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 " "
54 .set drivernamemax "64"
60 . /////////////////////////////////////////////////////////////////////////////
61 . Additional xfpt markup used by this document, over and above the default
62 . provided in the xfpt library.
63 . /////////////////////////////////////////////////////////////////////////////
65 . --- Override the &$ flag to automatically insert a $ with the variable name.
67 .flag &$ $& "<varname>$" "</varname>"
69 . --- Short flags for daggers in option headings. They will always be inside
70 . --- an italic string, but we want the daggers to be in Roman.
72 .flag &!! "</emphasis>†<emphasis>"
73 .flag &!? "</emphasis>‡<emphasis>"
75 . --- A macro for an Exim option definition heading, generating a one-line
76 . --- table with four columns. For cases when the option name is given with
77 . --- a space, so that it can be split, a fifth argument is used for the
87 .itable all 0 0 4 8* left 6* center 6* center 6* right
88 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
92 . --- A macro for the common 2-column tables. The width of the first column
93 . --- is suitable for the many tables at the start of the main options chapter;
94 . --- a small number of other 2-column tables override it.
96 .macro table2 196pt 254pt
97 .itable none 0 0 2 $1 left $2 left
100 . --- A macro that generates .row, but puts &I; at the start of the first
101 . --- argument, thus indenting it. Assume a minimum of two arguments, and
102 . --- allow up to four arguments, which is as many as we'll ever need.
106 .row "&I;$1" "$2" "$3" "$4"
110 .row "&I;$1" "$2" "$3"
118 . --- Macros for option, variable, and concept index entries. For a "range"
119 . --- style of entry, use .scindex for the start and .ecindex for the end. The
120 . --- first argument of .scindex and the only argument of .ecindex must be the
121 . --- ID that ties them together.
124 &<indexterm role="concept">&
125 &<primary>&$1&</primary>&
127 &<secondary>&$2&</secondary>&
133 &<indexterm role="concept" id="$1" class="startofrange">&
134 &<primary>&$2&</primary>&
136 &<secondary>&$3&</secondary>&
142 &<indexterm role="concept" startref="$1" class="endofrange"/>&
146 &<indexterm role="option">&
147 &<primary>&$1&</primary>&
149 &<secondary>&$2&</secondary>&
155 &<indexterm role="variable">&
156 &<primary>&$1&</primary>&
158 &<secondary>&$2&</secondary>&
164 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
168 . use this for a concept-index entry for a header line
170 .cindex "&'$1'& header line"
171 .cindex "header lines" $1
173 . ////////////////////////////////////////////////////////////////////////////
176 . ////////////////////////////////////////////////////////////////////////////
177 . The <bookinfo> element is removed from the XML before processing for ASCII
179 . ////////////////////////////////////////////////////////////////////////////
183 <title>Specification of the Exim Mail Transfer Agent</title>
184 <titleabbrev>The Exim MTA</titleabbrev>
188 <author><firstname>Exim</firstname><surname>Maintainers</surname></author>
189 <authorinitials>EM</authorinitials>
190 <revhistory><revision>
192 <authorinitials>EM</authorinitials>
193 </revision></revhistory>
196 </year><holder>University of Cambridge</holder></copyright>
201 . /////////////////////////////////////////////////////////////////////////////
202 . This chunk of literal XML implements index entries of the form "x, see y" and
203 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
204 . at the top level, so we have to put the .chapter directive first.
206 . These do not turn up in the HTML output, unfortunately. The PDF does get them.
207 . /////////////////////////////////////////////////////////////////////////////
209 .chapter "Introduction" "CHID1"
212 <indexterm role="variable">
213 <primary>$1, $2, etc.</primary>
214 <see><emphasis>numerical variables</emphasis></see>
216 <indexterm role="concept">
217 <primary>address</primary>
218 <secondary>rewriting</secondary>
219 <see><emphasis>rewriting</emphasis></see>
221 <indexterm role="concept">
222 <primary>Bounce Address Tag Validation</primary>
223 <see><emphasis>BATV</emphasis></see>
225 <indexterm role="concept">
226 <primary>Client SMTP Authorization</primary>
227 <see><emphasis>CSA</emphasis></see>
229 <indexterm role="concept">
230 <primary>CR character</primary>
231 <see><emphasis>carriage return</emphasis></see>
233 <indexterm role="concept">
234 <primary>CRL</primary>
235 <see><emphasis>certificate revocation list</emphasis></see>
237 <indexterm role="concept">
238 <primary>delivery</primary>
239 <secondary>failure report</secondary>
240 <see><emphasis>bounce message</emphasis></see>
242 <indexterm role="concept">
243 <primary>de-tainting</primary>
244 <see><emphasis>tainting, de-tainting</emphasis></see>
246 <indexterm role="concept">
247 <primary>detainting</primary>
248 <see><emphasis>tainting, de-tainting</emphasis></see>
250 <indexterm role="concept">
251 <primary>dialup</primary>
252 <see><emphasis>intermittently connected hosts</emphasis></see>
254 <indexterm role="concept">
255 <primary>exiscan</primary>
256 <see><emphasis>content scanning</emphasis></see>
258 <indexterm role="concept">
259 <primary>failover</primary>
260 <see><emphasis>fallback</emphasis></see>
262 <indexterm role="concept">
263 <primary>fallover</primary>
264 <see><emphasis>fallback</emphasis></see>
266 <indexterm role="concept">
267 <primary>filter</primary>
268 <secondary>Sieve</secondary>
269 <see><emphasis>Sieve filter</emphasis></see>
271 <indexterm role="concept">
272 <primary>ident</primary>
273 <see><emphasis>RFC 1413</emphasis></see>
275 <indexterm role="concept">
276 <primary>LF character</primary>
277 <see><emphasis>linefeed</emphasis></see>
279 <indexterm role="concept">
280 <primary>maximum</primary>
281 <seealso><emphasis>limit</emphasis></seealso>
283 <indexterm role="concept">
284 <primary>monitor</primary>
285 <see><emphasis>Exim monitor</emphasis></see>
287 <indexterm role="concept">
288 <primary>no_<emphasis>xxx</emphasis></primary>
289 <see>entry for xxx</see>
291 <indexterm role="concept">
292 <primary>NUL</primary>
293 <see><emphasis>binary zero</emphasis></see>
295 <indexterm role="concept">
296 <primary>passwd file</primary>
297 <see><emphasis>/etc/passwd</emphasis></see>
299 <indexterm role="concept">
300 <primary>process id</primary>
301 <see><emphasis>pid</emphasis></see>
303 <indexterm role="concept">
304 <primary>RBL</primary>
305 <see><emphasis>DNS list</emphasis></see>
307 <indexterm role="concept">
308 <primary>redirection</primary>
309 <see><emphasis>address redirection</emphasis></see>
311 <indexterm role="concept">
312 <primary>return path</primary>
313 <seealso><emphasis>envelope sender</emphasis></seealso>
315 <indexterm role="concept">
316 <primary>scanning</primary>
317 <see><emphasis>content scanning</emphasis></see>
319 <indexterm role="concept">
320 <primary>SSL</primary>
321 <see><emphasis>TLS</emphasis></see>
323 <indexterm role="concept">
324 <primary>string</primary>
325 <secondary>expansion</secondary>
326 <see><emphasis>expansion</emphasis></see>
328 <indexterm role="concept">
329 <primary>top bit</primary>
330 <see><emphasis>8-bit characters</emphasis></see>
332 <indexterm role="concept">
333 <primary>variables</primary>
334 <see><emphasis>expansion, variables</emphasis></see>
336 <indexterm role="concept">
337 <primary>zero, binary</primary>
338 <see><emphasis>binary zero</emphasis></see>
340 <indexterm role="concept">
341 <primary>headers</primary>
342 <see><emphasis>header lines</emphasis></see>
348 . /////////////////////////////////////////////////////////////////////////////
349 . This is the real start of the first chapter. See the comment above as to why
350 . we can't have the .chapter line here.
351 . chapter "Introduction"
352 . /////////////////////////////////////////////////////////////////////////////
354 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
355 Unix-like operating systems. It was designed on the assumption that it would be
356 run on hosts that are permanently connected to the Internet. However, it can be
357 used on intermittently connected hosts with suitable configuration adjustments.
359 Configuration files currently exist for the following operating systems: AIX,
360 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
361 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
362 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
363 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and UnixWare.
364 Some of these operating systems are no longer current and cannot easily be
365 tested, so the configuration files may no longer work in practice.
367 There are also configuration files for compiling Exim in the Cygwin environment
368 that can be installed on systems running Windows. However, this document does
369 not contain any information about running Exim in the Cygwin environment.
371 The terms and conditions for the use and distribution of Exim are contained in
372 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
373 Public Licence, a copy of which may be found in the file &_LICENCE_&.
375 The use, supply, or promotion of Exim for the purpose of sending bulk,
376 unsolicited electronic mail is incompatible with the basic aims of Exim,
377 which revolve around the free provision of a service that enhances the quality
378 of personal communications. The author of Exim regards indiscriminate
379 mass-mailing as an antisocial, irresponsible abuse of the Internet.
381 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
382 experience of running and working on the Smail 3 code, I could never have
383 contemplated starting to write a new MTA. Many of the ideas and user interfaces
384 were originally taken from Smail 3, though the actual code of Exim is entirely
385 new, and has developed far beyond the initial concept.
387 Many people, both in Cambridge and around the world, have contributed to the
388 development and the testing of Exim, and to porting it to various operating
389 systems. I am grateful to them all. The distribution now contains a file called
390 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
394 .section "Exim documentation" "SECID1"
395 . Keep this example change bar when updating the documentation!
398 .cindex "documentation"
399 This edition of the Exim specification applies to version &version() of Exim.
400 Substantive changes from the &previousversion; edition are marked in some
401 renditions of this document; this paragraph is so marked if the rendition is
402 capable of showing a change indicator.
405 This document is very much a reference manual; it is not a tutorial. The reader
406 is expected to have some familiarity with the SMTP mail transfer protocol and
407 with general Unix system administration. Although there are some discussions
408 and examples in places, the information is mostly organized in a way that makes
409 it easy to look up, rather than in a natural order for sequential reading.
410 Furthermore, this manual aims to cover every aspect of Exim in detail, including
411 a number of rarely-used, special-purpose features that are unlikely to be of
414 .cindex "books about Exim"
415 An &"easier"& discussion of Exim which provides more in-depth explanatory,
416 introductory, and tutorial material can be found in a book entitled &'The Exim
417 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
418 (&url(https://www.uit.co.uk/exim-book/)).
420 The book also contains a chapter that gives a general introduction to SMTP and
421 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
422 with the latest release of Exim. (Note that the earlier book about Exim,
423 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
425 .cindex "Debian" "information sources"
426 If you are using a Debian distribution of Exim, you will find information about
427 Debian-specific features in the file
428 &_/usr/share/doc/exim4-base/README.Debian_&.
429 The command &(man update-exim.conf)& is another source of Debian-specific
432 .cindex "&_doc/NewStuff_&"
433 .cindex "&_doc/ChangeLog_&"
435 As Exim develops, there may be features in newer versions that have not
436 yet made it into this document, which is updated only when the most significant
437 digit of the fractional part of the version number changes. Specifications of
438 new features that are not yet in this manual are placed in the file
439 &_doc/NewStuff_& in the Exim distribution.
441 Some features may be classified as &"experimental"&. These may change
442 incompatibly while they are developing, or even be withdrawn. For this reason,
443 they are not documented in this manual. Information about experimental features
444 can be found in the file &_doc/experimental.txt_&.
446 All changes to Exim (whether new features, bug fixes, or other kinds of
447 change) are noted briefly in the file called &_doc/ChangeLog_&.
449 .cindex "&_doc/spec.txt_&"
450 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
451 that it can easily be searched with a text editor. Other files in the &_doc_&
455 .row &_OptionLists.txt_& "list of all options in alphabetical order"
456 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
457 .row &_exim.8_& "a man page of Exim's command line options"
458 .row &_experimental.txt_& "documentation of experimental features"
459 .row &_filter.txt_& "specification of the filter language"
460 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
461 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
462 .row &_openssl.txt_& "installing a current OpenSSL release"
465 The main specification and the specification of the filtering language are also
466 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
467 &<<SECTavail>>& below tells you how to get hold of these.
471 .section "FTP site and websites" "SECID2"
474 The primary site for Exim source distributions is the &%exim.org%& FTP site,
475 available over HTTPS, HTTP and FTP. These services, and the &%exim.org%&
476 website, are hosted at the University of Cambridge.
480 As well as Exim distribution tar files, the Exim website contains a number of
481 differently formatted versions of the documentation. A recent addition to the
482 online information is the Exim wiki (&url(https://wiki.exim.org)),
483 which contains what used to be a separate FAQ, as well as various other
484 examples, tips, and know-how that have been contributed by Exim users.
485 The wiki site should always redirect to the correct place, which is currently
486 provided by GitHub, and is open to editing by anyone with a GitHub account.
489 An Exim Bugzilla exists at &url(https://bugs.exim.org). You can use
490 this to report bugs, and also to add items to the wish list. Please search
491 first to check that you are not duplicating a previous entry.
492 Please do not ask for configuration help in the bug-tracker.
495 .section "Mailing lists" "SECID3"
496 .cindex "mailing lists" "for Exim users"
497 The following Exim mailing lists exist:
500 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
501 .row &'exim-users@exim.org'& "General discussion list"
502 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
503 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
506 You can subscribe to these lists, change your existing subscriptions, and view
507 or search the archives via the mailing lists link on the Exim home page.
508 .cindex "Debian" "mailing list for"
509 If you are using a Debian distribution of Exim, you may wish to subscribe to
510 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
513 &url(https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-exim4-users)
515 Please ask Debian-specific questions on that list and not on the general Exim
518 .section "Bug reports" "SECID5"
519 .cindex "bug reports"
520 .cindex "reporting bugs"
521 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
522 via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
523 whether some behaviour is a bug or not, the best thing to do is to post a
524 message to the &'exim-dev'& mailing list and have it discussed.
528 .section "Where to find the Exim distribution" "SECTavail"
530 .cindex "HTTPS download site"
531 .cindex "distribution" "FTP site"
532 .cindex "distribution" "https site"
533 The master distribution site for the Exim distribution is
535 &url(https://downloads.exim.org/)
537 The service is available over HTTPS, HTTP and FTP.
538 We encourage people to migrate to HTTPS.
540 The content served at &url(https://downloads.exim.org/) is identical to the
541 content served at &url(https://ftp.exim.org/pub/exim) and
542 &url(ftp://ftp.exim.org/pub/exim).
544 If accessing via a hostname containing &'ftp'&, then the file references that
545 follow are relative to the &_exim_& directories at these sites.
546 If accessing via the hostname &'downloads'& then the subdirectories described
547 here are top-level directories.
549 There are now quite a number of independent mirror sites around
550 the world. Those that I know about are listed in the file called &_Mirrors_&.
552 Within the top exim directory there are subdirectories called &_exim3_& (for
553 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
554 distributions), and &_Testing_& for testing versions. In the &_exim4_&
555 subdirectory, the current release can always be found in files called
559 &_exim-n.nn.tar.bz2_&
561 where &'n.nn'& is the highest such version number in the directory. The three
562 files contain identical data; the only difference is the type of compression.
563 The &_.xz_& file is usually the smallest, while the &_.gz_& file is the
564 most portable to old systems.
566 .cindex "distribution" "signing details"
567 .cindex "distribution" "public key"
568 .cindex "public key for signed distribution"
569 The distributions will be PGP signed by an individual key of the Release
570 Coordinator. This key will have a uid containing an email address in the
571 &'exim.org'& domain and will have signatures from other people, including
572 other Exim maintainers. We expect that the key will be in the "strong set" of
573 PGP keys. There should be a trust path to that key from the Exim Maintainer's
574 PGP keys, a version of which can be found in the release directory in the file
575 &_Exim-Maintainers-Keyring.asc_&. All keys used will be available in public keyserver pools,
576 such as &'pool.sks-keyservers.net'&.
578 At the time of the last update, releases were being made by Jeremy Harris and signed
579 with key &'0xBCE58C8CE41F32DF'&. Other recent keys used for signing are those
580 of Heiko Schlittermann, &'0x26101B62F69376CE'&,
581 and of Phil Pennock, &'0x4D1E900E14C1CC04'&.
583 The signatures for the tar bundles are in:
585 &_exim-n.nn.tar.xz.asc_&
586 &_exim-n.nn.tar.gz.asc_&
587 &_exim-n.nn.tar.bz2.asc_&
589 For each released version, the log of changes is made available in a
590 separate file in the directory &_ChangeLogs_& so that it is possible to
591 find out what has changed without having to download the entire distribution.
593 .cindex "documentation" "available formats"
594 The main distribution contains ASCII versions of this specification and other
595 documentation; other formats of the documents are available in separate files
596 inside the &_exim4_& directory of the FTP site:
598 &_exim-html-n.nn.tar.gz_&
599 &_exim-pdf-n.nn.tar.gz_&
600 &_exim-postscript-n.nn.tar.gz_&
601 &_exim-texinfo-n.nn.tar.gz_&
603 These tar files contain only the &_doc_& directory, not the complete
604 distribution, and are also available in &_.bz2_& and &_.xz_& forms.
607 .section "Limitations" "SECID6"
609 .cindex "limitations of Exim"
610 .cindex "bang paths" "not handled by Exim"
611 Exim is designed for use as an Internet MTA, and therefore handles addresses in
612 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
613 simple two-component bang paths can be converted by a straightforward rewriting
614 configuration. This restriction does not prevent Exim from being interfaced to
615 UUCP as a transport mechanism, provided that domain addresses are used.
617 .cindex "domainless addresses"
618 .cindex "address" "without domain"
619 Exim insists that every address it handles has a domain attached. For incoming
620 local messages, domainless addresses are automatically qualified with a
621 configured domain value. Configuration options specify from which remote
622 systems unqualified addresses are acceptable. These are then qualified on
625 .cindex "transport" "external"
626 .cindex "external transports"
627 The only external transport mechanisms that are currently implemented are SMTP
628 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
629 transport is available, and there are facilities for writing messages to files
630 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
631 to send messages to other transport mechanisms such as UUCP, provided they can
632 handle domain-style addresses. Batched SMTP input is also catered for.
634 Exim is not designed for storing mail for dial-in hosts. When the volumes of
635 such mail are large, it is better to get the messages &"delivered"& into files
636 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
639 Although Exim does have basic facilities for scanning incoming messages, these
640 are not comprehensive enough to do full virus or spam scanning. Such operations
641 are best carried out using additional specialized software packages. If you
642 compile Exim with the content-scanning extension, straightforward interfaces to
643 a number of common scanners are provided.
647 .section "Runtime configuration" "SECID7"
648 Exim's runtime configuration is held in a single text file that is divided
649 into a number of sections. The entries in this file consist of keywords and
650 values, in the style of Smail 3 configuration files. A default configuration
651 file which is suitable for simple online installations is provided in the
652 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
655 .section "Calling interface" "SECID8"
656 .cindex "Sendmail compatibility" "command line interface"
657 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
658 can be a straight replacement for &_/usr/lib/sendmail_& or
659 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
660 about Sendmail in order to run Exim. For actions other than sending messages,
661 Sendmail-compatible options also exist, but those that produce output (for
662 example, &%-bp%&, which lists the messages in the queue) do so in Exim's own
663 format. There are also some additional options that are compatible with Smail
664 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
665 documents all Exim's command line options. This information is automatically
666 made into the man page that forms part of the Exim distribution.
668 Control of messages in the queue can be done via certain privileged command
669 line options. There is also an optional monitor program called &'eximon'&,
670 which displays current information in an X window, and which contains a menu
671 interface to Exim's command line administration options.
675 .section "Terminology" "SECID9"
676 .cindex "terminology definitions"
677 .cindex "body of message" "definition of"
678 The &'body'& of a message is the actual data that the sender wants to transmit.
679 It is the last part of a message and is separated from the &'header'& (see
680 below) by a blank line.
682 .cindex "bounce message" "definition of"
683 When a message cannot be delivered, it is normally returned to the sender in a
684 delivery failure message or a &"non-delivery report"& (NDR). The term
685 &'bounce'& is commonly used for this action, and the error reports are often
686 called &'bounce messages'&. This is a convenient shorthand for &"delivery
687 failure error report"&. Such messages have an empty sender address in the
688 message's &'envelope'& (see below) to ensure that they cannot themselves give
689 rise to further bounce messages.
691 The term &'default'& appears frequently in this manual. It is used to qualify a
692 value which is used in the absence of any setting in the configuration. It may
693 also qualify an action which is taken unless a configuration setting specifies
696 The term &'defer'& is used when the delivery of a message to a specific
697 destination cannot immediately take place for some reason (a remote host may be
698 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
701 The word &'domain'& is sometimes used to mean all but the first component of a
702 host's name. It is &'not'& used in that sense here, where it normally refers to
703 the part of an email address following the @ sign.
705 .cindex "envelope, definition of"
706 .cindex "sender" "definition of"
707 A message in transit has an associated &'envelope'&, as well as a header and a
708 body. The envelope contains a sender address (to which bounce messages should
709 be delivered), and any number of recipient addresses. References to the
710 sender or the recipients of a message usually mean the addresses in the
711 envelope. An MTA uses these addresses for delivery, and for returning bounce
712 messages, not the addresses that appear in the header lines.
714 .cindex "message" "header, definition of"
715 .cindex "header section" "definition of"
716 The &'header'& of a message is the first part of a message's text, consisting
717 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
718 &'Subject:'&, etc. Long header lines can be split over several text lines by
719 indenting the continuations. The header is separated from the body by a blank
722 .cindex "local part" "definition of"
723 .cindex "domain" "definition of"
724 The term &'local part'&, which is taken from RFC 2822, is used to refer to the
725 part of an email address that precedes the @ sign. The part that follows the
726 @ sign is called the &'domain'& or &'mail domain'&.
728 .cindex "local delivery" "definition of"
729 .cindex "remote delivery, definition of"
730 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
731 delivery to a file or a pipe on the local host from delivery by SMTP over
732 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
733 host it is running on are &'remote'&.
735 .cindex "return path" "definition of"
736 &'Return path'& is another name that is used for the sender address in a
739 .cindex "queue" "definition of"
740 The term &'queue'& is used to refer to the set of messages awaiting delivery
741 because this term is in widespread use in the context of MTAs. However, in
742 Exim's case, the reality is more like a pool than a queue, because there is
743 normally no ordering of waiting messages.
745 .cindex "queue runner" "definition of"
746 The term &'queue runner'& is used to describe a process that scans the queue
747 and attempts to deliver those messages whose retry times have come. This term
748 is used by other MTAs and also relates to the command &%runq%&, but in Exim
749 the waiting messages are normally processed in an unpredictable order.
751 .cindex "spool directory" "definition of"
752 The term &'spool directory'& is used for a directory in which Exim keeps the
753 messages in its queue &-- that is, those that it is in the process of
754 delivering. This should not be confused with the directory in which local
755 mailboxes are stored, which is called a &"spool directory"& by some people. In
756 the Exim documentation, &"spool"& is always used in the first sense.
763 . ////////////////////////////////////////////////////////////////////////////
764 . ////////////////////////////////////////////////////////////////////////////
766 .chapter "Incorporated code" "CHID2"
767 .cindex "incorporated code"
768 .cindex "regular expressions" "library"
771 A number of pieces of external code are included in the Exim distribution.
774 Regular expressions are supported in the main Exim program and in the
775 Exim monitor using the freely-distributable PCRE library, copyright
776 © University of Cambridge. The source to PCRE is no longer shipped with
777 Exim, so you will need to use the version of PCRE shipped with your system,
778 or obtain and install the full version of the library from
779 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
781 .cindex "cdb" "acknowledgment"
782 Support for the cdb (Constant DataBase) lookup method is provided by code
783 contributed by Nigel Metheringham of (at the time he contributed it) Planet
784 Online Ltd. The implementation is completely contained within the code of Exim.
785 It does not link against an external cdb library. The code contains the
786 following statements:
789 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
791 This program is free software; you can redistribute it and/or modify it under
792 the terms of the GNU General Public License as published by the Free Software
793 Foundation; either version 2 of the License, or (at your option) any later
795 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
796 the spec and sample code for cdb can be obtained from
797 &url(https://cr.yp.to/cdb.html). This implementation borrows
798 some code from Dan Bernstein's implementation (which has no license
799 restrictions applied to it).
802 .cindex "SPA authentication"
803 .cindex "Samba project"
804 .cindex "Microsoft Secure Password Authentication"
805 Client support for Microsoft's &'Secure Password Authentication'& is provided
806 by code contributed by Marc Prud'hommeaux. Server support was contributed by
807 Tom Kistner. This includes code taken from the Samba project, which is released
811 .cindex "&'pwcheck'& daemon"
812 .cindex "&'pwauthd'& daemon"
813 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
814 by code taken from the Cyrus-SASL library and adapted by Alexander S.
815 Sabourenkov. The permission notice appears below, in accordance with the
816 conditions expressed therein.
819 Copyright © 2001 Carnegie Mellon University. All rights reserved.
821 Redistribution and use in source and binary forms, with or without
822 modification, are permitted provided that the following conditions
826 Redistributions of source code must retain the above copyright
827 notice, this list of conditions and the following disclaimer.
829 Redistributions in binary form must reproduce the above copyright
830 notice, this list of conditions and the following disclaimer in
831 the documentation and/or other materials provided with the
834 The name &"Carnegie Mellon University"& must not be used to
835 endorse or promote products derived from this software without
836 prior written permission. For permission or any other legal
837 details, please contact
839 Office of Technology Transfer
840 Carnegie Mellon University
842 Pittsburgh, PA 15213-3890
843 (412) 268-4387, fax: (412) 268-7395
844 tech-transfer@andrew.cmu.edu
847 Redistributions of any form whatsoever must retain the following
850 &"This product includes software developed by Computing Services
851 at Carnegie Mellon University (&url(https://www.cmu.edu/computing/)."&
853 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
854 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
855 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
856 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
857 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
858 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
859 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
864 .cindex "Exim monitor" "acknowledgment"
867 The Exim Monitor program, which is an X-Window application, includes
868 modified versions of the Athena StripChart and TextPop widgets.
869 This code is copyright by DEC and MIT, and their permission notice appears
870 below, in accordance with the conditions expressed therein.
873 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
874 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
878 Permission to use, copy, modify, and distribute this software and its
879 documentation for any purpose and without fee is hereby granted,
880 provided that the above copyright notice appear in all copies and that
881 both that copyright notice and this permission notice appear in
882 supporting documentation, and that the names of Digital or MIT not be
883 used in advertising or publicity pertaining to distribution of the
884 software without specific, written prior permission.
886 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
887 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
888 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
889 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
890 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
891 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
896 .cindex "opendmarc" "acknowledgment"
897 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
898 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
899 derived code are indicated in the respective source files. The full OpenDMARC
900 license is provided in the LICENSE.opendmarc file contained in the distributed
904 Many people have contributed code fragments, some large, some small, that were
905 not covered by any specific license requirements. It is assumed that the
906 contributors are happy to see their code incorporated into Exim under the GPL.
913 . ////////////////////////////////////////////////////////////////////////////
914 . ////////////////////////////////////////////////////////////////////////////
916 .chapter "How Exim receives and delivers mail" "CHID11" &&&
917 "Receiving and delivering mail"
920 .section "Overall philosophy" "SECID10"
921 .cindex "design philosophy"
922 Exim is designed to work efficiently on systems that are permanently connected
923 to the Internet and are handling a general mix of mail. In such circumstances,
924 most messages can be delivered immediately. Consequently, Exim does not
925 maintain independent queues of messages for specific domains or hosts, though
926 it does try to send several messages in a single SMTP connection after a host
927 has been down, and it also maintains per-host retry information.
930 .section "Policy control" "SECID11"
931 .cindex "policy control" "overview"
932 Policy controls are now an important feature of MTAs that are connected to the
933 Internet. Perhaps their most important job is to stop MTAs from being abused as
934 &"open relays"& by misguided individuals who send out vast amounts of
935 unsolicited junk and want to disguise its source. Exim provides flexible
936 facilities for specifying policy controls on incoming mail:
939 .cindex "&ACL;" "introduction"
940 Exim 4 (unlike previous versions of Exim) implements policy controls on
941 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
942 series of statements that may either grant or deny access. ACLs can be used at
943 several places in the SMTP dialogue while receiving a message from a remote
944 host. However, the most common places are after each RCPT command, and at the
945 very end of the message. The sysadmin can specify conditions for accepting or
946 rejecting individual recipients or the entire message, respectively, at these
947 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
950 An ACL is also available for locally generated, non-SMTP messages. In this
951 case, the only available actions are to accept or deny the entire message.
953 When Exim is compiled with the content-scanning extension, facilities are
954 provided in the ACL mechanism for passing the message to external virus and/or
955 spam scanning software. The result of such a scan is passed back to the ACL,
956 which can then use it to decide what to do with the message.
958 When a message has been received, either from a remote host or from the local
959 host, but before the final acknowledgment has been sent, a locally supplied C
960 function called &[local_scan()]& can be run to inspect the message and decide
961 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
962 is accepted, the list of recipients can be modified by the function.
964 Using the &[local_scan()]& mechanism is another way of calling external scanner
965 software. The &%SA-Exim%& add-on package works this way. It does not require
966 Exim to be compiled with the content-scanning extension.
968 After a message has been accepted, a further checking mechanism is available in
969 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
970 runs at the start of every delivery process.
975 .section "User filters" "SECID12"
976 .cindex "filter" "introduction"
977 .cindex "Sieve filter"
978 In a conventional Exim configuration, users are able to run private filters by
979 setting up appropriate &_.forward_& files in their home directories. See
980 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
981 configuration needed to support this, and the separate document entitled
982 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
983 of filtering are available:
986 Sieve filters are written in the standard filtering language that is defined
989 Exim filters are written in a syntax that is unique to Exim, but which is more
990 powerful than Sieve, which it pre-dates.
993 User filters are run as part of the routing process, described below.
997 .section "Message identification" "SECTmessiden"
998 .cindex "message ids" "details of format"
999 .cindex "format" "of message id"
1000 .cindex "id of message"
1005 Every message handled by Exim is given a &'message id'& which is sixteen
1006 characters long. It is divided into three parts, separated by hyphens, for
1007 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
1008 normally encoding numbers in base 62. However, in the Darwin operating
1009 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
1010 (avoiding the use of lower case letters) is used instead, because the message
1011 id is used to construct filenames, and the names of files in those systems are
1012 not always case-sensitive.
1014 .cindex "pid (process id)" "re-use of"
1015 The detail of the contents of the message id have changed as Exim has evolved.
1016 Earlier versions relied on the operating system not re-using a process id (pid)
1017 within one second. On modern operating systems, this assumption can no longer
1018 be made, so the algorithm had to be changed. To retain backward compatibility,
1019 the format of the message id was retained, which is why the following rules are
1023 The first six characters of the message id are the time at which the message
1024 started to be received, to a granularity of one second. That is, this field
1025 contains the number of seconds since the start of the epoch (the normal Unix
1026 way of representing the date and time of day).
1028 After the first hyphen, the next six characters are the id of the process that
1029 received the message.
1031 There are two different possibilities for the final two characters:
1033 .oindex "&%localhost_number%&"
1034 If &%localhost_number%& is not set, this value is the fractional part of the
1035 time of reception, normally in units of 1/2000 of a second, but for systems
1036 that must use base 36 instead of base 62 (because of case-insensitive file
1037 systems), the units are 1/1000 of a second.
1039 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1040 the fractional part of the time, which in this case is in units of 1/200
1041 (1/100) of a second.
1045 After a message has been received, Exim waits for the clock to tick at the
1046 appropriate resolution before proceeding, so that if another message is
1047 received by the same process, or by another process with the same (re-used)
1048 pid, it is guaranteed that the time will be different. In most cases, the clock
1049 will already have ticked while the message was being received.
1052 .section "Receiving mail" "SECID13"
1053 .cindex "receiving mail"
1054 .cindex "message" "reception"
1055 The only way Exim can receive mail from another host is using SMTP over
1056 TCP/IP, in which case the sender and recipient addresses are transferred using
1057 SMTP commands. However, from a locally running process (such as a user's MUA),
1058 there are several possibilities:
1061 If the process runs Exim with the &%-bm%& option, the message is read
1062 non-interactively (usually via a pipe), with the recipients taken from the
1063 command line, or from the body of the message if &%-t%& is also used.
1065 If the process runs Exim with the &%-bS%& option, the message is also read
1066 non-interactively, but in this case the recipients are listed at the start of
1067 the message in a series of SMTP RCPT commands, terminated by a DATA
1068 command. This is called &"batch SMTP"& format,
1069 but it isn't really SMTP. The SMTP commands are just another way of passing
1070 envelope addresses in a non-interactive submission.
1072 If the process runs Exim with the &%-bs%& option, the message is read
1073 interactively, using the SMTP protocol. A two-way pipe is normally used for
1074 passing data between the local process and the Exim process.
1075 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1076 example, the ACLs for SMTP commands are used for this form of submission.
1078 A local process may also make a TCP/IP call to the host's loopback address
1079 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1080 does not treat the loopback address specially. It treats all such connections
1081 in the same way as connections from other hosts.
1085 .cindex "message sender, constructed by Exim"
1086 .cindex "sender" "constructed by Exim"
1087 In the three cases that do not involve TCP/IP, the sender address is
1088 constructed from the login name of the user that called Exim and a default
1089 qualification domain (which can be set by the &%qualify_domain%& configuration
1090 option). For local or batch SMTP, a sender address that is passed using the
1091 SMTP MAIL command is ignored. However, the system administrator may allow
1092 certain users (&"trusted users"&) to specify a different sender addresses
1093 unconditionally, or all users to specify certain forms of different sender
1094 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1095 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1096 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1097 users to change sender addresses.
1099 Messages received by either of the non-interactive mechanisms are subject to
1100 checking by the non-SMTP ACL if one is defined. Messages received using SMTP
1101 (either over TCP/IP or interacting with a local process) can be checked by a
1102 number of ACLs that operate at different times during the SMTP session. Either
1103 individual recipients or the entire message can be rejected if local policy
1104 requirements are not met. The &[local_scan()]& function (see chapter
1105 &<<CHAPlocalscan>>&) is run for all incoming messages.
1107 Exim can be configured not to start a delivery process when a message is
1108 received; this can be unconditional, or depend on the number of incoming SMTP
1109 connections or the system load. In these situations, new messages wait on the
1110 queue until a queue runner process picks them up. However, in standard
1111 configurations under normal conditions, delivery is started as soon as a
1112 message is received.
1118 .section "Handling an incoming message" "SECID14"
1119 .cindex "spool directory" "files that hold a message"
1120 .cindex "file" "how a message is held"
1121 When Exim accepts a message, it writes two files in its spool directory. The
1122 first contains the envelope information, the current status of the message, and
1123 the header lines, and the second contains the body of the message. The names of
1124 the two spool files consist of the message id, followed by &`-H`& for the
1125 file containing the envelope and header, and &`-D`& for the data file.
1127 .cindex "spool directory" "&_input_& sub-directory"
1128 By default, all these message files are held in a single directory called
1129 &_input_& inside the general Exim spool directory. Some operating systems do
1130 not perform very well if the number of files in a directory gets large; to
1131 improve performance in such cases, the &%split_spool_directory%& option can be
1132 used. This causes Exim to split up the input files into 62 sub-directories
1133 whose names are single letters or digits. When this is done, the queue is
1134 processed one sub-directory at a time instead of all at once, which can improve
1135 overall performance even when there are not enough files in each directory to
1136 affect file system performance.
1138 The envelope information consists of the address of the message's sender and
1139 the addresses of the recipients. This information is entirely separate from
1140 any addresses contained in the header lines. The status of the message includes
1141 a list of recipients who have already received the message. The format of the
1142 first spool file is described in chapter &<<CHAPspool>>&.
1144 .cindex "rewriting" "addresses"
1145 Address rewriting that is specified in the rewrite section of the configuration
1146 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1147 both in the header lines and the envelope, at the time the message is accepted.
1148 If during the course of delivery additional addresses are generated (for
1149 example, via aliasing), these new addresses are rewritten as soon as they are
1150 generated. At the time a message is actually delivered (transported) further
1151 rewriting can take place; because this is a transport option, it can be
1152 different for different forms of delivery. It is also possible to specify the
1153 addition or removal of certain header lines at the time the message is
1154 delivered (see chapters &<<CHAProutergeneric>>& and
1155 &<<CHAPtransportgeneric>>&).
1159 .section "Life of a message" "SECID15"
1160 .cindex "message" "life of"
1161 .cindex "message" "frozen"
1162 A message remains in the spool directory until it is completely delivered to
1163 its recipients or to an error address, or until it is deleted by an
1164 administrator or by the user who originally created it. In cases when delivery
1165 cannot proceed &-- for example when a message can neither be delivered to its
1166 recipients nor returned to its sender, the message is marked &"frozen"& on the
1167 spool, and no more deliveries are attempted.
