1 . /////////////////////////////////////////////////////////////////////////////
2 . This is the primary source of the Exim Manual. It is an xfpt document that is
3 . converted into DocBook XML for subsequent conversion into printable and online
4 . formats. The markup used herein is "standard" xfpt markup, with some extras.
5 . The markup is summarized in a file called Markup.txt.
7 . WARNING: When you use the .new macro, make sure it appears *before* any
8 . adjacent index items; otherwise you get an empty "paragraph" which causes
9 . unwanted vertical space.
10 . /////////////////////////////////////////////////////////////////////////////
15 . /////////////////////////////////////////////////////////////////////////////
16 . This outputs the standard DocBook boilerplate.
17 . /////////////////////////////////////////////////////////////////////////////
21 . /////////////////////////////////////////////////////////////////////////////
22 . These lines are processing instructions for the Simple DocBook Processor that
23 . Philip Hazel has developed as a less cumbersome way of making PostScript and
24 . PDFs than using xmlto and fop. They will be ignored by all other XML
26 . /////////////////////////////////////////////////////////////////////////////
30 foot_right_recto="&chaptertitle; (&chapternumber;)"
31 foot_right_verso="&chaptertitle; (&chapternumber;)"
32 toc_chapter_blanks="yes,yes"
33 table_warn_overflow="overprint"
37 . /////////////////////////////////////////////////////////////////////////////
38 . This generates the outermost <book> element that wraps the entire document.
39 . /////////////////////////////////////////////////////////////////////////////
43 . /////////////////////////////////////////////////////////////////////////////
44 . These definitions set some parameters and save some typing.
45 . Update the Copyright year (only) when changing content.
46 . /////////////////////////////////////////////////////////////////////////////
48 .set previousversion "4.94"
49 .include ./local_params
51 .set ACL "access control lists (ACLs)"
52 .set I " "
58 . /////////////////////////////////////////////////////////////////////////////
59 . Additional xfpt markup used by this document, over and above the default
60 . provided in the xfpt library.
61 . /////////////////////////////////////////////////////////////////////////////
63 . --- Override the &$ flag to automatically insert a $ with the variable name.
65 .flag &$ $& "<varname>$" "</varname>"
67 . --- Short flags for daggers in option headings. They will always be inside
68 . --- an italic string, but we want the daggers to be in Roman.
70 .flag &!! "</emphasis>†<emphasis>"
71 .flag &!? "</emphasis>‡<emphasis>"
73 . --- A macro for an Exim option definition heading, generating a one-line
74 . --- table with four columns. For cases when the option name is given with
75 . --- a space, so that it can be split, a fifth argument is used for the
85 .itable all 0 0 4 8* left 6* center 6* center 6* right
86 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
90 . --- A macro for the common 2-column tables. The width of the first column
91 . --- is suitable for the many tables at the start of the main options chapter;
92 . --- a small number of other 2-column tables override it.
94 .macro table2 196pt 254pt
95 .itable none 0 0 2 $1 left $2 left
98 . --- A macro that generates .row, but puts &I; at the start of the first
99 . --- argument, thus indenting it. Assume a minimum of two arguments, and
100 . --- allow up to four arguments, which is as many as we'll ever need.
104 .row "&I;$1" "$2" "$3" "$4"
108 .row "&I;$1" "$2" "$3"
116 . --- Macros for option, variable, and concept index entries. For a "range"
117 . --- style of entry, use .scindex for the start and .ecindex for the end. The
118 . --- first argument of .scindex and the only argument of .ecindex must be the
119 . --- ID that ties them together.
122 &<indexterm role="concept">&
123 &<primary>&$1&</primary>&
125 &<secondary>&$2&</secondary>&
131 &<indexterm role="concept" id="$1" class="startofrange">&
132 &<primary>&$2&</primary>&
134 &<secondary>&$3&</secondary>&
140 &<indexterm role="concept" startref="$1" class="endofrange"/>&
144 &<indexterm role="option">&
145 &<primary>&$1&</primary>&
147 &<secondary>&$2&</secondary>&
153 &<indexterm role="variable">&
154 &<primary>&$1&</primary>&
156 &<secondary>&$2&</secondary>&
162 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
166 . use this for a concept-index entry for a header line
168 .cindex "&'$1'& header line"
169 .cindex "header lines" $1
171 . ////////////////////////////////////////////////////////////////////////////
174 . ////////////////////////////////////////////////////////////////////////////
175 . The <bookinfo> element is removed from the XML before processing for ASCII
177 . ////////////////////////////////////////////////////////////////////////////
181 <title>Specification of the Exim Mail Transfer Agent</title>
182 <titleabbrev>The Exim MTA</titleabbrev>
186 <author><firstname>Exim</firstname><surname>Maintainers</surname></author>
187 <authorinitials>EM</authorinitials>
188 <revhistory><revision>
190 <authorinitials>EM</authorinitials>
191 </revision></revhistory>
194 </year><holder>University of Cambridge</holder></copyright>
199 . /////////////////////////////////////////////////////////////////////////////
200 . This chunk of literal XML implements index entries of the form "x, see y" and
201 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
202 . at the top level, so we have to put the .chapter directive first.
204 . These do not turn up in the HTML output, unfortunately. The PDF does get them.
205 . /////////////////////////////////////////////////////////////////////////////
207 .chapter "Introduction" "CHID1"
210 <indexterm role="variable">
211 <primary>$1, $2, etc.</primary>
212 <see><emphasis>numerical variables</emphasis></see>
214 <indexterm role="concept">
215 <primary>address</primary>
216 <secondary>rewriting</secondary>
217 <see><emphasis>rewriting</emphasis></see>
219 <indexterm role="concept">
220 <primary>Bounce Address Tag Validation</primary>
221 <see><emphasis>BATV</emphasis></see>
223 <indexterm role="concept">
224 <primary>Client SMTP Authorization</primary>
225 <see><emphasis>CSA</emphasis></see>
227 <indexterm role="concept">
228 <primary>CR character</primary>
229 <see><emphasis>carriage return</emphasis></see>
231 <indexterm role="concept">
232 <primary>CRL</primary>
233 <see><emphasis>certificate revocation list</emphasis></see>
235 <indexterm role="concept">
236 <primary>delivery</primary>
237 <secondary>failure report</secondary>
238 <see><emphasis>bounce message</emphasis></see>
240 <indexterm role="concept">
241 <primary>dialup</primary>
242 <see><emphasis>intermittently connected hosts</emphasis></see>
244 <indexterm role="concept">
245 <primary>exiscan</primary>
246 <see><emphasis>content scanning</emphasis></see>
248 <indexterm role="concept">
249 <primary>failover</primary>
250 <see><emphasis>fallback</emphasis></see>
252 <indexterm role="concept">
253 <primary>fallover</primary>
254 <see><emphasis>fallback</emphasis></see>
256 <indexterm role="concept">
257 <primary>filter</primary>
258 <secondary>Sieve</secondary>
259 <see><emphasis>Sieve filter</emphasis></see>
261 <indexterm role="concept">
262 <primary>ident</primary>
263 <see><emphasis>RFC 1413</emphasis></see>
265 <indexterm role="concept">
266 <primary>LF character</primary>
267 <see><emphasis>linefeed</emphasis></see>
269 <indexterm role="concept">
270 <primary>maximum</primary>
271 <seealso><emphasis>limit</emphasis></seealso>
273 <indexterm role="concept">
274 <primary>monitor</primary>
275 <see><emphasis>Exim monitor</emphasis></see>
277 <indexterm role="concept">
278 <primary>no_<emphasis>xxx</emphasis></primary>
279 <see>entry for xxx</see>
281 <indexterm role="concept">
282 <primary>NUL</primary>
283 <see><emphasis>binary zero</emphasis></see>
285 <indexterm role="concept">
286 <primary>passwd file</primary>
287 <see><emphasis>/etc/passwd</emphasis></see>
289 <indexterm role="concept">
290 <primary>process id</primary>
291 <see><emphasis>pid</emphasis></see>
293 <indexterm role="concept">
294 <primary>RBL</primary>
295 <see><emphasis>DNS list</emphasis></see>
297 <indexterm role="concept">
298 <primary>redirection</primary>
299 <see><emphasis>address redirection</emphasis></see>
301 <indexterm role="concept">
302 <primary>return path</primary>
303 <seealso><emphasis>envelope sender</emphasis></seealso>
305 <indexterm role="concept">
306 <primary>scanning</primary>
307 <see><emphasis>content scanning</emphasis></see>
309 <indexterm role="concept">
310 <primary>SSL</primary>
311 <see><emphasis>TLS</emphasis></see>
313 <indexterm role="concept">
314 <primary>string</primary>
315 <secondary>expansion</secondary>
316 <see><emphasis>expansion</emphasis></see>
318 <indexterm role="concept">
319 <primary>top bit</primary>
320 <see><emphasis>8-bit characters</emphasis></see>
322 <indexterm role="concept">
323 <primary>variables</primary>
324 <see><emphasis>expansion, variables</emphasis></see>
326 <indexterm role="concept">
327 <primary>zero, binary</primary>
328 <see><emphasis>binary zero</emphasis></see>
330 <indexterm role="concept">
331 <primary>headers</primary>
332 <see><emphasis>header lines</emphasis></see>
338 . /////////////////////////////////////////////////////////////////////////////
339 . This is the real start of the first chapter. See the comment above as to why
340 . we can't have the .chapter line here.
341 . chapter "Introduction"
342 . /////////////////////////////////////////////////////////////////////////////
344 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
345 Unix-like operating systems. It was designed on the assumption that it would be
346 run on hosts that are permanently connected to the Internet. However, it can be
347 used on intermittently connected hosts with suitable configuration adjustments.
349 Configuration files currently exist for the following operating systems: AIX,
350 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
351 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
352 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
353 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and UnixWare.
354 Some of these operating systems are no longer current and cannot easily be
355 tested, so the configuration files may no longer work in practice.
357 There are also configuration files for compiling Exim in the Cygwin environment
358 that can be installed on systems running Windows. However, this document does
359 not contain any information about running Exim in the Cygwin environment.
361 The terms and conditions for the use and distribution of Exim are contained in
362 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
363 Public Licence, a copy of which may be found in the file &_LICENCE_&.
365 The use, supply, or promotion of Exim for the purpose of sending bulk,
366 unsolicited electronic mail is incompatible with the basic aims of Exim,
367 which revolve around the free provision of a service that enhances the quality
368 of personal communications. The author of Exim regards indiscriminate
369 mass-mailing as an antisocial, irresponsible abuse of the Internet.
371 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
372 experience of running and working on the Smail 3 code, I could never have
373 contemplated starting to write a new MTA. Many of the ideas and user interfaces
374 were originally taken from Smail 3, though the actual code of Exim is entirely
375 new, and has developed far beyond the initial concept.
377 Many people, both in Cambridge and around the world, have contributed to the
378 development and the testing of Exim, and to porting it to various operating
379 systems. I am grateful to them all. The distribution now contains a file called
380 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
384 .section "Exim documentation" "SECID1"
385 . Keep this example change bar when updating the documentation!
388 .cindex "documentation"
389 This edition of the Exim specification applies to version &version() of Exim.
390 Substantive changes from the &previousversion; edition are marked in some
391 renditions of this document; this paragraph is so marked if the rendition is
392 capable of showing a change indicator.
395 This document is very much a reference manual; it is not a tutorial. The reader
396 is expected to have some familiarity with the SMTP mail transfer protocol and
397 with general Unix system administration. Although there are some discussions
398 and examples in places, the information is mostly organized in a way that makes
399 it easy to look up, rather than in a natural order for sequential reading.
400 Furthermore, this manual aims to cover every aspect of Exim in detail, including
401 a number of rarely-used, special-purpose features that are unlikely to be of
404 .cindex "books about Exim"
405 An &"easier"& discussion of Exim which provides more in-depth explanatory,
406 introductory, and tutorial material can be found in a book entitled &'The Exim
407 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
408 (&url(https://www.uit.co.uk/exim-book/)).
410 The book also contains a chapter that gives a general introduction to SMTP and
411 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
412 with the latest release of Exim. (Note that the earlier book about Exim,
413 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
415 .cindex "Debian" "information sources"
416 If you are using a Debian distribution of Exim, you will find information about
417 Debian-specific features in the file
418 &_/usr/share/doc/exim4-base/README.Debian_&.
419 The command &(man update-exim.conf)& is another source of Debian-specific
422 .cindex "&_doc/NewStuff_&"
423 .cindex "&_doc/ChangeLog_&"
425 As Exim develops, there may be features in newer versions that have not
426 yet made it into this document, which is updated only when the most significant
427 digit of the fractional part of the version number changes. Specifications of
428 new features that are not yet in this manual are placed in the file
429 &_doc/NewStuff_& in the Exim distribution.
431 Some features may be classified as &"experimental"&. These may change
432 incompatibly while they are developing, or even be withdrawn. For this reason,
433 they are not documented in this manual. Information about experimental features
434 can be found in the file &_doc/experimental.txt_&.
436 All changes to Exim (whether new features, bug fixes, or other kinds of
437 change) are noted briefly in the file called &_doc/ChangeLog_&.
439 .cindex "&_doc/spec.txt_&"
440 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
441 that it can easily be searched with a text editor. Other files in the &_doc_&
445 .row &_OptionLists.txt_& "list of all options in alphabetical order"
446 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
447 .row &_exim.8_& "a man page of Exim's command line options"
448 .row &_experimental.txt_& "documentation of experimental features"
449 .row &_filter.txt_& "specification of the filter language"
450 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
451 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
452 .row &_openssl.txt_& "installing a current OpenSSL release"
455 The main specification and the specification of the filtering language are also
456 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
457 &<<SECTavail>>& below tells you how to get hold of these.
461 .section "FTP site and websites" "SECID2"
464 The primary site for Exim source distributions is the &%exim.org%& FTP site,
465 available over HTTPS, HTTP and FTP. These services, and the &%exim.org%&
466 website, are hosted at the University of Cambridge.
470 As well as Exim distribution tar files, the Exim website contains a number of
471 differently formatted versions of the documentation. A recent addition to the
472 online information is the Exim wiki (&url(https://wiki.exim.org)),
473 which contains what used to be a separate FAQ, as well as various other
474 examples, tips, and know-how that have been contributed by Exim users.
475 The wiki site should always redirect to the correct place, which is currently
476 provided by GitHub, and is open to editing by anyone with a GitHub account.
479 An Exim Bugzilla exists at &url(https://bugs.exim.org). You can use
480 this to report bugs, and also to add items to the wish list. Please search
481 first to check that you are not duplicating a previous entry.
482 Please do not ask for configuration help in the bug-tracker.
485 .section "Mailing lists" "SECID3"
486 .cindex "mailing lists" "for Exim users"
487 The following Exim mailing lists exist:
490 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
491 .row &'exim-users@exim.org'& "General discussion list"
492 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
493 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
496 You can subscribe to these lists, change your existing subscriptions, and view
497 or search the archives via the mailing lists link on the Exim home page.
498 .cindex "Debian" "mailing list for"
499 If you are using a Debian distribution of Exim, you may wish to subscribe to
500 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
503 &url(https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-exim4-users)
505 Please ask Debian-specific questions on that list and not on the general Exim
508 .section "Bug reports" "SECID5"
509 .cindex "bug reports"
510 .cindex "reporting bugs"
511 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
512 via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
513 whether some behaviour is a bug or not, the best thing to do is to post a
514 message to the &'exim-dev'& mailing list and have it discussed.
518 .section "Where to find the Exim distribution" "SECTavail"
520 .cindex "HTTPS download site"
521 .cindex "distribution" "FTP site"
522 .cindex "distribution" "https site"
523 The master distribution site for the Exim distribution is
525 &url(https://downloads.exim.org/)
527 The service is available over HTTPS, HTTP and FTP.
528 We encourage people to migrate to HTTPS.
530 The content served at &url(https://downloads.exim.org/) is identical to the
531 content served at &url(https://ftp.exim.org/pub/exim) and
532 &url(ftp://ftp.exim.org/pub/exim).
534 If accessing via a hostname containing &'ftp'&, then the file references that
535 follow are relative to the &_exim_& directories at these sites.
536 If accessing via the hostname &'downloads'& then the subdirectories described
537 here are top-level directories.
539 There are now quite a number of independent mirror sites around
540 the world. Those that I know about are listed in the file called &_Mirrors_&.
542 Within the top exim directory there are subdirectories called &_exim3_& (for
543 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
544 distributions), and &_Testing_& for testing versions. In the &_exim4_&
545 subdirectory, the current release can always be found in files called
549 &_exim-n.nn.tar.bz2_&
551 where &'n.nn'& is the highest such version number in the directory. The three
552 files contain identical data; the only difference is the type of compression.
553 The &_.xz_& file is usually the smallest, while the &_.gz_& file is the
554 most portable to old systems.
556 .cindex "distribution" "signing details"
557 .cindex "distribution" "public key"
558 .cindex "public key for signed distribution"
559 The distributions will be PGP signed by an individual key of the Release
560 Coordinator. This key will have a uid containing an email address in the
561 &'exim.org'& domain and will have signatures from other people, including
562 other Exim maintainers. We expect that the key will be in the "strong set" of
563 PGP keys. There should be a trust path to that key from the Exim Maintainer's
564 PGP keys, a version of which can be found in the release directory in the file
565 &_Exim-Maintainers-Keyring.asc_&. All keys used will be available in public keyserver pools,
566 such as &'pool.sks-keyservers.net'&.
568 At the time of the last update, releases were being made by Jeremy Harris and signed
569 with key &'0xBCE58C8CE41F32DF'&. Other recent keys used for signing are those
570 of Heiko Schlittermann, &'0x26101B62F69376CE'&,
571 and of Phil Pennock, &'0x4D1E900E14C1CC04'&.
573 The signatures for the tar bundles are in:
575 &_exim-n.nn.tar.xz.asc_&
576 &_exim-n.nn.tar.gz.asc_&
577 &_exim-n.nn.tar.bz2.asc_&
579 For each released version, the log of changes is made available in a
580 separate file in the directory &_ChangeLogs_& so that it is possible to
581 find out what has changed without having to download the entire distribution.
583 .cindex "documentation" "available formats"
584 The main distribution contains ASCII versions of this specification and other
585 documentation; other formats of the documents are available in separate files
586 inside the &_exim4_& directory of the FTP site:
588 &_exim-html-n.nn.tar.gz_&
589 &_exim-pdf-n.nn.tar.gz_&
590 &_exim-postscript-n.nn.tar.gz_&
591 &_exim-texinfo-n.nn.tar.gz_&
593 These tar files contain only the &_doc_& directory, not the complete
594 distribution, and are also available in &_.bz2_& and &_.xz_& forms.
597 .section "Limitations" "SECID6"
599 .cindex "limitations of Exim"
600 .cindex "bang paths" "not handled by Exim"
601 Exim is designed for use as an Internet MTA, and therefore handles addresses in
602 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
603 simple two-component bang paths can be converted by a straightforward rewriting
604 configuration. This restriction does not prevent Exim from being interfaced to
605 UUCP as a transport mechanism, provided that domain addresses are used.
607 .cindex "domainless addresses"
608 .cindex "address" "without domain"
609 Exim insists that every address it handles has a domain attached. For incoming
610 local messages, domainless addresses are automatically qualified with a
611 configured domain value. Configuration options specify from which remote
612 systems unqualified addresses are acceptable. These are then qualified on
615 .cindex "transport" "external"
616 .cindex "external transports"
617 The only external transport mechanisms that are currently implemented are SMTP
618 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
619 transport is available, and there are facilities for writing messages to files
620 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
621 to send messages to other transport mechanisms such as UUCP, provided they can
622 handle domain-style addresses. Batched SMTP input is also catered for.
624 Exim is not designed for storing mail for dial-in hosts. When the volumes of
625 such mail are large, it is better to get the messages &"delivered"& into files
626 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
629 Although Exim does have basic facilities for scanning incoming messages, these
630 are not comprehensive enough to do full virus or spam scanning. Such operations
631 are best carried out using additional specialized software packages. If you
632 compile Exim with the content-scanning extension, straightforward interfaces to
633 a number of common scanners are provided.
637 .section "Runtime configuration" "SECID7"
638 Exim's runtime configuration is held in a single text file that is divided
639 into a number of sections. The entries in this file consist of keywords and
640 values, in the style of Smail 3 configuration files. A default configuration
641 file which is suitable for simple online installations is provided in the
642 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
645 .section "Calling interface" "SECID8"
646 .cindex "Sendmail compatibility" "command line interface"
647 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
648 can be a straight replacement for &_/usr/lib/sendmail_& or
649 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
650 about Sendmail in order to run Exim. For actions other than sending messages,
651 Sendmail-compatible options also exist, but those that produce output (for
652 example, &%-bp%&, which lists the messages in the queue) do so in Exim's own
653 format. There are also some additional options that are compatible with Smail
654 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
655 documents all Exim's command line options. This information is automatically
656 made into the man page that forms part of the Exim distribution.
658 Control of messages in the queue can be done via certain privileged command
659 line options. There is also an optional monitor program called &'eximon'&,
660 which displays current information in an X window, and which contains a menu
661 interface to Exim's command line administration options.
665 .section "Terminology" "SECID9"
666 .cindex "terminology definitions"
667 .cindex "body of message" "definition of"
668 The &'body'& of a message is the actual data that the sender wants to transmit.
669 It is the last part of a message and is separated from the &'header'& (see
670 below) by a blank line.
672 .cindex "bounce message" "definition of"
673 When a message cannot be delivered, it is normally returned to the sender in a
674 delivery failure message or a &"non-delivery report"& (NDR). The term
675 &'bounce'& is commonly used for this action, and the error reports are often
676 called &'bounce messages'&. This is a convenient shorthand for &"delivery
677 failure error report"&. Such messages have an empty sender address in the
678 message's &'envelope'& (see below) to ensure that they cannot themselves give
679 rise to further bounce messages.
681 The term &'default'& appears frequently in this manual. It is used to qualify a
682 value which is used in the absence of any setting in the configuration. It may
683 also qualify an action which is taken unless a configuration setting specifies
686 The term &'defer'& is used when the delivery of a message to a specific
687 destination cannot immediately take place for some reason (a remote host may be
688 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
691 The word &'domain'& is sometimes used to mean all but the first component of a
692 host's name. It is &'not'& used in that sense here, where it normally refers to
693 the part of an email address following the @ sign.
695 .cindex "envelope, definition of"
696 .cindex "sender" "definition of"
697 A message in transit has an associated &'envelope'&, as well as a header and a
698 body. The envelope contains a sender address (to which bounce messages should
699 be delivered), and any number of recipient addresses. References to the
700 sender or the recipients of a message usually mean the addresses in the
701 envelope. An MTA uses these addresses for delivery, and for returning bounce
702 messages, not the addresses that appear in the header lines.
704 .cindex "message" "header, definition of"
705 .cindex "header section" "definition of"
706 The &'header'& of a message is the first part of a message's text, consisting
707 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
708 &'Subject:'&, etc. Long header lines can be split over several text lines by
709 indenting the continuations. The header is separated from the body by a blank
712 .cindex "local part" "definition of"
713 .cindex "domain" "definition of"
714 The term &'local part'&, which is taken from RFC 2822, is used to refer to the
715 part of an email address that precedes the @ sign. The part that follows the
716 @ sign is called the &'domain'& or &'mail domain'&.
718 .cindex "local delivery" "definition of"
719 .cindex "remote delivery, definition of"
720 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
721 delivery to a file or a pipe on the local host from delivery by SMTP over
722 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
723 host it is running on are &'remote'&.
725 .cindex "return path" "definition of"
726 &'Return path'& is another name that is used for the sender address in a
729 .cindex "queue" "definition of"
730 The term &'queue'& is used to refer to the set of messages awaiting delivery
731 because this term is in widespread use in the context of MTAs. However, in
732 Exim's case, the reality is more like a pool than a queue, because there is
733 normally no ordering of waiting messages.
735 .cindex "queue runner" "definition of"
736 The term &'queue runner'& is used to describe a process that scans the queue
737 and attempts to deliver those messages whose retry times have come. This term
738 is used by other MTAs and also relates to the command &%runq%&, but in Exim
739 the waiting messages are normally processed in an unpredictable order.
741 .cindex "spool directory" "definition of"
742 The term &'spool directory'& is used for a directory in which Exim keeps the
743 messages in its queue &-- that is, those that it is in the process of
744 delivering. This should not be confused with the directory in which local
745 mailboxes are stored, which is called a &"spool directory"& by some people. In
746 the Exim documentation, &"spool"& is always used in the first sense.
753 . ////////////////////////////////////////////////////////////////////////////
754 . ////////////////////////////////////////////////////////////////////////////
756 .chapter "Incorporated code" "CHID2"
757 .cindex "incorporated code"
758 .cindex "regular expressions" "library"
761 A number of pieces of external code are included in the Exim distribution.
764 Regular expressions are supported in the main Exim program and in the
765 Exim monitor using the freely-distributable PCRE library, copyright
766 © University of Cambridge. The source to PCRE is no longer shipped with
767 Exim, so you will need to use the version of PCRE shipped with your system,
768 or obtain and install the full version of the library from
769 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
771 .cindex "cdb" "acknowledgment"
772 Support for the cdb (Constant DataBase) lookup method is provided by code
773 contributed by Nigel Metheringham of (at the time he contributed it) Planet
774 Online Ltd. The implementation is completely contained within the code of Exim.
775 It does not link against an external cdb library. The code contains the
776 following statements:
779 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
781 This program is free software; you can redistribute it and/or modify it under
782 the terms of the GNU General Public License as published by the Free Software
783 Foundation; either version 2 of the License, or (at your option) any later
785 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
786 the spec and sample code for cdb can be obtained from
787 &url(https://cr.yp.to/cdb.html). This implementation borrows
788 some code from Dan Bernstein's implementation (which has no license
789 restrictions applied to it).
792 .cindex "SPA authentication"
793 .cindex "Samba project"
794 .cindex "Microsoft Secure Password Authentication"
795 Client support for Microsoft's &'Secure Password Authentication'& is provided
796 by code contributed by Marc Prud'hommeaux. Server support was contributed by
797 Tom Kistner. This includes code taken from the Samba project, which is released
801 .cindex "&'pwcheck'& daemon"
802 .cindex "&'pwauthd'& daemon"
803 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
804 by code taken from the Cyrus-SASL library and adapted by Alexander S.
805 Sabourenkov. The permission notice appears below, in accordance with the
806 conditions expressed therein.
809 Copyright © 2001 Carnegie Mellon University. All rights reserved.
811 Redistribution and use in source and binary forms, with or without
812 modification, are permitted provided that the following conditions
816 Redistributions of source code must retain the above copyright
817 notice, this list of conditions and the following disclaimer.
819 Redistributions in binary form must reproduce the above copyright
820 notice, this list of conditions and the following disclaimer in
821 the documentation and/or other materials provided with the
824 The name &"Carnegie Mellon University"& must not be used to
825 endorse or promote products derived from this software without
826 prior written permission. For permission or any other legal
827 details, please contact
829 Office of Technology Transfer
830 Carnegie Mellon University
832 Pittsburgh, PA 15213-3890
833 (412) 268-4387, fax: (412) 268-7395
834 tech-transfer@andrew.cmu.edu
837 Redistributions of any form whatsoever must retain the following
840 &"This product includes software developed by Computing Services
841 at Carnegie Mellon University (&url(https://www.cmu.edu/computing/)."&
843 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
844 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
845 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
846 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
847 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
848 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
849 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
854 .cindex "Exim monitor" "acknowledgment"
857 The Exim Monitor program, which is an X-Window application, includes
858 modified versions of the Athena StripChart and TextPop widgets.
859 This code is copyright by DEC and MIT, and their permission notice appears
860 below, in accordance with the conditions expressed therein.
863 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
864 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
868 Permission to use, copy, modify, and distribute this software and its
869 documentation for any purpose and without fee is hereby granted,
870 provided that the above copyright notice appear in all copies and that
871 both that copyright notice and this permission notice appear in
872 supporting documentation, and that the names of Digital or MIT not be
873 used in advertising or publicity pertaining to distribution of the
874 software without specific, written prior permission.
876 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
877 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
878 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
879 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
880 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
881 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
886 .cindex "opendmarc" "acknowledgment"
887 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
888 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
889 derived code are indicated in the respective source files. The full OpenDMARC
890 license is provided in the LICENSE.opendmarc file contained in the distributed
894 Many people have contributed code fragments, some large, some small, that were
895 not covered by any specific license requirements. It is assumed that the
896 contributors are happy to see their code incorporated into Exim under the GPL.
903 . ////////////////////////////////////////////////////////////////////////////
904 . ////////////////////////////////////////////////////////////////////////////
906 .chapter "How Exim receives and delivers mail" "CHID11" &&&
907 "Receiving and delivering mail"
910 .section "Overall philosophy" "SECID10"
911 .cindex "design philosophy"
912 Exim is designed to work efficiently on systems that are permanently connected
913 to the Internet and are handling a general mix of mail. In such circumstances,
914 most messages can be delivered immediately. Consequently, Exim does not
915 maintain independent queues of messages for specific domains or hosts, though
916 it does try to send several messages in a single SMTP connection after a host
917 has been down, and it also maintains per-host retry information.
920 .section "Policy control" "SECID11"
921 .cindex "policy control" "overview"
922 Policy controls are now an important feature of MTAs that are connected to the
923 Internet. Perhaps their most important job is to stop MTAs from being abused as
924 &"open relays"& by misguided individuals who send out vast amounts of
925 unsolicited junk and want to disguise its source. Exim provides flexible
926 facilities for specifying policy controls on incoming mail:
929 .cindex "&ACL;" "introduction"
930 Exim 4 (unlike previous versions of Exim) implements policy controls on
931 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
932 series of statements that may either grant or deny access. ACLs can be used at
933 several places in the SMTP dialogue while receiving a message from a remote
934 host. However, the most common places are after each RCPT command, and at the
935 very end of the message. The sysadmin can specify conditions for accepting or
936 rejecting individual recipients or the entire message, respectively, at these
937 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
940 An ACL is also available for locally generated, non-SMTP messages. In this
941 case, the only available actions are to accept or deny the entire message.
943 When Exim is compiled with the content-scanning extension, facilities are
944 provided in the ACL mechanism for passing the message to external virus and/or
945 spam scanning software. The result of such a scan is passed back to the ACL,
946 which can then use it to decide what to do with the message.
948 When a message has been received, either from a remote host or from the local
949 host, but before the final acknowledgment has been sent, a locally supplied C
950 function called &[local_scan()]& can be run to inspect the message and decide
951 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
952 is accepted, the list of recipients can be modified by the function.
954 Using the &[local_scan()]& mechanism is another way of calling external scanner
955 software. The &%SA-Exim%& add-on package works this way. It does not require
956 Exim to be compiled with the content-scanning extension.
958 After a message has been accepted, a further checking mechanism is available in
959 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
960 runs at the start of every delivery process.
965 .section "User filters" "SECID12"
966 .cindex "filter" "introduction"
967 .cindex "Sieve filter"
968 In a conventional Exim configuration, users are able to run private filters by
969 setting up appropriate &_.forward_& files in their home directories. See
970 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
971 configuration needed to support this, and the separate document entitled
972 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
973 of filtering are available:
976 Sieve filters are written in the standard filtering language that is defined
979 Exim filters are written in a syntax that is unique to Exim, but which is more
980 powerful than Sieve, which it pre-dates.
983 User filters are run as part of the routing process, described below.
987 .section "Message identification" "SECTmessiden"
988 .cindex "message ids" "details of format"
989 .cindex "format" "of message id"
990 .cindex "id of message"
995 Every message handled by Exim is given a &'message id'& which is sixteen
996 characters long. It is divided into three parts, separated by hyphens, for
997 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
998 normally encoding numbers in base 62. However, in the Darwin operating
999 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
1000 (avoiding the use of lower case letters) is used instead, because the message
1001 id is used to construct filenames, and the names of files in those systems are
1002 not always case-sensitive.
1004 .cindex "pid (process id)" "re-use of"
1005 The detail of the contents of the message id have changed as Exim has evolved.
1006 Earlier versions relied on the operating system not re-using a process id (pid)
1007 within one second. On modern operating systems, this assumption can no longer
1008 be made, so the algorithm had to be changed. To retain backward compatibility,
1009 the format of the message id was retained, which is why the following rules are
1013 The first six characters of the message id are the time at which the message
1014 started to be received, to a granularity of one second. That is, this field
1015 contains the number of seconds since the start of the epoch (the normal Unix
1016 way of representing the date and time of day).
1018 After the first hyphen, the next six characters are the id of the process that
1019 received the message.
1021 There are two different possibilities for the final two characters:
1023 .oindex "&%localhost_number%&"
1024 If &%localhost_number%& is not set, this value is the fractional part of the
1025 time of reception, normally in units of 1/2000 of a second, but for systems
1026 that must use base 36 instead of base 62 (because of case-insensitive file
1027 systems), the units are 1/1000 of a second.
1029 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1030 the fractional part of the time, which in this case is in units of 1/200
1031 (1/100) of a second.
1035 After a message has been received, Exim waits for the clock to tick at the
1036 appropriate resolution before proceeding, so that if another message is
1037 received by the same process, or by another process with the same (re-used)
1038 pid, it is guaranteed that the time will be different. In most cases, the clock
1039 will already have ticked while the message was being received.
1042 .section "Receiving mail" "SECID13"
1043 .cindex "receiving mail"
1044 .cindex "message" "reception"
1045 The only way Exim can receive mail from another host is using SMTP over
1046 TCP/IP, in which case the sender and recipient addresses are transferred using
1047 SMTP commands. However, from a locally running process (such as a user's MUA),
1048 there are several possibilities:
1051 If the process runs Exim with the &%-bm%& option, the message is read
1052 non-interactively (usually via a pipe), with the recipients taken from the
1053 command line, or from the body of the message if &%-t%& is also used.
1055 If the process runs Exim with the &%-bS%& option, the message is also read
1056 non-interactively, but in this case the recipients are listed at the start of
1057 the message in a series of SMTP RCPT commands, terminated by a DATA
1058 command. This is called &"batch SMTP"& format,
1059 but it isn't really SMTP. The SMTP commands are just another way of passing
1060 envelope addresses in a non-interactive submission.
1062 If the process runs Exim with the &%-bs%& option, the message is read
1063 interactively, using the SMTP protocol. A two-way pipe is normally used for
1064 passing data between the local process and the Exim process.
1065 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1066 example, the ACLs for SMTP commands are used for this form of submission.
1068 A local process may also make a TCP/IP call to the host's loopback address
1069 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1070 does not treat the loopback address specially. It treats all such connections
1071 in the same way as connections from other hosts.
1075 .cindex "message sender, constructed by Exim"
1076 .cindex "sender" "constructed by Exim"
1077 In the three cases that do not involve TCP/IP, the sender address is
1078 constructed from the login name of the user that called Exim and a default
1079 qualification domain (which can be set by the &%qualify_domain%& configuration
1080 option). For local or batch SMTP, a sender address that is passed using the
1081 SMTP MAIL command is ignored. However, the system administrator may allow
1082 certain users (&"trusted users"&) to specify a different sender addresses
1083 unconditionally, or all users to specify certain forms of different sender
1084 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1085 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1086 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1087 users to change sender addresses.
1089 Messages received by either of the non-interactive mechanisms are subject to
1090 checking by the non-SMTP ACL if one is defined. Messages received using SMTP
1091 (either over TCP/IP or interacting with a local process) can be checked by a
1092 number of ACLs that operate at different times during the SMTP session. Either
1093 individual recipients or the entire message can be rejected if local policy
1094 requirements are not met. The &[local_scan()]& function (see chapter
1095 &<<CHAPlocalscan>>&) is run for all incoming messages.
1097 Exim can be configured not to start a delivery process when a message is
1098 received; this can be unconditional, or depend on the number of incoming SMTP
1099 connections or the system load. In these situations, new messages wait on the
1100 queue until a queue runner process picks them up. However, in standard
1101 configurations under normal conditions, delivery is started as soon as a
1102 message is received.
1108 .section "Handling an incoming message" "SECID14"
1109 .cindex "spool directory" "files that hold a message"
1110 .cindex "file" "how a message is held"
1111 When Exim accepts a message, it writes two files in its spool directory. The
1112 first contains the envelope information, the current status of the message, and
1113 the header lines, and the second contains the body of the message. The names of
1114 the two spool files consist of the message id, followed by &`-H`& for the
1115 file containing the envelope and header, and &`-D`& for the data file.
1117 .cindex "spool directory" "&_input_& sub-directory"
1118 By default, all these message files are held in a single directory called
1119 &_input_& inside the general Exim spool directory. Some operating systems do
1120 not perform very well if the number of files in a directory gets large; to
1121 improve performance in such cases, the &%split_spool_directory%& option can be
1122 used. This causes Exim to split up the input files into 62 sub-directories
1123 whose names are single letters or digits. When this is done, the queue is
1124 processed one sub-directory at a time instead of all at once, which can improve
1125 overall performance even when there are not enough files in each directory to
1126 affect file system performance.
1128 The envelope information consists of the address of the message's sender and
1129 the addresses of the recipients. This information is entirely separate from
1130 any addresses contained in the header lines. The status of the message includes
1131 a list of recipients who have already received the message. The format of the
1132 first spool file is described in chapter &<<CHAPspool>>&.
1134 .cindex "rewriting" "addresses"
1135 Address rewriting that is specified in the rewrite section of the configuration
1136 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1137 both in the header lines and the envelope, at the time the message is accepted.
1138 If during the course of delivery additional addresses are generated (for
1139 example, via aliasing), these new addresses are rewritten as soon as they are
1140 generated. At the time a message is actually delivered (transported) further
1141 rewriting can take place; because this is a transport option, it can be
1142 different for different forms of delivery. It is also possible to specify the
1143 addition or removal of certain header lines at the time the message is
1144 delivered (see chapters &<<CHAProutergeneric>>& and
1145 &<<CHAPtransportgeneric>>&).
1149 .section "Life of a message" "SECID15"
1150 .cindex "message" "life of"
1151 .cindex "message" "frozen"
1152 A message remains in the spool directory until it is completely delivered to
1153 its recipients or to an error address, or until it is deleted by an
1154 administrator or by the user who originally created it. In cases when delivery
1155 cannot proceed &-- for example when a message can neither be delivered to its
1156 recipients nor returned to its sender, the message is marked &"frozen"& on the
1157 spool, and no more deliveries are attempted.
1159 .cindex "frozen messages" "thawing"
1160 .cindex "message" "thawing frozen"
1161 An administrator can &"thaw"& such messages when the problem has been
1162 corrected, and can also freeze individual messages by hand if necessary. In
1163 addition, an administrator can force a delivery error, causing a bounce message
1166 .oindex "&%timeout_frozen_after%&"
1167 .oindex "&%ignore_bounce_errors_after%&"
1168 There are options called &%ignore_bounce_errors_after%& and
1169 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1170 The first applies only to frozen bounces, the second to all frozen messages.
1172 .cindex "message" "log file for"
1173 .cindex "log" "file for each message"
1174 While Exim is working on a message, it writes information about each delivery
1175 attempt to its main log file. This includes successful, unsuccessful, and
1176 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1177 lines are also written to a separate &'message log'& file for each message.
1178 These logs are solely for the benefit of the administrator and are normally
1179 deleted along with the spool files when processing of a message is complete.
1180 The use of individual message logs can be disabled by setting
1181 &%no_message_logs%&; this might give an improvement in performance on very busy
1184 .cindex "journal file"
1185 .cindex "file" "journal"
1186 All the information Exim itself needs to set up a delivery is kept in the first
1187 spool file, along with the header lines. When a successful delivery occurs, the
1188 address is immediately written at the end of a journal file, whose name is the
1189 message id followed by &`-J`&. At the end of a delivery run, if there are some
1190 addresses left to be tried again later, the first spool file (the &`-H`& file)
1191 is updated to indicate which these are, and the journal file is then deleted.
1192 Updating the spool file is done by writing a new file and renaming it, to
1193 minimize the possibility of data loss.
1195 Should the system or Exim crash after a successful delivery but before
1196 the spool file has been updated, the journal is left lying around. The next
1197 time Exim attempts to deliver the message, it reads the journal file and
1198 updates the spool file before proceeding. This minimizes the chances of double
1199 deliveries caused by crashes.
1203 .section "Processing an address for delivery" "SECTprocaddress"
1204 .cindex "drivers" "definition of"
1205 .cindex "router" "definition of"
1206 .cindex "transport" "definition of"
1207 The main delivery processing elements of Exim are called &'routers'& and
1208 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1209 number of them is provided in the source distribution, and compile-time options
1210 specify which ones are included in the binary. Runtime options specify which
1211 ones are actually used for delivering messages.
1213 .cindex "drivers" "instance definition"
1214 Each driver that is specified in the runtime configuration is an &'instance'&
1215 of that particular driver type. Multiple instances are allowed; for example,
1216 you can set up several different &(smtp)& transports, each with different
1217 option values that might specify different ports or different timeouts. Each
1218 instance has its own identifying name. In what follows we will normally use the
1219 instance name when discussing one particular instance (that is, one specific
1220 configuration of the driver), and the generic driver name when discussing
1221 the driver's features in general.
1223 A &'router'& is a driver that operates on an address, either determining how
1224 its delivery should happen, by assigning it to a specific transport, or
1225 converting the address into one or more new addresses (for example, via an
1226 alias file). A router may also explicitly choose to fail an address, causing it
1229 A &'transport'& is a driver that transmits a copy of the message from Exim's
1230 spool to some destination. There are two kinds of transport: for a &'local'&
1231 transport, the destination is a file or a pipe on the local host, whereas for a
1232 &'remote'& transport the destination is some other host. A message is passed
1233 to a specific transport as a result of successful routing. If a message has
1234 several recipients, it may be passed to a number of different transports.
1236 .cindex "preconditions" "definition of"
1237 An address is processed by passing it to each configured router instance in
1238 turn, subject to certain preconditions, until a router accepts the address or
1239 specifies that it should be bounced. We will describe this process in more
1240 detail shortly. First, as a simple example, we consider how each recipient
1241 address in a message is processed in a small configuration of three routers.
1243 To make this a more concrete example, it is described in terms of some actual
1244 routers, but remember, this is only an example. You can configure Exim's
1245 routers in many different ways, and there may be any number of routers in a
1248 The first router that is specified in a configuration is often one that handles
1249 addresses in domains that are not recognized specifically by the local host.
1250 Typically these are addresses for arbitrary domains on the Internet. A precondition
1251 is set up which looks for the special domains known to the host (for example,
1252 its own domain name), and the router is run for addresses that do &'not'&
1253 match. Typically, this is a router that looks up domains in the DNS in order to
1254 find the hosts to which this address routes. If it succeeds, the address is
1255 assigned to a suitable SMTP transport; if it does not succeed, the router is
1256 configured to fail the address.
1258 The second router is reached only when the domain is recognized as one that
1259 &"belongs"& to the local host. This router does redirection &-- also known as
1260 aliasing and forwarding. When it generates one or more new addresses from the
1261 original, each of them is routed independently from the start. Otherwise, the
1262 router may cause an address to fail, or it may simply decline to handle the
1263 address, in which case the address is passed to the next router.
1265 The final router in many configurations is one that checks to see if the
1266 address belongs to a local mailbox. The precondition may involve a check to
1267 see if the local part is the name of a login account, or it may look up the
1268 local part in a file or a database. If its preconditions are not met, or if
1269 the router declines, we have reached the end of the routers. When this happens,
1270 the address is bounced.
1274 .section "Processing an address for verification" "SECID16"
1275 .cindex "router" "for verification"
1276 .cindex "verifying address" "overview"
1277 As well as being used to decide how to deliver to an address, Exim's routers
1278 are also used for &'address verification'&. Verification can be requested as
1279 one of the checks to be performed in an ACL for incoming messages, on both
1280 sender and recipient addresses, and it can be tested using the &%-bv%& and
1281 &%-bvs%& command line options.
1283 When an address is being verified, the routers are run in &"verify mode"&. This
1284 does not affect the way the routers work, but it is a state that can be
1285 detected. By this means, a router can be skipped or made to behave differently
1286 when verifying. A common example is a configuration in which the first router
1287 sends all messages to a message-scanning program unless they have been
1288 previously scanned. Thus, the first router accepts all addresses without any
1289 checking, making it useless for verifying. Normally, the &%no_verify%& option
1290 would be set for such a router, causing it to be skipped in verify mode.
1295 .section "Running an individual router" "SECTrunindrou"
1296 .cindex "router" "running details"
1297 .cindex "preconditions" "checking"
1298 .cindex "router" "result of running"
1299 As explained in the example above, a number of preconditions are checked before
1300 running a router. If any are not met, the router is skipped, and the address is
1301 passed to the next router. When all the preconditions on a router &'are'& met,
1302 the router is run. What happens next depends on the outcome, which is one of
1306 &'accept'&: The router accepts the address, and either assigns it to a
1307 transport or generates one or more &"child"& addresses. Processing the
1308 original address ceases
1309 .oindex "&%unseen%&"
1310 unless the &%unseen%& option is set on the router. This option
1311 can be used to set up multiple deliveries with different routing (for example,
1312 for keeping archive copies of messages). When &%unseen%& is set, the address is
1313 passed to the next router. Normally, however, an &'accept'& return marks the
1316 Any child addresses generated by the router are processed independently,
1317 starting with the first router by default. It is possible to change this by
1318 setting the &%redirect_router%& option to specify which router to start at for
1319 child addresses. Unlike &%pass_router%& (see below) the router specified by
1320 &%redirect_router%& may be anywhere in the router configuration.
1322 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1323 requests that the address be passed to another router. By default, the address
1324 is passed to the next router, but this can be changed by setting the
1325 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1326 must be below the current router (to avoid loops).
1328 &'decline'&: The router declines to accept the address because it does not
1329 recognize it at all. By default, the address is passed to the next router, but
1330 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1331 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1332 &'decline'& into &'fail'&.
1334 &'fail'&: The router determines that the address should fail, and queues it for
1335 the generation of a bounce message. There is no further processing of the
1336 original address unless &%unseen%& is set on the router.
1338 &'defer'&: The router cannot handle the address at the present time. (A
1339 database may be offline, or a DNS lookup may have timed out.) No further
1340 processing of the address happens in this delivery attempt. It is tried again
1341 next time the message is considered for delivery.
1343 &'error'&: There is some error in the router (for example, a syntax error in
1344 its configuration). The action is as for defer.
1347 If an address reaches the end of the routers without having been accepted by
1348 any of them, it is bounced as unrouteable. The default error message in this
1349 situation is &"unrouteable address"&, but you can set your own message by
1350 making use of the &%cannot_route_message%& option. This can be set for any
1351 router; the value from the last router that &"saw"& the address is used.
1353 Sometimes while routing you want to fail a delivery when some conditions are
1354 met but others are not, instead of passing the address on for further routing.
1355 You can do this by having a second router that explicitly fails the delivery
1356 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1357 facility for this purpose.
1360 .section "Duplicate addresses" "SECID17"
1361 .cindex "case of local parts"
1362 .cindex "address duplicate, discarding"
1363 .cindex "duplicate addresses"
1364 Once routing is complete, Exim scans the addresses that are assigned to local
1365 and remote transports and discards any duplicates that it finds. During this
1366 check, local parts are treated case-sensitively. This happens only when
1367 actually delivering a message; when testing routers with &%-bt%&, all the
1368 routed addresses are shown.
1372 .section "Router preconditions" "SECTrouprecon"
1373 .cindex "router" "preconditions, order of processing"
1374 .cindex "preconditions" "order of processing"
1375 The preconditions that are tested for each router are listed below, in the
1376 order in which they are tested. The individual configuration options are
1377 described in more detail in chapter &<<CHAProutergeneric>>&.
1380 .cindex affix "router precondition"
1381 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1382 the local parts handled by the router may or must have certain prefixes and/or
1383 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1384 skipped. These conditions are tested first. When an affix is present, it is
1385 removed from the local part before further processing, including the evaluation
1386 of any other conditions.
1388 Routers can be designated for use only when not verifying an address, that is,
1389 only when routing it for delivery (or testing its delivery routing). If the
1390 &%verify%& option is set false, the router is skipped when Exim is verifying an
1392 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1393 &%verify_recipient%&, which independently control the use of the router for
1394 sender and recipient verification. You can set these options directly if
1395 you want a router to be used for only one type of verification.
1396 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1398 If the &%address_test%& option is set false, the router is skipped when Exim is
1399 run with the &%-bt%& option to test an address routing. This can be helpful
1400 when the first router sends all new messages to a scanner of some sort; it
1401 makes it possible to use &%-bt%& to test subsequent delivery routing without
1402 having to simulate the effect of the scanner.
1404 Routers can be designated for use only when verifying an address, as
1405 opposed to routing it for delivery. The &%verify_only%& option controls this.
1406 Again, cutthrough delivery counts as a verification.
1408 Individual routers can be explicitly skipped when running the routers to
1409 check an address given in the SMTP EXPN command (see the &%expn%& option).
1412 If the &%domains%& option is set, the domain of the address must be in the set
1413 of domains that it defines.
1415 .cindex "tainted data" "de-tainting"
1416 A match verifies the variable &$domain$& (which carries tainted data)
1417 and assigns an untainted value to the &$domain_data$& variable.
1418 Such an untainted value is often needed in the transport.
1419 For specifics of the matching operation and the resulting untainted value,
1420 refer to section &<<SECTdomainlist>>&.
1422 When an untainted value is wanted, use this option
1423 rather than the generic &%condition%& option.
1427 .vindex "&$local_part_prefix$&"
1428 .vindex "&$local_part_prefix_v$&"
1429 .vindex "&$local_part$&"
1430 .vindex "&$local_part_suffix$&"
1431 .vindex "&$local_part_suffix_v$&"
1432 .cindex affix "router precondition"
1433 If the &%local_parts%& option is set, the local part of the address must be in
1434 the set of local parts that it defines.
1436 A match verifies the variable &$local_part$& (which carries tainted data)
1437 and assigns an untainted value to the &$local_part_data$& variable.
1438 Such an untainted value is often needed in the transport.
1439 For specifics of the matching operation and the resulting untainted value,
1440 refer to section &<<SECTlocparlis>>&.
1442 When an untainted value is wanted, use this option
1443 rather than the generic &%condition%& option.
1446 If &%local_part_prefix%& or
1447 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1448 part before this check. If you want to do precondition tests on local parts
1449 that include affixes, you can do so by using a &%condition%& option (see below)
1450 that uses the variables &$local_part$&, &$local_part_prefix$&,
1451 &$local_part_prefix_v$&, &$local_part_suffix$&
1452 and &$local_part_suffix_v$& as necessary.
1455 .vindex "&$local_user_uid$&"
1456 .vindex "&$local_user_gid$&"
1458 If the &%check_local_user%& option is set, the local part must be the name of
1459 an account on the local host. If this check succeeds, the uid and gid of the
1460 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1461 user's home directory is placed in &$home$&; these values can be used in the
1462 remaining preconditions.
1465 If the &%router_home_directory%& option is set, it is expanded at this point,
1466 because it overrides the value of &$home$&. If this expansion were left till
1467 later, the value of &$home$& as set by &%check_local_user%& would be used in
1468 subsequent tests. Having two different values of &$home$& in the same router
1469 could lead to confusion.
1472 If the &%senders%& option is set, the envelope sender address must be in the
1473 set of addresses that it defines.
1476 If the &%require_files%& option is set, the existence or non-existence of
1477 specified files is tested.
1480 .cindex "customizing" "precondition"
1481 If the &%condition%& option is set, it is evaluated and tested. This option
1482 uses an expanded string to allow you to set up your own custom preconditions.
1483 Expanded strings are described in chapter &<<CHAPexpand>>&.
1486 Note that while using
1487 this option for address matching technically works,
1488 it does not set any de-tainted values.
1489 Such values are often needed, either for router-specific options or
1490 for transport options.
1491 Using the &%domains%& and &%local_parts%& options is usually the most
1492 convenient way to obtain them.
1497 Note that &%require_files%& comes near the end of the list, so you cannot use
1498 it to check for the existence of a file in which to lookup up a domain, local
1499 part, or sender. However, as these options are all expanded, you can use the
1500 &%exists%& expansion condition to make such tests within each condition. The
1501 &%require_files%& option is intended for checking files that the router may be
1502 going to use internally, or which are needed by a specific transport (for
1503 example, &_.procmailrc_&).
1507 .section "Delivery in detail" "SECID18"
1508 .cindex "delivery" "in detail"
1509 When a message is to be delivered, the sequence of events is as follows:
1512 If a system-wide filter file is specified, the message is passed to it. The
1513 filter may add recipients to the message, replace the recipients, discard the
1514 message, cause a new message to be generated, or cause the message delivery to
1515 fail. The format of the system filter file is the same as for Exim user filter
1516 files, described in the separate document entitled &'Exim's interfaces to mail
1518 .cindex "Sieve filter" "not available for system filter"
1519 (&*Note*&: Sieve cannot be used for system filter files.)
1521 Some additional features are available in system filters &-- see chapter
1522 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1523 filter only once per delivery attempt, however many recipients it has. However,
1524 if there are several delivery attempts because one or more addresses could not
1525 be immediately delivered, the system filter is run each time. The filter
1526 condition &%first_delivery%& can be used to detect the first run of the system
1529 Each recipient address is offered to each configured router, in turn, subject to
1530 its preconditions, until one is able to handle it. If no router can handle the
1531 address, that is, if they all decline, the address is failed. Because routers
1532 can be targeted at particular domains, several locally handled domains can be
1533 processed entirely independently of each other.
1535 .cindex "routing" "loops in"
1536 .cindex "loop" "while routing"
1537 A router that accepts an address may assign it to a local or a remote
1538 transport. However, the transport is not run at this time. Instead, the address
1539 is placed on a list for the particular transport, which will be run later.
1540 Alternatively, the router may generate one or more new addresses (typically
1541 from alias, forward, or filter files). New addresses are fed back into this
1542 process from the top, but in order to avoid loops, a router ignores any address
1543 which has an identically-named ancestor that was processed by itself.
1545 When all the routing has been done, addresses that have been successfully
1546 handled are passed to their assigned transports. When local transports are
1547 doing real local deliveries, they handle only one address at a time, but if a
1548 local transport is being used as a pseudo-remote transport (for example, to
1549 collect batched SMTP messages for transmission by some other means) multiple
1550 addresses can be handled. Remote transports can always handle more than one
1551 address at a time, but can be configured not to do so, or to restrict multiple
1552 addresses to the same domain.
1554 Each local delivery to a file or a pipe runs in a separate process under a
1555 non-privileged uid, and these deliveries are run one at a time. Remote
1556 deliveries also run in separate processes, normally under a uid that is private
1557 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1558 run in parallel. The maximum number of simultaneous remote deliveries for any
1559 one message is set by the &%remote_max_parallel%& option.
1560 The order in which deliveries are done is not defined, except that all local
1561 deliveries happen before any remote deliveries.
1563 .cindex "queue runner"
1564 When it encounters a local delivery during a queue run, Exim checks its retry
1565 database to see if there has been a previous temporary delivery failure for the
1566 address before running the local transport. If there was a previous failure,
1567 Exim does not attempt a new delivery until the retry time for the address is
1568 reached. However, this happens only for delivery attempts that are part of a
1569 queue run. Local deliveries are always attempted when delivery immediately
1570 follows message reception, even if retry times are set for them. This makes for
1571 better behaviour if one particular message is causing problems (for example,
1572 causing quota overflow, or provoking an error in a filter file).
1574 .cindex "delivery" "retry in remote transports"
1575 Remote transports do their own retry handling, since an address may be
1576 deliverable to one of a number of hosts, each of which may have a different
1577 retry time. If there have been previous temporary failures and no host has
1578 reached its retry time, no delivery is attempted, whether in a queue run or
1579 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1581 If there were any permanent errors, a bounce message is returned to an
1582 appropriate address (the sender in the common case), with details of the error
1583 for each failing address. Exim can be configured to send copies of bounce
1584 messages to other addresses.
1586 .cindex "delivery" "deferral"
1587 If one or more addresses suffered a temporary failure, the message is left on
1588 the queue, to be tried again later. Delivery of these addresses is said to be
1591 When all the recipient addresses have either been delivered or bounced,
1592 handling of the message is complete. The spool files and message log are
1593 deleted, though the message log can optionally be preserved if required.
1599 .section "Retry mechanism" "SECID19"
1600 .cindex "delivery" "retry mechanism"
1601 .cindex "retry" "description of mechanism"
1602 .cindex "queue runner"
1603 Exim's mechanism for retrying messages that fail to get delivered at the first
1604 attempt is the queue runner process. You must either run an Exim daemon that
1605 uses the &%-q%& option with a time interval to start queue runners at regular
1606 intervals or use some other means (such as &'cron'&) to start them. If you do
1607 not arrange for queue runners to be run, messages that fail temporarily at the
1608 first attempt will remain in your queue forever. A queue runner process works
1609 its way through the queue, one message at a time, trying each delivery that has
1610 passed its retry time.
1611 You can run several queue runners at once.
1613 Exim uses a set of configured rules to determine when next to retry the failing
1614 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1615 should give up trying to deliver to the address, at which point it generates a
1616 bounce message. If no retry rules are set for a particular host, address, and
1617 error combination, no retries are attempted, and temporary errors are treated
1622 .section "Temporary delivery failure" "SECID20"
1623 .cindex "delivery" "temporary failure"
1624 There are many reasons why a message may not be immediately deliverable to a
1625 particular address. Failure to connect to a remote machine (because it, or the
1626 connection to it, is down) is one of the most common. Temporary failures may be
1627 detected during routing as well as during the transport stage of delivery.
1628 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1629 is on a file system where the user is over quota. Exim can be configured to
1630 impose its own quotas on local mailboxes; where system quotas are set they will
1633 If a host is unreachable for a period of time, a number of messages may be
1634 waiting for it by the time it recovers, and sending them in a single SMTP
1635 connection is clearly beneficial. Whenever a delivery to a remote host is
1637 .cindex "hints database" "deferred deliveries"
1638 Exim makes a note in its hints database, and whenever a successful
1639 SMTP delivery has happened, it looks to see if any other messages are waiting
1640 for the same host. If any are found, they are sent over the same SMTP
1641 connection, subject to a configuration limit as to the maximum number in any
1646 .section "Permanent delivery failure" "SECID21"
1647 .cindex "delivery" "permanent failure"
1648 .cindex "bounce message" "when generated"
1649 When a message cannot be delivered to some or all of its intended recipients, a
1650 bounce message is generated. Temporary delivery failures turn into permanent
1651 errors when their timeout expires. All the addresses that fail in a given
1652 delivery attempt are listed in a single message. If the original message has
1653 many recipients, it is possible for some addresses to fail in one delivery
1654 attempt and others to fail subsequently, giving rise to more than one bounce
1655 message. The wording of bounce messages can be customized by the administrator.
1656 See chapter &<<CHAPemsgcust>>& for details.
1658 .cindex "&'X-Failed-Recipients:'& header line"
1659 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1660 failed addresses, for the benefit of programs that try to analyse such messages
1663 .cindex "bounce message" "recipient of"
1664 A bounce message is normally sent to the sender of the original message, as
1665 obtained from the message's envelope. For incoming SMTP messages, this is the
1666 address given in the MAIL command. However, when an address is expanded via a
1667 forward or alias file, an alternative address can be specified for delivery
1668 failures of the generated addresses. For a mailing list expansion (see section
1669 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1674 .section "Failures to deliver bounce messages" "SECID22"
1675 .cindex "bounce message" "failure to deliver"
1676 If a bounce message (either locally generated or received from a remote host)
1677 itself suffers a permanent delivery failure, the message is left in the queue,
1678 but it is frozen, awaiting the attention of an administrator. There are options
1679 that can be used to make Exim discard such failed messages, or to keep them
1680 for only a short time (see &%timeout_frozen_after%& and
1681 &%ignore_bounce_errors_after%&).
1687 . ////////////////////////////////////////////////////////////////////////////
1688 . ////////////////////////////////////////////////////////////////////////////
1690 .chapter "Building and installing Exim" "CHID3"
1691 .scindex IIDbuex "building Exim"
1693 .section "Unpacking" "SECID23"
1694 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1695 creates a directory with the name of the current release (for example,
1696 &_exim-&version()_&) into which the following files are placed:
1699 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1700 .irow &_CHANGES_& "contains a reference to where changes are &&&
1702 .irow &_LICENCE_& "the GNU General Public Licence"
1703 .irow &_Makefile_& "top-level make file"
1704 .irow &_NOTICE_& "conditions for the use of Exim"
1705 .irow &_README_& "list of files, directories and simple build &&&
1709 Other files whose names begin with &_README_& may also be present. The
1710 following subdirectories are created:
1713 .irow &_Local_& "an empty directory for local configuration files"
1714 .irow &_OS_& "OS-specific files"
1715 .irow &_doc_& "documentation files"
1716 .irow &_exim_monitor_& "source files for the Exim monitor"
1717 .irow &_scripts_& "scripts used in the build process"
1718 .irow &_src_& "remaining source files"
1719 .irow &_util_& "independent utilities"
1722 The main utility programs are contained in the &_src_& directory and are built
1723 with the Exim binary. The &_util_& directory contains a few optional scripts
1724 that may be useful to some sites.
1727 .section "Multiple machine architectures and operating systems" "SECID24"
1728 .cindex "building Exim" "multiple OS/architectures"
1729 The building process for Exim is arranged to make it easy to build binaries for
1730 a number of different architectures and operating systems from the same set of
1731 source files. Compilation does not take place in the &_src_& directory.
1732 Instead, a &'build directory'& is created for each architecture and operating
1734 .cindex "symbolic link" "to build directory"
1735 Symbolic links to the sources are installed in this directory, which is where
1736 the actual building takes place. In most cases, Exim can discover the machine
1737 architecture and operating system for itself, but the defaults can be
1738 overridden if necessary.
1739 .cindex compiler requirements
1740 .cindex compiler version
1741 A C99-capable compiler will be required for the build.
1744 .section "PCRE library" "SECTpcre"
1745 .cindex "PCRE library"
1746 Exim no longer has an embedded PCRE library as the vast majority of
1747 modern systems include PCRE as a system library, although you may need to
1748 install the PCRE package or the PCRE development package for your operating
1749 system. If your system has a normal PCRE installation the Exim build
1750 process will need no further configuration. If the library or the
1751 headers are in an unusual location you will need to either set the PCRE_LIBS
1752 and INCLUDE directives appropriately,
1753 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1754 If your operating system has no
1755 PCRE support then you will need to obtain and build the current PCRE
1756 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1757 More information on PCRE is available at &url(https://www.pcre.org/).
1759 .section "DBM libraries" "SECTdb"
1760 .cindex "DBM libraries" "discussion of"
1761 .cindex "hints database" "DBM files used for"
1762 Even if you do not use any DBM files in your configuration, Exim still needs a
1763 DBM library in order to operate, because it uses indexed files for its hints
1764 databases. Unfortunately, there are a number of DBM libraries in existence, and
1765 different operating systems often have different ones installed.
1767 .cindex "Solaris" "DBM library for"
1768 .cindex "IRIX, DBM library for"
1769 .cindex "BSD, DBM library for"
1770 .cindex "Linux, DBM library for"
1771 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1772 Linux distribution, the DBM configuration should happen automatically, and you
1773 may be able to ignore this section. Otherwise, you may have to learn more than
1774 you would like about DBM libraries from what follows.
1776 .cindex "&'ndbm'& DBM library"
1777 Licensed versions of Unix normally contain a library of DBM functions operating
1778 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1779 versions of Unix seem to vary in what they contain as standard. In particular,
1780 some early versions of Linux have no default DBM library, and different
1781 distributors have chosen to bundle different libraries with their packaged
1782 versions. However, the more recent releases seem to have standardized on the
1783 Berkeley DB library.
1785 Different DBM libraries have different conventions for naming the files they
1786 use. When a program opens a file called &_dbmfile_&, there are several
1790 A traditional &'ndbm'& implementation, such as that supplied as part of
1791 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1793 .cindex "&'gdbm'& DBM library"
1794 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1795 compatibility interface it makes two different hard links to it with names
1796 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1797 filename is used unmodified.
1799 .cindex "Berkeley DB library"
1800 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1801 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1802 programmer exactly the same as the traditional &'ndbm'& implementation.
1804 If the Berkeley package is used in its native mode, it operates on a single
1805 file called &_dbmfile_&; the programmer's interface is somewhat different to
1806 the traditional &'ndbm'& interface.
1808 To complicate things further, there are several very different versions of the
1809 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1810 2.&'x'& and 3.&'x'& were current for a while, but the latest versions when Exim last revamped support were numbered 4.&'x'&.
1811 Maintenance of some of the earlier releases has ceased. All versions of
1812 Berkeley DB could be obtained from
1813 &url(http://www.sleepycat.com/), which is now a redirect to their new owner's
1814 page with far newer versions listed.
1815 It is probably wise to plan to move your storage configurations away from
1816 Berkeley DB format, as today there are smaller and simpler alternatives more
1817 suited to Exim's usage model.
1819 .cindex "&'tdb'& DBM library"
1820 Yet another DBM library, called &'tdb'&, is available from
1821 &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
1822 operates on a single file.
1826 .cindex "DBM libraries" "configuration for building"
1827 Exim and its utilities can be compiled to use any of these interfaces. In order
1828 to use any version of the Berkeley DB package in native mode, you must set
1829 USE_DB in an appropriate configuration file (typically
1830 &_Local/Makefile_&). For example:
1834 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1835 error is diagnosed if you set more than one of these.
1837 At the lowest level, the build-time configuration sets none of these options,
1838 thereby assuming an interface of type (1). However, some operating system
1839 configuration files (for example, those for the BSD operating systems and
1840 Linux) assume type (4) by setting USE_DB as their default, and the
1841 configuration files for Cygwin set USE_GDBM. Anything you set in
1842 &_Local/Makefile_&, however, overrides these system defaults.
1844 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1845 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1846 in one of these lines:
1851 Settings like that will work if the DBM library is installed in the standard
1852 place. Sometimes it is not, and the library's header file may also not be in
1853 the default path. You may need to set INCLUDE to specify where the header
1854 file is, and to specify the path to the library more fully in DBMLIB, as in
1857 INCLUDE=-I/usr/local/include/db-4.1
1858 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1860 There is further detailed discussion about the various DBM libraries in the
1861 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1865 .section "Pre-building configuration" "SECID25"
1866 .cindex "building Exim" "pre-building configuration"
1867 .cindex "configuration for building Exim"
1868 .cindex "&_Local/Makefile_&"
1869 .cindex "&_src/EDITME_&"
1870 Before building Exim, a local configuration file that specifies options
1871 independent of any operating system has to be created with the name
1872 &_Local/Makefile_&. A template for this file is supplied as the file
1873 &_src/EDITME_&, and it contains full descriptions of all the option settings
1874 therein. These descriptions are therefore not repeated here. If you are
1875 building Exim for the first time, the simplest thing to do is to copy
1876 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1878 There are three settings that you must supply, because Exim will not build
1879 without them. They are the location of the runtime configuration file
1880 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1881 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1882 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1883 a colon-separated list of filenames; Exim uses the first of them that exists.
1885 There are a few other parameters that can be specified either at build time or
1886 at runtime, to enable the same binary to be used on a number of different
1887 machines. However, if the locations of Exim's spool directory and log file
1888 directory (if not within the spool directory) are fixed, it is recommended that
1889 you specify them in &_Local/Makefile_& instead of at runtime, so that errors
1890 detected early in Exim's execution (such as a malformed configuration file) can
1893 .cindex "content scanning" "specifying at build time"
1894 Exim's interfaces for calling virus and spam scanning software directly from
1895 access control lists are not compiled by default. If you want to include these
1896 facilities, you need to set
1898 WITH_CONTENT_SCAN=yes
1900 in your &_Local/Makefile_&. For details of the facilities themselves, see
1901 chapter &<<CHAPexiscan>>&.
1904 .cindex "&_Local/eximon.conf_&"
1905 .cindex "&_exim_monitor/EDITME_&"
1906 If you are going to build the Exim monitor, a similar configuration process is
1907 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1908 your installation and saved under the name &_Local/eximon.conf_&. If you are
1909 happy with the default settings described in &_exim_monitor/EDITME_&,
1910 &_Local/eximon.conf_& can be empty, but it must exist.
1912 This is all the configuration that is needed in straightforward cases for known
1913 operating systems. However, the building process is set up so that it is easy
1914 to override options that are set by default or by operating-system-specific
1915 configuration files, for example, to change the C compiler, which
1916 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1921 .section "Support for iconv()" "SECID26"
1922 .cindex "&[iconv()]& support"
1924 The contents of header lines in messages may be encoded according to the rules
1925 described RFC 2047. This makes it possible to transmit characters that are not
1926 in the ASCII character set, and to label them as being in a particular
1927 character set. When Exim is inspecting header lines by means of the &%$h_%&
1928 mechanism, it decodes them, and translates them into a specified character set
1929 (default is set at build time). The translation is possible only if the operating system
1930 supports the &[iconv()]& function.
1932 However, some of the operating systems that supply &[iconv()]& do not support
1933 very many conversions. The GNU &%libiconv%& library (available from
1934 &url(https://www.gnu.org/software/libiconv/)) can be installed on such
1935 systems to remedy this deficiency, as well as on systems that do not supply
1936 &[iconv()]& at all. After installing &%libiconv%&, you should add
1940 to your &_Local/Makefile_& and rebuild Exim.
1944 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1945 .cindex "TLS" "including support for TLS"
1946 .cindex "encryption" "including support for"
1947 .cindex "OpenSSL" "building Exim with"
1948 .cindex "GnuTLS" "building Exim with"
1949 Exim is usually built to support encrypted SMTP connections, using the STARTTLS
1950 command as per RFC 2487. It can also support clients that expect to
1951 start a TLS session immediately on connection to a non-standard port (see the
1952 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1955 If you want to build Exim with TLS support, you must first install either the
1956 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1959 If you do not want TLS support you should set
1963 in &_Local/Makefile_&.
1965 If OpenSSL is installed, you should set
1968 TLS_LIBS=-lssl -lcrypto
1970 in &_Local/Makefile_&. You may also need to specify the locations of the
1971 OpenSSL library and include files. For example:
1974 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1975 TLS_INCLUDE=-I/usr/local/openssl/include/
1977 .cindex "pkg-config" "OpenSSL"
1978 If you have &'pkg-config'& available, then instead you can just use:
1981 USE_OPENSSL_PC=openssl
1983 .cindex "USE_GNUTLS"
1984 If GnuTLS is installed, you should set
1987 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1989 in &_Local/Makefile_&, and again you may need to specify the locations of the
1990 library and include files. For example:
1993 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1994 TLS_INCLUDE=-I/usr/gnu/include
1996 .cindex "pkg-config" "GnuTLS"
1997 If you have &'pkg-config'& available, then instead you can just use:
2000 USE_GNUTLS_PC=gnutls
2003 You do not need to set TLS_INCLUDE if the relevant directory is already
2004 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
2005 given in chapter &<<CHAPTLS>>&.
2010 .section "Use of tcpwrappers" "SECID27"
2012 .cindex "tcpwrappers, building Exim to support"
2013 .cindex "USE_TCP_WRAPPERS"
2014 .cindex "TCP_WRAPPERS_DAEMON_NAME"
2015 .cindex "tcp_wrappers_daemon_name"
2016 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
2017 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
2018 alternative to Exim's own checking facilities for installations that are
2019 already making use of &'tcpwrappers'& for other purposes. To do this, you
2020 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
2021 &_tcpd.h_& to be available at compile time, and also ensure that the library
2022 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
2023 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
2026 USE_TCP_WRAPPERS=yes
2027 CFLAGS=-O -I/usr/local/include
2028 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
2030 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
2031 files is &"exim"&. For example, the line
2033 exim : LOCAL 192.168.1. .friendly.domain.example
2035 in your &_/etc/hosts.allow_& file allows connections from the local host, from
2036 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
2037 All other connections are denied. The daemon name used by &'tcpwrappers'&
2038 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
2039 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
2040 configure file. Consult the &'tcpwrappers'& documentation for
2044 .section "Including support for IPv6" "SECID28"
2045 .cindex "IPv6" "including support for"
2046 Exim contains code for use on systems that have IPv6 support. Setting
2047 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
2048 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
2049 where the IPv6 support is not fully integrated into the normal include and
2052 Two different types of DNS record for handling IPv6 addresses have been
2053 defined. AAAA records (analogous to A records for IPv4) are in use, and are
2054 currently seen as the mainstream. Another record type called A6 was proposed
2055 as better than AAAA because it had more flexibility. However, it was felt to be
2056 over-complex, and its status was reduced to &"experimental"&.
2058 have a compile option for including A6 record support but this has now been
2063 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
2064 .cindex "lookup modules"
2065 .cindex "dynamic modules"
2066 .cindex ".so building"
2067 On some platforms, Exim supports not compiling all lookup types directly into
2068 the main binary, instead putting some into external modules which can be loaded
2070 This permits packagers to build Exim with support for lookups with extensive
2071 library dependencies without requiring all users to install all of those
2073 Most, but not all, lookup types can be built this way.
2075 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2076 installed; Exim will only load modules from that directory, as a security
2077 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2078 for your OS; see &_OS/Makefile-Linux_& for an example.
2079 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2080 see &_src/EDITME_& for details.
2082 Then, for each module to be loaded dynamically, define the relevant
2083 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2084 For example, this will build in lsearch but load sqlite and mysql support
2093 .section "The building process" "SECID29"
2094 .cindex "build directory"
2095 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2096 created, run &'make'& at the top level. It determines the architecture and
2097 operating system types, and creates a build directory if one does not exist.
2098 For example, on a Sun system running Solaris 8, the directory
2099 &_build-SunOS5-5.8-sparc_& is created.
2100 .cindex "symbolic link" "to source files"
2101 Symbolic links to relevant source files are installed in the build directory.
2103 If this is the first time &'make'& has been run, it calls a script that builds
2104 a make file inside the build directory, using the configuration files from the
2105 &_Local_& directory. The new make file is then passed to another instance of
2106 &'make'&. This does the real work, building a number of utility scripts, and
2107 then compiling and linking the binaries for the Exim monitor (if configured), a
2108 number of utility programs, and finally Exim itself. The command &`make
2109 makefile`& can be used to force a rebuild of the make file in the build
2110 directory, should this ever be necessary.
2112 If you have problems building Exim, check for any comments there may be in the
2113 &_README_& file concerning your operating system, and also take a look at the
2114 FAQ, where some common problems are covered.
2118 .section 'Output from &"make"&' "SECID283"
2119 The output produced by the &'make'& process for compile lines is often very
2120 unreadable, because these lines can be very long. For this reason, the normal
2121 output is suppressed by default, and instead output similar to that which
2122 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2123 each module that is being compiled or linked. However, it is still possible to
2124 get the full output, by calling &'make'& like this:
2128 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2129 command reflection in &'make'&. When you ask for the full output, it is
2130 given in addition to the short output.
2134 .section "Overriding build-time options for Exim" "SECToverride"
2135 .cindex "build-time options, overriding"
2136 The main make file that is created at the beginning of the building process
2137 consists of the concatenation of a number of files which set configuration
2138 values, followed by a fixed set of &'make'& instructions. If a value is set
2139 more than once, the last setting overrides any previous ones. This provides a
2140 convenient way of overriding defaults. The files that are concatenated are, in
2143 &_OS/Makefile-Default_&
2144 &_OS/Makefile-_&<&'ostype'&>
2146 &_Local/Makefile-_&<&'ostype'&>
2147 &_Local/Makefile-_&<&'archtype'&>
2148 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2149 &_OS/Makefile-Base_&
2151 .cindex "&_Local/Makefile_&"
2152 .cindex "building Exim" "operating system type"
2153 .cindex "building Exim" "architecture type"
2154 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2155 architecture type. &_Local/Makefile_& is required to exist, and the building
2156 process fails if it is absent. The other three &_Local_& files are optional,
2157 and are often not needed.
2159 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2160 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2161 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2162 values are used, thereby providing a means of forcing particular settings.
2163 Otherwise, the scripts try to get values from the &%uname%& command. If this
2164 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2165 of &'ad hoc'& transformations are then applied, to produce the standard names
2166 that Exim expects. You can run these scripts directly from the shell in order
2167 to find out what values are being used on your system.
2170 &_OS/Makefile-Default_& contains comments about the variables that are set
2171 therein. Some (but not all) are mentioned below. If there is something that
2172 needs changing, review the contents of this file and the contents of the make
2173 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2177 .cindex "building Exim" "overriding default settings"
2178 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2179 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2180 need to change the original files. Instead, you should make the changes by
2181 putting the new values in an appropriate &_Local_& file. For example,
2182 .cindex "Tru64-Unix build-time settings"
2183 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2184 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2185 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2186 called with the option &%-std1%&, to make it recognize some of the features of
2187 Standard C that Exim uses. (Most other compilers recognize Standard C by
2188 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2189 containing the lines
2194 If you are compiling for just one operating system, it may be easier to put
2195 these lines directly into &_Local/Makefile_&.
2197 Keeping all your local configuration settings separate from the distributed
2198 files makes it easy to transfer them to new versions of Exim simply by copying
2199 the contents of the &_Local_& directory.
2202 .cindex "NIS lookup type" "including support for"
2203 .cindex "NIS+ lookup type" "including support for"
2204 .cindex "LDAP" "including support for"
2205 .cindex "lookup" "inclusion in binary"
2206 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2207 lookup, but not all systems have these components installed, so the default is
2208 not to include the relevant code in the binary. All the different kinds of file
2209 and database lookup that Exim supports are implemented as separate code modules
2210 which are included only if the relevant compile-time options are set. In the
2211 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2217 and similar settings apply to the other lookup types. They are all listed in
2218 &_src/EDITME_&. In many cases the relevant include files and interface
2219 libraries need to be installed before compiling Exim.
2220 .cindex "cdb" "including support for"
2221 However, there are some optional lookup types (such as cdb) for which
2222 the code is entirely contained within Exim, and no external include
2223 files or libraries are required. When a lookup type is not included in the
2224 binary, attempts to configure Exim to use it cause runtime configuration
2227 .cindex "pkg-config" "lookups"
2228 .cindex "pkg-config" "authenticators"
2229 Many systems now use a tool called &'pkg-config'& to encapsulate information
2230 about how to compile against a library; Exim has some initial support for
2231 being able to use pkg-config for lookups and authenticators. For any given
2232 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2233 variable with the &`_PC`& suffix in the name and assign as the value the
2234 name of the package to be queried. The results of querying via the
2235 &'pkg-config'& command will be added to the appropriate Makefile variables
2236 with &`+=`& directives, so your version of &'make'& will need to support that
2237 syntax. For instance:
2240 LOOKUP_SQLITE_PC=sqlite3
2242 AUTH_GSASL_PC=libgsasl
2243 AUTH_HEIMDAL_GSSAPI=yes
2244 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2247 .cindex "Perl" "including support for"
2248 Exim can be linked with an embedded Perl interpreter, allowing Perl
2249 subroutines to be called during string expansion. To enable this facility,
2253 must be defined in &_Local/Makefile_&. Details of this facility are given in
2254 chapter &<<CHAPperl>>&.
2256 .cindex "X11 libraries, location of"
2257 The location of the X11 libraries is something that varies a lot between
2258 operating systems, and there may be different versions of X11 to cope
2259 with. Exim itself makes no use of X11, but if you are compiling the Exim
2260 monitor, the X11 libraries must be available.
2261 The following three variables are set in &_OS/Makefile-Default_&:
2264 XINCLUDE=-I$(X11)/include
2265 XLFLAGS=-L$(X11)/lib
2267 These are overridden in some of the operating-system configuration files. For
2268 example, in &_OS/Makefile-SunOS5_& there is
2271 XINCLUDE=-I$(X11)/include
2272 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2274 If you need to override the default setting for your operating system, place a
2275 definition of all three of these variables into your
2276 &_Local/Makefile-<ostype>_& file.
2279 If you need to add any extra libraries to the link steps, these can be put in a
2280 variable called EXTRALIBS, which appears in all the link commands, but by
2281 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2282 command for linking the main Exim binary, and not for any associated utilities.
2284 .cindex "DBM libraries" "configuration for building"
2285 There is also DBMLIB, which appears in the link commands for binaries that
2286 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2287 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2288 binary, and which can be used, for example, to include additional X11
2291 .cindex "configuration file" "editing"
2292 The make file copes with rebuilding Exim correctly if any of the configuration
2293 files are edited. However, if an optional configuration file is deleted, it is
2294 necessary to touch the associated non-optional file (that is,
2295 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2298 .section "OS-specific header files" "SECID30"
2300 .cindex "building Exim" "OS-specific C header files"
2301 The &_OS_& directory contains a number of files with names of the form
2302 &_os.h-<ostype>_&. These are system-specific C header files that should not
2303 normally need to be changed. There is a list of macro settings that are
2304 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2305 are porting Exim to a new operating system.
2309 .section "Overriding build-time options for the monitor" "SECID31"
2310 .cindex "building Eximon"
2311 A similar process is used for overriding things when building the Exim monitor,
2312 where the files that are involved are
2314 &_OS/eximon.conf-Default_&
2315 &_OS/eximon.conf-_&<&'ostype'&>
2316 &_Local/eximon.conf_&
2317 &_Local/eximon.conf-_&<&'ostype'&>
2318 &_Local/eximon.conf-_&<&'archtype'&>
2319 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2321 .cindex "&_Local/eximon.conf_&"
2322 As with Exim itself, the final three files need not exist, and in this case the
2323 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2324 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2325 variables of the same name, preceded by EXIMON_. For example, setting
2326 EXIMON_LOG_DEPTH in the environment overrides the value of
2327 LOG_DEPTH at runtime.
2331 .section "Installing Exim binaries and scripts" "SECID32"
2332 .cindex "installing Exim"
2333 .cindex "BIN_DIRECTORY"
2334 The command &`make install`& runs the &(exim_install)& script with no
2335 arguments. The script copies binaries and utility scripts into the directory
2336 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2337 .cindex "setuid" "installing Exim with"
2338 The install script copies files only if they are newer than the files they are
2339 going to replace. The Exim binary is required to be owned by root and have the
2340 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2341 install`& as root so that it can set up the Exim binary in this way. However, in
2342 some special situations (for example, if a host is doing no local deliveries)
2343 it may be possible to run Exim without making the binary setuid root (see
2344 chapter &<<CHAPsecurity>>& for details).
2346 .cindex "CONFIGURE_FILE"
2347 Exim's runtime configuration file is named by the CONFIGURE_FILE setting
2348 in &_Local/Makefile_&. If this names a single file, and the file does not
2349 exist, the default configuration file &_src/configure.default_& is copied there
2350 by the installation script. If a runtime configuration file already exists, it
2351 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2352 alternative files, no default is installed.
2354 .cindex "system aliases file"
2355 .cindex "&_/etc/aliases_&"
2356 One change is made to the default configuration file when it is installed: the
2357 default configuration contains a router that references a system aliases file.
2358 The path to this file is set to the value specified by
2359 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2360 If the system aliases file does not exist, the installation script creates it,
2361 and outputs a comment to the user.
2363 The created file contains no aliases, but it does contain comments about the
2364 aliases a site should normally have. Mail aliases have traditionally been
2365 kept in &_/etc/aliases_&. However, some operating systems are now using
2366 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2367 Exim's configuration if necessary.
2369 The default configuration uses the local host's name as the only local domain,
2370 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2371 running as the local user. System aliases and &_.forward_& files in users' home
2372 directories are supported, but no NIS or NIS+ support is configured. Domains
2373 other than the name of the local host are routed using the DNS, with delivery
2376 It is possible to install Exim for special purposes (such as building a binary
2377 distribution) in a private part of the file system. You can do this by a
2380 make DESTDIR=/some/directory/ install
2382 This has the effect of pre-pending the specified directory to all the file
2383 paths, except the name of the system aliases file that appears in the default
2384 configuration. (If a default alias file is created, its name &'is'& modified.)
2385 For backwards compatibility, ROOT is used if DESTDIR is not set,
2386 but this usage is deprecated.
2388 .cindex "installing Exim" "what is not installed"
2389 Running &'make install'& does not copy the Exim 4 conversion script
2390 &'convert4r4'&. You will probably run this only once if you are
2391 upgrading from Exim 3. None of the documentation files in the &_doc_&
2392 directory are copied, except for the info files when you have set
2393 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2395 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2396 to their names. The Exim binary itself, however, is handled differently. It is
2397 installed under a name that includes the version number and the compile number,
2398 for example, &_exim-&version()-1_&. The script then arranges for a symbolic link
2399 called &_exim_& to point to the binary. If you are updating a previous version
2400 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2401 from the directory (as seen by other processes).
2403 .cindex "installing Exim" "testing the script"
2404 If you want to see what the &'make install'& will do before running it for
2405 real, you can pass the &%-n%& option to the installation script by this
2408 make INSTALL_ARG=-n install
2410 The contents of the variable INSTALL_ARG are passed to the installation
2411 script. You do not need to be root to run this test. Alternatively, you can run
2412 the installation script directly, but this must be from within the build
2413 directory. For example, from the top-level Exim directory you could use this
2416 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2418 .cindex "installing Exim" "install script options"
2419 There are two other options that can be supplied to the installation script.
2422 &%-no_chown%& bypasses the call to change the owner of the installed binary
2423 to root, and the call to make it a setuid binary.
2425 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2429 INSTALL_ARG can be used to pass these options to the script. For example:
2431 make INSTALL_ARG=-no_symlink install
2433 The installation script can also be given arguments specifying which files are
2434 to be copied. For example, to install just the Exim binary, and nothing else,
2435 without creating the symbolic link, you could use:
2437 make INSTALL_ARG='-no_symlink exim' install
2442 .section "Installing info documentation" "SECTinsinfdoc"
2443 .cindex "installing Exim" "&'info'& documentation"
2444 Not all systems use the GNU &'info'& system for documentation, and for this
2445 reason, the Texinfo source of Exim's documentation is not included in the main
2446 distribution. Instead it is available separately from the FTP site (see section
2449 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2450 source of the documentation is found in the source tree, running &`make
2451 install`& automatically builds the info files and installs them.
2455 .section "Setting up the spool directory" "SECID33"
2456 .cindex "spool directory" "creating"
2457 When it starts up, Exim tries to create its spool directory if it does not
2458 exist. The Exim uid and gid are used for the owner and group of the spool
2459 directory. Sub-directories are automatically created in the spool directory as
2465 .section "Testing" "SECID34"
2466 .cindex "testing" "installation"
2467 Having installed Exim, you can check that the runtime configuration file is
2468 syntactically valid by running the following command, which assumes that the
2469 Exim binary directory is within your PATH environment variable:
2473 If there are any errors in the configuration file, Exim outputs error messages.
2474 Otherwise it outputs the version number and build date,
2475 the DBM library that is being used, and information about which drivers and
2476 other optional code modules are included in the binary.
2477 Some simple routing tests can be done by using the address testing option. For
2480 &`exim -bt`& <&'local username'&>
2482 should verify that it recognizes a local mailbox, and
2484 &`exim -bt`& <&'remote address'&>
2486 a remote one. Then try getting it to deliver mail, both locally and remotely.
2487 This can be done by passing messages directly to Exim, without going through a
2488 user agent. For example:
2490 exim -v postmaster@your.domain.example
2491 From: user@your.domain.example
2492 To: postmaster@your.domain.example
2493 Subject: Testing Exim
2495 This is a test message.
2498 The &%-v%& option causes Exim to output some verification of what it is doing.
2499 In this case you should see copies of three log lines, one for the message's
2500 arrival, one for its delivery, and one containing &"Completed"&.
2502 .cindex "delivery" "problems with"
2503 If you encounter problems, look at Exim's log files (&'mainlog'& and
2504 &'paniclog'&) to see if there is any relevant information there. Another source
2505 of information is running Exim with debugging turned on, by specifying the
2506 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2507 with debugging turned on by a command of the form
2509 &`exim -d -M`& <&'exim-message-id'&>
2511 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2512 produces rather a lot of output, but you can cut this down to specific areas.
2513 For example, if you use &%-d-all+route%& only the debugging information
2514 relevant to routing is included. (See the &%-d%& option in chapter
2515 &<<CHAPcommandline>>& for more details.)
2517 .cindex '&"sticky"& bit'
2518 .cindex "lock files"
2519 One specific problem that has shown up on some sites is the inability to do
2520 local deliveries into a shared mailbox directory, because it does not have the
2521 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2522 writing to a mailbox file, and if it cannot create the lock file, the delivery
2523 is deferred. You can get round this either by setting the &"sticky bit"& on the
2524 directory, or by setting a specific group for local deliveries and allowing
2525 that group to create files in the directory (see the comments above the
2526 &(local_delivery)& transport in the default configuration file). Another
2527 approach is to configure Exim not to use lock files, but just to rely on
2528 &[fcntl()]& locking instead. However, you should do this only if all user
2529 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2530 see chapter &<<CHAPappendfile>>&.
2532 One thing that cannot be tested on a system that is already running an MTA is
2533 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2534 &%-oX%& option can be used to run an Exim daemon that listens on some other
2535 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2536 &'exim_checkaccess'& utility can be used to check out policy controls on
2539 Testing a new version on a system that is already running Exim can most easily
2540 be done by building a binary with a different CONFIGURE_FILE setting. From
2541 within the runtime configuration, all other file and directory names
2542 that Exim uses can be altered, in order to keep it entirely clear of the
2546 .section "Replacing another MTA with Exim" "SECID35"
2547 .cindex "replacing another MTA"
2548 Building and installing Exim for the first time does not of itself put it in
2549 general use. The name by which the system's MTA is called by mail user agents
2550 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2551 operating system), and it is necessary to make this name point to the &'exim'&
2552 binary in order to get the user agents to pass messages to Exim. This is
2553 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2554 or &_/usr/lib/sendmail_&
2555 .cindex "symbolic link" "to &'exim'& binary"
2556 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2557 privilege and executable status from the old MTA. It is then necessary to stop
2558 and restart the mailer daemon, if one is running.
2560 .cindex "FreeBSD, MTA indirection"
2561 .cindex "&_/etc/mail/mailer.conf_&"
2562 Some operating systems have introduced alternative ways of switching MTAs. For
2563 example, if you are running FreeBSD, you need to edit the file
2564 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2565 described. A typical example of the contents of this file for running Exim is
2568 sendmail /usr/exim/bin/exim
2569 send-mail /usr/exim/bin/exim
2570 mailq /usr/exim/bin/exim -bp
2571 newaliases /usr/bin/true
2573 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2574 your Exim installation is &"live"&. Check it by sending a message from your
2575 favourite user agent.
2577 You should consider what to tell your users about the change of MTA. Exim may
2578 have different capabilities to what was previously running, and there are
2579 various operational differences such as the text of messages produced by
2580 command line options and in bounce messages. If you allow your users to make
2581 use of Exim's filtering capabilities, you should make the document entitled
2582 &'Exim's interface to mail filtering'& available to them.
2586 .section "Upgrading Exim" "SECID36"
2587 .cindex "upgrading Exim"
2588 If you are already running Exim on your host, building and installing a new
2589 version automatically makes it available to MUAs, or any other programs that
2590 call the MTA directly. However, if you are running an Exim daemon, you do need
2591 .cindex restart "on HUP signal"
2592 .cindex signal "HUP, to restart"
2593 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2594 new binary. You do not need to stop processing mail in order to install a new
2595 version of Exim. The install script does not modify an existing runtime
2601 .section "Stopping the Exim daemon on Solaris" "SECID37"
2602 .cindex "Solaris" "stopping Exim on"
2603 The standard command for stopping the mailer daemon on Solaris is
2605 /etc/init.d/sendmail stop
2607 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2608 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2609 for the text &"sendmail"&; this is not present because the actual program name
2610 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2611 solution is to replace the line that finds the process id with something like
2613 pid=`cat /var/spool/exim/exim-daemon.pid`
2615 to obtain the daemon's pid directly from the file that Exim saves it in.
2617 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2618 still be received from local processes, and if automatic delivery is configured
2619 (the normal case), deliveries will still occur.
2624 . ////////////////////////////////////////////////////////////////////////////
2625 . ////////////////////////////////////////////////////////////////////////////
2627 .chapter "The Exim command line" "CHAPcommandline"
2628 .scindex IIDclo1 "command line" "options"
2629 .scindex IIDclo2 "options" "command line"
2630 Exim's command line takes the standard Unix form of a sequence of options,
2631 each starting with a hyphen character, followed by a number of arguments. The
2632 options are compatible with the main options of Sendmail, and there are also
2633 some additional options, some of which are compatible with Smail 3. Certain
2634 combinations of options do not make sense, and provoke an error if used.
2635 The form of the arguments depends on which options are set.
2638 .section "Setting options by program name" "SECID38"
2640 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2641 were present before any other options.
2642 The &%-bp%& option requests a listing of the contents of the mail queue on the
2644 This feature is for compatibility with some systems that contain a command of
2645 that name in one of the standard libraries, symbolically linked to
2646 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2649 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2650 were present before any other options, for compatibility with Smail. The
2651 &%-bS%& option is used for reading in a number of messages in batched SMTP
2655 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2656 &%-oee%& options were present before any other options, for compatibility with
2657 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2660 .cindex "queue runner"
2661 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2662 were present before any other options, for compatibility with Smail. The &%-q%&
2663 option causes a single queue runner process to be started.
2665 .cindex "&'newaliases'&"
2666 .cindex "alias file" "building"
2667 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2668 If Exim is called under the name &'newaliases'& it behaves as if the option
2669 &%-bi%& were present before any other options, for compatibility with Sendmail.
2670 This option is used for rebuilding Sendmail's alias file. Exim does not have
2671 the concept of a single alias file, but can be configured to run a given
2672 command if called with the &%-bi%& option.
2675 .section "Trusted and admin users" "SECTtrustedadmin"
2676 Some Exim options are available only to &'trusted users'& and others are
2677 available only to &'admin users'&. In the description below, the phrases &"Exim
2678 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2679 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2680 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2683 .cindex "trusted users" "definition of"
2684 .cindex "user" "trusted definition of"
2685 The trusted users are root, the Exim user, any user listed in the
2686 &%trusted_users%& configuration option, and any user whose current group or any
2687 supplementary group is one of those listed in the &%trusted_groups%&
2688 configuration option. Note that the Exim group is not automatically trusted.
2690 .cindex '&"From"& line'
2691 .cindex "envelope from"
2692 .cindex "envelope sender"
2693 Trusted users are always permitted to use the &%-f%& option or a leading
2694 &"From&~"& line to specify the envelope sender of a message that is passed to
2695 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2696 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2697 users to set envelope senders.
2701 For a trusted user, there is never any check on the contents of the &'From:'&
2702 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2703 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2705 Trusted users may also specify a host name, host address, interface address,
2706 protocol name, ident value, and authentication data when submitting a message
2707 locally. Thus, they are able to insert messages into Exim's queue locally that
2708 have the characteristics of messages received from a remote host. Untrusted
2709 users may in some circumstances use &%-f%&, but can never set the other values
2710 that are available to trusted users.
2712 .cindex "user" "admin definition of"
2713 .cindex "admin user" "definition of"
2714 The admin users are root, the Exim user, and any user that is a member of the
2715 Exim group or of any group listed in the &%admin_groups%& configuration option.
2716 The current group does not have to be one of these groups.
2718 Admin users are permitted to list the queue, and to carry out certain
2719 operations on messages, for example, to force delivery failures. It is also
2720 necessary to be an admin user in order to see the full information provided by
2721 the Exim monitor, and full debugging output.
2723 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2724 Exim to attempt delivery of messages on its queue is restricted to admin users.
2725 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2726 option false (that is, specifying &%no_prod_requires_admin%&).
2728 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2729 is restricted to admin users unless &%queue_list_requires_admin%& is set
2734 &*Warning*&: If you configure your system so that admin users are able to
2735 edit Exim's configuration file, you are giving those users an easy way of
2736 getting root. There is further discussion of this issue at the start of chapter
2742 .section "Command line options" "SECID39"
2743 Exim's command line options are described in alphabetical order below. If none
2744 of the options that specifies a specific action (such as starting the daemon or
2745 a queue runner, or testing an address, or receiving a message in a specific
2746 format, or listing the queue) are present, and there is at least one argument
2747 on the command line, &%-bm%& (accept a local message on the standard input,
2748 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2749 outputs a brief message about itself and exits.
2751 . ////////////////////////////////////////////////////////////////////////////
2752 . Insert a stylized XML comment here, to identify the start of the command line
2753 . options. This is for the benefit of the Perl script that automatically
2754 . creates a man page for the options.
2755 . ////////////////////////////////////////////////////////////////////////////
2758 <!-- === Start of command line options === -->
2765 .cindex "options" "command line; terminating"
2766 This is a pseudo-option whose only purpose is to terminate the options and
2767 therefore to cause subsequent command line items to be treated as arguments
2768 rather than options, even if they begin with hyphens.
2771 .oindex "&%--help%&"
2772 This option causes Exim to output a few sentences stating what it is.
2773 The same output is generated if the Exim binary is called with no options and
2776 .vitem &%--version%&
2777 .oindex "&%--version%&"
2778 This option is an alias for &%-bV%& and causes version information to be
2785 These options are used by Sendmail for selecting configuration files and are
2788 .vitem &%-B%&<&'type'&>
2790 .cindex "8-bit characters"
2791 .cindex "Sendmail compatibility" "8-bit characters"
2792 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2793 clean; it ignores this option.
2798 .cindex "SMTP" "listener"
2799 .cindex "queue runner"
2800 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2801 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2802 that the daemon should also initiate periodic queue runs.
2804 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2805 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2806 disconnect from the controlling terminal. When running this way, it can be
2807 stopped by pressing ctrl-C.
2809 By default, Exim listens for incoming connections to the standard SMTP port on
2810 all the host's running interfaces. However, it is possible to listen on other
2811 ports, on multiple ports, and only on specific interfaces. Chapter
2812 &<<CHAPinterfaces>>& contains a description of the options that control this.
2814 When a listening daemon
2815 .cindex "daemon" "process id (pid)"
2816 .cindex "pid (process id)" "of daemon"
2817 is started without the use of &%-oX%& (that is, without overriding the normal
2818 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2819 in Exim's spool directory. This location can be overridden by setting
2820 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2823 When &%-oX%& is used on the command line to start a listening daemon, the
2824 process id is not written to the normal pid file path. However, &%-oP%& can be
2825 used to specify a path on the command line if a pid file is required.
2829 .cindex restart "on HUP signal"
2830 .cindex signal "HUP, to restart"
2831 .cindex "daemon" "restarting"
2832 .cindex signal "to reload configuration"
2833 .cindex daemon "reload configuration"
2834 .cindex reload configuration
2835 can be used to cause the daemon to re-execute itself. This should be done
2836 whenever Exim's configuration file, or any file that is incorporated into it by
2837 means of the &%.include%& facility, is changed, and also whenever a new version
2838 of Exim is installed. It is not necessary to do this when other files that are
2839 referenced from the configuration (for example, alias files) are changed,
2840 because these are reread each time they are used.
2844 This option has the same effect as &%-bd%& except that it never disconnects
2845 from the controlling terminal, even when no debugging is specified.
2849 .cindex "testing" "string expansion"
2850 .cindex "expansion" "testing"
2851 Run Exim in expansion testing mode. Exim discards its root privilege, to
2852 prevent ordinary users from using this mode to read otherwise inaccessible
2853 files. If no arguments are given, Exim runs interactively, prompting for lines
2854 of data. Otherwise, it processes each argument in turn.
2856 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2857 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2858 used without command line arguments. If successful, it uses the &[readline()]&
2859 function, which provides extensive line-editing facilities, for reading the
2860 test data. A line history is supported.
2862 Long expansion expressions can be split over several lines by using backslash
2863 continuations. As in Exim's runtime configuration, white space at the start of
2864 continuation lines is ignored. Each argument or data line is passed through the
2865 string expansion mechanism, and the result is output. Variable values from the
2866 configuration file (for example, &$qualify_domain$&) are available, but no
2867 message-specific values (such as &$message_exim_id$&) are set, because no message
2868 is being processed (but see &%-bem%& and &%-Mset%&).
2870 &*Note*&: If you use this mechanism to test lookups, and you change the data
2871 files or databases you are using, you must exit and restart Exim before trying
2872 the same lookup again. Otherwise, because each Exim process caches the results
2873 of lookups, you will just get the same result as before.
2875 Macro processing is done on lines before string-expansion: new macros can be
2876 defined and macros will be expanded.
2877 Because macros in the config file are often used for secrets, those are only
2878 available to admin users.
2880 .vitem &%-bem%&&~<&'filename'&>
2882 .cindex "testing" "string expansion"
2883 .cindex "expansion" "testing"
2884 This option operates like &%-be%& except that it must be followed by the name
2885 of a file. For example:
2887 exim -bem /tmp/testmessage
2889 The file is read as a message (as if receiving a locally-submitted non-SMTP
2890 message) before any of the test expansions are done. Thus, message-specific
2891 variables such as &$message_size$& and &$header_from:$& are available. However,
2892 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2893 recipients are read from the headers in the normal way, and are shown in the
2894 &$recipients$& variable. Note that recipients cannot be given on the command
2895 line, because further arguments are taken as strings to expand (just like
2898 .vitem &%-bF%&&~<&'filename'&>
2900 .cindex "system filter" "testing"
2901 .cindex "testing" "system filter"
2902 This option is the same as &%-bf%& except that it assumes that the filter being
2903 tested is a system filter. The additional commands that are available only in
2904 system filters are recognized.
2906 .vitem &%-bf%&&~<&'filename'&>
2908 .cindex "filter" "testing"
2909 .cindex "testing" "filter file"
2910 .cindex "forward file" "testing"
2911 .cindex "testing" "forward file"
2912 .cindex "Sieve filter" "testing"
2913 This option runs Exim in user filter testing mode; the file is the filter file
2914 to be tested, and a test message must be supplied on the standard input. If
2915 there are no message-dependent tests in the filter, an empty file can be
2918 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2919 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2920 filter and a user filter in the same run. For example:
2922 exim -bF /system/filter -bf /user/filter </test/message
2924 This is helpful when the system filter adds header lines or sets filter
2925 variables that are used by the user filter.
2927 If the test filter file does not begin with one of the special lines
2932 it is taken to be a normal &_.forward_& file, and is tested for validity under
2933 that interpretation. See sections &<<SECTitenonfilred>>& to
2934 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2937 The result of an Exim command that uses &%-bf%&, provided no errors are
2938 detected, is a list of the actions that Exim would try to take if presented
2939 with the message for real. More details of filter testing are given in the
2940 separate document entitled &'Exim's interfaces to mail filtering'&.
2942 When testing a filter file,
2943 .cindex "&""From""& line"
2944 .cindex "envelope from"
2945 .cindex "envelope sender"
2946 .oindex "&%-f%&" "for filter testing"
2947 the envelope sender can be set by the &%-f%& option,
2948 or by a &"From&~"& line at the start of the test message. Various parameters
2949 that would normally be taken from the envelope recipient address of the message
2950 can be set by means of additional command line options (see the next four
2953 .vitem &%-bfd%&&~<&'domain'&>
2955 .vindex "&$qualify_domain$&"
2956 This sets the domain of the recipient address when a filter file is being
2957 tested by means of the &%-bf%& option. The default is the value of
2960 .vitem &%-bfl%&&~<&'local&~part'&>
2962 This sets the local part of the recipient address when a filter file is being
2963 tested by means of the &%-bf%& option. The default is the username of the
2964 process that calls Exim. A local part should be specified with any prefix or
2965 suffix stripped, because that is how it appears to the filter when a message is
2966 actually being delivered.
2968 .vitem &%-bfp%&&~<&'prefix'&>
2970 .cindex affix "filter testing"
2971 This sets the prefix of the local part of the recipient address when a filter
2972 file is being tested by means of the &%-bf%& option. The default is an empty
2975 .vitem &%-bfs%&&~<&'suffix'&>
2977 .cindex affix "filter testing"
2978 This sets the suffix of the local part of the recipient address when a filter
2979 file is being tested by means of the &%-bf%& option. The default is an empty
2982 .vitem &%-bh%&&~<&'IP&~address'&>
2984 .cindex "testing" "incoming SMTP"
2985 .cindex "SMTP" "testing incoming"
2986 .cindex "testing" "relay control"
2987 .cindex "relaying" "testing configuration"
2988 .cindex "policy control" "testing"
2989 .cindex "debugging" "&%-bh%& option"
2990 This option runs a fake SMTP session as if from the given IP address, using the
2991 standard input and output. The IP address may include a port number at the end,
2992 after a full stop. For example:
2994 exim -bh 10.9.8.7.1234
2995 exim -bh fe80::a00:20ff:fe86:a061.5678
2997 When an IPv6 address is given, it is converted into canonical form. In the case
2998 of the second example above, the value of &$sender_host_address$& after
2999 conversion to the canonical form is
3000 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
3002 Comments as to what is going on are written to the standard error file. These
3003 include lines beginning with &"LOG"& for anything that would have been logged.
3004 This facility is provided for testing configuration options for incoming
3005 messages, to make sure they implement the required policy. For example, you can
3006 test your relay controls using &%-bh%&.
3010 You can test features of the configuration that rely on ident (RFC 1413)
3011 information by using the &%-oMt%& option. However, Exim cannot actually perform
3012 an ident callout when testing using &%-bh%& because there is no incoming SMTP
3015 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
3016 are also skipped when testing using &%-bh%&. If you want these callouts to
3017 occur, use &%-bhc%& instead.
3019 Messages supplied during the testing session are discarded, and nothing is
3020 written to any of the real log files. There may be pauses when DNS (and other)
3021 lookups are taking place, and of course these may time out. The &%-oMi%& option
3022 can be used to specify a specific IP interface and port if this is important,
3023 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
3024 session were authenticated.
3026 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
3027 output just states whether a given recipient address from a given host is
3028 acceptable or not. See section &<<SECTcheckaccess>>&.
3030 Features such as authentication and encryption, where the client input is not
3031 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
3032 specialized SMTP test program such as
3033 &url(https://www.jetmore.org/john/code/swaks/,swaks).
3035 .vitem &%-bhc%&&~<&'IP&~address'&>
3037 This option operates in the same way as &%-bh%&, except that address
3038 verification callouts are performed if required. This includes consulting and
3039 updating the callout cache database.
3043 .cindex "alias file" "building"
3044 .cindex "building alias file"
3045 .cindex "Sendmail compatibility" "&%-bi%& option"
3046 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
3047 Exim does not have the concept of a single alias file, and so it cannot mimic
3048 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
3049 tend to appear in various scripts such as NIS make files, so the option must be
3052 If &%-bi%& is encountered, the command specified by the &%bi_command%&
3053 configuration option is run, under the uid and gid of the caller of Exim. If
3054 the &%-oA%& option is used, its value is passed to the command as an argument.
3055 The command set by &%bi_command%& may not contain arguments. The command can
3056 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
3057 if this is required. If the &%bi_command%& option is not set, calling Exim with
3060 . // Keep :help first, then the rest in alphabetical order
3062 .oindex "&%-bI:help%&"
3063 .cindex "querying exim information"
3064 We shall provide various options starting &`-bI:`& for querying Exim for
3065 information. The output of many of these will be intended for machine
3066 consumption. This one is not. The &%-bI:help%& option asks Exim for a
3067 synopsis of supported options beginning &`-bI:`&. Use of any of these
3068 options shall cause Exim to exit after producing the requested output.
3071 .oindex "&%-bI:dscp%&"
3072 .cindex "DSCP" "values"
3073 This option causes Exim to emit an alphabetically sorted list of all
3074 recognised DSCP names.
3076 .vitem &%-bI:sieve%&
3077 .oindex "&%-bI:sieve%&"
3078 .cindex "Sieve filter" "capabilities"
3079 This option causes Exim to emit an alphabetically sorted list of all supported
3080 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3081 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3082 &`SIEVE`& capability response line. As the precise list may depend upon
3083 compile-time build options, which this option will adapt to, this is the only
3084 way to guarantee a correct response.
3088 .cindex "local message reception"
3089 This option runs an Exim receiving process that accepts an incoming,
3090 locally-generated message on the standard input. The recipients are given as the
3091 command arguments (except when &%-t%& is also present &-- see below). Each
3092 argument can be a comma-separated list of RFC 2822 addresses. This is the
3093 default option for selecting the overall action of an Exim call; it is assumed
3094 if no other conflicting option is present.
3096 If any addresses in the message are unqualified (have no domain), they are
3097 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3098 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3099 suppressing this for special cases.
3101 Policy checks on the contents of local messages can be enforced by means of
3102 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3104 .cindex "return code" "for &%-bm%&"
3105 The return code is zero if the message is successfully accepted. Otherwise, the
3106 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3109 .cindex "message" "format"
3110 .cindex "format" "message"
3111 .cindex "&""From""& line"
3112 .cindex "UUCP" "&""From""& line"
3113 .cindex "Sendmail compatibility" "&""From""& line"
3114 of the message must be as defined in RFC 2822, except that, for
3115 compatibility with Sendmail and Smail, a line in one of the forms
3117 From sender Fri Jan 5 12:55 GMT 1997
3118 From sender Fri, 5 Jan 97 12:55:01
3120 (with the weekday optional, and possibly with additional text after the date)
3121 is permitted to appear at the start of the message. There appears to be no
3122 authoritative specification of the format of this line. Exim recognizes it by
3123 matching against the regular expression defined by the &%uucp_from_pattern%&
3124 option, which can be changed if necessary.
3126 .oindex "&%-f%&" "overriding &""From""& line"
3127 The specified sender is treated as if it were given as the argument to the
3128 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3129 preference to the address taken from the message. The caller of Exim must be a
3130 trusted user for the sender of a message to be set in this way.
3132 .vitem &%-bmalware%&&~<&'filename'&>
3133 .oindex "&%-bmalware%&"
3134 .cindex "testing", "malware"
3135 .cindex "malware scan test"
3136 This debugging option causes Exim to scan the given file or directory
3137 (depending on the used scanner interface),
3138 using the malware scanning framework. The option of &%av_scanner%& influences
3139 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3140 the expansion should have defaults which apply to this invocation. ACLs are
3141 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3142 will never be populated and &%-bmalware%& will fail.
3144 Exim will have changed working directory before resolving the filename, so
3145 using fully qualified pathnames is advisable. Exim will be running as the Exim
3146 user when it tries to open the file, rather than as the invoking user.
3147 This option requires admin privileges.
3149 The &%-bmalware%& option will not be extended to be more generally useful,
3150 there are better tools for file-scanning. This option exists to help
3151 administrators verify their Exim and AV scanner configuration.
3155 .cindex "address qualification, suppressing"
3156 By default, Exim automatically qualifies unqualified addresses (those
3157 without domains) that appear in messages that are submitted locally (that
3158 is, not over TCP/IP). This qualification applies both to addresses in
3159 envelopes, and addresses in header lines. Sender addresses are qualified using
3160 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3161 defaults to the value of &%qualify_domain%&).
3163 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3164 being used to re-submit messages that originally came from remote hosts after
3165 content scanning, you probably do not want to qualify unqualified addresses in
3166 header lines. (Such lines will be present only if you have not enabled a header
3167 syntax check in the appropriate ACL.)
3169 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3170 messages that originate on the local host. When this is used, unqualified
3171 addresses in the envelope provoke errors (causing message rejection) and
3172 unqualified addresses in header lines are left alone.
3177 .cindex "configuration options" "extracting"
3178 .cindex "options" "configuration &-- extracting"
3179 If this option is given with no arguments, it causes the values of all Exim's
3180 main configuration options to be written to the standard output. The values
3181 of one or more specific options can be requested by giving their names as
3182 arguments, for example:
3184 exim -bP qualify_domain hold_domains
3186 .cindex "hiding configuration option values"
3187 .cindex "configuration options" "hiding value of"
3188 .cindex "options" "hiding value of"
3189 However, any option setting that is preceded by the word &"hide"& in the
3190 configuration file is not shown in full, except to an admin user. For other
3191 users, the output is as in this example:
3193 mysql_servers = <value not displayable>
3195 If &%config%& is given as an argument, the config is
3196 output, as it was parsed, any include file resolved, any comment removed.
3198 If &%config_file%& is given as an argument, the name of the runtime
3199 configuration file is output. (&%configure_file%& works too, for
3200 backward compatibility.)
3201 If a list of configuration files was supplied, the value that is output here
3202 is the name of the file that was actually used.
3204 .cindex "options" "hiding name of"
3205 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3206 name will not be output.
3208 .cindex "daemon" "process id (pid)"
3209 .cindex "pid (process id)" "of daemon"
3210 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3211 directories where log files and daemon pid files are written are output,
3212 respectively. If these values are unset, log files are written in a
3213 sub-directory of the spool directory called &%log%&, and the pid file is
3214 written directly into the spool directory.
3216 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3218 exim -bP +local_domains
3220 it searches for a matching named list of any type (domain, host, address, or
3221 local part) and outputs what it finds.
3223 .cindex "options" "router &-- extracting"
3224 .cindex "options" "transport &-- extracting"
3225 .cindex "options" "authenticator &-- extracting"
3226 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3227 followed by the name of an appropriate driver instance, the option settings for
3228 that driver are output. For example:
3230 exim -bP transport local_delivery
3232 The generic driver options are output first, followed by the driver's private
3233 options. A list of the names of drivers of a particular type can be obtained by
3234 using one of the words &%router_list%&, &%transport_list%&, or
3235 &%authenticator_list%&, and a complete list of all drivers with their option
3236 settings can be obtained by using &%routers%&, &%transports%&, or
3239 .cindex "environment"
3240 If &%environment%& is given as an argument, the set of environment
3241 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3244 .cindex "options" "macro &-- extracting"
3245 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3246 are available, similarly to the drivers. Because macros are sometimes used
3247 for storing passwords, this option is restricted.
3248 The output format is one item per line.
3249 For the "-bP macro <name>" form, if no such macro is found
3250 the exit status will be nonzero.
3254 .cindex "queue" "listing messages in"
3255 .cindex "listing" "messages in the queue"
3256 This option requests a listing of the contents of the mail queue on the
3257 standard output. If the &%-bp%& option is followed by a list of message ids,
3258 just those messages are listed. By default, this option can be used only by an
3259 admin user. However, the &%queue_list_requires_admin%& option can be set false
3260 to allow any user to see the queue.
3262 Each message in the queue is displayed as in the following example:
3264 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3265 red.king@looking-glass.fict.example
3268 .cindex "message" "size in queue listing"
3269 .cindex "size" "of message"
3270 The first line contains the length of time the message has been in the queue
3271 (in this case 25 minutes), the size of the message (2.9K), the unique local
3272 identifier for the message, and the message sender, as contained in the
3273 envelope. For bounce messages, the sender address is empty, and appears as
3274 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3275 the default sender address, the user's login name is shown in parentheses
3276 before the sender address.
3278 .cindex "frozen messages" "in queue listing"
3279 If the message is frozen (attempts to deliver it are suspended) then the text
3280 &"*** frozen ***"& is displayed at the end of this line.
3282 The recipients of the message (taken from the envelope, not the headers) are
3283 displayed on subsequent lines. Those addresses to which the message has already
3284 been delivered are marked with the letter D. If an original address gets
3285 expanded into several addresses via an alias or forward file, the original is
3286 displayed with a D only when deliveries for all of its child addresses are
3292 This option operates like &%-bp%&, but in addition it shows delivered addresses
3293 that were generated from the original top level address(es) in each message by
3294 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3300 .cindex "queue" "count of messages on"
3301 This option counts the number of messages in the queue, and writes the total
3302 to the standard output. It is restricted to admin users, unless
3303 &%queue_list_requires_admin%& is set false.
3308 This option operates like &%-bp%&, but the output is not sorted into
3309 chronological order of message arrival. This can speed it up when there are
3310 lots of messages in the queue, and is particularly useful if the output is
3311 going to be post-processed in a way that doesn't need the sorting.
3315 This option is a combination of &%-bpr%& and &%-bpa%&.
3319 This option is a combination of &%-bpr%& and &%-bpu%&.
3324 This option operates like &%-bp%& but shows only undelivered top-level
3325 addresses for each message displayed. Addresses generated by aliasing or
3326 forwarding are not shown, unless the message was deferred after processing by a
3327 router with the &%one_time%& option set.
3332 .cindex "testing" "retry configuration"
3333 .cindex "retry" "configuration testing"
3334 This option is for testing retry rules, and it must be followed by up to three
3335 arguments. It causes Exim to look for a retry rule that matches the values
3336 and to write it to the standard output. For example:
3338 exim -brt bach.comp.mus.example
3339 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3341 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3342 argument, which is required, can be a complete address in the form
3343 &'local_part@domain'&, or it can be just a domain name. If the second argument
3344 contains a dot, it is interpreted as an optional second domain name; if no
3345 retry rule is found for the first argument, the second is tried. This ties in
3346 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3347 rule is found that matches the host, one that matches the mail domain is
3348 sought. Finally, an argument that is the name of a specific delivery error, as
3349 used in setting up retry rules, can be given. For example:
3351 exim -brt haydn.comp.mus.example quota_3d
3352 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3357 .cindex "testing" "rewriting"
3358 .cindex "rewriting" "testing"
3359 This option is for testing address rewriting rules, and it must be followed by
3360 a single argument, consisting of either a local part without a domain, or a
3361 complete address with a fully qualified domain. Exim outputs how this address
3362 would be rewritten for each possible place it might appear. See chapter
3363 &<<CHAPrewrite>>& for further details.
3367 .cindex "SMTP" "batched incoming"
3368 .cindex "batched SMTP input"
3369 This option is used for batched SMTP input, which is an alternative interface
3370 for non-interactive local message submission. A number of messages can be
3371 submitted in a single run. However, despite its name, this is not really SMTP
3372 input. Exim reads each message's envelope from SMTP commands on the standard
3373 input, but generates no responses. If the caller is trusted, or
3374 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3375 believed; otherwise the sender is always the caller of Exim.
3377 The message itself is read from the standard input, in SMTP format (leading
3378 dots doubled), terminated by a line containing just a single dot. An error is
3379 provoked if the terminating dot is missing. A further message may then follow.
3381 As for other local message submissions, the contents of incoming batch SMTP
3382 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3383 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3384 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3386 Some other SMTP commands are recognized in the input. HELO and EHLO act
3387 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3388 QUIT quits, ignoring the rest of the standard input.
3390 .cindex "return code" "for &%-bS%&"
3391 If any error is encountered, reports are written to the standard output and
3392 error streams, and Exim gives up immediately. The return code is 0 if no error
3393 was detected; it is 1 if one or more messages were accepted before the error
3394 was detected; otherwise it is 2.
3396 More details of input using batched SMTP are given in section
3397 &<<SECTincomingbatchedSMTP>>&.
3401 .cindex "SMTP" "local input"
3402 .cindex "local SMTP input"
3403 This option causes Exim to accept one or more messages by reading SMTP commands
3404 on the standard input, and producing SMTP replies on the standard output. SMTP
3405 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3406 Some user agents use this interface as a way of passing locally-generated
3407 messages to the MTA.
3410 .cindex "sender" "source of"
3411 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3412 set, the senders of messages are taken from the SMTP MAIL commands.
3413 Otherwise the content of these commands is ignored and the sender is set up as
3414 the calling user. Unqualified addresses are automatically qualified using
3415 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3416 &%-bnq%& option is used.
3420 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3421 using a listening daemon. Exim can distinguish the two cases by checking
3422 whether the standard input is a TCP/IP socket. When Exim is called from
3423 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3424 above concerning senders and qualification do not apply. In this situation,
3425 Exim behaves in exactly the same way as it does when receiving a message via
3426 the listening daemon.
3430 .cindex "testing" "addresses"
3431 .cindex "address" "testing"
3432 This option runs Exim in address testing mode, in which each argument is taken
3433 as a recipient address to be tested for deliverability. The results are
3434 written to the standard output. If a test fails, and the caller is not an admin
3435 user, no details of the failure are output, because these might contain
3436 sensitive information such as usernames and passwords for database lookups.
3438 If no arguments are given, Exim runs in an interactive manner, prompting with a
3439 right angle bracket for addresses to be tested.
3441 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3442 &[readline()]& function, because it is running as &'root'& and there are
3445 Each address is handled as if it were the recipient address of a message
3446 (compare the &%-bv%& option). It is passed to the routers and the result is
3447 written to the standard output. However, any router that has
3448 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3449 genuine routing tests if your first router passes everything to a scanner
3452 .cindex "return code" "for &%-bt%&"
3453 The return code is 2 if any address failed outright; it is 1 if no address
3454 failed outright but at least one could not be resolved for some reason. Return
3455 code 0 is given only when all addresses succeed.
3457 .cindex "duplicate addresses"
3458 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3459 addresses after routing is complete, so that only one delivery takes place.
3460 This does not happen when testing with &%-bt%&; the full results of routing are
3463 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3464 routers in the configuration makes any tests on the sender address of a
3466 .oindex "&%-f%&" "for address testing"
3467 you can use the &%-f%& option to set an appropriate sender when running
3468 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3469 default qualifying domain. However, if you have set up (for example) routers
3470 whose behaviour depends on the contents of an incoming message, you cannot test
3471 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3476 .cindex "version number of Exim"
3477 This option causes Exim to write the current version number, compilation
3478 number, and compilation date of the &'exim'& binary to the standard output.
3479 It also lists the DBM library that is being used, the optional modules (such as
3480 specific lookup types), the drivers that are included in the binary, and the
3481 name of the runtime configuration file that is in use.
3483 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3484 configuration file. However, this is a static check only. It cannot check
3485 values that are to be expanded. For example, although a misspelt ACL verb is
3486 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3487 alone to discover (for example) all the typos in the configuration; some
3488 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3489 dynamic testing facilities.
3493 .cindex "verifying address" "using &%-bv%&"
3494 .cindex "address" "verification"
3495 This option runs Exim in address verification mode, in which each argument is
3496 taken as a recipient address to be verified by the routers. (This does
3497 not involve any verification callouts). During normal operation, verification
3498 happens mostly as a consequence processing a &%verify%& condition in an ACL
3499 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3500 including callouts, see the &%-bh%& and &%-bhc%& options.
3502 If verification fails, and the caller is not an admin user, no details of the
3503 failure are output, because these might contain sensitive information such as
3504 usernames and passwords for database lookups.
3506 If no arguments are given, Exim runs in an interactive manner, prompting with a
3507 right angle bracket for addresses to be verified.
3509 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3510 &[readline()]& function, because it is running as &'exim'& and there are
3513 Verification differs from address testing (the &%-bt%& option) in that routers
3514 that have &%no_verify%& set are skipped, and if the address is accepted by a
3515 router that has &%fail_verify%& set, verification fails. The address is
3516 verified as a recipient if &%-bv%& is used; to test verification for a sender
3517 address, &%-bvs%& should be used.
3519 If the &%-v%& option is not set, the output consists of a single line for each
3520 address, stating whether it was verified or not, and giving a reason in the
3521 latter case. Without &%-v%&, generating more than one address by redirection
3522 causes verification to end successfully, without considering the generated
3523 addresses. However, if just one address is generated, processing continues,
3524 and the generated address must verify successfully for the overall verification
3527 When &%-v%& is set, more details are given of how the address has been handled,
3528 and in the case of address redirection, all the generated addresses are also
3529 considered. Verification may succeed for some and fail for others.
3532 .cindex "return code" "for &%-bv%&"
3533 return code is 2 if any address failed outright; it is 1 if no address
3534 failed outright but at least one could not be resolved for some reason. Return
3535 code 0 is given only when all addresses succeed.
3537 If any of the routers in the configuration makes any tests on the sender
3538 address of a message, you should use the &%-f%& option to set an appropriate
3539 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3540 calling user at the default qualifying domain.
3544 This option acts like &%-bv%&, but verifies the address as a sender rather
3545 than a recipient address. This affects any rewriting and qualification that
3552 .cindex "inetd" "wait mode"
3553 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3554 similarly to the &%-bd%& option. All port specifications on the command-line
3555 and in the configuration file are ignored. Queue-running may not be specified.
3557 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3558 listening for connections. This permits the system to start up and have
3559 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3560 each port only when the first connection is received.
3562 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3563 which the daemon will exit, which should cause inetd to listen once more.
3565 .vitem &%-C%&&~<&'filelist'&>
3567 .cindex "configuration file" "alternate"
3568 .cindex "CONFIGURE_FILE"
3569 .cindex "alternate configuration file"
3570 This option causes Exim to find the runtime configuration file from the given
3571 list instead of from the list specified by the CONFIGURE_FILE
3572 compile-time setting. Usually, the list will consist of just a single filename,
3573 but it can be a colon-separated list of names. In this case, the first
3574 file that exists is used. Failure to open an existing file stops Exim from
3575 proceeding any further along the list, and an error is generated.
3577 When this option is used by a caller other than root, and the list is different
3578 from the compiled-in list, Exim gives up its root privilege immediately, and
3579 runs with the real and effective uid and gid set to those of the caller.
3580 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3581 file contains a list of full pathnames, one per line, for configuration files
3582 which are trusted. Root privilege is retained for any configuration file so
3583 listed, as long as the caller is the Exim user (or the user specified in the
3584 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3585 not writeable by inappropriate users or groups.
3587 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3588 configuration using &%-C%& right through message reception and delivery,
3589 even if the caller is root. The reception works, but by that time, Exim is
3590 running as the Exim user, so when it re-executes to regain privilege for the
3591 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3592 test reception and delivery using two separate commands (one to put a message
3593 in the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3595 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3596 prefix string with which any file named in a &%-C%& command line option
3597 must start. In addition, the filename must not contain the sequence &`/../`&.
3598 However, if the value of the &%-C%& option is identical to the value of
3599 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3600 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3601 unset, any filename can be used with &%-C%&.
3603 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3604 to a directory to which only root has access. This prevents someone who has
3605 broken into the Exim account from running a privileged Exim with an arbitrary
3608 The &%-C%& facility is useful for ensuring that configuration files are
3609 syntactically correct, but cannot be used for test deliveries, unless the
3610 caller is privileged, or unless it is an exotic configuration that does not
3611 require privilege. No check is made on the owner or group of the files
3612 specified by this option.
3615 .vitem &%-D%&<&'macro'&>=<&'value'&>
3617 .cindex "macro" "setting on command line"
3618 This option can be used to override macro definitions in the configuration file
3619 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3620 unprivileged caller, it causes Exim to give up its root privilege.
3621 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3622 completely disabled, and its use causes an immediate error exit.
3624 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3625 colon-separated list of macros which are considered safe and, if &%-D%& only
3626 supplies macros from this list, and the values are acceptable, then Exim will
3627 not give up root privilege if the caller is root, the Exim run-time user, or
3628 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3629 to be removed in the future. Acceptable values for the macros satisfy the
3630 regexp: &`^[A-Za-z0-9_/.-]*$`&
3632 The entire option (including equals sign if present) must all be within one
3633 command line item. &%-D%& can be used to set the value of a macro to the empty
3634 string, in which case the equals sign is optional. These two commands are
3640 To include spaces in a macro definition item, quotes must be used. If you use
3641 quotes, spaces are permitted around the macro name and the equals sign. For
3644 exim '-D ABC = something' ...
3646 &%-D%& may be repeated up to 10 times on a command line.
3647 Only macro names up to 22 letters long can be set.
3650 .vitem &%-d%&<&'debug&~options'&>
3652 .cindex "debugging" "list of selectors"
3653 .cindex "debugging" "&%-d%& option"
3654 This option causes debugging information to be written to the standard
3655 error stream. It is restricted to admin users because debugging output may show
3656 database queries that contain password information. Also, the details of users'
3657 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3658 writes an error message to the standard error stream and exits with a non-zero
3661 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3662 standard debugging data is output. This can be reduced, or increased to include
3663 some more rarely needed information, by directly following &%-d%& with a string
3664 made up of names preceded by plus or minus characters. These add or remove sets
3665 of debugging data, respectively. For example, &%-d+filter%& adds filter
3666 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3667 no spaces are allowed in the debug setting. The available debugging categories
3670 &`acl `& ACL interpretation
3671 &`auth `& authenticators
3672 &`deliver `& general delivery logic
3673 &`dns `& DNS lookups (see also resolver)
3674 &`dnsbl `& DNS black list (aka RBL) code
3675 &`exec `& arguments for &[execv()]& calls
3676 &`expand `& detailed debugging for string expansions
3677 &`filter `& filter handling
3678 &`hints_lookup `& hints data lookups
3679 &`host_lookup `& all types of name-to-IP address handling
3680 &`ident `& ident lookup
3681 &`interface `& lists of local interfaces
3682 &`lists `& matching things in lists
3683 &`load `& system load checks
3684 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3685 &<<CHAPlocalscan>>&)
3686 &`lookup `& general lookup code and all lookups
3687 &`memory `& memory handling
3688 &`noutf8 `& modifier: avoid UTF-8 line-drawing
3689 &`pid `& modifier: add pid to debug output lines
3690 &`process_info `& setting info for the process log
3691 &`queue_run `& queue runs
3692 &`receive `& general message reception logic
3693 &`resolver `& turn on the DNS resolver's debugging output
3694 &`retry `& retry handling
3695 &`rewrite `& address rewriting
3696 &`route `& address routing
3697 &`timestamp `& modifier: add timestamp to debug output lines
3699 &`transport `& transports
3700 &`uid `& changes of uid/gid and looking up uid/gid
3701 &`verify `& address verification logic
3702 &`all `& almost all of the above (see below), and also &%-v%&
3704 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3705 for &`-all`&. The reason for this is that &`+all`& is something that people
3706 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3707 is included, an awful lot of output that is very rarely of interest is
3708 generated, so it now has to be explicitly requested. However, &`-all`& does
3709 turn everything off.
3711 .cindex "resolver, debugging output"
3712 .cindex "DNS resolver, debugging output"
3713 The &`resolver`& option produces output only if the DNS resolver was compiled
3714 with DEBUG enabled. This is not the case in some operating systems. Also,
3715 unfortunately, debugging output from the DNS resolver is written to stdout
3718 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3719 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3720 However, the &`pid`& selector is forced when debugging is turned on for a
3721 daemon, which then passes it on to any re-executed Exims. Exim also
3722 automatically adds the pid to debug lines when several remote deliveries are
3725 The &`timestamp`& selector causes the current time to be inserted at the start
3726 of all debug output lines. This can be useful when trying to track down delays
3729 .cindex debugging "UTF-8 in"
3730 .cindex UTF-8 "in debug output"
3731 The &`noutf8`& selector disables the use of
3732 UTF-8 line-drawing characters to group related information.
3733 When disabled. ascii-art is used instead.
3734 Using the &`+all`& option does not set this modifier,
3736 If the &%debug_print%& option is set in any driver, it produces output whenever
3737 any debugging is selected, or if &%-v%& is used.
3739 .vitem &%-dd%&<&'debug&~options'&>
3741 This option behaves exactly like &%-d%& except when used on a command that
3742 starts a daemon process. In that case, debugging is turned off for the
3743 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3744 behaviour of the daemon without creating as much output as full debugging does.
3747 .oindex "&%-dropcr%&"
3748 This is an obsolete option that is now a no-op. It used to affect the way Exim
3749 handled CR and LF characters in incoming messages. What happens now is
3750 described in section &<<SECTlineendings>>&.
3754 .cindex "bounce message" "generating"
3755 This option specifies that an incoming message is a locally-generated delivery
3756 failure report. It is used internally by Exim when handling delivery failures
3757 and is not intended for external use. Its only effect is to stop Exim
3758 generating certain messages to the postmaster, as otherwise message cascades
3759 could occur in some situations. As part of the same option, a message id may
3760 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3761 new message contains the id, following &"R="&, as a cross-reference.
3764 .oindex "&%-e%&&'x'&"
3765 There are a number of Sendmail options starting with &%-oe%& which seem to be
3766 called by various programs without the leading &%o%& in the option. For
3767 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3768 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3770 .vitem &%-F%&&~<&'string'&>
3772 .cindex "sender" "name"
3773 .cindex "name" "of sender"
3774 This option sets the sender's full name for use when a locally-generated
3775 message is being accepted. In the absence of this option, the user's &'gecos'&
3776 entry from the password data is used. As users are generally permitted to alter
3777 their &'gecos'& entries, no security considerations are involved. White space
3778 between &%-F%& and the <&'string'&> is optional.
3780 .vitem &%-f%&&~<&'address'&>
3782 .cindex "sender" "address"
3783 .cindex "address" "sender"
3784 .cindex "trusted users"
3785 .cindex "envelope from"
3786 .cindex "envelope sender"
3787 .cindex "user" "trusted"
3788 This option sets the address of the envelope sender of a locally-generated
3789 message (also known as the return path). The option can normally be used only
3790 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3793 Processes running as root or the Exim user are always trusted. Other
3794 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3795 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3796 of a local message is set to the caller's login name at the default qualify
3799 There is one exception to the restriction on the use of &%-f%&: an empty sender
3800 can be specified by any user, trusted or not, to create a message that can
3801 never provoke a bounce. An empty sender can be specified either as an empty
3802 string, or as a pair of angle brackets with nothing between them, as in these
3803 examples of shell commands:
3805 exim -f '<>' user@domain
3806 exim -f "" user@domain
3808 In addition, the use of &%-f%& is not restricted when testing a filter file
3809 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3812 Allowing untrusted users to change the sender address does not of itself make
3813 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3814 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3815 though this can be overridden by setting &%no_local_from_check%&.
3818 .cindex "&""From""& line"
3819 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3820 given as two arguments or one combined argument). The sender of a
3821 locally-generated message can also be set (when permitted) by an initial
3822 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3823 if &%-f%& is also present, it overrides &"From&~"&.
3827 .cindex "submission fixups, suppressing (command-line)"
3828 This option is equivalent to an ACL applying:
3830 control = suppress_local_fixups
3832 for every message received. Note that Sendmail will complain about such
3833 bad formatting, where Exim silently just does not fix it up. This may change
3836 As this affects audit information, the caller must be a trusted user to use
3839 .vitem &%-h%&&~<&'number'&>
3841 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3842 This option is accepted for compatibility with Sendmail, but has no effect. (In
3843 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3848 .cindex "Solaris" "&'mail'& command"
3849 .cindex "dot" "in incoming non-SMTP message"
3850 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3851 line by itself should not terminate an incoming, non-SMTP message. I can find
3852 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3853 command in Solaris 2.4 uses it. See also &%-ti%&.
3855 .vitem &%-L%&&~<&'tag'&>
3857 .cindex "syslog" "process name; set with flag"
3858 This option is equivalent to setting &%syslog_processname%& in the config
3859 file and setting &%log_file_path%& to &`syslog`&.
3860 Its use is restricted to administrators. The configuration file has to be
3861 read and parsed, to determine access rights, before this is set and takes
3862 effect, so early configuration file errors will not honour this flag.
3864 The tag should not be longer than 32 characters.
3866 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3868 .cindex "forcing delivery"
3869 .cindex "delivery" "forcing attempt"
3870 .cindex "frozen messages" "forcing delivery"
3871 This option requests Exim to run a delivery attempt on each message in turn. If
3872 any of the messages are frozen, they are automatically thawed before the
3873 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3874 and &%hold_domains%& are ignored.
3877 .cindex "hints database" "overriding retry hints"
3878 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3879 the normal retry time has not yet been reached. This option requires the caller
3880 to be an admin user. However, there is an option called &%prod_requires_admin%&
3881 which can be set false to relax this restriction (and also the same requirement
3882 for the &%-q%&, &%-R%&, and &%-S%& options).
3884 The deliveries happen synchronously, that is, the original Exim process does
3885 not terminate until all the delivery attempts have finished. No output is
3886 produced unless there is a serious error. If you want to see what is happening,
3887 use the &%-v%& option as well, or inspect Exim's main log.
3889 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3891 .cindex "message" "adding recipients"
3892 .cindex "recipient" "adding"
3893 This option requests Exim to add the addresses to the list of recipients of the
3894 message (&"ar"& for &"add recipients"&). The first argument must be a message
3895 id, and the remaining ones must be email addresses. However, if the message is
3896 active (in the middle of a delivery attempt), it is not altered. This option
3897 can be used only by an admin user.
3899 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&&&
3901 &~<&'sequence&~number'&>&&&
3902 &~<&'message&~id'&>"
3904 .cindex "SMTP" "passed connection"
3905 .cindex "SMTP" "multiple deliveries"
3906 .cindex "multiple SMTP deliveries"
3907 This option is not intended for use by external callers. It is used internally
3908 by Exim to invoke another instance of itself to deliver a waiting message using
3909 an existing SMTP connection, which is passed as the standard input. Details are
3910 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3911 must be root or the Exim user in order to use it.
3915 This option is not intended for use by external callers. It is used internally
3916 by Exim in conjunction with the &%-MC%& option. It signifies that the
3917 connection to the remote host has been authenticated.
3921 This option is not intended for use by external callers. It is used internally
3922 by Exim in conjunction with the &%-MC%& option. It signifies that the
3923 remote host supports the ESMTP &_DSN_& extension.
3927 This option is not intended for use by external callers. It is used internally
3928 by Exim in conjunction with the &%-d%& option
3929 to pass on an information string on the purpose of the process.
3931 .vitem &%-MCG%&&~<&'queue&~name'&>
3933 This option is not intended for use by external callers. It is used internally
3934 by Exim in conjunction with the &%-MC%& option. It signifies that an
3935 alternate queue is used, named by the following argument.
3939 This option is not intended for use by external callers. It is used internally
3940 by Exim in conjunction with the &%-MC%& option. It signifies that a
3941 remote host supports the ESMTP &_CHUNKING_& extension.
3946 This option is not intended for use by external callers. It is used internally
3947 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3948 which Exim is connected advertised limits on numbers of mails, recipients or
3950 The limits are given by the following three arguments.
3955 This option is not intended for use by external callers. It is used internally
3956 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3957 which Exim is connected supports pipelining.
3962 This option is not intended for use by external callers. It is used internally
3963 by Exim in conjunction with the &%-MC%& option. It signifies that the connection
3964 t a remote server is via a SOCKS proxy, using addresses and ports given by
3965 the following four arguments.
3968 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3970 This option is not intended for use by external callers. It is used internally
3971 by Exim in conjunction with the &%-MC%& option when the original delivery was
3972 started by a queue runner. It passes on the process id of the queue runner,
3973 together with the file descriptor number of an open pipe. Closure of the pipe
3974 signals the final completion of the sequence of processes that are passing
3975 messages through the same SMTP connection.
3978 .vitem &%-MCq%&&~<&'recipient&~address'&>&~<&'size'&>
3980 This option is not intended for use by external callers. It is used internally
3981 by Exim to implement quota checking for local users.
3986 This option is not intended for use by external callers. It is used internally
3987 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3988 ESMTP SIZE option should be used on messages delivered down the existing
3993 This option is not intended for use by external callers. It is used internally
3994 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3995 host to which Exim is connected supports TLS encryption.
3998 .vitem &%-MCr%&&~<&'SNI'&> &&&
4002 These options are not intended for use by external callers. It is used internally
4003 by Exim in conjunction with the &%-MCt%& option, and passes on the fact that
4004 a TLS Server Name Indication was sent as part of the channel establishment.
4005 The argument gives the SNI string.
4006 The "r" variant indicates a DANE-verified connection.
4009 .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
4011 This option is not intended for use by external callers. It is used internally
4012 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
4013 connection is being proxied by a parent process for handling TLS encryption.
4014 The arguments give the local address and port being proxied, and the TLS cipher.
4016 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4018 .cindex "hints database" "not overridden by &%-Mc%&"
4019 .cindex "delivery" "manually started &-- not forced"
4020 This option requests Exim to run a delivery attempt on each message, in turn,
4021 but unlike the &%-M%& option, it does check for retry hints, and respects any
4022 that are found. This option is not very useful to external callers. It is
4023 provided mainly for internal use by Exim when it needs to re-invoke itself in
4024 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
4025 However, &%-Mc%& can be useful when testing, in order to run a delivery that
4026 respects retry times and other options such as &%hold_domains%& that are
4027 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
4028 If you want to run a specific delivery as if in a queue run, you should use
4029 &%-q%& with a message id argument. A distinction between queue run deliveries
4030 and other deliveries is made in one or two places.
4032 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
4034 .cindex "message" "changing sender"
4035 .cindex "sender" "changing"
4036 This option requests Exim to change the sender address in the message to the
4037 given address, which must be a fully qualified address or &"<>"& (&"es"& for
4038 &"edit sender"&). There must be exactly two arguments. The first argument must
4039 be a message id, and the second one an email address. However, if the message
4040 is active (in the middle of a delivery attempt), its status is not altered.
4041 This option can be used only by an admin user.
4043 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4045 .cindex "freezing messages"
4046 .cindex "message" "manually freezing"
4047 This option requests Exim to mark each listed message as &"frozen"&. This
4048 prevents any delivery attempts taking place until the message is &"thawed"&,
4049 either manually or as a result of the &%auto_thaw%& configuration option.
4050 However, if any of the messages are active (in the middle of a delivery
4051 attempt), their status is not altered. This option can be used only by an admin
4054 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4056 .cindex "giving up on messages"
4057 .cindex "message" "abandoning delivery attempts"
4058 .cindex "delivery" "abandoning further attempts"
4059 This option requests Exim to give up trying to deliver the listed messages,
4060 including any that are frozen. However, if any of the messages are active,
4061 their status is not altered. For non-bounce messages, a delivery error message
4062 is sent to the sender, containing the text &"cancelled by administrator"&.
4063 Bounce messages are just discarded. This option can be used only by an admin
4066 .vitem &%-MG%&&~<&'queue&~name'&>&~<&'message&~id'&>&~<&'message&~id'&>&~...
4069 .cindex "named queues" "moving messages"
4070 .cindex "queue" "moving messages"
4071 This option requests that each listed message be moved from its current
4072 queue to the given named queue.
4073 The destination queue name argument is required, but can be an empty
4074 string to define the default queue.
4075 If the messages are not currently located in the default queue,
4076 a &%-qG<name>%& option will be required to define the source queue.
4078 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4080 .cindex "delivery" "cancelling all"
4081 This option requests Exim to mark all the recipient addresses in the messages
4082 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
4083 message is active (in the middle of a delivery attempt), its status is not
4084 altered. This option can be used only by an admin user.
4086 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
4088 .cindex "delivery" "cancelling by address"
4089 .cindex "recipient" "removing"
4090 .cindex "removing recipients"
4091 This option requests Exim to mark the given addresses as already delivered
4092 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
4093 the remaining ones must be email addresses. These are matched to recipient
4094 addresses in the message in a case-sensitive manner. If the message is active
4095 (in the middle of a delivery attempt), its status is not altered. This option
4096 can be used only by an admin user.
4098 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4100 .cindex "removing messages"
4101 .cindex "abandoning mail"
4102 .cindex "message" "manually discarding"
4103 This option requests Exim to remove the given messages from the queue. No
4104 bounce messages are sent; each message is simply forgotten. However, if any of
4105 the messages are active, their status is not altered. This option can be used
4106 only by an admin user or by the user who originally caused the message to be
4107 placed in the queue.
4112 . .cindex REQUIRETLS
4113 . This option is used to request REQUIRETLS processing on the message.
4114 . It is used internally by Exim in conjunction with -E when generating
4118 .vitem &%-Mset%&&~<&'message&~id'&>
4120 .cindex "testing" "string expansion"
4121 .cindex "expansion" "testing"
4122 This option is useful only in conjunction with &%-be%& (that is, when testing
4123 string expansions). Exim loads the given message from its spool before doing
4124 the test expansions, thus setting message-specific variables such as
4125 &$message_size$& and the header variables. The &$recipients$& variable is made
4126 available. This feature is provided to make it easier to test expansions that
4127 make use of these variables. However, this option can be used only by an admin
4128 user. See also &%-bem%&.
4130 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4132 .cindex "thawing messages"
4133 .cindex "unfreezing messages"
4134 .cindex "frozen messages" "thawing"
4135 .cindex "message" "thawing frozen"
4136 This option requests Exim to &"thaw"& any of the listed messages that are
4137 &"frozen"&, so that delivery attempts can resume. However, if any of the
4138 messages are active, their status is not altered. This option can be used only
4141 .vitem &%-Mvb%&&~<&'message&~id'&>
4143 .cindex "listing" "message body"
4144 .cindex "message" "listing body of"
4145 This option causes the contents of the message body (-D) spool file to be
4146 written to the standard output. This option can be used only by an admin user.
4148 .vitem &%-Mvc%&&~<&'message&~id'&>
4150 .cindex "message" "listing in RFC 2822 format"
4151 .cindex "listing" "message in RFC 2822 format"
4152 This option causes a copy of the complete message (header lines plus body) to
4153 be written to the standard output in RFC 2822 format. This option can be used
4154 only by an admin user.
4156 .vitem &%-Mvh%&&~<&'message&~id'&>
4158 .cindex "listing" "message headers"
4159 .cindex "header lines" "listing"
4160 .cindex "message" "listing header lines"
4161 This option causes the contents of the message headers (-H) spool file to be
4162 written to the standard output. This option can be used only by an admin user.
4164 .vitem &%-Mvl%&&~<&'message&~id'&>
4166 .cindex "listing" "message log"
4167 .cindex "message" "listing message log"
4168 This option causes the contents of the message log spool file to be written to
4169 the standard output. This option can be used only by an admin user.
4173 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
4174 treats it that way too.
4178 .cindex "debugging" "&%-N%& option"
4179 .cindex "debugging" "suppressing delivery"
4180 This is a debugging option that inhibits delivery of a message at the transport
4181 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4182 it just doesn't actually transport the message, but instead behaves as if it
4183 had successfully done so. However, it does not make any updates to the retry
4184 database, and the log entries for deliveries are flagged with &"*>"& rather
4187 Because &%-N%& discards any message to which it applies, only root or the Exim
4188 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4189 words, an ordinary user can use it only when supplying an incoming message to
4190 which it will apply. Although transportation never fails when &%-N%& is set, an
4191 address may be deferred because of a configuration problem on a transport, or a
4192 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4193 the message, and applies to any subsequent delivery attempts that may happen
4198 This option is interpreted by Sendmail to mean &"no aliasing"&.
4199 For normal modes of operation, it is ignored by Exim.
4200 When combined with &%-bP%& it makes the output more terse (suppresses
4201 option names, environment values and config pretty printing).
4203 .vitem &%-O%&&~<&'data'&>
4205 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4208 .vitem &%-oA%&&~<&'file&~name'&>
4210 .cindex "Sendmail compatibility" "&%-oA%& option"
4211 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4212 alternative alias filename. Exim handles &%-bi%& differently; see the
4215 .vitem &%-oB%&&~<&'n'&>
4217 .cindex "SMTP" "passed connection"
4218 .cindex "SMTP" "multiple deliveries"
4219 .cindex "multiple SMTP deliveries"
4220 This is a debugging option which limits the maximum number of messages that can
4221 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4222 transport. If <&'n'&> is omitted, the limit is set to 1.
4226 .cindex "background delivery"
4227 .cindex "delivery" "in the background"
4228 This option applies to all modes in which Exim accepts incoming messages,
4229 including the listening daemon. It requests &"background"& delivery of such
4230 messages, which means that the accepting process automatically starts a
4231 delivery process for each message received, but does not wait for the delivery
4232 processes to finish.
4234 When all the messages have been received, the reception process exits,
4235 leaving the delivery processes to finish in their own time. The standard output
4236 and error streams are closed at the start of each delivery process.
4237 This is the default action if none of the &%-od%& options are present.
4239 If one of the queueing options in the configuration file
4240 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4241 overrides it if &%queue_only_override%& is set true, which is the default
4242 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4246 .cindex "foreground delivery"
4247 .cindex "delivery" "in the foreground"
4248 This option requests &"foreground"& (synchronous) delivery when Exim has
4249 accepted a locally-generated message. (For the daemon it is exactly the same as
4250 &%-odb%&.) A delivery process is automatically started to deliver the message,
4251 and Exim waits for it to complete before proceeding.
4253 The original Exim reception process does not finish until the delivery
4254 process for the final message has ended. The standard error stream is left open
4257 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4258 false and one of the queueing options in the configuration file is in effect.
4260 If there is a temporary delivery error during foreground delivery, the
4261 message is left in the queue for later delivery, and the original reception
4262 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4263 restricted configuration that never queues messages.
4268 This option is synonymous with &%-odf%&. It is provided for compatibility with
4273 .cindex "non-immediate delivery"
4274 .cindex "delivery" "suppressing immediate"
4275 .cindex "queueing incoming messages"
4276 This option applies to all modes in which Exim accepts incoming messages,
4277 including the listening daemon. It specifies that the accepting process should
4278 not automatically start a delivery process for each message received. Messages
4279 are placed in the queue, and remain there until a subsequent queue runner
4280 process encounters them. There are several configuration options (such as
4281 &%queue_only%&) that can be used to queue incoming messages under certain
4282 conditions. This option overrides all of them and also &%-odqs%&. It always
4287 .cindex "SMTP" "delaying delivery"
4288 .cindex "first pass routing"
4289 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4290 However, like &%-odb%& and &%-odi%&, this option has no effect if
4291 &%queue_only_override%& is false and one of the queueing options in the
4292 configuration file is in effect.
4294 When &%-odqs%& does operate, a delivery process is started for each incoming
4295 message, in the background by default, but in the foreground if &%-odi%& is
4296 also present. The recipient addresses are routed, and local deliveries are done
4297 in the normal way. However, if any SMTP deliveries are required, they are not
4298 done at this time, so the message remains in the queue until a subsequent queue
4299 runner process encounters it. Because routing was done, Exim knows which
4300 messages are waiting for which hosts, and so a number of messages for the same
4301 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4302 configuration option has the same effect for specific domains. See also the
4307 .cindex "error" "reporting"
4308 If an error is detected while a non-SMTP message is being received (for
4309 example, a malformed address), the error is reported to the sender in a mail
4312 .cindex "return code" "for &%-oee%&"
4314 this error message is successfully sent, the Exim receiving process
4315 exits with a return code of zero. If not, the return code is 2 if the problem
4316 is that the original message has no recipients, or 1 for any other error.
4317 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4321 .cindex "error" "reporting"
4322 .cindex "return code" "for &%-oem%&"
4323 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4324 return code, whether or not the error message was successfully sent.
4325 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4329 .cindex "error" "reporting"
4330 If an error is detected while a non-SMTP message is being received, the
4331 error is reported by writing a message to the standard error file (stderr).
4332 .cindex "return code" "for &%-oep%&"
4333 The return code is 1 for all errors.
4337 .cindex "error" "reporting"
4338 This option is supported for compatibility with Sendmail, but has the same
4343 .cindex "error" "reporting"
4344 This option is supported for compatibility with Sendmail, but has the same
4349 .cindex "dot" "in incoming non-SMTP message"
4350 This option, which has the same effect as &%-i%&, specifies that a dot on a
4351 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4352 single dot does terminate, though Exim does no special processing for other
4353 lines that start with a dot. This option is set by default if Exim is called as
4354 &'rmail'&. See also &%-ti%&.
4357 .oindex "&%-oitrue%&"
4358 This option is treated as synonymous with &%-oi%&.
4360 .vitem &%-oMa%&&~<&'host&~address'&>
4362 .cindex "sender" "host address, specifying for local message"
4363 A number of options starting with &%-oM%& can be used to set values associated
4364 with remote hosts on locally-submitted messages (that is, messages not received
4365 over TCP/IP). These options can be used by any caller in conjunction with the
4366 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4367 other circumstances, they are ignored unless the caller is trusted.
4369 The &%-oMa%& option sets the sender host address. This may include a port
4370 number at the end, after a full stop (period). For example:
4372 exim -bs -oMa 10.9.8.7.1234
4374 An alternative syntax is to enclose the IP address in square brackets,
4375 followed by a colon and the port number:
4377 exim -bs -oMa [10.9.8.7]:1234
4379 The IP address is placed in the &$sender_host_address$& variable, and the
4380 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4381 are present on the command line, the sender host IP address is taken from
4382 whichever one is last.
4384 .vitem &%-oMaa%&&~<&'name'&>
4386 .cindex "authentication" "name, specifying for local message"
4387 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4388 option sets the value of &$sender_host_authenticated$& (the authenticator
4389 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4390 This option can be used with &%-bh%& and &%-bs%& to set up an
4391 authenticated SMTP session without actually using the SMTP AUTH command.
4393 .vitem &%-oMai%&&~<&'string'&>
4395 .cindex "authentication" "id, specifying for local message"
4396 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4397 option sets the value of &$authenticated_id$& (the id that was authenticated).
4398 This overrides the default value (the caller's login id, except with &%-bh%&,
4399 where there is no default) for messages from local sources. See chapter
4400 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4402 .vitem &%-oMas%&&~<&'address'&>
4404 .cindex "authentication" "sender, specifying for local message"
4405 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4406 option sets the authenticated sender value in &$authenticated_sender$&. It
4407 overrides the sender address that is created from the caller's login id for
4408 messages from local sources, except when &%-bh%& is used, when there is no
4409 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4410 specified on a MAIL command overrides this value. See chapter
4411 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4413 .vitem &%-oMi%&&~<&'interface&~address'&>
4415 .cindex "interface" "address, specifying for local message"
4416 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4417 option sets the IP interface address value. A port number may be included,
4418 using the same syntax as for &%-oMa%&. The interface address is placed in
4419 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4421 .vitem &%-oMm%&&~<&'message&~reference'&>
4423 .cindex "message reference" "message reference, specifying for local message"
4424 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4425 option sets the message reference, e.g. message-id, and is logged during
4426 delivery. This is useful when some kind of audit trail is required to tie
4427 messages together. The format of the message reference is checked and will
4428 abort if the format is invalid. The option will only be accepted if exim is
4429 running in trusted mode, not as any regular user.
4431 The best example of a message reference is when Exim sends a bounce message.
4432 The message reference is the message-id of the original message for which Exim
4433 is sending the bounce.
4435 .vitem &%-oMr%&&~<&'protocol&~name'&>
4437 .cindex "protocol, specifying for local message"
4438 .vindex "&$received_protocol$&"
4439 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4440 option sets the received protocol value that is stored in
4441 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4442 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4443 SMTP protocol names (see the description of &$received_protocol$& in section
4444 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4445 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4446 be set by &%-oMr%&. Repeated use of this option is not supported.
4448 .vitem &%-oMs%&&~<&'host&~name'&>
4450 .cindex "sender" "host name, specifying for local message"
4451 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4452 option sets the sender host name in &$sender_host_name$&. When this option is
4453 present, Exim does not attempt to look up a host name from an IP address; it
4454 uses the name it is given.
4456 .vitem &%-oMt%&&~<&'ident&~string'&>
4458 .cindex "sender" "ident string, specifying for local message"
4459 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4460 option sets the sender ident value in &$sender_ident$&. The default setting for
4461 local callers is the login id of the calling process, except when &%-bh%& is
4462 used, when there is no default.
4466 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4467 In Sendmail, this option means &"me too"&, indicating that the sender of a
4468 message should receive a copy of the message if the sender appears in an alias
4469 expansion. Exim always does this, so the option does nothing.
4473 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4474 This option is ignored. In Sendmail it specifies &"old style headers"&,
4475 whatever that means.
4477 .vitem &%-oP%&&~<&'path'&>
4479 .cindex "pid (process id)" "of daemon"
4480 .cindex "daemon" "process id (pid)"
4481 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4482 value. The option specifies the file to which the process id of the daemon is
4483 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4484 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4485 because in those cases, the normal pid file is not used.
4489 .cindex "pid (process id)" "of daemon"
4490 .cindex "daemon" "process id (pid)"
4491 This option is not intended for general use.
4492 The daemon uses it when terminating due to a SIGTEM, possibly in
4493 combination with &%-oP%&&~<&'path'&>.
4494 It causes the pid file to be removed.
4496 .vitem &%-or%&&~<&'time'&>
4498 .cindex "timeout" "for non-SMTP input"
4499 This option sets a timeout value for incoming non-SMTP messages. If it is not
4500 set, Exim will wait forever for the standard input. The value can also be set
4501 by the &%receive_timeout%& option. The format used for specifying times is
4502 described in section &<<SECTtimeformat>>&.
4504 .vitem &%-os%&&~<&'time'&>
4506 .cindex "timeout" "for SMTP input"
4507 .cindex "SMTP" "input timeout"
4508 This option sets a timeout value for incoming SMTP messages. The timeout
4509 applies to each SMTP command and block of data. The value can also be set by
4510 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4511 for specifying times is described in section &<<SECTtimeformat>>&.
4515 This option has exactly the same effect as &%-v%&.
4517 .vitem &%-oX%&&~<&'number&~or&~string'&>
4519 .cindex "TCP/IP" "setting listening ports"
4520 .cindex "TCP/IP" "setting listening interfaces"
4521 .cindex "port" "receiving TCP/IP"
4522 This option is relevant only when the &%-bd%& (start listening daemon) option
4523 is also given. It controls which ports and interfaces the daemon uses. Details
4524 of the syntax, and how it interacts with configuration file options, are given
4525 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4526 file is written unless &%-oP%& is also present to specify a pid filename.
4531 .cindex "daemon notifier socket"
4532 This option controls the creation of an inter-process communications endpoint
4534 It is only relevant when the &%-bd%& (start listening daemon) option is also
4536 Normally the daemon creates this socket, unless a &%-oX%& and &*no*& &%-oP%&
4537 option is also present.
4538 If this option is given then the socket will not be created. This could be
4539 required if the system is running multiple daemons.
4541 The socket is currently used for
4543 fast ramp-up of queue runner processes
4545 obtaining a current queue size
4551 .cindex "Perl" "starting the interpreter"
4552 This option applies when an embedded Perl interpreter is linked with Exim (see
4553 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4554 option, forcing the starting of the interpreter to be delayed until it is
4559 .cindex "Perl" "starting the interpreter"
4560 This option applies when an embedded Perl interpreter is linked with Exim (see
4561 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4562 option, forcing the starting of the interpreter to occur as soon as Exim is
4565 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4567 For compatibility with Sendmail, this option is equivalent to
4569 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4571 It sets the incoming protocol and host name (for trusted callers). The
4572 host name and its colon can be omitted when only the protocol is to be set.
4573 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4574 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4575 or &`s`& using this option (but that does not seem a real limitation).
4576 Repeated use of this option is not supported.
4580 .cindex "queue runner" "starting manually"
4581 This option is normally restricted to admin users. However, there is a
4582 configuration option called &%prod_requires_admin%& which can be set false to
4583 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4584 and &%-S%& options).
4586 .cindex "queue runner" "description of operation"
4587 If other commandline options do not specify an action,
4588 the &%-q%& option starts one queue runner process. This scans the queue of
4589 waiting messages, and runs a delivery process for each one in turn. It waits
4590 for each delivery process to finish before starting the next one. A delivery
4591 process may not actually do any deliveries if the retry times for the addresses
4592 have not been reached. Use &%-qf%& (see below) if you want to override this.
4595 .cindex "SMTP" "passed connection"
4596 .cindex "SMTP" "multiple deliveries"
4597 .cindex "multiple SMTP deliveries"
4598 the delivery process spawns other processes to deliver other messages down
4599 passed SMTP connections, the queue runner waits for these to finish before
4602 When all the queued messages have been considered, the original queue runner
4603 process terminates. In other words, a single pass is made over the waiting
4604 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4605 this to be repeated periodically.
4607 Exim processes the waiting messages in an unpredictable order. It isn't very
4608 random, but it is likely to be different each time, which is all that matters.
4609 If one particular message screws up a remote MTA, other messages to the same
4610 MTA have a chance of getting through if they get tried first.
4612 It is possible to cause the messages to be processed in lexical message id
4613 order, which is essentially the order in which they arrived, by setting the
4614 &%queue_run_in_order%& option, but this is not recommended for normal use.
4616 .vitem &%-q%&<&'qflags'&>
4617 The &%-q%& option may be followed by one or more flag letters that change its
4618 behaviour. They are all optional, but if more than one is present, they must
4619 appear in the correct order. Each flag is described in a separate item below.
4623 .cindex "queue" "double scanning"
4624 .cindex "queue" "routing"
4625 .cindex "routing" "whole queue before delivery"
4626 .cindex "first pass routing"
4627 .cindex "queue runner" "two phase"
4628 An option starting with &%-qq%& requests a two-stage queue run. In the first
4629 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4630 every domain. Addresses are routed, local deliveries happen, but no remote
4633 Performance will be best if the &%queue_run_in_order%& option is false.
4634 If that is so and the &%queue_fast_ramp%& option is true then
4635 in the first phase of the run,
4636 once a threshold number of messages are routed for a given host,
4637 a delivery process is forked in parallel with the rest of the scan.
4639 .cindex "hints database" "remembering routing"
4640 The hints database that remembers which messages are waiting for specific hosts
4641 is updated, as if delivery to those hosts had been deferred. After this is
4642 complete, a second, normal queue scan happens, with routing and delivery taking
4643 place as normal. Messages that are routed to the same host should mostly be
4644 delivered down a single SMTP
4645 .cindex "SMTP" "passed connection"
4646 .cindex "SMTP" "multiple deliveries"
4647 .cindex "multiple SMTP deliveries"
4648 connection because of the hints that were set up during the first queue scan.
4649 This option may be useful for hosts that are connected to the Internet
4652 .vitem &%-q[q]i...%&
4654 .cindex "queue" "initial delivery"
4655 If the &'i'& flag is present, the queue runner runs delivery processes only for
4656 those messages that haven't previously been tried. (&'i'& stands for &"initial
4657 delivery"&.) This can be helpful if you are putting messages in the queue using
4658 &%-odq%& and want a queue runner just to process the new messages.
4660 .vitem &%-q[q][i]f...%&
4662 .cindex "queue" "forcing delivery"
4663 .cindex "delivery" "forcing in queue run"
4664 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4665 message, whereas without &'f'& only those non-frozen addresses that have passed
4666 their retry times are tried.
4668 .vitem &%-q[q][i]ff...%&
4670 .cindex "frozen messages" "forcing delivery"
4671 If &'ff'& is present, a delivery attempt is forced for every message, whether
4674 .vitem &%-q[q][i][f[f]]l%&
4676 .cindex "queue" "local deliveries only"
4677 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4678 be done. If a message requires any remote deliveries, it remains in the queue
4681 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4684 .cindex "named queues" "deliver from"
4685 .cindex "queue" "delivering specific messages"
4686 If the &'G'& flag and a name is present, the queue runner operates on the
4687 queue with the given name rather than the default queue.
4688 The name should not contain a &'/'& character.
4689 For a periodic queue run (see below)
4690 append to the name a slash and a time value.
4692 If other commandline options specify an action, a &'-qG<name>'& option
4693 will specify a queue to operate on.
4696 exim -bp -qGquarantine
4698 exim -qGoffpeak -Rf @special.domain.example
4701 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4702 When scanning the queue, Exim can be made to skip over messages whose ids are
4703 lexically less than a given value by following the &%-q%& option with a
4704 starting message id. For example:
4706 exim -q 0t5C6f-0000c8-00
4708 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4709 second message id is given, messages whose ids are lexically greater than it
4710 are also skipped. If the same id is given twice, for example,
4712 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4714 just one delivery process is started, for that message. This differs from
4715 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4716 that it counts as a delivery from a queue run. Note that the selection
4717 mechanism does not affect the order in which the messages are scanned. There
4718 are also other ways of selecting specific sets of messages for delivery in a
4719 queue run &-- see &%-R%& and &%-S%&.
4721 .vitem &%-q%&<&'qflags'&><&'time'&>
4722 .cindex "queue runner" "starting periodically"
4723 .cindex "periodic queue running"
4724 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4725 starting a queue runner process at intervals specified by the given time value
4726 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4727 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4728 single daemon process handles both functions. A common way of starting up a
4729 combined daemon at system boot time is to use a command such as
4731 /usr/exim/bin/exim -bd -q30m
4733 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4734 process every 30 minutes.
4736 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4737 pid file is written unless one is explicitly requested by the &%-oP%& option.
4739 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4741 This option is synonymous with &%-R%&. It is provided for Sendmail
4744 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4746 This option is synonymous with &%-S%&.
4748 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4750 .cindex "queue runner" "for specific recipients"
4751 .cindex "delivery" "to given domain"
4752 .cindex "domain" "delivery to"
4753 The <&'rsflags'&> may be empty, in which case the white space before the string
4754 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4755 which are the possible values for <&'rsflags'&>. White space is required if
4756 <&'rsflags'&> is not empty.
4758 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4759 perform a single queue run, except that, when scanning the messages on the
4760 queue, Exim processes only those that have at least one undelivered recipient
4761 address containing the given string, which is checked in a case-independent
4762 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4763 regular expression; otherwise it is a literal string.
4765 If you want to do periodic queue runs for messages with specific recipients,
4766 you can combine &%-R%& with &%-q%& and a time value. For example:
4768 exim -q25m -R @special.domain.example
4770 This example does a queue run for messages with recipients in the given domain
4771 every 25 minutes. Any additional flags that are specified with &%-q%& are
4772 applied to each queue run.
4774 Once a message is selected for delivery by this mechanism, all its addresses
4775 are processed. For the first selected message, Exim overrides any retry
4776 information and forces a delivery attempt for each undelivered address. This
4777 means that if delivery of any address in the first message is successful, any
4778 existing retry information is deleted, and so delivery attempts for that
4779 address in subsequently selected messages (which are processed without forcing)
4780 will run. However, if delivery of any address does not succeed, the retry
4781 information is updated, and in subsequently selected messages, the failing
4782 address will be skipped.
4784 .cindex "frozen messages" "forcing delivery"
4785 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4786 all selected messages, not just the first; frozen messages are included when
4789 The &%-R%& option makes it straightforward to initiate delivery of all messages
4790 to a given domain after a host has been down for some time. When the SMTP
4791 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4792 effect is to run Exim with the &%-R%& option, but it can be configured to run
4793 an arbitrary command instead.
4797 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4799 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4801 .cindex "delivery" "from given sender"
4802 .cindex "queue runner" "for specific senders"
4803 This option acts like &%-R%& except that it checks the string against each
4804 message's sender instead of against the recipients. If &%-R%& is also set, both
4805 conditions must be met for a message to be selected. If either of the options
4806 has &'f'& or &'ff'& in its flags, the associated action is taken.
4808 .vitem &%-Tqt%&&~<&'times'&>
4810 This is an option that is exclusively for use by the Exim testing suite. It is not
4811 recognized when Exim is run normally. It allows for the setting up of explicit
4812 &"queue times"& so that various warning/retry features can be tested.
4816 .cindex "recipient" "extracting from header lines"
4820 When Exim is receiving a locally-generated, non-SMTP message on its standard
4821 input, the &%-t%& option causes the recipients of the message to be obtained
4822 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4823 from the command arguments. The addresses are extracted before any rewriting
4824 takes place and the &'Bcc:'& header line, if present, is then removed.
4826 .cindex "Sendmail compatibility" "&%-t%& option"
4827 If the command has any arguments, they specify addresses to which the message
4828 is &'not'& to be delivered. That is, the argument addresses are removed from
4829 the recipients list obtained from the headers. This is compatible with Smail 3
4830 and in accordance with the documented behaviour of several versions of
4831 Sendmail, as described in man pages on a number of operating systems (e.g.
4832 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4833 argument addresses to those obtained from the headers, and the O'Reilly
4834 Sendmail book documents it that way. Exim can be made to add argument addresses
4835 instead of subtracting them by setting the option
4836 &%extract_addresses_remove_arguments%& false.
4838 .cindex "&%Resent-%& header lines" "with &%-t%&"
4839 If there are any &%Resent-%& header lines in the message, Exim extracts
4840 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4841 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4842 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4843 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4845 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4846 message is resent several times). The RFC also specifies that they should be
4847 added at the front of the message, and separated by &'Received:'& lines. It is
4848 not at all clear how &%-t%& should operate in the present of multiple sets,
4849 nor indeed exactly what constitutes a &"set"&.
4850 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4851 are often added at the end of the header, and if a message is resent more than
4852 once, it is common for the original set of &%Resent-%& headers to be renamed as
4853 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4857 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4858 compatibility with Sendmail.
4860 .vitem &%-tls-on-connect%&
4861 .oindex "&%-tls-on-connect%&"
4862 .cindex "TLS" "use without STARTTLS"
4863 .cindex "TLS" "automatic start"
4864 This option is available when Exim is compiled with TLS support. It forces all
4865 incoming SMTP connections to behave as if the incoming port is listed in the
4866 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4867 &<<CHAPTLS>>& for further details.
4872 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4873 Sendmail uses this option for &"initial message submission"&, and its
4874 documentation states that in future releases, it may complain about
4875 syntactically invalid messages rather than fixing them when this flag is not
4876 set. Exim ignores this option.
4880 This option causes Exim to write information to the standard error stream,
4881 describing what it is doing. In particular, it shows the log lines for
4882 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4883 dialogue is shown. Some of the log lines shown may not actually be written to
4884 the log if the setting of &%log_selector%& discards them. Any relevant
4885 selectors are shown with each log line. If none are shown, the logging is
4890 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4891 National Language Support extended characters in the body of the mail item"&).
4892 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4895 .vitem &%-X%&&~<&'logfile'&>
4897 This option is interpreted by Sendmail to cause debug information to be sent
4898 to the named file. It is ignored by Exim.
4900 .vitem &%-z%&&~<&'log-line'&>
4902 This option writes its argument to Exim's logfile.
4903 Use is restricted to administrators; the intent is for operational notes.
4904 Quotes should be used to maintain a multi-word item as a single argument,
4912 . ////////////////////////////////////////////////////////////////////////////
4913 . Insert a stylized DocBook comment here, to identify the end of the command
4914 . line options. This is for the benefit of the Perl script that automatically
4915 . creates a man page for the options.
4916 . ////////////////////////////////////////////////////////////////////////////
4919 <!-- === End of command line options === -->
4926 . ////////////////////////////////////////////////////////////////////////////
4927 . ////////////////////////////////////////////////////////////////////////////
4930 .chapter "The Exim runtime configuration file" "CHAPconf" &&&
4931 "The runtime configuration file"
4933 .cindex "runtime configuration"
4934 .cindex "configuration file" "general description"
4935 .cindex "CONFIGURE_FILE"
4936 .cindex "configuration file" "errors in"
4937 .cindex "error" "in configuration file"
4938 .cindex "return code" "for bad configuration"
4939 Exim uses a single runtime configuration file that is read whenever an Exim
4940 binary is executed. Note that in normal operation, this happens frequently,
4941 because Exim is designed to operate in a distributed manner, without central
4944 If a syntax error is detected while reading the configuration file, Exim
4945 writes a message on the standard error, and exits with a non-zero return code.
4946 The message is also written to the panic log. &*Note*&: Only simple syntax
4947 errors can be detected at this time. The values of any expanded options are
4948 not checked until the expansion happens, even when the expansion does not
4949 actually alter the string.
4951 The name of the configuration file is compiled into the binary for security
4952 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4953 most configurations, this specifies a single file. However, it is permitted to
4954 give a colon-separated list of filenames, in which case Exim uses the first
4955 existing file in the list.
4958 .cindex "EXIM_GROUP"
4959 .cindex "CONFIGURE_OWNER"
4960 .cindex "CONFIGURE_GROUP"
4961 .cindex "configuration file" "ownership"
4962 .cindex "ownership" "configuration file"
4963 The runtime configuration file must be owned by root or by the user that is
4964 specified at compile time by the CONFIGURE_OWNER option (if set). The
4965 configuration file must not be world-writeable, or group-writeable unless its
4966 group is the root group or the one specified at compile time by the
4967 CONFIGURE_GROUP option.
4969 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4970 to root, anybody who is able to edit the runtime configuration file has an
4971 easy way to run commands as root. If you specify a user or group in the
4972 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4973 who are members of that group will trivially be able to obtain root privileges.
4975 Up to Exim version 4.72, the runtime configuration file was also permitted to
4976 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4977 since it offered a simple privilege escalation for any attacker who managed to
4978 compromise the Exim user account.
4980 A default configuration file, which will work correctly in simple situations,
4981 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4982 defines just one filename, the installation process copies the default
4983 configuration to a new file of that name if it did not previously exist. If
4984 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4985 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4990 .section "Using a different configuration file" "SECID40"
4991 .cindex "configuration file" "alternate"
4992 A one-off alternate configuration can be specified by the &%-C%& command line
4993 option, which may specify a single file or a list of files. However, when
4994 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4995 unless the argument for &%-C%& is identical to the built-in value from
4996 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4997 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4998 is useful mainly for checking the syntax of configuration files before
4999 installing them. No owner or group checks are done on a configuration file
5000 specified by &%-C%&, if root privilege has been dropped.
5002 Even the Exim user is not trusted to specify an arbitrary configuration file
5003 with the &%-C%& option to be used with root privileges, unless that file is
5004 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
5005 testing a configuration using &%-C%& right through message reception and
5006 delivery, even if the caller is root. The reception works, but by that time,
5007 Exim is running as the Exim user, so when it re-execs to regain privilege for
5008 the delivery, the use of &%-C%& causes privilege to be lost. However, root
5009 can test reception and delivery using two separate commands (one to put a
5010 message in the queue, using &%-odq%&, and another to do the delivery, using
5013 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
5014 prefix string with which any file named in a &%-C%& command line option must
5015 start. In addition, the filename must not contain the sequence &"&`/../`&"&.
5016 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any
5017 filename can be used with &%-C%&.
5019 One-off changes to a configuration can be specified by the &%-D%& command line
5020 option, which defines and overrides values for macros used inside the
5021 configuration file. However, like &%-C%&, the use of this option by a
5022 non-privileged user causes Exim to discard its root privilege.
5023 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
5024 completely disabled, and its use causes an immediate error exit.
5026 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
5027 to declare certain macro names trusted, such that root privilege will not
5028 necessarily be discarded.
5029 WHITELIST_D_MACROS defines a colon-separated list of macros which are
5030 considered safe and, if &%-D%& only supplies macros from this list, and the
5031 values are acceptable, then Exim will not give up root privilege if the caller
5032 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
5033 transition mechanism and is expected to be removed in the future. Acceptable
5034 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
5036 Some sites may wish to use the same Exim binary on different machines that
5037 share a file system, but to use different configuration files on each machine.
5038 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
5039 looks for a file whose name is the configuration filename followed by a dot
5040 and the machine's node name, as obtained from the &[uname()]& function. If this
5041 file does not exist, the standard name is tried. This processing occurs for
5042 each filename in the list given by CONFIGURE_FILE or &%-C%&.
5044 In some esoteric situations different versions of Exim may be run under
5045 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
5046 help with this. See the comments in &_src/EDITME_& for details.
5050 .section "Configuration file format" "SECTconffilfor"
5051 .cindex "configuration file" "format of"
5052 .cindex "format" "configuration file"
5053 Exim's configuration file is divided into a number of different parts. General
5054 option settings must always appear at the start of the file. The other parts
5055 are all optional, and may appear in any order. Each part other than the first
5056 is introduced by the word &"begin"& followed by at least one literal
5057 space, and the name of the part. The optional parts are:
5060 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
5063 .cindex "AUTH" "configuration"
5064 &'authenticators'&: Configuration settings for the authenticator drivers. These
5065 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
5067 &'routers'&: Configuration settings for the router drivers. Routers process
5068 addresses and determine how the message is to be delivered (see chapters
5069 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
5071 &'transports'&: Configuration settings for the transport drivers. Transports
5072 define mechanisms for copying messages to destinations (see chapters
5073 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
5075 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
5076 If there is no retry section, or if it is empty (that is, no retry rules are
5077 defined), Exim will not retry deliveries. In this situation, temporary errors
5078 are treated the same as permanent errors. Retry rules are discussed in chapter
5081 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
5082 when new addresses are generated during delivery. Rewriting is discussed in
5083 chapter &<<CHAPrewrite>>&.
5085 &'local_scan'&: Private options for the &[local_scan()]& function. If you
5086 want to use this feature, you must set
5088 LOCAL_SCAN_HAS_OPTIONS=yes
5090 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
5091 facility are given in chapter &<<CHAPlocalscan>>&.
5094 .cindex "configuration file" "leading white space in"
5095 .cindex "configuration file" "trailing white space in"
5096 .cindex "white space" "in configuration file"
5097 Leading and trailing white space in configuration lines is always ignored.
5099 Blank lines in the file, and lines starting with a # character (ignoring
5100 leading white space) are treated as comments and are ignored. &*Note*&: A
5101 # character other than at the beginning of a line is not treated specially,
5102 and does not introduce a comment.
5104 Any non-comment line can be continued by ending it with a backslash. Note that
5105 the general rule for white space means that trailing white space after the
5106 backslash and leading white space at the start of continuation
5107 lines is ignored. Comment lines beginning with # (but not empty lines) may
5108 appear in the middle of a sequence of continuation lines.
5110 A convenient way to create a configuration file is to start from the
5111 default, which is supplied in &_src/configure.default_&, and add, delete, or
5112 change settings as required.
5114 The ACLs, retry rules, and rewriting rules have their own syntax which is
5115 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
5116 respectively. The other parts of the configuration file have some syntactic
5117 items in common, and these are described below, from section &<<SECTcos>>&
5118 onwards. Before that, the inclusion, macro, and conditional facilities are
5123 .section "File inclusions in the configuration file" "SECID41"
5124 .cindex "inclusions in configuration file"
5125 .cindex "configuration file" "including other files"
5126 .cindex "&`.include`& in configuration file"
5127 .cindex "&`.include_if_exists`& in configuration file"
5128 You can include other files inside Exim's runtime configuration file by
5131 &`.include`& <&'filename'&>
5132 &`.include_if_exists`& <&'filename'&>
5134 on a line by itself. Double quotes round the filename are optional. If you use
5135 the first form, a configuration error occurs if the file does not exist; the
5136 second form does nothing for non-existent files.
5137 The first form allows a relative name. It is resolved relative to
5138 the directory of the including file. For the second form an absolute filename
5141 Includes may be nested to any depth, but remember that Exim reads its
5142 configuration file often, so it is a good idea to keep them to a minimum.
5143 If you change the contents of an included file, you must HUP the daemon,
5144 because an included file is read only when the configuration itself is read.
5146 The processing of inclusions happens early, at a physical line level, so, like
5147 comment lines, an inclusion can be used in the middle of an option setting,
5150 hosts_lookup = a.b.c \
5153 Include processing happens after macro processing (see below). Its effect is to
5154 process the lines of the included file as if they occurred inline where the
5159 .section "Macros in the configuration file" "SECTmacrodefs"
5160 .cindex "macro" "description of"
5161 .cindex "configuration file" "macros"
5162 If a line in the main part of the configuration (that is, before the first
5163 &"begin"& line) begins with an upper case letter, it is taken as a macro
5164 definition, and must be of the form
5166 <&'name'&> = <&'rest of line'&>
5168 The name must consist of letters, digits, and underscores, and need not all be
5169 in upper case, though that is recommended. The rest of the line, including any
5170 continuations, is the replacement text, and has leading and trailing white
5171 space removed. Quotes are not removed. The replacement text can never end with
5172 a backslash character, but this doesn't seem to be a serious limitation.
5174 Macros may also be defined between router, transport, authenticator, or ACL
5175 definitions. They may not, however, be defined within an individual driver or
5176 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
5178 .section "Macro substitution" "SECID42"
5179 Once a macro is defined, all subsequent lines in the file (and any included
5180 files) are scanned for the macro name; if there are several macros, the line is
5181 scanned for each, in turn, in the order in which the macros are defined. The
5182 replacement text is not re-scanned for the current macro, though it is scanned
5183 for subsequently defined macros. For this reason, a macro name may not contain
5184 the name of a previously defined macro as a substring. You could, for example,
5187 &`ABCD_XYZ = `&<&'something'&>
5188 &`ABCD = `&<&'something else'&>
5190 but putting the definitions in the opposite order would provoke a configuration
5191 error. Macro expansion is applied to individual physical lines from the file,
5192 before checking for line continuation or file inclusion (see above). If a line
5193 consists solely of a macro name, and the expansion of the macro is empty, the
5194 line is ignored. A macro at the start of a line may turn the line into a
5195 comment line or a &`.include`& line.
5198 .section "Redefining macros" "SECID43"
5199 Once defined, the value of a macro can be redefined later in the configuration
5200 (or in an included file). Redefinition is specified by using &'=='& instead of
5205 MAC == updated value
5207 Redefinition does not alter the order in which the macros are applied to the
5208 subsequent lines of the configuration file. It is still the same order in which
5209 the macros were originally defined. All that changes is the macro's value.
5210 Redefinition makes it possible to accumulate values. For example:
5214 MAC == MAC and something added
5216 This can be helpful in situations where the configuration file is built
5217 from a number of other files.
5219 .section "Overriding macro values" "SECID44"
5220 The values set for macros in the configuration file can be overridden by the
5221 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5222 used, unless called by root or the Exim user. A definition on the command line
5223 using the &%-D%& option causes all definitions and redefinitions within the
5228 .section "Example of macro usage" "SECID45"
5229 As an example of macro usage, consider a configuration where aliases are looked
5230 up in a MySQL database. It helps to keep the file less cluttered if long
5231 strings such as SQL statements are defined separately as macros, for example:
5233 ALIAS_QUERY = select mailbox from user where \
5234 login='${quote_mysql:$local_part}';
5236 This can then be used in a &(redirect)& router setting like this:
5238 data = ${lookup mysql{ALIAS_QUERY}}
5240 In earlier versions of Exim macros were sometimes used for domain, host, or
5241 address lists. In Exim 4 these are handled better by named lists &-- see
5242 section &<<SECTnamedlists>>&.
5245 .section "Builtin macros" "SECTbuiltinmacros"
5246 Exim defines some macros depending on facilities available, which may
5247 differ due to build-time definitions and from one release to another.
5248 All of these macros start with an underscore.
5249 They can be used to conditionally include parts of a configuration
5252 The following classes of macros are defined:
5254 &` _HAVE_* `& build-time defines
5255 &` _DRIVER_ROUTER_* `& router drivers
5256 &` _DRIVER_TRANSPORT_* `& transport drivers
5257 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5258 &` _LOG_* `& log_selector values
5259 &` _OPT_MAIN_* `& main config options
5260 &` _OPT_ROUTERS_* `& generic router options
5261 &` _OPT_TRANSPORTS_* `& generic transport options
5262 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5263 &` _OPT_ROUTER_*_* `& private router options
5264 &` _OPT_TRANSPORT_*_* `& private transport options
5265 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5268 Use an &"exim -bP macros"& command to get the list of macros.
5271 .section "Conditional skips in the configuration file" "SECID46"
5272 .cindex "configuration file" "conditional skips"
5273 .cindex "&`.ifdef`&"
5274 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5275 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5276 portions of the configuration file. The processing happens whenever the file is
5277 read (that is, when an Exim binary starts to run).
5279 The implementation is very simple. Instances of the first four directives must
5280 be followed by text that includes the names of one or macros. The condition
5281 that is tested is whether or not any macro substitution has taken place in the
5285 message_size_limit = 50M
5287 message_size_limit = 100M
5290 sets a message size limit of 50M if the macro &`AAA`& is defined
5291 (or &`A`& or &`AA`&), and 100M
5292 otherwise. If there is more than one macro named on the line, the condition
5293 is true if any of them are defined. That is, it is an &"or"& condition. To
5294 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5296 Although you can use a macro expansion to generate one of these directives,
5297 it is not very useful, because the condition &"there was a macro substitution
5298 in this line"& will always be true.
5300 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5301 to clarify complicated nestings.
5305 .section "Common option syntax" "SECTcos"
5306 .cindex "common option syntax"
5307 .cindex "syntax of common options"
5308 .cindex "configuration file" "common option syntax"
5309 For the main set of options, driver options, and &[local_scan()]& options,
5310 each setting is on a line by itself, and starts with a name consisting of
5311 lower-case letters and underscores. Many options require a data value, and in
5312 these cases the name must be followed by an equals sign (with optional white
5313 space) and then the value. For example:
5315 qualify_domain = mydomain.example.com
5317 .cindex "hiding configuration option values"
5318 .cindex "configuration options" "hiding value of"
5319 .cindex "options" "hiding value of"
5320 Some option settings may contain sensitive data, for example, passwords for
5321 accessing databases. To stop non-admin users from using the &%-bP%& command
5322 line option to read these values, you can precede the option settings with the
5323 word &"hide"&. For example:
5325 hide mysql_servers = localhost/users/admin/secret-password
5327 For non-admin users, such options are displayed like this:
5329 mysql_servers = <value not displayable>
5331 If &"hide"& is used on a driver option, it hides the value of that option on
5332 all instances of the same driver.
5334 The following sections describe the syntax used for the different data types
5335 that are found in option settings.
5338 .section "Boolean options" "SECID47"
5339 .cindex "format" "boolean"
5340 .cindex "boolean configuration values"
5341 .oindex "&%no_%&&'xxx'&"
5342 .oindex "&%not_%&&'xxx'&"
5343 Options whose type is given as boolean are on/off switches. There are two
5344 different ways of specifying such options: with and without a data value. If
5345 the option name is specified on its own without data, the switch is turned on;
5346 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5347 boolean options may be followed by an equals sign and one of the words
5348 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5349 the following two settings have exactly the same effect:
5354 The following two lines also have the same (opposite) effect:
5359 You can use whichever syntax you prefer.
5364 .section "Integer values" "SECID48"
5365 .cindex "integer configuration values"
5366 .cindex "format" "integer"
5367 If an option's type is given as &"integer"&, the value can be given in decimal,
5368 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5369 number is assumed. Otherwise, it is treated as an octal number unless it starts
5370 with the characters &"0x"&, in which case the remainder is interpreted as a
5373 If an integer value is followed by the letter K, it is multiplied by 1024; if
5374 it is followed by the letter M, it is multiplied by 1024x1024;
5375 if by the letter G, 1024x1024x1024.
5377 of integer option settings are output, values which are an exact multiple of
5378 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5379 and M. The printing style is independent of the actual input format that was
5383 .section "Octal integer values" "SECID49"
5384 .cindex "integer format"
5385 .cindex "format" "octal integer"
5386 If an option's type is given as &"octal integer"&, its value is always
5387 interpreted as an octal number, whether or not it starts with the digit zero.
5388 Such options are always output in octal.
5391 .section "Fixed point numbers" "SECID50"
5392 .cindex "fixed point configuration values"
5393 .cindex "format" "fixed point"
5394 If an option's type is given as &"fixed-point"&, its value must be a decimal
5395 integer, optionally followed by a decimal point and up to three further digits.
5399 .section "Time intervals" "SECTtimeformat"
5400 .cindex "time interval" "specifying in configuration"
5401 .cindex "format" "time interval"
5402 A time interval is specified as a sequence of numbers, each followed by one of
5403 the following letters, with no intervening white space:
5413 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5414 intervals are output in the same format. Exim does not restrict the values; it
5415 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5419 .section "String values" "SECTstrings"
5420 .cindex "string" "format of configuration values"
5421 .cindex "format" "string"
5422 If an option's type is specified as &"string"&, the value can be specified with
5423 or without double-quotes. If it does not start with a double-quote, the value
5424 consists of the remainder of the line plus any continuation lines, starting at
5425 the first character after any leading white space, with trailing white space
5426 removed, and with no interpretation of the characters in the string. Because
5427 Exim removes comment lines (those beginning with #) at an early stage, they can
5428 appear in the middle of a multi-line string. The following two settings are
5429 therefore equivalent:
5431 trusted_users = uucp:mail
5432 trusted_users = uucp:\
5433 # This comment line is ignored
5436 .cindex "string" "quoted"
5437 .cindex "escape characters in quoted strings"
5438 If a string does start with a double-quote, it must end with a closing
5439 double-quote, and any backslash characters other than those used for line
5440 continuation are interpreted as escape characters, as follows:
5443 .irow &`\\`& "single backslash"
5444 .irow &`\n`& "newline"
5445 .irow &`\r`& "carriage return"
5447 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5448 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5452 If a backslash is followed by some other character, including a double-quote
5453 character, that character replaces the pair.
5455 Quoting is necessary only if you want to make use of the backslash escapes to
5456 insert special characters, or if you need to specify a value with leading or
5457 trailing spaces. These cases are rare, so quoting is almost never needed in
5458 current versions of Exim. In versions of Exim before 3.14, quoting was required
5459 in order to continue lines, so you may come across older configuration files
5460 and examples that apparently quote unnecessarily.
5463 .section "Expanded strings" "SECID51"
5464 .cindex "expansion" "definition of"
5465 Some strings in the configuration file are subjected to &'string expansion'&,
5466 by which means various parts of the string may be changed according to the
5467 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5468 is as just described; in particular, the handling of backslashes in quoted
5469 strings is done as part of the input process, before expansion takes place.
5470 However, backslash is also an escape character for the expander, so any
5471 backslashes that are required for that reason must be doubled if they are
5472 within a quoted configuration string.
