 If this option is set, the RFC 2822 domain literal format is permitted in
15150 email addresses. The option is not set by default, because the domain literal
15151 format is not normally required these days, and few people know about it. It
15152 has, however, been exploited by mail abusers.
15154 Unfortunately, it seems that some DNS black list maintainers are using this
15155 format to report black listing to postmasters. If you want to accept messages
15156 addressed to your hosts by IP address, you need to set
15157 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
15158 domains (defined in the named domain list &%local_domains%& in the default
15159 configuration). This &"magic string"& matches the domain literal form of all
15160 the local host's IP addresses.
15162 .option allow_mx_to_ip main boolean false
15163 .cindex "MX record" "pointing to IP address"
15164 It appears that more and more DNS zone administrators are breaking the rules
15165 and putting domain names that look like IP addresses on the right hand side of
15166 MX records. Exim follows the rules and rejects this, giving an error message
15167 that explains the misconfiguration. However, some other MTAs support this
15168 practice, so to avoid &"Why can't Exim do this?"& complaints,
15169 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
15170 recommended, except when you have no other choice.
15172 .option allow_utf8_domains main boolean false
15173 .cindex "domain" "UTF-8 characters in"
15174 .cindex "UTF-8" "in domain name"
15175 Lots of discussion is going on about internationalized domain names. One
15176 camp is strongly in favour of just using UTF-8 characters, and it seems
15177 that at least two other MTAs permit this.
15178 This option allows Exim users to experiment if they wish.
15180 If it is set true, Exim's domain parsing function allows valid
15181 UTF-8 multicharacters to appear in domain name components, in addition to
15182 letters, digits, and hyphens.
15184 If Exim is built with internationalization support
15185 and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
15186 this option can be left as default.
15188 if you want to look up such domain names in the DNS, you must also
15189 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
15190 suitable setting is:
15192 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
15193 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
15195 Alternatively, you can just disable this feature by setting
15197 dns_check_names_pattern =
15199 That is, set the option to an empty string so that no check is done.
15202 .option auth_advertise_hosts main "host list&!!" *
15203 .cindex "authentication" "advertising"
15204 .cindex "AUTH" "advertising"
15205 .cindex "ESMTP extensions" AUTH
15206 If any server authentication mechanisms are configured, Exim advertises them in
15207 response to an EHLO command only if the calling host matches this list.
15208 Otherwise, Exim does not advertise AUTH.
15209 Exim does not accept AUTH commands from clients to which it has not
15210 advertised the availability of AUTH. The advertising of individual
15211 authentication mechanisms can be controlled by the use of the
15212 &%server_advertise_condition%& generic authenticator option on the individual
15213 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
15215 Certain mail clients (for example, Netscape) require the user to provide a name
15216 and password for authentication if AUTH is advertised, even though it may
15217 not be needed (the host may accept messages from hosts on its local LAN without
15218 authentication, for example). The &%auth_advertise_hosts%& option can be used
15219 to make these clients more friendly by excluding them from the set of hosts to
15220 which Exim advertises AUTH.
15222 .cindex "AUTH" "advertising when encrypted"
15223 If you want to advertise the availability of AUTH only when the connection
15224 is encrypted using TLS, you can make use of the fact that the value of this
15225 option is expanded, with a setting like this:
15227 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
15229 .vindex "&$tls_in_cipher$&"
15230 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
15231 the expansion is empty, thus matching no hosts. Otherwise, the result of the
15232 expansion is *, which matches all hosts.
15235 .option auto_thaw main time 0s
15236 .cindex "thawing messages"
15237 .cindex "unfreezing messages"
15238 If this option is set to a time greater than zero, a queue runner will try a
15239 new delivery attempt on any frozen message, other than a bounce message, if
15240 this much time has passed since it was frozen. This may result in the message
15241 being re-frozen if nothing has changed since the last attempt. It is a way of
15242 saying &"keep on trying, even though there are big problems"&.
15244 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
15245 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
15246 thought to be very useful any more, and its use should probably be avoided.
15249 .option av_scanner main string "see below"
15250 This option is available if Exim is built with the content-scanning extension.
15251 It specifies which anti-virus scanner to use. The default value is:
15253 sophie:/var/run/sophie
15255 If the value of &%av_scanner%& starts with a dollar character, it is expanded
15256 before use. See section &<<SECTscanvirus>>& for further details.
15259 .option bi_command main string unset
15261 This option supplies the name of a command that is run when Exim is called with
15262 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
15263 just the command name, it is not a complete command line. If an argument is
15264 required, it must come from the &%-oA%& command line option.
15267 .option bounce_message_file main string&!! unset
15268 .cindex "bounce message" "customizing"
15269 .cindex "customizing" "bounce message"
15270 This option defines a template file containing paragraphs of text to be used
15271 for constructing bounce messages. Details of the file's contents are given in
15272 chapter &<<CHAPemsgcust>>&.
15273 .cindex bounce_message_file "tainted data"
15274 The option is expanded to give the file path, which must be
15275 absolute and untainted.
15276 See also &%warn_message_file%&.
15279 .option bounce_message_text main string unset
15280 When this option is set, its contents are included in the default bounce
15281 message immediately after &"This message was created automatically by mail
15282 delivery software."& It is not used if &%bounce_message_file%& is set.
15284 .option bounce_return_body main boolean true
15285 .cindex "bounce message" "including body"
15286 This option controls whether the body of an incoming message is included in a
15287 bounce message when &%bounce_return_message%& is true. The default setting
15288 causes the entire message, both header and body, to be returned (subject to the
15289 value of &%bounce_return_size_limit%&). If this option is false, only the
15290 message header is included. In the case of a non-SMTP message containing an
15291 error that is detected during reception, only those header lines preceding the
15292 point at which the error was detected are returned.
15293 .cindex "bounce message" "including original"
15295 .option bounce_return_linesize_limit main integer 998
15296 .cindex "size" "of bounce lines, limit"
15297 .cindex "bounce message" "line length limit"
15298 .cindex "limit" "bounce message line length"
15299 This option sets a limit in bytes on the line length of messages
15300 that are returned to senders due to delivery problems,
15301 when &%bounce_return_message%& is true.
15302 The default value corresponds to RFC limits.
15303 If the message being returned has lines longer than this value it is
15304 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
15306 The option also applies to bounces returned when an error is detected
15307 during reception of a message.
15308 In this case lines from the original are truncated.
15310 The option does not apply to messages generated by an &(autoreply)& transport.
15313 .option bounce_return_message main boolean true
15314 If this option is set false, none of the original message is included in
15315 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
15316 &%bounce_return_body%&.
15319 .option bounce_return_size_limit main integer 100K
15320 .cindex "size" "of bounce, limit"
15321 .cindex "bounce message" "size limit"
15322 .cindex "limit" "bounce message size"
15323 This option sets a limit in bytes on the size of messages that are returned to
15324 senders as part of bounce messages when &%bounce_return_message%& is true. The
15325 limit should be less than the value of the global &%message_size_limit%& and of
15326 any &%message_size_limit%& settings on transports, to allow for the bounce text
15327 that Exim generates. If this option is set to zero there is no limit.
15329 When the body of any message that is to be included in a bounce message is
15330 greater than the limit, it is truncated, and a comment pointing this out is
15331 added at the top. The actual cutoff may be greater than the value given, owing
15332 to the use of buffering for transferring the message in chunks (typically 8K in
15333 size). The idea is to save bandwidth on those undeliverable 15-megabyte
15336 .option bounce_sender_authentication main string unset
15337 .cindex "bounce message" "sender authentication"
15338 .cindex "authentication" "bounce message"
15339 .cindex "AUTH" "on bounce message"
15340 This option provides an authenticated sender address that is sent with any
15341 bounce messages generated by Exim that are sent over an authenticated SMTP
15342 connection. A typical setting might be:
15344 bounce_sender_authentication = mailer-daemon@my.domain.example
15346 which would cause bounce messages to be sent using the SMTP command:
15348 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
15350 The value of &%bounce_sender_authentication%& must always be a complete email
15353 .option callout_domain_negative_expire main time 3h
15354 .cindex "caching" "callout timeouts"
15355 .cindex "callout" "caching timeouts"
15356 This option specifies the expiry time for negative callout cache data for a
15357 domain. See section &<<SECTcallver>>& for details of callout verification, and
15358 section &<<SECTcallvercache>>& for details of the caching.
15361 .option callout_domain_positive_expire main time 7d
15362 This option specifies the expiry time for positive callout cache data for a
15363 domain. See section &<<SECTcallver>>& for details of callout verification, and
15364 section &<<SECTcallvercache>>& for details of the caching.
15367 .option callout_negative_expire main time 2h
15368 This option specifies the expiry time for negative callout cache data for an
15369 address. See section &<<SECTcallver>>& for details of callout verification, and
15370 section &<<SECTcallvercache>>& for details of the caching.
15373 .option callout_positive_expire main time 24h
15374 This option specifies the expiry time for positive callout cache data for an
15375 address. See section &<<SECTcallver>>& for details of callout verification, and
15376 section &<<SECTcallvercache>>& for details of the caching.
15379 .option callout_random_local_part main string&!! "see below"
15380 This option defines the &"random"& local part that can be used as part of
15381 callout verification. The default value is
15383 $primary_hostname-$tod_epoch-testing
15385 See section &<<CALLaddparcall>>& for details of how this value is used.
15388 .option check_log_inodes main integer 100
15389 See &%check_spool_space%& below.
15392 .option check_log_space main integer 10M
15393 See &%check_spool_space%& below.
15395 .oindex "&%check_rfc2047_length%&"
15396 .cindex "RFC 2047" "disabling length check"
15397 .option check_rfc2047_length main boolean true
15398 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
15399 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
15400 word; strings to be encoded that exceed this length are supposed to use
15401 multiple encoded words. By default, Exim does not recognize encoded words that
15402 exceed the maximum length. However, it seems that some software, in violation
15403 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
15404 set false, Exim recognizes encoded words of any length.
15407 .option check_spool_inodes main integer 100
15408 See &%check_spool_space%& below.
15411 .option check_spool_space main integer 10M
15412 .cindex "checking disk space"
15413 .cindex "disk space, checking"
15414 .cindex "spool directory" "checking space"
15415 The four &%check_...%& options allow for checking of disk resources before a
15416 message is accepted.
15418 .vindex "&$log_inodes$&"
15419 .vindex "&$log_space$&"
15420 .vindex "&$spool_inodes$&"
15421 .vindex "&$spool_space$&"
15422 When any of these options are nonzero, they apply to all incoming messages. If you
15423 want to apply different checks to different kinds of message, you can do so by
15424 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
15425 &$spool_space$& in an ACL with appropriate additional conditions.
15428 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
15429 either value is greater than zero, for example:
15431 check_spool_space = 100M
15432 check_spool_inodes = 100
15434 The spool partition is the one that contains the directory defined by
15435 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
15438 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
15439 files are written if either is greater than zero. These should be set only if
15440 &%log_file_path%& and &%spool_directory%& refer to different partitions.
15442 If there is less space or fewer inodes than requested, Exim refuses to accept
15443 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
15444 error response to the MAIL command. If ESMTP is in use and there was a
15445 SIZE parameter on the MAIL command, its value is added to the
15446 &%check_spool_space%& value, and the check is performed even if
15447 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
15449 The values for &%check_spool_space%& and &%check_log_space%& are held as a
15450 number of kilobytes (though specified in bytes).
15451 If a non-multiple of 1024 is specified, it is rounded up.
15453 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
15454 failure a message is written to stderr and Exim exits with a non-zero code, as
15455 it obviously cannot send an error message of any kind.
15457 There is a slight performance penalty for these checks.
15458 Versions of Exim preceding 4.88 had these disabled by default;
15459 high-rate installations confident they will never run out of resources
15460 may wish to deliberately disable them.
15462 .option chunking_advertise_hosts main "host list&!!" *
15463 .cindex CHUNKING advertisement
15464 .cindex "RFC 3030" "CHUNKING"
15465 .cindex "ESMTP extensions" CHUNKING
15466 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
15468 Hosts may use the BDAT command as an alternate to DATA.
15470 .option commandline_checks_require_admin main boolean &`false`&
15471 .cindex "restricting access to features"
15472 This option restricts various basic checking features to require an
15473 administrative user.
15474 This affects most of the &%-b*%& options, such as &%-be%&.
15476 .option debug_store main boolean &`false`&
15477 .cindex debugging "memory corruption"
15478 .cindex memory debugging
15479 This option, when true, enables extra checking in Exim's internal memory
15480 management. For use when a memory corruption issue is being investigated,
15481 it should normally be left as default.
15483 .option daemon_smtp_ports main string &`smtp`&
15484 .cindex "port" "for daemon"
15485 .cindex "TCP/IP" "setting listening ports"
15486 This option specifies one or more default SMTP ports on which the Exim daemon
15487 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
15488 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
15490 .option daemon_startup_retries main integer 9
15491 .cindex "daemon startup, retrying"
15492 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
15493 the daemon at startup when it cannot immediately bind a listening socket
15494 (typically because the socket is already in use): &%daemon_startup_retries%&
15495 defines the number of retries after the first failure, and
15496 &%daemon_startup_sleep%& defines the length of time to wait between retries.
15498 .option daemon_startup_sleep main time 30s
15499 See &%daemon_startup_retries%&.
15501 .option delay_warning main "time list" 24h
15502 .cindex "warning of delay"
15503 .cindex "delay warning, specifying"
15504 .cindex "queue" "delay warning"
15505 When a message is delayed, Exim sends a warning message to the sender at
15506 intervals specified by this option. The data is a colon-separated list of times
15507 after which to send warning messages. If the value of the option is an empty
15508 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
15509 message has been in the queue for longer than the last time, the last interval
15510 between the times is used to compute subsequent warning times. For example,
15513 delay_warning = 4h:8h:24h
15515 the first message is sent after 4 hours, the second after 8 hours, and
15516 the third one after 24 hours. After that, messages are sent every 16 hours,
15517 because that is the interval between the last two times on the list. If you set
15518 just one time, it specifies the repeat interval. For example, with:
15522 messages are repeated every six hours. To stop warnings after a given time, set
15523 a very large time at the end of the list. For example:
15525 delay_warning = 2h:12h:99d
15527 Note that the option is only evaluated at the time a delivery attempt fails,
15528 which depends on retry and queue-runner configuration.
15529 Typically retries will be configured more frequently than warning messages.
15531 .option delay_warning_condition main string&!! "see below"
15532 .vindex "&$domain$&"
15533 The string is expanded at the time a warning message might be sent. If all the
15534 deferred addresses have the same domain, it is set in &$domain$& during the
15535 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
15536 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
15537 &"false"& (the comparison being done caselessly) then the warning message is
15538 not sent. The default is:
15540 delay_warning_condition = ${if or {\
15541 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
15542 { match{$h_precedence:}{(?i)bulk|list|junk} }\
15543 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
15546 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
15547 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
15548 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
15549 &"auto-replied"& in an &'Auto-Submitted:'& header.
15551 .option deliver_drop_privilege main boolean false
15552 .cindex "unprivileged delivery"
15553 .cindex "delivery" "unprivileged"
15554 If this option is set true, Exim drops its root privilege at the start of a
15555 delivery process, and runs as the Exim user throughout. This severely restricts
15556 the kinds of local delivery that are possible, but is viable in certain types
15557 of configuration. There is a discussion about the use of root privilege in
15558 chapter &<<CHAPsecurity>>&.
15560 .option deliver_queue_load_max main fixed-point unset
15561 .cindex "load average"
15562 .cindex "queue runner" "abandoning"
15563 When this option is set, a queue run is abandoned if the system load average
15564 becomes greater than the value of the option. The option has no effect on
15565 ancient operating systems on which Exim cannot determine the load average.
15566 See also &%queue_only_load%& and &%smtp_load_reserve%&.
15569 .option delivery_date_remove main boolean true
15570 .cindex "&'Delivery-date:'& header line"
15571 Exim's transports have an option for adding a &'Delivery-date:'& header to a
15572 message when it is delivered, in exactly the same way as &'Return-path:'& is
15573 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
15574 should not be present in incoming messages, and this option causes them to be
15575 removed at the time the message is received, to avoid any problems that might
15576 occur when a delivered message is subsequently sent on to some other recipient.
15578 .option disable_fsync main boolean false
15579 .cindex "&[fsync()]&, disabling"
15580 This option is available only if Exim was built with the compile-time option
15581 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
15582 a runtime configuration generates an &"unknown option"& error. You should not
15583 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
15584 really, really, really understand what you are doing. &'No pre-compiled
15585 distributions of Exim should ever make this option available.'&
15587 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
15588 updated files' data to be written to disc before continuing. Unexpected events
15589 such as crashes and power outages may cause data to be lost or scrambled.
15590 Here be Dragons. &*Beware.*&
15593 .option disable_ipv6 main boolean false
15594 .cindex "IPv6" "disabling"
15595 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
15596 activities take place. AAAA records are never looked up, and any IPv6 addresses
15597 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
15598 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
15599 to handle IPv6 literal addresses.
15602 .option dkim_verify_hashes main "string list" "sha256 : sha512"
15603 .cindex DKIM "selecting signature algorithms"
15604 This option gives a list of hash types which are acceptable in signatures,
15605 and an order of processing.
15606 Signatures with algorithms not in the list will be ignored.
15608 Acceptable values include:
15615 Note that the acceptance of sha1 violates RFC 8301.
15617 .option dkim_verify_keytypes main "string list" "ed25519 : rsa"
15618 This option gives a list of key types which are acceptable in signatures,
15619 and an order of processing.
15620 Signatures with algorithms not in the list will be ignored.
15623 .option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250"
15624 This option gives a list of key sizes which are acceptable in signatures.
15625 The list is keyed by the algorithm type for the key; the values are in bits.
15626 Signatures with keys smaller than given by this option will fail verification.
15628 The default enforces the RFC 8301 minimum key size for RSA signatures.
15630 .option dkim_verify_minimal main boolean false
15631 If set to true, verification of signatures will terminate after the
15634 .option dkim_verify_signers main "domain list&!!" $dkim_signers
15635 .cindex DKIM "controlling calls to the ACL"
15636 This option gives a list of DKIM domains for which the DKIM ACL is run.
15637 It is expanded after the message is received; by default it runs
15638 the ACL once for each signature in the message.
15639 See section &<<SECDKIMVFY>>&.
15642 .option dmarc_forensic_sender main string&!! unset
15643 .option dmarc_history_file main string unset
15644 .option dmarc_tld_file main string unset
15645 .cindex DMARC "main section options"
15646 These options control DMARC processing.
15647 See section &<<SECDMARC>>& for details.
15650 .option dns_again_means_nonexist main "domain list&!!" unset
15651 .cindex "DNS" "&""try again""& response; overriding"
15652 DNS lookups give a &"try again"& response for the DNS errors
15653 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
15654 keep trying to deliver a message, or to give repeated temporary errors to
15655 incoming mail. Sometimes the effect is caused by a badly set up name server and
15656 may persist for a long time. If a domain which exhibits this problem matches
15657 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
15658 This option should be used with care. You can make it apply to reverse lookups
15659 by a setting such as this:
15661 dns_again_means_nonexist = *.in-addr.arpa
15663 This option applies to all DNS lookups that Exim does,
15665 except for TLSA lookups (where knowing about such failures
15666 is security-relevant).
15668 It also applies when the
15669 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
15670 since these are most likely to be caused by DNS lookup problems. The
15671 &(dnslookup)& router has some options of its own for controlling what happens
15672 when lookups for MX or SRV records give temporary errors. These more specific
15673 options are applied after this global option.
15675 .option dns_check_names_pattern main string "see below"
15676 .cindex "DNS" "pre-check of name syntax"
15677 When this option is set to a non-empty string, it causes Exim to check domain
15678 names for characters that are not allowed in host names before handing them to
15679 the DNS resolver, because some resolvers give temporary errors for names that
15680 contain unusual characters. If a domain name contains any unwanted characters,
15681 a &"not found"& result is forced, and the resolver is not called. The check is
15682 done by matching the domain name against a regular expression, which is the
15683 value of this option. The default pattern is
15685 dns_check_names_pattern = \
15686 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
15688 which permits only letters, digits, slashes, and hyphens in components, but
15689 they must start and end with a letter or digit. Slashes are not, in fact,
15690 permitted in host names, but they are found in certain NS records (which can be
15691 accessed in Exim by using a &%dnsdb%& lookup). If you set
15692 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
15695 .option dns_csa_search_limit main integer 5
15696 This option controls the depth of parental searching for CSA SRV records in the
15697 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
15699 .option dns_csa_use_reverse main boolean true
15700 This option controls whether or not an IP address, given as a CSA domain, is
15701 reversed and looked up in the reverse DNS, as described in more detail in
15702 section &<<SECTverifyCSA>>&.
15704 .option dns_cname_loops main integer 1
15705 .cindex DNS "CNAME following"
15706 This option controls the following of CNAME chains, needed if the resolver does
15707 not do it internally.
15708 As of 2018 most should, and the default can be left.
15709 If you have an ancient one, a value of 10 is likely needed.
15711 The default value of one CNAME-follow is needed
15712 thanks to the observed return for an MX request,
15713 given no MX presence but a CNAME to an A, of the CNAME.
15716 .option dns_dnssec_ok main integer -1
15717 .cindex "DNS" "resolver options"
15718 .cindex "DNS" "DNSSEC"
15719 If this option is set to a non-negative number then Exim will initialise the
15720 DNS resolver library to either use or not use DNSSEC, overriding the system
15721 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
15723 If the resolver library does not support DNSSEC then this option has no effect.
15725 On Linux with glibc 2.31 or newer this is insufficient, the resolver library
15726 will default to stripping out a successful validation status.
15727 This will break a previously working Exim installation.
15728 Provided that you do trust the resolver (ie, is on localhost) you can tell
15729 glibc to pass through any successful validation with a new option in
15730 &_/etc/resolv.conf_&:
15736 .option dns_ipv4_lookup main "domain list&!!" unset
15737 .cindex "IPv6" "DNS lookup for AAAA records"
15738 .cindex "DNS" "IPv6 lookup for AAAA records"
15739 .cindex DNS "IPv6 disabling"
15740 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
15741 looks for IPv6 address records (AAAA records) as well as IPv4 address records
15742 (A records) when trying to find IP addresses for hosts, unless the host's
15743 domain matches this list.
15745 This is a fudge to help with name servers that give big delays or otherwise do
15746 not work for the AAAA record type. In due course, when the world's name
15747 servers have all been upgraded, there should be no need for this option.
15748 Note that all lookups, including those done for verification, are affected;
15749 this will result in verify failure for IPv6 connections or ones using names
15750 only valid for IPv6 addresses.
15753 .option dns_retrans main time 0s
15754 .cindex "DNS" "resolver options"
15755 .cindex timeout "dns lookup"
15756 .cindex "DNS" timeout
15757 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
15758 retransmission and retry parameters for DNS lookups. Values of zero (the
15759 defaults) leave the system default settings unchanged. The first value is the
15760 time between retries, and the second is the number of retries. It isn't
15761 totally clear exactly how these settings affect the total time a DNS lookup may
15762 take. I haven't found any documentation about timeouts on DNS lookups; these
15763 parameter values are available in the external resolver interface structure,
15764 but nowhere does it seem to describe how they are used or what you might want
15766 See also the &%slow_lookup_log%& option.
15769 .option dns_retry main integer 0
15770 See &%dns_retrans%& above.
15773 .option dns_trust_aa main "domain list&!!" unset
15774 .cindex "DNS" "resolver options"
15775 .cindex "DNS" "DNSSEC"
15776 If this option is set then lookup results marked with the AA bit
15777 (Authoritative Answer) are trusted the same way as if they were
15778 DNSSEC-verified. The authority section's name of the answer must
15779 match with this expanded domain list.
15781 Use this option only if you talk directly to a resolver that is
15782 authoritative for some zones and does not set the AD (Authentic Data)
15783 bit in the answer. Some DNS servers may have an configuration option to
15784 mark the answers from their own zones as verified (they set the AD bit).
15785 Others do not have this option. It is considered as poor practice using
15786 a resolver that is an authoritative server for some zones.
15788 Use this option only if you really have to (e.g. if you want
15789 to use DANE for remote delivery to a server that is listed in the DNS
15790 zones that your resolver is authoritative for).
15792 If the DNS answer packet has the AA bit set and contains resource record
15793 in the answer section, the name of the first NS record appearing in the
15794 authority section is compared against the list. If the answer packet is
15795 authoritative but the answer section is empty, the name of the first SOA
15796 record in the authoritative section is used instead.
15798 .cindex "DNS" "resolver options"
15799 .option dns_use_edns0 main integer -1
15800 .cindex "DNS" "resolver options"
15801 .cindex "DNS" "EDNS0"
15802 .cindex "DNS" "OpenBSD
15803 If this option is set to a non-negative number then Exim will initialise the
15804 DNS resolver library to either use or not use EDNS0 extensions, overriding
15805 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
15808 If the resolver library does not support EDNS0 then this option has no effect.
15810 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
15811 means that DNSSEC will not work with Exim on that platform either, unless Exim
15812 is linked against an alternative DNS client library.
15815 .option drop_cr main boolean false
15816 This is an obsolete option that is now a no-op. It used to affect the way Exim
15817 handled CR and LF characters in incoming messages. What happens now is
15818 described in section &<<SECTlineendings>>&.
15820 .option dsn_advertise_hosts main "host list&!!" unset
15821 .cindex "bounce messages" "success"
15822 .cindex "DSN" "success"
15823 .cindex "Delivery Status Notification" "success"
15824 .cindex "ESMTP extensions" DSN
15825 DSN extensions (RFC3461) will be advertised in the EHLO message to,
15826 and accepted from, these hosts.
15827 Hosts may use the NOTIFY and ORCPT options on RCPT TO commands,
15828 and RET and ENVID options on MAIL FROM commands.
15829 A NOTIFY=SUCCESS option requests success-DSN messages.
15830 A NOTIFY= option with no argument requests that no delay or failure DSNs
15832 &*Note*&: Supplying success-DSN messages has been criticised
15833 on privacy grounds; it can leak details of internal forwarding.
15835 .option dsn_from main "string&!!" "see below"
15836 .cindex "&'From:'& header line" "in bounces"
15837 .cindex "bounce messages" "&'From:'& line, specifying"
15838 This option can be used to vary the contents of &'From:'& header lines in
15839 bounces and other automatically generated messages (&"Delivery Status
15840 Notifications"& &-- hence the name of the option). The default setting is:
15842 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
15844 The value is expanded every time it is needed. If the expansion fails, a
15845 panic is logged, and the default value is used.
15847 .option envelope_to_remove main boolean true
15848 .cindex "&'Envelope-to:'& header line"
15849 Exim's transports have an option for adding an &'Envelope-to:'& header to a
15850 message when it is delivered, in exactly the same way as &'Return-path:'& is
15851 handled. &'Envelope-to:'& records the original recipient address from the
15852 message's envelope that caused the delivery to happen. Such headers should not
15853 be present in incoming messages, and this option causes them to be removed at
15854 the time the message is received, to avoid any problems that might occur when a
15855 delivered message is subsequently sent on to some other recipient.
15858 .option errors_copy main "string list&!!" unset
15859 .cindex "bounce message" "copy to other address"
15860 .cindex "copy of bounce message"
15861 Setting this option causes Exim to send bcc copies of bounce messages that it
15862 generates to other addresses. &*Note*&: This does not apply to bounce messages
15863 coming from elsewhere. The value of the option is a colon-separated list of
15864 items. Each item consists of a pattern, terminated by white space, followed by
15865 a comma-separated list of email addresses. If a pattern contains spaces, it
15866 must be enclosed in double quotes.
15868 Each pattern is processed in the same way as a single item in an address list
15869 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
15870 the bounce message, the message is copied to the addresses on the list. The
15871 items are scanned in order, and once a matching one is found, no further items
15872 are examined. For example:
15874 errors_copy = spqr@mydomain postmaster@mydomain.example :\
15875 rqps@mydomain hostmaster@mydomain.example,\
15876 postmaster@mydomain.example
15878 .vindex "&$domain$&"
15879 .vindex "&$local_part$&"
15880 The address list is expanded before use. The expansion variables &$local_part$&
15881 and &$domain$& are set from the original recipient of the error message, and if
15882 there was any wildcard matching in the pattern, the expansion
15883 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
15884 variables &$0$&, &$1$&, etc. are set in the normal way.
15887 .option errors_reply_to main string unset
15888 .cindex "bounce message" "&'Reply-to:'& in"
15889 By default, Exim's bounce and delivery warning messages contain the header line
15891 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
15893 .oindex &%quota_warn_message%&
15894 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
15895 A warning message that is generated by the &%quota_warn_message%& option in an
15896 &(appendfile)& transport may contain its own &'From:'& header line that
15897 overrides the default.
15899 Experience shows that people reply to bounce messages. If the
15900 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
15901 and warning messages. For example:
15903 errors_reply_to = postmaster@my.domain.example
15905 The value of the option is not expanded. It must specify a valid RFC 2822
15906 address. However, if a warning message that is generated by the
15907 &%quota_warn_message%& option in an &(appendfile)& transport contain its
15908 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
15912 .option event_action main string&!! unset
15914 This option declares a string to be expanded for Exim's events mechanism.
15915 For details see chapter &<<CHAPevents>>&.
15918 .option exim_group main string "compile-time configured"
15919 .cindex "gid (group id)" "Exim's own"
15920 .cindex "Exim group"
15921 This option changes the gid under which Exim runs when it gives up root
15922 privilege. The default value is compiled into the binary. The value of this
15923 option is used only when &%exim_user%& is also set. Unless it consists entirely
15924 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
15925 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
15929 .option exim_path main string "see below"
15930 .cindex "Exim binary, path name"
15931 This option specifies the path name of the Exim binary, which is used when Exim
15932 needs to re-exec itself. The default is set up to point to the file &'exim'& in
15933 the directory configured at compile time by the BIN_DIRECTORY setting. It
15934 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
15936 &*Warning*&: Do not use a macro to define the value of this option, because
15937 you will break those Exim utilities that scan the configuration file to find
15938 where the binary is. (They then use the &%-bP%& option to extract option
15939 settings such as the value of &%spool_directory%&.)
15942 .option exim_user main string "compile-time configured"
15943 .cindex "uid (user id)" "Exim's own"
15944 .cindex "Exim user"
15945 This option changes the uid under which Exim runs when it gives up root
15946 privilege. The default value is compiled into the binary. Ownership of the run
15947 time configuration file and the use of the &%-C%& and &%-D%& command line
15948 options is checked against the values in the binary, not what is set here.
15950 Unless it consists entirely of digits, the string is looked up using
15951 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
15952 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
15953 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
15956 .option exim_version main string "current version"
15957 .cindex "Exim version"
15958 .cindex customizing "version number"
15959 .cindex "version number of Exim" override
15960 This option overrides the &$version_number$&/&$exim_version$& that Exim reports in
15961 various places. Use with care; this may fool stupid security scanners.
15964 .option extra_local_interfaces main "string list" unset
15965 This option defines network interfaces that are to be considered local when
15966 routing, but which are not used for listening by the daemon. See section
15967 &<<SECTreclocipadd>>& for details.
15970 . Allow this long option name to split; give it unsplit as a fifth argument
15971 . for the automatic .oindex that is generated by .option.
15973 .option "extract_addresses_remove_arguments" main boolean true &&&
15974 extract_addresses_remove_arguments
15976 .cindex "command line" "addresses with &%-t%&"
15977 .cindex "Sendmail compatibility" "&%-t%& option"
15978 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
15979 are present on the command line when the &%-t%& option is used to build an
15980 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
15981 line addresses are removed from the recipients list. This is also how Smail
15982 behaves. However, other Sendmail documentation (the O'Reilly book) states that
15983 command line addresses are added to those obtained from the header lines. When
15984 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
15985 argument headers. If it is set false, Exim adds rather than removes argument
15989 .option finduser_retries main integer 0
15990 .cindex "NIS, retrying user lookups"
15991 On systems running NIS or other schemes in which user and group information is
15992 distributed from a remote system, there can be times when &[getpwnam()]& and
15993 related functions fail, even when given valid data, because things time out.
15994 Unfortunately these failures cannot be distinguished from genuine &"not found"&
15995 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
15996 many extra times to find a user or a group, waiting for one second between
15999 .cindex "&_/etc/passwd_&" "multiple reading of"
16000 You should not set this option greater than zero if your user information is in
16001 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
16002 search the file multiple times for non-existent users, and also cause delay.
16006 .option freeze_tell main "string list, comma separated" unset
16007 .cindex "freezing messages" "sending a message when freezing"
16008 On encountering certain errors, or when configured to do so in a system filter,
16009 ACL, or special router, Exim freezes a message. This means that no further
16010 delivery attempts take place until an administrator thaws the message, or the
16011 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
16012 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
16013 warning message whenever it freezes something, unless the message it is
16014 freezing is a locally-generated bounce message. (Without this exception there
16015 is the possibility of looping.) The warning message is sent to the addresses
16016 supplied as the comma-separated value of this option. If several of the
16017 message's addresses cause freezing, only a single message is sent. If the
16018 freezing was automatic, the reason(s) for freezing can be found in the message
16019 log. If you configure freezing in a filter or ACL, you must arrange for any
16020 logging that you require.
16023 .option gecos_name main string&!! unset
16025 .cindex "&""gecos""& field, parsing"
16026 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
16027 password file to hold other information in addition to users' real names. Exim
16028 looks up this field for use when it is creating &'Sender:'& or &'From:'&
16029 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
16030 of the field are used unchanged, except that, if an ampersand is encountered,
16031 it is replaced by the user's login name with the first character forced to
16032 upper case, since this is a convention that is observed on many systems.
16034 When these options are set, &%gecos_pattern%& is treated as a regular
16035 expression that is to be applied to the field (again with && replaced by the
16036 login name), and if it matches, &%gecos_name%& is expanded and used as the
16039 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
16040 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
16041 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
16042 name terminates at the first comma, the following can be used:
16044 gecos_pattern = ([^,]*)
16048 .option gecos_pattern main string unset
16049 See &%gecos_name%& above.
16052 .option gnutls_compat_mode main boolean unset
16053 This option controls whether GnuTLS is used in compatibility mode in an Exim
16054 server. This reduces security slightly, but improves interworking with older
16055 implementations of TLS.
16058 .option gnutls_allow_auto_pkcs11 main boolean unset
16059 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
16060 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
16063 &url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
16068 .option headers_charset main string "see below"
16069 This option sets a default character set for translating from encoded MIME
16070 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
16071 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
16072 ultimate default is ISO-8859-1. For more details see the description of header
16073 insertions in section &<<SECTexpansionitems>>&.
16077 .option header_maxsize main integer "see below"
16078 .cindex "header section" "maximum size of"
16079 .cindex "limit" "size of message header section"
16080 This option controls the overall maximum size of a message's header
16081 section. The default is the value of HEADER_MAXSIZE in
16082 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
16083 sections are rejected.
16086 .option header_line_maxsize main integer 0
16087 .cindex "header lines" "maximum size of"
16088 .cindex "limit" "size of one header line"
16089 This option limits the length of any individual header line in a message, after
16090 all the continuations have been joined together. Messages with individual
16091 header lines that are longer than the limit are rejected. The default value of
16092 zero means &"no limit"&.
16097 .option helo_accept_junk_hosts main "host list&!!" unset
16098 .cindex "HELO" "accepting junk data"
16099 .cindex "EHLO" "accepting junk data"
16100 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
16101 mail, and gives an error response for invalid data. Unfortunately, there are
16102 some SMTP clients that send syntactic junk. They can be accommodated by setting
16103 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
16104 if you want to do semantic checking.
16105 See also &%helo_allow_chars%& for a way of extending the permitted character
16109 .option helo_allow_chars main string unset
16110 .cindex "HELO" "underscores in"
16111 .cindex "EHLO" "underscores in"
16112 .cindex "underscore in EHLO/HELO"
16113 This option can be set to a string of rogue characters that are permitted in
16114 all EHLO and HELO names in addition to the standard letters, digits,
16115 hyphens, and dots. If you really must allow underscores, you can set
16117 helo_allow_chars = _
16119 Note that the value is one string, not a list.
16122 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
16123 .cindex "HELO" "forcing reverse lookup"
16124 .cindex "EHLO" "forcing reverse lookup"
16125 If the domain given by a client in a HELO or EHLO command matches this
16126 list, a reverse lookup is done in order to establish the host's true name. The
16127 default forces a lookup if the client host gives the server's name or any of
16128 its IP addresses (in brackets), something that broken clients have been seen to
16132 .option helo_try_verify_hosts main "host list&!!" unset
16133 .cindex "HELO verifying" "optional"
16134 .cindex "EHLO" "verifying, optional"
16135 By default, Exim just checks the syntax of HELO and EHLO commands (see
16136 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
16137 to do more extensive checking of the data supplied by these commands. The ACL
16138 condition &`verify = helo`& is provided to make this possible.
16139 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
16140 to force the check to occur. From release 4.53 onwards, this is no longer
16141 necessary. If the check has not been done before &`verify = helo`& is
16142 encountered, it is done at that time. Consequently, this option is obsolete.
16143 Its specification is retained here for backwards compatibility.
16145 When an EHLO or HELO command is received, if the calling host matches
16146 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
16147 EHLO command either:
16150 is an IP literal matching the calling address of the host, or
16152 .cindex "DNS" "reverse lookup"
16153 .cindex "reverse DNS lookup"
16154 matches the host name that Exim obtains by doing a reverse lookup of the
16155 calling host address, or
16157 when looked up in DNS yields the calling host address.
16160 However, the EHLO or HELO command is not rejected if any of the checks
16161 fail. Processing continues, but the result of the check is remembered, and can
16162 be detected later in an ACL by the &`verify = helo`& condition.
16164 If DNS was used for successful verification, the variable
16165 .cindex "DNS" "DNSSEC"
16166 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
16168 .option helo_verify_hosts main "host list&!!" unset
16169 .cindex "HELO verifying" "mandatory"
16170 .cindex "EHLO" "verifying, mandatory"
16171 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
16172 backwards compatibility. For hosts that match this option, Exim checks the host
16173 name given in the HELO or EHLO in the same way as for
16174 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
16175 rejected with a 550 error, and entries are written to the main and reject logs.
16176 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
16179 .option hold_domains main "domain list&!!" unset
16180 .cindex "domain" "delaying delivery"
16181 .cindex "delivery" "delaying certain domains"
16182 This option allows mail for particular domains to be held in the queue
16183 manually. The option is overridden if a message delivery is forced with the
16184 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
16185 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
16186 item in &%hold_domains%&, no routing or delivery for that address is done, and
16187 it is deferred every time the message is looked at.
16189 This option is intended as a temporary operational measure for delaying the
16190 delivery of mail while some problem is being sorted out, or some new
16191 configuration tested. If you just want to delay the processing of some
16192 domains until a queue run occurs, you should use &%queue_domains%& or
16193 &%queue_smtp_domains%&, not &%hold_domains%&.
16195 A setting of &%hold_domains%& does not override Exim's code for removing
16196 messages from the queue if they have been there longer than the longest retry
16197 time in any retry rule. If you want to hold messages for longer than the normal
16198 retry times, insert a dummy retry rule with a long retry time.
16201 .option host_lookup main "host list&!!" unset
16202 .cindex "host name" "lookup, forcing"
16203 Exim does not look up the name of a calling host from its IP address unless it
16204 is required to compare against some host list, or the host matches
16205 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
16206 option (which normally contains IP addresses rather than host names). The
16207 default configuration file contains
16211 which causes a lookup to happen for all hosts. If the expense of these lookups
16212 is felt to be too great, the setting can be changed or removed.
16214 After a successful reverse lookup, Exim does a forward lookup on the name it
16215 has obtained, to verify that it yields the IP address that it started with. If
16216 this check fails, Exim behaves as if the name lookup failed.
16218 .vindex "&$host_lookup_failed$&"
16219 .vindex "&$sender_host_name$&"
16220 After any kind of failure, the host name (in &$sender_host_name$&) remains
16221 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
16222 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
16223 &`verify = reverse_host_lookup`& in ACLs.
16226 .option host_lookup_order main "string list" &`bydns:byaddr`&
16227 This option specifies the order of different lookup methods when Exim is trying
16228 to find a host name from an IP address. The default is to do a DNS lookup
16229 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
16230 if that fails. You can change the order of these lookups, or omit one entirely,
16233 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
16234 multiple PTR records in the DNS and the IP address is not listed in
16235 &_/etc/hosts_&. Different operating systems give different results in this
16236 case. That is why the default tries a DNS lookup first.
16240 .option host_reject_connection main "host list&!!" unset
16241 .cindex "host" "rejecting connections from"
16242 If this option is set, incoming SMTP calls from the hosts listed are rejected
16243 as soon as the connection is made.
16244 This option is obsolete, and retained only for backward compatibility, because
16245 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
16246 connections immediately.
16249 If the connection is on a TLS-on-connect port then the TCP connection is
16250 just dropped. Otherwise, an SMTP error is sent first.
16253 The ability to give an immediate rejection (either by this option or using an
16254 ACL) is provided for use in unusual cases. Many hosts will just try again,
16255 sometimes without much delay. Normally, it is better to use an ACL to reject
16256 incoming messages at a later stage, such as after RCPT commands. See
16257 chapter &<<CHAPACL>>&.
16260 .option hosts_connection_nolog main "host list&!!" unset
16261 .cindex "host" "not logging connections from"
16262 This option defines a list of hosts for which connection logging does not
16263 happen, even though the &%smtp_connection%& log selector is set. For example,
16264 you might want not to log SMTP connections from local processes, or from
16265 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
16266 the daemon; you should therefore strive to restrict its value to a short inline
16267 list of IP addresses and networks. To disable logging SMTP connections from
16268 local processes, you must create a host list with an empty item. For example:
16270 hosts_connection_nolog = :
16273 The hosts affected by this option also do not log "no MAIL in SMTP connection"
16274 lines, as may commonly be produced by a monitoring system.
16278 .option hosts_require_alpn main "host list&!!" unset
16279 .cindex ALPN "require negotiation in server"
16281 .cindex TLS "Application Layer Protocol Names"
16282 If the TLS library supports ALPN
16283 then a successful negotiation of ALPN will be required for any client
16284 matching the list, for TLS to be used.
16285 See also the &%tls_alpn%& option.
16287 &*Note*&: prevention of fallback to in-clear connection is not
16288 managed by this option, and should be done separately.
16291 .option hosts_require_helo main "host list&!!" *
16292 .cindex "HELO/EHLO" requiring
16293 Exim will require an accepted HELO or EHLO command from a host matching
16294 this list, before accepting a MAIL command.
16297 .option hosts_proxy main "host list&!!" unset
16298 .cindex proxy "proxy protocol"
16299 This option enables use of Proxy Protocol proxies for incoming
16300 connections. For details see section &<<SECTproxyInbound>>&.
16303 .option hosts_treat_as_local main "domain list&!!" unset
16304 .cindex "local host" "domains treated as"
16305 .cindex "host" "treated as local"
16306 If this option is set, any host names that match the domain list are treated as
16307 if they were the local host when Exim is scanning host lists obtained from MX
16309 or other sources. Note that the value of this option is a domain list, not a
16310 host list, because it is always used to check host names, not IP addresses.
16312 This option also applies when Exim is matching the special items
16313 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
16314 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
16315 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
16316 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
16317 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
16318 interfaces and recognizing the local host.
16321 .option ibase_servers main "string list" unset
16322 .cindex "InterBase" "server list"
16323 This option provides a list of InterBase servers and associated connection data,
16324 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
16325 The option is available only if Exim has been built with InterBase support.
16329 .option ignore_bounce_errors_after main time 10w
16330 .cindex "bounce message" "discarding"
16331 .cindex "discarding bounce message"
16332 This option affects the processing of bounce messages that cannot be delivered,
16333 that is, those that suffer a permanent delivery failure. (Bounce messages that
16334 suffer temporary delivery failures are of course retried in the usual way.)
16336 After a permanent delivery failure, bounce messages are frozen,
16337 because there is no sender to whom they can be returned. When a frozen bounce
16338 message has been in the queue for more than the given time, it is unfrozen at
16339 the next queue run, and a further delivery is attempted. If delivery fails
16340 again, the bounce message is discarded. This makes it possible to keep failed
16341 bounce messages around for a shorter time than the normal maximum retry time
16342 for frozen messages. For example,
16344 ignore_bounce_errors_after = 12h
16346 retries failed bounce message deliveries after 12 hours, discarding any further
16347 failures. If the value of this option is set to a zero time period, bounce
16348 failures are discarded immediately. Setting a very long time (as in the default
16349 value) has the effect of disabling this option. For ways of automatically
16350 dealing with other kinds of frozen message, see &%auto_thaw%& and
16351 &%timeout_frozen_after%&.
16354 .option ignore_fromline_hosts main "host list&!!" unset
16355 .cindex "&""From""& line"
16356 .cindex "UUCP" "&""From""& line"
16357 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
16358 the headers of a message. By default this is treated as the start of the
16359 message's body, which means that any following headers are not recognized as
16360 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
16361 match those hosts that insist on sending it. If the sender is actually a local
16362 process rather than a remote host, and is using &%-bs%& to inject the messages,
16363 &%ignore_fromline_local%& must be set to achieve this effect.
16366 .option ignore_fromline_local main boolean false
16367 See &%ignore_fromline_hosts%& above.
16369 .option keep_environment main "string list" unset
16370 .cindex "environment" "values from"
16371 This option contains a string list of environment variables to keep.
16372 You have to trust these variables or you have to be sure that
16373 these variables do not impose any security risk. Keep in mind that
16374 during the startup phase Exim is running with an effective UID 0 in most
16375 installations. As the default value is an empty list, the default
16376 environment for using libraries, running embedded Perl code, or running
16377 external binaries is empty, and does not not even contain PATH or HOME.
16379 Actually the list is interpreted as a list of patterns
16380 (&<<SECTlistexpand>>&), except that it is not expanded first.
16382 WARNING: Macro substitution is still done first, so having a macro
16383 FOO and having FOO_HOME in your &%keep_environment%& option may have
16384 unexpected results. You may work around this using a regular expression
16385 that does not match the macro name: ^[F]OO_HOME$.
16387 Current versions of Exim issue a warning during startup if you do not mention
16388 &%keep_environment%& in your runtime configuration file and if your
16389 current environment is not empty. Future versions may not issue that warning
16392 See the &%add_environment%& main config option for a way to set
16393 environment variables to a fixed value. The environment for &(pipe)&
16394 transports is handled separately, see section &<<SECTpipeenv>>& for
16398 .option keep_malformed main time 4d
16399 This option specifies the length of time to keep messages whose spool files
16400 have been corrupted in some way. This should, of course, never happen. At the
16401 next attempt to deliver such a message, it gets removed. The incident is
16405 .option ldap_ca_cert_dir main string unset
16406 .cindex "LDAP", "TLS CA certificate directory"
16407 .cindex certificate "directory for LDAP"
16408 This option indicates which directory contains CA certificates for verifying
16409 a TLS certificate presented by an LDAP server.
16410 While Exim does not provide a default value, your SSL library may.
16411 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16412 and constrained to be a directory.
16415 .option ldap_ca_cert_file main string unset
16416 .cindex "LDAP", "TLS CA certificate file"
16417 .cindex certificate "file for LDAP"
16418 This option indicates which file contains CA certificates for verifying
16419 a TLS certificate presented by an LDAP server.
16420 While Exim does not provide a default value, your SSL library may.
16421 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16422 and constrained to be a file.
16425 .option ldap_cert_file main string unset
16426 .cindex "LDAP" "TLS client certificate file"
16427 .cindex certificate "file for LDAP"
16428 This option indicates which file contains an TLS client certificate which
16429 Exim should present to the LDAP server during TLS negotiation.
16430 Should be used together with &%ldap_cert_key%&.
16433 .option ldap_cert_key main string unset
16434 .cindex "LDAP" "TLS client key file"
16435 .cindex certificate "key for LDAP"
16436 This option indicates which file contains the secret/private key to use
16437 to prove identity to the LDAP server during TLS negotiation.
16438 Should be used together with &%ldap_cert_file%&, which contains the
16439 identity to be proven.
16442 .option ldap_cipher_suite main string unset
16443 .cindex "LDAP" "TLS cipher suite"
16444 This controls the TLS cipher-suite negotiation during TLS negotiation with
16445 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
16446 cipher-suite options with OpenSSL (as used by LDAP client libraries).
16449 .option ldap_default_servers main "string list" unset
16450 .cindex "LDAP" "default servers"
16451 This option provides a list of LDAP servers which are tried in turn when an
16452 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
16453 details of LDAP queries. This option is available only when Exim has been built
16457 .option ldap_require_cert main string unset.
16458 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
16459 This should be one of the values "hard", "demand", "allow", "try" or "never".
16460 A value other than one of these is interpreted as "never".
16461 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
16462 Although Exim does not set a default, the LDAP library probably defaults
16466 .option ldap_start_tls main boolean false
16467 .cindex "LDAP" "whether or not to negotiate TLS"
16468 If set, Exim will attempt to negotiate TLS with the LDAP server when
16469 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
16470 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
16472 In the event of failure to negotiate TLS, the action taken is controlled
16473 by &%ldap_require_cert%&.
16474 This option is ignored for &`ldapi`& connections.
16477 .option ldap_version main integer unset
16478 .cindex "LDAP" "protocol version, forcing"
16479 This option can be used to force Exim to set a specific protocol version for
16480 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
16481 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
16482 the LDAP headers; otherwise it is 2. This option is available only when Exim
16483 has been built with LDAP support.
16487 .option local_from_check main boolean true
16488 .cindex "&'Sender:'& header line" "disabling addition of"
16489 .cindex "&'From:'& header line" "disabling checking of"
16490 When a message is submitted locally (that is, not over a TCP/IP connection) by
16491 an untrusted user, Exim removes any existing &'Sender:'& header line, and
16492 checks that the &'From:'& header line matches the login of the calling user and
16493 the domain specified by &%qualify_domain%&.
16495 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
16496 locally submitted message is automatically qualified by Exim, unless the
16497 &%-bnq%& command line option is used.
16499 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
16500 on the local part. If the &'From:'& header line does not match, Exim adds a
16501 &'Sender:'& header with an address constructed from the calling user's login
16502 and the default qualify domain.
16504 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
16505 and no &'Sender:'& header is ever added. If, in addition, you want to retain
16506 &'Sender:'& header lines supplied by untrusted users, you must also set
16507 &%local_sender_retain%& to be true.
16509 .cindex "envelope from"
16510 .cindex "envelope sender"
16511 These options affect only the header lines in the message. The envelope sender
16512 is still forced to be the login id at the qualify domain unless
16513 &%untrusted_set_sender%& permits the user to supply an envelope sender.
16515 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
16516 request similar header line checking. See section &<<SECTthesenhea>>&, which
16517 has more details about &'Sender:'& processing.
16522 .option local_from_prefix main string unset
16523 When Exim checks the &'From:'& header line of locally submitted messages for
16524 matching the login id (see &%local_from_check%& above), it can be configured to
16525 ignore certain prefixes and suffixes in the local part of the address. This is
16526 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
16527 appropriate lists, in the same form as the &%local_part_prefix%& and
16528 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
16531 local_from_prefix = *-
16533 is set, a &'From:'& line containing
16535 From: anything-user@your.domain.example
16537 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
16538 matches the actual sender address that is constructed from the login name and
16542 .option local_from_suffix main string unset
16543 See &%local_from_prefix%& above.
16546 .option local_interfaces main "string list" "see below"
16547 This option controls which network interfaces are used by the daemon for
16548 listening; they are also used to identify the local host when routing. Chapter
16549 &<<CHAPinterfaces>>& contains a full description of this option and the related
16550 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
16551 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
16552 &%local_interfaces%& is
16554 local_interfaces = 0.0.0.0
16556 when Exim is built without IPv6 support; otherwise it is
16558 local_interfaces = <; ::0 ; 0.0.0.0
16561 .option local_scan_timeout main time 5m
16562 .cindex "timeout" "for &[local_scan()]& function"
16563 .cindex "&[local_scan()]& function" "timeout"
16564 This timeout applies to the &[local_scan()]& function (see chapter
16565 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
16566 the incoming message is rejected with a temporary error if it is an SMTP
16567 message. For a non-SMTP message, the message is dropped and Exim ends with a
16568 non-zero code. The incident is logged on the main and reject logs.
16572 .option local_sender_retain main boolean false
16573 .cindex "&'Sender:'& header line" "retaining from local submission"
16574 When a message is submitted locally (that is, not over a TCP/IP connection) by
16575 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
16576 do not want this to happen, you must set &%local_sender_retain%&, and you must
16577 also set &%local_from_check%& to be false (Exim will complain if you do not).
16578 See also the ACL modifier &`control = suppress_local_fixups`&. Section
16579 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
16584 .option localhost_number main string&!! unset
16585 .cindex "host" "locally unique number for"
16586 .cindex "message ids" "with multiple hosts"
16587 .vindex "&$localhost_number$&"
16588 Exim's message ids are normally unique only within the local host. If
16589 uniqueness among a set of hosts is required, each host must set a different
16590 value for the &%localhost_number%& option. The string is expanded immediately
16591 after reading the configuration file (so that a number can be computed from the
16592 host name, for example) and the result of the expansion must be a number in the
16593 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
16594 systems). This is available in subsequent string expansions via the variable
16595 &$localhost_number$&. When &%localhost_number is set%&, the final two
16596 characters of the message id, instead of just being a fractional part of the
16597 time, are computed from the time and the local host number as described in
16598 section &<<SECTmessiden>>&.
16602 .option log_file_path main "string list&!!" "set at compile time"
16603 .cindex "log" "file path for"
16604 This option sets the path which is used to determine the names of Exim's log
16605 files, or indicates that logging is to be to syslog, or both. It is expanded
16606 when Exim is entered, so it can, for example, contain a reference to the host
16607 name. If no specific path is set for the log files at compile or runtime,
16608 or if the option is unset at runtime (i.e. &`log_file_path = `&)
16609 they are written in a sub-directory called &_log_& in Exim's spool directory.
16610 A path must start with a slash.
16611 To send to syslog, use the word &"syslog"&.
16612 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
16613 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
16614 used. If this string is fixed at your installation (contains no expansion
16615 variables) it is recommended that you do not set this option in the
16616 configuration file, but instead supply the path using LOG_FILE_PATH in
16617 &_Local/Makefile_& so that it is available to Exim for logging errors detected
16618 early on &-- in particular, failure to read the configuration file.
16621 .option log_selector main string unset
16622 .cindex "log" "selectors"
16623 This option can be used to reduce or increase the number of things that Exim
16624 writes to its log files. Its argument is made up of names preceded by plus or
16625 minus characters. For example:
16627 log_selector = +arguments -retry_defer
16629 A list of possible names and what they control is given in the chapter on
16630 logging, in section &<<SECTlogselector>>&.
16633 .option log_timezone main boolean false
16634 .cindex "log" "timezone for entries"
16635 .vindex "&$tod_log$&"
16636 .vindex "&$tod_zone$&"
16637 By default, the timestamps on log lines are in local time without the
16638 timezone. This means that if your timezone changes twice a year, the timestamps
16639 in log lines are ambiguous for an hour when the clocks go back. One way of
16640 avoiding this problem is to set the timezone to UTC. An alternative is to set
16641 &%log_timezone%& true. This turns on the addition of the timezone offset to
16642 timestamps in log lines. Turning on this option can add quite a lot to the size
16643 of log files because each line is extended by 6 characters. Note that the
16644 &$tod_log$& variable contains the log timestamp without the zone, but there is
16645 another variable called &$tod_zone$& that contains just the timezone offset.
16648 .option lookup_open_max main integer 25
16649 .cindex "too many open files"
16650 .cindex "open files, too many"
16651 .cindex "file" "too many open"
16652 .cindex "lookup" "maximum open files"
16653 .cindex "limit" "open files for lookups"
16654 This option limits the number of simultaneously open files for single-key
16655 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
16656 Exim normally keeps these files open during routing, because often the same
16657 file is required several times. If the limit is reached, Exim closes the least
16658 recently used file. Note that if you are using the &'ndbm'& library, it
16659 actually opens two files for each logical DBM database, though it still counts
16660 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
16661 open files"& errors with NDBM, you need to reduce the value of
16662 &%lookup_open_max%&.
16665 .option max_username_length main integer 0
16666 .cindex "length of login name"
16667 .cindex "user name" "maximum length"
16668 .cindex "limit" "user name length"
16669 Some operating systems are broken in that they truncate long arguments to
16670 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
16671 this option is set greater than zero, any attempt to call &[getpwnam()]& with
16672 an argument that is longer behaves as if &[getpwnam()]& failed.
16675 .option message_body_newlines main bool false
16676 .cindex "message body" "newlines in variables"
16677 .cindex "newline" "in message body variables"
16678 .vindex "&$message_body$&"
16679 .vindex "&$message_body_end$&"
16680 By default, newlines in the message body are replaced by spaces when setting
16681 the &$message_body$& and &$message_body_end$& expansion variables. If this
16682 option is set true, this no longer happens.
16685 .option message_body_visible main integer 500
16686 .cindex "body of message" "visible size"
16687 .cindex "message body" "visible size"
16688 .vindex "&$message_body$&"
16689 .vindex "&$message_body_end$&"
16690 This option specifies how much of a message's body is to be included in the
16691 &$message_body$& and &$message_body_end$& expansion variables.
16694 .option message_id_header_domain main string&!! unset
16695 .cindex "&'Message-ID:'& header line"
16696 If this option is set, the string is expanded and used as the right hand side
16697 (domain) of the &'Message-ID:'& header that Exim creates if a
16698 locally-originated incoming message does not have one. &"Locally-originated"&
16699 means &"not received over TCP/IP."&
16700 Otherwise, the primary host name is used.
16701 Only letters, digits, dot and hyphen are accepted; any other characters are
16702 replaced by hyphens. If the expansion is forced to fail, or if the result is an
16703 empty string, the option is ignored.
16706 .option message_id_header_text main string&!! unset
16707 If this variable is set, the string is expanded and used to augment the text of
16708 the &'Message-id:'& header that Exim creates if a locally-originated incoming
16709 message does not have one. The text of this header is required by RFC 2822 to
16710 take the form of an address. By default, Exim uses its internal message id as
16711 the local part, and the primary host name as the domain. If this option is set,
16712 it is expanded, and provided the expansion is not forced to fail, and does not
16713 yield an empty string, the result is inserted into the header immediately
16714 before the @, separated from the internal message id by a dot. Any characters
16715 that are illegal in an address are automatically converted into hyphens. This
16716 means that variables such as &$tod_log$& can be used, because the spaces and
16717 colons will become hyphens.
16720 .option message_logs main boolean true
16721 .cindex "message logs" "disabling"
16722 .cindex "log" "message log; disabling"
16723 If this option is turned off, per-message log files are not created in the
16724 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
16725 Exim, by reducing the number of files involved in handling a message from a
16726 minimum of four (header spool file, body spool file, delivery journal, and
16727 per-message log) to three. The other major I/O activity is Exim's main log,
16728 which is not affected by this option.
16731 .option message_size_limit main string&!! 50M
16732 .cindex "message" "size limit"
16733 .cindex "limit" "message size"
16734 .cindex "size" "of message, limit"
16735 This option limits the maximum size of message that Exim will process. The
16736 value is expanded for each incoming connection so, for example, it can be made
16737 to depend on the IP address of the remote host for messages arriving via
16738 TCP/IP. After expansion, the value must be a sequence of decimal digits,
16739 optionally followed by K or M.
16741 .cindex "SIZE" "ESMTP extension, advertising"
16742 .cindex "ESMTP extensions" SIZE
16743 If nonzero the value will be advertised as a parameter to the ESMTP SIZE
16744 service extension keyword.
16746 &*Note*&: This limit cannot be made to depend on a message's sender or any
16747 other properties of an individual message, because it has to be advertised in
16748 the server's response to EHLO. String expansion failure causes a temporary
16749 error. A value of zero means no limit, but its use is not recommended. See also
16750 &%bounce_return_size_limit%&.
16752 Incoming SMTP messages are failed with a 552 error if the limit is
16753 exceeded; locally-generated messages either get a stderr message or a delivery
16754 failure message to the sender, depending on the &%-oe%& setting. Rejection of
16755 an oversized message is logged in both the main and the reject logs. See also
16756 the generic transport option &%message_size_limit%&, which limits the size of
16757 message that an individual transport can process.
16759 If you use a virus-scanner and set this option to to a value larger than the
16760 maximum size that your virus-scanner is configured to support, you may get
16761 failures triggered by large mails. The right size to configure for the
16762 virus-scanner depends upon what data is passed and the options in use but it's
16763 probably safest to just set it to a little larger than this value. E.g., with a
16764 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
16765 some problems may result.
16767 A value of 0 will disable size limit checking; Exim will still advertise the
16768 SIZE extension in an EHLO response, but without a limit, so as to permit
16769 SMTP clients to still indicate the message size along with the MAIL verb.
16772 .option move_frozen_messages main boolean false
16773 .cindex "frozen messages" "moving"
16774 This option, which is available only if Exim has been built with the setting
16776 SUPPORT_MOVE_FROZEN_MESSAGES=yes
16778 in &_Local/Makefile_&, causes frozen messages and their message logs to be
16779 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
16780 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
16781 standard utilities for handling such moved messages, and they do not show up in
16782 lists generated by &%-bp%& or by the Exim monitor.
16785 .option mua_wrapper main boolean false
16786 Setting this option true causes Exim to run in a very restrictive mode in which
16787 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
16788 contains a full description of this facility.
16792 .option mysql_servers main "string list" unset
16793 .cindex "MySQL" "server list"
16794 This option provides a list of MySQL servers and associated connection data, to
16795 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
16796 option is available only if Exim has been built with MySQL support.
16799 .option never_users main "string list&!!" unset
16800 This option is expanded just once, at the start of Exim's processing. Local
16801 message deliveries are normally run in processes that are setuid to the
16802 recipient, and remote deliveries are normally run under Exim's own uid and gid.
16803 It is usually desirable to prevent any deliveries from running as root, as a
16806 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
16807 list of users that must not be used for local deliveries. This list is fixed in
16808 the binary and cannot be overridden by the configuration file. By default, it
16809 contains just the single user name &"root"&. The &%never_users%& runtime option
16810 can be used to add more users to the fixed list.
16812 If a message is to be delivered as one of the users on the fixed list or the
16813 &%never_users%& list, an error occurs, and delivery is deferred. A common
16816 never_users = root:daemon:bin
16818 Including root is redundant if it is also on the fixed list, but it does no
16819 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
16823 .option notifier_socket main string "$spool_directory/exim_daemon_notify"
16824 This option gives the name for a unix-domain socket on which the daemon
16825 listens for work and information-requests.
16826 Only installations running multiple daemons sharing a spool directory
16827 should need to modify the default.
16829 The option is expanded before use.
16830 If the platform supports Linux-style abstract socket names, the result
16831 is used with a nul byte prefixed.
16833 it should be a full path name and use a directory accessible
16836 If this option is set as empty,
16837 or the command line &%-oY%& option is used, or
16838 the command line uses a &%-oX%& option and does not use &%-oP%&,
16839 then a notifier socket is not created.
16842 .option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation"
16843 .cindex "OpenSSL "compatibility options"
16844 This option allows an administrator to adjust the SSL options applied
16845 by OpenSSL to connections. It is given as a space-separated list of items,
16846 each one to be +added or -subtracted from the current value.
16848 This option is only available if Exim is built against OpenSSL. The values
16849 available for this option vary according to the age of your OpenSSL install.
16850 The &"all"& value controls a subset of flags which are available, typically
16851 the bug workaround options. The &'SSL_CTX_set_options'& man page will
16852 list the values known on your system and Exim should support all the
16853 &"bug workaround"& options and many of the &"modifying"& options. The Exim
16854 names lose the leading &"SSL_OP_"& and are lower-cased.
16856 Note that adjusting the options can have severe impact upon the security of
16857 SSL as used by Exim. It is possible to disable safety checks and shoot
16858 yourself in the foot in various unpleasant ways. This option should not be
16859 adjusted lightly. An unrecognised item will be detected at startup, by
16860 invoking Exim with the &%-bV%& flag.
16862 The option affects Exim operating both as a server and as a client.
16864 Historical note: prior to release 4.80, Exim defaulted this value to
16865 "+dont_insert_empty_fragments", which may still be needed for compatibility
16866 with some clients, but which lowers security by increasing exposure to
16867 some now infamous attacks.
16871 # Make both old MS and old Eudora happy:
16872 openssl_options = -all +microsoft_big_sslv3_buffer \
16873 +dont_insert_empty_fragments
16875 # Disable older protocol versions:
16876 openssl_options = +no_sslv2 +no_sslv3
16879 Possible options may include:
16883 &`allow_unsafe_legacy_renegotiation`&
16885 &`cipher_server_preference`&
16887 &`dont_insert_empty_fragments`&
16891 &`legacy_server_connect`&
16893 &`microsoft_big_sslv3_buffer`&
16895 &`microsoft_sess_id_bug`&
16897 &`msie_sslv2_rsa_padding`&
16899 &`netscape_challenge_bug`&
16901 &`netscape_reuse_cipher_change_bug`&
16905 &`no_session_resumption_on_renegotiation`&
16919 &`safari_ecdhe_ecdsa_bug`&
16923 &`single_ecdh_use`&
16925 &`ssleay_080_client_dh_bug`&
16927 &`sslref2_reuse_cert_type_bug`&
16929 &`tls_block_padding_bug`&
16933 &`tls_rollback_bug`&
16936 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
16937 all clients connecting using the MacOS SecureTransport TLS facility prior
16938 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
16939 to negotiate TLS then this option value might help, provided that your OpenSSL
16940 release is new enough to contain this work-around. This may be a situation
16941 where you have to upgrade OpenSSL to get buggy clients working.
16944 .option oracle_servers main "string list" unset
16945 .cindex "Oracle" "server list"
16946 This option provides a list of Oracle servers and associated connection data,
16947 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
16948 The option is available only if Exim has been built with Oracle support.
16952 .option panic_coredump main boolean false
16953 This option is rarely needed but can help for some debugging investigations.
16954 If set, when an internal error is detected by Exim which is sufficient
16955 to terminate the process
16956 (all such are logged in the paniclog)
16957 then a coredump is requested.
16959 Note that most systems require additional administrative configuration
16960 to permit write a core file for a setuid program, which is Exim's
16961 common installed configuration.
16964 .option percent_hack_domains main "domain list&!!" unset
16965 .cindex "&""percent hack""&"
16966 .cindex "source routing" "in email address"
16967 .cindex "address" "source-routed"
16968 The &"percent hack"& is the convention whereby a local part containing a
16969 percent sign is re-interpreted as a new email address, with the percent
16970 replaced by @. This is sometimes called &"source routing"&, though that term is
16971 also applied to RFC 2822 addresses that begin with an @ character. If this
16972 option is set, Exim implements the percent facility for those domains listed,
16973 but no others. This happens before an incoming SMTP address is tested against
16976 &*Warning*&: The &"percent hack"& has often been abused by people who are
16977 trying to get round relaying restrictions. For this reason, it is best avoided
16978 if at all possible. Unfortunately, a number of less security-conscious MTAs
16979 implement it unconditionally. If you are running Exim on a gateway host, and
16980 routing mail through to internal MTAs without processing the local parts, it is
16981 a good idea to reject recipient addresses with percent characters in their
16982 local parts. Exim's default configuration does this.
16985 .option perl_at_start main boolean false
16987 This option is available only when Exim is built with an embedded Perl
16988 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16991 .option perl_startup main string unset
16993 This option is available only when Exim is built with an embedded Perl
16994 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16996 .option perl_taintmode main boolean false
16998 This option enables the taint mode of the embedded Perl interpreter.
17001 .option pgsql_servers main "string list" unset
17002 .cindex "PostgreSQL lookup type" "server list"
17003 This option provides a list of PostgreSQL servers and associated connection
17004 data, to be used in conjunction with &(pgsql)& lookups (see section
17005 &<<SECID72>>&). The option is available only if Exim has been built with
17006 PostgreSQL support.
17009 .option pid_file_path main string&!! "set at compile time"
17010 .cindex "daemon" "pid file path"
17011 .cindex "pid file, path for"
17012 This option sets the name of the file to which the Exim daemon writes its
17013 process id. The string is expanded, so it can contain, for example, references
17016 pid_file_path = /var/log/$primary_hostname/exim.pid
17018 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
17020 The value set by the option can be overridden by the &%-oP%& command line
17021 option. A pid file is not written if a &"non-standard"& daemon is run by means
17022 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
17025 .option pipelining_advertise_hosts main "host list&!!" *
17026 .cindex "PIPELINING" "suppressing advertising"
17027 .cindex "ESMTP extensions" PIPELINING
17028 This option can be used to suppress the advertisement of the SMTP
17029 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
17030 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
17031 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
17032 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
17033 that clients will use it; &"out of order"& commands that are &"expected"& do
17034 not count as protocol errors (see &%smtp_max_synprot_errors%&).
17036 .option pipelining_connect_advertise_hosts main "host list&!!" *
17037 .cindex "pipelining" "early connection"
17038 .cindex "pipelining" PIPECONNECT
17039 .cindex "ESMTP extensions" PIPECONNECT
17040 If Exim is built without the DISABLE_PIPE_CONNECT build option
17041 this option controls which hosts the facility is advertised to
17042 and from which pipeline early-connection (before MAIL) SMTP
17043 commands are acceptable.
17044 When used, the pipelining saves on roundtrip times.
17046 See also the &%hosts_pipe_connect%& smtp transport option.
17048 The SMTP service extension keyword advertised is &"PIPECONNECT"&;
17049 it permits the client to pipeline
17050 TCP connection and hello command (inclear phase),
17051 or TLS-establishment and hello command (encrypted phase),
17052 on later connections to the same host.
17055 .option prdr_enable main boolean false
17056 .cindex "PRDR" "enabling on server"
17057 .cindex "ESMTP extensions" PRDR
17058 This option can be used to enable the Per-Recipient Data Response extension
17059 to SMTP, defined by Eric Hall.
17060 If the option is set, PRDR is advertised by Exim when operating as a server.
17061 If the client requests PRDR, and more than one recipient, for a message
17062 an additional ACL is called for each recipient after the message content
17063 is received. See section &<<SECTPRDRACL>>&.
17065 .option preserve_message_logs main boolean false
17066 .cindex "message logs" "preserving"
17067 If this option is set, message log files are not deleted when messages are
17068 completed. Instead, they are moved to a sub-directory of the spool directory
17069 called &_msglog.OLD_&, where they remain available for statistical or debugging
17070 purposes. This is a dangerous option to set on systems with any appreciable
17071 volume of mail. Use with care!
17074 .option primary_hostname main string "see below"
17075 .cindex "name" "of local host"
17076 .cindex "host" "name of local"
17077 .cindex "local host" "name of"
17078 .vindex "&$primary_hostname$&"
17079 This specifies the name of the current host. It is used in the default EHLO or
17080 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
17081 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
17082 The value is also used by default in some SMTP response messages from an Exim
17083 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
17085 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
17086 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
17087 contains only one component, Exim passes it to &[gethostbyname()]& (or
17088 &[getipnodebyname()]& when available) in order to obtain the fully qualified
17089 version. The variable &$primary_hostname$& contains the host name, whether set
17090 explicitly by this option, or defaulted.
17093 .option print_topbitchars main boolean false
17094 .cindex "printing characters"
17095 .cindex "8-bit characters"
17096 By default, Exim considers only those characters whose codes lie in the range
17097 32&--126 to be printing characters. In a number of circumstances (for example,
17098 when writing log entries) non-printing characters are converted into escape
17099 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
17100 is set, code values of 128 and above are also considered to be printing
17103 This option also affects the header syntax checks performed by the
17104 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
17105 the user's full name when constructing From: and Sender: addresses (as
17106 described in section &<<SECTconstr>>&). Setting this option can cause
17107 Exim to generate eight bit message headers that do not conform to the
17111 .option process_log_path main string unset
17112 .cindex "process log path"
17113 .cindex "log" "process log"
17114 .cindex "&'exiwhat'&"
17115 This option sets the name of the file to which an Exim process writes its
17116 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
17117 utility script. If this option is unset, the file called &_exim-process.info_&
17118 in Exim's spool directory is used. The ability to specify the name explicitly
17119 can be useful in environments where two different Exims are running, using
17120 different spool directories.
17123 .option prod_requires_admin main boolean true
17124 .cindex "restricting access to features"
17128 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
17129 admin user unless &%prod_requires_admin%& is set false. See also
17130 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
17133 .option proxy_protocol_timeout main time 3s
17134 .cindex proxy "proxy protocol"
17135 This option sets the timeout for proxy protocol negotiation.
17136 For details see section &<<SECTproxyInbound>>&.
17139 .option qualify_domain main string "see below"
17140 .cindex "domain" "for qualifying addresses"
17141 .cindex "address" "qualification"
17142 This option specifies the domain name that is added to any envelope sender
17143 addresses that do not have a domain qualification. It also applies to
17144 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
17145 are accepted by default only for locally-generated messages. Qualification is
17146 also applied to addresses in header lines such as &'From:'& and &'To:'& for
17147 locally-generated messages, unless the &%-bnq%& command line option is used.
17149 Messages from external sources must always contain fully qualified addresses,
17150 unless the sending host matches &%sender_unqualified_hosts%& or
17151 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
17152 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
17153 necessary. Internally, Exim always works with fully qualified envelope
17154 addresses. If &%qualify_domain%& is not set, it defaults to the
17155 &%primary_hostname%& value.
17158 .option qualify_recipient main string "see below"
17159 This option allows you to specify a different domain for qualifying recipient
17160 addresses to the one that is used for senders. See &%qualify_domain%& above.
17164 .option queue_domains main "domain list&!!" unset
17165 .cindex "domain" "specifying non-immediate delivery"
17166 .cindex "queueing incoming messages"
17167 .cindex "message" "queueing certain domains"
17168 This option lists domains for which immediate delivery is not required.
17169 A delivery process is started whenever a message is received, but only those
17170 domains that do not match are processed. All other deliveries wait until the
17171 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
17174 .option queue_fast_ramp main boolean true
17175 .cindex "queue runner" "two phase"
17176 .cindex "queue" "double scanning"
17177 If set to true, two-phase queue runs, initiated using &%-qq%& on the
17178 command line, may start parallel delivery processes during their first
17179 phase. This will be done when a threshold number of messages have been
17180 routed for a single host.
17183 .option queue_list_requires_admin main boolean true
17184 .cindex "restricting access to features"
17186 The &%-bp%& command-line option, which lists the messages that are on the
17187 queue, requires the caller to be an admin user unless
17188 &%queue_list_requires_admin%& is set false.
17189 See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
17192 .option queue_only main boolean false
17193 .cindex "queueing incoming messages"
17194 .cindex "message" "queueing unconditionally"
17195 If &%queue_only%& is set, a delivery process is not automatically started
17196 whenever a message is received. Instead, the message waits in the queue for the
17197 next queue run. Even if &%queue_only%& is false, incoming messages may not get
17198 delivered immediately when certain conditions (such as heavy load) occur.
17200 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
17201 and &%-odi%& command line options override &%queue_only%& unless
17202 &%queue_only_override%& is set false. See also &%queue_only_file%&,
17203 &%queue_only_load%&, and &%smtp_accept_queue%&.
17206 .option queue_only_file main string unset
17207 .cindex "queueing incoming messages"
17208 .cindex "message" "queueing by file existence"
17209 This option can be set to a colon-separated list of absolute path names, each
17210 one optionally preceded by &"smtp"&. When Exim is receiving a message,
17211 it tests for the existence of each listed path using a call to &[stat()]&. For
17212 each path that exists, the corresponding queueing option is set.
17213 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
17214 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
17216 queue_only_file = smtp/some/file
17218 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
17219 &_/some/file_& exists.
17222 .option queue_only_load main fixed-point unset
17223 .cindex "load average"
17224 .cindex "queueing incoming messages"
17225 .cindex "message" "queueing by load"
17226 If the system load average is higher than this value, incoming messages from
17227 all sources are queued, and no automatic deliveries are started. If this
17228 happens during local or remote SMTP input, all subsequent messages received on
17229 the same SMTP connection are queued by default, whatever happens to the load in
17230 the meantime, but this can be changed by setting &%queue_only_load_latch%&
17233 Deliveries will subsequently be performed by queue runner processes. This
17234 option has no effect on ancient operating systems on which Exim cannot
17235 determine the load average. See also &%deliver_queue_load_max%& and
17236 &%smtp_load_reserve%&.
17239 .option queue_only_load_latch main boolean true
17240 .cindex "load average" "re-evaluating per message"
17241 When this option is true (the default), once one message has been queued
17242 because the load average is higher than the value set by &%queue_only_load%&,
17243 all subsequent messages received on the same SMTP connection are also queued.
17244 This is a deliberate choice; even though the load average may fall below the
17245 threshold, it doesn't seem right to deliver later messages on the same
17246 connection when not delivering earlier ones. However, there are special
17247 circumstances such as very long-lived connections from scanning appliances
17248 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
17249 should be set false. This causes the value of the load average to be
17250 re-evaluated for each message.
17253 .option queue_only_override main boolean true
17254 .cindex "queueing incoming messages"
17255 When this option is true, the &%-od%&&'x'& command line options override the
17256 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
17257 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
17258 to override; they are accepted, but ignored.
17261 .option queue_run_in_order main boolean false
17262 .cindex "queue runner" "processing messages in order"
17263 If this option is set, queue runs happen in order of message arrival instead of
17264 in an arbitrary order. For this to happen, a complete list of the entire queue
17265 must be set up before the deliveries start. When the queue is all held in a
17266 single directory (the default), a single list is created for both the ordered
17267 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
17268 single list is not created when &%queue_run_in_order%& is false. In this case,
17269 the sub-directories are processed one at a time (in a random order), and this
17270 avoids setting up one huge list for the whole queue. Thus, setting
17271 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
17272 when the queue is large, because of the extra work in setting up the single,
17273 large list. In most situations, &%queue_run_in_order%& should not be set.
17277 .option queue_run_max main integer&!! 5
17278 .cindex "queue runner" "maximum number of"
17279 This controls the maximum number of queue runner processes that an Exim daemon
17280 can run simultaneously. This does not mean that it starts them all at once,
17281 but rather that if the maximum number are still running when the time comes to
17282 start another one, it refrains from starting another one. This can happen with
17283 very large queues and/or very sluggish deliveries. This option does not,
17284 however, interlock with other processes, so additional queue runners can be
17285 started by other means, or by killing and restarting the daemon.
17287 Setting this option to zero does not suppress queue runs; rather, it disables
17288 the limit, allowing any number of simultaneous queue runner processes to be
17289 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
17290 the daemon's command line.
17292 .cindex queues named
17293 .cindex "named queues" "resource limit"
17294 To set limits for different named queues use
17295 an expansion depending on the &$queue_name$& variable.
17297 .option queue_smtp_domains main "domain list&!!" unset
17298 .cindex "queueing incoming messages"
17299 .cindex "message" "queueing remote deliveries"
17300 .cindex "first pass routing"
17301 When this option is set, a delivery process is started whenever a message is
17302 received, routing is performed, and local deliveries take place.
17303 However, if any SMTP deliveries are required for domains that match
17304 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
17305 message waits in the queue for the next queue run. Since routing of the message
17306 has taken place, Exim knows to which remote hosts it must be delivered, and so
17307 when the queue run happens, multiple messages for the same host are delivered
17308 over a single SMTP connection. The &%-odqs%& command line option causes all
17309 SMTP deliveries to be queued in this way, and is equivalent to setting
17310 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
17314 .option receive_timeout main time 0s
17315 .cindex "timeout" "for non-SMTP input"
17316 This option sets the timeout for accepting a non-SMTP message, that is, the
17317 maximum time that Exim waits when reading a message on the standard input. If
17318 the value is zero, it will wait forever. This setting is overridden by the
17319 &%-or%& command line option. The timeout for incoming SMTP messages is
17320 controlled by &%smtp_receive_timeout%&.
17322 .option received_header_text main string&!! "see below"
17323 .cindex "customizing" "&'Received:'& header"
17324 .cindex "&'Received:'& header line" "customizing"
17325 This string defines the contents of the &'Received:'& message header that is
17326 added to each message, except for the timestamp, which is automatically added
17327 on at the end (preceded by a semicolon). The string is expanded each time it is
17328 used. If the expansion yields an empty string, no &'Received:'& header line is
17329 added to the message. Otherwise, the string should start with the text
17330 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
17332 The default setting is:
17335 received_header_text = Received: \
17336 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
17337 {${if def:sender_ident \
17338 {from ${quote_local_part:$sender_ident} }}\
17339 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
17340 by $primary_hostname \
17341 ${if def:received_protocol {with $received_protocol }}\
17342 ${if def:tls_in_ver { ($tls_in_ver)}}\
17343 ${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\
17344 (Exim $version_number)\n\t\
17345 ${if def:sender_address \
17346 {(envelope-from <$sender_address>)\n\t}}\
17347 id $message_exim_id\
17348 ${if def:received_for {\n\tfor $received_for}}
17351 The references to the TLS version and cipher are
17352 omitted when Exim is built without TLS
17353 support. The use of conditional expansions ensures that this works for both
17354 locally generated messages and messages received from remote hosts, giving
17355 header lines such as the following:
17357 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
17358 by marley.carol.example with esmtp (Exim 4.00)
17359 (envelope-from <bob@carol.example>)
17360 id 16IOWa-00019l-00
17361 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
17362 Received: by scrooge.carol.example with local (Exim 4.00)
17363 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
17365 Until the body of the message has been received, the timestamp is the time when
17366 the message started to be received. Once the body has arrived, and all policy
17367 checks have taken place, the timestamp is updated to the time at which the
17368 message was accepted.
17371 .option received_headers_max main integer 30
17372 .cindex "loop" "prevention"
17373 .cindex "mail loop prevention"
17374 .cindex "&'Received:'& header line" "counting"
17375 When a message is to be delivered, the number of &'Received:'& headers is
17376 counted, and if it is greater than this parameter, a mail loop is assumed to
17377 have occurred, the delivery is abandoned, and an error message is generated.
17378 This applies to both local and remote deliveries.
17381 .option recipient_unqualified_hosts main "host list&!!" unset
17382 .cindex "unqualified addresses"
17383 .cindex "host" "unqualified addresses from"
17384 This option lists those hosts from which Exim is prepared to accept unqualified
17385 recipient addresses in message envelopes. The addresses are made fully
17386 qualified by the addition of the &%qualify_recipient%& value. This option also
17387 affects message header lines. Exim does not reject unqualified recipient
17388 addresses in headers, but it qualifies them only if the message came from a
17389 host that matches &%recipient_unqualified_hosts%&,
17390 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
17391 option was not set.
17394 .option recipients_max main integer 50000
17395 .cindex "limit" "number of recipients"
17396 .cindex "recipient" "maximum number"
17397 If this option is set greater than zero, it specifies the maximum number of
17398 original recipients for any message. Additional recipients that are generated
17399 by aliasing or forwarding do not count. SMTP messages get a 452 response for
17400 all recipients over the limit; earlier recipients are delivered as normal.
17401 Non-SMTP messages with too many recipients are failed, and no deliveries are
17404 .cindex "RCPT" "maximum number of incoming"
17405 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
17406 RCPT commands in a single message.
17409 .option recipients_max_reject main boolean false
17410 If this option is set true, Exim rejects SMTP messages containing too many
17411 recipients by giving 552 errors to the surplus RCPT commands, and a 554
17412 error to the eventual DATA command. Otherwise (the default) it gives a 452
17413 error to the surplus RCPT commands and accepts the message on behalf of the
17414 initial set of recipients. The remote server should then re-send the message
17415 for the remaining recipients at a later time.
17418 .option remote_max_parallel main integer 4
17419 .cindex "delivery" "parallelism for remote"
17420 This option controls parallel delivery of one message to a number of remote
17421 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
17422 does all the remote deliveries for a message one by one. Otherwise, if a single
17423 message has to be delivered to more than one remote host, or if several copies
17424 have to be sent to the same remote host, up to &%remote_max_parallel%&
17425 deliveries are done simultaneously. If more than &%remote_max_parallel%&
17426 deliveries are required, the maximum number of processes are started, and as
17427 each one finishes, another is begun. The order of starting processes is the
17428 same as if sequential delivery were being done, and can be controlled by the
17429 &%remote_sort_domains%& option. If parallel delivery takes place while running
17430 with debugging turned on, the debugging output from each delivery process is
17431 tagged with its process id.
17433 This option controls only the maximum number of parallel deliveries for one
17434 message in one Exim delivery process. Because Exim has no central queue
17435 manager, there is no way of controlling the total number of simultaneous
17436 deliveries if the configuration allows a delivery attempt as soon as a message
17439 See also the &%max_parallel%& generic transport option,
17440 and the &%serialize_hosts%& smtp transport option.
17442 .cindex "number of deliveries"
17443 .cindex "delivery" "maximum number of"
17444 If you want to control the total number of deliveries on the system, you
17445 need to set the &%queue_only%& option. This ensures that all incoming messages
17446 are added to the queue without starting a delivery process. Then set up an Exim
17447 daemon to start queue runner processes at appropriate intervals (probably
17448 fairly often, for example, every minute), and limit the total number of queue
17449 runners by setting the &%queue_run_max%& parameter. Because each queue runner
17450 delivers only one message at a time, the maximum number of deliveries that can
17451 then take place at once is &%queue_run_max%& multiplied by
17452 &%remote_max_parallel%&.
17454 If it is purely remote deliveries you want to control, use
17455 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
17456 doing the SMTP routing before queueing, so that several messages for the same
17457 host will eventually get delivered down the same connection.
17460 .option remote_sort_domains main "domain list&!!" unset
17461 .cindex "sorting remote deliveries"
17462 .cindex "delivery" "sorting remote"
17463 When there are a number of remote deliveries for a message, they are sorted by
17464 domain into the order given by this list. For example,
17466 remote_sort_domains = *.cam.ac.uk:*.uk
17468 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
17469 then to those in the &%uk%& domain, then to any others.
17472 .option retry_data_expire main time 7d
17473 .cindex "hints database" "data expiry"
17474 This option sets a &"use before"& time on retry information in Exim's hints
17475 database. Any older retry data is ignored. This means that, for example, once a
17476 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
17480 .option retry_interval_max main time 24h
17481 .cindex "retry" "limit on interval"
17482 .cindex "limit" "on retry interval"
17483 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
17484 intervals between delivery attempts for messages that cannot be delivered
17485 straight away. This option sets an overall limit to the length of time between
17486 retries. It cannot be set greater than 24 hours; any attempt to do so forces
17490 .option return_path_remove main boolean true
17491 .cindex "&'Return-path:'& header line" "removing"
17492 RFC 2821, section 4.4, states that an SMTP server must insert a
17493 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
17494 The &'Return-path:'& header preserves the sender address as received in the
17495 MAIL command. This description implies that this header should not be present
17496 in an incoming message. If &%return_path_remove%& is true, any existing
17497 &'Return-path:'& headers are removed from messages at the time they are
17498 received. Exim's transports have options for adding &'Return-path:'& headers at
17499 the time of delivery. They are normally used only for final local deliveries.
17502 .option return_size_limit main integer 100K
17503 This option is an obsolete synonym for &%bounce_return_size_limit%&.
17506 .option rfc1413_hosts main "host list&!!" @[]
17508 .cindex "host" "for RFC 1413 calls"
17509 RFC 1413 identification calls are made to any client host which matches
17510 an item in the list.
17511 The default value specifies just this host, being any local interface
17514 .option rfc1413_query_timeout main time 0s
17515 .cindex "RFC 1413" "query timeout"
17516 .cindex "timeout" "for RFC 1413 call"
17517 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
17518 no RFC 1413 calls are ever made.
17521 .option sender_unqualified_hosts main "host list&!!" unset
17522 .cindex "unqualified addresses"
17523 .cindex "host" "unqualified addresses from"
17524 This option lists those hosts from which Exim is prepared to accept unqualified
17525 sender addresses. The addresses are made fully qualified by the addition of
17526 &%qualify_domain%&. This option also affects message header lines. Exim does
17527 not reject unqualified addresses in headers that contain sender addresses, but
17528 it qualifies them only if the message came from a host that matches
17529 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
17530 using TCP/IP), and the &%-bnq%& option was not set.
17533 .option slow_lookup_log main integer 0
17534 .cindex "logging" "slow lookups"
17535 .cindex "dns" "logging slow lookups"
17536 This option controls logging of slow lookups.
17537 If the value is nonzero it is taken as a number of milliseconds
17538 and lookups taking longer than this are logged.
17539 Currently this applies only to DNS lookups.
17543 .option smtp_accept_keepalive main boolean true
17544 .cindex "keepalive" "on incoming connection"
17545 This option controls the setting of the SO_KEEPALIVE option on incoming
17546 TCP/IP socket connections. When set, it causes the kernel to probe idle
17547 connections periodically, by sending packets with &"old"& sequence numbers. The
17548 other end of the connection should send an acknowledgment if the connection is
17549 still okay or a reset if the connection has been aborted. The reason for doing
17550 this is that it has the beneficial effect of freeing up certain types of
17551 connection that can get stuck when the remote host is disconnected without
17552 tidying up the TCP/IP call properly. The keepalive mechanism takes several
17553 hours to detect unreachable hosts.
17557 .option smtp_accept_max main integer 20
17558 .cindex "limit" "incoming SMTP connections"
17559 .cindex "SMTP" "incoming connection count"
17561 This option specifies the maximum number of simultaneous incoming SMTP calls
17562 that Exim will accept. It applies only to the listening daemon; there is no
17563 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
17564 value is set to zero, no limit is applied. However, it is required to be
17565 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
17566 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
17568 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
17569 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
17570 that limit has not been reached for the client host, &%smtp_accept_reserve%&
17571 and &%smtp_load_reserve%& are then checked before accepting the connection.
17574 .option smtp_accept_max_nonmail main integer 10
17575 .cindex "limit" "non-mail SMTP commands"
17576 .cindex "SMTP" "limiting non-mail commands"
17577 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
17578 the connection if there are too many. This option defines &"too many"&. The
17579 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
17580 client looping sending EHLO, for example. The check is applied only if the
17581 client host matches &%smtp_accept_max_nonmail_hosts%&.
17583 When a new message is expected, one occurrence of RSET is not counted. This
17584 allows a client to send one RSET between messages (this is not necessary,
17585 but some clients do it). Exim also allows one uncounted occurrence of HELO
17586 or EHLO, and one occurrence of STARTTLS between messages. After
17587 starting up a TLS session, another EHLO is expected, and so it too is not
17588 counted. The first occurrence of AUTH in a connection, or immediately
17589 following STARTTLS is not counted. Otherwise, all commands other than
17590 MAIL, RCPT, DATA, and QUIT are counted.
17593 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
17594 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
17595 check by setting this option. The default value makes it apply to all hosts. By
17596 changing the value, you can exclude any badly-behaved hosts that you have to
17600 . Allow this long option name to split; give it unsplit as a fifth argument
17601 . for the automatic .oindex that is generated by .option.
17602 . We insert " &~&~" which is both pretty nasty visually and results in
17603 . non-searchable text. HowItWorks.txt mentions an option for inserting
17604 . zero-width-space, which would be nicer visually and results in (at least)
17605 . html that Firefox will split on when it's forced to reflow (rather than
17606 . inserting a horizontal scrollbar). However, the text is still not
17607 . searchable. NM changed this occurrence for bug 1197 to no longer allow
17608 . the option name to split.
17610 .option "smtp_accept_max_per_connection" main integer&!! 1000 &&&
17611 smtp_accept_max_per_connection
17612 .cindex "SMTP" "limiting incoming message count"
17613 .cindex "limit" "messages per SMTP connection"
17614 The value of this option limits the number of MAIL commands that Exim is
17615 prepared to accept over a single SMTP connection, whether or not each command
17616 results in the transfer of a message. After the limit is reached, a 421
17617 response is given to subsequent MAIL commands. This limit is a safety
17618 precaution against a client that goes mad (incidents of this type have been
17620 The option is expanded after the HELO or EHLO is received
17621 and may depend on values available at that time.
17622 An empty or zero value after expansion removes the limit.
17625 .option smtp_accept_max_per_host main string&!! unset
17626 .cindex "limit" "SMTP connections from one host"
17627 .cindex "host" "limiting SMTP connections from"
17628 This option restricts the number of simultaneous IP connections from a single
17629 host (strictly, from a single IP address) to the Exim daemon. The option is
17630 expanded, to enable different limits to be applied to different hosts by
17631 reference to &$sender_host_address$&. Once the limit is reached, additional
17632 connection attempts from the same host are rejected with error code 421. This
17633 is entirely independent of &%smtp_accept_reserve%&. The option's default value
17634 of zero imposes no limit. If this option is set greater than zero, it is
17635 required that &%smtp_accept_max%& be non-zero.
17637 &*Warning*&: When setting this option you should not use any expansion
17638 constructions that take an appreciable amount of time. The expansion and test
17639 happen in the main daemon loop, in order to reject additional connections
17640 without forking additional processes (otherwise a denial-of-service attack
17641 could cause a vast number or processes to be created). While the daemon is
17642 doing this processing, it cannot accept any other incoming connections.
17646 .option smtp_accept_queue main integer 0
17647 .cindex "SMTP" "incoming connection count"
17648 .cindex "queueing incoming messages"
17649 .cindex "message" "queueing by SMTP connection count"
17650 If the number of simultaneous incoming SMTP connections being handled via the
17651 listening daemon exceeds this value, messages received by SMTP are just placed
17652 in the queue; no delivery processes are started automatically. The count is
17653 fixed at the start of an SMTP connection. It cannot be updated in the
17654 subprocess that receives messages, and so the queueing or not queueing applies
17655 to all messages received in the same connection.
17657 A value of zero implies no limit, and clearly any non-zero value is useful only
17658 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
17659 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
17660 various &%-od%&&'x'& command line options.
17663 . See the comment on smtp_accept_max_per_connection
17665 .option "smtp_accept_queue_per_connection" main integer 10 &&&
17666 smtp_accept_queue_per_connection
17667 .cindex "queueing incoming messages"
17668 .cindex "message" "queueing by message count"
17669 This option limits the number of delivery processes that Exim starts
17670 automatically when receiving messages via SMTP, whether via the daemon or by
17671 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
17672 and the number of messages received in a single SMTP session exceeds this
17673 number, subsequent messages are placed in the queue, but no delivery processes
17674 are started. This helps to limit the number of Exim processes when a server
17675 restarts after downtime and there is a lot of mail waiting for it on other
17676 systems. On large systems, the default should probably be increased, and on
17677 dial-in client systems it should probably be set to zero (that is, disabled).
17680 .option smtp_accept_reserve main integer 0
17681 .cindex "SMTP" "incoming call count"
17682 .cindex "host" "reserved"
17683 When &%smtp_accept_max%& is set greater than zero, this option specifies a
17684 number of SMTP connections that are reserved for connections from the hosts
17685 that are specified in &%smtp_reserve_hosts%&. The value set in
17686 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
17687 restricted to this number of connections; the option specifies a minimum number
17688 of connection slots for them, not a maximum. It is a guarantee that this group
17689 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
17690 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
17693 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
17694 set to 5, once there are 45 active connections (from any hosts), new
17695 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
17696 provided the other criteria for acceptance are met.
17699 .option smtp_active_hostname main string&!! unset
17700 .cindex "host" "name in SMTP responses"
17701 .cindex "SMTP" "host name in responses"
17702 .vindex "&$primary_hostname$&"
17703 This option is provided for multi-homed servers that want to masquerade as
17704 several different hosts. At the start of an incoming SMTP connection, its value
17705 is expanded and used instead of the value of &$primary_hostname$& in SMTP
17706 responses. For example, it is used as domain name in the response to an
17707 incoming HELO or EHLO command.
17709 .vindex "&$smtp_active_hostname$&"
17710 The active hostname is placed in the &$smtp_active_hostname$& variable, which
17711 is saved with any messages that are received. It is therefore available for use
17712 in routers and transports when the message is later delivered.
17714 If this option is unset, or if its expansion is forced to fail, or if the
17715 expansion results in an empty string, the value of &$primary_hostname$& is
17716 used. Other expansion failures cause a message to be written to the main and
17717 panic logs, and the SMTP command receives a temporary error. Typically, the
17718 value of &%smtp_active_hostname%& depends on the incoming interface address.
17721 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
17722 {cox.mydomain}{box.mydomain}}
17725 Although &$smtp_active_hostname$& is primarily concerned with incoming
17726 messages, it is also used as the default for HELO commands in callout
17727 verification if there is no remote transport from which to obtain a
17728 &%helo_data%& value.
17730 .option smtp_backlog_monitor main integer 0
17731 .cindex "connection backlog" monitoring
17732 If this option is set to greater than zero, and the backlog of available
17733 TCP connections on a socket listening for SMTP is larger than it, a line
17734 is logged giving the value and the socket address and port.
17735 The value is retrived jsut before an accept call.
17736 This facility is only available on Linux.
17738 .option smtp_banner main string&!! "see below"
17739 .cindex "SMTP" "welcome banner"
17740 .cindex "banner for SMTP"
17741 .cindex "welcome banner for SMTP"
17742 .cindex "customizing" "SMTP banner"
17743 If a connect ACL does not supply a message,
17744 this string (which is expanded every time it is used) is output as the initial
17745 positive response to an SMTP connection. The default setting is:
17747 smtp_banner = $smtp_active_hostname ESMTP Exim \
17748 $version_number $tod_full
17751 Failure to expand the string causes a panic error;
17752 a forced fail just closes the connection.
17754 If you want to create a
17755 multiline response to the initial SMTP connection, use &"\n"& in the string at
17756 appropriate points, but not at the end. Note that the 220 code is not included
17757 in this string. Exim adds it automatically (several times in the case of a
17758 multiline response).
17761 .option smtp_check_spool_space main boolean true
17762 .cindex "checking disk space"
17763 .cindex "disk space, checking"
17764 .cindex "spool directory" "checking space"
17765 When this option is set, if an incoming SMTP session encounters the SIZE
17766 option on a MAIL command, it checks that there is enough space in the
17767 spool directory's partition to accept a message of that size, while still
17768 leaving free the amount specified by &%check_spool_space%& (even if that value
17769 is zero). If there isn't enough space, a temporary error code is returned.
17772 .option smtp_connect_backlog main integer 20
17773 .cindex "connection backlog" "set maximum"
17774 .cindex "SMTP" "connection backlog"
17775 .cindex "backlog of connections"
17776 This option specifies a maximum number of waiting SMTP connections. Exim passes
17777 this value to the TCP/IP system when it sets up its listener. Once this number
17778 of connections are waiting for the daemon's attention, subsequent connection
17779 attempts are refused at the TCP/IP level. At least, that is what the manuals
17780 say; in some circumstances such connection attempts have been observed to time
17781 out instead. For large systems it is probably a good idea to increase the
17782 value (to 50, say). It also gives some protection against denial-of-service
17783 attacks by SYN flooding.
17786 .option smtp_enforce_sync main boolean true
17787 .cindex "SMTP" "synchronization checking"
17788 .cindex "synchronization checking in SMTP"
17789 The SMTP protocol specification requires the client to wait for a response from
17790 the server at certain points in the dialogue. Without PIPELINING these
17791 synchronization points are after every command; with PIPELINING they are
17792 fewer, but they still exist.
17794 Some spamming sites send out a complete set of SMTP commands without waiting
17795 for any response. Exim protects against this by rejecting a message if the
17796 client has sent further input when it should not have. The error response &"554
17797 SMTP synchronization error"& is sent, and the connection is dropped. Testing
17798 for this error cannot be perfect because of transmission delays (unexpected
17799 input may be on its way but not yet received when Exim checks). However, it
17800 does detect many instances.
17802 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
17803 If you want to disable the check selectively (for example, only for certain
17804 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
17805 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
17809 .option smtp_etrn_command main string&!! unset
17810 .cindex "ETRN" "command to be run"
17811 .cindex "ESMTP extensions" ETRN
17812 .vindex "&$domain$&"
17813 If this option is set, the given command is run whenever an SMTP ETRN
17814 command is received from a host that is permitted to issue such commands (see
17815 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
17816 are independently expanded. The expansion variable &$domain$& is set to the
17817 argument of the ETRN command, and no syntax checking is done on it. For
17820 smtp_etrn_command = /etc/etrn_command $domain \
17821 $sender_host_address
17823 If the option is not set, the argument for the ETRN command must
17824 be a &'#'& followed by an address string.
17825 In this case an &'exim -R <string>'& command is used;
17826 if the ETRN ACL has set up a named-queue then &'-MCG <queue>'& is appended.
17828 A new process is created to run the command, but Exim does not wait for it to
17829 complete. Consequently, its status cannot be checked. If the command cannot be
17830 run, a line is written to the panic log, but the ETRN caller still receives
17831 a 250 success response. Exim is normally running under its own uid when
17832 receiving SMTP, so it is not possible for it to change the uid before running
17836 .option smtp_etrn_serialize main boolean true
17837 .cindex "ETRN" "serializing"
17838 When this option is set, it prevents the simultaneous execution of more than
17839 one identical command as a result of ETRN in an SMTP connection. See
17840 section &<<SECTETRN>>& for details.
17843 .option smtp_load_reserve main fixed-point unset
17844 .cindex "load average"
17845 If the system load average ever gets higher than this, incoming SMTP calls are
17846 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
17847 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
17848 the load is over the limit. The option has no effect on ancient operating
17849 systems on which Exim cannot determine the load average. See also
17850 &%deliver_queue_load_max%& and &%queue_only_load%&.
17854 .option smtp_max_synprot_errors main integer 3
17855 .cindex "SMTP" "limiting syntax and protocol errors"
17856 .cindex "limit" "SMTP syntax and protocol errors"
17857 Exim rejects SMTP commands that contain syntax or protocol errors. In
17858 particular, a syntactically invalid email address, as in this command:
17860 RCPT TO:<abc xyz@a.b.c>
17862 causes immediate rejection of the command, before any other tests are done.
17863 (The ACL cannot be run if there is no valid address to set up for it.) An
17864 example of a protocol error is receiving RCPT before MAIL. If there are
17865 too many syntax or protocol errors in one SMTP session, the connection is
17866 dropped. The limit is set by this option.
17868 .cindex "PIPELINING" "expected errors"
17869 When the PIPELINING extension to SMTP is in use, some protocol errors are
17870 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
17871 Exim assumes that PIPELINING will be used if it advertises it (see
17872 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
17873 not count towards the limit.
17877 .option smtp_max_unknown_commands main integer 3
17878 .cindex "SMTP" "limiting unknown commands"
17879 .cindex "limit" "unknown SMTP commands"
17880 If there are too many unrecognized commands in an incoming SMTP session, an
17881 Exim server drops the connection. This is a defence against some kinds of abuse
17884 into making connections to SMTP ports; in these circumstances, a number of
17885 non-SMTP command lines are sent first.
17889 .option smtp_ratelimit_hosts main "host list&!!" unset
17890 .cindex "SMTP" "rate limiting"
17891 .cindex "limit" "rate of message arrival"
17892 .cindex "RCPT" "rate limiting"
17893 Some sites find it helpful to be able to limit the rate at which certain hosts
17894 can send them messages, and the rate at which an individual message can specify
17897 Exim has two rate-limiting facilities. This section describes the older
17898 facility, which can limit rates within a single connection. The newer
17899 &%ratelimit%& ACL condition can limit rates across all connections. See section
17900 &<<SECTratelimiting>>& for details of the newer facility.
17902 When a host matches &%smtp_ratelimit_hosts%&, the values of
17903 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
17904 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
17905 respectively. Each option, if set, must contain a set of four comma-separated
17909 A threshold, before which there is no rate limiting.
17911 An initial time delay. Unlike other times in Exim, numbers with decimal
17912 fractional parts are allowed here.
17914 A factor by which to increase the delay each time.
17916 A maximum value for the delay. This should normally be less than 5 minutes,
17917 because after that time, the client is liable to timeout the SMTP command.
17920 For example, these settings have been used successfully at the site which
17921 first suggested this feature, for controlling mail from their customers:
17923 smtp_ratelimit_mail = 2,0.5s,1.05,4m
17924 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
17926 The first setting specifies delays that are applied to MAIL commands after
17927 two have been received over a single connection. The initial delay is 0.5
17928 seconds, increasing by a factor of 1.05 each time. The second setting applies
17929 delays to RCPT commands when more than four occur in a single message.
17932 .option smtp_ratelimit_mail main string unset
17933 See &%smtp_ratelimit_hosts%& above.
17936 .option smtp_ratelimit_rcpt main string unset
17937 See &%smtp_ratelimit_hosts%& above.
17940 .option smtp_receive_timeout main time&!! 5m
17941 .cindex "timeout" "for SMTP input"
17942 .cindex "SMTP" "input timeout"
17943 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
17944 input, including batch SMTP. If a line of input (either an SMTP command or a
17945 data line) is not received within this time, the SMTP connection is dropped and
17946 the message is abandoned.
17947 A line is written to the log containing one of the following messages:
17949 SMTP command timeout on connection from...
17950 SMTP data timeout on connection from...
17952 The former means that Exim was expecting to read an SMTP command; the latter
17953 means that it was in the DATA phase, reading the contents of a message.
17955 If the first character of the option is a &"$"& the option is
17956 expanded before use and may depend on
17957 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
17961 The value set by this option can be overridden by the
17962 &%-os%& command-line option. A setting of zero time disables the timeout, but
17963 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
17964 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
17965 timeout is controlled by &%receive_timeout%& and &%-or%&.
17968 .option smtp_reserve_hosts main "host list&!!" unset
17969 This option defines hosts for which SMTP connections are reserved; see
17970 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
17973 .option smtp_return_error_details main boolean false
17974 .cindex "SMTP" "details policy failures"
17975 .cindex "policy control" "rejection, returning details"
17976 In the default state, Exim uses bland messages such as
17977 &"Administrative prohibition"& when it rejects SMTP commands for policy
17978 reasons. Many sysadmins like this because it gives away little information
17979 to spammers. However, some other sysadmins who are applying strict checking
17980 policies want to give out much fuller information about failures. Setting
17981 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
17982 example, instead of &"Administrative prohibition"&, it might give:
17984 550-Rejected after DATA: '>' missing at end of address:
17985 550 failing address in "From" header is: <user@dom.ain
17989 .option smtputf8_advertise_hosts main "host list&!!" *
17990 .cindex "SMTPUTF8" "ESMTP extension, advertising"
17991 .cindex "ESMTP extensions" SMTPUTF8
17992 When Exim is built with support for internationalised mail names,
17993 the availability thereof is advertised in
17994 response to EHLO only to those client hosts that match this option. See
17995 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
17998 .option spamd_address main string "127.0.0.1 783"
17999 This option is available when Exim is compiled with the content-scanning
18000 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
18001 See section &<<SECTscanspamass>>& for more details.
18005 .option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
18006 This option is available when Exim is compiled with SPF support.
18007 See section &<<SECSPF>>& for more details.
18009 .option spf_smtp_comment_template main string&!! "Please%_see%_http://www.open-spf.org/Why"
18010 This option is available when Exim is compiled with SPF support. It
18011 allows the customisation of the SMTP comment that the SPF library
18012 generates. You are strongly encouraged to link to your own explanative
18013 site. The template must not contain spaces. If you need spaces in the
18014 output, use the proper placeholder. If libspf2 can not parse the
18015 template, it uses a built-in default broken link. The following placeholders
18016 (along with Exim variables (but see below)) are allowed in the template:
18020 &*%{L}*&: Envelope sender's local part.
18022 &*%{S}*&: Envelope sender.
18024 &*%{O}*&: Envelope sender's domain.
18026 &*%{D}*&: Current(?) domain.
18028 &*%{I}*&: SMTP client Ip.
18030 &*%{C}*&: SMTP client pretty IP.
18032 &*%{T}*&: Epoch time (UTC).
18034 &*%{P}*&: SMTP client domain name.
18036 &*%{V}*&: IP version.
18038 &*%{H}*&: EHLO/HELO domain.
18040 &*%{R}*&: Receiving domain.
18042 The capitalized placeholders do proper URL encoding, if you use them
18043 lowercased, no encoding takes place. This list was compiled from the
18046 A note on using Exim variables: As
18047 currently the SPF library is initialized before the SMTP EHLO phase,
18048 the variables useful for expansion are quite limited.
18051 .option split_spool_directory main boolean false
18052 .cindex "multiple spool directories"
18053 .cindex "spool directory" "split"
18054 .cindex "directories, multiple"
18055 If this option is set, it causes Exim to split its input directory into 62
18056 subdirectories, each with a single alphanumeric character as its name. The
18057 sixth character of the message id is used to allocate messages to
18058 subdirectories; this is the least significant base-62 digit of the time of
18059 arrival of the message.
18061 Splitting up the spool in this way may provide better performance on systems
18062 where there are long mail queues, by reducing the number of files in any one
18063 directory. The msglog directory is also split up in a similar way to the input
18064 directory; however, if &%preserve_message_logs%& is set, all old msglog files
18065 are still placed in the single directory &_msglog.OLD_&.
18067 It is not necessary to take any special action for existing messages when
18068 changing &%split_spool_directory%&. Exim notices messages that are in the
18069 &"wrong"& place, and continues to process them. If the option is turned off
18070 after a period of being on, the subdirectories will eventually empty and be
18071 automatically deleted.
18073 When &%split_spool_directory%& is set, the behaviour of queue runner processes
18074 changes. Instead of creating a list of all messages in the queue, and then
18075 trying to deliver each one, in turn, it constructs a list of those in one
18076 sub-directory and tries to deliver them, before moving on to the next
18077 sub-directory. The sub-directories are processed in a random order. This
18078 spreads out the scanning of the input directories, and uses less memory. It is
18079 particularly beneficial when there are lots of messages in the queue. However,
18080 if &%queue_run_in_order%& is set, none of this new processing happens. The
18081 entire queue has to be scanned and sorted before any deliveries can start.
18084 .option spool_directory main string&!! "set at compile time"
18085 .cindex "spool directory" "path to"
18086 This defines the directory in which Exim keeps its spool, that is, the messages
18087 it is waiting to deliver. The default value is taken from the compile-time
18088 configuration setting, if there is one. If not, this option must be set. The
18089 string is expanded, so it can contain, for example, a reference to
18090 &$primary_hostname$&.
18092 If the spool directory name is fixed on your installation, it is recommended
18093 that you set it at build time rather than from this option, particularly if the
18094 log files are being written to the spool directory (see &%log_file_path%&).
18095 Otherwise log files cannot be used for errors that are detected early on, such
18096 as failures in the configuration file.
18098 By using this option to override the compiled-in path, it is possible to run
18099 tests of Exim without using the standard spool.
18101 .option spool_wireformat main boolean false
18102 .cindex "spool directory" "file formats"
18103 If this option is set, Exim may for some messages use an alternative format
18104 for data-files in the spool which matches the wire format.
18105 Doing this permits more efficient message reception and transmission.
18106 Currently it is only done for messages received using the ESMTP CHUNKING
18109 The following variables will not have useful values:
18111 $max_received_linelength
18116 Users of the local_scan() API (see &<<CHAPlocalscan>>&),
18117 and any external programs which are passed a reference to a message data file
18118 (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
18119 will need to be aware of the different formats potentially available.
18121 Using any of the ACL conditions noted will negate the reception benefit
18122 (as a Unix-mbox-format file is constructed for them).
18123 The transmission benefit is maintained.
18125 .option sqlite_lock_timeout main time 5s
18126 .cindex "sqlite lookup type" "lock timeout"
18127 This option controls the timeout that the &(sqlite)& lookup uses when trying to
18128 access an SQLite database. See section &<<SECTsqlite>>& for more details.
18130 .option strict_acl_vars main boolean false
18131 .cindex "&ACL;" "variables, handling unset"
18132 This option controls what happens if a syntactically valid but undefined ACL
18133 variable is referenced. If it is false (the default), an empty string
18134 is substituted; if it is true, an error is generated. See section
18135 &<<SECTaclvariables>>& for details of ACL variables.
18137 .option strip_excess_angle_brackets main boolean false
18138 .cindex "angle brackets, excess"
18139 If this option is set, redundant pairs of angle brackets round &"route-addr"&
18140 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
18141 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
18142 passed on to another MTA, the excess angle brackets are not passed on. If this
18143 option is not set, multiple pairs of angle brackets cause a syntax error.
18146 .option strip_trailing_dot main boolean false
18147 .cindex "trailing dot on domain"
18148 .cindex "dot" "trailing on domain"
18149 If this option is set, a trailing dot at the end of a domain in an address is
18150 ignored. If this is in the envelope and the message is passed on to another
18151 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
18152 domain causes a syntax error.
18153 However, addresses in header lines are checked only when an ACL requests header
18157 .option syslog_duplication main boolean true
18158 .cindex "syslog" "duplicate log lines; suppressing"
18159 When Exim is logging to syslog, it writes the log lines for its three
18160 separate logs at different syslog priorities so that they can in principle
18161 be separated on the logging hosts. Some installations do not require this
18162 separation, and in those cases, the duplication of certain log lines is a
18163 nuisance. If &%syslog_duplication%& is set false, only one copy of any
18164 particular log line is written to syslog. For lines that normally go to
18165 both the main log and the reject log, the reject log version (possibly
18166 containing message header lines) is written, at LOG_NOTICE priority.
18167 Lines that normally go to both the main and the panic log are written at
18168 the LOG_ALERT priority.
18171 .option syslog_facility main string unset
18172 .cindex "syslog" "facility; setting"
18173 This option sets the syslog &"facility"& name, used when Exim is logging to
18174 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
18175 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
18176 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
18177 details of Exim's logging.
18180 .option syslog_pid main boolean true
18181 .cindex "syslog" "pid"
18182 If &%syslog_pid%& is set false, the PID on Exim's log lines are
18183 omitted when these lines are sent to syslog. (Syslog normally prefixes
18184 the log lines with the PID of the logging process automatically.) You need
18185 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
18186 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
18190 .option syslog_processname main string &`exim`&
18191 .cindex "syslog" "process name; setting"
18192 This option sets the syslog &"ident"& name, used when Exim is logging to
18193 syslog. The value must be no longer than 32 characters. See chapter
18194 &<<CHAPlog>>& for details of Exim's logging.
18198 .option syslog_timestamp main boolean true
18199 .cindex "syslog" "timestamps"
18200 .cindex timestamps syslog
18201 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
18202 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
18203 details of Exim's logging.
18206 .option system_filter main string&!! unset
18207 .cindex "filter" "system filter"
18208 .cindex "system filter" "specifying"
18209 .cindex "Sieve filter" "not available for system filter"
18210 This option specifies an Exim filter file that is applied to all messages at
18211 the start of each delivery attempt, before any routing is done. System filters
18212 must be Exim filters; they cannot be Sieve filters. If the system filter
18213 generates any deliveries to files or pipes, or any new mail messages, the
18214 appropriate &%system_filter_..._transport%& option(s) must be set, to define
18215 which transports are to be used. Details of this facility are given in chapter
18216 &<<CHAPsystemfilter>>&.
18217 A forced expansion failure results in no filter operation.
18220 .option system_filter_directory_transport main string&!! unset
18221 .vindex "&$address_file$&"
18222 This sets the name of the transport driver that is to be used when the
18223 &%save%& command in a system message filter specifies a path ending in &"/"&,
18224 implying delivery of each message into a separate file in some directory.
18225 During the delivery, the variable &$address_file$& contains the path name.
18228 .option system_filter_file_transport main string&!! unset
18229 .cindex "file" "transport for system filter"
18230 This sets the name of the transport driver that is to be used when the &%save%&
18231 command in a system message filter specifies a path not ending in &"/"&. During
18232 the delivery, the variable &$address_file$& contains the path name.
18234 .option system_filter_group main string unset
18235 .cindex "gid (group id)" "system filter"
18236 This option is used only when &%system_filter_user%& is also set. It sets the
18237 gid under which the system filter is run, overriding any gid that is associated
18238 with the user. The value may be numerical or symbolic.
18240 .option system_filter_pipe_transport main string&!! unset
18241 .cindex "&(pipe)& transport" "for system filter"
18242 .vindex "&$address_pipe$&"
18243 This specifies the transport driver that is to be used when a &%pipe%& command
18244 is used in a system filter. During the delivery, the variable &$address_pipe$&
18245 contains the pipe command.
18248 .option system_filter_reply_transport main string&!! unset
18249 .cindex "&(autoreply)& transport" "for system filter"
18250 This specifies the transport driver that is to be used when a &%mail%& command
18251 is used in a system filter.
18254 .option system_filter_user main string unset
18255 .cindex "uid (user id)" "system filter"
18256 If this option is set to root, the system filter is run in the main Exim
18257 delivery process, as root. Otherwise, the system filter runs in a separate
18258 process, as the given user, defaulting to the Exim run-time user.
18259 Unless the string consists entirely of digits, it
18260 is looked up in the password data. Failure to find the named user causes a
18261 configuration error. The gid is either taken from the password data, or
18262 specified by &%system_filter_group%&. When the uid is specified numerically,
18263 &%system_filter_group%& is required to be set.
18265 If the system filter generates any pipe, file, or reply deliveries, the uid
18266 under which the filter is run is used when transporting them, unless a
18267 transport option overrides.
18270 .option tcp_nodelay main boolean true
18271 .cindex "daemon" "TCP_NODELAY on sockets"
18272 .cindex "Nagle algorithm"
18273 .cindex "TCP_NODELAY on listening sockets"
18274 If this option is set false, it stops the Exim daemon setting the
18275 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
18276 turns off the &"Nagle algorithm"&, which is a way of improving network
18277 performance in interactive (character-by-character) situations. Turning it off
18278 should improve Exim's performance a bit, so that is what happens by default.
18279 However, it appears that some broken clients cannot cope, and time out. Hence
18280 this option. It affects only those sockets that are set up for listening by the
18281 daemon. Sockets created by the smtp transport for delivering mail always set
18285 .option timeout_frozen_after main time 0s
18286 .cindex "frozen messages" "timing out"
18287 .cindex "timeout" "frozen messages"
18288 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
18289 message of any kind that has been in the queue for longer than the given time
18290 is automatically cancelled at the next queue run. If the frozen message is a
18291 bounce message, it is just discarded; otherwise, a bounce is sent to the
18292 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
18293 If you want to timeout frozen bounce messages earlier than other kinds of
18294 frozen message, see &%ignore_bounce_errors_after%&.
18296 &*Note:*& the default value of zero means no timeouts; with this setting,
18297 frozen messages remain in the queue forever (except for any frozen bounce
18298 messages that are released by &%ignore_bounce_errors_after%&).
18301 .option timezone main string unset
18302 .cindex "timezone, setting"
18303 .cindex "environment" "values from"
18304 The value of &%timezone%& is used to set the environment variable TZ while
18305 running Exim (if it is different on entry). This ensures that all timestamps
18306 created by Exim are in the required timezone. If you want all your timestamps
18307 to be in UTC (aka GMT) you should set
18311 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
18312 or, if that is not set, from the value of the TZ environment variable when Exim
18313 is built. If &%timezone%& is set to the empty string, either at build or run
18314 time, any existing TZ variable is removed from the environment when Exim
18315 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
18316 unfortunately not all, operating systems.
18319 .option tls_advertise_hosts main "host list&!!" *
18320 .cindex "TLS" "advertising"
18321 .cindex "encryption" "on SMTP connection"
18322 .cindex "SMTP" "encrypted connection"
18323 .cindex "ESMTP extensions" STARTTLS
18324 When Exim is built with support for TLS encrypted connections, the availability
18325 of the STARTTLS command to set up an encrypted session is advertised in
18326 response to EHLO only to those client hosts that match this option. See
18327 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
18328 Note that the default value requires that a certificate be supplied
18329 using the &%tls_certificate%& option. If TLS support for incoming connections
18330 is not required the &%tls_advertise_hosts%& option should be set empty.
18333 .option tls_alpn main "string list&!!" "smtp : esmtp"
18334 .cindex TLS "Application Layer Protocol Names"
18336 .cindex ALPN "set acceptable names for server"
18337 If this option is set,
18338 the TLS library supports ALPN,
18339 and the client offers either more than
18340 ALPN name or a name which does not match the list,
18341 the TLS connection is declined.
18344 .option tls_certificate main "string list&!!" unset
18345 .cindex "TLS" "server certificate; location of"
18346 .cindex "certificate" "server, location of"
18347 The value of this option is expanded, and must then be a list of absolute paths to
18348 files which contain the server's certificates (in PEM format).
18349 Commonly only one file is needed.
18350 The server's private key is also
18351 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
18352 &<<CHAPTLS>>& for further details.
18354 &*Note*&: The certificates defined by this option are used only when Exim is
18355 receiving incoming messages as a server. If you want to supply certificates for
18356 use when sending messages as a client, you must set the &%tls_certificate%&
18357 option in the relevant &(smtp)& transport.
18359 &*Note*&: If you use filenames based on IP addresses, change the list
18360 separator in the usual way (&<<SECTlistsepchange>>&) to avoid confusion under IPv6.
18362 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
18363 when a list of more than one
18364 file is used, the &$tls_in_ourcert$& variable is unreliable.
18365 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
18367 .cindex SNI "selecting server certificate based on"
18368 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
18369 if the OpenSSL build supports TLS extensions and the TLS client sends the
18370 Server Name Indication extension, then this option and others documented in
18371 &<<SECTtlssni>>& will be re-expanded.
18373 If this option is unset or empty a self-signed certificate will be
18375 Under Linux this is generated at daemon startup; on other platforms it will be
18376 generated fresh for every connection.
18378 .option tls_crl main string&!! unset
18379 .cindex "TLS" "server certificate revocation list"
18380 .cindex "certificate" "revocation list for server"
18381 This option specifies a certificate revocation list. The expanded value must
18382 be the name of a file that contains CRLs in PEM format.
18384 Under OpenSSL the option can specify a directory with CRL files.
18386 &*Note:*& Under OpenSSL the option must, if given, supply a CRL
18387 for each signing element of the certificate chain (i.e. all but the leaf).
18388 For the file variant this can be multiple PEM blocks in the one file.
18390 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18393 .option tls_dh_max_bits main integer 2236
18394 .cindex "TLS" "D-H bit count"
18395 The number of bits used for Diffie-Hellman key-exchange may be suggested by
18396 the chosen TLS library. That value might prove to be too high for
18397 interoperability. This option provides a maximum clamp on the value
18398 suggested, trading off security for interoperability.
18400 The value must be at least 1024.
18402 The value 2236 was chosen because, at time of adding the option, it was the
18403 hard-coded maximum value supported by the NSS cryptographic library, as used
18404 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
18406 If you prefer more security and are willing to break some clients, raise this
18409 Note that the value passed to GnuTLS for *generating* a new prime may be a
18410 little less than this figure, because GnuTLS is inexact and may produce a
18411 larger prime than requested.
18414 .option tls_dhparam main string&!! unset
18415 .cindex "TLS" "D-H parameters for server"
18416 The value of this option is expanded and indicates the source of DH parameters
18417 to be used by Exim.
18419 &*Note: The Exim Maintainers strongly recommend using a filename with site-generated
18420 local DH parameters*&, which has been supported across all versions of Exim. The
18421 other specific constants available are a fallback so that even when
18422 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
18424 If &%tls_dhparam%& is a filename starting with a &`/`&,
18425 then it names a file from which DH
18426 parameters should be loaded. If the file exists, it should hold a PEM-encoded
18427 PKCS#3 representation of the DH prime. If the file does not exist, for
18428 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
18429 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
18430 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
18431 and treated as though the &%tls_dhparam%& were set to "none".
18433 If this option expands to the string "none", then no DH parameters will be
18436 If this option expands to the string "historic" and Exim is using GnuTLS, then
18437 Exim will attempt to load a file from inside the spool directory. If the file
18438 does not exist, Exim will attempt to create it.
18439 See section &<<SECTgnutlsparam>>& for further details.
18441 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
18442 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
18444 In older versions of Exim the default was the 2048 bit prime described in section
18445 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
18446 in IKE is assigned number 23.
18448 Otherwise, the option must expand to the name used by Exim for any of a number
18449 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
18450 sources. As names, Exim uses a standard specified name, else "ike" followed by
18451 the number used by IKE, or "default" which corresponds to
18452 &`exim.dev.20160529.3`&.
18454 The available standard primes are:
18455 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
18456 &`ike1`&, &`ike2`&, &`ike5`&,
18457 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
18458 &`ike22`&, &`ike23`& and &`ike24`&.
18460 The available additional primes are:
18461 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
18463 Some of these will be too small to be accepted by clients.
18464 Some may be too large to be accepted by clients.
18465 The open cryptographic community has suspicions about the integrity of some
18466 of the later IKE values, which led into RFC7919 providing new fixed constants
18467 (the "ffdhe" identifiers).
18469 At this point, all of the "ike" values should be considered obsolete;
18470 they are still in Exim to avoid breaking unusual configurations, but are
18471 candidates for removal the next time we have backwards-incompatible changes.
18472 Two of them in particular (&`ike1`& and &`ike22`&) are called out by RFC 8247
18473 as MUST NOT use for IPSEC, and two more (&`ike23`& and &`ike24`&) as
18475 Because of this, Exim regards them as deprecated; if either of the first pair
18476 are used, warnings will be logged in the paniclog, and if any are used then
18477 warnings will be logged in the mainlog.
18478 All four will be removed in a future Exim release.
18480 The TLS protocol does not negotiate an acceptable size for this; clients tend
18481 to hard-drop connections if what is offered by the server is unacceptable,
18482 whether too large or too small, and there's no provision for the client to
18483 tell the server what these constraints are. Thus, as a server operator, you
18484 need to make an educated guess as to what is most likely to work for your
18487 Some known size constraints suggest that a bit-size in the range 2048 to 2236
18488 is most likely to maximise interoperability. The upper bound comes from
18489 applications using the Mozilla Network Security Services (NSS) library, which
18490 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
18491 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
18492 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
18493 acceptable bound from 1024 to 2048.