1169 .cindex "frozen messages" "thawing"
1170 .cindex "message" "thawing frozen"
1171 An administrator can &"thaw"& such messages when the problem has been
1172 corrected, and can also freeze individual messages by hand if necessary. In
1173 addition, an administrator can force a delivery error, causing a bounce message
1176 .oindex "&%timeout_frozen_after%&"
1177 .oindex "&%ignore_bounce_errors_after%&"
1178 There are options called &%ignore_bounce_errors_after%& and
1179 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1180 The first applies only to frozen bounces, the second to all frozen messages.
1182 .cindex "message" "log file for"
1183 .cindex "log" "file for each message"
1184 While Exim is working on a message, it writes information about each delivery
1185 attempt to its main log file. This includes successful, unsuccessful, and
1186 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1187 lines are also written to a separate &'message log'& file for each message.
1188 These logs are solely for the benefit of the administrator and are normally
1189 deleted along with the spool files when processing of a message is complete.
1190 The use of individual message logs can be disabled by setting
1191 &%no_message_logs%&; this might give an improvement in performance on very busy
1194 .cindex "journal file"
1195 .cindex "file" "journal"
1196 All the information Exim itself needs to set up a delivery is kept in the first
1197 spool file, along with the header lines. When a successful delivery occurs, the
1198 address is immediately written at the end of a journal file, whose name is the
1199 message id followed by &`-J`&. At the end of a delivery run, if there are some
1200 addresses left to be tried again later, the first spool file (the &`-H`& file)
1201 is updated to indicate which these are, and the journal file is then deleted.
1202 Updating the spool file is done by writing a new file and renaming it, to
1203 minimize the possibility of data loss.
1205 Should the system or Exim crash after a successful delivery but before
1206 the spool file has been updated, the journal is left lying around. The next
1207 time Exim attempts to deliver the message, it reads the journal file and
1208 updates the spool file before proceeding. This minimizes the chances of double
1209 deliveries caused by crashes.
1213 .section "Processing an address for delivery" "SECTprocaddress"
1214 .cindex "drivers" "definition of"
1215 .cindex "router" "definition of"
1216 .cindex "transport" "definition of"
1217 The main delivery processing elements of Exim are called &'routers'& and
1218 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1219 number of them is provided in the source distribution, and compile-time options
1220 specify which ones are included in the binary. Runtime options specify which
1221 ones are actually used for delivering messages.
1223 .cindex "drivers" "instance definition"
1224 Each driver that is specified in the runtime configuration is an &'instance'&
1225 of that particular driver type. Multiple instances are allowed; for example,
1226 you can set up several different &(smtp)& transports, each with different
1227 option values that might specify different ports or different timeouts. Each
1228 instance has its own identifying name. In what follows we will normally use the
1229 instance name when discussing one particular instance (that is, one specific
1230 configuration of the driver), and the generic driver name when discussing
1231 the driver's features in general.
1233 A &'router'& is a driver that operates on an address, either determining how
1234 its delivery should happen, by assigning it to a specific transport, or
1235 converting the address into one or more new addresses (for example, via an
1236 alias file). A router may also explicitly choose to fail an address, causing it
1239 A &'transport'& is a driver that transmits a copy of the message from Exim's
1240 spool to some destination. There are two kinds of transport: for a &'local'&
1241 transport, the destination is a file or a pipe on the local host, whereas for a
1242 &'remote'& transport the destination is some other host. A message is passed
1243 to a specific transport as a result of successful routing. If a message has
1244 several recipients, it may be passed to a number of different transports.
1246 .cindex "preconditions" "definition of"
1247 An address is processed by passing it to each configured router instance in
1248 turn, subject to certain preconditions, until a router accepts the address or
1249 specifies that it should be bounced. We will describe this process in more
1250 detail shortly. First, as a simple example, we consider how each recipient
1251 address in a message is processed in a small configuration of three routers.
1253 To make this a more concrete example, it is described in terms of some actual
1254 routers, but remember, this is only an example. You can configure Exim's
1255 routers in many different ways, and there may be any number of routers in a
1258 The first router that is specified in a configuration is often one that handles
1259 addresses in domains that are not recognized specifically by the local host.
1260 Typically these are addresses for arbitrary domains on the Internet. A precondition
1261 is set up which looks for the special domains known to the host (for example,
1262 its own domain name), and the router is run for addresses that do &'not'&
1263 match. Typically, this is a router that looks up domains in the DNS in order to
1264 find the hosts to which this address routes. If it succeeds, the address is
1265 assigned to a suitable SMTP transport; if it does not succeed, the router is
1266 configured to fail the address.
1268 The second router is reached only when the domain is recognized as one that
1269 &"belongs"& to the local host. This router does redirection &-- also known as
1270 aliasing and forwarding. When it generates one or more new addresses from the
1271 original, each of them is routed independently from the start. Otherwise, the
1272 router may cause an address to fail, or it may simply decline to handle the
1273 address, in which case the address is passed to the next router.
1275 The final router in many configurations is one that checks to see if the
1276 address belongs to a local mailbox. The precondition may involve a check to
1277 see if the local part is the name of a login account, or it may look up the
1278 local part in a file or a database. If its preconditions are not met, or if
1279 the router declines, we have reached the end of the routers. When this happens,
1280 the address is bounced.
1284 .section "Processing an address for verification" "SECID16"
1285 .cindex "router" "for verification"
1286 .cindex "verifying address" "overview"
1287 As well as being used to decide how to deliver to an address, Exim's routers
1288 are also used for &'address verification'&. Verification can be requested as
1289 one of the checks to be performed in an ACL for incoming messages, on both
1290 sender and recipient addresses, and it can be tested using the &%-bv%& and
1291 &%-bvs%& command line options.
1293 When an address is being verified, the routers are run in &"verify mode"&. This
1294 does not affect the way the routers work, but it is a state that can be
1295 detected. By this means, a router can be skipped or made to behave differently
1296 when verifying. A common example is a configuration in which the first router
1297 sends all messages to a message-scanning program unless they have been
1298 previously scanned. Thus, the first router accepts all addresses without any
1299 checking, making it useless for verifying. Normally, the &%no_verify%& option
1300 would be set for such a router, causing it to be skipped in verify mode.
1305 .section "Running an individual router" "SECTrunindrou"
1306 .cindex "router" "running details"
1307 .cindex "preconditions" "checking"
1308 .cindex "router" "result of running"
1309 As explained in the example above, a number of preconditions are checked before
1310 running a router. If any are not met, the router is skipped, and the address is
1311 passed to the next router. When all the preconditions on a router &'are'& met,
1312 the router is run. What happens next depends on the outcome, which is one of
1316 &'accept'&: The router accepts the address, and either assigns it to a
1317 transport or generates one or more &"child"& addresses. Processing the
1318 original address ceases
1319 .oindex "&%unseen%&"
1320 unless the &%unseen%& option is set on the router. This option
1321 can be used to set up multiple deliveries with different routing (for example,
1322 for keeping archive copies of messages). When &%unseen%& is set, the address is
1323 passed to the next router. Normally, however, an &'accept'& return marks the
1326 Any child addresses generated by the router are processed independently,
1327 starting with the first router by default. It is possible to change this by
1328 setting the &%redirect_router%& option to specify which router to start at for
1329 child addresses. Unlike &%pass_router%& (see below) the router specified by
1330 &%redirect_router%& may be anywhere in the router configuration.
1332 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1333 requests that the address be passed to another router. By default, the address
1334 is passed to the next router, but this can be changed by setting the
1335 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1336 must be below the current router (to avoid loops).
1338 &'decline'&: The router declines to accept the address because it does not
1339 recognize it at all. By default, the address is passed to the next router, but
1340 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1341 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1342 &'decline'& into &'fail'&.
1344 &'fail'&: The router determines that the address should fail, and queues it for
1345 the generation of a bounce message. There is no further processing of the
1346 original address unless &%unseen%& is set on the router.
1348 &'defer'&: The router cannot handle the address at the present time. (A
1349 database may be offline, or a DNS lookup may have timed out.) No further
1350 processing of the address happens in this delivery attempt. It is tried again
1351 next time the message is considered for delivery.
1353 &'error'&: There is some error in the router (for example, a syntax error in
1354 its configuration). The action is as for defer.
1357 If an address reaches the end of the routers without having been accepted by
1358 any of them, it is bounced as unrouteable. The default error message in this
1359 situation is &"unrouteable address"&, but you can set your own message by
1360 making use of the &%cannot_route_message%& option. This can be set for any
1361 router; the value from the last router that &"saw"& the address is used.
1363 Sometimes while routing you want to fail a delivery when some conditions are
1364 met but others are not, instead of passing the address on for further routing.
1365 You can do this by having a second router that explicitly fails the delivery
1366 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1367 facility for this purpose.
1370 .section "Duplicate addresses" "SECID17"
1371 .cindex "case of local parts"
1372 .cindex "address duplicate, discarding"
1373 .cindex "duplicate addresses"
1374 Once routing is complete, Exim scans the addresses that are assigned to local
1375 and remote transports and discards any duplicates that it finds. During this
1376 check, local parts are treated case-sensitively. This happens only when
1377 actually delivering a message; when testing routers with &%-bt%&, all the
1378 routed addresses are shown.
1382 .section "Router preconditions" "SECTrouprecon"
1383 .cindex "router" "preconditions, order of processing"
1384 .cindex "preconditions" "order of processing"
1385 The preconditions that are tested for each router are listed below, in the
1386 order in which they are tested. The individual configuration options are
1387 described in more detail in chapter &<<CHAProutergeneric>>&.
1390 .cindex affix "router precondition"
1391 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1392 the local parts handled by the router may or must have certain prefixes and/or
1393 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1394 skipped. These conditions are tested first. When an affix is present, it is
1395 removed from the local part before further processing, including the evaluation
1396 of any other conditions.
1398 Routers can be designated for use only when not verifying an address, that is,
1399 only when routing it for delivery (or testing its delivery routing). If the
1400 &%verify%& option is set false, the router is skipped when Exim is verifying an
1402 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1403 &%verify_recipient%&, which independently control the use of the router for
1404 sender and recipient verification. You can set these options directly if
1405 you want a router to be used for only one type of verification.
1406 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1408 If the &%address_test%& option is set false, the router is skipped when Exim is
1409 run with the &%-bt%& option to test an address routing. This can be helpful
1410 when the first router sends all new messages to a scanner of some sort; it
1411 makes it possible to use &%-bt%& to test subsequent delivery routing without
1412 having to simulate the effect of the scanner.
1414 Routers can be designated for use only when verifying an address, as
1415 opposed to routing it for delivery. The &%verify_only%& option controls this.
1416 Again, cutthrough delivery counts as a verification.
1418 Individual routers can be explicitly skipped when running the routers to
1419 check an address given in the SMTP EXPN command (see the &%expn%& option).
1422 If the &%domains%& option is set, the domain of the address must be in the set
1423 of domains that it defines.
1425 .cindex "tainted data" "de-tainting"
1426 A match verifies the variable &$domain$& (which carries tainted data)
1427 and assigns an untainted value to the &$domain_data$& variable.
1428 Such an untainted value is often needed in the transport.
1429 For specifics of the matching operation and the resulting untainted value,
1430 refer to section &<<SECTdomainlist>>&.
1432 When an untainted value is wanted, use this option
1433 rather than the generic &%condition%& option.
1437 .vindex "&$local_part_prefix$&"
1438 .vindex "&$local_part_prefix_v$&"
1439 .vindex "&$local_part$&"
1440 .vindex "&$local_part_suffix$&"
1441 .vindex "&$local_part_suffix_v$&"
1442 .cindex affix "router precondition"
1443 If the &%local_parts%& option is set, the local part of the address must be in
1444 the set of local parts that it defines.
1446 A match verifies the variable &$local_part$& (which carries tainted data)
1447 and assigns an untainted value to the &$local_part_data$& variable.
1448 Such an untainted value is often needed in the transport.
1449 For specifics of the matching operation and the resulting untainted value,
1450 refer to section &<<SECTlocparlis>>&.
1452 When an untainted value is wanted, use this option
1453 rather than the generic &%condition%& option.
1456 If &%local_part_prefix%& or
1457 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1458 part before this check. If you want to do precondition tests on local parts
1459 that include affixes, you can do so by using a &%condition%& option (see below)
1460 that uses the variables &$local_part$&, &$local_part_prefix$&,
1461 &$local_part_prefix_v$&, &$local_part_suffix$&
1462 and &$local_part_suffix_v$& as necessary.
1465 .vindex "&$local_user_uid$&"
1466 .vindex "&$local_user_gid$&"
1468 If the &%check_local_user%& option is set, the local part must be the name of
1469 an account on the local host. If this check succeeds, the uid and gid of the
1470 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1471 user's home directory is placed in &$home$&; these values can be used in the
1472 remaining preconditions.
1475 If the &%router_home_directory%& option is set, it is expanded at this point,
1476 because it overrides the value of &$home$&. If this expansion were left till
1477 later, the value of &$home$& as set by &%check_local_user%& would be used in
1478 subsequent tests. Having two different values of &$home$& in the same router
1479 could lead to confusion.
1482 If the &%senders%& option is set, the envelope sender address must be in the
1483 set of addresses that it defines.
1486 If the &%require_files%& option is set, the existence or non-existence of
1487 specified files is tested.
1490 .cindex "customizing" "precondition"
1491 If the &%condition%& option is set, it is evaluated and tested. This option
1492 uses an expanded string to allow you to set up your own custom preconditions.
1493 Expanded strings are described in chapter &<<CHAPexpand>>&.
1496 Note that while using
1497 this option for address matching technically works,
1498 it does not set any de-tainted values.
1499 Such values are often needed, either for router-specific options or
1500 for transport options.
1501 Using the &%domains%& and &%local_parts%& options is usually the most
1502 convenient way to obtain them.
1507 Note that &%require_files%& comes near the end of the list, so you cannot use
1508 it to check for the existence of a file in which to lookup up a domain, local
1509 part, or sender. However, as these options are all expanded, you can use the
1510 &%exists%& expansion condition to make such tests within each condition. The
1511 &%require_files%& option is intended for checking files that the router may be
1512 going to use internally, or which are needed by a specific transport (for
1513 example, &_.procmailrc_&).
1517 .section "Delivery in detail" "SECID18"
1518 .cindex "delivery" "in detail"
1519 When a message is to be delivered, the sequence of events is as follows:
1522 If a system-wide filter file is specified, the message is passed to it. The
1523 filter may add recipients to the message, replace the recipients, discard the
1524 message, cause a new message to be generated, or cause the message delivery to
1525 fail. The format of the system filter file is the same as for Exim user filter
1526 files, described in the separate document entitled &'Exim's interfaces to mail
1528 .cindex "Sieve filter" "not available for system filter"
1529 (&*Note*&: Sieve cannot be used for system filter files.)
1531 Some additional features are available in system filters &-- see chapter
1532 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1533 filter only once per delivery attempt, however many recipients it has. However,
1534 if there are several delivery attempts because one or more addresses could not
1535 be immediately delivered, the system filter is run each time. The filter
1536 condition &%first_delivery%& can be used to detect the first run of the system
1539 Each recipient address is offered to each configured router, in turn, subject to
1540 its preconditions, until one is able to handle it. If no router can handle the
1541 address, that is, if they all decline, the address is failed. Because routers
1542 can be targeted at particular domains, several locally handled domains can be
1543 processed entirely independently of each other.
1545 .cindex "routing" "loops in"
1546 .cindex "loop" "while routing"
1547 A router that accepts an address may assign it to a local or a remote
1548 transport. However, the transport is not run at this time. Instead, the address
1549 is placed on a list for the particular transport, which will be run later.
1550 Alternatively, the router may generate one or more new addresses (typically
1551 from alias, forward, or filter files). New addresses are fed back into this
1552 process from the top, but in order to avoid loops, a router ignores any address
1553 which has an identically-named ancestor that was processed by itself.
1555 When all the routing has been done, addresses that have been successfully
1556 handled are passed to their assigned transports. When local transports are
1557 doing real local deliveries, they handle only one address at a time, but if a
1558 local transport is being used as a pseudo-remote transport (for example, to
1559 collect batched SMTP messages for transmission by some other means) multiple
1560 addresses can be handled. Remote transports can always handle more than one
1561 address at a time, but can be configured not to do so, or to restrict multiple
1562 addresses to the same domain.
1564 Each local delivery to a file or a pipe runs in a separate process under a
1565 non-privileged uid, and these deliveries are run one at a time. Remote
1566 deliveries also run in separate processes, normally under a uid that is private
1567 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1568 run in parallel. The maximum number of simultaneous remote deliveries for any
1569 one message is set by the &%remote_max_parallel%& option.
1570 The order in which deliveries are done is not defined, except that all local
1571 deliveries happen before any remote deliveries.
1573 .cindex "queue runner"
1574 When it encounters a local delivery during a queue run, Exim checks its retry
1575 database to see if there has been a previous temporary delivery failure for the
1576 address before running the local transport. If there was a previous failure,
1577 Exim does not attempt a new delivery until the retry time for the address is
1578 reached. However, this happens only for delivery attempts that are part of a
1579 queue run. Local deliveries are always attempted when delivery immediately
1580 follows message reception, even if retry times are set for them. This makes for
1581 better behaviour if one particular message is causing problems (for example,
1582 causing quota overflow, or provoking an error in a filter file).
1584 .cindex "delivery" "retry in remote transports"
1585 Remote transports do their own retry handling, since an address may be
1586 deliverable to one of a number of hosts, each of which may have a different
1587 retry time. If there have been previous temporary failures and no host has
1588 reached its retry time, no delivery is attempted, whether in a queue run or
1589 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1591 If there were any permanent errors, a bounce message is returned to an
1592 appropriate address (the sender in the common case), with details of the error
1593 for each failing address. Exim can be configured to send copies of bounce
1594 messages to other addresses.
1596 .cindex "delivery" "deferral"
1597 If one or more addresses suffered a temporary failure, the message is left on
1598 the queue, to be tried again later. Delivery of these addresses is said to be
1601 When all the recipient addresses have either been delivered or bounced,
1602 handling of the message is complete. The spool files and message log are
1603 deleted, though the message log can optionally be preserved if required.
1609 .section "Retry mechanism" "SECID19"
1610 .cindex "delivery" "retry mechanism"
1611 .cindex "retry" "description of mechanism"
1612 .cindex "queue runner"
1613 Exim's mechanism for retrying messages that fail to get delivered at the first
1614 attempt is the queue runner process. You must either run an Exim daemon that
1615 uses the &%-q%& option with a time interval to start queue runners at regular
1616 intervals or use some other means (such as &'cron'&) to start them. If you do
1617 not arrange for queue runners to be run, messages that fail temporarily at the
1618 first attempt will remain in your queue forever. A queue runner process works
1619 its way through the queue, one message at a time, trying each delivery that has
1620 passed its retry time.
1621 You can run several queue runners at once.
1623 Exim uses a set of configured rules to determine when next to retry the failing
1624 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1625 should give up trying to deliver to the address, at which point it generates a
1626 bounce message. If no retry rules are set for a particular host, address, and
1627 error combination, no retries are attempted, and temporary errors are treated
1632 .section "Temporary delivery failure" "SECID20"
1633 .cindex "delivery" "temporary failure"
1634 There are many reasons why a message may not be immediately deliverable to a
1635 particular address. Failure to connect to a remote machine (because it, or the
1636 connection to it, is down) is one of the most common. Temporary failures may be
1637 detected during routing as well as during the transport stage of delivery.
1638 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1639 is on a file system where the user is over quota. Exim can be configured to
1640 impose its own quotas on local mailboxes; where system quotas are set they will
1643 If a host is unreachable for a period of time, a number of messages may be
1644 waiting for it by the time it recovers, and sending them in a single SMTP
1645 connection is clearly beneficial. Whenever a delivery to a remote host is
1647 .cindex "hints database" "deferred deliveries"
1648 Exim makes a note in its hints database, and whenever a successful
1649 SMTP delivery has happened, it looks to see if any other messages are waiting
1650 for the same host. If any are found, they are sent over the same SMTP
1651 connection, subject to a configuration limit as to the maximum number in any
1656 .section "Permanent delivery failure" "SECID21"
1657 .cindex "delivery" "permanent failure"
1658 .cindex "bounce message" "when generated"
1659 When a message cannot be delivered to some or all of its intended recipients, a
1660 bounce message is generated. Temporary delivery failures turn into permanent
1661 errors when their timeout expires. All the addresses that fail in a given
1662 delivery attempt are listed in a single message. If the original message has
1663 many recipients, it is possible for some addresses to fail in one delivery
1664 attempt and others to fail subsequently, giving rise to more than one bounce
1665 message. The wording of bounce messages can be customized by the administrator.
1666 See chapter &<<CHAPemsgcust>>& for details.
1668 .cindex "&'X-Failed-Recipients:'& header line"
1669 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1670 failed addresses, for the benefit of programs that try to analyse such messages
1673 .cindex "bounce message" "recipient of"
1674 A bounce message is normally sent to the sender of the original message, as
1675 obtained from the message's envelope. For incoming SMTP messages, this is the
1676 address given in the MAIL command. However, when an address is expanded via a
1677 forward or alias file, an alternative address can be specified for delivery
1678 failures of the generated addresses. For a mailing list expansion (see section
1679 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1684 .section "Failures to deliver bounce messages" "SECID22"
1685 .cindex "bounce message" "failure to deliver"
1686 If a bounce message (either locally generated or received from a remote host)
1687 itself suffers a permanent delivery failure, the message is left in the queue,
1688 but it is frozen, awaiting the attention of an administrator. There are options
1689 that can be used to make Exim discard such failed messages, or to keep them
1690 for only a short time (see &%timeout_frozen_after%& and
1691 &%ignore_bounce_errors_after%&).
1697 . ////////////////////////////////////////////////////////////////////////////
1698 . ////////////////////////////////////////////////////////////////////////////
1700 .chapter "Building and installing Exim" "CHID3"
1701 .scindex IIDbuex "building Exim"
1703 .section "Unpacking" "SECID23"
1704 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1705 creates a directory with the name of the current release (for example,
1706 &_exim-&version()_&) into which the following files are placed:
1709 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1710 .irow &_CHANGES_& "contains a reference to where changes are &&&
1712 .irow &_LICENCE_& "the GNU General Public Licence"
1713 .irow &_Makefile_& "top-level make file"
1714 .irow &_NOTICE_& "conditions for the use of Exim"
1715 .irow &_README_& "list of files, directories and simple build &&&
1719 Other files whose names begin with &_README_& may also be present. The
1720 following subdirectories are created:
1723 .irow &_Local_& "an empty directory for local configuration files"
1724 .irow &_OS_& "OS-specific files"
1725 .irow &_doc_& "documentation files"
1726 .irow &_exim_monitor_& "source files for the Exim monitor"
1727 .irow &_scripts_& "scripts used in the build process"
1728 .irow &_src_& "remaining source files"
1729 .irow &_util_& "independent utilities"
1732 The main utility programs are contained in the &_src_& directory and are built
1733 with the Exim binary. The &_util_& directory contains a few optional scripts
1734 that may be useful to some sites.
1737 .section "Multiple machine architectures and operating systems" "SECID24"
1738 .cindex "building Exim" "multiple OS/architectures"
1739 The building process for Exim is arranged to make it easy to build binaries for
1740 a number of different architectures and operating systems from the same set of
1741 source files. Compilation does not take place in the &_src_& directory.
1742 Instead, a &'build directory'& is created for each architecture and operating
1744 .cindex "symbolic link" "to build directory"
1745 Symbolic links to the sources are installed in this directory, which is where
1746 the actual building takes place. In most cases, Exim can discover the machine
1747 architecture and operating system for itself, but the defaults can be
1748 overridden if necessary.
1749 .cindex compiler requirements
1750 .cindex compiler version
1751 A C99-capable compiler will be required for the build.
1754 .section "PCRE library" "SECTpcre"
1755 .cindex "PCRE library"
1756 Exim no longer has an embedded PCRE library as the vast majority of
1757 modern systems include PCRE as a system library, although you may need to
1758 install the PCRE package or the PCRE development package for your operating
1759 system. If your system has a normal PCRE installation the Exim build
1760 process will need no further configuration. If the library or the
1761 headers are in an unusual location you will need to either set the PCRE_LIBS
1762 and INCLUDE directives appropriately,
1763 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1764 If your operating system has no
1765 PCRE support then you will need to obtain and build the current PCRE
1766 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1767 More information on PCRE is available at &url(https://www.pcre.org/).
1769 .section "DBM libraries" "SECTdb"
1770 .cindex "DBM libraries" "discussion of"
1771 .cindex "hints database" "DBM files used for"
1772 Even if you do not use any DBM files in your configuration, Exim still needs a
1773 DBM library in order to operate, because it uses indexed files for its hints
1774 databases. Unfortunately, there are a number of DBM libraries in existence, and
1775 different operating systems often have different ones installed.
1777 .cindex "Solaris" "DBM library for"
1778 .cindex "IRIX, DBM library for"
1779 .cindex "BSD, DBM library for"
1780 .cindex "Linux, DBM library for"
1781 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1782 Linux distribution, the DBM configuration should happen automatically, and you
1783 may be able to ignore this section. Otherwise, you may have to learn more than
1784 you would like about DBM libraries from what follows.
1786 .cindex "&'ndbm'& DBM library"
1787 Licensed versions of Unix normally contain a library of DBM functions operating
1788 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1789 versions of Unix seem to vary in what they contain as standard. In particular,
1790 some early versions of Linux have no default DBM library, and different
1791 distributors have chosen to bundle different libraries with their packaged
1792 versions. However, the more recent releases seem to have standardized on the
1793 Berkeley DB library.
1795 Different DBM libraries have different conventions for naming the files they
1796 use. When a program opens a file called &_dbmfile_&, there are several
1800 A traditional &'ndbm'& implementation, such as that supplied as part of
1801 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1803 .cindex "&'gdbm'& DBM library"
1804 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1805 compatibility interface it makes two different hard links to it with names
1806 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1807 filename is used unmodified.
1809 .cindex "Berkeley DB library"
1810 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1811 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1812 programmer exactly the same as the traditional &'ndbm'& implementation.
1814 If the Berkeley package is used in its native mode, it operates on a single
1815 file called &_dbmfile_&; the programmer's interface is somewhat different to
1816 the traditional &'ndbm'& interface.
1818 To complicate things further, there are several very different versions of the
1819 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1820 2.&'x'& and 3.&'x'& were current for a while, but the latest versions when Exim last revamped support were numbered 4.&'x'&.
1821 Maintenance of some of the earlier releases has ceased. All versions of
1822 Berkeley DB could be obtained from
1823 &url(http://www.sleepycat.com/), which is now a redirect to their new owner's
1824 page with far newer versions listed.
1825 It is probably wise to plan to move your storage configurations away from
1826 Berkeley DB format, as today there are smaller and simpler alternatives more
1827 suited to Exim's usage model.
1829 .cindex "&'tdb'& DBM library"
1830 Yet another DBM library, called &'tdb'&, is available from
1831 &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
1832 operates on a single file.
1836 .cindex "DBM libraries" "configuration for building"
1837 Exim and its utilities can be compiled to use any of these interfaces. In order
1838 to use any version of the Berkeley DB package in native mode, you must set
1839 USE_DB in an appropriate configuration file (typically
1840 &_Local/Makefile_&). For example:
1844 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1845 error is diagnosed if you set more than one of these.
1847 At the lowest level, the build-time configuration sets none of these options,
1848 thereby assuming an interface of type (1). However, some operating system
1849 configuration files (for example, those for the BSD operating systems and
1850 Linux) assume type (4) by setting USE_DB as their default, and the
1851 configuration files for Cygwin set USE_GDBM. Anything you set in
1852 &_Local/Makefile_&, however, overrides these system defaults.
1854 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1855 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1856 in one of these lines:
1861 Settings like that will work if the DBM library is installed in the standard
1862 place. Sometimes it is not, and the library's header file may also not be in
1863 the default path. You may need to set INCLUDE to specify where the header
1864 file is, and to specify the path to the library more fully in DBMLIB, as in
1867 INCLUDE=-I/usr/local/include/db-4.1
1868 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1870 There is further detailed discussion about the various DBM libraries in the
1871 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1875 .section "Pre-building configuration" "SECID25"
1876 .cindex "building Exim" "pre-building configuration"
1877 .cindex "configuration for building Exim"
1878 .cindex "&_Local/Makefile_&"
1879 .cindex "&_src/EDITME_&"
1880 Before building Exim, a local configuration file that specifies options
1881 independent of any operating system has to be created with the name
1882 &_Local/Makefile_&. A template for this file is supplied as the file
1883 &_src/EDITME_&, and it contains full descriptions of all the option settings
1884 therein. These descriptions are therefore not repeated here. If you are
1885 building Exim for the first time, the simplest thing to do is to copy
1886 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1888 There are three settings that you must supply, because Exim will not build
1889 without them. They are the location of the runtime configuration file
1890 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1891 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1892 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1893 a colon-separated list of filenames; Exim uses the first of them that exists.
1895 There are a few other parameters that can be specified either at build time or
1896 at runtime, to enable the same binary to be used on a number of different
1897 machines. However, if the locations of Exim's spool directory and log file
1898 directory (if not within the spool directory) are fixed, it is recommended that
1899 you specify them in &_Local/Makefile_& instead of at runtime, so that errors
1900 detected early in Exim's execution (such as a malformed configuration file) can
1903 .cindex "content scanning" "specifying at build time"
1904 Exim's interfaces for calling virus and spam scanning software directly from
1905 access control lists are not compiled by default. If you want to include these
1906 facilities, you need to set
1908 WITH_CONTENT_SCAN=yes
1910 in your &_Local/Makefile_&. For details of the facilities themselves, see
1911 chapter &<<CHAPexiscan>>&.
1914 .cindex "&_Local/eximon.conf_&"
1915 .cindex "&_exim_monitor/EDITME_&"
1916 If you are going to build the Exim monitor, a similar configuration process is
1917 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1918 your installation and saved under the name &_Local/eximon.conf_&. If you are
1919 happy with the default settings described in &_exim_monitor/EDITME_&,
1920 &_Local/eximon.conf_& can be empty, but it must exist.
1922 This is all the configuration that is needed in straightforward cases for known
1923 operating systems. However, the building process is set up so that it is easy
1924 to override options that are set by default or by operating-system-specific
1925 configuration files, for example, to change the C compiler, which
1926 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1931 .section "Support for iconv()" "SECID26"
1932 .cindex "&[iconv()]& support"
1934 The contents of header lines in messages may be encoded according to the rules
1935 described RFC 2047. This makes it possible to transmit characters that are not
1936 in the ASCII character set, and to label them as being in a particular
1937 character set. When Exim is inspecting header lines by means of the &%$h_%&
1938 mechanism, it decodes them, and translates them into a specified character set
1939 (default is set at build time). The translation is possible only if the operating system
1940 supports the &[iconv()]& function.
1942 However, some of the operating systems that supply &[iconv()]& do not support
1943 very many conversions. The GNU &%libiconv%& library (available from
1944 &url(https://www.gnu.org/software/libiconv/)) can be installed on such
1945 systems to remedy this deficiency, as well as on systems that do not supply
1946 &[iconv()]& at all. After installing &%libiconv%&, you should add
1950 to your &_Local/Makefile_& and rebuild Exim.
1954 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1955 .cindex "TLS" "including support for TLS"
1956 .cindex "encryption" "including support for"
1957 .cindex "OpenSSL" "building Exim with"
1958 .cindex "GnuTLS" "building Exim with"
1959 Exim is usually built to support encrypted SMTP connections, using the STARTTLS
1960 command as per RFC 2487. It can also support clients that expect to
1961 start a TLS session immediately on connection to a non-standard port (see the
1962 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1965 If you want to build Exim with TLS support, you must first install either the
1966 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1969 If you do not want TLS support you should set
1973 in &_Local/Makefile_&.
1975 If OpenSSL is installed, you should set
1978 TLS_LIBS=-lssl -lcrypto
1980 in &_Local/Makefile_&. You may also need to specify the locations of the
1981 OpenSSL library and include files. For example:
1984 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1985 TLS_INCLUDE=-I/usr/local/openssl/include/
1987 .cindex "pkg-config" "OpenSSL"
1988 If you have &'pkg-config'& available, then instead you can just use:
1991 USE_OPENSSL_PC=openssl
1993 .cindex "USE_GNUTLS"
1994 If GnuTLS is installed, you should set
1997 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1999 in &_Local/Makefile_&, and again you may need to specify the locations of the
2000 library and include files. For example:
2003 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
2004 TLS_INCLUDE=-I/usr/gnu/include
2006 .cindex "pkg-config" "GnuTLS"
2007 If you have &'pkg-config'& available, then instead you can just use:
2010 USE_GNUTLS_PC=gnutls
2013 You do not need to set TLS_INCLUDE if the relevant directory is already
2014 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
2015 given in chapter &<<CHAPTLS>>&.
2020 .section "Use of tcpwrappers" "SECID27"
2022 .cindex "tcpwrappers, building Exim to support"
2023 .cindex "USE_TCP_WRAPPERS"
2024 .cindex "TCP_WRAPPERS_DAEMON_NAME"
2025 .cindex "tcp_wrappers_daemon_name"
2026 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
2027 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
2028 alternative to Exim's own checking facilities for installations that are
2029 already making use of &'tcpwrappers'& for other purposes. To do this, you
2030 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
2031 &_tcpd.h_& to be available at compile time, and also ensure that the library
2032 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
2033 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
2036 USE_TCP_WRAPPERS=yes
2037 CFLAGS=-O -I/usr/local/include
2038 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
2040 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
2041 files is &"exim"&. For example, the line
2043 exim : LOCAL 192.168.1. .friendly.domain.example
2045 in your &_/etc/hosts.allow_& file allows connections from the local host, from
2046 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
2047 All other connections are denied. The daemon name used by &'tcpwrappers'&
2048 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
2049 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
2050 configure file. Consult the &'tcpwrappers'& documentation for
2054 .section "Including support for IPv6" "SECID28"
2055 .cindex "IPv6" "including support for"
2056 Exim contains code for use on systems that have IPv6 support. Setting
2057 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
2058 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
2059 where the IPv6 support is not fully integrated into the normal include and
2062 Two different types of DNS record for handling IPv6 addresses have been
2063 defined. AAAA records (analogous to A records for IPv4) are in use, and are
2064 currently seen as the mainstream. Another record type called A6 was proposed
2065 as better than AAAA because it had more flexibility. However, it was felt to be
2066 over-complex, and its status was reduced to &"experimental"&.
2068 have a compile option for including A6 record support but this has now been
2073 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
2074 .cindex "lookup modules"
2075 .cindex "dynamic modules"
2076 .cindex ".so building"
2077 On some platforms, Exim supports not compiling all lookup types directly into
2078 the main binary, instead putting some into external modules which can be loaded
2080 This permits packagers to build Exim with support for lookups with extensive
2081 library dependencies without requiring all users to install all of those
2083 Most, but not all, lookup types can be built this way.
2085 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2086 installed; Exim will only load modules from that directory, as a security
2087 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2088 for your OS; see &_OS/Makefile-Linux_& for an example.
2089 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2090 see &_src/EDITME_& for details.
2092 Then, for each module to be loaded dynamically, define the relevant
2093 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2094 For example, this will build in lsearch but load sqlite and mysql support
2103 .section "The building process" "SECID29"
2104 .cindex "build directory"
2105 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2106 created, run &'make'& at the top level. It determines the architecture and
2107 operating system types, and creates a build directory if one does not exist.
2108 For example, on a Sun system running Solaris 8, the directory
2109 &_build-SunOS5-5.8-sparc_& is created.
2110 .cindex "symbolic link" "to source files"
2111 Symbolic links to relevant source files are installed in the build directory.
2113 If this is the first time &'make'& has been run, it calls a script that builds
2114 a make file inside the build directory, using the configuration files from the
2115 &_Local_& directory. The new make file is then passed to another instance of
2116 &'make'&. This does the real work, building a number of utility scripts, and
2117 then compiling and linking the binaries for the Exim monitor (if configured), a
2118 number of utility programs, and finally Exim itself. The command &`make
2119 makefile`& can be used to force a rebuild of the make file in the build
2120 directory, should this ever be necessary.
2122 If you have problems building Exim, check for any comments there may be in the
2123 &_README_& file concerning your operating system, and also take a look at the
2124 FAQ, where some common problems are covered.
2128 .section 'Output from &"make"&' "SECID283"
2129 The output produced by the &'make'& process for compile lines is often very
2130 unreadable, because these lines can be very long. For this reason, the normal
2131 output is suppressed by default, and instead output similar to that which
2132 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2133 each module that is being compiled or linked. However, it is still possible to
2134 get the full output, by calling &'make'& like this:
2138 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2139 command reflection in &'make'&. When you ask for the full output, it is
2140 given in addition to the short output.