5475 .section "User and group names" "SECID52"
5476 .cindex "user name" "format of"
5477 .cindex "format" "user name"
5478 .cindex "groups" "name format"
5479 .cindex "format" "group name"
5480 User and group names are specified as strings, using the syntax described
5481 above, but the strings are interpreted specially. A user or group name must
5482 either consist entirely of digits, or be a name that can be looked up using the
5483 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5486 .section "List construction" "SECTlistconstruct"
5487 .cindex "list" "syntax of in configuration"
5488 .cindex "format" "list item in configuration"
5489 .cindex "string" "list, definition of"
5490 The data for some configuration options is a list of items, with colon as the
5491 default separator. Many of these options are shown with type &"string list"& in
5492 the descriptions later in this document. Others are listed as &"domain list"&,
5493 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5494 are all the same; however, those other than &"string list"& are subject to
5495 particular kinds of interpretation, as described in chapter
5496 &<<CHAPdomhosaddlists>>&.
5498 In all these cases, the entire list is treated as a single string as far as the
5499 input syntax is concerned. The &%trusted_users%& setting in section
5500 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5501 in a list, it must be entered as two colons. Leading and trailing white space
5502 on each item in a list is ignored. This makes it possible to include items that
5503 start with a colon, and in particular, certain forms of IPv6 address. For
5506 local_interfaces = 127.0.0.1 : ::::1
5508 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5510 &*Note*&: Although leading and trailing white space is ignored in individual
5511 list items, it is not ignored when parsing the list. The spaces around the first
5512 colon in the example above are necessary. If they were not there, the list would
5513 be interpreted as the two items 127.0.0.1:: and 1.
5515 .section "Changing list separators" "SECTlistsepchange"
5516 .cindex "list separator" "changing"
5517 .cindex "IPv6" "addresses in lists"
5518 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5519 introduced to allow the separator character to be changed. If a list begins
5520 with a left angle bracket, followed by any punctuation character, that
5521 character is used instead of colon as the list separator. For example, the list
5522 above can be rewritten to use a semicolon separator like this:
5524 local_interfaces = <; 127.0.0.1 ; ::1
5526 This facility applies to all lists, with the exception of the list in
5527 &%log_file_path%&. It is recommended that the use of non-colon separators be
5528 confined to circumstances where they really are needed.
5530 .cindex "list separator" "newline as"
5531 .cindex "newline" "as list separator"
5532 It is also possible to use newline and other control characters (those with
5533 code values less than 32, plus DEL) as separators in lists. Such separators
5534 must be provided literally at the time the list is processed. For options that
5535 are string-expanded, you can write the separator using a normal escape
5536 sequence. This will be processed by the expander before the string is
5537 interpreted as a list. For example, if a newline-separated list of domains is
5538 generated by a lookup, you can process it directly by a line such as this:
5540 domains = <\n ${lookup mysql{.....}}
5542 This avoids having to change the list separator in such data. You are unlikely
5543 to want to use a control character as a separator in an option that is not
5544 expanded, because the value is literal text. However, it can be done by giving
5545 the value in quotes. For example:
5547 local_interfaces = "<\n 127.0.0.1 \n ::1"
5549 Unlike printing character separators, which can be included in list items by
5550 doubling, it is not possible to include a control character as data when it is
5551 set as the separator. Two such characters in succession are interpreted as
5552 enclosing an empty list item.
5556 .section "Empty items in lists" "SECTempitelis"
5557 .cindex "list" "empty item in"
5558 An empty item at the end of a list is always ignored. In other words, trailing
5559 separator characters are ignored. Thus, the list in
5561 senders = user@domain :
5563 contains only a single item. If you want to include an empty string as one item
5564 in a list, it must not be the last item. For example, this list contains three
5565 items, the second of which is empty:
5567 senders = user1@domain : : user2@domain
5569 &*Note*&: There must be white space between the two colons, as otherwise they
5570 are interpreted as representing a single colon data character (and the list
5571 would then contain just one item). If you want to specify a list that contains
5572 just one, empty item, you can do it as in this example:
5576 In this case, the first item is empty, and the second is discarded because it
5577 is at the end of the list.
5582 .section "Format of driver configurations" "SECTfordricon"
5583 .cindex "drivers" "configuration format"
5584 There are separate parts in the configuration for defining routers, transports,
5585 and authenticators. In each part, you are defining a number of driver
5586 instances, each with its own set of options. Each driver instance is defined by
5587 a sequence of lines like this:
5589 <&'instance name'&>:
5594 In the following example, the instance name is &(localuser)&, and it is
5595 followed by three options settings:
5600 transport = local_delivery
5602 For each driver instance, you specify which Exim code module it uses &-- by the
5603 setting of the &%driver%& option &-- and (optionally) some configuration
5604 settings. For example, in the case of transports, if you want a transport to
5605 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5606 a local file you would use the &(appendfile)& driver. Each of the drivers is
5607 described in detail in its own separate chapter later in this manual.
5609 You can have several routers, transports, or authenticators that are based on
5610 the same underlying driver (each must have a different instance name).
5612 The order in which routers are defined is important, because addresses are
5613 passed to individual routers one by one, in order. The order in which
5614 transports are defined does not matter at all. The order in which
5615 authenticators are defined is used only when Exim, as a client, is searching
5616 them to find one that matches an authentication mechanism offered by the
5619 .cindex "generic options"
5620 .cindex "options" "generic &-- definition of"
5621 Within a driver instance definition, there are two kinds of option: &'generic'&
5622 and &'private'&. The generic options are those that apply to all drivers of the
5623 same type (that is, all routers, all transports or all authenticators). The
5624 &%driver%& option is a generic option that must appear in every definition.
5625 .cindex "private options"
5626 The private options are special for each driver, and none need appear, because
5627 they all have default values.
5629 The options may appear in any order, except that the &%driver%& option must
5630 precede any private options, since these depend on the particular driver. For
5631 this reason, it is recommended that &%driver%& always be the first option.
5633 Driver instance names, which are used for reference in log entries and
5634 elsewhere, can be any sequence of letters, digits, and underscores (starting
5635 with a letter) and must be unique among drivers of the same type. A router and
5636 a transport (for example) can each have the same name, but no two router
5637 instances can have the same name. The name of a driver instance should not be
5638 confused with the name of the underlying driver module. For example, the
5639 configuration lines:
5644 create an instance of the &(smtp)& transport driver whose name is
5645 &(remote_smtp)&. The same driver code can be used more than once, with
5646 different instance names and different option settings each time. A second
5647 instance of the &(smtp)& transport, with different options, might be defined
5653 command_timeout = 10s
5655 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5656 these transport instances from routers, and these names would appear in log
5659 Comment lines may be present in the middle of driver specifications. The full
5660 list of option settings for any particular driver instance, including all the
5661 defaulted values, can be extracted by making use of the &%-bP%& command line
5669 . ////////////////////////////////////////////////////////////////////////////
5670 . ////////////////////////////////////////////////////////////////////////////
5672 .chapter "The default configuration file" "CHAPdefconfil"
5673 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5674 .cindex "default" "configuration file &""walk through""&"
5675 The default configuration file supplied with Exim as &_src/configure.default_&
5676 is sufficient for a host with simple mail requirements. As an introduction to
5677 the way Exim is configured, this chapter &"walks through"& the default
5678 configuration, giving brief explanations of the settings. Detailed descriptions
5679 of the options are given in subsequent chapters. The default configuration file
5680 itself contains extensive comments about ways you might want to modify the
5681 initial settings. However, note that there are many options that are not
5682 mentioned at all in the default configuration.
5686 .section "Macros" "SECTdefconfmacros"
5687 All macros should be defined before any options.
5689 One macro is specified, but commented out, in the default configuration:
5691 # ROUTER_SMARTHOST=MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
5693 If all off-site mail is expected to be delivered to a "smarthost", then set the
5694 hostname here and uncomment the macro. This will affect which router is used
5695 later on. If this is left commented out, then Exim will perform direct-to-MX
5696 deliveries using a &(dnslookup)& router.
5698 In addition to macros defined here, Exim includes a number of built-in macros
5699 to enable configuration to be guarded by a binary built with support for a
5700 given feature. See section &<<SECTbuiltinmacros>>& for more details.
5703 .section "Main configuration settings" "SECTdefconfmain"
5704 The main (global) configuration option settings section must always come first
5705 in the file, after the macros.
5706 The first thing you'll see in the file, after some initial comments, is the line
5708 # primary_hostname =
5710 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5711 to know the official, fully qualified name of your host, and this is where you
5712 can specify it. However, in most cases you do not need to set this option. When
5713 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5715 The first three non-comment configuration lines are as follows:
5717 domainlist local_domains = @
5718 domainlist relay_to_domains =
5719 hostlist relay_from_hosts = 127.0.0.1
5721 These are not, in fact, option settings. They are definitions of two named
5722 domain lists and one named host list. Exim allows you to give names to lists of
5723 domains, hosts, and email addresses, in order to make it easier to manage the
5724 configuration file (see section &<<SECTnamedlists>>&).
5726 The first line defines a domain list called &'local_domains'&; this is used
5727 later in the configuration to identify domains that are to be delivered
5730 .cindex "@ in a domain list"
5731 There is just one item in this list, the string &"@"&. This is a special form
5732 of entry which means &"the name of the local host"&. Thus, if the local host is
5733 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5734 be delivered locally. Because the local host's name is referenced indirectly,
5735 the same configuration file can be used on different hosts.
5737 The second line defines a domain list called &'relay_to_domains'&, but the
5738 list itself is empty. Later in the configuration we will come to the part that
5739 controls mail relaying through the local host; it allows relaying to any
5740 domains in this list. By default, therefore, no relaying on the basis of a mail
5741 domain is permitted.
5743 The third line defines a host list called &'relay_from_hosts'&. This list is
5744 used later in the configuration to permit relaying from any host or IP address
5745 that matches the list. The default contains just the IP address of the IPv4
5746 loopback interface, which means that processes on the local host are able to
5747 submit mail for relaying by sending it over TCP/IP to that interface. No other
5748 hosts are permitted to submit messages for relaying.
5750 Just to be sure there's no misunderstanding: at this point in the configuration
5751 we aren't actually setting up any controls. We are just defining some domains
5752 and hosts that will be used in the controls that are specified later.
5754 The next two configuration lines are genuine option settings:
5756 acl_smtp_rcpt = acl_check_rcpt
5757 acl_smtp_data = acl_check_data
5759 These options specify &'Access Control Lists'& (ACLs) that are to be used
5760 during an incoming SMTP session for every recipient of a message (every RCPT
5761 command), and after the contents of the message have been received,
5762 respectively. The names of the lists are &'acl_check_rcpt'& and
5763 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5764 section of the configuration. The RCPT ACL controls which recipients are
5765 accepted for an incoming message &-- if a configuration does not provide an ACL
5766 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5767 contents of a message to be checked.
5769 Two commented-out option settings are next:
5771 # av_scanner = clamd:/tmp/clamd
5772 # spamd_address = 127.0.0.1 783
5774 These are example settings that can be used when Exim is compiled with the
5775 content-scanning extension. The first specifies the interface to the virus
5776 scanner, and the second specifies the interface to SpamAssassin. Further
5777 details are given in chapter &<<CHAPexiscan>>&.
5779 Three more commented-out option settings follow:
5781 # tls_advertise_hosts = *
5782 # tls_certificate = /etc/ssl/exim.crt
5783 # tls_privatekey = /etc/ssl/exim.pem
5785 These are example settings that can be used when Exim is compiled with
5786 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5787 first one specifies the list of clients that are allowed to use TLS when
5788 connecting to this server; in this case, the wildcard means all clients. The
5789 other options specify where Exim should find its TLS certificate and private
5790 key, which together prove the server's identity to any clients that connect.
5791 More details are given in chapter &<<CHAPTLS>>&.
5793 Another two commented-out option settings follow:
5795 # daemon_smtp_ports = 25 : 465 : 587
5796 # tls_on_connect_ports = 465
5798 .cindex "port" "465 and 587"
5799 .cindex "port" "for message submission"
5800 .cindex "message" "submission, ports for"
5801 .cindex "submissions protocol"
5802 .cindex "smtps protocol"
5803 .cindex "ssmtp protocol"
5804 .cindex "SMTP" "submissions protocol"
5805 .cindex "SMTP" "ssmtp protocol"
5806 .cindex "SMTP" "smtps protocol"
5807 These options provide better support for roaming users who wish to use this
5808 server for message submission. They are not much use unless you have turned on
5809 TLS (as described in the previous paragraph) and authentication (about which
5810 more in section &<<SECTdefconfauth>>&).
5811 Mail submission from mail clients (MUAs) should be separate from inbound mail
5812 to your domain (MX delivery) for various good reasons (eg, ability to impose
5813 much saner TLS protocol and ciphersuite requirements without unintended
5815 RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
5816 which uses STARTTLS, so this is the &"submission"& port.
5817 RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
5818 which should be used in preference to 587.
5819 You should also consider deploying SRV records to help clients find
5821 Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
5823 Two more commented-out options settings follow:
5826 # qualify_recipient =
5828 The first of these specifies a domain that Exim uses when it constructs a
5829 complete email address from a local login name. This is often needed when Exim
5830 receives a message from a local process. If you do not set &%qualify_domain%&,
5831 the value of &%primary_hostname%& is used. If you set both of these options,
5832 you can have different qualification domains for sender and recipient
5833 addresses. If you set only the first one, its value is used in both cases.
5835 .cindex "domain literal" "recognizing format"
5836 The following line must be uncommented if you want Exim to recognize
5837 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5838 (an IP address within square brackets) instead of a named domain.
5840 # allow_domain_literals
5842 The RFCs still require this form, but many people think that in the modern
5843 Internet it makes little sense to permit mail to be sent to specific hosts by
5844 quoting their IP addresses. This ancient format has been used by people who
5845 try to abuse hosts by using them for unwanted relaying. However, some
5846 people believe there are circumstances (for example, messages addressed to
5847 &'postmaster'&) where domain literals are still useful.
5849 The next configuration line is a kind of trigger guard:
5853 It specifies that no delivery must ever be run as the root user. The normal
5854 convention is to set up &'root'& as an alias for the system administrator. This
5855 setting is a guard against slips in the configuration.
5856 The list of users specified by &%never_users%& is not, however, the complete
5857 list; the build-time configuration in &_Local/Makefile_& has an option called
5858 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5859 contents of &%never_users%& are added to this list. By default
5860 FIXED_NEVER_USERS also specifies root.
5862 When a remote host connects to Exim in order to send mail, the only information
5863 Exim has about the host's identity is its IP address. The next configuration
5868 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5869 in order to get a host name. This improves the quality of the logging
5870 information, but if you feel it is too expensive, you can remove it entirely,
5871 or restrict the lookup to hosts on &"nearby"& networks.
5872 Note that it is not always possible to find a host name from an IP address,
5873 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5876 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5877 1413 (hence their names):
5880 rfc1413_query_timeout = 0s
5882 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5883 Few hosts offer RFC1413 service these days; calls have to be
5884 terminated by a timeout and this needlessly delays the startup
5885 of an incoming SMTP connection.
5886 If you have hosts for which you trust RFC1413 and need this
5887 information, you can change this.
5889 This line enables an efficiency SMTP option. It is negotiated by clients
5890 and not expected to cause problems but can be disabled if needed.
5895 When Exim receives messages over SMTP connections, it expects all addresses to
5896 be fully qualified with a domain, as required by the SMTP definition. However,
5897 if you are running a server to which simple clients submit messages, you may
5898 find that they send unqualified addresses. The two commented-out options:
5900 # sender_unqualified_hosts =
5901 # recipient_unqualified_hosts =
5903 show how you can specify hosts that are permitted to send unqualified sender
5904 and recipient addresses, respectively.
5906 The &%log_selector%& option is used to increase the detail of logging
5909 log_selector = +smtp_protocol_error +smtp_syntax_error \
5910 +tls_certificate_verified
5913 The &%percent_hack_domains%& option is also commented out:
5915 # percent_hack_domains =
5917 It provides a list of domains for which the &"percent hack"& is to operate.
5918 This is an almost obsolete form of explicit email routing. If you do not know
5919 anything about it, you can safely ignore this topic.
5921 The next two settings in the main part of the default configuration are
5922 concerned with messages that have been &"frozen"& on Exim's queue. When a
5923 message is frozen, Exim no longer continues to try to deliver it. Freezing
5924 occurs when a bounce message encounters a permanent failure because the sender
5925 address of the original message that caused the bounce is invalid, so the
5926 bounce cannot be delivered. This is probably the most common case, but there
5927 are also other conditions that cause freezing, and frozen messages are not
5928 always bounce messages.
5930 ignore_bounce_errors_after = 2d
5931 timeout_frozen_after = 7d
5933 The first of these options specifies that failing bounce messages are to be
5934 discarded after 2 days in the queue. The second specifies that any frozen
5935 message (whether a bounce message or not) is to be timed out (and discarded)
5936 after a week. In this configuration, the first setting ensures that no failing
5937 bounce message ever lasts a week.
5939 Exim queues it's messages in a spool directory. If you expect to have
5940 large queues, you may consider using this option. It splits the spool
5941 directory into subdirectories to avoid file system degradation from
5942 many files in a single directory, resulting in better performance.
5943 Manual manipulation of queued messages becomes more complex (though fortunately
5946 # split_spool_directory = true
5949 In an ideal world everybody follows the standards. For non-ASCII
5950 messages RFC 2047 is a standard, allowing a maximum line length of 76
5951 characters. Exim adheres that standard and won't process messages which
5952 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5953 In particular, the Exim maintainers have had multiple reports of
5954 problems from Russian administrators of issues until they disable this
5955 check, because of some popular, yet buggy, mail composition software.
5957 # check_rfc2047_length = false
5960 If you need to be strictly RFC compliant you may wish to disable the
5961 8BITMIME advertisement. Use this, if you exchange mails with systems
5962 that are not 8-bit clean.
5964 # accept_8bitmime = false
5967 Libraries you use may depend on specific environment settings. This
5968 imposes a security risk (e.g. PATH). There are two lists:
5969 &%keep_environment%& for the variables to import as they are, and
5970 &%add_environment%& for variables we want to set to a fixed value.
5971 Note that TZ is handled separately, by the $%timezone%$ runtime
5972 option and by the TIMEZONE_DEFAULT buildtime option.
5974 # keep_environment = ^LDAP
5975 # add_environment = PATH=/usr/bin::/bin
5979 .section "ACL configuration" "SECID54"
5980 .cindex "default" "ACLs"
5981 .cindex "&ACL;" "default configuration"
5982 In the default configuration, the ACL section follows the main configuration.
5983 It starts with the line
5987 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5988 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5989 and &%acl_smtp_data%& above.
5991 .cindex "RCPT" "ACL for"
5992 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5993 RCPT command specifies one of the message's recipients. The ACL statements
5994 are considered in order, until the recipient address is either accepted or
5995 rejected. The RCPT command is then accepted or rejected, according to the
5996 result of the ACL processing.
6000 This line, consisting of a name terminated by a colon, marks the start of the
6005 This ACL statement accepts the recipient if the sending host matches the list.
6006 But what does that strange list mean? It doesn't actually contain any host
6007 names or IP addresses. The presence of the colon puts an empty item in the
6008 list; Exim matches this only if the incoming message did not come from a remote
6009 host, because in that case, the remote hostname is empty. The colon is
6010 important. Without it, the list itself is empty, and can never match anything.
6012 What this statement is doing is to accept unconditionally all recipients in
6013 messages that are submitted by SMTP from local processes using the standard
6014 input and output (that is, not using TCP/IP). A number of MUAs operate in this
6017 deny domains = +local_domains
6018 local_parts = ^[.] : ^.*[@%!/|]
6019 message = Restricted characters in address
6021 deny domains = !+local_domains
6022 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
6023 message = Restricted characters in address
6025 These statements are concerned with local parts that contain any of the
6026 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
6027 Although these characters are entirely legal in local parts (in the case of
6028 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
6029 in Internet mail addresses.
6031 The first three have in the past been associated with explicitly routed
6032 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
6033 option). Addresses containing these characters are regularly tried by spammers
6034 in an attempt to bypass relaying restrictions, and also by open relay testing
6035 programs. Unless you really need them it is safest to reject these characters
6036 at this early stage. This configuration is heavy-handed in rejecting these
6037 characters for all messages it accepts from remote hosts. This is a deliberate
6038 policy of being as safe as possible.
6040 The first rule above is stricter, and is applied to messages that are addressed
6041 to one of the local domains handled by this host. This is implemented by the
6042 first condition, which restricts it to domains that are listed in the
6043 &'local_domains'& domain list. The &"+"& character is used to indicate a
6044 reference to a named list. In this configuration, there is just one domain in
6045 &'local_domains'&, but in general there may be many.
6047 The second condition on the first statement uses two regular expressions to
6048 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
6049 or &"|"&. If you have local accounts that include these characters, you will
6050 have to modify this rule.
6052 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
6053 allows them because they have been encountered in practice. (Consider the
6054 common convention of local parts constructed as
6055 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
6056 the author of Exim, who has no second initial.) However, a local part starting
6057 with a dot or containing &"/../"& can cause trouble if it is used as part of a
6058 filename (for example, for a mailing list). This is also true for local parts
6059 that contain slashes. A pipe symbol can also be troublesome if the local part
6060 is incorporated unthinkingly into a shell command line.
6062 The second rule above applies to all other domains, and is less strict. This
6063 allows your own users to send outgoing messages to sites that use slashes
6064 and vertical bars in their local parts. It blocks local parts that begin
6065 with a dot, slash, or vertical bar, but allows these characters within the
6066 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
6067 and &"!"& is blocked, as before. The motivation here is to prevent your users
6068 (or your users' viruses) from mounting certain kinds of attack on remote sites.
6070 accept local_parts = postmaster
6071 domains = +local_domains
6073 This statement, which has two conditions, accepts an incoming address if the
6074 local part is &'postmaster'& and the domain is one of those listed in the
6075 &'local_domains'& domain list. The &"+"& character is used to indicate a
6076 reference to a named list. In this configuration, there is just one domain in
6077 &'local_domains'&, but in general there may be many.
6079 The presence of this statement means that mail to postmaster is never blocked
6080 by any of the subsequent tests. This can be helpful while sorting out problems
6081 in cases where the subsequent tests are incorrectly denying access.
6083 require verify = sender
6085 This statement requires the sender address to be verified before any subsequent
6086 ACL statement can be used. If verification fails, the incoming recipient
6087 address is refused. Verification consists of trying to route the address, to
6088 see if a bounce message could be delivered to it. In the case of remote
6089 addresses, basic verification checks only the domain, but &'callouts'& can be
6090 used for more verification if required. Section &<<SECTaddressverification>>&
6091 discusses the details of address verification.
6093 accept hosts = +relay_from_hosts
6094 control = submission
6096 This statement accepts the address if the message is coming from one of the
6097 hosts that are defined as being allowed to relay through this host. Recipient
6098 verification is omitted here, because in many cases the clients are dumb MUAs
6099 that do not cope well with SMTP error responses. For the same reason, the
6100 second line specifies &"submission mode"& for messages that are accepted. This
6101 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
6102 messages that are deficient in some way, for example, because they lack a
6103 &'Date:'& header line. If you are actually relaying out from MTAs, you should
6104 probably add recipient verification here, and disable submission mode.
6106 accept authenticated = *
6107 control = submission
6109 This statement accepts the address if the client host has authenticated itself.
6110 Submission mode is again specified, on the grounds that such messages are most
6111 likely to come from MUAs. The default configuration does not define any
6112 authenticators, though it does include some nearly complete commented-out
6113 examples described in &<<SECTdefconfauth>>&. This means that no client can in
6114 fact authenticate until you complete the authenticator definitions.
6116 require message = relay not permitted
6117 domains = +local_domains : +relay_to_domains
6119 This statement rejects the address if its domain is neither a local domain nor
6120 one of the domains for which this host is a relay.
6122 require verify = recipient
6124 This statement requires the recipient address to be verified; if verification
6125 fails, the address is rejected.
6127 # deny dnslists = black.list.example
6128 # message = rejected because $sender_host_address \
6129 # is in a black list at $dnslist_domain\n\
6132 # warn dnslists = black.list.example
6133 # add_header = X-Warning: $sender_host_address is in \
6134 # a black list at $dnslist_domain
6135 # log_message = found in $dnslist_domain
6137 These commented-out lines are examples of how you could configure Exim to check
6138 sending hosts against a DNS black list. The first statement rejects messages
6139 from blacklisted hosts, whereas the second just inserts a warning header
6142 # require verify = csa
6144 This commented-out line is an example of how you could turn on client SMTP
6145 authorization (CSA) checking. Such checks do DNS lookups for special SRV
6150 The final statement in the first ACL unconditionally accepts any recipient
6151 address that has successfully passed all the previous tests.
6155 This line marks the start of the second ACL, and names it. Most of the contents
6156 of this ACL are commented out:
6159 # message = This message contains a virus \
6162 These lines are examples of how to arrange for messages to be scanned for
6163 viruses when Exim has been compiled with the content-scanning extension, and a
6164 suitable virus scanner is installed. If the message is found to contain a
6165 virus, it is rejected with the given custom error message.
6167 # warn spam = nobody
6168 # message = X-Spam_score: $spam_score\n\
6169 # X-Spam_score_int: $spam_score_int\n\
6170 # X-Spam_bar: $spam_bar\n\
6171 # X-Spam_report: $spam_report
6173 These lines are an example of how to arrange for messages to be scanned by
6174 SpamAssassin when Exim has been compiled with the content-scanning extension,
6175 and SpamAssassin has been installed. The SpamAssassin check is run with
6176 &`nobody`& as its user parameter, and the results are added to the message as a
6177 series of extra header line. In this case, the message is not rejected,
6178 whatever the spam score.
6182 This final line in the DATA ACL accepts the message unconditionally.
6185 .section "Router configuration" "SECID55"
6186 .cindex "default" "routers"
6187 .cindex "routers" "default"
6188 The router configuration comes next in the default configuration, introduced
6193 Routers are the modules in Exim that make decisions about where to send
6194 messages. An address is passed to each router, in turn, until it is either
6195 accepted, or failed. This means that the order in which you define the routers
6196 matters. Each router is fully described in its own chapter later in this
6197 manual. Here we give only brief overviews.
6200 # driver = ipliteral
6201 # domains = !+local_domains
6202 # transport = remote_smtp
6204 .cindex "domain literal" "default router"
6205 This router is commented out because the majority of sites do not want to
6206 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
6207 you uncomment this router, you also need to uncomment the setting of
6208 &%allow_domain_literals%& in the main part of the configuration.
6210 Which router is used next depends upon whether or not the ROUTER_SMARTHOST
6211 macro has been defined, per
6213 .ifdef ROUTER_SMARTHOST
6222 If ROUTER_SMARTHOST has been defined, either at the top of the file or on the
6223 command-line, then we route all non-local mail to that smarthost; otherwise, we'll
6224 perform DNS lookups for direct-to-MX lookup. Any mail which is to a local domain will
6225 skip these routers because of the &%domains%& option.
6229 driver = manualroute
6230 domains = ! +local_domains
6231 transport = smarthost_smtp
6232 route_data = ROUTER_SMARTHOST
6233 ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
6236 This router only handles mail which is not to any local domains; this is
6237 specified by the line
6239 domains = ! +local_domains
6241 The &%domains%& option lists the domains to which this router applies, but the
6242 exclamation mark is a negation sign, so the router is used only for domains
6243 that are not in the domain list called &'local_domains'& (which was defined at
6244 the start of the configuration). The plus sign before &'local_domains'&
6245 indicates that it is referring to a named list. Addresses in other domains are
6246 passed on to the following routers.
6248 The name of the router driver is &(manualroute)& because we are manually
6249 specifying how mail should be routed onwards, instead of using DNS MX.
6250 While the name of this router instance is arbitrary, the &%driver%& option must
6251 be one of the driver modules that is in the Exim binary.
6253 With no pre-conditions other than &%domains%&, all mail for non-local domains
6254 will be handled by this router, and the &%no_more%& setting will ensure that no
6255 other routers will be used for messages matching the pre-conditions. See
6256 &<<SECTrouprecon>>& for more on how the pre-conditions apply. For messages which
6257 are handled by this router, we provide a hostname to deliver to in &%route_data%&
6258 and the macro supplies the value; the address is then queued for the
6259 &(smarthost_smtp)& transport.
6264 domains = ! +local_domains
6265 transport = remote_smtp
6266 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
6269 The &%domains%& option behaves as per smarthost, above.
6271 The name of the router driver is &(dnslookup)&,
6272 and is specified by the &%driver%& option. Do not be confused by the fact that
6273 the name of this router instance is the same as the name of the driver. The
6274 instance name is arbitrary, but the name set in the &%driver%& option must be
6275 one of the driver modules that is in the Exim binary.
6277 The &(dnslookup)& router routes addresses by looking up their domains in the
6278 DNS in order to obtain a list of hosts to which the address is routed. If the
6279 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6280 specified by the &%transport%& option. If the router does not find the domain
6281 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6282 the address fails and is bounced.
6284 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6285 be entirely ignored. This option is present because a number of cases have been
6286 encountered where MX records in the DNS point to host names
6287 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6288 Completely ignoring these IP addresses causes Exim to fail to route the
6289 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6290 continue to try to deliver the message periodically until the address timed
6297 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6299 file_transport = address_file
6300 pipe_transport = address_pipe
6302 Control reaches this and subsequent routers only for addresses in the local
6303 domains. This router checks to see whether the local part is defined as an
6304 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6305 data that it looks up from that file. If no data is found for the local part,
6306 the value of the &%data%& option is empty, causing the address to be passed to
6309 &_/etc/aliases_& is a conventional name for the system aliases file that is
6310 often used. That is why it is referenced by from the default configuration
6311 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6312 &_Local/Makefile_& before building Exim.
6317 # local_part_suffix = +* : -*
6318 # local_part_suffix_optional
6319 file = $home/.forward
6324 file_transport = address_file
6325 pipe_transport = address_pipe
6326 reply_transport = address_reply
6328 This is the most complicated router in the default configuration. It is another
6329 redirection router, but this time it is looking for forwarding data set up by
6330 individual users. The &%check_local_user%& setting specifies a check that the
6331 local part of the address is the login name of a local user. If it is not, the
6332 router is skipped. The two commented options that follow &%check_local_user%&,
6335 # local_part_suffix = +* : -*
6336 # local_part_suffix_optional
6338 .vindex "&$local_part_suffix$&"
6339 show how you can specify the recognition of local part suffixes. If the first
6340 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6341 by any sequence of characters, is removed from the local part and placed in the
6342 variable &$local_part_suffix$&. The second suffix option specifies that the
6343 presence of a suffix in the local part is optional. When a suffix is present,
6344 the check for a local login uses the local part with the suffix removed.
6346 When a local user account is found, the file called &_.forward_& in the user's
6347 home directory is consulted. If it does not exist, or is empty, the router
6348 declines. Otherwise, the contents of &_.forward_& are interpreted as
6349 redirection data (see chapter &<<CHAPredirect>>& for more details).
6351 .cindex "Sieve filter" "enabling in default router"
6352 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6353 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6354 is commented out by default), the contents of the file are interpreted as a set
6355 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6356 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6357 separate document entitled &'Exim's interfaces to mail filtering'&.
6359 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6360 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6361 There are two reasons for doing this:
6364 Whether or not a local user has a &_.forward_& file is not really relevant when
6365 checking an address for validity; it makes sense not to waste resources doing
6368 More importantly, when Exim is verifying addresses or handling an EXPN
6369 command during an SMTP session, it is running as the Exim user, not as root.
6370 The group is the Exim group, and no additional groups are set up.
6371 It may therefore not be possible for Exim to read users' &_.forward_& files at
6375 The setting of &%check_ancestor%& prevents the router from generating a new
6376 address that is the same as any previous address that was redirected. (This
6377 works round a problem concerning a bad interaction between aliasing and
6378 forwarding &-- see section &<<SECTredlocmai>>&).
6380 The final three option settings specify the transports that are to be used when
6381 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6382 auto-reply, respectively. For example, if a &_.forward_& file contains
6384 a.nother@elsewhere.example, /home/spqr/archive
6386 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6392 # local_part_suffix = +* : -*
6393 # local_part_suffix_optional
6394 transport = local_delivery
6396 The final router sets up delivery into local mailboxes, provided that the local
6397 part is the name of a local login, by accepting the address and assigning it to
6398 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6399 routers, so the address is bounced. The commented suffix settings fulfil the
6400 same purpose as they do for the &(userforward)& router.
6403 .section "Transport configuration" "SECID56"
6404 .cindex "default" "transports"
6405 .cindex "transports" "default"
6406 Transports define mechanisms for actually delivering messages. They operate
6407 only when referenced from routers, so the order in which they are defined does
6408 not matter. The transports section of the configuration starts with
6412 Two remote transports and four local transports are defined.
6416 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6421 This transport is used for delivering messages over SMTP connections.
6422 The list of remote hosts comes from the router.
6423 The &%message_size_limit%& usage is a hack to avoid sending on messages
6424 with over-long lines.
6426 The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
6427 negotiated between client and server and not expected to cause problems
6428 but can be disabled if needed. The built-in macro _HAVE_PRDR guards the
6429 use of the &%hosts_try_prdr%& configuration option.
6431 The other remote transport is used when delivering to a specific smarthost
6432 with whom there must be some kind of existing relationship, instead of the
6433 usual federated system.
6438 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6442 # Comment out any of these which you have to, then file a Support
6443 # request with your smarthost provider to get things fixed:
6444 hosts_require_tls = *
6445 tls_verify_hosts = *
6446 # As long as tls_verify_hosts is enabled, this this will have no effect,
6447 # but if you have to comment it out then this will at least log whether
6448 # you succeed or not:
6449 tls_try_verify_hosts = *
6451 # The SNI name should match the name which we'll expect to verify;
6452 # many mail systems don't use SNI and this doesn't matter, but if it does,
6453 # we need to send a name which the remote site will recognize.
6454 # This _should_ be the name which the smarthost operators specified as
6455 # the hostname for sending your mail to.
6456 tls_sni = ROUTER_SMARTHOST
6458 .ifdef _HAVE_OPENSSL
6459 tls_require_ciphers = HIGH:!aNULL:@STRENGTH
6462 tls_require_ciphers = SECURE192:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1
6469 After the same &%message_size_limit%& hack, we then specify that this Transport
6470 can handle messages to multiple domains in one run. The assumption here is
6471 that you're routing all non-local mail to the same place and that place is
6472 happy to take all messages from you as quickly as possible.
6473 All other options depend upon built-in macros; if Exim was built without TLS support
6474 then no other options are defined.
6475 If TLS is available, then we configure "stronger than default" TLS ciphersuites
6476 and versions using the &%tls_require_ciphers%& option, where the value to be
6477 used depends upon the library providing TLS.
6478 Beyond that, the options adopt the stance that you should have TLS support available
6479 from your smarthost on today's Internet, so we turn on requiring TLS for the
6480 mail to be delivered, and requiring that the certificate be valid, and match
6481 the expected hostname. The &%tls_sni%& option can be used by service providers
6482 to select an appropriate certificate to present to you and here we re-use the
6483 ROUTER_SMARTHOST macro, because that is unaffected by CNAMEs present in DNS.
6484 You want to specify the hostname which you'll expect to validate for, and that
6485 should not be subject to insecure tampering via DNS results.
6487 For the &%hosts_try_prdr%& option see the previous transport.
6489 All other options are defaulted.
6493 file = /var/mail/$local_part_data
6500 This &(appendfile)& transport is used for local delivery to user mailboxes in
6501 traditional BSD mailbox format.
6503 We prefer to avoid using &$local_part$& directly to define the mailbox filename,
6504 as it is provided by a potential bad actor.
6505 Instead we use &$local_part_data$&,
6506 the result of looking up &$local_part$& in the user database
6507 (done by using &%check_local_user%& in the the router).
6509 By default &(appendfile)& runs under the uid and gid of the
6510 local user, which requires the sticky bit to be set on the &_/var/mail_&
6511 directory. Some systems use the alternative approach of running mail deliveries
6512 under a particular group instead of using the sticky bit. The commented options
6513 show how this can be done.
6515 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6516 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6517 similarly-named options above.
6523 This transport is used for handling deliveries to pipes that are generated by
6524 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6525 option specifies that any output on stdout or stderr generated by the pipe is to
6526 be returned to the sender.
6534 This transport is used for handling deliveries to files that are generated by
6535 redirection. The name of the file is not specified in this instance of
6536 &(appendfile)&, because it comes from the &(redirect)& router.
6541 This transport is used for handling automatic replies generated by users'
6546 .section "Default retry rule" "SECID57"
6547 .cindex "retry" "default rule"
6548 .cindex "default" "retry rule"
6549 The retry section of the configuration file contains rules which affect the way
6550 Exim retries deliveries that cannot be completed at the first attempt. It is
6551 introduced by the line
6555 In the default configuration, there is just one rule, which applies to all
6558 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6560 This causes any temporarily failing address to be retried every 15 minutes for
6561 2 hours, then at intervals starting at one hour and increasing by a factor of
6562 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6563 is not delivered after 4 days of temporary failure, it is bounced. The time is
6564 measured from first failure, not from the time the message was received.
6566 If the retry section is removed from the configuration, or is empty (that is,
6567 if no retry rules are defined), Exim will not retry deliveries. This turns
6568 temporary errors into permanent errors.
6571 .section "Rewriting configuration" "SECID58"
6572 The rewriting section of the configuration, introduced by
6576 contains rules for rewriting addresses in messages as they arrive. There are no
6577 rewriting rules in the default configuration file.
6581 .section "Authenticators configuration" "SECTdefconfauth"
6582 .cindex "AUTH" "configuration"
6583 The authenticators section of the configuration, introduced by
6585 begin authenticators
6587 defines mechanisms for the use of the SMTP AUTH command. The default
6588 configuration file contains two commented-out example authenticators
6589 which support plaintext username/password authentication using the
6590 standard PLAIN mechanism and the traditional but non-standard LOGIN
6591 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6592 to support most MUA software.
6594 The example PLAIN authenticator looks like this:
6597 # driver = plaintext
6598 # server_set_id = $auth2
6599 # server_prompts = :
6600 # server_condition = Authentication is not yet configured
6601 # server_advertise_condition = ${if def:tls_in_cipher }
6603 And the example LOGIN authenticator looks like this:
6606 # driver = plaintext
6607 # server_set_id = $auth1
6608 # server_prompts = <| Username: | Password:
6609 # server_condition = Authentication is not yet configured
6610 # server_advertise_condition = ${if def:tls_in_cipher }
6613 The &%server_set_id%& option makes Exim remember the authenticated username
6614 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6615 &%server_prompts%& option configures the &(plaintext)& authenticator so
6616 that it implements the details of the specific authentication mechanism,
6617 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6618 when Exim offers authentication to clients; in the examples, this is only
6619 when TLS or SSL has been started, so to enable the authenticators you also
6620 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6622 The &%server_condition%& setting defines how to verify that the username and
6623 password are correct. In the examples it just produces an error message.
6624 To make the authenticators work, you can use a string expansion
6625 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6627 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6628 usercode and password are in different positions.
6629 Chapter &<<CHAPplaintext>>& covers both.
6631 .ecindex IIDconfiwal
6635 . ////////////////////////////////////////////////////////////////////////////
6636 . ////////////////////////////////////////////////////////////////////////////
6638 .chapter "Regular expressions" "CHAPregexp"
6640 .cindex "regular expressions" "library"
6642 Exim supports the use of regular expressions in many of its options. It
6643 uses the PCRE regular expression library; this provides regular expression
6644 matching that is compatible with Perl 5. The syntax and semantics of
6645 regular expressions is discussed in
6646 online Perl manpages, in
6647 many Perl reference books, and also in
6648 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6649 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6650 . --- the http: URL here redirects to another page with the ISBN in the URL
6651 . --- where trying to use https: just redirects back to http:, so sticking
6652 . --- to the old URL for now. 2018-09-07.
6654 The documentation for the syntax and semantics of the regular expressions that
6655 are supported by PCRE is included in the PCRE distribution, and no further
6656 description is included here. The PCRE functions are called from Exim using
6657 the default option settings (that is, with no PCRE options set), except that
6658 the PCRE_CASELESS option is set when the matching is required to be
6661 In most cases, when a regular expression is required in an Exim configuration,
6662 it has to start with a circumflex, in order to distinguish it from plain text
6663 or an &"ends with"& wildcard. In this example of a configuration setting, the
6664 second item in the colon-separated list is a regular expression.
6666 domains = a.b.c : ^\\d{3} : *.y.z : ...
6668 The doubling of the backslash is required because of string expansion that
6669 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6670 of this issue, and a way of avoiding the need for doubling backslashes. The
6671 regular expression that is eventually used in this example contains just one
6672 backslash. The circumflex is included in the regular expression, and has the
6673 normal effect of &"anchoring"& it to the start of the string that is being
6676 There are, however, two cases where a circumflex is not required for the
6677 recognition of a regular expression: these are the &%match%& condition in a
6678 string expansion, and the &%matches%& condition in an Exim filter file. In
6679 these cases, the relevant string is always treated as a regular expression; if
6680 it does not start with a circumflex, the expression is not anchored, and can
6681 match anywhere in the subject string.
6683 In all cases, if you want a regular expression to match at the end of a string,
6684 you must code the $ metacharacter to indicate this. For example:
6686 domains = ^\\d{3}\\.example
6688 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6691 domains = ^\\d{3}\\.example\$
6693 if you want &'example'& to be the top-level domain. The backslash before the
6694 $ is needed because string expansion also interprets dollar characters.
6698 . ////////////////////////////////////////////////////////////////////////////
6699 . ////////////////////////////////////////////////////////////////////////////
6701 .chapter "File and database lookups" "CHAPfdlookup"
6702 .scindex IIDfidalo1 "file" "lookups"
6703 .scindex IIDfidalo2 "database" "lookups"
6704 .cindex "lookup" "description of"
6705 Exim can be configured to look up data in files or databases as it processes
6706 messages. Two different kinds of syntax are used:
6709 A string that is to be expanded may contain explicit lookup requests. These
6710 cause parts of the string to be replaced by data that is obtained from the
6711 lookup. Lookups of this type are conditional expansion items. Different results
6712 can be defined for the cases of lookup success and failure. See chapter
6713 &<<CHAPexpand>>&, where string expansions are described in detail.
6714 The key for the lookup is &*specified*& as part of the string expansion.
6716 Lists of domains, hosts, and email addresses can contain lookup requests as a
6717 way of avoiding excessively long linear lists. In this case, the data that is
6718 returned by the lookup is often (but not always) discarded; whether the lookup
6719 succeeds or fails is what really counts. These kinds of list are described in
6720 chapter &<<CHAPdomhosaddlists>>&.
6721 The key for the lookup is &*implicit*&,
6722 given by the context in which the list is expanded.
6725 String expansions, lists, and lookups interact with each other in such a way
6726 that there is no order in which to describe any one of them that does not
6727 involve references to the others. Each of these three chapters makes more sense
6728 if you have read the other two first. If you are reading this for the first
6729 time, be aware that some of it will make a lot more sense after you have read
6730 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6732 .section "Examples of different lookup syntax" "SECID60"
6733 It is easy to confuse the two different kinds of lookup, especially as the
6734 lists that may contain the second kind are always expanded before being
6735 processed as lists. Therefore, they may also contain lookups of the first kind.
6736 Be careful to distinguish between the following two examples:
6738 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6739 domains = lsearch;/some/file
6741 The first uses a string expansion, the result of which must be a domain list.
6742 No strings have been specified for a successful or a failing lookup; the
6743 defaults in this case are the looked-up data and an empty string, respectively.
6744 The expansion takes place before the string is processed as a list, and the
6745 file that is searched could contain lines like this:
6747 192.168.3.4: domain1:domain2:...
6748 192.168.1.9: domain3:domain4:...
6750 When the lookup succeeds, the result of the expansion is a list of domains (and
6751 possibly other types of item that are allowed in domain lists).
6752 .cindex "tainted data" "de-tainting"
6753 The result of the expansion is not tainted.
6755 In the second example, the lookup is a single item in a domain list. It causes
6756 Exim to use a lookup to see if the domain that is being processed can be found
6758 The file could contains lines like this:
6763 Any data that follows the keys is not relevant when checking that the domain
6764 matches the list item.
6766 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6767 Consider a file containing lines like this:
6769 192.168.5.6: lsearch;/another/file
6771 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6772 first &%domains%& setting above generates the second setting, which therefore
6773 causes a second lookup to occur.
6776 The lookup type may optionally be followed by a comma
6777 and a comma-separated list of options.
6778 Each option is a &"name=value"& pair.
6779 Whether an option is meaningful depends on the lookup type.
6781 All lookups support the option &"cache=no_rd"&.
6782 If this is given then the cache that Exim manages for lookup results
6783 is not checked before doing the lookup.
6784 The result of the lookup is still written to the cache.
6787 The rest of this chapter describes the different lookup types that are
6788 available. Any of them can be used in any part of the configuration where a
6789 lookup is permitted.
6792 .section "Lookup types" "SECID61"
6793 .cindex "lookup" "types of"
6794 .cindex "single-key lookup" "definition of"
6795 Two different types of data lookup are implemented:
6798 The &'single-key'& type requires the specification of a file in which to look,
6799 and a single key to search for. The key must be a non-empty string for the
6800 lookup to succeed. The lookup type determines how the file is searched.
6801 .cindex "tainted data" "single-key lookups"
6802 The file string may not be tainted
6804 .cindex "tainted data" "de-tainting"
6805 All single-key lookups support the option &"ret=key"&.
6806 If this is given and the lookup
6807 (either underlying implementation or cached value)
6808 returns data, the result is replaced with a non-tainted
6809 version of the lookup key.
6810 .cindex "tainted data" "de-tainting"
6812 .cindex "query-style lookup" "definition of"
6813 The &'query-style'& type accepts a generalized database query. No particular
6814 key value is assumed by Exim for query-style lookups. You can use whichever
6815 Exim variables you need to construct the database query.
6818 The code for each lookup type is in a separate source file that is included in
6819 the binary of Exim only if the corresponding compile-time option is set. The
6820 default settings in &_src/EDITME_& are:
6825 which means that only linear searching and DBM lookups are included by default.
6826 For some types of lookup (e.g. SQL databases), you need to install appropriate
6827 libraries and header files before building Exim.
6832 .section "Single-key lookup types" "SECTsinglekeylookups"
6833 .cindex "lookup" "single-key types"
6834 .cindex "single-key lookup" "list of types"
6835 The following single-key lookup types are implemented:
6838 .cindex "cdb" "description of"
6839 .cindex "lookup" "cdb"
6840 .cindex "binary zero" "in lookup key"
6841 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6842 string without a terminating binary zero. The cdb format is designed for
6843 indexed files that are read frequently and never updated, except by total
6844 re-creation. As such, it is particularly suitable for large files containing
6845 aliases or other indexed data referenced by an MTA. Information about cdb and
6846 tools for building the files can be found in several places:
6848 &url(https://cr.yp.to/cdb.html)
6849 &url(https://www.corpit.ru/mjt/tinycdb.html)
6850 &url(https://packages.debian.org/stable/utils/freecdb)
6851 &url(https://github.com/philpennock/cdbtools) (in Go)
6853 A cdb distribution is not needed in order to build Exim with cdb support,
6854 because the code for reading cdb files is included directly in Exim itself.
6855 However, no means of building or testing cdb files is provided with Exim, so
6856 you need to obtain a cdb distribution in order to do this.
6858 .cindex "DBM" "lookup type"
6859 .cindex "lookup" "dbm"
6860 .cindex "binary zero" "in lookup key"
6861 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6862 DBM file by looking up the record with the given key. A terminating binary
6863 zero is included in the key that is passed to the DBM library. See section
6864 &<<SECTdb>>& for a discussion of DBM libraries.
6866 .cindex "Berkeley DB library" "file format"
6867 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6868 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6869 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6870 the DB_UNKNOWN option. This enables it to handle any of the types of database
6871 that the library supports, and can be useful for accessing DBM files created by
6872 other applications. (For earlier DB versions, DB_HASH is always used.)
6874 .cindex "lookup" "dbmjz"
6875 .cindex "lookup" "dbm &-- embedded NULs"
6877 .cindex "dbmjz lookup type"
6878 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6879 interpreted as an Exim list; the elements of the list are joined together with
6880 ASCII NUL characters to form the lookup key. An example usage would be to
6881 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6882 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6883 &(cram_md5)& authenticator.
6885 .cindex "lookup" "dbmnz"
6886 .cindex "lookup" "dbm &-- terminating zero"
6887 .cindex "binary zero" "in lookup key"
6889 .cindex "&_/etc/userdbshadow.dat_&"
6890 .cindex "dbmnz lookup type"
6891 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6892 is not included in the key that is passed to the DBM library. You may need this
6893 if you want to look up data in files that are created by or shared with some
6894 other application that does not use terminating zeros. For example, you need to
6895 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6896 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6897 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6898 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6900 .cindex "lookup" "dsearch"
6901 .cindex "dsearch lookup type"
6902 &(dsearch)&: The given file must be an
6904 directory path; this is searched for an entry
6905 whose name is the key by calling the &[lstat()]& function.
6907 contain any forward slash characters.
6908 If &[lstat()]& succeeds then so does the lookup.
6909 .cindex "tainted data" "dsearch result"
6910 The result is regarded as untainted.
6912 Options for the lookup can be given by appending them after the word "dsearch",
6913 separated by a comma. Options, if present, are a comma-separated list having
6914 each element starting with a tag name and an equals.
6916 Two options are supported, for the return value and for filtering match
6918 The "ret" option requests an alternate result value of
6919 the entire path for the entry. Example:
6921 ${lookup {passwd} dsearch,ret=full {/etc}}
6923 The default result is just the requested entry.
6924 The "filter" option requests that only directory entries of a given type
6925 are matched. The match value is one of "file", "dir" or "subdir" (the latter
6926 not matching "." or ".."). Example:
6928 ${lookup {passwd} dsearch,filter=file {/etc}}
6930 The default matching is for any entry type, including directories
6933 An example of how this
6934 lookup can be used to support virtual domains is given in section
6935 &<<SECTvirtualdomains>>&.
6937 .cindex "lookup" "iplsearch"
6938 .cindex "iplsearch lookup type"
6939 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6940 terminated by a colon or white space or the end of the line. The keys in the
6941 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6942 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6943 being interpreted as a key terminator. For example:
6945 1.2.3.4: data for 1.2.3.4
6946 192.168.0.0/16: data for 192.168.0.0/16
6947 "abcd::cdab": data for abcd::cdab
6948 "abcd:abcd::/32" data for abcd:abcd::/32
6950 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6951 file is searched linearly, using the CIDR masks where present, until a matching
6952 key is found. The first key that matches is used; there is no attempt to find a
6953 &"best"& match. Apart from the way the keys are matched, the processing for
6954 &(iplsearch)& is the same as for &(lsearch)&.
6956 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6957 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6958 lookup types support only literal keys.
6960 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6961 the implicit key is the host's IP address rather than its name (see section
6962 &<<SECThoslispatsikey>>&).
6964 &*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
6965 IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
6966 notation before executing the lookup.)
6969 One option is supported, "ret=full", to request the return of the entire line
6970 rather than omitting the key porttion.
6971 Note however that the key portion will have been de-quoted.
6976 .cindex json "lookup type"
6977 .cindex JSON expansions
6978 &(json)&: The given file is a text file with a JSON structure.
6979 An element of the structure is extracted, defined by the search key.
6980 The key is a list of subelement selectors
6981 (colon-separated by default but changeable in the usual way)
6982 which are applied in turn to select smaller and smaller portions
6983 of the JSON structure.
6984 If a selector is numeric, it must apply to a JSON array; the (zero-based)
6985 nunbered array element is selected.
6986 Otherwise it must apply to a JSON object; the named element is selected.
6987 The final resulting element can be a simple JSON type or a JSON object
6988 or array; for the latter two a string-representation of the JSON
6990 For elements of type string, the returned value is de-quoted.
6997 .cindex database lmdb
6998 &(lmdb)&: The given file is an LMDB database.
6999 LMDB is a memory-mapped key-value store,
7000 with API modeled loosely on that of BerkeleyDB.
7001 See &url(https://symas.com/products/lightning-memory-mapped-database/)
7002 for the feature set and operation modes.
7004 Exim provides read-only access via the LMDB C library.
7005 The library can be obtained from &url(https://github.com/LMDB/lmdb)
7006 or your operating system package repository.
7007 To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&.
7009 You will need to separately create the LMDB database file,
7010 possibly using the &"mdb_load"& utility.
7015 .cindex "linear search"
7016 .cindex "lookup" "lsearch"
7017 .cindex "lsearch lookup type"
7018 .cindex "case sensitivity" "in lsearch lookup"
7019 &(lsearch)&: The given file is a text file that is searched linearly for a
7020 line beginning with the search key, terminated by a colon or white space or the
7021 end of the line. The search is case-insensitive; that is, upper and lower case
7022 letters are treated as the same. The first occurrence of the key that is found
7023 in the file is used.
7025 White space between the key and the colon is permitted. The remainder of the
7026 line, with leading and trailing white space removed, is the data. This can be
7027 continued onto subsequent lines by starting them with any amount of white
7028 space, but only a single space character is included in the data at such a
7029 junction. If the data begins with a colon, the key must be terminated by a
7034 Empty lines and lines beginning with # are ignored, even if they occur in the
7035 middle of an item. This is the traditional textual format of alias files. Note
7036 that the keys in an &(lsearch)& file are literal strings. There is no
7037 wildcarding of any kind.
7039 .cindex "lookup" "lsearch &-- colons in keys"
7040 .cindex "white space" "in lsearch key"
7041 In most &(lsearch)& files, keys are not required to contain colons or #
7042 characters, or white space. However, if you need this feature, it is available.
7043 If a key begins with a doublequote character, it is terminated only by a
7044 matching quote (or end of line), and the normal escaping rules apply to its
7045 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
7046 quoted keys (exactly as for unquoted keys). There is no special handling of
7047 quotes for the data part of an &(lsearch)& line.
7050 .cindex "NIS lookup type"
7051 .cindex "lookup" "NIS"
7052 .cindex "binary zero" "in lookup key"
7053 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
7054 the given key, without a terminating binary zero. There is a variant called
7055 &(nis0)& which does include the terminating binary zero in the key. This is
7056 reportedly needed for Sun-style alias files. Exim does not recognize NIS
7057 aliases; the full map names must be used.
7060 .cindex "wildlsearch lookup type"
7061 .cindex "lookup" "wildlsearch"
7062 .cindex "nwildlsearch lookup type"
7063 .cindex "lookup" "nwildlsearch"
7064 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
7065 &(lsearch)&, but instead of being interpreted as a literal string, each key in
7066 the file may be wildcarded. The difference between these two lookup types is
7067 that for &(wildlsearch)&, each key in the file is string-expanded before being
7068 used, whereas for &(nwildlsearch)&, no expansion takes place.
7070 .cindex "case sensitivity" "in (n)wildlsearch lookup"
7071 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
7072 file that are regular expressions can be made case-sensitive by the use of
7073 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
7075 . ==== As this is a nested list, any displays it contains must be indented
7076 . ==== as otherwise they are too far to the left.
7079 The string may begin with an asterisk to mean &"ends with"&. For example:
7081 *.a.b.c data for anything.a.b.c
7082 *fish data for anythingfish
7085 The string may begin with a circumflex to indicate a regular expression. For
7086 example, for &(wildlsearch)&:
7088 ^\N\d+\.a\.b\N data for <digits>.a.b
7090 Note the use of &`\N`& to disable expansion of the contents of the regular
7091 expression. If you are using &(nwildlsearch)&, where the keys are not
7092 string-expanded, the equivalent entry is:
7094 ^\d+\.a\.b data for <digits>.a.b
7096 The case-insensitive flag is set at the start of compiling the regular
7097 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
7098 For example, to make the entire pattern case-sensitive:
7100 ^(?-i)\d+\.a\.b data for <digits>.a.b
7103 If the regular expression contains white space or colon characters, you must
7104 either quote it (see &(lsearch)& above), or represent these characters in other
7105 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
7106 colon. This may be easier than quoting, because if you quote, you have to
7107 escape all the backslashes inside the quotes.
7109 &*Note*&: It is not possible to capture substrings in a regular expression
7110 match for later use, because the results of all lookups are cached. If a lookup
7111 is repeated, the result is taken from the cache, and no actual pattern matching
7112 takes place. The values of all the numeric variables are unset after a
7113 &((n)wildlsearch)& match.
7116 Although I cannot see it being of much use, the general matching function that
7117 is used to implement &((n)wildlsearch)& means that the string may begin with a
7118 lookup name terminated by a semicolon, and followed by lookup data. For
7121 cdb;/some/file data for keys that match the file
7123 The data that is obtained from the nested lookup is discarded.
7126 Keys that do not match any of these patterns are interpreted literally. The
7127 continuation rules for the data are the same as for &(lsearch)&, and keys may
7128 be followed by optional colons.
7130 &*Warning*&: Unlike most other single-key lookup types, a file of data for
7131 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
7132 lookup types support only literal keys.
7135 .cindex "spf lookup type"
7136 .cindex "lookup" "spf"
7137 &(spf)&: If Exim is built with SPF support, manual lookups can be done
7138 (as opposed to the standard ACL condition method).
7139 For details see section &<<SECSPF>>&.
7143 .section "Query-style lookup types" "SECTquerystylelookups"
7144 .cindex "lookup" "query-style types"
7145 .cindex "query-style lookup" "list of types"
7146 The supported query-style lookup types are listed below. Further details about
7147 many of them are given in later sections.
7150 .cindex "DNS" "as a lookup type"
7151 .cindex "lookup" "DNS"
7152 &(dnsdb)&: This does a DNS search for one or more records whose domain names
7153 are given in the supplied query. The resulting data is the contents of the
7154 records. See section &<<SECTdnsdb>>&.
7156 .cindex "InterBase lookup type"
7157 .cindex "lookup" "InterBase"
7158 &(ibase)&: This does a lookup in an InterBase database.
7160 .cindex "LDAP" "lookup type"
7161 .cindex "lookup" "LDAP"
7162 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
7163 returns attributes from a single entry. There is a variant called &(ldapm)&
7164 that permits values from multiple entries to be returned. A third variant
7165 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
7166 any attribute values. See section &<<SECTldap>>&.
7168 .cindex "MySQL" "lookup type"
7169 .cindex "lookup" "MySQL"
7170 &(mysql)&: The format of the query is an SQL statement that is passed to a
7171 MySQL database. See section &<<SECTsql>>&.
7173 .cindex "NIS+ lookup type"
7174 .cindex "lookup" "NIS+"
7175 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
7176 the field to be returned. See section &<<SECTnisplus>>&.
7178 .cindex "Oracle" "lookup type"
7179 .cindex "lookup" "Oracle"
7180 &(oracle)&: The format of the query is an SQL statement that is passed to an
7181 Oracle database. See section &<<SECTsql>>&.
7183 .cindex "lookup" "passwd"
7184 .cindex "passwd lookup type"
7185 .cindex "&_/etc/passwd_&"
7186 &(passwd)& is a query-style lookup with queries that are just user names. The
7187 lookup calls &[getpwnam()]& to interrogate the system password data, and on
7188 success, the result string is the same as you would get from an &(lsearch)&
7189 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
7190 password value. For example:
7192 *:42:42:King Rat:/home/kr:/bin/bash
7195 .cindex "PostgreSQL lookup type"
7196 .cindex "lookup" "PostgreSQL"
7197 &(pgsql)&: The format of the query is an SQL statement that is passed to a
7198 PostgreSQL database. See section &<<SECTsql>>&.
7201 .cindex "Redis lookup type"
7202 .cindex lookup Redis
7203 &(redis)&: The format of the query is either a simple get or simple set,
7204 passed to a Redis database. See section &<<SECTsql>>&.
7207 .cindex "sqlite lookup type"
7208 .cindex "lookup" "sqlite"
7209 &(sqlite)&: The format of the query is
7210 an SQL statement that is passed to an SQLite database. See section &<<SECTsqlite>>&.
7213 &(testdb)&: This is a lookup type that is used for testing Exim. It is
7214 not likely to be useful in normal operation.
7216 .cindex "whoson lookup type"
7217 .cindex "lookup" "whoson"
7218 . --- still http:-only, 2018-09-07
7219 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
7220 allows a server to check whether a particular (dynamically allocated) IP
7221 address is currently allocated to a known (trusted) user and, optionally, to
7222 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
7223 at one time for &"POP before SMTP"& authentication, but that approach has been
7224 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
7225 &"POP before SMTP"& checking using ACL statements such as
7227 require condition = \
7228 ${lookup whoson {$sender_host_address}{yes}{no}}
7230 The query consists of a single IP address. The value returned is the name of
7231 the authenticated user, which is stored in the variable &$value$&. However, in
7232 this example, the data in &$value$& is not used; the result of the lookup is
7233 one of the fixed strings &"yes"& or &"no"&.
7238 .section "Temporary errors in lookups" "SECID63"
7239 .cindex "lookup" "temporary error in"
7240 Lookup functions can return temporary error codes if the lookup cannot be
7241 completed. For example, an SQL or LDAP database might be unavailable. For this
7242 reason, it is not advisable to use a lookup that might do this for critical
7243 options such as a list of local domains.
7245 When a lookup cannot be completed in a router or transport, delivery
7246 of the message (to the relevant address) is deferred, as for any other
7247 temporary error. In other circumstances Exim may assume the lookup has failed,
7248 or may give up altogether.
7252 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
7253 .cindex "wildcard lookups"
7254 .cindex "lookup" "default values"
7255 .cindex "lookup" "wildcard"
7256 .cindex "lookup" "* added to type"
7257 .cindex "default" "in single-key lookups"
7258 In this context, a &"default value"& is a value specified by the administrator
7259 that is to be used if a lookup fails.
7261 &*Note:*& This section applies only to single-key lookups. For query-style
7262 lookups, the facilities of the query language must be used. An attempt to
7263 specify a default for a query-style lookup provokes an error.
7265 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
7266 and the initial lookup fails, the key &"*"& is looked up in the file to
7267 provide a default value. See also the section on partial matching below.
7269 .cindex "*@ with single-key lookup"
7270 .cindex "lookup" "*@ added to type"
7271 .cindex "alias file" "per-domain default"
7272 Alternatively, if &"*@"& is added to a single-key lookup type (for example
7273 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
7274 character, a second lookup is done with everything before the last @ replaced
7275 by *. This makes it possible to provide per-domain defaults in alias files
7276 that include the domains in the keys. If the second lookup fails (or doesn't
7277 take place because there is no @ in the key), &"*"& is looked up.
7278 For example, a &(redirect)& router might contain:
7280 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
7282 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
7283 looks up these keys, in this order:
7289 The data is taken from whichever key it finds first. &*Note*&: In an
7290 &(lsearch)& file, this does not mean the first of these keys in the file. A
7291 complete scan is done for each key, and only if it is not found at all does
7292 Exim move on to try the next key.
7296 .section "Partial matching in single-key lookups" "SECTpartiallookup"
7297 .cindex "partial matching"
7298 .cindex "wildcard lookups"
7299 .cindex "lookup" "partial matching"
7300 .cindex "lookup" "wildcard"
7301 .cindex "asterisk" "in search type"
7302 The normal operation of a single-key lookup is to search the file for an exact
7303 match with the given key. However, in a number of situations where domains are
7304 being looked up, it is useful to be able to do partial matching. In this case,
7305 information in the file that has a key starting with &"*."& is matched by any
7306 domain that ends with the components that follow the full stop. For example, if
7307 a key in a DBM file is
7309 *.dates.fict.example
7311 then when partial matching is enabled this is matched by (amongst others)
7312 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
7313 by &'dates.fict.example'&, if that does not appear as a separate key in the
7316 &*Note*&: Partial matching is not available for query-style lookups. It is
7317 also not available for any lookup items in address lists (see section
7318 &<<SECTaddresslist>>&).
7320 Partial matching is implemented by doing a series of separate lookups using
7321 keys constructed by modifying the original subject key. This means that it can
7322 be used with any of the single-key lookup types, provided that
7323 partial matching keys
7324 beginning with a special prefix (default &"*."&) are included in the data file.
7325 Keys in the file that do not begin with the prefix are matched only by
7326 unmodified subject keys when partial matching is in use.
7328 Partial matching is requested by adding the string &"partial-"& to the front of
7329 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
7330 is done, the subject key is first looked up unmodified; if that fails, &"*."&
7331 is added at the start of the subject key, and it is looked up again. If that
7332 fails, further lookups are tried with dot-separated components removed from the
7333 start of the subject key, one-by-one, and &"*."& added on the front of what
7336 A minimum number of two non-* components are required. This can be adjusted
7337 by including a number before the hyphen in the search type. For example,
7338 &%partial3-lsearch%& specifies a minimum of three non-* components in the
7339 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
7340 subject key is &'2250.dates.fict.example'& then the following keys are looked
7341 up when the minimum number of non-* components is two:
7343 2250.dates.fict.example
7344 *.2250.dates.fict.example
7345 *.dates.fict.example
7348 As soon as one key in the sequence is successfully looked up, the lookup
7351 .cindex "lookup" "partial matching &-- changing prefix"
7352 .cindex "prefix" "for partial matching"
7353 The use of &"*."& as the partial matching prefix is a default that can be
7354 changed. The motivation for this feature is to allow Exim to operate with file
7355 formats that are used by other MTAs. A different prefix can be supplied in
7356 parentheses instead of the hyphen after &"partial"&. For example:
7358 domains = partial(.)lsearch;/some/file
7360 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
7361 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
7362 components is unchanged). The prefix may consist of any punctuation characters
7363 other than a closing parenthesis. It may be empty, for example:
7365 domains = partial1()cdb;/some/file
7367 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
7368 &`a.b.c`&, &`b.c`&, and &`c`&.
7370 If &"partial0"& is specified, what happens at the end (when the lookup with
7371 just one non-wild component has failed, and the original key is shortened right
7372 down to the null string) depends on the prefix:
7375 If the prefix has zero length, the whole lookup fails.
7377 If the prefix has length 1, a lookup for just the prefix is done. For
7378 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
7380 Otherwise, if the prefix ends in a dot, the dot is removed, and the
7381 remainder is looked up. With the default prefix, therefore, the final lookup is
7382 for &"*"& on its own.
7384 Otherwise, the whole prefix is looked up.
7388 If the search type ends in &"*"& or &"*@"& (see section
7389 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
7390 this implies happens after all partial lookups have failed. If &"partial0"& is
7391 specified, adding &"*"& to the search type has no effect with the default
7392 prefix, because the &"*"& key is already included in the sequence of partial
7393 lookups. However, there might be a use for lookup types such as
7394 &"partial0(.)lsearch*"&.
7396 The use of &"*"& in lookup partial matching differs from its use as a wildcard
7397 in domain lists and the like. Partial matching works only in terms of
7398 dot-separated components; a key such as &`*fict.example`&
7399 in a database file is useless, because the asterisk in a partial matching
7400 subject key is always followed by a dot.
7405 .section "Lookup caching" "SECID64"
7406 .cindex "lookup" "caching"
7407 .cindex "caching" "lookup data"
7408 Exim caches all lookup results in order to avoid needless repetition of
7409 lookups. However, because (apart from the daemon) Exim operates as a collection
7410 of independent, short-lived processes, this caching applies only within a
7411 single Exim process. There is no inter-process lookup caching facility.
7413 For single-key lookups, Exim keeps the relevant files open in case there is
7414 another lookup that needs them. In some types of configuration this can lead to
7415 many files being kept open for messages with many recipients. To avoid hitting
7416 the operating system limit on the number of simultaneously open files, Exim
7417 closes the least recently used file when it needs to open more files than its
7418 own internal limit, which can be changed via the &%lookup_open_max%& option.
7420 The single-key lookup files are closed and the lookup caches are flushed at
7421 strategic points during delivery &-- for example, after all routing is
7427 .section "Quoting lookup data" "SECID65"
7428 .cindex "lookup" "quoting"
7429 .cindex "quoting" "in lookups"
7430 When data from an incoming message is included in a query-style lookup, there
7431 is the possibility of special characters in the data messing up the syntax of
7432 the query. For example, a NIS+ query that contains
7436 will be broken if the local part happens to contain a closing square bracket.
7437 For NIS+, data can be enclosed in double quotes like this:
7439 [name="$local_part"]
7441 but this still leaves the problem of a double quote in the data. The rule for
7442 NIS+ is that double quotes must be doubled. Other lookup types have different
7443 rules, and to cope with the differing requirements, an expansion operator
7444 of the following form is provided:
7446 ${quote_<lookup-type>:<string>}
7448 For example, the safest way to write the NIS+ query is
7450 [name="${quote_nisplus:$local_part}"]
7452 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
7453 operator can be used for all lookup types, but has no effect for single-key
7454 lookups, since no quoting is ever needed in their key strings.
7459 .section "More about dnsdb" "SECTdnsdb"
7460 .cindex "dnsdb lookup"
7461 .cindex "lookup" "dnsdb"
7462 .cindex "DNS" "as a lookup type"
7463 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7464 of a record type and a domain name, separated by an equals sign. For example,
7465 an expansion string could contain:
7467 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7469 If the lookup succeeds, the result is placed in &$value$&, which in this case
7470 is used on its own as the result. If the lookup does not succeed, the
7471 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7472 &<<SECTforexpfai>>& for an explanation of what this means.
7474 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7475 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7476 If no type is given, TXT is assumed.
7478 For any record type, if multiple records are found, the data is returned as a
7479 concatenation, with newline as the default separator. The order, of course,
7480 depends on the DNS resolver. You can specify a different separator character
7481 between multiple records by putting a right angle-bracket followed immediately
7482 by the new separator at the start of the query. For example:
7484 ${lookup dnsdb{>: a=host1.example}}
7486 It is permitted to specify a space as the separator character. Further
7487 white space is ignored.
7488 For lookup types that return multiple fields per record,
7489 an alternate field separator can be specified using a comma after the main
7490 separator character, followed immediately by the field separator.
7492 .cindex "PTR record" "in &(dnsdb)& lookup"
7493 When the type is PTR,
7494 the data can be an IP address, written as normal; inversion and the addition of
7495 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7497 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7499 If the data for a PTR record is not a syntactically valid IP address, it is not
7500 altered and nothing is added.
7502 .cindex "MX record" "in &(dnsdb)& lookup"
7503 .cindex "SRV record" "in &(dnsdb)& lookup"
7504 For an MX lookup, both the preference value and the host name are returned for
7505 each record, separated by a space. For an SRV lookup, the priority, weight,
7506 port, and host name are returned for each record, separated by spaces.
7507 The field separator can be modified as above.
7509 .cindex "TXT record" "in &(dnsdb)& lookup"
7510 .cindex "SPF record" "in &(dnsdb)& lookup"
7511 For TXT records with multiple items of data, only the first item is returned,
7512 unless a field separator is specified.
7513 To concatenate items without a separator, use a semicolon instead.
7515 default behaviour is to concatenate multiple items without using a separator.
7517 ${lookup dnsdb{>\n,: txt=a.b.example}}
7518 ${lookup dnsdb{>\n; txt=a.b.example}}
7519 ${lookup dnsdb{spf=example.org}}
7521 It is permitted to specify a space as the separator character. Further
7522 white space is ignored.
7524 .cindex "SOA record" "in &(dnsdb)& lookup"
7525 For an SOA lookup, while no result is obtained the lookup is redone with
7526 successively more leading components dropped from the given domain.
7527 Only the primary-nameserver field is returned unless a field separator is
7530 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7533 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7534 .cindex "dnsdb modifiers"
7535 .cindex "modifiers" "dnsdb"
7536 .cindex "options" "dnsdb"
7537 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7538 each followed by a comma,
7539 that may appear before the record type.
7541 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7542 temporary DNS error for any of them, the behaviour is controlled by
7543 a defer-option modifier.
7544 The possible keywords are
7545 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7546 With &"strict"& behaviour, any temporary DNS error causes the
7547 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7548 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7549 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7550 error causes the whole lookup to defer only if none of the other lookups
7551 succeed. The default is &"lax"&, so the following lookups are equivalent:
7553 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7554 ${lookup dnsdb{a=one.host.com:two.host.com}}
7556 Thus, in the default case, as long as at least one of the DNS lookups
7557 yields some data, the lookup succeeds.
7559 .cindex "DNSSEC" "dns lookup"
7560 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7561 The possible keywords are
7562 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7563 With &"strict"& or &"lax"& DNSSEC information is requested
7565 With &"strict"& a response from the DNS resolver that
7566 is not labelled as authenticated data
7567 is treated as equivalent to a temporary DNS error.
7568 The default is &"lax"&.
7570 See also the &$lookup_dnssec_authenticated$& variable.
7572 .cindex timeout "dns lookup"
7573 .cindex "DNS" timeout
7574 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7575 The form is &"retrans_VAL"& where VAL is an Exim time specification
7577 The default value is set by the main configuration option &%dns_retrans%&.
7579 Retries for the dnsdb lookup can be controlled by a retry modifier.
7580 The form if &"retry_VAL"& where VAL is an integer.
7581 The default count is set by the main configuration option &%dns_retry%&.
7583 .cindex caching "of dns lookup"
7584 .cindex TTL "of dns lookup"
7586 Dnsdb lookup results are cached within a single process (and its children).
7587 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7588 value of the set of returned DNS records.
7591 .section "Pseudo dnsdb record types" "SECID66"
7592 .cindex "MX record" "in &(dnsdb)& lookup"
7593 By default, both the preference value and the host name are returned for
7594 each MX record, separated by a space. If you want only host names, you can use
7595 the pseudo-type MXH:
7597 ${lookup dnsdb{mxh=a.b.example}}
7599 In this case, the preference values are omitted, and just the host names are
7602 .cindex "name server for enclosing domain"
7603 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7604 records on the given domain, but if none are found, it removes the first
7605 component of the domain name, and tries again. This process continues until NS
7606 records are found or there are no more components left (or there is a DNS
7607 error). In other words, it may return the name servers for a top-level domain,
7608 but it never returns the root name servers. If there are no NS records for the
7609 top-level domain, the lookup fails. Consider these examples:
7611 ${lookup dnsdb{zns=xxx.quercite.com}}
7612 ${lookup dnsdb{zns=xxx.edu}}
7614 Assuming that in each case there are no NS records for the full domain name,
7615 the first returns the name servers for &%quercite.com%&, and the second returns
7616 the name servers for &%edu%&.
7618 You should be careful about how you use this lookup because, unless the
7619 top-level domain does not exist, the lookup always returns some host names. The
7620 sort of use to which this might be put is for seeing if the name servers for a
7621 given domain are on a blacklist. You can probably assume that the name servers
7622 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7625 .cindex "CSA" "in &(dnsdb)& lookup"
7626 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7627 records according to the CSA rules, which are described in section
7628 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7629 not sufficient because of the extra parent domain search behaviour of CSA. The
7630 result of a successful lookup such as:
7632 ${lookup dnsdb {csa=$sender_helo_name}}
7634 has two space-separated fields: an authorization code and a target host name.
7635 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7636 authorization required but absent, or &"?"& for unknown.
7638 .cindex "A+" "in &(dnsdb)& lookup"
7639 The pseudo-type A+ performs an AAAA
7640 and then an A lookup. All results are returned; defer processing
7641 (see below) is handled separately for each lookup. Example:
7643 ${lookup dnsdb {>; a+=$sender_helo_name}}
7647 .section "Multiple dnsdb lookups" "SECID67"
7648 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7649 However, you can specify a list of domains or IP addresses in a single
7650 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7651 the default separator, but with the ability to change this. For example:
7653 ${lookup dnsdb{one.domain.com:two.domain.com}}
7654 ${lookup dnsdb{a=one.host.com:two.host.com}}
7655 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7657 In order to retain backwards compatibility, there is one special case: if
7658 the lookup type is PTR and no change of separator is specified, Exim looks
7659 to see if the rest of the string is precisely one IPv6 address. In this
7660 case, it does not treat it as a list.
7662 The data from each lookup is concatenated, with newline separators by default,
7663 in the same way that multiple DNS records for a single item are handled. A
7664 different separator can be specified, as described above.
7669 .section "More about LDAP" "SECTldap"
7670 .cindex "LDAP" "lookup, more about"
7671 .cindex "lookup" "LDAP"
7672 .cindex "Solaris" "LDAP"
7673 The original LDAP implementation came from the University of Michigan; this has
7674 become &"Open LDAP"&, and there are now two different releases. Another
7675 implementation comes from Netscape, and Solaris 7 and subsequent releases
7676 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7677 the lookup function level, their error handling is different. For this reason
7678 it is necessary to set a compile-time variable when building Exim with LDAP, to
7679 indicate which LDAP library is in use. One of the following should appear in
7680 your &_Local/Makefile_&:
7682 LDAP_LIB_TYPE=UMICHIGAN
7683 LDAP_LIB_TYPE=OPENLDAP1
7684 LDAP_LIB_TYPE=OPENLDAP2
7685 LDAP_LIB_TYPE=NETSCAPE
7686 LDAP_LIB_TYPE=SOLARIS
7688 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7689 same interface as the University of Michigan version.
7691 There are three LDAP lookup types in Exim. These behave slightly differently in
7692 the way they handle the results of a query:
7695 &(ldap)& requires the result to contain just one entry; if there are more, it
7698 &(ldapdn)& also requires the result to contain just one entry, but it is the
7699 Distinguished Name that is returned rather than any attribute values.
7701 &(ldapm)& permits the result to contain more than one entry; the attributes
7702 from all of them are returned.
7706 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7707 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7708 the data returned by a successful lookup is described in the next section.
7709 First we explain how LDAP queries are coded.
7712 .section "Format of LDAP queries" "SECTforldaque"
7713 .cindex "LDAP" "query format"
7714 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7715 the configuration of a &(redirect)& router one might have this setting:
7717 data = ${lookup ldap \
7718 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7719 c=UK?mailbox?base?}}
7721 .cindex "LDAP" "with TLS"
7722 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7723 secure (encrypted) LDAP connections. The second of these ensures that an
7724 encrypted TLS connection is used.
7726 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7727 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7728 See the &%ldap_start_tls%& option.
7730 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7731 controlled. Every part of the TLS configuration can be configured by settings in
7732 &_exim.conf_&. Depending on the version of the client libraries installed on
7733 your system, some of the initialization may have required setting options in
7734 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7735 certificates. This revealed a nuance where the current UID that exim was
7736 running as could affect which config files it read. With Exim 4.83, these
7737 methods become optional, only taking effect if not specifically set in
7741 .section "LDAP quoting" "SECID68"
7742 .cindex "LDAP" "quoting"
7743 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7744 and the second because the LDAP query is represented as a URL. Furthermore,
7745 within an LDAP query, two different kinds of quoting are required. For this
7746 reason, there are two different LDAP-specific quoting operators.
7748 The &%quote_ldap%& operator is designed for use on strings that are part of
7749 filter specifications. Conceptually, it first does the following conversions on
7757 in accordance with RFC 2254. The resulting string is then quoted according
7758 to the rules for URLs, that is, all non-alphanumeric characters except
7762 are converted to their hex values, preceded by a percent sign. For example:
7764 ${quote_ldap: a(bc)*, a<yz>; }
7768 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7770 Removing the URL quoting, this is (with a leading and a trailing space):
7772 a\28bc\29\2A, a<yz>;
7774 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7775 base DN specifications in queries. Conceptually, it first converts the string
7776 by inserting a backslash in front of any of the following characters:
7780 It also inserts a backslash before any leading spaces or # characters, and
7781 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7782 is then quoted according to the rules for URLs. For example:
7784 ${quote_ldap_dn: a(bc)*, a<yz>; }
7788 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7790 Removing the URL quoting, this is (with a trailing space):
7792 \ a(bc)*\, a\<yz\>\;\
7794 There are some further comments about quoting in the section on LDAP
7795 authentication below.
7798 .section "LDAP connections" "SECID69"
7799 .cindex "LDAP" "connections"
7800 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7801 is in use, via a Unix domain socket. The example given above does not specify
7802 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7805 ldap://<hostname>:<port>/...
7807 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7808 used. When no server is specified in a query, a list of default servers is
7809 taken from the &%ldap_default_servers%& configuration option. This supplies a
7810 colon-separated list of servers which are tried in turn until one successfully
7811 handles a query, or there is a serious error. Successful handling either
7812 returns the requested data, or indicates that it does not exist. Serious errors
7813 are syntactical, or multiple values when only a single value is expected.
7814 Errors which cause the next server to be tried are connection failures, bind
7815 failures, and timeouts.
7817 For each server name in the list, a port number can be given. The standard way
7818 of specifying a host and port is to use a colon separator (RFC 1738). Because
7819 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7820 doubled. For example
7822 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7824 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7825 to the LDAP library with no server name, and the library's default (normally
7826 the local host) is used.
7828 If you are using the OpenLDAP library, you can connect to an LDAP server using
7829 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7830 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7831 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7834 For this type of connection, instead of a host name for the server, a pathname
7835 for the socket is required, and the port number is not relevant. The pathname
7836 can be specified either as an item in &%ldap_default_servers%&, or inline in
7837 the query. In the former case, you can have settings such as
7839 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7841 When the pathname is given in the query, you have to escape the slashes as
7842 &`%2F`& to fit in with the LDAP URL syntax. For example:
7844 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7846 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7847 a pathname, it uses the Unix domain socket code, even if the query actually
7848 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7849 socket connection. This behaviour means that you can use a setting of
7850 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7851 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7852 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7855 If an explicit &`ldapi`& type is given in a query when a host name is
7856 specified, an error is diagnosed. However, if there are more items in
7857 &%ldap_default_servers%&, they are tried. In other words:
7860 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7863 Using &`ldapi`& with a host name causes an error.
7867 Using &`ldapi`& with no host or path in the query, and no setting of
7868 &%ldap_default_servers%&, does whatever the library does by default.
7872 .section "LDAP authentication and control information" "SECID70"
7873 .cindex "LDAP" "authentication"
7874 The LDAP URL syntax provides no way of passing authentication and other control
7875 information to the server. To make this possible, the URL in an LDAP query may
7876 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7877 spaces. If a value contains spaces it must be enclosed in double quotes, and
7878 when double quotes are used, backslash is interpreted in the usual way inside
7879 them. The following names are recognized:
7881 &`DEREFERENCE`& set the dereferencing parameter
7882 &`NETTIME `& set a timeout for a network operation
7883 &`USER `& set the DN, for authenticating the LDAP bind
7884 &`PASS `& set the password, likewise
7885 &`REFERRALS `& set the referrals parameter
7886 &`SERVERS `& set alternate server list for this query only
7887 &`SIZE `& set the limit for the number of entries returned
7888 &`TIME `& set the maximum waiting time for a query
7890 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7891 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7892 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7893 library from trying to follow referrals issued by the LDAP server.
7895 .cindex LDAP timeout
7896 .cindex timeout "LDAP lookup"
7897 The name CONNECT is an obsolete name for NETTIME, retained for
7898 backwards compatibility. This timeout (specified as a number of seconds) is
7899 enforced from the client end for operations that can be carried out over a
7900 network. Specifically, it applies to network connections and calls to the
7901 &'ldap_result()'& function. If the value is greater than zero, it is used if
7902 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7903 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7904 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7905 Netscape SDK; for OpenLDAP no action is taken.
7907 The TIME parameter (also a number of seconds) is passed to the server to
7908 set a server-side limit on the time taken to complete a search.
7910 The SERVERS parameter allows you to specify an alternate list of ldap servers
7911 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7912 default list of ldap servers, and a single lookup can specify a single ldap
7913 server to use. But when you need to do a lookup with a list of servers that is
7914 different than the default list (maybe different order, maybe a completely
7915 different set of servers), the SERVERS parameter allows you to specify this
7916 alternate list (colon-separated).
7918 Here is an example of an LDAP query in an Exim lookup that uses some of these
7919 values. This is a single line, folded to fit on the page:
7922 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7923 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7926 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7927 any of the auxiliary data. Exim configuration settings that include lookups
7928 which contain password information should be preceded by &"hide"& to prevent
7929 non-admin users from using the &%-bP%& option to see their values.
7931 The auxiliary data items may be given in any order. The default is no
7932 connection timeout (the system timeout is used), no user or password, no limit
7933 on the number of entries returned, and no time limit on queries.
7935 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7936 removes any URL quoting that it may contain before passing it LDAP. Apparently
7937 some libraries do this for themselves, but some do not. Removing the URL
7938 quoting has two advantages:
7941 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7942 DNs as with DNs inside actual queries.
7944 It permits spaces inside USER= DNs.
7947 For example, a setting such as
7949 USER=cn=${quote_ldap_dn:$1}
7951 should work even if &$1$& contains spaces.
7953 Expanded data for the PASS= value should be quoted using the &%quote%&
7954 expansion operator, rather than the LDAP quote operators. The only reason this
7955 field needs quoting is to ensure that it conforms to the Exim syntax, which
7956 does not allow unquoted spaces. For example:
7960 The LDAP authentication mechanism can be used to check passwords as part of
7961 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7966 .section "Format of data returned by LDAP" "SECID71"
7967 .cindex "LDAP" "returned data formats"
7968 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7969 as a sequence of values, for example
7971 cn=manager,o=University of Cambridge,c=UK
7973 The &(ldap)& lookup type generates an error if more than one entry matches the
7974 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7975 the result between the data from different entries. It is possible for multiple
7976 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7977 you know that whatever values are returned all came from a single entry in the
7980 In the common case where you specify a single attribute in your LDAP query, the
7981 result is not quoted, and does not contain the attribute name. If the attribute
7982 has multiple values, they are separated by commas. Any comma that is
7983 part of an attribute's value is doubled.
7985 If you specify multiple attributes, the result contains space-separated, quoted
7986 strings, each preceded by the attribute name and an equals sign. Within the
7987 quotes, the quote character, backslash, and newline are escaped with
7988 backslashes, and commas are used to separate multiple values for the attribute.
7989 Any commas in attribute values are doubled
7990 (permitting treatment of the values as a comma-separated list).
7991 Apart from the escaping, the string within quotes takes the same form as the
7992 output when a single attribute is requested. Specifying no attributes is the
7993 same as specifying all of an entry's attributes.
7995 Here are some examples of the output format. The first line of each pair is an
7996 LDAP query, and the second is the data that is returned. The attribute called
7997 &%attr1%& has two values, one of them with an embedded comma, whereas
7998 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7999 (they have SUP &%attr%& in their schema definitions).
8002 ldap:///o=base?attr1?sub?(uid=fred)
8005 ldap:///o=base?attr2?sub?(uid=fred)
8008 ldap:///o=base?attr?sub?(uid=fred)
8009 value1.1,value1,,2,value two
8011 ldap:///o=base?attr1,attr2?sub?(uid=fred)
8012 attr1="value1.1,value1,,2" attr2="value two"
8014 ldap:///o=base??sub?(uid=fred)
8015 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
8018 make use of Exim's &%-be%& option to run expansion tests and thereby check the
8019 results of LDAP lookups.
8020 The &%extract%& operator in string expansions can be used to pick out
8021 individual fields from data that consists of &'key'&=&'value'& pairs.
8022 The &%listextract%& operator should be used to pick out individual values
8023 of attributes, even when only a single value is expected.
8024 The doubling of embedded commas allows you to use the returned data as a
8025 comma separated list (using the "<," syntax for changing the input list separator).
8030 .section "More about NIS+" "SECTnisplus"
8031 .cindex "NIS+ lookup type"
8032 .cindex "lookup" "NIS+"
8033 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
8034 and field name. If this is given, the result of a successful query is the
8035 contents of the named field; otherwise the result consists of a concatenation
8036 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
8037 values containing spaces are quoted. For example, the query
8039 [name=mg1456],passwd.org_dir
8041 might return the string
8043 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
8044 home=/home/mg1456 shell=/bin/bash shadow=""
8046 (split over two lines here to fit on the page), whereas
8048 [name=mg1456],passwd.org_dir:gcos
8054 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
8055 for the given indexed key. The effect of the &%quote_nisplus%& expansion
8056 operator is to double any quote characters within the text.
8060 .section "SQL lookups" "SECTsql"
8061 .cindex "SQL lookup types"
8062 .cindex "MySQL" "lookup type"
8063 .cindex "PostgreSQL lookup type"
8064 .cindex "lookup" "MySQL"
8065 .cindex "lookup" "PostgreSQL"
8066 .cindex "Oracle" "lookup type"
8067 .cindex "lookup" "Oracle"
8068 .cindex "InterBase lookup type"
8069 .cindex "lookup" "InterBase"
8070 .cindex "Redis lookup type"
8071 .cindex lookup Redis
8072 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
8074 databases. Queries for these databases contain SQL statements, so an example
8077 ${lookup mysql{select mailbox from users where id='userx'}\
8080 If the result of the query contains more than one field, the data for each
8081 field in the row is returned, preceded by its name, so the result of
8083 ${lookup pgsql{select home,name from users where id='userx'}\
8088 home=/home/userx name="Mister X"
8090 Empty values and values containing spaces are double quoted, with embedded
8091 quotes escaped by a backslash. If the result of the query contains just one
8092 field, the value is passed back verbatim, without a field name, for example:
8096 If the result of the query yields more than one row, it is all concatenated,
8097 with a newline between the data for each row.
8100 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
8101 .cindex "MySQL" "lookup type"
8102 .cindex "PostgreSQL lookup type"
8103 .cindex "lookup" "MySQL"
8104 .cindex "lookup" "PostgreSQL"
8105 .cindex "Oracle" "lookup type"
8106 .cindex "lookup" "Oracle"
8107 .cindex "InterBase lookup type"
8108 .cindex "lookup" "InterBase"
8109 .cindex "Redis lookup type"
8110 .cindex lookup Redis
8111 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
8112 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
8113 or &%redis_servers%&
8114 option (as appropriate) must be set to a colon-separated list of server
8116 .oindex &%mysql_servers%&
8117 .oindex &%pgsql_servers%&
8118 .oindex &%oracle_servers%&
8119 .oindex &%ibase_servers%&
8120 .oindex &%redis_servers%&
8121 (For MySQL and PostgreSQL, the global option need not be set if all
8122 queries contain their own server information &-- see section
8123 &<<SECTspeserque>>&.)
8125 each item in the list is a slash-separated list of four
8126 items: host name, database name, user name, and password. In the case of
8127 Oracle, the host name field is used for the &"service name"&, and the database
8128 name field is not used and should be empty. For example:
8130 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
8132 Because password data is sensitive, you should always precede the setting with
8133 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
8134 option. Here is an example where two MySQL servers are listed:
8136 hide mysql_servers = localhost/users/root/secret:\
8137 otherhost/users/root/othersecret
8139 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
8140 because this is a colon-separated list, the colon has to be doubled. For each
8141 query, these parameter groups are tried in order until a connection is made and
8142 a query is successfully processed. The result of a query may be that no data is
8143 found, but that is still a successful query. In other words, the list of
8144 servers provides a backup facility, not a list of different places to look.
8146 For Redis the global option need not be specified if all queries contain their
8147 own server information &-- see section &<<SECTspeserque>>&.
8148 If specified, the option must be set to a colon-separated list of server
8150 Each item in the list is a slash-separated list of three items:
8151 host, database number, and password.
8153 The host is required and may be either an IPv4 address and optional
8154 port number (separated by a colon, which needs doubling due to the
8155 higher-level list), or a Unix socket pathname enclosed in parentheses
8157 The database number is optional; if present that number is selected in the backend
8159 The password is optional; if present it is used to authenticate to the backend
8162 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
8163 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
8164 respectively, and the characters single-quote, double-quote, and backslash
8165 itself are escaped with backslashes.
8167 The &%quote_redis%& expansion operator
8168 escapes whitespace and backslash characters with a backslash.
8170 .section "Specifying the server in the query" "SECTspeserque"
8171 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
8172 it is possible to specify a list of servers with an individual query. This is
8173 done by appending a comma-separated option to the query type:
8175 &`,servers=`&&'server1:server2:server3:...'&
8177 Each item in the list may take one of two forms:
8179 If it contains no slashes it is assumed to be just a host name. The appropriate
8180 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
8181 of the same name, and the remaining parameters (database, user, password) are
8184 If it contains any slashes, it is taken as a complete parameter set.
8186 The list of servers is used in exactly the same way as the global list.
8187 Once a connection to a server has happened and a query has been
8188 successfully executed, processing of the lookup ceases.
8190 This feature is intended for use in master/slave situations where updates
8191 are occurring and you want to update the master rather than a slave. If the
8192 master is in the list as a backup for reading, you might have a global setting
8195 mysql_servers = slave1/db/name/pw:\
8199 In an updating lookup, you could then write:
8201 ${lookup mysql,servers=master {UPDATE ...} }
8203 That query would then be sent only to the master server. If, on the other hand,
8204 the master is not to be used for reading, and so is not present in the global
8205 option, you can still update it by a query of this form:
8207 ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
8210 An older syntax places the servers specification before the query,
8211 semicolon separated:
8213 ${lookup mysql{servers=master; UPDATE ...} }
8215 The new version avoids potential issues with tainted
8216 arguments in the query, for explicit expansion.
8217 &*Note*&: server specifications in list-style lookups are still problematic.
8220 .section "Special MySQL features" "SECID73"
8221 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
8222 causes a connection to the server on the local host by means of a Unix domain
8223 socket. An alternate socket can be specified in parentheses.
8224 An option group name for MySQL option files can be specified in square brackets;
8225 the default value is &"exim"&.
8226 The full syntax of each item in &%mysql_servers%& is:
8228 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
8229 <&'database'&>/<&'user'&>/<&'password'&>
8231 Any of the four sub-parts of the first field can be omitted. For normal use on
8232 the local host it can be left blank or set to just &"localhost"&.
8234 No database need be supplied &-- but if it is absent here, it must be given in
8237 If a MySQL query is issued that does not request any data (an insert, update,
8238 or delete command), the result of the lookup is the number of rows affected.
8240 &*Warning*&: This can be misleading. If an update does not actually change
8241 anything (for example, setting a field to the value it already has), the result
8242 is zero because no rows are affected.
8245 .section "Special PostgreSQL features" "SECID74"
8246 PostgreSQL lookups can also use Unix domain socket connections to the database.
8247 This is usually faster and costs less CPU time than a TCP/IP connection.
8248 However it can be used only if the mail server runs on the same machine as the
8249 database server. A configuration line for PostgreSQL via Unix domain sockets
8252 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
8254 In other words, instead of supplying a host name, a path to the socket is
8255 given. The path name is enclosed in parentheses so that its slashes aren't
8256 visually confused with the delimiters for the other server parameters.
8258 If a PostgreSQL query is issued that does not request any data (an insert,
8259 update, or delete command), the result of the lookup is the number of rows
8262 .section "More about SQLite" "SECTsqlite"
8263 .cindex "lookup" "SQLite"
8264 .cindex "sqlite lookup type"
8265 SQLite is different to the other SQL lookups because a filename is required in
8266 addition to the SQL query. An SQLite database is a single file, and there is no
8267 daemon as in the other SQL databases.
8270 .oindex &%sqlite_dbfile%&
8271 There are two ways of
8272 specifying the file.
8273 The first is is by using the &%sqlite_dbfile%& main option.
8274 The second, which allows separate files for each query,
8275 is to use an option appended, comma-separated, to the &"sqlite"&
8276 lookup type word. The option is the word &"file"&, then an equals,
8278 The filename in this case cannot contain whitespace or open-brace charachters.
8281 A deprecated method is available, prefixing the query with the filename
8282 separated by white space.
8284 .cindex "tainted data" "sqlite file"
8285 the query cannot use any tainted values, as that taints
8286 the entire query including the filename - resulting in a refusal to open
8289 In all the above cases the filename must be an absolute path.
8291 Here is a lookup expansion example:
8293 sqlite_dbfile = /some/thing/sqlitedb
8295 ${lookup sqlite {select name from aliases where id='userx';}}
8297 In a list, the syntax is similar. For example:
8299 domainlist relay_to_domains = sqlite;\
8300 select * from relays where ip='$sender_host_address';
8302 The only character affected by the &%quote_sqlite%& operator is a single
8303 quote, which it doubles.
8305 .cindex timeout SQLite
8306 .cindex sqlite "lookup timeout"
8307 The SQLite library handles multiple simultaneous accesses to the database
8308 internally. Multiple readers are permitted, but only one process can
8309 update at once. Attempts to access the database while it is being updated
8310 are rejected after a timeout period, during which the SQLite library
8311 waits for the lock to be released. In Exim, the default timeout is set
8312 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
8315 .section "More about Redis" "SECTredis"
8316 .cindex "lookup" "Redis"
8317 .cindex "redis lookup type"
8318 Redis is a non-SQL database. Commands are simple get and set.
8321 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
8322 ${lookup redis{get keyname}}
8325 As of release 4.91, "lightweight" support for Redis Cluster is available.
8326 Requires &%redis_servers%& list to contain all the servers in the cluster, all
8327 of which must be reachable from the running exim instance. If the cluster has
8328 master/slave replication, the list must contain all the master and slave
8331 When the Redis Cluster returns a "MOVED" response to a query, Exim does not
8332 immediately follow the redirection but treats the response as a DEFER, moving on
8333 to the next server in the &%redis_servers%& list until the correct server is
8340 . ////////////////////////////////////////////////////////////////////////////
8341 . ////////////////////////////////////////////////////////////////////////////
8343 .chapter "Domain, host, address, and local part lists" &&&
8344 "CHAPdomhosaddlists" &&&
8345 "Domain, host, and address lists"
8346 .scindex IIDdohoadli "lists of domains; hosts; etc."
8347 A number of Exim configuration options contain lists of domains, hosts,
8348 email addresses, or local parts. For example, the &%hold_domains%& option
8349 contains a list of domains whose delivery is currently suspended. These lists
8350 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
8351 arguments to expansion conditions such as &%match_domain%&.
8353 Each item in one of these lists is a pattern to be matched against a domain,
8354 host, email address, or local part, respectively. In the sections below, the
8355 different types of pattern for each case are described, but first we cover some
8356 general facilities that apply to all four kinds of list.
8358 Note that other parts of Exim use a &'string list'& which does not
8359 support all the complexity available in
8360 domain, host, address and local part lists.
8364 .section "Expansion of lists" "SECTlistexpand"
8365 .cindex "expansion" "of lists"
8366 Each list is expanded as a single string before it is used.
8368 &'Exception: the router headers_remove option, where list-item
8369 splitting is done before string-expansion.'&
8372 expansion must be a list, possibly containing empty items, which is split up
8373 into separate items for matching. By default, colon is the separator character,
8374 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
8375 &<<SECTempitelis>>& for details of the list syntax; the second of these
8376 discusses the way to specify empty list items.
8379 If the string expansion is forced to fail, Exim behaves as if the item it is
8380 testing (domain, host, address, or local part) is not in the list. Other
8381 expansion failures cause temporary errors.
8383 If an item in a list is a regular expression, backslashes, dollars and possibly
8384 other special characters in the expression must be protected against
8385 misinterpretation by the string expander. The easiest way to do this is to use
8386 the &`\N`& expansion feature to indicate that the contents of the regular
8387 expression should not be expanded. For example, in an ACL you might have:
8389 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
8390 ${lookup{$domain}lsearch{/badsenders/bydomain}}
8392 The first item is a regular expression that is protected from expansion by
8393 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
8394 senders based on the receiving domain.
8399 .section "Negated items in lists" "SECID76"
8400 .cindex "list" "negation"
8401 .cindex "negation" "in lists"
8402 Items in a list may be positive or negative. Negative items are indicated by a
8403 leading exclamation mark, which may be followed by optional white space. A list
8404 defines a set of items (domains, etc). When Exim processes one of these lists,
8405 it is trying to find out whether a domain, host, address, or local part
8406 (respectively) is in the set that is defined by the list. It works like this:
8408 The list is scanned from left to right. If a positive item is matched, the
8409 subject that is being checked is in the set; if a negative item is matched, the
8410 subject is not in the set. If the end of the list is reached without the
8411 subject having matched any of the patterns, it is in the set if the last item
8412 was a negative one, but not if it was a positive one. For example, the list in
8414 domainlist relay_to_domains = !a.b.c : *.b.c
8416 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
8417 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
8418 list is positive. However, if the setting were
8420 domainlist relay_to_domains = !a.b.c
8422 then all domains other than &'a.b.c'& would match because the last item in the
8423 list is negative. In other words, a list that ends with a negative item behaves
8424 as if it had an extra item &`:*`& on the end.
8426 Another way of thinking about positive and negative items in lists is to read
8427 the connector as &"or"& after a positive item and as &"and"& after a negative
8432 .section "File names in lists" "SECTfilnamlis"
8433 .cindex "list" "filename in"
8434 If an item in a domain, host, address, or local part list is an absolute
8435 filename (beginning with a slash character), each line of the file is read and
8436 processed as if it were an independent item in the list, except that further
8437 filenames are not allowed,
8438 and no expansion of the data from the file takes place.
8439 Empty lines in the file are ignored, and the file may also contain comment
8443 For domain and host lists, if a # character appears anywhere in a line of the
8444 file, it and all following characters are ignored.
8446 Because local parts may legitimately contain # characters, a comment in an
8447 address list or local part list file is recognized only if # is preceded by
8448 white space or the start of the line. For example:
8450 not#comment@x.y.z # but this is a comment
8454 Putting a filename in a list has the same effect as inserting each line of the
8455 file as an item in the list (blank lines and comments excepted). However, there
8456 is one important difference: the file is read each time the list is processed,
8457 so if its contents vary over time, Exim's behaviour changes.
8459 If a filename is preceded by an exclamation mark, the sense of any match
8460 within the file is inverted. For example, if
8462 hold_domains = !/etc/nohold-domains
8464 and the file contains the lines
8469 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
8470 any domain matching &`*.b.c`& is not.
8474 .section "An lsearch file is not an out-of-line list" "SECID77"
8475 As will be described in the sections that follow, lookups can be used in lists
8476 to provide indexed methods of checking list membership. There has been some
8477 confusion about the way &(lsearch)& lookups work in lists. Because
8478 an &(lsearch)& file contains plain text and is scanned sequentially, it is
8479 sometimes thought that it is allowed to contain wild cards and other kinds of
8480 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
8481 always fixed strings, just as for any other single-key lookup type.
8483 If you want to use a file to contain wild-card patterns that form part of a
8484 list, just give the filename on its own, without a search type, as described
8485 in the previous section. You could also use the &(wildlsearch)& or
8486 &(nwildlsearch)&, but there is no advantage in doing this.
8491 .section "Results of list checking" SECTlistresults
8492 The primary result of doing a list check is a truth value.
8493 In some contexts additional information is stored
8494 about the list element that matched:
8497 A &%hosts%& ACL condition
8498 will store a result in the &$host_data$& variable.
8500 A &%local_parts%& router option or &%local_parts%& ACL condition
8501 will store a result in the &$local_part_data$& variable.
8504 A &%domains%& router option or &%domains%& ACL condition
8505 will store a result in the &$domain_data$& variable
8508 A &%senders%& router option or &%senders%& ACL condition
8509 will store a result in the &$sender_data$& variable.
8511 A &%recipients%& ACL condition
8512 will store a result in the &$recipient_data$& variable.
8515 The detail of the additional information depends on the
8516 type of match and is given below as the &*value*& information.
8521 .section "Named lists" "SECTnamedlists"
8522 .cindex "named lists"
8523 .cindex "list" "named"
8524 A list of domains, hosts, email addresses, or local parts can be given a name
8525 which is then used to refer to the list elsewhere in the configuration. This is
8526 particularly convenient if the same list is required in several different
8527 places. It also allows lists to be given meaningful names, which can improve
8528 the readability of the configuration. For example, it is conventional to define
8529 a domain list called &'local_domains'& for all the domains that are handled
8530 locally on a host, using a configuration line such as
8532 domainlist local_domains = localhost:my.dom.example
8534 Named lists are referenced by giving their name preceded by a plus sign, so,
8535 for example, a router that is intended to handle local domains would be
8536 configured with the line
8538 domains = +local_domains
8540 The first router in a configuration is often one that handles all domains
8541 except the local ones, using a configuration with a negated item like this:
8545 domains = ! +local_domains
8546 transport = remote_smtp
8549 The four kinds of named list are created by configuration lines starting with
8550 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8551 respectively. Then there follows the name that you are defining, followed by an
8552 equals sign and the list itself. For example:
8554 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8555 addresslist bad_senders = cdb;/etc/badsenders
8557 A named list may refer to other named lists:
8559 domainlist dom1 = first.example : second.example
8560 domainlist dom2 = +dom1 : third.example
8561 domainlist dom3 = fourth.example : +dom2 : fifth.example
8563 &*Warning*&: If the last item in a referenced list is a negative one, the
8564 effect may not be what you intended, because the negation does not propagate
8565 out to the higher level. For example, consider:
8567 domainlist dom1 = !a.b
8568 domainlist dom2 = +dom1 : *.b
8570 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8571 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8572 means it matches the second list as well. The effect is not the same as
8574 domainlist dom2 = !a.b : *.b
8576 where &'x.y'& does not match. It's best to avoid negation altogether in
8577 referenced lists if you can.
8579 .cindex "hiding named list values"
8580 .cindex "named lists" "hiding value of"
8581 Some named list definitions may contain sensitive data, for example, passwords for
8582 accessing databases. To stop non-admin users from using the &%-bP%& command
8583 line option to read these values, you can precede the definition with the
8584 word &"hide"&. For example:
8586 hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
8590 Named lists may have a performance advantage. When Exim is routing an
8591 address or checking an incoming message, it caches the result of tests on named
8592 lists. So, if you have a setting such as
8594 domains = +local_domains
8596 on several of your routers
8597 or in several ACL statements,
8598 the actual test is done only for the first one. However, the caching works only
8599 if there are no expansions within the list itself or any sublists that it
8600 references. In other words, caching happens only for lists that are known to be
8601 the same each time they are referenced.
8603 By default, there may be up to 16 named lists of each type. This limit can be
8604 extended by changing a compile-time variable. The use of domain and host lists
8605 is recommended for concepts such as local domains, relay domains, and relay
8606 hosts. The default configuration is set up like this.
8610 .section "Named lists compared with macros" "SECID78"
8611 .cindex "list" "named compared with macro"
8612 .cindex "macro" "compared with named list"
8613 At first sight, named lists might seem to be no different from macros in the
8614 configuration file. However, macros are just textual substitutions. If you
8617 ALIST = host1 : host2
8618 auth_advertise_hosts = !ALIST
8620 it probably won't do what you want, because that is exactly the same as
8622 auth_advertise_hosts = !host1 : host2
8624 Notice that the second host name is not negated. However, if you use a host
8627 hostlist alist = host1 : host2
8628 auth_advertise_hosts = ! +alist
8630 the negation applies to the whole list, and so that is equivalent to
8632 auth_advertise_hosts = !host1 : !host2
8636 .section "Named list caching" "SECID79"
8637 .cindex "list" "caching of named"
8638 .cindex "caching" "named lists"
8639 While processing a message, Exim caches the result of checking a named list if
8640 it is sure that the list is the same each time. In practice, this means that
8641 the cache operates only if the list contains no $ characters, which guarantees
8642 that it will not change when it is expanded. Sometimes, however, you may have
8643 an expanded list that you know will be the same each time within a given
8644 message. For example:
8646 domainlist special_domains = \
8647 ${lookup{$sender_host_address}cdb{/some/file}}
8649 This provides a list of domains that depends only on the sending host's IP
8650 address. If this domain list is referenced a number of times (for example,
8651 in several ACL lines, or in several routers) the result of the check is not
8652 cached by default, because Exim does not know that it is going to be the
8653 same list each time.
8655 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8656 cache the result anyway. For example:
8658 domainlist_cache special_domains = ${lookup{...
8660 If you do this, you should be absolutely sure that caching is going to do
8661 the right thing in all cases. When in doubt, leave it out.
8665 .section "Domain lists" "SECTdomainlist"
8666 .cindex "domain list" "patterns for"
8667 .cindex "list" "domain list"
8668 Domain lists contain patterns that are to be matched against a mail domain.
8669 The following types of item may appear in domain lists:
8672 .cindex "primary host name"
8673 .cindex "host name" "matched in domain list"
8674 .oindex "&%primary_hostname%&"
8675 .cindex "domain list" "matching primary host name"
8676 .cindex "@ in a domain list"
8677 If a pattern consists of a single @ character, it matches the local host name,
8678 as set by the &%primary_hostname%& option (or defaulted). This makes it
8679 possible to use the same configuration file on several different hosts that
8680 differ only in their names.
8682 The value for a match will be the primary host name.
8686 .cindex "@[] in a domain list"
8687 .cindex "domain list" "matching local IP interfaces"
8688 .cindex "domain literal"
8689 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8690 in square brackets (as in an email address that contains a domain literal), but
8691 only if that IP address is recognized as local for email routing purposes. The
8692 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8693 control which of a host's several IP addresses are treated as local.
8694 In today's Internet, the use of domain literals is controversial;
8695 see the &%allow_domain_literals%& main option.
8697 The value for a match will be the string &`@[]`&.
8702 .cindex "@mx_primary"
8703 .cindex "@mx_secondary"
8704 .cindex "domain list" "matching MX pointers to local host"
8705 If a pattern consists of the string &`@mx_any`& it matches any domain that
8706 has an MX record pointing to the local host or to any host that is listed in
8707 .oindex "&%hosts_treat_as_local%&"
8708 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8709 are similar, except that the first matches only when a primary MX target is the
8710 local host, and the second only when no primary MX target is the local host,
8711 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8712 preference value &-- there may of course be more than one of them.
8714 The MX lookup that takes place when matching a pattern of this type is
8715 performed with the resolver options for widening names turned off. Thus, for
8716 example, a single-component domain will &'not'& be expanded by adding the
8717 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8718 options of the &(dnslookup)& router for a discussion of domain widening.
8720 Sometimes you may want to ignore certain IP addresses when using one of these
8721 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8722 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8723 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8724 on a router). For example:
8726 domains = @mx_any/ignore=127.0.0.1
8728 This example matches any domain that has an MX record pointing to one of
8729 the local host's IP addresses other than 127.0.0.1.
8731 The list of IP addresses is in fact processed by the same code that processes
8732 host lists, so it may contain CIDR-coded network specifications and it may also
8733 contain negative items.
8735 Because the list of IP addresses is a sublist within a domain list, you have to
8736 be careful about delimiters if there is more than one address. Like any other
8737 list, the default delimiter can be changed. Thus, you might have:
8739 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8740 an.other.domain : ...
8742 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8743 involved, it is easiest to change the delimiter for the main list as well:
8745 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8746 an.other.domain ? ...
8748 The value for a match will be the list element string (starting &`@mx_`&).
8752 .cindex "asterisk" "in domain list"
8753 .cindex "domain list" "asterisk in"
8754 .cindex "domain list" "matching &""ends with""&"
8755 If a pattern starts with an asterisk, the remaining characters of the pattern
8756 are compared with the terminating characters of the domain. The use of &"*"& in
8757 domain lists differs from its use in partial matching lookups. In a domain
8758 list, the character following the asterisk need not be a dot, whereas partial
8759 matching works only in terms of dot-separated components. For example, a domain
8760 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8763 The value for a match will be the list element string (starting with the asterisk).
8764 Additionally, &$0$& will be set to the matched string
8765 and &$1$& to the variable portion which the asterisk matched.
8768 .cindex "regular expressions" "in domain list"
8769 .cindex "domain list" "matching regular expression"
8770 If a pattern starts with a circumflex character, it is treated as a regular
8771 expression, and matched against the domain using a regular expression matching
8772 function. The circumflex is treated as part of the regular expression.
8773 Email domains are case-independent, so this regular expression match is by
8774 default case-independent, but you can make it case-dependent by starting it
8775 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8776 are given in chapter &<<CHAPregexp>>&.
8778 &*Warning*&: Because domain lists are expanded before being processed, you
8779 must escape any backslash and dollar characters in the regular expression, or
8780 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8781 it is not to be expanded (unless you really do want to build a regular
8782 expression by expansion, of course).
8784 The value for a match will be the list element string (starting with the circumflex).
8785 Additionally, &$0$& will be set to the string matching the regular expression,
8786 and &$1$& (onwards) to any submatches identified by parentheses.
8791 .cindex "lookup" "in domain list"
8792 .cindex "domain list" "matching by lookup"
8793 If a pattern starts with the name of a single-key lookup type followed by a
8794 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8795 must be a filename in a suitable format for the lookup type. For example, for
8796 &"cdb;"& it must be an absolute path:
8798 domains = cdb;/etc/mail/local_domains.cdb
8800 The appropriate type of lookup is done on the file using the domain name as the
8801 key. In most cases, the value resulting from the lookup is not used; Exim is interested
8802 only in whether or not the key is present in the file. However, when a lookup
8803 is used for the &%domains%& option on a router
8804 or a &%domains%& condition in an ACL statement, the value is preserved in the
8805 &$domain_data$& variable and can be referred to in other router options or
8806 other statements in the same ACL.
8807 .cindex "tainted data" "de-tainting"
8808 The value will be untainted.
8811 &*Note*&: If the data result of the lookup (as opposed to the key)
8812 is empty, then this empty value is stored in &$domain_data$&.
8813 The option to return the key for the lookup, as the value,
8814 may be what is wanted.
8819 Any of the single-key lookup type names may be preceded by
8820 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8822 domains = partial-dbm;/partial/domains
8824 This causes partial matching logic to be invoked; a description of how this
8825 works is given in section &<<SECTpartiallookup>>&.
8828 .cindex "asterisk" "in lookup type"
8829 Any of the single-key lookup types may be followed by an asterisk. This causes
8830 a default lookup for a key consisting of a single asterisk to be done if the
8831 original lookup fails. This is not a useful feature when using a domain list to
8832 select particular domains (because any domain would match), but it might have
8833 value if the result of the lookup is being used via the &$domain_data$&
8837 If the pattern starts with the name of a query-style lookup type followed by a
8838 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8839 pattern must be an appropriate query for the lookup type, as described in
8840 chapter &<<CHAPfdlookup>>&. For example:
8842 hold_domains = mysql;select domain from holdlist \
8843 where domain = '${quote_mysql:$domain}';
8845 In most cases, the value resulting from the lookup is not used (so for an SQL query, for
8846 example, it doesn't matter what field you select). Exim is interested only in
8847 whether or not the query succeeds. However, when a lookup is used for the
8848 &%domains%& option on a router, the value is preserved in the &$domain_data$&
8849 variable and can be referred to in other options.
8850 .cindex "tainted data" "de-tainting"
8851 The value will be untainted.
8854 If the pattern starts with the name of a lookup type
8855 of either kind (single-key or query-style) it may be
8856 followed by a comma and options,
8857 The options are lookup-type specific and consist of a comma-separated list.
8858 Each item starts with a tag and and equals "=".
8861 .cindex "domain list" "matching literal domain name"
8862 If none of the above cases apply, a caseless textual comparison is made
8863 between the pattern and the domain.
8865 The value for a match will be the list element string.
8866 .cindex "tainted data" "de-tainting"
8867 Note that this is commonly untainted
8868 (depending on the way the list was created).
8869 Specifically, explicit text in the configuration file in not tainted.
8870 This is a useful way of obtaining an untainted equivalent to
8871 the domain, for later operations.
8873 However if the list (including one-element lists)
8874 is created by expanding a variable containing tainted data,
8875 it is tainted and so will the match value be.
8879 Here is an example that uses several different kinds of pattern:
8881 domainlist funny_domains = \
8884 *.foundation.fict.example : \
8885 \N^[1-2]\d{3}\.fict\.example$\N : \
8886 partial-dbm;/opt/data/penguin/book : \
8887 nis;domains.byname : \
8888 nisplus;[name=$domain,status=local],domains.org_dir
8890 There are obvious processing trade-offs among the various matching modes. Using
8891 an asterisk is faster than a regular expression, and listing a few names
8892 explicitly probably is too. The use of a file or database lookup is expensive,
8893 but may be the only option if hundreds of names are required. Because the
8894 patterns are tested in order, it makes sense to put the most commonly matched
8899 .section "Host lists" "SECThostlist"
8900 .cindex "host list" "patterns in"
8901 .cindex "list" "host list"
8902 Host lists are used to control what remote hosts are allowed to do. For
8903 example, some hosts may be allowed to use the local host as a relay, and some
8904 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8905 two different ways, by name or by IP address. In a host list, some types of
8906 pattern are matched to a host name, and some are matched to an IP address.
8907 You need to be particularly careful with this when single-key lookups are
8908 involved, to ensure that the right value is being used as the key.
8911 .section "Special host list patterns" "SECID80"
8912 .cindex "empty item in hosts list"
8913 .cindex "host list" "empty string in"
8914 If a host list item is the empty string, it matches only when no remote host is
8915 involved. This is the case when a message is being received from a local
8916 process using SMTP on the standard input, that is, when a TCP/IP connection is
8919 .cindex "asterisk" "in host list"
8920 The special pattern &"*"& in a host list matches any host or no host. Neither
8921 the IP address nor the name is actually inspected.
8925 .section "Host list patterns that match by IP address" "SECThoslispatip"
8926 .cindex "host list" "matching IP addresses"
8927 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8928 the incoming address actually appears in the IPv6 host as
8929 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8930 list, it is converted into a traditional IPv4 address first. (Not all operating
8931 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8934 The following types of pattern in a host list check the remote host by
8935 inspecting its IP address:
8938 If the pattern is a plain domain name (not a regular expression, not starting
8939 with *, not a lookup of any kind), Exim calls the operating system function
8940 to find the associated IP address(es). Exim uses the newer
8941 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8942 This typically causes a forward DNS lookup of the name. The result is compared
8943 with the IP address of the subject host.
8945 If there is a temporary problem (such as a DNS timeout) with the host name
8946 lookup, a temporary error occurs. For example, if the list is being used in an
8947 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8948 temporary SMTP error code. If no IP address can be found for the host name,
8949 what happens is described in section &<<SECTbehipnot>>& below.
8952 .cindex "@ in a host list"
8953 If the pattern is &"@"&, the primary host name is substituted and used as a
8954 domain name, as just described.
8957 If the pattern is an IP address, it is matched against the IP address of the
8958 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8959 IPv6 addresses can be given in colon-separated format, but the colons have to
8960 be doubled so as not to be taken as item separators when the default list
8961 separator is used. IPv6 addresses are recognized even when Exim is compiled
8962 without IPv6 support. This means that if they appear in a host list on an
8963 IPv4-only host, Exim will not treat them as host names. They are just addresses
8964 that can never match a client host.
8967 .cindex "@[] in a host list"
8968 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8969 the local host. For example, if the local host is an IPv4 host with one
8970 interface address 10.45.23.56, these two ACL statements have the same effect:
8972 accept hosts = 127.0.0.1 : 10.45.23.56
8976 .cindex "CIDR notation"
8977 If the pattern is an IP address followed by a slash and a mask length (for
8978 example 10.11.42.0/24), it is matched against the IP address of the subject
8979 host under the given mask. This allows, an entire network of hosts to be
8980 included (or excluded) by a single item. The mask uses CIDR notation; it
8981 specifies the number of address bits that must match, starting from the most
8982 significant end of the address.
8984 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8985 of a range of addresses. It is the number of bits in the network portion of the
8986 address. The above example specifies a 24-bit netmask, so it matches all 256
8987 addresses in the 10.11.42.0 network. An item such as
8991 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8992 32 for an IPv4 address is the same as no mask at all; just a single address
8995 Here is another example which shows an IPv4 and an IPv6 network:
8997 recipient_unqualified_hosts = 192.168.0.0/16: \
8998 3ffe::ffff::836f::::/48
9000 The doubling of list separator characters applies only when these items
9001 appear inline in a host list. It is not required when indirecting via a file.
9004 recipient_unqualified_hosts = /opt/exim/unqualnets
9006 could make use of a file containing
9011 to have exactly the same effect as the previous example. When listing IPv6
9012 addresses inline, it is usually more convenient to use the facility for
9013 changing separator characters. This list contains the same two networks:
9015 recipient_unqualified_hosts = <; 172.16.0.0/12; \
9018 The separator is changed to semicolon by the leading &"<;"& at the start of the
9024 .section "Host list patterns for single-key lookups by host address" &&&
9025 "SECThoslispatsikey"
9026 .cindex "host list" "lookup of IP address"
9027 When a host is to be identified by a single-key lookup of its complete IP
9028 address, the pattern takes this form:
9030 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
9034 hosts_lookup = net-cdb;/hosts-by-ip.db
9036 The text form of the IP address of the subject host is used as the lookup key.
9037 IPv6 addresses are converted to an unabbreviated form, using lower case
9038 letters, with dots as separators because colon is the key terminator in
9039 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
9040 quoting the keys, but this is a facility that was added later.] The data
9041 returned by the lookup is not used.
9043 .cindex "IP address" "masking"
9044 .cindex "host list" "masked IP address"
9045 Single-key lookups can also be performed using masked IP addresses, using
9046 patterns of this form:
9048 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
9052 net24-dbm;/networks.db
9054 The IP address of the subject host is masked using <&'number'&> as the mask
9055 length. A textual string is constructed from the masked value, followed by the
9056 mask, and this is used as the lookup key. For example, if the host's IP address
9057 is 192.168.34.6, the key that is looked up for the above example is
9058 &"192.168.34.0/24"&.
9060 When an IPv6 address is converted to a string, dots are normally used instead
9061 of colons, so that keys in &(lsearch)& files need not contain colons (which
9062 terminate &(lsearch)& keys). This was implemented some time before the ability
9063 to quote keys was made available in &(lsearch)& files. However, the more
9064 recently implemented &(iplsearch)& files do require colons in IPv6 keys
9065 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
9066 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
9067 converted using colons and not dots.
9068 In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
9069 addresses are always used.
9070 The latter are converted to IPv4 addresses, in dotted-quad form.
9072 Ideally, it would be nice to tidy up this anomalous situation by changing to
9073 colons in all cases, given that quoting is now available for &(lsearch)&.
9074 However, this would be an incompatible change that might break some existing
9077 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
9078 IPv6 address) is not the same as specifying just &%net-%& without a number. In
9079 the former case the key strings include the mask value, whereas in the latter
9080 case the IP address is used on its own.
9084 .section "Host list patterns that match by host name" "SECThoslispatnam"
9085 .cindex "host" "lookup failures"
9086 .cindex "unknown host name"
9087 .cindex "host list" "matching host name"
9088 There are several types of pattern that require Exim to know the name of the
9089 remote host. These are either wildcard patterns or lookups by name. (If a
9090 complete hostname is given without any wildcarding, it is used to find an IP
9091 address to match against, as described in section &<<SECThoslispatip>>&
9094 If the remote host name is not already known when Exim encounters one of these
9095 patterns, it has to be found from the IP address.
9096 Although many sites on the Internet are conscientious about maintaining reverse
9097 DNS data for their hosts, there are also many that do not do this.
9098 Consequently, a name cannot always be found, and this may lead to unwanted
9099 effects. Take care when configuring host lists with wildcarded name patterns.
9100 Consider what will happen if a name cannot be found.
9102 Because of the problems of determining host names from IP addresses, matching
9103 against host names is not as common as matching against IP addresses.
9105 By default, in order to find a host name, Exim first does a reverse DNS lookup;
9106 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
9107 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
9108 are done can be changed by setting the &%host_lookup_order%& option. For
9109 security, once Exim has found one or more names, it looks up the IP addresses
9110 for these names and compares them with the IP address that it started with.
9111 Only those names whose IP addresses match are accepted. Any other names are
9112 discarded. If no names are left, Exim behaves as if the host name cannot be
9113 found. In the most common case there is only one name and one IP address.
9115 There are some options that control what happens if a host name cannot be
9116 found. These are described in section &<<SECTbehipnot>>& below.
9118 .cindex "host" "alias for"
9119 .cindex "alias for host"
9120 As a result of aliasing, hosts may have more than one name. When processing any
9121 of the following types of pattern, all the host's names are checked:
9124 .cindex "asterisk" "in host list"
9125 If a pattern starts with &"*"& the remainder of the item must match the end of
9126 the host name. For example, &`*.b.c`& matches all hosts whose names end in
9127 &'.b.c'&. This special simple form is provided because this is a very common
9128 requirement. Other kinds of wildcarding require the use of a regular
9131 .cindex "regular expressions" "in host list"
9132 .cindex "host list" "regular expression in"
9133 If the item starts with &"^"& it is taken to be a regular expression which is
9134 matched against the host name. Host names are case-independent, so this regular
9135 expression match is by default case-independent, but you can make it
9136 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
9137 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
9142 is a regular expression that matches either of the two hosts &'a.c.d'& or
9143 &'b.c.d'&. When a regular expression is used in a host list, you must take care
9144 that backslash and dollar characters are not misinterpreted as part of the
9145 string expansion. The simplest way to do this is to use &`\N`& to mark that
9146 part of the string as non-expandable. For example:
9148 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
9150 &*Warning*&: If you want to match a complete host name, you must include the
9151 &`$`& terminating metacharacter in the regular expression, as in the above
9152 example. Without it, a match at the start of the host name is all that is
9159 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
9160 .cindex "host" "lookup failures, permanent"
9161 While processing a host list, Exim may need to look up an IP address from a
9162 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
9163 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
9164 behaviour when it fails to find the information it is seeking is the same.
9166 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
9167 apply to temporary DNS errors, whose handling is described in the next section.
9169 .cindex "&`+include_unknown`&"
9170 .cindex "&`+ignore_unknown`&"
9171 Exim parses a host list from left to right. If it encounters a permanent
9172 lookup failure in any item in the host list before it has found a match,
9173 Exim treats it as a failure and the default behavior is as if the host
9174 does not match the list. This may not always be what you want to happen.
9175 To change Exim's behaviour, the special items &`+include_unknown`& or
9176 &`+ignore_unknown`& may appear in the list (at top level &-- they are
9177 not recognized in an indirected file).
9180 If any item that follows &`+include_unknown`& requires information that
9181 cannot found, Exim behaves as if the host does match the list. For example,
9183 host_reject_connection = +include_unknown:*.enemy.ex
9185 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
9186 any hosts whose name it cannot find.
9189 If any item that follows &`+ignore_unknown`& requires information that cannot
9190 be found, Exim ignores that item and proceeds to the rest of the list. For
9193 accept hosts = +ignore_unknown : friend.example : \
9196 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
9197 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
9198 name can be found for 192.168.4.5, it is rejected.
9201 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
9202 list. The effect of each one lasts until the next, or until the end of the
9205 .section "Mixing wildcarded host names and addresses in host lists" &&&
9207 .cindex "host list" "mixing names and addresses in"
9209 This section explains the host/ip processing logic with the same concepts
9210 as the previous section, but specifically addresses what happens when a
9211 wildcarded hostname is one of the items in the hostlist.
9214 If you have name lookups or wildcarded host names and
9215 IP addresses in the same host list, you should normally put the IP
9216 addresses first. For example, in an ACL you could have:
9218 accept hosts = 10.9.8.7 : *.friend.example
9220 The reason you normally would order it this way lies in the
9221 left-to-right way that Exim processes lists. It can test IP addresses
9222 without doing any DNS lookups, but when it reaches an item that requires
9223 a host name, it fails if it cannot find a host name to compare with the
9224 pattern. If the above list is given in the opposite order, the
9225 &%accept%& statement fails for a host whose name cannot be found, even
9226 if its IP address is 10.9.8.7.
9229 If you really do want to do the name check first, and still recognize the IP
9230 address, you can rewrite the ACL like this:
9232 accept hosts = *.friend.example
9233 accept hosts = 10.9.8.7
9235 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
9236 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
9237 &`+ignore_unknown`&, which was discussed in depth in the first example in
9242 .section "Temporary DNS errors when looking up host information" &&&
9244 .cindex "host" "lookup failures, temporary"
9245 .cindex "&`+include_defer`&"
9246 .cindex "&`+ignore_defer`&"
9247 A temporary DNS lookup failure normally causes a defer action (except when
9248 &%dns_again_means_nonexist%& converts it into a permanent error). However,
9249 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
9250 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
9251 section. These options should be used with care, probably only in non-critical
9252 host lists such as whitelists.
9256 .section "Host list patterns for single-key lookups by host name" &&&
9257 "SECThoslispatnamsk"
9258 .cindex "unknown host name"
9259 .cindex "host list" "matching host name"
9260 If a pattern is of the form
9262 <&'single-key-search-type'&>;<&'search-data'&>
9266 dbm;/host/accept/list
9268 a single-key lookup is performed, using the host name as its key. If the
9269 lookup succeeds, the host matches the item. The actual data that is looked up
9272 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
9273 keys in the file, not IP addresses. If you want to do lookups based on IP
9274 addresses, you must precede the search type with &"net-"& (see section
9275 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
9276 two items in the same list, one doing an address lookup and one doing a name
9277 lookup, both using the same file.
9281 .section "Host list patterns for query-style lookups" "SECID81"
9282 If a pattern is of the form
9284 <&'query-style-search-type'&>;<&'query'&>
9286 the query is obeyed, and if it succeeds, the host matches the item. The actual
9287 data that is looked up is not used. The variables &$sender_host_address$& and
9288 &$sender_host_name$& can be used in the query. For example:
9290 hosts_lookup = pgsql;\
9291 select ip from hostlist where ip='$sender_host_address'
9293 The value of &$sender_host_address$& for an IPv6 address contains colons. You
9294 can use the &%sg%& expansion item to change this if you need to. If you want to
9295 use masked IP addresses in database queries, you can use the &%mask%& expansion
9298 If the query contains a reference to &$sender_host_name$&, Exim automatically
9299 looks up the host name if it has not already done so. (See section
9300 &<<SECThoslispatnam>>& for comments on finding host names.)
9302 Historical note: prior to release 4.30, Exim would always attempt to find a
9303 host name before running the query, unless the search type was preceded by
9304 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
9305 still recognized for query-style lookups, but its presence or absence has no
9306 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
9307 See section &<<SECThoslispatsikey>>&.)
9313 .section "Address lists" "SECTaddresslist"
9314 .cindex "list" "address list"
9315 .cindex "address list" "empty item"
9316 .cindex "address list" "patterns"
9317 Address lists contain patterns that are matched against mail addresses. There
9318 is one special case to be considered: the sender address of a bounce message is
9319 always empty. You can test for this by providing an empty item in an address
9320 list. For example, you can set up a router to process bounce messages by
9321 using this option setting:
9325 The presence of the colon creates an empty item. If you do not provide any
9326 data, the list is empty and matches nothing. The empty sender can also be
9327 detected by a regular expression that matches an empty string,
9328 and by a query-style lookup that succeeds when &$sender_address$& is empty.
9330 Non-empty items in an address list can be straightforward email addresses. For
9333 senders = jbc@askone.example : hs@anacreon.example
9335 A certain amount of wildcarding is permitted. If a pattern contains an @
9336 character, but is not a regular expression and does not begin with a
9337 semicolon-terminated lookup type (described below), the local part of the
9338 subject address is compared with the local part of the pattern, which may start
9339 with an asterisk. If the local parts match, the domain is checked in exactly
9340 the same way as for a pattern in a domain list. For example, the domain can be
9341 wildcarded, refer to a named list, or be a lookup:
9343 deny senders = *@*.spamming.site:\
9344 *@+hostile_domains:\
9345 bozo@partial-lsearch;/list/of/dodgy/sites:\
9346 *@dbm;/bad/domains.db
9348 .cindex "local part" "starting with !"
9349 .cindex "address list" "local part starting with !"
9350 If a local part that begins with an exclamation mark is required, it has to be
9351 specified using a regular expression, because otherwise the exclamation mark is
9352 treated as a sign of negation, as is standard in lists.
9354 If a non-empty pattern that is not a regular expression or a lookup does not
9355 contain an @ character, it is matched against the domain part of the subject
9356 address. The only two formats that are recognized this way are a literal
9357 domain, or a domain pattern that starts with *. In both these cases, the effect
9358 is the same as if &`*@`& preceded the pattern. For example:
9360 deny senders = enemy.domain : *.enemy.domain
9363 The following kinds of more complicated address list pattern can match any
9364 address, including the empty address that is characteristic of bounce message
9368 .cindex "regular expressions" "in address list"
9369 .cindex "address list" "regular expression in"
9370 If (after expansion) a pattern starts with &"^"&, a regular expression match is
9371 done against the complete address, with the pattern as the regular expression.
9372 You must take care that backslash and dollar characters are not misinterpreted
9373 as part of the string expansion. The simplest way to do this is to use &`\N`&
9374 to mark that part of the string as non-expandable. For example:
9376 deny senders = \N^.*this.*@example\.com$\N : \
9377 \N^\d{8}.+@spamhaus.example$\N : ...
9379 The &`\N`& sequences are removed by the expansion, so these items do indeed
9380 start with &"^"& by the time they are being interpreted as address patterns.
9383 .cindex "address list" "lookup for complete address"
9384 Complete addresses can be looked up by using a pattern that starts with a
9385 lookup type terminated by a semicolon, followed by the data for the lookup. For
9388 deny senders = cdb;/etc/blocked.senders : \
9389 mysql;select address from blocked where \
9390 address='${quote_mysql:$sender_address}'
9392 Both query-style and single-key lookup types can be used. For a single-key
9393 lookup type, Exim uses the complete address as the key. However, empty keys are
9394 not supported for single-key lookups, so a match against the empty address
9395 always fails. This restriction does not apply to query-style lookups.
9397 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
9398 cannot be used, and is ignored if specified, with an entry being written to the
9400 .cindex "*@ with single-key lookup"
9401 However, you can configure lookup defaults, as described in section
9402 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
9403 default. For example, with this lookup:
9405 accept senders = lsearch*@;/some/file
9407 the file could contains lines like this:
9409 user1@domain1.example
9412 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
9415 nimrod@jaeger.example
9419 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
9420 would mean that every address matches, thus rendering the test useless.
9422 &*Warning 2*&: Do not confuse these two kinds of item:
9424 deny recipients = dbm*@;/some/file
9425 deny recipients = *@dbm;/some/file
9427 The first does a whole address lookup, with defaulting, as just described,
9428 because it starts with a lookup type. The second matches the local part and
9429 domain independently, as described in a bullet point below.
9433 The following kinds of address list pattern can match only non-empty addresses.
9434 If the subject address is empty, a match against any of these pattern types
9439 .cindex "@@ with single-key lookup"
9440 .cindex "address list" "@@ lookup type"
9441 .cindex "address list" "split local part and domain"
9442 If a pattern starts with &"@@"& followed by a single-key lookup item
9443 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
9444 split into a local part and a domain. The domain is looked up in the file. If
9445 it is not found, there is no match. If it is found, the data that is looked up
9446 from the file is treated as a colon-separated list of local part patterns, each
9447 of which is matched against the subject local part in turn.
9449 .cindex "asterisk" "in address list"
9450 The lookup may be a partial one, and/or one involving a search for a default
9451 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
9452 patterns that are looked up can be regular expressions or begin with &"*"&, or
9453 even be further lookups. They may also be independently negated. For example,
9456 deny senders = @@dbm;/etc/reject-by-domain
9458 the data from which the DBM file is built could contain lines like
9460 baddomain.com: !postmaster : *
9462 to reject all senders except &%postmaster%& from that domain.
9464 .cindex "local part" "starting with !"
9465 If a local part that actually begins with an exclamation mark is required, it
9466 has to be specified using a regular expression. In &(lsearch)& files, an entry
9467 may be split over several lines by indenting the second and subsequent lines,
9468 but the separating colon must still be included at line breaks. White space
9469 surrounding the colons is ignored. For example:
9471 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
9474 As in all colon-separated lists in Exim, a colon can be included in an item by
9477 If the last item in the list starts with a right angle-bracket, the remainder
9478 of the item is taken as a new key to look up in order to obtain a continuation
9479 list of local parts. The new key can be any sequence of characters. Thus one
9480 might have entries like
9482 aol.com: spammer1 : spammer 2 : >*
9483 xyz.com: spammer3 : >*
9486 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
9487 local parts for all domains, in addition to the specific local parts listed for
9488 each domain. Of course, using this feature costs another lookup each time a
9489 chain is followed, but the effort needed to maintain the data is reduced.
9491 .cindex "loop" "in lookups"
9492 It is possible to construct loops using this facility, and in order to catch
9493 them, the chains may be no more than fifty items long.
9496 The @@<&'lookup'&> style of item can also be used with a query-style
9497 lookup, but in this case, the chaining facility is not available. The lookup
9498 can only return a single list of local parts.
9501 &*Warning*&: There is an important difference between the address list items
9502 in these two examples:
9505 senders = *@+my_list
9507 In the first one, &`my_list`& is a named address list, whereas in the second
9508 example it is a named domain list.
9513 .section "Case of letters in address lists" "SECTcasletadd"
9514 .cindex "case of local parts"
9515 .cindex "address list" "case forcing"
9516 .cindex "case forcing in address lists"
9517 Domains in email addresses are always handled caselessly, but for local parts
9518 case may be significant on some systems (see &%caseful_local_part%& for how
9519 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
9520 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
9521 blocking lists should be done in a case-independent manner. Since most address
9522 lists in Exim are used for this kind of control, Exim attempts to do this by
9525 The domain portion of an address is always lowercased before matching it to an
9526 address list. The local part is lowercased by default, and any string
9527 comparisons that take place are done caselessly. This means that the data in
9528 the address list itself, in files included as plain filenames, and in any file
9529 that is looked up using the &"@@"& mechanism, can be in any case. However, the
9530 keys in files that are looked up by a search type other than &(lsearch)& (which
9531 works caselessly) must be in lower case, because these lookups are not
9534 .cindex "&`+caseful`&"
9535 To allow for the possibility of caseful address list matching, if an item in
9536 an address list is the string &"+caseful"&, the original case of the local
9537 part is restored for any comparisons that follow, and string comparisons are no
9538 longer case-independent. This does not affect the domain, which remains in
9539 lower case. However, although independent matches on the domain alone are still
9540 performed caselessly, regular expressions that match against an entire address
9541 become case-sensitive after &"+caseful"& has been seen.
9545 .section "Local part lists" "SECTlocparlis"
9546 .cindex "list" "local part list"
9547 .cindex "local part" "list"
9548 These behave in the same way as domain and host lists, with the following
9551 Case-sensitivity in local part lists is handled in the same way as for address
9552 lists, as just described. The &"+caseful"& item can be used if required. In a
9553 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
9554 set false, the subject is lowercased and the matching is initially
9555 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
9556 matching in the local part list, but not elsewhere in the router. If
9557 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
9558 option is case-sensitive from the start.
9560 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
9561 comments are handled in the same way as address lists &-- they are recognized
9562 only if the # is preceded by white space or the start of the line.
9563 Otherwise, local part lists are matched in the same way as domain lists, except
9564 that the special items that refer to the local host (&`@`&, &`@[]`&,
9565 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
9566 Refer to section &<<SECTdomainlist>>& for details of the other available item
9568 .ecindex IIDdohoadli
9573 . ////////////////////////////////////////////////////////////////////////////
9574 . ////////////////////////////////////////////////////////////////////////////
9576 .chapter "String expansions" "CHAPexpand"
9577 .scindex IIDstrexp "expansion" "of strings"
9578 Many strings in Exim's runtime configuration are expanded before use. Some of
9579 them are expanded every time they are used; others are expanded only once.
9581 When a string is being expanded it is copied verbatim from left to right except
9582 .cindex expansion "string concatenation"
9583 when a dollar or backslash character is encountered. A dollar specifies the
9584 start of a portion of the string that is interpreted and replaced as described
9585 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
9586 escape character, as described in the following section.
9588 Whether a string is expanded depends upon the context. Usually this is solely
9589 dependent upon the option for which a value is sought; in this documentation,
9590 options for which string expansion is performed are marked with † after
9591 the data type. ACL rules always expand strings. A couple of expansion
9592 conditions do not expand some of the brace-delimited branches, for security
9594 .cindex "tainted data" expansion
9595 .cindex "tainted data" definition
9596 .cindex expansion "tainted data"
9597 and expansion of data deriving from the sender (&"tainted data"&)
9599 is not permitted (including acessing a file using a tainted name).
9603 Common ways of obtaining untainted equivalents of variables with
9605 .cindex "tainted data" "de-tainting"
9606 come down to using the tainted value as a lookup key in a trusted database.
9607 This database could be the filesystem structure,
9608 or the password file,
9609 or accessed via a DBMS.
9610 Specific methods are indexed under &"de-tainting"&.
9615 .section "Literal text in expanded strings" "SECTlittext"
9616 .cindex "expansion" "including literal text"
9617 An uninterpreted dollar can be included in an expanded string by putting a
9618 backslash in front of it. A backslash can be used to prevent any special
9619 character being treated specially in an expansion, including backslash itself.
9620 If the string appears in quotes in the configuration file, two backslashes are
9621 required because the quotes themselves cause interpretation of backslashes when
9622 the string is read in (see section &<<SECTstrings>>&).
9624 .cindex "expansion" "non-expandable substrings"
9625 A portion of the string can specified as non-expandable by placing it between
9626 two occurrences of &`\N`&. This is particularly useful for protecting regular
9627 expressions, which often contain backslashes and dollar signs. For example:
9629 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
9631 On encountering the first &`\N`&, the expander copies subsequent characters
9632 without interpretation until it reaches the next &`\N`& or the end of the
9637 .section "Character escape sequences in expanded strings" "SECID82"
9638 .cindex "expansion" "escape sequences"
9639 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9640 expanded string is recognized as an escape sequence for the character newline,
9641 carriage return, or tab, respectively. A backslash followed by up to three
9642 octal digits is recognized as an octal encoding for a single character, and a
9643 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9646 These escape sequences are also recognized in quoted strings when they are read
9647 in. Their interpretation in expansions as well is useful for unquoted strings,
9648 and for other cases such as looked-up strings that are then expanded.
9651 .section "Testing string expansions" "SECID83"
9652 .cindex "expansion" "testing"
9653 .cindex "testing" "string expansion"
9655 Many expansions can be tested by calling Exim with the &%-be%& option. This
9656 takes the command arguments, or lines from the standard input if there are no
9657 arguments, runs them through the string expansion code, and writes the results
9658 to the standard output. Variables based on configuration values are set up, but
9659 since no message is being processed, variables such as &$local_part$& have no
9660 value. Nevertheless the &%-be%& option can be useful for checking out file and
9661 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9664 Exim gives up its root privilege when it is called with the &%-be%& option, and
9665 instead runs under the uid and gid it was called with, to prevent users from
9666 using &%-be%& for reading files to which they do not have access.
9669 If you want to test expansions that include variables whose values are taken
9670 from a message, there are two other options that can be used. The &%-bem%&
9671 option is like &%-be%& except that it is followed by a filename. The file is
9672 read as a message before doing the test expansions. For example:
9674 exim -bem /tmp/test.message '$h_subject:'
9676 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9677 Exim message identifier. For example:
9679 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9681 This loads the message from Exim's spool before doing the test expansions, and
9682 is therefore restricted to admin users.
9685 .section "Forced expansion failure" "SECTforexpfai"
9686 .cindex "expansion" "forced failure"
9687 A number of expansions that are described in the following section have
9688 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9689 (which are sometimes called &"curly brackets"&). Which of the two strings is
9690 used depends on some condition that is evaluated as part of the expansion. If,
9691 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9692 the entire string expansion fails in a way that can be detected by the code
9693 that requested the expansion. This is called &"forced expansion failure"&, and
9694 its consequences depend on the circumstances. In some cases it is no different
9695 from any other expansion failure, but in others a different action may be
9696 taken. Such variations are mentioned in the documentation of the option that is
9702 .section "Expansion items" "SECTexpansionitems"
9703 The following items are recognized in expanded strings. White space may be used
9704 between sub-items that are keywords or substrings enclosed in braces inside an
9705 outer set of braces, to improve readability. &*Warning*&: Within braces,
9706 white space is significant.
9709 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9710 .cindex "expansion" "variables"
9711 Substitute the contents of the named variable, for example:
9716 The second form can be used to separate the name from subsequent alphanumeric
9717 characters. This form (using braces) is available only for variables; it does
9718 &'not'& apply to message headers. The names of the variables are given in
9719 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9720 given, the expansion fails.
9722 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9723 .cindex "expansion" "operators"
9724 The string is first itself expanded, and then the operation specified by
9725 <&'op'&> is applied to it. For example:
9729 The string starts with the first character after the colon, which may be
9730 leading white space. A list of operators is given in section &<<SECTexpop>>&
9731 below. The operator notation is used for simple expansion items that have just
9732 one argument, because it reduces the number of braces and therefore makes the
9733 string easier to understand.
9735 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9736 This item inserts &"basic"& header lines. It is described with the &%header%&
9737 expansion item below.
9740 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9741 .cindex "expansion" "calling an acl"
9742 .cindex "&%acl%&" "call from expansion"
9743 The name and zero to nine argument strings are first expanded separately. The expanded
9744 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9745 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9746 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9747 and may use the variables; if another acl expansion is used the values
9748 are restored after it returns. If the ACL sets
9749 a value using a "message =" modifier and returns accept or deny, the value becomes
9750 the result of the expansion.
9751 If no message is set and the ACL returns accept or deny
9752 the expansion result is an empty string.
9753 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9756 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
9757 .cindex authentication "results header"
9758 .chindex Authentication-Results:
9759 .cindex authentication "expansion item"
9760 This item returns a string suitable for insertion as an
9761 &'Authentication-Results:'&
9763 The given <&'authserv-id'&> is included in the result; typically this
9764 will be a domain name identifying the system performing the authentications.
9765 Methods that might be present in the result include:
9774 Example use (as an ACL modifier):
9776 add_header = :at_start:${authresults {$primary_hostname}}
9778 This is safe even if no authentication results are available.
9781 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9782 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9783 .cindex "expansion" "extracting certificate fields"
9784 .cindex "&%certextract%&" "certificate fields"
9785 .cindex "certificate" "extracting fields"
9786 The <&'certificate'&> must be a variable of type certificate.
9787 The field name is expanded and used to retrieve the relevant field from
9788 the certificate. Supported fields are:
9792 &`subject `& RFC4514 DN
9793 &`issuer `& RFC4514 DN
9798 &`subj_altname `& tagged list
9802 If the field is found,
9803 <&'string2'&> is expanded, and replaces the whole item;
9804 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9805 variable &$value$& contains the value that has been extracted. Afterwards, it
9806 is restored to any previous value it might have had.
9808 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9809 key is not found. If {<&'string2'&>} is also omitted, the value that was
9812 Some field names take optional modifiers, appended and separated by commas.
9814 The field selectors marked as "RFC4514" above
9815 output a Distinguished Name string which is
9817 parseable by Exim as a comma-separated tagged list
9818 (the exceptions being elements containing commas).
9819 RDN elements of a single type may be selected by
9820 a modifier of the type label; if so the expansion
9821 result is a list (newline-separated by default).
9822 The separator may be changed by another modifier of
9823 a right angle-bracket followed immediately by the new separator.
9824 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9826 The field selectors marked as "time" above
9827 take an optional modifier of "int"
9828 for which the result is the number of seconds since epoch.
9829 Otherwise the result is a human-readable string
9830 in the timezone selected by the main "timezone" option.
9832 The field selectors marked as "list" above return a list,
9833 newline-separated by default,
9834 (embedded separator characters in elements are doubled).
9835 The separator may be changed by a modifier of
9836 a right angle-bracket followed immediately by the new separator.
9838 The field selectors marked as "tagged" above
9839 prefix each list element with a type string and an equals sign.
9840 Elements of only one type may be selected by a modifier
9841 which is one of "dns", "uri" or "mail";
9842 if so the element tags are omitted.
9844 If not otherwise noted field values are presented in human-readable form.
9846 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9847 {*&<&'arg'&>&*}...}*&"
9849 This expansion dynamically loads and then calls a locally-written C function.
9850 This functionality is available only if Exim is compiled with
9854 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9855 object so that it doesn't reload the same object file in the same Exim process
9856 (but of course Exim does start new processes frequently).
9858 There may be from zero to eight arguments to the function.
9861 a local function that is to be called in this way,
9862 first &_DLFUNC_IMPL_& should be defined,
9863 and second &_local_scan.h_& should be included.
9864 The Exim variables and functions that are defined by that API
9865 are also available for dynamically loaded functions. The function itself
9866 must have the following type:
9868 int dlfunction(uschar **yield, int argc, uschar *argv[])
9870 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9871 function should return one of the following values:
9873 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9874 into the expanded string that is being built.
9876 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9877 from &'yield'&, if it is set.
9879 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9880 taken from &'yield'& if it is set.
9882 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9884 When compiling a function that is to be used in this way with gcc,
9885 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9886 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9889 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9890 .cindex "expansion" "extracting value from environment"
9891 .cindex "environment" "values from"
9892 The key is first expanded separately, and leading and trailing white space
9894 This is then searched for as a name in the environment.
9895 If a variable is found then its value is placed in &$value$&
9896 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9898 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9899 appear, for example:
9901 ${env{USER}{$value} fail }
9903 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9904 {<&'string1'&>} must be present for &"fail"& to be recognized.
9906 If {<&'string2'&>} is omitted an empty string is substituted on
9908 If {<&'string1'&>} is omitted the search result is substituted on
9911 The environment is adjusted by the &%keep_environment%& and
9912 &%add_environment%& main section options.
9915 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9916 {*&<&'string3'&>&*}}*&"
9917 .cindex "expansion" "extracting substrings by key"
9918 .cindex "&%extract%&" "substrings by key"
9919 The key and <&'string1'&> are first expanded separately. Leading and trailing
9920 white space is removed from the key (but not from any of the strings). The key
9921 must not be empty and must not consist entirely of digits.
9922 The expanded <&'string1'&> must be of the form:
9924 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9927 where the equals signs and spaces (but not both) are optional. If any of the
9928 values contain white space, they must be enclosed in double quotes, and any
9929 values that are enclosed in double quotes are subject to escape processing as
9930 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9931 for the value that corresponds to the key. The search is case-insensitive. If
9932 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9933 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9934 variable &$value$& contains the value that has been extracted. Afterwards, it
9935 is restored to any previous value it might have had.
9937 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9938 key is not found. If {<&'string2'&>} is also omitted, the value that was
9939 extracted is used. Thus, for example, these two expansions are identical, and
9942 ${extract{gid}{uid=1984 gid=2001}}
9943 ${extract{gid}{uid=1984 gid=2001}{$value}}
9945 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9946 appear, for example:
9948 ${extract{Z}{A=... B=...}{$value} fail }
9950 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9951 {<&'string2'&>} must be present for &"fail"& to be recognized.
9953 .vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9954 {*&<&'string3'&>&*}}*&" &&&
9955 "&*${extract jsons{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9956 {*&<&'string3'&>&*}}*&"
9957 .cindex "expansion" "extracting from JSON object"
9958 .cindex JSON expansions
9959 The key and <&'string1'&> are first expanded separately. Leading and trailing
9960 white space is removed from the key (but not from any of the strings). The key
9961 must not be empty and must not consist entirely of digits.
9962 The expanded <&'string1'&> must be of the form:
9964 { <&'"key1"'&> : <&'value1'&> , <&'"key2"'&> , <&'value2'&> ... }
9967 The braces, commas and colons, and the quoting of the member name are required;
9968 the spaces are optional.
9969 Matching of the key against the member names is done case-sensitively.
9970 For the &"json"& variant,
9971 if a returned value is a JSON string, it retains its leading and
9973 For the &"jsons"& variant, which is intended for use with JSON strings, the
9974 leading and trailing quotes are removed from the returned value.
9975 . XXX should be a UTF-8 compare
9977 The results of matching are handled as above.
9980 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9981 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9982 .cindex "expansion" "extracting substrings by number"
9983 .cindex "&%extract%&" "substrings by number"
9984 The <&'number'&> argument must consist entirely of decimal digits,
9985 apart from leading and trailing white space, which is ignored.
9986 This is what distinguishes this form of &%extract%& from the previous kind. It
9987 behaves in the same way, except that, instead of extracting a named field, it
9988 extracts from <&'string1'&> the field whose number is given as the first
9989 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9990 <&'string3'&> as before.
9992 The fields in the string are separated by any one of the characters in the
9993 separator string. These may include space or tab characters.
9994 The first field is numbered one. If the number is negative, the fields are
9995 counted from the end of the string, with the rightmost one numbered -1. If the
9996 number given is zero, the entire string is returned. If the modulus of the
9997 number is greater than the number of fields in the string, the result is the
9998 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9999 provided. For example:
10001 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
10005 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
10007 yields &"99"&. Two successive separators mean that the field between them is
10008 empty (for example, the fifth field above).
10011 .vitem "&*${extract json {*&<&'number'&>&*}}&&&
10012 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" &&&
10013 "&*${extract jsons{*&<&'number'&>&*}}&&&
10014 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10015 .cindex "expansion" "extracting from JSON array"
10016 .cindex JSON expansions
10017 The <&'number'&> argument must consist entirely of decimal digits,
10018 apart from leading and trailing white space, which is ignored.
10020 Field selection and result handling is as above;
10021 there is no choice of field separator.
10022 For the &"json"& variant,
10023 if a returned value is a JSON string, it retains its leading and
10025 For the &"jsons"& variant, which is intended for use with JSON strings, the
10026 leading and trailing quotes are removed from the returned value.
10029 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
10030 .cindex "list" "selecting by condition"
10031 .cindex "expansion" "selecting from list by condition"
10033 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10034 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10036 in this list, its value is place in &$item$&, and then the condition is
10037 evaluated. If the condition is true, &$item$& is added to the output as an
10038 item in a new list; if the condition is false, the item is discarded. The
10039 separator used for the output list is the same as the one used for the
10040 input, but a separator setting is not included in the output. For example:
10042 ${filter{a:b:c}{!eq{$item}{b}}}
10044 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
10045 to what it was before. See also the &%map%& and &%reduce%& expansion items.
10048 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10049 .cindex "hash function" "textual"
10050 .cindex "expansion" "textual hash"
10051 This is a textual hashing function, and was the first to be implemented in
10052 early versions of Exim. In current releases, there are other hashing functions
10053 (numeric, MD5, and SHA-1), which are described below.
10055 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
10056 <&'n'&>. If you are using fixed values for these numbers, that is, if
10057 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
10058 use the simpler operator notation that avoids some of the braces:
10060 ${hash_<n>_<m>:<string>}
10062 The second number is optional (in both notations). If <&'n'&> is greater than
10063 or equal to the length of the string, the expansion item returns the string.
10064 Otherwise it computes a new string of length <&'n'&> by applying a hashing
10065 function to the string. The new string consists of characters taken from the
10066 first <&'m'&> characters of the string
10068 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
10070 If <&'m'&> is not present the value 26 is used, so that only lower case
10071 letters appear. For example:
10073 &`$hash{3}{monty}} `& yields &`jmg`&
10074 &`$hash{5}{monty}} `& yields &`monty`&
10075 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
10078 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
10079 &*$h_*&<&'header&~name'&>&*:*&" &&&
10080 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10081 &*$bh_*&<&'header&~name'&>&*:*&" &&&
10082 "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10083 &*$lh_*&<&'header&~name'&>&*:*&" &&&
10084 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10085 &*$rh_*&<&'header&~name'&>&*:*&"
10086 .cindex "expansion" "header insertion"
10087 .vindex "&$header_$&"
10088 .vindex "&$bheader_$&"
10089 .vindex "&$lheader_$&"
10090 .vindex "&$rheader_$&"
10091 .cindex "header lines" "in expansion strings"
10092 .cindex "header lines" "character sets"
10093 .cindex "header lines" "decoding"
10094 Substitute the contents of the named message header line, for example
10098 The newline that terminates a header line is not included in the expansion, but
10099 internal newlines (caused by splitting the header line over several physical
10100 lines) may be present.
10102 The difference between the four pairs of expansions is in the way
10103 the data in the header line is interpreted.
10106 .cindex "white space" "in header lines"
10107 &%rheader%& gives the original &"raw"& content of the header line, with no
10108 processing at all, and without the removal of leading and trailing white space.
10111 .cindex "list" "of header lines"
10112 &%lheader%& gives a colon-separated list, one element per header when there
10113 are multiple headers with a given name.
10114 Any embedded colon characters within an element are doubled, so normal Exim
10115 list-processing facilities can be used.
10116 The terminating newline of each element is removed; in other respects
10117 the content is &"raw"&.
10120 .cindex "base64 encoding" "in header lines"
10121 &%bheader%& removes leading and trailing white space, and then decodes base64
10122 or quoted-printable MIME &"words"& within the header text, but does no
10123 character set translation. If decoding of what looks superficially like a MIME
10124 &"word"& fails, the raw string is returned. If decoding
10125 .cindex "binary zero" "in header line"
10126 produces a binary zero character, it is replaced by a question mark &-- this is
10127 what Exim does for binary zeros that are actually received in header lines.
10130 &%header%& tries to translate the string as decoded by &%bheader%& to a
10131 standard character set. This is an attempt to produce the same string as would
10132 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
10133 returned. Translation is attempted only on operating systems that support the
10134 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
10135 a system Makefile or in &_Local/Makefile_&.
10138 In a filter file, the target character set for &%header%& can be specified by a
10139 command of the following form:
10141 headers charset "UTF-8"
10143 This command affects all references to &$h_$& (or &$header_$&) expansions in
10144 subsequently obeyed filter commands. In the absence of this command, the target
10145 character set in a filter is taken from the setting of the &%headers_charset%&
10146 option in the runtime configuration. The value of this option defaults to the
10147 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
10150 Header names follow the syntax of RFC 2822, which states that they may contain
10151 any printing characters except space and colon. Consequently, curly brackets
10152 &'do not'& terminate header names, and should not be used to enclose them as
10153 if they were variables. Attempting to do so causes a syntax error.
10155 Only header lines that are common to all copies of a message are visible to
10156 this mechanism. These are the original header lines that are received with the
10157 message, and any that are added by an ACL statement or by a system
10158 filter. Header lines that are added to a particular copy of a message by a
10159 router or transport are not accessible.
10161 For incoming SMTP messages, no header lines are visible in
10162 ACLs that are obeyed before the data phase completes,
10163 because the header structure is not set up until the message is received.
10164 They are visible in DKIM, PRDR and DATA ACLs.
10165 Header lines that are added in a RCPT ACL (for example)
10166 are saved until the message's incoming header lines are available, at which
10167 point they are added.
10168 When any of the above ACLs ar
10169 running, however, header lines added by earlier ACLs are visible.
10171 Upper case and lower case letters are synonymous in header names. If the
10172 following character is white space, the terminating colon may be omitted, but
10173 this is not recommended, because you may then forget it when it is needed. When
10174 white space terminates the header name, this white space is included in the
10175 expanded string. If the message does not contain the given header, the
10176 expansion item is replaced by an empty string. (See the &%def%& condition in
10177 section &<<SECTexpcond>>& for a means of testing for the existence of a
10180 If there is more than one header with the same name, they are all concatenated
10181 to form the substitution string, up to a maximum length of 64K. Unless
10182 &%rheader%& is being used, leading and trailing white space is removed from
10183 each header before concatenation, and a completely empty header is ignored. A
10184 newline character is then inserted between non-empty headers, but there is no
10185 newline at the very end. For the &%header%& and &%bheader%& expansion, for
10186 those headers that contain lists of addresses, a comma is also inserted at the
10187 junctions between headers. This does not happen for the &%rheader%& expansion.
10189 .cindex "tainted data" "message headers"
10190 When the headers are from an incoming message,
10191 the result of expanding any of these variables is tainted.
10194 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
10195 .cindex "expansion" "hmac hashing"
10197 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
10198 shared secret and some text into a message authentication code, as specified in
10199 RFC 2104. This differs from &`${md5:secret_text...}`& or
10200 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
10201 cryptographic hash, allowing for authentication that is not possible with MD5
10202 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
10203 present. For example:
10205 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
10207 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
10210 dd97e3ba5d1a61b5006108f8c8252953
10212 As an example of how this might be used, you might put in the main part of
10213 an Exim configuration:
10215 SPAMSCAN_SECRET=cohgheeLei2thahw
10217 In a router or a transport you could then have:
10220 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
10221 ${hmac{md5}{SPAMSCAN_SECRET}\
10222 {${primary_hostname},${message_exim_id},$h_message-id:}}
10224 Then given a message, you can check where it was scanned by looking at the
10225 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
10226 this header line is authentic by recomputing the authentication code from the
10227 host name, message ID and the &'Message-id:'& header line. This can be done
10228 using Exim's &%-be%& option, or by other means, for example, by using the
10229 &'hmac_md5_hex()'& function in Perl.
10232 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10233 .cindex "expansion" "conditional"
10234 .cindex "&%if%&, expansion item"
10235 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
10236 item; otherwise <&'string2'&> is used. The available conditions are described
10237 in section &<<SECTexpcond>>& below. For example:
10239 ${if eq {$local_part}{postmaster} {yes}{no} }
10241 The second string need not be present; if it is not and the condition is not
10242 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
10243 be present instead of the second string (without any curly brackets). In this
10244 case, the expansion is forced to fail if the condition is not true (see section
10245 &<<SECTforexpfai>>&).
10247 If both strings are omitted, the result is the string &`true`& if the condition
10248 is true, and the empty string if the condition is false. This makes it less
10249 cumbersome to write custom ACL and router conditions. For example, instead of
10251 condition = ${if >{$acl_m4}{3}{true}{false}}
10255 condition = ${if >{$acl_m4}{3}}
10260 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
10261 .cindex expansion "imap folder"
10262 .cindex "&%imapfolder%& expansion item"
10263 This item converts a (possibly multilevel, or with non-ASCII characters)
10264 folder specification to a Maildir name for filesystem use.
10265 For information on internationalisation support see &<<SECTi18nMDA>>&.
10269 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10270 .cindex "expansion" "string truncation"
10271 .cindex "&%length%& expansion item"
10272 The &%length%& item is used to extract the initial portion of a string. Both
10273 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
10274 you are using a fixed value for the number, that is, if <&'string1'&> does not
10275 change when expanded, you can use the simpler operator notation that avoids
10276 some of the braces:
10278 ${length_<n>:<string>}
10280 The result of this item is either the first <&'n'&> bytes or the whole
10281 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
10282 &%strlen%&, which gives the length of a string.
10283 All measurement is done in bytes and is not UTF-8 aware.
10286 .vitem "&*${listextract{*&<&'number'&>&*}&&&
10287 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10288 .cindex "expansion" "extracting list elements by number"
10289 .cindex "&%listextract%&" "extract list elements by number"
10290 .cindex "list" "extracting elements by number"
10291 The <&'number'&> argument must consist entirely of decimal digits,
10292 apart from an optional leading minus,
10293 and leading and trailing white space (which is ignored).
10295 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10296 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10298 The first field of the list is numbered one.
10299 If the number is negative, the fields are
10300 counted from the end of the list, with the rightmost one numbered -1.
10301 The numbered element of the list is extracted and placed in &$value$&,
10302 then <&'string2'&> is expanded as the result.
10304 If the modulus of the
10305 number is zero or greater than the number of fields in the string,
10306 the result is the expansion of <&'string3'&>.
10310 ${listextract{2}{x:42:99}}
10314 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
10316 yields &"result: 42"&.
10318 If {<&'string3'&>} is omitted, an empty string is used for string3.
10319 If {<&'string2'&>} is also omitted, the value that was
10321 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
10325 .vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*&
10326 .cindex quoting "for list"
10327 .cindex list quoting
10328 This item doubles any occurrence of the separator character
10329 in the given string.
10330 An empty string is replaced with a single space.
10331 This converts the string into a safe form for use as a list element,
10332 in a list using the given separator.
10336 .vitem "&*${lookup&~{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
10337 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" &&&
10338 "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
10339 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
10340 .cindex "expansion" "lookup in"
10341 .cindex "file" "lookups"
10342 .cindex "lookup" "in expanded string"
10343 The two forms of lookup item specify data lookups in files and databases, as
10344 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
10345 lookups, and the second is used for query-style lookups. The <&'key'&>,
10346 <&'file'&>, and <&'query'&> strings are expanded before use.
10348 If there is any white space in a lookup item which is part of a filter command,
10349 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
10350 other place where white space is significant, the lookup item must be enclosed
10351 in double quotes. The use of data lookups in users' filter files may be locked
10352 out by the system administrator.
10354 .vindex "&$value$&"
10355 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
10356 During its expansion, the variable &$value$& contains the data returned by the
10357 lookup. Afterwards it reverts to the value it had previously (at the outer
10358 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
10359 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
10360 string on failure. If <&'string2'&> is provided, it can itself be a nested
10361 lookup, thus providing a mechanism for looking up a default value when the
10362 original lookup fails.
10364 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
10365 data for the outer lookup while the parameters of the second lookup are
10366 expanded, and also while <&'string2'&> of the second lookup is expanded, should
10367 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
10368 appear, and in this case, if the lookup fails, the entire expansion is forced
10369 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
10370 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
10371 successful lookup, and nothing in the case of failure.
10373 For single-key lookups, the string &"partial"& is permitted to precede the
10374 search type in order to do partial matching, and * or *@ may follow a search
10375 type to request default lookups if the key does not match (see sections
10376 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
10378 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
10379 If a partial search is used, the variables &$1$& and &$2$& contain the wild
10380 and non-wild parts of the key during the expansion of the replacement text.
10381 They return to their previous values at the end of the lookup item.
10383 This example looks up the postmaster alias in the conventional alias file:
10385 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
10387 This example uses NIS+ to look up the full name of the user corresponding to
10388 the local part of an address, forcing the expansion to fail if it is not found:
10390 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
10395 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10396 .cindex "expansion" "list creation"
10398 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10399 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10401 in this list, its value is place in &$item$&, and then <&'string2'&> is
10402 expanded and added to the output as an item in a new list. The separator used
10403 for the output list is the same as the one used for the input, but a separator
10404 setting is not included in the output. For example:
10406 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
10408 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
10409 value of &$item$& is restored to what it was before. See also the &%filter%&
10410 and &%reduce%& expansion items.
10412 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10413 .cindex "expansion" "numeric hash"
10414 .cindex "hash function" "numeric"
10415 The three strings are expanded; the first two must yield numbers. Call them
10416 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10417 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10418 can use the simpler operator notation that avoids some of the braces:
10420 ${nhash_<n>_<m>:<string>}
10422 The second number is optional (in both notations). If there is only one number,
10423 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
10424 processed by a div/mod hash function that returns two numbers, separated by a
10425 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
10428 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
10430 returns the string &"6/33"&.
10434 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
10435 .cindex "Perl" "use in expanded string"
10436 .cindex "expansion" "calling Perl from"
10437 This item is available only if Exim has been built to include an embedded Perl
10438 interpreter. The subroutine name and the arguments are first separately
10439 expanded, and then the Perl subroutine is called with those arguments. No
10440 additional arguments need be given; the maximum number permitted, including the
10441 name of the subroutine, is nine.
10443 The return value of the subroutine is inserted into the expanded string, unless
10444 the return value is &%undef%&. In that case, the expansion fails in the same
10445 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
10446 Whatever you return is evaluated in a scalar context. For example, if you
10447 return the name of a Perl vector, the return value is the size of the vector,
10450 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
10451 with the error message that was passed to &%die%&. More details of the embedded
10452 Perl facility are given in chapter &<<CHAPperl>>&.
10454 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
10455 out the use of this expansion item in filter files.
10458 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
10459 .cindex "&%prvs%& expansion item"
10460 The first argument is a complete email address and the second is secret
10461 keystring. The third argument, specifying a key number, is optional. If absent,
10462 it defaults to 0. The result of the expansion is a prvs-signed email address,
10463 to be typically used with the &%return_path%& option on an &(smtp)& transport
10464 as part of a bounce address tag validation (BATV) scheme. For more discussion
10465 and an example, see section &<<SECTverifyPRVS>>&.
10467 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
10468 {*&<&'string'&>&*}}*&"
10469 .cindex "&%prvscheck%& expansion item"
10470 This expansion item is the complement of the &%prvs%& item. It is used for
10471 checking prvs-signed addresses. If the expansion of the first argument does not
10472 yield a syntactically valid prvs-signed address, the whole item expands to the
10473 empty string. When the first argument does expand to a syntactically valid
10474 prvs-signed address, the second argument is expanded, with the prvs-decoded
10475 version of the address and the key number extracted from the address in the
10476 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
10478 These two variables can be used in the expansion of the second argument to
10479 retrieve the secret. The validity of the prvs-signed address is then checked
10480 against the secret. The result is stored in the variable &$prvscheck_result$&,
10481 which is empty for failure or &"1"& for success.
10483 The third argument is optional; if it is missing, it defaults to an empty
10484 string. This argument is now expanded. If the result is an empty string, the
10485 result of the expansion is the decoded version of the address. This is the case
10486 whether or not the signature was valid. Otherwise, the result of the expansion
10487 is the expansion of the third argument.
10489 All three variables can be used in the expansion of the third argument.
10490 However, once the expansion is complete, only &$prvscheck_result$& remains set.
10491 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
10493 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
10494 .cindex "expansion" "inserting an entire file"
10495 .cindex "file" "inserting into expansion"
10496 .cindex "&%readfile%& expansion item"
10497 The filename and end-of-line string are first expanded separately. The file is
10498 then read, and its contents replace the entire item. All newline characters in
10499 the file are replaced by the end-of-line string if it is present. Otherwise,
10500 newlines are left in the string.
10501 String expansion is not applied to the contents of the file. If you want this,
10502 you must wrap the item in an &%expand%& operator. If the file cannot be read,
10503 the string expansion fails.
10505 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
10506 locks out the use of this expansion item in filter files.
10510 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
10511 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
10512 .cindex "expansion" "inserting from a socket"
10513 .cindex "socket, use of in expansion"
10514 .cindex "&%readsocket%& expansion item"
10515 This item inserts data from a Unix domain or TCP socket into the expanded
10516 string. The minimal way of using it uses just two arguments, as in these
10519 ${readsocket{/socket/name}{request string}}
10520 ${readsocket{inet:some.host:1234}{request string}}
10522 For a Unix domain socket, the first substring must be the path to the socket.
10523 For an Internet socket, the first substring must contain &`inet:`& followed by
10524 a host name or IP address, followed by a colon and a port, which can be a
10525 number or the name of a TCP port in &_/etc/services_&. An IP address may
10526 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
10529 ${readsocket{inet:[::1]:1234}{request string}}
10531 Only a single host name may be given, but if looking it up yields more than
10532 one IP address, they are each tried in turn until a connection is made. For
10533 both kinds of socket, Exim makes a connection, writes the request string
10534 unless it is an empty string; and no terminating NUL is ever sent)
10535 and reads from the socket until an end-of-file
10536 is read. A timeout of 5 seconds is applied. Additional, optional arguments
10537 extend what can be done. Firstly, you can vary the timeout. For example:
10539 ${readsocket{/socket/name}{request string}{3s}}
10542 The third argument is a list of options, of which the first element is the timeout
10543 and must be present if any options are given.
10544 Further elements are options of form &'name=value'&.
10547 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
10550 The following option names are recognised:
10553 Defines if the result data can be cached for use by a later identical
10554 request in the same process.
10555 Values are &"yes"& or &"no"& (the default).
10556 If not, all cached results for this connection specification
10557 will be invalidated.
10561 Defines whether or not a write-shutdown is done on the connection after
10562 sending the request. Values are &"yes"& (the default) or &"no"&
10563 (preferred, eg. by some webservers).
10567 Controls the use of TLS on the connection.
10568 Values are &"yes"& or &"no"& (the default).
10569 If it is enabled, a shutdown as descripbed above is never done.
10573 A fourth argument allows you to change any newlines that are in the data
10574 that is read, in the same way as for &%readfile%& (see above). This example
10575 turns them into spaces:
10577 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
10579 As with all expansions, the substrings are expanded before the processing
10580 happens. Errors in these sub-expansions cause the expansion to fail. In
10581 addition, the following errors can occur:
10584 Failure to create a socket file descriptor;
10586 Failure to connect the socket;
10588 Failure to write the request string;
10590 Timeout on reading from the socket.
10593 By default, any of these errors causes the expansion to fail. However, if
10594 you supply a fifth substring, it is expanded and used when any of the above
10595 errors occurs. For example:
10597 ${readsocket{/socket/name}{request string}{3s}{\n}\
10600 You can test for the existence of a Unix domain socket by wrapping this
10601 expansion in &`${if exists`&, but there is a race condition between that test
10602 and the actual opening of the socket, so it is safer to use the fifth argument
10603 if you want to be absolutely sure of avoiding an expansion error for a
10604 non-existent Unix domain socket, or a failure to connect to an Internet socket.
10606 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
10607 locks out the use of this expansion item in filter files.
10610 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10611 .cindex "expansion" "reducing a list to a scalar"
10612 .cindex "list" "reducing to a scalar"
10613 .vindex "&$value$&"
10615 This operation reduces a list to a single, scalar string. After expansion,
10616 <&'string1'&> is interpreted as a list, colon-separated by default, but the
10617 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10618 Then <&'string2'&> is expanded and
10619 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
10620 list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
10621 them. The result of that expansion is assigned to &$value$& before the next
10622 iteration. When the end of the list is reached, the final value of &$value$& is
10623 added to the expansion output. The &%reduce%& expansion item can be used in a
10624 number of ways. For example, to add up a list of numbers:
10626 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
10628 The result of that expansion would be &`6`&. The maximum of a list of numbers
10631 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
10633 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
10634 restored to what they were before. See also the &%filter%& and &%map%&
10637 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
10638 This item inserts &"raw"& header lines. It is described with the &%header%&
10639 expansion item in section &<<SECTexpansionitems>>& above.
10641 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
10642 {*&<&'string2'&>&*}}*&"
10643 .cindex "expansion" "running a command"
10644 .cindex "&%run%& expansion item"
10645 The command and its arguments are first expanded as one string. The string is
10646 split apart into individual arguments by spaces, and then the command is run
10647 in a separate process, but under the same uid and gid. As in other command
10648 executions from Exim, a shell is not used by default. If the command requires
10649 a shell, you must explicitly code it.
10651 Since the arguments are split by spaces, when there is a variable expansion
10652 which has an empty result, it will cause the situation that the argument will
10653 simply be omitted when the program is actually executed by Exim. If the
10654 script/program requires a specific number of arguments and the expanded
10655 variable could possibly result in this empty expansion, the variable must be
10656 quoted. This is more difficult if the expanded variable itself could result
10657 in a string containing quotes, because it would interfere with the quotes
10658 around the command arguments. A possible guard against this is to wrap the
10659 variable in the &%sg%& operator to change any quote marks to some other
10662 The standard input for the command exists, but is empty. The standard output
10663 and standard error are set to the same file descriptor.
10664 .cindex "return code" "from &%run%& expansion"
10665 .vindex "&$value$&"
10666 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
10667 and replaces the entire item; during this expansion, the standard output/error
10668 from the command is in the variable &$value$&. If the command fails,
10669 <&'string2'&>, if present, is expanded and used. Once again, during the
10670 expansion, the standard output/error from the command is in the variable
10673 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
10674 can be the word &"fail"& (not in braces) to force expansion failure if the
10675 command does not succeed. If both strings are omitted, the result is contents
10676 of the standard output/error on success, and nothing on failure.
10678 .vindex "&$run_in_acl$&"
10679 The standard output/error of the command is put in the variable &$value$&.
10680 In this ACL example, the output of a command is logged for the admin to
10683 warn condition = ${run{/usr/bin/id}{yes}{no}}
10684 log_message = Output of id: $value
10686 If the command requires shell idioms, such as the > redirect operator, the
10687 shell must be invoked directly, such as with:
10689 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
10692 .vindex "&$runrc$&"
10693 The return code from the command is put in the variable &$runrc$&, and this
10694 remains set afterwards, so in a filter file you can do things like this:
10696 if "${run{x y z}{}}$runrc" is 1 then ...
10697 elif $runrc is 2 then ...
10701 If execution of the command fails (for example, the command does not exist),
10702 the return code is 127 &-- the same code that shells use for non-existent
10705 &*Warning*&: In a router or transport, you cannot assume the order in which
10706 option values are expanded, except for those preconditions whose order of
10707 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
10708 by the expansion of one option, and use it in another.
10710 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
10711 out the use of this expansion item in filter files.
10714 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
10715 .cindex "expansion" "string substitution"
10716 .cindex "&%sg%& expansion item"
10717 This item works like Perl's substitution operator (s) with the global (/g)
10718 option; hence its name. However, unlike the Perl equivalent, Exim does not
10719 modify the subject string; instead it returns the modified string for insertion
10720 into the overall expansion. The item takes three arguments: the subject string,
10721 a regular expression, and a substitution string. For example:
10723 ${sg{abcdefabcdef}{abc}{xyz}}
10725 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
10726 if any $, } or \ characters are required in the regular expression or in the
10727 substitution string, they have to be escaped. For example:
10729 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
10731 yields &"defabc"&, and
10733 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
10735 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
10736 the regular expression from string expansion.
10738 The regular expression is compiled in 8-bit mode, working against bytes
10739 rather than any Unicode-aware character handling.
10742 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
10743 .cindex sorting "a list"
10744 .cindex list sorting
10745 .cindex expansion "list sorting"
10746 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10747 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10748 The <&'comparator'&> argument is interpreted as the operator
10749 of a two-argument expansion condition.
10750 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
10751 The comparison should return true when applied to two values
10752 if the first value should sort before the second value.
10753 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
10754 the element being placed in &$item$&,
10755 to give values for comparison.
10757 The item result is a sorted list,
10758 with the original list separator,
10759 of the list elements (in full) of the original.
10763 ${sort{3:2:1:4}{<}{$item}}
10765 sorts a list of numbers, and
10767 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10769 will sort an MX lookup into priority order.
10774 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
10775 SRS encoding. See SECT &<<SECTSRS>>& for details.
10780 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10781 .cindex "&%substr%& expansion item"
10782 .cindex "substring extraction"
10783 .cindex "expansion" "substring extraction"
10784 The three strings are expanded; the first two must yield numbers. Call them
10785 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10786 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10787 can use the simpler operator notation that avoids some of the braces:
10789 ${substr_<n>_<m>:<string>}
10791 The second number is optional (in both notations).
10792 If it is absent in the simpler format, the preceding underscore must also be
10795 The &%substr%& item can be used to extract more general substrings than
10796 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10797 length required. For example
10799 ${substr{3}{2}{$local_part}}
10801 If the starting offset is greater than the string length the result is the
10802 null string; if the length plus starting offset is greater than the string
10803 length, the result is the right-hand part of the string, starting from the
10804 given offset. The first byte (character) in the string has offset zero.
10806 The &%substr%& expansion item can take negative offset values to count
10807 from the right-hand end of its operand. The last byte (character) is offset -1,
10808 the second-last is offset -2, and so on. Thus, for example,
10810 ${substr{-5}{2}{1234567}}
10812 yields &"34"&. If the absolute value of a negative offset is greater than the
10813 length of the string, the substring starts at the beginning of the string, and
10814 the length is reduced by the amount of overshoot. Thus, for example,
10816 ${substr{-5}{2}{12}}
10818 yields an empty string, but
10820 ${substr{-3}{2}{12}}
10824 When the second number is omitted from &%substr%&, the remainder of the string
10825 is taken if the offset is positive. If it is negative, all bytes (characters) in the
10826 string preceding the offset point are taken. For example, an offset of -1 and
10827 no length, as in these semantically identical examples:
10830 ${substr{-1}{abcde}}
10832 yields all but the last character of the string, that is, &"abcd"&.
10834 All measurement is done in bytes and is not UTF-8 aware.
10838 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10839 {*&<&'replacements'&>&*}}*&"
10840 .cindex "expansion" "character translation"
10841 .cindex "&%tr%& expansion item"
10842 This item does single-character (in bytes) translation on its subject string. The second
10843 argument is a list of characters to be translated in the subject string. Each
10844 matching character is replaced by the corresponding character from the
10845 replacement list. For example
10847 ${tr{abcdea}{ac}{13}}
10849 yields &`1b3de1`&. If there are duplicates in the second character string, the
10850 last occurrence is used. If the third string is shorter than the second, its
10851 last character is replicated. However, if it is empty, no translation takes
10854 All character handling is done in bytes and is not UTF-8 aware.
10860 .section "Expansion operators" "SECTexpop"
10861 .cindex "expansion" "operators"
10862 For expansion items that perform transformations on a single argument string,
10863 the &"operator"& notation is used because it is simpler and uses fewer braces.
10864 The substring is first expanded before the operation is applied to it. The
10865 following operations can be performed:
10868 .vitem &*${address:*&<&'string'&>&*}*&
10869 .cindex "expansion" "RFC 2822 address handling"
10870 .cindex "&%address%& expansion item"
10871 The string is interpreted as an RFC 2822 address, as it might appear in a
10872 header line, and the effective address is extracted from it. If the string does
10873 not parse successfully, the result is empty.
10875 The parsing correctly handles SMTPUTF8 Unicode in the string.
10878 .vitem &*${addresses:*&<&'string'&>&*}*&
10879 .cindex "expansion" "RFC 2822 address handling"
10880 .cindex "&%addresses%& expansion item"
10881 The string (after expansion) is interpreted as a list of addresses in RFC
10882 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10883 operative address (&'local-part@domain'&) is extracted from each item, and the
10884 result of the expansion is a colon-separated list, with appropriate
10885 doubling of colons should any happen to be present in the email addresses.
10886 Syntactically invalid RFC2822 address items are omitted from the output.
10888 It is possible to specify a character other than colon for the output
10889 separator by starting the string with > followed by the new separator
10890 character. For example:
10892 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10894 expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
10895 first, so if the expanded string starts with >, it may change the output
10896 separator unintentionally. This can be avoided by setting the output
10897 separator explicitly:
10899 ${addresses:>:$h_from:}
10902 Compare the &%address%& (singular)
10903 expansion item, which extracts the working address from a single RFC2822
10904 address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
10907 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10908 a strict interpretation of header line formatting. Exim parses the bare,
10909 unquoted portion of an email address and if it finds a comma, treats it as an
10910 email address separator. For the example header line:
10912 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10914 The first example below demonstrates that Q-encoded email addresses are parsed
10915 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10916 It does not see the comma because it's still encoded as "=2C". The second
10917 example below is passed the contents of &`$header_from:`&, meaning it gets
10918 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10919 The third example shows that the presence of a comma is skipped when it is
10920 quoted. The fourth example shows SMTPUTF8 handling.
10922 # exim -be '${addresses:From: \
10923 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10925 # exim -be '${addresses:From: Last, First <user@example.com>}'
10926 Last:user@example.com
10927 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10929 # exim -be '${addresses:フィル <フィリップ@example.jp>}'
10933 .vitem &*${base32:*&<&'digits'&>&*}*&
10934 .cindex "&%base32%& expansion item"
10935 .cindex "expansion" "conversion to base 32"
10936 The string must consist entirely of decimal digits. The number is converted to
10937 base 32 and output as a (empty, for zero) string of characters.
10938 Only lowercase letters are used.
10940 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10941 .cindex "&%base32d%& expansion item"
10942 .cindex "expansion" "conversion to base 32"
10943 The string must consist entirely of base-32 digits.
10944 The number is converted to decimal and output as a string.
10946 .vitem &*${base62:*&<&'digits'&>&*}*&
10947 .cindex "&%base62%& expansion item"
10948 .cindex "expansion" "conversion to base 62"
10949 The string must consist entirely of decimal digits. The number is converted to
10950 base 62 and output as a string of six characters, including leading zeros. In
10951 the few operating environments where Exim uses base 36 instead of base 62 for
10952 its message identifiers (because those systems do not have case-sensitive
10953 filenames), base 36 is used by this operator, despite its name. &*Note*&: Just
10954 to be absolutely clear: this is &'not'& base64 encoding.
10956 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10957 .cindex "&%base62d%& expansion item"
10958 .cindex "expansion" "conversion to base 62"
10959 The string must consist entirely of base-62 digits, or, in operating
10960 environments where Exim uses base 36 instead of base 62 for its message
10961 identifiers, base-36 digits. The number is converted to decimal and output as a
10964 .vitem &*${base64:*&<&'string'&>&*}*&
10965 .cindex "expansion" "base64 encoding"
10966 .cindex "base64 encoding" "in string expansion"
10967 .cindex "&%base64%& expansion item"
10968 .cindex certificate "base64 of DER"
10969 This operator converts a string into one that is base64 encoded.
10971 If the string is a single variable of type certificate,
10972 returns the base64 encoding of the DER form of the certificate.
10975 .vitem &*${base64d:*&<&'string'&>&*}*&
10976 .cindex "expansion" "base64 decoding"
10977 .cindex "base64 decoding" "in string expansion"
10978 .cindex "&%base64d%& expansion item"
10979 This operator converts a base64-encoded string into the un-coded form.
10982 .vitem &*${domain:*&<&'string'&>&*}*&
10983 .cindex "domain" "extraction"
10984 .cindex "expansion" "domain extraction"
10985 The string is interpreted as an RFC 2822 address and the domain is extracted
10986 from it. If the string does not parse successfully, the result is empty.
10989 .vitem &*${escape:*&<&'string'&>&*}*&
10990 .cindex "expansion" "escaping non-printing characters"
10991 .cindex "&%escape%& expansion item"
10992 If the string contains any non-printing characters, they are converted to
10993 escape sequences starting with a backslash. Whether characters with the most
10994 significant bit set (so-called &"8-bit characters"&) count as printing or not
10995 is controlled by the &%print_topbitchars%& option.
10997 .vitem &*${escape8bit:*&<&'string'&>&*}*&
10998 .cindex "expansion" "escaping 8-bit characters"
10999 .cindex "&%escape8bit%& expansion item"
11000 If the string contains and characters with the most significant bit set,
11001 they are converted to escape sequences starting with a backslash.
11002 Backslashes and DEL characters are also converted.
11005 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
11006 .cindex "expansion" "expression evaluation"
11007 .cindex "expansion" "arithmetic expression"
11008 .cindex "&%eval%& expansion item"
11009 These items supports simple arithmetic and bitwise logical operations in
11010 expansion strings. The string (after expansion) must be a conventional
11011 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
11012 logical operators, and parentheses. All operations are carried out using
11013 integer arithmetic. The operator priorities are as follows (the same as in the
11014 C programming language):
11016 .irow &'highest:'& "not (~), negate (-)"
11017 .irow "" "multiply (*), divide (/), remainder (%)"
11018 .irow "" "plus (+), minus (-)"
11019 .irow "" "shift-left (<<), shift-right (>>)"
11020 .irow "" "and (&&)"
11022 .irow &'lowest:'& "or (|)"
11024 Binary operators with the same priority are evaluated from left to right. White
11025 space is permitted before or after operators.
11027 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
11028 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
11029 decimal, even if they start with a leading zero; hexadecimal numbers are not
11030 permitted. This can be useful when processing numbers extracted from dates or
11031 times, which often do have leading zeros.
11033 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
11035 respectively. Negative numbers are supported. The result of the computation is
11036 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
11039 &`${eval:1+1} `& yields 2
11040 &`${eval:1+2*3} `& yields 7
11041 &`${eval:(1+2)*3} `& yields 9
11042 &`${eval:2+42%5} `& yields 4
11043 &`${eval:0xc&5} `& yields 4
11044 &`${eval:0xc|5} `& yields 13
11045 &`${eval:0xc^5} `& yields 9
11046 &`${eval:0xc>>1} `& yields 6
11047 &`${eval:0xc<<1} `& yields 24
11048 &`${eval:~255&0x1234} `& yields 4608
11049 &`${eval:-(~255&0x1234)} `& yields -4608
11052 As a more realistic example, in an ACL you might have
11056 {>{$rcpt_count}{10}} \
11059 {$recipients_count} \
11060 {${eval:$rcpt_count/2}} \
11063 message = Too many bad recipients
11065 The condition is true if there have been more than 10 RCPT commands and
11066 fewer than half of them have resulted in a valid recipient.
11069 .vitem &*${expand:*&<&'string'&>&*}*&
11070 .cindex "expansion" "re-expansion of substring"
11071 The &%expand%& operator causes a string to be expanded for a second time. For
11074 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
11076 first looks up a string in a file while expanding the operand for &%expand%&,
11077 and then re-expands what it has found.
11080 .vitem &*${from_utf8:*&<&'string'&>&*}*&
11082 .cindex "UTF-8" "conversion from"
11083 .cindex "expansion" "UTF-8 conversion"
11084 .cindex "&%from_utf8%& expansion item"
11085 The world is slowly moving towards Unicode, although there are no standards for
11086 email yet. However, other applications (including some databases) are starting
11087 to store data in Unicode, using UTF-8 encoding. This operator converts from a
11088 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
11089 converted to underscores. The input must be a valid UTF-8 string. If it is not,
11090 the result is an undefined sequence of bytes.
11092 Unicode code points with values less than 256 are compatible with ASCII and
11093 ISO-8859-1 (also known as Latin-1).
11094 For example, character 169 is the copyright symbol in both cases, though the
11095 way it is encoded is different. In UTF-8, more than one byte is needed for
11096 characters with code values greater than 127, whereas ISO-8859-1 is a
11097 single-byte encoding (but thereby limited to 256 characters). This makes
11098 translation from UTF-8 to ISO-8859-1 straightforward.
11101 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11102 .cindex "hash function" "textual"
11103 .cindex "expansion" "textual hash"
11104 The &%hash%& operator is a simpler interface to the hashing function that can
11105 be used when the two parameters are fixed numbers (as opposed to strings that
11106 change when expanded). The effect is the same as
11108 ${hash{<n>}{<m>}{<string>}}
11110 See the description of the general &%hash%& item above for details. The
11111 abbreviation &%h%& can be used when &%hash%& is used as an operator.