18496 .option tls_eccurve main string list&!! &`auto`&
18497 .cindex TLS "EC cryptography"
18498 This option selects EC curves for use by Exim when used with OpenSSL.
18499 It has no effect when Exim is used with GnuTLS
18500 (the equivalent can be done using a priority string for the
18501 &%tls_require_ciphers%& option).
18503 After expansion it must contain
18505 one or (only for OpenSSL versiona 1.1.1 onwards) more
18507 EC curve names, such as &`prime256v1`&, &`secp384r1`&, or &`P-521`&.
18508 Consult your OpenSSL manual for valid curve names.
18510 For OpenSSL versions before (and not including) 1.0.2, the string
18511 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
18512 &`auto`& tells the library to choose.
18515 If the option expands to an empty string, the effect is undefined.
18519 .option tls_ocsp_file main string&!! unset
18520 .cindex TLS "certificate status"
18521 .cindex TLS "OCSP proof file"
18523 must if set expand to the absolute path to a file which contains a current
18524 status proof for the server's certificate, as obtained from the
18525 Certificate Authority.
18527 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
18528 The macro "_HAVE_TLS_OCSP" will be defined for those versions.
18530 For OpenSSL 1.1.0 or later, and
18531 for GnuTLS 3.5.6 or later the expanded value of this option can be a list
18532 of files, to match a list given for the &%tls_certificate%& option.
18533 The ordering of the two lists must match.
18534 The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
18536 The file(s) should be in DER format,
18537 except for GnuTLS 3.6.3 or later
18539 when an optional filetype prefix can be used.
18540 The prefix must be one of "DER" or "PEM", followed by
18541 a single space. If one is used it sets the format for subsequent
18542 files in the list; the initial format is DER.
18543 If multiple proofs are wanted, for multiple chain elements
18544 (this only works under TLS1.3)
18545 they must be coded as a combined OCSP response.
18547 Although GnuTLS will accept PEM files with multiple separate
18548 PEM blobs (ie. separate OCSP responses), it sends them in the
18549 TLS Certificate record interleaved with the certificates of the chain;
18550 although a GnuTLS client is happy with that, an OpenSSL client is not.
18552 .option tls_on_connect_ports main "string list" unset
18555 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
18556 operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
18557 set up without waiting for the client to issue a STARTTLS command. For
18558 further details, see section &<<SECTsupobssmt>>&.
18562 .option tls_privatekey main "string list&!!" unset
18563 .cindex "TLS" "server private key; location of"
18564 The value of this option is expanded, and must then be a list of absolute paths to
18565 files which contains the server's private keys.
18566 If this option is unset, or if
18567 the expansion is forced to fail, or the result is an empty string, the private
18568 key is assumed to be in the same file as the server's certificates. See chapter
18569 &<<CHAPTLS>>& for further details.
18571 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18574 .option tls_remember_esmtp main boolean false
18575 .cindex "TLS" "esmtp state; remembering"
18576 .cindex "TLS" "broken clients"
18577 If this option is set true, Exim violates the RFCs by remembering that it is in
18578 &"esmtp"& state after successfully negotiating a TLS session. This provides
18579 support for broken clients that fail to send a new EHLO after starting a
18583 .option tls_require_ciphers main string&!! unset
18584 .cindex "TLS" "requiring specific ciphers"
18585 .cindex "cipher" "requiring specific"
18586 This option controls which ciphers can be used for incoming TLS connections.
18587 The &(smtp)& transport has an option of the same name for controlling outgoing
18588 connections. This option is expanded for each connection, so can be varied for
18589 different clients if required. The value of this option must be a list of
18590 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
18591 in somewhat different ways. If GnuTLS is being used, the client controls the
18592 preference order of the available ciphers. Details are given in sections
18593 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
18596 .option tls_resumption_hosts main "host list&!!" unset
18597 .cindex TLS resumption
18598 This option controls which connections to offer the TLS resumption feature.
18599 See &<<SECTresumption>>& for details.
18602 .option tls_try_verify_hosts main "host list&!!" unset
18603 .cindex "TLS" "client certificate verification"
18604 .cindex "certificate" "verification of client"
18605 See &%tls_verify_hosts%& below.
18608 .option tls_verify_certificates main string&!! system
18609 .cindex "TLS" "client certificate verification"
18610 .cindex "certificate" "verification of client"
18611 The value of this option is expanded, and must then be either the
18613 or the absolute path to
18614 a file or directory containing permitted certificates for clients that
18615 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
18617 The "system" value for the option will use a
18618 system default location compiled into the SSL library.
18619 This is not available for GnuTLS versions preceding 3.0.20,
18620 and will be taken as empty; an explicit location
18623 The use of a directory for the option value is not available for GnuTLS versions
18624 preceding 3.3.6 and a single file must be used.
18626 With OpenSSL the certificates specified
18628 either by file or directory
18629 are added to those given by the system default location.
18631 These certificates should be for the certificate authorities trusted, rather
18632 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
18633 the value is a file then the certificates are sent by Exim as a server to
18634 connecting clients, defining the list of accepted certificate authorities.
18635 Thus the values defined should be considered public data. To avoid this,
18636 use the explicit directory version. (If your peer is Exim up to 4.85,
18637 using GnuTLS, you may need to send the CAs (thus using the file
18638 variant). Otherwise the peer doesn't send its certificate.)
18640 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18642 A forced expansion failure or setting to an empty string is equivalent to
18646 .option tls_verify_hosts main "host list&!!" unset
18647 .cindex "TLS" "client certificate verification"
18648 .cindex "certificate" "verification of client"
18649 This option, along with &%tls_try_verify_hosts%&, controls the checking of
18650 certificates from clients. The expected certificates are defined by
18651 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
18652 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
18653 &%tls_verify_certificates%& is not set.
18655 Any client that matches &%tls_verify_hosts%& is constrained by
18656 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
18657 present one of the listed certificates. If it does not, the connection is
18659 &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
18660 the host to use TLS. It can still send SMTP commands through unencrypted
18661 connections. Forcing a client to use TLS has to be done separately using an
18662 ACL to reject inappropriate commands when the connection is not encrypted.
18664 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
18665 matches this option (but not &%tls_verify_hosts%&), Exim requests a
18666 certificate and checks it against &%tls_verify_certificates%&, but does not
18667 abort the connection if there is no certificate or if it does not match. This
18668 state can be detected in an ACL, which makes it possible to implement policies
18669 such as &"accept for relay only if a verified certificate has been received,
18670 but accept for local delivery if encrypted, even without a verified
18673 Client hosts that match neither of these lists are not asked to present
18677 .option trusted_groups main "string list&!!" unset
18678 .cindex "trusted groups"
18679 .cindex "groups" "trusted"
18680 This option is expanded just once, at the start of Exim's processing. If this
18681 option is set, any process that is running in one of the listed groups, or
18682 which has one of them as a supplementary group, is trusted. The groups can be
18683 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
18684 details of what trusted callers are permitted to do. If neither
18685 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
18688 .option trusted_users main "string list&!!" unset
18689 .cindex "trusted users"
18690 .cindex "user" "trusted"
18691 This option is expanded just once, at the start of Exim's processing. If this
18692 option is set, any process that is running as one of the listed users is
18693 trusted. The users can be specified numerically or by name. See section
18694 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
18695 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
18696 Exim user are trusted.
18698 .option unknown_login main string&!! unset
18699 .cindex "uid (user id)" "unknown caller"
18700 .vindex "&$caller_uid$&"
18701 This is a specialized feature for use in unusual configurations. By default, if
18702 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
18703 gives up. The &%unknown_login%& option can be used to set a login name to be
18704 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
18705 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
18706 is used for the user's real name (gecos field), unless this has been set by the
18709 .option unknown_username main string unset
18710 See &%unknown_login%&.
18712 .option untrusted_set_sender main "address list&!!" unset
18713 .cindex "trusted users"
18714 .cindex "sender" "setting by untrusted user"
18715 .cindex "untrusted user setting sender"
18716 .cindex "user" "untrusted setting sender"
18717 .cindex "envelope from"
18718 .cindex "envelope sender"
18719 When an untrusted user submits a message to Exim using the standard input, Exim
18720 normally creates an envelope sender address from the user's login and the
18721 default qualification domain. Data from the &%-f%& option (for setting envelope
18722 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
18723 is used) is ignored.
18725 However, untrusted users are permitted to set an empty envelope sender address,
18726 to declare that a message should never generate any bounces. For example:
18728 exim -f '<>' user@domain.example
18730 .vindex "&$sender_ident$&"
18731 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
18732 other envelope sender addresses in a controlled way. When it is set, untrusted
18733 users are allowed to set envelope sender addresses that match any of the
18734 patterns in the list. Like all address lists, the string is expanded. The
18735 identity of the user is in &$sender_ident$&, so you can, for example, restrict
18736 users to setting senders that start with their login ids
18737 followed by a hyphen
18738 by a setting like this:
18740 untrusted_set_sender = ^$sender_ident-
18742 If you want to allow untrusted users to set envelope sender addresses without
18743 restriction, you can use
18745 untrusted_set_sender = *
18747 The &%untrusted_set_sender%& option applies to all forms of local input, but
18748 only to the setting of the envelope sender. It does not permit untrusted users
18749 to use the other options which trusted user can use to override message
18750 parameters. Furthermore, it does not stop Exim from removing an existing
18751 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
18752 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
18753 overriding these actions. The handling of the &'Sender:'& header is also
18754 described in section &<<SECTthesenhea>>&.
18756 The log line for a message's arrival shows the envelope sender following
18757 &"<="&. For local messages, the user's login always follows, after &"U="&. In
18758 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
18759 envelope sender address, the user's login is shown in parentheses after the
18763 .option uucp_from_pattern main string "see below"
18764 .cindex "&""From""& line"
18765 .cindex "UUCP" "&""From""& line"
18766 Some applications that pass messages to an MTA via a command line interface use
18767 an initial line starting with &"From&~"& to pass the envelope sender. In
18768 particular, this is used by UUCP software. Exim recognizes such a line by means
18769 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
18770 matches, the sender address is constructed by expanding the contents of
18771 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
18772 default pattern recognizes lines in the following two forms:
18774 From ph10 Fri Jan 5 12:35 GMT 1996
18775 From ph10 Fri, 7 Jan 97 14:00:00 GMT
18777 The pattern can be seen by running
18779 exim -bP uucp_from_pattern
18781 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
18782 year in the second case. The first word after &"From&~"& is matched in the
18783 regular expression by a parenthesized subpattern. The default value for
18784 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
18785 (&"ph10"& in the example above) as the message's sender. See also
18786 &%ignore_fromline_hosts%&.
18789 .option uucp_from_sender main string&!! &`$1`&
18790 See &%uucp_from_pattern%& above.
18793 .option warn_message_file main string&!! unset
18794 .cindex "warning of delay" "customizing the message"
18795 .cindex "customizing" "warning message"
18796 This option defines a template file containing paragraphs of text to be used
18797 for constructing the warning message which is sent by Exim when a message has
18798 been in the queue for a specified amount of time, as specified by
18799 &%delay_warning%&. Details of the file's contents are given in chapter
18800 &<<CHAPemsgcust>>&.
18801 .cindex warn_message_file "tainted data"
18802 The option is expanded to give the file path, which must be
18803 absolute and untainted.
18804 See also &%bounce_message_file%&.
18807 .option write_rejectlog main boolean true
18808 .cindex "reject log" "disabling"
18809 If this option is set false, Exim no longer writes anything to the reject log.
18810 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
18811 .ecindex IIDconfima
18812 .ecindex IIDmaiconf
18817 . ////////////////////////////////////////////////////////////////////////////
18818 . ////////////////////////////////////////////////////////////////////////////
18820 .chapter "Generic options for routers" "CHAProutergeneric"
18821 .scindex IIDgenoprou1 "options" "generic; for routers"
18822 .scindex IIDgenoprou2 "generic options" "router"
18823 This chapter describes the generic options that apply to all routers.
18824 Those that are preconditions are marked with ‡ in the &"use"& field.
18826 For a general description of how a router operates, see sections
18827 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
18828 which the preconditions are tested. The order of expansion of the options that
18829 provide data for a transport is: &%errors_to%&, &%headers_add%&,
18830 &%headers_remove%&, &%transport%&.
18832 The name of a router is limited to be &drivernamemax; ASCII characters long;
18833 prior to Exim 4.95 names would be silently truncated at this length, but now
18837 .option address_data routers string&!! unset
18838 .cindex "router" "data attached to address"
18839 The string is expanded just before the router is run, that is, after all the
18840 precondition tests have succeeded. If the expansion is forced to fail, the
18841 router declines, the value of &%address_data%& remains unchanged, and the
18842 &%more%& option controls what happens next. Other expansion failures cause
18843 delivery of the address to be deferred.
18845 .vindex "&$address_data$&"
18846 When the expansion succeeds, the value is retained with the address, and can be
18847 accessed using the variable &$address_data$& in the current router, subsequent
18848 routers, and the eventual transport.
18850 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
18851 that runs a user's filter file, the contents of &$address_data$& are accessible
18852 in the filter. This is not normally a problem, because such data is usually
18853 either not confidential or it &"belongs"& to the current user, but if you do
18854 put confidential data into &$address_data$& you need to remember this point.
18856 Even if the router declines or passes, the value of &$address_data$& remains
18857 with the address, though it can be changed by another &%address_data%& setting
18858 on a subsequent router. If a router generates child addresses, the value of
18859 &$address_data$& propagates to them. This also applies to the special kind of
18860 &"child"& that is generated by a router with the &%unseen%& option.
18862 The idea of &%address_data%& is that you can use it to look up a lot of data
18863 for the address once, and then pick out parts of the data later. For example,
18864 you could use a single LDAP lookup to return a string of the form
18866 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
18868 In the transport you could pick out the mailbox by a setting such as
18870 file = ${extract{mailbox}{$address_data}}
18872 This makes the configuration file less messy, and also reduces the number of
18873 lookups (though Exim does cache lookups).
18875 See also the &%set%& option below.
18877 .vindex "&$sender_address_data$&"
18878 .vindex "&$address_data$&"
18879 The &%address_data%& facility is also useful as a means of passing information
18880 from one router to another, and from a router to a transport. In addition, if
18881 &$address_data$& is set by a router when verifying a recipient address from an
18882 ACL, it remains available for use in the rest of the ACL statement. After
18883 verifying a sender, the value is transferred to &$sender_address_data$&.
18887 .option address_test routers&!? boolean true
18889 .cindex "router" "skipping when address testing"
18890 If this option is set false, the router is skipped when routing is being tested
18891 by means of the &%-bt%& command line option. This can be a convenience when
18892 your first router sends messages to an external scanner, because it saves you
18893 having to set the &"already scanned"& indicator when testing real address
18898 .option cannot_route_message routers string&!! unset
18899 .cindex "router" "customizing &""cannot route""& message"
18900 .cindex "customizing" "&""cannot route""& message"
18901 This option specifies a text message that is used when an address cannot be
18902 routed because Exim has run out of routers. The default message is
18903 &"Unrouteable address"&. This option is useful only on routers that have
18904 &%more%& set false, or on the very last router in a configuration, because the
18905 value that is used is taken from the last router that is considered. This
18906 includes a router that is skipped because its preconditions are not met, as
18907 well as a router that declines. For example, using the default configuration,
18910 cannot_route_message = Remote domain not found in DNS
18912 on the first router, which is a &(dnslookup)& router with &%more%& set false,
18915 cannot_route_message = Unknown local user
18917 on the final router that checks for local users. If string expansion fails for
18918 this option, the default message is used. Unless the expansion failure was
18919 explicitly forced, a message about the failure is written to the main and panic
18920 logs, in addition to the normal message about the routing failure.
18923 .option caseful_local_part routers boolean false
18924 .cindex "case of local parts"
18925 .cindex "router" "case of local parts"
18926 By default, routers handle the local parts of addresses in a case-insensitive
18927 manner, though the actual case is preserved for transmission with the message.
18928 If you want the case of letters to be significant in a router, you must set
18929 this option true. For individual router options that contain address or local
18930 part lists (for example, &%local_parts%&), case-sensitive matching can be
18931 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
18934 .vindex "&$local_part$&"
18935 .vindex "&$original_local_part$&"
18936 .vindex "&$parent_local_part$&"
18937 The value of the &$local_part$& variable is forced to lower case while a
18938 router is running unless &%caseful_local_part%& is set. When a router assigns
18939 an address to a transport, the value of &$local_part$& when the transport runs
18940 is the same as it was in the router. Similarly, when a router generates child
18941 addresses by aliasing or forwarding, the values of &$original_local_part$&
18942 and &$parent_local_part$& are those that were used by the redirecting router.
18944 This option applies to the processing of an address by a router. When a
18945 recipient address is being processed in an ACL, there is a separate &%control%&
18946 modifier that can be used to specify case-sensitive processing within the ACL
18947 (see section &<<SECTcontrols>>&).
18951 .option check_local_user routers&!? boolean false
18952 .cindex "local user, checking in router"
18953 .cindex "router" "checking for local user"
18954 .cindex "&_/etc/passwd_&"
18956 When this option is true, Exim checks that the local part of the recipient
18957 address (with affixes removed if relevant) is the name of an account on the
18958 local system. The check is done by calling the &[getpwnam()]& function rather
18959 than trying to read &_/etc/passwd_& directly. This means that other methods of
18960 holding password data (such as NIS) are supported. If the local part is a local
18962 .cindex "tainted data" "de-tainting"
18963 .cindex "de-tainting" "using router check_local_user option"
18964 &$local_part_data$& is set to an untainted version of the local part and
18965 &$home$& is set from the password data. The latter can be tested in other
18966 preconditions that are evaluated after this one (the order of evaluation is
18967 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
18968 overridden by &%router_home_directory%&. If the local part is not a local user,
18969 the router is skipped.
18971 If you want to check that the local part is either the name of a local user
18972 or matches something else, you cannot combine &%check_local_user%& with a
18973 setting of &%local_parts%&, because that specifies the logical &'and'& of the
18974 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
18975 setting to achieve this. For example:
18977 local_parts = passwd;$local_part : lsearch;/etc/other/users
18979 Note, however, that the side effects of &%check_local_user%& (such as setting
18980 up a home directory) do not occur when a &(passwd)& lookup is used in a
18981 &%local_parts%& (or any other) precondition.
18985 .option condition routers&!? string&!! unset
18986 .cindex "router" "customized precondition"
18987 This option specifies a general precondition test that has to succeed for the
18988 router to be called. The &%condition%& option is the last precondition to be
18989 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
18990 result is a forced failure, or an empty string, or one of the strings &"0"& or
18991 &"no"& or &"false"& (checked without regard to the case of the letters), the
18992 router is skipped, and the address is offered to the next one.
18994 If the result is any other value, the router is run (as this is the last
18995 precondition to be evaluated, all the other preconditions must be true).
18997 This option is unusual in that multiple &%condition%& options may be present.
18998 All &%condition%& options must succeed.
19000 The &%condition%& option provides a means of applying custom conditions to the
19001 running of routers. Note that in the case of a simple conditional expansion,
19002 the default expansion values are exactly what is wanted. For example:
19004 condition = ${if >{$message_age}{600}}
19006 Because of the default behaviour of the string expansion, this is equivalent to
19008 condition = ${if >{$message_age}{600}{true}{}}
19011 A multiple condition example, which succeeds:
19013 condition = ${if >{$message_age}{600}}
19014 condition = ${if !eq{${lc:$local_part}}{postmaster}}
19018 If the expansion fails (other than forced failure) delivery is deferred. Some
19019 of the other precondition options are common special cases that could in fact
19020 be specified using &%condition%&.
19022 Historical note: We have &%condition%& on ACLs and on Routers. Routers
19023 are far older, and use one set of semantics. ACLs are newer and when
19024 they were created, the ACL &%condition%& process was given far stricter
19025 parse semantics. The &%bool{}%& expansion condition uses the same rules as
19026 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
19027 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
19028 Router rules processing behavior.
19030 This is best illustrated in an example:
19032 # If used in an ACL condition will fail with a syntax error, but
19033 # in a router condition any extra characters are treated as a string
19035 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
19038 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
19041 In each example above, the &%if%& statement actually ends after
19042 &"{google.com}}"&. Since no true or false braces were defined, the
19043 default &%if%& behavior is to return a boolean true or a null answer
19044 (which evaluates to false). The rest of the line is then treated as a
19045 string. So the first example resulted in the boolean answer &"true"&
19046 with the string &" {yes} {no}}"& appended to it. The second example
19047 resulted in the null output (indicating false) with the string
19048 &" {yes} {no}}"& appended to it.
19050 In fact you can put excess forward braces in too. In the router
19051 &%condition%&, Exim's parser only looks for &"{"& symbols when they
19052 mean something, like after a &"$"& or when required as part of a
19053 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
19056 Thus, in a Router, the above expansion strings will both always evaluate
19057 true, as the result of expansion is a non-empty string which doesn't
19058 match an explicit false value. This can be tricky to debug. By
19059 contrast, in an ACL either of those strings will always result in an
19060 expansion error because the result doesn't look sufficiently boolean.
19063 .option debug_print routers string&!! unset
19064 .cindex "testing" "variables in drivers"
19065 If this option is set and debugging is enabled (see the &%-d%& command line
19066 option) or in address-testing mode (see the &%-bt%& command line option),
19067 the string is expanded and included in the debugging output.
19068 If expansion of the string fails, the error message is written to the debugging
19069 output, and Exim carries on processing.
19070 This option is provided to help with checking out the values of variables and
19071 so on when debugging router configurations. For example, if a &%condition%&
19072 option appears not to be working, &%debug_print%& can be used to output the
19073 variables it references. The output happens after checks for &%domains%&,
19074 &%local_parts%&, and &%check_local_user%& but before any other preconditions
19075 are tested. A newline is added to the text if it does not end with one.
19076 The variable &$router_name$& contains the name of the router.
19080 .option disable_logging routers boolean false
19081 If this option is set true, nothing is logged for any routing errors
19082 or for any deliveries caused by this router. You should not set this option
19083 unless you really, really know what you are doing. See also the generic
19084 transport option of the same name.
19086 .option dnssec_request_domains routers "domain list&!!" *
19087 .cindex "MX record" "security"
19088 .cindex "DNSSEC" "MX lookup"
19089 .cindex "security" "MX lookup"
19090 .cindex "DNS" "DNSSEC"
19091 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
19092 the DNSSEC request bit set.
19093 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19095 .option dnssec_require_domains routers "domain list&!!" unset
19096 .cindex "MX record" "security"
19097 .cindex "DNSSEC" "MX lookup"
19098 .cindex "security" "MX lookup"
19099 .cindex "DNS" "DNSSEC"
19100 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
19101 the DNSSEC request bit set. Any returns not having the Authenticated Data bit
19102 (AD bit) set will be ignored and logged as a host-lookup failure.
19103 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19106 .option domains routers&!? "domain list&!!" unset
19107 .cindex "router" "restricting to specific domains"
19108 .vindex "&$domain_data$&"
19109 If this option is set, the router is skipped unless the current domain matches
19110 the list. If the match is achieved by means of a file lookup, the data that the
19111 lookup returned for the domain is placed in &$domain_data$& for use in string
19112 expansions of the driver's private options and in the transport.
19113 See section &<<SECTrouprecon>>& for
19114 a list of the order in which preconditions are evaluated.
19118 .option driver routers string unset
19119 This option must always be set. It specifies which of the available routers is
19123 .option dsn_lasthop routers boolean false
19124 .cindex "DSN" "success"
19125 .cindex "Delivery Status Notification" "success"
19126 If this option is set true, and extended DSN (RFC3461) processing is in effect,
19127 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
19128 instead send a success DSN as if the next hop does not support DSN.
19129 Not effective on redirect routers.
19133 .option errors_to routers string&!! unset
19134 .cindex "envelope from"
19135 .cindex "envelope sender"
19136 .cindex "router" "changing address for errors"
19137 If a router successfully handles an address, it may assign the address to a
19138 transport for delivery or it may generate child addresses. In both cases, if
19139 there is a delivery problem during later processing, the resulting bounce
19140 message is sent to the address that results from expanding this string,
19141 provided that the address verifies successfully. The &%errors_to%& option is
19142 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
19144 The &%errors_to%& setting associated with an address can be overridden if it
19145 subsequently passes through other routers that have their own &%errors_to%&
19146 settings, or if the message is delivered by a transport with a &%return_path%&
19149 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
19150 the expansion fails to verify, the errors address associated with the incoming
19151 address is used. At top level, this is the envelope sender. A non-forced
19152 expansion failure causes delivery to be deferred.
19154 If an address for which &%errors_to%& has been set ends up being delivered over
19155 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
19156 any bounces that are generated by other MTAs on the delivery route are also
19157 sent there. You can set &%errors_to%& to the empty string by either of these
19163 An expansion item that yields an empty string has the same effect. If you do
19164 this, a locally detected delivery error for addresses processed by this router
19165 no longer gives rise to a bounce message; the error is discarded. If the
19166 address is delivered to a remote host, the return path is set to &`<>`&, unless
19167 overridden by the &%return_path%& option on the transport.
19169 .vindex "&$address_data$&"
19170 If for some reason you want to discard local errors, but use a non-empty
19171 MAIL command for remote delivery, you can preserve the original return
19172 path in &$address_data$& in the router, and reinstate it in the transport by
19173 setting &%return_path%&.
19175 The most common use of &%errors_to%& is to direct mailing list bounces to the
19176 manager of the list, as described in section &<<SECTmailinglists>>&, or to
19177 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
19181 .option expn routers&!? boolean true
19182 .cindex "address" "testing"
19183 .cindex "testing" "addresses"
19184 .cindex "EXPN" "router skipping"
19185 .cindex "router" "skipping for EXPN"
19186 If this option is turned off, the router is skipped when testing an address
19187 as a result of processing an SMTP EXPN command. You might, for example,
19188 want to turn it off on a router for users' &_.forward_& files, while leaving it
19189 on for the system alias file.
19190 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19193 The use of the SMTP EXPN command is controlled by an ACL (see chapter
19194 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
19195 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
19199 .option fail_verify routers boolean false
19200 .cindex "router" "forcing verification failure"
19201 Setting this option has the effect of setting both &%fail_verify_sender%& and
19202 &%fail_verify_recipient%& to the same value.
19206 .option fail_verify_recipient routers boolean false
19207 If this option is true and an address is accepted by this router when
19208 verifying a recipient, verification fails.
19212 .option fail_verify_sender routers boolean false
19213 If this option is true and an address is accepted by this router when
19214 verifying a sender, verification fails.
19218 .option fallback_hosts routers "string list" unset
19219 .cindex "router" "fallback hosts"
19220 .cindex "fallback" "hosts specified on router"
19221 String expansion is not applied to this option. The argument must be a
19222 colon-separated list of host names or IP addresses. The list separator can be
19223 changed (see section &<<SECTlistsepchange>>&), and a port can be specified with
19224 each name or address. In fact, the format of each item is exactly the same as
19225 defined for the list of hosts in a &(manualroute)& router (see section
19226 &<<SECTformatonehostitem>>&).
19228 If a router queues an address for a remote transport, this host list is
19229 associated with the address, and used instead of the transport's fallback host
19230 list. If &%hosts_randomize%& is set on the transport, the order of the list is
19231 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
19232 transport for further details.
19235 .option group routers string&!! "see below"
19236 .cindex "gid (group id)" "local delivery"
19237 .cindex "local transports" "uid and gid"
19238 .cindex "transport" "local"
19239 .cindex "router" "setting group"
19240 When a router queues an address for a transport, and the transport does not
19241 specify a group, the group given here is used when running the delivery
19243 The group may be specified numerically or by name. If expansion fails, the
19244 error is logged and delivery is deferred.
19245 The default is unset, unless &%check_local_user%& is set, when the default
19246 is taken from the password information. See also &%initgroups%& and &%user%&
19247 and the discussion in chapter &<<CHAPenvironment>>&.
19251 .option headers_add routers list&!! unset
19252 .cindex "header lines" "adding"
19253 .cindex "router" "adding header lines"
19254 This option specifies a list of text headers,
19255 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19256 that is associated with any addresses that are accepted by the router.
19257 Each item is separately expanded, at routing time. However, this
19258 option has no effect when an address is just being verified. The way in which
19259 the text is used to add header lines at transport time is described in section
19260 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
19261 message is in the process of being transported. This means that references to
19262 header lines in string expansions in the transport's configuration do not
19263 &"see"& the added header lines.
19265 The &%headers_add%& option is expanded after &%errors_to%&, but before
19266 &%headers_remove%& and &%transport%&. If an item is empty, or if
19267 an item expansion is forced to fail, the item has no effect. Other expansion
19268 failures are treated as configuration errors.
19270 Unlike most options, &%headers_add%& can be specified multiple times
19271 for a router; all listed headers are added.
19273 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
19274 router that has the &%one_time%& option set.
19276 .cindex "duplicate addresses"
19277 .oindex "&%unseen%&"
19278 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19279 additions are deleted when the address is passed on to subsequent routers.
19280 For a &%redirect%& router, if a generated address is the same as the incoming
19281 address, this can lead to duplicate addresses with different header
19282 modifications. Exim does not do duplicate deliveries (except, in certain
19283 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
19284 which of the duplicates is discarded, so this ambiguous situation should be
19285 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
19289 .option headers_remove routers list&!! unset
19290 .cindex "header lines" "removing"
19291 .cindex "router" "removing header lines"
19292 This option specifies a list of text headers,
19293 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19294 that is associated with any addresses that are accepted by the router.
19295 However, the option has no effect when an address is just being verified.
19296 Each list item is separately expanded, at transport time.
19297 If an item ends in *, it will match any header with the given prefix.
19299 the text is used to remove header lines at transport time is described in
19300 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
19301 the message is in the process of being transported. This means that references
19302 to header lines in string expansions in the transport's configuration still
19303 &"see"& the original header lines.
19305 The &%headers_remove%& option is handled after &%errors_to%& and
19306 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
19307 the item has no effect. Other expansion failures are treated as configuration
19310 Unlike most options, &%headers_remove%& can be specified multiple times
19311 for a router; all listed headers are removed.
19313 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
19314 router that has the &%one_time%& option set.
19316 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19317 removal requests are deleted when the address is passed on to subsequent
19318 routers, and this can lead to problems with duplicates -- see the similar
19319 warning for &%headers_add%& above.
19321 &*Warning 3*&: Because of the separate expansion of the list items,
19322 items that contain a list separator must have it doubled.
19323 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
19327 .option ignore_target_hosts routers "host list&!!" unset
19328 .cindex "IP address" "discarding"
19329 .cindex "router" "discarding IP addresses"
19330 Although this option is a host list, it should normally contain IP address
19331 entries rather than names. If any host that is looked up by the router has an
19332 IP address that matches an item in this list, Exim behaves as if that IP
19333 address did not exist. This option allows you to cope with rogue DNS entries
19336 remote.domain.example. A 127.0.0.1
19340 ignore_target_hosts = 127.0.0.1
19342 on the relevant router. If all the hosts found by a &(dnslookup)& router are
19343 discarded in this way, the router declines. In a conventional configuration, an
19344 attempt to mail to such a domain would normally provoke the &"unrouteable
19345 domain"& error, and an attempt to verify an address in the domain would fail.
19346 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
19347 router declines if presented with one of the listed addresses.
19349 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
19350 means of the first or the second of the following settings, respectively:
19352 ignore_target_hosts = 0.0.0.0/0
19353 ignore_target_hosts = <; 0::0/0
19355 The pattern in the first line matches all IPv4 addresses, whereas the pattern
19356 in the second line matches all IPv6 addresses.
19358 This option may also be useful for ignoring link-local and site-local IPv6
19359 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
19360 is expanded before use as a list, it is possible to make it dependent on the
19361 domain that is being routed.
19363 .vindex "&$host_address$&"
19364 During its expansion, &$host_address$& is set to the IP address that is being
19367 .option initgroups routers boolean false
19368 .cindex "additional groups"
19369 .cindex "groups" "additional"
19370 .cindex "local transports" "uid and gid"
19371 .cindex "transport" "local"
19372 If the router queues an address for a transport, and this option is true, and
19373 the uid supplied by the router is not overridden by the transport, the
19374 &[initgroups()]& function is called when running the transport to ensure that
19375 any additional groups associated with the uid are set up. See also &%group%&
19376 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
19380 .option local_part_prefix routers&!? "string list" unset
19381 .cindex affix "router precondition"
19382 .cindex "router" "prefix for local part"
19383 .cindex "prefix" "for local part, used in router"
19384 If this option is set, the router is skipped unless the local part starts with
19385 one of the given strings, or &%local_part_prefix_optional%& is true. See
19386 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
19389 The list is scanned from left to right, and the first prefix that matches is
19390 used. A limited form of wildcard is available; if the prefix begins with an
19391 asterisk, it matches the longest possible sequence of arbitrary characters at
19392 the start of the local part. An asterisk should therefore always be followed by
19393 some character that does not occur in normal local parts.
19394 .cindex "multiple mailboxes"
19395 .cindex "mailbox" "multiple"
19396 Wildcarding can be used to set up multiple user mailboxes, as described in
19397 section &<<SECTmulbox>>&.
19399 .vindex "&$local_part$&"
19400 .vindex "&$local_part_prefix$&"
19401 During the testing of the &%local_parts%& option, and while the router is
19402 running, the prefix is removed from the local part, and is available in the
19403 expansion variable &$local_part_prefix$&. When a message is being delivered, if
19404 the router accepts the address, this remains true during subsequent delivery by
19405 a transport. In particular, the local part that is transmitted in the RCPT
19406 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
19407 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
19408 the relevant transport.
19410 .vindex &$local_part_prefix_v$&
19411 If wildcarding (above) was used then the part of the prefix matching the
19412 wildcard is available in &$local_part_prefix_v$&.
19414 When an address is being verified, &%local_part_prefix%& affects only the
19415 behaviour of the router. If the callout feature of verification is in use, this
19416 means that the full address, including the prefix, will be used during the
19419 The prefix facility is commonly used to handle local parts of the form
19420 &%owner-something%&. Another common use is to support local parts of the form
19421 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
19422 to tell a user their forwarding is broken &-- by placing a router like this one
19423 immediately before the router that handles &_.forward_& files:
19427 local_part_prefix = real-
19429 transport = local_delivery
19431 For security, it would probably be a good idea to restrict the use of this
19432 router to locally-generated messages, using a condition such as this:
19434 condition = ${if match {$sender_host_address}\
19435 {\N^(|127\.0\.0\.1)$\N}}
19438 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
19439 both conditions must be met if not optional. Care must be taken if wildcards
19440 are used in both a prefix and a suffix on the same router. Different
19441 separator characters must be used to avoid ambiguity.
19444 .option local_part_prefix_optional routers boolean false
19445 See &%local_part_prefix%& above.
19449 .option local_part_suffix routers&!? "string list" unset
19450 .cindex "router" "suffix for local part"
19451 .cindex "suffix for local part" "used in router"
19452 This option operates in the same way as &%local_part_prefix%&, except that the
19453 local part must end (rather than start) with the given string, the
19454 &%local_part_suffix_optional%& option determines whether the suffix is
19455 mandatory, and the wildcard * character, if present, must be the last
19456 character of the suffix. This option facility is commonly used to handle local
19457 parts of the form &%something-request%& and multiple user mailboxes of the form
19461 .option local_part_suffix_optional routers boolean false
19462 See &%local_part_suffix%& above.
19466 .option local_parts routers&!? "local part list&!!" unset
19467 .cindex "router" "restricting to specific local parts"
19468 .cindex "local part" "checking in router"
19469 The router is run only if the local part of the address matches the list.
19470 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19472 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
19473 string is expanded, it is possible to make it depend on the domain, for
19476 local_parts = dbm;/usr/local/specials/$domain_data
19478 .vindex "&$local_part_data$&"
19479 If the match is achieved by a lookup, the data that the lookup returned
19480 for the local part is placed in the variable &$local_part_data$& for use in
19481 expansions of the router's private options or in the transport.
19482 You might use this option, for
19483 example, if you have a large number of local virtual domains, and you want to
19484 send all postmaster mail to the same place without having to set up an alias in
19485 each virtual domain:
19489 local_parts = postmaster
19490 data = postmaster@real.domain.example
19494 .option log_as_local routers boolean "see below"
19495 .cindex "log" "delivery line"
19496 .cindex "delivery" "log line format"
19497 Exim has two logging styles for delivery, the idea being to make local
19498 deliveries stand out more visibly from remote ones. In the &"local"& style, the
19499 recipient address is given just as the local part, without a domain. The use of
19500 this style is controlled by this option. It defaults to true for the &(accept)&
19501 router, and false for all the others. This option applies only when a
19502 router assigns an address to a transport. It has no effect on routers that
19503 redirect addresses.
19507 .option more routers boolean&!! true
19508 The result of string expansion for this option must be a valid boolean value,
19509 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19510 result causes an error, and delivery is deferred. If the expansion is forced to
19511 fail, the default value for the option (true) is used. Other failures cause
19512 delivery to be deferred.
19514 If this option is set false, and the router declines to handle the address, no
19515 further routers are tried, routing fails, and the address is bounced.
19517 However, if the router explicitly passes an address to the following router by
19518 means of the setting
19522 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
19523 does not affect the behaviour if one of the precondition tests fails. In that
19524 case, the address is always passed to the next router.
19526 Note that &%address_data%& is not considered to be a precondition. If its
19527 expansion is forced to fail, the router declines, and the value of &%more%&
19528 controls what happens next.
19531 .option pass_on_timeout routers boolean false
19532 .cindex "timeout" "of router"
19533 .cindex "router" "timeout"
19534 If a router times out during a host lookup, it normally causes deferral of the
19535 address. If &%pass_on_timeout%& is set, the address is passed on to the next
19536 router, overriding &%no_more%&. This may be helpful for systems that are
19537 intermittently connected to the Internet, or those that want to pass to a smart
19538 host any messages that cannot immediately be delivered.
19540 There are occasional other temporary errors that can occur while doing DNS
19541 lookups. They are treated in the same way as a timeout, and this option
19542 applies to all of them.
19546 .option pass_router routers string unset
19547 .cindex "router" "go to after &""pass""&"
19548 Routers that recognize the generic &%self%& option (&(dnslookup)&,
19549 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
19550 routing to continue, and overriding a false setting of &%more%&. When one of
19551 these routers returns &"pass"&, the address is normally handed on to the next
19552 router in sequence. This can be changed by setting &%pass_router%& to the name
19553 of another router. However (unlike &%redirect_router%&) the named router must
19554 be below the current router, to avoid loops. Note that this option applies only
19555 to the special case of &"pass"&. It does not apply when a router returns
19556 &"decline"& because it cannot handle an address.
19560 .option redirect_router routers string unset
19561 .cindex "router" "start at after redirection"
19562 Sometimes an administrator knows that it is pointless to reprocess addresses
19563 generated from alias or forward files with the same router again. For
19564 example, if an alias file translates real names into login ids there is no
19565 point searching the alias file a second time, especially if it is a large file.
19567 The &%redirect_router%& option can be set to the name of any router instance.
19568 It causes the routing of any generated addresses to start at the named router
19569 instead of at the first router. This option has no effect if the router in
19570 which it is set does not generate new addresses.
19574 .option require_files routers&!? "string list&!!" unset
19575 .cindex "file" "requiring for router"
19576 .cindex "router" "requiring file existence"
19577 This option provides a general mechanism for predicating the running of a
19578 router on the existence or non-existence of certain files or directories.
19579 Before running a router, as one of its precondition tests, Exim works its way
19580 through the &%require_files%& list, expanding each item separately.
19582 Because the list is split before expansion, any colons in expansion items must
19583 be doubled, or the facility for using a different list separator must be used
19584 (&<<SECTlistsepchange>>&).
19585 If any expansion is forced to fail, the item is ignored. Other expansion
19586 failures cause routing of the address to be deferred.
19588 If any expanded string is empty, it is ignored. Otherwise, except as described
19589 below, each string must be a fully qualified file path, optionally preceded by
19590 &"!"&. The paths are passed to the &[stat()]& function to test for the
19591 existence of the files or directories. The router is skipped if any paths not
19592 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
19595 If &[stat()]& cannot determine whether a file exists or not, delivery of
19596 the message is deferred. This can happen when NFS-mounted filesystems are
19599 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
19600 options, so you cannot use it to check for the existence of a file in which to
19601 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
19602 full list of the order in which preconditions are evaluated.) However, as
19603 these options are all expanded, you can use the &%exists%& expansion condition
19604 to make such tests. The &%require_files%& option is intended for checking files
19605 that the router may be going to use internally, or which are needed by a
19606 transport (e.g., &_.procmailrc_&).
19608 During delivery, the &[stat()]& function is run as root, but there is a
19609 facility for some checking of the accessibility of a file by another user.
19610 This is not a proper permissions check, but just a &"rough"& check that
19611 operates as follows:
19613 If an item in a &%require_files%& list does not contain any forward slash
19614 characters, it is taken to be the user (and optional group, separated by a
19615 comma) to be checked for subsequent files in the list. If no group is specified
19616 but the user is specified symbolically, the gid associated with the uid is
19619 require_files = mail:/some/file
19620 require_files = $local_part_data:$home/.procmailrc
19622 If a user or group name in a &%require_files%& list does not exist, the
19623 &%require_files%& condition fails.
19625 Exim performs the check by scanning along the components of the file path, and
19626 checking the access for the given uid and gid. It checks for &"x"& access on
19627 directories, and &"r"& access on the final file. Note that this means that file
19628 access control lists, if the operating system has them, are ignored.
19630 &*Warning 1*&: When the router is being run to verify addresses for an
19631 incoming SMTP message, Exim is not running as root, but under its own uid. This
19632 may affect the result of a &%require_files%& check. In particular, &[stat()]&
19633 may yield the error EACCES (&"Permission denied"&). This means that the Exim
19634 user is not permitted to read one of the directories on the file's path.
19636 &*Warning 2*&: Even when Exim is running as root while delivering a message,
19637 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
19638 without root access. In this case, if a check for access by a particular user
19639 is requested, Exim creates a subprocess that runs as that user, and tries the
19640 check again in that process.
19642 The default action for handling an unresolved EACCES is to consider it to
19643 be caused by a configuration error, and routing is deferred because the
19644 existence or non-existence of the file cannot be determined. However, in some
19645 circumstances it may be desirable to treat this condition as if the file did
19646 not exist. If the filename (or the exclamation mark that precedes the filename
19647 for non-existence) is preceded by a plus sign, the EACCES error is treated
19648 as if the file did not exist. For example:
19650 require_files = +/some/file
19652 If the router is not an essential part of verification (for example, it
19653 handles users' &_.forward_& files), another solution is to set the &%verify%&
19654 option false so that the router is skipped when verifying.
19658 .option retry_use_local_part routers boolean "see below"
19659 .cindex "hints database" "retry keys"
19660 .cindex "local part" "in retry keys"
19661 When a delivery suffers a temporary routing failure, a retry record is created
19662 in Exim's hints database. For addresses whose routing depends only on the
19663 domain, the key for the retry record should not involve the local part, but for
19664 other addresses, both the domain and the local part should be included.
19665 Usually, remote routing is of the former kind, and local routing is of the
19668 This option controls whether the local part is used to form the key for retry
19669 hints for addresses that suffer temporary errors while being handled by this
19670 router. The default value is true for any router that has any of
19671 &%check_local_user%&,
19674 &%local_part_prefix%&,
19675 &%local_part_suffix%&,
19678 set, and false otherwise. Note that this option does not apply to hints keys
19679 for transport delays; they are controlled by a generic transport option of the
19682 Failing to set this option when it is needed
19683 (because a remote router handles only some of the local-parts for a domain)
19684 can result in incorrect error messages being generated.
19686 The setting of &%retry_use_local_part%& applies only to the router on which it
19687 appears. If the router generates child addresses, they are routed
19688 independently; this setting does not become attached to them.
19692 .option router_home_directory routers string&!! unset
19693 .cindex "router" "home directory for"
19694 .cindex "home directory" "for router"
19696 This option sets a home directory for use while the router is running. (Compare
19697 &%transport_home_directory%&, which sets a home directory for later
19698 transporting.) In particular, if used on a &(redirect)& router, this option
19699 sets a value for &$home$& while a filter is running. The value is expanded;
19700 forced expansion failure causes the option to be ignored &-- other failures
19701 cause the router to defer.
19703 Expansion of &%router_home_directory%& happens immediately after the
19704 &%check_local_user%& test (if configured), before any further expansions take
19706 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19708 While the router is running, &%router_home_directory%& overrides the value of
19709 &$home$& that came from &%check_local_user%&.
19711 When a router accepts an address and assigns it to a local transport (including
19712 the cases when a &(redirect)& router generates a pipe, file, or autoreply
19713 delivery), the home directory setting for the transport is taken from the first
19714 of these values that is set:
19717 The &%home_directory%& option on the transport;
19719 The &%transport_home_directory%& option on the router;
19721 The password data if &%check_local_user%& is set on the router;
19723 The &%router_home_directory%& option on the router.
19726 In other words, &%router_home_directory%& overrides the password data for the
19727 router, but not for the transport.
19731 .option self routers string freeze
19732 .cindex "MX record" "pointing to local host"
19733 .cindex "local host" "MX pointing to"
19734 This option applies to those routers that use a recipient address to find a
19735 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
19736 and &(manualroute)& routers.
19737 Certain configurations of the &(queryprogram)& router can also specify a list
19739 Usually such routers are configured to send the message to a remote host via an
19740 &(smtp)& transport. The &%self%& option specifies what happens when the first
19741 host on the list turns out to be the local host.
19742 The way in which Exim checks for the local host is described in section
19743 &<<SECTreclocipadd>>&.
19745 Normally this situation indicates either an error in Exim's configuration (for
19746 example, the router should be configured not to process this domain), or an
19747 error in the DNS (for example, the MX should not point to this host). For this
19748 reason, the default action is to log the incident, defer the address, and
19749 freeze the message. The following alternatives are provided for use in special
19754 Delivery of the message is tried again later, but the message is not frozen.
19756 .vitem "&%reroute%&: <&'domain'&>"
19757 The domain is changed to the given domain, and the address is passed back to
19758 be reprocessed by the routers. No rewriting of headers takes place. This
19759 behaviour is essentially a redirection.
19761 .vitem "&%reroute: rewrite:%& <&'domain'&>"
19762 The domain is changed to the given domain, and the address is passed back to be
19763 reprocessed by the routers. Any headers that contain the original domain are
19768 .vindex "&$self_hostname$&"
19769 The router passes the address to the next router, or to the router named in the
19770 &%pass_router%& option if it is set. This overrides &%no_more%&. During
19771 subsequent routing and delivery, the variable &$self_hostname$& contains the
19772 name of the local host that the router encountered. This can be used to
19773 distinguish between different cases for hosts with multiple names. The
19779 ensures that only those addresses that routed to the local host are passed on.
19780 Without &%no_more%&, addresses that were declined for other reasons would also
19781 be passed to the next router.
19784 Delivery fails and an error report is generated.
19787 .cindex "local host" "sending to"
19788 The anomaly is ignored and the address is queued for the transport. This
19789 setting should be used with extreme caution. For an &(smtp)& transport, it
19790 makes sense only in cases where the program that is listening on the SMTP port
19791 is not this version of Exim. That is, it must be some other MTA, or Exim with a
19792 different configuration file that handles the domain in another way.
19797 .option senders routers&!? "address list&!!" unset
19798 .cindex "router" "checking senders"
19799 If this option is set, the router is skipped unless the message's sender
19800 address matches something on the list.
19801 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19804 There are issues concerning verification when the running of routers is
19805 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
19806 setting, it sets the sender to the null string. When using the &%-bt%& option
19807 to check a configuration file, it is necessary also to use the &%-f%& option to
19808 set an appropriate sender. For incoming mail, the sender is unset when
19809 verifying the sender, but is available when verifying any recipients. If the
19810 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
19814 .option set routers "string list" unset
19815 .cindex router variables
19816 This option may be used multiple times on a router;
19817 because of this the list aspect is mostly irrelevant.
19818 The list separator is a semicolon but can be changed in the
19821 Each list-element given must be of the form &"name = value"&
19822 and the names used must start with the string &"r_"&.
19823 Values containing a list-separator should have them doubled.
19824 When a router runs, the strings are evaluated in order,
19825 to create variables which are added to the set associated with
19827 This is done immediately after all the preconditions, before the
19828 evaluation of the &%address_data%& option.
19829 The variable is set with the expansion of the value.
19830 The variables can be used by the router options
19831 (not including any preconditions)
19832 and by the transport.
19833 Later definitions of a given named variable will override former ones.
19834 Variable use is via the usual &$r_...$& syntax.
19836 This is similar to the &%address_data%& option, except that
19837 many independent variables can be used, with choice of naming.
19840 .option translate_ip_address routers string&!! unset
19841 .cindex "IP address" "translating"
19842 .cindex "packet radio"
19843 .cindex "router" "IP address translation"
19844 There exist some rare networking situations (for example, packet radio) where
19845 it is helpful to be able to translate IP addresses generated by normal routing
19846 mechanisms into other IP addresses, thus performing a kind of manual IP
19847 routing. This should be done only if the normal IP routing of the TCP/IP stack
19848 is inadequate or broken. Because this is an extremely uncommon requirement, the
19849 code to support this option is not included in the Exim binary unless
19850 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
19852 .vindex "&$host_address$&"
19853 The &%translate_ip_address%& string is expanded for every IP address generated
19854 by the router, with the generated address set in &$host_address$&. If the
19855 expansion is forced to fail, no action is taken.
19856 For any other expansion error, delivery of the message is deferred.
19857 If the result of the expansion is an IP address, that replaces the original
19858 address; otherwise the result is assumed to be a host name &-- this is looked
19859 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
19860 produce one or more replacement IP addresses. For example, to subvert all IP
19861 addresses in some specific networks, this could be added to a router:
19863 translate_ip_address = \
19864 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
19867 The file would contain lines like
19869 10.2.3.128/26 some.host
19870 10.8.4.34/26 10.44.8.15
19872 You should not make use of this facility unless you really understand what you
19877 .option transport routers string&!! unset
19878 This option specifies the transport to be used when a router accepts an address
19879 and sets it up for delivery. A transport is never needed if a router is used
19880 only for verification. The value of the option is expanded at routing time,
19881 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
19882 and result must be the name of one of the configured transports. If it is not,
19883 delivery is deferred.
19885 The &%transport%& option is not used by the &(redirect)& router, but it does
19886 have some private options that set up transports for pipe and file deliveries
19887 (see chapter &<<CHAPredirect>>&).
19891 .option transport_current_directory routers string&!! unset
19892 .cindex "current directory for local transport"
19893 This option associates a current directory with any address that is routed
19894 to a local transport. This can happen either because a transport is
19895 explicitly configured for the router, or because it generates a delivery to a
19896 file or a pipe. During the delivery process (that is, at transport time), this
19897 option string is expanded and is set as the current directory, unless
19898 overridden by a setting on the transport.
19899 If the expansion fails for any reason, including forced failure, an error is
19900 logged, and delivery is deferred.
19901 See chapter &<<CHAPenvironment>>& for details of the local delivery
19907 .option transport_home_directory routers string&!! "see below"
19908 .cindex "home directory" "for local transport"
19909 This option associates a home directory with any address that is routed to a
19910 local transport. This can happen either because a transport is explicitly
19911 configured for the router, or because it generates a delivery to a file or a
19912 pipe. During the delivery process (that is, at transport time), the option
19913 string is expanded and is set as the home directory, unless overridden by a
19914 setting of &%home_directory%& on the transport.
19915 If the expansion fails for any reason, including forced failure, an error is
19916 logged, and delivery is deferred.
19918 If the transport does not specify a home directory, and
19919 &%transport_home_directory%& is not set for the router, the home directory for
19920 the transport is taken from the password data if &%check_local_user%& is set for
19921 the router. Otherwise it is taken from &%router_home_directory%& if that option
19922 is set; if not, no home directory is set for the transport.
19924 See chapter &<<CHAPenvironment>>& for further details of the local delivery
19930 .option unseen routers boolean&!! false
19931 .cindex "router" "carrying on after success"
19932 The result of string expansion for this option must be a valid boolean value,
19933 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19934 result causes an error, and delivery is deferred. If the expansion is forced to
19935 fail, the default value for the option (false) is used. Other failures cause
19936 delivery to be deferred.
19938 When this option is set true, routing does not cease if the router accepts the
19939 address. Instead, a copy of the incoming address is passed to the next router,
19940 overriding a false setting of &%more%&. There is little point in setting
19941 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
19942 the value of &%unseen%& contains expansion items (and therefore, presumably, is
19943 sometimes true and sometimes false).
19945 .cindex "copy of message (&%unseen%& option)"
19946 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
19947 qualifier in filter files. It can be used to cause copies of messages to be
19948 delivered to some other destination, while also carrying out a normal delivery.
19949 In effect, the current address is made into a &"parent"& that has two children
19950 &-- one that is delivered as specified by this router, and a clone that goes on
19951 to be routed further. For this reason, &%unseen%& may not be combined with the
19952 &%one_time%& option in a &(redirect)& router.
19954 &*Warning*&: Header lines added to the address (or specified for removal) by
19955 this router or by previous routers affect the &"unseen"& copy of the message
19956 only. The clone that continues to be processed by further routers starts with
19957 no added headers and none specified for removal. For a &%redirect%& router, if
19958 a generated address is the same as the incoming address, this can lead to
19959 duplicate addresses with different header modifications. Exim does not do
19960 duplicate deliveries (except, in certain circumstances, to pipes -- see section
19961 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
19962 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
19963 &%redirect%& router may be of help.
19965 Unlike the handling of header modifications, any data that was set by the
19966 &%address_data%& option in the current or previous routers &'is'& passed on to
19967 subsequent routers.
19970 .option user routers string&!! "see below"
19971 .cindex "uid (user id)" "local delivery"
19972 .cindex "local transports" "uid and gid"
19973 .cindex "transport" "local"
19974 .cindex "router" "user for filter processing"
19975 .cindex "filter" "user for processing"
19976 When a router queues an address for a transport, and the transport does not
19977 specify a user, the user given here is used when running the delivery process.
19978 The user may be specified numerically or by name. If expansion fails, the
19979 error is logged and delivery is deferred.
19980 This user is also used by the &(redirect)& router when running a filter file.
19981 The default is unset, except when &%check_local_user%& is set. In this case,
19982 the default is taken from the password information. If the user is specified as
19983 a name, and &%group%& is not set, the group associated with the user is used.
19984 See also &%initgroups%& and &%group%& and the discussion in chapter
19985 &<<CHAPenvironment>>&.
19989 .option verify routers&!? boolean true
19990 Setting this option has the effect of setting &%verify_sender%& and
19991 &%verify_recipient%& to the same value.
19994 .option verify_only routers&!? boolean false
19995 .cindex "EXPN" "with &%verify_only%&"
19997 .cindex "router" "used only when verifying"
19998 If this option is set, the router is used only when verifying an address,
19999 delivering in cutthrough mode or
20000 testing with the &%-bv%& option, not when actually doing a delivery, testing
20001 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
20002 restricted to verifying only senders or recipients by means of
20003 &%verify_sender%& and &%verify_recipient%&.
20005 &*Warning*&: When the router is being run to verify addresses for an incoming
20006 SMTP message, Exim is not running as root, but under its own uid. If the router
20007 accesses any files, you need to make sure that they are accessible to the Exim
20011 .option verify_recipient routers&!? boolean true
20012 If this option is false, the router is skipped when verifying recipient
20014 delivering in cutthrough mode
20015 or testing recipient verification using &%-bv%&.
20016 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
20018 See also the &$verify_mode$& variable.
20021 .option verify_sender routers&!? boolean true
20022 If this option is false, the router is skipped when verifying sender addresses
20023 or testing sender verification using &%-bvs%&.
20024 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
20026 See also the &$verify_mode$& variable.
20027 .ecindex IIDgenoprou1
20028 .ecindex IIDgenoprou2
20035 . ////////////////////////////////////////////////////////////////////////////
20036 . ////////////////////////////////////////////////////////////////////////////
20038 .chapter "The accept router" "CHID4"
20039 .cindex "&(accept)& router"
20040 .cindex "routers" "&(accept)&"
20041 The &(accept)& router has no private options of its own. Unless it is being
20042 used purely for verification (see &%verify_only%&) a transport is required to
20043 be defined by the generic &%transport%& option. If the preconditions that are
20044 specified by generic options are met, the router accepts the address and queues
20045 it for the given transport. The most common use of this router is for setting
20046 up deliveries to local mailboxes. For example:
20050 domains = mydomain.example
20052 transport = local_delivery
20054 The &%domains%& condition in this example checks the domain of the address, and
20055 &%check_local_user%& checks that the local part is the login of a local user.
20056 When both preconditions are met, the &(accept)& router runs, and queues the
20057 address for the &(local_delivery)& transport.
20064 . ////////////////////////////////////////////////////////////////////////////
20065 . ////////////////////////////////////////////////////////////////////////////
20067 .chapter "The dnslookup router" "CHAPdnslookup"
20068 .scindex IIDdnsrou1 "&(dnslookup)& router"
20069 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
20070 The &(dnslookup)& router looks up the hosts that handle mail for the
20071 recipient's domain in the DNS. A transport must always be set for this router,
20072 unless &%verify_only%& is set.
20074 If SRV support is configured (see &%check_srv%& below), Exim first searches for
20075 SRV records. If none are found, or if SRV support is not configured,
20076 MX records are looked up. If no MX records exist, address records are sought.
20077 However, &%mx_domains%& can be set to disable the direct use of address
20080 MX records of equal priority are sorted by Exim into a random order. Exim then
20081 looks for address records for the host names obtained from MX or SRV records.
20082 When a host has more than one IP address, they are sorted into a random order,
20083 except that IPv6 addresses are sorted before IPv4 addresses. If all the
20084 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
20085 generic option, the router declines.
20087 Unless they have the highest priority (lowest MX value), MX records that point
20088 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
20089 are discarded, together with any other MX records of equal or lower priority.
20091 .cindex "MX record" "pointing to local host"
20092 .cindex "local host" "MX pointing to"
20093 .oindex "&%self%&" "in &(dnslookup)& router"
20094 If the host pointed to by the highest priority MX record, or looked up as an
20095 address record, is the local host, or matches &%hosts_treat_as_local%&, what
20096 happens is controlled by the generic &%self%& option.
20099 .section "Problems with DNS lookups" "SECTprowitdnsloo"
20100 There have been problems with DNS servers when SRV records are looked up.
20101 Some misbehaving servers return a DNS error or timeout when a non-existent
20102 SRV record is sought. Similar problems have in the past been reported for
20103 MX records. The global &%dns_again_means_nonexist%& option can help with this
20104 problem, but it is heavy-handed because it is a global option.
20106 For this reason, there are two options, &%srv_fail_domains%& and
20107 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
20108 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
20109 an attempt to look up an SRV or MX record causes one of these results, and the
20110 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
20111 such record"&. In the case of an SRV lookup, this means that the router
20112 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
20113 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
20114 case routing fails.
20117 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
20118 .cindex "&(dnslookup)& router" "declines"
20119 There are a few cases where a &(dnslookup)& router will decline to accept
20120 an address; if such a router is expected to handle "all remaining non-local
20121 domains", then it is important to set &%no_more%&.
20123 The router will defer rather than decline if the domain
20124 is found in the &%fail_defer_domains%& router option.
20126 Reasons for a &(dnslookup)& router to decline currently include:
20128 The domain does not exist in DNS
20130 The domain exists but the MX record's host part is just "."; this is a common
20131 convention (borrowed from SRV) used to indicate that there is no such service
20132 for this domain and to not fall back to trying A/AAAA records.
20134 Ditto, but for SRV records, when &%check_srv%& is set on this router.
20136 MX record points to a non-existent host.
20138 MX record points to an IP address and the main section option
20139 &%allow_mx_to_ip%& is not set.
20141 MX records exist and point to valid hosts, but all hosts resolve only to
20142 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
20144 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
20145 &%dns_check_names_pattern%& for handling one variant of this)
20147 &%check_secondary_mx%& is set on this router but the local host can
20148 not be found in the MX records (see below)
20154 .section "Private options for dnslookup" "SECID118"
20155 .cindex "options" "&(dnslookup)& router"
20156 The private options for the &(dnslookup)& router are as follows:
20158 .option check_secondary_mx dnslookup boolean false
20159 .cindex "MX record" "checking for secondary"
20160 If this option is set, the router declines unless the local host is found in
20161 (and removed from) the list of hosts obtained by MX lookup. This can be used to
20162 process domains for which the local host is a secondary mail exchanger
20163 differently to other domains. The way in which Exim decides whether a host is
20164 the local host is described in section &<<SECTreclocipadd>>&.
20167 .option check_srv dnslookup string&!! unset
20168 .cindex "SRV record" "enabling use of"
20169 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
20170 addition to MX and address records. The support is disabled by default. To
20171 enable SRV support, set the &%check_srv%& option to the name of the service
20172 required. For example,
20176 looks for SRV records that refer to the normal smtp service. The option is
20177 expanded, so the service name can vary from message to message or address
20178 to address. This might be helpful if SRV records are being used for a
20179 submission service. If the expansion is forced to fail, the &%check_srv%&
20180 option is ignored, and the router proceeds to look for MX records in the
20183 When the expansion succeeds, the router searches first for SRV records for
20184 the given service (it assumes TCP protocol). A single SRV record with a
20185 host name that consists of just a single dot indicates &"no such service for
20186 this domain"&; if this is encountered, the router declines. If other kinds of
20187 SRV record are found, they are used to construct a host list for delivery
20188 according to the rules of RFC 2782. MX records are not sought in this case.
20190 When no SRV records are found, MX records (and address records) are sought in
20191 the traditional way. In other words, SRV records take precedence over MX
20192 records, just as MX records take precedence over address records. Note that
20193 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
20194 defined it. It is apparently believed that MX records are sufficient for email
20195 and that SRV records should not be used for this purpose. However, SRV records
20196 have an additional &"weight"& feature which some people might find useful when
20197 trying to split an SMTP load between hosts of different power.
20199 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
20200 when there is a DNS lookup error.
20205 .option fail_defer_domains dnslookup "domain list&!!" unset
20206 .cindex "MX record" "not found"
20207 DNS lookups for domains matching &%fail_defer_domains%&
20208 which find no matching record will cause the router to defer
20209 rather than the default behaviour of decline.
20210 This maybe be useful for queueing messages for a newly created
20211 domain while the DNS configuration is not ready.
20212 However, it will result in any message with mistyped domains
20216 .option ipv4_only "string&!!" unset
20217 .cindex IPv6 disabling
20218 .cindex DNS "IPv6 disabling"
20219 The string is expanded, and if the result is anything but a forced failure,
20220 or an empty string, or one of the strings “0” or “no” or “false”
20221 (checked without regard to the case of the letters),
20222 only A records are used.
20224 .option ipv4_prefer "string&!!" unset
20225 .cindex IPv4 preference
20226 .cindex DNS "IPv4 preference"
20227 The string is expanded, and if the result is anything but a forced failure,
20228 or an empty string, or one of the strings “0” or “no” or “false”
20229 (checked without regard to the case of the letters),
20230 A records are sorted before AAAA records (inverting the default).
20232 .option mx_domains dnslookup "domain list&!!" unset
20233 .cindex "MX record" "required to exist"
20234 .cindex "SRV record" "required to exist"
20235 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
20236 record in order to be recognized. (The name of this option could be improved.)
20237 For example, if all the mail hosts in &'fict.example'& are known to have MX
20238 records, except for those in &'discworld.fict.example'&, you could use this
20241 mx_domains = ! *.discworld.fict.example : *.fict.example
20243 This specifies that messages addressed to a domain that matches the list but
20244 has no MX record should be bounced immediately instead of being routed using
20245 the address record.
20248 .option mx_fail_domains dnslookup "domain list&!!" unset
20249 If the DNS lookup for MX records for one of the domains in this list causes a
20250 DNS lookup error, Exim behaves as if no MX records were found. See section
20251 &<<SECTprowitdnsloo>>& for more discussion.
20256 .option qualify_single dnslookup boolean true
20257 .cindex "DNS" "resolver options"
20258 .cindex "DNS" "qualifying single-component names"
20259 When this option is true, the resolver option RES_DEFNAMES is set for DNS
20260 lookups. Typically, but not standardly, this causes the resolver to qualify
20261 single-component names with the default domain. For example, on a machine
20262 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
20263 &'thesaurus.ref.example'& inside the resolver. For details of what your
20264 resolver actually does, consult your man pages for &'resolver'& and
20269 .option rewrite_headers dnslookup boolean true
20270 .cindex "rewriting" "header lines"
20271 .cindex "header lines" "rewriting"
20272 If the domain name in the address that is being processed is not fully
20273 qualified, it may be expanded to its full form by a DNS lookup. For example, if
20274 an address is specified as &'dormouse@teaparty'&, the domain might be
20275 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
20276 occur as a result of setting the &%widen_domains%& option. If
20277 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
20278 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
20279 header lines of the message are rewritten with the full domain name.
20281 This option should be turned off only when it is known that no message is
20282 ever going to be sent outside an environment where the abbreviation makes
20285 When an MX record is looked up in the DNS and matches a wildcard record, name
20286 servers normally return a record containing the name that has been looked up,
20287 making it impossible to detect whether a wildcard was present or not. However,
20288 some name servers have recently been seen to return the wildcard entry. If the
20289 name returned by a DNS lookup begins with an asterisk, it is not used for
20293 .option same_domain_copy_routing dnslookup boolean false
20294 .cindex "address" "copying routing"
20295 Addresses with the same domain are normally routed by the &(dnslookup)& router
20296 to the same list of hosts. However, this cannot be presumed, because the router
20297 options and preconditions may refer to the local part of the address. By
20298 default, therefore, Exim routes each address in a message independently. DNS
20299 servers run caches, so repeated DNS lookups are not normally expensive, and in
20300 any case, personal messages rarely have more than a few recipients.
20302 If you are running mailing lists with large numbers of subscribers at the same
20303 domain, and you are using a &(dnslookup)& router which is independent of the
20304 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20305 lookups for identical domains in one message. In this case, when &(dnslookup)&
20306 routes an address to a remote transport, any other unrouted addresses in the
20307 message that have the same domain are automatically given the same routing
20308 without processing them independently,
20309 provided the following conditions are met:
20312 No router that processed the address specified &%headers_add%& or
20313 &%headers_remove%&.
20315 The router did not change the address in any way, for example, by &"widening"&
20322 .option search_parents dnslookup boolean false
20323 .cindex "DNS" "resolver options"
20324 When this option is true, the resolver option RES_DNSRCH is set for DNS
20325 lookups. This is different from the &%qualify_single%& option in that it
20326 applies to domains containing dots. Typically, but not standardly, it causes
20327 the resolver to search for the name in the current domain and in parent
20328 domains. For example, on a machine in the &'fict.example'& domain, if looking
20329 up &'teaparty.wonderland'& failed, the resolver would try
20330 &'teaparty.wonderland.fict.example'&. For details of what your resolver
20331 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
20333 Setting this option true can cause problems in domains that have a wildcard MX
20334 record, because any domain that does not have its own MX record matches the
20339 .option srv_fail_domains dnslookup "domain list&!!" unset
20340 If the DNS lookup for SRV records for one of the domains in this list causes a
20341 DNS lookup error, Exim behaves as if no SRV records were found. See section
20342 &<<SECTprowitdnsloo>>& for more discussion.
20347 .option widen_domains dnslookup "string list" unset
20348 .cindex "domain" "partial; widening"
20349 If a DNS lookup fails and this option is set, each of its strings in turn is
20350 added onto the end of the domain, and the lookup is tried again. For example,
20353 widen_domains = fict.example:ref.example
20355 is set and a lookup of &'klingon.dictionary'& fails,
20356 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
20357 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
20358 and &%search_parents%& options can cause some widening to be undertaken inside
20359 the DNS resolver. &%widen_domains%& is not applied to sender addresses
20360 when verifying, unless &%rewrite_headers%& is false (not the default).
20363 .section "Effect of qualify_single and search_parents" "SECID119"
20364 When a domain from an envelope recipient is changed by the resolver as a result
20365 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
20366 corresponding address in the message's header lines unless &%rewrite_headers%&
20367 is set false. Exim then re-routes the address, using the full domain.
20369 These two options affect only the DNS lookup that takes place inside the router
20370 for the domain of the address that is being routed. They do not affect lookups
20371 such as that implied by
20375 that may happen while processing a router precondition before the router is
20376 entered. No widening ever takes place for these lookups.
20377 .ecindex IIDdnsrou1
20378 .ecindex IIDdnsrou2
20388 . ////////////////////////////////////////////////////////////////////////////
20389 . ////////////////////////////////////////////////////////////////////////////
20391 .chapter "The ipliteral router" "CHID5"
20392 .cindex "&(ipliteral)& router"
20393 .cindex "domain literal" "routing"
20394 .cindex "routers" "&(ipliteral)&"
20395 This router has no private options. Unless it is being used purely for
20396 verification (see &%verify_only%&) a transport is required to be defined by the
20397 generic &%transport%& option. The router accepts the address if its domain part
20398 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
20399 router handles the address
20403 by setting up delivery to the host with that IP address. IPv4 domain literals
20404 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
20405 are similar, but the address is preceded by &`ipv6:`&. For example:
20407 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
20409 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
20410 grounds that sooner or later somebody will try it.
20412 .oindex "&%self%&" "in &(ipliteral)& router"
20413 If the IP address matches something in &%ignore_target_hosts%&, the router
20414 declines. If an IP literal turns out to refer to the local host, the generic
20415 &%self%& option determines what happens.
20417 The RFCs require support for domain literals; however, their use is
20418 controversial in today's Internet. If you want to use this router, you must
20419 also set the main configuration option &%allow_domain_literals%&. Otherwise,
20420 Exim will not recognize the domain literal syntax in addresses.
20424 . ////////////////////////////////////////////////////////////////////////////
20425 . ////////////////////////////////////////////////////////////////////////////
20427 .chapter "The iplookup router" "CHID6"
20428 .cindex "&(iplookup)& router"
20429 .cindex "routers" "&(iplookup)&"
20430 The &(iplookup)& router was written to fulfil a specific requirement in
20431 Cambridge University (which in fact no longer exists). For this reason, it is
20432 not included in the binary of Exim by default. If you want to include it, you
20435 ROUTER_IPLOOKUP=yes
20437 in your &_Local/Makefile_& configuration file.
20439 The &(iplookup)& router routes an address by sending it over a TCP or UDP
20440 connection to one or more specific hosts. The host can then return the same or
20441 a different address &-- in effect rewriting the recipient address in the
20442 message's envelope. The new address is then passed on to subsequent routers. If
20443 this process fails, the address can be passed on to other routers, or delivery
20444 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
20445 must not be specified for it.
20447 .cindex "options" "&(iplookup)& router"
20448 .option hosts iplookup string unset
20449 This option must be supplied. Its value is a colon-separated list of host
20450 names. The hosts are looked up using &[gethostbyname()]&
20451 (or &[getipnodebyname()]& when available)
20452 and are tried in order until one responds to the query. If none respond, what
20453 happens is controlled by &%optional%&.
20456 .option optional iplookup boolean false
20457 If &%optional%& is true, if no response is obtained from any host, the address
20458 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
20459 delivery to the address is deferred.
20462 .option port iplookup integer 0
20463 .cindex "port" "&(iplookup)& router"
20464 This option must be supplied. It specifies the port number for the TCP or UDP
20468 .option protocol iplookup string udp
20469 This option can be set to &"udp"& or &"tcp"& to specify which of the two
20470 protocols is to be used.
20473 .option query iplookup string&!! "see below"
20474 This defines the content of the query that is sent to the remote hosts. The
20477 $local_part@$domain $local_part@$domain
20479 The repetition serves as a way of checking that a response is to the correct
20480 query in the default case (see &%response_pattern%& below).
20483 .option reroute iplookup string&!! unset
20484 If this option is not set, the rerouted address is precisely the byte string
20485 returned by the remote host, up to the first white space, if any. If set, the
20486 string is expanded to form the rerouted address. It can include parts matched
20487 in the response by &%response_pattern%& by means of numeric variables such as
20488 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
20489 whether or not a pattern is in use. In all cases, the rerouted address must end
20490 up in the form &'local_part@domain'&.
20493 .option response_pattern iplookup string unset
20494 This option can be set to a regular expression that is applied to the string
20495 returned from the remote host. If the pattern does not match the response, the
20496 router declines. If &%response_pattern%& is not set, no checking of the
20497 response is done, unless the query was defaulted, in which case there is a
20498 check that the text returned after the first white space is the original
20499 address. This checks that the answer that has been received is in response to
20500 the correct question. For example, if the response is just a new domain, the
20501 following could be used:
20503 response_pattern = ^([^@]+)$
20504 reroute = $local_part@$1
20507 .option timeout iplookup time 5s
20508 This specifies the amount of time to wait for a response from the remote
20509 machine. The same timeout is used for the &[connect()]& function for a TCP
20510 call. It does not apply to UDP.
20515 . ////////////////////////////////////////////////////////////////////////////
20516 . ////////////////////////////////////////////////////////////////////////////
20518 .chapter "The manualroute router" "CHID7"
20519 .scindex IIDmanrou1 "&(manualroute)& router"
20520 .scindex IIDmanrou2 "routers" "&(manualroute)&"
20521 .cindex "domain" "manually routing"
20522 The &(manualroute)& router is so-called because it provides a way of manually
20523 routing an address according to its domain. It is mainly used when you want to
20524 route addresses to remote hosts according to your own rules, bypassing the
20525 normal DNS routing that looks up MX records. However, &(manualroute)& can also
20526 route to local transports, a facility that may be useful if you want to save
20527 messages for dial-in hosts in local files.
20529 The &(manualroute)& router compares a list of domain patterns with the domain
20530 it is trying to route. If there is no match, the router declines. Each pattern
20531 has associated with it a list of hosts and some other optional data, which may
20532 include a transport. The combination of a pattern and its data is called a
20533 &"routing rule"&. For patterns that do not have an associated transport, the
20534 generic &%transport%& option must specify a transport, unless the router is
20535 being used purely for verification (see &%verify_only%&).
20538 In the case of verification, matching the domain pattern is sufficient for the
20539 router to accept the address. When actually routing an address for delivery,
20540 an address that matches a domain pattern is queued for the associated
20541 transport. If the transport is not a local one, a host list must be associated
20542 with the pattern; IP addresses are looked up for the hosts, and these are
20543 passed to the transport along with the mail address. For local transports, a
20544 host list is optional. If it is present, it is passed in &$host$& as a single
20547 The list of routing rules can be provided as an inline string in
20548 &%route_list%&, or the data can be obtained by looking up the domain in a file
20549 or database by setting &%route_data%&. Only one of these settings may appear in
20550 any one instance of &(manualroute)&. The format of routing rules is described
20551 below, following the list of private options.
20554 .section "Private options for manualroute" "SECTprioptman"
20556 .cindex "options" "&(manualroute)& router"
20557 The private options for the &(manualroute)& router are as follows:
20559 .option host_all_ignored manualroute string defer
20560 See &%host_find_failed%&.
20562 .option host_find_failed manualroute string freeze
20563 This option controls what happens when &(manualroute)& tries to find an IP
20564 address for a host, and the host does not exist. The option can be set to one
20565 of the following values:
20574 The default (&"freeze"&) assumes that this state is a serious configuration
20575 error. The difference between &"pass"& and &"decline"& is that the former
20576 forces the address to be passed to the next router (or the router defined by
20579 overriding &%no_more%&, whereas the latter passes the address to the next
20580 router only if &%more%& is true.
20582 The value &"ignore"& causes Exim to completely ignore a host whose IP address
20583 cannot be found. If all the hosts in the list are ignored, the behaviour is
20584 controlled by the &%host_all_ignored%& option. This takes the same values
20585 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
20587 The &%host_find_failed%& option applies only to a definite &"does not exist"&
20588 state; if a host lookup gets a temporary error, delivery is deferred unless the
20589 generic &%pass_on_timeout%& option is set.
20592 .option hosts_randomize manualroute boolean false
20593 .cindex "randomized host list"
20594 .cindex "host" "list of; randomized"
20595 If this option is set, the order of the items in a host list in a routing rule
20596 is randomized each time the list is used, unless an option in the routing rule
20597 overrides (see below). Randomizing the order of a host list can be used to do
20598 crude load sharing. However, if more than one mail address is routed by the
20599 same router to the same host list, the host lists are considered to be the same
20600 (even though they may be randomized into different orders) for the purpose of
20601 deciding whether to batch the deliveries into a single SMTP transaction.
20603 When &%hosts_randomize%& is true, a host list may be split
20604 into groups whose order is separately randomized. This makes it possible to
20605 set up MX-like behaviour. The boundaries between groups are indicated by an
20606 item that is just &`+`& in the host list. For example:
20608 route_list = * host1:host2:host3:+:host4:host5
20610 The order of the first three hosts and the order of the last two hosts is
20611 randomized for each use, but the first three always end up before the last two.
20612 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
20613 randomized host list is passed to an &(smtp)& transport that also has
20614 &%hosts_randomize set%&, the list is not re-randomized.
20617 .option route_data manualroute string&!! unset
20618 If this option is set, it must expand to yield the data part of a routing rule.
20619 Typically, the expansion string includes a lookup based on the domain. For
20622 route_data = ${lookup{$domain}dbm{/etc/routes}}
20624 If the expansion is forced to fail, or the result is an empty string, the
20625 router declines. Other kinds of expansion failure cause delivery to be
20629 .option route_list manualroute "string list" unset
20630 This string is a list of routing rules, in the form defined below. Note that,
20631 unlike most string lists, the items are separated by semicolons. This is so
20632 that they may contain colon-separated host lists.
20635 .option same_domain_copy_routing manualroute boolean false
20636 .cindex "address" "copying routing"
20637 Addresses with the same domain are normally routed by the &(manualroute)&
20638 router to the same list of hosts. However, this cannot be presumed, because the
20639 router options and preconditions may refer to the local part of the address. By
20640 default, therefore, Exim routes each address in a message independently. DNS
20641 servers run caches, so repeated DNS lookups are not normally expensive, and in
20642 any case, personal messages rarely have more than a few recipients.
20644 If you are running mailing lists with large numbers of subscribers at the same
20645 domain, and you are using a &(manualroute)& router which is independent of the
20646 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20647 lookups for identical domains in one message. In this case, when
20648 &(manualroute)& routes an address to a remote transport, any other unrouted
20649 addresses in the message that have the same domain are automatically given the
20650 same routing without processing them independently. However, this is only done
20651 if &%headers_add%& and &%headers_remove%& are unset.
20656 .section "Routing rules in route_list" "SECID120"
20657 The value of &%route_list%& is a string consisting of a sequence of routing
20658 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
20659 entered as two semicolons. Alternatively, the list separator can be changed as
20660 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
20661 Empty rules are ignored. The format of each rule is
20663 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
20665 The following example contains two rules, each with a simple domain pattern and
20669 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
20670 thes.ref.example mail-3.ref.example:mail-4.ref.example
20672 The three parts of a rule are separated by white space. The pattern and the
20673 list of hosts can be enclosed in quotes if necessary, and if they are, the
20674 usual quoting rules apply. Each rule in a &%route_list%& must start with a
20675 single domain pattern, which is the only mandatory item in the rule. The
20676 pattern is in the same format as one item in a domain list (see section
20677 &<<SECTdomainlist>>&),
20678 except that it may not be the name of an interpolated file.
20679 That is, it may be wildcarded, or a regular expression, or a file or database
20680 lookup (with semicolons doubled, because of the use of semicolon as a separator
20681 in a &%route_list%&).
20683 The rules in &%route_list%& are searched in order until one of the patterns
20684 matches the domain that is being routed. The list of hosts and then options are
20685 then used as described below. If there is no match, the router declines. When
20686 &%route_list%& is set, &%route_data%& must not be set.
20690 .section "Routing rules in route_data" "SECID121"
20691 The use of &%route_list%& is convenient when there are only a small number of
20692 routing rules. For larger numbers, it is easier to use a file or database to
20693 hold the routing information, and use the &%route_data%& option instead.
20694 The value of &%route_data%& is a list of hosts, followed by (optional) options.
20695 Most commonly, &%route_data%& is set as a string that contains an
20696 expansion lookup. For example, suppose we place two routing rules in a file
20699 dict.ref.example: mail-1.ref.example:mail-2.ref.example
20700 thes.ref.example: mail-3.ref.example:mail-4.ref.example
20702 This data can be accessed by setting
20704 route_data = ${lookup{$domain}lsearch{/the/file/name}}
20706 Failure of the lookup results in an empty string, causing the router to
20707 decline. However, you do not have to use a lookup in &%route_data%&. The only
20708 requirement is that the result of expanding the string is a list of hosts,
20709 possibly followed by options, separated by white space. The list of hosts must
20710 be enclosed in quotes if it contains white space.
20715 .section "Format of the list of hosts" "SECID122"
20716 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
20717 always separately expanded before use. If the expansion fails, the router
20718 declines. The result of the expansion must be a colon-separated list of names
20719 and/or IP addresses, optionally also including ports.
20720 If the list is written with spaces, it must be protected with quotes.
20721 The format of each item
20722 in the list is described in the next section. The list separator can be changed
20723 as described in section &<<SECTlistsepchange>>&.
20725 If the list of hosts was obtained from a &%route_list%& item, the following
20726 variables are set during its expansion:
20729 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
20730 If the domain was matched against a regular expression, the numeric variables
20731 &$1$&, &$2$&, etc. may be set. For example:
20733 route_list = ^domain(\d+) host-$1.text.example
20736 &$0$& is always set to the entire domain.
20738 &$1$& is also set when partial matching is done in a file lookup.
20741 .vindex "&$value$&"
20742 If the pattern that matched the domain was a lookup item, the data that was
20743 looked up is available in the expansion variable &$value$&. For example:
20745 route_list = lsearch;;/some/file.routes $value
20749 Note the doubling of the semicolon in the pattern that is necessary because
20750 semicolon is the default route list separator.
20754 .section "Format of one host item" "SECTformatonehostitem"
20755 Each item in the list of hosts can be either a host name or an IP address,
20756 optionally with an attached port number, or it can be a single "+"
20757 (see &%hosts_randomize%&).
20758 When no port is given, an IP address
20759 is not enclosed in brackets. When a port is specified, it overrides the port
20760 specification on the transport. The port is separated from the name or address
20761 by a colon. This leads to some complications:
20764 Because colon is the default separator for the list of hosts, either
20765 the colon that specifies a port must be doubled, or the list separator must
20766 be changed. The following two examples have the same effect:
20768 route_list = * "host1.tld::1225 : host2.tld::1226"
20769 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
20772 When IPv6 addresses are involved, it gets worse, because they contain
20773 colons of their own. To make this case easier, it is permitted to
20774 enclose an IP address (either v4 or v6) in square brackets if a port
20775 number follows. For example:
20777 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
20781 .section "How the list of hosts is used" "SECThostshowused"
20782 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
20783 the hosts is tried, in the order specified, when carrying out the SMTP
20784 delivery. However, the order can be changed by setting the &%hosts_randomize%&
20785 option, either on the router (see section &<<SECTprioptman>>& above), or on the
20788 Hosts may be listed by name or by IP address. An unadorned name in the list of
20789 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
20790 interpreted as an indirection to a sublist of hosts obtained by looking up MX
20791 records in the DNS. For example:
20793 route_list = * x.y.z:p.q.r/MX:e.f.g
20795 If this feature is used with a port specifier, the port must come last. For
20798 route_list = * dom1.tld/mx::1225
20800 If the &%hosts_randomize%& option is set, the order of the items in the list is
20801 randomized before any lookups are done. Exim then scans the list; for any name
20802 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
20803 be an interface on the local host and the item is not the first in the list,
20804 Exim discards it and any subsequent items. If it is the first item, what
20805 happens is controlled by the
20806 .oindex "&%self%&" "in &(manualroute)& router"
20807 &%self%& option of the router.
20809 A name on the list that is followed by &`/MX`& is replaced with the list of
20810 hosts obtained by looking up MX records for the name. This is always a DNS
20811 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
20812 below) are not relevant here. The order of these hosts is determined by the
20813 preference values in the MX records, according to the usual rules. Because
20814 randomizing happens before the MX lookup, it does not affect the order that is
20815 defined by MX preferences.
20817 If the local host is present in the sublist obtained from MX records, but is
20818 not the most preferred host in that list, it and any equally or less
20819 preferred hosts are removed before the sublist is inserted into the main list.
20821 If the local host is the most preferred host in the MX list, what happens
20822 depends on where in the original list of hosts the &`/MX`& item appears. If it
20823 is not the first item (that is, there are previous hosts in the main list),
20824 Exim discards this name and any subsequent items in the main list.
20826 If the MX item is first in the list of hosts, and the local host is the
20827 most preferred host, what happens is controlled by the &%self%& option of the
20830 DNS failures when lookup up the MX records are treated in the same way as DNS
20831 failures when looking up IP addresses: &%pass_on_timeout%& and
20832 &%host_find_failed%& are used when relevant.
20834 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
20835 whether obtained from an MX lookup or not.
20839 .section "How the options are used" "SECThowoptused"
20840 The options are a sequence of words, space-separated.
20841 One of the words can be the name of a transport; this overrides the
20842 &%transport%& option on the router for this particular routing rule only. The
20843 other words (if present) control randomization of the list of hosts on a
20844 per-rule basis, and how the IP addresses of the hosts are to be found when
20845 routing to a remote transport. These options are as follows:
20848 &%randomize%&: randomize the order of the hosts in this list, overriding the
20849 setting of &%hosts_randomize%& for this routing rule only.
20851 &%no_randomize%&: do not randomize the order of the hosts in this list,
20852 overriding the setting of &%hosts_randomize%& for this routing rule only.
20854 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
20855 find IP addresses. This function may ultimately cause a DNS lookup, but it may
20856 also look in &_/etc/hosts_& or other sources of information.
20858 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
20859 no address records are found. If there is a temporary DNS error (such as a
20860 timeout), delivery is deferred.
20862 &%ipv4_only%&: in direct DNS lookups, look up only A records.
20864 &%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
20869 route_list = domain1 host1:host2:host3 randomize bydns;\
20870 domain2 host4:host5
20872 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
20873 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
20874 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
20875 or &[gethostbyname()]&, and the result of the lookup is the result of that
20878 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
20879 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
20880 instead of TRY_AGAIN. That is why the default action is to try a DNS
20881 lookup first. Only if that gives a definite &"no such host"& is the local
20884 &*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
20885 inadvertent constraint that a transport name as an option had to be the last
20890 If no IP address for a host can be found, what happens is controlled by the
20891 &%host_find_failed%& option.
20894 When an address is routed to a local transport, IP addresses are not looked up.
20895 The host list is passed to the transport in the &$host$& variable.
20899 .section "Manualroute examples" "SECID123"
20900 In some of the examples that follow, the presence of the &%remote_smtp%&
20901 transport, as defined in the default configuration file, is assumed:
20904 .cindex "smart host" "example router"
20905 The &(manualroute)& router can be used to forward all external mail to a
20906 &'smart host'&. If you have set up, in the main part of the configuration, a
20907 named domain list that contains your local domains, for example:
20909 domainlist local_domains = my.domain.example
20911 You can arrange for all other domains to be routed to a smart host by making
20912 your first router something like this:
20915 driver = manualroute
20916 domains = !+local_domains
20917 transport = remote_smtp
20918 route_list = * smarthost.ref.example
20920 This causes all non-local addresses to be sent to the single host
20921 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
20922 they are tried in order
20923 (but you can use &%hosts_randomize%& to vary the order each time).
20924 Another way of configuring the same thing is this:
20927 driver = manualroute
20928 transport = remote_smtp
20929 route_list = !+local_domains smarthost.ref.example
20931 There is no difference in behaviour between these two routers as they stand.
20932 However, they behave differently if &%no_more%& is added to them. In the first
20933 example, the router is skipped if the domain does not match the &%domains%&
20934 precondition; the following router is always tried. If the router runs, it
20935 always matches the domain and so can never decline. Therefore, &%no_more%&
20936 would have no effect. In the second case, the router is never skipped; it
20937 always runs. However, if it doesn't match the domain, it declines. In this case
20938 &%no_more%& would prevent subsequent routers from running.
20941 .cindex "mail hub example"
20942 A &'mail hub'& is a host which receives mail for a number of domains via MX
20943 records in the DNS and delivers it via its own private routing mechanism. Often
20944 the final destinations are behind a firewall, with the mail hub being the one
20945 machine that can connect to machines both inside and outside the firewall. The
20946 &(manualroute)& router is usually used on a mail hub to route incoming messages
20947 to the correct hosts. For a small number of domains, the routing can be inline,
20948 using the &%route_list%& option, but for a larger number a file or database
20949 lookup is easier to manage.
20951 If the domain names are in fact the names of the machines to which the mail is
20952 to be sent by the mail hub, the configuration can be quite simple. For
20956 driver = manualroute
20957 transport = remote_smtp
20958 route_list = *.rhodes.tvs.example $domain
20960 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
20961 whose names are the same as the mail domains. A similar approach can be taken
20962 if the host name can be obtained from the domain name by a string manipulation
20963 that the expansion facilities can handle. Otherwise, a lookup based on the
20964 domain can be used to find the host:
20967 driver = manualroute
20968 transport = remote_smtp
20969 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
20971 The result of the lookup must be the name or IP address of the host (or
20972 hosts) to which the address is to be routed. If the lookup fails, the route
20973 data is empty, causing the router to decline. The address then passes to the
20977 .cindex "batched SMTP output example"
20978 .cindex "SMTP" "batched outgoing; example"
20979 You can use &(manualroute)& to deliver messages to pipes or files in batched
20980 SMTP format for onward transportation by some other means. This is one way of
20981 storing mail for a dial-up host when it is not connected. The route list entry
20982 can be as simple as a single domain name in a configuration like this:
20985 driver = manualroute
20986 transport = batchsmtp_appendfile
20987 route_list = saved.domain.example
20989 though often a pattern is used to pick up more than one domain. If there are
20990 several domains or groups of domains with different transport requirements,
20991 different transports can be listed in the routing information:
20994 driver = manualroute
20996 *.saved.domain1.example $domain batch_appendfile; \
20997 *.saved.domain2.example \
20998 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
21001 .vindex "&$domain$&"
21003 The first of these just passes the domain in the &$host$& variable, which
21004 doesn't achieve much (since it is also in &$domain$&), but the second does a
21005 file lookup to find a value to pass, causing the router to decline to handle
21006 the address if the lookup fails.
21009 .cindex "UUCP" "example of router for"
21010 Routing mail directly to UUCP software is a specific case of the use of
21011 &(manualroute)& in a gateway to another mail environment. This is an example of
21012 one way it can be done:
21018 command = /usr/local/bin/uux -r - \
21019 ${substr_-5:$host}!rmail ${local_part}
21020 return_fail_output = true
21025 driver = manualroute
21027 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
21029 The file &_/usr/local/exim/uucphosts_& contains entries like
21031 darksite.ethereal.example: darksite.UUCP
21033 It can be set up more simply without adding and removing &".UUCP"& but this way
21034 makes clear the distinction between the domain name
21035 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
21037 .ecindex IIDmanrou1
21038 .ecindex IIDmanrou2
21047 . ////////////////////////////////////////////////////////////////////////////
21048 . ////////////////////////////////////////////////////////////////////////////
21050 .chapter "The queryprogram router" "CHAPdriverlast"
21051 .scindex IIDquerou1 "&(queryprogram)& router"
21052 .scindex IIDquerou2 "routers" "&(queryprogram)&"
21053 .cindex "routing" "by external program"
21054 The &(queryprogram)& router routes an address by running an external command
21055 and acting on its output. This is an expensive way to route, and is intended
21056 mainly for use in lightly-loaded systems, or for performing experiments.
21057 However, if it is possible to use the precondition options (&%domains%&,
21058 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
21059 be used in special cases, even on a busy host. There are the following private
21061 .cindex "options" "&(queryprogram)& router"
21063 .option command queryprogram string&!! unset
21064 This option must be set. It specifies the command that is to be run. The
21065 command is split up into a command name and arguments, and then each is
21066 expanded separately (exactly as for a &(pipe)& transport, described in chapter
21067 &<<CHAPpipetransport>>&).
21070 .option command_group queryprogram string unset
21071 .cindex "gid (group id)" "in &(queryprogram)& router"
21072 This option specifies a gid to be set when running the command while routing an
21073 address for deliver. It must be set if &%command_user%& specifies a numerical
21074 uid. If it begins with a digit, it is interpreted as the numerical value of the
21075 gid. Otherwise it is looked up using &[getgrnam()]&.
21078 .option command_user queryprogram string unset
21079 .cindex "uid (user id)" "for &(queryprogram)&"
21080 This option must be set. It specifies the uid which is set when running the
21081 command while routing an address for delivery. If the value begins with a digit,
21082 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
21083 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
21084 not set, a value for the gid also.
21086 &*Warning:*& Changing uid and gid is possible only when Exim is running as
21087 root, which it does during a normal delivery in a conventional configuration.
21088 However, when an address is being verified during message reception, Exim is
21089 usually running as the Exim user, not as root. If the &(queryprogram)& router
21090 is called from a non-root process, Exim cannot change uid or gid before running
21091 the command. In this circumstance the command runs under the current uid and
21095 .option current_directory queryprogram string /
21096 This option specifies an absolute path which is made the current directory
21097 before running the command.
21100 .option timeout queryprogram time 1h
21101 If the command does not complete within the timeout period, its process group
21102 is killed and the message is frozen. A value of zero time specifies no
21106 The standard output of the command is connected to a pipe, which is read when
21107 the command terminates. It should consist of a single line of output,
21108 containing up to five fields, separated by white space. The maximum length of
21109 the line is 1023 characters. Longer lines are silently truncated. The first
21110 field is one of the following words (case-insensitive):
21113 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
21116 &'Decline'&: the router declines; pass the address to the next router, unless
21117 &%no_more%& is set.
21119 &'Fail'&: routing failed; do not pass the address to any more routers. Any
21120 subsequent text on the line is an error message. If the router is run as part
21121 of address verification during an incoming SMTP message, the message is
21122 included in the SMTP response.
21124 &'Defer'&: routing could not be completed at this time; try again later. Any
21125 subsequent text on the line is an error message which is logged. It is not
21126 included in any SMTP response.
21128 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
21130 &'Pass'&: pass the address to the next router (or the router specified by
21131 &%pass_router%&), overriding &%no_more%&.
21133 &'Redirect'&: the message is redirected. The remainder of the line is a list of
21134 new addresses, which are routed independently, starting with the first router,
21135 or the router specified by &%redirect_router%&, if set.
21138 When the first word is &'accept'&, the remainder of the line consists of a
21139 number of keyed data values, as follows (split into two lines here, to fit on
21142 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
21143 LOOKUP=byname|bydns DATA=<text>
21145 The data items can be given in any order, and all are optional. If no transport
21146 is included, the transport specified by the generic &%transport%& option is
21147 used. The list of hosts and the lookup type are needed only if the transport is
21148 an &(smtp)& transport that does not itself supply a list of hosts.
21150 The format of the list of hosts is the same as for the &(manualroute)& router.
21151 As well as host names and IP addresses with optional port numbers, as described
21152 in section &<<SECTformatonehostitem>>&, it may contain names followed by
21153 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
21154 (see section &<<SECThostshowused>>&).
21156 If the lookup type is not specified, Exim behaves as follows when trying to
21157 find an IP address for each host: First, a DNS lookup is done. If this yields
21158 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
21159 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
21160 result of the lookup is the result of that call.
21162 .vindex "&$address_data$&"
21163 If the DATA field is set, its value is placed in the &$address_data$&
21164 variable. For example, this return line
21166 accept hosts=x1.y.example:x2.y.example data="rule1"
21168 routes the address to the default transport, passing a list of two hosts. When
21169 the transport runs, the string &"rule1"& is in &$address_data$&.
21170 .ecindex IIDquerou1
21171 .ecindex IIDquerou2
21176 . ////////////////////////////////////////////////////////////////////////////
21177 . ////////////////////////////////////////////////////////////////////////////
21179 .chapter "The redirect router" "CHAPredirect"
21180 .scindex IIDredrou1 "&(redirect)& router"
21181 .scindex IIDredrou2 "routers" "&(redirect)&"
21182 .cindex "alias file" "in a &(redirect)& router"
21183 .cindex "address redirection" "&(redirect)& router"
21184 The &(redirect)& router handles several kinds of address redirection. Its most
21185 common uses are for resolving local part aliases from a central alias file
21186 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
21187 files, but it has many other potential uses. The incoming address can be
21188 redirected in several different ways:
21191 It can be replaced by one or more new addresses which are themselves routed
21194 It can be routed to be delivered to a given file or directory.
21196 It can be routed to be delivered to a specified pipe command.
21198 It can cause an automatic reply to be generated.
21200 It can be forced to fail, optionally with a custom error message.
21202 It can be temporarily deferred, optionally with a custom message.
21204 It can be discarded.
21207 The generic &%transport%& option must not be set for &(redirect)& routers.
21208 However, there are some private options which define transports for delivery to
21209 files and pipes, and for generating autoreplies. See the &%file_transport%&,
21210 &%pipe_transport%& and &%reply_transport%& descriptions below.
21212 If success DSNs have been requested
21213 .cindex "DSN" "success"
21214 .cindex "Delivery Status Notification" "success"
21215 redirection triggers one and the DSN options are not passed any further.
21219 .section "Redirection data" "SECID124"
21220 The router operates by interpreting a text string which it obtains either by
21221 expanding the contents of the &%data%& option, or by reading the entire
21222 contents of a file whose name is given in the &%file%& option. These two
21223 options are mutually exclusive. The first is commonly used for handling system
21224 aliases, in a configuration like this:
21228 data = ${lookup{$local_part}lsearch{/etc/aliases}}
21230 If the lookup fails, the expanded string in this example is empty. When the
21231 expansion of &%data%& results in an empty string, the router declines. A forced
21232 expansion failure also causes the router to decline; other expansion failures
21233 cause delivery to be deferred.
21235 A configuration using &%file%& is commonly used for handling users'
21236 &_.forward_& files, like this:
21241 file = $home/.forward
21244 If the file does not exist, or causes no action to be taken (for example, it is
21245 empty or consists only of comments), the router declines. &*Warning*&: This
21246 is not the case when the file contains syntactically valid items that happen to
21247 yield empty addresses, for example, items containing only RFC 2822 address
21250 .cindex "tainted data" "in filenames"
21251 .cindex redirect "tainted data"
21252 Tainted data may not be used for a filename.
21254 &*Warning*&: It is unwise to use &$local_part$& or &$domain$&
21255 directly for redirection,
21256 as they are provided by a potential attacker.
21257 In the examples above, &$local_part$& is used for looking up data held locally
21258 on the system, and not used directly (the second example derives &$home$& via
21259 the passsword file or database, using &$local_part$&).
21263 .section "Forward files and address verification" "SECID125"
21264 .cindex "address redirection" "while verifying"
21265 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
21266 &_.forward_& files, as in the example above. There are two reasons for this:
21269 When Exim is receiving an incoming SMTP message from a remote host, it is
21270 running under the Exim uid, not as root. Exim is unable to change uid to read
21271 the file as the user, and it may not be able to read it as the Exim user. So in
21272 practice the router may not be able to operate.
21274 However, even when the router can operate, the existence of a &_.forward_& file
21275 is unimportant when verifying an address. What should be checked is whether the
21276 local part is a valid user name or not. Cutting out the redirection processing
21277 saves some resources.
21285 .section "Interpreting redirection data" "SECID126"
21286 .cindex "Sieve filter" "specifying in redirection data"
21287 .cindex "filter" "specifying in redirection data"
21288 The contents of the data string, whether obtained from &%data%& or &%file%&,
21289 can be interpreted in two different ways:
21292 If the &%allow_filter%& option is set true, and the data begins with the text
21293 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
21294 &'filtering'& instructions in the form of an Exim or Sieve filter file,
21295 respectively. Details of the syntax and semantics of filter files are described
21296 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
21297 document is intended for use by end users.
21299 Otherwise, the data must be a comma-separated list of redirection items, as
21300 described in the next section.
21303 When a message is redirected to a file (a &"mail folder"&), the filename given
21304 in a non-filter redirection list must always be an absolute path. A filter may
21305 generate a relative path &-- how this is handled depends on the transport's
21306 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
21307 for the &(appendfile)& transport.
21311 .section "Items in a non-filter redirection list" "SECTitenonfilred"
21312 .cindex "address redirection" "non-filter list items"
21313 When the redirection data is not an Exim or Sieve filter, for example, if it
21314 comes from a conventional alias or forward file, it consists of a list of
21315 addresses, filenames, pipe commands, or certain special items (see section
21316 &<<SECTspecitredli>>& below). The special items can be individually enabled or
21317 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
21318 depending on their default values. The items in the list are separated by
21319 commas or newlines.
21320 If a comma is required in an item, the entire item must be enclosed in double
21323 Lines starting with a # character are comments, and are ignored, and # may
21324 also appear following a comma, in which case everything between the # and the
21325 next newline character is ignored.
21327 If an item is entirely enclosed in double quotes, these are removed. Otherwise
21328 double quotes are retained because some forms of mail address require their use
21329 (but never to enclose the entire address). In the following description,
21330 &"item"& refers to what remains after any surrounding double quotes have been
21333 .vindex "&$local_part$&"
21334 &*Warning*&: If you use an Exim expansion to construct a redirection address,
21335 and the expansion contains a reference to &$local_part$&, you should make use
21336 of the &%quote_local_part%& expansion operator, in case the local part contains
21337 special characters. For example, to redirect all mail for the domain
21338 &'obsolete.example'&, retaining the existing local part, you could use this
21341 data = ${quote_local_part:$local_part}@newdomain.example
21345 .section "Redirecting to a local mailbox" "SECTredlocmai"
21346 .cindex "routing" "loops in"
21347 .cindex "loop" "while routing, avoidance of"
21348 .cindex "address redirection" "to local mailbox"
21349 A redirection item may safely be the same as the address currently under
21350 consideration. This does not cause a routing loop, because a router is
21351 automatically skipped if any ancestor of the address that is being processed
21352 is the same as the current address and was processed by the current router.
21353 Such an address is therefore passed to the following routers, so it is handled
21354 as if there were no redirection. When making this loop-avoidance test, the
21355 complete local part, including any prefix or suffix, is used.
21357 .cindex "address redirection" "local part without domain"
21358 Specifying the same local part without a domain is a common usage in personal
21359 filter files when the user wants to have messages delivered to the local
21360 mailbox and also forwarded elsewhere. For example, the user whose login is
21361 &'cleo'& might have a &_.forward_& file containing this:
21363 cleo, cleopatra@egypt.example
21365 .cindex "backslash in alias file"
21366 .cindex "alias file" "backslash in"
21367 For compatibility with other MTAs, such unqualified local parts may be
21368 preceded by &"\"&, but this is not a requirement for loop prevention. However,
21369 it does make a difference if more than one domain is being handled
21372 If an item begins with &"\"& and the rest of the item parses as a valid RFC
21373 2822 address that does not include a domain, the item is qualified using the
21374 domain of the incoming address. In the absence of a leading &"\"&, unqualified
21375 addresses are qualified using the value in &%qualify_recipient%&, but you can
21376 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
21378 Care must be taken if there are alias names for local users.
21379 Consider an MTA handling a single local domain where the system alias file
21384 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
21385 messages in the local mailbox, and also forward copies elsewhere. He creates
21388 Sam.Reman, spqr@reme.elsewhere.example
21390 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
21391 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
21392 second time round, because it has previously routed it,
21393 and the following routers presumably cannot handle the alias. The forward file
21394 should really contain
21396 spqr, spqr@reme.elsewhere.example
21398 but because this is such a common error, the &%check_ancestor%& option (see
21399 below) exists to provide a way to get round it. This is normally set on a
21400 &(redirect)& router that is handling users' &_.forward_& files.
21404 .section "Special items in redirection lists" "SECTspecitredli"
21405 In addition to addresses, the following types of item may appear in redirection
21406 lists (that is, in non-filter redirection data):
21409 .cindex "pipe" "in redirection list"
21410 .cindex "address redirection" "to pipe"
21411 An item is treated as a pipe command if it begins with &"|"& and does not parse
21412 as a valid RFC 2822 address that includes a domain. A transport for running the
21413 command must be specified by the &%pipe_transport%& option.
21414 Normally, either the router or the transport specifies a user and a group under
21415 which to run the delivery. The default is to use the Exim user and group.
21417 Single or double quotes can be used for enclosing the individual arguments of
21418 the pipe command; no interpretation of escapes is done for single quotes. If
21419 the command contains a comma character, it is necessary to put the whole item
21420 in double quotes, for example:
21422 "|/some/command ready,steady,go"
21424 since items in redirection lists are terminated by commas. Do not, however,
21425 quote just the command. An item such as
21427 |"/some/command ready,steady,go"
21429 is interpreted as a pipe with a rather strange command name, and no arguments.
21431 Note that the above example assumes that the text comes from a lookup source
21432 of some sort, so that the quotes are part of the data. If composing a
21433 redirect router with a &%data%& option directly specifying this command, the
21434 quotes will be used by the configuration parser to define the extent of one
21435 string, but will not be passed down into the redirect router itself. There
21436 are two main approaches to get around this: escape quotes to be part of the
21437 data itself, or avoid using this mechanism and instead create a custom
21438 transport with the &%command%& option set and reference that transport from
21439 an &%accept%& router.
21442 .cindex "file" "in redirection list"
21443 .cindex "address redirection" "to file"
21444 An item is interpreted as a path name if it begins with &"/"& and does not
21445 parse as a valid RFC 2822 address that includes a domain. For example,
21447 /home/world/minbari
21449 is treated as a filename, but
21451 /s=molari/o=babylon/@x400gate.way
21453 is treated as an address. For a filename, a transport must be specified using
21454 the &%file_transport%& option. However, if the generated path name ends with a
21455 forward slash character, it is interpreted as a directory name rather than a
21456 filename, and &%directory_transport%& is used instead.
21458 Normally, either the router or the transport specifies a user and a group under
21459 which to run the delivery. The default is to use the Exim user and group.
21461 .cindex "&_/dev/null_&"
21462 However, if a redirection item is the path &_/dev/null_&, delivery to it is
21463 bypassed at a high level, and the log entry shows &"**bypassed**"&
21464 instead of a transport name. In this case the user and group are not used.
21467 .cindex "included address list"
21468 .cindex "address redirection" "included external list"
21469 If an item is of the form
21471 :include:<path name>
21473 a list of further items is taken from the given file and included at that
21474 point. &*Note*&: Such a file can not be a filter file; it is just an
21475 out-of-line addition to the list. The items in the included list are separated
21476 by commas or newlines and are not subject to expansion. If this is the first
21477 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
21478 the alias name. This example is incorrect:
21480 list1 :include:/opt/lists/list1
21482 It must be given as
21484 list1: :include:/opt/lists/list1
21486 .cindex "tainted data" "in filenames"
21487 .cindex redirect "tainted data"
21488 Tainted data may not be used for a filename.
21490 .cindex "address redirection" "to black hole"
21491 .cindex "delivery" "discard"
21492 .cindex "delivery" "blackhole"
21493 .cindex "black hole"
21494 .cindex "abandoning mail"
21495 Sometimes you want to throw away mail to a particular local part. Making the
21496 &%data%& option expand to an empty string does not work, because that causes
21497 the router to decline. Instead, the alias item
21501 can be used. It does what its name implies. No delivery is
21502 done, and no error message is generated. This has the same effect as specifying
21503 &_/dev/null_& as a destination, but it can be independently disabled.
21505 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
21506 delivery is done for the original local part, even if other redirection items
21507 are present. If you are generating a multi-item list (for example, by reading a
21508 database) and need the ability to provide a no-op item, you must use
21512 .cindex "delivery" "forcing failure"
21513 .cindex "delivery" "forcing deferral"
21514 .cindex "failing delivery" "forcing"
21515 .cindex "deferred delivery, forcing"
21516 .cindex "customizing" "failure message"
21517 An attempt to deliver a particular address can be deferred or forced to fail by
21518 redirection items of the form
21523 respectively. When a redirection list contains such an item, it applies
21524 to the entire redirection; any other items in the list are ignored. Any
21525 text following &':fail:'& or &':defer:'& is placed in the error text
21526 associated with the failure. For example, an alias file might contain:
21528 X.Employee: :fail: Gone away, no forwarding address
21530 In the case of an address that is being verified from an ACL or as the subject
21532 .cindex "VRFY" "error text, display of"
21533 VRFY command, the text is included in the SMTP error response by
21535 .cindex "EXPN" "error text, display of"
21536 The text is not included in the response to an EXPN command. In non-SMTP cases
21537 the text is included in the error message that Exim generates.
21539 .cindex "SMTP" "error codes"
21540 By default for verify, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
21541 &':fail:'&. However, if the message starts with three digits followed by a
21542 space, optionally followed by an extended code of the form &'n.n.n'&, also
21543 followed by a space, and the very first digit is the same as the default error
21544 code, the code from the message is used instead. If the very first digit is
21545 incorrect, a panic error is logged, and the default code is used. You can
21546 suppress the use of the supplied code in a redirect router by setting the
21547 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
21550 .vindex "&$acl_verify_message$&"
21551 In an ACL, an explicitly provided message overrides the default, but the
21552 default message is available in the variable &$acl_verify_message$& and can
21553 therefore be included in a custom message if this is desired.
21555 Normally the error text is the rest of the redirection list &-- a comma does
21556 not terminate it &-- but a newline does act as a terminator. Newlines are not
21557 normally present in alias expansions. In &(lsearch)& lookups they are removed
21558 as part of the continuation process, but they may exist in other kinds of
21559 lookup and in &':include:'& files.
21561 During routing for message delivery (as opposed to verification), a redirection
21562 containing &':fail:'& causes an immediate failure of the incoming address,
21563 whereas &':defer:'& causes the message to remain in the queue so that a
21564 subsequent delivery attempt can happen at a later time. If an address is
21565 deferred for too long, it will ultimately fail, because the normal retry
21569 .cindex "alias file" "exception to default"
21570 Sometimes it is useful to use a single-key search type with a default (see
21571 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
21572 for exceptions to the default. These can be handled by aliasing them to
21573 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
21574 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
21575 results in an empty redirection list has the same effect.
21579 .section "Duplicate addresses" "SECTdupaddr"
21580 .cindex "duplicate addresses"
21581 .cindex "address duplicate, discarding"
21582 .cindex "pipe" "duplicated"
21583 Exim removes duplicate addresses from the list to which it is delivering, so as
21584 to deliver just one copy to each address. This does not apply to deliveries
21585 routed to pipes by different immediate parent addresses, but an indirect
21586 aliasing scheme of the type
21588 pipe: |/some/command $local_part
21592 does not work with a message that is addressed to both local parts, because
21593 when the second is aliased to the intermediate local part &"pipe"& it gets
21594 discarded as being the same as a previously handled address. However, a scheme
21597 localpart1: |/some/command $local_part
21598 localpart2: |/some/command $local_part
21600 does result in two different pipe deliveries, because the immediate parents of
21601 the pipes are distinct.
21605 .section "Repeated redirection expansion" "SECID128"
21606 .cindex "repeated redirection expansion"
21607 .cindex "address redirection" "repeated for each delivery attempt"
21608 When a message cannot be delivered to all of its recipients immediately,
21609 leading to two or more delivery attempts, redirection expansion is carried out
21610 afresh each time for those addresses whose children were not all previously
21611 delivered. If redirection is being used as a mailing list, this can lead to new
21612 members of the list receiving copies of old messages. The &%one_time%& option
21613 can be used to avoid this.
21616 .section "Errors in redirection lists" "SECID129"
21617 .cindex "address redirection" "errors"
21618 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
21619 error is skipped, and an entry is written to the main log. This may be useful
21620 for mailing lists that are automatically managed. Otherwise, if an error is
21621 detected while generating the list of new addresses, the original address is
21622 deferred. See also &%syntax_errors_to%&.
21626 .section "Private options for the redirect router" "SECID130"
21628 .cindex "options" "&(redirect)& router"
21629 The private options for the &(redirect)& router are as follows:
21632 .option allow_defer redirect boolean false
21633 Setting this option allows the use of &':defer:'& in non-filter redirection
21634 data, or the &%defer%& command in an Exim filter file.
21637 .option allow_fail redirect boolean false
21638 .cindex "failing delivery" "from filter"
21639 If this option is true, the &':fail:'& item can be used in a redirection list,
21640 and the &%fail%& command may be used in an Exim filter file.
21643 .option allow_filter redirect boolean false
21644 .cindex "filter" "enabling use of"
21645 .cindex "Sieve filter" "enabling use of"
21646 Setting this option allows Exim to interpret redirection data that starts with
21647 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
21648 are some features of Exim filter files that some administrators may wish to
21649 lock out; see the &%forbid_filter_%&&'xxx'& options below.
21651 It is also possible to lock out Exim filters or Sieve filters while allowing
21652 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
21655 The filter is run using the uid and gid set by the generic &%user%& and
21656 &%group%& options. These take their defaults from the password data if
21657 &%check_local_user%& is set, so in the normal case of users' personal filter
21658 files, the filter is run as the relevant user. When &%allow_filter%& is set
21659 true, Exim insists that either &%check_local_user%& or &%user%& is set.
21663 .option allow_freeze redirect boolean false
21664 .cindex "freezing messages" "allowing in filter"
21665 Setting this option allows the use of the &%freeze%& command in an Exim filter.
21666 This command is more normally encountered in system filters, and is disabled by
21667 default for redirection filters because it isn't something you usually want to
21668 let ordinary users do.
21672 .option check_ancestor redirect boolean false
21673 This option is concerned with handling generated addresses that are the same
21674 as some address in the list of redirection ancestors of the current address.
21675 Although it is turned off by default in the code, it is set in the default
21676 configuration file for handling users' &_.forward_& files. It is recommended
21677 for this use of the &(redirect)& router.
21679 When &%check_ancestor%& is set, if a generated address (including the domain)
21680 is the same as any ancestor of the current address, it is replaced by a copy of
21681 the current address. This helps in the case where local part A is aliased to B,
21682 and B has a &_.forward_& file pointing back to A. For example, within a single
21683 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
21684 &_&~jb/.forward_& contains:
21686 \Joe.Bloggs, <other item(s)>
21688 Without the &%check_ancestor%& setting, either local part (&"jb"& or
21689 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
21690 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
21691 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
21692 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
21693 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
21694 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
21695 original address. See also the &%repeat_use%& option below.
21698 .option check_group redirect boolean "see below"
21699 When the &%file%& option is used, the group owner of the file is checked only
21700 when this option is set. The permitted groups are those listed in the
21701 &%owngroups%& option, together with the user's default group if
21702 &%check_local_user%& is set. If the file has the wrong group, routing is
21703 deferred. The default setting for this option is true if &%check_local_user%&
21704 is set and the &%modemask%& option permits the group write bit, or if the
21705 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
21709 .option check_owner redirect boolean "see below"
21710 When the &%file%& option is used, the owner of the file is checked only when
21711 this option is set. If &%check_local_user%& is set, the local user is
21712 permitted; otherwise the owner must be one of those listed in the &%owners%&
21713 option. The default value for this option is true if &%check_local_user%& or
21714 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
21717 .option data redirect string&!! unset
21718 This option is mutually exclusive with &%file%&. One or other of them must be
21719 set, but not both. The contents of &%data%& are expanded, and then used as the
21720 list of forwarding items, or as a set of filtering instructions. If the
21721 expansion is forced to fail, or the result is an empty string or a string that
21722 has no effect (consists entirely of comments), the router declines.
21724 When filtering instructions are used, the string must begin with &"#Exim
21725 filter"&, and all comments in the string, including this initial one, must be
21726 terminated with newline characters. For example:
21728 data = #Exim filter\n\
21729 if $h_to: contains Exim then save $home/mail/exim endif
21731 If you are reading the data from a database where newlines cannot be included,
21732 you can use the &${sg}$& expansion item to turn the escape string of your
21733 choice into a newline.
21736 .option directory_transport redirect string&!! unset
21737 A &(redirect)& router sets up a direct delivery to a directory when a path name
21738 ending with a slash is specified as a new &"address"&. The transport used is
21739 specified by this option, which, after expansion, must be the name of a
21740 configured transport. This should normally be an &(appendfile)& transport.
21743 .option file redirect string&!! unset
21744 This option specifies the name of a file that contains the redirection data. It
21745 is mutually exclusive with the &%data%& option. The string is expanded before
21746 use; if the expansion is forced to fail, the router declines. Other expansion
21747 failures cause delivery to be deferred. The result of a successful expansion
21748 must be an absolute path. The entire file is read and used as the redirection
21749 data. If the data is an empty string or a string that has no effect (consists
21750 entirely of comments), the router declines.
21752 .cindex "NFS" "checking for file existence"
21753 If the attempt to open the file fails with a &"does not exist"& error, Exim
21754 runs a check on the containing directory,
21755 unless &%ignore_enotdir%& is true (see below).
21756 If the directory does not appear to exist, delivery is deferred. This can
21757 happen when users' &_.forward_& files are in NFS-mounted directories, and there
21758 is a mount problem. If the containing directory does exist, but the file does
21759 not, the router declines.
21762 .option file_transport redirect string&!! unset
21763 .vindex "&$address_file$&"
21764 A &(redirect)& router sets up a direct delivery to a file when a path name not
21765 ending in a slash is specified as a new &"address"&. The transport used is
21766 specified by this option, which, after expansion, must be the name of a
21767 configured transport. This should normally be an &(appendfile)& transport. When
21768 it is running, the filename is in &$address_file$&.
21771 .option filter_prepend_home redirect boolean true
21772 When this option is true, if a &(save)& command in an Exim filter specifies a
21773 relative path, and &$home$& is defined, it is automatically prepended to the
21774 relative path. If this option is set false, this action does not happen. The
21775 relative path is then passed to the transport unmodified.
21778 .option forbid_blackhole redirect boolean false
21779 .cindex "restricting access to features"
21780 .cindex "filter" "locking out certain features"
21781 If this option is true, the &':blackhole:'& item may not appear in a
21785 .option forbid_exim_filter redirect boolean false
21786 .cindex "restricting access to features"
21787 .cindex "filter" "locking out certain features"
21788 If this option is set true, only Sieve filters are permitted when
21789 &%allow_filter%& is true.
21794 .option forbid_file redirect boolean false
21795 .cindex "restricting access to features"
21796 .cindex "delivery" "to file; forbidding"
21797 .cindex "filter" "locking out certain features"
21798 .cindex "Sieve filter" "forbidding delivery to a file"
21799 .cindex "Sieve filter" "&""keep""& facility; disabling"
21800 If this option is true, this router may not generate a new address that
21801 specifies delivery to a local file or directory, either from a filter or from a
21802 conventional forward file. This option is forced to be true if &%one_time%& is
21803 set. It applies to Sieve filters as well as to Exim filters, but if true, it
21804 locks out the Sieve's &"keep"& facility.
21807 .option forbid_filter_dlfunc redirect boolean false
21808 .cindex "restricting access to features"
21809 .cindex "filter" "locking out certain features"
21810 If this option is true, string expansions in Exim filters are not allowed to
21811 make use of the &%dlfunc%& expansion facility to run dynamically loaded
21814 .option forbid_filter_existstest redirect boolean false
21815 .cindex "restricting access to features"
21816 .cindex "filter" "locking out certain features"
21817 .cindex "expansion" "statting a file"
21818 If this option is true, string expansions in Exim filters are not allowed to
21819 make use of the &%exists%& condition or the &%stat%& expansion item.
21821 .option forbid_filter_logwrite redirect boolean false
21822 .cindex "restricting access to features"
21823 .cindex "filter" "locking out certain features"
21824 If this option is true, use of the logging facility in Exim filters is not
21825 permitted. Logging is in any case available only if the filter is being run
21826 under some unprivileged uid (which is normally the case for ordinary users'
21827 &_.forward_& files).
21830 .option forbid_filter_lookup redirect boolean false
21831 .cindex "restricting access to features"
21832 .cindex "filter" "locking out certain features"
21833 If this option is true, string expansions in Exim filter files are not allowed
21834 to make use of &%lookup%& items.
21837 .option forbid_filter_perl redirect boolean false
21838 .cindex "restricting access to features"
21839 .cindex "filter" "locking out certain features"
21840 This option has an effect only if Exim is built with embedded Perl support. If
21841 it is true, string expansions in Exim filter files are not allowed to make use
21842 of the embedded Perl support.
21845 .option forbid_filter_readfile redirect boolean false
21846 .cindex "restricting access to features"
21847 .cindex "filter" "locking out certain features"
21848 If this option is true, string expansions in Exim filter files are not allowed
21849 to make use of &%readfile%& items.
21852 .option forbid_filter_readsocket redirect boolean false
21853 .cindex "restricting access to features"
21854 .cindex "filter" "locking out certain features"
21855 If this option is true, string expansions in Exim filter files are not allowed
21856 to make use of &%readsocket%& items.
21859 .option forbid_filter_reply redirect boolean false
21860 .cindex "restricting access to features"
21861 .cindex "filter" "locking out certain features"
21862 If this option is true, this router may not generate an automatic reply
21863 message. Automatic replies can be generated only from Exim or Sieve filter
21864 files, not from traditional forward files. This option is forced to be true if
21865 &%one_time%& is set.
21868 .option forbid_filter_run redirect boolean false
21869 .cindex "restricting access to features"
21870 .cindex "filter" "locking out certain features"
21871 If this option is true, string expansions in Exim filter files are not allowed
21872 to make use of &%run%& items.
21875 .option forbid_include redirect boolean false
21876 .cindex "restricting access to features"
21877 .cindex "filter" "locking out certain features"
21878 If this option is true, items of the form
21880 :include:<path name>
21882 are not permitted in non-filter redirection lists.
21885 .option forbid_pipe redirect boolean false
21886 .cindex "restricting access to features"
21887 .cindex "filter" "locking out certain features"
21888 .cindex "delivery" "to pipe; forbidding"
21889 If this option is true, this router may not generate a new address which
21890 specifies delivery to a pipe, either from an Exim filter or from a conventional
21891 forward file. This option is forced to be true if &%one_time%& is set.
21894 .option forbid_sieve_filter redirect boolean false
21895 .cindex "restricting access to features"
21896 .cindex "filter" "locking out certain features"
21897 If this option is set true, only Exim filters are permitted when
21898 &%allow_filter%& is true.
21901 .cindex "SMTP" "error codes"
21902 .option forbid_smtp_code redirect boolean false
21903 If this option is set true, any SMTP error codes that are present at the start
21904 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
21905 the default codes (451 and 550, respectively) are always used.
21910 .option hide_child_in_errmsg redirect boolean false
21911 .cindex "bounce message" "redirection details; suppressing"
21912 If this option is true, it prevents Exim from quoting a child address if it
21913 generates a bounce or delay message for it. Instead it says &"an address
21914 generated from <&'the top level address'&>"&. Of course, this applies only to
21915 bounces generated locally. If a message is forwarded to another host, &'its'&
21916 bounce may well quote the generated address.
21919 .option ignore_eacces redirect boolean false
21921 If this option is set and an attempt to open a redirection file yields the
21922 EACCES error (permission denied), the &(redirect)& router behaves as if the
21923 file did not exist.
21926 .option ignore_enotdir redirect boolean false
21928 If this option is set and an attempt to open a redirection file yields the
21929 ENOTDIR error (something on the path is not a directory), the &(redirect)&
21930 router behaves as if the file did not exist.
21932 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
21933 router that has the &%file%& option set discovers that the file does not exist
21934 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
21935 against unmounted NFS directories. If the parent can not be statted, delivery
21936 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
21937 is set, because that option tells Exim to ignore &"something on the path is not
21938 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
21939 that some operating systems give ENOENT where others give ENOTDIR.
21943 .option include_directory redirect string unset
21944 If this option is set, the path names of any &':include:'& items in a
21945 redirection list must start with this directory.
21948 .option modemask redirect "octal integer" 022
21949 This specifies mode bits which must not be set for a file specified by the
21950 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
21953 .option one_time redirect boolean false
21954 .cindex "one-time aliasing/forwarding expansion"
21955 .cindex "alias file" "one-time expansion"
21956 .cindex "forward file" "one-time expansion"
21957 .cindex "mailing lists" "one-time expansion"
21958 .cindex "address redirection" "one-time expansion"
21959 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
21960 files each time it tries to deliver a message causes a problem when one or more
21961 of the generated addresses fails be delivered at the first attempt. The problem
21962 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
21963 but of what happens when the redirection list changes during the time that the
21964 message is on Exim's queue. This is particularly true in the case of mailing
21965 lists, where new subscribers might receive copies of messages that were posted
21966 before they subscribed.
21968 If &%one_time%& is set and any addresses generated by the router fail to
21969 deliver at the first attempt, the failing addresses are added to the message as
21970 &"top level"& addresses, and the parent address that generated them is marked
21971 &"delivered"&. Thus, redirection does not happen again at the next delivery
21974 &*Warning 1*&: Any header line addition or removal that is specified by this
21975 router would be lost if delivery did not succeed at the first attempt. For this
21976 reason, the &%headers_add%& and &%headers_remove%& generic options are not
21977 permitted when &%one_time%& is set.