2144 .section "Overriding build-time options for Exim" "SECToverride"
2145 .cindex "build-time options, overriding"
2146 The main make file that is created at the beginning of the building process
2147 consists of the concatenation of a number of files which set configuration
2148 values, followed by a fixed set of &'make'& instructions. If a value is set
2149 more than once, the last setting overrides any previous ones. This provides a
2150 convenient way of overriding defaults. The files that are concatenated are, in
2153 &_OS/Makefile-Default_&
2154 &_OS/Makefile-_&<&'ostype'&>
2156 &_Local/Makefile-_&<&'ostype'&>
2157 &_Local/Makefile-_&<&'archtype'&>
2158 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2159 &_OS/Makefile-Base_&
2161 .cindex "&_Local/Makefile_&"
2162 .cindex "building Exim" "operating system type"
2163 .cindex "building Exim" "architecture type"
2164 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2165 architecture type. &_Local/Makefile_& is required to exist, and the building
2166 process fails if it is absent. The other three &_Local_& files are optional,
2167 and are often not needed.
2169 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2170 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2171 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2172 values are used, thereby providing a means of forcing particular settings.
2173 Otherwise, the scripts try to get values from the &%uname%& command. If this
2174 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2175 of &'ad hoc'& transformations are then applied, to produce the standard names
2176 that Exim expects. You can run these scripts directly from the shell in order
2177 to find out what values are being used on your system.
2180 &_OS/Makefile-Default_& contains comments about the variables that are set
2181 therein. Some (but not all) are mentioned below. If there is something that
2182 needs changing, review the contents of this file and the contents of the make
2183 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2187 .cindex "building Exim" "overriding default settings"
2188 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2189 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2190 need to change the original files. Instead, you should make the changes by
2191 putting the new values in an appropriate &_Local_& file. For example,
2192 .cindex "Tru64-Unix build-time settings"
2193 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2194 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2195 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2196 called with the option &%-std1%&, to make it recognize some of the features of
2197 Standard C that Exim uses. (Most other compilers recognize Standard C by
2198 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2199 containing the lines
2204 If you are compiling for just one operating system, it may be easier to put
2205 these lines directly into &_Local/Makefile_&.
2207 Keeping all your local configuration settings separate from the distributed
2208 files makes it easy to transfer them to new versions of Exim simply by copying
2209 the contents of the &_Local_& directory.
2212 .cindex "NIS lookup type" "including support for"
2213 .cindex "NIS+ lookup type" "including support for"
2214 .cindex "LDAP" "including support for"
2215 .cindex "lookup" "inclusion in binary"
2216 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2217 lookup, but not all systems have these components installed, so the default is
2218 not to include the relevant code in the binary. All the different kinds of file
2219 and database lookup that Exim supports are implemented as separate code modules
2220 which are included only if the relevant compile-time options are set. In the
2221 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2227 and similar settings apply to the other lookup types. They are all listed in
2228 &_src/EDITME_&. In many cases the relevant include files and interface
2229 libraries need to be installed before compiling Exim.
2230 .cindex "cdb" "including support for"
2231 However, there are some optional lookup types (such as cdb) for which
2232 the code is entirely contained within Exim, and no external include
2233 files or libraries are required. When a lookup type is not included in the
2234 binary, attempts to configure Exim to use it cause runtime configuration
2237 .cindex "pkg-config" "lookups"
2238 .cindex "pkg-config" "authenticators"
2239 Many systems now use a tool called &'pkg-config'& to encapsulate information
2240 about how to compile against a library; Exim has some initial support for
2241 being able to use pkg-config for lookups and authenticators. For any given
2242 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2243 variable with the &`_PC`& suffix in the name and assign as the value the
2244 name of the package to be queried. The results of querying via the
2245 &'pkg-config'& command will be added to the appropriate Makefile variables
2246 with &`+=`& directives, so your version of &'make'& will need to support that
2247 syntax. For instance:
2250 LOOKUP_SQLITE_PC=sqlite3
2252 AUTH_GSASL_PC=libgsasl
2253 AUTH_HEIMDAL_GSSAPI=yes
2254 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2257 .cindex "Perl" "including support for"
2258 Exim can be linked with an embedded Perl interpreter, allowing Perl
2259 subroutines to be called during string expansion. To enable this facility,
2263 must be defined in &_Local/Makefile_&. Details of this facility are given in
2264 chapter &<<CHAPperl>>&.
2266 .cindex "X11 libraries, location of"
2267 The location of the X11 libraries is something that varies a lot between
2268 operating systems, and there may be different versions of X11 to cope
2269 with. Exim itself makes no use of X11, but if you are compiling the Exim
2270 monitor, the X11 libraries must be available.
2271 The following three variables are set in &_OS/Makefile-Default_&:
2274 XINCLUDE=-I$(X11)/include
2275 XLFLAGS=-L$(X11)/lib
2277 These are overridden in some of the operating-system configuration files. For
2278 example, in &_OS/Makefile-SunOS5_& there is
2281 XINCLUDE=-I$(X11)/include
2282 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2284 If you need to override the default setting for your operating system, place a
2285 definition of all three of these variables into your
2286 &_Local/Makefile-<ostype>_& file.
2289 If you need to add any extra libraries to the link steps, these can be put in a
2290 variable called EXTRALIBS, which appears in all the link commands, but by
2291 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2292 command for linking the main Exim binary, and not for any associated utilities.
2294 .cindex "DBM libraries" "configuration for building"
2295 There is also DBMLIB, which appears in the link commands for binaries that
2296 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2297 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2298 binary, and which can be used, for example, to include additional X11
2301 .cindex "configuration file" "editing"
2302 The make file copes with rebuilding Exim correctly if any of the configuration
2303 files are edited. However, if an optional configuration file is deleted, it is
2304 necessary to touch the associated non-optional file (that is,
2305 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2308 .section "OS-specific header files" "SECID30"
2310 .cindex "building Exim" "OS-specific C header files"
2311 The &_OS_& directory contains a number of files with names of the form
2312 &_os.h-<ostype>_&. These are system-specific C header files that should not
2313 normally need to be changed. There is a list of macro settings that are
2314 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2315 are porting Exim to a new operating system.
2319 .section "Overriding build-time options for the monitor" "SECID31"
2320 .cindex "building Eximon"
2321 A similar process is used for overriding things when building the Exim monitor,
2322 where the files that are involved are
2324 &_OS/eximon.conf-Default_&
2325 &_OS/eximon.conf-_&<&'ostype'&>
2326 &_Local/eximon.conf_&
2327 &_Local/eximon.conf-_&<&'ostype'&>
2328 &_Local/eximon.conf-_&<&'archtype'&>
2329 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2331 .cindex "&_Local/eximon.conf_&"
2332 As with Exim itself, the final three files need not exist, and in this case the
2333 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2334 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2335 variables of the same name, preceded by EXIMON_. For example, setting
2336 EXIMON_LOG_DEPTH in the environment overrides the value of
2337 LOG_DEPTH at runtime.
2341 .section "Installing Exim binaries and scripts" "SECID32"
2342 .cindex "installing Exim"
2343 .cindex "BIN_DIRECTORY"
2344 The command &`make install`& runs the &(exim_install)& script with no
2345 arguments. The script copies binaries and utility scripts into the directory
2346 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2347 .cindex "setuid" "installing Exim with"
2348 The install script copies files only if they are newer than the files they are
2349 going to replace. The Exim binary is required to be owned by root and have the
2350 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2351 install`& as root so that it can set up the Exim binary in this way. However, in
2352 some special situations (for example, if a host is doing no local deliveries)
2353 it may be possible to run Exim without making the binary setuid root (see
2354 chapter &<<CHAPsecurity>>& for details).
2356 .cindex "CONFIGURE_FILE"
2357 Exim's runtime configuration file is named by the CONFIGURE_FILE setting
2358 in &_Local/Makefile_&. If this names a single file, and the file does not
2359 exist, the default configuration file &_src/configure.default_& is copied there
2360 by the installation script. If a runtime configuration file already exists, it
2361 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2362 alternative files, no default is installed.
2364 .cindex "system aliases file"
2365 .cindex "&_/etc/aliases_&"
2366 One change is made to the default configuration file when it is installed: the
2367 default configuration contains a router that references a system aliases file.
2368 The path to this file is set to the value specified by
2369 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2370 If the system aliases file does not exist, the installation script creates it,
2371 and outputs a comment to the user.
2373 The created file contains no aliases, but it does contain comments about the
2374 aliases a site should normally have. Mail aliases have traditionally been
2375 kept in &_/etc/aliases_&. However, some operating systems are now using
2376 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2377 Exim's configuration if necessary.
2379 The default configuration uses the local host's name as the only local domain,
2380 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2381 running as the local user. System aliases and &_.forward_& files in users' home
2382 directories are supported, but no NIS or NIS+ support is configured. Domains
2383 other than the name of the local host are routed using the DNS, with delivery
2386 It is possible to install Exim for special purposes (such as building a binary
2387 distribution) in a private part of the file system. You can do this by a
2390 make DESTDIR=/some/directory/ install
2392 This has the effect of pre-pending the specified directory to all the file
2393 paths, except the name of the system aliases file that appears in the default
2394 configuration. (If a default alias file is created, its name &'is'& modified.)
2395 For backwards compatibility, ROOT is used if DESTDIR is not set,
2396 but this usage is deprecated.
2398 .cindex "installing Exim" "what is not installed"
2399 Running &'make install'& does not copy the Exim 4 conversion script
2400 &'convert4r4'&. You will probably run this only once if you are
2401 upgrading from Exim 3. None of the documentation files in the &_doc_&
2402 directory are copied, except for the info files when you have set
2403 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2405 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2406 to their names. The Exim binary itself, however, is handled differently. It is
2407 installed under a name that includes the version number and the compile number,
2408 for example, &_exim-&version()-1_&. The script then arranges for a symbolic link
2409 called &_exim_& to point to the binary. If you are updating a previous version
2410 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2411 from the directory (as seen by other processes).
2413 .cindex "installing Exim" "testing the script"
2414 If you want to see what the &'make install'& will do before running it for
2415 real, you can pass the &%-n%& option to the installation script by this
2418 make INSTALL_ARG=-n install
2420 The contents of the variable INSTALL_ARG are passed to the installation
2421 script. You do not need to be root to run this test. Alternatively, you can run
2422 the installation script directly, but this must be from within the build
2423 directory. For example, from the top-level Exim directory you could use this
2426 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2428 .cindex "installing Exim" "install script options"
2429 There are two other options that can be supplied to the installation script.
2432 &%-no_chown%& bypasses the call to change the owner of the installed binary
2433 to root, and the call to make it a setuid binary.
2435 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2439 INSTALL_ARG can be used to pass these options to the script. For example:
2441 make INSTALL_ARG=-no_symlink install
2443 The installation script can also be given arguments specifying which files are
2444 to be copied. For example, to install just the Exim binary, and nothing else,
2445 without creating the symbolic link, you could use:
2447 make INSTALL_ARG='-no_symlink exim' install
2452 .section "Installing info documentation" "SECTinsinfdoc"
2453 .cindex "installing Exim" "&'info'& documentation"
2454 Not all systems use the GNU &'info'& system for documentation, and for this
2455 reason, the Texinfo source of Exim's documentation is not included in the main
2456 distribution. Instead it is available separately from the FTP site (see section
2459 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2460 source of the documentation is found in the source tree, running &`make
2461 install`& automatically builds the info files and installs them.
2465 .section "Setting up the spool directory" "SECID33"
2466 .cindex "spool directory" "creating"
2467 When it starts up, Exim tries to create its spool directory if it does not
2468 exist. The Exim uid and gid are used for the owner and group of the spool
2469 directory. Sub-directories are automatically created in the spool directory as
2475 .section "Testing" "SECID34"
2476 .cindex "testing" "installation"
2477 Having installed Exim, you can check that the runtime configuration file is
2478 syntactically valid by running the following command, which assumes that the
2479 Exim binary directory is within your PATH environment variable:
2483 If there are any errors in the configuration file, Exim outputs error messages.
2484 Otherwise it outputs the version number and build date,
2485 the DBM library that is being used, and information about which drivers and
2486 other optional code modules are included in the binary.
2487 Some simple routing tests can be done by using the address testing option. For
2490 &`exim -bt`& <&'local username'&>
2492 should verify that it recognizes a local mailbox, and
2494 &`exim -bt`& <&'remote address'&>
2496 a remote one. Then try getting it to deliver mail, both locally and remotely.
2497 This can be done by passing messages directly to Exim, without going through a
2498 user agent. For example:
2500 exim -v postmaster@your.domain.example
2501 From: user@your.domain.example
2502 To: postmaster@your.domain.example
2503 Subject: Testing Exim
2505 This is a test message.
2508 The &%-v%& option causes Exim to output some verification of what it is doing.
2509 In this case you should see copies of three log lines, one for the message's
2510 arrival, one for its delivery, and one containing &"Completed"&.
2512 .cindex "delivery" "problems with"
2513 If you encounter problems, look at Exim's log files (&'mainlog'& and
2514 &'paniclog'&) to see if there is any relevant information there. Another source
2515 of information is running Exim with debugging turned on, by specifying the
2516 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2517 with debugging turned on by a command of the form
2519 &`exim -d -M`& <&'exim-message-id'&>
2521 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2522 produces rather a lot of output, but you can cut this down to specific areas.
2523 For example, if you use &%-d-all+route%& only the debugging information
2524 relevant to routing is included. (See the &%-d%& option in chapter
2525 &<<CHAPcommandline>>& for more details.)
2527 .cindex '&"sticky"& bit'
2528 .cindex "lock files"
2529 One specific problem that has shown up on some sites is the inability to do
2530 local deliveries into a shared mailbox directory, because it does not have the
2531 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2532 writing to a mailbox file, and if it cannot create the lock file, the delivery
2533 is deferred. You can get round this either by setting the &"sticky bit"& on the
2534 directory, or by setting a specific group for local deliveries and allowing
2535 that group to create files in the directory (see the comments above the
2536 &(local_delivery)& transport in the default configuration file). Another
2537 approach is to configure Exim not to use lock files, but just to rely on
2538 &[fcntl()]& locking instead. However, you should do this only if all user
2539 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2540 see chapter &<<CHAPappendfile>>&.
2542 One thing that cannot be tested on a system that is already running an MTA is
2543 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2544 &%-oX%& option can be used to run an Exim daemon that listens on some other
2545 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2546 &'exim_checkaccess'& utility can be used to check out policy controls on
2549 Testing a new version on a system that is already running Exim can most easily
2550 be done by building a binary with a different CONFIGURE_FILE setting. From
2551 within the runtime configuration, all other file and directory names
2552 that Exim uses can be altered, in order to keep it entirely clear of the
2556 .section "Replacing another MTA with Exim" "SECID35"
2557 .cindex "replacing another MTA"
2558 Building and installing Exim for the first time does not of itself put it in
2559 general use. The name by which the system's MTA is called by mail user agents
2560 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2561 operating system), and it is necessary to make this name point to the &'exim'&
2562 binary in order to get the user agents to pass messages to Exim. This is
2563 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2564 or &_/usr/lib/sendmail_&
2565 .cindex "symbolic link" "to &'exim'& binary"
2566 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2567 privilege and executable status from the old MTA. It is then necessary to stop
2568 and restart the mailer daemon, if one is running.
2570 .cindex "FreeBSD, MTA indirection"
2571 .cindex "&_/etc/mail/mailer.conf_&"
2572 Some operating systems have introduced alternative ways of switching MTAs. For
2573 example, if you are running FreeBSD, you need to edit the file
2574 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2575 described. A typical example of the contents of this file for running Exim is
2578 sendmail /usr/exim/bin/exim
2579 send-mail /usr/exim/bin/exim
2580 mailq /usr/exim/bin/exim -bp
2581 newaliases /usr/bin/true
2583 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2584 your Exim installation is &"live"&. Check it by sending a message from your
2585 favourite user agent.
2587 You should consider what to tell your users about the change of MTA. Exim may
2588 have different capabilities to what was previously running, and there are
2589 various operational differences such as the text of messages produced by
2590 command line options and in bounce messages. If you allow your users to make
2591 use of Exim's filtering capabilities, you should make the document entitled
2592 &'Exim's interface to mail filtering'& available to them.
2596 .section "Upgrading Exim" "SECID36"
2597 .cindex "upgrading Exim"
2598 If you are already running Exim on your host, building and installing a new
2599 version automatically makes it available to MUAs, or any other programs that
2600 call the MTA directly. However, if you are running an Exim daemon, you do need
2601 .cindex restart "on HUP signal"
2602 .cindex signal "HUP, to restart"
2603 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2604 new binary. You do not need to stop processing mail in order to install a new
2605 version of Exim. The install script does not modify an existing runtime
2611 .section "Stopping the Exim daemon on Solaris" "SECID37"
2612 .cindex "Solaris" "stopping Exim on"
2613 The standard command for stopping the mailer daemon on Solaris is
2615 /etc/init.d/sendmail stop
2617 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2618 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2619 for the text &"sendmail"&; this is not present because the actual program name
2620 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2621 solution is to replace the line that finds the process id with something like
2623 pid=`cat /var/spool/exim/exim-daemon.pid`
2625 to obtain the daemon's pid directly from the file that Exim saves it in.
2627 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2628 still be received from local processes, and if automatic delivery is configured
2629 (the normal case), deliveries will still occur.
2634 . ////////////////////////////////////////////////////////////////////////////
2635 . ////////////////////////////////////////////////////////////////////////////
2637 .chapter "The Exim command line" "CHAPcommandline"
2638 .scindex IIDclo1 "command line" "options"
2639 .scindex IIDclo2 "options" "command line"
2640 Exim's command line takes the standard Unix form of a sequence of options,
2641 each starting with a hyphen character, followed by a number of arguments. The
2642 options are compatible with the main options of Sendmail, and there are also
2643 some additional options, some of which are compatible with Smail 3. Certain
2644 combinations of options do not make sense, and provoke an error if used.
2645 The form of the arguments depends on which options are set.
2648 .section "Setting options by program name" "SECID38"
2650 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2651 were present before any other options.
2652 The &%-bp%& option requests a listing of the contents of the mail queue on the
2654 This feature is for compatibility with some systems that contain a command of
2655 that name in one of the standard libraries, symbolically linked to
2656 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2659 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2660 were present before any other options, for compatibility with Smail. The
2661 &%-bS%& option is used for reading in a number of messages in batched SMTP
2665 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2666 &%-oee%& options were present before any other options, for compatibility with
2667 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2670 .cindex "queue runner"
2671 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2672 were present before any other options, for compatibility with Smail. The &%-q%&
2673 option causes a single queue runner process to be started.
2675 .cindex "&'newaliases'&"
2676 .cindex "alias file" "building"
2677 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2678 If Exim is called under the name &'newaliases'& it behaves as if the option
2679 &%-bi%& were present before any other options, for compatibility with Sendmail.
2680 This option is used for rebuilding Sendmail's alias file. Exim does not have
2681 the concept of a single alias file, but can be configured to run a given
2682 command if called with the &%-bi%& option.
2685 .section "Trusted and admin users" "SECTtrustedadmin"
2686 Some Exim options are available only to &'trusted users'& and others are
2687 available only to &'admin users'&. In the description below, the phrases &"Exim
2688 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2689 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2690 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2693 .cindex "trusted users" "definition of"
2694 .cindex "user" "trusted definition of"
2695 The trusted users are root, the Exim user, any user listed in the
2696 &%trusted_users%& configuration option, and any user whose current group or any
2697 supplementary group is one of those listed in the &%trusted_groups%&
2698 configuration option. Note that the Exim group is not automatically trusted.
2700 .cindex '&"From"& line'
2701 .cindex "envelope from"
2702 .cindex "envelope sender"
2703 Trusted users are always permitted to use the &%-f%& option or a leading
2704 &"From&~"& line to specify the envelope sender of a message that is passed to
2705 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2706 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2707 users to set envelope senders.
2711 For a trusted user, there is never any check on the contents of the &'From:'&
2712 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2713 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2715 Trusted users may also specify a host name, host address, interface address,
2716 protocol name, ident value, and authentication data when submitting a message
2717 locally. Thus, they are able to insert messages into Exim's queue locally that
2718 have the characteristics of messages received from a remote host. Untrusted
2719 users may in some circumstances use &%-f%&, but can never set the other values
2720 that are available to trusted users.
2722 .cindex "user" "admin definition of"
2723 .cindex "admin user" "definition of"
2724 The admin users are root, the Exim user, and any user that is a member of the
2725 Exim group or of any group listed in the &%admin_groups%& configuration option.
2726 The current group does not have to be one of these groups.
2728 Admin users are permitted to list the queue, and to carry out certain
2729 operations on messages, for example, to force delivery failures. It is also
2730 necessary to be an admin user in order to see the full information provided by
2731 the Exim monitor, and full debugging output.
2733 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2734 Exim to attempt delivery of messages on its queue is restricted to admin users.
2735 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2736 option false (that is, specifying &%no_prod_requires_admin%&).
2738 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2739 is restricted to admin users unless &%queue_list_requires_admin%& is set
2744 &*Warning*&: If you configure your system so that admin users are able to
2745 edit Exim's configuration file, you are giving those users an easy way of
2746 getting root. There is further discussion of this issue at the start of chapter
2752 .section "Command line options" "SECID39"
2753 Exim's command line options are described in alphabetical order below. If none
2754 of the options that specifies a specific action (such as starting the daemon or
2755 a queue runner, or testing an address, or receiving a message in a specific
2756 format, or listing the queue) are present, and there is at least one argument
2757 on the command line, &%-bm%& (accept a local message on the standard input,
2758 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2759 outputs a brief message about itself and exits.
2761 . ////////////////////////////////////////////////////////////////////////////
2762 . Insert a stylized XML comment here, to identify the start of the command line
2763 . options. This is for the benefit of the Perl script that automatically
2764 . creates a man page for the options.
2765 . ////////////////////////////////////////////////////////////////////////////
2768 <!-- === Start of command line options === -->
2775 .cindex "options" "command line; terminating"
2776 This is a pseudo-option whose only purpose is to terminate the options and
2777 therefore to cause subsequent command line items to be treated as arguments
2778 rather than options, even if they begin with hyphens.
2781 .oindex "&%--help%&"
2782 This option causes Exim to output a few sentences stating what it is.
2783 The same output is generated if the Exim binary is called with no options and
2786 .vitem &%--version%&
2787 .oindex "&%--version%&"
2788 This option is an alias for &%-bV%& and causes version information to be
2795 These options are used by Sendmail for selecting configuration files and are
2798 .vitem &%-B%&<&'type'&>
2800 .cindex "8-bit characters"
2801 .cindex "Sendmail compatibility" "8-bit characters"
2802 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2803 clean; it ignores this option.
2808 .cindex "SMTP" "listener"
2809 .cindex "queue runner"
2810 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2811 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2812 that the daemon should also initiate periodic queue runs.
2814 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2815 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2816 disconnect from the controlling terminal. When running this way, it can be
2817 stopped by pressing ctrl-C.
2819 By default, Exim listens for incoming connections to the standard SMTP port on
2820 all the host's running interfaces. However, it is possible to listen on other
2821 ports, on multiple ports, and only on specific interfaces. Chapter
2822 &<<CHAPinterfaces>>& contains a description of the options that control this.
2824 When a listening daemon
2825 .cindex "daemon" "process id (pid)"
2826 .cindex "pid (process id)" "of daemon"
2827 is started without the use of &%-oX%& (that is, without overriding the normal
2828 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2829 in Exim's spool directory. This location can be overridden by setting
2830 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2833 When &%-oX%& is used on the command line to start a listening daemon, the
2834 process id is not written to the normal pid file path. However, &%-oP%& can be
2835 used to specify a path on the command line if a pid file is required.
2839 .cindex restart "on HUP signal"
2840 .cindex signal "HUP, to restart"
2841 .cindex "daemon" "restarting"
2842 .cindex signal "to reload configuration"
2843 .cindex daemon "reload configuration"
2844 .cindex reload configuration
2845 can be used to cause the daemon to re-execute itself. This should be done
2846 whenever Exim's configuration file, or any file that is incorporated into it by
2847 means of the &%.include%& facility, is changed, and also whenever a new version
2848 of Exim is installed. It is not necessary to do this when other files that are
2849 referenced from the configuration (for example, alias files) are changed,
2850 because these are reread each time they are used.
2854 This option has the same effect as &%-bd%& except that it never disconnects
2855 from the controlling terminal, even when no debugging is specified.
2859 .cindex "testing" "string expansion"
2860 .cindex "expansion" "testing"
2861 Run Exim in expansion testing mode. Exim discards its root privilege, to
2862 prevent ordinary users from using this mode to read otherwise inaccessible
2863 files. If no arguments are given, Exim runs interactively, prompting for lines
2864 of data. Otherwise, it processes each argument in turn.
2866 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2867 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2868 used without command line arguments. If successful, it uses the &[readline()]&
2869 function, which provides extensive line-editing facilities, for reading the
2870 test data. A line history is supported.
2872 Long expansion expressions can be split over several lines by using backslash
2873 continuations. As in Exim's runtime configuration, white space at the start of
2874 continuation lines is ignored. Each argument or data line is passed through the
2875 string expansion mechanism, and the result is output. Variable values from the
2876 configuration file (for example, &$qualify_domain$&) are available, but no
2877 message-specific values (such as &$message_exim_id$&) are set, because no message
2878 is being processed (but see &%-bem%& and &%-Mset%&).
2880 &*Note*&: If you use this mechanism to test lookups, and you change the data
2881 files or databases you are using, you must exit and restart Exim before trying
2882 the same lookup again. Otherwise, because each Exim process caches the results
2883 of lookups, you will just get the same result as before.
2885 Macro processing is done on lines before string-expansion: new macros can be
2886 defined and macros will be expanded.
2887 Because macros in the config file are often used for secrets, those are only
2888 available to admin users.
2890 .vitem &%-bem%&&~<&'filename'&>
2892 .cindex "testing" "string expansion"
2893 .cindex "expansion" "testing"
2894 This option operates like &%-be%& except that it must be followed by the name
2895 of a file. For example:
2897 exim -bem /tmp/testmessage
2899 The file is read as a message (as if receiving a locally-submitted non-SMTP
2900 message) before any of the test expansions are done. Thus, message-specific
2901 variables such as &$message_size$& and &$header_from:$& are available. However,
2902 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2903 recipients are read from the headers in the normal way, and are shown in the
2904 &$recipients$& variable. Note that recipients cannot be given on the command
2905 line, because further arguments are taken as strings to expand (just like
2908 .vitem &%-bF%&&~<&'filename'&>
2910 .cindex "system filter" "testing"
2911 .cindex "testing" "system filter"
2912 This option is the same as &%-bf%& except that it assumes that the filter being
2913 tested is a system filter. The additional commands that are available only in
2914 system filters are recognized.
2916 .vitem &%-bf%&&~<&'filename'&>
2918 .cindex "filter" "testing"
2919 .cindex "testing" "filter file"
2920 .cindex "forward file" "testing"
2921 .cindex "testing" "forward file"
2922 .cindex "Sieve filter" "testing"
2923 This option runs Exim in user filter testing mode; the file is the filter file
2924 to be tested, and a test message must be supplied on the standard input. If
2925 there are no message-dependent tests in the filter, an empty file can be
2928 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2929 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2930 filter and a user filter in the same run. For example:
2932 exim -bF /system/filter -bf /user/filter </test/message
2934 This is helpful when the system filter adds header lines or sets filter
2935 variables that are used by the user filter.
2937 If the test filter file does not begin with one of the special lines
2942 it is taken to be a normal &_.forward_& file, and is tested for validity under
2943 that interpretation. See sections &<<SECTitenonfilred>>& to
2944 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2947 The result of an Exim command that uses &%-bf%&, provided no errors are
2948 detected, is a list of the actions that Exim would try to take if presented
2949 with the message for real. More details of filter testing are given in the
2950 separate document entitled &'Exim's interfaces to mail filtering'&.
2952 When testing a filter file,
2953 .cindex "&""From""& line"
2954 .cindex "envelope from"
2955 .cindex "envelope sender"
2956 .oindex "&%-f%&" "for filter testing"
2957 the envelope sender can be set by the &%-f%& option,
2958 or by a &"From&~"& line at the start of the test message. Various parameters
2959 that would normally be taken from the envelope recipient address of the message
2960 can be set by means of additional command line options (see the next four
2963 .vitem &%-bfd%&&~<&'domain'&>
2965 .vindex "&$qualify_domain$&"
2966 This sets the domain of the recipient address when a filter file is being
2967 tested by means of the &%-bf%& option. The default is the value of
2970 .vitem &%-bfl%&&~<&'local&~part'&>
2972 This sets the local part of the recipient address when a filter file is being
2973 tested by means of the &%-bf%& option. The default is the username of the
2974 process that calls Exim. A local part should be specified with any prefix or
2975 suffix stripped, because that is how it appears to the filter when a message is
2976 actually being delivered.
2978 .vitem &%-bfp%&&~<&'prefix'&>
2980 .cindex affix "filter testing"
2981 This sets the prefix of the local part of the recipient address when a filter
2982 file is being tested by means of the &%-bf%& option. The default is an empty
2985 .vitem &%-bfs%&&~<&'suffix'&>
2987 .cindex affix "filter testing"
2988 This sets the suffix of the local part of the recipient address when a filter
2989 file is being tested by means of the &%-bf%& option. The default is an empty
2992 .vitem &%-bh%&&~<&'IP&~address'&>
2994 .cindex "testing" "incoming SMTP"
2995 .cindex "SMTP" "testing incoming"
2996 .cindex "testing" "relay control"
2997 .cindex "relaying" "testing configuration"
2998 .cindex "policy control" "testing"
2999 .cindex "debugging" "&%-bh%& option"
3000 This option runs a fake SMTP session as if from the given IP address, using the
3001 standard input and output. The IP address may include a port number at the end,
3002 after a full stop. For example:
3004 exim -bh 10.9.8.7.1234
3005 exim -bh fe80::a00:20ff:fe86:a061.5678
3007 When an IPv6 address is given, it is converted into canonical form. In the case
3008 of the second example above, the value of &$sender_host_address$& after
3009 conversion to the canonical form is
3010 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
3012 Comments as to what is going on are written to the standard error file. These
3013 include lines beginning with &"LOG"& for anything that would have been logged.
3014 This facility is provided for testing configuration options for incoming
3015 messages, to make sure they implement the required policy. For example, you can
3016 test your relay controls using &%-bh%&.
3020 You can test features of the configuration that rely on ident (RFC 1413)
3021 information by using the &%-oMt%& option. However, Exim cannot actually perform
3022 an ident callout when testing using &%-bh%& because there is no incoming SMTP
3025 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
3026 are also skipped when testing using &%-bh%&. If you want these callouts to
3027 occur, use &%-bhc%& instead.
3029 Messages supplied during the testing session are discarded, and nothing is
3030 written to any of the real log files. There may be pauses when DNS (and other)
3031 lookups are taking place, and of course these may time out. The &%-oMi%& option
3032 can be used to specify a specific IP interface and port if this is important,
3033 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
3034 session were authenticated.
3036 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
3037 output just states whether a given recipient address from a given host is
3038 acceptable or not. See section &<<SECTcheckaccess>>&.
3040 Features such as authentication and encryption, where the client input is not
3041 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
3042 specialized SMTP test program such as
3043 &url(https://www.jetmore.org/john/code/swaks/,swaks).
3045 .vitem &%-bhc%&&~<&'IP&~address'&>
3047 This option operates in the same way as &%-bh%&, except that address
3048 verification callouts are performed if required. This includes consulting and
3049 updating the callout cache database.
3053 .cindex "alias file" "building"
3054 .cindex "building alias file"
3055 .cindex "Sendmail compatibility" "&%-bi%& option"
3056 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
3057 Exim does not have the concept of a single alias file, and so it cannot mimic
3058 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
3059 tend to appear in various scripts such as NIS make files, so the option must be
3062 If &%-bi%& is encountered, the command specified by the &%bi_command%&
3063 configuration option is run, under the uid and gid of the caller of Exim. If
3064 the &%-oA%& option is used, its value is passed to the command as an argument.
3065 The command set by &%bi_command%& may not contain arguments. The command can
3066 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
3067 if this is required. If the &%bi_command%& option is not set, calling Exim with
3070 . // Keep :help first, then the rest in alphabetical order
3072 .oindex "&%-bI:help%&"
3073 .cindex "querying exim information"
3074 We shall provide various options starting &`-bI:`& for querying Exim for
3075 information. The output of many of these will be intended for machine
3076 consumption. This one is not. The &%-bI:help%& option asks Exim for a
3077 synopsis of supported options beginning &`-bI:`&. Use of any of these
3078 options shall cause Exim to exit after producing the requested output.
3081 .oindex "&%-bI:dscp%&"
3082 .cindex "DSCP" "values"
3083 This option causes Exim to emit an alphabetically sorted list of all
3084 recognised DSCP names.
3086 .vitem &%-bI:sieve%&
3087 .oindex "&%-bI:sieve%&"
3088 .cindex "Sieve filter" "capabilities"
3089 This option causes Exim to emit an alphabetically sorted list of all supported
3090 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3091 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3092 &`SIEVE`& capability response line. As the precise list may depend upon
3093 compile-time build options, which this option will adapt to, this is the only
3094 way to guarantee a correct response.
3098 .cindex "local message reception"
3099 This option runs an Exim receiving process that accepts an incoming,
3100 locally-generated message on the standard input. The recipients are given as the
3101 command arguments (except when &%-t%& is also present &-- see below). Each
3102 argument can be a comma-separated list of RFC 2822 addresses. This is the
3103 default option for selecting the overall action of an Exim call; it is assumed
3104 if no other conflicting option is present.
3106 If any addresses in the message are unqualified (have no domain), they are
3107 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3108 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3109 suppressing this for special cases.
3111 Policy checks on the contents of local messages can be enforced by means of
3112 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3114 .cindex "return code" "for &%-bm%&"
3115 The return code is zero if the message is successfully accepted. Otherwise, the
3116 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3119 .cindex "message" "format"
3120 .cindex "format" "message"
3121 .cindex "&""From""& line"
3122 .cindex "UUCP" "&""From""& line"
3123 .cindex "Sendmail compatibility" "&""From""& line"
3124 of the message must be as defined in RFC 2822, except that, for
3125 compatibility with Sendmail and Smail, a line in one of the forms
3127 From sender Fri Jan 5 12:55 GMT 1997
3128 From sender Fri, 5 Jan 97 12:55:01
3130 (with the weekday optional, and possibly with additional text after the date)
3131 is permitted to appear at the start of the message. There appears to be no
3132 authoritative specification of the format of this line. Exim recognizes it by
3133 matching against the regular expression defined by the &%uucp_from_pattern%&
3134 option, which can be changed if necessary.
3136 .oindex "&%-f%&" "overriding &""From""& line"
3137 The specified sender is treated as if it were given as the argument to the
3138 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3139 preference to the address taken from the message. The caller of Exim must be a
3140 trusted user for the sender of a message to be set in this way.
3142 .vitem &%-bmalware%&&~<&'filename'&>
3143 .oindex "&%-bmalware%&"
3144 .cindex "testing", "malware"
3145 .cindex "malware scan test"
3146 This debugging option causes Exim to scan the given file or directory
3147 (depending on the used scanner interface),
3148 using the malware scanning framework. The option of &%av_scanner%& influences
3149 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3150 the expansion should have defaults which apply to this invocation. ACLs are
3151 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3152 will never be populated and &%-bmalware%& will fail.
3154 Exim will have changed working directory before resolving the filename, so
3155 using fully qualified pathnames is advisable. Exim will be running as the Exim
3156 user when it tries to open the file, rather than as the invoking user.
3157 This option requires admin privileges.
3159 The &%-bmalware%& option will not be extended to be more generally useful,
3160 there are better tools for file-scanning. This option exists to help
3161 administrators verify their Exim and AV scanner configuration.
3165 .cindex "address qualification, suppressing"
3166 By default, Exim automatically qualifies unqualified addresses (those
3167 without domains) that appear in messages that are submitted locally (that
3168 is, not over TCP/IP). This qualification applies both to addresses in
3169 envelopes, and addresses in header lines. Sender addresses are qualified using
3170 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3171 defaults to the value of &%qualify_domain%&).
3173 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3174 being used to re-submit messages that originally came from remote hosts after
3175 content scanning, you probably do not want to qualify unqualified addresses in
3176 header lines. (Such lines will be present only if you have not enabled a header
3177 syntax check in the appropriate ACL.)
3179 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3180 messages that originate on the local host. When this is used, unqualified
3181 addresses in the envelope provoke errors (causing message rejection) and
3182 unqualified addresses in header lines are left alone.