11115 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
11116 .cindex "base64 encoding" "conversion from hex"
11117 .cindex "expansion" "hex to base64"
11118 .cindex "&%hex2b64%& expansion item"
11119 This operator converts a hex string into one that is base64 encoded. This can
11120 be useful for processing the output of the various hashing functions.
11124 .vitem &*${hexquote:*&<&'string'&>&*}*&
11125 .cindex "quoting" "hex-encoded unprintable characters"
11126 .cindex "&%hexquote%& expansion item"
11127 This operator converts non-printable characters in a string into a hex
11128 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
11129 as is, and other byte values are converted to &`\xNN`&, for example, a
11130 byte value 127 is converted to &`\x7f`&.
11133 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
11134 .cindex "&%ipv6denorm%& expansion item"
11135 .cindex "IP address" normalisation
11136 This expands an IPv6 address to a full eight-element colon-separated set
11137 of hex digits including leading zeroes.
11138 A trailing ipv4-style dotted-decimal set is converted to hex.
11139 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11141 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
11142 .cindex "&%ipv6norm%& expansion item"
11143 .cindex "IP address" normalisation
11144 .cindex "IP address" "canonical form"
11145 This converts an IPv6 address to canonical form.
11146 Leading zeroes of groups are omitted, and the longest
11147 set of zero-valued groups is replaced with a double colon.
11148 A trailing ipv4-style dotted-decimal set is converted to hex.
11149 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11152 .vitem &*${lc:*&<&'string'&>&*}*&
11153 .cindex "case forcing in strings"
11154 .cindex "string" "case forcing"
11155 .cindex "lower casing"
11156 .cindex "expansion" "case forcing"
11157 .cindex "&%lc%& expansion item"
11158 This forces the letters in the string into lower-case, for example:
11162 Case is defined per the system C locale.
11164 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
11165 .cindex "expansion" "string truncation"
11166 .cindex "&%length%& expansion item"
11167 The &%length%& operator is a simpler interface to the &%length%& function that
11168 can be used when the parameter is a fixed number (as opposed to a string that
11169 changes when expanded). The effect is the same as
11171 ${length{<number>}{<string>}}
11173 See the description of the general &%length%& item above for details. Note that
11174 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
11175 when &%length%& is used as an operator.
11176 All measurement is done in bytes and is not UTF-8 aware.
11179 .vitem &*${listcount:*&<&'string'&>&*}*&
11180 .cindex "expansion" "list item count"
11181 .cindex "list" "item count"
11182 .cindex "list" "count of items"
11183 .cindex "&%listcount%& expansion item"
11184 The string is interpreted as a list and the number of items is returned.
11187 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
11188 .cindex "expansion" "named list"
11189 .cindex "&%listnamed%& expansion item"
11190 The name is interpreted as a named list and the content of the list is returned,
11191 expanding any referenced lists, re-quoting as needed for colon-separation.
11192 If the optional type is given it must be one of "a", "d", "h" or "l"
11193 and selects address-, domain-, host- or localpart- lists to search among respectively.
11194 Otherwise all types are searched in an undefined order and the first
11195 matching list is returned.
11197 &*Note*&: Neither string-expansion of lists referenced by named-list syntax elements,
11198 nor expansion of lookup elements, is done by the &%listnamed%& operator.
11202 .vitem &*${local_part:*&<&'string'&>&*}*&
11203 .cindex "expansion" "local part extraction"
11204 .cindex "&%local_part%& expansion item"
11205 The string is interpreted as an RFC 2822 address and the local part is
11206 extracted from it. If the string does not parse successfully, the result is
11208 The parsing correctly handles SMTPUTF8 Unicode in the string.
11211 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
11212 .cindex "masked IP address"
11213 .cindex "IP address" "masking"
11214 .cindex "CIDR notation"
11215 .cindex "expansion" "IP address masking"
11216 .cindex "&%mask%& expansion item"
11217 If the form of the string to be operated on is not an IP address followed by a
11218 slash and an integer (that is, a network address in CIDR notation), the
11219 expansion fails. Otherwise, this operator converts the IP address to binary,
11220 masks off the least significant bits according to the bit count, and converts
11221 the result back to text, with mask appended. For example,
11223 ${mask:10.111.131.206/28}
11225 returns the string &"10.111.131.192/28"&. Since this operation is expected to
11226 be mostly used for looking up masked addresses in files, the result for an IPv6
11227 address uses dots to separate components instead of colons, because colon
11228 terminates a key string in lsearch files. So, for example,
11230 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
11234 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
11236 Letters in IPv6 addresses are always output in lower case.
11239 .vitem &*${md5:*&<&'string'&>&*}*&
11241 .cindex "expansion" "MD5 hash"
11242 .cindex certificate fingerprint
11243 .cindex "&%md5%& expansion item"
11244 The &%md5%& operator computes the MD5 hash value of the string, and returns it
11245 as a 32-digit hexadecimal number, in which any letters are in lower case.
11247 If the string is a single variable of type certificate,
11248 returns the MD5 hash fingerprint of the certificate.
11251 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11252 .cindex "expansion" "numeric hash"
11253 .cindex "hash function" "numeric"
11254 The &%nhash%& operator is a simpler interface to the numeric hashing function
11255 that can be used when the two parameters are fixed numbers (as opposed to
11256 strings that change when expanded). The effect is the same as
11258 ${nhash{<n>}{<m>}{<string>}}
11260 See the description of the general &%nhash%& item above for details.
11263 .vitem &*${quote:*&<&'string'&>&*}*&
11264 .cindex "quoting" "in string expansions"
11265 .cindex "expansion" "quoting"
11266 .cindex "&%quote%& expansion item"
11267 The &%quote%& operator puts its argument into double quotes if it
11268 is an empty string or
11269 contains anything other than letters, digits, underscores, dots, and hyphens.
11270 Any occurrences of double quotes and backslashes are escaped with a backslash.
11271 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
11272 respectively For example,
11280 The place where this is useful is when the argument is a substitution from a
11281 variable or a message header.
11283 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
11284 .cindex "&%quote_local_part%& expansion item"
11285 This operator is like &%quote%&, except that it quotes the string only if
11286 required to do so by the rules of RFC 2822 for quoting local parts. For
11287 example, a plus sign would not cause quoting (but it would for &%quote%&).
11288 If you are creating a new email address from the contents of &$local_part$&
11289 (or any other unknown data), you should always use this operator.
11291 This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
11292 will likely use the quoting form.
11293 Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
11296 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
11297 .cindex "quoting" "lookup-specific"
11298 This operator applies lookup-specific quoting rules to the string. Each
11299 query-style lookup type has its own quoting rules which are described with
11300 the lookups in chapter &<<CHAPfdlookup>>&. For example,
11302 ${quote_ldap:two * two}
11308 For single-key lookup types, no quoting is ever necessary and this operator
11309 yields an unchanged string.
11312 .vitem &*${randint:*&<&'n'&>&*}*&
11313 .cindex "random number"
11314 This operator returns a somewhat random number which is less than the
11315 supplied number and is at least 0. The quality of this randomness depends
11316 on how Exim was built; the values are not suitable for keying material.
11317 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
11318 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
11319 for versions of GnuTLS with that function.
11320 Otherwise, the implementation may be arc4random(), random() seeded by
11321 srandomdev() or srandom(), or a custom implementation even weaker than
11325 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
11326 .cindex "expansion" "IP address"
11327 This operator reverses an IP address; for IPv4 addresses, the result is in
11328 dotted-quad decimal form, while for IPv6 addresses the result is in
11329 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
11330 for DNS. For example,
11332 ${reverse_ip:192.0.2.4}
11333 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
11338 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
11342 .vitem &*${rfc2047:*&<&'string'&>&*}*&
11343 .cindex "expansion" "RFC 2047"
11344 .cindex "RFC 2047" "expansion operator"
11345 .cindex "&%rfc2047%& expansion item"
11346 This operator encodes text according to the rules of RFC 2047. This is an
11347 encoding that is used in header lines to encode non-ASCII characters. It is
11348 assumed that the input string is in the encoding specified by the
11349 &%headers_charset%& option, which gets its default at build time. If the string
11350 contains only characters in the range 33&--126, and no instances of the
11353 ? = ( ) < > @ , ; : \ " . [ ] _
11355 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
11356 string, using as many &"encoded words"& as necessary to encode all the
11360 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
11361 .cindex "expansion" "RFC 2047"
11362 .cindex "RFC 2047" "decoding"
11363 .cindex "&%rfc2047d%& expansion item"
11364 This operator decodes strings that are encoded as per RFC 2047. Binary zero
11365 bytes are replaced by question marks. Characters are converted into the
11366 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
11367 not recognized unless &%check_rfc2047_length%& is set false.
11369 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
11370 access a header line, RFC 2047 decoding is done automatically. You do not need
11371 to use this operator as well.
11375 .vitem &*${rxquote:*&<&'string'&>&*}*&
11376 .cindex "quoting" "in regular expressions"
11377 .cindex "regular expressions" "quoting"
11378 .cindex "&%rxquote%& expansion item"
11379 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
11380 characters in its argument. This is useful when substituting the values of
11381 variables or headers inside regular expressions.
11384 .vitem &*${sha1:*&<&'string'&>&*}*&
11385 .cindex "SHA-1 hash"
11386 .cindex "expansion" "SHA-1 hashing"
11387 .cindex certificate fingerprint
11388 .cindex "&%sha1%& expansion item"
11389 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
11390 it as a 40-digit hexadecimal number, in which any letters are in upper case.
11392 If the string is a single variable of type certificate,
11393 returns the SHA-1 hash fingerprint of the certificate.
11396 .vitem &*${sha256:*&<&'string'&>&*}*& &&&
11397 &*${sha2:*&<&'string'&>&*}*& &&&
11398 &*${sha2_<n>:*&<&'string'&>&*}*&
11399 .cindex "SHA-256 hash"
11400 .cindex "SHA-2 hash"
11401 .cindex certificate fingerprint
11402 .cindex "expansion" "SHA-256 hashing"
11403 .cindex "&%sha256%& expansion item"
11404 .cindex "&%sha2%& expansion item"
11405 The &%sha256%& operator computes the SHA-256 hash value of the string
11407 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11409 If the string is a single variable of type certificate,
11410 returns the SHA-256 hash fingerprint of the certificate.
11412 The operator can also be spelled &%sha2%& and does the same as &%sha256%&
11413 (except for certificates, which are not supported).
11414 Finally, if an underbar
11415 and a number is appended it specifies the output length, selecting a
11416 member of the SHA-2 family of hash functions.
11417 Values of 256, 384 and 512 are accepted, with 256 being the default.
11420 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
11421 &*${sha3_<n>:*&<&'string'&>&*}*&
11422 .cindex "SHA3 hash"
11423 .cindex "expansion" "SHA3 hashing"
11424 .cindex "&%sha3%& expansion item"
11425 The &%sha3%& operator computes the SHA3-256 hash value of the string
11427 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11429 If a number is appended, separated by an underbar, it specifies
11430 the output length. Values of 224, 256, 384 and 512 are accepted;
11431 with 256 being the default.
11433 The &%sha3%& expansion item is only supported if Exim has been
11434 compiled with GnuTLS 3.5.0 or later,
11435 or OpenSSL 1.1.1 or later.
11436 The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
11439 .vitem &*${stat:*&<&'string'&>&*}*&
11440 .cindex "expansion" "statting a file"
11441 .cindex "file" "extracting characteristics"
11442 .cindex "&%stat%& expansion item"
11443 The string, after expansion, must be a file path. A call to the &[stat()]&
11444 function is made for this path. If &[stat()]& fails, an error occurs and the
11445 expansion fails. If it succeeds, the data from the stat replaces the item, as a
11446 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
11447 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
11448 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
11449 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
11450 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
11451 can extract individual fields using the &%extract%& expansion item.
11453 The use of the &%stat%& expansion in users' filter files can be locked out by
11454 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
11455 systems for files larger than 2GB.
11457 .vitem &*${str2b64:*&<&'string'&>&*}*&
11458 .cindex "&%str2b64%& expansion item"
11459 Now deprecated, a synonym for the &%base64%& expansion operator.
11463 .vitem &*${strlen:*&<&'string'&>&*}*&
11464 .cindex "expansion" "string length"
11465 .cindex "string" "length in expansion"
11466 .cindex "&%strlen%& expansion item"
11467 The item is replace by the length of the expanded string, expressed as a
11468 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
11469 All measurement is done in bytes and is not UTF-8 aware.
11472 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
11473 .cindex "&%substr%& expansion item"
11474 .cindex "substring extraction"
11475 .cindex "expansion" "substring expansion"
11476 The &%substr%& operator is a simpler interface to the &%substr%& function that
11477 can be used when the two parameters are fixed numbers (as opposed to strings
11478 that change when expanded). The effect is the same as
11480 ${substr{<start>}{<length>}{<string>}}
11482 See the description of the general &%substr%& item above for details. The
11483 abbreviation &%s%& can be used when &%substr%& is used as an operator.
11484 All measurement is done in bytes and is not UTF-8 aware.
11486 .vitem &*${time_eval:*&<&'string'&>&*}*&
11487 .cindex "&%time_eval%& expansion item"
11488 .cindex "time interval" "decoding"
11489 This item converts an Exim time interval such as &`2d4h5m`& into a number of
11492 .vitem &*${time_interval:*&<&'string'&>&*}*&
11493 .cindex "&%time_interval%& expansion item"
11494 .cindex "time interval" "formatting"
11495 The argument (after sub-expansion) must be a sequence of decimal digits that
11496 represents an interval of time as a number of seconds. It is converted into a
11497 number of larger units and output in Exim's normal time format, for example,
11500 .vitem &*${uc:*&<&'string'&>&*}*&
11501 .cindex "case forcing in strings"
11502 .cindex "string" "case forcing"
11503 .cindex "upper casing"
11504 .cindex "expansion" "case forcing"
11505 .cindex "&%uc%& expansion item"
11506 This forces the letters in the string into upper-case.
11507 Case is defined per the system C locale.
11509 .vitem &*${utf8clean:*&<&'string'&>&*}*&
11510 .cindex "correction of invalid utf-8 sequences in strings"
11511 .cindex "utf-8" "utf-8 sequences"
11512 .cindex "incorrect utf-8"
11513 .cindex "expansion" "utf-8 forcing"
11514 .cindex "&%utf8clean%& expansion item"
11515 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
11516 In versions of Exim before 4.92, this did not correctly do so for a truncated
11517 final codepoint's encoding, and the character would be silently dropped.
11518 If you must handle detection of this scenario across both sets of Exim behavior,
11519 the complexity will depend upon the task.
11520 For instance, to detect if the first character is multibyte and a 1-byte
11521 extraction can be successfully used as a path component (as is common for
11522 dividing up delivery folders), you might use:
11524 condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
11526 (which will false-positive if the first character of the local part is a
11527 literal question mark).
11529 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
11530 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
11531 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
11532 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
11533 .cindex expansion UTF-8
11534 .cindex UTF-8 expansion
11536 .cindex internationalisation
11537 .cindex "&%utf8_domain_to_alabel%& expansion item"
11538 .cindex "&%utf8_domain_from_alabel%& expansion item"
11539 .cindex "&%utf8_localpart_to_alabel%& expansion item"
11540 .cindex "&%utf8_localpart_from_alabel%& expansion item"
11541 These convert EAI mail name components between UTF-8 and a-label forms.
11542 For information on internationalisation support see &<<SECTi18nMTA>>&.
11550 .section "Expansion conditions" "SECTexpcond"
11551 .scindex IIDexpcond "expansion" "conditions"
11552 The following conditions are available for testing by the &%${if%& construct
11553 while expanding strings:
11556 .vitem &*!*&<&'condition'&>
11557 .cindex "expansion" "negating a condition"
11558 .cindex "negation" "in expansion condition"
11559 Preceding any condition with an exclamation mark negates the result of the
11562 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11563 .cindex "numeric comparison"
11564 .cindex "expansion" "numeric comparison"
11565 There are a number of symbolic operators for doing numeric comparisons. They
11571 &`>= `& greater or equal
11573 &`<= `& less or equal
11577 ${if >{$message_size}{10M} ...
11579 Note that the general negation operator provides for inequality testing. The
11580 two strings must take the form of optionally signed decimal integers,
11581 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
11582 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
11583 As a special case, the numerical value of an empty string is taken as
11586 In all cases, a relative comparator OP is testing if <&'string1'&> OP
11587 <&'string2'&>; the above example is checking if &$message_size$& is larger than
11588 10M, not if 10M is larger than &$message_size$&.
11591 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
11592 {*&<&'arg2'&>&*}...}*&
11593 .cindex "expansion" "calling an acl"
11594 .cindex "&%acl%&" "expansion condition"
11595 The name and zero to nine argument strings are first expanded separately. The expanded
11596 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
11597 Any unused are made empty. The variable &$acl_narg$& is set to the number of
11598 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
11599 and may use the variables; if another acl expansion is used the values
11600 are restored after it returns. If the ACL sets
11601 a value using a "message =" modifier the variable $value becomes
11602 the result of the expansion, otherwise it is empty.
11603 If the ACL returns accept the condition is true; if deny, false.
11604 If the ACL returns defer the result is a forced-fail.
11606 .vitem &*bool&~{*&<&'string'&>&*}*&
11607 .cindex "expansion" "boolean parsing"
11608 .cindex "&%bool%& expansion condition"
11609 This condition turns a string holding a true or false representation into
11610 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
11611 (case-insensitively); also integer numbers map to true if non-zero,
11613 An empty string is treated as false.
11614 Leading and trailing whitespace is ignored;
11615 thus a string consisting only of whitespace is false.
11616 All other string values will result in expansion failure.
11618 When combined with ACL variables, this expansion condition will let you
11619 make decisions in one place and act on those decisions in another place.
11622 ${if bool{$acl_m_privileged_sender} ...
11626 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
11627 .cindex "expansion" "boolean parsing"
11628 .cindex "&%bool_lax%& expansion condition"
11629 Like &%bool%&, this condition turns a string into a boolean state. But
11630 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
11631 loose definition that the Router &%condition%& option uses. The empty string
11632 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
11633 true. Leading and trailing whitespace is ignored.
11635 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
11637 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11638 .cindex "expansion" "encrypted comparison"
11639 .cindex "encrypted strings, comparing"
11640 .cindex "&%crypteq%& expansion condition"
11641 This condition is included in the Exim binary if it is built to support any
11642 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
11643 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
11644 included in the binary.
11646 The &%crypteq%& condition has two arguments. The first is encrypted and
11647 compared against the second, which is already encrypted. The second string may
11648 be in the LDAP form for storing encrypted strings, which starts with the
11649 encryption type in curly brackets, followed by the data. If the second string
11650 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
11651 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
11652 Typically this will be a field from a password file. An example of an encrypted
11653 string in LDAP form is:
11655 {md5}CY9rzUYh03PK3k6DJie09g==
11657 If such a string appears directly in an expansion, the curly brackets have to
11658 be quoted, because they are part of the expansion syntax. For example:
11660 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
11662 The following encryption types (whose names are matched case-independently) are
11667 .cindex "base64 encoding" "in encrypted password"
11668 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
11669 printable characters to compare with the remainder of the second string. If the
11670 length of the comparison string is 24, Exim assumes that it is base64 encoded
11671 (as in the above example). If the length is 32, Exim assumes that it is a
11672 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
11676 .cindex "SHA-1 hash"
11677 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
11678 printable characters to compare with the remainder of the second string. If the
11679 length of the comparison string is 28, Exim assumes that it is base64 encoded.
11680 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
11681 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
11684 .cindex "&[crypt()]&"
11685 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
11686 only the first eight characters of the password. However, in modern operating
11687 systems this is no longer true, and in many cases the entire password is used,
11688 whatever its length.
11691 .cindex "&[crypt16()]&"
11692 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
11693 use up to 16 characters of the password in some operating systems. Again, in
11694 modern operating systems, more characters may be used.
11696 Exim has its own version of &[crypt16()]&, which is just a double call to
11697 &[crypt()]&. For operating systems that have their own version, setting
11698 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
11699 operating system version instead of its own. This option is set by default in
11700 the OS-dependent &_Makefile_& for those operating systems that are known to
11701 support &[crypt16()]&.
11703 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
11704 it was not using the same algorithm as some operating systems' versions. It
11705 turns out that as well as &[crypt16()]& there is a function called
11706 &[bigcrypt()]& in some operating systems. This may or may not use the same
11707 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
11709 However, since there is now a move away from the traditional &[crypt()]&
11710 functions towards using SHA1 and other algorithms, tidying up this area of
11711 Exim is seen as very low priority.
11713 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
11714 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
11715 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
11716 default is &`{crypt}`&. Whatever the default, you can always use either
11717 function by specifying it explicitly in curly brackets.
11719 .vitem &*def:*&<&'variable&~name'&>
11720 .cindex "expansion" "checking for empty variable"
11721 .cindex "&%def%& expansion condition"
11722 The &%def%& condition must be followed by the name of one of the expansion
11723 variables defined in section &<<SECTexpvar>>&. The condition is true if the
11724 variable does not contain the empty string. For example:
11726 ${if def:sender_ident {from $sender_ident}}
11728 Note that the variable name is given without a leading &%$%& character. If the
11729 variable does not exist, the expansion fails.
11731 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
11732 &~&*def:h_*&<&'header&~name'&>&*:*&"
11733 .cindex "expansion" "checking header line existence"
11734 This condition is true if a message is being processed and the named header
11735 exists in the message. For example,
11737 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
11739 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
11740 the header name must be terminated by a colon if white space does not follow.
11742 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11743 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11744 .cindex "string" "comparison"
11745 .cindex "expansion" "string comparison"
11746 .cindex "&%eq%& expansion condition"
11747 .cindex "&%eqi%& expansion condition"
11748 The two substrings are first expanded. The condition is true if the two
11749 resulting strings are identical. For &%eq%& the comparison includes the case of
11750 letters, whereas for &%eqi%& the comparison is case-independent, where
11751 case is defined per the system C locale.
11753 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
11754 .cindex "expansion" "file existence test"
11755 .cindex "file" "existence test"
11756 .cindex "&%exists%&, expansion condition"
11757 The substring is first expanded and then interpreted as an absolute path. The
11758 condition is true if the named file (or directory) exists. The existence test
11759 is done by calling the &[stat()]& function. The use of the &%exists%& test in
11760 users' filter files may be locked out by the system administrator.
11763 &*Note:*& Testing a path using this condition is not a sufficient way of
11765 Consider using a dsearch lookup.
11768 .vitem &*first_delivery*&
11769 .cindex "delivery" "first"
11770 .cindex "first delivery"
11771 .cindex "expansion" "first delivery test"
11772 .cindex "&%first_delivery%& expansion condition"
11773 This condition, which has no data, is true during a message's first delivery
11774 attempt. It is false during any subsequent delivery attempts.
11777 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
11778 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
11779 .cindex "list" "iterative conditions"
11780 .cindex "expansion" "&*forall*& condition"
11781 .cindex "expansion" "&*forany*& condition"
11783 These conditions iterate over a list. The first argument is expanded to form
11784 the list. By default, the list separator is a colon, but it can be changed by
11785 the normal method (&<<SECTlistsepchange>>&).
11786 The second argument is interpreted as a condition that is to
11787 be applied to each item in the list in turn. During the interpretation of the
11788 condition, the current list item is placed in a variable called &$item$&.
11790 For &*forany*&, interpretation stops if the condition is true for any item, and
11791 the result of the whole condition is true. If the condition is false for all
11792 items in the list, the overall condition is false.
11794 For &*forall*&, interpretation stops if the condition is false for any item,
11795 and the result of the whole condition is false. If the condition is true for
11796 all items in the list, the overall condition is true.
11798 Note that negation of &*forany*& means that the condition must be false for all
11799 items for the overall condition to succeed, and negation of &*forall*& means
11800 that the condition must be false for at least one item. In this example, the
11801 list separator is changed to a comma:
11803 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
11805 The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
11806 being processed, to enable these expansion items to be nested.
11808 To scan a named list, expand it with the &*listnamed*& operator.
11810 .vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11811 "&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11812 "&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11813 "&*forany_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&"
11814 .cindex JSON "iterative conditions"
11815 .cindex JSON expansions
11816 .cindex expansion "&*forall_json*& condition"
11817 .cindex expansion "&*forany_json*& condition"
11818 .cindex expansion "&*forall_jsons*& condition"
11819 .cindex expansion "&*forany_jsons*& condition"
11820 As for the above, except that the first argument must, after expansion,
11822 The array separator is not changeable.
11823 For the &"jsons"& variants the elements are expected to be JSON strings
11824 and have their quotes removed before the evaluation of the condition.
11828 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11829 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11830 .cindex "string" "comparison"
11831 .cindex "expansion" "string comparison"
11832 .cindex "&%ge%& expansion condition"
11833 .cindex "&%gei%& expansion condition"
11834 The two substrings are first expanded. The condition is true if the first
11835 string is lexically greater than or equal to the second string. For &%ge%& the
11836 comparison includes the case of letters, whereas for &%gei%& the comparison is
11838 Case and collation order are defined per the system C locale.
11840 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11841 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11842 .cindex "string" "comparison"
11843 .cindex "expansion" "string comparison"
11844 .cindex "&%gt%& expansion condition"
11845 .cindex "&%gti%& expansion condition"
11846 The two substrings are first expanded. The condition is true if the first
11847 string is lexically greater than the second string. For &%gt%& the comparison
11848 includes the case of letters, whereas for &%gti%& the comparison is
11850 Case and collation order are defined per the system C locale.
11854 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
11855 SRS decode. See SECT &<<SECTSRS>>& for details.
11859 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11860 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11861 .cindex "string" "comparison"
11862 .cindex "list" "iterative conditions"
11863 Both strings are expanded; the second string is treated as a list of simple
11864 strings; if the first string is a member of the second, then the condition
11866 For the case-independent &%inlisti%& condition, case is defined per the system C locale.
11868 These are simpler to use versions of the more powerful &*forany*& condition.
11869 Examples, and the &*forany*& equivalents:
11871 ${if inlist{needle}{foo:needle:bar}}
11872 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11873 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11874 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11877 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11878 &*isip4&~{*&<&'string'&>&*}*& &&&
11879 &*isip6&~{*&<&'string'&>&*}*&
11880 .cindex "IP address" "testing string format"
11881 .cindex "string" "testing for IP address"
11882 .cindex "&%isip%& expansion condition"
11883 .cindex "&%isip4%& expansion condition"
11884 .cindex "&%isip6%& expansion condition"
11885 The substring is first expanded, and then tested to see if it has the form of
11886 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11887 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11889 For an IPv4 address, the test is for four dot-separated components, each of
11890 which consists of from one to three digits. For an IPv6 address, up to eight
11891 colon-separated components are permitted, each containing from one to four
11892 hexadecimal digits. There may be fewer than eight components if an empty
11893 component (adjacent colons) is present. Only one empty component is permitted.
11895 &*Note*&: The checks used to be just on the form of the address; actual numerical
11896 values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
11898 This is no longer the case.
11900 The main use of these tests is to distinguish between IP addresses and
11901 host names, or between IPv4 and IPv6 addresses. For example, you could use
11903 ${if isip4{$sender_host_address}...
11905 to test which IP version an incoming SMTP connection is using.
11907 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11908 .cindex "LDAP" "use for authentication"
11909 .cindex "expansion" "LDAP authentication test"
11910 .cindex "&%ldapauth%& expansion condition"
11911 This condition supports user authentication using LDAP. See section
11912 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11913 queries. For this use, the query must contain a user name and password. The
11914 query itself is not used, and can be empty. The condition is true if the
11915 password is not empty, and the user name and password are accepted by the LDAP
11916 server. An empty password is rejected without calling LDAP because LDAP binds
11917 with an empty password are considered anonymous regardless of the username, and
11918 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11919 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11923 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11924 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11925 .cindex "string" "comparison"
11926 .cindex "expansion" "string comparison"
11927 .cindex "&%le%& expansion condition"
11928 .cindex "&%lei%& expansion condition"
11929 The two substrings are first expanded. The condition is true if the first
11930 string is lexically less than or equal to the second string. For &%le%& the
11931 comparison includes the case of letters, whereas for &%lei%& the comparison is
11933 Case and collation order are defined per the system C locale.
11935 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11936 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11937 .cindex "string" "comparison"
11938 .cindex "expansion" "string comparison"
11939 .cindex "&%lt%& expansion condition"
11940 .cindex "&%lti%& expansion condition"
11941 The two substrings are first expanded. The condition is true if the first
11942 string is lexically less than the second string. For &%lt%& the comparison
11943 includes the case of letters, whereas for &%lti%& the comparison is
11945 Case and collation order are defined per the system C locale.
11948 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11949 .cindex "expansion" "regular expression comparison"
11950 .cindex "regular expressions" "match in expanded string"
11951 .cindex "&%match%& expansion condition"
11952 The two substrings are first expanded. The second is then treated as a regular
11953 expression and applied to the first. Because of the pre-expansion, if the
11954 regular expression contains dollar, or backslash characters, they must be
11955 escaped. Care must also be taken if the regular expression contains braces
11956 (curly brackets). A closing brace must be escaped so that it is not taken as a
11957 premature termination of <&'string2'&>. The easiest approach is to use the
11958 &`\N`& feature to disable expansion of the regular expression.
11961 ${if match {$local_part}{\N^\d{3}\N} ...
11963 If the whole expansion string is in double quotes, further escaping of
11964 backslashes is also required.
11966 The condition is true if the regular expression match succeeds.
11967 The regular expression is not required to begin with a circumflex
11968 metacharacter, but if there is no circumflex, the expression is not anchored,
11969 and it may match anywhere in the subject, not just at the start. If you want
11970 the pattern to match at the end of the subject, you must include the &`$`&
11971 metacharacter at an appropriate point.
11972 All character handling is done in bytes and is not UTF-8 aware,
11973 but we might change this in a future Exim release.
11975 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11976 At the start of an &%if%& expansion the values of the numeric variable
11977 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11978 succeeds causes them to be reset to the substrings of that condition and they
11979 will have these values during the expansion of the success string. At the end
11980 of the &%if%& expansion, the previous values are restored. After testing a
11981 combination of conditions using &%or%&, the subsequent values of the numeric
11982 variables are those of the condition that succeeded.
11984 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11985 .cindex "&%match_address%& expansion condition"
11986 See &*match_local_part*&.
11988 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11989 .cindex "&%match_domain%& expansion condition"
11990 See &*match_local_part*&.
11992 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11993 .cindex "&%match_ip%& expansion condition"
11994 This condition matches an IP address to a list of IP address patterns. It must
11995 be followed by two argument strings. The first (after expansion) must be an IP
11996 address or an empty string. The second (not expanded) is a restricted host
11997 list that can match only an IP address, not a host name. For example:
11999 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
12001 The specific types of host list item that are permitted in the list are:
12004 An IP address, optionally with a CIDR mask.
12006 A single asterisk, which matches any IP address.
12008 An empty item, which matches only if the IP address is empty. This could be
12009 useful for testing for a locally submitted message or one from specific hosts
12010 in a single test such as
12011 . ==== As this is a nested list, any displays it contains must be indented
12012 . ==== as otherwise they are too far to the left. This comment applies to
12013 . ==== the use of xmlto plus fop. There's no problem when formatting with
12014 . ==== sdop, with or without the extra indent.
12016 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
12018 where the first item in the list is the empty string.
12020 The item @[] matches any of the local host's interface addresses.
12022 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
12023 even if &`net-`& is not specified. There is never any attempt to turn the IP
12024 address into a host name. The most common type of linear search for
12025 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
12026 masks. For example:
12028 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
12030 It is of course possible to use other kinds of lookup, and in such a case, you
12031 do need to specify the &`net-`& prefix if you want to specify a specific
12032 address mask, for example:
12034 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
12036 However, unless you are combining a &%match_ip%& condition with others, it is
12037 just as easy to use the fact that a lookup is itself a condition, and write:
12039 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
12043 Note that <&'string2'&> is not itself subject to string expansion, unless
12044 Exim was built with the EXPAND_LISTMATCH_RHS option.
12046 Consult section &<<SECThoslispatip>>& for further details of these patterns.
12048 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12049 .cindex "domain list" "in expansion condition"
12050 .cindex "address list" "in expansion condition"
12051 .cindex "local part" "list, in expansion condition"
12052 .cindex "&%match_local_part%& expansion condition"
12053 This condition, together with &%match_address%& and &%match_domain%&, make it
12054 possible to test domain, address, and local part lists within expansions. Each
12055 condition requires two arguments: an item and a list to match. A trivial
12058 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
12060 In each case, the second argument may contain any of the allowable items for a
12061 list of the appropriate type. Also, because the second argument
12062 is a standard form of list, it is possible to refer to a named list.
12063 Thus, you can use conditions like this:
12065 ${if match_domain{$domain}{+local_domains}{...
12067 .cindex "&`+caseful`&"
12068 For address lists, the matching starts off caselessly, but the &`+caseful`&
12069 item can be used, as in all address lists, to cause subsequent items to
12070 have their local parts matched casefully. Domains are always matched
12073 Note that <&'string2'&> is not itself subject to string expansion, unless
12074 Exim was built with the EXPAND_LISTMATCH_RHS option.
12076 &*Note*&: Host lists are &'not'& supported in this way. This is because
12077 hosts have two identities: a name and an IP address, and it is not clear
12078 how to specify cleanly how such a test would work. However, IP addresses can be
12079 matched using &%match_ip%&.
12081 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
12082 .cindex "PAM authentication"
12083 .cindex "AUTH" "with PAM"
12084 .cindex "Solaris" "PAM support"
12085 .cindex "expansion" "PAM authentication test"
12086 .cindex "&%pam%& expansion condition"
12087 &'Pluggable Authentication Modules'&
12088 (&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
12089 available in the latest releases of Solaris and in some GNU/Linux
12090 distributions. The Exim support, which is intended for use in conjunction with
12091 the SMTP AUTH command, is available only if Exim is compiled with
12095 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
12096 in some releases of GNU/Linux &%-ldl%& is also needed.
12098 The argument string is first expanded, and the result must be a
12099 colon-separated list of strings. Leading and trailing white space is ignored.
12100 The PAM module is initialized with the service name &"exim"& and the user name
12101 taken from the first item in the colon-separated data string (<&'string1'&>).
12102 The remaining items in the data string are passed over in response to requests
12103 from the authentication function. In the simple case there will only be one
12104 request, for a password, so the data consists of just two strings.
12106 There can be problems if any of the strings are permitted to contain colon
12107 characters. In the usual way, these have to be doubled to avoid being taken as
12109 The &%listquote%& expansion item can be used for this.
12110 For example, the configuration
12111 of a LOGIN authenticator might contain this setting:
12113 server_condition = ${if pam{$auth1:${listquote{:}{$auth2}}}}
12115 In some operating systems, PAM authentication can be done only from a process
12116 running as root. Since Exim is running as the Exim user when receiving
12117 messages, this means that PAM cannot be used directly in those systems.
12118 . --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that
12121 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
12122 .cindex "&'pwcheck'& daemon"
12124 .cindex "expansion" "&'pwcheck'& authentication test"
12125 .cindex "&%pwcheck%& expansion condition"
12126 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
12127 This is one way of making it possible for passwords to be checked by a process
12128 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
12129 deprecated. Its replacement is &'saslauthd'& (see below).
12131 The pwcheck support is not included in Exim by default. You need to specify
12132 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
12133 building Exim. For example:
12135 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
12137 You do not need to install the full Cyrus software suite in order to use
12138 the pwcheck daemon. You can compile and install just the daemon alone
12139 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
12140 access to the &_/var/pwcheck_& directory.
12142 The &%pwcheck%& condition takes one argument, which must be the user name and
12143 password, separated by a colon. For example, in a LOGIN authenticator
12144 configuration, you might have this:
12146 server_condition = ${if pwcheck{$auth1:$auth2}}
12148 Again, for a PLAIN authenticator configuration, this would be:
12150 server_condition = ${if pwcheck{$auth2:$auth3}}
12152 .vitem &*queue_running*&
12153 .cindex "queue runner" "detecting when delivering from"
12154 .cindex "expansion" "queue runner test"
12155 .cindex "&%queue_running%& expansion condition"
12156 This condition, which has no data, is true during delivery attempts that are
12157 initiated by queue runner processes, and false otherwise.
12160 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
12162 .cindex "expansion" "Radius authentication"
12163 .cindex "&%radius%& expansion condition"
12164 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
12165 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
12166 the Radius client configuration file in order to build Exim with Radius
12169 With just that one setting, Exim expects to be linked with the &%radiusclient%&
12170 library, using the original API. If you are using release 0.4.0 or later of
12171 this library, you need to set
12173 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
12175 in &_Local/Makefile_& when building Exim. You can also link Exim with the
12176 &%libradius%& library that comes with FreeBSD. To do this, set
12178 RADIUS_LIB_TYPE=RADLIB
12180 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
12181 You may also have to supply a suitable setting in EXTRALIBS so that the
12182 Radius library can be found when Exim is linked.
12184 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
12185 Radius client library, which calls the Radius server. The condition is true if
12186 the authentication is successful. For example:
12188 server_condition = ${if radius{<arguments>}}
12192 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
12193 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
12194 .cindex "&'saslauthd'& daemon"
12196 .cindex "expansion" "&'saslauthd'& authentication test"
12197 .cindex "&%saslauthd%& expansion condition"
12198 This condition supports user authentication using the Cyrus &'saslauthd'&
12199 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
12200 Using this daemon is one way of making it possible for passwords to be checked
12201 by a process that is not running as root.
12203 The saslauthd support is not included in Exim by default. You need to specify
12204 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
12205 building Exim. For example:
12207 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
12209 You do not need to install the full Cyrus software suite in order to use
12210 the saslauthd daemon. You can compile and install just the daemon alone
12211 from the Cyrus SASL library.
12213 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
12214 two are mandatory. For example:
12216 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
12218 The service and the realm are optional (which is why the arguments are enclosed
12219 in their own set of braces). For details of the meaning of the service and
12220 realm, and how to run the daemon, consult the Cyrus documentation.
12225 .section "Combining expansion conditions" "SECID84"
12226 .cindex "expansion" "combining conditions"
12227 Several conditions can be tested at once by combining them using the &%and%&
12228 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
12229 conditions on their own, and precede their lists of sub-conditions. Each
12230 sub-condition must be enclosed in braces within the overall braces that contain
12231 the list. No repetition of &%if%& is used.
12235 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12236 .cindex "&""or""& expansion condition"
12237 .cindex "expansion" "&""or""& of conditions"
12238 The sub-conditions are evaluated from left to right. The condition is true if
12239 any one of the sub-conditions is true.
12242 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
12244 When a true sub-condition is found, the following ones are parsed but not
12245 evaluated. If there are several &"match"& sub-conditions the values of the
12246 numeric variables afterwards are taken from the first one that succeeds.
12248 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12249 .cindex "&""and""& expansion condition"
12250 .cindex "expansion" "&""and""& of conditions"
12251 The sub-conditions are evaluated from left to right. The condition is true if
12252 all of the sub-conditions are true. If there are several &"match"&
12253 sub-conditions, the values of the numeric variables afterwards are taken from
12254 the last one. When a false sub-condition is found, the following ones are
12255 parsed but not evaluated.
12257 .ecindex IIDexpcond
12262 .section "Expansion variables" "SECTexpvar"
12263 .cindex "expansion" "variables, list of"
12264 This section contains an alphabetical list of all the expansion variables. Some
12265 of them are available only when Exim is compiled with specific options such as
12266 support for TLS or the content scanning extension.
12269 .vitem "&$0$&, &$1$&, etc"
12270 .cindex "numerical variables (&$1$& &$2$& etc)"
12271 When a &%match%& expansion condition succeeds, these variables contain the
12272 captured substrings identified by the regular expression during subsequent
12273 processing of the success string of the containing &%if%& expansion item.
12274 In the expansion condition case
12275 they do not retain their values afterwards; in fact, their previous
12276 values are restored at the end of processing an &%if%& item. The numerical
12277 variables may also be set externally by some other matching process which
12278 precedes the expansion of the string. For example, the commands available in
12279 Exim filter files include an &%if%& command with its own regular expression
12280 matching condition.
12282 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
12283 Within an acl condition, expansion condition or expansion item
12284 any arguments are copied to these variables,
12285 any unused variables being made empty.
12287 .vitem "&$acl_c...$&"
12288 Values can be placed in these variables by the &%set%& modifier in an ACL. They
12289 can be given any name that starts with &$acl_c$& and is at least six characters
12290 long, but the sixth character must be either a digit or an underscore. For
12291 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
12292 variables persist throughout the lifetime of an SMTP connection. They can be
12293 used to pass information between ACLs and between different invocations of the
12294 same ACL. When a message is received, the values of these variables are saved
12295 with the message, and can be accessed by filters, routers, and transports
12296 during subsequent delivery.
12298 .vitem "&$acl_m...$&"
12299 These variables are like the &$acl_c...$& variables, except that their values
12300 are reset after a message has been received. Thus, if several messages are
12301 received in one SMTP connection, &$acl_m...$& values are not passed on from one
12302 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
12303 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
12304 message is received, the values of these variables are saved with the message,
12305 and can be accessed by filters, routers, and transports during subsequent
12308 .vitem &$acl_narg$&
12309 Within an acl condition, expansion condition or expansion item
12310 this variable has the number of arguments.
12312 .vitem &$acl_verify_message$&
12313 .vindex "&$acl_verify_message$&"
12314 After an address verification has failed, this variable contains the failure
12315 message. It retains its value for use in subsequent modifiers. The message can
12316 be preserved by coding like this:
12318 warn !verify = sender
12319 set acl_m0 = $acl_verify_message
12321 You can use &$acl_verify_message$& during the expansion of the &%message%& or
12322 &%log_message%& modifiers, to include information about the verification
12325 .vitem &$address_data$&
12326 .vindex "&$address_data$&"
12327 This variable is set by means of the &%address_data%& option in routers. The
12328 value then remains with the address while it is processed by subsequent routers
12329 and eventually a transport. If the transport is handling multiple addresses,
12330 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
12331 for more details. &*Note*&: The contents of &$address_data$& are visible in
12334 If &$address_data$& is set when the routers are called from an ACL to verify
12335 a recipient address, the final value is still in the variable for subsequent
12336 conditions and modifiers of the ACL statement. If routing the address caused it
12337 to be redirected to just one address, the child address is also routed as part
12338 of the verification, and in this case the final value of &$address_data$& is
12339 from the child's routing.
12341 If &$address_data$& is set when the routers are called from an ACL to verify a
12342 sender address, the final value is also preserved, but this time in
12343 &$sender_address_data$&, to distinguish it from data from a recipient
12346 In both cases (recipient and sender verification), the value does not persist
12347 after the end of the current ACL statement. If you want to preserve
12348 these values for longer, you can save them in ACL variables.
12350 .vitem &$address_file$&
12351 .vindex "&$address_file$&"
12352 When, as a result of aliasing, forwarding, or filtering, a message is directed
12353 to a specific file, this variable holds the name of the file when the transport
12354 is running. At other times, the variable is empty. For example, using the
12355 default configuration, if user &%r2d2%& has a &_.forward_& file containing
12357 /home/r2d2/savemail
12359 then when the &(address_file)& transport is running, &$address_file$&
12360 contains the text string &`/home/r2d2/savemail`&.
12361 .cindex "Sieve filter" "value of &$address_file$&"
12362 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
12363 then up to the transport configuration to generate an appropriate absolute path
12364 to the relevant file.
12366 .vitem &$address_pipe$&
12367 .vindex "&$address_pipe$&"
12368 When, as a result of aliasing or forwarding, a message is directed to a pipe,
12369 this variable holds the pipe command when the transport is running.
12371 .vitem "&$auth1$& &-- &$auth4$&"
12372 .vindex "&$auth1$&, &$auth2$&, etc"
12373 These variables are used in SMTP authenticators (see chapters
12374 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
12376 .vitem &$authenticated_id$&
12377 .cindex "authentication" "id"
12378 .vindex "&$authenticated_id$&"
12379 When a server successfully authenticates a client it may be configured to
12380 preserve some of the authentication information in the variable
12381 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
12382 user/password authenticator configuration might preserve the user name for use
12383 in the routers. Note that this is not the same information that is saved in
12384 &$sender_host_authenticated$&.
12386 When a message is submitted locally (that is, not over a TCP connection)
12387 the value of &$authenticated_id$& is normally the login name of the calling
12388 process. However, a trusted user can override this by means of the &%-oMai%&
12389 command line option.
12390 This second case also sets up information used by the
12391 &$authresults$& expansion item.
12393 .vitem &$authenticated_fail_id$&
12394 .cindex "authentication" "fail" "id"
12395 .vindex "&$authenticated_fail_id$&"
12396 When an authentication attempt fails, the variable &$authenticated_fail_id$&
12397 will contain the failed authentication id. If more than one authentication
12398 id is attempted, it will contain only the last one. The variable is
12399 available for processing in the ACL's, generally the quit or notquit ACL.
12400 A message to a local recipient could still be accepted without requiring
12401 authentication, which means this variable could also be visible in all of
12405 .vitem &$authenticated_sender$&
12406 .cindex "sender" "authenticated"
12407 .cindex "authentication" "sender"
12408 .cindex "AUTH" "on MAIL command"
12409 .vindex "&$authenticated_sender$&"
12410 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
12411 SMTP MAIL command if it believes the sender is sufficiently trusted, as
12412 described in section &<<SECTauthparamail>>&. Unless the data is the string
12413 &"<>"&, it is set as the authenticated sender of the message, and the value is
12414 available during delivery in the &$authenticated_sender$& variable. If the
12415 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
12417 .vindex "&$qualify_domain$&"
12418 When a message is submitted locally (that is, not over a TCP connection), the
12419 value of &$authenticated_sender$& is an address constructed from the login
12420 name of the calling process and &$qualify_domain$&, except that a trusted user
12421 can override this by means of the &%-oMas%& command line option.
12424 .vitem &$authentication_failed$&
12425 .cindex "authentication" "failure"
12426 .vindex "&$authentication_failed$&"
12427 This variable is set to &"1"& in an Exim server if a client issues an AUTH
12428 command that does not succeed. Otherwise it is set to &"0"&. This makes it
12429 possible to distinguish between &"did not try to authenticate"&
12430 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
12431 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
12432 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
12433 negative response to an AUTH command, including (for example) an attempt to use
12434 an undefined mechanism.
12436 .vitem &$av_failed$&
12437 .cindex "content scanning" "AV scanner failure"
12438 This variable is available when Exim is compiled with the content-scanning
12439 extension. It is set to &"0"& by default, but will be set to &"1"& if any
12440 problem occurs with the virus scanner (specified by &%av_scanner%&) during
12441 the ACL malware condition.
12443 .vitem &$body_linecount$&
12444 .cindex "message body" "line count"
12445 .cindex "body of message" "line count"
12446 .vindex "&$body_linecount$&"
12447 When a message is being received or delivered, this variable contains the
12448 number of lines in the message's body. See also &$message_linecount$&.
12450 .vitem &$body_zerocount$&
12451 .cindex "message body" "binary zero count"
12452 .cindex "body of message" "binary zero count"
12453 .cindex "binary zero" "in message body"
12454 .vindex "&$body_zerocount$&"
12455 When a message is being received or delivered, this variable contains the
12456 number of binary zero bytes (ASCII NULs) in the message's body.
12458 .vitem &$bounce_recipient$&
12459 .vindex "&$bounce_recipient$&"
12460 This is set to the recipient address of a bounce message while Exim is creating
12461 it. It is useful if a customized bounce message text file is in use (see
12462 chapter &<<CHAPemsgcust>>&).
12464 .vitem &$bounce_return_size_limit$&
12465 .vindex "&$bounce_return_size_limit$&"
12466 This contains the value set in the &%bounce_return_size_limit%& option, rounded
12467 up to a multiple of 1000. It is useful when a customized error message text
12468 file is in use (see chapter &<<CHAPemsgcust>>&).
12470 .vitem &$caller_gid$&
12471 .cindex "gid (group id)" "caller"
12472 .vindex "&$caller_gid$&"
12473 The real group id under which the process that called Exim was running. This is
12474 not the same as the group id of the originator of a message (see
12475 &$originator_gid$&). If Exim re-execs itself, this variable in the new
12476 incarnation normally contains the Exim gid.
12478 .vitem &$caller_uid$&
12479 .cindex "uid (user id)" "caller"
12480 .vindex "&$caller_uid$&"
12481 The real user id under which the process that called Exim was running. This is
12482 not the same as the user id of the originator of a message (see
12483 &$originator_uid$&). If Exim re-execs itself, this variable in the new
12484 incarnation normally contains the Exim uid.
12486 .vitem &$callout_address$&
12487 .vindex "&$callout_address$&"
12488 After a callout for verification, spamd or malware daemon service, the
12489 address that was connected to.
12491 .vitem &$compile_number$&
12492 .vindex "&$compile_number$&"
12493 The building process for Exim keeps a count of the number
12494 of times it has been compiled. This serves to distinguish different
12495 compilations of the same version of Exim.
12497 .vitem &$config_dir$&
12498 .vindex "&$config_dir$&"
12499 The directory name of the main configuration file. That is, the content of
12500 &$config_file$& with the last component stripped. The value does not
12501 contain the trailing slash. If &$config_file$& does not contain a slash,
12502 &$config_dir$& is ".".
12504 .vitem &$config_file$&
12505 .vindex "&$config_file$&"
12506 The name of the main configuration file Exim is using.
12508 .vitem &$dkim_verify_status$&
12509 Results of DKIM verification.
12510 For details see section &<<SECDKIMVFY>>&.
12512 .vitem &$dkim_cur_signer$& &&&
12513 &$dkim_verify_reason$& &&&
12514 &$dkim_domain$& &&&
12515 &$dkim_identity$& &&&
12516 &$dkim_selector$& &&&
12518 &$dkim_canon_body$& &&&
12519 &$dkim_canon_headers$& &&&
12520 &$dkim_copiedheaders$& &&&
12521 &$dkim_bodylength$& &&&
12522 &$dkim_created$& &&&
12523 &$dkim_expires$& &&&
12524 &$dkim_headernames$& &&&
12525 &$dkim_key_testing$& &&&
12526 &$dkim_key_nosubdomains$& &&&
12527 &$dkim_key_srvtype$& &&&
12528 &$dkim_key_granularity$& &&&
12529 &$dkim_key_notes$& &&&
12530 &$dkim_key_length$&
12531 These variables are only available within the DKIM ACL.
12532 For details see section &<<SECDKIMVFY>>&.
12534 .vitem &$dkim_signers$&
12535 .vindex &$dkim_signers$&
12536 When a message has been received this variable contains
12537 a colon-separated list of signer domains and identities for the message.
12538 For details see section &<<SECDKIMVFY>>&.
12540 .vitem &$dmarc_domain_policy$& &&&
12541 &$dmarc_status$& &&&
12542 &$dmarc_status_text$& &&&
12543 &$dmarc_used_domains$&
12544 Results of DMARC verification.
12545 For details see section &<<SECDMARC>>&.
12547 .vitem &$dnslist_domain$& &&&
12548 &$dnslist_matched$& &&&
12549 &$dnslist_text$& &&&
12551 .vindex "&$dnslist_domain$&"
12552 .vindex "&$dnslist_matched$&"
12553 .vindex "&$dnslist_text$&"
12554 .vindex "&$dnslist_value$&"
12555 .cindex "black list (DNS)"
12556 When a DNS (black) list lookup succeeds, these variables are set to contain
12557 the following data from the lookup: the list's domain name, the key that was
12558 looked up, the contents of any associated TXT record, and the value from the
12559 main A record. See section &<<SECID204>>& for more details.
12562 .vindex "&$domain$&"
12563 When an address is being routed, or delivered on its own, this variable
12564 contains the domain. Uppercase letters in the domain are converted into lower
12565 case for &$domain$&.
12567 Global address rewriting happens when a message is received, so the value of
12568 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
12569 is set during user filtering, but not during system filtering, because a
12570 message may have many recipients and the system filter is called just once.
12572 When more than one address is being delivered at once (for example, several
12573 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
12574 have the same domain. Transports can be restricted to handling only one domain
12575 at a time if the value of &$domain$& is required at transport time &-- this is
12576 the default for local transports. For further details of the environment in
12577 which local transports are run, see chapter &<<CHAPenvironment>>&.
12579 .oindex "&%delay_warning_condition%&"
12580 At the end of a delivery, if all deferred addresses have the same domain, it is
12581 set in &$domain$& during the expansion of &%delay_warning_condition%&.
12583 The &$domain$& variable is also used in some other circumstances:
12586 When an ACL is running for a RCPT command, &$domain$& contains the domain of
12587 the recipient address. The domain of the &'sender'& address is in
12588 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
12589 normally set during the running of the MAIL ACL. However, if the sender address
12590 is verified with a callout during the MAIL ACL, the sender domain is placed in
12591 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
12592 the &(smtp)& transport.
12595 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12596 &$domain$& contains the domain portion of the address that is being rewritten;
12597 it can be used in the expansion of the replacement address, for example, to
12598 rewrite domains by file lookup.
12601 With one important exception, whenever a domain list is being scanned,
12602 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
12603 a &%sender_domains%& condition in an ACL is being processed, the subject domain
12604 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
12605 that, in a RCPT ACL, the sender domain list can be dependent on the
12606 recipient domain (which is what is in &$domain$& at this time).
12609 .cindex "ETRN" "value of &$domain$&"
12610 .oindex "&%smtp_etrn_command%&"
12611 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
12612 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
12615 .cindex "tainted data"
12616 If the origin of the data is an incoming message,
12617 the result of expanding this variable is tainted and may not
12618 be further expanded or used as a filename.
12619 When an untainted version is needed, one should be obtained from
12620 looking up the value in a local (therefore trusted) database.
12621 Often &$domain_data$& is usable in this role.
12624 .vitem &$domain_data$&
12625 .vindex "&$domain_data$&"
12626 When the &%domains%& condition on a router
12630 against a list, the match value is copied to &$domain_data$&.
12631 This is an enhancement over previous versions of Exim, when it only
12632 applied to the data read by a lookup.
12633 For details on match values see section &<<SECTlistresults>>& et. al.
12636 If the router routes the
12637 address to a transport, the value is available in that transport. If the
12638 transport is handling multiple addresses, the value from the first address is
12641 &$domain_data$& set in an ACL is available during
12642 the rest of the ACL statement.
12644 .vitem &$exim_gid$&
12645 .vindex "&$exim_gid$&"
12646 This variable contains the numerical value of the Exim group id.
12648 .vitem &$exim_path$&
12649 .vindex "&$exim_path$&"
12650 This variable contains the path to the Exim binary.
12652 .vitem &$exim_uid$&
12653 .vindex "&$exim_uid$&"
12654 This variable contains the numerical value of the Exim user id.
12656 .vitem &$exim_version$&
12657 .vindex "&$exim_version$&"
12658 This variable contains the version string of the Exim build.
12659 The first character is a major version number, currently 4.
12660 Then after a dot, the next group of digits is a minor version number.
12661 There may be other characters following the minor version.
12662 This value may be overridden by the &%exim_version%& main config option.
12664 .vitem &$header_$&<&'name'&>
12665 This is not strictly an expansion variable. It is expansion syntax for
12666 inserting the message header line with the given name. Note that the name must
12667 be terminated by colon or white space, because it may contain a wide variety of
12668 characters. Note also that braces must &'not'& be used.
12669 See the full description in section &<<SECTexpansionitems>>& above.
12671 .vitem &$headers_added$&
12672 .vindex "&$headers_added$&"
12673 Within an ACL this variable contains the headers added so far by
12674 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
12675 The headers are a newline-separated list.
12679 When the &%check_local_user%& option is set for a router, the user's home
12680 directory is placed in &$home$& when the check succeeds. In particular, this
12681 means it is set during the running of users' filter files. A router may also
12682 explicitly set a home directory for use by a transport; this can be overridden
12683 by a setting on the transport itself.
12685 When running a filter test via the &%-bf%& option, &$home$& is set to the value
12686 of the environment variable HOME, which is subject to the
12687 &%keep_environment%& and &%add_environment%& main config options.
12691 If a router assigns an address to a transport (any transport), and passes a
12692 list of hosts with the address, the value of &$host$& when the transport starts
12693 to run is the name of the first host on the list. Note that this applies both
12694 to local and remote transports.
12696 .cindex "transport" "filter"
12697 .cindex "filter" "transport filter"
12698 For the &(smtp)& transport, if there is more than one host, the value of
12699 &$host$& changes as the transport works its way through the list. In
12700 particular, when the &(smtp)& transport is expanding its options for encryption
12701 using TLS, or for specifying a transport filter (see chapter
12702 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
12705 When used in the client part of an authenticator configuration (see chapter
12706 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
12707 client is connected.
12710 .vitem &$host_address$&
12711 .vindex "&$host_address$&"
12712 This variable is set to the remote host's IP address whenever &$host$& is set
12713 for a remote connection. It is also set to the IP address that is being checked
12714 when the &%ignore_target_hosts%& option is being processed.
12716 .vitem &$host_data$&
12717 .vindex "&$host_data$&"
12718 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
12719 result of the lookup is made available in the &$host_data$& variable. This
12720 allows you, for example, to do things like this:
12722 deny hosts = net-lsearch;/some/file
12723 message = $host_data
12725 .vitem &$host_lookup_deferred$&
12726 .cindex "host name" "lookup, failure of"
12727 .vindex "&$host_lookup_deferred$&"
12728 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
12729 message comes from a remote host and there is an attempt to look up the host's
12730 name from its IP address, and the attempt is not successful, one of these
12731 variables is set to &"1"&.
12734 If the lookup receives a definite negative response (for example, a DNS lookup
12735 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
12738 If there is any kind of problem during the lookup, such that Exim cannot
12739 tell whether or not the host name is defined (for example, a timeout for a DNS
12740 lookup), &$host_lookup_deferred$& is set to &"1"&.
12743 Looking up a host's name from its IP address consists of more than just a
12744 single reverse lookup. Exim checks that a forward lookup of at least one of the
12745 names it receives from a reverse lookup yields the original IP address. If this
12746 is not the case, Exim does not accept the looked up name(s), and
12747 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
12748 IP address (for example, the existence of a PTR record in the DNS) is not
12749 sufficient on its own for the success of a host name lookup. If the reverse
12750 lookup succeeds, but there is a lookup problem such as a timeout when checking
12751 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
12752 &"1"&. See also &$sender_host_name$&.
12754 .cindex authentication "expansion item"
12755 Performing these checks sets up information used by the
12756 &%authresults%& expansion item.
12759 .vitem &$host_lookup_failed$&
12760 .vindex "&$host_lookup_failed$&"
12761 See &$host_lookup_deferred$&.
12763 .vitem &$host_port$&
12764 .vindex "&$host_port$&"
12765 This variable is set to the remote host's TCP port whenever &$host$& is set
12766 for an outbound connection.
12768 .vitem &$initial_cwd$&
12769 .vindex "&$initial_cwd$&
12770 This variable contains the full path name of the initial working
12771 directory of the current Exim process. This may differ from the current
12772 working directory, as Exim changes this to "/" during early startup, and
12773 to &$spool_directory$& later.
12776 .vindex "&$inode$&"
12777 The only time this variable is set is while expanding the &%directory_file%&
12778 option in the &(appendfile)& transport. The variable contains the inode number
12779 of the temporary file which is about to be renamed. It can be used to construct
12780 a unique name for the file.
12782 .vitem &$interface_address$&
12783 .vindex "&$interface_address$&"
12784 This is an obsolete name for &$received_ip_address$&.
12786 .vitem &$interface_port$&
12787 .vindex "&$interface_port$&"
12788 This is an obsolete name for &$received_port$&.
12792 This variable is used during the expansion of &*forall*& and &*forany*&
12793 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
12794 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
12798 .vindex "&$ldap_dn$&"
12799 This variable, which is available only when Exim is compiled with LDAP support,
12800 contains the DN from the last entry in the most recently successful LDAP
12803 .vitem &$load_average$&
12804 .vindex "&$load_average$&"
12805 This variable contains the system load average, multiplied by 1000 so that it
12806 is an integer. For example, if the load average is 0.21, the value of the
12807 variable is 210. The value is recomputed every time the variable is referenced.
12809 .vitem &$local_part$&
12810 .vindex "&$local_part$&"
12811 When an address is being routed, or delivered on its own, this
12812 variable contains the local part. When a number of addresses are being
12813 delivered together (for example, multiple RCPT commands in an SMTP
12814 session), &$local_part$& is not set.
12816 Global address rewriting happens when a message is received, so the value of
12817 &$local_part$& during routing and delivery is the value after rewriting.
12818 &$local_part$& is set during user filtering, but not during system filtering,
12819 because a message may have many recipients and the system filter is called just
12822 .cindex "tainted data"
12823 If the origin of the data is an incoming message,
12824 the result of expanding this variable is tainted and
12825 may not be further expanded or used as a filename.
12827 &*Warning*&: the content of this variable is usually provided by a potential
12829 Consider carefully the implications of using it unvalidated as a name
12831 This presents issues for users' &_.forward_& and filter files.
12832 For traditional full user accounts, use &%check_local_users%& and the
12833 &$local_part_data$& variable rather than this one.
12834 For virtual users, store a suitable pathname component in the database
12835 which is used for account name validation, and use that retrieved value
12836 rather than this variable.
12837 Often &$local_part_data$& is usable in this role.
12838 If needed, use a router &%address_data%& or &%set%& option for
12839 the retrieved data.
12841 When a message is being delivered to a file, pipe, or autoreply transport as a
12842 result of aliasing or forwarding, &$local_part$& is set to the local part of
12843 the parent address, not to the filename or command (see &$address_file$& and
12846 When an ACL is running for a RCPT command, &$local_part$& contains the
12847 local part of the recipient address.
12849 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12850 &$local_part$& contains the local part of the address that is being rewritten;
12851 it can be used in the expansion of the replacement address, for example.
12853 In all cases, all quoting is removed from the local part. For example, for both
12856 "abc:xyz"@test.example
12857 abc\:xyz@test.example
12859 the value of &$local_part$& is
12863 If you use &$local_part$& to create another address, you should always wrap it
12864 inside a quoting operator. For example, in a &(redirect)& router you could
12867 data = ${quote_local_part:$local_part}@new.domain.example
12869 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
12870 to process local parts in a case-dependent manner in a router, you can set the
12871 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
12873 .vitem &$local_part_data$&
12874 .vindex "&$local_part_data$&"
12875 When the &%local_parts%& condition on a router or ACL
12876 matches a local part list
12878 the match value is copied to &$local_part_data$&.
12879 This is an enhancement over previous versions of Exim, when it only
12880 applied to the data read by a lookup.
12881 For details on match values see section &<<SECTlistresults>>& et. al.
12884 The &%check_local_user%& router option also sets this variable.
12886 .vindex &$local_part_prefix$& &&&
12887 &$local_part_prefix_v$& &&&
12888 &$local_part_suffix$& &&&
12889 &$local_part_suffix_v$&
12890 .cindex affix variables
12891 If a local part prefix or suffix has been recognized, it is not included in the
12892 value of &$local_part$& during routing and subsequent delivery. The values of
12893 any prefix or suffix are in &$local_part_prefix$& and
12894 &$local_part_suffix$&, respectively.
12895 .cindex "tainted data"
12896 If the specification did not include a wildcard then
12897 the affix variable value is not tainted.
12899 If the affix specification included a wildcard then the portion of
12900 the affix matched by the wildcard is in
12901 &$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate,
12902 and both the whole and varying values are tainted.
12904 .vitem &$local_scan_data$&
12905 .vindex "&$local_scan_data$&"
12906 This variable contains the text returned by the &[local_scan()]& function when
12907 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
12909 .vitem &$local_user_gid$&
12910 .vindex "&$local_user_gid$&"
12911 See &$local_user_uid$&.
12913 .vitem &$local_user_uid$&
12914 .vindex "&$local_user_uid$&"
12915 This variable and &$local_user_gid$& are set to the uid and gid after the
12916 &%check_local_user%& router precondition succeeds. This means that their values
12917 are available for the remaining preconditions (&%senders%&, &%require_files%&,
12918 and &%condition%&), for the &%address_data%& expansion, and for any
12919 router-specific expansions. At all other times, the values in these variables
12920 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
12922 .vitem &$localhost_number$&
12923 .vindex "&$localhost_number$&"
12924 This contains the expanded value of the
12925 &%localhost_number%& option. The expansion happens after the main options have
12928 .vitem &$log_inodes$&
12929 .vindex "&$log_inodes$&"
12930 The number of free inodes in the disk partition where Exim's
12931 log files are being written. The value is recalculated whenever the variable is
12932 referenced. If the relevant file system does not have the concept of inodes,
12933 the value of is -1. See also the &%check_log_inodes%& option.
12935 .vitem &$log_space$&
12936 .vindex "&$log_space$&"
12937 The amount of free space (as a number of kilobytes) in the disk
12938 partition where Exim's log files are being written. The value is recalculated
12939 whenever the variable is referenced. If the operating system does not have the
12940 ability to find the amount of free space (only true for experimental systems),
12941 the space value is -1. See also the &%check_log_space%& option.
12944 .vitem &$lookup_dnssec_authenticated$&
12945 .vindex "&$lookup_dnssec_authenticated$&"
12946 This variable is set after a DNS lookup done by
12947 a dnsdb lookup expansion, dnslookup router or smtp transport.
12948 .cindex "DNS" "DNSSEC"
12949 It will be empty if &(DNSSEC)& was not requested,
12950 &"no"& if the result was not labelled as authenticated data
12951 and &"yes"& if it was.
12952 Results that are labelled as authoritative answer that match
12953 the &%dns_trust_aa%& configuration variable count also
12954 as authenticated data.
12956 .vitem &$mailstore_basename$&
12957 .vindex "&$mailstore_basename$&"
12958 This variable is set only when doing deliveries in &"mailstore"& format in the
12959 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
12960 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
12961 contains the basename of the files that are being written, that is, the name
12962 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
12965 .vitem &$malware_name$&
12966 .vindex "&$malware_name$&"
12967 This variable is available when Exim is compiled with the
12968 content-scanning extension. It is set to the name of the virus that was found
12969 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12971 .vitem &$max_received_linelength$&
12972 .vindex "&$max_received_linelength$&"
12973 .cindex "maximum" "line length"
12974 .cindex "line length" "maximum"
12975 This variable contains the number of bytes in the longest line that was
12976 received as part of the message, not counting the line termination
12978 It is not valid if the &%spool_files_wireformat%& option is used.
12980 .vitem &$message_age$&
12981 .cindex "message" "age of"
12982 .vindex "&$message_age$&"
12983 This variable is set at the start of a delivery attempt to contain the number
12984 of seconds since the message was received. It does not change during a single
12987 .vitem &$message_body$&
12988 .cindex "body of message" "expansion variable"
12989 .cindex "message body" "in expansion"
12990 .cindex "binary zero" "in message body"
12991 .vindex "&$message_body$&"
12992 .oindex "&%message_body_visible%&"
12993 This variable contains the initial portion of a message's body while it is
12994 being delivered, and is intended mainly for use in filter files. The maximum
12995 number of characters of the body that are put into the variable is set by the
12996 &%message_body_visible%& configuration option; the default is 500.
12998 .oindex "&%message_body_newlines%&"
12999 By default, newlines are converted into spaces in &$message_body$&, to make it
13000 easier to search for phrases that might be split over a line break. However,
13001 this can be disabled by setting &%message_body_newlines%& to be true. Binary
13002 zeros are always converted into spaces.
13004 .vitem &$message_body_end$&
13005 .cindex "body of message" "expansion variable"
13006 .cindex "message body" "in expansion"
13007 .vindex "&$message_body_end$&"
13008 This variable contains the final portion of a message's
13009 body while it is being delivered. The format and maximum size are as for
13012 .vitem &$message_body_size$&
13013 .cindex "body of message" "size"
13014 .cindex "message body" "size"
13015 .vindex "&$message_body_size$&"
13016 When a message is being delivered, this variable contains the size of the body
13017 in bytes. The count starts from the character after the blank line that
13018 separates the body from the header. Newlines are included in the count. See
13019 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
13021 If the spool file is wireformat
13022 (see the &%spool_files_wireformat%& main option)
13023 the CRLF line-terminators are included in the count.
13025 .vitem &$message_exim_id$&
13026 .vindex "&$message_exim_id$&"
13027 When a message is being received or delivered, this variable contains the
13028 unique message id that is generated and used by Exim to identify the message.
13029 An id is not created for a message until after its header has been successfully
13030 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
13031 line; it is the local id that Exim assigns to the message, for example:
13032 &`1BXTIK-0001yO-VA`&.
13034 .vitem &$message_headers$&
13035 .vindex &$message_headers$&
13036 This variable contains a concatenation of all the header lines when a message
13037 is being processed, except for lines added by routers or transports. The header
13038 lines are separated by newline characters. Their contents are decoded in the
13039 same way as a header line that is inserted by &%bheader%&.
13041 .vitem &$message_headers_raw$&
13042 .vindex &$message_headers_raw$&
13043 This variable is like &$message_headers$& except that no processing of the
13044 contents of header lines is done.
13046 .vitem &$message_id$&
13047 This is an old name for &$message_exim_id$&. It is now deprecated.
13049 .vitem &$message_linecount$&
13050 .vindex "&$message_linecount$&"
13051 This variable contains the total number of lines in the header and body of the
13052 message. Compare &$body_linecount$&, which is the count for the body only.
13053 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
13054 number of lines received. Before delivery happens (that is, before filters,
13055 routers, and transports run) the count is increased to include the
13056 &'Received:'& header line that Exim standardly adds, and also any other header
13057 lines that are added by ACLs. The blank line that separates the message header
13058 from the body is not counted.
13060 As with the special case of &$message_size$&, during the expansion of the
13061 appendfile transport's maildir_tag option in maildir format, the value of
13062 &$message_linecount$& is the precise size of the number of newlines in the
13063 file that has been written (minus one for the blank line between the
13064 header and the body).
13066 Here is an example of the use of this variable in a DATA ACL:
13069 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
13070 message = Too many lines in message header
13072 In the MAIL and RCPT ACLs, the value is zero because at that stage the
13073 message has not yet been received.
13075 This variable is not valid if the &%spool_files_wireformat%& option is used.
13077 .vitem &$message_size$&
13078 .cindex "size" "of message"
13079 .cindex "message" "size"
13080 .vindex "&$message_size$&"
13081 When a message is being processed, this variable contains its size in bytes. In
13082 most cases, the size includes those headers that were received with the
13083 message, but not those (such as &'Envelope-to:'&) that are added to individual
13084 deliveries as they are written. However, there is one special case: during the
13085 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
13086 doing a delivery in maildir format, the value of &$message_size$& is the
13087 precise size of the file that has been written. See also
13088 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
13090 .cindex "RCPT" "value of &$message_size$&"
13091 While running a per message ACL (mail/rcpt/predata), &$message_size$&
13092 contains the size supplied on the MAIL command, or -1 if no size was given. The
13093 value may not, of course, be truthful.
13095 .vitem &$mime_$&&'xxx'&
13096 A number of variables whose names start with &$mime$& are
13097 available when Exim is compiled with the content-scanning extension. For
13098 details, see section &<<SECTscanmimepart>>&.
13100 .vitem "&$n0$& &-- &$n9$&"
13101 These variables are counters that can be incremented by means
13102 of the &%add%& command in filter files.
13104 .vitem &$original_domain$&
13105 .vindex "&$domain$&"
13106 .vindex "&$original_domain$&"
13107 When a top-level address is being processed for delivery, this contains the
13108 same value as &$domain$&. However, if a &"child"& address (for example,
13109 generated by an alias, forward, or filter file) is being processed, this
13110 variable contains the domain of the original address (lower cased). This
13111 differs from &$parent_domain$& only when there is more than one level of
13112 aliasing or forwarding. When more than one address is being delivered in a
13113 single transport run, &$original_domain$& is not set.
13115 If a new address is created by means of a &%deliver%& command in a system
13116 filter, it is set up with an artificial &"parent"& address. This has the local
13117 part &'system-filter'& and the default qualify domain.
13119 .vitem &$original_local_part$&
13120 .vindex "&$local_part$&"
13121 .vindex "&$original_local_part$&"
13122 When a top-level address is being processed for delivery, this contains the
13123 same value as &$local_part$&, unless a prefix or suffix was removed from the
13124 local part, because &$original_local_part$& always contains the full local
13125 part. When a &"child"& address (for example, generated by an alias, forward, or
13126 filter file) is being processed, this variable contains the full local part of
13127 the original address.
13129 If the router that did the redirection processed the local part
13130 case-insensitively, the value in &$original_local_part$& is in lower case.
13131 This variable differs from &$parent_local_part$& only when there is more than
13132 one level of aliasing or forwarding. When more than one address is being
13133 delivered in a single transport run, &$original_local_part$& is not set.
13135 If a new address is created by means of a &%deliver%& command in a system
13136 filter, it is set up with an artificial &"parent"& address. This has the local
13137 part &'system-filter'& and the default qualify domain.
13139 .vitem &$originator_gid$&
13140 .cindex "gid (group id)" "of originating user"
13141 .cindex "sender" "gid"
13142 .vindex "&$caller_gid$&"
13143 .vindex "&$originator_gid$&"
13144 This variable contains the value of &$caller_gid$& that was set when the
13145 message was received. For messages received via the command line, this is the
13146 gid of the sending user. For messages received by SMTP over TCP/IP, this is
13147 normally the gid of the Exim user.
13149 .vitem &$originator_uid$&
13150 .cindex "uid (user id)" "of originating user"
13151 .cindex "sender" "uid"
13152 .vindex "&$caller_uid$&"
13153 .vindex "&$originator_uid$&"
13154 The value of &$caller_uid$& that was set when the message was received. For
13155 messages received via the command line, this is the uid of the sending user.
13156 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
13159 .vitem &$parent_domain$&
13160 .vindex "&$parent_domain$&"
13161 This variable is similar to &$original_domain$& (see
13162 above), except that it refers to the immediately preceding parent address.
13164 .vitem &$parent_local_part$&
13165 .vindex "&$parent_local_part$&"
13166 This variable is similar to &$original_local_part$&
13167 (see above), except that it refers to the immediately preceding parent address.
13170 .cindex "pid (process id)" "of current process"
13172 This variable contains the current process id.
13174 .vitem &$pipe_addresses$&
13175 .cindex "filter" "transport filter"
13176 .cindex "transport" "filter"
13177 .vindex "&$pipe_addresses$&"
13178 This is not an expansion variable, but is mentioned here because the string
13179 &`$pipe_addresses`& is handled specially in the command specification for the
13180 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
13181 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
13182 It cannot be used in general expansion strings, and provokes an &"unknown
13183 variable"& error if encountered.
13185 .vitem &$primary_hostname$&
13186 .vindex "&$primary_hostname$&"
13187 This variable contains the value set by &%primary_hostname%& in the
13188 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
13189 a single-component name, Exim calls &[gethostbyname()]& (or
13190 &[getipnodebyname()]& where available) in an attempt to acquire a fully
13191 qualified host name. See also &$smtp_active_hostname$&.
13194 .vitem &$proxy_external_address$& &&&
13195 &$proxy_external_port$& &&&
13196 &$proxy_local_address$& &&&
13197 &$proxy_local_port$& &&&
13199 These variables are only available when built with Proxy Protocol
13201 For details see chapter &<<SECTproxyInbound>>&.
13203 .vitem &$prdr_requested$&
13204 .cindex "PRDR" "variable for"
13205 This variable is set to &"yes"& if PRDR was requested by the client for the
13206 current message, otherwise &"no"&.
13208 .vitem &$prvscheck_address$&
13209 This variable is used in conjunction with the &%prvscheck%& expansion item,
13210 which is described in sections &<<SECTexpansionitems>>& and
13211 &<<SECTverifyPRVS>>&.
13213 .vitem &$prvscheck_keynum$&
13214 This variable is used in conjunction with the &%prvscheck%& expansion item,
13215 which is described in sections &<<SECTexpansionitems>>& and
13216 &<<SECTverifyPRVS>>&.
13218 .vitem &$prvscheck_result$&
13219 This variable is used in conjunction with the &%prvscheck%& expansion item,
13220 which is described in sections &<<SECTexpansionitems>>& and
13221 &<<SECTverifyPRVS>>&.
13223 .vitem &$qualify_domain$&
13224 .vindex "&$qualify_domain$&"
13225 The value set for the &%qualify_domain%& option in the configuration file.
13227 .vitem &$qualify_recipient$&
13228 .vindex "&$qualify_recipient$&"
13229 The value set for the &%qualify_recipient%& option in the configuration file,
13230 or if not set, the value of &$qualify_domain$&.
13232 .vitem &$queue_name$&
13233 .vindex &$queue_name$&
13234 .cindex "named queues" variable
13235 .cindex queues named
13236 The name of the spool queue in use; empty for the default queue.
13238 .vitem &$queue_size$&
13239 .vindex "&$queue_size$&"
13240 .cindex "queue" "size of"
13241 .cindex "spool" "number of messages"
13242 This variable contains the number of messages queued.
13243 It is evaluated on demand, but no more often than once every minute.
13244 If there is no daemon notifier socket open, the value will be
13249 .cindex router variables
13250 Values can be placed in these variables by the &%set%& option of a router.
13251 They can be given any name that starts with &$r_$&.
13252 The values persist for the address being handled through subsequent routers
13253 and the eventual transport.
13255 .vitem &$rcpt_count$&
13256 .vindex "&$rcpt_count$&"
13257 When a message is being received by SMTP, this variable contains the number of
13258 RCPT commands received for the current message. If this variable is used in a
13259 RCPT ACL, its value includes the current command.
13261 .vitem &$rcpt_defer_count$&
13262 .vindex "&$rcpt_defer_count$&"
13263 .cindex "4&'xx'& responses" "count of"
13264 When a message is being received by SMTP, this variable contains the number of
13265 RCPT commands in the current message that have previously been rejected with a
13266 temporary (4&'xx'&) response.
13268 .vitem &$rcpt_fail_count$&
13269 .vindex "&$rcpt_fail_count$&"
13270 When a message is being received by SMTP, this variable contains the number of
13271 RCPT commands in the current message that have previously been rejected with a
13272 permanent (5&'xx'&) response.
13274 .vitem &$received_count$&
13275 .vindex "&$received_count$&"
13276 This variable contains the number of &'Received:'& header lines in the message,
13277 including the one added by Exim (so its value is always greater than zero). It
13278 is available in the DATA ACL, the non-SMTP ACL, and while routing and
13281 .vitem &$received_for$&
13282 .vindex "&$received_for$&"
13283 If there is only a single recipient address in an incoming message, this
13284 variable contains that address when the &'Received:'& header line is being
13285 built. The value is copied after recipient rewriting has happened, but before
13286 the &[local_scan()]& function is run.
13288 .vitem &$received_ip_address$&
13289 .vindex "&$received_ip_address$&"
13290 As soon as an Exim server starts processing an incoming TCP/IP connection, this
13291 variable is set to the address of the local IP interface, and &$received_port$&
13292 is set to the local port number. (The remote IP address and port are in
13293 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
13294 the port value is -1 unless it has been set using the &%-oMi%& command line
13297 As well as being useful in ACLs (including the &"connect"& ACL), these variable
13298 could be used, for example, to make the filename for a TLS certificate depend
13299 on which interface and/or port is being used for the incoming connection. The
13300 values of &$received_ip_address$& and &$received_port$& are saved with any
13301 messages that are received, thus making these variables available at delivery
13303 For outbound connections see &$sending_ip_address$&.
13305 .vitem &$received_port$&
13306 .vindex "&$received_port$&"
13307 See &$received_ip_address$&.
13309 .vitem &$received_protocol$&
13310 .vindex "&$received_protocol$&"
13311 When a message is being processed, this variable contains the name of the
13312 protocol by which it was received. Most of the names used by Exim are defined
13313 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
13314 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
13315 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
13316 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
13317 connection and the client was successfully authenticated.
13319 Exim uses the protocol name &"smtps"& for the case when encryption is
13320 automatically set up on connection without the use of STARTTLS (see
13321 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
13322 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
13323 where the client initially uses EHLO, sets up an encrypted connection using
13324 STARTTLS, and then uses HELO afterwards.
13326 The &%-oMr%& option provides a way of specifying a custom protocol name for
13327 messages that are injected locally by trusted callers. This is commonly used to
13328 identify messages that are being re-injected after some kind of scanning.
13330 .vitem &$received_time$&
13331 .vindex "&$received_time$&"
13332 This variable contains the date and time when the current message was received,
13333 as a number of seconds since the start of the Unix epoch.
13335 .vitem &$recipient_data$&
13336 .vindex "&$recipient_data$&"
13337 This variable is set after an indexing lookup success in an ACL &%recipients%&
13338 condition. It contains the data from the lookup, and the value remains set
13339 until the next &%recipients%& test. Thus, you can do things like this:
13341 &`require recipients = cdb*@;/some/file`&
13342 &`deny `&&'some further test involving'& &`$recipient_data`&
13344 &*Warning*&: This variable is set only when a lookup is used as an indexing
13345 method in the address list, using the semicolon syntax as in the example above.
13346 The variable is not set for a lookup that is used as part of the string
13347 expansion that all such lists undergo before being interpreted.
13349 .vitem &$recipient_verify_failure$&
13350 .vindex "&$recipient_verify_failure$&"
13351 In an ACL, when a recipient verification fails, this variable contains
13352 information about the failure. It is set to one of the following words:
13355 &"qualify"&: The address was unqualified (no domain), and the message
13356 was neither local nor came from an exempted host.
13359 &"route"&: Routing failed.
13362 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
13363 or before the MAIL command (that is, on initial connection, HELO, or
13367 &"recipient"&: The RCPT command in a callout was rejected.
13370 &"postmaster"&: The postmaster check in a callout was rejected.
13373 The main use of this variable is expected to be to distinguish between
13374 rejections of MAIL and rejections of RCPT.
13376 .vitem &$recipients$&
13377 .vindex "&$recipients$&"
13378 This variable contains a list of envelope recipients for a message. A comma and
13379 a space separate the addresses in the replacement text. However, the variable
13380 is not generally available, to prevent exposure of Bcc recipients in
13381 unprivileged users' filter files. You can use &$recipients$& only in these
13385 In a system filter file.
13387 In the ACLs associated with the DATA command and with non-SMTP messages, that
13388 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
13389 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
13390 &%acl_not_smtp_mime%&.
13392 From within a &[local_scan()]& function.
13396 .vitem &$recipients_count$&
13397 .vindex "&$recipients_count$&"
13398 When a message is being processed, this variable contains the number of
13399 envelope recipients that came with the message. Duplicates are not excluded
13400 from the count. While a message is being received over SMTP, the number
13401 increases for each accepted recipient. It can be referenced in an ACL.
13404 .vitem &$regex_match_string$&
13405 .vindex "&$regex_match_string$&"
13406 This variable is set to contain the matching regular expression after a
13407 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
13409 .vitem "&$regex1$&, &$regex2$&, etc"
13410 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
13411 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
13412 these variables contain the
13413 captured substrings identified by the regular expression.
13416 .vitem &$reply_address$&
13417 .vindex "&$reply_address$&"
13418 When a message is being processed, this variable contains the contents of the
13419 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
13420 contents of the &'From:'& header line. Apart from the removal of leading
13421 white space, the value is not processed in any way. In particular, no RFC 2047
13422 decoding or character code translation takes place.
13424 .vitem &$return_path$&
13425 .vindex "&$return_path$&"
13426 When a message is being delivered, this variable contains the return path &--
13427 the sender field that will be sent as part of the envelope. It is not enclosed
13428 in <> characters. At the start of routing an address, &$return_path$& has the
13429 same value as &$sender_address$&, but if, for example, an incoming message to a
13430 mailing list has been expanded by a router which specifies a different address
13431 for bounce messages, &$return_path$& subsequently contains the new bounce
13432 address, whereas &$sender_address$& always contains the original sender address
13433 that was received with the message. In other words, &$sender_address$& contains
13434 the incoming envelope sender, and &$return_path$& contains the outgoing
13437 .vitem &$return_size_limit$&
13438 .vindex "&$return_size_limit$&"
13439 This is an obsolete name for &$bounce_return_size_limit$&.
13441 .vitem &$router_name$&
13442 .cindex "router" "name"
13443 .cindex "name" "of router"
13444 .vindex "&$router_name$&"
13445 During the running of a router this variable contains its name.
13448 .cindex "return code" "from &%run%& expansion"
13449 .vindex "&$runrc$&"
13450 This variable contains the return code from a command that is run by the
13451 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
13452 assume the order in which option values are expanded, except for those
13453 preconditions whose order of testing is documented. Therefore, you cannot
13454 reliably expect to set &$runrc$& by the expansion of one option, and use it in
13457 .vitem &$self_hostname$&
13458 .oindex "&%self%&" "value of host name"
13459 .vindex "&$self_hostname$&"
13460 When an address is routed to a supposedly remote host that turns out to be the
13461 local host, what happens is controlled by the &%self%& generic router option.
13462 One of its values causes the address to be passed to another router. When this
13463 happens, &$self_hostname$& is set to the name of the local host that the
13464 original router encountered. In other circumstances its contents are null.
13466 .vitem &$sender_address$&
13467 .vindex "&$sender_address$&"
13468 When a message is being processed, this variable contains the sender's address
13469 that was received in the message's envelope. The case of letters in the address
13470 is retained, in both the local part and the domain. For bounce messages, the
13471 value of this variable is the empty string. See also &$return_path$&.
13473 .vitem &$sender_address_data$&
13474 .vindex "&$address_data$&"
13475 .vindex "&$sender_address_data$&"
13476 If &$address_data$& is set when the routers are called from an ACL to verify a
13477 sender address, the final value is preserved in &$sender_address_data$&, to
13478 distinguish it from data from a recipient address. The value does not persist
13479 after the end of the current ACL statement. If you want to preserve it for
13480 longer, you can save it in an ACL variable.
13482 .vitem &$sender_address_domain$&
13483 .vindex "&$sender_address_domain$&"
13484 The domain portion of &$sender_address$&.
13486 .vitem &$sender_address_local_part$&
13487 .vindex "&$sender_address_local_part$&"
13488 The local part portion of &$sender_address$&.
13490 .vitem &$sender_data$&
13491 .vindex "&$sender_data$&"
13492 This variable is set after a lookup success in an ACL &%senders%& condition or
13493 in a router &%senders%& option. It contains the data from the lookup, and the
13494 value remains set until the next &%senders%& test. Thus, you can do things like
13497 &`require senders = cdb*@;/some/file`&
13498 &`deny `&&'some further test involving'& &`$sender_data`&
13500 &*Warning*&: This variable is set only when a lookup is used as an indexing
13501 method in the address list, using the semicolon syntax as in the example above.
13502 The variable is not set for a lookup that is used as part of the string
13503 expansion that all such lists undergo before being interpreted.
13505 .vitem &$sender_fullhost$&
13506 .vindex "&$sender_fullhost$&"
13507 When a message is received from a remote host, this variable contains the host
13508 name and IP address in a single string. It ends with the IP address in square
13509 brackets, followed by a colon and a port number if the logging of ports is
13510 enabled. The format of the rest of the string depends on whether the host
13511 issued a HELO or EHLO SMTP command, and whether the host name was verified by
13512 looking up its IP address. (Looking up the IP address can be forced by the
13513 &%host_lookup%& option, independent of verification.) A plain host name at the
13514 start of the string is a verified host name; if this is not present,
13515 verification either failed or was not requested. A host name in parentheses is
13516 the argument of a HELO or EHLO command. This is omitted if it is identical to
13517 the verified host name or to the host's IP address in square brackets.
13519 .vitem &$sender_helo_dnssec$&
13520 .vindex "&$sender_helo_dnssec$&"
13521 This boolean variable is true if a successful HELO verification was
13522 .cindex "DNS" "DNSSEC"
13523 done using DNS information the resolver library stated was authenticated data.
13525 .vitem &$sender_helo_name$&
13526 .vindex "&$sender_helo_name$&"
13527 When a message is received from a remote host that has issued a HELO or EHLO
13528 command, the argument of that command is placed in this variable. It is also
13529 set if HELO or EHLO is used when a message is received using SMTP locally via
13530 the &%-bs%& or &%-bS%& options.
13532 .vitem &$sender_host_address$&
13533 .vindex "&$sender_host_address$&"
13534 When a message is received from a remote host using SMTP,
13535 this variable contains that
13536 host's IP address. For locally non-SMTP submitted messages, it is empty.
13538 .vitem &$sender_host_authenticated$&
13539 .vindex "&$sender_host_authenticated$&"
13540 This variable contains the name (not the public name) of the authenticator
13541 driver that successfully authenticated the client from which the message was
13542 received. It is empty if there was no successful authentication. See also
13543 &$authenticated_id$&.
13545 .vitem &$sender_host_dnssec$&
13546 .vindex "&$sender_host_dnssec$&"
13547 If an attempt to populate &$sender_host_name$& has been made
13548 (by reference, &%hosts_lookup%& or
13549 otherwise) then this boolean will have been set true if, and only if, the
13550 resolver library states that both
13551 the reverse and forward DNS were authenticated data. At all
13552 other times, this variable is false.
13554 .cindex "DNS" "DNSSEC"
13555 It is likely that you will need to coerce DNSSEC support on in the resolver
13556 library, by setting:
13561 In addition, on Linux with glibc 2.31 or newer the resolver library will
13562 default to stripping out a successful validation status.
13563 This will break a previously working Exim installation.
13564 Provided that you do trust the resolver (ie, is on localhost) you can tell
13565 glibc to pass through any successful validation with a new option in
13566 &_/etc/resolv.conf_&:
13571 Exim does not perform DNSSEC validation itself, instead leaving that to a
13572 validating resolver (e.g. unbound, or bind with suitable configuration).
13574 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
13575 mechanism in the list, then this variable will be false.
13577 This requires that your system resolver library support EDNS0 (and that
13578 DNSSEC flags exist in the system headers). If the resolver silently drops
13579 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
13580 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
13583 .vitem &$sender_host_name$&
13584 .vindex "&$sender_host_name$&"
13585 When a message is received from a remote host, this variable contains the
13586 host's name as obtained by looking up its IP address. For messages received by
13587 other means, this variable is empty.
13589 .vindex "&$host_lookup_failed$&"
13590 If the host name has not previously been looked up, a reference to
13591 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
13592 A looked up name is accepted only if it leads back to the original IP address
13593 via a forward lookup. If either the reverse or the forward lookup fails to find
13594 any data, or if the forward lookup does not yield the original IP address,
13595 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
13597 .vindex "&$host_lookup_deferred$&"
13598 However, if either of the lookups cannot be completed (for example, there is a
13599 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
13600 &$host_lookup_failed$& remains set to &"0"&.
13602 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
13603 host name again if there is a subsequent reference to &$sender_host_name$&
13604 in the same Exim process, but it does try again if &$host_lookup_deferred$&
13607 Exim does not automatically look up every calling host's name. If you want
13608 maximum efficiency, you should arrange your configuration so that it avoids
13609 these lookups altogether. The lookup happens only if one or more of the
13610 following are true:
13613 A string containing &$sender_host_name$& is expanded.
13615 The calling host matches the list in &%host_lookup%&. In the default
13616 configuration, this option is set to *, so it must be changed if lookups are
13617 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
13619 Exim needs the host name in order to test an item in a host list. The items
13620 that require this are described in sections &<<SECThoslispatnam>>& and
13621 &<<SECThoslispatnamsk>>&.
13623 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
13624 In this case, the host name is required to compare with the name quoted in any
13625 EHLO or HELO commands that the client issues.
13627 The remote host issues a EHLO or HELO command that quotes one of the
13628 domains in &%helo_lookup_domains%&. The default value of this option is
13629 . ==== As this is a nested list, any displays it contains must be indented
13630 . ==== as otherwise they are too far to the left.
13632 helo_lookup_domains = @ : @[]
13634 which causes a lookup if a remote host (incorrectly) gives the server's name or
13635 IP address in an EHLO or HELO command.
13639 .vitem &$sender_host_port$&
13640 .vindex "&$sender_host_port$&"
13641 When a message is received from a remote host, this variable contains the port
13642 number that was used on the remote host.
13644 .vitem &$sender_ident$&
13645 .vindex "&$sender_ident$&"
13646 When a message is received from a remote host, this variable contains the
13647 identification received in response to an RFC 1413 request. When a message has
13648 been received locally, this variable contains the login name of the user that
13651 .vitem &$sender_rate_$&&'xxx'&
13652 A number of variables whose names begin &$sender_rate_$& are set as part of the
13653 &%ratelimit%& ACL condition. Details are given in section
13654 &<<SECTratelimiting>>&.
13656 .vitem &$sender_rcvhost$&
13657 .cindex "DNS" "reverse lookup"
13658 .cindex "reverse DNS lookup"
13659 .vindex "&$sender_rcvhost$&"
13660 This is provided specifically for use in &'Received:'& headers. It starts with
13661 either the verified host name (as obtained from a reverse DNS lookup) or, if
13662 there is no verified host name, the IP address in square brackets. After that
13663 there may be text in parentheses. When the first item is a verified host name,
13664 the first thing in the parentheses is the IP address in square brackets,
13665 followed by a colon and a port number if port logging is enabled. When the
13666 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
13669 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
13670 was used and its argument was not identical to the real host name or IP
13671 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
13672 all three items are present in the parentheses, a newline and tab are inserted
13673 into the string, to improve the formatting of the &'Received:'& header.
13675 .vitem &$sender_verify_failure$&
13676 .vindex "&$sender_verify_failure$&"
13677 In an ACL, when a sender verification fails, this variable contains information
13678 about the failure. The details are the same as for
13679 &$recipient_verify_failure$&.
13681 .vitem &$sending_ip_address$&
13682 .vindex "&$sending_ip_address$&"
13683 This variable is set whenever an outgoing SMTP connection to another host has
13684 been set up. It contains the IP address of the local interface that is being
13685 used. This is useful if a host that has more than one IP address wants to take
13686 on different personalities depending on which one is being used. For incoming
13687 connections, see &$received_ip_address$&.
13689 .vitem &$sending_port$&
13690 .vindex "&$sending_port$&"
13691 This variable is set whenever an outgoing SMTP connection to another host has
13692 been set up. It contains the local port that is being used. For incoming
13693 connections, see &$received_port$&.
13695 .vitem &$smtp_active_hostname$&
13696 .vindex "&$smtp_active_hostname$&"
13697 During an incoming SMTP session, this variable contains the value of the active
13698 host name, as specified by the &%smtp_active_hostname%& option. The value of
13699 &$smtp_active_hostname$& is saved with any message that is received, so its
13700 value can be consulted during routing and delivery.
13702 .vitem &$smtp_command$&
13703 .vindex "&$smtp_command$&"
13704 During the processing of an incoming SMTP command, this variable contains the
13705 entire command. This makes it possible to distinguish between HELO and EHLO in
13706 the HELO ACL, and also to distinguish between commands such as these:
13711 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
13712 command, the address in &$smtp_command$& is the original address before any
13713 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
13714 the address after SMTP-time rewriting.
13716 .vitem &$smtp_command_argument$&
13717 .cindex "SMTP" "command, argument for"
13718 .vindex "&$smtp_command_argument$&"
13719 While an ACL is running to check an SMTP command, this variable contains the
13720 argument, that is, the text that follows the command name, with leading white
13721 space removed. Following the introduction of &$smtp_command$&, this variable is
13722 somewhat redundant, but is retained for backwards compatibility.
13724 .vitem &$smtp_command_history$&
13725 .cindex SMTP "command history"
13726 .vindex "&$smtp_command_history$&"
13727 A comma-separated list (with no whitespace) of the most-recent SMTP commands
13728 received, in time-order left to right. Only a limited number of commands
13731 .vitem &$smtp_count_at_connection_start$&
13732 .vindex "&$smtp_count_at_connection_start$&"
13733 This variable is set greater than zero only in processes spawned by the Exim
13734 daemon for handling incoming SMTP connections. The name is deliberately long,
13735 in order to emphasize what the contents are. When the daemon accepts a new
13736 connection, it increments this variable. A copy of the variable is passed to
13737 the child process that handles the connection, but its value is fixed, and
13738 never changes. It is only an approximation of how many incoming connections
13739 there actually are, because many other connections may come and go while a
13740 single connection is being processed. When a child process terminates, the
13741 daemon decrements its copy of the variable.
13743 .vitem "&$sn0$& &-- &$sn9$&"
13744 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
13745 that were current at the end of the system filter file. This allows a system
13746 filter file to set values that can be tested in users' filter files. For
13747 example, a system filter could set a value indicating how likely it is that a
13748 message is junk mail.
13750 .vitem &$spam_score$& &&&
13751 &$spam_score_int$& &&&
13753 &$spam_report$& &&&
13755 A number of variables whose names start with &$spam$& are available when Exim
13756 is compiled with the content-scanning extension. For details, see section
13757 &<<SECTscanspamass>>&.
13759 .vitem &$spf_header_comment$& &&&
13760 &$spf_received$& &&&
13762 &$spf_result_guessed$& &&&
13763 &$spf_smtp_comment$&
13764 These variables are only available if Exim is built with SPF support.
13765 For details see section &<<SECSPF>>&.
13767 .vitem &$spool_directory$&
13768 .vindex "&$spool_directory$&"
13769 The name of Exim's spool directory.
13771 .vitem &$spool_inodes$&
13772 .vindex "&$spool_inodes$&"
13773 The number of free inodes in the disk partition where Exim's spool files are
13774 being written. The value is recalculated whenever the variable is referenced.
13775 If the relevant file system does not have the concept of inodes, the value of
13776 is -1. See also the &%check_spool_inodes%& option.
13778 .vitem &$spool_space$&
13779 .vindex "&$spool_space$&"
13780 The amount of free space (as a number of kilobytes) in the disk partition where
13781 Exim's spool files are being written. The value is recalculated whenever the
13782 variable is referenced. If the operating system does not have the ability to
13783 find the amount of free space (only true for experimental systems), the space
13784 value is -1. For example, to check in an ACL that there is at least 50
13785 megabytes free on the spool, you could write:
13787 condition = ${if > {$spool_space}{50000}}
13789 See also the &%check_spool_space%& option.
13792 .vitem &$thisaddress$&
13793 .vindex "&$thisaddress$&"
13794 This variable is set only during the processing of the &%foranyaddress%&
13795 command in a filter file. Its use is explained in the description of that
13796 command, which can be found in the separate document entitled &'Exim's
13797 interfaces to mail filtering'&.
13799 .vitem &$tls_in_bits$&
13800 .vindex "&$tls_in_bits$&"
13801 Contains an approximation of the TLS cipher's bit-strength
13802 on the inbound connection; the meaning of
13803 this depends upon the TLS implementation used.
13804 If TLS has not been negotiated, the value will be 0.
13805 The value of this is automatically fed into the Cyrus SASL authenticator
13806 when acting as a server, to specify the "external SSF" (a SASL term).
13808 The deprecated &$tls_bits$& variable refers to the inbound side
13809 except when used in the context of an outbound SMTP delivery, when it refers to
13812 .vitem &$tls_out_bits$&
13813 .vindex "&$tls_out_bits$&"
13814 Contains an approximation of the TLS cipher's bit-strength
13815 on an outbound SMTP connection; the meaning of
13816 this depends upon the TLS implementation used.
13817 If TLS has not been negotiated, the value will be 0.
13819 .vitem &$tls_in_ourcert$&
13820 .vindex "&$tls_in_ourcert$&"
13821 .cindex certificate variables
13822 This variable refers to the certificate presented to the peer of an
13823 inbound connection when the message was received.
13824 It is only useful as the argument of a
13825 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13826 or a &%def%& condition.
13828 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
13829 when a list of more than one
13830 file is used for &%tls_certificate%&, this variable is not reliable.
13831 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
13833 .vitem &$tls_in_peercert$&
13834 .vindex "&$tls_in_peercert$&"
13835 This variable refers to the certificate presented by the peer of an
13836 inbound connection when the message was received.
13837 It is only useful as the argument of a
13838 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13839 or a &%def%& condition.
13840 If certificate verification fails it may refer to a failing chain element
13841 which is not the leaf.
13843 .vitem &$tls_out_ourcert$&
13844 .vindex "&$tls_out_ourcert$&"
13845 This variable refers to the certificate presented to the peer of an
13846 outbound connection. It is only useful as the argument of a
13847 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13848 or a &%def%& condition.
13850 .vitem &$tls_out_peercert$&
13851 .vindex "&$tls_out_peercert$&"
13852 This variable refers to the certificate presented by the peer of an
13853 outbound connection. It is only useful as the argument of a
13854 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13855 or a &%def%& condition.
13856 If certificate verification fails it may refer to a failing chain element
13857 which is not the leaf.
13859 .vitem &$tls_in_certificate_verified$&
13860 .vindex "&$tls_in_certificate_verified$&"
13861 This variable is set to &"1"& if a TLS certificate was verified when the
13862 message was received, and &"0"& otherwise.
13864 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
13865 except when used in the context of an outbound SMTP delivery, when it refers to
13868 .vitem &$tls_out_certificate_verified$&
13869 .vindex "&$tls_out_certificate_verified$&"
13870 This variable is set to &"1"& if a TLS certificate was verified when an
13871 outbound SMTP connection was made,
13872 and &"0"& otherwise.
13874 .vitem &$tls_in_cipher$&
13875 .vindex "&$tls_in_cipher$&"
13876 .vindex "&$tls_cipher$&"
13877 When a message is received from a remote host over an encrypted SMTP
13878 connection, this variable is set to the cipher suite that was negotiated, for
13879 example DES-CBC3-SHA. In other circumstances, in particular, for message
13880 received over unencrypted connections, the variable is empty. Testing
13881 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
13882 non-encrypted connections during ACL processing.
13884 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
13885 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
13886 becomes the same as &$tls_out_cipher$&.
13888 .vitem &$tls_in_cipher_std$&
13889 .vindex "&$tls_in_cipher_std$&"
13890 As above, but returning the RFC standard name for the cipher suite.
13892 .vitem &$tls_out_cipher$&
13893 .vindex "&$tls_out_cipher$&"
13895 cleared before any outgoing SMTP connection is made,
13896 and then set to the outgoing cipher suite if one is negotiated. See chapter
13897 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
13898 details of the &(smtp)& transport.
13900 .vitem &$tls_out_cipher_std$&
13901 .vindex "&$tls_out_cipher_std$&"
13902 As above, but returning the RFC standard name for the cipher suite.
13904 .vitem &$tls_out_dane$&
13905 .vindex &$tls_out_dane$&
13906 DANE active status. See section &<<SECDANE>>&.
13908 .vitem &$tls_in_ocsp$&
13909 .vindex "&$tls_in_ocsp$&"
13910 When a message is received from a remote client connection
13911 the result of any OCSP request from the client is encoded in this variable:
13913 0 OCSP proof was not requested (default value)
13914 1 No response to request
13915 2 Response not verified
13916 3 Verification failed
13917 4 Verification succeeded
13920 .vitem &$tls_out_ocsp$&
13921 .vindex "&$tls_out_ocsp$&"
13922 When a message is sent to a remote host connection
13923 the result of any OCSP request made is encoded in this variable.
13924 See &$tls_in_ocsp$& for values.
13926 .vitem &$tls_in_peerdn$&
13927 .vindex "&$tls_in_peerdn$&"
13928 .vindex "&$tls_peerdn$&"
13929 .cindex certificate "extracting fields"
13930 When a message is received from a remote host over an encrypted SMTP
13931 connection, and Exim is configured to request a certificate from the client,
13932 the value of the Distinguished Name of the certificate is made available in the
13933 &$tls_in_peerdn$& during subsequent processing.
13934 If certificate verification fails it may refer to a failing chain element
13935 which is not the leaf.
13937 The deprecated &$tls_peerdn$& variable refers to the inbound side
13938 except when used in the context of an outbound SMTP delivery, when it refers to
13941 .vitem &$tls_out_peerdn$&
13942 .vindex "&$tls_out_peerdn$&"
13943 When a message is being delivered to a remote host over an encrypted SMTP
13944 connection, and Exim is configured to request a certificate from the server,
13945 the value of the Distinguished Name of the certificate is made available in the
13946 &$tls_out_peerdn$& during subsequent processing.
13947 If certificate verification fails it may refer to a failing chain element
13948 which is not the leaf.
13952 .vitem &$tls_in_resumption$& &&&
13953 &$tls_out_resumption$&
13954 .vindex &$tls_in_resumption$&
13955 .vindex &$tls_out_resumption$&
13956 .cindex TLS resumption
13957 Observability for TLS session resumption. See &<<SECTresumption>>& for details.
13961 .vitem &$tls_in_sni$&
13962 .vindex "&$tls_in_sni$&"
13963 .vindex "&$tls_sni$&"
13964 .cindex "TLS" "Server Name Indication"
13966 .cindex SNI "observability on server"
13967 When a TLS session is being established, if the client sends the Server
13968 Name Indication extension, the value will be placed in this variable.
13969 If the variable appears in &%tls_certificate%& then this option and
13970 some others, described in &<<SECTtlssni>>&,
13971 will be re-expanded early in the TLS session, to permit
13972 a different certificate to be presented (and optionally a different key to be
13973 used) to the client, based upon the value of the SNI extension.
13975 The deprecated &$tls_sni$& variable refers to the inbound side
13976 except when used in the context of an outbound SMTP delivery, when it refers to
13979 .vitem &$tls_out_sni$&
13980 .vindex "&$tls_out_sni$&"
13981 .cindex "TLS" "Server Name Indication"
13983 .cindex SNI "observability in client"
13985 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
13988 .vitem &$tls_out_tlsa_usage$&
13989 .vindex &$tls_out_tlsa_usage$&
13990 Bitfield of TLSA record types found. See section &<<SECDANE>>&.
13992 .vitem &$tls_in_ver$&
13993 .vindex "&$tls_in_ver$&"
13994 When a message is received from a remote host over an encrypted SMTP connection
13995 this variable is set to the protocol version, eg &'TLS1.2'&.
13997 .vitem &$tls_out_ver$&
13998 .vindex "&$tls_out_ver$&"
13999 When a message is being delivered to a remote host over an encrypted SMTP connection
14000 this variable is set to the protocol version.
14003 .vitem &$tod_bsdinbox$&
14004 .vindex "&$tod_bsdinbox$&"
14005 The time of day and the date, in the format required for BSD-style mailbox
14006 files, for example: Thu Oct 17 17:14:09 1995.
14008 .vitem &$tod_epoch$&
14009 .vindex "&$tod_epoch$&"
14010 The time and date as a number of seconds since the start of the Unix epoch.
14012 .vitem &$tod_epoch_l$&
14013 .vindex "&$tod_epoch_l$&"
14014 The time and date as a number of microseconds since the start of the Unix epoch.
14016 .vitem &$tod_full$&
14017 .vindex "&$tod_full$&"
14018 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
14019 +0100. The timezone is always given as a numerical offset from UTC, with
14020 positive values used for timezones that are ahead (east) of UTC, and negative
14021 values for those that are behind (west).
14024 .vindex "&$tod_log$&"
14025 The time and date in the format used for writing Exim's log files, for example:
14026 1995-10-12 15:32:29, but without a timezone.
14028 .vitem &$tod_logfile$&
14029 .vindex "&$tod_logfile$&"
14030 This variable contains the date in the format yyyymmdd. This is the format that
14031 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
14034 .vitem &$tod_zone$&
14035 .vindex "&$tod_zone$&"
14036 This variable contains the numerical value of the local timezone, for example:
14039 .vitem &$tod_zulu$&
14040 .vindex "&$tod_zulu$&"
14041 This variable contains the UTC date and time in &"Zulu"& format, as specified
14042 by ISO 8601, for example: 20030221154023Z.
14044 .vitem &$transport_name$&
14045 .cindex "transport" "name"
14046 .cindex "name" "of transport"
14047 .vindex "&$transport_name$&"
14048 During the running of a transport, this variable contains its name.
14051 .vindex "&$value$&"
14052 This variable contains the result of an expansion lookup, extraction operation,
14053 or external command, as described above. It is also used during a
14054 &*reduce*& expansion.
14056 .vitem &$verify_mode$&
14057 .vindex "&$verify_mode$&"
14058 While a router or transport is being run in verify mode or for cutthrough delivery,
14059 contains "S" for sender-verification or "R" for recipient-verification.
14062 .vitem &$version_number$&
14063 .vindex "&$version_number$&"
14064 The version number of Exim. Same as &$exim_version$&, may be overridden
14065 by the &%exim_version%& main config option.
14067 .vitem &$warn_message_delay$&
14068 .vindex "&$warn_message_delay$&"
14069 This variable is set only during the creation of a message warning about a
14070 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14072 .vitem &$warn_message_recipients$&
14073 .vindex "&$warn_message_recipients$&"
14074 This variable is set only during the creation of a message warning about a
14075 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14081 . ////////////////////////////////////////////////////////////////////////////
14082 . ////////////////////////////////////////////////////////////////////////////
14084 .chapter "Embedded Perl" "CHAPperl"
14085 .scindex IIDperl "Perl" "calling from Exim"
14086 Exim can be built to include an embedded Perl interpreter. When this is done,
14087 Perl subroutines can be called as part of the string expansion process. To make
14088 use of the Perl support, you need version 5.004 or later of Perl installed on
14089 your system. To include the embedded interpreter in the Exim binary, include
14094 in your &_Local/Makefile_& and then build Exim in the normal way.
14097 .section "Setting up so Perl can be used" "SECID85"
14098 .oindex "&%perl_startup%&"
14099 Access to Perl subroutines is via a global configuration option called
14100 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
14101 no &%perl_startup%& option in the Exim configuration file then no Perl
14102 interpreter is started and there is almost no overhead for Exim (since none of
14103 the Perl library will be paged in unless used). If there is a &%perl_startup%&
14104 option then the associated value is taken to be Perl code which is executed in
14105 a newly created Perl interpreter.
14107 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
14108 need backslashes before any characters to escape special meanings. The option
14109 should usually be something like
14111 perl_startup = do '/etc/exim.pl'
14113 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
14114 use from Exim. Exim can be configured either to start up a Perl interpreter as
14115 soon as it is entered, or to wait until the first time it is needed. Starting
14116 the interpreter at the beginning ensures that it is done while Exim still has
14117 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
14118 fact used in a particular run. Also, note that this does not mean that Exim is
14119 necessarily running as root when Perl is called at a later time. By default,
14120 the interpreter is started only when it is needed, but this can be changed in
14124 .oindex "&%perl_at_start%&"
14125 Setting &%perl_at_start%& (a boolean option) in the configuration requests
14126 a startup when Exim is entered.
14128 The command line option &%-ps%& also requests a startup when Exim is entered,
14129 overriding the setting of &%perl_at_start%&.
14132 There is also a command line option &%-pd%& (for delay) which suppresses the
14133 initial startup, even if &%perl_at_start%& is set.
14136 .oindex "&%perl_taintmode%&"
14137 .cindex "Perl" "taintmode"
14138 To provide more security executing Perl code via the embedded Perl
14139 interpreter, the &%perl_taintmode%& option can be set. This enables the
14140 taint mode of the Perl interpreter. You are encouraged to set this
14141 option to a true value. To avoid breaking existing installations, it
14145 &*Note*&: This is entirely separate from Exim's tainted-data tracking.
14149 .section "Calling Perl subroutines" "SECID86"
14150 When the configuration file includes a &%perl_startup%& option you can make use
14151 of the string expansion item to call the Perl subroutines that are defined
14152 by the &%perl_startup%& code. The operator is used in any of the following
14156 ${perl{foo}{argument}}
14157 ${perl{foo}{argument1}{argument2} ... }
14159 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
14160 arguments may be passed. Passing more than this results in an expansion failure
14161 with an error message of the form
14163 Too many arguments passed to Perl subroutine "foo" (max is 8)
14165 The return value of the Perl subroutine is evaluated in a scalar context before
14166 it is passed back to Exim to be inserted into the expanded string. If the
14167 return value is &'undef'&, the expansion is forced to fail in the same way as
14168 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
14169 by obeying Perl's &%die%& function, the expansion fails with the error message
14170 that was passed to &%die%&.
14173 .section "Calling Exim functions from Perl" "SECID87"
14174 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
14175 is available to call back into Exim's string expansion function. For example,
14178 my $lp = Exim::expand_string('$local_part');
14180 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
14181 Note those are single quotes and not double quotes to protect against
14182 &$local_part$& being interpolated as a Perl variable.
14184 If the string expansion is forced to fail by a &"fail"& item, the result of
14185 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
14186 expansion string, the Perl call from the original expansion string fails with
14187 an appropriate error message, in the same way as if &%die%& were used.
14189 .cindex "debugging" "from embedded Perl"
14190 .cindex "log" "writing from embedded Perl"
14191 Two other Exim functions are available for use from within Perl code.
14192 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
14193 debugging is enabled. If you want a newline at the end, you must supply it.
14194 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
14195 timestamp. In this case, you should not supply a terminating newline.
14198 .section "Use of standard output and error by Perl" "SECID88"
14199 .cindex "Perl" "standard output and error"
14200 You should not write to the standard error or output streams from within your
14201 Perl code, as it is not defined how these are set up. In versions of Exim
14202 before 4.50, it is possible for the standard output or error to refer to the
14203 SMTP connection during message reception via the daemon. Writing to this stream
14204 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
14205 error streams are connected to &_/dev/null_& in the daemon. The chaos is
14206 avoided, but the output is lost.
14208 .cindex "Perl" "use of &%warn%&"
14209 The Perl &%warn%& statement writes to the standard error stream by default.
14210 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
14211 you have no control. When Exim starts up the Perl interpreter, it arranges for
14212 output from the &%warn%& statement to be written to the Exim main log. You can
14213 change this by including appropriate Perl magic somewhere in your Perl code.
14214 For example, to discard &%warn%& output completely, you need this:
14216 $SIG{__WARN__} = sub { };
14218 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
14219 example, the code for the subroutine is empty, so it does nothing, but you can
14220 include any Perl code that you like. The text of the &%warn%& message is passed
14221 as the first subroutine argument.
14225 . ////////////////////////////////////////////////////////////////////////////
14226 . ////////////////////////////////////////////////////////////////////////////
14228 .chapter "Starting the daemon and the use of network interfaces" &&&
14229 "CHAPinterfaces" &&&
14230 "Starting the daemon"
14231 .cindex "daemon" "starting"
14232 .cindex "interface" "listening"
14233 .cindex "network interface"
14234 .cindex "interface" "network"
14235 .cindex "IP address" "for listening"
14236 .cindex "daemon" "listening IP addresses"
14237 .cindex "TCP/IP" "setting listening interfaces"
14238 .cindex "TCP/IP" "setting listening ports"
14239 A host that is connected to a TCP/IP network may have one or more physical
14240 hardware network interfaces. Each of these interfaces may be configured as one
14241 or more &"logical"& interfaces, which are the entities that a program actually
14242 works with. Each of these logical interfaces is associated with an IP address.
14243 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
14244 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
14245 knowledge about the host's interfaces for use in three different circumstances:
14248 When a listening daemon is started, Exim needs to know which interfaces
14249 and ports to listen on.
14251 When Exim is routing an address, it needs to know which IP addresses
14252 are associated with local interfaces. This is required for the correct
14253 processing of MX lists by removing the local host and others with the
14254 same or higher priority values. Also, Exim needs to detect cases
14255 when an address is routed to an IP address that in fact belongs to the
14256 local host. Unless the &%self%& router option or the &%allow_localhost%&
14257 option of the smtp transport is set (as appropriate), this is treated
14258 as an error situation.
14260 When Exim connects to a remote host, it may need to know which interface to use
14261 for the outgoing connection.
14265 Exim's default behaviour is likely to be appropriate in the vast majority
14266 of cases. If your host has only one interface, and you want all its IP
14267 addresses to be treated in the same way, and you are using only the
14268 standard SMTP port, you should not need to take any special action. The
14269 rest of this chapter does not apply to you.
14271 In a more complicated situation you may want to listen only on certain
14272 interfaces, or on different ports, and for this reason there are a number of
14273 options that can be used to influence Exim's behaviour. The rest of this
14274 chapter describes how they operate.
14276 When a message is received over TCP/IP, the interface and port that were
14277 actually used are set in &$received_ip_address$& and &$received_port$&.
14281 .section "Starting a listening daemon" "SECID89"
14282 When a listening daemon is started (by means of the &%-bd%& command line
14283 option), the interfaces and ports on which it listens are controlled by the
14287 &%daemon_smtp_ports%& contains a list of default ports
14289 (For backward compatibility, this option can also be specified in the singular.)
14291 &%local_interfaces%& contains list of interface IP addresses on which to
14292 listen. Each item may optionally also specify a port.
14295 The default list separator in both cases is a colon, but this can be changed as
14296 described in section &<<SECTlistsepchange>>&. When IPv6 addresses are involved,
14297 it is usually best to change the separator to avoid having to double all the
14298 colons. For example:
14300 local_interfaces = <; 127.0.0.1 ; \
14303 3ffe:ffff:836f::fe86:a061
14305 There are two different formats for specifying a port along with an IP address
14306 in &%local_interfaces%&:
14309 The port is added onto the address with a dot separator. For example, to listen
14310 on port 1234 on two different IP addresses:
14312 local_interfaces = <; 192.168.23.65.1234 ; \
14313 3ffe:ffff:836f::fe86:a061.1234
14316 The IP address is enclosed in square brackets, and the port is added
14317 with a colon separator, for example:
14319 local_interfaces = <; [192.168.23.65]:1234 ; \
14320 [3ffe:ffff:836f::fe86:a061]:1234
14324 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
14325 default setting contains just one port:
14327 daemon_smtp_ports = smtp
14329 If more than one port is listed, each interface that does not have its own port
14330 specified listens on all of them. Ports that are listed in
14331 &%daemon_smtp_ports%& can be identified either by name (defined in
14332 &_/etc/services_&) or by number. However, when ports are given with individual
14333 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
14337 .section "Special IP listening addresses" "SECID90"
14338 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
14339 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
14340 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
14341 instead of setting up separate listening sockets for each interface. The
14342 default value of &%local_interfaces%& is
14344 local_interfaces = 0.0.0.0
14346 when Exim is built without IPv6 support; otherwise it is:
14348 local_interfaces = <; ::0 ; 0.0.0.0
14350 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
14354 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
14355 The &%-oX%& command line option can be used to override the values of
14356 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
14357 instance. Another way of doing this would be to use macros and the &%-D%&
14358 option. However, &%-oX%& can be used by any admin user, whereas modification of
14359 the runtime configuration by &%-D%& is allowed only when the caller is root or
14362 The value of &%-oX%& is a list of items. The default colon separator can be
14363 changed in the usual way (&<<SECTlistsepchange>>&) if required.
14364 If there are any items that do not
14365 contain dots or colons (that is, are not IP addresses), the value of
14366 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
14367 items that do contain dots or colons, the value of &%local_interfaces%& is
14368 replaced by those items. Thus, for example,
14372 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
14375 -oX 192.168.34.5.1125
14377 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
14378 (However, since &%local_interfaces%& now contains no items without ports, the
14379 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
14383 .section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
14384 .cindex "submissions protocol"
14385 .cindex "ssmtp protocol"
14386 .cindex "smtps protocol"
14387 .cindex "SMTP" "ssmtp protocol"
14388 .cindex "SMTP" "smtps protocol"
14389 Exim supports the use of TLS-on-connect, used by mail clients in the
14390 &"submissions"& protocol, historically also known as SMTPS or SSMTP.
14391 For some years, IETF Standards Track documents only blessed the
14392 STARTTLS-based Submission service (port 587) while common practice was to support
14393 the same feature set on port 465, but using TLS-on-connect.
14394 If your installation needs to provide service to mail clients
14395 (Mail User Agents, MUAs) then you should provide service on both the 587 and
14398 If the &%tls_on_connect_ports%& option is set to a list of port numbers or
14399 service names, connections to those ports must first establish TLS, before
14400 proceeding to the application layer use of the SMTP protocol.
14402 The common use of this option is expected to be
14404 tls_on_connect_ports = 465
14407 There is also a command line option &%-tls-on-connect%&, which forces all ports
14408 to behave in this way when a daemon is started.
14410 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
14411 daemon to listen on those ports. You must still specify them in
14412 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
14413 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
14414 connections via the daemon.)
14419 .section "IPv6 address scopes" "SECID92"
14420 .cindex "IPv6" "address scopes"
14421 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
14422 can, in principle, have the same link-local IPv6 address on different
14423 interfaces. Thus, additional information is needed, over and above the IP
14424 address, to distinguish individual interfaces. A convention of using a
14425 percent sign followed by something (often the interface name) has been
14426 adopted in some cases, leading to addresses like this:
14428 fe80::202:b3ff:fe03:45c1%eth0
14430 To accommodate this usage, a percent sign followed by an arbitrary string is
14431 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
14432 to convert a textual IPv6 address for actual use. This function recognizes the
14433 percent convention in operating systems that support it, and it processes the
14434 address appropriately. Unfortunately, some older libraries have problems with
14435 &[getaddrinfo()]&. If
14437 IPV6_USE_INET_PTON=yes
14439 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
14440 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
14441 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
14442 function.) Of course, this means that the additional functionality of
14443 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
14445 .section "Disabling IPv6" "SECID93"
14446 .cindex "IPv6" "disabling"
14447 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
14448 run on a host whose kernel does not support IPv6. The binary will fall back to
14449 using IPv4, but it may waste resources looking up AAAA records, and trying to
14450 connect to IPv6 addresses, causing delays to mail delivery. If you set the
14451 .oindex "&%disable_ipv6%&"
14452 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
14453 activities take place. AAAA records are never looked up, and any IPv6 addresses
14454 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
14455 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14456 to handle IPv6 literal addresses.
14458 On the other hand, when IPv6 is in use, there may be times when you want to
14459 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
14460 option to globally suppress the lookup of AAAA records for specified domains,
14461 and you can use the &%ignore_target_hosts%& generic router option to ignore
14462 IPv6 addresses in an individual router.
14466 .section "Examples of starting a listening daemon" "SECID94"
14467 The default case in an IPv6 environment is
14469 daemon_smtp_ports = smtp
14470 local_interfaces = <; ::0 ; 0.0.0.0
14472 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
14473 Either one or two sockets may be used, depending on the characteristics of
14474 the TCP/IP stack. (This is complicated and messy; for more information,
14475 read the comments in the &_daemon.c_& source file.)
14477 To specify listening on ports 25 and 26 on all interfaces:
14479 daemon_smtp_ports = 25 : 26
14481 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
14483 local_interfaces = <; ::0.25 ; ::0.26 \
14484 0.0.0.0.25 ; 0.0.0.0.26
14486 To listen on the default port on all IPv4 interfaces, and on port 26 on the
14487 IPv4 loopback address only:
14489 local_interfaces = 0.0.0.0 : 127.0.0.1.26
14491 To specify listening on the default port on specific interfaces only:
14493 local_interfaces = 10.0.0.67 : 192.168.34.67
14495 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
14499 .section "Recognizing the local host" "SECTreclocipadd"
14500 The &%local_interfaces%& option is also used when Exim needs to determine
14501 whether or not an IP address refers to the local host. That is, the IP
14502 addresses of all the interfaces on which a daemon is listening are always
14505 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
14506 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
14507 available interfaces from the operating system, and extracts the relevant
14508 (that is, IPv4 or IPv6) addresses to use for checking.
14510 Some systems set up large numbers of virtual interfaces in order to provide
14511 many virtual web servers. In this situation, you may want to listen for
14512 email on only a few of the available interfaces, but nevertheless treat all
14513 interfaces as local when routing. You can do this by setting
14514 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
14515 &"all"& wildcard values. These addresses are recognized as local, but are not
14516 used for listening. Consider this example:
14518 local_interfaces = <; 127.0.0.1 ; ::1 ; \
14520 3ffe:2101:12:1:a00:20ff:fe86:a061
14522 extra_local_interfaces = <; ::0 ; 0.0.0.0
14524 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
14525 address, but all available interface addresses are treated as local when
14528 In some environments the local host name may be in an MX list, but with an IP
14529 address that is not assigned to any local interface. In other cases it may be
14530 desirable to treat other host names as if they referred to the local host. Both
14531 these cases can be handled by setting the &%hosts_treat_as_local%& option.
14532 This contains host names rather than IP addresses. When a host is referenced
14533 during routing, either via an MX record or directly, it is treated as the local
14534 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
14535 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
14539 .section "Delivering to a remote host" "SECID95"
14540 Delivery to a remote host is handled by the smtp transport. By default, it
14541 allows the system's TCP/IP functions to choose which interface to use (if
14542 there is more than one) when connecting to a remote host. However, the
14543 &%interface%& option can be set to specify which interface is used. See the
14544 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
14550 . ////////////////////////////////////////////////////////////////////////////
14551 . ////////////////////////////////////////////////////////////////////////////
14553 .chapter "Main configuration" "CHAPmainconfig"
14554 .scindex IIDconfima "configuration file" "main section"
14555 .scindex IIDmaiconf "main configuration"
14556 The first part of the runtime configuration file contains three types of item:
14559 Macro definitions: These lines start with an upper case letter. See section
14560 &<<SECTmacrodefs>>& for details of macro processing.
14562 Named list definitions: These lines start with one of the words &"domainlist"&,
14563 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
14564 section &<<SECTnamedlists>>&.
14566 Main configuration settings: Each setting occupies one line of the file
14567 (with possible continuations). If any setting is preceded by the word
14568 &"hide"&, the &%-bP%& command line option displays its value to admin users
14569 only. See section &<<SECTcos>>& for a description of the syntax of these option
14573 This chapter specifies all the main configuration options, along with their
14574 types and default values. For ease of finding a particular option, they appear
14575 in alphabetical order in section &<<SECTalomo>>& below. However, because there
14576 are now so many options, they are first listed briefly in functional groups, as
14577 an aid to finding the name of the option you are looking for. Some options are
14578 listed in more than one group.
14580 .section "Miscellaneous" "SECID96"
14582 .row &%add_environment%& "environment variables"
14583 .row &%bi_command%& "to run for &%-bi%& command line option"
14584 .row &%debug_store%& "do extra internal checks"
14585 .row &%disable_ipv6%& "do no IPv6 processing"
14586 .row &%keep_environment%& "environment variables"
14587 .row &%keep_malformed%& "for broken files &-- should not happen"
14588 .row &%localhost_number%& "for unique message ids in clusters"
14589 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
14590 .row &%message_body_visible%& "how much to show in &$message_body$&"
14591 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
14592 .row &%print_topbitchars%& "top-bit characters are printing"
14593 .row &%spool_wireformat%& "use wire-format spool data files when possible"
14594 .row &%timezone%& "force time zone"
14598 .section "Exim parameters" "SECID97"
14600 .row &%exim_group%& "override compiled-in value"
14601 .row &%exim_path%& "override compiled-in value"
14602 .row &%exim_user%& "override compiled-in value"
14603 .row &%primary_hostname%& "default from &[uname()]&"
14604 .row &%split_spool_directory%& "use multiple directories"
14605 .row &%spool_directory%& "override compiled-in value"
14610 .section "Privilege controls" "SECID98"
14612 .row &%admin_groups%& "groups that are Exim admin users"
14613 .row &%commandline_checks_require_admin%& "require admin for various checks"
14614 .row &%deliver_drop_privilege%& "drop root for delivery processes"
14615 .row &%local_from_check%& "insert &'Sender:'& if necessary"
14616 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
14617 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
14618 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
14619 .row &%never_users%& "do not run deliveries as these"
14620 .row &%prod_requires_admin%& "forced delivery requires admin user"
14621 .row &%queue_list_requires_admin%& "queue listing requires admin user"
14622 .row &%trusted_groups%& "groups that are trusted"
14623 .row &%trusted_users%& "users that are trusted"
14628 .section "Logging" "SECID99"
14630 .row &%event_action%& "custom logging"
14631 .row &%hosts_connection_nolog%& "exemption from connect logging"
14632 .row &%log_file_path%& "override compiled-in value"
14633 .row &%log_selector%& "set/unset optional logging"
14634 .row &%log_timezone%& "add timezone to log lines"
14635 .row &%message_logs%& "create per-message logs"
14636 .row &%preserve_message_logs%& "after message completion"
14637 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
14638 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
14639 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
14640 .row &%syslog_facility%& "set syslog &""facility""& field"
14641 .row &%syslog_pid%& "pid in syslog lines"
14642 .row &%syslog_processname%& "set syslog &""ident""& field"
14643 .row &%syslog_timestamp%& "timestamp syslog lines"
14644 .row &%write_rejectlog%& "control use of message log"
14649 .section "Frozen messages" "SECID100"
14651 .row &%auto_thaw%& "sets time for retrying frozen messages"
14652 .row &%freeze_tell%& "send message when freezing"
14653 .row &%move_frozen_messages%& "to another directory"
14654 .row &%timeout_frozen_after%& "keep frozen messages only so long"
14659 .section "Data lookups" "SECID101"
14661 .row &%ibase_servers%& "InterBase servers"
14662 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
14663 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
14664 .row &%ldap_cert_file%& "client cert file for LDAP"
14665 .row &%ldap_cert_key%& "client key file for LDAP"
14666 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
14667 .row &%ldap_default_servers%& "used if no server in query"
14668 .row &%ldap_require_cert%& "action to take without LDAP server cert"
14669 .row &%ldap_start_tls%& "require TLS within LDAP"
14670 .row &%ldap_version%& "set protocol version"
14671 .row &%lookup_open_max%& "lookup files held open"
14672 .row &%mysql_servers%& "default MySQL servers"
14673 .row &%oracle_servers%& "Oracle servers"
14674 .row &%pgsql_servers%& "default PostgreSQL servers"
14675 .row &%sqlite_lock_timeout%& "as it says"
14680 .section "Message ids" "SECID102"
14682 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
14683 .row &%message_id_header_text%& "ditto"
14688 .section "Embedded Perl Startup" "SECID103"
14690 .row &%perl_at_start%& "always start the interpreter"
14691 .row &%perl_startup%& "code to obey when starting Perl"
14692 .row &%perl_taintmode%& "enable taint mode in Perl"
14697 .section "Daemon" "SECID104"
14699 .row &%daemon_smtp_ports%& "default ports"
14700 .row &%daemon_startup_retries%& "number of times to retry"
14701 .row &%daemon_startup_sleep%& "time to sleep between tries"
14702 .row &%extra_local_interfaces%& "not necessarily listened on"
14703 .row &%local_interfaces%& "on which to listen, with optional ports"
14704 .row &%notifier_socket%& "override compiled-in value"
14705 .row &%pid_file_path%& "override compiled-in value"
14706 .row &%queue_run_max%& "maximum simultaneous queue runners"
14711 .section "Resource control" "SECID105"
14713 .row &%check_log_inodes%& "before accepting a message"
14714 .row &%check_log_space%& "before accepting a message"
14715 .row &%check_spool_inodes%& "before accepting a message"
14716 .row &%check_spool_space%& "before accepting a message"
14717 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
14718 .row &%queue_only_load%& "queue incoming if load high"
14719 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14720 .row &%queue_run_max%& "maximum simultaneous queue runners"
14721 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14722 .row &%smtp_accept_max%& "simultaneous incoming connections"
14723 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14724 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14725 .row &%smtp_accept_max_per_connection%& "messages per connection"
14726 .row &%smtp_accept_max_per_host%& "connections from one host"
14727 .row &%smtp_accept_queue%& "queue mail if more connections"
14728 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14730 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14731 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14732 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14733 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
14734 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14739 .section "Policy controls" "SECID106"
14741 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
14742 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
14743 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
14744 .row &%acl_smtp_auth%& "ACL for AUTH"
14745 .row &%acl_smtp_connect%& "ACL for connection"
14746 .row &%acl_smtp_data%& "ACL for DATA"
14747 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
14748 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
14749 .row &%acl_smtp_etrn%& "ACL for ETRN"
14750 .row &%acl_smtp_expn%& "ACL for EXPN"
14751 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
14752 .row &%acl_smtp_mail%& "ACL for MAIL"
14753 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
14754 .row &%acl_smtp_mime%& "ACL for MIME parts"
14755 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
14756 .row &%acl_smtp_predata%& "ACL for start of data"
14757 .row &%acl_smtp_quit%& "ACL for QUIT"
14758 .row &%acl_smtp_rcpt%& "ACL for RCPT"
14759 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
14760 .row &%acl_smtp_vrfy%& "ACL for VRFY"
14761 .row &%av_scanner%& "specify virus scanner"
14762 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14764 .row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
14765 .row &%dns_csa_search_limit%& "control CSA parent search depth"
14766 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
14767 .row &%header_maxsize%& "total size of message header"
14768 .row &%header_line_maxsize%& "individual header line limit"
14769 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
14770 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
14771 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
14772 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
14773 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
14774 .row &%host_lookup%& "host name looked up for these hosts"
14775 .row &%host_lookup_order%& "order of DNS and local name lookups"
14776 .row &%hosts_proxy%& "use proxy protocol for these hosts"
14777 .row &%host_reject_connection%& "reject connection from these hosts"
14778 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
14779 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
14780 .row &%message_size_limit%& "for all messages"
14781 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14782 .row &%proxy_protocol_timeout%& "timeout for proxy protocol negotiation"
14783 .row &%spamd_address%& "set interface to SpamAssassin"
14784 .row &%strict_acl_vars%& "object to unset ACL variables"
14785 .row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&"
14790 .section "Callout cache" "SECID107"
14792 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
14794 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
14796 .row &%callout_negative_expire%& "timeout for negative address cache item"
14797 .row &%callout_positive_expire%& "timeout for positive address cache item"
14798 .row &%callout_random_local_part%& "string to use for &""random""& testing"
14803 .section "TLS" "SECID108"
14805 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
14806 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
14807 .row &%openssl_options%& "adjust OpenSSL compatibility options"
14808 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14809 .row &%tls_certificate%& "location of server certificate"
14810 .row &%tls_crl%& "certificate revocation list"
14811 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
14812 .row &%tls_dhparam%& "DH parameters for server"
14813 .row &%tls_eccurve%& "EC curve selection for server"
14814 .row &%tls_ocsp_file%& "location of server certificate status proof"
14815 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
14816 .row &%tls_privatekey%& "location of server private key"
14817 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
14818 .row &%tls_require_ciphers%& "specify acceptable ciphers"
14819 .row &%tls_try_verify_hosts%& "try to verify client certificate"
14820 .row &%tls_verify_certificates%& "expected client certificates"
14821 .row &%tls_verify_hosts%& "insist on client certificate verify"
14826 .section "Local user handling" "SECID109"
14828 .row &%finduser_retries%& "useful in NIS environments"
14829 .row &%gecos_name%& "used when creating &'Sender:'&"
14830 .row &%gecos_pattern%& "ditto"
14831 .row &%max_username_length%& "for systems that truncate"
14832 .row &%unknown_login%& "used when no login name found"
14833 .row &%unknown_username%& "ditto"
14834 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
14835 .row &%uucp_from_sender%& "ditto"
14840 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
14842 .row &%header_maxsize%& "total size of message header"
14843 .row &%header_line_maxsize%& "individual header line limit"
14844 .row &%message_size_limit%& "applies to all messages"
14845 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14846 .row &%received_header_text%& "expanded to make &'Received:'&"
14847 .row &%received_headers_max%& "for mail loop detection"
14848 .row &%recipients_max%& "limit per message"
14849 .row &%recipients_max_reject%& "permanently reject excess recipients"
14855 .section "Non-SMTP incoming messages" "SECID111"
14857 .row &%receive_timeout%& "for non-SMTP messages"
14864 .section "Incoming SMTP messages" "SECID112"
14865 See also the &'Policy controls'& section above.
14868 .row &%dkim_verify_hashes%& "DKIM hash methods accepted for signatures"
14869 .row &%dkim_verify_keytypes%& "DKIM key types accepted for signatures"
14870 .row &%dkim_verify_min_keysizes%& "DKIM key sizes accepted for signatures"
14871 .row &%dkim_verify_signers%& "DKIM domains for which DKIM ACL is run"
14872 .row &%dmarc_forensic_sender%& "DMARC sender for report messages"
14873 .row &%dmarc_history_file%& "DMARC results log"
14874 .row &%dmarc_tld_file%& "DMARC toplevel domains file"
14875 .row &%host_lookup%& "host name looked up for these hosts"
14876 .row &%host_lookup_order%& "order of DNS and local name lookups"
14877 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
14878 .row &%rfc1413_hosts%& "make ident calls to these hosts"
14879 .row &%rfc1413_query_timeout%& "zero disables ident calls"
14880 .row &%sender_unqualified_hosts%& "may send unqualified senders"
14881 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
14882 .row &%smtp_accept_max%& "simultaneous incoming connections"
14883 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14884 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14885 .row &%smtp_accept_max_per_connection%& "messages per connection"
14886 .row &%smtp_accept_max_per_host%& "connections from one host"
14887 .row &%smtp_accept_queue%& "queue mail if more connections"
14888 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14890 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14891 .row &%smtp_active_hostname%& "host name to use in messages"
14892 .row &%smtp_banner%& "text for welcome banner"
14893 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14894 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14895 .row &%smtp_enforce_sync%& "of SMTP command/responses"
14896 .row &%smtp_etrn_command%& "what to run for ETRN"
14897 .row &%smtp_etrn_serialize%& "only one at once"
14898 .row &%smtp_load_reserve%& "only reserve hosts if this load"
14899 .row &%smtp_max_unknown_commands%& "before dropping connection"
14900 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
14901 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
14902 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
14903 .row &%smtp_receive_timeout%& "per command or data line"
14904 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14905 .row &%smtp_return_error_details%& "give detail on rejections"
14910 .section "SMTP extensions" "SECID113"
14912 .row &%accept_8bitmime%& "advertise 8BITMIME"
14913 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
14914 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
14915 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
14916 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
14917 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
14918 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
14919 .row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts"
14920 .row &%prdr_enable%& "advertise PRDR to all hosts"
14921 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
14922 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14927 .section "Processing messages" "SECID114"
14929 .row &%allow_domain_literals%& "recognize domain literal syntax"
14930 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
14931 .row &%allow_utf8_domains%& "in addresses"
14932 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14934 .row &%delivery_date_remove%& "from incoming messages"
14935 .row &%envelope_to_remove%& "from incoming messages"
14936 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
14937 .row &%headers_charset%& "default for translations"
14938 .row &%qualify_domain%& "default for senders"
14939 .row &%qualify_recipient%& "default for recipients"
14940 .row &%return_path_remove%& "from incoming messages"
14941 .row &%strip_excess_angle_brackets%& "in addresses"
14942 .row &%strip_trailing_dot%& "at end of addresses"
14943 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
14948 .section "System filter" "SECID115"
14950 .row &%system_filter%& "locate system filter"
14951 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
14953 .row &%system_filter_file_transport%& "transport for delivery to a file"
14954 .row &%system_filter_group%& "group for filter running"
14955 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
14956 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
14957 .row &%system_filter_user%& "user for filter running"
14962 .section "Routing and delivery" "SECID116"
14964 .row &%disable_ipv6%& "do no IPv6 processing"
14965 .row &%dns_again_means_nonexist%& "for broken domains"
14966 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
14967 .row &%dns_dnssec_ok%& "parameter for resolver"
14968 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
14969 .row &%dns_retrans%& "parameter for resolver"
14970 .row &%dns_retry%& "parameter for resolver"
14971 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
14972 .row &%dns_use_edns0%& "parameter for resolver"
14973 .row &%hold_domains%& "hold delivery for these domains"
14974 .row &%local_interfaces%& "for routing checks"
14975 .row &%queue_domains%& "no immediate delivery for these"
14976 .row &%queue_fast_ramp%& "parallel delivery with 2-phase queue run"
14977 .row &%queue_only%& "no immediate delivery at all"
14978 .row &%queue_only_file%& "no immediate delivery if file exists"
14979 .row &%queue_only_load%& "no immediate delivery if load is high"
14980 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14981 .row &%queue_only_override%& "allow command line to override"
14982 .row &%queue_run_in_order%& "order of arrival"
14983 .row &%queue_run_max%& "of simultaneous queue runners"
14984 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
14985 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14986 .row &%remote_sort_domains%& "order of remote deliveries"
14987 .row &%retry_data_expire%& "timeout for retry data"
14988 .row &%retry_interval_max%& "safety net for retry rules"
14993 .section "Bounce and warning messages" "SECID117"
14995 .row &%bounce_message_file%& "content of bounce"
14996 .row &%bounce_message_text%& "content of bounce"
14997 .row &%bounce_return_body%& "include body if returning message"
14998 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
14999 .row &%bounce_return_message%& "include original message in bounce"
15000 .row &%bounce_return_size_limit%& "limit on returned message"
15001 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
15002 .row &%dsn_from%& "set &'From:'& contents in bounces"
15003 .row &%errors_copy%& "copy bounce messages"
15004 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
15005 .row &%delay_warning%& "time schedule"
15006 .row &%delay_warning_condition%& "condition for warning messages"
15007 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
15008 .row &%smtp_return_error_details%& "give detail on rejections"
15009 .row &%warn_message_file%& "content of warning message"
15014 .section "Alphabetical list of main options" "SECTalomo"
15015 Those options that undergo string expansion before use are marked with
15018 .option accept_8bitmime main boolean true
15020 .cindex "8-bit characters"
15021 .cindex "log" "selectors"
15022 .cindex "log" "8BITMIME"
15023 .cindex "ESMTP extensions" 8BITMIME
15024 This option causes Exim to send 8BITMIME in its response to an SMTP
15025 EHLO command, and to accept the BODY= parameter on MAIL commands.
15026 However, though Exim is 8-bit clean, it is not a protocol converter, and it
15027 takes no steps to do anything special with messages received by this route.
15029 Historically Exim kept this option off by default, but the maintainers
15030 feel that in today's Internet, this causes more problems than it solves.
15031 It now defaults to true.
15032 A more detailed analysis of the issues is provided by Dan Bernstein:
15034 &url(https://cr.yp.to/smtp/8bitmime.html)
15037 To log received 8BITMIME status use
15039 log_selector = +8bitmime
15042 .option acl_not_smtp main string&!! unset
15043 .cindex "&ACL;" "for non-SMTP messages"
15044 .cindex "non-SMTP messages" "ACLs for"
15045 This option defines the ACL that is run when a non-SMTP message has been
15046 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
15049 .option acl_not_smtp_mime main string&!! unset
15050 This option defines the ACL that is run for individual MIME parts of non-SMTP
15051 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
15054 .option acl_not_smtp_start main string&!! unset
15055 .cindex "&ACL;" "at start of non-SMTP message"
15056 .cindex "non-SMTP messages" "ACLs for"
15057 This option defines the ACL that is run before Exim starts reading a
15058 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
15060 .option acl_smtp_auth main string&!! unset
15061 .cindex "&ACL;" "setting up for SMTP commands"
15062 .cindex "AUTH" "ACL for"
15063 This option defines the ACL that is run when an SMTP AUTH command is
15064 received. See chapter &<<CHAPACL>>& for further details.
15066 .option acl_smtp_connect main string&!! unset
15067 .cindex "&ACL;" "on SMTP connection"
15068 This option defines the ACL that is run when an SMTP connection is received.
15069 See chapter &<<CHAPACL>>& for further details.
15071 .option acl_smtp_data main string&!! unset
15072 .cindex "DATA" "ACL for"
15073 This option defines the ACL that is run after an SMTP DATA command has been
15074 processed and the message itself has been received, but before the final
15075 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15077 .option acl_smtp_data_prdr main string&!! accept
15078 .cindex "PRDR" "ACL for"
15079 .cindex "DATA" "PRDR ACL for"
15080 .cindex "&ACL;" "PRDR-related"
15081 .cindex "&ACL;" "per-user data processing"
15082 This option defines the ACL that,
15083 if the PRDR feature has been negotiated,
15084 is run for each recipient after an SMTP DATA command has been
15085 processed and the message itself has been received, but before the
15086 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15088 .option acl_smtp_dkim main string&!! unset
15089 .cindex DKIM "ACL for"
15090 This option defines the ACL that is run for each DKIM signature
15091 (by default, or as specified in the dkim_verify_signers option)
15092 of a received message.
15093 See section &<<SECDKIMVFY>>& for further details.
15095 .option acl_smtp_etrn main string&!! unset
15096 .cindex "ETRN" "ACL for"
15097 This option defines the ACL that is run when an SMTP ETRN command is
15098 received. See chapter &<<CHAPACL>>& for further details.
15100 .option acl_smtp_expn main string&!! unset
15101 .cindex "EXPN" "ACL for"
15102 This option defines the ACL that is run when an SMTP EXPN command is
15103 received. See chapter &<<CHAPACL>>& for further details.
15105 .option acl_smtp_helo main string&!! unset
15106 .cindex "EHLO" "ACL for"
15107 .cindex "HELO" "ACL for"
15108 This option defines the ACL that is run when an SMTP EHLO or HELO
15109 command is received. See chapter &<<CHAPACL>>& for further details.
15112 .option acl_smtp_mail main string&!! unset
15113 .cindex "MAIL" "ACL for"
15114 This option defines the ACL that is run when an SMTP MAIL command is
15115 received. See chapter &<<CHAPACL>>& for further details.
15117 .option acl_smtp_mailauth main string&!! unset
15118 .cindex "AUTH" "on MAIL command"
15119 This option defines the ACL that is run when there is an AUTH parameter on
15120 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
15121 &<<CHAPSMTPAUTH>>& for details of authentication.
15123 .option acl_smtp_mime main string&!! unset
15124 .cindex "MIME content scanning" "ACL for"
15125 This option is available when Exim is built with the content-scanning
15126 extension. It defines the ACL that is run for each MIME part in a message. See
15127 section &<<SECTscanmimepart>>& for details.
15129 .option acl_smtp_notquit main string&!! unset
15130 .cindex "not-QUIT, ACL for"
15131 This option defines the ACL that is run when an SMTP session
15132 ends without a QUIT command being received.
15133 See chapter &<<CHAPACL>>& for further details.
15135 .option acl_smtp_predata main string&!! unset
15136 This option defines the ACL that is run when an SMTP DATA command is
15137 received, before the message itself is received. See chapter &<<CHAPACL>>& for
15140 .option acl_smtp_quit main string&!! unset
15141 .cindex "QUIT, ACL for"
15142 This option defines the ACL that is run when an SMTP QUIT command is
15143 received. See chapter &<<CHAPACL>>& for further details.
15145 .option acl_smtp_rcpt main string&!! unset
15146 .cindex "RCPT" "ACL for"
15147 This option defines the ACL that is run when an SMTP RCPT command is
15148 received. See chapter &<<CHAPACL>>& for further details.
15150 .option acl_smtp_starttls main string&!! unset
15151 .cindex "STARTTLS, ACL for"
15152 This option defines the ACL that is run when an SMTP STARTTLS command is
15153 received. See chapter &<<CHAPACL>>& for further details.
15155 .option acl_smtp_vrfy main string&!! unset
15156 .cindex "VRFY" "ACL for"
15157 This option defines the ACL that is run when an SMTP VRFY command is
15158 received. See chapter &<<CHAPACL>>& for further details.
15160 .option add_environment main "string list" empty
15161 .cindex "environment" "set values"
15162 This option adds individual environment variables that the
15163 currently linked libraries and programs in child processes may use.
15164 Each list element should be of the form &"name=value"&.
15166 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
15168 .option admin_groups main "string list&!!" unset
15169 .cindex "admin user"
15170 This option is expanded just once, at the start of Exim's processing. If the
15171 current group or any of the supplementary groups of an Exim caller is in this
15172 colon-separated list, the caller has admin privileges. If all your system
15173 programmers are in a specific group, for example, you can give them all Exim
15174 admin privileges by putting that group in &%admin_groups%&. However, this does
15175 not permit them to read Exim's spool files (whose group owner is the Exim gid).
15176 To permit this, you have to add individuals to the Exim group.
15178 .option allow_domain_literals main boolean false
15179 .cindex "domain literal"
15180 If this option is set, the RFC 2822 domain literal format is permitted in
15181 email addresses. The option is not set by default, because the domain literal
15182 format is not normally required these days, and few people know about it. It
15183 has, however, been exploited by mail abusers.
15185 Unfortunately, it seems that some DNS black list maintainers are using this
15186 format to report black listing to postmasters. If you want to accept messages
15187 addressed to your hosts by IP address, you need to set
15188 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
15189 domains (defined in the named domain list &%local_domains%& in the default
15190 configuration). This &"magic string"& matches the domain literal form of all
15191 the local host's IP addresses.
15194 .option allow_mx_to_ip main boolean false
15195 .cindex "MX record" "pointing to IP address"
15196 It appears that more and more DNS zone administrators are breaking the rules
15197 and putting domain names that look like IP addresses on the right hand side of
15198 MX records. Exim follows the rules and rejects this, giving an error message
15199 that explains the misconfiguration. However, some other MTAs support this
15200 practice, so to avoid &"Why can't Exim do this?"& complaints,
15201 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
15202 recommended, except when you have no other choice.
15204 .option allow_utf8_domains main boolean false
15205 .cindex "domain" "UTF-8 characters in"
15206 .cindex "UTF-8" "in domain name"
15207 Lots of discussion is going on about internationalized domain names. One
15208 camp is strongly in favour of just using UTF-8 characters, and it seems
15209 that at least two other MTAs permit this.
15210 This option allows Exim users to experiment if they wish.
15212 If it is set true, Exim's domain parsing function allows valid
15213 UTF-8 multicharacters to appear in domain name components, in addition to
15214 letters, digits, and hyphens.
15216 If Exim is built with internationalization support
15217 and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
15218 this option can be left as default.
15220 if you want to look up such domain names in the DNS, you must also
15221 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
15222 suitable setting is:
15224 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
15225 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
15227 Alternatively, you can just disable this feature by setting
15229 dns_check_names_pattern =
15231 That is, set the option to an empty string so that no check is done.
15234 .option auth_advertise_hosts main "host list&!!" *
15235 .cindex "authentication" "advertising"
15236 .cindex "AUTH" "advertising"
15237 .cindex "ESMTP extensions" AUTH
15238 If any server authentication mechanisms are configured, Exim advertises them in
15239 response to an EHLO command only if the calling host matches this list.
15240 Otherwise, Exim does not advertise AUTH.
15241 Exim does not accept AUTH commands from clients to which it has not
15242 advertised the availability of AUTH. The advertising of individual
15243 authentication mechanisms can be controlled by the use of the
15244 &%server_advertise_condition%& generic authenticator option on the individual
15245 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
15247 Certain mail clients (for example, Netscape) require the user to provide a name
15248 and password for authentication if AUTH is advertised, even though it may
15249 not be needed (the host may accept messages from hosts on its local LAN without
15250 authentication, for example). The &%auth_advertise_hosts%& option can be used
15251 to make these clients more friendly by excluding them from the set of hosts to
15252 which Exim advertises AUTH.
15254 .cindex "AUTH" "advertising when encrypted"
15255 If you want to advertise the availability of AUTH only when the connection
15256 is encrypted using TLS, you can make use of the fact that the value of this
15257 option is expanded, with a setting like this:
15259 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
15261 .vindex "&$tls_in_cipher$&"
15262 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
15263 the expansion is empty, thus matching no hosts. Otherwise, the result of the
15264 expansion is *, which matches all hosts.
15267 .option auto_thaw main time 0s
15268 .cindex "thawing messages"
15269 .cindex "unfreezing messages"
15270 If this option is set to a time greater than zero, a queue runner will try a
15271 new delivery attempt on any frozen message, other than a bounce message, if
15272 this much time has passed since it was frozen. This may result in the message
15273 being re-frozen if nothing has changed since the last attempt. It is a way of
15274 saying &"keep on trying, even though there are big problems"&.
15276 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
15277 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
15278 thought to be very useful any more, and its use should probably be avoided.
15281 .option av_scanner main string "see below"
15282 This option is available if Exim is built with the content-scanning extension.
15283 It specifies which anti-virus scanner to use. The default value is:
15285 sophie:/var/run/sophie
15287 If the value of &%av_scanner%& starts with a dollar character, it is expanded
15288 before use. See section &<<SECTscanvirus>>& for further details.
15291 .option bi_command main string unset
15293 This option supplies the name of a command that is run when Exim is called with
15294 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
15295 just the command name, it is not a complete command line. If an argument is
15296 required, it must come from the &%-oA%& command line option.
15299 .option bounce_message_file main string&!! unset
15300 .cindex "bounce message" "customizing"
15301 .cindex "customizing" "bounce message"
15302 This option defines a template file containing paragraphs of text to be used
15303 for constructing bounce messages. Details of the file's contents are given in
15304 chapter &<<CHAPemsgcust>>&.
15305 .cindex bounce_message_file "tainted data"
15306 The option is expanded to give the file path, which must be
15307 absolute and untainted.
15308 See also &%warn_message_file%&.
15311 .option bounce_message_text main string unset
15312 When this option is set, its contents are included in the default bounce
15313 message immediately after &"This message was created automatically by mail
15314 delivery software."& It is not used if &%bounce_message_file%& is set.
15316 .option bounce_return_body main boolean true
15317 .cindex "bounce message" "including body"
15318 This option controls whether the body of an incoming message is included in a
15319 bounce message when &%bounce_return_message%& is true. The default setting
15320 causes the entire message, both header and body, to be returned (subject to the
15321 value of &%bounce_return_size_limit%&). If this option is false, only the
15322 message header is included. In the case of a non-SMTP message containing an
15323 error that is detected during reception, only those header lines preceding the
15324 point at which the error was detected are returned.
15325 .cindex "bounce message" "including original"
15327 .option bounce_return_linesize_limit main integer 998
15328 .cindex "size" "of bounce lines, limit"
15329 .cindex "bounce message" "line length limit"
15330 .cindex "limit" "bounce message line length"
15331 This option sets a limit in bytes on the line length of messages
15332 that are returned to senders due to delivery problems,
15333 when &%bounce_return_message%& is true.
15334 The default value corresponds to RFC limits.
15335 If the message being returned has lines longer than this value it is
15336 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
15338 The option also applies to bounces returned when an error is detected
15339 during reception of a message.
15340 In this case lines from the original are truncated.
15342 The option does not apply to messages generated by an &(autoreply)& transport.
15345 .option bounce_return_message main boolean true
15346 If this option is set false, none of the original message is included in
15347 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
15348 &%bounce_return_body%&.
15351 .option bounce_return_size_limit main integer 100K
15352 .cindex "size" "of bounce, limit"
15353 .cindex "bounce message" "size limit"
15354 .cindex "limit" "bounce message size"
15355 This option sets a limit in bytes on the size of messages that are returned to
15356 senders as part of bounce messages when &%bounce_return_message%& is true. The
15357 limit should be less than the value of the global &%message_size_limit%& and of
15358 any &%message_size_limit%& settings on transports, to allow for the bounce text
15359 that Exim generates. If this option is set to zero there is no limit.
15361 When the body of any message that is to be included in a bounce message is
15362 greater than the limit, it is truncated, and a comment pointing this out is
15363 added at the top. The actual cutoff may be greater than the value given, owing
15364 to the use of buffering for transferring the message in chunks (typically 8K in
15365 size). The idea is to save bandwidth on those undeliverable 15-megabyte
15368 .option bounce_sender_authentication main string unset
15369 .cindex "bounce message" "sender authentication"
15370 .cindex "authentication" "bounce message"
15371 .cindex "AUTH" "on bounce message"
15372 This option provides an authenticated sender address that is sent with any
15373 bounce messages generated by Exim that are sent over an authenticated SMTP
15374 connection. A typical setting might be:
15376 bounce_sender_authentication = mailer-daemon@my.domain.example
15378 which would cause bounce messages to be sent using the SMTP command:
15380 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
15382 The value of &%bounce_sender_authentication%& must always be a complete email
15385 .option callout_domain_negative_expire main time 3h
15386 .cindex "caching" "callout timeouts"
15387 .cindex "callout" "caching timeouts"
15388 This option specifies the expiry time for negative callout cache data for a
15389 domain. See section &<<SECTcallver>>& for details of callout verification, and
15390 section &<<SECTcallvercache>>& for details of the caching.
15393 .option callout_domain_positive_expire main time 7d
15394 This option specifies the expiry time for positive callout cache data for a
15395 domain. See section &<<SECTcallver>>& for details of callout verification, and
15396 section &<<SECTcallvercache>>& for details of the caching.
15399 .option callout_negative_expire main time 2h
15400 This option specifies the expiry time for negative callout cache data for an
15401 address. See section &<<SECTcallver>>& for details of callout verification, and
15402 section &<<SECTcallvercache>>& for details of the caching.
15405 .option callout_positive_expire main time 24h
15406 This option specifies the expiry time for positive callout cache data for an
15407 address. See section &<<SECTcallver>>& for details of callout verification, and
15408 section &<<SECTcallvercache>>& for details of the caching.
15411 .option callout_random_local_part main string&!! "see below"
15412 This option defines the &"random"& local part that can be used as part of
15413 callout verification. The default value is
15415 $primary_hostname-$tod_epoch-testing
15417 See section &<<CALLaddparcall>>& for details of how this value is used.
15420 .option check_log_inodes main integer 100
15421 See &%check_spool_space%& below.
15424 .option check_log_space main integer 10M
15425 See &%check_spool_space%& below.
15427 .oindex "&%check_rfc2047_length%&"
15428 .cindex "RFC 2047" "disabling length check"
15429 .option check_rfc2047_length main boolean true
15430 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
15431 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
15432 word; strings to be encoded that exceed this length are supposed to use
15433 multiple encoded words. By default, Exim does not recognize encoded words that
15434 exceed the maximum length. However, it seems that some software, in violation
15435 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
15436 set false, Exim recognizes encoded words of any length.
15439 .option check_spool_inodes main integer 100
15440 See &%check_spool_space%& below.
15443 .option check_spool_space main integer 10M
15444 .cindex "checking disk space"
15445 .cindex "disk space, checking"
15446 .cindex "spool directory" "checking space"
15447 The four &%check_...%& options allow for checking of disk resources before a
15448 message is accepted.
15450 .vindex "&$log_inodes$&"
15451 .vindex "&$log_space$&"
15452 .vindex "&$spool_inodes$&"
15453 .vindex "&$spool_space$&"
15454 When any of these options are nonzero, they apply to all incoming messages. If you
15455 want to apply different checks to different kinds of message, you can do so by
15456 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
15457 &$spool_space$& in an ACL with appropriate additional conditions.
15460 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
15461 either value is greater than zero, for example:
15463 check_spool_space = 100M
15464 check_spool_inodes = 100
15466 The spool partition is the one that contains the directory defined by
15467 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
15470 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
15471 files are written if either is greater than zero. These should be set only if
15472 &%log_file_path%& and &%spool_directory%& refer to different partitions.
15474 If there is less space or fewer inodes than requested, Exim refuses to accept
15475 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
15476 error response to the MAIL command. If ESMTP is in use and there was a
15477 SIZE parameter on the MAIL command, its value is added to the
15478 &%check_spool_space%& value, and the check is performed even if
15479 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
15481 The values for &%check_spool_space%& and &%check_log_space%& are held as a
15482 number of kilobytes (though specified in bytes).
15483 If a non-multiple of 1024 is specified, it is rounded up.
15485 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
15486 failure a message is written to stderr and Exim exits with a non-zero code, as
15487 it obviously cannot send an error message of any kind.
15489 There is a slight performance penalty for these checks.
15490 Versions of Exim preceding 4.88 had these disabled by default;
15491 high-rate installations confident they will never run out of resources
15492 may wish to deliberately disable them.
15494 .option chunking_advertise_hosts main "host list&!!" *
15495 .cindex CHUNKING advertisement
15496 .cindex "RFC 3030" "CHUNKING"
15497 .cindex "ESMTP extensions" CHUNKING
15498 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
15500 Hosts may use the BDAT command as an alternate to DATA.
15502 .option commandline_checks_require_admin main boolean &`false`&
15503 .cindex "restricting access to features"
15504 This option restricts various basic checking features to require an
15505 administrative user.
15506 This affects most of the &%-b*%& options, such as &%-be%&.
15508 .option debug_store main boolean &`false`&
15509 .cindex debugging "memory corruption"
15510 .cindex memory debugging
15511 This option, when true, enables extra checking in Exim's internal memory
15512 management. For use when a memory corruption issue is being investigated,
15513 it should normally be left as default.
15515 .option daemon_smtp_ports main string &`smtp`&
15516 .cindex "port" "for daemon"
15517 .cindex "TCP/IP" "setting listening ports"
15518 This option specifies one or more default SMTP ports on which the Exim daemon
15519 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
15520 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
15522 .option daemon_startup_retries main integer 9
15523 .cindex "daemon startup, retrying"
15524 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
15525 the daemon at startup when it cannot immediately bind a listening socket
15526 (typically because the socket is already in use): &%daemon_startup_retries%&
15527 defines the number of retries after the first failure, and
15528 &%daemon_startup_sleep%& defines the length of time to wait between retries.
15530 .option daemon_startup_sleep main time 30s
15531 See &%daemon_startup_retries%&.
15533 .option delay_warning main "time list" 24h
15534 .cindex "warning of delay"
15535 .cindex "delay warning, specifying"
15536 .cindex "queue" "delay warning"
15537 When a message is delayed, Exim sends a warning message to the sender at
15538 intervals specified by this option. The data is a colon-separated list of times
15539 after which to send warning messages. If the value of the option is an empty
15540 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
15541 message has been in the queue for longer than the last time, the last interval
15542 between the times is used to compute subsequent warning times. For example,
15545 delay_warning = 4h:8h:24h
15547 the first message is sent after 4 hours, the second after 8 hours, and
15548 the third one after 24 hours. After that, messages are sent every 16 hours,
15549 because that is the interval between the last two times on the list. If you set
15550 just one time, it specifies the repeat interval. For example, with:
15554 messages are repeated every six hours. To stop warnings after a given time, set
15555 a very large time at the end of the list. For example:
15557 delay_warning = 2h:12h:99d
15559 Note that the option is only evaluated at the time a delivery attempt fails,
15560 which depends on retry and queue-runner configuration.
15561 Typically retries will be configured more frequently than warning messages.
15563 .option delay_warning_condition main string&!! "see below"
15564 .vindex "&$domain$&"
15565 The string is expanded at the time a warning message might be sent. If all the
15566 deferred addresses have the same domain, it is set in &$domain$& during the
15567 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
15568 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
15569 &"false"& (the comparison being done caselessly) then the warning message is
15570 not sent. The default is:
15572 delay_warning_condition = ${if or {\
15573 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
15574 { match{$h_precedence:}{(?i)bulk|list|junk} }\
15575 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
15578 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
15579 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
15580 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
15581 &"auto-replied"& in an &'Auto-Submitted:'& header.
15583 .option deliver_drop_privilege main boolean false
15584 .cindex "unprivileged delivery"
15585 .cindex "delivery" "unprivileged"
15586 If this option is set true, Exim drops its root privilege at the start of a
15587 delivery process, and runs as the Exim user throughout. This severely restricts
15588 the kinds of local delivery that are possible, but is viable in certain types
15589 of configuration. There is a discussion about the use of root privilege in
15590 chapter &<<CHAPsecurity>>&.
15592 .option deliver_queue_load_max main fixed-point unset
15593 .cindex "load average"
15594 .cindex "queue runner" "abandoning"
15595 When this option is set, a queue run is abandoned if the system load average
15596 becomes greater than the value of the option. The option has no effect on
15597 ancient operating systems on which Exim cannot determine the load average.
15598 See also &%queue_only_load%& and &%smtp_load_reserve%&.
15601 .option delivery_date_remove main boolean true
15602 .cindex "&'Delivery-date:'& header line"
15603 Exim's transports have an option for adding a &'Delivery-date:'& header to a
15604 message when it is delivered, in exactly the same way as &'Return-path:'& is
15605 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
15606 should not be present in incoming messages, and this option causes them to be
15607 removed at the time the message is received, to avoid any problems that might
15608 occur when a delivered message is subsequently sent on to some other recipient.
15610 .option disable_fsync main boolean false
15611 .cindex "&[fsync()]&, disabling"
15612 This option is available only if Exim was built with the compile-time option
15613 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
15614 a runtime configuration generates an &"unknown option"& error. You should not
15615 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
15616 really, really, really understand what you are doing. &'No pre-compiled
15617 distributions of Exim should ever make this option available.'&
15619 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
15620 updated files' data to be written to disc before continuing. Unexpected events
15621 such as crashes and power outages may cause data to be lost or scrambled.
15622 Here be Dragons. &*Beware.*&
15625 .option disable_ipv6 main boolean false
15626 .cindex "IPv6" "disabling"
15627 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
15628 activities take place. AAAA records are never looked up, and any IPv6 addresses
15629 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
15630 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
15631 to handle IPv6 literal addresses.
15634 .option dkim_verify_hashes main "string list" "sha256 : sha512"
15635 .cindex DKIM "selecting signature algorithms"
15636 This option gives a list of hash types which are acceptable in signatures,
15637 and an order of processing.
15638 Signatures with algorithms not in the list will be ignored.
15640 Acceptable values include:
15647 Note that the acceptance of sha1 violates RFC 8301.
15649 .option dkim_verify_keytypes main "string list" "ed25519 : rsa"
15650 This option gives a list of key types which are acceptable in signatures,
15651 and an order of processing.
15652 Signatures with algorithms not in the list will be ignored.
15655 .option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250"
15656 This option gives a list of key sizes which are acceptable in signatures.
15657 The list is keyed by the algorithm type for the key; the values are in bits.
15658 Signatures with keys smaller than given by this option will fail verification.
15660 The default enforces the RFC 8301 minimum key size for RSA signatures.
15662 .option dkim_verify_minimal main boolean false
15663 If set to true, verification of signatures will terminate after the
15666 .option dkim_verify_signers main "domain list&!!" $dkim_signers
15667 .cindex DKIM "controlling calls to the ACL"
15668 This option gives a list of DKIM domains for which the DKIM ACL is run.
15669 It is expanded after the message is received; by default it runs
15670 the ACL once for each signature in the message.
15671 See section &<<SECDKIMVFY>>&.
15674 .option dmarc_forensic_sender main string&!! unset
15675 .option dmarc_history_file main string unset
15676 .option dmarc_tld_file main string unset
15677 .cindex DMARC "main section options"
15678 These options control DMARC processing.
15679 See section &<<SECDMARC>>& for details.
15682 .option dns_again_means_nonexist main "domain list&!!" unset
15683 .cindex "DNS" "&""try again""& response; overriding"
15684 DNS lookups give a &"try again"& response for the DNS errors
15685 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
15686 keep trying to deliver a message, or to give repeated temporary errors to
15687 incoming mail. Sometimes the effect is caused by a badly set up name server and
15688 may persist for a long time. If a domain which exhibits this problem matches
15689 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
15690 This option should be used with care. You can make it apply to reverse lookups
15691 by a setting such as this:
15693 dns_again_means_nonexist = *.in-addr.arpa
15695 This option applies to all DNS lookups that Exim does. It also applies when the
15696 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
15697 since these are most likely to be caused by DNS lookup problems. The
15698 &(dnslookup)& router has some options of its own for controlling what happens
15699 when lookups for MX or SRV records give temporary errors. These more specific
15700 options are applied after this global option.
15702 .option dns_check_names_pattern main string "see below"
15703 .cindex "DNS" "pre-check of name syntax"
15704 When this option is set to a non-empty string, it causes Exim to check domain
15705 names for characters that are not allowed in host names before handing them to
15706 the DNS resolver, because some resolvers give temporary errors for names that
15707 contain unusual characters. If a domain name contains any unwanted characters,
15708 a &"not found"& result is forced, and the resolver is not called. The check is
15709 done by matching the domain name against a regular expression, which is the
15710 value of this option. The default pattern is
15712 dns_check_names_pattern = \
15713 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
15715 which permits only letters, digits, slashes, and hyphens in components, but
15716 they must start and end with a letter or digit. Slashes are not, in fact,
15717 permitted in host names, but they are found in certain NS records (which can be
15718 accessed in Exim by using a &%dnsdb%& lookup). If you set
15719 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
15722 .option dns_csa_search_limit main integer 5
15723 This option controls the depth of parental searching for CSA SRV records in the
15724 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
15726 .option dns_csa_use_reverse main boolean true
15727 This option controls whether or not an IP address, given as a CSA domain, is
15728 reversed and looked up in the reverse DNS, as described in more detail in
15729 section &<<SECTverifyCSA>>&.
15731 .option dns_cname_loops main integer 1
15732 .cindex DNS "CNAME following"
15733 This option controls the following of CNAME chains, needed if the resolver does
15734 not do it internally.
15735 As of 2018 most should, and the default can be left.
15736 If you have an ancient one, a value of 10 is likely needed.
15738 The default value of one CNAME-follow is needed
15739 thanks to the observed return for an MX request,
15740 given no MX presence but a CNAME to an A, of the CNAME.
15743 .option dns_dnssec_ok main integer -1
15744 .cindex "DNS" "resolver options"
15745 .cindex "DNS" "DNSSEC"
15746 If this option is set to a non-negative number then Exim will initialise the
15747 DNS resolver library to either use or not use DNSSEC, overriding the system
15748 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
15750 If the resolver library does not support DNSSEC then this option has no effect.
15752 On Linux with glibc 2.31 or newer this is insufficient, the resolver library
15753 will default to stripping out a successful validation status.
15754 This will break a previously working Exim installation.
15755 Provided that you do trust the resolver (ie, is on localhost) you can tell
15756 glibc to pass through any successful validation with a new option in
15757 &_/etc/resolv.conf_&:
15763 .option dns_ipv4_lookup main "domain list&!!" unset
15764 .cindex "IPv6" "DNS lookup for AAAA records"
15765 .cindex "DNS" "IPv6 lookup for AAAA records"
15766 .cindex DNS "IPv6 disabling"
15767 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
15768 looks for IPv6 address records (AAAA records) as well as IPv4 address records
15769 (A records) when trying to find IP addresses for hosts, unless the host's
15770 domain matches this list.
15772 This is a fudge to help with name servers that give big delays or otherwise do
15773 not work for the AAAA record type. In due course, when the world's name
15774 servers have all been upgraded, there should be no need for this option.
15775 Note that all lookups, including those done for verification, are affected;
15776 this will result in verify failure for IPv6 connections or ones using names
15777 only valid for IPv6 addresses.
15780 .option dns_retrans main time 0s
15781 .cindex "DNS" "resolver options"
15782 .cindex timeout "dns lookup"
15783 .cindex "DNS" timeout
15784 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
15785 retransmission and retry parameters for DNS lookups. Values of zero (the
15786 defaults) leave the system default settings unchanged. The first value is the
15787 time between retries, and the second is the number of retries. It isn't
15788 totally clear exactly how these settings affect the total time a DNS lookup may
15789 take. I haven't found any documentation about timeouts on DNS lookups; these
15790 parameter values are available in the external resolver interface structure,
15791 but nowhere does it seem to describe how they are used or what you might want
15793 See also the &%slow_lookup_log%& option.
15796 .option dns_retry main integer 0
15797 See &%dns_retrans%& above.
15800 .option dns_trust_aa main "domain list&!!" unset
15801 .cindex "DNS" "resolver options"
15802 .cindex "DNS" "DNSSEC"
15803 If this option is set then lookup results marked with the AA bit
15804 (Authoritative Answer) are trusted the same way as if they were
15805 DNSSEC-verified. The authority section's name of the answer must
15806 match with this expanded domain list.
15808 Use this option only if you talk directly to a resolver that is
15809 authoritative for some zones and does not set the AD (Authentic Data)
15810 bit in the answer. Some DNS servers may have an configuration option to
15811 mark the answers from their own zones as verified (they set the AD bit).
15812 Others do not have this option. It is considered as poor practice using
15813 a resolver that is an authoritative server for some zones.
15815 Use this option only if you really have to (e.g. if you want
15816 to use DANE for remote delivery to a server that is listed in the DNS
15817 zones that your resolver is authoritative for).
15819 If the DNS answer packet has the AA bit set and contains resource record
15820 in the answer section, the name of the first NS record appearing in the
15821 authority section is compared against the list. If the answer packet is
15822 authoritative but the answer section is empty, the name of the first SOA
15823 record in the authoritative section is used instead.
15825 .cindex "DNS" "resolver options"
15826 .option dns_use_edns0 main integer -1
15827 .cindex "DNS" "resolver options"
15828 .cindex "DNS" "EDNS0"
15829 .cindex "DNS" "OpenBSD
15830 If this option is set to a non-negative number then Exim will initialise the
15831 DNS resolver library to either use or not use EDNS0 extensions, overriding
15832 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
15835 If the resolver library does not support EDNS0 then this option has no effect.
15837 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
15838 means that DNSSEC will not work with Exim on that platform either, unless Exim
15839 is linked against an alternative DNS client library.
15842 .option drop_cr main boolean false
15843 This is an obsolete option that is now a no-op. It used to affect the way Exim
15844 handled CR and LF characters in incoming messages. What happens now is
15845 described in section &<<SECTlineendings>>&.
15847 .option dsn_advertise_hosts main "host list&!!" unset
15848 .cindex "bounce messages" "success"
15849 .cindex "DSN" "success"
15850 .cindex "Delivery Status Notification" "success"
15851 .cindex "ESMTP extensions" DSN
15852 DSN extensions (RFC3461) will be advertised in the EHLO message to,
15853 and accepted from, these hosts.
15854 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
15855 and RET and ORCPT options on MAIL FROM commands.
15856 A NOTIFY=SUCCESS option requests success-DSN messages.
15857 A NOTIFY= option with no argument requests that no delay or failure DSNs
15859 &*Note*&: Supplying success-DSN messages has been criticised
15860 on privacy grounds; it can leak details of internal forwarding.
15862 .option dsn_from main "string&!!" "see below"
15863 .cindex "&'From:'& header line" "in bounces"
15864 .cindex "bounce messages" "&'From:'& line, specifying"
15865 This option can be used to vary the contents of &'From:'& header lines in
15866 bounces and other automatically generated messages (&"Delivery Status
15867 Notifications"& &-- hence the name of the option). The default setting is:
15869 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
15871 The value is expanded every time it is needed. If the expansion fails, a
15872 panic is logged, and the default value is used.
15874 .option envelope_to_remove main boolean true
15875 .cindex "&'Envelope-to:'& header line"
15876 Exim's transports have an option for adding an &'Envelope-to:'& header to a
15877 message when it is delivered, in exactly the same way as &'Return-path:'& is
15878 handled. &'Envelope-to:'& records the original recipient address from the
15879 message's envelope that caused the delivery to happen. Such headers should not
15880 be present in incoming messages, and this option causes them to be removed at
15881 the time the message is received, to avoid any problems that might occur when a
15882 delivered message is subsequently sent on to some other recipient.
15885 .option errors_copy main "string list&!!" unset
15886 .cindex "bounce message" "copy to other address"
15887 .cindex "copy of bounce message"
15888 Setting this option causes Exim to send bcc copies of bounce messages that it
15889 generates to other addresses. &*Note*&: This does not apply to bounce messages
15890 coming from elsewhere. The value of the option is a colon-separated list of
15891 items. Each item consists of a pattern, terminated by white space, followed by
15892 a comma-separated list of email addresses. If a pattern contains spaces, it
15893 must be enclosed in double quotes.
15895 Each pattern is processed in the same way as a single item in an address list
15896 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
15897 the bounce message, the message is copied to the addresses on the list. The
15898 items are scanned in order, and once a matching one is found, no further items
15899 are examined. For example:
15901 errors_copy = spqr@mydomain postmaster@mydomain.example :\
15902 rqps@mydomain hostmaster@mydomain.example,\
15903 postmaster@mydomain.example
15905 .vindex "&$domain$&"
15906 .vindex "&$local_part$&"
15907 The address list is expanded before use. The expansion variables &$local_part$&
15908 and &$domain$& are set from the original recipient of the error message, and if
15909 there was any wildcard matching in the pattern, the expansion
15910 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
15911 variables &$0$&, &$1$&, etc. are set in the normal way.
15914 .option errors_reply_to main string unset
15915 .cindex "bounce message" "&'Reply-to:'& in"
15916 By default, Exim's bounce and delivery warning messages contain the header line
15918 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
15920 .oindex &%quota_warn_message%&
15921 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
15922 A warning message that is generated by the &%quota_warn_message%& option in an
15923 &(appendfile)& transport may contain its own &'From:'& header line that
15924 overrides the default.
15926 Experience shows that people reply to bounce messages. If the
15927 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
15928 and warning messages. For example:
15930 errors_reply_to = postmaster@my.domain.example
15932 The value of the option is not expanded. It must specify a valid RFC 2822
15933 address. However, if a warning message that is generated by the
15934 &%quota_warn_message%& option in an &(appendfile)& transport contain its
15935 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
15939 .option event_action main string&!! unset
15941 This option declares a string to be expanded for Exim's events mechanism.
15942 For details see chapter &<<CHAPevents>>&.
15945 .option exim_group main string "compile-time configured"
15946 .cindex "gid (group id)" "Exim's own"
15947 .cindex "Exim group"
15948 This option changes the gid under which Exim runs when it gives up root
15949 privilege. The default value is compiled into the binary. The value of this
15950 option is used only when &%exim_user%& is also set. Unless it consists entirely
15951 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
15952 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
15956 .option exim_path main string "see below"
15957 .cindex "Exim binary, path name"
15958 This option specifies the path name of the Exim binary, which is used when Exim
15959 needs to re-exec itself. The default is set up to point to the file &'exim'& in
15960 the directory configured at compile time by the BIN_DIRECTORY setting. It
15961 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
15963 &*Warning*&: Do not use a macro to define the value of this option, because
15964 you will break those Exim utilities that scan the configuration file to find
15965 where the binary is. (They then use the &%-bP%& option to extract option
15966 settings such as the value of &%spool_directory%&.)
15969 .option exim_user main string "compile-time configured"
15970 .cindex "uid (user id)" "Exim's own"
15971 .cindex "Exim user"
15972 This option changes the uid under which Exim runs when it gives up root
15973 privilege. The default value is compiled into the binary. Ownership of the run
15974 time configuration file and the use of the &%-C%& and &%-D%& command line
15975 options is checked against the values in the binary, not what is set here.
15977 Unless it consists entirely of digits, the string is looked up using
15978 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
15979 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
15980 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
15983 .option exim_version main string "current version"
15984 .cindex "Exim version"
15985 .cindex customizing "version number"
15986 .cindex "version number of Exim" override
15987 This option overrides the &$version_number$&/&$exim_version$& that Exim reports in
15988 various places. Use with care; this may fool stupid security scanners.
15991 .option extra_local_interfaces main "string list" unset
15992 This option defines network interfaces that are to be considered local when
15993 routing, but which are not used for listening by the daemon. See section
15994 &<<SECTreclocipadd>>& for details.
15997 . Allow this long option name to split; give it unsplit as a fifth argument
15998 . for the automatic .oindex that is generated by .option.
16000 .option "extract_addresses_remove_arguments" main boolean true &&&
16001 extract_addresses_remove_arguments
16003 .cindex "command line" "addresses with &%-t%&"
16004 .cindex "Sendmail compatibility" "&%-t%& option"
16005 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
16006 are present on the command line when the &%-t%& option is used to build an
16007 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
16008 line addresses are removed from the recipients list. This is also how Smail
16009 behaves. However, other Sendmail documentation (the O'Reilly book) states that
16010 command line addresses are added to those obtained from the header lines. When
16011 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
16012 argument headers. If it is set false, Exim adds rather than removes argument
16016 .option finduser_retries main integer 0
16017 .cindex "NIS, retrying user lookups"
16018 On systems running NIS or other schemes in which user and group information is
16019 distributed from a remote system, there can be times when &[getpwnam()]& and
16020 related functions fail, even when given valid data, because things time out.
16021 Unfortunately these failures cannot be distinguished from genuine &"not found"&
16022 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
16023 many extra times to find a user or a group, waiting for one second between
16026 .cindex "&_/etc/passwd_&" "multiple reading of"
16027 You should not set this option greater than zero if your user information is in
16028 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
16029 search the file multiple times for non-existent users, and also cause delay.
16033 .option freeze_tell main "string list, comma separated" unset
16034 .cindex "freezing messages" "sending a message when freezing"
16035 On encountering certain errors, or when configured to do so in a system filter,
16036 ACL, or special router, Exim freezes a message. This means that no further
16037 delivery attempts take place until an administrator thaws the message, or the
16038 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
16039 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
16040 warning message whenever it freezes something, unless the message it is
16041 freezing is a locally-generated bounce message. (Without this exception there
16042 is the possibility of looping.) The warning message is sent to the addresses
16043 supplied as the comma-separated value of this option. If several of the
16044 message's addresses cause freezing, only a single message is sent. If the
16045 freezing was automatic, the reason(s) for freezing can be found in the message
16046 log. If you configure freezing in a filter or ACL, you must arrange for any
16047 logging that you require.
16050 .option gecos_name main string&!! unset
16052 .cindex "&""gecos""& field, parsing"
16053 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
16054 password file to hold other information in addition to users' real names. Exim
16055 looks up this field for use when it is creating &'Sender:'& or &'From:'&
16056 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
16057 of the field are used unchanged, except that, if an ampersand is encountered,
16058 it is replaced by the user's login name with the first character forced to
16059 upper case, since this is a convention that is observed on many systems.
16061 When these options are set, &%gecos_pattern%& is treated as a regular
16062 expression that is to be applied to the field (again with && replaced by the
16063 login name), and if it matches, &%gecos_name%& is expanded and used as the
16066 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
16067 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
16068 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
16069 name terminates at the first comma, the following can be used:
16071 gecos_pattern = ([^,]*)
16075 .option gecos_pattern main string unset
16076 See &%gecos_name%& above.
16079 .option gnutls_compat_mode main boolean unset
16080 This option controls whether GnuTLS is used in compatibility mode in an Exim
16081 server. This reduces security slightly, but improves interworking with older
16082 implementations of TLS.
16085 .option gnutls_allow_auto_pkcs11 main boolean unset
16086 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
16087 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
16090 &url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
16095 .option headers_charset main string "see below"
16096 This option sets a default character set for translating from encoded MIME
16097 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
16098 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
16099 ultimate default is ISO-8859-1. For more details see the description of header
16100 insertions in section &<<SECTexpansionitems>>&.
16104 .option header_maxsize main integer "see below"
16105 .cindex "header section" "maximum size of"
16106 .cindex "limit" "size of message header section"
16107 This option controls the overall maximum size of a message's header
16108 section. The default is the value of HEADER_MAXSIZE in
16109 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
16110 sections are rejected.
16113 .option header_line_maxsize main integer 0
16114 .cindex "header lines" "maximum size of"
16115 .cindex "limit" "size of one header line"
16116 This option limits the length of any individual header line in a message, after
16117 all the continuations have been joined together. Messages with individual
16118 header lines that are longer than the limit are rejected. The default value of
16119 zero means &"no limit"&.
16124 .option helo_accept_junk_hosts main "host list&!!" unset
16125 .cindex "HELO" "accepting junk data"
16126 .cindex "EHLO" "accepting junk data"
16127 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
16128 mail, and gives an error response for invalid data. Unfortunately, there are
16129 some SMTP clients that send syntactic junk. They can be accommodated by setting
16130 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
16131 if you want to do semantic checking.
16132 See also &%helo_allow_chars%& for a way of extending the permitted character
16136 .option helo_allow_chars main string unset
16137 .cindex "HELO" "underscores in"
16138 .cindex "EHLO" "underscores in"
16139 .cindex "underscore in EHLO/HELO"
16140 This option can be set to a string of rogue characters that are permitted in
16141 all EHLO and HELO names in addition to the standard letters, digits,
16142 hyphens, and dots. If you really must allow underscores, you can set
16144 helo_allow_chars = _
16146 Note that the value is one string, not a list.
16149 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
16150 .cindex "HELO" "forcing reverse lookup"
16151 .cindex "EHLO" "forcing reverse lookup"
16152 If the domain given by a client in a HELO or EHLO command matches this
16153 list, a reverse lookup is done in order to establish the host's true name. The
16154 default forces a lookup if the client host gives the server's name or any of
16155 its IP addresses (in brackets), something that broken clients have been seen to
16159 .option helo_try_verify_hosts main "host list&!!" unset
16160 .cindex "HELO verifying" "optional"
16161 .cindex "EHLO" "verifying, optional"
16162 By default, Exim just checks the syntax of HELO and EHLO commands (see
16163 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
16164 to do more extensive checking of the data supplied by these commands. The ACL
16165 condition &`verify = helo`& is provided to make this possible.
16166 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
16167 to force the check to occur. From release 4.53 onwards, this is no longer
16168 necessary. If the check has not been done before &`verify = helo`& is
16169 encountered, it is done at that time. Consequently, this option is obsolete.
16170 Its specification is retained here for backwards compatibility.
16172 When an EHLO or HELO command is received, if the calling host matches
16173 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
16174 EHLO command either:
16177 is an IP literal matching the calling address of the host, or
16179 .cindex "DNS" "reverse lookup"
16180 .cindex "reverse DNS lookup"
16181 matches the host name that Exim obtains by doing a reverse lookup of the
16182 calling host address, or
16184 when looked up in DNS yields the calling host address.
16187 However, the EHLO or HELO command is not rejected if any of the checks
16188 fail. Processing continues, but the result of the check is remembered, and can
16189 be detected later in an ACL by the &`verify = helo`& condition.
16191 If DNS was used for successful verification, the variable
16192 .cindex "DNS" "DNSSEC"
16193 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
16195 .option helo_verify_hosts main "host list&!!" unset
16196 .cindex "HELO verifying" "mandatory"
16197 .cindex "EHLO" "verifying, mandatory"
16198 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
16199 backwards compatibility. For hosts that match this option, Exim checks the host
16200 name given in the HELO or EHLO in the same way as for
16201 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
16202 rejected with a 550 error, and entries are written to the main and reject logs.
16203 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
16206 .option hold_domains main "domain list&!!" unset
16207 .cindex "domain" "delaying delivery"
16208 .cindex "delivery" "delaying certain domains"
16209 This option allows mail for particular domains to be held in the queue
16210 manually. The option is overridden if a message delivery is forced with the
16211 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
16212 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
16213 item in &%hold_domains%&, no routing or delivery for that address is done, and
16214 it is deferred every time the message is looked at.
16216 This option is intended as a temporary operational measure for delaying the
16217 delivery of mail while some problem is being sorted out, or some new
16218 configuration tested. If you just want to delay the processing of some
16219 domains until a queue run occurs, you should use &%queue_domains%& or
16220 &%queue_smtp_domains%&, not &%hold_domains%&.
16222 A setting of &%hold_domains%& does not override Exim's code for removing
16223 messages from the queue if they have been there longer than the longest retry
16224 time in any retry rule. If you want to hold messages for longer than the normal
16225 retry times, insert a dummy retry rule with a long retry time.
16228 .option host_lookup main "host list&!!" unset
16229 .cindex "host name" "lookup, forcing"
16230 Exim does not look up the name of a calling host from its IP address unless it
16231 is required to compare against some host list, or the host matches
16232 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
16233 option (which normally contains IP addresses rather than host names). The
16234 default configuration file contains
16238 which causes a lookup to happen for all hosts. If the expense of these lookups
16239 is felt to be too great, the setting can be changed or removed.
16241 After a successful reverse lookup, Exim does a forward lookup on the name it
16242 has obtained, to verify that it yields the IP address that it started with. If
16243 this check fails, Exim behaves as if the name lookup failed.
16245 .vindex "&$host_lookup_failed$&"
16246 .vindex "&$sender_host_name$&"
16247 After any kind of failure, the host name (in &$sender_host_name$&) remains
16248 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
16249 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
16250 &`verify = reverse_host_lookup`& in ACLs.
16253 .option host_lookup_order main "string list" &`bydns:byaddr`&
16254 This option specifies the order of different lookup methods when Exim is trying
16255 to find a host name from an IP address. The default is to do a DNS lookup
16256 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
16257 if that fails. You can change the order of these lookups, or omit one entirely,
16260 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
16261 multiple PTR records in the DNS and the IP address is not listed in
16262 &_/etc/hosts_&. Different operating systems give different results in this
16263 case. That is why the default tries a DNS lookup first.
16267 .option host_reject_connection main "host list&!!" unset
16268 .cindex "host" "rejecting connections from"
16269 If this option is set, incoming SMTP calls from the hosts listed are rejected
16270 as soon as the connection is made.
16271 This option is obsolete, and retained only for backward compatibility, because
16272 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
16273 connections immediately.
16275 The ability to give an immediate rejection (either by this option or using an
16276 ACL) is provided for use in unusual cases. Many hosts will just try again,
16277 sometimes without much delay. Normally, it is better to use an ACL to reject
16278 incoming messages at a later stage, such as after RCPT commands. See
16279 chapter &<<CHAPACL>>&.