21979 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
21980 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
21981 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
21983 &*Warning 3*&: The &%unseen%& generic router option may not be set with
21986 The original top-level address is remembered with each of the generated
21987 addresses, and is output in any log messages. However, any intermediate parent
21988 addresses are not recorded. This makes a difference to the log only if
21989 &%all_parents%& log selector is set. It is expected that &%one_time%& will
21990 typically be used for mailing lists, where there is normally just one level of
21994 .option owners redirect "string list" unset
21995 .cindex "ownership" "alias file"
21996 .cindex "ownership" "forward file"
21997 .cindex "alias file" "ownership"
21998 .cindex "forward file" "ownership"
21999 This specifies a list of permitted owners for the file specified by &%file%&.
22000 This list is in addition to the local user when &%check_local_user%& is set.
22001 See &%check_owner%& above.
22004 .option owngroups redirect "string list" unset
22005 This specifies a list of permitted groups for the file specified by &%file%&.
22006 The list is in addition to the local user's primary group when
22007 &%check_local_user%& is set. See &%check_group%& above.
22010 .option pipe_transport redirect string&!! unset
22011 .vindex "&$address_pipe$&"
22012 A &(redirect)& router sets up a direct delivery to a pipe when a string
22013 starting with a vertical bar character is specified as a new &"address"&. The
22014 transport used is specified by this option, which, after expansion, must be the
22015 name of a configured transport. This should normally be a &(pipe)& transport.
22016 When the transport is run, the pipe command is in &$address_pipe$&.
22019 .option qualify_domain redirect string&!! unset
22020 .vindex "&$qualify_recipient$&"
22021 If this option is set, and an unqualified address (one without a domain) is
22022 generated, and that address would normally be qualified by the global setting
22023 in &%qualify_recipient%&, it is instead qualified with the domain specified by
22024 expanding this string. If the expansion fails, the router declines. If you want
22025 to revert to the default, you can have the expansion generate
22026 &$qualify_recipient$&.
22028 This option applies to all unqualified addresses generated by Exim filters,
22029 but for traditional &_.forward_& files, it applies only to addresses that are
22030 not preceded by a backslash. Sieve filters cannot generate unqualified
22033 .option qualify_preserve_domain redirect boolean false
22034 .cindex "domain" "in redirection; preserving"
22035 .cindex "preserving domain in redirection"
22036 .cindex "address redirection" "domain; preserving"
22037 If this option is set, the router's local &%qualify_domain%& option must not be
22038 set (a configuration error occurs if it is). If an unqualified address (one
22039 without a domain) is generated, it is qualified with the domain of the parent
22040 address (the immediately preceding ancestor) instead of the global
22041 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
22042 this applies whether or not the address is preceded by a backslash.
22045 .option repeat_use redirect boolean true
22046 If this option is set false, the router is skipped for a child address that has
22047 any ancestor that was routed by this router. This test happens before any of
22048 the other preconditions are tested. Exim's default anti-looping rules skip
22049 only when the ancestor is the same as the current address. See also
22050 &%check_ancestor%& above and the generic &%redirect_router%& option.
22053 .option reply_transport redirect string&!! unset
22054 A &(redirect)& router sets up an automatic reply when a &%mail%& or
22055 &%vacation%& command is used in a filter file. The transport used is specified
22056 by this option, which, after expansion, must be the name of a configured
22057 transport. This should normally be an &(autoreply)& transport. Other transports
22058 are unlikely to do anything sensible or useful.
22061 .option rewrite redirect boolean true
22062 .cindex "address redirection" "disabling rewriting"
22063 If this option is set false, addresses generated by the router are not
22064 subject to address rewriting. Otherwise, they are treated like new addresses
22065 and are rewritten according to the global rewriting rules.
22068 .option sieve_subaddress redirect string&!! unset
22069 The value of this option is passed to a Sieve filter to specify the
22070 :subaddress part of an address.
22072 .option sieve_useraddress redirect string&!! unset
22073 The value of this option is passed to a Sieve filter to specify the :user part
22074 of an address. However, if it is unset, the entire original local part
22075 (including any prefix or suffix) is used for :user.
22078 .option sieve_vacation_directory redirect string&!! unset
22079 .cindex "Sieve filter" "vacation directory"
22080 To enable the &"vacation"& extension for Sieve filters, you must set
22081 &%sieve_vacation_directory%& to the directory where vacation databases are held
22082 (do not put anything else in that directory), and ensure that the
22083 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
22084 needs their own directory; Exim will create it if necessary.
22088 .option skip_syntax_errors redirect boolean false
22089 .cindex "forward file" "broken"
22090 .cindex "address redirection" "broken files"
22091 .cindex "alias file" "broken"
22092 .cindex "broken alias or forward files"
22093 .cindex "ignoring faulty addresses"
22094 .cindex "skipping faulty addresses"
22095 .cindex "error" "skipping bad syntax"
22096 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
22097 non-filter redirection data are skipped, and each failing address is logged. If
22098 &%syntax_errors_to%& is set, a message is sent to the address it defines,
22099 giving details of the failures. If &%syntax_errors_text%& is set, its contents
22100 are expanded and placed at the head of the error message generated by
22101 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
22102 be the same address as the generic &%errors_to%& option. The
22103 &%skip_syntax_errors%& option is often used when handling mailing lists.
22105 If all the addresses in a redirection list are skipped because of syntax
22106 errors, the router declines to handle the original address, and it is passed to
22107 the following routers.
22109 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
22110 error in the filter causes filtering to be abandoned without any action being
22111 taken. The incident is logged, and the router declines to handle the address,
22112 so it is passed to the following routers.
22114 .cindex "Sieve filter" "syntax errors in"
22115 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
22116 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
22117 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
22119 &%skip_syntax_errors%& can be used to specify that errors in users' forward
22120 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
22121 option, used with an address that does not get redirected, can be used to
22122 notify users of these errors, by means of a router like this:
22128 file = $home/.forward
22129 file_transport = address_file
22130 pipe_transport = address_pipe
22131 reply_transport = address_reply
22134 syntax_errors_to = real-$local_part@$domain
22135 syntax_errors_text = \
22136 This is an automatically generated message. An error has\n\
22137 been found in your .forward file. Details of the error are\n\
22138 reported below. While this error persists, you will receive\n\
22139 a copy of this message for every message that is addressed\n\
22140 to you. If your .forward file is a filter file, or if it is\n\
22141 a non-filter file containing no valid forwarding addresses,\n\
22142 a copy of each incoming message will be put in your normal\n\
22143 mailbox. If a non-filter file contains at least one valid\n\
22144 forwarding address, forwarding to the valid addresses will\n\
22145 happen, and those will be the only deliveries that occur.
22147 You also need a router to ensure that local addresses that are prefixed by
22148 &`real-`& are recognized, but not forwarded or filtered. For example, you could
22149 put this immediately before the &(userforward)& router:
22154 local_part_prefix = real-
22155 transport = local_delivery
22157 For security, it would probably be a good idea to restrict the use of this
22158 router to locally-generated messages, using a condition such as this:
22160 condition = ${if match {$sender_host_address}\
22161 {\N^(|127\.0\.0\.1)$\N}}
22165 .option syntax_errors_text redirect string&!! unset
22166 See &%skip_syntax_errors%& above.
22169 .option syntax_errors_to redirect string unset
22170 See &%skip_syntax_errors%& above.
22171 .ecindex IIDredrou1
22172 .ecindex IIDredrou2
22179 . ////////////////////////////////////////////////////////////////////////////
22180 . ////////////////////////////////////////////////////////////////////////////
22182 .chapter "Environment for running local transports" "CHAPenvironment" &&&
22183 "Environment for local transports"
22184 .scindex IIDenvlotra1 "local transports" "environment for"
22185 .scindex IIDenvlotra2 "environment" "local transports"
22186 .scindex IIDenvlotra3 "transport" "local; environment for"
22187 Local transports handle deliveries to files and pipes. (The &(autoreply)&
22188 transport can be thought of as similar to a pipe.) Exim always runs transports
22189 in subprocesses, under specified uids and gids. Typical deliveries to local
22190 mailboxes run under the uid and gid of the local user.
22192 Exim also sets a specific current directory while running the transport; for
22193 some transports a home directory setting is also relevant. The &(pipe)&
22194 transport is the only one that sets up environment variables; see section
22195 &<<SECTpipeenv>>& for details.
22197 The values used for the uid, gid, and the directories may come from several
22198 different places. In many cases, the router that handles the address associates
22199 settings with that address as a result of its &%check_local_user%&, &%group%&,
22200 or &%user%& options. However, values may also be given in the transport's own
22201 configuration, and these override anything that comes from the router.
22205 .section "Concurrent deliveries" "SECID131"
22206 .cindex "concurrent deliveries"
22207 .cindex "simultaneous deliveries"
22208 If two different messages for the same local recipient arrive more or less
22209 simultaneously, the two delivery processes are likely to run concurrently. When
22210 the &(appendfile)& transport is used to write to a file, Exim applies locking
22211 rules to stop concurrent processes from writing to the same file at the same
22214 However, when you use a &(pipe)& transport, it is up to you to arrange any
22215 locking that is needed. Here is a silly example:
22219 command = /bin/sh -c 'cat >>/some/file'
22221 This is supposed to write the message at the end of the file. However, if two
22222 messages arrive at the same time, the file will be scrambled. You can use the
22223 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
22224 file using the same algorithm that Exim itself uses.
22229 .section "Uids and gids" "SECTenvuidgid"
22230 .cindex "local transports" "uid and gid"
22231 .cindex "transport" "local; uid and gid"
22232 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
22233 overrides any group that the router set in the address, even if &%user%& is not
22234 set for the transport. This makes it possible, for example, to run local mail
22235 delivery under the uid of the recipient (set by the router), but in a special
22236 group (set by the transport). For example:
22239 # User/group are set by check_local_user in this router
22243 transport = group_delivery
22246 # This transport overrides the group
22248 driver = appendfile
22249 file = /var/spool/mail/$local_part_data
22252 If &%user%& is set for a transport, its value overrides what is set in the
22253 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
22254 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
22257 .oindex "&%initgroups%&"
22258 When the uid is taken from the transport's configuration, the &[initgroups()]&
22259 function is called for the groups associated with that uid if the
22260 &%initgroups%& option is set for the transport. When the uid is not specified
22261 by the transport, but is associated with the address by a router, the option
22262 for calling &[initgroups()]& is taken from the router configuration.
22264 .cindex "&(pipe)& transport" "uid for"
22265 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
22266 is set and &%user%& is not set, the uid of the process that called Exim to
22267 receive the message is used, and if &%group%& is not set, the corresponding
22268 original gid is also used.
22270 This is the detailed preference order for obtaining a gid; the first of the
22271 following that is set is used:
22274 A &%group%& setting of the transport;
22276 A &%group%& setting of the router;
22278 A gid associated with a user setting of the router, either as a result of
22279 &%check_local_user%& or an explicit non-numeric &%user%& setting;
22281 The group associated with a non-numeric &%user%& setting of the transport;
22283 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
22284 the uid is the creator's uid;
22286 The Exim gid if the Exim uid is being used as a default.
22289 If, for example, the user is specified numerically on the router and there are
22290 no group settings, no gid is available. In this situation, an error occurs.
22291 This is different for the uid, for which there always is an ultimate default.
22292 The first of the following that is set is used:
22295 A &%user%& setting of the transport;
22297 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
22299 A &%user%& setting of the router;
22301 A &%check_local_user%& setting of the router;
22306 Of course, an error will still occur if the uid that is chosen is on the
22307 &%never_users%& list.
22313 .section "Current and home directories" "SECID132"
22314 .cindex "current directory for local transport"
22315 .cindex "home directory" "for local transport"
22316 .cindex "transport" "local; home directory for"
22317 .cindex "transport" "local; current directory for"
22318 Routers may set current and home directories for local transports by means of
22319 the &%transport_current_directory%& and &%transport_home_directory%& options.
22320 However, if the transport's &%current_directory%& or &%home_directory%& options
22321 are set, they override the router's values. In detail, the home directory
22322 for a local transport is taken from the first of these values that is set:
22325 The &%home_directory%& option on the transport;
22327 The &%transport_home_directory%& option on the router;
22329 The password data if &%check_local_user%& is set on the router;
22331 The &%router_home_directory%& option on the router.
22334 The current directory is taken from the first of these values that is set:
22337 The &%current_directory%& option on the transport;
22339 The &%transport_current_directory%& option on the router.
22343 If neither the router nor the transport sets a current directory, Exim uses the
22344 value of the home directory, if it is set. Otherwise it sets the current
22345 directory to &_/_& before running a local transport.
22349 .section "Expansion variables derived from the address" "SECID133"
22350 .vindex "&$domain$&"
22351 .vindex "&$local_part$&"
22352 .vindex "&$original_domain$&"
22353 Normally a local delivery is handling a single address, and in that case the
22354 variables such as &$domain$& and &$local_part$& are set during local
22355 deliveries. However, in some circumstances more than one address may be handled
22356 at once (for example, while writing batch SMTP for onward transmission by some
22357 other means). In this case, the variables associated with the local part are
22358 never set, &$domain$& is set only if all the addresses have the same domain,
22359 and &$original_domain$& is never set.
22360 .ecindex IIDenvlotra1
22361 .ecindex IIDenvlotra2
22362 .ecindex IIDenvlotra3
22370 . ////////////////////////////////////////////////////////////////////////////
22371 . ////////////////////////////////////////////////////////////////////////////
22373 .chapter "Generic options for transports" "CHAPtransportgeneric"
22374 .scindex IIDgenoptra1 "generic options" "transport"
22375 .scindex IIDgenoptra2 "options" "generic; for transports"
22376 .scindex IIDgenoptra3 "transport" "generic options for"
22377 The name of a transport is limited to be &drivernamemax; ASCII characters long;
22378 prior to Exim 4.95 names would be silently truncated at this length, but now
22381 The following generic options apply to all transports:
22384 .option body_only transports boolean false
22385 .cindex "transport" "body only"
22386 .cindex "message" "transporting body only"
22387 .cindex "body of message" "transporting"
22388 If this option is set, the message's headers are not transported. It is
22389 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
22390 or &(pipe)& transports, the settings of &%message_prefix%& and
22391 &%message_suffix%& should be checked, because this option does not
22392 automatically suppress them.
22395 .option current_directory transports string&!! unset
22396 .cindex "transport" "current directory for"
22397 This specifies the current directory that is to be set while running the
22398 transport, overriding any value that may have been set by the router.
22399 If the expansion fails for any reason, including forced failure, an error is
22400 logged, and delivery is deferred.
22403 .option disable_logging transports boolean false
22404 If this option is set true, nothing is logged for any
22405 deliveries by the transport or for any
22406 transport errors. You should not set this option unless you really, really know
22407 what you are doing.
22410 .option debug_print transports string&!! unset
22411 .cindex "testing" "variables in drivers"
22412 If this option is set and debugging is enabled (see the &%-d%& command line
22413 option), the string is expanded and included in the debugging output when the
22415 If expansion of the string fails, the error message is written to the debugging
22416 output, and Exim carries on processing.
22417 This facility is provided to help with checking out the values of variables and
22418 so on when debugging driver configurations. For example, if a &%headers_add%&
22419 option is not working properly, &%debug_print%& could be used to output the
22420 variables it references. A newline is added to the text if it does not end with
22422 The variables &$transport_name$& and &$router_name$& contain the name of the
22423 transport and the router that called it.
22425 .option delivery_date_add transports boolean false
22426 .cindex "&'Delivery-date:'& header line"
22427 If this option is true, a &'Delivery-date:'& header is added to the message.
22428 This gives the actual time the delivery was made. As this is not a standard
22429 header, Exim has a configuration option (&%delivery_date_remove%&) which
22430 requests its removal from incoming messages, so that delivered messages can
22431 safely be resent to other recipients.
22434 .option driver transports string unset
22435 This specifies which of the available transport drivers is to be used.
22436 There is no default, and this option must be set for every transport.
22439 .option envelope_to_add transports boolean false
22440 .cindex "&'Envelope-to:'& header line"
22441 If this option is true, an &'Envelope-to:'& header is added to the message.
22442 This gives the original address(es) in the incoming envelope that caused this
22443 delivery to happen. More than one address may be present if the transport is
22444 configured to handle several addresses at once, or if more than one original
22445 address was redirected to the same final address. As this is not a standard
22446 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
22447 its removal from incoming messages, so that delivered messages can safely be
22448 resent to other recipients.
22450 &*Note:*& If used on a transport handling multiple recipients
22451 (the smtp transport unless &%max_rcpt%& is 1, the appendfile, pipe or lmtp
22452 transport if &%batch_max%& is greater than 1)
22453 then information about Bcc recipients will be leaked.
22454 Doing so is generally not advised.
22457 .option event_action transports string&!! unset
22459 This option declares a string to be expanded for Exim's events mechanism.
22460 For details see chapter &<<CHAPevents>>&.
22463 .option group transports string&!! "Exim group"
22464 .cindex "transport" "group; specifying"
22465 This option specifies a gid for running the transport process, overriding any
22466 value that the router supplies, and also overriding any value associated with
22467 &%user%& (see below).
22470 .option headers_add transports list&!! unset
22471 .cindex "header lines" "adding in transport"
22472 .cindex "transport" "header lines; adding"
22473 This option specifies a list of text headers,
22474 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22475 which are (separately) expanded and added to the header
22476 portion of a message as it is transported, as described in section
22477 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
22478 routers. If the result of the expansion is an empty string, or if the expansion
22479 is forced to fail, no action is taken. Other expansion failures are treated as
22480 errors and cause the delivery to be deferred.
22482 Unlike most options, &%headers_add%& can be specified multiple times
22483 for a transport; all listed headers are added.
22486 .option headers_only transports boolean false
22487 .cindex "transport" "header lines only"
22488 .cindex "message" "transporting headers only"
22489 .cindex "header lines" "transporting"
22490 If this option is set, the message's body is not transported. It is mutually
22491 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
22492 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
22493 checked, since this option does not automatically suppress them.
22496 .option headers_remove transports list&!! unset
22497 .cindex "header lines" "removing"
22498 .cindex "transport" "header lines; removing"
22499 This option specifies a list of text headers,
22500 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22501 to be removed from the message.
22502 However, the option has no effect when an address is just being verified.
22503 Each list item is separately expanded.
22504 If the result of the expansion is an empty string, or if the expansion
22505 is forced to fail, no action is taken. Other expansion failures are treated as
22506 errors and cause the delivery to be deferred.
22507 If an item ends in *, it will match any header with the given prefix.
22509 Matching headers are omitted from the message as it is transported, as described
22510 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
22513 Unlike most options, &%headers_remove%& can be specified multiple times
22514 for a transport; all listed headers are removed.
22516 &*Warning*&: Because of the separate expansion of the list items,
22517 items that contain a list separator must have it doubled.
22518 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
22522 .option headers_rewrite transports string unset
22523 .cindex "transport" "header lines; rewriting"
22524 .cindex "rewriting" "at transport time"
22525 This option allows addresses in header lines to be rewritten at transport time,
22526 that is, as the message is being copied to its destination. The contents of the
22527 option are a colon-separated list of rewriting rules. Each rule is in exactly
22528 the same form as one of the general rewriting rules that are applied when a
22529 message is received. These are described in chapter &<<CHAPrewrite>>&. For
22532 headers_rewrite = a@b c@d f : \
22535 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
22536 &'w@z'& in all address-bearing header lines. The rules are applied to the
22537 header lines just before they are written out at transport time, so they affect
22538 only those copies of the message that pass through the transport. However, only
22539 the message's original header lines, and any that were added by a system
22540 filter, are rewritten. If a router or transport adds header lines, they are not
22541 affected by this option. These rewriting rules are &'not'& applied to the
22542 envelope. You can change the return path using &%return_path%&, but you cannot
22543 change envelope recipients at this time.
22546 .option home_directory transports string&!! unset
22547 .cindex "transport" "home directory for"
22549 This option specifies a home directory setting for a local transport,
22550 overriding any value that may be set by the router. The home directory is
22551 placed in &$home$& while expanding the transport's private options. It is also
22552 used as the current directory if no current directory is set by the
22553 &%current_directory%& option on the transport or the
22554 &%transport_current_directory%& option on the router. If the expansion fails
22555 for any reason, including forced failure, an error is logged, and delivery is
22559 .option initgroups transports boolean false
22560 .cindex "additional groups"
22561 .cindex "groups" "additional"
22562 .cindex "transport" "group; additional"
22563 If this option is true and the uid for the delivery process is provided by the
22564 transport, the &[initgroups()]& function is called when running the transport
22565 to ensure that any additional groups associated with the uid are set up.
22568 .option max_parallel transports integer&!! unset
22569 .cindex limit "transport parallelism"
22570 .cindex transport "parallel processes"
22571 .cindex transport "concurrency limit"
22572 .cindex "delivery" "parallelism for transport"
22573 If this option is set and expands to an integer greater than zero
22574 it limits the number of concurrent runs of the transport.
22575 The control does not apply to shadow transports.
22577 .cindex "hints database" "transport concurrency control"
22578 Exim implements this control by means of a hints database in which a record is
22579 incremented whenever a transport process is being created. The record
22580 is decremented and possibly removed when the process terminates.
22581 Obviously there is scope for
22582 records to get left lying around if there is a system or program crash. To
22583 guard against this, Exim ignores any records that are more than six hours old.
22585 If you use this option, you should also arrange to delete the
22586 relevant hints database whenever your system reboots. The names of the files
22587 start with &_misc_& and they are kept in the &_spool/db_& directory. There
22588 may be one or two files, depending on the type of DBM in use. The same files
22589 are used for ETRN and smtp transport serialization.
22592 .option message_size_limit transports string&!! 0
22593 .cindex "limit" "message size per transport"
22594 .cindex "size" "of message, limit"
22595 .cindex "transport" "message size; limiting"
22596 This option controls the size of messages passed through the transport. It is
22597 expanded before use; the result of the expansion must be a sequence of decimal
22598 digits, optionally followed by K or M. If the expansion fails for any reason,
22599 including forced failure, or if the result is not of the required form,
22600 delivery is deferred. If the value is greater than zero and the size of a
22601 message exceeds this limit, the address is failed. If there is any chance that
22602 the resulting bounce message could be routed to the same transport, you should
22603 ensure that &%return_size_limit%& is less than the transport's
22604 &%message_size_limit%&, as otherwise the bounce message will fail to get
22609 .option rcpt_include_affixes transports boolean false
22610 .cindex "prefix" "for local part, including in envelope"
22611 .cindex "suffix for local part" "including in envelope"
22612 .cindex "local part" "prefix"
22613 .cindex "local part" "suffix"
22614 When this option is false (the default), and an address that has had any
22615 affixes (prefixes or suffixes) removed from the local part is delivered by any
22616 form of SMTP or LMTP, the affixes are not included. For example, if a router
22619 local_part_prefix = *-
22621 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
22624 RCPT TO:<xyz@some.domain>
22626 This is also the case when an ACL-time callout is being used to verify a
22627 recipient address. However, if &%rcpt_include_affixes%& is set true, the
22628 whole local part is included in the RCPT command. This option applies to BSMTP
22629 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
22630 &(lmtp)& and &(smtp)& transports.
22633 .option retry_use_local_part transports boolean "see below"
22634 .cindex "hints database" "retry keys"
22635 When a delivery suffers a temporary failure, a retry record is created
22636 in Exim's hints database. For remote deliveries, the key for the retry record
22637 is based on the name and/or IP address of the failing remote host. For local
22638 deliveries, the key is normally the entire address, including both the local
22639 part and the domain. This is suitable for most common cases of local delivery
22640 temporary failure &-- for example, exceeding a mailbox quota should delay only
22641 deliveries to that mailbox, not to the whole domain.
22643 However, in some special cases you may want to treat a temporary local delivery
22644 as a failure associated with the domain, and not with a particular local part.
22645 (For example, if you are storing all mail for some domain in files.) You can do
22646 this by setting &%retry_use_local_part%& false.
22648 For all the local transports, its default value is true. For remote transports,
22649 the default value is false for tidiness, but changing the value has no effect
22650 on a remote transport in the current implementation.
22653 .option return_path transports string&!! unset
22654 .cindex "envelope sender"
22655 .cindex "envelope from"
22656 .cindex "transport" "return path; changing"
22657 .cindex "return path" "changing in transport"
22658 If this option is set, the string is expanded at transport time and replaces
22659 the existing return path (envelope sender) value in the copy of the message
22660 that is being delivered. An empty return path is permitted. This feature is
22661 designed for remote deliveries, where the value of this option is used in the
22662 SMTP MAIL command. If you set &%return_path%& for a local transport, the
22663 only effect is to change the address that is placed in the &'Return-path:'&
22664 header line, if one is added to the message (see the next option).
22666 &*Note:*& A changed return path is not logged unless you add
22667 &%return_path_on_delivery%& to the log selector.
22669 .vindex "&$return_path$&"
22670 The expansion can refer to the existing value via &$return_path$&. This is
22671 either the message's envelope sender, or an address set by the
22672 &%errors_to%& option on a router. If the expansion is forced to fail, no
22673 replacement occurs; if it fails for another reason, delivery is deferred. This
22674 option can be used to support VERP (Variable Envelope Return Paths) &-- see
22675 section &<<SECTverp>>&.
22677 &*Note*&: If a delivery error is detected locally, including the case when a
22678 remote server rejects a message at SMTP time, the bounce message is not sent to
22679 the value of this option. It is sent to the previously set errors address.
22680 This defaults to the incoming sender address, but can be changed by setting
22681 &%errors_to%& in a router.
22685 .option return_path_add transports boolean false
22686 .chindex Return-path:
22687 If this option is true, a &'Return-path:'& header is added to the message.
22688 Although the return path is normally available in the prefix line of BSD
22689 mailboxes, this is commonly not displayed by MUAs, and so the user does not
22690 have easy access to it.
22692 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
22693 the delivery SMTP server makes the final delivery"&. This implies that this
22694 header should not be present in incoming messages. Exim has a configuration
22695 option, &%return_path_remove%&, which requests removal of this header from
22696 incoming messages, so that delivered messages can safely be resent to other
22700 .option shadow_condition transports string&!! unset
22701 See &%shadow_transport%& below.
22704 .option shadow_transport transports string unset
22705 .cindex "shadow transport"
22706 .cindex "transport" "shadow"
22707 A local transport may set the &%shadow_transport%& option to the name of
22708 another local transport. Shadow remote transports are not supported.
22710 Whenever a delivery to the main transport succeeds, and either
22711 &%shadow_condition%& is unset, or its expansion does not result in the empty
22712 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
22713 passed to the shadow transport, with the same delivery address or addresses. If
22714 expansion fails, no action is taken except that non-forced expansion failures
22715 cause a log line to be written.
22717 The result of the shadow transport is discarded and does not affect the
22718 subsequent processing of the message. Only a single level of shadowing is
22719 provided; the &%shadow_transport%& option is ignored on any transport when it
22720 is running as a shadow. Options concerned with output from pipes are also
22721 ignored. The log line for the successful delivery has an item added on the end,
22724 ST=<shadow transport name>
22726 If the shadow transport did not succeed, the error message is put in
22727 parentheses afterwards. Shadow transports can be used for a number of different
22728 purposes, including keeping more detailed log information than Exim normally
22729 provides, and implementing automatic acknowledgment policies based on message
22730 headers that some sites insist on.
22733 .option transport_filter transports string&!! unset
22734 .cindex "transport" "filter"
22735 .cindex "filter" "transport filter"
22736 This option sets up a filtering (in the Unix shell sense) process for messages
22737 at transport time. It should not be confused with mail filtering as set up by
22738 individual users or via a system filter.
22739 If unset, or expanding to an empty string, no filtering is done.
22741 When the message is about to be written out, the command specified by
22742 &%transport_filter%& is started up in a separate, parallel process, and
22743 the entire message, including the header lines, is passed to it on its standard
22744 input (this in fact is done from a third process, to avoid deadlock). The
22745 command must be specified as an absolute path.
22747 The lines of the message that are written to the transport filter are
22748 terminated by newline (&"\n"&). The message is passed to the filter before any
22749 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
22750 lines beginning with a dot, and also before any processing implied by the
22751 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
22752 &(pipe)& transports.
22754 The standard error for the filter process is set to the same destination as its
22755 standard output; this is read and written to the message's ultimate
22756 destination. The process that writes the message to the filter, the
22757 filter itself, and the original process that reads the result and delivers it
22758 are all run in parallel, like a shell pipeline.
22760 The filter can perform any transformations it likes, but of course should take
22761 care not to break RFC 2822 syntax. Exim does not check the result, except to
22762 test for a final newline when SMTP is in use. All messages transmitted over
22763 SMTP must end with a newline, so Exim supplies one if it is missing.
22765 .cindex "content scanning" "per user"
22766 A transport filter can be used to provide content-scanning on a per-user basis
22767 at delivery time if the only required effect of the scan is to modify the
22768 message. For example, a content scan could insert a new header line containing
22769 a spam score. This could be interpreted by a filter in the user's MUA. It is
22770 not possible to discard a message at this stage.
22772 .cindex "SIZE" "ESMTP extension"
22773 A problem might arise if the filter increases the size of a message that is
22774 being sent down an SMTP connection. If the receiving SMTP server has indicated
22775 support for the SIZE parameter, Exim will have sent the size of the message
22776 at the start of the SMTP session. If what is actually sent is substantially
22777 more, the server might reject the message. This can be worked round by setting
22778 the &%size_addition%& option on the &(smtp)& transport, either to allow for
22779 additions to the message, or to disable the use of SIZE altogether.
22781 .vindex "&$pipe_addresses$&"
22782 The value of the &%transport_filter%& option is the command string for starting
22783 the filter, which is run directly from Exim, not under a shell. The string is
22784 parsed by Exim in the same way as a command string for the &(pipe)& transport:
22785 Exim breaks it up into arguments and then expands each argument separately (see
22786 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
22787 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
22788 of arguments, one for each address that applies to this delivery. (This isn't
22789 an ideal name for this feature here, but as it was already implemented for the
22790 &(pipe)& transport, it seemed sensible not to change it.)
22793 .vindex "&$host_address$&"
22794 The expansion variables &$host$& and &$host_address$& are available when the
22795 transport is a remote one. They contain the name and IP address of the host to
22796 which the message is being sent. For example:
22797 . used to have $sender_address in this cmdline, but it's tainted
22799 transport_filter = /some/directory/transport-filter.pl \
22800 $host $host_address $pipe_addresses
22803 Two problems arise if you want to use more complicated expansion items to
22804 generate transport filter commands, both of which due to the fact that the
22805 command is split up &'before'& expansion.
22807 If an expansion item contains white space, you must quote it, so that it is all
22808 part of the same command item. If the entire option setting is one such
22809 expansion item, you have to take care what kind of quoting you use. For
22812 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
22814 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
22815 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
22816 stripped by Exim when it read the option's value. When the value is used, if
22817 the single quotes were missing, the line would be split into two items,
22818 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
22819 Exim tried to expand the first one.
22821 Except for the special case of &$pipe_addresses$& that is mentioned above, an
22822 expansion cannot generate multiple arguments, or a command name followed by
22823 arguments. Consider this example:
22825 transport_filter = ${lookup{$host}lsearch{/a/file}\
22826 {$value}{/bin/cat}}
22828 The result of the lookup is interpreted as the name of the command, even
22829 if it contains white space. The simplest way round this is to use a shell:
22831 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
22832 {$value}{/bin/cat}}
22836 The filter process is run under the same uid and gid as the normal delivery.
22837 For remote deliveries this is the Exim uid/gid by default. The command should
22838 normally yield a zero return code. Transport filters are not supposed to fail.
22839 A non-zero code is taken to mean that the transport filter encountered some
22840 serious problem. Delivery of the message is deferred; the message remains on
22841 the queue and is tried again later. It is not possible to cause a message to be
22842 bounced from a transport filter.
22844 If a transport filter is set on an autoreply transport, the original message is
22845 passed through the filter as it is being copied into the newly generated
22846 message, which happens if the &%return_message%& option is set.
22849 .option transport_filter_timeout transports time 5m
22850 .cindex "transport" "filter, timeout"
22851 When Exim is reading the output of a transport filter, it applies a timeout
22852 that can be set by this option. Exceeding the timeout is normally treated as a
22853 temporary delivery failure. However, if a transport filter is used with a
22854 &(pipe)& transport, a timeout in the transport filter is treated in the same
22855 way as a timeout in the pipe command itself. By default, a timeout is a hard
22856 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
22857 becomes a temporary error.
22860 .option user transports string&!! "Exim user"
22861 .cindex "uid (user id)" "local delivery"
22862 .cindex "transport" "user, specifying"
22863 This option specifies the user under whose uid the delivery process is to be
22864 run, overriding any uid that may have been set by the router. If the user is
22865 given as a name, the uid is looked up from the password data, and the
22866 associated group is taken as the value of the gid to be used if the &%group%&
22869 For deliveries that use local transports, a user and group are normally
22870 specified explicitly or implicitly (for example, as a result of
22871 &%check_local_user%&) by the router or transport.
22873 .cindex "hints database" "access by remote transport"
22874 For remote transports, you should leave this option unset unless you really are
22875 sure you know what you are doing. When a remote transport is running, it needs
22876 to be able to access Exim's hints databases, because each host may have its own
22878 .ecindex IIDgenoptra1
22879 .ecindex IIDgenoptra2
22880 .ecindex IIDgenoptra3
22887 . ////////////////////////////////////////////////////////////////////////////
22888 . ////////////////////////////////////////////////////////////////////////////
22890 .chapter "Address batching in local transports" "CHAPbatching" &&&
22892 .cindex "transport" "local; address batching in"
22893 The only remote transport (&(smtp)&) is normally configured to handle more than
22894 one address at a time, so that when several addresses are routed to the same
22895 remote host, just one copy of the message is sent. Local transports, however,
22896 normally handle one address at a time. That is, a separate instance of the
22897 transport is run for each address that is routed to the transport. A separate
22898 copy of the message is delivered each time.
22900 .cindex "batched local delivery"
22901 .oindex "&%batch_max%&"
22902 .oindex "&%batch_id%&"
22903 In special cases, it may be desirable to handle several addresses at once in a
22904 local transport, for example:
22907 In an &(appendfile)& transport, when storing messages in files for later
22908 delivery by some other means, a single copy of the message with multiple
22909 recipients saves space.
22911 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
22912 a single copy saves time, and is the normal way LMTP is expected to work.
22914 In a &(pipe)& transport, when passing the message
22915 to a scanner program or
22916 to some other delivery mechanism such as UUCP, multiple recipients may be
22920 These three local transports all have the same options for controlling multiple
22921 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
22922 repeating the information for each transport, these options are described here.
22924 The &%batch_max%& option specifies the maximum number of addresses that can be
22925 delivered together in a single run of the transport. Its default value is one
22926 (no batching). When more than one address is routed to a transport that has a
22927 &%batch_max%& value greater than one, the addresses are delivered in a batch
22928 (that is, in a single run of the transport with multiple recipients), subject
22929 to certain conditions:
22932 .vindex "&$local_part$&"
22933 If any of the transport's options contain a reference to &$local_part$&, no
22934 batching is possible.
22936 .vindex "&$domain$&"
22937 If any of the transport's options contain a reference to &$domain$&, only
22938 addresses with the same domain are batched.
22940 .cindex "customizing" "batching condition"
22941 If &%batch_id%& is set, it is expanded for each address, and only those
22942 addresses with the same expanded value are batched. This allows you to specify
22943 customized batching conditions. Failure of the expansion for any reason,
22944 including forced failure, disables batching, but it does not stop the delivery
22947 Batched addresses must also have the same errors address (where to send
22948 delivery errors), the same header additions and removals, the same user and
22949 group for the transport, and if a host list is present, the first host must
22953 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
22954 both when the file or pipe command is specified in the transport, and when it
22955 is specified by a &(redirect)& router, but all the batched addresses must of
22956 course be routed to the same file or pipe command. These two transports have an
22957 option called &%use_bsmtp%&, which causes them to deliver the message in
22958 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
22959 &%check_string%& and &%escape_string%& options are forced to the values
22962 escape_string = ".."
22964 when batched SMTP is in use. A full description of the batch SMTP mechanism is
22965 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
22966 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
22968 .cindex "&'Envelope-to:'& header line"
22969 If the generic &%envelope_to_add%& option is set for a batching transport, the
22970 &'Envelope-to:'& header that is added to the message contains all the addresses
22971 that are being processed together. If you are using a batching &(appendfile)&
22972 transport without &%use_bsmtp%&, the only way to preserve the recipient
22973 addresses is to set the &%envelope_to_add%& option.
22975 .cindex "&(pipe)& transport" "with multiple addresses"
22976 .vindex "&$pipe_addresses$&"
22977 If you are using a &(pipe)& transport without BSMTP, and setting the
22978 transport's &%command%& option, you can include &$pipe_addresses$& as part of
22979 the command. This is not a true variable; it is a bit of magic that causes each
22980 of the recipient addresses to be inserted into the command as a separate
22981 argument. This provides a way of accessing all the addresses that are being
22982 delivered in the batch. &*Note:*& This is not possible for pipe commands that
22983 are specified by a &(redirect)& router.
22988 . ////////////////////////////////////////////////////////////////////////////
22989 . ////////////////////////////////////////////////////////////////////////////
22991 .chapter "The appendfile transport" "CHAPappendfile"
22992 .scindex IIDapptra1 "&(appendfile)& transport"
22993 .scindex IIDapptra2 "transports" "&(appendfile)&"
22994 .cindex "directory creation"
22995 .cindex "creating directories"
22996 The &(appendfile)& transport delivers a message by appending it to an existing
22997 file, or by creating an entirely new file in a specified directory. Single
22998 files to which messages are appended can be in the traditional Unix mailbox
22999 format, or optionally in the MBX format supported by the Pine MUA and
23000 University of Washington IMAP daemon, &'inter alia'&. When each message is
23001 being delivered as a separate file, &"maildir"& format can optionally be used
23002 to give added protection against failures that happen part-way through the
23003 delivery. A third form of separate-file delivery known as &"mailstore"& is also
23004 supported. For all file formats, Exim attempts to create as many levels of
23005 directory as necessary, provided that &%create_directory%& is set.
23007 The code for the optional formats is not included in the Exim binary by
23008 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
23009 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
23012 .cindex "quota" "system"
23013 Exim recognizes system quota errors, and generates an appropriate message. Exim
23014 also supports its own quota control within the transport, for use when the
23015 system facility is unavailable or cannot be used for some reason.
23017 If there is an error while appending to a file (for example, quota exceeded or
23018 partition filled), Exim attempts to reset the file's length and last
23019 modification time back to what they were before. If there is an error while
23020 creating an entirely new file, the new file is removed.
23022 Before appending to a file, a number of security checks are made, and the
23023 file is locked. A detailed description is given below, after the list of
23026 The &(appendfile)& transport is most commonly used for local deliveries to
23027 users' mailboxes. However, it can also be used as a pseudo-remote transport for
23028 putting messages into files for remote delivery by some means other than Exim.
23029 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
23034 .section "The file and directory options" "SECTfildiropt"
23035 The &%file%& option specifies a single file, to which the message is appended;
23036 the &%directory%& option specifies a directory, in which a new file containing
23037 the message is created. Only one of these two options can be set, and for
23038 normal deliveries to mailboxes, one of them &'must'& be set.
23040 .vindex "&$address_file$&"
23041 .vindex "&$local_part$&"
23042 However, &(appendfile)& is also used for delivering messages to files or
23043 directories whose names (or parts of names) are obtained from alias,
23044 forwarding, or filtering operations (for example, a &%save%& command in a
23045 user's Exim filter). When such a transport is running, &$local_part$& contains
23046 the local part that was aliased or forwarded, and &$address_file$& contains the
23047 name (or partial name) of the file or directory generated by the redirection
23048 operation. There are two cases:
23051 If neither &%file%& nor &%directory%& is set, the redirection operation
23052 must specify an absolute path (one that begins with &`/`&). This is the most
23053 common case when users with local accounts use filtering to sort mail into
23054 different folders. See for example, the &(address_file)& transport in the
23055 default configuration. If the path ends with a slash, it is assumed to be the
23056 name of a directory. A delivery to a directory can also be forced by setting
23057 &%maildir_format%& or &%mailstore_format%&.
23059 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
23060 used to determine the file or directory name for the delivery. Normally, the
23061 contents of &$address_file$& are used in some way in the string expansion.
23063 If the &%create_file%& option is set to a path which
23064 matches (see the option definition below for details)
23065 a file or directory name
23066 for the delivery, that name becomes de-tainted.
23068 .cindex "tainted data" "in filenames"
23069 .cindex appendfile "tainted data"
23070 Tainted data may not be used for a file or directory name.
23071 This means that, for instance, &$local_part$& cannot be used directly
23072 as a component of a path. It can however be used as the key for a lookup
23073 which returns a path (or component).
23076 .cindex "Sieve filter" "configuring &(appendfile)&"
23077 .cindex "Sieve filter" "relative mailbox path handling"
23078 As an example of the second case, consider an environment where users do not
23079 have home directories. They may be permitted to use Exim filter commands of the
23084 or Sieve filter commands of the form:
23086 require "fileinto";
23087 fileinto "folder23";
23089 In this situation, the expansion of &%file%& or &%directory%& in the transport
23090 must transform the relative path into an appropriate absolute filename. In the
23091 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
23092 is used as a result of a &"keep"& action in the filter. This example shows one
23093 way of handling this requirement:
23095 file = ${if eq{$address_file}{inbox} \
23096 {/var/mail/$local_part_data} \
23097 {${if eq{${substr_0_1:$address_file}}{/} \
23099 {$home/mail/$address_file} \
23103 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
23104 location, absolute paths are used without change, and other folders are in the
23105 &_mail_& directory within the home directory.
23107 &*Note 1*&: While processing an Exim filter, a relative path such as
23108 &_folder23_& is turned into an absolute path if a home directory is known to
23109 the router. In particular, this is the case if &%check_local_user%& is set. If
23110 you want to prevent this happening at routing time, you can set
23111 &%router_home_directory%& empty. This forces the router to pass the relative
23112 path to the transport.
23114 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
23115 the &%file%& or &%directory%& option is still used if it is set.
23120 .section "Private options for appendfile" "SECID134"
23121 .cindex "options" "&(appendfile)& transport"
23125 .option allow_fifo appendfile boolean false
23126 .cindex "fifo (named pipe)"
23127 .cindex "named pipe (fifo)"
23128 .cindex "pipe" "named (fifo)"
23129 Setting this option permits delivery to named pipes (FIFOs) as well as to
23130 regular files. If no process is reading the named pipe at delivery time, the
23131 delivery is deferred.
23134 .option allow_symlink appendfile boolean false
23135 .cindex "symbolic link" "to mailbox"
23136 .cindex "mailbox" "symbolic link"
23137 By default, &(appendfile)& will not deliver if the path name for the file is
23138 that of a symbolic link. Setting this option relaxes that constraint, but there
23139 are security issues involved in the use of symbolic links. Be sure you know
23140 what you are doing if you set this. Details of exactly what this option affects
23141 are included in the discussion which follows this list of options.
23144 .option batch_id appendfile string&!! unset
23145 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23146 However, batching is automatically disabled for &(appendfile)& deliveries that
23147 happen as a result of forwarding or aliasing or other redirection directly to a
23151 .option batch_max appendfile integer 1
23152 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23155 .option check_group appendfile boolean false
23156 When this option is set, the group owner of the file defined by the &%file%&
23157 option is checked to see that it is the same as the group under which the
23158 delivery process is running. The default setting is false because the default
23159 file mode is 0600, which means that the group is irrelevant.
23162 .option check_owner appendfile boolean true
23163 When this option is set, the owner of the file defined by the &%file%& option
23164 is checked to ensure that it is the same as the user under which the delivery
23165 process is running.
23168 .option check_string appendfile string "see below"
23169 .cindex "&""From""& line"
23170 As &(appendfile)& writes the message, the start of each line is tested for
23171 matching &%check_string%&, and if it does, the initial matching characters are
23172 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
23173 a literal string, not a regular expression, and the case of any letters it
23174 contains is significant.
23176 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
23177 are forced to &"."& and &".."& respectively, and any settings in the
23178 configuration are ignored. Otherwise, they default to &"From&~"& and
23179 &">From&~"& when the &%file%& option is set, and unset when any of the
23180 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
23182 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
23183 suitable for traditional &"BSD"& mailboxes, where a line beginning with
23184 &"From&~"& indicates the start of a new message. All four options need changing
23185 if another format is used. For example, to deliver to mailboxes in MMDF format:
23186 .cindex "MMDF format mailbox"
23187 .cindex "mailbox" "MMDF format"
23189 check_string = "\1\1\1\1\n"
23190 escape_string = "\1\1\1\1 \n"
23191 message_prefix = "\1\1\1\1\n"
23192 message_suffix = "\1\1\1\1\n"
23194 .option create_directory appendfile boolean true
23195 .cindex "directory creation"
23196 When this option is true, Exim attempts to create any missing superior
23197 directories for the file that it is about to write. A created directory's mode
23198 is given by the &%directory_mode%& option.
23200 The group ownership of a newly created directory is highly dependent on the
23201 operating system (and possibly the file system) that is being used. For
23202 example, in Solaris, if the parent directory has the setgid bit set, its group
23203 is propagated to the child; if not, the currently set group is used. However,
23204 in FreeBSD, the parent's group is always used.
23208 .option create_file appendfile string anywhere
23209 This option constrains the location of files and directories that are created
23210 by this transport. It applies to files defined by the &%file%& option and
23211 directories defined by the &%directory%& option. In the case of maildir
23212 delivery, it applies to the top level directory, not the maildir directories
23215 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
23216 &"belowhome"&, or to an absolute path.
23218 In the second and third cases, a home directory must have been
23219 set for the transport, and the file or directory being created must
23221 The "belowhome" checking additionally checks for attempts to use "../"
23222 to evade the testing.
23223 This option is not useful when an explicit filename is
23224 given for normal mailbox deliveries. It is intended for the case when filenames
23225 are generated from users' &_.forward_& files. These are usually handled
23226 by an &(appendfile)& transport called &%address_file%&. See also
23227 &%file_must_exist%&.
23229 In the fourth case,
23230 the value given for this option must be an absolute path for an
23231 existing directory.
23232 The value is used for checking instead of a home directory;
23233 checking is done in "belowhome" mode.
23235 .cindex "tainted data" "de-tainting"
23236 .cindex "de-tainting" "using appendfile create_file option"
23237 If "belowhome" checking is used, the file or directory path
23238 becomes de-tainted.
23241 .option directory appendfile string&!! unset
23242 This option is mutually exclusive with the &%file%& option, but one of &%file%&
23243 or &%directory%& must be set, unless the delivery is the direct result of a
23244 redirection (see section &<<SECTfildiropt>>&).
23246 When &%directory%& is set, the string is expanded, and the message is delivered
23247 into a new file or files in or below the given directory, instead of being
23248 appended to a single mailbox file. A number of different formats are provided
23249 (see &%maildir_format%& and &%mailstore_format%&), and see section
23250 &<<SECTopdir>>& for further details of this form of delivery.
23252 The result of expansion must not be tainted, unless the &%create_file%& option
23256 .option directory_file appendfile string&!! "see below"
23258 .vindex "&$inode$&"
23259 When &%directory%& is set, but neither &%maildir_format%& nor
23260 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
23261 whose name is obtained by expanding this string. The default value is:
23263 q${base62:$tod_epoch}-$inode
23265 This generates a unique name from the current time, in base 62 form, and the
23266 inode of the file. The variable &$inode$& is available only when expanding this
23270 .option directory_mode appendfile "octal integer" 0700
23271 If &(appendfile)& creates any directories as a result of the
23272 &%create_directory%& option, their mode is specified by this option.
23275 .option escape_string appendfile string "see description"
23276 See &%check_string%& above.
23279 .option file appendfile string&!! unset
23280 This option is mutually exclusive with the &%directory%& option, but one of
23281 &%file%& or &%directory%& must be set, unless the delivery is the direct result
23282 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
23283 specifies a single file, to which the message is appended. One or more of
23284 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
23287 The result of expansion must not be tainted, unless the &%create_file%& option
23290 .cindex "NFS" "lock file"
23291 .cindex "locking files"
23292 .cindex "lock files"
23293 If you are using more than one host to deliver over NFS into the same
23294 mailboxes, you should always use lock files.
23296 The string value is expanded for each delivery, and must yield an absolute
23297 path. The most common settings of this option are variations on one of these
23300 file = /var/spool/mail/$local_part_data
23301 file = /home/$local_part_data/inbox
23304 .cindex "&""sticky""& bit"
23305 In the first example, all deliveries are done into the same directory. If Exim
23306 is configured to use lock files (see &%use_lockfile%& below) it must be able to
23307 create a file in the directory, so the &"sticky"& bit must be turned on for
23308 deliveries to be possible, or alternatively the &%group%& option can be used to
23309 run the delivery under a group id which has write access to the directory.
23313 .option file_format appendfile string unset
23314 .cindex "file" "mailbox; checking existing format"
23315 This option requests the transport to check the format of an existing file
23316 before adding to it. The check consists of matching a specific string at the
23317 start of the file. The value of the option consists of an even number of
23318 colon-separated strings. The first of each pair is the test string, and the
23319 second is the name of a transport. If the transport associated with a matched
23320 string is not the current transport, control is passed over to the other
23321 transport. For example, suppose the standard &(local_delivery)& transport has
23324 file_format = "From : local_delivery :\
23325 \1\1\1\1\n : local_mmdf_delivery"
23327 Mailboxes that begin with &"From"& are still handled by this transport, but if
23328 a mailbox begins with four binary ones followed by a newline, control is passed
23329 to a transport called &%local_mmdf_delivery%&, which presumably is configured
23330 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
23331 is assumed to match the current transport. If the start of a mailbox doesn't
23332 match any string, or if the transport named for a given string is not defined,
23333 delivery is deferred.
23336 .option file_must_exist appendfile boolean false
23337 If this option is true, the file specified by the &%file%& option must exist.
23338 A temporary error occurs if it does not, causing delivery to be deferred.
23339 If this option is false, the file is created if it does not exist.
23342 .option lock_fcntl_timeout appendfile time 0s
23343 .cindex "timeout" "mailbox locking"
23344 .cindex "mailbox" "locking, blocking and non-blocking"
23345 .cindex "locking files"
23346 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
23347 when locking an open mailbox file. If the call fails, the delivery process
23348 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
23349 Non-blocking calls are used so that the file is not kept open during the wait
23350 for the lock; the reason for this is to make it as safe as possible for
23351 deliveries over NFS in the case when processes might be accessing an NFS
23352 mailbox without using a lock file. This should not be done, but
23353 misunderstandings and hence misconfigurations are not unknown.
23355 On a busy system, however, the performance of a non-blocking lock approach is
23356 not as good as using a blocking lock with a timeout. In this case, the waiting
23357 is done inside the system call, and Exim's delivery process acquires the lock
23358 and can proceed as soon as the previous lock holder releases it.
23360 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
23361 timeout, are used. There may still be some retrying: the maximum number of
23364 (lock_retries * lock_interval) / lock_fcntl_timeout
23366 rounded up to the next whole number. In other words, the total time during
23367 which &(appendfile)& is trying to get a lock is roughly the same, unless
23368 &%lock_fcntl_timeout%& is set very large.
23370 You should consider setting this option if you are getting a lot of delayed
23371 local deliveries because of errors of the form
23373 failed to lock mailbox /some/file (fcntl)
23376 .option lock_flock_timeout appendfile time 0s
23377 This timeout applies to file locking when using &[flock()]& (see
23378 &%use_flock%&); the timeout operates in a similar manner to
23379 &%lock_fcntl_timeout%&.
23382 .option lock_interval appendfile time 3s
23383 This specifies the time to wait between attempts to lock the file. See below
23384 for details of locking.
23387 .option lock_retries appendfile integer 10
23388 This specifies the maximum number of attempts to lock the file. A value of zero
23389 is treated as 1. See below for details of locking.
23392 .option lockfile_mode appendfile "octal integer" 0600
23393 This specifies the mode of the created lock file, when a lock file is being
23394 used (see &%use_lockfile%& and &%use_mbx_lock%&).
23397 .option lockfile_timeout appendfile time 30m
23398 .cindex "timeout" "mailbox locking"
23399 When a lock file is being used (see &%use_lockfile%&), if a lock file already
23400 exists and is older than this value, it is assumed to have been left behind by
23401 accident, and Exim attempts to remove it.
23404 .option mailbox_filecount appendfile string&!! unset
23405 .cindex "mailbox" "specifying size of"
23406 .cindex "size" "of mailbox"
23407 If this option is set, it is expanded, and the result is taken as the current
23408 number of files in the mailbox. It must be a decimal number, optionally
23409 followed by K or M. This provides a way of obtaining this information from an
23410 external source that maintains the data.
23413 .option mailbox_size appendfile string&!! unset
23414 .cindex "mailbox" "specifying size of"
23415 .cindex "size" "of mailbox"
23416 If this option is set, it is expanded, and the result is taken as the current
23417 size the mailbox. It must be a decimal number, optionally followed by K or M.
23418 This provides a way of obtaining this information from an external source that
23419 maintains the data. This is likely to be helpful for maildir deliveries where
23420 it is computationally expensive to compute the size of a mailbox.
23424 .option maildir_format appendfile boolean false
23425 .cindex "maildir format" "specifying"
23426 If this option is set with the &%directory%& option, the delivery is into a new
23427 file, in the &"maildir"& format that is used by other mail software. When the
23428 transport is activated directly from a &(redirect)& router (for example, the
23429 &(address_file)& transport in the default configuration), setting
23430 &%maildir_format%& causes the path received from the router to be treated as a
23431 directory, whether or not it ends with &`/`&. This option is available only if
23432 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
23433 &<<SECTmaildirdelivery>>& below for further details.
23436 .option maildir_quota_directory_regex appendfile string "See below"
23437 .cindex "maildir format" "quota; directories included in"
23438 .cindex "quota" "maildir; directories included in"
23439 This option is relevant only when &%maildir_use_size_file%& is set. It defines
23440 a regular expression for specifying directories, relative to the quota
23441 directory (see &%quota_directory%&), that should be included in the quota
23442 calculation. The default value is:
23444 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
23446 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
23447 (directories whose names begin with a dot). If you want to exclude the
23449 folder from the count (as some sites do), you need to change this setting to
23451 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
23453 This uses a negative lookahead in the regular expression to exclude the
23454 directory whose name is &_.Trash_&. When a directory is excluded from quota
23455 calculations, quota processing is bypassed for any messages that are delivered
23456 directly into that directory.
23459 .option maildir_retries appendfile integer 10
23460 This option specifies the number of times to retry when writing a file in
23461 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
23464 .option maildir_tag appendfile string&!! unset
23465 This option applies only to deliveries in maildir format, and is described in
23466 section &<<SECTmaildirdelivery>>& below.
23469 .option maildir_use_size_file appendfile&!! boolean false
23470 .cindex "maildir format" "&_maildirsize_& file"
23471 The result of string expansion for this option must be a valid boolean value.
23472 If it is true, it enables support for &_maildirsize_& files. Exim
23473 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
23474 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
23475 value is zero. See &%maildir_quota_directory_regex%& above and section
23476 &<<SECTmaildirdelivery>>& below for further details.
23478 .option maildirfolder_create_regex appendfile string unset
23479 .cindex "maildir format" "&_maildirfolder_& file"
23480 .cindex "&_maildirfolder_&, creating"
23481 The value of this option is a regular expression. If it is unset, it has no
23482 effect. Otherwise, before a maildir delivery takes place, the pattern is
23483 matched against the name of the maildir directory, that is, the directory
23484 containing the &_new_& and &_tmp_& subdirectories that will be used for the
23485 delivery. If there is a match, Exim checks for the existence of a file called
23486 &_maildirfolder_& in the directory, and creates it if it does not exist.
23487 See section &<<SECTmaildirdelivery>>& for more details.
23490 .option mailstore_format appendfile boolean false
23491 .cindex "mailstore format" "specifying"
23492 If this option is set with the &%directory%& option, the delivery is into two
23493 new files in &"mailstore"& format. The option is available only if
23494 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
23495 below for further details.
23498 .option mailstore_prefix appendfile string&!! unset
23499 This option applies only to deliveries in mailstore format, and is described in
23500 section &<<SECTopdir>>& below.
23503 .option mailstore_suffix appendfile string&!! unset
23504 This option applies only to deliveries in mailstore format, and is described in
23505 section &<<SECTopdir>>& below.
23508 .option mbx_format appendfile boolean false
23509 .cindex "locking files"
23510 .cindex "file" "locking"
23511 .cindex "file" "MBX format"
23512 .cindex "MBX format, specifying"
23513 This option is available only if Exim has been compiled with SUPPORT_MBX
23514 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
23515 the message is appended to the mailbox file in MBX format instead of
23516 traditional Unix format. This format is supported by Pine4 and its associated
23517 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
23519 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
23520 automatically changed by the use of &%mbx_format%&. They should normally be set
23521 empty when using MBX format, so this option almost always appears in this
23528 If none of the locking options are mentioned in the configuration,
23529 &%use_mbx_lock%& is assumed and the other locking options default to false. It
23530 is possible to specify the other kinds of locking with &%mbx_format%&, but
23531 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
23532 interworks with &'c-client'&, providing for shared access to the mailbox. It
23533 should not be used if any program that does not use this form of locking is
23534 going to access the mailbox, nor should it be used if the mailbox file is NFS
23535 mounted, because it works only when the mailbox is accessed from a single host.
23537 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
23538 the standard version of &'c-client'&, because as long as it has a mailbox open
23539 (this means for the whole of a Pine or IMAP session), Exim will not be able to
23540 append messages to it.
23543 .option message_prefix appendfile string&!! "see below"
23544 .cindex "&""From""& line"
23545 The string specified here is expanded and output at the start of every message.
23546 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23547 in which case it is:
23549 message_prefix = "From ${if def:return_path{$return_path}\
23550 {MAILER-DAEMON}} $tod_bsdinbox\n"
23552 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23553 &`\n`& to &`\r\n`& in &%message_prefix%&.
23555 .option message_suffix appendfile string&!! "see below"
23556 The string specified here is expanded and output at the end of every message.
23557 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23558 in which case it is a single newline character. The suffix can be suppressed by
23563 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23564 &`\n`& to &`\r\n`& in &%message_suffix%&.
23566 .option mode appendfile "octal integer" 0600
23567 If the output file is created, it is given this mode. If it already exists and
23568 has wider permissions, they are reduced to this mode. If it has narrower
23569 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
23570 if the delivery is the result of a &%save%& command in a filter file specifying
23571 a particular mode, the mode of the output file is always forced to take that
23572 value, and this option is ignored.
23575 .option mode_fail_narrower appendfile boolean true
23576 This option applies in the case when an existing mailbox file has a narrower
23577 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
23578 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
23579 continues with the delivery attempt, using the existing mode of the file.
23582 .option notify_comsat appendfile boolean false
23583 If this option is true, the &'comsat'& daemon is notified after every
23584 successful delivery to a user mailbox. This is the daemon that notifies logged
23585 on users about incoming mail.
23588 .option quota appendfile string&!! unset
23589 .cindex "quota" "imposed by Exim"
23590 This option imposes a limit on the size of the file to which Exim is appending,
23591 or to the total space used in the directory tree when the &%directory%& option
23592 is set. In the latter case, computation of the space used is expensive, because
23593 all the files in the directory (and any sub-directories) have to be
23594 individually inspected and their sizes summed. (See &%quota_size_regex%& and
23595 &%maildir_use_size_file%& for ways to avoid this in environments where users
23596 have no shell access to their mailboxes).
23598 As there is no interlock against two simultaneous deliveries into a
23599 multi-file mailbox, it is possible for the quota to be overrun in this case.
23600 For single-file mailboxes, of course, an interlock is a necessity.
23602 A file's size is taken as its &'used'& value. Because of blocking effects, this
23603 may be a lot less than the actual amount of disk space allocated to the file.
23604 If the sizes of a number of files are being added up, the rounding effect can
23605 become quite noticeable, especially on systems that have large block sizes.
23606 Nevertheless, it seems best to stick to the &'used'& figure, because this is
23607 the obvious value which users understand most easily.
23609 The value of the option is expanded, and must then be a numerical value
23610 (decimal point allowed), optionally followed by one of the letters K, M, or G,
23611 for kilobytes, megabytes, or gigabytes, optionally followed by a slash
23612 and further option modifiers. If Exim is running on a system with
23613 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
23616 The option modifier &%no_check%& can be used to force delivery even if the over
23617 quota condition is met. The quota gets updated as usual.
23619 &*Note*&: A value of zero is interpreted as &"no quota"&.
23621 The expansion happens while Exim is running as root, before it changes uid for
23622 the delivery. This means that files that are inaccessible to the end user can
23623 be used to hold quota values that are looked up in the expansion. When delivery
23624 fails because this quota is exceeded, the handling of the error is as for
23625 system quota failures.
23627 By default, Exim's quota checking mimics system quotas, and restricts the
23628 mailbox to the specified maximum size, though the value is not accurate to the
23629 last byte, owing to separator lines and additional headers that may get added
23630 during message delivery. When a mailbox is nearly full, large messages may get
23631 refused even though small ones are accepted, because the size of the current
23632 message is added to the quota when the check is made. This behaviour can be
23633 changed by setting &%quota_is_inclusive%& false. When this is done, the check
23634 for exceeding the quota does not include the current message. Thus, deliveries
23635 continue until the quota has been exceeded; thereafter, no further messages are
23636 delivered. See also &%quota_warn_threshold%&.
23639 .option quota_directory appendfile string&!! unset
23640 This option defines the directory to check for quota purposes when delivering
23641 into individual files. The default is the delivery directory, or, if a file
23642 called &_maildirfolder_& exists in a maildir directory, the parent of the
23643 delivery directory.
23646 .option quota_filecount appendfile string&!! 0
23647 This option applies when the &%directory%& option is set. It limits the total
23648 number of files in the directory (compare the inode limit in system quotas). It
23649 can only be used if &%quota%& is also set. The value is expanded; an expansion
23650 failure causes delivery to be deferred. A value of zero is interpreted as
23653 The option modifier &%no_check%& can be used to force delivery even if the over
23654 quota condition is met. The quota gets updated as usual.
23656 .option quota_is_inclusive appendfile boolean true
23657 See &%quota%& above.
23660 .option quota_size_regex appendfile string unset
23661 This option applies when one of the delivery modes that writes a separate file
23662 for each message is being used. When Exim wants to find the size of one of
23663 these files in order to test the quota, it first checks &%quota_size_regex%&.
23664 If this is set to a regular expression that matches the filename, and it
23665 captures one string, that string is interpreted as a representation of the
23666 file's size. The value of &%quota_size_regex%& is not expanded.
23668 This feature is useful only when users have no shell access to their mailboxes
23669 &-- otherwise they could defeat the quota simply by renaming the files. This
23670 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
23671 the file length to the filename. For example:
23673 maildir_tag = ,S=$message_size
23674 quota_size_regex = ,S=(\d+)
23676 An alternative to &$message_size$& is &$message_linecount$&, which contains the
23677 number of lines in the message.
23679 The regular expression should not assume that the length is at the end of the
23680 filename (even though &%maildir_tag%& puts it there) because maildir MUAs
23681 sometimes add other information onto the ends of message filenames.
23683 Section &<<SECID136>>& contains further information.
23685 This option should not be used when other message-handling software
23686 may duplicate messages by making hardlinks to the files. When that is done Exim
23687 will count the message size once for each filename, in contrast with the actual
23688 disk usage. When the option is not set, calculating total usage requires
23689 a system-call per file to get the size; the number of links is then available also
23690 as is used to adjust the effective size.
23693 .option quota_warn_message appendfile string&!! "see below"
23694 See below for the use of this option. If it is not set when
23695 &%quota_warn_threshold%& is set, it defaults to
23697 quota_warn_message = "\
23698 To: $local_part@$domain\n\
23699 Subject: Your mailbox\n\n\
23700 This message is automatically created \
23701 by mail delivery software.\n\n\
23702 The size of your mailbox has exceeded \
23703 a warning threshold that is\n\
23704 set by the system administrator.\n"
23708 .option quota_warn_threshold appendfile string&!! 0
23709 .cindex "quota" "warning threshold"
23710 .cindex "mailbox" "size warning"
23711 .cindex "size" "of mailbox"
23712 This option is expanded in the same way as &%quota%& (see above). If the
23713 resulting value is greater than zero, and delivery of the message causes the
23714 size of the file or total space in the directory tree to cross the given
23715 threshold, a warning message is sent. If &%quota%& is also set, the threshold
23716 may be specified as a percentage of it by following the value with a percent
23720 quota_warn_threshold = 75%
23722 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
23723 percent sign is ignored.
23725 The warning message itself is specified by the &%quota_warn_message%& option,
23726 and it must start with a &'To:'& header line containing the recipient(s) of the
23727 warning message. These do not necessarily have to include the recipient(s) of
23728 the original message. A &'Subject:'& line should also normally be supplied. You
23729 can include any other header lines that you want. If you do not include a
23730 &'From:'& line, the default is:
23732 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
23734 .oindex &%errors_reply_to%&
23735 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
23738 The &%quota%& option does not have to be set in order to use this option; they
23739 are independent of one another except when the threshold is specified as a
23743 .option use_bsmtp appendfile boolean false
23744 .cindex "envelope from"
23745 .cindex "envelope sender"
23746 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
23747 format, with the envelope sender and recipient(s) included as SMTP commands. If
23748 you want to include a leading HELO command with such messages, you can do
23749 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
23750 for details of batch SMTP.
23753 .option use_crlf appendfile boolean false
23754 .cindex "carriage return"
23756 This option causes lines to be terminated with the two-character CRLF sequence
23757 (carriage return, linefeed) instead of just a linefeed character. In the case
23758 of batched SMTP, the byte sequence written to the file is then an exact image
23759 of what would be sent down a real SMTP connection.
23761 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
23762 (which are used to supply the traditional &"From&~"& and blank line separators
23763 in Berkeley-style mailboxes) are written verbatim, so must contain their own
23764 carriage return characters if these are needed. In cases where these options
23765 have non-empty defaults, the values end with a single linefeed, so they must be
23766 changed to end with &`\r\n`& if &%use_crlf%& is set.
23769 .option use_fcntl_lock appendfile boolean "see below"
23770 This option controls the use of the &[fcntl()]& function to lock a file for
23771 exclusive use when a message is being appended. It is set by default unless
23772 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
23773 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
23774 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
23777 .option use_flock_lock appendfile boolean false
23778 This option is provided to support the use of &[flock()]& for file locking, for
23779 the few situations where it is needed. Most modern operating systems support
23780 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
23781 each other. Exim uses &[fcntl()]& locking by default.
23783 This option is required only if you are using an operating system where
23784 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
23785 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
23786 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
23788 .cindex "Solaris" "&[flock()]& support"
23789 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
23790 have it (and some, I think, provide a not quite right version built on top of
23791 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
23792 the ability to use it, and any attempt to do so will cause a configuration
23795 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
23796 is just being mapped onto &[fcntl()]& by the OS).
23799 .option use_lockfile appendfile boolean "see below"
23800 If this option is turned off, Exim does not attempt to create a lock file when
23801 appending to a mailbox file. In this situation, the only locking is by
23802 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
23803 sure that every MUA that is ever going to look at your users' mailboxes uses
23804 &[fcntl()]& rather than a lock file, and even then only when you are not
23805 delivering over NFS from more than one host.
23807 .cindex "NFS" "lock file"
23808 In order to append to an NFS file safely from more than one host, it is
23809 necessary to take out a lock &'before'& opening the file, and the lock file
23810 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
23813 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
23814 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
23815 except when &%mbx_format%& is set.
23818 .option use_mbx_lock appendfile boolean "see below"
23819 This option is available only if Exim has been compiled with SUPPORT_MBX
23820 set in &_Local/Makefile_&. Setting the option specifies that special MBX
23821 locking rules be used. It is set by default if &%mbx_format%& is set and none
23822 of the locking options are mentioned in the configuration. The locking rules
23823 are the same as are used by the &'c-client'& library that underlies Pine and
23824 the IMAP4 and POP daemons that come with it (see the discussion below). The
23825 rules allow for shared access to the mailbox. However, this kind of locking
23826 does not work when the mailbox is NFS mounted.
23828 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
23829 &%use_flock_lock%& to control what kind of locking is used in implementing the
23830 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
23831 without &%use_fcntl_lock%& or &%use_flock_lock%&.
23836 .section "Operational details for appending" "SECTopappend"
23837 .cindex "appending to a file"
23838 .cindex "file" "appending"
23839 Before appending to a file, the following preparations are made:
23842 If the name of the file is &_/dev/null_&, no action is taken, and a success
23846 .cindex "directory creation"
23847 If any directories on the file's path are missing, Exim creates them if the
23848 &%create_directory%& option is set. A created directory's mode is given by the
23849 &%directory_mode%& option.
23852 If &%file_format%& is set, the format of an existing file is checked. If this
23853 indicates that a different transport should be used, control is passed to that
23857 .cindex "file" "locking"
23858 .cindex "locking files"
23859 .cindex "NFS" "lock file"
23860 If &%use_lockfile%& is set, a lock file is built in a way that will work
23861 reliably over NFS, as follows:
23864 Create a &"hitching post"& file whose name is that of the lock file with the
23865 current time, primary host name, and process id added, by opening for writing
23866 as a new file. If this fails with an access error, delivery is deferred.
23868 Close the hitching post file, and hard link it to the lock filename.
23870 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
23871 Unlink the hitching post name.
23873 Otherwise, use &[stat()]& to get information about the hitching post file, and
23874 then unlink hitching post name. If the number of links is exactly two, creation
23875 of the lock file succeeded but something (for example, an NFS server crash and
23876 restart) caused this fact not to be communicated to the &[link()]& call.
23878 If creation of the lock file failed, wait for &%lock_interval%& and try again,
23879 up to &%lock_retries%& times. However, since any program that writes to a
23880 mailbox should complete its task very quickly, it is reasonable to time out old
23881 lock files that are normally the result of user agent and system crashes. If an
23882 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
23883 it before trying again.
23887 A call is made to &[lstat()]& to discover whether the main file exists, and if
23888 so, what its characteristics are. If &[lstat()]& fails for any reason other
23889 than non-existence, delivery is deferred.
23892 .cindex "symbolic link" "to mailbox"
23893 .cindex "mailbox" "symbolic link"
23894 If the file does exist and is a symbolic link, delivery is deferred, unless the
23895 &%allow_symlink%& option is set, in which case the ownership of the link is
23896 checked, and then &[stat()]& is called to find out about the real file, which
23897 is then subjected to the checks below. The check on the top-level link
23898 ownership prevents one user creating a link for another's mailbox in a sticky
23899 directory, though allowing symbolic links in this case is definitely not a good
23900 idea. If there is a chain of symbolic links, the intermediate ones are not
23904 If the file already exists but is not a regular file, or if the file's owner
23905 and group (if the group is being checked &-- see &%check_group%& above) are
23906 different from the user and group under which the delivery is running,
23907 delivery is deferred.
23910 If the file's permissions are more generous than specified, they are reduced.
23911 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
23912 is set false, in which case the delivery is tried using the existing
23916 The file's inode number is saved, and the file is then opened for appending.
23917 If this fails because the file has vanished, &(appendfile)& behaves as if it
23918 hadn't existed (see below). For any other failures, delivery is deferred.
23921 If the file is opened successfully, check that the inode number hasn't
23922 changed, that it is still a regular file, and that the owner and permissions
23923 have not changed. If anything is wrong, defer delivery and freeze the message.
23926 If the file did not exist originally, defer delivery if the &%file_must_exist%&
23927 option is set. Otherwise, check that the file is being created in a permitted
23928 directory if the &%create_file%& option is set (deferring on failure), and then
23929 open for writing as a new file, with the O_EXCL and O_CREAT options,
23930 except when dealing with a symbolic link (the &%allow_symlink%& option must be
23931 set). In this case, which can happen if the link points to a non-existent file,
23932 the file is opened for writing using O_CREAT but not O_EXCL, because
23933 that prevents link following.
23936 .cindex "loop" "while file testing"
23937 If opening fails because the file exists, obey the tests given above for
23938 existing files. However, to avoid looping in a situation where the file is
23939 being continuously created and destroyed, the exists/not-exists loop is broken
23940 after 10 repetitions, and the message is then frozen.
23943 If opening fails with any other error, defer delivery.
23946 .cindex "file" "locking"
23947 .cindex "locking files"
23948 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
23949 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
23950 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
23951 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
23952 file, and an exclusive lock on the file whose name is
23954 /tmp/.<device-number>.<inode-number>
23956 using the device and inode numbers of the open mailbox file, in accordance with
23957 the MBX locking rules. This file is created with a mode that is specified by
23958 the &%lockfile_mode%& option.
23960 If Exim fails to lock the file, there are two possible courses of action,
23961 depending on the value of the locking timeout. This is obtained from
23962 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
23964 If the timeout value is zero, the file is closed, Exim waits for
23965 &%lock_interval%&, and then goes back and re-opens the file as above and tries
23966 to lock it again. This happens up to &%lock_retries%& times, after which the
23967 delivery is deferred.
23969 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
23970 &[flock()]& are used (with the given timeout), so there has already been some
23971 waiting involved by the time locking fails. Nevertheless, Exim does not give up
23972 immediately. It retries up to
23974 (lock_retries * lock_interval) / <timeout>
23976 times (rounded up).
23979 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
23980 and/or &[flock()]& locks) and then deletes the lock file if one was created.
23983 .section "Operational details for delivery to a new file" "SECTopdir"
23984 .cindex "delivery" "to single file"
23985 .cindex "&""From""& line"
23986 When the &%directory%& option is set instead of &%file%&, each message is
23987 delivered into a newly-created file or set of files. When &(appendfile)& is
23988 activated directly from a &(redirect)& router, neither &%file%& nor
23989 &%directory%& is normally set, because the path for delivery is supplied by the
23990 router. (See for example, the &(address_file)& transport in the default
23991 configuration.) In this case, delivery is to a new file if either the path name
23992 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
23994 No locking is required while writing the message to a new file, so the various
23995 locking options of the transport are ignored. The &"From"& line that by default
23996 separates messages in a single file is not normally needed, nor is the escaping
23997 of message lines that start with &"From"&, and there is no need to ensure a
23998 newline at the end of each message. Consequently, the default values for
23999 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
24000 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
24002 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
24003 the files in the delivery directory by default. However, you can specify a
24004 different directory by setting &%quota_directory%&. Also, for maildir
24005 deliveries (see below) the &_maildirfolder_& convention is honoured.
24008 .cindex "maildir format"
24009 .cindex "mailstore format"
24010 There are three different ways in which delivery to individual files can be
24011 done, controlled by the settings of the &%maildir_format%& and
24012 &%mailstore_format%& options. Note that code to support maildir or mailstore
24013 formats is not included in the binary unless SUPPORT_MAILDIR or
24014 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
24016 .cindex "directory creation"
24017 In all three cases an attempt is made to create the directory and any necessary
24018 sub-directories if they do not exist, provided that the &%create_directory%&
24019 option is set (the default). The location of a created directory can be
24020 constrained by setting &%create_file%&. A created directory's mode is given by
24021 the &%directory_mode%& option. If creation fails, or if the
24022 &%create_directory%& option is not set when creation is required, delivery is
24027 .section "Maildir delivery" "SECTmaildirdelivery"
24028 .cindex "maildir format" "description of"
24029 If the &%maildir_format%& option is true, Exim delivers each message by writing
24030 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
24031 directory that is defined by the &%directory%& option (the &"delivery
24032 directory"&). If the delivery is successful, the file is renamed into the
24033 &_new_& subdirectory.
24035 In the filename, <&'stime'&> is the current time of day in seconds, and
24036 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
24037 Exim checks that the time-of-day clock has moved on by at least one microsecond
24038 before terminating the delivery process. This guarantees uniqueness for the
24039 filename. However, as a precaution, Exim calls &[stat()]& for the file before
24040 opening it. If any response other than ENOENT (does not exist) is given,
24041 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
24043 Before Exim carries out a maildir delivery, it ensures that subdirectories
24044 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
24045 do not exist, Exim tries to create them and any superior directories in their
24046 path, subject to the &%create_directory%& and &%create_file%& options. If the
24047 &%maildirfolder_create_regex%& option is set, and the regular expression it
24048 contains matches the delivery directory, Exim also ensures that a file called
24049 &_maildirfolder_& exists in the delivery directory. If a missing directory or
24050 &_maildirfolder_& file cannot be created, delivery is deferred.
24052 These features make it possible to use Exim to create all the necessary files
24053 and directories in a maildir mailbox, including subdirectories for maildir++
24054 folders. Consider this example:
24056 maildir_format = true
24057 directory = /var/mail/$local_part_data\
24058 ${if eq{$local_part_suffix}{}{}\
24059 {/.${substr_1:$local_part_suffix}}}
24060 maildirfolder_create_regex = /\.[^/]+$
24062 If &$local_part_suffix$& is empty (there was no suffix for the local part),
24063 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
24064 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
24065 not match this name, so Exim will not look for or create the file
24066 &_/var/mail/pimbo/maildirfolder_&, though it will create
24067 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
24069 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
24070 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
24071 does match &%maildirfolder_create_regex%&. In this case, Exim will create
24072 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
24073 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
24075 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
24076 not inadvertently match the toplevel maildir directory, because a
24077 &_maildirfolder_& file at top level would completely break quota calculations.
24079 .cindex "quota" "in maildir delivery"
24080 .cindex "maildir++"
24081 If Exim is required to check a &%quota%& setting before a maildir delivery, and
24082 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
24083 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
24084 Exim assumes the directory is a maildir++ folder directory, which is one level
24085 down from the user's top level mailbox directory. This causes it to start at
24086 the parent directory instead of the current directory when calculating the
24087 amount of space used.
24089 One problem with delivering into a multi-file mailbox is that it is
24090 computationally expensive to compute the size of the mailbox for quota
24091 checking. Various approaches have been taken to reduce the amount of work
24092 needed. The next two sections describe two of them. A third alternative is to
24093 use some external process for maintaining the size data, and use the expansion
24094 of the &%mailbox_size%& option as a way of importing it into Exim.
24099 .section "Using tags to record message sizes" "SECID135"
24100 If &%maildir_tag%& is set, the string is expanded for each delivery.
24101 When the maildir file is renamed into the &_new_& sub-directory, the
24102 tag is added to its name. However, if adding the tag takes the length of the
24103 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
24104 the tag is dropped and the maildir file is created with no tag.
24107 .vindex "&$message_size$&"
24108 Tags can be used to encode the size of files in their names; see
24109 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
24110 happens after the message has been written. The value of the &$message_size$&
24111 variable is set to the number of bytes actually written. If the expansion is
24112 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
24113 be deferred. The expanded tag may contain any printing characters except &"/"&.
24114 Non-printing characters in the string are ignored; if the resulting string is
24115 empty, it is ignored. If it starts with an alphanumeric character, a leading
24116 colon is inserted; this default has not proven to be the path that popular
24117 maildir implementations have chosen (but changing it in Exim would break
24118 backwards compatibility).
24120 For one common implementation, you might set:
24122 maildir_tag = ,S=${message_size}
24124 but you should check the documentation of the other software to be sure.
24126 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
24127 as this allows Exim to extract the size from your tag, instead of having to
24128 &[stat()]& each message file.
24131 .section "Using a maildirsize file" "SECID136"
24132 .cindex "quota" "in maildir delivery"
24133 .cindex "maildir format" "&_maildirsize_& file"
24134 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
24135 storing quota and message size information in a file called &_maildirsize_&
24136 within the toplevel maildir directory. If this file does not exist, Exim
24137 creates it, setting the quota from the &%quota%& option of the transport. If
24138 the maildir directory itself does not exist, it is created before any attempt
24139 to write a &_maildirsize_& file.
24141 The &_maildirsize_& file is used to hold information about the sizes of
24142 messages in the maildir, thus speeding up quota calculations. The quota value
24143 in the file is just a cache; if the quota is changed in the transport, the new
24144 value overrides the cached value when the next message is delivered. The cache
24145 is maintained for the benefit of other programs that access the maildir and
24146 need to know the quota.
24148 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
24149 file is maintained (with a zero quota setting), but no quota is imposed.
24151 A regular expression is available for controlling which directories in the
24152 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
24153 See the description of the &%maildir_quota_directory_regex%& option above for
24157 .section "Mailstore delivery" "SECID137"
24158 .cindex "mailstore format" "description of"
24159 If the &%mailstore_format%& option is true, each message is written as two
24160 files in the given directory. A unique base name is constructed from the
24161 message id and the current delivery process, and the files that are written use
24162 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
24163 contains the message's envelope, and the &_.msg_& file contains the message
24164 itself. The base name is placed in the variable &$mailstore_basename$&.
24166 During delivery, the envelope is first written to a file with the suffix
24167 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
24168 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
24169 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
24170 file before accessing either of them. An alternative approach is to wait for
24171 the absence of a &_.tmp_& file.
24173 The envelope file starts with any text defined by the &%mailstore_prefix%&
24174 option, expanded and terminated by a newline if there isn't one. Then follows
24175 the sender address on one line, then all the recipient addresses, one per line.
24176 There can be more than one recipient only if the &%batch_max%& option is set
24177 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
24178 appended to the file, followed by a newline if it does not end with one.
24180 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
24181 failure, it is ignored. Other expansion errors are treated as serious
24182 configuration errors, and delivery is deferred. The variable
24183 &$mailstore_basename$& is available for use during these expansions.
24186 .section "Non-special new file delivery" "SECID138"
24187 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
24188 file is created directly in the named directory. For example, when delivering
24189 messages into files in batched SMTP format for later delivery to some host (see
24190 section &<<SECTbatchSMTP>>&), a setting such as
24192 directory = /var/bsmtp/$host
24194 might be used. A message is written to a file with a temporary name, which is
24195 then renamed when the delivery is complete. The final name is obtained by
24196 expanding the contents of the &%directory_file%& option.
24197 .ecindex IIDapptra1
24198 .ecindex IIDapptra2
24205 . ////////////////////////////////////////////////////////////////////////////
24206 . ////////////////////////////////////////////////////////////////////////////
24208 .chapter "The autoreply transport" "CHID8"
24209 .scindex IIDauttra1 "transports" "&(autoreply)&"
24210 .scindex IIDauttra2 "&(autoreply)& transport"
24211 The &(autoreply)& transport is not a true transport in that it does not cause
24212 the message to be transmitted. Instead, it generates a new mail message as an
24213 automatic reply to the incoming message. &'References:'& and
24214 &'Auto-Submitted:'& header lines are included. These are constructed according
24215 to the rules in RFCs 2822 and 3834, respectively.
24217 If the router that passes the message to this transport does not have the
24218 &%unseen%& option set, the original message (for the current recipient) is not
24219 delivered anywhere. However, when the &%unseen%& option is set on the router
24220 that passes the message to this transport, routing of the address continues, so
24221 another router can set up a normal message delivery.
24224 The &(autoreply)& transport is usually run as the result of mail filtering, a
24225 &"vacation"& message being the standard example. However, it can also be run
24226 directly from a router like any other transport. To reduce the possibility of
24227 message cascades, messages created by the &(autoreply)& transport always have
24228 empty envelope sender addresses, like bounce messages.
24230 The parameters of the message to be sent can be specified in the configuration
24231 by options described below. However, these are used only when the address
24232 passed to the transport does not contain its own reply information. When the
24233 transport is run as a consequence of a
24235 or &%vacation%& command in a filter file, the parameters of the message are
24236 supplied by the filter, and passed with the address. The transport's options
24237 that define the message are then ignored (so they are not usually set in this
24238 case). The message is specified entirely by the filter or by the transport; it
24239 is never built from a mixture of options. However, the &%file_optional%&,
24240 &%mode%&, and &%return_message%& options apply in all cases.
24242 &(Autoreply)& is implemented as a local transport. When used as a result of a
24243 command in a user's filter file, &(autoreply)& normally runs under the uid and
24244 gid of the user, and with appropriate current and home directories (see chapter
24245 &<<CHAPenvironment>>&).
24247 There is a subtle difference between routing a message to a &(pipe)& transport
24248 that generates some text to be returned to the sender, and routing it to an
24249 &(autoreply)& transport. This difference is noticeable only if more than one
24250 address from the same message is so handled. In the case of a pipe, the
24251 separate outputs from the different addresses are gathered up and returned to
24252 the sender in a single message, whereas if &(autoreply)& is used, a separate
24253 message is generated for each address that is passed to it.
24255 Non-printing characters are not permitted in the header lines generated for the
24256 message that &(autoreply)& creates, with the exception of newlines that are
24257 immediately followed by white space. If any non-printing characters are found,
24258 the transport defers.
24259 Whether characters with the top bit set count as printing characters or not is
24260 controlled by the &%print_topbitchars%& global option.
24262 If any of the generic options for manipulating headers (for example,
24263 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
24264 of the original message that is included in the generated message when
24265 &%return_message%& is set. They do not apply to the generated message itself.
24267 .vindex "&$sender_address$&"
24268 If the &(autoreply)& transport receives return code 2 from Exim when it submits
24269 the message, indicating that there were no recipients, it does not treat this
24270 as an error. This means that autoreplies sent to &$sender_address$& when this
24271 is empty (because the incoming message is a bounce message) do not cause
24272 problems. They are just discarded.
24276 .section "Private options for autoreply" "SECID139"
24277 .cindex "options" "&(autoreply)& transport"
24279 .option bcc autoreply string&!! unset
24280 This specifies the addresses that are to receive &"blind carbon copies"& of the
24281 message when the message is specified by the transport.
24284 .option cc autoreply string&!! unset
24285 This specifies recipients of the message and the contents of the &'Cc:'& header
24286 when the message is specified by the transport.
24289 .option file autoreply string&!! unset
24290 The contents of the file are sent as the body of the message when the message
24291 is specified by the transport. If both &%file%& and &%text%& are set, the text
24292 string comes first.
24295 .option file_expand autoreply boolean false
24296 If this is set, the contents of the file named by the &%file%& option are
24297 subjected to string expansion as they are added to the message.
24300 .option file_optional autoreply boolean false
24301 If this option is true, no error is generated if the file named by the &%file%&
24302 option or passed with the address does not exist or cannot be read.
24305 .option from autoreply string&!! unset
24306 This specifies the contents of the &'From:'& header when the message is
24307 specified by the transport.
24310 .option headers autoreply string&!! unset
24311 This specifies additional RFC 2822 headers that are to be added to the message
24312 when the message is specified by the transport. Several can be given by using
24313 &"\n"& to separate them. There is no check on the format.
24316 .option log autoreply string&!! unset
24317 This option names a file in which a record of every message sent is logged when
24318 the message is specified by the transport.
24321 .option mode autoreply "octal integer" 0600
24322 If either the log file or the &"once"& file has to be created, this mode is
24326 .option never_mail autoreply "address list&!!" unset
24327 If any run of the transport creates a message with a recipient that matches any
24328 item in the list, that recipient is quietly discarded. If all recipients are
24329 discarded, no message is created. This applies both when the recipients are
24330 generated by a filter and when they are specified in the transport.
24334 .option once autoreply string&!! unset
24335 This option names a file or DBM database in which a record of each &'To:'&
24336 recipient is kept when the message is specified by the transport. &*Note*&:
24337 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
24339 If &%once%& is unset, or is set to an empty string, the message is always sent.
24340 By default, if &%once%& is set to a non-empty filename, the message
24341 is not sent if a potential recipient is already listed in the database.
24342 However, if the &%once_repeat%& option specifies a time greater than zero, the
24343 message is sent if that much time has elapsed since a message was last sent to
24344 this recipient. A setting of zero time for &%once_repeat%& (the default)
24345 prevents a message from being sent a second time &-- in this case, zero means
24348 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
24349 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
24350 greater than zero, it changes the way Exim implements the &%once%& option.
24351 Instead of using a DBM file to record every recipient it sends to, it uses a
24352 regular file, whose size will never get larger than the given value.
24354 In the file, Exim keeps a linear list of recipient addresses and the times at
24355 which they were sent messages. If the file is full when a new address needs to
24356 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
24357 means that a given recipient may receive multiple messages, but at
24358 unpredictable intervals that depend on the rate of turnover of addresses in the
24359 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
24362 .option once_file_size autoreply integer 0
24363 See &%once%& above.
24366 .option once_repeat autoreply time&!! 0s
24367 See &%once%& above.
24368 After expansion, the value of this option must be a valid time value.
24371 .option reply_to autoreply string&!! unset
24372 This specifies the contents of the &'Reply-To:'& header when the message is
24373 specified by the transport.
24376 .option return_message autoreply boolean false
24377 If this is set, a copy of the original message is returned with the new
24378 message, subject to the maximum size set in the &%return_size_limit%& global
24379 configuration option.
24382 .option subject autoreply string&!! unset
24383 This specifies the contents of the &'Subject:'& header when the message is
24384 specified by the transport. It is tempting to quote the original subject in
24385 automatic responses. For example:
24387 subject = Re: $h_subject:
24389 There is a danger in doing this, however. It may allow a third party to
24390 subscribe your users to an opt-in mailing list, provided that the list accepts
24391 bounce messages as subscription confirmations. Well-managed lists require a
24392 non-bounce message to confirm a subscription, so the danger is relatively
24397 .option text autoreply string&!! unset
24398 This specifies a single string to be used as the body of the message when the
24399 message is specified by the transport. If both &%text%& and &%file%& are set,
24400 the text comes first.
24403 .option to autoreply string&!! unset
24404 This specifies recipients of the message and the contents of the &'To:'& header
24405 when the message is specified by the transport.
24406 .ecindex IIDauttra1
24407 .ecindex IIDauttra2
24412 . ////////////////////////////////////////////////////////////////////////////
24413 . ////////////////////////////////////////////////////////////////////////////
24415 .chapter "The lmtp transport" "CHAPLMTP"
24416 .cindex "transports" "&(lmtp)&"
24417 .cindex "&(lmtp)& transport"
24418 .cindex "LMTP" "over a pipe"
24419 .cindex "LMTP" "over a socket"
24420 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
24422 or by interacting with a Unix domain socket.
24423 This transport is something of a cross between the &(pipe)& and &(smtp)&
24424 transports. Exim also has support for using LMTP over TCP/IP; this is
24425 implemented as an option for the &(smtp)& transport. Because LMTP is expected
24426 to be of minority interest, the default build-time configure in &_src/EDITME_&
24427 has it commented out. You need to ensure that
24431 .cindex "options" "&(lmtp)& transport"
24432 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
24433 included in the Exim binary. The private options of the &(lmtp)& transport are
24436 .option batch_id lmtp string&!! unset
24437 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24440 .option batch_max lmtp integer 1
24441 This limits the number of addresses that can be handled in a single delivery.
24442 Most LMTP servers can handle several addresses at once, so it is normally a
24443 good idea to increase this value. See the description of local delivery
24444 batching in chapter &<<CHAPbatching>>&.
24447 .option command lmtp string&!! unset
24448 This option must be set if &%socket%& is not set. The string is a command which
24449 is run in a separate process. It is split up into a command name and list of
24450 arguments, each of which is separately expanded (so expansion cannot change the
24451 number of arguments). The command is run directly, not via a shell. The message
24452 is passed to the new process using the standard input and output to operate the
24455 .option ignore_quota lmtp boolean false
24456 .cindex "LMTP" "ignoring quota errors"
24457 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
24458 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
24459 in its response to the LHLO command.
24461 .option socket lmtp string&!! unset
24462 This option must be set if &%command%& is not set. The result of expansion must
24463 be the name of a Unix domain socket. The transport connects to the socket and
24464 delivers the message to it using the LMTP protocol.
24467 .option timeout lmtp time 5m
24468 The transport is aborted if the created process or Unix domain socket does not
24469 respond to LMTP commands or message input within this timeout. Delivery
24470 is deferred, and will be tried again later. Here is an example of a typical
24475 command = /some/local/lmtp/delivery/program
24479 This delivers up to 20 addresses at a time, in a mixture of domains if
24480 necessary, running as the user &'exim'&.
24484 . ////////////////////////////////////////////////////////////////////////////
24485 . ////////////////////////////////////////////////////////////////////////////
24487 .chapter "The pipe transport" "CHAPpipetransport"
24488 .scindex IIDpiptra1 "transports" "&(pipe)&"
24489 .scindex IIDpiptra2 "&(pipe)& transport"
24490 The &(pipe)& transport is used to deliver messages via a pipe to a command
24491 running in another process. One example is the use of &(pipe)& as a
24492 pseudo-remote transport for passing messages to some other delivery mechanism
24493 (such as UUCP). Another is the use by individual users to automatically process
24494 their incoming messages. The &(pipe)& transport can be used in one of the
24498 .vindex "&$local_part$&"
24499 A router routes one address to a transport in the normal way, and the
24500 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
24501 contains the local part of the address (as usual), and the command that is run
24502 is specified by the &%command%& option on the transport.
24504 .vindex "&$pipe_addresses$&"
24505 If the &%batch_max%& option is set greater than 1 (the default is 1), the
24506 transport can handle more than one address in a single run. In this case, when
24507 more than one address is routed to the transport, &$local_part$& is not set
24508 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
24509 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
24510 that are routed to the transport.
24512 .vindex "&$address_pipe$&"
24513 A router redirects an address directly to a pipe command (for example, from an
24514 alias or forward file). In this case, &$address_pipe$& contains the text of the
24515 pipe command, and the &%command%& option on the transport is ignored unless
24516 &%force_command%& is set. If only one address is being transported
24517 (&%batch_max%& is not greater than one, or only one address was redirected to
24518 this pipe command), &$local_part$& contains the local part that was redirected.
24522 The &(pipe)& transport is a non-interactive delivery method. Exim can also
24523 deliver messages over pipes using the LMTP interactive protocol. This is
24524 implemented by the &(lmtp)& transport.
24526 In the case when &(pipe)& is run as a consequence of an entry in a local user's
24527 &_.forward_& file, the command runs under the uid and gid of that user. In
24528 other cases, the uid and gid have to be specified explicitly, either on the
24529 transport or on the router that handles the address. Current and &"home"&
24530 directories are also controllable. See chapter &<<CHAPenvironment>>& for
24531 details of the local delivery environment and chapter &<<CHAPbatching>>&
24532 for a discussion of local delivery batching.
24534 .cindex "tainted data" "in pipe command"
24535 .cindex pipe "tainted data"
24536 Tainted data may not be used for the command name.
24539 .section "Concurrent delivery" "SECID140"
24540 If two messages arrive at almost the same time, and both are routed to a pipe
24541 delivery, the two pipe transports may be run concurrently. You must ensure that
24542 any pipe commands you set up are robust against this happening. If the commands
24543 write to a file, the &%exim_lock%& utility might be of use.
24544 Alternatively the &%max_parallel%& option could be used with a value
24545 of "1" to enforce serialization.
24550 .section "Returned status and data" "SECID141"
24551 .cindex "&(pipe)& transport" "returned data"
24552 If the command exits with a non-zero return code, the delivery is deemed to
24553 have failed, unless either the &%ignore_status%& option is set (in which case
24554 the return code is treated as zero), or the return code is one of those listed
24555 in the &%temp_errors%& option, which are interpreted as meaning &"try again
24556 later"&. In this case, delivery is deferred. Details of a permanent failure are
24557 logged, but are not included in the bounce message, which merely contains
24558 &"local delivery failed"&.
24560 If the command exits on a signal and the &%freeze_signal%& option is set then
24561 the message will be frozen in the queue. If that option is not set, a bounce
24562 will be sent as normal.
24564 If the return code is greater than 128 and the command being run is a shell
24565 script, it normally means that the script was terminated by a signal whose
24566 value is the return code minus 128. The &%freeze_signal%& option does not
24567 apply in this case.
24569 If Exim is unable to run the command (that is, if &[execve()]& fails), the
24570 return code is set to 127. This is the value that a shell returns if it is
24571 asked to run a non-existent command. The wording for the log line suggests that
24572 a non-existent command may be the problem.
24574 The &%return_output%& option can affect the result of a pipe delivery. If it is
24575 set and the command produces any output on its standard output or standard
24576 error streams, the command is considered to have failed, even if it gave a zero
24577 return code or if &%ignore_status%& is set. The output from the command is
24578 included as part of the bounce message. The &%return_fail_output%& option is
24579 similar, except that output is returned only when the command exits with a
24580 failure return code, that is, a value other than zero or a code that matches
24585 .section "How the command is run" "SECThowcommandrun"
24586 .cindex "&(pipe)& transport" "path for command"
24587 The command line is (by default) broken down into a command name and arguments
24588 by the &(pipe)& transport itself. The &%allow_commands%& and
24589 &%restrict_to_path%& options can be used to restrict the commands that may be
24592 .cindex "quoting" "in pipe command"
24593 Unquoted arguments are delimited by white space. If an argument appears in
24594 double quotes, backslash is interpreted as an escape character in the usual
24595 way. If an argument appears in single quotes, no escaping is done.
24597 String expansion is applied to the command line except when it comes from a
24598 traditional &_.forward_& file (commands from a filter file are expanded). The
24599 expansion is applied to each argument in turn rather than to the whole line.
24600 For this reason, any string expansion item that contains white space must be
24601 quoted so as to be contained within a single argument. A setting such as
24603 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
24605 will not work, because the expansion item gets split between several
24606 arguments. You have to write
24608 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
24610 to ensure that it is all in one argument. The expansion is done in this way,
24611 argument by argument, so that the number of arguments cannot be changed as a
24612 result of expansion, and quotes or backslashes in inserted variables do not
24613 interact with external quoting. However, this leads to problems if you want to
24614 generate multiple arguments (or the command name plus arguments) from a single
24615 expansion. In this situation, the simplest solution is to use a shell. For
24618 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
24621 .cindex "transport" "filter"
24622 .cindex "filter" "transport filter"
24623 .vindex "&$pipe_addresses$&"
24624 Special handling takes place when an argument consists of precisely the text
24625 &`$pipe_addresses`& (no quotes).
24626 This is not a general expansion variable; the only
24627 place this string is recognized is when it appears as an argument for a pipe or
24628 transport filter command. It causes each address that is being handled to be
24629 inserted in the argument list at that point &'as a separate argument'&. This
24630 avoids any problems with spaces or shell metacharacters, and is of use when a
24631 &(pipe)& transport is handling groups of addresses in a batch.
24633 If &%force_command%& is enabled on the transport, special handling takes place
24634 for an argument that consists of precisely the text &`$address_pipe`&. It
24635 is handled similarly to &$pipe_addresses$& above. It is expanded and each
24636 argument is inserted in the argument list at that point
24637 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
24638 the only item in the argument; in fact, if it were then &%force_command%&
24639 should behave as a no-op. Rather, it should be used to adjust the command
24640 run while preserving the argument vector separation.
24642 After splitting up into arguments and expansion, the resulting command is run
24643 in a subprocess directly from the transport, &'not'& under a shell. The
24644 message that is being delivered is supplied on the standard input, and the
24645 standard output and standard error are both connected to a single pipe that is
24646 read by Exim. The &%max_output%& option controls how much output the command
24647 may produce, and the &%return_output%& and &%return_fail_output%& options
24648 control what is done with it.
24650 Not running the command under a shell (by default) lessens the security risks
24651 in cases when a command from a user's filter file is built out of data that was
24652 taken from an incoming message. If a shell is required, it can of course be
24653 explicitly specified as the command to be run. However, there are circumstances
24654 where existing commands (for example, in &_.forward_& files) expect to be run
24655 under a shell and cannot easily be modified. To allow for these cases, there is
24656 an option called &%use_shell%&, which changes the way the &(pipe)& transport
24657 works. Instead of breaking up the command line as just described, it expands it
24658 as a single string and passes the result to &_/bin/sh_&. The
24659 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
24660 with &%use_shell%&, and the whole mechanism is inherently less secure.
24664 .section "Environment variables" "SECTpipeenv"
24665 .cindex "&(pipe)& transport" "environment for command"
24666 .cindex "environment" "&(pipe)& transport"
24667 The environment variables listed below are set up when the command is invoked.
24668 This list is a compromise for maximum compatibility with other MTAs. Note that
24669 the &%environment%& option can be used to add additional variables to this
24670 environment. The environment for the &(pipe)& transport is not subject
24671 to the &%add_environment%& and &%keep_environment%& main config options.
24672 &*Note*&: Using enviroment variables loses track of tainted data.
24673 Writers of &(pipe)& transport commands should be wary of data supplied
24674 by potential attackers.
24676 &`DOMAIN `& the domain of the address
24677 &`HOME `& the home directory, if set
24678 &`HOST `& the host name when called from a router (see below)
24679 &`LOCAL_PART `& see below
24680 &`LOCAL_PART_PREFIX `& see below
24681 &`LOCAL_PART_SUFFIX `& see below
24682 &`LOGNAME `& see below
24683 &`MESSAGE_ID `& Exim's local ID for the message
24684 &`PATH `& as specified by the &%path%& option below
24685 &`QUALIFY_DOMAIN `& the sender qualification domain
24686 &`RECIPIENT `& the complete recipient address
24687 &`SENDER `& the sender of the message (empty if a bounce)
24688 &`SHELL `& &`/bin/sh`&
24689 &`TZ `& the value of the &%timezone%& option, if set
24690 &`USER `& see below
24692 When a &(pipe)& transport is called directly from (for example) an &(accept)&
24693 router, LOCAL_PART is set to the local part of the address. When it is
24694 called as a result of a forward or alias expansion, LOCAL_PART is set to
24695 the local part of the address that was expanded. In both cases, any affixes are
24696 removed from the local part, and made available in LOCAL_PART_PREFIX and
24697 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
24698 same value as LOCAL_PART for compatibility with other MTAs.
24701 HOST is set only when a &(pipe)& transport is called from a router that
24702 associates hosts with an address, typically when using &(pipe)& as a
24703 pseudo-remote transport. HOST is set to the first host name specified by
24707 If the transport's generic &%home_directory%& option is set, its value is used
24708 for the HOME environment variable. Otherwise, a home directory may be set
24709 by the router's &%transport_home_directory%& option, which defaults to the
24710 user's home directory if &%check_local_user%& is set.
24713 .section "Private options for pipe" "SECID142"
24714 .cindex "options" "&(pipe)& transport"
24718 .option allow_commands pipe "string list&!!" unset
24719 .cindex "&(pipe)& transport" "permitted commands"
24720 The string is expanded, and is then interpreted as a colon-separated list of
24721 permitted commands. If &%restrict_to_path%& is not set, the only commands
24722 permitted are those in the &%allow_commands%& list. They need not be absolute
24723 paths; the &%path%& option is still used for relative paths. If
24724 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
24725 in the &%allow_commands%& list, or a name without any slashes that is found on
24726 the path. In other words, if neither &%allow_commands%& nor
24727 &%restrict_to_path%& is set, there is no restriction on the command, but
24728 otherwise only commands that are permitted by one or the other are allowed. For
24731 allow_commands = /usr/bin/vacation
24733 and &%restrict_to_path%& is not set, the only permitted command is
24734 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
24735 &%use_shell%& is set.
24738 .option batch_id pipe string&!! unset
24739 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24742 .option batch_max pipe integer 1
24743 This limits the number of addresses that can be handled in a single delivery.
24744 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24747 .option check_string pipe string unset
24748 As &(pipe)& writes the message, the start of each line is tested for matching
24749 &%check_string%&, and if it does, the initial matching characters are replaced
24750 by the contents of &%escape_string%&, provided both are set. The value of
24751 &%check_string%& is a literal string, not a regular expression, and the case of
24752 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
24753 of &%check_string%& and &%escape_string%& are forced to values that implement
24754 the SMTP escaping protocol. Any settings made in the configuration file are
24758 .option command pipe string&!! unset
24759 This option need not be set when &(pipe)& is being used to deliver to pipes
24760 obtained directly from address redirections. In other cases, the option must be
24761 set, to provide a command to be run. It need not yield an absolute path (see
24762 the &%path%& option below). The command is split up into separate arguments by
24763 Exim, and each argument is separately expanded, as described in section
24764 &<<SECThowcommandrun>>& above.
24766 .cindex "tainted data"
24767 No part of the resulting command may be tainted.
24770 .option environment pipe string&!! unset
24771 .cindex "&(pipe)& transport" "environment for command"
24772 .cindex "environment" "&(pipe)& transport"
24773 This option is used to add additional variables to the environment in which the
24774 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
24775 a string which is expanded, and then interpreted as a colon-separated list of
24776 environment settings of the form <&'name'&>=<&'value'&>.
24779 .option escape_string pipe string unset
24780 See &%check_string%& above.
24783 .option freeze_exec_fail pipe boolean false
24784 .cindex "exec failure"
24785 .cindex "failure of exec"
24786 .cindex "&(pipe)& transport" "failure of exec"
24787 Failure to exec the command in a pipe transport is by default treated like
24788 any other failure while running the command. However, if &%freeze_exec_fail%&
24789 is set, failure to exec is treated specially, and causes the message to be
24790 frozen, whatever the setting of &%ignore_status%&.
24793 .option freeze_signal pipe boolean false
24794 .cindex "signal exit"
24795 .cindex "&(pipe)& transport", "signal exit"
24796 Normally if the process run by a command in a pipe transport exits on a signal,
24797 a bounce message is sent. If &%freeze_signal%& is set, the message will be
24798 frozen in Exim's queue instead.
24801 .option force_command pipe boolean false
24802 .cindex "force command"
24803 .cindex "&(pipe)& transport", "force command"
24804 Normally when a router redirects an address directly to a pipe command
24805 the &%command%& option on the transport is ignored. If &%force_command%&
24806 is set, the &%command%& option will used. This is especially
24807 useful for forcing a wrapper or additional argument to be added to the
24808 command. For example:
24810 command = /usr/bin/remote_exec myhost -- $address_pipe
24814 Note that &$address_pipe$& is handled specially in &%command%& when
24815 &%force_command%& is set, expanding out to the original argument vector as
24816 separate items, similarly to a Unix shell &`"$@"`& construct.
24819 .option ignore_status pipe boolean false
24820 If this option is true, the status returned by the subprocess that is set up to
24821 run the command is ignored, and Exim behaves as if zero had been returned.
24822 Otherwise, a non-zero status or termination by signal causes an error return
24823 from the transport unless the status value is one of those listed in
24824 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
24826 &*Note*&: This option does not apply to timeouts, which do not return a status.
24827 See the &%timeout_defer%& option for how timeouts are handled.
24830 .option log_defer_output pipe boolean false
24831 .cindex "&(pipe)& transport" "logging output"
24832 If this option is set, and the status returned by the command is
24833 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
24834 and any output was produced on stdout or stderr, the first line of it is
24835 written to the main log.
24838 .option log_fail_output pipe boolean false
24839 If this option is set, and the command returns any output on stdout or
24840 stderr, and also ends with a return code that is neither zero nor one of
24841 the return codes listed in &%temp_errors%& (that is, the delivery
24842 failed), the first line of output is written to the main log. This
24843 option and &%log_output%& are mutually exclusive. Only one of them may
24847 .option log_output pipe boolean false
24848 If this option is set and the command returns any output on stdout or
24849 stderr, the first line of output is written to the main log, whatever
24850 the return code. This option and &%log_fail_output%& are mutually
24851 exclusive. Only one of them may be set.
24854 .option max_output pipe integer 20K
24855 This specifies the maximum amount of output that the command may produce on its
24856 standard output and standard error file combined. If the limit is exceeded, the
24857 process running the command is killed. This is intended as a safety measure to
24858 catch runaway processes. The limit is applied independently of the settings of
24859 the options that control what is done with such output (for example,
24860 &%return_output%&). Because of buffering effects, the amount of output may
24861 exceed the limit by a small amount before Exim notices.
24864 .option message_prefix pipe string&!! "see below"
24865 The string specified here is expanded and output at the start of every message.
24866 The default is unset if &%use_bsmtp%& is set. Otherwise it is
24869 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
24873 .cindex "&%tmail%&"
24874 .cindex "&""From""& line"
24875 This is required by the commonly used &_/usr/bin/vacation_& program.
24876 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
24877 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
24882 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24883 &`\n`& to &`\r\n`& in &%message_prefix%&.
24886 .option message_suffix pipe string&!! "see below"
24887 The string specified here is expanded and output at the end of every message.
24888 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
24889 The suffix can be suppressed by setting
24893 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24894 &`\n`& to &`\r\n`& in &%message_suffix%&.
24897 .option path pipe string&!! "/bin:/usr/bin"
24898 This option is expanded and
24899 specifies the string that is set up in the PATH environment
24900 variable of the subprocess.
24901 If the &%command%& option does not yield an absolute path name, the command is
24902 sought in the PATH directories, in the usual way. &*Warning*&: This does not
24903 apply to a command specified as a transport filter.
24906 .option permit_coredump pipe boolean false
24907 Normally Exim inhibits core-dumps during delivery. If you have a need to get
24908 a core-dump of a pipe command, enable this command. This enables core-dumps
24909 during delivery and affects both the Exim binary and the pipe command run.
24910 It is recommended that this option remain off unless and until you have a need
24911 for it and that this only be enabled when needed, as the risk of excessive
24912 resource consumption can be quite high. Note also that Exim is typically
24913 installed as a setuid binary and most operating systems will inhibit coredumps
24914 of these by default, so further OS-specific action may be required.
24917 .option pipe_as_creator pipe boolean false
24918 .cindex "uid (user id)" "local delivery"
24919 If the generic &%user%& option is not set and this option is true, the delivery
24920 process is run under the uid that was in force when Exim was originally called
24921 to accept the message. If the group id is not otherwise set (via the generic
24922 &%group%& option), the gid that was in force when Exim was originally called to
24923 accept the message is used.
24926 .option restrict_to_path pipe boolean false
24927 When this option is set, any command name not listed in &%allow_commands%& must
24928 contain no slashes. The command is searched for only in the directories listed
24929 in the &%path%& option. This option is intended for use in the case when a pipe
24930 command has been generated from a user's &_.forward_& file. This is usually
24931 handled by a &(pipe)& transport called &%address_pipe%&.
24934 .option return_fail_output pipe boolean false
24935 If this option is true, and the command produced any output and ended with a
24936 return code other than zero or one of the codes listed in &%temp_errors%& (that
24937 is, the delivery failed), the output is returned in the bounce message.
24938 However, if the message has a null sender (that is, it is itself a bounce
24939 message), output from the command is discarded. This option and
24940 &%return_output%& are mutually exclusive. Only one of them may be set.
24944 .option return_output pipe boolean false
24945 If this option is true, and the command produced any output, the delivery is
24946 deemed to have failed whatever the return code from the command, and the output
24947 is returned in the bounce message. Otherwise, the output is just discarded.
24948 However, if the message has a null sender (that is, it is a bounce message),
24949 output from the command is always discarded, whatever the setting of this
24950 option. This option and &%return_fail_output%& are mutually exclusive. Only one
24951 of them may be set.
24955 .option temp_errors pipe "string list" "see below"
24956 .cindex "&(pipe)& transport" "temporary failure"
24957 This option contains either a colon-separated list of numbers, or a single
24958 asterisk. If &%ignore_status%& is false
24959 and &%return_output%& is not set,
24960 and the command exits with a non-zero return code, the failure is treated as
24961 temporary and the delivery is deferred if the return code matches one of the
24962 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
24963 codes are treated as permanent errors. The default setting contains the codes
24964 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
24965 compiled on a system that does not define these macros, it assumes values of 75
24966 and 73, respectively.
24969 .option timeout pipe time 1h
24970 If the command fails to complete within this time, it is killed. This normally
24971 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
24972 specifies no timeout. In order to ensure that any subprocesses created by the
24973 command are also killed, Exim makes the initial process a process group leader,
24974 and kills the whole process group on a timeout. However, this can be defeated
24975 if one of the processes starts a new process group.
24977 .option timeout_defer pipe boolean false
24978 A timeout in a &(pipe)& transport, either in the command that the transport
24979 runs, or in a transport filter that is associated with it, is by default
24980 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
24981 is set true, both kinds of timeout become temporary errors, causing the
24982 delivery to be deferred.
24984 .option umask pipe "octal integer" 022
24985 This specifies the umask setting for the subprocess that runs the command.
24988 .option use_bsmtp pipe boolean false
24989 .cindex "envelope sender"
24990 If this option is set true, the &(pipe)& transport writes messages in &"batch
24991 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
24992 commands. If you want to include a leading HELO command with such messages,
24993 you can do so by setting the &%message_prefix%& option. See section
24994 &<<SECTbatchSMTP>>& for details of batch SMTP.
24996 .option use_classresources pipe boolean false
24997 .cindex "class resources (BSD)"
24998 This option is available only when Exim is running on FreeBSD, NetBSD, or
24999 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
25000 resource limits when a &(pipe)& transport is run to perform a delivery. The
25001 limits for the uid under which the pipe is to run are obtained from the login
25005 .option use_crlf pipe boolean false
25006 .cindex "carriage return"
25008 This option causes lines to be terminated with the two-character CRLF sequence
25009 (carriage return, linefeed) instead of just a linefeed character. In the case
25010 of batched SMTP, the byte sequence written to the pipe is then an exact image
25011 of what would be sent down a real SMTP connection.
25013 The contents of the &%message_prefix%& and &%message_suffix%& options are
25014 written verbatim, so must contain their own carriage return characters if these
25015 are needed. When &%use_bsmtp%& is not set, the default values for both
25016 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
25017 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
25020 .option use_shell pipe boolean false
25021 .vindex "&$pipe_addresses$&"
25022 If this option is set, it causes the command to be passed to &_/bin/sh_&
25023 instead of being run directly from the transport, as described in section
25024 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
25025 where the command is expected to be run under a shell and cannot easily be
25026 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
25027 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
25028 command is expanded as a single string, and handed to &_/bin/sh_& as data for
25033 .section "Using an external local delivery agent" "SECID143"
25034 .cindex "local delivery" "using an external agent"
25035 .cindex "&'procmail'&"
25036 .cindex "external local delivery"
25037 .cindex "delivery" "&'procmail'&"
25038 .cindex "delivery" "by external agent"
25039 The &(pipe)& transport can be used to pass all messages that require local
25040 delivery to a separate local delivery agent such as &%procmail%&. When doing
25041 this, care must be taken to ensure that the pipe is run under an appropriate
25042 uid and gid. In some configurations one wants this to be a uid that is trusted
25043 by the delivery agent to supply the correct sender of the message. It may be
25044 necessary to recompile or reconfigure the delivery agent so that it trusts an
25045 appropriate user. The following is an example transport and router
25046 configuration for &%procmail%&:
25051 command = /usr/local/bin/procmail -d $local_part_data
25055 check_string = "From "
25056 escape_string = ">From "
25058 user = $local_part_data
25065 transport = procmail_pipe
25067 In this example, the pipe is run as the local user, but with the group set to
25068 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
25069 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
25070 user to supply a correct sender address. If you do not specify either a
25071 &%group%& or a &%user%& option, the pipe command is run as the local user. The
25072 home directory is the user's home directory by default.
25074 &*Note*&: The command that the pipe transport runs does &'not'& begin with
25078 as shown in some &%procmail%& documentation, because Exim does not by default
25079 use a shell to run pipe commands.
25082 The next example shows a transport and a router for a system where local
25083 deliveries are handled by the Cyrus IMAP server.
25084 . Used to have R: local_part_suffix = .* + T: -m $local_part_suffix_v
25085 . but that suffix is tainted so cannot be used in a command arg
25086 . Really, you'd want to use a lookup for acceptable suffixes to do real detainting
25089 local_delivery_cyrus:
25091 command = /usr/cyrus/bin/deliver \
25092 -- $local_part_data
25104 transport = local_delivery_cyrus
25106 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
25107 &%return_output%& to cause any text written by Cyrus to be returned to the
25109 .ecindex IIDpiptra1
25110 .ecindex IIDpiptra2
25113 . ////////////////////////////////////////////////////////////////////////////
25114 . ////////////////////////////////////////////////////////////////////////////
25116 .chapter "The smtp transport" "CHAPsmtptrans"
25117 .scindex IIDsmttra1 "transports" "&(smtp)&"
25118 .scindex IIDsmttra2 "&(smtp)& transport"
25119 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
25120 or LMTP protocol. The list of hosts to try can either be taken from the address
25121 that is being processed (having been set up by the router), or specified
25122 explicitly for the transport. Timeout and retry processing (see chapter
25123 &<<CHAPretry>>&) is applied to each IP address independently.
25126 .section "Multiple messages on a single connection" "SECID144"
25127 The sending of multiple messages over a single TCP/IP connection can arise in
25131 If a message contains more than &%max_rcpt%& (see below) addresses that are
25132 routed to the same host, more than one copy of the message has to be sent to
25133 that host. In this situation, multiple copies may be sent in a single run of
25134 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
25135 does when it has too many addresses to send in one message also depends on the
25136 value of the global &%remote_max_parallel%& option. Details are given in
25137 section &<<SECToutSMTPTCP>>&.)
25139 .cindex "hints database" "remembering routing"
25140 When a message has been successfully delivered over a TCP/IP connection, Exim
25141 looks in its hints database to see if there are any other messages awaiting a
25142 connection to the same host. If there are, a new delivery process is started
25143 for one of them, and the current TCP/IP connection is passed on to it. The new
25144 process may in turn send multiple copies and possibly create yet another
25149 For each copy sent over the same TCP/IP connection, a sequence counter is
25150 incremented, and if it ever gets to the value of &%connection_max_messages%&,
25151 no further messages are sent over that connection.
25155 .section "Use of the $host and $host_address variables" "SECID145"
25157 .vindex "&$host_address$&"
25158 At the start of a run of the &(smtp)& transport, the values of &$host$& and
25159 &$host_address$& are the name and IP address of the first host on the host list
25160 passed by the router. However, when the transport is about to connect to a
25161 specific host, and while it is connected to that host, &$host$& and
25162 &$host_address$& are set to the values for that host. These are the values
25163 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
25164 &%serialize_hosts%&, and the various TLS options are expanded.
25167 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
25168 .vindex &$tls_bits$&
25169 .vindex &$tls_cipher$&
25170 .vindex &$tls_peerdn$&
25171 .vindex &$tls_sni$&
25172 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
25173 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
25174 are the values that were set when the message was received.
25175 These are the values that are used for options that are expanded before any
25176 SMTP connections are made. Just before each connection is made, these four
25177 variables are emptied. If TLS is subsequently started, they are set to the
25178 appropriate values for the outgoing connection, and these are the values that
25179 are in force when any authenticators are run and when the
25180 &%authenticated_sender%& option is expanded.
25182 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
25183 and will be removed in a future release.
25186 .section "Private options for smtp" "SECID146"
25187 .cindex "options" "&(smtp)& transport"
25188 The private options of the &(smtp)& transport are as follows:
25191 .option address_retry_include_sender smtp boolean true
25192 .cindex "4&'xx'& responses" "retrying after"
25193 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
25194 is the combination of sender and recipient that is delayed in subsequent queue
25195 runs until the retry time is reached. You can delay the recipient without
25196 reference to the sender (which is what earlier versions of Exim did), by
25197 setting &%address_retry_include_sender%& false. However, this can lead to
25198 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
25200 .option allow_localhost smtp boolean false
25201 .cindex "local host" "sending to"
25202 .cindex "fallback" "hosts specified on transport"
25203 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
25204 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
25205 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
25206 the delivery anyway. This should be used only in special cases when the
25207 configuration ensures that no looping will result (for example, a differently
25208 configured Exim is listening on the port to which the message is sent).
25211 .option authenticated_sender smtp string&!! unset
25213 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
25214 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
25215 overriding any existing authenticated sender value. If the string expansion is
25216 forced to fail, the option is ignored. Other expansion failures cause delivery
25217 to be deferred. If the result of expansion is an empty string, that is also
25220 The expansion happens after the outgoing connection has been made and TLS
25221 started, if required. This means that the &$host$&, &$host_address$&,
25222 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
25223 particular connection.
25225 If the SMTP session is not authenticated, the expansion of
25226 &%authenticated_sender%& still happens (and can cause the delivery to be
25227 deferred if it fails), but no AUTH= item is added to MAIL commands
25228 unless &%authenticated_sender_force%& is true.
25230 This option allows you to use the &(smtp)& transport in LMTP mode to
25231 deliver mail to Cyrus IMAP and provide the proper local part as the
25232 &"authenticated sender"&, via a setting such as:
25234 authenticated_sender = $local_part
25236 This removes the need for IMAP subfolders to be assigned special ACLs to
25237 allow direct delivery to those subfolders.
25239 Because of expected uses such as that just described for Cyrus (when no
25240 domain is involved), there is no checking on the syntax of the provided
25244 .option authenticated_sender_force smtp boolean false
25245 If this option is set true, the &%authenticated_sender%& option's value
25246 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
25247 authenticated as a client.
25250 .option command_timeout smtp time 5m
25251 .cindex timeout "smtp transport command"
25252 This sets a timeout for receiving a response to an SMTP command that has been
25253 sent out. It is also used when waiting for the initial banner line from the
25254 remote host. Its value must not be zero.
25257 .option connect_timeout smtp time 5m
25258 .cindex timeout "smtp transport connect"
25259 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
25260 to a remote host. A setting of zero allows the system timeout (typically
25261 several minutes) to act. To have any effect, the value of this option must be
25262 less than the system timeout. However, it has been observed that on some
25263 systems there is no system timeout, which is why the default value for this
25264 option is 5 minutes, a value recommended by RFC 1123.
25267 .option connection_max_messages smtp integer 500
25268 .cindex "SMTP" "passed connection"
25269 .cindex "SMTP" "multiple deliveries"
25270 .cindex "multiple SMTP deliveries"
25271 This controls the maximum number of separate message deliveries that are sent
25272 over a single TCP/IP connection. If the value is zero, there is no limit.
25273 For testing purposes, this value can be overridden by the &%-oB%& command line
25277 .option dane_require_tls_ciphers smtp string&!! unset
25278 .cindex "TLS" "requiring specific ciphers for DANE"
25279 .cindex "cipher" "requiring specific"
25280 .cindex DANE "TLS ciphers"
25281 This option may be used to override &%tls_require_ciphers%& for connections
25282 where DANE has been determined to be in effect.
25283 If not set, then &%tls_require_ciphers%& will be used.
25284 Normal SMTP delivery is not able to make strong demands of TLS cipher
25285 configuration, because delivery will fall back to plaintext. Once DANE has
25286 been determined to be in effect, there is no plaintext fallback and making the
25287 TLS cipherlist configuration stronger will increase security, rather than
25288 counter-intuitively decreasing it.
25289 If the option expands to be empty or is forced to fail, then it will
25290 be treated as unset and &%tls_require_ciphers%& will be used instead.
25293 .option data_timeout smtp time 5m
25294 .cindex timeout "for transmitted SMTP data blocks"
25295 This sets a timeout for the transmission of each block in the data portion of
25296 the message. As a result, the overall timeout for a message depends on the size
25297 of the message. Its value must not be zero. See also &%final_timeout%&.
25300 .option dkim_canon smtp string&!! unset
25301 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25302 .option dkim_domain smtp "string list&!!" unset
25303 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25304 .option dkim_hash smtp string&!! sha256
25305 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25306 .option dkim_identity smtp string&!! unset
25307 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25308 .option dkim_private_key smtp string&!! unset
25309 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25310 .option dkim_selector smtp string&!! unset
25311 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25312 .option dkim_strict smtp string&!! unset
25313 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25314 .option dkim_sign_headers smtp string&!! "per RFC"
25315 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25316 .option dkim_timestamps smtp string&!! unset
25317 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25320 .option delay_after_cutoff smtp boolean true
25321 .cindex "final cutoff" "retries, controlling"
25322 .cindex retry "final cutoff"
25323 This option controls what happens when all remote IP addresses for a given
25324 domain have been inaccessible for so long that they have passed their retry
25327 In the default state, if the next retry time has not been reached for any of
25328 them, the address is bounced without trying any deliveries. In other words,
25329 Exim delays retrying an IP address after the final cutoff time until a new
25330 retry time is reached, and can therefore bounce an address without ever trying
25331 a delivery, when machines have been down for a long time. Some people are
25332 unhappy at this prospect, so...
25334 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25335 addresses are past their final cutoff time, Exim tries to deliver to those
25336 IP addresses that have not been tried since the message arrived. If there are
25337 none, of if they all fail, the address is bounced. In other words, it does not
25338 delay when a new message arrives, but immediately tries those expired IP
25339 addresses that haven't been tried since the message arrived. If there is a
25340 continuous stream of messages for the dead hosts, unsetting
25341 &%delay_after_cutoff%& means that there will be many more attempts to deliver
25345 .option dns_qualify_single smtp boolean true
25346 If the &%hosts%& or &%fallback_hosts%& option is being used,
25347 and the &%gethostbyname%& option is false,
25348 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
25349 in chapter &<<CHAPdnslookup>>& for more details.
25352 .option dns_search_parents smtp boolean false
25353 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
25354 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
25355 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
25359 .option dnssec_request_domains smtp "domain list&!!" *
25360 .cindex "MX record" "security"
25361 .cindex "DNSSEC" "MX lookup"
25362 .cindex "security" "MX lookup"
25363 .cindex "DNS" "DNSSEC"
25364 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
25365 the DNSSEC request bit set. Setting this transport option is only useful if the
25366 transport overrides or sets the host names. See the &%dnssec_request_domains%&
25371 .option dnssec_require_domains smtp "domain list&!!" unset
25372 .cindex "MX record" "security"
25373 .cindex "DNSSEC" "MX lookup"
25374 .cindex "security" "MX lookup"
25375 .cindex "DNS" "DNSSEC"
25376 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
25377 the DNSSEC request bit set. Setting this transport option is only
25378 useful if the transport overrides or sets the host names. See the
25379 &%dnssec_require_domains%& router option.
25383 .option dscp smtp string&!! unset
25384 .cindex "DCSP" "outbound"
25385 This option causes the DSCP value associated with a socket to be set to one
25386 of a number of fixed strings or to numeric value.