3187 .cindex "configuration options" "extracting"
3188 .cindex "options" "configuration &-- extracting"
3189 If this option is given with no arguments, it causes the values of all Exim's
3190 main configuration options to be written to the standard output. The values
3191 of one or more specific options can be requested by giving their names as
3192 arguments, for example:
3194 exim -bP qualify_domain hold_domains
3196 .cindex "hiding configuration option values"
3197 .cindex "configuration options" "hiding value of"
3198 .cindex "options" "hiding value of"
3199 However, any option setting that is preceded by the word &"hide"& in the
3200 configuration file is not shown in full, except to an admin user. For other
3201 users, the output is as in this example:
3203 mysql_servers = <value not displayable>
3205 If &%config%& is given as an argument, the config is
3206 output, as it was parsed, any include file resolved, any comment removed.
3208 If &%config_file%& is given as an argument, the name of the runtime
3209 configuration file is output. (&%configure_file%& works too, for
3210 backward compatibility.)
3211 If a list of configuration files was supplied, the value that is output here
3212 is the name of the file that was actually used.
3214 .cindex "options" "hiding name of"
3215 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3216 name will not be output.
3218 .cindex "daemon" "process id (pid)"
3219 .cindex "pid (process id)" "of daemon"
3220 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3221 directories where log files and daemon pid files are written are output,
3222 respectively. If these values are unset, log files are written in a
3223 sub-directory of the spool directory called &%log%&, and the pid file is
3224 written directly into the spool directory.
3226 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3228 exim -bP +local_domains
3230 it searches for a matching named list of any type (domain, host, address, or
3231 local part) and outputs what it finds.
3233 .cindex "options" "router &-- extracting"
3234 .cindex "options" "transport &-- extracting"
3235 .cindex "options" "authenticator &-- extracting"
3236 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3237 followed by the name of an appropriate driver instance, the option settings for
3238 that driver are output. For example:
3240 exim -bP transport local_delivery
3242 The generic driver options are output first, followed by the driver's private
3243 options. A list of the names of drivers of a particular type can be obtained by
3244 using one of the words &%router_list%&, &%transport_list%&, or
3245 &%authenticator_list%&, and a complete list of all drivers with their option
3246 settings can be obtained by using &%routers%&, &%transports%&, or
3249 .cindex "environment"
3250 If &%environment%& is given as an argument, the set of environment
3251 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3254 .cindex "options" "macro &-- extracting"
3255 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3256 are available, similarly to the drivers. Because macros are sometimes used
3257 for storing passwords, this option is restricted.
3258 The output format is one item per line.
3259 For the "-bP macro <name>" form, if no such macro is found
3260 the exit status will be nonzero.
3264 .cindex "queue" "listing messages in"
3265 .cindex "listing" "messages in the queue"
3266 This option requests a listing of the contents of the mail queue on the
3267 standard output. If the &%-bp%& option is followed by a list of message ids,
3268 just those messages are listed. By default, this option can be used only by an
3269 admin user. However, the &%queue_list_requires_admin%& option can be set false
3270 to allow any user to see the queue.
3272 Each message in the queue is displayed as in the following example:
3274 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3275 red.king@looking-glass.fict.example
3278 .cindex "message" "size in queue listing"
3279 .cindex "size" "of message"
3280 The first line contains the length of time the message has been in the queue
3281 (in this case 25 minutes), the size of the message (2.9K), the unique local
3282 identifier for the message, and the message sender, as contained in the
3283 envelope. For bounce messages, the sender address is empty, and appears as
3284 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3285 the default sender address, the user's login name is shown in parentheses
3286 before the sender address.
3288 .cindex "frozen messages" "in queue listing"
3289 If the message is frozen (attempts to deliver it are suspended) then the text
3290 &"*** frozen ***"& is displayed at the end of this line.
3292 The recipients of the message (taken from the envelope, not the headers) are
3293 displayed on subsequent lines. Those addresses to which the message has already
3294 been delivered are marked with the letter D. If an original address gets
3295 expanded into several addresses via an alias or forward file, the original is
3296 displayed with a D only when deliveries for all of its child addresses are
3302 This option operates like &%-bp%&, but in addition it shows delivered addresses
3303 that were generated from the original top level address(es) in each message by
3304 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3310 .cindex "queue" "count of messages on"
3311 This option counts the number of messages in the queue, and writes the total
3312 to the standard output. It is restricted to admin users, unless
3313 &%queue_list_requires_admin%& is set false.
3318 This option operates like &%-bp%&, but the output is not sorted into
3319 chronological order of message arrival. This can speed it up when there are
3320 lots of messages in the queue, and is particularly useful if the output is
3321 going to be post-processed in a way that doesn't need the sorting.
3325 This option is a combination of &%-bpr%& and &%-bpa%&.
3329 This option is a combination of &%-bpr%& and &%-bpu%&.
3334 This option operates like &%-bp%& but shows only undelivered top-level
3335 addresses for each message displayed. Addresses generated by aliasing or
3336 forwarding are not shown, unless the message was deferred after processing by a
3337 router with the &%one_time%& option set.
3342 .cindex "testing" "retry configuration"
3343 .cindex "retry" "configuration testing"
3344 This option is for testing retry rules, and it must be followed by up to three
3345 arguments. It causes Exim to look for a retry rule that matches the values
3346 and to write it to the standard output. For example:
3348 exim -brt bach.comp.mus.example
3349 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3351 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3352 argument, which is required, can be a complete address in the form
3353 &'local_part@domain'&, or it can be just a domain name. If the second argument
3354 contains a dot, it is interpreted as an optional second domain name; if no
3355 retry rule is found for the first argument, the second is tried. This ties in
3356 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3357 rule is found that matches the host, one that matches the mail domain is
3358 sought. Finally, an argument that is the name of a specific delivery error, as
3359 used in setting up retry rules, can be given. For example:
3361 exim -brt haydn.comp.mus.example quota_3d
3362 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3367 .cindex "testing" "rewriting"
3368 .cindex "rewriting" "testing"
3369 This option is for testing address rewriting rules, and it must be followed by
3370 a single argument, consisting of either a local part without a domain, or a
3371 complete address with a fully qualified domain. Exim outputs how this address
3372 would be rewritten for each possible place it might appear. See chapter
3373 &<<CHAPrewrite>>& for further details.
3377 .cindex "SMTP" "batched incoming"
3378 .cindex "batched SMTP input"
3379 This option is used for batched SMTP input, which is an alternative interface
3380 for non-interactive local message submission. A number of messages can be
3381 submitted in a single run. However, despite its name, this is not really SMTP
3382 input. Exim reads each message's envelope from SMTP commands on the standard
3383 input, but generates no responses. If the caller is trusted, or
3384 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3385 believed; otherwise the sender is always the caller of Exim.
3387 The message itself is read from the standard input, in SMTP format (leading
3388 dots doubled), terminated by a line containing just a single dot. An error is
3389 provoked if the terminating dot is missing. A further message may then follow.
3391 As for other local message submissions, the contents of incoming batch SMTP
3392 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3393 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3394 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3396 Some other SMTP commands are recognized in the input. HELO and EHLO act
3397 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3398 QUIT quits, ignoring the rest of the standard input.
3400 .cindex "return code" "for &%-bS%&"
3401 If any error is encountered, reports are written to the standard output and
3402 error streams, and Exim gives up immediately. The return code is 0 if no error
3403 was detected; it is 1 if one or more messages were accepted before the error
3404 was detected; otherwise it is 2.
3406 More details of input using batched SMTP are given in section
3407 &<<SECTincomingbatchedSMTP>>&.
3411 .cindex "SMTP" "local input"
3412 .cindex "local SMTP input"
3413 This option causes Exim to accept one or more messages by reading SMTP commands
3414 on the standard input, and producing SMTP replies on the standard output. SMTP
3415 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3416 Some user agents use this interface as a way of passing locally-generated
3417 messages to the MTA.
3420 .cindex "sender" "source of"
3421 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3422 set, the senders of messages are taken from the SMTP MAIL commands.
3423 Otherwise the content of these commands is ignored and the sender is set up as
3424 the calling user. Unqualified addresses are automatically qualified using
3425 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3426 &%-bnq%& option is used.
3430 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3431 using a listening daemon. Exim can distinguish the two cases by checking
3432 whether the standard input is a TCP/IP socket. When Exim is called from
3433 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3434 above concerning senders and qualification do not apply. In this situation,
3435 Exim behaves in exactly the same way as it does when receiving a message via
3436 the listening daemon.
3440 .cindex "testing" "addresses"
3441 .cindex "address" "testing"
3442 This option runs Exim in address testing mode, in which each argument is taken
3443 as a recipient address to be tested for deliverability. The results are
3444 written to the standard output. If a test fails, and the caller is not an admin
3445 user, no details of the failure are output, because these might contain
3446 sensitive information such as usernames and passwords for database lookups.
3448 If no arguments are given, Exim runs in an interactive manner, prompting with a
3449 right angle bracket for addresses to be tested.
3451 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3452 &[readline()]& function, because it is running as &'root'& and there are
3455 Each address is handled as if it were the recipient address of a message
3456 (compare the &%-bv%& option). It is passed to the routers and the result is
3457 written to the standard output. However, any router that has
3458 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3459 genuine routing tests if your first router passes everything to a scanner
3462 .cindex "return code" "for &%-bt%&"
3463 The return code is 2 if any address failed outright; it is 1 if no address
3464 failed outright but at least one could not be resolved for some reason. Return
3465 code 0 is given only when all addresses succeed.
3467 .cindex "duplicate addresses"
3468 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3469 addresses after routing is complete, so that only one delivery takes place.
3470 This does not happen when testing with &%-bt%&; the full results of routing are
3473 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3474 routers in the configuration makes any tests on the sender address of a
3476 .oindex "&%-f%&" "for address testing"
3477 you can use the &%-f%& option to set an appropriate sender when running
3478 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3479 default qualifying domain. However, if you have set up (for example) routers
3480 whose behaviour depends on the contents of an incoming message, you cannot test
3481 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3486 .cindex "version number of Exim"
3487 This option causes Exim to write the current version number, compilation
3488 number, and compilation date of the &'exim'& binary to the standard output.
3489 It also lists the DBM library that is being used, the optional modules (such as
3490 specific lookup types), the drivers that are included in the binary, and the
3491 name of the runtime configuration file that is in use.
3493 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3494 configuration file. However, this is a static check only. It cannot check
3495 values that are to be expanded. For example, although a misspelt ACL verb is
3496 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3497 alone to discover (for example) all the typos in the configuration; some
3498 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3499 dynamic testing facilities.
3503 .cindex "verifying address" "using &%-bv%&"
3504 .cindex "address" "verification"
3505 This option runs Exim in address verification mode, in which each argument is
3506 taken as a recipient address to be verified by the routers. (This does
3507 not involve any verification callouts). During normal operation, verification
3508 happens mostly as a consequence processing a &%verify%& condition in an ACL
3509 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3510 including callouts, see the &%-bh%& and &%-bhc%& options.
3512 If verification fails, and the caller is not an admin user, no details of the
3513 failure are output, because these might contain sensitive information such as
3514 usernames and passwords for database lookups.
3516 If no arguments are given, Exim runs in an interactive manner, prompting with a
3517 right angle bracket for addresses to be verified.
3519 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3520 &[readline()]& function, because it is running as &'exim'& and there are
3523 Verification differs from address testing (the &%-bt%& option) in that routers
3524 that have &%no_verify%& set are skipped, and if the address is accepted by a
3525 router that has &%fail_verify%& set, verification fails. The address is
3526 verified as a recipient if &%-bv%& is used; to test verification for a sender
3527 address, &%-bvs%& should be used.
3529 If the &%-v%& option is not set, the output consists of a single line for each
3530 address, stating whether it was verified or not, and giving a reason in the
3531 latter case. Without &%-v%&, generating more than one address by redirection
3532 causes verification to end successfully, without considering the generated
3533 addresses. However, if just one address is generated, processing continues,
3534 and the generated address must verify successfully for the overall verification
3537 When &%-v%& is set, more details are given of how the address has been handled,
3538 and in the case of address redirection, all the generated addresses are also
3539 considered. Verification may succeed for some and fail for others.
3542 .cindex "return code" "for &%-bv%&"
3543 return code is 2 if any address failed outright; it is 1 if no address
3544 failed outright but at least one could not be resolved for some reason. Return
3545 code 0 is given only when all addresses succeed.
3547 If any of the routers in the configuration makes any tests on the sender
3548 address of a message, you should use the &%-f%& option to set an appropriate
3549 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3550 calling user at the default qualifying domain.
3554 This option acts like &%-bv%&, but verifies the address as a sender rather
3555 than a recipient address. This affects any rewriting and qualification that
3562 .cindex "inetd" "wait mode"
3563 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3564 similarly to the &%-bd%& option. All port specifications on the command-line
3565 and in the configuration file are ignored. Queue-running may not be specified.
3567 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3568 listening for connections. This permits the system to start up and have
3569 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3570 each port only when the first connection is received.
3572 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3573 which the daemon will exit, which should cause inetd to listen once more.
3575 .vitem &%-C%&&~<&'filelist'&>
3577 .cindex "configuration file" "alternate"
3578 .cindex "CONFIGURE_FILE"
3579 .cindex "alternate configuration file"
3580 This option causes Exim to find the runtime configuration file from the given
3581 list instead of from the list specified by the CONFIGURE_FILE
3582 compile-time setting. Usually, the list will consist of just a single filename,
3583 but it can be a colon-separated list of names. In this case, the first
3584 file that exists is used. Failure to open an existing file stops Exim from
3585 proceeding any further along the list, and an error is generated.
3587 When this option is used by a caller other than root, and the list is different
3588 from the compiled-in list, Exim gives up its root privilege immediately, and
3589 runs with the real and effective uid and gid set to those of the caller.
3590 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3591 file contains a list of full pathnames, one per line, for configuration files
3592 which are trusted. Root privilege is retained for any configuration file so
3593 listed, as long as the caller is the Exim user (or the user specified in the
3594 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3595 not writeable by inappropriate users or groups.
3597 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3598 configuration using &%-C%& right through message reception and delivery,
3599 even if the caller is root. The reception works, but by that time, Exim is
3600 running as the Exim user, so when it re-executes to regain privilege for the
3601 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3602 test reception and delivery using two separate commands (one to put a message
3603 in the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3605 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3606 prefix string with which any file named in a &%-C%& command line option
3607 must start. In addition, the filename must not contain the sequence &`/../`&.
3608 However, if the value of the &%-C%& option is identical to the value of
3609 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3610 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3611 unset, any filename can be used with &%-C%&.
3613 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3614 to a directory to which only root has access. This prevents someone who has
3615 broken into the Exim account from running a privileged Exim with an arbitrary
3618 The &%-C%& facility is useful for ensuring that configuration files are
3619 syntactically correct, but cannot be used for test deliveries, unless the
3620 caller is privileged, or unless it is an exotic configuration that does not
3621 require privilege. No check is made on the owner or group of the files
3622 specified by this option.
3625 .vitem &%-D%&<&'macro'&>=<&'value'&>
3627 .cindex "macro" "setting on command line"
3628 This option can be used to override macro definitions in the configuration file
3629 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3630 unprivileged caller, it causes Exim to give up its root privilege.
3631 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3632 completely disabled, and its use causes an immediate error exit.
3634 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3635 colon-separated list of macros which are considered safe and, if &%-D%& only
3636 supplies macros from this list, and the values are acceptable, then Exim will
3637 not give up root privilege if the caller is root, the Exim run-time user, or
3638 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3639 to be removed in the future. Acceptable values for the macros satisfy the
3640 regexp: &`^[A-Za-z0-9_/.-]*$`&
3642 The entire option (including equals sign if present) must all be within one
3643 command line item. &%-D%& can be used to set the value of a macro to the empty
3644 string, in which case the equals sign is optional. These two commands are
3650 To include spaces in a macro definition item, quotes must be used. If you use
3651 quotes, spaces are permitted around the macro name and the equals sign. For
3654 exim '-D ABC = something' ...
3656 &%-D%& may be repeated up to 10 times on a command line.
3657 Only macro names up to 22 letters long can be set.
3660 .vitem &%-d%&<&'debug&~options'&>
3662 .cindex "debugging" "list of selectors"
3663 .cindex "debugging" "&%-d%& option"
3664 This option causes debugging information to be written to the standard
3665 error stream. It is restricted to admin users because debugging output may show
3666 database queries that contain password information. Also, the details of users'
3667 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3668 writes an error message to the standard error stream and exits with a non-zero
3671 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3672 standard debugging data is output. This can be reduced, or increased to include
3673 some more rarely needed information, by directly following &%-d%& with a string
3674 made up of names preceded by plus or minus characters. These add or remove sets
3675 of debugging data, respectively. For example, &%-d+filter%& adds filter
3676 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3677 no spaces are allowed in the debug setting. The available debugging categories
3680 &`acl `& ACL interpretation
3681 &`auth `& authenticators
3682 &`deliver `& general delivery logic
3683 &`dns `& DNS lookups (see also resolver)
3684 &`dnsbl `& DNS black list (aka RBL) code
3685 &`exec `& arguments for &[execv()]& calls
3686 &`expand `& detailed debugging for string expansions
3687 &`filter `& filter handling
3688 &`hints_lookup `& hints data lookups
3689 &`host_lookup `& all types of name-to-IP address handling
3690 &`ident `& ident lookup
3691 &`interface `& lists of local interfaces
3692 &`lists `& matching things in lists
3693 &`load `& system load checks
3694 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3695 &<<CHAPlocalscan>>&)
3696 &`lookup `& general lookup code and all lookups
3697 &`memory `& memory handling
3698 &`noutf8 `& modifier: avoid UTF-8 line-drawing
3699 &`pid `& modifier: add pid to debug output lines
3700 &`process_info `& setting info for the process log
3701 &`queue_run `& queue runs
3702 &`receive `& general message reception logic
3703 &`resolver `& turn on the DNS resolver's debugging output
3704 &`retry `& retry handling
3705 &`rewrite `& address rewriting
3706 &`route `& address routing
3707 &`timestamp `& modifier: add timestamp to debug output lines
3709 &`transport `& transports
3710 &`uid `& changes of uid/gid and looking up uid/gid
3711 &`verify `& address verification logic
3712 &`all `& almost all of the above (see below), and also &%-v%&
3714 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3715 for &`-all`&. The reason for this is that &`+all`& is something that people
3716 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3717 is included, an awful lot of output that is very rarely of interest is
3718 generated, so it now has to be explicitly requested. However, &`-all`& does
3719 turn everything off.
3721 .cindex "resolver, debugging output"
3722 .cindex "DNS resolver, debugging output"
3723 The &`resolver`& option produces output only if the DNS resolver was compiled
3724 with DEBUG enabled. This is not the case in some operating systems. Also,
3725 unfortunately, debugging output from the DNS resolver is written to stdout
3728 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3729 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3730 However, the &`pid`& selector is forced when debugging is turned on for a
3731 daemon, which then passes it on to any re-executed Exims. Exim also
3732 automatically adds the pid to debug lines when several remote deliveries are
3735 The &`timestamp`& selector causes the current time to be inserted at the start
3736 of all debug output lines. This can be useful when trying to track down delays
3739 .cindex debugging "UTF-8 in"
3740 .cindex UTF-8 "in debug output"
3741 The &`noutf8`& selector disables the use of
3742 UTF-8 line-drawing characters to group related information.
3743 When disabled. ascii-art is used instead.
3744 Using the &`+all`& option does not set this modifier,
3746 If the &%debug_print%& option is set in any driver, it produces output whenever
3747 any debugging is selected, or if &%-v%& is used.
3749 .vitem &%-dd%&<&'debug&~options'&>
3751 This option behaves exactly like &%-d%& except when used on a command that
3752 starts a daemon process. In that case, debugging is turned off for the
3753 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3754 behaviour of the daemon without creating as much output as full debugging does.
3757 .oindex "&%-dropcr%&"
3758 This is an obsolete option that is now a no-op. It used to affect the way Exim
3759 handled CR and LF characters in incoming messages. What happens now is
3760 described in section &<<SECTlineendings>>&.
3764 .cindex "bounce message" "generating"
3765 This option specifies that an incoming message is a locally-generated delivery
3766 failure report. It is used internally by Exim when handling delivery failures
3767 and is not intended for external use. Its only effect is to stop Exim
3768 generating certain messages to the postmaster, as otherwise message cascades
3769 could occur in some situations. As part of the same option, a message id may
3770 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3771 new message contains the id, following &"R="&, as a cross-reference.
3774 .oindex "&%-e%&&'x'&"
3775 There are a number of Sendmail options starting with &%-oe%& which seem to be
3776 called by various programs without the leading &%o%& in the option. For
3777 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3778 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3780 .vitem &%-F%&&~<&'string'&>
3782 .cindex "sender" "name"
3783 .cindex "name" "of sender"
3784 This option sets the sender's full name for use when a locally-generated
3785 message is being accepted. In the absence of this option, the user's &'gecos'&
3786 entry from the password data is used. As users are generally permitted to alter
3787 their &'gecos'& entries, no security considerations are involved. White space
3788 between &%-F%& and the <&'string'&> is optional.
3790 .vitem &%-f%&&~<&'address'&>
3792 .cindex "sender" "address"
3793 .cindex "address" "sender"
3794 .cindex "trusted users"
3795 .cindex "envelope from"
3796 .cindex "envelope sender"
3797 .cindex "user" "trusted"
3798 This option sets the address of the envelope sender of a locally-generated
3799 message (also known as the return path). The option can normally be used only
3800 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3803 Processes running as root or the Exim user are always trusted. Other
3804 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3805 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3806 of a local message is set to the caller's login name at the default qualify
3809 There is one exception to the restriction on the use of &%-f%&: an empty sender
3810 can be specified by any user, trusted or not, to create a message that can
3811 never provoke a bounce. An empty sender can be specified either as an empty
3812 string, or as a pair of angle brackets with nothing between them, as in these
3813 examples of shell commands:
3815 exim -f '<>' user@domain
3816 exim -f "" user@domain
3818 In addition, the use of &%-f%& is not restricted when testing a filter file
3819 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3822 Allowing untrusted users to change the sender address does not of itself make
3823 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3824 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3825 though this can be overridden by setting &%no_local_from_check%&.
3828 .cindex "&""From""& line"
3829 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3830 given as two arguments or one combined argument). The sender of a
3831 locally-generated message can also be set (when permitted) by an initial
3832 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3833 if &%-f%& is also present, it overrides &"From&~"&.
3837 .cindex "submission fixups, suppressing (command-line)"
3838 This option is equivalent to an ACL applying:
3840 control = suppress_local_fixups
3842 for every message received. Note that Sendmail will complain about such
3843 bad formatting, where Exim silently just does not fix it up. This may change
3846 As this affects audit information, the caller must be a trusted user to use
3849 .vitem &%-h%&&~<&'number'&>
3851 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3852 This option is accepted for compatibility with Sendmail, but has no effect. (In
3853 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3858 .cindex "Solaris" "&'mail'& command"
3859 .cindex "dot" "in incoming non-SMTP message"
3860 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3861 line by itself should not terminate an incoming, non-SMTP message.
3862 Solaris 2.4 (SunOS 5.4) Sendmail has a similar &%-i%& processing option
3863 &url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf),
3864 p. 1M-529), and therefore a &%-oi%& command line option, which both are used
3865 by its &'mailx'& command.
3867 .vitem &%-L%&&~<&'tag'&>
3869 .cindex "syslog" "process name; set with flag"
3870 This option is equivalent to setting &%syslog_processname%& in the config
3871 file and setting &%log_file_path%& to &`syslog`&.
3872 Its use is restricted to administrators. The configuration file has to be
3873 read and parsed, to determine access rights, before this is set and takes
3874 effect, so early configuration file errors will not honour this flag.
3876 The tag should not be longer than 32 characters.
3878 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3880 .cindex "forcing delivery"
3881 .cindex "delivery" "forcing attempt"
3882 .cindex "frozen messages" "forcing delivery"
3883 This option requests Exim to run a delivery attempt on each message in turn. If
3884 any of the messages are frozen, they are automatically thawed before the
3885 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3886 and &%hold_domains%& are ignored.
3889 .cindex "hints database" "overriding retry hints"
3890 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3891 the normal retry time has not yet been reached. This option requires the caller
3892 to be an admin user. However, there is an option called &%prod_requires_admin%&
3893 which can be set false to relax this restriction (and also the same requirement
3894 for the &%-q%&, &%-R%&, and &%-S%& options).
3896 The deliveries happen synchronously, that is, the original Exim process does
3897 not terminate until all the delivery attempts have finished. No output is
3898 produced unless there is a serious error. If you want to see what is happening,
3899 use the &%-v%& option as well, or inspect Exim's main log.
3901 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3903 .cindex "message" "adding recipients"
3904 .cindex "recipient" "adding"
3905 This option requests Exim to add the addresses to the list of recipients of the
3906 message (&"ar"& for &"add recipients"&). The first argument must be a message
3907 id, and the remaining ones must be email addresses. However, if the message is
3908 active (in the middle of a delivery attempt), it is not altered. This option
3909 can be used only by an admin user.
3911 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&&&
3913 &~<&'sequence&~number'&>&&&
3914 &~<&'message&~id'&>"
3916 .cindex "SMTP" "passed connection"
3917 .cindex "SMTP" "multiple deliveries"
3918 .cindex "multiple SMTP deliveries"
3919 This option is not intended for use by external callers. It is used internally
3920 by Exim to invoke another instance of itself to deliver a waiting message using
3921 an existing SMTP connection, which is passed as the standard input. Details are
3922 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3923 must be root or the Exim user in order to use it.
3927 This option is not intended for use by external callers. It is used internally
3928 by Exim in conjunction with the &%-MC%& option. It signifies that the
3929 connection to the remote host has been authenticated.
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 the
3935 remote host supports the ESMTP &_DSN_& extension.
3939 This option is not intended for use by external callers. It is used internally
3940 by Exim in conjunction with the &%-d%& option
3941 to pass on an information string on the purpose of the process.
3943 .vitem &%-MCG%&&~<&'queue&~name'&>
3945 This option is not intended for use by external callers. It is used internally
3946 by Exim in conjunction with the &%-MC%& option. It signifies that an
3947 alternate queue is used, named by the following argument.
3951 This option is not intended for use by external callers. It is used internally
3952 by Exim in conjunction with the &%-MC%& option. It signifies that a
3953 remote host supports the ESMTP &_CHUNKING_& extension.
3958 This option is not intended for use by external callers. It is used internally
3959 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3960 which Exim is connected advertised limits on numbers of mails, recipients or
3962 The limits are given by the following three arguments.
3967 This option is not intended for use by external callers. It is used internally
3968 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3969 which Exim is connected supports pipelining.
3974 This option is not intended for use by external callers. It is used internally
3975 by Exim in conjunction with the &%-MC%& option. It signifies that the connection
3976 t a remote server is via a SOCKS proxy, using addresses and ports given by
3977 the following four arguments.
3980 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3982 This option is not intended for use by external callers. It is used internally
3983 by Exim in conjunction with the &%-MC%& option when the original delivery was
3984 started by a queue runner. It passes on the process id of the queue runner,
3985 together with the file descriptor number of an open pipe. Closure of the pipe
3986 signals the final completion of the sequence of processes that are passing
3987 messages through the same SMTP connection.
3990 .vitem &%-MCq%&&~<&'recipient&~address'&>&~<&'size'&>
3992 This option is not intended for use by external callers. It is used internally
3993 by Exim to implement quota checking for local users.
3998 This option is not intended for use by external callers. It is used internally
3999 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
4000 ESMTP SIZE option should be used on messages delivered down the existing
4005 This option is not intended for use by external callers. It is used internally
4006 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
4007 host to which Exim is connected supports TLS encryption.
4010 .vitem &%-MCr%&&~<&'SNI'&> &&&
4014 These options are not intended for use by external callers. It is used internally
4015 by Exim in conjunction with the &%-MCt%& option, and passes on the fact that
4016 a TLS Server Name Indication was sent as part of the channel establishment.
4017 The argument gives the SNI string.
4018 The "r" variant indicates a DANE-verified connection.
4021 .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
4023 This option is not intended for use by external callers. It is used internally
4024 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
4025 connection is being proxied by a parent process for handling TLS encryption.
4026 The arguments give the local address and port being proxied, and the TLS cipher.
4028 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4030 .cindex "hints database" "not overridden by &%-Mc%&"
4031 .cindex "delivery" "manually started &-- not forced"
4032 This option requests Exim to run a delivery attempt on each message, in turn,
4033 but unlike the &%-M%& option, it does check for retry hints, and respects any
4034 that are found. This option is not very useful to external callers. It is
4035 provided mainly for internal use by Exim when it needs to re-invoke itself in
4036 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
4037 However, &%-Mc%& can be useful when testing, in order to run a delivery that
4038 respects retry times and other options such as &%hold_domains%& that are
4039 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
4040 If you want to run a specific delivery as if in a queue run, you should use
4041 &%-q%& with a message id argument. A distinction between queue run deliveries
4042 and other deliveries is made in one or two places.
4044 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
4046 .cindex "message" "changing sender"
4047 .cindex "sender" "changing"
4048 This option requests Exim to change the sender address in the message to the
4049 given address, which must be a fully qualified address or &"<>"& (&"es"& for
4050 &"edit sender"&). There must be exactly two arguments. The first argument must
4051 be a message id, and the second one an email address. However, if the message
4052 is active (in the middle of a delivery attempt), its status is not altered.
4053 This option can be used only by an admin user.
4055 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4057 .cindex "freezing messages"
4058 .cindex "message" "manually freezing"
4059 This option requests Exim to mark each listed message as &"frozen"&. This
4060 prevents any delivery attempts taking place until the message is &"thawed"&,
4061 either manually or as a result of the &%auto_thaw%& configuration option.
4062 However, if any of the messages are active (in the middle of a delivery
4063 attempt), their status is not altered. This option can be used only by an admin
4066 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4068 .cindex "giving up on messages"
4069 .cindex "message" "abandoning delivery attempts"
4070 .cindex "delivery" "abandoning further attempts"
4071 This option requests Exim to give up trying to deliver the listed messages,
4072 including any that are frozen. However, if any of the messages are active,
4073 their status is not altered. For non-bounce messages, a delivery error message
4074 is sent to the sender, containing the text &"cancelled by administrator"&.
4075 Bounce messages are just discarded. This option can be used only by an admin
4078 .vitem &%-MG%&&~<&'queue&~name'&>&~<&'message&~id'&>&~<&'message&~id'&>&~...
4081 .cindex "named queues" "moving messages"
4082 .cindex "queue" "moving messages"
4083 This option requests that each listed message be moved from its current
4084 queue to the given named queue.
4085 The destination queue name argument is required, but can be an empty
4086 string to define the default queue.
4087 If the messages are not currently located in the default queue,
4088 a &%-qG<name>%& option will be required to define the source queue.
4090 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4092 .cindex "delivery" "cancelling all"
4093 This option requests Exim to mark all the recipient addresses in the messages
4094 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
4095 message is active (in the middle of a delivery attempt), its status is not
4096 altered. This option can be used only by an admin user.
4098 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
4100 .cindex "delivery" "cancelling by address"
4101 .cindex "recipient" "removing"
4102 .cindex "removing recipients"
4103 This option requests Exim to mark the given addresses as already delivered
4104 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
4105 the remaining ones must be email addresses. These are matched to recipient
4106 addresses in the message in a case-sensitive manner. If the message is active
4107 (in the middle of a delivery attempt), its status is not altered. This option
4108 can be used only by an admin user.
4110 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4112 .cindex "removing messages"
4113 .cindex "abandoning mail"
4114 .cindex "message" "manually discarding"
4115 This option requests Exim to remove the given messages from the queue. No
4116 bounce messages are sent; each message is simply forgotten. However, if any of
4117 the messages are active, their status is not altered. This option can be used
4118 only by an admin user or by the user who originally caused the message to be
4119 placed in the queue.
4124 . .cindex REQUIRETLS
4125 . This option is used to request REQUIRETLS processing on the message.
4126 . It is used internally by Exim in conjunction with -E when generating
4130 .vitem &%-Mset%&&~<&'message&~id'&>
4132 .cindex "testing" "string expansion"
4133 .cindex "expansion" "testing"
4134 This option is useful only in conjunction with &%-be%& (that is, when testing
4135 string expansions). Exim loads the given message from its spool before doing
4136 the test expansions, thus setting message-specific variables such as
4137 &$message_size$& and the header variables. The &$recipients$& variable is made
4138 available. This feature is provided to make it easier to test expansions that
4139 make use of these variables. However, this option can be used only by an admin
4140 user. See also &%-bem%&.
4142 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4144 .cindex "thawing messages"
4145 .cindex "unfreezing messages"
4146 .cindex "frozen messages" "thawing"
4147 .cindex "message" "thawing frozen"
4148 This option requests Exim to &"thaw"& any of the listed messages that are
4149 &"frozen"&, so that delivery attempts can resume. However, if any of the
4150 messages are active, their status is not altered. This option can be used only
4153 .vitem &%-Mvb%&&~<&'message&~id'&>
4155 .cindex "listing" "message body"
4156 .cindex "message" "listing body of"
4157 This option causes the contents of the message body (-D) spool file to be
4158 written to the standard output. This option can be used only by an admin user.
4160 .vitem &%-Mvc%&&~<&'message&~id'&>
4162 .cindex "message" "listing in RFC 2822 format"
4163 .cindex "listing" "message in RFC 2822 format"
4164 This option causes a copy of the complete message (header lines plus body) to
4165 be written to the standard output in RFC 2822 format. This option can be used
4166 only by an admin user.
4168 .vitem &%-Mvh%&&~<&'message&~id'&>
4170 .cindex "listing" "message headers"
4171 .cindex "header lines" "listing"
4172 .cindex "message" "listing header lines"
4173 This option causes the contents of the message headers (-H) spool file to be
4174 written to the standard output. This option can be used only by an admin user.
4176 .vitem &%-Mvl%&&~<&'message&~id'&>
4178 .cindex "listing" "message log"
4179 .cindex "message" "listing message log"
4180 This option causes the contents of the message log spool file to be written to
4181 the standard output. This option can be used only by an admin user.
4185 This is a synonym for &%-om%& that is accepted by Sendmail
4186 (&url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf)
4187 p. 1M-258), so Exim treats it that way too.
4191 .cindex "debugging" "&%-N%& option"
4192 .cindex "debugging" "suppressing delivery"
4193 This is a debugging option that inhibits delivery of a message at the transport
4194 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4195 it just doesn't actually transport the message, but instead behaves as if it
4196 had successfully done so. However, it does not make any updates to the retry
4197 database, and the log entries for deliveries are flagged with &"*>"& rather
4200 Because &%-N%& discards any message to which it applies, only root or the Exim
4201 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4202 words, an ordinary user can use it only when supplying an incoming message to
4203 which it will apply. Although transportation never fails when &%-N%& is set, an
4204 address may be deferred because of a configuration problem on a transport, or a
4205 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4206 the message, and applies to any subsequent delivery attempts that may happen
4211 This option is interpreted by Sendmail to mean &"no aliasing"&.
4212 For normal modes of operation, it is ignored by Exim.
4213 When combined with &%-bP%& it makes the output more terse (suppresses
4214 option names, environment values and config pretty printing).
4216 .vitem &%-O%&&~<&'data'&>
4218 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4221 .vitem &%-oA%&&~<&'file&~name'&>
4223 .cindex "Sendmail compatibility" "&%-oA%& option"
4224 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4225 alternative alias filename. Exim handles &%-bi%& differently; see the
4228 .vitem &%-oB%&&~<&'n'&>
4230 .cindex "SMTP" "passed connection"
4231 .cindex "SMTP" "multiple deliveries"
4232 .cindex "multiple SMTP deliveries"
4233 This is a debugging option which limits the maximum number of messages that can
4234 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4235 transport. If <&'n'&> is omitted, the limit is set to 1.
4239 .cindex "background delivery"
4240 .cindex "delivery" "in the background"
4241 This option applies to all modes in which Exim accepts incoming messages,
4242 including the listening daemon. It requests &"background"& delivery of such
4243 messages, which means that the accepting process automatically starts a
4244 delivery process for each message received, but does not wait for the delivery
4245 processes to finish.
4247 When all the messages have been received, the reception process exits,
4248 leaving the delivery processes to finish in their own time. The standard output
4249 and error streams are closed at the start of each delivery process.
4250 This is the default action if none of the &%-od%& options are present.
4252 If one of the queueing options in the configuration file
4253 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4254 overrides it if &%queue_only_override%& is set true, which is the default
4255 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4259 .cindex "foreground delivery"
4260 .cindex "delivery" "in the foreground"
4261 This option requests &"foreground"& (synchronous) delivery when Exim has
4262 accepted a locally-generated message. (For the daemon it is exactly the same as
4263 &%-odb%&.) A delivery process is automatically started to deliver the message,
4264 and Exim waits for it to complete before proceeding.