16282 .option hosts_connection_nolog main "host list&!!" unset
16283 .cindex "host" "not logging connections from"
16284 This option defines a list of hosts for which connection logging does not
16285 happen, even though the &%smtp_connection%& log selector is set. For example,
16286 you might want not to log SMTP connections from local processes, or from
16287 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
16288 the daemon; you should therefore strive to restrict its value to a short inline
16289 list of IP addresses and networks. To disable logging SMTP connections from
16290 local processes, you must create a host list with an empty item. For example:
16292 hosts_connection_nolog = :
16294 If the &%smtp_connection%& log selector is not set, this option has no effect.
16298 .option hosts_proxy main "host list&!!" unset
16299 .cindex proxy "proxy protocol"
16300 This option enables use of Proxy Protocol proxies for incoming
16301 connections. For details see section &<<SECTproxyInbound>>&.
16304 .option hosts_treat_as_local main "domain list&!!" unset
16305 .cindex "local host" "domains treated as"
16306 .cindex "host" "treated as local"
16307 If this option is set, any host names that match the domain list are treated as
16308 if they were the local host when Exim is scanning host lists obtained from MX
16310 or other sources. Note that the value of this option is a domain list, not a
16311 host list, because it is always used to check host names, not IP addresses.
16313 This option also applies when Exim is matching the special items
16314 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
16315 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
16316 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
16317 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
16318 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
16319 interfaces and recognizing the local host.
16322 .option ibase_servers main "string list" unset
16323 .cindex "InterBase" "server list"
16324 This option provides a list of InterBase servers and associated connection data,
16325 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
16326 The option is available only if Exim has been built with InterBase support.
16330 .option ignore_bounce_errors_after main time 10w
16331 .cindex "bounce message" "discarding"
16332 .cindex "discarding bounce message"
16333 This option affects the processing of bounce messages that cannot be delivered,
16334 that is, those that suffer a permanent delivery failure. (Bounce messages that
16335 suffer temporary delivery failures are of course retried in the usual way.)
16337 After a permanent delivery failure, bounce messages are frozen,
16338 because there is no sender to whom they can be returned. When a frozen bounce
16339 message has been in the queue for more than the given time, it is unfrozen at
16340 the next queue run, and a further delivery is attempted. If delivery fails
16341 again, the bounce message is discarded. This makes it possible to keep failed
16342 bounce messages around for a shorter time than the normal maximum retry time
16343 for frozen messages. For example,
16345 ignore_bounce_errors_after = 12h
16347 retries failed bounce message deliveries after 12 hours, discarding any further
16348 failures. If the value of this option is set to a zero time period, bounce
16349 failures are discarded immediately. Setting a very long time (as in the default
16350 value) has the effect of disabling this option. For ways of automatically
16351 dealing with other kinds of frozen message, see &%auto_thaw%& and
16352 &%timeout_frozen_after%&.
16355 .option ignore_fromline_hosts main "host list&!!" unset
16356 .cindex "&""From""& line"
16357 .cindex "UUCP" "&""From""& line"
16358 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
16359 the headers of a message. By default this is treated as the start of the
16360 message's body, which means that any following headers are not recognized as
16361 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
16362 match those hosts that insist on sending it. If the sender is actually a local
16363 process rather than a remote host, and is using &%-bs%& to inject the messages,
16364 &%ignore_fromline_local%& must be set to achieve this effect.
16367 .option ignore_fromline_local main boolean false
16368 See &%ignore_fromline_hosts%& above.
16370 .option keep_environment main "string list" unset
16371 .cindex "environment" "values from"
16372 This option contains a string list of environment variables to keep.
16373 You have to trust these variables or you have to be sure that
16374 these variables do not impose any security risk. Keep in mind that
16375 during the startup phase Exim is running with an effective UID 0 in most
16376 installations. As the default value is an empty list, the default
16377 environment for using libraries, running embedded Perl code, or running
16378 external binaries is empty, and does not not even contain PATH or HOME.
16380 Actually the list is interpreted as a list of patterns
16381 (&<<SECTlistexpand>>&), except that it is not expanded first.
16383 WARNING: Macro substitution is still done first, so having a macro
16384 FOO and having FOO_HOME in your &%keep_environment%& option may have
16385 unexpected results. You may work around this using a regular expression
16386 that does not match the macro name: ^[F]OO_HOME$.
16388 Current versions of Exim issue a warning during startup if you do not mention
16389 &%keep_environment%& in your runtime configuration file and if your
16390 current environment is not empty. Future versions may not issue that warning
16393 See the &%add_environment%& main config option for a way to set
16394 environment variables to a fixed value. The environment for &(pipe)&
16395 transports is handled separately, see section &<<SECTpipeenv>>& for
16399 .option keep_malformed main time 4d
16400 This option specifies the length of time to keep messages whose spool files
16401 have been corrupted in some way. This should, of course, never happen. At the
16402 next attempt to deliver such a message, it gets removed. The incident is
16406 .option ldap_ca_cert_dir main string unset
16407 .cindex "LDAP", "TLS CA certificate directory"
16408 .cindex certificate "directory for LDAP"
16409 This option indicates which directory contains CA certificates for verifying
16410 a TLS certificate presented by an LDAP server.
16411 While Exim does not provide a default value, your SSL library may.
16412 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16413 and constrained to be a directory.
16416 .option ldap_ca_cert_file main string unset
16417 .cindex "LDAP", "TLS CA certificate file"
16418 .cindex certificate "file for LDAP"
16419 This option indicates which file contains CA certificates for verifying
16420 a TLS certificate presented by an LDAP server.
16421 While Exim does not provide a default value, your SSL library may.
16422 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16423 and constrained to be a file.
16426 .option ldap_cert_file main string unset
16427 .cindex "LDAP" "TLS client certificate file"
16428 .cindex certificate "file for LDAP"
16429 This option indicates which file contains an TLS client certificate which
16430 Exim should present to the LDAP server during TLS negotiation.
16431 Should be used together with &%ldap_cert_key%&.
16434 .option ldap_cert_key main string unset
16435 .cindex "LDAP" "TLS client key file"
16436 .cindex certificate "key for LDAP"
16437 This option indicates which file contains the secret/private key to use
16438 to prove identity to the LDAP server during TLS negotiation.
16439 Should be used together with &%ldap_cert_file%&, which contains the
16440 identity to be proven.
16443 .option ldap_cipher_suite main string unset
16444 .cindex "LDAP" "TLS cipher suite"
16445 This controls the TLS cipher-suite negotiation during TLS negotiation with
16446 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
16447 cipher-suite options with OpenSSL (as used by LDAP client libraries).
16450 .option ldap_default_servers main "string list" unset
16451 .cindex "LDAP" "default servers"
16452 This option provides a list of LDAP servers which are tried in turn when an
16453 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
16454 details of LDAP queries. This option is available only when Exim has been built
16458 .option ldap_require_cert main string unset.
16459 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
16460 This should be one of the values "hard", "demand", "allow", "try" or "never".
16461 A value other than one of these is interpreted as "never".
16462 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
16463 Although Exim does not set a default, the LDAP library probably defaults
16467 .option ldap_start_tls main boolean false
16468 .cindex "LDAP" "whether or not to negotiate TLS"
16469 If set, Exim will attempt to negotiate TLS with the LDAP server when
16470 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
16471 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
16473 In the event of failure to negotiate TLS, the action taken is controlled
16474 by &%ldap_require_cert%&.
16475 This option is ignored for &`ldapi`& connections.
16478 .option ldap_version main integer unset
16479 .cindex "LDAP" "protocol version, forcing"
16480 This option can be used to force Exim to set a specific protocol version for
16481 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
16482 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
16483 the LDAP headers; otherwise it is 2. This option is available only when Exim
16484 has been built with LDAP support.
16488 .option local_from_check main boolean true
16489 .cindex "&'Sender:'& header line" "disabling addition of"
16490 .cindex "&'From:'& header line" "disabling checking of"
16491 When a message is submitted locally (that is, not over a TCP/IP connection) by
16492 an untrusted user, Exim removes any existing &'Sender:'& header line, and
16493 checks that the &'From:'& header line matches the login of the calling user and
16494 the domain specified by &%qualify_domain%&.
16496 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
16497 locally submitted message is automatically qualified by Exim, unless the
16498 &%-bnq%& command line option is used.
16500 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
16501 on the local part. If the &'From:'& header line does not match, Exim adds a
16502 &'Sender:'& header with an address constructed from the calling user's login
16503 and the default qualify domain.
16505 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
16506 and no &'Sender:'& header is ever added. If, in addition, you want to retain
16507 &'Sender:'& header lines supplied by untrusted users, you must also set
16508 &%local_sender_retain%& to be true.
16510 .cindex "envelope from"
16511 .cindex "envelope sender"
16512 These options affect only the header lines in the message. The envelope sender
16513 is still forced to be the login id at the qualify domain unless
16514 &%untrusted_set_sender%& permits the user to supply an envelope sender.
16516 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
16517 request similar header line checking. See section &<<SECTthesenhea>>&, which
16518 has more details about &'Sender:'& processing.
16523 .option local_from_prefix main string unset
16524 When Exim checks the &'From:'& header line of locally submitted messages for
16525 matching the login id (see &%local_from_check%& above), it can be configured to
16526 ignore certain prefixes and suffixes in the local part of the address. This is
16527 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
16528 appropriate lists, in the same form as the &%local_part_prefix%& and
16529 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
16532 local_from_prefix = *-
16534 is set, a &'From:'& line containing
16536 From: anything-user@your.domain.example
16538 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
16539 matches the actual sender address that is constructed from the login name and
16543 .option local_from_suffix main string unset
16544 See &%local_from_prefix%& above.
16547 .option local_interfaces main "string list" "see below"
16548 This option controls which network interfaces are used by the daemon for
16549 listening; they are also used to identify the local host when routing. Chapter
16550 &<<CHAPinterfaces>>& contains a full description of this option and the related
16551 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
16552 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
16553 &%local_interfaces%& is
16555 local_interfaces = 0.0.0.0
16557 when Exim is built without IPv6 support; otherwise it is
16559 local_interfaces = <; ::0 ; 0.0.0.0
16562 .option local_scan_timeout main time 5m
16563 .cindex "timeout" "for &[local_scan()]& function"
16564 .cindex "&[local_scan()]& function" "timeout"
16565 This timeout applies to the &[local_scan()]& function (see chapter
16566 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
16567 the incoming message is rejected with a temporary error if it is an SMTP
16568 message. For a non-SMTP message, the message is dropped and Exim ends with a
16569 non-zero code. The incident is logged on the main and reject logs.
16573 .option local_sender_retain main boolean false
16574 .cindex "&'Sender:'& header line" "retaining from local submission"
16575 When a message is submitted locally (that is, not over a TCP/IP connection) by
16576 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
16577 do not want this to happen, you must set &%local_sender_retain%&, and you must
16578 also set &%local_from_check%& to be false (Exim will complain if you do not).
16579 See also the ACL modifier &`control = suppress_local_fixups`&. Section
16580 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
16585 .option localhost_number main string&!! unset
16586 .cindex "host" "locally unique number for"
16587 .cindex "message ids" "with multiple hosts"
16588 .vindex "&$localhost_number$&"
16589 Exim's message ids are normally unique only within the local host. If
16590 uniqueness among a set of hosts is required, each host must set a different
16591 value for the &%localhost_number%& option. The string is expanded immediately
16592 after reading the configuration file (so that a number can be computed from the
16593 host name, for example) and the result of the expansion must be a number in the
16594 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
16595 systems). This is available in subsequent string expansions via the variable
16596 &$localhost_number$&. When &%localhost_number is set%&, the final two
16597 characters of the message id, instead of just being a fractional part of the
16598 time, are computed from the time and the local host number as described in
16599 section &<<SECTmessiden>>&.
16603 .option log_file_path main "string list&!!" "set at compile time"
16604 .cindex "log" "file path for"
16605 This option sets the path which is used to determine the names of Exim's log
16606 files, or indicates that logging is to be to syslog, or both. It is expanded
16607 when Exim is entered, so it can, for example, contain a reference to the host
16608 name. If no specific path is set for the log files at compile or runtime,
16609 or if the option is unset at runtime (i.e. &`log_file_path = `&)
16610 they are written in a sub-directory called &_log_& in Exim's spool directory.
16611 A path must start with a slash.
16612 To send to syslog, use the word &"syslog"&.
16613 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
16614 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
16615 used. If this string is fixed at your installation (contains no expansion
16616 variables) it is recommended that you do not set this option in the
16617 configuration file, but instead supply the path using LOG_FILE_PATH in
16618 &_Local/Makefile_& so that it is available to Exim for logging errors detected
16619 early on &-- in particular, failure to read the configuration file.
16622 .option log_selector main string unset
16623 .cindex "log" "selectors"
16624 This option can be used to reduce or increase the number of things that Exim
16625 writes to its log files. Its argument is made up of names preceded by plus or
16626 minus characters. For example:
16628 log_selector = +arguments -retry_defer
16630 A list of possible names and what they control is given in the chapter on
16631 logging, in section &<<SECTlogselector>>&.
16634 .option log_timezone main boolean false
16635 .cindex "log" "timezone for entries"
16636 .vindex "&$tod_log$&"
16637 .vindex "&$tod_zone$&"
16638 By default, the timestamps on log lines are in local time without the
16639 timezone. This means that if your timezone changes twice a year, the timestamps
16640 in log lines are ambiguous for an hour when the clocks go back. One way of
16641 avoiding this problem is to set the timezone to UTC. An alternative is to set
16642 &%log_timezone%& true. This turns on the addition of the timezone offset to
16643 timestamps in log lines. Turning on this option can add quite a lot to the size
16644 of log files because each line is extended by 6 characters. Note that the
16645 &$tod_log$& variable contains the log timestamp without the zone, but there is
16646 another variable called &$tod_zone$& that contains just the timezone offset.
16649 .option lookup_open_max main integer 25
16650 .cindex "too many open files"
16651 .cindex "open files, too many"
16652 .cindex "file" "too many open"
16653 .cindex "lookup" "maximum open files"
16654 .cindex "limit" "open files for lookups"
16655 This option limits the number of simultaneously open files for single-key
16656 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
16657 Exim normally keeps these files open during routing, because often the same
16658 file is required several times. If the limit is reached, Exim closes the least
16659 recently used file. Note that if you are using the &'ndbm'& library, it
16660 actually opens two files for each logical DBM database, though it still counts
16661 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
16662 open files"& errors with NDBM, you need to reduce the value of
16663 &%lookup_open_max%&.
16666 .option max_username_length main integer 0
16667 .cindex "length of login name"
16668 .cindex "user name" "maximum length"
16669 .cindex "limit" "user name length"
16670 Some operating systems are broken in that they truncate long arguments to
16671 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
16672 this option is set greater than zero, any attempt to call &[getpwnam()]& with
16673 an argument that is longer behaves as if &[getpwnam()]& failed.
16676 .option message_body_newlines main bool false
16677 .cindex "message body" "newlines in variables"
16678 .cindex "newline" "in message body variables"
16679 .vindex "&$message_body$&"
16680 .vindex "&$message_body_end$&"
16681 By default, newlines in the message body are replaced by spaces when setting
16682 the &$message_body$& and &$message_body_end$& expansion variables. If this
16683 option is set true, this no longer happens.
16686 .option message_body_visible main integer 500
16687 .cindex "body of message" "visible size"
16688 .cindex "message body" "visible size"
16689 .vindex "&$message_body$&"
16690 .vindex "&$message_body_end$&"
16691 This option specifies how much of a message's body is to be included in the
16692 &$message_body$& and &$message_body_end$& expansion variables.
16695 .option message_id_header_domain main string&!! unset
16696 .cindex "&'Message-ID:'& header line"
16697 If this option is set, the string is expanded and used as the right hand side
16698 (domain) of the &'Message-ID:'& header that Exim creates if a
16699 locally-originated incoming message does not have one. &"Locally-originated"&
16700 means &"not received over TCP/IP."&
16701 Otherwise, the primary host name is used.
16702 Only letters, digits, dot and hyphen are accepted; any other characters are
16703 replaced by hyphens. If the expansion is forced to fail, or if the result is an
16704 empty string, the option is ignored.
16707 .option message_id_header_text main string&!! unset
16708 If this variable is set, the string is expanded and used to augment the text of
16709 the &'Message-id:'& header that Exim creates if a locally-originated incoming
16710 message does not have one. The text of this header is required by RFC 2822 to
16711 take the form of an address. By default, Exim uses its internal message id as
16712 the local part, and the primary host name as the domain. If this option is set,
16713 it is expanded, and provided the expansion is not forced to fail, and does not
16714 yield an empty string, the result is inserted into the header immediately
16715 before the @, separated from the internal message id by a dot. Any characters
16716 that are illegal in an address are automatically converted into hyphens. This
16717 means that variables such as &$tod_log$& can be used, because the spaces and
16718 colons will become hyphens.
16721 .option message_logs main boolean true
16722 .cindex "message logs" "disabling"
16723 .cindex "log" "message log; disabling"
16724 If this option is turned off, per-message log files are not created in the
16725 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
16726 Exim, by reducing the number of files involved in handling a message from a
16727 minimum of four (header spool file, body spool file, delivery journal, and
16728 per-message log) to three. The other major I/O activity is Exim's main log,
16729 which is not affected by this option.
16732 .option message_size_limit main string&!! 50M
16733 .cindex "message" "size limit"
16734 .cindex "limit" "message size"
16735 .cindex "size" "of message, limit"
16736 This option limits the maximum size of message that Exim will process. The
16737 value is expanded for each incoming connection so, for example, it can be made
16738 to depend on the IP address of the remote host for messages arriving via
16739 TCP/IP. After expansion, the value must be a sequence of decimal digits,
16740 optionally followed by K or M.
16742 .cindex "SIZE" "ESMTP extension, advertising"
16743 .cindex "ESMTP extensions" SIZE
16744 If nonzero the value will be advertised as a parameter to the ESMTP SIZE
16745 service extension keyword.
16747 &*Note*&: This limit cannot be made to depend on a message's sender or any
16748 other properties of an individual message, because it has to be advertised in
16749 the server's response to EHLO. String expansion failure causes a temporary
16750 error. A value of zero means no limit, but its use is not recommended. See also
16751 &%bounce_return_size_limit%&.
16753 Incoming SMTP messages are failed with a 552 error if the limit is
16754 exceeded; locally-generated messages either get a stderr message or a delivery
16755 failure message to the sender, depending on the &%-oe%& setting. Rejection of
16756 an oversized message is logged in both the main and the reject logs. See also
16757 the generic transport option &%message_size_limit%&, which limits the size of
16758 message that an individual transport can process.
16760 If you use a virus-scanner and set this option to to a value larger than the
16761 maximum size that your virus-scanner is configured to support, you may get
16762 failures triggered by large mails. The right size to configure for the
16763 virus-scanner depends upon what data is passed and the options in use but it's
16764 probably safest to just set it to a little larger than this value. E.g., with a
16765 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
16766 some problems may result.
16768 A value of 0 will disable size limit checking; Exim will still advertise the
16769 SIZE extension in an EHLO response, but without a limit, so as to permit
16770 SMTP clients to still indicate the message size along with the MAIL verb.
16773 .option move_frozen_messages main boolean false
16774 .cindex "frozen messages" "moving"
16775 This option, which is available only if Exim has been built with the setting
16777 SUPPORT_MOVE_FROZEN_MESSAGES=yes
16779 in &_Local/Makefile_&, causes frozen messages and their message logs to be
16780 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
16781 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
16782 standard utilities for handling such moved messages, and they do not show up in
16783 lists generated by &%-bp%& or by the Exim monitor.
16786 .option mua_wrapper main boolean false
16787 Setting this option true causes Exim to run in a very restrictive mode in which
16788 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
16789 contains a full description of this facility.
16793 .option mysql_servers main "string list" unset
16794 .cindex "MySQL" "server list"
16795 This option provides a list of MySQL servers and associated connection data, to
16796 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
16797 option is available only if Exim has been built with MySQL support.
16800 .option never_users main "string list&!!" unset
16801 This option is expanded just once, at the start of Exim's processing. Local
16802 message deliveries are normally run in processes that are setuid to the
16803 recipient, and remote deliveries are normally run under Exim's own uid and gid.
16804 It is usually desirable to prevent any deliveries from running as root, as a
16807 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
16808 list of users that must not be used for local deliveries. This list is fixed in
16809 the binary and cannot be overridden by the configuration file. By default, it
16810 contains just the single user name &"root"&. The &%never_users%& runtime option
16811 can be used to add more users to the fixed list.
16813 If a message is to be delivered as one of the users on the fixed list or the
16814 &%never_users%& list, an error occurs, and delivery is deferred. A common
16817 never_users = root:daemon:bin
16819 Including root is redundant if it is also on the fixed list, but it does no
16820 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
16824 .option notifier_socket main string "$spool_directory/exim_daemon_notify"
16825 This option gives the name for a unix-domain socket on which the daemon
16826 listens for work and information-requests.
16827 Only installations running multiple daemons sharing a spool directory
16828 should need to modify the default.
16830 The option is expanded before use.
16831 If the platform supports Linux-style abstract socket names, the result
16832 is used with a nul byte prefixed.
16834 .new "if nonempty,"
16835 it should be a full path name and use a directory accessible
16839 If this option is set as empty,
16840 or the command line &%-oY%& option is used, or
16842 the command line uses a &%-oX%& option and does not use &%-oP%&,
16843 then a notifier socket is not created.
16846 .option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation"
16847 .cindex "OpenSSL "compatibility options"
16848 This option allows an administrator to adjust the SSL options applied
16849 by OpenSSL to connections. It is given as a space-separated list of items,
16850 each one to be +added or -subtracted from the current value.
16852 This option is only available if Exim is built against OpenSSL. The values
16853 available for this option vary according to the age of your OpenSSL install.
16854 The &"all"& value controls a subset of flags which are available, typically
16855 the bug workaround options. The &'SSL_CTX_set_options'& man page will
16856 list the values known on your system and Exim should support all the
16857 &"bug workaround"& options and many of the &"modifying"& options. The Exim
16858 names lose the leading &"SSL_OP_"& and are lower-cased.
16860 Note that adjusting the options can have severe impact upon the security of
16861 SSL as used by Exim. It is possible to disable safety checks and shoot
16862 yourself in the foot in various unpleasant ways. This option should not be
16863 adjusted lightly. An unrecognised item will be detected at startup, by
16864 invoking Exim with the &%-bV%& flag.
16866 The option affects Exim operating both as a server and as a client.
16868 Historical note: prior to release 4.80, Exim defaulted this value to
16869 "+dont_insert_empty_fragments", which may still be needed for compatibility
16870 with some clients, but which lowers security by increasing exposure to
16871 some now infamous attacks.
16875 # Make both old MS and old Eudora happy:
16876 openssl_options = -all +microsoft_big_sslv3_buffer \
16877 +dont_insert_empty_fragments
16879 # Disable older protocol versions:
16880 openssl_options = +no_sslv2 +no_sslv3
16883 Possible options may include:
16887 &`allow_unsafe_legacy_renegotiation`&
16889 &`cipher_server_preference`&
16891 &`dont_insert_empty_fragments`&
16895 &`legacy_server_connect`&
16897 &`microsoft_big_sslv3_buffer`&
16899 &`microsoft_sess_id_bug`&
16901 &`msie_sslv2_rsa_padding`&
16903 &`netscape_challenge_bug`&
16905 &`netscape_reuse_cipher_change_bug`&
16909 &`no_session_resumption_on_renegotiation`&
16923 &`safari_ecdhe_ecdsa_bug`&
16927 &`single_ecdh_use`&
16929 &`ssleay_080_client_dh_bug`&
16931 &`sslref2_reuse_cert_type_bug`&
16933 &`tls_block_padding_bug`&
16937 &`tls_rollback_bug`&
16940 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
16941 all clients connecting using the MacOS SecureTransport TLS facility prior
16942 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
16943 to negotiate TLS then this option value might help, provided that your OpenSSL
16944 release is new enough to contain this work-around. This may be a situation
16945 where you have to upgrade OpenSSL to get buggy clients working.
16948 .option oracle_servers main "string list" unset
16949 .cindex "Oracle" "server list"
16950 This option provides a list of Oracle servers and associated connection data,
16951 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
16952 The option is available only if Exim has been built with Oracle support.
16955 .option percent_hack_domains main "domain list&!!" unset
16956 .cindex "&""percent hack""&"
16957 .cindex "source routing" "in email address"
16958 .cindex "address" "source-routed"
16959 The &"percent hack"& is the convention whereby a local part containing a
16960 percent sign is re-interpreted as a new email address, with the percent
16961 replaced by @. This is sometimes called &"source routing"&, though that term is
16962 also applied to RFC 2822 addresses that begin with an @ character. If this
16963 option is set, Exim implements the percent facility for those domains listed,
16964 but no others. This happens before an incoming SMTP address is tested against
16967 &*Warning*&: The &"percent hack"& has often been abused by people who are
16968 trying to get round relaying restrictions. For this reason, it is best avoided
16969 if at all possible. Unfortunately, a number of less security-conscious MTAs
16970 implement it unconditionally. If you are running Exim on a gateway host, and
16971 routing mail through to internal MTAs without processing the local parts, it is
16972 a good idea to reject recipient addresses with percent characters in their
16973 local parts. Exim's default configuration does this.
16976 .option perl_at_start main boolean false
16978 This option is available only when Exim is built with an embedded Perl
16979 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16982 .option perl_startup main string unset
16984 This option is available only when Exim is built with an embedded Perl
16985 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16987 .option perl_taintmode main boolean false
16989 This option enables the taint mode of the embedded Perl interpreter.
16992 .option pgsql_servers main "string list" unset
16993 .cindex "PostgreSQL lookup type" "server list"
16994 This option provides a list of PostgreSQL servers and associated connection
16995 data, to be used in conjunction with &(pgsql)& lookups (see section
16996 &<<SECID72>>&). The option is available only if Exim has been built with
16997 PostgreSQL support.
17000 .option pid_file_path main string&!! "set at compile time"
17001 .cindex "daemon" "pid file path"
17002 .cindex "pid file, path for"
17003 This option sets the name of the file to which the Exim daemon writes its
17004 process id. The string is expanded, so it can contain, for example, references
17007 pid_file_path = /var/log/$primary_hostname/exim.pid
17009 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
17011 The value set by the option can be overridden by the &%-oP%& command line
17012 option. A pid file is not written if a &"non-standard"& daemon is run by means
17013 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
17016 .option pipelining_advertise_hosts main "host list&!!" *
17017 .cindex "PIPELINING" "suppressing advertising"
17018 .cindex "ESMTP extensions" PIPELINING
17019 This option can be used to suppress the advertisement of the SMTP
17020 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
17021 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
17022 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
17023 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
17024 that clients will use it; &"out of order"& commands that are &"expected"& do
17025 not count as protocol errors (see &%smtp_max_synprot_errors%&).
17027 .option pipelining_connect_advertise_hosts main "host list&!!" *
17028 .cindex "pipelining" "early connection"
17029 .cindex "pipelining" PIPE_CONNECT
17030 .cindex "ESMTP extensions" PIPE_CONNECT
17031 If Exim is built with the SUPPORT_PIPE_CONNECT build option
17032 this option controls which hosts the facility is advertised to
17033 and from which pipeline early-connection (before MAIL) SMTP
17034 commands are acceptable.
17035 When used, the pipelining saves on roundtrip times.
17037 See also the &%hosts_pipe_connect%& smtp transport option.
17040 The SMTP service extension keyword advertised is &"PIPE_CONNECT"&.
17044 .option prdr_enable main boolean false
17045 .cindex "PRDR" "enabling on server"
17046 .cindex "ESMTP extensions" PRDR
17047 This option can be used to enable the Per-Recipient Data Response extension
17048 to SMTP, defined by Eric Hall.
17049 If the option is set, PRDR is advertised by Exim when operating as a server.
17050 If the client requests PRDR, and more than one recipient, for a message
17051 an additional ACL is called for each recipient after the message content
17052 is received. See section &<<SECTPRDRACL>>&.
17054 .option preserve_message_logs main boolean false
17055 .cindex "message logs" "preserving"
17056 If this option is set, message log files are not deleted when messages are
17057 completed. Instead, they are moved to a sub-directory of the spool directory
17058 called &_msglog.OLD_&, where they remain available for statistical or debugging
17059 purposes. This is a dangerous option to set on systems with any appreciable
17060 volume of mail. Use with care!
17063 .option primary_hostname main string "see below"
17064 .cindex "name" "of local host"
17065 .cindex "host" "name of local"
17066 .cindex "local host" "name of"
17067 .vindex "&$primary_hostname$&"
17068 This specifies the name of the current host. It is used in the default EHLO or
17069 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
17070 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
17071 The value is also used by default in some SMTP response messages from an Exim
17072 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
17074 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
17075 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
17076 contains only one component, Exim passes it to &[gethostbyname()]& (or
17077 &[getipnodebyname()]& when available) in order to obtain the fully qualified
17078 version. The variable &$primary_hostname$& contains the host name, whether set
17079 explicitly by this option, or defaulted.
17082 .option print_topbitchars main boolean false
17083 .cindex "printing characters"
17084 .cindex "8-bit characters"
17085 By default, Exim considers only those characters whose codes lie in the range
17086 32&--126 to be printing characters. In a number of circumstances (for example,
17087 when writing log entries) non-printing characters are converted into escape
17088 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
17089 is set, code values of 128 and above are also considered to be printing
17092 This option also affects the header syntax checks performed by the
17093 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
17094 the user's full name when constructing From: and Sender: addresses (as
17095 described in section &<<SECTconstr>>&). Setting this option can cause
17096 Exim to generate eight bit message headers that do not conform to the
17100 .option process_log_path main string unset
17101 .cindex "process log path"
17102 .cindex "log" "process log"
17103 .cindex "&'exiwhat'&"
17104 This option sets the name of the file to which an Exim process writes its
17105 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
17106 utility script. If this option is unset, the file called &_exim-process.info_&
17107 in Exim's spool directory is used. The ability to specify the name explicitly
17108 can be useful in environments where two different Exims are running, using
17109 different spool directories.
17112 .option prod_requires_admin main boolean true
17113 .cindex "restricting access to features"
17117 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
17118 admin user unless &%prod_requires_admin%& is set false. See also
17119 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
17123 .option proxy_protocol_timeout main time 3s
17124 .cindex proxy "proxy protocol"
17125 This option sets the timeout for proxy protocol negotiation.
17126 For details see section &<<SECTproxyInbound>>&.
17130 .option qualify_domain main string "see below"
17131 .cindex "domain" "for qualifying addresses"
17132 .cindex "address" "qualification"
17133 This option specifies the domain name that is added to any envelope sender
17134 addresses that do not have a domain qualification. It also applies to
17135 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
17136 are accepted by default only for locally-generated messages. Qualification is
17137 also applied to addresses in header lines such as &'From:'& and &'To:'& for
17138 locally-generated messages, unless the &%-bnq%& command line option is used.
17140 Messages from external sources must always contain fully qualified addresses,
17141 unless the sending host matches &%sender_unqualified_hosts%& or
17142 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
17143 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
17144 necessary. Internally, Exim always works with fully qualified envelope
17145 addresses. If &%qualify_domain%& is not set, it defaults to the
17146 &%primary_hostname%& value.
17149 .option qualify_recipient main string "see below"
17150 This option allows you to specify a different domain for qualifying recipient
17151 addresses to the one that is used for senders. See &%qualify_domain%& above.
17155 .option queue_domains main "domain list&!!" unset
17156 .cindex "domain" "specifying non-immediate delivery"
17157 .cindex "queueing incoming messages"
17158 .cindex "message" "queueing certain domains"
17159 This option lists domains for which immediate delivery is not required.
17160 A delivery process is started whenever a message is received, but only those
17161 domains that do not match are processed. All other deliveries wait until the
17162 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
17166 .option queue_fast_ramp main boolean false
17167 .cindex "queue runner" "two phase"
17168 .cindex "queue" "double scanning"
17169 If set to true, two-phase queue runs, initiated using &%-qq%& on the
17170 command line, may start parallel delivery processes during their first
17171 phase. This will be done when a threshold number of messages have been
17172 routed for a single host.
17176 .option queue_list_requires_admin main boolean true
17177 .cindex "restricting access to features"
17179 The &%-bp%& command-line option, which lists the messages that are on the
17180 queue, requires the caller to be an admin user unless
17181 &%queue_list_requires_admin%& is set false.
17182 See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
17185 .option queue_only main boolean false
17186 .cindex "queueing incoming messages"
17187 .cindex "message" "queueing unconditionally"
17188 If &%queue_only%& is set, a delivery process is not automatically started
17189 whenever a message is received. Instead, the message waits in the queue for the
17190 next queue run. Even if &%queue_only%& is false, incoming messages may not get
17191 delivered immediately when certain conditions (such as heavy load) occur.
17193 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
17194 and &%-odi%& command line options override &%queue_only%& unless
17195 &%queue_only_override%& is set false. See also &%queue_only_file%&,
17196 &%queue_only_load%&, and &%smtp_accept_queue%&.
17199 .option queue_only_file main string unset
17200 .cindex "queueing incoming messages"
17201 .cindex "message" "queueing by file existence"
17202 This option can be set to a colon-separated list of absolute path names, each
17203 one optionally preceded by &"smtp"&. When Exim is receiving a message,
17204 it tests for the existence of each listed path using a call to &[stat()]&. For
17205 each path that exists, the corresponding queueing option is set.
17206 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
17207 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
17209 queue_only_file = smtp/some/file
17211 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
17212 &_/some/file_& exists.
17215 .option queue_only_load main fixed-point unset
17216 .cindex "load average"
17217 .cindex "queueing incoming messages"
17218 .cindex "message" "queueing by load"
17219 If the system load average is higher than this value, incoming messages from
17220 all sources are queued, and no automatic deliveries are started. If this
17221 happens during local or remote SMTP input, all subsequent messages received on
17222 the same SMTP connection are queued by default, whatever happens to the load in
17223 the meantime, but this can be changed by setting &%queue_only_load_latch%&
17226 Deliveries will subsequently be performed by queue runner processes. This
17227 option has no effect on ancient operating systems on which Exim cannot
17228 determine the load average. See also &%deliver_queue_load_max%& and
17229 &%smtp_load_reserve%&.
17232 .option queue_only_load_latch main boolean true
17233 .cindex "load average" "re-evaluating per message"
17234 When this option is true (the default), once one message has been queued
17235 because the load average is higher than the value set by &%queue_only_load%&,
17236 all subsequent messages received on the same SMTP connection are also queued.
17237 This is a deliberate choice; even though the load average may fall below the
17238 threshold, it doesn't seem right to deliver later messages on the same
17239 connection when not delivering earlier ones. However, there are special
17240 circumstances such as very long-lived connections from scanning appliances
17241 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
17242 should be set false. This causes the value of the load average to be
17243 re-evaluated for each message.
17246 .option queue_only_override main boolean true
17247 .cindex "queueing incoming messages"
17248 When this option is true, the &%-od%&&'x'& command line options override the
17249 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
17250 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
17251 to override; they are accepted, but ignored.
17254 .option queue_run_in_order main boolean false
17255 .cindex "queue runner" "processing messages in order"
17256 If this option is set, queue runs happen in order of message arrival instead of
17257 in an arbitrary order. For this to happen, a complete list of the entire queue
17258 must be set up before the deliveries start. When the queue is all held in a
17259 single directory (the default), a single list is created for both the ordered
17260 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
17261 single list is not created when &%queue_run_in_order%& is false. In this case,
17262 the sub-directories are processed one at a time (in a random order), and this
17263 avoids setting up one huge list for the whole queue. Thus, setting
17264 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
17265 when the queue is large, because of the extra work in setting up the single,
17266 large list. In most situations, &%queue_run_in_order%& should not be set.
17270 .option queue_run_max main integer&!! 5
17271 .cindex "queue runner" "maximum number of"
17272 This controls the maximum number of queue runner processes that an Exim daemon
17273 can run simultaneously. This does not mean that it starts them all at once,
17274 but rather that if the maximum number are still running when the time comes to
17275 start another one, it refrains from starting another one. This can happen with
17276 very large queues and/or very sluggish deliveries. This option does not,
17277 however, interlock with other processes, so additional queue runners can be
17278 started by other means, or by killing and restarting the daemon.
17280 Setting this option to zero does not suppress queue runs; rather, it disables
17281 the limit, allowing any number of simultaneous queue runner processes to be
17282 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
17283 the daemon's command line.
17285 .cindex queues named
17286 .cindex "named queues" "resource limit"
17287 To set limits for different named queues use
17288 an expansion depending on the &$queue_name$& variable.
17290 .option queue_smtp_domains main "domain list&!!" unset
17291 .cindex "queueing incoming messages"
17292 .cindex "message" "queueing remote deliveries"
17293 .cindex "first pass routing"
17294 When this option is set, a delivery process is started whenever a message is
17295 received, routing is performed, and local deliveries take place.
17296 However, if any SMTP deliveries are required for domains that match
17297 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
17298 message waits in the queue for the next queue run. Since routing of the message
17299 has taken place, Exim knows to which remote hosts it must be delivered, and so
17300 when the queue run happens, multiple messages for the same host are delivered
17301 over a single SMTP connection. The &%-odqs%& command line option causes all
17302 SMTP deliveries to be queued in this way, and is equivalent to setting
17303 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
17307 .option receive_timeout main time 0s
17308 .cindex "timeout" "for non-SMTP input"
17309 This option sets the timeout for accepting a non-SMTP message, that is, the
17310 maximum time that Exim waits when reading a message on the standard input. If
17311 the value is zero, it will wait forever. This setting is overridden by the
17312 &%-or%& command line option. The timeout for incoming SMTP messages is
17313 controlled by &%smtp_receive_timeout%&.
17315 .option received_header_text main string&!! "see below"
17316 .cindex "customizing" "&'Received:'& header"
17317 .cindex "&'Received:'& header line" "customizing"
17318 This string defines the contents of the &'Received:'& message header that is
17319 added to each message, except for the timestamp, which is automatically added
17320 on at the end (preceded by a semicolon). The string is expanded each time it is
17321 used. If the expansion yields an empty string, no &'Received:'& header line is
17322 added to the message. Otherwise, the string should start with the text
17323 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
17325 The default setting is:
17328 received_header_text = Received: \
17329 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
17330 {${if def:sender_ident \
17331 {from ${quote_local_part:$sender_ident} }}\
17332 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
17333 by $primary_hostname \
17334 ${if def:received_protocol {with $received_protocol }}\
17335 ${if def:tls_in_ver { ($tls_in_ver)}}\
17336 ${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\
17337 (Exim $version_number)\n\t\
17338 ${if def:sender_address \
17339 {(envelope-from <$sender_address>)\n\t}}\
17340 id $message_exim_id\
17341 ${if def:received_for {\n\tfor $received_for}}
17344 The references to the TLS version and cipher are
17345 omitted when Exim is built without TLS
17346 support. The use of conditional expansions ensures that this works for both
17347 locally generated messages and messages received from remote hosts, giving
17348 header lines such as the following:
17350 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
17351 by marley.carol.example with esmtp (Exim 4.00)
17352 (envelope-from <bob@carol.example>)
17353 id 16IOWa-00019l-00
17354 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
17355 Received: by scrooge.carol.example with local (Exim 4.00)
17356 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
17358 Until the body of the message has been received, the timestamp is the time when
17359 the message started to be received. Once the body has arrived, and all policy
17360 checks have taken place, the timestamp is updated to the time at which the
17361 message was accepted.
17364 .option received_headers_max main integer 30
17365 .cindex "loop" "prevention"
17366 .cindex "mail loop prevention"
17367 .cindex "&'Received:'& header line" "counting"
17368 When a message is to be delivered, the number of &'Received:'& headers is
17369 counted, and if it is greater than this parameter, a mail loop is assumed to
17370 have occurred, the delivery is abandoned, and an error message is generated.
17371 This applies to both local and remote deliveries.
17374 .option recipient_unqualified_hosts main "host list&!!" unset
17375 .cindex "unqualified addresses"
17376 .cindex "host" "unqualified addresses from"
17377 This option lists those hosts from which Exim is prepared to accept unqualified
17378 recipient addresses in message envelopes. The addresses are made fully
17379 qualified by the addition of the &%qualify_recipient%& value. This option also
17380 affects message header lines. Exim does not reject unqualified recipient
17381 addresses in headers, but it qualifies them only if the message came from a
17382 host that matches &%recipient_unqualified_hosts%&,
17383 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
17384 option was not set.
17387 .option recipients_max main integer 0
17388 .cindex "limit" "number of recipients"
17389 .cindex "recipient" "maximum number"
17390 If this option is set greater than zero, it specifies the maximum number of
17391 original recipients for any message. Additional recipients that are generated
17392 by aliasing or forwarding do not count. SMTP messages get a 452 response for
17393 all recipients over the limit; earlier recipients are delivered as normal.
17394 Non-SMTP messages with too many recipients are failed, and no deliveries are
17397 .cindex "RCPT" "maximum number of incoming"
17398 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
17399 RCPT commands in a single message.
17402 .option recipients_max_reject main boolean false
17403 If this option is set true, Exim rejects SMTP messages containing too many
17404 recipients by giving 552 errors to the surplus RCPT commands, and a 554
17405 error to the eventual DATA command. Otherwise (the default) it gives a 452
17406 error to the surplus RCPT commands and accepts the message on behalf of the
17407 initial set of recipients. The remote server should then re-send the message
17408 for the remaining recipients at a later time.
17411 .option remote_max_parallel main integer 2
17412 .cindex "delivery" "parallelism for remote"
17413 This option controls parallel delivery of one message to a number of remote
17414 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
17415 does all the remote deliveries for a message one by one. Otherwise, if a single
17416 message has to be delivered to more than one remote host, or if several copies
17417 have to be sent to the same remote host, up to &%remote_max_parallel%&
17418 deliveries are done simultaneously. If more than &%remote_max_parallel%&
17419 deliveries are required, the maximum number of processes are started, and as
17420 each one finishes, another is begun. The order of starting processes is the
17421 same as if sequential delivery were being done, and can be controlled by the
17422 &%remote_sort_domains%& option. If parallel delivery takes place while running
17423 with debugging turned on, the debugging output from each delivery process is
17424 tagged with its process id.
17426 This option controls only the maximum number of parallel deliveries for one
17427 message in one Exim delivery process. Because Exim has no central queue
17428 manager, there is no way of controlling the total number of simultaneous
17429 deliveries if the configuration allows a delivery attempt as soon as a message
17432 See also the &%max_parallel%& generic transport option,
17433 and the &%serialize_hosts%& smtp transport option.
17435 .cindex "number of deliveries"
17436 .cindex "delivery" "maximum number of"
17437 If you want to control the total number of deliveries on the system, you
17438 need to set the &%queue_only%& option. This ensures that all incoming messages
17439 are added to the queue without starting a delivery process. Then set up an Exim
17440 daemon to start queue runner processes at appropriate intervals (probably
17441 fairly often, for example, every minute), and limit the total number of queue
17442 runners by setting the &%queue_run_max%& parameter. Because each queue runner
17443 delivers only one message at a time, the maximum number of deliveries that can
17444 then take place at once is &%queue_run_max%& multiplied by
17445 &%remote_max_parallel%&.
17447 If it is purely remote deliveries you want to control, use
17448 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
17449 doing the SMTP routing before queueing, so that several messages for the same
17450 host will eventually get delivered down the same connection.
17453 .option remote_sort_domains main "domain list&!!" unset
17454 .cindex "sorting remote deliveries"
17455 .cindex "delivery" "sorting remote"
17456 When there are a number of remote deliveries for a message, they are sorted by
17457 domain into the order given by this list. For example,
17459 remote_sort_domains = *.cam.ac.uk:*.uk
17461 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
17462 then to those in the &%uk%& domain, then to any others.
17465 .option retry_data_expire main time 7d
17466 .cindex "hints database" "data expiry"
17467 This option sets a &"use before"& time on retry information in Exim's hints
17468 database. Any older retry data is ignored. This means that, for example, once a
17469 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
17473 .option retry_interval_max main time 24h
17474 .cindex "retry" "limit on interval"
17475 .cindex "limit" "on retry interval"
17476 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
17477 intervals between delivery attempts for messages that cannot be delivered
17478 straight away. This option sets an overall limit to the length of time between
17479 retries. It cannot be set greater than 24 hours; any attempt to do so forces
17483 .option return_path_remove main boolean true
17484 .cindex "&'Return-path:'& header line" "removing"
17485 RFC 2821, section 4.4, states that an SMTP server must insert a
17486 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
17487 The &'Return-path:'& header preserves the sender address as received in the
17488 MAIL command. This description implies that this header should not be present
17489 in an incoming message. If &%return_path_remove%& is true, any existing
17490 &'Return-path:'& headers are removed from messages at the time they are
17491 received. Exim's transports have options for adding &'Return-path:'& headers at
17492 the time of delivery. They are normally used only for final local deliveries.
17495 .option return_size_limit main integer 100K
17496 This option is an obsolete synonym for &%bounce_return_size_limit%&.
17499 .option rfc1413_hosts main "host list&!!" @[]
17501 .cindex "host" "for RFC 1413 calls"
17502 RFC 1413 identification calls are made to any client host which matches
17503 an item in the list.
17504 The default value specifies just this host, being any local interface
17507 .option rfc1413_query_timeout main time 0s
17508 .cindex "RFC 1413" "query timeout"
17509 .cindex "timeout" "for RFC 1413 call"
17510 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
17511 no RFC 1413 calls are ever made.
17514 .option sender_unqualified_hosts main "host list&!!" unset
17515 .cindex "unqualified addresses"
17516 .cindex "host" "unqualified addresses from"
17517 This option lists those hosts from which Exim is prepared to accept unqualified
17518 sender addresses. The addresses are made fully qualified by the addition of
17519 &%qualify_domain%&. This option also affects message header lines. Exim does
17520 not reject unqualified addresses in headers that contain sender addresses, but
17521 it qualifies them only if the message came from a host that matches
17522 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
17523 using TCP/IP), and the &%-bnq%& option was not set.
17526 .option slow_lookup_log main integer 0
17527 .cindex "logging" "slow lookups"
17528 .cindex "dns" "logging slow lookups"
17529 This option controls logging of slow lookups.
17530 If the value is nonzero it is taken as a number of milliseconds
17531 and lookups taking longer than this are logged.
17532 Currently this applies only to DNS lookups.
17536 .option smtp_accept_keepalive main boolean true
17537 .cindex "keepalive" "on incoming connection"
17538 This option controls the setting of the SO_KEEPALIVE option on incoming
17539 TCP/IP socket connections. When set, it causes the kernel to probe idle
17540 connections periodically, by sending packets with &"old"& sequence numbers. The
17541 other end of the connection should send an acknowledgment if the connection is
17542 still okay or a reset if the connection has been aborted. The reason for doing
17543 this is that it has the beneficial effect of freeing up certain types of
17544 connection that can get stuck when the remote host is disconnected without
17545 tidying up the TCP/IP call properly. The keepalive mechanism takes several
17546 hours to detect unreachable hosts.
17550 .option smtp_accept_max main integer 20
17551 .cindex "limit" "incoming SMTP connections"
17552 .cindex "SMTP" "incoming connection count"
17554 This option specifies the maximum number of simultaneous incoming SMTP calls
17555 that Exim will accept. It applies only to the listening daemon; there is no
17556 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
17557 value is set to zero, no limit is applied. However, it is required to be
17558 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
17559 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
17561 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
17562 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
17563 that limit has not been reached for the client host, &%smtp_accept_reserve%&
17564 and &%smtp_load_reserve%& are then checked before accepting the connection.
17567 .option smtp_accept_max_nonmail main integer 10
17568 .cindex "limit" "non-mail SMTP commands"
17569 .cindex "SMTP" "limiting non-mail commands"
17570 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
17571 the connection if there are too many. This option defines &"too many"&. The
17572 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
17573 client looping sending EHLO, for example. The check is applied only if the
17574 client host matches &%smtp_accept_max_nonmail_hosts%&.
17576 When a new message is expected, one occurrence of RSET is not counted. This
17577 allows a client to send one RSET between messages (this is not necessary,
17578 but some clients do it). Exim also allows one uncounted occurrence of HELO
17579 or EHLO, and one occurrence of STARTTLS between messages. After
17580 starting up a TLS session, another EHLO is expected, and so it too is not
17581 counted. The first occurrence of AUTH in a connection, or immediately
17582 following STARTTLS is not counted. Otherwise, all commands other than
17583 MAIL, RCPT, DATA, and QUIT are counted.
17586 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
17587 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
17588 check by setting this option. The default value makes it apply to all hosts. By
17589 changing the value, you can exclude any badly-behaved hosts that you have to
17593 . Allow this long option name to split; give it unsplit as a fifth argument
17594 . for the automatic .oindex that is generated by .option.
17595 . We insert " &~&~" which is both pretty nasty visually and results in
17596 . non-searchable text. HowItWorks.txt mentions an option for inserting
17597 . zero-width-space, which would be nicer visually and results in (at least)
17598 . html that Firefox will split on when it's forced to reflow (rather than
17599 . inserting a horizontal scrollbar). However, the text is still not
17600 . searchable. NM changed this occurrence for bug 1197 to no longer allow
17601 . the option name to split.
17603 .option "smtp_accept_max_per_connection" main integer&!! 1000 &&&
17604 smtp_accept_max_per_connection
17605 .cindex "SMTP" "limiting incoming message count"
17606 .cindex "limit" "messages per SMTP connection"
17607 The value of this option limits the number of MAIL commands that Exim is
17608 prepared to accept over a single SMTP connection, whether or not each command
17609 results in the transfer of a message. After the limit is reached, a 421
17610 response is given to subsequent MAIL commands. This limit is a safety
17611 precaution against a client that goes mad (incidents of this type have been
17614 The option is expanded after the HELO or EHLO is received
17615 and may depend on values available at that time.
17616 An empty or zero value after expansion removes the limit.
17620 .option smtp_accept_max_per_host main string&!! unset
17621 .cindex "limit" "SMTP connections from one host"
17622 .cindex "host" "limiting SMTP connections from"
17623 This option restricts the number of simultaneous IP connections from a single
17624 host (strictly, from a single IP address) to the Exim daemon. The option is
17625 expanded, to enable different limits to be applied to different hosts by
17626 reference to &$sender_host_address$&. Once the limit is reached, additional
17627 connection attempts from the same host are rejected with error code 421. This
17628 is entirely independent of &%smtp_accept_reserve%&. The option's default value
17629 of zero imposes no limit. If this option is set greater than zero, it is
17630 required that &%smtp_accept_max%& be non-zero.
17632 &*Warning*&: When setting this option you should not use any expansion
17633 constructions that take an appreciable amount of time. The expansion and test
17634 happen in the main daemon loop, in order to reject additional connections
17635 without forking additional processes (otherwise a denial-of-service attack
17636 could cause a vast number or processes to be created). While the daemon is
17637 doing this processing, it cannot accept any other incoming connections.
17641 .option smtp_accept_queue main integer 0
17642 .cindex "SMTP" "incoming connection count"
17643 .cindex "queueing incoming messages"
17644 .cindex "message" "queueing by SMTP connection count"
17645 If the number of simultaneous incoming SMTP connections being handled via the
17646 listening daemon exceeds this value, messages received by SMTP are just placed
17647 in the queue; no delivery processes are started automatically. The count is
17648 fixed at the start of an SMTP connection. It cannot be updated in the
17649 subprocess that receives messages, and so the queueing or not queueing applies
17650 to all messages received in the same connection.
17652 A value of zero implies no limit, and clearly any non-zero value is useful only
17653 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
17654 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
17655 various &%-od%&&'x'& command line options.
17658 . See the comment on smtp_accept_max_per_connection
17660 .option "smtp_accept_queue_per_connection" main integer 10 &&&
17661 smtp_accept_queue_per_connection
17662 .cindex "queueing incoming messages"
17663 .cindex "message" "queueing by message count"
17664 This option limits the number of delivery processes that Exim starts
17665 automatically when receiving messages via SMTP, whether via the daemon or by
17666 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
17667 and the number of messages received in a single SMTP session exceeds this
17668 number, subsequent messages are placed in the queue, but no delivery processes
17669 are started. This helps to limit the number of Exim processes when a server
17670 restarts after downtime and there is a lot of mail waiting for it on other
17671 systems. On large systems, the default should probably be increased, and on
17672 dial-in client systems it should probably be set to zero (that is, disabled).
17675 .option smtp_accept_reserve main integer 0
17676 .cindex "SMTP" "incoming call count"
17677 .cindex "host" "reserved"
17678 When &%smtp_accept_max%& is set greater than zero, this option specifies a
17679 number of SMTP connections that are reserved for connections from the hosts
17680 that are specified in &%smtp_reserve_hosts%&. The value set in
17681 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
17682 restricted to this number of connections; the option specifies a minimum number
17683 of connection slots for them, not a maximum. It is a guarantee that this group
17684 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
17685 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
17688 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
17689 set to 5, once there are 45 active connections (from any hosts), new
17690 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
17691 provided the other criteria for acceptance are met.
17694 .option smtp_active_hostname main string&!! unset
17695 .cindex "host" "name in SMTP responses"
17696 .cindex "SMTP" "host name in responses"
17697 .vindex "&$primary_hostname$&"
17698 This option is provided for multi-homed servers that want to masquerade as
17699 several different hosts. At the start of an incoming SMTP connection, its value
17700 is expanded and used instead of the value of &$primary_hostname$& in SMTP
17701 responses. For example, it is used as domain name in the response to an
17702 incoming HELO or EHLO command.
17704 .vindex "&$smtp_active_hostname$&"
17705 The active hostname is placed in the &$smtp_active_hostname$& variable, which
17706 is saved with any messages that are received. It is therefore available for use
17707 in routers and transports when the message is later delivered.
17709 If this option is unset, or if its expansion is forced to fail, or if the
17710 expansion results in an empty string, the value of &$primary_hostname$& is
17711 used. Other expansion failures cause a message to be written to the main and
17712 panic logs, and the SMTP command receives a temporary error. Typically, the
17713 value of &%smtp_active_hostname%& depends on the incoming interface address.
17716 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
17717 {cox.mydomain}{box.mydomain}}
17720 Although &$smtp_active_hostname$& is primarily concerned with incoming
17721 messages, it is also used as the default for HELO commands in callout
17722 verification if there is no remote transport from which to obtain a
17723 &%helo_data%& value.
17725 .option smtp_banner main string&!! "see below"
17726 .cindex "SMTP" "welcome banner"
17727 .cindex "banner for SMTP"
17728 .cindex "welcome banner for SMTP"
17729 .cindex "customizing" "SMTP banner"
17730 This string, which is expanded every time it is used, is output as the initial
17731 positive response to an SMTP connection. The default setting is:
17733 smtp_banner = $smtp_active_hostname ESMTP Exim \
17734 $version_number $tod_full
17736 Failure to expand the string causes a panic error. If you want to create a
17737 multiline response to the initial SMTP connection, use &"\n"& in the string at
17738 appropriate points, but not at the end. Note that the 220 code is not included
17739 in this string. Exim adds it automatically (several times in the case of a
17740 multiline response).
17743 .option smtp_check_spool_space main boolean true
17744 .cindex "checking disk space"
17745 .cindex "disk space, checking"
17746 .cindex "spool directory" "checking space"
17747 When this option is set, if an incoming SMTP session encounters the SIZE
17748 option on a MAIL command, it checks that there is enough space in the
17749 spool directory's partition to accept a message of that size, while still
17750 leaving free the amount specified by &%check_spool_space%& (even if that value
17751 is zero). If there isn't enough space, a temporary error code is returned.
17754 .option smtp_connect_backlog main integer 20
17755 .cindex "connection backlog"
17756 .cindex "SMTP" "connection backlog"
17757 .cindex "backlog of connections"
17758 This option specifies a maximum number of waiting SMTP connections. Exim passes
17759 this value to the TCP/IP system when it sets up its listener. Once this number
17760 of connections are waiting for the daemon's attention, subsequent connection
17761 attempts are refused at the TCP/IP level. At least, that is what the manuals
17762 say; in some circumstances such connection attempts have been observed to time
17763 out instead. For large systems it is probably a good idea to increase the
17764 value (to 50, say). It also gives some protection against denial-of-service
17765 attacks by SYN flooding.
17768 .option smtp_enforce_sync main boolean true
17769 .cindex "SMTP" "synchronization checking"
17770 .cindex "synchronization checking in SMTP"
17771 The SMTP protocol specification requires the client to wait for a response from
17772 the server at certain points in the dialogue. Without PIPELINING these
17773 synchronization points are after every command; with PIPELINING they are
17774 fewer, but they still exist.
17776 Some spamming sites send out a complete set of SMTP commands without waiting
17777 for any response. Exim protects against this by rejecting a message if the
17778 client has sent further input when it should not have. The error response &"554
17779 SMTP synchronization error"& is sent, and the connection is dropped. Testing
17780 for this error cannot be perfect because of transmission delays (unexpected
17781 input may be on its way but not yet received when Exim checks). However, it
17782 does detect many instances.
17784 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
17785 If you want to disable the check selectively (for example, only for certain
17786 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
17787 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
17791 .option smtp_etrn_command main string&!! unset
17792 .cindex "ETRN" "command to be run"
17793 .cindex "ESMTP extensions" ETRN
17794 .vindex "&$domain$&"
17795 If this option is set, the given command is run whenever an SMTP ETRN
17796 command is received from a host that is permitted to issue such commands (see
17797 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
17798 are independently expanded. The expansion variable &$domain$& is set to the
17799 argument of the ETRN command, and no syntax checking is done on it. For
17802 smtp_etrn_command = /etc/etrn_command $domain \
17803 $sender_host_address
17805 If the option is not set, the argument for the ETRN command must
17806 be a &'#'& followed by an address string.
17807 In this case an &'exim -R <string>'& command is used;
17808 if the ETRN ACL has set up a named-queue then &'-MCG <queue>'& is appended.
17810 A new process is created to run the command, but Exim does not wait for it to
17811 complete. Consequently, its status cannot be checked. If the command cannot be
17812 run, a line is written to the panic log, but the ETRN caller still receives
17813 a 250 success response. Exim is normally running under its own uid when
17814 receiving SMTP, so it is not possible for it to change the uid before running
17818 .option smtp_etrn_serialize main boolean true
17819 .cindex "ETRN" "serializing"
17820 When this option is set, it prevents the simultaneous execution of more than
17821 one identical command as a result of ETRN in an SMTP connection. See
17822 section &<<SECTETRN>>& for details.
17825 .option smtp_load_reserve main fixed-point unset
17826 .cindex "load average"
17827 If the system load average ever gets higher than this, incoming SMTP calls are
17828 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
17829 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
17830 the load is over the limit. The option has no effect on ancient operating
17831 systems on which Exim cannot determine the load average. See also
17832 &%deliver_queue_load_max%& and &%queue_only_load%&.
17836 .option smtp_max_synprot_errors main integer 3
17837 .cindex "SMTP" "limiting syntax and protocol errors"
17838 .cindex "limit" "SMTP syntax and protocol errors"
17839 Exim rejects SMTP commands that contain syntax or protocol errors. In
17840 particular, a syntactically invalid email address, as in this command:
17842 RCPT TO:<abc xyz@a.b.c>
17844 causes immediate rejection of the command, before any other tests are done.
17845 (The ACL cannot be run if there is no valid address to set up for it.) An
17846 example of a protocol error is receiving RCPT before MAIL. If there are
17847 too many syntax or protocol errors in one SMTP session, the connection is
17848 dropped. The limit is set by this option.
17850 .cindex "PIPELINING" "expected errors"
17851 When the PIPELINING extension to SMTP is in use, some protocol errors are
17852 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
17853 Exim assumes that PIPELINING will be used if it advertises it (see
17854 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
17855 not count towards the limit.
17859 .option smtp_max_unknown_commands main integer 3
17860 .cindex "SMTP" "limiting unknown commands"
17861 .cindex "limit" "unknown SMTP commands"
17862 If there are too many unrecognized commands in an incoming SMTP session, an
17863 Exim server drops the connection. This is a defence against some kinds of abuse
17866 into making connections to SMTP ports; in these circumstances, a number of
17867 non-SMTP command lines are sent first.
17871 .option smtp_ratelimit_hosts main "host list&!!" unset
17872 .cindex "SMTP" "rate limiting"
17873 .cindex "limit" "rate of message arrival"
17874 .cindex "RCPT" "rate limiting"
17875 Some sites find it helpful to be able to limit the rate at which certain hosts
17876 can send them messages, and the rate at which an individual message can specify
17879 Exim has two rate-limiting facilities. This section describes the older
17880 facility, which can limit rates within a single connection. The newer
17881 &%ratelimit%& ACL condition can limit rates across all connections. See section
17882 &<<SECTratelimiting>>& for details of the newer facility.
17884 When a host matches &%smtp_ratelimit_hosts%&, the values of
17885 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
17886 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
17887 respectively. Each option, if set, must contain a set of four comma-separated
17891 A threshold, before which there is no rate limiting.
17893 An initial time delay. Unlike other times in Exim, numbers with decimal
17894 fractional parts are allowed here.
17896 A factor by which to increase the delay each time.
17898 A maximum value for the delay. This should normally be less than 5 minutes,
17899 because after that time, the client is liable to timeout the SMTP command.
17902 For example, these settings have been used successfully at the site which
17903 first suggested this feature, for controlling mail from their customers:
17905 smtp_ratelimit_mail = 2,0.5s,1.05,4m
17906 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
17908 The first setting specifies delays that are applied to MAIL commands after
17909 two have been received over a single connection. The initial delay is 0.5
17910 seconds, increasing by a factor of 1.05 each time. The second setting applies
17911 delays to RCPT commands when more than four occur in a single message.
17914 .option smtp_ratelimit_mail main string unset
17915 See &%smtp_ratelimit_hosts%& above.
17918 .option smtp_ratelimit_rcpt main string unset
17919 See &%smtp_ratelimit_hosts%& above.
17922 .option smtp_receive_timeout main time&!! 5m
17923 .cindex "timeout" "for SMTP input"
17924 .cindex "SMTP" "input timeout"
17925 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
17926 input, including batch SMTP. If a line of input (either an SMTP command or a
17927 data line) is not received within this time, the SMTP connection is dropped and
17928 the message is abandoned.
17929 A line is written to the log containing one of the following messages:
17931 SMTP command timeout on connection from...
17932 SMTP data timeout on connection from...
17934 The former means that Exim was expecting to read an SMTP command; the latter
17935 means that it was in the DATA phase, reading the contents of a message.
17937 If the first character of the option is a &"$"& the option is
17938 expanded before use and may depend on
17939 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
17943 The value set by this option can be overridden by the
17944 &%-os%& command-line option. A setting of zero time disables the timeout, but
17945 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
17946 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
17947 timeout is controlled by &%receive_timeout%& and &%-or%&.
17950 .option smtp_reserve_hosts main "host list&!!" unset
17951 This option defines hosts for which SMTP connections are reserved; see
17952 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
17955 .option smtp_return_error_details main boolean false
17956 .cindex "SMTP" "details policy failures"
17957 .cindex "policy control" "rejection, returning details"
17958 In the default state, Exim uses bland messages such as
17959 &"Administrative prohibition"& when it rejects SMTP commands for policy
17960 reasons. Many sysadmins like this because it gives away little information
17961 to spammers. However, some other sysadmins who are applying strict checking
17962 policies want to give out much fuller information about failures. Setting
17963 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
17964 example, instead of &"Administrative prohibition"&, it might give:
17966 550-Rejected after DATA: '>' missing at end of address:
17967 550 failing address in "From" header is: <user@dom.ain
17971 .option smtputf8_advertise_hosts main "host list&!!" *
17972 .cindex "SMTPUTF8" "ESMTP extension, advertising"
17973 .cindex "ESMTP extensions" SMTPUTF8
17974 When Exim is built with support for internationalised mail names,
17975 the availability thereof is advertised in
17976 response to EHLO only to those client hosts that match this option. See
17977 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
17980 .option spamd_address main string "127.0.0.1 783"
17981 This option is available when Exim is compiled with the content-scanning
17982 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
17983 See section &<<SECTscanspamass>>& for more details.
17987 .option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
17988 This option is available when Exim is compiled with SPF support.
17989 See section &<<SECSPF>>& for more details.
17991 .option spf_smtp_comment_template main string&!! "Please%_see%_http://www.open-spf.org/Why"
17992 This option is available when Exim is compiled with SPF support. It
17993 allows the customisation of the SMTP comment that the SPF library
17994 generates. You are strongly encouraged to link to your own explanative
17995 site. The template must not contain spaces. If you need spaces in the
17996 output, use the proper placeholder. If libspf2 can not parse the
17997 template, it uses a built-in default broken link. The following placeholders
17998 (along with Exim variables (but see below)) are allowed in the template:
18002 &*%{L}*&: Envelope sender's local part.
18004 &*%{S}*&: Envelope sender.
18006 &*%{O}*&: Envelope sender's domain.
18008 &*%{D}*&: Current(?) domain.
18010 &*%{I}*&: SMTP client Ip.
18012 &*%{C}*&: SMTP client pretty IP.
18014 &*%{T}*&: Epoch time (UTC).
18016 &*%{P}*&: SMTP client domain name.
18018 &*%{V}*&: IP version.
18020 &*%{H}*&: EHLO/HELO domain.
18022 &*%{R}*&: Receiving domain.
18024 The capitalized placeholders do proper URL encoding, if you use them
18025 lowercased, no encoding takes place. This list was compiled from the
18028 A note on using Exim variables: As
18029 currently the SPF library is initialized before the SMTP EHLO phase,
18030 the variables useful for expansion are quite limited.
18033 .option split_spool_directory main boolean false
18034 .cindex "multiple spool directories"
18035 .cindex "spool directory" "split"
18036 .cindex "directories, multiple"
18037 If this option is set, it causes Exim to split its input directory into 62
18038 subdirectories, each with a single alphanumeric character as its name. The
18039 sixth character of the message id is used to allocate messages to
18040 subdirectories; this is the least significant base-62 digit of the time of
18041 arrival of the message.
18043 Splitting up the spool in this way may provide better performance on systems
18044 where there are long mail queues, by reducing the number of files in any one
18045 directory. The msglog directory is also split up in a similar way to the input
18046 directory; however, if &%preserve_message_logs%& is set, all old msglog files
18047 are still placed in the single directory &_msglog.OLD_&.
18049 It is not necessary to take any special action for existing messages when
18050 changing &%split_spool_directory%&. Exim notices messages that are in the
18051 &"wrong"& place, and continues to process them. If the option is turned off
18052 after a period of being on, the subdirectories will eventually empty and be
18053 automatically deleted.
18055 When &%split_spool_directory%& is set, the behaviour of queue runner processes
18056 changes. Instead of creating a list of all messages in the queue, and then
18057 trying to deliver each one, in turn, it constructs a list of those in one
18058 sub-directory and tries to deliver them, before moving on to the next
18059 sub-directory. The sub-directories are processed in a random order. This
18060 spreads out the scanning of the input directories, and uses less memory. It is
18061 particularly beneficial when there are lots of messages in the queue. However,
18062 if &%queue_run_in_order%& is set, none of this new processing happens. The
18063 entire queue has to be scanned and sorted before any deliveries can start.
18066 .option spool_directory main string&!! "set at compile time"
18067 .cindex "spool directory" "path to"
18068 This defines the directory in which Exim keeps its spool, that is, the messages
18069 it is waiting to deliver. The default value is taken from the compile-time
18070 configuration setting, if there is one. If not, this option must be set. The
18071 string is expanded, so it can contain, for example, a reference to
18072 &$primary_hostname$&.
18074 If the spool directory name is fixed on your installation, it is recommended
18075 that you set it at build time rather than from this option, particularly if the
18076 log files are being written to the spool directory (see &%log_file_path%&).
18077 Otherwise log files cannot be used for errors that are detected early on, such
18078 as failures in the configuration file.
18080 By using this option to override the compiled-in path, it is possible to run
18081 tests of Exim without using the standard spool.
18083 .option spool_wireformat main boolean false
18084 .cindex "spool directory" "file formats"
18085 If this option is set, Exim may for some messages use an alternative format
18086 for data-files in the spool which matches the wire format.
18087 Doing this permits more efficient message reception and transmission.
18088 Currently it is only done for messages received using the ESMTP CHUNKING
18091 The following variables will not have useful values:
18093 $max_received_linelength
18098 Users of the local_scan() API (see &<<CHAPlocalscan>>&),
18099 and any external programs which are passed a reference to a message data file
18100 (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
18101 will need to be aware of the different formats potentially available.
18103 Using any of the ACL conditions noted will negate the reception benefit
18104 (as a Unix-mbox-format file is constructed for them).
18105 The transmission benefit is maintained.
18107 .option sqlite_lock_timeout main time 5s
18108 .cindex "sqlite lookup type" "lock timeout"
18109 This option controls the timeout that the &(sqlite)& lookup uses when trying to
18110 access an SQLite database. See section &<<SECTsqlite>>& for more details.
18112 .option strict_acl_vars main boolean false
18113 .cindex "&ACL;" "variables, handling unset"
18114 This option controls what happens if a syntactically valid but undefined ACL
18115 variable is referenced. If it is false (the default), an empty string
18116 is substituted; if it is true, an error is generated. See section
18117 &<<SECTaclvariables>>& for details of ACL variables.
18119 .option strip_excess_angle_brackets main boolean false
18120 .cindex "angle brackets, excess"
18121 If this option is set, redundant pairs of angle brackets round &"route-addr"&
18122 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
18123 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
18124 passed on to another MTA, the excess angle brackets are not passed on. If this
18125 option is not set, multiple pairs of angle brackets cause a syntax error.
18128 .option strip_trailing_dot main boolean false
18129 .cindex "trailing dot on domain"
18130 .cindex "dot" "trailing on domain"
18131 If this option is set, a trailing dot at the end of a domain in an address is
18132 ignored. If this is in the envelope and the message is passed on to another
18133 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
18134 domain causes a syntax error.
18135 However, addresses in header lines are checked only when an ACL requests header
18139 .option syslog_duplication main boolean true
18140 .cindex "syslog" "duplicate log lines; suppressing"
18141 When Exim is logging to syslog, it writes the log lines for its three
18142 separate logs at different syslog priorities so that they can in principle
18143 be separated on the logging hosts. Some installations do not require this
18144 separation, and in those cases, the duplication of certain log lines is a
18145 nuisance. If &%syslog_duplication%& is set false, only one copy of any
18146 particular log line is written to syslog. For lines that normally go to
18147 both the main log and the reject log, the reject log version (possibly
18148 containing message header lines) is written, at LOG_NOTICE priority.
18149 Lines that normally go to both the main and the panic log are written at
18150 the LOG_ALERT priority.
18153 .option syslog_facility main string unset
18154 .cindex "syslog" "facility; setting"
18155 This option sets the syslog &"facility"& name, used when Exim is logging to
18156 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
18157 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
18158 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
18159 details of Exim's logging.
18162 .option syslog_pid main boolean true
18163 .cindex "syslog" "pid"
18164 If &%syslog_pid%& is set false, the PID on Exim's log lines are
18165 omitted when these lines are sent to syslog. (Syslog normally prefixes
18166 the log lines with the PID of the logging process automatically.) You need
18167 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
18168 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
18172 .option syslog_processname main string &`exim`&
18173 .cindex "syslog" "process name; setting"
18174 This option sets the syslog &"ident"& name, used when Exim is logging to
18175 syslog. The value must be no longer than 32 characters. See chapter
18176 &<<CHAPlog>>& for details of Exim's logging.
18180 .option syslog_timestamp main boolean true
18181 .cindex "syslog" "timestamps"
18182 .cindex timestamps syslog
18183 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
18184 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
18185 details of Exim's logging.
18188 .option system_filter main string&!! unset
18189 .cindex "filter" "system filter"
18190 .cindex "system filter" "specifying"
18191 .cindex "Sieve filter" "not available for system filter"
18192 This option specifies an Exim filter file that is applied to all messages at
18193 the start of each delivery attempt, before any routing is done. System filters
18194 must be Exim filters; they cannot be Sieve filters. If the system filter
18195 generates any deliveries to files or pipes, or any new mail messages, the
18196 appropriate &%system_filter_..._transport%& option(s) must be set, to define
18197 which transports are to be used. Details of this facility are given in chapter
18198 &<<CHAPsystemfilter>>&.
18199 A forced expansion failure results in no filter operation.
18202 .option system_filter_directory_transport main string&!! unset
18203 .vindex "&$address_file$&"
18204 This sets the name of the transport driver that is to be used when the
18205 &%save%& command in a system message filter specifies a path ending in &"/"&,
18206 implying delivery of each message into a separate file in some directory.
18207 During the delivery, the variable &$address_file$& contains the path name.
18210 .option system_filter_file_transport main string&!! unset
18211 .cindex "file" "transport for system filter"
18212 This sets the name of the transport driver that is to be used when the &%save%&
18213 command in a system message filter specifies a path not ending in &"/"&. During
18214 the delivery, the variable &$address_file$& contains the path name.
18216 .option system_filter_group main string unset
18217 .cindex "gid (group id)" "system filter"
18218 This option is used only when &%system_filter_user%& is also set. It sets the
18219 gid under which the system filter is run, overriding any gid that is associated
18220 with the user. The value may be numerical or symbolic.
18222 .option system_filter_pipe_transport main string&!! unset
18223 .cindex "&(pipe)& transport" "for system filter"
18224 .vindex "&$address_pipe$&"
18225 This specifies the transport driver that is to be used when a &%pipe%& command
18226 is used in a system filter. During the delivery, the variable &$address_pipe$&
18227 contains the pipe command.
18230 .option system_filter_reply_transport main string&!! unset
18231 .cindex "&(autoreply)& transport" "for system filter"
18232 This specifies the transport driver that is to be used when a &%mail%& command
18233 is used in a system filter.
18236 .option system_filter_user main string unset
18237 .cindex "uid (user id)" "system filter"
18238 If this option is set to root, the system filter is run in the main Exim
18239 delivery process, as root. Otherwise, the system filter runs in a separate
18240 process, as the given user, defaulting to the Exim run-time user.
18241 Unless the string consists entirely of digits, it
18242 is looked up in the password data. Failure to find the named user causes a
18243 configuration error. The gid is either taken from the password data, or
18244 specified by &%system_filter_group%&. When the uid is specified numerically,
18245 &%system_filter_group%& is required to be set.
18247 If the system filter generates any pipe, file, or reply deliveries, the uid
18248 under which the filter is run is used when transporting them, unless a
18249 transport option overrides.
18252 .option tcp_nodelay main boolean true
18253 .cindex "daemon" "TCP_NODELAY on sockets"
18254 .cindex "Nagle algorithm"
18255 .cindex "TCP_NODELAY on listening sockets"
18256 If this option is set false, it stops the Exim daemon setting the
18257 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
18258 turns off the &"Nagle algorithm"&, which is a way of improving network
18259 performance in interactive (character-by-character) situations. Turning it off
18260 should improve Exim's performance a bit, so that is what happens by default.
18261 However, it appears that some broken clients cannot cope, and time out. Hence
18262 this option. It affects only those sockets that are set up for listening by the
18263 daemon. Sockets created by the smtp transport for delivering mail always set
18267 .option timeout_frozen_after main time 0s
18268 .cindex "frozen messages" "timing out"
18269 .cindex "timeout" "frozen messages"
18270 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
18271 message of any kind that has been in the queue for longer than the given time
18272 is automatically cancelled at the next queue run. If the frozen message is a
18273 bounce message, it is just discarded; otherwise, a bounce is sent to the
18274 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
18275 If you want to timeout frozen bounce messages earlier than other kinds of
18276 frozen message, see &%ignore_bounce_errors_after%&.
18278 &*Note:*& the default value of zero means no timeouts; with this setting,
18279 frozen messages remain in the queue forever (except for any frozen bounce
18280 messages that are released by &%ignore_bounce_errors_after%&).
18283 .option timezone main string unset
18284 .cindex "timezone, setting"
18285 .cindex "environment" "values from"
18286 The value of &%timezone%& is used to set the environment variable TZ while
18287 running Exim (if it is different on entry). This ensures that all timestamps
18288 created by Exim are in the required timezone. If you want all your timestamps
18289 to be in UTC (aka GMT) you should set
18293 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
18294 or, if that is not set, from the value of the TZ environment variable when Exim
18295 is built. If &%timezone%& is set to the empty string, either at build or run
18296 time, any existing TZ variable is removed from the environment when Exim
18297 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
18298 unfortunately not all, operating systems.
18301 .option tls_advertise_hosts main "host list&!!" *
18302 .cindex "TLS" "advertising"
18303 .cindex "encryption" "on SMTP connection"
18304 .cindex "SMTP" "encrypted connection"
18305 .cindex "ESMTP extensions" STARTTLS
18306 When Exim is built with support for TLS encrypted connections, the availability
18307 of the STARTTLS command to set up an encrypted session is advertised in
18308 response to EHLO only to those client hosts that match this option. See
18309 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
18310 Note that the default value requires that a certificate be supplied
18311 using the &%tls_certificate%& option. If TLS support for incoming connections
18312 is not required the &%tls_advertise_hosts%& option should be set empty.
18315 .option tls_certificate main string list&!! unset
18316 .cindex "TLS" "server certificate; location of"
18317 .cindex "certificate" "server, location of"
18318 The value of this option is expanded, and must then be a list of absolute paths to
18319 files which contain the server's certificates (in PEM format).
18320 Commonly only one file is needed.
18321 The server's private key is also
18322 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
18323 &<<CHAPTLS>>& for further details.
18325 &*Note*&: The certificates defined by this option are used only when Exim is
18326 receiving incoming messages as a server. If you want to supply certificates for
18327 use when sending messages as a client, you must set the &%tls_certificate%&
18328 option in the relevant &(smtp)& transport.
18330 &*Note*&: If you use filenames based on IP addresses, change the list
18331 separator in the usual way (&<<SECTlistsepchange>>&) to avoid confusion under IPv6.
18333 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
18334 when a list of more than one
18335 file is used, the &$tls_in_ourcert$& variable is unreliable.
18336 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
18338 .cindex SNI "selecting server certificate based on"
18339 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
18340 if the OpenSSL build supports TLS extensions and the TLS client sends the
18341 Server Name Indication extension, then this option and others documented in
18342 &<<SECTtlssni>>& will be re-expanded.
18344 If this option is unset or empty a fresh self-signed certificate will be
18345 generated for every connection.
18347 .option tls_crl main string&!! unset
18348 .cindex "TLS" "server certificate revocation list"
18349 .cindex "certificate" "revocation list for server"
18350 This option specifies a certificate revocation list. The expanded value must
18351 be the name of a file that contains CRLs in PEM format.
18353 Under OpenSSL the option can specify a directory with CRL files.
18355 &*Note:*& Under OpenSSL the option must, if given, supply a CRL
18356 for each signing element of the certificate chain (i.e. all but the leaf).
18357 For the file variant this can be multiple PEM blocks in the one file.
18359 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18362 .option tls_dh_max_bits main integer 2236
18363 .cindex "TLS" "D-H bit count"
18364 The number of bits used for Diffie-Hellman key-exchange may be suggested by
18365 the chosen TLS library. That value might prove to be too high for
18366 interoperability. This option provides a maximum clamp on the value
18367 suggested, trading off security for interoperability.
18369 The value must be at least 1024.
18371 The value 2236 was chosen because, at time of adding the option, it was the
18372 hard-coded maximum value supported by the NSS cryptographic library, as used
18373 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
18375 If you prefer more security and are willing to break some clients, raise this
18378 Note that the value passed to GnuTLS for *generating* a new prime may be a
18379 little less than this figure, because GnuTLS is inexact and may produce a
18380 larger prime than requested.
18383 .option tls_dhparam main string&!! unset
18384 .cindex "TLS" "D-H parameters for server"
18385 The value of this option is expanded and indicates the source of DH parameters
18386 to be used by Exim.
18388 This option is ignored for GnuTLS version 3.6.0 and later.
18389 The library manages parameter negotiation internally.
18391 &*Note: The Exim Maintainers strongly recommend,
18392 for other TLS library versions,
18393 using a filename with site-generated
18394 local DH parameters*&, which has been supported across all versions of Exim. The
18395 other specific constants available are a fallback so that even when
18396 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
18398 If &%tls_dhparam%& is a filename starting with a &`/`&,
18399 then it names a file from which DH
18400 parameters should be loaded. If the file exists, it should hold a PEM-encoded
18401 PKCS#3 representation of the DH prime. If the file does not exist, for
18402 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
18403 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
18404 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
18405 and treated as though the &%tls_dhparam%& were set to "none".
18407 If this option expands to the string "none", then no DH parameters will be
18410 If this option expands to the string "historic" and Exim is using GnuTLS, then
18411 Exim will attempt to load a file from inside the spool directory. If the file
18412 does not exist, Exim will attempt to create it.
18413 See section &<<SECTgnutlsparam>>& for further details.
18415 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
18416 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
18418 In older versions of Exim the default was the 2048 bit prime described in section
18419 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
18420 in IKE is assigned number 23.
18422 Otherwise, the option must expand to the name used by Exim for any of a number
18423 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
18424 sources. As names, Exim uses a standard specified name, else "ike" followed by
18425 the number used by IKE, or "default" which corresponds to
18426 &`exim.dev.20160529.3`&.
18428 The available standard primes are:
18429 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
18430 &`ike1`&, &`ike2`&, &`ike5`&,
18431 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
18432 &`ike22`&, &`ike23`& and &`ike24`&.
18434 The available additional primes are:
18435 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
18437 Some of these will be too small to be accepted by clients.
18438 Some may be too large to be accepted by clients.
18439 The open cryptographic community has suspicions about the integrity of some
18440 of the later IKE values, which led into RFC7919 providing new fixed constants
18441 (the "ffdhe" identifiers).
18443 At this point, all of the "ike" values should be considered obsolete;
18444 they're still in Exim to avoid breaking unusual configurations, but are
18445 candidates for removal the next time we have backwards-incompatible changes.
18447 The TLS protocol does not negotiate an acceptable size for this; clients tend
18448 to hard-drop connections if what is offered by the server is unacceptable,
18449 whether too large or too small, and there's no provision for the client to
18450 tell the server what these constraints are. Thus, as a server operator, you
18451 need to make an educated guess as to what is most likely to work for your
18454 Some known size constraints suggest that a bit-size in the range 2048 to 2236
18455 is most likely to maximise interoperability. The upper bound comes from
18456 applications using the Mozilla Network Security Services (NSS) library, which
18457 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
18458 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
18459 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
18460 acceptable bound from 1024 to 2048.
18463 .option tls_eccurve main string&!! &`auto`&
18464 .cindex TLS "EC cryptography"
18465 This option selects a EC curve for use by Exim when used with OpenSSL.
18466 It has no effect when Exim is used with GnuTLS.
18468 After expansion it must contain a valid EC curve parameter, such as
18469 &`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
18470 for valid selections.
18472 For OpenSSL versions before (and not including) 1.0.2, the string
18473 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
18474 &`auto`& tells the library to choose.
18476 If the option expands to an empty string, no EC curves will be enabled.
18479 .option tls_ocsp_file main string&!! unset
18480 .cindex TLS "certificate status"
18481 .cindex TLS "OCSP proof file"
18483 must if set expand to the absolute path to a file which contains a current
18484 status proof for the server's certificate, as obtained from the
18485 Certificate Authority.
18487 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
18488 The macro "_HAVE_TLS_OCSP" will be defined for those versions.
18490 For OpenSSL 1.1.0 or later, and
18491 for GnuTLS 3.5.6 or later the expanded value of this option can be a list
18492 of files, to match a list given for the &%tls_certificate%& option.
18493 The ordering of the two lists must match.
18494 The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
18496 The file(s) should be in DER format,
18497 except for GnuTLS 3.6.3 or later
18499 when an optional filetype prefix can be used.
18500 The prefix must be one of "DER" or "PEM", followed by
18501 a single space. If one is used it sets the format for subsequent
18502 files in the list; the initial format is DER.
18503 If multiple proofs are wanted, for multiple chain elements
18504 (this only works under TLS1.3)
18505 they must be coded as a combined OCSP response.
18507 Although GnuTLS will accept PEM files with multiple separate
18508 PEM blobs (ie. separate OCSP responses), it sends them in the
18509 TLS Certificate record interleaved with the certificates of the chain;
18510 although a GnuTLS client is happy with that, an OpenSSL client is not.
18512 .option tls_on_connect_ports main "string list" unset
18515 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
18516 operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
18517 set up without waiting for the client to issue a STARTTLS command. For
18518 further details, see section &<<SECTsupobssmt>>&.
18522 .option tls_privatekey main string list&!! unset
18523 .cindex "TLS" "server private key; location of"
18524 The value of this option is expanded, and must then be a list of absolute paths to
18525 files which contains the server's private keys.
18526 If this option is unset, or if
18527 the expansion is forced to fail, or the result is an empty string, the private
18528 key is assumed to be in the same file as the server's certificates. See chapter
18529 &<<CHAPTLS>>& for further details.
18531 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18534 .option tls_remember_esmtp main boolean false
18535 .cindex "TLS" "esmtp state; remembering"
18536 .cindex "TLS" "broken clients"
18537 If this option is set true, Exim violates the RFCs by remembering that it is in
18538 &"esmtp"& state after successfully negotiating a TLS session. This provides
18539 support for broken clients that fail to send a new EHLO after starting a
18543 .option tls_require_ciphers main string&!! unset
18544 .cindex "TLS" "requiring specific ciphers"
18545 .cindex "cipher" "requiring specific"
18546 This option controls which ciphers can be used for incoming TLS connections.
18547 The &(smtp)& transport has an option of the same name for controlling outgoing
18548 connections. This option is expanded for each connection, so can be varied for
18549 different clients if required. The value of this option must be a list of
18550 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
18551 in somewhat different ways. If GnuTLS is being used, the client controls the
18552 preference order of the available ciphers. Details are given in sections
18553 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
18557 .option tls_resumption_hosts main "host list&!!" unset
18558 .cindex TLS resumption
18559 This option controls which connections to offer the TLS resumption feature.
18560 See &<<SECTresumption>>& for details.
18564 .option tls_try_verify_hosts main "host list&!!" unset
18565 .cindex "TLS" "client certificate verification"
18566 .cindex "certificate" "verification of client"
18567 See &%tls_verify_hosts%& below.
18570 .option tls_verify_certificates main string&!! system
18571 .cindex "TLS" "client certificate verification"
18572 .cindex "certificate" "verification of client"
18573 The value of this option is expanded, and must then be either the
18575 or the absolute path to
18576 a file or directory containing permitted certificates for clients that
18577 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
18579 The "system" value for the option will use a
18580 system default location compiled into the SSL library.
18581 This is not available for GnuTLS versions preceding 3.0.20,
18582 and will be taken as empty; an explicit location
18585 The use of a directory for the option value is not available for GnuTLS versions
18586 preceding 3.3.6 and a single file must be used.
18588 With OpenSSL the certificates specified
18590 either by file or directory
18591 are added to those given by the system default location.
18593 These certificates should be for the certificate authorities trusted, rather
18594 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
18595 the value is a file then the certificates are sent by Exim as a server to
18596 connecting clients, defining the list of accepted certificate authorities.
18597 Thus the values defined should be considered public data. To avoid this,
18598 use the explicit directory version. (If your peer is Exim up to 4.85,
18599 using GnuTLS, you may need to send the CAs (thus using the file
18600 variant). Otherwise the peer doesn't send its certificate.)
18602 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18604 A forced expansion failure or setting to an empty string is equivalent to
18608 .option tls_verify_hosts main "host list&!!" unset
18609 .cindex "TLS" "client certificate verification"
18610 .cindex "certificate" "verification of client"
18611 This option, along with &%tls_try_verify_hosts%&, controls the checking of
18612 certificates from clients. The expected certificates are defined by
18613 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
18614 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
18615 &%tls_verify_certificates%& is not set.
18617 Any client that matches &%tls_verify_hosts%& is constrained by
18618 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
18619 present one of the listed certificates. If it does not, the connection is
18620 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
18621 the host to use TLS. It can still send SMTP commands through unencrypted
18622 connections. Forcing a client to use TLS has to be done separately using an
18623 ACL to reject inappropriate commands when the connection is not encrypted.
18625 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
18626 matches this option (but not &%tls_verify_hosts%&), Exim requests a
18627 certificate and checks it against &%tls_verify_certificates%&, but does not
18628 abort the connection if there is no certificate or if it does not match. This
18629 state can be detected in an ACL, which makes it possible to implement policies
18630 such as &"accept for relay only if a verified certificate has been received,
18631 but accept for local delivery if encrypted, even without a verified
18634 Client hosts that match neither of these lists are not asked to present
18638 .option trusted_groups main "string list&!!" unset
18639 .cindex "trusted groups"
18640 .cindex "groups" "trusted"
18641 This option is expanded just once, at the start of Exim's processing. If this
18642 option is set, any process that is running in one of the listed groups, or
18643 which has one of them as a supplementary group, is trusted. The groups can be
18644 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
18645 details of what trusted callers are permitted to do. If neither
18646 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
18649 .option trusted_users main "string list&!!" unset
18650 .cindex "trusted users"
18651 .cindex "user" "trusted"
18652 This option is expanded just once, at the start of Exim's processing. If this
18653 option is set, any process that is running as one of the listed users is
18654 trusted. The users can be specified numerically or by name. See section
18655 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
18656 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
18657 Exim user are trusted.
18659 .option unknown_login main string&!! unset
18660 .cindex "uid (user id)" "unknown caller"
18661 .vindex "&$caller_uid$&"
18662 This is a specialized feature for use in unusual configurations. By default, if
18663 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
18664 gives up. The &%unknown_login%& option can be used to set a login name to be
18665 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
18666 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
18667 is used for the user's real name (gecos field), unless this has been set by the
18670 .option unknown_username main string unset
18671 See &%unknown_login%&.
18673 .option untrusted_set_sender main "address list&!!" unset
18674 .cindex "trusted users"
18675 .cindex "sender" "setting by untrusted user"
18676 .cindex "untrusted user setting sender"
18677 .cindex "user" "untrusted setting sender"
18678 .cindex "envelope from"
18679 .cindex "envelope sender"
18680 When an untrusted user submits a message to Exim using the standard input, Exim
18681 normally creates an envelope sender address from the user's login and the
18682 default qualification domain. Data from the &%-f%& option (for setting envelope
18683 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
18684 is used) is ignored.
18686 However, untrusted users are permitted to set an empty envelope sender address,
18687 to declare that a message should never generate any bounces. For example:
18689 exim -f '<>' user@domain.example
18691 .vindex "&$sender_ident$&"
18692 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
18693 other envelope sender addresses in a controlled way. When it is set, untrusted
18694 users are allowed to set envelope sender addresses that match any of the
18695 patterns in the list. Like all address lists, the string is expanded. The
18696 identity of the user is in &$sender_ident$&, so you can, for example, restrict
18697 users to setting senders that start with their login ids
18698 followed by a hyphen
18699 by a setting like this:
18701 untrusted_set_sender = ^$sender_ident-
18703 If you want to allow untrusted users to set envelope sender addresses without
18704 restriction, you can use
18706 untrusted_set_sender = *
18708 The &%untrusted_set_sender%& option applies to all forms of local input, but
18709 only to the setting of the envelope sender. It does not permit untrusted users
18710 to use the other options which trusted user can use to override message
18711 parameters. Furthermore, it does not stop Exim from removing an existing
18712 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
18713 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
18714 overriding these actions. The handling of the &'Sender:'& header is also
18715 described in section &<<SECTthesenhea>>&.
18717 The log line for a message's arrival shows the envelope sender following
18718 &"<="&. For local messages, the user's login always follows, after &"U="&. In
18719 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
18720 envelope sender address, the user's login is shown in parentheses after the
18724 .option uucp_from_pattern main string "see below"
18725 .cindex "&""From""& line"
18726 .cindex "UUCP" "&""From""& line"
18727 Some applications that pass messages to an MTA via a command line interface use
18728 an initial line starting with &"From&~"& to pass the envelope sender. In
18729 particular, this is used by UUCP software. Exim recognizes such a line by means
18730 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
18731 matches, the sender address is constructed by expanding the contents of
18732 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
18733 default pattern recognizes lines in the following two forms:
18735 From ph10 Fri Jan 5 12:35 GMT 1996
18736 From ph10 Fri, 7 Jan 97 14:00:00 GMT
18738 The pattern can be seen by running
18740 exim -bP uucp_from_pattern
18742 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
18743 year in the second case. The first word after &"From&~"& is matched in the
18744 regular expression by a parenthesized subpattern. The default value for
18745 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
18746 (&"ph10"& in the example above) as the message's sender. See also
18747 &%ignore_fromline_hosts%&.
18750 .option uucp_from_sender main string&!! &`$1`&
18751 See &%uucp_from_pattern%& above.
18754 .option warn_message_file main string&!! unset
18755 .cindex "warning of delay" "customizing the message"
18756 .cindex "customizing" "warning message"
18757 This option defines a template file containing paragraphs of text to be used
18758 for constructing the warning message which is sent by Exim when a message has
18759 been in the queue for a specified amount of time, as specified by
18760 &%delay_warning%&. Details of the file's contents are given in chapter
18761 &<<CHAPemsgcust>>&.
18762 .cindex warn_message_file "tainted data"
18763 The option is expanded to give the file path, which must be
18764 absolute and untainted.
18765 See also &%bounce_message_file%&.
18768 .option write_rejectlog main boolean true
18769 .cindex "reject log" "disabling"
18770 If this option is set false, Exim no longer writes anything to the reject log.
18771 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
18772 .ecindex IIDconfima
18773 .ecindex IIDmaiconf
18778 . ////////////////////////////////////////////////////////////////////////////
18779 . ////////////////////////////////////////////////////////////////////////////
18781 .chapter "Generic options for routers" "CHAProutergeneric"
18782 .scindex IIDgenoprou1 "options" "generic; for routers"
18783 .scindex IIDgenoprou2 "generic options" "router"
18784 This chapter describes the generic options that apply to all routers.
18785 Those that are preconditions are marked with ‡ in the &"use"& field.
18787 For a general description of how a router operates, see sections
18788 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
18789 which the preconditions are tested. The order of expansion of the options that
18790 provide data for a transport is: &%errors_to%&, &%headers_add%&,
18791 &%headers_remove%&, &%transport%&.
18795 .option address_data routers string&!! unset
18796 .cindex "router" "data attached to address"
18797 The string is expanded just before the router is run, that is, after all the
18798 precondition tests have succeeded. If the expansion is forced to fail, the
18799 router declines, the value of &%address_data%& remains unchanged, and the
18800 &%more%& option controls what happens next. Other expansion failures cause
18801 delivery of the address to be deferred.
18803 .vindex "&$address_data$&"
18804 When the expansion succeeds, the value is retained with the address, and can be
18805 accessed using the variable &$address_data$& in the current router, subsequent
18806 routers, and the eventual transport.
18808 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
18809 that runs a user's filter file, the contents of &$address_data$& are accessible
18810 in the filter. This is not normally a problem, because such data is usually
18811 either not confidential or it &"belongs"& to the current user, but if you do
18812 put confidential data into &$address_data$& you need to remember this point.
18814 Even if the router declines or passes, the value of &$address_data$& remains
18815 with the address, though it can be changed by another &%address_data%& setting
18816 on a subsequent router. If a router generates child addresses, the value of
18817 &$address_data$& propagates to them. This also applies to the special kind of
18818 &"child"& that is generated by a router with the &%unseen%& option.
18820 The idea of &%address_data%& is that you can use it to look up a lot of data
18821 for the address once, and then pick out parts of the data later. For example,
18822 you could use a single LDAP lookup to return a string of the form
18824 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
18826 In the transport you could pick out the mailbox by a setting such as
18828 file = ${extract{mailbox}{$address_data}}
18830 This makes the configuration file less messy, and also reduces the number of
18831 lookups (though Exim does cache lookups).
18833 See also the &%set%& option below.
18835 .vindex "&$sender_address_data$&"
18836 .vindex "&$address_data$&"
18837 The &%address_data%& facility is also useful as a means of passing information
18838 from one router to another, and from a router to a transport. In addition, if
18839 &$address_data$& is set by a router when verifying a recipient address from an
18840 ACL, it remains available for use in the rest of the ACL statement. After
18841 verifying a sender, the value is transferred to &$sender_address_data$&.
18845 .option address_test routers&!? boolean true
18847 .cindex "router" "skipping when address testing"
18848 If this option is set false, the router is skipped when routing is being tested
18849 by means of the &%-bt%& command line option. This can be a convenience when
18850 your first router sends messages to an external scanner, because it saves you
18851 having to set the &"already scanned"& indicator when testing real address
18856 .option cannot_route_message routers string&!! unset
18857 .cindex "router" "customizing &""cannot route""& message"
18858 .cindex "customizing" "&""cannot route""& message"
18859 This option specifies a text message that is used when an address cannot be
18860 routed because Exim has run out of routers. The default message is
18861 &"Unrouteable address"&. This option is useful only on routers that have
18862 &%more%& set false, or on the very last router in a configuration, because the
18863 value that is used is taken from the last router that is considered. This
18864 includes a router that is skipped because its preconditions are not met, as
18865 well as a router that declines. For example, using the default configuration,
18868 cannot_route_message = Remote domain not found in DNS
18870 on the first router, which is a &(dnslookup)& router with &%more%& set false,
18873 cannot_route_message = Unknown local user
18875 on the final router that checks for local users. If string expansion fails for
18876 this option, the default message is used. Unless the expansion failure was
18877 explicitly forced, a message about the failure is written to the main and panic
18878 logs, in addition to the normal message about the routing failure.
18881 .option caseful_local_part routers boolean false
18882 .cindex "case of local parts"
18883 .cindex "router" "case of local parts"
18884 By default, routers handle the local parts of addresses in a case-insensitive
18885 manner, though the actual case is preserved for transmission with the message.
18886 If you want the case of letters to be significant in a router, you must set
18887 this option true. For individual router options that contain address or local
18888 part lists (for example, &%local_parts%&), case-sensitive matching can be
18889 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
18892 .vindex "&$local_part$&"
18893 .vindex "&$original_local_part$&"
18894 .vindex "&$parent_local_part$&"
18895 The value of the &$local_part$& variable is forced to lower case while a
18896 router is running unless &%caseful_local_part%& is set. When a router assigns
18897 an address to a transport, the value of &$local_part$& when the transport runs
18898 is the same as it was in the router. Similarly, when a router generates child
18899 addresses by aliasing or forwarding, the values of &$original_local_part$&
18900 and &$parent_local_part$& are those that were used by the redirecting router.
18902 This option applies to the processing of an address by a router. When a
18903 recipient address is being processed in an ACL, there is a separate &%control%&
18904 modifier that can be used to specify case-sensitive processing within the ACL
18905 (see section &<<SECTcontrols>>&).
18909 .option check_local_user routers&!? boolean false
18910 .cindex "local user, checking in router"
18911 .cindex "router" "checking for local user"
18912 .cindex "&_/etc/passwd_&"
18914 When this option is true, Exim checks that the local part of the recipient
18915 address (with affixes removed if relevant) is the name of an account on the
18916 local system. The check is done by calling the &[getpwnam()]& function rather
18917 than trying to read &_/etc/passwd_& directly. This means that other methods of
18918 holding password data (such as NIS) are supported. If the local part is a local
18920 .cindex "tainted data" "de-tainting"
18921 &$local_part_data$& is set to an untainted version of the local part and
18922 &$home$& is set from the password data. The latter can be tested in other
18923 preconditions that are evaluated after this one (the order of evaluation is
18924 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
18925 overridden by &%router_home_directory%&. If the local part is not a local user,
18926 the router is skipped.
18928 If you want to check that the local part is either the name of a local user
18929 or matches something else, you cannot combine &%check_local_user%& with a
18930 setting of &%local_parts%&, because that specifies the logical &'and'& of the
18931 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
18932 setting to achieve this. For example:
18934 local_parts = passwd;$local_part : lsearch;/etc/other/users
18936 Note, however, that the side effects of &%check_local_user%& (such as setting
18937 up a home directory) do not occur when a &(passwd)& lookup is used in a
18938 &%local_parts%& (or any other) precondition.
18942 .option condition routers&!? string&!! unset
18943 .cindex "router" "customized precondition"
18944 This option specifies a general precondition test that has to succeed for the
18945 router to be called. The &%condition%& option is the last precondition to be
18946 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
18947 result is a forced failure, or an empty string, or one of the strings &"0"& or
18948 &"no"& or &"false"& (checked without regard to the case of the letters), the
18949 router is skipped, and the address is offered to the next one.
18951 If the result is any other value, the router is run (as this is the last
18952 precondition to be evaluated, all the other preconditions must be true).
18954 This option is unusual in that multiple &%condition%& options may be present.
18955 All &%condition%& options must succeed.
18957 The &%condition%& option provides a means of applying custom conditions to the
18958 running of routers. Note that in the case of a simple conditional expansion,
18959 the default expansion values are exactly what is wanted. For example:
18961 condition = ${if >{$message_age}{600}}
18963 Because of the default behaviour of the string expansion, this is equivalent to
18965 condition = ${if >{$message_age}{600}{true}{}}
18968 A multiple condition example, which succeeds:
18970 condition = ${if >{$message_age}{600}}
18971 condition = ${if !eq{${lc:$local_part}}{postmaster}}
18975 If the expansion fails (other than forced failure) delivery is deferred. Some
18976 of the other precondition options are common special cases that could in fact
18977 be specified using &%condition%&.
18979 Historical note: We have &%condition%& on ACLs and on Routers. Routers
18980 are far older, and use one set of semantics. ACLs are newer and when
18981 they were created, the ACL &%condition%& process was given far stricter
18982 parse semantics. The &%bool{}%& expansion condition uses the same rules as
18983 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
18984 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
18985 Router rules processing behavior.
18987 This is best illustrated in an example:
18989 # If used in an ACL condition will fail with a syntax error, but
18990 # in a router condition any extra characters are treated as a string
18992 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
18995 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
18998 In each example above, the &%if%& statement actually ends after
18999 &"{google.com}}"&. Since no true or false braces were defined, the
19000 default &%if%& behavior is to return a boolean true or a null answer
19001 (which evaluates to false). The rest of the line is then treated as a
19002 string. So the first example resulted in the boolean answer &"true"&
19003 with the string &" {yes} {no}}"& appended to it. The second example
19004 resulted in the null output (indicating false) with the string
19005 &" {yes} {no}}"& appended to it.
19007 In fact you can put excess forward braces in too. In the router
19008 &%condition%&, Exim's parser only looks for &"{"& symbols when they
19009 mean something, like after a &"$"& or when required as part of a
19010 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
19013 Thus, in a Router, the above expansion strings will both always evaluate
19014 true, as the result of expansion is a non-empty string which doesn't
19015 match an explicit false value. This can be tricky to debug. By
19016 contrast, in an ACL either of those strings will always result in an
19017 expansion error because the result doesn't look sufficiently boolean.
19020 .option debug_print routers string&!! unset
19021 .cindex "testing" "variables in drivers"
19022 If this option is set and debugging is enabled (see the &%-d%& command line
19023 option) or in address-testing mode (see the &%-bt%& command line option),
19024 the string is expanded and included in the debugging output.
19025 If expansion of the string fails, the error message is written to the debugging
19026 output, and Exim carries on processing.
19027 This option is provided to help with checking out the values of variables and
19028 so on when debugging router configurations. For example, if a &%condition%&
19029 option appears not to be working, &%debug_print%& can be used to output the
19030 variables it references. The output happens after checks for &%domains%&,
19031 &%local_parts%&, and &%check_local_user%& but before any other preconditions
19032 are tested. A newline is added to the text if it does not end with one.
19033 The variable &$router_name$& contains the name of the router.
19037 .option disable_logging routers boolean false
19038 If this option is set true, nothing is logged for any routing errors
19039 or for any deliveries caused by this router. You should not set this option
19040 unless you really, really know what you are doing. See also the generic
19041 transport option of the same name.
19043 .option dnssec_request_domains routers "domain list&!!" *
19044 .cindex "MX record" "security"
19045 .cindex "DNSSEC" "MX lookup"
19046 .cindex "security" "MX lookup"
19047 .cindex "DNS" "DNSSEC"
19048 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
19049 the DNSSEC request bit set.
19050 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19052 .option dnssec_require_domains routers "domain list&!!" unset
19053 .cindex "MX record" "security"
19054 .cindex "DNSSEC" "MX lookup"
19055 .cindex "security" "MX lookup"
19056 .cindex "DNS" "DNSSEC"
19057 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
19058 the DNSSEC request bit set. Any returns not having the Authenticated Data bit
19059 (AD bit) set will be ignored and logged as a host-lookup failure.
19060 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19063 .option domains routers&!? "domain list&!!" unset
19064 .cindex "router" "restricting to specific domains"
19065 .vindex "&$domain_data$&"
19066 If this option is set, the router is skipped unless the current domain matches
19067 the list. If the match is achieved by means of a file lookup, the data that the
19068 lookup returned for the domain is placed in &$domain_data$& for use in string
19069 expansions of the driver's private options and in the transport.
19070 See section &<<SECTrouprecon>>& for
19071 a list of the order in which preconditions are evaluated.
19075 .option driver routers string unset
19076 This option must always be set. It specifies which of the available routers is
19080 .option dsn_lasthop routers boolean false
19081 .cindex "DSN" "success"
19082 .cindex "Delivery Status Notification" "success"
19083 If this option is set true, and extended DSN (RFC3461) processing is in effect,
19084 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
19085 instead send a success DSN as if the next hop does not support DSN.
19086 Not effective on redirect routers.
19090 .option errors_to routers string&!! unset
19091 .cindex "envelope from"
19092 .cindex "envelope sender"
19093 .cindex "router" "changing address for errors"
19094 If a router successfully handles an address, it may assign the address to a
19095 transport for delivery or it may generate child addresses. In both cases, if
19096 there is a delivery problem during later processing, the resulting bounce
19097 message is sent to the address that results from expanding this string,
19098 provided that the address verifies successfully. The &%errors_to%& option is
19099 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
19101 The &%errors_to%& setting associated with an address can be overridden if it
19102 subsequently passes through other routers that have their own &%errors_to%&
19103 settings, or if the message is delivered by a transport with a &%return_path%&
19106 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
19107 the expansion fails to verify, the errors address associated with the incoming
19108 address is used. At top level, this is the envelope sender. A non-forced
19109 expansion failure causes delivery to be deferred.
19111 If an address for which &%errors_to%& has been set ends up being delivered over
19112 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
19113 any bounces that are generated by other MTAs on the delivery route are also
19114 sent there. You can set &%errors_to%& to the empty string by either of these
19120 An expansion item that yields an empty string has the same effect. If you do
19121 this, a locally detected delivery error for addresses processed by this router
19122 no longer gives rise to a bounce message; the error is discarded. If the
19123 address is delivered to a remote host, the return path is set to &`<>`&, unless
19124 overridden by the &%return_path%& option on the transport.
19126 .vindex "&$address_data$&"
19127 If for some reason you want to discard local errors, but use a non-empty
19128 MAIL command for remote delivery, you can preserve the original return
19129 path in &$address_data$& in the router, and reinstate it in the transport by
19130 setting &%return_path%&.
19132 The most common use of &%errors_to%& is to direct mailing list bounces to the
19133 manager of the list, as described in section &<<SECTmailinglists>>&, or to
19134 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
19138 .option expn routers&!? boolean true
19139 .cindex "address" "testing"
19140 .cindex "testing" "addresses"
19141 .cindex "EXPN" "router skipping"
19142 .cindex "router" "skipping for EXPN"
19143 If this option is turned off, the router is skipped when testing an address
19144 as a result of processing an SMTP EXPN command. You might, for example,
19145 want to turn it off on a router for users' &_.forward_& files, while leaving it
19146 on for the system alias file.
19147 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19150 The use of the SMTP EXPN command is controlled by an ACL (see chapter
19151 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
19152 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
19156 .option fail_verify routers boolean false
19157 .cindex "router" "forcing verification failure"
19158 Setting this option has the effect of setting both &%fail_verify_sender%& and
19159 &%fail_verify_recipient%& to the same value.
19163 .option fail_verify_recipient routers boolean false
19164 If this option is true and an address is accepted by this router when
19165 verifying a recipient, verification fails.
19169 .option fail_verify_sender routers boolean false
19170 If this option is true and an address is accepted by this router when
19171 verifying a sender, verification fails.
19175 .option fallback_hosts routers "string list" unset
19176 .cindex "router" "fallback hosts"
19177 .cindex "fallback" "hosts specified on router"
19178 String expansion is not applied to this option. The argument must be a
19179 colon-separated list of host names or IP addresses. The list separator can be
19180 changed (see section &<<SECTlistsepchange>>&), and a port can be specified with
19181 each name or address. In fact, the format of each item is exactly the same as
19182 defined for the list of hosts in a &(manualroute)& router (see section
19183 &<<SECTformatonehostitem>>&).
19185 If a router queues an address for a remote transport, this host list is
19186 associated with the address, and used instead of the transport's fallback host
19187 list. If &%hosts_randomize%& is set on the transport, the order of the list is
19188 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
19189 transport for further details.
19192 .option group routers string&!! "see below"
19193 .cindex "gid (group id)" "local delivery"
19194 .cindex "local transports" "uid and gid"
19195 .cindex "transport" "local"
19196 .cindex "router" "setting group"
19197 When a router queues an address for a transport, and the transport does not
19198 specify a group, the group given here is used when running the delivery
19200 The group may be specified numerically or by name. If expansion fails, the
19201 error is logged and delivery is deferred.
19202 The default is unset, unless &%check_local_user%& is set, when the default
19203 is taken from the password information. See also &%initgroups%& and &%user%&
19204 and the discussion in chapter &<<CHAPenvironment>>&.
19208 .option headers_add routers list&!! unset
19209 .cindex "header lines" "adding"
19210 .cindex "router" "adding header lines"
19211 This option specifies a list of text headers,
19212 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19213 that is associated with any addresses that are accepted by the router.
19214 Each item is separately expanded, at routing time. However, this
19215 option has no effect when an address is just being verified. The way in which
19216 the text is used to add header lines at transport time is described in section
19217 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
19218 message is in the process of being transported. This means that references to
19219 header lines in string expansions in the transport's configuration do not
19220 &"see"& the added header lines.
19222 The &%headers_add%& option is expanded after &%errors_to%&, but before
19223 &%headers_remove%& and &%transport%&. If an item is empty, or if
19224 an item expansion is forced to fail, the item has no effect. Other expansion
19225 failures are treated as configuration errors.
19227 Unlike most options, &%headers_add%& can be specified multiple times
19228 for a router; all listed headers are added.
19230 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
19231 router that has the &%one_time%& option set.
19233 .cindex "duplicate addresses"
19234 .oindex "&%unseen%&"
19235 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19236 additions are deleted when the address is passed on to subsequent routers.
19237 For a &%redirect%& router, if a generated address is the same as the incoming
19238 address, this can lead to duplicate addresses with different header
19239 modifications. Exim does not do duplicate deliveries (except, in certain
19240 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
19241 which of the duplicates is discarded, so this ambiguous situation should be
19242 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
19246 .option headers_remove routers list&!! unset
19247 .cindex "header lines" "removing"
19248 .cindex "router" "removing header lines"
19249 This option specifies a list of text headers,
19250 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19251 that is associated with any addresses that are accepted by the router.
19252 However, the option has no effect when an address is just being verified.
19253 Each list item is separately expanded, at transport time.
19254 If an item ends in *, it will match any header with the given prefix.
19256 the text is used to remove header lines at transport time is described in
19257 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
19258 the message is in the process of being transported. This means that references
19259 to header lines in string expansions in the transport's configuration still
19260 &"see"& the original header lines.
19262 The &%headers_remove%& option is handled after &%errors_to%& and
19263 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
19264 the item has no effect. Other expansion failures are treated as configuration
19267 Unlike most options, &%headers_remove%& can be specified multiple times
19268 for a router; all listed headers are removed.
19270 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
19271 router that has the &%one_time%& option set.
19273 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19274 removal requests are deleted when the address is passed on to subsequent
19275 routers, and this can lead to problems with duplicates -- see the similar
19276 warning for &%headers_add%& above.
19278 &*Warning 3*&: Because of the separate expansion of the list items,
19279 items that contain a list separator must have it doubled.
19280 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
19284 .option ignore_target_hosts routers "host list&!!" unset
19285 .cindex "IP address" "discarding"
19286 .cindex "router" "discarding IP addresses"
19287 Although this option is a host list, it should normally contain IP address
19288 entries rather than names. If any host that is looked up by the router has an
19289 IP address that matches an item in this list, Exim behaves as if that IP
19290 address did not exist. This option allows you to cope with rogue DNS entries
19293 remote.domain.example. A 127.0.0.1
19297 ignore_target_hosts = 127.0.0.1
19299 on the relevant router. If all the hosts found by a &(dnslookup)& router are
19300 discarded in this way, the router declines. In a conventional configuration, an
19301 attempt to mail to such a domain would normally provoke the &"unrouteable
19302 domain"& error, and an attempt to verify an address in the domain would fail.
19303 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
19304 router declines if presented with one of the listed addresses.
19306 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
19307 means of the first or the second of the following settings, respectively:
19309 ignore_target_hosts = 0.0.0.0/0
19310 ignore_target_hosts = <; 0::0/0
19312 The pattern in the first line matches all IPv4 addresses, whereas the pattern
19313 in the second line matches all IPv6 addresses.
19315 This option may also be useful for ignoring link-local and site-local IPv6
19316 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
19317 is expanded before use as a list, it is possible to make it dependent on the
19318 domain that is being routed.
19320 .vindex "&$host_address$&"
19321 During its expansion, &$host_address$& is set to the IP address that is being
19324 .option initgroups routers boolean false
19325 .cindex "additional groups"
19326 .cindex "groups" "additional"
19327 .cindex "local transports" "uid and gid"
19328 .cindex "transport" "local"
19329 If the router queues an address for a transport, and this option is true, and
19330 the uid supplied by the router is not overridden by the transport, the
19331 &[initgroups()]& function is called when running the transport to ensure that
19332 any additional groups associated with the uid are set up. See also &%group%&
19333 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
19337 .option local_part_prefix routers&!? "string list" unset
19338 .cindex affix "router precondition"
19339 .cindex "router" "prefix for local part"
19340 .cindex "prefix" "for local part, used in router"
19341 If this option is set, the router is skipped unless the local part starts with
19342 one of the given strings, or &%local_part_prefix_optional%& is true. See
19343 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
19346 The list is scanned from left to right, and the first prefix that matches is
19347 used. A limited form of wildcard is available; if the prefix begins with an
19348 asterisk, it matches the longest possible sequence of arbitrary characters at
19349 the start of the local part. An asterisk should therefore always be followed by
19350 some character that does not occur in normal local parts.
19351 .cindex "multiple mailboxes"
19352 .cindex "mailbox" "multiple"
19353 Wildcarding can be used to set up multiple user mailboxes, as described in
19354 section &<<SECTmulbox>>&.
19356 .vindex "&$local_part$&"
19357 .vindex "&$local_part_prefix$&"
19358 During the testing of the &%local_parts%& option, and while the router is
19359 running, the prefix is removed from the local part, and is available in the
19360 expansion variable &$local_part_prefix$&. When a message is being delivered, if
19361 the router accepts the address, this remains true during subsequent delivery by
19362 a transport. In particular, the local part that is transmitted in the RCPT
19363 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
19364 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
19365 the relevant transport.
19367 .vindex &$local_part_prefix_v$&
19368 If wildcarding (above) was used then the part of the prefix matching the
19369 wildcard is available in &$local_part_prefix_v$&.
19371 When an address is being verified, &%local_part_prefix%& affects only the
19372 behaviour of the router. If the callout feature of verification is in use, this
19373 means that the full address, including the prefix, will be used during the
19376 The prefix facility is commonly used to handle local parts of the form
19377 &%owner-something%&. Another common use is to support local parts of the form
19378 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
19379 to tell a user their forwarding is broken &-- by placing a router like this one
19380 immediately before the router that handles &_.forward_& files:
19384 local_part_prefix = real-
19386 transport = local_delivery
19388 For security, it would probably be a good idea to restrict the use of this
19389 router to locally-generated messages, using a condition such as this:
19391 condition = ${if match {$sender_host_address}\
19392 {\N^(|127\.0\.0\.1)$\N}}
19395 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
19396 both conditions must be met if not optional. Care must be taken if wildcards
19397 are used in both a prefix and a suffix on the same router. Different
19398 separator characters must be used to avoid ambiguity.
19401 .option local_part_prefix_optional routers boolean false
19402 See &%local_part_prefix%& above.
19406 .option local_part_suffix routers&!? "string list" unset
19407 .cindex "router" "suffix for local part"
19408 .cindex "suffix for local part" "used in router"
19409 This option operates in the same way as &%local_part_prefix%&, except that the
19410 local part must end (rather than start) with the given string, the
19411 &%local_part_suffix_optional%& option determines whether the suffix is
19412 mandatory, and the wildcard * character, if present, must be the last
19413 character of the suffix. This option facility is commonly used to handle local
19414 parts of the form &%something-request%& and multiple user mailboxes of the form
19418 .option local_part_suffix_optional routers boolean false
19419 See &%local_part_suffix%& above.
19423 .option local_parts routers&!? "local part list&!!" unset
19424 .cindex "router" "restricting to specific local parts"
19425 .cindex "local part" "checking in router"
19426 The router is run only if the local part of the address matches the list.
19427 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19429 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
19430 string is expanded, it is possible to make it depend on the domain, for
19433 local_parts = dbm;/usr/local/specials/$domain_data
19435 .vindex "&$local_part_data$&"
19436 If the match is achieved by a lookup, the data that the lookup returned
19437 for the local part is placed in the variable &$local_part_data$& for use in
19438 expansions of the router's private options or in the transport.
19439 You might use this option, for
19440 example, if you have a large number of local virtual domains, and you want to
19441 send all postmaster mail to the same place without having to set up an alias in
19442 each virtual domain:
19446 local_parts = postmaster
19447 data = postmaster@real.domain.example
19451 .option log_as_local routers boolean "see below"
19452 .cindex "log" "delivery line"
19453 .cindex "delivery" "log line format"
19454 Exim has two logging styles for delivery, the idea being to make local
19455 deliveries stand out more visibly from remote ones. In the &"local"& style, the
19456 recipient address is given just as the local part, without a domain. The use of
19457 this style is controlled by this option. It defaults to true for the &(accept)&
19458 router, and false for all the others. This option applies only when a
19459 router assigns an address to a transport. It has no effect on routers that
19460 redirect addresses.
19464 .option more routers boolean&!! true
19465 The result of string expansion for this option must be a valid boolean value,
19466 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19467 result causes an error, and delivery is deferred. If the expansion is forced to
19468 fail, the default value for the option (true) is used. Other failures cause
19469 delivery to be deferred.
19471 If this option is set false, and the router declines to handle the address, no
19472 further routers are tried, routing fails, and the address is bounced.
19474 However, if the router explicitly passes an address to the following router by
19475 means of the setting
19479 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
19480 does not affect the behaviour if one of the precondition tests fails. In that
19481 case, the address is always passed to the next router.
19483 Note that &%address_data%& is not considered to be a precondition. If its
19484 expansion is forced to fail, the router declines, and the value of &%more%&
19485 controls what happens next.
19488 .option pass_on_timeout routers boolean false
19489 .cindex "timeout" "of router"
19490 .cindex "router" "timeout"
19491 If a router times out during a host lookup, it normally causes deferral of the
19492 address. If &%pass_on_timeout%& is set, the address is passed on to the next
19493 router, overriding &%no_more%&. This may be helpful for systems that are
19494 intermittently connected to the Internet, or those that want to pass to a smart
19495 host any messages that cannot immediately be delivered.
19497 There are occasional other temporary errors that can occur while doing DNS
19498 lookups. They are treated in the same way as a timeout, and this option
19499 applies to all of them.
19503 .option pass_router routers string unset
19504 .cindex "router" "go to after &""pass""&"
19505 Routers that recognize the generic &%self%& option (&(dnslookup)&,
19506 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
19507 routing to continue, and overriding a false setting of &%more%&. When one of
19508 these routers returns &"pass"&, the address is normally handed on to the next
19509 router in sequence. This can be changed by setting &%pass_router%& to the name
19510 of another router. However (unlike &%redirect_router%&) the named router must
19511 be below the current router, to avoid loops. Note that this option applies only
19512 to the special case of &"pass"&. It does not apply when a router returns
19513 &"decline"& because it cannot handle an address.
19517 .option redirect_router routers string unset
19518 .cindex "router" "start at after redirection"
19519 Sometimes an administrator knows that it is pointless to reprocess addresses
19520 generated from alias or forward files with the same router again. For
19521 example, if an alias file translates real names into login ids there is no
19522 point searching the alias file a second time, especially if it is a large file.
19524 The &%redirect_router%& option can be set to the name of any router instance.
19525 It causes the routing of any generated addresses to start at the named router
19526 instead of at the first router. This option has no effect if the router in
19527 which it is set does not generate new addresses.
19531 .option require_files routers&!? "string list&!!" unset
19532 .cindex "file" "requiring for router"
19533 .cindex "router" "requiring file existence"
19534 This option provides a general mechanism for predicating the running of a
19535 router on the existence or non-existence of certain files or directories.
19536 Before running a router, as one of its precondition tests, Exim works its way
19537 through the &%require_files%& list, expanding each item separately.
19539 Because the list is split before expansion, any colons in expansion items must
19540 be doubled, or the facility for using a different list separator must be used
19541 (&<<SECTlistsepchange>>&).
19542 If any expansion is forced to fail, the item is ignored. Other expansion
19543 failures cause routing of the address to be deferred.
19545 If any expanded string is empty, it is ignored. Otherwise, except as described
19546 below, each string must be a fully qualified file path, optionally preceded by
19547 &"!"&. The paths are passed to the &[stat()]& function to test for the
19548 existence of the files or directories. The router is skipped if any paths not
19549 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
19552 If &[stat()]& cannot determine whether a file exists or not, delivery of
19553 the message is deferred. This can happen when NFS-mounted filesystems are
19556 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
19557 options, so you cannot use it to check for the existence of a file in which to
19558 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
19559 full list of the order in which preconditions are evaluated.) However, as
19560 these options are all expanded, you can use the &%exists%& expansion condition
19561 to make such tests. The &%require_files%& option is intended for checking files
19562 that the router may be going to use internally, or which are needed by a
19563 transport (e.g., &_.procmailrc_&).
19565 During delivery, the &[stat()]& function is run as root, but there is a
19566 facility for some checking of the accessibility of a file by another user.
19567 This is not a proper permissions check, but just a &"rough"& check that
19568 operates as follows:
19570 If an item in a &%require_files%& list does not contain any forward slash
19571 characters, it is taken to be the user (and optional group, separated by a
19572 comma) to be checked for subsequent files in the list. If no group is specified
19573 but the user is specified symbolically, the gid associated with the uid is
19576 require_files = mail:/some/file
19577 require_files = $local_part_data:$home/.procmailrc
19579 If a user or group name in a &%require_files%& list does not exist, the
19580 &%require_files%& condition fails.
19582 Exim performs the check by scanning along the components of the file path, and
19583 checking the access for the given uid and gid. It checks for &"x"& access on
19584 directories, and &"r"& access on the final file. Note that this means that file
19585 access control lists, if the operating system has them, are ignored.
19587 &*Warning 1*&: When the router is being run to verify addresses for an
19588 incoming SMTP message, Exim is not running as root, but under its own uid. This
19589 may affect the result of a &%require_files%& check. In particular, &[stat()]&
19590 may yield the error EACCES (&"Permission denied"&). This means that the Exim
19591 user is not permitted to read one of the directories on the file's path.
19593 &*Warning 2*&: Even when Exim is running as root while delivering a message,
19594 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
19595 without root access. In this case, if a check for access by a particular user
19596 is requested, Exim creates a subprocess that runs as that user, and tries the
19597 check again in that process.
19599 The default action for handling an unresolved EACCES is to consider it to
19600 be caused by a configuration error, and routing is deferred because the
19601 existence or non-existence of the file cannot be determined. However, in some
19602 circumstances it may be desirable to treat this condition as if the file did
19603 not exist. If the filename (or the exclamation mark that precedes the filename
19604 for non-existence) is preceded by a plus sign, the EACCES error is treated
19605 as if the file did not exist. For example:
19607 require_files = +/some/file
19609 If the router is not an essential part of verification (for example, it
19610 handles users' &_.forward_& files), another solution is to set the &%verify%&
19611 option false so that the router is skipped when verifying.
19615 .option retry_use_local_part routers boolean "see below"
19616 .cindex "hints database" "retry keys"
19617 .cindex "local part" "in retry keys"
19618 When a delivery suffers a temporary routing failure, a retry record is created
19619 in Exim's hints database. For addresses whose routing depends only on the
19620 domain, the key for the retry record should not involve the local part, but for
19621 other addresses, both the domain and the local part should be included.
19622 Usually, remote routing is of the former kind, and local routing is of the
19625 This option controls whether the local part is used to form the key for retry
19626 hints for addresses that suffer temporary errors while being handled by this
19627 router. The default value is true for any router that has any of
19628 &%check_local_user%&,
19631 &%local_part_prefix%&,
19632 &%local_part_suffix%&,
19635 set, and false otherwise. Note that this option does not apply to hints keys
19636 for transport delays; they are controlled by a generic transport option of the
19639 Failing to set this option when it is needed
19640 (because a remote router handles only some of the local-parts for a domain)
19641 can result in incorrect error messages being generated.
19643 The setting of &%retry_use_local_part%& applies only to the router on which it
19644 appears. If the router generates child addresses, they are routed
19645 independently; this setting does not become attached to them.
19649 .option router_home_directory routers string&!! unset
19650 .cindex "router" "home directory for"
19651 .cindex "home directory" "for router"
19653 This option sets a home directory for use while the router is running. (Compare
19654 &%transport_home_directory%&, which sets a home directory for later
19655 transporting.) In particular, if used on a &(redirect)& router, this option
19656 sets a value for &$home$& while a filter is running. The value is expanded;
19657 forced expansion failure causes the option to be ignored &-- other failures
19658 cause the router to defer.
19660 Expansion of &%router_home_directory%& happens immediately after the
19661 &%check_local_user%& test (if configured), before any further expansions take
19663 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19665 While the router is running, &%router_home_directory%& overrides the value of
19666 &$home$& that came from &%check_local_user%&.
19668 When a router accepts an address and assigns it to a local transport (including
19669 the cases when a &(redirect)& router generates a pipe, file, or autoreply
19670 delivery), the home directory setting for the transport is taken from the first
19671 of these values that is set:
19674 The &%home_directory%& option on the transport;
19676 The &%transport_home_directory%& option on the router;
19678 The password data if &%check_local_user%& is set on the router;
19680 The &%router_home_directory%& option on the router.
19683 In other words, &%router_home_directory%& overrides the password data for the
19684 router, but not for the transport.
19688 .option self routers string freeze
19689 .cindex "MX record" "pointing to local host"
19690 .cindex "local host" "MX pointing to"
19691 This option applies to those routers that use a recipient address to find a
19692 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
19693 and &(manualroute)& routers.
19694 Certain configurations of the &(queryprogram)& router can also specify a list
19696 Usually such routers are configured to send the message to a remote host via an
19697 &(smtp)& transport. The &%self%& option specifies what happens when the first
19698 host on the list turns out to be the local host.
19699 The way in which Exim checks for the local host is described in section
19700 &<<SECTreclocipadd>>&.
19702 Normally this situation indicates either an error in Exim's configuration (for
19703 example, the router should be configured not to process this domain), or an
19704 error in the DNS (for example, the MX should not point to this host). For this
19705 reason, the default action is to log the incident, defer the address, and
19706 freeze the message. The following alternatives are provided for use in special
19711 Delivery of the message is tried again later, but the message is not frozen.
19713 .vitem "&%reroute%&: <&'domain'&>"
19714 The domain is changed to the given domain, and the address is passed back to
19715 be reprocessed by the routers. No rewriting of headers takes place. This
19716 behaviour is essentially a redirection.
19718 .vitem "&%reroute: rewrite:%& <&'domain'&>"
19719 The domain is changed to the given domain, and the address is passed back to be
19720 reprocessed by the routers. Any headers that contain the original domain are
19725 .vindex "&$self_hostname$&"
19726 The router passes the address to the next router, or to the router named in the
19727 &%pass_router%& option if it is set. This overrides &%no_more%&. During
19728 subsequent routing and delivery, the variable &$self_hostname$& contains the
19729 name of the local host that the router encountered. This can be used to
19730 distinguish between different cases for hosts with multiple names. The
19736 ensures that only those addresses that routed to the local host are passed on.
19737 Without &%no_more%&, addresses that were declined for other reasons would also
19738 be passed to the next router.
19741 Delivery fails and an error report is generated.
19744 .cindex "local host" "sending to"
19745 The anomaly is ignored and the address is queued for the transport. This
19746 setting should be used with extreme caution. For an &(smtp)& transport, it
19747 makes sense only in cases where the program that is listening on the SMTP port
19748 is not this version of Exim. That is, it must be some other MTA, or Exim with a
19749 different configuration file that handles the domain in another way.
19754 .option senders routers&!? "address list&!!" unset
19755 .cindex "router" "checking senders"
19756 If this option is set, the router is skipped unless the message's sender
19757 address matches something on the list.
19758 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19761 There are issues concerning verification when the running of routers is
19762 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
19763 setting, it sets the sender to the null string. When using the &%-bt%& option
19764 to check a configuration file, it is necessary also to use the &%-f%& option to
19765 set an appropriate sender. For incoming mail, the sender is unset when
19766 verifying the sender, but is available when verifying any recipients. If the
19767 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
19771 .option set routers "string list" unset
19772 .cindex router variables
19773 This option may be used multiple times on a router;
19774 because of this the list aspect is mostly irrelevant.
19775 The list separator is a semicolon but can be changed in the
19778 Each list-element given must be of the form &"name = value"&
19779 and the names used must start with the string &"r_"&.
19780 Values containing a list-separator should have them doubled.
19781 When a router runs, the strings are evaluated in order,
19782 to create variables which are added to the set associated with
19785 This is done immediately after all the preconditions, before the
19786 evaluation of the &%address_data%& option.
19788 The variable is set with the expansion of the value.
19789 The variables can be used by the router options
19790 (not including any preconditions)
19791 and by the transport.
19792 Later definitions of a given named variable will override former ones.
19793 Variable use is via the usual &$r_...$& syntax.
19795 This is similar to the &%address_data%& option, except that
19796 many independent variables can be used, with choice of naming.
19799 .option translate_ip_address routers string&!! unset
19800 .cindex "IP address" "translating"
19801 .cindex "packet radio"
19802 .cindex "router" "IP address translation"
19803 There exist some rare networking situations (for example, packet radio) where
19804 it is helpful to be able to translate IP addresses generated by normal routing
19805 mechanisms into other IP addresses, thus performing a kind of manual IP
19806 routing. This should be done only if the normal IP routing of the TCP/IP stack
19807 is inadequate or broken. Because this is an extremely uncommon requirement, the
19808 code to support this option is not included in the Exim binary unless
19809 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
19811 .vindex "&$host_address$&"
19812 The &%translate_ip_address%& string is expanded for every IP address generated
19813 by the router, with the generated address set in &$host_address$&. If the
19814 expansion is forced to fail, no action is taken.
19815 For any other expansion error, delivery of the message is deferred.
19816 If the result of the expansion is an IP address, that replaces the original
19817 address; otherwise the result is assumed to be a host name &-- this is looked
19818 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
19819 produce one or more replacement IP addresses. For example, to subvert all IP
19820 addresses in some specific networks, this could be added to a router:
19822 translate_ip_address = \
19823 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
19826 The file would contain lines like
19828 10.2.3.128/26 some.host
19829 10.8.4.34/26 10.44.8.15
19831 You should not make use of this facility unless you really understand what you
19836 .option transport routers string&!! unset
19837 This option specifies the transport to be used when a router accepts an address
19838 and sets it up for delivery. A transport is never needed if a router is used
19839 only for verification. The value of the option is expanded at routing time,
19840 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
19841 and result must be the name of one of the configured transports. If it is not,
19842 delivery is deferred.
19844 The &%transport%& option is not used by the &(redirect)& router, but it does
19845 have some private options that set up transports for pipe and file deliveries
19846 (see chapter &<<CHAPredirect>>&).
19850 .option transport_current_directory routers string&!! unset
19851 .cindex "current directory for local transport"
19852 This option associates a current directory with any address that is routed
19853 to a local transport. This can happen either because a transport is
19854 explicitly configured for the router, or because it generates a delivery to a
19855 file or a pipe. During the delivery process (that is, at transport time), this
19856 option string is expanded and is set as the current directory, unless
19857 overridden by a setting on the transport.
19858 If the expansion fails for any reason, including forced failure, an error is
19859 logged, and delivery is deferred.
19860 See chapter &<<CHAPenvironment>>& for details of the local delivery
19866 .option transport_home_directory routers string&!! "see below"
19867 .cindex "home directory" "for local transport"
19868 This option associates a home directory with any address that is routed to a
19869 local transport. This can happen either because a transport is explicitly
19870 configured for the router, or because it generates a delivery to a file or a
19871 pipe. During the delivery process (that is, at transport time), the option
19872 string is expanded and is set as the home directory, unless overridden by a
19873 setting of &%home_directory%& on the transport.
19874 If the expansion fails for any reason, including forced failure, an error is
19875 logged, and delivery is deferred.
19877 If the transport does not specify a home directory, and
19878 &%transport_home_directory%& is not set for the router, the home directory for
19879 the transport is taken from the password data if &%check_local_user%& is set for
19880 the router. Otherwise it is taken from &%router_home_directory%& if that option
19881 is set; if not, no home directory is set for the transport.
19883 See chapter &<<CHAPenvironment>>& for further details of the local delivery
19889 .option unseen routers boolean&!! false
19890 .cindex "router" "carrying on after success"
19891 The result of string expansion for this option must be a valid boolean value,
19892 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19893 result causes an error, and delivery is deferred. If the expansion is forced to
19894 fail, the default value for the option (false) is used. Other failures cause
19895 delivery to be deferred.
19897 When this option is set true, routing does not cease if the router accepts the
19898 address. Instead, a copy of the incoming address is passed to the next router,
19899 overriding a false setting of &%more%&. There is little point in setting
19900 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
19901 the value of &%unseen%& contains expansion items (and therefore, presumably, is
19902 sometimes true and sometimes false).
19904 .cindex "copy of message (&%unseen%& option)"
19905 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
19906 qualifier in filter files. It can be used to cause copies of messages to be
19907 delivered to some other destination, while also carrying out a normal delivery.
19908 In effect, the current address is made into a &"parent"& that has two children
19909 &-- one that is delivered as specified by this router, and a clone that goes on
19910 to be routed further. For this reason, &%unseen%& may not be combined with the
19911 &%one_time%& option in a &(redirect)& router.
19913 &*Warning*&: Header lines added to the address (or specified for removal) by
19914 this router or by previous routers affect the &"unseen"& copy of the message
19915 only. The clone that continues to be processed by further routers starts with
19916 no added headers and none specified for removal. For a &%redirect%& router, if
19917 a generated address is the same as the incoming address, this can lead to
19918 duplicate addresses with different header modifications. Exim does not do
19919 duplicate deliveries (except, in certain circumstances, to pipes -- see section
19920 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
19921 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
19922 &%redirect%& router may be of help.
19924 Unlike the handling of header modifications, any data that was set by the
19925 &%address_data%& option in the current or previous routers &'is'& passed on to
19926 subsequent routers.
19929 .option user routers string&!! "see below"
19930 .cindex "uid (user id)" "local delivery"
19931 .cindex "local transports" "uid and gid"
19932 .cindex "transport" "local"
19933 .cindex "router" "user for filter processing"
19934 .cindex "filter" "user for processing"
19935 When a router queues an address for a transport, and the transport does not
19936 specify a user, the user given here is used when running the delivery process.
19937 The user may be specified numerically or by name. If expansion fails, the
19938 error is logged and delivery is deferred.
19939 This user is also used by the &(redirect)& router when running a filter file.
19940 The default is unset, except when &%check_local_user%& is set. In this case,
19941 the default is taken from the password information. If the user is specified as
19942 a name, and &%group%& is not set, the group associated with the user is used.
19943 See also &%initgroups%& and &%group%& and the discussion in chapter
19944 &<<CHAPenvironment>>&.
19948 .option verify routers&!? boolean true
19949 Setting this option has the effect of setting &%verify_sender%& and
19950 &%verify_recipient%& to the same value.
19953 .option verify_only routers&!? boolean false
19954 .cindex "EXPN" "with &%verify_only%&"
19956 .cindex "router" "used only when verifying"
19957 If this option is set, the router is used only when verifying an address,
19958 delivering in cutthrough mode or
19959 testing with the &%-bv%& option, not when actually doing a delivery, testing
19960 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
19961 restricted to verifying only senders or recipients by means of
19962 &%verify_sender%& and &%verify_recipient%&.
19964 &*Warning*&: When the router is being run to verify addresses for an incoming
19965 SMTP message, Exim is not running as root, but under its own uid. If the router
19966 accesses any files, you need to make sure that they are accessible to the Exim
19970 .option verify_recipient routers&!? boolean true
19971 If this option is false, the router is skipped when verifying recipient
19973 delivering in cutthrough mode
19974 or testing recipient verification using &%-bv%&.
19975 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19977 See also the &$verify_mode$& variable.
19980 .option verify_sender routers&!? boolean true
19981 If this option is false, the router is skipped when verifying sender addresses
19982 or testing sender verification using &%-bvs%&.
19983 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19985 See also the &$verify_mode$& variable.
19986 .ecindex IIDgenoprou1
19987 .ecindex IIDgenoprou2
19994 . ////////////////////////////////////////////////////////////////////////////
19995 . ////////////////////////////////////////////////////////////////////////////
19997 .chapter "The accept router" "CHID4"
19998 .cindex "&(accept)& router"
19999 .cindex "routers" "&(accept)&"
20000 The &(accept)& router has no private options of its own. Unless it is being
20001 used purely for verification (see &%verify_only%&) a transport is required to
20002 be defined by the generic &%transport%& option. If the preconditions that are
20003 specified by generic options are met, the router accepts the address and queues
20004 it for the given transport. The most common use of this router is for setting
20005 up deliveries to local mailboxes. For example:
20009 domains = mydomain.example
20011 transport = local_delivery
20013 The &%domains%& condition in this example checks the domain of the address, and
20014 &%check_local_user%& checks that the local part is the login of a local user.
20015 When both preconditions are met, the &(accept)& router runs, and queues the
20016 address for the &(local_delivery)& transport.
20023 . ////////////////////////////////////////////////////////////////////////////
20024 . ////////////////////////////////////////////////////////////////////////////
20026 .chapter "The dnslookup router" "CHAPdnslookup"
20027 .scindex IIDdnsrou1 "&(dnslookup)& router"
20028 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
20029 The &(dnslookup)& router looks up the hosts that handle mail for the
20030 recipient's domain in the DNS. A transport must always be set for this router,
20031 unless &%verify_only%& is set.
20033 If SRV support is configured (see &%check_srv%& below), Exim first searches for
20034 SRV records. If none are found, or if SRV support is not configured,
20035 MX records are looked up. If no MX records exist, address records are sought.
20036 However, &%mx_domains%& can be set to disable the direct use of address
20039 MX records of equal priority are sorted by Exim into a random order. Exim then
20040 looks for address records for the host names obtained from MX or SRV records.
20041 When a host has more than one IP address, they are sorted into a random order,
20042 except that IPv6 addresses are sorted before IPv4 addresses. If all the
20043 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
20044 generic option, the router declines.
20046 Unless they have the highest priority (lowest MX value), MX records that point
20047 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
20048 are discarded, together with any other MX records of equal or lower priority.
20050 .cindex "MX record" "pointing to local host"
20051 .cindex "local host" "MX pointing to"
20052 .oindex "&%self%&" "in &(dnslookup)& router"
20053 If the host pointed to by the highest priority MX record, or looked up as an
20054 address record, is the local host, or matches &%hosts_treat_as_local%&, what
20055 happens is controlled by the generic &%self%& option.
20058 .section "Problems with DNS lookups" "SECTprowitdnsloo"
20059 There have been problems with DNS servers when SRV records are looked up.
20060 Some misbehaving servers return a DNS error or timeout when a non-existent
20061 SRV record is sought. Similar problems have in the past been reported for
20062 MX records. The global &%dns_again_means_nonexist%& option can help with this
20063 problem, but it is heavy-handed because it is a global option.
20065 For this reason, there are two options, &%srv_fail_domains%& and
20066 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
20067 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
20068 an attempt to look up an SRV or MX record causes one of these results, and the
20069 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
20070 such record"&. In the case of an SRV lookup, this means that the router
20071 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
20072 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
20073 case routing fails.
20076 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
20077 .cindex "&(dnslookup)& router" "declines"
20078 There are a few cases where a &(dnslookup)& router will decline to accept
20079 an address; if such a router is expected to handle "all remaining non-local
20080 domains", then it is important to set &%no_more%&.
20082 The router will defer rather than decline if the domain
20083 is found in the &%fail_defer_domains%& router option.
20085 Reasons for a &(dnslookup)& router to decline currently include:
20087 The domain does not exist in DNS
20089 The domain exists but the MX record's host part is just "."; this is a common
20090 convention (borrowed from SRV) used to indicate that there is no such service
20091 for this domain and to not fall back to trying A/AAAA records.
20093 Ditto, but for SRV records, when &%check_srv%& is set on this router.
20095 MX record points to a non-existent host.
20097 MX record points to an IP address and the main section option
20098 &%allow_mx_to_ip%& is not set.
20100 MX records exist and point to valid hosts, but all hosts resolve only to
20101 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
20103 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
20104 &%dns_check_names_pattern%& for handling one variant of this)
20106 &%check_secondary_mx%& is set on this router but the local host can
20107 not be found in the MX records (see below)
20113 .section "Private options for dnslookup" "SECID118"
20114 .cindex "options" "&(dnslookup)& router"
20115 The private options for the &(dnslookup)& router are as follows:
20117 .option check_secondary_mx dnslookup boolean false
20118 .cindex "MX record" "checking for secondary"
20119 If this option is set, the router declines unless the local host is found in
20120 (and removed from) the list of hosts obtained by MX lookup. This can be used to
20121 process domains for which the local host is a secondary mail exchanger
20122 differently to other domains. The way in which Exim decides whether a host is
20123 the local host is described in section &<<SECTreclocipadd>>&.
20126 .option check_srv dnslookup string&!! unset
20127 .cindex "SRV record" "enabling use of"
20128 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
20129 addition to MX and address records. The support is disabled by default. To
20130 enable SRV support, set the &%check_srv%& option to the name of the service
20131 required. For example,
20135 looks for SRV records that refer to the normal smtp service. The option is
20136 expanded, so the service name can vary from message to message or address
20137 to address. This might be helpful if SRV records are being used for a
20138 submission service. If the expansion is forced to fail, the &%check_srv%&
20139 option is ignored, and the router proceeds to look for MX records in the
20142 When the expansion succeeds, the router searches first for SRV records for
20143 the given service (it assumes TCP protocol). A single SRV record with a
20144 host name that consists of just a single dot indicates &"no such service for
20145 this domain"&; if this is encountered, the router declines. If other kinds of
20146 SRV record are found, they are used to construct a host list for delivery
20147 according to the rules of RFC 2782. MX records are not sought in this case.
20149 When no SRV records are found, MX records (and address records) are sought in
20150 the traditional way. In other words, SRV records take precedence over MX
20151 records, just as MX records take precedence over address records. Note that
20152 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
20153 defined it. It is apparently believed that MX records are sufficient for email
20154 and that SRV records should not be used for this purpose. However, SRV records
20155 have an additional &"weight"& feature which some people might find useful when
20156 trying to split an SMTP load between hosts of different power.
20158 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
20159 when there is a DNS lookup error.
20164 .option fail_defer_domains dnslookup "domain list&!!" unset
20165 .cindex "MX record" "not found"
20166 DNS lookups for domains matching &%fail_defer_domains%&
20167 which find no matching record will cause the router to defer
20168 rather than the default behaviour of decline.
20169 This maybe be useful for queueing messages for a newly created
20170 domain while the DNS configuration is not ready.
20171 However, it will result in any message with mistyped domains
20175 .option ipv4_only "string&!!" unset
20176 .cindex IPv6 disabling
20177 .cindex DNS "IPv6 disabling"
20178 The string is expanded, and if the result is anything but a forced failure,
20179 or an empty string, or one of the strings “0” or “no” or “false”
20180 (checked without regard to the case of the letters),
20181 only A records are used.
20183 .option ipv4_prefer "string&!!" unset
20184 .cindex IPv4 preference
20185 .cindex DNS "IPv4 preference"
20186 The string is expanded, and if the result is anything but a forced failure,
20187 or an empty string, or one of the strings “0” or “no” or “false”
20188 (checked without regard to the case of the letters),
20189 A records are sorted before AAAA records (inverting the default).
20191 .option mx_domains dnslookup "domain list&!!" unset
20192 .cindex "MX record" "required to exist"
20193 .cindex "SRV record" "required to exist"
20194 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
20195 record in order to be recognized. (The name of this option could be improved.)
20196 For example, if all the mail hosts in &'fict.example'& are known to have MX
20197 records, except for those in &'discworld.fict.example'&, you could use this
20200 mx_domains = ! *.discworld.fict.example : *.fict.example
20202 This specifies that messages addressed to a domain that matches the list but
20203 has no MX record should be bounced immediately instead of being routed using
20204 the address record.
20207 .option mx_fail_domains dnslookup "domain list&!!" unset
20208 If the DNS lookup for MX records for one of the domains in this list causes a
20209 DNS lookup error, Exim behaves as if no MX records were found. See section
20210 &<<SECTprowitdnsloo>>& for more discussion.
20215 .option qualify_single dnslookup boolean true
20216 .cindex "DNS" "resolver options"
20217 .cindex "DNS" "qualifying single-component names"
20218 When this option is true, the resolver option RES_DEFNAMES is set for DNS
20219 lookups. Typically, but not standardly, this causes the resolver to qualify
20220 single-component names with the default domain. For example, on a machine
20221 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
20222 &'thesaurus.ref.example'& inside the resolver. For details of what your
20223 resolver actually does, consult your man pages for &'resolver'& and
20228 .option rewrite_headers dnslookup boolean true
20229 .cindex "rewriting" "header lines"
20230 .cindex "header lines" "rewriting"
20231 If the domain name in the address that is being processed is not fully
20232 qualified, it may be expanded to its full form by a DNS lookup. For example, if
20233 an address is specified as &'dormouse@teaparty'&, the domain might be
20234 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
20235 occur as a result of setting the &%widen_domains%& option. If
20236 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
20237 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
20238 header lines of the message are rewritten with the full domain name.
20240 This option should be turned off only when it is known that no message is
20241 ever going to be sent outside an environment where the abbreviation makes
20244 When an MX record is looked up in the DNS and matches a wildcard record, name
20245 servers normally return a record containing the name that has been looked up,
20246 making it impossible to detect whether a wildcard was present or not. However,
20247 some name servers have recently been seen to return the wildcard entry. If the
20248 name returned by a DNS lookup begins with an asterisk, it is not used for
20252 .option same_domain_copy_routing dnslookup boolean false
20253 .cindex "address" "copying routing"
20254 Addresses with the same domain are normally routed by the &(dnslookup)& router
20255 to the same list of hosts. However, this cannot be presumed, because the router
20256 options and preconditions may refer to the local part of the address. By
20257 default, therefore, Exim routes each address in a message independently. DNS
20258 servers run caches, so repeated DNS lookups are not normally expensive, and in
20259 any case, personal messages rarely have more than a few recipients.
20261 If you are running mailing lists with large numbers of subscribers at the same
20262 domain, and you are using a &(dnslookup)& router which is independent of the
20263 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20264 lookups for identical domains in one message. In this case, when &(dnslookup)&
20265 routes an address to a remote transport, any other unrouted addresses in the
20266 message that have the same domain are automatically given the same routing
20267 without processing them independently,
20268 provided the following conditions are met:
20271 No router that processed the address specified &%headers_add%& or
20272 &%headers_remove%&.
20274 The router did not change the address in any way, for example, by &"widening"&
20281 .option search_parents dnslookup boolean false
20282 .cindex "DNS" "resolver options"
20283 When this option is true, the resolver option RES_DNSRCH is set for DNS
20284 lookups. This is different from the &%qualify_single%& option in that it
20285 applies to domains containing dots. Typically, but not standardly, it causes
20286 the resolver to search for the name in the current domain and in parent
20287 domains. For example, on a machine in the &'fict.example'& domain, if looking
20288 up &'teaparty.wonderland'& failed, the resolver would try
20289 &'teaparty.wonderland.fict.example'&. For details of what your resolver
20290 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
20292 Setting this option true can cause problems in domains that have a wildcard MX
20293 record, because any domain that does not have its own MX record matches the
20298 .option srv_fail_domains dnslookup "domain list&!!" unset
20299 If the DNS lookup for SRV records for one of the domains in this list causes a
20300 DNS lookup error, Exim behaves as if no SRV records were found. See section
20301 &<<SECTprowitdnsloo>>& for more discussion.
20306 .option widen_domains dnslookup "string list" unset
20307 .cindex "domain" "partial; widening"
20308 If a DNS lookup fails and this option is set, each of its strings in turn is
20309 added onto the end of the domain, and the lookup is tried again. For example,
20312 widen_domains = fict.example:ref.example
20314 is set and a lookup of &'klingon.dictionary'& fails,
20315 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
20316 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
20317 and &%search_parents%& options can cause some widening to be undertaken inside
20318 the DNS resolver. &%widen_domains%& is not applied to sender addresses
20319 when verifying, unless &%rewrite_headers%& is false (not the default).
20322 .section "Effect of qualify_single and search_parents" "SECID119"
20323 When a domain from an envelope recipient is changed by the resolver as a result
20324 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
20325 corresponding address in the message's header lines unless &%rewrite_headers%&
20326 is set false. Exim then re-routes the address, using the full domain.
20328 These two options affect only the DNS lookup that takes place inside the router
20329 for the domain of the address that is being routed. They do not affect lookups
20330 such as that implied by
20334 that may happen while processing a router precondition before the router is
20335 entered. No widening ever takes place for these lookups.
20336 .ecindex IIDdnsrou1
20337 .ecindex IIDdnsrou2
20347 . ////////////////////////////////////////////////////////////////////////////
20348 . ////////////////////////////////////////////////////////////////////////////
20350 .chapter "The ipliteral router" "CHID5"
20351 .cindex "&(ipliteral)& router"
20352 .cindex "domain literal" "routing"
20353 .cindex "routers" "&(ipliteral)&"
20354 This router has no private options. Unless it is being used purely for
20355 verification (see &%verify_only%&) a transport is required to be defined by the
20356 generic &%transport%& option. The router accepts the address if its domain part
20357 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
20358 router handles the address
20362 by setting up delivery to the host with that IP address. IPv4 domain literals
20363 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
20364 are similar, but the address is preceded by &`ipv6:`&. For example:
20366 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
20368 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
20369 grounds that sooner or later somebody will try it.
20371 .oindex "&%self%&" "in &(ipliteral)& router"
20372 If the IP address matches something in &%ignore_target_hosts%&, the router
20373 declines. If an IP literal turns out to refer to the local host, the generic
20374 &%self%& option determines what happens.
20376 The RFCs require support for domain literals; however, their use is
20377 controversial in today's Internet. If you want to use this router, you must
20378 also set the main configuration option &%allow_domain_literals%&. Otherwise,
20379 Exim will not recognize the domain literal syntax in addresses.
20383 . ////////////////////////////////////////////////////////////////////////////
20384 . ////////////////////////////////////////////////////////////////////////////
20386 .chapter "The iplookup router" "CHID6"
20387 .cindex "&(iplookup)& router"
20388 .cindex "routers" "&(iplookup)&"
20389 The &(iplookup)& router was written to fulfil a specific requirement in
20390 Cambridge University (which in fact no longer exists). For this reason, it is
20391 not included in the binary of Exim by default. If you want to include it, you
20394 ROUTER_IPLOOKUP=yes
20396 in your &_Local/Makefile_& configuration file.
20398 The &(iplookup)& router routes an address by sending it over a TCP or UDP
20399 connection to one or more specific hosts. The host can then return the same or
20400 a different address &-- in effect rewriting the recipient address in the
20401 message's envelope. The new address is then passed on to subsequent routers. If
20402 this process fails, the address can be passed on to other routers, or delivery
20403 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
20404 must not be specified for it.
20406 .cindex "options" "&(iplookup)& router"
20407 .option hosts iplookup string unset
20408 This option must be supplied. Its value is a colon-separated list of host
20409 names. The hosts are looked up using &[gethostbyname()]&
20410 (or &[getipnodebyname()]& when available)
20411 and are tried in order until one responds to the query. If none respond, what
20412 happens is controlled by &%optional%&.
20415 .option optional iplookup boolean false
20416 If &%optional%& is true, if no response is obtained from any host, the address
20417 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
20418 delivery to the address is deferred.
20421 .option port iplookup integer 0
20422 .cindex "port" "&(iplookup)& router"
20423 This option must be supplied. It specifies the port number for the TCP or UDP
20427 .option protocol iplookup string udp
20428 This option can be set to &"udp"& or &"tcp"& to specify which of the two
20429 protocols is to be used.
20432 .option query iplookup string&!! "see below"
20433 This defines the content of the query that is sent to the remote hosts. The
20436 $local_part@$domain $local_part@$domain
20438 The repetition serves as a way of checking that a response is to the correct
20439 query in the default case (see &%response_pattern%& below).
20442 .option reroute iplookup string&!! unset
20443 If this option is not set, the rerouted address is precisely the byte string
20444 returned by the remote host, up to the first white space, if any. If set, the
20445 string is expanded to form the rerouted address. It can include parts matched
20446 in the response by &%response_pattern%& by means of numeric variables such as
20447 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
20448 whether or not a pattern is in use. In all cases, the rerouted address must end
20449 up in the form &'local_part@domain'&.
20452 .option response_pattern iplookup string unset
20453 This option can be set to a regular expression that is applied to the string
20454 returned from the remote host. If the pattern does not match the response, the
20455 router declines. If &%response_pattern%& is not set, no checking of the
20456 response is done, unless the query was defaulted, in which case there is a
20457 check that the text returned after the first white space is the original
20458 address. This checks that the answer that has been received is in response to
20459 the correct question. For example, if the response is just a new domain, the
20460 following could be used:
20462 response_pattern = ^([^@]+)$
20463 reroute = $local_part@$1
20466 .option timeout iplookup time 5s
20467 This specifies the amount of time to wait for a response from the remote
20468 machine. The same timeout is used for the &[connect()]& function for a TCP
20469 call. It does not apply to UDP.
20474 . ////////////////////////////////////////////////////////////////////////////
20475 . ////////////////////////////////////////////////////////////////////////////
20477 .chapter "The manualroute router" "CHID7"
20478 .scindex IIDmanrou1 "&(manualroute)& router"
20479 .scindex IIDmanrou2 "routers" "&(manualroute)&"
20480 .cindex "domain" "manually routing"
20481 The &(manualroute)& router is so-called because it provides a way of manually
20482 routing an address according to its domain. It is mainly used when you want to
20483 route addresses to remote hosts according to your own rules, bypassing the
20484 normal DNS routing that looks up MX records. However, &(manualroute)& can also
20485 route to local transports, a facility that may be useful if you want to save
20486 messages for dial-in hosts in local files.
20488 The &(manualroute)& router compares a list of domain patterns with the domain
20489 it is trying to route. If there is no match, the router declines. Each pattern
20490 has associated with it a list of hosts and some other optional data, which may
20491 include a transport. The combination of a pattern and its data is called a
20492 &"routing rule"&. For patterns that do not have an associated transport, the
20493 generic &%transport%& option must specify a transport, unless the router is
20494 being used purely for verification (see &%verify_only%&).
20497 In the case of verification, matching the domain pattern is sufficient for the
20498 router to accept the address. When actually routing an address for delivery,
20499 an address that matches a domain pattern is queued for the associated
20500 transport. If the transport is not a local one, a host list must be associated
20501 with the pattern; IP addresses are looked up for the hosts, and these are
20502 passed to the transport along with the mail address. For local transports, a
20503 host list is optional. If it is present, it is passed in &$host$& as a single
20506 The list of routing rules can be provided as an inline string in
20507 &%route_list%&, or the data can be obtained by looking up the domain in a file
20508 or database by setting &%route_data%&. Only one of these settings may appear in
20509 any one instance of &(manualroute)&. The format of routing rules is described
20510 below, following the list of private options.
20513 .section "Private options for manualroute" "SECTprioptman"
20515 .cindex "options" "&(manualroute)& router"
20516 The private options for the &(manualroute)& router are as follows:
20518 .option host_all_ignored manualroute string defer
20519 See &%host_find_failed%&.
20521 .option host_find_failed manualroute string freeze
20522 This option controls what happens when &(manualroute)& tries to find an IP
20523 address for a host, and the host does not exist. The option can be set to one
20524 of the following values:
20533 The default (&"freeze"&) assumes that this state is a serious configuration
20534 error. The difference between &"pass"& and &"decline"& is that the former
20535 forces the address to be passed to the next router (or the router defined by
20538 overriding &%no_more%&, whereas the latter passes the address to the next
20539 router only if &%more%& is true.
20541 The value &"ignore"& causes Exim to completely ignore a host whose IP address
20542 cannot be found. If all the hosts in the list are ignored, the behaviour is
20543 controlled by the &%host_all_ignored%& option. This takes the same values
20544 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
20546 The &%host_find_failed%& option applies only to a definite &"does not exist"&
20547 state; if a host lookup gets a temporary error, delivery is deferred unless the
20548 generic &%pass_on_timeout%& option is set.
20551 .option hosts_randomize manualroute boolean false
20552 .cindex "randomized host list"
20553 .cindex "host" "list of; randomized"
20554 If this option is set, the order of the items in a host list in a routing rule
20555 is randomized each time the list is used, unless an option in the routing rule
20556 overrides (see below). Randomizing the order of a host list can be used to do
20557 crude load sharing. However, if more than one mail address is routed by the
20558 same router to the same host list, the host lists are considered to be the same
20559 (even though they may be randomized into different orders) for the purpose of
20560 deciding whether to batch the deliveries into a single SMTP transaction.
20562 When &%hosts_randomize%& is true, a host list may be split
20563 into groups whose order is separately randomized. This makes it possible to
20564 set up MX-like behaviour. The boundaries between groups are indicated by an
20565 item that is just &`+`& in the host list. For example:
20567 route_list = * host1:host2:host3:+:host4:host5
20569 The order of the first three hosts and the order of the last two hosts is
20570 randomized for each use, but the first three always end up before the last two.
20571 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
20572 randomized host list is passed to an &(smtp)& transport that also has
20573 &%hosts_randomize set%&, the list is not re-randomized.
20576 .option route_data manualroute string&!! unset
20577 If this option is set, it must expand to yield the data part of a routing rule.
20578 Typically, the expansion string includes a lookup based on the domain. For
20581 route_data = ${lookup{$domain}dbm{/etc/routes}}
20583 If the expansion is forced to fail, or the result is an empty string, the
20584 router declines. Other kinds of expansion failure cause delivery to be
20588 .option route_list manualroute "string list" unset
20589 This string is a list of routing rules, in the form defined below. Note that,
20590 unlike most string lists, the items are separated by semicolons. This is so
20591 that they may contain colon-separated host lists.
20594 .option same_domain_copy_routing manualroute boolean false
20595 .cindex "address" "copying routing"
20596 Addresses with the same domain are normally routed by the &(manualroute)&
20597 router to the same list of hosts. However, this cannot be presumed, because the
20598 router options and preconditions may refer to the local part of the address. By
20599 default, therefore, Exim routes each address in a message independently. DNS
20600 servers run caches, so repeated DNS lookups are not normally expensive, and in
20601 any case, personal messages rarely have more than a few recipients.
20603 If you are running mailing lists with large numbers of subscribers at the same
20604 domain, and you are using a &(manualroute)& router which is independent of the
20605 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20606 lookups for identical domains in one message. In this case, when
20607 &(manualroute)& routes an address to a remote transport, any other unrouted
20608 addresses in the message that have the same domain are automatically given the
20609 same routing without processing them independently. However, this is only done
20610 if &%headers_add%& and &%headers_remove%& are unset.
20615 .section "Routing rules in route_list" "SECID120"
20616 The value of &%route_list%& is a string consisting of a sequence of routing
20617 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
20618 entered as two semicolons. Alternatively, the list separator can be changed as
20619 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
20620 Empty rules are ignored. The format of each rule is
20622 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
20624 The following example contains two rules, each with a simple domain pattern and
20628 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
20629 thes.ref.example mail-3.ref.example:mail-4.ref.example
20631 The three parts of a rule are separated by white space. The pattern and the
20632 list of hosts can be enclosed in quotes if necessary, and if they are, the
20633 usual quoting rules apply. Each rule in a &%route_list%& must start with a
20634 single domain pattern, which is the only mandatory item in the rule. The
20635 pattern is in the same format as one item in a domain list (see section
20636 &<<SECTdomainlist>>&),
20637 except that it may not be the name of an interpolated file.
20638 That is, it may be wildcarded, or a regular expression, or a file or database
20639 lookup (with semicolons doubled, because of the use of semicolon as a separator
20640 in a &%route_list%&).
20642 The rules in &%route_list%& are searched in order until one of the patterns
20643 matches the domain that is being routed. The list of hosts and then options are
20644 then used as described below. If there is no match, the router declines. When
20645 &%route_list%& is set, &%route_data%& must not be set.
20649 .section "Routing rules in route_data" "SECID121"
20650 The use of &%route_list%& is convenient when there are only a small number of
20651 routing rules. For larger numbers, it is easier to use a file or database to
20652 hold the routing information, and use the &%route_data%& option instead.
20653 The value of &%route_data%& is a list of hosts, followed by (optional) options.
20654 Most commonly, &%route_data%& is set as a string that contains an
20655 expansion lookup. For example, suppose we place two routing rules in a file
20658 dict.ref.example: mail-1.ref.example:mail-2.ref.example
20659 thes.ref.example: mail-3.ref.example:mail-4.ref.example
20661 This data can be accessed by setting
20663 route_data = ${lookup{$domain}lsearch{/the/file/name}}
20665 Failure of the lookup results in an empty string, causing the router to
20666 decline. However, you do not have to use a lookup in &%route_data%&. The only
20667 requirement is that the result of expanding the string is a list of hosts,
20668 possibly followed by options, separated by white space. The list of hosts must
20669 be enclosed in quotes if it contains white space.
20674 .section "Format of the list of hosts" "SECID122"
20675 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
20676 always separately expanded before use. If the expansion fails, the router
20677 declines. The result of the expansion must be a colon-separated list of names
20678 and/or IP addresses, optionally also including ports.
20679 If the list is written with spaces, it must be protected with quotes.
20680 The format of each item
20681 in the list is described in the next section. The list separator can be changed
20682 as described in section &<<SECTlistsepchange>>&.
20684 If the list of hosts was obtained from a &%route_list%& item, the following
20685 variables are set during its expansion:
20688 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
20689 If the domain was matched against a regular expression, the numeric variables
20690 &$1$&, &$2$&, etc. may be set. For example:
20692 route_list = ^domain(\d+) host-$1.text.example
20695 &$0$& is always set to the entire domain.
20697 &$1$& is also set when partial matching is done in a file lookup.
20700 .vindex "&$value$&"
20701 If the pattern that matched the domain was a lookup item, the data that was
20702 looked up is available in the expansion variable &$value$&. For example:
20704 route_list = lsearch;;/some/file.routes $value
20708 Note the doubling of the semicolon in the pattern that is necessary because
20709 semicolon is the default route list separator.
20713 .section "Format of one host item" "SECTformatonehostitem"
20714 Each item in the list of hosts can be either a host name or an IP address,
20715 optionally with an attached port number, or it can be a single "+"
20716 (see &%hosts_randomize%&).
20717 When no port is given, an IP address
20718 is not enclosed in brackets. When a port is specified, it overrides the port
20719 specification on the transport. The port is separated from the name or address
20720 by a colon. This leads to some complications:
20723 Because colon is the default separator for the list of hosts, either
20724 the colon that specifies a port must be doubled, or the list separator must
20725 be changed. The following two examples have the same effect:
20727 route_list = * "host1.tld::1225 : host2.tld::1226"
20728 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
20731 When IPv6 addresses are involved, it gets worse, because they contain
20732 colons of their own. To make this case easier, it is permitted to
20733 enclose an IP address (either v4 or v6) in square brackets if a port
20734 number follows. For example:
20736 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
20740 .section "How the list of hosts is used" "SECThostshowused"
20741 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
20742 the hosts is tried, in the order specified, when carrying out the SMTP
20743 delivery. However, the order can be changed by setting the &%hosts_randomize%&
20744 option, either on the router (see section &<<SECTprioptman>>& above), or on the
20747 Hosts may be listed by name or by IP address. An unadorned name in the list of
20748 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
20749 interpreted as an indirection to a sublist of hosts obtained by looking up MX
20750 records in the DNS. For example:
20752 route_list = * x.y.z:p.q.r/MX:e.f.g
20754 If this feature is used with a port specifier, the port must come last. For
20757 route_list = * dom1.tld/mx::1225
20759 If the &%hosts_randomize%& option is set, the order of the items in the list is
20760 randomized before any lookups are done. Exim then scans the list; for any name
20761 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
20762 be an interface on the local host and the item is not the first in the list,
20763 Exim discards it and any subsequent items. If it is the first item, what
20764 happens is controlled by the
20765 .oindex "&%self%&" "in &(manualroute)& router"
20766 &%self%& option of the router.
20768 A name on the list that is followed by &`/MX`& is replaced with the list of
20769 hosts obtained by looking up MX records for the name. This is always a DNS
20770 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
20771 below) are not relevant here. The order of these hosts is determined by the
20772 preference values in the MX records, according to the usual rules. Because
20773 randomizing happens before the MX lookup, it does not affect the order that is
20774 defined by MX preferences.
20776 If the local host is present in the sublist obtained from MX records, but is
20777 not the most preferred host in that list, it and any equally or less
20778 preferred hosts are removed before the sublist is inserted into the main list.
20780 If the local host is the most preferred host in the MX list, what happens
20781 depends on where in the original list of hosts the &`/MX`& item appears. If it
20782 is not the first item (that is, there are previous hosts in the main list),
20783 Exim discards this name and any subsequent items in the main list.
20785 If the MX item is first in the list of hosts, and the local host is the
20786 most preferred host, what happens is controlled by the &%self%& option of the
20789 DNS failures when lookup up the MX records are treated in the same way as DNS
20790 failures when looking up IP addresses: &%pass_on_timeout%& and
20791 &%host_find_failed%& are used when relevant.
20793 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
20794 whether obtained from an MX lookup or not.
20798 .section "How the options are used" "SECThowoptused"
20799 The options are a sequence of words, space-separated.
20800 One of the words can be the name of a transport; this overrides the
20801 &%transport%& option on the router for this particular routing rule only. The
20802 other words (if present) control randomization of the list of hosts on a
20803 per-rule basis, and how the IP addresses of the hosts are to be found when
20804 routing to a remote transport. These options are as follows:
20807 &%randomize%&: randomize the order of the hosts in this list, overriding the
20808 setting of &%hosts_randomize%& for this routing rule only.
20810 &%no_randomize%&: do not randomize the order of the hosts in this list,
20811 overriding the setting of &%hosts_randomize%& for this routing rule only.
20813 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
20814 find IP addresses. This function may ultimately cause a DNS lookup, but it may
20815 also look in &_/etc/hosts_& or other sources of information.
20817 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
20818 no address records are found. If there is a temporary DNS error (such as a
20819 timeout), delivery is deferred.
20821 &%ipv4_only%&: in direct DNS lookups, look up only A records.
20823 &%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
20828 route_list = domain1 host1:host2:host3 randomize bydns;\
20829 domain2 host4:host5
20831 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
20832 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
20833 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
20834 or &[gethostbyname()]&, and the result of the lookup is the result of that
20837 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
20838 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
20839 instead of TRY_AGAIN. That is why the default action is to try a DNS
20840 lookup first. Only if that gives a definite &"no such host"& is the local
20843 &*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
20844 inadvertent constraint that a transport name as an option had to be the last
20849 If no IP address for a host can be found, what happens is controlled by the
20850 &%host_find_failed%& option.
20853 When an address is routed to a local transport, IP addresses are not looked up.
20854 The host list is passed to the transport in the &$host$& variable.
20858 .section "Manualroute examples" "SECID123"
20859 In some of the examples that follow, the presence of the &%remote_smtp%&
20860 transport, as defined in the default configuration file, is assumed:
20863 .cindex "smart host" "example router"
20864 The &(manualroute)& router can be used to forward all external mail to a
20865 &'smart host'&. If you have set up, in the main part of the configuration, a
20866 named domain list that contains your local domains, for example:
20868 domainlist local_domains = my.domain.example
20870 You can arrange for all other domains to be routed to a smart host by making
20871 your first router something like this:
20874 driver = manualroute
20875 domains = !+local_domains
20876 transport = remote_smtp
20877 route_list = * smarthost.ref.example
20879 This causes all non-local addresses to be sent to the single host
20880 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
20881 they are tried in order
20882 (but you can use &%hosts_randomize%& to vary the order each time).
20883 Another way of configuring the same thing is this:
20886 driver = manualroute
20887 transport = remote_smtp
20888 route_list = !+local_domains smarthost.ref.example
20890 There is no difference in behaviour between these two routers as they stand.
20891 However, they behave differently if &%no_more%& is added to them. In the first
20892 example, the router is skipped if the domain does not match the &%domains%&
20893 precondition; the following router is always tried. If the router runs, it
20894 always matches the domain and so can never decline. Therefore, &%no_more%&
20895 would have no effect. In the second case, the router is never skipped; it
20896 always runs. However, if it doesn't match the domain, it declines. In this case
20897 &%no_more%& would prevent subsequent routers from running.
20900 .cindex "mail hub example"
20901 A &'mail hub'& is a host which receives mail for a number of domains via MX
20902 records in the DNS and delivers it via its own private routing mechanism. Often
20903 the final destinations are behind a firewall, with the mail hub being the one
20904 machine that can connect to machines both inside and outside the firewall. The
20905 &(manualroute)& router is usually used on a mail hub to route incoming messages
20906 to the correct hosts. For a small number of domains, the routing can be inline,
20907 using the &%route_list%& option, but for a larger number a file or database
20908 lookup is easier to manage.
20910 If the domain names are in fact the names of the machines to which the mail is
20911 to be sent by the mail hub, the configuration can be quite simple. For
20915 driver = manualroute
20916 transport = remote_smtp
20917 route_list = *.rhodes.tvs.example $domain
20919 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
20920 whose names are the same as the mail domains. A similar approach can be taken
20921 if the host name can be obtained from the domain name by a string manipulation
20922 that the expansion facilities can handle. Otherwise, a lookup based on the
20923 domain can be used to find the host:
20926 driver = manualroute
20927 transport = remote_smtp
20928 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
20930 The result of the lookup must be the name or IP address of the host (or
20931 hosts) to which the address is to be routed. If the lookup fails, the route
20932 data is empty, causing the router to decline. The address then passes to the
20936 .cindex "batched SMTP output example"
20937 .cindex "SMTP" "batched outgoing; example"
20938 You can use &(manualroute)& to deliver messages to pipes or files in batched
20939 SMTP format for onward transportation by some other means. This is one way of
20940 storing mail for a dial-up host when it is not connected. The route list entry
20941 can be as simple as a single domain name in a configuration like this:
20944 driver = manualroute
20945 transport = batchsmtp_appendfile
20946 route_list = saved.domain.example
20948 though often a pattern is used to pick up more than one domain. If there are
20949 several domains or groups of domains with different transport requirements,
20950 different transports can be listed in the routing information:
20953 driver = manualroute
20955 *.saved.domain1.example $domain batch_appendfile; \
20956 *.saved.domain2.example \
20957 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
20960 .vindex "&$domain$&"
20962 The first of these just passes the domain in the &$host$& variable, which
20963 doesn't achieve much (since it is also in &$domain$&), but the second does a
20964 file lookup to find a value to pass, causing the router to decline to handle
20965 the address if the lookup fails.
20968 .cindex "UUCP" "example of router for"
20969 Routing mail directly to UUCP software is a specific case of the use of
20970 &(manualroute)& in a gateway to another mail environment. This is an example of
20971 one way it can be done:
20977 command = /usr/local/bin/uux -r - \
20978 ${substr_-5:$host}!rmail ${local_part}
20979 return_fail_output = true
20984 driver = manualroute
20986 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
20988 The file &_/usr/local/exim/uucphosts_& contains entries like
20990 darksite.ethereal.example: darksite.UUCP
20992 It can be set up more simply without adding and removing &".UUCP"& but this way
20993 makes clear the distinction between the domain name
20994 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
20996 .ecindex IIDmanrou1
20997 .ecindex IIDmanrou2
21006 . ////////////////////////////////////////////////////////////////////////////
21007 . ////////////////////////////////////////////////////////////////////////////
21009 .chapter "The queryprogram router" "CHAPdriverlast"
21010 .scindex IIDquerou1 "&(queryprogram)& router"
21011 .scindex IIDquerou2 "routers" "&(queryprogram)&"
21012 .cindex "routing" "by external program"
21013 The &(queryprogram)& router routes an address by running an external command
21014 and acting on its output. This is an expensive way to route, and is intended
21015 mainly for use in lightly-loaded systems, or for performing experiments.
21016 However, if it is possible to use the precondition options (&%domains%&,
21017 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
21018 be used in special cases, even on a busy host. There are the following private
21020 .cindex "options" "&(queryprogram)& router"
21022 .option command queryprogram string&!! unset
21023 This option must be set. It specifies the command that is to be run. The
21024 command is split up into a command name and arguments, and then each is
21025 expanded separately (exactly as for a &(pipe)& transport, described in chapter
21026 &<<CHAPpipetransport>>&).
21029 .option command_group queryprogram string unset
21030 .cindex "gid (group id)" "in &(queryprogram)& router"
21031 This option specifies a gid to be set when running the command while routing an
21032 address for deliver. It must be set if &%command_user%& specifies a numerical
21033 uid. If it begins with a digit, it is interpreted as the numerical value of the
21034 gid. Otherwise it is looked up using &[getgrnam()]&.
21037 .option command_user queryprogram string unset
21038 .cindex "uid (user id)" "for &(queryprogram)&"
21039 This option must be set. It specifies the uid which is set when running the
21040 command while routing an address for delivery. If the value begins with a digit,
21041 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
21042 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
21043 not set, a value for the gid also.
21045 &*Warning:*& Changing uid and gid is possible only when Exim is running as
21046 root, which it does during a normal delivery in a conventional configuration.
21047 However, when an address is being verified during message reception, Exim is
21048 usually running as the Exim user, not as root. If the &(queryprogram)& router
21049 is called from a non-root process, Exim cannot change uid or gid before running
21050 the command. In this circumstance the command runs under the current uid and
21054 .option current_directory queryprogram string /
21055 This option specifies an absolute path which is made the current directory
21056 before running the command.
21059 .option timeout queryprogram time 1h
21060 If the command does not complete within the timeout period, its process group
21061 is killed and the message is frozen. A value of zero time specifies no
21065 The standard output of the command is connected to a pipe, which is read when
21066 the command terminates. It should consist of a single line of output,
21067 containing up to five fields, separated by white space. The maximum length of
21068 the line is 1023 characters. Longer lines are silently truncated. The first
21069 field is one of the following words (case-insensitive):
21072 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
21075 &'Decline'&: the router declines; pass the address to the next router, unless
21076 &%no_more%& is set.
21078 &'Fail'&: routing failed; do not pass the address to any more routers. Any
21079 subsequent text on the line is an error message. If the router is run as part
21080 of address verification during an incoming SMTP message, the message is
21081 included in the SMTP response.
21083 &'Defer'&: routing could not be completed at this time; try again later. Any
21084 subsequent text on the line is an error message which is logged. It is not
21085 included in any SMTP response.
21087 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
21089 &'Pass'&: pass the address to the next router (or the router specified by
21090 &%pass_router%&), overriding &%no_more%&.
21092 &'Redirect'&: the message is redirected. The remainder of the line is a list of
21093 new addresses, which are routed independently, starting with the first router,
21094 or the router specified by &%redirect_router%&, if set.
21097 When the first word is &'accept'&, the remainder of the line consists of a
21098 number of keyed data values, as follows (split into two lines here, to fit on
21101 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
21102 LOOKUP=byname|bydns DATA=<text>
21104 The data items can be given in any order, and all are optional. If no transport
21105 is included, the transport specified by the generic &%transport%& option is
21106 used. The list of hosts and the lookup type are needed only if the transport is
21107 an &(smtp)& transport that does not itself supply a list of hosts.
21109 The format of the list of hosts is the same as for the &(manualroute)& router.
21110 As well as host names and IP addresses with optional port numbers, as described
21111 in section &<<SECTformatonehostitem>>&, it may contain names followed by
21112 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
21113 (see section &<<SECThostshowused>>&).
21115 If the lookup type is not specified, Exim behaves as follows when trying to
21116 find an IP address for each host: First, a DNS lookup is done. If this yields
21117 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
21118 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
21119 result of the lookup is the result of that call.
21121 .vindex "&$address_data$&"
21122 If the DATA field is set, its value is placed in the &$address_data$&
21123 variable. For example, this return line
21125 accept hosts=x1.y.example:x2.y.example data="rule1"
21127 routes the address to the default transport, passing a list of two hosts. When
21128 the transport runs, the string &"rule1"& is in &$address_data$&.
21129 .ecindex IIDquerou1
21130 .ecindex IIDquerou2
21135 . ////////////////////////////////////////////////////////////////////////////
21136 . ////////////////////////////////////////////////////////////////////////////
21138 .chapter "The redirect router" "CHAPredirect"
21139 .scindex IIDredrou1 "&(redirect)& router"
21140 .scindex IIDredrou2 "routers" "&(redirect)&"
21141 .cindex "alias file" "in a &(redirect)& router"
21142 .cindex "address redirection" "&(redirect)& router"
21143 The &(redirect)& router handles several kinds of address redirection. Its most
21144 common uses are for resolving local part aliases from a central alias file
21145 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
21146 files, but it has many other potential uses. The incoming address can be
21147 redirected in several different ways:
21150 It can be replaced by one or more new addresses which are themselves routed
21153 It can be routed to be delivered to a given file or directory.
21155 It can be routed to be delivered to a specified pipe command.
21157 It can cause an automatic reply to be generated.
21159 It can be forced to fail, optionally with a custom error message.
21161 It can be temporarily deferred, optionally with a custom message.
21163 It can be discarded.
21166 The generic &%transport%& option must not be set for &(redirect)& routers.
21167 However, there are some private options which define transports for delivery to
21168 files and pipes, and for generating autoreplies. See the &%file_transport%&,
21169 &%pipe_transport%& and &%reply_transport%& descriptions below.
21171 If success DSNs have been requested
21172 .cindex "DSN" "success"
21173 .cindex "Delivery Status Notification" "success"
21174 redirection triggers one and the DSN options are not passed any further.
21178 .section "Redirection data" "SECID124"
21179 The router operates by interpreting a text string which it obtains either by
21180 expanding the contents of the &%data%& option, or by reading the entire
21181 contents of a file whose name is given in the &%file%& option. These two
21182 options are mutually exclusive. The first is commonly used for handling system
21183 aliases, in a configuration like this:
21187 data = ${lookup{$local_part}lsearch{/etc/aliases}}
21189 If the lookup fails, the expanded string in this example is empty. When the
21190 expansion of &%data%& results in an empty string, the router declines. A forced
21191 expansion failure also causes the router to decline; other expansion failures
21192 cause delivery to be deferred.
21194 A configuration using &%file%& is commonly used for handling users'
21195 &_.forward_& files, like this:
21200 file = $home/.forward
21203 If the file does not exist, or causes no action to be taken (for example, it is
21204 empty or consists only of comments), the router declines. &*Warning*&: This
21205 is not the case when the file contains syntactically valid items that happen to
21206 yield empty addresses, for example, items containing only RFC 2822 address
21209 .cindex "tainted data" "in filenames"
21210 .cindex redirect "tainted data"
21211 Tainted data may not be used for a filename.
21213 &*Warning*&: It is unwise to use &$local_part$& or &$domain$&
21214 directly for redirection,
21215 as they are provided by a potential attacker.
21216 In the examples above, &$local_part$& is used for looking up data held locally
21217 on the system, and not used directly (the second example derives &$home$& via
21218 the passsword file or database, using &$local_part$&).
21222 .section "Forward files and address verification" "SECID125"
21223 .cindex "address redirection" "while verifying"
21224 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
21225 &_.forward_& files, as in the example above. There are two reasons for this:
21228 When Exim is receiving an incoming SMTP message from a remote host, it is
21229 running under the Exim uid, not as root. Exim is unable to change uid to read
21230 the file as the user, and it may not be able to read it as the Exim user. So in
21231 practice the router may not be able to operate.
21233 However, even when the router can operate, the existence of a &_.forward_& file
21234 is unimportant when verifying an address. What should be checked is whether the
21235 local part is a valid user name or not. Cutting out the redirection processing
21236 saves some resources.
21244 .section "Interpreting redirection data" "SECID126"
21245 .cindex "Sieve filter" "specifying in redirection data"
21246 .cindex "filter" "specifying in redirection data"
21247 The contents of the data string, whether obtained from &%data%& or &%file%&,
21248 can be interpreted in two different ways:
21251 If the &%allow_filter%& option is set true, and the data begins with the text
21252 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
21253 &'filtering'& instructions in the form of an Exim or Sieve filter file,
21254 respectively. Details of the syntax and semantics of filter files are described
21255 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
21256 document is intended for use by end users.
21258 Otherwise, the data must be a comma-separated list of redirection items, as
21259 described in the next section.
21262 When a message is redirected to a file (a &"mail folder"&), the filename given
21263 in a non-filter redirection list must always be an absolute path. A filter may
21264 generate a relative path &-- how this is handled depends on the transport's
21265 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
21266 for the &(appendfile)& transport.
21270 .section "Items in a non-filter redirection list" "SECTitenonfilred"
21271 .cindex "address redirection" "non-filter list items"
21272 When the redirection data is not an Exim or Sieve filter, for example, if it
21273 comes from a conventional alias or forward file, it consists of a list of
21274 addresses, filenames, pipe commands, or certain special items (see section
21275 &<<SECTspecitredli>>& below). The special items can be individually enabled or
21276 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
21277 depending on their default values. The items in the list are separated by
21278 commas or newlines.
21279 If a comma is required in an item, the entire item must be enclosed in double
21282 Lines starting with a # character are comments, and are ignored, and # may
21283 also appear following a comma, in which case everything between the # and the
21284 next newline character is ignored.
21286 If an item is entirely enclosed in double quotes, these are removed. Otherwise
21287 double quotes are retained because some forms of mail address require their use
21288 (but never to enclose the entire address). In the following description,
21289 &"item"& refers to what remains after any surrounding double quotes have been
21292 .vindex "&$local_part$&"
21293 &*Warning*&: If you use an Exim expansion to construct a redirection address,
21294 and the expansion contains a reference to &$local_part$&, you should make use
21295 of the &%quote_local_part%& expansion operator, in case the local part contains
21296 special characters. For example, to redirect all mail for the domain
21297 &'obsolete.example'&, retaining the existing local part, you could use this
21300 data = ${quote_local_part:$local_part}@newdomain.example
21304 .section "Redirecting to a local mailbox" "SECTredlocmai"
21305 .cindex "routing" "loops in"
21306 .cindex "loop" "while routing, avoidance of"
21307 .cindex "address redirection" "to local mailbox"
21308 A redirection item may safely be the same as the address currently under
21309 consideration. This does not cause a routing loop, because a router is
21310 automatically skipped if any ancestor of the address that is being processed
21311 is the same as the current address and was processed by the current router.
21312 Such an address is therefore passed to the following routers, so it is handled
21313 as if there were no redirection. When making this loop-avoidance test, the
21314 complete local part, including any prefix or suffix, is used.
21316 .cindex "address redirection" "local part without domain"
21317 Specifying the same local part without a domain is a common usage in personal
21318 filter files when the user wants to have messages delivered to the local
21319 mailbox and also forwarded elsewhere. For example, the user whose login is
21320 &'cleo'& might have a &_.forward_& file containing this:
21322 cleo, cleopatra@egypt.example
21324 .cindex "backslash in alias file"
21325 .cindex "alias file" "backslash in"
21326 For compatibility with other MTAs, such unqualified local parts may be
21327 preceded by &"\"&, but this is not a requirement for loop prevention. However,
21328 it does make a difference if more than one domain is being handled
21331 If an item begins with &"\"& and the rest of the item parses as a valid RFC
21332 2822 address that does not include a domain, the item is qualified using the
21333 domain of the incoming address. In the absence of a leading &"\"&, unqualified
21334 addresses are qualified using the value in &%qualify_recipient%&, but you can
21335 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
21337 Care must be taken if there are alias names for local users.
21338 Consider an MTA handling a single local domain where the system alias file
21343 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
21344 messages in the local mailbox, and also forward copies elsewhere. He creates
21347 Sam.Reman, spqr@reme.elsewhere.example
21349 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
21350 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
21351 second time round, because it has previously routed it,
21352 and the following routers presumably cannot handle the alias. The forward file
21353 should really contain
21355 spqr, spqr@reme.elsewhere.example
21357 but because this is such a common error, the &%check_ancestor%& option (see
21358 below) exists to provide a way to get round it. This is normally set on a
21359 &(redirect)& router that is handling users' &_.forward_& files.
21363 .section "Special items in redirection lists" "SECTspecitredli"
21364 In addition to addresses, the following types of item may appear in redirection
21365 lists (that is, in non-filter redirection data):
21368 .cindex "pipe" "in redirection list"
21369 .cindex "address redirection" "to pipe"
21370 An item is treated as a pipe command if it begins with &"|"& and does not parse
21371 as a valid RFC 2822 address that includes a domain. A transport for running the
21372 command must be specified by the &%pipe_transport%& option.
21373 Normally, either the router or the transport specifies a user and a group under
21374 which to run the delivery. The default is to use the Exim user and group.
21376 Single or double quotes can be used for enclosing the individual arguments of
21377 the pipe command; no interpretation of escapes is done for single quotes. If
21378 the command contains a comma character, it is necessary to put the whole item
21379 in double quotes, for example:
21381 "|/some/command ready,steady,go"
21383 since items in redirection lists are terminated by commas. Do not, however,
21384 quote just the command. An item such as
21386 |"/some/command ready,steady,go"
21388 is interpreted as a pipe with a rather strange command name, and no arguments.
21390 Note that the above example assumes that the text comes from a lookup source
21391 of some sort, so that the quotes are part of the data. If composing a
21392 redirect router with a &%data%& option directly specifying this command, the
21393 quotes will be used by the configuration parser to define the extent of one
21394 string, but will not be passed down into the redirect router itself. There
21395 are two main approaches to get around this: escape quotes to be part of the
21396 data itself, or avoid using this mechanism and instead create a custom
21397 transport with the &%command%& option set and reference that transport from
21398 an &%accept%& router.
21401 .cindex "file" "in redirection list"
21402 .cindex "address redirection" "to file"
21403 An item is interpreted as a path name if it begins with &"/"& and does not
21404 parse as a valid RFC 2822 address that includes a domain. For example,
21406 /home/world/minbari
21408 is treated as a filename, but
21410 /s=molari/o=babylon/@x400gate.way
21412 is treated as an address. For a filename, a transport must be specified using
21413 the &%file_transport%& option. However, if the generated path name ends with a
21414 forward slash character, it is interpreted as a directory name rather than a
21415 filename, and &%directory_transport%& is used instead.
21417 Normally, either the router or the transport specifies a user and a group under
21418 which to run the delivery. The default is to use the Exim user and group.
21420 .cindex "&_/dev/null_&"
21421 However, if a redirection item is the path &_/dev/null_&, delivery to it is
21422 bypassed at a high level, and the log entry shows &"**bypassed**"&
21423 instead of a transport name. In this case the user and group are not used.
21426 .cindex "included address list"
21427 .cindex "address redirection" "included external list"
21428 If an item is of the form
21430 :include:<path name>
21432 a list of further items is taken from the given file and included at that
21433 point. &*Note*&: Such a file can not be a filter file; it is just an
21434 out-of-line addition to the list. The items in the included list are separated
21435 by commas or newlines and are not subject to expansion. If this is the first
21436 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
21437 the alias name. This example is incorrect:
21439 list1 :include:/opt/lists/list1
21441 It must be given as
21443 list1: :include:/opt/lists/list1
21445 .cindex "tainted data" "in filenames"
21446 .cindex redirect "tainted data"
21447 Tainted data may not be used for a filename.
21449 .cindex "address redirection" "to black hole"
21450 .cindex "delivery" "discard"
21451 .cindex "delivery" "blackhole"
21452 .cindex "black hole"
21453 .cindex "abandoning mail"
21454 Sometimes you want to throw away mail to a particular local part. Making the
21455 &%data%& option expand to an empty string does not work, because that causes
21456 the router to decline. Instead, the alias item
21460 can be used. It does what its name implies. No delivery is
21461 done, and no error message is generated. This has the same effect as specifying
21462 &_/dev/null_& as a destination, but it can be independently disabled.