25387 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
25388 Common values include &`throughput`&, &`mincost`&, and on newer systems
25389 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
25391 The outbound packets from Exim will be marked with this value in the header
25392 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
25393 that these values will have any effect, not be stripped by networking
25394 equipment, or do much of anything without cooperation with your Network
25395 Engineer and those of all network operators between the source and destination.
25398 .option fallback_hosts smtp "string list" unset
25399 .cindex "fallback" "hosts specified on transport"
25400 String expansion is not applied to this option. The argument must be a
25401 colon-separated list of host names or IP addresses, optionally also including
25402 port numbers, though the separator can be changed, as described in section
25403 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25404 item in a &%route_list%& setting for the &(manualroute)& router, as described
25405 in section &<<SECTformatonehostitem>>&.
25407 Fallback hosts can also be specified on routers, which associate them with the
25408 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
25409 &%fallback_hosts%& specified on the transport is used only if the address does
25410 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
25411 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
25412 However, &%hosts_randomize%& does apply to fallback host lists.
25414 If Exim is unable to deliver to any of the hosts for a particular address, and
25415 the errors are not permanent rejections, the address is put on a separate
25416 transport queue with its host list replaced by the fallback hosts, unless the
25417 address was routed via MX records and the current host was in the original MX
25418 list. In that situation, the fallback host list is not used.
25420 Once normal deliveries are complete, the fallback queue is delivered by
25421 re-running the same transports with the new host lists. If several failing
25422 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
25423 copy of the message is sent.
25425 The resolution of the host names on the fallback list is controlled by the
25426 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
25427 both to cases when the host list comes with the address and when it is taken
25428 from &%hosts%&. This option provides a &"use a smart host only if delivery
25432 .option final_timeout smtp time 10m
25433 .cindex timeout "for transmitted SMTP data accept"
25434 This is the timeout that applies while waiting for the response to the final
25435 line containing just &"."& that terminates a message. Its value must not be
25438 .option gethostbyname smtp boolean false
25439 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
25440 being used, names are looked up using &[gethostbyname()]&
25441 (or &[getipnodebyname()]& when available)
25442 instead of using the DNS. Of course, that function may in fact use the DNS, but
25443 it may also consult other sources of information such as &_/etc/hosts_&.
25445 .option gnutls_compat_mode smtp boolean unset
25446 This option controls whether GnuTLS is used in compatibility mode in an Exim
25447 server. This reduces security slightly, but improves interworking with older
25448 implementations of TLS.
25450 .option helo_data smtp string&!! "see below"
25451 .cindex "HELO" "argument, setting"
25452 .cindex "EHLO" "argument, setting"
25453 .cindex "LHLO argument setting"
25454 The value of this option is expanded after a connection to a another host has
25455 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
25456 command that starts the outgoing SMTP or LMTP session. The default value of the
25461 During the expansion, the variables &$host$& and &$host_address$& are set to
25462 the identity of the remote host, and the variables &$sending_ip_address$& and
25463 &$sending_port$& are set to the local IP address and port number that are being
25464 used. These variables can be used to generate different values for different
25465 servers or different local IP addresses. For example, if you want the string
25466 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
25467 interface address, you could use this:
25469 helo_data = ${lookup dnsdb{ptr=$sending_ip_address} \
25470 {${listextract{1}{<\n $value}}} \
25471 {$primary_hostname}}
25473 The use of &%helo_data%& applies both to sending messages and when doing
25476 .option host_name_extract smtp "string list&!!" "see below"
25477 .cindex "load balancer" "hosts behind"
25478 .cindex TLS resumption
25479 Some mail-accepting sites
25480 (notably Microsoft)
25481 operate many servers behind a network load-balancer. When this is done,
25482 with separated TLS session caches, TLS session resuption becomes problematic.
25483 It will only succeed when the same server happens to be selected by the
25484 load-balancer, matching the session stored in the client's cache.
25486 Exim can pull out a server name, if there is one, from the response to the
25487 client's SMTP EHLO command.
25488 The default value of this option:
25490 ${if and { {match {$host} {.outlook.com\$}} \
25491 {match {$item} {\N^250-([\w.]+)\s\N}} \
25494 suffices for one known case.
25495 During the expansion of this option the &$item$& variable will have the
25496 server's EHLO response.
25497 The result of the option expansion is included in the key used to store and
25498 retrieve the TLS session, for session resumption.
25500 Operators of high-load sites may wish to evaluate their logs for indications
25501 of other destination sites operating load-balancers, and develop a suitable
25502 expression for this option.
25503 The smtp:ehlo event and the &$tls_out_resumption$& variable
25504 will be useful for such work.
25506 .option hosts smtp "string list&!!" unset
25507 Hosts are associated with an address by a router such as &(dnslookup)&, which
25508 finds the hosts by looking up the address domain in the DNS, or by
25509 &(manualroute)&, which has lists of hosts in its configuration. However,
25510 email addresses can be passed to the &(smtp)& transport by any router, and not
25511 all of them can provide an associated list of hosts.
25513 The &%hosts%& option specifies a list of hosts to be used if the address being
25514 processed does not have any hosts associated with it. The hosts specified by
25515 &%hosts%& are also used, whether or not the address has its own hosts, if
25516 &%hosts_override%& is set.
25518 The string is first expanded, before being interpreted as a colon-separated
25519 list of host names or IP addresses, possibly including port numbers. The
25520 separator may be changed to something other than colon, as described in section
25521 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25522 item in a &%route_list%& setting for the &(manualroute)& router, as described
25523 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
25524 of the &(manualroute)& router is not available here.
25526 If the expansion fails, delivery is deferred. Unless the failure was caused by
25527 the inability to complete a lookup, the error is logged to the panic log as
25528 well as the main log. Host names are looked up either by searching directly for
25529 address records in the DNS or by calling &[gethostbyname()]& (or
25530 &[getipnodebyname()]& when available), depending on the setting of the
25531 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
25532 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
25535 During delivery, the hosts are tried in order, subject to their retry status,
25536 unless &%hosts_randomize%& is set.
25539 .option hosts_avoid_esmtp smtp "host list&!!" unset
25540 .cindex "ESMTP, avoiding use of"
25541 .cindex "HELO" "forcing use of"
25542 .cindex "EHLO" "avoiding use of"
25543 .cindex "PIPELINING" "avoiding the use of"
25544 This option is for use with broken hosts that announce ESMTP facilities (for
25545 example, PIPELINING) and then fail to implement them properly. When a host
25546 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
25547 start of the SMTP session. This means that it cannot use any of the ESMTP
25548 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
25551 .option hosts_avoid_pipelining smtp "host list&!!" unset
25552 .cindex "PIPELINING" "avoiding the use of"
25553 .cindex "ESMTP extensions" PIPELINING
25554 Exim will not use the ESMTP PIPELINING extension when delivering to any host
25555 that matches this list, even if the server host advertises PIPELINING support.
25557 .option hosts_pipe_connect smtp "host list&!!" unset
25558 .cindex "pipelining" "early connection"
25559 .cindex "pipelining" PIPECONNECT
25560 If Exim is built with the SUPPORT_PIPE_CONNECT build option
25561 this option controls which to hosts the facility watched for
25562 and recorded, and used for subsequent connections.
25564 The retry hints database is used for the record,
25565 and records are subject to the &%retry_data_expire%& option.
25566 When used, the pipelining saves on roundtrip times.
25567 It also turns SMTP into a client-first protocol
25568 so combines well with TCP Fast Open.
25570 See also the &%pipelining_connect_advertise_hosts%& main option.
25573 When the facility is used, if the transport &%interface%& option is unset
25574 the &%helo_data%& option
25575 will be expanded before the &$sending_ip_address$& variable
25577 A check is made for the use of that variable, without the
25578 presence of a &"def:"& test on it, but suitably complex coding
25579 can avoid the check and produce unexpected results.
25580 You have been warned.
25583 .option hosts_avoid_tls smtp "host list&!!" unset
25584 .cindex "TLS" "avoiding for certain hosts"
25585 Exim will not try to start a TLS session when delivering to any host that
25586 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25588 .option hosts_verify_avoid_tls smtp "host list&!!" unset
25589 .cindex "TLS" "avoiding for certain hosts"
25590 Exim will not try to start a TLS session for a verify callout,
25591 or when delivering in cutthrough mode,
25592 to any host that matches this list.
25595 .option hosts_max_try smtp integer 5
25596 .cindex "host" "maximum number to try"
25597 .cindex "limit" "number of hosts tried"
25598 .cindex "limit" "number of MX tried"
25599 .cindex "MX record" "maximum tried"
25600 This option limits the number of IP addresses that are tried for any one
25601 delivery in cases where there are temporary delivery errors. Section
25602 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
25605 .option hosts_max_try_hardlimit smtp integer 50
25606 This is an additional check on the maximum number of IP addresses that Exim
25607 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
25612 .option hosts_nopass_tls smtp "host list&!!" unset
25613 .cindex "TLS" "passing connection"
25614 .cindex "multiple SMTP deliveries"
25615 .cindex "TLS" "multiple message deliveries"
25616 For any host that matches this list, a connection on which a TLS session has
25617 been started will not be passed to a new delivery process for sending another
25618 message on the same connection. See section &<<SECTmulmessam>>& for an
25619 explanation of when this might be needed.
25621 .option hosts_noproxy_tls smtp "host list&!!" unset
25622 .cindex "TLS" "passing connection"
25623 .cindex "multiple SMTP deliveries"
25624 .cindex "TLS" "multiple message deliveries"
25625 For any host that matches this list, a TLS session which has
25626 been started will not be passed to a new delivery process for sending another
25627 message on the same session.
25629 The traditional implementation closes down TLS and re-starts it in the new
25630 process, on the same open TCP connection, for each successive message
25631 sent. If permitted by this option a pipe to to the new process is set up
25632 instead, and the original process maintains the TLS connection and proxies
25633 the SMTP connection from and to the new process and any subsequents.
25634 The new process has no access to TLS information, so cannot include it in
25639 .option hosts_override smtp boolean false
25640 If this option is set and the &%hosts%& option is also set, any hosts that are
25641 attached to the address are ignored, and instead the hosts specified by the
25642 &%hosts%& option are always used. This option does not apply to
25643 &%fallback_hosts%&.
25646 .option hosts_randomize smtp boolean false
25647 .cindex "randomized host list"
25648 .cindex "host" "list of; randomized"
25649 .cindex "fallback" "randomized hosts"
25650 If this option is set, and either the list of hosts is taken from the
25651 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
25652 were not obtained from MX records (this includes fallback hosts from the
25653 router), and were not randomized by the router, the order of trying the hosts
25654 is randomized each time the transport runs. Randomizing the order of a host
25655 list can be used to do crude load sharing.
25657 When &%hosts_randomize%& is true, a host list may be split into groups whose
25658 order is separately randomized. This makes it possible to set up MX-like
25659 behaviour. The boundaries between groups are indicated by an item that is just
25660 &`+`& in the host list. For example:
25662 hosts = host1:host2:host3:+:host4:host5
25664 The order of the first three hosts and the order of the last two hosts is
25665 randomized for each use, but the first three always end up before the last two.
25666 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
25668 .option hosts_require_auth smtp "host list&!!" unset
25669 .cindex "authentication" "required by client"
25670 This option provides a list of servers for which authentication must succeed
25671 before Exim will try to transfer a message. If authentication fails for
25672 servers which are not in this list, Exim tries to send unauthenticated. If
25673 authentication fails for one of these servers, delivery is deferred. This
25674 temporary error is detectable in the retry rules, so it can be turned into a
25675 hard failure if required. See also &%hosts_try_auth%&, and chapter
25676 &<<CHAPSMTPAUTH>>& for details of authentication.
25679 .option hosts_request_ocsp smtp "host list&!!" "see below"
25680 .cindex "TLS" "requiring for certain servers"
25681 Exim will request a Certificate Status on a
25682 TLS session for any host that matches this list.
25683 &%tls_verify_certificates%& should also be set for the transport.
25686 The default is &"**"& if DANE is not in use for the connection,
25687 or if DANE-TA us used.
25688 It is empty if DANE-EE is used.
25691 .option hosts_require_alpn smtp "host list&!!" unset
25692 .cindex ALPN "require negotiation in client"
25694 .cindex TLS "Application Layer Protocol Names"
25695 If the TLS library supports ALPN
25696 then a successful negotiation of ALPN will be required for any host
25697 matching the list, for TLS to be used.
25698 See also the &%tls_alpn%& option.
25700 &*Note*&: prevention of fallback to in-clear connection is not
25701 managed by this option; see &%hosts_require_tls%&.
25703 .option hosts_require_dane smtp "host list&!!" unset
25704 .cindex DANE "transport options"
25705 .cindex DANE "requiring for certain servers"
25706 If built with DANE support, Exim will require that a DNSSEC-validated
25707 TLSA record is present for any host matching the list,
25708 and that a DANE-verified TLS connection is made.
25709 There will be no fallback to in-clear communication.
25710 See the &%dnssec_request_domains%& router and transport options.
25711 See section &<<SECDANE>>&.
25713 .option hosts_require_ocsp smtp "host list&!!" unset
25714 .cindex "TLS" "requiring for certain servers"
25715 Exim will request, and check for a valid Certificate Status being given, on a
25716 TLS session for any host that matches this list.
25717 &%tls_verify_certificates%& should also be set for the transport.
25719 .option hosts_require_tls smtp "host list&!!" unset
25720 .cindex "TLS" "requiring for certain servers"
25721 Exim will insist on using a TLS session when delivering to any host that
25722 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25723 &*Note*&: This option affects outgoing mail only. To insist on TLS for
25724 incoming messages, use an appropriate ACL.
25726 .option hosts_try_auth smtp "host list&!!" unset
25727 .cindex "authentication" "optional in client"
25728 This option provides a list of servers to which, provided they announce
25729 authentication support, Exim will attempt to authenticate as a client when it
25730 connects. If authentication fails
25731 and &%hosts_require_auth%& permits,
25732 Exim will try to transfer the message unauthenticated.
25733 See also chapter &<<CHAPSMTPAUTH>>& for details of authentication.
25735 .option hosts_try_chunking smtp "host list&!!" *
25736 .cindex CHUNKING "enabling, in client"
25737 .cindex BDAT "SMTP command"
25738 .cindex "RFC 3030" "CHUNKING"
25739 This option provides a list of servers to which, provided they announce
25740 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
25741 Unless DKIM signing is being done,
25742 BDAT will not be used in conjunction with a transport filter.
25744 .option hosts_try_dane smtp "host list&!!" *
25745 .cindex DANE "transport options"
25746 .cindex DANE "attempting for certain servers"
25747 If built with DANE support, Exim will look up a
25748 TLSA record for any host matching the list,
25749 If one is found and that lookup was DNSSEC-validated,
25750 then Exim requires that a DANE-verified TLS connection is made for that host;
25751 there will be no fallback to in-clear communication.
25752 See the &%dnssec_request_domains%& router and transport options.
25753 See section &<<SECDANE>>&.
25755 .option hosts_try_fastopen smtp "host list&!!" *
25756 .cindex "fast open, TCP" "enabling, in client"
25757 .cindex "TCP Fast Open" "enabling, in client"
25758 .cindex "RFC 7413" "TCP Fast Open"
25759 This option provides a list of servers to which, provided
25760 the facility is supported by this system, Exim will attempt to
25761 perform a TCP Fast Open.
25762 No data is sent on the SYN segment but, if the remote server also
25763 supports the facility, it can send its SMTP banner immediately after
25764 the SYN,ACK segment. This can save up to one round-trip time.
25766 The facility is only active for previously-contacted servers,
25767 as the initiator must present a cookie in the SYN segment.
25769 On (at least some) current Linux distributions the facility must be enabled
25770 in the kernel by the sysadmin before the support is usable.
25771 There is no option for control of the server side; if the system supports
25772 it it is always enabled. Note that lengthy operations in the connect ACL,
25773 such as DNSBL lookups, will still delay the emission of the SMTP banner.
25775 .option hosts_try_prdr smtp "host list&!!" *
25776 .cindex "PRDR" "enabling, optional in client"
25777 .cindex "ESMTP extensions" PRDR
25778 This option provides a list of servers to which, provided they announce
25779 PRDR support, Exim will attempt to negotiate PRDR
25780 for multi-recipient messages.
25781 The option can usually be left as default.
25783 .option interface smtp "string list&!!" unset
25784 .cindex "bind IP address"
25785 .cindex "IP address" "binding"
25787 .vindex "&$host_address$&"
25788 This option specifies which interface to bind to when making an outgoing SMTP
25789 call. The value is an IP address, not an interface name such as
25790 &`eth0`&. Do not confuse this with the interface address that was used when a
25791 message was received, which is in &$received_ip_address$&, formerly known as
25792 &$interface_address$&. The name was changed to minimize confusion with the
25793 outgoing interface address. There is no variable that contains an outgoing
25794 interface address because, unless it is set by this option, its value is
25797 During the expansion of the &%interface%& option the variables &$host$& and
25798 &$host_address$& refer to the host to which a connection is about to be made
25799 during the expansion of the string. Forced expansion failure, or an empty
25800 string result causes the option to be ignored. Otherwise, after expansion, the
25801 string must be a list of IP addresses, colon-separated by default, but the
25802 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
25805 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
25807 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
25808 connection. If none of them are the correct type, the option is ignored. If
25809 &%interface%& is not set, or is ignored, the system's IP functions choose which
25810 interface to use if the host has more than one.
25813 .option keepalive smtp boolean true
25814 .cindex "keepalive" "on outgoing connection"
25815 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
25816 connections. When set, it causes the kernel to probe idle connections
25817 periodically, by sending packets with &"old"& sequence numbers. The other end
25818 of the connection should send a acknowledgment if the connection is still okay
25819 or a reset if the connection has been aborted. The reason for doing this is
25820 that it has the beneficial effect of freeing up certain types of connection
25821 that can get stuck when the remote host is disconnected without tidying up the
25822 TCP/IP call properly. The keepalive mechanism takes several hours to detect
25826 .option lmtp_ignore_quota smtp boolean false
25827 .cindex "LMTP" "ignoring quota errors"
25828 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
25829 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
25830 has advertised support for IGNOREQUOTA in its response to the LHLO command.
25832 .option max_rcpt smtp integer&!! 100
25833 .cindex "RCPT" "maximum number of outgoing"
25838 limits the number of RCPT commands that are sent in a single
25839 SMTP message transaction.
25840 A value setting of zero disables the limit.
25843 If a constant is given,
25845 each set of addresses is treated independently, and
25846 so can cause parallel connections to the same host if &%remote_max_parallel%&
25850 .option message_linelength_limit smtp integer 998
25851 .cindex "line length" limit
25852 This option sets the maximum line length, in bytes, that the transport
25853 will send. Any messages with lines exceeding the given value
25854 will fail and a failure-DSN ("bounce") message will if possible be returned
25856 The default value is that defined by the SMTP standards.
25858 It is generally wise to also check in the data ACL so that messages
25859 received via SMTP can be refused without producing a bounce.
25862 .option multi_domain smtp boolean&!! true
25863 .vindex "&$domain$&"
25864 When this option is set, the &(smtp)& transport can handle a number of
25865 addresses containing a mixture of different domains provided they all resolve
25866 to the same list of hosts. Turning the option off restricts the transport to
25867 handling only one domain at a time. This is useful if you want to use
25868 &$domain$& in an expansion for the transport, because it is set only when there
25869 is a single domain involved in a remote delivery.
25871 It is expanded per-address and can depend on any of
25872 &$address_data$&, &$domain_data$&, &$local_part_data$&,
25873 &$host$&, &$host_address$& and &$host_port$&.
25875 If the connection is DANE-enabled then this option is ignored;
25876 only messages having the domain used for the DANE TLSA lookup are
25877 sent on the connection.
25879 .option port smtp string&!! "see below"
25880 .cindex "port" "sending TCP/IP"
25881 .cindex "TCP/IP" "setting outgoing port"
25882 This option specifies the TCP/IP port on the server to which Exim connects.
25883 &*Note:*& Do not confuse this with the port that was used when a message was
25884 received, which is in &$received_port$&, formerly known as &$interface_port$&.
25885 The name was changed to minimize confusion with the outgoing port. There is no
25886 variable that contains an outgoing port.
25888 If the value of this option begins with a digit it is taken as a port number;
25889 otherwise it is looked up using &[getservbyname()]&. The default value is
25891 but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"&
25892 and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
25893 If the expansion fails, or if a port number cannot be found, delivery
25896 Note that at least one Linux distribution has been seen failing
25897 to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
25901 .option protocol smtp string smtp
25902 .cindex "LMTP" "over TCP/IP"
25903 .cindex "ssmtp protocol" "outbound"
25904 .cindex "TLS" "SSL-on-connect outbound"
25906 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
25907 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
25908 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
25909 deliveries into closed message stores. Exim also has support for running LMTP
25910 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
25912 If this option is set to &"smtps"&, the default value for the &%port%& option
25913 changes to &"smtps"&, and the transport initiates TLS immediately after
25914 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
25915 The Internet standards bodies used to strongly discourage use of this mode,
25916 but as of RFC 8314 it is preferred over STARTTLS for message submission
25917 (as distinct from MTA-MTA communication).
25920 .option retry_include_ip_address smtp boolean&!! true
25921 Exim normally includes both the host name and the IP address in the key it
25922 constructs for indexing retry data after a temporary delivery failure. This
25923 means that when one of several IP addresses for a host is failing, it gets
25924 tried periodically (controlled by the retry rules), but use of the other IP
25925 addresses is not affected.
25927 However, in some dialup environments hosts are assigned a different IP address
25928 each time they connect. In this situation the use of the IP address as part of
25929 the retry key leads to undesirable behaviour. Setting this option false causes
25930 Exim to use only the host name.
25931 Since it is expanded it can be made to depend on the host or domain.
25934 .option serialize_hosts smtp "host list&!!" unset
25935 .cindex "serializing connections"
25936 .cindex "host" "serializing connections"
25937 Because Exim operates in a distributed manner, if several messages for the same
25938 host arrive at around the same time, more than one simultaneous connection to
25939 the remote host can occur. This is not usually a problem except when there is a
25940 slow link between the hosts. In that situation it may be helpful to restrict
25941 Exim to one connection at a time. This can be done by setting
25942 &%serialize_hosts%& to match the relevant hosts.
25944 .cindex "hints database" "serializing deliveries to a host"
25945 Exim implements serialization by means of a hints database in which a record is
25946 written whenever a process connects to one of the restricted hosts. The record
25947 is deleted when the connection is completed. Obviously there is scope for
25948 records to get left lying around if there is a system or program crash. To
25949 guard against this, Exim ignores any records that are more than six hours old.
25951 If you set up this kind of serialization, you should also arrange to delete the
25952 relevant hints database whenever your system reboots. The names of the files
25953 start with &_misc_& and they are kept in the &_spool/db_& directory. There
25954 may be one or two files, depending on the type of DBM in use. The same files
25955 are used for ETRN serialization.
25957 See also the &%max_parallel%& generic transport option.
25960 .option size_addition smtp integer 1024
25961 .cindex "SIZE" "ESMTP extension"
25962 .cindex "message" "size issue for transport filter"
25963 .cindex "size" "of message"
25964 .cindex "transport" "filter"
25965 .cindex "filter" "transport filter"
25966 If a remote SMTP server indicates that it supports the SIZE option of the
25967 MAIL command, Exim uses this to pass over the message size at the start of
25968 an SMTP transaction. It adds the value of &%size_addition%& to the value it
25969 sends, to allow for headers and other text that may be added during delivery by
25970 configuration options or in a transport filter. It may be necessary to increase
25971 this if a lot of text is added to messages.
25973 Alternatively, if the value of &%size_addition%& is set negative, it disables
25974 the use of the SIZE option altogether.
25977 .option socks_proxy smtp string&!! unset
25978 .cindex proxy SOCKS
25979 This option enables use of SOCKS proxies for connections made by the
25980 transport. For details see section &<<SECTproxySOCKS>>&.
25983 .option tls_alpn smtp string&!! unset
25984 .cindex TLS "Application Layer Protocol Names"
25986 .cindex ALPN "set name in client"
25987 If this option is set
25988 and the TLS library supports ALPN,
25989 the value given is used.
25991 As of writing no value has been standardised for email use.
25992 The authors suggest using &"smtp"&.
25996 .option tls_certificate smtp string&!! unset
25997 .cindex "TLS" "client certificate, location of"
25998 .cindex "certificate" "client, location of"
26000 .vindex "&$host_address$&"
26001 The value of this option must be the absolute path to a file which contains the
26002 client's certificate, for possible use when sending a message over an encrypted
26003 connection. The values of &$host$& and &$host_address$& are set to the name and
26004 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
26007 &*Note*&: This option must be set if you want Exim to be able to use a TLS
26008 certificate when sending messages as a client. The global option of the same
26009 name specifies the certificate for Exim as a server; it is not automatically
26010 assumed that the same certificate should be used when Exim is operating as a
26014 .option tls_crl smtp string&!! unset
26015 .cindex "TLS" "client certificate revocation list"
26016 .cindex "certificate" "revocation list for client"
26017 This option specifies a certificate revocation list. The expanded value must
26018 be the name of a file that contains a CRL in PEM format.
26021 .option tls_dh_min_bits smtp integer 1024
26022 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
26023 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
26024 key agreement is negotiated, the server will provide a large prime number
26025 for use. This option establishes the minimum acceptable size of that number.
26026 If the parameter offered by the server is too small, then the TLS handshake
26029 Only supported when using GnuTLS.
26032 .option tls_privatekey smtp string&!! unset
26033 .cindex "TLS" "client private key, location of"
26035 .vindex "&$host_address$&"
26036 The value of this option must be the absolute path to a file which contains the
26037 client's private key. This is used when sending a message over an encrypted
26038 connection using a client certificate. The values of &$host$& and
26039 &$host_address$& are set to the name and address of the server during the
26040 expansion. If this option is unset, or the expansion is forced to fail, or the
26041 result is an empty string, the private key is assumed to be in the same file as
26042 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
26045 .option tls_require_ciphers smtp string&!! unset
26046 .cindex "TLS" "requiring specific ciphers"
26047 .cindex "cipher" "requiring specific"
26049 .vindex "&$host_address$&"
26050 The value of this option must be a list of permitted cipher suites, for use
26051 when setting up an outgoing encrypted connection. (There is a global option of
26052 the same name for controlling incoming connections.) The values of &$host$& and
26053 &$host_address$& are set to the name and address of the server during the
26054 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
26055 is used in different ways by OpenSSL and GnuTLS (see sections
26056 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
26057 ciphers is a preference order.
26060 .option tls_resumption_hosts smtp "host list&!!" unset
26061 .cindex TLS resumption
26062 This option controls which connections to use the TLS resumption feature.
26063 See &<<SECTresumption>>& for details.
26067 .option tls_sni smtp string&!! unset
26068 .cindex "TLS" "Server Name Indication"
26070 .cindex SNI "setting in client"
26071 .vindex "&$tls_sni$&"
26072 If this option is set
26073 and the connection is not DANE-validated
26074 then it sets the $tls_out_sni variable and causes any
26075 TLS session to pass this value as the Server Name Indication extension to
26076 the remote side, which can be used by the remote side to select an appropriate
26077 certificate and private key for the session.
26079 See &<<SECTtlssni>>& for more information.
26081 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
26087 .option tls_tempfail_tryclear smtp boolean true
26088 .cindex "4&'xx'& responses" "to STARTTLS"
26089 When the server host is not in &%hosts_require_tls%&, and there is a problem in
26090 setting up a TLS session, this option determines whether or not Exim should try
26091 to deliver the message unencrypted. If it is set false, delivery to the
26092 current host is deferred; if there are other hosts, they are tried. If this
26093 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
26094 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
26095 TLS negotiation fails, Exim closes the current connection (because it is in an
26096 unknown state), opens a new one to the same host, and then tries the delivery
26100 .option tls_try_verify_hosts smtp "host list&!!" *
26101 .cindex "TLS" "server certificate verification"
26102 .cindex "certificate" "verification of server"
26103 This option gives a list of hosts for which, on encrypted connections,
26104 certificate verification will be tried but need not succeed.
26105 The &%tls_verify_certificates%& option must also be set.
26106 Note that unless the host is in this list
26107 TLS connections will be denied to hosts using self-signed certificates
26108 when &%tls_verify_certificates%& is matched.
26109 The &$tls_out_certificate_verified$& variable is set when
26110 certificate verification succeeds.
26113 .option tls_verify_cert_hostnames smtp "host list&!!" *
26114 .cindex "TLS" "server certificate hostname verification"
26115 .cindex "certificate" "verification of server"
26116 This option give a list of hosts for which,
26117 while verifying the server certificate,
26118 checks will be included on the host name
26119 (note that this will generally be the result of a DNS MX lookup)
26120 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
26121 limited to being the initial component of a 3-or-more component FQDN.
26123 There is no equivalent checking on client certificates.
26126 .option tls_verify_certificates smtp string&!! system
26127 .cindex "TLS" "server certificate verification"
26128 .cindex "certificate" "verification of server"
26130 .vindex "&$host_address$&"
26131 The value of this option must be either the
26133 or the absolute path to
26134 a file or directory containing permitted certificates for servers,
26135 for use when setting up an encrypted connection.
26137 The "system" value for the option will use a location compiled into the SSL library.
26138 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
26139 is taken as empty and an explicit location
26142 The use of a directory for the option value is not available for GnuTLS versions
26143 preceding 3.3.6 and a single file must be used.
26145 With OpenSSL the certificates specified
26147 either by file or directory
26148 are added to those given by the system default location.
26150 The values of &$host$& and
26151 &$host_address$& are set to the name and address of the server during the
26152 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
26154 For back-compatibility,
26155 if neither tls_verify_hosts nor tls_try_verify_hosts are set
26156 (a single-colon empty list counts as being set)
26157 and certificate verification fails the TLS connection is closed.
26160 .option tls_verify_hosts smtp "host list&!!" unset
26161 .cindex "TLS" "server certificate verification"
26162 .cindex "certificate" "verification of server"
26163 This option gives a list of hosts for which, on encrypted connections,
26164 certificate verification must succeed.
26165 The &%tls_verify_certificates%& option must also be set.
26166 If both this option and &%tls_try_verify_hosts%& are unset
26167 operation is as if this option selected all hosts.
26168 &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
26169 that connections use TLS.
26170 Fallback to in-clear communication will be done unless restricted by
26171 the &%hosts_require_tls%& option.
26173 .option utf8_downconvert smtp integer&!! -1
26174 .cindex utf8 "address downconversion"
26175 .cindex i18n "utf8 address downconversion"
26176 If built with internationalization support,
26177 this option controls conversion of UTF-8 in message envelope addresses
26179 If, after expansion, the value is 1, 0, or -1 then this value overrides
26180 any value previously set for the message. Otherwise, any previously
26181 set value is used. To permit use of a previous value,
26182 set this option to an empty string.
26183 For details on the values see section &<<SECTi18nMTA>>&.
26188 .section "How the limits for the number of hosts to try are used" &&&
26190 .cindex "host" "maximum number to try"
26191 .cindex "limit" "hosts; maximum number tried"
26192 There are two options that are concerned with the number of hosts that are
26193 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
26194 &%hosts_max_try_hardlimit%&.
26197 The &%hosts_max_try%& option limits the number of hosts that are tried
26198 for a single delivery. However, despite the term &"host"& in its name, the
26199 option actually applies to each IP address independently. In other words, a
26200 multihomed host is treated as several independent hosts, just as it is for
26203 Many of the larger ISPs have multiple MX records which often point to
26204 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
26205 created as a result of routing one of these domains.
26207 Trying every single IP address on such a long list does not seem sensible; if
26208 several at the top of the list fail, it is reasonable to assume there is some
26209 problem that is likely to affect all of them. Roughly speaking, the value of
26210 &%hosts_max_try%& is the maximum number that are tried before deferring the
26211 delivery. However, the logic cannot be quite that simple.
26213 Firstly, IP addresses that are skipped because their retry times have not
26214 arrived do not count, and in addition, addresses that are past their retry
26215 limits are also not counted, even when they are tried. This means that when
26216 some IP addresses are past their retry limits, more than the value of
26217 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
26218 that all IP addresses are considered before timing out an email address (but
26219 see below for an exception).
26221 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
26222 list to see if there is a subsequent host with a different (higher valued) MX.
26223 If there is, that host is considered next, and the current IP address is used
26224 but not counted. This behaviour helps in the case of a domain with a retry rule
26225 that hardly ever delays any hosts, as is now explained:
26227 Consider the case of a long list of hosts with one MX value, and a few with a
26228 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
26229 hosts at the top of the list are tried at first. With the default retry rule,
26230 which specifies increasing retry times, the higher MX hosts are eventually
26231 tried when those at the top of the list are skipped because they have not
26232 reached their retry times.
26234 However, it is common practice to put a fixed short retry time on domains for
26235 large ISPs, on the grounds that their servers are rarely down for very long.
26236 Unfortunately, these are exactly the domains that tend to resolve to long lists
26237 of hosts. The short retry time means that the lowest MX hosts are tried every
26238 time. The attempts may be in a different order because of random sorting, but
26239 without the special MX check, the higher MX hosts would never be tried until
26240 all the lower MX hosts had timed out (which might be several days), because
26241 there are always some lower MX hosts that have reached their retry times. With
26242 the special check, Exim considers at least one IP address from each MX value at
26243 every delivery attempt, even if the &%hosts_max_try%& limit has already been
26246 The above logic means that &%hosts_max_try%& is not a hard limit, and in
26247 particular, Exim normally eventually tries all the IP addresses before timing
26248 out an email address. When &%hosts_max_try%& was implemented, this seemed a
26249 reasonable thing to do. Recently, however, some lunatic DNS configurations have
26250 been set up with hundreds of IP addresses for some domains. It can
26251 take a very long time indeed for an address to time out in these cases.
26253 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
26254 Exim never tries more than this number of IP addresses; if it hits this limit
26255 and they are all timed out, the email address is bounced, even though not all
26256 possible IP addresses have been tried.
26257 .ecindex IIDsmttra1
26258 .ecindex IIDsmttra2
26264 . ////////////////////////////////////////////////////////////////////////////
26265 . ////////////////////////////////////////////////////////////////////////////
26267 .chapter "Address rewriting" "CHAPrewrite"
26268 .scindex IIDaddrew "rewriting" "addresses"
26269 There are some circumstances in which Exim automatically rewrites domains in
26270 addresses. The two most common are when an address is given without a domain
26271 (referred to as an &"unqualified address"&) or when an address contains an
26272 abbreviated domain that is expanded by DNS lookup.
26274 Unqualified envelope addresses are accepted only for locally submitted
26275 messages, or for messages that are received from hosts matching
26276 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
26277 appropriate. Unqualified addresses in header lines are qualified if they are in
26278 locally submitted messages, or messages from hosts that are permitted to send
26279 unqualified envelope addresses. Otherwise, unqualified addresses in header
26280 lines are neither qualified nor rewritten.
26282 One situation in which Exim does &'not'& automatically rewrite a domain is
26283 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
26284 such a domain should be rewritten using the &"canonical"& name, and some MTAs
26285 do this. The new RFCs do not contain this suggestion.
26288 .section "Explicitly configured address rewriting" "SECID147"
26289 This chapter describes the rewriting rules that can be used in the
26290 main rewrite section of the configuration file, and also in the generic
26291 &%headers_rewrite%& option that can be set on any transport.
26293 Some people believe that configured address rewriting is a Mortal Sin.
26294 Others believe that life is not possible without it. Exim provides the
26295 facility; you do not have to use it.
26297 The main rewriting rules that appear in the &"rewrite"& section of the
26298 configuration file are applied to addresses in incoming messages, both envelope
26299 addresses and addresses in header lines. Each rule specifies the types of
26300 address to which it applies.
26302 Whether or not addresses in header lines are rewritten depends on the origin of
26303 the headers and the type of rewriting. Global rewriting, that is, rewriting
26304 rules from the rewrite section of the configuration file, is applied only to
26305 those headers that were received with the message. Header lines that are added
26306 by ACLs or by a system filter or by individual routers or transports (which
26307 are specific to individual recipient addresses) are not rewritten by the global
26310 Rewriting at transport time, by means of the &%headers_rewrite%& option,
26311 applies all headers except those added by routers and transports. That is, as
26312 well as the headers that were received with the message, it also applies to
26313 headers that were added by an ACL or a system filter.
26316 In general, rewriting addresses from your own system or domain has some
26317 legitimacy. Rewriting other addresses should be done only with great care and
26318 in special circumstances. The author of Exim believes that rewriting should be
26319 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
26320 Although it can sometimes be used as a routing tool, this is very strongly
26323 There are two commonly encountered circumstances where rewriting is used, as
26324 illustrated by these examples:
26327 The company whose domain is &'hitch.fict.example'& has a number of hosts that
26328 exchange mail with each other behind a firewall, but there is only a single
26329 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
26330 &'hitch.fict.example'& when sending mail off-site.
26332 A host rewrites the local parts of its own users so that, for example,
26333 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
26338 .section "When does rewriting happen?" "SECID148"
26339 .cindex "rewriting" "timing of"
26340 .cindex "&ACL;" "rewriting addresses in"
26341 Configured address rewriting can take place at several different stages of a
26342 message's processing.
26344 .vindex "&$sender_address$&"
26345 At the start of an ACL for MAIL, the sender address may have been rewritten
26346 by a special SMTP-time rewrite rule (see section &<<SSECTrewriteS>>&), but no
26347 ordinary rewrite rules have yet been applied. If, however, the sender address
26348 is verified in the ACL, it is rewritten before verification, and remains
26349 rewritten thereafter. The subsequent value of &$sender_address$& is the
26350 rewritten address. This also applies if sender verification happens in a
26351 RCPT ACL. Otherwise, when the sender address is not verified, it is
26352 rewritten as soon as a message's header lines have been received.
26354 .vindex "&$domain$&"
26355 .vindex "&$local_part$&"
26356 Similarly, at the start of an ACL for RCPT, the current recipient's address
26357 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
26358 rewrite rules have yet been applied to it. However, the behaviour is different
26359 from the sender address when a recipient is verified. The address is rewritten
26360 for the verification, but the rewriting is not remembered at this stage. The
26361 value of &$local_part$& and &$domain$& after verification are always the same
26362 as they were before (that is, they contain the unrewritten &-- except for
26363 SMTP-time rewriting &-- address).
26365 As soon as a message's header lines have been received, all the envelope
26366 recipient addresses are permanently rewritten, and rewriting is also applied to
26367 the addresses in the header lines (if configured). This happens before adding
26368 any header lines that were specified in MAIL or RCPT ACLs, and
26369 .cindex "&[local_scan()]& function" "address rewriting; timing of"
26370 before the DATA ACL and &[local_scan()]& functions are run.
26372 When an address is being routed, either for delivery or for verification,
26373 rewriting is applied immediately to child addresses that are generated by
26374 redirection, unless &%no_rewrite%& is set on the router.
26376 .cindex "envelope from"
26377 .cindex "envelope sender" "rewriting at transport time"
26378 .cindex "rewriting" "at transport time"
26379 .cindex "header lines" "rewriting at transport time"
26380 At transport time, additional rewriting of addresses in header lines can be
26381 specified by setting the generic &%headers_rewrite%& option on a transport.
26382 This option contains rules that are identical in form to those in the rewrite
26383 section of the configuration file. They are applied to the original message
26384 header lines and any that were added by ACLs or a system filter. They are not
26385 applied to header lines that are added by routers or the transport.
26387 The outgoing envelope sender can be rewritten by means of the &%return_path%&
26388 transport option. However, it is not possible to rewrite envelope recipients at
26394 .section "Testing the rewriting rules that apply on input" "SECID149"
26395 .cindex "rewriting" "testing"
26396 .cindex "testing" "rewriting"
26397 Exim's input rewriting configuration appears in a part of the runtime
26398 configuration file headed by &"begin rewrite"&. It can be tested by the
26399 &%-brw%& command line option. This takes an address (which can be a full RFC
26400 2822 address) as its argument. The output is a list of how the address would be
26401 transformed by the rewriting rules for each of the different places it might
26402 appear in an incoming message, that is, for each different header and for the
26403 envelope sender and recipient fields. For example,
26405 exim -brw ph10@exim.workshop.example
26407 might produce the output
26409 sender: Philip.Hazel@exim.workshop.example
26410 from: Philip.Hazel@exim.workshop.example
26411 to: ph10@exim.workshop.example
26412 cc: ph10@exim.workshop.example
26413 bcc: ph10@exim.workshop.example
26414 reply-to: Philip.Hazel@exim.workshop.example
26415 env-from: Philip.Hazel@exim.workshop.example
26416 env-to: ph10@exim.workshop.example
26418 which shows that rewriting has been set up for that address when used in any of
26419 the source fields, but not when it appears as a recipient address. At the
26420 present time, there is no equivalent way of testing rewriting rules that are
26421 set for a particular transport.
26424 .section "Rewriting rules" "SECID150"
26425 .cindex "rewriting" "rules"
26426 The rewrite section of the configuration file consists of lines of rewriting
26429 <&'source pattern'&> <&'replacement'&> <&'flags'&>
26431 Rewriting rules that are specified for the &%headers_rewrite%& generic
26432 transport option are given as a colon-separated list. Each item in the list
26433 takes the same form as a line in the main rewriting configuration (except that
26434 any colons must be doubled, of course).
26436 The formats of source patterns and replacement strings are described below.
26437 Each is terminated by white space, unless enclosed in double quotes, in which
26438 case normal quoting conventions apply inside the quotes. The flags are single
26439 characters which may appear in any order. Spaces and tabs between them are
26442 For each address that could potentially be rewritten, the rules are scanned in
26443 order, and replacements for the address from earlier rules can themselves be
26444 replaced by later rules (but see the &"q"& and &"R"& flags).
26446 The order in which addresses are rewritten is undefined, may change between
26447 releases, and must not be relied on, with one exception: when a message is
26448 received, the envelope sender is always rewritten first, before any header
26449 lines are rewritten. For example, the replacement string for a rewrite of an
26450 address in &'To:'& must not assume that the message's address in &'From:'& has
26451 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
26452 that the envelope sender has already been rewritten.
26454 .vindex "&$domain$&"
26455 .vindex "&$local_part$&"
26456 The variables &$local_part$& and &$domain$& can be used in the replacement
26457 string to refer to the address that is being rewritten. Note that lookup-driven
26458 rewriting can be done by a rule of the form
26462 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
26463 refer to the address that is being rewritten.
26466 .section "Rewriting patterns" "SECID151"
26467 .cindex "rewriting" "patterns"
26468 .cindex "address list" "in a rewriting pattern"
26469 The source pattern in a rewriting rule is any item which may appear in an
26470 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
26471 single-item address list, which means that it is expanded before being tested
26472 against the address. As always, if you use a regular expression as a pattern,
26473 you must take care to escape dollar and backslash characters, or use the &`\N`&
26474 facility to suppress string expansion within the regular expression.
26476 Domains in patterns should be given in lower case. Local parts in patterns are
26477 case-sensitive. If you want to do case-insensitive matching of local parts, you
26478 can use a regular expression that starts with &`^(?i)`&.
26480 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
26481 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
26482 depending on the type of match which occurred. These can be used in the
26483 replacement string to insert portions of the incoming address. &$0$& always
26484 refers to the complete incoming address. When a regular expression is used, the
26485 numerical variables are set from its capturing subexpressions. For other types
26486 of pattern they are set as follows:
26489 If a local part or domain starts with an asterisk, the numerical variables
26490 refer to the character strings matched by asterisks, with &$1$& associated with
26491 the first asterisk, and &$2$& with the second, if present. For example, if the
26494 *queen@*.fict.example
26496 is matched against the address &'hearts-queen@wonderland.fict.example'& then
26498 $0 = hearts-queen@wonderland.fict.example
26502 Note that if the local part does not start with an asterisk, but the domain
26503 does, it is &$1$& that contains the wild part of the domain.
26506 If the domain part of the pattern is a partial lookup, the wild and fixed parts
26507 of the domain are placed in the next available numerical variables. Suppose,
26508 for example, that the address &'foo@bar.baz.example'& is processed by a
26509 rewriting rule of the form
26511 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
26513 and the key in the file that matches the domain is &`*.baz.example`&. Then
26519 If the address &'foo@baz.example'& is looked up, this matches the same
26520 wildcard file entry, and in this case &$2$& is set to the empty string, but
26521 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
26522 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
26523 whole domain. For non-partial domain lookups, no numerical variables are set.
26527 .section "Rewriting replacements" "SECID152"
26528 .cindex "rewriting" "replacements"
26529 If the replacement string for a rule is a single asterisk, addresses that
26530 match the pattern and the flags are &'not'& rewritten, and no subsequent
26531 rewriting rules are scanned. For example,
26533 hatta@lookingglass.fict.example * f
26535 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
26538 .vindex "&$domain$&"
26539 .vindex "&$local_part$&"
26540 If the replacement string is not a single asterisk, it is expanded, and must
26541 yield a fully qualified address. Within the expansion, the variables
26542 &$local_part$& and &$domain$& refer to the address that is being rewritten.
26543 Any letters they contain retain their original case &-- they are not lower
26544 cased. The numerical variables are set up according to the type of pattern that
26545 matched the address, as described above. If the expansion is forced to fail by
26546 the presence of &"fail"& in a conditional or lookup item, rewriting by the
26547 current rule is abandoned, but subsequent rules may take effect. Any other
26548 expansion failure causes the entire rewriting operation to be abandoned, and an
26549 entry written to the panic log.
26553 .subsection "Rewriting flags" "SSECID153"
26554 There are three different kinds of flag that may appear on rewriting rules:
26557 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
26560 A flag that specifies rewriting at SMTP time: S.
26562 Flags that control the rewriting process: Q, q, R, w.
26565 For rules that are part of the &%headers_rewrite%& generic transport option,
26566 E, F, T, and S are not permitted.
26570 .subsection "Flags specifying which headers and envelope addresses to rewrite" &&&
26572 .cindex rewriting flags
26573 If none of the following flag letters, nor the &"S"& flag (see section
26574 &<<SSECTrewriteS>>&) are present, a main rewriting rule applies to all headers
26575 and to both the sender and recipient fields of the envelope, whereas a
26576 transport-time rewriting rule just applies to all headers. Otherwise, the
26577 rewriting rule is skipped unless the relevant addresses are being processed.
26579 &`E`& rewrite all envelope fields
26580 &`F`& rewrite the envelope From field
26581 &`T`& rewrite the envelope To field
26582 &`b`& rewrite the &'Bcc:'& header
26583 &`c`& rewrite the &'Cc:'& header
26584 &`f`& rewrite the &'From:'& header
26585 &`h`& rewrite all headers
26586 &`r`& rewrite the &'Reply-To:'& header
26587 &`s`& rewrite the &'Sender:'& header
26588 &`t`& rewrite the &'To:'& header
26590 "All headers" means all of the headers listed above that can be selected
26591 individually, plus their &'Resent-'& versions. It does not include
26592 other headers such as &'Subject:'& etc.
26594 You should be particularly careful about rewriting &'Sender:'& headers, and
26595 restrict this to special known cases in your own domains.
26598 .subsection "The SMTP-time rewriting flag" SSECTrewriteS
26599 .cindex SMTP "rewriting malformed addresses"
26600 .cindex RCPT "rewriting argument of"
26601 .cindex MAIL "rewriting argument of"
26602 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
26603 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
26604 before any other processing; even before syntax checking. The pattern is
26605 required to be a regular expression, and it is matched against the whole of the
26606 data for the command, including any surrounding angle brackets.
26608 .vindex "&$domain$&"
26609 .vindex "&$local_part$&"
26610 This form of rewrite rule allows for the handling of addresses that are not
26611 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
26612 input). Because the input is not required to be a syntactically valid address,
26613 the variables &$local_part$& and &$domain$& are not available during the
26614 expansion of the replacement string. The result of rewriting replaces the
26615 original address in the MAIL or RCPT command.
26618 .subsection "Flags controlling the rewriting process" SSECID155
26619 There are four flags which control the way the rewriting process works. These
26620 take effect only when a rule is invoked, that is, when the address is of the
26621 correct type (matches the flags) and matches the pattern:
26624 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
26625 unqualified local part. It is qualified with &%qualify_recipient%&. In the
26626 absence of &"Q"& the rewritten address must always include a domain.
26628 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
26629 even if no rewriting actually takes place because of a &"fail"& in the
26630 expansion. The &"q"& flag is not effective if the address is of the wrong type
26631 (does not match the flags) or does not match the pattern.
26633 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
26634 address, up to ten times. It can be combined with the &"q"& flag, to stop
26635 rewriting once it fails to match (after at least one successful rewrite).
26637 .cindex "rewriting" "whole addresses"
26638 When an address in a header is rewritten, the rewriting normally applies only
26639 to the working part of the address, with any comments and RFC 2822 &"phrase"&
26640 left unchanged. For example, rewriting might change
26642 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
26646 From: Ford Prefect <prefectf@hitch.fict.example>
26649 Sometimes there is a need to replace the whole address item, and this can be
26650 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
26651 causes an address in a header line to be rewritten, the entire address is
26652 replaced, not just the working part. The replacement must be a complete RFC
26653 2822 address, including the angle brackets if necessary. If text outside angle
26654 brackets contains a character whose value is greater than 126 or less than 32
26655 (except for tab), the text is encoded according to RFC 2047. The character set
26656 is taken from &%headers_charset%&, which gets its default at build time.
26658 When the &"w"& flag is set on a rule that causes an envelope address to be
26659 rewritten, all but the working part of the replacement address is discarded.
26663 .section "Rewriting examples" "SECID156"
26664 Here is an example of the two common rewriting paradigms:
26666 *@*.hitch.fict.example $1@hitch.fict.example
26667 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
26668 {$value}fail}@hitch.fict.example bctfrF
26670 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
26671 the string expansion to fail if the lookup does not succeed. In this context it
26672 has the effect of leaving the original address unchanged, but Exim goes on to
26673 consider subsequent rewriting rules, if any, because the &"q"& flag is not
26674 present in that rule. An alternative to &"fail"& would be to supply &$1$&
26675 explicitly, which would cause the rewritten address to be the same as before,
26676 at the cost of a small bit of processing. Not supplying either of these is an
26677 error, since the rewritten address would then contain no local part.
26679 The first example above replaces the domain with a superior, more general
26680 domain. This may not be desirable for certain local parts. If the rule
26682 root@*.hitch.fict.example *
26684 were inserted before the first rule, rewriting would be suppressed for the
26685 local part &'root'& at any domain ending in &'hitch.fict.example'&.
26687 Rewriting can be made conditional on a number of tests, by making use of
26688 &${if$& in the expansion item. For example, to apply a rewriting rule only to
26689 messages that originate outside the local host:
26691 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
26692 {$1@hitch.fict.example}fail}"
26694 The replacement string is quoted in this example because it contains white
26697 .cindex "rewriting" "bang paths"
26698 .cindex "bang paths" "rewriting"
26699 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
26700 an address it treats it as an unqualified local part which it qualifies with
26701 the local qualification domain (if the source of the message is local or if the
26702 remote host is permitted to send unqualified addresses). Rewriting can
26703 sometimes be used to handle simple bang paths with a fixed number of
26704 components. For example, the rule
26706 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
26708 rewrites a two-component bang path &'host.name!user'& as the domain address
26709 &'user@host.name'&. However, there is a security implication in using this as
26710 a global rewriting rule for envelope addresses. It can provide a backdoor
26711 method for using your system as a relay, because the incoming addresses appear
26712 to be local. If the bang path addresses are received via SMTP, it is safer to
26713 use the &"S"& flag to rewrite them as they are received, so that relay checking
26714 can be done on the rewritten addresses.
26721 . ////////////////////////////////////////////////////////////////////////////
26722 . ////////////////////////////////////////////////////////////////////////////
26724 .chapter "Retry configuration" "CHAPretry"
26725 .scindex IIDretconf1 "retry" "configuration, description of"
26726 .scindex IIDregconf2 "configuration file" "retry section"
26727 The &"retry"& section of the runtime configuration file contains a list of
26728 retry rules that control how often Exim tries to deliver messages that cannot
26729 be delivered at the first attempt. If there are no retry rules (the section is
26730 empty or not present), there are no retries. In this situation, temporary
26731 errors are treated as permanent. The default configuration contains a single,
26732 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
26733 line option can be used to test which retry rule will be used for a given
26734 address, domain and error.
26736 The most common cause of retries is temporary failure to deliver to a remote
26737 host because the host is down, or inaccessible because of a network problem.
26738 Exim's retry processing in this case is applied on a per-host (strictly, per IP
26739 address) basis, not on a per-message basis. Thus, if one message has recently
26740 been delayed, delivery of a new message to the same host is not immediately
26741 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
26742 log selector is set, the message
26743 .cindex "retry" "time not reached"
26744 &"retry time not reached"& is written to the main log whenever a delivery is
26745 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
26746 the handling of errors during remote deliveries.
26748 Retry processing applies to routing as well as to delivering, except as covered
26749 in the next paragraph. The retry rules do not distinguish between these
26750 actions. It is not possible, for example, to specify different behaviour for
26751 failures to route the domain &'snark.fict.example'& and failures to deliver to
26752 the host &'snark.fict.example'&. I didn't think anyone would ever need this
26753 added complication, so did not implement it. However, although they share the
26754 same retry rule, the actual retry times for routing and transporting a given
26755 domain are maintained independently.
26757 When a delivery is not part of a queue run (typically an immediate delivery on
26758 receipt of a message), the routers are always run, and local deliveries are
26759 always attempted, even if retry times are set for them. This makes for better
26760 behaviour if one particular message is causing problems (for example, causing
26761 quota overflow, or provoking an error in a filter file). If such a delivery
26762 suffers a temporary failure, the retry data is updated as normal, and
26763 subsequent delivery attempts from queue runs occur only when the retry time for
26764 the local address is reached.
26766 .section "Changing retry rules" "SECID157"
26767 If you change the retry rules in your configuration, you should consider
26768 whether or not to delete the retry data that is stored in Exim's spool area in
26769 files with names like &_db/retry_&. Deleting any of Exim's hints files is
26770 always safe; that is why they are called &"hints"&.
26772 The hints retry data contains suggested retry times based on the previous
26773 rules. In the case of a long-running problem with a remote host, it might
26774 record the fact that the host has timed out. If your new rules increase the
26775 timeout time for such a host, you should definitely remove the old retry data
26776 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
26777 messages that it should now be retaining.
26781 .section "Format of retry rules" "SECID158"
26782 .cindex "retry" "rules"
26783 Each retry rule occupies one line and consists of three or four parts,
26784 separated by white space: a pattern, an error name, an optional list of sender
26785 addresses, and a list of retry parameters. The pattern and sender lists must be
26786 enclosed in double quotes if they contain white space. The rules are searched
26787 in order until one is found where the pattern, error name, and sender list (if
26788 present) match the failing host or address, the error that occurred, and the
26789 message's sender, respectively.
26792 The pattern is any single item that may appear in an address list (see section
26793 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
26794 which means that it is expanded before being tested against the address that
26795 has been delayed. A negated address list item is permitted. Address
26796 list processing treats a plain domain name as if it were preceded by &"*@"&,
26797 which makes it possible for many retry rules to start with just a domain. For
26800 lookingglass.fict.example * F,24h,30m;
26802 provides a rule for any address in the &'lookingglass.fict.example'& domain,
26805 alice@lookingglass.fict.example * F,24h,30m;
26807 applies only to temporary failures involving the local part &%alice%&.
26808 In practice, almost all rules start with a domain name pattern without a local
26811 .cindex "regular expressions" "in retry rules"
26812 &*Warning*&: If you use a regular expression in a retry rule pattern, it
26813 must match a complete address, not just a domain, because that is how regular
26814 expressions work in address lists.
26816 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
26817 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
26821 .section "Choosing which retry rule to use for address errors" "SECID159"
26822 When Exim is looking for a retry rule after a routing attempt has failed (for
26823 example, after a DNS timeout), each line in the retry configuration is tested
26824 against the complete address only if &%retry_use_local_part%& is set for the
26825 router. Otherwise, only the domain is used, except when matching against a
26826 regular expression, when the local part of the address is replaced with &"*"&.
26827 A domain on its own can match a domain pattern, or a pattern that starts with
26828 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
26829 &%check_local_user%& is true, and false for other routers.
26831 Similarly, when Exim is looking for a retry rule after a local delivery has
26832 failed (for example, after a mailbox full error), each line in the retry
26833 configuration is tested against the complete address only if
26834 &%retry_use_local_part%& is set for the transport (it defaults true for all
26837 .cindex "4&'xx'& responses" "retry rules for"
26838 However, when Exim is looking for a retry rule after a remote delivery attempt
26839 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
26840 whole address is always used as the key when searching the retry rules. The
26841 rule that is found is used to create a retry time for the combination of the
26842 failing address and the message's sender. It is the combination of sender and
26843 recipient that is delayed in subsequent queue runs until its retry time is
26844 reached. You can delay the recipient without regard to the sender by setting
26845 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
26846 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
26851 .section "Choosing which retry rule to use for host and message errors" &&&
26853 For a temporary error that is not related to an individual address (for
26854 example, a connection timeout), each line in the retry configuration is checked
26855 twice. First, the name of the remote host is used as a domain name (preceded by
26856 &"*@"& when matching a regular expression). If this does not match the line,
26857 the domain from the email address is tried in a similar fashion. For example,
26858 suppose the MX records for &'a.b.c.example'& are
26860 a.b.c.example MX 5 x.y.z.example
26864 and the retry rules are
26866 p.q.r.example * F,24h,30m;
26867 a.b.c.example * F,4d,45m;
26869 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
26870 first rule matches neither the host nor the domain, so Exim looks at the second
26871 rule. This does not match the host, but it does match the domain, so it is used
26872 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
26873 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
26874 first retry rule is used, because it matches the host.
26876 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
26877 first rule to determine retry times, but for all the other hosts for the domain
26878 &'a.b.c.example'&, the second rule is used. The second rule is also used if
26879 routing to &'a.b.c.example'& suffers a temporary failure.
26881 &*Note*&: The host name is used when matching the patterns, not its IP address.
26882 However, if a message is routed directly to an IP address without the use of a
26883 host name, for example, if a &(manualroute)& router contains a setting such as:
26885 route_list = *.a.example 192.168.34.23
26887 then the &"host name"& that is used when searching for a retry rule is the
26888 textual form of the IP address.
26890 .section "Retry rules for specific errors" "SECID161"
26891 .cindex "retry" "specific errors; specifying"
26892 The second field in a retry rule is the name of a particular error, or an
26893 asterisk, which matches any error. The errors that can be tested for are:
26896 .vitem &%auth_failed%&
26897 Authentication failed when trying to send to a host in the
26898 &%hosts_require_auth%& list in an &(smtp)& transport.
26900 .vitem &%data_4xx%&
26901 A 4&'xx'& error was received for an outgoing DATA command, either immediately
26902 after the command, or after sending the message's data.
26904 .vitem &%mail_4xx%&
26905 A 4&'xx'& error was received for an outgoing MAIL command.
26907 .vitem &%rcpt_4xx%&
26908 A 4&'xx'& error was received for an outgoing RCPT command.
26911 For the three 4&'xx'& errors, either the first or both of the x's can be given
26912 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
26913 recognize 452 errors given to RCPT commands for addresses in a certain domain,
26914 and have retries every ten minutes with a one-hour timeout, you could set up a
26915 retry rule of this form:
26917 the.domain.name rcpt_452 F,1h,10m
26919 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
26920 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
26923 .vitem &%lost_connection%&
26924 A server unexpectedly closed the SMTP connection. There may, of course,
26925 legitimate reasons for this (host died, network died), but if it repeats a lot
26926 for the same host, it indicates something odd.
26929 A DNS lookup for a host failed.
26930 Note that a &%dnslookup%& router will need to have matched
26931 its &%fail_defer_domains%& option for this retry type to be usable.
26932 Also note that a &%manualroute%& router will probably need
26933 its &%host_find_failed%& option set to &%defer%&.
26935 .vitem &%refused_MX%&
26936 A connection to a host obtained from an MX record was refused.
26938 .vitem &%refused_A%&
26939 A connection to a host not obtained from an MX record was refused.
26942 A connection was refused.
26944 .vitem &%timeout_connect_MX%&
26945 A connection attempt to a host obtained from an MX record timed out.
26947 .vitem &%timeout_connect_A%&
26948 A connection attempt to a host not obtained from an MX record timed out.
26950 .vitem &%timeout_connect%&
26951 A connection attempt timed out.
26953 .vitem &%timeout_MX%&
26954 There was a timeout while connecting or during an SMTP session with a host
26955 obtained from an MX record.
26957 .vitem &%timeout_A%&
26958 There was a timeout while connecting or during an SMTP session with a host not
26959 obtained from an MX record.
26962 There was a timeout while connecting or during an SMTP session.
26964 .vitem &%tls_required%&
26965 The server was required to use TLS (it matched &%hosts_require_tls%& in the
26966 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
26967 to STARTTLS, or there was a problem setting up the TLS connection.
26970 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26973 .vitem &%quota_%&<&'time'&>
26974 .cindex "quota" "error testing in retry rule"
26975 .cindex "retry" "quota error testing"
26976 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26977 transport, and the mailbox has not been accessed for <&'time'&>. For example,
26978 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
26982 .cindex "mailbox" "time of last read"
26983 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
26984 timeouts when the mailbox is full and is not being read by its owner. Ideally,
26985 it should be based on the last time that the user accessed the mailbox.
26986 However, it is not always possible to determine this. Exim uses the following
26990 If the mailbox is a single file, the time of last access (the &"atime"&) is
26991 used. As no new messages are being delivered (because the mailbox is over
26992 quota), Exim does not access the file, so this is the time of last user access.
26994 .cindex "maildir format" "time of last read"
26995 For a maildir delivery, the time of last modification of the &_new_&
26996 subdirectory is used. As the mailbox is over quota, no new files are created in
26997 the &_new_& subdirectory, because no new messages are being delivered. Any
26998 change to the &_new_& subdirectory is therefore assumed to be the result of an
26999 MUA moving a new message to the &_cur_& directory when it is first read. The
27000 time that is used is therefore the last time that the user read a new message.
27002 For other kinds of multi-file mailbox, the time of last access cannot be
27003 obtained, so a retry rule that uses this type of error field is never matched.
27006 The quota errors apply both to system-enforced quotas and to Exim's own quota
27007 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
27008 when a local delivery is deferred because a partition is full (the ENOSPC
27013 .section "Retry rules for specified senders" "SECID162"
27014 .cindex "retry" "rules; sender-specific"
27015 You can specify retry rules that apply only when the failing message has a
27016 specific sender. In particular, this can be used to define retry rules that
27017 apply only to bounce messages. The third item in a retry rule can be of this
27020 &`senders=`&<&'address list'&>
27022 The retry timings themselves are then the fourth item. For example:
27024 * rcpt_4xx senders=: F,1h,30m
27026 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
27027 host. If the address list contains white space, it must be enclosed in quotes.
27030 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
27032 &*Warning*&: This facility can be unhelpful if it is used for host errors
27033 (which do not depend on the recipient). The reason is that the sender is used
27034 only to match the retry rule. Once the rule has been found for a host error,
27035 its contents are used to set a retry time for the host, and this will apply to
27036 all messages, not just those with specific senders.
27038 When testing retry rules using &%-brt%&, you can supply a sender using the
27039 &%-f%& command line option, like this:
27041 exim -f "" -brt user@dom.ain
27043 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
27044 list is never matched.
27050 .section "Retry parameters" "SECID163"
27051 .cindex "retry" "parameters in rules"
27052 The third (or fourth, if a senders list is present) field in a retry rule is a
27053 sequence of retry parameter sets, separated by semicolons. Each set consists of
27055 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
27057 The letter identifies the algorithm for computing a new retry time; the cutoff
27058 time is the time beyond which this algorithm no longer applies, and the
27059 arguments vary the algorithm's action. The cutoff time is measured from the
27060 time that the first failure for the domain (combined with the local part if
27061 relevant) was detected, not from the time the message was received.
27063 .cindex "retry" "algorithms"
27064 .cindex "retry" "fixed intervals"
27065 .cindex "retry" "increasing intervals"
27066 .cindex "retry" "random intervals"
27067 The available algorithms are:
27070 &'F'&: retry at fixed intervals. There is a single time parameter specifying
27073 &'G'&: retry at geometrically increasing intervals. The first argument
27074 specifies a starting value for the interval, and the second a multiplier, which
27075 is used to increase the size of the interval at each retry.
27077 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
27078 retry, the previous interval is multiplied by the factor in order to get a
27079 maximum for the next interval. The minimum interval is the first argument of
27080 the parameter, and an actual interval is chosen randomly between them. Such a
27081 rule has been found to be helpful in cluster configurations when all the
27082 members of the cluster restart at once, and may therefore synchronize their
27083 queue processing times.
27086 When computing the next retry time, the algorithm definitions are scanned in
27087 order until one whose cutoff time has not yet passed is reached. This is then
27088 used to compute a new retry time that is later than the current time. In the
27089 case of fixed interval retries, this simply means adding the interval to the
27090 current time. For geometrically increasing intervals, retry intervals are
27091 computed from the rule's parameters until one that is greater than the previous
27092 interval is found. The main configuration variable
27093 .cindex "limit" "retry interval"
27094 .cindex "retry" "interval, maximum"
27095 .oindex "&%retry_interval_max%&"
27096 &%retry_interval_max%& limits the maximum interval between retries. It
27097 cannot be set greater than &`24h`&, which is its default value.
27099 A single remote domain may have a number of hosts associated with it, and each
27100 host may have more than one IP address. Retry algorithms are selected on the
27101 basis of the domain name, but are applied to each IP address independently. If,
27102 for example, a host has two IP addresses and one is unusable, Exim will
27103 generate retry times for it and will not try to use it until its next retry
27104 time comes. Thus the good IP address is likely to be tried first most of the
27107 .cindex "hints database" "use for retrying"
27108 Retry times are hints rather than promises. Exim does not make any attempt to
27109 run deliveries exactly at the computed times. Instead, a queue runner process
27110 starts delivery processes for delayed messages periodically, and these attempt
27111 new deliveries only for those addresses that have passed their next retry time.
27112 If a new message arrives for a deferred address, an immediate delivery attempt
27113 occurs only if the address has passed its retry time. In the absence of new
27114 messages, the minimum time between retries is the interval between queue runner
27115 processes. There is not much point in setting retry times of five minutes if
27116 your queue runners happen only once an hour, unless there are a significant
27117 number of incoming messages (which might be the case on a system that is
27118 sending everything to a smart host, for example).
27120 The data in the retry hints database can be inspected by using the
27121 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
27122 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
27123 &'exinext'& utility script can be used to find out what the next retry times
27124 are for the hosts associated with a particular mail domain, and also for local
27125 deliveries that have been deferred.
27128 .section "Retry rule examples" "SECID164"
27129 Here are some example retry rules:
27131 alice@wonderland.fict.example quota_5d F,7d,3h
27132 wonderland.fict.example quota_5d
27133 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
27134 lookingglass.fict.example * F,24h,30m;
27135 * refused_A F,2h,20m;
27136 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
27138 The first rule sets up special handling for mail to
27139 &'alice@wonderland.fict.example'& when there is an over-quota error and the
27140 mailbox has not been read for at least 5 days. Retries continue every three
27141 hours for 7 days. The second rule handles over-quota errors for all other local
27142 parts at &'wonderland.fict.example'&; the absence of a local part has the same
27143 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
27144 fail are bounced immediately if the mailbox has not been read for at least 5
27147 The third rule handles all other errors at &'wonderland.fict.example'&; retries
27148 happen every 15 minutes for an hour, then with geometrically increasing
27149 intervals until two days have passed since a delivery first failed. After the
27150 first hour there is a delay of one hour, then two hours, then four hours, and
27151 so on (this is a rather extreme example).
27153 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
27154 They happen every 30 minutes for 24 hours only. The remaining two rules handle
27155 all other domains, with special action for connection refusal from hosts that
27156 were not obtained from an MX record.
27158 The final rule in a retry configuration should always have asterisks in the
27159 first two fields so as to provide a general catch-all for any addresses that do
27160 not have their own special handling. This example tries every 15 minutes for 2
27161 hours, then with intervals starting at one hour and increasing by a factor of
27162 1.5 up to 16 hours, then every 8 hours up to 5 days.
27166 .section "Timeout of retry data" "SECID165"
27167 .cindex "timeout" "of retry data"
27168 .oindex "&%retry_data_expire%&"
27169 .cindex "hints database" "data expiry"
27170 .cindex "retry" "timeout of data"
27171 Exim timestamps the data that it writes to its retry hints database. When it
27172 consults the data during a delivery it ignores any that is older than the value
27173 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
27174 been tried for 7 days, Exim will try to deliver to it immediately a message
27175 arrives, and if that fails, it will calculate a retry time as if it were
27176 failing for the first time.
27178 This improves the behaviour for messages routed to rarely-used hosts such as MX
27179 backups. If such a host was down at one time, and happens to be down again when
27180 Exim tries a month later, using the old retry data would imply that it had been
27181 down all the time, which is not a justified assumption.
27183 If a host really is permanently dead, this behaviour causes a burst of retries
27184 every now and again, but only if messages routed to it are rare. If there is a
27185 message at least once every 7 days the retry data never expires.
27190 .section "Long-term failures" "SECID166"
27191 .cindex "delivery failure, long-term"
27192 .cindex "retry" "after long-term failure"
27193 Special processing happens when an email address has been failing for so long
27194 that the cutoff time for the last algorithm is reached. For example, using the
27195 default retry rule:
27197 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
27199 the cutoff time is four days. Reaching the retry cutoff is independent of how
27200 long any specific message has been failing; it is the length of continuous
27201 failure for the recipient address that counts.
27203 When the cutoff time is reached for a local delivery, or for all the IP
27204 addresses associated with a remote delivery, a subsequent delivery failure
27205 causes Exim to give up on the address, and a bounce message is generated.
27206 In order to cater for new messages that use the failing address, a next retry
27207 time is still computed from the final algorithm, and is used as follows:
27209 For local deliveries, one delivery attempt is always made for any subsequent
27210 messages. If this delivery fails, the address fails immediately. The
27211 post-cutoff retry time is not used.
27213 .cindex "final cutoff" "retries, controlling"
27214 .cindex retry "final cutoff"
27215 If the delivery is remote, there are two possibilities, controlled by the
27216 .oindex "&%delay_after_cutoff%&"
27217 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
27218 default. Until the post-cutoff retry time for one of the IP addresses,
27219 as set by the &%retry_data_expire%& option, is
27220 reached, the failing email address is bounced immediately, without a delivery
27221 attempt taking place. After that time, one new delivery attempt is made to
27222 those IP addresses that are past their retry times, and if that still fails,
27223 the address is bounced and new retry times are computed.
27225 In other words, when all the hosts for a given email address have been failing
27226 for a long time, Exim bounces rather then defers until one of the hosts' retry
27227 times is reached. Then it tries once, and bounces if that attempt fails. This
27228 behaviour ensures that few resources are wasted in repeatedly trying to deliver
27229 to a broken destination, but if the host does recover, Exim will eventually
27232 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
27233 addresses are past their final cutoff time, Exim tries to deliver to those IP
27234 addresses that have not been tried since the message arrived. If there are
27235 no suitable IP addresses, or if they all fail, the address is bounced. In other
27236 words, it does not delay when a new message arrives, but tries the expired
27237 addresses immediately, unless they have been tried since the message arrived.
27238 If there is a continuous stream of messages for the failing domains, setting
27239 &%delay_after_cutoff%& false means that there will be many more attempts to
27240 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
27243 .section "Deliveries that work intermittently" "SECID167"
27244 .cindex "retry" "intermittently working deliveries"
27245 Some additional logic is needed to cope with cases where a host is
27246 intermittently available, or when a message has some attribute that prevents
27247 its delivery when others to the same address get through. In this situation,
27248 because some messages are successfully delivered, the &"retry clock"& for the
27249 host or address keeps getting reset by the successful deliveries, and so
27250 failing messages remain in the queue for ever because the cutoff time is never
27253 Two exceptional actions are applied to prevent this happening. The first
27254 applies to errors that are related to a message rather than a remote host.
27255 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
27256 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
27257 commands, and quota failures. For this type of error, if a message's arrival
27258 time is earlier than the &"first failed"& time for the error, the earlier time
27259 is used when scanning the retry rules to decide when to try next and when to
27260 time out the address.
27262 The exceptional second action applies in all cases. If a message has been on
27263 the queue for longer than the cutoff time of any applicable retry rule for a
27264 given address, a delivery is attempted for that address, even if it is not yet
27265 time, and if this delivery fails, the address is timed out. A new retry time is
27266 not computed in this case, so that other messages for the same address are
27267 considered immediately.
27268 .ecindex IIDretconf1
27269 .ecindex IIDregconf2
27276 . ////////////////////////////////////////////////////////////////////////////
27277 . ////////////////////////////////////////////////////////////////////////////
27279 .chapter "SMTP authentication" "CHAPSMTPAUTH"
27280 .scindex IIDauthconf1 "SMTP" "authentication configuration"
27281 .scindex IIDauthconf2 "authentication"
27282 The &"authenticators"& section of Exim's runtime configuration is concerned
27283 with SMTP authentication. This facility is an extension to the SMTP protocol,
27284 described in RFC 2554, which allows a client SMTP host to authenticate itself
27285 to a server. This is a common way for a server to recognize clients that are
27286 permitted to use it as a relay. SMTP authentication is not of relevance to the
27287 transfer of mail between servers that have no managerial connection with each
27290 The name of an authenticator is limited to be &drivernamemax; ASCII characters long;
27291 prior to Exim 4.95 names would be silently truncated at this length, but now
27294 .cindex "AUTH" "description of"
27295 .cindex "ESMTP extensions" AUTH
27296 Very briefly, the way SMTP authentication works is as follows:
27299 The server advertises a number of authentication &'mechanisms'& in response to
27300 the client's EHLO command.
27302 The client issues an AUTH command, naming a specific mechanism. The command
27303 may, optionally, contain some authentication data.
27305 The server may issue one or more &'challenges'&, to which the client must send
27306 appropriate responses. In simple authentication mechanisms, the challenges are
27307 just prompts for user names and passwords. The server does not have to issue
27308 any challenges &-- in some mechanisms the relevant data may all be transmitted
27309 with the AUTH command.
27311 The server either accepts or denies authentication.
27313 If authentication succeeds, the client may optionally make use of the AUTH
27314 option on the MAIL command to pass an authenticated sender in subsequent
27315 mail transactions. Authentication lasts for the remainder of the SMTP
27318 If authentication fails, the client may give up, or it may try a different
27319 authentication mechanism, or it may try transferring mail over the
27320 unauthenticated connection.
27323 If you are setting up a client, and want to know which authentication
27324 mechanisms the server supports, you can use Telnet to connect to port 25 (the
27325 SMTP port) on the server, and issue an EHLO command. The response to this
27326 includes the list of supported mechanisms. For example:
27328 &`$ `&&*&`telnet server.example 25`&*&
27329 &`Trying 192.168.34.25...`&
27330 &`Connected to server.example.`&
27331 &`Escape character is '^]'.`&
27332 &`220 server.example ESMTP Exim 4.20 ...`&
27333 &*&`ehlo client.example`&*&
27334 &`250-server.example Hello client.example [10.8.4.5]`&
27335 &`250-SIZE 52428800`&
27340 The second-last line of this example output shows that the server supports
27341 authentication using the PLAIN mechanism. In Exim, the different authentication
27342 mechanisms are configured by specifying &'authenticator'& drivers. Like the
27343 routers and transports, which authenticators are included in the binary is
27344 controlled by build-time definitions. The following are currently available,
27345 included by setting
27348 AUTH_CYRUS_SASL=yes
27352 AUTH_HEIMDAL_GSSAPI=yes
27357 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
27358 authentication mechanism (RFC 2195), and the second provides an interface to
27359 the Cyrus SASL authentication library.
27360 The third is an interface to Dovecot's authentication system, delegating the
27361 work via a socket interface.
27362 The fourth provides for negotiation of authentication done via non-SMTP means,
27363 as defined by RFC 4422 Appendix A.
27364 The fifth provides an interface to the GNU SASL authentication library, which
27365 provides mechanisms but typically not data sources.
27366 The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
27367 supporting setting a server keytab.
27368 The seventh can be configured to support
27369 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
27370 not formally documented, but used by several MUAs.
27371 The eighth authenticator
27372 supports Microsoft's &'Secure Password Authentication'& mechanism.
27373 The last is an Exim authenticator but not an SMTP one;
27374 instead it can use information from a TLS negotiation.
27376 The authenticators are configured using the same syntax as other drivers (see
27377 section &<<SECTfordricon>>&). If no authenticators are required, no
27378 authentication section need be present in the configuration file. Each
27379 authenticator can in principle have both server and client functions. When Exim
27380 is receiving SMTP mail, it is acting as a server; when it is sending out
27381 messages over SMTP, it is acting as a client. Authenticator configuration
27382 options are provided for use in both these circumstances.
27384 To make it clear which options apply to which situation, the prefixes
27385 &%server_%& and &%client_%& are used on option names that are specific to
27386 either the server or the client function, respectively. Server and client
27387 functions are disabled if none of their options are set. If an authenticator is
27388 to be used for both server and client functions, a single definition, using
27389 both sets of options, is required. For example:
27393 public_name = CRAM-MD5
27394 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
27396 client_secret = secret2
27398 The &%server_%& option is used when Exim is acting as a server, and the
27399 &%client_%& options when it is acting as a client.
27401 Descriptions of the individual authenticators are given in subsequent chapters.
27402 The remainder of this chapter covers the generic options for the
27403 authenticators, followed by general discussion of the way authentication works
27406 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
27407 per-mechanism basis. Please read carefully to determine which variables hold
27408 account labels such as usercodes and which hold passwords or other
27409 authenticating data.
27411 Note that some mechanisms support two different identifiers for accounts: the
27412 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
27413 and &'authz'& are commonly encountered. The American spelling is standard here.
27414 Conceptually, authentication data such as passwords are tied to the identifier
27415 used to authenticate; servers may have rules to permit one user to act as a
27416 second user, so that after login the session is treated as though that second
27417 user had logged in. That second user is the &'authorization id'&. A robust
27418 configuration might confirm that the &'authz'& field is empty or matches the
27419 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
27420 as verified data, the &'authz'& as an unverified request which the server might
27423 A &'realm'& is a text string, typically a domain name, presented by a server
27424 to a client to help it select an account and credentials to use. In some
27425 mechanisms, the client and server provably agree on the realm, but clients
27426 typically can not treat the realm as secure data to be blindly trusted.
27430 .section "Generic options for authenticators" "SECID168"
27431 .cindex "authentication" "generic options"
27432 .cindex "options" "generic; for authenticators"
27434 .option client_condition authenticators string&!! unset
27435 When Exim is authenticating as a client, it skips any authenticator whose
27436 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
27437 used, for example, to skip plain text authenticators when the connection is not
27438 encrypted by a setting such as:
27440 client_condition = ${if !eq{$tls_out_cipher}{}}
27444 .option client_set_id authenticators string&!! unset
27445 When client authentication succeeds, this condition is expanded; the
27446 result is used in the log lines for outbound messages.
27447 Typically it will be the user name used for authentication.
27450 .option driver authenticators string unset
27451 This option must always be set. It specifies which of the available
27452 authenticators is to be used.
27455 .option public_name authenticators string unset
27456 This option specifies the name of the authentication mechanism that the driver
27457 implements, and by which it is known to the outside world. These names should
27458 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
27459 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
27460 defaults to the driver's instance name.
27463 .option server_advertise_condition authenticators string&!! unset
27464 When a server is about to advertise an authentication mechanism, the condition
27465 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
27466 mechanism is not advertised.
27467 If the expansion fails, the mechanism is not advertised. If the failure was not
27468 forced, and was not caused by a lookup defer, the incident is logged.
27469 See section &<<SECTauthexiser>>& below for further discussion.
27472 .option server_condition authenticators string&!! unset
27473 This option must be set for a &%plaintext%& server authenticator, where it
27474 is used directly to control authentication. See section &<<SECTplainserver>>&
27477 For the &(gsasl)& authenticator, this option is required for various
27478 mechanisms; see chapter &<<CHAPgsasl>>& for details.
27480 For the other authenticators, &%server_condition%& can be used as an additional
27481 authentication or authorization mechanism that is applied after the other
27482 authenticator conditions succeed. If it is set, it is expanded when the
27483 authenticator would otherwise return a success code. If the expansion is forced
27484 to fail, authentication fails. Any other expansion failure causes a temporary
27485 error code to be returned. If the result of a successful expansion is an empty
27486 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27487 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
27488 other result, a temporary error code is returned, with the expanded string as
27492 .option server_debug_print authenticators string&!! unset
27493 If this option is set and authentication debugging is enabled (see the &%-d%&
27494 command line option), the string is expanded and included in the debugging
27495 output when the authenticator is run as a server. This can help with checking
27496 out the values of variables.
27497 If expansion of the string fails, the error message is written to the debugging
27498 output, and Exim carries on processing.
27501 .option server_set_id authenticators string&!! unset
27502 .vindex "&$authenticated_id$&"
27503 .vindex "&$authenticated_fail_id$&"
27504 When an Exim server successfully authenticates a client, this string is
27505 expanded using data from the authentication, and preserved for any incoming
27506 messages in the variable &$authenticated_id$&. It is also included in the log
27507 lines for incoming messages. For example, a user/password authenticator
27508 configuration might preserve the user name that was used to authenticate, and
27509 refer to it subsequently during delivery of the message.
27510 On a failing authentication the expansion result is instead saved in
27511 the &$authenticated_fail_id$& variable.
27512 If expansion fails, the option is ignored.
27515 .option server_mail_auth_condition authenticators string&!! unset
27516 This option allows a server to discard authenticated sender addresses supplied
27517 as part of MAIL commands in SMTP connections that are authenticated by the
27518 driver on which &%server_mail_auth_condition%& is set. The option is not used
27519 as part of the authentication process; instead its (unexpanded) value is
27520 remembered for later use.
27521 How it is used is described in the following section.
27527 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
27528 .cindex "authentication" "sender; authenticated"
27529 .cindex "AUTH" "on MAIL command"
27530 When a client supplied an AUTH= item on a MAIL command, Exim applies
27531 the following checks before accepting it as the authenticated sender of the
27535 If the connection is not using extended SMTP (that is, HELO was used rather
27536 than EHLO), the use of AUTH= is a syntax error.
27538 If the value of the AUTH= parameter is &"<>"&, it is ignored.
27540 .vindex "&$authenticated_sender$&"
27541 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
27542 running, the value of &$authenticated_sender$& is set to the value obtained
27543 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
27544 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
27545 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
27546 given for the MAIL command.
27548 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
27549 is accepted and placed in &$authenticated_sender$& only if the client has
27552 If the AUTH= value was accepted by either of the two previous rules, and
27553 the client has authenticated, and the authenticator has a setting for the
27554 &%server_mail_auth_condition%&, the condition is checked at this point. The
27555 valued that was saved from the authenticator is expanded. If the expansion
27556 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
27557 &$authenticated_sender$& is deleted. If the expansion yields any other value,
27558 the value of &$authenticated_sender$& is retained and passed on with the
27563 When &$authenticated_sender$& is set for a message, it is passed on to other
27564 hosts to which Exim authenticates as a client. Do not confuse this value with
27565 &$authenticated_id$&, which is a string obtained from the authentication
27566 process, and which is not usually a complete email address.
27568 .vindex "&$sender_address$&"
27569 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
27570 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
27571 therefore make use of &$authenticated_sender$&. The converse is not true: the
27572 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
27577 .section "Authentication on an Exim server" "SECTauthexiser"
27578 .cindex "authentication" "on an Exim server"
27579 When Exim receives an EHLO command, it advertises the public names of those
27580 authenticators that are configured as servers, subject to the following
27584 The client host must match &%auth_advertise_hosts%& (default *).
27586 If the &%server_advertise_condition%& option is set, its expansion must not
27587 yield the empty string, &"0"&, &"no"&, or &"false"&.
27590 The order in which the authenticators are defined controls the order in which
27591 the mechanisms are advertised.
27593 Some mail clients (for example, some versions of Netscape) require the user to
27594 provide a name and password for authentication whenever AUTH is advertised,
27595 even though authentication may not in fact be needed (for example, Exim may be
27596 set up to allow unconditional relaying from the client by an IP address check).
27597 You can make such clients more friendly by not advertising AUTH to them.
27598 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
27599 that runs for RCPT) to relay without authentication, you should set
27601 auth_advertise_hosts = ! 10.9.8.0/24
27603 so that no authentication mechanisms are advertised to them.
27605 The &%server_advertise_condition%& controls the advertisement of individual
27606 authentication mechanisms. For example, it can be used to restrict the
27607 advertisement of a particular mechanism to encrypted connections, by a setting
27610 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
27612 .vindex "&$tls_in_cipher$&"
27613 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
27614 yields &"yes"&, which allows the advertisement to happen.
27616 When an Exim server receives an AUTH command from a client, it rejects it
27617 immediately if AUTH was not advertised in response to an earlier EHLO
27618 command. This is the case if
27621 The client host does not match &%auth_advertise_hosts%&; or
27623 No authenticators are configured with server options; or
27625 Expansion of &%server_advertise_condition%& blocked the advertising of all the
27626 server authenticators.
27630 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
27631 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
27632 AUTH is accepted from any client host.
27634 If AUTH is not rejected by the ACL, Exim searches its configuration for a
27635 server authentication mechanism that was advertised in response to EHLO and
27636 that matches the one named in the AUTH command. If it finds one, it runs
27637 the appropriate authentication protocol, and authentication either succeeds or
27638 fails. If there is no matching advertised mechanism, the AUTH command is
27639 rejected with a 504 error.
27641 .vindex "&$received_protocol$&"
27642 .vindex "&$sender_host_authenticated$&"
27643 When a message is received from an authenticated host, the value of
27644 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
27645 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
27646 public name) of the authenticator driver that successfully authenticated the
27647 client from which the message was received. This variable is empty if there was
27648 no successful authentication.
27650 .cindex authentication "expansion item"
27651 Successful authentication sets up information used by the
27652 &%authresults%& expansion item.
27655 .cindex authentication "failure event, server"
27656 If an authenticator is run and does not succeed,
27657 an event (see &<<CHAPevents>>&) of type "auth:fail" is raised.
27658 While the event is being processed the variables
27659 &$sender_host_authenticated$& (with the authenticator name)
27660 and &$authenticated_fail_id$& (as set by the authenticator &%server_set_id%& option)
27662 If the event is serviced and a string is returned then the string will be logged
27663 instead of the default log line.
27664 See <<CHAPevents>> for details on events.
27668 .section "Testing server authentication" "SECID169"
27669 .cindex "authentication" "testing a server"
27670 .cindex "AUTH" "testing a server"
27671 .cindex "base64 encoding" "creating authentication test data"
27672 Exim's &%-bh%& option can be useful for testing server authentication
27673 configurations. The data for the AUTH command has to be sent using base64
27674 encoding. A quick way to produce such data for testing is the following Perl
27678 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
27680 .cindex "binary zero" "in authentication data"
27681 This interprets its argument as a Perl string, and then encodes it. The
27682 interpretation as a Perl string allows binary zeros, which are required for
27683 some kinds of authentication, to be included in the data. For example, a
27684 command line to run this script on such data might be
27686 encode '\0user\0password'
27688 Note the use of single quotes to prevent the shell interpreting the
27689 backslashes, so that they can be interpreted by Perl to specify characters
27690 whose code value is zero.
27692 &*Warning 1*&: If either of the user or password strings starts with an octal
27693 digit, you must use three zeros instead of one after the leading backslash. If
27694 you do not, the octal digit that starts your string will be incorrectly
27695 interpreted as part of the code for the first character.
27697 &*Warning 2*&: If there are characters in the strings that Perl interprets
27698 specially, you must use a Perl escape to prevent them being misinterpreted. For
27699 example, a command such as
27701 encode '\0user@domain.com\0pas$$word'
27703 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
27705 If you have the &%mimencode%& command installed, another way to produce
27706 base64-encoded strings is to run the command
27708 echo -e -n `\0user\0password' | mimencode
27710 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
27711 in the argument, and the &%-n%& option specifies no newline at the end of its
27712 output. However, not all versions of &%echo%& recognize these options, so you
27713 should check your version before relying on this suggestion.
27717 .section "Authentication by an Exim client" "SECID170"
27718 .cindex "authentication" "on an Exim client"
27719 The &(smtp)& transport has two options called &%hosts_require_auth%& and
27720 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
27721 announces support for authentication, and the host matches an entry in either
27722 of these options, Exim (as a client) tries to authenticate as follows:
27725 For each authenticator that is configured as a client, in the order in which
27726 they are defined in the configuration, it searches the authentication
27727 mechanisms announced by the server for one whose name matches the public name
27728 of the authenticator.
27731 .vindex "&$host_address$&"
27732 When it finds one that matches, it runs the authenticator's client code. The
27733 variables &$host$& and &$host_address$& are available for any string expansions
27734 that the client might do. They are set to the server's name and IP address. If
27735 any expansion is forced to fail, the authentication attempt is abandoned, and
27736 Exim moves on to the next authenticator. Otherwise an expansion failure causes
27737 delivery to be deferred.
27739 If the result of the authentication attempt is a temporary error or a timeout,
27740 Exim abandons trying to send the message to the host for the moment. It will
27741 try again later. If there are any backup hosts available, they are tried in the
27746 .cindex authentication "failure event, client"
27747 If the response to authentication is a permanent error (5&'xx'& code),
27748 an event (see &<<CHAPevents>>&) of type "auth:fail" is raised.
27749 While the event is being processed the variable
27750 &$sender_host_authenticated$& (with the authenticator name)
27752 If the event is serviced and a string is returned then the string will be logged.
27753 See <<CHAPevents>> for details on events.
27757 If the response to authentication is a permanent error (5&'xx'& code), Exim
27758 carries on searching the list of authenticators and tries another one if
27759 possible. If all authentication attempts give permanent errors, or if there are
27760 no attempts because no mechanisms match (or option expansions force failure),
27761 what happens depends on whether the host matches &%hosts_require_auth%& or
27762 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
27763 delivery is deferred. The error can be detected in the retry rules, and thereby
27764 turned into a permanent error if you wish. In the second case, Exim tries to
27765 deliver the message unauthenticated.
27768 Note that the hostlist test for whether to do authentication can be
27769 confused if name-IP lookups change between the time the peer is decided
27770 upon and the time that the transport runs. For example, with a manualroute
27771 router given a host name, and with DNS "round-robin" used by that name: if
27772 the local resolver cache times out between the router and the transport
27773 running, the transport may get an IP for the name for its authentication
27774 check which does not match the connection peer IP.
27775 No authentication will then be done, despite the names being identical.
27777 For such cases use a separate transport which always authenticates.
27779 .cindex "AUTH" "on MAIL command"
27780 When Exim has authenticated itself to a remote server, it adds the AUTH
27781 parameter to the MAIL commands it sends, if it has an authenticated sender for
27782 the message. If the message came from a remote host, the authenticated sender
27783 is the one that was receiving on an incoming MAIL command, provided that the
27784 incoming connection was authenticated and the &%server_mail_auth%& condition
27785 allowed the authenticated sender to be retained. If a local process calls Exim
27786 to send a message, the sender address that is built from the login name and
27787 &%qualify_domain%& is treated as authenticated. However, if the
27788 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
27789 the authenticated sender that was received with the message.
27790 .ecindex IIDauthconf1
27791 .ecindex IIDauthconf2
27798 . ////////////////////////////////////////////////////////////////////////////
27799 . ////////////////////////////////////////////////////////////////////////////
27801 .chapter "The plaintext authenticator" "CHAPplaintext"
27802 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
27803 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
27804 The &(plaintext)& authenticator can be configured to support the PLAIN and
27805 LOGIN authentication mechanisms, both of which transfer authentication data as
27806 plain (unencrypted) text (though base64 encoded). The use of plain text is a
27807 security risk; you are strongly advised to insist on the use of SMTP encryption
27808 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
27809 use unencrypted plain text, you should not use the same passwords for SMTP
27810 connections as you do for login accounts.
27812 .section "Avoiding cleartext use" "SECTplain_TLS"
27813 The following generic option settings will disable &(plaintext)& authenticators when
27814 TLS is not being used:
27816 server_advertise_condition = ${if def:tls_in_cipher }
27817 client_condition = ${if def:tls_out_cipher}
27820 &*Note*&: a plaintext SMTP AUTH done inside TLS is not vulnerable to casual snooping,
27821 but is still vulnerable to a Man In The Middle attack unless certificates
27822 (including their names) have been properly verified.
27824 .section "Plaintext server options" "SECID171"
27825 .cindex "options" "&(plaintext)& authenticator (server)"
27826 When configured as a server, &(plaintext)& uses the following options:
27828 .option server_condition authenticators string&!! unset
27829 This is actually a global authentication option, but it must be set in order to
27830 configure the &(plaintext)& driver as a server. Its use is described below.
27832 .option server_prompts plaintext "string list&!!" unset
27833 The contents of this option, after expansion, must be a colon-separated list of
27834 prompt strings. If expansion fails, a temporary authentication rejection is
27837 .section "Using plaintext in a server" "SECTplainserver"
27838 .cindex "AUTH" "in &(plaintext)& authenticator"
27839 .cindex "binary zero" "in &(plaintext)& authenticator"
27840 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
27841 "in &(plaintext)& authenticator"
27842 .vindex "&$auth1$&, &$auth2$&, etc"
27843 .cindex "base64 encoding" "in &(plaintext)& authenticator"
27845 When running as a server, &(plaintext)& performs the authentication test by
27846 expanding a string. The data sent by the client with the AUTH command, or in
27847 response to subsequent prompts, is base64 encoded, and so may contain any byte
27848 values when decoded. If any data is supplied with the command, it is treated as
27849 a list of strings, separated by NULs (binary zeros), the first three of which
27850 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
27851 (neither LOGIN nor PLAIN uses more than three strings).
27853 For compatibility with previous releases of Exim, the values are also placed in
27854 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
27855 variables for this purpose is now deprecated, as it can lead to confusion in
27856 string expansions that also use them for other things.
27858 If there are more strings in &%server_prompts%& than the number of strings
27859 supplied with the AUTH command, the remaining prompts are used to obtain more
27860 data. Each response from the client may be a list of NUL-separated strings.
27862 .vindex "&$authenticated_id$&"
27863 Once a sufficient number of data strings have been received,
27864 &%server_condition%& is expanded. If the expansion is forced to fail,
27865 authentication fails. Any other expansion failure causes a temporary error code
27866 to be returned. If the result of a successful expansion is an empty string,
27867 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27868 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
27869 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
27870 For any other result, a temporary error code is returned, with the expanded
27871 string as the error text.
27873 &*Warning*&: If you use a lookup in the expansion to find the user's
27874 password, be sure to make the authentication fail if the user is unknown.
27875 There are good and bad examples at the end of the next section.
27879 .section "The PLAIN authentication mechanism" "SECID172"
27880 .cindex "PLAIN authentication mechanism"
27881 .cindex authentication PLAIN
27882 .cindex "binary zero" "in &(plaintext)& authenticator"
27883 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
27884 sent as one item of data (that is, one combined string containing two NUL
27885 separators). The data is sent either as part of the AUTH command, or
27886 subsequently in response to an empty prompt from the server.
27888 The second and third strings are a user name and a corresponding password.
27889 Using a single fixed user name and password as an example, this could be
27890 configured as follows:
27894 public_name = PLAIN
27896 server_condition = \
27897 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
27898 server_set_id = $auth2
27900 Note that the default result strings from &%if%& (&"true"& or an empty string)
27901 are exactly what we want here, so they need not be specified. Obviously, if the
27902 password contains expansion-significant characters such as dollar, backslash,
27903 or closing brace, they have to be escaped.
27905 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
27906 the end of a string list are ignored). If all the data comes as part of the
27907 AUTH command, as is commonly the case, the prompt is not used. This
27908 authenticator is advertised in the response to EHLO as
27912 and a client host can authenticate itself by sending the command
27914 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
27916 As this contains three strings (more than the number of prompts), no further
27917 data is required from the client. Alternatively, the client may just send
27921 to initiate authentication, in which case the server replies with an empty
27922 prompt. The client must respond with the combined data string.
27924 The data string is base64 encoded, as required by the RFC. This example,
27925 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
27926 represents a zero byte. This is split up into three strings, the first of which
27927 is empty. The &%server_condition%& option in the authenticator checks that the
27928 second two are &`username`& and &`mysecret`& respectively.
27930 Having just one fixed user name and password, as in this example, is not very
27931 realistic, though for a small organization with only a handful of
27932 authenticating clients it could make sense.
27934 A more sophisticated instance of this authenticator could use the user name in
27935 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
27936 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
27937 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
27938 This is an incorrect example:
27940 server_condition = \
27941 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
27943 The expansion uses the user name (&$auth2$&) as the key to look up a password,
27944 which it then compares to the supplied password (&$auth3$&). Why is this example
27945 incorrect? It works fine for existing users, but consider what happens if a
27946 non-existent user name is given. The lookup fails, but as no success/failure
27947 strings are given for the lookup, it yields an empty string. Thus, to defeat
27948 the authentication, all a client has to do is to supply a non-existent user
27949 name and an empty password. The correct way of writing this test is:
27951 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
27952 {${if eq{$value}{$auth3}}} {false}}
27954 In this case, if the lookup succeeds, the result is checked; if the lookup
27955 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
27956 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
27957 always fails if its second argument is empty. However, the second way of
27958 writing the test makes the logic clearer.
27961 .section "The LOGIN authentication mechanism" "SECID173"
27962 .cindex "LOGIN authentication mechanism"
27963 .cindex authentication LOGIN
27964 The LOGIN authentication mechanism is not documented in any RFC, but is in use
27965 in a number of programs. No data is sent with the AUTH command. Instead, a
27966 user name and password are supplied separately, in response to prompts. The
27967 plaintext authenticator can be configured to support this as in this example:
27971 public_name = LOGIN
27972 server_prompts = User Name : Password
27973 server_condition = \
27974 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
27975 server_set_id = $auth1
27977 Because of the way plaintext operates, this authenticator accepts data supplied
27978 with the AUTH command (in contravention of the specification of LOGIN), but
27979 if the client does not supply it (as is the case for LOGIN clients), the prompt
27980 strings are used to obtain two data items.
27982 Some clients are very particular about the precise text of the prompts. For
27983 example, Outlook Express is reported to recognize only &"Username:"& and
27984 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
27985 strings. It uses the &%ldapauth%& expansion condition to check the user
27986 name and password by binding to an LDAP server:
27990 public_name = LOGIN
27991 server_prompts = Username:: : Password::
27992 server_condition = ${if and{{ \
27995 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
27996 pass=${quote:$auth2} \
27997 ldap://ldap.example.org/} }} }
27998 server_set_id = uid=$auth1,ou=people,o=example.org
28000 We have to check that the username is not empty before using it, because LDAP
28001 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
28002 operator to correctly quote the DN for authentication. However, the basic
28003 &%quote%& operator, rather than any of the LDAP quoting operators, is the
28004 correct one to use for the password, because quoting is needed only to make
28005 the password conform to the Exim syntax. At the LDAP level, the password is an
28006 uninterpreted string.
28009 .section "Support for different kinds of authentication" "SECID174"
28010 A number of string expansion features are provided for the purpose of
28011 interfacing to different ways of user authentication. These include checking
28012 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
28013 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
28019 .section "Using plaintext in a client" "SECID175"
28020 .cindex "options" "&(plaintext)& authenticator (client)"
28021 The &(plaintext)& authenticator has two client options:
28023 .option client_ignore_invalid_base64 plaintext boolean false
28024 If the client receives a server prompt that is not a valid base64 string,
28025 authentication is abandoned by default. However, if this option is set true,
28026 the error in the challenge is ignored and the client sends the response as
28029 .option client_send plaintext string&!! unset
28030 The string is a colon-separated list of authentication data strings. Each
28031 string is independently expanded before being sent to the server. The first
28032 string is sent with the AUTH command; any more strings are sent in response
28033 to prompts from the server. Before each string is expanded, the value of the
28034 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
28035 with &$auth1$& for the first prompt. Up to three prompts are stored in this
28036 way. Thus, the prompt that is received in response to sending the first string
28037 (with the AUTH command) can be used in the expansion of the second string, and
28038 so on. If an invalid base64 string is received when
28039 &%client_ignore_invalid_base64%& is set, an empty string is put in the
28040 &$auth$&<&'n'&> variable.
28042 &*Note*&: You cannot use expansion to create multiple strings, because
28043 splitting takes priority and happens first.
28045 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
28046 the data, further processing is applied to each string before it is sent. If
28047 there are any single circumflex characters in the string, they are converted to
28048 NULs. Should an actual circumflex be required as data, it must be doubled in
28051 This is an example of a client configuration that implements the PLAIN
28052 authentication mechanism with a fixed user name and password:
28056 public_name = PLAIN
28057 client_send = ^username^mysecret
28059 The lack of colons means that the entire text is sent with the AUTH
28060 command, with the circumflex characters converted to NULs.
28061 Note that due to the ambiguity of parsing three consectutive circumflex characters
28062 there is no way to provide a password having a leading circumflex.
28066 that uses the LOGIN mechanism is:
28070 public_name = LOGIN
28071 client_send = : username : mysecret
28073 The initial colon means that the first string is empty, so no data is sent with
28074 the AUTH command itself. The remaining strings are sent in response to
28076 .ecindex IIDplaiauth1
28077 .ecindex IIDplaiauth2
28082 . ////////////////////////////////////////////////////////////////////////////
28083 . ////////////////////////////////////////////////////////////////////////////
28085 .chapter "The cram_md5 authenticator" "CHID9"
28086 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
28087 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
28088 .cindex "CRAM-MD5 authentication mechanism"
28089 .cindex authentication CRAM-MD5
28090 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
28091 sends a challenge string to the client, and the response consists of a user
28092 name and the CRAM-MD5 digest of the challenge string combined with a secret
28093 string (password) which is known to both server and client. Thus, the secret
28094 is not sent over the network as plain text, which makes this authenticator more
28095 secure than &(plaintext)&. However, the downside is that the secret has to be
28096 available in plain text at either end.
28099 .section "Using cram_md5 as a server" "SECID176"
28100 .cindex "options" "&(cram_md5)& authenticator (server)"
28101 This authenticator has one server option, which must be set to configure the
28102 authenticator as a server:
28104 .option server_secret cram_md5 string&!! unset
28105 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
28106 When the server receives the client's response, the user name is placed in
28107 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
28108 obtain the password for that user. The server then computes the CRAM-MD5 digest
28109 that the client should have sent, and checks that it received the correct
28110 string. If the expansion of &%server_secret%& is forced to fail, authentication
28111 fails. If the expansion fails for some other reason, a temporary error code is
28112 returned to the client.
28114 For compatibility with previous releases of Exim, the user name is also placed
28115 in &$1$&. However, the use of this variables for this purpose is now
28116 deprecated, as it can lead to confusion in string expansions that also use
28117 numeric variables for other things.
28119 For example, the following authenticator checks that the user name given by the
28120 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
28121 user name, authentication fails.
28125 public_name = CRAM-MD5
28126 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
28127 server_set_id = $auth1
28129 .vindex "&$authenticated_id$&"
28130 If authentication succeeds, the setting of &%server_set_id%& preserves the user
28131 name in &$authenticated_id$&. A more typical configuration might look up the
28132 secret string in a file, using the user name as the key. For example:
28136 public_name = CRAM-MD5
28137 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
28139 server_set_id = $auth1
28141 Note that this expansion explicitly forces failure if the lookup fails
28142 because &$auth1$& contains an unknown user name.
28144 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
28145 using the relevant libraries, you need to know the realm to specify in the
28146 lookup and then ask for the &"userPassword"& attribute for that user in that
28151 public_name = CRAM-MD5
28152 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
28153 dbmjz{/etc/sasldb2}{$value}fail}
28154 server_set_id = $auth1
28157 .section "Using cram_md5 as a client" "SECID177"
28158 .cindex "options" "&(cram_md5)& authenticator (client)"
28159 When used as a client, the &(cram_md5)& authenticator has two options:
28163 .option client_name cram_md5 string&!! "the primary host name"
28164 This string is expanded, and the result used as the user name data when
28165 computing the response to the server's challenge.
28168 .option client_secret cram_md5 string&!! unset
28169 This option must be set for the authenticator to work as a client. Its value is
28170 expanded and the result used as the secret string when computing the response.
28174 .vindex "&$host_address$&"
28175 Different user names and secrets can be used for different servers by referring
28176 to &$host$& or &$host_address$& in the options. Forced failure of either
28177 expansion string is treated as an indication that this authenticator is not
28178 prepared to handle this case. Exim moves on to the next configured client
28179 authenticator. Any other expansion failure causes Exim to give up trying to
28180 send the message to the current server.
28182 A simple example configuration of a &(cram_md5)& authenticator, using fixed
28187 public_name = CRAM-MD5
28189 client_secret = secret
28191 .ecindex IIDcramauth1
28192 .ecindex IIDcramauth2
28196 . ////////////////////////////////////////////////////////////////////////////
28197 . ////////////////////////////////////////////////////////////////////////////
28199 .chapter "The cyrus_sasl authenticator" "CHID10"
28200 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
28201 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
28202 .cindex "Cyrus" "SASL library"
28204 The code for this authenticator was provided by Matthew Byng-Maddick while
28205 at A L Digital Ltd.
28207 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
28208 library implementation of the RFC 2222 (&"Simple Authentication and Security
28209 Layer"&). This library supports a number of authentication mechanisms,
28210 including PLAIN and LOGIN, but also several others that Exim does not support
28211 directly. In particular, there is support for Kerberos authentication.
28213 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
28214 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
28215 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
28216 name of the driver to determine which mechanism to support.
28218 Where access to some kind of secret file is required, for example, in GSSAPI
28219 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
28220 user, and that the Cyrus SASL library has no way of escalating privileges
28221 by default. You may also find you need to set environment variables,
28222 depending on the driver you are using.
28224 The application name provided by Exim is &"exim"&, so various SASL options may
28225 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
28226 Kerberos, note that because of limitations in the GSSAPI interface,
28227 changing the server keytab might need to be communicated down to the Kerberos
28228 layer independently. The mechanism for doing so is dependent upon the Kerberos
28231 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
28232 may be set to point to an alternative keytab file. Exim will pass this
28233 variable through from its own inherited environment when started as root or the
28234 Exim user. The keytab file needs to be readable by the Exim user.
28235 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
28236 environment variable. In practice, for those releases, the Cyrus authenticator
28237 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
28238 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
28241 .section "Using cyrus_sasl as a server" "SECID178"
28242 The &(cyrus_sasl)& authenticator has four private options. It puts the username
28243 (on a successful authentication) into &$auth1$&. For compatibility with
28244 previous releases of Exim, the username is also placed in &$1$&. However, the
28245 use of this variable for this purpose is now deprecated, as it can lead to
28246 confusion in string expansions that also use numeric variables for other
28250 .option server_hostname cyrus_sasl string&!! "see below"
28251 This option selects the hostname that is used when communicating with the
28252 library. The default value is &`$primary_hostname`&. It is up to the underlying
28253 SASL plug-in what it does with this data.
28256 .option server_mech cyrus_sasl string "see below"
28257 This option selects the authentication mechanism this driver should use. The
28258 default is the value of the generic &%public_name%& option. This option allows
28259 you to use a different underlying mechanism from the advertised name. For
28263 driver = cyrus_sasl
28264 public_name = X-ANYTHING
28265 server_mech = CRAM-MD5
28266 server_set_id = $auth1
28269 .option server_realm cyrus_sasl string&!! unset
28270 This specifies the SASL realm that the server claims to be in.
28273 .option server_service cyrus_sasl string &`smtp`&
28274 This is the SASL service that the server claims to implement.
28277 For straightforward cases, you do not need to set any of the authenticator's
28278 private options. All you need to do is to specify an appropriate mechanism as
28279 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
28280 PLAIN, you could have two authenticators as follows:
28283 driver = cyrus_sasl
28284 public_name = CRAM-MD5
28285 server_set_id = $auth1
28288 driver = cyrus_sasl
28289 public_name = PLAIN
28290 server_set_id = $auth2
28292 Cyrus SASL does implement the LOGIN authentication method, even though it is
28293 not a standard method. It is disabled by default in the source distribution,
28294 but it is present in many binary distributions.
28295 .ecindex IIDcyrauth1
28296 .ecindex IIDcyrauth2
28301 . ////////////////////////////////////////////////////////////////////////////
28302 . ////////////////////////////////////////////////////////////////////////////
28303 .chapter "The dovecot authenticator" "CHAPdovecot"
28304 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
28305 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
28306 This authenticator is an interface to the authentication facility of the
28307 Dovecot 2 POP/IMAP server, which can support a number of authentication methods.
28308 Note that Dovecot must be configured to use auth-client not auth-userdb.
28309 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
28310 to use the same mechanisms for SMTP authentication. This is a server
28311 authenticator only. There is only one non-generic option:
28313 .option server_socket dovecot string unset
28315 This option must specify the UNIX socket that is the interface to Dovecot
28316 authentication. The &%public_name%& option must specify an authentication
28317 mechanism that Dovecot is configured to support. You can have several
28318 authenticators for different mechanisms. For example:
28322 public_name = PLAIN
28323 server_advertise_condition = ${if def:tls_in_cipher}
28324 server_socket = /var/run/dovecot/auth-client
28325 server_set_id = $auth1
28330 server_socket = /var/run/dovecot/auth-client
28331 server_set_id = $auth1
28335 &*Note*&: plaintext authentication methods such as PLAIN and LOGIN
28336 should not be advertised on cleartext SMTP connections.
28337 See the discussion in section &<<SECTplain_TLS>>&.
28340 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
28341 &$received_ip_address$& (that is, the connection is local), the &"secured"&
28342 option is passed in the Dovecot authentication command. If, for a TLS
28343 connection, a client certificate has been verified, the &"valid-client-cert"&
28344 option is passed. When authentication succeeds, the identity of the user
28345 who authenticated is placed in &$auth1$&.
28347 The Dovecot configuration to match the above will look
28350 conf.d/10-master.conf :-
28355 unix_listener auth-client {
28362 conf.d/10-auth.conf :-
28364 auth_mechanisms = plain login ntlm
28367 .ecindex IIDdcotauth1
28368 .ecindex IIDdcotauth2
28371 . ////////////////////////////////////////////////////////////////////////////
28372 . ////////////////////////////////////////////////////////////////////////////
28373 .chapter "The gsasl authenticator" "CHAPgsasl"
28374 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
28375 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
28376 .cindex "authentication" "GNU SASL"
28377 .cindex "authentication" "SASL"
28378 .cindex "authentication" "EXTERNAL"
28379 .cindex "authentication" "ANONYMOUS"
28380 .cindex "authentication" "PLAIN"
28381 .cindex "authentication" "LOGIN"
28382 .cindex "authentication" "DIGEST-MD5"
28383 .cindex "authentication" "CRAM-MD5"
28384 .cindex "authentication" "SCRAM family"
28385 The &(gsasl)& authenticator provides integration for the GNU SASL
28386 library and the mechanisms it provides. This is new as of the 4.80 release
28387 and there are a few areas where the library does not let Exim smoothly
28388 scale to handle future authentication mechanisms, so no guarantee can be
28389 made that any particular new authentication mechanism will be supported
28390 without code changes in Exim.
28392 The library is expected to add support in an upcoming
28393 realease for the SCRAM-SHA-256 method.
28394 The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
28397 To see the list of mechanisms supported by the library run Exim with "auth" debug
28398 enabled and look for a line containing "GNU SASL supports".
28399 Note however that some may not have been tested from Exim.
28402 .option client_authz gsasl string&!! unset
28403 This option can be used to supply an &'authorization id'&
28404 which is different to the &'authentication_id'& provided
28405 by &%client_username%& option.
28406 If unset or (after expansion) empty it is not used,
28407 which is the common case.
28409 .option client_channelbinding gsasl boolean false
28410 See &%server_channelbinding%& below.
28412 .option client_password gsasl string&!! unset
28413 This option is exapanded before use, and should result in
28414 the password to be used, in clear.
28416 .option client_username gsasl string&!! unset
28417 This option is exapanded before use, and should result in
28418 the account name to be used.
28421 .option client_spassword gsasl string&!! unset
28422 This option is only supported for library versions 1.9.1 and greater.
28423 The macro _HAVE_AUTH_GSASL_SCRAM_S_KEY will be defined when this is so.
28425 If a SCRAM mechanism is being used and this option is set
28426 and correctly sized
28427 it is used in preference to &%client_password%&.
28428 The value after expansion should be
28429 a 40 (for SHA-1) or 64 (for SHA-256) character string
28430 with the PBKDF2-prepared password, hex-encoded.
28432 Note that this value will depend on the salt and iteration-count
28433 supplied by the server.
28434 The option is expanded before use.
28435 During the expansion &$auth1$& is set with the client username,
28436 &$auth2$& with the iteration count, and
28437 &$auth3$& with the salt.
28439 The intent of this option
28440 is to support clients that can cache thes salted password
28441 to save on recalculation costs.
28442 The cache lookup should return an unusable value
28443 (eg. an empty string)
28444 if the salt or iteration count has changed
28446 If the authentication succeeds then the above variables are set,
28447 .vindex "&$auth4$&"
28448 plus the calculated salted password value value in &$auth4$&,
28449 during the expansion of the &%client_set_id%& option.
28450 A side-effect of this expansion can be used to prime the cache.
28453 .option server_channelbinding gsasl boolean false
28454 Some authentication mechanisms are able to use external context at both ends
28455 of the session to bind the authentication to that context, and fail the
28456 authentication process if that context differs. Specifically, some TLS
28457 ciphersuites can provide identifying information about the cryptographic
28460 This should have meant that certificate identity and verification becomes a
28461 non-issue, as a man-in-the-middle attack will cause the correct client and
28462 server to see different identifiers and authentication will fail.
28465 only usable by mechanisms which support "channel binding"; at time of
28466 writing, that's the SCRAM family.
28467 When using this feature the "-PLUS" variants of the method names need to be used.
28469 This defaults off to ensure smooth upgrade across Exim releases, in case
28470 this option causes some clients to start failing. Some future release
28471 of Exim might have switched the default to be true.
28473 . However, Channel Binding in TLS has proven to be vulnerable in current versions.
28474 . Do not plan to rely upon this feature for security, ever, without consulting
28475 . with a subject matter expert (a cryptographic engineer).
28477 This option was deprecated in previous releases due to doubts over
28478 the "Triple Handshake" vulnerability.
28479 Exim takes suitable precausions (requiring Extended Master Secret if TLS
28480 Session Resumption was used) for safety.
28483 .option server_hostname gsasl string&!! "see below"
28484 This option selects the hostname that is used when communicating with the
28485 library. The default value is &`$primary_hostname`&.
28486 Some mechanisms will use this data.
28489 .option server_mech gsasl string "see below"
28490 This option selects the authentication mechanism this driver should use. The
28491 default is the value of the generic &%public_name%& option. This option allows
28492 you to use a different underlying mechanism from the advertised name. For
28497 public_name = X-ANYTHING
28498 server_mech = CRAM-MD5
28499 server_set_id = $auth1
28503 .option server_password gsasl string&!! unset
28504 Various mechanisms need access to the cleartext password on the server, so
28505 that proof-of-possession can be demonstrated on the wire, without sending
28506 the password itself.
28508 The data available for lookup varies per mechanism.
28509 In all cases, &$auth1$& is set to the &'authentication id'&.
28510 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
28511 if available, else the empty string.
28512 The &$auth3$& variable will always be the &'realm'& if available,
28513 else the empty string.
28515 A forced failure will cause authentication to defer.
28517 If using this option, it may make sense to set the &%server_condition%&
28518 option to be simply "true".
28521 .option server_realm gsasl string&!! unset
28522 This specifies the SASL realm that the server claims to be in.
28523 Some mechanisms will use this data.
28526 .option server_scram_iter gsasl string&!! 4096
28527 This option provides data for the SCRAM family of mechanisms.
28528 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28529 when this option is expanded.
28531 The result of expansion should be a decimal number,
28532 and represents both a lower-bound on the security, and
28533 a compute cost factor imposed on the client
28534 (if it does not cache results, or the server changes
28535 either the iteration count or the salt).
28536 A minimum value of 4096 is required by the standards
28537 for all current SCRAM mechanism variants.
28539 .option server_scram_salt gsasl string&!! unset
28540 This option provides data for the SCRAM family of mechanisms.
28541 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28542 when this option is expanded.
28543 The value should be a base64-encoded string,
28544 of random data typically 4-to-16 bytes long.
28545 If unset or empty after expansion the library will provides a value for the
28546 protocol conversation.
28549 .option server_key gsasl string&!! unset
28550 .option server_skey gsasl string&!! unset
28551 These options can be used for the SCRAM family of mechanisms
28552 to provide stored information related to a password,
28553 the storage of which is preferable to plaintext.
28555 &%server_key%& is the value defined in the SCRAM standards as ServerKey;
28556 &%server_skey%& is StoredKey.
28558 They are only available for version 1.9.0 (or later) of the gsasl library.
28559 When this is so, the macros
28560 _OPT_AUTHENTICATOR_GSASL_SERVER_KEY
28561 and _HAVE_AUTH_GSASL_SCRAM_S_KEY
28564 The &$authN$& variables are available when these options are expanded.
28566 If set, the results of expansion should for each
28567 should be a 28 (for SHA-1) or 44 (for SHA-256) character string
28568 of base64-coded data, and will be used in preference to the
28569 &%server_password%& option.
28570 If unset or not of the right length, &%server_password%& will be used.
28572 The libgsasl library release includes a utility &'gsasl'& which can be used
28573 to generate these values.
28576 .option server_service gsasl string &`smtp`&
28577 This is the SASL service that the server claims to implement.
28578 Some mechanisms will use this data.
28581 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
28582 .vindex "&$auth1$&, &$auth2$&, etc"
28583 These may be set when evaluating specific options, as detailed above.
28584 They will also be set when evaluating &%server_condition%&.
28586 Unless otherwise stated below, the &(gsasl)& integration will use the following
28587 meanings for these variables:
28590 .vindex "&$auth1$&"
28591 &$auth1$&: the &'authentication id'&
28593 .vindex "&$auth2$&"
28594 &$auth2$&: the &'authorization id'&
28596 .vindex "&$auth3$&"
28597 &$auth3$&: the &'realm'&
28600 On a per-mechanism basis:
28603 .cindex "authentication" "EXTERNAL"
28604 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
28605 the &%server_condition%& option must be present.
28607 .cindex "authentication" "ANONYMOUS"
28608 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
28609 the &%server_condition%& option must be present.
28611 .cindex "authentication" "GSSAPI"
28612 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
28613 &$auth2$& will be set to the &'authorization id'&,
28614 the &%server_condition%& option must be present.
28617 An &'anonymous token'& is something passed along as an unauthenticated
28618 identifier; this is analogous to FTP anonymous authentication passing an
28619 email address, or software-identifier@, as the "password".
28622 An example showing the password having the realm specified in the callback
28623 and demonstrating a Cyrus SASL to GSASL migration approach is:
28625 gsasl_cyrusless_crammd5:
28627 public_name = CRAM-MD5
28628 server_realm = imap.example.org
28629 server_password = ${lookup{$auth1:$auth3:userPassword}\
28630 dbmjz{/etc/sasldb2}{$value}fail}
28631 server_set_id = ${quote:$auth1}
28632 server_condition = yes
28636 . ////////////////////////////////////////////////////////////////////////////
28637 . ////////////////////////////////////////////////////////////////////////////
28639 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
28640 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
28641 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
28642 .cindex "authentication" "GSSAPI"
28643 .cindex "authentication" "Kerberos"
28644 The &(heimdal_gssapi)& authenticator provides server integration for the
28645 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
28648 .option server_hostname heimdal_gssapi string&!! "see below"
28649 This option selects the hostname that is used, with &%server_service%&,
28650 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
28651 identifier. The default value is &`$primary_hostname`&.
28653 .option server_keytab heimdal_gssapi string&!! unset
28654 If set, then Heimdal will not use the system default keytab (typically
28655 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
28656 The value should be a pathname, with no &"file:"& prefix.
28658 .option server_service heimdal_gssapi string&!! "smtp"
28659 This option specifies the service identifier used, in conjunction with
28660 &%server_hostname%&, for building the identifier for finding credentials
28664 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
28665 Beware that these variables will typically include a realm, thus will appear
28666 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
28667 not verified, so a malicious client can set it to anything.
28669 The &$auth1$& field should be safely trustable as a value from the Key
28670 Distribution Center. Note that these are not quite email addresses.
28671 Each identifier is for a role, and so the left-hand-side may include a
28672 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
28674 .vindex "&$auth1$&, &$auth2$&, etc"
28676 .vindex "&$auth1$&"
28677 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
28679 .vindex "&$auth2$&"
28680 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
28681 authentication. If that was empty, this will also be set to the
28686 . ////////////////////////////////////////////////////////////////////////////
28687 . ////////////////////////////////////////////////////////////////////////////
28689 .chapter "The spa authenticator" "CHAPspa"
28690 .scindex IIDspaauth1 "&(spa)& authenticator"
28691 .scindex IIDspaauth2 "authenticators" "&(spa)&"
28692 .cindex "authentication" "Microsoft Secure Password"
28693 .cindex "authentication" "NTLM"
28694 .cindex "Microsoft Secure Password Authentication"
28695 .cindex "NTLM authentication"
28696 The &(spa)& authenticator provides client support for Microsoft's &'Secure
28697 Password Authentication'& mechanism,
28698 which is also sometimes known as NTLM (NT LanMan). The code for client side of
28699 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
28700 taken from the Samba project (&url(https://www.samba.org/)). The code for the
28701 server side was subsequently contributed by Tom Kistner. The mechanism works as
28705 After the AUTH command has been accepted, the client sends an SPA
28706 authentication request based on the user name and optional domain.
28708 The server sends back a challenge.
28710 The client builds a challenge response which makes use of the user's password
28711 and sends it to the server, which then accepts or rejects it.
28714 Encryption is used to protect the password in transit.
28718 .section "Using spa as a server" "SECID179"
28719 .cindex "options" "&(spa)& authenticator (server)"
28720 The &(spa)& authenticator has just one server option:
28722 .option server_password spa string&!! unset
28723 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
28724 This option is expanded, and the result must be the cleartext password for the
28725 authenticating user, whose name is at this point in &$auth1$&. For
28726 compatibility with previous releases of Exim, the user name is also placed in
28727 &$1$&. However, the use of this variable for this purpose is now deprecated, as
28728 it can lead to confusion in string expansions that also use numeric variables
28729 for other things. For example:
28734 server_password = \
28735 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
28737 If the expansion is forced to fail, authentication fails. Any other expansion
28738 failure causes a temporary error code to be returned.
28744 .section "Using spa as a client" "SECID180"
28745 .cindex "options" "&(spa)& authenticator (client)"
28746 The &(spa)& authenticator has the following client options:
28750 .option client_domain spa string&!! unset
28751 This option specifies an optional domain for the authentication.
28754 .option client_password spa string&!! unset
28755 This option specifies the user's password, and must be set.
28758 .option client_username spa string&!! unset
28759 This option specifies the user name, and must be set. Here is an example of a
28760 configuration of this authenticator for use with the mail servers at
28766 client_username = msn/msn_username
28767 client_password = msn_plaintext_password
28768 client_domain = DOMAIN_OR_UNSET
28770 .ecindex IIDspaauth1
28771 .ecindex IIDspaauth2
28777 . ////////////////////////////////////////////////////////////////////////////
28778 . ////////////////////////////////////////////////////////////////////////////
28780 .chapter "The external authenticator" "CHAPexternauth"
28781 .scindex IIDexternauth1 "&(external)& authenticator"
28782 .scindex IIDexternauth2 "authenticators" "&(external)&"
28783 .cindex "authentication" "Client Certificate"
28784 .cindex "authentication" "X509"
28785 .cindex "Certificate-based authentication"
28786 The &(external)& authenticator provides support for
28787 authentication based on non-SMTP information.
28788 The specification is in RFC 4422 Appendix A
28789 (&url(https://tools.ietf.org/html/rfc4422)).
28790 It is only a transport and negotiation mechanism;
28791 the process of authentication is entirely controlled
28792 by the server configuration.
28794 The client presents an identity in-clear.
28795 It is probably wise for a server to only advertise,
28796 and for clients to only attempt,
28797 this authentication method on a secure (eg. under TLS) connection.
28799 One possible use, compatible with the
28800 K-9 Mail Android client (&url(https://k9mail.github.io/)),
28801 is for using X509 client certificates.
28803 It thus overlaps in function with the TLS authenticator
28804 (see &<<CHAPtlsauth>>&)
28805 but is a full SMTP SASL authenticator
28806 rather than being implicit for TLS-connection carried
28807 client certificates only.
28809 The examples and discussion in this chapter assume that
28810 client-certificate authentication is being done.
28812 The client must present a certificate,
28813 for which it must have been requested via the
28814 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28815 (see &<<CHAPTLS>>&).
28816 For authentication to be effective the certificate should be
28817 verifiable against a trust-anchor certificate known to the server.
28819 .section "External options" "SECTexternsoptions"
28820 .cindex "options" "&(external)& authenticator (server)"
28821 The &(external)& authenticator has two server options:
28823 .option server_param2 external string&!! unset
28824 .option server_param3 external string&!! unset
28825 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(external)& authenticator"
28826 These options are expanded before the &%server_condition%& option
28827 and the result are placed in &$auth2$& and &$auth3$& resectively.
28828 If the expansion is forced to fail, authentication fails. Any other expansion
28829 failure causes a temporary error code to be returned.