4266 The original Exim reception process does not finish until the delivery
4267 process for the final message has ended. The standard error stream is left open
4270 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4271 false and one of the queueing options in the configuration file is in effect.
4273 If there is a temporary delivery error during foreground delivery, the
4274 message is left in the queue for later delivery, and the original reception
4275 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4276 restricted configuration that never queues messages.
4281 This option is synonymous with &%-odf%&. It is provided for compatibility with
4286 .cindex "non-immediate delivery"
4287 .cindex "delivery" "suppressing immediate"
4288 .cindex "queueing incoming messages"
4289 This option applies to all modes in which Exim accepts incoming messages,
4290 including the listening daemon. It specifies that the accepting process should
4291 not automatically start a delivery process for each message received. Messages
4292 are placed in the queue, and remain there until a subsequent queue runner
4293 process encounters them. There are several configuration options (such as
4294 &%queue_only%&) that can be used to queue incoming messages under certain
4295 conditions. This option overrides all of them and also &%-odqs%&. It always
4300 .cindex "SMTP" "delaying delivery"
4301 .cindex "first pass routing"
4302 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4303 However, like &%-odb%& and &%-odi%&, this option has no effect if
4304 &%queue_only_override%& is false and one of the queueing options in the
4305 configuration file is in effect.
4307 When &%-odqs%& does operate, a delivery process is started for each incoming
4308 message, in the background by default, but in the foreground if &%-odi%& is
4309 also present. The recipient addresses are routed, and local deliveries are done
4310 in the normal way. However, if any SMTP deliveries are required, they are not
4311 done at this time, so the message remains in the queue until a subsequent queue
4312 runner process encounters it. Because routing was done, Exim knows which
4313 messages are waiting for which hosts, and so a number of messages for the same
4314 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4315 configuration option has the same effect for specific domains. See also the
4320 .cindex "error" "reporting"
4321 If an error is detected while a non-SMTP message is being received (for
4322 example, a malformed address), the error is reported to the sender in a mail
4325 .cindex "return code" "for &%-oee%&"
4327 this error message is successfully sent, the Exim receiving process
4328 exits with a return code of zero. If not, the return code is 2 if the problem
4329 is that the original message has no recipients, or 1 for any other error.
4330 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4334 .cindex "error" "reporting"
4335 .cindex "return code" "for &%-oem%&"
4336 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4337 return code, whether or not the error message was successfully sent.
4338 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4342 .cindex "error" "reporting"
4343 If an error is detected while a non-SMTP message is being received, the
4344 error is reported by writing a message to the standard error file (stderr).
4345 .cindex "return code" "for &%-oep%&"
4346 The return code is 1 for all errors.
4350 .cindex "error" "reporting"
4351 This option is supported for compatibility with Sendmail, but has the same
4356 .cindex "error" "reporting"
4357 This option is supported for compatibility with Sendmail, but has the same
4362 .cindex "dot" "in incoming non-SMTP message"
4363 This option, which has the same effect as &%-i%&, specifies that a dot on a
4364 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4365 single dot does terminate, though Exim does no special processing for other
4366 lines that start with a dot. This option is set by default if Exim is called as
4367 &'rmail'&. See also &%-ti%&.
4370 .oindex "&%-oitrue%&"
4371 This option is treated as synonymous with &%-oi%&.
4373 .vitem &%-oMa%&&~<&'host&~address'&>
4375 .cindex "sender" "host address, specifying for local message"
4376 A number of options starting with &%-oM%& can be used to set values associated
4377 with remote hosts on locally-submitted messages (that is, messages not received
4378 over TCP/IP). These options can be used by any caller in conjunction with the
4379 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4380 other circumstances, they are ignored unless the caller is trusted.
4382 The &%-oMa%& option sets the sender host address. This may include a port
4383 number at the end, after a full stop (period). For example:
4385 exim -bs -oMa 10.9.8.7.1234
4387 An alternative syntax is to enclose the IP address in square brackets,
4388 followed by a colon and the port number:
4390 exim -bs -oMa [10.9.8.7]:1234
4392 The IP address is placed in the &$sender_host_address$& variable, and the
4393 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4394 are present on the command line, the sender host IP address is taken from
4395 whichever one is last.
4397 .vitem &%-oMaa%&&~<&'name'&>
4399 .cindex "authentication" "name, specifying for local message"
4400 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4401 option sets the value of &$sender_host_authenticated$& (the authenticator
4402 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4403 This option can be used with &%-bh%& and &%-bs%& to set up an
4404 authenticated SMTP session without actually using the SMTP AUTH command.
4406 .vitem &%-oMai%&&~<&'string'&>
4408 .cindex "authentication" "id, specifying for local message"
4409 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4410 option sets the value of &$authenticated_id$& (the id that was authenticated).
4411 This overrides the default value (the caller's login id, except with &%-bh%&,
4412 where there is no default) for messages from local sources. See chapter
4413 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4415 .vitem &%-oMas%&&~<&'address'&>
4417 .cindex "authentication" "sender, specifying for local message"
4418 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4419 option sets the authenticated sender value in &$authenticated_sender$&. It
4420 overrides the sender address that is created from the caller's login id for
4421 messages from local sources, except when &%-bh%& is used, when there is no
4422 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4423 specified on a MAIL command overrides this value. See chapter
4424 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4426 .vitem &%-oMi%&&~<&'interface&~address'&>
4428 .cindex "interface" "address, specifying for local message"
4429 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4430 option sets the IP interface address value. A port number may be included,
4431 using the same syntax as for &%-oMa%&. The interface address is placed in
4432 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4434 .vitem &%-oMm%&&~<&'message&~reference'&>
4436 .cindex "message reference" "message reference, specifying for local message"
4437 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4438 option sets the message reference, e.g. message-id, and is logged during
4439 delivery. This is useful when some kind of audit trail is required to tie
4440 messages together. The format of the message reference is checked and will
4441 abort if the format is invalid. The option will only be accepted if exim is
4442 running in trusted mode, not as any regular user.
4444 The best example of a message reference is when Exim sends a bounce message.
4445 The message reference is the message-id of the original message for which Exim
4446 is sending the bounce.
4448 .vitem &%-oMr%&&~<&'protocol&~name'&>
4450 .cindex "protocol, specifying for local message"
4451 .vindex "&$received_protocol$&"
4452 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4453 option sets the received protocol value that is stored in
4454 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4455 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4456 SMTP protocol names (see the description of &$received_protocol$& in section
4457 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4458 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4459 be set by &%-oMr%&. Repeated use of this option is not supported.
4461 .vitem &%-oMs%&&~<&'host&~name'&>
4463 .cindex "sender" "host name, specifying for local message"
4464 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4465 option sets the sender host name in &$sender_host_name$&. When this option is
4466 present, Exim does not attempt to look up a host name from an IP address; it
4467 uses the name it is given.
4469 .vitem &%-oMt%&&~<&'ident&~string'&>
4471 .cindex "sender" "ident string, specifying for local message"
4472 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4473 option sets the sender ident value in &$sender_ident$&. The default setting for
4474 local callers is the login id of the calling process, except when &%-bh%& is
4475 used, when there is no default.
4479 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4480 In Sendmail, this option means &"me too"&, indicating that the sender of a
4481 message should receive a copy of the message if the sender appears in an alias
4482 expansion. Exim always does this, so the option does nothing.
4486 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4487 This option is ignored. In Sendmail it specifies &"old style headers"&,
4488 whatever that means.
4490 .vitem &%-oP%&&~<&'path'&>
4492 .cindex "pid (process id)" "of daemon"
4493 .cindex "daemon" "process id (pid)"
4494 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4495 value. The option specifies the file to which the process id of the daemon is
4496 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4497 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4498 because in those cases, the normal pid file is not used.
4502 .cindex "pid (process id)" "of daemon"
4503 .cindex "daemon" "process id (pid)"
4504 This option is not intended for general use.
4505 The daemon uses it when terminating due to a SIGTEM, possibly in
4506 combination with &%-oP%&&~<&'path'&>.
4507 It causes the pid file to be removed.
4509 .vitem &%-or%&&~<&'time'&>
4511 .cindex "timeout" "for non-SMTP input"
4512 This option sets a timeout value for incoming non-SMTP messages. If it is not
4513 set, Exim will wait forever for the standard input. The value can also be set
4514 by the &%receive_timeout%& option. The format used for specifying times is
4515 described in section &<<SECTtimeformat>>&.
4517 .vitem &%-os%&&~<&'time'&>
4519 .cindex "timeout" "for SMTP input"
4520 .cindex "SMTP" "input timeout"
4521 This option sets a timeout value for incoming SMTP messages. The timeout
4522 applies to each SMTP command and block of data. The value can also be set by
4523 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4524 for specifying times is described in section &<<SECTtimeformat>>&.
4528 This option has exactly the same effect as &%-v%&.
4530 .vitem &%-oX%&&~<&'number&~or&~string'&>
4532 .cindex "TCP/IP" "setting listening ports"
4533 .cindex "TCP/IP" "setting listening interfaces"
4534 .cindex "port" "receiving TCP/IP"
4535 This option is relevant only when the &%-bd%& (start listening daemon) option
4536 is also given. It controls which ports and interfaces the daemon uses. Details
4537 of the syntax, and how it interacts with configuration file options, are given
4538 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4539 file is written unless &%-oP%& is also present to specify a pid filename.
4544 .cindex "daemon notifier socket"
4545 This option controls the creation of an inter-process communications endpoint
4547 It is only relevant when the &%-bd%& (start listening daemon) option is also
4549 Normally the daemon creates this socket, unless a &%-oX%& and &*no*& &%-oP%&
4550 option is also present.
4551 If this option is given then the socket will not be created. This could be
4552 required if the system is running multiple daemons.
4554 The socket is currently used for
4556 fast ramp-up of queue runner processes
4558 obtaining a current queue size
4564 .cindex "Perl" "starting the interpreter"
4565 This option applies when an embedded Perl interpreter is linked with Exim (see
4566 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4567 option, forcing the starting of the interpreter to be delayed until it is
4572 .cindex "Perl" "starting the interpreter"
4573 This option applies when an embedded Perl interpreter is linked with Exim (see
4574 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4575 option, forcing the starting of the interpreter to occur as soon as Exim is
4578 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4580 For compatibility with Sendmail, this option is equivalent to
4582 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4584 It sets the incoming protocol and host name (for trusted callers). The
4585 host name and its colon can be omitted when only the protocol is to be set.
4586 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4587 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4588 or &`s`& using this option (but that does not seem a real limitation).
4589 Repeated use of this option is not supported.
4593 .cindex "queue runner" "starting manually"
4594 This option is normally restricted to admin users. However, there is a
4595 configuration option called &%prod_requires_admin%& which can be set false to
4596 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4597 and &%-S%& options).
4599 .cindex "queue runner" "description of operation"
4600 If other commandline options do not specify an action,
4601 the &%-q%& option starts one queue runner process. This scans the queue of
4602 waiting messages, and runs a delivery process for each one in turn. It waits
4603 for each delivery process to finish before starting the next one. A delivery
4604 process may not actually do any deliveries if the retry times for the addresses
4605 have not been reached. Use &%-qf%& (see below) if you want to override this.
4608 .cindex "SMTP" "passed connection"
4609 .cindex "SMTP" "multiple deliveries"
4610 .cindex "multiple SMTP deliveries"
4611 the delivery process spawns other processes to deliver other messages down
4612 passed SMTP connections, the queue runner waits for these to finish before
4615 When all the queued messages have been considered, the original queue runner
4616 process terminates. In other words, a single pass is made over the waiting
4617 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4618 this to be repeated periodically.
4620 Exim processes the waiting messages in an unpredictable order. It isn't very
4621 random, but it is likely to be different each time, which is all that matters.
4622 If one particular message screws up a remote MTA, other messages to the same
4623 MTA have a chance of getting through if they get tried first.
4625 It is possible to cause the messages to be processed in lexical message id
4626 order, which is essentially the order in which they arrived, by setting the
4627 &%queue_run_in_order%& option, but this is not recommended for normal use.
4629 .vitem &%-q%&<&'qflags'&>
4630 The &%-q%& option may be followed by one or more flag letters that change its
4631 behaviour. They are all optional, but if more than one is present, they must
4632 appear in the correct order. Each flag is described in a separate item below.
4636 .cindex "queue" "double scanning"
4637 .cindex "queue" "routing"
4638 .cindex "routing" "whole queue before delivery"
4639 .cindex "first pass routing"
4640 .cindex "queue runner" "two phase"
4641 An option starting with &%-qq%& requests a two-stage queue run. In the first
4642 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4643 every domain. Addresses are routed, local deliveries happen, but no remote
4646 Performance will be best if the &%queue_run_in_order%& option is false.
4647 If that is so and the &%queue_fast_ramp%& option is true then
4648 in the first phase of the run,
4649 once a threshold number of messages are routed for a given host,
4650 a delivery process is forked in parallel with the rest of the scan.
4652 .cindex "hints database" "remembering routing"
4653 The hints database that remembers which messages are waiting for specific hosts
4654 is updated, as if delivery to those hosts had been deferred. After this is
4655 complete, a second, normal queue scan happens, with routing and delivery taking
4656 place as normal. Messages that are routed to the same host should mostly be
4657 delivered down a single SMTP
4658 .cindex "SMTP" "passed connection"
4659 .cindex "SMTP" "multiple deliveries"
4660 .cindex "multiple SMTP deliveries"
4661 connection because of the hints that were set up during the first queue scan.
4662 This option may be useful for hosts that are connected to the Internet
4665 .vitem &%-q[q]i...%&
4667 .cindex "queue" "initial delivery"
4668 If the &'i'& flag is present, the queue runner runs delivery processes only for
4669 those messages that haven't previously been tried. (&'i'& stands for &"initial
4670 delivery"&.) This can be helpful if you are putting messages in the queue using
4671 &%-odq%& and want a queue runner just to process the new messages.
4673 .vitem &%-q[q][i]f...%&
4675 .cindex "queue" "forcing delivery"
4676 .cindex "delivery" "forcing in queue run"
4677 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4678 message, whereas without &'f'& only those non-frozen addresses that have passed
4679 their retry times are tried.
4681 .vitem &%-q[q][i]ff...%&
4683 .cindex "frozen messages" "forcing delivery"
4684 If &'ff'& is present, a delivery attempt is forced for every message, whether
4687 .vitem &%-q[q][i][f[f]]l%&
4689 .cindex "queue" "local deliveries only"
4690 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4691 be done. If a message requires any remote deliveries, it remains in the queue
4694 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4697 .cindex "named queues" "deliver from"
4698 .cindex "queue" "delivering specific messages"
4699 If the &'G'& flag and a name is present, the queue runner operates on the
4700 queue with the given name rather than the default queue.
4701 The name should not contain a &'/'& character.
4702 For a periodic queue run (see below)
4703 append to the name a slash and a time value.
4705 If other commandline options specify an action, a &'-qG<name>'& option
4706 will specify a queue to operate on.
4709 exim -bp -qGquarantine
4711 exim -qGoffpeak -Rf @special.domain.example
4714 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4715 When scanning the queue, Exim can be made to skip over messages whose ids are
4716 lexically less than a given value by following the &%-q%& option with a
4717 starting message id. For example:
4719 exim -q 0t5C6f-0000c8-00
4721 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4722 second message id is given, messages whose ids are lexically greater than it
4723 are also skipped. If the same id is given twice, for example,
4725 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4727 just one delivery process is started, for that message. This differs from
4728 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4729 that it counts as a delivery from a queue run. Note that the selection
4730 mechanism does not affect the order in which the messages are scanned. There
4731 are also other ways of selecting specific sets of messages for delivery in a
4732 queue run &-- see &%-R%& and &%-S%&.
4734 .vitem &%-q%&<&'qflags'&><&'time'&>
4735 .cindex "queue runner" "starting periodically"
4736 .cindex "periodic queue running"
4737 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4738 starting a queue runner process at intervals specified by the given time value
4739 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4740 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4741 single daemon process handles both functions. A common way of starting up a
4742 combined daemon at system boot time is to use a command such as
4744 /usr/exim/bin/exim -bd -q30m
4746 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4747 process every 30 minutes.
4749 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4750 pid file is written unless one is explicitly requested by the &%-oP%& option.
4752 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4754 This option is synonymous with &%-R%&. It is provided for Sendmail
4757 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4759 This option is synonymous with &%-S%&.
4761 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4763 .cindex "queue runner" "for specific recipients"
4764 .cindex "delivery" "to given domain"
4765 .cindex "domain" "delivery to"
4766 The <&'rsflags'&> may be empty, in which case the white space before the string
4767 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4768 which are the possible values for <&'rsflags'&>. White space is required if
4769 <&'rsflags'&> is not empty.
4771 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4772 perform a single queue run, except that, when scanning the messages on the
4773 queue, Exim processes only those that have at least one undelivered recipient
4774 address containing the given string, which is checked in a case-independent
4775 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4776 regular expression; otherwise it is a literal string.
4778 If you want to do periodic queue runs for messages with specific recipients,
4779 you can combine &%-R%& with &%-q%& and a time value. For example:
4781 exim -q25m -R @special.domain.example
4783 This example does a queue run for messages with recipients in the given domain
4784 every 25 minutes. Any additional flags that are specified with &%-q%& are
4785 applied to each queue run.
4787 Once a message is selected for delivery by this mechanism, all its addresses
4788 are processed. For the first selected message, Exim overrides any retry
4789 information and forces a delivery attempt for each undelivered address. This
4790 means that if delivery of any address in the first message is successful, any
4791 existing retry information is deleted, and so delivery attempts for that
4792 address in subsequently selected messages (which are processed without forcing)
4793 will run. However, if delivery of any address does not succeed, the retry
4794 information is updated, and in subsequently selected messages, the failing
4795 address will be skipped.
4797 .cindex "frozen messages" "forcing delivery"
4798 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4799 all selected messages, not just the first; frozen messages are included when
4802 The &%-R%& option makes it straightforward to initiate delivery of all messages
4803 to a given domain after a host has been down for some time. When the SMTP
4804 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4805 effect is to run Exim with the &%-R%& option, but it can be configured to run
4806 an arbitrary command instead.
4810 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4812 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4814 .cindex "delivery" "from given sender"
4815 .cindex "queue runner" "for specific senders"
4816 This option acts like &%-R%& except that it checks the string against each
4817 message's sender instead of against the recipients. If &%-R%& is also set, both
4818 conditions must be met for a message to be selected. If either of the options
4819 has &'f'& or &'ff'& in its flags, the associated action is taken.
4821 .vitem &%-Tqt%&&~<&'times'&>
4823 This is an option that is exclusively for use by the Exim testing suite. It is not
4824 recognized when Exim is run normally. It allows for the setting up of explicit
4825 &"queue times"& so that various warning/retry features can be tested.
4829 .cindex "recipient" "extracting from header lines"
4833 When Exim is receiving a locally-generated, non-SMTP message on its standard
4834 input, the &%-t%& option causes the recipients of the message to be obtained
4835 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4836 from the command arguments. The addresses are extracted before any rewriting
4837 takes place and the &'Bcc:'& header line, if present, is then removed.
4839 .cindex "Sendmail compatibility" "&%-t%& option"
4840 If the command has any arguments, they specify addresses to which the message
4841 is &'not'& to be delivered. That is, the argument addresses are removed from
4842 the recipients list obtained from the headers. This is compatible with Smail 3
4843 and in accordance with the documented behaviour of several versions of
4844 Sendmail, as described in man pages on a number of operating systems (e.g.
4845 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4846 argument addresses to those obtained from the headers, and the O'Reilly
4847 Sendmail book documents it that way. Exim can be made to add argument addresses
4848 instead of subtracting them by setting the option
4849 &%extract_addresses_remove_arguments%& false.
4851 .cindex "&%Resent-%& header lines" "with &%-t%&"
4852 If there are any &%Resent-%& header lines in the message, Exim extracts
4853 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4854 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4855 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4856 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4858 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4859 message is resent several times). The RFC also specifies that they should be
4860 added at the front of the message, and separated by &'Received:'& lines. It is
4861 not at all clear how &%-t%& should operate in the present of multiple sets,
4862 nor indeed exactly what constitutes a &"set"&.
4863 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4864 are often added at the end of the header, and if a message is resent more than
4865 once, it is common for the original set of &%Resent-%& headers to be renamed as
4866 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4870 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4871 compatibility with Sendmail.
4873 .vitem &%-tls-on-connect%&
4874 .oindex "&%-tls-on-connect%&"
4875 .cindex "TLS" "use without STARTTLS"
4876 .cindex "TLS" "automatic start"
4877 This option is available when Exim is compiled with TLS support. It forces all
4878 incoming SMTP connections to behave as if the incoming port is listed in the
4879 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4880 &<<CHAPTLS>>& for further details.
4885 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4886 Sendmail uses this option for &"initial message submission"&, and its
4887 documentation states that in future releases, it may complain about
4888 syntactically invalid messages rather than fixing them when this flag is not
4889 set. Exim ignores this option.
4893 This option causes Exim to write information to the standard error stream,
4894 describing what it is doing. In particular, it shows the log lines for
4895 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4896 dialogue is shown. Some of the log lines shown may not actually be written to
4897 the log if the setting of &%log_selector%& discards them. Any relevant
4898 selectors are shown with each log line. If none are shown, the logging is
4903 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4904 National Language Support extended characters in the body of the mail item"&).
4905 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4908 .vitem &%-X%&&~<&'logfile'&>
4910 This option is interpreted by Sendmail to cause debug information to be sent
4911 to the named file. It is ignored by Exim.
4913 .vitem &%-z%&&~<&'log-line'&>
4915 This option writes its argument to Exim's logfile.
4916 Use is restricted to administrators; the intent is for operational notes.
4917 Quotes should be used to maintain a multi-word item as a single argument,
4925 . ////////////////////////////////////////////////////////////////////////////
4926 . Insert a stylized DocBook comment here, to identify the end of the command
4927 . line options. This is for the benefit of the Perl script that automatically
4928 . creates a man page for the options.
4929 . ////////////////////////////////////////////////////////////////////////////
4932 <!-- === End of command line options === -->
4939 . ////////////////////////////////////////////////////////////////////////////
4940 . ////////////////////////////////////////////////////////////////////////////
4943 .chapter "The Exim runtime configuration file" "CHAPconf" &&&
4944 "The runtime configuration file"
4946 .cindex "runtime configuration"
4947 .cindex "configuration file" "general description"
4948 .cindex "CONFIGURE_FILE"
4949 .cindex "configuration file" "errors in"
4950 .cindex "error" "in configuration file"
4951 .cindex "return code" "for bad configuration"
4952 Exim uses a single runtime configuration file that is read whenever an Exim
4953 binary is executed. Note that in normal operation, this happens frequently,
4954 because Exim is designed to operate in a distributed manner, without central
4957 If a syntax error is detected while reading the configuration file, Exim
4958 writes a message on the standard error, and exits with a non-zero return code.
4959 The message is also written to the panic log. &*Note*&: Only simple syntax
4960 errors can be detected at this time. The values of any expanded options are
4961 not checked until the expansion happens, even when the expansion does not
4962 actually alter the string.
4964 The name of the configuration file is compiled into the binary for security
4965 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4966 most configurations, this specifies a single file. However, it is permitted to
4967 give a colon-separated list of filenames, in which case Exim uses the first
4968 existing file in the list.
4971 .cindex "EXIM_GROUP"
4972 .cindex "CONFIGURE_OWNER"
4973 .cindex "CONFIGURE_GROUP"
4974 .cindex "configuration file" "ownership"
4975 .cindex "ownership" "configuration file"
4976 The runtime configuration file must be owned by root or by the user that is
4977 specified at compile time by the CONFIGURE_OWNER option (if set). The
4978 configuration file must not be world-writeable, or group-writeable unless its
4979 group is the root group or the one specified at compile time by the
4980 CONFIGURE_GROUP option.
4982 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4983 to root, anybody who is able to edit the runtime configuration file has an
4984 easy way to run commands as root. If you specify a user or group in the
4985 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4986 who are members of that group will trivially be able to obtain root privileges.
4988 Up to Exim version 4.72, the runtime configuration file was also permitted to
4989 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4990 since it offered a simple privilege escalation for any attacker who managed to
4991 compromise the Exim user account.
4993 A default configuration file, which will work correctly in simple situations,
4994 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4995 defines just one filename, the installation process copies the default
4996 configuration to a new file of that name if it did not previously exist. If
4997 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4998 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
5003 .section "Using a different configuration file" "SECID40"
5004 .cindex "configuration file" "alternate"
5005 A one-off alternate configuration can be specified by the &%-C%& command line
5006 option, which may specify a single file or a list of files. However, when
5007 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
5008 unless the argument for &%-C%& is identical to the built-in value from
5009 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
5010 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
5011 is useful mainly for checking the syntax of configuration files before
5012 installing them. No owner or group checks are done on a configuration file
5013 specified by &%-C%&, if root privilege has been dropped.
5015 Even the Exim user is not trusted to specify an arbitrary configuration file
5016 with the &%-C%& option to be used with root privileges, unless that file is
5017 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
5018 testing a configuration using &%-C%& right through message reception and
5019 delivery, even if the caller is root. The reception works, but by that time,
5020 Exim is running as the Exim user, so when it re-execs to regain privilege for
5021 the delivery, the use of &%-C%& causes privilege to be lost. However, root
5022 can test reception and delivery using two separate commands (one to put a
5023 message in the queue, using &%-odq%&, and another to do the delivery, using
5026 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
5027 prefix string with which any file named in a &%-C%& command line option must
5028 start. In addition, the filename must not contain the sequence &"&`/../`&"&.
5029 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any
5030 filename can be used with &%-C%&.
5032 One-off changes to a configuration can be specified by the &%-D%& command line
5033 option, which defines and overrides values for macros used inside the
5034 configuration file. However, like &%-C%&, the use of this option by a
5035 non-privileged user causes Exim to discard its root privilege.
5036 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
5037 completely disabled, and its use causes an immediate error exit.
5039 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
5040 to declare certain macro names trusted, such that root privilege will not
5041 necessarily be discarded.
5042 WHITELIST_D_MACROS defines a colon-separated list of macros which are
5043 considered safe and, if &%-D%& only supplies macros from this list, and the
5044 values are acceptable, then Exim will not give up root privilege if the caller
5045 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
5046 transition mechanism and is expected to be removed in the future. Acceptable
5047 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
5049 Some sites may wish to use the same Exim binary on different machines that
5050 share a file system, but to use different configuration files on each machine.
5051 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
5052 looks for a file whose name is the configuration filename followed by a dot
5053 and the machine's node name, as obtained from the &[uname()]& function. If this
5054 file does not exist, the standard name is tried. This processing occurs for
5055 each filename in the list given by CONFIGURE_FILE or &%-C%&.
5057 In some esoteric situations different versions of Exim may be run under
5058 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
5059 help with this. See the comments in &_src/EDITME_& for details.
5063 .section "Configuration file format" "SECTconffilfor"
5064 .cindex "configuration file" "format of"
5065 .cindex "format" "configuration file"
5066 Exim's configuration file is divided into a number of different parts. General
5067 option settings must always appear at the start of the file. The other parts
5068 are all optional, and may appear in any order. Each part other than the first
5069 is introduced by the word &"begin"& followed by at least one literal
5070 space, and the name of the part. The optional parts are:
5073 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
5076 .cindex "AUTH" "configuration"
5077 &'authenticators'&: Configuration settings for the authenticator drivers. These
5078 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
5080 &'routers'&: Configuration settings for the router drivers. Routers process
5081 addresses and determine how the message is to be delivered (see chapters
5082 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
5084 &'transports'&: Configuration settings for the transport drivers. Transports
5085 define mechanisms for copying messages to destinations (see chapters
5086 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
5088 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
5089 If there is no retry section, or if it is empty (that is, no retry rules are
5090 defined), Exim will not retry deliveries. In this situation, temporary errors
5091 are treated the same as permanent errors. Retry rules are discussed in chapter
5094 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
5095 when new addresses are generated during delivery. Rewriting is discussed in
5096 chapter &<<CHAPrewrite>>&.
5098 &'local_scan'&: Private options for the &[local_scan()]& function. If you
5099 want to use this feature, you must set
5101 LOCAL_SCAN_HAS_OPTIONS=yes
5103 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
5104 facility are given in chapter &<<CHAPlocalscan>>&.
5107 .cindex "configuration file" "leading white space in"
5108 .cindex "configuration file" "trailing white space in"
5109 .cindex "white space" "in configuration file"
5110 Leading and trailing white space in configuration lines is always ignored.
5112 Blank lines in the file, and lines starting with a # character (ignoring
5113 leading white space) are treated as comments and are ignored. &*Note*&: A
5114 # character other than at the beginning of a line is not treated specially,
5115 and does not introduce a comment.
5117 Any non-comment line can be continued by ending it with a backslash. Note that
5118 the general rule for white space means that trailing white space after the
5119 backslash and leading white space at the start of continuation
5120 lines is ignored. Comment lines beginning with # (but not empty lines) may
5121 appear in the middle of a sequence of continuation lines.
5123 A convenient way to create a configuration file is to start from the
5124 default, which is supplied in &_src/configure.default_&, and add, delete, or
5125 change settings as required.
5127 The ACLs, retry rules, and rewriting rules have their own syntax which is
5128 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
5129 respectively. The other parts of the configuration file have some syntactic
5130 items in common, and these are described below, from section &<<SECTcos>>&
5131 onwards. Before that, the inclusion, macro, and conditional facilities are
5136 .section "File inclusions in the configuration file" "SECID41"
5137 .cindex "inclusions in configuration file"
5138 .cindex "configuration file" "including other files"
5139 .cindex "&`.include`& in configuration file"
5140 .cindex "&`.include_if_exists`& in configuration file"
5141 You can include other files inside Exim's runtime configuration file by
5144 &`.include`& <&'filename'&>
5145 &`.include_if_exists`& <&'filename'&>
5147 on a line by itself. Double quotes round the filename are optional. If you use
5148 the first form, a configuration error occurs if the file does not exist; the
5149 second form does nothing for non-existent files.
5150 The first form allows a relative name. It is resolved relative to
5151 the directory of the including file. For the second form an absolute filename
5154 Includes may be nested to any depth, but remember that Exim reads its
5155 configuration file often, so it is a good idea to keep them to a minimum.
5156 If you change the contents of an included file, you must HUP the daemon,
5157 because an included file is read only when the configuration itself is read.
5159 The processing of inclusions happens early, at a physical line level, so, like
5160 comment lines, an inclusion can be used in the middle of an option setting,
5163 hosts_lookup = a.b.c \
5166 Include processing happens after macro processing (see below). Its effect is to
5167 process the lines of the included file as if they occurred inline where the
5172 .section "Macros in the configuration file" "SECTmacrodefs"
5173 .cindex "macro" "description of"
5174 .cindex "configuration file" "macros"
5175 If a line in the main part of the configuration (that is, before the first
5176 &"begin"& line) begins with an upper case letter, it is taken as a macro
5177 definition, and must be of the form
5179 <&'name'&> = <&'rest of line'&>
5181 The name must consist of letters, digits, and underscores, and need not all be
5182 in upper case, though that is recommended. The rest of the line, including any
5183 continuations, is the replacement text, and has leading and trailing white
5184 space removed. Quotes are not removed. The replacement text can never end with
5185 a backslash character, but this doesn't seem to be a serious limitation.
5187 Macros may also be defined between router, transport, authenticator, or ACL
5188 definitions. They may not, however, be defined within an individual driver or
5189 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
5191 .section "Macro substitution" "SECID42"
5192 Once a macro is defined, all subsequent lines in the file (and any included
5193 files) are scanned for the macro name; if there are several macros, the line is
5194 scanned for each, in turn, in the order in which the macros are defined. The
5195 replacement text is not re-scanned for the current macro, though it is scanned
5196 for subsequently defined macros. For this reason, a macro name may not contain
5197 the name of a previously defined macro as a substring. You could, for example,
5200 &`ABCD_XYZ = `&<&'something'&>
5201 &`ABCD = `&<&'something else'&>
5203 but putting the definitions in the opposite order would provoke a configuration
5204 error. Macro expansion is applied to individual physical lines from the file,
5205 before checking for line continuation or file inclusion (see above). If a line
5206 consists solely of a macro name, and the expansion of the macro is empty, the
5207 line is ignored. A macro at the start of a line may turn the line into a
5208 comment line or a &`.include`& line.
5211 .section "Redefining macros" "SECID43"
5212 Once defined, the value of a macro can be redefined later in the configuration
5213 (or in an included file). Redefinition is specified by using &'=='& instead of
5218 MAC == updated value
5220 Redefinition does not alter the order in which the macros are applied to the
5221 subsequent lines of the configuration file. It is still the same order in which
5222 the macros were originally defined. All that changes is the macro's value.
5223 Redefinition makes it possible to accumulate values. For example:
5227 MAC == MAC and something added
5229 This can be helpful in situations where the configuration file is built
5230 from a number of other files.
5232 .section "Overriding macro values" "SECID44"
5233 The values set for macros in the configuration file can be overridden by the
5234 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5235 used, unless called by root or the Exim user. A definition on the command line
5236 using the &%-D%& option causes all definitions and redefinitions within the
5241 .section "Example of macro usage" "SECID45"
5242 As an example of macro usage, consider a configuration where aliases are looked
5243 up in a MySQL database. It helps to keep the file less cluttered if long
5244 strings such as SQL statements are defined separately as macros, for example:
5246 ALIAS_QUERY = select mailbox from user where \
5247 login='${quote_mysql:$local_part}';
5249 This can then be used in a &(redirect)& router setting like this:
5251 data = ${lookup mysql{ALIAS_QUERY}}
5253 In earlier versions of Exim macros were sometimes used for domain, host, or
5254 address lists. In Exim 4 these are handled better by named lists &-- see
5255 section &<<SECTnamedlists>>&.
5258 .section "Builtin macros" "SECTbuiltinmacros"
5259 Exim defines some macros depending on facilities available, which may
5260 differ due to build-time definitions and from one release to another.
5261 All of these macros start with an underscore.
5262 They can be used to conditionally include parts of a configuration
5265 The following classes of macros are defined:
5267 &` _HAVE_* `& build-time defines
5268 &` _DRIVER_ROUTER_* `& router drivers
5269 &` _DRIVER_TRANSPORT_* `& transport drivers
5270 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5271 &` _LOG_* `& log_selector values
5272 &` _OPT_MAIN_* `& main config options
5273 &` _OPT_ROUTERS_* `& generic router options
5274 &` _OPT_TRANSPORTS_* `& generic transport options
5275 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5276 &` _OPT_ROUTER_*_* `& private router options
5277 &` _OPT_TRANSPORT_*_* `& private transport options
5278 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5281 Use an &"exim -bP macros"& command to get the list of macros.
5284 .section "Conditional skips in the configuration file" "SECID46"
5285 .cindex "configuration file" "conditional skips"
5286 .cindex "&`.ifdef`&"
5287 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5288 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5289 portions of the configuration file. The processing happens whenever the file is
5290 read (that is, when an Exim binary starts to run).
5292 The implementation is very simple. Instances of the first four directives must
5293 be followed by text that includes the names of one or macros. The condition
5294 that is tested is whether or not any macro substitution has taken place in the
5298 message_size_limit = 50M
5300 message_size_limit = 100M
5303 sets a message size limit of 50M if the macro &`AAA`& is defined
5304 (or &`A`& or &`AA`&), and 100M
5305 otherwise. If there is more than one macro named on the line, the condition
5306 is true if any of them are defined. That is, it is an &"or"& condition. To
5307 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5309 Although you can use a macro expansion to generate one of these directives,
5310 it is not very useful, because the condition &"there was a macro substitution
5311 in this line"& will always be true.
5313 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5314 to clarify complicated nestings.
5318 .section "Common option syntax" "SECTcos"
5319 .cindex "common option syntax"
5320 .cindex "syntax of common options"
5321 .cindex "configuration file" "common option syntax"
5322 For the main set of options, driver options, and &[local_scan()]& options,
5323 each setting is on a line by itself, and starts with a name consisting of
5324 lower-case letters and underscores. Many options require a data value, and in
5325 these cases the name must be followed by an equals sign (with optional white
5326 space) and then the value. For example:
5328 qualify_domain = mydomain.example.com
5330 .cindex "hiding configuration option values"
5331 .cindex "configuration options" "hiding value of"
5332 .cindex "options" "hiding value of"
5333 Some option settings may contain sensitive data, for example, passwords for
5334 accessing databases. To stop non-admin users from using the &%-bP%& command
5335 line option to read these values, you can precede the option settings with the
5336 word &"hide"&. For example:
5338 hide mysql_servers = localhost/users/admin/secret-password
5340 For non-admin users, such options are displayed like this:
5342 mysql_servers = <value not displayable>
5344 If &"hide"& is used on a driver option, it hides the value of that option on
5345 all instances of the same driver.
5347 The following sections describe the syntax used for the different data types
5348 that are found in option settings.