21464 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
21465 delivery is done for the original local part, even if other redirection items
21466 are present. If you are generating a multi-item list (for example, by reading a
21467 database) and need the ability to provide a no-op item, you must use
21471 .cindex "delivery" "forcing failure"
21472 .cindex "delivery" "forcing deferral"
21473 .cindex "failing delivery" "forcing"
21474 .cindex "deferred delivery, forcing"
21475 .cindex "customizing" "failure message"
21476 An attempt to deliver a particular address can be deferred or forced to fail by
21477 redirection items of the form
21482 respectively. When a redirection list contains such an item, it applies
21483 to the entire redirection; any other items in the list are ignored. Any
21484 text following &':fail:'& or &':defer:'& is placed in the error text
21485 associated with the failure. For example, an alias file might contain:
21487 X.Employee: :fail: Gone away, no forwarding address
21489 In the case of an address that is being verified from an ACL or as the subject
21491 .cindex "VRFY" "error text, display of"
21492 VRFY command, the text is included in the SMTP error response by
21494 .cindex "EXPN" "error text, display of"
21495 The text is not included in the response to an EXPN command. In non-SMTP cases
21496 the text is included in the error message that Exim generates.
21498 .cindex "SMTP" "error codes"
21499 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
21500 &':fail:'&. However, if the message starts with three digits followed by a
21501 space, optionally followed by an extended code of the form &'n.n.n'&, also
21502 followed by a space, and the very first digit is the same as the default error
21503 code, the code from the message is used instead. If the very first digit is
21504 incorrect, a panic error is logged, and the default code is used. You can
21505 suppress the use of the supplied code in a redirect router by setting the
21506 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
21509 .vindex "&$acl_verify_message$&"
21510 In an ACL, an explicitly provided message overrides the default, but the
21511 default message is available in the variable &$acl_verify_message$& and can
21512 therefore be included in a custom message if this is desired.
21514 Normally the error text is the rest of the redirection list &-- a comma does
21515 not terminate it &-- but a newline does act as a terminator. Newlines are not
21516 normally present in alias expansions. In &(lsearch)& lookups they are removed
21517 as part of the continuation process, but they may exist in other kinds of
21518 lookup and in &':include:'& files.
21520 During routing for message delivery (as opposed to verification), a redirection
21521 containing &':fail:'& causes an immediate failure of the incoming address,
21522 whereas &':defer:'& causes the message to remain in the queue so that a
21523 subsequent delivery attempt can happen at a later time. If an address is
21524 deferred for too long, it will ultimately fail, because the normal retry
21528 .cindex "alias file" "exception to default"
21529 Sometimes it is useful to use a single-key search type with a default (see
21530 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
21531 for exceptions to the default. These can be handled by aliasing them to
21532 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
21533 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
21534 results in an empty redirection list has the same effect.
21538 .section "Duplicate addresses" "SECTdupaddr"
21539 .cindex "duplicate addresses"
21540 .cindex "address duplicate, discarding"
21541 .cindex "pipe" "duplicated"
21542 Exim removes duplicate addresses from the list to which it is delivering, so as
21543 to deliver just one copy to each address. This does not apply to deliveries
21544 routed to pipes by different immediate parent addresses, but an indirect
21545 aliasing scheme of the type
21547 pipe: |/some/command $local_part
21551 does not work with a message that is addressed to both local parts, because
21552 when the second is aliased to the intermediate local part &"pipe"& it gets
21553 discarded as being the same as a previously handled address. However, a scheme
21556 localpart1: |/some/command $local_part
21557 localpart2: |/some/command $local_part
21559 does result in two different pipe deliveries, because the immediate parents of
21560 the pipes are distinct.
21564 .section "Repeated redirection expansion" "SECID128"
21565 .cindex "repeated redirection expansion"
21566 .cindex "address redirection" "repeated for each delivery attempt"
21567 When a message cannot be delivered to all of its recipients immediately,
21568 leading to two or more delivery attempts, redirection expansion is carried out
21569 afresh each time for those addresses whose children were not all previously
21570 delivered. If redirection is being used as a mailing list, this can lead to new
21571 members of the list receiving copies of old messages. The &%one_time%& option
21572 can be used to avoid this.
21575 .section "Errors in redirection lists" "SECID129"
21576 .cindex "address redirection" "errors"
21577 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
21578 error is skipped, and an entry is written to the main log. This may be useful
21579 for mailing lists that are automatically managed. Otherwise, if an error is
21580 detected while generating the list of new addresses, the original address is
21581 deferred. See also &%syntax_errors_to%&.
21585 .section "Private options for the redirect router" "SECID130"
21587 .cindex "options" "&(redirect)& router"
21588 The private options for the &(redirect)& router are as follows:
21591 .option allow_defer redirect boolean false
21592 Setting this option allows the use of &':defer:'& in non-filter redirection
21593 data, or the &%defer%& command in an Exim filter file.
21596 .option allow_fail redirect boolean false
21597 .cindex "failing delivery" "from filter"
21598 If this option is true, the &':fail:'& item can be used in a redirection list,
21599 and the &%fail%& command may be used in an Exim filter file.
21602 .option allow_filter redirect boolean false
21603 .cindex "filter" "enabling use of"
21604 .cindex "Sieve filter" "enabling use of"
21605 Setting this option allows Exim to interpret redirection data that starts with
21606 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
21607 are some features of Exim filter files that some administrators may wish to
21608 lock out; see the &%forbid_filter_%&&'xxx'& options below.
21610 It is also possible to lock out Exim filters or Sieve filters while allowing
21611 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
21614 The filter is run using the uid and gid set by the generic &%user%& and
21615 &%group%& options. These take their defaults from the password data if
21616 &%check_local_user%& is set, so in the normal case of users' personal filter
21617 files, the filter is run as the relevant user. When &%allow_filter%& is set
21618 true, Exim insists that either &%check_local_user%& or &%user%& is set.
21622 .option allow_freeze redirect boolean false
21623 .cindex "freezing messages" "allowing in filter"
21624 Setting this option allows the use of the &%freeze%& command in an Exim filter.
21625 This command is more normally encountered in system filters, and is disabled by
21626 default for redirection filters because it isn't something you usually want to
21627 let ordinary users do.
21631 .option check_ancestor redirect boolean false
21632 This option is concerned with handling generated addresses that are the same
21633 as some address in the list of redirection ancestors of the current address.
21634 Although it is turned off by default in the code, it is set in the default
21635 configuration file for handling users' &_.forward_& files. It is recommended
21636 for this use of the &(redirect)& router.
21638 When &%check_ancestor%& is set, if a generated address (including the domain)
21639 is the same as any ancestor of the current address, it is replaced by a copy of
21640 the current address. This helps in the case where local part A is aliased to B,
21641 and B has a &_.forward_& file pointing back to A. For example, within a single
21642 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
21643 &_&~jb/.forward_& contains:
21645 \Joe.Bloggs, <other item(s)>
21647 Without the &%check_ancestor%& setting, either local part (&"jb"& or
21648 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
21649 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
21650 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
21651 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
21652 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
21653 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
21654 original address. See also the &%repeat_use%& option below.
21657 .option check_group redirect boolean "see below"
21658 When the &%file%& option is used, the group owner of the file is checked only
21659 when this option is set. The permitted groups are those listed in the
21660 &%owngroups%& option, together with the user's default group if
21661 &%check_local_user%& is set. If the file has the wrong group, routing is
21662 deferred. The default setting for this option is true if &%check_local_user%&
21663 is set and the &%modemask%& option permits the group write bit, or if the
21664 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
21668 .option check_owner redirect boolean "see below"
21669 When the &%file%& option is used, the owner of the file is checked only when
21670 this option is set. If &%check_local_user%& is set, the local user is
21671 permitted; otherwise the owner must be one of those listed in the &%owners%&
21672 option. The default value for this option is true if &%check_local_user%& or
21673 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
21676 .option data redirect string&!! unset
21677 This option is mutually exclusive with &%file%&. One or other of them must be
21678 set, but not both. The contents of &%data%& are expanded, and then used as the
21679 list of forwarding items, or as a set of filtering instructions. If the
21680 expansion is forced to fail, or the result is an empty string or a string that
21681 has no effect (consists entirely of comments), the router declines.
21683 When filtering instructions are used, the string must begin with &"#Exim
21684 filter"&, and all comments in the string, including this initial one, must be
21685 terminated with newline characters. For example:
21687 data = #Exim filter\n\
21688 if $h_to: contains Exim then save $home/mail/exim endif
21690 If you are reading the data from a database where newlines cannot be included,
21691 you can use the &${sg}$& expansion item to turn the escape string of your
21692 choice into a newline.
21695 .option directory_transport redirect string&!! unset
21696 A &(redirect)& router sets up a direct delivery to a directory when a path name
21697 ending with a slash is specified as a new &"address"&. The transport used is
21698 specified by this option, which, after expansion, must be the name of a
21699 configured transport. This should normally be an &(appendfile)& transport.
21702 .option file redirect string&!! unset
21703 This option specifies the name of a file that contains the redirection data. It
21704 is mutually exclusive with the &%data%& option. The string is expanded before
21705 use; if the expansion is forced to fail, the router declines. Other expansion
21706 failures cause delivery to be deferred. The result of a successful expansion
21707 must be an absolute path. The entire file is read and used as the redirection
21708 data. If the data is an empty string or a string that has no effect (consists
21709 entirely of comments), the router declines.
21711 .cindex "NFS" "checking for file existence"
21712 If the attempt to open the file fails with a &"does not exist"& error, Exim
21713 runs a check on the containing directory,
21714 unless &%ignore_enotdir%& is true (see below).
21715 If the directory does not appear to exist, delivery is deferred. This can
21716 happen when users' &_.forward_& files are in NFS-mounted directories, and there
21717 is a mount problem. If the containing directory does exist, but the file does
21718 not, the router declines.
21721 .option file_transport redirect string&!! unset
21722 .vindex "&$address_file$&"
21723 A &(redirect)& router sets up a direct delivery to a file when a path name not
21724 ending in a slash is specified as a new &"address"&. The transport used is
21725 specified by this option, which, after expansion, must be the name of a
21726 configured transport. This should normally be an &(appendfile)& transport. When
21727 it is running, the filename is in &$address_file$&.
21730 .option filter_prepend_home redirect boolean true
21731 When this option is true, if a &(save)& command in an Exim filter specifies a
21732 relative path, and &$home$& is defined, it is automatically prepended to the
21733 relative path. If this option is set false, this action does not happen. The
21734 relative path is then passed to the transport unmodified.
21737 .option forbid_blackhole redirect boolean false
21738 .cindex "restricting access to features"
21739 .cindex "filter" "locking out certain features"
21740 If this option is true, the &':blackhole:'& item may not appear in a
21744 .option forbid_exim_filter redirect boolean false
21745 .cindex "restricting access to features"
21746 .cindex "filter" "locking out certain features"
21747 If this option is set true, only Sieve filters are permitted when
21748 &%allow_filter%& is true.
21753 .option forbid_file redirect boolean false
21754 .cindex "restricting access to features"
21755 .cindex "delivery" "to file; forbidding"
21756 .cindex "filter" "locking out certain features"
21757 .cindex "Sieve filter" "forbidding delivery to a file"
21758 .cindex "Sieve filter" "&""keep""& facility; disabling"
21759 If this option is true, this router may not generate a new address that
21760 specifies delivery to a local file or directory, either from a filter or from a
21761 conventional forward file. This option is forced to be true if &%one_time%& is
21762 set. It applies to Sieve filters as well as to Exim filters, but if true, it
21763 locks out the Sieve's &"keep"& facility.
21766 .option forbid_filter_dlfunc redirect boolean false
21767 .cindex "restricting access to features"
21768 .cindex "filter" "locking out certain features"
21769 If this option is true, string expansions in Exim filters are not allowed to
21770 make use of the &%dlfunc%& expansion facility to run dynamically loaded
21773 .option forbid_filter_existstest redirect boolean false
21774 .cindex "restricting access to features"
21775 .cindex "filter" "locking out certain features"
21776 .cindex "expansion" "statting a file"
21777 If this option is true, string expansions in Exim filters are not allowed to
21778 make use of the &%exists%& condition or the &%stat%& expansion item.
21780 .option forbid_filter_logwrite redirect boolean false
21781 .cindex "restricting access to features"
21782 .cindex "filter" "locking out certain features"
21783 If this option is true, use of the logging facility in Exim filters is not
21784 permitted. Logging is in any case available only if the filter is being run
21785 under some unprivileged uid (which is normally the case for ordinary users'
21786 &_.forward_& files).
21789 .option forbid_filter_lookup redirect boolean false
21790 .cindex "restricting access to features"
21791 .cindex "filter" "locking out certain features"
21792 If this option is true, string expansions in Exim filter files are not allowed
21793 to make use of &%lookup%& items.
21796 .option forbid_filter_perl redirect boolean false
21797 .cindex "restricting access to features"
21798 .cindex "filter" "locking out certain features"
21799 This option has an effect only if Exim is built with embedded Perl support. If
21800 it is true, string expansions in Exim filter files are not allowed to make use
21801 of the embedded Perl support.
21804 .option forbid_filter_readfile redirect boolean false
21805 .cindex "restricting access to features"
21806 .cindex "filter" "locking out certain features"
21807 If this option is true, string expansions in Exim filter files are not allowed
21808 to make use of &%readfile%& items.
21811 .option forbid_filter_readsocket redirect boolean false
21812 .cindex "restricting access to features"
21813 .cindex "filter" "locking out certain features"
21814 If this option is true, string expansions in Exim filter files are not allowed
21815 to make use of &%readsocket%& items.
21818 .option forbid_filter_reply redirect boolean false
21819 .cindex "restricting access to features"
21820 .cindex "filter" "locking out certain features"
21821 If this option is true, this router may not generate an automatic reply
21822 message. Automatic replies can be generated only from Exim or Sieve filter
21823 files, not from traditional forward files. This option is forced to be true if
21824 &%one_time%& is set.
21827 .option forbid_filter_run redirect boolean false
21828 .cindex "restricting access to features"
21829 .cindex "filter" "locking out certain features"
21830 If this option is true, string expansions in Exim filter files are not allowed
21831 to make use of &%run%& items.
21834 .option forbid_include redirect boolean false
21835 .cindex "restricting access to features"
21836 .cindex "filter" "locking out certain features"
21837 If this option is true, items of the form
21839 :include:<path name>
21841 are not permitted in non-filter redirection lists.
21844 .option forbid_pipe redirect boolean false
21845 .cindex "restricting access to features"
21846 .cindex "filter" "locking out certain features"
21847 .cindex "delivery" "to pipe; forbidding"
21848 If this option is true, this router may not generate a new address which
21849 specifies delivery to a pipe, either from an Exim filter or from a conventional
21850 forward file. This option is forced to be true if &%one_time%& is set.
21853 .option forbid_sieve_filter redirect boolean false
21854 .cindex "restricting access to features"
21855 .cindex "filter" "locking out certain features"
21856 If this option is set true, only Exim filters are permitted when
21857 &%allow_filter%& is true.
21860 .cindex "SMTP" "error codes"
21861 .option forbid_smtp_code redirect boolean false
21862 If this option is set true, any SMTP error codes that are present at the start
21863 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
21864 the default codes (451 and 550, respectively) are always used.
21869 .option hide_child_in_errmsg redirect boolean false
21870 .cindex "bounce message" "redirection details; suppressing"
21871 If this option is true, it prevents Exim from quoting a child address if it
21872 generates a bounce or delay message for it. Instead it says &"an address
21873 generated from <&'the top level address'&>"&. Of course, this applies only to
21874 bounces generated locally. If a message is forwarded to another host, &'its'&
21875 bounce may well quote the generated address.
21878 .option ignore_eacces redirect boolean false
21880 If this option is set and an attempt to open a redirection file yields the
21881 EACCES error (permission denied), the &(redirect)& router behaves as if the
21882 file did not exist.
21885 .option ignore_enotdir redirect boolean false
21887 If this option is set and an attempt to open a redirection file yields the
21888 ENOTDIR error (something on the path is not a directory), the &(redirect)&
21889 router behaves as if the file did not exist.
21891 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
21892 router that has the &%file%& option set discovers that the file does not exist
21893 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
21894 against unmounted NFS directories. If the parent can not be statted, delivery
21895 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
21896 is set, because that option tells Exim to ignore &"something on the path is not
21897 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
21898 that some operating systems give ENOENT where others give ENOTDIR.
21902 .option include_directory redirect string unset
21903 If this option is set, the path names of any &':include:'& items in a
21904 redirection list must start with this directory.
21907 .option modemask redirect "octal integer" 022
21908 This specifies mode bits which must not be set for a file specified by the
21909 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
21912 .option one_time redirect boolean false
21913 .cindex "one-time aliasing/forwarding expansion"
21914 .cindex "alias file" "one-time expansion"
21915 .cindex "forward file" "one-time expansion"
21916 .cindex "mailing lists" "one-time expansion"
21917 .cindex "address redirection" "one-time expansion"
21918 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
21919 files each time it tries to deliver a message causes a problem when one or more
21920 of the generated addresses fails be delivered at the first attempt. The problem
21921 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
21922 but of what happens when the redirection list changes during the time that the
21923 message is on Exim's queue. This is particularly true in the case of mailing
21924 lists, where new subscribers might receive copies of messages that were posted
21925 before they subscribed.
21927 If &%one_time%& is set and any addresses generated by the router fail to
21928 deliver at the first attempt, the failing addresses are added to the message as
21929 &"top level"& addresses, and the parent address that generated them is marked
21930 &"delivered"&. Thus, redirection does not happen again at the next delivery
21933 &*Warning 1*&: Any header line addition or removal that is specified by this
21934 router would be lost if delivery did not succeed at the first attempt. For this
21935 reason, the &%headers_add%& and &%headers_remove%& generic options are not
21936 permitted when &%one_time%& is set.
21938 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
21939 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
21940 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
21942 &*Warning 3*&: The &%unseen%& generic router option may not be set with
21945 The original top-level address is remembered with each of the generated
21946 addresses, and is output in any log messages. However, any intermediate parent
21947 addresses are not recorded. This makes a difference to the log only if
21948 &%all_parents%& log selector is set. It is expected that &%one_time%& will
21949 typically be used for mailing lists, where there is normally just one level of
21953 .option owners redirect "string list" unset
21954 .cindex "ownership" "alias file"
21955 .cindex "ownership" "forward file"
21956 .cindex "alias file" "ownership"
21957 .cindex "forward file" "ownership"
21958 This specifies a list of permitted owners for the file specified by &%file%&.
21959 This list is in addition to the local user when &%check_local_user%& is set.
21960 See &%check_owner%& above.
21963 .option owngroups redirect "string list" unset
21964 This specifies a list of permitted groups for the file specified by &%file%&.
21965 The list is in addition to the local user's primary group when
21966 &%check_local_user%& is set. See &%check_group%& above.
21969 .option pipe_transport redirect string&!! unset
21970 .vindex "&$address_pipe$&"
21971 A &(redirect)& router sets up a direct delivery to a pipe when a string
21972 starting with a vertical bar character is specified as a new &"address"&. The
21973 transport used is specified by this option, which, after expansion, must be the
21974 name of a configured transport. This should normally be a &(pipe)& transport.
21975 When the transport is run, the pipe command is in &$address_pipe$&.
21978 .option qualify_domain redirect string&!! unset
21979 .vindex "&$qualify_recipient$&"
21980 If this option is set, and an unqualified address (one without a domain) is
21981 generated, and that address would normally be qualified by the global setting
21982 in &%qualify_recipient%&, it is instead qualified with the domain specified by
21983 expanding this string. If the expansion fails, the router declines. If you want
21984 to revert to the default, you can have the expansion generate
21985 &$qualify_recipient$&.
21987 This option applies to all unqualified addresses generated by Exim filters,
21988 but for traditional &_.forward_& files, it applies only to addresses that are
21989 not preceded by a backslash. Sieve filters cannot generate unqualified
21992 .option qualify_preserve_domain redirect boolean false
21993 .cindex "domain" "in redirection; preserving"
21994 .cindex "preserving domain in redirection"
21995 .cindex "address redirection" "domain; preserving"
21996 If this option is set, the router's local &%qualify_domain%& option must not be
21997 set (a configuration error occurs if it is). If an unqualified address (one
21998 without a domain) is generated, it is qualified with the domain of the parent
21999 address (the immediately preceding ancestor) instead of the global
22000 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
22001 this applies whether or not the address is preceded by a backslash.
22004 .option repeat_use redirect boolean true
22005 If this option is set false, the router is skipped for a child address that has
22006 any ancestor that was routed by this router. This test happens before any of
22007 the other preconditions are tested. Exim's default anti-looping rules skip
22008 only when the ancestor is the same as the current address. See also
22009 &%check_ancestor%& above and the generic &%redirect_router%& option.
22012 .option reply_transport redirect string&!! unset
22013 A &(redirect)& router sets up an automatic reply when a &%mail%& or
22014 &%vacation%& command is used in a filter file. The transport used is specified
22015 by this option, which, after expansion, must be the name of a configured
22016 transport. This should normally be an &(autoreply)& transport. Other transports
22017 are unlikely to do anything sensible or useful.
22020 .option rewrite redirect boolean true
22021 .cindex "address redirection" "disabling rewriting"
22022 If this option is set false, addresses generated by the router are not
22023 subject to address rewriting. Otherwise, they are treated like new addresses
22024 and are rewritten according to the global rewriting rules.
22027 .option sieve_subaddress redirect string&!! unset
22028 The value of this option is passed to a Sieve filter to specify the
22029 :subaddress part of an address.
22031 .option sieve_useraddress redirect string&!! unset
22032 The value of this option is passed to a Sieve filter to specify the :user part
22033 of an address. However, if it is unset, the entire original local part
22034 (including any prefix or suffix) is used for :user.
22037 .option sieve_vacation_directory redirect string&!! unset
22038 .cindex "Sieve filter" "vacation directory"
22039 To enable the &"vacation"& extension for Sieve filters, you must set
22040 &%sieve_vacation_directory%& to the directory where vacation databases are held
22041 (do not put anything else in that directory), and ensure that the
22042 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
22043 needs their own directory; Exim will create it if necessary.
22047 .option skip_syntax_errors redirect boolean false
22048 .cindex "forward file" "broken"
22049 .cindex "address redirection" "broken files"
22050 .cindex "alias file" "broken"
22051 .cindex "broken alias or forward files"
22052 .cindex "ignoring faulty addresses"
22053 .cindex "skipping faulty addresses"
22054 .cindex "error" "skipping bad syntax"
22055 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
22056 non-filter redirection data are skipped, and each failing address is logged. If
22057 &%syntax_errors_to%& is set, a message is sent to the address it defines,
22058 giving details of the failures. If &%syntax_errors_text%& is set, its contents
22059 are expanded and placed at the head of the error message generated by
22060 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
22061 be the same address as the generic &%errors_to%& option. The
22062 &%skip_syntax_errors%& option is often used when handling mailing lists.
22064 If all the addresses in a redirection list are skipped because of syntax
22065 errors, the router declines to handle the original address, and it is passed to
22066 the following routers.
22068 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
22069 error in the filter causes filtering to be abandoned without any action being
22070 taken. The incident is logged, and the router declines to handle the address,
22071 so it is passed to the following routers.
22073 .cindex "Sieve filter" "syntax errors in"
22074 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
22075 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
22076 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
22078 &%skip_syntax_errors%& can be used to specify that errors in users' forward
22079 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
22080 option, used with an address that does not get redirected, can be used to
22081 notify users of these errors, by means of a router like this:
22087 file = $home/.forward
22088 file_transport = address_file
22089 pipe_transport = address_pipe
22090 reply_transport = address_reply
22093 syntax_errors_to = real-$local_part@$domain
22094 syntax_errors_text = \
22095 This is an automatically generated message. An error has\n\
22096 been found in your .forward file. Details of the error are\n\
22097 reported below. While this error persists, you will receive\n\
22098 a copy of this message for every message that is addressed\n\
22099 to you. If your .forward file is a filter file, or if it is\n\
22100 a non-filter file containing no valid forwarding addresses,\n\
22101 a copy of each incoming message will be put in your normal\n\
22102 mailbox. If a non-filter file contains at least one valid\n\
22103 forwarding address, forwarding to the valid addresses will\n\
22104 happen, and those will be the only deliveries that occur.
22106 You also need a router to ensure that local addresses that are prefixed by
22107 &`real-`& are recognized, but not forwarded or filtered. For example, you could
22108 put this immediately before the &(userforward)& router:
22113 local_part_prefix = real-
22114 transport = local_delivery
22116 For security, it would probably be a good idea to restrict the use of this
22117 router to locally-generated messages, using a condition such as this:
22119 condition = ${if match {$sender_host_address}\
22120 {\N^(|127\.0\.0\.1)$\N}}
22124 .option syntax_errors_text redirect string&!! unset
22125 See &%skip_syntax_errors%& above.
22128 .option syntax_errors_to redirect string unset
22129 See &%skip_syntax_errors%& above.
22130 .ecindex IIDredrou1
22131 .ecindex IIDredrou2
22138 . ////////////////////////////////////////////////////////////////////////////
22139 . ////////////////////////////////////////////////////////////////////////////
22141 .chapter "Environment for running local transports" "CHAPenvironment" &&&
22142 "Environment for local transports"
22143 .scindex IIDenvlotra1 "local transports" "environment for"
22144 .scindex IIDenvlotra2 "environment" "local transports"
22145 .scindex IIDenvlotra3 "transport" "local; environment for"
22146 Local transports handle deliveries to files and pipes. (The &(autoreply)&
22147 transport can be thought of as similar to a pipe.) Exim always runs transports
22148 in subprocesses, under specified uids and gids. Typical deliveries to local
22149 mailboxes run under the uid and gid of the local user.
22151 Exim also sets a specific current directory while running the transport; for
22152 some transports a home directory setting is also relevant. The &(pipe)&
22153 transport is the only one that sets up environment variables; see section
22154 &<<SECTpipeenv>>& for details.
22156 The values used for the uid, gid, and the directories may come from several
22157 different places. In many cases, the router that handles the address associates
22158 settings with that address as a result of its &%check_local_user%&, &%group%&,
22159 or &%user%& options. However, values may also be given in the transport's own
22160 configuration, and these override anything that comes from the router.
22164 .section "Concurrent deliveries" "SECID131"
22165 .cindex "concurrent deliveries"
22166 .cindex "simultaneous deliveries"
22167 If two different messages for the same local recipient arrive more or less
22168 simultaneously, the two delivery processes are likely to run concurrently. When
22169 the &(appendfile)& transport is used to write to a file, Exim applies locking
22170 rules to stop concurrent processes from writing to the same file at the same
22173 However, when you use a &(pipe)& transport, it is up to you to arrange any
22174 locking that is needed. Here is a silly example:
22178 command = /bin/sh -c 'cat >>/some/file'
22180 This is supposed to write the message at the end of the file. However, if two
22181 messages arrive at the same time, the file will be scrambled. You can use the
22182 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
22183 file using the same algorithm that Exim itself uses.
22188 .section "Uids and gids" "SECTenvuidgid"
22189 .cindex "local transports" "uid and gid"
22190 .cindex "transport" "local; uid and gid"
22191 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
22192 overrides any group that the router set in the address, even if &%user%& is not
22193 set for the transport. This makes it possible, for example, to run local mail
22194 delivery under the uid of the recipient (set by the router), but in a special
22195 group (set by the transport). For example:
22198 # User/group are set by check_local_user in this router
22202 transport = group_delivery
22205 # This transport overrides the group
22207 driver = appendfile
22208 file = /var/spool/mail/$local_part_data
22211 If &%user%& is set for a transport, its value overrides what is set in the
22212 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
22213 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
22216 .oindex "&%initgroups%&"
22217 When the uid is taken from the transport's configuration, the &[initgroups()]&
22218 function is called for the groups associated with that uid if the
22219 &%initgroups%& option is set for the transport. When the uid is not specified
22220 by the transport, but is associated with the address by a router, the option
22221 for calling &[initgroups()]& is taken from the router configuration.
22223 .cindex "&(pipe)& transport" "uid for"
22224 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
22225 is set and &%user%& is not set, the uid of the process that called Exim to
22226 receive the message is used, and if &%group%& is not set, the corresponding
22227 original gid is also used.
22229 This is the detailed preference order for obtaining a gid; the first of the
22230 following that is set is used:
22233 A &%group%& setting of the transport;
22235 A &%group%& setting of the router;
22237 A gid associated with a user setting of the router, either as a result of
22238 &%check_local_user%& or an explicit non-numeric &%user%& setting;
22240 The group associated with a non-numeric &%user%& setting of the transport;
22242 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
22243 the uid is the creator's uid;
22245 The Exim gid if the Exim uid is being used as a default.
22248 If, for example, the user is specified numerically on the router and there are
22249 no group settings, no gid is available. In this situation, an error occurs.
22250 This is different for the uid, for which there always is an ultimate default.
22251 The first of the following that is set is used:
22254 A &%user%& setting of the transport;
22256 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
22258 A &%user%& setting of the router;
22260 A &%check_local_user%& setting of the router;
22265 Of course, an error will still occur if the uid that is chosen is on the
22266 &%never_users%& list.
22272 .section "Current and home directories" "SECID132"
22273 .cindex "current directory for local transport"
22274 .cindex "home directory" "for local transport"
22275 .cindex "transport" "local; home directory for"
22276 .cindex "transport" "local; current directory for"
22277 Routers may set current and home directories for local transports by means of
22278 the &%transport_current_directory%& and &%transport_home_directory%& options.
22279 However, if the transport's &%current_directory%& or &%home_directory%& options
22280 are set, they override the router's values. In detail, the home directory
22281 for a local transport is taken from the first of these values that is set:
22284 The &%home_directory%& option on the transport;
22286 The &%transport_home_directory%& option on the router;
22288 The password data if &%check_local_user%& is set on the router;
22290 The &%router_home_directory%& option on the router.
22293 The current directory is taken from the first of these values that is set:
22296 The &%current_directory%& option on the transport;
22298 The &%transport_current_directory%& option on the router.
22302 If neither the router nor the transport sets a current directory, Exim uses the
22303 value of the home directory, if it is set. Otherwise it sets the current
22304 directory to &_/_& before running a local transport.
22308 .section "Expansion variables derived from the address" "SECID133"
22309 .vindex "&$domain$&"
22310 .vindex "&$local_part$&"
22311 .vindex "&$original_domain$&"
22312 Normally a local delivery is handling a single address, and in that case the
22313 variables such as &$domain$& and &$local_part$& are set during local
22314 deliveries. However, in some circumstances more than one address may be handled
22315 at once (for example, while writing batch SMTP for onward transmission by some
22316 other means). In this case, the variables associated with the local part are
22317 never set, &$domain$& is set only if all the addresses have the same domain,
22318 and &$original_domain$& is never set.
22319 .ecindex IIDenvlotra1
22320 .ecindex IIDenvlotra2
22321 .ecindex IIDenvlotra3
22329 . ////////////////////////////////////////////////////////////////////////////
22330 . ////////////////////////////////////////////////////////////////////////////
22332 .chapter "Generic options for transports" "CHAPtransportgeneric"
22333 .scindex IIDgenoptra1 "generic options" "transport"
22334 .scindex IIDgenoptra2 "options" "generic; for transports"
22335 .scindex IIDgenoptra3 "transport" "generic options for"
22336 The following generic options apply to all transports:
22339 .option body_only transports boolean false
22340 .cindex "transport" "body only"
22341 .cindex "message" "transporting body only"
22342 .cindex "body of message" "transporting"
22343 If this option is set, the message's headers are not transported. It is
22344 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
22345 or &(pipe)& transports, the settings of &%message_prefix%& and
22346 &%message_suffix%& should be checked, because this option does not
22347 automatically suppress them.
22350 .option current_directory transports string&!! unset
22351 .cindex "transport" "current directory for"
22352 This specifies the current directory that is to be set while running the
22353 transport, overriding any value that may have been set by the router.
22354 If the expansion fails for any reason, including forced failure, an error is
22355 logged, and delivery is deferred.
22358 .option disable_logging transports boolean false
22359 If this option is set true, nothing is logged for any
22360 deliveries by the transport or for any
22361 transport errors. You should not set this option unless you really, really know
22362 what you are doing.
22365 .option debug_print transports string&!! unset
22366 .cindex "testing" "variables in drivers"
22367 If this option is set and debugging is enabled (see the &%-d%& command line
22368 option), the string is expanded and included in the debugging output when the
22370 If expansion of the string fails, the error message is written to the debugging
22371 output, and Exim carries on processing.
22372 This facility is provided to help with checking out the values of variables and
22373 so on when debugging driver configurations. For example, if a &%headers_add%&
22374 option is not working properly, &%debug_print%& could be used to output the
22375 variables it references. A newline is added to the text if it does not end with
22377 The variables &$transport_name$& and &$router_name$& contain the name of the
22378 transport and the router that called it.
22380 .option delivery_date_add transports boolean false
22381 .cindex "&'Delivery-date:'& header line"
22382 If this option is true, a &'Delivery-date:'& header is added to the message.
22383 This gives the actual time the delivery was made. As this is not a standard
22384 header, Exim has a configuration option (&%delivery_date_remove%&) which
22385 requests its removal from incoming messages, so that delivered messages can
22386 safely be resent to other recipients.
22389 .option driver transports string unset
22390 This specifies which of the available transport drivers is to be used.
22391 There is no default, and this option must be set for every transport.
22394 .option envelope_to_add transports boolean false
22395 .cindex "&'Envelope-to:'& header line"
22396 If this option is true, an &'Envelope-to:'& header is added to the message.
22397 This gives the original address(es) in the incoming envelope that caused this
22398 delivery to happen. More than one address may be present if the transport is
22399 configured to handle several addresses at once, or if more than one original
22400 address was redirected to the same final address. As this is not a standard
22401 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
22402 its removal from incoming messages, so that delivered messages can safely be
22403 resent to other recipients.
22406 .option event_action transports string&!! unset
22408 This option declares a string to be expanded for Exim's events mechanism.
22409 For details see chapter &<<CHAPevents>>&.
22412 .option group transports string&!! "Exim group"
22413 .cindex "transport" "group; specifying"
22414 This option specifies a gid for running the transport process, overriding any
22415 value that the router supplies, and also overriding any value associated with
22416 &%user%& (see below).
22419 .option headers_add transports list&!! unset
22420 .cindex "header lines" "adding in transport"
22421 .cindex "transport" "header lines; adding"
22422 This option specifies a list of text headers,
22423 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22424 which are (separately) expanded and added to the header
22425 portion of a message as it is transported, as described in section
22426 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
22427 routers. If the result of the expansion is an empty string, or if the expansion
22428 is forced to fail, no action is taken. Other expansion failures are treated as
22429 errors and cause the delivery to be deferred.
22431 Unlike most options, &%headers_add%& can be specified multiple times
22432 for a transport; all listed headers are added.
22435 .option headers_only transports boolean false
22436 .cindex "transport" "header lines only"
22437 .cindex "message" "transporting headers only"
22438 .cindex "header lines" "transporting"
22439 If this option is set, the message's body is not transported. It is mutually
22440 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
22441 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
22442 checked, since this option does not automatically suppress them.
22445 .option headers_remove transports list&!! unset
22446 .cindex "header lines" "removing"
22447 .cindex "transport" "header lines; removing"
22448 This option specifies a list of text headers,
22449 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22450 to be removed from the message.
22451 However, the option has no effect when an address is just being verified.
22452 Each list item is separately expanded.
22453 If the result of the expansion is an empty string, or if the expansion
22454 is forced to fail, no action is taken. Other expansion failures are treated as
22455 errors and cause the delivery to be deferred.
22456 If an item ends in *, it will match any header with the given prefix.
22458 Matching headers are omitted from the message as it is transported, as described
22459 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
22462 Unlike most options, &%headers_remove%& can be specified multiple times
22463 for a transport; all listed headers are removed.
22465 &*Warning*&: Because of the separate expansion of the list items,
22466 items that contain a list separator must have it doubled.
22467 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
22471 .option headers_rewrite transports string unset
22472 .cindex "transport" "header lines; rewriting"
22473 .cindex "rewriting" "at transport time"
22474 This option allows addresses in header lines to be rewritten at transport time,
22475 that is, as the message is being copied to its destination. The contents of the
22476 option are a colon-separated list of rewriting rules. Each rule is in exactly
22477 the same form as one of the general rewriting rules that are applied when a
22478 message is received. These are described in chapter &<<CHAPrewrite>>&. For
22481 headers_rewrite = a@b c@d f : \
22484 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
22485 &'w@z'& in all address-bearing header lines. The rules are applied to the
22486 header lines just before they are written out at transport time, so they affect
22487 only those copies of the message that pass through the transport. However, only
22488 the message's original header lines, and any that were added by a system
22489 filter, are rewritten. If a router or transport adds header lines, they are not
22490 affected by this option. These rewriting rules are &'not'& applied to the
22491 envelope. You can change the return path using &%return_path%&, but you cannot
22492 change envelope recipients at this time.
22495 .option home_directory transports string&!! unset
22496 .cindex "transport" "home directory for"
22498 This option specifies a home directory setting for a local transport,
22499 overriding any value that may be set by the router. The home directory is
22500 placed in &$home$& while expanding the transport's private options. It is also
22501 used as the current directory if no current directory is set by the
22502 &%current_directory%& option on the transport or the
22503 &%transport_current_directory%& option on the router. If the expansion fails
22504 for any reason, including forced failure, an error is logged, and delivery is
22508 .option initgroups transports boolean false
22509 .cindex "additional groups"
22510 .cindex "groups" "additional"
22511 .cindex "transport" "group; additional"
22512 If this option is true and the uid for the delivery process is provided by the
22513 transport, the &[initgroups()]& function is called when running the transport
22514 to ensure that any additional groups associated with the uid are set up.
22517 .option max_parallel transports integer&!! unset
22518 .cindex limit "transport parallelism"
22519 .cindex transport "parallel processes"
22520 .cindex transport "concurrency limit"
22521 .cindex "delivery" "parallelism for transport"
22522 If this option is set and expands to an integer greater than zero
22523 it limits the number of concurrent runs of the transport.
22524 The control does not apply to shadow transports.
22526 .cindex "hints database" "transport concurrency control"
22527 Exim implements this control by means of a hints database in which a record is
22528 incremented whenever a transport process is being created. The record
22529 is decremented and possibly removed when the process terminates.
22530 Obviously there is scope for
22531 records to get left lying around if there is a system or program crash. To
22532 guard against this, Exim ignores any records that are more than six hours old.
22534 If you use this option, you should also arrange to delete the
22535 relevant hints database whenever your system reboots. The names of the files
22536 start with &_misc_& and they are kept in the &_spool/db_& directory. There
22537 may be one or two files, depending on the type of DBM in use. The same files
22538 are used for ETRN and smtp transport serialization.
22541 .option message_size_limit transports string&!! 0
22542 .cindex "limit" "message size per transport"
22543 .cindex "size" "of message, limit"
22544 .cindex "transport" "message size; limiting"
22545 This option controls the size of messages passed through the transport. It is
22546 expanded before use; the result of the expansion must be a sequence of decimal
22547 digits, optionally followed by K or M. If the expansion fails for any reason,
22548 including forced failure, or if the result is not of the required form,
22549 delivery is deferred. If the value is greater than zero and the size of a
22550 message exceeds this limit, the address is failed. If there is any chance that
22551 the resulting bounce message could be routed to the same transport, you should
22552 ensure that &%return_size_limit%& is less than the transport's
22553 &%message_size_limit%&, as otherwise the bounce message will fail to get
22558 .option rcpt_include_affixes transports boolean false
22559 .cindex "prefix" "for local part, including in envelope"
22560 .cindex "suffix for local part" "including in envelope"
22561 .cindex "local part" "prefix"
22562 .cindex "local part" "suffix"
22563 When this option is false (the default), and an address that has had any
22564 affixes (prefixes or suffixes) removed from the local part is delivered by any
22565 form of SMTP or LMTP, the affixes are not included. For example, if a router
22568 local_part_prefix = *-
22570 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
22573 RCPT TO:<xyz@some.domain>
22575 This is also the case when an ACL-time callout is being used to verify a
22576 recipient address. However, if &%rcpt_include_affixes%& is set true, the
22577 whole local part is included in the RCPT command. This option applies to BSMTP
22578 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
22579 &(lmtp)& and &(smtp)& transports.
22582 .option retry_use_local_part transports boolean "see below"
22583 .cindex "hints database" "retry keys"
22584 When a delivery suffers a temporary failure, a retry record is created
22585 in Exim's hints database. For remote deliveries, the key for the retry record
22586 is based on the name and/or IP address of the failing remote host. For local
22587 deliveries, the key is normally the entire address, including both the local
22588 part and the domain. This is suitable for most common cases of local delivery
22589 temporary failure &-- for example, exceeding a mailbox quota should delay only
22590 deliveries to that mailbox, not to the whole domain.
22592 However, in some special cases you may want to treat a temporary local delivery
22593 as a failure associated with the domain, and not with a particular local part.
22594 (For example, if you are storing all mail for some domain in files.) You can do
22595 this by setting &%retry_use_local_part%& false.
22597 For all the local transports, its default value is true. For remote transports,
22598 the default value is false for tidiness, but changing the value has no effect
22599 on a remote transport in the current implementation.
22602 .option return_path transports string&!! unset
22603 .cindex "envelope sender"
22604 .cindex "envelope from"
22605 .cindex "transport" "return path; changing"
22606 .cindex "return path" "changing in transport"
22607 If this option is set, the string is expanded at transport time and replaces
22608 the existing return path (envelope sender) value in the copy of the message
22609 that is being delivered. An empty return path is permitted. This feature is
22610 designed for remote deliveries, where the value of this option is used in the
22611 SMTP MAIL command. If you set &%return_path%& for a local transport, the
22612 only effect is to change the address that is placed in the &'Return-path:'&
22613 header line, if one is added to the message (see the next option).
22615 &*Note:*& A changed return path is not logged unless you add
22616 &%return_path_on_delivery%& to the log selector.
22618 .vindex "&$return_path$&"
22619 The expansion can refer to the existing value via &$return_path$&. This is
22620 either the message's envelope sender, or an address set by the
22621 &%errors_to%& option on a router. If the expansion is forced to fail, no
22622 replacement occurs; if it fails for another reason, delivery is deferred. This
22623 option can be used to support VERP (Variable Envelope Return Paths) &-- see
22624 section &<<SECTverp>>&.
22626 &*Note*&: If a delivery error is detected locally, including the case when a
22627 remote server rejects a message at SMTP time, the bounce message is not sent to
22628 the value of this option. It is sent to the previously set errors address.
22629 This defaults to the incoming sender address, but can be changed by setting
22630 &%errors_to%& in a router.
22634 .option return_path_add transports boolean false
22635 .chindex Return-path:
22636 If this option is true, a &'Return-path:'& header is added to the message.
22637 Although the return path is normally available in the prefix line of BSD
22638 mailboxes, this is commonly not displayed by MUAs, and so the user does not
22639 have easy access to it.
22641 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
22642 the delivery SMTP server makes the final delivery"&. This implies that this
22643 header should not be present in incoming messages. Exim has a configuration
22644 option, &%return_path_remove%&, which requests removal of this header from
22645 incoming messages, so that delivered messages can safely be resent to other
22649 .option shadow_condition transports string&!! unset
22650 See &%shadow_transport%& below.
22653 .option shadow_transport transports string unset
22654 .cindex "shadow transport"
22655 .cindex "transport" "shadow"
22656 A local transport may set the &%shadow_transport%& option to the name of
22657 another local transport. Shadow remote transports are not supported.
22659 Whenever a delivery to the main transport succeeds, and either
22660 &%shadow_condition%& is unset, or its expansion does not result in the empty
22661 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
22662 passed to the shadow transport, with the same delivery address or addresses. If
22663 expansion fails, no action is taken except that non-forced expansion failures
22664 cause a log line to be written.
22666 The result of the shadow transport is discarded and does not affect the
22667 subsequent processing of the message. Only a single level of shadowing is
22668 provided; the &%shadow_transport%& option is ignored on any transport when it
22669 is running as a shadow. Options concerned with output from pipes are also
22670 ignored. The log line for the successful delivery has an item added on the end,
22673 ST=<shadow transport name>
22675 If the shadow transport did not succeed, the error message is put in
22676 parentheses afterwards. Shadow transports can be used for a number of different
22677 purposes, including keeping more detailed log information than Exim normally
22678 provides, and implementing automatic acknowledgment policies based on message
22679 headers that some sites insist on.
22682 .option transport_filter transports string&!! unset
22683 .cindex "transport" "filter"
22684 .cindex "filter" "transport filter"
22685 This option sets up a filtering (in the Unix shell sense) process for messages
22686 at transport time. It should not be confused with mail filtering as set up by
22687 individual users or via a system filter.
22688 If unset, or expanding to an empty string, no filtering is done.
22690 When the message is about to be written out, the command specified by
22691 &%transport_filter%& is started up in a separate, parallel process, and
22692 the entire message, including the header lines, is passed to it on its standard
22693 input (this in fact is done from a third process, to avoid deadlock). The
22694 command must be specified as an absolute path.
22696 The lines of the message that are written to the transport filter are
22697 terminated by newline (&"\n"&). The message is passed to the filter before any
22698 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
22699 lines beginning with a dot, and also before any processing implied by the
22700 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
22701 &(pipe)& transports.
22703 The standard error for the filter process is set to the same destination as its
22704 standard output; this is read and written to the message's ultimate
22705 destination. The process that writes the message to the filter, the
22706 filter itself, and the original process that reads the result and delivers it
22707 are all run in parallel, like a shell pipeline.
22709 The filter can perform any transformations it likes, but of course should take
22710 care not to break RFC 2822 syntax. Exim does not check the result, except to
22711 test for a final newline when SMTP is in use. All messages transmitted over
22712 SMTP must end with a newline, so Exim supplies one if it is missing.
22714 .cindex "content scanning" "per user"
22715 A transport filter can be used to provide content-scanning on a per-user basis
22716 at delivery time if the only required effect of the scan is to modify the
22717 message. For example, a content scan could insert a new header line containing
22718 a spam score. This could be interpreted by a filter in the user's MUA. It is
22719 not possible to discard a message at this stage.
22721 .cindex "SIZE" "ESMTP extension"
22722 A problem might arise if the filter increases the size of a message that is
22723 being sent down an SMTP connection. If the receiving SMTP server has indicated
22724 support for the SIZE parameter, Exim will have sent the size of the message
22725 at the start of the SMTP session. If what is actually sent is substantially
22726 more, the server might reject the message. This can be worked round by setting
22727 the &%size_addition%& option on the &(smtp)& transport, either to allow for
22728 additions to the message, or to disable the use of SIZE altogether.
22730 .vindex "&$pipe_addresses$&"
22731 The value of the &%transport_filter%& option is the command string for starting
22732 the filter, which is run directly from Exim, not under a shell. The string is
22733 parsed by Exim in the same way as a command string for the &(pipe)& transport:
22734 Exim breaks it up into arguments and then expands each argument separately (see
22735 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
22736 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
22737 of arguments, one for each address that applies to this delivery. (This isn't
22738 an ideal name for this feature here, but as it was already implemented for the
22739 &(pipe)& transport, it seemed sensible not to change it.)
22742 .vindex "&$host_address$&"
22743 The expansion variables &$host$& and &$host_address$& are available when the
22744 transport is a remote one. They contain the name and IP address of the host to
22745 which the message is being sent. For example:
22747 transport_filter = /some/directory/transport-filter.pl \
22748 $host $host_address $sender_address $pipe_addresses
22751 Two problems arise if you want to use more complicated expansion items to
22752 generate transport filter commands, both of which due to the fact that the
22753 command is split up &'before'& expansion.
22755 If an expansion item contains white space, you must quote it, so that it is all
22756 part of the same command item. If the entire option setting is one such
22757 expansion item, you have to take care what kind of quoting you use. For
22760 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
22762 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
22763 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
22764 stripped by Exim when it read the option's value. When the value is used, if
22765 the single quotes were missing, the line would be split into two items,
22766 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
22767 Exim tried to expand the first one.
22769 Except for the special case of &$pipe_addresses$& that is mentioned above, an
22770 expansion cannot generate multiple arguments, or a command name followed by
22771 arguments. Consider this example:
22773 transport_filter = ${lookup{$host}lsearch{/a/file}\
22774 {$value}{/bin/cat}}
22776 The result of the lookup is interpreted as the name of the command, even
22777 if it contains white space. The simplest way round this is to use a shell:
22779 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
22780 {$value}{/bin/cat}}
22784 The filter process is run under the same uid and gid as the normal delivery.
22785 For remote deliveries this is the Exim uid/gid by default. The command should
22786 normally yield a zero return code. Transport filters are not supposed to fail.
22787 A non-zero code is taken to mean that the transport filter encountered some
22788 serious problem. Delivery of the message is deferred; the message remains on
22789 the queue and is tried again later. It is not possible to cause a message to be
22790 bounced from a transport filter.
22792 If a transport filter is set on an autoreply transport, the original message is
22793 passed through the filter as it is being copied into the newly generated
22794 message, which happens if the &%return_message%& option is set.
22797 .option transport_filter_timeout transports time 5m
22798 .cindex "transport" "filter, timeout"
22799 When Exim is reading the output of a transport filter, it applies a timeout
22800 that can be set by this option. Exceeding the timeout is normally treated as a
22801 temporary delivery failure. However, if a transport filter is used with a
22802 &(pipe)& transport, a timeout in the transport filter is treated in the same
22803 way as a timeout in the pipe command itself. By default, a timeout is a hard
22804 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
22805 becomes a temporary error.
22808 .option user transports string&!! "Exim user"
22809 .cindex "uid (user id)" "local delivery"
22810 .cindex "transport" "user, specifying"
22811 This option specifies the user under whose uid the delivery process is to be
22812 run, overriding any uid that may have been set by the router. If the user is
22813 given as a name, the uid is looked up from the password data, and the
22814 associated group is taken as the value of the gid to be used if the &%group%&
22817 For deliveries that use local transports, a user and group are normally
22818 specified explicitly or implicitly (for example, as a result of
22819 &%check_local_user%&) by the router or transport.
22821 .cindex "hints database" "access by remote transport"
22822 For remote transports, you should leave this option unset unless you really are
22823 sure you know what you are doing. When a remote transport is running, it needs
22824 to be able to access Exim's hints databases, because each host may have its own
22826 .ecindex IIDgenoptra1
22827 .ecindex IIDgenoptra2
22828 .ecindex IIDgenoptra3
22835 . ////////////////////////////////////////////////////////////////////////////
22836 . ////////////////////////////////////////////////////////////////////////////
22838 .chapter "Address batching in local transports" "CHAPbatching" &&&
22840 .cindex "transport" "local; address batching in"
22841 The only remote transport (&(smtp)&) is normally configured to handle more than
22842 one address at a time, so that when several addresses are routed to the same
22843 remote host, just one copy of the message is sent. Local transports, however,
22844 normally handle one address at a time. That is, a separate instance of the
22845 transport is run for each address that is routed to the transport. A separate
22846 copy of the message is delivered each time.
22848 .cindex "batched local delivery"
22849 .oindex "&%batch_max%&"
22850 .oindex "&%batch_id%&"
22851 In special cases, it may be desirable to handle several addresses at once in a
22852 local transport, for example:
22855 In an &(appendfile)& transport, when storing messages in files for later
22856 delivery by some other means, a single copy of the message with multiple
22857 recipients saves space.
22859 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
22860 a single copy saves time, and is the normal way LMTP is expected to work.
22862 In a &(pipe)& transport, when passing the message
22863 to a scanner program or
22864 to some other delivery mechanism such as UUCP, multiple recipients may be
22868 These three local transports all have the same options for controlling multiple
22869 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
22870 repeating the information for each transport, these options are described here.
22872 The &%batch_max%& option specifies the maximum number of addresses that can be
22873 delivered together in a single run of the transport. Its default value is one
22874 (no batching). When more than one address is routed to a transport that has a
22875 &%batch_max%& value greater than one, the addresses are delivered in a batch
22876 (that is, in a single run of the transport with multiple recipients), subject
22877 to certain conditions:
22880 .vindex "&$local_part$&"
22881 If any of the transport's options contain a reference to &$local_part$&, no
22882 batching is possible.
22884 .vindex "&$domain$&"
22885 If any of the transport's options contain a reference to &$domain$&, only
22886 addresses with the same domain are batched.
22888 .cindex "customizing" "batching condition"
22889 If &%batch_id%& is set, it is expanded for each address, and only those
22890 addresses with the same expanded value are batched. This allows you to specify
22891 customized batching conditions. Failure of the expansion for any reason,
22892 including forced failure, disables batching, but it does not stop the delivery
22895 Batched addresses must also have the same errors address (where to send
22896 delivery errors), the same header additions and removals, the same user and
22897 group for the transport, and if a host list is present, the first host must
22901 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
22902 both when the file or pipe command is specified in the transport, and when it
22903 is specified by a &(redirect)& router, but all the batched addresses must of
22904 course be routed to the same file or pipe command. These two transports have an
22905 option called &%use_bsmtp%&, which causes them to deliver the message in
22906 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
22907 &%check_string%& and &%escape_string%& options are forced to the values
22910 escape_string = ".."
22912 when batched SMTP is in use. A full description of the batch SMTP mechanism is
22913 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
22914 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
22916 .cindex "&'Envelope-to:'& header line"
22917 If the generic &%envelope_to_add%& option is set for a batching transport, the
22918 &'Envelope-to:'& header that is added to the message contains all the addresses
22919 that are being processed together. If you are using a batching &(appendfile)&
22920 transport without &%use_bsmtp%&, the only way to preserve the recipient
22921 addresses is to set the &%envelope_to_add%& option.
22923 .cindex "&(pipe)& transport" "with multiple addresses"
22924 .vindex "&$pipe_addresses$&"
22925 If you are using a &(pipe)& transport without BSMTP, and setting the
22926 transport's &%command%& option, you can include &$pipe_addresses$& as part of
22927 the command. This is not a true variable; it is a bit of magic that causes each
22928 of the recipient addresses to be inserted into the command as a separate
22929 argument. This provides a way of accessing all the addresses that are being
22930 delivered in the batch. &*Note:*& This is not possible for pipe commands that
22931 are specified by a &(redirect)& router.
22936 . ////////////////////////////////////////////////////////////////////////////
22937 . ////////////////////////////////////////////////////////////////////////////
22939 .chapter "The appendfile transport" "CHAPappendfile"
22940 .scindex IIDapptra1 "&(appendfile)& transport"
22941 .scindex IIDapptra2 "transports" "&(appendfile)&"
22942 .cindex "directory creation"
22943 .cindex "creating directories"
22944 The &(appendfile)& transport delivers a message by appending it to an existing
22945 file, or by creating an entirely new file in a specified directory. Single
22946 files to which messages are appended can be in the traditional Unix mailbox
22947 format, or optionally in the MBX format supported by the Pine MUA and
22948 University of Washington IMAP daemon, &'inter alia'&. When each message is
22949 being delivered as a separate file, &"maildir"& format can optionally be used
22950 to give added protection against failures that happen part-way through the
22951 delivery. A third form of separate-file delivery known as &"mailstore"& is also
22952 supported. For all file formats, Exim attempts to create as many levels of
22953 directory as necessary, provided that &%create_directory%& is set.
22955 The code for the optional formats is not included in the Exim binary by
22956 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
22957 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
22960 .cindex "quota" "system"
22961 Exim recognizes system quota errors, and generates an appropriate message. Exim
22962 also supports its own quota control within the transport, for use when the
22963 system facility is unavailable or cannot be used for some reason.
22965 If there is an error while appending to a file (for example, quota exceeded or
22966 partition filled), Exim attempts to reset the file's length and last
22967 modification time back to what they were before. If there is an error while
22968 creating an entirely new file, the new file is removed.
22970 Before appending to a file, a number of security checks are made, and the
22971 file is locked. A detailed description is given below, after the list of
22974 The &(appendfile)& transport is most commonly used for local deliveries to
22975 users' mailboxes. However, it can also be used as a pseudo-remote transport for
22976 putting messages into files for remote delivery by some means other than Exim.
22977 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
22982 .section "The file and directory options" "SECTfildiropt"
22983 The &%file%& option specifies a single file, to which the message is appended;
22984 the &%directory%& option specifies a directory, in which a new file containing
22985 the message is created. Only one of these two options can be set, and for
22986 normal deliveries to mailboxes, one of them &'must'& be set.
22988 .vindex "&$address_file$&"
22989 .vindex "&$local_part$&"
22990 However, &(appendfile)& is also used for delivering messages to files or
22991 directories whose names (or parts of names) are obtained from alias,
22992 forwarding, or filtering operations (for example, a &%save%& command in a
22993 user's Exim filter). When such a transport is running, &$local_part$& contains
22994 the local part that was aliased or forwarded, and &$address_file$& contains the
22995 name (or partial name) of the file or directory generated by the redirection
22996 operation. There are two cases:
22999 If neither &%file%& nor &%directory%& is set, the redirection operation
23000 must specify an absolute path (one that begins with &`/`&). This is the most
23001 common case when users with local accounts use filtering to sort mail into
23002 different folders. See for example, the &(address_file)& transport in the
23003 default configuration. If the path ends with a slash, it is assumed to be the
23004 name of a directory. A delivery to a directory can also be forced by setting
23005 &%maildir_format%& or &%mailstore_format%&.
23007 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
23008 used to determine the file or directory name for the delivery. Normally, the
23009 contents of &$address_file$& are used in some way in the string expansion.
23011 If the &%create_file%& option is set to a path which
23012 matches (see the option definition below for details)
23013 a file or directory name
23014 for the delivery, that name becomes de-tainted.
23016 .cindex "tainted data" "in filenames"
23017 .cindex appendfile "tainted data"
23018 Tainted data may not be used for a file or directory name.
23019 This means that, for instance, &$local_part$& cannot be used directly
23020 as a component of a path. It can however be used as the key for a lookup
23021 which returns a path (or component).
23024 .cindex "Sieve filter" "configuring &(appendfile)&"
23025 .cindex "Sieve filter" "relative mailbox path handling"
23026 As an example of the second case, consider an environment where users do not
23027 have home directories. They may be permitted to use Exim filter commands of the
23032 or Sieve filter commands of the form:
23034 require "fileinto";
23035 fileinto "folder23";
23037 In this situation, the expansion of &%file%& or &%directory%& in the transport
23038 must transform the relative path into an appropriate absolute filename. In the
23039 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
23040 is used as a result of a &"keep"& action in the filter. This example shows one
23041 way of handling this requirement:
23043 file = ${if eq{$address_file}{inbox} \
23044 {/var/mail/$local_part_data} \
23045 {${if eq{${substr_0_1:$address_file}}{/} \
23047 {$home/mail/$address_file} \
23051 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
23052 location, absolute paths are used without change, and other folders are in the
23053 &_mail_& directory within the home directory.
23055 &*Note 1*&: While processing an Exim filter, a relative path such as
23056 &_folder23_& is turned into an absolute path if a home directory is known to
23057 the router. In particular, this is the case if &%check_local_user%& is set. If
23058 you want to prevent this happening at routing time, you can set
23059 &%router_home_directory%& empty. This forces the router to pass the relative
23060 path to the transport.
23062 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
23063 the &%file%& or &%directory%& option is still used if it is set.
23068 .section "Private options for appendfile" "SECID134"
23069 .cindex "options" "&(appendfile)& transport"
23073 .option allow_fifo appendfile boolean false
23074 .cindex "fifo (named pipe)"
23075 .cindex "named pipe (fifo)"
23076 .cindex "pipe" "named (fifo)"
23077 Setting this option permits delivery to named pipes (FIFOs) as well as to
23078 regular files. If no process is reading the named pipe at delivery time, the
23079 delivery is deferred.
23082 .option allow_symlink appendfile boolean false
23083 .cindex "symbolic link" "to mailbox"
23084 .cindex "mailbox" "symbolic link"
23085 By default, &(appendfile)& will not deliver if the path name for the file is
23086 that of a symbolic link. Setting this option relaxes that constraint, but there
23087 are security issues involved in the use of symbolic links. Be sure you know
23088 what you are doing if you set this. Details of exactly what this option affects
23089 are included in the discussion which follows this list of options.
23092 .option batch_id appendfile string&!! unset
23093 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23094 However, batching is automatically disabled for &(appendfile)& deliveries that
23095 happen as a result of forwarding or aliasing or other redirection directly to a
23099 .option batch_max appendfile integer 1
23100 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23103 .option check_group appendfile boolean false
23104 When this option is set, the group owner of the file defined by the &%file%&
23105 option is checked to see that it is the same as the group under which the
23106 delivery process is running. The default setting is false because the default
23107 file mode is 0600, which means that the group is irrelevant.
23110 .option check_owner appendfile boolean true
23111 When this option is set, the owner of the file defined by the &%file%& option
23112 is checked to ensure that it is the same as the user under which the delivery
23113 process is running.
23116 .option check_string appendfile string "see below"
23117 .cindex "&""From""& line"
23118 As &(appendfile)& writes the message, the start of each line is tested for
23119 matching &%check_string%&, and if it does, the initial matching characters are
23120 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
23121 a literal string, not a regular expression, and the case of any letters it
23122 contains is significant.
23124 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
23125 are forced to &"."& and &".."& respectively, and any settings in the
23126 configuration are ignored. Otherwise, they default to &"From&~"& and
23127 &">From&~"& when the &%file%& option is set, and unset when any of the
23128 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
23130 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
23131 suitable for traditional &"BSD"& mailboxes, where a line beginning with
23132 &"From&~"& indicates the start of a new message. All four options need changing
23133 if another format is used. For example, to deliver to mailboxes in MMDF format:
23134 .cindex "MMDF format mailbox"
23135 .cindex "mailbox" "MMDF format"
23137 check_string = "\1\1\1\1\n"
23138 escape_string = "\1\1\1\1 \n"
23139 message_prefix = "\1\1\1\1\n"
23140 message_suffix = "\1\1\1\1\n"
23142 .option create_directory appendfile boolean true
23143 .cindex "directory creation"
23144 When this option is true, Exim attempts to create any missing superior
23145 directories for the file that it is about to write. A created directory's mode
23146 is given by the &%directory_mode%& option.
23148 The group ownership of a newly created directory is highly dependent on the
23149 operating system (and possibly the file system) that is being used. For
23150 example, in Solaris, if the parent directory has the setgid bit set, its group
23151 is propagated to the child; if not, the currently set group is used. However,
23152 in FreeBSD, the parent's group is always used.
23156 .option create_file appendfile string anywhere
23157 This option constrains the location of files and directories that are created
23158 by this transport. It applies to files defined by the &%file%& option and
23159 directories defined by the &%directory%& option. In the case of maildir
23160 delivery, it applies to the top level directory, not the maildir directories
23164 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
23165 &"belowhome"&, or to an absolute path.
23168 In the second and third cases, a home directory must have been
23169 set for the transport, and the file or directory being created must
23171 The "belowhome" checking additionally checks for attempts to use "../"
23172 to evade the testing.
23173 This option is not useful when an explicit filename is
23174 given for normal mailbox deliveries. It is intended for the case when filenames
23175 are generated from users' &_.forward_& files. These are usually handled
23176 by an &(appendfile)& transport called &%address_file%&. See also
23177 &%file_must_exist%&.
23180 In the fourth case,
23181 the value given for this option must be an absolute path for an
23182 existing directory.
23183 The value is used for checking instead of a home directory;
23184 checking is done in "belowhome" mode.
23186 .cindex "tainted data" "de-tainting"
23187 If "belowhome" checking is used, the file or directory path
23188 becomes de-tainted.
23192 .option directory appendfile string&!! unset
23193 This option is mutually exclusive with the &%file%& option, but one of &%file%&
23194 or &%directory%& must be set, unless the delivery is the direct result of a
23195 redirection (see section &<<SECTfildiropt>>&).
23197 When &%directory%& is set, the string is expanded, and the message is delivered
23198 into a new file or files in or below the given directory, instead of being
23199 appended to a single mailbox file. A number of different formats are provided
23200 (see &%maildir_format%& and &%mailstore_format%&), and see section
23201 &<<SECTopdir>>& for further details of this form of delivery.
23204 The result of expansion must not be tainted, unless the &%create_file%& option
23209 .option directory_file appendfile string&!! "see below"
23211 .vindex "&$inode$&"
23212 When &%directory%& is set, but neither &%maildir_format%& nor
23213 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
23214 whose name is obtained by expanding this string. The default value is:
23216 q${base62:$tod_epoch}-$inode
23218 This generates a unique name from the current time, in base 62 form, and the
23219 inode of the file. The variable &$inode$& is available only when expanding this
23223 .option directory_mode appendfile "octal integer" 0700
23224 If &(appendfile)& creates any directories as a result of the
23225 &%create_directory%& option, their mode is specified by this option.
23228 .option escape_string appendfile string "see description"
23229 See &%check_string%& above.
23232 .option file appendfile string&!! unset
23233 This option is mutually exclusive with the &%directory%& option, but one of
23234 &%file%& or &%directory%& must be set, unless the delivery is the direct result
23235 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
23236 specifies a single file, to which the message is appended. One or more of
23237 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
23241 The result of expansion must not be tainted, unless the &%create_file%& option
23245 .cindex "NFS" "lock file"
23246 .cindex "locking files"
23247 .cindex "lock files"
23248 If you are using more than one host to deliver over NFS into the same
23249 mailboxes, you should always use lock files.
23251 The string value is expanded for each delivery, and must yield an absolute
23252 path. The most common settings of this option are variations on one of these
23255 file = /var/spool/mail/$local_part_data
23256 file = /home/$local_part_data/inbox
23259 .cindex "&""sticky""& bit"
23260 In the first example, all deliveries are done into the same directory. If Exim
23261 is configured to use lock files (see &%use_lockfile%& below) it must be able to
23262 create a file in the directory, so the &"sticky"& bit must be turned on for
23263 deliveries to be possible, or alternatively the &%group%& option can be used to
23264 run the delivery under a group id which has write access to the directory.
23268 .option file_format appendfile string unset
23269 .cindex "file" "mailbox; checking existing format"
23270 This option requests the transport to check the format of an existing file
23271 before adding to it. The check consists of matching a specific string at the
23272 start of the file. The value of the option consists of an even number of
23273 colon-separated strings. The first of each pair is the test string, and the
23274 second is the name of a transport. If the transport associated with a matched
23275 string is not the current transport, control is passed over to the other
23276 transport. For example, suppose the standard &(local_delivery)& transport has
23279 file_format = "From : local_delivery :\
23280 \1\1\1\1\n : local_mmdf_delivery"
23282 Mailboxes that begin with &"From"& are still handled by this transport, but if
23283 a mailbox begins with four binary ones followed by a newline, control is passed
23284 to a transport called &%local_mmdf_delivery%&, which presumably is configured
23285 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
23286 is assumed to match the current transport. If the start of a mailbox doesn't
23287 match any string, or if the transport named for a given string is not defined,
23288 delivery is deferred.
23291 .option file_must_exist appendfile boolean false
23292 If this option is true, the file specified by the &%file%& option must exist.
23293 A temporary error occurs if it does not, causing delivery to be deferred.
23294 If this option is false, the file is created if it does not exist.
23297 .option lock_fcntl_timeout appendfile time 0s
23298 .cindex "timeout" "mailbox locking"
23299 .cindex "mailbox" "locking, blocking and non-blocking"
23300 .cindex "locking files"
23301 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
23302 when locking an open mailbox file. If the call fails, the delivery process
23303 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
23304 Non-blocking calls are used so that the file is not kept open during the wait
23305 for the lock; the reason for this is to make it as safe as possible for
23306 deliveries over NFS in the case when processes might be accessing an NFS
23307 mailbox without using a lock file. This should not be done, but
23308 misunderstandings and hence misconfigurations are not unknown.
23310 On a busy system, however, the performance of a non-blocking lock approach is
23311 not as good as using a blocking lock with a timeout. In this case, the waiting
23312 is done inside the system call, and Exim's delivery process acquires the lock
23313 and can proceed as soon as the previous lock holder releases it.
23315 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
23316 timeout, are used. There may still be some retrying: the maximum number of
23319 (lock_retries * lock_interval) / lock_fcntl_timeout
23321 rounded up to the next whole number. In other words, the total time during
23322 which &(appendfile)& is trying to get a lock is roughly the same, unless
23323 &%lock_fcntl_timeout%& is set very large.
23325 You should consider setting this option if you are getting a lot of delayed
23326 local deliveries because of errors of the form
23328 failed to lock mailbox /some/file (fcntl)
23331 .option lock_flock_timeout appendfile time 0s
23332 This timeout applies to file locking when using &[flock()]& (see
23333 &%use_flock%&); the timeout operates in a similar manner to
23334 &%lock_fcntl_timeout%&.
23337 .option lock_interval appendfile time 3s
23338 This specifies the time to wait between attempts to lock the file. See below
23339 for details of locking.
23342 .option lock_retries appendfile integer 10
23343 This specifies the maximum number of attempts to lock the file. A value of zero
23344 is treated as 1. See below for details of locking.
23347 .option lockfile_mode appendfile "octal integer" 0600
23348 This specifies the mode of the created lock file, when a lock file is being
23349 used (see &%use_lockfile%& and &%use_mbx_lock%&).
23352 .option lockfile_timeout appendfile time 30m
23353 .cindex "timeout" "mailbox locking"
23354 When a lock file is being used (see &%use_lockfile%&), if a lock file already
23355 exists and is older than this value, it is assumed to have been left behind by
23356 accident, and Exim attempts to remove it.
23359 .option mailbox_filecount appendfile string&!! unset
23360 .cindex "mailbox" "specifying size of"
23361 .cindex "size" "of mailbox"
23362 If this option is set, it is expanded, and the result is taken as the current
23363 number of files in the mailbox. It must be a decimal number, optionally
23364 followed by K or M. This provides a way of obtaining this information from an
23365 external source that maintains the data.
23368 .option mailbox_size appendfile string&!! unset
23369 .cindex "mailbox" "specifying size of"
23370 .cindex "size" "of mailbox"
23371 If this option is set, it is expanded, and the result is taken as the current
23372 size the mailbox. It must be a decimal number, optionally followed by K or M.
23373 This provides a way of obtaining this information from an external source that
23374 maintains the data. This is likely to be helpful for maildir deliveries where
23375 it is computationally expensive to compute the size of a mailbox.
23379 .option maildir_format appendfile boolean false
23380 .cindex "maildir format" "specifying"
23381 If this option is set with the &%directory%& option, the delivery is into a new
23382 file, in the &"maildir"& format that is used by other mail software. When the
23383 transport is activated directly from a &(redirect)& router (for example, the
23384 &(address_file)& transport in the default configuration), setting
23385 &%maildir_format%& causes the path received from the router to be treated as a
23386 directory, whether or not it ends with &`/`&. This option is available only if
23387 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
23388 &<<SECTmaildirdelivery>>& below for further details.
23391 .option maildir_quota_directory_regex appendfile string "See below"
23392 .cindex "maildir format" "quota; directories included in"
23393 .cindex "quota" "maildir; directories included in"
23394 This option is relevant only when &%maildir_use_size_file%& is set. It defines
23395 a regular expression for specifying directories, relative to the quota
23396 directory (see &%quota_directory%&), that should be included in the quota
23397 calculation. The default value is:
23399 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
23401 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
23402 (directories whose names begin with a dot). If you want to exclude the
23404 folder from the count (as some sites do), you need to change this setting to
23406 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
23408 This uses a negative lookahead in the regular expression to exclude the
23409 directory whose name is &_.Trash_&. When a directory is excluded from quota
23410 calculations, quota processing is bypassed for any messages that are delivered
23411 directly into that directory.
23414 .option maildir_retries appendfile integer 10
23415 This option specifies the number of times to retry when writing a file in
23416 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
23419 .option maildir_tag appendfile string&!! unset
23420 This option applies only to deliveries in maildir format, and is described in
23421 section &<<SECTmaildirdelivery>>& below.
23424 .option maildir_use_size_file appendfile&!! boolean false
23425 .cindex "maildir format" "&_maildirsize_& file"
23426 The result of string expansion for this option must be a valid boolean value.
23427 If it is true, it enables support for &_maildirsize_& files. Exim
23428 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
23429 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
23430 value is zero. See &%maildir_quota_directory_regex%& above and section
23431 &<<SECTmaildirdelivery>>& below for further details.
23433 .option maildirfolder_create_regex appendfile string unset
23434 .cindex "maildir format" "&_maildirfolder_& file"
23435 .cindex "&_maildirfolder_&, creating"
23436 The value of this option is a regular expression. If it is unset, it has no
23437 effect. Otherwise, before a maildir delivery takes place, the pattern is
23438 matched against the name of the maildir directory, that is, the directory
23439 containing the &_new_& and &_tmp_& subdirectories that will be used for the
23440 delivery. If there is a match, Exim checks for the existence of a file called
23441 &_maildirfolder_& in the directory, and creates it if it does not exist.
23442 See section &<<SECTmaildirdelivery>>& for more details.
23445 .option mailstore_format appendfile boolean false
23446 .cindex "mailstore format" "specifying"
23447 If this option is set with the &%directory%& option, the delivery is into two
23448 new files in &"mailstore"& format. The option is available only if
23449 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
23450 below for further details.
23453 .option mailstore_prefix appendfile string&!! unset
23454 This option applies only to deliveries in mailstore format, and is described in
23455 section &<<SECTopdir>>& below.
23458 .option mailstore_suffix appendfile string&!! unset
23459 This option applies only to deliveries in mailstore format, and is described in
23460 section &<<SECTopdir>>& below.
23463 .option mbx_format appendfile boolean false
23464 .cindex "locking files"
23465 .cindex "file" "locking"
23466 .cindex "file" "MBX format"
23467 .cindex "MBX format, specifying"
23468 This option is available only if Exim has been compiled with SUPPORT_MBX
23469 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
23470 the message is appended to the mailbox file in MBX format instead of
23471 traditional Unix format. This format is supported by Pine4 and its associated
23472 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
23474 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
23475 automatically changed by the use of &%mbx_format%&. They should normally be set
23476 empty when using MBX format, so this option almost always appears in this
23483 If none of the locking options are mentioned in the configuration,
23484 &%use_mbx_lock%& is assumed and the other locking options default to false. It
23485 is possible to specify the other kinds of locking with &%mbx_format%&, but
23486 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
23487 interworks with &'c-client'&, providing for shared access to the mailbox. It
23488 should not be used if any program that does not use this form of locking is
23489 going to access the mailbox, nor should it be used if the mailbox file is NFS
23490 mounted, because it works only when the mailbox is accessed from a single host.
23492 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
23493 the standard version of &'c-client'&, because as long as it has a mailbox open
23494 (this means for the whole of a Pine or IMAP session), Exim will not be able to
23495 append messages to it.
23498 .option message_prefix appendfile string&!! "see below"
23499 .cindex "&""From""& line"
23500 The string specified here is expanded and output at the start of every message.
23501 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23502 in which case it is:
23504 message_prefix = "From ${if def:return_path{$return_path}\
23505 {MAILER-DAEMON}} $tod_bsdinbox\n"
23507 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23508 &`\n`& to &`\r\n`& in &%message_prefix%&.
23510 .option message_suffix appendfile string&!! "see below"
23511 The string specified here is expanded and output at the end of every message.
23512 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23513 in which case it is a single newline character. The suffix can be suppressed by
23518 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23519 &`\n`& to &`\r\n`& in &%message_suffix%&.
23521 .option mode appendfile "octal integer" 0600
23522 If the output file is created, it is given this mode. If it already exists and
23523 has wider permissions, they are reduced to this mode. If it has narrower
23524 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
23525 if the delivery is the result of a &%save%& command in a filter file specifying
23526 a particular mode, the mode of the output file is always forced to take that
23527 value, and this option is ignored.
23530 .option mode_fail_narrower appendfile boolean true
23531 This option applies in the case when an existing mailbox file has a narrower
23532 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
23533 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
23534 continues with the delivery attempt, using the existing mode of the file.
23537 .option notify_comsat appendfile boolean false
23538 If this option is true, the &'comsat'& daemon is notified after every
23539 successful delivery to a user mailbox. This is the daemon that notifies logged
23540 on users about incoming mail.
23543 .option quota appendfile string&!! unset
23544 .cindex "quota" "imposed by Exim"
23545 This option imposes a limit on the size of the file to which Exim is appending,
23546 or to the total space used in the directory tree when the &%directory%& option
23547 is set. In the latter case, computation of the space used is expensive, because
23548 all the files in the directory (and any sub-directories) have to be
23549 individually inspected and their sizes summed. (See &%quota_size_regex%& and
23550 &%maildir_use_size_file%& for ways to avoid this in environments where users
23551 have no shell access to their mailboxes).
23553 As there is no interlock against two simultaneous deliveries into a
23554 multi-file mailbox, it is possible for the quota to be overrun in this case.
23555 For single-file mailboxes, of course, an interlock is a necessity.
23557 A file's size is taken as its &'used'& value. Because of blocking effects, this
23558 may be a lot less than the actual amount of disk space allocated to the file.
23559 If the sizes of a number of files are being added up, the rounding effect can
23560 become quite noticeable, especially on systems that have large block sizes.
23561 Nevertheless, it seems best to stick to the &'used'& figure, because this is
23562 the obvious value which users understand most easily.
23564 The value of the option is expanded, and must then be a numerical value
23565 (decimal point allowed), optionally followed by one of the letters K, M, or G,
23566 for kilobytes, megabytes, or gigabytes, optionally followed by a slash
23567 and further option modifiers. If Exim is running on a system with
23568 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
23571 The option modifier &%no_check%& can be used to force delivery even if the over
23572 quota condition is met. The quota gets updated as usual.
23574 &*Note*&: A value of zero is interpreted as &"no quota"&.
23576 The expansion happens while Exim is running as root, before it changes uid for
23577 the delivery. This means that files that are inaccessible to the end user can
23578 be used to hold quota values that are looked up in the expansion. When delivery
23579 fails because this quota is exceeded, the handling of the error is as for
23580 system quota failures.
23582 By default, Exim's quota checking mimics system quotas, and restricts the
23583 mailbox to the specified maximum size, though the value is not accurate to the
23584 last byte, owing to separator lines and additional headers that may get added
23585 during message delivery. When a mailbox is nearly full, large messages may get
23586 refused even though small ones are accepted, because the size of the current
23587 message is added to the quota when the check is made. This behaviour can be
23588 changed by setting &%quota_is_inclusive%& false. When this is done, the check
23589 for exceeding the quota does not include the current message. Thus, deliveries
23590 continue until the quota has been exceeded; thereafter, no further messages are
23591 delivered. See also &%quota_warn_threshold%&.
23594 .option quota_directory appendfile string&!! unset
23595 This option defines the directory to check for quota purposes when delivering
23596 into individual files. The default is the delivery directory, or, if a file
23597 called &_maildirfolder_& exists in a maildir directory, the parent of the
23598 delivery directory.
23601 .option quota_filecount appendfile string&!! 0
23602 This option applies when the &%directory%& option is set. It limits the total
23603 number of files in the directory (compare the inode limit in system quotas). It
23604 can only be used if &%quota%& is also set. The value is expanded; an expansion
23605 failure causes delivery to be deferred. A value of zero is interpreted as
23608 The option modifier &%no_check%& can be used to force delivery even if the over
23609 quota condition is met. The quota gets updated as usual.
23611 .option quota_is_inclusive appendfile boolean true
23612 See &%quota%& above.
23615 .option quota_size_regex appendfile string unset
23616 This option applies when one of the delivery modes that writes a separate file
23617 for each message is being used. When Exim wants to find the size of one of
23618 these files in order to test the quota, it first checks &%quota_size_regex%&.
23619 If this is set to a regular expression that matches the filename, and it
23620 captures one string, that string is interpreted as a representation of the
23621 file's size. The value of &%quota_size_regex%& is not expanded.
23623 This feature is useful only when users have no shell access to their mailboxes
23624 &-- otherwise they could defeat the quota simply by renaming the files. This
23625 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
23626 the file length to the filename. For example:
23628 maildir_tag = ,S=$message_size
23629 quota_size_regex = ,S=(\d+)
23631 An alternative to &$message_size$& is &$message_linecount$&, which contains the
23632 number of lines in the message.
23634 The regular expression should not assume that the length is at the end of the
23635 filename (even though &%maildir_tag%& puts it there) because maildir MUAs
23636 sometimes add other information onto the ends of message filenames.
23638 Section &<<SECID136>>& contains further information.
23640 This option should not be used when other message-handling software
23641 may duplicate messages by making hardlinks to the files. When that is done Exim
23642 will count the message size once for each filename, in contrast with the actual
23643 disk usage. When the option is not set, calculating total usage requires
23644 a system-call per file to get the size; the number of links is then available also
23645 as is used to adjust the effective size.
23648 .option quota_warn_message appendfile string&!! "see below"
23649 See below for the use of this option. If it is not set when
23650 &%quota_warn_threshold%& is set, it defaults to
23652 quota_warn_message = "\
23653 To: $local_part@$domain\n\
23654 Subject: Your mailbox\n\n\
23655 This message is automatically created \
23656 by mail delivery software.\n\n\
23657 The size of your mailbox has exceeded \
23658 a warning threshold that is\n\
23659 set by the system administrator.\n"
23663 .option quota_warn_threshold appendfile string&!! 0
23664 .cindex "quota" "warning threshold"
23665 .cindex "mailbox" "size warning"
23666 .cindex "size" "of mailbox"
23667 This option is expanded in the same way as &%quota%& (see above). If the
23668 resulting value is greater than zero, and delivery of the message causes the
23669 size of the file or total space in the directory tree to cross the given
23670 threshold, a warning message is sent. If &%quota%& is also set, the threshold
23671 may be specified as a percentage of it by following the value with a percent
23675 quota_warn_threshold = 75%
23677 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
23678 percent sign is ignored.
23680 The warning message itself is specified by the &%quota_warn_message%& option,
23681 and it must start with a &'To:'& header line containing the recipient(s) of the
23682 warning message. These do not necessarily have to include the recipient(s) of
23683 the original message. A &'Subject:'& line should also normally be supplied. You
23684 can include any other header lines that you want. If you do not include a
23685 &'From:'& line, the default is:
23687 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
23689 .oindex &%errors_reply_to%&
23690 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
23693 The &%quota%& option does not have to be set in order to use this option; they
23694 are independent of one another except when the threshold is specified as a
23698 .option use_bsmtp appendfile boolean false
23699 .cindex "envelope from"
23700 .cindex "envelope sender"
23701 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
23702 format, with the envelope sender and recipient(s) included as SMTP commands. If
23703 you want to include a leading HELO command with such messages, you can do
23704 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
23705 for details of batch SMTP.
23708 .option use_crlf appendfile boolean false
23709 .cindex "carriage return"
23711 This option causes lines to be terminated with the two-character CRLF sequence
23712 (carriage return, linefeed) instead of just a linefeed character. In the case
23713 of batched SMTP, the byte sequence written to the file is then an exact image
23714 of what would be sent down a real SMTP connection.
23716 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
23717 (which are used to supply the traditional &"From&~"& and blank line separators
23718 in Berkeley-style mailboxes) are written verbatim, so must contain their own
23719 carriage return characters if these are needed. In cases where these options
23720 have non-empty defaults, the values end with a single linefeed, so they must be
23721 changed to end with &`\r\n`& if &%use_crlf%& is set.
23724 .option use_fcntl_lock appendfile boolean "see below"
23725 This option controls the use of the &[fcntl()]& function to lock a file for
23726 exclusive use when a message is being appended. It is set by default unless
23727 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
23728 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
23729 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
23732 .option use_flock_lock appendfile boolean false
23733 This option is provided to support the use of &[flock()]& for file locking, for
23734 the few situations where it is needed. Most modern operating systems support
23735 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
23736 each other. Exim uses &[fcntl()]& locking by default.
23738 This option is required only if you are using an operating system where
23739 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
23740 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
23741 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
23743 .cindex "Solaris" "&[flock()]& support"
23744 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
23745 have it (and some, I think, provide a not quite right version built on top of
23746 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
23747 the ability to use it, and any attempt to do so will cause a configuration
23750 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
23751 is just being mapped onto &[fcntl()]& by the OS).
23754 .option use_lockfile appendfile boolean "see below"
23755 If this option is turned off, Exim does not attempt to create a lock file when
23756 appending to a mailbox file. In this situation, the only locking is by
23757 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
23758 sure that every MUA that is ever going to look at your users' mailboxes uses
23759 &[fcntl()]& rather than a lock file, and even then only when you are not
23760 delivering over NFS from more than one host.
23762 .cindex "NFS" "lock file"
23763 In order to append to an NFS file safely from more than one host, it is
23764 necessary to take out a lock &'before'& opening the file, and the lock file
23765 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
23768 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
23769 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
23770 except when &%mbx_format%& is set.
23773 .option use_mbx_lock appendfile boolean "see below"
23774 This option is available only if Exim has been compiled with SUPPORT_MBX
23775 set in &_Local/Makefile_&. Setting the option specifies that special MBX
23776 locking rules be used. It is set by default if &%mbx_format%& is set and none
23777 of the locking options are mentioned in the configuration. The locking rules
23778 are the same as are used by the &'c-client'& library that underlies Pine and
23779 the IMAP4 and POP daemons that come with it (see the discussion below). The
23780 rules allow for shared access to the mailbox. However, this kind of locking
23781 does not work when the mailbox is NFS mounted.
23783 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
23784 &%use_flock_lock%& to control what kind of locking is used in implementing the
23785 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
23786 without &%use_fcntl_lock%& or &%use_flock_lock%&.
23791 .section "Operational details for appending" "SECTopappend"
23792 .cindex "appending to a file"
23793 .cindex "file" "appending"
23794 Before appending to a file, the following preparations are made:
23797 If the name of the file is &_/dev/null_&, no action is taken, and a success
23801 .cindex "directory creation"
23802 If any directories on the file's path are missing, Exim creates them if the
23803 &%create_directory%& option is set. A created directory's mode is given by the
23804 &%directory_mode%& option.
23807 If &%file_format%& is set, the format of an existing file is checked. If this
23808 indicates that a different transport should be used, control is passed to that
23812 .cindex "file" "locking"
23813 .cindex "locking files"
23814 .cindex "NFS" "lock file"
23815 If &%use_lockfile%& is set, a lock file is built in a way that will work
23816 reliably over NFS, as follows:
23819 Create a &"hitching post"& file whose name is that of the lock file with the
23820 current time, primary host name, and process id added, by opening for writing
23821 as a new file. If this fails with an access error, delivery is deferred.
23823 Close the hitching post file, and hard link it to the lock filename.
23825 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
23826 Unlink the hitching post name.
23828 Otherwise, use &[stat()]& to get information about the hitching post file, and
23829 then unlink hitching post name. If the number of links is exactly two, creation
23830 of the lock file succeeded but something (for example, an NFS server crash and
23831 restart) caused this fact not to be communicated to the &[link()]& call.
23833 If creation of the lock file failed, wait for &%lock_interval%& and try again,
23834 up to &%lock_retries%& times. However, since any program that writes to a
23835 mailbox should complete its task very quickly, it is reasonable to time out old
23836 lock files that are normally the result of user agent and system crashes. If an
23837 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
23838 it before trying again.
23842 A call is made to &[lstat()]& to discover whether the main file exists, and if
23843 so, what its characteristics are. If &[lstat()]& fails for any reason other
23844 than non-existence, delivery is deferred.
23847 .cindex "symbolic link" "to mailbox"
23848 .cindex "mailbox" "symbolic link"
23849 If the file does exist and is a symbolic link, delivery is deferred, unless the
23850 &%allow_symlink%& option is set, in which case the ownership of the link is
23851 checked, and then &[stat()]& is called to find out about the real file, which
23852 is then subjected to the checks below. The check on the top-level link
23853 ownership prevents one user creating a link for another's mailbox in a sticky
23854 directory, though allowing symbolic links in this case is definitely not a good
23855 idea. If there is a chain of symbolic links, the intermediate ones are not
23859 If the file already exists but is not a regular file, or if the file's owner
23860 and group (if the group is being checked &-- see &%check_group%& above) are
23861 different from the user and group under which the delivery is running,
23862 delivery is deferred.
23865 If the file's permissions are more generous than specified, they are reduced.
23866 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
23867 is set false, in which case the delivery is tried using the existing
23871 The file's inode number is saved, and the file is then opened for appending.
23872 If this fails because the file has vanished, &(appendfile)& behaves as if it
23873 hadn't existed (see below). For any other failures, delivery is deferred.
23876 If the file is opened successfully, check that the inode number hasn't
23877 changed, that it is still a regular file, and that the owner and permissions
23878 have not changed. If anything is wrong, defer delivery and freeze the message.
23881 If the file did not exist originally, defer delivery if the &%file_must_exist%&
23882 option is set. Otherwise, check that the file is being created in a permitted
23883 directory if the &%create_file%& option is set (deferring on failure), and then
23884 open for writing as a new file, with the O_EXCL and O_CREAT options,
23885 except when dealing with a symbolic link (the &%allow_symlink%& option must be
23886 set). In this case, which can happen if the link points to a non-existent file,
23887 the file is opened for writing using O_CREAT but not O_EXCL, because
23888 that prevents link following.
23891 .cindex "loop" "while file testing"
23892 If opening fails because the file exists, obey the tests given above for
23893 existing files. However, to avoid looping in a situation where the file is
23894 being continuously created and destroyed, the exists/not-exists loop is broken
23895 after 10 repetitions, and the message is then frozen.
23898 If opening fails with any other error, defer delivery.
23901 .cindex "file" "locking"
23902 .cindex "locking files"
23903 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
23904 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
23905 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
23906 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
23907 file, and an exclusive lock on the file whose name is
23909 /tmp/.<device-number>.<inode-number>
23911 using the device and inode numbers of the open mailbox file, in accordance with
23912 the MBX locking rules. This file is created with a mode that is specified by
23913 the &%lockfile_mode%& option.
23915 If Exim fails to lock the file, there are two possible courses of action,
23916 depending on the value of the locking timeout. This is obtained from
23917 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
23919 If the timeout value is zero, the file is closed, Exim waits for
23920 &%lock_interval%&, and then goes back and re-opens the file as above and tries
23921 to lock it again. This happens up to &%lock_retries%& times, after which the
23922 delivery is deferred.
23924 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
23925 &[flock()]& are used (with the given timeout), so there has already been some
23926 waiting involved by the time locking fails. Nevertheless, Exim does not give up
23927 immediately. It retries up to
23929 (lock_retries * lock_interval) / <timeout>
23931 times (rounded up).
23934 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
23935 and/or &[flock()]& locks) and then deletes the lock file if one was created.
23938 .section "Operational details for delivery to a new file" "SECTopdir"
23939 .cindex "delivery" "to single file"
23940 .cindex "&""From""& line"
23941 When the &%directory%& option is set instead of &%file%&, each message is
23942 delivered into a newly-created file or set of files. When &(appendfile)& is
23943 activated directly from a &(redirect)& router, neither &%file%& nor
23944 &%directory%& is normally set, because the path for delivery is supplied by the
23945 router. (See for example, the &(address_file)& transport in the default
23946 configuration.) In this case, delivery is to a new file if either the path name
23947 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
23949 No locking is required while writing the message to a new file, so the various
23950 locking options of the transport are ignored. The &"From"& line that by default
23951 separates messages in a single file is not normally needed, nor is the escaping
23952 of message lines that start with &"From"&, and there is no need to ensure a
23953 newline at the end of each message. Consequently, the default values for
23954 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
23955 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
23957 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
23958 the files in the delivery directory by default. However, you can specify a
23959 different directory by setting &%quota_directory%&. Also, for maildir
23960 deliveries (see below) the &_maildirfolder_& convention is honoured.
23963 .cindex "maildir format"
23964 .cindex "mailstore format"
23965 There are three different ways in which delivery to individual files can be
23966 done, controlled by the settings of the &%maildir_format%& and
23967 &%mailstore_format%& options. Note that code to support maildir or mailstore
23968 formats is not included in the binary unless SUPPORT_MAILDIR or
23969 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
23971 .cindex "directory creation"
23972 In all three cases an attempt is made to create the directory and any necessary
23973 sub-directories if they do not exist, provided that the &%create_directory%&
23974 option is set (the default). The location of a created directory can be
23975 constrained by setting &%create_file%&. A created directory's mode is given by
23976 the &%directory_mode%& option. If creation fails, or if the
23977 &%create_directory%& option is not set when creation is required, delivery is
23982 .section "Maildir delivery" "SECTmaildirdelivery"
23983 .cindex "maildir format" "description of"
23984 If the &%maildir_format%& option is true, Exim delivers each message by writing
23985 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
23986 directory that is defined by the &%directory%& option (the &"delivery
23987 directory"&). If the delivery is successful, the file is renamed into the
23988 &_new_& subdirectory.
23990 In the filename, <&'stime'&> is the current time of day in seconds, and
23991 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
23992 Exim checks that the time-of-day clock has moved on by at least one microsecond
23993 before terminating the delivery process. This guarantees uniqueness for the
23994 filename. However, as a precaution, Exim calls &[stat()]& for the file before
23995 opening it. If any response other than ENOENT (does not exist) is given,
23996 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
23998 Before Exim carries out a maildir delivery, it ensures that subdirectories
23999 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
24000 do not exist, Exim tries to create them and any superior directories in their
24001 path, subject to the &%create_directory%& and &%create_file%& options. If the
24002 &%maildirfolder_create_regex%& option is set, and the regular expression it
24003 contains matches the delivery directory, Exim also ensures that a file called
24004 &_maildirfolder_& exists in the delivery directory. If a missing directory or
24005 &_maildirfolder_& file cannot be created, delivery is deferred.
24007 These features make it possible to use Exim to create all the necessary files
24008 and directories in a maildir mailbox, including subdirectories for maildir++
24009 folders. Consider this example:
24011 maildir_format = true
24012 directory = /var/mail/$local_part_data\
24013 ${if eq{$local_part_suffix}{}{}\
24014 {/.${substr_1:$local_part_suffix}}}
24015 maildirfolder_create_regex = /\.[^/]+$
24017 If &$local_part_suffix$& is empty (there was no suffix for the local part),
24018 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
24019 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
24020 not match this name, so Exim will not look for or create the file
24021 &_/var/mail/pimbo/maildirfolder_&, though it will create
24022 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
24024 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
24025 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
24026 does match &%maildirfolder_create_regex%&. In this case, Exim will create
24027 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
24028 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
24030 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
24031 not inadvertently match the toplevel maildir directory, because a
24032 &_maildirfolder_& file at top level would completely break quota calculations.
24034 .cindex "quota" "in maildir delivery"
24035 .cindex "maildir++"
24036 If Exim is required to check a &%quota%& setting before a maildir delivery, and
24037 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
24038 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
24039 Exim assumes the directory is a maildir++ folder directory, which is one level
24040 down from the user's top level mailbox directory. This causes it to start at
24041 the parent directory instead of the current directory when calculating the
24042 amount of space used.
24044 One problem with delivering into a multi-file mailbox is that it is
24045 computationally expensive to compute the size of the mailbox for quota
24046 checking. Various approaches have been taken to reduce the amount of work
24047 needed. The next two sections describe two of them. A third alternative is to
24048 use some external process for maintaining the size data, and use the expansion
24049 of the &%mailbox_size%& option as a way of importing it into Exim.
24054 .section "Using tags to record message sizes" "SECID135"
24055 If &%maildir_tag%& is set, the string is expanded for each delivery.
24056 When the maildir file is renamed into the &_new_& sub-directory, the
24057 tag is added to its name. However, if adding the tag takes the length of the
24058 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
24059 the tag is dropped and the maildir file is created with no tag.
24062 .vindex "&$message_size$&"
24063 Tags can be used to encode the size of files in their names; see
24064 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
24065 happens after the message has been written. The value of the &$message_size$&
24066 variable is set to the number of bytes actually written. If the expansion is
24067 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
24068 be deferred. The expanded tag may contain any printing characters except &"/"&.
24069 Non-printing characters in the string are ignored; if the resulting string is
24070 empty, it is ignored. If it starts with an alphanumeric character, a leading
24071 colon is inserted; this default has not proven to be the path that popular
24072 maildir implementations have chosen (but changing it in Exim would break
24073 backwards compatibility).
24075 For one common implementation, you might set:
24077 maildir_tag = ,S=${message_size}
24079 but you should check the documentation of the other software to be sure.
24081 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
24082 as this allows Exim to extract the size from your tag, instead of having to
24083 &[stat()]& each message file.
24086 .section "Using a maildirsize file" "SECID136"
24087 .cindex "quota" "in maildir delivery"
24088 .cindex "maildir format" "&_maildirsize_& file"
24089 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
24090 storing quota and message size information in a file called &_maildirsize_&
24091 within the toplevel maildir directory. If this file does not exist, Exim
24092 creates it, setting the quota from the &%quota%& option of the transport. If
24093 the maildir directory itself does not exist, it is created before any attempt
24094 to write a &_maildirsize_& file.
24096 The &_maildirsize_& file is used to hold information about the sizes of
24097 messages in the maildir, thus speeding up quota calculations. The quota value
24098 in the file is just a cache; if the quota is changed in the transport, the new
24099 value overrides the cached value when the next message is delivered. The cache
24100 is maintained for the benefit of other programs that access the maildir and
24101 need to know the quota.
24103 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
24104 file is maintained (with a zero quota setting), but no quota is imposed.
24106 A regular expression is available for controlling which directories in the
24107 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
24108 See the description of the &%maildir_quota_directory_regex%& option above for
24112 .section "Mailstore delivery" "SECID137"
24113 .cindex "mailstore format" "description of"
24114 If the &%mailstore_format%& option is true, each message is written as two
24115 files in the given directory. A unique base name is constructed from the
24116 message id and the current delivery process, and the files that are written use
24117 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
24118 contains the message's envelope, and the &_.msg_& file contains the message
24119 itself. The base name is placed in the variable &$mailstore_basename$&.
24121 During delivery, the envelope is first written to a file with the suffix
24122 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
24123 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
24124 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
24125 file before accessing either of them. An alternative approach is to wait for
24126 the absence of a &_.tmp_& file.
24128 The envelope file starts with any text defined by the &%mailstore_prefix%&
24129 option, expanded and terminated by a newline if there isn't one. Then follows
24130 the sender address on one line, then all the recipient addresses, one per line.
24131 There can be more than one recipient only if the &%batch_max%& option is set
24132 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
24133 appended to the file, followed by a newline if it does not end with one.
24135 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
24136 failure, it is ignored. Other expansion errors are treated as serious
24137 configuration errors, and delivery is deferred. The variable
24138 &$mailstore_basename$& is available for use during these expansions.
24141 .section "Non-special new file delivery" "SECID138"
24142 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
24143 file is created directly in the named directory. For example, when delivering
24144 messages into files in batched SMTP format for later delivery to some host (see
24145 section &<<SECTbatchSMTP>>&), a setting such as
24147 directory = /var/bsmtp/$host
24149 might be used. A message is written to a file with a temporary name, which is
24150 then renamed when the delivery is complete. The final name is obtained by
24151 expanding the contents of the &%directory_file%& option.
24152 .ecindex IIDapptra1
24153 .ecindex IIDapptra2
24160 . ////////////////////////////////////////////////////////////////////////////
24161 . ////////////////////////////////////////////////////////////////////////////
24163 .chapter "The autoreply transport" "CHID8"
24164 .scindex IIDauttra1 "transports" "&(autoreply)&"
24165 .scindex IIDauttra2 "&(autoreply)& transport"
24166 The &(autoreply)& transport is not a true transport in that it does not cause
24167 the message to be transmitted. Instead, it generates a new mail message as an
24168 automatic reply to the incoming message. &'References:'& and
24169 &'Auto-Submitted:'& header lines are included. These are constructed according
24170 to the rules in RFCs 2822 and 3834, respectively.
24172 If the router that passes the message to this transport does not have the
24173 &%unseen%& option set, the original message (for the current recipient) is not
24174 delivered anywhere. However, when the &%unseen%& option is set on the router
24175 that passes the message to this transport, routing of the address continues, so
24176 another router can set up a normal message delivery.
24179 The &(autoreply)& transport is usually run as the result of mail filtering, a
24180 &"vacation"& message being the standard example. However, it can also be run
24181 directly from a router like any other transport. To reduce the possibility of
24182 message cascades, messages created by the &(autoreply)& transport always have
24183 empty envelope sender addresses, like bounce messages.
24185 The parameters of the message to be sent can be specified in the configuration
24186 by options described below. However, these are used only when the address
24187 passed to the transport does not contain its own reply information. When the
24188 transport is run as a consequence of a
24190 or &%vacation%& command in a filter file, the parameters of the message are
24191 supplied by the filter, and passed with the address. The transport's options
24192 that define the message are then ignored (so they are not usually set in this
24193 case). The message is specified entirely by the filter or by the transport; it
24194 is never built from a mixture of options. However, the &%file_optional%&,
24195 &%mode%&, and &%return_message%& options apply in all cases.
24197 &(Autoreply)& is implemented as a local transport. When used as a result of a
24198 command in a user's filter file, &(autoreply)& normally runs under the uid and
24199 gid of the user, and with appropriate current and home directories (see chapter
24200 &<<CHAPenvironment>>&).
24202 There is a subtle difference between routing a message to a &(pipe)& transport
24203 that generates some text to be returned to the sender, and routing it to an
24204 &(autoreply)& transport. This difference is noticeable only if more than one
24205 address from the same message is so handled. In the case of a pipe, the
24206 separate outputs from the different addresses are gathered up and returned to
24207 the sender in a single message, whereas if &(autoreply)& is used, a separate
24208 message is generated for each address that is passed to it.
24210 Non-printing characters are not permitted in the header lines generated for the
24211 message that &(autoreply)& creates, with the exception of newlines that are
24212 immediately followed by white space. If any non-printing characters are found,
24213 the transport defers.
24214 Whether characters with the top bit set count as printing characters or not is
24215 controlled by the &%print_topbitchars%& global option.
24217 If any of the generic options for manipulating headers (for example,
24218 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
24219 of the original message that is included in the generated message when
24220 &%return_message%& is set. They do not apply to the generated message itself.
24222 .vindex "&$sender_address$&"
24223 If the &(autoreply)& transport receives return code 2 from Exim when it submits
24224 the message, indicating that there were no recipients, it does not treat this
24225 as an error. This means that autoreplies sent to &$sender_address$& when this
24226 is empty (because the incoming message is a bounce message) do not cause
24227 problems. They are just discarded.
24231 .section "Private options for autoreply" "SECID139"
24232 .cindex "options" "&(autoreply)& transport"
24234 .option bcc autoreply string&!! unset
24235 This specifies the addresses that are to receive &"blind carbon copies"& of the
24236 message when the message is specified by the transport.
24239 .option cc autoreply string&!! unset
24240 This specifies recipients of the message and the contents of the &'Cc:'& header
24241 when the message is specified by the transport.
24244 .option file autoreply string&!! unset
24245 The contents of the file are sent as the body of the message when the message
24246 is specified by the transport. If both &%file%& and &%text%& are set, the text
24247 string comes first.
24250 .option file_expand autoreply boolean false
24251 If this is set, the contents of the file named by the &%file%& option are
24252 subjected to string expansion as they are added to the message.
24255 .option file_optional autoreply boolean false
24256 If this option is true, no error is generated if the file named by the &%file%&
24257 option or passed with the address does not exist or cannot be read.
24260 .option from autoreply string&!! unset
24261 This specifies the contents of the &'From:'& header when the message is
24262 specified by the transport.
24265 .option headers autoreply string&!! unset
24266 This specifies additional RFC 2822 headers that are to be added to the message
24267 when the message is specified by the transport. Several can be given by using
24268 &"\n"& to separate them. There is no check on the format.
24271 .option log autoreply string&!! unset
24272 This option names a file in which a record of every message sent is logged when
24273 the message is specified by the transport.
24276 .option mode autoreply "octal integer" 0600
24277 If either the log file or the &"once"& file has to be created, this mode is
24281 .option never_mail autoreply "address list&!!" unset
24282 If any run of the transport creates a message with a recipient that matches any
24283 item in the list, that recipient is quietly discarded. If all recipients are
24284 discarded, no message is created. This applies both when the recipients are
24285 generated by a filter and when they are specified in the transport.
24289 .option once autoreply string&!! unset
24290 This option names a file or DBM database in which a record of each &'To:'&
24291 recipient is kept when the message is specified by the transport. &*Note*&:
24292 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
24294 If &%once%& is unset, or is set to an empty string, the message is always sent.
24295 By default, if &%once%& is set to a non-empty filename, the message
24296 is not sent if a potential recipient is already listed in the database.
24297 However, if the &%once_repeat%& option specifies a time greater than zero, the
24298 message is sent if that much time has elapsed since a message was last sent to
24299 this recipient. A setting of zero time for &%once_repeat%& (the default)
24300 prevents a message from being sent a second time &-- in this case, zero means
24303 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
24304 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
24305 greater than zero, it changes the way Exim implements the &%once%& option.
24306 Instead of using a DBM file to record every recipient it sends to, it uses a
24307 regular file, whose size will never get larger than the given value.
24309 In the file, Exim keeps a linear list of recipient addresses and the times at
24310 which they were sent messages. If the file is full when a new address needs to
24311 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
24312 means that a given recipient may receive multiple messages, but at
24313 unpredictable intervals that depend on the rate of turnover of addresses in the
24314 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
24317 .option once_file_size autoreply integer 0
24318 See &%once%& above.
24321 .option once_repeat autoreply time&!! 0s
24322 See &%once%& above.
24323 After expansion, the value of this option must be a valid time value.
24326 .option reply_to autoreply string&!! unset
24327 This specifies the contents of the &'Reply-To:'& header when the message is
24328 specified by the transport.
24331 .option return_message autoreply boolean false
24332 If this is set, a copy of the original message is returned with the new
24333 message, subject to the maximum size set in the &%return_size_limit%& global
24334 configuration option.
24337 .option subject autoreply string&!! unset
24338 This specifies the contents of the &'Subject:'& header when the message is
24339 specified by the transport. It is tempting to quote the original subject in
24340 automatic responses. For example:
24342 subject = Re: $h_subject:
24344 There is a danger in doing this, however. It may allow a third party to
24345 subscribe your users to an opt-in mailing list, provided that the list accepts
24346 bounce messages as subscription confirmations. Well-managed lists require a
24347 non-bounce message to confirm a subscription, so the danger is relatively
24352 .option text autoreply string&!! unset
24353 This specifies a single string to be used as the body of the message when the
24354 message is specified by the transport. If both &%text%& and &%file%& are set,
24355 the text comes first.
24358 .option to autoreply string&!! unset
24359 This specifies recipients of the message and the contents of the &'To:'& header
24360 when the message is specified by the transport.
24361 .ecindex IIDauttra1
24362 .ecindex IIDauttra2
24367 . ////////////////////////////////////////////////////////////////////////////
24368 . ////////////////////////////////////////////////////////////////////////////
24370 .chapter "The lmtp transport" "CHAPLMTP"
24371 .cindex "transports" "&(lmtp)&"
24372 .cindex "&(lmtp)& transport"
24373 .cindex "LMTP" "over a pipe"
24374 .cindex "LMTP" "over a socket"
24375 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
24377 or by interacting with a Unix domain socket.
24378 This transport is something of a cross between the &(pipe)& and &(smtp)&
24379 transports. Exim also has support for using LMTP over TCP/IP; this is
24380 implemented as an option for the &(smtp)& transport. Because LMTP is expected
24381 to be of minority interest, the default build-time configure in &_src/EDITME_&
24382 has it commented out. You need to ensure that
24386 .cindex "options" "&(lmtp)& transport"
24387 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
24388 included in the Exim binary. The private options of the &(lmtp)& transport are
24391 .option batch_id lmtp string&!! unset
24392 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24395 .option batch_max lmtp integer 1
24396 This limits the number of addresses that can be handled in a single delivery.
24397 Most LMTP servers can handle several addresses at once, so it is normally a
24398 good idea to increase this value. See the description of local delivery
24399 batching in chapter &<<CHAPbatching>>&.
24402 .option command lmtp string&!! unset
24403 This option must be set if &%socket%& is not set. The string is a command which
24404 is run in a separate process. It is split up into a command name and list of
24405 arguments, each of which is separately expanded (so expansion cannot change the
24406 number of arguments). The command is run directly, not via a shell. The message
24407 is passed to the new process using the standard input and output to operate the
24410 .option ignore_quota lmtp boolean false
24411 .cindex "LMTP" "ignoring quota errors"
24412 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
24413 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
24414 in its response to the LHLO command.
24416 .option socket lmtp string&!! unset
24417 This option must be set if &%command%& is not set. The result of expansion must
24418 be the name of a Unix domain socket. The transport connects to the socket and
24419 delivers the message to it using the LMTP protocol.
24422 .option timeout lmtp time 5m
24423 The transport is aborted if the created process or Unix domain socket does not
24424 respond to LMTP commands or message input within this timeout. Delivery
24425 is deferred, and will be tried again later. Here is an example of a typical
24430 command = /some/local/lmtp/delivery/program
24434 This delivers up to 20 addresses at a time, in a mixture of domains if
24435 necessary, running as the user &'exim'&.
24439 . ////////////////////////////////////////////////////////////////////////////
24440 . ////////////////////////////////////////////////////////////////////////////
24442 .chapter "The pipe transport" "CHAPpipetransport"
24443 .scindex IIDpiptra1 "transports" "&(pipe)&"
24444 .scindex IIDpiptra2 "&(pipe)& transport"
24445 The &(pipe)& transport is used to deliver messages via a pipe to a command
24446 running in another process. One example is the use of &(pipe)& as a
24447 pseudo-remote transport for passing messages to some other delivery mechanism
24448 (such as UUCP). Another is the use by individual users to automatically process
24449 their incoming messages. The &(pipe)& transport can be used in one of the
24453 .vindex "&$local_part$&"
24454 A router routes one address to a transport in the normal way, and the
24455 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
24456 contains the local part of the address (as usual), and the command that is run
24457 is specified by the &%command%& option on the transport.
24459 .vindex "&$pipe_addresses$&"
24460 If the &%batch_max%& option is set greater than 1 (the default is 1), the
24461 transport can handle more than one address in a single run. In this case, when
24462 more than one address is routed to the transport, &$local_part$& is not set
24463 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
24464 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
24465 that are routed to the transport.
24467 .vindex "&$address_pipe$&"
24468 A router redirects an address directly to a pipe command (for example, from an
24469 alias or forward file). In this case, &$address_pipe$& contains the text of the
24470 pipe command, and the &%command%& option on the transport is ignored unless
24471 &%force_command%& is set. If only one address is being transported
24472 (&%batch_max%& is not greater than one, or only one address was redirected to
24473 this pipe command), &$local_part$& contains the local part that was redirected.
24477 The &(pipe)& transport is a non-interactive delivery method. Exim can also
24478 deliver messages over pipes using the LMTP interactive protocol. This is
24479 implemented by the &(lmtp)& transport.
24481 In the case when &(pipe)& is run as a consequence of an entry in a local user's
24482 &_.forward_& file, the command runs under the uid and gid of that user. In
24483 other cases, the uid and gid have to be specified explicitly, either on the
24484 transport or on the router that handles the address. Current and &"home"&
24485 directories are also controllable. See chapter &<<CHAPenvironment>>& for
24486 details of the local delivery environment and chapter &<<CHAPbatching>>&
24487 for a discussion of local delivery batching.
24489 .cindex "tainted data" "in pipe command"
24490 .cindex pipe "tainted data"
24491 Tainted data may not be used for the command name.
24494 .section "Concurrent delivery" "SECID140"
24495 If two messages arrive at almost the same time, and both are routed to a pipe
24496 delivery, the two pipe transports may be run concurrently. You must ensure that
24497 any pipe commands you set up are robust against this happening. If the commands
24498 write to a file, the &%exim_lock%& utility might be of use.
24499 Alternatively the &%max_parallel%& option could be used with a value
24500 of "1" to enforce serialization.
24505 .section "Returned status and data" "SECID141"
24506 .cindex "&(pipe)& transport" "returned data"
24507 If the command exits with a non-zero return code, the delivery is deemed to
24508 have failed, unless either the &%ignore_status%& option is set (in which case
24509 the return code is treated as zero), or the return code is one of those listed
24510 in the &%temp_errors%& option, which are interpreted as meaning &"try again
24511 later"&. In this case, delivery is deferred. Details of a permanent failure are
24512 logged, but are not included in the bounce message, which merely contains
24513 &"local delivery failed"&.
24515 If the command exits on a signal and the &%freeze_signal%& option is set then
24516 the message will be frozen in the queue. If that option is not set, a bounce
24517 will be sent as normal.
24519 If the return code is greater than 128 and the command being run is a shell
24520 script, it normally means that the script was terminated by a signal whose
24521 value is the return code minus 128. The &%freeze_signal%& option does not
24522 apply in this case.
24524 If Exim is unable to run the command (that is, if &[execve()]& fails), the
24525 return code is set to 127. This is the value that a shell returns if it is
24526 asked to run a non-existent command. The wording for the log line suggests that
24527 a non-existent command may be the problem.
24529 The &%return_output%& option can affect the result of a pipe delivery. If it is
24530 set and the command produces any output on its standard output or standard
24531 error streams, the command is considered to have failed, even if it gave a zero
24532 return code or if &%ignore_status%& is set. The output from the command is
24533 included as part of the bounce message. The &%return_fail_output%& option is
24534 similar, except that output is returned only when the command exits with a
24535 failure return code, that is, a value other than zero or a code that matches
24540 .section "How the command is run" "SECThowcommandrun"
24541 .cindex "&(pipe)& transport" "path for command"
24542 The command line is (by default) broken down into a command name and arguments
24543 by the &(pipe)& transport itself. The &%allow_commands%& and
24544 &%restrict_to_path%& options can be used to restrict the commands that may be
24547 .cindex "quoting" "in pipe command"
24548 Unquoted arguments are delimited by white space. If an argument appears in
24549 double quotes, backslash is interpreted as an escape character in the usual
24550 way. If an argument appears in single quotes, no escaping is done.
24552 String expansion is applied to the command line except when it comes from a
24553 traditional &_.forward_& file (commands from a filter file are expanded). The
24554 expansion is applied to each argument in turn rather than to the whole line.
24555 For this reason, any string expansion item that contains white space must be
24556 quoted so as to be contained within a single argument. A setting such as
24558 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
24560 will not work, because the expansion item gets split between several
24561 arguments. You have to write
24563 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
24565 to ensure that it is all in one argument. The expansion is done in this way,
24566 argument by argument, so that the number of arguments cannot be changed as a
24567 result of expansion, and quotes or backslashes in inserted variables do not
24568 interact with external quoting. However, this leads to problems if you want to
24569 generate multiple arguments (or the command name plus arguments) from a single
24570 expansion. In this situation, the simplest solution is to use a shell. For
24573 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
24576 .cindex "transport" "filter"
24577 .cindex "filter" "transport filter"
24578 .vindex "&$pipe_addresses$&"
24579 Special handling takes place when an argument consists of precisely the text
24580 &`$pipe_addresses`& (no quotes).
24581 This is not a general expansion variable; the only
24582 place this string is recognized is when it appears as an argument for a pipe or
24583 transport filter command. It causes each address that is being handled to be
24584 inserted in the argument list at that point &'as a separate argument'&. This
24585 avoids any problems with spaces or shell metacharacters, and is of use when a
24586 &(pipe)& transport is handling groups of addresses in a batch.
24588 If &%force_command%& is enabled on the transport, special handling takes place
24589 for an argument that consists of precisely the text &`$address_pipe`&. It
24590 is handled similarly to &$pipe_addresses$& above. It is expanded and each
24591 argument is inserted in the argument list at that point
24592 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
24593 the only item in the argument; in fact, if it were then &%force_command%&
24594 should behave as a no-op. Rather, it should be used to adjust the command
24595 run while preserving the argument vector separation.
24597 After splitting up into arguments and expansion, the resulting command is run
24598 in a subprocess directly from the transport, &'not'& under a shell. The
24599 message that is being delivered is supplied on the standard input, and the
24600 standard output and standard error are both connected to a single pipe that is
24601 read by Exim. The &%max_output%& option controls how much output the command
24602 may produce, and the &%return_output%& and &%return_fail_output%& options
24603 control what is done with it.
24605 Not running the command under a shell (by default) lessens the security risks
24606 in cases when a command from a user's filter file is built out of data that was
24607 taken from an incoming message. If a shell is required, it can of course be
24608 explicitly specified as the command to be run. However, there are circumstances
24609 where existing commands (for example, in &_.forward_& files) expect to be run
24610 under a shell and cannot easily be modified. To allow for these cases, there is
24611 an option called &%use_shell%&, which changes the way the &(pipe)& transport
24612 works. Instead of breaking up the command line as just described, it expands it
24613 as a single string and passes the result to &_/bin/sh_&. The
24614 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
24615 with &%use_shell%&, and the whole mechanism is inherently less secure.
24619 .section "Environment variables" "SECTpipeenv"
24620 .cindex "&(pipe)& transport" "environment for command"
24621 .cindex "environment" "&(pipe)& transport"
24622 The environment variables listed below are set up when the command is invoked.
24623 This list is a compromise for maximum compatibility with other MTAs. Note that
24624 the &%environment%& option can be used to add additional variables to this
24625 environment. The environment for the &(pipe)& transport is not subject
24626 to the &%add_environment%& and &%keep_environment%& main config options.
24628 &`DOMAIN `& the domain of the address
24629 &`HOME `& the home directory, if set
24630 &`HOST `& the host name when called from a router (see below)
24631 &`LOCAL_PART `& see below
24632 &`LOCAL_PART_PREFIX `& see below
24633 &`LOCAL_PART_SUFFIX `& see below
24634 &`LOGNAME `& see below
24635 &`MESSAGE_ID `& Exim's local ID for the message
24636 &`PATH `& as specified by the &%path%& option below
24637 &`QUALIFY_DOMAIN `& the sender qualification domain
24638 &`RECIPIENT `& the complete recipient address
24639 &`SENDER `& the sender of the message (empty if a bounce)
24640 &`SHELL `& &`/bin/sh`&
24641 &`TZ `& the value of the &%timezone%& option, if set
24642 &`USER `& see below
24644 When a &(pipe)& transport is called directly from (for example) an &(accept)&
24645 router, LOCAL_PART is set to the local part of the address. When it is
24646 called as a result of a forward or alias expansion, LOCAL_PART is set to
24647 the local part of the address that was expanded. In both cases, any affixes are
24648 removed from the local part, and made available in LOCAL_PART_PREFIX and
24649 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
24650 same value as LOCAL_PART for compatibility with other MTAs.
24653 HOST is set only when a &(pipe)& transport is called from a router that
24654 associates hosts with an address, typically when using &(pipe)& as a
24655 pseudo-remote transport. HOST is set to the first host name specified by
24659 If the transport's generic &%home_directory%& option is set, its value is used
24660 for the HOME environment variable. Otherwise, a home directory may be set
24661 by the router's &%transport_home_directory%& option, which defaults to the
24662 user's home directory if &%check_local_user%& is set.
24665 .section "Private options for pipe" "SECID142"
24666 .cindex "options" "&(pipe)& transport"
24670 .option allow_commands pipe "string list&!!" unset
24671 .cindex "&(pipe)& transport" "permitted commands"
24672 The string is expanded, and is then interpreted as a colon-separated list of
24673 permitted commands. If &%restrict_to_path%& is not set, the only commands
24674 permitted are those in the &%allow_commands%& list. They need not be absolute
24675 paths; the &%path%& option is still used for relative paths. If
24676 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
24677 in the &%allow_commands%& list, or a name without any slashes that is found on
24678 the path. In other words, if neither &%allow_commands%& nor
24679 &%restrict_to_path%& is set, there is no restriction on the command, but
24680 otherwise only commands that are permitted by one or the other are allowed. For
24683 allow_commands = /usr/bin/vacation
24685 and &%restrict_to_path%& is not set, the only permitted command is
24686 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
24687 &%use_shell%& is set.
24690 .option batch_id pipe string&!! unset
24691 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24694 .option batch_max pipe integer 1
24695 This limits the number of addresses that can be handled in a single delivery.
24696 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24699 .option check_string pipe string unset
24700 As &(pipe)& writes the message, the start of each line is tested for matching
24701 &%check_string%&, and if it does, the initial matching characters are replaced
24702 by the contents of &%escape_string%&, provided both are set. The value of
24703 &%check_string%& is a literal string, not a regular expression, and the case of
24704 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
24705 of &%check_string%& and &%escape_string%& are forced to values that implement
24706 the SMTP escaping protocol. Any settings made in the configuration file are
24710 .option command pipe string&!! unset
24711 This option need not be set when &(pipe)& is being used to deliver to pipes
24712 obtained directly from address redirections. In other cases, the option must be
24713 set, to provide a command to be run. It need not yield an absolute path (see
24714 the &%path%& option below). The command is split up into separate arguments by
24715 Exim, and each argument is separately expanded, as described in section
24716 &<<SECThowcommandrun>>& above.
24719 .option environment pipe string&!! unset
24720 .cindex "&(pipe)& transport" "environment for command"
24721 .cindex "environment" "&(pipe)& transport"
24722 This option is used to add additional variables to the environment in which the
24723 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
24724 a string which is expanded, and then interpreted as a colon-separated list of
24725 environment settings of the form <&'name'&>=<&'value'&>.
24728 .option escape_string pipe string unset
24729 See &%check_string%& above.
24732 .option freeze_exec_fail pipe boolean false
24733 .cindex "exec failure"
24734 .cindex "failure of exec"
24735 .cindex "&(pipe)& transport" "failure of exec"
24736 Failure to exec the command in a pipe transport is by default treated like
24737 any other failure while running the command. However, if &%freeze_exec_fail%&
24738 is set, failure to exec is treated specially, and causes the message to be
24739 frozen, whatever the setting of &%ignore_status%&.
24742 .option freeze_signal pipe boolean false
24743 .cindex "signal exit"
24744 .cindex "&(pipe)& transport", "signal exit"
24745 Normally if the process run by a command in a pipe transport exits on a signal,
24746 a bounce message is sent. If &%freeze_signal%& is set, the message will be
24747 frozen in Exim's queue instead.
24750 .option force_command pipe boolean false
24751 .cindex "force command"
24752 .cindex "&(pipe)& transport", "force command"
24753 Normally when a router redirects an address directly to a pipe command
24754 the &%command%& option on the transport is ignored. If &%force_command%&
24755 is set, the &%command%& option will used. This is especially
24756 useful for forcing a wrapper or additional argument to be added to the
24757 command. For example:
24759 command = /usr/bin/remote_exec myhost -- $address_pipe
24763 Note that &$address_pipe$& is handled specially in &%command%& when
24764 &%force_command%& is set, expanding out to the original argument vector as
24765 separate items, similarly to a Unix shell &`"$@"`& construct.
24768 .option ignore_status pipe boolean false
24769 If this option is true, the status returned by the subprocess that is set up to
24770 run the command is ignored, and Exim behaves as if zero had been returned.
24771 Otherwise, a non-zero status or termination by signal causes an error return
24772 from the transport unless the status value is one of those listed in
24773 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
24775 &*Note*&: This option does not apply to timeouts, which do not return a status.
24776 See the &%timeout_defer%& option for how timeouts are handled.
24779 .option log_defer_output pipe boolean false
24780 .cindex "&(pipe)& transport" "logging output"
24781 If this option is set, and the status returned by the command is
24782 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
24783 and any output was produced on stdout or stderr, the first line of it is
24784 written to the main log.
24787 .option log_fail_output pipe boolean false
24788 If this option is set, and the command returns any output on stdout or
24789 stderr, and also ends with a return code that is neither zero nor one of
24790 the return codes listed in &%temp_errors%& (that is, the delivery
24791 failed), the first line of output is written to the main log. This
24792 option and &%log_output%& are mutually exclusive. Only one of them may
24796 .option log_output pipe boolean false
24797 If this option is set and the command returns any output on stdout or
24798 stderr, the first line of output is written to the main log, whatever
24799 the return code. This option and &%log_fail_output%& are mutually
24800 exclusive. Only one of them may be set.
24803 .option max_output pipe integer 20K
24804 This specifies the maximum amount of output that the command may produce on its
24805 standard output and standard error file combined. If the limit is exceeded, the
24806 process running the command is killed. This is intended as a safety measure to
24807 catch runaway processes. The limit is applied independently of the settings of
24808 the options that control what is done with such output (for example,
24809 &%return_output%&). Because of buffering effects, the amount of output may
24810 exceed the limit by a small amount before Exim notices.
24813 .option message_prefix pipe string&!! "see below"
24814 The string specified here is expanded and output at the start of every message.
24815 The default is unset if &%use_bsmtp%& is set. Otherwise it is
24818 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
24822 .cindex "&%tmail%&"
24823 .cindex "&""From""& line"
24824 This is required by the commonly used &_/usr/bin/vacation_& program.
24825 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
24826 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
24831 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24832 &`\n`& to &`\r\n`& in &%message_prefix%&.
24835 .option message_suffix pipe string&!! "see below"
24836 The string specified here is expanded and output at the end of every message.
24837 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
24838 The suffix can be suppressed by setting
24842 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24843 &`\n`& to &`\r\n`& in &%message_suffix%&.
24846 .option path pipe string&!! "/bin:/usr/bin"
24847 This option is expanded and
24848 specifies the string that is set up in the PATH environment
24849 variable of the subprocess.
24850 If the &%command%& option does not yield an absolute path name, the command is
24851 sought in the PATH directories, in the usual way. &*Warning*&: This does not
24852 apply to a command specified as a transport filter.
24855 .option permit_coredump pipe boolean false
24856 Normally Exim inhibits core-dumps during delivery. If you have a need to get
24857 a core-dump of a pipe command, enable this command. This enables core-dumps
24858 during delivery and affects both the Exim binary and the pipe command run.
24859 It is recommended that this option remain off unless and until you have a need
24860 for it and that this only be enabled when needed, as the risk of excessive
24861 resource consumption can be quite high. Note also that Exim is typically
24862 installed as a setuid binary and most operating systems will inhibit coredumps
24863 of these by default, so further OS-specific action may be required.
24866 .option pipe_as_creator pipe boolean false
24867 .cindex "uid (user id)" "local delivery"
24868 If the generic &%user%& option is not set and this option is true, the delivery
24869 process is run under the uid that was in force when Exim was originally called
24870 to accept the message. If the group id is not otherwise set (via the generic
24871 &%group%& option), the gid that was in force when Exim was originally called to
24872 accept the message is used.
24875 .option restrict_to_path pipe boolean false
24876 When this option is set, any command name not listed in &%allow_commands%& must
24877 contain no slashes. The command is searched for only in the directories listed
24878 in the &%path%& option. This option is intended for use in the case when a pipe
24879 command has been generated from a user's &_.forward_& file. This is usually
24880 handled by a &(pipe)& transport called &%address_pipe%&.
24883 .option return_fail_output pipe boolean false
24884 If this option is true, and the command produced any output and ended with a
24885 return code other than zero or one of the codes listed in &%temp_errors%& (that
24886 is, the delivery failed), the output is returned in the bounce message.
24887 However, if the message has a null sender (that is, it is itself a bounce
24888 message), output from the command is discarded. This option and
24889 &%return_output%& are mutually exclusive. Only one of them may be set.
24893 .option return_output pipe boolean false
24894 If this option is true, and the command produced any output, the delivery is
24895 deemed to have failed whatever the return code from the command, and the output
24896 is returned in the bounce message. Otherwise, the output is just discarded.
24897 However, if the message has a null sender (that is, it is a bounce message),
24898 output from the command is always discarded, whatever the setting of this
24899 option. This option and &%return_fail_output%& are mutually exclusive. Only one
24900 of them may be set.
24904 .option temp_errors pipe "string list" "see below"
24905 .cindex "&(pipe)& transport" "temporary failure"
24906 This option contains either a colon-separated list of numbers, or a single
24907 asterisk. If &%ignore_status%& is false
24908 and &%return_output%& is not set,
24909 and the command exits with a non-zero return code, the failure is treated as
24910 temporary and the delivery is deferred if the return code matches one of the
24911 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
24912 codes are treated as permanent errors. The default setting contains the codes
24913 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
24914 compiled on a system that does not define these macros, it assumes values of 75
24915 and 73, respectively.
24918 .option timeout pipe time 1h
24919 If the command fails to complete within this time, it is killed. This normally
24920 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
24921 specifies no timeout. In order to ensure that any subprocesses created by the
24922 command are also killed, Exim makes the initial process a process group leader,
24923 and kills the whole process group on a timeout. However, this can be defeated
24924 if one of the processes starts a new process group.
24926 .option timeout_defer pipe boolean false
24927 A timeout in a &(pipe)& transport, either in the command that the transport
24928 runs, or in a transport filter that is associated with it, is by default
24929 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
24930 is set true, both kinds of timeout become temporary errors, causing the
24931 delivery to be deferred.
24933 .option umask pipe "octal integer" 022
24934 This specifies the umask setting for the subprocess that runs the command.
24937 .option use_bsmtp pipe boolean false
24938 .cindex "envelope sender"
24939 If this option is set true, the &(pipe)& transport writes messages in &"batch
24940 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
24941 commands. If you want to include a leading HELO command with such messages,
24942 you can do so by setting the &%message_prefix%& option. See section
24943 &<<SECTbatchSMTP>>& for details of batch SMTP.
24945 .option use_classresources pipe boolean false
24946 .cindex "class resources (BSD)"
24947 This option is available only when Exim is running on FreeBSD, NetBSD, or
24948 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
24949 resource limits when a &(pipe)& transport is run to perform a delivery. The
24950 limits for the uid under which the pipe is to run are obtained from the login
24954 .option use_crlf pipe boolean false
24955 .cindex "carriage return"
24957 This option causes lines to be terminated with the two-character CRLF sequence
24958 (carriage return, linefeed) instead of just a linefeed character. In the case
24959 of batched SMTP, the byte sequence written to the pipe is then an exact image
24960 of what would be sent down a real SMTP connection.
24962 The contents of the &%message_prefix%& and &%message_suffix%& options are
24963 written verbatim, so must contain their own carriage return characters if these
24964 are needed. When &%use_bsmtp%& is not set, the default values for both
24965 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
24966 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
24969 .option use_shell pipe boolean false
24970 .vindex "&$pipe_addresses$&"
24971 If this option is set, it causes the command to be passed to &_/bin/sh_&
24972 instead of being run directly from the transport, as described in section
24973 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
24974 where the command is expected to be run under a shell and cannot easily be
24975 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
24976 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
24977 command is expanded as a single string, and handed to &_/bin/sh_& as data for
24982 .section "Using an external local delivery agent" "SECID143"
24983 .cindex "local delivery" "using an external agent"
24984 .cindex "&'procmail'&"
24985 .cindex "external local delivery"
24986 .cindex "delivery" "&'procmail'&"
24987 .cindex "delivery" "by external agent"
24988 The &(pipe)& transport can be used to pass all messages that require local
24989 delivery to a separate local delivery agent such as &%procmail%&. When doing
24990 this, care must be taken to ensure that the pipe is run under an appropriate
24991 uid and gid. In some configurations one wants this to be a uid that is trusted
24992 by the delivery agent to supply the correct sender of the message. It may be
24993 necessary to recompile or reconfigure the delivery agent so that it trusts an
24994 appropriate user. The following is an example transport and router
24995 configuration for &%procmail%&:
25000 command = /usr/local/bin/procmail -d $local_part_data
25004 check_string = "From "
25005 escape_string = ">From "
25007 user = $local_part_data
25014 transport = procmail_pipe
25016 In this example, the pipe is run as the local user, but with the group set to
25017 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
25018 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
25019 user to supply a correct sender address. If you do not specify either a
25020 &%group%& or a &%user%& option, the pipe command is run as the local user. The
25021 home directory is the user's home directory by default.
25023 &*Note*&: The command that the pipe transport runs does &'not'& begin with
25027 as shown in some &%procmail%& documentation, because Exim does not by default
25028 use a shell to run pipe commands.
25031 The next example shows a transport and a router for a system where local
25032 deliveries are handled by the Cyrus IMAP server.
25035 local_delivery_cyrus:
25037 command = /usr/cyrus/bin/deliver \
25038 -m ${substr_1:$local_part_suffix} -- $local_part
25050 local_part_suffix = .*
25051 transport = local_delivery_cyrus
25053 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
25054 &%return_output%& to cause any text written by Cyrus to be returned to the
25056 .ecindex IIDpiptra1
25057 .ecindex IIDpiptra2
25060 . ////////////////////////////////////////////////////////////////////////////
25061 . ////////////////////////////////////////////////////////////////////////////
25063 .chapter "The smtp transport" "CHAPsmtptrans"
25064 .scindex IIDsmttra1 "transports" "&(smtp)&"
25065 .scindex IIDsmttra2 "&(smtp)& transport"
25066 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
25067 or LMTP protocol. The list of hosts to try can either be taken from the address
25068 that is being processed (having been set up by the router), or specified
25069 explicitly for the transport. Timeout and retry processing (see chapter
25070 &<<CHAPretry>>&) is applied to each IP address independently.
25073 .section "Multiple messages on a single connection" "SECID144"
25074 The sending of multiple messages over a single TCP/IP connection can arise in
25078 If a message contains more than &%max_rcpt%& (see below) addresses that are
25079 routed to the same host, more than one copy of the message has to be sent to
25080 that host. In this situation, multiple copies may be sent in a single run of
25081 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
25082 does when it has too many addresses to send in one message also depends on the
25083 value of the global &%remote_max_parallel%& option. Details are given in
25084 section &<<SECToutSMTPTCP>>&.)
25086 .cindex "hints database" "remembering routing"
25087 When a message has been successfully delivered over a TCP/IP connection, Exim
25088 looks in its hints database to see if there are any other messages awaiting a
25089 connection to the same host. If there are, a new delivery process is started
25090 for one of them, and the current TCP/IP connection is passed on to it. The new
25091 process may in turn send multiple copies and possibly create yet another
25096 For each copy sent over the same TCP/IP connection, a sequence counter is
25097 incremented, and if it ever gets to the value of &%connection_max_messages%&,
25098 no further messages are sent over that connection.
25102 .section "Use of the $host and $host_address variables" "SECID145"
25104 .vindex "&$host_address$&"
25105 At the start of a run of the &(smtp)& transport, the values of &$host$& and
25106 &$host_address$& are the name and IP address of the first host on the host list
25107 passed by the router. However, when the transport is about to connect to a
25108 specific host, and while it is connected to that host, &$host$& and
25109 &$host_address$& are set to the values for that host. These are the values
25110 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
25111 &%serialize_hosts%&, and the various TLS options are expanded.
25114 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
25115 .vindex &$tls_bits$&
25116 .vindex &$tls_cipher$&
25117 .vindex &$tls_peerdn$&
25118 .vindex &$tls_sni$&
25119 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
25120 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
25121 are the values that were set when the message was received.
25122 These are the values that are used for options that are expanded before any
25123 SMTP connections are made. Just before each connection is made, these four
25124 variables are emptied. If TLS is subsequently started, they are set to the
25125 appropriate values for the outgoing connection, and these are the values that
25126 are in force when any authenticators are run and when the
25127 &%authenticated_sender%& option is expanded.
25129 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
25130 and will be removed in a future release.
25133 .section "Private options for smtp" "SECID146"
25134 .cindex "options" "&(smtp)& transport"
25135 The private options of the &(smtp)& transport are as follows:
25138 .option address_retry_include_sender smtp boolean true
25139 .cindex "4&'xx'& responses" "retrying after"
25140 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
25141 is the combination of sender and recipient that is delayed in subsequent queue
25142 runs until the retry time is reached. You can delay the recipient without
25143 reference to the sender (which is what earlier versions of Exim did), by
25144 setting &%address_retry_include_sender%& false. However, this can lead to
25145 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
25147 .option allow_localhost smtp boolean false
25148 .cindex "local host" "sending to"
25149 .cindex "fallback" "hosts specified on transport"
25150 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
25151 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
25152 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
25153 the delivery anyway. This should be used only in special cases when the
25154 configuration ensures that no looping will result (for example, a differently
25155 configured Exim is listening on the port to which the message is sent).
25158 .option authenticated_sender smtp string&!! unset
25160 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
25161 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
25162 overriding any existing authenticated sender value. If the string expansion is
25163 forced to fail, the option is ignored. Other expansion failures cause delivery
25164 to be deferred. If the result of expansion is an empty string, that is also
25167 The expansion happens after the outgoing connection has been made and TLS
25168 started, if required. This means that the &$host$&, &$host_address$&,
25169 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
25170 particular connection.
25172 If the SMTP session is not authenticated, the expansion of
25173 &%authenticated_sender%& still happens (and can cause the delivery to be
25174 deferred if it fails), but no AUTH= item is added to MAIL commands
25175 unless &%authenticated_sender_force%& is true.
25177 This option allows you to use the &(smtp)& transport in LMTP mode to
25178 deliver mail to Cyrus IMAP and provide the proper local part as the
25179 &"authenticated sender"&, via a setting such as:
25181 authenticated_sender = $local_part
25183 This removes the need for IMAP subfolders to be assigned special ACLs to
25184 allow direct delivery to those subfolders.
25186 Because of expected uses such as that just described for Cyrus (when no
25187 domain is involved), there is no checking on the syntax of the provided
25191 .option authenticated_sender_force smtp boolean false
25192 If this option is set true, the &%authenticated_sender%& option's value
25193 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
25194 authenticated as a client.
25197 .option command_timeout smtp time 5m
25198 .cindex timeout "smtp transport command"
25199 This sets a timeout for receiving a response to an SMTP command that has been
25200 sent out. It is also used when waiting for the initial banner line from the
25201 remote host. Its value must not be zero.
25204 .option connect_timeout smtp time 5m
25205 .cindex timeout "smtp transport connect"
25206 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
25207 to a remote host. A setting of zero allows the system timeout (typically
25208 several minutes) to act. To have any effect, the value of this option must be
25209 less than the system timeout. However, it has been observed that on some
25210 systems there is no system timeout, which is why the default value for this
25211 option is 5 minutes, a value recommended by RFC 1123.
25214 .option connection_max_messages smtp integer 500
25215 .cindex "SMTP" "passed connection"
25216 .cindex "SMTP" "multiple deliveries"
25217 .cindex "multiple SMTP deliveries"
25218 This controls the maximum number of separate message deliveries that are sent
25219 over a single TCP/IP connection. If the value is zero, there is no limit.
25220 For testing purposes, this value can be overridden by the &%-oB%& command line
25224 .option dane_require_tls_ciphers smtp string&!! unset
25225 .cindex "TLS" "requiring specific ciphers for DANE"
25226 .cindex "cipher" "requiring specific"
25227 .cindex DANE "TLS ciphers"
25228 This option may be used to override &%tls_require_ciphers%& for connections
25229 where DANE has been determined to be in effect.
25230 If not set, then &%tls_require_ciphers%& will be used.
25231 Normal SMTP delivery is not able to make strong demands of TLS cipher
25232 configuration, because delivery will fall back to plaintext. Once DANE has
25233 been determined to be in effect, there is no plaintext fallback and making the
25234 TLS cipherlist configuration stronger will increase security, rather than
25235 counter-intuitively decreasing it.
25236 If the option expands to be empty or is forced to fail, then it will
25237 be treated as unset and &%tls_require_ciphers%& will be used instead.
25240 .option data_timeout smtp time 5m
25241 .cindex timeout "for transmitted SMTP data blocks"
25242 This sets a timeout for the transmission of each block in the data portion of
25243 the message. As a result, the overall timeout for a message depends on the size
25244 of the message. Its value must not be zero. See also &%final_timeout%&.
25247 .option dkim_canon smtp string&!! unset
25248 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25249 .option dkim_domain smtp string list&!! unset
25250 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25251 .option dkim_hash smtp string&!! sha256
25252 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25253 .option dkim_identity smtp string&!! unset
25254 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25255 .option dkim_private_key smtp string&!! unset
25256 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25257 .option dkim_selector smtp string&!! unset
25258 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25259 .option dkim_strict smtp string&!! unset
25260 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25261 .option dkim_sign_headers smtp string&!! "per RFC"
25262 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25263 .option dkim_timestamps smtp string&!! unset
25264 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25267 .option delay_after_cutoff smtp boolean true
25268 .cindex "final cutoff" "retries, controlling"
25269 .cindex retry "final cutoff"
25270 This option controls what happens when all remote IP addresses for a given
25271 domain have been inaccessible for so long that they have passed their retry
25274 In the default state, if the next retry time has not been reached for any of
25275 them, the address is bounced without trying any deliveries. In other words,
25276 Exim delays retrying an IP address after the final cutoff time until a new
25277 retry time is reached, and can therefore bounce an address without ever trying
25278 a delivery, when machines have been down for a long time. Some people are
25279 unhappy at this prospect, so...
25281 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25282 addresses are past their final cutoff time, Exim tries to deliver to those
25283 IP addresses that have not been tried since the message arrived. If there are
25284 none, of if they all fail, the address is bounced. In other words, it does not
25285 delay when a new message arrives, but immediately tries those expired IP
25286 addresses that haven't been tried since the message arrived. If there is a
25287 continuous stream of messages for the dead hosts, unsetting
25288 &%delay_after_cutoff%& means that there will be many more attempts to deliver
25292 .option dns_qualify_single smtp boolean true
25293 If the &%hosts%& or &%fallback_hosts%& option is being used,
25294 and the &%gethostbyname%& option is false,
25295 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
25296 in chapter &<<CHAPdnslookup>>& for more details.
25299 .option dns_search_parents smtp boolean false
25300 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
25301 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
25302 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
25306 .option dnssec_request_domains smtp "domain list&!!" *
25307 .cindex "MX record" "security"
25308 .cindex "DNSSEC" "MX lookup"
25309 .cindex "security" "MX lookup"
25310 .cindex "DNS" "DNSSEC"
25311 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
25312 the DNSSEC request bit set. Setting this transport option is only useful if the
25313 transport overrides or sets the host names. See the &%dnssec_request_domains%&
25318 .option dnssec_require_domains smtp "domain list&!!" unset
25319 .cindex "MX record" "security"
25320 .cindex "DNSSEC" "MX lookup"
25321 .cindex "security" "MX lookup"
25322 .cindex "DNS" "DNSSEC"
25323 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
25324 the DNSSEC request bit set. Setting this transport option is only
25325 useful if the transport overrides or sets the host names. See the
25326 &%dnssec_require_domains%& router option.
25330 .option dscp smtp string&!! unset
25331 .cindex "DCSP" "outbound"
25332 This option causes the DSCP value associated with a socket to be set to one
25333 of a number of fixed strings or to numeric value.
25334 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
25335 Common values include &`throughput`&, &`mincost`&, and on newer systems
25336 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
25338 The outbound packets from Exim will be marked with this value in the header
25339 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
25340 that these values will have any effect, not be stripped by networking
25341 equipment, or do much of anything without cooperation with your Network
25342 Engineer and those of all network operators between the source and destination.
25345 .option fallback_hosts smtp "string list" unset
25346 .cindex "fallback" "hosts specified on transport"
25347 String expansion is not applied to this option. The argument must be a
25348 colon-separated list of host names or IP addresses, optionally also including
25349 port numbers, though the separator can be changed, as described in section
25350 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25351 item in a &%route_list%& setting for the &(manualroute)& router, as described
25352 in section &<<SECTformatonehostitem>>&.
25354 Fallback hosts can also be specified on routers, which associate them with the
25355 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
25356 &%fallback_hosts%& specified on the transport is used only if the address does
25357 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
25358 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
25359 However, &%hosts_randomize%& does apply to fallback host lists.
25361 If Exim is unable to deliver to any of the hosts for a particular address, and
25362 the errors are not permanent rejections, the address is put on a separate
25363 transport queue with its host list replaced by the fallback hosts, unless the
25364 address was routed via MX records and the current host was in the original MX
25365 list. In that situation, the fallback host list is not used.
25367 Once normal deliveries are complete, the fallback queue is delivered by
25368 re-running the same transports with the new host lists. If several failing
25369 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
25370 copy of the message is sent.
25372 The resolution of the host names on the fallback list is controlled by the
25373 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
25374 both to cases when the host list comes with the address and when it is taken
25375 from &%hosts%&. This option provides a &"use a smart host only if delivery
25379 .option final_timeout smtp time 10m
25380 .cindex timeout "for transmitted SMTP data accept"
25381 This is the timeout that applies while waiting for the response to the final
25382 line containing just &"."& that terminates a message. Its value must not be
25385 .option gethostbyname smtp boolean false
25386 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
25387 being used, names are looked up using &[gethostbyname()]&
25388 (or &[getipnodebyname()]& when available)
25389 instead of using the DNS. Of course, that function may in fact use the DNS, but
25390 it may also consult other sources of information such as &_/etc/hosts_&.
25392 .option gnutls_compat_mode smtp boolean unset
25393 This option controls whether GnuTLS is used in compatibility mode in an Exim
25394 server. This reduces security slightly, but improves interworking with older
25395 implementations of TLS.
25397 .option helo_data smtp string&!! "see below"
25398 .cindex "HELO" "argument, setting"
25399 .cindex "EHLO" "argument, setting"
25400 .cindex "LHLO argument setting"
25401 The value of this option is expanded after a connection to a another host has
25402 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
25403 command that starts the outgoing SMTP or LMTP session. The default value of the
25408 During the expansion, the variables &$host$& and &$host_address$& are set to
25409 the identity of the remote host, and the variables &$sending_ip_address$& and
25410 &$sending_port$& are set to the local IP address and port number that are being
25411 used. These variables can be used to generate different values for different
25412 servers or different local IP addresses. For example, if you want the string
25413 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
25414 interface address, you could use this:
25416 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
25417 {$primary_hostname}}
25419 The use of &%helo_data%& applies both to sending messages and when doing
25422 .option hosts smtp "string list&!!" unset
25423 Hosts are associated with an address by a router such as &(dnslookup)&, which
25424 finds the hosts by looking up the address domain in the DNS, or by
25425 &(manualroute)&, which has lists of hosts in its configuration. However,
25426 email addresses can be passed to the &(smtp)& transport by any router, and not
25427 all of them can provide an associated list of hosts.
25429 The &%hosts%& option specifies a list of hosts to be used if the address being
25430 processed does not have any hosts associated with it. The hosts specified by
25431 &%hosts%& are also used, whether or not the address has its own hosts, if
25432 &%hosts_override%& is set.
25434 The string is first expanded, before being interpreted as a colon-separated
25435 list of host names or IP addresses, possibly including port numbers. The
25436 separator may be changed to something other than colon, as described in section
25437 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25438 item in a &%route_list%& setting for the &(manualroute)& router, as described
25439 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
25440 of the &(manualroute)& router is not available here.
25442 If the expansion fails, delivery is deferred. Unless the failure was caused by
25443 the inability to complete a lookup, the error is logged to the panic log as
25444 well as the main log. Host names are looked up either by searching directly for
25445 address records in the DNS or by calling &[gethostbyname()]& (or
25446 &[getipnodebyname()]& when available), depending on the setting of the
25447 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
25448 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
25451 During delivery, the hosts are tried in order, subject to their retry status,
25452 unless &%hosts_randomize%& is set.
25455 .option hosts_avoid_esmtp smtp "host list&!!" unset
25456 .cindex "ESMTP, avoiding use of"
25457 .cindex "HELO" "forcing use of"
25458 .cindex "EHLO" "avoiding use of"
25459 .cindex "PIPELINING" "avoiding the use of"
25460 This option is for use with broken hosts that announce ESMTP facilities (for
25461 example, PIPELINING) and then fail to implement them properly. When a host
25462 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
25463 start of the SMTP session. This means that it cannot use any of the ESMTP
25464 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
25467 .option hosts_avoid_pipelining smtp "host list&!!" unset
25468 .cindex "PIPELINING" "avoiding the use of"
25469 .cindex "ESMTP extensions" PIPELINING
25470 Exim will not use the ESMTP PIPELINING extension when delivering to any host
25471 that matches this list, even if the server host advertises PIPELINING support.
25473 .option hosts_pipe_connect smtp "host list&!!" unset
25474 .cindex "pipelining" "early connection"
25475 .cindex "pipelining" PIPE_CONNECT
25476 If Exim is built with the SUPPORT_PIPE_CONNECT build option
25477 this option controls which to hosts the facility watched for
25478 and recorded, and used for subsequent connections.
25480 The retry hints database is used for the record,
25481 and records are subject to the &%retry_data_expire%& option.
25482 When used, the pipelining saves on roundtrip times.
25483 It also turns SMTP into a client-first protocol
25484 so combines well with TCP Fast Open.
25486 See also the &%pipelining_connect_advertise_hosts%& main option.
25489 When the facility is used, the transport &%helo_data%& option
25490 will be expanded before the &$sending_ip_address$& variable
25492 A check is made for the use of that variable, without the
25493 presence of a &"def:"& test on it, but suitably complex coding
25494 can avoid the check and produce unexpected results.
25495 You have been warned.
25498 .option hosts_avoid_tls smtp "host list&!!" unset
25499 .cindex "TLS" "avoiding for certain hosts"
25500 Exim will not try to start a TLS session when delivering to any host that
25501 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25503 .option hosts_verify_avoid_tls smtp "host list&!!" unset
25504 .cindex "TLS" "avoiding for certain hosts"
25505 Exim will not try to start a TLS session for a verify callout,
25506 or when delivering in cutthrough mode,
25507 to any host that matches this list.
25510 .option hosts_max_try smtp integer 5
25511 .cindex "host" "maximum number to try"
25512 .cindex "limit" "number of hosts tried"
25513 .cindex "limit" "number of MX tried"
25514 .cindex "MX record" "maximum tried"
25515 This option limits the number of IP addresses that are tried for any one
25516 delivery in cases where there are temporary delivery errors. Section
25517 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
25520 .option hosts_max_try_hardlimit smtp integer 50
25521 This is an additional check on the maximum number of IP addresses that Exim
25522 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
25527 .option hosts_nopass_tls smtp "host list&!!" unset
25528 .cindex "TLS" "passing connection"
25529 .cindex "multiple SMTP deliveries"
25530 .cindex "TLS" "multiple message deliveries"
25531 For any host that matches this list, a connection on which a TLS session has
25532 been started will not be passed to a new delivery process for sending another
25533 message on the same connection. See section &<<SECTmulmessam>>& for an
25534 explanation of when this might be needed.
25536 .option hosts_noproxy_tls smtp "host list&!!" unset
25537 .cindex "TLS" "passing connection"
25538 .cindex "multiple SMTP deliveries"
25539 .cindex "TLS" "multiple message deliveries"
25540 For any host that matches this list, a TLS session which has
25541 been started will not be passed to a new delivery process for sending another
25542 message on the same session.
25544 The traditional implementation closes down TLS and re-starts it in the new
25545 process, on the same open TCP connection, for each successive message
25546 sent. If permitted by this option a pipe to to the new process is set up
25547 instead, and the original process maintains the TLS connection and proxies
25548 the SMTP connection from and to the new process and any subsequents.
25549 The new process has no access to TLS information, so cannot include it in
25554 .option hosts_override smtp boolean false
25555 If this option is set and the &%hosts%& option is also set, any hosts that are
25556 attached to the address are ignored, and instead the hosts specified by the
25557 &%hosts%& option are always used. This option does not apply to
25558 &%fallback_hosts%&.
25561 .option hosts_randomize smtp boolean false
25562 .cindex "randomized host list"
25563 .cindex "host" "list of; randomized"
25564 .cindex "fallback" "randomized hosts"
25565 If this option is set, and either the list of hosts is taken from the
25566 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
25567 were not obtained from MX records (this includes fallback hosts from the
25568 router), and were not randomized by the router, the order of trying the hosts
25569 is randomized each time the transport runs. Randomizing the order of a host
25570 list can be used to do crude load sharing.
25572 When &%hosts_randomize%& is true, a host list may be split into groups whose
25573 order is separately randomized. This makes it possible to set up MX-like
25574 behaviour. The boundaries between groups are indicated by an item that is just
25575 &`+`& in the host list. For example:
25577 hosts = host1:host2:host3:+:host4:host5
25579 The order of the first three hosts and the order of the last two hosts is
25580 randomized for each use, but the first three always end up before the last two.
25581 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
25583 .option hosts_require_auth smtp "host list&!!" unset
25584 .cindex "authentication" "required by client"
25585 This option provides a list of servers for which authentication must succeed
25586 before Exim will try to transfer a message. If authentication fails for
25587 servers which are not in this list, Exim tries to send unauthenticated. If
25588 authentication fails for one of these servers, delivery is deferred. This
25589 temporary error is detectable in the retry rules, so it can be turned into a
25590 hard failure if required. See also &%hosts_try_auth%&, and chapter
25591 &<<CHAPSMTPAUTH>>& for details of authentication.
25594 .option hosts_request_ocsp smtp "host list&!!" *
25595 .cindex "TLS" "requiring for certain servers"
25596 Exim will request a Certificate Status on a
25597 TLS session for any host that matches this list.
25598 &%tls_verify_certificates%& should also be set for the transport.
25600 .option hosts_require_dane smtp "host list&!!" unset
25601 .cindex DANE "transport options"
25602 .cindex DANE "requiring for certain servers"
25603 If built with DANE support, Exim will require that a DNSSEC-validated
25604 TLSA record is present for any host matching the list,
25605 and that a DANE-verified TLS connection is made.
25606 There will be no fallback to in-clear communication.
25607 See the &%dnssec_request_domains%& router and transport options.
25608 See section &<<SECDANE>>&.
25610 .option hosts_require_ocsp smtp "host list&!!" unset
25611 .cindex "TLS" "requiring for certain servers"
25612 Exim will request, and check for a valid Certificate Status being given, on a
25613 TLS session for any host that matches this list.
25614 &%tls_verify_certificates%& should also be set for the transport.
25616 .option hosts_require_tls smtp "host list&!!" unset
25617 .cindex "TLS" "requiring for certain servers"
25618 Exim will insist on using a TLS session when delivering to any host that
25619 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25620 &*Note*&: This option affects outgoing mail only. To insist on TLS for
25621 incoming messages, use an appropriate ACL.
25623 .option hosts_try_auth smtp "host list&!!" unset
25624 .cindex "authentication" "optional in client"
25625 This option provides a list of servers to which, provided they announce
25626 authentication support, Exim will attempt to authenticate as a client when it
25627 connects. If authentication fails
25629 and &%hosts_require_auth%& permits,
25631 Exim will try to transfer the message unauthenticated.
25632 See also chapter &<<CHAPSMTPAUTH>>& for details of authentication.
25634 .option hosts_try_chunking smtp "host list&!!" *
25635 .cindex CHUNKING "enabling, in client"
25636 .cindex BDAT "SMTP command"
25637 .cindex "RFC 3030" "CHUNKING"
25638 This option provides a list of servers to which, provided they announce
25639 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
25640 Unless DKIM signing is being done,
25641 BDAT will not be used in conjunction with a transport filter.
25643 .option hosts_try_dane smtp "host list&!!" *
25644 .cindex DANE "transport options"
25645 .cindex DANE "attempting for certain servers"
25647 If built with DANE support, Exim will look up a
25648 TLSA record for any host matching the list,
25649 If one is found and that lookup was DNSSEC-validated,
25650 then Exim requires that a DANE-verified TLS connection is made for that host;
25651 there will be no fallback to in-clear communication.
25653 See the &%dnssec_request_domains%& router and transport options.
25654 See section &<<SECDANE>>&.
25656 .option hosts_try_fastopen smtp "host list&!!" *
25657 .cindex "fast open, TCP" "enabling, in client"
25658 .cindex "TCP Fast Open" "enabling, in client"
25659 .cindex "RFC 7413" "TCP Fast Open"
25660 This option provides a list of servers to which, provided
25661 the facility is supported by this system, Exim will attempt to
25662 perform a TCP Fast Open.
25663 No data is sent on the SYN segment but, if the remote server also
25664 supports the facility, it can send its SMTP banner immediately after
25665 the SYN,ACK segment. This can save up to one round-trip time.
25667 The facility is only active for previously-contacted servers,
25668 as the initiator must present a cookie in the SYN segment.
25670 On (at least some) current Linux distributions the facility must be enabled
25671 in the kernel by the sysadmin before the support is usable.
25672 There is no option for control of the server side; if the system supports
25673 it it is always enabled. Note that lengthy operations in the connect ACL,
25674 such as DNSBL lookups, will still delay the emission of the SMTP banner.
25676 .option hosts_try_prdr smtp "host list&!!" *
25677 .cindex "PRDR" "enabling, optional in client"
25678 .cindex "ESMTP extensions" PRDR
25679 This option provides a list of servers to which, provided they announce
25680 PRDR support, Exim will attempt to negotiate PRDR
25681 for multi-recipient messages.
25682 The option can usually be left as default.
25684 .option interface smtp "string list&!!" unset
25685 .cindex "bind IP address"
25686 .cindex "IP address" "binding"
25688 .vindex "&$host_address$&"
25689 This option specifies which interface to bind to when making an outgoing SMTP
25690 call. The value is an IP address, not an interface name such as
25691 &`eth0`&. Do not confuse this with the interface address that was used when a
25692 message was received, which is in &$received_ip_address$&, formerly known as
25693 &$interface_address$&. The name was changed to minimize confusion with the
25694 outgoing interface address. There is no variable that contains an outgoing
25695 interface address because, unless it is set by this option, its value is
25698 During the expansion of the &%interface%& option the variables &$host$& and
25699 &$host_address$& refer to the host to which a connection is about to be made
25700 during the expansion of the string. Forced expansion failure, or an empty
25701 string result causes the option to be ignored. Otherwise, after expansion, the
25702 string must be a list of IP addresses, colon-separated by default, but the
25703 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
25706 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
25708 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
25709 connection. If none of them are the correct type, the option is ignored. If
25710 &%interface%& is not set, or is ignored, the system's IP functions choose which
25711 interface to use if the host has more than one.
25714 .option keepalive smtp boolean true
25715 .cindex "keepalive" "on outgoing connection"
25716 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
25717 connections. When set, it causes the kernel to probe idle connections
25718 periodically, by sending packets with &"old"& sequence numbers. The other end
25719 of the connection should send a acknowledgment if the connection is still okay
25720 or a reset if the connection has been aborted. The reason for doing this is
25721 that it has the beneficial effect of freeing up certain types of connection
25722 that can get stuck when the remote host is disconnected without tidying up the
25723 TCP/IP call properly. The keepalive mechanism takes several hours to detect
25727 .option lmtp_ignore_quota smtp boolean false
25728 .cindex "LMTP" "ignoring quota errors"
25729 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
25730 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
25731 has advertised support for IGNOREQUOTA in its response to the LHLO command.
25733 .option max_rcpt smtp integer 100
25734 .cindex "RCPT" "maximum number of outgoing"
25735 This option limits the number of RCPT commands that are sent in a single
25736 SMTP message transaction. Each set of addresses is treated independently, and
25737 so can cause parallel connections to the same host if &%remote_max_parallel%&
25738 permits this. A value setting of zero disables the limit.
25742 .option message_linelength_limit smtp integer 998
25743 .cindex "line length" limit
25744 This option sets the maximum line length, in bytes, that the transport
25745 will send. Any messages with lines exceeding the given value
25746 will fail and a failure-DSN ("bounce") message will if possible be returned
25748 The default value is that defined by the SMTP standards.
25750 It is generally wise to also check in the data ACL so that messages
25751 received via SMTP can be refused without producing a bounce.
25755 .option multi_domain smtp boolean&!! true
25756 .vindex "&$domain$&"
25757 When this option is set, the &(smtp)& transport can handle a number of
25758 addresses containing a mixture of different domains provided they all resolve
25759 to the same list of hosts. Turning the option off restricts the transport to
25760 handling only one domain at a time. This is useful if you want to use
25761 &$domain$& in an expansion for the transport, because it is set only when there
25762 is a single domain involved in a remote delivery.
25764 It is expanded per-address and can depend on any of
25765 &$address_data$&, &$domain_data$&, &$local_part_data$&,
25766 &$host$&, &$host_address$& and &$host_port$&.
25769 If the connection is DANE-enabled then this option is ignored;
25770 only messages having the domain used for the DANE TLSA lookup are
25771 sent on the connection.
25774 .option port smtp string&!! "see below"
25775 .cindex "port" "sending TCP/IP"
25776 .cindex "TCP/IP" "setting outgoing port"
25777 This option specifies the TCP/IP port on the server to which Exim connects.
25778 &*Note:*& Do not confuse this with the port that was used when a message was
25779 received, which is in &$received_port$&, formerly known as &$interface_port$&.
25780 The name was changed to minimize confusion with the outgoing port. There is no
25781 variable that contains an outgoing port.
25783 If the value of this option begins with a digit it is taken as a port number;
25784 otherwise it is looked up using &[getservbyname()]&. The default value is
25786 but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"&
25787 and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
25788 If the expansion fails, or if a port number cannot be found, delivery
25791 Note that at least one Linux distribution has been seen failing
25792 to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
25796 .option protocol smtp string smtp
25797 .cindex "LMTP" "over TCP/IP"
25798 .cindex "ssmtp protocol" "outbound"
25799 .cindex "TLS" "SSL-on-connect outbound"
25801 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
25802 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
25803 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
25804 deliveries into closed message stores. Exim also has support for running LMTP
25805 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
25807 If this option is set to &"smtps"&, the default value for the &%port%& option
25808 changes to &"smtps"&, and the transport initiates TLS immediately after
25809 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
25810 The Internet standards bodies used to strongly discourage use of this mode,
25811 but as of RFC 8314 it is preferred over STARTTLS for message submission
25812 (as distinct from MTA-MTA communication).
25815 .option retry_include_ip_address smtp boolean&!! true
25816 Exim normally includes both the host name and the IP address in the key it
25817 constructs for indexing retry data after a temporary delivery failure. This
25818 means that when one of several IP addresses for a host is failing, it gets
25819 tried periodically (controlled by the retry rules), but use of the other IP
25820 addresses is not affected.
25822 However, in some dialup environments hosts are assigned a different IP address
25823 each time they connect. In this situation the use of the IP address as part of
25824 the retry key leads to undesirable behaviour. Setting this option false causes
25825 Exim to use only the host name.
25826 Since it is expanded it can be made to depend on the host or domain.
25829 .option serialize_hosts smtp "host list&!!" unset
25830 .cindex "serializing connections"
25831 .cindex "host" "serializing connections"
25832 Because Exim operates in a distributed manner, if several messages for the same
25833 host arrive at around the same time, more than one simultaneous connection to
25834 the remote host can occur. This is not usually a problem except when there is a
25835 slow link between the hosts. In that situation it may be helpful to restrict
25836 Exim to one connection at a time. This can be done by setting
25837 &%serialize_hosts%& to match the relevant hosts.
25839 .cindex "hints database" "serializing deliveries to a host"
25840 Exim implements serialization by means of a hints database in which a record is
25841 written whenever a process connects to one of the restricted hosts. The record
25842 is deleted when the connection is completed. Obviously there is scope for
25843 records to get left lying around if there is a system or program crash. To
25844 guard against this, Exim ignores any records that are more than six hours old.
25846 If you set up this kind of serialization, you should also arrange to delete the
25847 relevant hints database whenever your system reboots. The names of the files
25848 start with &_misc_& and they are kept in the &_spool/db_& directory. There
25849 may be one or two files, depending on the type of DBM in use. The same files
25850 are used for ETRN serialization.
25852 See also the &%max_parallel%& generic transport option.
25855 .option size_addition smtp integer 1024
25856 .cindex "SIZE" "ESMTP extension"
25857 .cindex "message" "size issue for transport filter"
25858 .cindex "size" "of message"
25859 .cindex "transport" "filter"
25860 .cindex "filter" "transport filter"
25861 If a remote SMTP server indicates that it supports the SIZE option of the
25862 MAIL command, Exim uses this to pass over the message size at the start of
25863 an SMTP transaction. It adds the value of &%size_addition%& to the value it
25864 sends, to allow for headers and other text that may be added during delivery by
25865 configuration options or in a transport filter. It may be necessary to increase
25866 this if a lot of text is added to messages.
25868 Alternatively, if the value of &%size_addition%& is set negative, it disables
25869 the use of the SIZE option altogether.
25872 .option socks_proxy smtp string&!! unset
25873 .cindex proxy SOCKS
25874 This option enables use of SOCKS proxies for connections made by the
25875 transport. For details see section &<<SECTproxySOCKS>>&.
25878 .option tls_certificate smtp string&!! unset
25879 .cindex "TLS" "client certificate, location of"
25880 .cindex "certificate" "client, location of"
25882 .vindex "&$host_address$&"
25883 The value of this option must be the absolute path to a file which contains the
25884 client's certificate, for possible use when sending a message over an encrypted
25885 connection. The values of &$host$& and &$host_address$& are set to the name and
25886 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
25889 &*Note*&: This option must be set if you want Exim to be able to use a TLS
25890 certificate when sending messages as a client. The global option of the same
25891 name specifies the certificate for Exim as a server; it is not automatically
25892 assumed that the same certificate should be used when Exim is operating as a
25896 .option tls_crl smtp string&!! unset
25897 .cindex "TLS" "client certificate revocation list"
25898 .cindex "certificate" "revocation list for client"
25899 This option specifies a certificate revocation list. The expanded value must
25900 be the name of a file that contains a CRL in PEM format.
25903 .option tls_dh_min_bits smtp integer 1024
25904 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
25905 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
25906 key agreement is negotiated, the server will provide a large prime number
25907 for use. This option establishes the minimum acceptable size of that number.
25908 If the parameter offered by the server is too small, then the TLS handshake
25911 Only supported when using GnuTLS.
25914 .option tls_privatekey smtp string&!! unset
25915 .cindex "TLS" "client private key, location of"
25917 .vindex "&$host_address$&"
25918 The value of this option must be the absolute path to a file which contains the
25919 client's private key. This is used when sending a message over an encrypted
25920 connection using a client certificate. The values of &$host$& and
25921 &$host_address$& are set to the name and address of the server during the
25922 expansion. If this option is unset, or the expansion is forced to fail, or the
25923 result is an empty string, the private key is assumed to be in the same file as
25924 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
25927 .option tls_require_ciphers smtp string&!! unset
25928 .cindex "TLS" "requiring specific ciphers"
25929 .cindex "cipher" "requiring specific"
25931 .vindex "&$host_address$&"
25932 The value of this option must be a list of permitted cipher suites, for use
25933 when setting up an outgoing encrypted connection. (There is a global option of
25934 the same name for controlling incoming connections.) The values of &$host$& and
25935 &$host_address$& are set to the name and address of the server during the
25936 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
25937 is used in different ways by OpenSSL and GnuTLS (see sections
25938 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
25939 ciphers is a preference order.
25943 .option tls_resumption_hosts smtp "host list&!!" unset
25944 .cindex TLS resumption
25945 This option controls which connections to use the TLS resumption feature.
25946 See &<<SECTresumption>>& for details.
25951 .option tls_sni smtp string&!! unset
25952 .cindex "TLS" "Server Name Indication"
25954 .cindex SNI "setting in client"
25955 .vindex "&$tls_sni$&"
25956 If this option is set
25958 and the connection is not DANE-validated
25960 then it sets the $tls_out_sni variable and causes any
25961 TLS session to pass this value as the Server Name Indication extension to
25962 the remote side, which can be used by the remote side to select an appropriate
25963 certificate and private key for the session.
25965 See &<<SECTtlssni>>& for more information.
25967 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
25973 .option tls_tempfail_tryclear smtp boolean true
25974 .cindex "4&'xx'& responses" "to STARTTLS"
25975 When the server host is not in &%hosts_require_tls%&, and there is a problem in
25976 setting up a TLS session, this option determines whether or not Exim should try
25977 to deliver the message unencrypted. If it is set false, delivery to the
25978 current host is deferred; if there are other hosts, they are tried. If this
25979 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
25980 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
25981 TLS negotiation fails, Exim closes the current connection (because it is in an
25982 unknown state), opens a new one to the same host, and then tries the delivery
25986 .option tls_try_verify_hosts smtp "host list&!!" *
25987 .cindex "TLS" "server certificate verification"
25988 .cindex "certificate" "verification of server"
25989 This option gives a list of hosts for which, on encrypted connections,
25990 certificate verification will be tried but need not succeed.
25991 The &%tls_verify_certificates%& option must also be set.
25992 Note that unless the host is in this list
25993 TLS connections will be denied to hosts using self-signed certificates
25994 when &%tls_verify_certificates%& is matched.
25995 The &$tls_out_certificate_verified$& variable is set when
25996 certificate verification succeeds.
25999 .option tls_verify_cert_hostnames smtp "host list&!!" *
26000 .cindex "TLS" "server certificate hostname verification"
26001 .cindex "certificate" "verification of server"
26002 This option give a list of hosts for which,
26003 while verifying the server certificate,
26004 checks will be included on the host name
26005 (note that this will generally be the result of a DNS MX lookup)
26006 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
26007 limited to being the initial component of a 3-or-more component FQDN.
26009 There is no equivalent checking on client certificates.
26012 .option tls_verify_certificates smtp string&!! system
26013 .cindex "TLS" "server certificate verification"
26014 .cindex "certificate" "verification of server"
26016 .vindex "&$host_address$&"
26017 The value of this option must be either the
26019 or the absolute path to
26020 a file or directory containing permitted certificates for servers,
26021 for use when setting up an encrypted connection.
26023 The "system" value for the option will use a location compiled into the SSL library.
26024 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
26025 is taken as empty and an explicit location
26028 The use of a directory for the option value is not available for GnuTLS versions
26029 preceding 3.3.6 and a single file must be used.
26031 With OpenSSL the certificates specified
26033 either by file or directory
26034 are added to those given by the system default location.
26036 The values of &$host$& and
26037 &$host_address$& are set to the name and address of the server during the
26038 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
26040 For back-compatibility,
26041 if neither tls_verify_hosts nor tls_try_verify_hosts are set
26042 (a single-colon empty list counts as being set)
26043 and certificate verification fails the TLS connection is closed.
26046 .option tls_verify_hosts smtp "host list&!!" unset
26047 .cindex "TLS" "server certificate verification"
26048 .cindex "certificate" "verification of server"
26049 This option gives a list of hosts for which, on encrypted connections,
26050 certificate verification must succeed.
26051 The &%tls_verify_certificates%& option must also be set.
26052 If both this option and &%tls_try_verify_hosts%& are unset
26053 operation is as if this option selected all hosts.
26055 .option utf8_downconvert smtp integer&!! -1
26056 .cindex utf8 "address downconversion"
26057 .cindex i18n "utf8 address downconversion"
26058 If built with internationalization support,
26059 this option controls conversion of UTF-8 in message envelope addresses
26061 If, after expansion, the value is 1, 0, or -1 then this value overrides
26062 any value previously set for the message. Otherwise, any previously
26063 set value is used. To permit use of a previous value,
26064 set this option to an empty string.
26065 For details on the values see section &<<SECTi18nMTA>>&.
26070 .section "How the limits for the number of hosts to try are used" &&&
26072 .cindex "host" "maximum number to try"
26073 .cindex "limit" "hosts; maximum number tried"
26074 There are two options that are concerned with the number of hosts that are
26075 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
26076 &%hosts_max_try_hardlimit%&.
26079 The &%hosts_max_try%& option limits the number of hosts that are tried
26080 for a single delivery. However, despite the term &"host"& in its name, the
26081 option actually applies to each IP address independently. In other words, a
26082 multihomed host is treated as several independent hosts, just as it is for
26085 Many of the larger ISPs have multiple MX records which often point to
26086 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
26087 created as a result of routing one of these domains.
26089 Trying every single IP address on such a long list does not seem sensible; if
26090 several at the top of the list fail, it is reasonable to assume there is some
26091 problem that is likely to affect all of them. Roughly speaking, the value of
26092 &%hosts_max_try%& is the maximum number that are tried before deferring the
26093 delivery. However, the logic cannot be quite that simple.
26095 Firstly, IP addresses that are skipped because their retry times have not
26096 arrived do not count, and in addition, addresses that are past their retry
26097 limits are also not counted, even when they are tried. This means that when
26098 some IP addresses are past their retry limits, more than the value of
26099 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
26100 that all IP addresses are considered before timing out an email address (but
26101 see below for an exception).
26103 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
26104 list to see if there is a subsequent host with a different (higher valued) MX.
26105 If there is, that host is considered next, and the current IP address is used
26106 but not counted. This behaviour helps in the case of a domain with a retry rule
26107 that hardly ever delays any hosts, as is now explained:
26109 Consider the case of a long list of hosts with one MX value, and a few with a
26110 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
26111 hosts at the top of the list are tried at first. With the default retry rule,
26112 which specifies increasing retry times, the higher MX hosts are eventually
26113 tried when those at the top of the list are skipped because they have not
26114 reached their retry times.
26116 However, it is common practice to put a fixed short retry time on domains for
26117 large ISPs, on the grounds that their servers are rarely down for very long.
26118 Unfortunately, these are exactly the domains that tend to resolve to long lists
26119 of hosts. The short retry time means that the lowest MX hosts are tried every
26120 time. The attempts may be in a different order because of random sorting, but
26121 without the special MX check, the higher MX hosts would never be tried until
26122 all the lower MX hosts had timed out (which might be several days), because
26123 there are always some lower MX hosts that have reached their retry times. With
26124 the special check, Exim considers at least one IP address from each MX value at
26125 every delivery attempt, even if the &%hosts_max_try%& limit has already been
26128 The above logic means that &%hosts_max_try%& is not a hard limit, and in
26129 particular, Exim normally eventually tries all the IP addresses before timing
26130 out an email address. When &%hosts_max_try%& was implemented, this seemed a
26131 reasonable thing to do. Recently, however, some lunatic DNS configurations have
26132 been set up with hundreds of IP addresses for some domains. It can
26133 take a very long time indeed for an address to time out in these cases.
26135 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
26136 Exim never tries more than this number of IP addresses; if it hits this limit
26137 and they are all timed out, the email address is bounced, even though not all
26138 possible IP addresses have been tried.
26139 .ecindex IIDsmttra1
26140 .ecindex IIDsmttra2
26146 . ////////////////////////////////////////////////////////////////////////////
26147 . ////////////////////////////////////////////////////////////////////////////
26149 .chapter "Address rewriting" "CHAPrewrite"
26150 .scindex IIDaddrew "rewriting" "addresses"
26151 There are some circumstances in which Exim automatically rewrites domains in
26152 addresses. The two most common are when an address is given without a domain
26153 (referred to as an &"unqualified address"&) or when an address contains an
26154 abbreviated domain that is expanded by DNS lookup.
26156 Unqualified envelope addresses are accepted only for locally submitted
26157 messages, or for messages that are received from hosts matching
26158 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
26159 appropriate. Unqualified addresses in header lines are qualified if they are in
26160 locally submitted messages, or messages from hosts that are permitted to send
26161 unqualified envelope addresses. Otherwise, unqualified addresses in header
26162 lines are neither qualified nor rewritten.
26164 One situation in which Exim does &'not'& automatically rewrite a domain is
26165 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
26166 such a domain should be rewritten using the &"canonical"& name, and some MTAs
26167 do this. The new RFCs do not contain this suggestion.
26170 .section "Explicitly configured address rewriting" "SECID147"
26171 This chapter describes the rewriting rules that can be used in the
26172 main rewrite section of the configuration file, and also in the generic
26173 &%headers_rewrite%& option that can be set on any transport.
26175 Some people believe that configured address rewriting is a Mortal Sin.
26176 Others believe that life is not possible without it. Exim provides the
26177 facility; you do not have to use it.
26179 The main rewriting rules that appear in the &"rewrite"& section of the
26180 configuration file are applied to addresses in incoming messages, both envelope
26181 addresses and addresses in header lines. Each rule specifies the types of
26182 address to which it applies.
26184 Whether or not addresses in header lines are rewritten depends on the origin of
26185 the headers and the type of rewriting. Global rewriting, that is, rewriting
26186 rules from the rewrite section of the configuration file, is applied only to
26187 those headers that were received with the message. Header lines that are added
26188 by ACLs or by a system filter or by individual routers or transports (which
26189 are specific to individual recipient addresses) are not rewritten by the global
26192 Rewriting at transport time, by means of the &%headers_rewrite%& option,
26193 applies all headers except those added by routers and transports. That is, as
26194 well as the headers that were received with the message, it also applies to
26195 headers that were added by an ACL or a system filter.
26198 In general, rewriting addresses from your own system or domain has some
26199 legitimacy. Rewriting other addresses should be done only with great care and
26200 in special circumstances. The author of Exim believes that rewriting should be
26201 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
26202 Although it can sometimes be used as a routing tool, this is very strongly
26205 There are two commonly encountered circumstances where rewriting is used, as
26206 illustrated by these examples:
26209 The company whose domain is &'hitch.fict.example'& has a number of hosts that
26210 exchange mail with each other behind a firewall, but there is only a single
26211 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
26212 &'hitch.fict.example'& when sending mail off-site.
26214 A host rewrites the local parts of its own users so that, for example,
26215 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
26220 .section "When does rewriting happen?" "SECID148"
26221 .cindex "rewriting" "timing of"
26222 .cindex "&ACL;" "rewriting addresses in"
26223 Configured address rewriting can take place at several different stages of a
26224 message's processing.
26226 .vindex "&$sender_address$&"
26227 At the start of an ACL for MAIL, the sender address may have been rewritten
26228 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
26229 ordinary rewrite rules have yet been applied. If, however, the sender address
26230 is verified in the ACL, it is rewritten before verification, and remains
26231 rewritten thereafter. The subsequent value of &$sender_address$& is the
26232 rewritten address. This also applies if sender verification happens in a
26233 RCPT ACL. Otherwise, when the sender address is not verified, it is
26234 rewritten as soon as a message's header lines have been received.
26236 .vindex "&$domain$&"
26237 .vindex "&$local_part$&"
26238 Similarly, at the start of an ACL for RCPT, the current recipient's address
26239 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
26240 rewrite rules have yet been applied to it. However, the behaviour is different
26241 from the sender address when a recipient is verified. The address is rewritten
26242 for the verification, but the rewriting is not remembered at this stage. The
26243 value of &$local_part$& and &$domain$& after verification are always the same
26244 as they were before (that is, they contain the unrewritten &-- except for
26245 SMTP-time rewriting &-- address).
26247 As soon as a message's header lines have been received, all the envelope
26248 recipient addresses are permanently rewritten, and rewriting is also applied to
26249 the addresses in the header lines (if configured). This happens before adding
26250 any header lines that were specified in MAIL or RCPT ACLs, and
26251 .cindex "&[local_scan()]& function" "address rewriting; timing of"
26252 before the DATA ACL and &[local_scan()]& functions are run.
26254 When an address is being routed, either for delivery or for verification,
26255 rewriting is applied immediately to child addresses that are generated by
26256 redirection, unless &%no_rewrite%& is set on the router.
26258 .cindex "envelope from"
26259 .cindex "envelope sender" "rewriting at transport time"
26260 .cindex "rewriting" "at transport time"
26261 .cindex "header lines" "rewriting at transport time"
26262 At transport time, additional rewriting of addresses in header lines can be
26263 specified by setting the generic &%headers_rewrite%& option on a transport.
26264 This option contains rules that are identical in form to those in the rewrite
26265 section of the configuration file. They are applied to the original message
26266 header lines and any that were added by ACLs or a system filter. They are not
26267 applied to header lines that are added by routers or the transport.
26269 The outgoing envelope sender can be rewritten by means of the &%return_path%&
26270 transport option. However, it is not possible to rewrite envelope recipients at
26276 .section "Testing the rewriting rules that apply on input" "SECID149"
26277 .cindex "rewriting" "testing"
26278 .cindex "testing" "rewriting"
26279 Exim's input rewriting configuration appears in a part of the runtime
26280 configuration file headed by &"begin rewrite"&. It can be tested by the
26281 &%-brw%& command line option. This takes an address (which can be a full RFC
26282 2822 address) as its argument. The output is a list of how the address would be
26283 transformed by the rewriting rules for each of the different places it might
26284 appear in an incoming message, that is, for each different header and for the
26285 envelope sender and recipient fields. For example,
26287 exim -brw ph10@exim.workshop.example
26289 might produce the output
26291 sender: Philip.Hazel@exim.workshop.example
26292 from: Philip.Hazel@exim.workshop.example
26293 to: ph10@exim.workshop.example
26294 cc: ph10@exim.workshop.example
26295 bcc: ph10@exim.workshop.example
26296 reply-to: Philip.Hazel@exim.workshop.example
26297 env-from: Philip.Hazel@exim.workshop.example
26298 env-to: ph10@exim.workshop.example
26300 which shows that rewriting has been set up for that address when used in any of
26301 the source fields, but not when it appears as a recipient address. At the
26302 present time, there is no equivalent way of testing rewriting rules that are
26303 set for a particular transport.
26306 .section "Rewriting rules" "SECID150"
26307 .cindex "rewriting" "rules"
26308 The rewrite section of the configuration file consists of lines of rewriting
26311 <&'source pattern'&> <&'replacement'&> <&'flags'&>
26313 Rewriting rules that are specified for the &%headers_rewrite%& generic
26314 transport option are given as a colon-separated list. Each item in the list
26315 takes the same form as a line in the main rewriting configuration (except that
26316 any colons must be doubled, of course).
26318 The formats of source patterns and replacement strings are described below.
26319 Each is terminated by white space, unless enclosed in double quotes, in which
26320 case normal quoting conventions apply inside the quotes. The flags are single
26321 characters which may appear in any order. Spaces and tabs between them are
26324 For each address that could potentially be rewritten, the rules are scanned in
26325 order, and replacements for the address from earlier rules can themselves be
26326 replaced by later rules (but see the &"q"& and &"R"& flags).
26328 The order in which addresses are rewritten is undefined, may change between
26329 releases, and must not be relied on, with one exception: when a message is
26330 received, the envelope sender is always rewritten first, before any header
26331 lines are rewritten. For example, the replacement string for a rewrite of an
26332 address in &'To:'& must not assume that the message's address in &'From:'& has
26333 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
26334 that the envelope sender has already been rewritten.
26336 .vindex "&$domain$&"
26337 .vindex "&$local_part$&"
26338 The variables &$local_part$& and &$domain$& can be used in the replacement
26339 string to refer to the address that is being rewritten. Note that lookup-driven
26340 rewriting can be done by a rule of the form
26344 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
26345 refer to the address that is being rewritten.
26348 .section "Rewriting patterns" "SECID151"
26349 .cindex "rewriting" "patterns"
26350 .cindex "address list" "in a rewriting pattern"
26351 The source pattern in a rewriting rule is any item which may appear in an
26352 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
26353 single-item address list, which means that it is expanded before being tested
26354 against the address. As always, if you use a regular expression as a pattern,
26355 you must take care to escape dollar and backslash characters, or use the &`\N`&
26356 facility to suppress string expansion within the regular expression.
26358 Domains in patterns should be given in lower case. Local parts in patterns are
26359 case-sensitive. If you want to do case-insensitive matching of local parts, you
26360 can use a regular expression that starts with &`^(?i)`&.
26362 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
26363 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
26364 depending on the type of match which occurred. These can be used in the
26365 replacement string to insert portions of the incoming address. &$0$& always
26366 refers to the complete incoming address. When a regular expression is used, the
26367 numerical variables are set from its capturing subexpressions. For other types
26368 of pattern they are set as follows:
26371 If a local part or domain starts with an asterisk, the numerical variables
26372 refer to the character strings matched by asterisks, with &$1$& associated with
26373 the first asterisk, and &$2$& with the second, if present. For example, if the
26376 *queen@*.fict.example
26378 is matched against the address &'hearts-queen@wonderland.fict.example'& then
26380 $0 = hearts-queen@wonderland.fict.example
26384 Note that if the local part does not start with an asterisk, but the domain
26385 does, it is &$1$& that contains the wild part of the domain.
26388 If the domain part of the pattern is a partial lookup, the wild and fixed parts
26389 of the domain are placed in the next available numerical variables. Suppose,
26390 for example, that the address &'foo@bar.baz.example'& is processed by a
26391 rewriting rule of the form
26393 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
26395 and the key in the file that matches the domain is &`*.baz.example`&. Then
26401 If the address &'foo@baz.example'& is looked up, this matches the same
26402 wildcard file entry, and in this case &$2$& is set to the empty string, but
26403 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
26404 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
26405 whole domain. For non-partial domain lookups, no numerical variables are set.
26409 .section "Rewriting replacements" "SECID152"
26410 .cindex "rewriting" "replacements"
26411 If the replacement string for a rule is a single asterisk, addresses that
26412 match the pattern and the flags are &'not'& rewritten, and no subsequent
26413 rewriting rules are scanned. For example,
26415 hatta@lookingglass.fict.example * f
26417 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
26420 .vindex "&$domain$&"
26421 .vindex "&$local_part$&"
26422 If the replacement string is not a single asterisk, it is expanded, and must
26423 yield a fully qualified address. Within the expansion, the variables
26424 &$local_part$& and &$domain$& refer to the address that is being rewritten.
26425 Any letters they contain retain their original case &-- they are not lower
26426 cased. The numerical variables are set up according to the type of pattern that
26427 matched the address, as described above. If the expansion is forced to fail by
26428 the presence of &"fail"& in a conditional or lookup item, rewriting by the
26429 current rule is abandoned, but subsequent rules may take effect. Any other
26430 expansion failure causes the entire rewriting operation to be abandoned, and an
26431 entry written to the panic log.
26435 .section "Rewriting flags" "SECID153"
26436 There are three different kinds of flag that may appear on rewriting rules:
26439 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
26442 A flag that specifies rewriting at SMTP time: S.
26444 Flags that control the rewriting process: Q, q, R, w.
26447 For rules that are part of the &%headers_rewrite%& generic transport option,
26448 E, F, T, and S are not permitted.
26452 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
26454 .cindex "rewriting" "flags"
26455 If none of the following flag letters, nor the &"S"& flag (see section
26456 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
26457 and to both the sender and recipient fields of the envelope, whereas a
26458 transport-time rewriting rule just applies to all headers. Otherwise, the
26459 rewriting rule is skipped unless the relevant addresses are being processed.
26461 &`E`& rewrite all envelope fields
26462 &`F`& rewrite the envelope From field
26463 &`T`& rewrite the envelope To field
26464 &`b`& rewrite the &'Bcc:'& header
26465 &`c`& rewrite the &'Cc:'& header
26466 &`f`& rewrite the &'From:'& header
26467 &`h`& rewrite all headers
26468 &`r`& rewrite the &'Reply-To:'& header
26469 &`s`& rewrite the &'Sender:'& header
26470 &`t`& rewrite the &'To:'& header
26472 "All headers" means all of the headers listed above that can be selected
26473 individually, plus their &'Resent-'& versions. It does not include
26474 other headers such as &'Subject:'& etc.
26476 You should be particularly careful about rewriting &'Sender:'& headers, and
26477 restrict this to special known cases in your own domains.
26480 .section "The SMTP-time rewriting flag" "SECTrewriteS"
26481 .cindex "SMTP" "rewriting malformed addresses"
26482 .cindex "RCPT" "rewriting argument of"
26483 .cindex "MAIL" "rewriting argument of"
26484 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
26485 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
26486 before any other processing; even before syntax checking. The pattern is
26487 required to be a regular expression, and it is matched against the whole of the
26488 data for the command, including any surrounding angle brackets.
26490 .vindex "&$domain$&"
26491 .vindex "&$local_part$&"
26492 This form of rewrite rule allows for the handling of addresses that are not
26493 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
26494 input). Because the input is not required to be a syntactically valid address,
26495 the variables &$local_part$& and &$domain$& are not available during the
26496 expansion of the replacement string. The result of rewriting replaces the
26497 original address in the MAIL or RCPT command.
26500 .section "Flags controlling the rewriting process" "SECID155"
26501 There are four flags which control the way the rewriting process works. These
26502 take effect only when a rule is invoked, that is, when the address is of the
26503 correct type (matches the flags) and matches the pattern:
26506 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
26507 unqualified local part. It is qualified with &%qualify_recipient%&. In the
26508 absence of &"Q"& the rewritten address must always include a domain.
26510 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
26511 even if no rewriting actually takes place because of a &"fail"& in the
26512 expansion. The &"q"& flag is not effective if the address is of the wrong type
26513 (does not match the flags) or does not match the pattern.
26515 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
26516 address, up to ten times. It can be combined with the &"q"& flag, to stop
26517 rewriting once it fails to match (after at least one successful rewrite).
26519 .cindex "rewriting" "whole addresses"
26520 When an address in a header is rewritten, the rewriting normally applies only
26521 to the working part of the address, with any comments and RFC 2822 &"phrase"&
26522 left unchanged. For example, rewriting might change
26524 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
26528 From: Ford Prefect <prefectf@hitch.fict.example>
26531 Sometimes there is a need to replace the whole address item, and this can be
26532 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
26533 causes an address in a header line to be rewritten, the entire address is
26534 replaced, not just the working part. The replacement must be a complete RFC
26535 2822 address, including the angle brackets if necessary. If text outside angle
26536 brackets contains a character whose value is greater than 126 or less than 32
26537 (except for tab), the text is encoded according to RFC 2047. The character set
26538 is taken from &%headers_charset%&, which gets its default at build time.