28831 They can be used to clarify the coding of a complex &%server_condition%&.
28833 .section "Using external in a server" "SECTexternserver"
28834 .cindex "AUTH" "in &(external)& authenticator"
28835 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
28836 "in &(external)& authenticator"
28837 .vindex "&$auth1$&, &$auth2$&, etc"
28838 .cindex "base64 encoding" "in &(external)& authenticator"
28840 When running as a server, &(external)& performs the authentication test by
28841 expanding a string. The data sent by the client with the AUTH command, or in
28842 response to subsequent prompts, is base64 encoded, and so may contain any byte
28843 values when decoded. The decoded value is treated as
28844 an identity for authentication and
28845 placed in the expansion variable &$auth1$&.
28847 For compatibility with previous releases of Exim, the value is also placed in
28848 the expansion variable &$1$&. However, the use of this
28849 variable for this purpose is now deprecated, as it can lead to confusion in
28850 string expansions that also use them for other things.
28852 .vindex "&$authenticated_id$&"
28853 Once an identity has been received,
28854 &%server_condition%& is expanded. If the expansion is forced to fail,
28855 authentication fails. Any other expansion failure causes a temporary error code
28856 to be returned. If the result of a successful expansion is an empty string,
28857 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
28858 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
28859 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
28860 For any other result, a temporary error code is returned, with the expanded
28861 string as the error text.
28865 ext_ccert_san_mail:
28867 public_name = EXTERNAL
28869 server_advertise_condition = $tls_in_certificate_verified
28870 server_param2 = ${certextract {subj_altname,mail,>:} \
28871 {$tls_in_peercert}}
28872 server_condition = ${if forany {$auth2} \
28873 {eq {$item}{$auth1}}}
28874 server_set_id = $auth1
28876 This accepts a client certificate that is verifiable against any
28877 of your configured trust-anchors
28878 (which usually means the full set of public CAs)
28879 and which has a mail-SAN matching the claimed identity sent by the client.
28881 &*Note*&: up to TLS1.2, the client cert is on the wire in-clear, including the SAN.
28882 The account name is therefore guessable by an opponent.
28883 TLS 1.3 protects both server and client certificates, and is not vulnerable
28887 .section "Using external in a client" "SECTexternclient"
28888 .cindex "options" "&(external)& authenticator (client)"
28889 The &(external)& authenticator has one client option:
28891 .option client_send external string&!! unset
28892 This option is expanded and sent with the AUTH command as the
28893 identity being asserted.
28899 public_name = EXTERNAL
28901 client_condition = ${if !eq{$tls_out_cipher}{}}
28902 client_send = myaccount@smarthost.example.net
28906 .ecindex IIDexternauth1
28907 .ecindex IIDexternauth2
28913 . ////////////////////////////////////////////////////////////////////////////
28914 . ////////////////////////////////////////////////////////////////////////////
28916 .chapter "The tls authenticator" "CHAPtlsauth"
28917 .scindex IIDtlsauth1 "&(tls)& authenticator"
28918 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
28919 .cindex "authentication" "Client Certificate"
28920 .cindex "authentication" "X509"
28921 .cindex "Certificate-based authentication"
28922 The &(tls)& authenticator provides server support for
28923 authentication based on client certificates.
28925 It is not an SMTP authentication mechanism and is not
28926 advertised by the server as part of the SMTP EHLO response.
28927 It is an Exim authenticator in the sense that it affects
28928 the protocol element of the log line, can be tested for
28929 by the &%authenticated%& ACL condition, and can set
28930 the &$authenticated_id$& variable.
28932 The client must present a verifiable certificate,
28933 for which it must have been requested via the
28934 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28935 (see &<<CHAPTLS>>&).
28937 If an authenticator of this type is configured it is
28938 run before any SMTP-level communication is done,
28939 and can authenticate the connection.
28940 If it does, SMTP authentication is not offered.
28942 A maximum of one authenticator of this type may be present.
28945 .cindex "options" "&(tls)& authenticator (server)"
28946 The &(tls)& authenticator has three server options:
28948 .option server_param1 tls string&!! unset
28949 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
28950 This option is expanded after the TLS negotiation and
28951 the result is placed in &$auth1$&.
28952 If the expansion is forced to fail, authentication fails. Any other expansion
28953 failure causes a temporary error code to be returned.
28955 .option server_param2 tls string&!! unset
28956 .option server_param3 tls string&!! unset
28957 As above, for &$auth2$& and &$auth3$&.
28959 &%server_param1%& may also be spelled &%server_param%&.
28966 server_param1 = ${certextract {subj_altname,mail,>:} \
28967 {$tls_in_peercert}}
28968 server_condition = ${if and { {eq{$tls_in_certificate_verified}{1}} \
28971 {${lookup ldap{ldap:///\
28972 mailname=${quote_ldap_dn:${lc:$item}},\
28973 ou=users,LDAP_DC?mailid} {$value}{0} \
28975 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
28977 This accepts a client certificate that is verifiable against any
28978 of your configured trust-anchors
28979 (which usually means the full set of public CAs)
28980 and which has a SAN with a good account name.
28982 Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
28983 The account name is therefore guessable by an opponent.
28984 TLS 1.3 protects both server and client certificates, and is not vulnerable
28986 Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
28988 . An alternative might use
28990 . server_param1 = ${sha256:$tls_in_peercert}
28992 . to require one of a set of specific certs that define a given account
28993 . (the verification is still required, but mostly irrelevant).
28994 . This would help for per-device use.
28996 . However, for the future we really need support for checking a
28997 . user cert in LDAP - which probably wants a base-64 DER.
28999 .ecindex IIDtlsauth1
29000 .ecindex IIDtlsauth2
29003 Note that because authentication is traditionally an SMTP operation,
29004 the &%authenticated%& ACL condition cannot be used in
29005 a connect- or helo-ACL.
29009 . ////////////////////////////////////////////////////////////////////////////
29010 . ////////////////////////////////////////////////////////////////////////////
29012 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
29013 "Encrypted SMTP connections"
29014 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
29015 .scindex IIDencsmtp2 "SMTP" "encryption"
29016 .cindex "TLS" "on SMTP connection"
29019 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
29020 Sockets Layer), is implemented by making use of the OpenSSL library or the
29021 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
29022 cryptographic code in the Exim distribution itself for implementing TLS. In
29023 order to use this feature you must install OpenSSL or GnuTLS, and then build a
29024 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
29025 You also need to understand the basic concepts of encryption at a managerial
29026 level, and in particular, the way that public keys, private keys, and
29027 certificates are used.
29029 RFC 3207 defines how SMTP connections can make use of encryption. Once a
29030 connection is established, the client issues a STARTTLS command. If the
29031 server accepts this, the client and the server negotiate an encryption
29032 mechanism. If the negotiation succeeds, the data that subsequently passes
29033 between them is encrypted.
29035 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
29036 and if so, what cipher suite is in use, whether the client supplied a
29037 certificate, and whether or not that certificate was verified. This makes it
29038 possible for an Exim server to deny or accept certain commands based on the
29041 &*Warning*&: Certain types of firewall and certain anti-virus products can
29042 disrupt TLS connections. You need to turn off SMTP scanning for these products
29043 in order to get TLS to work.
29047 .section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
29049 .cindex "submissions protocol"
29050 .cindex "ssmtp protocol"
29051 .cindex "smtps protocol"
29052 .cindex "SMTP" "submissions protocol"
29053 .cindex "SMTP" "ssmtp protocol"
29054 .cindex "SMTP" "smtps protocol"
29055 The history of port numbers for TLS in SMTP is a little messy and has been
29056 contentious. As of RFC 8314, the common practice of using the historically
29057 allocated port 465 for "email submission but with TLS immediately upon connect
29058 instead of using STARTTLS" is officially blessed by the IETF, and recommended
29059 by them in preference to STARTTLS.
29061 The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
29062 clarity emerged over the dual roles of SMTP, for MX delivery and Email
29063 Submission, nomenclature has shifted. The modern name is now &"submissions"&.
29065 This approach was, for a while, officially abandoned when encrypted SMTP was
29066 standardized, but many clients kept using it, even as the TCP port number was
29067 reassigned for other use.
29068 Thus you may encounter guidance claiming that you shouldn't enable use of
29070 In practice, a number of mail-clients have only ever supported submissions,
29071 not submission with STARTTLS upgrade.
29072 Ideally, offer both submission (587) and submissions (465) service.
29074 Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
29075 global option. Its value must be a list of port numbers;
29076 the most common use is expected to be:
29078 tls_on_connect_ports = 465
29080 The port numbers specified by this option apply to all SMTP connections, both
29081 via the daemon and via &'inetd'&. You still need to specify all the ports that
29082 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
29083 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
29084 an extra port &-- rather, it specifies different behaviour on a port that is
29087 There is also a &%-tls-on-connect%& command line option. This overrides
29088 &%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
29095 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
29096 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
29097 TLS is supported in Exim using either the OpenSSL or GnuTLS library.
29098 To build Exim to use OpenSSL you need to set
29104 To build Exim to use GnuTLS, you need to set
29110 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
29111 include files and libraries for GnuTLS can be found.
29113 There are some differences in usage when using GnuTLS instead of OpenSSL:
29116 The &%tls_verify_certificates%& option
29117 cannot be the path of a directory
29118 for GnuTLS versions before 3.3.6
29119 (for later versions, or OpenSSL, it can be either).
29121 The default value for &%tls_dhparam%& differs for historical reasons.
29123 .vindex "&$tls_in_peerdn$&"
29124 .vindex "&$tls_out_peerdn$&"
29125 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
29126 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
29127 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
29129 OpenSSL identifies cipher suites using hyphens as separators, for example:
29130 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
29131 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
29132 in a cipher list. To make life simpler, Exim changes underscores to hyphens
29133 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
29134 to handle its own older variants) when processing lists of cipher suites in the
29135 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
29138 The &%tls_require_ciphers%& options operate differently, as described in the
29139 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
29141 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
29142 When using OpenSSL, this option is ignored.
29143 (If an API is found to let OpenSSL be configured in this way,
29144 let the Exim Maintainers know and we'll likely use it).
29146 With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
29147 main option, it must be ordered to match the &%tls_certificate%& list.
29149 Some other recently added features may only be available in one or the other.
29150 This should be documented with the feature. If the documentation does not
29151 explicitly state that the feature is infeasible in the other TLS
29152 implementation, then patches are welcome.
29154 The output from "exim -bV" will show which (if any) support was included
29156 Also, the macro "_HAVE_OPENSSL" or "_HAVE_GNUTLS" will be defined.
29160 .section "GnuTLS parameter computation" "SECTgnutlsparam"
29161 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
29162 an explicit path; if the latter, then the text about generation still applies,
29163 but not the chosen filename.
29164 By default, as of Exim 4.80 a hard-coded D-H prime is used.
29165 See the documentation of &%tls_dhparam%& for more information.
29167 GnuTLS uses D-H parameters that may take a substantial amount of time
29168 to compute. It is unreasonable to re-compute them for every TLS session.
29169 Therefore, Exim keeps this data in a file in its spool directory, called
29170 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
29172 The file is owned by the Exim user and is readable only by
29173 its owner. Every Exim process that start up GnuTLS reads the D-H
29174 parameters from this file. If the file does not exist, the first Exim process
29175 that needs it computes the data and writes it to a temporary file which is
29176 renamed once it is complete. It does not matter if several Exim processes do
29177 this simultaneously (apart from wasting a few resources). Once a file is in
29178 place, new Exim processes immediately start using it.
29180 For maximum security, the parameters that are stored in this file should be
29181 recalculated periodically, the frequency depending on your paranoia level.
29182 If you are avoiding using the fixed D-H primes published in RFCs, then you
29183 are concerned about some advanced attacks and will wish to do this; if you do
29184 not regenerate then you might as well stick to the standard primes.
29186 Arranging this is easy in principle; just delete the file when you want new
29187 values to be computed. However, there may be a problem. The calculation of new
29188 parameters needs random numbers, and these are obtained from &_/dev/random_&.
29189 If the system is not very active, &_/dev/random_& may delay returning data
29190 until enough randomness (entropy) is available. This may cause Exim to hang for
29191 a substantial amount of time, causing timeouts on incoming connections.
29193 The solution is to generate the parameters externally to Exim. They are stored
29194 in &_gnutls-params-N_& in PEM format, which means that they can be
29195 generated externally using the &(certtool)& command that is part of GnuTLS.
29197 To replace the parameters with new ones, instead of deleting the file
29198 and letting Exim re-create it, you can generate new parameters using
29199 &(certtool)& and, when this has been done, replace Exim's cache file by
29200 renaming. The relevant commands are something like this:
29203 [ look for file; assume gnutls-params-2236 is the most recent ]
29206 # chown exim:exim new-params
29207 # chmod 0600 new-params
29208 # certtool --generate-dh-params --bits 2236 >>new-params
29209 # openssl dhparam -noout -text -in new-params | head
29210 [ check the first line, make sure it's not more than 2236;
29211 if it is, then go back to the start ("rm") and repeat
29212 until the size generated is at most the size requested ]
29213 # chmod 0400 new-params
29214 # mv new-params gnutls-params-2236
29216 If Exim never has to generate the parameters itself, the possibility of
29217 stalling is removed.
29219 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
29220 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
29221 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
29222 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
29223 and Exim does so. This attempt to remove Exim from TLS policy decisions
29224 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
29225 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
29226 which applies to all D-H usage, client or server. If the value returned by
29227 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
29228 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
29229 limit, which is still much higher than Exim historically used.
29231 The filename and bits used will change as the GnuTLS maintainers change the
29232 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
29233 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
29234 2432 bits, while NSS is limited to 2236 bits.
29236 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
29237 increase the chance of the generated prime actually being within acceptable
29238 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
29239 procedure above. There is no sane procedure available to Exim to double-check
29240 the size of the generated prime, so it might still be too large.
29243 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
29244 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
29245 .oindex "&%tls_require_ciphers%&" "OpenSSL"
29246 There is a function in the OpenSSL library that can be passed a list of cipher
29247 suites before the cipher negotiation takes place. This specifies which ciphers
29248 are acceptable for TLS versions prior to 1.3.
29249 The list is colon separated and may contain names like
29250 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
29251 directly to this function call.
29252 Many systems will install the OpenSSL manual-pages, so you may have
29253 &'ciphers(1)'& available to you.
29254 The following quotation from the OpenSSL
29255 documentation specifies what forms of item are allowed in the cipher string:
29258 It can consist of a single cipher suite such as RC4-SHA.
29260 It can represent a list of cipher suites containing a certain algorithm,
29261 or cipher suites of a certain type. For example SHA1 represents all
29262 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
29265 Lists of cipher suites can be combined in a single cipher string using
29266 the + character. This is used as a logical and operation. For example
29267 SHA1+DES represents all cipher suites containing the SHA1 and the DES
29271 Each cipher string can be optionally preceded by one of the characters &`!`&,
29274 If &`!`& is used, the ciphers are permanently deleted from the list. The
29275 ciphers deleted can never reappear in the list even if they are explicitly
29278 If &`-`& is used, the ciphers are deleted from the list, but some or all
29279 of the ciphers can be added again by later options.
29281 If &`+`& is used, the ciphers are moved to the end of the list. This
29282 option does not add any new ciphers; it just moves matching existing ones.
29285 If none of these characters is present, the string is interpreted as
29286 a list of ciphers to be appended to the current preference list. If the list
29287 includes any ciphers already present they will be ignored: that is, they will
29288 not be moved to the end of the list.
29291 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
29294 # note single-quotes to get ! past any shell history expansion
29295 $ openssl ciphers 'HIGH:!MD5:!SHA1'
29298 This example will let the library defaults be permitted on the MX port, where
29299 there's probably no identity verification anyway, but ups the ante on the
29300 submission ports where the administrator might have some influence on the
29301 choice of clients used:
29303 # OpenSSL variant; see man ciphers(1)
29304 tls_require_ciphers = ${if =={$received_port}{25}\
29309 This example will prefer ECDSA-authenticated ciphers over RSA ones:
29311 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
29314 For TLS version 1.3 the control available is less fine-grained
29315 and Exim does not provide access to it at present.
29316 The value of the &%tls_require_ciphers%& option is ignored when
29317 TLS version 1.3 is negotiated.
29319 As of writing the library default cipher suite list for TLSv1.3 is
29321 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
29325 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
29327 .cindex "GnuTLS" "specifying parameters for"
29328 .cindex "TLS" "specifying ciphers (GnuTLS)"
29329 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
29330 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
29331 .cindex "TLS" "specifying protocols (GnuTLS)"
29332 .cindex "TLS" "specifying priority string (GnuTLS)"
29333 .oindex "&%tls_require_ciphers%&" "GnuTLS"
29334 The GnuTLS library allows the caller to provide a "priority string", documented
29335 as part of the &[gnutls_priority_init]& function. This is very similar to the
29336 ciphersuite specification in OpenSSL.
29338 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
29339 and controls both protocols and ciphers.
29341 The &%tls_require_ciphers%& option is available both as an global option,
29342 controlling how Exim behaves as a server, and also as an option of the
29343 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
29344 the value is string expanded. The resulting string is not an Exim list and
29345 the string is given to the GnuTLS library, so that Exim does not need to be
29346 aware of future feature enhancements of GnuTLS.
29348 Documentation of the strings accepted may be found in the GnuTLS manual, under
29349 "Priority strings". This is online as
29350 &url(https://www.gnutls.org/manual/html_node/Priority-Strings.html),
29351 but beware that this relates to GnuTLS 3, which may be newer than the version
29352 installed on your system. If you are using GnuTLS 3,
29353 then the example code
29354 &url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
29355 on that site can be used to test a given string.
29359 # Disable older versions of protocols
29360 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
29363 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
29364 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
29365 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
29367 This example will let the library defaults be permitted on the MX port, where
29368 there's probably no identity verification anyway, and lowers security further
29369 by increasing compatibility; but this ups the ante on the submission ports
29370 where the administrator might have some influence on the choice of clients
29374 tls_require_ciphers = ${if =={$received_port}{25}\
29380 .section "Configuring an Exim server to use TLS" "SECID182"
29381 .cindex "TLS" "configuring an Exim server"
29382 .cindex "ESMTP extensions" STARTTLS
29383 When Exim has been built with TLS support, it advertises the availability of
29384 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
29385 but not to any others. The default value of this option is *, which means
29386 that STARTTLS is always advertised. Set it to blank to never advertise;
29387 this is reasonable for systems that want to use TLS only as a client.
29389 If STARTTLS is to be used you
29390 need to set some other options in order to make TLS available.
29392 If a client issues a STARTTLS command and there is some configuration
29393 problem in the server, the command is rejected with a 454 error. If the client
29394 persists in trying to issue SMTP commands, all except QUIT are rejected
29397 554 Security failure
29399 If a STARTTLS command is issued within an existing TLS session, it is
29400 rejected with a 554 error code.
29402 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
29403 must be set to match some hosts. The default is * which matches all hosts.
29405 If this is all you do, TLS encryption will be enabled but not authentication -
29406 meaning that the peer has no assurance it is actually you he is talking to.
29407 You gain protection from a passive sniffer listening on the wire but not
29408 from someone able to intercept the communication.
29410 Further protection requires some further configuration at the server end.
29412 To make TLS work you need to set, in the server,
29414 tls_certificate = /some/file/name
29415 tls_privatekey = /some/file/name
29417 These options are, in fact, expanded strings, so you can make them depend on
29418 the identity of the client that is connected if you wish. The first file
29419 contains the server's X509 certificate, and the second contains the private key
29420 that goes with it. These files need to be
29421 PEM format and readable by the Exim user, and must
29422 always be given as full path names.
29423 The key must not be password-protected.
29424 They can be the same file if both the
29425 certificate and the key are contained within it. If &%tls_privatekey%& is not
29426 set, or if its expansion is forced to fail or results in an empty string, this
29427 is assumed to be the case. The certificate file may also contain intermediate
29428 certificates that need to be sent to the client to enable it to authenticate
29429 the server's certificate.
29431 For dual-stack (eg. RSA and ECDSA) configurations, these options can be
29432 colon-separated lists of file paths. Ciphers using given authentication
29433 algorithms require the presence of a suitable certificate to supply the
29434 public-key. The server selects among the certificates to present to the
29435 client depending on the selected cipher, hence the priority ordering for
29436 ciphers will affect which certificate is used.
29438 If you do not understand about certificates and keys, please try to find a
29439 source of this background information, which is not Exim-specific. (There are a
29440 few comments below in section &<<SECTcerandall>>&.)
29442 &*Note*&: These options do not apply when Exim is operating as a client &--
29443 they apply only in the case of a server. If you need to use a certificate in an
29444 Exim client, you must set the options of the same names in an &(smtp)&
29447 With just these options, an Exim server will be able to use TLS. It does not
29448 require the client to have a certificate (but see below for how to insist on
29449 this). There is one other option that may be needed in other situations. If
29451 tls_dhparam = /some/file/name
29453 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
29454 with the parameters contained in the file.
29455 Set this to &`none`& to disable use of DH entirely, by making no prime
29460 This may also be set to a string identifying a standard prime to be used for
29461 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
29462 used is &`ike23`&. There are a few standard primes available, see the
29463 documentation for &%tls_dhparam%& for the complete list.
29469 for a way of generating file data.
29471 The strings supplied for these three options are expanded every time a client
29472 host connects. It is therefore possible to use different certificates and keys
29473 for different hosts, if you so wish, by making use of the client's IP address
29474 in &$sender_host_address$& to control the expansion. If a string expansion is
29475 forced to fail, Exim behaves as if the option is not set.
29477 .cindex "cipher" "logging"
29478 .cindex "log" "TLS cipher"
29479 .vindex "&$tls_in_cipher$&"
29480 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
29481 an incoming TLS connection. It is included in the &'Received:'& header of an
29482 incoming message (by default &-- you can, of course, change this), and it is
29483 also included in the log line that records a message's arrival, keyed by
29484 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
29485 condition can be used to test for specific cipher suites in ACLs.
29487 Once TLS has been established, the ACLs that run for subsequent SMTP commands
29488 can check the name of the cipher suite and vary their actions accordingly. The
29489 cipher suite names vary, depending on which TLS library is being used. For
29490 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
29491 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
29492 documentation for more details.
29494 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
29495 (again depending on the &%tls_cipher%& log selector).
29498 .subsection "Requesting and verifying client certificates"
29499 .cindex "certificate" "verification of client"
29500 .cindex "TLS" "client certificate verification"
29501 If you want an Exim server to request a certificate when negotiating a TLS
29502 session with a client, you must set either &%tls_verify_hosts%& or
29503 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
29504 apply to all TLS connections. For any host that matches one of these options,
29505 Exim requests a certificate as part of the setup of the TLS session. The
29506 contents of the certificate are verified by comparing it with a list of
29507 expected trust-anchors or certificates.
29508 These may be the system default set (depending on library version),
29509 an explicit file or,
29510 depending on library version, a directory, identified by
29511 &%tls_verify_certificates%&.
29513 A file can contain multiple certificates, concatenated end to end. If a
29516 each certificate must be in a separate file, with a name (or a symbolic link)
29517 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
29518 certificate. You can compute the relevant hash by running the command
29520 openssl x509 -hash -noout -in /cert/file
29522 where &_/cert/file_& contains a single certificate.
29524 There is no checking of names of the client against the certificate
29525 Subject Name or Subject Alternate Names.
29527 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
29528 what happens if the client does not supply a certificate, or if the certificate
29529 does not match any of the certificates in the collection named by
29530 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
29531 attempt to set up a TLS session is aborted, and the incoming connection is
29532 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
29533 session continues. ACLs that run for subsequent SMTP commands can detect the
29534 fact that no certificate was verified, and vary their actions accordingly. For
29535 example, you can insist on a certificate before accepting a message for
29536 relaying, but not when the message is destined for local delivery.
29538 .vindex "&$tls_in_peerdn$&"
29539 When a client supplies a certificate (whether it verifies or not), the value of
29540 the Distinguished Name of the certificate is made available in the variable
29541 &$tls_in_peerdn$& during subsequent processing of the message.
29543 .cindex "log" "distinguished name"
29544 Because it is often a long text string, it is not included in the log line or
29545 &'Received:'& header by default. You can arrange for it to be logged, keyed by
29546 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
29547 &%received_header_text%& to change the &'Received:'& header. When no
29548 certificate is supplied, &$tls_in_peerdn$& is empty.
29551 .subsection "Caching of static server configuration items" "SSECTserverTLScache"
29552 .cindex certificate caching
29553 .cindex privatekey caching
29554 .cindex crl caching
29555 .cindex ocsp caching
29556 .cindex ciphers caching
29557 .cindex "CA bundle" caching
29558 .cindex "certificate authorities" caching
29559 .cindex tls_certificate caching
29560 .cindex tls_privatekey caching
29561 .cindex tls_crl caching
29562 .cindex tls_ocsp_file caching
29563 .cindex tls_require_ciphers caching
29564 .cindex tls_verify_certificate caching
29565 .cindex caching certificate
29566 .cindex caching privatekey
29567 .cindex caching crl
29568 .cindex caching ocsp
29569 .cindex caching ciphers
29570 .cindex caching "certificate authorities
29571 If any of the main configuration options &%tls_certificate%&, &%tls_privatekey%&,
29572 &%tls_crl%& and &%tls_ocsp_file%& have values with no
29573 expandable elements,
29574 then the associated information is loaded at daemon startup.
29575 It is made available
29576 to child processes forked for handling received SMTP connections.
29578 This caching is currently only supported under Linux and FreeBSD.
29580 If caching is not possible, for example if an item has to be dependent
29581 on the peer host so contains a &$sender_host_name$& expansion, the load
29582 of the associated information is done at the startup of the TLS connection.
29584 The cache is invalidated and reloaded after any changes to the directories
29585 containing files specified by these options.
29587 The information specified by the main option &%tls_verify_certificates%&
29588 is similarly cached so long as it specifies files explicitly
29589 or (under GnuTLS) is the string &"system,cache"&.
29590 The latter case is not automatically invalidated;
29591 it is the operator's responsibility to arrange for a daemon restart
29592 any time the system certificate authority bundle is updated.
29593 A HUP signal is sufficient for this.
29594 The value &"system"& results in no caching under GnuTLS.
29596 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29597 is acceptable in configurations for the Exim executavble.
29599 Caching of the system Certificate Authorities bundle can
29600 save siginificant time and processing on every TLS connection
29606 .section "Configuring an Exim client to use TLS" "SECTclientTLS"
29607 .cindex "cipher" "logging"
29608 .cindex "log" "TLS cipher"
29609 .cindex "log" "distinguished name"
29610 .cindex "TLS" "configuring an Exim client"
29611 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
29612 deliveries as well as to incoming, the latter one causing logging of the
29613 server certificate's DN. The remaining client configuration for TLS is all
29614 within the &(smtp)& transport.
29616 .cindex "ESMTP extensions" STARTTLS
29617 It is not necessary to set any options to have TLS work in the &(smtp)&
29618 transport. If Exim is built with TLS support, and TLS is advertised by a
29619 server, the &(smtp)& transport always tries to start a TLS session. However,
29620 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
29621 transport) to a list of server hosts for which TLS should not be used.
29623 If you do not want Exim to attempt to send messages unencrypted when an attempt
29624 to set up an encrypted connection fails in any way, you can set
29625 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
29626 those hosts, delivery is always deferred if an encrypted connection cannot be
29627 set up. If there are any other hosts for the address, they are tried in the
29630 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
29631 the message unencrypted. It always does this if the response to STARTTLS is
29632 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
29633 session after a success response code, what happens is controlled by the
29634 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
29635 delivery to this host is deferred, and other hosts (if available) are tried. If
29636 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
29637 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
29638 negotiation fails, Exim closes the current connection (because it is in an
29639 unknown state), opens a new one to the same host, and then tries the delivery
29642 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
29643 transport provide the client with a certificate, which is passed to the server
29645 This is an optional thing for TLS connections, although either end
29647 If the server is Exim, it will request a certificate only if
29648 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
29650 &*Note*&: Do not use a certificate which has the OCSP-must-staple extension,
29651 for client use (they are usable for server use).
29652 As the TLS protocol has no means for the client to staple before TLS 1.3 it will result
29653 in failed connections.
29655 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
29656 specifies a collection of expected server certificates.
29658 the system default set (depending on library version),
29660 or (depending on library version) a directory.
29661 The client verifies the server's certificate
29662 against this collection, taking into account any revoked certificates that are
29663 in the list defined by &%tls_crl%&.
29664 Failure to verify fails the TLS connection unless either of the
29665 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
29667 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
29668 certificate verification to the listed servers. Verification either must
29669 or need not succeed respectively.
29671 The &%tls_verify_cert_hostnames%& option lists hosts for which additional
29672 name checks are made on the server certificate.
29673 The match against this list is, as per other Exim usage, the
29674 IP for the host. That is most closely associated with the
29675 name on the DNS A (or AAAA) record for the host.
29676 However, the name that needs to be in the certificate
29677 is the one at the head of any CNAME chain leading to the A record.
29678 The option defaults to always checking.
29680 The &(smtp)& transport has two OCSP-related options:
29681 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
29682 is requested and required for the connection to proceed. The default
29684 &%hosts_request_ocsp%&; a host-list for which (additionally)
29685 a Certificate Status is requested (but not necessarily verified). The default
29686 value is "*" meaning that requests are made unless configured
29689 The host(s) should also be in &%hosts_require_tls%&, and
29690 &%tls_verify_certificates%& configured for the transport,
29691 for OCSP to be relevant.
29694 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
29695 list of permitted cipher suites. If either of these checks fails, delivery to
29696 the current host is abandoned, and the &(smtp)& transport tries to deliver to
29697 alternative hosts, if any.
29700 These options must be set in the &(smtp)& transport for Exim to use TLS when it
29701 is operating as a client. Exim does not assume that a server certificate (set
29702 by the global options of the same name) should also be used when operating as a
29706 .vindex "&$host_address$&"
29707 All the TLS options in the &(smtp)& transport are expanded before use, with
29708 &$host$& and &$host_address$& containing the name and address of the server to
29709 which the client is connected. Forced failure of an expansion causes Exim to
29710 behave as if the relevant option were unset.
29712 .vindex &$tls_out_bits$&
29713 .vindex &$tls_out_cipher$&
29714 .vindex &$tls_out_peerdn$&
29715 .vindex &$tls_out_sni$&
29716 Before an SMTP connection is established, the
29717 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
29718 variables are emptied. (Until the first connection, they contain the values
29719 that were set when the message was received.) If STARTTLS is subsequently
29720 successfully obeyed, these variables are set to the relevant values for the
29721 outgoing connection.
29725 .subsection "Caching of static client configuration items" SECTclientTLScache
29726 .cindex certificate caching
29727 .cindex privatekey caching
29728 .cindex crl caching
29729 .cindex ciphers caching
29730 .cindex "CA bundle" caching
29731 .cindex "certificate authorities" caching
29732 .cindex tls_certificate caching
29733 .cindex tls_privatekey caching
29734 .cindex tls_crl caching
29735 .cindex tls_require_ciphers caching
29736 .cindex tls_verify_certificate caching
29737 .cindex caching certificate
29738 .cindex caching privatekey
29739 .cindex caching crl
29740 .cindex caching ciphers
29741 .cindex caching "certificate authorities
29742 If any of the transport configuration options &%tls_certificate%&, &%tls_privatekey%&
29743 and &%tls_crl%& have values with no
29744 expandable elements,
29745 then the associated information is loaded per smtp transport
29746 at daemon startup, at the start of a queue run, or on a
29747 command-line specified message delivery.
29748 It is made available
29749 to child processes forked for handling making SMTP connections.
29751 This caching is currently only supported under Linux.
29753 If caching is not possible, the load
29754 of the associated information is done at the startup of the TLS connection.
29756 The cache is invalidated in the daemon
29757 and reloaded after any changes to the directories
29758 containing files specified by these options.
29760 The information specified by the main option &%tls_verify_certificates%&
29761 is similarly cached so long as it specifies files explicitly
29762 or (under GnuTLS) is the string &"system,cache"&.
29763 The latter case is not automatically invaludated;
29764 it is the operator's responsibility to arrange for a daemon restart
29765 any time the system certificate authority bundle is updated.
29766 A HUP signal is sufficient for this.
29767 The value &"system"& results in no caching under GnuTLS.
29769 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29770 is acceptable in configurations for the Exim executavble.
29772 Caching of the system Certificate Authorities bundle can
29773 save siginificant time and processing on every TLS connection
29779 .section "Use of TLS Server Name Indication" "SECTtlssni"
29780 .cindex "TLS" "Server Name Indication"
29783 .vindex "&$tls_in_sni$&"
29784 .oindex "&%tls_in_sni%&"
29785 With TLS1.0 or above, there is an extension mechanism by which extra
29786 information can be included at various points in the protocol. One of these
29787 extensions, documented in RFC 6066 (and before that RFC 4366) is
29788 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
29789 client in the initial handshake, so that the server can examine the servername
29790 within and possibly choose to use different certificates and keys (and more)
29793 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
29794 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
29797 With SMTP to MX, there are the same problems here as in choosing the identity
29798 against which to validate a certificate: you can't rely on insecure DNS to
29799 provide the identity which you then cryptographically verify. So this will
29800 be of limited use in that environment.
29802 With SMTP to Submission, there is a well-defined hostname which clients are
29803 connecting to and can validate certificates against. Thus clients &*can*&
29804 choose to include this information in the TLS negotiation. If this becomes
29805 wide-spread, then hosters can choose to present different certificates to
29806 different clients. Or even negotiate different cipher suites.
29808 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
29809 if not empty, will be sent on a TLS session as part of the handshake. There's
29810 nothing more to it. Choosing a sensible value not derived insecurely is the
29811 only point of caution. The &$tls_out_sni$& variable will be set to this string
29812 for the lifetime of the client connection (including during authentication).
29814 If DANE validated the connection attempt then the value of the &%tls_sni%& option
29815 is forced to the name of the destination host, after any MX- or CNAME-following.
29817 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
29818 received from a client.
29819 It can be logged with the &%log_selector%& item &`+tls_sni`&.
29821 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
29822 option (prior to expansion) then the following options will be re-expanded
29823 during TLS session handshake, to permit alternative values to be chosen:
29826 &%tls_certificate%&
29832 &%tls_verify_certificates%&
29837 Great care should be taken to deal with matters of case, various injection
29838 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
29839 can always be referenced; it is important to remember that &$tls_in_sni$& is
29840 arbitrary unverified data provided prior to authentication.
29841 Further, the initial certificate is loaded before SNI has arrived, so
29842 an expansion for &%tls_certificate%& must have a default which is used
29843 when &$tls_in_sni$& is empty.
29845 The Exim developers are proceeding cautiously and so far no other TLS options
29848 When Exim is built against OpenSSL, OpenSSL must have been built with support
29849 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
29850 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
29851 see &`-servername`& in the output, then OpenSSL has support.
29853 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
29854 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
29855 built, then you have SNI support).
29859 .cindex ALPN "general information"
29860 .cindex TLS "Application Layer Protocol Names"
29861 There is a TLS feature related to SNI
29862 called Application Layer Protocol Name (ALPN).
29863 This is intended to declare, or select, what protocol layer will be using a TLS
29865 The client for the connection proposes a set of protocol names, and
29866 the server responds with a selected one.
29867 It is not, as of 2021, commonly used for SMTP connections.
29868 However, to guard against misdirected or malicious use of web clients
29869 (which often do use ALPN) against MTA ports, Exim by default check that
29870 there is no incompatible ALPN specified by a client for a TLS connection.
29871 If there is, the connection is rejected.
29873 As a client Exim does not supply ALPN by default.
29874 The behaviour of both client and server can be configured using the options
29875 &%tls_alpn%& and &%hosts_require_alpn%&.
29876 There are no variables providing observability.
29877 Some feature-specific logging may appear on denied connections, but this
29878 depends on the behaviour of the peer
29879 (not all peers can send a feature-specific TLS Alert).
29881 This feature is available when Exim is built with
29882 OpenSSL 1.1.0 or later or GnuTLS 3.2.0 or later;
29883 the macro _HAVE_TLS_ALPN will be defined when this is so.
29887 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
29889 .cindex "multiple SMTP deliveries with TLS"
29890 .cindex "TLS" "multiple message deliveries"
29891 Exim sends multiple messages down the same TCP/IP connection by starting up
29892 an entirely new delivery process for each message, passing the socket from
29893 one process to the next. This implementation does not fit well with the use
29894 of TLS, because there is quite a lot of state information associated with a TLS
29895 connection, not just a socket identification. Passing all the state information
29896 to a new process is not feasible. Consequently, for sending using TLS Exim
29897 starts an additional proxy process for handling the encryption, piping the
29898 unencrypted data stream from and to the delivery processes.
29900 An older mode of operation can be enabled on a per-host basis by the
29901 &%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
29902 this list the proxy process described above is not used; instead Exim
29903 shuts down an existing TLS session being run by the delivery process
29904 before passing the socket to a new process. The new process may then
29905 try to start a new TLS session, and if successful, may try to re-authenticate
29906 if AUTH is in use, before sending the next message.
29908 The RFC is not clear as to whether or not an SMTP session continues in clear
29909 after TLS has been shut down, or whether TLS may be restarted again later, as
29910 just described. However, if the server is Exim, this shutdown and
29911 reinitialization works. It is not known which (if any) other servers operate
29912 successfully if the client closes a TLS session and continues with unencrypted
29913 SMTP, but there are certainly some that do not work. For such servers, Exim
29914 should not pass the socket to another process, because the failure of the
29915 subsequent attempt to use it would cause Exim to record a temporary host error,
29916 and delay other deliveries to that host.
29918 To test for this case, Exim sends an EHLO command to the server after
29919 closing down the TLS session. If this fails in any way, the connection is
29920 closed instead of being passed to a new delivery process, but no retry
29921 information is recorded.
29923 There is also a manual override; you can set &%hosts_nopass_tls%& on the
29924 &(smtp)& transport to match those hosts for which Exim should not pass
29925 connections to new processes if TLS has been used.
29930 .section "Certificates and all that" "SECTcerandall"
29931 .cindex "certificate" "references to discussion"
29932 In order to understand fully how TLS works, you need to know about
29933 certificates, certificate signing, and certificate authorities.
29934 This is a large topic and an introductory guide is unsuitable for the Exim
29935 reference manual, so instead we provide pointers to existing documentation.
29937 The Apache web-server was for a long time the canonical guide, so their
29938 documentation is a good place to start; their SSL module's Introduction
29939 document is currently at
29941 &url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html)
29943 and their FAQ is at
29945 &url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html)
29948 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
29949 0-201-61598-3) in 2001, contains both introductory and more in-depth
29951 More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&,
29952 published by Feisty Duck (ISBN 978-1907117046) in 2013 is good.
29953 Ivan is the author of the popular TLS testing tools at
29954 &url(https://www.ssllabs.com/).
29957 .subsection "Certificate chains" SECID186
29958 A file named by &%tls_certificate%& may contain more than one
29959 certificate. This is useful in the case where the certificate that is being
29960 sent is validated by an intermediate certificate which the other end does
29961 not have. Multiple certificates must be in the correct order in the file.
29962 First the host's certificate itself, then the first intermediate
29963 certificate to validate the issuer of the host certificate, then the next
29964 intermediate certificate to validate the issuer of the first intermediate
29965 certificate, and so on, until finally (optionally) the root certificate.
29966 The root certificate must already be trusted by the recipient for
29967 validation to succeed, of course, but if it's not preinstalled, sending the
29968 root certificate along with the rest makes it available for the user to
29969 install if the receiving end is a client MUA that can interact with a user.
29971 Note that certificates using MD5 are unlikely to work on today's Internet;
29972 even if your libraries allow loading them for use in Exim when acting as a
29973 server, increasingly clients will not accept such certificates. The error
29974 diagnostics in such a case can be frustratingly vague.
29978 .subsection "Self-signed certificates" SECID187
29979 .cindex "certificate" "self-signed"
29980 You can create a self-signed certificate using the &'req'& command provided
29981 with OpenSSL, like this:
29982 . ==== Do not shorten the duration here without reading and considering
29983 . ==== the text below. Please leave it at 9999 days.
29985 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
29988 &_file1_& and &_file2_& can be the same file; the key and the certificate are
29989 delimited and so can be identified independently. The &%-days%& option
29990 specifies a period for which the certificate is valid. The &%-nodes%& option is
29991 important: if you do not set it, the key is encrypted with a passphrase
29992 that you are prompted for, and any use that is made of the key causes more
29993 prompting for the passphrase. This is not helpful if you are going to use
29994 this certificate and key in an MTA, where prompting is not possible.
29996 . ==== I expect to still be working 26 years from now. The less technical
29997 . ==== debt I create, in terms of storing up trouble for my later years, the
29998 . ==== happier I will be then. We really have reached the point where we
29999 . ==== should start, at the very least, provoking thought and making folks
30000 . ==== pause before proceeding, instead of leaving all the fixes until two
30001 . ==== years before 2^31 seconds after the 1970 Unix epoch.
30003 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
30004 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
30005 the above command might produce a date in the past. Think carefully about
30006 the lifetime of the systems you're deploying, and either reduce the duration
30007 of the certificate or reconsider your platform deployment. (At time of
30008 writing, reducing the duration is the most likely choice, but the inexorable
30009 progression of time takes us steadily towards an era where this will not
30010 be a sensible resolution).
30012 A self-signed certificate made in this way is sufficient for testing, and
30013 may be adequate for all your requirements if you are mainly interested in
30014 encrypting transfers, and not in secure identification.
30016 However, many clients require that the certificate presented by the server be a
30017 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
30018 certificate. In this situation, the self-signed certificate described above
30019 must be installed on the client host as a trusted root &'certification
30020 authority'& (CA), and the certificate used by Exim must be a user certificate
30021 signed with that self-signed certificate.
30023 For information on creating self-signed CA certificates and using them to sign
30024 user certificates, see the &'General implementation overview'& chapter of the
30025 Open-source PKI book, available online at
30026 &url(https://sourceforge.net/projects/ospkibook/).
30029 .subsection "Revoked certificates"
30030 .cindex "TLS" "revoked certificates"
30031 .cindex "revocation list"
30032 .cindex "certificate" "revocation list"
30033 .cindex "OCSP" "stapling"
30034 There are three ways for a certificate to be made unusable
30038 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
30039 certificates are revoked. If you have such a list, you can pass it to an Exim
30040 server using the global option called &%tls_crl%& and to an Exim client using
30041 an identically named option for the &(smtp)& transport. In each case, the value
30042 of the option is expanded and must then be the name of a file that contains a
30044 The downside is that clients have to periodically re-download a potentially huge
30045 file from every certificate authority they know of.
30048 The way with most moving parts at query time is Online Certificate
30049 Status Protocol (OCSP), where the client verifies the certificate
30050 against an OCSP server run by the CA. This lets the CA track all
30051 usage of the certs. It requires running software with access to the
30052 private key of the CA, to sign the responses to the OCSP queries. OCSP
30053 is based on HTTP and can be proxied accordingly.
30055 The only widespread OCSP server implementation (known to this writer)
30056 comes as part of OpenSSL and aborts on an invalid request, such as
30057 connecting to the port and then disconnecting. This requires
30058 re-entering the passphrase each time some random client does this.
30061 The third way is OCSP Stapling; in this, the server using a certificate
30062 issued by the CA periodically requests an OCSP proof of validity from
30063 the OCSP server, then serves it up inline as part of the TLS
30064 negotiation. This approach adds no extra round trips, does not let the
30065 CA track users, scales well with number of certs issued by the CA and is
30066 resilient to temporary OCSP server failures, as long as the server
30067 starts retrying to fetch an OCSP proof some time before its current
30068 proof expires. The downside is that it requires server support.
30070 Unless Exim is built with the support disabled,
30071 or with GnuTLS earlier than version 3.3.16 / 3.4.8
30072 support for OCSP stapling is included.
30074 There is a global option called &%tls_ocsp_file%&.
30075 The file specified therein is expected to be in DER format, and contain
30076 an OCSP proof. Exim will serve it as part of the TLS handshake. This
30077 option will be re-expanded for SNI, if the &%tls_certificate%& option
30078 contains &`tls_in_sni`&, as per other TLS options.
30080 Exim does not at this time implement any support for fetching a new OCSP
30081 proof. The burden is on the administrator to handle this, outside of
30082 Exim. The file specified should be replaced atomically, so that the
30083 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
30084 on each connection, so a new file will be handled transparently on the
30087 When built with OpenSSL Exim will check for a valid next update timestamp
30088 in the OCSP proof; if not present, or if the proof has expired, it will be
30091 For the client to be able to verify the stapled OCSP the server must
30092 also supply, in its stapled information, any intermediate
30093 certificates for the chain leading to the OCSP proof from the signer
30094 of the server certificate. There may be zero or one such. These
30095 intermediate certificates should be added to the server OCSP stapling
30096 file named by &%tls_ocsp_file%&.
30098 Note that the proof only covers the terminal server certificate,
30099 not any of the chain from CA to it.
30101 There is no current way to staple a proof for a client certificate.
30104 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
30105 OCSP server is supplied. The server URL may be included in the
30106 server certificate, if the CA is helpful.
30108 One failure mode seen was the OCSP Signer cert expiring before the end
30109 of validity of the OCSP proof. The checking done by Exim/OpenSSL
30110 noted this as invalid overall, but the re-fetch script did not.
30115 .ecindex IIDencsmtp1
30116 .ecindex IIDencsmtp2
30119 .section "TLS Resumption" "SECTresumption"
30120 .cindex TLS resumption
30121 TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
30122 in RFC 5077 for 1.2). The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1
30125 Session resumption (this is the "stateless" variant) involves the server sending
30126 a "session ticket" to the client on one connection, which can be stored by the
30127 client and used for a later session. The ticket contains sufficient state for
30128 the server to reconstruct the TLS session, avoiding some expensive crypto
30129 calculation and (on TLS1.2) one full packet roundtrip time.
30132 Operational cost/benefit:
30134 The extra data being transmitted costs a minor amount, and the client has
30135 extra costs in storing and retrieving the data.
30137 In the Exim/Gnutls implementation the extra cost on an initial connection
30138 which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware.
30139 The saved cost on a subsequent connection is about 4ms; three or more
30140 connections become a net win. On longer network paths, two or more
30141 connections will have an average lower startup time thanks to the one
30142 saved packet roundtrip. TLS1.3 will save the crypto cpu costs but not any
30145 .cindex "hints database" tls
30146 Since a new hints DB is used on the TLS client,
30147 the hints DB maintenance should be updated to additionally handle "tls".
30152 The session ticket is encrypted, but is obviously an additional security
30153 vulnarability surface. An attacker able to decrypt it would have access
30154 all connections using the resumed session.
30155 The session ticket encryption key is not committed to storage by the server
30156 and is rotated regularly (OpenSSL: 1hr, and one previous key is used for
30157 overlap; GnuTLS 6hr but does not specify any overlap).
30158 Tickets have limited lifetime (2hr, and new ones issued after 1hr under
30159 OpenSSL. GnuTLS 2hr, appears to not do overlap).
30161 There is a question-mark over the security of the Diffie-Helman parameters
30162 used for session negotiation.
30167 The &%log_selector%& "tls_resumption" appends an asterisk to the tls_cipher "X="
30170 The variables &$tls_in_resumption$& and &$tls_out_resumption$&
30171 have bits 0-4 indicating respectively
30172 support built, client requested ticket, client offered session,
30173 server issued ticket, resume used. A suitable decode list is provided
30174 in the builtin macro _RESUME_DECODE for in &%listextract%& expansions.
30179 The &%tls_resumption_hosts%& main option specifies a hostlist for which
30180 exim, operating as a server, will offer resumption to clients.
30181 Current best practice is to not offer the feature to MUA connection.
30182 Commonly this can be done like this:
30184 tls_resumption_hosts = ${if inlist {$received_port}{587:465} {:}{*}}
30186 If the peer host matches the list after expansion then resumption
30187 is offered and/or accepted.
30189 The &%tls_resumption_hosts%& smtp transport option performs the
30190 equivalent function for operation as a client.
30191 If the peer host matches the list after expansion then resumption
30192 is attempted (if a stored session is available) or the information
30193 stored (if supplied by the peer).
30199 In a resumed session:
30201 The variables &$tls_{in,out}_cipher$& will have values different
30202 to the original (under GnuTLS).
30204 The variables &$tls_{in,out}_ocsp$& will be "not requested" or "no response",
30205 and the &%hosts_require_ocsp%& smtp trasnport option will fail.
30206 . XXX need to do something with that hosts_require_ocsp
30212 .section DANE "SECDANE"
30214 DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
30215 it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
30216 operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
30217 you and the server still think you have an encrypted connection) and, if one of the "well known" set of
30218 Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
30219 certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
30221 What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
30222 that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
30223 by (a) is thought to be smaller than that of the set of root CAs.
30225 It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
30226 fail to pass on a server's STARTTLS.
30228 DANE scales better than having to maintain (and communicate via side-channel) copies of server certificates
30229 for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
30230 client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
30232 DANE requires a server operator to do three things:
30234 Run DNSSEC. This provides assurance to clients
30235 that DNS lookups they do for the server have not been tampered with. The domain MX record applying
30236 to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
30239 Add TLSA DNS records. These say what the server certificate for a TLS connection should be.
30241 Offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
30244 There are no changes to Exim specific to server-side operation of DANE.
30245 Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
30246 in &_Local/Makefile_&.
30247 If it has been included, the macro "_HAVE_DANE" will be defined.
30249 .subsection "DNS records"
30250 A TLSA record consist of 4 fields, the "Certificate Usage", the
30251 "Selector", the "Matching type", and the "Certificate Association Data".
30252 For a detailed description of the TLSA record see
30253 &url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671).
30255 The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3).
30256 These are the "Trust Anchor" and "End Entity" variants.
30257 The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
30258 (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
30259 this is appropriate for a single system, using a self-signed certificate.
30260 DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
30262 A private CA at simplest is just a self-signed certificate (with certain
30263 attributes) which is used to sign server certificates, but running one securely
30264 does require careful arrangement.
30265 With DANE-TA, as implemented in Exim and commonly in other MTAs,
30266 the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
30267 DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
30268 all of which point to a single TLSA record.
30269 DANE-TA and DANE-EE can both be used together.
30271 Our recommendation is to use DANE with a certificate from a public CA,
30272 because this enables a variety of strategies for remote clients to verify
30274 You can then publish information both via DANE and another technology,
30275 "MTA-STS", described below.
30277 When you use DANE-TA to publish trust anchor information, you ask entities
30278 outside your administrative control to trust the Certificate Authority for
30279 connections to you.
30280 If using a private CA then you should expect others to still apply the
30281 technical criteria they'd use for a public CA to your certificates.
30282 In particular, you should probably try to follow current best practices for CA
30283 operation around hash algorithms and key sizes.
30284 Do not expect other organizations to lower their security expectations just
30285 because a particular profile might be reasonable for your own internal use.
30287 When this text was last updated, this in practice means to avoid use of SHA-1
30288 and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
30289 than 4096, for interoperability); to use keyUsage fields correctly; to use
30290 random serial numbers.
30291 The list of requirements is subject to change as best practices evolve.
30292 If you're not already using a private CA, or it doesn't meet these
30293 requirements, then we encourage you to avoid all these issues and use a public
30294 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
30296 The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
30297 a "Matching Type" (3rd) field of SHA2-512(2).
30299 For the "Certificate Authority Data" (4th) field, commands like
30302 openssl x509 -pubkey -noout <certificate.pem \
30303 | openssl rsa -outform der -pubin 2>/dev/null \
30308 are workable to create a hash of the certificate's public key.
30310 An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like
30313 _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E...
30316 At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
30317 is useful for quickly generating TLSA records.
30320 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
30322 The Certificate issued by the CA published in the DANE-TA model should be
30323 issued using a strong hash algorithm.
30324 Exim, and importantly various other MTAs sending to you, will not
30325 re-enable hash algorithms which have been disabled by default in TLS
30327 This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
30328 interoperability (and probably the maximum too, in 2018).
30330 .subsection "Interaction with OCSP"
30331 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
30332 be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
30333 default of requesting OCSP for all hosts is modified iff DANE is in use, to:
30336 hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
30337 {= {4}{$tls_out_tlsa_usage}} } \
30341 The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
30342 The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
30343 found. If the definition of &%hosts_request_ocsp%& includes the
30344 string "tls_out_tlsa_usage", they are re-expanded in time to
30345 control the OCSP request.
30347 This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
30348 those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
30351 .subsection "Client configuration"
30352 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
30353 and &%dane_require_tls_ciphers%&.
30354 The &"require"& variant will result in failure if the target host is not
30355 DNSSEC-secured. To get DNSSEC-secured hostname resolution, use
30356 the &%dnssec_request_domains%& router or transport option.
30358 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
30360 A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using DNSSEC.
30361 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
30362 will be required for the host. If it does not, the host will not
30363 be used; there is no fallback to non-DANE or non-TLS.
30365 If DANE is requested and usable, then the TLS cipher list configuration
30366 prefers to use the option &%dane_require_tls_ciphers%& and falls
30367 back to &%tls_require_ciphers%& only if that is unset.
30368 This lets you configure "decent crypto" for DANE and "better than nothing
30369 crypto" as the default. Note though that while GnuTLS lets the string control
30370 which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
30371 limited to ciphersuite constraints.
30373 If DANE is requested and useable (see above) the following transport options are ignored:
30377 tls_try_verify_hosts
30378 tls_verify_certificates
30380 tls_verify_cert_hostnames
30384 If DANE is not usable, whether requested or not, and CA-anchored
30385 verification evaluation is wanted, the above variables should be set appropriately.
30387 The router and transport option &%dnssec_request_domains%& must not be
30388 set to &"never"&, and &%dnssec_require_domains%& is ignored.
30390 .subsection Observability
30391 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
30393 There is a new variable &$tls_out_dane$& which will have "yes" if
30394 verification succeeded using DANE and "no" otherwise (only useful
30395 in combination with events; see &<<CHAPevents>>&),
30396 and a new variable &$tls_out_tlsa_usage$& (detailed above).
30398 .cindex DANE reporting
30399 An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
30400 to achieve DANE-verified connection, if one was either requested and offered, or
30401 required. This is intended to support TLS-reporting as defined in
30402 &url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
30403 The &$event_data$& will be one of the Result Types defined in
30404 Section 4.3 of that document.
30406 .subsection General
30407 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
30409 DANE is specified in published RFCs and decouples certificate authority trust
30410 selection from a "race to the bottom" of "you must trust everything for mail
30412 There is an alternative technology called MTA-STS, which
30413 instead publishes MX trust anchor information on an HTTPS website. At the
30414 time this text was last updated, MTA-STS was still a draft, not yet an RFC.
30415 Exim has no support for MTA-STS as a client, but Exim mail server operators
30416 can choose to publish information describing their TLS configuration using
30417 MTA-STS to let those clients who do use that protocol derive trust
30420 The MTA-STS design requires a certificate from a public Certificate Authority
30421 which is recognized by clients sending to you.
30422 That selection of which CAs are trusted by others is outside your control.
30424 The most interoperable course of action is probably to use
30425 &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
30426 renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
30427 records for DANE clients (such as Exim and Postfix) and to publish anchor
30428 information for MTA-STS as well. This is what is done for the &'exim.org'&
30429 domain itself (with caveats around occasionally broken MTA-STS because of
30430 incompatible specification changes prior to reaching RFC status).
30434 . ////////////////////////////////////////////////////////////////////////////
30435 . ////////////////////////////////////////////////////////////////////////////
30437 .chapter "Access control lists" "CHAPACL"
30438 .scindex IIDacl "&ACL;" "description"
30439 .cindex "control of incoming mail"
30440 .cindex "message" "controlling incoming"
30441 .cindex "policy control" "access control lists"
30442 Access Control Lists (ACLs) are defined in a separate section of the runtime
30443 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
30444 name, terminated by a colon. Here is a complete ACL section that contains just
30445 one very small ACL:
30449 accept hosts = one.host.only
30451 You can have as many lists as you like in the ACL section, and the order in
30452 which they appear does not matter. The lists are self-terminating.
30454 The majority of ACLs are used to control Exim's behaviour when it receives
30455 certain SMTP commands. This applies both to incoming TCP/IP connections, and
30456 when a local process submits a message using SMTP by specifying the &%-bs%&
30457 option. The most common use is for controlling which recipients are accepted
30458 in incoming messages. In addition, you can define an ACL that is used to check
30459 local non-SMTP messages. The default configuration file contains an example of
30460 a realistic ACL for checking RCPT commands. This is discussed in chapter
30461 &<<CHAPdefconfil>>&.
30464 .section "Testing ACLs" "SECID188"
30465 The &%-bh%& command line option provides a way of testing your ACL
30466 configuration locally by running a fake SMTP session with which you interact.
30469 .section "Specifying when ACLs are used" "SECID189"
30470 .cindex "&ACL;" "options for specifying"
30471 In order to cause an ACL to be used, you have to name it in one of the relevant
30472 options in the main part of the configuration. These options are:
30473 .cindex "AUTH" "ACL for"
30474 .cindex "DATA" "ACLs for"
30475 .cindex "ETRN" "ACL for"
30476 .cindex "EXPN" "ACL for"
30477 .cindex "HELO" "ACL for"
30478 .cindex "EHLO" "ACL for"
30479 .cindex "DKIM" "ACL for"
30480 .cindex "MAIL" "ACL for"
30481 .cindex "QUIT, ACL for"
30482 .cindex "RCPT" "ACL for"
30483 .cindex "STARTTLS, ACL for"
30484 .cindex "VRFY" "ACL for"
30485 .cindex "SMTP" "connection, ACL for"
30486 .cindex "non-SMTP messages" "ACLs for"
30487 .cindex "MIME content scanning" "ACL for"
30488 .cindex "PRDR" "ACL for"
30491 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
30492 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
30493 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
30494 .irow &%acl_smtp_auth%& "ACL for AUTH"
30495 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
30496 .irow &%acl_smtp_data%& "ACL after DATA is complete"
30497 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
30498 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
30499 .irow &%acl_smtp_etrn%& "ACL for ETRN"
30500 .irow &%acl_smtp_expn%& "ACL for EXPN"
30501 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
30502 .irow &%acl_smtp_mail%& "ACL for MAIL"
30503 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
30504 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
30505 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
30506 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
30507 .irow &%acl_smtp_quit%& "ACL for QUIT"
30508 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
30509 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
30510 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
30513 For example, if you set
30515 acl_smtp_rcpt = small_acl
30517 the little ACL defined above is used whenever Exim receives a RCPT command
30518 in an SMTP dialogue. The majority of policy tests on incoming messages can be
30519 done when RCPT commands arrive. A rejection of RCPT should cause the
30520 sending MTA to give up on the recipient address contained in the RCPT
30521 command, whereas rejection at other times may cause the client MTA to keep on
30522 trying to deliver the message. It is therefore recommended that you do as much
30523 testing as possible at RCPT time.
30526 .subsection "The non-SMTP ACLs" SECID190
30527 .cindex "non-SMTP messages" "ACLs for"
30528 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
30529 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
30530 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
30531 the state of the SMTP connection such as encryption and authentication) are not
30532 relevant and are forbidden in these ACLs. However, the sender and recipients
30533 are known, so the &%senders%& and &%sender_domains%& conditions and the
30534 &$sender_address$& and &$recipients$& variables can be used. Variables such as
30535 &$authenticated_sender$& are also available. You can specify added header lines
30536 in any of these ACLs.
30538 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
30539 non-SMTP message, before any of the message has been read. (This is the
30540 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
30541 batched SMTP input, it runs after the DATA command has been reached. The
30542 result of this ACL is ignored; it cannot be used to reject a message. If you
30543 really need to, you could set a value in an ACL variable here and reject based
30544 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
30545 controls, and in particular, it can be used to set
30547 control = suppress_local_fixups
30549 This cannot be used in the other non-SMTP ACLs because by the time they are
30550 run, it is too late.
30552 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
30553 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30555 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
30556 kind of rejection is treated as permanent, because there is no way of sending a
30557 temporary error for these kinds of message.
30560 .subsection "The SMTP connect ACL" SECID191
30561 .cindex "SMTP" "connection, ACL for"
30562 .oindex &%smtp_banner%&
30563 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
30564 session, after the test specified by &%host_reject_connection%& (which is now
30565 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
30566 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
30567 the message override the banner message that is otherwise specified by the
30568 &%smtp_banner%& option.
30571 For tls-on-connect connections, the ACL is run before the TLS connection
30572 is accepted; if the ACL does not accept then the TCP connection is dropped without
30573 any TLS startup attempt and without any SMTP response being transmitted.
30577 .subsection "The EHLO/HELO ACL" SECID192
30578 .cindex "EHLO" "ACL for"
30579 .cindex "HELO" "ACL for"
30580 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
30581 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
30582 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
30583 Note that a client may issue more than one EHLO or HELO command in an SMTP
30584 session, and indeed is required to issue a new EHLO or HELO after successfully
30585 setting up encryption following a STARTTLS command.
30587 Note also that a deny neither forces the client to go away nor means that
30588 mail will be refused on the connection. Consider checking for
30589 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
30591 If the command is accepted by an &%accept%& verb that has a &%message%&
30592 modifier, the message may not contain more than one line (it will be truncated
30593 at the first newline and a panic logged if it does). Such a message cannot
30594 affect the EHLO options that are listed on the second and subsequent lines of
30598 .subsection "The DATA ACLs" SECID193
30599 .cindex "DATA" "ACLs for"
30600 Two ACLs are associated with the DATA command, because it is two-stage
30601 command, with two responses being sent to the client.
30602 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
30603 is obeyed. This gives you control after all the RCPT commands, but before
30604 the message itself is received. It offers the opportunity to give a negative
30605 response to the DATA command before the data is transmitted. Header lines
30606 added by MAIL or RCPT ACLs are not visible at this time, but any that
30607 are defined here are visible when the &%acl_smtp_data%& ACL is run.
30609 You cannot test the contents of the message, for example, to verify addresses
30610 in the headers, at RCPT time or when the DATA command is received. Such
30611 tests have to appear in the ACL that is run after the message itself has been
30612 received, before the final response to the DATA command is sent. This is
30613 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
30614 associated with the DATA command.
30616 .cindex CHUNKING "BDAT command"
30617 .cindex BDAT "SMTP command"
30618 .cindex "RFC 3030" CHUNKING
30619 If CHUNKING was advertised and a BDAT command sequence is received,
30620 the &%acl_smtp_predata%& ACL is not run.
30621 . XXX why not? It should be possible, for the first BDAT.
30622 The &%acl_smtp_data%& is run after the last BDAT command and all of
30623 the data specified is received.
30625 For both of these ACLs, it is not possible to reject individual recipients. An
30626 error response rejects the entire message. Unfortunately, it is known that some
30627 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
30628 before or after the data) correctly &-- they keep the message on their queues
30629 and try again later, but that is their problem, though it does waste some of
30632 The &%acl_smtp_data%& ACL is run after
30633 the &%acl_smtp_data_prdr%&,
30634 the &%acl_smtp_dkim%&
30635 and the &%acl_smtp_mime%& ACLs.
30637 .subsection "The SMTP DKIM ACL" SECTDKIMACL
30638 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
30639 enabled (which is the default).
30641 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
30642 received, and is executed for each DKIM signature found in a message. If not
30643 otherwise specified, the default action is to accept.
30645 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
30647 For details on the operation of DKIM, see section &<<SECDKIM>>&.
30650 .subsection "The SMTP MIME ACL" SECID194
30651 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
30652 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30654 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30657 .subsection "The SMTP PRDR ACL" SECTPRDRACL
30658 .cindex "PRDR" "ACL for"
30659 .oindex "&%prdr_enable%&"
30660 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
30661 with PRDR support enabled (which is the default).
30662 It becomes active only when the PRDR feature is negotiated between
30663 client and server for a message, and more than one recipient
30666 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
30667 has been received, and is executed once for each recipient of the message
30668 with &$local_part$& and &$domain$& valid.
30669 The test may accept, defer or deny for individual recipients.
30670 The &%acl_smtp_data%& will still be called after this ACL and
30671 can reject the message overall, even if this ACL has accepted it
30672 for some or all recipients.
30674 PRDR may be used to support per-user content filtering. Without it
30675 one must defer any recipient after the first that has a different
30676 content-filter configuration. With PRDR, the RCPT-time check
30677 .cindex "PRDR" "variable for"
30678 for this can be disabled when the variable &$prdr_requested$&
30680 Any required difference in behaviour of the main DATA-time
30681 ACL should however depend on the PRDR-time ACL having run, as Exim
30682 will avoid doing so in some situations (e.g. single-recipient mails).
30684 See also the &%prdr_enable%& global option
30685 and the &%hosts_try_prdr%& smtp transport option.
30687 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30688 If the ACL is not defined, processing completes as if
30689 the feature was not requested by the client.
30691 .subsection "The QUIT ACL" SECTQUITACL
30692 .cindex "QUIT, ACL for"
30693 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
30694 does not affect the response code to QUIT, which is always 221. Thus, the ACL
30695 does not in fact control any access.
30696 For this reason, it may only accept
30697 or warn as its final result.
30699 This ACL can be used for tasks such as custom logging at the end of an SMTP
30700 session. For example, you can use ACL variables in other ACLs to count
30701 messages, recipients, etc., and log the totals at QUIT time using one or
30702 more &%logwrite%& modifiers on a &%warn%& verb.
30704 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
30705 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
30707 You do not need to have a final &%accept%&, but if you do, you can use a
30708 &%message%& modifier to specify custom text that is sent as part of the 221
30711 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
30712 failure (for example, failure to open a log file, or when Exim is bombing out
30713 because it has detected an unrecoverable error), all SMTP commands from the
30714 client are given temporary error responses until QUIT is received or the
30715 connection is closed. In these special cases, the QUIT ACL does not run.
30718 .subsection "The not-QUIT ACL" SECTNOTQUITACL
30719 .vindex &$acl_smtp_notquit$&
30720 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
30721 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
30722 trouble, such as being unable to write to its log files, this ACL is not run,
30723 because it might try to do things (such as write to log files) that make the
30724 situation even worse.
30726 Like the QUIT ACL, this ACL is provided to make it possible to do customized
30727 logging or to gather statistics, and its outcome is ignored. The &%delay%&
30728 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
30731 .vindex &$smtp_notquit_reason$&
30732 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
30733 to a string that indicates the reason for the termination of the SMTP
30734 connection. The possible values are:
30736 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
30737 .irow &`bad-commands`& "Too many unknown or non-mail commands"
30738 .irow &`command-timeout`& "Timeout while reading SMTP commands"
30739 .irow &`connection-lost`& "The SMTP connection has been lost"
30740 .irow &`data-timeout`& "Timeout while reading message data"
30741 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
30742 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
30743 .irow &`signal-exit`& "SIGTERM or SIGINT"
30744 .irow &`synchronization-error`& "SMTP synchronization error"
30745 .irow &`tls-failed`& "TLS failed to start"
30747 In most cases when an SMTP connection is closed without having received QUIT,
30748 Exim sends an SMTP response message before actually closing the connection.
30749 With the exception of the &`acl-drop`& case, the default message can be
30750 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
30751 &%drop%& verb in another ACL, it is the message from the other ACL that is
30755 .section "Finding an ACL to use" "SECID195"
30756 .cindex "&ACL;" "finding which to use"
30757 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
30758 you can use different ACLs in different circumstances. For example,
30760 acl_smtp_rcpt = ${if ={25}{$interface_port} \
30761 {acl_check_rcpt} {acl_check_rcpt_submit} }
30763 In the default configuration file there are some example settings for
30764 providing an RFC 4409 message &"submission"& service on port 587 and
30765 an RFC 8314 &"submissions"& service on port 465. You can use a string
30766 expansion like this to choose an ACL for MUAs on these ports which is
30767 more appropriate for this purpose than the default ACL on port 25.
30769 The expanded string does not have to be the name of an ACL in the
30770 configuration file; there are other possibilities. Having expanded the
30771 string, Exim searches for an ACL as follows:
30774 If the string begins with a slash, Exim uses it as a filename, and reads its
30775 contents as an ACL. The lines are processed in the same way as lines in the
30776 Exim configuration file. In particular, continuation lines are supported, blank
30777 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
30778 If the file does not exist or cannot be read, an error occurs (typically
30779 causing a temporary failure of whatever caused the ACL to be run). For example:
30781 acl_smtp_data = /etc/acls/\
30782 ${lookup{$sender_host_address}lsearch\
30783 {/etc/acllist}{$value}{default}}
30785 This looks up an ACL file to use on the basis of the host's IP address, falling
30786 back to a default if the lookup fails. If an ACL is successfully read from a
30787 file, it is retained in memory for the duration of the Exim process, so that it
30788 can be re-used without having to re-read the file.
30790 If the string does not start with a slash, and does not contain any spaces,
30791 Exim searches the ACL section of the configuration for an ACL whose name
30792 matches the string.
30794 If no named ACL is found, or if the string contains spaces, Exim parses
30795 the string as an inline ACL. This can save typing in cases where you just
30796 want to have something like
30798 acl_smtp_vrfy = accept
30800 in order to allow free use of the VRFY command. Such a string may contain
30801 newlines; it is processed in the same way as an ACL that is read from a file.
30807 .section "ACL return codes" "SECID196"
30808 .cindex "&ACL;" "return codes"
30809 Except for the QUIT ACL, which does not affect the SMTP return code (see
30810 section &<<SECTQUITACL>>& above), the result of running an ACL is either
30811 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
30812 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
30813 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
30814 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
30815 This also causes a 4&'xx'& return code.
30817 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
30818 &"deny"&, because there is no mechanism for passing temporary errors to the
30819 submitters of non-SMTP messages.
30822 ACLs that are relevant to message reception may also return &"discard"&. This
30823 has the effect of &"accept"&, but causes either the entire message or an
30824 individual recipient address to be discarded. In other words, it is a
30825 blackholing facility. Use it with care.
30827 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
30828 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
30829 RCPT ACL is to discard just the one recipient address. If there are no
30830 recipients left when the message's data is received, the DATA ACL is not
30831 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
30832 remaining recipients. The &"discard"& return is not permitted for the
30833 &%acl_smtp_predata%& ACL.
30835 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
30836 is done on the address and the result determines the SMTP response.
30839 .cindex "&[local_scan()]& function" "when all recipients discarded"
30840 The &[local_scan()]& function is always run, even if there are no remaining
30841 recipients; it may create new recipients.
30845 .section "Unset ACL options" "SECID197"
30846 .cindex "&ACL;" "unset options"
30847 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
30848 all the same. &*Note*&: These defaults apply only when the relevant ACL is
30849 not defined at all. For any defined ACL, the default action when control
30850 reaches the end of the ACL statements is &"deny"&.
30852 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
30853 these two are ACLs that are used only for their side effects. They cannot be
30854 used to accept or reject anything.
30856 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
30857 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
30858 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
30859 when the ACL is not defined is &"accept"&.
30861 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
30862 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
30863 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
30864 messages over an SMTP connection. For an example, see the ACL in the default
30865 configuration file.
30870 .section "Data for message ACLs" "SECID198"
30871 .cindex "&ACL;" "data for message ACL"
30873 .vindex &$local_part$&
30874 .vindex &$sender_address$&
30875 .vindex &$sender_host_address$&
30876 .vindex &$smtp_command$&
30877 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
30878 that contain information about the host and the message's sender (for example,
30879 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
30880 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
30881 &$local_part$& are set from the argument address. The entire SMTP command
30882 is available in &$smtp_command$&.
30884 When an ACL for the AUTH parameter of MAIL is running, the variables that
30885 contain information about the host are set, but &$sender_address$& is not yet
30886 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
30889 .vindex "&$message_size$&"
30890 The &$message_size$& variable is set to the value of the SIZE parameter on
30891 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
30892 that parameter is not given. The value is updated to the true message size by
30893 the time the final DATA ACL is run (after the message data has been
30896 .vindex "&$rcpt_count$&"
30897 .vindex "&$recipients_count$&"
30898 The &$rcpt_count$& variable increases by one for each RCPT command received.
30899 The &$recipients_count$& variable increases by one each time a RCPT command is
30900 accepted, so while an ACL for RCPT is being processed, it contains the number
30901 of previously accepted recipients. At DATA time (for both the DATA ACLs),
30902 &$rcpt_count$& contains the total number of RCPT commands, and
30903 &$recipients_count$& contains the total number of accepted recipients.
30909 .section "Data for non-message ACLs" "SECTdatfornon"
30910 .cindex "&ACL;" "data for non-message ACL"
30911 .vindex &$smtp_command_argument$&
30912 .vindex &$smtp_command$&
30913 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
30914 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
30915 and the entire SMTP command is available in &$smtp_command$&.
30916 These variables can be tested using a &%condition%& condition. For example,
30917 here is an ACL for use with AUTH, which insists that either the session is
30918 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
30919 does not permit authentication methods that use cleartext passwords on
30920 unencrypted connections.
30923 accept encrypted = *
30924 accept condition = ${if eq{${uc:$smtp_command_argument}}\
30926 deny message = TLS encryption or CRAM-MD5 required
30928 (Another way of applying this restriction is to arrange for the authenticators
30929 that use cleartext passwords not to be advertised when the connection is not
30930 encrypted. You can use the generic &%server_advertise_condition%& authenticator
30931 option to do this.)
30935 .section "Format of an ACL" "SECID199"
30936 .cindex "&ACL;" "format of"
30937 .cindex "&ACL;" "verbs, definition of"
30938 An individual ACL consists of a number of statements. Each statement starts
30939 with a verb, optionally followed by a number of conditions and &"modifiers"&.
30940 Modifiers can change the way the verb operates, define error and log messages,
30941 set variables, insert delays, and vary the processing of accepted messages.
30943 If all the conditions are met, the verb is obeyed. The same condition may be
30944 used (with different arguments) more than once in the same statement. This
30945 provides a means of specifying an &"and"& conjunction between conditions. For
30948 deny dnslists = list1.example
30949 dnslists = list2.example
30951 If there are no conditions, the verb is always obeyed. Exim stops evaluating
30952 the conditions and modifiers when it reaches a condition that fails. What
30953 happens then depends on the verb (and in one case, on a special modifier). Not
30954 all the conditions make sense at every testing point. For example, you cannot
30955 test a sender address in the ACL that is run for a VRFY command.
30958 .section "ACL verbs" "SECID200"
30959 The ACL verbs are as follows:
30962 .cindex "&%accept%& ACL verb"
30963 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
30964 of the conditions are not met, what happens depends on whether &%endpass%&
30965 appears among the conditions (for syntax see below). If the failing condition
30966 is before &%endpass%&, control is passed to the next ACL statement; if it is
30967 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
30968 check a RCPT command:
30970 accept domains = +local_domains
30974 If the recipient domain does not match the &%domains%& condition, control
30975 passes to the next statement. If it does match, the recipient is verified, and
30976 the command is accepted if verification succeeds. However, if verification
30977 fails, the ACL yields &"deny"&, because the failing condition is after
30980 The &%endpass%& feature has turned out to be confusing to many people, so its
30981 use is not recommended nowadays. It is always possible to rewrite an ACL so
30982 that &%endpass%& is not needed, and it is no longer used in the default
30985 .cindex "&%message%& ACL modifier" "with &%accept%&"
30986 If a &%message%& modifier appears on an &%accept%& statement, its action
30987 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
30988 (when an &%accept%& verb either accepts or passes control to the next
30989 statement), &%message%& can be used to vary the message that is sent when an
30990 SMTP command is accepted. For example, in a RCPT ACL you could have:
30992 &`accept `&<&'some conditions'&>
30993 &` message = OK, I will allow you through today`&
30995 You can specify an SMTP response code, optionally followed by an &"extended
30996 response code"& at the start of the message, but the first digit must be the
30997 same as would be sent by default, which is 2 for an &%accept%& verb.
30999 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
31000 an error message that is used when access is denied. This behaviour is retained
31001 for backward compatibility, but current &"best practice"& is to avoid the use
31006 .cindex "&%defer%& ACL verb"
31007 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
31008 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
31009 &%defer%& is the same as &%deny%&, because there is no way of sending a
31010 temporary error. For a RCPT command, &%defer%& is much the same as using a
31011 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
31012 be used in any ACL, and even for a recipient it might be a simpler approach.
31016 .cindex "&%deny%& ACL verb"
31017 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
31018 the conditions are not met, control is passed to the next ACL statement. For
31021 deny dnslists = blackholes.mail-abuse.org
31023 rejects commands from hosts that are on a DNS black list.
31027 .cindex "&%discard%& ACL verb"
31028 &%discard%&: This verb behaves like &%accept%&, except that it returns
31029 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
31030 that are concerned with receiving messages. When all the conditions are true,
31031 the sending entity receives a &"success"& response. However, &%discard%& causes
31032 recipients to be discarded. If it is used in an ACL for RCPT, just the one
31033 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
31034 message's recipients are discarded. Recipients that are discarded before DATA
31035 do not appear in the log line when the &%received_recipients%& log selector is set.
31037 If the &%log_message%& modifier is set when &%discard%& operates,
31038 its contents are added to the line that is automatically written to the log.
31039 The &%message%& modifier operates exactly as it does for &%accept%&.
31043 .cindex "&%drop%& ACL verb"
31044 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
31045 forcibly closed after the 5&'xx'& error message has been sent. For example:
31047 drop condition = ${if > {$rcpt_count}{20}}
31048 message = I don't take more than 20 RCPTs
31050 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
31051 The connection is always dropped after sending a 550 response.
31054 .cindex "&%require%& ACL verb"
31055 &%require%&: If all the conditions are met, control is passed to the next ACL
31056 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
31057 example, when checking a RCPT command,
31059 require message = Sender did not verify
31062 passes control to subsequent statements only if the message's sender can be
31063 verified. Otherwise, it rejects the command. Note the positioning of the
31064 &%message%& modifier, before the &%verify%& condition. The reason for this is
31065 discussed in section &<<SECTcondmodproc>>&.
31068 .cindex "&%warn%& ACL verb"
31069 &%warn%&: If all the conditions are true, a line specified by the
31070 &%log_message%& modifier is written to Exim's main log. Control always passes
31071 to the next ACL statement. If any condition is false, the log line is not
31072 written. If an identical log line is requested several times in the same
31073 message, only one copy is actually written to the log. If you want to force
31074 duplicates to be written, use the &%logwrite%& modifier instead.
31076 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
31077 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
31078 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
31079 first failing condition. There is more about adding header lines in section
31080 &<<SECTaddheadacl>>&.
31082 If any condition on a &%warn%& statement cannot be completed (that is, there is
31083 some sort of defer), the log line specified by &%log_message%& is not written.
31084 This does not include the case of a forced failure from a lookup, which
31085 is considered to be a successful completion. After a defer, no further
31086 conditions or modifiers in the &%warn%& statement are processed. The incident
31087 is logged, and the ACL continues to be processed, from the next statement
31091 .vindex "&$acl_verify_message$&"
31092 When one of the &%warn%& conditions is an address verification that fails, the
31093 text of the verification failure message is in &$acl_verify_message$&. If you
31094 want this logged, you must set it up explicitly. For example:
31096 warn !verify = sender
31097 log_message = sender verify failed: $acl_verify_message
31101 At the end of each ACL there is an implicit unconditional &%deny%&.
31103 As you can see from the examples above, the conditions and modifiers are
31104 written one to a line, with the first one on the same line as the verb, and
31105 subsequent ones on following lines. If you have a very long condition, you can
31106 continue it onto several physical lines by the usual backslash continuation
31107 mechanism. It is conventional to align the conditions vertically.
31111 .section "ACL variables" "SECTaclvariables"
31112 .cindex "&ACL;" "variables"
31113 There are some special variables that can be set during ACL processing. They
31114 can be used to pass information between different ACLs, different invocations
31115 of the same ACL in the same SMTP connection, and between ACLs and the routers,
31116 transports, and filters that are used to deliver a message. The names of these
31117 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
31118 an underscore, but the remainder of the name can be any sequence of
31119 alphanumeric characters and underscores that you choose. There is no limit on
31120 the number of ACL variables. The two sets act as follows:
31122 The values of those variables whose names begin with &$acl_c$& persist
31123 throughout an SMTP connection. They are never reset. Thus, a value that is set
31124 while receiving one message is still available when receiving the next message
31125 on the same SMTP connection.
31127 The values of those variables whose names begin with &$acl_m$& persist only
31128 while a message is being received. They are reset afterwards. They are also
31129 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
31132 When a message is accepted, the current values of all the ACL variables are
31133 preserved with the message and are subsequently made available at delivery
31134 time. The ACL variables are set by a modifier called &%set%&. For example:
31136 accept hosts = whatever
31137 set acl_m4 = some value
31138 accept authenticated = *
31139 set acl_c_auth = yes
31141 &*Note*&: A leading dollar sign is not used when naming a variable that is to
31142 be set. If you want to set a variable without taking any action, you can use a
31143 &%warn%& verb without any other modifiers or conditions.
31145 .oindex &%strict_acl_vars%&
31146 What happens if a syntactically valid but undefined ACL variable is
31147 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
31148 false (the default), an empty string is substituted; if it is true, an
31149 error is generated.
31151 Versions of Exim before 4.64 have a limited set of numbered variables, but
31152 their names are compatible, so there is no problem with upgrading.
31155 .section "Condition and modifier processing" "SECTcondmodproc"
31156 .cindex "&ACL;" "conditions; processing"
31157 .cindex "&ACL;" "modifiers; processing"
31158 An exclamation mark preceding a condition negates its result. For example:
31160 deny domains = *.dom.example
31161 !verify = recipient
31163 causes the ACL to return &"deny"& if the recipient domain ends in
31164 &'dom.example'& and the recipient address cannot be verified. Sometimes
31165 negation can be used on the right-hand side of a condition. For example, these
31166 two statements are equivalent:
31168 deny hosts = !192.168.3.4
31169 deny !hosts = 192.168.3.4
31171 However, for many conditions (&%verify%& being a good example), only left-hand
31172 side negation of the whole condition is possible.
31174 The arguments of conditions and modifiers are expanded. A forced failure
31175 of an expansion causes a condition to be ignored, that is, it behaves as if the
31176 condition is true. Consider these two statements:
31178 accept senders = ${lookup{$host_name}lsearch\
31179 {/some/file}{$value}fail}
31180 accept senders = ${lookup{$host_name}lsearch\
31181 {/some/file}{$value}{}}
31183 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
31184 the returned list is searched, but if the lookup fails the behaviour is
31185 different in the two cases. The &%fail%& in the first statement causes the
31186 condition to be ignored, leaving no further conditions. The &%accept%& verb
31187 therefore succeeds. The second statement, however, generates an empty list when
31188 the lookup fails. No sender can match an empty list, so the condition fails,
31189 and therefore the &%accept%& also fails.
31191 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
31192 specify actions that are taken as the conditions for a statement are checked;
31193 others specify text for messages that are used when access is denied or a
31194 warning is generated. The &%control%& modifier affects the way an incoming
31195 message is handled.
31197 The positioning of the modifiers in an ACL statement is important, because the
31198 processing of a verb ceases as soon as its outcome is known. Only those
31199 modifiers that have already been encountered will take effect. For example,
31200 consider this use of the &%message%& modifier:
31202 require message = Can't verify sender
31204 message = Can't verify recipient
31206 message = This message cannot be used
31208 If sender verification fails, Exim knows that the result of the statement is
31209 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
31210 so its text is used as the error message. If sender verification succeeds, but
31211 recipient verification fails, the second message is used. If recipient
31212 verification succeeds, the third message becomes &"current"&, but is never used
31213 because there are no more conditions to cause failure.
31215 For the &%deny%& verb, on the other hand, it is always the last &%message%&
31216 modifier that is used, because all the conditions must be true for rejection to
31217 happen. Specifying more than one &%message%& modifier does not make sense, and
31218 the message can even be specified after all the conditions. For example:
31221 !senders = *@my.domain.example
31222 message = Invalid sender from client host
31224 The &"deny"& result does not happen until the end of the statement is reached,
31225 by which time Exim has set up the message.
31229 .section "ACL modifiers" "SECTACLmodi"
31230 .cindex "&ACL;" "modifiers; list of"
31231 The ACL modifiers are as follows:
31234 .vitem &*add_header*&&~=&~<&'text'&>
31235 This modifier specifies one or more header lines that are to be added to an
31236 incoming message, assuming, of course, that the message is ultimately
31237 accepted. For details, see section &<<SECTaddheadacl>>&.
31239 .vitem &*continue*&&~=&~<&'text'&>
31240 .cindex "&%continue%& ACL modifier"
31241 .cindex "database" "updating in ACL"
31242 This modifier does nothing of itself, and processing of the ACL always
31243 continues with the next condition or modifier. The value of &%continue%& is in
31244 the side effects of expanding its argument. Typically this could be used to
31245 update a database. It is really just a syntactic tidiness, to avoid having to
31246 write rather ugly lines like this:
31248 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
31250 Instead, all you need is
31252 &`continue = `&<&'some expansion'&>
31255 .vitem &*control*&&~=&~<&'text'&>
31256 .cindex "&%control%& ACL modifier"
31257 This modifier affects the subsequent processing of the SMTP connection or of an
31258 incoming message that is accepted. The effect of the first type of control
31259 lasts for the duration of the connection, whereas the effect of the second type
31260 lasts only until the current message has been received. The message-specific
31261 controls always apply to the whole message, not to individual recipients,
31262 even if the &%control%& modifier appears in a RCPT ACL.
31264 As there are now quite a few controls that can be applied, they are described
31265 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
31266 in several different ways. For example:
31268 . ==== As this is a nested list, any displays it contains must be indented
31269 . ==== as otherwise they are too far to the left. That comment applies only
31270 . ==== when xmlto and fop are used; formatting with sdop gets it right either
31274 It can be at the end of an &%accept%& statement:
31276 accept ...some conditions
31279 In this case, the control is applied when this statement yields &"accept"&, in
31280 other words, when the conditions are all true.
31283 It can be in the middle of an &%accept%& statement:
31285 accept ...some conditions...
31287 ...some more conditions...
31289 If the first set of conditions are true, the control is applied, even if the
31290 statement does not accept because one of the second set of conditions is false.
31291 In this case, some subsequent statement must yield &"accept"& for the control
31295 It can be used with &%warn%& to apply the control, leaving the
31296 decision about accepting or denying to a subsequent verb. For
31299 warn ...some conditions...
31303 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
31304 &%logwrite%&, so it does not add anything to the message and does not write a
31308 If you want to apply a control unconditionally, you can use it with a
31309 &%require%& verb. For example:
31311 require control = no_multiline_responses
31315 .vitem &*delay*&&~=&~<&'time'&>
31316 .cindex "&%delay%& ACL modifier"
31318 This modifier may appear in any ACL except notquit. It causes Exim to wait for
31319 the time interval before proceeding. However, when testing Exim using the
31320 &%-bh%& option, the delay is not actually imposed (an appropriate message is
31321 output instead). The time is given in the usual Exim notation, and the delay
31322 happens as soon as the modifier is processed. In an SMTP session, pending
31323 output is flushed before the delay is imposed.
31325 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
31328 deny ...some conditions...
31331 The delay happens if all the conditions are true, before the statement returns
31332 &"deny"&. Compare this with:
31335 ...some conditions...
31337 which waits for 30s before processing the conditions. The &%delay%& modifier
31338 can also be used with &%warn%& and together with &%control%&:
31340 warn ...some conditions...
31346 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
31347 responses to several commands are no longer buffered and sent in one packet (as
31348 they would normally be) because all output is flushed before imposing the
31349 delay. This optimization is disabled so that a number of small delays do not
31350 appear to the client as one large aggregated delay that might provoke an
31351 unwanted timeout. You can, however, disable output flushing for &%delay%& by
31352 using a &%control%& modifier to set &%no_delay_flush%&.
31356 .cindex "&%endpass%& ACL modifier"
31357 This modifier, which has no argument, is recognized only in &%accept%& and
31358 &%discard%& statements. It marks the boundary between the conditions whose
31359 failure causes control to pass to the next statement, and the conditions whose
31360 failure causes the ACL to return &"deny"&. This concept has proved to be
31361 confusing to some people, so the use of &%endpass%& is no longer recommended as
31362 &"best practice"&. See the description of &%accept%& above for more details.
31365 .vitem &*log_message*&&~=&~<&'text'&>
31366 .cindex "&%log_message%& ACL modifier"
31367 This modifier sets up a message that is used as part of the log message if the
31368 ACL denies access or a &%warn%& statement's conditions are true. For example:
31370 require log_message = wrong cipher suite $tls_in_cipher
31371 encrypted = DES-CBC3-SHA
31373 &%log_message%& is also used when recipients are discarded by &%discard%&. For
31376 &`discard `&<&'some conditions'&>
31377 &` log_message = Discarded $local_part@$domain because...`&
31379 When access is denied, &%log_message%& adds to any underlying error message
31380 that may exist because of a condition failure. For example, while verifying a
31381 recipient address, a &':fail:'& redirection might have already set up a
31384 The message may be defined before the conditions to which it applies, because
31385 the string expansion does not happen until Exim decides that access is to be
31386 denied. This means that any variables that are set by the condition are
31387 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
31388 variables are set after a DNS black list lookup succeeds. If the expansion of
31389 &%log_message%& fails, or if the result is an empty string, the modifier is
31392 .vindex "&$acl_verify_message$&"
31393 If you want to use a &%warn%& statement to log the result of an address
31394 verification, you can use &$acl_verify_message$& to include the verification
31397 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
31398 the start of the logged message. If the same warning log message is requested
31399 more than once while receiving a single email message, only one copy is
31400 actually logged. If you want to log multiple copies, use &%logwrite%& instead
31401 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
31402 is logged for a successful &%warn%& statement.
31404 If &%log_message%& is not present and there is no underlying error message (for
31405 example, from the failure of address verification), but &%message%& is present,
31406 the &%message%& text is used for logging rejections. However, if any text for
31407 logging contains newlines, only the first line is logged. In the absence of
31408 both &%log_message%& and &%message%&, a default built-in message is used for
31409 logging rejections.
31412 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
31413 .cindex "&%log_reject_target%& ACL modifier"
31414 .cindex "logging in ACL" "specifying which log"
31415 This modifier makes it possible to specify which logs are used for messages
31416 about ACL rejections. Its argument is a colon-separated list of words that can
31417 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
31418 may be empty, in which case a rejection is not logged at all. For example, this
31419 ACL fragment writes no logging information when access is denied:
31421 &`deny `&<&'some conditions'&>
31422 &` log_reject_target =`&
31424 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
31425 permanent and temporary rejections. Its effect lasts for the rest of the
31429 .vitem &*logwrite*&&~=&~<&'text'&>
31430 .cindex "&%logwrite%& ACL modifier"
31431 .cindex "logging in ACL" "immediate"
31432 This modifier writes a message to a log file as soon as it is encountered when
31433 processing an ACL. (Compare &%log_message%&, which, except in the case of
31434 &%warn%& and &%discard%&, is used only if the ACL statement denies
31435 access.) The &%logwrite%& modifier can be used to log special incidents in
31438 &`accept `&<&'some special conditions'&>
31439 &` control = freeze`&
31440 &` logwrite = froze message because ...`&
31442 By default, the message is written to the main log. However, it may begin
31443 with a colon, followed by a comma-separated list of log names, and then
31444 another colon, to specify exactly which logs are to be written. For
31447 logwrite = :main,reject: text for main and reject logs
31448 logwrite = :panic: text for panic log only
31452 .vitem &*message*&&~=&~<&'text'&>
31453 .cindex "&%message%& ACL modifier"
31454 This modifier sets up a text string that is expanded and used as a response
31455 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
31456 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
31457 there is some complication if &%endpass%& is involved; see the description of
31458 &%accept%& for details.)
31460 The expansion of the message happens at the time Exim decides that the ACL is
31461 to end, not at the time it processes &%message%&. If the expansion fails, or
31462 generates an empty string, the modifier is ignored. Here is an example where
31463 &%message%& must be specified first, because the ACL ends with a rejection if
31464 the &%hosts%& condition fails:
31466 require message = Host not recognized
31469 (Once a condition has failed, no further conditions or modifiers are
31472 .cindex "SMTP" "error codes"
31473 .oindex "&%smtp_banner%&
31474 For ACLs that are triggered by SMTP commands, the message is returned as part
31475 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
31476 is meaningful only for SMTP, as no message is returned when a non-SMTP message
31477 is accepted. In the case of the connect ACL, accepting with a message modifier
31478 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
31479 accept message may not contain more than one line (otherwise it will be
31480 truncated at the first newline and a panic logged), and it cannot affect the
31483 When SMTP is involved, the message may begin with an overriding response code,
31484 consisting of three digits optionally followed by an &"extended response code"&
31485 of the form &'n.n.n'&, each code being followed by a space. For example:
31487 deny message = 599 1.2.3 Host not welcome
31488 hosts = 192.168.34.0/24
31490 The first digit of the supplied response code must be the same as would be sent
31491 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
31492 access, but for the predata ACL, note that the default success code is 354, not
31495 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
31496 the message modifier cannot override the 221 response code.
31498 The text in a &%message%& modifier is literal; any quotes are taken as
31499 literals, but because the string is expanded, backslash escapes are processed
31500 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
31503 .vindex "&$acl_verify_message$&"
31504 While the text is being expanded, the &$acl_verify_message$& variable
31505 contains any message previously set.
31506 Afterwards, &$acl_verify_message$& is cleared.
31508 If &%message%& is used on a statement that verifies an address, the message
31509 specified overrides any message that is generated by the verification process.
31510 However, the original message is available in the variable
31511 &$acl_verify_message$&, so you can incorporate it into your message if you
31512 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
31513 routers to be passed back as part of the SMTP response, you should either not
31514 use a &%message%& modifier, or make use of &$acl_verify_message$&.
31516 For compatibility with previous releases of Exim, a &%message%& modifier that
31517 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
31518 modifier, but this usage is now deprecated. However, &%message%& acts only when
31519 all the conditions are true, wherever it appears in an ACL command, whereas
31520 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
31521 &%warn%& in an ACL that is not concerned with receiving a message, it has no
31525 .vitem &*queue*&&~=&~<&'text'&>
31526 .cindex "&%queue%& ACL modifier"
31527 .cindex "named queues" "selecting in ACL"
31528 This modifier specifies the use of a named queue for spool files
31530 It can only be used before the message is received (i.e. not in
31532 This could be used, for example, for known high-volume burst sources
31533 of traffic, or for quarantine of messages.
31534 Separate queue-runner processes will be needed for named queues.
31535 If the text after expansion is empty, the default queue is used.
31538 .vitem &*remove_header*&&~=&~<&'text'&>
31539 This modifier specifies one or more header names in a colon-separated list
31540 that are to be removed from an incoming message, assuming, of course, that
31541 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
31544 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
31545 .cindex "&%set%& ACL modifier"
31546 This modifier puts a value into one of the ACL variables (see section
31547 &<<SECTaclvariables>>&).
31550 .vitem &*udpsend*&&~=&~<&'parameters'&>
31551 .cindex "UDP communications"
31552 This modifier sends a UDP packet, for purposes such as statistics
31553 collection or behaviour monitoring. The parameters are expanded, and
31554 the result of the expansion must be a colon-separated list consisting
31555 of a destination server, port number, and the packet contents. The
31556 server can be specified as a host name or IPv4 or IPv6 address. The
31557 separator can be changed with the usual angle bracket syntax. For
31558 example, you might want to collect information on which hosts connect
31561 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
31562 $tod_zulu $sender_host_address
31569 .section "Use of the control modifier" "SECTcontrols"
31570 .cindex "&%control%& ACL modifier"
31571 The &%control%& modifier supports the following settings:
31574 .vitem &*control&~=&~allow_auth_unadvertised*&
31575 This modifier allows a client host to use the SMTP AUTH command even when it
31576 has not been advertised in response to EHLO. Furthermore, because there are
31577 apparently some really broken clients that do this, Exim will accept AUTH after
31578 HELO (rather than EHLO) when this control is set. It should be used only if you
31579 really need it, and you should limit its use to those broken clients that do
31580 not work without it. For example:
31582 warn hosts = 192.168.34.25
31583 control = allow_auth_unadvertised
31585 Normally, when an Exim server receives an AUTH command, it checks the name of
31586 the authentication mechanism that is given in the command to ensure that it
31587 matches an advertised mechanism. When this control is set, the check that a
31588 mechanism has been advertised is bypassed. Any configured mechanism can be used
31589 by the client. This control is permitted only in the connection and HELO ACLs.
31592 .vitem &*control&~=&~caseful_local_part*& &&&
31593 &*control&~=&~caselower_local_part*&
31594 .cindex "&ACL;" "case of local part in"
31595 .cindex "case of local parts"
31596 .vindex "&$local_part$&"
31597 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
31598 (that is, during RCPT processing). By default, the contents of &$local_part$&
31599 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
31600 any uppercase letters in the original local part are restored in &$local_part$&
31601 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
31604 These controls affect only the current recipient. Moreover, they apply only to
31605 local part handling that takes place directly in the ACL (for example, as a key
31606 in lookups). If a test to verify the recipient is obeyed, the case-related
31607 handling of the local part during the verification is controlled by the router
31608 configuration (see the &%caseful_local_part%& generic router option).
31610 This facility could be used, for example, to add a spam score to local parts
31611 containing upper case letters. For example, using &$acl_m4$& to accumulate the
31614 warn control = caseful_local_part
31615 set acl_m4 = ${eval:\
31617 ${if match{$local_part}{[A-Z]}{1}{0}}\
31619 control = caselower_local_part
31621 Notice that we put back the lower cased version afterwards, assuming that
31622 is what is wanted for subsequent tests.
31625 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
31626 .cindex "&ACL;" "cutthrough routing"
31627 .cindex "cutthrough" "requesting"
31628 This option requests delivery be attempted while the item is being received.
31630 The option is usable in the RCPT ACL.
31631 If enabled for a message received via smtp and routed to an smtp transport,
31632 and only one transport, interface, destination host and port combination
31633 is used for all recipients of the message,
31634 then the delivery connection is made while the receiving connection is open
31635 and data is copied from one to the other.
31637 An attempt to set this option for any recipient but the first
31638 for a mail will be quietly ignored.
31639 If a recipient-verify callout
31641 connection is subsequently
31642 requested in the same ACL it is held open and used for
31643 any subsequent recipients and the data,
31644 otherwise one is made after the initial RCPT ACL completes.
31646 Note that routers are used in verify mode,
31647 and cannot depend on content of received headers.
31648 Note also that headers cannot be
31649 modified by any of the post-data ACLs (DATA, MIME and DKIM).
31650 Headers may be modified by routers (subject to the above) and transports.
31651 The &'Received-By:'& header is generated as soon as the body reception starts,
31652 rather than the traditional time after the full message is received;
31653 this will affect the timestamp.
31655 All the usual ACLs are called; if one results in the message being
31656 rejected, all effort spent in delivery (including the costs on
31657 the ultimate destination) will be wasted.
31658 Note that in the case of data-time ACLs this includes the entire
31661 Cutthrough delivery is not supported via transport-filters or when DKIM signing
31662 of outgoing messages is done, because it sends data to the ultimate destination
31663 before the entire message has been received from the source.
31664 It is not supported for messages received with the SMTP PRDR
31668 Should the ultimate destination system positively accept or reject the mail,
31669 a corresponding indication is given to the source system and nothing is queued.
31670 If the item is successfully delivered in cutthrough mode
31671 the delivery log lines are tagged with ">>" rather than "=>" and appear
31672 before the acceptance "<=" line.
31674 If there is a temporary error the item is queued for later delivery in the
31676 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
31677 to the control; the default value is &"spool"& and the alternate value
31678 &"pass"& copies an SMTP defer response from the target back to the initiator
31679 and does not queue the message.
31680 Note that this is independent of any recipient verify conditions in the ACL.
31682 Delivery in this mode avoids the generation of a bounce mail to a
31684 sender when the destination system is doing content-scan based rejection.
31687 .vitem &*control&~=&~debug/*&<&'options'&>
31688 .cindex "&ACL;" "enabling debug logging"
31689 .cindex "debugging" "enabling from an ACL"
31690 This control turns on debug logging, almost as though Exim had been invoked
31691 with &`-d`&, with the output going to a new logfile in the usual logs directory,
31692 by default called &'debuglog'&.
31694 Logging set up by the control will be maintained across spool residency.
31696 Options are a slash-separated list.
31697 If an option takes an argument, the option name and argument are separated by
31698 an equals character.
31699 Several options are supported:
31701 tag=<&'suffix'&> The filename can be adjusted with thise option.
31702 The argument, which may access any variables already defined,
31703 is appended to the default name.
31705 opts=<&'debug&~options'&> The argument specififes what is to be logged,
31706 using the same values as the &`-d`& command-line option.
31708 stop Logging started with this control may be
31709 stopped by using this option.
31711 kill Logging started with this control may be
31712 stopped by using this option.
31713 Additionally the debug file will be removed,
31714 providing one means for speculative debug tracing.
31716 pretrigger=<&'size'&> This option specifies a memory buffuer to be used
31717 for pre-trigger debug capture.
31718 Debug lines are recorded in the buffer until
31719 and if) a trigger occurs; at which time they are
31720 dumped to the debug file. Newer lines displace the
31721 oldest if the buffer is full. After a trigger,
31722 immediate writes to file are done as normal.
31724 trigger=<&'reason'&> This option selects cause for the pretrigger buffer
31725 see above) to be copied to file. A reason of &*now*&
31726 take effect immediately; one of &*paniclog*& triggers
31727 on a write to the panic log.
31730 Some examples (which depend on variables that don't exist in all
31734 control = debug/tag=.$sender_host_address
31735 control = debug/opts=+expand+acl
31736 control = debug/tag=.$message_exim_id/opts=+expand
31737 control = debug/kill
31738 control = debug/opts=+all/pretrigger=1024/trigger=paniclog
31739 control = debug/trigger=now
31743 .vitem &*control&~=&~dkim_disable_verify*&
31744 .cindex "disable DKIM verify"
31745 .cindex "DKIM" "disable verify"
31746 This control turns off DKIM verification processing entirely. For details on
31747 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
31750 .vitem &*control&~=&~dmarc_disable_verify*&
31751 .cindex "disable DMARC verify"
31752 .cindex "DMARC" "disable verify"
31753 This control turns off DMARC verification processing entirely. For details on
31754 the operation and configuration of DMARC, see section &<<SECDMARC>>&.
31757 .vitem &*control&~=&~dscp/*&<&'value'&>
31758 .cindex "&ACL;" "setting DSCP value"
31759 .cindex "DSCP" "inbound"
31760 This option causes the DSCP value associated with the socket for the inbound
31761 connection to be adjusted to a given value, given as one of a number of fixed
31762 strings or to numeric value.
31763 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
31764 Common values include &`throughput`&, &`mincost`&, and on newer systems
31765 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
31767 The outbound packets from Exim will be marked with this value in the header
31768 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
31769 that these values will have any effect, not be stripped by networking
31770 equipment, or do much of anything without cooperation with your Network
31771 Engineer and those of all network operators between the source and destination.
31774 .vitem &*control&~=&~enforce_sync*& &&&
31775 &*control&~=&~no_enforce_sync*&
31776 .cindex "SMTP" "synchronization checking"
31777 .cindex "synchronization checking in SMTP"
31778 These controls make it possible to be selective about when SMTP synchronization
31779 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
31780 state of the switch (it is true by default). See the description of this option
31781 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
31783 The effect of these two controls lasts for the remainder of the SMTP
31784 connection. They can appear in any ACL except the one for the non-SMTP
31785 messages. The most straightforward place to put them is in the ACL defined by
31786 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
31787 before the first synchronization check. The expected use is to turn off the
31788 synchronization checks for badly-behaved hosts that you nevertheless need to
31792 .vitem &*control&~=&~fakedefer/*&<&'message'&>
31793 .cindex "fake defer"
31794 .cindex "defer, fake"
31795 This control works in exactly the same way as &%fakereject%& (described below)
31796 except that it causes an SMTP 450 response after the message data instead of a
31797 550 response. You must take care when using &%fakedefer%& because it causes the
31798 messages to be duplicated when the sender retries. Therefore, you should not
31799 use &%fakedefer%& if the message is to be delivered normally.
31801 .vitem &*control&~=&~fakereject/*&<&'message'&>
31802 .cindex "fake rejection"
31803 .cindex "rejection, fake"
31804 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
31805 words, only when an SMTP message is being received. If Exim accepts the
31806 message, instead the final 250 response, a 550 rejection message is sent.
31807 However, Exim proceeds to deliver the message as normal. The control applies
31808 only to the current message, not to any subsequent ones that may be received in
31809 the same SMTP connection.
31811 The text for the 550 response is taken from the &%control%& modifier. If no
31812 message is supplied, the following is used:
31814 550-Your message has been rejected but is being
31815 550-kept for evaluation.
31816 550-If it was a legitimate message, it may still be
31817 550 delivered to the target recipient(s).
31819 This facility should be used with extreme caution.
31821 .vitem &*control&~=&~freeze*&
31822 .cindex "frozen messages" "forcing in ACL"
31823 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31824 other words, only when a message is being received. If the message is accepted,
31825 it is placed on Exim's queue and frozen. The control applies only to the
31826 current message, not to any subsequent ones that may be received in the same
31829 This modifier can optionally be followed by &`/no_tell`&. If the global option
31830 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
31831 is told about the freezing), provided all the &*control=freeze*& modifiers that
31832 are obeyed for the current message have the &`/no_tell`& option.
31834 .vitem &*control&~=&~no_delay_flush*&
31835 .cindex "SMTP" "output flushing, disabling for delay"
31836 Exim normally flushes SMTP output before implementing a delay in an ACL, to
31837 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31838 use. This control, as long as it is encountered before the &%delay%& modifier,
31839 disables such output flushing.
31841 .vitem &*control&~=&~no_callout_flush*&
31842 .cindex "SMTP" "output flushing, disabling for callout"
31843 Exim normally flushes SMTP output before performing a callout in an ACL, to
31844 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31845 use. This control, as long as it is encountered before the &%verify%& condition
31846 that causes the callout, disables such output flushing.
31848 .vitem &*control&~=&~no_mbox_unspool*&
31849 This control is available when Exim is compiled with the content scanning
31850 extension. Content scanning may require a copy of the current message, or parts
31851 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
31852 or spam scanner. Normally, such copies are deleted when they are no longer
31853 needed. If this control is set, the copies are not deleted. The control applies
31854 only to the current message, not to any subsequent ones that may be received in
31855 the same SMTP connection. It is provided for debugging purposes and is unlikely
31856 to be useful in production.
31858 .vitem &*control&~=&~no_multiline_responses*&
31859 .cindex "multiline responses, suppressing"
31860 This control is permitted for any ACL except the one for non-SMTP messages.
31861 It seems that there are broken clients in use that cannot handle multiline
31862 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
31864 If this control is set, multiline SMTP responses from ACL rejections are
31865 suppressed. One way of doing this would have been to put out these responses as
31866 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
31867 (&"use multiline responses for more"& it says &-- ha!), and some of the
31868 responses might get close to that. So this facility, which is after all only a
31869 sop to broken clients, is implemented by doing two very easy things:
31872 Extra information that is normally output as part of a rejection caused by
31873 sender verification failure is omitted. Only the final line (typically &"sender
31874 verification failed"&) is sent.
31876 If a &%message%& modifier supplies a multiline response, only the first
31880 The setting of the switch can, of course, be made conditional on the
31881 calling host. Its effect lasts until the end of the SMTP connection.
31883 .vitem &*control&~=&~no_pipelining*&
31884 .cindex "PIPELINING" "suppressing advertising"
31885 .cindex "ESMTP extensions" PIPELINING
31886 This control turns off the advertising of the PIPELINING extension to SMTP in
31887 the current session. To be useful, it must be obeyed before Exim sends its
31888 response to an EHLO command. Therefore, it should normally appear in an ACL
31889 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
31890 &%pipelining_advertise_hosts%&.
31892 .vitem &*control&~=&~queue/*&<&'options'&>* &&&
31893 &*control&~=&~queue_only*&
31894 .oindex "&%queue%&"
31895 .oindex "&%queue_only%&"
31896 .cindex "queueing incoming messages"
31897 .cindex queueing "forcing in ACL"
31898 .cindex "first pass routing"
31899 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31900 other words, only when a message is being received. If the message is accepted,
31901 it is placed on Exim's queue and left there for delivery by a subsequent queue
31903 If used with no options set,
31904 no immediate delivery process is started. In other words, it has the
31905 effect as the &%queue_only%& global option or &'-odq'& command-line option.
31907 If the &'first_pass_route'& option is given then
31908 the behaviour is like the command-line &'-oqds'& option;
31909 a delivery process is started which stops short of making
31910 any SMTP delivery. The benefit is that the hints database will be updated for
31911 the message being waiting for a specific host, and a later queue run will be
31912 able to send all such messages on a single connection.
31914 The control only applies to the current message, not to any subsequent ones that
31915 may be received in the same SMTP connection.
31917 .vitem &*control&~=&~submission/*&<&'options'&>
31918 .cindex "message" "submission"
31919 .cindex "submission mode"
31920 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
31921 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
31922 the current message is a submission from a local MUA. In this case, Exim
31923 operates in &"submission mode"&, and applies certain fixups to the message if
31924 necessary. For example, it adds a &'Date:'& header line if one is not present.
31925 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
31926 late (the message has already been created).
31928 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
31929 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
31930 submission mode; the available options for this control are described there.
31931 The control applies only to the current message, not to any subsequent ones
31932 that may be received in the same SMTP connection.
31934 .vitem &*control&~=&~suppress_local_fixups*&
31935 .cindex "submission fixups, suppressing"
31936 This control applies to locally submitted (non TCP/IP) messages, and is the
31937 complement of &`control = submission`&. It disables the fixups that are
31938 normally applied to locally-submitted messages. Specifically:
31941 Any &'Sender:'& header line is left alone (in this respect, it is a
31942 dynamic version of &%local_sender_retain%&).
31944 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
31946 There is no check that &'From:'& corresponds to the actual sender.
31949 This control may be useful when a remotely-originated message is accepted,
31950 passed to some scanning program, and then re-submitted for delivery. It can be
31951 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
31952 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
31955 &*Note:*& This control applies only to the current message, not to any others
31956 that are being submitted at the same time using &%-bs%& or &%-bS%&.
31958 .vitem &*control&~=&~utf8_downconvert*&
31959 This control enables conversion of UTF-8 in message envelope addresses
31961 For details see section &<<SECTi18nMTA>>&.
31965 .section "Summary of message fixup control" "SECTsummesfix"
31966 All four possibilities for message fixups can be specified:
31969 Locally submitted, fixups applied: the default.
31971 Locally submitted, no fixups applied: use
31972 &`control = suppress_local_fixups`&.
31974 Remotely submitted, no fixups applied: the default.
31976 Remotely submitted, fixups applied: use &`control = submission`&.
31981 .section "Adding header lines in ACLs" "SECTaddheadacl"
31982 .cindex "header lines" "adding in an ACL"
31983 .cindex "header lines" "position of added lines"
31984 .cindex "&%add_header%& ACL modifier"
31985 The &%add_header%& modifier can be used to add one or more extra header lines
31986 to an incoming message, as in this example:
31988 warn dnslists = sbl.spamhaus.org : \
31989 dialup.mail-abuse.org
31990 add_header = X-blacklisted-at: $dnslist_domain
31992 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31993 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31994 receiving a message). The message must ultimately be accepted for
31995 &%add_header%& to have any significant effect. You can use &%add_header%& with
31996 any ACL verb, including &%deny%& (though this is potentially useful only in a
31999 Headers will not be added to the message if the modifier is used in
32000 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
32002 Leading and trailing newlines are removed from
32003 the data for the &%add_header%& modifier; if it then
32004 contains one or more newlines that
32005 are not followed by a space or a tab, it is assumed to contain multiple header
32006 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
32007 front of any line that is not a valid header line.
32009 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
32010 They are added to the message before processing the DATA and MIME ACLs.
32011 However, if an identical header line is requested more than once, only one copy
32012 is actually added to the message. Further header lines may be accumulated
32013 during the DATA and MIME ACLs, after which they are added to the message, again
32014 with duplicates suppressed. Thus, it is possible to add two identical header
32015 lines to an SMTP message, but only if one is added before DATA and one after.
32016 In the case of non-SMTP messages, new headers are accumulated during the
32017 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
32018 message is rejected after DATA or by the non-SMTP ACL, all added header lines
32019 are included in the entry that is written to the reject log.
32021 .cindex "header lines" "added; visibility of"
32022 Header lines are not visible in string expansions
32024 until they are added to the
32025 message. It follows that header lines defined in the MAIL, RCPT, and predata
32026 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
32027 header lines that are added by the DATA or MIME ACLs are not visible in those
32028 ACLs. Because of this restriction, you cannot use header lines as a way of
32029 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
32030 this, you can use ACL variables, as described in section
32031 &<<SECTaclvariables>>&.
32033 The list of headers yet to be added is given by the &%$headers_added%& variable.
32035 The &%add_header%& modifier acts immediately as it is encountered during the
32036 processing of an ACL. Notice the difference between these two cases:
32038 &`accept add_header = ADDED: some text`&
32039 &` `&<&'some condition'&>
32041 &`accept `&<&'some condition'&>
32042 &` add_header = ADDED: some text`&
32044 In the first case, the header line is always added, whether or not the
32045 condition is true. In the second case, the header line is added only if the
32046 condition is true. Multiple occurrences of &%add_header%& may occur in the same
32047 ACL statement. All those that are encountered before a condition fails are
32050 .cindex "&%warn%& ACL verb"
32051 For compatibility with previous versions of Exim, a &%message%& modifier for a
32052 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
32053 effect only if all the conditions are true, even if it appears before some of
32054 them. Furthermore, only the last occurrence of &%message%& is honoured. This
32055 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
32056 are present on a &%warn%& verb, both are processed according to their
32059 By default, new header lines are added to a message at the end of the existing
32060 header lines. However, you can specify that any particular header line should
32061 be added right at the start (before all the &'Received:'& lines), immediately
32062 after the first block of &'Received:'& lines, or immediately before any line
32063 that is not a &'Received:'& or &'Resent-something:'& header.
32065 This is done by specifying &":at_start:"&, &":after_received:"&, or
32066 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
32067 header line, respectively. (Header text cannot start with a colon, as there has
32068 to be a header name first.) For example:
32070 warn add_header = \
32071 :after_received:X-My-Header: something or other...
32073 If more than one header line is supplied in a single &%add_header%& modifier,
32074 each one is treated independently and can therefore be placed differently. If
32075 you add more than one line at the start, or after the Received: block, they end
32076 up in reverse order.
32078 &*Warning*&: This facility currently applies only to header lines that are
32079 added in an ACL. It does NOT work for header lines that are added in a
32080 system filter or in a router or transport.
32084 .section "Removing header lines in ACLs" "SECTremoveheadacl"
32085 .cindex "header lines" "removing in an ACL"
32086 .cindex "header lines" "position of removed lines"
32087 .cindex "&%remove_header%& ACL modifier"
32088 The &%remove_header%& modifier can be used to remove one or more header lines
32089 from an incoming message, as in this example:
32091 warn message = Remove internal headers
32092 remove_header = x-route-mail1 : x-route-mail2
32094 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
32095 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
32096 receiving a message). The message must ultimately be accepted for
32097 &%remove_header%& to have any significant effect. You can use &%remove_header%&
32098 with any ACL verb, including &%deny%&, though this is really not useful for
32099 any verb that doesn't result in a delivered message.
32101 Headers will not be removed from the message if the modifier is used in
32102 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
32104 More than one header can be removed at the same time by using a colon separated
32105 list of header names. The header matching is case insensitive. Wildcards are
32106 not permitted, nor is list expansion performed, so you cannot use hostlists to
32107 create a list of headers, however both connection and message variable expansion
32108 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
32110 warn hosts = +internal_hosts
32111 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
32112 warn message = Remove internal headers
32113 remove_header = $acl_c_ihdrs
32115 Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
32116 Matching header lines are removed from the message before processing the DATA and MIME ACLs.
32117 If multiple header lines match, all are removed.
32118 There is no harm in attempting to remove the same header twice nor in removing
32119 a non-existent header. Further header lines to be removed may be accumulated
32120 during the DATA and MIME ACLs, after which they are removed from the message,
32121 if present. In the case of non-SMTP messages, headers to be removed are
32122 accumulated during the non-SMTP ACLs, and are removed from the message after
32123 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
32124 ACL, there really is no effect because there is no logging of what headers
32125 would have been removed.
32127 .cindex "header lines" "removed; visibility of"
32128 Header lines are not visible in string expansions until the DATA phase when it
32129 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
32130 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
32131 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
32132 this restriction, you cannot use header lines as a way of controlling data
32133 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
32134 you should instead use ACL variables, as described in section
32135 &<<SECTaclvariables>>&.
32137 The &%remove_header%& modifier acts immediately as it is encountered during the
32138 processing of an ACL. Notice the difference between these two cases:
32140 &`accept remove_header = X-Internal`&
32141 &` `&<&'some condition'&>
32143 &`accept `&<&'some condition'&>
32144 &` remove_header = X-Internal`&
32146 In the first case, the header line is always removed, whether or not the
32147 condition is true. In the second case, the header line is removed only if the
32148 condition is true. Multiple occurrences of &%remove_header%& may occur in the
32149 same ACL statement. All those that are encountered before a condition fails
32152 &*Warning*&: This facility currently applies only to header lines that are
32153 present during ACL processing. It does NOT remove header lines that are added
32154 in a system filter or in a router or transport.
32159 .section "ACL conditions" "SECTaclconditions"
32160 .cindex "&ACL;" "conditions; list of"
32161 Some of the conditions listed in this section are available only when Exim is
32162 compiled with the content-scanning extension. They are included here briefly
32163 for completeness. More detailed descriptions can be found in the discussion on
32164 content scanning in chapter &<<CHAPexiscan>>&.
32166 Not all conditions are relevant in all circumstances. For example, testing
32167 senders and recipients does not make sense in an ACL that is being run as the
32168 result of the arrival of an ETRN command, and checks on message headers can be
32169 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
32170 can use the same condition (with different parameters) more than once in the
32171 same ACL statement. This provides a way of specifying an &"and"& conjunction.
32172 The conditions are as follows:
32176 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
32177 .cindex "&ACL;" "nested"
32178 .cindex "&ACL;" "indirect"
32179 .cindex "&ACL;" "arguments"
32180 .cindex "&%acl%& ACL condition"
32181 The possible values of the argument are the same as for the
32182 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
32183 &"accept"& the condition is true; if it returns &"deny"& the condition is
32184 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
32185 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
32186 condition false. This means that further processing of the &%warn%& verb
32187 ceases, but processing of the ACL continues.
32189 If the argument is a named ACL, up to nine space-separated optional values
32190 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
32191 and $acl_narg is set to the count of values.
32192 Previous values of these variables are restored after the call returns.
32193 The name and values are expanded separately.
32194 Note that spaces in complex expansions which are used as arguments
32195 will act as argument separators.
32197 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
32198 the connection is dropped. If it returns &"discard"&, the verb must be
32199 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
32200 conditions are tested.
32202 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
32203 loops. This condition allows you to use different ACLs in different
32204 circumstances. For example, different ACLs can be used to handle RCPT commands
32205 for different local users or different local domains.
32207 .vitem &*authenticated&~=&~*&<&'string&~list'&>
32208 .cindex "&%authenticated%& ACL condition"
32209 .cindex "authentication" "ACL checking"
32210 .cindex "&ACL;" "testing for authentication"
32211 If the SMTP connection is not authenticated, the condition is false. Otherwise,
32212 the name of the authenticator is tested against the list. To test for
32213 authentication by any authenticator, you can set
32218 .vitem &*condition&~=&~*&<&'string'&>
32219 .cindex "&%condition%& ACL condition"
32220 .cindex "customizing" "ACL condition"
32221 .cindex "&ACL;" "customized test"
32222 .cindex "&ACL;" "testing, customized"
32223 This feature allows you to make up custom conditions. If the result of
32224 expanding the string is an empty string, the number zero, or one of the strings
32225 &"no"& or &"false"&, the condition is false. If the result is any non-zero
32226 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
32227 any other value, some error is assumed to have occurred, and the ACL returns
32228 &"defer"&. However, if the expansion is forced to fail, the condition is
32229 ignored. The effect is to treat it as true, whether it is positive or
32232 .vitem &*decode&~=&~*&<&'location'&>
32233 .cindex "&%decode%& ACL condition"
32234 This condition is available only when Exim is compiled with the
32235 content-scanning extension, and it is allowed only in the ACL defined by
32236 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
32237 If all goes well, the condition is true. It is false only if there are
32238 problems such as a syntax error or a memory shortage. For more details, see
32239 chapter &<<CHAPexiscan>>&.
32241 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
32242 .cindex "&%dnslists%& ACL condition"
32243 .cindex "DNS list" "in ACL"
32244 .cindex "black list (DNS)"
32245 .cindex "&ACL;" "testing a DNS list"
32246 This condition checks for entries in DNS black lists. These are also known as
32247 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
32248 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
32249 different variants of this condition to describe briefly here. See sections
32250 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
32252 .vitem &*domains&~=&~*&<&'domain&~list'&>
32253 .cindex "&%domains%& ACL condition"
32254 .cindex "domain" "ACL checking"
32255 .cindex "&ACL;" "testing a recipient domain"
32256 .vindex "&$domain_data$&"
32257 This condition is relevant only in a RCPT ACL. It checks that the domain
32258 of the recipient address is in the domain list. If percent-hack processing is
32259 enabled, it is done before this test is done. If the check succeeds with a
32260 lookup, the result of the lookup is placed in &$domain_data$& until the next
32263 &*Note carefully*& (because many people seem to fall foul of this): you cannot
32264 use &%domains%& in a DATA ACL.
32267 .vitem &*encrypted&~=&~*&<&'string&~list'&>
32268 .cindex "&%encrypted%& ACL condition"
32269 .cindex "encryption" "checking in an ACL"
32270 .cindex "&ACL;" "testing for encryption"
32271 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
32272 name of the cipher suite in use is tested against the list. To test for
32273 encryption without testing for any specific cipher suite(s), set
32279 .vitem &*hosts&~=&~*&<&'host&~list'&>
32280 .cindex "&%hosts%& ACL condition"
32281 .cindex "host" "ACL checking"
32282 .cindex "&ACL;" "testing the client host"
32283 This condition tests that the calling host matches the host list. If you have
32284 name lookups or wildcarded host names and IP addresses in the same host list,
32285 you should normally put the IP addresses first. For example, you could have:
32287 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
32289 The lookup in this example uses the host name for its key. This is implied by
32290 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
32291 and it wouldn't matter which way round you had these two items.)
32293 The reason for the problem with host names lies in the left-to-right way that
32294 Exim processes lists. It can test IP addresses without doing any DNS lookups,
32295 but when it reaches an item that requires a host name, it fails if it cannot
32296 find a host name to compare with the pattern. If the above list is given in the
32297 opposite order, the &%accept%& statement fails for a host whose name cannot be
32298 found, even if its IP address is 10.9.8.7.
32300 If you really do want to do the name check first, and still recognize the IP
32301 address even if the name lookup fails, you can rewrite the ACL like this:
32303 accept hosts = dbm;/etc/friendly/hosts
32304 accept hosts = 10.9.8.7
32306 The default action on failing to find the host name is to assume that the host
32307 is not in the list, so the first &%accept%& statement fails. The second
32308 statement can then check the IP address.
32310 .vindex "&$host_data$&"
32311 If a &%hosts%& condition is satisfied by means of a lookup, the result
32312 of the lookup is made available in the &$host_data$& variable. This
32313 allows you, for example, to set up a statement like this:
32315 deny hosts = net-lsearch;/some/file
32316 message = $host_data
32318 which gives a custom error message for each denied host.
32320 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
32321 .cindex "&%local_parts%& ACL condition"
32322 .cindex "local part" "ACL checking"
32323 .cindex "&ACL;" "testing a local part"
32324 .vindex "&$local_part_data$&"
32325 This condition is relevant only in a RCPT ACL. It checks that the local
32326 part of the recipient address is in the list. If percent-hack processing is
32327 enabled, it is done before this test. If the check succeeds with a lookup, the
32328 result of the lookup is placed in &$local_part_data$&, which remains set until
32329 the next &%local_parts%& test.
32331 .vitem &*malware&~=&~*&<&'option'&>
32332 .cindex "&%malware%& ACL condition"
32333 .cindex "&ACL;" "virus scanning"
32334 .cindex "&ACL;" "scanning for viruses"
32335 This condition is available only when Exim is compiled with the
32336 content-scanning extension
32337 and only after a DATA command.
32338 It causes the incoming message to be scanned for
32339 viruses. For details, see chapter &<<CHAPexiscan>>&.
32341 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32342 .cindex "&%mime_regex%& ACL condition"
32343 .cindex "&ACL;" "testing by regex matching"
32344 This condition is available only when Exim is compiled with the
32345 content-scanning extension, and it is allowed only in the ACL defined by
32346 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
32347 with any of the regular expressions. For details, see chapter
32350 .vitem &*ratelimit&~=&~*&<&'parameters'&>
32351 .cindex "rate limiting"
32352 This condition can be used to limit the rate at which a user or host submits
32353 messages. Details are given in section &<<SECTratelimiting>>&.
32355 .vitem &*recipients&~=&~*&<&'address&~list'&>
32356 .cindex "&%recipients%& ACL condition"
32357 .cindex "recipient" "ACL checking"
32358 .cindex "&ACL;" "testing a recipient"
32359 This condition is relevant only in a RCPT ACL. It checks the entire
32360 recipient address against a list of recipients.
32362 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32363 .cindex "&%regex%& ACL condition"
32364 .cindex "&ACL;" "testing by regex matching"
32365 This condition is available only when Exim is compiled with the
32366 content-scanning extension, and is available only in the DATA, MIME, and
32367 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
32368 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
32370 .vitem &*seen&~=&~*&<&'parameters'&>
32371 .cindex "&%seen%& ACL condition"
32372 This condition can be used to test if a situation has been previously met,
32373 for example for greylisting.