5351 .section "Boolean options" "SECID47"
5352 .cindex "format" "boolean"
5353 .cindex "boolean configuration values"
5354 .oindex "&%no_%&&'xxx'&"
5355 .oindex "&%not_%&&'xxx'&"
5356 Options whose type is given as boolean are on/off switches. There are two
5357 different ways of specifying such options: with and without a data value. If
5358 the option name is specified on its own without data, the switch is turned on;
5359 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5360 boolean options may be followed by an equals sign and one of the words
5361 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5362 the following two settings have exactly the same effect:
5367 The following two lines also have the same (opposite) effect:
5372 You can use whichever syntax you prefer.
5377 .section "Integer values" "SECID48"
5378 .cindex "integer configuration values"
5379 .cindex "format" "integer"
5380 If an option's type is given as &"integer"&, the value can be given in decimal,
5381 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5382 number is assumed. Otherwise, it is treated as an octal number unless it starts
5383 with the characters &"0x"&, in which case the remainder is interpreted as a
5386 If an integer value is followed by the letter K, it is multiplied by 1024; if
5387 it is followed by the letter M, it is multiplied by 1024x1024;
5388 if by the letter G, 1024x1024x1024.
5390 of integer option settings are output, values which are an exact multiple of
5391 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5392 and M. The printing style is independent of the actual input format that was
5396 .section "Octal integer values" "SECID49"
5397 .cindex "integer format"
5398 .cindex "format" "octal integer"
5399 If an option's type is given as &"octal integer"&, its value is always
5400 interpreted as an octal number, whether or not it starts with the digit zero.
5401 Such options are always output in octal.
5404 .section "Fixed point numbers" "SECID50"
5405 .cindex "fixed point configuration values"
5406 .cindex "format" "fixed point"
5407 If an option's type is given as &"fixed-point"&, its value must be a decimal
5408 integer, optionally followed by a decimal point and up to three further digits.
5412 .section "Time intervals" "SECTtimeformat"
5413 .cindex "time interval" "specifying in configuration"
5414 .cindex "format" "time interval"
5415 A time interval is specified as a sequence of numbers, each followed by one of
5416 the following letters, with no intervening white space:
5426 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5427 intervals are output in the same format. Exim does not restrict the values; it
5428 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5432 .section "String values" "SECTstrings"
5433 .cindex "string" "format of configuration values"
5434 .cindex "format" "string"
5435 If an option's type is specified as &"string"&, the value can be specified with
5436 or without double-quotes. If it does not start with a double-quote, the value
5437 consists of the remainder of the line plus any continuation lines, starting at
5438 the first character after any leading white space, with trailing white space
5439 removed, and with no interpretation of the characters in the string. Because
5440 Exim removes comment lines (those beginning with #) at an early stage, they can
5441 appear in the middle of a multi-line string. The following two settings are
5442 therefore equivalent:
5444 trusted_users = uucp:mail
5445 trusted_users = uucp:\
5446 # This comment line is ignored
5449 .cindex "string" "quoted"
5450 .cindex "escape characters in quoted strings"
5451 If a string does start with a double-quote, it must end with a closing
5452 double-quote, and any backslash characters other than those used for line
5453 continuation are interpreted as escape characters, as follows:
5456 .irow &`\\`& "single backslash"
5457 .irow &`\n`& "newline"
5458 .irow &`\r`& "carriage return"
5460 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5461 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5465 If a backslash is followed by some other character, including a double-quote
5466 character, that character replaces the pair.
5468 Quoting is necessary only if you want to make use of the backslash escapes to
5469 insert special characters, or if you need to specify a value with leading or
5470 trailing spaces. These cases are rare, so quoting is almost never needed in
5471 current versions of Exim. In versions of Exim before 3.14, quoting was required
5472 in order to continue lines, so you may come across older configuration files
5473 and examples that apparently quote unnecessarily.
5476 .section "Expanded strings" "SECID51"
5477 .cindex "expansion" "definition of"
5478 Some strings in the configuration file are subjected to &'string expansion'&,
5479 by which means various parts of the string may be changed according to the
5480 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5481 is as just described; in particular, the handling of backslashes in quoted
5482 strings is done as part of the input process, before expansion takes place.
5483 However, backslash is also an escape character for the expander, so any
5484 backslashes that are required for that reason must be doubled if they are
5485 within a quoted configuration string.
5488 .section "User and group names" "SECID52"
5489 .cindex "user name" "format of"
5490 .cindex "format" "user name"
5491 .cindex "groups" "name format"
5492 .cindex "format" "group name"
5493 User and group names are specified as strings, using the syntax described
5494 above, but the strings are interpreted specially. A user or group name must
5495 either consist entirely of digits, or be a name that can be looked up using the
5496 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5499 .section "List construction" "SECTlistconstruct"
5500 .cindex "list" "syntax of in configuration"
5501 .cindex "format" "list item in configuration"
5502 .cindex "string" "list, definition of"
5503 The data for some configuration options is a list of items, with colon as the
5504 default separator. Many of these options are shown with type &"string list"& in
5505 the descriptions later in this document. Others are listed as &"domain list"&,
5506 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5507 are all the same; however, those other than &"string list"& are subject to
5508 particular kinds of interpretation, as described in chapter
5509 &<<CHAPdomhosaddlists>>&.
5511 In all these cases, the entire list is treated as a single string as far as the
5512 input syntax is concerned. The &%trusted_users%& setting in section
5513 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5514 in a list, it must be entered as two colons. Leading and trailing white space
5515 on each item in a list is ignored. This makes it possible to include items that
5516 start with a colon, and in particular, certain forms of IPv6 address. For
5519 local_interfaces = 127.0.0.1 : ::::1
5521 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5523 &*Note*&: Although leading and trailing white space is ignored in individual
5524 list items, it is not ignored when parsing the list. The spaces around the first
5525 colon in the example above are necessary. If they were not there, the list would
5526 be interpreted as the two items 127.0.0.1:: and 1.
5528 .section "Changing list separators" "SECTlistsepchange"
5529 .cindex "list separator" "changing"
5530 .cindex "IPv6" "addresses in lists"
5531 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5532 introduced to allow the separator character to be changed. If a list begins
5533 with a left angle bracket, followed by any punctuation character, that
5534 character is used instead of colon as the list separator. For example, the list
5535 above can be rewritten to use a semicolon separator like this:
5537 local_interfaces = <; 127.0.0.1 ; ::1
5539 This facility applies to all lists, with the exception of the list in
5540 &%log_file_path%&. It is recommended that the use of non-colon separators be
5541 confined to circumstances where they really are needed.
5543 .cindex "list separator" "newline as"
5544 .cindex "newline" "as list separator"
5545 It is also possible to use newline and other control characters (those with
5546 code values less than 32, plus DEL) as separators in lists. Such separators
5547 must be provided literally at the time the list is processed. For options that
5548 are string-expanded, you can write the separator using a normal escape
5549 sequence. This will be processed by the expander before the string is
5550 interpreted as a list. For example, if a newline-separated list of domains is
5551 generated by a lookup, you can process it directly by a line such as this:
5553 domains = <\n ${lookup mysql{.....}}
5555 This avoids having to change the list separator in such data. You are unlikely
5556 to want to use a control character as a separator in an option that is not
5557 expanded, because the value is literal text. However, it can be done by giving
5558 the value in quotes. For example:
5560 local_interfaces = "<\n 127.0.0.1 \n ::1"
5562 Unlike printing character separators, which can be included in list items by
5563 doubling, it is not possible to include a control character as data when it is
5564 set as the separator. Two such characters in succession are interpreted as
5565 enclosing an empty list item.
5569 .section "Empty items in lists" "SECTempitelis"
5570 .cindex "list" "empty item in"
5571 An empty item at the end of a list is always ignored. In other words, trailing
5572 separator characters are ignored. Thus, the list in
5574 senders = user@domain :
5576 contains only a single item. If you want to include an empty string as one item
5577 in a list, it must not be the last item. For example, this list contains three
5578 items, the second of which is empty:
5580 senders = user1@domain : : user2@domain
5582 &*Note*&: There must be white space between the two colons, as otherwise they
5583 are interpreted as representing a single colon data character (and the list
5584 would then contain just one item). If you want to specify a list that contains
5585 just one, empty item, you can do it as in this example:
5589 In this case, the first item is empty, and the second is discarded because it
5590 is at the end of the list.
5595 .section "Format of driver configurations" "SECTfordricon"
5596 .cindex "drivers" "configuration format"
5597 There are separate parts in the configuration for defining routers, transports,
5598 and authenticators. In each part, you are defining a number of driver
5599 instances, each with its own set of options. Each driver instance is defined by
5600 a sequence of lines like this:
5602 <&'instance name'&>:
5607 In the following example, the instance name is &(localuser)&, and it is
5608 followed by three options settings:
5613 transport = local_delivery
5615 For each driver instance, you specify which Exim code module it uses &-- by the
5616 setting of the &%driver%& option &-- and (optionally) some configuration
5617 settings. For example, in the case of transports, if you want a transport to
5618 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5619 a local file you would use the &(appendfile)& driver. Each of the drivers is
5620 described in detail in its own separate chapter later in this manual.
5622 You can have several routers, transports, or authenticators that are based on
5623 the same underlying driver (each must have a different instance name).
5625 The order in which routers are defined is important, because addresses are
5626 passed to individual routers one by one, in order. The order in which
5627 transports are defined does not matter at all. The order in which
5628 authenticators are defined is used only when Exim, as a client, is searching
5629 them to find one that matches an authentication mechanism offered by the
5632 .cindex "generic options"
5633 .cindex "options" "generic &-- definition of"
5634 Within a driver instance definition, there are two kinds of option: &'generic'&
5635 and &'private'&. The generic options are those that apply to all drivers of the
5636 same type (that is, all routers, all transports or all authenticators). The
5637 &%driver%& option is a generic option that must appear in every definition.
5638 .cindex "private options"
5639 The private options are special for each driver, and none need appear, because
5640 they all have default values.
5642 The options may appear in any order, except that the &%driver%& option must
5643 precede any private options, since these depend on the particular driver. For
5644 this reason, it is recommended that &%driver%& always be the first option.
5646 Driver instance names, which are used for reference in log entries and
5647 elsewhere, can be any sequence of letters, digits, and underscores (starting
5648 with a letter) and must be unique among drivers of the same type. A router and
5649 a transport (for example) can each have the same name, but no two router
5650 instances can have the same name. The name of a driver instance should not be
5651 confused with the name of the underlying driver module. For example, the
5652 configuration lines:
5657 create an instance of the &(smtp)& transport driver whose name is
5658 &(remote_smtp)&. The same driver code can be used more than once, with
5659 different instance names and different option settings each time. A second
5660 instance of the &(smtp)& transport, with different options, might be defined
5666 command_timeout = 10s
5668 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5669 these transport instances from routers, and these names would appear in log
5672 Comment lines may be present in the middle of driver specifications. The full
5673 list of option settings for any particular driver instance, including all the
5674 defaulted values, can be extracted by making use of the &%-bP%& command line
5682 . ////////////////////////////////////////////////////////////////////////////
5683 . ////////////////////////////////////////////////////////////////////////////
5685 .chapter "The default configuration file" "CHAPdefconfil"
5686 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5687 .cindex "default" "configuration file &""walk through""&"
5688 The default configuration file supplied with Exim as &_src/configure.default_&
5689 is sufficient for a host with simple mail requirements. As an introduction to
5690 the way Exim is configured, this chapter &"walks through"& the default
5691 configuration, giving brief explanations of the settings. Detailed descriptions
5692 of the options are given in subsequent chapters. The default configuration file
5693 itself contains extensive comments about ways you might want to modify the
5694 initial settings. However, note that there are many options that are not
5695 mentioned at all in the default configuration.
5699 .section "Macros" "SECTdefconfmacros"
5700 All macros should be defined before any options.
5702 One macro is specified, but commented out, in the default configuration:
5704 # ROUTER_SMARTHOST=MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
5706 If all off-site mail is expected to be delivered to a "smarthost", then set the
5707 hostname here and uncomment the macro. This will affect which router is used
5708 later on. If this is left commented out, then Exim will perform direct-to-MX
5709 deliveries using a &(dnslookup)& router.
5711 In addition to macros defined here, Exim includes a number of built-in macros
5712 to enable configuration to be guarded by a binary built with support for a
5713 given feature. See section &<<SECTbuiltinmacros>>& for more details.
5716 .section "Main configuration settings" "SECTdefconfmain"
5717 The main (global) configuration option settings section must always come first
5718 in the file, after the macros.
5719 The first thing you'll see in the file, after some initial comments, is the line
5721 # primary_hostname =
5723 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5724 to know the official, fully qualified name of your host, and this is where you
5725 can specify it. However, in most cases you do not need to set this option. When
5726 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5728 The first three non-comment configuration lines are as follows:
5730 domainlist local_domains = @
5731 domainlist relay_to_domains =
5732 hostlist relay_from_hosts = 127.0.0.1
5734 These are not, in fact, option settings. They are definitions of two named
5735 domain lists and one named host list. Exim allows you to give names to lists of
5736 domains, hosts, and email addresses, in order to make it easier to manage the
5737 configuration file (see section &<<SECTnamedlists>>&).
5739 The first line defines a domain list called &'local_domains'&; this is used
5740 later in the configuration to identify domains that are to be delivered
5743 .cindex "@ in a domain list"
5744 There is just one item in this list, the string &"@"&. This is a special form
5745 of entry which means &"the name of the local host"&. Thus, if the local host is
5746 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5747 be delivered locally. Because the local host's name is referenced indirectly,
5748 the same configuration file can be used on different hosts.
5750 The second line defines a domain list called &'relay_to_domains'&, but the
5751 list itself is empty. Later in the configuration we will come to the part that
5752 controls mail relaying through the local host; it allows relaying to any
5753 domains in this list. By default, therefore, no relaying on the basis of a mail
5754 domain is permitted.
5756 The third line defines a host list called &'relay_from_hosts'&. This list is
5757 used later in the configuration to permit relaying from any host or IP address
5758 that matches the list. The default contains just the IP address of the IPv4
5759 loopback interface, which means that processes on the local host are able to
5760 submit mail for relaying by sending it over TCP/IP to that interface. No other
5761 hosts are permitted to submit messages for relaying.
5763 Just to be sure there's no misunderstanding: at this point in the configuration
5764 we aren't actually setting up any controls. We are just defining some domains
5765 and hosts that will be used in the controls that are specified later.
5767 The next two configuration lines are genuine option settings:
5769 acl_smtp_rcpt = acl_check_rcpt
5770 acl_smtp_data = acl_check_data
5772 These options specify &'Access Control Lists'& (ACLs) that are to be used
5773 during an incoming SMTP session for every recipient of a message (every RCPT
5774 command), and after the contents of the message have been received,
5775 respectively. The names of the lists are &'acl_check_rcpt'& and
5776 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5777 section of the configuration. The RCPT ACL controls which recipients are
5778 accepted for an incoming message &-- if a configuration does not provide an ACL
5779 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5780 contents of a message to be checked.
5782 Two commented-out option settings are next:
5784 # av_scanner = clamd:/tmp/clamd
5785 # spamd_address = 127.0.0.1 783
5787 These are example settings that can be used when Exim is compiled with the
5788 content-scanning extension. The first specifies the interface to the virus
5789 scanner, and the second specifies the interface to SpamAssassin. Further
5790 details are given in chapter &<<CHAPexiscan>>&.
5792 Three more commented-out option settings follow:
5794 # tls_advertise_hosts = *
5795 # tls_certificate = /etc/ssl/exim.crt
5796 # tls_privatekey = /etc/ssl/exim.pem
5798 These are example settings that can be used when Exim is compiled with
5799 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5800 first one specifies the list of clients that are allowed to use TLS when
5801 connecting to this server; in this case, the wildcard means all clients. The
5802 other options specify where Exim should find its TLS certificate and private
5803 key, which together prove the server's identity to any clients that connect.
5804 More details are given in chapter &<<CHAPTLS>>&.
5806 Another two commented-out option settings follow:
5808 # daemon_smtp_ports = 25 : 465 : 587
5809 # tls_on_connect_ports = 465
5811 .cindex "port" "465 and 587"
5812 .cindex "port" "for message submission"
5813 .cindex "message" "submission, ports for"
5814 .cindex "submissions protocol"
5815 .cindex "smtps protocol"
5816 .cindex "ssmtp protocol"
5817 .cindex "SMTP" "submissions protocol"
5818 .cindex "SMTP" "ssmtp protocol"
5819 .cindex "SMTP" "smtps protocol"
5820 These options provide better support for roaming users who wish to use this
5821 server for message submission. They are not much use unless you have turned on
5822 TLS (as described in the previous paragraph) and authentication (about which
5823 more in section &<<SECTdefconfauth>>&).
5824 Mail submission from mail clients (MUAs) should be separate from inbound mail
5825 to your domain (MX delivery) for various good reasons (eg, ability to impose
5826 much saner TLS protocol and ciphersuite requirements without unintended
5828 RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
5829 which uses STARTTLS, so this is the &"submission"& port.
5830 RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
5831 which should be used in preference to 587.
5832 You should also consider deploying SRV records to help clients find
5834 Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
5836 Two more commented-out options settings follow:
5839 # qualify_recipient =
5841 The first of these specifies a domain that Exim uses when it constructs a
5842 complete email address from a local login name. This is often needed when Exim
5843 receives a message from a local process. If you do not set &%qualify_domain%&,
5844 the value of &%primary_hostname%& is used. If you set both of these options,
5845 you can have different qualification domains for sender and recipient
5846 addresses. If you set only the first one, its value is used in both cases.
5848 .cindex "domain literal" "recognizing format"
5849 The following line must be uncommented if you want Exim to recognize
5850 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5851 (an IP address within square brackets) instead of a named domain.
5853 # allow_domain_literals
5855 The RFCs still require this form, but many people think that in the modern
5856 Internet it makes little sense to permit mail to be sent to specific hosts by
5857 quoting their IP addresses. This ancient format has been used by people who
5858 try to abuse hosts by using them for unwanted relaying. However, some
5859 people believe there are circumstances (for example, messages addressed to
5860 &'postmaster'&) where domain literals are still useful.
5862 The next configuration line is a kind of trigger guard:
5866 It specifies that no delivery must ever be run as the root user. The normal
5867 convention is to set up &'root'& as an alias for the system administrator. This
5868 setting is a guard against slips in the configuration.
5869 The list of users specified by &%never_users%& is not, however, the complete
5870 list; the build-time configuration in &_Local/Makefile_& has an option called
5871 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5872 contents of &%never_users%& are added to this list. By default
5873 FIXED_NEVER_USERS also specifies root.
5875 When a remote host connects to Exim in order to send mail, the only information
5876 Exim has about the host's identity is its IP address. The next configuration
5881 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5882 in order to get a host name. This improves the quality of the logging
5883 information, but if you feel it is too expensive, you can remove it entirely,
5884 or restrict the lookup to hosts on &"nearby"& networks.
5885 Note that it is not always possible to find a host name from an IP address,
5886 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5889 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5890 1413 (hence their names):
5893 rfc1413_query_timeout = 0s
5895 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5896 Few hosts offer RFC1413 service these days; calls have to be
5897 terminated by a timeout and this needlessly delays the startup
5898 of an incoming SMTP connection.
5899 If you have hosts for which you trust RFC1413 and need this
5900 information, you can change this.
5902 This line enables an efficiency SMTP option. It is negotiated by clients
5903 and not expected to cause problems but can be disabled if needed.
5908 When Exim receives messages over SMTP connections, it expects all addresses to
5909 be fully qualified with a domain, as required by the SMTP definition. However,
5910 if you are running a server to which simple clients submit messages, you may
5911 find that they send unqualified addresses. The two commented-out options:
5913 # sender_unqualified_hosts =
5914 # recipient_unqualified_hosts =
5916 show how you can specify hosts that are permitted to send unqualified sender
5917 and recipient addresses, respectively.
5919 The &%log_selector%& option is used to increase the detail of logging
5922 log_selector = +smtp_protocol_error +smtp_syntax_error \
5923 +tls_certificate_verified
5926 The &%percent_hack_domains%& option is also commented out:
5928 # percent_hack_domains =
5930 It provides a list of domains for which the &"percent hack"& is to operate.
5931 This is an almost obsolete form of explicit email routing. If you do not know
5932 anything about it, you can safely ignore this topic.
5934 The next two settings in the main part of the default configuration are
5935 concerned with messages that have been &"frozen"& on Exim's queue. When a
5936 message is frozen, Exim no longer continues to try to deliver it. Freezing
5937 occurs when a bounce message encounters a permanent failure because the sender
5938 address of the original message that caused the bounce is invalid, so the
5939 bounce cannot be delivered. This is probably the most common case, but there
5940 are also other conditions that cause freezing, and frozen messages are not
5941 always bounce messages.
5943 ignore_bounce_errors_after = 2d
5944 timeout_frozen_after = 7d
5946 The first of these options specifies that failing bounce messages are to be
5947 discarded after 2 days in the queue. The second specifies that any frozen
5948 message (whether a bounce message or not) is to be timed out (and discarded)
5949 after a week. In this configuration, the first setting ensures that no failing
5950 bounce message ever lasts a week.
5952 Exim queues it's messages in a spool directory. If you expect to have
5953 large queues, you may consider using this option. It splits the spool
5954 directory into subdirectories to avoid file system degradation from
5955 many files in a single directory, resulting in better performance.
5956 Manual manipulation of queued messages becomes more complex (though fortunately
5959 # split_spool_directory = true
5962 In an ideal world everybody follows the standards. For non-ASCII
5963 messages RFC 2047 is a standard, allowing a maximum line length of 76
5964 characters. Exim adheres that standard and won't process messages which
5965 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5966 In particular, the Exim maintainers have had multiple reports of
5967 problems from Russian administrators of issues until they disable this
5968 check, because of some popular, yet buggy, mail composition software.
5970 # check_rfc2047_length = false
5973 If you need to be strictly RFC compliant you may wish to disable the
5974 8BITMIME advertisement. Use this, if you exchange mails with systems
5975 that are not 8-bit clean.
5977 # accept_8bitmime = false
5980 Libraries you use may depend on specific environment settings. This
5981 imposes a security risk (e.g. PATH). There are two lists:
5982 &%keep_environment%& for the variables to import as they are, and
5983 &%add_environment%& for variables we want to set to a fixed value.
5984 Note that TZ is handled separately, by the &%timezone%& runtime
5985 option and by the TIMEZONE_DEFAULT buildtime option.
5987 # keep_environment = ^LDAP
5988 # add_environment = PATH=/usr/bin::/bin
5992 .section "ACL configuration" "SECID54"
5993 .cindex "default" "ACLs"
5994 .cindex "&ACL;" "default configuration"
5995 In the default configuration, the ACL section follows the main configuration.
5996 It starts with the line
6000 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
6001 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
6002 and &%acl_smtp_data%& above.
6004 .cindex "RCPT" "ACL for"
6005 The first ACL is used for every RCPT command in an incoming SMTP message. Each
6006 RCPT command specifies one of the message's recipients. The ACL statements
6007 are considered in order, until the recipient address is either accepted or
6008 rejected. The RCPT command is then accepted or rejected, according to the
6009 result of the ACL processing.
6013 This line, consisting of a name terminated by a colon, marks the start of the
6018 This ACL statement accepts the recipient if the sending host matches the list.
6019 But what does that strange list mean? It doesn't actually contain any host
6020 names or IP addresses. The presence of the colon puts an empty item in the
6021 list; Exim matches this only if the incoming message did not come from a remote
6022 host, because in that case, the remote hostname is empty. The colon is
6023 important. Without it, the list itself is empty, and can never match anything.
6025 What this statement is doing is to accept unconditionally all recipients in
6026 messages that are submitted by SMTP from local processes using the standard
6027 input and output (that is, not using TCP/IP). A number of MUAs operate in this
6030 deny domains = +local_domains
6031 local_parts = ^[.] : ^.*[@%!/|]
6032 message = Restricted characters in address
6034 deny domains = !+local_domains
6035 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
6036 message = Restricted characters in address
6038 These statements are concerned with local parts that contain any of the
6039 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
6040 Although these characters are entirely legal in local parts (in the case of
6041 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
6042 in Internet mail addresses.
6044 The first three have in the past been associated with explicitly routed
6045 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
6046 option). Addresses containing these characters are regularly tried by spammers
6047 in an attempt to bypass relaying restrictions, and also by open relay testing
6048 programs. Unless you really need them it is safest to reject these characters
6049 at this early stage. This configuration is heavy-handed in rejecting these
6050 characters for all messages it accepts from remote hosts. This is a deliberate
6051 policy of being as safe as possible.
6053 The first rule above is stricter, and is applied to messages that are addressed
6054 to one of the local domains handled by this host. This is implemented by the
6055 first condition, which restricts it to domains that are listed in the
6056 &'local_domains'& domain list. The &"+"& character is used to indicate a
6057 reference to a named list. In this configuration, there is just one domain in
6058 &'local_domains'&, but in general there may be many.
6060 The second condition on the first statement uses two regular expressions to
6061 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
6062 or &"|"&. If you have local accounts that include these characters, you will
6063 have to modify this rule.
6065 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
6066 allows them because they have been encountered in practice. (Consider the
6067 common convention of local parts constructed as
6068 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
6069 the author of Exim, who has no second initial.) However, a local part starting
6070 with a dot or containing &"/../"& can cause trouble if it is used as part of a
6071 filename (for example, for a mailing list). This is also true for local parts
6072 that contain slashes. A pipe symbol can also be troublesome if the local part
6073 is incorporated unthinkingly into a shell command line.
6075 The second rule above applies to all other domains, and is less strict. This
6076 allows your own users to send outgoing messages to sites that use slashes
6077 and vertical bars in their local parts. It blocks local parts that begin
6078 with a dot, slash, or vertical bar, but allows these characters within the
6079 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
6080 and &"!"& is blocked, as before. The motivation here is to prevent your users
6081 (or your users' viruses) from mounting certain kinds of attack on remote sites.
6083 accept local_parts = postmaster
6084 domains = +local_domains
6086 This statement, which has two conditions, accepts an incoming address if the
6087 local part is &'postmaster'& and the domain is one of those listed in the
6088 &'local_domains'& domain list. The &"+"& character is used to indicate a
6089 reference to a named list. In this configuration, there is just one domain in
6090 &'local_domains'&, but in general there may be many.
6092 The presence of this statement means that mail to postmaster is never blocked
6093 by any of the subsequent tests. This can be helpful while sorting out problems
6094 in cases where the subsequent tests are incorrectly denying access.
6096 require verify = sender
6098 This statement requires the sender address to be verified before any subsequent
6099 ACL statement can be used. If verification fails, the incoming recipient
6100 address is refused. Verification consists of trying to route the address, to
6101 see if a bounce message could be delivered to it. In the case of remote
6102 addresses, basic verification checks only the domain, but &'callouts'& can be
6103 used for more verification if required. Section &<<SECTaddressverification>>&
6104 discusses the details of address verification.
6106 accept hosts = +relay_from_hosts
6107 control = submission
6109 This statement accepts the address if the message is coming from one of the
6110 hosts that are defined as being allowed to relay through this host. Recipient
6111 verification is omitted here, because in many cases the clients are dumb MUAs
6112 that do not cope well with SMTP error responses. For the same reason, the
6113 second line specifies &"submission mode"& for messages that are accepted. This
6114 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
6115 messages that are deficient in some way, for example, because they lack a
6116 &'Date:'& header line. If you are actually relaying out from MTAs, you should
6117 probably add recipient verification here, and disable submission mode.
6119 accept authenticated = *
6120 control = submission
6122 This statement accepts the address if the client host has authenticated itself.
6123 Submission mode is again specified, on the grounds that such messages are most
6124 likely to come from MUAs. The default configuration does not define any
6125 authenticators, though it does include some nearly complete commented-out
6126 examples described in &<<SECTdefconfauth>>&. This means that no client can in
6127 fact authenticate until you complete the authenticator definitions.
6129 require message = relay not permitted
6130 domains = +local_domains : +relay_to_domains
6132 This statement rejects the address if its domain is neither a local domain nor
6133 one of the domains for which this host is a relay.
6135 require verify = recipient
6137 This statement requires the recipient address to be verified; if verification
6138 fails, the address is rejected.
6140 # deny dnslists = black.list.example
6141 # message = rejected because $sender_host_address \
6142 # is in a black list at $dnslist_domain\n\
6145 # warn dnslists = black.list.example
6146 # add_header = X-Warning: $sender_host_address is in \
6147 # a black list at $dnslist_domain
6148 # log_message = found in $dnslist_domain
6150 These commented-out lines are examples of how you could configure Exim to check
6151 sending hosts against a DNS black list. The first statement rejects messages
6152 from blacklisted hosts, whereas the second just inserts a warning header
6155 # require verify = csa
6157 This commented-out line is an example of how you could turn on client SMTP
6158 authorization (CSA) checking. Such checks do DNS lookups for special SRV
6163 The final statement in the first ACL unconditionally accepts any recipient
6164 address that has successfully passed all the previous tests.
6168 This line marks the start of the second ACL, and names it. Most of the contents
6169 of this ACL are commented out:
6172 # message = This message contains a virus \
6175 These lines are examples of how to arrange for messages to be scanned for
6176 viruses when Exim has been compiled with the content-scanning extension, and a
6177 suitable virus scanner is installed. If the message is found to contain a
6178 virus, it is rejected with the given custom error message.
6180 # warn spam = nobody
6181 # message = X-Spam_score: $spam_score\n\
6182 # X-Spam_score_int: $spam_score_int\n\
6183 # X-Spam_bar: $spam_bar\n\
6184 # X-Spam_report: $spam_report
6186 These lines are an example of how to arrange for messages to be scanned by
6187 SpamAssassin when Exim has been compiled with the content-scanning extension,
6188 and SpamAssassin has been installed. The SpamAssassin check is run with
6189 &`nobody`& as its user parameter, and the results are added to the message as a
6190 series of extra header line. In this case, the message is not rejected,
6191 whatever the spam score.
6195 This final line in the DATA ACL accepts the message unconditionally.
6198 .section "Router configuration" "SECID55"
6199 .cindex "default" "routers"
6200 .cindex "routers" "default"
6201 The router configuration comes next in the default configuration, introduced
6206 Routers are the modules in Exim that make decisions about where to send
6207 messages. An address is passed to each router, in turn, until it is either
6208 accepted, or failed. This means that the order in which you define the routers
6209 matters. Each router is fully described in its own chapter later in this
6210 manual. Here we give only brief overviews.
6213 # driver = ipliteral
6214 # domains = !+local_domains
6215 # transport = remote_smtp
6217 .cindex "domain literal" "default router"
6218 This router is commented out because the majority of sites do not want to
6219 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
6220 you uncomment this router, you also need to uncomment the setting of
6221 &%allow_domain_literals%& in the main part of the configuration.
6223 Which router is used next depends upon whether or not the ROUTER_SMARTHOST
6224 macro has been defined, per
6226 .ifdef ROUTER_SMARTHOST
6235 If ROUTER_SMARTHOST has been defined, either at the top of the file or on the
6236 command-line, then we route all non-local mail to that smarthost; otherwise, we'll
6237 perform DNS lookups for direct-to-MX lookup. Any mail which is to a local domain will
6238 skip these routers because of the &%domains%& option.
6242 driver = manualroute
6243 domains = ! +local_domains
6244 transport = smarthost_smtp
6245 route_data = ROUTER_SMARTHOST
6246 ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
6249 This router only handles mail which is not to any local domains; this is
6250 specified by the line
6252 domains = ! +local_domains
6254 The &%domains%& option lists the domains to which this router applies, but the
6255 exclamation mark is a negation sign, so the router is used only for domains
6256 that are not in the domain list called &'local_domains'& (which was defined at
6257 the start of the configuration). The plus sign before &'local_domains'&
6258 indicates that it is referring to a named list. Addresses in other domains are
6259 passed on to the following routers.
6261 The name of the router driver is &(manualroute)& because we are manually
6262 specifying how mail should be routed onwards, instead of using DNS MX.
6263 While the name of this router instance is arbitrary, the &%driver%& option must
6264 be one of the driver modules that is in the Exim binary.
6266 With no pre-conditions other than &%domains%&, all mail for non-local domains
6267 will be handled by this router, and the &%no_more%& setting will ensure that no
6268 other routers will be used for messages matching the pre-conditions. See
6269 &<<SECTrouprecon>>& for more on how the pre-conditions apply. For messages which
6270 are handled by this router, we provide a hostname to deliver to in &%route_data%&
6271 and the macro supplies the value; the address is then queued for the
6272 &(smarthost_smtp)& transport.
6277 domains = ! +local_domains
6278 transport = remote_smtp
6279 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
6282 The &%domains%& option behaves as per smarthost, above.
6284 The name of the router driver is &(dnslookup)&,
6285 and is specified by the &%driver%& option. Do not be confused by the fact that
6286 the name of this router instance is the same as the name of the driver. The
6287 instance name is arbitrary, but the name set in the &%driver%& option must be
6288 one of the driver modules that is in the Exim binary.
6290 The &(dnslookup)& router routes addresses by looking up their domains in the
6291 DNS in order to obtain a list of hosts to which the address is routed. If the
6292 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6293 specified by the &%transport%& option. If the router does not find the domain
6294 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6295 the address fails and is bounced.
6297 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6298 be entirely ignored. This option is present because a number of cases have been
6299 encountered where MX records in the DNS point to host names
6300 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6301 Completely ignoring these IP addresses causes Exim to fail to route the
6302 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6303 continue to try to deliver the message periodically until the address timed
6310 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6312 file_transport = address_file
6313 pipe_transport = address_pipe
6315 Control reaches this and subsequent routers only for addresses in the local
6316 domains. This router checks to see whether the local part is defined as an
6317 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6318 data that it looks up from that file. If no data is found for the local part,
6319 the value of the &%data%& option is empty, causing the address to be passed to
6322 &_/etc/aliases_& is a conventional name for the system aliases file that is
6323 often used. That is why it is referenced by from the default configuration
6324 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6325 &_Local/Makefile_& before building Exim.
6330 # local_part_suffix = +* : -*
6331 # local_part_suffix_optional
6332 file = $home/.forward
6337 file_transport = address_file
6338 pipe_transport = address_pipe
6339 reply_transport = address_reply
6341 This is the most complicated router in the default configuration. It is another
6342 redirection router, but this time it is looking for forwarding data set up by
6343 individual users. The &%check_local_user%& setting specifies a check that the
6344 local part of the address is the login name of a local user. If it is not, the
6345 router is skipped. The two commented options that follow &%check_local_user%&,
6348 # local_part_suffix = +* : -*
6349 # local_part_suffix_optional
6351 .vindex "&$local_part_suffix$&"
6352 show how you can specify the recognition of local part suffixes. If the first
6353 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6354 by any sequence of characters, is removed from the local part and placed in the
6355 variable &$local_part_suffix$&. The second suffix option specifies that the
6356 presence of a suffix in the local part is optional. When a suffix is present,
6357 the check for a local login uses the local part with the suffix removed.
6359 When a local user account is found, the file called &_.forward_& in the user's
6360 home directory is consulted. If it does not exist, or is empty, the router
6361 declines. Otherwise, the contents of &_.forward_& are interpreted as
6362 redirection data (see chapter &<<CHAPredirect>>& for more details).
6364 .cindex "Sieve filter" "enabling in default router"
6365 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6366 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6367 is commented out by default), the contents of the file are interpreted as a set
6368 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6369 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6370 separate document entitled &'Exim's interfaces to mail filtering'&.
6372 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6373 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6374 There are two reasons for doing this:
6377 Whether or not a local user has a &_.forward_& file is not really relevant when
6378 checking an address for validity; it makes sense not to waste resources doing
6381 More importantly, when Exim is verifying addresses or handling an EXPN
6382 command during an SMTP session, it is running as the Exim user, not as root.
6383 The group is the Exim group, and no additional groups are set up.
6384 It may therefore not be possible for Exim to read users' &_.forward_& files at
6388 The setting of &%check_ancestor%& prevents the router from generating a new
6389 address that is the same as any previous address that was redirected. (This
6390 works round a problem concerning a bad interaction between aliasing and
6391 forwarding &-- see section &<<SECTredlocmai>>&).
6393 The final three option settings specify the transports that are to be used when
6394 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6395 auto-reply, respectively. For example, if a &_.forward_& file contains
6397 a.nother@elsewhere.example, /home/spqr/archive
6399 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6405 # local_part_suffix = +* : -*
6406 # local_part_suffix_optional
6407 transport = local_delivery
6409 The final router sets up delivery into local mailboxes, provided that the local
6410 part is the name of a local login, by accepting the address and assigning it to
6411 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6412 routers, so the address is bounced. The commented suffix settings fulfil the
6413 same purpose as they do for the &(userforward)& router.