26540 When the &"w"& flag is set on a rule that causes an envelope address to be
26541 rewritten, all but the working part of the replacement address is discarded.
26545 .section "Rewriting examples" "SECID156"
26546 Here is an example of the two common rewriting paradigms:
26548 *@*.hitch.fict.example $1@hitch.fict.example
26549 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
26550 {$value}fail}@hitch.fict.example bctfrF
26552 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
26553 the string expansion to fail if the lookup does not succeed. In this context it
26554 has the effect of leaving the original address unchanged, but Exim goes on to
26555 consider subsequent rewriting rules, if any, because the &"q"& flag is not
26556 present in that rule. An alternative to &"fail"& would be to supply &$1$&
26557 explicitly, which would cause the rewritten address to be the same as before,
26558 at the cost of a small bit of processing. Not supplying either of these is an
26559 error, since the rewritten address would then contain no local part.
26561 The first example above replaces the domain with a superior, more general
26562 domain. This may not be desirable for certain local parts. If the rule
26564 root@*.hitch.fict.example *
26566 were inserted before the first rule, rewriting would be suppressed for the
26567 local part &'root'& at any domain ending in &'hitch.fict.example'&.
26569 Rewriting can be made conditional on a number of tests, by making use of
26570 &${if$& in the expansion item. For example, to apply a rewriting rule only to
26571 messages that originate outside the local host:
26573 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
26574 {$1@hitch.fict.example}fail}"
26576 The replacement string is quoted in this example because it contains white
26579 .cindex "rewriting" "bang paths"
26580 .cindex "bang paths" "rewriting"
26581 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
26582 an address it treats it as an unqualified local part which it qualifies with
26583 the local qualification domain (if the source of the message is local or if the
26584 remote host is permitted to send unqualified addresses). Rewriting can
26585 sometimes be used to handle simple bang paths with a fixed number of
26586 components. For example, the rule
26588 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
26590 rewrites a two-component bang path &'host.name!user'& as the domain address
26591 &'user@host.name'&. However, there is a security implication in using this as
26592 a global rewriting rule for envelope addresses. It can provide a backdoor
26593 method for using your system as a relay, because the incoming addresses appear
26594 to be local. If the bang path addresses are received via SMTP, it is safer to
26595 use the &"S"& flag to rewrite them as they are received, so that relay checking
26596 can be done on the rewritten addresses.
26603 . ////////////////////////////////////////////////////////////////////////////
26604 . ////////////////////////////////////////////////////////////////////////////
26606 .chapter "Retry configuration" "CHAPretry"
26607 .scindex IIDretconf1 "retry" "configuration, description of"
26608 .scindex IIDregconf2 "configuration file" "retry section"
26609 The &"retry"& section of the runtime configuration file contains a list of
26610 retry rules that control how often Exim tries to deliver messages that cannot
26611 be delivered at the first attempt. If there are no retry rules (the section is
26612 empty or not present), there are no retries. In this situation, temporary
26613 errors are treated as permanent. The default configuration contains a single,
26614 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
26615 line option can be used to test which retry rule will be used for a given
26616 address, domain and error.
26618 The most common cause of retries is temporary failure to deliver to a remote
26619 host because the host is down, or inaccessible because of a network problem.
26620 Exim's retry processing in this case is applied on a per-host (strictly, per IP
26621 address) basis, not on a per-message basis. Thus, if one message has recently
26622 been delayed, delivery of a new message to the same host is not immediately
26623 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
26624 log selector is set, the message
26625 .cindex "retry" "time not reached"
26626 &"retry time not reached"& is written to the main log whenever a delivery is
26627 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
26628 the handling of errors during remote deliveries.
26630 Retry processing applies to routing as well as to delivering, except as covered
26631 in the next paragraph. The retry rules do not distinguish between these
26632 actions. It is not possible, for example, to specify different behaviour for
26633 failures to route the domain &'snark.fict.example'& and failures to deliver to
26634 the host &'snark.fict.example'&. I didn't think anyone would ever need this
26635 added complication, so did not implement it. However, although they share the
26636 same retry rule, the actual retry times for routing and transporting a given
26637 domain are maintained independently.
26639 When a delivery is not part of a queue run (typically an immediate delivery on
26640 receipt of a message), the routers are always run, and local deliveries are
26641 always attempted, even if retry times are set for them. This makes for better
26642 behaviour if one particular message is causing problems (for example, causing
26643 quota overflow, or provoking an error in a filter file). If such a delivery
26644 suffers a temporary failure, the retry data is updated as normal, and
26645 subsequent delivery attempts from queue runs occur only when the retry time for
26646 the local address is reached.
26648 .section "Changing retry rules" "SECID157"
26649 If you change the retry rules in your configuration, you should consider
26650 whether or not to delete the retry data that is stored in Exim's spool area in
26651 files with names like &_db/retry_&. Deleting any of Exim's hints files is
26652 always safe; that is why they are called &"hints"&.
26654 The hints retry data contains suggested retry times based on the previous
26655 rules. In the case of a long-running problem with a remote host, it might
26656 record the fact that the host has timed out. If your new rules increase the
26657 timeout time for such a host, you should definitely remove the old retry data
26658 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
26659 messages that it should now be retaining.
26663 .section "Format of retry rules" "SECID158"
26664 .cindex "retry" "rules"
26665 Each retry rule occupies one line and consists of three or four parts,
26666 separated by white space: a pattern, an error name, an optional list of sender
26667 addresses, and a list of retry parameters. The pattern and sender lists must be
26668 enclosed in double quotes if they contain white space. The rules are searched
26669 in order until one is found where the pattern, error name, and sender list (if
26670 present) match the failing host or address, the error that occurred, and the
26671 message's sender, respectively.
26674 The pattern is any single item that may appear in an address list (see section
26675 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
26676 which means that it is expanded before being tested against the address that
26677 has been delayed. A negated address list item is permitted. Address
26678 list processing treats a plain domain name as if it were preceded by &"*@"&,
26679 which makes it possible for many retry rules to start with just a domain. For
26682 lookingglass.fict.example * F,24h,30m;
26684 provides a rule for any address in the &'lookingglass.fict.example'& domain,
26687 alice@lookingglass.fict.example * F,24h,30m;
26689 applies only to temporary failures involving the local part &%alice%&.
26690 In practice, almost all rules start with a domain name pattern without a local
26693 .cindex "regular expressions" "in retry rules"
26694 &*Warning*&: If you use a regular expression in a retry rule pattern, it
26695 must match a complete address, not just a domain, because that is how regular
26696 expressions work in address lists.
26698 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
26699 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
26703 .section "Choosing which retry rule to use for address errors" "SECID159"
26704 When Exim is looking for a retry rule after a routing attempt has failed (for
26705 example, after a DNS timeout), each line in the retry configuration is tested
26706 against the complete address only if &%retry_use_local_part%& is set for the
26707 router. Otherwise, only the domain is used, except when matching against a
26708 regular expression, when the local part of the address is replaced with &"*"&.
26709 A domain on its own can match a domain pattern, or a pattern that starts with
26710 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
26711 &%check_local_user%& is true, and false for other routers.
26713 Similarly, when Exim is looking for a retry rule after a local delivery has
26714 failed (for example, after a mailbox full error), each line in the retry
26715 configuration is tested against the complete address only if
26716 &%retry_use_local_part%& is set for the transport (it defaults true for all
26719 .cindex "4&'xx'& responses" "retry rules for"
26720 However, when Exim is looking for a retry rule after a remote delivery attempt
26721 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
26722 whole address is always used as the key when searching the retry rules. The
26723 rule that is found is used to create a retry time for the combination of the
26724 failing address and the message's sender. It is the combination of sender and
26725 recipient that is delayed in subsequent queue runs until its retry time is
26726 reached. You can delay the recipient without regard to the sender by setting
26727 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
26728 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
26733 .section "Choosing which retry rule to use for host and message errors" &&&
26735 For a temporary error that is not related to an individual address (for
26736 example, a connection timeout), each line in the retry configuration is checked
26737 twice. First, the name of the remote host is used as a domain name (preceded by
26738 &"*@"& when matching a regular expression). If this does not match the line,
26739 the domain from the email address is tried in a similar fashion. For example,
26740 suppose the MX records for &'a.b.c.example'& are
26742 a.b.c.example MX 5 x.y.z.example
26746 and the retry rules are
26748 p.q.r.example * F,24h,30m;
26749 a.b.c.example * F,4d,45m;
26751 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
26752 first rule matches neither the host nor the domain, so Exim looks at the second
26753 rule. This does not match the host, but it does match the domain, so it is used
26754 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
26755 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
26756 first retry rule is used, because it matches the host.
26758 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
26759 first rule to determine retry times, but for all the other hosts for the domain
26760 &'a.b.c.example'&, the second rule is used. The second rule is also used if
26761 routing to &'a.b.c.example'& suffers a temporary failure.
26763 &*Note*&: The host name is used when matching the patterns, not its IP address.
26764 However, if a message is routed directly to an IP address without the use of a
26765 host name, for example, if a &(manualroute)& router contains a setting such as:
26767 route_list = *.a.example 192.168.34.23
26769 then the &"host name"& that is used when searching for a retry rule is the
26770 textual form of the IP address.
26772 .section "Retry rules for specific errors" "SECID161"
26773 .cindex "retry" "specific errors; specifying"
26774 The second field in a retry rule is the name of a particular error, or an
26775 asterisk, which matches any error. The errors that can be tested for are:
26778 .vitem &%auth_failed%&
26779 Authentication failed when trying to send to a host in the
26780 &%hosts_require_auth%& list in an &(smtp)& transport.
26782 .vitem &%data_4xx%&
26783 A 4&'xx'& error was received for an outgoing DATA command, either immediately
26784 after the command, or after sending the message's data.
26786 .vitem &%mail_4xx%&
26787 A 4&'xx'& error was received for an outgoing MAIL command.
26789 .vitem &%rcpt_4xx%&
26790 A 4&'xx'& error was received for an outgoing RCPT command.
26793 For the three 4&'xx'& errors, either the first or both of the x's can be given
26794 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
26795 recognize 452 errors given to RCPT commands for addresses in a certain domain,
26796 and have retries every ten minutes with a one-hour timeout, you could set up a
26797 retry rule of this form:
26799 the.domain.name rcpt_452 F,1h,10m
26801 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
26802 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
26805 .vitem &%lost_connection%&
26806 A server unexpectedly closed the SMTP connection. There may, of course,
26807 legitimate reasons for this (host died, network died), but if it repeats a lot
26808 for the same host, it indicates something odd.
26811 A DNS lookup for a host failed.
26812 Note that a &%dnslookup%& router will need to have matched
26813 its &%fail_defer_domains%& option for this retry type to be usable.
26814 Also note that a &%manualroute%& router will probably need
26815 its &%host_find_failed%& option set to &%defer%&.
26817 .vitem &%refused_MX%&
26818 A connection to a host obtained from an MX record was refused.
26820 .vitem &%refused_A%&
26821 A connection to a host not obtained from an MX record was refused.
26824 A connection was refused.
26826 .vitem &%timeout_connect_MX%&
26827 A connection attempt to a host obtained from an MX record timed out.
26829 .vitem &%timeout_connect_A%&
26830 A connection attempt to a host not obtained from an MX record timed out.
26832 .vitem &%timeout_connect%&
26833 A connection attempt timed out.
26835 .vitem &%timeout_MX%&
26836 There was a timeout while connecting or during an SMTP session with a host
26837 obtained from an MX record.
26839 .vitem &%timeout_A%&
26840 There was a timeout while connecting or during an SMTP session with a host not
26841 obtained from an MX record.
26844 There was a timeout while connecting or during an SMTP session.
26846 .vitem &%tls_required%&
26847 The server was required to use TLS (it matched &%hosts_require_tls%& in the
26848 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
26849 to STARTTLS, or there was a problem setting up the TLS connection.
26852 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26855 .vitem &%quota_%&<&'time'&>
26856 .cindex "quota" "error testing in retry rule"
26857 .cindex "retry" "quota error testing"
26858 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26859 transport, and the mailbox has not been accessed for <&'time'&>. For example,
26860 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
26864 .cindex "mailbox" "time of last read"
26865 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
26866 timeouts when the mailbox is full and is not being read by its owner. Ideally,
26867 it should be based on the last time that the user accessed the mailbox.
26868 However, it is not always possible to determine this. Exim uses the following
26872 If the mailbox is a single file, the time of last access (the &"atime"&) is
26873 used. As no new messages are being delivered (because the mailbox is over
26874 quota), Exim does not access the file, so this is the time of last user access.
26876 .cindex "maildir format" "time of last read"
26877 For a maildir delivery, the time of last modification of the &_new_&
26878 subdirectory is used. As the mailbox is over quota, no new files are created in
26879 the &_new_& subdirectory, because no new messages are being delivered. Any
26880 change to the &_new_& subdirectory is therefore assumed to be the result of an
26881 MUA moving a new message to the &_cur_& directory when it is first read. The
26882 time that is used is therefore the last time that the user read a new message.
26884 For other kinds of multi-file mailbox, the time of last access cannot be
26885 obtained, so a retry rule that uses this type of error field is never matched.
26888 The quota errors apply both to system-enforced quotas and to Exim's own quota
26889 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
26890 when a local delivery is deferred because a partition is full (the ENOSPC
26895 .section "Retry rules for specified senders" "SECID162"
26896 .cindex "retry" "rules; sender-specific"
26897 You can specify retry rules that apply only when the failing message has a
26898 specific sender. In particular, this can be used to define retry rules that
26899 apply only to bounce messages. The third item in a retry rule can be of this
26902 &`senders=`&<&'address list'&>
26904 The retry timings themselves are then the fourth item. For example:
26906 * rcpt_4xx senders=: F,1h,30m
26908 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
26909 host. If the address list contains white space, it must be enclosed in quotes.
26912 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
26914 &*Warning*&: This facility can be unhelpful if it is used for host errors
26915 (which do not depend on the recipient). The reason is that the sender is used
26916 only to match the retry rule. Once the rule has been found for a host error,
26917 its contents are used to set a retry time for the host, and this will apply to
26918 all messages, not just those with specific senders.
26920 When testing retry rules using &%-brt%&, you can supply a sender using the
26921 &%-f%& command line option, like this:
26923 exim -f "" -brt user@dom.ain
26925 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
26926 list is never matched.
26932 .section "Retry parameters" "SECID163"
26933 .cindex "retry" "parameters in rules"
26934 The third (or fourth, if a senders list is present) field in a retry rule is a
26935 sequence of retry parameter sets, separated by semicolons. Each set consists of
26937 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
26939 The letter identifies the algorithm for computing a new retry time; the cutoff
26940 time is the time beyond which this algorithm no longer applies, and the
26941 arguments vary the algorithm's action. The cutoff time is measured from the
26942 time that the first failure for the domain (combined with the local part if
26943 relevant) was detected, not from the time the message was received.
26945 .cindex "retry" "algorithms"
26946 .cindex "retry" "fixed intervals"
26947 .cindex "retry" "increasing intervals"
26948 .cindex "retry" "random intervals"
26949 The available algorithms are:
26952 &'F'&: retry at fixed intervals. There is a single time parameter specifying
26955 &'G'&: retry at geometrically increasing intervals. The first argument
26956 specifies a starting value for the interval, and the second a multiplier, which
26957 is used to increase the size of the interval at each retry.
26959 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
26960 retry, the previous interval is multiplied by the factor in order to get a
26961 maximum for the next interval. The minimum interval is the first argument of
26962 the parameter, and an actual interval is chosen randomly between them. Such a
26963 rule has been found to be helpful in cluster configurations when all the
26964 members of the cluster restart at once, and may therefore synchronize their
26965 queue processing times.
26968 When computing the next retry time, the algorithm definitions are scanned in
26969 order until one whose cutoff time has not yet passed is reached. This is then
26970 used to compute a new retry time that is later than the current time. In the
26971 case of fixed interval retries, this simply means adding the interval to the
26972 current time. For geometrically increasing intervals, retry intervals are
26973 computed from the rule's parameters until one that is greater than the previous
26974 interval is found. The main configuration variable
26975 .cindex "limit" "retry interval"
26976 .cindex "retry" "interval, maximum"
26977 .oindex "&%retry_interval_max%&"
26978 &%retry_interval_max%& limits the maximum interval between retries. It
26979 cannot be set greater than &`24h`&, which is its default value.
26981 A single remote domain may have a number of hosts associated with it, and each
26982 host may have more than one IP address. Retry algorithms are selected on the
26983 basis of the domain name, but are applied to each IP address independently. If,
26984 for example, a host has two IP addresses and one is unusable, Exim will
26985 generate retry times for it and will not try to use it until its next retry
26986 time comes. Thus the good IP address is likely to be tried first most of the
26989 .cindex "hints database" "use for retrying"
26990 Retry times are hints rather than promises. Exim does not make any attempt to
26991 run deliveries exactly at the computed times. Instead, a queue runner process
26992 starts delivery processes for delayed messages periodically, and these attempt
26993 new deliveries only for those addresses that have passed their next retry time.
26994 If a new message arrives for a deferred address, an immediate delivery attempt
26995 occurs only if the address has passed its retry time. In the absence of new
26996 messages, the minimum time between retries is the interval between queue runner
26997 processes. There is not much point in setting retry times of five minutes if
26998 your queue runners happen only once an hour, unless there are a significant
26999 number of incoming messages (which might be the case on a system that is
27000 sending everything to a smart host, for example).
27002 The data in the retry hints database can be inspected by using the
27003 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
27004 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
27005 &'exinext'& utility script can be used to find out what the next retry times
27006 are for the hosts associated with a particular mail domain, and also for local
27007 deliveries that have been deferred.
27010 .section "Retry rule examples" "SECID164"
27011 Here are some example retry rules:
27013 alice@wonderland.fict.example quota_5d F,7d,3h
27014 wonderland.fict.example quota_5d
27015 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
27016 lookingglass.fict.example * F,24h,30m;
27017 * refused_A F,2h,20m;
27018 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
27020 The first rule sets up special handling for mail to
27021 &'alice@wonderland.fict.example'& when there is an over-quota error and the
27022 mailbox has not been read for at least 5 days. Retries continue every three
27023 hours for 7 days. The second rule handles over-quota errors for all other local
27024 parts at &'wonderland.fict.example'&; the absence of a local part has the same
27025 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
27026 fail are bounced immediately if the mailbox has not been read for at least 5
27029 The third rule handles all other errors at &'wonderland.fict.example'&; retries
27030 happen every 15 minutes for an hour, then with geometrically increasing
27031 intervals until two days have passed since a delivery first failed. After the
27032 first hour there is a delay of one hour, then two hours, then four hours, and
27033 so on (this is a rather extreme example).
27035 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
27036 They happen every 30 minutes for 24 hours only. The remaining two rules handle
27037 all other domains, with special action for connection refusal from hosts that
27038 were not obtained from an MX record.
27040 The final rule in a retry configuration should always have asterisks in the
27041 first two fields so as to provide a general catch-all for any addresses that do
27042 not have their own special handling. This example tries every 15 minutes for 2
27043 hours, then with intervals starting at one hour and increasing by a factor of
27044 1.5 up to 16 hours, then every 8 hours up to 5 days.
27048 .section "Timeout of retry data" "SECID165"
27049 .cindex "timeout" "of retry data"
27050 .oindex "&%retry_data_expire%&"
27051 .cindex "hints database" "data expiry"
27052 .cindex "retry" "timeout of data"
27053 Exim timestamps the data that it writes to its retry hints database. When it
27054 consults the data during a delivery it ignores any that is older than the value
27055 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
27056 been tried for 7 days, Exim will try to deliver to it immediately a message
27057 arrives, and if that fails, it will calculate a retry time as if it were
27058 failing for the first time.
27060 This improves the behaviour for messages routed to rarely-used hosts such as MX
27061 backups. If such a host was down at one time, and happens to be down again when
27062 Exim tries a month later, using the old retry data would imply that it had been
27063 down all the time, which is not a justified assumption.
27065 If a host really is permanently dead, this behaviour causes a burst of retries
27066 every now and again, but only if messages routed to it are rare. If there is a
27067 message at least once every 7 days the retry data never expires.
27072 .section "Long-term failures" "SECID166"
27073 .cindex "delivery failure, long-term"
27074 .cindex "retry" "after long-term failure"
27075 Special processing happens when an email address has been failing for so long
27076 that the cutoff time for the last algorithm is reached. For example, using the
27077 default retry rule:
27079 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
27081 the cutoff time is four days. Reaching the retry cutoff is independent of how
27082 long any specific message has been failing; it is the length of continuous
27083 failure for the recipient address that counts.
27085 When the cutoff time is reached for a local delivery, or for all the IP
27086 addresses associated with a remote delivery, a subsequent delivery failure
27087 causes Exim to give up on the address, and a bounce message is generated.
27088 In order to cater for new messages that use the failing address, a next retry
27089 time is still computed from the final algorithm, and is used as follows:
27091 For local deliveries, one delivery attempt is always made for any subsequent
27092 messages. If this delivery fails, the address fails immediately. The
27093 post-cutoff retry time is not used.
27095 .cindex "final cutoff" "retries, controlling"
27096 .cindex retry "final cutoff"
27097 If the delivery is remote, there are two possibilities, controlled by the
27098 .oindex "&%delay_after_cutoff%&"
27099 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
27100 default. Until the post-cutoff retry time for one of the IP addresses,
27101 as set by the &%retry_data_expire%& option, is
27102 reached, the failing email address is bounced immediately, without a delivery
27103 attempt taking place. After that time, one new delivery attempt is made to
27104 those IP addresses that are past their retry times, and if that still fails,
27105 the address is bounced and new retry times are computed.
27107 In other words, when all the hosts for a given email address have been failing
27108 for a long time, Exim bounces rather then defers until one of the hosts' retry
27109 times is reached. Then it tries once, and bounces if that attempt fails. This
27110 behaviour ensures that few resources are wasted in repeatedly trying to deliver
27111 to a broken destination, but if the host does recover, Exim will eventually
27114 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
27115 addresses are past their final cutoff time, Exim tries to deliver to those IP
27116 addresses that have not been tried since the message arrived. If there are
27117 no suitable IP addresses, or if they all fail, the address is bounced. In other
27118 words, it does not delay when a new message arrives, but tries the expired
27119 addresses immediately, unless they have been tried since the message arrived.
27120 If there is a continuous stream of messages for the failing domains, setting
27121 &%delay_after_cutoff%& false means that there will be many more attempts to
27122 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
27125 .section "Deliveries that work intermittently" "SECID167"
27126 .cindex "retry" "intermittently working deliveries"
27127 Some additional logic is needed to cope with cases where a host is
27128 intermittently available, or when a message has some attribute that prevents
27129 its delivery when others to the same address get through. In this situation,
27130 because some messages are successfully delivered, the &"retry clock"& for the
27131 host or address keeps getting reset by the successful deliveries, and so
27132 failing messages remain in the queue for ever because the cutoff time is never
27135 Two exceptional actions are applied to prevent this happening. The first
27136 applies to errors that are related to a message rather than a remote host.
27137 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
27138 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
27139 commands, and quota failures. For this type of error, if a message's arrival
27140 time is earlier than the &"first failed"& time for the error, the earlier time
27141 is used when scanning the retry rules to decide when to try next and when to
27142 time out the address.
27144 The exceptional second action applies in all cases. If a message has been on
27145 the queue for longer than the cutoff time of any applicable retry rule for a
27146 given address, a delivery is attempted for that address, even if it is not yet
27147 time, and if this delivery fails, the address is timed out. A new retry time is
27148 not computed in this case, so that other messages for the same address are
27149 considered immediately.
27150 .ecindex IIDretconf1
27151 .ecindex IIDregconf2
27158 . ////////////////////////////////////////////////////////////////////////////
27159 . ////////////////////////////////////////////////////////////////////////////
27161 .chapter "SMTP authentication" "CHAPSMTPAUTH"
27162 .scindex IIDauthconf1 "SMTP" "authentication configuration"
27163 .scindex IIDauthconf2 "authentication"
27164 The &"authenticators"& section of Exim's runtime configuration is concerned
27165 with SMTP authentication. This facility is an extension to the SMTP protocol,
27166 described in RFC 2554, which allows a client SMTP host to authenticate itself
27167 to a server. This is a common way for a server to recognize clients that are
27168 permitted to use it as a relay. SMTP authentication is not of relevance to the
27169 transfer of mail between servers that have no managerial connection with each
27172 .cindex "AUTH" "description of"
27173 .cindex "ESMTP extensions" AUTH
27174 Very briefly, the way SMTP authentication works is as follows:
27177 The server advertises a number of authentication &'mechanisms'& in response to
27178 the client's EHLO command.
27180 The client issues an AUTH command, naming a specific mechanism. The command
27181 may, optionally, contain some authentication data.
27183 The server may issue one or more &'challenges'&, to which the client must send
27184 appropriate responses. In simple authentication mechanisms, the challenges are
27185 just prompts for user names and passwords. The server does not have to issue
27186 any challenges &-- in some mechanisms the relevant data may all be transmitted
27187 with the AUTH command.
27189 The server either accepts or denies authentication.
27191 If authentication succeeds, the client may optionally make use of the AUTH
27192 option on the MAIL command to pass an authenticated sender in subsequent
27193 mail transactions. Authentication lasts for the remainder of the SMTP
27196 If authentication fails, the client may give up, or it may try a different
27197 authentication mechanism, or it may try transferring mail over the
27198 unauthenticated connection.
27201 If you are setting up a client, and want to know which authentication
27202 mechanisms the server supports, you can use Telnet to connect to port 25 (the
27203 SMTP port) on the server, and issue an EHLO command. The response to this
27204 includes the list of supported mechanisms. For example:
27206 &`$ `&&*&`telnet server.example 25`&*&
27207 &`Trying 192.168.34.25...`&
27208 &`Connected to server.example.`&
27209 &`Escape character is '^]'.`&
27210 &`220 server.example ESMTP Exim 4.20 ...`&
27211 &*&`ehlo client.example`&*&
27212 &`250-server.example Hello client.example [10.8.4.5]`&
27213 &`250-SIZE 52428800`&
27218 The second-last line of this example output shows that the server supports
27219 authentication using the PLAIN mechanism. In Exim, the different authentication
27220 mechanisms are configured by specifying &'authenticator'& drivers. Like the
27221 routers and transports, which authenticators are included in the binary is
27222 controlled by build-time definitions. The following are currently available,
27223 included by setting
27226 AUTH_CYRUS_SASL=yes
27230 AUTH_HEIMDAL_GSSAPI=yes
27235 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
27236 authentication mechanism (RFC 2195), and the second provides an interface to
27237 the Cyrus SASL authentication library.
27238 The third is an interface to Dovecot's authentication system, delegating the
27239 work via a socket interface.
27240 The fourth provides for negotiation of authentication done via non-SMTP means,
27241 as defined by RFC 4422 Appendix A.
27242 The fifth provides an interface to the GNU SASL authentication library, which
27243 provides mechanisms but typically not data sources.
27244 The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
27245 supporting setting a server keytab.
27246 The seventh can be configured to support
27247 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
27248 not formally documented, but used by several MUAs.
27249 The eighth authenticator
27250 supports Microsoft's &'Secure Password Authentication'& mechanism.
27251 The last is an Exim authenticator but not an SMTP one;
27252 instead it can use information from a TLS negotiation.
27254 The authenticators are configured using the same syntax as other drivers (see
27255 section &<<SECTfordricon>>&). If no authenticators are required, no
27256 authentication section need be present in the configuration file. Each
27257 authenticator can in principle have both server and client functions. When Exim
27258 is receiving SMTP mail, it is acting as a server; when it is sending out
27259 messages over SMTP, it is acting as a client. Authenticator configuration
27260 options are provided for use in both these circumstances.
27262 To make it clear which options apply to which situation, the prefixes
27263 &%server_%& and &%client_%& are used on option names that are specific to
27264 either the server or the client function, respectively. Server and client
27265 functions are disabled if none of their options are set. If an authenticator is
27266 to be used for both server and client functions, a single definition, using
27267 both sets of options, is required. For example:
27271 public_name = CRAM-MD5
27272 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
27274 client_secret = secret2
27276 The &%server_%& option is used when Exim is acting as a server, and the
27277 &%client_%& options when it is acting as a client.
27279 Descriptions of the individual authenticators are given in subsequent chapters.
27280 The remainder of this chapter covers the generic options for the
27281 authenticators, followed by general discussion of the way authentication works
27284 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
27285 per-mechanism basis. Please read carefully to determine which variables hold
27286 account labels such as usercodes and which hold passwords or other
27287 authenticating data.
27289 Note that some mechanisms support two different identifiers for accounts: the
27290 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
27291 and &'authz'& are commonly encountered. The American spelling is standard here.
27292 Conceptually, authentication data such as passwords are tied to the identifier
27293 used to authenticate; servers may have rules to permit one user to act as a
27294 second user, so that after login the session is treated as though that second
27295 user had logged in. That second user is the &'authorization id'&. A robust
27296 configuration might confirm that the &'authz'& field is empty or matches the
27297 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
27298 as verified data, the &'authz'& as an unverified request which the server might
27301 A &'realm'& is a text string, typically a domain name, presented by a server
27302 to a client to help it select an account and credentials to use. In some
27303 mechanisms, the client and server provably agree on the realm, but clients
27304 typically can not treat the realm as secure data to be blindly trusted.
27308 .section "Generic options for authenticators" "SECID168"
27309 .cindex "authentication" "generic options"
27310 .cindex "options" "generic; for authenticators"
27312 .option client_condition authenticators string&!! unset
27313 When Exim is authenticating as a client, it skips any authenticator whose
27314 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
27315 used, for example, to skip plain text authenticators when the connection is not
27316 encrypted by a setting such as:
27318 client_condition = ${if !eq{$tls_out_cipher}{}}
27322 .option client_set_id authenticators string&!! unset
27323 When client authentication succeeds, this condition is expanded; the
27324 result is used in the log lines for outbound messages.
27325 Typically it will be the user name used for authentication.
27328 .option driver authenticators string unset
27329 This option must always be set. It specifies which of the available
27330 authenticators is to be used.
27333 .option public_name authenticators string unset
27334 This option specifies the name of the authentication mechanism that the driver
27335 implements, and by which it is known to the outside world. These names should
27336 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
27337 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
27338 defaults to the driver's instance name.
27341 .option server_advertise_condition authenticators string&!! unset
27342 When a server is about to advertise an authentication mechanism, the condition
27343 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
27344 mechanism is not advertised.
27345 If the expansion fails, the mechanism is not advertised. If the failure was not
27346 forced, and was not caused by a lookup defer, the incident is logged.
27347 See section &<<SECTauthexiser>>& below for further discussion.
27350 .option server_condition authenticators string&!! unset
27351 This option must be set for a &%plaintext%& server authenticator, where it
27352 is used directly to control authentication. See section &<<SECTplainserver>>&
27355 For the &(gsasl)& authenticator, this option is required for various
27356 mechanisms; see chapter &<<CHAPgsasl>>& for details.
27358 For the other authenticators, &%server_condition%& can be used as an additional
27359 authentication or authorization mechanism that is applied after the other
27360 authenticator conditions succeed. If it is set, it is expanded when the
27361 authenticator would otherwise return a success code. If the expansion is forced
27362 to fail, authentication fails. Any other expansion failure causes a temporary
27363 error code to be returned. If the result of a successful expansion is an empty
27364 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27365 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
27366 other result, a temporary error code is returned, with the expanded string as
27370 .option server_debug_print authenticators string&!! unset
27371 If this option is set and authentication debugging is enabled (see the &%-d%&
27372 command line option), the string is expanded and included in the debugging
27373 output when the authenticator is run as a server. This can help with checking
27374 out the values of variables.
27375 If expansion of the string fails, the error message is written to the debugging
27376 output, and Exim carries on processing.
27379 .option server_set_id authenticators string&!! unset
27380 .vindex "&$authenticated_id$&"
27381 .vindex "&$authenticated_fail_id$&"
27382 When an Exim server successfully authenticates a client, this string is
27383 expanded using data from the authentication, and preserved for any incoming
27384 messages in the variable &$authenticated_id$&. It is also included in the log
27385 lines for incoming messages. For example, a user/password authenticator
27386 configuration might preserve the user name that was used to authenticate, and
27387 refer to it subsequently during delivery of the message.
27388 On a failing authentication the expansion result is instead saved in
27389 the &$authenticated_fail_id$& variable.
27390 If expansion fails, the option is ignored.
27393 .option server_mail_auth_condition authenticators string&!! unset
27394 This option allows a server to discard authenticated sender addresses supplied
27395 as part of MAIL commands in SMTP connections that are authenticated by the
27396 driver on which &%server_mail_auth_condition%& is set. The option is not used
27397 as part of the authentication process; instead its (unexpanded) value is
27398 remembered for later use.
27399 How it is used is described in the following section.
27405 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
27406 .cindex "authentication" "sender; authenticated"
27407 .cindex "AUTH" "on MAIL command"
27408 When a client supplied an AUTH= item on a MAIL command, Exim applies
27409 the following checks before accepting it as the authenticated sender of the
27413 If the connection is not using extended SMTP (that is, HELO was used rather
27414 than EHLO), the use of AUTH= is a syntax error.
27416 If the value of the AUTH= parameter is &"<>"&, it is ignored.
27418 .vindex "&$authenticated_sender$&"
27419 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
27420 running, the value of &$authenticated_sender$& is set to the value obtained
27421 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
27422 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
27423 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
27424 given for the MAIL command.
27426 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
27427 is accepted and placed in &$authenticated_sender$& only if the client has
27430 If the AUTH= value was accepted by either of the two previous rules, and
27431 the client has authenticated, and the authenticator has a setting for the
27432 &%server_mail_auth_condition%&, the condition is checked at this point. The
27433 valued that was saved from the authenticator is expanded. If the expansion
27434 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
27435 &$authenticated_sender$& is deleted. If the expansion yields any other value,
27436 the value of &$authenticated_sender$& is retained and passed on with the
27441 When &$authenticated_sender$& is set for a message, it is passed on to other
27442 hosts to which Exim authenticates as a client. Do not confuse this value with
27443 &$authenticated_id$&, which is a string obtained from the authentication
27444 process, and which is not usually a complete email address.
27446 .vindex "&$sender_address$&"
27447 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
27448 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
27449 therefore make use of &$authenticated_sender$&. The converse is not true: the
27450 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
27455 .section "Authentication on an Exim server" "SECTauthexiser"
27456 .cindex "authentication" "on an Exim server"
27457 When Exim receives an EHLO command, it advertises the public names of those
27458 authenticators that are configured as servers, subject to the following
27462 The client host must match &%auth_advertise_hosts%& (default *).
27464 If the &%server_advertise_condition%& option is set, its expansion must not
27465 yield the empty string, &"0"&, &"no"&, or &"false"&.
27468 The order in which the authenticators are defined controls the order in which
27469 the mechanisms are advertised.
27471 Some mail clients (for example, some versions of Netscape) require the user to
27472 provide a name and password for authentication whenever AUTH is advertised,
27473 even though authentication may not in fact be needed (for example, Exim may be
27474 set up to allow unconditional relaying from the client by an IP address check).
27475 You can make such clients more friendly by not advertising AUTH to them.
27476 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
27477 that runs for RCPT) to relay without authentication, you should set
27479 auth_advertise_hosts = ! 10.9.8.0/24
27481 so that no authentication mechanisms are advertised to them.
27483 The &%server_advertise_condition%& controls the advertisement of individual
27484 authentication mechanisms. For example, it can be used to restrict the
27485 advertisement of a particular mechanism to encrypted connections, by a setting
27488 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
27490 .vindex "&$tls_in_cipher$&"
27491 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
27492 yields &"yes"&, which allows the advertisement to happen.
27494 When an Exim server receives an AUTH command from a client, it rejects it
27495 immediately if AUTH was not advertised in response to an earlier EHLO
27496 command. This is the case if
27499 The client host does not match &%auth_advertise_hosts%&; or
27501 No authenticators are configured with server options; or
27503 Expansion of &%server_advertise_condition%& blocked the advertising of all the
27504 server authenticators.
27508 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
27509 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
27510 AUTH is accepted from any client host.
27512 If AUTH is not rejected by the ACL, Exim searches its configuration for a
27513 server authentication mechanism that was advertised in response to EHLO and
27514 that matches the one named in the AUTH command. If it finds one, it runs
27515 the appropriate authentication protocol, and authentication either succeeds or
27516 fails. If there is no matching advertised mechanism, the AUTH command is
27517 rejected with a 504 error.
27519 .vindex "&$received_protocol$&"
27520 .vindex "&$sender_host_authenticated$&"
27521 When a message is received from an authenticated host, the value of
27522 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
27523 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
27524 public name) of the authenticator driver that successfully authenticated the
27525 client from which the message was received. This variable is empty if there was
27526 no successful authentication.
27528 .cindex authentication "expansion item"
27529 Successful authentication sets up information used by the
27530 &%authresults%& expansion item.
27535 .section "Testing server authentication" "SECID169"
27536 .cindex "authentication" "testing a server"
27537 .cindex "AUTH" "testing a server"
27538 .cindex "base64 encoding" "creating authentication test data"
27539 Exim's &%-bh%& option can be useful for testing server authentication
27540 configurations. The data for the AUTH command has to be sent using base64
27541 encoding. A quick way to produce such data for testing is the following Perl
27545 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
27547 .cindex "binary zero" "in authentication data"
27548 This interprets its argument as a Perl string, and then encodes it. The
27549 interpretation as a Perl string allows binary zeros, which are required for
27550 some kinds of authentication, to be included in the data. For example, a
27551 command line to run this script on such data might be
27553 encode '\0user\0password'
27555 Note the use of single quotes to prevent the shell interpreting the
27556 backslashes, so that they can be interpreted by Perl to specify characters
27557 whose code value is zero.
27559 &*Warning 1*&: If either of the user or password strings starts with an octal
27560 digit, you must use three zeros instead of one after the leading backslash. If
27561 you do not, the octal digit that starts your string will be incorrectly
27562 interpreted as part of the code for the first character.
27564 &*Warning 2*&: If there are characters in the strings that Perl interprets
27565 specially, you must use a Perl escape to prevent them being misinterpreted. For
27566 example, a command such as
27568 encode '\0user@domain.com\0pas$$word'
27570 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
27572 If you have the &%mimencode%& command installed, another way to produce
27573 base64-encoded strings is to run the command
27575 echo -e -n `\0user\0password' | mimencode
27577 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
27578 in the argument, and the &%-n%& option specifies no newline at the end of its
27579 output. However, not all versions of &%echo%& recognize these options, so you
27580 should check your version before relying on this suggestion.
27584 .section "Authentication by an Exim client" "SECID170"
27585 .cindex "authentication" "on an Exim client"
27586 The &(smtp)& transport has two options called &%hosts_require_auth%& and
27587 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
27588 announces support for authentication, and the host matches an entry in either
27589 of these options, Exim (as a client) tries to authenticate as follows:
27592 For each authenticator that is configured as a client, in the order in which
27593 they are defined in the configuration, it searches the authentication
27594 mechanisms announced by the server for one whose name matches the public name
27595 of the authenticator.
27598 .vindex "&$host_address$&"
27599 When it finds one that matches, it runs the authenticator's client code. The
27600 variables &$host$& and &$host_address$& are available for any string expansions
27601 that the client might do. They are set to the server's name and IP address. If
27602 any expansion is forced to fail, the authentication attempt is abandoned, and
27603 Exim moves on to the next authenticator. Otherwise an expansion failure causes
27604 delivery to be deferred.
27606 If the result of the authentication attempt is a temporary error or a timeout,
27607 Exim abandons trying to send the message to the host for the moment. It will
27608 try again later. If there are any backup hosts available, they are tried in the
27611 If the response to authentication is a permanent error (5&'xx'& code), Exim
27612 carries on searching the list of authenticators and tries another one if
27613 possible. If all authentication attempts give permanent errors, or if there are
27614 no attempts because no mechanisms match (or option expansions force failure),
27615 what happens depends on whether the host matches &%hosts_require_auth%& or
27616 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
27617 delivery is deferred. The error can be detected in the retry rules, and thereby
27618 turned into a permanent error if you wish. In the second case, Exim tries to
27619 deliver the message unauthenticated.
27622 Note that the hostlist test for whether to do authentication can be
27623 confused if name-IP lookups change between the time the peer is decided
27624 upon and the time that the transport runs. For example, with a manualroute
27625 router given a host name, and with DNS "round-robin" used by that name: if
27626 the local resolver cache times out between the router and the transport
27627 running, the transport may get an IP for the name for its authentication
27628 check which does not match the connection peer IP.
27629 No authentication will then be done, despite the names being identical.
27631 For such cases use a separate transport which always authenticates.
27633 .cindex "AUTH" "on MAIL command"
27634 When Exim has authenticated itself to a remote server, it adds the AUTH
27635 parameter to the MAIL commands it sends, if it has an authenticated sender for
27636 the message. If the message came from a remote host, the authenticated sender
27637 is the one that was receiving on an incoming MAIL command, provided that the
27638 incoming connection was authenticated and the &%server_mail_auth%& condition
27639 allowed the authenticated sender to be retained. If a local process calls Exim
27640 to send a message, the sender address that is built from the login name and
27641 &%qualify_domain%& is treated as authenticated. However, if the
27642 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
27643 the authenticated sender that was received with the message.
27644 .ecindex IIDauthconf1
27645 .ecindex IIDauthconf2
27652 . ////////////////////////////////////////////////////////////////////////////
27653 . ////////////////////////////////////////////////////////////////////////////
27655 .chapter "The plaintext authenticator" "CHAPplaintext"
27656 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
27657 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
27658 The &(plaintext)& authenticator can be configured to support the PLAIN and
27659 LOGIN authentication mechanisms, both of which transfer authentication data as
27660 plain (unencrypted) text (though base64 encoded). The use of plain text is a
27661 security risk; you are strongly advised to insist on the use of SMTP encryption
27662 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
27663 use unencrypted plain text, you should not use the same passwords for SMTP
27664 connections as you do for login accounts.
27666 .section "Avoiding cleartext use" "SECTplain_TLS"
27667 The following generic option settings will disable &(plaintext)& authenticators when
27668 TLS is not being used:
27670 server_advertise_condition = ${if def:tls_in_cipher }
27671 client_condition = ${if def:tls_out_cipher}
27674 &*Note*&: a plaintext SMTP AUTH done inside TLS is not vulnerable to casual snooping,
27675 but is still vulnerable to a Man In The Middle attack unless certificates
27676 (including their names) have been properly verified.
27678 .section "Plaintext server options" "SECID171"
27679 .cindex "options" "&(plaintext)& authenticator (server)"
27680 When configured as a server, &(plaintext)& uses the following options:
27682 .option server_condition authenticators string&!! unset
27683 This is actually a global authentication option, but it must be set in order to
27684 configure the &(plaintext)& driver as a server. Its use is described below.
27686 .option server_prompts plaintext "string list&!!" unset
27687 The contents of this option, after expansion, must be a colon-separated list of
27688 prompt strings. If expansion fails, a temporary authentication rejection is
27691 .section "Using plaintext in a server" "SECTplainserver"
27692 .cindex "AUTH" "in &(plaintext)& authenticator"
27693 .cindex "binary zero" "in &(plaintext)& authenticator"
27694 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
27695 "in &(plaintext)& authenticator"
27696 .vindex "&$auth1$&, &$auth2$&, etc"
27697 .cindex "base64 encoding" "in &(plaintext)& authenticator"
27699 When running as a server, &(plaintext)& performs the authentication test by
27700 expanding a string. The data sent by the client with the AUTH command, or in
27701 response to subsequent prompts, is base64 encoded, and so may contain any byte
27702 values when decoded. If any data is supplied with the command, it is treated as
27703 a list of strings, separated by NULs (binary zeros), the first three of which
27704 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
27705 (neither LOGIN nor PLAIN uses more than three strings).
27707 For compatibility with previous releases of Exim, the values are also placed in
27708 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
27709 variables for this purpose is now deprecated, as it can lead to confusion in
27710 string expansions that also use them for other things.
27712 If there are more strings in &%server_prompts%& than the number of strings
27713 supplied with the AUTH command, the remaining prompts are used to obtain more
27714 data. Each response from the client may be a list of NUL-separated strings.
27716 .vindex "&$authenticated_id$&"
27717 Once a sufficient number of data strings have been received,
27718 &%server_condition%& is expanded. If the expansion is forced to fail,
27719 authentication fails. Any other expansion failure causes a temporary error code
27720 to be returned. If the result of a successful expansion is an empty string,
27721 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27722 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
27723 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
27724 For any other result, a temporary error code is returned, with the expanded
27725 string as the error text.
27727 &*Warning*&: If you use a lookup in the expansion to find the user's
27728 password, be sure to make the authentication fail if the user is unknown.
27729 There are good and bad examples at the end of the next section.
27733 .section "The PLAIN authentication mechanism" "SECID172"
27734 .cindex "PLAIN authentication mechanism"
27735 .cindex authentication PLAIN
27736 .cindex "binary zero" "in &(plaintext)& authenticator"
27737 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
27738 sent as one item of data (that is, one combined string containing two NUL
27739 separators). The data is sent either as part of the AUTH command, or
27740 subsequently in response to an empty prompt from the server.
27742 The second and third strings are a user name and a corresponding password.
27743 Using a single fixed user name and password as an example, this could be
27744 configured as follows:
27748 public_name = PLAIN
27750 server_condition = \
27751 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
27752 server_set_id = $auth2
27754 Note that the default result strings from &%if%& (&"true"& or an empty string)
27755 are exactly what we want here, so they need not be specified. Obviously, if the
27756 password contains expansion-significant characters such as dollar, backslash,
27757 or closing brace, they have to be escaped.
27759 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
27760 the end of a string list are ignored). If all the data comes as part of the
27761 AUTH command, as is commonly the case, the prompt is not used. This
27762 authenticator is advertised in the response to EHLO as
27766 and a client host can authenticate itself by sending the command
27768 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
27770 As this contains three strings (more than the number of prompts), no further
27771 data is required from the client. Alternatively, the client may just send
27775 to initiate authentication, in which case the server replies with an empty
27776 prompt. The client must respond with the combined data string.
27778 The data string is base64 encoded, as required by the RFC. This example,
27779 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
27780 represents a zero byte. This is split up into three strings, the first of which
27781 is empty. The &%server_condition%& option in the authenticator checks that the
27782 second two are &`username`& and &`mysecret`& respectively.
27784 Having just one fixed user name and password, as in this example, is not very
27785 realistic, though for a small organization with only a handful of
27786 authenticating clients it could make sense.
27788 A more sophisticated instance of this authenticator could use the user name in
27789 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
27790 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
27791 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
27792 This is an incorrect example:
27794 server_condition = \
27795 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
27797 The expansion uses the user name (&$auth2$&) as the key to look up a password,
27798 which it then compares to the supplied password (&$auth3$&). Why is this example
27799 incorrect? It works fine for existing users, but consider what happens if a
27800 non-existent user name is given. The lookup fails, but as no success/failure
27801 strings are given for the lookup, it yields an empty string. Thus, to defeat
27802 the authentication, all a client has to do is to supply a non-existent user
27803 name and an empty password. The correct way of writing this test is:
27805 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
27806 {${if eq{$value}{$auth3}}} {false}}
27808 In this case, if the lookup succeeds, the result is checked; if the lookup
27809 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
27810 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
27811 always fails if its second argument is empty. However, the second way of
27812 writing the test makes the logic clearer.
27815 .section "The LOGIN authentication mechanism" "SECID173"
27816 .cindex "LOGIN authentication mechanism"
27817 .cindex authentication LOGIN
27818 The LOGIN authentication mechanism is not documented in any RFC, but is in use
27819 in a number of programs. No data is sent with the AUTH command. Instead, a
27820 user name and password are supplied separately, in response to prompts. The
27821 plaintext authenticator can be configured to support this as in this example:
27825 public_name = LOGIN
27826 server_prompts = User Name : Password
27827 server_condition = \
27828 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
27829 server_set_id = $auth1
27831 Because of the way plaintext operates, this authenticator accepts data supplied
27832 with the AUTH command (in contravention of the specification of LOGIN), but
27833 if the client does not supply it (as is the case for LOGIN clients), the prompt
27834 strings are used to obtain two data items.
27836 Some clients are very particular about the precise text of the prompts. For
27837 example, Outlook Express is reported to recognize only &"Username:"& and
27838 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
27839 strings. It uses the &%ldapauth%& expansion condition to check the user
27840 name and password by binding to an LDAP server:
27844 public_name = LOGIN
27845 server_prompts = Username:: : Password::
27846 server_condition = ${if and{{ \
27849 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
27850 pass=${quote:$auth2} \
27851 ldap://ldap.example.org/} }} }
27852 server_set_id = uid=$auth1,ou=people,o=example.org
27854 We have to check that the username is not empty before using it, because LDAP
27855 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
27856 operator to correctly quote the DN for authentication. However, the basic
27857 &%quote%& operator, rather than any of the LDAP quoting operators, is the
27858 correct one to use for the password, because quoting is needed only to make
27859 the password conform to the Exim syntax. At the LDAP level, the password is an
27860 uninterpreted string.
27863 .section "Support for different kinds of authentication" "SECID174"
27864 A number of string expansion features are provided for the purpose of
27865 interfacing to different ways of user authentication. These include checking
27866 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
27867 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
27873 .section "Using plaintext in a client" "SECID175"
27874 .cindex "options" "&(plaintext)& authenticator (client)"
27875 The &(plaintext)& authenticator has two client options:
27877 .option client_ignore_invalid_base64 plaintext boolean false
27878 If the client receives a server prompt that is not a valid base64 string,
27879 authentication is abandoned by default. However, if this option is set true,
27880 the error in the challenge is ignored and the client sends the response as
27883 .option client_send plaintext string&!! unset
27884 The string is a colon-separated list of authentication data strings. Each
27885 string is independently expanded before being sent to the server. The first
27886 string is sent with the AUTH command; any more strings are sent in response
27887 to prompts from the server. Before each string is expanded, the value of the
27888 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
27889 with &$auth1$& for the first prompt. Up to three prompts are stored in this
27890 way. Thus, the prompt that is received in response to sending the first string
27891 (with the AUTH command) can be used in the expansion of the second string, and
27892 so on. If an invalid base64 string is received when
27893 &%client_ignore_invalid_base64%& is set, an empty string is put in the
27894 &$auth$&<&'n'&> variable.
27896 &*Note*&: You cannot use expansion to create multiple strings, because
27897 splitting takes priority and happens first.
27899 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
27900 the data, further processing is applied to each string before it is sent. If
27901 there are any single circumflex characters in the string, they are converted to
27902 NULs. Should an actual circumflex be required as data, it must be doubled in
27905 This is an example of a client configuration that implements the PLAIN
27906 authentication mechanism with a fixed user name and password:
27910 public_name = PLAIN
27911 client_send = ^username^mysecret
27913 The lack of colons means that the entire text is sent with the AUTH
27914 command, with the circumflex characters converted to NULs.
27916 Note that due to the ambiguity of parsing three consectutive circumflex characters
27917 there is no way to provide a password having a leading circumflex.
27922 that uses the LOGIN mechanism is:
27926 public_name = LOGIN
27927 client_send = : username : mysecret
27929 The initial colon means that the first string is empty, so no data is sent with
27930 the AUTH command itself. The remaining strings are sent in response to
27932 .ecindex IIDplaiauth1
27933 .ecindex IIDplaiauth2
27938 . ////////////////////////////////////////////////////////////////////////////
27939 . ////////////////////////////////////////////////////////////////////////////
27941 .chapter "The cram_md5 authenticator" "CHID9"
27942 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
27943 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
27944 .cindex "CRAM-MD5 authentication mechanism"
27945 .cindex authentication CRAM-MD5
27946 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
27947 sends a challenge string to the client, and the response consists of a user
27948 name and the CRAM-MD5 digest of the challenge string combined with a secret
27949 string (password) which is known to both server and client. Thus, the secret
27950 is not sent over the network as plain text, which makes this authenticator more
27951 secure than &(plaintext)&. However, the downside is that the secret has to be
27952 available in plain text at either end.
27955 .section "Using cram_md5 as a server" "SECID176"
27956 .cindex "options" "&(cram_md5)& authenticator (server)"
27957 This authenticator has one server option, which must be set to configure the
27958 authenticator as a server:
27960 .option server_secret cram_md5 string&!! unset
27961 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
27962 When the server receives the client's response, the user name is placed in
27963 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
27964 obtain the password for that user. The server then computes the CRAM-MD5 digest
27965 that the client should have sent, and checks that it received the correct
27966 string. If the expansion of &%server_secret%& is forced to fail, authentication
27967 fails. If the expansion fails for some other reason, a temporary error code is
27968 returned to the client.
27970 For compatibility with previous releases of Exim, the user name is also placed
27971 in &$1$&. However, the use of this variables for this purpose is now
27972 deprecated, as it can lead to confusion in string expansions that also use
27973 numeric variables for other things.
27975 For example, the following authenticator checks that the user name given by the
27976 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
27977 user name, authentication fails.
27981 public_name = CRAM-MD5
27982 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
27983 server_set_id = $auth1
27985 .vindex "&$authenticated_id$&"
27986 If authentication succeeds, the setting of &%server_set_id%& preserves the user
27987 name in &$authenticated_id$&. A more typical configuration might look up the
27988 secret string in a file, using the user name as the key. For example:
27992 public_name = CRAM-MD5
27993 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
27995 server_set_id = $auth1
27997 Note that this expansion explicitly forces failure if the lookup fails
27998 because &$auth1$& contains an unknown user name.
28000 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
28001 using the relevant libraries, you need to know the realm to specify in the
28002 lookup and then ask for the &"userPassword"& attribute for that user in that
28007 public_name = CRAM-MD5
28008 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
28009 dbmjz{/etc/sasldb2}{$value}fail}
28010 server_set_id = $auth1
28013 .section "Using cram_md5 as a client" "SECID177"
28014 .cindex "options" "&(cram_md5)& authenticator (client)"
28015 When used as a client, the &(cram_md5)& authenticator has two options:
28019 .option client_name cram_md5 string&!! "the primary host name"
28020 This string is expanded, and the result used as the user name data when
28021 computing the response to the server's challenge.
28024 .option client_secret cram_md5 string&!! unset
28025 This option must be set for the authenticator to work as a client. Its value is
28026 expanded and the result used as the secret string when computing the response.
28030 .vindex "&$host_address$&"
28031 Different user names and secrets can be used for different servers by referring
28032 to &$host$& or &$host_address$& in the options. Forced failure of either
28033 expansion string is treated as an indication that this authenticator is not
28034 prepared to handle this case. Exim moves on to the next configured client
28035 authenticator. Any other expansion failure causes Exim to give up trying to
28036 send the message to the current server.
28038 A simple example configuration of a &(cram_md5)& authenticator, using fixed
28043 public_name = CRAM-MD5
28045 client_secret = secret
28047 .ecindex IIDcramauth1
28048 .ecindex IIDcramauth2
28052 . ////////////////////////////////////////////////////////////////////////////
28053 . ////////////////////////////////////////////////////////////////////////////
28055 .chapter "The cyrus_sasl authenticator" "CHID10"
28056 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
28057 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
28058 .cindex "Cyrus" "SASL library"
28060 The code for this authenticator was provided by Matthew Byng-Maddick while
28061 at A L Digital Ltd.
28063 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
28064 library implementation of the RFC 2222 (&"Simple Authentication and Security
28065 Layer"&). This library supports a number of authentication mechanisms,
28066 including PLAIN and LOGIN, but also several others that Exim does not support
28067 directly. In particular, there is support for Kerberos authentication.
28069 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
28070 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
28071 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
28072 name of the driver to determine which mechanism to support.
28074 Where access to some kind of secret file is required, for example, in GSSAPI
28075 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
28076 user, and that the Cyrus SASL library has no way of escalating privileges
28077 by default. You may also find you need to set environment variables,
28078 depending on the driver you are using.
28080 The application name provided by Exim is &"exim"&, so various SASL options may
28081 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
28082 Kerberos, note that because of limitations in the GSSAPI interface,
28083 changing the server keytab might need to be communicated down to the Kerberos
28084 layer independently. The mechanism for doing so is dependent upon the Kerberos
28087 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
28088 may be set to point to an alternative keytab file. Exim will pass this
28089 variable through from its own inherited environment when started as root or the
28090 Exim user. The keytab file needs to be readable by the Exim user.
28091 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
28092 environment variable. In practice, for those releases, the Cyrus authenticator
28093 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
28094 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
28097 .section "Using cyrus_sasl as a server" "SECID178"
28098 The &(cyrus_sasl)& authenticator has four private options. It puts the username
28099 (on a successful authentication) into &$auth1$&. For compatibility with
28100 previous releases of Exim, the username is also placed in &$1$&. However, the
28101 use of this variable for this purpose is now deprecated, as it can lead to
28102 confusion in string expansions that also use numeric variables for other
28106 .option server_hostname cyrus_sasl string&!! "see below"
28107 This option selects the hostname that is used when communicating with the
28108 library. The default value is &`$primary_hostname`&. It is up to the underlying
28109 SASL plug-in what it does with this data.
28112 .option server_mech cyrus_sasl string "see below"
28113 This option selects the authentication mechanism this driver should use. The
28114 default is the value of the generic &%public_name%& option. This option allows
28115 you to use a different underlying mechanism from the advertised name. For
28119 driver = cyrus_sasl
28120 public_name = X-ANYTHING
28121 server_mech = CRAM-MD5
28122 server_set_id = $auth1
28125 .option server_realm cyrus_sasl string&!! unset
28126 This specifies the SASL realm that the server claims to be in.
28129 .option server_service cyrus_sasl string &`smtp`&
28130 This is the SASL service that the server claims to implement.
28133 For straightforward cases, you do not need to set any of the authenticator's
28134 private options. All you need to do is to specify an appropriate mechanism as
28135 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
28136 PLAIN, you could have two authenticators as follows:
28139 driver = cyrus_sasl
28140 public_name = CRAM-MD5
28141 server_set_id = $auth1
28144 driver = cyrus_sasl
28145 public_name = PLAIN
28146 server_set_id = $auth2
28148 Cyrus SASL does implement the LOGIN authentication method, even though it is
28149 not a standard method. It is disabled by default in the source distribution,
28150 but it is present in many binary distributions.
28151 .ecindex IIDcyrauth1
28152 .ecindex IIDcyrauth2
28157 . ////////////////////////////////////////////////////////////////////////////
28158 . ////////////////////////////////////////////////////////////////////////////
28159 .chapter "The dovecot authenticator" "CHAPdovecot"
28160 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
28161 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
28162 This authenticator is an interface to the authentication facility of the
28163 Dovecot 2 POP/IMAP server, which can support a number of authentication methods.
28164 Note that Dovecot must be configured to use auth-client not auth-userdb.
28165 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
28166 to use the same mechanisms for SMTP authentication. This is a server
28167 authenticator only. There is only one option:
28169 .option server_socket dovecot string unset
28171 This option must specify the UNIX socket that is the interface to Dovecot
28172 authentication. The &%public_name%& option must specify an authentication
28173 mechanism that Dovecot is configured to support. You can have several
28174 authenticators for different mechanisms. For example:
28178 public_name = PLAIN
28179 server_socket = /var/run/dovecot/auth-client
28180 server_set_id = $auth1
28185 server_socket = /var/run/dovecot/auth-client
28186 server_set_id = $auth1
28188 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
28189 &$received_ip_address$& (that is, the connection is local), the &"secured"&
28190 option is passed in the Dovecot authentication command. If, for a TLS
28191 connection, a client certificate has been verified, the &"valid-client-cert"&
28192 option is passed. When authentication succeeds, the identity of the user
28193 who authenticated is placed in &$auth1$&.
28195 The Dovecot configuration to match the above will look
28198 conf.d/10-master.conf :-
28203 unix_listener auth-client {
28210 conf.d/10-auth.conf :-
28212 auth_mechanisms = plain login ntlm
28215 .ecindex IIDdcotauth1
28216 .ecindex IIDdcotauth2
28219 . ////////////////////////////////////////////////////////////////////////////
28220 . ////////////////////////////////////////////////////////////////////////////
28221 .chapter "The gsasl authenticator" "CHAPgsasl"
28222 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
28223 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
28224 .cindex "authentication" "GNU SASL"
28225 .cindex "authentication" "SASL"
28226 .cindex "authentication" "EXTERNAL"
28227 .cindex "authentication" "ANONYMOUS"
28228 .cindex "authentication" "PLAIN"
28229 .cindex "authentication" "LOGIN"
28230 .cindex "authentication" "DIGEST-MD5"
28231 .cindex "authentication" "CRAM-MD5"
28232 .cindex "authentication" "SCRAM family"
28233 The &(gsasl)& authenticator provides integration for the GNU SASL
28234 library and the mechanisms it provides. This is new as of the 4.80 release
28235 and there are a few areas where the library does not let Exim smoothly
28236 scale to handle future authentication mechanisms, so no guarantee can be
28237 made that any particular new authentication mechanism will be supported
28238 without code changes in Exim.
28240 The library is expected to add support in an upcoming
28241 realease for the SCRAM-SHA-256 method.
28242 The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
28246 To see the list of mechanisms supported by the library run Exim with "auth" debug
28247 enabled and look for a line containing "GNU SASL supports".
28248 Note however that some may not have been tested from Exim.
28252 .option client_authz gsasl string&!! unset
28253 This option can be used to supply an &'authorization id'&
28254 which is different to the &'authentication_id'& provided
28255 by &%client_username%& option.
28256 If unset or (after expansion) empty it is not used,
28257 which is the common case.
28259 .option client_channelbinding gsasl boolean false
28260 See &%server_channelbinding%& below.
28262 .option client_password gsasl string&!! unset
28263 This option is exapanded before use, and should result in
28264 the password to be used, in clear.
28266 .option client_username gsasl string&!! unset
28267 This option is exapanded before use, and should result in
28268 the account name to be used.
28271 .option client_spassword gsasl string&!! unset
28273 This option is only supported for library versions 1.9.1 and greater.
28274 The macro _HAVE_AUTH_GSASL_SCRAM_S_KEY will be defined when this is so.
28277 If a SCRAM mechanism is being used and this option is set
28278 and correctly sized
28279 it is used in preference to &%client_password%&.
28280 The value after expansion should be
28281 a 40 (for SHA-1) or 64 (for SHA-256) character string
28282 with the PBKDF2-prepared password, hex-encoded.
28284 Note that this value will depend on the salt and iteration-count
28285 supplied by the server.
28286 The option is expanded before use.
28288 During the expansion &$auth1$& is set with the client username,
28289 &$auth2$& with the iteration count, and
28290 &$auth3$& with the salt.
28292 The intent of this option
28293 is to support clients that can cache thes salted password
28294 to save on recalculation costs.
28295 The cache lookup should return an unusable value
28296 (eg. an empty string)
28297 if the salt or iteration count has changed
28299 If the authentication succeeds then the above variables are set,
28300 .vindex "&$auth4$&"
28301 plus the calculated salted password value value in &$auth4$&,
28302 during the expansion of the &%client_set_id%& option.
28303 A side-effect of this expansion can be used to prime the cache.
28307 .option server_channelbinding gsasl boolean false
28308 Some authentication mechanisms are able to use external context at both ends
28309 of the session to bind the authentication to that context, and fail the
28310 authentication process if that context differs. Specifically, some TLS
28311 ciphersuites can provide identifying information about the cryptographic
28314 This should have meant that certificate identity and verification becomes a
28315 non-issue, as a man-in-the-middle attack will cause the correct client and
28316 server to see different identifiers and authentication will fail.
28319 only usable by mechanisms which support "channel binding"; at time of
28320 writing, that's the SCRAM family.
28321 When using this feature the "-PLUS" variants of the method names need to be used.
28323 This defaults off to ensure smooth upgrade across Exim releases, in case
28324 this option causes some clients to start failing. Some future release
28325 of Exim might have switched the default to be true.
28327 . However, Channel Binding in TLS has proven to be vulnerable in current versions.
28328 . Do not plan to rely upon this feature for security, ever, without consulting
28329 . with a subject matter expert (a cryptographic engineer).
28332 This option was deprecated in previous releases due to doubts over
28333 the "Triple Handshake" vulnerability.
28334 Exim takes suitable precausions (requiring Extended Master Secret if TLS
28335 Session Resumption was used) for safety.
28339 .option server_hostname gsasl string&!! "see below"
28340 This option selects the hostname that is used when communicating with the
28341 library. The default value is &`$primary_hostname`&.
28342 Some mechanisms will use this data.
28345 .option server_mech gsasl string "see below"
28346 This option selects the authentication mechanism this driver should use. The
28347 default is the value of the generic &%public_name%& option. This option allows
28348 you to use a different underlying mechanism from the advertised name. For
28353 public_name = X-ANYTHING
28354 server_mech = CRAM-MD5
28355 server_set_id = $auth1
28359 .option server_password gsasl string&!! unset
28360 Various mechanisms need access to the cleartext password on the server, so
28361 that proof-of-possession can be demonstrated on the wire, without sending
28362 the password itself.
28364 The data available for lookup varies per mechanism.
28365 In all cases, &$auth1$& is set to the &'authentication id'&.
28366 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
28367 if available, else the empty string.
28368 The &$auth3$& variable will always be the &'realm'& if available,
28369 else the empty string.
28371 A forced failure will cause authentication to defer.
28373 If using this option, it may make sense to set the &%server_condition%&
28374 option to be simply "true".
28377 .option server_realm gsasl string&!! unset
28378 This specifies the SASL realm that the server claims to be in.
28379 Some mechanisms will use this data.
28382 .option server_scram_iter gsasl string&!! 4096
28383 This option provides data for the SCRAM family of mechanisms.
28384 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28385 when this option is expanded.
28387 The result of expansion should be a decimal number,
28388 and represents both a lower-bound on the security, and
28389 a compute cost factor imposed on the client
28390 (if it does not cache results, or the server changes
28391 either the iteration count or the salt).
28392 A minimum value of 4096 is required by the standards
28393 for all current SCRAM mechanism variants.
28395 .option server_scram_salt gsasl string&!! unset
28396 This option provides data for the SCRAM family of mechanisms.
28397 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28398 when this option is expanded.
28399 The value should be a base64-encoded string,
28400 of random data typically 4-to-16 bytes long.
28401 If unset or empty after expansion the library will provides a value for the
28402 protocol conversation.
28405 .option server_key gsasl string&!! unset
28406 .option server_skey gsasl string&!! unset
28407 These options can be used for the SCRAM family of mechanisms
28408 to provide stored information related to a password,
28409 the storage of which is preferable to plaintext.
28411 &%server_key%& is the value defined in the SCRAM standards as ServerKey;
28412 &%server_skey%& is StoredKey.
28414 They are only available for version 1.9.0 (or later) of the gsasl library.
28415 When this is so, the macros
28416 _OPT_AUTHENTICATOR_GSASL_SERVER_KEY
28417 and _HAVE_AUTH_GSASL_SCRAM_S_KEY
28420 The &$authN$& variables are available when these options are expanded.
28422 If set, the results of expansion should for each
28423 should be a 28 (for SHA-1) or 44 (for SHA-256) character string
28424 of base64-coded data, and will be used in preference to the
28425 &%server_password%& option.
28426 If unset or not of the right length, &%server_password%& will be used.
28428 The libgsasl library release includes a utility &'gsasl'& which can be used
28429 to generate these values.
28432 .option server_service gsasl string &`smtp`&
28433 This is the SASL service that the server claims to implement.
28434 Some mechanisms will use this data.
28437 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
28438 .vindex "&$auth1$&, &$auth2$&, etc"
28439 These may be set when evaluating specific options, as detailed above.
28440 They will also be set when evaluating &%server_condition%&.
28442 Unless otherwise stated below, the &(gsasl)& integration will use the following
28443 meanings for these variables:
28446 .vindex "&$auth1$&"
28447 &$auth1$&: the &'authentication id'&
28449 .vindex "&$auth2$&"
28450 &$auth2$&: the &'authorization id'&
28452 .vindex "&$auth3$&"
28453 &$auth3$&: the &'realm'&
28456 On a per-mechanism basis:
28459 .cindex "authentication" "EXTERNAL"
28460 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
28461 the &%server_condition%& option must be present.
28463 .cindex "authentication" "ANONYMOUS"
28464 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
28465 the &%server_condition%& option must be present.
28467 .cindex "authentication" "GSSAPI"
28468 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
28469 &$auth2$& will be set to the &'authorization id'&,
28470 the &%server_condition%& option must be present.
28473 An &'anonymous token'& is something passed along as an unauthenticated
28474 identifier; this is analogous to FTP anonymous authentication passing an
28475 email address, or software-identifier@, as the "password".
28478 An example showing the password having the realm specified in the callback
28479 and demonstrating a Cyrus SASL to GSASL migration approach is:
28481 gsasl_cyrusless_crammd5:
28483 public_name = CRAM-MD5
28484 server_realm = imap.example.org
28485 server_password = ${lookup{$auth1:$auth3:userPassword}\
28486 dbmjz{/etc/sasldb2}{$value}fail}
28487 server_set_id = ${quote:$auth1}
28488 server_condition = yes
28492 . ////////////////////////////////////////////////////////////////////////////
28493 . ////////////////////////////////////////////////////////////////////////////
28495 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
28496 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
28497 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
28498 .cindex "authentication" "GSSAPI"
28499 .cindex "authentication" "Kerberos"
28500 The &(heimdal_gssapi)& authenticator provides server integration for the
28501 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
28504 .option server_hostname heimdal_gssapi string&!! "see below"
28505 This option selects the hostname that is used, with &%server_service%&,
28506 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
28507 identifier. The default value is &`$primary_hostname`&.
28509 .option server_keytab heimdal_gssapi string&!! unset
28510 If set, then Heimdal will not use the system default keytab (typically
28511 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
28512 The value should be a pathname, with no &"file:"& prefix.
28514 .option server_service heimdal_gssapi string&!! "smtp"
28515 This option specifies the service identifier used, in conjunction with
28516 &%server_hostname%&, for building the identifier for finding credentials
28520 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
28521 Beware that these variables will typically include a realm, thus will appear
28522 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
28523 not verified, so a malicious client can set it to anything.
28525 The &$auth1$& field should be safely trustable as a value from the Key
28526 Distribution Center. Note that these are not quite email addresses.
28527 Each identifier is for a role, and so the left-hand-side may include a
28528 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
28530 .vindex "&$auth1$&, &$auth2$&, etc"
28532 .vindex "&$auth1$&"
28533 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
28535 .vindex "&$auth2$&"
28536 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
28537 authentication. If that was empty, this will also be set to the
28542 . ////////////////////////////////////////////////////////////////////////////
28543 . ////////////////////////////////////////////////////////////////////////////
28545 .chapter "The spa authenticator" "CHAPspa"
28546 .scindex IIDspaauth1 "&(spa)& authenticator"
28547 .scindex IIDspaauth2 "authenticators" "&(spa)&"
28548 .cindex "authentication" "Microsoft Secure Password"
28549 .cindex "authentication" "NTLM"
28550 .cindex "Microsoft Secure Password Authentication"
28551 .cindex "NTLM authentication"
28552 The &(spa)& authenticator provides client support for Microsoft's &'Secure
28553 Password Authentication'& mechanism,
28554 which is also sometimes known as NTLM (NT LanMan). The code for client side of
28555 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
28556 taken from the Samba project (&url(https://www.samba.org/)). The code for the
28557 server side was subsequently contributed by Tom Kistner. The mechanism works as
28561 After the AUTH command has been accepted, the client sends an SPA
28562 authentication request based on the user name and optional domain.
28564 The server sends back a challenge.
28566 The client builds a challenge response which makes use of the user's password
28567 and sends it to the server, which then accepts or rejects it.
28570 Encryption is used to protect the password in transit.
28574 .section "Using spa as a server" "SECID179"
28575 .cindex "options" "&(spa)& authenticator (server)"
28576 The &(spa)& authenticator has just one server option:
28578 .option server_password spa string&!! unset
28579 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
28580 This option is expanded, and the result must be the cleartext password for the
28581 authenticating user, whose name is at this point in &$auth1$&. For
28582 compatibility with previous releases of Exim, the user name is also placed in
28583 &$1$&. However, the use of this variable for this purpose is now deprecated, as
28584 it can lead to confusion in string expansions that also use numeric variables
28585 for other things. For example:
28590 server_password = \
28591 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
28593 If the expansion is forced to fail, authentication fails. Any other expansion
28594 failure causes a temporary error code to be returned.
28600 .section "Using spa as a client" "SECID180"
28601 .cindex "options" "&(spa)& authenticator (client)"
28602 The &(spa)& authenticator has the following client options:
28606 .option client_domain spa string&!! unset
28607 This option specifies an optional domain for the authentication.
28610 .option client_password spa string&!! unset
28611 This option specifies the user's password, and must be set.
28614 .option client_username spa string&!! unset
28615 This option specifies the user name, and must be set. Here is an example of a
28616 configuration of this authenticator for use with the mail servers at
28622 client_username = msn/msn_username
28623 client_password = msn_plaintext_password
28624 client_domain = DOMAIN_OR_UNSET
28626 .ecindex IIDspaauth1
28627 .ecindex IIDspaauth2
28633 . ////////////////////////////////////////////////////////////////////////////
28634 . ////////////////////////////////////////////////////////////////////////////
28636 .chapter "The external authenticator" "CHAPexternauth"
28637 .scindex IIDexternauth1 "&(external)& authenticator"
28638 .scindex IIDexternauth2 "authenticators" "&(external)&"
28639 .cindex "authentication" "Client Certificate"
28640 .cindex "authentication" "X509"
28641 .cindex "Certificate-based authentication"
28642 The &(external)& authenticator provides support for
28643 authentication based on non-SMTP information.
28644 The specification is in RFC 4422 Appendix A
28645 (&url(https://tools.ietf.org/html/rfc4422)).
28646 It is only a transport and negotiation mechanism;
28647 the process of authentication is entirely controlled
28648 by the server configuration.
28650 The client presents an identity in-clear.
28651 It is probably wise for a server to only advertise,
28652 and for clients to only attempt,
28653 this authentication method on a secure (eg. under TLS) connection.
28655 One possible use, compatible with the
28656 K-9 Mail Android client (&url(https://k9mail.github.io/)),
28657 is for using X509 client certificates.
28659 It thus overlaps in function with the TLS authenticator
28660 (see &<<CHAPtlsauth>>&)
28661 but is a full SMTP SASL authenticator
28662 rather than being implicit for TLS-connection carried
28663 client certificates only.
28665 The examples and discussion in this chapter assume that
28666 client-certificate authentication is being done.
28668 The client must present a certificate,
28669 for which it must have been requested via the
28670 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28671 (see &<<CHAPTLS>>&).
28672 For authentication to be effective the certificate should be
28673 verifiable against a trust-anchor certificate known to the server.
28675 .section "External options" "SECTexternsoptions"
28676 .cindex "options" "&(external)& authenticator (server)"
28677 The &(external)& authenticator has two server options:
28679 .option server_param2 external string&!! unset
28680 .option server_param3 external string&!! unset
28681 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(external)& authenticator"
28682 These options are expanded before the &%server_condition%& option
28683 and the result are placed in &$auth2$& and &$auth3$& resectively.
28684 If the expansion is forced to fail, authentication fails. Any other expansion
28685 failure causes a temporary error code to be returned.
28687 They can be used to clarify the coding of a complex &%server_condition%&.
28689 .section "Using external in a server" "SECTexternserver"
28690 .cindex "AUTH" "in &(external)& authenticator"
28691 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
28692 "in &(external)& authenticator"
28693 .vindex "&$auth1$&, &$auth2$&, etc"
28694 .cindex "base64 encoding" "in &(external)& authenticator"
28696 When running as a server, &(external)& performs the authentication test by
28697 expanding a string. The data sent by the client with the AUTH command, or in
28698 response to subsequent prompts, is base64 encoded, and so may contain any byte
28699 values when decoded. The decoded value is treated as
28700 an identity for authentication and
28701 placed in the expansion variable &$auth1$&.
28703 For compatibility with previous releases of Exim, the value is also placed in
28704 the expansion variable &$1$&. However, the use of this
28705 variable for this purpose is now deprecated, as it can lead to confusion in
28706 string expansions that also use them for other things.
28708 .vindex "&$authenticated_id$&"
28709 Once an identity has been received,
28710 &%server_condition%& is expanded. If the expansion is forced to fail,
28711 authentication fails. Any other expansion failure causes a temporary error code
28712 to be returned. If the result of a successful expansion is an empty string,
28713 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
28714 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
28715 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
28716 For any other result, a temporary error code is returned, with the expanded
28717 string as the error text.
28721 ext_ccert_san_mail:
28723 public_name = EXTERNAL
28725 server_advertise_condition = $tls_in_certificate_verified
28726 server_param2 = ${certextract {subj_altname,mail,>:} \
28727 {$tls_in_peercert}}
28728 server_condition = ${if forany {$auth2} \
28729 {eq {$item}{$auth1}}}
28730 server_set_id = $auth1
28732 This accepts a client certificate that is verifiable against any
28733 of your configured trust-anchors
28734 (which usually means the full set of public CAs)
28735 and which has a mail-SAN matching the claimed identity sent by the client.
28737 &*Note*&: up to TLS1.2, the client cert is on the wire in-clear, including the SAN.
28738 The account name is therefore guessable by an opponent.
28739 TLS 1.3 protects both server and client certificates, and is not vulnerable
28743 .section "Using external in a client" "SECTexternclient"
28744 .cindex "options" "&(external)& authenticator (client)"
28745 The &(external)& authenticator has one client option:
28747 .option client_send external string&!! unset
28748 This option is expanded and sent with the AUTH command as the
28749 identity being asserted.
28755 public_name = EXTERNAL
28757 client_condition = ${if !eq{$tls_out_cipher}{}}
28758 client_send = myaccount@smarthost.example.net
28762 .ecindex IIDexternauth1
28763 .ecindex IIDexternauth2
28769 . ////////////////////////////////////////////////////////////////////////////
28770 . ////////////////////////////////////////////////////////////////////////////
28772 .chapter "The tls authenticator" "CHAPtlsauth"
28773 .scindex IIDtlsauth1 "&(tls)& authenticator"
28774 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
28775 .cindex "authentication" "Client Certificate"
28776 .cindex "authentication" "X509"
28777 .cindex "Certificate-based authentication"
28778 The &(tls)& authenticator provides server support for
28779 authentication based on client certificates.
28781 It is not an SMTP authentication mechanism and is not
28782 advertised by the server as part of the SMTP EHLO response.
28783 It is an Exim authenticator in the sense that it affects
28784 the protocol element of the log line, can be tested for
28785 by the &%authenticated%& ACL condition, and can set
28786 the &$authenticated_id$& variable.
28788 The client must present a verifiable certificate,
28789 for which it must have been requested via the
28790 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28791 (see &<<CHAPTLS>>&).
28793 If an authenticator of this type is configured it is
28794 run before any SMTP-level communication is done,
28795 and can authenticate the connection.
28796 If it does, SMTP authentication is not offered.
28798 A maximum of one authenticator of this type may be present.
28801 .cindex "options" "&(tls)& authenticator (server)"
28802 The &(tls)& authenticator has three server options:
28804 .option server_param1 tls string&!! unset
28805 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
28806 This option is expanded after the TLS negotiation and
28807 the result is placed in &$auth1$&.
28808 If the expansion is forced to fail, authentication fails. Any other expansion
28809 failure causes a temporary error code to be returned.
28811 .option server_param2 tls string&!! unset
28812 .option server_param3 tls string&!! unset
28813 As above, for &$auth2$& and &$auth3$&.
28815 &%server_param1%& may also be spelled &%server_param%&.
28822 server_param1 = ${certextract {subj_altname,mail,>:} \
28823 {$tls_in_peercert}}
28824 server_condition = ${if and { {eq{$tls_in_certificate_verified}{1}} \
28827 {${lookup ldap{ldap:///\
28828 mailname=${quote_ldap_dn:${lc:$item}},\
28829 ou=users,LDAP_DC?mailid} {$value}{0} \
28831 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
28833 This accepts a client certificate that is verifiable against any
28834 of your configured trust-anchors
28835 (which usually means the full set of public CAs)
28836 and which has a SAN with a good account name.
28838 Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
28839 The account name is therefore guessable by an opponent.
28840 TLS 1.3 protects both server and client certificates, and is not vulnerable
28842 Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
28844 . An alternative might use
28846 . server_param1 = ${sha256:$tls_in_peercert}
28848 . to require one of a set of specific certs that define a given account
28849 . (the verification is still required, but mostly irrelevant).
28850 . This would help for per-device use.
28852 . However, for the future we really need support for checking a
28853 . user cert in LDAP - which probably wants a base-64 DER.
28855 .ecindex IIDtlsauth1
28856 .ecindex IIDtlsauth2
28859 Note that because authentication is traditionally an SMTP operation,
28860 the &%authenticated%& ACL condition cannot be used in
28861 a connect- or helo-ACL.
28865 . ////////////////////////////////////////////////////////////////////////////
28866 . ////////////////////////////////////////////////////////////////////////////
28868 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
28869 "Encrypted SMTP connections"
28870 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
28871 .scindex IIDencsmtp2 "SMTP" "encryption"
28872 .cindex "TLS" "on SMTP connection"
28875 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
28876 Sockets Layer), is implemented by making use of the OpenSSL library or the
28877 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
28878 cryptographic code in the Exim distribution itself for implementing TLS. In
28879 order to use this feature you must install OpenSSL or GnuTLS, and then build a
28880 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
28881 You also need to understand the basic concepts of encryption at a managerial
28882 level, and in particular, the way that public keys, private keys, and
28883 certificates are used.
28885 RFC 3207 defines how SMTP connections can make use of encryption. Once a
28886 connection is established, the client issues a STARTTLS command. If the
28887 server accepts this, the client and the server negotiate an encryption
28888 mechanism. If the negotiation succeeds, the data that subsequently passes
28889 between them is encrypted.
28891 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
28892 and if so, what cipher suite is in use, whether the client supplied a
28893 certificate, and whether or not that certificate was verified. This makes it
28894 possible for an Exim server to deny or accept certain commands based on the
28897 &*Warning*&: Certain types of firewall and certain anti-virus products can
28898 disrupt TLS connections. You need to turn off SMTP scanning for these products
28899 in order to get TLS to work.
28903 .section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
28905 .cindex "submissions protocol"
28906 .cindex "ssmtp protocol"
28907 .cindex "smtps protocol"
28908 .cindex "SMTP" "submissions protocol"
28909 .cindex "SMTP" "ssmtp protocol"
28910 .cindex "SMTP" "smtps protocol"
28911 The history of port numbers for TLS in SMTP is a little messy and has been
28912 contentious. As of RFC 8314, the common practice of using the historically
28913 allocated port 465 for "email submission but with TLS immediately upon connect
28914 instead of using STARTTLS" is officially blessed by the IETF, and recommended
28915 by them in preference to STARTTLS.
28917 The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
28918 clarity emerged over the dual roles of SMTP, for MX delivery and Email
28919 Submission, nomenclature has shifted. The modern name is now &"submissions"&.
28921 This approach was, for a while, officially abandoned when encrypted SMTP was
28922 standardized, but many clients kept using it, even as the TCP port number was
28923 reassigned for other use.
28924 Thus you may encounter guidance claiming that you shouldn't enable use of
28926 In practice, a number of mail-clients have only ever supported submissions,
28927 not submission with STARTTLS upgrade.
28928 Ideally, offer both submission (587) and submissions (465) service.
28930 Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
28931 global option. Its value must be a list of port numbers;
28932 the most common use is expected to be:
28934 tls_on_connect_ports = 465
28936 The port numbers specified by this option apply to all SMTP connections, both
28937 via the daemon and via &'inetd'&. You still need to specify all the ports that
28938 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
28939 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
28940 an extra port &-- rather, it specifies different behaviour on a port that is
28943 There is also a &%-tls-on-connect%& command line option. This overrides
28944 &%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
28951 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
28952 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
28953 TLS is supported in Exim using either the OpenSSL or GnuTLS library.
28954 To build Exim to use OpenSSL you need to set
28960 To build Exim to use GnuTLS, you need to set
28966 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
28967 include files and libraries for GnuTLS can be found.
28969 There are some differences in usage when using GnuTLS instead of OpenSSL:
28972 The &%tls_verify_certificates%& option
28973 cannot be the path of a directory
28974 for GnuTLS versions before 3.3.6
28975 (for later versions, or OpenSSL, it can be either).
28977 The default value for &%tls_dhparam%& differs for historical reasons.
28979 .vindex "&$tls_in_peerdn$&"
28980 .vindex "&$tls_out_peerdn$&"
28981 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
28982 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
28983 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
28985 OpenSSL identifies cipher suites using hyphens as separators, for example:
28986 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
28987 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
28988 in a cipher list. To make life simpler, Exim changes underscores to hyphens
28989 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
28990 to handle its own older variants) when processing lists of cipher suites in the
28991 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
28994 The &%tls_require_ciphers%& options operate differently, as described in the
28995 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
28997 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
28998 When using OpenSSL, this option is ignored.
28999 (If an API is found to let OpenSSL be configured in this way,
29000 let the Exim Maintainers know and we'll likely use it).
29002 With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
29003 main option, it must be ordered to match the &%tls_certificate%& list.
29005 Some other recently added features may only be available in one or the other.
29006 This should be documented with the feature. If the documentation does not
29007 explicitly state that the feature is infeasible in the other TLS
29008 implementation, then patches are welcome.
29011 The output from "exim -bV" will show which (if any) support was included
29013 Also, the macro "_HAVE_OPENSSL" or "_HAVE_GNUTLS" will be defined.
29018 .section "GnuTLS parameter computation" "SECTgnutlsparam"
29019 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
29020 an explicit path; if the latter, then the text about generation still applies,
29021 but not the chosen filename.
29022 By default, as of Exim 4.80 a hard-coded D-H prime is used.
29023 See the documentation of &%tls_dhparam%& for more information.
29025 GnuTLS uses D-H parameters that may take a substantial amount of time
29026 to compute. It is unreasonable to re-compute them for every TLS session.
29027 Therefore, Exim keeps this data in a file in its spool directory, called
29028 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
29030 The file is owned by the Exim user and is readable only by
29031 its owner. Every Exim process that start up GnuTLS reads the D-H
29032 parameters from this file. If the file does not exist, the first Exim process
29033 that needs it computes the data and writes it to a temporary file which is
29034 renamed once it is complete. It does not matter if several Exim processes do
29035 this simultaneously (apart from wasting a few resources). Once a file is in
29036 place, new Exim processes immediately start using it.
29038 For maximum security, the parameters that are stored in this file should be
29039 recalculated periodically, the frequency depending on your paranoia level.
29040 If you are avoiding using the fixed D-H primes published in RFCs, then you
29041 are concerned about some advanced attacks and will wish to do this; if you do
29042 not regenerate then you might as well stick to the standard primes.
29044 Arranging this is easy in principle; just delete the file when you want new
29045 values to be computed. However, there may be a problem. The calculation of new
29046 parameters needs random numbers, and these are obtained from &_/dev/random_&.
29047 If the system is not very active, &_/dev/random_& may delay returning data
29048 until enough randomness (entropy) is available. This may cause Exim to hang for
29049 a substantial amount of time, causing timeouts on incoming connections.
29051 The solution is to generate the parameters externally to Exim. They are stored
29052 in &_gnutls-params-N_& in PEM format, which means that they can be
29053 generated externally using the &(certtool)& command that is part of GnuTLS.
29055 To replace the parameters with new ones, instead of deleting the file
29056 and letting Exim re-create it, you can generate new parameters using
29057 &(certtool)& and, when this has been done, replace Exim's cache file by
29058 renaming. The relevant commands are something like this:
29061 [ look for file; assume gnutls-params-2236 is the most recent ]
29064 # chown exim:exim new-params
29065 # chmod 0600 new-params
29066 # certtool --generate-dh-params --bits 2236 >>new-params
29067 # openssl dhparam -noout -text -in new-params | head
29068 [ check the first line, make sure it's not more than 2236;
29069 if it is, then go back to the start ("rm") and repeat
29070 until the size generated is at most the size requested ]
29071 # chmod 0400 new-params
29072 # mv new-params gnutls-params-2236
29074 If Exim never has to generate the parameters itself, the possibility of
29075 stalling is removed.
29077 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
29078 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
29079 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
29080 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
29081 and Exim does so. This attempt to remove Exim from TLS policy decisions
29082 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
29083 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
29084 which applies to all D-H usage, client or server. If the value returned by
29085 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
29086 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
29087 limit, which is still much higher than Exim historically used.
29089 The filename and bits used will change as the GnuTLS maintainers change the
29090 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
29091 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
29092 2432 bits, while NSS is limited to 2236 bits.
29094 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
29095 increase the chance of the generated prime actually being within acceptable
29096 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
29097 procedure above. There is no sane procedure available to Exim to double-check
29098 the size of the generated prime, so it might still be too large.
29101 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
29102 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
29103 .oindex "&%tls_require_ciphers%&" "OpenSSL"
29104 There is a function in the OpenSSL library that can be passed a list of cipher
29105 suites before the cipher negotiation takes place. This specifies which ciphers
29106 are acceptable for TLS versions prior to 1.3.
29107 The list is colon separated and may contain names like
29108 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
29109 directly to this function call.
29110 Many systems will install the OpenSSL manual-pages, so you may have
29111 &'ciphers(1)'& available to you.
29112 The following quotation from the OpenSSL
29113 documentation specifies what forms of item are allowed in the cipher string:
29116 It can consist of a single cipher suite such as RC4-SHA.
29118 It can represent a list of cipher suites containing a certain algorithm,
29119 or cipher suites of a certain type. For example SHA1 represents all
29120 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
29123 Lists of cipher suites can be combined in a single cipher string using
29124 the + character. This is used as a logical and operation. For example
29125 SHA1+DES represents all cipher suites containing the SHA1 and the DES
29129 Each cipher string can be optionally preceded by one of the characters &`!`&,
29132 If &`!`& is used, the ciphers are permanently deleted from the list. The
29133 ciphers deleted can never reappear in the list even if they are explicitly
29136 If &`-`& is used, the ciphers are deleted from the list, but some or all
29137 of the ciphers can be added again by later options.
29139 If &`+`& is used, the ciphers are moved to the end of the list. This
29140 option does not add any new ciphers; it just moves matching existing ones.
29143 If none of these characters is present, the string is interpreted as
29144 a list of ciphers to be appended to the current preference list. If the list
29145 includes any ciphers already present they will be ignored: that is, they will
29146 not be moved to the end of the list.
29149 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
29152 # note single-quotes to get ! past any shell history expansion
29153 $ openssl ciphers 'HIGH:!MD5:!SHA1'
29156 This example will let the library defaults be permitted on the MX port, where
29157 there's probably no identity verification anyway, but ups the ante on the
29158 submission ports where the administrator might have some influence on the
29159 choice of clients used:
29161 # OpenSSL variant; see man ciphers(1)
29162 tls_require_ciphers = ${if =={$received_port}{25}\
29167 This example will prefer ECDSA-authenticated ciphers over RSA ones:
29169 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
29172 For TLS version 1.3 the control available is less fine-grained
29173 and Exim does not provide access to it at present.
29174 The value of the &%tls_require_ciphers%& option is ignored when
29175 TLS version 1.3 is negotiated.
29177 As of writing the library default cipher suite list for TLSv1.3 is
29179 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
29183 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
29185 .cindex "GnuTLS" "specifying parameters for"
29186 .cindex "TLS" "specifying ciphers (GnuTLS)"
29187 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
29188 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
29189 .cindex "TLS" "specifying protocols (GnuTLS)"
29190 .cindex "TLS" "specifying priority string (GnuTLS)"
29191 .oindex "&%tls_require_ciphers%&" "GnuTLS"
29192 The GnuTLS library allows the caller to provide a "priority string", documented
29193 as part of the &[gnutls_priority_init]& function. This is very similar to the
29194 ciphersuite specification in OpenSSL.
29196 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
29197 and controls both protocols and ciphers.
29199 The &%tls_require_ciphers%& option is available both as an global option,
29200 controlling how Exim behaves as a server, and also as an option of the
29201 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
29202 the value is string expanded. The resulting string is not an Exim list and
29203 the string is given to the GnuTLS library, so that Exim does not need to be
29204 aware of future feature enhancements of GnuTLS.
29206 Documentation of the strings accepted may be found in the GnuTLS manual, under
29207 "Priority strings". This is online as
29208 &url(https://www.gnutls.org/manual/html_node/Priority-Strings.html),
29209 but beware that this relates to GnuTLS 3, which may be newer than the version
29210 installed on your system. If you are using GnuTLS 3,
29211 then the example code
29212 &url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
29213 on that site can be used to test a given string.
29217 # Disable older versions of protocols
29218 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
29221 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
29222 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
29223 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
29225 This example will let the library defaults be permitted on the MX port, where
29226 there's probably no identity verification anyway, and lowers security further
29227 by increasing compatibility; but this ups the ante on the submission ports
29228 where the administrator might have some influence on the choice of clients
29232 tls_require_ciphers = ${if =={$received_port}{25}\
29238 .section "Configuring an Exim server to use TLS" "SECID182"
29239 .cindex "TLS" "configuring an Exim server"
29240 .cindex "ESMTP extensions" STARTTLS
29241 When Exim has been built with TLS support, it advertises the availability of
29242 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
29243 but not to any others. The default value of this option is *, which means
29244 that STARTTLS is always advertised. Set it to blank to never advertise;
29245 this is reasonable for systems that want to use TLS only as a client.
29247 If STARTTLS is to be used you
29248 need to set some other options in order to make TLS available.
29250 If a client issues a STARTTLS command and there is some configuration
29251 problem in the server, the command is rejected with a 454 error. If the client
29252 persists in trying to issue SMTP commands, all except QUIT are rejected
29255 554 Security failure
29257 If a STARTTLS command is issued within an existing TLS session, it is
29258 rejected with a 554 error code.
29260 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
29261 must be set to match some hosts. The default is * which matches all hosts.
29263 If this is all you do, TLS encryption will be enabled but not authentication -
29264 meaning that the peer has no assurance it is actually you he is talking to.
29265 You gain protection from a passive sniffer listening on the wire but not
29266 from someone able to intercept the communication.
29268 Further protection requires some further configuration at the server end.
29270 To make TLS work you need to set, in the server,
29272 tls_certificate = /some/file/name
29273 tls_privatekey = /some/file/name
29275 These options are, in fact, expanded strings, so you can make them depend on
29276 the identity of the client that is connected if you wish. The first file
29277 contains the server's X509 certificate, and the second contains the private key
29278 that goes with it. These files need to be
29279 PEM format and readable by the Exim user, and must
29280 always be given as full path names.
29281 The key must not be password-protected.
29282 They can be the same file if both the
29283 certificate and the key are contained within it. If &%tls_privatekey%& is not
29284 set, or if its expansion is forced to fail or results in an empty string, this
29285 is assumed to be the case. The certificate file may also contain intermediate
29286 certificates that need to be sent to the client to enable it to authenticate
29287 the server's certificate.
29289 For dual-stack (eg. RSA and ECDSA) configurations, these options can be
29290 colon-separated lists of file paths. Ciphers using given authentication
29291 algorithms require the presence of a suitable certificate to supply the
29292 public-key. The server selects among the certificates to present to the
29293 client depending on the selected cipher, hence the priority ordering for
29294 ciphers will affect which certificate is used.
29296 If you do not understand about certificates and keys, please try to find a
29297 source of this background information, which is not Exim-specific. (There are a
29298 few comments below in section &<<SECTcerandall>>&.)
29300 &*Note*&: These options do not apply when Exim is operating as a client &--
29301 they apply only in the case of a server. If you need to use a certificate in an
29302 Exim client, you must set the options of the same names in an &(smtp)&
29305 With just these options, an Exim server will be able to use TLS. It does not
29306 require the client to have a certificate (but see below for how to insist on
29307 this). There is one other option that may be needed in other situations. If
29309 tls_dhparam = /some/file/name
29311 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
29312 with the parameters contained in the file.
29313 Set this to &`none`& to disable use of DH entirely, by making no prime
29318 This may also be set to a string identifying a standard prime to be used for
29319 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
29320 used is &`ike23`&. There are a few standard primes available, see the
29321 documentation for &%tls_dhparam%& for the complete list.
29327 for a way of generating file data.
29329 The strings supplied for these three options are expanded every time a client
29330 host connects. It is therefore possible to use different certificates and keys
29331 for different hosts, if you so wish, by making use of the client's IP address
29332 in &$sender_host_address$& to control the expansion. If a string expansion is
29333 forced to fail, Exim behaves as if the option is not set.
29335 .cindex "cipher" "logging"
29336 .cindex "log" "TLS cipher"
29337 .vindex "&$tls_in_cipher$&"
29338 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
29339 an incoming TLS connection. It is included in the &'Received:'& header of an
29340 incoming message (by default &-- you can, of course, change this), and it is
29341 also included in the log line that records a message's arrival, keyed by
29342 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
29343 condition can be used to test for specific cipher suites in ACLs.
29345 Once TLS has been established, the ACLs that run for subsequent SMTP commands
29346 can check the name of the cipher suite and vary their actions accordingly. The
29347 cipher suite names vary, depending on which TLS library is being used. For
29348 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
29349 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
29350 documentation for more details.
29352 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
29353 (again depending on the &%tls_cipher%& log selector).
29356 .section "Requesting and verifying client certificates" "SECID183"
29357 .cindex "certificate" "verification of client"
29358 .cindex "TLS" "client certificate verification"
29359 If you want an Exim server to request a certificate when negotiating a TLS
29360 session with a client, you must set either &%tls_verify_hosts%& or
29361 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
29362 apply to all TLS connections. For any host that matches one of these options,
29363 Exim requests a certificate as part of the setup of the TLS session. The
29364 contents of the certificate are verified by comparing it with a list of
29365 expected trust-anchors or certificates.
29366 These may be the system default set (depending on library version),
29367 an explicit file or,
29368 depending on library version, a directory, identified by
29369 &%tls_verify_certificates%&.
29371 A file can contain multiple certificates, concatenated end to end. If a
29374 each certificate must be in a separate file, with a name (or a symbolic link)
29375 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
29376 certificate. You can compute the relevant hash by running the command
29378 openssl x509 -hash -noout -in /cert/file
29380 where &_/cert/file_& contains a single certificate.
29382 There is no checking of names of the client against the certificate
29383 Subject Name or Subject Alternate Names.
29385 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
29386 what happens if the client does not supply a certificate, or if the certificate
29387 does not match any of the certificates in the collection named by
29388 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
29389 attempt to set up a TLS session is aborted, and the incoming connection is
29390 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
29391 session continues. ACLs that run for subsequent SMTP commands can detect the
29392 fact that no certificate was verified, and vary their actions accordingly. For
29393 example, you can insist on a certificate before accepting a message for
29394 relaying, but not when the message is destined for local delivery.
29396 .vindex "&$tls_in_peerdn$&"
29397 When a client supplies a certificate (whether it verifies or not), the value of
29398 the Distinguished Name of the certificate is made available in the variable
29399 &$tls_in_peerdn$& during subsequent processing of the message.
29401 .cindex "log" "distinguished name"
29402 Because it is often a long text string, it is not included in the log line or
29403 &'Received:'& header by default. You can arrange for it to be logged, keyed by
29404 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
29405 &%received_header_text%& to change the &'Received:'& header. When no
29406 certificate is supplied, &$tls_in_peerdn$& is empty.
29409 .section "Revoked certificates" "SECID184"
29410 .cindex "TLS" "revoked certificates"
29411 .cindex "revocation list"
29412 .cindex "certificate" "revocation list"
29413 .cindex "OCSP" "stapling"
29414 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
29415 certificates are revoked. If you have such a list, you can pass it to an Exim
29416 server using the global option called &%tls_crl%& and to an Exim client using
29417 an identically named option for the &(smtp)& transport. In each case, the value
29418 of the option is expanded and must then be the name of a file that contains a
29420 The downside is that clients have to periodically re-download a potentially huge
29421 file from every certificate authority they know of.
29423 The way with most moving parts at query time is Online Certificate
29424 Status Protocol (OCSP), where the client verifies the certificate
29425 against an OCSP server run by the CA. This lets the CA track all
29426 usage of the certs. It requires running software with access to the
29427 private key of the CA, to sign the responses to the OCSP queries. OCSP
29428 is based on HTTP and can be proxied accordingly.
29430 The only widespread OCSP server implementation (known to this writer)
29431 comes as part of OpenSSL and aborts on an invalid request, such as
29432 connecting to the port and then disconnecting. This requires
29433 re-entering the passphrase each time some random client does this.
29435 The third way is OCSP Stapling; in this, the server using a certificate
29436 issued by the CA periodically requests an OCSP proof of validity from
29437 the OCSP server, then serves it up inline as part of the TLS
29438 negotiation. This approach adds no extra round trips, does not let the
29439 CA track users, scales well with number of certs issued by the CA and is
29440 resilient to temporary OCSP server failures, as long as the server
29441 starts retrying to fetch an OCSP proof some time before its current
29442 proof expires. The downside is that it requires server support.
29444 Unless Exim is built with the support disabled,
29445 or with GnuTLS earlier than version 3.3.16 / 3.4.8
29446 support for OCSP stapling is included.
29448 There is a global option called &%tls_ocsp_file%&.
29449 The file specified therein is expected to be in DER format, and contain
29450 an OCSP proof. Exim will serve it as part of the TLS handshake. This
29451 option will be re-expanded for SNI, if the &%tls_certificate%& option
29452 contains &`tls_in_sni`&, as per other TLS options.
29454 Exim does not at this time implement any support for fetching a new OCSP
29455 proof. The burden is on the administrator to handle this, outside of
29456 Exim. The file specified should be replaced atomically, so that the
29457 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
29458 on each connection, so a new file will be handled transparently on the
29461 When built with OpenSSL Exim will check for a valid next update timestamp
29462 in the OCSP proof; if not present, or if the proof has expired, it will be
29465 For the client to be able to verify the stapled OCSP the server must
29466 also supply, in its stapled information, any intermediate
29467 certificates for the chain leading to the OCSP proof from the signer
29468 of the server certificate. There may be zero or one such. These
29469 intermediate certificates should be added to the server OCSP stapling
29470 file named by &%tls_ocsp_file%&.
29472 Note that the proof only covers the terminal server certificate,
29473 not any of the chain from CA to it.
29475 There is no current way to staple a proof for a client certificate.
29478 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
29479 OCSP server is supplied. The server URL may be included in the
29480 server certificate, if the CA is helpful.
29482 One failure mode seen was the OCSP Signer cert expiring before the end
29483 of validity of the OCSP proof. The checking done by Exim/OpenSSL
29484 noted this as invalid overall, but the re-fetch script did not.
29489 .section "Caching of static server configuration items" "SECTserverTLScache"
29490 .cindex certificate caching
29491 .cindex privatekey caching
29492 .cindex crl caching
29493 .cindex ocsp caching
29494 .cindex ciphers caching
29495 .cindex "CA bundle" caching
29496 .cindex "certificate authorities" caching
29497 .cindex tls_certificate caching
29498 .cindex tls_privatekey caching
29499 .cindex tls_crl caching
29500 .cindex tls_ocsp_file caching
29501 .cindex tls_require_ciphers caching
29502 .cindex tls_verify_certificate caching
29503 .cindex caching certificate
29504 .cindex caching privatekey
29505 .cindex caching crl
29506 .cindex caching ocsp
29507 .cindex caching ciphers
29508 .cindex caching "certificate authorities
29509 If any of the main configuration options &%tls_certificate%&, &%tls_privatekey%&,
29510 &%tls_crl%& and &%tls_ocsp_file%& have values with no
29511 expandable elements,
29512 then the associated information is loaded at daemon startup.
29513 It is made available
29514 to child processes forked for handling received SMTP connections.
29516 This caching is currently only supported under Linux and FreeBSD.
29518 If caching is not possible, for example if an item has to be dependent
29519 on the peer host so contains a &$sender_host_name$& expansion, the load
29520 of the associated information is done at the startup of the TLS connection.
29522 The cache is invalidated and reloaded after any changes to the directories
29523 containing files specified by these options.
29525 The information specified by the main option &%tls_verify_certificates%&
29526 is similarly cached so long as it specifies files explicitly
29527 or (under GnuTLS) is the string &"system,cache"&.
29528 The latter case is not automatically invalidated;
29529 it is the operator's responsibility to arrange for a daemon restart
29530 any time the system certificate authority bundle is updated.
29531 A HUP signal is sufficient for this.
29532 The value &"system"& results in no caching under GnuTLS.
29534 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29535 is acceptable in configurations for the Exim executavble.
29537 Caching of the system Certificate Authorities bundle can
29538 save siginificant time and processing on every TLS connection
29545 .section "Configuring an Exim client to use TLS" "SECTclientTLS"
29546 .cindex "cipher" "logging"
29547 .cindex "log" "TLS cipher"
29548 .cindex "log" "distinguished name"
29549 .cindex "TLS" "configuring an Exim client"
29550 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
29551 deliveries as well as to incoming, the latter one causing logging of the
29552 server certificate's DN. The remaining client configuration for TLS is all
29553 within the &(smtp)& transport.
29555 .cindex "ESMTP extensions" STARTTLS
29556 It is not necessary to set any options to have TLS work in the &(smtp)&
29557 transport. If Exim is built with TLS support, and TLS is advertised by a
29558 server, the &(smtp)& transport always tries to start a TLS session. However,
29559 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
29560 transport) to a list of server hosts for which TLS should not be used.
29562 If you do not want Exim to attempt to send messages unencrypted when an attempt
29563 to set up an encrypted connection fails in any way, you can set
29564 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
29565 those hosts, delivery is always deferred if an encrypted connection cannot be
29566 set up. If there are any other hosts for the address, they are tried in the
29569 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
29570 the message unencrypted. It always does this if the response to STARTTLS is
29571 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
29572 session after a success response code, what happens is controlled by the
29573 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
29574 delivery to this host is deferred, and other hosts (if available) are tried. If
29575 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
29576 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
29577 negotiation fails, Exim closes the current connection (because it is in an
29578 unknown state), opens a new one to the same host, and then tries the delivery
29581 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
29582 transport provide the client with a certificate, which is passed to the server
29584 This is an optional thing for TLS connections, although either end
29586 If the server is Exim, it will request a certificate only if
29587 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
29589 &*Note*&: Do not use a certificate which has the OCSP-must-staple extension,
29590 for client use (they are usable for server use).
29591 As the TLS protocol has no means for the client to staple before TLS 1.3 it will result
29592 in failed connections.
29594 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
29595 specifies a collection of expected server certificates.
29597 the system default set (depending on library version),
29599 or (depending on library version) a directory.
29600 The client verifies the server's certificate
29601 against this collection, taking into account any revoked certificates that are
29602 in the list defined by &%tls_crl%&.
29603 Failure to verify fails the TLS connection unless either of the
29604 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
29606 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
29607 certificate verification to the listed servers. Verification either must
29608 or need not succeed respectively.
29610 The &%tls_verify_cert_hostnames%& option lists hosts for which additional
29611 name checks are made on the server certificate.
29613 The match against this list is, as per other Exim usage, the
29614 IP for the host. That is most closely associated with the
29615 name on the DNS A (or AAAA) record for the host.
29616 However, the name that needs to be in the certificate
29617 is the one at the head of any CNAME chain leading to the A record.
29619 The option defaults to always checking.
29621 The &(smtp)& transport has two OCSP-related options:
29622 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
29623 is requested and required for the connection to proceed. The default
29625 &%hosts_request_ocsp%&; a host-list for which (additionally)
29626 a Certificate Status is requested (but not necessarily verified). The default
29627 value is "*" meaning that requests are made unless configured
29630 The host(s) should also be in &%hosts_require_tls%&, and
29631 &%tls_verify_certificates%& configured for the transport,
29632 for OCSP to be relevant.
29635 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
29636 list of permitted cipher suites. If either of these checks fails, delivery to
29637 the current host is abandoned, and the &(smtp)& transport tries to deliver to
29638 alternative hosts, if any.
29641 These options must be set in the &(smtp)& transport for Exim to use TLS when it
29642 is operating as a client. Exim does not assume that a server certificate (set
29643 by the global options of the same name) should also be used when operating as a
29647 .vindex "&$host_address$&"
29648 All the TLS options in the &(smtp)& transport are expanded before use, with
29649 &$host$& and &$host_address$& containing the name and address of the server to
29650 which the client is connected. Forced failure of an expansion causes Exim to
29651 behave as if the relevant option were unset.
29653 .vindex &$tls_out_bits$&
29654 .vindex &$tls_out_cipher$&
29655 .vindex &$tls_out_peerdn$&
29656 .vindex &$tls_out_sni$&
29657 Before an SMTP connection is established, the
29658 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
29659 variables are emptied. (Until the first connection, they contain the values
29660 that were set when the message was received.) If STARTTLS is subsequently
29661 successfully obeyed, these variables are set to the relevant values for the
29662 outgoing connection.
29667 .section "Caching of static client configuration items" "SECTclientTLScache"
29668 .cindex certificate caching
29669 .cindex privatekey caching
29670 .cindex crl caching
29671 .cindex ciphers caching
29672 .cindex "CA bundle" caching
29673 .cindex "certificate authorities" caching
29674 .cindex tls_certificate caching
29675 .cindex tls_privatekey caching
29676 .cindex tls_crl caching
29677 .cindex tls_require_ciphers caching
29678 .cindex tls_verify_certificate caching
29679 .cindex caching certificate
29680 .cindex caching privatekey
29681 .cindex caching crl
29682 .cindex caching ciphers
29683 .cindex caching "certificate authorities
29684 If any of the transport configuration options &%tls_certificate%&, &%tls_privatekey%&
29685 and &%tls_crl%& have values with no
29686 expandable elements,
29687 then the associated information is loaded per smtp transport
29688 at daemon startup, at the start of a queue run, or on a
29689 command-line specified message delivery.
29690 It is made available
29691 to child processes forked for handling making SMTP connections.
29693 This caching is currently only supported under Linux.
29695 If caching is not possible, the load
29696 of the associated information is done at the startup of the TLS connection.
29698 The cache is invalidated in the daemon
29699 and reloaded after any changes to the directories
29700 containing files specified by these options.
29702 The information specified by the main option &%tls_verify_certificates%&
29703 is similarly cached so long as it specifies files explicitly
29704 or (under GnuTLS) is the string &"system,cache"&.
29705 The latter case is not automatically invaludated;
29706 it is the operator's responsibility to arrange for a daemon restart
29707 any time the system certificate authority bundle is updated.
29708 A HUP signal is sufficient for this.
29709 The value &"system"& results in no caching under GnuTLS.
29711 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29712 is acceptable in configurations for the Exim executavble.
29714 Caching of the system Certificate Authorities bundle can
29715 save siginificant time and processing on every TLS connection
29722 .section "Use of TLS Server Name Indication" "SECTtlssni"
29723 .cindex "TLS" "Server Name Indication"
29726 .vindex "&$tls_in_sni$&"
29727 .oindex "&%tls_in_sni%&"
29728 With TLS1.0 or above, there is an extension mechanism by which extra
29729 information can be included at various points in the protocol. One of these
29730 extensions, documented in RFC 6066 (and before that RFC 4366) is
29731 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
29732 client in the initial handshake, so that the server can examine the servername
29733 within and possibly choose to use different certificates and keys (and more)
29736 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
29737 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
29740 With SMTP to MX, there are the same problems here as in choosing the identity
29741 against which to validate a certificate: you can't rely on insecure DNS to
29742 provide the identity which you then cryptographically verify. So this will
29743 be of limited use in that environment.
29745 With SMTP to Submission, there is a well-defined hostname which clients are
29746 connecting to and can validate certificates against. Thus clients &*can*&
29747 choose to include this information in the TLS negotiation. If this becomes
29748 wide-spread, then hosters can choose to present different certificates to
29749 different clients. Or even negotiate different cipher suites.
29751 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
29752 if not empty, will be sent on a TLS session as part of the handshake. There's
29753 nothing more to it. Choosing a sensible value not derived insecurely is the
29754 only point of caution. The &$tls_out_sni$& variable will be set to this string
29755 for the lifetime of the client connection (including during authentication).
29758 If DANE validated the connection attempt then the value of the &%tls_sni%& option
29759 is forced to the domain part of the recipient address.
29762 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
29763 received from a client.
29764 It can be logged with the &%log_selector%& item &`+tls_sni`&.
29766 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
29767 option (prior to expansion) then the following options will be re-expanded
29768 during TLS session handshake, to permit alternative values to be chosen:
29771 &%tls_certificate%&
29777 &%tls_verify_certificates%&
29782 Great care should be taken to deal with matters of case, various injection
29783 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
29784 can always be referenced; it is important to remember that &$tls_in_sni$& is
29785 arbitrary unverified data provided prior to authentication.
29786 Further, the initial certificate is loaded before SNI has arrived, so
29787 an expansion for &%tls_certificate%& must have a default which is used
29788 when &$tls_in_sni$& is empty.
29790 The Exim developers are proceeding cautiously and so far no other TLS options
29793 When Exim is built against OpenSSL, OpenSSL must have been built with support
29794 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
29795 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
29796 see &`-servername`& in the output, then OpenSSL has support.
29798 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
29799 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
29800 built, then you have SNI support).
29804 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
29806 .cindex "multiple SMTP deliveries with TLS"
29807 .cindex "TLS" "multiple message deliveries"
29808 Exim sends multiple messages down the same TCP/IP connection by starting up
29809 an entirely new delivery process for each message, passing the socket from
29810 one process to the next. This implementation does not fit well with the use
29811 of TLS, because there is quite a lot of state information associated with a TLS
29812 connection, not just a socket identification. Passing all the state information
29813 to a new process is not feasible. Consequently, for sending using TLS Exim
29814 starts an additional proxy process for handling the encryption, piping the
29815 unencrypted data stream from and to the delivery processes.
29817 An older mode of operation can be enabled on a per-host basis by the
29818 &%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
29819 this list the proxy process described above is not used; instead Exim
29820 shuts down an existing TLS session being run by the delivery process
29821 before passing the socket to a new process. The new process may then
29822 try to start a new TLS session, and if successful, may try to re-authenticate
29823 if AUTH is in use, before sending the next message.
29825 The RFC is not clear as to whether or not an SMTP session continues in clear
29826 after TLS has been shut down, or whether TLS may be restarted again later, as
29827 just described. However, if the server is Exim, this shutdown and
29828 reinitialization works. It is not known which (if any) other servers operate
29829 successfully if the client closes a TLS session and continues with unencrypted
29830 SMTP, but there are certainly some that do not work. For such servers, Exim
29831 should not pass the socket to another process, because the failure of the
29832 subsequent attempt to use it would cause Exim to record a temporary host error,
29833 and delay other deliveries to that host.
29835 To test for this case, Exim sends an EHLO command to the server after
29836 closing down the TLS session. If this fails in any way, the connection is
29837 closed instead of being passed to a new delivery process, but no retry
29838 information is recorded.
29840 There is also a manual override; you can set &%hosts_nopass_tls%& on the
29841 &(smtp)& transport to match those hosts for which Exim should not pass
29842 connections to new processes if TLS has been used.
29847 .section "Certificates and all that" "SECTcerandall"
29848 .cindex "certificate" "references to discussion"
29849 In order to understand fully how TLS works, you need to know about
29850 certificates, certificate signing, and certificate authorities.
29851 This is a large topic and an introductory guide is unsuitable for the Exim
29852 reference manual, so instead we provide pointers to existing documentation.
29854 The Apache web-server was for a long time the canonical guide, so their
29855 documentation is a good place to start; their SSL module's Introduction
29856 document is currently at
29858 &url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html)
29860 and their FAQ is at
29862 &url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html)
29865 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
29866 0-201-61598-3) in 2001, contains both introductory and more in-depth
29868 More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&,
29869 published by Feisty Duck (ISBN 978-1907117046) in 2013 is good.
29870 Ivan is the author of the popular TLS testing tools at
29871 &url(https://www.ssllabs.com/).
29874 .section "Certificate chains" "SECID186"
29875 A file named by &%tls_certificate%& may contain more than one
29876 certificate. This is useful in the case where the certificate that is being
29877 sent is validated by an intermediate certificate which the other end does
29878 not have. Multiple certificates must be in the correct order in the file.
29879 First the host's certificate itself, then the first intermediate
29880 certificate to validate the issuer of the host certificate, then the next
29881 intermediate certificate to validate the issuer of the first intermediate
29882 certificate, and so on, until finally (optionally) the root certificate.
29883 The root certificate must already be trusted by the recipient for
29884 validation to succeed, of course, but if it's not preinstalled, sending the
29885 root certificate along with the rest makes it available for the user to
29886 install if the receiving end is a client MUA that can interact with a user.
29888 Note that certificates using MD5 are unlikely to work on today's Internet;
29889 even if your libraries allow loading them for use in Exim when acting as a
29890 server, increasingly clients will not accept such certificates. The error
29891 diagnostics in such a case can be frustratingly vague.
29895 .section "Self-signed certificates" "SECID187"
29896 .cindex "certificate" "self-signed"
29897 You can create a self-signed certificate using the &'req'& command provided
29898 with OpenSSL, like this:
29899 . ==== Do not shorten the duration here without reading and considering
29900 . ==== the text below. Please leave it at 9999 days.
29902 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
29905 &_file1_& and &_file2_& can be the same file; the key and the certificate are
29906 delimited and so can be identified independently. The &%-days%& option
29907 specifies a period for which the certificate is valid. The &%-nodes%& option is
29908 important: if you do not set it, the key is encrypted with a passphrase
29909 that you are prompted for, and any use that is made of the key causes more
29910 prompting for the passphrase. This is not helpful if you are going to use
29911 this certificate and key in an MTA, where prompting is not possible.
29913 . ==== I expect to still be working 26 years from now. The less technical
29914 . ==== debt I create, in terms of storing up trouble for my later years, the
29915 . ==== happier I will be then. We really have reached the point where we
29916 . ==== should start, at the very least, provoking thought and making folks
29917 . ==== pause before proceeding, instead of leaving all the fixes until two
29918 . ==== years before 2^31 seconds after the 1970 Unix epoch.
29920 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
29921 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
29922 the above command might produce a date in the past. Think carefully about
29923 the lifetime of the systems you're deploying, and either reduce the duration
29924 of the certificate or reconsider your platform deployment. (At time of
29925 writing, reducing the duration is the most likely choice, but the inexorable
29926 progression of time takes us steadily towards an era where this will not
29927 be a sensible resolution).
29929 A self-signed certificate made in this way is sufficient for testing, and
29930 may be adequate for all your requirements if you are mainly interested in
29931 encrypting transfers, and not in secure identification.
29933 However, many clients require that the certificate presented by the server be a
29934 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
29935 certificate. In this situation, the self-signed certificate described above
29936 must be installed on the client host as a trusted root &'certification
29937 authority'& (CA), and the certificate used by Exim must be a user certificate
29938 signed with that self-signed certificate.
29940 For information on creating self-signed CA certificates and using them to sign
29941 user certificates, see the &'General implementation overview'& chapter of the
29942 Open-source PKI book, available online at
29943 &url(https://sourceforge.net/projects/ospkibook/).
29944 .ecindex IIDencsmtp1
29945 .ecindex IIDencsmtp2
29949 .section "TLS Resumption" "SECTresumption"
29950 .cindex TLS resumption
29951 TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
29952 in RFC 5077 for 1.2). The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1
29955 Session resumption (this is the "stateless" variant) involves the server sending
29956 a "session ticket" to the client on one connection, which can be stored by the
29957 client and used for a later session. The ticket contains sufficient state for
29958 the server to reconstruct the TLS session, avoiding some expensive crypto
29959 calculation and (on TLS1.2) one full packet roundtrip time.
29962 Operational cost/benefit:
29964 The extra data being transmitted costs a minor amount, and the client has
29965 extra costs in storing and retrieving the data.
29967 In the Exim/Gnutls implementation the extra cost on an initial connection
29968 which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware.
29969 The saved cost on a subsequent connection is about 4ms; three or more
29970 connections become a net win. On longer network paths, two or more
29971 connections will have an average lower startup time thanks to the one
29972 saved packet roundtrip. TLS1.3 will save the crypto cpu costs but not any
29975 .cindex "hints database" tls
29976 Since a new hints DB is used on the TLS client,
29977 the hints DB maintenance should be updated to additionally handle "tls".
29982 The session ticket is encrypted, but is obviously an additional security
29983 vulnarability surface. An attacker able to decrypt it would have access
29984 all connections using the resumed session.
29985 The session ticket encryption key is not committed to storage by the server
29986 and is rotated regularly (OpenSSL: 1hr, and one previous key is used for
29987 overlap; GnuTLS 6hr but does not specify any overlap).
29988 Tickets have limited lifetime (2hr, and new ones issued after 1hr under
29989 OpenSSL. GnuTLS 2hr, appears to not do overlap).
29991 There is a question-mark over the security of the Diffie-Helman parameters
29992 used for session negotiation.
29997 The &%log_selector%& "tls_resumption" appends an asterisk to the tls_cipher "X="
30000 The variables &$tls_in_resumption$& and &$tls_out_resumption$&
30001 have bits 0-4 indicating respectively
30002 support built, client requested ticket, client offered session,
30003 server issued ticket, resume used. A suitable decode list is provided
30004 in the builtin macro _RESUME_DECODE for in &%listextract%& expansions.
30009 The &%tls_resumption_hosts%& main option specifies a hostlist for which
30010 exim, operating as a server, will offer resumption to clients.
30011 Current best practice is to not offer the feature to MUA connection.
30012 Commonly this can be done like this:
30014 tls_resumption_hosts = ${if inlist {$received_port}{587:465} {:}{*}}
30016 If the peer host matches the list after expansion then resumption
30017 is offered and/or accepted.
30019 The &%tls_resumption_hosts%& smtp transport option performs the
30020 equivalent function for operation as a client.
30021 If the peer host matches the list after expansion then resumption
30022 is attempted (if a stored session is available) or the information
30023 stored (if supplied by the peer).
30029 In a resumed session:
30031 The variables &$tls_{in,out}_cipher$& will have values different
30032 to the original (under GnuTLS).
30034 The variables &$tls_{in,out}_ocsp$& will be "not requested" or "no response",
30035 and the &%hosts_require_ocsp%& smtp trasnport option will fail.
30036 . XXX need to do something with that hosts_require_ocsp
30043 .section DANE "SECDANE"
30045 DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
30046 it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
30047 operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
30048 you and the server still think you have an encrypted connection) and, if one of the "well known" set of
30049 Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
30050 certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
30052 What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
30053 that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
30054 by (a) is thought to be smaller than that of the set of root CAs.
30056 It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
30057 fail to pass on a server's STARTTLS.
30059 DANE scales better than having to maintain (and communicate via side-channel) copies of server certificates
30060 for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
30061 client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
30063 DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
30064 that DNS lookups they do for the server have not been tampered with. The domain MX record applying
30065 to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
30067 2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
30068 3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
30070 There are no changes to Exim specific to server-side operation of DANE.
30071 Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
30072 in &_Local/Makefile_&.
30073 If it has been included, the macro "_HAVE_DANE" will be defined.
30075 A TLSA record consist of 4 fields, the "Certificate Usage", the
30076 "Selector", the "Matching type", and the "Certificate Association Data".
30077 For a detailed description of the TLSA record see
30078 &url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671).
30080 The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3).
30081 These are the "Trust Anchor" and "End Entity" variants.
30082 The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
30083 (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
30084 this is appropriate for a single system, using a self-signed certificate.
30085 DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
30087 A private CA at simplest is just a self-signed certificate (with certain
30088 attributes) which is used to sign server certificates, but running one securely
30089 does require careful arrangement.
30090 With DANE-TA, as implemented in Exim and commonly in other MTAs,
30091 the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
30092 DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
30093 all of which point to a single TLSA record.
30094 DANE-TA and DANE-EE can both be used together.
30096 Our recommendation is to use DANE with a certificate from a public CA,
30097 because this enables a variety of strategies for remote clients to verify
30099 You can then publish information both via DANE and another technology,
30100 "MTA-STS", described below.
30102 When you use DANE-TA to publish trust anchor information, you ask entities
30103 outside your administrative control to trust the Certificate Authority for
30104 connections to you.
30105 If using a private CA then you should expect others to still apply the
30106 technical criteria they'd use for a public CA to your certificates.
30107 In particular, you should probably try to follow current best practices for CA
30108 operation around hash algorithms and key sizes.
30109 Do not expect other organizations to lower their security expectations just
30110 because a particular profile might be reasonable for your own internal use.
30112 When this text was last updated, this in practice means to avoid use of SHA-1
30113 and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
30114 than 4096, for interoperability); to use keyUsage fields correctly; to use
30115 random serial numbers.
30116 The list of requirements is subject to change as best practices evolve.
30117 If you're not already using a private CA, or it doesn't meet these
30118 requirements, then we encourage you to avoid all these issues and use a public
30119 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
30121 The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
30122 a "Matching Type" (3rd) field of SHA2-512(2).
30124 For the "Certificate Authority Data" (4th) field, commands like
30127 openssl x509 -pubkey -noout <certificate.pem \
30128 | openssl rsa -outform der -pubin 2>/dev/null \
30133 are workable to create a hash of the certificate's public key.
30135 An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like
30138 _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E...
30141 At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
30142 is useful for quickly generating TLSA records.
30145 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
30147 The Certificate issued by the CA published in the DANE-TA model should be
30148 issued using a strong hash algorithm.
30149 Exim, and importantly various other MTAs sending to you, will not
30150 re-enable hash algorithms which have been disabled by default in TLS
30152 This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
30153 interoperability (and probably the maximum too, in 2018).
30155 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
30156 be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
30157 default of requesting OCSP for all hosts is modified iff DANE is in use, to:
30160 hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
30161 {= {4}{$tls_out_tlsa_usage}} } \
30165 The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
30166 The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
30167 found. If the definition of &%hosts_request_ocsp%& includes the
30168 string "tls_out_tlsa_usage", they are re-expanded in time to
30169 control the OCSP request.
30171 This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
30172 those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
30175 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
30176 and &%dane_require_tls_ciphers%&.
30177 The &"require"& variant will result in failure if the target host is not
30178 DNSSEC-secured. To get DNSSEC-secured hostname resolution, use
30179 the &%dnssec_request_domains%& router or transport option.
30181 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
30183 A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using DNSSEC.
30184 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
30185 will be required for the host. If it does not, the host will not
30186 be used; there is no fallback to non-DANE or non-TLS.
30188 If DANE is requested and usable, then the TLS cipher list configuration
30189 prefers to use the option &%dane_require_tls_ciphers%& and falls
30190 back to &%tls_require_ciphers%& only if that is unset.
30191 This lets you configure "decent crypto" for DANE and "better than nothing
30192 crypto" as the default. Note though that while GnuTLS lets the string control
30193 which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
30194 limited to ciphersuite constraints.
30196 If DANE is requested and useable (see above) the following transport options are ignored:
30200 tls_try_verify_hosts
30201 tls_verify_certificates
30203 tls_verify_cert_hostnames
30207 If DANE is not usable, whether requested or not, and CA-anchored
30208 verification evaluation is wanted, the above variables should be set appropriately.
30210 The router and transport option &%dnssec_request_domains%& must not be
30211 set to &"never"&, and &%dnssec_require_domains%& is ignored.
30213 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
30215 There is a new variable &$tls_out_dane$& which will have "yes" if
30216 verification succeeded using DANE and "no" otherwise (only useful
30217 in combination with events; see &<<CHAPevents>>&),
30218 and a new variable &$tls_out_tlsa_usage$& (detailed above).
30220 .cindex DANE reporting
30221 An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
30222 to achieve DANE-verified connection, if one was either requested and offered, or
30223 required. This is intended to support TLS-reporting as defined in
30224 &url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
30225 The &$event_data$& will be one of the Result Types defined in
30226 Section 4.3 of that document.
30228 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
30230 DANE is specified in published RFCs and decouples certificate authority trust
30231 selection from a "race to the bottom" of "you must trust everything for mail
30232 to get through". There is an alternative technology called MTA-STS, which
30233 instead publishes MX trust anchor information on an HTTPS website. At the
30234 time this text was last updated, MTA-STS was still a draft, not yet an RFC.
30235 Exim has no support for MTA-STS as a client, but Exim mail server operators
30236 can choose to publish information describing their TLS configuration using
30237 MTA-STS to let those clients who do use that protocol derive trust
30240 The MTA-STS design requires a certificate from a public Certificate Authority
30241 which is recognized by clients sending to you.
30242 That selection of which CAs are trusted by others is outside your control.
30244 The most interoperable course of action is probably to use
30245 &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
30246 renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
30247 records for DANE clients (such as Exim and Postfix) and to publish anchor
30248 information for MTA-STS as well. This is what is done for the &'exim.org'&
30249 domain itself (with caveats around occasionally broken MTA-STS because of
30250 incompatible specification changes prior to reaching RFC status).
30254 . ////////////////////////////////////////////////////////////////////////////
30255 . ////////////////////////////////////////////////////////////////////////////
30257 .chapter "Access control lists" "CHAPACL"
30258 .scindex IIDacl "&ACL;" "description"
30259 .cindex "control of incoming mail"
30260 .cindex "message" "controlling incoming"
30261 .cindex "policy control" "access control lists"
30262 Access Control Lists (ACLs) are defined in a separate section of the runtime
30263 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
30264 name, terminated by a colon. Here is a complete ACL section that contains just
30265 one very small ACL:
30269 accept hosts = one.host.only
30271 You can have as many lists as you like in the ACL section, and the order in
30272 which they appear does not matter. The lists are self-terminating.
30274 The majority of ACLs are used to control Exim's behaviour when it receives
30275 certain SMTP commands. This applies both to incoming TCP/IP connections, and
30276 when a local process submits a message using SMTP by specifying the &%-bs%&
30277 option. The most common use is for controlling which recipients are accepted
30278 in incoming messages. In addition, you can define an ACL that is used to check
30279 local non-SMTP messages. The default configuration file contains an example of
30280 a realistic ACL for checking RCPT commands. This is discussed in chapter
30281 &<<CHAPdefconfil>>&.
30284 .section "Testing ACLs" "SECID188"
30285 The &%-bh%& command line option provides a way of testing your ACL
30286 configuration locally by running a fake SMTP session with which you interact.
30289 .section "Specifying when ACLs are used" "SECID189"
30290 .cindex "&ACL;" "options for specifying"
30291 In order to cause an ACL to be used, you have to name it in one of the relevant
30292 options in the main part of the configuration. These options are:
30293 .cindex "AUTH" "ACL for"
30294 .cindex "DATA" "ACLs for"
30295 .cindex "ETRN" "ACL for"
30296 .cindex "EXPN" "ACL for"
30297 .cindex "HELO" "ACL for"
30298 .cindex "EHLO" "ACL for"
30299 .cindex "DKIM" "ACL for"
30300 .cindex "MAIL" "ACL for"
30301 .cindex "QUIT, ACL for"
30302 .cindex "RCPT" "ACL for"
30303 .cindex "STARTTLS, ACL for"
30304 .cindex "VRFY" "ACL for"
30305 .cindex "SMTP" "connection, ACL for"
30306 .cindex "non-SMTP messages" "ACLs for"
30307 .cindex "MIME content scanning" "ACL for"
30308 .cindex "PRDR" "ACL for"
30311 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
30312 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
30313 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
30314 .irow &%acl_smtp_auth%& "ACL for AUTH"
30315 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
30316 .irow &%acl_smtp_data%& "ACL after DATA is complete"
30317 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
30318 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
30319 .irow &%acl_smtp_etrn%& "ACL for ETRN"
30320 .irow &%acl_smtp_expn%& "ACL for EXPN"
30321 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
30322 .irow &%acl_smtp_mail%& "ACL for MAIL"
30323 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
30324 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
30325 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
30326 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
30327 .irow &%acl_smtp_quit%& "ACL for QUIT"
30328 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
30329 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
30330 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
30333 For example, if you set
30335 acl_smtp_rcpt = small_acl
30337 the little ACL defined above is used whenever Exim receives a RCPT command
30338 in an SMTP dialogue. The majority of policy tests on incoming messages can be
30339 done when RCPT commands arrive. A rejection of RCPT should cause the
30340 sending MTA to give up on the recipient address contained in the RCPT
30341 command, whereas rejection at other times may cause the client MTA to keep on
30342 trying to deliver the message. It is therefore recommended that you do as much
30343 testing as possible at RCPT time.
30346 .section "The non-SMTP ACLs" "SECID190"
30347 .cindex "non-SMTP messages" "ACLs for"
30348 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
30349 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
30350 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
30351 the state of the SMTP connection such as encryption and authentication) are not
30352 relevant and are forbidden in these ACLs. However, the sender and recipients
30353 are known, so the &%senders%& and &%sender_domains%& conditions and the
30354 &$sender_address$& and &$recipients$& variables can be used. Variables such as
30355 &$authenticated_sender$& are also available. You can specify added header lines
30356 in any of these ACLs.
30358 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
30359 non-SMTP message, before any of the message has been read. (This is the
30360 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
30361 batched SMTP input, it runs after the DATA command has been reached. The
30362 result of this ACL is ignored; it cannot be used to reject a message. If you
30363 really need to, you could set a value in an ACL variable here and reject based
30364 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
30365 controls, and in particular, it can be used to set
30367 control = suppress_local_fixups
30369 This cannot be used in the other non-SMTP ACLs because by the time they are
30370 run, it is too late.
30372 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
30373 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30375 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
30376 kind of rejection is treated as permanent, because there is no way of sending a
30377 temporary error for these kinds of message.
30380 .section "The SMTP connect ACL" "SECID191"
30381 .cindex "SMTP" "connection, ACL for"
30382 .oindex &%smtp_banner%&
30383 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
30384 session, after the test specified by &%host_reject_connection%& (which is now
30385 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
30386 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
30387 the message override the banner message that is otherwise specified by the
30388 &%smtp_banner%& option.
30391 .section "The EHLO/HELO ACL" "SECID192"
30392 .cindex "EHLO" "ACL for"
30393 .cindex "HELO" "ACL for"
30394 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
30395 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
30396 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
30397 Note that a client may issue more than one EHLO or HELO command in an SMTP
30398 session, and indeed is required to issue a new EHLO or HELO after successfully
30399 setting up encryption following a STARTTLS command.
30401 Note also that a deny neither forces the client to go away nor means that
30402 mail will be refused on the connection. Consider checking for
30403 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
30405 If the command is accepted by an &%accept%& verb that has a &%message%&
30406 modifier, the message may not contain more than one line (it will be truncated
30407 at the first newline and a panic logged if it does). Such a message cannot
30408 affect the EHLO options that are listed on the second and subsequent lines of
30412 .section "The DATA ACLs" "SECID193"
30413 .cindex "DATA" "ACLs for"
30414 Two ACLs are associated with the DATA command, because it is two-stage
30415 command, with two responses being sent to the client.
30416 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
30417 is obeyed. This gives you control after all the RCPT commands, but before
30418 the message itself is received. It offers the opportunity to give a negative
30419 response to the DATA command before the data is transmitted. Header lines
30420 added by MAIL or RCPT ACLs are not visible at this time, but any that
30421 are defined here are visible when the &%acl_smtp_data%& ACL is run.
30423 You cannot test the contents of the message, for example, to verify addresses
30424 in the headers, at RCPT time or when the DATA command is received. Such
30425 tests have to appear in the ACL that is run after the message itself has been
30426 received, before the final response to the DATA command is sent. This is
30427 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
30428 associated with the DATA command.
30430 .cindex CHUNKING "BDAT command"
30431 .cindex BDAT "SMTP command"
30432 .cindex "RFC 3030" CHUNKING
30433 If CHUNKING was advertised and a BDAT command sequence is received,
30434 the &%acl_smtp_predata%& ACL is not run.
30435 . XXX why not? It should be possible, for the first BDAT.
30436 The &%acl_smtp_data%& is run after the last BDAT command and all of
30437 the data specified is received.
30439 For both of these ACLs, it is not possible to reject individual recipients. An
30440 error response rejects the entire message. Unfortunately, it is known that some
30441 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
30442 before or after the data) correctly &-- they keep the message on their queues
30443 and try again later, but that is their problem, though it does waste some of
30446 The &%acl_smtp_data%& ACL is run after
30447 the &%acl_smtp_data_prdr%&,
30448 the &%acl_smtp_dkim%&
30449 and the &%acl_smtp_mime%& ACLs.
30451 .section "The SMTP DKIM ACL" "SECTDKIMACL"
30452 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
30453 enabled (which is the default).
30455 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
30456 received, and is executed for each DKIM signature found in a message. If not
30457 otherwise specified, the default action is to accept.
30459 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
30461 For details on the operation of DKIM, see section &<<SECDKIM>>&.
30464 .section "The SMTP MIME ACL" "SECID194"
30465 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
30466 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30468 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30471 .section "The SMTP PRDR ACL" "SECTPRDRACL"
30472 .cindex "PRDR" "ACL for"
30473 .oindex "&%prdr_enable%&"
30474 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
30475 with PRDR support enabled (which is the default).
30476 It becomes active only when the PRDR feature is negotiated between
30477 client and server for a message, and more than one recipient
30480 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
30481 has been received, and is executed once for each recipient of the message
30482 with &$local_part$& and &$domain$& valid.
30483 The test may accept, defer or deny for individual recipients.
30484 The &%acl_smtp_data%& will still be called after this ACL and
30485 can reject the message overall, even if this ACL has accepted it
30486 for some or all recipients.
30488 PRDR may be used to support per-user content filtering. Without it
30489 one must defer any recipient after the first that has a different
30490 content-filter configuration. With PRDR, the RCPT-time check
30491 .cindex "PRDR" "variable for"
30492 for this can be disabled when the variable &$prdr_requested$&
30494 Any required difference in behaviour of the main DATA-time
30495 ACL should however depend on the PRDR-time ACL having run, as Exim
30496 will avoid doing so in some situations (e.g. single-recipient mails).
30498 See also the &%prdr_enable%& global option
30499 and the &%hosts_try_prdr%& smtp transport option.
30501 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30502 If the ACL is not defined, processing completes as if
30503 the feature was not requested by the client.
30505 .section "The QUIT ACL" "SECTQUITACL"
30506 .cindex "QUIT, ACL for"
30507 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
30508 does not affect the response code to QUIT, which is always 221. Thus, the ACL
30509 does not in fact control any access.
30510 For this reason, it may only accept
30511 or warn as its final result.
30513 This ACL can be used for tasks such as custom logging at the end of an SMTP
30514 session. For example, you can use ACL variables in other ACLs to count
30515 messages, recipients, etc., and log the totals at QUIT time using one or
30516 more &%logwrite%& modifiers on a &%warn%& verb.
30518 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
30519 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
30521 You do not need to have a final &%accept%&, but if you do, you can use a
30522 &%message%& modifier to specify custom text that is sent as part of the 221
30525 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
30526 failure (for example, failure to open a log file, or when Exim is bombing out
30527 because it has detected an unrecoverable error), all SMTP commands from the
30528 client are given temporary error responses until QUIT is received or the
30529 connection is closed. In these special cases, the QUIT ACL does not run.
30532 .section "The not-QUIT ACL" "SECTNOTQUITACL"
30533 .vindex &$acl_smtp_notquit$&
30534 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
30535 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
30536 trouble, such as being unable to write to its log files, this ACL is not run,
30537 because it might try to do things (such as write to log files) that make the
30538 situation even worse.
30540 Like the QUIT ACL, this ACL is provided to make it possible to do customized
30541 logging or to gather statistics, and its outcome is ignored. The &%delay%&
30542 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
30545 .vindex &$smtp_notquit_reason$&
30546 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
30547 to a string that indicates the reason for the termination of the SMTP
30548 connection. The possible values are:
30550 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
30551 .irow &`bad-commands`& "Too many unknown or non-mail commands"
30552 .irow &`command-timeout`& "Timeout while reading SMTP commands"
30553 .irow &`connection-lost`& "The SMTP connection has been lost"
30554 .irow &`data-timeout`& "Timeout while reading message data"
30555 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
30556 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
30557 .irow &`signal-exit`& "SIGTERM or SIGINT"
30558 .irow &`synchronization-error`& "SMTP synchronization error"
30559 .irow &`tls-failed`& "TLS failed to start"
30561 In most cases when an SMTP connection is closed without having received QUIT,
30562 Exim sends an SMTP response message before actually closing the connection.
30563 With the exception of the &`acl-drop`& case, the default message can be
30564 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
30565 &%drop%& verb in another ACL, it is the message from the other ACL that is
30569 .section "Finding an ACL to use" "SECID195"
30570 .cindex "&ACL;" "finding which to use"
30571 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
30572 you can use different ACLs in different circumstances. For example,
30574 acl_smtp_rcpt = ${if ={25}{$interface_port} \
30575 {acl_check_rcpt} {acl_check_rcpt_submit} }
30577 In the default configuration file there are some example settings for
30578 providing an RFC 4409 message &"submission"& service on port 587 and
30579 an RFC 8314 &"submissions"& service on port 465. You can use a string
30580 expansion like this to choose an ACL for MUAs on these ports which is
30581 more appropriate for this purpose than the default ACL on port 25.
30583 The expanded string does not have to be the name of an ACL in the
30584 configuration file; there are other possibilities. Having expanded the
30585 string, Exim searches for an ACL as follows:
30588 If the string begins with a slash, Exim uses it as a filename, and reads its
30589 contents as an ACL. The lines are processed in the same way as lines in the
30590 Exim configuration file. In particular, continuation lines are supported, blank
30591 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
30592 If the file does not exist or cannot be read, an error occurs (typically
30593 causing a temporary failure of whatever caused the ACL to be run). For example:
30595 acl_smtp_data = /etc/acls/\
30596 ${lookup{$sender_host_address}lsearch\
30597 {/etc/acllist}{$value}{default}}
30599 This looks up an ACL file to use on the basis of the host's IP address, falling
30600 back to a default if the lookup fails. If an ACL is successfully read from a
30601 file, it is retained in memory for the duration of the Exim process, so that it
30602 can be re-used without having to re-read the file.
30604 If the string does not start with a slash, and does not contain any spaces,
30605 Exim searches the ACL section of the configuration for an ACL whose name
30606 matches the string.
30608 If no named ACL is found, or if the string contains spaces, Exim parses
30609 the string as an inline ACL. This can save typing in cases where you just
30610 want to have something like
30612 acl_smtp_vrfy = accept
30614 in order to allow free use of the VRFY command. Such a string may contain
30615 newlines; it is processed in the same way as an ACL that is read from a file.
30621 .section "ACL return codes" "SECID196"
30622 .cindex "&ACL;" "return codes"
30623 Except for the QUIT ACL, which does not affect the SMTP return code (see
30624 section &<<SECTQUITACL>>& above), the result of running an ACL is either
30625 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
30626 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
30627 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
30628 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
30629 This also causes a 4&'xx'& return code.
30631 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
30632 &"deny"&, because there is no mechanism for passing temporary errors to the
30633 submitters of non-SMTP messages.
30636 ACLs that are relevant to message reception may also return &"discard"&. This
30637 has the effect of &"accept"&, but causes either the entire message or an
30638 individual recipient address to be discarded. In other words, it is a
30639 blackholing facility. Use it with care.
30641 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
30642 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
30643 RCPT ACL is to discard just the one recipient address. If there are no
30644 recipients left when the message's data is received, the DATA ACL is not
30645 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
30646 remaining recipients. The &"discard"& return is not permitted for the
30647 &%acl_smtp_predata%& ACL.
30649 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
30650 is done on the address and the result determines the SMTP response.
30653 .cindex "&[local_scan()]& function" "when all recipients discarded"
30654 The &[local_scan()]& function is always run, even if there are no remaining
30655 recipients; it may create new recipients.
30659 .section "Unset ACL options" "SECID197"
30660 .cindex "&ACL;" "unset options"
30661 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
30662 all the same. &*Note*&: These defaults apply only when the relevant ACL is
30663 not defined at all. For any defined ACL, the default action when control
30664 reaches the end of the ACL statements is &"deny"&.
30666 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
30667 these two are ACLs that are used only for their side effects. They cannot be
30668 used to accept or reject anything.
30670 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
30671 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
30672 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
30673 when the ACL is not defined is &"accept"&.
30675 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
30676 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
30677 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
30678 messages over an SMTP connection. For an example, see the ACL in the default
30679 configuration file.
30684 .section "Data for message ACLs" "SECID198"
30685 .cindex "&ACL;" "data for message ACL"
30687 .vindex &$local_part$&
30688 .vindex &$sender_address$&
30689 .vindex &$sender_host_address$&
30690 .vindex &$smtp_command$&
30691 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
30692 that contain information about the host and the message's sender (for example,
30693 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
30694 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
30695 &$local_part$& are set from the argument address. The entire SMTP command
30696 is available in &$smtp_command$&.
30698 When an ACL for the AUTH parameter of MAIL is running, the variables that
30699 contain information about the host are set, but &$sender_address$& is not yet
30700 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
30703 .vindex "&$message_size$&"
30704 The &$message_size$& variable is set to the value of the SIZE parameter on
30705 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
30706 that parameter is not given. The value is updated to the true message size by
30707 the time the final DATA ACL is run (after the message data has been
30710 .vindex "&$rcpt_count$&"
30711 .vindex "&$recipients_count$&"
30712 The &$rcpt_count$& variable increases by one for each RCPT command received.
30713 The &$recipients_count$& variable increases by one each time a RCPT command is
30714 accepted, so while an ACL for RCPT is being processed, it contains the number
30715 of previously accepted recipients. At DATA time (for both the DATA ACLs),
30716 &$rcpt_count$& contains the total number of RCPT commands, and
30717 &$recipients_count$& contains the total number of accepted recipients.
30723 .section "Data for non-message ACLs" "SECTdatfornon"
30724 .cindex "&ACL;" "data for non-message ACL"
30725 .vindex &$smtp_command_argument$&
30726 .vindex &$smtp_command$&
30727 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
30728 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
30729 and the entire SMTP command is available in &$smtp_command$&.
30730 These variables can be tested using a &%condition%& condition. For example,
30731 here is an ACL for use with AUTH, which insists that either the session is
30732 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
30733 does not permit authentication methods that use cleartext passwords on
30734 unencrypted connections.
30737 accept encrypted = *
30738 accept condition = ${if eq{${uc:$smtp_command_argument}}\
30740 deny message = TLS encryption or CRAM-MD5 required
30742 (Another way of applying this restriction is to arrange for the authenticators
30743 that use cleartext passwords not to be advertised when the connection is not
30744 encrypted. You can use the generic &%server_advertise_condition%& authenticator
30745 option to do this.)
30749 .section "Format of an ACL" "SECID199"
30750 .cindex "&ACL;" "format of"
30751 .cindex "&ACL;" "verbs, definition of"
30752 An individual ACL consists of a number of statements. Each statement starts
30753 with a verb, optionally followed by a number of conditions and &"modifiers"&.
30754 Modifiers can change the way the verb operates, define error and log messages,
30755 set variables, insert delays, and vary the processing of accepted messages.
30757 If all the conditions are met, the verb is obeyed. The same condition may be
30758 used (with different arguments) more than once in the same statement. This
30759 provides a means of specifying an &"and"& conjunction between conditions. For
30762 deny dnslists = list1.example
30763 dnslists = list2.example
30765 If there are no conditions, the verb is always obeyed. Exim stops evaluating
30766 the conditions and modifiers when it reaches a condition that fails. What
30767 happens then depends on the verb (and in one case, on a special modifier). Not
30768 all the conditions make sense at every testing point. For example, you cannot
30769 test a sender address in the ACL that is run for a VRFY command.
30772 .section "ACL verbs" "SECID200"
30773 The ACL verbs are as follows:
30776 .cindex "&%accept%& ACL verb"
30777 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
30778 of the conditions are not met, what happens depends on whether &%endpass%&
30779 appears among the conditions (for syntax see below). If the failing condition
30780 is before &%endpass%&, control is passed to the next ACL statement; if it is
30781 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
30782 check a RCPT command:
30784 accept domains = +local_domains
30788 If the recipient domain does not match the &%domains%& condition, control
30789 passes to the next statement. If it does match, the recipient is verified, and
30790 the command is accepted if verification succeeds. However, if verification
30791 fails, the ACL yields &"deny"&, because the failing condition is after
30794 The &%endpass%& feature has turned out to be confusing to many people, so its
30795 use is not recommended nowadays. It is always possible to rewrite an ACL so
30796 that &%endpass%& is not needed, and it is no longer used in the default
30799 .cindex "&%message%& ACL modifier" "with &%accept%&"
30800 If a &%message%& modifier appears on an &%accept%& statement, its action
30801 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
30802 (when an &%accept%& verb either accepts or passes control to the next
30803 statement), &%message%& can be used to vary the message that is sent when an
30804 SMTP command is accepted. For example, in a RCPT ACL you could have:
30806 &`accept `&<&'some conditions'&>
30807 &` message = OK, I will allow you through today`&
30809 You can specify an SMTP response code, optionally followed by an &"extended
30810 response code"& at the start of the message, but the first digit must be the
30811 same as would be sent by default, which is 2 for an &%accept%& verb.
30813 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
30814 an error message that is used when access is denied. This behaviour is retained
30815 for backward compatibility, but current &"best practice"& is to avoid the use
30820 .cindex "&%defer%& ACL verb"
30821 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
30822 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
30823 &%defer%& is the same as &%deny%&, because there is no way of sending a
30824 temporary error. For a RCPT command, &%defer%& is much the same as using a
30825 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
30826 be used in any ACL, and even for a recipient it might be a simpler approach.
30830 .cindex "&%deny%& ACL verb"
30831 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
30832 the conditions are not met, control is passed to the next ACL statement. For
30835 deny dnslists = blackholes.mail-abuse.org
30837 rejects commands from hosts that are on a DNS black list.
30841 .cindex "&%discard%& ACL verb"
30842 &%discard%&: This verb behaves like &%accept%&, except that it returns
30843 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
30844 that are concerned with receiving messages. When all the conditions are true,
30845 the sending entity receives a &"success"& response. However, &%discard%& causes
30846 recipients to be discarded. If it is used in an ACL for RCPT, just the one
30847 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
30848 message's recipients are discarded. Recipients that are discarded before DATA
30849 do not appear in the log line when the &%received_recipients%& log selector is set.
30851 If the &%log_message%& modifier is set when &%discard%& operates,
30852 its contents are added to the line that is automatically written to the log.
30853 The &%message%& modifier operates exactly as it does for &%accept%&.
30857 .cindex "&%drop%& ACL verb"
30858 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
30859 forcibly closed after the 5&'xx'& error message has been sent. For example:
30861 drop condition = ${if > {$rcpt_count}{20}}
30862 message = I don't take more than 20 RCPTs
30864 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
30865 The connection is always dropped after sending a 550 response.
30868 .cindex "&%require%& ACL verb"
30869 &%require%&: If all the conditions are met, control is passed to the next ACL
30870 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
30871 example, when checking a RCPT command,
30873 require message = Sender did not verify
30876 passes control to subsequent statements only if the message's sender can be
30877 verified. Otherwise, it rejects the command. Note the positioning of the
30878 &%message%& modifier, before the &%verify%& condition. The reason for this is
30879 discussed in section &<<SECTcondmodproc>>&.
30882 .cindex "&%warn%& ACL verb"
30883 &%warn%&: If all the conditions are true, a line specified by the
30884 &%log_message%& modifier is written to Exim's main log. Control always passes
30885 to the next ACL statement. If any condition is false, the log line is not
30886 written. If an identical log line is requested several times in the same
30887 message, only one copy is actually written to the log. If you want to force
30888 duplicates to be written, use the &%logwrite%& modifier instead.
30890 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
30891 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
30892 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
30893 first failing condition. There is more about adding header lines in section
30894 &<<SECTaddheadacl>>&.
30896 If any condition on a &%warn%& statement cannot be completed (that is, there is
30897 some sort of defer), the log line specified by &%log_message%& is not written.
30898 This does not include the case of a forced failure from a lookup, which
30899 is considered to be a successful completion. After a defer, no further
30900 conditions or modifiers in the &%warn%& statement are processed. The incident
30901 is logged, and the ACL continues to be processed, from the next statement
30905 .vindex "&$acl_verify_message$&"
30906 When one of the &%warn%& conditions is an address verification that fails, the
30907 text of the verification failure message is in &$acl_verify_message$&. If you
30908 want this logged, you must set it up explicitly. For example:
30910 warn !verify = sender
30911 log_message = sender verify failed: $acl_verify_message
30915 At the end of each ACL there is an implicit unconditional &%deny%&.
30917 As you can see from the examples above, the conditions and modifiers are
30918 written one to a line, with the first one on the same line as the verb, and
30919 subsequent ones on following lines. If you have a very long condition, you can
30920 continue it onto several physical lines by the usual backslash continuation
30921 mechanism. It is conventional to align the conditions vertically.
30925 .section "ACL variables" "SECTaclvariables"
30926 .cindex "&ACL;" "variables"
30927 There are some special variables that can be set during ACL processing. They
30928 can be used to pass information between different ACLs, different invocations
30929 of the same ACL in the same SMTP connection, and between ACLs and the routers,
30930 transports, and filters that are used to deliver a message. The names of these
30931 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
30932 an underscore, but the remainder of the name can be any sequence of
30933 alphanumeric characters and underscores that you choose. There is no limit on
30934 the number of ACL variables. The two sets act as follows:
30936 The values of those variables whose names begin with &$acl_c$& persist
30937 throughout an SMTP connection. They are never reset. Thus, a value that is set
30938 while receiving one message is still available when receiving the next message
30939 on the same SMTP connection.
30941 The values of those variables whose names begin with &$acl_m$& persist only
30942 while a message is being received. They are reset afterwards. They are also
30943 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
30946 When a message is accepted, the current values of all the ACL variables are
30947 preserved with the message and are subsequently made available at delivery
30948 time. The ACL variables are set by a modifier called &%set%&. For example:
30950 accept hosts = whatever
30951 set acl_m4 = some value
30952 accept authenticated = *
30953 set acl_c_auth = yes
30955 &*Note*&: A leading dollar sign is not used when naming a variable that is to
30956 be set. If you want to set a variable without taking any action, you can use a
30957 &%warn%& verb without any other modifiers or conditions.
30959 .oindex &%strict_acl_vars%&
30960 What happens if a syntactically valid but undefined ACL variable is
30961 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
30962 false (the default), an empty string is substituted; if it is true, an
30963 error is generated.
30965 Versions of Exim before 4.64 have a limited set of numbered variables, but
30966 their names are compatible, so there is no problem with upgrading.
30969 .section "Condition and modifier processing" "SECTcondmodproc"
30970 .cindex "&ACL;" "conditions; processing"
30971 .cindex "&ACL;" "modifiers; processing"
30972 An exclamation mark preceding a condition negates its result. For example:
30974 deny domains = *.dom.example
30975 !verify = recipient
30977 causes the ACL to return &"deny"& if the recipient domain ends in
30978 &'dom.example'& and the recipient address cannot be verified. Sometimes
30979 negation can be used on the right-hand side of a condition. For example, these
30980 two statements are equivalent:
30982 deny hosts = !192.168.3.4
30983 deny !hosts = 192.168.3.4
30985 However, for many conditions (&%verify%& being a good example), only left-hand
30986 side negation of the whole condition is possible.
30988 The arguments of conditions and modifiers are expanded. A forced failure
30989 of an expansion causes a condition to be ignored, that is, it behaves as if the
30990 condition is true. Consider these two statements:
30992 accept senders = ${lookup{$host_name}lsearch\
30993 {/some/file}{$value}fail}
30994 accept senders = ${lookup{$host_name}lsearch\
30995 {/some/file}{$value}{}}
30997 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
30998 the returned list is searched, but if the lookup fails the behaviour is
30999 different in the two cases. The &%fail%& in the first statement causes the
31000 condition to be ignored, leaving no further conditions. The &%accept%& verb
31001 therefore succeeds. The second statement, however, generates an empty list when
31002 the lookup fails. No sender can match an empty list, so the condition fails,
31003 and therefore the &%accept%& also fails.
31005 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
31006 specify actions that are taken as the conditions for a statement are checked;
31007 others specify text for messages that are used when access is denied or a
31008 warning is generated. The &%control%& modifier affects the way an incoming
31009 message is handled.
31011 The positioning of the modifiers in an ACL statement is important, because the
31012 processing of a verb ceases as soon as its outcome is known. Only those
31013 modifiers that have already been encountered will take effect. For example,
31014 consider this use of the &%message%& modifier:
31016 require message = Can't verify sender
31018 message = Can't verify recipient
31020 message = This message cannot be used
31022 If sender verification fails, Exim knows that the result of the statement is
31023 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
31024 so its text is used as the error message. If sender verification succeeds, but
31025 recipient verification fails, the second message is used. If recipient
31026 verification succeeds, the third message becomes &"current"&, but is never used
31027 because there are no more conditions to cause failure.
31029 For the &%deny%& verb, on the other hand, it is always the last &%message%&
31030 modifier that is used, because all the conditions must be true for rejection to
31031 happen. Specifying more than one &%message%& modifier does not make sense, and
31032 the message can even be specified after all the conditions. For example:
31035 !senders = *@my.domain.example
31036 message = Invalid sender from client host
31038 The &"deny"& result does not happen until the end of the statement is reached,
31039 by which time Exim has set up the message.
31043 .section "ACL modifiers" "SECTACLmodi"
31044 .cindex "&ACL;" "modifiers; list of"
31045 The ACL modifiers are as follows:
31048 .vitem &*add_header*&&~=&~<&'text'&>
31049 This modifier specifies one or more header lines that are to be added to an
31050 incoming message, assuming, of course, that the message is ultimately
31051 accepted. For details, see section &<<SECTaddheadacl>>&.
31053 .vitem &*continue*&&~=&~<&'text'&>
31054 .cindex "&%continue%& ACL modifier"
31055 .cindex "database" "updating in ACL"
31056 This modifier does nothing of itself, and processing of the ACL always
31057 continues with the next condition or modifier. The value of &%continue%& is in
31058 the side effects of expanding its argument. Typically this could be used to
31059 update a database. It is really just a syntactic tidiness, to avoid having to
31060 write rather ugly lines like this:
31062 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
31064 Instead, all you need is
31066 &`continue = `&<&'some expansion'&>
31069 .vitem &*control*&&~=&~<&'text'&>
31070 .cindex "&%control%& ACL modifier"
31071 This modifier affects the subsequent processing of the SMTP connection or of an
31072 incoming message that is accepted. The effect of the first type of control
31073 lasts for the duration of the connection, whereas the effect of the second type
31074 lasts only until the current message has been received. The message-specific
31075 controls always apply to the whole message, not to individual recipients,
31076 even if the &%control%& modifier appears in a RCPT ACL.
31078 As there are now quite a few controls that can be applied, they are described
31079 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
31080 in several different ways. For example:
31082 . ==== As this is a nested list, any displays it contains must be indented
31083 . ==== as otherwise they are too far to the left. That comment applies only
31084 . ==== when xmlto and fop are used; formatting with sdop gets it right either
31088 It can be at the end of an &%accept%& statement:
31090 accept ...some conditions
31093 In this case, the control is applied when this statement yields &"accept"&, in
31094 other words, when the conditions are all true.
31097 It can be in the middle of an &%accept%& statement:
31099 accept ...some conditions...
31101 ...some more conditions...
31103 If the first set of conditions are true, the control is applied, even if the
31104 statement does not accept because one of the second set of conditions is false.
31105 In this case, some subsequent statement must yield &"accept"& for the control
31109 It can be used with &%warn%& to apply the control, leaving the
31110 decision about accepting or denying to a subsequent verb. For
31113 warn ...some conditions...
31117 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
31118 &%logwrite%&, so it does not add anything to the message and does not write a
31122 If you want to apply a control unconditionally, you can use it with a
31123 &%require%& verb. For example:
31125 require control = no_multiline_responses
31129 .vitem &*delay*&&~=&~<&'time'&>
31130 .cindex "&%delay%& ACL modifier"
31132 This modifier may appear in any ACL except notquit. It causes Exim to wait for
31133 the time interval before proceeding. However, when testing Exim using the
31134 &%-bh%& option, the delay is not actually imposed (an appropriate message is
31135 output instead). The time is given in the usual Exim notation, and the delay
31136 happens as soon as the modifier is processed. In an SMTP session, pending
31137 output is flushed before the delay is imposed.
31139 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
31142 deny ...some conditions...
31145 The delay happens if all the conditions are true, before the statement returns
31146 &"deny"&. Compare this with:
31149 ...some conditions...
31151 which waits for 30s before processing the conditions. The &%delay%& modifier
31152 can also be used with &%warn%& and together with &%control%&:
31154 warn ...some conditions...
31160 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
31161 responses to several commands are no longer buffered and sent in one packet (as
31162 they would normally be) because all output is flushed before imposing the
31163 delay. This optimization is disabled so that a number of small delays do not
31164 appear to the client as one large aggregated delay that might provoke an
31165 unwanted timeout. You can, however, disable output flushing for &%delay%& by
31166 using a &%control%& modifier to set &%no_delay_flush%&.
31170 .cindex "&%endpass%& ACL modifier"
31171 This modifier, which has no argument, is recognized only in &%accept%& and
31172 &%discard%& statements. It marks the boundary between the conditions whose
31173 failure causes control to pass to the next statement, and the conditions whose
31174 failure causes the ACL to return &"deny"&. This concept has proved to be
31175 confusing to some people, so the use of &%endpass%& is no longer recommended as
31176 &"best practice"&. See the description of &%accept%& above for more details.
31179 .vitem &*log_message*&&~=&~<&'text'&>
31180 .cindex "&%log_message%& ACL modifier"
31181 This modifier sets up a message that is used as part of the log message if the
31182 ACL denies access or a &%warn%& statement's conditions are true. For example:
31184 require log_message = wrong cipher suite $tls_in_cipher
31185 encrypted = DES-CBC3-SHA
31187 &%log_message%& is also used when recipients are discarded by &%discard%&. For
31190 &`discard `&<&'some conditions'&>
31191 &` log_message = Discarded $local_part@$domain because...`&
31193 When access is denied, &%log_message%& adds to any underlying error message
31194 that may exist because of a condition failure. For example, while verifying a
31195 recipient address, a &':fail:'& redirection might have already set up a
31198 The message may be defined before the conditions to which it applies, because
31199 the string expansion does not happen until Exim decides that access is to be
31200 denied. This means that any variables that are set by the condition are
31201 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
31202 variables are set after a DNS black list lookup succeeds. If the expansion of
31203 &%log_message%& fails, or if the result is an empty string, the modifier is
31206 .vindex "&$acl_verify_message$&"
31207 If you want to use a &%warn%& statement to log the result of an address
31208 verification, you can use &$acl_verify_message$& to include the verification
31211 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
31212 the start of the logged message. If the same warning log message is requested
31213 more than once while receiving a single email message, only one copy is
31214 actually logged. If you want to log multiple copies, use &%logwrite%& instead
31215 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
31216 is logged for a successful &%warn%& statement.
31218 If &%log_message%& is not present and there is no underlying error message (for
31219 example, from the failure of address verification), but &%message%& is present,
31220 the &%message%& text is used for logging rejections. However, if any text for
31221 logging contains newlines, only the first line is logged. In the absence of
31222 both &%log_message%& and &%message%&, a default built-in message is used for
31223 logging rejections.
31226 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
31227 .cindex "&%log_reject_target%& ACL modifier"
31228 .cindex "logging in ACL" "specifying which log"
31229 This modifier makes it possible to specify which logs are used for messages
31230 about ACL rejections. Its argument is a colon-separated list of words that can
31231 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
31232 may be empty, in which case a rejection is not logged at all. For example, this
31233 ACL fragment writes no logging information when access is denied:
31235 &`deny `&<&'some conditions'&>
31236 &` log_reject_target =`&
31238 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
31239 permanent and temporary rejections. Its effect lasts for the rest of the
31243 .vitem &*logwrite*&&~=&~<&'text'&>
31244 .cindex "&%logwrite%& ACL modifier"
31245 .cindex "logging in ACL" "immediate"
31246 This modifier writes a message to a log file as soon as it is encountered when
31247 processing an ACL. (Compare &%log_message%&, which, except in the case of
31248 &%warn%& and &%discard%&, is used only if the ACL statement denies
31249 access.) The &%logwrite%& modifier can be used to log special incidents in
31252 &`accept `&<&'some special conditions'&>
31253 &` control = freeze`&
31254 &` logwrite = froze message because ...`&
31256 By default, the message is written to the main log. However, it may begin
31257 with a colon, followed by a comma-separated list of log names, and then
31258 another colon, to specify exactly which logs are to be written. For
31261 logwrite = :main,reject: text for main and reject logs
31262 logwrite = :panic: text for panic log only
31266 .vitem &*message*&&~=&~<&'text'&>
31267 .cindex "&%message%& ACL modifier"
31268 This modifier sets up a text string that is expanded and used as a response
31269 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
31270 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
31271 there is some complication if &%endpass%& is involved; see the description of
31272 &%accept%& for details.)
31274 The expansion of the message happens at the time Exim decides that the ACL is
31275 to end, not at the time it processes &%message%&. If the expansion fails, or
31276 generates an empty string, the modifier is ignored. Here is an example where
31277 &%message%& must be specified first, because the ACL ends with a rejection if
31278 the &%hosts%& condition fails:
31280 require message = Host not recognized
31283 (Once a condition has failed, no further conditions or modifiers are
31286 .cindex "SMTP" "error codes"
31287 .oindex "&%smtp_banner%&
31288 For ACLs that are triggered by SMTP commands, the message is returned as part
31289 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
31290 is meaningful only for SMTP, as no message is returned when a non-SMTP message
31291 is accepted. In the case of the connect ACL, accepting with a message modifier
31292 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
31293 accept message may not contain more than one line (otherwise it will be
31294 truncated at the first newline and a panic logged), and it cannot affect the
31297 When SMTP is involved, the message may begin with an overriding response code,
31298 consisting of three digits optionally followed by an &"extended response code"&
31299 of the form &'n.n.n'&, each code being followed by a space. For example:
31301 deny message = 599 1.2.3 Host not welcome
31302 hosts = 192.168.34.0/24
31304 The first digit of the supplied response code must be the same as would be sent
31305 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
31306 access, but for the predata ACL, note that the default success code is 354, not
31309 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
31310 the message modifier cannot override the 221 response code.
31312 The text in a &%message%& modifier is literal; any quotes are taken as
31313 literals, but because the string is expanded, backslash escapes are processed
31314 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
31317 .vindex "&$acl_verify_message$&"
31318 For ACLs that are called by an &%acl =%& ACL condition, the message is
31319 stored in &$acl_verify_message$&, from which the calling ACL may use it.
31321 If &%message%& is used on a statement that verifies an address, the message
31322 specified overrides any message that is generated by the verification process.
31323 However, the original message is available in the variable
31324 &$acl_verify_message$&, so you can incorporate it into your message if you
31325 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
31326 routers to be passed back as part of the SMTP response, you should either not
31327 use a &%message%& modifier, or make use of &$acl_verify_message$&.
31329 For compatibility with previous releases of Exim, a &%message%& modifier that
31330 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
31331 modifier, but this usage is now deprecated. However, &%message%& acts only when
31332 all the conditions are true, wherever it appears in an ACL command, whereas
31333 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
31334 &%warn%& in an ACL that is not concerned with receiving a message, it has no
31338 .vitem &*queue*&&~=&~<&'text'&>
31339 .cindex "&%queue%& ACL modifier"
31340 .cindex "named queues" "selecting in ACL"
31341 This modifier specifies the use of a named queue for spool files
31343 It can only be used before the message is received (i.e. not in
31345 This could be used, for example, for known high-volume burst sources
31346 of traffic, or for quarantine of messages.
31347 Separate queue-runner processes will be needed for named queues.
31348 If the text after expansion is empty, the default queue is used.
31351 .vitem &*remove_header*&&~=&~<&'text'&>
31352 This modifier specifies one or more header names in a colon-separated list
31353 that are to be removed from an incoming message, assuming, of course, that
31354 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
31357 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
31358 .cindex "&%set%& ACL modifier"
31359 This modifier puts a value into one of the ACL variables (see section
31360 &<<SECTaclvariables>>&).
31363 .vitem &*udpsend*&&~=&~<&'parameters'&>
31364 .cindex "UDP communications"
31365 This modifier sends a UDP packet, for purposes such as statistics
31366 collection or behaviour monitoring. The parameters are expanded, and
31367 the result of the expansion must be a colon-separated list consisting
31368 of a destination server, port number, and the packet contents. The
31369 server can be specified as a host name or IPv4 or IPv6 address. The
31370 separator can be changed with the usual angle bracket syntax. For
31371 example, you might want to collect information on which hosts connect
31374 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
31375 $tod_zulu $sender_host_address
31382 .section "Use of the control modifier" "SECTcontrols"
31383 .cindex "&%control%& ACL modifier"
31384 The &%control%& modifier supports the following settings:
31387 .vitem &*control&~=&~allow_auth_unadvertised*&
31388 This modifier allows a client host to use the SMTP AUTH command even when it
31389 has not been advertised in response to EHLO. Furthermore, because there are
31390 apparently some really broken clients that do this, Exim will accept AUTH after
31391 HELO (rather than EHLO) when this control is set. It should be used only if you
31392 really need it, and you should limit its use to those broken clients that do
31393 not work without it. For example:
31395 warn hosts = 192.168.34.25
31396 control = allow_auth_unadvertised
31398 Normally, when an Exim server receives an AUTH command, it checks the name of
31399 the authentication mechanism that is given in the command to ensure that it
31400 matches an advertised mechanism. When this control is set, the check that a
31401 mechanism has been advertised is bypassed. Any configured mechanism can be used
31402 by the client. This control is permitted only in the connection and HELO ACLs.
31405 .vitem &*control&~=&~caseful_local_part*& &&&
31406 &*control&~=&~caselower_local_part*&
31407 .cindex "&ACL;" "case of local part in"
31408 .cindex "case of local parts"
31409 .vindex "&$local_part$&"
31410 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
31411 (that is, during RCPT processing). By default, the contents of &$local_part$&
31412 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
31413 any uppercase letters in the original local part are restored in &$local_part$&
31414 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
31417 These controls affect only the current recipient. Moreover, they apply only to
31418 local part handling that takes place directly in the ACL (for example, as a key
31419 in lookups). If a test to verify the recipient is obeyed, the case-related
31420 handling of the local part during the verification is controlled by the router
31421 configuration (see the &%caseful_local_part%& generic router option).
31423 This facility could be used, for example, to add a spam score to local parts
31424 containing upper case letters. For example, using &$acl_m4$& to accumulate the
31427 warn control = caseful_local_part
31428 set acl_m4 = ${eval:\
31430 ${if match{$local_part}{[A-Z]}{1}{0}}\
31432 control = caselower_local_part
31434 Notice that we put back the lower cased version afterwards, assuming that
31435 is what is wanted for subsequent tests.
31438 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
31439 .cindex "&ACL;" "cutthrough routing"
31440 .cindex "cutthrough" "requesting"
31441 This option requests delivery be attempted while the item is being received.
31443 The option is usable in the RCPT ACL.
31444 If enabled for a message received via smtp and routed to an smtp transport,
31445 and only one transport, interface, destination host and port combination
31446 is used for all recipients of the message,
31447 then the delivery connection is made while the receiving connection is open
31448 and data is copied from one to the other.
31450 An attempt to set this option for any recipient but the first
31451 for a mail will be quietly ignored.
31452 If a recipient-verify callout
31454 connection is subsequently
31455 requested in the same ACL it is held open and used for
31456 any subsequent recipients and the data,
31457 otherwise one is made after the initial RCPT ACL completes.
31459 Note that routers are used in verify mode,
31460 and cannot depend on content of received headers.
31461 Note also that headers cannot be
31462 modified by any of the post-data ACLs (DATA, MIME and DKIM).
31463 Headers may be modified by routers (subject to the above) and transports.
31464 The &'Received-By:'& header is generated as soon as the body reception starts,
31465 rather than the traditional time after the full message is received;
31466 this will affect the timestamp.
31468 All the usual ACLs are called; if one results in the message being
31469 rejected, all effort spent in delivery (including the costs on
31470 the ultimate destination) will be wasted.
31471 Note that in the case of data-time ACLs this includes the entire
31474 Cutthrough delivery is not supported via transport-filters or when DKIM signing
31475 of outgoing messages is done, because it sends data to the ultimate destination
31476 before the entire message has been received from the source.
31477 It is not supported for messages received with the SMTP PRDR
31481 Should the ultimate destination system positively accept or reject the mail,
31482 a corresponding indication is given to the source system and nothing is queued.
31483 If the item is successfully delivered in cutthrough mode
31484 the delivery log lines are tagged with ">>" rather than "=>" and appear
31485 before the acceptance "<=" line.
31487 If there is a temporary error the item is queued for later delivery in the
31489 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
31490 to the control; the default value is &"spool"& and the alternate value
31491 &"pass"& copies an SMTP defer response from the target back to the initiator
31492 and does not queue the message.
31493 Note that this is independent of any recipient verify conditions in the ACL.
31495 Delivery in this mode avoids the generation of a bounce mail to a
31497 sender when the destination system is doing content-scan based rejection.
31500 .vitem &*control&~=&~debug/*&<&'options'&>
31501 .cindex "&ACL;" "enabling debug logging"
31502 .cindex "debugging" "enabling from an ACL"
31503 This control turns on debug logging, almost as though Exim had been invoked
31504 with &`-d`&, with the output going to a new logfile in the usual logs directory,
31505 by default called &'debuglog'&.
31506 The filename can be adjusted with the &'tag'& option, which
31507 may access any variables already defined. The logging may be adjusted with
31508 the &'opts'& option, which takes the same values as the &`-d`& command-line
31510 Logging started this way may be stopped, and the file removed,
31511 with the &'kill'& option.
31512 Some examples (which depend on variables that don't exist in all
31516 control = debug/tag=.$sender_host_address
31517 control = debug/opts=+expand+acl
31518 control = debug/tag=.$message_exim_id/opts=+expand
31519 control = debug/kill
31523 .vitem &*control&~=&~dkim_disable_verify*&
31524 .cindex "disable DKIM verify"
31525 .cindex "DKIM" "disable verify"
31526 This control turns off DKIM verification processing entirely. For details on
31527 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
31530 .vitem &*control&~=&~dmarc_disable_verify*&
31531 .cindex "disable DMARC verify"
31532 .cindex "DMARC" "disable verify"
31533 This control turns off DMARC verification processing entirely. For details on
31534 the operation and configuration of DMARC, see section &<<SECDMARC>>&.
31537 .vitem &*control&~=&~dscp/*&<&'value'&>
31538 .cindex "&ACL;" "setting DSCP value"
31539 .cindex "DSCP" "inbound"
31540 This option causes the DSCP value associated with the socket for the inbound
31541 connection to be adjusted to a given value, given as one of a number of fixed
31542 strings or to numeric value.
31543 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
31544 Common values include &`throughput`&, &`mincost`&, and on newer systems
31545 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
31547 The outbound packets from Exim will be marked with this value in the header
31548 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
31549 that these values will have any effect, not be stripped by networking
31550 equipment, or do much of anything without cooperation with your Network
31551 Engineer and those of all network operators between the source and destination.
31554 .vitem &*control&~=&~enforce_sync*& &&&
31555 &*control&~=&~no_enforce_sync*&
31556 .cindex "SMTP" "synchronization checking"
31557 .cindex "synchronization checking in SMTP"
31558 These controls make it possible to be selective about when SMTP synchronization
31559 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
31560 state of the switch (it is true by default). See the description of this option
31561 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
31563 The effect of these two controls lasts for the remainder of the SMTP
31564 connection. They can appear in any ACL except the one for the non-SMTP
31565 messages. The most straightforward place to put them is in the ACL defined by
31566 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
31567 before the first synchronization check. The expected use is to turn off the
31568 synchronization checks for badly-behaved hosts that you nevertheless need to
31572 .vitem &*control&~=&~fakedefer/*&<&'message'&>
31573 .cindex "fake defer"
31574 .cindex "defer, fake"
31575 This control works in exactly the same way as &%fakereject%& (described below)
31576 except that it causes an SMTP 450 response after the message data instead of a
31577 550 response. You must take care when using &%fakedefer%& because it causes the
31578 messages to be duplicated when the sender retries. Therefore, you should not
31579 use &%fakedefer%& if the message is to be delivered normally.
31581 .vitem &*control&~=&~fakereject/*&<&'message'&>
31582 .cindex "fake rejection"
31583 .cindex "rejection, fake"
31584 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
31585 words, only when an SMTP message is being received. If Exim accepts the
31586 message, instead the final 250 response, a 550 rejection message is sent.
31587 However, Exim proceeds to deliver the message as normal. The control applies
31588 only to the current message, not to any subsequent ones that may be received in
31589 the same SMTP connection.
31591 The text for the 550 response is taken from the &%control%& modifier. If no
31592 message is supplied, the following is used:
31594 550-Your message has been rejected but is being
31595 550-kept for evaluation.
31596 550-If it was a legitimate message, it may still be
31597 550 delivered to the target recipient(s).
31599 This facility should be used with extreme caution.
31601 .vitem &*control&~=&~freeze*&
31602 .cindex "frozen messages" "forcing in ACL"
31603 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31604 other words, only when a message is being received. If the message is accepted,
31605 it is placed on Exim's queue and frozen. The control applies only to the
31606 current message, not to any subsequent ones that may be received in the same
31609 This modifier can optionally be followed by &`/no_tell`&. If the global option
31610 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
31611 is told about the freezing), provided all the &*control=freeze*& modifiers that
31612 are obeyed for the current message have the &`/no_tell`& option.
31614 .vitem &*control&~=&~no_delay_flush*&
31615 .cindex "SMTP" "output flushing, disabling for delay"
31616 Exim normally flushes SMTP output before implementing a delay in an ACL, to
31617 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31618 use. This control, as long as it is encountered before the &%delay%& modifier,
31619 disables such output flushing.
31621 .vitem &*control&~=&~no_callout_flush*&
31622 .cindex "SMTP" "output flushing, disabling for callout"
31623 Exim normally flushes SMTP output before performing a callout in an ACL, to
31624 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31625 use. This control, as long as it is encountered before the &%verify%& condition
31626 that causes the callout, disables such output flushing.
31628 .vitem &*control&~=&~no_mbox_unspool*&
31629 This control is available when Exim is compiled with the content scanning
31630 extension. Content scanning may require a copy of the current message, or parts
31631 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
31632 or spam scanner. Normally, such copies are deleted when they are no longer
31633 needed. If this control is set, the copies are not deleted. The control applies
31634 only to the current message, not to any subsequent ones that may be received in
31635 the same SMTP connection. It is provided for debugging purposes and is unlikely
31636 to be useful in production.
31638 .vitem &*control&~=&~no_multiline_responses*&
31639 .cindex "multiline responses, suppressing"
31640 This control is permitted for any ACL except the one for non-SMTP messages.
31641 It seems that there are broken clients in use that cannot handle multiline
31642 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
31644 If this control is set, multiline SMTP responses from ACL rejections are
31645 suppressed. One way of doing this would have been to put out these responses as
31646 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
31647 (&"use multiline responses for more"& it says &-- ha!), and some of the
31648 responses might get close to that. So this facility, which is after all only a
31649 sop to broken clients, is implemented by doing two very easy things:
31652 Extra information that is normally output as part of a rejection caused by
31653 sender verification failure is omitted. Only the final line (typically &"sender
31654 verification failed"&) is sent.
31656 If a &%message%& modifier supplies a multiline response, only the first
31660 The setting of the switch can, of course, be made conditional on the
31661 calling host. Its effect lasts until the end of the SMTP connection.
31663 .vitem &*control&~=&~no_pipelining*&
31664 .cindex "PIPELINING" "suppressing advertising"
31665 .cindex "ESMTP extensions" PIPELINING
31666 This control turns off the advertising of the PIPELINING extension to SMTP in
31667 the current session. To be useful, it must be obeyed before Exim sends its
31668 response to an EHLO command. Therefore, it should normally appear in an ACL
31669 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
31670 &%pipelining_advertise_hosts%&.
31672 .vitem &*control&~=&~queue/*&<&'options'&>* &&&
31673 &*control&~=&~queue_only*&
31674 .oindex "&%queue%&"
31675 .oindex "&%queue_only%&"
31676 .cindex "queueing incoming messages"
31677 .cindex queueing "forcing in ACL"
31678 .cindex "first pass routing"
31679 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31680 other words, only when a message is being received. If the message is accepted,
31681 it is placed on Exim's queue and left there for delivery by a subsequent queue
31683 If used with no options set,
31684 no immediate delivery process is started. In other words, it has the
31685 effect as the &%queue_only%& global option or &'-odq'& command-line option.
31687 If the &'first_pass_route'& option is given then
31688 the behaviour is like the command-line &'-oqds'& option;
31689 a delivery process is started which stops short of making
31690 any SMTP delivery. The benefit is that the hints database will be updated for
31691 the message being waiting for a specific host, and a later queue run will be
31692 able to send all such messages on a single connection.
31694 The control only applies to the current message, not to any subsequent ones that
31695 may be received in the same SMTP connection.
31697 .vitem &*control&~=&~submission/*&<&'options'&>
31698 .cindex "message" "submission"
31699 .cindex "submission mode"
31700 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
31701 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
31702 the current message is a submission from a local MUA. In this case, Exim
31703 operates in &"submission mode"&, and applies certain fixups to the message if
31704 necessary. For example, it adds a &'Date:'& header line if one is not present.
31705 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
31706 late (the message has already been created).
31708 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
31709 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
31710 submission mode; the available options for this control are described there.
31711 The control applies only to the current message, not to any subsequent ones
31712 that may be received in the same SMTP connection.
31714 .vitem &*control&~=&~suppress_local_fixups*&
31715 .cindex "submission fixups, suppressing"
31716 This control applies to locally submitted (non TCP/IP) messages, and is the
31717 complement of &`control = submission`&. It disables the fixups that are
31718 normally applied to locally-submitted messages. Specifically:
31721 Any &'Sender:'& header line is left alone (in this respect, it is a
31722 dynamic version of &%local_sender_retain%&).
31724 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
31726 There is no check that &'From:'& corresponds to the actual sender.
31729 This control may be useful when a remotely-originated message is accepted,
31730 passed to some scanning program, and then re-submitted for delivery. It can be
31731 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
31732 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
31735 &*Note:*& This control applies only to the current message, not to any others
31736 that are being submitted at the same time using &%-bs%& or &%-bS%&.
31738 .vitem &*control&~=&~utf8_downconvert*&
31739 This control enables conversion of UTF-8 in message envelope addresses
31741 For details see section &<<SECTi18nMTA>>&.
31745 .section "Summary of message fixup control" "SECTsummesfix"
31746 All four possibilities for message fixups can be specified:
31749 Locally submitted, fixups applied: the default.
31751 Locally submitted, no fixups applied: use
31752 &`control = suppress_local_fixups`&.
31754 Remotely submitted, no fixups applied: the default.
31756 Remotely submitted, fixups applied: use &`control = submission`&.
31761 .section "Adding header lines in ACLs" "SECTaddheadacl"
31762 .cindex "header lines" "adding in an ACL"
31763 .cindex "header lines" "position of added lines"
31764 .cindex "&%add_header%& ACL modifier"
31765 The &%add_header%& modifier can be used to add one or more extra header lines
31766 to an incoming message, as in this example:
31768 warn dnslists = sbl.spamhaus.org : \
31769 dialup.mail-abuse.org
31770 add_header = X-blacklisted-at: $dnslist_domain
31772 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31773 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31774 receiving a message). The message must ultimately be accepted for
31775 &%add_header%& to have any significant effect. You can use &%add_header%& with
31776 any ACL verb, including &%deny%& (though this is potentially useful only in a
31779 Headers will not be added to the message if the modifier is used in
31780 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31782 Leading and trailing newlines are removed from
31783 the data for the &%add_header%& modifier; if it then
31784 contains one or more newlines that
31785 are not followed by a space or a tab, it is assumed to contain multiple header
31786 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
31787 front of any line that is not a valid header line.
31789 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
31790 They are added to the message before processing the DATA and MIME ACLs.
31791 However, if an identical header line is requested more than once, only one copy
31792 is actually added to the message. Further header lines may be accumulated
31793 during the DATA and MIME ACLs, after which they are added to the message, again
31794 with duplicates suppressed. Thus, it is possible to add two identical header
31795 lines to an SMTP message, but only if one is added before DATA and one after.
31796 In the case of non-SMTP messages, new headers are accumulated during the
31797 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
31798 message is rejected after DATA or by the non-SMTP ACL, all added header lines
31799 are included in the entry that is written to the reject log.
31801 .cindex "header lines" "added; visibility of"
31802 Header lines are not visible in string expansions
31804 until they are added to the
31805 message. It follows that header lines defined in the MAIL, RCPT, and predata
31806 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
31807 header lines that are added by the DATA or MIME ACLs are not visible in those
31808 ACLs. Because of this restriction, you cannot use header lines as a way of
31809 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
31810 this, you can use ACL variables, as described in section
31811 &<<SECTaclvariables>>&.
31813 The list of headers yet to be added is given by the &%$headers_added%& variable.
31815 The &%add_header%& modifier acts immediately as it is encountered during the
31816 processing of an ACL. Notice the difference between these two cases:
31818 &`accept add_header = ADDED: some text`&
31819 &` `&<&'some condition'&>
31821 &`accept `&<&'some condition'&>
31822 &` add_header = ADDED: some text`&
31824 In the first case, the header line is always added, whether or not the
31825 condition is true. In the second case, the header line is added only if the
31826 condition is true. Multiple occurrences of &%add_header%& may occur in the same
31827 ACL statement. All those that are encountered before a condition fails are
31830 .cindex "&%warn%& ACL verb"
31831 For compatibility with previous versions of Exim, a &%message%& modifier for a
31832 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
31833 effect only if all the conditions are true, even if it appears before some of
31834 them. Furthermore, only the last occurrence of &%message%& is honoured. This
31835 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
31836 are present on a &%warn%& verb, both are processed according to their
31839 By default, new header lines are added to a message at the end of the existing
31840 header lines. However, you can specify that any particular header line should
31841 be added right at the start (before all the &'Received:'& lines), immediately
31842 after the first block of &'Received:'& lines, or immediately before any line
31843 that is not a &'Received:'& or &'Resent-something:'& header.
31845 This is done by specifying &":at_start:"&, &":after_received:"&, or
31846 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
31847 header line, respectively. (Header text cannot start with a colon, as there has
31848 to be a header name first.) For example:
31850 warn add_header = \
31851 :after_received:X-My-Header: something or other...
31853 If more than one header line is supplied in a single &%add_header%& modifier,
31854 each one is treated independently and can therefore be placed differently. If
31855 you add more than one line at the start, or after the Received: block, they end
31856 up in reverse order.
31858 &*Warning*&: This facility currently applies only to header lines that are
31859 added in an ACL. It does NOT work for header lines that are added in a
31860 system filter or in a router or transport.
31864 .section "Removing header lines in ACLs" "SECTremoveheadacl"
31865 .cindex "header lines" "removing in an ACL"
31866 .cindex "header lines" "position of removed lines"
31867 .cindex "&%remove_header%& ACL modifier"
31868 The &%remove_header%& modifier can be used to remove one or more header lines
31869 from an incoming message, as in this example:
31871 warn message = Remove internal headers
31872 remove_header = x-route-mail1 : x-route-mail2
31874 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31875 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31876 receiving a message). The message must ultimately be accepted for
31877 &%remove_header%& to have any significant effect. You can use &%remove_header%&
31878 with any ACL verb, including &%deny%&, though this is really not useful for
31879 any verb that doesn't result in a delivered message.
31881 Headers will not be removed from the message if the modifier is used in
31882 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31884 More than one header can be removed at the same time by using a colon separated
31885 list of header names. The header matching is case insensitive. Wildcards are
31886 not permitted, nor is list expansion performed, so you cannot use hostlists to
31887 create a list of headers, however both connection and message variable expansion
31888 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
31890 warn hosts = +internal_hosts
31891 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
31892 warn message = Remove internal headers
31893 remove_header = $acl_c_ihdrs
31895 Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
31896 Matching header lines are removed from the message before processing the DATA and MIME ACLs.
31897 If multiple header lines match, all are removed.
31898 There is no harm in attempting to remove the same header twice nor in removing
31899 a non-existent header. Further header lines to be removed may be accumulated
31900 during the DATA and MIME ACLs, after which they are removed from the message,
31901 if present. In the case of non-SMTP messages, headers to be removed are
31902 accumulated during the non-SMTP ACLs, and are removed from the message after
31903 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
31904 ACL, there really is no effect because there is no logging of what headers
31905 would have been removed.