32374 Details are given in section &<<SECTseen>>&.
32376 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
32377 .cindex "&%sender_domains%& ACL condition"
32378 .cindex "sender" "ACL checking"
32379 .cindex "&ACL;" "testing a sender domain"
32380 .vindex "&$domain$&"
32381 .vindex "&$sender_address_domain$&"
32382 This condition tests the domain of the sender of the message against the given
32383 domain list. &*Note*&: The domain of the sender address is in
32384 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
32385 of this condition. This is an exception to the general rule for testing domain
32386 lists. It is done this way so that, if this condition is used in an ACL for a
32387 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
32388 influence the sender checking.
32390 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32391 relaying, because sender addresses are easily, and commonly, forged.
32393 .vitem &*senders&~=&~*&<&'address&~list'&>
32394 .cindex "&%senders%& ACL condition"
32395 .cindex "sender" "ACL checking"
32396 .cindex "&ACL;" "testing a sender"
32397 This condition tests the sender of the message against the given list. To test
32398 for a bounce message, which has an empty sender, set
32402 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32403 relaying, because sender addresses are easily, and commonly, forged.
32405 .vitem &*spam&~=&~*&<&'username'&>
32406 .cindex "&%spam%& ACL condition"
32407 .cindex "&ACL;" "scanning for spam"
32408 This condition is available only when Exim is compiled with the
32409 content-scanning extension. It causes the incoming message to be scanned by
32410 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
32412 .vitem &*verify&~=&~certificate*&
32413 .cindex "&%verify%& ACL condition"
32414 .cindex "TLS" "client certificate verification"
32415 .cindex "certificate" "verification of client"
32416 .cindex "&ACL;" "certificate verification"
32417 .cindex "&ACL;" "testing a TLS certificate"
32418 This condition is true in an SMTP session if the session is encrypted, and a
32419 certificate was received from the client, and the certificate was verified. The
32420 server requests a certificate only if the client matches &%tls_verify_hosts%&
32421 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
32423 .vitem &*verify&~=&~csa*&
32424 .cindex "CSA verification"
32425 This condition checks whether the sending host (the client) is authorized to
32426 send email. Details of how this works are given in section
32427 &<<SECTverifyCSA>>&.
32429 .vitem &*verify&~=&~header_names_ascii*&
32430 .cindex "&%verify%& ACL condition"
32431 .cindex "&ACL;" "verifying header names only ASCII"
32432 .cindex "header lines" "verifying header names only ASCII"
32433 .cindex "verifying" "header names only ASCII"
32434 This condition is relevant only in an ACL that is run after a message has been
32436 This usually means an ACL specified by &%acl_smtp_data%& or &%acl_not_smtp%&.
32437 It checks all header names (not the content) to make sure
32438 there are no non-ASCII characters, also excluding control characters. The
32439 allowable characters are decimal ASCII values 33 through 126.
32441 Exim itself will handle headers with non-ASCII characters, but it can cause
32442 problems for downstream applications, so this option will allow their
32443 detection and rejection in the DATA ACL's.
32445 .vitem &*verify&~=&~header_sender/*&<&'options'&>
32446 .cindex "&%verify%& ACL condition"
32447 .cindex "&ACL;" "verifying sender in the header"
32448 .cindex "header lines" "verifying the sender in"
32449 .cindex "sender" "verifying in header"
32450 .cindex "verifying" "sender in header"
32451 This condition is relevant only in an ACL that is run after a message has been
32452 received, that is, in an ACL specified by &%acl_smtp_data%& or
32453 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
32454 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
32455 is loosely thought of as a &"sender"& address (hence the name of the test).
32456 However, an address that appears in one of these headers need not be an address
32457 that accepts bounce messages; only sender addresses in envelopes are required
32458 to accept bounces. Therefore, if you use the callout option on this check, you
32459 might want to arrange for a non-empty address in the MAIL command.
32461 Details of address verification and the options are given later, starting at
32462 section &<<SECTaddressverification>>& (callouts are described in section
32463 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
32464 condition to restrict it to bounce messages only:
32467 !verify = header_sender
32468 message = A valid sender header is required for bounces
32471 .vitem &*verify&~=&~header_syntax*&
32472 .cindex "&%verify%& ACL condition"
32473 .cindex "&ACL;" "verifying header syntax"
32474 .cindex "header lines" "verifying syntax"
32475 .cindex "verifying" "header syntax"
32476 This condition is relevant only in an ACL that is run after a message has been
32477 received, that is, in an ACL specified by &%acl_smtp_data%& or
32478 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
32479 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
32480 and &'Bcc:'&), returning true if there are no problems.
32481 Unqualified addresses (local parts without domains) are
32482 permitted only in locally generated messages and from hosts that match
32483 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
32486 Note that this condition is a syntax check only. However, a common spamming
32487 ploy used to be to send syntactically invalid headers such as
32491 and this condition can be used to reject such messages, though they are not as
32492 common as they used to be.
32494 .vitem &*verify&~=&~helo*&
32495 .cindex "&%verify%& ACL condition"
32496 .cindex "&ACL;" "verifying HELO/EHLO"
32497 .cindex "HELO" "verifying"
32498 .cindex "EHLO" "verifying"
32499 .cindex "verifying" "EHLO"
32500 .cindex "verifying" "HELO"
32501 This condition is true if a HELO or EHLO command has been received from the
32502 client host, and its contents have been verified. If there has been no previous
32503 attempt to verify the HELO/EHLO contents, it is carried out when this
32504 condition is encountered. See the description of the &%helo_verify_hosts%& and
32505 &%helo_try_verify_hosts%& options for details of how to request verification
32506 independently of this condition, and for detail of the verification.
32508 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
32509 option), this condition is always true.
32512 .vitem &*verify&~=&~not_blind/*&<&'options'&>
32513 .cindex "verifying" "not blind"
32514 .cindex "bcc recipients, verifying none"
32515 This condition checks that there are no blind (bcc) recipients in the message.
32516 Every envelope recipient must appear either in a &'To:'& header line or in a
32517 &'Cc:'& header line for this condition to be true. Local parts are checked
32518 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
32519 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
32520 used only in a DATA or non-SMTP ACL.
32522 There is one possible option, &`case_insensitive`&. If this is present then
32523 local parts are checked case-insensitively.
32525 There are, of course, many legitimate messages that make use of blind (bcc)
32526 recipients. This check should not be used on its own for blocking messages.
32529 .vitem &*verify&~=&~recipient/*&<&'options'&>
32530 .cindex "&%verify%& ACL condition"
32531 .cindex "&ACL;" "verifying recipient"
32532 .cindex "recipient" "verifying"
32533 .cindex "verifying" "recipient"
32534 .vindex "&$address_data$&"
32535 This condition is relevant only after a RCPT command. It verifies the current
32536 recipient. Details of address verification are given later, starting at section
32537 &<<SECTaddressverification>>&. After a recipient has been verified, the value
32538 of &$address_data$& is the last value that was set while routing the address.
32539 This applies even if the verification fails. When an address that is being
32540 verified is redirected to a single address, verification continues with the new
32541 address, and in that case, the subsequent value of &$address_data$& is the
32542 value for the child address.
32544 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
32545 .cindex "&%verify%& ACL condition"
32546 .cindex "&ACL;" "verifying host reverse lookup"
32547 .cindex "host" "verifying reverse lookup"
32548 This condition ensures that a verified host name has been looked up from the IP
32549 address of the client host. (This may have happened already if the host name
32550 was needed for checking a host list, or if the host matched &%host_lookup%&.)
32551 Verification ensures that the host name obtained from a reverse DNS lookup, or
32552 one of its aliases, does, when it is itself looked up in the DNS, yield the
32553 original IP address.
32555 There is one possible option, &`defer_ok`&. If this is present and a
32556 DNS operation returns a temporary error, the verify condition succeeds.
32558 If this condition is used for a locally generated message (that is, when there
32559 is no client host involved), it always succeeds.
32561 .vitem &*verify&~=&~sender/*&<&'options'&>
32562 .cindex "&%verify%& ACL condition"
32563 .cindex "&ACL;" "verifying sender"
32564 .cindex "sender" "verifying"
32565 .cindex "verifying" "sender"
32566 This condition is relevant only after a MAIL or RCPT command, or after a
32567 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
32568 the message's sender is empty (that is, this is a bounce message), the
32569 condition is true. Otherwise, the sender address is verified.
32571 .vindex "&$address_data$&"
32572 .vindex "&$sender_address_data$&"
32573 If there is data in the &$address_data$& variable at the end of routing, its
32574 value is placed in &$sender_address_data$& at the end of verification. This
32575 value can be used in subsequent conditions and modifiers in the same ACL
32576 statement. It does not persist after the end of the current statement. If you
32577 want to preserve the value for longer, you can save it in an ACL variable.
32579 Details of verification are given later, starting at section
32580 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
32581 to avoid doing it more than once per message.
32583 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
32584 .cindex "&%verify%& ACL condition"
32585 This is a variation of the previous option, in which a modified address is
32586 verified as a sender.
32588 Note that '/' is legal in local-parts; if the address may have such
32589 (eg. is generated from the received message)
32590 they must be protected from the options parsing by doubling:
32592 verify = sender=${listquote{/}{${address:$h_sender:}}}
32598 .section "Using DNS lists" "SECTmorednslists"
32599 .cindex "DNS list" "in ACL"
32600 .cindex "black list (DNS)"
32601 .cindex "&ACL;" "testing a DNS list"
32602 In its simplest form, the &%dnslists%& condition tests whether the calling host
32603 is on at least one of a number of DNS lists by looking up the inverted IP
32604 address in one or more DNS domains. (Note that DNS list domains are not mail
32605 domains, so the &`+`& syntax for named lists doesn't work - it is used for
32606 special options instead.) For example, if the calling host's IP
32607 address is 192.168.62.43, and the ACL statement is
32609 deny dnslists = blackholes.mail-abuse.org : \
32610 dialups.mail-abuse.org
32612 the following records are looked up:
32614 43.62.168.192.blackholes.mail-abuse.org
32615 43.62.168.192.dialups.mail-abuse.org
32617 As soon as Exim finds an existing DNS record, processing of the list stops.
32618 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
32619 to test that a host is on more than one list (an &"and"& conjunction), you can
32620 use two separate conditions:
32622 deny dnslists = blackholes.mail-abuse.org
32623 dnslists = dialups.mail-abuse.org
32625 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
32626 behaves as if the host does not match the list item, that is, as if the DNS
32627 record does not exist. If there are further items in the DNS list, they are
32630 This is usually the required action when &%dnslists%& is used with &%deny%&
32631 (which is the most common usage), because it prevents a DNS failure from
32632 blocking mail. However, you can change this behaviour by putting one of the
32633 following special items in the list:
32634 .itable none 0 0 2 25* left 75* left
32635 .irow "+include_unknown" "behave as if the item is on the list"
32636 .irow "+exclude_unknown" "behave as if the item is not on the list (default)"
32637 .irow "+defer_unknown " "give a temporary error"
32639 .cindex "&`+include_unknown`&"
32640 .cindex "&`+exclude_unknown`&"
32641 .cindex "&`+defer_unknown`&"
32642 Each of these applies to any subsequent items on the list. For example:
32644 deny dnslists = +defer_unknown : foo.bar.example
32646 Testing the list of domains stops as soon as a match is found. If you want to
32647 warn for one list and block for another, you can use two different statements:
32649 deny dnslists = blackholes.mail-abuse.org
32650 warn dnslists = dialups.mail-abuse.org
32651 message = X-Warn: sending host is on dialups list
32653 .cindex caching "of dns lookup"
32655 DNS list lookups are cached by Exim for the duration of the SMTP session
32656 (but limited by the DNS return TTL value),
32657 so a lookup based on the IP address is done at most once for any incoming
32658 connection (assuming long-enough TTL).
32659 Exim does not share information between multiple incoming
32660 connections (but your local name server cache should be active).
32662 There are a number of DNS lists to choose from, some commercial, some free,
32663 or free for small deployments. An overview can be found at
32664 &url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists).
32668 .subsection "Specifying the IP address for a DNS list lookup" SECID201
32669 .cindex "DNS list" "keyed by explicit IP address"
32670 By default, the IP address that is used in a DNS list lookup is the IP address
32671 of the calling host. However, you can specify another IP address by listing it
32672 after the domain name, introduced by a slash. For example:
32674 deny dnslists = black.list.tld/192.168.1.2
32676 This feature is not very helpful with explicit IP addresses; it is intended for
32677 use with IP addresses that are looked up, for example, the IP addresses of the
32678 MX hosts or nameservers of an email sender address. For an example, see section
32679 &<<SECTmulkeyfor>>& below.
32684 .subsection "DNS lists keyed on domain names" SECID202
32685 .cindex "DNS list" "keyed by domain name"
32686 There are some lists that are keyed on domain names rather than inverted IP
32687 addresses (see, e.g., the &'domain based zones'& link at
32688 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
32689 with these lists. You can change the name that is looked up in a DNS list by
32690 listing it after the domain name, introduced by a slash. For example,
32692 deny dnslists = dsn.rfc-ignorant.org/$sender_address_domain
32693 message = Sender's domain is listed at $dnslist_domain
32695 This particular example is useful only in ACLs that are obeyed after the
32696 RCPT or DATA commands, when a sender address is available. If (for
32697 example) the message's sender is &'user@tld.example'& the name that is looked
32698 up by this example is
32700 tld.example.dsn.rfc-ignorant.org
32702 A single &%dnslists%& condition can contain entries for both names and IP
32703 addresses. For example:
32705 deny dnslists = sbl.spamhaus.org : \
32706 dsn.rfc-ignorant.org/$sender_address_domain
32708 The first item checks the sending host's IP address; the second checks a domain
32709 name. The whole condition is true if either of the DNS lookups succeeds.
32714 .subsection "Multiple explicit keys for a DNS list" SECTmulkeyfor
32715 .cindex "DNS list" "multiple keys for"
32716 The syntax described above for looking up explicitly-defined values (either
32717 names or IP addresses) in a DNS blacklist is a simplification. After the domain
32718 name for the DNS list, what follows the slash can in fact be a list of items.
32719 As with all lists in Exim, the default separator is a colon. However, because
32720 this is a sublist within the list of DNS blacklist domains, it is necessary
32721 either to double the separators like this:
32723 dnslists = black.list.tld/name.1::name.2
32725 or to change the separator character, like this:
32727 dnslists = black.list.tld/<;name.1;name.2
32729 If an item in the list is an IP address, it is inverted before the DNS
32730 blacklist domain is appended. If it is not an IP address, no inversion
32731 occurs. Consider this condition:
32733 dnslists = black.list.tld/<;192.168.1.2;a.domain
32735 The DNS lookups that occur are:
32737 2.1.168.192.black.list.tld
32738 a.domain.black.list.tld
32740 Once a DNS record has been found (that matches a specific IP return
32741 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
32742 are done. If there is a temporary DNS error, the rest of the sublist of domains
32743 or IP addresses is tried. A temporary error for the whole dnslists item occurs
32744 only if no other DNS lookup in this sublist succeeds. In other words, a
32745 successful lookup for any of the items in the sublist overrides a temporary
32746 error for a previous item.
32748 The ability to supply a list of items after the slash is in some sense just a
32749 syntactic convenience. These two examples have the same effect:
32751 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
32752 dnslists = black.list.tld/a.domain::b.domain
32754 However, when the data for the list is obtained from a lookup, the second form
32755 is usually much more convenient. Consider this example:
32757 deny dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
32758 ${lookup dnsdb {>|mxh=\
32759 $sender_address_domain} }} }
32760 message = The mail servers for the domain \
32761 $sender_address_domain \
32762 are listed at $dnslist_domain ($dnslist_value); \
32765 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
32766 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
32767 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
32768 of expanding the condition might be something like this:
32770 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
32772 Thus, this example checks whether or not the IP addresses of the sender
32773 domain's mail servers are on the Spamhaus black list.
32775 The key that was used for a successful DNS list lookup is put into the variable
32776 &$dnslist_matched$& (see section &<<SECID204>>&).
32781 .subsection "Data returned by DNS lists" SECID203
32782 .cindex "DNS list" "data returned from"
32783 DNS lists are constructed using address records in the DNS. The original RBL
32784 just used the address 127.0.0.1 on the right hand side of each record, but the
32785 RBL+ list and some other lists use a number of values with different meanings.
32786 The values used on the RBL+ list are:
32787 .itable none 0 0 2 20* left 80* left
32788 .irow 127.1.0.1 "RBL"
32789 .irow 127.1.0.2 "DUL"
32790 .irow 127.1.0.3 "DUL and RBL"
32791 .irow 127.1.0.4 "RSS"
32792 .irow 127.1.0.5 "RSS and RBL"
32793 .irow 127.1.0.6 "RSS and DUL"
32794 .irow 127.1.0.7 "RSS and DUL and RBL"
32796 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
32797 different values. Some DNS lists may return more than one address record;
32798 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
32800 Values returned by a properly running DBSBL should be in the 127.0.0.0/8
32801 range. If a DNSBL operator loses control of the domain, lookups on it
32802 may start returning other addresses. Because of this, Exim now ignores
32803 returned values outside the 127/8 region.
32806 .subsection "Variables set from DNS lists" SECID204
32807 .cindex "expansion" "variables, set from DNS list"
32808 .cindex "DNS list" "variables set from"
32809 .vindex "&$dnslist_domain$&"
32810 .vindex "&$dnslist_matched$&"
32811 .vindex "&$dnslist_text$&"
32812 .vindex "&$dnslist_value$&"
32813 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
32814 the name of the overall domain that matched (for example,
32815 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
32816 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
32817 the DNS record. When the key is an IP address, it is not reversed in
32818 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
32819 cases, for example:
32821 deny dnslists = spamhaus.example
32823 the key is also available in another variable (in this case,
32824 &$sender_host_address$&). In more complicated cases, however, this is not true.
32825 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
32826 might generate a dnslists lookup like this:
32828 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
32830 If this condition succeeds, the value in &$dnslist_matched$& might be
32831 &`192.168.6.7`& (for example).
32833 If more than one address record is returned by the DNS lookup, all the IP
32834 addresses are included in &$dnslist_value$&, separated by commas and spaces.
32835 The variable &$dnslist_text$& contains the contents of any associated TXT
32836 record. For lists such as RBL+ the TXT record for a merged entry is often not
32837 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
32840 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
32841 &-- even if these appear before the condition in the ACL, they are not
32842 expanded until after it has failed. For example:
32844 deny hosts = !+local_networks
32845 message = $sender_host_address is listed \
32847 dnslists = rbl-plus.mail-abuse.example
32852 .subsection "Additional matching conditions for DNS lists" SECTaddmatcon
32853 .cindex "DNS list" "matching specific returned data"
32854 You can add an equals sign and an IP address after a &%dnslists%& domain name
32855 in order to restrict its action to DNS records with a matching right hand side.
32858 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
32860 rejects only those hosts that yield 127.0.0.2. Without this additional data,
32861 any address record is considered to be a match. For the moment, we assume
32862 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
32863 describes how multiple records are handled.
32865 More than one IP address may be given for checking, using a comma as a
32866 separator. These are alternatives &-- if any one of them matches, the
32867 &%dnslists%& condition is true. For example:
32869 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32871 If you want to specify a constraining address list and also specify names or IP
32872 addresses to be looked up, the constraining address list must be specified
32873 first. For example:
32875 deny dnslists = dsn.rfc-ignorant.org\
32876 =127.0.0.2/$sender_address_domain
32879 If the character &`&&`& is used instead of &`=`&, the comparison for each
32880 listed IP address is done by a bitwise &"and"& instead of by an equality test.
32881 In other words, the listed addresses are used as bit masks. The comparison is
32882 true if all the bits in the mask are present in the address that is being
32883 tested. For example:
32885 dnslists = a.b.c&0.0.0.3
32887 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
32888 want to test whether one bit or another bit is present (as opposed to both
32889 being present), you must use multiple values. For example:
32891 dnslists = a.b.c&0.0.0.1,0.0.0.2
32893 matches if the final component of the address is an odd number or two times
32898 .subsection "Negated DNS matching conditions" SECID205
32899 You can supply a negative list of IP addresses as part of a &%dnslists%&
32902 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32904 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32905 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
32907 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
32909 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32910 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
32911 words, the result of the test is inverted if an exclamation mark appears before
32912 the &`=`& (or the &`&&`&) sign.
32914 &*Note*&: This kind of negation is not the same as negation in a domain,
32915 host, or address list (which is why the syntax is different).
32917 If you are using just one list, the negation syntax does not gain you much. The
32918 previous example is precisely equivalent to
32920 deny dnslists = a.b.c
32921 !dnslists = a.b.c=127.0.0.2,127.0.0.3
32923 However, if you are using multiple lists, the negation syntax is clearer.
32924 Consider this example:
32926 deny dnslists = sbl.spamhaus.org : \
32928 dnsbl.njabl.org!=127.0.0.3 : \
32931 Using only positive lists, this would have to be:
32933 deny dnslists = sbl.spamhaus.org : \
32935 deny dnslists = dnsbl.njabl.org
32936 !dnslists = dnsbl.njabl.org=127.0.0.3
32937 deny dnslists = relays.ordb.org
32939 which is less clear, and harder to maintain.
32941 Negation can also be used with a bitwise-and restriction.
32942 The dnslists condition with only be trus if a result is returned
32943 by the lookup which, anded with the restriction, is all zeroes.
32946 deny dnslists = zen.spamhaus.org!&0.255.255.0
32952 .subsection "Handling multiple DNS records from a DNS list" SECThanmuldnsrec
32953 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
32954 thereby providing more than one IP address. When an item in a &%dnslists%& list
32955 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
32956 the match to specific results from the DNS lookup, there are two ways in which
32957 the checking can be handled. For example, consider the condition:
32959 dnslists = a.b.c=127.0.0.1
32961 What happens if the DNS lookup for the incoming IP address yields both
32962 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
32963 condition true because at least one given value was found, or is it false
32964 because at least one of the found values was not listed? And how does this
32965 affect negated conditions? Both possibilities are provided for with the help of
32966 additional separators &`==`& and &`=&&`&.
32969 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
32970 IP addresses matches one of the listed addresses. For the example above, the
32971 condition is true because 127.0.0.1 matches.
32973 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
32974 looked up IP addresses matches one of the listed addresses. If the condition is
32977 dnslists = a.b.c==127.0.0.1
32979 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32980 false because 127.0.0.2 is not listed. You would need to have:
32982 dnslists = a.b.c==127.0.0.1,127.0.0.2
32984 for the condition to be true.
32987 When &`!`& is used to negate IP address matching, it inverts the result, giving
32988 the precise opposite of the behaviour above. Thus:
32990 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
32991 addresses matches one of the listed addresses. Consider:
32993 dnslists = a.b.c!&0.0.0.1
32995 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32996 false because 127.0.0.1 matches.
32998 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
32999 looked up IP address that does not match. Consider:
33001 dnslists = a.b.c!=&0.0.0.1
33003 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
33004 true, because 127.0.0.2 does not match. You would need to have:
33006 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
33008 for the condition to be false.
33010 When the DNS lookup yields only a single IP address, there is no difference
33011 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
33016 .subsection "Detailed information from merged DNS lists" SECTmordetinf
33017 .cindex "DNS list" "information from merged"
33018 When the facility for restricting the matching IP values in a DNS list is used,
33019 the text from the TXT record that is set in &$dnslist_text$& may not reflect
33020 the true reason for rejection. This happens when lists are merged and the IP
33021 address in the A record is used to distinguish them; unfortunately there is
33022 only one TXT record. One way round this is not to use merged lists, but that
33023 can be inefficient because it requires multiple DNS lookups where one would do
33024 in the vast majority of cases when the host of interest is not on any of the
33027 A less inefficient way of solving this problem is available. If
33028 two domain names, comma-separated, are given, the second is used first to
33029 do an initial check, making use of any IP value restrictions that are set.
33030 If there is a match, the first domain is used, without any IP value
33031 restrictions, to get the TXT record. As a byproduct of this, there is also
33032 a check that the IP being tested is indeed on the first list. The first
33033 domain is the one that is put in &$dnslist_domain$&. For example:
33036 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
33037 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
33039 rejected because $sender_host_address is blacklisted \
33040 at $dnslist_domain\n$dnslist_text
33042 For the first blacklist item, this starts by doing a lookup in
33043 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
33044 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
33045 value, and as long as something is found, it looks for the corresponding TXT
33046 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
33047 The second blacklist item is processed similarly.
33049 If you are interested in more than one merged list, the same list must be
33050 given several times, but because the results of the DNS lookups are cached,
33051 the DNS calls themselves are not repeated. For example:
33054 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
33055 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
33056 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
33057 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
33059 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
33060 values matches (or if no record is found), this is the only lookup that is
33061 done. Only if there is a match is one of the more specific lists consulted.
33065 .subsection "DNS lists and IPv6" SECTmorednslistslast
33066 .cindex "IPv6" "DNS black lists"
33067 .cindex "DNS list" "IPv6 usage"
33068 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
33069 nibble by nibble. For example, if the calling host's IP address is
33070 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
33072 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
33073 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
33075 (split over two lines here to fit on the page). Unfortunately, some of the DNS
33076 lists contain wildcard records, intended for IPv4, that interact badly with
33077 IPv6. For example, the DNS entry
33079 *.3.some.list.example. A 127.0.0.1
33081 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
33082 Unfortunately, it also matches the entire 3::/4 IPv6 network.
33084 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
33085 &%condition%& condition, as in this example:
33087 deny condition = ${if isip4{$sender_host_address}}
33088 dnslists = some.list.example
33091 If an explicit key is being used for a DNS lookup and it may be an IPv6
33092 address you should specify alternate list separators for both the outer
33093 (DNS list name) list and inner (lookup keys) list:
33095 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
33099 .section "Previously seen user and hosts" "SECTseen"
33100 .cindex "&%seen%& ACL condition"
33101 .cindex greylisting
33102 The &%seen%& ACL condition can be used to test whether a
33103 situation has been previously met.
33104 It uses a hints database to record a timestamp against a key.
33105 The syntax of the condition is:
33107 &`seen =`& <&'optional flag'&><&'time interval'&> &`/`& <&'options'&>
33112 defer seen = -5m / key=${sender_host_address}_$local_part@$domain
33114 in a RCPT ACL will implement simple greylisting.
33116 The parameters for the condition are
33117 a possible minus sign,
33119 then, slash-separated, a list of options.
33120 The interval is taken as an offset before the current time,
33121 and used for the test.
33122 If the interval is preceded by a minus sign then the condition returns
33123 whether a record is found which is before the test time.
33124 Otherwise, the condition returns whether one is found which is since the
33127 Options are read in order with later ones overriding earlier ones.
33129 The default key is &$sender_host_address$&.
33130 An explicit key can be set using a &%key=value%& option.
33132 If a &%readonly%& option is given then
33133 no record create or update is done.
33134 If a &%write%& option is given then
33135 a record create or update is always done.
33136 An update is done if the test is for &"since"&.
33137 If none of those hold and there was no existing record,
33138 a record is created.
33140 Creates and updates are marked with the current time.
33142 Finally, a &"before"& test which succeeds, and for which the record
33143 is old enough, will be refreshed with a timestamp of the test time.
33144 This can prevent tidying of the database from removing the entry.
33145 The interval for this is, by default, 10 days.
33146 An explicit interval can be set using a
33147 &%refresh=value%& option.
33149 Note that &"seen"& should be added to the list of hints databases
33150 for maintenance if this ACL condition is used.
33153 .section "Rate limiting incoming messages" "SECTratelimiting"
33154 .cindex "rate limiting" "client sending"
33155 .cindex "limiting client sending rates"
33156 .oindex "&%smtp_ratelimit_*%&"
33157 The &%ratelimit%& ACL condition can be used to measure and control the rate at
33158 which clients can send email. This is more powerful than the
33159 &%smtp_ratelimit_*%& options, because those options control the rate of
33160 commands in a single SMTP session only, whereas the &%ratelimit%& condition
33161 works across all connections (concurrent and sequential) from the same client
33162 host. The syntax of the &%ratelimit%& condition is:
33164 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
33166 If the average client sending rate is less than &'m'& messages per time
33167 period &'p'& then the condition is false; otherwise it is true.
33169 As a side-effect, the &%ratelimit%& condition sets the expansion variable
33170 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
33171 configured value of &'m'&, and &$sender_rate_period$& to the configured value
33174 The parameter &'p'& is the smoothing time constant, in the form of an Exim
33175 time interval, for example, &`8h`& for eight hours. A larger time constant
33176 means that it takes Exim longer to forget a client's past behaviour. The
33177 parameter &'m'& is the maximum number of messages that a client is permitted to
33178 send in each time interval. It also specifies the number of messages permitted
33179 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
33180 constant, you can allow a client to send more messages in a burst without
33181 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
33182 both small, messages must be sent at an even rate.
33184 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
33185 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
33186 when deploying the &%ratelimit%& ACL condition. The script prints usage
33187 instructions when it is run with no arguments.
33189 The key is used to look up the data for calculating the client's average
33190 sending rate. This data is stored in Exim's spool directory, alongside the
33191 retry and other hints databases. The default key is &$sender_host_address$&,
33192 which means Exim computes the sending rate of each client host IP address.
33193 By changing the key you can change how Exim identifies clients for the purpose
33194 of ratelimiting. For example, to limit the sending rate of each authenticated
33195 user, independent of the computer they are sending from, set the key to
33196 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
33197 example, &$authenticated_id$& is only meaningful if the client has
33198 authenticated (which you can check with the &%authenticated%& ACL condition).
33200 The lookup key does not have to identify clients: If you want to limit the
33201 rate at which a recipient receives messages, you can use the key
33202 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
33205 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
33206 specifies what Exim measures the rate of, for example, messages or recipients
33207 or bytes. You can adjust the measurement using the &%unique=%& and/or
33208 &%count=%& options. You can also control when Exim updates the recorded rate
33209 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
33210 separated by a slash, like the other parameters. They may appear in any order.
33212 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
33213 any options that alter the meaning of the stored data. The limit &'m'& is not
33214 stored, so you can alter the configured maximum rate and Exim will still
33215 remember clients' past behaviour. If you change the &%per_*%& mode or add or
33216 remove the &%unique=%& option, the lookup key changes so Exim will forget past
33217 behaviour. The lookup key is not affected by changes to the update mode and
33218 the &%count=%& option.
33221 .subsection "Ratelimit options for what is being measured" ratoptmea
33222 .cindex "rate limiting" "per_* options"
33225 .cindex "rate limiting" per_conn
33226 This option limits the client's connection rate. It is not
33227 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
33228 &%acl_not_smtp_start%& ACLs.
33231 .cindex "rate limiting" per_conn
33232 This option limits the client's rate of sending messages. This is
33233 the default if none of the &%per_*%& options is specified. It can be used in
33234 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
33235 &%acl_smtp_data%&, or &%acl_not_smtp%&.
33238 .cindex "rate limiting" per_conn
33239 This option limits the sender's email bandwidth. It can be used in
33240 the same ACLs as the &%per_mail%& option, though it is best to use this option
33241 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
33242 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
33243 in its MAIL command, which may be inaccurate or completely missing. You can
33244 follow the limit &'m'& in the configuration with K, M, or G to specify limits
33245 in kilobytes, megabytes, or gigabytes, respectively.
33248 .cindex "rate limiting" per_rcpt
33249 This option causes Exim to limit the rate at which recipients are
33250 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
33251 &%acl_smtp_mime%&, or &%acl_smtp_data%& ACLs. In
33252 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
33253 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
33254 in either case the rate limiting engine will see a message with many
33255 recipients as a large high-speed burst.
33258 .cindex "rate limiting" per_addr
33259 This option is like the &%per_rcpt%& option, except it counts the
33260 number of different recipients that the client has sent messages to in the
33261 last time period. That is, if the client repeatedly sends messages to the same
33262 recipient, its measured rate is not increased. This option can only be used in
33266 .cindex "rate limiting" per_cmd
33267 This option causes Exim to recompute the rate every time the
33268 condition is processed. This can be used to limit the rate of any SMTP
33269 command. If it is used in multiple ACLs it can limit the aggregate rate of
33270 multiple different commands.
33273 .cindex "rate limiting" count
33274 This option can be used to alter how much Exim adds to the client's
33276 A value is required, after an equals sign.
33277 For example, the &%per_byte%& option is equivalent to
33278 &`per_mail/count=$message_size`&.
33279 If there is no &%count=%& option, Exim
33280 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
33281 other than &%acl_smtp_rcpt%&).
33282 The count does not have to be an integer.
33285 .cindex "rate limiting" unique
33286 This option is described in section &<<ratoptuniq>>& below.
33290 .subsection "Ratelimit update modes" ratoptupd
33291 .cindex "rate limiting" "reading data without updating"
33292 You can specify one of three options with the &%ratelimit%& condition to
33293 control when its database is updated. This section describes the &%readonly%&
33294 mode, and the next section describes the &%strict%& and &%leaky%& modes.
33296 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
33297 previously-computed rate to check against the limit.
33299 For example, you can test the client's sending rate and deny it access (when
33300 it is too fast) in the connect ACL. If the client passes this check then it
33301 can go on to send a message, in which case its recorded rate will be updated
33302 in the MAIL ACL. Subsequent connections from the same client will check this
33306 deny ratelimit = 100 / 5m / readonly
33307 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
33308 (max $sender_rate_limit)
33311 warn ratelimit = 100 / 5m / strict
33312 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
33313 (max $sender_rate_limit)
33316 If Exim encounters multiple &%ratelimit%& conditions with the same key when
33317 processing a message then it may increase the client's measured rate more than
33318 it should. For example, this will happen if you check the &%per_rcpt%& option
33319 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
33320 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
33321 multiple update problems by using the &%readonly%& option on later ratelimit
33324 The &%per_*%& options described above do not make sense in some ACLs. If you
33325 use a &%per_*%& option in an ACL where it is not normally permitted then the
33326 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
33327 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
33328 next section) so you must specify the &%readonly%& option explicitly.
33331 .subsection "Ratelimit options for handling fast clients" ratoptfast
33332 .cindex "rate limiting" "strict and leaky modes"
33333 If a client's average rate is greater than the maximum, the rate limiting
33334 engine can react in two possible ways, depending on the presence of the
33335 &%strict%& or &%leaky%& update modes. This is independent of the other
33336 counter-measures (such as rejecting the message) that may be specified by the
33339 The &%leaky%& (default) option means that the client's recorded rate is not
33340 updated if it is above the limit. The effect of this is that Exim measures the
33341 client's average rate of successfully sent email,
33342 up to the given limit.
33343 This is appropriate if the countermeasure when the condition is true
33344 consists of refusing the message, and
33345 is generally the better choice if you have clients that retry automatically.
33346 If the action when true is anything more complex then this option is
33347 likely not what is wanted.
33349 The &%strict%& option means that the client's recorded rate is always
33350 updated. The effect of this is that Exim measures the client's average rate
33351 of attempts to send email, which can be much higher than the maximum it is
33352 actually allowed. If the client is over the limit it may be subjected to
33353 counter-measures by the ACL. It must slow down and allow sufficient time to
33354 pass that its computed rate falls below the maximum before it can send email
33355 again. The time (the number of smoothing periods) it must wait and not
33356 attempt to send mail can be calculated with this formula:
33358 ln(peakrate/maxrate)
33362 .subsection "Limiting the rate of different events" ratoptuniq
33363 .cindex "rate limiting" "counting unique events"
33364 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
33365 rate of different events. For example, the &%per_addr%& option uses this
33366 mechanism to count the number of different recipients that the client has
33367 sent messages to in the last time period; it is equivalent to
33368 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
33369 measure the rate that a client uses different sender addresses with the
33370 options &`per_mail/unique=$sender_address`&.
33372 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
33373 has seen for that key. The whole set is thrown away when it is older than the
33374 rate smoothing period &'p'&, so each different event is counted at most once
33375 per period. In the &%leaky%& update mode, an event that causes the client to
33376 go over the limit is not added to the set, in the same way that the client's
33377 recorded rate is not updated in the same situation.
33379 When you combine the &%unique=%& and &%readonly%& options, the specific
33380 &%unique=%& value is ignored, and Exim just retrieves the client's stored
33383 The &%unique=%& mechanism needs more space in the ratelimit database than the
33384 other &%ratelimit%& options in order to store the event set. The number of
33385 unique values is potentially as large as the rate limit, so the extra space
33386 required increases with larger limits.
33388 The uniqueification is not perfect: there is a small probability that Exim
33389 will think a new event has happened before. If the sender's rate is less than
33390 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
33391 the measured rate can go above the limit, in which case Exim may under-count
33392 events by a significant margin. Fortunately, if the rate is high enough (2.7
33393 times the limit) that the false positive rate goes above 9%, then Exim will
33394 throw away the over-full event set before the measured rate falls below the
33395 limit. Therefore the only harm should be that exceptionally high sending rates
33396 are logged incorrectly; any countermeasures you configure will be as effective
33400 .subsection "Using rate limiting" useratlim
33401 Exim's other ACL facilities are used to define what counter-measures are taken
33402 when the rate limit is exceeded. This might be anything from logging a warning
33403 (for example, while measuring existing sending rates in order to define
33404 policy), through time delays to slow down fast senders, up to rejecting the
33405 message. For example:
33407 # Log all senders' rates
33408 warn ratelimit = 0 / 1h / strict
33409 log_message = Sender rate $sender_rate / $sender_rate_period
33411 # Slow down fast senders; note the need to truncate $sender_rate
33412 # at the decimal point.
33413 warn ratelimit = 100 / 1h / per_rcpt / strict
33414 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
33415 $sender_rate_limit }s
33417 # Keep authenticated users under control
33418 deny authenticated = *
33419 ratelimit = 100 / 1d / strict / $authenticated_id
33421 # System-wide rate limit
33422 defer ratelimit = 10 / 1s / $primary_hostname
33423 message = Sorry, too busy. Try again later.
33425 # Restrict incoming rate from each host, with a default
33426 # set using a macro and special cases looked up in a table.
33427 defer ratelimit = ${lookup {$sender_host_address} \
33428 cdb {DB/ratelimits.cdb} \
33429 {$value} {RATELIMIT} }
33430 message = Sender rate exceeds $sender_rate_limit \
33431 messages per $sender_rate_period
33433 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
33434 especially with the &%per_rcpt%& option, you may suffer from a performance
33435 bottleneck caused by locking on the ratelimit hints database. Apart from
33436 making your ACLs less complicated, you can reduce the problem by using a
33437 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
33438 this means that Exim will lose its hints data after a reboot (including retry
33439 hints, the callout cache, and ratelimit data).
33443 .section "Address verification" "SECTaddressverification"
33444 .cindex "verifying address" "options for"
33445 .cindex "policy control" "address verification"
33446 Several of the &%verify%& conditions described in section
33447 &<<SECTaclconditions>>& cause addresses to be verified. Section
33448 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
33449 The verification conditions can be followed by options that modify the
33450 verification process. The options are separated from the keyword and from each
33451 other by slashes, and some of them contain parameters. For example:
33453 verify = sender/callout
33454 verify = recipient/defer_ok/callout=10s,defer_ok
33456 The first stage of address verification, which always happens, is to run the
33457 address through the routers, in &"verify mode"&. Routers can detect the
33458 difference between verification and routing for delivery, and their actions can
33459 be varied by a number of generic options such as &%verify%& and &%verify_only%&
33460 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
33461 The available options are as follows:
33464 If the &%callout%& option is specified, successful routing to one or more
33465 remote hosts is followed by a &"callout"& to those hosts as an additional
33466 check. Callouts and their sub-options are discussed in the next section.
33468 If there is a defer error while doing verification routing, the ACL
33469 normally returns &"defer"&. However, if you include &%defer_ok%& in the
33470 options, the condition is forced to be true instead. Note that this is a main
33471 verification option as well as a suboption for callouts.
33473 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
33474 discusses the reporting of sender address verification failures.
33476 The &%success_on_redirect%& option causes verification always to succeed
33477 immediately after a successful redirection. By default, if a redirection
33478 generates just one address, that address is also verified. See further
33479 discussion in section &<<SECTredirwhilveri>>&.
33481 If the &%quota%& option is specified for recipient verify,
33482 successful routing to an appendfile transport is followed by a call into
33483 the transport to evaluate the quota status for the recipient.
33484 No actual delivery is done, but verification will succeed if the quota
33485 is sufficient for the message (if the sender gave a message size) or
33486 not already exceeded (otherwise).
33489 .cindex "verifying address" "differentiating failures"
33490 .vindex "&$recipient_verify_failure$&"
33491 .vindex "&$sender_verify_failure$&"
33492 .vindex "&$acl_verify_message$&"
33493 After an address verification failure, &$acl_verify_message$& contains the
33494 error message that is associated with the failure. It can be preserved by
33497 warn !verify = sender
33498 set acl_m0 = $acl_verify_message
33500 If you are writing your own custom rejection message or log message when
33501 denying access, you can use this variable to include information about the
33502 verification failure.
33503 This variable is cleared at the end of processing the ACL verb.
33505 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
33506 appropriate) contains one of the following words:
33509 &%qualify%&: The address was unqualified (no domain), and the message
33510 was neither local nor came from an exempted host.
33512 &%route%&: Routing failed.
33514 &%mail%&: Routing succeeded, and a callout was attempted; rejection
33515 occurred at or before the MAIL command (that is, on initial
33516 connection, HELO, or MAIL).
33518 &%recipient%&: The RCPT command in a callout was rejected.
33520 &%postmaster%&: The postmaster check in a callout was rejected.
33522 &%quota%&: The quota check for a local recipient did non pass.
33525 The main use of these variables is expected to be to distinguish between
33526 rejections of MAIL and rejections of RCPT in callouts.
33528 The above variables may also be set after a &*successful*&
33529 address verification to:
33532 &%random%&: A random local-part callout succeeded
33538 .section "Callout verification" "SECTcallver"
33539 .cindex "verifying address" "by callout"
33540 .cindex "callout" "verification"
33541 .cindex "SMTP" "callout verification"
33542 For non-local addresses, routing verifies the domain, but is unable to do any
33543 checking of the local part. There are situations where some means of verifying
33544 the local part is desirable. One way this can be done is to make an SMTP
33545 &'callback'& to a delivery host for the sender address or a &'callforward'& to
33546 a subsequent host for a recipient address, to see if the host accepts the
33547 address. We use the term &'callout'& to cover both cases. Note that for a
33548 sender address, the callback is not to the client host that is trying to
33549 deliver the message, but to one of the hosts that accepts incoming mail for the
33552 Exim does not do callouts by default. If you want them to happen, you must
33553 request them by setting appropriate options on the &%verify%& condition, as
33554 described below. This facility should be used with care, because it can add a
33555 lot of resource usage to the cost of verifying an address. However, Exim does
33556 cache the results of callouts, which helps to reduce the cost. Details of
33557 caching are in section &<<SECTcallvercache>>&.
33559 Recipient callouts are usually used only between hosts that are controlled by
33560 the same administration. For example, a corporate gateway host could use
33561 callouts to check for valid recipients on an internal mailserver. A successful
33562 callout does not guarantee that a real delivery to the address would succeed;
33563 on the other hand, a failing callout does guarantee that a delivery would fail.
33565 If the &%callout%& option is present on a condition that verifies an address, a
33566 second stage of verification occurs if the address is successfully routed to
33567 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
33568 &(manualroute)& router, where the router specifies the hosts. However, if a
33569 router that does not set up hosts routes to an &(smtp)& transport with a
33570 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
33571 &%hosts_override%& set, its hosts are always used, whether or not the router
33572 supplies a host list.
33573 Callouts are only supported on &(smtp)& transports.
33575 The port that is used is taken from the transport, if it is specified and is a
33576 remote transport. (For routers that do verification only, no transport need be
33577 specified.) Otherwise, the default SMTP port is used. If a remote transport
33578 specifies an outgoing interface, this is used; otherwise the interface is not
33579 specified. Likewise, the text that is used for the HELO command is taken from
33580 the transport's &%helo_data%& option; if there is no transport, the value of
33581 &$smtp_active_hostname$& is used.
33583 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
33584 test whether a bounce message could be delivered to the sender address. The
33585 following SMTP commands are sent:
33587 &`HELO `&<&'local host name'&>
33589 &`RCPT TO:`&<&'the address to be tested'&>
33592 LHLO is used instead of HELO if the transport's &%protocol%& option is
33595 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
33598 A recipient callout check is similar. By default, it also uses an empty address
33599 for the sender. This default is chosen because most hosts do not make use of
33600 the sender address when verifying a recipient. Using the same address means
33601 that a single cache entry can be used for each recipient. Some sites, however,
33602 do make use of the sender address when verifying. These are catered for by the
33603 &%use_sender%& and &%use_postmaster%& options, described in the next section.
33605 If the response to the RCPT command is a 2&'xx'& code, the verification
33606 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
33607 Exim tries the next host, if any. If there is a problem with all the remote
33608 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
33609 &%callout%& option is given, in which case the condition is forced to succeed.
33611 .cindex "SMTP" "output flushing, disabling for callout"
33612 A callout may take a little time. For this reason, Exim normally flushes SMTP
33613 output before performing a callout in an ACL, to avoid unexpected timeouts in
33614 clients when the SMTP PIPELINING extension is in use. The flushing can be
33615 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
33617 .cindex "tainted data" "de-tainting"
33618 .cindex "de-tainting" "using recipient verify"
33619 A recipient callout which gets a 2&'xx'& code
33620 will assign untainted values to the
33621 &$domain_data$& and &$local_part_data$& variables,
33622 corresponding to the domain and local parts of the recipient address.
33627 .subsection "Additional parameters for callouts" CALLaddparcall
33628 .cindex "callout" "additional parameters for"
33629 The &%callout%& option can be followed by an equals sign and a number of
33630 optional parameters, separated by commas. For example:
33632 verify = recipient/callout=10s,defer_ok
33634 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
33635 separate verify options, is retained for backwards compatibility, but is now
33636 deprecated. The additional parameters for &%callout%& are as follows:
33640 .vitem <&'a&~time&~interval'&>
33641 .cindex "callout" "timeout, specifying"
33642 This specifies the timeout that applies for the callout attempt to each host.
33645 verify = sender/callout=5s
33647 The default is 30 seconds. The timeout is used for each response from the
33648 remote host. It is also used for the initial connection, unless overridden by
33649 the &%connect%& parameter.
33652 .vitem &*connect&~=&~*&<&'time&~interval'&>
33653 .cindex "callout" "connection timeout, specifying"
33654 This parameter makes it possible to set a different (usually smaller) timeout
33655 for making the SMTP connection. For example:
33657 verify = sender/callout=5s,connect=1s
33659 If not specified, this timeout defaults to the general timeout value.
33661 .vitem &*defer_ok*&
33662 .cindex "callout" "defer, action on"
33663 When this parameter is present, failure to contact any host, or any other kind
33664 of temporary error, is treated as success by the ACL. However, the cache is not
33665 updated in this circumstance.
33667 .vitem &*fullpostmaster*&
33668 .cindex "callout" "full postmaster check"
33669 This operates like the &%postmaster%& option (see below), but if the check for
33670 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
33671 accordance with the specification in RFC 2821. The RFC states that the
33672 unqualified address &'postmaster'& should be accepted.
33675 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
33676 .cindex "callout" "sender when verifying header"
33677 When verifying addresses in header lines using the &%header_sender%&
33678 verification option, Exim behaves by default as if the addresses are envelope
33679 sender addresses from a message. Callout verification therefore tests to see
33680 whether a bounce message could be delivered, by using an empty address in the
33681 MAIL command. However, it is arguable that these addresses might never be used
33682 as envelope senders, and could therefore justifiably reject bounce messages
33683 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
33684 address to use in the MAIL command. For example:
33686 require verify = header_sender/callout=mailfrom=abcd@x.y.z
33688 This parameter is available only for the &%header_sender%& verification option.
33691 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
33692 .cindex "callout" "overall timeout, specifying"
33693 This parameter sets an overall timeout for performing a callout verification.
33696 verify = sender/callout=5s,maxwait=30s
33698 This timeout defaults to four times the callout timeout for individual SMTP
33699 commands. The overall timeout applies when there is more than one host that can
33700 be tried. The timeout is checked before trying the next host. This prevents
33701 very long delays if there are a large number of hosts and all are timing out
33702 (for example, when network connections are timing out).
33705 .vitem &*no_cache*&
33706 .cindex "callout" "cache, suppressing"
33707 .cindex "caching callout, suppressing"
33708 When this parameter is given, the callout cache is neither read nor updated.
33710 .vitem &*postmaster*&
33711 .cindex "callout" "postmaster; checking"
33712 When this parameter is set, a successful callout check is followed by a similar
33713 check for the local part &'postmaster'& at the same domain. If this address is
33714 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
33715 the postmaster check is recorded in a cache record; if it is a failure, this is
33716 used to fail subsequent callouts for the domain without a connection being
33717 made, until the cache record expires.
33719 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
33720 The postmaster check uses an empty sender in the MAIL command by default.
33721 You can use this parameter to do a postmaster check using a different address.
33724 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
33726 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
33727 one overrides. The &%postmaster%& parameter is equivalent to this example:
33729 require verify = sender/callout=postmaster_mailfrom=
33731 &*Warning*&: The caching arrangements for postmaster checking do not take
33732 account of the sender address. It is assumed that either the empty address or
33733 a fixed non-empty address will be used. All that Exim remembers is that the
33734 postmaster check for the domain succeeded or failed.
33738 .cindex "callout" "&""random""& check"
33739 When this parameter is set, before doing the normal callout check, Exim does a
33740 check for a &"random"& local part at the same domain. The local part is not
33741 really random &-- it is defined by the expansion of the option
33742 &%callout_random_local_part%&, which defaults to
33744 $primary_hostname-$tod_epoch-testing
33746 The idea here is to try to determine whether the remote host accepts all local
33747 parts without checking. If it does, there is no point in doing callouts for
33748 specific local parts. If the &"random"& check succeeds, the result is saved in
33749 a cache record, and used to force the current and subsequent callout checks to
33750 succeed without a connection being made, until the cache record expires.
33752 .vitem &*use_postmaster*&
33753 .cindex "callout" "sender for recipient check"
33754 This parameter applies to recipient callouts only. For example:
33756 deny !verify = recipient/callout=use_postmaster
33758 .vindex "&$qualify_domain$&"
33759 It causes a non-empty postmaster address to be used in the MAIL command when
33760 performing the callout for the recipient, and also for a &"random"& check if
33761 that is configured. The local part of the address is &`postmaster`& and the
33762 domain is the contents of &$qualify_domain$&.
33764 .vitem &*use_sender*&
33765 This option applies to recipient callouts only. For example:
33767 require verify = recipient/callout=use_sender
33769 It causes the message's actual sender address to be used in the MAIL
33770 command when performing the callout, instead of an empty address. There is no
33771 need to use this option unless you know that the called hosts make use of the
33772 sender when checking recipients. If used indiscriminately, it reduces the
33773 usefulness of callout caching.
33776 This option applies to recipient callouts only. For example:
33778 require verify = recipient/callout=use_sender,hold
33780 It causes the connection to be held open and used for any further recipients
33781 and for eventual delivery (should that be done quickly).
33782 Doing this saves on TCP and SMTP startup costs, and TLS costs also
33783 when that is used for the connections.
33784 The advantage is only gained if there are no callout cache hits
33785 (which could be enforced by the no_cache option),
33786 if the use_sender option is used,
33787 if neither the random nor the use_postmaster option is used,
33788 and if no other callouts intervene.
33791 If you use any of the parameters that set a non-empty sender for the MAIL
33792 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
33793 &%use_sender%&), you should think about possible loops. Recipient checking is
33794 usually done between two hosts that are under the same management, and the host
33795 that receives the callouts is not normally configured to do callouts itself.
33796 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
33797 these circumstances.
33799 However, if you use a non-empty sender address for a callout to an arbitrary
33800 host, there is the likelihood that the remote host will itself initiate a
33801 callout check back to your host. As it is checking what appears to be a message
33802 sender, it is likely to use an empty address in MAIL, thus avoiding a
33803 callout loop. However, to be on the safe side it would be best to set up your
33804 own ACLs so that they do not do sender verification checks when the recipient
33805 is the address you use for header sender or postmaster callout checking.
33807 Another issue to think about when using non-empty senders for callouts is
33808 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
33809 by the sender/recipient combination; thus, for any given recipient, many more
33810 actual callouts are performed than when an empty sender or postmaster is used.
33815 .subsection "Callout caching" SECTcallvercache
33816 .cindex "hints database" "callout cache"
33817 .cindex "callout" "cache, description of"
33818 .cindex "caching" "callout"
33819 Exim caches the results of callouts in order to reduce the amount of resources
33820 used, unless you specify the &%no_cache%& parameter with the &%callout%&
33821 option. A hints database called &"callout"& is used for the cache. Two
33822 different record types are used: one records the result of a callout check for
33823 a specific address, and the other records information that applies to the
33824 entire domain (for example, that it accepts the local part &'postmaster'&).
33826 When an original callout fails, a detailed SMTP error message is given about
33827 the failure. However, for subsequent failures that use the cache data, this message
33830 The expiry times for negative and positive address cache records are
33831 independent, and can be set by the global options &%callout_negative_expire%&
33832 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
33834 If a host gives a negative response to an SMTP connection, or rejects any
33835 commands up to and including
33839 (but not including the MAIL command with a non-empty address),
33840 any callout attempt is bound to fail. Exim remembers such failures in a
33841 domain cache record, which it uses to fail callouts for the domain without
33842 making new connections, until the domain record times out. There are two
33843 separate expiry times for domain cache records:
33844 &%callout_domain_negative_expire%& (default 3h) and
33845 &%callout_domain_positive_expire%& (default 7d).
33847 Domain records expire when the negative expiry time is reached if callouts
33848 cannot be made for the domain, or if the postmaster check failed.
33849 Otherwise, they expire when the positive expiry time is reached. This
33850 ensures that, for example, a host that stops accepting &"random"& local parts
33851 will eventually be noticed.
33853 The callout caching mechanism is based on the domain of the address that is
33854 being tested. If the domain routes to several hosts, it is assumed that their
33855 behaviour will be the same.
33859 .section "Quota caching" "SECTquotacache"
33860 .cindex "hints database" "quota cache"
33861 .cindex "quota" "cache, description of"
33862 .cindex "caching" "quota"
33863 Exim caches the results of quota verification
33864 in order to reduce the amount of resources used.
33865 The &"callout"& hints database is used.
33867 The default cache periods are five minutes for a positive (good) result
33868 and one hour for a negative result.
33869 To change the periods the &%quota%& option can be followed by an equals sign
33870 and a number of optional paramemters, separated by commas.
33873 verify = recipient/quota=cachepos=1h,cacheneg=1d
33875 Possible parameters are:
33877 .vitem &*cachepos&~=&~*&<&'time&~interval'&>
33878 .cindex "quota cache" "positive entry expiry, specifying"
33879 Set the lifetime for a positive cache entry.
33880 A value of zero seconds is legitimate.
33882 .vitem &*cacheneg&~=&~*&<&'time&~interval'&>
33883 .cindex "quota cache" "negative entry expiry, specifying"
33884 As above, for a negative entry.
33886 .vitem &*no_cache*&
33887 Set both positive and negative lifetimes to zero.
33889 .section "Sender address verification reporting" "SECTsenaddver"
33890 .cindex "verifying" "suppressing error details"
33891 See section &<<SECTaddressverification>>& for a general discussion of
33892 verification. When sender verification fails in an ACL, the details of the
33893 failure are given as additional output lines before the 550 response to the
33894 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
33897 MAIL FROM:<xyz@abc.example>
33899 RCPT TO:<pqr@def.example>
33900 550-Verification failed for <xyz@abc.example>
33901 550-Called: 192.168.34.43
33902 550-Sent: RCPT TO:<xyz@abc.example>
33903 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
33904 550 Sender verification failed
33906 If more than one RCPT command fails in the same way, the details are given
33907 only for the first of them. However, some administrators do not want to send
33908 out this much information. You can suppress the details by adding
33909 &`/no_details`& to the ACL statement that requests sender verification. For
33912 verify = sender/no_details
33915 .section "Redirection while verifying" "SECTredirwhilveri"
33916 .cindex "verifying" "redirection while"
33917 .cindex "address redirection" "while verifying"
33918 A dilemma arises when a local address is redirected by aliasing or forwarding
33919 during verification: should the generated addresses themselves be verified,
33920 or should the successful expansion of the original address be enough to verify
33921 it? By default, Exim takes the following pragmatic approach:
33924 When an incoming address is redirected to just one child address, verification
33925 continues with the child address, and if that fails to verify, the original
33926 verification also fails.
33928 When an incoming address is redirected to more than one child address,
33929 verification does not continue. A success result is returned.
33932 This seems the most reasonable behaviour for the common use of aliasing as a
33933 way of redirecting different local parts to the same mailbox. It means, for
33934 example, that a pair of alias entries of the form
33937 aw123: :fail: Gone away, no forwarding address
33939 work as expected, with both local parts causing verification failure. When a
33940 redirection generates more than one address, the behaviour is more like a
33941 mailing list, where the existence of the alias itself is sufficient for
33942 verification to succeed.
33944 It is possible, however, to change the default behaviour so that all successful
33945 redirections count as successful verifications, however many new addresses are
33946 generated. This is specified by the &%success_on_redirect%& verification
33947 option. For example:
33949 require verify = recipient/success_on_redirect/callout=10s
33951 In this example, verification succeeds if a router generates a new address, and
33952 the callout does not occur, because no address was routed to a remote host.
33954 When verification is being tested via the &%-bv%& option, the treatment of
33955 redirections is as just described, unless the &%-v%& or any debugging option is
33956 also specified. In that case, full verification is done for every generated
33957 address and a report is output for each of them.
33961 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
33962 .cindex "CSA" "verifying"
33963 Client SMTP Authorization is a system that allows a site to advertise
33964 which machines are and are not permitted to send email. This is done by placing
33965 special SRV records in the DNS; these are looked up using the client's HELO
33966 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
33967 Authorization checks in Exim are performed by the ACL condition:
33971 This fails if the client is not authorized. If there is a DNS problem, or if no
33972 valid CSA SRV record is found, or if the client is authorized, the condition
33973 succeeds. These three cases can be distinguished using the expansion variable
33974 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
33975 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
33976 be likely to cause problems for legitimate email.
33978 The error messages produced by the CSA code include slightly more
33979 detail. If &$csa_status$& is &"defer"&, this may be because of problems
33980 looking up the CSA SRV record, or problems looking up the CSA target
33981 address record. There are four reasons for &$csa_status$& being &"fail"&:
33984 The client's host name is explicitly not authorized.
33986 The client's IP address does not match any of the CSA target IP addresses.
33988 The client's host name is authorized but it has no valid target IP addresses
33989 (for example, the target's addresses are IPv6 and the client is using IPv4).
33991 The client's host name has no CSA SRV record but a parent domain has asserted
33992 that all subdomains must be explicitly authorized.
33995 The &%csa%& verification condition can take an argument which is the domain to
33996 use for the DNS query. The default is:
33998 verify = csa/$sender_helo_name
34000 This implementation includes an extension to CSA. If the query domain
34001 is an address literal such as [192.0.2.95], or if it is a bare IP
34002 address, Exim searches for CSA SRV records in the reverse DNS as if
34003 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
34006 verify = csa/$sender_host_address
34008 In fact, this is the check that Exim performs if the client does not say HELO.
34009 This extension can be turned off by setting the main configuration option
34010 &%dns_csa_use_reverse%& to be false.
34012 If a CSA SRV record is not found for the domain itself, a search
34013 is performed through its parent domains for a record which might be
34014 making assertions about subdomains. The maximum depth of this search is limited
34015 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
34016 default. Exim does not look for CSA SRV records in a top level domain, so the
34017 default settings handle HELO domains as long as seven
34018 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
34019 of legitimate HELO domains.
34021 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
34022 direct SRV lookups, this is not sufficient because of the extra parent domain
34023 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
34024 addresses into lookups in the reverse DNS space. The result of a successful
34027 ${lookup dnsdb {csa=$sender_helo_name}}
34029 has two space-separated fields: an authorization code and a target host name.
34030 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
34031 authorization required but absent, or &"?"& for unknown.
34036 .section "Bounce address tag validation" "SECTverifyPRVS"
34037 .cindex "BATV, verifying"
34038 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
34039 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
34040 Genuine incoming bounce messages should therefore always be addressed to
34041 recipients that have a valid tag. This scheme is a way of detecting unwanted
34042 bounce messages caused by sender address forgeries (often called &"collateral
34043 spam"&), because the recipients of such messages do not include valid tags.
34045 There are two expansion items to help with the implementation of the BATV
34046 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
34047 the original envelope sender address by using a simple key to add a hash of the
34048 address and some time-based randomizing information. The &%prvs%& expansion
34049 item creates a signed address, and the &%prvscheck%& expansion item checks one.
34050 The syntax of these expansion items is described in section
34051 &<<SECTexpansionitems>>&.
34052 The validity period on signed addresses is seven days.
34054 As an example, suppose the secret per-address keys are stored in an MySQL
34055 database. A query to look up the key for an address could be defined as a macro
34058 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
34059 WHERE sender='${quote_mysql:$prvscheck_address}'\
34062 Suppose also that the senders who make use of BATV are defined by an address
34063 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
34066 # Bounces: drop unsigned addresses for BATV senders
34068 recipients = +batv_senders
34069 message = This address does not send an unsigned reverse path
34071 # Bounces: In case of prvs-signed address, check signature.
34073 condition = ${prvscheck {$local_part@$domain}\
34074 {PRVSCHECK_SQL}{1}}
34075 !condition = $prvscheck_result
34076 message = Invalid reverse path signature.
34078 The first statement rejects recipients for bounce messages that are addressed
34079 to plain BATV sender addresses, because it is known that BATV senders do not
34080 send out messages with plain sender addresses. The second statement rejects
34081 recipients that are prvs-signed, but with invalid signatures (either because
34082 the key is wrong, or the signature has timed out).
34084 A non-prvs-signed address is not rejected by the second statement, because the
34085 &%prvscheck%& expansion yields an empty string if its first argument is not a
34086 prvs-signed address, thus causing the &%condition%& condition to be false. If
34087 the first argument is a syntactically valid prvs-signed address, the yield is
34088 the third string (in this case &"1"&), whether or not the cryptographic and
34089 timeout checks succeed. The &$prvscheck_result$& variable contains the result
34090 of the checks (empty for failure, &"1"& for success).
34092 There is one more issue you must consider when implementing prvs-signing:
34093 you have to ensure that the routers accept prvs-signed addresses and
34094 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
34095 router to remove the signature with a configuration along these lines:
34099 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
34101 This works because, if the third argument of &%prvscheck%& is empty, the result
34102 of the expansion of a prvs-signed address is the decoded value of the original
34103 address. This router should probably be the first of your routers that handles
34106 To create BATV-signed addresses in the first place, a transport of this form
34109 external_smtp_batv:
34111 return_path = ${prvs {$return_path} \
34112 {${lookup mysql{SELECT \
34113 secret FROM batv_prvs WHERE \
34114 sender='${quote_mysql:$sender_address}'} \
34117 If no key can be found for the existing return path, no signing takes place.
34121 .section "Using an ACL to control relaying" "SECTrelaycontrol"
34122 .cindex "&ACL;" "relay control"
34123 .cindex "relaying" "control by ACL"
34124 .cindex "policy control" "relay control"
34125 An MTA is said to &'relay'& a message if it receives it from some host and
34126 delivers it directly to another host as a result of a remote address contained
34127 within it. Redirecting a local address via an alias or forward file and then
34128 passing the message on to another host is not relaying,
34129 .cindex "&""percent hack""&"
34130 but a redirection as a result of the &"percent hack"& is.
34132 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
34133 A host which is acting as a gateway or an MX backup is concerned with incoming
34134 relaying from arbitrary hosts to a specific set of domains. On the other hand,
34135 a host which is acting as a smart host for a number of clients is concerned
34136 with outgoing relaying from those clients to the Internet at large. Often the
34137 same host is fulfilling both functions,
34139 . as illustrated in the diagram below,
34141 but in principle these two kinds of relaying are entirely independent. What is
34142 not wanted is the transmission of mail from arbitrary remote hosts through your
34143 system to arbitrary domains.
34146 You can implement relay control by means of suitable statements in the ACL that
34147 runs for each RCPT command. For convenience, it is often easiest to use
34148 Exim's named list facility to define the domains and hosts involved. For
34149 example, suppose you want to do the following:
34152 Deliver a number of domains to mailboxes on the local host (or process them
34153 locally in some other way). Let's say these are &'my.dom1.example'& and
34154 &'my.dom2.example'&.
34156 Relay mail for a number of other domains for which you are the secondary MX.
34157 These might be &'friend1.example'& and &'friend2.example'&.
34159 Relay mail from the hosts on your local LAN, to whatever domains are involved.
34160 Suppose your LAN is 192.168.45.0/24.
34164 In the main part of the configuration, you put the following definitions:
34166 domainlist local_domains = my.dom1.example : my.dom2.example
34167 domainlist relay_to_domains = friend1.example : friend2.example
34168 hostlist relay_from_hosts = 192.168.45.0/24
34170 Now you can use these definitions in the ACL that is run for every RCPT
34174 accept domains = +local_domains : +relay_to_domains
34175 accept hosts = +relay_from_hosts
34177 The first statement accepts any RCPT command that contains an address in
34178 the local or relay domains. For any other domain, control passes to the second
34179 statement, which accepts the command only if it comes from one of the relay
34180 hosts. In practice, you will probably want to make your ACL more sophisticated
34181 than this, for example, by including sender and recipient verification. The
34182 default configuration includes a more comprehensive example, which is described
34183 in chapter &<<CHAPdefconfil>>&.
34187 .section "Checking a relay configuration" "SECTcheralcon"
34188 .cindex "relaying" "checking control of"
34189 You can check the relay characteristics of your configuration in the same way
34190 that you can test any ACL behaviour for an incoming SMTP connection, by using
34191 the &%-bh%& option to run a fake SMTP session with which you interact.
34196 . ////////////////////////////////////////////////////////////////////////////
34197 . ////////////////////////////////////////////////////////////////////////////
34199 .chapter "Content scanning at ACL time" "CHAPexiscan"
34200 .scindex IIDcosca "content scanning" "at ACL time"
34201 The extension of Exim to include content scanning at ACL time, formerly known
34202 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
34203 was integrated into the main source for Exim release 4.50, and Tom continues to
34204 maintain it. Most of the wording of this chapter is taken from Tom's
34207 It is also possible to scan the content of messages at other times. The
34208 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
34209 scanning after all the ACLs have run. A transport filter can be used to scan
34210 messages at delivery time (see the &%transport_filter%& option, described in
34211 chapter &<<CHAPtransportgeneric>>&).
34213 If you want to include the ACL-time content-scanning features when you compile
34214 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
34215 &_Local/Makefile_&. When you do that, the Exim binary is built with:
34218 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
34219 for all MIME parts for SMTP and non-SMTP messages, respectively.
34221 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
34222 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
34223 run at the end of message reception (the &%acl_smtp_data%& ACL).
34225 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
34226 of messages, or parts of messages, for debugging purposes.
34228 Additional expansion variables that are set in the new ACL and by the new
34231 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
34234 Content-scanning is continually evolving, and new features are still being
34235 added. While such features are still unstable and liable to incompatible
34236 changes, they are made available in Exim by setting options whose names begin
34237 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
34238 this manual. You can find out about them by reading the file called
34239 &_doc/experimental.txt_&.
34241 All the content-scanning facilities work on a MBOX copy of the message that is
34242 temporarily created in a file called:
34244 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
34246 The &_.eml_& extension is a friendly hint to virus scanners that they can
34247 expect an MBOX-like structure inside that file. The file is created when the
34248 first content scanning facility is called. Subsequent calls to content
34249 scanning conditions open the same file again. The directory is recursively
34250 removed when the &%acl_smtp_data%& ACL has finished running, unless
34252 control = no_mbox_unspool
34254 has been encountered. When the MIME ACL decodes files, they are put into the
34255 same directory by default.
34259 .section "Scanning for viruses" "SECTscanvirus"
34260 .cindex "virus scanning"
34261 .cindex "content scanning" "for viruses"
34262 .cindex "content scanning" "the &%malware%& condition"
34263 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
34264 It supports a &"generic"& interface to scanners called via the shell, and
34265 specialized interfaces for &"daemon"& type virus scanners, which are resident
34266 in memory and thus are much faster.
34268 Since message data needs to have arrived,
34269 the condition may be only called in ACL defined by
34271 &%acl_smtp_data_prdr%&,
34272 &%acl_smtp_mime%& or
34275 A timeout of 2 minutes is applied to a scanner call (by default);
34276 if it expires then a defer action is taken.
34278 .oindex "&%av_scanner%&"
34279 You can set the &%av_scanner%& option in the main part of the configuration
34280 to specify which scanner to use, together with any additional options that
34281 are needed. The basic syntax is as follows:
34283 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
34285 If you do not set &%av_scanner%&, it defaults to
34287 av_scanner = sophie:/var/run/sophie
34289 If the value of &%av_scanner%& starts with a dollar character, it is expanded
34291 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
34292 The following scanner types are supported in this release,
34293 though individual ones can be included or not at build time:
34297 .cindex "virus scanners" "avast"
34298 This is the scanner daemon of Avast. It has been tested with Avast Core
34299 Security (currently at version 2.2.0).
34300 You can get a trial version at &url(https://www.avast.com) or for Linux
34301 at &url(https://www.avast.com/linux-server-antivirus).
34302 This scanner type takes one option,
34303 which can be either a full path to a UNIX socket,
34304 or host and port specifiers separated by white space.
34305 The host may be a name or an IP address; the port is either a
34306 single number or a pair of numbers with a dash between.
34307 A list of options may follow. These options are interpreted on the
34308 Exim's side of the malware scanner, or are given on separate lines to
34309 the daemon as options before the main scan command.
34311 .cindex &`pass_unscanned`& "avast"
34312 If &`pass_unscanned`&
34313 is set, any files the Avast scanner can't scan (e.g.
34314 decompression bombs, or invalid archives) are considered clean. Use with
34319 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
34320 av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
34321 av_scanner = avast:192.168.2.22 5036
34323 If you omit the argument, the default path
34324 &_/var/run/avast/scan.sock_&
34326 If you use a remote host,
34327 you need to make Exim's spool directory available to it,
34328 as the scanner is passed a file path, not file contents.
34329 For information about available commands and their options you may use
34331 $ socat UNIX:/var/run/avast/scan.sock STDIO:
34337 If the scanner returns a temporary failure (e.g. license issues, or
34338 permission problems), the message is deferred and a paniclog entry is
34339 written. The usual &`defer_ok`& option is available.
34341 .vitem &%aveserver%&
34342 .cindex "virus scanners" "Kaspersky"
34343 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
34344 at &url(https://www.kaspersky.com/). This scanner type takes one option,
34345 which is the path to the daemon's UNIX socket. The default is shown in this
34348 av_scanner = aveserver:/var/run/aveserver
34353 .cindex "virus scanners" "clamd"
34354 This daemon-type scanner is GPL and free. You can get it at
34355 &url(https://www.clamav.net/). Some older versions of clamd do not seem to
34356 unpack MIME containers, so it used to be recommended to unpack MIME attachments
34357 in the MIME ACL. This is no longer believed to be necessary.
34359 The options are a list of server specifiers, which may be
34360 a UNIX socket specification,
34361 a TCP socket specification,
34362 or a (global) option.
34364 A socket specification consists of a space-separated list.
34365 For a Unix socket the first element is a full path for the socket,
34366 for a TCP socket the first element is the IP address
34367 and the second a port number,
34368 Any further elements are per-server (non-global) options.
34369 These per-server options are supported:
34371 retry=<timespec> Retry on connect fail
34374 The &`retry`& option specifies a time after which a single retry for
34375 a failed connect is made. The default is to not retry.
34377 If a Unix socket file is specified, only one server is supported.
34381 av_scanner = clamd:/opt/clamd/socket
34382 av_scanner = clamd:192.0.2.3 1234
34383 av_scanner = clamd:192.0.2.3 1234:local
34384 av_scanner = clamd:192.0.2.3 1234 retry=10s
34385 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
34387 If the value of av_scanner points to a UNIX socket file or contains the
34389 option, then the ClamAV interface will pass a filename containing the data
34390 to be scanned, which should normally result in less I/O happening and be
34391 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
34392 Exim does not assume that there is a common filesystem with the remote host.
34394 The final example shows that multiple TCP targets can be specified. Exim will
34395 randomly use one for each incoming email (i.e. it load balances them). Note
34396 that only TCP targets may be used if specifying a list of scanners; a UNIX
34397 socket cannot be mixed in with TCP targets. If one of the servers becomes
34398 unavailable, Exim will try the remaining one(s) until it finds one that works.
34399 When a clamd server becomes unreachable, Exim will log a message. Exim does
34400 not keep track of scanner state between multiple messages, and the scanner
34401 selection is random, so the message will get logged in the mainlog for each
34402 email that the down scanner gets chosen first (message wrapped to be readable):
34404 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
34405 clamd: connection to localhost, port 3310 failed
34406 (Connection refused)
34409 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
34410 contributing the code for this scanner.
34413 .cindex "virus scanners" "command line interface"
34414 This is the keyword for the generic command line scanner interface. It can be
34415 used to attach virus scanners that are invoked from the shell. This scanner
34416 type takes 3 mandatory options:
34419 The full path and name of the scanner binary, with all command line options,
34420 and a placeholder (&`%s`&) for the directory to scan.
34423 A regular expression to match against the STDOUT and STDERR output of the
34424 virus scanner. If the expression matches, a virus was found. You must make
34425 absolutely sure that this expression matches on &"virus found"&. This is called
34426 the &"trigger"& expression.
34429 Another regular expression, containing exactly one pair of parentheses, to
34430 match the name of the virus found in the scanners output. This is called the
34431 &"name"& expression.
34434 For example, Sophos Sweep reports a virus on a line like this:
34436 Virus 'W32/Magistr-B' found in file ./those.bat
34438 For the trigger expression, we can match the phrase &"found in file"&. For the
34439 name expression, we want to extract the W32/Magistr-B string, so we can match
34440 for the single quotes left and right of it. Altogether, this makes the
34441 configuration setting:
34443 av_scanner = cmdline:\
34444 /path/to/sweep -ss -all -rec -archive %s:\
34445 found in file:'(.+)'
34448 .cindex "virus scanners" "DrWeb"
34449 The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface
34451 either a full path to a UNIX socket,
34452 or host and port specifiers separated by white space.
34453 The host may be a name or an IP address; the port is either a
34454 single number or a pair of numbers with a dash between.
34457 av_scanner = drweb:/var/run/drwebd.sock
34458 av_scanner = drweb:192.168.2.20 31337
34460 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
34461 is used. Thanks to Alex Miller for contributing the code for this scanner.
34464 .cindex "virus scanners" "f-protd"
34465 The f-protd scanner is accessed via HTTP over TCP.
34466 One argument is taken, being a space-separated hostname and port number
34470 av_scanner = f-protd:localhost 10200-10204
34472 If you omit the argument, the default values shown above are used.
34474 .vitem &%f-prot6d%&
34475 .cindex "virus scanners" "f-prot6d"
34476 The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
34477 One argument is taken, being a space-separated hostname and port number.
34480 av_scanner = f-prot6d:localhost 10200
34482 If you omit the argument, the default values show above are used.
34485 .cindex "virus scanners" "F-Secure"
34486 The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one
34487 argument which is the path to a UNIX socket. For example:
34489 av_scanner = fsecure:/path/to/.fsav
34491 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
34492 Thelmen for contributing the code for this scanner.
34494 .vitem &%kavdaemon%&
34495 .cindex "virus scanners" "Kaspersky"
34496 This is the scanner daemon of Kaspersky Version 4. This version of the
34497 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
34498 scanner type takes one option, which is the path to the daemon's UNIX socket.
34501 av_scanner = kavdaemon:/opt/AVP/AvpCtl
34503 The default path is &_/var/run/AvpCtl_&.
34506 .cindex "virus scanners" "mksd"
34507 This was a daemon type scanner that is aimed mainly at Polish users,
34508 though some documentation was available in English.
34509 The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir)
34510 and this appears to be a candidate for removal from Exim, unless
34511 we are informed of other virus scanners which use the same protocol
34513 The only option for this scanner type is
34514 the maximum number of processes used simultaneously to scan the attachments,
34515 provided that mksd has
34516 been run with at least the same number of child processes. For example:
34518 av_scanner = mksd:2
34520 You can safely omit this option (the default value is 1).
34523 .cindex "virus scanners" "simple socket-connected"
34524 This is a general-purpose way of talking to simple scanner daemons
34525 running on the local machine.
34526 There are four options:
34527 an address (which may be an IP address and port, or the path of a Unix socket),
34528 a commandline to send (may include a single %s which will be replaced with
34529 the path to the mail file to be scanned),
34530 an RE to trigger on from the returned data,
34531 and an RE to extract malware_name from the returned data.
34534 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
34536 Note that surrounding whitespace is stripped from each option, meaning
34537 there is no way to specify a trailing newline.
34538 The socket specifier and both regular-expressions are required.
34539 Default for the commandline is &_%s\n_& (note this does have a trailing newline);
34540 specify an empty element to get this.
34543 .cindex "virus scanners" "Sophos and Sophie"
34544 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
34545 You can get Sophie at &url(http://sophie.sourceforge.net/). The only option
34546 for this scanner type is the path to the UNIX socket that Sophie uses for
34547 client communication. For example:
34549 av_scanner = sophie:/tmp/sophie
34551 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
34555 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
34556 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
34559 The &%av_scanner%& option is expanded each time &%malware%& is called. This
34560 makes it possible to use different scanners. See further below for an example.
34561 The &%malware%& condition caches its results, so when you use it multiple times
34562 for the same message, the actual scanning process is only carried out once.
34563 However, using expandable items in &%av_scanner%& disables this caching, in
34564 which case each use of the &%malware%& condition causes a new scan of the
34567 The &%malware%& condition takes a right-hand argument that is expanded before
34568 use and taken as a list, slash-separated by default.
34569 The first element can then be one of
34572 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
34573 The condition succeeds if a virus was found, and fail otherwise. This is the
34576 &"false"& or &"0"& or an empty string, in which case no scanning is done and
34577 the condition fails immediately.
34579 A regular expression, in which case the message is scanned for viruses. The
34580 condition succeeds if a virus is found and its name matches the regular
34581 expression. This allows you to take special actions on certain types of virus.
34582 Note that &"/"& characters in the RE must be doubled due to the list-processing,
34583 unless the separator is changed (in the usual way &<<SECTlistsepchange>>&).
34586 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
34587 messages even if there is a problem with the virus scanner.
34588 Otherwise, such a problem causes the ACL to defer.
34590 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
34591 specify a non-default timeout. The default is two minutes.
34594 malware = * / defer_ok / tmo=10s
34596 A timeout causes the ACL to defer.
34598 .vindex "&$callout_address$&"
34599 When a connection is made to the scanner the expansion variable &$callout_address$&
34600 is set to record the actual address used.
34602 .vindex "&$malware_name$&"
34603 When a virus is found, the condition sets up an expansion variable called
34604 &$malware_name$& that contains the name of the virus. You can use it in a
34605 &%message%& modifier that specifies the error returned to the sender, and/or in
34608 Beware the interaction of Exim's &%message_size_limit%& with any size limits
34609 imposed by your anti-virus scanner.
34611 Here is a very simple scanning example:
34614 message = This message contains malware ($malware_name)
34616 The next example accepts messages when there is a problem with the scanner:
34618 deny malware = */defer_ok
34619 message = This message contains malware ($malware_name)
34621 The next example shows how to use an ACL variable to scan with both sophie and
34622 aveserver. It assumes you have set:
34624 av_scanner = $acl_m0
34626 in the main Exim configuration.
34628 deny set acl_m0 = sophie
34630 message = This message contains malware ($malware_name)
34632 deny set acl_m0 = aveserver
34634 message = This message contains malware ($malware_name)
34638 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
34639 .cindex "content scanning" "for spam"
34640 .cindex "spam scanning"
34641 .cindex "SpamAssassin"
34643 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
34644 score and a report for the message.
34645 Support is also provided for Rspamd.
34647 For more information about installation and configuration of SpamAssassin or
34648 Rspamd refer to their respective websites at
34649 &url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/)
34651 SpamAssassin can be installed with CPAN by running:
34653 perl -MCPAN -e 'install Mail::SpamAssassin'
34655 SpamAssassin has its own set of configuration files. Please review its
34656 documentation to see how you can tweak it. The default installation should work
34659 .oindex "&%spamd_address%&"
34660 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
34661 intend to use an instance running on the local host you do not need to set
34662 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
34663 you must set the &%spamd_address%& option in the global part of the Exim
34664 configuration as follows (example):
34666 spamd_address = 192.168.99.45 783
34668 The SpamAssassin protocol relies on a TCP half-close from the client.
34669 If your SpamAssassin client side is running a Linux system with an
34670 iptables firewall, consider setting
34671 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
34672 timeout, Exim uses when waiting for a response from the SpamAssassin
34673 server (currently defaulting to 120s). With a lower value the Linux
34674 connection tracking may consider your half-closed connection as dead too
34678 To use Rspamd (which by default listens on all local addresses
34680 you should add &%variant=rspamd%& after the address/port pair, for example:
34682 spamd_address = 127.0.0.1 11333 variant=rspamd
34685 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
34686 sockets. If you want to us these, supply &%spamd_address%& with an absolute
34687 filename instead of an address/port pair:
34689 spamd_address = /var/run/spamd_socket
34691 You can have multiple &%spamd%& servers to improve scalability. These can
34692 reside on other hardware reachable over the network. To specify multiple
34693 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
34694 option, separated with colons (the separator can be changed in the usual way &<<SECTlistsepchange>>&):
34696 spamd_address = 192.168.2.10 783 : \
34697 192.168.2.11 783 : \
34700 Up to 32 &%spamd%& servers are supported.
34701 When a server fails to respond to the connection attempt, all other
34702 servers are tried until one succeeds. If no server responds, the &%spam%&
34705 Unix and TCP socket specifications may be mixed in any order.
34706 Each element of the list is a list itself, space-separated by default
34707 and changeable in the usual way (&<<SECTlistsepchange>>&);
34708 take care to not double the separator.
34710 For TCP socket specifications a host name or IP (v4 or v6, but
34711 subject to list-separator quoting rules) address can be used,
34712 and the port can be one or a dash-separated pair.
34713 In the latter case, the range is tried in strict order.
34715 Elements after the first for Unix sockets, or second for TCP socket,
34717 The supported options are:
34719 pri=<priority> Selection priority
34720 weight=<value> Selection bias
34721 time=<start>-<end> Use only between these times of day
34722 retry=<timespec> Retry on connect fail
34723 tmo=<timespec> Connection time limit
34724 variant=rspamd Use Rspamd rather than SpamAssassin protocol
34727 The &`pri`& option specifies a priority for the server within the list,
34728 higher values being tried first.
34729 The default priority is 1.
34731 The &`weight`& option specifies a selection bias.
34732 Within a priority set
34733 servers are queried in a random fashion, weighted by this value.
34734 The default value for selection bias is 1.
34736 Time specifications for the &`time`& option are <hour>.<minute>.<second>
34737 in the local time zone; each element being one or more digits.
34738 Either the seconds or both minutes and seconds, plus the leading &`.`&
34739 characters, may be omitted and will be taken as zero.
34741 Timeout specifications for the &`retry`& and &`tmo`& options
34742 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
34744 The &`tmo`& option specifies an overall timeout for communication.
34745 The default value is two minutes.
34747 The &`retry`& option specifies a time after which a single retry for
34748 a failed connect is made.
34749 The default is to not retry.
34751 The &%spamd_address%& variable is expanded before use if it starts with
34752 a dollar sign. In this case, the expansion may return a string that is
34753 used as the list so that multiple spamd servers can be the result of an
34756 .vindex "&$callout_address$&"
34757 When a connection is made to the server the expansion variable &$callout_address$&
34758 is set to record the actual address used.
34760 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
34761 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
34764 message = This message was classified as SPAM
34766 The right-hand side of the &%spam%& condition specifies a name. This is
34767 relevant if you have set up multiple SpamAssassin profiles. If you do not want
34768 to scan using a specific profile, but rather use the SpamAssassin system-wide
34769 default profile, you can scan for an unknown name, or simply use &"nobody"&.
34770 Rspamd does not use this setting. However, you must put something on the
34773 The name allows you to use per-domain or per-user antispam profiles in
34774 principle, but this is not straightforward in practice, because a message may
34775 have multiple recipients, not necessarily all in the same domain. Because the
34776 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
34777 read the contents of the message, the variables &$local_part$& and &$domain$&
34779 Careful enforcement of single-recipient messages
34780 (e.g. by responding with defer in the recipient ACL for all recipients
34782 or the use of PRDR,
34783 .cindex "PRDR" "use for per-user SpamAssassin profiles"
34784 are needed to use this feature.
34786 The right-hand side of the &%spam%& condition is expanded before being used, so
34787 you can put lookups or conditions there. When the right-hand side evaluates to
34788 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
34791 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
34792 large ones may cause significant performance degradation. As most spam messages
34793 are quite small, it is recommended that you do not scan the big ones. For
34796 deny condition = ${if < {$message_size}{10K}}
34798 message = This message was classified as SPAM
34801 The &%spam%& condition returns true if the threshold specified in the user's
34802 SpamAssassin profile has been matched or exceeded. If you want to use the
34803 &%spam%& condition for its side effects (see the variables below), you can make
34804 it always return &"true"& by appending &`:true`& to the username.
34806 .cindex "spam scanning" "returned variables"
34807 When the &%spam%& condition is run, it sets up a number of expansion
34809 Except for &$spam_report$&,
34810 these variables are saved with the received message so are
34811 available for use at delivery time.
34814 .vitem &$spam_score$&
34815 The spam score of the message, for example, &"3.4"& or &"30.5"&. This is useful
34816 for inclusion in log or reject messages.
34818 .vitem &$spam_score_int$&
34819 The spam score of the message, multiplied by ten, as an integer value. For
34820 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
34821 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
34822 The integer value is useful for numeric comparisons in conditions.
34824 .vitem &$spam_bar$&
34825 A string consisting of a number of &"+"& or &"-"& characters, representing the
34826 integer part of the spam score value. A spam score of 4.4 would have a
34827 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
34828 headers, since MUAs can match on such strings. The maximum length of the
34829 spam bar is 50 characters.
34831 .vitem &$spam_report$&
34832 A multiline text table, containing the full SpamAssassin report for the
34833 message. Useful for inclusion in headers or reject messages.
34834 This variable is only usable in a DATA-time ACL.
34835 Beware that SpamAssassin may return non-ASCII characters, especially
34836 when running in country-specific locales, which are not legal
34837 unencoded in headers.
34839 .vitem &$spam_action$&
34840 For SpamAssassin either 'reject' or 'no action' depending on the
34841 spam score versus threshold.
34842 For Rspamd, the recommended action.
34846 The &%spam%& condition caches its results unless expansion in
34847 spamd_address was used. If you call it again with the same user name, it
34848 does not scan again, but rather returns the same values as before.
34850 The &%spam%& condition returns DEFER if there is any error while running
34851 the message through SpamAssassin or if the expansion of spamd_address
34852 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
34853 statement block), append &`/defer_ok`& to the right-hand side of the
34854 spam condition, like this:
34856 deny spam = joe/defer_ok
34857 message = This message was classified as SPAM
34859 This causes messages to be accepted even if there is a problem with &%spamd%&.
34861 Here is a longer, commented example of the use of the &%spam%&
34864 # put headers in all messages (no matter if spam or not)
34865 warn spam = nobody:true
34866 add_header = X-Spam-Score: $spam_score ($spam_bar)
34867 add_header = X-Spam-Report: $spam_report
34869 # add second subject line with *SPAM* marker when message
34870 # is over threshold
34872 add_header = Subject: *SPAM* $h_Subject:
34874 # reject spam at high scores (> 12)
34875 deny spam = nobody:true
34876 condition = ${if >{$spam_score_int}{120}{1}{0}}
34877 message = This message scored $spam_score spam points.
34882 .section "Scanning MIME parts" "SECTscanmimepart"
34883 .cindex "content scanning" "MIME parts"
34884 .cindex "MIME content scanning"
34885 .oindex "&%acl_smtp_mime%&"
34886 .oindex "&%acl_not_smtp_mime%&"
34887 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
34888 each MIME part of an SMTP message, including multipart types, in the sequence
34889 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
34890 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
34891 options may both refer to the same ACL if you want the same processing in both
34894 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
34895 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
34896 the case of a non-SMTP message. However, a MIME ACL is called only if the
34897 message contains a &'Content-Type:'& header line. When a call to a MIME
34898 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
34899 result code is sent to the client. In the case of an SMTP message, the
34900 &%acl_smtp_data%& ACL is not called when this happens.
34902 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
34903 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
34904 condition to match against the raw MIME part. You can also use the
34905 &%mime_regex%& condition to match against the decoded MIME part (see section
34906 &<<SECTscanregex>>&).
34908 At the start of a MIME ACL, a number of variables are set from the header
34909 information for the relevant MIME part. These are described below. The contents
34910 of the MIME part are not by default decoded into a disk file except for MIME
34911 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
34912 part into a disk file, you can use the &%decode%& condition. The general
34915 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
34917 The right hand side is expanded before use. After expansion,
34921 &"0"& or &"false"&, in which case no decoding is done.
34923 The string &"default"&. In that case, the file is put in the temporary
34924 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
34925 a sequential filename consisting of the message id and a sequence number. The
34926 full path and name is available in &$mime_decoded_filename$& after decoding.
34928 A full path name starting with a slash. If the full name is an existing
34929 directory, it is used as a replacement for the default directory. The filename
34930 is then sequentially assigned. If the path does not exist, it is used as
34931 the full path and filename.
34933 If the string does not start with a slash, it is used as the
34934 filename, and the default path is then used.
34936 The &%decode%& condition normally succeeds. It is only false for syntax
34937 errors or unusual circumstances such as memory shortages. You can easily decode
34938 a file with its original, proposed filename using
34940 decode = $mime_filename
34942 However, you should keep in mind that &$mime_filename$& might contain
34943 anything. If you place files outside of the default path, they are not
34944 automatically unlinked.
34946 For RFC822 attachments (these are messages attached to messages, with a
34947 content-type of &"message/rfc822"&), the ACL is called again in the same manner
34948 as for the primary message, only that the &$mime_is_rfc822$& expansion
34949 variable is set (see below). Attached messages are always decoded to disk
34950 before being checked, and the files are unlinked once the check is done.
34952 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
34953 used to match regular expressions against raw and decoded MIME parts,
34954 respectively. They are described in section &<<SECTscanregex>>&.
34956 .cindex "MIME content scanning" "returned variables"
34957 The following list describes all expansion variables that are
34958 available in the MIME ACL:
34961 .vitem &$mime_anomaly_level$& &&&
34962 &$mime_anomaly_text$&
34963 .vindex &$mime_anomaly_level$&
34964 .vindex &$mime_anomaly_text$&
34965 If there are problems decoding, these variables contain information on
34966 the detected issue.
34968 .vitem &$mime_boundary$&
34969 .vindex &$mime_boundary$&
34970 If the current part is a multipart (see &$mime_is_multipart$& below), it should
34971 have a boundary string, which is stored in this variable. If the current part
34972 has no boundary parameter in the &'Content-Type:'& header, this variable
34973 contains the empty string.
34975 .vitem &$mime_charset$&
34976 .vindex &$mime_charset$&
34977 This variable contains the character set identifier, if one was found in the
34978 &'Content-Type:'& header. Examples for charset identifiers are:
34984 Please note that this value is not normalized, so you should do matches
34985 case-insensitively.
34987 .vitem &$mime_content_description$&
34988 .vindex &$mime_content_description$&
34989 This variable contains the normalized content of the &'Content-Description:'&
34990 header. It can contain a human-readable description of the parts content. Some
34991 implementations repeat the filename for attachments here, but they are usually
34992 only used for display purposes.
34994 .vitem &$mime_content_disposition$&
34995 .vindex &$mime_content_disposition$&
34996 This variable contains the normalized content of the &'Content-Disposition:'&
34997 header. You can expect strings like &"attachment"& or &"inline"& here.
34999 .vitem &$mime_content_id$&
35000 .vindex &$mime_content_id$&
35001 This variable contains the normalized content of the &'Content-ID:'& header.
35002 This is a unique ID that can be used to reference a part from another part.
35004 .vitem &$mime_content_size$&
35005 .vindex &$mime_content_size$&
35006 This variable is set only after the &%decode%& modifier (see above) has been
35007 successfully run. It contains the size of the decoded part in kilobytes. The
35008 size is always rounded up to full kilobytes, so only a completely empty part
35009 has a &$mime_content_size$& of zero.
35011 .vitem &$mime_content_transfer_encoding$&
35012 .vindex &$mime_content_transfer_encoding$&
35013 This variable contains the normalized content of the
35014 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
35015 type. Typical values are &"base64"& and &"quoted-printable"&.
35017 .vitem &$mime_content_type$&
35018 .vindex &$mime_content_type$&
35019 If the MIME part has a &'Content-Type:'& header, this variable contains its
35020 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
35021 are some examples of popular MIME types, as they may appear in this variable:
35025 application/octet-stream
35029 If the MIME part has no &'Content-Type:'& header, this variable contains the
35032 .vitem &$mime_decoded_filename$&
35033 .vindex &$mime_decoded_filename$&
35034 This variable is set only after the &%decode%& modifier (see above) has been
35035 successfully run. It contains the full path and filename of the file
35036 containing the decoded data.
35041 .vitem &$mime_filename$&
35042 .vindex &$mime_filename$&
35043 This is perhaps the most important of the MIME variables. It contains a
35044 proposed filename for an attachment, if one was found in either the
35045 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
35048 decoded, but no additional sanity checks are done.
35050 found, this variable contains the empty string.
35052 .vitem &$mime_is_coverletter$&
35053 .vindex &$mime_is_coverletter$&
35054 This variable attempts to differentiate the &"cover letter"& of an e-mail from
35055 attached data. It can be used to clamp down on flashy or unnecessarily encoded
35056 content in the cover letter, while not restricting attachments at all.
35058 The variable contains 1 (true) for a MIME part believed to be part of the
35059 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
35063 The outermost MIME part of a message is always a cover letter.
35066 If a multipart/alternative or multipart/related MIME part is a cover letter,
35067 so are all MIME subparts within that multipart.
35070 If any other multipart is a cover letter, the first subpart is a cover letter,
35071 and the rest are attachments.
35074 All parts contained within an attachment multipart are attachments.
35077 As an example, the following will ban &"HTML mail"& (including that sent with
35078 alternative plain text), while allowing HTML files to be attached. HTML
35079 coverletter mail attached to non-HTML coverletter mail will also be allowed:
35081 deny !condition = $mime_is_rfc822
35082 condition = $mime_is_coverletter
35083 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
35084 message = HTML mail is not accepted here
35087 .vitem &$mime_is_multipart$&
35088 .vindex &$mime_is_multipart$&
35089 This variable has the value 1 (true) when the current part has the main type
35090 &"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
35091 Since multipart entities only serve as containers for other parts, you may not
35092 want to carry out specific actions on them.
35094 .vitem &$mime_is_rfc822$&
35095 .vindex &$mime_is_rfc822$&
35096 This variable has the value 1 (true) if the current part is not a part of the
35097 checked message itself, but part of an attached message. Attached message
35098 decoding is fully recursive.
35100 .vitem &$mime_part_count$&
35101 .vindex &$mime_part_count$&
35102 This variable is a counter that is raised for each processed MIME part. It
35103 starts at zero for the very first part (which is usually a multipart). The
35104 counter is per-message, so it is reset when processing RFC822 attachments (see
35105 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
35106 complete, so you can use it in the DATA ACL to determine the number of MIME
35107 parts of a message. For non-MIME messages, this variable contains the value -1.
35112 .section "Scanning with regular expressions" "SECTscanregex"
35113 .cindex "content scanning" "with regular expressions"
35114 .cindex "regular expressions" "content scanning with"
35115 You can specify your own custom regular expression matches on the full body of
35116 the message, or on individual MIME parts.
35118 The &%regex%& condition takes one or more regular expressions as arguments and
35119 matches them against the full message (when called in the DATA ACL) or a raw
35120 MIME part (when called in the MIME ACL). The &%regex%& condition matches
35121 linewise, with a maximum line length of 32K characters. That means you cannot
35122 have multiline matches with the &%regex%& condition.
35124 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
35125 to 32K of decoded content (the whole content at once, not linewise). If the
35126 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
35127 is decoded automatically when &%mime_regex%& is executed (using default path
35128 and filename values). If the decoded data is larger than 32K, only the first
35129 32K characters are checked.
35131 The regular expressions are passed as a colon-separated list. To include a
35132 literal colon, you must double it. Since the whole right-hand side string is
35133 expanded before being used, you must also escape dollar signs and backslashes
35134 with more backslashes, or use the &`\N`& facility to disable expansion.
35135 Here is a simple example that contains two regular expressions:
35137 deny regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
35138 message = contains blacklisted regex ($regex_match_string)
35140 The conditions returns true if any one of the regular expressions matches. The
35141 &$regex_match_string$& expansion variable is then set up and contains the
35142 matching regular expression.
35143 The expansion variables &$regex1$& &$regex2$& etc
35144 are set to any substrings captured by the regular expression.
35146 &*Warning*&: With large messages, these conditions can be fairly
35154 . ////////////////////////////////////////////////////////////////////////////
35155 . ////////////////////////////////////////////////////////////////////////////
35157 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
35158 "Local scan function"
35159 .scindex IIDlosca "&[local_scan()]& function" "description of"
35160 .cindex "customizing" "input scan using C function"
35161 .cindex "policy control" "by local scan function"
35162 In these days of email worms, viruses, and ever-increasing spam, some sites
35163 want to apply a lot of checking to messages before accepting them.
35165 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
35166 passing messages to external virus and spam scanning software. You can also do
35167 a certain amount in Exim itself through string expansions and the &%condition%&
35168 condition in the ACL that runs after the SMTP DATA command or the ACL for
35169 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
35171 To allow for further customization to a site's own requirements, there is the
35172 possibility of linking Exim with a private message scanning function, written
35173 in C. If you want to run code that is written in something other than C, you
35174 can of course use a little C stub to call it.
35176 The local scan function is run once for every incoming message, at the point
35177 when Exim is just about to accept the message.
35178 It can therefore be used to control non-SMTP messages from local processes as
35179 well as messages arriving via SMTP.
35181 Exim applies a timeout to calls of the local scan function, and there is an
35182 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
35183 Zero means &"no timeout"&.
35184 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
35185 before calling the local scan function, so that the most common types of crash
35186 are caught. If the timeout is exceeded or one of those signals is caught, the
35187 incoming message is rejected with a temporary error if it is an SMTP message.
35188 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
35189 code. The incident is logged on the main and reject logs.
35193 .section "Building Exim to use a local scan function" "SECID207"
35194 .cindex "&[local_scan()]& function" "building Exim to use"
35195 To make use of the local scan function feature, you must tell Exim where your
35196 function is before building Exim, by setting
35197 both HAVE_LOCAL_SCAN and
35198 LOCAL_SCAN_SOURCE in your
35199 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
35200 directory, so you might set
35202 HAVE_LOCAL_SCAN=yes
35203 LOCAL_SCAN_SOURCE=Local/local_scan.c
35205 for example. The function must be called &[local_scan()]&;
35206 the source file(s) for it should first #define LOCAL_SCAN
35207 and then #include "local_scan.h".
35209 Exim after it has received a message, when the success return code is about to
35210 be sent. This is after all the ACLs have been run. The return code from your
35211 function controls whether the message is actually accepted or not. There is a
35212 commented template function (that just accepts the message) in the file
35213 _src/local_scan.c_.
35215 If you want to make use of Exim's runtime configuration file to set options
35216 for your &[local_scan()]& function, you must also set
35218 LOCAL_SCAN_HAS_OPTIONS=yes
35220 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
35225 .section "API for local_scan()" "SECTapiforloc"
35226 .cindex "&[local_scan()]& function" "API description"
35227 .cindex &%dlfunc%& "API description"
35228 You must include this line near the start of your code:
35231 #include "local_scan.h"
35233 This header file defines a number of variables and other values, and the
35234 prototype for the function itself. Exim is coded to use unsigned char values
35235 almost exclusively, and one of the things this header defines is a shorthand
35236 for &`unsigned char`& called &`uschar`&.
35237 It also makes available the following macro definitions, to simplify casting character
35238 strings and pointers to character strings:
35240 #define CS (char *)
35241 #define CCS (const char *)
35242 #define CSS (char **)
35243 #define US (unsigned char *)
35244 #define CUS (const unsigned char *)
35245 #define USS (unsigned char **)
35247 The function prototype for &[local_scan()]& is:
35249 extern int local_scan(int fd, uschar **return_text);
35251 The arguments are as follows:
35254 &%fd%& is a file descriptor for the file that contains the body of the message
35255 (the -D file). The file is open for reading and writing, but updating it is not
35256 recommended. &*Warning*&: You must &'not'& close this file descriptor.
35258 The descriptor is positioned at character 19 of the file, which is the first
35259 character of the body itself, because the first 19 characters are the message
35260 id followed by &`-D`& and a newline. If you rewind the file, you should use the
35261 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
35262 case this changes in some future version.
35264 &%return_text%& is an address which you can use to return a pointer to a text
35265 string at the end of the function. The value it points to on entry is NULL.
35268 The function must return an &%int%& value which is one of the following macros:
35271 .vitem &`LOCAL_SCAN_ACCEPT`&
35272 .vindex "&$local_scan_data$&"
35273 The message is accepted. If you pass back a string of text, it is saved with
35274 the message, and made available in the variable &$local_scan_data$&. No
35275 newlines are permitted (if there are any, they are turned into spaces) and the
35276 maximum length of text is 1000 characters.
35278 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
35279 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
35280 queued without immediate delivery, and is frozen.
35282 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
35283 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
35284 queued without immediate delivery.
35286 .vitem &`LOCAL_SCAN_REJECT`&
35287 The message is rejected; the returned text is used as an error message which is
35288 passed back to the sender and which is also logged. Newlines are permitted &--
35289 they cause a multiline response for SMTP rejections, but are converted to
35290 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
35293 .vitem &`LOCAL_SCAN_TEMPREJECT`&
35294 The message is temporarily rejected; the returned text is used as an error
35295 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
35298 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
35299 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
35300 message is not written to the reject log. It has the effect of unsetting the
35301 &%rejected_header%& log selector for just this rejection. If
35302 &%rejected_header%& is already unset (see the discussion of the
35303 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
35304 same as LOCAL_SCAN_REJECT.
35306 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
35307 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
35308 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
35311 If the message is not being received by interactive SMTP, rejections are
35312 reported by writing to &%stderr%& or by sending an email, as configured by the
35313 &%-oe%& command line options.
35317 .section "Configuration options for local_scan()" "SECTconoptloc"
35318 .cindex "&[local_scan()]& function" "configuration options"
35319 It is possible to have option settings in the main configuration file
35320 that set values in static variables in the &[local_scan()]& module. If you
35321 want to do this, you must have the line
35323 LOCAL_SCAN_HAS_OPTIONS=yes
35325 in your &_Local/Makefile_& when you build Exim. (This line is in
35326 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
35327 file, you must define static variables to hold the option values, and a table
35330 The table must be a vector called &%local_scan_options%&, of type
35331 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
35332 and a pointer to the variable that holds the value. The entries must appear in
35333 alphabetical order. Following &%local_scan_options%& you must also define a
35334 variable called &%local_scan_options_count%& that contains the number of
35335 entries in the table. Here is a short example, showing two kinds of option:
35337 static int my_integer_option = 42;
35338 static uschar *my_string_option = US"a default string";
35340 optionlist local_scan_options[] = {
35341 { "my_integer", opt_int, &my_integer_option },
35342 { "my_string", opt_stringptr, &my_string_option }
35345 int local_scan_options_count =
35346 sizeof(local_scan_options)/sizeof(optionlist);
35348 The values of the variables can now be changed from Exim's runtime
35349 configuration file by including a local scan section as in this example:
35353 my_string = some string of text...
35355 The available types of option data are as follows:
35358 .vitem &*opt_bool*&
35359 This specifies a boolean (true/false) option. The address should point to a
35360 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
35361 that are defined as &"1"& and &"0"&, respectively. If you want to detect
35362 whether such a variable has been set at all, you can initialize it to
35363 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
35366 .vitem &*opt_fixed*&
35367 This specifies a fixed point number, such as is used for load averages.
35368 The address should point to a variable of type &`int`&. The value is stored
35369 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
35372 This specifies an integer; the address should point to a variable of type
35373 &`int`&. The value may be specified in any of the integer formats accepted by
35376 .vitem &*opt_mkint*&
35377 This is the same as &%opt_int%&, except that when such a value is output in a
35378 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
35379 printed with the suffix K or M.
35381 .vitem &*opt_octint*&
35382 This also specifies an integer, but the value is always interpreted as an
35383 octal integer, whether or not it starts with the digit zero, and it is
35384 always output in octal.
35386 .vitem &*opt_stringptr*&
35387 This specifies a string value; the address must be a pointer to a
35388 variable that points to a string (for example, of type &`uschar *`&).
35390 .vitem &*opt_time*&
35391 This specifies a time interval value. The address must point to a variable of
35392 type &`int`&. The value that is placed there is a number of seconds.
35395 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
35396 out the values of all the &[local_scan()]& options.
35400 .section "Available Exim variables" "SECID208"
35401 .cindex "&[local_scan()]& function" "available Exim variables"
35402 The header &_local_scan.h_& gives you access to a number of C variables. These
35403 are the only ones that are guaranteed to be maintained from release to release.
35404 Note, however, that you can obtain the value of any Exim expansion variable,
35405 including &$recipients$&, by calling &'expand_string()'&. The exported
35406 C variables are as follows:
35409 .vitem &*int&~body_linecount*&
35410 This variable contains the number of lines in the message's body.
35411 It is not valid if the &%spool_wireformat%& option is used.
35413 .vitem &*int&~body_zerocount*&
35414 This variable contains the number of binary zero bytes in the message's body.
35415 It is not valid if the &%spool_wireformat%& option is used.
35417 .vitem &*unsigned&~int&~debug_selector*&
35418 This variable is set to zero when no debugging is taking place. Otherwise, it
35419 is a bitmap of debugging selectors. Two bits are identified for use in
35420 &[local_scan()]&; they are defined as macros:
35423 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
35424 testing option that is not privileged &-- any caller may set it. All the
35425 other selector bits can be set only by admin users.
35428 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
35429 by the &`+local_scan`& debug selector. It is not included in the default set
35433 Thus, to write to the debugging output only when &`+local_scan`& has been
35434 selected, you should use code like this:
35436 if ((debug_selector & D_local_scan) != 0)
35437 debug_printf("xxx", ...);
35439 .vitem &*uschar&~*expand_string_message*&
35440 After a failing call to &'expand_string()'& (returned value NULL), the
35441 variable &%expand_string_message%& contains the error message, zero-terminated.
35443 .vitem &*header_line&~*header_list*&
35444 A pointer to a chain of header lines. The &%header_line%& structure is
35447 .vitem &*header_line&~*header_last*&
35448 A pointer to the last of the header lines.
35450 .vitem &*const&~uschar&~*headers_charset*&
35451 The value of the &%headers_charset%& configuration option.
35453 .vitem &*BOOL&~host_checking*&
35454 This variable is TRUE during a host checking session that is initiated by the
35455 &%-bh%& command line option.
35457 .vitem &*uschar&~*interface_address*&
35458 The IP address of the interface that received the message, as a string. This
35459 is NULL for locally submitted messages.
35461 .vitem &*int&~interface_port*&
35462 The port on which this message was received. When testing with the &%-bh%&
35463 command line option, the value of this variable is -1 unless a port has been
35464 specified via the &%-oMi%& option.
35466 .vitem &*uschar&~*message_id*&
35467 This variable contains Exim's message id for the incoming message (the value of
35468 &$message_exim_id$&) as a zero-terminated string.
35470 .vitem &*uschar&~*received_protocol*&
35471 The name of the protocol by which the message was received.
35473 .vitem &*int&~recipients_count*&
35474 The number of accepted recipients.
35476 .vitem &*recipient_item&~*recipients_list*&
35477 .cindex "recipient" "adding in local scan"
35478 .cindex "recipient" "removing in local scan"
35479 The list of accepted recipients, held in a vector of length
35480 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
35481 can add additional recipients by calling &'receive_add_recipient()'& (see
35482 below). You can delete recipients by removing them from the vector and
35483 adjusting the value in &%recipients_count%&. In particular, by setting
35484 &%recipients_count%& to zero you remove all recipients. If you then return the
35485 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
35486 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
35487 and then call &'receive_add_recipient()'& as often as needed.
35489 .vitem &*uschar&~*sender_address*&
35490 The envelope sender address. For bounce messages this is the empty string.
35492 .vitem &*uschar&~*sender_host_address*&
35493 The IP address of the sending host, as a string. This is NULL for
35494 locally-submitted messages.
35496 .vitem &*uschar&~*sender_host_authenticated*&
35497 The name of the authentication mechanism that was used, or NULL if the message
35498 was not received over an authenticated SMTP connection.
35500 .vitem &*uschar&~*sender_host_name*&
35501 The name of the sending host, if known.
35503 .vitem &*int&~sender_host_port*&
35504 The port on the sending host.
35506 .vitem &*BOOL&~smtp_input*&
35507 This variable is TRUE for all SMTP input, including BSMTP.
35509 .vitem &*BOOL&~smtp_batched_input*&
35510 This variable is TRUE for BSMTP input.
35512 .vitem &*int&~store_pool*&
35513 The contents of this variable control which pool of memory is used for new
35514 requests. See section &<<SECTmemhanloc>>& for details.
35518 .section "Structure of header lines" "SECID209"
35519 The &%header_line%& structure contains the members listed below.
35520 You can add additional header lines by calling the &'header_add()'& function
35521 (see below). You can cause header lines to be ignored (deleted) by setting
35526 .vitem &*struct&~header_line&~*next*&
35527 A pointer to the next header line, or NULL for the last line.
35529 .vitem &*int&~type*&
35530 A code identifying certain headers that Exim recognizes. The codes are printing
35531 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
35532 Notice in particular that any header line whose type is * is not transmitted
35533 with the message. This flagging is used for header lines that have been
35534 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
35535 lines.) Effectively, * means &"deleted"&.
35537 .vitem &*int&~slen*&
35538 The number of characters in the header line, including the terminating and any
35541 .vitem &*uschar&~*text*&
35542 A pointer to the text of the header. It always ends with a newline, followed by
35543 a zero byte. Internal newlines are preserved.
35548 .section "Structure of recipient items" "SECID210"
35549 The &%recipient_item%& structure contains these members:
35552 .vitem &*uschar&~*address*&
35553 This is a pointer to the recipient address as it was received.
35555 .vitem &*int&~pno*&
35556 This is used in later Exim processing when top level addresses are created by
35557 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
35558 and must always contain -1 at this stage.
35560 .vitem &*uschar&~*errors_to*&
35561 If this value is not NULL, bounce messages caused by failing to deliver to the
35562 recipient are sent to the address it contains. In other words, it overrides the
35563 envelope sender for this one recipient. (Compare the &%errors_to%& generic
35564 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
35565 an unqualified address, Exim qualifies it using the domain from
35566 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
35567 is NULL for all recipients.
35572 .section "Available Exim functions" "SECID211"
35573 .cindex "&[local_scan()]& function" "available Exim functions"
35574 The header &_local_scan.h_& gives you access to a number of Exim functions.
35575 These are the only ones that are guaranteed to be maintained from release to
35579 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
35580 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
35582 This function creates a child process that runs the command specified by
35583 &%argv%&. The environment for the process is specified by &%envp%&, which can
35584 be NULL if no environment variables are to be passed. A new umask is supplied
35585 for the process in &%newumask%&.
35587 Pipes to the standard input and output of the new process are set up
35588 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
35589 standard error is cloned to the standard output. If there are any file
35590 descriptors &"in the way"& in the new process, they are closed. If the final
35591 argument is TRUE, the new process is made into a process group leader.
35593 The function returns the pid of the new process, or -1 if things go wrong.
35595 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
35596 This function waits for a child process to terminate, or for a timeout (in
35597 seconds) to expire. A timeout value of zero means wait as long as it takes. The
35598 return value is as follows:
35603 The process terminated by a normal exit and the value is the process
35609 The process was terminated by a signal and the value is the negation of the
35615 The process timed out.
35619 The was some other error in wait(); &%errno%& is still set.
35622 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
35623 This function provide you with a means of submitting a new message to
35624 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
35625 want, but this packages it all up for you.) The function creates a pipe,
35626 forks a subprocess that is running
35628 exim -t -oem -oi -f <>
35630 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
35631 that is connected to the standard input. The yield of the function is the PID
35632 of the subprocess. You can then write a message to the file descriptor, with
35633 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
35635 When you have finished, call &'child_close()'& to wait for the process to
35636 finish and to collect its ending status. A timeout value of zero is usually
35637 fine in this circumstance. Unless you have made a mistake with the recipient
35638 addresses, you should get a return code of zero.
35641 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
35642 *sender_authentication)*&
35643 This function is a more sophisticated version of &'child_open()'&. The command
35646 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
35648 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
35651 .vitem &*void&~debug_printf(char&~*,&~...)*&
35652 This is Exim's debugging function, with arguments as for &'(printf()'&. The
35653 output is written to the standard error stream. If no debugging is selected,
35654 calls to &'debug_printf()'& have no effect. Normally, you should make calls
35655 conditional on the &`local_scan`& debug selector by coding like this:
35657 if ((debug_selector & D_local_scan) != 0)
35658 debug_printf("xxx", ...);
35661 .vitem &*uschar&~*expand_string(uschar&~*string)*&
35662 This is an interface to Exim's string expansion code. The return value is the
35663 expanded string, or NULL if there was an expansion failure.
35664 The C variable &%expand_string_message%& contains an error message after an
35665 expansion failure. If expansion does not change the string, the return value is
35666 the pointer to the input string. Otherwise, the return value points to a new
35667 block of memory that was obtained by a call to &'store_get()'&. See section
35668 &<<SECTmemhanloc>>& below for a discussion of memory handling.
35670 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
35671 This function allows you to an add additional header line at the end of the
35672 existing ones. The first argument is the type, and should normally be a space
35673 character. The second argument is a format string and any number of
35674 substitution arguments as for &[sprintf()]&. You may include internal newlines
35675 if you want, and you must ensure that the string ends with a newline.
35677 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
35678 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
35679 This function adds a new header line at a specified point in the header
35680 chain. The header itself is specified as for &'header_add()'&.
35682 If &%name%& is NULL, the new header is added at the end of the chain if
35683 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
35684 NULL, the header lines are searched for the first non-deleted header that
35685 matches the name. If one is found, the new header is added before it if
35686 &%after%& is false. If &%after%& is true, the new header is added after the
35687 found header and any adjacent subsequent ones with the same name (even if
35688 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
35689 option controls where the header is added. If it is true, addition is at the
35690 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
35691 headers, or at the top if there are no &'Received:'& headers, you could use
35693 header_add_at_position(TRUE, US"Received", TRUE,
35694 ' ', "X-xxx: ...");
35696 Normally, there is always at least one non-deleted &'Received:'& header, but
35697 there may not be if &%received_header_text%& expands to an empty string.
35700 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
35701 This function removes header lines. If &%occurrence%& is zero or negative, all
35702 occurrences of the header are removed. If occurrence is greater than zero, that
35703 particular instance of the header is removed. If no header(s) can be found that
35704 match the specification, the function does nothing.
35707 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
35708 int&~length,&~BOOL&~notdel)*&"
35709 This function tests whether the given header has the given name. It is not just
35710 a string comparison, because white space is permitted between the name and the
35711 colon. If the &%notdel%& argument is true, a false return is forced for all
35712 &"deleted"& headers; otherwise they are not treated specially. For example:
35714 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
35716 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
35717 .cindex "base64 encoding" "functions for &[local_scan()]& use"
35718 This function base64-encodes a string, which is passed by address and length.
35719 The text may contain bytes of any value, including zero. The result is passed
35720 back in dynamic memory that is obtained by calling &'store_get()'&. It is
35723 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
35724 This function decodes a base64-encoded string. Its arguments are a
35725 zero-terminated base64-encoded string and the address of a variable that is set
35726 to point to the result, which is in dynamic memory. The length of the decoded
35727 string is the yield of the function. If the input is invalid base64 data, the
35728 yield is -1. A zero byte is added to the end of the output string to make it
35729 easy to interpret as a C string (assuming it contains no zeros of its own). The
35730 added zero byte is not included in the returned count.
35732 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
35733 This function checks for a match in a domain list. Domains are always
35734 matched caselessly. The return value is one of the following:
35735 .itable none 0 0 2 15* left 85* left
35736 .irow &`OK`& "match succeeded"
35737 .irow &`FAIL`& "match failed"
35738 .irow &`DEFER`& "match deferred"
35740 DEFER is usually caused by some kind of lookup defer, such as the
35741 inability to contact a database.
35743 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
35745 This function checks for a match in a local part list. The third argument
35746 controls case-sensitivity. The return values are as for
35747 &'lss_match_domain()'&.
35749 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
35751 This function checks for a match in an address list. The third argument
35752 controls the case-sensitivity of the local part match. The domain is always
35753 matched caselessly. The return values are as for &'lss_match_domain()'&.
35755 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
35757 This function checks for a match in a host list. The most common usage is
35760 lss_match_host(sender_host_name, sender_host_address, ...)
35762 .vindex "&$sender_host_address$&"
35763 An empty address field matches an empty item in the host list. If the host name
35764 is NULL, the name corresponding to &$sender_host_address$& is automatically
35765 looked up if a host name is required to match an item in the list. The return
35766 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
35767 returns ERROR in the case when it had to look up a host name, but the lookup
35770 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
35772 This function writes to Exim's log files. The first argument should be zero (it
35773 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
35774 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
35775 them. It specifies to which log or logs the message is written. The remaining
35776 arguments are a format and relevant insertion arguments. The string should not
35777 contain any newlines, not even at the end.
35780 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
35781 This function adds an additional recipient to the message. The first argument
35782 is the recipient address. If it is unqualified (has no domain), it is qualified
35783 with the &%qualify_recipient%& domain. The second argument must always be -1.
35785 This function does not allow you to specify a private &%errors_to%& address (as
35786 described with the structure of &%recipient_item%& above), because it pre-dates
35787 the addition of that field to the structure. However, it is easy to add such a
35788 value afterwards. For example:
35790 receive_add_recipient(US"monitor@mydom.example", -1);
35791 recipients_list[recipients_count-1].errors_to =
35792 US"postmaster@mydom.example";
35795 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
35796 This is a convenience function to remove a named recipient from the list of
35797 recipients. It returns true if a recipient was removed, and false if no
35798 matching recipient could be found. The argument must be a complete email
35805 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
35806 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
35807 This function decodes strings that are encoded according to RFC 2047. Typically
35808 these are the contents of header lines. First, each &"encoded word"& is decoded
35809 from the Q or B encoding into a byte-string. Then, if provided with the name of
35810 a charset encoding, and if the &[iconv()]& function is available, an attempt is
35811 made to translate the result to the named character set. If this fails, the
35812 binary string is returned with an error message.
35814 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
35815 maximum MIME word length is enforced. The third argument is the target
35816 encoding, or NULL if no translation is wanted.
35818 .cindex "binary zero" "in RFC 2047 decoding"
35819 .cindex "RFC 2047" "binary zero in"
35820 If a binary zero is encountered in the decoded string, it is replaced by the
35821 contents of the &%zeroval%& argument. For use with Exim headers, the value must
35822 not be 0 because header lines are handled as zero-terminated strings.
35824 The function returns the result of processing the string, zero-terminated; if
35825 &%lenptr%& is not NULL, the length of the result is set in the variable to
35826 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
35828 If an error is encountered, the function returns NULL and uses the &%error%&
35829 argument to return an error message. The variable pointed to by &%error%& is
35830 set to NULL if there is no error; it may be set non-NULL even when the function
35831 returns a non-NULL value if decoding was successful, but there was a problem
35835 .vitem &*int&~smtp_fflush(void)*&
35836 This function is used in conjunction with &'smtp_printf()'&, as described
35839 .vitem &*void&~smtp_printf(char&~*,BOOL,&~...)*&
35840 The arguments of this function are almost like &[printf()]&; it writes to the SMTP
35841 output stream. You should use this function only when there is an SMTP output
35842 stream, that is, when the incoming message is being received via interactive
35843 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
35844 is FALSE. If you want to test for an incoming message from another host (as
35845 opposed to a local process that used the &%-bs%& command line option), you can
35846 test the value of &%sender_host_address%&, which is non-NULL when a remote host
35849 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
35850 output function, so it can be used for all forms of SMTP connection.
35852 The second argument is used to request that the data be buffered
35853 (when TRUE) or flushed (along with any previously buffered, when FALSE).
35854 This is advisory only, but likely to save on system-calls and packets
35855 sent when a sequence of calls to the function are made.
35857 The argument was added in Exim version 4.90 - changing the API/ABI.
35858 Nobody noticed until 4.93 was imminent, at which point the
35859 ABI version number was incremented.
35861 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
35862 must start with an appropriate response code: 550 if you are going to return
35863 LOCAL_SCAN_REJECT, 451 if you are going to return
35864 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
35865 initial lines of a multi-line response, the code must be followed by a hyphen
35866 to indicate that the line is not the final response line. You must also ensure
35867 that the lines you write terminate with CRLF. For example:
35869 smtp_printf("550-this is some extra info\r\n");
35870 return LOCAL_SCAN_REJECT;
35872 Note that you can also create multi-line responses by including newlines in
35873 the data returned via the &%return_text%& argument. The added value of using
35874 &'smtp_printf()'& is that, for instance, you could introduce delays between
35875 multiple output lines.
35877 The &'smtp_printf()'& function does not return any error indication, because it
35879 guarantee a flush of
35880 pending output, and therefore does not test
35881 the state of the stream. (In the main code of Exim, flushing and error
35882 detection is done when Exim is ready for the next SMTP input command.) If
35883 you want to flush the output and check for an error (for example, the
35884 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
35885 arguments. It flushes the output stream, and returns a non-zero value if there
35888 .vitem &*void&~*store_get(int,BOOL)*&
35889 This function accesses Exim's internal store (memory) manager. It gets a new
35890 chunk of memory whose size is given by the first argument.
35891 The second argument should be given as TRUE if the memory will be used for
35892 data possibly coming from an attacker (eg. the message content),
35893 FALSE if it is locally-sourced.
35894 Exim bombs out if it ever
35895 runs out of memory. See the next section for a discussion of memory handling.
35897 .vitem &*void&~*store_get_perm(int,BOOL)*&
35898 This function is like &'store_get()'&, but it always gets memory from the
35899 permanent pool. See the next section for a discussion of memory handling.
35901 .vitem &*uschar&~*string_copy(uschar&~*string)*&
35904 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
35907 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
35908 These three functions create strings using Exim's dynamic memory facilities.
35909 The first makes a copy of an entire string. The second copies up to a maximum
35910 number of characters, indicated by the second argument. The third uses a format
35911 and insertion arguments to create a new string. In each case, the result is a
35912 pointer to a new string in the current memory pool. See the next section for
35918 .section "More about Exim's memory handling" "SECTmemhanloc"
35919 .cindex "&[local_scan()]& function" "memory handling"
35920 No function is provided for freeing memory, because that is never needed.
35921 The dynamic memory that Exim uses when receiving a message is automatically
35922 recycled if another message is received by the same process (this applies only
35923 to incoming SMTP connections &-- other input methods can supply only one
35924 message at a time). After receiving the last message, a reception process
35927 Because it is recycled, the normal dynamic memory cannot be used for holding
35928 data that must be preserved over a number of incoming messages on the same SMTP
35929 connection. However, Exim in fact uses two pools of dynamic memory; the second
35930 one is not recycled, and can be used for this purpose.
35932 If you want to allocate memory that remains available for subsequent messages
35933 in the same SMTP connection, you should set
35935 store_pool = POOL_PERM
35937 before calling the function that does the allocation. There is no need to
35938 restore the value if you do not need to; however, if you do want to revert to
35939 the normal pool, you can either restore the previous value of &%store_pool%& or
35940 set it explicitly to POOL_MAIN.
35942 The pool setting applies to all functions that get dynamic memory, including
35943 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
35944 There is also a convenience function called &'store_get_perm()'& that gets a
35945 block of memory from the permanent pool while preserving the value of
35952 . ////////////////////////////////////////////////////////////////////////////
35953 . ////////////////////////////////////////////////////////////////////////////
35955 .chapter "System-wide message filtering" "CHAPsystemfilter"
35956 .scindex IIDsysfil1 "filter" "system filter"
35957 .scindex IIDsysfil2 "filtering all mail"
35958 .scindex IIDsysfil3 "system filter"
35959 The previous chapters (on ACLs and the local scan function) describe checks
35960 that can be applied to messages before they are accepted by a host. There is
35961 also a mechanism for checking messages once they have been received, but before
35962 they are delivered. This is called the &'system filter'&.
35964 The system filter operates in a similar manner to users' filter files, but it
35965 is run just once per message (however many recipients the message has).
35966 It should not normally be used as a substitute for routing, because &%deliver%&
35967 commands in a system router provide new envelope recipient addresses.