6416 .section "Transport configuration" "SECID56"
6417 .cindex "default" "transports"
6418 .cindex "transports" "default"
6419 Transports define mechanisms for actually delivering messages. They operate
6420 only when referenced from routers, so the order in which they are defined does
6421 not matter. The transports section of the configuration starts with
6425 Two remote transports and four local transports are defined.
6429 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6434 This transport is used for delivering messages over SMTP connections.
6435 The list of remote hosts comes from the router.
6436 The &%message_size_limit%& usage is a hack to avoid sending on messages
6437 with over-long lines.
6439 The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
6440 negotiated between client and server and not expected to cause problems
6441 but can be disabled if needed. The built-in macro _HAVE_PRDR guards the
6442 use of the &%hosts_try_prdr%& configuration option.
6444 The other remote transport is used when delivering to a specific smarthost
6445 with whom there must be some kind of existing relationship, instead of the
6446 usual federated system.
6451 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6455 # Comment out any of these which you have to, then file a Support
6456 # request with your smarthost provider to get things fixed:
6457 hosts_require_tls = *
6458 tls_verify_hosts = *
6459 # As long as tls_verify_hosts is enabled, this this will have no effect,
6460 # but if you have to comment it out then this will at least log whether
6461 # you succeed or not:
6462 tls_try_verify_hosts = *
6464 # The SNI name should match the name which we'll expect to verify;
6465 # many mail systems don't use SNI and this doesn't matter, but if it does,
6466 # we need to send a name which the remote site will recognize.
6467 # This _should_ be the name which the smarthost operators specified as
6468 # the hostname for sending your mail to.
6469 tls_sni = ROUTER_SMARTHOST
6471 .ifdef _HAVE_OPENSSL
6472 tls_require_ciphers = HIGH:!aNULL:@STRENGTH
6475 tls_require_ciphers = SECURE192:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1
6482 After the same &%message_size_limit%& hack, we then specify that this Transport
6483 can handle messages to multiple domains in one run. The assumption here is
6484 that you're routing all non-local mail to the same place and that place is
6485 happy to take all messages from you as quickly as possible.
6486 All other options depend upon built-in macros; if Exim was built without TLS support
6487 then no other options are defined.
6488 If TLS is available, then we configure "stronger than default" TLS ciphersuites
6489 and versions using the &%tls_require_ciphers%& option, where the value to be
6490 used depends upon the library providing TLS.
6491 Beyond that, the options adopt the stance that you should have TLS support available
6492 from your smarthost on today's Internet, so we turn on requiring TLS for the
6493 mail to be delivered, and requiring that the certificate be valid, and match
6494 the expected hostname. The &%tls_sni%& option can be used by service providers
6495 to select an appropriate certificate to present to you and here we re-use the
6496 ROUTER_SMARTHOST macro, because that is unaffected by CNAMEs present in DNS.
6497 You want to specify the hostname which you'll expect to validate for, and that
6498 should not be subject to insecure tampering via DNS results.
6500 For the &%hosts_try_prdr%& option see the previous transport.
6502 All other options are defaulted.
6506 file = /var/mail/$local_part_data
6513 This &(appendfile)& transport is used for local delivery to user mailboxes in
6514 traditional BSD mailbox format.
6516 We prefer to avoid using &$local_part$& directly to define the mailbox filename,
6517 as it is provided by a potential bad actor.
6518 Instead we use &$local_part_data$&,
6519 the result of looking up &$local_part$& in the user database
6520 (done by using &%check_local_user%& in the the router).
6522 By default &(appendfile)& runs under the uid and gid of the
6523 local user, which requires the sticky bit to be set on the &_/var/mail_&
6524 directory. Some systems use the alternative approach of running mail deliveries
6525 under a particular group instead of using the sticky bit. The commented options
6526 show how this can be done.
6528 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6529 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6530 similarly-named options above.
6536 This transport is used for handling deliveries to pipes that are generated by
6537 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6538 option specifies that any output on stdout or stderr generated by the pipe is to
6539 be returned to the sender.
6547 This transport is used for handling deliveries to files that are generated by
6548 redirection. The name of the file is not specified in this instance of
6549 &(appendfile)&, because it comes from the &(redirect)& router.
6554 This transport is used for handling automatic replies generated by users'
6559 .section "Default retry rule" "SECID57"
6560 .cindex "retry" "default rule"
6561 .cindex "default" "retry rule"
6562 The retry section of the configuration file contains rules which affect the way
6563 Exim retries deliveries that cannot be completed at the first attempt. It is
6564 introduced by the line
6568 In the default configuration, there is just one rule, which applies to all
6571 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6573 This causes any temporarily failing address to be retried every 15 minutes for
6574 2 hours, then at intervals starting at one hour and increasing by a factor of
6575 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6576 is not delivered after 4 days of temporary failure, it is bounced. The time is
6577 measured from first failure, not from the time the message was received.
6579 If the retry section is removed from the configuration, or is empty (that is,
6580 if no retry rules are defined), Exim will not retry deliveries. This turns
6581 temporary errors into permanent errors.
6584 .section "Rewriting configuration" "SECID58"
6585 The rewriting section of the configuration, introduced by
6589 contains rules for rewriting addresses in messages as they arrive. There are no
6590 rewriting rules in the default configuration file.
6594 .section "Authenticators configuration" "SECTdefconfauth"
6595 .cindex "AUTH" "configuration"
6596 The authenticators section of the configuration, introduced by
6598 begin authenticators
6600 defines mechanisms for the use of the SMTP AUTH command. The default
6601 configuration file contains two commented-out example authenticators
6602 which support plaintext username/password authentication using the
6603 standard PLAIN mechanism and the traditional but non-standard LOGIN
6604 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6605 to support most MUA software.
6607 The example PLAIN authenticator looks like this:
6610 # driver = plaintext
6611 # server_set_id = $auth2
6612 # server_prompts = :
6613 # server_condition = Authentication is not yet configured
6614 # server_advertise_condition = ${if def:tls_in_cipher }
6616 And the example LOGIN authenticator looks like this:
6619 # driver = plaintext
6620 # server_set_id = $auth1
6621 # server_prompts = <| Username: | Password:
6622 # server_condition = Authentication is not yet configured
6623 # server_advertise_condition = ${if def:tls_in_cipher }
6626 The &%server_set_id%& option makes Exim remember the authenticated username
6627 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6628 &%server_prompts%& option configures the &(plaintext)& authenticator so
6629 that it implements the details of the specific authentication mechanism,
6630 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6631 when Exim offers authentication to clients; in the examples, this is only
6632 when TLS or SSL has been started, so to enable the authenticators you also
6633 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6635 The &%server_condition%& setting defines how to verify that the username and
6636 password are correct. In the examples it just produces an error message.
6637 To make the authenticators work, you can use a string expansion
6638 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6640 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6641 usercode and password are in different positions.
6642 Chapter &<<CHAPplaintext>>& covers both.
6644 .ecindex IIDconfiwal
6648 . ////////////////////////////////////////////////////////////////////////////
6649 . ////////////////////////////////////////////////////////////////////////////
6651 .chapter "Regular expressions" "CHAPregexp"
6653 .cindex "regular expressions" "library"
6655 Exim supports the use of regular expressions in many of its options. It
6656 uses the PCRE regular expression library; this provides regular expression
6657 matching that is compatible with Perl 5. The syntax and semantics of
6658 regular expressions is discussed in
6659 online Perl manpages, in
6660 many Perl reference books, and also in
6661 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6662 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6663 . --- the http: URL here redirects to another page with the ISBN in the URL
6664 . --- where trying to use https: just redirects back to http:, so sticking
6665 . --- to the old URL for now. 2018-09-07.
6667 The documentation for the syntax and semantics of the regular expressions that
6668 are supported by PCRE is included in the PCRE distribution, and no further
6669 description is included here. The PCRE functions are called from Exim using
6670 the default option settings (that is, with no PCRE options set), except that
6671 the PCRE_CASELESS option is set when the matching is required to be
6674 In most cases, when a regular expression is required in an Exim configuration,
6675 it has to start with a circumflex, in order to distinguish it from plain text
6676 or an &"ends with"& wildcard. In this example of a configuration setting, the
6677 second item in the colon-separated list is a regular expression.
6679 domains = a.b.c : ^\\d{3} : *.y.z : ...
6681 The doubling of the backslash is required because of string expansion that
6682 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6683 of this issue, and a way of avoiding the need for doubling backslashes. The
6684 regular expression that is eventually used in this example contains just one
6685 backslash. The circumflex is included in the regular expression, and has the
6686 normal effect of &"anchoring"& it to the start of the string that is being
6689 There are, however, two cases where a circumflex is not required for the
6690 recognition of a regular expression: these are the &%match%& condition in a
6691 string expansion, and the &%matches%& condition in an Exim filter file. In
6692 these cases, the relevant string is always treated as a regular expression; if
6693 it does not start with a circumflex, the expression is not anchored, and can
6694 match anywhere in the subject string.
6696 In all cases, if you want a regular expression to match at the end of a string,
6697 you must code the $ metacharacter to indicate this. For example:
6699 domains = ^\\d{3}\\.example
6701 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6704 domains = ^\\d{3}\\.example\$
6706 if you want &'example'& to be the top-level domain. The backslash before the
6707 $ is needed because string expansion also interprets dollar characters.
6711 . ////////////////////////////////////////////////////////////////////////////
6712 . ////////////////////////////////////////////////////////////////////////////
6714 .chapter "File and database lookups" "CHAPfdlookup"
6715 .scindex IIDfidalo1 "file" "lookups"
6716 .scindex IIDfidalo2 "database" "lookups"
6717 .cindex "lookup" "description of"
6718 Exim can be configured to look up data in files or databases as it processes
6719 messages. Two different kinds of syntax are used:
6722 A string that is to be expanded may contain explicit lookup requests. These
6723 cause parts of the string to be replaced by data that is obtained from the
6724 lookup. Lookups of this type are conditional expansion items. Different results
6725 can be defined for the cases of lookup success and failure. See chapter
6726 &<<CHAPexpand>>&, where string expansions are described in detail.
6727 The key for the lookup is &*specified*& as part of the string expansion.
6729 Lists of domains, hosts, and email addresses can contain lookup requests as a
6730 way of avoiding excessively long linear lists. In this case, the data that is
6731 returned by the lookup is often (but not always) discarded; whether the lookup
6732 succeeds or fails is what really counts. These kinds of list are described in
6733 chapter &<<CHAPdomhosaddlists>>&.
6734 The key for the lookup is &*implicit*&,
6735 given by the context in which the list is expanded.
6738 String expansions, lists, and lookups interact with each other in such a way
6739 that there is no order in which to describe any one of them that does not
6740 involve references to the others. Each of these three chapters makes more sense
6741 if you have read the other two first. If you are reading this for the first
6742 time, be aware that some of it will make a lot more sense after you have read
6743 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6745 .section "Examples of different lookup syntax" "SECID60"
6746 It is easy to confuse the two different kinds of lookup, especially as the
6747 lists that may contain the second kind are always expanded before being
6748 processed as lists. Therefore, they may also contain lookups of the first kind.
6749 Be careful to distinguish between the following two examples:
6751 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6752 domains = lsearch;/some/file
6754 The first uses a string expansion, the result of which must be a domain list.
6755 No strings have been specified for a successful or a failing lookup; the
6756 defaults in this case are the looked-up data and an empty string, respectively.
6757 The expansion takes place before the string is processed as a list, and the
6758 file that is searched could contain lines like this:
6760 192.168.3.4: domain1:domain2:...
6761 192.168.1.9: domain3:domain4:...
6763 When the lookup succeeds, the result of the expansion is a list of domains (and
6764 possibly other types of item that are allowed in domain lists).
6765 .cindex "tainted data" "de-tainting"
6766 The result of the expansion is not tainted.
6768 In the second example, the lookup is a single item in a domain list. It causes
6769 Exim to use a lookup to see if the domain that is being processed can be found
6771 The file could contains lines like this:
6776 Any data that follows the keys is not relevant when checking that the domain
6777 matches the list item.
6779 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6780 Consider a file containing lines like this:
6782 192.168.5.6: lsearch;/another/file
6784 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6785 first &%domains%& setting above generates the second setting, which therefore
6786 causes a second lookup to occur.
6789 The lookup type may optionally be followed by a comma
6790 and a comma-separated list of options.
6791 Each option is a &"name=value"& pair.
6792 Whether an option is meaningful depends on the lookup type.
6794 All lookups support the option &"cache=no_rd"&.
6795 If this is given then the cache that Exim manages for lookup results
6796 is not checked before doing the lookup.
6797 The result of the lookup is still written to the cache.
6800 The rest of this chapter describes the different lookup types that are
6801 available. Any of them can be used in any part of the configuration where a
6802 lookup is permitted.
6805 .section "Lookup types" "SECID61"
6806 .cindex "lookup" "types of"
6807 .cindex "single-key lookup" "definition of"
6808 Two different types of data lookup are implemented:
6811 The &'single-key'& type requires the specification of a file in which to look,
6812 and a single key to search for. The key must be a non-empty string for the
6813 lookup to succeed. The lookup type determines how the file is searched.
6814 .cindex "tainted data" "single-key lookups"
6815 The file string may not be tainted
6817 .cindex "tainted data" "de-tainting"
6818 All single-key lookups support the option &"ret=key"&.
6819 If this is given and the lookup
6820 (either underlying implementation or cached value)
6821 returns data, the result is replaced with a non-tainted
6822 version of the lookup key.
6823 .cindex "tainted data" "de-tainting"
6825 .cindex "query-style lookup" "definition of"
6826 The &'query-style'& type accepts a generalized database query. No particular
6827 key value is assumed by Exim for query-style lookups. You can use whichever
6828 Exim variables you need to construct the database query.
6831 The code for each lookup type is in a separate source file that is included in
6832 the binary of Exim only if the corresponding compile-time option is set. The
6833 default settings in &_src/EDITME_& are:
6838 which means that only linear searching and DBM lookups are included by default.
6839 For some types of lookup (e.g. SQL databases), you need to install appropriate
6840 libraries and header files before building Exim.
6845 .section "Single-key lookup types" "SECTsinglekeylookups"
6846 .cindex "lookup" "single-key types"
6847 .cindex "single-key lookup" "list of types"
6848 The following single-key lookup types are implemented:
6851 .cindex "cdb" "description of"
6852 .cindex "lookup" "cdb"
6853 .cindex "binary zero" "in lookup key"
6854 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6855 string without a terminating binary zero. The cdb format is designed for
6856 indexed files that are read frequently and never updated, except by total
6857 re-creation. As such, it is particularly suitable for large files containing
6858 aliases or other indexed data referenced by an MTA. Information about cdb and
6859 tools for building the files can be found in several places:
6861 &url(https://cr.yp.to/cdb.html)
6862 &url(https://www.corpit.ru/mjt/tinycdb.html)
6863 &url(https://packages.debian.org/stable/utils/freecdb)
6864 &url(https://github.com/philpennock/cdbtools) (in Go)
6866 A cdb distribution is not needed in order to build Exim with cdb support,
6867 because the code for reading cdb files is included directly in Exim itself.
6868 However, no means of building or testing cdb files is provided with Exim, so
6869 you need to obtain a cdb distribution in order to do this.
6871 .cindex "DBM" "lookup type"
6872 .cindex "lookup" "dbm"
6873 .cindex "binary zero" "in lookup key"
6874 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6875 DBM file by looking up the record with the given key. A terminating binary
6876 zero is included in the key that is passed to the DBM library. See section
6877 &<<SECTdb>>& for a discussion of DBM libraries.
6879 .cindex "Berkeley DB library" "file format"
6880 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6881 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6882 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6883 the DB_UNKNOWN option. This enables it to handle any of the types of database
6884 that the library supports, and can be useful for accessing DBM files created by
6885 other applications. (For earlier DB versions, DB_HASH is always used.)
6887 .cindex "lookup" "dbmjz"
6888 .cindex "lookup" "dbm &-- embedded NULs"
6890 .cindex "dbmjz lookup type"
6891 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6892 interpreted as an Exim list; the elements of the list are joined together with
6893 ASCII NUL characters to form the lookup key. An example usage would be to
6894 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6895 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6896 &(cram_md5)& authenticator.
6898 .cindex "lookup" "dbmnz"
6899 .cindex "lookup" "dbm &-- terminating zero"
6900 .cindex "binary zero" "in lookup key"
6902 .cindex "&_/etc/userdbshadow.dat_&"
6903 .cindex "dbmnz lookup type"
6904 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6905 is not included in the key that is passed to the DBM library. You may need this
6906 if you want to look up data in files that are created by or shared with some
6907 other application that does not use terminating zeros. For example, you need to
6908 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6909 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6910 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6911 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6913 .cindex "lookup" "dsearch"
6914 .cindex "dsearch lookup type"
6915 &(dsearch)&: The given file must be an
6917 directory path; this is searched for an entry
6918 whose name is the key by calling the &[lstat()]& function.
6920 contain any forward slash characters.
6921 If &[lstat()]& succeeds then so does the lookup.
6922 .cindex "tainted data" "dsearch result"
6923 The result is regarded as untainted.
6925 Options for the lookup can be given by appending them after the word "dsearch",
6926 separated by a comma. Options, if present, are a comma-separated list having
6927 each element starting with a tag name and an equals.
6929 Two options are supported, for the return value and for filtering match
6931 The "ret" option requests an alternate result value of
6932 the entire path for the entry. Example:
6934 ${lookup {passwd} dsearch,ret=full {/etc}}
6936 The default result is just the requested entry.
6937 The "filter" option requests that only directory entries of a given type
6938 are matched. The match value is one of "file", "dir" or "subdir" (the latter
6939 not matching "." or ".."). Example:
6941 ${lookup {passwd} dsearch,filter=file {/etc}}
6943 The default matching is for any entry type, including directories
6946 An example of how this
6947 lookup can be used to support virtual domains is given in section
6948 &<<SECTvirtualdomains>>&.
6950 .cindex "lookup" "iplsearch"
6951 .cindex "iplsearch lookup type"
6952 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6953 terminated by a colon or white space or the end of the line. The keys in the
6954 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6955 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6956 being interpreted as a key terminator. For example:
6958 1.2.3.4: data for 1.2.3.4
6959 192.168.0.0/16: data for 192.168.0.0/16
6960 "abcd::cdab": data for abcd::cdab
6961 "abcd:abcd::/32" data for abcd:abcd::/32
6963 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6964 file is searched linearly, using the CIDR masks where present, until a matching
6965 key is found. The first key that matches is used; there is no attempt to find a
6966 &"best"& match. Apart from the way the keys are matched, the processing for
6967 &(iplsearch)& is the same as for &(lsearch)&.
6969 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6970 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6971 lookup types support only literal keys.
6973 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6974 the implicit key is the host's IP address rather than its name (see section
6975 &<<SECThoslispatsikey>>&).
6977 &*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
6978 IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
6979 notation before executing the lookup.)
6982 One option is supported, "ret=full", to request the return of the entire line
6983 rather than omitting the key porttion.
6984 Note however that the key portion will have been de-quoted.
6989 .cindex json "lookup type"
6990 .cindex JSON expansions
6991 &(json)&: The given file is a text file with a JSON structure.
6992 An element of the structure is extracted, defined by the search key.
6993 The key is a list of subelement selectors
6994 (colon-separated by default but changeable in the usual way)
6995 which are applied in turn to select smaller and smaller portions
6996 of the JSON structure.
6997 If a selector is numeric, it must apply to a JSON array; the (zero-based)
6998 nunbered array element is selected.
6999 Otherwise it must apply to a JSON object; the named element is selected.
7000 The final resulting element can be a simple JSON type or a JSON object
7001 or array; for the latter two a string-representation of the JSON
7003 For elements of type string, the returned value is de-quoted.
7010 .cindex database lmdb
7011 &(lmdb)&: The given file is an LMDB database.
7012 LMDB is a memory-mapped key-value store,
7013 with API modeled loosely on that of BerkeleyDB.
7014 See &url(https://symas.com/products/lightning-memory-mapped-database/)
7015 for the feature set and operation modes.
7017 Exim provides read-only access via the LMDB C library.
7018 The library can be obtained from &url(https://github.com/LMDB/lmdb)
7019 or your operating system package repository.
7020 To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&.
7022 You will need to separately create the LMDB database file,
7023 possibly using the &"mdb_load"& utility.
7028 .cindex "linear search"
7029 .cindex "lookup" "lsearch"
7030 .cindex "lsearch lookup type"
7031 .cindex "case sensitivity" "in lsearch lookup"
7032 &(lsearch)&: The given file is a text file that is searched linearly for a
7033 line beginning with the search key, terminated by a colon or white space or the
7034 end of the line. The search is case-insensitive; that is, upper and lower case
7035 letters are treated as the same. The first occurrence of the key that is found
7036 in the file is used.
7038 White space between the key and the colon is permitted. The remainder of the
7039 line, with leading and trailing white space removed, is the data. This can be
7040 continued onto subsequent lines by starting them with any amount of white
7041 space, but only a single space character is included in the data at such a
7042 junction. If the data begins with a colon, the key must be terminated by a
7047 Empty lines and lines beginning with # are ignored, even if they occur in the
7048 middle of an item. This is the traditional textual format of alias files. Note
7049 that the keys in an &(lsearch)& file are literal strings. There is no
7050 wildcarding of any kind.
7052 .cindex "lookup" "lsearch &-- colons in keys"
7053 .cindex "white space" "in lsearch key"
7054 In most &(lsearch)& files, keys are not required to contain colons or #
7055 characters, or white space. However, if you need this feature, it is available.
7056 If a key begins with a doublequote character, it is terminated only by a
7057 matching quote (or end of line), and the normal escaping rules apply to its
7058 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
7059 quoted keys (exactly as for unquoted keys). There is no special handling of
7060 quotes for the data part of an &(lsearch)& line.
7063 .cindex "NIS lookup type"
7064 .cindex "lookup" "NIS"
7065 .cindex "binary zero" "in lookup key"
7066 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
7067 the given key, without a terminating binary zero. There is a variant called
7068 &(nis0)& which does include the terminating binary zero in the key. This is
7069 reportedly needed for Sun-style alias files. Exim does not recognize NIS
7070 aliases; the full map names must be used.
7073 .cindex "wildlsearch lookup type"
7074 .cindex "lookup" "wildlsearch"
7075 .cindex "nwildlsearch lookup type"
7076 .cindex "lookup" "nwildlsearch"
7077 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
7078 &(lsearch)&, but instead of being interpreted as a literal string, each key in
7079 the file may be wildcarded. The difference between these two lookup types is
7080 that for &(wildlsearch)&, each key in the file is string-expanded before being
7081 used, whereas for &(nwildlsearch)&, no expansion takes place.
7083 .cindex "case sensitivity" "in (n)wildlsearch lookup"
7084 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
7085 file that are regular expressions can be made case-sensitive by the use of
7086 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
7088 . ==== As this is a nested list, any displays it contains must be indented
7089 . ==== as otherwise they are too far to the left.
7092 The string may begin with an asterisk to mean &"ends with"&. For example:
7094 *.a.b.c data for anything.a.b.c
7095 *fish data for anythingfish
7098 The string may begin with a circumflex to indicate a regular expression. For
7099 example, for &(wildlsearch)&:
7101 ^\N\d+\.a\.b\N data for <digits>.a.b
7103 Note the use of &`\N`& to disable expansion of the contents of the regular
7104 expression. If you are using &(nwildlsearch)&, where the keys are not
7105 string-expanded, the equivalent entry is:
7107 ^\d+\.a\.b data for <digits>.a.b
7109 The case-insensitive flag is set at the start of compiling the regular
7110 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
7111 For example, to make the entire pattern case-sensitive:
7113 ^(?-i)\d+\.a\.b data for <digits>.a.b
7116 If the regular expression contains white space or colon characters, you must
7117 either quote it (see &(lsearch)& above), or represent these characters in other
7118 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
7119 colon. This may be easier than quoting, because if you quote, you have to
7120 escape all the backslashes inside the quotes.
7122 &*Note*&: It is not possible to capture substrings in a regular expression
7123 match for later use, because the results of all lookups are cached. If a lookup
7124 is repeated, the result is taken from the cache, and no actual pattern matching
7125 takes place. The values of all the numeric variables are unset after a
7126 &((n)wildlsearch)& match.
7129 Although I cannot see it being of much use, the general matching function that
7130 is used to implement &((n)wildlsearch)& means that the string may begin with a
7131 lookup name terminated by a semicolon, and followed by lookup data. For
7134 cdb;/some/file data for keys that match the file
7136 The data that is obtained from the nested lookup is discarded.
7139 Keys that do not match any of these patterns are interpreted literally. The
7140 continuation rules for the data are the same as for &(lsearch)&, and keys may
7141 be followed by optional colons.
7143 &*Warning*&: Unlike most other single-key lookup types, a file of data for
7144 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
7145 lookup types support only literal keys.
7148 .cindex "spf lookup type"
7149 .cindex "lookup" "spf"
7150 &(spf)&: If Exim is built with SPF support, manual lookups can be done
7151 (as opposed to the standard ACL condition method).
7152 For details see section &<<SECSPF>>&.
7156 .section "Query-style lookup types" "SECTquerystylelookups"
7157 .cindex "lookup" "query-style types"
7158 .cindex "query-style lookup" "list of types"
7159 The supported query-style lookup types are listed below. Further details about
7160 many of them are given in later sections.
7163 .cindex "DNS" "as a lookup type"
7164 .cindex "lookup" "DNS"
7165 &(dnsdb)&: This does a DNS search for one or more records whose domain names
7166 are given in the supplied query. The resulting data is the contents of the
7167 records. See section &<<SECTdnsdb>>&.
7169 .cindex "InterBase lookup type"
7170 .cindex "lookup" "InterBase"
7171 &(ibase)&: This does a lookup in an InterBase database.
7173 .cindex "LDAP" "lookup type"
7174 .cindex "lookup" "LDAP"
7175 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
7176 returns attributes from a single entry. There is a variant called &(ldapm)&
7177 that permits values from multiple entries to be returned. A third variant
7178 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
7179 any attribute values. See section &<<SECTldap>>&.
7181 .cindex "MySQL" "lookup type"
7182 .cindex "lookup" "MySQL"
7183 &(mysql)&: The format of the query is an SQL statement that is passed to a
7184 MySQL database. See section &<<SECTsql>>&.
7186 .cindex "NIS+ lookup type"
7187 .cindex "lookup" "NIS+"
7188 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
7189 the field to be returned. See section &<<SECTnisplus>>&.
7191 .cindex "Oracle" "lookup type"
7192 .cindex "lookup" "Oracle"
7193 &(oracle)&: The format of the query is an SQL statement that is passed to an
7194 Oracle database. See section &<<SECTsql>>&.
7196 .cindex "lookup" "passwd"
7197 .cindex "passwd lookup type"
7198 .cindex "&_/etc/passwd_&"
7199 &(passwd)& is a query-style lookup with queries that are just user names. The
7200 lookup calls &[getpwnam()]& to interrogate the system password data, and on
7201 success, the result string is the same as you would get from an &(lsearch)&
7202 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
7203 password value. For example:
7205 *:42:42:King Rat:/home/kr:/bin/bash
7208 .cindex "PostgreSQL lookup type"
7209 .cindex "lookup" "PostgreSQL"
7210 &(pgsql)&: The format of the query is an SQL statement that is passed to a
7211 PostgreSQL database. See section &<<SECTsql>>&.
7214 .cindex "Redis lookup type"
7215 .cindex lookup Redis
7216 &(redis)&: The format of the query is either a simple get or simple set,
7217 passed to a Redis database. See section &<<SECTsql>>&.
7220 .cindex "sqlite lookup type"
7221 .cindex "lookup" "sqlite"
7222 &(sqlite)&: The format of the query is
7223 an SQL statement that is passed to an SQLite database. See section &<<SECTsqlite>>&.
7226 &(testdb)&: This is a lookup type that is used for testing Exim. It is
7227 not likely to be useful in normal operation.
7229 .cindex "whoson lookup type"
7230 .cindex "lookup" "whoson"
7231 . --- still http:-only, 2018-09-07
7232 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
7233 allows a server to check whether a particular (dynamically allocated) IP
7234 address is currently allocated to a known (trusted) user and, optionally, to
7235 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
7236 at one time for &"POP before SMTP"& authentication, but that approach has been
7237 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
7238 &"POP before SMTP"& checking using ACL statements such as
7240 require condition = \
7241 ${lookup whoson {$sender_host_address}{yes}{no}}
7243 The query consists of a single IP address. The value returned is the name of
7244 the authenticated user, which is stored in the variable &$value$&. However, in
7245 this example, the data in &$value$& is not used; the result of the lookup is
7246 one of the fixed strings &"yes"& or &"no"&.
7251 .section "Temporary errors in lookups" "SECID63"
7252 .cindex "lookup" "temporary error in"
7253 Lookup functions can return temporary error codes if the lookup cannot be
7254 completed. For example, an SQL or LDAP database might be unavailable. For this
7255 reason, it is not advisable to use a lookup that might do this for critical
7256 options such as a list of local domains.
7258 When a lookup cannot be completed in a router or transport, delivery
7259 of the message (to the relevant address) is deferred, as for any other
7260 temporary error. In other circumstances Exim may assume the lookup has failed,
7261 or may give up altogether.
7265 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
7266 .cindex "wildcard lookups"
7267 .cindex "lookup" "default values"
7268 .cindex "lookup" "wildcard"
7269 .cindex "lookup" "* added to type"
7270 .cindex "default" "in single-key lookups"
7271 In this context, a &"default value"& is a value specified by the administrator
7272 that is to be used if a lookup fails.
7274 &*Note:*& This section applies only to single-key lookups. For query-style
7275 lookups, the facilities of the query language must be used. An attempt to
7276 specify a default for a query-style lookup provokes an error.
7278 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
7279 and the initial lookup fails, the key &"*"& is looked up in the file to
7280 provide a default value. See also the section on partial matching below.
7282 .cindex "*@ with single-key lookup"
7283 .cindex "lookup" "*@ added to type"
7284 .cindex "alias file" "per-domain default"
7285 Alternatively, if &"*@"& is added to a single-key lookup type (for example
7286 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
7287 character, a second lookup is done with everything before the last @ replaced
7288 by *. This makes it possible to provide per-domain defaults in alias files
7289 that include the domains in the keys. If the second lookup fails (or doesn't
7290 take place because there is no @ in the key), &"*"& is looked up.
7291 For example, a &(redirect)& router might contain:
7293 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
7295 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
7296 looks up these keys, in this order:
7302 The data is taken from whichever key it finds first. &*Note*&: In an
7303 &(lsearch)& file, this does not mean the first of these keys in the file. A
7304 complete scan is done for each key, and only if it is not found at all does
7305 Exim move on to try the next key.
7309 .section "Partial matching in single-key lookups" "SECTpartiallookup"
7310 .cindex "partial matching"
7311 .cindex "wildcard lookups"
7312 .cindex "lookup" "partial matching"
7313 .cindex "lookup" "wildcard"
7314 .cindex "asterisk" "in search type"
7315 The normal operation of a single-key lookup is to search the file for an exact
7316 match with the given key. However, in a number of situations where domains are
7317 being looked up, it is useful to be able to do partial matching. In this case,
7318 information in the file that has a key starting with &"*."& is matched by any
7319 domain that ends with the components that follow the full stop. For example, if
7320 a key in a DBM file is
7322 *.dates.fict.example
7324 then when partial matching is enabled this is matched by (amongst others)
7325 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
7326 by &'dates.fict.example'&, if that does not appear as a separate key in the
7329 &*Note*&: Partial matching is not available for query-style lookups. It is
7330 also not available for any lookup items in address lists (see section
7331 &<<SECTaddresslist>>&).
7333 Partial matching is implemented by doing a series of separate lookups using
7334 keys constructed by modifying the original subject key. This means that it can
7335 be used with any of the single-key lookup types, provided that
7336 partial matching keys
7337 beginning with a special prefix (default &"*."&) are included in the data file.
7338 Keys in the file that do not begin with the prefix are matched only by
7339 unmodified subject keys when partial matching is in use.
7341 Partial matching is requested by adding the string &"partial-"& to the front of
7342 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
7343 is done, the subject key is first looked up unmodified; if that fails, &"*."&
7344 is added at the start of the subject key, and it is looked up again. If that
7345 fails, further lookups are tried with dot-separated components removed from the
7346 start of the subject key, one-by-one, and &"*."& added on the front of what
7349 A minimum number of two non-* components are required. This can be adjusted
7350 by including a number before the hyphen in the search type. For example,
7351 &%partial3-lsearch%& specifies a minimum of three non-* components in the
7352 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
7353 subject key is &'2250.dates.fict.example'& then the following keys are looked
7354 up when the minimum number of non-* components is two:
7356 2250.dates.fict.example
7357 *.2250.dates.fict.example
7358 *.dates.fict.example
7361 As soon as one key in the sequence is successfully looked up, the lookup
7364 .cindex "lookup" "partial matching &-- changing prefix"
7365 .cindex "prefix" "for partial matching"
7366 The use of &"*."& as the partial matching prefix is a default that can be
7367 changed. The motivation for this feature is to allow Exim to operate with file
7368 formats that are used by other MTAs. A different prefix can be supplied in
7369 parentheses instead of the hyphen after &"partial"&. For example:
7371 domains = partial(.)lsearch;/some/file
7373 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
7374 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
7375 components is unchanged). The prefix may consist of any punctuation characters
7376 other than a closing parenthesis. It may be empty, for example:
7378 domains = partial1()cdb;/some/file
7380 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
7381 &`a.b.c`&, &`b.c`&, and &`c`&.
7383 If &"partial0"& is specified, what happens at the end (when the lookup with
7384 just one non-wild component has failed, and the original key is shortened right
7385 down to the null string) depends on the prefix:
7388 If the prefix has zero length, the whole lookup fails.
7390 If the prefix has length 1, a lookup for just the prefix is done. For
7391 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
7393 Otherwise, if the prefix ends in a dot, the dot is removed, and the
7394 remainder is looked up. With the default prefix, therefore, the final lookup is
7395 for &"*"& on its own.
7397 Otherwise, the whole prefix is looked up.
7401 If the search type ends in &"*"& or &"*@"& (see section
7402 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
7403 this implies happens after all partial lookups have failed. If &"partial0"& is
7404 specified, adding &"*"& to the search type has no effect with the default
7405 prefix, because the &"*"& key is already included in the sequence of partial
7406 lookups. However, there might be a use for lookup types such as
7407 &"partial0(.)lsearch*"&.
7409 The use of &"*"& in lookup partial matching differs from its use as a wildcard
7410 in domain lists and the like. Partial matching works only in terms of
7411 dot-separated components; a key such as &`*fict.example`&
7412 in a database file is useless, because the asterisk in a partial matching
7413 subject key is always followed by a dot.
7418 .section "Lookup caching" "SECID64"
7419 .cindex "lookup" "caching"
7420 .cindex "caching" "lookup data"
7421 Exim caches all lookup results in order to avoid needless repetition of
7422 lookups. However, because (apart from the daemon) Exim operates as a collection
7423 of independent, short-lived processes, this caching applies only within a
7424 single Exim process. There is no inter-process lookup caching facility.
7427 If an option &"cache=no_rd"& is used on the lookup then
7428 the cache is only written to, cached data is not used for the operation
7429 and a real lookup is done.
7432 For single-key lookups, Exim keeps the relevant files open in case there is
7433 another lookup that needs them. In some types of configuration this can lead to
7434 many files being kept open for messages with many recipients. To avoid hitting
7435 the operating system limit on the number of simultaneously open files, Exim
7436 closes the least recently used file when it needs to open more files than its
7437 own internal limit, which can be changed via the &%lookup_open_max%& option.
7439 The single-key lookup files are closed and the lookup caches are flushed at
7440 strategic points during delivery &-- for example, after all routing is
7446 .section "Quoting lookup data" "SECID65"
7447 .cindex "lookup" "quoting"
7448 .cindex "quoting" "in lookups"
7449 When data from an incoming message is included in a query-style lookup, there
7450 is the possibility of special characters in the data messing up the syntax of
7451 the query. For example, a NIS+ query that contains
7455 will be broken if the local part happens to contain a closing square bracket.
7456 For NIS+, data can be enclosed in double quotes like this:
7458 [name="$local_part"]
7460 but this still leaves the problem of a double quote in the data. The rule for
7461 NIS+ is that double quotes must be doubled. Other lookup types have different
7462 rules, and to cope with the differing requirements, an expansion operator
7463 of the following form is provided:
7465 ${quote_<lookup-type>:<string>}
7467 For example, the safest way to write the NIS+ query is
7469 [name="${quote_nisplus:$local_part}"]
7471 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
7472 operator can be used for all lookup types, but has no effect for single-key
7473 lookups, since no quoting is ever needed in their key strings.