31907 .cindex "header lines" "removed; visibility of"
31908 Header lines are not visible in string expansions until the DATA phase when it
31909 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
31910 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
31911 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
31912 this restriction, you cannot use header lines as a way of controlling data
31913 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
31914 you should instead use ACL variables, as described in section
31915 &<<SECTaclvariables>>&.
31917 The &%remove_header%& modifier acts immediately as it is encountered during the
31918 processing of an ACL. Notice the difference between these two cases:
31920 &`accept remove_header = X-Internal`&
31921 &` `&<&'some condition'&>
31923 &`accept `&<&'some condition'&>
31924 &` remove_header = X-Internal`&
31926 In the first case, the header line is always removed, whether or not the
31927 condition is true. In the second case, the header line is removed only if the
31928 condition is true. Multiple occurrences of &%remove_header%& may occur in the
31929 same ACL statement. All those that are encountered before a condition fails
31932 &*Warning*&: This facility currently applies only to header lines that are
31933 present during ACL processing. It does NOT remove header lines that are added
31934 in a system filter or in a router or transport.
31939 .section "ACL conditions" "SECTaclconditions"
31940 .cindex "&ACL;" "conditions; list of"
31941 Some of the conditions listed in this section are available only when Exim is
31942 compiled with the content-scanning extension. They are included here briefly
31943 for completeness. More detailed descriptions can be found in the discussion on
31944 content scanning in chapter &<<CHAPexiscan>>&.
31946 Not all conditions are relevant in all circumstances. For example, testing
31947 senders and recipients does not make sense in an ACL that is being run as the
31948 result of the arrival of an ETRN command, and checks on message headers can be
31949 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
31950 can use the same condition (with different parameters) more than once in the
31951 same ACL statement. This provides a way of specifying an &"and"& conjunction.
31952 The conditions are as follows:
31956 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
31957 .cindex "&ACL;" "nested"
31958 .cindex "&ACL;" "indirect"
31959 .cindex "&ACL;" "arguments"
31960 .cindex "&%acl%& ACL condition"
31961 The possible values of the argument are the same as for the
31962 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
31963 &"accept"& the condition is true; if it returns &"deny"& the condition is
31964 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
31965 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
31966 condition false. This means that further processing of the &%warn%& verb
31967 ceases, but processing of the ACL continues.
31969 If the argument is a named ACL, up to nine space-separated optional values
31970 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
31971 and $acl_narg is set to the count of values.
31972 Previous values of these variables are restored after the call returns.
31973 The name and values are expanded separately.
31974 Note that spaces in complex expansions which are used as arguments
31975 will act as argument separators.
31977 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
31978 the connection is dropped. If it returns &"discard"&, the verb must be
31979 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
31980 conditions are tested.
31982 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
31983 loops. This condition allows you to use different ACLs in different
31984 circumstances. For example, different ACLs can be used to handle RCPT commands
31985 for different local users or different local domains.
31987 .vitem &*authenticated&~=&~*&<&'string&~list'&>
31988 .cindex "&%authenticated%& ACL condition"
31989 .cindex "authentication" "ACL checking"
31990 .cindex "&ACL;" "testing for authentication"
31991 If the SMTP connection is not authenticated, the condition is false. Otherwise,
31992 the name of the authenticator is tested against the list. To test for
31993 authentication by any authenticator, you can set
31998 .vitem &*condition&~=&~*&<&'string'&>
31999 .cindex "&%condition%& ACL condition"
32000 .cindex "customizing" "ACL condition"
32001 .cindex "&ACL;" "customized test"
32002 .cindex "&ACL;" "testing, customized"
32003 This feature allows you to make up custom conditions. If the result of
32004 expanding the string is an empty string, the number zero, or one of the strings
32005 &"no"& or &"false"&, the condition is false. If the result is any non-zero
32006 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
32007 any other value, some error is assumed to have occurred, and the ACL returns
32008 &"defer"&. However, if the expansion is forced to fail, the condition is
32009 ignored. The effect is to treat it as true, whether it is positive or
32012 .vitem &*decode&~=&~*&<&'location'&>
32013 .cindex "&%decode%& ACL condition"
32014 This condition is available only when Exim is compiled with the
32015 content-scanning extension, and it is allowed only in the ACL defined by
32016 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
32017 If all goes well, the condition is true. It is false only if there are
32018 problems such as a syntax error or a memory shortage. For more details, see
32019 chapter &<<CHAPexiscan>>&.
32021 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
32022 .cindex "&%dnslists%& ACL condition"
32023 .cindex "DNS list" "in ACL"
32024 .cindex "black list (DNS)"
32025 .cindex "&ACL;" "testing a DNS list"
32026 This condition checks for entries in DNS black lists. These are also known as
32027 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
32028 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
32029 different variants of this condition to describe briefly here. See sections
32030 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
32032 .vitem &*domains&~=&~*&<&'domain&~list'&>
32033 .cindex "&%domains%& ACL condition"
32034 .cindex "domain" "ACL checking"
32035 .cindex "&ACL;" "testing a recipient domain"
32036 .vindex "&$domain_data$&"
32037 This condition is relevant only after a RCPT command. It checks that the domain
32038 of the recipient address is in the domain list. If percent-hack processing is
32039 enabled, it is done before this test is done. If the check succeeds with a
32040 lookup, the result of the lookup is placed in &$domain_data$& until the next
32043 &*Note carefully*& (because many people seem to fall foul of this): you cannot
32044 use &%domains%& in a DATA ACL.
32047 .vitem &*encrypted&~=&~*&<&'string&~list'&>
32048 .cindex "&%encrypted%& ACL condition"
32049 .cindex "encryption" "checking in an ACL"
32050 .cindex "&ACL;" "testing for encryption"
32051 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
32052 name of the cipher suite in use is tested against the list. To test for
32053 encryption without testing for any specific cipher suite(s), set
32059 .vitem &*hosts&~=&~*&<&'host&~list'&>
32060 .cindex "&%hosts%& ACL condition"
32061 .cindex "host" "ACL checking"
32062 .cindex "&ACL;" "testing the client host"
32063 This condition tests that the calling host matches the host list. If you have
32064 name lookups or wildcarded host names and IP addresses in the same host list,
32065 you should normally put the IP addresses first. For example, you could have:
32067 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
32069 The lookup in this example uses the host name for its key. This is implied by
32070 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
32071 and it wouldn't matter which way round you had these two items.)
32073 The reason for the problem with host names lies in the left-to-right way that
32074 Exim processes lists. It can test IP addresses without doing any DNS lookups,
32075 but when it reaches an item that requires a host name, it fails if it cannot
32076 find a host name to compare with the pattern. If the above list is given in the
32077 opposite order, the &%accept%& statement fails for a host whose name cannot be
32078 found, even if its IP address is 10.9.8.7.
32080 If you really do want to do the name check first, and still recognize the IP
32081 address even if the name lookup fails, you can rewrite the ACL like this:
32083 accept hosts = dbm;/etc/friendly/hosts
32084 accept hosts = 10.9.8.7
32086 The default action on failing to find the host name is to assume that the host
32087 is not in the list, so the first &%accept%& statement fails. The second
32088 statement can then check the IP address.
32090 .vindex "&$host_data$&"
32091 If a &%hosts%& condition is satisfied by means of a lookup, the result
32092 of the lookup is made available in the &$host_data$& variable. This
32093 allows you, for example, to set up a statement like this:
32095 deny hosts = net-lsearch;/some/file
32096 message = $host_data
32098 which gives a custom error message for each denied host.
32100 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
32101 .cindex "&%local_parts%& ACL condition"
32102 .cindex "local part" "ACL checking"
32103 .cindex "&ACL;" "testing a local part"
32104 .vindex "&$local_part_data$&"
32105 This condition is relevant only after a RCPT command. It checks that the local
32106 part of the recipient address is in the list. If percent-hack processing is
32107 enabled, it is done before this test. If the check succeeds with a lookup, the
32108 result of the lookup is placed in &$local_part_data$&, which remains set until
32109 the next &%local_parts%& test.
32111 .vitem &*malware&~=&~*&<&'option'&>
32112 .cindex "&%malware%& ACL condition"
32113 .cindex "&ACL;" "virus scanning"
32114 .cindex "&ACL;" "scanning for viruses"
32115 This condition is available only when Exim is compiled with the
32116 content-scanning extension
32117 and only after a DATA command.
32118 It causes the incoming message to be scanned for
32119 viruses. For details, see chapter &<<CHAPexiscan>>&.
32121 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32122 .cindex "&%mime_regex%& ACL condition"
32123 .cindex "&ACL;" "testing by regex matching"
32124 This condition is available only when Exim is compiled with the
32125 content-scanning extension, and it is allowed only in the ACL defined by
32126 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
32127 with any of the regular expressions. For details, see chapter
32130 .vitem &*ratelimit&~=&~*&<&'parameters'&>
32131 .cindex "rate limiting"
32132 This condition can be used to limit the rate at which a user or host submits
32133 messages. Details are given in section &<<SECTratelimiting>>&.
32135 .vitem &*recipients&~=&~*&<&'address&~list'&>
32136 .cindex "&%recipients%& ACL condition"
32137 .cindex "recipient" "ACL checking"
32138 .cindex "&ACL;" "testing a recipient"
32139 This condition is relevant only after a RCPT command. It checks the entire
32140 recipient address against a list of recipients.
32142 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32143 .cindex "&%regex%& ACL condition"
32144 .cindex "&ACL;" "testing by regex matching"
32145 This condition is available only when Exim is compiled with the
32146 content-scanning extension, and is available only in the DATA, MIME, and
32147 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
32148 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
32150 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
32151 .cindex "&%sender_domains%& ACL condition"
32152 .cindex "sender" "ACL checking"
32153 .cindex "&ACL;" "testing a sender domain"
32154 .vindex "&$domain$&"
32155 .vindex "&$sender_address_domain$&"
32156 This condition tests the domain of the sender of the message against the given
32157 domain list. &*Note*&: The domain of the sender address is in
32158 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
32159 of this condition. This is an exception to the general rule for testing domain
32160 lists. It is done this way so that, if this condition is used in an ACL for a
32161 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
32162 influence the sender checking.
32164 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32165 relaying, because sender addresses are easily, and commonly, forged.
32167 .vitem &*senders&~=&~*&<&'address&~list'&>
32168 .cindex "&%senders%& ACL condition"
32169 .cindex "sender" "ACL checking"
32170 .cindex "&ACL;" "testing a sender"
32171 This condition tests the sender of the message against the given list. To test
32172 for a bounce message, which has an empty sender, set
32176 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32177 relaying, because sender addresses are easily, and commonly, forged.
32179 .vitem &*spam&~=&~*&<&'username'&>
32180 .cindex "&%spam%& ACL condition"
32181 .cindex "&ACL;" "scanning for spam"
32182 This condition is available only when Exim is compiled with the
32183 content-scanning extension. It causes the incoming message to be scanned by
32184 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
32186 .vitem &*verify&~=&~certificate*&
32187 .cindex "&%verify%& ACL condition"
32188 .cindex "TLS" "client certificate verification"
32189 .cindex "certificate" "verification of client"
32190 .cindex "&ACL;" "certificate verification"
32191 .cindex "&ACL;" "testing a TLS certificate"
32192 This condition is true in an SMTP session if the session is encrypted, and a
32193 certificate was received from the client, and the certificate was verified. The
32194 server requests a certificate only if the client matches &%tls_verify_hosts%&
32195 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
32197 .vitem &*verify&~=&~csa*&
32198 .cindex "CSA verification"
32199 This condition checks whether the sending host (the client) is authorized to
32200 send email. Details of how this works are given in section
32201 &<<SECTverifyCSA>>&.
32203 .vitem &*verify&~=&~header_names_ascii*&
32204 .cindex "&%verify%& ACL condition"
32205 .cindex "&ACL;" "verifying header names only ASCII"
32206 .cindex "header lines" "verifying header names only ASCII"
32207 .cindex "verifying" "header names only ASCII"
32208 This condition is relevant only in an ACL that is run after a message has been
32210 This usually means an ACL specified by &%acl_smtp_data%& or &%acl_not_smtp%&.
32211 It checks all header names (not the content) to make sure
32212 there are no non-ASCII characters, also excluding control characters. The
32213 allowable characters are decimal ASCII values 33 through 126.
32215 Exim itself will handle headers with non-ASCII characters, but it can cause
32216 problems for downstream applications, so this option will allow their
32217 detection and rejection in the DATA ACL's.
32219 .vitem &*verify&~=&~header_sender/*&<&'options'&>
32220 .cindex "&%verify%& ACL condition"
32221 .cindex "&ACL;" "verifying sender in the header"
32222 .cindex "header lines" "verifying the sender in"
32223 .cindex "sender" "verifying in header"
32224 .cindex "verifying" "sender in header"
32225 This condition is relevant only in an ACL that is run after a message has been
32226 received, that is, in an ACL specified by &%acl_smtp_data%& or
32227 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
32228 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
32229 is loosely thought of as a &"sender"& address (hence the name of the test).
32230 However, an address that appears in one of these headers need not be an address
32231 that accepts bounce messages; only sender addresses in envelopes are required
32232 to accept bounces. Therefore, if you use the callout option on this check, you
32233 might want to arrange for a non-empty address in the MAIL command.
32235 Details of address verification and the options are given later, starting at
32236 section &<<SECTaddressverification>>& (callouts are described in section
32237 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
32238 condition to restrict it to bounce messages only:
32241 !verify = header_sender
32242 message = A valid sender header is required for bounces
32245 .vitem &*verify&~=&~header_syntax*&
32246 .cindex "&%verify%& ACL condition"
32247 .cindex "&ACL;" "verifying header syntax"
32248 .cindex "header lines" "verifying syntax"
32249 .cindex "verifying" "header syntax"
32250 This condition is relevant only in an ACL that is run after a message has been
32251 received, that is, in an ACL specified by &%acl_smtp_data%& or
32252 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
32253 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
32254 and &'Bcc:'&), returning true if there are no problems.
32255 Unqualified addresses (local parts without domains) are
32256 permitted only in locally generated messages and from hosts that match
32257 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
32260 Note that this condition is a syntax check only. However, a common spamming
32261 ploy used to be to send syntactically invalid headers such as
32265 and this condition can be used to reject such messages, though they are not as
32266 common as they used to be.
32268 .vitem &*verify&~=&~helo*&
32269 .cindex "&%verify%& ACL condition"
32270 .cindex "&ACL;" "verifying HELO/EHLO"
32271 .cindex "HELO" "verifying"
32272 .cindex "EHLO" "verifying"
32273 .cindex "verifying" "EHLO"
32274 .cindex "verifying" "HELO"
32275 This condition is true if a HELO or EHLO command has been received from the
32276 client host, and its contents have been verified. If there has been no previous
32277 attempt to verify the HELO/EHLO contents, it is carried out when this
32278 condition is encountered. See the description of the &%helo_verify_hosts%& and
32279 &%helo_try_verify_hosts%& options for details of how to request verification
32280 independently of this condition, and for detail of the verification.
32282 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
32283 option), this condition is always true.
32286 .vitem &*verify&~=&~not_blind/*&<&'options'&>
32287 .cindex "verifying" "not blind"
32288 .cindex "bcc recipients, verifying none"
32289 This condition checks that there are no blind (bcc) recipients in the message.
32290 Every envelope recipient must appear either in a &'To:'& header line or in a
32291 &'Cc:'& header line for this condition to be true. Local parts are checked
32292 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
32293 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
32294 used only in a DATA or non-SMTP ACL.
32296 There is one possible option, &`case_insensitive`&. If this is present then
32297 local parts are checked case-insensitively.
32299 There are, of course, many legitimate messages that make use of blind (bcc)
32300 recipients. This check should not be used on its own for blocking messages.
32303 .vitem &*verify&~=&~recipient/*&<&'options'&>
32304 .cindex "&%verify%& ACL condition"
32305 .cindex "&ACL;" "verifying recipient"
32306 .cindex "recipient" "verifying"
32307 .cindex "verifying" "recipient"
32308 .vindex "&$address_data$&"
32309 This condition is relevant only after a RCPT command. It verifies the current
32310 recipient. Details of address verification are given later, starting at section
32311 &<<SECTaddressverification>>&. After a recipient has been verified, the value
32312 of &$address_data$& is the last value that was set while routing the address.
32313 This applies even if the verification fails. When an address that is being
32314 verified is redirected to a single address, verification continues with the new
32315 address, and in that case, the subsequent value of &$address_data$& is the
32316 value for the child address.
32318 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
32319 .cindex "&%verify%& ACL condition"
32320 .cindex "&ACL;" "verifying host reverse lookup"
32321 .cindex "host" "verifying reverse lookup"
32322 This condition ensures that a verified host name has been looked up from the IP
32323 address of the client host. (This may have happened already if the host name
32324 was needed for checking a host list, or if the host matched &%host_lookup%&.)
32325 Verification ensures that the host name obtained from a reverse DNS lookup, or
32326 one of its aliases, does, when it is itself looked up in the DNS, yield the
32327 original IP address.
32329 There is one possible option, &`defer_ok`&. If this is present and a
32330 DNS operation returns a temporary error, the verify condition succeeds.
32332 If this condition is used for a locally generated message (that is, when there
32333 is no client host involved), it always succeeds.
32335 .vitem &*verify&~=&~sender/*&<&'options'&>
32336 .cindex "&%verify%& ACL condition"
32337 .cindex "&ACL;" "verifying sender"
32338 .cindex "sender" "verifying"
32339 .cindex "verifying" "sender"
32340 This condition is relevant only after a MAIL or RCPT command, or after a
32341 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
32342 the message's sender is empty (that is, this is a bounce message), the
32343 condition is true. Otherwise, the sender address is verified.
32345 .vindex "&$address_data$&"
32346 .vindex "&$sender_address_data$&"
32347 If there is data in the &$address_data$& variable at the end of routing, its
32348 value is placed in &$sender_address_data$& at the end of verification. This
32349 value can be used in subsequent conditions and modifiers in the same ACL
32350 statement. It does not persist after the end of the current statement. If you
32351 want to preserve the value for longer, you can save it in an ACL variable.
32353 Details of verification are given later, starting at section
32354 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
32355 to avoid doing it more than once per message.
32357 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
32358 .cindex "&%verify%& ACL condition"
32359 This is a variation of the previous option, in which a modified address is
32360 verified as a sender.
32362 Note that '/' is legal in local-parts; if the address may have such
32363 (eg. is generated from the received message)
32364 they must be protected from the options parsing by doubling:
32366 verify = sender=${listquote{/}{${address:$h_sender:}}}
32372 .section "Using DNS lists" "SECTmorednslists"
32373 .cindex "DNS list" "in ACL"
32374 .cindex "black list (DNS)"
32375 .cindex "&ACL;" "testing a DNS list"
32376 In its simplest form, the &%dnslists%& condition tests whether the calling host
32377 is on at least one of a number of DNS lists by looking up the inverted IP
32378 address in one or more DNS domains. (Note that DNS list domains are not mail
32379 domains, so the &`+`& syntax for named lists doesn't work - it is used for
32380 special options instead.) For example, if the calling host's IP
32381 address is 192.168.62.43, and the ACL statement is
32383 deny dnslists = blackholes.mail-abuse.org : \
32384 dialups.mail-abuse.org
32386 the following records are looked up:
32388 43.62.168.192.blackholes.mail-abuse.org
32389 43.62.168.192.dialups.mail-abuse.org
32391 As soon as Exim finds an existing DNS record, processing of the list stops.
32392 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
32393 to test that a host is on more than one list (an &"and"& conjunction), you can
32394 use two separate conditions:
32396 deny dnslists = blackholes.mail-abuse.org
32397 dnslists = dialups.mail-abuse.org
32399 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
32400 behaves as if the host does not match the list item, that is, as if the DNS
32401 record does not exist. If there are further items in the DNS list, they are
32404 This is usually the required action when &%dnslists%& is used with &%deny%&
32405 (which is the most common usage), because it prevents a DNS failure from
32406 blocking mail. However, you can change this behaviour by putting one of the
32407 following special items in the list:
32409 &`+include_unknown `& behave as if the item is on the list
32410 &`+exclude_unknown `& behave as if the item is not on the list (default)
32411 &`+defer_unknown `& give a temporary error
32413 .cindex "&`+include_unknown`&"
32414 .cindex "&`+exclude_unknown`&"
32415 .cindex "&`+defer_unknown`&"
32416 Each of these applies to any subsequent items on the list. For example:
32418 deny dnslists = +defer_unknown : foo.bar.example
32420 Testing the list of domains stops as soon as a match is found. If you want to
32421 warn for one list and block for another, you can use two different statements:
32423 deny dnslists = blackholes.mail-abuse.org
32424 warn dnslists = dialups.mail-abuse.org
32425 message = X-Warn: sending host is on dialups list
32427 .cindex caching "of dns lookup"
32429 DNS list lookups are cached by Exim for the duration of the SMTP session
32430 (but limited by the DNS return TTL value),
32431 so a lookup based on the IP address is done at most once for any incoming
32432 connection (assuming long-enough TTL).
32433 Exim does not share information between multiple incoming
32434 connections (but your local name server cache should be active).
32436 There are a number of DNS lists to choose from, some commercial, some free,
32437 or free for small deployments. An overview can be found at
32438 &url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists).
32442 .section "Specifying the IP address for a DNS list lookup" "SECID201"
32443 .cindex "DNS list" "keyed by explicit IP address"
32444 By default, the IP address that is used in a DNS list lookup is the IP address
32445 of the calling host. However, you can specify another IP address by listing it
32446 after the domain name, introduced by a slash. For example:
32448 deny dnslists = black.list.tld/192.168.1.2
32450 This feature is not very helpful with explicit IP addresses; it is intended for
32451 use with IP addresses that are looked up, for example, the IP addresses of the
32452 MX hosts or nameservers of an email sender address. For an example, see section
32453 &<<SECTmulkeyfor>>& below.
32458 .section "DNS lists keyed on domain names" "SECID202"
32459 .cindex "DNS list" "keyed by domain name"
32460 There are some lists that are keyed on domain names rather than inverted IP
32461 addresses (see, e.g., the &'domain based zones'& link at
32462 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
32463 with these lists. You can change the name that is looked up in a DNS list by
32464 listing it after the domain name, introduced by a slash. For example,
32466 deny dnslists = dsn.rfc-ignorant.org/$sender_address_domain
32467 message = Sender's domain is listed at $dnslist_domain
32469 This particular example is useful only in ACLs that are obeyed after the
32470 RCPT or DATA commands, when a sender address is available. If (for
32471 example) the message's sender is &'user@tld.example'& the name that is looked
32472 up by this example is
32474 tld.example.dsn.rfc-ignorant.org
32476 A single &%dnslists%& condition can contain entries for both names and IP
32477 addresses. For example:
32479 deny dnslists = sbl.spamhaus.org : \
32480 dsn.rfc-ignorant.org/$sender_address_domain
32482 The first item checks the sending host's IP address; the second checks a domain
32483 name. The whole condition is true if either of the DNS lookups succeeds.
32488 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
32489 .cindex "DNS list" "multiple keys for"
32490 The syntax described above for looking up explicitly-defined values (either
32491 names or IP addresses) in a DNS blacklist is a simplification. After the domain
32492 name for the DNS list, what follows the slash can in fact be a list of items.
32493 As with all lists in Exim, the default separator is a colon. However, because
32494 this is a sublist within the list of DNS blacklist domains, it is necessary
32495 either to double the separators like this:
32497 dnslists = black.list.tld/name.1::name.2
32499 or to change the separator character, like this:
32501 dnslists = black.list.tld/<;name.1;name.2
32503 If an item in the list is an IP address, it is inverted before the DNS
32504 blacklist domain is appended. If it is not an IP address, no inversion
32505 occurs. Consider this condition:
32507 dnslists = black.list.tld/<;192.168.1.2;a.domain
32509 The DNS lookups that occur are:
32511 2.1.168.192.black.list.tld
32512 a.domain.black.list.tld
32514 Once a DNS record has been found (that matches a specific IP return
32515 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
32516 are done. If there is a temporary DNS error, the rest of the sublist of domains
32517 or IP addresses is tried. A temporary error for the whole dnslists item occurs
32518 only if no other DNS lookup in this sublist succeeds. In other words, a
32519 successful lookup for any of the items in the sublist overrides a temporary
32520 error for a previous item.
32522 The ability to supply a list of items after the slash is in some sense just a
32523 syntactic convenience. These two examples have the same effect:
32525 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
32526 dnslists = black.list.tld/a.domain::b.domain
32528 However, when the data for the list is obtained from a lookup, the second form
32529 is usually much more convenient. Consider this example:
32531 deny dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
32532 ${lookup dnsdb {>|mxh=\
32533 $sender_address_domain} }} }
32534 message = The mail servers for the domain \
32535 $sender_address_domain \
32536 are listed at $dnslist_domain ($dnslist_value); \
32539 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
32540 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
32541 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
32542 of expanding the condition might be something like this:
32544 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
32546 Thus, this example checks whether or not the IP addresses of the sender
32547 domain's mail servers are on the Spamhaus black list.
32549 The key that was used for a successful DNS list lookup is put into the variable
32550 &$dnslist_matched$& (see section &<<SECID204>>&).
32555 .section "Data returned by DNS lists" "SECID203"
32556 .cindex "DNS list" "data returned from"
32557 DNS lists are constructed using address records in the DNS. The original RBL
32558 just used the address 127.0.0.1 on the right hand side of each record, but the
32559 RBL+ list and some other lists use a number of values with different meanings.
32560 The values used on the RBL+ list are:
32564 127.1.0.3 DUL and RBL
32566 127.1.0.5 RSS and RBL
32567 127.1.0.6 RSS and DUL
32568 127.1.0.7 RSS and DUL and RBL
32570 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
32571 different values. Some DNS lists may return more than one address record;
32572 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
32575 Values returned by a properly running DBSBL should be in the 127.0.0.0/8
32576 range. If a DNSBL operator loses control of the domain, lookups on it
32577 may start returning other addresses. Because of this, Exim now ignores
32578 returned values outside the 127/8 region.
32582 .section "Variables set from DNS lists" "SECID204"
32583 .cindex "expansion" "variables, set from DNS list"
32584 .cindex "DNS list" "variables set from"
32585 .vindex "&$dnslist_domain$&"
32586 .vindex "&$dnslist_matched$&"
32587 .vindex "&$dnslist_text$&"
32588 .vindex "&$dnslist_value$&"
32589 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
32590 the name of the overall domain that matched (for example,
32591 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
32592 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
32593 the DNS record. When the key is an IP address, it is not reversed in
32594 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
32595 cases, for example:
32597 deny dnslists = spamhaus.example
32599 the key is also available in another variable (in this case,
32600 &$sender_host_address$&). In more complicated cases, however, this is not true.
32601 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
32602 might generate a dnslists lookup like this:
32604 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
32606 If this condition succeeds, the value in &$dnslist_matched$& might be
32607 &`192.168.6.7`& (for example).
32609 If more than one address record is returned by the DNS lookup, all the IP
32610 addresses are included in &$dnslist_value$&, separated by commas and spaces.
32611 The variable &$dnslist_text$& contains the contents of any associated TXT
32612 record. For lists such as RBL+ the TXT record for a merged entry is often not
32613 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
32616 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
32617 &-- even if these appear before the condition in the ACL, they are not
32618 expanded until after it has failed. For example:
32620 deny hosts = !+local_networks
32621 message = $sender_host_address is listed \
32623 dnslists = rbl-plus.mail-abuse.example
32628 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
32629 .cindex "DNS list" "matching specific returned data"
32630 You can add an equals sign and an IP address after a &%dnslists%& domain name
32631 in order to restrict its action to DNS records with a matching right hand side.
32634 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
32636 rejects only those hosts that yield 127.0.0.2. Without this additional data,
32637 any address record is considered to be a match. For the moment, we assume
32638 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
32639 describes how multiple records are handled.
32641 More than one IP address may be given for checking, using a comma as a
32642 separator. These are alternatives &-- if any one of them matches, the
32643 &%dnslists%& condition is true. For example:
32645 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32647 If you want to specify a constraining address list and also specify names or IP
32648 addresses to be looked up, the constraining address list must be specified
32649 first. For example:
32651 deny dnslists = dsn.rfc-ignorant.org\
32652 =127.0.0.2/$sender_address_domain
32655 If the character &`&&`& is used instead of &`=`&, the comparison for each
32656 listed IP address is done by a bitwise &"and"& instead of by an equality test.
32657 In other words, the listed addresses are used as bit masks. The comparison is
32658 true if all the bits in the mask are present in the address that is being
32659 tested. For example:
32661 dnslists = a.b.c&0.0.0.3
32663 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
32664 want to test whether one bit or another bit is present (as opposed to both
32665 being present), you must use multiple values. For example:
32667 dnslists = a.b.c&0.0.0.1,0.0.0.2
32669 matches if the final component of the address is an odd number or two times
32674 .section "Negated DNS matching conditions" "SECID205"
32675 You can supply a negative list of IP addresses as part of a &%dnslists%&
32678 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32680 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32681 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
32683 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
32685 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32686 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
32687 words, the result of the test is inverted if an exclamation mark appears before
32688 the &`=`& (or the &`&&`&) sign.
32690 &*Note*&: This kind of negation is not the same as negation in a domain,
32691 host, or address list (which is why the syntax is different).
32693 If you are using just one list, the negation syntax does not gain you much. The
32694 previous example is precisely equivalent to
32696 deny dnslists = a.b.c
32697 !dnslists = a.b.c=127.0.0.2,127.0.0.3
32699 However, if you are using multiple lists, the negation syntax is clearer.
32700 Consider this example:
32702 deny dnslists = sbl.spamhaus.org : \
32704 dnsbl.njabl.org!=127.0.0.3 : \
32707 Using only positive lists, this would have to be:
32709 deny dnslists = sbl.spamhaus.org : \
32711 deny dnslists = dnsbl.njabl.org
32712 !dnslists = dnsbl.njabl.org=127.0.0.3
32713 deny dnslists = relays.ordb.org
32715 which is less clear, and harder to maintain.
32717 Negation can also be used with a bitwise-and restriction.
32718 The dnslists condition with only be trus if a result is returned
32719 by the lookup which, anded with the restriction, is all zeroes.
32722 deny dnslists = zen.spamhaus.org!&0.255.255.0
32728 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
32729 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
32730 thereby providing more than one IP address. When an item in a &%dnslists%& list
32731 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
32732 the match to specific results from the DNS lookup, there are two ways in which
32733 the checking can be handled. For example, consider the condition:
32735 dnslists = a.b.c=127.0.0.1
32737 What happens if the DNS lookup for the incoming IP address yields both
32738 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
32739 condition true because at least one given value was found, or is it false
32740 because at least one of the found values was not listed? And how does this
32741 affect negated conditions? Both possibilities are provided for with the help of
32742 additional separators &`==`& and &`=&&`&.
32745 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
32746 IP addresses matches one of the listed addresses. For the example above, the
32747 condition is true because 127.0.0.1 matches.
32749 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
32750 looked up IP addresses matches one of the listed addresses. If the condition is
32753 dnslists = a.b.c==127.0.0.1
32755 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32756 false because 127.0.0.2 is not listed. You would need to have:
32758 dnslists = a.b.c==127.0.0.1,127.0.0.2
32760 for the condition to be true.
32763 When &`!`& is used to negate IP address matching, it inverts the result, giving
32764 the precise opposite of the behaviour above. Thus:
32766 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
32767 addresses matches one of the listed addresses. Consider:
32769 dnslists = a.b.c!&0.0.0.1
32771 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32772 false because 127.0.0.1 matches.
32774 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
32775 looked up IP address that does not match. Consider:
32777 dnslists = a.b.c!=&0.0.0.1
32779 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32780 true, because 127.0.0.2 does not match. You would need to have:
32782 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
32784 for the condition to be false.
32786 When the DNS lookup yields only a single IP address, there is no difference
32787 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
32792 .section "Detailed information from merged DNS lists" "SECTmordetinf"
32793 .cindex "DNS list" "information from merged"
32794 When the facility for restricting the matching IP values in a DNS list is used,
32795 the text from the TXT record that is set in &$dnslist_text$& may not reflect
32796 the true reason for rejection. This happens when lists are merged and the IP
32797 address in the A record is used to distinguish them; unfortunately there is
32798 only one TXT record. One way round this is not to use merged lists, but that
32799 can be inefficient because it requires multiple DNS lookups where one would do
32800 in the vast majority of cases when the host of interest is not on any of the
32803 A less inefficient way of solving this problem is available. If
32804 two domain names, comma-separated, are given, the second is used first to
32805 do an initial check, making use of any IP value restrictions that are set.
32806 If there is a match, the first domain is used, without any IP value
32807 restrictions, to get the TXT record. As a byproduct of this, there is also
32808 a check that the IP being tested is indeed on the first list. The first
32809 domain is the one that is put in &$dnslist_domain$&. For example:
32812 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
32813 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32815 rejected because $sender_host_address is blacklisted \
32816 at $dnslist_domain\n$dnslist_text
32818 For the first blacklist item, this starts by doing a lookup in
32819 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
32820 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
32821 value, and as long as something is found, it looks for the corresponding TXT
32822 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
32823 The second blacklist item is processed similarly.
32825 If you are interested in more than one merged list, the same list must be
32826 given several times, but because the results of the DNS lookups are cached,
32827 the DNS calls themselves are not repeated. For example:
32830 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
32831 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
32832 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
32833 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32835 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
32836 values matches (or if no record is found), this is the only lookup that is
32837 done. Only if there is a match is one of the more specific lists consulted.
32841 .section "DNS lists and IPv6" "SECTmorednslistslast"
32842 .cindex "IPv6" "DNS black lists"
32843 .cindex "DNS list" "IPv6 usage"
32844 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
32845 nibble by nibble. For example, if the calling host's IP address is
32846 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
32848 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
32849 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
32851 (split over two lines here to fit on the page). Unfortunately, some of the DNS
32852 lists contain wildcard records, intended for IPv4, that interact badly with
32853 IPv6. For example, the DNS entry
32855 *.3.some.list.example. A 127.0.0.1
32857 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
32858 Unfortunately, it also matches the entire 3::/4 IPv6 network.
32860 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
32861 &%condition%& condition, as in this example:
32863 deny condition = ${if isip4{$sender_host_address}}
32864 dnslists = some.list.example
32867 If an explicit key is being used for a DNS lookup and it may be an IPv6
32868 address you should specify alternate list separators for both the outer
32869 (DNS list name) list and inner (lookup keys) list:
32871 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
32874 .section "Rate limiting incoming messages" "SECTratelimiting"
32875 .cindex "rate limiting" "client sending"
32876 .cindex "limiting client sending rates"
32877 .oindex "&%smtp_ratelimit_*%&"
32878 The &%ratelimit%& ACL condition can be used to measure and control the rate at
32879 which clients can send email. This is more powerful than the
32880 &%smtp_ratelimit_*%& options, because those options control the rate of
32881 commands in a single SMTP session only, whereas the &%ratelimit%& condition
32882 works across all connections (concurrent and sequential) from the same client
32883 host. The syntax of the &%ratelimit%& condition is:
32885 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
32887 If the average client sending rate is less than &'m'& messages per time
32888 period &'p'& then the condition is false; otherwise it is true.
32890 As a side-effect, the &%ratelimit%& condition sets the expansion variable
32891 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
32892 configured value of &'m'&, and &$sender_rate_period$& to the configured value
32895 The parameter &'p'& is the smoothing time constant, in the form of an Exim
32896 time interval, for example, &`8h`& for eight hours. A larger time constant
32897 means that it takes Exim longer to forget a client's past behaviour. The
32898 parameter &'m'& is the maximum number of messages that a client is permitted to
32899 send in each time interval. It also specifies the number of messages permitted
32900 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
32901 constant, you can allow a client to send more messages in a burst without
32902 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
32903 both small, messages must be sent at an even rate.
32905 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
32906 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
32907 when deploying the &%ratelimit%& ACL condition. The script prints usage
32908 instructions when it is run with no arguments.
32910 The key is used to look up the data for calculating the client's average
32911 sending rate. This data is stored in Exim's spool directory, alongside the
32912 retry and other hints databases. The default key is &$sender_host_address$&,
32913 which means Exim computes the sending rate of each client host IP address.
32914 By changing the key you can change how Exim identifies clients for the purpose
32915 of ratelimiting. For example, to limit the sending rate of each authenticated
32916 user, independent of the computer they are sending from, set the key to
32917 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
32918 example, &$authenticated_id$& is only meaningful if the client has
32919 authenticated (which you can check with the &%authenticated%& ACL condition).
32921 The lookup key does not have to identify clients: If you want to limit the
32922 rate at which a recipient receives messages, you can use the key
32923 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
32926 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
32927 specifies what Exim measures the rate of, for example, messages or recipients
32928 or bytes. You can adjust the measurement using the &%unique=%& and/or
32929 &%count=%& options. You can also control when Exim updates the recorded rate
32930 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
32931 separated by a slash, like the other parameters. They may appear in any order.
32933 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
32934 any options that alter the meaning of the stored data. The limit &'m'& is not
32935 stored, so you can alter the configured maximum rate and Exim will still
32936 remember clients' past behaviour. If you change the &%per_*%& mode or add or
32937 remove the &%unique=%& option, the lookup key changes so Exim will forget past
32938 behaviour. The lookup key is not affected by changes to the update mode and
32939 the &%count=%& option.
32942 .section "Ratelimit options for what is being measured" "ratoptmea"
32943 .cindex "rate limiting" "per_* options"
32944 The &%per_conn%& option limits the client's connection rate. It is not
32945 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
32946 &%acl_not_smtp_start%& ACLs.
32948 The &%per_mail%& option limits the client's rate of sending messages. This is
32949 the default if none of the &%per_*%& options is specified. It can be used in
32950 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
32951 &%acl_smtp_data%&, or &%acl_not_smtp%&.
32953 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
32954 the same ACLs as the &%per_mail%& option, though it is best to use this option
32955 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
32956 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
32957 in its MAIL command, which may be inaccurate or completely missing. You can
32958 follow the limit &'m'& in the configuration with K, M, or G to specify limits
32959 in kilobytes, megabytes, or gigabytes, respectively.
32961 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
32962 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
32963 &%acl_smtp_mime%&, or &%acl_smtp_data%& ACLs. In
32964 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
32965 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
32966 in either case the rate limiting engine will see a message with many
32967 recipients as a large high-speed burst.
32969 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
32970 number of different recipients that the client has sent messages to in the
32971 last time period. That is, if the client repeatedly sends messages to the same
32972 recipient, its measured rate is not increased. This option can only be used in
32975 The &%per_cmd%& option causes Exim to recompute the rate every time the
32976 condition is processed. This can be used to limit the rate of any SMTP
32977 command. If it is used in multiple ACLs it can limit the aggregate rate of
32978 multiple different commands.
32980 The &%count=%& option can be used to alter how much Exim adds to the client's
32981 measured rate. For example, the &%per_byte%& option is equivalent to
32982 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
32983 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
32984 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
32986 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
32989 .section "Ratelimit update modes" "ratoptupd"
32990 .cindex "rate limiting" "reading data without updating"
32991 You can specify one of three options with the &%ratelimit%& condition to
32992 control when its database is updated. This section describes the &%readonly%&
32993 mode, and the next section describes the &%strict%& and &%leaky%& modes.
32995 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
32996 previously-computed rate to check against the limit.
32998 For example, you can test the client's sending rate and deny it access (when
32999 it is too fast) in the connect ACL. If the client passes this check then it
33000 can go on to send a message, in which case its recorded rate will be updated
33001 in the MAIL ACL. Subsequent connections from the same client will check this
33005 deny ratelimit = 100 / 5m / readonly
33006 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
33007 (max $sender_rate_limit)
33010 warn ratelimit = 100 / 5m / strict
33011 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
33012 (max $sender_rate_limit)
33015 If Exim encounters multiple &%ratelimit%& conditions with the same key when
33016 processing a message then it may increase the client's measured rate more than
33017 it should. For example, this will happen if you check the &%per_rcpt%& option
33018 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
33019 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
33020 multiple update problems by using the &%readonly%& option on later ratelimit
33023 The &%per_*%& options described above do not make sense in some ACLs. If you
33024 use a &%per_*%& option in an ACL where it is not normally permitted then the
33025 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
33026 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
33027 next section) so you must specify the &%readonly%& option explicitly.
33030 .section "Ratelimit options for handling fast clients" "ratoptfast"
33031 .cindex "rate limiting" "strict and leaky modes"
33032 If a client's average rate is greater than the maximum, the rate limiting
33033 engine can react in two possible ways, depending on the presence of the
33034 &%strict%& or &%leaky%& update modes. This is independent of the other
33035 counter-measures (such as rejecting the message) that may be specified by the
33038 The &%leaky%& (default) option means that the client's recorded rate is not
33039 updated if it is above the limit. The effect of this is that Exim measures the
33040 client's average rate of successfully sent email,
33041 up to the given limit.
33042 This is appropriate if the countermeasure when the condition is true
33043 consists of refusing the message, and
33044 is generally the better choice if you have clients that retry automatically.
33045 If the action when true is anything more complex then this option is
33046 likely not what is wanted.
33048 The &%strict%& option means that the client's recorded rate is always
33049 updated. The effect of this is that Exim measures the client's average rate
33050 of attempts to send email, which can be much higher than the maximum it is
33051 actually allowed. If the client is over the limit it may be subjected to
33052 counter-measures by the ACL. It must slow down and allow sufficient time to
33053 pass that its computed rate falls below the maximum before it can send email
33054 again. The time (the number of smoothing periods) it must wait and not
33055 attempt to send mail can be calculated with this formula:
33057 ln(peakrate/maxrate)
33061 .section "Limiting the rate of different events" "ratoptuniq"
33062 .cindex "rate limiting" "counting unique events"
33063 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
33064 rate of different events. For example, the &%per_addr%& option uses this
33065 mechanism to count the number of different recipients that the client has
33066 sent messages to in the last time period; it is equivalent to
33067 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
33068 measure the rate that a client uses different sender addresses with the
33069 options &`per_mail/unique=$sender_address`&.
33071 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
33072 has seen for that key. The whole set is thrown away when it is older than the
33073 rate smoothing period &'p'&, so each different event is counted at most once
33074 per period. In the &%leaky%& update mode, an event that causes the client to
33075 go over the limit is not added to the set, in the same way that the client's
33076 recorded rate is not updated in the same situation.
33078 When you combine the &%unique=%& and &%readonly%& options, the specific
33079 &%unique=%& value is ignored, and Exim just retrieves the client's stored
33082 The &%unique=%& mechanism needs more space in the ratelimit database than the
33083 other &%ratelimit%& options in order to store the event set. The number of
33084 unique values is potentially as large as the rate limit, so the extra space
33085 required increases with larger limits.
33087 The uniqueification is not perfect: there is a small probability that Exim
33088 will think a new event has happened before. If the sender's rate is less than
33089 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
33090 the measured rate can go above the limit, in which case Exim may under-count
33091 events by a significant margin. Fortunately, if the rate is high enough (2.7
33092 times the limit) that the false positive rate goes above 9%, then Exim will
33093 throw away the over-full event set before the measured rate falls below the
33094 limit. Therefore the only harm should be that exceptionally high sending rates
33095 are logged incorrectly; any countermeasures you configure will be as effective
33099 .section "Using rate limiting" "useratlim"
33100 Exim's other ACL facilities are used to define what counter-measures are taken
33101 when the rate limit is exceeded. This might be anything from logging a warning
33102 (for example, while measuring existing sending rates in order to define
33103 policy), through time delays to slow down fast senders, up to rejecting the
33104 message. For example:
33106 # Log all senders' rates
33107 warn ratelimit = 0 / 1h / strict
33108 log_message = Sender rate $sender_rate / $sender_rate_period
33110 # Slow down fast senders; note the need to truncate $sender_rate
33111 # at the decimal point.
33112 warn ratelimit = 100 / 1h / per_rcpt / strict
33113 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
33114 $sender_rate_limit }s
33116 # Keep authenticated users under control
33117 deny authenticated = *
33118 ratelimit = 100 / 1d / strict / $authenticated_id
33120 # System-wide rate limit
33121 defer ratelimit = 10 / 1s / $primary_hostname
33122 message = Sorry, too busy. Try again later.
33124 # Restrict incoming rate from each host, with a default
33125 # set using a macro and special cases looked up in a table.
33126 defer ratelimit = ${lookup {$sender_host_address} \
33127 cdb {DB/ratelimits.cdb} \
33128 {$value} {RATELIMIT} }
33129 message = Sender rate exceeds $sender_rate_limit \
33130 messages per $sender_rate_period
33132 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
33133 especially with the &%per_rcpt%& option, you may suffer from a performance
33134 bottleneck caused by locking on the ratelimit hints database. Apart from
33135 making your ACLs less complicated, you can reduce the problem by using a
33136 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
33137 this means that Exim will lose its hints data after a reboot (including retry
33138 hints, the callout cache, and ratelimit data).
33142 .section "Address verification" "SECTaddressverification"
33143 .cindex "verifying address" "options for"
33144 .cindex "policy control" "address verification"
33145 Several of the &%verify%& conditions described in section
33146 &<<SECTaclconditions>>& cause addresses to be verified. Section
33147 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
33148 The verification conditions can be followed by options that modify the
33149 verification process. The options are separated from the keyword and from each
33150 other by slashes, and some of them contain parameters. For example:
33152 verify = sender/callout
33153 verify = recipient/defer_ok/callout=10s,defer_ok
33155 The first stage of address verification, which always happens, is to run the
33156 address through the routers, in &"verify mode"&. Routers can detect the
33157 difference between verification and routing for delivery, and their actions can
33158 be varied by a number of generic options such as &%verify%& and &%verify_only%&
33159 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
33160 The available options are as follows:
33163 If the &%callout%& option is specified, successful routing to one or more
33164 remote hosts is followed by a &"callout"& to those hosts as an additional
33165 check. Callouts and their sub-options are discussed in the next section.
33167 If there is a defer error while doing verification routing, the ACL
33168 normally returns &"defer"&. However, if you include &%defer_ok%& in the
33169 options, the condition is forced to be true instead. Note that this is a main
33170 verification option as well as a suboption for callouts.
33172 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
33173 discusses the reporting of sender address verification failures.
33175 The &%success_on_redirect%& option causes verification always to succeed
33176 immediately after a successful redirection. By default, if a redirection
33177 generates just one address, that address is also verified. See further
33178 discussion in section &<<SECTredirwhilveri>>&.
33181 If the &%quota%& option is specified for recipient verify,
33182 successful routing to an appendfile transport is followed by a call into
33183 the transport to evaluate the quota status for the recipient.
33184 No actual delivery is done, but verification will succeed if the quota
33185 is sufficient for the message (if the sender gave a message size) or
33186 not already exceeded (otherwise).
33190 .cindex "verifying address" "differentiating failures"
33191 .vindex "&$recipient_verify_failure$&"
33192 .vindex "&$sender_verify_failure$&"
33193 .vindex "&$acl_verify_message$&"
33194 After an address verification failure, &$acl_verify_message$& contains the
33195 error message that is associated with the failure. It can be preserved by
33198 warn !verify = sender
33199 set acl_m0 = $acl_verify_message
33201 If you are writing your own custom rejection message or log message when
33202 denying access, you can use this variable to include information about the
33203 verification failure.
33205 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
33206 appropriate) contains one of the following words:
33209 &%qualify%&: The address was unqualified (no domain), and the message
33210 was neither local nor came from an exempted host.
33212 &%route%&: Routing failed.
33214 &%mail%&: Routing succeeded, and a callout was attempted; rejection
33215 occurred at or before the MAIL command (that is, on initial
33216 connection, HELO, or MAIL).
33218 &%recipient%&: The RCPT command in a callout was rejected.
33220 &%postmaster%&: The postmaster check in a callout was rejected.
33223 &%quota%&: The quota check for a local recipient did non pass.
33226 The main use of these variables is expected to be to distinguish between
33227 rejections of MAIL and rejections of RCPT in callouts.
33229 The above variables may also be set after a &*successful*&
33230 address verification to:
33233 &%random%&: A random local-part callout succeeded
33239 .section "Callout verification" "SECTcallver"
33240 .cindex "verifying address" "by callout"
33241 .cindex "callout" "verification"
33242 .cindex "SMTP" "callout verification"
33243 For non-local addresses, routing verifies the domain, but is unable to do any
33244 checking of the local part. There are situations where some means of verifying
33245 the local part is desirable. One way this can be done is to make an SMTP
33246 &'callback'& to a delivery host for the sender address or a &'callforward'& to
33247 a subsequent host for a recipient address, to see if the host accepts the
33248 address. We use the term &'callout'& to cover both cases. Note that for a
33249 sender address, the callback is not to the client host that is trying to
33250 deliver the message, but to one of the hosts that accepts incoming mail for the
33253 Exim does not do callouts by default. If you want them to happen, you must
33254 request them by setting appropriate options on the &%verify%& condition, as
33255 described below. This facility should be used with care, because it can add a
33256 lot of resource usage to the cost of verifying an address. However, Exim does
33257 cache the results of callouts, which helps to reduce the cost. Details of
33258 caching are in section &<<SECTcallvercache>>&.
33260 Recipient callouts are usually used only between hosts that are controlled by
33261 the same administration. For example, a corporate gateway host could use
33262 callouts to check for valid recipients on an internal mailserver. A successful
33263 callout does not guarantee that a real delivery to the address would succeed;
33264 on the other hand, a failing callout does guarantee that a delivery would fail.
33266 If the &%callout%& option is present on a condition that verifies an address, a
33267 second stage of verification occurs if the address is successfully routed to
33268 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
33269 &(manualroute)& router, where the router specifies the hosts. However, if a
33270 router that does not set up hosts routes to an &(smtp)& transport with a
33271 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
33272 &%hosts_override%& set, its hosts are always used, whether or not the router
33273 supplies a host list.
33274 Callouts are only supported on &(smtp)& transports.
33276 The port that is used is taken from the transport, if it is specified and is a
33277 remote transport. (For routers that do verification only, no transport need be
33278 specified.) Otherwise, the default SMTP port is used. If a remote transport
33279 specifies an outgoing interface, this is used; otherwise the interface is not
33280 specified. Likewise, the text that is used for the HELO command is taken from
33281 the transport's &%helo_data%& option; if there is no transport, the value of
33282 &$smtp_active_hostname$& is used.
33284 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
33285 test whether a bounce message could be delivered to the sender address. The
33286 following SMTP commands are sent:
33288 &`HELO `&<&'local host name'&>
33290 &`RCPT TO:`&<&'the address to be tested'&>
33293 LHLO is used instead of HELO if the transport's &%protocol%& option is
33296 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
33299 A recipient callout check is similar. By default, it also uses an empty address
33300 for the sender. This default is chosen because most hosts do not make use of
33301 the sender address when verifying a recipient. Using the same address means
33302 that a single cache entry can be used for each recipient. Some sites, however,
33303 do make use of the sender address when verifying. These are catered for by the
33304 &%use_sender%& and &%use_postmaster%& options, described in the next section.
33306 If the response to the RCPT command is a 2&'xx'& code, the verification
33307 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
33308 Exim tries the next host, if any. If there is a problem with all the remote
33309 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
33310 &%callout%& option is given, in which case the condition is forced to succeed.
33312 .cindex "SMTP" "output flushing, disabling for callout"
33313 A callout may take a little time. For this reason, Exim normally flushes SMTP
33314 output before performing a callout in an ACL, to avoid unexpected timeouts in
33315 clients when the SMTP PIPELINING extension is in use. The flushing can be
33316 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
33321 .section "Additional parameters for callouts" "CALLaddparcall"
33322 .cindex "callout" "additional parameters for"
33323 The &%callout%& option can be followed by an equals sign and a number of
33324 optional parameters, separated by commas. For example:
33326 verify = recipient/callout=10s,defer_ok
33328 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
33329 separate verify options, is retained for backwards compatibility, but is now
33330 deprecated. The additional parameters for &%callout%& are as follows:
33334 .vitem <&'a&~time&~interval'&>
33335 .cindex "callout" "timeout, specifying"
33336 This specifies the timeout that applies for the callout attempt to each host.
33339 verify = sender/callout=5s
33341 The default is 30 seconds. The timeout is used for each response from the
33342 remote host. It is also used for the initial connection, unless overridden by
33343 the &%connect%& parameter.
33346 .vitem &*connect&~=&~*&<&'time&~interval'&>
33347 .cindex "callout" "connection timeout, specifying"
33348 This parameter makes it possible to set a different (usually smaller) timeout
33349 for making the SMTP connection. For example:
33351 verify = sender/callout=5s,connect=1s
33353 If not specified, this timeout defaults to the general timeout value.
33355 .vitem &*defer_ok*&
33356 .cindex "callout" "defer, action on"
33357 When this parameter is present, failure to contact any host, or any other kind
33358 of temporary error, is treated as success by the ACL. However, the cache is not
33359 updated in this circumstance.
33361 .vitem &*fullpostmaster*&
33362 .cindex "callout" "full postmaster check"
33363 This operates like the &%postmaster%& option (see below), but if the check for
33364 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
33365 accordance with the specification in RFC 2821. The RFC states that the
33366 unqualified address &'postmaster'& should be accepted.
33369 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
33370 .cindex "callout" "sender when verifying header"
33371 When verifying addresses in header lines using the &%header_sender%&
33372 verification option, Exim behaves by default as if the addresses are envelope
33373 sender addresses from a message. Callout verification therefore tests to see
33374 whether a bounce message could be delivered, by using an empty address in the
33375 MAIL command. However, it is arguable that these addresses might never be used
33376 as envelope senders, and could therefore justifiably reject bounce messages
33377 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
33378 address to use in the MAIL command. For example:
33380 require verify = header_sender/callout=mailfrom=abcd@x.y.z
33382 This parameter is available only for the &%header_sender%& verification option.
33385 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
33386 .cindex "callout" "overall timeout, specifying"
33387 This parameter sets an overall timeout for performing a callout verification.
33390 verify = sender/callout=5s,maxwait=30s
33392 This timeout defaults to four times the callout timeout for individual SMTP
33393 commands. The overall timeout applies when there is more than one host that can
33394 be tried. The timeout is checked before trying the next host. This prevents
33395 very long delays if there are a large number of hosts and all are timing out
33396 (for example, when network connections are timing out).
33399 .vitem &*no_cache*&
33400 .cindex "callout" "cache, suppressing"
33401 .cindex "caching callout, suppressing"
33402 When this parameter is given, the callout cache is neither read nor updated.
33404 .vitem &*postmaster*&
33405 .cindex "callout" "postmaster; checking"
33406 When this parameter is set, a successful callout check is followed by a similar
33407 check for the local part &'postmaster'& at the same domain. If this address is
33408 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
33409 the postmaster check is recorded in a cache record; if it is a failure, this is
33410 used to fail subsequent callouts for the domain without a connection being
33411 made, until the cache record expires.
33413 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
33414 The postmaster check uses an empty sender in the MAIL command by default.
33415 You can use this parameter to do a postmaster check using a different address.
33418 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
33420 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
33421 one overrides. The &%postmaster%& parameter is equivalent to this example:
33423 require verify = sender/callout=postmaster_mailfrom=
33425 &*Warning*&: The caching arrangements for postmaster checking do not take
33426 account of the sender address. It is assumed that either the empty address or
33427 a fixed non-empty address will be used. All that Exim remembers is that the
33428 postmaster check for the domain succeeded or failed.
33432 .cindex "callout" "&""random""& check"
33433 When this parameter is set, before doing the normal callout check, Exim does a
33434 check for a &"random"& local part at the same domain. The local part is not
33435 really random &-- it is defined by the expansion of the option
33436 &%callout_random_local_part%&, which defaults to
33438 $primary_hostname-$tod_epoch-testing
33440 The idea here is to try to determine whether the remote host accepts all local
33441 parts without checking. If it does, there is no point in doing callouts for
33442 specific local parts. If the &"random"& check succeeds, the result is saved in
33443 a cache record, and used to force the current and subsequent callout checks to
33444 succeed without a connection being made, until the cache record expires.
33446 .vitem &*use_postmaster*&
33447 .cindex "callout" "sender for recipient check"
33448 This parameter applies to recipient callouts only. For example:
33450 deny !verify = recipient/callout=use_postmaster
33452 .vindex "&$qualify_domain$&"
33453 It causes a non-empty postmaster address to be used in the MAIL command when
33454 performing the callout for the recipient, and also for a &"random"& check if
33455 that is configured. The local part of the address is &`postmaster`& and the
33456 domain is the contents of &$qualify_domain$&.
33458 .vitem &*use_sender*&
33459 This option applies to recipient callouts only. For example:
33461 require verify = recipient/callout=use_sender
33463 It causes the message's actual sender address to be used in the MAIL
33464 command when performing the callout, instead of an empty address. There is no
33465 need to use this option unless you know that the called hosts make use of the
33466 sender when checking recipients. If used indiscriminately, it reduces the
33467 usefulness of callout caching.
33470 This option applies to recipient callouts only. For example:
33472 require verify = recipient/callout=use_sender,hold
33474 It causes the connection to be held open and used for any further recipients
33475 and for eventual delivery (should that be done quickly).
33476 Doing this saves on TCP and SMTP startup costs, and TLS costs also
33477 when that is used for the connections.
33478 The advantage is only gained if there are no callout cache hits
33479 (which could be enforced by the no_cache option),
33480 if the use_sender option is used,
33481 if neither the random nor the use_postmaster option is used,
33482 and if no other callouts intervene.
33485 If you use any of the parameters that set a non-empty sender for the MAIL
33486 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
33487 &%use_sender%&), you should think about possible loops. Recipient checking is
33488 usually done between two hosts that are under the same management, and the host
33489 that receives the callouts is not normally configured to do callouts itself.
33490 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
33491 these circumstances.
33493 However, if you use a non-empty sender address for a callout to an arbitrary
33494 host, there is the likelihood that the remote host will itself initiate a
33495 callout check back to your host. As it is checking what appears to be a message
33496 sender, it is likely to use an empty address in MAIL, thus avoiding a
33497 callout loop. However, to be on the safe side it would be best to set up your
33498 own ACLs so that they do not do sender verification checks when the recipient
33499 is the address you use for header sender or postmaster callout checking.
33501 Another issue to think about when using non-empty senders for callouts is
33502 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
33503 by the sender/recipient combination; thus, for any given recipient, many more
33504 actual callouts are performed than when an empty sender or postmaster is used.
33509 .section "Callout caching" "SECTcallvercache"
33510 .cindex "hints database" "callout cache"
33511 .cindex "callout" "cache, description of"
33512 .cindex "caching" "callout"
33513 Exim caches the results of callouts in order to reduce the amount of resources
33514 used, unless you specify the &%no_cache%& parameter with the &%callout%&
33515 option. A hints database called &"callout"& is used for the cache. Two
33516 different record types are used: one records the result of a callout check for
33517 a specific address, and the other records information that applies to the
33518 entire domain (for example, that it accepts the local part &'postmaster'&).
33520 When an original callout fails, a detailed SMTP error message is given about
33521 the failure. However, for subsequent failures use the cache data, this message
33524 The expiry times for negative and positive address cache records are
33525 independent, and can be set by the global options &%callout_negative_expire%&
33526 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
33528 If a host gives a negative response to an SMTP connection, or rejects any
33529 commands up to and including
33533 (but not including the MAIL command with a non-empty address),
33534 any callout attempt is bound to fail. Exim remembers such failures in a
33535 domain cache record, which it uses to fail callouts for the domain without
33536 making new connections, until the domain record times out. There are two
33537 separate expiry times for domain cache records:
33538 &%callout_domain_negative_expire%& (default 3h) and
33539 &%callout_domain_positive_expire%& (default 7d).
33541 Domain records expire when the negative expiry time is reached if callouts
33542 cannot be made for the domain, or if the postmaster check failed.
33543 Otherwise, they expire when the positive expiry time is reached. This
33544 ensures that, for example, a host that stops accepting &"random"& local parts
33545 will eventually be noticed.
33547 The callout caching mechanism is based on the domain of the address that is
33548 being tested. If the domain routes to several hosts, it is assumed that their
33549 behaviour will be the same.
33554 .section "Quota caching" "SECTquotacache"
33555 .cindex "hints database" "quota cache"
33556 .cindex "quota" "cache, description of"
33557 .cindex "caching" "quota"
33558 Exim caches the results of quota verification
33559 in order to reduce the amount of resources used.
33560 The &"callout"& hints database is used.
33562 The default cache periods are five minutes for a positive (good) result
33563 and one hour for a negative result.
33564 To change the periods the &%quota%& option can be followed by an equals sign
33565 and a number of optional paramemters, separated by commas.
33568 verify = recipient/quota=cachepos=1h,cacheneg=1d
33570 Possible parameters are:
33572 .vitem &*cachepos&~=&~*&<&'time&~interval'&>
33573 .cindex "quota cache" "positive entry expiry, specifying"
33574 Set the lifetime for a positive cache entry.
33575 A value of zero seconds is legitimate.
33577 .vitem &*cacheneg&~=&~*&<&'time&~interval'&>
33578 .cindex "quota cache" "negative entry expiry, specifying"
33579 As above, for a negative entry.
33581 .vitem &*no_cache*&
33582 Set both positive and negative lifetimes to zero.
33585 .section "Sender address verification reporting" "SECTsenaddver"
33586 .cindex "verifying" "suppressing error details"
33587 See section &<<SECTaddressverification>>& for a general discussion of
33588 verification. When sender verification fails in an ACL, the details of the
33589 failure are given as additional output lines before the 550 response to the
33590 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
33593 MAIL FROM:<xyz@abc.example>
33595 RCPT TO:<pqr@def.example>
33596 550-Verification failed for <xyz@abc.example>
33597 550-Called: 192.168.34.43
33598 550-Sent: RCPT TO:<xyz@abc.example>
33599 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
33600 550 Sender verification failed
33602 If more than one RCPT command fails in the same way, the details are given
33603 only for the first of them. However, some administrators do not want to send
33604 out this much information. You can suppress the details by adding
33605 &`/no_details`& to the ACL statement that requests sender verification. For
33608 verify = sender/no_details
33611 .section "Redirection while verifying" "SECTredirwhilveri"
33612 .cindex "verifying" "redirection while"
33613 .cindex "address redirection" "while verifying"
33614 A dilemma arises when a local address is redirected by aliasing or forwarding
33615 during verification: should the generated addresses themselves be verified,
33616 or should the successful expansion of the original address be enough to verify
33617 it? By default, Exim takes the following pragmatic approach:
33620 When an incoming address is redirected to just one child address, verification
33621 continues with the child address, and if that fails to verify, the original
33622 verification also fails.
33624 When an incoming address is redirected to more than one child address,
33625 verification does not continue. A success result is returned.
33628 This seems the most reasonable behaviour for the common use of aliasing as a
33629 way of redirecting different local parts to the same mailbox. It means, for
33630 example, that a pair of alias entries of the form
33633 aw123: :fail: Gone away, no forwarding address
33635 work as expected, with both local parts causing verification failure. When a
33636 redirection generates more than one address, the behaviour is more like a
33637 mailing list, where the existence of the alias itself is sufficient for
33638 verification to succeed.
33640 It is possible, however, to change the default behaviour so that all successful
33641 redirections count as successful verifications, however many new addresses are
33642 generated. This is specified by the &%success_on_redirect%& verification
33643 option. For example:
33645 require verify = recipient/success_on_redirect/callout=10s
33647 In this example, verification succeeds if a router generates a new address, and
33648 the callout does not occur, because no address was routed to a remote host.
33650 When verification is being tested via the &%-bv%& option, the treatment of
33651 redirections is as just described, unless the &%-v%& or any debugging option is
33652 also specified. In that case, full verification is done for every generated
33653 address and a report is output for each of them.
33657 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
33658 .cindex "CSA" "verifying"
33659 Client SMTP Authorization is a system that allows a site to advertise
33660 which machines are and are not permitted to send email. This is done by placing
33661 special SRV records in the DNS; these are looked up using the client's HELO
33662 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
33663 Authorization checks in Exim are performed by the ACL condition:
33667 This fails if the client is not authorized. If there is a DNS problem, or if no
33668 valid CSA SRV record is found, or if the client is authorized, the condition
33669 succeeds. These three cases can be distinguished using the expansion variable
33670 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
33671 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
33672 be likely to cause problems for legitimate email.
33674 The error messages produced by the CSA code include slightly more
33675 detail. If &$csa_status$& is &"defer"&, this may be because of problems
33676 looking up the CSA SRV record, or problems looking up the CSA target
33677 address record. There are four reasons for &$csa_status$& being &"fail"&:
33680 The client's host name is explicitly not authorized.
33682 The client's IP address does not match any of the CSA target IP addresses.
33684 The client's host name is authorized but it has no valid target IP addresses
33685 (for example, the target's addresses are IPv6 and the client is using IPv4).
33687 The client's host name has no CSA SRV record but a parent domain has asserted
33688 that all subdomains must be explicitly authorized.
33691 The &%csa%& verification condition can take an argument which is the domain to
33692 use for the DNS query. The default is:
33694 verify = csa/$sender_helo_name
33696 This implementation includes an extension to CSA. If the query domain
33697 is an address literal such as [192.0.2.95], or if it is a bare IP
33698 address, Exim searches for CSA SRV records in the reverse DNS as if
33699 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
33702 verify = csa/$sender_host_address
33704 In fact, this is the check that Exim performs if the client does not say HELO.
33705 This extension can be turned off by setting the main configuration option
33706 &%dns_csa_use_reverse%& to be false.
33708 If a CSA SRV record is not found for the domain itself, a search
33709 is performed through its parent domains for a record which might be
33710 making assertions about subdomains. The maximum depth of this search is limited
33711 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
33712 default. Exim does not look for CSA SRV records in a top level domain, so the
33713 default settings handle HELO domains as long as seven
33714 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
33715 of legitimate HELO domains.
33717 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
33718 direct SRV lookups, this is not sufficient because of the extra parent domain
33719 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
33720 addresses into lookups in the reverse DNS space. The result of a successful
33723 ${lookup dnsdb {csa=$sender_helo_name}}
33725 has two space-separated fields: an authorization code and a target host name.
33726 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
33727 authorization required but absent, or &"?"& for unknown.
33732 .section "Bounce address tag validation" "SECTverifyPRVS"
33733 .cindex "BATV, verifying"
33734 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
33735 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
33736 Genuine incoming bounce messages should therefore always be addressed to
33737 recipients that have a valid tag. This scheme is a way of detecting unwanted
33738 bounce messages caused by sender address forgeries (often called &"collateral
33739 spam"&), because the recipients of such messages do not include valid tags.
33741 There are two expansion items to help with the implementation of the BATV
33742 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
33743 the original envelope sender address by using a simple key to add a hash of the
33744 address and some time-based randomizing information. The &%prvs%& expansion
33745 item creates a signed address, and the &%prvscheck%& expansion item checks one.
33746 The syntax of these expansion items is described in section
33747 &<<SECTexpansionitems>>&.
33748 The validity period on signed addresses is seven days.
33750 As an example, suppose the secret per-address keys are stored in an MySQL
33751 database. A query to look up the key for an address could be defined as a macro
33754 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
33755 WHERE sender='${quote_mysql:$prvscheck_address}'\
33758 Suppose also that the senders who make use of BATV are defined by an address
33759 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
33762 # Bounces: drop unsigned addresses for BATV senders
33764 recipients = +batv_senders
33765 message = This address does not send an unsigned reverse path
33767 # Bounces: In case of prvs-signed address, check signature.
33769 condition = ${prvscheck {$local_part@$domain}\
33770 {PRVSCHECK_SQL}{1}}
33771 !condition = $prvscheck_result
33772 message = Invalid reverse path signature.
33774 The first statement rejects recipients for bounce messages that are addressed
33775 to plain BATV sender addresses, because it is known that BATV senders do not
33776 send out messages with plain sender addresses. The second statement rejects
33777 recipients that are prvs-signed, but with invalid signatures (either because
33778 the key is wrong, or the signature has timed out).
33780 A non-prvs-signed address is not rejected by the second statement, because the
33781 &%prvscheck%& expansion yields an empty string if its first argument is not a
33782 prvs-signed address, thus causing the &%condition%& condition to be false. If
33783 the first argument is a syntactically valid prvs-signed address, the yield is
33784 the third string (in this case &"1"&), whether or not the cryptographic and
33785 timeout checks succeed. The &$prvscheck_result$& variable contains the result
33786 of the checks (empty for failure, &"1"& for success).
33788 There is one more issue you must consider when implementing prvs-signing:
33789 you have to ensure that the routers accept prvs-signed addresses and
33790 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
33791 router to remove the signature with a configuration along these lines:
33795 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
33797 This works because, if the third argument of &%prvscheck%& is empty, the result
33798 of the expansion of a prvs-signed address is the decoded value of the original
33799 address. This router should probably be the first of your routers that handles
33802 To create BATV-signed addresses in the first place, a transport of this form
33805 external_smtp_batv:
33807 return_path = ${prvs {$return_path} \
33808 {${lookup mysql{SELECT \
33809 secret FROM batv_prvs WHERE \
33810 sender='${quote_mysql:$sender_address}'} \
33813 If no key can be found for the existing return path, no signing takes place.
33817 .section "Using an ACL to control relaying" "SECTrelaycontrol"
33818 .cindex "&ACL;" "relay control"
33819 .cindex "relaying" "control by ACL"
33820 .cindex "policy control" "relay control"
33821 An MTA is said to &'relay'& a message if it receives it from some host and
33822 delivers it directly to another host as a result of a remote address contained
33823 within it. Redirecting a local address via an alias or forward file and then
33824 passing the message on to another host is not relaying,
33825 .cindex "&""percent hack""&"
33826 but a redirection as a result of the &"percent hack"& is.
33828 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
33829 A host which is acting as a gateway or an MX backup is concerned with incoming
33830 relaying from arbitrary hosts to a specific set of domains. On the other hand,
33831 a host which is acting as a smart host for a number of clients is concerned
33832 with outgoing relaying from those clients to the Internet at large. Often the
33833 same host is fulfilling both functions,
33835 . as illustrated in the diagram below,
33837 but in principle these two kinds of relaying are entirely independent. What is
33838 not wanted is the transmission of mail from arbitrary remote hosts through your
33839 system to arbitrary domains.
33842 You can implement relay control by means of suitable statements in the ACL that
33843 runs for each RCPT command. For convenience, it is often easiest to use
33844 Exim's named list facility to define the domains and hosts involved. For
33845 example, suppose you want to do the following:
33848 Deliver a number of domains to mailboxes on the local host (or process them
33849 locally in some other way). Let's say these are &'my.dom1.example'& and
33850 &'my.dom2.example'&.
33852 Relay mail for a number of other domains for which you are the secondary MX.
33853 These might be &'friend1.example'& and &'friend2.example'&.
33855 Relay mail from the hosts on your local LAN, to whatever domains are involved.
33856 Suppose your LAN is 192.168.45.0/24.
33860 In the main part of the configuration, you put the following definitions:
33862 domainlist local_domains = my.dom1.example : my.dom2.example
33863 domainlist relay_to_domains = friend1.example : friend2.example
33864 hostlist relay_from_hosts = 192.168.45.0/24
33866 Now you can use these definitions in the ACL that is run for every RCPT
33870 accept domains = +local_domains : +relay_to_domains
33871 accept hosts = +relay_from_hosts
33873 The first statement accepts any RCPT command that contains an address in
33874 the local or relay domains. For any other domain, control passes to the second
33875 statement, which accepts the command only if it comes from one of the relay
33876 hosts. In practice, you will probably want to make your ACL more sophisticated
33877 than this, for example, by including sender and recipient verification. The
33878 default configuration includes a more comprehensive example, which is described
33879 in chapter &<<CHAPdefconfil>>&.
33883 .section "Checking a relay configuration" "SECTcheralcon"
33884 .cindex "relaying" "checking control of"
33885 You can check the relay characteristics of your configuration in the same way
33886 that you can test any ACL behaviour for an incoming SMTP connection, by using
33887 the &%-bh%& option to run a fake SMTP session with which you interact.
33892 . ////////////////////////////////////////////////////////////////////////////
33893 . ////////////////////////////////////////////////////////////////////////////
33895 .chapter "Content scanning at ACL time" "CHAPexiscan"
33896 .scindex IIDcosca "content scanning" "at ACL time"
33897 The extension of Exim to include content scanning at ACL time, formerly known
33898 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
33899 was integrated into the main source for Exim release 4.50, and Tom continues to
33900 maintain it. Most of the wording of this chapter is taken from Tom's
33903 It is also possible to scan the content of messages at other times. The
33904 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
33905 scanning after all the ACLs have run. A transport filter can be used to scan
33906 messages at delivery time (see the &%transport_filter%& option, described in
33907 chapter &<<CHAPtransportgeneric>>&).
33909 If you want to include the ACL-time content-scanning features when you compile
33910 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
33911 &_Local/Makefile_&. When you do that, the Exim binary is built with:
33914 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
33915 for all MIME parts for SMTP and non-SMTP messages, respectively.
33917 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
33918 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
33919 run at the end of message reception (the &%acl_smtp_data%& ACL).
33921 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
33922 of messages, or parts of messages, for debugging purposes.
33924 Additional expansion variables that are set in the new ACL and by the new
33927 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
33930 Content-scanning is continually evolving, and new features are still being
33931 added. While such features are still unstable and liable to incompatible
33932 changes, they are made available in Exim by setting options whose names begin
33933 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
33934 this manual. You can find out about them by reading the file called
33935 &_doc/experimental.txt_&.
33937 All the content-scanning facilities work on a MBOX copy of the message that is
33938 temporarily created in a file called:
33940 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
33942 The &_.eml_& extension is a friendly hint to virus scanners that they can
33943 expect an MBOX-like structure inside that file. The file is created when the
33944 first content scanning facility is called. Subsequent calls to content
33945 scanning conditions open the same file again. The directory is recursively
33946 removed when the &%acl_smtp_data%& ACL has finished running, unless
33948 control = no_mbox_unspool
33950 has been encountered. When the MIME ACL decodes files, they are put into the
33951 same directory by default.
33955 .section "Scanning for viruses" "SECTscanvirus"
33956 .cindex "virus scanning"
33957 .cindex "content scanning" "for viruses"
33958 .cindex "content scanning" "the &%malware%& condition"
33959 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
33960 It supports a &"generic"& interface to scanners called via the shell, and
33961 specialized interfaces for &"daemon"& type virus scanners, which are resident
33962 in memory and thus are much faster.
33964 Since message data needs to have arrived,
33965 the condition may be only called in ACL defined by
33967 &%acl_smtp_data_prdr%&,
33968 &%acl_smtp_mime%& or
33971 A timeout of 2 minutes is applied to a scanner call (by default);
33972 if it expires then a defer action is taken.
33974 .oindex "&%av_scanner%&"
33975 You can set the &%av_scanner%& option in the main part of the configuration
33976 to specify which scanner to use, together with any additional options that
33977 are needed. The basic syntax is as follows:
33979 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
33981 If you do not set &%av_scanner%&, it defaults to
33983 av_scanner = sophie:/var/run/sophie
33985 If the value of &%av_scanner%& starts with a dollar character, it is expanded
33987 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
33988 The following scanner types are supported in this release,
33989 though individual ones can be included or not at build time:
33993 .cindex "virus scanners" "avast"
33994 This is the scanner daemon of Avast. It has been tested with Avast Core
33995 Security (currently at version 2.2.0).
33996 You can get a trial version at &url(https://www.avast.com) or for Linux
33997 at &url(https://www.avast.com/linux-server-antivirus).
33998 This scanner type takes one option,
33999 which can be either a full path to a UNIX socket,
34000 or host and port specifiers separated by white space.
34001 The host may be a name or an IP address; the port is either a
34002 single number or a pair of numbers with a dash between.
34003 A list of options may follow. These options are interpreted on the
34004 Exim's side of the malware scanner, or are given on separate lines to
34005 the daemon as options before the main scan command.
34007 .cindex &`pass_unscanned`& "avast"
34008 If &`pass_unscanned`&
34009 is set, any files the Avast scanner can't scan (e.g.
34010 decompression bombs, or invalid archives) are considered clean. Use with
34015 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
34016 av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
34017 av_scanner = avast:192.168.2.22 5036
34019 If you omit the argument, the default path
34020 &_/var/run/avast/scan.sock_&
34022 If you use a remote host,
34023 you need to make Exim's spool directory available to it,
34024 as the scanner is passed a file path, not file contents.
34025 For information about available commands and their options you may use
34027 $ socat UNIX:/var/run/avast/scan.sock STDIO:
34033 If the scanner returns a temporary failure (e.g. license issues, or
34034 permission problems), the message is deferred and a paniclog entry is
34035 written. The usual &`defer_ok`& option is available.
34037 .vitem &%aveserver%&
34038 .cindex "virus scanners" "Kaspersky"
34039 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
34040 at &url(https://www.kaspersky.com/). This scanner type takes one option,
34041 which is the path to the daemon's UNIX socket. The default is shown in this
34044 av_scanner = aveserver:/var/run/aveserver
34049 .cindex "virus scanners" "clamd"
34050 This daemon-type scanner is GPL and free. You can get it at
34051 &url(https://www.clamav.net/). Some older versions of clamd do not seem to
34052 unpack MIME containers, so it used to be recommended to unpack MIME attachments
34053 in the MIME ACL. This is no longer believed to be necessary.
34055 The options are a list of server specifiers, which may be
34056 a UNIX socket specification,
34057 a TCP socket specification,
34058 or a (global) option.
34060 A socket specification consists of a space-separated list.
34061 For a Unix socket the first element is a full path for the socket,
34062 for a TCP socket the first element is the IP address
34063 and the second a port number,
34064 Any further elements are per-server (non-global) options.
34065 These per-server options are supported:
34067 retry=<timespec> Retry on connect fail
34070 The &`retry`& option specifies a time after which a single retry for
34071 a failed connect is made. The default is to not retry.
34073 If a Unix socket file is specified, only one server is supported.
34077 av_scanner = clamd:/opt/clamd/socket
34078 av_scanner = clamd:192.0.2.3 1234
34079 av_scanner = clamd:192.0.2.3 1234:local
34080 av_scanner = clamd:192.0.2.3 1234 retry=10s
34081 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
34083 If the value of av_scanner points to a UNIX socket file or contains the
34085 option, then the ClamAV interface will pass a filename containing the data
34086 to be scanned, which should normally result in less I/O happening and be
34087 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
34088 Exim does not assume that there is a common filesystem with the remote host.
34090 The final example shows that multiple TCP targets can be specified. Exim will
34091 randomly use one for each incoming email (i.e. it load balances them). Note
34092 that only TCP targets may be used if specifying a list of scanners; a UNIX
34093 socket cannot be mixed in with TCP targets. If one of the servers becomes
34094 unavailable, Exim will try the remaining one(s) until it finds one that works.
34095 When a clamd server becomes unreachable, Exim will log a message. Exim does
34096 not keep track of scanner state between multiple messages, and the scanner
34097 selection is random, so the message will get logged in the mainlog for each
34098 email that the down scanner gets chosen first (message wrapped to be readable):
34100 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
34101 clamd: connection to localhost, port 3310 failed
34102 (Connection refused)
34105 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
34106 contributing the code for this scanner.
34109 .cindex "virus scanners" "command line interface"
34110 This is the keyword for the generic command line scanner interface. It can be
34111 used to attach virus scanners that are invoked from the shell. This scanner
34112 type takes 3 mandatory options:
34115 The full path and name of the scanner binary, with all command line options,
34116 and a placeholder (&`%s`&) for the directory to scan.
34119 A regular expression to match against the STDOUT and STDERR output of the
34120 virus scanner. If the expression matches, a virus was found. You must make
34121 absolutely sure that this expression matches on &"virus found"&. This is called
34122 the &"trigger"& expression.
34125 Another regular expression, containing exactly one pair of parentheses, to
34126 match the name of the virus found in the scanners output. This is called the
34127 &"name"& expression.
34130 For example, Sophos Sweep reports a virus on a line like this:
34132 Virus 'W32/Magistr-B' found in file ./those.bat
34134 For the trigger expression, we can match the phrase &"found in file"&. For the
34135 name expression, we want to extract the W32/Magistr-B string, so we can match
34136 for the single quotes left and right of it. Altogether, this makes the
34137 configuration setting:
34139 av_scanner = cmdline:\
34140 /path/to/sweep -ss -all -rec -archive %s:\
34141 found in file:'(.+)'
34144 .cindex "virus scanners" "DrWeb"
34145 The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface
34147 either a full path to a UNIX socket,
34148 or host and port specifiers separated by white space.
34149 The host may be a name or an IP address; the port is either a
34150 single number or a pair of numbers with a dash between.
34153 av_scanner = drweb:/var/run/drwebd.sock
34154 av_scanner = drweb:192.168.2.20 31337
34156 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
34157 is used. Thanks to Alex Miller for contributing the code for this scanner.
34160 .cindex "virus scanners" "f-protd"
34161 The f-protd scanner is accessed via HTTP over TCP.
34162 One argument is taken, being a space-separated hostname and port number
34166 av_scanner = f-protd:localhost 10200-10204
34168 If you omit the argument, the default values shown above are used.
34170 .vitem &%f-prot6d%&
34171 .cindex "virus scanners" "f-prot6d"
34172 The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
34173 One argument is taken, being a space-separated hostname and port number.
34176 av_scanner = f-prot6d:localhost 10200
34178 If you omit the argument, the default values show above are used.
34181 .cindex "virus scanners" "F-Secure"
34182 The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one
34183 argument which is the path to a UNIX socket. For example:
34185 av_scanner = fsecure:/path/to/.fsav
34187 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
34188 Thelmen for contributing the code for this scanner.
34190 .vitem &%kavdaemon%&
34191 .cindex "virus scanners" "Kaspersky"
34192 This is the scanner daemon of Kaspersky Version 4. This version of the
34193 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
34194 scanner type takes one option, which is the path to the daemon's UNIX socket.
34197 av_scanner = kavdaemon:/opt/AVP/AvpCtl
34199 The default path is &_/var/run/AvpCtl_&.
34202 .cindex "virus scanners" "mksd"
34203 This was a daemon type scanner that is aimed mainly at Polish users,
34204 though some documentation was available in English.
34205 The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir)
34206 and this appears to be a candidate for removal from Exim, unless
34207 we are informed of other virus scanners which use the same protocol
34209 The only option for this scanner type is
34210 the maximum number of processes used simultaneously to scan the attachments,
34211 provided that mksd has
34212 been run with at least the same number of child processes. For example:
34214 av_scanner = mksd:2
34216 You can safely omit this option (the default value is 1).
34219 .cindex "virus scanners" "simple socket-connected"
34220 This is a general-purpose way of talking to simple scanner daemons
34221 running on the local machine.
34222 There are four options:
34223 an address (which may be an IP address and port, or the path of a Unix socket),
34224 a commandline to send (may include a single %s which will be replaced with
34225 the path to the mail file to be scanned),
34226 an RE to trigger on from the returned data,
34227 and an RE to extract malware_name from the returned data.
34230 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
34232 Note that surrounding whitespace is stripped from each option, meaning
34233 there is no way to specify a trailing newline.
34234 The socket specifier and both regular-expressions are required.
34235 Default for the commandline is &_%s\n_& (note this does have a trailing newline);
34236 specify an empty element to get this.
34239 .cindex "virus scanners" "Sophos and Sophie"
34240 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
34241 You can get Sophie at &url(http://sophie.sourceforge.net/). The only option
34242 for this scanner type is the path to the UNIX socket that Sophie uses for
34243 client communication. For example:
34245 av_scanner = sophie:/tmp/sophie
34247 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
34251 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
34252 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
34255 The &%av_scanner%& option is expanded each time &%malware%& is called. This
34256 makes it possible to use different scanners. See further below for an example.
34257 The &%malware%& condition caches its results, so when you use it multiple times
34258 for the same message, the actual scanning process is only carried out once.
34259 However, using expandable items in &%av_scanner%& disables this caching, in
34260 which case each use of the &%malware%& condition causes a new scan of the
34263 The &%malware%& condition takes a right-hand argument that is expanded before
34264 use and taken as a list, slash-separated by default.
34265 The first element can then be one of
34268 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
34269 The condition succeeds if a virus was found, and fail otherwise. This is the
34272 &"false"& or &"0"& or an empty string, in which case no scanning is done and
34273 the condition fails immediately.
34275 A regular expression, in which case the message is scanned for viruses. The
34276 condition succeeds if a virus is found and its name matches the regular
34277 expression. This allows you to take special actions on certain types of virus.
34278 Note that &"/"& characters in the RE must be doubled due to the list-processing,
34279 unless the separator is changed (in the usual way &<<SECTlistsepchange>>&).
34282 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
34283 messages even if there is a problem with the virus scanner.
34284 Otherwise, such a problem causes the ACL to defer.
34286 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
34287 specify a non-default timeout. The default is two minutes.
34290 malware = * / defer_ok / tmo=10s
34292 A timeout causes the ACL to defer.
34294 .vindex "&$callout_address$&"
34295 When a connection is made to the scanner the expansion variable &$callout_address$&
34296 is set to record the actual address used.
34298 .vindex "&$malware_name$&"
34299 When a virus is found, the condition sets up an expansion variable called
34300 &$malware_name$& that contains the name of the virus. You can use it in a
34301 &%message%& modifier that specifies the error returned to the sender, and/or in
34304 Beware the interaction of Exim's &%message_size_limit%& with any size limits
34305 imposed by your anti-virus scanner.
34307 Here is a very simple scanning example:
34310 message = This message contains malware ($malware_name)
34312 The next example accepts messages when there is a problem with the scanner:
34314 deny malware = */defer_ok
34315 message = This message contains malware ($malware_name)
34317 The next example shows how to use an ACL variable to scan with both sophie and
34318 aveserver. It assumes you have set:
34320 av_scanner = $acl_m0
34322 in the main Exim configuration.
34324 deny set acl_m0 = sophie
34326 message = This message contains malware ($malware_name)
34328 deny set acl_m0 = aveserver
34330 message = This message contains malware ($malware_name)
34334 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
34335 .cindex "content scanning" "for spam"
34336 .cindex "spam scanning"
34337 .cindex "SpamAssassin"
34339 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
34340 score and a report for the message.
34341 Support is also provided for Rspamd.
34343 For more information about installation and configuration of SpamAssassin or
34344 Rspamd refer to their respective websites at
34345 &url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/)
34347 SpamAssassin can be installed with CPAN by running:
34349 perl -MCPAN -e 'install Mail::SpamAssassin'
34351 SpamAssassin has its own set of configuration files. Please review its
34352 documentation to see how you can tweak it. The default installation should work
34355 .oindex "&%spamd_address%&"
34356 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
34357 intend to use an instance running on the local host you do not need to set
34358 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
34359 you must set the &%spamd_address%& option in the global part of the Exim
34360 configuration as follows (example):
34362 spamd_address = 192.168.99.45 783
34364 The SpamAssassin protocol relies on a TCP half-close from the client.
34365 If your SpamAssassin client side is running a Linux system with an
34366 iptables firewall, consider setting
34367 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
34368 timeout, Exim uses when waiting for a response from the SpamAssassin
34369 server (currently defaulting to 120s). With a lower value the Linux
34370 connection tracking may consider your half-closed connection as dead too
34374 To use Rspamd (which by default listens on all local addresses
34376 you should add &%variant=rspamd%& after the address/port pair, for example:
34378 spamd_address = 127.0.0.1 11333 variant=rspamd
34381 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
34382 sockets. If you want to us these, supply &%spamd_address%& with an absolute
34383 filename instead of an address/port pair:
34385 spamd_address = /var/run/spamd_socket
34387 You can have multiple &%spamd%& servers to improve scalability. These can
34388 reside on other hardware reachable over the network. To specify multiple
34389 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
34390 option, separated with colons (the separator can be changed in the usual way &<<SECTlistsepchange>>&):
34392 spamd_address = 192.168.2.10 783 : \
34393 192.168.2.11 783 : \
34396 Up to 32 &%spamd%& servers are supported.
34397 When a server fails to respond to the connection attempt, all other
34398 servers are tried until one succeeds. If no server responds, the &%spam%&
34401 Unix and TCP socket specifications may be mixed in any order.
34402 Each element of the list is a list itself, space-separated by default
34403 and changeable in the usual way (&<<SECTlistsepchange>>&);
34404 take care to not double the separator.
34406 For TCP socket specifications a host name or IP (v4 or v6, but
34407 subject to list-separator quoting rules) address can be used,
34408 and the port can be one or a dash-separated pair.
34409 In the latter case, the range is tried in strict order.
34411 Elements after the first for Unix sockets, or second for TCP socket,
34413 The supported options are:
34415 pri=<priority> Selection priority
34416 weight=<value> Selection bias
34417 time=<start>-<end> Use only between these times of day
34418 retry=<timespec> Retry on connect fail
34419 tmo=<timespec> Connection time limit
34420 variant=rspamd Use Rspamd rather than SpamAssassin protocol
34423 The &`pri`& option specifies a priority for the server within the list,
34424 higher values being tried first.
34425 The default priority is 1.
34427 The &`weight`& option specifies a selection bias.
34428 Within a priority set
34429 servers are queried in a random fashion, weighted by this value.
34430 The default value for selection bias is 1.
34432 Time specifications for the &`time`& option are <hour>.<minute>.<second>
34433 in the local time zone; each element being one or more digits.
34434 Either the seconds or both minutes and seconds, plus the leading &`.`&
34435 characters, may be omitted and will be taken as zero.
34437 Timeout specifications for the &`retry`& and &`tmo`& options
34438 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
34440 The &`tmo`& option specifies an overall timeout for communication.
34441 The default value is two minutes.
34443 The &`retry`& option specifies a time after which a single retry for
34444 a failed connect is made.
34445 The default is to not retry.
34447 The &%spamd_address%& variable is expanded before use if it starts with
34448 a dollar sign. In this case, the expansion may return a string that is
34449 used as the list so that multiple spamd servers can be the result of an
34452 .vindex "&$callout_address$&"
34453 When a connection is made to the server the expansion variable &$callout_address$&
34454 is set to record the actual address used.
34456 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
34457 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
34460 message = This message was classified as SPAM
34462 The right-hand side of the &%spam%& condition specifies a name. This is
34463 relevant if you have set up multiple SpamAssassin profiles. If you do not want
34464 to scan using a specific profile, but rather use the SpamAssassin system-wide
34465 default profile, you can scan for an unknown name, or simply use &"nobody"&.
34466 Rspamd does not use this setting. However, you must put something on the
34469 The name allows you to use per-domain or per-user antispam profiles in
34470 principle, but this is not straightforward in practice, because a message may
34471 have multiple recipients, not necessarily all in the same domain. Because the
34472 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
34473 read the contents of the message, the variables &$local_part$& and &$domain$&
34475 Careful enforcement of single-recipient messages
34476 (e.g. by responding with defer in the recipient ACL for all recipients
34478 or the use of PRDR,
34479 .cindex "PRDR" "use for per-user SpamAssassin profiles"
34480 are needed to use this feature.
34482 The right-hand side of the &%spam%& condition is expanded before being used, so
34483 you can put lookups or conditions there. When the right-hand side evaluates to
34484 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
34487 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
34488 large ones may cause significant performance degradation. As most spam messages
34489 are quite small, it is recommended that you do not scan the big ones. For
34492 deny condition = ${if < {$message_size}{10K}}
34494 message = This message was classified as SPAM
34497 The &%spam%& condition returns true if the threshold specified in the user's
34498 SpamAssassin profile has been matched or exceeded. If you want to use the
34499 &%spam%& condition for its side effects (see the variables below), you can make
34500 it always return &"true"& by appending &`:true`& to the username.
34502 .cindex "spam scanning" "returned variables"
34503 When the &%spam%& condition is run, it sets up a number of expansion
34505 Except for &$spam_report$&,
34506 these variables are saved with the received message so are
34507 available for use at delivery time.
34510 .vitem &$spam_score$&
34511 The spam score of the message, for example, &"3.4"& or &"30.5"&. This is useful
34512 for inclusion in log or reject messages.
34514 .vitem &$spam_score_int$&
34515 The spam score of the message, multiplied by ten, as an integer value. For
34516 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
34517 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
34518 The integer value is useful for numeric comparisons in conditions.
34520 .vitem &$spam_bar$&
34521 A string consisting of a number of &"+"& or &"-"& characters, representing the
34522 integer part of the spam score value. A spam score of 4.4 would have a
34523 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
34524 headers, since MUAs can match on such strings. The maximum length of the
34525 spam bar is 50 characters.
34527 .vitem &$spam_report$&
34528 A multiline text table, containing the full SpamAssassin report for the
34529 message. Useful for inclusion in headers or reject messages.
34530 This variable is only usable in a DATA-time ACL.
34531 Beware that SpamAssassin may return non-ASCII characters, especially
34532 when running in country-specific locales, which are not legal
34533 unencoded in headers.
34535 .vitem &$spam_action$&
34536 For SpamAssassin either 'reject' or 'no action' depending on the
34537 spam score versus threshold.
34538 For Rspamd, the recommended action.
34542 The &%spam%& condition caches its results unless expansion in
34543 spamd_address was used. If you call it again with the same user name, it
34544 does not scan again, but rather returns the same values as before.
34546 The &%spam%& condition returns DEFER if there is any error while running
34547 the message through SpamAssassin or if the expansion of spamd_address
34548 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
34549 statement block), append &`/defer_ok`& to the right-hand side of the
34550 spam condition, like this:
34552 deny spam = joe/defer_ok
34553 message = This message was classified as SPAM
34555 This causes messages to be accepted even if there is a problem with &%spamd%&.
34557 Here is a longer, commented example of the use of the &%spam%&
34560 # put headers in all messages (no matter if spam or not)
34561 warn spam = nobody:true
34562 add_header = X-Spam-Score: $spam_score ($spam_bar)
34563 add_header = X-Spam-Report: $spam_report
34565 # add second subject line with *SPAM* marker when message
34566 # is over threshold
34568 add_header = Subject: *SPAM* $h_Subject:
34570 # reject spam at high scores (> 12)
34571 deny spam = nobody:true
34572 condition = ${if >{$spam_score_int}{120}{1}{0}}
34573 message = This message scored $spam_score spam points.
34578 .section "Scanning MIME parts" "SECTscanmimepart"
34579 .cindex "content scanning" "MIME parts"
34580 .cindex "MIME content scanning"
34581 .oindex "&%acl_smtp_mime%&"
34582 .oindex "&%acl_not_smtp_mime%&"
34583 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
34584 each MIME part of an SMTP message, including multipart types, in the sequence
34585 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
34586 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
34587 options may both refer to the same ACL if you want the same processing in both
34590 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
34591 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
34592 the case of a non-SMTP message. However, a MIME ACL is called only if the
34593 message contains a &'Content-Type:'& header line. When a call to a MIME
34594 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
34595 result code is sent to the client. In the case of an SMTP message, the
34596 &%acl_smtp_data%& ACL is not called when this happens.
34598 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
34599 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
34600 condition to match against the raw MIME part. You can also use the
34601 &%mime_regex%& condition to match against the decoded MIME part (see section
34602 &<<SECTscanregex>>&).
34604 At the start of a MIME ACL, a number of variables are set from the header
34605 information for the relevant MIME part. These are described below. The contents
34606 of the MIME part are not by default decoded into a disk file except for MIME
34607 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
34608 part into a disk file, you can use the &%decode%& condition. The general
34611 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
34613 The right hand side is expanded before use. After expansion,
34617 &"0"& or &"false"&, in which case no decoding is done.
34619 The string &"default"&. In that case, the file is put in the temporary
34620 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
34621 a sequential filename consisting of the message id and a sequence number. The
34622 full path and name is available in &$mime_decoded_filename$& after decoding.
34624 A full path name starting with a slash. If the full name is an existing
34625 directory, it is used as a replacement for the default directory. The filename
34626 is then sequentially assigned. If the path does not exist, it is used as
34627 the full path and filename.
34629 If the string does not start with a slash, it is used as the
34630 filename, and the default path is then used.
34632 The &%decode%& condition normally succeeds. It is only false for syntax
34633 errors or unusual circumstances such as memory shortages. You can easily decode
34634 a file with its original, proposed filename using
34636 decode = $mime_filename
34638 However, you should keep in mind that &$mime_filename$& might contain
34639 anything. If you place files outside of the default path, they are not
34640 automatically unlinked.
34642 For RFC822 attachments (these are messages attached to messages, with a
34643 content-type of &"message/rfc822"&), the ACL is called again in the same manner
34644 as for the primary message, only that the &$mime_is_rfc822$& expansion
34645 variable is set (see below). Attached messages are always decoded to disk
34646 before being checked, and the files are unlinked once the check is done.
34648 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
34649 used to match regular expressions against raw and decoded MIME parts,
34650 respectively. They are described in section &<<SECTscanregex>>&.
34652 .cindex "MIME content scanning" "returned variables"
34653 The following list describes all expansion variables that are
34654 available in the MIME ACL:
34657 .vitem &$mime_anomaly_level$& &&&
34658 &$mime_anomaly_text$&
34659 .vindex &$mime_anomaly_level$&
34660 .vindex &$mime_anomaly_text$&
34661 If there are problems decoding, these variables contain information on
34662 the detected issue.
34664 .vitem &$mime_boundary$&
34665 .vindex &$mime_boundary$&
34666 If the current part is a multipart (see &$mime_is_multipart$& below), it should
34667 have a boundary string, which is stored in this variable. If the current part
34668 has no boundary parameter in the &'Content-Type:'& header, this variable
34669 contains the empty string.
34671 .vitem &$mime_charset$&
34672 .vindex &$mime_charset$&
34673 This variable contains the character set identifier, if one was found in the
34674 &'Content-Type:'& header. Examples for charset identifiers are:
34680 Please note that this value is not normalized, so you should do matches
34681 case-insensitively.
34683 .vitem &$mime_content_description$&
34684 .vindex &$mime_content_description$&
34685 This variable contains the normalized content of the &'Content-Description:'&
34686 header. It can contain a human-readable description of the parts content. Some
34687 implementations repeat the filename for attachments here, but they are usually
34688 only used for display purposes.
34690 .vitem &$mime_content_disposition$&
34691 .vindex &$mime_content_disposition$&
34692 This variable contains the normalized content of the &'Content-Disposition:'&
34693 header. You can expect strings like &"attachment"& or &"inline"& here.
34695 .vitem &$mime_content_id$&
34696 .vindex &$mime_content_id$&
34697 This variable contains the normalized content of the &'Content-ID:'& header.
34698 This is a unique ID that can be used to reference a part from another part.
34700 .vitem &$mime_content_size$&
34701 .vindex &$mime_content_size$&
34702 This variable is set only after the &%decode%& modifier (see above) has been
34703 successfully run. It contains the size of the decoded part in kilobytes. The
34704 size is always rounded up to full kilobytes, so only a completely empty part
34705 has a &$mime_content_size$& of zero.
34707 .vitem &$mime_content_transfer_encoding$&
34708 .vindex &$mime_content_transfer_encoding$&
34709 This variable contains the normalized content of the
34710 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
34711 type. Typical values are &"base64"& and &"quoted-printable"&.
34713 .vitem &$mime_content_type$&
34714 .vindex &$mime_content_type$&
34715 If the MIME part has a &'Content-Type:'& header, this variable contains its
34716 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
34717 are some examples of popular MIME types, as they may appear in this variable:
34721 application/octet-stream
34725 If the MIME part has no &'Content-Type:'& header, this variable contains the
34728 .vitem &$mime_decoded_filename$&
34729 .vindex &$mime_decoded_filename$&
34730 This variable is set only after the &%decode%& modifier (see above) has been
34731 successfully run. It contains the full path and filename of the file
34732 containing the decoded data.
34737 .vitem &$mime_filename$&
34738 .vindex &$mime_filename$&
34739 This is perhaps the most important of the MIME variables. It contains a
34740 proposed filename for an attachment, if one was found in either the
34741 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
34744 decoded, but no additional sanity checks are done.
34746 found, this variable contains the empty string.
34748 .vitem &$mime_is_coverletter$&
34749 .vindex &$mime_is_coverletter$&
34750 This variable attempts to differentiate the &"cover letter"& of an e-mail from
34751 attached data. It can be used to clamp down on flashy or unnecessarily encoded
34752 content in the cover letter, while not restricting attachments at all.
34754 The variable contains 1 (true) for a MIME part believed to be part of the
34755 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
34759 The outermost MIME part of a message is always a cover letter.
34762 If a multipart/alternative or multipart/related MIME part is a cover letter,
34763 so are all MIME subparts within that multipart.
34766 If any other multipart is a cover letter, the first subpart is a cover letter,
34767 and the rest are attachments.
34770 All parts contained within an attachment multipart are attachments.
34773 As an example, the following will ban &"HTML mail"& (including that sent with
34774 alternative plain text), while allowing HTML files to be attached. HTML
34775 coverletter mail attached to non-HTML coverletter mail will also be allowed:
34777 deny !condition = $mime_is_rfc822
34778 condition = $mime_is_coverletter
34779 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
34780 message = HTML mail is not accepted here
34783 .vitem &$mime_is_multipart$&
34784 .vindex &$mime_is_multipart$&
34785 This variable has the value 1 (true) when the current part has the main type
34786 &"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
34787 Since multipart entities only serve as containers for other parts, you may not
34788 want to carry out specific actions on them.
34790 .vitem &$mime_is_rfc822$&
34791 .vindex &$mime_is_rfc822$&
34792 This variable has the value 1 (true) if the current part is not a part of the
34793 checked message itself, but part of an attached message. Attached message
34794 decoding is fully recursive.
34796 .vitem &$mime_part_count$&
34797 .vindex &$mime_part_count$&
34798 This variable is a counter that is raised for each processed MIME part. It
34799 starts at zero for the very first part (which is usually a multipart). The
34800 counter is per-message, so it is reset when processing RFC822 attachments (see
34801 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
34802 complete, so you can use it in the DATA ACL to determine the number of MIME
34803 parts of a message. For non-MIME messages, this variable contains the value -1.
34808 .section "Scanning with regular expressions" "SECTscanregex"
34809 .cindex "content scanning" "with regular expressions"
34810 .cindex "regular expressions" "content scanning with"
34811 You can specify your own custom regular expression matches on the full body of
34812 the message, or on individual MIME parts.
34814 The &%regex%& condition takes one or more regular expressions as arguments and
34815 matches them against the full message (when called in the DATA ACL) or a raw
34816 MIME part (when called in the MIME ACL). The &%regex%& condition matches
34817 linewise, with a maximum line length of 32K characters. That means you cannot
34818 have multiline matches with the &%regex%& condition.
34820 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
34821 to 32K of decoded content (the whole content at once, not linewise). If the
34822 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
34823 is decoded automatically when &%mime_regex%& is executed (using default path
34824 and filename values). If the decoded data is larger than 32K, only the first
34825 32K characters are checked.
34827 The regular expressions are passed as a colon-separated list. To include a
34828 literal colon, you must double it. Since the whole right-hand side string is
34829 expanded before being used, you must also escape dollar signs and backslashes
34830 with more backslashes, or use the &`\N`& facility to disable expansion.
34831 Here is a simple example that contains two regular expressions:
34833 deny regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
34834 message = contains blacklisted regex ($regex_match_string)
34836 The conditions returns true if any one of the regular expressions matches. The
34837 &$regex_match_string$& expansion variable is then set up and contains the
34838 matching regular expression.
34839 The expansion variables &$regex1$& &$regex2$& etc
34840 are set to any substrings captured by the regular expression.
34842 &*Warning*&: With large messages, these conditions can be fairly
34850 . ////////////////////////////////////////////////////////////////////////////
34851 . ////////////////////////////////////////////////////////////////////////////
34853 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
34854 "Local scan function"
34855 .scindex IIDlosca "&[local_scan()]& function" "description of"
34856 .cindex "customizing" "input scan using C function"
34857 .cindex "policy control" "by local scan function"
34858 In these days of email worms, viruses, and ever-increasing spam, some sites
34859 want to apply a lot of checking to messages before accepting them.
34861 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
34862 passing messages to external virus and spam scanning software. You can also do
34863 a certain amount in Exim itself through string expansions and the &%condition%&
34864 condition in the ACL that runs after the SMTP DATA command or the ACL for
34865 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
34867 To allow for further customization to a site's own requirements, there is the
34868 possibility of linking Exim with a private message scanning function, written
34869 in C. If you want to run code that is written in something other than C, you
34870 can of course use a little C stub to call it.
34872 The local scan function is run once for every incoming message, at the point
34873 when Exim is just about to accept the message.
34874 It can therefore be used to control non-SMTP messages from local processes as
34875 well as messages arriving via SMTP.
34877 Exim applies a timeout to calls of the local scan function, and there is an
34878 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
34879 Zero means &"no timeout"&.
34880 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
34881 before calling the local scan function, so that the most common types of crash
34882 are caught. If the timeout is exceeded or one of those signals is caught, the
34883 incoming message is rejected with a temporary error if it is an SMTP message.
34884 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
34885 code. The incident is logged on the main and reject logs.
34889 .section "Building Exim to use a local scan function" "SECID207"
34890 .cindex "&[local_scan()]& function" "building Exim to use"
34891 To make use of the local scan function feature, you must tell Exim where your
34892 function is before building Exim, by setting
34893 both HAVE_LOCAL_SCAN and
34894 LOCAL_SCAN_SOURCE in your
34895 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
34896 directory, so you might set
34898 HAVE_LOCAL_SCAN=yes
34899 LOCAL_SCAN_SOURCE=Local/local_scan.c
34901 for example. The function must be called &[local_scan()]&;
34902 the source file(s) for it should first #define LOCAL_SCAN
34903 and then #include "local_scan.h".
34905 Exim after it has received a message, when the success return code is about to
34906 be sent. This is after all the ACLs have been run. The return code from your
34907 function controls whether the message is actually accepted or not. There is a
34908 commented template function (that just accepts the message) in the file
34909 _src/local_scan.c_.
34911 If you want to make use of Exim's runtime configuration file to set options
34912 for your &[local_scan()]& function, you must also set
34914 LOCAL_SCAN_HAS_OPTIONS=yes
34916 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
34921 .section "API for local_scan()" "SECTapiforloc"
34922 .cindex "&[local_scan()]& function" "API description"
34923 .cindex &%dlfunc%& "API description"
34924 You must include this line near the start of your code:
34927 #include "local_scan.h"
34929 This header file defines a number of variables and other values, and the
34930 prototype for the function itself. Exim is coded to use unsigned char values
34931 almost exclusively, and one of the things this header defines is a shorthand
34932 for &`unsigned char`& called &`uschar`&.
34933 It also makes available the following macro definitions, to simplify casting character
34934 strings and pointers to character strings:
34936 #define CS (char *)
34937 #define CCS (const char *)
34938 #define CSS (char **)
34939 #define US (unsigned char *)
34940 #define CUS (const unsigned char *)
34941 #define USS (unsigned char **)
34943 The function prototype for &[local_scan()]& is:
34945 extern int local_scan(int fd, uschar **return_text);
34947 The arguments are as follows:
34950 &%fd%& is a file descriptor for the file that contains the body of the message
34951 (the -D file). The file is open for reading and writing, but updating it is not
34952 recommended. &*Warning*&: You must &'not'& close this file descriptor.
34954 The descriptor is positioned at character 19 of the file, which is the first
34955 character of the body itself, because the first 19 characters are the message
34956 id followed by &`-D`& and a newline. If you rewind the file, you should use the
34957 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
34958 case this changes in some future version.
34960 &%return_text%& is an address which you can use to return a pointer to a text
34961 string at the end of the function. The value it points to on entry is NULL.
34964 The function must return an &%int%& value which is one of the following macros:
34967 .vitem &`LOCAL_SCAN_ACCEPT`&
34968 .vindex "&$local_scan_data$&"
34969 The message is accepted. If you pass back a string of text, it is saved with
34970 the message, and made available in the variable &$local_scan_data$&. No
34971 newlines are permitted (if there are any, they are turned into spaces) and the
34972 maximum length of text is 1000 characters.
34974 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
34975 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
34976 queued without immediate delivery, and is frozen.
34978 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
34979 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
34980 queued without immediate delivery.
34982 .vitem &`LOCAL_SCAN_REJECT`&
34983 The message is rejected; the returned text is used as an error message which is
34984 passed back to the sender and which is also logged. Newlines are permitted &--
34985 they cause a multiline response for SMTP rejections, but are converted to
34986 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
34989 .vitem &`LOCAL_SCAN_TEMPREJECT`&
34990 The message is temporarily rejected; the returned text is used as an error
34991 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
34994 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
34995 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
34996 message is not written to the reject log. It has the effect of unsetting the
34997 &%rejected_header%& log selector for just this rejection. If
34998 &%rejected_header%& is already unset (see the discussion of the
34999 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
35000 same as LOCAL_SCAN_REJECT.
35002 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
35003 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
35004 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
35007 If the message is not being received by interactive SMTP, rejections are
35008 reported by writing to &%stderr%& or by sending an email, as configured by the
35009 &%-oe%& command line options.
35013 .section "Configuration options for local_scan()" "SECTconoptloc"
35014 .cindex "&[local_scan()]& function" "configuration options"
35015 It is possible to have option settings in the main configuration file
35016 that set values in static variables in the &[local_scan()]& module. If you
35017 want to do this, you must have the line
35019 LOCAL_SCAN_HAS_OPTIONS=yes
35021 in your &_Local/Makefile_& when you build Exim. (This line is in
35022 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
35023 file, you must define static variables to hold the option values, and a table
35026 The table must be a vector called &%local_scan_options%&, of type
35027 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
35028 and a pointer to the variable that holds the value. The entries must appear in
35029 alphabetical order. Following &%local_scan_options%& you must also define a
35030 variable called &%local_scan_options_count%& that contains the number of
35031 entries in the table. Here is a short example, showing two kinds of option:
35033 static int my_integer_option = 42;
35034 static uschar *my_string_option = US"a default string";
35036 optionlist local_scan_options[] = {
35037 { "my_integer", opt_int, &my_integer_option },
35038 { "my_string", opt_stringptr, &my_string_option }
35041 int local_scan_options_count =
35042 sizeof(local_scan_options)/sizeof(optionlist);
35044 The values of the variables can now be changed from Exim's runtime
35045 configuration file by including a local scan section as in this example:
35049 my_string = some string of text...
35051 The available types of option data are as follows:
35054 .vitem &*opt_bool*&
35055 This specifies a boolean (true/false) option. The address should point to a
35056 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
35057 that are defined as &"1"& and &"0"&, respectively. If you want to detect
35058 whether such a variable has been set at all, you can initialize it to
35059 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
35062 .vitem &*opt_fixed*&
35063 This specifies a fixed point number, such as is used for load averages.
35064 The address should point to a variable of type &`int`&. The value is stored
35065 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
35068 This specifies an integer; the address should point to a variable of type
35069 &`int`&. The value may be specified in any of the integer formats accepted by
35072 .vitem &*opt_mkint*&
35073 This is the same as &%opt_int%&, except that when such a value is output in a
35074 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
35075 printed with the suffix K or M.
35077 .vitem &*opt_octint*&
35078 This also specifies an integer, but the value is always interpreted as an
35079 octal integer, whether or not it starts with the digit zero, and it is
35080 always output in octal.
35082 .vitem &*opt_stringptr*&
35083 This specifies a string value; the address must be a pointer to a
35084 variable that points to a string (for example, of type &`uschar *`&).
35086 .vitem &*opt_time*&
35087 This specifies a time interval value. The address must point to a variable of
35088 type &`int`&. The value that is placed there is a number of seconds.
35091 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
35092 out the values of all the &[local_scan()]& options.
35096 .section "Available Exim variables" "SECID208"
35097 .cindex "&[local_scan()]& function" "available Exim variables"
35098 The header &_local_scan.h_& gives you access to a number of C variables. These
35099 are the only ones that are guaranteed to be maintained from release to release.
35100 Note, however, that you can obtain the value of any Exim expansion variable,
35101 including &$recipients$&, by calling &'expand_string()'&. The exported
35102 C variables are as follows:
35105 .vitem &*int&~body_linecount*&
35106 This variable contains the number of lines in the message's body.
35107 It is not valid if the &%spool_files_wireformat%& option is used.
35109 .vitem &*int&~body_zerocount*&
35110 This variable contains the number of binary zero bytes in the message's body.
35111 It is not valid if the &%spool_files_wireformat%& option is used.
35113 .vitem &*unsigned&~int&~debug_selector*&
35114 This variable is set to zero when no debugging is taking place. Otherwise, it
35115 is a bitmap of debugging selectors. Two bits are identified for use in
35116 &[local_scan()]&; they are defined as macros:
35119 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
35120 testing option that is not privileged &-- any caller may set it. All the
35121 other selector bits can be set only by admin users.
35124 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
35125 by the &`+local_scan`& debug selector. It is not included in the default set
35129 Thus, to write to the debugging output only when &`+local_scan`& has been
35130 selected, you should use code like this:
35132 if ((debug_selector & D_local_scan) != 0)
35133 debug_printf("xxx", ...);
35135 .vitem &*uschar&~*expand_string_message*&
35136 After a failing call to &'expand_string()'& (returned value NULL), the
35137 variable &%expand_string_message%& contains the error message, zero-terminated.
35139 .vitem &*header_line&~*header_list*&
35140 A pointer to a chain of header lines. The &%header_line%& structure is
35143 .vitem &*header_line&~*header_last*&
35144 A pointer to the last of the header lines.
35146 .vitem &*uschar&~*headers_charset*&
35147 The value of the &%headers_charset%& configuration option.
35149 .vitem &*BOOL&~host_checking*&
35150 This variable is TRUE during a host checking session that is initiated by the
35151 &%-bh%& command line option.
35153 .vitem &*uschar&~*interface_address*&
35154 The IP address of the interface that received the message, as a string. This
35155 is NULL for locally submitted messages.
35157 .vitem &*int&~interface_port*&
35158 The port on which this message was received. When testing with the &%-bh%&
35159 command line option, the value of this variable is -1 unless a port has been
35160 specified via the &%-oMi%& option.
35162 .vitem &*uschar&~*message_id*&
35163 This variable contains Exim's message id for the incoming message (the value of
35164 &$message_exim_id$&) as a zero-terminated string.
35166 .vitem &*uschar&~*received_protocol*&
35167 The name of the protocol by which the message was received.
35169 .vitem &*int&~recipients_count*&
35170 The number of accepted recipients.
35172 .vitem &*recipient_item&~*recipients_list*&
35173 .cindex "recipient" "adding in local scan"
35174 .cindex "recipient" "removing in local scan"
35175 The list of accepted recipients, held in a vector of length
35176 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
35177 can add additional recipients by calling &'receive_add_recipient()'& (see
35178 below). You can delete recipients by removing them from the vector and
35179 adjusting the value in &%recipients_count%&. In particular, by setting
35180 &%recipients_count%& to zero you remove all recipients. If you then return the
35181 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
35182 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
35183 and then call &'receive_add_recipient()'& as often as needed.
35185 .vitem &*uschar&~*sender_address*&
35186 The envelope sender address. For bounce messages this is the empty string.
35188 .vitem &*uschar&~*sender_host_address*&
35189 The IP address of the sending host, as a string. This is NULL for
35190 locally-submitted messages.
35192 .vitem &*uschar&~*sender_host_authenticated*&
35193 The name of the authentication mechanism that was used, or NULL if the message
35194 was not received over an authenticated SMTP connection.
35196 .vitem &*uschar&~*sender_host_name*&
35197 The name of the sending host, if known.
35199 .vitem &*int&~sender_host_port*&
35200 The port on the sending host.
35202 .vitem &*BOOL&~smtp_input*&
35203 This variable is TRUE for all SMTP input, including BSMTP.
35205 .vitem &*BOOL&~smtp_batched_input*&
35206 This variable is TRUE for BSMTP input.
35208 .vitem &*int&~store_pool*&
35209 The contents of this variable control which pool of memory is used for new
35210 requests. See section &<<SECTmemhanloc>>& for details.
35214 .section "Structure of header lines" "SECID209"
35215 The &%header_line%& structure contains the members listed below.
35216 You can add additional header lines by calling the &'header_add()'& function
35217 (see below). You can cause header lines to be ignored (deleted) by setting
35222 .vitem &*struct&~header_line&~*next*&
35223 A pointer to the next header line, or NULL for the last line.
35225 .vitem &*int&~type*&
35226 A code identifying certain headers that Exim recognizes. The codes are printing
35227 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
35228 Notice in particular that any header line whose type is * is not transmitted
35229 with the message. This flagging is used for header lines that have been
35230 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
35231 lines.) Effectively, * means &"deleted"&.
35233 .vitem &*int&~slen*&
35234 The number of characters in the header line, including the terminating and any
35237 .vitem &*uschar&~*text*&
35238 A pointer to the text of the header. It always ends with a newline, followed by
35239 a zero byte. Internal newlines are preserved.
35244 .section "Structure of recipient items" "SECID210"
35245 The &%recipient_item%& structure contains these members:
35248 .vitem &*uschar&~*address*&
35249 This is a pointer to the recipient address as it was received.
35251 .vitem &*int&~pno*&
35252 This is used in later Exim processing when top level addresses are created by
35253 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
35254 and must always contain -1 at this stage.
35256 .vitem &*uschar&~*errors_to*&
35257 If this value is not NULL, bounce messages caused by failing to deliver to the
35258 recipient are sent to the address it contains. In other words, it overrides the
35259 envelope sender for this one recipient. (Compare the &%errors_to%& generic
35260 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
35261 an unqualified address, Exim qualifies it using the domain from
35262 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
35263 is NULL for all recipients.
35268 .section "Available Exim functions" "SECID211"
35269 .cindex "&[local_scan()]& function" "available Exim functions"
35270 The header &_local_scan.h_& gives you access to a number of Exim functions.
35271 These are the only ones that are guaranteed to be maintained from release to
35275 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
35276 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
35278 This function creates a child process that runs the command specified by
35279 &%argv%&. The environment for the process is specified by &%envp%&, which can
35280 be NULL if no environment variables are to be passed. A new umask is supplied
35281 for the process in &%newumask%&.
35283 Pipes to the standard input and output of the new process are set up
35284 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
35285 standard error is cloned to the standard output. If there are any file
35286 descriptors &"in the way"& in the new process, they are closed. If the final
35287 argument is TRUE, the new process is made into a process group leader.
35289 The function returns the pid of the new process, or -1 if things go wrong.
35291 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
35292 This function waits for a child process to terminate, or for a timeout (in
35293 seconds) to expire. A timeout value of zero means wait as long as it takes. The
35294 return value is as follows:
35299 The process terminated by a normal exit and the value is the process
35305 The process was terminated by a signal and the value is the negation of the
35311 The process timed out.
35315 The was some other error in wait(); &%errno%& is still set.
35318 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
35319 This function provide you with a means of submitting a new message to
35320 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
35321 want, but this packages it all up for you.) The function creates a pipe,
35322 forks a subprocess that is running
35324 exim -t -oem -oi -f <>
35326 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
35327 that is connected to the standard input. The yield of the function is the PID
35328 of the subprocess. You can then write a message to the file descriptor, with
35329 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
35331 When you have finished, call &'child_close()'& to wait for the process to
35332 finish and to collect its ending status. A timeout value of zero is usually
35333 fine in this circumstance. Unless you have made a mistake with the recipient
35334 addresses, you should get a return code of zero.
35337 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
35338 *sender_authentication)*&
35339 This function is a more sophisticated version of &'child_open()'&. The command
35342 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
35344 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
35347 .vitem &*void&~debug_printf(char&~*,&~...)*&
35348 This is Exim's debugging function, with arguments as for &'(printf()'&. The
35349 output is written to the standard error stream. If no debugging is selected,
35350 calls to &'debug_printf()'& have no effect. Normally, you should make calls
35351 conditional on the &`local_scan`& debug selector by coding like this:
35353 if ((debug_selector & D_local_scan) != 0)
35354 debug_printf("xxx", ...);
35357 .vitem &*uschar&~*expand_string(uschar&~*string)*&
35358 This is an interface to Exim's string expansion code. The return value is the
35359 expanded string, or NULL if there was an expansion failure.
35360 The C variable &%expand_string_message%& contains an error message after an
35361 expansion failure. If expansion does not change the string, the return value is
35362 the pointer to the input string. Otherwise, the return value points to a new
35363 block of memory that was obtained by a call to &'store_get()'&. See section
35364 &<<SECTmemhanloc>>& below for a discussion of memory handling.
35366 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
35367 This function allows you to an add additional header line at the end of the
35368 existing ones. The first argument is the type, and should normally be a space
35369 character. The second argument is a format string and any number of
35370 substitution arguments as for &[sprintf()]&. You may include internal newlines
35371 if you want, and you must ensure that the string ends with a newline.
35373 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
35374 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
35375 This function adds a new header line at a specified point in the header
35376 chain. The header itself is specified as for &'header_add()'&.
35378 If &%name%& is NULL, the new header is added at the end of the chain if
35379 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
35380 NULL, the header lines are searched for the first non-deleted header that
35381 matches the name. If one is found, the new header is added before it if
35382 &%after%& is false. If &%after%& is true, the new header is added after the
35383 found header and any adjacent subsequent ones with the same name (even if
35384 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
35385 option controls where the header is added. If it is true, addition is at the
35386 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
35387 headers, or at the top if there are no &'Received:'& headers, you could use
35389 header_add_at_position(TRUE, US"Received", TRUE,
35390 ' ', "X-xxx: ...");
35392 Normally, there is always at least one non-deleted &'Received:'& header, but
35393 there may not be if &%received_header_text%& expands to an empty string.
35396 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
35397 This function removes header lines. If &%occurrence%& is zero or negative, all
35398 occurrences of the header are removed. If occurrence is greater than zero, that
35399 particular instance of the header is removed. If no header(s) can be found that
35400 match the specification, the function does nothing.
35403 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
35404 int&~length,&~BOOL&~notdel)*&"
35405 This function tests whether the given header has the given name. It is not just
35406 a string comparison, because white space is permitted between the name and the
35407 colon. If the &%notdel%& argument is true, a false return is forced for all
35408 &"deleted"& headers; otherwise they are not treated specially. For example:
35410 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
35412 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
35413 .cindex "base64 encoding" "functions for &[local_scan()]& use"
35414 This function base64-encodes a string, which is passed by address and length.
35415 The text may contain bytes of any value, including zero. The result is passed
35416 back in dynamic memory that is obtained by calling &'store_get()'&. It is
35419 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
35420 This function decodes a base64-encoded string. Its arguments are a
35421 zero-terminated base64-encoded string and the address of a variable that is set
35422 to point to the result, which is in dynamic memory. The length of the decoded
35423 string is the yield of the function. If the input is invalid base64 data, the
35424 yield is -1. A zero byte is added to the end of the output string to make it
35425 easy to interpret as a C string (assuming it contains no zeros of its own). The
35426 added zero byte is not included in the returned count.
35428 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
35429 This function checks for a match in a domain list. Domains are always
35430 matched caselessly. The return value is one of the following:
35432 &`OK `& match succeeded
35433 &`FAIL `& match failed
35434 &`DEFER `& match deferred
35436 DEFER is usually caused by some kind of lookup defer, such as the
35437 inability to contact a database.
35439 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
35441 This function checks for a match in a local part list. The third argument
35442 controls case-sensitivity. The return values are as for
35443 &'lss_match_domain()'&.
35445 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
35447 This function checks for a match in an address list. The third argument
35448 controls the case-sensitivity of the local part match. The domain is always
35449 matched caselessly. The return values are as for &'lss_match_domain()'&.
35451 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
35453 This function checks for a match in a host list. The most common usage is
35456 lss_match_host(sender_host_name, sender_host_address, ...)
35458 .vindex "&$sender_host_address$&"
35459 An empty address field matches an empty item in the host list. If the host name
35460 is NULL, the name corresponding to &$sender_host_address$& is automatically
35461 looked up if a host name is required to match an item in the list. The return
35462 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
35463 returns ERROR in the case when it had to look up a host name, but the lookup
35466 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
35468 This function writes to Exim's log files. The first argument should be zero (it
35469 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
35470 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
35471 them. It specifies to which log or logs the message is written. The remaining
35472 arguments are a format and relevant insertion arguments. The string should not
35473 contain any newlines, not even at the end.
35476 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
35477 This function adds an additional recipient to the message. The first argument
35478 is the recipient address. If it is unqualified (has no domain), it is qualified
35479 with the &%qualify_recipient%& domain. The second argument must always be -1.
35481 This function does not allow you to specify a private &%errors_to%& address (as
35482 described with the structure of &%recipient_item%& above), because it pre-dates
35483 the addition of that field to the structure. However, it is easy to add such a
35484 value afterwards. For example:
35486 receive_add_recipient(US"monitor@mydom.example", -1);
35487 recipients_list[recipients_count-1].errors_to =
35488 US"postmaster@mydom.example";
35491 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
35492 This is a convenience function to remove a named recipient from the list of
35493 recipients. It returns true if a recipient was removed, and false if no
35494 matching recipient could be found. The argument must be a complete email
35501 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
35502 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
35503 This function decodes strings that are encoded according to RFC 2047. Typically
35504 these are the contents of header lines. First, each &"encoded word"& is decoded
35505 from the Q or B encoding into a byte-string. Then, if provided with the name of
35506 a charset encoding, and if the &[iconv()]& function is available, an attempt is
35507 made to translate the result to the named character set. If this fails, the
35508 binary string is returned with an error message.
35510 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
35511 maximum MIME word length is enforced. The third argument is the target
35512 encoding, or NULL if no translation is wanted.
35514 .cindex "binary zero" "in RFC 2047 decoding"
35515 .cindex "RFC 2047" "binary zero in"
35516 If a binary zero is encountered in the decoded string, it is replaced by the
35517 contents of the &%zeroval%& argument. For use with Exim headers, the value must
35518 not be 0 because header lines are handled as zero-terminated strings.
35520 The function returns the result of processing the string, zero-terminated; if
35521 &%lenptr%& is not NULL, the length of the result is set in the variable to
35522 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
35524 If an error is encountered, the function returns NULL and uses the &%error%&
35525 argument to return an error message. The variable pointed to by &%error%& is
35526 set to NULL if there is no error; it may be set non-NULL even when the function
35527 returns a non-NULL value if decoding was successful, but there was a problem
35531 .vitem &*int&~smtp_fflush(void)*&
35532 This function is used in conjunction with &'smtp_printf()'&, as described
35535 .vitem &*void&~smtp_printf(char&~*,BOOL,&~...)*&
35536 The arguments of this function are almost like &[printf()]&; it writes to the SMTP
35537 output stream. You should use this function only when there is an SMTP output
35538 stream, that is, when the incoming message is being received via interactive
35539 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
35540 is FALSE. If you want to test for an incoming message from another host (as
35541 opposed to a local process that used the &%-bs%& command line option), you can
35542 test the value of &%sender_host_address%&, which is non-NULL when a remote host
35545 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
35546 output function, so it can be used for all forms of SMTP connection.
35548 The second argument is used to request that the data be buffered
35549 (when TRUE) or flushed (along with any previously buffered, when FALSE).
35550 This is advisory only, but likely to save on system-calls and packets
35551 sent when a sequence of calls to the function are made.
35553 The argument was added in Exim version 4.90 - changing the API/ABI.
35554 Nobody noticed until 4.93 was imminent, at which point the
35555 ABI version number was incremented.
35557 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
35558 must start with an appropriate response code: 550 if you are going to return
35559 LOCAL_SCAN_REJECT, 451 if you are going to return
35560 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
35561 initial lines of a multi-line response, the code must be followed by a hyphen
35562 to indicate that the line is not the final response line. You must also ensure
35563 that the lines you write terminate with CRLF. For example:
35565 smtp_printf("550-this is some extra info\r\n");
35566 return LOCAL_SCAN_REJECT;
35568 Note that you can also create multi-line responses by including newlines in
35569 the data returned via the &%return_text%& argument. The added value of using
35570 &'smtp_printf()'& is that, for instance, you could introduce delays between
35571 multiple output lines.
35573 The &'smtp_printf()'& function does not return any error indication, because it
35575 guarantee a flush of
35576 pending output, and therefore does not test
35577 the state of the stream. (In the main code of Exim, flushing and error
35578 detection is done when Exim is ready for the next SMTP input command.) If
35579 you want to flush the output and check for an error (for example, the
35580 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
35581 arguments. It flushes the output stream, and returns a non-zero value if there
35584 .vitem &*void&~*store_get(int,BOOL)*&
35585 This function accesses Exim's internal store (memory) manager. It gets a new
35586 chunk of memory whose size is given by the first argument.
35587 The second argument should be given as TRUE if the memory will be used for
35588 data possibly coming from an attacker (eg. the message content),
35589 FALSE if it is locally-sourced.
35590 Exim bombs out if it ever
35591 runs out of memory. See the next section for a discussion of memory handling.
35593 .vitem &*void&~*store_get_perm(int,BOOL)*&
35594 This function is like &'store_get()'&, but it always gets memory from the
35595 permanent pool. See the next section for a discussion of memory handling.
35597 .vitem &*uschar&~*string_copy(uschar&~*string)*&
35600 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
35603 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
35604 These three functions create strings using Exim's dynamic memory facilities.
35605 The first makes a copy of an entire string. The second copies up to a maximum
35606 number of characters, indicated by the second argument. The third uses a format
35607 and insertion arguments to create a new string. In each case, the result is a
35608 pointer to a new string in the current memory pool. See the next section for
35614 .section "More about Exim's memory handling" "SECTmemhanloc"
35615 .cindex "&[local_scan()]& function" "memory handling"
35616 No function is provided for freeing memory, because that is never needed.
35617 The dynamic memory that Exim uses when receiving a message is automatically
35618 recycled if another message is received by the same process (this applies only
35619 to incoming SMTP connections &-- other input methods can supply only one
35620 message at a time). After receiving the last message, a reception process
35623 Because it is recycled, the normal dynamic memory cannot be used for holding
35624 data that must be preserved over a number of incoming messages on the same SMTP
35625 connection. However, Exim in fact uses two pools of dynamic memory; the second
35626 one is not recycled, and can be used for this purpose.
35628 If you want to allocate memory that remains available for subsequent messages
35629 in the same SMTP connection, you should set
35631 store_pool = POOL_PERM
35633 before calling the function that does the allocation. There is no need to
35634 restore the value if you do not need to; however, if you do want to revert to
35635 the normal pool, you can either restore the previous value of &%store_pool%& or
35636 set it explicitly to POOL_MAIN.
35638 The pool setting applies to all functions that get dynamic memory, including
35639 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
35640 There is also a convenience function called &'store_get_perm()'& that gets a
35641 block of memory from the permanent pool while preserving the value of
35648 . ////////////////////////////////////////////////////////////////////////////
35649 . ////////////////////////////////////////////////////////////////////////////
35651 .chapter "System-wide message filtering" "CHAPsystemfilter"
35652 .scindex IIDsysfil1 "filter" "system filter"
35653 .scindex IIDsysfil2 "filtering all mail"
35654 .scindex IIDsysfil3 "system filter"
35655 The previous chapters (on ACLs and the local scan function) describe checks
35656 that can be applied to messages before they are accepted by a host. There is
35657 also a mechanism for checking messages once they have been received, but before
35658 they are delivered. This is called the &'system filter'&.
35660 The system filter operates in a similar manner to users' filter files, but it
35661 is run just once per message (however many recipients the message has).
35662 It should not normally be used as a substitute for routing, because &%deliver%&
35663 commands in a system router provide new envelope recipient addresses.
35664 The system filter must be an Exim filter. It cannot be a Sieve filter.
35666 The system filter is run at the start of a delivery attempt, before any routing
35667 is done. If a message fails to be completely delivered at the first attempt,
35668 the system filter is run again at the start of every retry.
35669 If you want your filter to do something only once per message, you can make use
35670 of the &%first_delivery%& condition in an &%if%& command in the filter to
35671 prevent it happening on retries.
35673 .vindex "&$domain$&"
35674 .vindex "&$local_part$&"
35675 &*Warning*&: Because the system filter runs just once, variables that are
35676 specific to individual recipient addresses, such as &$local_part$& and
35677 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
35678 you want to run a centrally-specified filter for each recipient address
35679 independently, you can do so by setting up a suitable &(redirect)& router, as
35680 described in section &<<SECTperaddfil>>& below.
35683 .section "Specifying a system filter" "SECID212"
35684 .cindex "uid (user id)" "system filter"
35685 .cindex "gid (group id)" "system filter"
35686 The name of the file that contains the system filter must be specified by
35687 setting &%system_filter%&. If you want the filter to run under a uid and gid
35688 other than root, you must also set &%system_filter_user%& and
35689 &%system_filter_group%& as appropriate. For example:
35691 system_filter = /etc/mail/exim.filter
35692 system_filter_user = exim
35694 If a system filter generates any deliveries directly to files or pipes (via the
35695 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
35696 specified by setting &%system_filter_file_transport%& and
35697 &%system_filter_pipe_transport%&, respectively. Similarly,
35698 &%system_filter_reply_transport%& must be set to handle any messages generated
35699 by the &%reply%& command.
35702 .section "Testing a system filter" "SECID213"
35703 You can run simple tests of a system filter in the same way as for a user
35704 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
35705 are permitted only in system filters are recognized.
35707 If you want to test the combined effect of a system filter and a user filter,
35708 you can use both &%-bF%& and &%-bf%& on the same command line.
35712 .section "Contents of a system filter" "SECID214"
35713 The language used to specify system filters is the same as for users' filter
35714 files. It is described in the separate end-user document &'Exim's interface to
35715 mail filtering'&. However, there are some additional features that are
35716 available only in system filters; these are described in subsequent sections.
35717 If they are encountered in a user's filter file or when testing with &%-bf%&,
35720 .cindex "frozen messages" "manual thaw; testing in filter"
35721 There are two special conditions which, though available in users' filter
35722 files, are designed for use in system filters. The condition &%first_delivery%&
35723 is true only for the first attempt at delivering a message, and
35724 &%manually_thawed%& is true only if the message has been frozen, and
35725 subsequently thawed by an admin user. An explicit forced delivery counts as a
35726 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
35728 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
35729 specify an &"unseen"& (non-significant) delivery, and that delivery does not
35730 succeed, it will not be tried again.
35731 If you want Exim to retry an unseen delivery until it succeeds, you should
35732 arrange to set it up every time the filter runs.
35734 When a system filter finishes running, the values of the variables &$n0$& &--
35735 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
35736 users' filter files. Thus a system filter can, for example, set up &"scores"&
35737 to which users' filter files can refer.
35741 .section "Additional variable for system filters" "SECID215"
35742 .vindex "&$recipients$&"
35743 The expansion variable &$recipients$&, containing a list of all the recipients
35744 of the message (separated by commas and white space), is available in system
35745 filters. It is not available in users' filters for privacy reasons.
35749 .section "Defer, freeze, and fail commands for system filters" "SECID216"
35750 .cindex "freezing messages"
35751 .cindex "message" "freezing"
35752 .cindex "message" "forced failure"
35753 .cindex "&%fail%&" "in system filter"
35754 .cindex "&%freeze%& in system filter"
35755 .cindex "&%defer%& in system filter"
35756 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
35757 always available in system filters, but are not normally enabled in users'
35758 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
35759 for the &(redirect)& router.) These commands can optionally be followed by the
35760 word &%text%& and a string containing an error message, for example:
35762 fail text "this message looks like spam to me"
35764 The keyword &%text%& is optional if the next character is a double quote.
35766 The &%defer%& command defers delivery of the original recipients of the
35767 message. The &%fail%& command causes all the original recipients to be failed,
35768 and a bounce message to be created. The &%freeze%& command suspends all
35769 delivery attempts for the original recipients. In all cases, any new deliveries
35770 that are specified by the filter are attempted as normal after the filter has
35773 The &%freeze%& command is ignored if the message has been manually unfrozen and
35774 not manually frozen since. This means that automatic freezing by a system
35775 filter can be used as a way of checking out suspicious messages. If a message
35776 is found to be all right, manually unfreezing it allows it to be delivered.
35778 .cindex "log" "&%fail%& command log line"
35779 .cindex "&%fail%&" "log line; reducing"
35780 The text given with a fail command is used as part of the bounce message as
35781 well as being written to the log. If the message is quite long, this can fill
35782 up a lot of log space when such failures are common. To reduce the size of the
35783 log message, Exim interprets the text in a special way if it starts with the
35784 two characters &`<<`& and contains &`>>`& later. The text between these two
35785 strings is written to the log, and the rest of the text is used in the bounce
35786 message. For example:
35788 fail "<<filter test 1>>Your message is rejected \
35789 because it contains attachments that we are \
35790 not prepared to receive."
35793 .cindex "loop" "caused by &%fail%&"
35794 Take great care with the &%fail%& command when basing the decision to fail on
35795 the contents of the message, because the bounce message will of course include
35796 the contents of the original message and will therefore trigger the &%fail%&
35797 command again (causing a mail loop) unless steps are taken to prevent this.
35798 Testing the &%error_message%& condition is one way to prevent this. You could
35801 if $message_body contains "this is spam" and not error_message
35802 then fail text "spam is not wanted here" endif
35804 though of course that might let through unwanted bounce messages. The
35805 alternative is clever checking of the body and/or headers to detect bounces
35806 generated by the filter.
35808 The interpretation of a system filter file ceases after a
35810 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
35811 set up earlier in the filter file are honoured, so you can use a sequence such
35817 to send a specified message when the system filter is freezing (or deferring or
35818 failing) a message. The normal deliveries for the message do not, of course,
35823 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
35824 .cindex "header lines" "adding; in system filter"
35825 .cindex "header lines" "removing; in system filter"
35826 .cindex "filter" "header lines; adding/removing"
35827 Two filter commands that are available only in system filters are:
35829 headers add <string>
35830 headers remove <string>
35832 The argument for the &%headers add%& is a string that is expanded and then
35833 added to the end of the message's headers. It is the responsibility of the
35834 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
35835 space is ignored, and if the string is otherwise empty, or if the expansion is
35836 forced to fail, the command has no effect.
35838 You can use &"\n"& within the string, followed by white space, to specify
35839 continued header lines. More than one header may be added in one command by
35840 including &"\n"& within the string without any following white space. For
35843 headers add "X-header-1: ....\n \
35844 continuation of X-header-1 ...\n\
35847 Note that the header line continuation white space after the first newline must
35848 be placed before the backslash that continues the input string, because white
35849 space after input continuations is ignored.
35851 The argument for &%headers remove%& is a colon-separated list of header names.
35852 This command applies only to those headers that are stored with the message;
35853 those that are added at delivery time (such as &'Envelope-To:'& and
35854 &'Return-Path:'&) cannot be removed by this means. If there is more than one
35855 header with the same name, they are all removed.
35857 The &%headers%& command in a system filter makes an immediate change to the set
35858 of header lines that was received with the message (with possible additions
35859 from ACL processing). Subsequent commands in the system filter operate on the
35860 modified set, which also forms the basis for subsequent message delivery.
35861 Unless further modified during routing or transporting, this set of headers is
35862 used for all recipients of the message.
35864 During routing and transporting, the variables that refer to the contents of
35865 header lines refer only to those lines that are in this set. Thus, header lines
35866 that are added by a system filter are visible to users' filter files and to all
35867 routers and transports. This contrasts with the manipulation of header lines by
35868 routers and transports, which is not immediate, but which instead is saved up
35869 until the message is actually being written (see section
35870 &<<SECTheadersaddrem>>&).
35872 If the message is not delivered at the first attempt, header lines that were
35873 added by the system filter are stored with the message, and so are still
35874 present at the next delivery attempt. Header lines that were removed are still
35875 present, but marked &"deleted"& so that they are not transported with the
35876 message. For this reason, it is usual to make the &%headers%& command
35877 conditional on &%first_delivery%& so that the set of header lines is not
35878 modified more than once.
35880 Because header modification in a system filter acts immediately, you have to
35881 use an indirect approach if you want to modify the contents of a header line.
35884 headers add "Old-Subject: $h_subject:"
35885 headers remove "Subject"
35886 headers add "Subject: new subject (was: $h_old-subject:)"
35887 headers remove "Old-Subject"
35892 .section "Setting an errors address in a system filter" "SECID217"
35893 .cindex "envelope from"
35894 .cindex "envelope sender"
35895 In a system filter, if a &%deliver%& command is followed by
35897 errors_to <some address>
35899 in order to change the envelope sender (and hence the error reporting) for that
35900 delivery, any address may be specified. (In a user filter, only the current
35901 user's address can be set.) For example, if some mail is being monitored, you
35904 unseen deliver monitor@spying.example errors_to root@local.example
35906 to take a copy which would not be sent back to the normal error reporting
35907 address if its delivery failed.
35911 .section "Per-address filtering" "SECTperaddfil"
35912 .vindex "&$domain_data$&"
35913 .vindex "&$local_part_data$&"
35914 In contrast to the system filter, which is run just once per message for each
35915 delivery attempt, it is also possible to set up a system-wide filtering
35916 operation that runs once for each recipient address. In this case, variables
35917 such as &$local_part_data$& and &$domain_data$& can be used,
35918 and indeed, the choice of filter file could be made dependent on them.
35919 This is an example of a router which implements such a filter:
35924 domains = +local_domains
35925 file = /central/filters/$local_part_data
35930 The filter is run in a separate process under its own uid. Therefore, either
35931 &%check_local_user%& must be set (as above), in which case the filter is run as
35932 the local user, or the &%user%& option must be used to specify which user to
35933 use. If both are set, &%user%& overrides.
35935 Care should be taken to ensure that none of the commands in the filter file
35936 specify a significant delivery if the message is to go on to be delivered to
35937 its intended recipient. The router will not then claim to have dealt with the
35938 address, so it will be passed on to subsequent routers to be delivered in the
35940 .ecindex IIDsysfil1
35941 .ecindex IIDsysfil2
35942 .ecindex IIDsysfil3
35949 . ////////////////////////////////////////////////////////////////////////////
35950 . ////////////////////////////////////////////////////////////////////////////
35952 .chapter "Message processing" "CHAPmsgproc"
35953 .scindex IIDmesproc "message" "general processing"
35954 Exim performs various transformations on the sender and recipient addresses of
35955 all messages that it handles, and also on the messages' header lines. Some of
35956 these are optional and configurable, while others always take place. All of
35957 this processing, except rewriting as a result of routing, and the addition or
35958 removal of header lines while delivering, happens when a message is received,
35959 before it is placed on Exim's queue.
35961 Some of the automatic processing takes place by default only for
35962 &"locally-originated"& messages. This adjective is used to describe messages
35963 that are not received over TCP/IP, but instead are passed to an Exim process on
35964 its standard input. This includes the interactive &"local SMTP"& case that is
35965 set up by the &%-bs%& command line option.
35967 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
35968 or ::1) are not considered to be locally-originated. Exim does not treat the
35969 loopback interface specially in any way.
35971 If you want the loopback interface to be treated specially, you must ensure
35972 that there are appropriate entries in your ACLs.
35977 .section "Submission mode for non-local messages" "SECTsubmodnon"
35978 .cindex "message" "submission"
35979 .cindex "submission mode"
35980 Processing that happens automatically for locally-originated messages (unless
35981 &%suppress_local_fixups%& is set) can also be requested for messages that are
35982 received over TCP/IP. The term &"submission mode"& is used to describe this
35983 state. Submission mode is set by the modifier
35985 control = submission
35987 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
35988 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
35989 a local submission, and is normally used when the source of the message is
35990 known to be an MUA running on a client host (as opposed to an MTA). For
35991 example, to set submission mode for messages originating on the IPv4 loopback
35992 interface, you could include the following in the MAIL ACL:
35994 warn hosts = 127.0.0.1
35995 control = submission
35997 .cindex "&%sender_retain%& submission option"
35998 There are some options that can be used when setting submission mode. A slash
35999 is used to separate options. For example:
36001 control = submission/sender_retain
36003 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
36004 true and &%local_from_check%& false for the current incoming message. The first
36005 of these allows an existing &'Sender:'& header in the message to remain, and
36006 the second suppresses the check to ensure that &'From:'& matches the
36007 authenticated sender. With this setting, Exim still fixes up messages by adding
36008 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
36009 attempt to check sender authenticity in header lines.
36011 When &%sender_retain%& is not set, a submission mode setting may specify a
36012 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
36015 control = submission/domain=some.domain
36017 The domain may be empty. How this value is used is described in sections
36018 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
36019 that allows you to specify the user's full name for inclusion in a created
36020 &'Sender:'& or &'From:'& header line. For example:
36022 accept authenticated = *
36023 control = submission/domain=wonderland.example/\
36024 name=${lookup {$authenticated_id} \
36025 lsearch {/etc/exim/namelist}}
36027 Because the name may contain any characters, including slashes, the &%name%&
36028 option must be given last. The remainder of the string is used as the name. For
36029 the example above, if &_/etc/exim/namelist_& contains:
36031 bigegg: Humpty Dumpty
36033 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
36036 Sender: Humpty Dumpty <bigegg@wonderland.example>
36038 .cindex "return path" "in submission mode"
36039 By default, submission mode forces the return path to the same address as is
36040 used to create the &'Sender:'& header. However, if &%sender_retain%& is
36041 specified, the return path is also left unchanged.
36043 &*Note*&: The changes caused by submission mode take effect after the predata
36044 ACL. This means that any sender checks performed before the fix-ups use the
36045 untrusted sender address specified by the user, not the trusted sender address
36046 specified by submission mode. Although this might be slightly unexpected, it
36047 does mean that you can configure ACL checks to spot that a user is trying to
36048 spoof another's address.
36050 .section "Line endings" "SECTlineendings"
36051 .cindex "line endings"
36052 .cindex "carriage return"
36054 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
36055 linefeed) is the line ending for messages transmitted over the Internet using
36056 SMTP over TCP/IP. However, within individual operating systems, different
36057 conventions are used. For example, Unix-like systems use just LF, but others
36058 use CRLF or just CR.
36060 Exim was designed for Unix-like systems, and internally, it stores messages
36061 using the system's convention of a single LF as a line terminator. When
36062 receiving a message, all line endings are translated to this standard format.
36063 Originally, it was thought that programs that passed messages directly to an
36064 MTA within an operating system would use that system's convention. Experience
36065 has shown that this is not the case; for example, there are Unix applications
36066 that use CRLF in this circumstance. For this reason, and for compatibility with
36067 other MTAs, the way Exim handles line endings for all messages is now as
36071 LF not preceded by CR is treated as a line ending.
36073 CR is treated as a line ending; if it is immediately followed by LF, the LF
36076 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
36077 nor a local message in the state where a line containing only a dot is a
36080 If a bare CR is encountered within a header line, an extra space is added after
36081 the line terminator so as not to end the header line. The reasoning behind this
36082 is that bare CRs in header lines are most likely either to be mistakes, or
36083 people trying to play silly games.
36085 If the first header line received in a message ends with CRLF, a subsequent
36086 bare LF in a header line is treated in the same way as a bare CR in a header
36094 .section "Unqualified addresses" "SECID218"
36095 .cindex "unqualified addresses"
36096 .cindex "address" "qualification"
36097 By default, Exim expects every envelope address it receives from an external
36098 host to be fully qualified. Unqualified addresses cause negative responses to
36099 SMTP commands. However, because SMTP is used as a means of transporting
36100 messages from MUAs running on personal workstations, there is sometimes a
36101 requirement to accept unqualified addresses from specific hosts or IP networks.
36103 Exim has two options that separately control which hosts may send unqualified
36104 sender or recipient addresses in SMTP commands, namely
36105 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
36106 cases, if an unqualified address is accepted, it is qualified by adding the
36107 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
36109 .oindex "&%qualify_domain%&"
36110 .oindex "&%qualify_recipient%&"
36111 Unqualified addresses in header lines are automatically qualified for messages
36112 that are locally originated, unless the &%-bnq%& option is given on the command
36113 line. For messages received over SMTP, unqualified addresses in header lines
36114 are qualified only if unqualified addresses are permitted in SMTP commands. In
36115 other words, such qualification is also controlled by
36116 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
36121 .section "The UUCP From line" "SECID219"
36122 .cindex "&""From""& line"
36123 .cindex "UUCP" "&""From""& line"
36124 .cindex "sender" "address"
36125 .oindex "&%uucp_from_pattern%&"
36126 .oindex "&%uucp_from_sender%&"
36127 .cindex "envelope from"
36128 .cindex "envelope sender"
36129 .cindex "Sendmail compatibility" "&""From""& line"
36130 Messages that have come from UUCP (and some other applications) often begin
36131 with a line containing the envelope sender and a timestamp, following the word
36132 &"From"&. Examples of two common formats are:
36134 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
36135 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
36137 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
36138 Exim recognizes such lines at the start of messages that are submitted to it
36139 via the command line (that is, on the standard input). It does not recognize
36140 such lines in incoming SMTP messages, unless the sending host matches
36141 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
36142 and &%ignore_fromline_local%& is set. The recognition is controlled by a
36143 regular expression that is defined by the &%uucp_from_pattern%& option, whose
36144 default value matches the two common cases shown above and puts the address
36145 that follows &"From"& into &$1$&.
36147 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
36148 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
36149 a trusted user, the message's sender address is constructed by expanding the
36150 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
36151 then parsed as an RFC 2822 address. If there is no domain, the local part is
36152 qualified with &%qualify_domain%& unless it is the empty string. However, if
36153 the command line &%-f%& option is used, it overrides the &"From"& line.
36155 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
36156 sender address is not changed. This is also the case for incoming SMTP messages
36157 that are permitted to contain &"From"& lines.
36159 Only one &"From"& line is recognized. If there is more than one, the second is
36160 treated as a data line that starts the body of the message, as it is not valid
36161 as a header line. This also happens if a &"From"& line is present in an
36162 incoming SMTP message from a source that is not permitted to send them.
36166 .section "Resent- header lines" "SECID220"
36168 RFC 2822 makes provision for sets of header lines starting with the string
36169 &`Resent-`& to be added to a message when it is resent by the original
36170 recipient to somebody else. These headers are &'Resent-Date:'&,
36171 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
36172 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
36175 &'Resent fields are strictly informational. They MUST NOT be used in the normal
36176 processing of replies or other such automatic actions on messages.'&
36179 This leaves things a bit vague as far as other processing actions such as
36180 address rewriting are concerned. Exim treats &%Resent-%& header lines as
36184 A &'Resent-From:'& line that just contains the login id of the submitting user
36185 is automatically rewritten in the same way as &'From:'& (see below).
36187 If there's a rewriting rule for a particular header line, it is also applied to
36188 &%Resent-%& header lines of the same type. For example, a rule that rewrites
36189 &'From:'& also rewrites &'Resent-From:'&.
36191 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
36194 For a locally-submitted message,
36195 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
36196 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
36197 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
36198 included in log lines in this case.
36200 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
36201 &%Resent-%& header lines are present.
36207 .section "The Auto-Submitted: header line" "SECID221"
36208 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
36209 includes the header line:
36211 Auto-Submitted: auto-replied
36214 .section "The Bcc: header line" "SECID222"
36215 .cindex "&'Bcc:'& header line"
36216 If Exim is called with the &%-t%& option, to take recipient addresses from a
36217 message's header, it removes any &'Bcc:'& header line that may exist (after
36218 extracting its addresses). If &%-t%& is not present on the command line, any
36219 existing &'Bcc:'& is not removed.
36222 .section "The Date: header line" "SECID223"
36224 If a locally-generated or submission-mode message has no &'Date:'& header line,
36225 Exim adds one, using the current date and time, unless the
36226 &%suppress_local_fixups%& control has been specified.
36228 .section "The Delivery-date: header line" "SECID224"
36229 .cindex "&'Delivery-date:'& header line"
36230 .oindex "&%delivery_date_remove%&"
36231 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
36232 set. Exim can be configured to add them to the final delivery of messages. (See
36233 the generic &%delivery_date_add%& transport option.) They should not be present
36234 in messages in transit. If the &%delivery_date_remove%& configuration option is
36235 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
36239 .section "The Envelope-to: header line" "SECID225"
36240 .chindex Envelope-to:
36241 .oindex "&%envelope_to_remove%&"
36242 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
36243 Exim can be configured to add them to the final delivery of messages. (See the
36244 generic &%envelope_to_add%& transport option.) They should not be present in
36245 messages in transit. If the &%envelope_to_remove%& configuration option is set
36246 (the default), Exim removes &'Envelope-to:'& header lines from incoming
36250 .section "The From: header line" "SECTthefrohea"
36252 .cindex "Sendmail compatibility" "&""From""& line"
36253 .cindex "message" "submission"
36254 .cindex "submission mode"
36255 If a submission-mode message does not contain a &'From:'& header line, Exim
36256 adds one if either of the following conditions is true:
36259 The envelope sender address is not empty (that is, this is not a bounce
36260 message). The added header line copies the envelope sender address.
36262 .vindex "&$authenticated_id$&"
36263 The SMTP session is authenticated and &$authenticated_id$& is not empty.
36265 .vindex "&$qualify_domain$&"
36266 If no domain is specified by the submission control, the local part is
36267 &$authenticated_id$& and the domain is &$qualify_domain$&.
36269 If a non-empty domain is specified by the submission control, the local
36270 part is &$authenticated_id$&, and the domain is the specified domain.
36272 If an empty domain is specified by the submission control,
36273 &$authenticated_id$& is assumed to be the complete address.
36277 A non-empty envelope sender takes precedence.
36279 If a locally-generated incoming message does not contain a &'From:'& header
36280 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
36281 containing the sender's address. The calling user's login name and full name
36282 are used to construct the address, as described in section &<<SECTconstr>>&.
36283 They are obtained from the password data by calling &[getpwuid()]& (but see the
36284 &%unknown_login%& configuration option). The address is qualified with
36285 &%qualify_domain%&.
36287 For compatibility with Sendmail, if an incoming, non-SMTP message has a
36288 &'From:'& header line containing just the unqualified login name of the calling
36289 user, this is replaced by an address containing the user's login name and full
36290 name as described in section &<<SECTconstr>>&.
36293 .section "The Message-ID: header line" "SECID226"
36294 .chindex Message-ID:
36295 .cindex "message" "submission"
36296 .oindex "&%message_id_header_text%&"
36297 If a locally-generated or submission-mode incoming message does not contain a
36298 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
36299 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
36300 to the message. If there are any &'Resent-:'& headers in the message, it
36301 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
36302 message id, preceded by the letter E to ensure it starts with a letter, and
36303 followed by @ and the primary host name. Additional information can be included
36304 in this header line by setting the &%message_id_header_text%& and/or
36305 &%message_id_header_domain%& options.
36308 .section "The Received: header line" "SECID227"
36310 A &'Received:'& header line is added at the start of every message. The
36311 contents are defined by the &%received_header_text%& configuration option, and
36312 Exim automatically adds a semicolon and a timestamp to the configured string.
36314 The &'Received:'& header is generated as soon as the message's header lines
36315 have been received. At this stage, the timestamp in the &'Received:'& header
36316 line is the time that the message started to be received. This is the value
36317 that is seen by the DATA ACL and by the &[local_scan()]& function.
36319 Once a message is accepted, the timestamp in the &'Received:'& header line is
36320 changed to the time of acceptance, which is (apart from a small delay while the
36321 -H spool file is written) the earliest time at which delivery could start.
36324 .section "The References: header line" "SECID228"
36325 .chindex References:
36326 Messages created by the &(autoreply)& transport include a &'References:'&
36327 header line. This is constructed according to the rules that are described in
36328 section 3.64 of RFC 2822 (which states that replies should contain such a
36329 header line), and section 3.14 of RFC 3834 (which states that automatic
36330 responses are not different in this respect). However, because some mail
36331 processing software does not cope well with very long header lines, no more
36332 than 12 message IDs are copied from the &'References:'& header line in the
36333 incoming message. If there are more than 12, the first one and then the final
36334 11 are copied, before adding the message ID of the incoming message.
36338 .section "The Return-path: header line" "SECID229"
36339 .chindex Return-path:
36340 .oindex "&%return_path_remove%&"
36341 &'Return-path:'& header lines are defined as something an MTA may insert when
36342 it does the final delivery of messages. (See the generic &%return_path_add%&
36343 transport option.) Therefore, they should not be present in messages in
36344 transit. If the &%return_path_remove%& configuration option is set (the
36345 default), Exim removes &'Return-path:'& header lines from incoming messages.
36349 .section "The Sender: header line" "SECTthesenhea"
36350 .cindex "&'Sender:'& header line"
36351 .cindex "message" "submission"
36353 For a locally-originated message from an untrusted user, Exim may remove an
36354 existing &'Sender:'& header line, and it may add a new one. You can modify
36355 these actions by setting the &%local_sender_retain%& option true, the
36356 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
36359 When a local message is received from an untrusted user and
36360 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
36361 control has not been set, a check is made to see if the address given in the
36362 &'From:'& header line is the correct (local) sender of the message. The address
36363 that is expected has the login name as the local part and the value of
36364 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
36365 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
36366 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
36367 line is added to the message.
36369 If you set &%local_from_check%& false, this checking does not occur. However,
36370 the removal of an existing &'Sender:'& line still happens, unless you also set
36371 &%local_sender_retain%& to be true. It is not possible to set both of these
36372 options true at the same time.
36374 .cindex "submission mode"
36375 By default, no processing of &'Sender:'& header lines is done for messages
36376 received over TCP/IP or for messages submitted by trusted users. However, when
36377 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
36378 not specified on the submission control, the following processing takes place:
36380 .vindex "&$authenticated_id$&"
36381 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
36382 authenticated, and &$authenticated_id$& is not empty, a sender address is
36383 created as follows:
36386 .vindex "&$qualify_domain$&"
36387 If no domain is specified by the submission control, the local part is
36388 &$authenticated_id$& and the domain is &$qualify_domain$&.
36390 If a non-empty domain is specified by the submission control, the local part
36391 is &$authenticated_id$&, and the domain is the specified domain.
36393 If an empty domain is specified by the submission control,
36394 &$authenticated_id$& is assumed to be the complete address.
36397 This address is compared with the address in the &'From:'& header line. If they
36398 are different, a &'Sender:'& header line containing the created address is
36399 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
36400 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
36402 .cindex "return path" "created from &'Sender:'&"
36403 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
36404 the message (the envelope sender address) is changed to be the same address,
36405 except in the case of submission mode when &%sender_retain%& is specified.
36409 .section "Adding and removing header lines in routers and transports" &&&
36410 "SECTheadersaddrem"
36411 .cindex "header lines" "adding; in router or transport"
36412 .cindex "header lines" "removing; in router or transport"
36413 When a message is delivered, the addition and removal of header lines can be
36414 specified in a system filter, or on any of the routers and transports that
36415 process the message. Section &<<SECTaddremheasys>>& contains details about
36416 modifying headers in a system filter. Header lines can also be added in an ACL
36417 as a message is received (see section &<<SECTaddheadacl>>&).
36419 In contrast to what happens in a system filter, header modifications that are
36420 specified on routers and transports apply only to the particular recipient
36421 addresses that are being processed by those routers and transports. These
36422 changes do not actually take place until a copy of the message is being
36423 transported. Therefore, they do not affect the basic set of header lines, and
36424 they do not affect the values of the variables that refer to header lines.
36426 &*Note*&: In particular, this means that any expansions in the configuration of
36427 the transport cannot refer to the modified header lines, because such
36428 expansions all occur before the message is actually transported.
36430 For both routers and transports, the argument of a &%headers_add%&
36431 option must be in the form of one or more RFC 2822 header lines, separated by
36432 newlines (coded as &"\n"&). For example:
36434 headers_add = X-added-header: added by $primary_hostname\n\
36435 X-added-second: another added header line
36437 Exim does not check the syntax of these added header lines.
36439 Multiple &%headers_add%& options for a single router or transport can be
36440 specified; the values will append to a single list of header lines.
36441 Each header-line is separately expanded.
36443 The argument of a &%headers_remove%& option must consist of a colon-separated
36444 list of header names. This is confusing, because header names themselves are
36445 often terminated by colons. In this case, the colons are the list separators,
36446 not part of the names. For example:
36448 headers_remove = return-receipt-to:acknowledge-to
36451 Multiple &%headers_remove%& options for a single router or transport can be
36452 specified; the arguments will append to a single header-names list.
36453 Each item is separately expanded.
36454 Note that colons in complex expansions which are used to
36455 form all or part of a &%headers_remove%& list
36456 will act as list separators.
36458 When &%headers_add%& or &%headers_remove%& is specified on a router,
36459 items are expanded at routing time,
36460 and then associated with all addresses that are
36461 accepted by that router, and also with any new addresses that it generates. If
36462 an address passes through several routers as a result of aliasing or
36463 forwarding, the changes are cumulative.
36465 .oindex "&%unseen%&"
36466 However, this does not apply to multiple routers that result from the use of
36467 the &%unseen%& option. Any header modifications that were specified by the
36468 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
36470 Addresses that end up with different &%headers_add%& or &%headers_remove%&
36471 settings cannot be delivered together in a batch, so a transport is always
36472 dealing with a set of addresses that have the same header-processing
36475 The transport starts by writing the original set of header lines that arrived
36476 with the message, possibly modified by the system filter. As it writes out
36477 these lines, it consults the list of header names that were attached to the
36478 recipient address(es) by &%headers_remove%& options in routers, and it also
36479 consults the transport's own &%headers_remove%& option. Header lines whose
36480 names are on either of these lists are not written out. If there are multiple
36481 instances of any listed header, they are all skipped.
36483 After the remaining original header lines have been written, new header
36484 lines that were specified by routers' &%headers_add%& options are written, in
36485 the order in which they were attached to the address. These are followed by any
36486 header lines specified by the transport's &%headers_add%& option.
36488 This way of handling header line modifications in routers and transports has
36489 the following consequences:
36492 The original set of header lines, possibly modified by the system filter,
36493 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
36494 to it, at all times.
36496 Header lines that are added by a router's
36497 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
36498 expansion syntax in subsequent routers or the transport.
36500 Conversely, header lines that are specified for removal by &%headers_remove%&
36501 in a router remain visible to subsequent routers and the transport.
36503 Headers added to an address by &%headers_add%& in a router cannot be removed by
36504 a later router or by a transport.
36506 An added header can refer to the contents of an original header that is to be
36507 removed, even it has the same name as the added header. For example:
36509 headers_remove = subject
36510 headers_add = Subject: new subject (was: $h_subject:)
36514 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
36515 for a &(redirect)& router that has the &%one_time%& option set.
36521 .section "Constructed addresses" "SECTconstr"
36522 .cindex "address" "constructed"
36523 .cindex "constructed address"
36524 When Exim constructs a sender address for a locally-generated message, it uses
36527 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
36531 Zaphod Beeblebrox <zaphod@end.univ.example>
36533 The user name is obtained from the &%-F%& command line option if set, or
36534 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
36535 &"gecos"& field from the password entry. If the &"gecos"& field contains an
36536 ampersand character, this is replaced by the login name with the first letter
36537 upper cased, as is conventional in a number of operating systems. See the
36538 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
36539 The &%unknown_username%& option can be used to specify user names in cases when
36540 there is no password file entry.
36543 In all cases, the user name is made to conform to RFC 2822 by quoting all or
36544 parts of it if necessary. In addition, if it contains any non-printing
36545 characters, it is encoded as described in RFC 2047, which defines a way of
36546 including non-ASCII characters in header lines. The value of the
36547 &%headers_charset%& option specifies the name of the encoding that is used (the
36548 characters are assumed to be in this encoding). The setting of
36549 &%print_topbitchars%& controls whether characters with the top bit set (that
36550 is, with codes greater than 127) count as printing characters or not.
36554 .section "Case of local parts" "SECID230"
36555 .cindex "case of local parts"
36556 .cindex "local part" "case of"
36557 RFC 2822 states that the case of letters in the local parts of addresses cannot
36558 be assumed to be non-significant. Exim preserves the case of local parts of
36559 addresses, but by default it uses a lower-cased form when it is routing,
36560 because on most Unix systems, usernames are in lower case and case-insensitive
36561 routing is required. However, any particular router can be made to use the
36562 original case for local parts by setting the &%caseful_local_part%& generic
36565 .cindex "mixed-case login names"
36566 If you must have mixed-case user names on your system, the best way to proceed,
36567 assuming you want case-independent handling of incoming email, is to set up
36568 your first router to convert incoming local parts in your domains to the
36569 correct case by means of a file lookup. For example:
36573 domains = +local_domains
36574 data = ${lookup{$local_part}cdb\
36575 {/etc/usercased.cdb}{$value}fail}\
36578 For this router, the local part is forced to lower case by the default action
36579 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
36580 up a new local part in the correct case. If you then set &%caseful_local_part%&
36581 on any subsequent routers which process your domains, they will operate on
36582 local parts with the correct case in a case-sensitive manner.
36586 .section "Dots in local parts" "SECID231"
36587 .cindex "dot" "in local part"
36588 .cindex "local part" "dots in"
36589 RFC 2822 forbids empty components in local parts. That is, an unquoted local
36590 part may not begin or end with a dot, nor have two consecutive dots in the
36591 middle. However, it seems that many MTAs do not enforce this, so Exim permits
36592 empty components for compatibility.
36596 .section "Rewriting addresses" "SECID232"
36597 .cindex "rewriting" "addresses"
36598 Rewriting of sender and recipient addresses, and addresses in headers, can
36599 happen automatically, or as the result of configuration options, as described
36600 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
36601 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
36603 Automatic rewriting includes qualification, as mentioned above. The other case
36604 in which it can happen is when an incomplete non-local domain is given. The
36605 routing process may cause this to be expanded into the full domain name. For
36606 example, a header such as
36610 might get rewritten as
36612 To: hare@teaparty.wonderland.fict.example
36614 Rewriting as a result of routing is the one kind of message processing that
36615 does not happen at input time, as it cannot be done until the address has
36618 Strictly, one should not do &'any'& deliveries of a message until all its
36619 addresses have been routed, in case any of the headers get changed as a
36620 result of routing. However, doing this in practice would hold up many
36621 deliveries for unreasonable amounts of time, just because one address could not
36622 immediately be routed. Exim therefore does not delay other deliveries when
36623 routing of one or more addresses is deferred.
36624 .ecindex IIDmesproc
36628 . ////////////////////////////////////////////////////////////////////////////
36629 . ////////////////////////////////////////////////////////////////////////////
36631 .chapter "SMTP processing" "CHAPSMTP"
36632 .scindex IIDsmtpproc1 "SMTP" "processing details"
36633 .scindex IIDsmtpproc2 "LMTP" "processing details"
36634 Exim supports a number of different ways of using the SMTP protocol, and its
36635 LMTP variant, which is an interactive protocol for transferring messages into a
36636 closed mail store application. This chapter contains details of how SMTP is
36637 processed. For incoming mail, the following are available:
36640 SMTP over TCP/IP (Exim daemon or &'inetd'&);
36642 SMTP over the standard input and output (the &%-bs%& option);
36644 Batched SMTP on the standard input (the &%-bS%& option).
36647 For mail delivery, the following are available:
36650 SMTP over TCP/IP (the &(smtp)& transport);
36652 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
36655 LMTP over a pipe to a process running in the local host (the &(lmtp)&
36658 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
36659 the &%use_bsmtp%& option set).
36662 &'Batched SMTP'& is the name for a process in which batches of messages are
36663 stored in or read from files (or pipes), in a format in which SMTP commands are
36664 used to contain the envelope information.
36668 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
36669 .cindex "SMTP" "outgoing over TCP/IP"
36670 .cindex "outgoing SMTP over TCP/IP"
36671 .cindex "LMTP" "over TCP/IP"
36672 .cindex "outgoing LMTP over TCP/IP"
36675 .cindex "SIZE" "option on MAIL command"
36676 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
36677 The &%protocol%& option selects which protocol is to be used, but the actual
36678 processing is the same in both cases.
36680 .cindex "ESMTP extensions" SIZE
36681 If, in response to its EHLO command, Exim is told that the SIZE
36682 extension is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
36683 command. The value of <&'n'&> is the message size plus the value of the
36684 &%size_addition%& option (default 1024) to allow for additions to the message
36685 such as per-transport header lines, or changes made in a
36686 .cindex "transport" "filter"
36687 .cindex "filter" "transport filter"
36688 transport filter. If &%size_addition%& is set negative, the use of SIZE is
36691 If the remote server advertises support for PIPELINING, Exim uses the
36692 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
36693 required for the transaction.
36695 If the remote server advertises support for the STARTTLS command, and Exim
36696 was built to support TLS encryption, it tries to start a TLS session unless the
36697 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
36698 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
36699 is called for verification.
36701 If the remote server advertises support for the AUTH command, Exim scans
36702 the authenticators configuration for any suitable client settings, as described
36703 in chapter &<<CHAPSMTPAUTH>>&.
36705 .cindex "carriage return"
36707 Responses from the remote host are supposed to be terminated by CR followed by
36708 LF. However, there are known to be hosts that do not send CR characters, so in
36709 order to be able to interwork with such hosts, Exim treats LF on its own as a
36712 If a message contains a number of different addresses, all those with the same
36713 characteristics (for example, the same envelope sender) that resolve to the
36714 same set of hosts, in the same order, are sent in a single SMTP transaction,
36715 even if they are for different domains, unless there are more than the setting
36716 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
36717 they are split into groups containing no more than &%max_rcpt%&s addresses
36718 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
36719 in parallel sessions. The order of hosts with identical MX values is not
36720 significant when checking whether addresses can be batched in this way.
36722 When the &(smtp)& transport suffers a temporary failure that is not
36723 message-related, Exim updates its transport-specific database, which contains
36724 records indexed by host name that remember which messages are waiting for each
36725 particular host. It also updates the retry database with new retry times.
36727 .cindex "hints database" "retry keys"
36728 Exim's retry hints are based on host name plus IP address, so if one address of
36729 a multi-homed host is broken, it will soon be skipped most of the time.
36730 See the next section for more detail about error handling.
36732 .cindex "SMTP" "passed connection"
36733 .cindex "SMTP" "batching over TCP/IP"
36734 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
36735 looks in the hints database for the transport to see if there are any queued
36736 messages waiting for the host to which it is connected. If it finds one, it
36737 creates a new Exim process using the &%-MC%& option (which can only be used by
36738 a process running as root or the Exim user) and passes the TCP/IP socket to it
36739 so that it can deliver another message using the same socket. The new process
36740 does only those deliveries that are routed to the connected host, and may in
36741 turn pass the socket on to a third process, and so on.
36743 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
36744 limit the number of messages sent down a single TCP/IP connection.
36746 .cindex "asterisk" "after IP address"
36747 The second and subsequent messages delivered down an existing connection are
36748 identified in the main log by the addition of an asterisk after the closing
36749 square bracket of the IP address.
36754 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
36755 .cindex "error" "in outgoing SMTP"
36756 .cindex "SMTP" "errors in outgoing"
36757 .cindex "host" "error"
36758 Three different kinds of error are recognized for outgoing SMTP: host errors,
36759 message errors, and recipient errors.
36762 .vitem "&*Host errors*&"
36763 A host error is not associated with a particular message or with a
36764 particular recipient of a message. The host errors are:
36767 Connection refused or timed out,
36769 Any error response code on connection,
36771 Any error response code to EHLO or HELO,
36773 Loss of connection at any time, except after &"."&,
36775 I/O errors at any time,
36777 Timeouts during the session, other than in response to MAIL, RCPT or
36778 the &"."& at the end of the data.
36781 For a host error, a permanent error response on connection, or in response to
36782 EHLO, causes all addresses routed to the host to be failed. Any other host
36783 error causes all addresses to be deferred, and retry data to be created for the
36784 host. It is not tried again, for any message, until its retry time arrives. If
36785 the current set of addresses are not all delivered in this run (to some
36786 alternative host), the message is added to the list of those waiting for this
36787 host, so if it is still undelivered when a subsequent successful delivery is
36788 made to the host, it will be sent down the same SMTP connection.
36790 .vitem "&*Message errors*&"
36791 .cindex "message" "error"
36792 A message error is associated with a particular message when sent to a
36793 particular host, but not with a particular recipient of the message. The
36794 message errors are:
36797 Any error response code to MAIL, DATA, or the &"."& that terminates
36800 Timeout after MAIL,
36802 Timeout or loss of connection after the &"."& that terminates the data. A
36803 timeout after the DATA command itself is treated as a host error, as is loss of
36804 connection at any other time.
36807 For a message error, a permanent error response (5&'xx'&) causes all addresses
36808 to be failed, and a delivery error report to be returned to the sender. A
36809 temporary error response (4&'xx'&), or one of the timeouts, causes all
36810 addresses to be deferred. Retry data is not created for the host, but instead,
36811 a retry record for the combination of host plus message id is created. The
36812 message is not added to the list of those waiting for this host. This ensures
36813 that the failing message will not be sent to this host again until the retry
36814 time arrives. However, other messages that are routed to the host are not
36815 affected, so if it is some property of the message that is causing the error,
36816 it will not stop the delivery of other mail.
36818 If the remote host specified support for the SIZE parameter in its response
36819 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
36820 over-large message will cause a message error because the error arrives as a
36823 .vitem "&*Recipient errors*&"
36824 .cindex "recipient" "error"
36825 A recipient error is associated with a particular recipient of a message. The
36826 recipient errors are:
36829 Any error response to RCPT,
36831 Timeout after RCPT.
36834 For a recipient error, a permanent error response (5&'xx'&) causes the
36835 recipient address to be failed, and a bounce message to be returned to the
36836 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
36837 address to be deferred, and routing retry data to be created for it. This is
36838 used to delay processing of the address in subsequent queue runs, until its
36839 routing retry time arrives. This applies to all messages, but because it
36840 operates only in queue runs, one attempt will be made to deliver a new message
36841 to the failing address before the delay starts to operate. This ensures that,
36842 if the failure is really related to the message rather than the recipient
36843 (&"message too big for this recipient"& is a possible example), other messages
36844 have a chance of getting delivered. If a delivery to the address does succeed,
36845 the retry information gets cleared, so all stuck messages get tried again, and
36846 the retry clock is reset.
36848 The message is not added to the list of those waiting for this host. Use of the
36849 host for other messages is unaffected, and except in the case of a timeout,
36850 other recipients are processed independently, and may be successfully delivered
36851 in the current SMTP session. After a timeout it is of course impossible to
36852 proceed with the session, so all addresses get deferred. However, those other
36853 than the one that failed do not suffer any subsequent retry delays. Therefore,
36854 if one recipient is causing trouble, the others have a chance of getting
36855 through when a subsequent delivery attempt occurs before the failing
36856 recipient's retry time.
36859 In all cases, if there are other hosts (or IP addresses) available for the
36860 current set of addresses (for example, from multiple MX records), they are
36861 tried in this run for any undelivered addresses, subject of course to their
36862 own retry data. In other words, recipient error retry data does not take effect
36863 until the next delivery attempt.
36865 Some hosts have been observed to give temporary error responses to every
36866 MAIL command at certain times (&"insufficient space"& has been seen). It
36867 would be nice if such circumstances could be recognized, and defer data for the
36868 host itself created, but this is not possible within the current Exim design.
36869 What actually happens is that retry data for every (host, message) combination
36872 The reason that timeouts after MAIL and RCPT are treated specially is that
36873 these can sometimes arise as a result of the remote host's verification
36874 procedures. Exim makes this assumption, and treats them as if a temporary error
36875 response had been received. A timeout after &"."& is treated specially because
36876 it is known that some broken implementations fail to recognize the end of the
36877 message if the last character of the last line is a binary zero. Thus, it is
36878 helpful to treat this case as a message error.
36880 Timeouts at other times are treated as host errors, assuming a problem with the
36881 host, or the connection to it. If a timeout after MAIL, RCPT,
36882 or &"."& is really a connection problem, the assumption is that at the next try
36883 the timeout is likely to occur at some other point in the dialogue, causing it
36884 then to be treated as a host error.
36886 There is experimental evidence that some MTAs drop the connection after the
36887 terminating &"."& if they do not like the contents of the message for some
36888 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
36889 should be given. That is why Exim treats this case as a message rather than a
36890 host error, in order not to delay other messages to the same host.
36895 .section "Incoming SMTP messages over TCP/IP" "SECID233"
36896 .cindex "SMTP" "incoming over TCP/IP"
36897 .cindex "incoming SMTP over TCP/IP"
36900 Incoming SMTP messages can be accepted in one of two ways: by running a
36901 listening daemon, or by using &'inetd'&. In the latter case, the entry in
36902 &_/etc/inetd.conf_& should be like this:
36904 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
36906 Exim distinguishes between this case and the case of a locally running user
36907 agent using the &%-bs%& option by checking whether or not the standard input is
36908 a socket. When it is, either the port must be privileged (less than 1024), or
36909 the caller must be root or the Exim user. If any other user passes a socket
36910 with an unprivileged port number, Exim prints a message on the standard error
36911 stream and exits with an error code.
36913 By default, Exim does not make a log entry when a remote host connects or
36914 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
36915 unexpected. It can be made to write such log entries by setting the
36916 &%smtp_connection%& log selector.
36918 .cindex "carriage return"
36920 Commands from the remote host are supposed to be terminated by CR followed by
36921 LF. However, there are known to be hosts that do not send CR characters. In
36922 order to be able to interwork with such hosts, Exim treats LF on its own as a
36924 Furthermore, because common code is used for receiving messages from all
36925 sources, a CR on its own is also interpreted as a line terminator. However, the
36926 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
36928 .cindex "EHLO" "invalid data"
36929 .cindex "HELO" "invalid data"
36930 One area that sometimes gives rise to problems concerns the EHLO or
36931 HELO commands. Some clients send syntactically invalid versions of these
36932 commands, which Exim rejects by default. (This is nothing to do with verifying
36933 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
36934 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
36935 match the broken hosts that send invalid commands.
36937 .cindex "SIZE option on MAIL command"
36938 .cindex "MAIL" "SIZE option"
36939 The amount of disk space available is checked whenever SIZE is received on
36940 a MAIL command, independently of whether &%message_size_limit%& or
36941 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
36942 false. A temporary error is given if there is not enough space. If
36943 &%check_spool_space%& is set, the check is for that amount of space plus the
36944 value given with SIZE, that is, it checks that the addition of the incoming
36945 message will not reduce the space below the threshold.
36947 When a message is successfully received, Exim includes the local message id in
36948 its response to the final &"."& that terminates the data. If the remote host
36949 logs this text it can help with tracing what has happened to a message.
36951 The Exim daemon can limit the number of simultaneous incoming connections it is
36952 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
36953 number of simultaneous incoming connections from a single remote host (see the
36954 &%smtp_accept_max_per_host%& option). Additional connection attempts are
36955 rejected using the SMTP temporary error code 421.
36957 The Exim daemon does not rely on the SIGCHLD signal to detect when a
36958 subprocess has finished, as this can get lost at busy times. Instead, it looks
36959 for completed subprocesses every time it wakes up. Provided there are other
36960 things happening (new incoming calls, starts of queue runs), completed
36961 processes will be noticed and tidied away. On very quiet systems you may
36962 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
36963 it will be noticed when the daemon next wakes up.
36965 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
36966 and can also be set up to reject SMTP calls from non-reserved hosts at times of
36967 high system load &-- for details see the &%smtp_accept_reserve%&,
36968 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
36969 applies in both the daemon and &'inetd'& cases.
36971 Exim normally starts a delivery process for each message received, though this
36972 can be varied by means of the &%-odq%& command line option and the
36973 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
36974 number of simultaneously running delivery processes started in this way from
36975 SMTP input can be limited by the &%smtp_accept_queue%& and
36976 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
36977 subsequently received messages are just put on the input queue without starting
36978 a delivery process.
36980 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
36981 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
36982 started up from the &'inetd'& daemon, because in that case each connection is
36983 handled by an entirely independent Exim process. Control by load average is,
36984 however, available with &'inetd'&.
36986 Exim can be configured to verify addresses in incoming SMTP commands as they
36987 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
36988 to rewrite addresses at this time &-- before any syntax checking is done. See
36989 section &<<SECTrewriteS>>&.
36991 Exim can also be configured to limit the rate at which a client host submits
36992 MAIL and RCPT commands in a single SMTP session. See the
36993 &%smtp_ratelimit_hosts%& option.
36997 .section "Unrecognized SMTP commands" "SECID234"
36998 .cindex "SMTP" "unrecognized commands"
36999 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
37000 commands during a single SMTP connection, it drops the connection after sending
37001 the error response to the last command. The default value for
37002 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
37003 abuse that subvert web servers into making connections to SMTP ports; in these
37004 circumstances, a number of non-SMTP lines are sent first.
37007 .section "Syntax and protocol errors in SMTP commands" "SECID235"
37008 .cindex "SMTP" "syntax errors"
37009 .cindex "SMTP" "protocol errors"
37010 A syntax error is detected if an SMTP command is recognized, but there is
37011 something syntactically wrong with its data, for example, a malformed email
37012 address in a RCPT command. Protocol errors include invalid command
37013 sequencing such as RCPT before MAIL. If Exim receives more than
37014 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
37015 drops the connection after sending the error response to the last command. The
37016 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
37017 broken clients that loop sending bad commands (yes, it has been seen).
37021 .section "Use of non-mail SMTP commands" "SECID236"
37022 .cindex "SMTP" "non-mail commands"
37023 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
37024 DATA. Exim counts such commands, and drops the connection if there are too
37025 many of them in a single SMTP session. This action catches some
37026 denial-of-service attempts and things like repeated failing AUTHs, or a mad
37027 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
37028 defines what &"too many"& means. Its default value is 10.
37030 When a new message is expected, one occurrence of RSET is not counted. This
37031 allows a client to send one RSET between messages (this is not necessary,
37032 but some clients do it). Exim also allows one uncounted occurrence of HELO
37033 or EHLO, and one occurrence of STARTTLS between messages. After
37034 starting up a TLS session, another EHLO is expected, and so it too is not
37037 The first occurrence of AUTH in a connection, or immediately following
37038 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
37039 RCPT, DATA, and QUIT are counted.
37041 You can control which hosts are subject to the limit set by
37042 &%smtp_accept_max_nonmail%& by setting
37043 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
37044 the limit apply to all hosts. This option means that you can exclude any
37045 specific badly-behaved hosts that you have to live with.
37050 .section "The VRFY and EXPN commands" "SECID237"
37051 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
37052 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
37053 appropriate) in order to decide whether the command should be accepted or not.
37055 .cindex "VRFY" "processing"
37056 When no ACL is defined for VRFY, or if it rejects without
37057 setting an explicit response code, the command is accepted
37058 (with a 252 SMTP response code)
37059 in order to support awkward clients that do a VRFY before every RCPT.
37060 When VRFY is accepted, it runs exactly the same code as when Exim is
37061 called with the &%-bv%& option, and returns 250/451/550
37062 SMTP response codes.
37064 .cindex "EXPN" "processing"
37065 If no ACL for EXPN is defined, the command is rejected.
37066 When EXPN is accepted, a single-level expansion of the address is done.
37067 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
37068 than a verification (the &%-bv%& option). If an unqualified local part is given
37069 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
37070 of VRFY and EXPN commands are logged on the main and reject logs, and
37071 VRFY verification failures are logged on the main log for consistency with
37076 .section "The ETRN command" "SECTETRN"
37077 .cindex "ETRN" "processing"
37078 .cindex "ESMTP extensions" ETRN
37079 RFC 1985 describes an ESMTP command called ETRN that is designed to
37080 overcome the security problems of the TURN command (which has fallen into
37081 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
37082 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
37083 should be accepted or not. If no ACL is defined, the command is rejected.
37085 The ETRN command is concerned with &"releasing"& messages that are awaiting
37086 delivery to certain hosts. As Exim does not organize its message queue by host,
37087 the only form of ETRN that is supported by default is the one where the
37088 text starts with the &"#"& prefix, in which case the remainder of the text is
37089 specific to the SMTP server. A valid ETRN command causes a run of Exim with
37090 the &%-R%& option to happen, with the remainder of the ETRN text as its
37091 argument. For example,
37099 which causes a delivery attempt on all messages with undelivered addresses
37100 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
37101 default), Exim prevents the simultaneous execution of more than one queue run
37102 for the same argument string as a result of an ETRN command. This stops
37103 a misbehaving client from starting more than one queue runner at once.
37105 .cindex "hints database" "ETRN serialization"
37106 Exim implements the serialization by means of a hints database in which a
37107 record is written whenever a process is started by ETRN, and deleted when
37108 the process completes. However, Exim does not keep the SMTP session waiting for
37109 the ETRN process to complete. Once ETRN is accepted, the client is sent
37110 a &"success"& return code. Obviously there is scope for hints records to get
37111 left lying around if there is a system or program crash. To guard against this,
37112 Exim ignores any records that are more than six hours old.
37114 .oindex "&%smtp_etrn_command%&"
37115 For more control over what ETRN does, the &%smtp_etrn_command%& option can
37116 used. This specifies a command that is run whenever ETRN is received,
37117 whatever the form of its argument. For
37120 smtp_etrn_command = /etc/etrn_command $domain \
37121 $sender_host_address
37123 .vindex "&$domain$&"
37124 The string is split up into arguments which are independently expanded. The
37125 expansion variable &$domain$& is set to the argument of the ETRN command,
37126 and no syntax checking is done on the contents of this argument. Exim does not
37127 wait for the command to complete, so its status code is not checked. Exim runs
37128 under its own uid and gid when receiving incoming SMTP, so it is not possible
37129 for it to change them before running the command.
37133 .section "Incoming local SMTP" "SECID238"
37134 .cindex "SMTP" "local incoming"
37135 Some user agents use SMTP to pass messages to their local MTA using the
37136 standard input and output, as opposed to passing the envelope on the command
37137 line and writing the message to the standard input. This is supported by the
37138 &%-bs%& option. This form of SMTP is handled in the same way as incoming
37139 messages over TCP/IP (including the use of ACLs), except that the envelope
37140 sender given in a MAIL command is ignored unless the caller is trusted. In
37141 an ACL you can detect this form of SMTP input by testing for an empty host
37142 identification. It is common to have this as the first line in the ACL that
37143 runs for RCPT commands:
37147 This accepts SMTP messages from local processes without doing any other tests.
37151 .section "Outgoing batched SMTP" "SECTbatchSMTP"
37152 .cindex "SMTP" "batched outgoing"
37153 .cindex "batched SMTP output"
37154 Both the &(appendfile)& and &(pipe)& transports can be used for handling
37155 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
37156 be output in BSMTP format. No SMTP responses are possible for this form of
37157 delivery. All it is doing is using SMTP commands as a way of transmitting the
37158 envelope along with the message.
37160 The message is written to the file or pipe preceded by the SMTP commands
37161 MAIL and RCPT, and followed by a line containing a single dot. Lines in
37162 the message that start with a dot have an extra dot added. The SMTP command
37163 HELO is not normally used. If it is required, the &%message_prefix%& option
37164 can be used to specify it.
37166 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
37167 one recipient address at a time by default. However, you can arrange for them
37168 to handle several addresses at once by setting the &%batch_max%& option. When
37169 this is done for BSMTP, messages may contain multiple RCPT commands. See
37170 chapter &<<CHAPbatching>>& for more details.
37173 When one or more addresses are routed to a BSMTP transport by a router that
37174 sets up a host list, the name of the first host on the list is available to the
37175 transport in the variable &$host$&. Here is an example of such a transport and
37180 driver = manualroute
37181 transport = smtp_appendfile
37182 route_list = domain.example batch.host.example
37186 driver = appendfile
37187 directory = /var/bsmtp/$host
37192 This causes messages addressed to &'domain.example'& to be written in BSMTP
37193 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
37194 message (unless there are more than 1000 recipients).
37198 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
37199 .cindex "SMTP" "batched incoming"
37200 .cindex "batched SMTP input"
37201 The &%-bS%& command line option causes Exim to accept one or more messages by
37202 reading SMTP on the standard input, but to generate no responses. If the caller
37203 is trusted, the senders in the MAIL commands are believed; otherwise the
37204 sender is always the caller of Exim. Unqualified senders and receivers are not
37205 rejected (there seems little point) but instead just get qualified. HELO
37206 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
37207 as NOOP; QUIT quits.
37209 Minimal policy checking is done for BSMTP input. Only the non-SMTP
37210 ACL is run in the same way as for non-SMTP local input.
37212 If an error is detected while reading a message, including a missing &"."& at
37213 the end, Exim gives up immediately. It writes details of the error to the
37214 standard output in a stylized way that the calling program should be able to
37215 make some use of automatically, for example:
37217 554 Unexpected end of file
37218 Transaction started in line 10
37219 Error detected in line 14
37221 It writes a more verbose version, for human consumption, to the standard error
37224 An error was detected while processing a file of BSMTP input.
37225 The error message was:
37227 501 '>' missing at end of address
37229 The SMTP transaction started in line 10.
37230 The error was detected in line 12.
37231 The SMTP command at fault was:
37233 rcpt to:<malformed@in.com.plete
37235 1 previous message was successfully processed.