35968 The system filter must be an Exim filter. It cannot be a Sieve filter.
35970 The system filter is run at the start of a delivery attempt, before any routing
35971 is done. If a message fails to be completely delivered at the first attempt,
35972 the system filter is run again at the start of every retry.
35973 If you want your filter to do something only once per message, you can make use
35974 .cindex retry condition
35975 of the &%first_delivery%& condition in an &%if%& command in the filter to
35976 prevent it happening on retries.
35978 .vindex "&$domain$&"
35979 .vindex "&$local_part$&"
35980 &*Warning*&: Because the system filter runs just once, variables that are
35981 specific to individual recipient addresses, such as &$local_part$& and
35982 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
35983 you want to run a centrally-specified filter for each recipient address
35984 independently, you can do so by setting up a suitable &(redirect)& router, as
35985 described in section &<<SECTperaddfil>>& below.
35988 .section "Specifying a system filter" "SECID212"
35989 .cindex "uid (user id)" "system filter"
35990 .cindex "gid (group id)" "system filter"
35991 The name of the file that contains the system filter must be specified by
35992 setting &%system_filter%&. If you want the filter to run under a uid and gid
35993 other than root, you must also set &%system_filter_user%& and
35994 &%system_filter_group%& as appropriate. For example:
35996 system_filter = /etc/mail/exim.filter
35997 system_filter_user = exim
35999 If a system filter generates any deliveries directly to files or pipes (via the
36000 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
36001 specified by setting &%system_filter_file_transport%& and
36002 &%system_filter_pipe_transport%&, respectively. Similarly,
36003 &%system_filter_reply_transport%& must be set to handle any messages generated
36004 by the &%reply%& command.
36007 .section "Testing a system filter" "SECID213"
36008 You can run simple tests of a system filter in the same way as for a user
36009 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
36010 are permitted only in system filters are recognized.
36012 If you want to test the combined effect of a system filter and a user filter,
36013 you can use both &%-bF%& and &%-bf%& on the same command line.
36017 .section "Contents of a system filter" "SECID214"
36018 The language used to specify system filters is the same as for users' filter
36019 files. It is described in the separate end-user document &'Exim's interface to
36020 mail filtering'&. However, there are some additional features that are
36021 available only in system filters; these are described in subsequent sections.
36022 If they are encountered in a user's filter file or when testing with &%-bf%&,
36025 .cindex "frozen messages" "manual thaw; testing in filter"
36026 There are two special conditions which, though available in users' filter
36027 files, are designed for use in system filters. The condition &%first_delivery%&
36028 is true only for the first attempt at delivering a message, and
36029 &%manually_thawed%& is true only if the message has been frozen, and
36030 subsequently thawed by an admin user. An explicit forced delivery counts as a
36031 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
36033 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
36034 specify an &"unseen"& (non-significant) delivery, and that delivery does not
36035 succeed, it will not be tried again.
36036 If you want Exim to retry an unseen delivery until it succeeds, you should
36037 arrange to set it up every time the filter runs.
36039 When a system filter finishes running, the values of the variables &$n0$& &--
36040 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
36041 users' filter files. Thus a system filter can, for example, set up &"scores"&
36042 to which users' filter files can refer.
36046 .section "Additional variable for system filters" "SECID215"
36047 .vindex "&$recipients$&"
36048 The expansion variable &$recipients$&, containing a list of all the recipients
36049 of the message (separated by commas and white space), is available in system
36050 filters. It is not available in users' filters for privacy reasons.
36054 .section "Defer, freeze, and fail commands for system filters" "SECID216"
36055 .cindex "freezing messages"
36056 .cindex "message" "freezing"
36057 .cindex "message" "forced failure"
36058 .cindex "&%fail%&" "in system filter"
36059 .cindex "&%freeze%& in system filter"
36060 .cindex "&%defer%& in system filter"
36061 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
36062 always available in system filters, but are not normally enabled in users'
36063 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
36064 for the &(redirect)& router.) These commands can optionally be followed by the
36065 word &%text%& and a string containing an error message, for example:
36067 fail text "this message looks like spam to me"
36069 The keyword &%text%& is optional if the next character is a double quote.
36071 The &%defer%& command defers delivery of the original recipients of the
36072 message. The &%fail%& command causes all the original recipients to be failed,
36073 and a bounce message to be created. The &%freeze%& command suspends all
36074 delivery attempts for the original recipients. In all cases, any new deliveries
36075 that are specified by the filter are attempted as normal after the filter has
36078 The &%freeze%& command is ignored if the message has been manually unfrozen and
36079 not manually frozen since. This means that automatic freezing by a system
36080 filter can be used as a way of checking out suspicious messages. If a message
36081 is found to be all right, manually unfreezing it allows it to be delivered.
36083 .cindex "log" "&%fail%& command log line"
36084 .cindex "&%fail%&" "log line; reducing"
36085 The text given with a fail command is used as part of the bounce message as
36086 well as being written to the log. If the message is quite long, this can fill
36087 up a lot of log space when such failures are common. To reduce the size of the
36088 log message, Exim interprets the text in a special way if it starts with the
36089 two characters &`<<`& and contains &`>>`& later. The text between these two
36090 strings is written to the log, and the rest of the text is used in the bounce
36091 message. For example:
36093 fail "<<filter test 1>>Your message is rejected \
36094 because it contains attachments that we are \
36095 not prepared to receive."
36098 .cindex "loop" "caused by &%fail%&"
36099 Take great care with the &%fail%& command when basing the decision to fail on
36100 the contents of the message, because the bounce message will of course include
36101 the contents of the original message and will therefore trigger the &%fail%&
36102 command again (causing a mail loop) unless steps are taken to prevent this.
36103 Testing the &%error_message%& condition is one way to prevent this. You could
36106 if $message_body contains "this is spam" and not error_message
36107 then fail text "spam is not wanted here" endif
36109 though of course that might let through unwanted bounce messages. The
36110 alternative is clever checking of the body and/or headers to detect bounces
36111 generated by the filter.
36113 The interpretation of a system filter file ceases after a
36115 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
36116 set up earlier in the filter file are honoured, so you can use a sequence such
36122 to send a specified message when the system filter is freezing (or deferring or
36123 failing) a message. The normal deliveries for the message do not, of course,
36128 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
36129 .cindex "header lines" "adding; in system filter"
36130 .cindex "header lines" "removing; in system filter"
36131 .cindex "filter" "header lines; adding/removing"
36132 Two filter commands that are available only in system filters are:
36134 headers add <string>
36135 headers remove <string>
36137 The argument for the &%headers add%& is a string that is expanded and then
36138 added to the end of the message's headers. It is the responsibility of the
36139 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
36140 space is ignored, and if the string is otherwise empty, or if the expansion is
36141 forced to fail, the command has no effect.
36143 You can use &"\n"& within the string, followed by white space, to specify
36144 continued header lines. More than one header may be added in one command by
36145 including &"\n"& within the string without any following white space. For
36148 headers add "X-header-1: ....\n \
36149 continuation of X-header-1 ...\n\
36152 Note that the header line continuation white space after the first newline must
36153 be placed before the backslash that continues the input string, because white
36154 space after input continuations is ignored.
36156 The argument for &%headers remove%& is a colon-separated list of header names.
36157 This command applies only to those headers that are stored with the message;
36158 those that are added at delivery time (such as &'Envelope-To:'& and
36159 &'Return-Path:'&) cannot be removed by this means. If there is more than one
36160 header with the same name, they are all removed.
36162 The &%headers%& command in a system filter makes an immediate change to the set
36163 of header lines that was received with the message (with possible additions
36164 from ACL processing). Subsequent commands in the system filter operate on the
36165 modified set, which also forms the basis for subsequent message delivery.
36166 Unless further modified during routing or transporting, this set of headers is
36167 used for all recipients of the message.
36169 During routing and transporting, the variables that refer to the contents of
36170 header lines refer only to those lines that are in this set. Thus, header lines
36171 that are added by a system filter are visible to users' filter files and to all
36172 routers and transports. This contrasts with the manipulation of header lines by
36173 routers and transports, which is not immediate, but which instead is saved up
36174 until the message is actually being written (see section
36175 &<<SECTheadersaddrem>>&).
36177 If the message is not delivered at the first attempt, header lines that were
36178 added by the system filter are stored with the message, and so are still
36179 present at the next delivery attempt. Header lines that were removed are still
36180 present, but marked &"deleted"& so that they are not transported with the
36181 message. For this reason, it is usual to make the &%headers%& command
36182 conditional on &%first_delivery%& so that the set of header lines is not
36183 modified more than once.
36185 Because header modification in a system filter acts immediately, you have to
36186 use an indirect approach if you want to modify the contents of a header line.
36189 headers add "Old-Subject: $h_subject:"
36190 headers remove "Subject"
36191 headers add "Subject: new subject (was: $h_old-subject:)"
36192 headers remove "Old-Subject"
36197 .section "Setting an errors address in a system filter" "SECID217"
36198 .cindex "envelope from"
36199 .cindex "envelope sender"
36200 In a system filter, if a &%deliver%& command is followed by
36202 errors_to <some address>
36204 in order to change the envelope sender (and hence the error reporting) for that
36205 delivery, any address may be specified. (In a user filter, only the current
36206 user's address can be set.) For example, if some mail is being monitored, you
36209 unseen deliver monitor@spying.example errors_to root@local.example
36211 to take a copy which would not be sent back to the normal error reporting
36212 address if its delivery failed.
36216 .section "Per-address filtering" "SECTperaddfil"
36217 .vindex "&$domain_data$&"
36218 .vindex "&$local_part_data$&"
36219 In contrast to the system filter, which is run just once per message for each
36220 delivery attempt, it is also possible to set up a system-wide filtering
36221 operation that runs once for each recipient address. In this case, variables
36222 such as &$local_part_data$& and &$domain_data$& can be used,
36223 and indeed, the choice of filter file could be made dependent on them.
36224 This is an example of a router which implements such a filter:
36229 domains = +local_domains
36230 file = /central/filters/$local_part_data
36235 The filter is run in a separate process under its own uid. Therefore, either
36236 &%check_local_user%& must be set (as above), in which case the filter is run as
36237 the local user, or the &%user%& option must be used to specify which user to
36238 use. If both are set, &%user%& overrides.
36240 Care should be taken to ensure that none of the commands in the filter file
36241 specify a significant delivery if the message is to go on to be delivered to
36242 its intended recipient. The router will not then claim to have dealt with the
36243 address, so it will be passed on to subsequent routers to be delivered in the
36245 .ecindex IIDsysfil1
36246 .ecindex IIDsysfil2
36247 .ecindex IIDsysfil3
36254 . ////////////////////////////////////////////////////////////////////////////
36255 . ////////////////////////////////////////////////////////////////////////////
36257 .chapter "Message processing" "CHAPmsgproc"
36258 .scindex IIDmesproc "message" "general processing"
36259 Exim performs various transformations on the sender and recipient addresses of
36260 all messages that it handles, and also on the messages' header lines. Some of
36261 these are optional and configurable, while others always take place. All of
36262 this processing, except rewriting as a result of routing, and the addition or
36263 removal of header lines while delivering, happens when a message is received,
36264 before it is placed on Exim's queue.
36266 Some of the automatic processing takes place by default only for
36267 &"locally-originated"& messages. This adjective is used to describe messages
36268 that are not received over TCP/IP, but instead are passed to an Exim process on
36269 its standard input. This includes the interactive &"local SMTP"& case that is
36270 set up by the &%-bs%& command line option.
36272 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
36273 or ::1) are not considered to be locally-originated. Exim does not treat the
36274 loopback interface specially in any way.
36276 If you want the loopback interface to be treated specially, you must ensure
36277 that there are appropriate entries in your ACLs.
36282 .section "Submission mode for non-local messages" "SECTsubmodnon"
36283 .cindex "message" "submission"
36284 .cindex "submission mode"
36285 Processing that happens automatically for locally-originated messages (unless
36286 &%suppress_local_fixups%& is set) can also be requested for messages that are
36287 received over TCP/IP. The term &"submission mode"& is used to describe this
36288 state. Submission mode is set by the modifier
36290 control = submission
36292 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
36293 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
36294 a local submission, and is normally used when the source of the message is
36295 known to be an MUA running on a client host (as opposed to an MTA). For
36296 example, to set submission mode for messages originating on the IPv4 loopback
36297 interface, you could include the following in the MAIL ACL:
36299 warn hosts = 127.0.0.1
36300 control = submission
36302 .cindex "&%sender_retain%& submission option"
36303 There are some options that can be used when setting submission mode. A slash
36304 is used to separate options. For example:
36306 control = submission/sender_retain
36308 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
36309 true and &%local_from_check%& false for the current incoming message. The first
36310 of these allows an existing &'Sender:'& header in the message to remain, and
36311 the second suppresses the check to ensure that &'From:'& matches the
36312 authenticated sender. With this setting, Exim still fixes up messages by adding
36313 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
36314 attempt to check sender authenticity in header lines.
36316 When &%sender_retain%& is not set, a submission mode setting may specify a
36317 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
36320 control = submission/domain=some.domain
36322 The domain may be empty. How this value is used is described in sections
36323 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
36324 that allows you to specify the user's full name for inclusion in a created
36325 &'Sender:'& or &'From:'& header line. For example:
36327 accept authenticated = *
36328 control = submission/domain=wonderland.example/\
36329 name=${lookup {$authenticated_id} \
36330 lsearch {/etc/exim/namelist}}
36332 Because the name may contain any characters, including slashes, the &%name%&
36333 option must be given last. The remainder of the string is used as the name. For
36334 the example above, if &_/etc/exim/namelist_& contains:
36336 bigegg: Humpty Dumpty
36338 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
36341 Sender: Humpty Dumpty <bigegg@wonderland.example>
36343 .cindex "return path" "in submission mode"
36344 By default, submission mode forces the return path to the same address as is
36345 used to create the &'Sender:'& header. However, if &%sender_retain%& is
36346 specified, the return path is also left unchanged.
36348 &*Note*&: The changes caused by submission mode take effect after the predata
36349 ACL. This means that any sender checks performed before the fix-ups use the
36350 untrusted sender address specified by the user, not the trusted sender address
36351 specified by submission mode. Although this might be slightly unexpected, it
36352 does mean that you can configure ACL checks to spot that a user is trying to
36353 spoof another's address.
36355 .section "Line endings" "SECTlineendings"
36356 .cindex "line endings"
36357 .cindex "carriage return"
36359 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
36360 linefeed) is the line ending for messages transmitted over the Internet using
36361 SMTP over TCP/IP. However, within individual operating systems, different
36362 conventions are used. For example, Unix-like systems use just LF, but others
36363 use CRLF or just CR.
36365 Exim was designed for Unix-like systems, and internally, it stores messages
36366 using the system's convention of a single LF as a line terminator. When
36367 receiving a message, all line endings are translated to this standard format.
36368 Originally, it was thought that programs that passed messages directly to an
36369 MTA within an operating system would use that system's convention. Experience
36370 has shown that this is not the case; for example, there are Unix applications
36371 that use CRLF in this circumstance. For this reason, and for compatibility with
36372 other MTAs, the way Exim handles line endings for all messages is now as
36376 LF not preceded by CR is treated as a line ending.
36378 CR is treated as a line ending; if it is immediately followed by LF, the LF
36381 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
36382 nor a local message in the state where a line containing only a dot is a
36385 If a bare CR is encountered within a header line, an extra space is added after
36386 the line terminator so as not to end the header line. The reasoning behind this
36387 is that bare CRs in header lines are most likely either to be mistakes, or
36388 people trying to play silly games.
36390 If the first header line received in a message ends with CRLF, a subsequent
36391 bare LF in a header line is treated in the same way as a bare CR in a header
36399 .section "Unqualified addresses" "SECID218"
36400 .cindex "unqualified addresses"
36401 .cindex "address" "qualification"
36402 By default, Exim expects every envelope address it receives from an external
36403 host to be fully qualified. Unqualified addresses cause negative responses to
36404 SMTP commands. However, because SMTP is used as a means of transporting
36405 messages from MUAs running on personal workstations, there is sometimes a
36406 requirement to accept unqualified addresses from specific hosts or IP networks.
36408 Exim has two options that separately control which hosts may send unqualified
36409 sender or recipient addresses in SMTP commands, namely
36410 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
36411 cases, if an unqualified address is accepted, it is qualified by adding the
36412 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
36414 .oindex "&%qualify_domain%&"
36415 .oindex "&%qualify_recipient%&"
36416 Unqualified addresses in header lines are automatically qualified for messages
36417 that are locally originated, unless the &%-bnq%& option is given on the command
36418 line. For messages received over SMTP, unqualified addresses in header lines
36419 are qualified only if unqualified addresses are permitted in SMTP commands. In
36420 other words, such qualification is also controlled by
36421 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
36426 .section "The UUCP From line" "SECID219"
36427 .cindex "&""From""& line"
36428 .cindex "UUCP" "&""From""& line"
36429 .cindex "sender" "address"
36430 .oindex "&%uucp_from_pattern%&"
36431 .oindex "&%uucp_from_sender%&"
36432 .cindex "envelope from"
36433 .cindex "envelope sender"
36434 .cindex "Sendmail compatibility" "&""From""& line"
36435 Messages that have come from UUCP (and some other applications) often begin
36436 with a line containing the envelope sender and a timestamp, following the word
36437 &"From"&. Examples of two common formats are:
36439 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
36440 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
36442 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
36443 Exim recognizes such lines at the start of messages that are submitted to it
36444 via the command line (that is, on the standard input). It does not recognize
36445 such lines in incoming SMTP messages, unless the sending host matches
36446 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
36447 and &%ignore_fromline_local%& is set. The recognition is controlled by a
36448 regular expression that is defined by the &%uucp_from_pattern%& option, whose
36449 default value matches the two common cases shown above and puts the address
36450 that follows &"From"& into &$1$&.
36452 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
36453 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
36454 a trusted user, the message's sender address is constructed by expanding the
36455 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
36456 then parsed as an RFC 2822 address. If there is no domain, the local part is
36457 qualified with &%qualify_domain%& unless it is the empty string. However, if
36458 the command line &%-f%& option is used, it overrides the &"From"& line.
36460 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
36461 sender address is not changed. This is also the case for incoming SMTP messages
36462 that are permitted to contain &"From"& lines.
36464 Only one &"From"& line is recognized. If there is more than one, the second is
36465 treated as a data line that starts the body of the message, as it is not valid
36466 as a header line. This also happens if a &"From"& line is present in an
36467 incoming SMTP message from a source that is not permitted to send them.
36471 .section "Header lines"
36472 .subsection "Resent- header lines" SECID220
36474 RFC 2822 makes provision for sets of header lines starting with the string
36475 &`Resent-`& to be added to a message when it is resent by the original
36476 recipient to somebody else. These headers are &'Resent-Date:'&,
36477 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
36478 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
36481 &'Resent fields are strictly informational. They MUST NOT be used in the normal
36482 processing of replies or other such automatic actions on messages.'&
36485 This leaves things a bit vague as far as other processing actions such as
36486 address rewriting are concerned. Exim treats &%Resent-%& header lines as
36490 A &'Resent-From:'& line that just contains the login id of the submitting user
36491 is automatically rewritten in the same way as &'From:'& (see below).
36493 If there's a rewriting rule for a particular header line, it is also applied to
36494 &%Resent-%& header lines of the same type. For example, a rule that rewrites
36495 &'From:'& also rewrites &'Resent-From:'&.
36497 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
36500 For a locally-submitted message,
36501 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
36502 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
36503 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
36504 included in log lines in this case.
36506 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
36507 &%Resent-%& header lines are present.
36513 .subsection Auto-Submitted: SECID221
36514 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
36515 includes the header line:
36517 Auto-Submitted: auto-replied
36520 .subsection Bcc: SECID222
36521 .cindex "&'Bcc:'& header line"
36522 If Exim is called with the &%-t%& option, to take recipient addresses from a
36523 message's header, it removes any &'Bcc:'& header line that may exist (after
36524 extracting its addresses). If &%-t%& is not present on the command line, any
36525 existing &'Bcc:'& is not removed.
36528 .subsection Date: SECID223
36530 If a locally-generated or submission-mode message has no &'Date:'& header line,
36531 Exim adds one, using the current date and time, unless the
36532 &%suppress_local_fixups%& control has been specified.
36534 .subsection Delivery-date: SECID224
36535 .cindex "&'Delivery-date:'& header line"
36536 .oindex "&%delivery_date_remove%&"
36537 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
36538 set. Exim can be configured to add them to the final delivery of messages. (See
36539 the generic &%delivery_date_add%& transport option.) They should not be present
36540 in messages in transit. If the &%delivery_date_remove%& configuration option is
36541 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
36545 .subsection Envelope-to: SECID225
36546 .chindex Envelope-to:
36547 .oindex "&%envelope_to_remove%&"
36548 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
36549 Exim can be configured to add them to the final delivery of messages. (See the
36550 generic &%envelope_to_add%& transport option.) They should not be present in
36551 messages in transit. If the &%envelope_to_remove%& configuration option is set
36552 (the default), Exim removes &'Envelope-to:'& header lines from incoming
36556 .subsection From: SECTthefrohea
36558 .cindex "Sendmail compatibility" "&""From""& line"
36559 .cindex "message" "submission"
36560 .cindex "submission mode"
36561 If a submission-mode message does not contain a &'From:'& header line, Exim
36562 adds one if either of the following conditions is true:
36565 The envelope sender address is not empty (that is, this is not a bounce
36566 message). The added header line copies the envelope sender address.
36568 .vindex "&$authenticated_id$&"
36569 The SMTP session is authenticated and &$authenticated_id$& is not empty.
36571 .vindex "&$qualify_domain$&"
36572 If no domain is specified by the submission control, the local part is
36573 &$authenticated_id$& and the domain is &$qualify_domain$&.
36575 If a non-empty domain is specified by the submission control, the local
36576 part is &$authenticated_id$&, and the domain is the specified domain.
36578 If an empty domain is specified by the submission control,
36579 &$authenticated_id$& is assumed to be the complete address.
36583 A non-empty envelope sender takes precedence.
36585 If a locally-generated incoming message does not contain a &'From:'& header
36586 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
36587 containing the sender's address. The calling user's login name and full name
36588 are used to construct the address, as described in section &<<SECTconstr>>&.
36589 They are obtained from the password data by calling &[getpwuid()]& (but see the
36590 &%unknown_login%& configuration option). The address is qualified with
36591 &%qualify_domain%&.
36593 For compatibility with Sendmail, if an incoming, non-SMTP message has a
36594 &'From:'& header line containing just the unqualified login name of the calling
36595 user, this is replaced by an address containing the user's login name and full
36596 name as described in section &<<SECTconstr>>&.
36599 .subsection Message-ID: SECID226
36600 .chindex Message-ID:
36601 .cindex "message" "submission"
36602 .oindex "&%message_id_header_text%&"
36603 If a locally-generated or submission-mode incoming message does not contain a
36604 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
36605 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
36606 to the message. If there are any &'Resent-:'& headers in the message, it
36607 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
36608 message id, preceded by the letter E to ensure it starts with a letter, and
36609 followed by @ and the primary host name. Additional information can be included
36610 in this header line by setting the &%message_id_header_text%& and/or
36611 &%message_id_header_domain%& options.
36614 .subsection Received: SECID227
36616 A &'Received:'& header line is added at the start of every message. The
36617 contents are defined by the &%received_header_text%& configuration option, and
36618 Exim automatically adds a semicolon and a timestamp to the configured string.
36620 The &'Received:'& header is generated as soon as the message's header lines
36621 have been received. At this stage, the timestamp in the &'Received:'& header
36622 line is the time that the message started to be received. This is the value
36623 that is seen by the DATA ACL and by the &[local_scan()]& function.
36625 Once a message is accepted, the timestamp in the &'Received:'& header line is
36626 changed to the time of acceptance, which is (apart from a small delay while the
36627 -H spool file is written) the earliest time at which delivery could start.
36630 .subsection References: SECID228
36631 .chindex References:
36632 Messages created by the &(autoreply)& transport include a &'References:'&
36633 header line. This is constructed according to the rules that are described in
36634 section 3.64 of RFC 2822 (which states that replies should contain such a
36635 header line), and section 3.14 of RFC 3834 (which states that automatic
36636 responses are not different in this respect). However, because some mail
36637 processing software does not cope well with very long header lines, no more
36638 than 12 message IDs are copied from the &'References:'& header line in the
36639 incoming message. If there are more than 12, the first one and then the final
36640 11 are copied, before adding the message ID of the incoming message.
36644 .subsection Return-path: SECID229
36645 .chindex Return-path:
36646 .oindex "&%return_path_remove%&"
36647 &'Return-path:'& header lines are defined as something an MTA may insert when
36648 it does the final delivery of messages. (See the generic &%return_path_add%&
36649 transport option.) Therefore, they should not be present in messages in
36650 transit. If the &%return_path_remove%& configuration option is set (the
36651 default), Exim removes &'Return-path:'& header lines from incoming messages.
36655 .subsection Sender: SECTthesenhea
36656 .cindex "&'Sender:'& header line"
36657 .cindex "message" "submission"
36659 For a locally-originated message from an untrusted user, Exim may remove an
36660 existing &'Sender:'& header line, and it may add a new one. You can modify
36661 these actions by setting the &%local_sender_retain%& option true, the
36662 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
36665 When a local message is received from an untrusted user and
36666 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
36667 control has not been set, a check is made to see if the address given in the
36668 &'From:'& header line is the correct (local) sender of the message. The address
36669 that is expected has the login name as the local part and the value of
36670 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
36671 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
36672 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
36673 line is added to the message.
36675 If you set &%local_from_check%& false, this checking does not occur. However,
36676 the removal of an existing &'Sender:'& line still happens, unless you also set
36677 &%local_sender_retain%& to be true. It is not possible to set both of these
36678 options true at the same time.
36680 .cindex "submission mode"
36681 By default, no processing of &'Sender:'& header lines is done for messages
36682 received over TCP/IP or for messages submitted by trusted users. However, when
36683 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
36684 not specified on the submission control, the following processing takes place:
36686 .vindex "&$authenticated_id$&"
36687 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
36688 authenticated, and &$authenticated_id$& is not empty, a sender address is
36689 created as follows:
36692 .vindex "&$qualify_domain$&"
36693 If no domain is specified by the submission control, the local part is
36694 &$authenticated_id$& and the domain is &$qualify_domain$&.
36696 If a non-empty domain is specified by the submission control, the local part
36697 is &$authenticated_id$&, and the domain is the specified domain.
36699 If an empty domain is specified by the submission control,
36700 &$authenticated_id$& is assumed to be the complete address.
36703 This address is compared with the address in the &'From:'& header line. If they
36704 are different, a &'Sender:'& header line containing the created address is
36705 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
36706 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
36708 .cindex "return path" "created from &'Sender:'&"
36709 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
36710 the message (the envelope sender address) is changed to be the same address,
36711 except in the case of submission mode when &%sender_retain%& is specified.
36715 .section "Adding and removing header lines in routers and transports" &&&
36716 "SECTheadersaddrem"
36717 .cindex "header lines" "adding; in router or transport"
36718 .cindex "header lines" "removing; in router or transport"
36719 When a message is delivered, the addition and removal of header lines can be
36720 specified in a system filter, or on any of the routers and transports that
36721 process the message. Section &<<SECTaddremheasys>>& contains details about
36722 modifying headers in a system filter. Header lines can also be added in an ACL
36723 as a message is received (see section &<<SECTaddheadacl>>&).
36725 In contrast to what happens in a system filter, header modifications that are
36726 specified on routers and transports apply only to the particular recipient
36727 addresses that are being processed by those routers and transports. These
36728 changes do not actually take place until a copy of the message is being
36729 transported. Therefore, they do not affect the basic set of header lines, and
36730 they do not affect the values of the variables that refer to header lines.
36732 &*Note*&: In particular, this means that any expansions in the configuration of
36733 the transport cannot refer to the modified header lines, because such
36734 expansions all occur before the message is actually transported.
36736 For both routers and transports, the argument of a &%headers_add%&
36737 option must be in the form of one or more RFC 2822 header lines, separated by
36738 newlines (coded as &"\n"&). For example:
36740 headers_add = X-added-header: added by $primary_hostname\n\
36741 X-added-second: another added header line
36743 Exim does not check the syntax of these added header lines.
36745 Multiple &%headers_add%& options for a single router or transport can be
36746 specified; the values will append to a single list of header lines.
36747 Each header-line is separately expanded.
36749 The argument of a &%headers_remove%& option must consist of a colon-separated
36750 list of header names. This is confusing, because header names themselves are
36751 often terminated by colons. In this case, the colons are the list separators,
36752 not part of the names. For example:
36754 headers_remove = return-receipt-to:acknowledge-to
36757 Multiple &%headers_remove%& options for a single router or transport can be
36758 specified; the arguments will append to a single header-names list.
36759 Each item is separately expanded.
36760 Note that colons in complex expansions which are used to
36761 form all or part of a &%headers_remove%& list
36762 will act as list separators.
36764 When &%headers_add%& or &%headers_remove%& is specified on a router,
36765 items are expanded at routing time,
36766 and then associated with all addresses that are
36767 accepted by that router, and also with any new addresses that it generates. If
36768 an address passes through several routers as a result of aliasing or
36769 forwarding, the changes are cumulative.
36771 .oindex "&%unseen%&"
36772 However, this does not apply to multiple routers that result from the use of
36773 the &%unseen%& option. Any header modifications that were specified by the
36774 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
36776 Addresses that end up with different &%headers_add%& or &%headers_remove%&
36777 settings cannot be delivered together in a batch, so a transport is always
36778 dealing with a set of addresses that have the same header-processing
36781 The transport starts by writing the original set of header lines that arrived
36782 with the message, possibly modified by the system filter. As it writes out
36783 these lines, it consults the list of header names that were attached to the
36784 recipient address(es) by &%headers_remove%& options in routers, and it also
36785 consults the transport's own &%headers_remove%& option. Header lines whose
36786 names are on either of these lists are not written out. If there are multiple
36787 instances of any listed header, they are all skipped.
36789 After the remaining original header lines have been written, new header
36790 lines that were specified by routers' &%headers_add%& options are written, in
36791 the order in which they were attached to the address. These are followed by any
36792 header lines specified by the transport's &%headers_add%& option.
36794 This way of handling header line modifications in routers and transports has
36795 the following consequences:
36798 The original set of header lines, possibly modified by the system filter,
36799 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
36800 to it, at all times.
36802 Header lines that are added by a router's
36803 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
36804 expansion syntax in subsequent routers or the transport.
36806 Conversely, header lines that are specified for removal by &%headers_remove%&
36807 in a router remain visible to subsequent routers and the transport.
36809 Headers added to an address by &%headers_add%& in a router cannot be removed by
36810 a later router or by a transport.
36812 An added header can refer to the contents of an original header that is to be
36813 removed, even it has the same name as the added header. For example:
36815 headers_remove = subject
36816 headers_add = Subject: new subject (was: $h_subject:)
36820 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
36821 for a &(redirect)& router that has the &%one_time%& option set.
36827 .section "Constructed addresses" "SECTconstr"
36828 .cindex "address" "constructed"
36829 .cindex "constructed address"
36830 When Exim constructs a sender address for a locally-generated message, it uses
36833 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
36837 Zaphod Beeblebrox <zaphod@end.univ.example>
36839 The user name is obtained from the &%-F%& command line option if set, or
36840 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
36841 &"gecos"& field from the password entry. If the &"gecos"& field contains an
36842 ampersand character, this is replaced by the login name with the first letter
36843 upper cased, as is conventional in a number of operating systems. See the
36844 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
36845 The &%unknown_username%& option can be used to specify user names in cases when
36846 there is no password file entry.
36849 In all cases, the user name is made to conform to RFC 2822 by quoting all or
36850 parts of it if necessary. In addition, if it contains any non-printing
36851 characters, it is encoded as described in RFC 2047, which defines a way of
36852 including non-ASCII characters in header lines. The value of the
36853 &%headers_charset%& option specifies the name of the encoding that is used (the
36854 characters are assumed to be in this encoding). The setting of
36855 &%print_topbitchars%& controls whether characters with the top bit set (that
36856 is, with codes greater than 127) count as printing characters or not.
36860 .section "Case of local parts" "SECID230"
36861 .cindex "case of local parts"
36862 .cindex "local part" "case of"
36863 RFC 2822 states that the case of letters in the local parts of addresses cannot
36864 be assumed to be non-significant. Exim preserves the case of local parts of
36865 addresses, but by default it uses a lower-cased form when it is routing,
36866 because on most Unix systems, usernames are in lower case and case-insensitive
36867 routing is required. However, any particular router can be made to use the
36868 original case for local parts by setting the &%caseful_local_part%& generic
36871 .cindex "mixed-case login names"
36872 If you must have mixed-case user names on your system, the best way to proceed,
36873 assuming you want case-independent handling of incoming email, is to set up
36874 your first router to convert incoming local parts in your domains to the
36875 correct case by means of a file lookup. For example:
36879 domains = +local_domains
36880 data = ${lookup{$local_part}cdb\
36881 {/etc/usercased.cdb}{$value}fail}\
36884 For this router, the local part is forced to lower case by the default action
36885 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
36886 up a new local part in the correct case. If you then set &%caseful_local_part%&
36887 on any subsequent routers which process your domains, they will operate on
36888 local parts with the correct case in a case-sensitive manner.
36892 .section "Dots in local parts" "SECID231"
36893 .cindex "dot" "in local part"
36894 .cindex "local part" "dots in"
36895 RFC 2822 forbids empty components in local parts. That is, an unquoted local
36896 part may not begin or end with a dot, nor have two consecutive dots in the
36897 middle. However, it seems that many MTAs do not enforce this, so Exim permits
36898 empty components for compatibility.
36902 .section "Rewriting addresses" "SECID232"
36903 .cindex "rewriting" "addresses"
36904 Rewriting of sender and recipient addresses, and addresses in headers, can
36905 happen automatically, or as the result of configuration options, as described
36906 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
36907 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
36909 Automatic rewriting includes qualification, as mentioned above. The other case
36910 in which it can happen is when an incomplete non-local domain is given. The
36911 routing process may cause this to be expanded into the full domain name. For
36912 example, a header such as
36916 might get rewritten as
36918 To: hare@teaparty.wonderland.fict.example
36920 Rewriting as a result of routing is the one kind of message processing that
36921 does not happen at input time, as it cannot be done until the address has
36924 Strictly, one should not do &'any'& deliveries of a message until all its
36925 addresses have been routed, in case any of the headers get changed as a
36926 result of routing. However, doing this in practice would hold up many
36927 deliveries for unreasonable amounts of time, just because one address could not
36928 immediately be routed. Exim therefore does not delay other deliveries when
36929 routing of one or more addresses is deferred.
36930 .ecindex IIDmesproc
36934 . ////////////////////////////////////////////////////////////////////////////
36935 . ////////////////////////////////////////////////////////////////////////////
36937 .chapter "SMTP processing" "CHAPSMTP"
36938 .scindex IIDsmtpproc1 "SMTP" "processing details"
36939 .scindex IIDsmtpproc2 "LMTP" "processing details"
36940 Exim supports a number of different ways of using the SMTP protocol, and its
36941 LMTP variant, which is an interactive protocol for transferring messages into a
36942 closed mail store application. This chapter contains details of how SMTP is
36943 processed. For incoming mail, the following are available:
36946 SMTP over TCP/IP (Exim daemon or &'inetd'&);
36948 SMTP over the standard input and output (the &%-bs%& option);
36950 Batched SMTP on the standard input (the &%-bS%& option).
36953 For mail delivery, the following are available:
36956 SMTP over TCP/IP (the &(smtp)& transport);
36958 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
36961 LMTP over a pipe to a process running in the local host (the &(lmtp)&
36964 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
36965 the &%use_bsmtp%& option set).
36968 &'Batched SMTP'& is the name for a process in which batches of messages are
36969 stored in or read from files (or pipes), in a format in which SMTP commands are
36970 used to contain the envelope information.
36974 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
36975 .cindex "SMTP" "outgoing over TCP/IP"
36976 .cindex "outgoing SMTP over TCP/IP"
36977 .cindex "LMTP" "over TCP/IP"
36978 .cindex "outgoing LMTP over TCP/IP"
36981 .cindex "SIZE" "option on MAIL command"
36982 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
36983 The &%protocol%& option selects which protocol is to be used, but the actual
36984 processing is the same in both cases.
36986 .cindex "ESMTP extensions" SIZE
36987 If, in response to its EHLO command, Exim is told that the SIZE
36988 extension is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
36989 command. The value of <&'n'&> is the message size plus the value of the
36990 &%size_addition%& option (default 1024) to allow for additions to the message
36991 such as per-transport header lines, or changes made in a
36992 .cindex "transport" "filter"
36993 .cindex "filter" "transport filter"
36994 transport filter. If &%size_addition%& is set negative, the use of SIZE is
36997 If the remote server advertises support for PIPELINING, Exim uses the
36998 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
36999 required for the transaction.
37001 If the remote server advertises support for the STARTTLS command, and Exim
37002 was built to support TLS encryption, it tries to start a TLS session unless the
37003 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
37004 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
37005 is called for verification.
37007 If the remote server advertises support for the AUTH command, Exim scans
37008 the authenticators configuration for any suitable client settings, as described
37009 in chapter &<<CHAPSMTPAUTH>>&.
37011 .cindex "carriage return"
37013 Responses from the remote host are supposed to be terminated by CR followed by
37014 LF. However, there are known to be hosts that do not send CR characters, so in
37015 order to be able to interwork with such hosts, Exim treats LF on its own as a
37018 If a message contains a number of different addresses, all those with the same
37019 characteristics (for example, the same envelope sender) that resolve to the
37020 same set of hosts, in the same order, are sent in a single SMTP transaction,
37021 even if they are for different domains, unless there are more than the setting
37022 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
37023 they are split into groups containing no more than &%max_rcpt%&s addresses
37024 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
37025 in parallel sessions. The order of hosts with identical MX values is not
37026 significant when checking whether addresses can be batched in this way.
37028 When the &(smtp)& transport suffers a temporary failure that is not
37029 message-related, Exim updates its transport-specific database, which contains
37030 records indexed by host name that remember which messages are waiting for each
37031 particular host. It also updates the retry database with new retry times.
37033 .cindex "hints database" "retry keys"
37034 Exim's retry hints are based on host name plus IP address, so if one address of
37035 a multi-homed host is broken, it will soon be skipped most of the time.
37036 See the next section for more detail about error handling.
37038 .cindex "SMTP" "passed connection"
37039 .cindex "SMTP" "batching over TCP/IP"
37040 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
37041 looks in the hints database for the transport to see if there are any queued
37042 messages waiting for the host to which it is connected. If it finds one, it
37043 creates a new Exim process using the &%-MC%& option (which can only be used by
37044 a process running as root or the Exim user) and passes the TCP/IP socket to it
37045 so that it can deliver another message using the same socket. The new process
37046 does only those deliveries that are routed to the connected host, and may in
37047 turn pass the socket on to a third process, and so on.
37049 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
37050 limit the number of messages sent down a single TCP/IP connection.
37052 .cindex "asterisk" "after IP address"
37053 The second and subsequent messages delivered down an existing connection are
37054 identified in the main log by the addition of an asterisk after the closing
37055 square bracket of the IP address.
37060 .subsection "Errors in outgoing SMTP" SECToutSMTPerr
37061 .cindex "error" "in outgoing SMTP"
37062 .cindex "SMTP" "errors in outgoing"
37063 .cindex "host" "error"
37064 Three different kinds of error are recognized for outgoing SMTP: host errors,
37065 message errors, and recipient errors.
37068 .vitem "&*Host errors*&"
37069 A host error is not associated with a particular message or with a
37070 particular recipient of a message. The host errors are:
37073 Connection refused or timed out,
37075 Any error response code on connection,
37077 Any error response code to EHLO or HELO,
37079 Loss of connection at any time, except after &"."&,
37081 I/O errors at any time,
37083 Timeouts during the session, other than in response to MAIL, RCPT or
37084 the &"."& at the end of the data.
37087 For a host error, a permanent error response on connection, or in response to
37088 EHLO, causes all addresses routed to the host to be failed. Any other host
37089 error causes all addresses to be deferred, and retry data to be created for the
37090 host. It is not tried again, for any message, until its retry time arrives. If
37091 the current set of addresses are not all delivered in this run (to some
37092 alternative host), the message is added to the list of those waiting for this
37093 host, so if it is still undelivered when a subsequent successful delivery is
37094 made to the host, it will be sent down the same SMTP connection.
37096 .vitem "&*Message errors*&"
37097 .cindex "message" "error"
37098 A message error is associated with a particular message when sent to a
37099 particular host, but not with a particular recipient of the message. The
37100 message errors are:
37103 Any error response code to MAIL, DATA, or the &"."& that terminates
37106 Timeout after MAIL,
37108 Timeout or loss of connection after the &"."& that terminates the data. A
37109 timeout after the DATA command itself is treated as a host error, as is loss of
37110 connection at any other time.
37113 For a message error, a permanent error response (5&'xx'&) causes all addresses
37114 to be failed, and a delivery error report to be returned to the sender. A
37115 temporary error response (4&'xx'&), or one of the timeouts, causes all
37116 addresses to be deferred. Retry data is not created for the host, but instead,
37117 a retry record for the combination of host plus message id is created. The
37118 message is not added to the list of those waiting for this host. This ensures
37119 that the failing message will not be sent to this host again until the retry
37120 time arrives. However, other messages that are routed to the host are not
37121 affected, so if it is some property of the message that is causing the error,
37122 it will not stop the delivery of other mail.
37124 If the remote host specified support for the SIZE parameter in its response
37125 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
37126 over-large message will cause a message error because the error arrives as a
37129 .vitem "&*Recipient errors*&"
37130 .cindex "recipient" "error"
37131 A recipient error is associated with a particular recipient of a message. The
37132 recipient errors are:
37135 Any error response to RCPT,
37137 Timeout after RCPT.
37140 For a recipient error, a permanent error response (5&'xx'&) causes the
37141 recipient address to be failed, and a bounce message to be returned to the
37142 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
37143 address to be deferred, and routing retry data to be created for it. This is
37144 used to delay processing of the address in subsequent queue runs, until its
37145 routing retry time arrives. This applies to all messages, but because it
37146 operates only in queue runs, one attempt will be made to deliver a new message
37147 to the failing address before the delay starts to operate. This ensures that,
37148 if the failure is really related to the message rather than the recipient
37149 (&"message too big for this recipient"& is a possible example), other messages
37150 have a chance of getting delivered. If a delivery to the address does succeed,
37151 the retry information gets cleared, so all stuck messages get tried again, and
37152 the retry clock is reset.
37154 The message is not added to the list of those waiting for this host. Use of the
37155 host for other messages is unaffected, and except in the case of a timeout,
37156 other recipients are processed independently, and may be successfully delivered
37157 in the current SMTP session. After a timeout it is of course impossible to
37158 proceed with the session, so all addresses get deferred. However, those other
37159 than the one that failed do not suffer any subsequent retry delays. Therefore,
37160 if one recipient is causing trouble, the others have a chance of getting
37161 through when a subsequent delivery attempt occurs before the failing
37162 recipient's retry time.
37165 In all cases, if there are other hosts (or IP addresses) available for the
37166 current set of addresses (for example, from multiple MX records), they are
37167 tried in this run for any undelivered addresses, subject of course to their
37168 own retry data. In other words, recipient error retry data does not take effect
37169 until the next delivery attempt.
37171 Some hosts have been observed to give temporary error responses to every
37172 MAIL command at certain times (&"insufficient space"& has been seen). It
37173 would be nice if such circumstances could be recognized, and defer data for the
37174 host itself created, but this is not possible within the current Exim design.
37175 What actually happens is that retry data for every (host, message) combination
37178 The reason that timeouts after MAIL and RCPT are treated specially is that
37179 these can sometimes arise as a result of the remote host's verification
37180 procedures. Exim makes this assumption, and treats them as if a temporary error
37181 response had been received. A timeout after &"."& is treated specially because
37182 it is known that some broken implementations fail to recognize the end of the
37183 message if the last character of the last line is a binary zero. Thus, it is
37184 helpful to treat this case as a message error.
37186 Timeouts at other times are treated as host errors, assuming a problem with the
37187 host, or the connection to it. If a timeout after MAIL, RCPT,
37188 or &"."& is really a connection problem, the assumption is that at the next try
37189 the timeout is likely to occur at some other point in the dialogue, causing it
37190 then to be treated as a host error.
37192 There is experimental evidence that some MTAs drop the connection after the
37193 terminating &"."& if they do not like the contents of the message for some
37194 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
37195 should be given. That is why Exim treats this case as a message rather than a
37196 host error, in order not to delay other messages to the same host.
37201 .section "Incoming SMTP messages over TCP/IP" "SECID233"
37202 .cindex "SMTP" "incoming over TCP/IP"
37203 .cindex "incoming SMTP over TCP/IP"
37206 Incoming SMTP messages can be accepted in one of two ways: by running a
37207 listening daemon, or by using &'inetd'&. In the latter case, the entry in
37208 &_/etc/inetd.conf_& should be like this:
37210 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
37212 Exim distinguishes between this case and the case of a locally running user
37213 agent using the &%-bs%& option by checking whether or not the standard input is
37214 a socket. When it is, either the port must be privileged (less than 1024), or
37215 the caller must be root or the Exim user. If any other user passes a socket
37216 with an unprivileged port number, Exim prints a message on the standard error
37217 stream and exits with an error code.
37219 By default, Exim does not make a log entry when a remote host connects or
37220 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
37221 unexpected. It can be made to write such log entries by setting the
37222 &%smtp_connection%& log selector.
37224 .cindex "carriage return"
37226 Commands from the remote host are supposed to be terminated by CR followed by
37227 LF. However, there are known to be hosts that do not send CR characters. In
37228 order to be able to interwork with such hosts, Exim treats LF on its own as a
37230 Furthermore, because common code is used for receiving messages from all
37231 sources, a CR on its own is also interpreted as a line terminator. However, the
37232 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
37234 .cindex "EHLO" "invalid data"
37235 .cindex "HELO" "invalid data"
37236 One area that sometimes gives rise to problems concerns the EHLO or
37237 HELO commands. Some clients send syntactically invalid versions of these
37238 commands, which Exim rejects by default. (This is nothing to do with verifying
37239 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
37240 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
37241 match the broken hosts that send invalid commands.
37243 .cindex "SIZE option on MAIL command"
37244 .cindex "MAIL" "SIZE option"
37245 The amount of disk space available is checked whenever SIZE is received on
37246 a MAIL command, independently of whether &%message_size_limit%& or
37247 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
37248 false. A temporary error is given if there is not enough space. If
37249 &%check_spool_space%& is set, the check is for that amount of space plus the
37250 value given with SIZE, that is, it checks that the addition of the incoming
37251 message will not reduce the space below the threshold.
37253 When a message is successfully received, Exim includes the local message id in
37254 its response to the final &"."& that terminates the data. If the remote host
37255 logs this text it can help with tracing what has happened to a message.
37257 The Exim daemon can limit the number of simultaneous incoming connections it is
37258 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
37259 number of simultaneous incoming connections from a single remote host (see the
37260 &%smtp_accept_max_per_host%& option). Additional connection attempts are
37261 rejected using the SMTP temporary error code 421.
37263 The Exim daemon does not rely on the SIGCHLD signal to detect when a
37264 subprocess has finished, as this can get lost at busy times. Instead, it looks
37265 for completed subprocesses every time it wakes up. Provided there are other
37266 things happening (new incoming calls, starts of queue runs), completed
37267 processes will be noticed and tidied away. On very quiet systems you may
37268 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
37269 it will be noticed when the daemon next wakes up.
37271 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
37272 and can also be set up to reject SMTP calls from non-reserved hosts at times of
37273 high system load &-- for details see the &%smtp_accept_reserve%&,
37274 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
37275 applies in both the daemon and &'inetd'& cases.
37277 Exim normally starts a delivery process for each message received, though this
37278 can be varied by means of the &%-odq%& command line option and the
37279 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
37280 number of simultaneously running delivery processes started in this way from
37281 SMTP input can be limited by the &%smtp_accept_queue%& and
37282 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
37283 subsequently received messages are just put on the input queue without starting
37284 a delivery process.
37286 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
37287 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
37288 started up from the &'inetd'& daemon, because in that case each connection is
37289 handled by an entirely independent Exim process. Control by load average is,
37290 however, available with &'inetd'&.
37292 Exim can be configured to verify addresses in incoming SMTP commands as they
37293 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
37294 to rewrite addresses at this time &-- before any syntax checking is done. See
37295 section &<<SSECTrewriteS>>&.
37297 Exim can also be configured to limit the rate at which a client host submits
37298 MAIL and RCPT commands in a single SMTP session. See the
37299 &%smtp_ratelimit_hosts%& option.
37303 .subsection "Unrecognized SMTP commands" SECID234
37304 .cindex "SMTP" "unrecognized commands"
37305 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
37306 commands during a single SMTP connection, it drops the connection after sending
37307 the error response to the last command. The default value for
37308 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
37309 abuse that subvert web servers into making connections to SMTP ports; in these
37310 circumstances, a number of non-SMTP lines are sent first.
37313 .subsection "Syntax and protocol errors in SMTP commands" SECID235
37314 .cindex "SMTP" "syntax errors"
37315 .cindex "SMTP" "protocol errors"
37316 A syntax error is detected if an SMTP command is recognized, but there is
37317 something syntactically wrong with its data, for example, a malformed email
37318 address in a RCPT command. Protocol errors include invalid command
37319 sequencing such as RCPT before MAIL. If Exim receives more than
37320 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
37321 drops the connection after sending the error response to the last command. The
37322 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
37323 broken clients that loop sending bad commands (yes, it has been seen).
37327 .subsection "Use of non-mail SMTP commands" SECID236
37328 .cindex "SMTP" "non-mail commands"
37329 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
37330 DATA. Exim counts such commands, and drops the connection if there are too
37331 many of them in a single SMTP session. This action catches some
37332 denial-of-service attempts and things like repeated failing AUTHs, or a mad
37333 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
37334 defines what &"too many"& means. Its default value is 10.
37336 When a new message is expected, one occurrence of RSET is not counted. This
37337 allows a client to send one RSET between messages (this is not necessary,
37338 but some clients do it). Exim also allows one uncounted occurrence of HELO
37339 or EHLO, and one occurrence of STARTTLS between messages. After
37340 starting up a TLS session, another EHLO is expected, and so it too is not
37343 The first occurrence of AUTH in a connection, or immediately following
37344 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
37345 RCPT, DATA, and QUIT are counted.
37347 You can control which hosts are subject to the limit set by
37348 &%smtp_accept_max_nonmail%& by setting
37349 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
37350 the limit apply to all hosts. This option means that you can exclude any
37351 specific badly-behaved hosts that you have to live with.
37356 .subsection "The VRFY and EXPN commands" SECID237
37357 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
37358 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
37359 appropriate) in order to decide whether the command should be accepted or not.
37361 .cindex "VRFY" "processing"
37362 When no ACL is defined for VRFY, or if it rejects without
37363 setting an explicit response code, the command is accepted
37364 (with a 252 SMTP response code)
37365 in order to support awkward clients that do a VRFY before every RCPT.
37366 When VRFY is accepted, it runs exactly the same code as when Exim is
37367 called with the &%-bv%& option, and returns 250/451/550
37368 SMTP response codes.
37370 .cindex "EXPN" "processing"
37371 If no ACL for EXPN is defined, the command is rejected.
37372 When EXPN is accepted, a single-level expansion of the address is done.
37373 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
37374 than a verification (the &%-bv%& option). If an unqualified local part is given
37375 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
37376 of VRFY and EXPN commands are logged on the main and reject logs, and
37377 VRFY verification failures are logged in the main log for consistency with
37382 .subsection "The ETRN command" SECTETRN
37383 .cindex "ETRN" "processing"
37384 .cindex "ESMTP extensions" ETRN
37385 RFC 1985 describes an ESMTP command called ETRN that is designed to
37386 overcome the security problems of the TURN command (which has fallen into
37387 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
37388 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
37389 should be accepted or not. If no ACL is defined, the command is rejected.
37391 The ETRN command is concerned with &"releasing"& messages that are awaiting
37392 delivery to certain hosts. As Exim does not organize its message queue by host,
37393 the only form of ETRN that is supported by default is the one where the
37394 text starts with the &"#"& prefix, in which case the remainder of the text is
37395 specific to the SMTP server. A valid ETRN command causes a run of Exim with
37396 the &%-R%& option to happen, with the remainder of the ETRN text as its
37397 argument. For example,
37405 which causes a delivery attempt on all messages with undelivered addresses
37406 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
37407 default), Exim prevents the simultaneous execution of more than one queue run
37408 for the same argument string as a result of an ETRN command. This stops
37409 a misbehaving client from starting more than one queue runner at once.
37411 .cindex "hints database" "ETRN serialization"
37412 Exim implements the serialization by means of a hints database in which a
37413 record is written whenever a process is started by ETRN, and deleted when
37414 the process completes. However, Exim does not keep the SMTP session waiting for
37415 the ETRN process to complete. Once ETRN is accepted, the client is sent
37416 a &"success"& return code. Obviously there is scope for hints records to get
37417 left lying around if there is a system or program crash. To guard against this,
37418 Exim ignores any records that are more than six hours old.
37420 .oindex "&%smtp_etrn_command%&"
37421 For more control over what ETRN does, the &%smtp_etrn_command%& option can
37422 used. This specifies a command that is run whenever ETRN is received,
37423 whatever the form of its argument. For
37426 smtp_etrn_command = /etc/etrn_command $domain \
37427 $sender_host_address
37429 .vindex "&$domain$&"
37430 The string is split up into arguments which are independently expanded. The
37431 expansion variable &$domain$& is set to the argument of the ETRN command,
37432 and no syntax checking is done on the contents of this argument. Exim does not
37433 wait for the command to complete, so its status code is not checked. Exim runs
37434 under its own uid and gid when receiving incoming SMTP, so it is not possible
37435 for it to change them before running the command.
37439 .section "Incoming local SMTP" "SECID238"
37440 .cindex "SMTP" "local incoming"
37441 Some user agents use SMTP to pass messages to their local MTA using the
37442 standard input and output, as opposed to passing the envelope on the command
37443 line and writing the message to the standard input. This is supported by the
37444 &%-bs%& option. This form of SMTP is handled in the same way as incoming
37445 messages over TCP/IP (including the use of ACLs), except that the envelope
37446 sender given in a MAIL command is ignored unless the caller is trusted. In
37447 an ACL you can detect this form of SMTP input by testing for an empty host
37448 identification. It is common to have this as the first line in the ACL that
37449 runs for RCPT commands:
37453 This accepts SMTP messages from local processes without doing any other tests.
37457 .section "Outgoing batched SMTP" "SECTbatchSMTP"
37458 .cindex "SMTP" "batched outgoing"
37459 .cindex "batched SMTP output"
37460 Both the &(appendfile)& and &(pipe)& transports can be used for handling
37461 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
37462 be output in BSMTP format. No SMTP responses are possible for this form of
37463 delivery. All it is doing is using SMTP commands as a way of transmitting the
37464 envelope along with the message.
37466 The message is written to the file or pipe preceded by the SMTP commands
37467 MAIL and RCPT, and followed by a line containing a single dot. Lines in
37468 the message that start with a dot have an extra dot added. The SMTP command
37469 HELO is not normally used. If it is required, the &%message_prefix%& option
37470 can be used to specify it.
37472 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
37473 one recipient address at a time by default. However, you can arrange for them
37474 to handle several addresses at once by setting the &%batch_max%& option. When
37475 this is done for BSMTP, messages may contain multiple RCPT commands. See
37476 chapter &<<CHAPbatching>>& for more details.
37479 When one or more addresses are routed to a BSMTP transport by a router that
37480 sets up a host list, the name of the first host on the list is available to the
37481 transport in the variable &$host$&. Here is an example of such a transport and
37486 driver = manualroute
37487 transport = smtp_appendfile
37488 route_list = domain.example batch.host.example
37492 driver = appendfile
37493 directory = /var/bsmtp/$host
37498 This causes messages addressed to &'domain.example'& to be written in BSMTP
37499 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
37500 message (unless there are more than 1000 recipients).
37504 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
37505 .cindex "SMTP" "batched incoming"
37506 .cindex "batched SMTP input"
37507 The &%-bS%& command line option causes Exim to accept one or more messages by
37508 reading SMTP on the standard input, but to generate no responses. If the caller
37509 is trusted, the senders in the MAIL commands are believed; otherwise the
37510 sender is always the caller of Exim. Unqualified senders and receivers are not
37511 rejected (there seems little point) but instead just get qualified. HELO
37512 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
37513 as NOOP; QUIT quits.
37515 Minimal policy checking is done for BSMTP input. Only the non-SMTP
37516 ACL is run in the same way as for non-SMTP local input.
37518 If an error is detected while reading a message, including a missing &"."& at
37519 the end, Exim gives up immediately. It writes details of the error to the
37520 standard output in a stylized way that the calling program should be able to
37521 make some use of automatically, for example:
37523 554 Unexpected end of file
37524 Transaction started in line 10
37525 Error detected in line 14
37527 It writes a more verbose version, for human consumption, to the standard error
37530 An error was detected while processing a file of BSMTP input.
37531 The error message was:
37533 501 '>' missing at end of address
37535 The SMTP transaction started in line 10.
37536 The error was detected in line 12.
37537 The SMTP command at fault was:
37539 rcpt to:<malformed@in.com.plete
37541 1 previous message was successfully processed.
37542 The rest of the batch was abandoned.
37544 The return code from Exim is zero only if there were no errors. It is 1 if some
37545 messages were accepted before an error was detected, and 2 if no messages were
37547 .ecindex IIDsmtpproc1
37548 .ecindex IIDsmtpproc2
37552 . ////////////////////////////////////////////////////////////////////////////
37553 . ////////////////////////////////////////////////////////////////////////////
37555 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
37556 "Customizing messages"
37557 When a message fails to be delivered, or remains in the queue for more than a
37558 configured amount of time, Exim sends a message to the original sender, or
37559 to an alternative configured address. The text of these messages is built into
37560 the code of Exim, but it is possible to change it, either by adding a single
37561 string, or by replacing each of the paragraphs by text supplied in a file.
37563 The &'From:'& and &'To:'& header lines are automatically generated; you can
37564 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
37565 option. Exim also adds the line
37567 Auto-Submitted: auto-generated
37569 to all warning and bounce messages,
37572 .section "Customizing bounce messages" "SECID239"
37573 .cindex "customizing" "bounce message"
37574 .cindex "bounce message" "customizing"
37575 If &%bounce_message_text%& is set, its contents are included in the default
37576 message immediately after &"This message was created automatically by mail
37577 delivery software."& The string is not expanded. It is not used if
37578 &%bounce_message_file%& is set.
37580 When &%bounce_message_file%& is set, it must point to a template file for
37581 constructing error messages. The file consists of a series of text items,
37582 separated by lines consisting of exactly four asterisks. If the file cannot be
37583 opened, default text is used and a message is written to the main and panic
37584 logs. If any text item in the file is empty, default text is used for that
37587 .vindex "&$bounce_recipient$&"
37588 .vindex "&$bounce_return_size_limit$&"
37589 Each item of text that is read from the file is expanded, and there are two
37590 expansion variables which can be of use here: &$bounce_recipient$& is set to
37591 the recipient of an error message while it is being created, and
37592 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
37593 option, rounded to a whole number.
37595 The items must appear in the file in the following order:
37598 The first item is included in the headers, and should include at least a
37599 &'Subject:'& header. Exim does not check the syntax of these headers.
37601 The second item forms the start of the error message. After it, Exim lists the
37602 failing addresses with their error messages.
37604 The third item is used to introduce any text from pipe transports that is to be
37605 returned to the sender. It is omitted if there is no such text.
37607 The fourth, fifth and sixth items will be ignored and may be empty.
37608 The fields exist for back-compatibility
37611 The default state (&%bounce_message_file%& unset) is equivalent to the
37612 following file, in which the sixth item is empty. The &'Subject:'& and some
37613 other lines have been split in order to fit them on the page:
37615 Subject: Mail delivery failed
37616 ${if eq{$sender_address}{$bounce_recipient}
37617 {: returning message to sender}}
37619 This message was created automatically by mail delivery software.
37621 A message ${if eq{$sender_address}{$bounce_recipient}
37622 {that you sent }{sent by
37626 }}could not be delivered to all of its recipients.
37627 This is a permanent error. The following address(es) failed:
37629 The following text was generated during the delivery attempt(s):
37631 ------ This is a copy of the message, including all the headers.
37634 ------ The body of the message is $message_size characters long;
37636 ------ $bounce_return_size_limit or so are included here.
37639 .section "Customizing warning messages" "SECTcustwarn"
37640 .cindex "customizing" "warning message"
37641 .cindex "warning of delay" "customizing the message"
37642 The option &%warn_message_file%& can be pointed at a template file for use when
37643 warnings about message delays are created. In this case there are only three
37647 The first item is included in the headers, and should include at least a
37648 &'Subject:'& header. Exim does not check the syntax of these headers.
37650 The second item forms the start of the warning message. After it, Exim lists
37651 the delayed addresses.
37653 The third item then ends the message.
37656 The default state is equivalent to the following file, except that some lines
37657 have been split here, in order to fit them on the page:
37659 Subject: Warning: message $message_exim_id delayed
37660 $warn_message_delay
37662 This message was created automatically by mail delivery software.
37664 A message ${if eq{$sender_address}{$warn_message_recipients}
37665 {that you sent }{sent by
37669 }}has not been delivered to all of its recipients after
37670 more than $warn_message_delay in the queue on $primary_hostname.
37672 The message identifier is: $message_exim_id
37673 The subject of the message is: $h_subject
37674 The date of the message is: $h_date
37676 The following address(es) have not yet been delivered:
37678 No action is required on your part. Delivery attempts will
37679 continue for some time, and this warning may be repeated at
37680 intervals if the message remains undelivered. Eventually the
37681 mail delivery software will give up, and when that happens,
37682 the message will be returned to you.
37684 .vindex "&$warn_message_delay$&"
37685 .vindex "&$warn_message_recipients$&"
37686 However, in the default state the subject and date lines are omitted if no
37687 appropriate headers exist. During the expansion of this file,
37688 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
37689 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
37690 of recipients for the warning message. There may be more than one if there are
37691 multiple addresses with different &%errors_to%& settings on the routers that
37697 . ////////////////////////////////////////////////////////////////////////////
37698 . ////////////////////////////////////////////////////////////////////////////
37700 .chapter "Some common configuration settings" "CHAPcomconreq"
37701 This chapter discusses some configuration settings that seem to be fairly
37702 common. More examples and discussion can be found in the Exim book.
37706 .section "Sending mail to a smart host" "SECID240"
37707 .cindex "smart host" "example router"
37708 If you want to send all mail for non-local domains to a &"smart host"&, you
37709 should replace the default &(dnslookup)& router with a router which does the
37710 routing explicitly:
37712 send_to_smart_host:
37713 driver = manualroute
37714 route_list = !+local_domains smart.host.name
37715 transport = remote_smtp
37717 You can use the smart host's IP address instead of the name if you wish.
37718 If you are using Exim only to submit messages to a smart host, and not for
37719 receiving incoming messages, you can arrange for it to do the submission
37720 synchronously by setting the &%mua_wrapper%& option (see chapter
37721 &<<CHAPnonqueueing>>&).
37726 .section "Using Exim to handle mailing lists" "SECTmailinglists"
37727 .cindex "mailing lists"
37728 Exim can be used to run simple mailing lists, but for large and/or complicated
37729 requirements, the use of additional specialized mailing list software such as
37730 Majordomo or Mailman is recommended.
37732 The &(redirect)& router can be used to handle mailing lists where each list
37733 is maintained in a separate file, which can therefore be managed by an
37734 independent manager. The &%domains%& router option can be used to run these
37735 lists in a separate domain from normal mail. For example:
37739 domains = lists.example
37740 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37743 errors_to = ${quote_local_part:$local_part-request}@lists.example
37746 This router is skipped for domains other than &'lists.example'&. For addresses
37747 in that domain, it looks for a file that matches the local part. If there is no
37748 such file, the router declines, but because &%no_more%& is set, no subsequent
37749 routers are tried, and so the whole delivery fails.
37751 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
37752 expanded into a filename or a pipe delivery, which is usually inappropriate in
37755 .oindex "&%errors_to%&"
37756 The &%errors_to%& option specifies that any delivery errors caused by addresses
37757 taken from a mailing list are to be sent to the given address rather than the
37758 original sender of the message. However, before acting on this, Exim verifies
37759 the error address, and ignores it if verification fails.
37761 For example, using the configuration above, mail sent to
37762 &'dicts@lists.example'& is passed on to those addresses contained in
37763 &_/usr/lists/dicts_&, with error reports directed to
37764 &'dicts-request@lists.example'&, provided that this address can be verified.
37765 There could be a file called &_/usr/lists/dicts-request_& containing
37766 the address(es) of this particular list's manager(s), but other approaches,
37767 such as setting up an earlier router (possibly using the &%local_part_prefix%&
37768 or &%local_part_suffix%& options) to handle addresses of the form
37769 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
37773 .section "Syntax errors in mailing lists" "SECID241"
37774 .cindex "mailing lists" "syntax errors in"
37775 If an entry in redirection data contains a syntax error, Exim normally defers
37776 delivery of the original address. That means that a syntax error in a mailing
37777 list holds up all deliveries to the list. This may not be appropriate when a
37778 list is being maintained automatically from data supplied by users, and the
37779 addresses are not rigorously checked.
37781 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
37782 entries that fail to parse, noting the incident in the log. If in addition
37783 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
37784 whenever a broken address is skipped. It is usually appropriate to set
37785 &%syntax_errors_to%& to the same address as &%errors_to%&.
37789 .section "Re-expansion of mailing lists" "SECID242"
37790 .cindex "mailing lists" "re-expansion of"
37791 Exim remembers every individual address to which a message has been delivered,
37792 in order to avoid duplication, but it normally stores only the original
37793 recipient addresses with a message. If all the deliveries to a mailing list
37794 cannot be done at the first attempt, the mailing list is re-expanded when the
37795 delivery is next tried. This means that alterations to the list are taken into
37796 account at each delivery attempt, so addresses that have been added to
37797 the list since the message arrived will therefore receive a copy of the
37798 message, even though it pre-dates their subscription.
37800 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
37801 on the &(redirect)& router. If this is done, any addresses generated by the
37802 router that fail to deliver at the first attempt are added to the message as
37803 &"top level"& addresses, and the parent address that generated them is marked
37804 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
37805 subsequent delivery attempts. The disadvantage of this is that if any of the
37806 failing addresses are incorrect, correcting them in the file has no effect on
37807 pre-existing messages.
37809 The original top-level address is remembered with each of the generated
37810 addresses, and is output in any log messages. However, any intermediate parent
37811 addresses are not recorded. This makes a difference to the log only if the
37812 &%all_parents%& selector is set, but for mailing lists there is normally only
37813 one level of expansion anyway.
37817 .section "Closed mailing lists" "SECID243"
37818 .cindex "mailing lists" "closed"
37819 The examples so far have assumed open mailing lists, to which anybody may
37820 send mail. It is also possible to set up closed lists, where mail is accepted
37821 from specified senders only. This is done by making use of the generic
37822 &%senders%& option to restrict the router that handles the list.
37824 The following example uses the same file as a list of recipients and as a list
37825 of permitted senders. It requires three routers:
37829 domains = lists.example
37830 local_part_suffix = -request
37831 local_parts = ${lookup {$local_part} dsearch,filter=file {/usr/lists}}
37832 file = /usr/lists/${local_part_data}-request
37837 domains = lists.example
37838 local_parts = ${lookup {$local_part} dsearch,filter=file,ret=full {/usr/lists}}
37839 senders = ${if exists {$local_part_data} {lsearch;$local_part_data}{*}}
37840 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37843 errors_to = ${quote_local_part:$local_part-request}@lists.example
37848 domains = lists.example
37850 data = :fail: $local_part@lists.example is a closed mailing list
37852 All three routers have the same &%domains%& setting, so for any other domains,
37853 they are all skipped. The first router runs only if the local part ends in
37854 &%-request%&. It handles messages to the list manager(s) by means of an open
37857 The second router runs only if the &%senders%& precondition is satisfied. It
37858 checks for the existence of a list that corresponds to the local part, and then
37859 checks that the sender is on the list by means of a linear search. It is
37860 necessary to check for the existence of the file before trying to search it,
37861 because otherwise Exim thinks there is a configuration error. If the file does
37862 not exist, the expansion of &%senders%& is *, which matches all senders. This
37863 means that the router runs, but because there is no list, declines, and
37864 &%no_more%& ensures that no further routers are run. The address fails with an
37865 &"unrouteable address"& error.
37867 The third router runs only if the second router is skipped, which happens when
37868 a mailing list exists, but the sender is not on it. This router forcibly fails
37869 the address, giving a suitable error message.
37874 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
37876 .cindex "Variable Envelope Return Paths"
37877 .cindex "envelope from"
37878 .cindex "envelope sender"
37879 Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
37880 are a way of helping mailing list administrators discover which subscription
37881 address is the cause of a particular delivery failure. The idea is to encode
37882 the original recipient address in the outgoing envelope sender address, so that
37883 if the message is forwarded by another host and then subsequently bounces, the
37884 original recipient can be extracted from the recipient address of the bounce.
37886 .oindex &%errors_to%&
37887 .oindex &%return_path%&
37888 Envelope sender addresses can be modified by Exim using two different
37889 facilities: the &%errors_to%& option on a router (as shown in previous mailing
37890 list examples), or the &%return_path%& option on a transport. The second of
37891 these is effective only if the message is successfully delivered to another
37892 host; it is not used for errors detected on the local host (see the description
37893 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
37894 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
37900 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37901 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37903 This has the effect of rewriting the return path (envelope sender) on outgoing
37904 SMTP messages, if the local part of the original return path ends in
37905 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
37906 local part and domain of the recipient into the return path. Suppose, for
37907 example, that a message whose return path has been set to
37908 &'somelist-request@your.dom.example'& is sent to
37909 &'subscriber@other.dom.example'&. In the transport, the return path is
37912 somelist-request+subscriber=other.dom.example@your.dom.example
37914 .vindex "&$local_part$&"
37915 For this to work, you must tell Exim to send multiple copies of messages that
37916 have more than one recipient, so that each copy has just one recipient. This is
37917 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
37918 might be sent to several different recipients in the same domain, in which case
37919 &$local_part$& is not available in the transport, because it is not unique.
37921 Unless your host is doing nothing but mailing list deliveries, you should
37922 probably use a separate transport for the VERP deliveries, so as not to use
37923 extra resources in making one-per-recipient copies for other deliveries. This
37924 can easily be done by expanding the &%transport%& option in the router:
37928 domains = ! +local_domains
37930 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37931 {verp_smtp}{remote_smtp}}
37934 If you want to change the return path using &%errors_to%& in a router instead
37935 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
37936 routers that handle mailing list addresses. This will ensure that all delivery
37937 errors, including those detected on the local host, are sent to the VERP
37940 On a host that does no local deliveries and has no manual routing, only the
37941 &(dnslookup)& router needs to be changed. A special transport is not needed for
37942 SMTP deliveries. Every mailing list recipient has its own return path value,
37943 and so Exim must hand them to the transport one at a time. Here is an example
37944 of a &(dnslookup)& router that implements VERP:
37948 domains = ! +local_domains
37949 transport = remote_smtp
37951 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
37952 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37955 Before you start sending out messages with VERPed return paths, you must also
37956 configure Exim to accept the bounce messages that come back to those paths.
37957 Typically this is done by setting a &%local_part_suffix%& option for a
37958 router, and using this to route the messages to wherever you want to handle
37961 The overhead incurred in using VERP depends very much on the size of the
37962 message, the number of recipient addresses that resolve to the same remote
37963 host, and the speed of the connection over which the message is being sent. If
37964 a lot of addresses resolve to the same host and the connection is slow, sending
37965 a separate copy of the message for each address may take substantially longer
37966 than sending a single copy with many recipients (for which VERP cannot be
37974 .section "Virtual domains" "SECTvirtualdomains"
37975 .cindex "virtual domains"
37976 .cindex "domain" "virtual"
37977 The phrase &'virtual domain'& is unfortunately used with two rather different
37981 A domain for which there are no real mailboxes; all valid local parts are
37982 aliases for other email addresses. Common examples are organizational
37983 top-level domains and &"vanity"& domains.
37985 One of a number of independent domains that are all handled by the same host,
37986 with mailboxes on that host, but where the mailbox owners do not necessarily
37987 have login accounts on that host.
37990 The first usage is probably more common, and does seem more &"virtual"& than
37991 the second. This kind of domain can be handled in Exim with a straightforward
37992 aliasing router. One approach is to create a separate alias file for each
37993 virtual domain. Exim can test for the existence of the alias file to determine
37994 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
37995 to a router of this form:
37999 domains = dsearch;/etc/mail/virtual
38000 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
38003 The &%domains%& option specifies that the router is to be skipped, unless there
38004 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
38005 domain that is being processed.
38006 The &(dsearch)& lookup used results in an untainted version of &$domain$&
38007 being placed into the &$domain_data$& variable.
38009 When the router runs, it looks up the local
38010 part in the file to find a new address (or list of addresses). The &%no_more%&
38011 setting ensures that if the lookup fails (leading to &%data%& being an empty
38012 string), Exim gives up on the address without trying any subsequent routers.
38014 This one router can handle all the virtual domains because the alias filenames
38015 follow a fixed pattern. Permissions can be arranged so that appropriate people
38016 can edit the different alias files. A successful aliasing operation results in
38017 a new envelope recipient address, which is then routed from scratch.
38019 The other kind of &"virtual"& domain can also be handled in a straightforward
38020 way. One approach is to create a file for each domain containing a list of
38021 valid local parts, and use it in a router like this:
38025 domains = dsearch;/etc/mail/domains
38026 local_parts = lsearch;/etc/mail/domains/$domain
38027 transport = my_mailboxes
38029 The address is accepted if there is a file for the domain, and the local part
38030 can be found in the file. The &%domains%& option is used to check for the
38031 file's existence because &%domains%& is tested before the &%local_parts%&
38032 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
38033 because that option is tested after &%local_parts%&. The transport is as
38037 driver = appendfile
38038 file = /var/mail/$domain_data/$local_part_data
38041 This uses a directory of mailboxes for each domain. The &%user%& setting is
38042 required, to specify which uid is to be used for writing to the mailboxes.
38044 The configuration shown here is just one example of how you might support this
38045 requirement. There are many other ways this kind of configuration can be set
38046 up, for example, by using a database instead of separate files to hold all the
38047 information about the domains.
38051 .section "Multiple user mailboxes" "SECTmulbox"
38052 .cindex "multiple mailboxes"
38053 .cindex "mailbox" "multiple"
38054 .cindex "local part" "prefix"
38055 .cindex "local part" "suffix"
38056 Heavy email users often want to operate with multiple mailboxes, into which
38057 incoming mail is automatically sorted. A popular way of handling this is to
38058 allow users to use multiple sender addresses, so that replies can easily be
38059 identified. Users are permitted to add prefixes or suffixes to their local
38060 parts for this purpose. The wildcard facility of the generic router options
38061 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
38062 example, consider this router:
38067 file = $home/.forward
38068 local_part_suffix = -*
38069 local_part_suffix_optional
38072 .vindex "&$local_part_suffix$&"
38073 It runs a user's &_.forward_& file for all local parts of the form
38074 &'username-*'&. Within the filter file the user can distinguish different
38075 cases by testing the variable &$local_part_suffix$&. For example:
38077 if $local_part_suffix contains -special then
38078 save /home/$local_part_data/Mail/special
38081 If the filter file does not exist, or does not deal with such addresses, they
38082 fall through to subsequent routers, and, assuming no subsequent use of the
38083 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
38084 control over which suffixes are valid.
38086 Alternatively, a suffix can be used to trigger the use of a different
38087 &_.forward_& file &-- which is the way a similar facility is implemented in
38093 local_part_suffix = -*
38094 local_part_suffix_optional
38095 file = ${lookup {.forward$local_part_suffix} dsearch,ret=full {$home} {$value}fail}
38098 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
38099 example, &_.forward-special_& is used. Once again, if the appropriate file
38100 does not exist, or does not deal with the address, it is passed on to
38101 subsequent routers, which could, if required, look for an unqualified
38102 &_.forward_& file to use as a default.
38106 .section "Simplified vacation processing" "SECID244"
38107 .cindex "vacation processing"
38108 The traditional way of running the &'vacation'& program is for a user to set up
38109 a pipe command in a &_.forward_& file
38110 (see section &<<SECTspecitredli>>& for syntax details).
38111 This is prone to error by inexperienced users. There are two features of Exim
38112 that can be used to make this process simpler for users:
38115 A local part prefix such as &"vacation-"& can be specified on a router which
38116 can cause the message to be delivered directly to the &'vacation'& program, or
38117 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
38118 &_.forward_& file are then much simpler. For example:
38120 spqr, vacation-spqr
38123 The &%require_files%& generic router option can be used to trigger a
38124 vacation delivery by checking for the existence of a certain file in the
38125 user's home directory. The &%unseen%& generic option should also be used, to
38126 ensure that the original delivery also proceeds. In this case, all the user has
38127 to do is to create a file called, say, &_.vacation_&, containing a vacation
38131 Another advantage of both these methods is that they both work even when the
38132 use of arbitrary pipes by users is locked out.
38136 .section "Taking copies of mail" "SECID245"
38137 .cindex "message" "copying every"
38138 Some installations have policies that require archive copies of all messages to
38139 be made. A single copy of each message can easily be taken by an appropriate
38140 command in a system filter, which could, for example, use a different file for
38141 each day's messages.
38143 There is also a shadow transport mechanism that can be used to take copies of
38144 messages that are successfully delivered by local transports, one copy per
38145 delivery. This could be used, &'inter alia'&, to implement automatic
38146 notification of delivery by sites that insist on doing such things.
38150 .section "Intermittently connected hosts" "SECID246"
38151 .cindex "intermittently connected hosts"
38152 It has become quite common (because it is cheaper) for hosts to connect to the
38153 Internet periodically rather than remain connected all the time. The normal
38154 arrangement is that mail for such hosts accumulates on a system that is
38155 permanently connected.
38157 Exim was designed for use on permanently connected hosts, and so it is not
38158 particularly well-suited to use in an intermittently connected environment.
38159 Nevertheless there are some features that can be used.
38162 .section "Exim on the upstream server host" "SECID247"
38163 It is tempting to arrange for incoming mail for the intermittently connected
38164 host to remain in Exim's queue until the client connects. However, this
38165 approach does not scale very well. Two different kinds of waiting message are
38166 being mixed up in the same queue &-- those that cannot be delivered because of
38167 some temporary problem, and those that are waiting for their destination host
38168 to connect. This makes it hard to manage the queue, as well as wasting
38169 resources, because each queue runner scans the entire queue.
38171 A better approach is to separate off those messages that are waiting for an
38172 intermittently connected host. This can be done by delivering these messages
38173 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
38174 format, from where they are transmitted by other software when their
38175 destination connects. This makes it easy to collect all the mail for one host
38176 in a single directory, and to apply local timeout rules on a per-message basis
38179 On a very small scale, leaving the mail on Exim's queue can be made to work. If
38180 you are doing this, you should configure Exim with a long retry period for the
38181 intermittent host. For example:
38183 cheshire.wonderland.fict.example * F,5d,24h
38185 This stops a lot of failed delivery attempts from occurring, but Exim remembers
38186 which messages it has queued up for that host. Once the intermittent host comes
38187 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
38188 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
38189 causes all the queued up messages to be delivered, often down a single SMTP
38190 connection. While the host remains connected, any new messages get delivered
38193 If the connecting hosts do not have fixed IP addresses, that is, if a host is
38194 issued with a different IP address each time it connects, Exim's retry
38195 mechanisms on the holding host get confused, because the IP address is normally
38196 used as part of the key string for holding retry information. This can be
38197 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
38198 Since this has disadvantages for permanently connected hosts, it is best to
38199 arrange a separate transport for the intermittently connected ones.
38203 .section "Exim on the intermittently connected client host" "SECID248"
38204 The value of &%smtp_accept_queue_per_connection%& should probably be
38205 increased, or even set to zero (that is, disabled) on the intermittently
38206 connected host, so that all incoming messages down a single connection get
38207 delivered immediately.
38209 .cindex "SMTP" "passed connection"
38210 .cindex "SMTP" "multiple deliveries"
38211 .cindex "multiple SMTP deliveries"
38212 .cindex "first pass routing"
38213 Mail waiting to be sent from an intermittently connected host will probably
38214 not have been routed, because without a connection DNS lookups are not
38215 possible. This means that if a normal queue run is done at connection time,
38216 each message is likely to be sent in a separate SMTP session. This can be
38217 avoided by starting the queue run with a command line option beginning with
38218 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
38219 first pass, routing is done but no deliveries take place. The second pass is a
38220 normal queue run; since all the messages have been previously routed, those
38221 destined for the same host are likely to get sent as multiple deliveries in a
38222 single SMTP connection.
38226 . ////////////////////////////////////////////////////////////////////////////
38227 . ////////////////////////////////////////////////////////////////////////////
38229 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
38230 "Exim as a non-queueing client"
38231 .cindex "client, non-queueing"
38232 .cindex "smart host" "suppressing queueing"
38233 On a personal computer, it is a common requirement for all
38234 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
38235 configured to operate that way, for all the popular operating systems.
38236 However, there are some MUAs for Unix-like systems that cannot be so
38237 configured: they submit messages using the command line interface of
38238 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
38241 If the personal computer runs continuously, there is no problem, because it can
38242 run a conventional MTA that handles delivery to the smart host, and deal with
38243 any delays via its queueing mechanism. However, if the computer does not run
38244 continuously or runs different operating systems at different times, queueing
38245 email is not desirable.
38247 There is therefore a requirement for something that can provide the
38248 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
38249 any queueing or retrying facilities. Furthermore, the delivery to the smart
38250 host should be synchronous, so that if it fails, the sending MUA is immediately
38251 informed. In other words, we want something that extends an MUA that submits
38252 to a local MTA via the command line so that it behaves like one that submits
38253 to a remote smart host using TCP/SMTP.
38255 There are a number of applications (for example, there is one called &'ssmtp'&)
38256 that do this job. However, people have found them to be lacking in various
38257 ways. For instance, you might want to allow aliasing and forwarding to be done
38258 before sending a message to the smart host.
38260 Exim already had the necessary infrastructure for doing this job. Just a few
38261 tweaks were needed to make it behave as required, though it is somewhat of an
38262 overkill to use a fully-featured MTA for this purpose.
38264 .oindex "&%mua_wrapper%&"
38265 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
38266 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
38267 assumes that it is being used to &"wrap"& a command-line MUA in the manner
38268 just described. As well as setting &%mua_wrapper%&, you also need to provide a
38269 compatible router and transport configuration. Typically there will be just one
38270 router and one transport, sending everything to a smart host.
38272 When run in MUA wrapping mode, the behaviour of Exim changes in the
38276 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
38277 In other words, the only way to submit messages is via the command line.
38279 Each message is synchronously delivered as soon as it is received (&%-odi%& is
38280 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
38281 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
38282 does not finish until the delivery attempt is complete. If the delivery is
38283 successful, a zero return code is given.
38285 Address redirection is permitted, but the final routing for all addresses must
38286 be to the same remote transport, and to the same list of hosts. Furthermore,
38287 the return address (envelope sender) must be the same for all recipients, as
38288 must any added or deleted header lines. In other words, it must be possible to
38289 deliver the message in a single SMTP transaction, however many recipients there
38292 If these conditions are not met, or if routing any address results in a
38293 failure or defer status, or if Exim is unable to deliver all the recipients
38294 successfully to one of the smart hosts, delivery of the entire message fails.
38296 Because no queueing is allowed, all failures are treated as permanent; there
38297 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
38298 smart host. Furthermore, because only a single yes/no response can be given to
38299 the caller, it is not possible to deliver to some recipients and not others. If
38300 there is an error (temporary or permanent) for any recipient, all are failed.
38302 If more than one smart host is listed, Exim will try another host after a
38303 connection failure or a timeout, in the normal way. However, if this kind of
38304 failure happens for all the hosts, the delivery fails.
38306 When delivery fails, an error message is written to the standard error stream
38307 (as well as to Exim's log), and Exim exits to the caller with a return code
38308 value 1. The message is expunged from Exim's spool files. No bounce messages
38309 are ever generated.
38311 No retry data is maintained, and any retry rules are ignored.
38313 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
38314 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
38315 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
38318 The overall effect is that Exim makes a single synchronous attempt to deliver
38319 the message, failing if there is any kind of problem. Because no local
38320 deliveries are done and no daemon can be run, Exim does not need root
38321 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
38322 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
38323 the advantages and disadvantages of running without root privilege.
38328 . ////////////////////////////////////////////////////////////////////////////
38329 . ////////////////////////////////////////////////////////////////////////////
38331 .chapter "Log files" "CHAPlog"
38332 .scindex IIDloggen "log" "general description"
38333 .cindex "log" "types of"
38334 Exim writes three different logs, referred to as the main log, the reject log,
38339 The main log records the arrival of each message and each delivery in a single
38340 line in each case. The format is as compact as possible, in an attempt to keep
38341 down the size of log files. Two-character flag sequences make it easy to pick
38342 out these lines. A number of other events are recorded in the main log. Some of
38343 them are optional, in which case the &%log_selector%& option controls whether
38344 they are included or not. A Perl script called &'eximstats'&, which does simple
38345 analysis of main log files, is provided in the Exim distribution (see section
38346 &<<SECTmailstat>>&).
38348 .cindex "reject log"
38349 The reject log records information from messages that are rejected as a result
38350 of a configuration option (that is, for policy reasons).
38351 The first line of each rejection is a copy of the line that is also written to
38352 the main log. Then, if the message's header has been read at the time the log
38353 is written, its contents are written to this log. Only the original header
38354 lines are available; header lines added by ACLs are not logged. You can use the
38355 reject log to check that your policy controls are working correctly; on a busy
38356 host this may be easier than scanning the main log for rejection messages. You
38357 can suppress the writing of the reject log by setting &%write_rejectlog%&
38360 .cindex "panic log"
38361 .cindex "system log"
38362 When certain serious errors occur, Exim writes entries to its panic log. If the
38363 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
38364 are usually written to the main log as well, but can get lost amid the mass of
38365 other entries. The panic log should be empty under normal circumstances. It is
38366 therefore a good idea to check it (or to have a &'cron'& script check it)
38367 regularly, in order to become aware of any problems. When Exim cannot open its
38368 panic log, it tries as a last resort to write to the system log (syslog). This
38369 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
38370 message itself is written at priority LOG_CRIT.
38373 Every log line starts with a timestamp, in the format shown in the following
38374 example. Note that many of the examples shown in this chapter are line-wrapped.
38375 In the log file, this would be all on one line:
38377 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
38380 By default, the timestamps are in the local timezone. There are two
38381 ways of changing this:
38384 You can set the &%timezone%& option to a different time zone; in particular, if
38389 the timestamps will be in UTC (aka GMT).
38391 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
38394 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
38398 .cindex "log" "process ids in"
38399 .cindex "pid (process id)" "in log lines"
38400 Exim does not include its process id in log lines by default, but you can
38401 request that it does so by specifying the &`pid`& log selector (see section
38402 &<<SECTlogselector>>&). When this is set, the process id is output, in square
38403 brackets, immediately after the time and date.
38408 .section "Where the logs are written" "SECTwhelogwri"
38409 .cindex "log" "destination"
38410 .cindex "log" "to file"
38411 .cindex "log" "to syslog"
38413 The logs may be written to local files, or to syslog, or both. However, it
38414 should be noted that many syslog implementations use UDP as a transport, and
38415 are therefore unreliable in the sense that messages are not guaranteed to
38416 arrive at the loghost, nor is the ordering of messages necessarily maintained.
38417 It has also been reported that on large log files (tens of megabytes) you may
38418 need to tweak syslog to prevent it syncing the file with each write &-- on
38419 Linux this has been seen to make syslog take 90% plus of CPU time.
38421 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
38422 &_Local/Makefile_& or by setting &%log_file_path%& in the runtime
38423 configuration. This latter string is expanded, so it can contain, for example,
38424 references to the host name:
38426 log_file_path = /var/log/$primary_hostname/exim_%slog
38428 It is generally advisable, however, to set the string in &_Local/Makefile_&
38429 rather than at runtime, because then the setting is available right from the
38430 start of Exim's execution. Otherwise, if there's something it wants to log
38431 before it has read the configuration file (for example, an error in the
38432 configuration file) it will not use the path you want, and may not be able to
38435 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
38436 list, currently limited to at most two items. This is one option where the
38437 facility for changing a list separator may not be used. The list must always be
38438 colon-separated. If an item in the list is &"syslog"& then syslog is used;
38439 otherwise the item must either be an absolute path, containing &`%s`& at the
38440 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
38441 implying the use of a default path.
38443 When Exim encounters an empty item in the list, it searches the list defined by
38444 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
38445 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
38446 mean &"use the path specified at build time"&. If no such item exists, log
38447 files are written in the &_log_& subdirectory of the spool directory. This is
38448 equivalent to the configuration file setting:
38450 log_file_path = $spool_directory/log/%slog
38452 If you do not specify anything at build time or runtime,
38453 or if you unset the option at runtime (i.e. &`log_file_path = `&),
38454 that is where the logs are written.
38456 A log file path may also contain &`%D`& or &`%M`& if datestamped log filenames
38457 are in use &-- see section &<<SECTdatlogfil>>& below.
38459 Here are some examples of possible Makefile settings:
38461 &`LOG_FILE_PATH=syslog `& syslog only
38462 &`LOG_FILE_PATH=:syslog `& syslog and default path
38463 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
38464 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
38466 If there are more than two paths in the list, the first is used and a panic
38471 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
38472 .cindex "log" "cycling local files"
38473 .cindex "cycling logs"
38474 .cindex "&'exicyclog'&"
38475 .cindex "log" "local files; writing to"
38476 Some operating systems provide centralized and standardized methods for cycling
38477 log files. For those that do not, a utility script called &'exicyclog'& is
38478 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
38479 main and reject logs each time it is called. The maximum number of old logs to
38480 keep can be set. It is suggested this script is run as a daily &'cron'& job.
38482 An Exim delivery process opens the main log when it first needs to write to it,
38483 and it keeps the file open in case subsequent entries are required &-- for
38484 example, if a number of different deliveries are being done for the same
38485 message. However, remote SMTP deliveries can take a long time, and this means
38486 that the file may be kept open long after it is renamed if &'exicyclog'& or
38487 something similar is being used to rename log files on a regular basis. To
38488 ensure that a switch of log files is noticed as soon as possible, Exim calls
38489 &[stat()]& on the main log's name before reusing an open file, and if the file
38490 does not exist, or its inode has changed, the old file is closed and Exim
38491 tries to open the main log from scratch. Thus, an old log file may remain open
38492 for quite some time, but no Exim processes should write to it once it has been
38497 .section "Datestamped log files" "SECTdatlogfil"
38498 .cindex "log" "datestamped files"
38499 Instead of cycling the main and reject log files by renaming them
38500 periodically, some sites like to use files whose names contain a datestamp,
38501 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
38502 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
38503 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
38504 point where the datestamp is required. For example:
38506 log_file_path = /var/spool/exim/log/%slog-%D
38507 log_file_path = /var/log/exim-%s-%D.log
38508 log_file_path = /var/spool/exim/log/%D-%slog
38509 log_file_path = /var/log/exim/%s.%M
38511 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
38512 examples of names generated by the above examples:
38514 /var/spool/exim/log/mainlog-20021225
38515 /var/log/exim-reject-20021225.log
38516 /var/spool/exim/log/20021225-mainlog
38517 /var/log/exim/main.200212
38519 When this form of log file is specified, Exim automatically switches to new
38520 files at midnight. It does not make any attempt to compress old logs; you
38521 will need to write your own script if you require this. You should not
38522 run &'exicyclog'& with this form of logging.
38524 The location of the panic log is also determined by &%log_file_path%&, but it
38525 is not datestamped, because rotation of the panic log does not make sense.
38526 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
38527 the string. In addition, if it immediately follows a slash, a following
38528 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
38529 character is removed. Thus, the four examples above would give these panic
38532 /var/spool/exim/log/paniclog
38533 /var/log/exim-panic.log
38534 /var/spool/exim/log/paniclog
38535 /var/log/exim/panic
38539 .section "Logging to syslog" "SECID249"
38540 .cindex "log" "syslog; writing to"
38541 The use of syslog does not change what Exim logs or the format of its messages,
38542 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
38543 Exim's log lines are omitted when these lines are sent to syslog. Apart from
38544 that, the same strings are written to syslog as to log files. The syslog
38545 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
38546 by default, but you can change these by setting the &%syslog_facility%& and
38547 &%syslog_processname%& options, respectively. If Exim was compiled with
38548 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
38549 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
38550 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
38551 the time and host name to each line.
38552 The three log streams are mapped onto syslog priorities as follows:
38555 &'mainlog'& is mapped to LOG_INFO
38557 &'rejectlog'& is mapped to LOG_NOTICE
38559 &'paniclog'& is mapped to LOG_ALERT
38562 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
38563 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
38564 these are routed by syslog to the same place. You can suppress this duplication
38565 by setting &%syslog_duplication%& false.
38567 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
38568 entries contain multiple lines when headers are included. To cope with both
38569 these cases, entries written to syslog are split into separate &[syslog()]&
38570 calls at each internal newline, and also after a maximum of
38571 870 data characters. (This allows for a total syslog line length of 1024, when
38572 additions such as timestamps are added.) If you are running a syslog
38573 replacement that can handle lines longer than the 1024 characters allowed by
38574 RFC 3164, you should set
38576 SYSLOG_LONG_LINES=yes
38578 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
38579 lines, but it still splits at internal newlines in &'reject'& log entries.
38581 To make it easy to re-assemble split lines later, each component of a split
38582 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
38583 where <&'n'&> is the component number and <&'m'&> is the total number of
38584 components in the entry. The / delimiter is used when the line was split
38585 because it was too long; if it was split because of an internal newline, the \
38586 delimiter is used. For example, supposing the length limit to be 50 instead of
38587 870, the following would be the result of a typical rejection message to
38588 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
38589 name, and pid as added by syslog:
38591 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
38592 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
38593 [3/5] when scanning for sender: missing or malformed lo
38594 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
38597 The same error might cause the following lines to be written to &"rejectlog"&
38600 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
38601 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
38602 [3/18] er when scanning for sender: missing or malformed
38603 [4/18] local part in "<>" (envelope sender is <ph10@cam
38605 [6\18] Recipients: ph10@some.domain.cam.example
38606 [7\18] P Received: from [127.0.0.1] (ident=ph10)
38607 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
38608 [9\18] id 16RdAL-0006pc-00
38609 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
38610 [11\18] 09:43 +0100
38612 [13\18] Subject: this is a test header
38613 [18\18] X-something: this is another header
38614 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
38617 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
38619 Log lines that are neither too long nor contain newlines are written to syslog
38620 without modification.
38622 If only syslog is being used, the Exim monitor is unable to provide a log tail
38623 display, unless syslog is routing &'mainlog'& to a file on the local host and
38624 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
38629 .section "Log line flags" "SECID250"
38630 One line is written to the main log for each message received, and for each
38631 successful, unsuccessful, and delayed delivery. These lines can readily be
38632 picked out by the distinctive two-character flags that immediately follow the
38633 timestamp. The flags are:
38634 .itable none 0 0 2 10* left 90* left
38635 .irow &%<=%& "message arrival"
38636 .irow &%(=%& "message fakereject"
38637 .irow &%=>%& "normal message delivery"
38638 .irow &%->%& "additional address in same delivery"
38639 .irow &%>>%& "cutthrough message delivery"
38640 .irow &%*>%& "delivery suppressed by &%-N%&"
38641 .irow &%**%& "delivery failed; address bounced"
38642 .irow &%==%& "delivery deferred; temporary problem"
38646 .section "Logging message reception" "SECID251"
38647 .cindex "log" "reception line"
38648 The format of the single-line entry in the main log that is written for every
38649 message received is shown in the basic example below, which is split over
38650 several lines in order to fit it on the page:
38652 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
38653 H=mailer.fict.example [192.168.123.123] U=exim
38654 P=smtp S=5678 id=<incoming message id>
38656 The address immediately following &"<="& is the envelope sender address. A
38657 bounce message is shown with the sender address &"<>"&, and if it is locally
38658 generated, this is followed by an item of the form
38662 which is a reference to the message that caused the bounce to be sent.
38666 For messages from other hosts, the H and U fields identify the remote host and
38667 record the RFC 1413 identity of the user that sent the message, if one was
38668 received. The number given in square brackets is the IP address of the sending
38669 host. If there is a single, unparenthesized host name in the H field, as
38670 above, it has been verified to correspond to the IP address (see the
38671 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
38672 by the remote host in the SMTP HELO or EHLO command, and has not been
38673 verified. If verification yields a different name to that given for HELO or
38674 EHLO, the verified name appears first, followed by the HELO or EHLO
38675 name in parentheses.
38677 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
38678 without brackets, in the HELO or EHLO command, leading to entries in
38679 the log containing text like these examples:
38681 H=(10.21.32.43) [192.168.8.34]
38682 H=([10.21.32.43]) [192.168.8.34]
38684 This can be confusing. Only the final address in square brackets can be relied
38687 For locally generated messages (that is, messages not received over TCP/IP),
38688 the H field is omitted, and the U field contains the login name of the caller
38691 .cindex "authentication" "logging"
38692 .cindex "AUTH" "logging"
38693 For all messages, the P field specifies the protocol used to receive the
38694 message. This is the value that is stored in &$received_protocol$&. In the case
38695 of incoming SMTP messages, the value indicates whether or not any SMTP
38696 extensions (ESMTP), encryption, or authentication were used. If the SMTP
38697 session was encrypted, there is an additional X field that records the cipher
38698 suite that was used.
38700 .cindex log protocol
38701 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
38702 hosts that have authenticated themselves using the SMTP AUTH command. The first
38703 value is used when the SMTP connection was encrypted (&"secure"&). In this case
38704 there is an additional item A= followed by the name of the authenticator that
38705 was used. If an authenticated identification was set up by the authenticator's
38706 &%server_set_id%& option, this is logged too, separated by a colon from the
38707 authenticator name.
38709 .cindex "size" "of message"
38710 The id field records the existing message id, if present. The size of the
38711 received message is given by the S field. When the message is delivered,
38712 headers may be removed or added, so that the size of delivered copies of the
38713 message may not correspond with this value (and indeed may be different to each
38716 The &%log_selector%& option can be used to request the logging of additional
38717 data when a message is received. See section &<<SECTlogselector>>& below.
38721 .section "Logging deliveries" "SECID252"
38722 .cindex "log" "delivery line"
38723 The format of the single-line entry in the main log that is written for every
38724 delivery is shown in one of the examples below, for local and remote
38725 deliveries, respectively. Each example has been split into multiple lines in order
38726 to fit it on the page:
38728 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
38729 <marv@hitch.fict.example> R=localuser T=local_delivery
38730 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
38731 monk@holistic.fict.example R=dnslookup T=remote_smtp
38732 H=holistic.fict.example [192.168.234.234]
38734 For ordinary local deliveries, the original address is given in angle brackets
38735 after the final delivery address, which might be a pipe or a file. If
38736 intermediate address(es) exist between the original and the final address, the
38737 last of these is given in parentheses after the final address. The R and T
38738 fields record the router and transport that were used to process the address.
38740 If SMTP AUTH was used for the delivery there is an additional item A=
38741 followed by the name of the authenticator that was used.
38742 If an authenticated identification was set up by the authenticator's &%client_set_id%&
38743 option, this is logged too, as a second colon-separated list item.
38744 Optionally (see the &%smtp_mailauth%& &%log_selector%&) there may be a third list item.
38746 If a shadow transport was run after a successful local delivery, the log line
38747 for the successful delivery has an item added on the end, of the form
38749 &`ST=<`&&'shadow transport name'&&`>`&
38751 If the shadow transport did not succeed, the error message is put in
38752 parentheses afterwards.
38754 .cindex "asterisk" "after IP address"
38755 When more than one address is included in a single delivery (for example, two
38756 SMTP RCPT commands in one transaction) the second and subsequent addresses are
38757 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
38758 down a single SMTP connection, an asterisk follows the
38759 remote IP address (and port if enabled)
38760 in the log lines for the second and subsequent messages.
38761 When two or more messages are delivered down a single TLS connection, the
38762 DNS and some TLS-related information logged for the first message delivered
38763 will not be present in the log lines for the second and subsequent messages.
38764 TLS cipher information is still available.
38766 .cindex "delivery" "cutthrough; logging"
38767 .cindex "cutthrough" "logging"
38768 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
38769 line precedes the reception line, since cutthrough waits for a possible
38770 rejection from the destination in case it can reject the sourced item.
38772 The generation of a reply message by a filter file gets logged as a
38773 &"delivery"& to the addressee, preceded by &">"&.
38775 The &%log_selector%& option can be used to request the logging of additional
38776 data when a message is delivered. See section &<<SECTlogselector>>& below.
38779 .section "Discarded deliveries" "SECID253"
38780 .cindex "discarded messages"
38781 .cindex "message" "discarded"
38782 .cindex "delivery" "discarded; logging"
38783 When a message is discarded as a result of the command &"seen finish"& being
38784 obeyed in a filter file which generates no deliveries, a log entry of the form
38786 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
38787 <low.club@bridge.example> R=userforward
38789 is written, to record why no deliveries are logged. When a message is discarded
38790 because it is aliased to &":blackhole:"& the log line is like this:
38792 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
38793 <hole@nowhere.example> R=blackhole_router
38797 .section "Deferred deliveries" "SECID254"
38798 When a delivery is deferred, a line of the following form is logged:
38800 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
38801 R=dnslookup T=smtp defer (146): Connection refused
38803 In the case of remote deliveries, the error is the one that was given for the
38804 last IP address that was tried. Details of individual SMTP failures are also
38805 written to the log, so the above line would be preceded by something like
38807 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
38808 mail1.endrest.example [192.168.239.239]: Connection refused
38810 When a deferred address is skipped because its retry time has not been reached,
38811 a message is written to the log, but this can be suppressed by setting an
38812 appropriate value in &%log_selector%&.
38816 .section "Delivery failures" "SECID255"
38817 .cindex "delivery" "failure; logging"
38818 If a delivery fails because an address cannot be routed, a line of the
38819 following form is logged:
38821 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
38822 <jim@trek99.example>: unknown mail domain
38824 If a delivery fails at transport time, the router and transport are shown, and
38825 the response from the remote host is included, as in this example:
38827 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
38828 R=dnslookup T=remote_smtp: SMTP error from remote mailer
38829 after pipelined RCPT TO:<ace400@pb.example>: host
38830 pbmail3.py.example [192.168.63.111]: 553 5.3.0
38831 <ace400@pb.example>...Addressee unknown
38833 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
38834 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
38835 disabling PIPELINING. The log lines for all forms of delivery failure are
38836 flagged with &`**`&.
38840 .section "Fake deliveries" "SECID256"
38841 .cindex "delivery" "fake; logging"
38842 If a delivery does not actually take place because the &%-N%& option has been
38843 used to suppress it, a normal delivery line is written to the log, except that
38844 &"=>"& is replaced by &"*>"&.
38848 .section "Completion" "SECID257"
38851 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
38853 is written to the main log when a message is about to be removed from the spool
38854 at the end of its processing.
38859 .section "Summary of Fields in Log Lines" "SECID258"
38860 .cindex "log" "summary of fields"
38861 A summary of the field identifiers that are used in log lines is shown in
38862 the following table:
38864 &`A `& authenticator name (and optional id and sender)
38865 &`C `& SMTP confirmation on delivery
38866 &` `& command list for &"no mail in SMTP session"&
38867 &`CV `& certificate verification status
38868 &`D `& duration of &"no mail in SMTP session"&
38869 &`DKIM`& domain verified in incoming message
38870 &`DN `& distinguished name from peer certificate
38871 &`DS `& DNSSEC secured lookups
38872 &`DT `& on &`=>`&, &'=='& and &'**'& lines: time taken for, or to attempt, a delivery
38873 &`F `& sender address (on delivery lines)
38874 &`H `& host name and IP address
38875 &`I `& local interface used
38876 &`id `& message id (from header) for incoming message
38877 &`K `& CHUNKING extension used
38878 &`L `& on &`<=`& and &`=>`& lines: PIPELINING extension used
38879 &`M8S `& 8BITMIME status for incoming message
38880 &`P `& on &`<=`& lines: protocol used
38881 &` `& on &`=>`& and &`**`& lines: return path
38882 &`PRDR`& PRDR extension used
38883 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
38884 &`Q `& alternate queue name
38885 &`QT `& on &`=>`& lines: time spent on queue so far
38886 &` `& on &"Completed"& lines: time spent on queue
38887 &`R `& on &`<=`& lines: reference for local bounce
38888 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
38889 &`RT `& on &`<=`& lines: time taken for reception
38890 &`S `& size of message in bytes
38891 &`SNI `& server name indication from TLS client hello
38892 &`ST `& shadow transport name
38893 &`T `& on &`<=`& lines: message subject (topic)
38894 &`TFO `& connection took advantage of TCP Fast Open
38895 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
38896 &`U `& local user or RFC 1413 identity
38897 &`X `& TLS cipher suite
38901 .section "Other log entries" "SECID259"
38902 Various other types of log entry are written from time to time. Most should be
38903 self-explanatory. Among the more common are:
38906 .cindex "retry" "time not reached"
38907 &'retry time not reached'&&~&~An address previously suffered a temporary error
38908 during routing or local delivery, and the time to retry has not yet arrived.
38909 This message is not written to an individual message log file unless it happens
38910 during the first delivery attempt.
38912 &'retry time not reached for any host'&&~&~An address previously suffered
38913 temporary errors during remote delivery, and the retry time has not yet arrived
38914 for any of the hosts to which it is routed.
38916 .cindex "spool directory" "file locked"
38917 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
38918 some other Exim process is already working on the message. This can be quite
38919 common if queue running processes are started at frequent intervals. The
38920 &'exiwhat'& utility script can be used to find out what Exim processes are
38923 .cindex "error" "ignored"
38924 &'error ignored'&&~&~There are several circumstances that give rise to this
38927 Exim failed to deliver a bounce message whose age was greater than
38928 &%ignore_bounce_errors_after%&. The bounce was discarded.
38930 A filter file set up a delivery using the &"noerror"& option, and the delivery
38931 failed. The delivery was discarded.
38933 A delivery set up by a router configured with
38934 . ==== As this is a nested list, any displays it contains must be indented
38935 . ==== as otherwise they are too far to the left.
38939 failed. The delivery was discarded.
38942 .cindex DKIM "log line"
38943 &'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
38944 logging and the message has a DKIM signature header.
38951 .section "Reducing or increasing what is logged" "SECTlogselector"
38952 .cindex "log" "selectors"
38953 By setting the &%log_selector%& global option, you can disable some of Exim's
38954 default logging, or you can request additional logging. The value of
38955 &%log_selector%& is made up of names preceded by plus or minus characters. For
38958 log_selector = +arguments -retry_defer
38960 The list of optional log items is in the following table, with the default
38961 selection marked by asterisks:
38962 .itable none 0 0 3 2.8in left 10pt center 3in left
38963 .irow &`8bitmime`& "received 8BITMIME status"
38964 .irow &`acl_warn_skipped`& * "skipped &%warn%& statement in ACL"
38965 .irow &`address_rewrite`& "address rewriting"
38966 .irow &`all_parents`& "all parents in => lines"
38967 .irow &`arguments`& "command line arguments"
38968 .irow &`connection_reject`& * "connection rejections"
38969 .irow &`delay_delivery`& * "immediate delivery delayed"
38970 .irow &`deliver_time`& "time taken to attempt delivery"
38971 .irow &`delivery_size`& "add &`S=`&&'nnn'& to => lines"
38972 .irow &`dkim`& * "DKIM verified domain on <= lines"
38973 .irow &`dkim_verbose`& "separate full DKIM verification result line, per signature"
38974 .irow &`dnslist_defer`& * "defers of DNS list (aka RBL) lookups"
38975 .irow &`dnssec`& "DNSSEC secured lookups"
38976 .irow &`etrn`& * "ETRN commands"
38977 .irow &`host_lookup_failed`& * "as it says"
38978 .irow &`ident_timeout`& "timeout for ident connection"
38979 .irow &`incoming_interface`& "local interface & port on <= and => lines"
38980 .irow &`incoming_port`& "remote port on <= lines"
38981 .irow &`lost_incoming_connection`& * "as it says (includes timeouts)"
38982 .irow &`millisec`& "millisecond timestamps and RT,QT,DT,D times"
38983 .irow &`msg_id`& * "on <= lines, Message-ID: header value"
38984 .irow &`msg_id_created`& "on <= lines, Message-ID: header value when one had to be added"
38985 .irow &`outgoing_interface`& "local interface on => lines"
38986 .irow &`outgoing_port`& "add remote port to => lines"
38987 .irow &`queue_run`& * "start and end queue runs"
38988 .irow &`queue_time`& "time on queue for one recipient"
38989 .irow &`queue_time_exclusive`& "exclude recieve time from QT times"
38990 .irow &`queue_time_overall`& "time on queue for whole message"
38991 .irow &`pid`& "Exim process id"
38992 .irow &`pipelining`& "PIPELINING use, on <= and => lines"
38993 .irow &`proxy`& "proxy address on <= and => lines"
38994 .irow &`receive_time`& "time taken to receive message"
38995 .irow &`received_recipients`& "recipients on <= lines"
38996 .irow &`received_sender`& "sender on <= lines"
38997 .irow &`rejected_header`& * "header contents on reject log"
38998 .irow &`retry_defer`& * "&<quote>&retry time not reached&</quote>&"
38999 .irow &`return_path_on_delivery`& "put return path on => and ** lines"
39000 .irow &`sender_on_delivery`& "add sender to => lines"
39001 .irow &`sender_verify_fail`& * "sender verification failures"
39002 .irow &`size_reject`& * "rejection because too big"
39003 .irow &`skip_delivery`& * "delivery skipped in a queue run"
39004 .irow &`smtp_confirmation`& * "SMTP confirmation on => lines"
39005 .irow &`smtp_connection`& "incoming SMTP connections"
39006 .irow &`smtp_incomplete_transaction`& "incomplete SMTP transactions"
39007 .irow &`smtp_mailauth`& "AUTH argument to MAIL commands"
39008 .irow &`smtp_no_mail`& "session with no MAIL commands"
39009 .irow &`smtp_protocol_error`& "SMTP protocol errors"
39010 .irow &`smtp_syntax_error`& "SMTP syntax errors"
39011 .irow &`subject`& "contents of &'Subject:'& on <= lines"
39012 .irow &`tls_certificate_verified`& * "certificate verification status"
39013 .irow &`tls_cipher`& * "TLS cipher suite on <= and => lines"
39014 .irow &`tls_peerdn`& "TLS peer DN on <= and => lines"
39015 .irow &`tls_resumption`& "append * to cipher field"
39016 .irow &`tls_sni`& "TLS SNI on <= lines"
39017 .irow &`unknown_in_list`& "DNS lookup failed in list match"
39018 .irow &`all`& "&*all of the above*&"
39020 See also the &%slow_lookup_log%& main configuration option,
39021 section &<<SECID99>>&
39023 More details on each of these items follows:
39027 .cindex "log" "8BITMIME"
39028 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
39029 which may help in tracking down interoperability issues with ancient MTAs
39030 that are not 8bit clean. This is added to the &"<="& line, tagged with
39031 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
39032 &`7BIT`& and &`8BITMIME`& respectively.
39034 .cindex "&%warn%& ACL verb" "log when skipping"
39035 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
39036 its conditions cannot be evaluated, a log line to this effect is written if
39037 this log selector is set.
39039 .cindex "log" "rewriting"
39040 .cindex "rewriting" "logging"
39041 &%address_rewrite%&: This applies both to global rewrites and per-transport
39042 rewrites, but not to rewrites in filters run as an unprivileged user (because
39043 such users cannot access the log).
39045 .cindex "log" "full parentage"
39046 &%all_parents%&: Normally only the original and final addresses are logged on
39047 delivery lines; with this selector, intermediate parents are given in
39048 parentheses between them.
39050 .cindex "log" "Exim arguments"
39051 .cindex "Exim arguments, logging"
39052 &%arguments%&: This causes Exim to write the arguments with which it was called
39053 to the main log, preceded by the current working directory. This is a debugging
39054 feature, added to make it easier to find out how certain MUAs call
39055 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
39056 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
39057 that are empty or that contain white space are quoted. Non-printing characters
39058 are shown as escape sequences. This facility cannot log unrecognized arguments,
39059 because the arguments are checked before the configuration file is read. The
39060 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
39061 between the caller and Exim.
39063 .cindex "log" "connection rejections"
39064 &%connection_reject%&: A log entry is written whenever an incoming SMTP
39065 connection is rejected, for whatever reason.
39067 .cindex "log" "delayed delivery"
39068 .cindex "delayed delivery, logging"
39069 &%delay_delivery%&: A log entry is written whenever a delivery process is not
39070 started for an incoming message because the load is too high or too many
39071 messages were received on one connection. Logging does not occur if no delivery
39072 process is started because &%queue_only%& is set or &%-odq%& was used.
39074 .cindex "log" "delivery duration"
39075 &%deliver_time%&: For each delivery, the amount of real time it has taken to
39076 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
39077 If millisecond logging is enabled, short times will be shown with greater
39078 precision, eg. &`DT=0.304s`&.
39080 .cindex "log" "message size on delivery"
39081 .cindex "size" "of message"
39082 &%delivery_size%&: For each delivery, the size of message delivered is added to
39083 the &"=>"& line, tagged with S=.
39085 .cindex log "DKIM verification"
39086 .cindex DKIM "verification logging"
39087 &%dkim%&: For message acceptance log lines, when an DKIM signature in the header
39088 verifies successfully a tag of DKIM is added, with one of the verified domains.
39090 .cindex log "DKIM verification"
39091 .cindex DKIM "verification logging"
39092 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
39094 .cindex "log" "dnslist defer"
39095 .cindex "DNS list" "logging defer"
39096 .cindex "black list (DNS)"
39097 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
39098 DNS black list suffers a temporary error.
39101 .cindex dnssec logging
39102 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
39103 dns lookups gave secure results a tag of DS is added.
39104 For acceptance this covers the reverse and forward lookups for host name verification.
39105 It does not cover helo-name verification.
39106 For delivery this covers the SRV, MX, A and/or AAAA lookups.
39108 .cindex "log" "ETRN commands"
39109 .cindex "ETRN" "logging"
39110 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
39111 is run to determine whether or not it is actually accepted. An invalid ETRN
39112 command, or one received within a message transaction is not logged by this
39113 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
39115 .cindex "log" "host lookup failure"
39116 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
39117 any addresses, or when a lookup of an IP address fails to find a host name, a
39118 log line is written. This logging does not apply to direct DNS lookups when
39119 routing email addresses, but it does apply to &"byname"& lookups.
39121 .cindex "log" "ident timeout"
39122 .cindex "RFC 1413" "logging timeout"
39123 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
39124 client's ident port times out.
39126 .cindex "log" "incoming interface"
39127 .cindex "log" "outgoing interface"
39128 .cindex "log" "local interface"
39129 .cindex "log" "local address and port"
39130 .cindex "TCP/IP" "logging local address and port"
39131 .cindex "interface" "logging"
39132 &%incoming_interface%&: The interface on which a message was received is added
39133 to the &"<="& line as an IP address in square brackets, tagged by I= and
39134 followed by a colon and the port number. The local interface and port are also
39135 added to other SMTP log lines, for example, &"SMTP connection from"&, to
39136 rejection lines, and (despite the name) to outgoing
39137 &"=>"&, &"->"&, &"=="& and &"**"& lines.
39138 The latter can be disabled by turning off the &%outgoing_interface%& option.
39140 .cindex log "incoming proxy address"
39141 .cindex proxy "logging proxy address"
39142 .cindex "TCP/IP" "logging proxy address"
39143 &%proxy%&: The internal (closest to the system running Exim) IP address
39144 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
39145 on a proxied connection
39146 or the &"=>"& line for a message delivered on a proxied connection.
39147 See &<<SECTproxyInbound>>& for more information.
39149 .cindex "log" "incoming remote port"
39150 .cindex "port" "logging remote"
39151 .cindex "TCP/IP" "logging incoming remote port"
39152 .vindex "&$sender_fullhost$&"
39153 .vindex "&$sender_rcvhost$&"
39154 &%incoming_port%&: The remote port number from which a message was received is
39155 added to log entries and &'Received:'& header lines, following the IP address
39156 in square brackets, and separated from it by a colon. This is implemented by
39157 changing the value that is put in the &$sender_fullhost$& and
39158 &$sender_rcvhost$& variables. Recording the remote port number has become more
39159 important with the widening use of NAT (see RFC 2505).
39161 .cindex "log" "dropped connection"
39162 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
39163 connection is unexpectedly dropped.
39165 .cindex "log" "millisecond timestamps"
39166 .cindex millisecond logging
39167 .cindex timestamps "millisecond, in logs"
39168 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
39169 appended to the seconds value.
39171 .cindex "log" "message id"
39172 &%msg_id%&: The value of the Message-ID: header.
39174 &%msg_id_created%&: The value of the Message-ID: header, when one had to be created.
39175 This will be either because the message is a bounce, or was submitted locally
39176 (submission mode) without one.
39177 The field identifier will have an asterix appended: &"id*="&.
39179 .cindex "log" "outgoing interface"
39180 .cindex "log" "local interface"
39181 .cindex "log" "local address and port"
39182 .cindex "TCP/IP" "logging local address and port"
39183 .cindex "interface" "logging"
39184 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
39185 interface on which a message was sent is added to delivery lines as an I= tag
39186 followed by IP address in square brackets. You can disable this by turning
39187 off the &%outgoing_interface%& option.
39189 .cindex "log" "outgoing remote port"
39190 .cindex "port" "logging outgoing remote"
39191 .cindex "TCP/IP" "logging outgoing remote port"
39192 &%outgoing_port%&: The remote port number is added to delivery log lines (those
39193 containing => tags) following the IP address.
39194 The local port is also added if &%incoming_interface%& and
39195 &%outgoing_interface%& are both enabled.
39196 This option is not included in the default setting, because for most ordinary
39197 configurations, the remote port number is always 25 (the SMTP port), and the
39198 local port is a random ephemeral port.
39200 .cindex "log" "process ids in"
39201 .cindex "pid (process id)" "in log lines"
39202 &%pid%&: The current process id is added to every log line, in square brackets,
39203 immediately after the time and date.
39205 .cindex log pipelining
39206 .cindex pipelining "logging outgoing"
39207 &%pipelining%&: A field is added to delivery and accept
39208 log lines when the ESMTP PIPELINING extension was used.
39209 The field is a single "L".
39211 On accept lines, where PIPELINING was offered but not used by the client,
39212 the field has a minus appended.
39214 .cindex "pipelining" "early connection"
39215 If Exim is built without the DISABLE_PIPE_CONNECT build option
39216 accept "L" fields have a period appended if the feature was
39217 offered but not used, or an asterisk appended if used.
39218 Delivery "L" fields have an asterisk appended if used.
39221 .cindex "log" "queue run"
39222 .cindex "queue runner" "logging"
39223 &%queue_run%&: The start and end of every queue run are logged.
39225 .cindex "log" "queue time"
39226 &%queue_time%&: The amount of time the message has been in the queue on the
39227 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
39229 If millisecond logging is enabled, short times will be shown with greater
39230 precision, eg. &`QT=1.578s`&.
39232 &%queue_time_overall%&: The amount of time the message has been in the queue on
39233 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
39234 example, &`QT=3m45s`&.
39236 .cindex "log" "receive duration"
39237 &%receive_time%&: For each message, the amount of real time it has taken to
39238 perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
39239 If millisecond logging is enabled, short times will be shown with greater
39240 precision, eg. &`RT=0.204s`&.
39242 .cindex "log" "recipients"
39243 &%received_recipients%&: The recipients of a message are listed in the main log
39244 as soon as the message is received. The list appears at the end of the log line
39245 that is written when a message is received, preceded by the word &"for"&. The
39246 addresses are listed after they have been qualified, but before any rewriting
39248 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
39251 .cindex "log" "sender reception"
39252 &%received_sender%&: The unrewritten original sender of a message is added to
39253 the end of the log line that records the message's arrival, after the word
39254 &"from"& (before the recipients if &%received_recipients%& is also set).
39256 .cindex "log" "header lines for rejection"
39257 &%rejected_header%&: If a message's header has been received at the time a
39258 rejection is written to the reject log, the complete header is added to the
39259 log. Header logging can be turned off individually for messages that are
39260 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
39262 .cindex "log" "retry defer"
39263 &%retry_defer%&: A log line is written if a delivery is deferred because a
39264 retry time has not yet been reached. However, this &"retry time not reached"&
39265 message is always omitted from individual message logs after the first delivery
39268 .cindex "log" "return path"
39269 &%return_path_on_delivery%&: The return path that is being transmitted with
39270 the message is included in delivery and bounce lines, using the tag P=.
39271 This is omitted if no delivery actually happens, for example, if routing fails,
39272 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
39274 .cindex "log" "sender on delivery"
39275 &%sender_on_delivery%&: The message's sender address is added to every delivery
39276 and bounce line, tagged by F= (for &"from"&).
39277 This is the original sender that was received with the message; it is not
39278 necessarily the same as the outgoing return path.
39280 .cindex "log" "sender verify failure"
39281 &%sender_verify_fail%&: If this selector is unset, the separate log line that
39282 gives details of a sender verification failure is not written. Log lines for
39283 the rejection of SMTP commands contain just &"sender verify failed"&, so some
39286 .cindex "log" "size rejection"
39287 &%size_reject%&: A log line is written whenever a message is rejected because
39290 .cindex "log" "frozen messages; skipped"
39291 .cindex "frozen messages" "logging skipping"
39292 &%skip_delivery%&: A log line is written whenever a message is skipped during a
39293 queue run because it another process is already delivering it or because
39295 .cindex "&""spool file is locked""&"
39296 .cindex "&""message is frozen""&"
39297 The message that is written is either &"spool file is locked"& or
39298 &"message is frozen"&.
39300 .cindex "log" "smtp confirmation"
39301 .cindex "SMTP" "logging confirmation"
39302 .cindex "LMTP" "logging confirmation"
39303 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
39304 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
39305 A number of MTAs (including Exim) return an identifying string in this
39308 .cindex "log" "SMTP connections"
39309 .cindex "SMTP" "logging connections"
39310 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
39311 established or closed, unless the connection is from a host that matches
39312 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
39313 only when the closure is unexpected.) This applies to connections from local
39314 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
39315 dropped in the middle of a message, a log line is always written, whether or
39316 not this selector is set, but otherwise nothing is written at the start and end
39317 of connections unless this selector is enabled.
39319 For TCP/IP connections to an Exim daemon, the current number of connections is
39320 included in the log message for each new connection, but note that the count is
39321 reset if the daemon is restarted.
39322 Also, because connections are closed (and the closure is logged) in
39323 subprocesses, the count may not include connections that have been closed but
39324 whose termination the daemon has not yet noticed. Thus, while it is possible to
39325 match up the opening and closing of connections in the log, the value of the
39326 logged counts may not be entirely accurate.
39328 .cindex "log" "SMTP transaction; incomplete"
39329 .cindex "SMTP" "logging incomplete transactions"
39330 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
39331 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
39332 and the message sender plus any accepted recipients are included in the log
39333 line. This can provide evidence of dictionary attacks.
39335 .cindex "log" "non-MAIL SMTP sessions"
39336 .cindex "MAIL" "logging session without"
39337 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
39338 connection terminates without having issued a MAIL command. This includes both
39339 the case when the connection is dropped, and the case when QUIT is used. It
39340 does not include cases where the connection is rejected right at the start (by
39341 an ACL, or because there are too many connections, or whatever). These cases
39342 already have their own log lines.
39344 The log line that is written contains the identity of the client in the usual
39345 way, followed by D= and a time, which records the duration of the connection.
39346 If the connection was authenticated, this fact is logged exactly as it is for
39347 an incoming message, with an A= item. If the connection was encrypted, CV=,
39348 DN=, and X= items may appear as they do for an incoming message, controlled by
39349 the same logging options.
39351 Finally, if any SMTP commands were issued during the connection, a C= item
39352 is added to the line, listing the commands that were used. For example,
39356 shows that the client issued QUIT straight after EHLO. If there were fewer
39357 than 20 commands, they are all listed. If there were more than 20 commands,
39358 the last 20 are listed, preceded by &"..."&. However, with the default
39359 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
39360 have been aborted before 20 non-mail commands are processed.
39362 &%smtp_mailauth%&: A third subfield with the authenticated sender,
39363 colon-separated, is appended to the A= item for a message arrival or delivery
39364 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
39365 was accepted or used.
39367 .cindex "log" "SMTP protocol error"
39368 .cindex "SMTP" "logging protocol error"
39369 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
39370 encountered. Exim does not have perfect detection of all protocol errors
39371 because of transmission delays and the use of pipelining. If PIPELINING has
39372 been advertised to a client, an Exim server assumes that the client will use
39373 it, and therefore it does not count &"expected"& errors (for example, RCPT
39374 received after rejecting MAIL) as protocol errors.
39376 .cindex "SMTP" "logging syntax errors"
39377 .cindex "SMTP" "syntax errors; logging"
39378 .cindex "SMTP" "unknown command; logging"
39379 .cindex "log" "unknown SMTP command"
39380 .cindex "log" "SMTP syntax error"
39381 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
39382 encountered. An unrecognized command is treated as a syntax error. For an
39383 external connection, the host identity is given; for an internal connection
39384 using &%-bs%& the sender identification (normally the calling user) is given.