37236 The rest of the batch was abandoned.
37238 The return code from Exim is zero only if there were no errors. It is 1 if some
37239 messages were accepted before an error was detected, and 2 if no messages were
37241 .ecindex IIDsmtpproc1
37242 .ecindex IIDsmtpproc2
37246 . ////////////////////////////////////////////////////////////////////////////
37247 . ////////////////////////////////////////////////////////////////////////////
37249 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
37250 "Customizing messages"
37251 When a message fails to be delivered, or remains in the queue for more than a
37252 configured amount of time, Exim sends a message to the original sender, or
37253 to an alternative configured address. The text of these messages is built into
37254 the code of Exim, but it is possible to change it, either by adding a single
37255 string, or by replacing each of the paragraphs by text supplied in a file.
37257 The &'From:'& and &'To:'& header lines are automatically generated; you can
37258 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
37259 option. Exim also adds the line
37261 Auto-Submitted: auto-generated
37263 to all warning and bounce messages,
37266 .section "Customizing bounce messages" "SECID239"
37267 .cindex "customizing" "bounce message"
37268 .cindex "bounce message" "customizing"
37269 If &%bounce_message_text%& is set, its contents are included in the default
37270 message immediately after &"This message was created automatically by mail
37271 delivery software."& The string is not expanded. It is not used if
37272 &%bounce_message_file%& is set.
37274 When &%bounce_message_file%& is set, it must point to a template file for
37275 constructing error messages. The file consists of a series of text items,
37276 separated by lines consisting of exactly four asterisks. If the file cannot be
37277 opened, default text is used and a message is written to the main and panic
37278 logs. If any text item in the file is empty, default text is used for that
37281 .vindex "&$bounce_recipient$&"
37282 .vindex "&$bounce_return_size_limit$&"
37283 Each item of text that is read from the file is expanded, and there are two
37284 expansion variables which can be of use here: &$bounce_recipient$& is set to
37285 the recipient of an error message while it is being created, and
37286 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
37287 option, rounded to a whole number.
37289 The items must appear in the file in the following order:
37292 The first item is included in the headers, and should include at least a
37293 &'Subject:'& header. Exim does not check the syntax of these headers.
37295 The second item forms the start of the error message. After it, Exim lists the
37296 failing addresses with their error messages.
37298 The third item is used to introduce any text from pipe transports that is to be
37299 returned to the sender. It is omitted if there is no such text.
37301 The fourth, fifth and sixth items will be ignored and may be empty.
37302 The fields exist for back-compatibility
37305 The default state (&%bounce_message_file%& unset) is equivalent to the
37306 following file, in which the sixth item is empty. The &'Subject:'& and some
37307 other lines have been split in order to fit them on the page:
37309 Subject: Mail delivery failed
37310 ${if eq{$sender_address}{$bounce_recipient}
37311 {: returning message to sender}}
37313 This message was created automatically by mail delivery software.
37315 A message ${if eq{$sender_address}{$bounce_recipient}
37316 {that you sent }{sent by
37320 }}could not be delivered to all of its recipients.
37321 This is a permanent error. The following address(es) failed:
37323 The following text was generated during the delivery attempt(s):
37325 ------ This is a copy of the message, including all the headers.
37328 ------ The body of the message is $message_size characters long;
37330 ------ $bounce_return_size_limit or so are included here.
37333 .section "Customizing warning messages" "SECTcustwarn"
37334 .cindex "customizing" "warning message"
37335 .cindex "warning of delay" "customizing the message"
37336 The option &%warn_message_file%& can be pointed at a template file for use when
37337 warnings about message delays are created. In this case there are only three
37341 The first item is included in the headers, and should include at least a
37342 &'Subject:'& header. Exim does not check the syntax of these headers.
37344 The second item forms the start of the warning message. After it, Exim lists
37345 the delayed addresses.
37347 The third item then ends the message.
37350 The default state is equivalent to the following file, except that some lines
37351 have been split here, in order to fit them on the page:
37353 Subject: Warning: message $message_exim_id delayed
37354 $warn_message_delay
37356 This message was created automatically by mail delivery software.
37358 A message ${if eq{$sender_address}{$warn_message_recipients}
37359 {that you sent }{sent by
37363 }}has not been delivered to all of its recipients after
37364 more than $warn_message_delay in the queue on $primary_hostname.
37366 The message identifier is: $message_exim_id
37367 The subject of the message is: $h_subject
37368 The date of the message is: $h_date
37370 The following address(es) have not yet been delivered:
37372 No action is required on your part. Delivery attempts will
37373 continue for some time, and this warning may be repeated at
37374 intervals if the message remains undelivered. Eventually the
37375 mail delivery software will give up, and when that happens,
37376 the message will be returned to you.
37378 .vindex "&$warn_message_delay$&"
37379 .vindex "&$warn_message_recipients$&"
37380 However, in the default state the subject and date lines are omitted if no
37381 appropriate headers exist. During the expansion of this file,
37382 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
37383 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
37384 of recipients for the warning message. There may be more than one if there are
37385 multiple addresses with different &%errors_to%& settings on the routers that
37391 . ////////////////////////////////////////////////////////////////////////////
37392 . ////////////////////////////////////////////////////////////////////////////
37394 .chapter "Some common configuration settings" "CHAPcomconreq"
37395 This chapter discusses some configuration settings that seem to be fairly
37396 common. More examples and discussion can be found in the Exim book.
37400 .section "Sending mail to a smart host" "SECID240"
37401 .cindex "smart host" "example router"
37402 If you want to send all mail for non-local domains to a &"smart host"&, you
37403 should replace the default &(dnslookup)& router with a router which does the
37404 routing explicitly:
37406 send_to_smart_host:
37407 driver = manualroute
37408 route_list = !+local_domains smart.host.name
37409 transport = remote_smtp
37411 You can use the smart host's IP address instead of the name if you wish.
37412 If you are using Exim only to submit messages to a smart host, and not for
37413 receiving incoming messages, you can arrange for it to do the submission
37414 synchronously by setting the &%mua_wrapper%& option (see chapter
37415 &<<CHAPnonqueueing>>&).
37420 .section "Using Exim to handle mailing lists" "SECTmailinglists"
37421 .cindex "mailing lists"
37422 Exim can be used to run simple mailing lists, but for large and/or complicated
37423 requirements, the use of additional specialized mailing list software such as
37424 Majordomo or Mailman is recommended.
37426 The &(redirect)& router can be used to handle mailing lists where each list
37427 is maintained in a separate file, which can therefore be managed by an
37428 independent manager. The &%domains%& router option can be used to run these
37429 lists in a separate domain from normal mail. For example:
37433 domains = lists.example
37434 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37437 errors_to = ${quote_local_part:$local_part-request}@lists.example
37440 This router is skipped for domains other than &'lists.example'&. For addresses
37441 in that domain, it looks for a file that matches the local part. If there is no
37442 such file, the router declines, but because &%no_more%& is set, no subsequent
37443 routers are tried, and so the whole delivery fails.
37445 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
37446 expanded into a filename or a pipe delivery, which is usually inappropriate in
37449 .oindex "&%errors_to%&"
37450 The &%errors_to%& option specifies that any delivery errors caused by addresses
37451 taken from a mailing list are to be sent to the given address rather than the
37452 original sender of the message. However, before acting on this, Exim verifies
37453 the error address, and ignores it if verification fails.
37455 For example, using the configuration above, mail sent to
37456 &'dicts@lists.example'& is passed on to those addresses contained in
37457 &_/usr/lists/dicts_&, with error reports directed to
37458 &'dicts-request@lists.example'&, provided that this address can be verified.
37459 There could be a file called &_/usr/lists/dicts-request_& containing
37460 the address(es) of this particular list's manager(s), but other approaches,
37461 such as setting up an earlier router (possibly using the &%local_part_prefix%&
37462 or &%local_part_suffix%& options) to handle addresses of the form
37463 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
37467 .section "Syntax errors in mailing lists" "SECID241"
37468 .cindex "mailing lists" "syntax errors in"
37469 If an entry in redirection data contains a syntax error, Exim normally defers
37470 delivery of the original address. That means that a syntax error in a mailing
37471 list holds up all deliveries to the list. This may not be appropriate when a
37472 list is being maintained automatically from data supplied by users, and the
37473 addresses are not rigorously checked.
37475 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
37476 entries that fail to parse, noting the incident in the log. If in addition
37477 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
37478 whenever a broken address is skipped. It is usually appropriate to set
37479 &%syntax_errors_to%& to the same address as &%errors_to%&.
37483 .section "Re-expansion of mailing lists" "SECID242"
37484 .cindex "mailing lists" "re-expansion of"
37485 Exim remembers every individual address to which a message has been delivered,
37486 in order to avoid duplication, but it normally stores only the original
37487 recipient addresses with a message. If all the deliveries to a mailing list
37488 cannot be done at the first attempt, the mailing list is re-expanded when the
37489 delivery is next tried. This means that alterations to the list are taken into
37490 account at each delivery attempt, so addresses that have been added to
37491 the list since the message arrived will therefore receive a copy of the
37492 message, even though it pre-dates their subscription.
37494 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
37495 on the &(redirect)& router. If this is done, any addresses generated by the
37496 router that fail to deliver at the first attempt are added to the message as
37497 &"top level"& addresses, and the parent address that generated them is marked
37498 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
37499 subsequent delivery attempts. The disadvantage of this is that if any of the
37500 failing addresses are incorrect, correcting them in the file has no effect on
37501 pre-existing messages.
37503 The original top-level address is remembered with each of the generated
37504 addresses, and is output in any log messages. However, any intermediate parent
37505 addresses are not recorded. This makes a difference to the log only if the
37506 &%all_parents%& selector is set, but for mailing lists there is normally only
37507 one level of expansion anyway.
37511 .section "Closed mailing lists" "SECID243"
37512 .cindex "mailing lists" "closed"
37513 The examples so far have assumed open mailing lists, to which anybody may
37514 send mail. It is also possible to set up closed lists, where mail is accepted
37515 from specified senders only. This is done by making use of the generic
37516 &%senders%& option to restrict the router that handles the list.
37518 The following example uses the same file as a list of recipients and as a list
37519 of permitted senders. It requires three routers:
37523 domains = lists.example
37524 local_part_suffix = -request
37525 local_parts = ${lookup {$local_part} dsearch,filter=file {/usr/lists}}
37526 file = /usr/lists/${local_part_data}-request
37531 domains = lists.example
37532 senders = ${if exists {/usr/lists/$local_part}\
37533 {lsearch;/usr/lists/$local_part}{*}}
37534 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37537 errors_to = ${quote_local_part:$local_part-request}@lists.example
37542 domains = lists.example
37544 data = :fail: $local_part@lists.example is a closed mailing list
37546 All three routers have the same &%domains%& setting, so for any other domains,
37547 they are all skipped. The first router runs only if the local part ends in
37548 &%-request%&. It handles messages to the list manager(s) by means of an open
37551 The second router runs only if the &%senders%& precondition is satisfied. It
37552 checks for the existence of a list that corresponds to the local part, and then
37553 checks that the sender is on the list by means of a linear search. It is
37554 necessary to check for the existence of the file before trying to search it,
37555 because otherwise Exim thinks there is a configuration error. If the file does
37556 not exist, the expansion of &%senders%& is *, which matches all senders. This
37557 means that the router runs, but because there is no list, declines, and
37558 &%no_more%& ensures that no further routers are run. The address fails with an
37559 &"unrouteable address"& error.
37561 The third router runs only if the second router is skipped, which happens when
37562 a mailing list exists, but the sender is not on it. This router forcibly fails
37563 the address, giving a suitable error message.
37568 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
37570 .cindex "Variable Envelope Return Paths"
37571 .cindex "envelope from"
37572 .cindex "envelope sender"
37573 Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
37574 are a way of helping mailing list administrators discover which subscription
37575 address is the cause of a particular delivery failure. The idea is to encode
37576 the original recipient address in the outgoing envelope sender address, so that
37577 if the message is forwarded by another host and then subsequently bounces, the
37578 original recipient can be extracted from the recipient address of the bounce.
37580 .oindex &%errors_to%&
37581 .oindex &%return_path%&
37582 Envelope sender addresses can be modified by Exim using two different
37583 facilities: the &%errors_to%& option on a router (as shown in previous mailing
37584 list examples), or the &%return_path%& option on a transport. The second of
37585 these is effective only if the message is successfully delivered to another
37586 host; it is not used for errors detected on the local host (see the description
37587 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
37588 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
37594 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37595 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37597 This has the effect of rewriting the return path (envelope sender) on outgoing
37598 SMTP messages, if the local part of the original return path ends in
37599 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
37600 local part and domain of the recipient into the return path. Suppose, for
37601 example, that a message whose return path has been set to
37602 &'somelist-request@your.dom.example'& is sent to
37603 &'subscriber@other.dom.example'&. In the transport, the return path is
37606 somelist-request+subscriber=other.dom.example@your.dom.example
37608 .vindex "&$local_part$&"
37609 For this to work, you must tell Exim to send multiple copies of messages that
37610 have more than one recipient, so that each copy has just one recipient. This is
37611 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
37612 might be sent to several different recipients in the same domain, in which case
37613 &$local_part$& is not available in the transport, because it is not unique.
37615 Unless your host is doing nothing but mailing list deliveries, you should
37616 probably use a separate transport for the VERP deliveries, so as not to use
37617 extra resources in making one-per-recipient copies for other deliveries. This
37618 can easily be done by expanding the &%transport%& option in the router:
37622 domains = ! +local_domains
37624 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37625 {verp_smtp}{remote_smtp}}
37628 If you want to change the return path using &%errors_to%& in a router instead
37629 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
37630 routers that handle mailing list addresses. This will ensure that all delivery
37631 errors, including those detected on the local host, are sent to the VERP
37634 On a host that does no local deliveries and has no manual routing, only the
37635 &(dnslookup)& router needs to be changed. A special transport is not needed for
37636 SMTP deliveries. Every mailing list recipient has its own return path value,
37637 and so Exim must hand them to the transport one at a time. Here is an example
37638 of a &(dnslookup)& router that implements VERP:
37642 domains = ! +local_domains
37643 transport = remote_smtp
37645 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
37646 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37649 Before you start sending out messages with VERPed return paths, you must also
37650 configure Exim to accept the bounce messages that come back to those paths.
37651 Typically this is done by setting a &%local_part_suffix%& option for a
37652 router, and using this to route the messages to wherever you want to handle
37655 The overhead incurred in using VERP depends very much on the size of the
37656 message, the number of recipient addresses that resolve to the same remote
37657 host, and the speed of the connection over which the message is being sent. If
37658 a lot of addresses resolve to the same host and the connection is slow, sending
37659 a separate copy of the message for each address may take substantially longer
37660 than sending a single copy with many recipients (for which VERP cannot be
37668 .section "Virtual domains" "SECTvirtualdomains"
37669 .cindex "virtual domains"
37670 .cindex "domain" "virtual"
37671 The phrase &'virtual domain'& is unfortunately used with two rather different
37675 A domain for which there are no real mailboxes; all valid local parts are
37676 aliases for other email addresses. Common examples are organizational
37677 top-level domains and &"vanity"& domains.
37679 One of a number of independent domains that are all handled by the same host,
37680 with mailboxes on that host, but where the mailbox owners do not necessarily
37681 have login accounts on that host.
37684 The first usage is probably more common, and does seem more &"virtual"& than
37685 the second. This kind of domain can be handled in Exim with a straightforward
37686 aliasing router. One approach is to create a separate alias file for each
37687 virtual domain. Exim can test for the existence of the alias file to determine
37688 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
37689 to a router of this form:
37693 domains = dsearch;/etc/mail/virtual
37694 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
37697 The &%domains%& option specifies that the router is to be skipped, unless there
37698 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
37699 domain that is being processed.
37700 The &(dsearch)& lookup used results in an untainted version of &$domain$&
37701 being placed into the &$domain_data$& variable.
37703 When the router runs, it looks up the local
37704 part in the file to find a new address (or list of addresses). The &%no_more%&
37705 setting ensures that if the lookup fails (leading to &%data%& being an empty
37706 string), Exim gives up on the address without trying any subsequent routers.
37708 This one router can handle all the virtual domains because the alias filenames
37709 follow a fixed pattern. Permissions can be arranged so that appropriate people
37710 can edit the different alias files. A successful aliasing operation results in
37711 a new envelope recipient address, which is then routed from scratch.
37713 The other kind of &"virtual"& domain can also be handled in a straightforward
37714 way. One approach is to create a file for each domain containing a list of
37715 valid local parts, and use it in a router like this:
37719 domains = dsearch;/etc/mail/domains
37720 local_parts = lsearch;/etc/mail/domains/$domain
37721 transport = my_mailboxes
37723 The address is accepted if there is a file for the domain, and the local part
37724 can be found in the file. The &%domains%& option is used to check for the
37725 file's existence because &%domains%& is tested before the &%local_parts%&
37726 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
37727 because that option is tested after &%local_parts%&. The transport is as
37731 driver = appendfile
37732 file = /var/mail/$domain_data/$local_part_data
37735 This uses a directory of mailboxes for each domain. The &%user%& setting is
37736 required, to specify which uid is to be used for writing to the mailboxes.
37738 The configuration shown here is just one example of how you might support this
37739 requirement. There are many other ways this kind of configuration can be set
37740 up, for example, by using a database instead of separate files to hold all the
37741 information about the domains.
37745 .section "Multiple user mailboxes" "SECTmulbox"
37746 .cindex "multiple mailboxes"
37747 .cindex "mailbox" "multiple"
37748 .cindex "local part" "prefix"
37749 .cindex "local part" "suffix"
37750 Heavy email users often want to operate with multiple mailboxes, into which
37751 incoming mail is automatically sorted. A popular way of handling this is to
37752 allow users to use multiple sender addresses, so that replies can easily be
37753 identified. Users are permitted to add prefixes or suffixes to their local
37754 parts for this purpose. The wildcard facility of the generic router options
37755 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
37756 example, consider this router:
37761 file = $home/.forward
37762 local_part_suffix = -*
37763 local_part_suffix_optional
37766 .vindex "&$local_part_suffix$&"
37767 It runs a user's &_.forward_& file for all local parts of the form
37768 &'username-*'&. Within the filter file the user can distinguish different
37769 cases by testing the variable &$local_part_suffix$&. For example:
37771 if $local_part_suffix contains -special then
37772 save /home/$local_part_data/Mail/special
37775 If the filter file does not exist, or does not deal with such addresses, they
37776 fall through to subsequent routers, and, assuming no subsequent use of the
37777 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
37778 control over which suffixes are valid.
37780 Alternatively, a suffix can be used to trigger the use of a different
37781 &_.forward_& file &-- which is the way a similar facility is implemented in
37787 local_part_suffix = -*
37788 local_part_suffix_optional
37789 file = ${lookup {.forward$local_part_suffix} dsearch,ret=full {$home} {$value}fail}
37792 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
37793 example, &_.forward-special_& is used. Once again, if the appropriate file
37794 does not exist, or does not deal with the address, it is passed on to
37795 subsequent routers, which could, if required, look for an unqualified
37796 &_.forward_& file to use as a default.
37800 .section "Simplified vacation processing" "SECID244"
37801 .cindex "vacation processing"
37802 The traditional way of running the &'vacation'& program is for a user to set up
37803 a pipe command in a &_.forward_& file
37804 (see section &<<SECTspecitredli>>& for syntax details).
37805 This is prone to error by inexperienced users. There are two features of Exim
37806 that can be used to make this process simpler for users:
37809 A local part prefix such as &"vacation-"& can be specified on a router which
37810 can cause the message to be delivered directly to the &'vacation'& program, or
37811 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
37812 &_.forward_& file are then much simpler. For example:
37814 spqr, vacation-spqr
37817 The &%require_files%& generic router option can be used to trigger a
37818 vacation delivery by checking for the existence of a certain file in the
37819 user's home directory. The &%unseen%& generic option should also be used, to
37820 ensure that the original delivery also proceeds. In this case, all the user has
37821 to do is to create a file called, say, &_.vacation_&, containing a vacation
37825 Another advantage of both these methods is that they both work even when the
37826 use of arbitrary pipes by users is locked out.
37830 .section "Taking copies of mail" "SECID245"
37831 .cindex "message" "copying every"
37832 Some installations have policies that require archive copies of all messages to
37833 be made. A single copy of each message can easily be taken by an appropriate
37834 command in a system filter, which could, for example, use a different file for
37835 each day's messages.
37837 There is also a shadow transport mechanism that can be used to take copies of
37838 messages that are successfully delivered by local transports, one copy per
37839 delivery. This could be used, &'inter alia'&, to implement automatic
37840 notification of delivery by sites that insist on doing such things.
37844 .section "Intermittently connected hosts" "SECID246"
37845 .cindex "intermittently connected hosts"
37846 It has become quite common (because it is cheaper) for hosts to connect to the
37847 Internet periodically rather than remain connected all the time. The normal
37848 arrangement is that mail for such hosts accumulates on a system that is
37849 permanently connected.
37851 Exim was designed for use on permanently connected hosts, and so it is not
37852 particularly well-suited to use in an intermittently connected environment.
37853 Nevertheless there are some features that can be used.
37856 .section "Exim on the upstream server host" "SECID247"
37857 It is tempting to arrange for incoming mail for the intermittently connected
37858 host to remain in Exim's queue until the client connects. However, this
37859 approach does not scale very well. Two different kinds of waiting message are
37860 being mixed up in the same queue &-- those that cannot be delivered because of
37861 some temporary problem, and those that are waiting for their destination host
37862 to connect. This makes it hard to manage the queue, as well as wasting
37863 resources, because each queue runner scans the entire queue.
37865 A better approach is to separate off those messages that are waiting for an
37866 intermittently connected host. This can be done by delivering these messages
37867 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
37868 format, from where they are transmitted by other software when their
37869 destination connects. This makes it easy to collect all the mail for one host
37870 in a single directory, and to apply local timeout rules on a per-message basis
37873 On a very small scale, leaving the mail on Exim's queue can be made to work. If
37874 you are doing this, you should configure Exim with a long retry period for the
37875 intermittent host. For example:
37877 cheshire.wonderland.fict.example * F,5d,24h
37879 This stops a lot of failed delivery attempts from occurring, but Exim remembers
37880 which messages it has queued up for that host. Once the intermittent host comes
37881 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
37882 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
37883 causes all the queued up messages to be delivered, often down a single SMTP
37884 connection. While the host remains connected, any new messages get delivered
37887 If the connecting hosts do not have fixed IP addresses, that is, if a host is
37888 issued with a different IP address each time it connects, Exim's retry
37889 mechanisms on the holding host get confused, because the IP address is normally
37890 used as part of the key string for holding retry information. This can be
37891 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
37892 Since this has disadvantages for permanently connected hosts, it is best to
37893 arrange a separate transport for the intermittently connected ones.
37897 .section "Exim on the intermittently connected client host" "SECID248"
37898 The value of &%smtp_accept_queue_per_connection%& should probably be
37899 increased, or even set to zero (that is, disabled) on the intermittently
37900 connected host, so that all incoming messages down a single connection get
37901 delivered immediately.
37903 .cindex "SMTP" "passed connection"
37904 .cindex "SMTP" "multiple deliveries"
37905 .cindex "multiple SMTP deliveries"
37906 .cindex "first pass routing"
37907 Mail waiting to be sent from an intermittently connected host will probably
37908 not have been routed, because without a connection DNS lookups are not
37909 possible. This means that if a normal queue run is done at connection time,
37910 each message is likely to be sent in a separate SMTP session. This can be
37911 avoided by starting the queue run with a command line option beginning with
37912 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
37913 first pass, routing is done but no deliveries take place. The second pass is a
37914 normal queue run; since all the messages have been previously routed, those
37915 destined for the same host are likely to get sent as multiple deliveries in a
37916 single SMTP connection.
37920 . ////////////////////////////////////////////////////////////////////////////
37921 . ////////////////////////////////////////////////////////////////////////////
37923 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
37924 "Exim as a non-queueing client"
37925 .cindex "client, non-queueing"
37926 .cindex "smart host" "suppressing queueing"
37927 On a personal computer, it is a common requirement for all
37928 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
37929 configured to operate that way, for all the popular operating systems.
37930 However, there are some MUAs for Unix-like systems that cannot be so
37931 configured: they submit messages using the command line interface of
37932 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
37935 If the personal computer runs continuously, there is no problem, because it can
37936 run a conventional MTA that handles delivery to the smart host, and deal with
37937 any delays via its queueing mechanism. However, if the computer does not run
37938 continuously or runs different operating systems at different times, queueing
37939 email is not desirable.
37941 There is therefore a requirement for something that can provide the
37942 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
37943 any queueing or retrying facilities. Furthermore, the delivery to the smart
37944 host should be synchronous, so that if it fails, the sending MUA is immediately
37945 informed. In other words, we want something that extends an MUA that submits
37946 to a local MTA via the command line so that it behaves like one that submits
37947 to a remote smart host using TCP/SMTP.
37949 There are a number of applications (for example, there is one called &'ssmtp'&)
37950 that do this job. However, people have found them to be lacking in various
37951 ways. For instance, you might want to allow aliasing and forwarding to be done
37952 before sending a message to the smart host.
37954 Exim already had the necessary infrastructure for doing this job. Just a few
37955 tweaks were needed to make it behave as required, though it is somewhat of an
37956 overkill to use a fully-featured MTA for this purpose.
37958 .oindex "&%mua_wrapper%&"
37959 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
37960 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
37961 assumes that it is being used to &"wrap"& a command-line MUA in the manner
37962 just described. As well as setting &%mua_wrapper%&, you also need to provide a
37963 compatible router and transport configuration. Typically there will be just one
37964 router and one transport, sending everything to a smart host.
37966 When run in MUA wrapping mode, the behaviour of Exim changes in the
37970 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
37971 In other words, the only way to submit messages is via the command line.
37973 Each message is synchronously delivered as soon as it is received (&%-odi%& is
37974 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
37975 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
37976 does not finish until the delivery attempt is complete. If the delivery is
37977 successful, a zero return code is given.
37979 Address redirection is permitted, but the final routing for all addresses must
37980 be to the same remote transport, and to the same list of hosts. Furthermore,
37981 the return address (envelope sender) must be the same for all recipients, as
37982 must any added or deleted header lines. In other words, it must be possible to
37983 deliver the message in a single SMTP transaction, however many recipients there
37986 If these conditions are not met, or if routing any address results in a
37987 failure or defer status, or if Exim is unable to deliver all the recipients
37988 successfully to one of the smart hosts, delivery of the entire message fails.
37990 Because no queueing is allowed, all failures are treated as permanent; there
37991 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
37992 smart host. Furthermore, because only a single yes/no response can be given to
37993 the caller, it is not possible to deliver to some recipients and not others. If
37994 there is an error (temporary or permanent) for any recipient, all are failed.
37996 If more than one smart host is listed, Exim will try another host after a
37997 connection failure or a timeout, in the normal way. However, if this kind of
37998 failure happens for all the hosts, the delivery fails.
38000 When delivery fails, an error message is written to the standard error stream
38001 (as well as to Exim's log), and Exim exits to the caller with a return code
38002 value 1. The message is expunged from Exim's spool files. No bounce messages
38003 are ever generated.
38005 No retry data is maintained, and any retry rules are ignored.
38007 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
38008 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
38009 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
38012 The overall effect is that Exim makes a single synchronous attempt to deliver
38013 the message, failing if there is any kind of problem. Because no local
38014 deliveries are done and no daemon can be run, Exim does not need root
38015 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
38016 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
38017 the advantages and disadvantages of running without root privilege.
38022 . ////////////////////////////////////////////////////////////////////////////
38023 . ////////////////////////////////////////////////////////////////////////////
38025 .chapter "Log files" "CHAPlog"
38026 .scindex IIDloggen "log" "general description"
38027 .cindex "log" "types of"
38028 Exim writes three different logs, referred to as the main log, the reject log,
38033 The main log records the arrival of each message and each delivery in a single
38034 line in each case. The format is as compact as possible, in an attempt to keep
38035 down the size of log files. Two-character flag sequences make it easy to pick
38036 out these lines. A number of other events are recorded in the main log. Some of
38037 them are optional, in which case the &%log_selector%& option controls whether
38038 they are included or not. A Perl script called &'eximstats'&, which does simple
38039 analysis of main log files, is provided in the Exim distribution (see section
38040 &<<SECTmailstat>>&).
38042 .cindex "reject log"
38043 The reject log records information from messages that are rejected as a result
38044 of a configuration option (that is, for policy reasons).
38045 The first line of each rejection is a copy of the line that is also written to
38046 the main log. Then, if the message's header has been read at the time the log
38047 is written, its contents are written to this log. Only the original header
38048 lines are available; header lines added by ACLs are not logged. You can use the
38049 reject log to check that your policy controls are working correctly; on a busy
38050 host this may be easier than scanning the main log for rejection messages. You
38051 can suppress the writing of the reject log by setting &%write_rejectlog%&
38054 .cindex "panic log"
38055 .cindex "system log"
38056 When certain serious errors occur, Exim writes entries to its panic log. If the
38057 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
38058 are usually written to the main log as well, but can get lost amid the mass of
38059 other entries. The panic log should be empty under normal circumstances. It is
38060 therefore a good idea to check it (or to have a &'cron'& script check it)
38061 regularly, in order to become aware of any problems. When Exim cannot open its
38062 panic log, it tries as a last resort to write to the system log (syslog). This
38063 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
38064 message itself is written at priority LOG_CRIT.
38067 Every log line starts with a timestamp, in the format shown in the following
38068 example. Note that many of the examples shown in this chapter are line-wrapped.
38069 In the log file, this would be all on one line:
38071 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
38074 By default, the timestamps are in the local timezone. There are two
38075 ways of changing this:
38078 You can set the &%timezone%& option to a different time zone; in particular, if
38083 the timestamps will be in UTC (aka GMT).
38085 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
38088 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
38092 .cindex "log" "process ids in"
38093 .cindex "pid (process id)" "in log lines"
38094 Exim does not include its process id in log lines by default, but you can
38095 request that it does so by specifying the &`pid`& log selector (see section
38096 &<<SECTlogselector>>&). When this is set, the process id is output, in square
38097 brackets, immediately after the time and date.
38102 .section "Where the logs are written" "SECTwhelogwri"
38103 .cindex "log" "destination"
38104 .cindex "log" "to file"
38105 .cindex "log" "to syslog"
38107 The logs may be written to local files, or to syslog, or both. However, it
38108 should be noted that many syslog implementations use UDP as a transport, and
38109 are therefore unreliable in the sense that messages are not guaranteed to
38110 arrive at the loghost, nor is the ordering of messages necessarily maintained.
38111 It has also been reported that on large log files (tens of megabytes) you may
38112 need to tweak syslog to prevent it syncing the file with each write &-- on
38113 Linux this has been seen to make syslog take 90% plus of CPU time.
38115 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
38116 &_Local/Makefile_& or by setting &%log_file_path%& in the runtime
38117 configuration. This latter string is expanded, so it can contain, for example,
38118 references to the host name:
38120 log_file_path = /var/log/$primary_hostname/exim_%slog
38122 It is generally advisable, however, to set the string in &_Local/Makefile_&
38123 rather than at runtime, because then the setting is available right from the
38124 start of Exim's execution. Otherwise, if there's something it wants to log
38125 before it has read the configuration file (for example, an error in the
38126 configuration file) it will not use the path you want, and may not be able to
38129 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
38130 list, currently limited to at most two items. This is one option where the
38131 facility for changing a list separator may not be used. The list must always be
38132 colon-separated. If an item in the list is &"syslog"& then syslog is used;
38133 otherwise the item must either be an absolute path, containing &`%s`& at the
38134 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
38135 implying the use of a default path.
38137 When Exim encounters an empty item in the list, it searches the list defined by
38138 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
38139 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
38140 mean &"use the path specified at build time"&. It no such item exists, log
38141 files are written in the &_log_& subdirectory of the spool directory. This is
38142 equivalent to the setting:
38144 log_file_path = $spool_directory/log/%slog
38146 If you do not specify anything at build time or runtime,
38147 or if you unset the option at runtime (i.e. &`log_file_path = `&),
38148 that is where the logs are written.
38150 A log file path may also contain &`%D`& or &`%M`& if datestamped log filenames
38151 are in use &-- see section &<<SECTdatlogfil>>& below.
38153 Here are some examples of possible settings:
38155 &`LOG_FILE_PATH=syslog `& syslog only
38156 &`LOG_FILE_PATH=:syslog `& syslog and default path
38157 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
38158 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
38160 If there are more than two paths in the list, the first is used and a panic
38165 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
38166 .cindex "log" "cycling local files"
38167 .cindex "cycling logs"
38168 .cindex "&'exicyclog'&"
38169 .cindex "log" "local files; writing to"
38170 Some operating systems provide centralized and standardized methods for cycling
38171 log files. For those that do not, a utility script called &'exicyclog'& is
38172 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
38173 main and reject logs each time it is called. The maximum number of old logs to
38174 keep can be set. It is suggested this script is run as a daily &'cron'& job.
38176 An Exim delivery process opens the main log when it first needs to write to it,
38177 and it keeps the file open in case subsequent entries are required &-- for
38178 example, if a number of different deliveries are being done for the same
38179 message. However, remote SMTP deliveries can take a long time, and this means
38180 that the file may be kept open long after it is renamed if &'exicyclog'& or
38181 something similar is being used to rename log files on a regular basis. To
38182 ensure that a switch of log files is noticed as soon as possible, Exim calls
38183 &[stat()]& on the main log's name before reusing an open file, and if the file
38184 does not exist, or its inode has changed, the old file is closed and Exim
38185 tries to open the main log from scratch. Thus, an old log file may remain open
38186 for quite some time, but no Exim processes should write to it once it has been
38191 .section "Datestamped log files" "SECTdatlogfil"
38192 .cindex "log" "datestamped files"
38193 Instead of cycling the main and reject log files by renaming them
38194 periodically, some sites like to use files whose names contain a datestamp,
38195 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
38196 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
38197 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
38198 point where the datestamp is required. For example:
38200 log_file_path = /var/spool/exim/log/%slog-%D
38201 log_file_path = /var/log/exim-%s-%D.log
38202 log_file_path = /var/spool/exim/log/%D-%slog
38203 log_file_path = /var/log/exim/%s.%M
38205 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
38206 examples of names generated by the above examples:
38208 /var/spool/exim/log/mainlog-20021225
38209 /var/log/exim-reject-20021225.log
38210 /var/spool/exim/log/20021225-mainlog
38211 /var/log/exim/main.200212
38213 When this form of log file is specified, Exim automatically switches to new
38214 files at midnight. It does not make any attempt to compress old logs; you
38215 will need to write your own script if you require this. You should not
38216 run &'exicyclog'& with this form of logging.
38218 The location of the panic log is also determined by &%log_file_path%&, but it
38219 is not datestamped, because rotation of the panic log does not make sense.
38220 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
38221 the string. In addition, if it immediately follows a slash, a following
38222 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
38223 character is removed. Thus, the four examples above would give these panic
38226 /var/spool/exim/log/paniclog
38227 /var/log/exim-panic.log
38228 /var/spool/exim/log/paniclog
38229 /var/log/exim/panic
38233 .section "Logging to syslog" "SECID249"
38234 .cindex "log" "syslog; writing to"
38235 The use of syslog does not change what Exim logs or the format of its messages,
38236 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
38237 Exim's log lines are omitted when these lines are sent to syslog. Apart from
38238 that, the same strings are written to syslog as to log files. The syslog
38239 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
38240 by default, but you can change these by setting the &%syslog_facility%& and
38241 &%syslog_processname%& options, respectively. If Exim was compiled with
38242 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
38243 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
38244 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
38245 the time and host name to each line.
38246 The three log streams are mapped onto syslog priorities as follows:
38249 &'mainlog'& is mapped to LOG_INFO
38251 &'rejectlog'& is mapped to LOG_NOTICE
38253 &'paniclog'& is mapped to LOG_ALERT
38256 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
38257 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
38258 these are routed by syslog to the same place. You can suppress this duplication
38259 by setting &%syslog_duplication%& false.
38261 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
38262 entries contain multiple lines when headers are included. To cope with both
38263 these cases, entries written to syslog are split into separate &[syslog()]&
38264 calls at each internal newline, and also after a maximum of
38265 870 data characters. (This allows for a total syslog line length of 1024, when
38266 additions such as timestamps are added.) If you are running a syslog
38267 replacement that can handle lines longer than the 1024 characters allowed by
38268 RFC 3164, you should set
38270 SYSLOG_LONG_LINES=yes
38272 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
38273 lines, but it still splits at internal newlines in &'reject'& log entries.
38275 To make it easy to re-assemble split lines later, each component of a split
38276 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
38277 where <&'n'&> is the component number and <&'m'&> is the total number of
38278 components in the entry. The / delimiter is used when the line was split
38279 because it was too long; if it was split because of an internal newline, the \
38280 delimiter is used. For example, supposing the length limit to be 50 instead of
38281 870, the following would be the result of a typical rejection message to
38282 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
38283 name, and pid as added by syslog:
38285 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
38286 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
38287 [3/5] when scanning for sender: missing or malformed lo
38288 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
38291 The same error might cause the following lines to be written to &"rejectlog"&
38294 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
38295 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
38296 [3/18] er when scanning for sender: missing or malformed
38297 [4/18] local part in "<>" (envelope sender is <ph10@cam
38299 [6\18] Recipients: ph10@some.domain.cam.example
38300 [7\18] P Received: from [127.0.0.1] (ident=ph10)
38301 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
38302 [9\18] id 16RdAL-0006pc-00
38303 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
38304 [11\18] 09:43 +0100
38306 [13\18] Subject: this is a test header
38307 [18\18] X-something: this is another header
38308 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
38311 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
38313 Log lines that are neither too long nor contain newlines are written to syslog
38314 without modification.
38316 If only syslog is being used, the Exim monitor is unable to provide a log tail
38317 display, unless syslog is routing &'mainlog'& to a file on the local host and
38318 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
38323 .section "Log line flags" "SECID250"
38324 One line is written to the main log for each message received, and for each
38325 successful, unsuccessful, and delayed delivery. These lines can readily be
38326 picked out by the distinctive two-character flags that immediately follow the
38327 timestamp. The flags are:
38329 &`<=`& message arrival
38330 &`(=`& message fakereject
38331 &`=>`& normal message delivery
38332 &`->`& additional address in same delivery
38333 &`>>`& cutthrough message delivery
38334 &`*>`& delivery suppressed by &%-N%&
38335 &`**`& delivery failed; address bounced
38336 &`==`& delivery deferred; temporary problem
38340 .section "Logging message reception" "SECID251"
38341 .cindex "log" "reception line"
38342 The format of the single-line entry in the main log that is written for every
38343 message received is shown in the basic example below, which is split over
38344 several lines in order to fit it on the page:
38346 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
38347 H=mailer.fict.example [192.168.123.123] U=exim
38348 P=smtp S=5678 id=<incoming message id>
38350 The address immediately following &"<="& is the envelope sender address. A
38351 bounce message is shown with the sender address &"<>"&, and if it is locally
38352 generated, this is followed by an item of the form
38356 which is a reference to the message that caused the bounce to be sent.
38360 For messages from other hosts, the H and U fields identify the remote host and
38361 record the RFC 1413 identity of the user that sent the message, if one was
38362 received. The number given in square brackets is the IP address of the sending
38363 host. If there is a single, unparenthesized host name in the H field, as
38364 above, it has been verified to correspond to the IP address (see the
38365 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
38366 by the remote host in the SMTP HELO or EHLO command, and has not been
38367 verified. If verification yields a different name to that given for HELO or
38368 EHLO, the verified name appears first, followed by the HELO or EHLO
38369 name in parentheses.
38371 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
38372 without brackets, in the HELO or EHLO command, leading to entries in
38373 the log containing text like these examples:
38375 H=(10.21.32.43) [192.168.8.34]
38376 H=([10.21.32.43]) [192.168.8.34]
38378 This can be confusing. Only the final address in square brackets can be relied
38381 For locally generated messages (that is, messages not received over TCP/IP),
38382 the H field is omitted, and the U field contains the login name of the caller
38385 .cindex "authentication" "logging"
38386 .cindex "AUTH" "logging"
38387 For all messages, the P field specifies the protocol used to receive the
38388 message. This is the value that is stored in &$received_protocol$&. In the case
38389 of incoming SMTP messages, the value indicates whether or not any SMTP
38390 extensions (ESMTP), encryption, or authentication were used. If the SMTP
38391 session was encrypted, there is an additional X field that records the cipher
38392 suite that was used.
38394 .cindex log protocol
38395 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
38396 hosts that have authenticated themselves using the SMTP AUTH command. The first
38397 value is used when the SMTP connection was encrypted (&"secure"&). In this case
38398 there is an additional item A= followed by the name of the authenticator that
38399 was used. If an authenticated identification was set up by the authenticator's
38400 &%server_set_id%& option, this is logged too, separated by a colon from the
38401 authenticator name.
38403 .cindex "size" "of message"
38404 The id field records the existing message id, if present. The size of the
38405 received message is given by the S field. When the message is delivered,
38406 headers may be removed or added, so that the size of delivered copies of the
38407 message may not correspond with this value (and indeed may be different to each
38410 The &%log_selector%& option can be used to request the logging of additional
38411 data when a message is received. See section &<<SECTlogselector>>& below.
38415 .section "Logging deliveries" "SECID252"
38416 .cindex "log" "delivery line"
38417 The format of the single-line entry in the main log that is written for every
38418 delivery is shown in one of the examples below, for local and remote
38419 deliveries, respectively. Each example has been split into multiple lines in order
38420 to fit it on the page:
38422 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
38423 <marv@hitch.fict.example> R=localuser T=local_delivery
38424 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
38425 monk@holistic.fict.example R=dnslookup T=remote_smtp
38426 H=holistic.fict.example [192.168.234.234]
38428 For ordinary local deliveries, the original address is given in angle brackets
38429 after the final delivery address, which might be a pipe or a file. If
38430 intermediate address(es) exist between the original and the final address, the
38431 last of these is given in parentheses after the final address. The R and T
38432 fields record the router and transport that were used to process the address.
38434 If SMTP AUTH was used for the delivery there is an additional item A=
38435 followed by the name of the authenticator that was used.
38436 If an authenticated identification was set up by the authenticator's &%client_set_id%&
38437 option, this is logged too, as a second colon-separated list item.
38438 Optionally (see the &%smtp_mailauth%& &%log_selector%&) there may be a third list item.
38440 If a shadow transport was run after a successful local delivery, the log line
38441 for the successful delivery has an item added on the end, of the form
38443 &`ST=<`&&'shadow transport name'&&`>`&
38445 If the shadow transport did not succeed, the error message is put in
38446 parentheses afterwards.
38448 .cindex "asterisk" "after IP address"
38449 When more than one address is included in a single delivery (for example, two
38450 SMTP RCPT commands in one transaction) the second and subsequent addresses are
38451 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
38452 down a single SMTP connection, an asterisk follows the
38454 remote IP address (and port if enabled)
38456 in the log lines for the second and subsequent messages.
38457 When two or more messages are delivered down a single TLS connection, the
38458 DNS and some TLS-related information logged for the first message delivered
38459 will not be present in the log lines for the second and subsequent messages.
38460 TLS cipher information is still available.
38462 .cindex "delivery" "cutthrough; logging"
38463 .cindex "cutthrough" "logging"
38464 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
38465 line precedes the reception line, since cutthrough waits for a possible
38466 rejection from the destination in case it can reject the sourced item.
38468 The generation of a reply message by a filter file gets logged as a
38469 &"delivery"& to the addressee, preceded by &">"&.
38471 The &%log_selector%& option can be used to request the logging of additional
38472 data when a message is delivered. See section &<<SECTlogselector>>& below.
38475 .section "Discarded deliveries" "SECID253"
38476 .cindex "discarded messages"
38477 .cindex "message" "discarded"
38478 .cindex "delivery" "discarded; logging"
38479 When a message is discarded as a result of the command &"seen finish"& being
38480 obeyed in a filter file which generates no deliveries, a log entry of the form
38482 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
38483 <low.club@bridge.example> R=userforward
38485 is written, to record why no deliveries are logged. When a message is discarded
38486 because it is aliased to &":blackhole:"& the log line is like this:
38488 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
38489 <hole@nowhere.example> R=blackhole_router
38493 .section "Deferred deliveries" "SECID254"
38494 When a delivery is deferred, a line of the following form is logged:
38496 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
38497 R=dnslookup T=smtp defer (146): Connection refused
38499 In the case of remote deliveries, the error is the one that was given for the
38500 last IP address that was tried. Details of individual SMTP failures are also
38501 written to the log, so the above line would be preceded by something like
38503 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
38504 mail1.endrest.example [192.168.239.239]: Connection refused
38506 When a deferred address is skipped because its retry time has not been reached,
38507 a message is written to the log, but this can be suppressed by setting an
38508 appropriate value in &%log_selector%&.
38512 .section "Delivery failures" "SECID255"
38513 .cindex "delivery" "failure; logging"
38514 If a delivery fails because an address cannot be routed, a line of the
38515 following form is logged:
38517 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
38518 <jim@trek99.example>: unknown mail domain
38520 If a delivery fails at transport time, the router and transport are shown, and
38521 the response from the remote host is included, as in this example:
38523 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
38524 R=dnslookup T=remote_smtp: SMTP error from remote mailer
38525 after pipelined RCPT TO:<ace400@pb.example>: host
38526 pbmail3.py.example [192.168.63.111]: 553 5.3.0
38527 <ace400@pb.example>...Addressee unknown
38529 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
38530 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
38531 disabling PIPELINING. The log lines for all forms of delivery failure are
38532 flagged with &`**`&.
38536 .section "Fake deliveries" "SECID256"
38537 .cindex "delivery" "fake; logging"
38538 If a delivery does not actually take place because the &%-N%& option has been
38539 used to suppress it, a normal delivery line is written to the log, except that
38540 &"=>"& is replaced by &"*>"&.
38544 .section "Completion" "SECID257"
38547 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
38549 is written to the main log when a message is about to be removed from the spool
38550 at the end of its processing.
38555 .section "Summary of Fields in Log Lines" "SECID258"
38556 .cindex "log" "summary of fields"
38557 A summary of the field identifiers that are used in log lines is shown in
38558 the following table:
38560 &`A `& authenticator name (and optional id and sender)
38561 &`C `& SMTP confirmation on delivery
38562 &` `& command list for &"no mail in SMTP session"&
38563 &`CV `& certificate verification status
38564 &`D `& duration of &"no mail in SMTP session"&
38565 &`DKIM`& domain verified in incoming message
38566 &`DN `& distinguished name from peer certificate
38567 &`DS `& DNSSEC secured lookups
38568 &`DT `& on &`=>`&, &'=='& and &'**'& lines: time taken for, or to attempt, a delivery
38569 &`F `& sender address (on delivery lines)
38570 &`H `& host name and IP address
38571 &`I `& local interface used
38572 &`id `& message id (from header) for incoming message
38573 &`K `& CHUNKING extension used
38574 &`L `& on &`<=`& and &`=>`& lines: PIPELINING extension used
38575 &`M8S `& 8BITMIME status for incoming message
38576 &`P `& on &`<=`& lines: protocol used
38577 &` `& on &`=>`& and &`**`& lines: return path
38578 &`PRDR`& PRDR extension used
38579 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
38580 &`Q `& alternate queue name
38581 &`QT `& on &`=>`& lines: time spent on queue so far
38582 &` `& on &"Completed"& lines: time spent on queue
38583 &`R `& on &`<=`& lines: reference for local bounce
38584 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
38585 &`RT `& on &`<=`& lines: time taken for reception
38586 &`S `& size of message in bytes
38587 &`SNI `& server name indication from TLS client hello
38588 &`ST `& shadow transport name
38589 &`T `& on &`<=`& lines: message subject (topic)
38590 &`TFO `& connection took advantage of TCP Fast Open
38591 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
38592 &`U `& local user or RFC 1413 identity
38593 &`X `& TLS cipher suite
38597 .section "Other log entries" "SECID259"
38598 Various other types of log entry are written from time to time. Most should be
38599 self-explanatory. Among the more common are:
38602 .cindex "retry" "time not reached"
38603 &'retry time not reached'&&~&~An address previously suffered a temporary error
38604 during routing or local delivery, and the time to retry has not yet arrived.
38605 This message is not written to an individual message log file unless it happens
38606 during the first delivery attempt.
38608 &'retry time not reached for any host'&&~&~An address previously suffered
38609 temporary errors during remote delivery, and the retry time has not yet arrived
38610 for any of the hosts to which it is routed.
38612 .cindex "spool directory" "file locked"
38613 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
38614 some other Exim process is already working on the message. This can be quite
38615 common if queue running processes are started at frequent intervals. The
38616 &'exiwhat'& utility script can be used to find out what Exim processes are
38619 .cindex "error" "ignored"
38620 &'error ignored'&&~&~There are several circumstances that give rise to this
38623 Exim failed to deliver a bounce message whose age was greater than
38624 &%ignore_bounce_errors_after%&. The bounce was discarded.
38626 A filter file set up a delivery using the &"noerror"& option, and the delivery
38627 failed. The delivery was discarded.
38629 A delivery set up by a router configured with
38630 . ==== As this is a nested list, any displays it contains must be indented
38631 . ==== as otherwise they are too far to the left.
38635 failed. The delivery was discarded.
38638 .cindex DKIM "log line"
38639 &'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
38640 logging and the message has a DKIM signature header.
38647 .section "Reducing or increasing what is logged" "SECTlogselector"
38648 .cindex "log" "selectors"
38649 By setting the &%log_selector%& global option, you can disable some of Exim's
38650 default logging, or you can request additional logging. The value of
38651 &%log_selector%& is made up of names preceded by plus or minus characters. For
38654 log_selector = +arguments -retry_defer
38656 The list of optional log items is in the following table, with the default
38657 selection marked by asterisks:
38659 &` 8bitmime `& received 8BITMIME status
38660 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
38661 &` address_rewrite `& address rewriting
38662 &` all_parents `& all parents in => lines
38663 &` arguments `& command line arguments
38664 &`*connection_reject `& connection rejections
38665 &`*delay_delivery `& immediate delivery delayed
38666 &` deliver_time `& time taken to attempt delivery
38667 &` delivery_size `& add &`S=`&&'nnn'& to => lines
38668 &`*dkim `& DKIM verified domain on <= lines
38669 &` dkim_verbose `& separate full DKIM verification result line, per signature
38670 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
38671 &` dnssec `& DNSSEC secured lookups
38672 &`*etrn `& ETRN commands
38673 &`*host_lookup_failed `& as it says
38674 &` ident_timeout `& timeout for ident connection
38675 &` incoming_interface `& local interface on <= and => lines
38676 &` incoming_port `& remote port on <= lines
38677 &`*lost_incoming_connection `& as it says (includes timeouts)
38678 &` millisec `& millisecond timestamps and RT,QT,DT,D times
38679 &`*msg_id `& on <= lines, Message-ID: header value
38680 &` msg_id_created `& on <= lines, Message-ID: header value when one had to be added
38681 &` outgoing_interface `& local interface on => lines
38682 &` outgoing_port `& add remote port to => lines
38683 &`*queue_run `& start and end queue runs
38684 &` queue_time `& time on queue for one recipient
38685 &`*queue_time_exclusive `& exclude recieve time from QT times
38686 &` queue_time_overall `& time on queue for whole message
38687 &` pid `& Exim process id
38688 &` pipelining `& PIPELINING use, on <= and => lines
38689 &` proxy `& proxy address on <= and => lines
38690 &` receive_time `& time taken to receive message
38691 &` received_recipients `& recipients on <= lines
38692 &` received_sender `& sender on <= lines
38693 &`*rejected_header `& header contents on reject log
38694 &`*retry_defer `& &"retry time not reached"&
38695 &` return_path_on_delivery `& put return path on => and ** lines
38696 &` sender_on_delivery `& add sender to => lines
38697 &`*sender_verify_fail `& sender verification failures
38698 &`*size_reject `& rejection because too big
38699 &`*skip_delivery `& delivery skipped in a queue run
38700 &`*smtp_confirmation `& SMTP confirmation on => lines
38701 &` smtp_connection `& incoming SMTP connections
38702 &` smtp_incomplete_transaction`& incomplete SMTP transactions
38703 &` smtp_mailauth `& AUTH argument to MAIL commands
38704 &` smtp_no_mail `& session with no MAIL commands
38705 &` smtp_protocol_error `& SMTP protocol errors
38706 &` smtp_syntax_error `& SMTP syntax errors
38707 &` subject `& contents of &'Subject:'& on <= lines
38708 &`*tls_certificate_verified `& certificate verification status
38709 &`*tls_cipher `& TLS cipher suite on <= and => lines
38710 &` tls_peerdn `& TLS peer DN on <= and => lines
38711 &` tls_resumption `& append * to cipher field
38712 &` tls_sni `& TLS SNI on <= lines
38713 &` unknown_in_list `& DNS lookup failed in list match
38715 &` all `& all of the above
38717 See also the &%slow_lookup_log%& main configuration option,
38718 section &<<SECID99>>&
38720 More details on each of these items follows:
38724 .cindex "log" "8BITMIME"
38725 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
38726 which may help in tracking down interoperability issues with ancient MTAs
38727 that are not 8bit clean. This is added to the &"<="& line, tagged with
38728 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
38729 &`7BIT`& and &`8BITMIME`& respectively.
38731 .cindex "&%warn%& ACL verb" "log when skipping"
38732 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
38733 its conditions cannot be evaluated, a log line to this effect is written if
38734 this log selector is set.
38736 .cindex "log" "rewriting"
38737 .cindex "rewriting" "logging"
38738 &%address_rewrite%&: This applies both to global rewrites and per-transport
38739 rewrites, but not to rewrites in filters run as an unprivileged user (because
38740 such users cannot access the log).
38742 .cindex "log" "full parentage"
38743 &%all_parents%&: Normally only the original and final addresses are logged on
38744 delivery lines; with this selector, intermediate parents are given in
38745 parentheses between them.
38747 .cindex "log" "Exim arguments"
38748 .cindex "Exim arguments, logging"
38749 &%arguments%&: This causes Exim to write the arguments with which it was called
38750 to the main log, preceded by the current working directory. This is a debugging
38751 feature, added to make it easier to find out how certain MUAs call
38752 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
38753 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
38754 that are empty or that contain white space are quoted. Non-printing characters
38755 are shown as escape sequences. This facility cannot log unrecognized arguments,
38756 because the arguments are checked before the configuration file is read. The
38757 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
38758 between the caller and Exim.
38760 .cindex "log" "connection rejections"
38761 &%connection_reject%&: A log entry is written whenever an incoming SMTP
38762 connection is rejected, for whatever reason.
38764 .cindex "log" "delayed delivery"
38765 .cindex "delayed delivery, logging"
38766 &%delay_delivery%&: A log entry is written whenever a delivery process is not
38767 started for an incoming message because the load is too high or too many
38768 messages were received on one connection. Logging does not occur if no delivery
38769 process is started because &%queue_only%& is set or &%-odq%& was used.
38771 .cindex "log" "delivery duration"
38772 &%deliver_time%&: For each delivery, the amount of real time it has taken to
38773 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
38774 If millisecond logging is enabled, short times will be shown with greater
38775 precision, eg. &`DT=0.304s`&.
38777 .cindex "log" "message size on delivery"
38778 .cindex "size" "of message"
38779 &%delivery_size%&: For each delivery, the size of message delivered is added to
38780 the &"=>"& line, tagged with S=.
38782 .cindex log "DKIM verification"
38783 .cindex DKIM "verification logging"
38784 &%dkim%&: For message acceptance log lines, when an DKIM signature in the header
38785 verifies successfully a tag of DKIM is added, with one of the verified domains.
38787 .cindex log "DKIM verification"
38788 .cindex DKIM "verification logging"
38789 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
38791 .cindex "log" "dnslist defer"
38792 .cindex "DNS list" "logging defer"
38793 .cindex "black list (DNS)"
38794 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
38795 DNS black list suffers a temporary error.
38798 .cindex dnssec logging
38799 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
38800 dns lookups gave secure results a tag of DS is added.
38801 For acceptance this covers the reverse and forward lookups for host name verification.
38802 It does not cover helo-name verification.
38803 For delivery this covers the SRV, MX, A and/or AAAA lookups.
38805 .cindex "log" "ETRN commands"
38806 .cindex "ETRN" "logging"
38807 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
38808 is run to determine whether or not it is actually accepted. An invalid ETRN
38809 command, or one received within a message transaction is not logged by this
38810 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
38812 .cindex "log" "host lookup failure"
38813 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
38814 any addresses, or when a lookup of an IP address fails to find a host name, a
38815 log line is written. This logging does not apply to direct DNS lookups when
38816 routing email addresses, but it does apply to &"byname"& lookups.
38818 .cindex "log" "ident timeout"
38819 .cindex "RFC 1413" "logging timeout"
38820 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
38821 client's ident port times out.
38823 .cindex "log" "incoming interface"
38824 .cindex "log" "outgoing interface"
38825 .cindex "log" "local interface"
38826 .cindex "log" "local address and port"
38827 .cindex "TCP/IP" "logging local address and port"
38828 .cindex "interface" "logging"
38829 &%incoming_interface%&: The interface on which a message was received is added
38830 to the &"<="& line as an IP address in square brackets, tagged by I= and
38831 followed by a colon and the port number. The local interface and port are also
38832 added to other SMTP log lines, for example, &"SMTP connection from"&, to
38833 rejection lines, and (despite the name) to outgoing
38835 &"=>"&, &"->"&, &"=="& and &"**"& lines.
38837 The latter can be disabled by turning off the &%outgoing_interface%& option.
38839 .cindex log "incoming proxy address"
38840 .cindex proxy "logging proxy address"
38841 .cindex "TCP/IP" "logging proxy address"
38842 &%proxy%&: The internal (closest to the system running Exim) IP address
38843 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
38844 on a proxied connection
38845 or the &"=>"& line for a message delivered on a proxied connection.
38846 See &<<SECTproxyInbound>>& for more information.
38848 .cindex "log" "incoming remote port"
38849 .cindex "port" "logging remote"
38850 .cindex "TCP/IP" "logging incoming remote port"
38851 .vindex "&$sender_fullhost$&"
38852 .vindex "&$sender_rcvhost$&"
38853 &%incoming_port%&: The remote port number from which a message was received is
38854 added to log entries and &'Received:'& header lines, following the IP address
38855 in square brackets, and separated from it by a colon. This is implemented by
38856 changing the value that is put in the &$sender_fullhost$& and
38857 &$sender_rcvhost$& variables. Recording the remote port number has become more
38858 important with the widening use of NAT (see RFC 2505).
38860 .cindex "log" "dropped connection"
38861 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
38862 connection is unexpectedly dropped.
38864 .cindex "log" "millisecond timestamps"
38865 .cindex millisecond logging
38866 .cindex timestamps "millisecond, in logs"
38867 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
38868 appended to the seconds value.
38870 .cindex "log" "message id"
38871 &%msg_id%&: The value of the Message-ID: header.
38873 &%msg_id_created%&: The value of the Message-ID: header, when one had to be created.
38874 This will be either because the message is a bounce, or was submitted locally
38875 (submission mode) without one.
38876 The field identifier will have an asterix appended: &"id*="&.
38878 .cindex "log" "outgoing interface"
38879 .cindex "log" "local interface"
38880 .cindex "log" "local address and port"
38881 .cindex "TCP/IP" "logging local address and port"
38882 .cindex "interface" "logging"
38883 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
38884 interface on which a message was sent is added to delivery lines as an I= tag
38885 followed by IP address in square brackets. You can disable this by turning
38886 off the &%outgoing_interface%& option.
38888 .cindex "log" "outgoing remote port"
38889 .cindex "port" "logging outgoing remote"
38890 .cindex "TCP/IP" "logging outgoing remote port"
38891 &%outgoing_port%&: The remote port number is added to delivery log lines (those
38892 containing => tags) following the IP address.
38893 The local port is also added if &%incoming_interface%& and
38894 &%outgoing_interface%& are both enabled.
38895 This option is not included in the default setting, because for most ordinary
38896 configurations, the remote port number is always 25 (the SMTP port), and the
38897 local port is a random ephemeral port.
38899 .cindex "log" "process ids in"
38900 .cindex "pid (process id)" "in log lines"
38901 &%pid%&: The current process id is added to every log line, in square brackets,
38902 immediately after the time and date.
38904 .cindex log pipelining
38905 .cindex pipelining "logging outgoing"
38906 &%pipelining%&: A field is added to delivery and accept
38907 log lines when the ESMTP PIPELINING extension was used.
38908 The field is a single "L".
38910 On accept lines, where PIPELINING was offered but not used by the client,
38911 the field has a minus appended.
38913 .cindex "pipelining" "early connection"
38914 If Exim is built with the SUPPORT_PIPE_CONNECT build option
38915 accept "L" fields have a period appended if the feature was
38916 offered but not used, or an asterisk appended if used.
38917 Delivery "L" fields have an asterisk appended if used.
38920 .cindex "log" "queue run"
38921 .cindex "queue runner" "logging"
38922 &%queue_run%&: The start and end of every queue run are logged.
38924 .cindex "log" "queue time"
38925 &%queue_time%&: The amount of time the message has been in the queue on the
38926 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
38928 If millisecond logging is enabled, short times will be shown with greater
38929 precision, eg. &`QT=1.578s`&.
38931 &%queue_time_overall%&: The amount of time the message has been in the queue on
38932 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
38933 example, &`QT=3m45s`&.
38935 .cindex "log" "receive duration"
38936 &%receive_time%&: For each message, the amount of real time it has taken to
38937 perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
38938 If millisecond logging is enabled, short times will be shown with greater
38939 precision, eg. &`RT=0.204s`&.
38941 .cindex "log" "recipients"
38942 &%received_recipients%&: The recipients of a message are listed in the main log
38943 as soon as the message is received. The list appears at the end of the log line
38944 that is written when a message is received, preceded by the word &"for"&. The
38945 addresses are listed after they have been qualified, but before any rewriting
38947 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
38950 .cindex "log" "sender reception"
38951 &%received_sender%&: The unrewritten original sender of a message is added to
38952 the end of the log line that records the message's arrival, after the word
38953 &"from"& (before the recipients if &%received_recipients%& is also set).
38955 .cindex "log" "header lines for rejection"
38956 &%rejected_header%&: If a message's header has been received at the time a
38957 rejection is written to the reject log, the complete header is added to the
38958 log. Header logging can be turned off individually for messages that are
38959 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
38961 .cindex "log" "retry defer"
38962 &%retry_defer%&: A log line is written if a delivery is deferred because a
38963 retry time has not yet been reached. However, this &"retry time not reached"&
38964 message is always omitted from individual message logs after the first delivery
38967 .cindex "log" "return path"
38968 &%return_path_on_delivery%&: The return path that is being transmitted with
38969 the message is included in delivery and bounce lines, using the tag P=.
38970 This is omitted if no delivery actually happens, for example, if routing fails,
38971 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
38973 .cindex "log" "sender on delivery"
38974 &%sender_on_delivery%&: The message's sender address is added to every delivery
38975 and bounce line, tagged by F= (for &"from"&).
38976 This is the original sender that was received with the message; it is not
38977 necessarily the same as the outgoing return path.
38979 .cindex "log" "sender verify failure"
38980 &%sender_verify_fail%&: If this selector is unset, the separate log line that
38981 gives details of a sender verification failure is not written. Log lines for
38982 the rejection of SMTP commands contain just &"sender verify failed"&, so some
38985 .cindex "log" "size rejection"
38986 &%size_reject%&: A log line is written whenever a message is rejected because
38989 .cindex "log" "frozen messages; skipped"
38990 .cindex "frozen messages" "logging skipping"
38991 &%skip_delivery%&: A log line is written whenever a message is skipped during a
38992 queue run because it is frozen or because another process is already delivering
38994 .cindex "&""spool file is locked""&"
38995 The message that is written is &"spool file is locked"&.
38997 .cindex "log" "smtp confirmation"
38998 .cindex "SMTP" "logging confirmation"
38999 .cindex "LMTP" "logging confirmation"
39000 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
39001 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
39002 A number of MTAs (including Exim) return an identifying string in this
39005 .cindex "log" "SMTP connections"
39006 .cindex "SMTP" "logging connections"
39007 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
39008 established or closed, unless the connection is from a host that matches
39009 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
39010 only when the closure is unexpected.) This applies to connections from local
39011 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
39012 dropped in the middle of a message, a log line is always written, whether or
39013 not this selector is set, but otherwise nothing is written at the start and end
39014 of connections unless this selector is enabled.
39016 For TCP/IP connections to an Exim daemon, the current number of connections is
39017 included in the log message for each new connection, but note that the count is
39018 reset if the daemon is restarted.
39019 Also, because connections are closed (and the closure is logged) in
39020 subprocesses, the count may not include connections that have been closed but
39021 whose termination the daemon has not yet noticed. Thus, while it is possible to
39022 match up the opening and closing of connections in the log, the value of the
39023 logged counts may not be entirely accurate.
39025 .cindex "log" "SMTP transaction; incomplete"
39026 .cindex "SMTP" "logging incomplete transactions"
39027 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
39028 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
39029 and the message sender plus any accepted recipients are included in the log
39030 line. This can provide evidence of dictionary attacks.
39032 .cindex "log" "non-MAIL SMTP sessions"
39033 .cindex "MAIL" "logging session without"
39034 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
39035 connection terminates without having issued a MAIL command. This includes both
39036 the case when the connection is dropped, and the case when QUIT is used. It
39037 does not include cases where the connection is rejected right at the start (by
39038 an ACL, or because there are too many connections, or whatever). These cases
39039 already have their own log lines.
39041 The log line that is written contains the identity of the client in the usual
39042 way, followed by D= and a time, which records the duration of the connection.
39043 If the connection was authenticated, this fact is logged exactly as it is for
39044 an incoming message, with an A= item. If the connection was encrypted, CV=,
39045 DN=, and X= items may appear as they do for an incoming message, controlled by
39046 the same logging options.
39048 Finally, if any SMTP commands were issued during the connection, a C= item
39049 is added to the line, listing the commands that were used. For example,
39053 shows that the client issued QUIT straight after EHLO. If there were fewer
39054 than 20 commands, they are all listed. If there were more than 20 commands,
39055 the last 20 are listed, preceded by &"..."&. However, with the default
39056 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
39057 have been aborted before 20 non-mail commands are processed.
39059 &%smtp_mailauth%&: A third subfield with the authenticated sender,
39060 colon-separated, is appended to the A= item for a message arrival or delivery
39061 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
39062 was accepted or used.
39064 .cindex "log" "SMTP protocol error"
39065 .cindex "SMTP" "logging protocol error"
39066 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
39067 encountered. Exim does not have perfect detection of all protocol errors
39068 because of transmission delays and the use of pipelining. If PIPELINING has
39069 been advertised to a client, an Exim server assumes that the client will use
39070 it, and therefore it does not count &"expected"& errors (for example, RCPT
39071 received after rejecting MAIL) as protocol errors.
39073 .cindex "SMTP" "logging syntax errors"
39074 .cindex "SMTP" "syntax errors; logging"
39075 .cindex "SMTP" "unknown command; logging"
39076 .cindex "log" "unknown SMTP command"
39077 .cindex "log" "SMTP syntax error"
39078 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
39079 encountered. An unrecognized command is treated as a syntax error. For an
39080 external connection, the host identity is given; for an internal connection
39081 using &%-bs%& the sender identification (normally the calling user) is given.
39083 .cindex "log" "subject"
39084 .cindex "subject, logging"
39085 &%subject%&: The subject of the message is added to the arrival log line,
39086 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
39087 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
39088 specifies whether characters with values greater than 127 should be logged
39089 unchanged, or whether they should be rendered as escape sequences.
39091 .cindex "log" "certificate verification"
39093 .cindex DANE logging
39094 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
39095 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
39097 using a CA trust anchor,
39098 &`CV=dane`& if using a DNS trust anchor,
39099 and &`CV=no`& if not.
39101 .cindex "log" "TLS cipher"
39102 .cindex "TLS" "logging cipher"
39103 &%tls_cipher%&: When a message is sent or received over an encrypted
39104 connection, the cipher suite used is added to the log line, preceded by X=.
39106 .cindex "log" "TLS peer DN"
39107 .cindex "TLS" "logging peer DN"
39108 &%tls_peerdn%&: When a message is sent or received over an encrypted
39109 connection, and a certificate is supplied by the remote host, the peer DN is
39110 added to the log line, preceded by DN=.
39112 .cindex "log" "TLS resumption"
39113 .cindex "TLS" "logging session resumption"
39115 &%tls_resumption%&: When a message is sent or received over an encrypted
39116 connection and the TLS session resumed one used on a previous TCP connection,
39117 an asterisk is appended to the X= cipher field in the log line.
39120 .cindex "log" "TLS SNI"
39121 .cindex "TLS" "logging SNI"
39122 .cindex SNI logging
39123 &%tls_sni%&: When a message is received over an encrypted connection, and
39124 the remote host provided the Server Name Indication extension, the SNI is
39125 added to the log line, preceded by SNI=.
39127 .cindex "log" "DNS failure in list"
39128 &%unknown_in_list%&: This setting causes a log entry to be written when the
39129 result of a list match is failure because a DNS lookup failed.
39133 .section "Message log" "SECID260"
39134 .cindex "message" "log file for"
39135 .cindex "log" "message log; description of"
39136 .cindex "&_msglog_& directory"
39137 .oindex "&%preserve_message_logs%&"
39138 In addition to the general log files, Exim writes a log file for each message
39139 that it handles. The names of these per-message logs are the message ids, and
39140 they are kept in the &_msglog_& sub-directory of the spool directory. Each
39141 message log contains copies of the log lines that apply to the message. This
39142 makes it easier to inspect the status of an individual message without having
39143 to search the main log. A message log is deleted when processing of the message
39144 is complete, unless &%preserve_message_logs%& is set, but this should be used
39145 only with great care because they can fill up your disk very quickly.
39147 On a heavily loaded system, it may be desirable to disable the use of
39148 per-message logs, in order to reduce disk I/O. This can be done by setting the
39149 &%message_logs%& option false.
39155 . ////////////////////////////////////////////////////////////////////////////
39156 . ////////////////////////////////////////////////////////////////////////////
39158 .chapter "Exim utilities" "CHAPutils"
39159 .scindex IIDutils "utilities"
39160 A number of utility scripts and programs are supplied with Exim and are
39161 described in this chapter. There is also the Exim Monitor, which is covered in
39162 the next chapter. The utilities described here are:
39164 .itable none 0 0 3 7* left 15* left 40* left
39165 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
39166 "list what Exim processes are doing"
39167 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
39168 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
39169 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
39170 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
39172 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
39173 .irow &<<SECTmailstat>>& &'eximstats'& &&&
39174 "extract statistics from the log"
39175 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
39176 "check address acceptance from given IP"
39177 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
39178 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
39179 .irow &<<SECTdumpdb>>& &'exim_dumpdb'& "dump a hints database"
39180 .irow &<<SECTtidydb>>& &'exim_tidydb'& "clean up a hints database"
39181 .irow &<<SECTfixdb>>& &'exim_fixdb'& "patch a hints database"
39182 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
39185 Another utility that might be of use to sites with many MTAs is Tom Kistner's
39186 &'exilog'&. It provides log visualizations across multiple Exim servers. See
39187 &url(https://duncanthrax.net/exilog/) for details.
39192 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
39193 .cindex "&'exiwhat'&"
39194 .cindex "process, querying"
39196 On operating systems that can restart a system call after receiving a signal
39197 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
39198 a line describing what it is doing to the file &_exim-process.info_& in the
39199 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
39200 processes it can find, having first emptied the file. It then waits for one
39201 second to allow the Exim processes to react before displaying the results. In
39202 order to run &'exiwhat'& successfully you have to have sufficient privilege to
39203 send the signal to the Exim processes, so it is normally run as root.
39205 &*Warning*&: This is not an efficient process. It is intended for occasional
39206 use by system administrators. It is not sensible, for example, to set up a
39207 script that sends SIGUSR1 signals to Exim processes at short intervals.
39210 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
39211 varies in different operating systems. Not only are different options used,
39212 but the format of the output is different. For this reason, there are some
39213 system configuration options that configure exactly how &'exiwhat'& works. If
39214 it doesn't seem to be working for you, check the following compile-time
39217 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
39218 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
39219 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
39220 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
39222 An example of typical output from &'exiwhat'& is
39224 164 daemon: -q1h, listening on port 25
39225 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
39226 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
39227 [10.19.42.42] (editor@ref.example)
39228 10592 handling incoming call from [192.168.243.242]
39229 10628 accepting a local non-SMTP message
39231 The first number in the output line is the process number. The third line has
39232 been split here, in order to fit it on the page.
39236 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
39237 .cindex "&'exiqgrep'&"
39238 .cindex "queue" "grepping"
39239 This utility is a Perl script contributed by Matt Hubbard. It runs
39243 or (in case &*-a*& switch is specified)
39247 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
39248 contain alternate exim configuration the queue management might be using.
39250 to obtain a queue listing, and then greps the output to select messages
39251 that match given criteria. The following selection options are available:
39254 .vitem &*-f*&&~<&'regex'&>
39255 Match the sender address using a case-insensitive search. The field that is
39256 tested is enclosed in angle brackets, so you can test for bounce messages with
39260 .vitem &*-r*&&~<&'regex'&>
39261 Match a recipient address using a case-insensitive search. The field that is
39262 tested is not enclosed in angle brackets.
39264 .vitem &*-s*&&~<&'regex'&>
39265 Match against the size field.
39267 .vitem &*-y*&&~<&'seconds'&>
39268 Match messages that are younger than the given time.
39270 .vitem &*-o*&&~<&'seconds'&>
39271 Match messages that are older than the given time.
39274 Match only frozen messages.
39277 Match only non-frozen messages.
39279 .vitem &*-G*&&~<&'queuename'&>
39280 Match only messages in the given queue. Without this, the default queue is searched.
39283 The following options control the format of the output:
39287 Display only the count of matching messages.
39290 Long format &-- display the full message information as output by Exim. This is
39294 Display message ids only.
39297 Brief format &-- one line per message.
39300 Display messages in reverse order.
39303 Include delivered recipients in queue listing.
39306 There is one more option, &%-h%&, which outputs a list of options.
39310 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
39311 .cindex "&'exiqsumm'&"
39312 .cindex "queue" "summary"
39313 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
39314 -bp`& and produces a summary of the messages in the queue. Thus, you use it by
39315 running a command such as
39317 exim -bp | exiqsumm
39319 The output consists of one line for each domain that has messages waiting for
39320 it, as in the following example:
39322 3 2322 74m 66m msn.com.example
39324 Each line lists the number of pending deliveries for a domain, their total
39325 volume, and the length of time that the oldest and the newest messages have
39326 been waiting. Note that the number of pending deliveries is greater than the
39327 number of messages when messages have more than one recipient.
39329 A summary line is output at the end. By default the output is sorted on the
39330 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
39331 the output to be sorted by oldest message and by count of messages,
39332 respectively. There are also three options that split the messages for each
39333 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
39334 separates frozen messages, and &%-s%& separates messages according to their
39337 The output of &'exim -bp'& contains the original addresses in the message, so
39338 this also applies to the output from &'exiqsumm'&. No domains from addresses
39339 generated by aliasing or forwarding are included (unless the &%one_time%&
39340 option of the &(redirect)& router has been used to convert them into &"top
39341 level"& addresses).
39346 .section "Extracting specific information from the log (exigrep)" &&&
39348 .cindex "&'exigrep'&"
39349 .cindex "log" "extracts; grepping for"
39350 The &'exigrep'& utility is a Perl script that searches one or more main log
39351 files for entries that match a given pattern. When it finds a match, it
39352 extracts all the log entries for the relevant message, not just those that
39353 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
39354 given message, or all mail for a given user, or for a given host, for example.
39355 The input files can be in Exim log format or syslog format.
39356 If a matching log line is not associated with a specific message, it is
39357 included in &'exigrep'&'s output without any additional lines. The usage is:
39359 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
39361 If no log filenames are given on the command line, the standard input is read.
39363 The &%-t%& argument specifies a number of seconds. It adds an additional
39364 condition for message selection. Messages that are complete are shown only if
39365 they spent more than <&'n'&> seconds in the queue.
39367 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
39368 makes it case-sensitive. This may give a performance improvement when searching
39369 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
39370 option; with &%-I%& they do not. In both cases it is possible to change the
39371 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
39373 The &%-l%& option means &"literal"&, that is, treat all characters in the
39374 pattern as standing for themselves. Otherwise the pattern must be a Perl
39375 regular expression.
39377 The &%-v%& option inverts the matching condition. That is, a line is selected
39378 if it does &'not'& match the pattern.
39380 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
39381 that are generated as a result/response to a message that &'exigrep'& matched
39385 user_a sends a message to user_b, which generates a bounce back to user_b. If
39386 &'exigrep'& is used to search for &"user_a"&, only the first message will be
39387 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
39388 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
39389 when searching for &"user_a"& will show both messages since the bounce is
39390 &"related"& to or a &"result"& of the first message that was found by the
39393 If the location of a &'zcat'& command is known from the definition of
39394 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
39395 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
39396 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
39397 autodetection of some well known compression extensions.
39400 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
39401 .cindex "&'exipick'&"
39402 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
39403 lists messages from the queue according to a variety of criteria. For details
39404 of &'exipick'&'s facilities, run &'exipick'& with
39405 the &%--help%& option.
39408 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
39409 .cindex "log" "cycling local files"
39410 .cindex "cycling logs"
39411 .cindex "&'exicyclog'&"
39412 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
39413 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
39414 you are using log files with datestamps in their names (see section
39415 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
39416 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
39417 There are two command line options for &'exicyclog'&:
39419 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
39420 default that is set when Exim is built. The default default is 10.
39422 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
39423 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
39424 overriding the script's default, which is to find the setting from Exim's
39428 Each time &'exicyclog'& is run the filenames get &"shuffled down"& by one. If
39429 the main log filename is &_mainlog_& (the default) then when &'exicyclog'& is
39430 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
39431 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
39432 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
39433 logs are handled similarly.
39435 If the limit is greater than 99, the script uses 3-digit numbers such as
39436 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
39437 to one that is greater, or &'vice versa'&, you will have to fix the names of
39438 any existing log files.
39440 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
39441 the end are deleted. All files with numbers greater than 01 are compressed,
39442 using a compression command which is configured by the COMPRESS_COMMAND
39443 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
39444 root &%crontab%& entry of the form
39446 1 0 * * * su exim -c /usr/exim/bin/exicyclog
39448 assuming you have used the name &"exim"& for the Exim user. You can run
39449 &'exicyclog'& as root if you wish, but there is no need.
39453 .section "Mail statistics (eximstats)" "SECTmailstat"
39454 .cindex "statistics"
39455 .cindex "&'eximstats'&"
39456 A Perl script called &'eximstats'& is provided for extracting statistical
39457 information from log files. The output is either plain text, or HTML.
39458 . --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan
39459 . --- 404 error and everything else points to that.
39461 The &'eximstats'& script has been hacked about quite a bit over time. The
39462 latest version is the result of some extensive revision by Steve Campbell. A
39463 lot of information is given by default, but there are options for suppressing
39464 various parts of it. Following any options, the arguments to the script are a
39465 list of files, which should be main log files. For example:
39467 eximstats -nr /var/spool/exim/log/mainlog.01
39469 By default, &'eximstats'& extracts information about the number and volume of
39470 messages received from or delivered to various hosts. The information is sorted
39471 both by message count and by volume, and the top fifty hosts in each category
39472 are listed on the standard output. Similar information, based on email
39473 addresses or domains instead of hosts can be requested by means of various
39474 options. For messages delivered and received locally, similar statistics are
39475 also produced per user.
39477 The output also includes total counts and statistics about delivery errors, and
39478 histograms showing the number of messages received and deliveries made in each
39479 hour of the day. A delivery with more than one address in its envelope (for
39480 example, an SMTP transaction with more than one RCPT command) is counted
39481 as a single delivery by &'eximstats'&.
39483 Though normally more deliveries than receipts are reported (as messages may
39484 have multiple recipients), it is possible for &'eximstats'& to report more
39485 messages received than delivered, even though the queue is empty at the start
39486 and end of the period in question. If an incoming message contains no valid
39487 recipients, no deliveries are recorded for it. A bounce message is handled as
39488 an entirely separate message.
39490 &'eximstats'& always outputs a grand total summary giving the volume and number
39491 of messages received and deliveries made, and the number of hosts involved in
39492 each case. It also outputs the number of messages that were delayed (that is,
39493 not completely delivered at the first attempt), and the number that had at
39494 least one address that failed.
39496 The remainder of the output is in sections that can be independently disabled
39497 or modified by various options. It consists of a summary of deliveries by
39498 transport, histograms of messages received and delivered per time interval
39499 (default per hour), information about the time messages spent in the queue,
39500 a list of relayed messages, lists of the top fifty sending hosts, local
39501 senders, destination hosts, and destination local users by count and by volume,
39502 and a list of delivery errors that occurred.
39504 The relay information lists messages that were actually relayed, that is, they
39505 came from a remote host and were directly delivered to some other remote host,
39506 without being processed (for example, for aliasing or forwarding) locally.
39508 There are quite a few options for &'eximstats'& to control exactly what it
39509 outputs. These are documented in the Perl script itself, and can be extracted
39510 by running the command &(perldoc)& on the script. For example:
39512 perldoc /usr/exim/bin/eximstats
39515 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
39516 .cindex "&'exim_checkaccess'&"
39517 .cindex "policy control" "checking access"
39518 .cindex "checking access"
39519 The &%-bh%& command line argument allows you to run a fake SMTP session with
39520 debugging output, in order to check what Exim is doing when it is applying
39521 policy controls to incoming SMTP mail. However, not everybody is sufficiently
39522 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
39523 sometimes you just want to answer the question &"Does this address have
39524 access?"& without bothering with any further details.
39526 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
39527 two arguments, an IP address and an email address:
39529 exim_checkaccess 10.9.8.7 A.User@a.domain.example
39531 The utility runs a call to Exim with the &%-bh%& option, to test whether the
39532 given email address would be accepted in a RCPT command in a TCP/IP
39533 connection from the host with the given IP address. The output of the utility
39534 is either the word &"accepted"&, or the SMTP error response, for example:
39537 550 Relay not permitted
39539 When running this test, the utility uses &`<>`& as the envelope sender address
39540 for the MAIL command, but you can change this by providing additional
39541 options. These are passed directly to the Exim command. For example, to specify
39542 that the test is to be run with the sender address &'himself@there.example'&
39545 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
39546 -f himself@there.example
39548 Note that these additional Exim command line items must be given after the two
39549 mandatory arguments.
39551 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
39552 while running its checks. You can run checks that include callouts by using
39553 &%-bhc%&, but this is not yet available in a &"packaged"& form.
39557 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
39558 .cindex "DBM" "building dbm files"
39559 .cindex "building DBM files"
39560 .cindex "&'exim_dbmbuild'&"
39561 .cindex "lower casing"
39562 .cindex "binary zero" "in lookup key"
39563 The &'exim_dbmbuild'& program reads an input file containing keys and data in
39564 the format used by the &(lsearch)& lookup (see section
39565 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
39566 names as keys and the remainder of the information as data. The lower-casing
39567 can be prevented by calling the program with the &%-nolc%& option.
39569 A terminating zero is included as part of the key string. This is expected by
39570 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
39571 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
39572 strings or the data strings. The &(dbmnz)& lookup type can be used with such
39575 The program requires two arguments: the name of the input file (which can be a
39576 single hyphen to indicate the standard input), and the name of the output file.
39577 It creates the output under a temporary name, and then renames it if all went
39581 If the native DB interface is in use (USE_DB is set in a compile-time
39582 configuration file &-- this is common in free versions of Unix) the two
39583 filenames must be different, because in this mode the Berkeley DB functions
39584 create a single output file using exactly the name given. For example,
39586 exim_dbmbuild /etc/aliases /etc/aliases.db
39588 reads the system alias file and creates a DBM version of it in
39589 &_/etc/aliases.db_&.
39591 In systems that use the &'ndbm'& routines (mostly proprietary versions of
39592 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
39593 environment, the suffixes are added to the second argument of
39594 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
39595 when the Berkeley functions are used in compatibility mode (though this is not
39596 recommended), because in that case it adds a &_.db_& suffix to the filename.
39598 If a duplicate key is encountered, the program outputs a warning, and when it
39599 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
39600 option is used. By default, only the first of a set of duplicates is used &--
39601 this makes it compatible with &(lsearch)& lookups. There is an option
39602 &%-lastdup%& which causes it to use the data for the last duplicate instead.
39603 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
39604 &%stderr%&. For other errors, where it doesn't actually make a new file, the
39610 .section "Finding individual retry times (exinext)" "SECTfinindret"
39611 .cindex "retry" "times"
39612 .cindex "&'exinext'&"
39613 A utility called &'exinext'& (mostly a Perl script) provides the ability to
39614 fish specific information out of the retry database. Given a mail domain (or a
39615 complete address), it looks up the hosts for that domain, and outputs any retry
39616 information for the hosts or for the domain. At present, the retry information
39617 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
39618 output. For example:
39620 $ exinext piglet@milne.fict.example
39621 kanga.milne.example:192.168.8.1 error 146: Connection refused
39622 first failed: 21-Feb-1996 14:57:34
39623 last tried: 21-Feb-1996 14:57:34
39624 next try at: 21-Feb-1996 15:02:34
39625 roo.milne.example:192.168.8.3 error 146: Connection refused
39626 first failed: 20-Jan-1996 13:12:08
39627 last tried: 21-Feb-1996 11:42:03
39628 next try at: 21-Feb-1996 19:42:03
39629 past final cutoff time
39631 You can also give &'exinext'& a local part, without a domain, and it
39632 will give any retry information for that local part in your default domain.
39633 A message id can be used to obtain retry information pertaining to a specific
39634 message. This exists only when an attempt to deliver a message to a remote host
39635 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
39636 &'exinext'& is not particularly efficient, but then it is not expected to be
39639 The &'exinext'& utility calls Exim to find out information such as the location
39640 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
39641 passed on to the &'exim'& commands. The first specifies an alternate Exim
39642 configuration file, and the second sets macros for use within the configuration
39643 file. These features are mainly to help in testing, but might also be useful in
39644 environments where more than one configuration file is in use.
39648 .section "Hints database maintenance" "SECThindatmai"
39649 .cindex "hints database" "maintenance"
39650 .cindex "maintaining Exim's hints database"
39651 Three utility programs are provided for maintaining the DBM files that Exim
39652 uses to contain its delivery hint information. Each program requires two
39653 arguments. The first specifies the name of Exim's spool directory, and the
39654 second is the name of the database it is to operate on. These are as follows:
39657 &'retry'&: the database of retry information
39659 &'wait-'&<&'transport name'&>: databases of information about messages waiting
39662 &'callout'&: the callout cache
39664 &'ratelimit'&: the data for implementing the ratelimit ACL condition
39667 &'tls'&: TLS session resumption data
39670 &'misc'&: other hints data
39673 The &'misc'& database is used for
39676 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
39678 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
39679 &(smtp)& transport)
39681 Limiting the concurrency of specific transports (when &%max_parallel%& is set
39687 .section "exim_dumpdb" "SECTdumpdb"
39688 .cindex "&'exim_dumpdb'&"
39689 The entire contents of a database are written to the standard output by the
39690 &'exim_dumpdb'& program, which has no options or arguments other than the
39691 spool and database names. For example, to dump the retry database:
39693 exim_dumpdb /var/spool/exim retry
39695 Two lines of output are produced for each entry:
39697 T:mail.ref.example:192.168.242.242 146 77 Connection refused
39698 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
39700 The first item on the first line is the key of the record. It starts with one
39701 of the letters R, or T, depending on whether it refers to a routing or
39702 transport retry. For a local delivery, the next part is the local address; for
39703 a remote delivery it is the name of the remote host, followed by its failing IP
39704 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
39705 transport). If the remote port is not the standard one (port 25), it is added
39706 to the IP address. Then there follows an error code, an additional error code,
39707 and a textual description of the error.
39709 The three times on the second line are the time of first failure, the time of
39710 the last delivery attempt, and the computed time for the next attempt. The line
39711 ends with an asterisk if the cutoff time for the last retry rule has been
39714 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
39715 consists of a host name followed by a list of ids for messages that are or were
39716 waiting to be delivered to that host. If there are a very large number for any
39717 one host, continuation records, with a sequence number added to the host name,
39718 may be seen. The data in these records is often out of date, because a message
39719 may be routed to several alternative hosts, and Exim makes no effort to keep
39724 .section "exim_tidydb" "SECTtidydb"
39725 .cindex "&'exim_tidydb'&"
39726 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
39727 database. If run with no options, it removes all records that are more than 30
39728 days old. The age is calculated from the date and time that the record was last
39729 updated. Note that, in the case of the retry database, it is &'not'& the time
39730 since the first delivery failure. Information about a host that has been down
39731 for more than 30 days will remain in the database, provided that the record is
39732 updated sufficiently often.
39734 The cutoff date can be altered by means of the &%-t%& option, which must be
39735 followed by a time. For example, to remove all records older than a week from
39736 the retry database:
39738 exim_tidydb -t 7d /var/spool/exim retry
39740 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
39741 message ids. In the former these appear as data in records keyed by host &--
39742 they were messages that were waiting for that host &-- and in the latter they
39743 are the keys for retry information for messages that have suffered certain
39744 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
39745 message ids in database records are those of messages that are still on the
39746 queue. Message ids for messages that no longer exist are removed from
39747 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
39748 For the &'retry'& database, records whose keys are non-existent message ids are
39749 removed. The &'exim_tidydb'& utility outputs comments on the standard output
39750 whenever it removes information from the database.
39752 Certain records are automatically removed by Exim when they are no longer
39753 needed, but others are not. For example, if all the MX hosts for a domain are
39754 down, a retry record is created for each one. If the primary MX host comes back
39755 first, its record is removed when Exim successfully delivers to it, but the
39756 records for the others remain because Exim has not tried to use those hosts.
39758 It is important, therefore, to run &'exim_tidydb'& periodically on all the
39759 hints databases. You should do this at a quiet time of day, because it requires
39760 a database to be locked (and therefore inaccessible to Exim) while it does its
39761 work. Removing records from a DBM file does not normally make the file smaller,
39762 but all the common DBM libraries are able to re-use the space that is released.
39763 After an initial phase of increasing in size, the databases normally reach a
39764 point at which they no longer get any bigger, as long as they are regularly
39767 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
39768 databases is likely to keep on increasing.
39773 .section "exim_fixdb" "SECTfixdb"
39774 .cindex "&'exim_fixdb'&"
39775 The &'exim_fixdb'& program is a utility for interactively modifying databases.
39776 Its main use is for testing Exim, but it might also be occasionally useful for
39777 getting round problems in a live system. It has no options, and its interface
39778 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
39779 key of a database record can then be entered, and the data for that record is
39782 If &"d"& is typed at the next prompt, the entire record is deleted. For all
39783 except the &'retry'& database, that is the only operation that can be carried
39784 out. For the &'retry'& database, each field is output preceded by a number, and
39785 data for individual fields can be changed by typing the field number followed
39786 by new data, for example:
39790 resets the time of the next delivery attempt. Time values are given as a
39791 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
39792 used as optional separators.
39797 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
39798 .cindex "mailbox" "maintenance"
39799 .cindex "&'exim_lock'&"
39800 .cindex "locking mailboxes"
39801 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
39802 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
39803 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
39804 a user agent while investigating a problem. The utility requires the name of
39805 the file as its first argument. If the locking is successful, the second
39806 argument is run as a command (using C's &[system()]& function); if there is no
39807 second argument, the value of the SHELL environment variable is used; if this
39808 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
39809 is unlocked and the utility ends. The following options are available:
39813 Use &[fcntl()]& locking on the open mailbox.
39816 Use &[flock()]& locking on the open mailbox, provided the operating system
39819 .vitem &%-interval%&
39820 This must be followed by a number, which is a number of seconds; it sets the
39821 interval to sleep between retries (default 3).
39823 .vitem &%-lockfile%&
39824 Create a lock file before opening the mailbox.
39827 Lock the mailbox using MBX rules.
39830 Suppress verification output.
39832 .vitem &%-retries%&
39833 This must be followed by a number; it sets the number of times to try to get
39834 the lock (default 10).
39836 .vitem &%-restore_time%&
39837 This option causes &%exim_lock%& to restore the modified and read times to the
39838 locked file before exiting. This allows you to access a locked mailbox (for
39839 example, to take a backup copy) without disturbing the times that the user
39842 .vitem &%-timeout%&
39843 This must be followed by a number, which is a number of seconds; it sets a
39844 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
39845 default), a non-blocking call is used.
39848 Generate verbose output.
39851 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
39852 default is to create a lock file and also to use &[fcntl()]& locking on the
39853 mailbox, which is the same as Exim's default. The use of &%-flock%& or
39854 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
39855 requires that the directory containing the file be writeable. Locking by lock
39856 file does not last forever; Exim assumes that a lock file is expired if it is
39857 more than 30 minutes old.
39859 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
39860 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
39861 to be taken out on the open mailbox, and an exclusive lock on the file
39862 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
39863 number of the mailbox file. When the locking is released, if an exclusive lock
39864 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
39866 The default output contains verification of the locking that takes place. The
39867 &%-v%& option causes some additional information to be given. The &%-q%& option
39868 suppresses all output except error messages.
39872 exim_lock /var/spool/mail/spqr
39874 runs an interactive shell while the file is locked, whereas
39876 &`exim_lock -q /var/spool/mail/spqr <<End`&
39877 <&'some commands'&>
39880 runs a specific non-interactive sequence of commands while the file is locked,
39881 suppressing all verification output. A single command can be run by a command
39884 exim_lock -q /var/spool/mail/spqr \
39885 "cp /var/spool/mail/spqr /some/where"
39887 Note that if a command is supplied, it must be entirely contained within the
39888 second argument &-- hence the quotes.
39892 . ////////////////////////////////////////////////////////////////////////////
39893 . ////////////////////////////////////////////////////////////////////////////
39895 .chapter "The Exim monitor" "CHAPeximon"
39896 .scindex IIDeximon "Exim monitor" "description"
39897 .cindex "X-windows"
39898 .cindex "&'eximon'&"
39899 .cindex "Local/eximon.conf"
39900 .cindex "&_exim_monitor/EDITME_&"
39901 The Exim monitor is an application which displays in an X window information
39902 about the state of Exim's queue and what Exim is doing. An admin user can
39903 perform certain operations on messages from this GUI interface; however all
39904 such facilities are also available from the command line, and indeed, the
39905 monitor itself makes use of the command line to perform any actions requested.
39909 .section "Running the monitor" "SECID264"
39910 The monitor is started by running the script called &'eximon'&. This is a shell
39911 script that sets up a number of environment variables, and then runs the
39912 binary called &_eximon.bin_&. The default appearance of the monitor window can
39913 be changed by editing the &_Local/eximon.conf_& file created by editing
39914 &_exim_monitor/EDITME_&. Comments in that file describe what the various
39915 parameters are for.
39917 The parameters that get built into the &'eximon'& script can be overridden for
39918 a particular invocation by setting up environment variables of the same names,
39919 preceded by &`EXIMON_`&. For example, a shell command such as
39921 EXIMON_LOG_DEPTH=400 eximon
39923 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
39924 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
39925 overrides the Exim log file configuration. This makes it possible to have
39926 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
39927 syslog messages are routed to a file on the local host.
39929 X resources can be used to change the appearance of the window in the normal
39930 way. For example, a resource setting of the form
39932 Eximon*background: gray94
39934 changes the colour of the background to light grey rather than white. The
39935 stripcharts are drawn with both the data lines and the reference lines in
39936 black. This means that the reference lines are not visible when on top of the
39937 data. However, their colour can be changed by setting a resource called
39938 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
39939 For example, if your X server is running Unix, you could set up lighter
39940 reference lines in the stripcharts by obeying
39943 Eximon*highlight: gray
39946 .cindex "admin user"
39947 In order to see the contents of messages in the queue, and to operate on them,
39948 &'eximon'& must either be run as root or by an admin user.
39950 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
39951 contain X11 resource parameters interpreted by the X11 library. In addition,
39952 if the first parameter starts with the string "gdb" then it is removed and the
39953 binary is invoked under gdb (the parameter is used as the gdb command-name, so
39954 versioned variants of gdb can be invoked).
39956 The monitor's window is divided into three parts. The first contains one or
39957 more stripcharts and two action buttons, the second contains a &"tail"& of the
39958 main log file, and the third is a display of the queue of messages awaiting
39959 delivery, with two more action buttons. The following sections describe these
39960 different parts of the display.
39965 .section "The stripcharts" "SECID265"
39966 .cindex "stripchart"
39967 The first stripchart is always a count of messages in the queue. Its name can
39968 be configured by setting QUEUE_STRIPCHART_NAME in the
39969 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
39970 configuration script by regular expression matches on log file entries, making
39971 it possible to display, for example, counts of messages delivered to certain
39972 hosts or using certain transports. The supplied defaults display counts of
39973 received and delivered messages, and of local and SMTP deliveries. The default
39974 period between stripchart updates is one minute; this can be adjusted by a
39975 parameter in the &_Local/eximon.conf_& file.
39977 The stripchart displays rescale themselves automatically as the value they are
39978 displaying changes. There are always 10 horizontal lines in each chart; the
39979 title string indicates the value of each division when it is greater than one.
39980 For example, &"x2"& means that each division represents a value of 2.
39982 It is also possible to have a stripchart which shows the percentage fullness of
39983 a particular disk partition, which is useful when local deliveries are confined
39984 to a single partition.
39986 .cindex "&%statvfs%& function"
39987 This relies on the availability of the &[statvfs()]& function or equivalent in
39988 the operating system. Most, but not all versions of Unix that support Exim have
39989 this. For this particular stripchart, the top of the chart always represents
39990 100%, and the scale is given as &"x10%"&. This chart is configured by setting
39991 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
39992 &_Local/eximon.conf_& file.
39997 .section "Main action buttons" "SECID266"
39998 .cindex "size" "of monitor window"
39999 .cindex "Exim monitor" "window size"
40000 .cindex "window size"
40001 Below the stripcharts there is an action button for quitting the monitor. Next
40002 to this is another button marked &"Size"&. They are placed here so that
40003 shrinking the window to its default minimum size leaves just the queue count
40004 stripchart and these two buttons visible. Pressing the &"Size"& button causes
40005 the window to expand to its maximum size, unless it is already at the maximum,
40006 in which case it is reduced to its minimum.
40008 When expanding to the maximum, if the window cannot be fully seen where it
40009 currently is, it is moved back to where it was the last time it was at full
40010 size. When it is expanding from its minimum size, the old position is
40011 remembered, and next time it is reduced to the minimum it is moved back there.
40013 The idea is that you can keep a reduced window just showing one or two
40014 stripcharts at a convenient place on your screen, easily expand it to show
40015 the full window when required, and just as easily put it back to what it was.
40016 The idea is copied from what the &'twm'& window manager does for its
40017 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
40018 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
40020 Normally, the monitor starts up with the window at its full size, but it can be
40021 built so that it starts up with the window at its smallest size, by setting
40022 START_SMALL=yes in &_Local/eximon.conf_&.
40026 .section "The log display" "SECID267"
40027 .cindex "log" "tail of; in monitor"
40028 The second section of the window is an area in which a display of the tail of
40029 the main log is maintained.
40030 To save space on the screen, the timestamp on each log line is shortened by
40031 removing the date and, if &%log_timezone%& is set, the timezone.
40032 The log tail is not available when the only destination for logging data is
40033 syslog, unless the syslog lines are routed to a local file whose name is passed
40034 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
40036 The log sub-window has a scroll bar at its lefthand side which can be used to
40037 move back to look at earlier text, and the up and down arrow keys also have a
40038 scrolling effect. The amount of log that is kept depends on the setting of
40039 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
40040 to use. When this is full, the earlier 50% of data is discarded &-- this is
40041 much more efficient than throwing it away line by line. The sub-window also has
40042 a horizontal scroll bar for accessing the ends of long log lines. This is the
40043 only means of horizontal scrolling; the right and left arrow keys are not
40044 available. Text can be cut from this part of the window using the mouse in the
40045 normal way. The size of this subwindow is controlled by parameters in the
40046 configuration file &_Local/eximon.conf_&.
40048 Searches of the text in the log window can be carried out by means of the ^R
40049 and ^S keystrokes, which default to a reverse and a forward search,
40050 respectively. The search covers only the text that is displayed in the window.
40051 It cannot go further back up the log.
40053 The point from which the search starts is indicated by a caret marker. This is
40054 normally at the end of the text in the window, but can be positioned explicitly
40055 by pointing and clicking with the left mouse button, and is moved automatically
40056 by a successful search. If new text arrives in the window when it is scrolled
40057 back, the caret remains where it is, but if the window is not scrolled back,
40058 the caret is moved to the end of the new text.
40060 Pressing ^R or ^S pops up a window into which the search text can be typed.
40061 There are buttons for selecting forward or reverse searching, for carrying out
40062 the search, and for cancelling. If the &"Search"& button is pressed, the search
40063 happens and the window remains so that further searches can be done. If the
40064 &"Return"& key is pressed, a single search is done and the window is closed. If
40065 ^C is typed the search is cancelled.
40067 The searching facility is implemented using the facilities of the Athena text
40068 widget. By default this pops up a window containing both &"search"& and
40069 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
40070 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
40071 However, the linkers in BSDI and HP-UX seem unable to handle an externally
40072 provided version of &%TextPop%& when the remaining parts of the text widget
40073 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
40074 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
40075 on these systems, at the expense of having unwanted items in the search popup
40080 .section "The queue display" "SECID268"
40081 .cindex "queue" "display in monitor"
40082 The bottom section of the monitor window contains a list of all messages that
40083 are in the queue, which includes those currently being received or delivered,
40084 as well as those awaiting delivery. The size of this subwindow is controlled by
40085 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
40086 at which it is updated is controlled by another parameter in the same file &--
40087 the default is 5 minutes, since queue scans can be quite expensive. However,
40088 there is an &"Update"& action button just above the display which can be used
40089 to force an update of the queue display at any time.
40091 When a host is down for some time, a lot of pending mail can build up for it,
40092 and this can make it hard to deal with other messages in the queue. To help
40093 with this situation there is a button next to &"Update"& called &"Hide"&. If
40094 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
40095 type anything in here and press &"Return"&, the text is added to a chain of
40096 such texts, and if every undelivered address in a message matches at least one
40097 of the texts, the message is not displayed.
40099 If there is an address that does not match any of the texts, all the addresses
40100 are displayed as normal. The matching happens on the ends of addresses so, for
40101 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
40102 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
40103 has been set up, a button called &"Unhide"& is displayed. If pressed, it
40104 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
40105 a hide request is automatically cancelled after one hour.
40107 While the dialogue box is displayed, you can't press any buttons or do anything
40108 else to the monitor window. For this reason, if you want to cut text from the
40109 queue display to use in the dialogue box, you have to do the cutting before
40110 pressing the &"Hide"& button.
40112 The queue display contains, for each unhidden queued message, the length of
40113 time it has been in the queue, the size of the message, the message id, the
40114 message sender, and the first undelivered recipient, all on one line. If it is
40115 a bounce message, the sender is shown as &"<>"&. If there is more than one
40116 recipient to which the message has not yet been delivered, subsequent ones are
40117 listed on additional lines, up to a maximum configured number, following which
40118 an ellipsis is displayed. Recipients that have already received the message are
40121 .cindex "frozen messages" "display"
40122 If a message is frozen, an asterisk is displayed at the left-hand side.
40124 The queue display has a vertical scroll bar, and can also be scrolled by means
40125 of the arrow keys. Text can be cut from it using the mouse in the normal way.
40126 The text searching facilities, as described above for the log window, are also
40127 available, but the caret is always moved to the end of the text when the queue
40128 display is updated.
40132 .section "The queue menu" "SECID269"
40133 .cindex "queue" "menu in monitor"
40134 If the &%shift%& key is held down and the left button is clicked when the mouse
40135 pointer is over the text for any message, an action menu pops up, and the first
40136 line of the queue display for the message is highlighted. This does not affect
40139 If you want to use some other event for popping up the menu, you can set the
40140 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
40141 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
40142 value set in this parameter is a standard X event description. For example, to
40143 run eximon using &%ctrl%& rather than &%shift%& you could use
40145 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
40147 The title of the menu is the message id, and it contains entries which act as
40151 &'message log'&: The contents of the message log for the message are displayed
40152 in a new text window.
40154 &'headers'&: Information from the spool file that contains the envelope
40155 information and headers is displayed in a new text window. See chapter
40156 &<<CHAPspool>>& for a description of the format of spool files.
40158 &'body'&: The contents of the spool file containing the body of the message are
40159 displayed in a new text window. There is a default limit of 20,000 bytes to the
40160 amount of data displayed. This can be changed by setting the BODY_MAX
40161 option at compile time, or the EXIMON_BODY_MAX option at runtime.
40163 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
40164 delivery of the message. This causes an automatic thaw if the message is
40165 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
40166 a new text window. The delivery is run in a separate process, to avoid holding
40167 up the monitor while the delivery proceeds.
40169 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
40170 that the message be frozen.
40172 .cindex "thawing messages"
40173 .cindex "unfreezing messages"
40174 .cindex "frozen messages" "thawing"
40175 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
40176 that the message be thawed.
40178 .cindex "delivery" "forcing failure"
40179 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
40180 that Exim gives up trying to deliver the message. A bounce message is generated
40181 for any remaining undelivered addresses.
40183 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
40184 that the message be deleted from the system without generating a bounce
40187 &'add recipient'&: A dialog box is displayed into which a recipient address can
40188 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40189 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40190 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40191 causes a call to Exim to be made using the &%-Mar%& option to request that an
40192 additional recipient be added to the message, unless the entry box is empty, in
40193 which case no action is taken.
40195 &'mark delivered'&: A dialog box is displayed into which a recipient address
40196 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40197 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40198 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40199 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
40200 recipient address as already delivered, unless the entry box is empty, in which
40201 case no action is taken.
40203 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
40204 mark all recipient addresses as already delivered.
40206 &'edit sender'&: A dialog box is displayed initialized with the current
40207 sender's address. Pressing RETURN causes a call to Exim to be made using the
40208 &%-Mes%& option to replace the sender address, unless the entry box is empty,
40209 in which case no action is taken. If you want to set an empty sender (as in
40210 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
40211 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
40212 the address is qualified with that domain.
40215 When a delivery is forced, a window showing the &%-v%& output is displayed. In
40216 other cases when a call to Exim is made, if there is any output from Exim (in
40217 particular, if the command fails) a window containing the command and the
40218 output is displayed. Otherwise, the results of the action are normally apparent
40219 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
40220 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
40221 if no output is generated.
40223 The queue display is automatically updated for actions such as freezing and
40224 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
40225 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
40226 force an update of the display after one of these actions.
40228 In any text window that is displayed as result of a menu action, the normal
40229 cut-and-paste facility is available, and searching can be carried out using ^R
40230 and ^S, as described above for the log tail window.
40237 . ////////////////////////////////////////////////////////////////////////////
40238 . ////////////////////////////////////////////////////////////////////////////
40240 .chapter "Security considerations" "CHAPsecurity"
40241 .scindex IIDsecurcon "security" "discussion of"
40242 This chapter discusses a number of issues concerned with security, some of
40243 which are also covered in other parts of this manual.
40245 For reasons that this author does not understand, some people have promoted
40246 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
40247 existence of this chapter in the documentation. However, the intent of the
40248 chapter is simply to describe the way Exim works in relation to certain
40249 security concerns, not to make any specific claims about the effectiveness of
40250 its security as compared with other MTAs.
40252 What follows is a description of the way Exim is supposed to be. Best efforts
40253 have been made to try to ensure that the code agrees with the theory, but an
40254 absence of bugs can never be guaranteed. Any that are reported will get fixed
40255 as soon as possible.
40258 .section "Building a more &""hardened""& Exim" "SECID286"
40259 .cindex "security" "build-time features"
40260 There are a number of build-time options that can be set in &_Local/Makefile_&
40261 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
40262 Exim administrator who does not have the root password, or by someone who has
40263 penetrated the Exim (but not the root) account. These options are as follows:
40266 ALT_CONFIG_PREFIX can be set to a string that is required to match the
40267 start of any filenames used with the &%-C%& option. When it is set, these
40268 filenames are also not allowed to contain the sequence &"/../"&. (However, if
40269 the value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
40270 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
40271 default setting for &%ALT_CONFIG_PREFIX%&.
40273 If the permitted configuration files are confined to a directory to
40274 which only root has access, this guards against someone who has broken
40275 into the Exim account from running a privileged Exim with an arbitrary
40276 configuration file, and using it to break into other accounts.
40279 If a non-trusted configuration file (i.e. not the default configuration file
40280 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
40281 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
40282 the next item), then root privilege is retained only if the caller of Exim is
40283 root. This locks out the possibility of testing a configuration using &%-C%&
40284 right through message reception and delivery, even if the caller is root. The
40285 reception works, but by that time, Exim is running as the Exim user, so when
40286 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
40287 privilege to be lost. However, root can test reception and delivery using two
40291 The WHITELIST_D_MACROS build option declares some macros to be safe to override
40292 with &%-D%& if the real uid is one of root, the Exim run-time user or the
40293 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
40294 requiring the run-time value supplied to &%-D%& to match a regex that errs on
40295 the restrictive side. Requiring build-time selection of safe macros is onerous
40296 but this option is intended solely as a transition mechanism to permit
40297 previously-working configurations to continue to work after release 4.73.
40299 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
40302 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
40303 never to be used for any deliveries. This is like the &%never_users%& runtime
40304 option, but it cannot be overridden; the runtime option adds additional users
40305 to the list. The default setting is &"root"&; this prevents a non-root user who
40306 is permitted to modify the runtime file from using Exim as a way to get root.
40311 .section "Root privilege" "SECID270"
40313 .cindex "root privilege"
40314 The Exim binary is normally setuid to root, which means that it gains root
40315 privilege (runs as root) when it starts execution. In some special cases (for
40316 example, when the daemon is not in use and there are no local deliveries), it
40317 may be possible to run Exim setuid to some user other than root. This is
40318 discussed in the next section. However, in most installations, root privilege
40319 is required for two things:
40322 To set up a socket connected to the standard SMTP port (25) when initialising
40323 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
40326 To be able to change uid and gid in order to read users' &_.forward_& files and
40327 perform local deliveries as the receiving user or as specified in the
40331 It is not necessary to be root to do any of the other things Exim does, such as
40332 receiving messages and delivering them externally over SMTP, and it is
40333 obviously more secure if Exim does not run as root except when necessary.
40334 For this reason, a user and group for Exim to use must be defined in
40335 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
40336 group"&. Their values can be changed by the runtime configuration, though this
40337 is not recommended. Often a user called &'exim'& is used, but some sites use
40338 &'mail'& or another user name altogether.
40340 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
40341 abdication; the process cannot regain root afterwards. Prior to release 4.00,
40342 &[seteuid()]& was used in some circumstances, but this is no longer the case.
40344 After a new Exim process has interpreted its command line options, it changes
40345 uid and gid in the following cases:
40350 If the &%-C%& option is used to specify an alternate configuration file, or if
40351 the &%-D%& option is used to define macro values for the configuration, and the
40352 calling process is not running as root, the uid and gid are changed to those of
40353 the calling process.
40354 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
40355 option may not be used at all.
40356 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
40357 can be supplied if the calling process is running as root, the Exim run-time
40358 user or CONFIGURE_OWNER, if defined.
40363 If the expansion test option (&%-be%&) or one of the filter testing options
40364 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
40367 If the process is not a daemon process or a queue runner process or a delivery
40368 process or a process for testing address routing (started with &%-bt%&), the
40369 uid and gid are changed to the Exim user and group. This means that Exim always
40370 runs under its own uid and gid when receiving messages. This also applies when
40371 testing address verification
40374 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
40377 For a daemon, queue runner, delivery, or address testing process, the uid
40378 remains as root at this stage, but the gid is changed to the Exim group.
40381 The processes that initially retain root privilege behave as follows:
40384 A daemon process changes the gid to the Exim group and the uid to the Exim
40385 user after setting up one or more listening sockets. The &[initgroups()]&
40386 function is called, so that if the Exim user is in any additional groups, they
40387 will be used during message reception.
40389 A queue runner process retains root privilege throughout its execution. Its
40390 job is to fork a controlled sequence of delivery processes.
40392 A delivery process retains root privilege throughout most of its execution,
40393 but any actual deliveries (that is, the transports themselves) are run in
40394 subprocesses which always change to a non-root uid and gid. For local
40395 deliveries this is typically the uid and gid of the owner of the mailbox; for
40396 remote deliveries, the Exim uid and gid are used. Once all the delivery
40397 subprocesses have been run, a delivery process changes to the Exim uid and gid
40398 while doing post-delivery tidying up such as updating the retry database and
40399 generating bounce and warning messages.
40401 While the recipient addresses in a message are being routed, the delivery
40402 process runs as root. However, if a user's filter file has to be processed,
40403 this is done in a subprocess that runs under the individual user's uid and
40404 gid. A system filter is run as root unless &%system_filter_user%& is set.
40406 A process that is testing addresses (the &%-bt%& option) runs as root so that
40407 the routing is done in the same environment as a message delivery.
40413 .section "Running Exim without privilege" "SECTrunexiwitpri"
40414 .cindex "privilege, running without"
40415 .cindex "unprivileged running"
40416 .cindex "root privilege" "running without"
40417 Some installations like to run Exim in an unprivileged state for more of its
40418 operation, for added security. Support for this mode of operation is provided
40419 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
40420 gid are changed to the Exim user and group at the start of a delivery process
40421 (and also queue runner and address testing processes). This means that address
40422 routing is no longer run as root, and the deliveries themselves cannot change
40426 .cindex "daemon" "restarting"
40427 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
40428 that the daemon can still be started in the usual way, and it can respond
40429 correctly to SIGHUP because the re-invocation regains root privilege.
40431 An alternative approach is to make Exim setuid to the Exim user and also setgid
40432 to the Exim group. If you do this, the daemon must be started from a root
40433 process. (Calling Exim from a root process makes it behave in the way it does
40434 when it is setuid root.) However, the daemon cannot restart itself after a
40435 SIGHUP signal because it cannot regain privilege.
40437 It is still useful to set &%deliver_drop_privilege%& in this case, because it
40438 stops Exim from trying to re-invoke itself to do a delivery after a message has
40439 been received. Such a re-invocation is a waste of resources because it has no
40442 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
40443 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
40444 to the Exim user seems a clean approach, but there is one complication:
40446 In this style of operation, Exim is running with the real uid and gid set to
40447 those of the calling process, and the effective uid/gid set to Exim's values.
40448 Ideally, any association with the calling process' uid/gid should be dropped,
40449 that is, the real uid/gid should be reset to the effective values so as to
40450 discard any privileges that the caller may have. While some operating systems
40451 have a function that permits this action for a non-root effective uid, quite a
40452 number of them do not. Because of this lack of standardization, Exim does not
40453 address this problem at this time.
40455 For this reason, the recommended approach for &"mostly unprivileged"& running
40456 is to keep the Exim binary setuid to root, and to set
40457 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
40458 be used in the most straightforward way.
40460 If you configure Exim not to run delivery processes as root, there are a
40461 number of restrictions on what you can do:
40464 You can deliver only as the Exim user/group. You should explicitly use the
40465 &%user%& and &%group%& options to override routers or local transports that
40466 normally deliver as the recipient. This makes sure that configurations that
40467 work in this mode function the same way in normal mode. Any implicit or
40468 explicit specification of another user causes an error.
40470 Use of &_.forward_& files is severely restricted, such that it is usually
40471 not worthwhile to include them in the configuration.
40473 Users who wish to use &_.forward_& would have to make their home directory and
40474 the file itself accessible to the Exim user. Pipe and append-to-file entries,
40475 and their equivalents in Exim filters, cannot be used. While they could be
40476 enabled in the Exim user's name, that would be insecure and not very useful.
40478 Unless the local user mailboxes are all owned by the Exim user (possible in
40479 some POP3 or IMAP-only environments):
40482 They must be owned by the Exim group and be writeable by that group. This
40483 implies you must set &%mode%& in the appendfile configuration, as well as the
40484 mode of the mailbox files themselves.
40486 You must set &%no_check_owner%&, since most or all of the files will not be
40487 owned by the Exim user.
40489 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
40490 on a newly created mailbox when unprivileged. This also implies that new
40491 mailboxes need to be created manually.
40496 These restrictions severely restrict what can be done in local deliveries.
40497 However, there are no restrictions on remote deliveries. If you are running a
40498 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
40499 gives more security at essentially no cost.
40501 If you are using the &%mua_wrapper%& facility (see chapter
40502 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
40507 .section "Delivering to local files" "SECID271"
40508 Full details of the checks applied by &(appendfile)& before it writes to a file
40509 are given in chapter &<<CHAPappendfile>>&.
40513 .section "Running local commands" "SECTsecconslocalcmds"
40514 .cindex "security" "local commands"
40515 .cindex "security" "command injection attacks"
40516 There are a number of ways in which an administrator can configure Exim to run
40517 commands based upon received, untrustworthy, data. Further, in some
40518 configurations a user who can control a &_.forward_& file can also arrange to
40519 run commands. Configuration to check includes, but is not limited to:
40522 Use of &%use_shell%& in the pipe transport: various forms of shell command
40523 injection may be possible with this option present. It is dangerous and should
40524 be used only with considerable caution. Consider constraints which whitelist
40525 allowed characters in a variable which is to be used in a pipe transport that
40526 has &%use_shell%& enabled.
40528 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
40529 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
40530 &_.forward_& files in a redirect router. If Exim is running on a central mail
40531 hub to which ordinary users do not have shell access, but home directories are
40532 NFS mounted (for instance) then administrators should review the list of these
40533 forbid options available, and should bear in mind that the options that may
40534 need forbidding can change as new features are added between releases.
40536 The &%${run...}%& expansion item does not use a shell by default, but
40537 administrators can configure use of &_/bin/sh_& as part of the command.
40538 Such invocations should be viewed with prejudicial suspicion.
40540 Administrators who use embedded Perl are advised to explore how Perl's
40541 taint checking might apply to their usage.
40543 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
40544 administrators are well advised to view its use with suspicion, in case (for
40545 instance) it allows a local-part to contain embedded Exim directives.
40547 Use of &%${match_local_part...}%& and friends becomes more dangerous if
40548 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
40549 each can reference arbitrary lists and files, rather than just being a list
40551 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
40552 real-world security vulnerabilities caused by its use with untrustworthy data
40553 injected in, for SQL injection attacks.
40554 Consider the use of the &%inlisti%& expansion condition instead.
40560 .section "Trust in configuration data" "SECTsecconfdata"
40561 .cindex "security" "data sources"
40562 .cindex "security" "regular expressions"
40563 .cindex "regular expressions" "security"
40564 .cindex "PCRE" "security"
40565 If configuration data for Exim can come from untrustworthy sources, there
40566 are some issues to be aware of:
40569 Use of &%${expand...}%& may provide a path for shell injection attacks.
40571 Letting untrusted data provide a regular expression is unwise.
40573 Using &%${match...}%& to apply a fixed regular expression against untrusted
40574 data may result in pathological behaviour within PCRE. Be aware of what
40575 "backtracking" means and consider options for being more strict with a regular
40576 expression. Avenues to explore include limiting what can match (avoiding &`.`&
40577 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
40578 possessive quantifiers or just not using regular expressions against untrusted
40581 It can be important to correctly use &%${quote:...}%&,
40582 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
40583 items to ensure that data is correctly constructed.
40585 Some lookups might return multiple results, even though normal usage is only
40586 expected to yield one result.
40592 .section "IPv4 source routing" "SECID272"
40593 .cindex "source routing" "in IP packets"
40594 .cindex "IP source routing"
40595 Many operating systems suppress IP source-routed packets in the kernel, but
40596 some cannot be made to do this, so Exim does its own check. It logs incoming
40597 IPv4 source-routed TCP calls, and then drops them. Things are all different in
40598 IPv6. No special checking is currently done.
40602 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
40603 Support for these SMTP commands is disabled by default. If required, they can
40604 be enabled by defining suitable ACLs.
40609 .section "Privileged users" "SECID274"
40610 .cindex "trusted users"
40611 .cindex "admin user"
40612 .cindex "privileged user"
40613 .cindex "user" "trusted"
40614 .cindex "user" "admin"
40615 Exim recognizes two sets of users with special privileges. Trusted users are
40616 able to submit new messages to Exim locally, but supply their own sender
40617 addresses and information about a sending host. For other users submitting
40618 local messages, Exim sets up the sender address from the uid, and doesn't
40619 permit a remote host to be specified.
40622 However, an untrusted user is permitted to use the &%-f%& command line option
40623 in the special form &%-f <>%& to indicate that a delivery failure for the
40624 message should not cause an error report. This affects the message's envelope,
40625 but it does not affect the &'Sender:'& header. Untrusted users may also be
40626 permitted to use specific forms of address with the &%-f%& option by setting
40627 the &%untrusted_set_sender%& option.
40629 Trusted users are used to run processes that receive mail messages from some
40630 other mail domain and pass them on to Exim for delivery either locally, or over
40631 the Internet. Exim trusts a caller that is running as root, as the Exim user,
40632 as any user listed in the &%trusted_users%& configuration option, or under any
40633 group listed in the &%trusted_groups%& option.
40635 Admin users are permitted to do things to the messages on Exim's queue. They
40636 can freeze or thaw messages, cause them to be returned to their senders, remove
40637 them entirely, or modify them in various ways. In addition, admin users can run
40638 the Exim monitor and see all the information it is capable of providing, which
40639 includes the contents of files on the spool.
40643 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
40644 delivery of messages on its queue is restricted to admin users. This
40645 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
40646 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
40647 queue is also restricted to admin users. This restriction can be relaxed by
40648 setting &%no_queue_list_requires_admin%&.
40650 Exim recognizes an admin user if the calling process is running as root or as
40651 the Exim user or if any of the groups associated with the calling process is
40652 the Exim group. It is not necessary actually to be running under the Exim
40653 group. However, if admin users who are not root or the Exim user are to access
40654 the contents of files on the spool via the Exim monitor (which runs
40655 unprivileged), Exim must be built to allow group read access to its spool
40658 By default, regular users are trusted to perform basic testing and
40659 introspection commands, as themselves. This setting can be tightened by
40660 setting the &%commandline_checks_require_admin%& option.
40661 This affects most of the checking options,
40662 such as &%-be%& and anything else &%-b*%&.
40665 .section "Spool files" "SECID275"
40666 .cindex "spool directory" "files"
40667 Exim's spool directory and everything it contains is owned by the Exim user and
40668 set to the Exim group. The mode for spool files is defined in the
40669 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
40670 any user who is a member of the Exim group can access these files.
40674 .section "Use of argv[0]" "SECID276"
40675 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
40676 of specific strings, Exim assumes certain options. For example, calling Exim
40677 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
40678 to calling it with the option &%-bS%&. There are no security implications in
40683 .section "Use of %f formatting" "SECID277"
40684 The only use made of &"%f"& by Exim is in formatting load average values. These
40685 are actually stored in integer variables as 1000 times the load average.
40686 Consequently, their range is limited and so therefore is the length of the
40691 .section "Embedded Exim path" "SECID278"
40692 Exim uses its own path name, which is embedded in the code, only when it needs
40693 to re-exec in order to regain root privilege. Therefore, it is not root when it
40694 does so. If some bug allowed the path to get overwritten, it would lead to an
40695 arbitrary program's being run as exim, not as root.
40699 .section "Dynamic module directory" "SECTdynmoddir"
40700 Any dynamically loadable modules must be installed into the directory
40701 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
40705 .section "Use of sprintf()" "SECID279"
40706 .cindex "&[sprintf()]&"
40707 A large number of occurrences of &"sprintf"& in the code are actually calls to
40708 &'string_sprintf()'&, a function that returns the result in malloc'd store.
40709 The intermediate formatting is done into a large fixed buffer by a function
40710 that runs through the format string itself, and checks the length of each
40711 conversion before performing it, thus preventing buffer overruns.
40713 The remaining uses of &[sprintf()]& happen in controlled circumstances where
40714 the output buffer is known to be sufficiently long to contain the converted
40719 .section "Use of debug_printf() and log_write()" "SECID280"
40720 Arbitrary strings are passed to both these functions, but they do their
40721 formatting by calling the function &'string_vformat()'&, which runs through
40722 the format string itself, and checks the length of each conversion.
40726 .section "Use of strcat() and strcpy()" "SECID281"
40727 These are used only in cases where the output buffer is known to be large
40728 enough to hold the result.
40729 .ecindex IIDsecurcon
40734 . ////////////////////////////////////////////////////////////////////////////
40735 . ////////////////////////////////////////////////////////////////////////////
40737 .chapter "Format of spool files" "CHAPspool"
40738 .scindex IIDforspo1 "format" "spool files"
40739 .scindex IIDforspo2 "spool directory" "format of files"
40740 .scindex IIDforspo3 "spool files" "format of"
40741 .cindex "spool files" "editing"
40742 A message on Exim's queue consists of two files, whose names are the message id
40743 followed by -D and -H, respectively. The data portion of the message is kept in
40744 the -D file on its own. The message's envelope, status, and headers are all
40745 kept in the -H file, whose format is described in this chapter. Each of these
40746 two files contains the final component of its own name as its first line. This
40747 is insurance against disk crashes where the directory is lost but the files
40748 themselves are recoverable.
40750 The file formats may be changed, or new formats added, at any release.
40751 Spool files are not intended as an interface to other programs
40752 and should not be used as such.
40754 Some people are tempted into editing -D files in order to modify messages. You
40755 need to be extremely careful if you do this; it is not recommended and you are
40756 on your own if you do it. Here are some of the pitfalls:
40759 You must ensure that Exim does not try to deliver the message while you are
40760 fiddling with it. The safest way is to take out a write lock on the -D file,
40761 which is what Exim itself does, using &[fcntl()]&. If you update the file in
40762 place, the lock will be retained. If you write a new file and rename it, the
40763 lock will be lost at the instant of rename.
40765 .vindex "&$body_linecount$&"
40766 If you change the number of lines in the file, the value of
40767 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
40768 cause incomplete transmission of messages or undeliverable messages.
40770 If the message is in MIME format, you must take care not to break it.
40772 If the message is cryptographically signed, any change will invalidate the
40775 All in all, modifying -D files is fraught with danger.
40777 Files whose names end with -J may also be seen in the &_input_& directory (or
40778 its subdirectories when &%split_spool_directory%& is set). These are journal
40779 files, used to record addresses to which the message has been delivered during
40780 the course of a delivery attempt. If there are still undelivered recipients at
40781 the end, the -H file is updated, and the -J file is deleted. If, however, there
40782 is some kind of crash (for example, a power outage) before this happens, the -J
40783 file remains in existence. When Exim next processes the message, it notices the
40784 -J file and uses it to update the -H file before starting the next delivery
40787 Files whose names end with -K or .eml may also be seen in the spool.
40788 These are temporaries used for DKIM or malware processing, when that is used.
40789 They should be tidied up by normal operations; any old ones are probably
40790 relics of crashes and can be removed.
40792 .section "Format of the -H file" "SECID282"
40793 .cindex "uid (user id)" "in spool file"
40794 .cindex "gid (group id)" "in spool file"
40795 The second line of the -H file contains the login name for the uid of the
40796 process that called Exim to read the message, followed by the numerical uid and
40797 gid. For a locally generated message, this is normally the user who sent the
40798 message. For a message received over TCP/IP via the daemon, it is
40799 normally the Exim user.
40801 The third line of the file contains the address of the message's sender as
40802 transmitted in the envelope, contained in angle brackets. The sender address is
40803 empty for bounce messages. For incoming SMTP mail, the sender address is given
40804 in the MAIL command. For locally generated mail, the sender address is
40805 created by Exim from the login name of the current user and the configured
40806 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
40807 leading &"From&~"& line if the caller is trusted, or if the supplied address is
40808 &"<>"& or an address that matches &%untrusted_set_senders%&.
40810 The fourth line contains two numbers. The first is the time that the message
40811 was received, in the conventional Unix form &-- the number of seconds since the
40812 start of the epoch. The second number is a count of the number of messages
40813 warning of delayed delivery that have been sent to the sender.
40815 There follow a number of lines starting with a hyphen. These can appear in any
40816 order, and are omitted when not relevant:
40819 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
40820 This item is obsolete, and is not generated from Exim release 4.61 onwards;
40821 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
40822 recognized, to provide backward compatibility. In the old format, a line of
40823 this form is present for every ACL variable that is not empty. The number
40824 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
40825 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
40826 the data string for the variable. The string itself starts at the beginning of
40827 the next line, and is followed by a newline character. It may contain internal
40830 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
40831 A line of this form is present for every ACL connection variable that is
40832 defined. Note that there is a space between &%-aclc%& and the rest of the name.
40833 The length is the length of the data string for the variable. The string itself
40834 starts at the beginning of the next line, and is followed by a newline
40835 character. It may contain internal newlines.
40837 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
40838 A line of this form is present for every ACL message variable that is defined.
40839 Note that there is a space between &%-aclm%& and the rest of the name. The
40840 length is the length of the data string for the variable. The string itself
40841 starts at the beginning of the next line, and is followed by a newline
40842 character. It may contain internal newlines.
40844 .vitem "&%-active_hostname%&&~<&'hostname'&>"
40845 This is present if, when the message was received over SMTP, the value of
40846 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
40848 .vitem &%-allow_unqualified_recipient%&
40849 This is present if unqualified recipient addresses are permitted in header
40850 lines (to stop such addresses from being qualified if rewriting occurs at
40851 transport time). Local messages that were input using &%-bnq%& and remote
40852 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
40854 .vitem &%-allow_unqualified_sender%&
40855 This is present if unqualified sender addresses are permitted in header lines
40856 (to stop such addresses from being qualified if rewriting occurs at transport
40857 time). Local messages that were input using &%-bnq%& and remote messages from
40858 hosts that match &%sender_unqualified_hosts%& set this flag.
40860 .vitem "&%-auth_id%&&~<&'text'&>"
40861 The id information for a message received on an authenticated SMTP connection
40862 &-- the value of the &$authenticated_id$& variable.
40864 .vitem "&%-auth_sender%&&~<&'address'&>"
40865 The address of an authenticated sender &-- the value of the
40866 &$authenticated_sender$& variable.
40868 .vitem "&%-body_linecount%&&~<&'number'&>"
40869 This records the number of lines in the body of the message, and is
40870 present unless &%-spool_file_wireformat%& is.
40872 .vitem "&%-body_zerocount%&&~<&'number'&>"
40873 This records the number of binary zero bytes in the body of the message, and is
40874 present if the number is greater than zero.
40876 .vitem &%-deliver_firsttime%&
40877 This is written when a new message is first added to the spool. When the spool
40878 file is updated after a deferral, it is omitted.
40880 .vitem "&%-frozen%&&~<&'time'&>"
40881 .cindex "frozen messages" "spool data"
40882 The message is frozen, and the freezing happened at <&'time'&>.
40884 .vitem "&%-helo_name%&&~<&'text'&>"
40885 This records the host name as specified by a remote host in a HELO or EHLO
40888 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
40889 This records the IP address of the host from which the message was received and
40890 the remote port number that was used. It is omitted for locally generated
40893 .vitem "&%-host_auth%&&~<&'text'&>"
40894 If the message was received on an authenticated SMTP connection, this records
40895 the name of the authenticator &-- the value of the
40896 &$sender_host_authenticated$& variable.
40898 .vitem &%-host_lookup_failed%&
40899 This is present if an attempt to look up the sending host's name from its IP
40900 address failed. It corresponds to the &$host_lookup_failed$& variable.
40902 .vitem "&%-host_name%&&~<&'text'&>"
40903 .cindex "reverse DNS lookup"
40904 .cindex "DNS" "reverse lookup"
40905 This records the name of the remote host from which the message was received,
40906 if the host name was looked up from the IP address when the message was being
40907 received. It is not present if no reverse lookup was done.
40909 .vitem "&%-ident%&&~<&'text'&>"
40910 For locally submitted messages, this records the login of the originating user,
40911 unless it was a trusted user and the &%-oMt%& option was used to specify an
40912 ident value. For messages received over TCP/IP, this records the ident string
40913 supplied by the remote host, if any.
40915 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
40916 This records the IP address of the local interface and the port number through
40917 which a message was received from a remote host. It is omitted for locally
40918 generated messages.
40921 The message is from a local sender.
40923 .vitem &%-localerror%&
40924 The message is a locally-generated bounce message.
40926 .vitem "&%-local_scan%&&~<&'string'&>"
40927 This records the data string that was returned by the &[local_scan()]& function
40928 when the message was received &-- the value of the &$local_scan_data$&
40929 variable. It is omitted if no data was returned.
40931 .vitem &%-manual_thaw%&
40932 The message was frozen but has been thawed manually, that is, by an explicit
40933 Exim command rather than via the auto-thaw process.
40936 A testing delivery process was started using the &%-N%& option to suppress any
40937 actual deliveries, but delivery was deferred. At any further delivery attempts,
40940 .vitem &%-received_protocol%&
40941 This records the value of the &$received_protocol$& variable, which contains
40942 the name of the protocol by which the message was received.
40944 .vitem &%-sender_set_untrusted%&
40945 The envelope sender of this message was set by an untrusted local caller (used
40946 to ensure that the caller is displayed in queue listings).
40948 .vitem "&%-spam_score_int%&&~<&'number'&>"
40949 If a message was scanned by SpamAssassin, this is present. It records the value
40950 of &$spam_score_int$&.
40952 .vitem &%-spool_file_wireformat%&
40953 The -D file for this message is in wire-format (for ESMTP CHUNKING)
40954 rather than Unix-format.
40955 The line-ending is CRLF rather than newline.
40956 There is still, however, no leading-dot-stuffing.
40958 .vitem &%-tls_certificate_verified%&
40959 A TLS certificate was received from the client that sent this message, and the
40960 certificate was verified by the server.
40962 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
40963 When the message was received over an encrypted connection, this records the
40964 name of the cipher suite that was used.
40966 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
40967 When the message was received over an encrypted connection, and a certificate
40968 was received from the client, this records the Distinguished Name from that
40972 Any of the above may have an extra hyphen prepended, to indicate the the
40973 corresponding data is untrusted.
40975 Following the options there is a list of those addresses to which the message
40976 is not to be delivered. This set of addresses is initialized from the command
40977 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
40978 is set; otherwise it starts out empty. Whenever a successful delivery is made,
40979 the address is added to this set. The addresses are kept internally as a
40980 balanced binary tree, and it is a representation of that tree which is written
40981 to the spool file. If an address is expanded via an alias or forward file, the
40982 original address is added to the tree when deliveries to all its child
40983 addresses are complete.
40985 If the tree is empty, there is a single line in the spool file containing just
40986 the text &"XX"&. Otherwise, each line consists of two letters, which are either
40987 Y or N, followed by an address. The address is the value for the node of the
40988 tree, and the letters indicate whether the node has a left branch and/or a
40989 right branch attached to it, respectively. If branches exist, they immediately
40990 follow. Here is an example of a three-node tree:
40992 YY darcy@austen.fict.example
40993 NN alice@wonderland.fict.example
40994 NN editor@thesaurus.ref.example
40996 After the non-recipients tree, there is a list of the message's recipients.
40997 This is a simple list, preceded by a count. It includes all the original
40998 recipients of the message, including those to whom the message has already been
40999 delivered. In the simplest case, the list contains one address per line. For
41003 editor@thesaurus.ref.example
41004 darcy@austen.fict.example
41006 alice@wonderland.fict.example
41008 However, when a child address has been added to the top-level addresses as a
41009 result of the use of the &%one_time%& option on a &(redirect)& router, each
41010 line is of the following form:
41012 <&'top-level address'&> <&'errors_to address'&> &&&
41013 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
41015 The 01 flag bit indicates the presence of the three other fields that follow
41016 the top-level address. Other bits may be used in future to support additional
41017 fields. The <&'parent number'&> is the offset in the recipients list of the
41018 original parent of the &"one time"& address. The first two fields are the
41019 envelope sender that is associated with this address and its length. If the
41020 length is zero, there is no special envelope sender (there are then two space
41021 characters in the line). A non-empty field can arise from a &(redirect)& router
41022 that has an &%errors_to%& setting.
41025 A blank line separates the envelope and status information from the headers
41026 which follow. A header may occupy several lines of the file, and to save effort
41027 when reading it in, each header is preceded by a number and an identifying
41028 character. The number is the number of characters in the header, including any
41029 embedded newlines and the terminating newline. The character is one of the
41033 .row <&'blank'&> "header in which Exim has no special interest"
41034 .row &`B`& "&'Bcc:'& header"
41035 .row &`C`& "&'Cc:'& header"
41036 .row &`F`& "&'From:'& header"
41037 .row &`I`& "&'Message-id:'& header"
41038 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
41039 .row &`R`& "&'Reply-To:'& header"
41040 .row &`S`& "&'Sender:'& header"
41041 .row &`T`& "&'To:'& header"
41042 .row &`*`& "replaced or deleted header"
41045 Deleted or replaced (rewritten) headers remain in the spool file for debugging
41046 purposes. They are not transmitted when the message is delivered. Here is a
41047 typical set of headers:
41049 111P Received: by hobbit.fict.example with local (Exim 4.00)
41050 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
41051 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
41052 038* X-rewrote-sender: bb@hobbit.fict.example
41053 042* From: Bilbo Baggins <bb@hobbit.fict.example>
41054 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
41055 099* To: alice@wonderland.fict.example, rdo@foundation,
41056 darcy@austen.fict.example, editor@thesaurus.ref.example
41057 104T To: alice@wonderland.fict.example, rdo@foundation.example,
41058 darcy@austen.fict.example, editor@thesaurus.ref.example
41059 038 Date: Fri, 11 May 2001 10:28:59 +0100
41061 The asterisked headers indicate that the envelope sender, &'From:'& header, and
41062 &'To:'& header have been rewritten, the last one because routing expanded the
41063 unqualified domain &'foundation'&.
41064 .ecindex IIDforspo1
41065 .ecindex IIDforspo2
41066 .ecindex IIDforspo3
41068 .section "Format of the -D file" "SECID282a"
41069 The data file is traditionally in Unix-standard format: lines are ended with
41070 an ASCII newline character.
41071 However, when the &%spool_wireformat%& main option is used some -D files
41072 can have an alternate format.
41073 This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
41074 The -D file lines (not including the first name-component line) are
41075 suitable for direct copying to the wire when transmitting using the
41076 ESMTP CHUNKING option, meaning lower processing overhead.
41077 Lines are terminated with an ASCII CRLF pair.
41078 There is no dot-stuffing (and no dot-termination).
41080 . ////////////////////////////////////////////////////////////////////////////
41081 . ////////////////////////////////////////////////////////////////////////////
41083 .chapter "DKIM, SPF, SRS and DMARC" "CHAPdkim" &&&
41084 "DKIM, SPF, SRS and DMARC Support"
41086 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
41089 DKIM is a mechanism by which messages sent by some entity can be provably
41090 linked to a domain which that entity controls. It permits reputation to
41091 be tracked on a per-domain basis, rather than merely upon source IP address.
41092 DKIM is documented in RFC 6376.
41094 As DKIM relies on the message being unchanged in transit, messages handled
41095 by a mailing-list (which traditionally adds to the message) will not match
41096 any original DKIM signature.
41098 DKIM support is compiled into Exim by default if TLS support is present.
41099 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
41101 Exim's DKIM implementation allows for
41103 Signing outgoing messages: This function is implemented in the SMTP transport.
41104 It can co-exist with all other Exim features
41105 (including transport filters)
41106 except cutthrough delivery.
41108 Verifying signatures in incoming messages: This is implemented by an additional
41109 ACL (acl_smtp_dkim), which can be called several times per message, with
41110 different signature contexts.
41113 In typical Exim style, the verification implementation does not include any
41114 default "policy". Instead it enables you to build your own policy using
41115 Exim's standard controls.
41117 Please note that verification of DKIM signatures in incoming mail is turned
41118 on by default for logging (in the <= line) purposes.
41120 Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
41121 When set, for each signature in incoming email,
41122 exim will log a line displaying the most important signature details, and the
41123 signature status. Here is an example (with line-breaks added for clarity):
41125 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
41126 d=facebookmail.com s=q1-2009b
41127 c=relaxed/relaxed a=rsa-sha1
41128 i=@facebookmail.com t=1252484542 [verification succeeded]
41131 You might want to turn off DKIM verification processing entirely for internal
41132 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
41133 control modifier. This should typically be done in the RCPT ACL, at points
41134 where you accept mail from relay sources (internal hosts or authenticated
41138 .section "Signing outgoing messages" "SECDKIMSIGN"
41139 .cindex "DKIM" "signing"
41141 For signing to be usable you must have published a DKIM record in DNS.
41142 Note that RFC 8301 (which does not cover EC keys) says:
41144 rsa-sha1 MUST NOT be used for signing or verifying.
41146 Signers MUST use RSA keys of at least 1024 bits for all keys.
41147 Signers SHOULD use RSA keys of at least 2048 bits.
41150 Note also that the key content (the 'p=' field)
41151 in the DNS record is different between RSA and EC keys;
41152 for the former it is the base64 of the ASN.1 for the RSA public key
41153 (equivalent to the private-key .pem with the header/trailer stripped)
41154 but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
41156 Signing is enabled by setting private options on the SMTP transport.
41157 These options take (expandable) strings as arguments.
41159 .option dkim_domain smtp "string list&!!" unset
41160 The domain(s) you want to sign with.
41161 After expansion, this can be a list.
41162 Each element in turn,
41164 is put into the &%$dkim_domain%& expansion variable
41165 while expanding the remaining signing options.
41166 If it is empty after expansion, DKIM signing is not done,
41167 and no error will result even if &%dkim_strict%& is set.
41169 .option dkim_selector smtp "string list&!!" unset
41170 This sets the key selector string.
41171 After expansion, which can use &$dkim_domain$&, this can be a list.
41172 Each element in turn is put in the expansion
41173 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
41174 option along with &%$dkim_domain%&.
41175 If the option is empty after expansion, DKIM signing is not done for this domain,
41176 and no error will result even if &%dkim_strict%& is set.
41179 To do, for example, dual-signing with RSA and EC keys
41180 this could be be used:
41182 dkim_selector = ec_sel : rsa_sel
41183 dkim_private_key = KEYS_DIR/$dkim_selector
41187 .option dkim_private_key smtp string&!! unset
41188 This sets the private key to use.
41189 You can use the &%$dkim_domain%& and
41190 &%$dkim_selector%& expansion variables to determine the private key to use.
41191 The result can either
41193 be a valid RSA private key in ASCII armor (.pem file), including line breaks
41195 with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41196 be a valid Ed25519 private key (same format as above)
41198 start with a slash, in which case it is treated as a file that contains
41201 be "0", "false" or the empty string, in which case the message will not
41202 be signed. This case will not result in an error, even if &%dkim_strict%&
41206 To generate keys under OpenSSL:
41208 openssl genrsa -out dkim_rsa.private 2048
41209 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
41211 The result file from the first command should be retained, and
41212 this option set to use it.
41213 Take the base-64 lines from the output of the second command, concatenated,
41214 for the DNS TXT record.
41215 See section 3.6 of RFC6376 for the record specification.
41219 certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
41220 certtool --load-privkey=dkim_rsa.private --pubkey-info
41223 Note that RFC 8301 says:
41225 Signers MUST use RSA keys of at least 1024 bits for all keys.
41226 Signers SHOULD use RSA keys of at least 2048 bits.
41229 EC keys for DKIM are defined by RFC 8463.
41230 They are considerably smaller than RSA keys for equivalent protection.
41231 As they are a recent development, users should consider dual-signing
41232 (by setting a list of selectors, and an expansion for this option)
41233 for some transition period.
41234 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41237 OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
41239 openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
41240 certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
41243 To produce the required public key value for a DNS record:
41245 openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
41246 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
41249 Exim also supports an alternate format
41250 of Ed25519 keys in DNS which was a candidate during development
41251 of the standard, but not adopted.
41252 A future release will probably drop that support.
41254 .option dkim_hash smtp string&!! sha256
41255 Can be set to any one of the supported hash methods, which are:
41257 &`sha1`& &-- should not be used, is old and insecure
41259 &`sha256`& &-- the default
41261 &`sha512`& &-- possibly more secure but less well supported
41264 Note that RFC 8301 says:
41266 rsa-sha1 MUST NOT be used for signing or verifying.
41269 .option dkim_identity smtp string&!! unset
41270 If set after expansion, the value is used to set an "i=" tag in
41271 the signing header. The DKIM standards restrict the permissible
41272 syntax of this optional tag to a mail address, with possibly-empty
41273 local part, an @, and a domain identical to or subdomain of the "d="
41274 tag value. Note that Exim does not check the value.
41276 .option dkim_canon smtp string&!! unset
41277 This option sets the canonicalization method used when signing a message.
41278 The DKIM RFC currently supports two methods: "simple" and "relaxed".
41279 The option defaults to "relaxed" when unset. Note: the current implementation
41280 only supports signing with the same canonicalization method for both headers and body.
41282 .option dkim_strict smtp string&!! unset
41283 This option defines how Exim behaves when signing a message that
41284 should be signed fails for some reason. When the expansion evaluates to
41285 either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message
41286 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
41289 .option dkim_sign_headers smtp string&!! "see below"
41290 If set, this option must expand to a colon-separated
41291 list of header names.
41292 Headers with these names, or the absence or such a header, will be included
41293 in the message signature.
41294 When unspecified, the header names listed in RFC4871 will be used,
41295 whether or not each header is present in the message.
41296 The default list is available for the expansion in the macro
41297 &"_DKIM_SIGN_HEADERS"&
41298 and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
41300 If a name is repeated, multiple headers by that name (or the absence thereof)
41301 will be signed. The textually later headers in the headers part of the
41302 message are signed first, if there are multiples.
41304 A name can be prefixed with either an &"="& or a &"+"& character.
41305 If an &"="& prefix is used, all headers that are present with this name
41307 If a &"+"& prefix if used, all headers that are present with this name
41308 will be signed, and one signature added for a missing header with the
41309 name will be appended.
41311 .option dkim_timestamps smtp integer&!! unset
41312 This option controls the inclusion of timestamp information in the signature.
41313 If not set, no such information will be included.
41314 Otherwise, must be an unsigned number giving an offset in seconds from the current time
41316 (eg. 1209600 for two weeks);
41317 both creation (t=) and expiry (x=) tags will be included.
41319 RFC 6376 lists these tags as RECOMMENDED.
41322 .section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
41323 .cindex "DKIM" "verification"
41325 Verification of DKIM signatures in SMTP incoming email is done for all
41326 messages for which an ACL control &%dkim_disable_verify%& has not been set.
41327 .cindex DKIM "selecting signature algorithms"
41328 Individual classes of signature algorithm can be ignored by changing
41329 the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
41330 The &%dkim_verify_minimal%& option can be set to cease verification
41331 processing for a message once the first passing signature is found.
41333 .cindex authentication "expansion item"
41334 Performing verification sets up information used by the
41335 &%authresults%& expansion item.
41337 For most purposes the default option settings suffice and the remainder
41338 of this section can be ignored.
41340 The results of verification are made available to the
41341 &%acl_smtp_dkim%& ACL, which can examine and modify them.
41342 A missing ACL definition defaults to accept.
41343 By default, the ACL is called once for each
41344 syntactically(!) correct signature in the incoming message.
41345 If any ACL call does not accept, the message is not accepted.
41346 If a cutthrough delivery was in progress for the message, that is
41347 summarily dropped (having wasted the transmission effort).
41349 To evaluate the verification result in the ACL
41350 a large number of expansion variables
41351 containing the signature status and its details are set up during the
41352 runtime of the ACL.
41354 Calling the ACL only for existing signatures is not sufficient to build
41355 more advanced policies. For that reason, the main option
41356 &%dkim_verify_signers%&, and an expansion variable
41357 &%$dkim_signers%& exist.
41359 The main option &%dkim_verify_signers%& can be set to a colon-separated
41360 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
41361 called. It is expanded when the message has been received. At this point,
41362 the expansion variable &%$dkim_signers%& already contains a colon-separated
41363 list of signer domains and identities for the message. When
41364 &%dkim_verify_signers%& is not specified in the main configuration,
41367 dkim_verify_signers = $dkim_signers
41369 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
41370 DKIM signature in the message. Current DKIM verifiers may want to explicitly
41371 call the ACL for known domains or identities. This would be achieved as follows:
41373 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
41375 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
41376 and "ebay.com", plus all domains and identities that have signatures in the message.
41377 You can also be more creative in constructing your policy. For example:
41379 dkim_verify_signers = $sender_address_domain:$dkim_signers
41382 If a domain or identity is listed several times in the (expanded) value of
41383 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
41385 Note that if the option is set using untrustworthy data
41386 (such as the From: header)
41387 care should be taken to force lowercase for domains
41388 and for the domain part if identities.
41389 The default setting can be regarded as trustworthy in this respect.
41391 If multiple signatures match a domain (or identity), the ACL is called once
41392 for each matching signature.
41395 Inside the DKIM ACL, the following expansion variables are
41396 available (from most to least important):
41400 .vitem &%$dkim_cur_signer%&
41401 The signer that is being evaluated in this ACL run. This can be a domain or
41402 an identity. This is one of the list items from the expanded main option
41403 &%dkim_verify_signers%& (see above).
41405 .vitem &%$dkim_verify_status%&
41406 Within the DKIM ACL,
41407 a string describing the general status of the signature. One of
41409 &%none%&: There is no signature in the message for the current domain or
41410 identity (as reflected by &%$dkim_cur_signer%&).
41412 &%invalid%&: The signature could not be verified due to a processing error.
41413 More detail is available in &%$dkim_verify_reason%&.
41415 &%fail%&: Verification of the signature failed. More detail is
41416 available in &%$dkim_verify_reason%&.
41418 &%pass%&: The signature passed verification. It is valid.
41421 This variable can be overwritten using an ACL 'set' modifier.
41422 This might, for instance, be done to enforce a policy restriction on
41423 hash-method or key-size:
41425 warn condition = ${if eq {$dkim_verify_status}{pass}}
41426 condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
41427 condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
41428 {< {$dkim_key_length}{1024}}}}
41429 logwrite = NOTE: forcing DKIM verify fail (was pass)
41430 set dkim_verify_status = fail
41431 set dkim_verify_reason = hash too weak or key too short
41434 So long as a DKIM ACL is defined (it need do no more than accept),
41435 after all the DKIM ACL runs have completed, the value becomes a
41436 colon-separated list of the values after each run.
41437 This is maintained for the mime, prdr and data ACLs.
41439 .vitem &%$dkim_verify_reason%&
41440 A string giving a little bit more detail when &%$dkim_verify_status%& is either
41441 "fail" or "invalid". One of
41443 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
41444 key for the domain could not be retrieved. This may be a temporary problem.
41446 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
41447 record for the domain is syntactically invalid.
41449 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
41450 body hash does not match the one specified in the signature header. This
41451 means that the message body was modified in transit.
41453 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
41454 could not be verified. This may mean that headers were modified,
41455 re-written or otherwise changed in a way which is incompatible with
41456 DKIM verification. It may of course also mean that the signature is forged.
41459 This variable can be overwritten, with any value, using an ACL 'set' modifier.
41461 .vitem &%$dkim_domain%&
41462 The signing domain. IMPORTANT: This variable is only populated if there is
41463 an actual signature in the message for the current domain or identity (as
41464 reflected by &%$dkim_cur_signer%&).
41466 .vitem &%$dkim_identity%&
41467 The signing identity, if present. IMPORTANT: This variable is only populated
41468 if there is an actual signature in the message for the current domain or
41469 identity (as reflected by &%$dkim_cur_signer%&).
41471 .vitem &%$dkim_selector%&
41472 The key record selector string.
41474 .vitem &%$dkim_algo%&
41475 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
41476 If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41477 may also be 'ed25519-sha256'.
41478 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41481 Note that RFC 8301 says:
41483 rsa-sha1 MUST NOT be used for signing or verifying.
41485 DKIM signatures identified as having been signed with historic
41486 algorithms (currently, rsa-sha1) have permanently failed evaluation
41489 To enforce this you must either have a DKIM ACL which checks this variable
41490 and overwrites the &$dkim_verify_status$& variable as discussed above,
41491 or have set the main option &%dkim_verify_hashes%& to exclude
41492 processing of such signatures.
41494 .vitem &%$dkim_canon_body%&
41495 The body canonicalization method. One of 'relaxed' or 'simple'.
41497 .vitem &%$dkim_canon_headers%&
41498 The header canonicalization method. One of 'relaxed' or 'simple'.
41500 .vitem &%$dkim_copiedheaders%&
41501 A transcript of headers and their values which are included in the signature
41502 (copied from the 'z=' tag of the signature).
41503 Note that RFC6376 requires that verification fail if the From: header is
41504 not included in the signature. Exim does not enforce this; sites wishing
41505 strict enforcement should code the check explicitly.
41507 .vitem &%$dkim_bodylength%&
41508 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
41509 limit was set by the signer, "9999999999999" is returned. This makes sure
41510 that this variable always expands to an integer value.
41511 &*Note:*& The presence of the signature tag specifying a signing body length
41512 is one possible route to spoofing of valid DKIM signatures.
41513 A paranoid implementation might wish to regard signature where this variable
41514 shows less than the "no limit" return as being invalid.
41516 .vitem &%$dkim_created%&
41517 UNIX timestamp reflecting the date and time when the signature was created.
41518 When this was not specified by the signer, "0" is returned.
41520 .vitem &%$dkim_expires%&
41521 UNIX timestamp reflecting the date and time when the signer wants the
41522 signature to be treated as "expired". When this was not specified by the
41523 signer, "9999999999999" is returned. This makes it possible to do useful
41524 integer size comparisons against this value.
41525 Note that Exim does not check this value.
41527 .vitem &%$dkim_headernames%&
41528 A colon-separated list of names of headers included in the signature.
41530 .vitem &%$dkim_key_testing%&
41531 "1" if the key record has the "testing" flag set, "0" if not.
41533 .vitem &%$dkim_key_nosubdomains%&
41534 "1" if the key record forbids subdomaining, "0" otherwise.
41536 .vitem &%$dkim_key_srvtype%&
41537 Service type (tag s=) from the key record. Defaults to "*" if not specified
41540 .vitem &%$dkim_key_granularity%&
41541 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
41544 .vitem &%$dkim_key_notes%&
41545 Notes from the key record (tag n=).
41547 .vitem &%$dkim_key_length%&
41548 Number of bits in the key.
41549 Valid only once the key is loaded, which is at the time the header signature
41550 is verified, which is after the body hash is.
41552 Note that RFC 8301 says:
41554 Verifiers MUST NOT consider signatures using RSA keys of
41555 less than 1024 bits as valid signatures.
41558 This is enforced by the default setting for the &%dkim_verify_min_keysizes%&
41563 In addition, two ACL conditions are provided:
41566 .vitem &%dkim_signers%&
41567 ACL condition that checks a colon-separated list of domains or identities
41568 for a match against the domain or identity that the ACL is currently verifying
41569 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
41570 verb to a group of domains or identities. For example:
41573 # Warn when Mail purportedly from GMail has no gmail signature
41574 warn sender_domains = gmail.com
41575 dkim_signers = gmail.com
41577 log_message = GMail sender without gmail.com DKIM signature
41580 Note that the above does not check for a total lack of DKIM signing;
41581 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
41583 .vitem &%dkim_status%&
41584 ACL condition that checks a colon-separated list of possible DKIM verification
41585 results against the actual result of verification. This is typically used
41586 to restrict an ACL verb to a list of verification outcomes, for example:
41589 deny sender_domains = paypal.com:paypal.de
41590 dkim_signers = paypal.com:paypal.de
41591 dkim_status = none:invalid:fail
41592 message = Mail from Paypal with invalid/missing signature
41595 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
41596 see the documentation of the &%$dkim_verify_status%& expansion variable above
41597 for more information of what they mean.
41603 .section "SPF (Sender Policy Framework)" SECSPF
41604 .cindex SPF verification
41606 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
41607 messages with its domain in the envelope from, documented by RFC 7208.
41608 For more information on SPF see &url(http://www.open-spf.org), a static copy of
41609 the &url(http://openspf.org).
41610 . --- 2019-10-28: still not https, open-spf.org is told to be a
41611 . --- web-archive copy of the now dead openspf.org site
41612 . --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a
41615 Messages sent by a system not authorised will fail checking of such assertions.
41616 This includes retransmissions done by traditional forwarders.
41618 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
41619 &_Local/Makefile_&. The support uses the &_libspf2_& library
41620 &url(https://www.libspf2.org/).
41621 There is no Exim involvement in the transmission of messages;
41622 publishing certain DNS records is all that is required.
41624 For verification, an ACL condition and an expansion lookup are provided.
41625 .cindex authentication "expansion item"
41626 Performing verification sets up information used by the
41627 &%authresults%& expansion item.
41630 .cindex SPF "ACL condition"
41631 .cindex ACL "spf condition"
41632 The ACL condition "spf" can be used at or after the MAIL ACL.
41633 It takes as an argument a list of strings giving the outcome of the SPF check,
41634 and will succeed for any matching outcome.
41638 The SPF check passed, the sending host is positively verified by SPF.
41641 The SPF check failed, the sending host is NOT allowed to send mail for the
41642 domain in the envelope-from address.
41644 .vitem &%softfail%&
41645 The SPF check failed, but the queried domain can't absolutely confirm that this
41649 The queried domain does not publish SPF records.
41652 The SPF check returned a "neutral" state. This means the queried domain has
41653 published a SPF record, but wants to allow outside servers to send mail under
41654 its domain as well. This should be treated like "none".
41656 .vitem &%permerror%&
41657 This indicates a syntax error in the SPF record of the queried domain.
41658 You may deny messages when this occurs.
41660 .vitem &%temperror%&
41661 This indicates a temporary error during all processing, including Exim's
41662 SPF processing. You may defer messages when this occurs.
41665 You can prefix each string with an exclamation mark to invert
41666 its meaning, for example "!fail" will match all results but
41667 "fail". The string list is evaluated left-to-right, in a
41668 short-circuit fashion.
41673 message = $sender_host_address is not allowed to send mail from \
41674 ${if def:sender_address_domain \
41675 {$sender_address_domain}{$sender_helo_name}}. \
41676 Please see http://www.open-spf.org/Why;\
41677 identity=${if def:sender_address_domain \
41678 {$sender_address}{$sender_helo_name}};\
41679 ip=$sender_host_address
41682 Note: The above mentioned URL may not be as helpful as expected. You are
41683 encouraged to replace the link with a link to a site with more
41686 When the spf condition has run, it sets up several expansion
41689 .cindex SPF "verification variables"
41691 .vitem &$spf_header_comment$&
41692 .vindex &$spf_header_comment$&
41693 This contains a human-readable string describing the outcome
41694 of the SPF check. You can add it to a custom header or use
41695 it for logging purposes.
41697 .vitem &$spf_received$&
41698 .vindex &$spf_received$&
41699 This contains a complete Received-SPF: header that can be
41700 added to the message. Please note that according to the SPF
41701 draft, this header must be added at the top of the header
41702 list. Please see section 10 on how you can do this.
41704 Note: in case of "Best-guess" (see below), the convention is
41705 to put this string in a header called X-SPF-Guess: instead.
41707 .vitem &$spf_result$&
41708 .vindex &$spf_result$&
41709 This contains the outcome of the SPF check in string form,
41710 one of pass, fail, softfail, none, neutral, permerror or
41713 .vitem &$spf_result_guessed$&
41714 .vindex &$spf_result_guessed$&
41715 This boolean is true only if a best-guess operation was used
41716 and required in order to obtain a result.
41718 .vitem &$spf_smtp_comment$&
41719 .vindex &$spf_smtp_comment$&
41720 .vindex &%spf_smtp_comment_template%&
41721 This contains a string that can be used in a SMTP response
41722 to the calling party. Useful for "fail".
41723 The string is generated by the SPF library from the template configured in the main config
41724 option &%spf_smtp_comment_template%&.
41728 .cindex SPF "ACL condition"
41729 .cindex ACL "spf_guess condition"
41730 .cindex SPF "best guess"
41731 In addition to SPF, you can also perform checks for so-called
41732 "Best-guess". Strictly speaking, "Best-guess" is not standard
41733 SPF, but it is supported by the same framework that enables SPF
41735 Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record)
41736 for a description of what it means.
41737 . --- 2019-10-28: still not https:
41739 To access this feature, simply use the spf_guess condition in place
41740 of the spf one. For example:
41743 deny spf_guess = fail
41744 message = $sender_host_address doesn't look trustworthy to me
41747 In case you decide to reject messages based on this check, you
41748 should note that although it uses the same framework, "Best-guess"
41749 is not SPF, and therefore you should not mention SPF at all in your
41752 When the spf_guess condition has run, it sets up the same expansion
41753 variables as when spf condition is run, described above.
41755 Additionally, since Best-guess is not standardized, you may redefine
41756 what "Best-guess" means to you by redefining the main configuration
41757 &%spf_guess%& option.
41758 For example, the following:
41761 spf_guess = v=spf1 a/16 mx/16 ptr ?all
41764 would relax host matching rules to a broader network range.
41767 .cindex SPF "lookup expansion"
41769 A lookup expansion is also available. It takes an email
41770 address as the key and an IP address
41775 ${lookup {username@domain} spf {ip.ip.ip.ip}}
41778 The lookup will return the same result strings as can appear in
41779 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
41785 .section "SRS (Sender Rewriting Scheme)" SECTSRS
41786 .cindex SRS "sender rewriting scheme"
41789 SRS can be used to modify sender addresses when forwarding so that
41790 SPF verification does not object to them.
41791 It operates by encoding the original envelope sender in a new
41792 sender local part and using a domain run by the forwarding site
41793 as the new domain for the sender. Any DSN message should be returned
41794 to this new sender at the forwarding site, which can extract the
41795 original sender from the coded local part and forward the DSN to
41798 This is a way of avoiding the breakage that SPF does to forwarding.
41799 The constructed local-part will be longer than the original,
41800 leading to possible problems with very long addresses.
41801 The changing of the sender address also hinders the tracing of mail
41804 Exim can be built to include native SRS support. To do this
41805 SUPPORT_SRS=yes must be defined in &_Local/Makefile_&.
41806 If this has been done, the macros _HAVE_SRS and _HAVE_NATIVE_SRS
41808 The support is limited to SRS0-encoding; SRS1 is not supported.
41810 .cindex SRS excoding
41811 To encode an address use this expansion item:
41813 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
41814 .cindex "&%srs_encode%& expansion item"
41815 .cindex SRS "expansion item"
41816 The first argument should be a secret known and used by all systems
41817 handling the recipient domain for the original message.
41818 There is no need to periodically change this key; a timestamp is also
41820 The second argument should be given as the envelope sender address before this
41821 encoding operation.
41822 The third argument should be the recipient domain of the message when
41823 it arrived at this system.
41826 .cindex SRS decoding
41827 To decode an address use this expansion condition:
41829 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
41830 The first argument should be the recipient local prt as is was received.
41831 The second argument is the site secret.
41833 If the messages is not for an SRS-encoded recipient the condition will
41834 return false. If it is, the condition will return true and the variable
41835 &$srs_recipient$& will be set to the decoded (original) value.
41841 SRS_SECRET = <pick something unique for your site for this. Use on all MXs.>
41847 # if outbound, and forwarding has been done, use an alternate transport
41848 domains = ! +my_domains
41849 transport = ${if eq {$local_part@$domain} \
41850 {$original_local_part@$original_domain} \
41851 {remote_smtp} {remote_forwarded_smtp}}
41856 domains = +my_domains
41857 # detect inbound bounces which are SRS'd, and decode them
41858 condition = ${if inbound_srs {$local_part} {SRS_SECRET}}
41859 data = $srs_recipient
41861 inbound_srs_failure:
41864 domains = +my_domains
41865 # detect inbound bounces which look SRS'd but are invalid
41866 condition = ${if inbound_srs {$local_part} {}}
41868 data = :fail: Invalid SRS recipient address
41870 #... further routers here
41873 # transport; should look like the non-forward outbound
41874 # one, plus the max_rcpt and return_path options
41875 remote_forwarded_smtp:
41877 # modify the envelope from, for mails that we forward
41879 return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}}
41887 .section DMARC SECDMARC
41888 .cindex DMARC verification
41890 DMARC combines feedback from SPF, DKIM, and header From: in order
41891 to attempt to provide better indicators of the authenticity of an
41892 email. This document does not explain the fundamentals; you
41893 should read and understand how it works by visiting the website at
41894 &url(http://www.dmarc.org/).
41896 If Exim is built with DMARC support,
41897 the libopendmarc library is used.
41899 For building Exim yourself, obtain the library from
41900 &url(http://sourceforge.net/projects/opendmarc/)
41901 to obtain a copy, or find it in your favorite package
41902 repository. You will need to attend to the local/Makefile feature
41903 SUPPORT_DMARC and the associated LDFLAGS addition.
41904 This description assumes
41905 that headers will be in /usr/local/include, and that the libraries
41906 are in /usr/local/lib.
41910 There are three main-configuration options:
41911 .cindex DMARC "configuration options"
41913 The &%dmarc_tld_file%& option
41914 .oindex &%dmarc_tld_file%&
41915 defines the location of a text file of valid
41916 top level domains the opendmarc library uses
41917 during domain parsing. Maintained by Mozilla,
41918 the most current version can be downloaded
41919 from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat).
41920 See also the util/renew-opendmarc-tlds.sh script.
41921 The default for the option is unset.
41922 If not set, DMARC processing is disabled.
41925 The &%dmarc_history_file%& option, if set
41926 .oindex &%dmarc_history_file%&
41927 defines the location of a file to log results
41928 of dmarc verification on inbound emails. The
41929 contents are importable by the opendmarc tools
41930 which will manage the data, send out DMARC
41931 reports, and expire the data. Make sure the
41932 directory of this file is writable by the user
41934 The default is unset.
41936 The &%dmarc_forensic_sender%& option
41937 .oindex &%dmarc_forensic_sender%&
41938 defines an alternate email address to use when sending a
41939 forensic report detailing alignment failures
41940 if a sender domain's dmarc record specifies it
41941 and you have configured Exim to send them.
41942 If set, this is expanded and used for the
41943 From: header line; the address is extracted
41944 from it and used for the envelope from.
41945 If not set (the default), the From: header is expanded from
41946 the dsn_from option, and <> is used for the
41949 . I wish we had subsections...
41951 .cindex DMARC controls
41952 By default, the DMARC processing will run for any remote,
41953 non-authenticated user. It makes sense to only verify DMARC
41954 status of messages coming from remote, untrusted sources. You can
41955 use standard conditions such as hosts, senders, etc, to decide that
41956 DMARC verification should *not* be performed for them and disable
41957 DMARC with an ACL control modifier:
41959 control = dmarc_disable_verify
41961 A DMARC record can also specify a "forensic address", which gives
41962 exim an email address to submit reports about failed alignment.
41963 Exim does not do this by default because in certain conditions it
41964 results in unintended information leakage (what lists a user might
41965 be subscribed to, etc). You must configure exim to submit forensic
41966 reports to the owner of the domain. If the DMARC record contains a
41967 forensic address and you specify the control statement below, then
41968 exim will send these forensic emails. It is also advised that you
41969 configure a &%dmarc_forensic_sender%& because the default sender address
41970 construction might be inadequate.
41972 control = dmarc_enable_forensic
41974 (AGAIN: You can choose not to send these forensic reports by simply
41975 not putting the dmarc_enable_forensic control line at any point in
41976 your exim config. If you don't tell exim to send them, it will not
41979 There are no options to either control. Both must appear before
41984 DMARC checks cam be run on incoming SMTP messages by using the
41985 &"dmarc_status"& ACL condition in the DATA ACL. You are required to
41986 call the &"spf"& condition first in the ACLs, then the &"dmarc_status"&
41987 condition. Putting this condition in the ACLs is required in order
41988 for a DMARC check to actually occur. All of the variables are set
41989 up before the DATA ACL, but there is no actual DMARC check that
41990 occurs until a &"dmarc_status"& condition is encountered in the ACLs.
41992 The &"dmarc_status"& condition takes a list of strings on its
41993 right-hand side. These strings describe recommended action based
41994 on the DMARC check. To understand what the policy recommendations
41995 mean, refer to the DMARC website above. Valid strings are:
41997 &'accept '& The DMARC check passed and the library recommends accepting the email.
41998 &'reject '& The DMARC check failed and the library recommends rejecting the email.
41999 &'quarantine '& The DMARC check failed and the library recommends keeping it for further inspection.
42000 &'none '& The DMARC check passed and the library recommends no specific action, neutral.
42001 &'norecord '& No policy section in the DMARC record for this RFC5322.From field
42002 &'nofrom '& Unable to determine the domain of the sender.
42003 &'temperror '& Library error or dns error.
42004 &'off '& The DMARC check was disabled for this email.
42006 You can prefix each string with an exclamation mark to invert its
42007 meaning, for example "!accept" will match all results but
42008 "accept". The string list is evaluated left-to-right in a
42009 short-circuit fashion. When a string matches the outcome of the
42010 DMARC check, the condition succeeds. If none of the listed
42011 strings matches the outcome of the DMARC check, the condition
42014 Of course, you can also use any other lookup method that Exim
42015 supports, including LDAP, Postgres, MySQL, etc, as long as the
42016 result is a list of colon-separated strings.
42018 Performing the check sets up information used by the
42019 &%authresults%& expansion item.
42021 Several expansion variables are set before the DATA ACL is
42022 processed, and you can use them in this ACL. The following
42023 expansion variables are available:
42026 .vitem &$dmarc_status$&
42027 .vindex &$dmarc_status$&
42028 .cindex DMARC result
42029 A one word status indicating what the DMARC library
42030 thinks of the email. It is a combination of the results of
42031 DMARC record lookup and the SPF/DKIM/DMARC processing results
42032 (if a DMARC record was found). The actual policy declared
42033 in the DMARC record is in a separate expansion variable.
42035 .vitem &$dmarc_status_text$&
42036 .vindex &$dmarc_status_text$&
42037 Slightly longer, human readable status.
42039 .vitem &$dmarc_used_domain$&
42040 .vindex &$dmarc_used_domain$&
42041 The domain which DMARC used to look up the DMARC policy record.
42043 .vitem &$dmarc_domain_policy$&
42044 .vindex &$dmarc_domain_policy$&
42045 The policy declared in the DMARC record. Valid values
42046 are "none", "reject" and "quarantine". It is blank when there
42047 is any error, including no DMARC record.
42052 By default, Exim's DMARC configuration is intended to be
42053 non-intrusive and conservative. To facilitate this, Exim will not
42054 create any type of logging files without explicit configuration by
42055 you, the admin. Nor will Exim send out any emails/reports about
42056 DMARC issues without explicit configuration by you, the admin (other
42057 than typical bounce messages that may come about due to ACL
42058 processing or failure delivery issues).
42060 In order to log statistics suitable to be imported by the opendmarc
42061 tools, you need to:
42063 Configure the global option &%dmarc_history_file%&
42065 Configure cron jobs to call the appropriate opendmarc history
42066 import scripts and truncating the dmarc_history_file
42069 In order to send forensic reports, you need to:
42071 Configure the global option &%dmarc_forensic_sender%&
42073 Configure, somewhere before the DATA ACL, the control option to
42074 enable sending DMARC forensic reports
42082 warn domains = +local_domains
42083 hosts = +local_hosts
42084 control = dmarc_disable_verify
42086 warn !domains = +screwed_up_dmarc_records
42087 control = dmarc_enable_forensic
42089 warn condition = (lookup if destined to mailing list)
42090 set acl_m_mailing_list = 1
42093 warn dmarc_status = accept : none : off
42095 log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
42097 warn dmarc_status = !accept
42099 log_message = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
42101 warn dmarc_status = quarantine
42103 set $acl_m_quarantine = 1
42104 # Do something in a transport with this flag variable
42106 deny condition = ${if eq{$dmarc_domain_policy}{reject}}
42107 condition = ${if eq{$acl_m_mailing_list}{1}}
42108 message = Messages from $dmarc_used_domain break mailing lists
42110 deny dmarc_status = reject
42112 message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
42114 warn add_header = :at_start:${authresults {$primary_hostname}}
42121 . ////////////////////////////////////////////////////////////////////////////
42122 . ////////////////////////////////////////////////////////////////////////////
42124 .chapter "Proxies" "CHAPproxies" &&&
42126 .cindex "proxy support"
42127 .cindex "proxy" "access via"
42129 A proxy is an intermediate system through which communication is passed.
42130 Proxies may provide a security, availability or load-distribution function.
42133 .section "Inbound proxies" SECTproxyInbound
42134 .cindex proxy inbound
42135 .cindex proxy "server side"
42136 .cindex proxy "Proxy protocol"
42137 .cindex "Proxy protocol" proxy
42139 Exim has support for receiving inbound SMTP connections via a proxy
42140 that uses &"Proxy Protocol"& to speak to it.
42141 To include this support, include &"SUPPORT_PROXY=yes"&
42144 It was built on the HAProxy specification, found at
42145 &url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt).
42147 The purpose of this facility is so that an application load balancer,
42148 such as HAProxy, can sit in front of several Exim servers
42149 to distribute load.
42150 Exim uses the local protocol communication with the proxy to obtain
42151 the remote SMTP system IP address and port information.
42152 There is no logging if a host passes or
42153 fails Proxy Protocol negotiation, but it can easily be determined and
42154 recorded in an ACL (example is below).
42156 Use of a proxy is enabled by setting the &%hosts_proxy%&
42157 main configuration option to a hostlist; connections from these
42158 hosts will use Proxy Protocol.
42159 Exim supports both version 1 and version 2 of the Proxy Protocol and
42160 automatically determines which version is in use.
42162 The Proxy Protocol header is the first data received on a TCP connection
42163 and is inserted before any TLS-on-connect handshake from the client; Exim
42164 negotiates TLS between Exim-as-server and the remote client, not between
42165 Exim and the proxy server. The Proxy Protocol header must be received
42166 within &%proxy_protocol_timeout%&, which defaults to 3s.
42168 The following expansion variables are usable
42169 (&"internal"& and &"external"& here refer to the interfaces
42172 &'proxy_external_address '& IP of host being proxied or IP of remote interface of proxy
42173 &'proxy_external_port '& Port of host being proxied or Port on remote interface of proxy
42174 &'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
42175 &'proxy_local_port '& Port of proxy server inbound or Port on local interface of proxy
42176 &'proxy_session '& boolean: SMTP connection via proxy
42178 If &$proxy_session$& is set but &$proxy_external_address$& is empty
42179 there was a protocol error.
42180 The variables &$sender_host_address$& and &$sender_host_port$&
42181 will have values for the actual client system, not the proxy.
42183 Since the real connections are all coming from the proxy, and the
42184 per host connection tracking is done before Proxy Protocol is
42185 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
42186 handle all of the parallel volume you expect per inbound proxy.
42187 With the option set so high, you lose the ability
42188 to protect your server from many connections from one IP.
42189 In order to prevent your server from overload, you
42190 need to add a per connection ratelimit to your connect ACL.
42191 A possible solution is:
42193 # Set max number of connections per host
42195 # Or do some kind of IP lookup in a flat file or database
42196 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
42198 defer ratelimit = LIMIT / 5s / per_conn / strict
42199 message = Too many connections from this IP right now
42204 .section "Outbound proxies" SECTproxySOCKS
42205 .cindex proxy outbound
42206 .cindex proxy "client side"
42207 .cindex proxy SOCKS
42208 .cindex SOCKS proxy
42209 Exim has support for sending outbound SMTP via a proxy
42210 using a protocol called SOCKS5 (defined by RFC1928).
42211 The support can be optionally included by defining SUPPORT_SOCKS=yes in
42214 Use of a proxy is enabled by setting the &%socks_proxy%& option
42215 on an smtp transport.
42216 The option value is expanded and should then be a list
42217 (colon-separated by default) of proxy specifiers.
42218 Each proxy specifier is a list
42219 (space-separated by default) where the initial element
42220 is an IP address and any subsequent elements are options.
42222 Options are a string <name>=<value>.
42223 The list of options is in the following table:
42225 &'auth '& authentication method
42226 &'name '& authentication username
42227 &'pass '& authentication password
42229 &'tmo '& connection timeout
42231 &'weight '& selection bias
42234 More details on each of these options follows:
42237 .cindex authentication "to proxy"
42238 .cindex proxy authentication
42239 &%auth%&: Either &"none"& (default) or &"name"&.
42240 Using &"name"& selects username/password authentication per RFC 1929
42241 for access to the proxy.
42242 Default is &"none"&.
42244 &%name%&: sets the username for the &"name"& authentication method.
42247 &%pass%&: sets the password for the &"name"& authentication method.
42250 &%port%&: the TCP port number to use for the connection to the proxy.
42253 &%tmo%&: sets a connection timeout in seconds for this proxy.
42256 &%pri%&: specifies a priority for the proxy within the list,
42257 higher values being tried first.
42258 The default priority is 1.
42260 &%weight%&: specifies a selection bias.
42261 Within a priority set servers are queried in a random fashion,
42262 weighted by this value.
42263 The default value for selection bias is 1.
42266 Proxies from the list are tried according to their priority
42267 and weight settings until one responds. The timeout for the
42268 overall connection applies to the set of proxied attempts.
42270 .section Logging SECTproxyLog
42271 To log the (local) IP of a proxy in the incoming or delivery logline,
42272 add &"+proxy"& to the &%log_selector%& option.
42273 This will add a component tagged with &"PRX="& to the line.
42275 . ////////////////////////////////////////////////////////////////////////////
42276 . ////////////////////////////////////////////////////////////////////////////
42278 .chapter "Internationalisation" "CHAPi18n" &&&
42279 "Internationalisation""
42280 .cindex internationalisation "email address"
42283 .cindex utf8 "mail name handling"
42285 Exim has support for Internationalised mail names.
42286 To include this it must be built with SUPPORT_I18N and the libidn library.
42287 Standards supported are RFCs 2060, 5890, 6530 and 6533.
42289 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
42290 instead of it) then IDNA2008 is supported; this adds an extra library
42291 requirement, upon libidn2.
42293 .section "MTA operations" SECTi18nMTA
42294 .cindex SMTPUTF8 "ESMTP option"
42295 .cindex "ESMTP extensions" SMTPUTF8
42296 The main configuration option &%smtputf8_advertise_hosts%& specifies
42297 a host list. If this matches the sending host and
42298 accept_8bitmime is true (the default) then the ESMTP option
42299 SMTPUTF8 will be advertised.
42301 If the sender specifies the SMTPUTF8 option on a MAIL command
42302 international handling for the message is enabled and
42303 the expansion variable &$message_smtputf8$& will have value TRUE.
42305 The option &%allow_utf8_domains%& is set to true for this
42306 message. All DNS lookups are converted to a-label form
42307 whatever the setting of &%allow_utf8_domains%&
42308 when Exim is built with SUPPORT_I18N.
42310 Both localparts and domain are maintained as the original
42311 UTF-8 form internally; any comparison or regular-expression use will
42312 require appropriate care. Filenames created, eg. by
42313 the appendfile transport, will have UTF-8 names.
42315 HELO names sent by the smtp transport will have any UTF-8
42316 components expanded to a-label form,
42317 and any certificate name checks will be done using the a-label
42320 .cindex log protocol
42321 .cindex SMTPUTF8 logging
42322 .cindex i18n logging
42323 Log lines and Received-by: header lines will acquire a "utf8"
42324 prefix on the protocol element, eg. utf8esmtp.
42326 The following expansion operators can be used:
42328 ${utf8_domain_to_alabel:str}
42329 ${utf8_domain_from_alabel:str}
42330 ${utf8_localpart_to_alabel:str}
42331 ${utf8_localpart_from_alabel:str}
42334 .cindex utf8 "address downconversion"
42335 .cindex i18n "utf8 address downconversion"
42337 may use the following modifier:
42339 control = utf8_downconvert
42340 control = utf8_downconvert/<value>
42342 This sets a flag requiring that envelope addresses are converted to
42343 a-label form before smtp delivery.
42344 This is usually for use in a Message Submission Agent context,
42345 but could be used for any message.
42347 If a value is appended it may be:
42349 &`1 `& mandatory downconversion
42350 &`0 `& no downconversion
42351 &`-1 `& if SMTPUTF8 not supported by destination host
42353 If no value is given, 1 is used.
42355 If mua_wrapper is set, the utf8_downconvert control
42356 is initially set to -1.
42358 The smtp transport has an option &%utf8_downconvert%&.
42359 If set it must expand to one of the three values described above,
42360 or an empty string.
42361 If non-empty it overrides value previously set
42362 (due to mua_wrapper or by an ACL control).
42365 There is no explicit support for VRFY and EXPN.
42366 Configurations supporting these should inspect
42367 &$smtp_command_argument$& for an SMTPUTF8 argument.
42369 There is no support for LMTP on Unix sockets.
42370 Using the "lmtp" protocol option on an smtp transport,
42371 for LMTP over TCP, should work as expected.
42373 There is no support for DSN unitext handling,
42374 and no provision for converting logging from or to UTF-8.
42378 .section "MDA operations" SECTi18nMDA
42379 To aid in constructing names suitable for IMAP folders
42380 the following expansion operator can be used:
42382 ${imapfolder {<string>} {<sep>} {<specials>}}
42385 The string is converted from the charset specified by
42386 the "headers charset" command (in a filter file)
42387 or &%headers_charset%& main configuration option (otherwise),
42389 modified UTF-7 encoding specified by RFC 2060,
42390 with the following exception: All occurrences of <sep>
42391 (which has to be a single character)
42392 are replaced with periods ("."), and all periods and slashes that are not
42393 <sep> and are not in the <specials> string are BASE64 encoded.
42395 The third argument can be omitted, defaulting to an empty string.
42396 The second argument can be omitted, defaulting to "/".
42398 This is the encoding used by Courier for Maildir names on disk, and followed
42399 by many other IMAP servers.
42403 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
42404 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
42405 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
42408 Note that the source charset setting is vital, and also that characters
42409 must be representable in UTF-16.
42412 . ////////////////////////////////////////////////////////////////////////////
42413 . ////////////////////////////////////////////////////////////////////////////
42415 .chapter "Events" "CHAPevents" &&&
42419 The events mechanism in Exim can be used to intercept processing at a number
42420 of points. It was originally invented to give a way to do customised logging
42421 actions (for example, to a database) but can also be used to modify some
42422 processing actions.
42424 Most installations will never need to use Events.
42425 The support can be left out of a build by defining DISABLE_EVENT=yes
42426 in &_Local/Makefile_&.
42428 There are two major classes of events: main and transport.
42429 The main configuration option &%event_action%& controls reception events;
42430 a transport option &%event_action%& controls delivery events.
42432 Both options are a string which is expanded when the event fires.
42433 An example might look like:
42434 .cindex logging custom
42436 event_action = ${if eq {msg:delivery}{$event_name} \
42437 {${lookup pgsql {SELECT * FROM record_Delivery( \
42438 '${quote_pgsql:$sender_address_domain}',\
42439 '${quote_pgsql:${lc:$sender_address_local_part}}', \
42440 '${quote_pgsql:$domain}', \
42441 '${quote_pgsql:${lc:$local_part}}', \
42442 '${quote_pgsql:$host_address}', \
42443 '${quote_pgsql:${lc:$host}}', \
42444 '${quote_pgsql:$message_exim_id}')}} \
42448 Events have names which correspond to the point in process at which they fire.
42449 The name is placed in the variable &$event_name$& and the event action
42450 expansion must check this, as it will be called for every possible event type.
42452 The current list of events is:
42454 &`dane:fail after transport `& per connection
42455 &`msg:complete after main `& per message
42456 &`msg:defer after transport `& per message per delivery try
42457 &`msg:delivery after transport `& per recipient
42458 &`msg:rcpt:host:defer after transport `& per recipient per host
42459 &`msg:rcpt:defer after transport `& per recipient
42460 &`msg:host:defer after transport `& per host per delivery try; host errors
42461 &`msg:fail:delivery after transport `& per recipient
42462 &`msg:fail:internal after main `& per recipient
42463 &`tcp:connect before transport `& per connection
42464 &`tcp:close after transport `& per connection
42465 &`tls:cert before both `& per certificate in verification chain
42466 &`smtp:connect after transport `& per connection
42467 &`smtp:ehlo after transport `& per connection
42469 New event types may be added in future.
42471 The event name is a colon-separated list, defining the type of
42472 event in a tree of possibilities. It may be used as a list
42473 or just matched on as a whole. There will be no spaces in the name.
42475 The second column in the table above describes whether the event fires
42476 before or after the action is associates with. Those which fire before
42477 can be used to affect that action (more on this below).
42479 The third column in the table above says what section of the configuration
42480 should define the event action.
42482 An additional variable, &$event_data$&, is filled with information varying
42483 with the event type:
42485 &`dane:fail `& failure reason
42486 &`msg:defer `& error string
42487 &`msg:delivery `& smtp confirmation message
42488 &`msg:fail:internal `& failure reason
42489 &`msg:fail:delivery `& smtp error message
42490 &`msg:host:defer `& error string
42491 &`msg:rcpt:host:defer `& error string
42492 &`msg:rcpt:defer `& error string
42493 &`tls:cert `& verification chain depth
42494 &`smtp:connect `& smtp banner
42495 &`smtp:ehlo `& smtp ehlo response
42498 The :defer events populate one extra variable: &$event_defer_errno$&.
42500 For complex operations an ACL expansion can be used in &%event_action%&
42501 however due to the multiple contexts that Exim operates in during
42502 the course of its processing:
42504 variables set in transport events will not be visible outside that
42507 acl_m variables in a server context are lost on a new connection,
42508 and after smtp helo/ehlo/mail/starttls/rset commands
42510 Using an ACL expansion with the logwrite modifier can be
42511 a useful way of writing to the main log.
42513 The expansion of the event_action option should normally
42514 return an empty string. Should it return anything else the
42515 following will be forced:
42517 &`tcp:connect `& do not connect
42518 &`tls:cert `& refuse verification
42519 &`smtp:connect `& close connection
42521 All other message types ignore the result string, and
42522 no other use is made of it.
42524 For a tcp:connect event, if the connection is being made to a proxy
42525 then the address and port variables will be that of the proxy and not
42528 For tls:cert events, if GnuTLS is in use this will trigger only per
42529 chain element received on the connection.
42530 For OpenSSL it will trigger for every chain element including those
42533 . ////////////////////////////////////////////////////////////////////////////
42534 . ////////////////////////////////////////////////////////////////////////////
42536 .chapter "Adding new drivers or lookup types" "CHID13" &&&
42537 "Adding drivers or lookups"
42538 .cindex "adding drivers"
42539 .cindex "new drivers, adding"
42540 .cindex "drivers" "adding new"
42541 The following actions have to be taken in order to add a new router, transport,
42542 authenticator, or lookup type to Exim:
42545 Choose a name for the driver or lookup type that does not conflict with any
42546 existing name; I will use &"newdriver"& in what follows.
42548 Add to &_src/EDITME_& the line:
42550 <&'type'&>&`_NEWDRIVER=yes`&
42552 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
42553 code is not to be included in the binary by default, comment this line out. You
42554 should also add any relevant comments about the driver or lookup type.
42556 Add to &_src/config.h.defaults_& the line:
42558 #define <type>_NEWDRIVER
42561 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
42562 and create a table entry as is done for all the other drivers and lookup types.
42564 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
42565 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
42566 Add your &`NEWDRIVER`& to that list.
42567 As long as the dynamic module would be named &_newdriver.so_&, you can use the
42568 simple form that most lookups have.
42570 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
42571 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
42572 driver or lookup type and add it to the definition of OBJ.
42574 Edit &_OS/Makefile-Base_& adding a &_.o_& file for the predefined-macros, to the
42575 definition of OBJ_MACRO. Add a set of line to do the compile also.
42577 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
42580 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
42581 as for other drivers and lookups.
42584 Then all you need to do is write the code! A good way to start is to make a
42585 proforma by copying an existing module of the same type, globally changing all
42586 occurrences of the name, and cutting out most of the code. Note that any
42587 options you create must be listed in alphabetical order, because the tables are
42588 searched using a binary chop procedure.
42590 There is a &_README_& file in each of the sub-directories of &_src_& describing
42591 the interface that is expected.
42596 . ////////////////////////////////////////////////////////////////////////////
42597 . ////////////////////////////////////////////////////////////////////////////
42599 . /////////////////////////////////////////////////////////////////////////////
42600 . These lines are processing instructions for the Simple DocBook Processor that
42601 . Philip Hazel has developed as a less cumbersome way of making PostScript and
42602 . PDFs than using xmlto and fop. They will be ignored by all other XML
42604 . /////////////////////////////////////////////////////////////////////////////
42609 foot_right_recto="&chaptertitle;"
42610 foot_right_verso="&chaptertitle;"
42614 .makeindex "Options index" "option"
42615 .makeindex "Variables index" "variable"
42616 .makeindex "Concept index" "concept"
42619 . /////////////////////////////////////////////////////////////////////////////
42620 . /////////////////////////////////////////////////////////////////////////////