39386 .cindex "log" "subject"
39387 .cindex "subject, logging"
39388 &%subject%&: The subject of the message is added to the arrival log line,
39389 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
39390 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
39391 specifies whether characters with values greater than 127 should be logged
39392 unchanged, or whether they should be rendered as escape sequences.
39394 .cindex "log" "certificate verification"
39396 .cindex DANE logging
39397 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
39398 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
39400 using a CA trust anchor,
39401 &`CV=dane`& if using a DNS trust anchor,
39402 and &`CV=no`& if not.
39404 .cindex "log" "TLS cipher"
39405 .cindex "TLS" "logging cipher"
39406 &%tls_cipher%&: When a message is sent or received over an encrypted
39407 connection, the cipher suite used is added to the log line, preceded by X=.
39409 .cindex "log" "TLS peer DN"
39410 .cindex "TLS" "logging peer DN"
39411 &%tls_peerdn%&: When a message is sent or received over an encrypted
39412 connection, and a certificate is supplied by the remote host, the peer DN is
39413 added to the log line, preceded by DN=.
39415 .cindex "log" "TLS resumption"
39416 .cindex "TLS" "logging session resumption"
39417 &%tls_resumption%&: When a message is sent or received over an encrypted
39418 connection and the TLS session resumed one used on a previous TCP connection,
39419 an asterisk is appended to the X= cipher field in the log line.
39421 .cindex "log" "TLS SNI"
39422 .cindex "TLS" "logging SNI"
39423 .cindex SNI logging
39424 &%tls_sni%&: When a message is received over an encrypted connection, and
39425 the remote host provided the Server Name Indication extension, the SNI is
39426 added to the log line, preceded by SNI=.
39428 .cindex "log" "DNS failure in list"
39429 &%unknown_in_list%&: This setting causes a log entry to be written when the
39430 result of a list match is failure because a DNS lookup failed.
39434 .section "Message log" "SECID260"
39435 .cindex "message" "log file for"
39436 .cindex "log" "message log; description of"
39437 .cindex "&_msglog_& directory"
39438 .oindex "&%preserve_message_logs%&"
39439 In addition to the general log files, Exim writes a log file for each message
39440 that it handles. The names of these per-message logs are the message ids, and
39441 they are kept in the &_msglog_& sub-directory of the spool directory. Each
39442 message log contains copies of the log lines that apply to the message. This
39443 makes it easier to inspect the status of an individual message without having
39444 to search the main log. A message log is deleted when processing of the message
39445 is complete, unless &%preserve_message_logs%& is set, but this should be used
39446 only with great care because they can fill up your disk very quickly.
39448 On a heavily loaded system, it may be desirable to disable the use of
39449 per-message logs, in order to reduce disk I/O. This can be done by setting the
39450 &%message_logs%& option false.
39456 . ////////////////////////////////////////////////////////////////////////////
39457 . ////////////////////////////////////////////////////////////////////////////
39459 .chapter "Exim utilities" "CHAPutils"
39460 .scindex IIDutils "utilities"
39461 A number of utility scripts and programs are supplied with Exim and are
39462 described in this chapter. There is also the Exim Monitor, which is covered in
39463 the next chapter. The utilities described here are:
39465 .itable none 0 0 3 7* left 15* left 40* left
39466 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
39467 "list what Exim processes are doing"
39468 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
39469 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
39470 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
39471 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
39473 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
39474 .irow &<<SECTmailstat>>& &'eximstats'& &&&
39475 "extract statistics from the log"
39476 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
39477 "check address acceptance from given IP"
39478 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
39479 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
39480 .irow &<<SECTdumpdb>>& &'exim_dumpdb'& "dump a hints database"
39481 .irow &<<SECTtidydb>>& &'exim_tidydb'& "clean up a hints database"
39482 .irow &<<SECTfixdb>>& &'exim_fixdb'& "patch a hints database"
39483 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
39484 .irow &<<SECTexim_msgdate>>& &'exim_msgdate'& "Message Ids for humans (exim_msgdate)"
39487 Another utility that might be of use to sites with many MTAs is Tom Kistner's
39488 &'exilog'&. It provides log visualizations across multiple Exim servers. See
39489 &url(https://duncanthrax.net/exilog/) for details.
39494 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
39495 .cindex "&'exiwhat'&"
39496 .cindex "process, querying"
39498 On operating systems that can restart a system call after receiving a signal
39499 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
39500 a line describing what it is doing to the file &_exim-process.info_& in the
39501 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
39502 processes it can find, having first emptied the file. It then waits for one
39503 second to allow the Exim processes to react before displaying the results. In
39504 order to run &'exiwhat'& successfully you have to have sufficient privilege to
39505 send the signal to the Exim processes, so it is normally run as root.
39507 &*Warning*&: This is not an efficient process. It is intended for occasional
39508 use by system administrators. It is not sensible, for example, to set up a
39509 script that sends SIGUSR1 signals to Exim processes at short intervals.
39512 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
39513 varies in different operating systems. Not only are different options used,
39514 but the format of the output is different. For this reason, there are some
39515 system configuration options that configure exactly how &'exiwhat'& works. If
39516 it doesn't seem to be working for you, check the following compile-time
39518 .itable none 0 0 2 30* left 70* left
39519 .irow &`EXIWHAT_PS_CMD`& "the command for running &'ps'&"
39520 .irow &`EXIWHAT_PS_ARG`& "the argument for &'ps'&"
39521 .irow &`EXIWHAT_EGREP_ARG`& "the argument for &'egrep'& to select from &'ps'& output"
39522 .irow &`EXIWHAT_KILL_ARG`& "the argument for the &'kill'& command"
39524 An example of typical output from &'exiwhat'& is
39526 164 daemon: -q1h, listening on port 25
39527 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
39528 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
39529 [10.19.42.42] (editor@ref.example)
39530 10592 handling incoming call from [192.168.243.242]
39531 10628 accepting a local non-SMTP message
39533 The first number in the output line is the process number. The third line has
39534 been split here, in order to fit it on the page.
39538 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
39539 .cindex "&'exiqgrep'&"
39540 .cindex "queue" "grepping"
39541 This utility is a Perl script contributed by Matt Hubbard. It runs
39545 or (in case &*-a*& switch is specified)
39549 to obtain a queue listing, and then greps the output to select messages
39550 that match given criteria. The following selection options are available:
39553 .vitem &*-f*&&~<&'regex'&>
39554 Match the sender address using a case-insensitive search. The field that is
39555 tested is enclosed in angle brackets, so you can test for bounce messages with
39559 .vitem &*-r*&&~<&'regex'&>
39560 Match a recipient address using a case-insensitive search. The field that is
39561 tested is not enclosed in angle brackets.
39563 .vitem &*-s*&&~<&'regex'&>
39564 Match against the size field.
39566 .vitem &*-y*&&~<&'seconds'&>
39567 Match messages that are younger than the given time.
39569 .vitem &*-o*&&~<&'seconds'&>
39570 Match messages that are older than the given time.
39573 Match only frozen messages.
39576 Match only non-frozen messages.
39578 .vitem &*-G*&&~<&'queuename'&>
39579 Match only messages in the given queue. Without this, the default queue is searched.
39582 The following options control the format of the output:
39586 Display only the count of matching messages.
39589 Long format &-- display the full message information as output by Exim. This is
39593 Display message ids only.
39596 Brief format &-- one line per message.
39599 Display messages in reverse order.
39602 Include delivered recipients in queue listing.
39605 The following options give alternates for configuration:
39608 .vitem &*-C*&&~<&'config&~file'&>
39609 is used to specify an alternate &_exim.conf_& which might
39610 contain alternate exim configuration the queue management might be using.
39612 .vitem &*-E*&&~<&'path'&>
39613 can be used to specify a path for the exim binary,
39614 overriding the built-in one.
39617 There is one more option, &%-h%&, which outputs a list of options.
39618 At least one selection option, or either the &*-c*& or &*-h*& option, must be given.
39622 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
39623 .cindex "&'exiqsumm'&"
39624 .cindex "queue" "summary"
39625 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
39626 -bp`& and produces a summary of the messages in the queue. Thus, you use it by
39627 running a command such as
39629 exim -bp | exiqsumm
39631 The output consists of one line for each domain that has messages waiting for
39632 it, as in the following example:
39634 3 2322 74m 66m msn.com.example
39636 Each line lists the number of pending deliveries for a domain, their total
39637 volume, and the length of time that the oldest and the newest messages have
39638 been waiting. Note that the number of pending deliveries is greater than the
39639 number of messages when messages have more than one recipient.
39641 A summary line is output at the end. By default the output is sorted on the
39642 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
39643 the output to be sorted by oldest message and by count of messages,
39644 respectively. There are also three options that split the messages for each
39645 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
39646 separates frozen messages, and &%-s%& separates messages according to their
39649 The output of &'exim -bp'& contains the original addresses in the message, so
39650 this also applies to the output from &'exiqsumm'&. No domains from addresses
39651 generated by aliasing or forwarding are included (unless the &%one_time%&
39652 option of the &(redirect)& router has been used to convert them into &"top
39653 level"& addresses).
39658 .section "Extracting specific information from the log (exigrep)" &&&
39660 .cindex "&'exigrep'&"
39661 .cindex "log" "extracts; grepping for"
39662 The &'exigrep'& utility is a Perl script that searches one or more main log
39663 files for entries that match a given pattern. When it finds a match, it
39664 extracts all the log entries for the relevant message, not just those that
39665 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
39666 given message, or all mail for a given user, or for a given host, for example.
39667 The input files can be in Exim log format or syslog format.
39668 If a matching log line is not associated with a specific message, it is
39669 included in &'exigrep'&'s output without any additional lines. The usage is:
39671 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
39673 If no log filenames are given on the command line, the standard input is read.
39675 The &%-t%& argument specifies a number of seconds. It adds an additional
39676 condition for message selection. Messages that are complete are shown only if
39677 they spent more than <&'n'&> seconds in the queue.
39679 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
39680 makes it case-sensitive. This may give a performance improvement when searching
39681 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
39682 option; with &%-I%& they do not. In both cases it is possible to change the
39683 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
39685 The &%-l%& option means &"literal"&, that is, treat all characters in the
39686 pattern as standing for themselves. Otherwise the pattern must be a Perl
39687 regular expression.
39689 The &%-v%& option inverts the matching condition. That is, a line is selected
39690 if it does &'not'& match the pattern.
39692 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
39693 that are generated as a result/response to a message that &'exigrep'& matched
39697 user_a sends a message to user_b, which generates a bounce back to user_b. If
39698 &'exigrep'& is used to search for &"user_a"&, only the first message will be
39699 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
39700 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
39701 when searching for &"user_a"& will show both messages since the bounce is
39702 &"related"& to or a &"result"& of the first message that was found by the
39705 If the location of a &'zcat'& command is known from the definition of
39706 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
39707 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
39708 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
39709 autodetection of some well known compression extensions.
39712 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
39713 .cindex "&'exipick'&"
39714 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
39715 lists messages from the queue according to a variety of criteria. For details
39716 of &'exipick'&'s facilities, run &'exipick'& with
39717 the &%--help%& option.
39720 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
39721 .cindex "log" "cycling local files"
39722 .cindex "cycling logs"
39723 .cindex "&'exicyclog'&"
39724 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
39725 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
39726 you are using log files with datestamps in their names (see section
39727 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
39728 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
39729 There are two command line options for &'exicyclog'&:
39731 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
39732 default that is set when Exim is built. The default default is 10.
39734 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
39735 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
39736 overriding the script's default, which is to find the setting from Exim's
39740 Each time &'exicyclog'& is run the filenames get &"shuffled down"& by one. If
39741 the main log filename is &_mainlog_& (the default) then when &'exicyclog'& is
39742 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
39743 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
39744 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
39745 logs are handled similarly.
39747 If the limit is greater than 99, the script uses 3-digit numbers such as
39748 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
39749 to one that is greater, or &'vice versa'&, you will have to fix the names of
39750 any existing log files.
39752 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
39753 the end are deleted. All files with numbers greater than 01 are compressed,
39754 using a compression command which is configured by the COMPRESS_COMMAND
39755 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
39756 root &%crontab%& entry of the form
39758 1 0 * * * su exim -c /usr/exim/bin/exicyclog
39760 assuming you have used the name &"exim"& for the Exim user. You can run
39761 &'exicyclog'& as root if you wish, but there is no need.
39765 .section "Mail statistics (eximstats)" "SECTmailstat"
39766 .cindex "statistics"
39767 .cindex "&'eximstats'&"
39768 A Perl script called &'eximstats'& is provided for extracting statistical
39769 information from log files. The output is either plain text, or HTML.
39770 . --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan
39771 . --- 404 error and everything else points to that.
39773 The &'eximstats'& script has been hacked about quite a bit over time. The
39774 latest version is the result of some extensive revision by Steve Campbell. A
39775 lot of information is given by default, but there are options for suppressing
39776 various parts of it. Following any options, the arguments to the script are a
39777 list of files, which should be main log files. For example:
39779 eximstats -nr /var/spool/exim/log/mainlog.01
39781 By default, &'eximstats'& extracts information about the number and volume of
39782 messages received from or delivered to various hosts. The information is sorted
39783 both by message count and by volume, and the top fifty hosts in each category
39784 are listed on the standard output. Similar information, based on email
39785 addresses or domains instead of hosts can be requested by means of various
39786 options. For messages delivered and received locally, similar statistics are
39787 also produced per user.
39789 The output also includes total counts and statistics about delivery errors, and
39790 histograms showing the number of messages received and deliveries made in each
39791 hour of the day. A delivery with more than one address in its envelope (for
39792 example, an SMTP transaction with more than one RCPT command) is counted
39793 as a single delivery by &'eximstats'&.
39795 Though normally more deliveries than receipts are reported (as messages may
39796 have multiple recipients), it is possible for &'eximstats'& to report more
39797 messages received than delivered, even though the queue is empty at the start
39798 and end of the period in question. If an incoming message contains no valid
39799 recipients, no deliveries are recorded for it. A bounce message is handled as
39800 an entirely separate message.
39802 &'eximstats'& always outputs a grand total summary giving the volume and number
39803 of messages received and deliveries made, and the number of hosts involved in
39804 each case. It also outputs the number of messages that were delayed (that is,
39805 not completely delivered at the first attempt), and the number that had at
39806 least one address that failed.
39808 The remainder of the output is in sections that can be independently disabled
39809 or modified by various options. It consists of a summary of deliveries by
39810 transport, histograms of messages received and delivered per time interval
39811 (default per hour), information about the time messages spent in the queue,
39812 a list of relayed messages, lists of the top fifty sending hosts, local
39813 senders, destination hosts, and destination local users by count and by volume,
39814 and a list of delivery errors that occurred.
39816 The relay information lists messages that were actually relayed, that is, they
39817 came from a remote host and were directly delivered to some other remote host,
39818 without being processed (for example, for aliasing or forwarding) locally.
39820 There are quite a few options for &'eximstats'& to control exactly what it
39821 outputs. These are documented in the Perl script itself, and can be extracted
39822 by running the command &(perldoc)& on the script. For example:
39824 perldoc /usr/exim/bin/eximstats
39827 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
39828 .cindex "&'exim_checkaccess'&"
39829 .cindex "policy control" "checking access"
39830 .cindex "checking access"
39831 The &%-bh%& command line argument allows you to run a fake SMTP session with
39832 debugging output, in order to check what Exim is doing when it is applying
39833 policy controls to incoming SMTP mail. However, not everybody is sufficiently
39834 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
39835 sometimes you just want to answer the question &"Does this address have
39836 access?"& without bothering with any further details.
39838 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
39839 two arguments, an IP address and an email address:
39841 exim_checkaccess 10.9.8.7 A.User@a.domain.example
39843 The utility runs a call to Exim with the &%-bh%& option, to test whether the
39844 given email address would be accepted in a RCPT command in a TCP/IP
39845 connection from the host with the given IP address. The output of the utility
39846 is either the word &"accepted"&, or the SMTP error response, for example:
39849 550 Relay not permitted
39851 When running this test, the utility uses &`<>`& as the envelope sender address
39852 for the MAIL command, but you can change this by providing additional
39853 options. These are passed directly to the Exim command. For example, to specify
39854 that the test is to be run with the sender address &'himself@there.example'&
39857 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
39858 -f himself@there.example
39860 Note that these additional Exim command line items must be given after the two
39861 mandatory arguments.
39863 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
39864 while running its checks. You can run checks that include callouts by using
39865 &%-bhc%&, but this is not yet available in a &"packaged"& form.
39869 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
39870 .cindex "DBM" "building dbm files"
39871 .cindex "building DBM files"
39872 .cindex "&'exim_dbmbuild'&"
39873 .cindex "lower casing"
39874 .cindex "binary zero" "in lookup key"
39875 The &'exim_dbmbuild'& program reads an input file containing keys and data in
39876 the format used by the &(lsearch)& lookup (see section
39877 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
39878 names as keys and the remainder of the information as data. The lower-casing
39879 can be prevented by calling the program with the &%-nolc%& option.
39881 A terminating zero is included as part of the key string. This is expected by
39882 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
39883 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
39884 strings or the data strings. The &(dbmnz)& lookup type can be used with such
39887 The program requires two arguments: the name of the input file (which can be a
39888 single hyphen to indicate the standard input), and the name of the output file.
39889 It creates the output under a temporary name, and then renames it if all went
39893 If the native DB interface is in use (USE_DB is set in a compile-time
39894 configuration file &-- this is common in free versions of Unix) the two
39895 filenames must be different, because in this mode the Berkeley DB functions
39896 create a single output file using exactly the name given. For example,
39898 exim_dbmbuild /etc/aliases /etc/aliases.db
39900 reads the system alias file and creates a DBM version of it in
39901 &_/etc/aliases.db_&.
39903 In systems that use the &'ndbm'& routines (mostly proprietary versions of
39904 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
39905 environment, the suffixes are added to the second argument of
39906 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
39907 when the Berkeley functions are used in compatibility mode (though this is not
39908 recommended), because in that case it adds a &_.db_& suffix to the filename.
39910 If a duplicate key is encountered, the program outputs a warning, and when it
39911 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
39912 option is used. By default, only the first of a set of duplicates is used &--
39913 this makes it compatible with &(lsearch)& lookups. There is an option
39914 &%-lastdup%& which causes it to use the data for the last duplicate instead.
39915 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
39916 &%stderr%&. For other errors, where it doesn't actually make a new file, the
39922 .section "Finding individual retry times (exinext)" "SECTfinindret"
39923 .cindex "retry" "times"
39924 .cindex "&'exinext'&"
39925 A utility called &'exinext'& (mostly a Perl script) provides the ability to
39926 fish specific information out of the retry database. Given a mail domain (or a
39927 complete address), it looks up the hosts for that domain, and outputs any retry
39928 information for the hosts or for the domain. At present, the retry information
39929 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
39930 output. For example:
39932 $ exinext piglet@milne.fict.example
39933 kanga.milne.example:192.168.8.1 error 146: Connection refused
39934 first failed: 21-Feb-1996 14:57:34
39935 last tried: 21-Feb-1996 14:57:34
39936 next try at: 21-Feb-1996 15:02:34
39937 roo.milne.example:192.168.8.3 error 146: Connection refused
39938 first failed: 20-Jan-1996 13:12:08
39939 last tried: 21-Feb-1996 11:42:03
39940 next try at: 21-Feb-1996 19:42:03
39941 past final cutoff time
39943 You can also give &'exinext'& a local part, without a domain, and it
39944 will give any retry information for that local part in your default domain.
39945 A message id can be used to obtain retry information pertaining to a specific
39946 message. This exists only when an attempt to deliver a message to a remote host
39947 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
39948 &'exinext'& is not particularly efficient, but then it is not expected to be
39951 The &'exinext'& utility calls Exim to find out information such as the location
39952 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
39953 passed on to the &'exim'& commands. The first specifies an alternate Exim
39954 configuration file, and the second sets macros for use within the configuration
39955 file. These features are mainly to help in testing, but might also be useful in
39956 environments where more than one configuration file is in use.
39960 .section "Hints database maintenance" "SECThindatmai"
39961 .cindex "hints database" "maintenance"
39962 .cindex "maintaining Exim's hints database"
39963 Three utility programs are provided for maintaining the DBM files that Exim
39964 uses to contain its delivery hint information. Each program requires two
39965 arguments. The first specifies the name of Exim's spool directory, and the
39966 second is the name of the database it is to operate on. These are as follows:
39969 &'retry'&: the database of retry information
39971 &'wait-'&<&'transport name'&>: databases of information about messages waiting
39974 &'callout'&: the callout cache
39976 &'ratelimit'&: the data for implementing the ratelimit ACL condition
39978 &'tls'&: TLS session resumption data
39980 &'misc'&: other hints data
39983 The &'misc'& database is used for
39986 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
39988 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
39989 &(smtp)& transport)
39991 Limiting the concurrency of specific transports (when &%max_parallel%& is set
39997 .section "exim_dumpdb" "SECTdumpdb"
39998 .cindex "&'exim_dumpdb'&"
39999 The entire contents of a database are written to the standard output by the
40000 &'exim_dumpdb'& program,
40001 taking as arguments the spool and database names.
40002 An option &'-z'& may be given to request times in UTC;
40003 otherwise times are in the local timezone.
40004 An option &'-k'& may be given to dump only the record keys.
40005 For example, to dump the retry database:
40007 exim_dumpdb /var/spool/exim retry
40009 For the retry database
40010 two lines of output are produced for each entry:
40012 T:mail.ref.example:192.168.242.242 146 77 Connection refused
40013 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
40015 The first item on the first line is the key of the record. It starts with one
40016 of the letters R, or T, depending on whether it refers to a routing or
40017 transport retry. For a local delivery, the next part is the local address; for
40018 a remote delivery it is the name of the remote host, followed by its failing IP
40019 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
40020 transport). If the remote port is not the standard one (port 25), it is added
40021 to the IP address. Then there follows an error code, an additional error code,
40022 and a textual description of the error.
40024 The three times on the second line are the time of first failure, the time of
40025 the last delivery attempt, and the computed time for the next attempt. The line
40026 ends with an asterisk if the cutoff time for the last retry rule has been
40029 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
40030 consists of a host name followed by a list of ids for messages that are or were
40031 waiting to be delivered to that host. If there are a very large number for any
40032 one host, continuation records, with a sequence number added to the host name,
40033 may be seen. The data in these records is often out of date, because a message
40034 may be routed to several alternative hosts, and Exim makes no effort to keep
40039 .section "exim_tidydb" "SECTtidydb"
40040 .cindex "&'exim_tidydb'&"
40041 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
40042 database. If run with no options, it removes all records that are more than 30
40043 days old. The age is calculated from the date and time that the record was last
40044 updated. Note that, in the case of the retry database, it is &'not'& the time
40045 since the first delivery failure. Information about a host that has been down
40046 for more than 30 days will remain in the database, provided that the record is
40047 updated sufficiently often.
40049 The cutoff date can be altered by means of the &%-t%& option, which must be
40050 followed by a time. For example, to remove all records older than a week from
40051 the retry database:
40053 exim_tidydb -t 7d /var/spool/exim retry
40055 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
40056 message ids. In the former these appear as data in records keyed by host &--
40057 they were messages that were waiting for that host &-- and in the latter they
40058 are the keys for retry information for messages that have suffered certain
40059 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
40060 message ids in database records are those of messages that are still on the
40061 queue. Message ids for messages that no longer exist are removed from
40062 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
40063 For the &'retry'& database, records whose keys are non-existent message ids are
40064 removed. The &'exim_tidydb'& utility outputs comments on the standard output
40065 whenever it removes information from the database.
40067 Certain records are automatically removed by Exim when they are no longer
40068 needed, but others are not. For example, if all the MX hosts for a domain are
40069 down, a retry record is created for each one. If the primary MX host comes back
40070 first, its record is removed when Exim successfully delivers to it, but the
40071 records for the others remain because Exim has not tried to use those hosts.
40073 It is important, therefore, to run &'exim_tidydb'& periodically on all the
40074 hints databases. You should do this at a quiet time of day, because it requires
40075 a database to be locked (and therefore inaccessible to Exim) while it does its
40076 work. Removing records from a DBM file does not normally make the file smaller,
40077 but all the common DBM libraries are able to re-use the space that is released.
40078 After an initial phase of increasing in size, the databases normally reach a
40079 point at which they no longer get any bigger, as long as they are regularly
40082 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
40083 databases is likely to keep on increasing.
40088 .section "exim_fixdb" "SECTfixdb"
40089 .cindex "&'exim_fixdb'&"
40090 The &'exim_fixdb'& program is a utility for interactively modifying databases.
40091 Its main use is for testing Exim, but it might also be occasionally useful for
40092 getting round problems in a live system. Its interface
40093 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
40094 key of a database record can then be entered, and the data for that record is
40097 If &"d"& is typed at the next prompt, the entire record is deleted. For all
40098 except the &'retry'& database, that is the only operation that can be carried
40099 out. For the &'retry'& database, each field is output preceded by a number, and
40100 data for individual fields can be changed by typing the field number followed
40101 by new data, for example:
40105 resets the time of the next delivery attempt. Time values are given as a
40106 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
40107 used as optional separators.
40109 Both displayed and input times are in the local timezone by default.
40110 If an option &'-z'& is used on the command line, displayed times
40116 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
40117 .cindex "mailbox" "maintenance"
40118 .cindex "&'exim_lock'&"
40119 .cindex "locking mailboxes"
40120 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
40121 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
40122 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
40123 a user agent while investigating a problem. The utility requires the name of
40124 the file as its first argument. If the locking is successful, the second
40125 argument is run as a command (using C's &[system()]& function); if there is no
40126 second argument, the value of the SHELL environment variable is used; if this
40127 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
40128 is unlocked and the utility ends. The following options are available:
40132 Use &[fcntl()]& locking on the open mailbox.
40135 Use &[flock()]& locking on the open mailbox, provided the operating system
40138 .vitem &%-interval%&
40139 This must be followed by a number, which is a number of seconds; it sets the
40140 interval to sleep between retries (default 3).
40142 .vitem &%-lockfile%&
40143 Create a lock file before opening the mailbox.
40146 Lock the mailbox using MBX rules.
40149 Suppress verification output.
40151 .vitem &%-retries%&
40152 This must be followed by a number; it sets the number of times to try to get
40153 the lock (default 10).
40155 .vitem &%-restore_time%&
40156 This option causes &%exim_lock%& to restore the modified and read times to the
40157 locked file before exiting. This allows you to access a locked mailbox (for
40158 example, to take a backup copy) without disturbing the times that the user
40161 .vitem &%-timeout%&
40162 This must be followed by a number, which is a number of seconds; it sets a
40163 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
40164 default), a non-blocking call is used.
40167 Generate verbose output.
40170 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
40171 default is to create a lock file and also to use &[fcntl()]& locking on the
40172 mailbox, which is the same as Exim's default. The use of &%-flock%& or
40173 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
40174 requires that the directory containing the file be writeable. Locking by lock
40175 file does not last forever; Exim assumes that a lock file is expired if it is
40176 more than 30 minutes old.
40178 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
40179 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
40180 to be taken out on the open mailbox, and an exclusive lock on the file
40181 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
40182 number of the mailbox file. When the locking is released, if an exclusive lock
40183 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
40185 The default output contains verification of the locking that takes place. The
40186 &%-v%& option causes some additional information to be given. The &%-q%& option
40187 suppresses all output except error messages.
40191 exim_lock /var/spool/mail/spqr
40193 runs an interactive shell while the file is locked, whereas
40195 &`exim_lock -q /var/spool/mail/spqr <<End`&
40196 <&'some commands'&>
40199 runs a specific non-interactive sequence of commands while the file is locked,
40200 suppressing all verification output. A single command can be run by a command
40203 exim_lock -q /var/spool/mail/spqr \
40204 "cp /var/spool/mail/spqr /some/where"
40206 Note that if a command is supplied, it must be entirely contained within the
40207 second argument &-- hence the quotes.
40210 .section "Message Ids for humans (exim_msgdate)" "SECTexim_msgdate"
40211 .cindex "exim_msgdate"
40212 The &'exim_msgdate'& utility is written by Andrew Aitchison and included in the Exim distribution.
40213 This Perl script converts an Exim Mesage ID back into a human readable form.
40214 For details of &'exim_msgdate'&'s options, run &'exim_msgdate'& with the &%--help%& option.
40216 Section &<<SECTmessiden>>& (Message identification) describes Exim Mesage IDs.
40218 . ////////////////////////////////////////////////////////////////////////////
40219 . ////////////////////////////////////////////////////////////////////////////
40221 .chapter "The Exim monitor" "CHAPeximon"
40222 .scindex IIDeximon "Exim monitor" "description"
40223 .cindex "X-windows"
40224 .cindex "&'eximon'&"
40225 .cindex "Local/eximon.conf"
40226 .cindex "&_exim_monitor/EDITME_&"
40227 The Exim monitor is an application which displays in an X window information
40228 about the state of Exim's queue and what Exim is doing. An admin user can
40229 perform certain operations on messages from this GUI interface; however all
40230 such facilities are also available from the command line, and indeed, the
40231 monitor itself makes use of the command line to perform any actions requested.
40235 .section "Running the monitor" "SECID264"
40236 The monitor is started by running the script called &'eximon'&. This is a shell
40237 script that sets up a number of environment variables, and then runs the
40238 binary called &_eximon.bin_&. The default appearance of the monitor window can
40239 be changed by editing the &_Local/eximon.conf_& file created by editing
40240 &_exim_monitor/EDITME_&. Comments in that file describe what the various
40241 parameters are for.
40243 The parameters that get built into the &'eximon'& script can be overridden for
40244 a particular invocation by setting up environment variables of the same names,
40245 preceded by &`EXIMON_`&. For example, a shell command such as
40247 EXIMON_LOG_DEPTH=400 eximon
40249 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
40250 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
40251 overrides the Exim log file configuration. This makes it possible to have
40252 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
40253 syslog messages are routed to a file on the local host.
40255 X resources can be used to change the appearance of the window in the normal
40256 way. For example, a resource setting of the form
40258 Eximon*background: gray94
40260 changes the colour of the background to light grey rather than white. The
40261 stripcharts are drawn with both the data lines and the reference lines in
40262 black. This means that the reference lines are not visible when on top of the
40263 data. However, their colour can be changed by setting a resource called
40264 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
40265 For example, if your X server is running Unix, you could set up lighter
40266 reference lines in the stripcharts by obeying
40269 Eximon*highlight: gray
40272 .cindex "admin user"
40273 In order to see the contents of messages in the queue, and to operate on them,
40274 &'eximon'& must either be run as root or by an admin user.
40276 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
40277 contain X11 resource parameters interpreted by the X11 library. In addition,
40278 if the first parameter starts with the string "gdb" then it is removed and the
40279 binary is invoked under gdb (the parameter is used as the gdb command-name, so
40280 versioned variants of gdb can be invoked).
40282 The monitor's window is divided into three parts. The first contains one or
40283 more stripcharts and two action buttons, the second contains a &"tail"& of the
40284 main log file, and the third is a display of the queue of messages awaiting
40285 delivery, with two more action buttons. The following sections describe these
40286 different parts of the display.
40291 .section "The stripcharts" "SECID265"
40292 .cindex "stripchart"
40293 The first stripchart is always a count of messages in the queue. Its name can
40294 be configured by setting QUEUE_STRIPCHART_NAME in the
40295 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
40296 configuration script by regular expression matches on log file entries, making
40297 it possible to display, for example, counts of messages delivered to certain
40298 hosts or using certain transports. The supplied defaults display counts of
40299 received and delivered messages, and of local and SMTP deliveries. The default
40300 period between stripchart updates is one minute; this can be adjusted by a
40301 parameter in the &_Local/eximon.conf_& file.
40303 The stripchart displays rescale themselves automatically as the value they are
40304 displaying changes. There are always 10 horizontal lines in each chart; the
40305 title string indicates the value of each division when it is greater than one.
40306 For example, &"x2"& means that each division represents a value of 2.
40308 It is also possible to have a stripchart which shows the percentage fullness of
40309 a particular disk partition, which is useful when local deliveries are confined
40310 to a single partition.
40312 .cindex "&%statvfs%& function"
40313 This relies on the availability of the &[statvfs()]& function or equivalent in
40314 the operating system. Most, but not all versions of Unix that support Exim have
40315 this. For this particular stripchart, the top of the chart always represents
40316 100%, and the scale is given as &"x10%"&. This chart is configured by setting
40317 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
40318 &_Local/eximon.conf_& file.
40323 .section "Main action buttons" "SECID266"
40324 .cindex "size" "of monitor window"
40325 .cindex "Exim monitor" "window size"
40326 .cindex "window size"
40327 Below the stripcharts there is an action button for quitting the monitor. Next
40328 to this is another button marked &"Size"&. They are placed here so that
40329 shrinking the window to its default minimum size leaves just the queue count
40330 stripchart and these two buttons visible. Pressing the &"Size"& button causes
40331 the window to expand to its maximum size, unless it is already at the maximum,
40332 in which case it is reduced to its minimum.
40334 When expanding to the maximum, if the window cannot be fully seen where it
40335 currently is, it is moved back to where it was the last time it was at full
40336 size. When it is expanding from its minimum size, the old position is
40337 remembered, and next time it is reduced to the minimum it is moved back there.
40339 The idea is that you can keep a reduced window just showing one or two
40340 stripcharts at a convenient place on your screen, easily expand it to show
40341 the full window when required, and just as easily put it back to what it was.
40342 The idea is copied from what the &'twm'& window manager does for its
40343 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
40344 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
40346 Normally, the monitor starts up with the window at its full size, but it can be
40347 built so that it starts up with the window at its smallest size, by setting
40348 START_SMALL=yes in &_Local/eximon.conf_&.
40352 .section "The log display" "SECID267"
40353 .cindex "log" "tail of; in monitor"
40354 The second section of the window is an area in which a display of the tail of
40355 the main log is maintained.
40356 To save space on the screen, the timestamp on each log line is shortened by
40357 removing the date and, if &%log_timezone%& is set, the timezone.
40358 The log tail is not available when the only destination for logging data is
40359 syslog, unless the syslog lines are routed to a local file whose name is passed
40360 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
40362 The log sub-window has a scroll bar at its lefthand side which can be used to
40363 move back to look at earlier text, and the up and down arrow keys also have a
40364 scrolling effect. The amount of log that is kept depends on the setting of
40365 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
40366 to use. When this is full, the earlier 50% of data is discarded &-- this is
40367 much more efficient than throwing it away line by line. The sub-window also has
40368 a horizontal scroll bar for accessing the ends of long log lines. This is the
40369 only means of horizontal scrolling; the right and left arrow keys are not
40370 available. Text can be cut from this part of the window using the mouse in the
40371 normal way. The size of this subwindow is controlled by parameters in the
40372 configuration file &_Local/eximon.conf_&.
40374 Searches of the text in the log window can be carried out by means of the ^R
40375 and ^S keystrokes, which default to a reverse and a forward search,
40376 respectively. The search covers only the text that is displayed in the window.
40377 It cannot go further back up the log.
40379 The point from which the search starts is indicated by a caret marker. This is
40380 normally at the end of the text in the window, but can be positioned explicitly
40381 by pointing and clicking with the left mouse button, and is moved automatically
40382 by a successful search. If new text arrives in the window when it is scrolled
40383 back, the caret remains where it is, but if the window is not scrolled back,
40384 the caret is moved to the end of the new text.
40386 Pressing ^R or ^S pops up a window into which the search text can be typed.
40387 There are buttons for selecting forward or reverse searching, for carrying out
40388 the search, and for cancelling. If the &"Search"& button is pressed, the search
40389 happens and the window remains so that further searches can be done. If the
40390 &"Return"& key is pressed, a single search is done and the window is closed. If
40391 ^C is typed the search is cancelled.
40393 The searching facility is implemented using the facilities of the Athena text
40394 widget. By default this pops up a window containing both &"search"& and
40395 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
40396 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
40397 However, the linkers in BSDI and HP-UX seem unable to handle an externally
40398 provided version of &%TextPop%& when the remaining parts of the text widget
40399 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
40400 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
40401 on these systems, at the expense of having unwanted items in the search popup
40406 .section "The queue display" "SECID268"
40407 .cindex "queue" "display in monitor"
40408 The bottom section of the monitor window contains a list of all messages that
40409 are in the queue, which includes those currently being received or delivered,
40410 as well as those awaiting delivery. The size of this subwindow is controlled by
40411 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
40412 at which it is updated is controlled by another parameter in the same file &--
40413 the default is 5 minutes, since queue scans can be quite expensive. However,
40414 there is an &"Update"& action button just above the display which can be used
40415 to force an update of the queue display at any time.
40417 When a host is down for some time, a lot of pending mail can build up for it,
40418 and this can make it hard to deal with other messages in the queue. To help
40419 with this situation there is a button next to &"Update"& called &"Hide"&. If
40420 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
40421 type anything in here and press &"Return"&, the text is added to a chain of
40422 such texts, and if every undelivered address in a message matches at least one
40423 of the texts, the message is not displayed.
40425 If there is an address that does not match any of the texts, all the addresses
40426 are displayed as normal. The matching happens on the ends of addresses so, for
40427 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
40428 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
40429 has been set up, a button called &"Unhide"& is displayed. If pressed, it
40430 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
40431 a hide request is automatically cancelled after one hour.
40433 While the dialogue box is displayed, you can't press any buttons or do anything
40434 else to the monitor window. For this reason, if you want to cut text from the
40435 queue display to use in the dialogue box, you have to do the cutting before
40436 pressing the &"Hide"& button.
40438 The queue display contains, for each unhidden queued message, the length of
40439 time it has been in the queue, the size of the message, the message id, the
40440 message sender, and the first undelivered recipient, all on one line. If it is
40441 a bounce message, the sender is shown as &"<>"&. If there is more than one
40442 recipient to which the message has not yet been delivered, subsequent ones are
40443 listed on additional lines, up to a maximum configured number, following which
40444 an ellipsis is displayed. Recipients that have already received the message are
40447 .cindex "frozen messages" "display"
40448 If a message is frozen, an asterisk is displayed at the left-hand side.
40450 The queue display has a vertical scroll bar, and can also be scrolled by means
40451 of the arrow keys. Text can be cut from it using the mouse in the normal way.
40452 The text searching facilities, as described above for the log window, are also
40453 available, but the caret is always moved to the end of the text when the queue
40454 display is updated.
40458 .section "The queue menu" "SECID269"
40459 .cindex "queue" "menu in monitor"
40460 If the &%shift%& key is held down and the left button is clicked when the mouse
40461 pointer is over the text for any message, an action menu pops up, and the first
40462 line of the queue display for the message is highlighted. This does not affect
40465 If you want to use some other event for popping up the menu, you can set the
40466 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
40467 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
40468 value set in this parameter is a standard X event description. For example, to
40469 run eximon using &%ctrl%& rather than &%shift%& you could use
40471 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
40473 The title of the menu is the message id, and it contains entries which act as
40477 &'message log'&: The contents of the message log for the message are displayed
40478 in a new text window.
40480 &'headers'&: Information from the spool file that contains the envelope
40481 information and headers is displayed in a new text window. See chapter
40482 &<<CHAPspool>>& for a description of the format of spool files.
40484 &'body'&: The contents of the spool file containing the body of the message are
40485 displayed in a new text window. There is a default limit of 20,000 bytes to the
40486 amount of data displayed. This can be changed by setting the BODY_MAX
40487 option at compile time, or the EXIMON_BODY_MAX option at runtime.
40489 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
40490 delivery of the message. This causes an automatic thaw if the message is
40491 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
40492 a new text window. The delivery is run in a separate process, to avoid holding
40493 up the monitor while the delivery proceeds.
40495 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
40496 that the message be frozen.
40498 .cindex "thawing messages"
40499 .cindex "unfreezing messages"
40500 .cindex "frozen messages" "thawing"
40501 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
40502 that the message be thawed.
40504 .cindex "delivery" "forcing failure"
40505 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
40506 that Exim gives up trying to deliver the message. A bounce message is generated
40507 for any remaining undelivered addresses.
40509 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
40510 that the message be deleted from the system without generating a bounce
40513 &'add recipient'&: A dialog box is displayed into which a recipient address can
40514 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40515 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40516 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40517 causes a call to Exim to be made using the &%-Mar%& option to request that an
40518 additional recipient be added to the message, unless the entry box is empty, in
40519 which case no action is taken.
40521 &'mark delivered'&: A dialog box is displayed into which a recipient address
40522 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40523 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40524 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40525 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
40526 recipient address as already delivered, unless the entry box is empty, in which
40527 case no action is taken.
40529 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
40530 mark all recipient addresses as already delivered.
40532 &'edit sender'&: A dialog box is displayed initialized with the current
40533 sender's address. Pressing RETURN causes a call to Exim to be made using the
40534 &%-Mes%& option to replace the sender address, unless the entry box is empty,
40535 in which case no action is taken. If you want to set an empty sender (as in
40536 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
40537 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
40538 the address is qualified with that domain.
40541 When a delivery is forced, a window showing the &%-v%& output is displayed. In
40542 other cases when a call to Exim is made, if there is any output from Exim (in
40543 particular, if the command fails) a window containing the command and the
40544 output is displayed. Otherwise, the results of the action are normally apparent
40545 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
40546 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
40547 if no output is generated.
40549 The queue display is automatically updated for actions such as freezing and
40550 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
40551 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
40552 force an update of the display after one of these actions.
40554 In any text window that is displayed as result of a menu action, the normal
40555 cut-and-paste facility is available, and searching can be carried out using ^R
40556 and ^S, as described above for the log tail window.
40563 . ////////////////////////////////////////////////////////////////////////////
40564 . ////////////////////////////////////////////////////////////////////////////
40566 .chapter "Security considerations" "CHAPsecurity"
40567 .scindex IIDsecurcon "security" "discussion of"
40568 This chapter discusses a number of issues concerned with security, some of
40569 which are also covered in other parts of this manual.
40571 For reasons that this author does not understand, some people have promoted
40572 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
40573 existence of this chapter in the documentation. However, the intent of the
40574 chapter is simply to describe the way Exim works in relation to certain
40575 security concerns, not to make any specific claims about the effectiveness of
40576 its security as compared with other MTAs.
40578 What follows is a description of the way Exim is supposed to be. Best efforts
40579 have been made to try to ensure that the code agrees with the theory, but an
40580 absence of bugs can never be guaranteed. Any that are reported will get fixed
40581 as soon as possible.
40584 .section "Building a more &""hardened""& Exim" "SECID286"
40585 .cindex "security" "build-time features"
40586 There are a number of build-time options that can be set in &_Local/Makefile_&
40587 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
40588 Exim administrator who does not have the root password, or by someone who has
40589 penetrated the Exim (but not the root) account. These options are as follows:
40592 ALT_CONFIG_PREFIX can be set to a string that is required to match the
40593 start of any filenames used with the &%-C%& option. When it is set, these
40594 filenames are also not allowed to contain the sequence &"/../"&. (However, if
40595 the value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
40596 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
40597 default setting for &%ALT_CONFIG_PREFIX%&.
40599 If the permitted configuration files are confined to a directory to
40600 which only root has access, this guards against someone who has broken
40601 into the Exim account from running a privileged Exim with an arbitrary
40602 configuration file, and using it to break into other accounts.
40605 If a non-trusted configuration file (i.e. not the default configuration file
40606 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
40607 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
40608 the next item), then root privilege is retained only if the caller of Exim is
40609 root. This locks out the possibility of testing a configuration using &%-C%&
40610 right through message reception and delivery, even if the caller is root. The
40611 reception works, but by that time, Exim is running as the Exim user, so when
40612 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
40613 privilege to be lost. However, root can test reception and delivery using two
40617 The WHITELIST_D_MACROS build option declares some macros to be safe to override
40618 with &%-D%& if the real uid is one of root, the Exim run-time user or the
40619 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
40620 requiring the run-time value supplied to &%-D%& to match a regex that errs on
40621 the restrictive side. Requiring build-time selection of safe macros is onerous
40622 but this option is intended solely as a transition mechanism to permit
40623 previously-working configurations to continue to work after release 4.73.
40625 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
40628 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
40629 never to be used for any deliveries. This is like the &%never_users%& runtime
40630 option, but it cannot be overridden; the runtime option adds additional users
40631 to the list. The default setting is &"root"&; this prevents a non-root user who
40632 is permitted to modify the runtime file from using Exim as a way to get root.
40637 .section "Root privilege" "SECID270"
40639 .cindex "root privilege"
40640 The Exim binary is normally setuid to root, which means that it gains root
40641 privilege (runs as root) when it starts execution. In some special cases (for
40642 example, when the daemon is not in use and there are no local deliveries), it
40643 may be possible to run Exim setuid to some user other than root. This is
40644 discussed in the next section. However, in most installations, root privilege
40645 is required for two things:
40648 To set up a socket connected to the standard SMTP port (25) when initialising
40649 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
40652 To be able to change uid and gid in order to read users' &_.forward_& files and
40653 perform local deliveries as the receiving user or as specified in the
40657 It is not necessary to be root to do any of the other things Exim does, such as
40658 receiving messages and delivering them externally over SMTP, and it is
40659 obviously more secure if Exim does not run as root except when necessary.
40660 For this reason, a user and group for Exim to use must be defined in
40661 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
40662 group"&. Their values can be changed by the runtime configuration, though this
40663 is not recommended. Often a user called &'exim'& is used, but some sites use
40664 &'mail'& or another user name altogether.
40666 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
40667 abdication; the process cannot regain root afterwards. Prior to release 4.00,
40668 &[seteuid()]& was used in some circumstances, but this is no longer the case.
40670 After a new Exim process has interpreted its command line options, it changes
40671 uid and gid in the following cases:
40676 If the &%-C%& option is used to specify an alternate configuration file, or if
40677 the &%-D%& option is used to define macro values for the configuration, and the
40678 calling process is not running as root, the uid and gid are changed to those of
40679 the calling process.
40680 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
40681 option may not be used at all.
40682 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
40683 can be supplied if the calling process is running as root, the Exim run-time
40684 user or CONFIGURE_OWNER, if defined.
40689 If the expansion test option (&%-be%&) or one of the filter testing options
40690 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
40693 If the process is not a daemon process or a queue runner process or a delivery
40694 process or a process for testing address routing (started with &%-bt%&), the
40695 uid and gid are changed to the Exim user and group. This means that Exim always
40696 runs under its own uid and gid when receiving messages. This also applies when
40697 testing address verification
40700 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
40703 For a daemon, queue runner, delivery, or address testing process, the uid
40704 remains as root at this stage, but the gid is changed to the Exim group.
40707 The processes that initially retain root privilege behave as follows:
40710 A daemon process changes the gid to the Exim group and the uid to the Exim
40711 user after setting up one or more listening sockets. The &[initgroups()]&
40712 function is called, so that if the Exim user is in any additional groups, they
40713 will be used during message reception.
40715 A queue runner process retains root privilege throughout its execution. Its
40716 job is to fork a controlled sequence of delivery processes.
40718 A delivery process retains root privilege throughout most of its execution,
40719 but any actual deliveries (that is, the transports themselves) are run in
40720 subprocesses which always change to a non-root uid and gid. For local
40721 deliveries this is typically the uid and gid of the owner of the mailbox; for
40722 remote deliveries, the Exim uid and gid are used. Once all the delivery
40723 subprocesses have been run, a delivery process changes to the Exim uid and gid
40724 while doing post-delivery tidying up such as updating the retry database and
40725 generating bounce and warning messages.
40727 While the recipient addresses in a message are being routed, the delivery
40728 process runs as root. However, if a user's filter file has to be processed,
40729 this is done in a subprocess that runs under the individual user's uid and
40730 gid. A system filter is run as root unless &%system_filter_user%& is set.
40732 A process that is testing addresses (the &%-bt%& option) runs as root so that
40733 the routing is done in the same environment as a message delivery.
40739 .section "Running Exim without privilege" "SECTrunexiwitpri"
40740 .cindex "privilege, running without"
40741 .cindex "unprivileged running"
40742 .cindex "root privilege" "running without"
40743 Some installations like to run Exim in an unprivileged state for more of its
40744 operation, for added security. Support for this mode of operation is provided
40745 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
40746 gid are changed to the Exim user and group at the start of a delivery process
40747 (and also queue runner and address testing processes). This means that address
40748 routing is no longer run as root, and the deliveries themselves cannot change
40752 .cindex "daemon" "restarting"
40753 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
40754 that the daemon can still be started in the usual way, and it can respond
40755 correctly to SIGHUP because the re-invocation regains root privilege.
40757 An alternative approach is to make Exim setuid to the Exim user and also setgid
40758 to the Exim group. If you do this, the daemon must be started from a root
40759 process. (Calling Exim from a root process makes it behave in the way it does
40760 when it is setuid root.) However, the daemon cannot restart itself after a
40761 SIGHUP signal because it cannot regain privilege.
40763 It is still useful to set &%deliver_drop_privilege%& in this case, because it
40764 stops Exim from trying to re-invoke itself to do a delivery after a message has
40765 been received. Such a re-invocation is a waste of resources because it has no
40768 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
40769 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
40770 to the Exim user seems a clean approach, but there is one complication:
40772 In this style of operation, Exim is running with the real uid and gid set to
40773 those of the calling process, and the effective uid/gid set to Exim's values.
40774 Ideally, any association with the calling process' uid/gid should be dropped,
40775 that is, the real uid/gid should be reset to the effective values so as to
40776 discard any privileges that the caller may have. While some operating systems
40777 have a function that permits this action for a non-root effective uid, quite a
40778 number of them do not. Because of this lack of standardization, Exim does not
40779 address this problem at this time.
40781 For this reason, the recommended approach for &"mostly unprivileged"& running
40782 is to keep the Exim binary setuid to root, and to set
40783 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
40784 be used in the most straightforward way.
40786 If you configure Exim not to run delivery processes as root, there are a
40787 number of restrictions on what you can do:
40790 You can deliver only as the Exim user/group. You should explicitly use the
40791 &%user%& and &%group%& options to override routers or local transports that
40792 normally deliver as the recipient. This makes sure that configurations that
40793 work in this mode function the same way in normal mode. Any implicit or
40794 explicit specification of another user causes an error.
40796 Use of &_.forward_& files is severely restricted, such that it is usually
40797 not worthwhile to include them in the configuration.
40799 Users who wish to use &_.forward_& would have to make their home directory and
40800 the file itself accessible to the Exim user. Pipe and append-to-file entries,
40801 and their equivalents in Exim filters, cannot be used. While they could be
40802 enabled in the Exim user's name, that would be insecure and not very useful.
40804 Unless the local user mailboxes are all owned by the Exim user (possible in
40805 some POP3 or IMAP-only environments):
40808 They must be owned by the Exim group and be writeable by that group. This
40809 implies you must set &%mode%& in the appendfile configuration, as well as the
40810 mode of the mailbox files themselves.
40812 You must set &%no_check_owner%&, since most or all of the files will not be
40813 owned by the Exim user.
40815 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
40816 on a newly created mailbox when unprivileged. This also implies that new
40817 mailboxes need to be created manually.
40822 These restrictions severely restrict what can be done in local deliveries.
40823 However, there are no restrictions on remote deliveries. If you are running a
40824 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
40825 gives more security at essentially no cost.
40827 If you are using the &%mua_wrapper%& facility (see chapter
40828 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
40833 .section "Delivering to local files" "SECID271"
40834 Full details of the checks applied by &(appendfile)& before it writes to a file
40835 are given in chapter &<<CHAPappendfile>>&.
40839 .section "Running local commands" "SECTsecconslocalcmds"
40840 .cindex "security" "local commands"
40841 .cindex "security" "command injection attacks"
40842 There are a number of ways in which an administrator can configure Exim to run
40843 commands based upon received, untrustworthy, data. Further, in some
40844 configurations a user who can control a &_.forward_& file can also arrange to
40845 run commands. Configuration to check includes, but is not limited to:
40848 Use of &%use_shell%& in the pipe transport: various forms of shell command
40849 injection may be possible with this option present. It is dangerous and should
40850 be used only with considerable caution. Consider constraints which whitelist
40851 allowed characters in a variable which is to be used in a pipe transport that
40852 has &%use_shell%& enabled.
40854 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
40855 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
40856 &_.forward_& files in a redirect router. If Exim is running on a central mail
40857 hub to which ordinary users do not have shell access, but home directories are
40858 NFS mounted (for instance) then administrators should review the list of these
40859 forbid options available, and should bear in mind that the options that may
40860 need forbidding can change as new features are added between releases.
40862 The &%${run...}%& expansion item does not use a shell by default, but
40863 administrators can configure use of &_/bin/sh_& as part of the command.
40864 Such invocations should be viewed with prejudicial suspicion.
40866 Administrators who use embedded Perl are advised to explore how Perl's
40867 taint checking might apply to their usage.
40869 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
40870 administrators are well advised to view its use with suspicion, in case (for
40871 instance) it allows a local-part to contain embedded Exim directives.
40873 Use of &%${match_local_part...}%& and friends becomes more dangerous if
40874 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
40875 each can reference arbitrary lists and files, rather than just being a list
40877 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
40878 real-world security vulnerabilities caused by its use with untrustworthy data
40879 injected in, for SQL injection attacks.
40880 Consider the use of the &%inlisti%& expansion condition instead.
40886 .section "Trust in configuration data" "SECTsecconfdata"
40887 .cindex "security" "data sources"
40888 .cindex "security" "regular expressions"
40889 .cindex "regular expressions" "security"
40890 .cindex "PCRE2" "security"
40891 If configuration data for Exim can come from untrustworthy sources, there
40892 are some issues to be aware of:
40895 Use of &%${expand...}%& may provide a path for shell injection attacks.
40897 Letting untrusted data provide a regular expression is unwise.
40899 Using &%${match...}%& to apply a fixed regular expression against untrusted
40900 data may result in pathological behaviour within PCRE2. Be aware of what
40901 "backtracking" means and consider options for being more strict with a regular
40902 expression. Avenues to explore include limiting what can match (avoiding &`.`&
40903 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
40904 possessive quantifiers or just not using regular expressions against untrusted
40907 It can be important to correctly use &%${quote:...}%&,
40908 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
40909 items to ensure that data is correctly constructed.
40911 Some lookups might return multiple results, even though normal usage is only
40912 expected to yield one result.
40918 .section "IPv4 source routing" "SECID272"
40919 .cindex "source routing" "in IP packets"
40920 .cindex "IP source routing"
40921 Many operating systems suppress IP source-routed packets in the kernel, but
40922 some cannot be made to do this, so Exim does its own check. It logs incoming
40923 IPv4 source-routed TCP calls, and then drops them. Things are all different in
40924 IPv6. No special checking is currently done.
40928 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
40929 Support for these SMTP commands is disabled by default. If required, they can
40930 be enabled by defining suitable ACLs.
40935 .section "Privileged users" "SECID274"
40936 .cindex "trusted users"
40937 .cindex "admin user"
40938 .cindex "privileged user"
40939 .cindex "user" "trusted"
40940 .cindex "user" "admin"
40941 Exim recognizes two sets of users with special privileges. Trusted users are
40942 able to submit new messages to Exim locally, but supply their own sender
40943 addresses and information about a sending host. For other users submitting
40944 local messages, Exim sets up the sender address from the uid, and doesn't
40945 permit a remote host to be specified.
40948 However, an untrusted user is permitted to use the &%-f%& command line option
40949 in the special form &%-f <>%& to indicate that a delivery failure for the
40950 message should not cause an error report. This affects the message's envelope,
40951 but it does not affect the &'Sender:'& header. Untrusted users may also be
40952 permitted to use specific forms of address with the &%-f%& option by setting
40953 the &%untrusted_set_sender%& option.
40955 Trusted users are used to run processes that receive mail messages from some
40956 other mail domain and pass them on to Exim for delivery either locally, or over
40957 the Internet. Exim trusts a caller that is running as root, as the Exim user,
40958 as any user listed in the &%trusted_users%& configuration option, or under any
40959 group listed in the &%trusted_groups%& option.
40961 Admin users are permitted to do things to the messages on Exim's queue. They
40962 can freeze or thaw messages, cause them to be returned to their senders, remove
40963 them entirely, or modify them in various ways. In addition, admin users can run
40964 the Exim monitor and see all the information it is capable of providing, which
40965 includes the contents of files on the spool.
40969 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
40970 delivery of messages on its queue is restricted to admin users. This
40971 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
40972 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
40973 queue is also restricted to admin users. This restriction can be relaxed by
40974 setting &%no_queue_list_requires_admin%&.
40976 Exim recognizes an admin user if the calling process is running as root or as
40977 the Exim user or if any of the groups associated with the calling process is
40978 the Exim group. It is not necessary actually to be running under the Exim
40979 group. However, if admin users who are not root or the Exim user are to access
40980 the contents of files on the spool via the Exim monitor (which runs
40981 unprivileged), Exim must be built to allow group read access to its spool
40984 By default, regular users are trusted to perform basic testing and
40985 introspection commands, as themselves. This setting can be tightened by
40986 setting the &%commandline_checks_require_admin%& option.
40987 This affects most of the checking options,
40988 such as &%-be%& and anything else &%-b*%&.
40991 .section "Spool files" "SECID275"
40992 .cindex "spool directory" "files"
40993 Exim's spool directory and everything it contains is owned by the Exim user and
40994 set to the Exim group. The mode for spool files is defined in the
40995 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
40996 any user who is a member of the Exim group can access these files.
41000 .section "Use of argv[0]" "SECID276"
41001 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
41002 of specific strings, Exim assumes certain options. For example, calling Exim
41003 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
41004 to calling it with the option &%-bS%&. There are no security implications in
41009 .section "Use of %f formatting" "SECID277"
41010 The only use made of &"%f"& by Exim is in formatting load average values. These
41011 are actually stored in integer variables as 1000 times the load average.
41012 Consequently, their range is limited and so therefore is the length of the
41017 .section "Embedded Exim path" "SECID278"
41018 Exim uses its own path name, which is embedded in the code, only when it needs
41019 to re-exec in order to regain root privilege. Therefore, it is not root when it
41020 does so. If some bug allowed the path to get overwritten, it would lead to an
41021 arbitrary program's being run as exim, not as root.
41025 .section "Dynamic module directory" "SECTdynmoddir"
41026 Any dynamically loadable modules must be installed into the directory
41027 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
41031 .section "Use of sprintf()" "SECID279"
41032 .cindex "&[sprintf()]&"
41033 A large number of occurrences of &"sprintf"& in the code are actually calls to
41034 &'string_sprintf()'&, a function that returns the result in malloc'd store.
41035 The intermediate formatting is done into a large fixed buffer by a function
41036 that runs through the format string itself, and checks the length of each
41037 conversion before performing it, thus preventing buffer overruns.
41039 The remaining uses of &[sprintf()]& happen in controlled circumstances where
41040 the output buffer is known to be sufficiently long to contain the converted
41045 .section "Use of debug_printf() and log_write()" "SECID280"
41046 Arbitrary strings are passed to both these functions, but they do their
41047 formatting by calling the function &'string_vformat()'&, which runs through
41048 the format string itself, and checks the length of each conversion.
41052 .section "Use of strcat() and strcpy()" "SECID281"
41053 These are used only in cases where the output buffer is known to be large
41054 enough to hold the result.
41055 .ecindex IIDsecurcon
41060 . ////////////////////////////////////////////////////////////////////////////
41061 . ////////////////////////////////////////////////////////////////////////////
41063 .chapter "Format of spool files" "CHAPspool"
41064 .scindex IIDforspo1 "format" "spool files"
41065 .scindex IIDforspo2 "spool directory" "format of files"
41066 .scindex IIDforspo3 "spool files" "format of"
41067 .cindex "spool files" "editing"
41068 A message on Exim's queue consists of two files, whose names are the message id
41069 followed by -D and -H, respectively. The data portion of the message is kept in
41070 the -D file on its own. The message's envelope, status, and headers are all
41071 kept in the -H file, whose format is described in this chapter. Each of these
41072 two files contains the final component of its own name as its first line. This
41073 is insurance against disk crashes where the directory is lost but the files
41074 themselves are recoverable.
41076 The file formats may be changed, or new formats added, at any release.
41077 Spool files are not intended as an interface to other programs
41078 and should not be used as such.
41080 Some people are tempted into editing -D files in order to modify messages. You
41081 need to be extremely careful if you do this; it is not recommended and you are
41082 on your own if you do it. Here are some of the pitfalls:
41085 You must ensure that Exim does not try to deliver the message while you are
41086 fiddling with it. The safest way is to take out a write lock on the -D file,
41087 which is what Exim itself does, using &[fcntl()]&. If you update the file in
41088 place, the lock will be retained. If you write a new file and rename it, the
41089 lock will be lost at the instant of rename.
41091 .vindex "&$body_linecount$&"
41092 If you change the number of lines in the file, the value of
41093 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
41094 cause incomplete transmission of messages or undeliverable messages.
41096 If the message is in MIME format, you must take care not to break it.
41098 If the message is cryptographically signed, any change will invalidate the
41101 All in all, modifying -D files is fraught with danger.
41103 Files whose names end with -J may also be seen in the &_input_& directory (or
41104 its subdirectories when &%split_spool_directory%& is set). These are journal
41105 files, used to record addresses to which the message has been delivered during
41106 the course of a delivery attempt. If there are still undelivered recipients at
41107 the end, the -H file is updated, and the -J file is deleted. If, however, there
41108 is some kind of crash (for example, a power outage) before this happens, the -J
41109 file remains in existence. When Exim next processes the message, it notices the
41110 -J file and uses it to update the -H file before starting the next delivery
41113 Files whose names end with -K or .eml may also be seen in the spool.
41114 These are temporaries used for DKIM or malware processing, when that is used.
41115 They should be tidied up by normal operations; any old ones are probably
41116 relics of crashes and can be removed.
41118 .section "Format of the -H file" "SECID282"
41119 .cindex "uid (user id)" "in spool file"
41120 .cindex "gid (group id)" "in spool file"
41121 The second line of the -H file contains the login name for the uid of the
41122 process that called Exim to read the message, followed by the numerical uid and
41123 gid. For a locally generated message, this is normally the user who sent the
41124 message. For a message received over TCP/IP via the daemon, it is
41125 normally the Exim user.
41127 The third line of the file contains the address of the message's sender as
41128 transmitted in the envelope, contained in angle brackets. The sender address is
41129 empty for bounce messages. For incoming SMTP mail, the sender address is given
41130 in the MAIL command. For locally generated mail, the sender address is
41131 created by Exim from the login name of the current user and the configured
41132 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
41133 leading &"From&~"& line if the caller is trusted, or if the supplied address is
41134 &"<>"& or an address that matches &%untrusted_set_senders%&.
41136 The fourth line contains two numbers. The first is the time that the message
41137 was received, in the conventional Unix form &-- the number of seconds since the
41138 start of the epoch. The second number is a count of the number of messages
41139 warning of delayed delivery that have been sent to the sender.
41141 There follow a number of lines starting with a hyphen.
41142 These contain variables, can appear in any
41143 order, and are omitted when not relevant.
41145 If there is a second hyphen after the first,
41146 the corresponding data is tainted.
41147 If there is a value in parentheses, the data is quoted for a lookup.
41149 The following word specifies a variable,
41150 and the remainder of the item depends on the variable.
41153 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
41154 This item is obsolete, and is not generated from Exim release 4.61 onwards;
41155 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
41156 recognized, to provide backward compatibility. In the old format, a line of
41157 this form is present for every ACL variable that is not empty. The number
41158 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
41159 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
41160 the data string for the variable. The string itself starts at the beginning of
41161 the next line, and is followed by a newline character. It may contain internal
41164 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
41165 A line of this form is present for every ACL connection variable that is
41166 defined. Note that there is a space between &%-aclc%& and the rest of the name.
41167 The length is the length of the data string for the variable. The string itself
41168 starts at the beginning of the next line, and is followed by a newline
41169 character. It may contain internal newlines.
41171 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
41172 A line of this form is present for every ACL message variable that is defined.
41173 Note that there is a space between &%-aclm%& and the rest of the name. The
41174 length is the length of the data string for the variable. The string itself
41175 starts at the beginning of the next line, and is followed by a newline
41176 character. It may contain internal newlines.
41178 .vitem "&%-active_hostname%&&~<&'hostname'&>"
41179 This is present if, when the message was received over SMTP, the value of
41180 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
41182 .vitem &%-allow_unqualified_recipient%&
41183 This is present if unqualified recipient addresses are permitted in header
41184 lines (to stop such addresses from being qualified if rewriting occurs at
41185 transport time). Local messages that were input using &%-bnq%& and remote
41186 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
41188 .vitem &%-allow_unqualified_sender%&
41189 This is present if unqualified sender addresses are permitted in header lines
41190 (to stop such addresses from being qualified if rewriting occurs at transport
41191 time). Local messages that were input using &%-bnq%& and remote messages from
41192 hosts that match &%sender_unqualified_hosts%& set this flag.
41194 .vitem "&%-auth_id%&&~<&'text'&>"
41195 The id information for a message received on an authenticated SMTP connection
41196 &-- the value of the &$authenticated_id$& variable.
41198 .vitem "&%-auth_sender%&&~<&'address'&>"
41199 The address of an authenticated sender &-- the value of the
41200 &$authenticated_sender$& variable.
41202 .vitem "&%-body_linecount%&&~<&'number'&>"
41203 This records the number of lines in the body of the message, and is
41204 present unless &%-spool_file_wireformat%& is.
41206 .vitem "&%-body_zerocount%&&~<&'number'&>"
41207 This records the number of binary zero bytes in the body of the message, and is
41208 present if the number is greater than zero.
41210 .vitem &%-deliver_firsttime%&
41211 This is written when a new message is first added to the spool. When the spool
41212 file is updated after a deferral, it is omitted.
41214 .vitem "&%-frozen%&&~<&'time'&>"
41215 .cindex "frozen messages" "spool data"
41216 The message is frozen, and the freezing happened at <&'time'&>.
41218 .vitem "&%-helo_name%&&~<&'text'&>"
41219 This records the host name as specified by a remote host in a HELO or EHLO
41222 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
41223 This records the IP address of the host from which the message was received and
41224 the remote port number that was used. It is omitted for locally generated
41227 .vitem "&%-host_auth%&&~<&'text'&>"
41228 If the message was received on an authenticated SMTP connection, this records
41229 the name of the authenticator &-- the value of the
41230 &$sender_host_authenticated$& variable.
41232 .vitem &%-host_lookup_failed%&
41233 This is present if an attempt to look up the sending host's name from its IP
41234 address failed. It corresponds to the &$host_lookup_failed$& variable.
41236 .vitem "&%-host_name%&&~<&'text'&>"
41237 .cindex "reverse DNS lookup"
41238 .cindex "DNS" "reverse lookup"
41239 This records the name of the remote host from which the message was received,
41240 if the host name was looked up from the IP address when the message was being
41241 received. It is not present if no reverse lookup was done.
41243 .vitem "&%-ident%&&~<&'text'&>"
41244 For locally submitted messages, this records the login of the originating user,
41245 unless it was a trusted user and the &%-oMt%& option was used to specify an
41246 ident value. For messages received over TCP/IP, this records the ident string
41247 supplied by the remote host, if any.
41249 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
41250 This records the IP address of the local interface and the port number through
41251 which a message was received from a remote host. It is omitted for locally
41252 generated messages.
41255 The message is from a local sender.
41257 .vitem &%-localerror%&
41258 The message is a locally-generated bounce message.
41260 .vitem "&%-local_scan%&&~<&'string'&>"
41261 This records the data string that was returned by the &[local_scan()]& function
41262 when the message was received &-- the value of the &$local_scan_data$&
41263 variable. It is omitted if no data was returned.
41265 .vitem &%-manual_thaw%&
41266 The message was frozen but has been thawed manually, that is, by an explicit
41267 Exim command rather than via the auto-thaw process.
41270 A testing delivery process was started using the &%-N%& option to suppress any
41271 actual deliveries, but delivery was deferred. At any further delivery attempts,
41274 .vitem &%-received_protocol%&
41275 This records the value of the &$received_protocol$& variable, which contains
41276 the name of the protocol by which the message was received.
41278 .vitem &%-sender_set_untrusted%&
41279 The envelope sender of this message was set by an untrusted local caller (used
41280 to ensure that the caller is displayed in queue listings).
41282 .vitem "&%-spam_score_int%&&~<&'number'&>"
41283 If a message was scanned by SpamAssassin, this is present. It records the value
41284 of &$spam_score_int$&.
41286 .vitem &%-spool_file_wireformat%&
41287 The -D file for this message is in wire-format (for ESMTP CHUNKING)
41288 rather than Unix-format.
41289 The line-ending is CRLF rather than newline.
41290 There is still, however, no leading-dot-stuffing.
41292 .vitem &%-tls_certificate_verified%&
41293 A TLS certificate was received from the client that sent this message, and the
41294 certificate was verified by the server.
41296 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
41297 When the message was received over an encrypted connection, this records the
41298 name of the cipher suite that was used.
41300 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
41301 When the message was received over an encrypted connection, and a certificate
41302 was received from the client, this records the Distinguished Name from that
41306 Following the options there is a list of those addresses to which the message
41307 is not to be delivered. This set of addresses is initialized from the command
41308 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
41309 is set; otherwise it starts out empty. Whenever a successful delivery is made,
41310 the address is added to this set. The addresses are kept internally as a
41311 balanced binary tree, and it is a representation of that tree which is written
41312 to the spool file. If an address is expanded via an alias or forward file, the
41313 original address is added to the tree when deliveries to all its child
41314 addresses are complete.
41316 If the tree is empty, there is a single line in the spool file containing just
41317 the text &"XX"&. Otherwise, each line consists of two letters, which are either
41318 Y or N, followed by an address. The address is the value for the node of the
41319 tree, and the letters indicate whether the node has a left branch and/or a
41320 right branch attached to it, respectively. If branches exist, they immediately
41321 follow. Here is an example of a three-node tree:
41323 YY darcy@austen.fict.example
41324 NN alice@wonderland.fict.example
41325 NN editor@thesaurus.ref.example
41327 After the non-recipients tree, there is a list of the message's recipients.
41328 This is a simple list, preceded by a count. It includes all the original
41329 recipients of the message, including those to whom the message has already been
41330 delivered. In the simplest case, the list contains one address per line. For
41334 editor@thesaurus.ref.example
41335 darcy@austen.fict.example
41337 alice@wonderland.fict.example
41339 However, when a child address has been added to the top-level addresses as a
41340 result of the use of the &%one_time%& option on a &(redirect)& router, each
41341 line is of the following form:
41343 <&'top-level address'&> <&'errors_to address'&> &&&
41344 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
41346 The 01 flag bit indicates the presence of the three other fields that follow
41347 the top-level address. Other bits may be used in future to support additional
41348 fields. The <&'parent number'&> is the offset in the recipients list of the
41349 original parent of the &"one time"& address. The first two fields are the
41350 envelope sender that is associated with this address and its length. If the
41351 length is zero, there is no special envelope sender (there are then two space
41352 characters in the line). A non-empty field can arise from a &(redirect)& router
41353 that has an &%errors_to%& setting.
41356 A blank line separates the envelope and status information from the headers
41357 which follow. A header may occupy several lines of the file, and to save effort
41358 when reading it in, each header is preceded by a number and an identifying
41359 character. The number is the number of characters in the header, including any
41360 embedded newlines and the terminating newline. The character is one of the
41364 .row <&'blank'&> "header in which Exim has no special interest"
41365 .row &`B`& "&'Bcc:'& header"
41366 .row &`C`& "&'Cc:'& header"
41367 .row &`F`& "&'From:'& header"
41368 .row &`I`& "&'Message-id:'& header"
41369 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
41370 .row &`R`& "&'Reply-To:'& header"
41371 .row &`S`& "&'Sender:'& header"
41372 .row &`T`& "&'To:'& header"
41373 .row &`*`& "replaced or deleted header"
41376 Deleted or replaced (rewritten) headers remain in the spool file for debugging
41377 purposes. They are not transmitted when the message is delivered. Here is a
41378 typical set of headers:
41380 111P Received: by hobbit.fict.example with local (Exim 4.00)
41381 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
41382 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
41383 038* X-rewrote-sender: bb@hobbit.fict.example
41384 042* From: Bilbo Baggins <bb@hobbit.fict.example>
41385 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
41386 099* To: alice@wonderland.fict.example, rdo@foundation,
41387 darcy@austen.fict.example, editor@thesaurus.ref.example
41388 104T To: alice@wonderland.fict.example, rdo@foundation.example,
41389 darcy@austen.fict.example, editor@thesaurus.ref.example
41390 038 Date: Fri, 11 May 2001 10:28:59 +0100
41392 The asterisked headers indicate that the envelope sender, &'From:'& header, and
41393 &'To:'& header have been rewritten, the last one because routing expanded the
41394 unqualified domain &'foundation'&.
41395 .ecindex IIDforspo1
41396 .ecindex IIDforspo2
41397 .ecindex IIDforspo3
41399 .section "Format of the -D file" "SECID282a"
41400 The data file is traditionally in Unix-standard format: lines are ended with
41401 an ASCII newline character.
41402 However, when the &%spool_wireformat%& main option is used some -D files
41403 can have an alternate format.
41404 This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
41405 The -D file lines (not including the first name-component line) are
41406 suitable for direct copying to the wire when transmitting using the
41407 ESMTP CHUNKING option, meaning lower processing overhead.
41408 Lines are terminated with an ASCII CRLF pair.
41409 There is no dot-stuffing (and no dot-termination).
41411 . ////////////////////////////////////////////////////////////////////////////
41412 . ////////////////////////////////////////////////////////////////////////////
41414 .chapter "DKIM, SPF, SRS and DMARC" "CHAPdkim" &&&
41415 "DKIM, SPF, SRS and DMARC Support"
41417 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
41420 DKIM is a mechanism by which messages sent by some entity can be provably
41421 linked to a domain which that entity controls. It permits reputation to
41422 be tracked on a per-domain basis, rather than merely upon source IP address.
41423 DKIM is documented in RFC 6376.
41425 As DKIM relies on the message being unchanged in transit, messages handled
41426 by a mailing-list (which traditionally adds to the message) will not match
41427 any original DKIM signature.
41429 DKIM support is compiled into Exim by default if TLS support is present.
41430 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
41432 Exim's DKIM implementation allows for
41434 Signing outgoing messages: This function is implemented in the SMTP transport.
41435 It can co-exist with all other Exim features
41436 (including transport filters)
41437 except cutthrough delivery.
41439 Verifying signatures in incoming messages: This is implemented by an additional
41440 ACL (acl_smtp_dkim), which can be called several times per message, with
41441 different signature contexts.
41444 In typical Exim style, the verification implementation does not include any
41445 default "policy". Instead it enables you to build your own policy using
41446 Exim's standard controls.
41448 Please note that verification of DKIM signatures in incoming mail is turned
41449 on by default for logging (in the <= line) purposes.
41451 Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
41452 When set, for each signature in incoming email,
41453 exim will log a line displaying the most important signature details, and the
41454 signature status. Here is an example (with line-breaks added for clarity):
41456 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
41457 d=facebookmail.com s=q1-2009b
41458 c=relaxed/relaxed a=rsa-sha1
41459 i=@facebookmail.com t=1252484542 [verification succeeded]
41462 You might want to turn off DKIM verification processing entirely for internal
41463 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
41464 control modifier. This should typically be done in the RCPT ACL, at points
41465 where you accept mail from relay sources (internal hosts or authenticated
41469 .subsection "Signing outgoing messages" SECDKIMSIGN
41470 .cindex DKIM signing
41472 For signing to be usable you must have published a DKIM record in DNS.
41473 Note that RFC 8301 (which does not cover EC keys) says:
41475 rsa-sha1 MUST NOT be used for signing or verifying.
41477 Signers MUST use RSA keys of at least 1024 bits for all keys.
41478 Signers SHOULD use RSA keys of at least 2048 bits.
41481 Note also that the key content (the 'p=' field)
41482 in the DNS record is different between RSA and EC keys;
41483 for the former it is the base64 of the ASN.1 for the RSA public key
41484 (equivalent to the private-key .pem with the header/trailer stripped)
41485 but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
41487 Signing is enabled by setting private options on the SMTP transport.
41488 These options take (expandable) strings as arguments.
41490 .option dkim_domain smtp "string list&!!" unset
41491 The domain(s) you want to sign with.
41492 After expansion, this can be a list.
41493 Each element in turn,
41495 .vindex "&$dkim_domain$&"
41496 is put into the &%$dkim_domain%& expansion variable
41497 while expanding the remaining signing options.
41498 If it is empty after expansion, DKIM signing is not done,
41499 and no error will result even if &%dkim_strict%& is set.
41501 .option dkim_selector smtp "string list&!!" unset
41502 This sets the key selector string.
41503 After expansion, which can use &$dkim_domain$&, this can be a list.
41504 Each element in turn is put in the expansion
41505 .vindex "&$dkim_selector$&"
41506 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
41507 option along with &%$dkim_domain%&.
41508 If the option is empty after expansion, DKIM signing is not done for this domain,
41509 and no error will result even if &%dkim_strict%& is set.
41511 To do, for example, dual-signing with RSA and EC keys
41512 this could be be used:
41514 dkim_selector = ec_sel : rsa_sel
41515 dkim_private_key = KEYS_DIR/$dkim_selector
41518 .option dkim_private_key smtp string&!! unset
41519 This sets the private key to use.
41520 You can use the &%$dkim_domain%& and
41521 &%$dkim_selector%& expansion variables to determine the private key to use.
41522 The result can either
41524 be a valid RSA private key in ASCII armor (.pem file), including line breaks
41526 with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41527 be a valid Ed25519 private key (same format as above)
41529 start with a slash, in which case it is treated as a file that contains
41532 be "0", "false" or the empty string, in which case the message will not
41533 be signed. This case will not result in an error, even if &%dkim_strict%&
41537 To generate keys under OpenSSL:
41539 openssl genrsa -out dkim_rsa.private 2048
41540 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
41542 The result file from the first command should be retained, and
41543 this option set to use it.
41544 Take the base-64 lines from the output of the second command, concatenated,
41545 for the DNS TXT record.
41546 See section 3.6 of RFC6376 for the record specification.
41550 certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
41551 certtool --load-privkey=dkim_rsa.private --pubkey-info
41554 Note that RFC 8301 says:
41556 Signers MUST use RSA keys of at least 1024 bits for all keys.
41557 Signers SHOULD use RSA keys of at least 2048 bits.
41560 EC keys for DKIM are defined by RFC 8463.
41561 They are considerably smaller than RSA keys for equivalent protection.
41562 As they are a recent development, users should consider dual-signing
41563 (by setting a list of selectors, and an expansion for this option)
41564 for some transition period.
41565 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41568 OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
41570 openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
41571 certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
41574 To produce the required public key value for a DNS record:
41576 openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
41577 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
41580 Exim also supports an alternate format
41581 of Ed25519 keys in DNS which was a candidate during development
41582 of the standard, but not adopted.
41583 A future release will probably drop that support.
41585 .option dkim_hash smtp string&!! sha256
41586 Can be set to any one of the supported hash methods, which are:
41588 &`sha1`& &-- should not be used, is old and insecure
41590 &`sha256`& &-- the default
41592 &`sha512`& &-- possibly more secure but less well supported
41595 Note that RFC 8301 says:
41597 rsa-sha1 MUST NOT be used for signing or verifying.
41600 .option dkim_identity smtp string&!! unset
41601 If set after expansion, the value is used to set an "i=" tag in
41602 the signing header. The DKIM standards restrict the permissible
41603 syntax of this optional tag to a mail address, with possibly-empty
41604 local part, an @, and a domain identical to or subdomain of the "d="
41605 tag value. Note that Exim does not check the value.
41607 .option dkim_canon smtp string&!! unset
41608 This option sets the canonicalization method used when signing a message.
41609 The DKIM RFC currently supports two methods: "simple" and "relaxed".
41610 The option defaults to "relaxed" when unset. Note: the current implementation
41611 only supports signing with the same canonicalization method for both headers and body.
41613 .option dkim_strict smtp string&!! unset
41614 This option defines how Exim behaves when signing a message that
41615 should be signed fails for some reason. When the expansion evaluates to
41616 either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message
41617 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
41620 .option dkim_sign_headers smtp string&!! "see below"
41621 If set, this option must expand to a colon-separated
41622 list of header names.
41623 Headers with these names, or the absence or such a header, will be included
41624 in the message signature.
41625 When unspecified, the header names listed in RFC4871 will be used,
41626 whether or not each header is present in the message.
41627 The default list is available for the expansion in the macro
41628 &"_DKIM_SIGN_HEADERS"&
41629 and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
41631 If a name is repeated, multiple headers by that name (or the absence thereof)
41632 will be signed. The textually later headers in the headers part of the
41633 message are signed first, if there are multiples.
41635 A name can be prefixed with either an &"="& or a &"+"& character.
41636 If an &"="& prefix is used, all headers that are present with this name
41638 If a &"+"& prefix if used, all headers that are present with this name
41639 will be signed, and one signature added for a missing header with the
41640 name will be appended.
41642 .option dkim_timestamps smtp integer&!! unset
41643 This option controls the inclusion of timestamp information in the signature.
41644 If not set, no such information will be included.
41645 Otherwise, must be an unsigned number giving an offset in seconds from the current time
41647 (eg. 1209600 for two weeks);
41648 both creation (t=) and expiry (x=) tags will be included.
41650 RFC 6376 lists these tags as RECOMMENDED.
41653 .subsection "Verifying DKIM signatures in incoming mail" SECDKIMVFY
41654 .cindex DKIM verification
41656 Verification of DKIM signatures in SMTP incoming email is done for all
41657 messages for which an ACL control &%dkim_disable_verify%& has not been set.
41658 .cindex DKIM "selecting signature algorithms"
41659 Individual classes of signature algorithm can be ignored by changing
41660 the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
41661 The &%dkim_verify_minimal%& option can be set to cease verification
41662 processing for a message once the first passing signature is found.
41664 .cindex authentication "expansion item"
41665 Performing verification sets up information used by the
41666 &%authresults%& expansion item.
41668 For most purposes the default option settings suffice and the remainder
41669 of this section can be ignored.
41671 The results of verification are made available to the
41672 &%acl_smtp_dkim%& ACL, which can examine and modify them.
41673 A missing ACL definition defaults to accept.
41674 By default, the ACL is called once for each
41675 syntactically(!) correct signature in the incoming message.
41676 If any ACL call does not accept, the message is not accepted.
41677 If a cutthrough delivery was in progress for the message, that is
41678 summarily dropped (having wasted the transmission effort).
41680 To evaluate the verification result in the ACL
41681 a large number of expansion variables
41682 containing the signature status and its details are set up during the
41683 runtime of the ACL.
41685 Calling the ACL only for existing signatures is not sufficient to build
41686 more advanced policies. For that reason, the main option
41687 &%dkim_verify_signers%&, and an expansion variable
41688 &%$dkim_signers%& exist.
41690 The main option &%dkim_verify_signers%& can be set to a colon-separated
41691 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
41692 called. It is expanded when the message has been received. At this point,
41693 the expansion variable &%$dkim_signers%& already contains a colon-separated
41694 list of signer domains and identities for the message. When
41695 &%dkim_verify_signers%& is not specified in the main configuration,
41698 dkim_verify_signers = $dkim_signers
41700 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
41701 DKIM signature in the message. Current DKIM verifiers may want to explicitly
41702 call the ACL for known domains or identities. This would be achieved as follows:
41704 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
41706 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
41707 and "ebay.com", plus all domains and identities that have signatures in the message.
41708 You can also be more creative in constructing your policy. For example:
41710 dkim_verify_signers = $sender_address_domain:$dkim_signers
41713 If a domain or identity is listed several times in the (expanded) value of
41714 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
41716 Note that if the option is set using untrustworthy data
41717 (such as the From: header)
41718 care should be taken to force lowercase for domains
41719 and for the domain part if identities.
41720 The default setting can be regarded as trustworthy in this respect.
41722 If multiple signatures match a domain (or identity), the ACL is called once
41723 for each matching signature.
41726 Inside the DKIM ACL, the following expansion variables are
41727 available (from most to least important):
41731 .vitem &%$dkim_cur_signer%&
41732 The signer that is being evaluated in this ACL run. This can be a domain or
41733 an identity. This is one of the list items from the expanded main option
41734 &%dkim_verify_signers%& (see above).
41736 .vitem &%$dkim_verify_status%&
41737 Within the DKIM ACL,
41738 a string describing the general status of the signature. One of
41740 &%none%&: There is no signature in the message for the current domain or
41741 identity (as reflected by &%$dkim_cur_signer%&).
41743 &%invalid%&: The signature could not be verified due to a processing error.
41744 More detail is available in &%$dkim_verify_reason%&.
41746 &%fail%&: Verification of the signature failed. More detail is
41747 available in &%$dkim_verify_reason%&.
41749 &%pass%&: The signature passed verification. It is valid.
41752 This variable can be overwritten using an ACL 'set' modifier.
41753 This might, for instance, be done to enforce a policy restriction on
41754 hash-method or key-size:
41756 warn condition = ${if eq {$dkim_verify_status}{pass}}
41757 condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
41758 condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
41759 {< {$dkim_key_length}{1024}}}}
41760 logwrite = NOTE: forcing DKIM verify fail (was pass)
41761 set dkim_verify_status = fail
41762 set dkim_verify_reason = hash too weak or key too short
41765 So long as a DKIM ACL is defined (it need do no more than accept),
41766 after all the DKIM ACL runs have completed, the value becomes a
41767 colon-separated list of the values after each run.
41768 This is maintained for the mime, prdr and data ACLs.
41770 .vitem &%$dkim_verify_reason%&
41771 A string giving a little bit more detail when &%$dkim_verify_status%& is either
41772 "fail" or "invalid". One of
41774 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
41775 key for the domain could not be retrieved. This may be a temporary problem.
41777 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
41778 record for the domain is syntactically invalid.
41780 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
41781 body hash does not match the one specified in the signature header. This
41782 means that the message body was modified in transit.
41784 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
41785 could not be verified. This may mean that headers were modified,
41786 re-written or otherwise changed in a way which is incompatible with
41787 DKIM verification. It may of course also mean that the signature is forged.
41790 This variable can be overwritten, with any value, using an ACL 'set' modifier.
41792 .vitem &%$dkim_domain%&
41793 The signing domain. IMPORTANT: This variable is only populated if there is
41794 an actual signature in the message for the current domain or identity (as
41795 reflected by &%$dkim_cur_signer%&).
41797 .vitem &%$dkim_identity%&
41798 The signing identity, if present. IMPORTANT: This variable is only populated
41799 if there is an actual signature in the message for the current domain or
41800 identity (as reflected by &%$dkim_cur_signer%&).
41802 .vitem &%$dkim_selector%&
41803 The key record selector string.
41805 .vitem &%$dkim_algo%&
41806 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
41807 If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41808 may also be 'ed25519-sha256'.
41809 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41812 Note that RFC 8301 says:
41814 rsa-sha1 MUST NOT be used for signing or verifying.
41816 DKIM signatures identified as having been signed with historic
41817 algorithms (currently, rsa-sha1) have permanently failed evaluation
41820 To enforce this you must either have a DKIM ACL which checks this variable
41821 and overwrites the &$dkim_verify_status$& variable as discussed above,
41822 or have set the main option &%dkim_verify_hashes%& to exclude
41823 processing of such signatures.
41825 .vitem &%$dkim_canon_body%&
41826 The body canonicalization method. One of 'relaxed' or 'simple'.
41828 .vitem &%$dkim_canon_headers%&
41829 The header canonicalization method. One of 'relaxed' or 'simple'.
41831 .vitem &%$dkim_copiedheaders%&
41832 A transcript of headers and their values which are included in the signature
41833 (copied from the 'z=' tag of the signature).
41834 Note that RFC6376 requires that verification fail if the From: header is
41835 not included in the signature. Exim does not enforce this; sites wishing
41836 strict enforcement should code the check explicitly.
41838 .vitem &%$dkim_bodylength%&
41839 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
41840 limit was set by the signer, "9999999999999" is returned. This makes sure
41841 that this variable always expands to an integer value.
41842 &*Note:*& The presence of the signature tag specifying a signing body length
41843 is one possible route to spoofing of valid DKIM signatures.
41844 A paranoid implementation might wish to regard signature where this variable
41845 shows less than the "no limit" return as being invalid.
41847 .vitem &%$dkim_created%&
41848 UNIX timestamp reflecting the date and time when the signature was created.
41849 When this was not specified by the signer, "0" is returned.
41851 .vitem &%$dkim_expires%&
41852 UNIX timestamp reflecting the date and time when the signer wants the
41853 signature to be treated as "expired". When this was not specified by the
41854 signer, "9999999999999" is returned. This makes it possible to do useful
41855 integer size comparisons against this value.
41856 Note that Exim does not check this value.
41858 .vitem &%$dkim_headernames%&
41859 A colon-separated list of names of headers included in the signature.
41861 .vitem &%$dkim_key_testing%&
41862 "1" if the key record has the "testing" flag set, "0" if not.
41864 .vitem &%$dkim_key_nosubdomains%&
41865 "1" if the key record forbids subdomaining, "0" otherwise.
41867 .vitem &%$dkim_key_srvtype%&
41868 Service type (tag s=) from the key record. Defaults to "*" if not specified
41871 .vitem &%$dkim_key_granularity%&
41872 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
41875 .vitem &%$dkim_key_notes%&
41876 Notes from the key record (tag n=).
41878 .vitem &%$dkim_key_length%&
41879 Number of bits in the key.
41880 Valid only once the key is loaded, which is at the time the header signature
41881 is verified, which is after the body hash is.
41883 Note that RFC 8301 says:
41885 Verifiers MUST NOT consider signatures using RSA keys of
41886 less than 1024 bits as valid signatures.
41889 This is enforced by the default setting for the &%dkim_verify_min_keysizes%&
41894 In addition, two ACL conditions are provided:
41897 .vitem &%dkim_signers%&
41898 ACL condition that checks a colon-separated list of domains or identities
41899 for a match against the domain or identity that the ACL is currently verifying
41900 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
41901 verb to a group of domains or identities. For example:
41904 # Warn when Mail purportedly from GMail has no gmail signature
41905 warn sender_domains = gmail.com
41906 dkim_signers = gmail.com
41908 log_message = GMail sender without gmail.com DKIM signature
41911 Note that the above does not check for a total lack of DKIM signing;
41912 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
41914 .vitem &%dkim_status%&
41915 ACL condition that checks a colon-separated list of possible DKIM verification
41916 results against the actual result of verification. This is typically used
41917 to restrict an ACL verb to a list of verification outcomes, for example:
41920 deny sender_domains = paypal.com:paypal.de
41921 dkim_signers = paypal.com:paypal.de
41922 dkim_status = none:invalid:fail
41923 message = Mail from Paypal with invalid/missing signature
41926 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
41927 see the documentation of the &%$dkim_verify_status%& expansion variable above
41928 for more information of what they mean.
41934 .section "SPF (Sender Policy Framework)" SECSPF
41935 .cindex SPF verification
41937 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
41938 messages with its domain in the envelope from, documented by RFC 7208.
41939 For more information on SPF see &url(http://www.open-spf.org), a static copy of
41940 the &url(http://openspf.org).
41941 . --- 2019-10-28: still not https, open-spf.org is told to be a
41942 . --- web-archive copy of the now dead openspf.org site
41943 . --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a
41946 Messages sent by a system not authorised will fail checking of such assertions.
41947 This includes retransmissions done by traditional forwarders.
41949 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
41950 &_Local/Makefile_&. The support uses the &_libspf2_& library
41951 &url(https://www.libspf2.org/).
41952 There is no Exim involvement in the transmission of messages;
41953 publishing certain DNS records is all that is required.
41955 For verification, an ACL condition and an expansion lookup are provided.
41956 .cindex authentication "expansion item"
41957 Performing verification sets up information used by the
41958 &%authresults%& expansion item.
41961 .cindex SPF "ACL condition"
41962 .cindex ACL "spf condition"
41963 The ACL condition "spf" can be used at or after the MAIL ACL.
41964 It takes as an argument a list of strings giving the outcome of the SPF check,
41965 and will succeed for any matching outcome.
41969 The SPF check passed, the sending host is positively verified by SPF.
41972 The SPF check failed, the sending host is NOT allowed to send mail for the
41973 domain in the envelope-from address.
41975 .vitem &%softfail%&
41976 The SPF check failed, but the queried domain can't absolutely confirm that this
41980 The queried domain does not publish SPF records.
41983 The SPF check returned a "neutral" state. This means the queried domain has
41984 published a SPF record, but wants to allow outside servers to send mail under
41985 its domain as well. This should be treated like "none".
41987 .vitem &%permerror%&
41988 This indicates a syntax error in the SPF record of the queried domain.
41989 You may deny messages when this occurs.
41991 .vitem &%temperror%&
41992 This indicates a temporary error during all processing, including Exim's
41993 SPF processing. You may defer messages when this occurs.
41996 There was an error during processing of the SPF lookup
41999 You can prefix each string with an exclamation mark to invert
42000 its meaning, for example "!fail" will match all results but
42001 "fail". The string list is evaluated left-to-right, in a
42002 short-circuit fashion.
42007 message = $sender_host_address is not allowed to send mail from \
42008 ${if def:sender_address_domain \
42009 {$sender_address_domain}{$sender_helo_name}}. \
42010 Please see http://www.open-spf.org/Why;\
42011 identity=${if def:sender_address_domain \
42012 {$sender_address}{$sender_helo_name}};\
42013 ip=$sender_host_address
42016 Note: The above mentioned URL may not be as helpful as expected. You are
42017 encouraged to replace the link with a link to a site with more
42020 When the spf condition has run, it sets up several expansion
42023 .cindex SPF "verification variables"
42025 .vitem &$spf_header_comment$&
42026 .vindex &$spf_header_comment$&
42027 This contains a human-readable string describing the outcome
42028 of the SPF check. You can add it to a custom header or use
42029 it for logging purposes.
42031 .vitem &$spf_received$&
42032 .vindex &$spf_received$&
42033 This contains a complete Received-SPF: header (name and
42034 content) that can be added to the message. Please note that
42035 according to the SPF draft, this header must be added at the
42036 top of the header list, i.e. with
42038 add_header = :at_start:$spf_received
42040 See section &<<SECTaddheadacl>>& for further details.
42042 Note: in case of "Best-guess" (see below), the convention is
42043 to put this string in a header called X-SPF-Guess: instead.
42045 .vitem &$spf_result$&
42046 .vindex &$spf_result$&
42047 This contains the outcome of the SPF check in string form,
42048 currently one of pass, fail, softfail, none, neutral, permerror,
42049 temperror, or &"(invalid)"&.
42051 .vitem &$spf_result_guessed$&
42052 .vindex &$spf_result_guessed$&
42053 This boolean is true only if a best-guess operation was used
42054 and required in order to obtain a result.
42056 .vitem &$spf_smtp_comment$&
42057 .vindex &$spf_smtp_comment$&
42058 .vindex &%spf_smtp_comment_template%&
42059 This contains a string that can be used in a SMTP response
42060 to the calling party. Useful for "fail".
42061 The string is generated by the SPF library from the template configured in the main config
42062 option &%spf_smtp_comment_template%&.
42066 .cindex SPF "ACL condition"
42067 .cindex ACL "spf_guess condition"
42068 .cindex SPF "best guess"
42069 In addition to SPF, you can also perform checks for so-called
42070 "Best-guess". Strictly speaking, "Best-guess" is not standard
42071 SPF, but it is supported by the same framework that enables SPF
42073 Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record)
42074 for a description of what it means.
42075 . --- 2019-10-28: still not https:
42077 To access this feature, simply use the spf_guess condition in place
42078 of the spf one. For example:
42081 deny spf_guess = fail
42082 message = $sender_host_address doesn't look trustworthy to me
42085 In case you decide to reject messages based on this check, you
42086 should note that although it uses the same framework, "Best-guess"
42087 is not SPF, and therefore you should not mention SPF at all in your
42090 When the spf_guess condition has run, it sets up the same expansion
42091 variables as when spf condition is run, described above.
42093 Additionally, since Best-guess is not standardized, you may redefine
42094 what "Best-guess" means to you by redefining the main configuration
42095 &%spf_guess%& option.
42096 For example, the following:
42099 spf_guess = v=spf1 a/16 mx/16 ptr ?all
42102 would relax host matching rules to a broader network range.
42105 .cindex SPF "lookup expansion"
42107 A lookup expansion is also available. It takes an email
42108 address as the key and an IP address
42113 ${lookup {username@domain} spf {ip.ip.ip.ip}}
42116 The lookup will return the same result strings as can appear in
42117 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
42123 .subsection "SRS (Sender Rewriting Scheme)" SECTSRS
42124 .cindex SRS "sender rewriting scheme"
42126 SRS can be used to modify sender addresses when forwarding so that
42127 SPF verification does not object to them.
42128 It operates by encoding the original envelope sender in a new
42129 sender local part and using a domain run by the forwarding site
42130 as the new domain for the sender. Any DSN message should be returned
42131 to this new sender at the forwarding site, which can extract the
42132 original sender from the coded local part and forward the DSN to
42135 This is a way of avoiding the breakage that SPF does to forwarding.
42136 The constructed local-part will be longer than the original,
42137 leading to possible problems with very long addresses.
42138 The changing of the sender address also hinders the tracing of mail
42141 Exim can be built to include native SRS support. To do this
42142 SUPPORT_SRS=yes must be defined in &_Local/Makefile_&.
42143 If this has been done, the macros _HAVE_SRS and _HAVE_NATIVE_SRS
42145 The support is limited to SRS0-encoding; SRS1 is not supported.
42147 .cindex SRS excoding
42148 To encode an address use this expansion item:
42150 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
42151 .cindex "&%srs_encode%& expansion item"
42152 .cindex SRS "expansion item"
42153 The first argument should be a secret known and used by all systems
42154 handling the recipient domain for the original message.
42155 There is no need to periodically change this key; a timestamp is also
42157 The second argument should be given as the envelope sender address before this
42158 encoding operation.
42159 If this value is empty the the expansion result will be empty.
42160 The third argument should be the recipient domain of the message when
42161 it arrived at this system.
42164 .cindex SRS decoding
42165 To decode an address use this expansion condition:
42167 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
42168 The first argument should be the recipient local prt as is was received.
42169 The second argument is the site secret.
42171 If the messages is not for an SRS-encoded recipient the condition will
42172 return false. If it is, the condition will return true and the variable
42173 &$srs_recipient$& will be set to the decoded (original) value.
42179 SRS_SECRET = <pick something unique for your site for this. Use on all MXs.>
42185 # if outbound, and forwarding has been done, use an alternate transport
42186 domains = ! +my_domains
42187 transport = ${if eq {$local_part@$domain} \
42188 {$original_local_part@$original_domain} \
42189 {remote_smtp} {remote_forwarded_smtp}}
42194 domains = +my_domains
42195 # detect inbound bounces which are SRS'd, and decode them
42196 condition = ${if inbound_srs {$local_part} {SRS_SECRET}}
42197 data = $srs_recipient
42199 inbound_srs_failure:
42202 domains = +my_domains
42203 # detect inbound bounces which look SRS'd but are invalid
42204 condition = ${if inbound_srs {$local_part} {}}
42206 data = :fail: Invalid SRS recipient address
42208 #... further routers here
42211 # transport; should look like the non-forward outbound
42212 # one, plus the max_rcpt and return_path options
42213 remote_forwarded_smtp:
42215 # modify the envelope from, for mails that we forward
42217 return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}}
42224 .section DMARC SECDMARC
42225 .cindex DMARC verification
42227 DMARC combines feedback from SPF, DKIM, and header From: in order
42228 to attempt to provide better indicators of the authenticity of an
42229 email. This document does not explain the fundamentals; you
42230 should read and understand how it works by visiting the website at
42231 &url(http://www.dmarc.org/).
42233 If Exim is built with DMARC support,
42234 the libopendmarc library is used.
42236 For building Exim yourself, obtain the library from
42237 &url(http://sourceforge.net/projects/opendmarc/)
42238 to obtain a copy, or find it in your favorite package
42239 repository. You will need to attend to the local/Makefile feature
42240 SUPPORT_DMARC and the associated LDFLAGS addition.
42241 This description assumes
42242 that headers will be in /usr/local/include, and that the libraries
42243 are in /usr/local/lib.
42245 .subsection Configuration SSECDMARCCONFIG
42246 .cindex DMARC configuration
42248 There are three main-configuration options:
42249 .cindex DMARC "configuration options"
42251 The &%dmarc_tld_file%& option
42252 .oindex &%dmarc_tld_file%&
42253 defines the location of a text file of valid
42254 top level domains the opendmarc library uses
42255 during domain parsing. Maintained by Mozilla,
42256 the most current version can be downloaded
42257 from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat).
42258 See also the util/renew-opendmarc-tlds.sh script.
42259 The default for the option is unset.
42260 If not set, DMARC processing is disabled.
42263 The &%dmarc_history_file%& option, if set
42264 .oindex &%dmarc_history_file%&
42265 defines the location of a file to log results
42266 of dmarc verification on inbound emails. The
42267 contents are importable by the opendmarc tools
42268 which will manage the data, send out DMARC
42269 reports, and expire the data. Make sure the
42270 directory of this file is writable by the user
42272 The default is unset.
42274 The &%dmarc_forensic_sender%& option
42275 .oindex &%dmarc_forensic_sender%&
42276 defines an alternate email address to use when sending a
42277 forensic report detailing alignment failures
42278 if a sender domain's dmarc record specifies it
42279 and you have configured Exim to send them.
42280 If set, this is expanded and used for the
42281 From: header line; the address is extracted
42282 from it and used for the envelope from.
42283 If not set (the default), the From: header is expanded from
42284 the dsn_from option, and <> is used for the
42287 .subsection Controls SSECDMARCCONTROLS
42288 .cindex DMARC controls
42290 By default, the DMARC processing will run for any remote,
42291 non-authenticated user. It makes sense to only verify DMARC
42292 status of messages coming from remote, untrusted sources. You can
42293 use standard conditions such as hosts, senders, etc, to decide that
42294 DMARC verification should *not* be performed for them and disable
42295 DMARC with an ACL control modifier:
42297 control = dmarc_disable_verify
42299 A DMARC record can also specify a "forensic address", which gives
42300 exim an email address to submit reports about failed alignment.
42301 Exim does not do this by default because in certain conditions it
42302 results in unintended information leakage (what lists a user might
42303 be subscribed to, etc). You must configure exim to submit forensic
42304 reports to the owner of the domain. If the DMARC record contains a
42305 forensic address and you specify the control statement below, then
42306 exim will send these forensic emails. It is also advised that you
42307 configure a &%dmarc_forensic_sender%& because the default sender address
42308 construction might be inadequate.
42310 control = dmarc_enable_forensic
42312 (AGAIN: You can choose not to send these forensic reports by simply
42313 not putting the dmarc_enable_forensic control line at any point in
42314 your exim config. If you don't tell exim to send them, it will not
42317 There are no options to either control. Both must appear before
42320 .subsection ACL SSECDMARCACL
42321 .cindex DMARC "ACL condition"
42323 DMARC checks can be run on incoming SMTP messages by using the
42324 &"dmarc_status"& ACL condition in the DATA ACL. You are required to
42325 call the &"spf"& condition first in the ACLs, then the &"dmarc_status"&
42326 condition. Putting this condition in the ACLs is required in order
42327 for a DMARC check to actually occur. All of the variables are set
42328 up before the DATA ACL, but there is no actual DMARC check that
42329 occurs until a &"dmarc_status"& condition is encountered in the ACLs.
42331 The &"dmarc_status"& condition takes a list of strings on its
42332 right-hand side. These strings describe recommended action based
42333 on the DMARC check. To understand what the policy recommendations
42334 mean, refer to the DMARC website above. Valid strings are:
42335 .itable none 0 0 2 20* left 80* left
42336 .irow &'accept'& "The DMARC check passed and the library recommends accepting the email"
42337 .irow &'reject'& "The DMARC check failed and the library recommends rejecting the email"
42338 .irow &'quarantine'& "The DMARC check failed and the library recommends keeping it for further inspection"
42339 .irow &'none'& "The DMARC check passed and the library recommends no specific action, neutral"
42340 .irow &'norecord'& "No policy section in the DMARC record for this RFC5322.From field"
42341 .irow &'nofrom'& "Unable to determine the domain of the sender"
42342 .irow &'temperror'& "Library error or dns error"
42343 .irow &'off'& "The DMARC check was disabled for this email"
42345 You can prefix each string with an exclamation mark to invert its
42346 meaning, for example "!accept" will match all results but
42347 "accept". The string list is evaluated left-to-right in a
42348 short-circuit fashion. When a string matches the outcome of the
42349 DMARC check, the condition succeeds. If none of the listed
42350 strings matches the outcome of the DMARC check, the condition
42353 Of course, you can also use any other lookup method that Exim
42354 supports, including LDAP, Postgres, MySQL, etc, as long as the
42355 result is a list of colon-separated strings.
42357 Performing the check sets up information used by the
42358 &%authresults%& expansion item.
42360 Several expansion variables are set before the DATA ACL is
42361 processed, and you can use them in this ACL. The following
42362 expansion variables are available:
42365 .vitem &$dmarc_status$&
42366 .vindex &$dmarc_status$&
42367 .cindex DMARC result
42368 A one word status indicating what the DMARC library
42369 thinks of the email. It is a combination of the results of
42370 DMARC record lookup and the SPF/DKIM/DMARC processing results
42371 (if a DMARC record was found). The actual policy declared
42372 in the DMARC record is in a separate expansion variable.
42374 .vitem &$dmarc_status_text$&
42375 .vindex &$dmarc_status_text$&
42376 Slightly longer, human readable status.
42378 .vitem &$dmarc_used_domain$&
42379 .vindex &$dmarc_used_domain$&
42380 The domain which DMARC used to look up the DMARC policy record.
42382 .vitem &$dmarc_domain_policy$&
42383 .vindex &$dmarc_domain_policy$&
42384 The policy declared in the DMARC record. Valid values
42385 are "none", "reject" and "quarantine". It is blank when there
42386 is any error, including no DMARC record.
42389 .subsection Logging SSECDMARCLOGGING
42390 .cindex DMARC logging
42392 By default, Exim's DMARC configuration is intended to be
42393 non-intrusive and conservative. To facilitate this, Exim will not
42394 create any type of logging files without explicit configuration by
42395 you, the admin. Nor will Exim send out any emails/reports about
42396 DMARC issues without explicit configuration by you, the admin (other
42397 than typical bounce messages that may come about due to ACL
42398 processing or failure delivery issues).
42400 In order to log statistics suitable to be imported by the opendmarc
42401 tools, you need to:
42403 Configure the global option &%dmarc_history_file%&
42405 Configure cron jobs to call the appropriate opendmarc history
42406 import scripts and truncating the dmarc_history_file
42409 In order to send forensic reports, you need to:
42411 Configure the global option &%dmarc_forensic_sender%&
42413 Configure, somewhere before the DATA ACL, the control option to
42414 enable sending DMARC forensic reports
42417 .subsection Example SSECDMARCEXAMPLE
42418 .cindex DMARC example
42423 warn domains = +local_domains
42424 hosts = +local_hosts
42425 control = dmarc_disable_verify
42427 warn !domains = +screwed_up_dmarc_records
42428 control = dmarc_enable_forensic
42430 warn condition = (lookup if destined to mailing list)
42431 set acl_m_mailing_list = 1
42434 warn dmarc_status = accept : none : off
42436 log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
42438 warn dmarc_status = !accept
42440 log_message = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
42442 warn dmarc_status = quarantine
42444 set $acl_m_quarantine = 1
42445 # Do something in a transport with this flag variable
42447 deny condition = ${if eq{$dmarc_domain_policy}{reject}}
42448 condition = ${if eq{$acl_m_mailing_list}{1}}
42449 message = Messages from $dmarc_used_domain break mailing lists
42451 deny dmarc_status = reject
42453 message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
42455 warn add_header = :at_start:${authresults {$primary_hostname}}
42462 . ////////////////////////////////////////////////////////////////////////////
42463 . ////////////////////////////////////////////////////////////////////////////
42465 .chapter "Proxies" "CHAPproxies" &&&
42467 .cindex "proxy support"
42468 .cindex "proxy" "access via"
42470 A proxy is an intermediate system through which communication is passed.
42471 Proxies may provide a security, availability or load-distribution function.
42474 .section "Inbound proxies" SECTproxyInbound
42475 .cindex proxy inbound
42476 .cindex proxy "server side"
42477 .cindex proxy "Proxy protocol"
42478 .cindex "Proxy protocol" proxy
42480 Exim has support for receiving inbound SMTP connections via a proxy
42481 that uses &"Proxy Protocol"& to speak to it.
42482 To include this support, include &"SUPPORT_PROXY=yes"&
42485 It was built on the HAProxy specification, found at
42486 &url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt).
42488 The purpose of this facility is so that an application load balancer,
42489 such as HAProxy, can sit in front of several Exim servers
42490 to distribute load.
42491 Exim uses the local protocol communication with the proxy to obtain
42492 the remote SMTP system IP address and port information.
42493 There is no logging if a host passes or
42494 fails Proxy Protocol negotiation, but it can easily be determined and
42495 recorded in an ACL (example is below).
42497 Use of a proxy is enabled by setting the &%hosts_proxy%&
42498 main configuration option to a hostlist; connections from these
42499 hosts will use Proxy Protocol.
42500 Exim supports both version 1 and version 2 of the Proxy Protocol and
42501 automatically determines which version is in use.
42503 The Proxy Protocol header is the first data received on a TCP connection
42504 and is inserted before any TLS-on-connect handshake from the client; Exim
42505 negotiates TLS between Exim-as-server and the remote client, not between
42506 Exim and the proxy server. The Proxy Protocol header must be received
42507 within &%proxy_protocol_timeout%&, which defaults to 3s.
42509 The following expansion variables are usable
42510 (&"internal"& and &"external"& here refer to the interfaces
42512 .itable none 0 0 2 30* left 70* left
42513 .irow $proxy_external_address "IP of host being proxied or IP of remote interface of proxy"
42514 .irow $proxy_external_port "Port of host being proxied or Port on remote interface of proxy"
42515 .irow $proxy_local_address "IP of proxy server inbound or IP of local interface of proxy"
42516 .irow $proxy_local_port "Port of proxy server inbound or Port on local interface of proxy"
42517 .irow $proxy_session "boolean: SMTP connection via proxy"
42519 If &$proxy_session$& is set but &$proxy_external_address$& is empty
42520 there was a protocol error.
42521 The variables &$sender_host_address$& and &$sender_host_port$&
42522 will have values for the actual client system, not the proxy.
42524 Since the real connections are all coming from the proxy, and the
42525 per host connection tracking is done before Proxy Protocol is
42526 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
42527 handle all of the parallel volume you expect per inbound proxy.
42528 With the option set so high, you lose the ability
42529 to protect your server from many connections from one IP.
42530 In order to prevent your server from overload, you
42531 need to add a per connection ratelimit to your connect ACL.
42532 A possible solution is:
42534 # Set max number of connections per host
42536 # Or do some kind of IP lookup in a flat file or database
42537 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
42539 defer ratelimit = LIMIT / 5s / per_conn / strict
42540 message = Too many connections from this IP right now
42545 .section "Outbound proxies" SECTproxySOCKS
42546 .cindex proxy outbound
42547 .cindex proxy "client side"
42548 .cindex proxy SOCKS
42549 .cindex SOCKS proxy
42550 Exim has support for sending outbound SMTP via a proxy
42551 using a protocol called SOCKS5 (defined by RFC1928).
42552 The support can be optionally included by defining SUPPORT_SOCKS=yes in
42555 Use of a proxy is enabled by setting the &%socks_proxy%& option
42556 on an smtp transport.
42557 The option value is expanded and should then be a list
42558 (colon-separated by default) of proxy specifiers.
42559 Each proxy specifier is a list
42560 (space-separated by default) where the initial element
42561 is an IP address and any subsequent elements are options.
42563 Options are a string <name>=<value>.
42564 The list of options is in the following table:
42565 .itable none 0 0 2 10* left 90* left
42566 .irow &'auth'& "authentication method"
42567 .irow &'name'& "authentication username"
42568 .irow &'pass'& "authentication password"
42569 .irow &'port'& "tcp port"
42570 .irow &'tmo'& "connection timeout"
42571 .irow &'pri'& "priority"
42572 .irow &'weight'& "selection bias"
42575 More details on each of these options follows:
42578 .cindex authentication "to proxy"
42579 .cindex proxy authentication
42580 &%auth%&: Either &"none"& (default) or &"name"&.
42581 Using &"name"& selects username/password authentication per RFC 1929
42582 for access to the proxy.
42583 Default is &"none"&.
42585 &%name%&: sets the username for the &"name"& authentication method.
42588 &%pass%&: sets the password for the &"name"& authentication method.
42591 &%port%&: the TCP port number to use for the connection to the proxy.
42594 &%tmo%&: sets a connection timeout in seconds for this proxy.
42597 &%pri%&: specifies a priority for the proxy within the list,
42598 higher values being tried first.
42599 The default priority is 1.
42601 &%weight%&: specifies a selection bias.
42602 Within a priority set servers are queried in a random fashion,
42603 weighted by this value.
42604 The default value for selection bias is 1.
42607 Proxies from the list are tried according to their priority
42608 and weight settings until one responds. The timeout for the
42609 overall connection applies to the set of proxied attempts.
42611 .section Logging SECTproxyLog
42612 To log the (local) IP of a proxy in the incoming or delivery logline,
42613 add &"+proxy"& to the &%log_selector%& option.
42614 This will add a component tagged with &"PRX="& to the line.
42616 . ////////////////////////////////////////////////////////////////////////////
42617 . ////////////////////////////////////////////////////////////////////////////
42619 .chapter "Internationalisation" "CHAPi18n" &&&
42620 "Internationalisation""
42621 .cindex internationalisation "email address"
42624 .cindex utf8 "mail name handling"
42626 Exim has support for Internationalised mail names.
42627 To include this it must be built with SUPPORT_I18N and the libidn library.
42628 Standards supported are RFCs 2060, 5890, 6530 and 6533.
42630 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
42631 instead of it) then IDNA2008 is supported; this adds an extra library
42632 requirement, upon libidn2.
42634 .section "MTA operations" SECTi18nMTA
42635 .cindex SMTPUTF8 "ESMTP option"
42636 .cindex "ESMTP extensions" SMTPUTF8
42637 The main configuration option &%smtputf8_advertise_hosts%& specifies
42638 a host list. If this matches the sending host and
42639 accept_8bitmime is true (the default) then the ESMTP option
42640 SMTPUTF8 will be advertised.
42642 If the sender specifies the SMTPUTF8 option on a MAIL command
42643 international handling for the message is enabled and
42644 the expansion variable &$message_smtputf8$& will have value TRUE.
42646 The option &%allow_utf8_domains%& is set to true for this
42647 message. All DNS lookups are converted to a-label form
42648 whatever the setting of &%allow_utf8_domains%&
42649 when Exim is built with SUPPORT_I18N.
42651 Both localparts and domain are maintained as the original
42652 UTF-8 form internally; any comparison or regular-expression use will
42653 require appropriate care. Filenames created, eg. by
42654 the appendfile transport, will have UTF-8 names.
42656 HELO names sent by the smtp transport will have any UTF-8
42657 components expanded to a-label form,
42658 and any certificate name checks will be done using the a-label
42661 .cindex log protocol
42662 .cindex SMTPUTF8 logging
42663 .cindex i18n logging
42664 Log lines and Received-by: header lines will acquire a "utf8"
42665 prefix on the protocol element, eg. utf8esmtp.
42667 The following expansion operators can be used:
42669 ${utf8_domain_to_alabel:str}
42670 ${utf8_domain_from_alabel:str}
42671 ${utf8_localpart_to_alabel:str}
42672 ${utf8_localpart_from_alabel:str}
42675 .cindex utf8 "address downconversion"
42676 .cindex i18n "utf8 address downconversion"
42678 may use the following modifier:
42680 control = utf8_downconvert
42681 control = utf8_downconvert/<value>
42683 This sets a flag requiring that envelope addresses are converted to
42684 a-label form before smtp delivery.
42685 This is usually for use in a Message Submission Agent context,
42686 but could be used for any message.
42688 If a value is appended it may be:
42689 .itable none 0 0 2 5* right 95* left
42690 .irow &`1`& "mandatory downconversion"
42691 .irow &`0`& "no downconversion"
42692 .irow &`-1`& "if SMTPUTF8 not supported by destination host"
42694 If no value is given, 1 is used.
42696 If mua_wrapper is set, the utf8_downconvert control
42697 is initially set to -1.
42699 The smtp transport has an option &%utf8_downconvert%&.
42700 If set it must expand to one of the three values described above,
42701 or an empty string.
42702 If non-empty it overrides value previously set
42703 (due to mua_wrapper or by an ACL control).
42706 There is no explicit support for VRFY and EXPN.
42707 Configurations supporting these should inspect
42708 &$smtp_command_argument$& for an SMTPUTF8 argument.
42710 There is no support for LMTP on Unix sockets.
42711 Using the "lmtp" protocol option on an smtp transport,
42712 for LMTP over TCP, should work as expected.
42714 There is no support for DSN unitext handling,
42715 and no provision for converting logging from or to UTF-8.
42719 .section "MDA operations" SECTi18nMDA
42720 To aid in constructing names suitable for IMAP folders
42721 the following expansion operator can be used:
42723 ${imapfolder {<string>} {<sep>} {<specials>}}
42726 The string is converted from the charset specified by
42727 the "headers charset" command (in a filter file)
42728 or &%headers_charset%& main configuration option (otherwise),
42730 modified UTF-7 encoding specified by RFC 2060,
42731 with the following exception: All occurrences of <sep>
42732 (which has to be a single character)
42733 are replaced with periods ("."), and all periods and slashes that are not
42734 <sep> and are not in the <specials> string are BASE64 encoded.
42736 The third argument can be omitted, defaulting to an empty string.
42737 The second argument can be omitted, defaulting to "/".
42739 This is the encoding used by Courier for Maildir names on disk, and followed
42740 by many other IMAP servers.
42744 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
42745 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
42746 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
42749 Note that the source charset setting is vital, and also that characters
42750 must be representable in UTF-16.
42753 . ////////////////////////////////////////////////////////////////////////////
42754 . ////////////////////////////////////////////////////////////////////////////
42756 .chapter "Events" "CHAPevents" &&&
42760 The events mechanism in Exim can be used to intercept processing at a number
42761 of points. It was originally invented to give a way to do customised logging
42762 actions (for example, to a database) but can also be used to modify some
42763 processing actions.
42765 Most installations will never need to use Events.
42766 The support can be left out of a build by defining DISABLE_EVENT=yes
42767 in &_Local/Makefile_&.
42769 There are two major classes of events: main and transport.
42770 The main configuration option &%event_action%& controls reception events;
42771 a transport option &%event_action%& controls delivery events.
42773 Both options are a string which is expanded when the event fires.
42774 An example might look like:
42775 .cindex logging custom
42777 event_action = ${if eq {msg:delivery}{$event_name} \
42778 {${lookup pgsql {SELECT * FROM record_Delivery( \
42779 '${quote_pgsql:$sender_address_domain}',\
42780 '${quote_pgsql:${lc:$sender_address_local_part}}', \
42781 '${quote_pgsql:$domain}', \
42782 '${quote_pgsql:${lc:$local_part}}', \
42783 '${quote_pgsql:$host_address}', \
42784 '${quote_pgsql:${lc:$host}}', \
42785 '${quote_pgsql:$message_exim_id}')}} \
42789 Events have names which correspond to the point in process at which they fire.
42790 The name is placed in the variable &$event_name$& and the event action
42791 expansion must check this, as it will be called for every possible event type.
42793 The current list of events is:
42794 .itable all 0 0 4 25* left 10* center 15* center 50* left
42795 .row auth:fail after both "per driver per authentication attempt"
42796 .row dane:fail after transport "per connection"
42797 .row msg:complete after main "per message"
42798 .row msg:defer after transport "per message per delivery try"
42799 .row msg:delivery after transport "per recipient"
42800 .row msg:rcpt:host:defer after transport "per recipient per host"
42801 .row msg:rcpt:defer after transport "per recipient"
42802 .row msg:host:defer after transport "per host per delivery try; host errors"
42803 .row msg:fail:delivery after transport "per recipient"
42804 .row msg:fail:internal after main "per recipient"
42805 .row tcp:connect before transport "per connection"
42806 .row tcp:close after transport "per connection"
42807 .row tls:cert before both "per certificate in verification chain"
42808 .row tls:fail:connect after main "per connection"
42809 .row smtp:connect after transport "per connection"
42810 .row smtp:ehlo after transport "per connection"
42812 New event types may be added in future.
42814 The event name is a colon-separated list, defining the type of
42815 event in a tree of possibilities. It may be used as a list
42816 or just matched on as a whole. There will be no spaces in the name.
42818 The second column in the table above describes whether the event fires
42819 before or after the action is associates with. Those which fire before
42820 can be used to affect that action (more on this below).
42822 The third column in the table above says what section of the configuration
42823 should define the event action.
42825 An additional variable, &$event_data$&, is filled with information varying
42826 with the event type:
42827 .itable all 0 0 2 20* left 80* left
42828 .row auth:fail "smtp response"
42829 .row dane:fail "failure reason"
42830 .row msg:defer "error string"
42831 .row msg:delivery "smtp confirmation message"
42832 .row msg:fail:internal "failure reason"
42833 .row msg:fail:delivery "smtp error message"
42834 .row msg:host:defer "error string"
42835 .row msg:rcpt:host:defer "error string"
42836 .row msg:rcpt:defer "error string"
42837 .row tls:cert "verification chain depth"
42838 .row tls:fail:connect "error string"
42839 .row smtp:connect "smtp banner"
42840 .row smtp:ehlo "smtp ehlo response"
42843 The :defer events populate one extra variable: &$event_defer_errno$&.
42845 For complex operations an ACL expansion can be used in &%event_action%&,
42846 however due to the multiple contexts that Exim operates in during
42847 the course of its processing:
42849 variables set in transport events will not be visible outside that
42852 acl_m variables in a server context are lost on a new connection,
42853 and after smtp helo/ehlo/mail/starttls/rset commands
42855 Using an ACL expansion with the logwrite modifier can be
42856 a useful way of writing to the main log.
42858 The expansion of the event_action option should normally
42859 return an empty string. Should it return anything else the
42860 following will be forced:
42861 .itable all 0 0 2 20* left 80* left
42862 .row auth:fail "log information to write"
42863 .row tcp:connect "do not connect"
42864 .row tls:cert "refuse verification"
42865 .row smtp:connect "close connection"
42867 All other message types ignore the result string, and
42868 no other use is made of it.
42870 For a tcp:connect event, if the connection is being made to a proxy
42871 then the address and port variables will be that of the proxy and not
42874 For tls:cert events, if GnuTLS is in use this will trigger only per
42875 chain element received on the connection.
42876 For OpenSSL it will trigger for every chain element including those
42879 . ////////////////////////////////////////////////////////////////////////////
42880 . ////////////////////////////////////////////////////////////////////////////
42882 .chapter "Adding new drivers or lookup types" "CHID13" &&&
42883 "Adding drivers or lookups"
42884 .cindex "adding drivers"
42885 .cindex "new drivers, adding"
42886 .cindex "drivers" "adding new"
42887 The following actions have to be taken in order to add a new router, transport,
42888 authenticator, or lookup type to Exim:
42891 Choose a name for the driver or lookup type that does not conflict with any
42892 existing name; I will use &"newdriver"& in what follows.
42894 Add to &_src/EDITME_& the line:
42896 <&'type'&>&`_NEWDRIVER=yes`&
42898 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
42899 code is not to be included in the binary by default, comment this line out. You
42900 should also add any relevant comments about the driver or lookup type.
42902 Add to &_src/config.h.defaults_& the line:
42904 #define <type>_NEWDRIVER
42907 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
42908 and create a table entry as is done for all the other drivers and lookup types.
42910 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
42911 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
42912 Add your &`NEWDRIVER`& to that list.
42913 As long as the dynamic module would be named &_newdriver.so_&, you can use the
42914 simple form that most lookups have.
42916 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
42917 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
42918 driver or lookup type and add it to the definition of OBJ.
42920 Edit &_OS/Makefile-Base_& adding a &_.o_& file for the predefined-macros, to the
42921 definition of OBJ_MACRO. Add a set of line to do the compile also.
42923 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
42926 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
42927 as for other drivers and lookups.
42930 Then all you need to do is write the code! A good way to start is to make a
42931 proforma by copying an existing module of the same type, globally changing all
42932 occurrences of the name, and cutting out most of the code. Note that any
42933 options you create must be listed in alphabetical order, because the tables are
42934 searched using a binary chop procedure.
42936 There is a &_README_& file in each of the sub-directories of &_src_& describing
42937 the interface that is expected.
42942 . ////////////////////////////////////////////////////////////////////////////
42943 . ////////////////////////////////////////////////////////////////////////////
42945 . /////////////////////////////////////////////////////////////////////////////
42946 . These lines are processing instructions for the Simple DocBook Processor that
42947 . Philip Hazel has developed as a less cumbersome way of making PostScript and
42948 . PDFs than using xmlto and fop. They will be ignored by all other XML
42950 . /////////////////////////////////////////////////////////////////////////////
42955 foot_right_recto="&chaptertitle;"
42956 foot_right_verso="&chaptertitle;"
42960 .makeindex "Options index" "option"
42961 .makeindex "Variables index" "variable"
42962 .makeindex "Concept index" "concept"
42965 . /////////////////////////////////////////////////////////////////////////////
42966 . /////////////////////////////////////////////////////////////////////////////