7478 .section "More about dnsdb" "SECTdnsdb"
7479 .cindex "dnsdb lookup"
7480 .cindex "lookup" "dnsdb"
7481 .cindex "DNS" "as a lookup type"
7482 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7483 of a record type and a domain name, separated by an equals sign. For example,
7484 an expansion string could contain:
7486 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7488 If the lookup succeeds, the result is placed in &$value$&, which in this case
7489 is used on its own as the result. If the lookup does not succeed, the
7490 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7491 &<<SECTforexpfai>>& for an explanation of what this means.
7493 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7494 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7495 If no type is given, TXT is assumed.
7497 For any record type, if multiple records are found, the data is returned as a
7498 concatenation, with newline as the default separator. The order, of course,
7499 depends on the DNS resolver. You can specify a different separator character
7500 between multiple records by putting a right angle-bracket followed immediately
7501 by the new separator at the start of the query. For example:
7503 ${lookup dnsdb{>: a=host1.example}}
7505 It is permitted to specify a space as the separator character. Further
7506 white space is ignored.
7507 For lookup types that return multiple fields per record,
7508 an alternate field separator can be specified using a comma after the main
7509 separator character, followed immediately by the field separator.
7511 .cindex "PTR record" "in &(dnsdb)& lookup"
7512 When the type is PTR,
7513 the data can be an IP address, written as normal; inversion and the addition of
7514 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7516 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7518 If the data for a PTR record is not a syntactically valid IP address, it is not
7519 altered and nothing is added.
7521 .cindex "MX record" "in &(dnsdb)& lookup"
7522 .cindex "SRV record" "in &(dnsdb)& lookup"
7523 For an MX lookup, both the preference value and the host name are returned for
7524 each record, separated by a space. For an SRV lookup, the priority, weight,
7525 port, and host name are returned for each record, separated by spaces.
7526 The field separator can be modified as above.
7528 .cindex "TXT record" "in &(dnsdb)& lookup"
7529 .cindex "SPF record" "in &(dnsdb)& lookup"
7530 For TXT records with multiple items of data, only the first item is returned,
7531 unless a field separator is specified.
7532 To concatenate items without a separator, use a semicolon instead.
7534 default behaviour is to concatenate multiple items without using a separator.
7536 ${lookup dnsdb{>\n,: txt=a.b.example}}
7537 ${lookup dnsdb{>\n; txt=a.b.example}}
7538 ${lookup dnsdb{spf=example.org}}
7540 It is permitted to specify a space as the separator character. Further
7541 white space is ignored.
7543 .cindex "SOA record" "in &(dnsdb)& lookup"
7544 For an SOA lookup, while no result is obtained the lookup is redone with
7545 successively more leading components dropped from the given domain.
7546 Only the primary-nameserver field is returned unless a field separator is
7549 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7552 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7553 .cindex "dnsdb modifiers"
7554 .cindex "modifiers" "dnsdb"
7555 .cindex "options" "dnsdb"
7556 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7557 each followed by a comma,
7558 that may appear before the record type.
7560 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7561 temporary DNS error for any of them, the behaviour is controlled by
7562 a defer-option modifier.
7563 The possible keywords are
7564 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7565 With &"strict"& behaviour, any temporary DNS error causes the
7566 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7567 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7568 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7569 error causes the whole lookup to defer only if none of the other lookups
7570 succeed. The default is &"lax"&, so the following lookups are equivalent:
7572 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7573 ${lookup dnsdb{a=one.host.com:two.host.com}}
7575 Thus, in the default case, as long as at least one of the DNS lookups
7576 yields some data, the lookup succeeds.
7578 .cindex "DNSSEC" "dns lookup"
7579 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7580 The possible keywords are
7581 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7582 With &"strict"& or &"lax"& DNSSEC information is requested
7584 With &"strict"& a response from the DNS resolver that
7585 is not labelled as authenticated data
7586 is treated as equivalent to a temporary DNS error.
7587 The default is &"lax"&.
7589 See also the &$lookup_dnssec_authenticated$& variable.
7591 .cindex timeout "dns lookup"
7592 .cindex "DNS" timeout
7593 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7594 The form is &"retrans_VAL"& where VAL is an Exim time specification
7596 The default value is set by the main configuration option &%dns_retrans%&.
7598 Retries for the dnsdb lookup can be controlled by a retry modifier.
7599 The form if &"retry_VAL"& where VAL is an integer.
7600 The default count is set by the main configuration option &%dns_retry%&.
7602 .cindex caching "of dns lookup"
7603 .cindex TTL "of dns lookup"
7605 Dnsdb lookup results are cached within a single process (and its children).
7606 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7607 value of the set of returned DNS records.
7610 .section "Pseudo dnsdb record types" "SECID66"
7611 .cindex "MX record" "in &(dnsdb)& lookup"
7612 By default, both the preference value and the host name are returned for
7613 each MX record, separated by a space. If you want only host names, you can use
7614 the pseudo-type MXH:
7616 ${lookup dnsdb{mxh=a.b.example}}
7618 In this case, the preference values are omitted, and just the host names are
7621 .cindex "name server for enclosing domain"
7622 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7623 records on the given domain, but if none are found, it removes the first
7624 component of the domain name, and tries again. This process continues until NS
7625 records are found or there are no more components left (or there is a DNS
7626 error). In other words, it may return the name servers for a top-level domain,
7627 but it never returns the root name servers. If there are no NS records for the
7628 top-level domain, the lookup fails. Consider these examples:
7630 ${lookup dnsdb{zns=xxx.quercite.com}}
7631 ${lookup dnsdb{zns=xxx.edu}}
7633 Assuming that in each case there are no NS records for the full domain name,
7634 the first returns the name servers for &%quercite.com%&, and the second returns
7635 the name servers for &%edu%&.
7637 You should be careful about how you use this lookup because, unless the
7638 top-level domain does not exist, the lookup always returns some host names. The
7639 sort of use to which this might be put is for seeing if the name servers for a
7640 given domain are on a blacklist. You can probably assume that the name servers
7641 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7644 .cindex "CSA" "in &(dnsdb)& lookup"
7645 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7646 records according to the CSA rules, which are described in section
7647 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7648 not sufficient because of the extra parent domain search behaviour of CSA. The
7649 result of a successful lookup such as:
7651 ${lookup dnsdb {csa=$sender_helo_name}}
7653 has two space-separated fields: an authorization code and a target host name.
7654 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7655 authorization required but absent, or &"?"& for unknown.
7657 .cindex "A+" "in &(dnsdb)& lookup"
7658 The pseudo-type A+ performs an AAAA
7659 and then an A lookup. All results are returned; defer processing
7660 (see below) is handled separately for each lookup. Example:
7662 ${lookup dnsdb {>; a+=$sender_helo_name}}
7666 .section "Multiple dnsdb lookups" "SECID67"
7667 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7668 However, you can specify a list of domains or IP addresses in a single
7669 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7670 the default separator, but with the ability to change this. For example:
7672 ${lookup dnsdb{one.domain.com:two.domain.com}}
7673 ${lookup dnsdb{a=one.host.com:two.host.com}}
7674 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7676 In order to retain backwards compatibility, there is one special case: if
7677 the lookup type is PTR and no change of separator is specified, Exim looks
7678 to see if the rest of the string is precisely one IPv6 address. In this
7679 case, it does not treat it as a list.
7681 The data from each lookup is concatenated, with newline separators by default,
7682 in the same way that multiple DNS records for a single item are handled. A
7683 different separator can be specified, as described above.
7688 .section "More about LDAP" "SECTldap"
7689 .cindex "LDAP" "lookup, more about"
7690 .cindex "lookup" "LDAP"
7691 .cindex "Solaris" "LDAP"
7692 The original LDAP implementation came from the University of Michigan; this has
7693 become &"Open LDAP"&, and there are now two different releases. Another
7694 implementation comes from Netscape, and Solaris 7 and subsequent releases
7695 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7696 the lookup function level, their error handling is different. For this reason
7697 it is necessary to set a compile-time variable when building Exim with LDAP, to
7698 indicate which LDAP library is in use. One of the following should appear in
7699 your &_Local/Makefile_&:
7701 LDAP_LIB_TYPE=UMICHIGAN
7702 LDAP_LIB_TYPE=OPENLDAP1
7703 LDAP_LIB_TYPE=OPENLDAP2
7704 LDAP_LIB_TYPE=NETSCAPE
7705 LDAP_LIB_TYPE=SOLARIS
7707 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7708 same interface as the University of Michigan version.
7710 There are three LDAP lookup types in Exim. These behave slightly differently in
7711 the way they handle the results of a query:
7714 &(ldap)& requires the result to contain just one entry; if there are more, it
7717 &(ldapdn)& also requires the result to contain just one entry, but it is the
7718 Distinguished Name that is returned rather than any attribute values.
7720 &(ldapm)& permits the result to contain more than one entry; the attributes
7721 from all of them are returned.
7725 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7726 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7727 the data returned by a successful lookup is described in the next section.
7728 First we explain how LDAP queries are coded.
7731 .section "Format of LDAP queries" "SECTforldaque"
7732 .cindex "LDAP" "query format"
7733 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7734 the configuration of a &(redirect)& router one might have this setting:
7736 data = ${lookup ldap \
7737 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7738 c=UK?mailbox?base?}}
7740 .cindex "LDAP" "with TLS"
7741 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7742 secure (encrypted) LDAP connections. The second of these ensures that an
7743 encrypted TLS connection is used.
7745 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7746 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7747 See the &%ldap_start_tls%& option.
7749 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7750 controlled. Every part of the TLS configuration can be configured by settings in
7751 &_exim.conf_&. Depending on the version of the client libraries installed on
7752 your system, some of the initialization may have required setting options in
7753 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7754 certificates. This revealed a nuance where the current UID that exim was
7755 running as could affect which config files it read. With Exim 4.83, these
7756 methods become optional, only taking effect if not specifically set in
7760 .section "LDAP quoting" "SECID68"
7761 .cindex "LDAP" "quoting"
7762 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7763 and the second because the LDAP query is represented as a URL. Furthermore,
7764 within an LDAP query, two different kinds of quoting are required. For this
7765 reason, there are two different LDAP-specific quoting operators.
7767 The &%quote_ldap%& operator is designed for use on strings that are part of
7768 filter specifications. Conceptually, it first does the following conversions on
7776 in accordance with RFC 2254. The resulting string is then quoted according
7777 to the rules for URLs, that is, all non-alphanumeric characters except
7781 are converted to their hex values, preceded by a percent sign. For example:
7783 ${quote_ldap: a(bc)*, a<yz>; }
7787 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7789 Removing the URL quoting, this is (with a leading and a trailing space):
7791 a\28bc\29\2A, a<yz>;
7793 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7794 base DN specifications in queries. Conceptually, it first converts the string
7795 by inserting a backslash in front of any of the following characters:
7799 It also inserts a backslash before any leading spaces or # characters, and
7800 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7801 is then quoted according to the rules for URLs. For example:
7803 ${quote_ldap_dn: a(bc)*, a<yz>; }
7807 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7809 Removing the URL quoting, this is (with a trailing space):
7811 \ a(bc)*\, a\<yz\>\;\
7813 There are some further comments about quoting in the section on LDAP
7814 authentication below.
7817 .section "LDAP connections" "SECID69"
7818 .cindex "LDAP" "connections"
7819 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7820 is in use, via a Unix domain socket. The example given above does not specify
7821 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7824 ldap://<hostname>:<port>/...
7826 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7827 used. When no server is specified in a query, a list of default servers is
7828 taken from the &%ldap_default_servers%& configuration option. This supplies a
7829 colon-separated list of servers which are tried in turn until one successfully
7830 handles a query, or there is a serious error. Successful handling either
7831 returns the requested data, or indicates that it does not exist. Serious errors
7832 are syntactical, or multiple values when only a single value is expected.
7833 Errors which cause the next server to be tried are connection failures, bind
7834 failures, and timeouts.
7836 For each server name in the list, a port number can be given. The standard way
7837 of specifying a host and port is to use a colon separator (RFC 1738). Because
7838 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7839 doubled. For example
7841 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7843 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7844 to the LDAP library with no server name, and the library's default (normally
7845 the local host) is used.
7847 If you are using the OpenLDAP library, you can connect to an LDAP server using
7848 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7849 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7850 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7853 For this type of connection, instead of a host name for the server, a pathname
7854 for the socket is required, and the port number is not relevant. The pathname
7855 can be specified either as an item in &%ldap_default_servers%&, or inline in
7856 the query. In the former case, you can have settings such as
7858 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7860 When the pathname is given in the query, you have to escape the slashes as
7861 &`%2F`& to fit in with the LDAP URL syntax. For example:
7863 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7865 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7866 a pathname, it uses the Unix domain socket code, even if the query actually
7867 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7868 socket connection. This behaviour means that you can use a setting of
7869 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7870 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7871 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7874 If an explicit &`ldapi`& type is given in a query when a host name is
7875 specified, an error is diagnosed. However, if there are more items in
7876 &%ldap_default_servers%&, they are tried. In other words:
7879 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7882 Using &`ldapi`& with a host name causes an error.
7886 Using &`ldapi`& with no host or path in the query, and no setting of
7887 &%ldap_default_servers%&, does whatever the library does by default.
7891 .section "LDAP authentication and control information" "SECID70"
7892 .cindex "LDAP" "authentication"
7893 The LDAP URL syntax provides no way of passing authentication and other control
7894 information to the server. To make this possible, the URL in an LDAP query may
7895 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7896 spaces. If a value contains spaces it must be enclosed in double quotes, and
7897 when double quotes are used, backslash is interpreted in the usual way inside
7898 them. The following names are recognized:
7900 &`DEREFERENCE`& set the dereferencing parameter
7901 &`NETTIME `& set a timeout for a network operation
7902 &`USER `& set the DN, for authenticating the LDAP bind
7903 &`PASS `& set the password, likewise
7904 &`REFERRALS `& set the referrals parameter
7905 &`SERVERS `& set alternate server list for this query only
7906 &`SIZE `& set the limit for the number of entries returned
7907 &`TIME `& set the maximum waiting time for a query
7909 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7910 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7911 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7912 library from trying to follow referrals issued by the LDAP server.
7914 .cindex LDAP timeout
7915 .cindex timeout "LDAP lookup"
7916 The name CONNECT is an obsolete name for NETTIME, retained for
7917 backwards compatibility. This timeout (specified as a number of seconds) is
7918 enforced from the client end for operations that can be carried out over a
7919 network. Specifically, it applies to network connections and calls to the
7920 &'ldap_result()'& function. If the value is greater than zero, it is used if
7921 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7922 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7923 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7924 Netscape SDK; for OpenLDAP no action is taken.
7926 The TIME parameter (also a number of seconds) is passed to the server to
7927 set a server-side limit on the time taken to complete a search.
7929 The SERVERS parameter allows you to specify an alternate list of ldap servers
7930 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7931 default list of ldap servers, and a single lookup can specify a single ldap
7932 server to use. But when you need to do a lookup with a list of servers that is
7933 different than the default list (maybe different order, maybe a completely
7934 different set of servers), the SERVERS parameter allows you to specify this
7935 alternate list (colon-separated).
7937 Here is an example of an LDAP query in an Exim lookup that uses some of these
7938 values. This is a single line, folded to fit on the page:
7941 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7942 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7945 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7946 any of the auxiliary data. Exim configuration settings that include lookups
7947 which contain password information should be preceded by &"hide"& to prevent
7948 non-admin users from using the &%-bP%& option to see their values.
7950 The auxiliary data items may be given in any order. The default is no
7951 connection timeout (the system timeout is used), no user or password, no limit
7952 on the number of entries returned, and no time limit on queries.
7954 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7955 removes any URL quoting that it may contain before passing it LDAP. Apparently
7956 some libraries do this for themselves, but some do not. Removing the URL
7957 quoting has two advantages:
7960 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7961 DNs as with DNs inside actual queries.
7963 It permits spaces inside USER= DNs.
7966 For example, a setting such as
7968 USER=cn=${quote_ldap_dn:$1}
7970 should work even if &$1$& contains spaces.
7972 Expanded data for the PASS= value should be quoted using the &%quote%&
7973 expansion operator, rather than the LDAP quote operators. The only reason this
7974 field needs quoting is to ensure that it conforms to the Exim syntax, which
7975 does not allow unquoted spaces. For example:
7979 The LDAP authentication mechanism can be used to check passwords as part of
7980 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7985 .section "Format of data returned by LDAP" "SECID71"
7986 .cindex "LDAP" "returned data formats"
7987 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7988 as a sequence of values, for example
7990 cn=manager,o=University of Cambridge,c=UK
7992 The &(ldap)& lookup type generates an error if more than one entry matches the
7993 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7994 the result between the data from different entries. It is possible for multiple
7995 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7996 you know that whatever values are returned all came from a single entry in the
7999 In the common case where you specify a single attribute in your LDAP query, the
8000 result is not quoted, and does not contain the attribute name. If the attribute
8001 has multiple values, they are separated by commas. Any comma that is
8002 part of an attribute's value is doubled.
8004 If you specify multiple attributes, the result contains space-separated, quoted
8005 strings, each preceded by the attribute name and an equals sign. Within the
8006 quotes, the quote character, backslash, and newline are escaped with
8007 backslashes, and commas are used to separate multiple values for the attribute.
8008 Any commas in attribute values are doubled
8009 (permitting treatment of the values as a comma-separated list).
8010 Apart from the escaping, the string within quotes takes the same form as the
8011 output when a single attribute is requested. Specifying no attributes is the
8012 same as specifying all of an entry's attributes.
8014 Here are some examples of the output format. The first line of each pair is an
8015 LDAP query, and the second is the data that is returned. The attribute called
8016 &%attr1%& has two values, one of them with an embedded comma, whereas
8017 &%attr2%& has only one value. Both attributes are derived from &%attr%&
8018 (they have SUP &%attr%& in their schema definitions).
8021 ldap:///o=base?attr1?sub?(uid=fred)
8024 ldap:///o=base?attr2?sub?(uid=fred)
8027 ldap:///o=base?attr?sub?(uid=fred)
8028 value1.1,value1,,2,value two
8030 ldap:///o=base?attr1,attr2?sub?(uid=fred)
8031 attr1="value1.1,value1,,2" attr2="value two"
8033 ldap:///o=base??sub?(uid=fred)
8034 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
8037 make use of Exim's &%-be%& option to run expansion tests and thereby check the
8038 results of LDAP lookups.
8039 The &%extract%& operator in string expansions can be used to pick out
8040 individual fields from data that consists of &'key'&=&'value'& pairs.
8041 The &%listextract%& operator should be used to pick out individual values
8042 of attributes, even when only a single value is expected.
8043 The doubling of embedded commas allows you to use the returned data as a
8044 comma separated list (using the "<," syntax for changing the input list separator).
8049 .section "More about NIS+" "SECTnisplus"
8050 .cindex "NIS+ lookup type"
8051 .cindex "lookup" "NIS+"
8052 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
8053 and field name. If this is given, the result of a successful query is the
8054 contents of the named field; otherwise the result consists of a concatenation
8055 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
8056 values containing spaces are quoted. For example, the query
8058 [name=mg1456],passwd.org_dir
8060 might return the string
8062 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
8063 home=/home/mg1456 shell=/bin/bash shadow=""
8065 (split over two lines here to fit on the page), whereas
8067 [name=mg1456],passwd.org_dir:gcos
8073 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
8074 for the given indexed key. The effect of the &%quote_nisplus%& expansion
8075 operator is to double any quote characters within the text.
8079 .section "SQL lookups" "SECTsql"
8080 .cindex "SQL lookup types"
8081 .cindex "MySQL" "lookup type"
8082 .cindex "PostgreSQL lookup type"
8083 .cindex "lookup" "MySQL"
8084 .cindex "lookup" "PostgreSQL"
8085 .cindex "Oracle" "lookup type"
8086 .cindex "lookup" "Oracle"
8087 .cindex "InterBase lookup type"
8088 .cindex "lookup" "InterBase"
8089 .cindex "Redis lookup type"
8090 .cindex lookup Redis
8091 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
8093 databases. Queries for these databases contain SQL statements, so an example
8096 ${lookup mysql{select mailbox from users where id='userx'}\
8099 If the result of the query contains more than one field, the data for each
8100 field in the row is returned, preceded by its name, so the result of
8102 ${lookup pgsql{select home,name from users where id='userx'}\
8107 home=/home/userx name="Mister X"
8109 Empty values and values containing spaces are double quoted, with embedded
8110 quotes escaped by a backslash. If the result of the query contains just one
8111 field, the value is passed back verbatim, without a field name, for example:
8115 If the result of the query yields more than one row, it is all concatenated,
8116 with a newline between the data for each row.
8119 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
8120 .cindex "MySQL" "lookup type"
8121 .cindex "PostgreSQL lookup type"
8122 .cindex "lookup" "MySQL"
8123 .cindex "lookup" "PostgreSQL"
8124 .cindex "Oracle" "lookup type"
8125 .cindex "lookup" "Oracle"
8126 .cindex "InterBase lookup type"
8127 .cindex "lookup" "InterBase"
8128 .cindex "Redis lookup type"
8129 .cindex lookup Redis
8130 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
8131 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
8132 or &%redis_servers%&
8133 option (as appropriate) must be set to a colon-separated list of server
8135 .oindex &%mysql_servers%&
8136 .oindex &%pgsql_servers%&
8137 .oindex &%oracle_servers%&
8138 .oindex &%ibase_servers%&
8139 .oindex &%redis_servers%&
8140 (For MySQL and PostgreSQL, the global option need not be set if all
8141 queries contain their own server information &-- see section
8142 &<<SECTspeserque>>&.)
8144 each item in the list is a slash-separated list of four
8145 items: host name, database name, user name, and password. In the case of
8146 Oracle, the host name field is used for the &"service name"&, and the database
8147 name field is not used and should be empty. For example:
8149 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
8151 Because password data is sensitive, you should always precede the setting with
8152 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
8153 option. Here is an example where two MySQL servers are listed:
8155 hide mysql_servers = localhost/users/root/secret:\
8156 otherhost/users/root/othersecret
8158 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
8159 because this is a colon-separated list, the colon has to be doubled. For each
8160 query, these parameter groups are tried in order until a connection is made and
8161 a query is successfully processed. The result of a query may be that no data is
8162 found, but that is still a successful query. In other words, the list of
8163 servers provides a backup facility, not a list of different places to look.
8165 For Redis the global option need not be specified if all queries contain their
8166 own server information &-- see section &<<SECTspeserque>>&.
8167 If specified, the option must be set to a colon-separated list of server
8169 Each item in the list is a slash-separated list of three items:
8170 host, database number, and password.
8172 The host is required and may be either an IPv4 address and optional
8173 port number (separated by a colon, which needs doubling due to the
8174 higher-level list), or a Unix socket pathname enclosed in parentheses
8176 The database number is optional; if present that number is selected in the backend
8178 The password is optional; if present it is used to authenticate to the backend
8181 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
8182 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
8183 respectively, and the characters single-quote, double-quote, and backslash
8184 itself are escaped with backslashes.
8186 The &%quote_redis%& expansion operator
8187 escapes whitespace and backslash characters with a backslash.
8189 .section "Specifying the server in the query" "SECTspeserque"
8190 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
8191 it is possible to specify a list of servers with an individual query. This is
8192 done by appending a comma-separated option to the query type:
8194 &`,servers=`&&'server1:server2:server3:...'&
8196 Each item in the list may take one of two forms:
8198 If it contains no slashes it is assumed to be just a host name. The appropriate
8199 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
8200 of the same name, and the remaining parameters (database, user, password) are
8203 If it contains any slashes, it is taken as a complete parameter set.
8205 The list of servers is used in exactly the same way as the global list.
8206 Once a connection to a server has happened and a query has been
8207 successfully executed, processing of the lookup ceases.
8209 This feature is intended for use in master/slave situations where updates
8210 are occurring and you want to update the master rather than a slave. If the
8211 master is in the list as a backup for reading, you might have a global setting
8214 mysql_servers = slave1/db/name/pw:\
8218 In an updating lookup, you could then write:
8220 ${lookup mysql,servers=master {UPDATE ...} }
8222 That query would then be sent only to the master server. If, on the other hand,
8223 the master is not to be used for reading, and so is not present in the global
8224 option, you can still update it by a query of this form:
8226 ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
8229 An older syntax places the servers specification before the query,
8230 semicolon separated:
8232 ${lookup mysql{servers=master; UPDATE ...} }
8234 The new version avoids potential issues with tainted
8235 arguments in the query, for explicit expansion.
8236 &*Note*&: server specifications in list-style lookups are still problematic.
8239 .section "Special MySQL features" "SECID73"
8240 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
8241 causes a connection to the server on the local host by means of a Unix domain
8242 socket. An alternate socket can be specified in parentheses.
8243 An option group name for MySQL option files can be specified in square brackets;
8244 the default value is &"exim"&.
8245 The full syntax of each item in &%mysql_servers%& is:
8247 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
8248 <&'database'&>/<&'user'&>/<&'password'&>
8250 Any of the four sub-parts of the first field can be omitted. For normal use on
8251 the local host it can be left blank or set to just &"localhost"&.
8253 No database need be supplied &-- but if it is absent here, it must be given in
8256 If a MySQL query is issued that does not request any data (an insert, update,
8257 or delete command), the result of the lookup is the number of rows affected.
8259 &*Warning*&: This can be misleading. If an update does not actually change
8260 anything (for example, setting a field to the value it already has), the result
8261 is zero because no rows are affected.
8264 .section "Special PostgreSQL features" "SECID74"
8265 PostgreSQL lookups can also use Unix domain socket connections to the database.
8266 This is usually faster and costs less CPU time than a TCP/IP connection.
8267 However it can be used only if the mail server runs on the same machine as the
8268 database server. A configuration line for PostgreSQL via Unix domain sockets
8271 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
8273 In other words, instead of supplying a host name, a path to the socket is
8274 given. The path name is enclosed in parentheses so that its slashes aren't
8275 visually confused with the delimiters for the other server parameters.
8277 If a PostgreSQL query is issued that does not request any data (an insert,
8278 update, or delete command), the result of the lookup is the number of rows
8281 .section "More about SQLite" "SECTsqlite"
8282 .cindex "lookup" "SQLite"
8283 .cindex "sqlite lookup type"
8284 SQLite is different to the other SQL lookups because a filename is required in
8285 addition to the SQL query. An SQLite database is a single file, and there is no
8286 daemon as in the other SQL databases.
8289 .oindex &%sqlite_dbfile%&
8290 There are two ways of
8291 specifying the file.
8292 The first is is by using the &%sqlite_dbfile%& main option.
8293 The second, which allows separate files for each query,
8294 is to use an option appended, comma-separated, to the &"sqlite"&
8295 lookup type word. The option is the word &"file"&, then an equals,
8297 The filename in this case cannot contain whitespace or open-brace charachters.
8300 A deprecated method is available, prefixing the query with the filename
8301 separated by white space.
8303 .cindex "tainted data" "sqlite file"
8304 the query cannot use any tainted values, as that taints
8305 the entire query including the filename - resulting in a refusal to open
8308 In all the above cases the filename must be an absolute path.
8310 Here is a lookup expansion example:
8312 sqlite_dbfile = /some/thing/sqlitedb
8314 ${lookup sqlite {select name from aliases where id='userx';}}
8316 In a list, the syntax is similar. For example:
8318 domainlist relay_to_domains = sqlite;\
8319 select * from relays where ip='$sender_host_address';
8321 The only character affected by the &%quote_sqlite%& operator is a single
8322 quote, which it doubles.
8324 .cindex timeout SQLite
8325 .cindex sqlite "lookup timeout"
8326 The SQLite library handles multiple simultaneous accesses to the database
8327 internally. Multiple readers are permitted, but only one process can
8328 update at once. Attempts to access the database while it is being updated
8329 are rejected after a timeout period, during which the SQLite library
8330 waits for the lock to be released. In Exim, the default timeout is set
8331 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
8334 .section "More about Redis" "SECTredis"
8335 .cindex "lookup" "Redis"
8336 .cindex "redis lookup type"
8337 Redis is a non-SQL database. Commands are simple get and set.
8340 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
8341 ${lookup redis{get keyname}}
8344 As of release 4.91, "lightweight" support for Redis Cluster is available.
8345 Requires &%redis_servers%& list to contain all the servers in the cluster, all
8346 of which must be reachable from the running exim instance. If the cluster has
8347 master/slave replication, the list must contain all the master and slave
8350 When the Redis Cluster returns a "MOVED" response to a query, Exim does not
8351 immediately follow the redirection but treats the response as a DEFER, moving on
8352 to the next server in the &%redis_servers%& list until the correct server is
8359 . ////////////////////////////////////////////////////////////////////////////
8360 . ////////////////////////////////////////////////////////////////////////////
8362 .chapter "Domain, host, address, and local part lists" &&&
8363 "CHAPdomhosaddlists" &&&
8364 "Domain, host, and address lists"
8365 .scindex IIDdohoadli "lists of domains; hosts; etc."
8366 A number of Exim configuration options contain lists of domains, hosts,
8367 email addresses, or local parts. For example, the &%hold_domains%& option
8368 contains a list of domains whose delivery is currently suspended. These lists
8369 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
8370 arguments to expansion conditions such as &%match_domain%&.
8372 Each item in one of these lists is a pattern to be matched against a domain,
8373 host, email address, or local part, respectively. In the sections below, the
8374 different types of pattern for each case are described, but first we cover some
8375 general facilities that apply to all four kinds of list.
8377 Note that other parts of Exim use a &'string list'& which does not
8378 support all the complexity available in
8379 domain, host, address and local part lists.
8383 .section "Expansion of lists" "SECTlistexpand"
8384 .cindex "expansion" "of lists"
8385 Each list is expanded as a single string before it is used.
8387 &'Exception: the router headers_remove option, where list-item
8388 splitting is done before string-expansion.'&
8391 expansion must be a list, possibly containing empty items, which is split up
8392 into separate items for matching. By default, colon is the separator character,
8393 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
8394 &<<SECTempitelis>>& for details of the list syntax; the second of these
8395 discusses the way to specify empty list items.
8398 If the string expansion is forced to fail, Exim behaves as if the item it is
8399 testing (domain, host, address, or local part) is not in the list. Other
8400 expansion failures cause temporary errors.
8402 If an item in a list is a regular expression, backslashes, dollars and possibly
8403 other special characters in the expression must be protected against
8404 misinterpretation by the string expander. The easiest way to do this is to use
8405 the &`\N`& expansion feature to indicate that the contents of the regular
8406 expression should not be expanded. For example, in an ACL you might have:
8408 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
8409 ${lookup{$domain}lsearch{/badsenders/bydomain}}
8411 The first item is a regular expression that is protected from expansion by
8412 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
8413 senders based on the receiving domain.
8418 .section "Negated items in lists" "SECID76"
8419 .cindex "list" "negation"
8420 .cindex "negation" "in lists"
8421 Items in a list may be positive or negative. Negative items are indicated by a
8422 leading exclamation mark, which may be followed by optional white space. A list
8423 defines a set of items (domains, etc). When Exim processes one of these lists,
8424 it is trying to find out whether a domain, host, address, or local part
8425 (respectively) is in the set that is defined by the list. It works like this:
8427 The list is scanned from left to right. If a positive item is matched, the
8428 subject that is being checked is in the set; if a negative item is matched, the
8429 subject is not in the set. If the end of the list is reached without the
8430 subject having matched any of the patterns, it is in the set if the last item
8431 was a negative one, but not if it was a positive one. For example, the list in
8433 domainlist relay_to_domains = !a.b.c : *.b.c
8435 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
8436 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
8437 list is positive. However, if the setting were
8439 domainlist relay_to_domains = !a.b.c
8441 then all domains other than &'a.b.c'& would match because the last item in the
8442 list is negative. In other words, a list that ends with a negative item behaves
8443 as if it had an extra item &`:*`& on the end.
8445 Another way of thinking about positive and negative items in lists is to read
8446 the connector as &"or"& after a positive item and as &"and"& after a negative
8451 .section "File names in lists" "SECTfilnamlis"
8452 .cindex "list" "filename in"
8453 If an item in a domain, host, address, or local part list is an absolute
8454 filename (beginning with a slash character), each line of the file is read and
8455 processed as if it were an independent item in the list, except that further
8456 filenames are not allowed,
8457 and no expansion of the data from the file takes place.
8458 Empty lines in the file are ignored, and the file may also contain comment
8462 For domain and host lists, if a # character appears anywhere in a line of the
8463 file, it and all following characters are ignored.
8465 Because local parts may legitimately contain # characters, a comment in an
8466 address list or local part list file is recognized only if # is preceded by
8467 white space or the start of the line. For example:
8469 not#comment@x.y.z # but this is a comment
8473 Putting a filename in a list has the same effect as inserting each line of the
8474 file as an item in the list (blank lines and comments excepted). However, there
8475 is one important difference: the file is read each time the list is processed,
8476 so if its contents vary over time, Exim's behaviour changes.
8478 If a filename is preceded by an exclamation mark, the sense of any match
8479 within the file is inverted. For example, if
8481 hold_domains = !/etc/nohold-domains
8483 and the file contains the lines
8488 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
8489 any domain matching &`*.b.c`& is not.
8493 .section "An lsearch file is not an out-of-line list" "SECID77"
8494 As will be described in the sections that follow, lookups can be used in lists
8495 to provide indexed methods of checking list membership. There has been some
8496 confusion about the way &(lsearch)& lookups work in lists. Because
8497 an &(lsearch)& file contains plain text and is scanned sequentially, it is
8498 sometimes thought that it is allowed to contain wild cards and other kinds of
8499 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
8500 always fixed strings, just as for any other single-key lookup type.
8502 If you want to use a file to contain wild-card patterns that form part of a
8503 list, just give the filename on its own, without a search type, as described
8504 in the previous section. You could also use the &(wildlsearch)& or
8505 &(nwildlsearch)&, but there is no advantage in doing this.
8510 .section "Results of list checking" SECTlistresults
8511 The primary result of doing a list check is a truth value.
8512 In some contexts additional information is stored
8513 about the list element that matched:
8516 A &%hosts%& ACL condition
8517 will store a result in the &$host_data$& variable.
8519 A &%local_parts%& router option or &%local_parts%& ACL condition
8520 will store a result in the &$local_part_data$& variable.
8523 A &%domains%& router option or &%domains%& ACL condition
8524 will store a result in the &$domain_data$& variable.
8527 A &%senders%& router option or &%senders%& ACL condition
8528 will store a result in the &$sender_data$& variable.
8530 A &%recipients%& ACL condition
8531 will store a result in the &$recipient_data$& variable.
8534 The detail of the additional information depends on the
8535 type of match and is given below as the &*value*& information.
8540 .section "Named lists" "SECTnamedlists"
8541 .cindex "named lists"
8542 .cindex "list" "named"
8543 A list of domains, hosts, email addresses, or local parts can be given a name
8544 which is then used to refer to the list elsewhere in the configuration. This is
8545 particularly convenient if the same list is required in several different
8546 places. It also allows lists to be given meaningful names, which can improve
8547 the readability of the configuration. For example, it is conventional to define
8548 a domain list called &'local_domains'& for all the domains that are handled
8549 locally on a host, using a configuration line such as
8551 domainlist local_domains = localhost:my.dom.example
8553 Named lists are referenced by giving their name preceded by a plus sign, so,
8554 for example, a router that is intended to handle local domains would be
8555 configured with the line
8557 domains = +local_domains
8559 The first router in a configuration is often one that handles all domains
8560 except the local ones, using a configuration with a negated item like this:
8564 domains = ! +local_domains
8565 transport = remote_smtp
8568 The four kinds of named list are created by configuration lines starting with
8569 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8570 respectively. Then there follows the name that you are defining, followed by an
8571 equals sign and the list itself. For example:
8573 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8574 addresslist bad_senders = cdb;/etc/badsenders
8576 A named list may refer to other named lists:
8578 domainlist dom1 = first.example : second.example
8579 domainlist dom2 = +dom1 : third.example
8580 domainlist dom3 = fourth.example : +dom2 : fifth.example
8582 &*Warning*&: If the last item in a referenced list is a negative one, the
8583 effect may not be what you intended, because the negation does not propagate
8584 out to the higher level. For example, consider:
8586 domainlist dom1 = !a.b
8587 domainlist dom2 = +dom1 : *.b
8589 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8590 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8591 means it matches the second list as well. The effect is not the same as
8593 domainlist dom2 = !a.b : *.b
8595 where &'x.y'& does not match. It's best to avoid negation altogether in
8596 referenced lists if you can.
8598 .cindex "hiding named list values"
8599 .cindex "named lists" "hiding value of"
8600 Some named list definitions may contain sensitive data, for example, passwords for
8601 accessing databases. To stop non-admin users from using the &%-bP%& command
8602 line option to read these values, you can precede the definition with the
8603 word &"hide"&. For example:
8605 hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
8609 Named lists may have a performance advantage. When Exim is routing an
8610 address or checking an incoming message, it caches the result of tests on named
8611 lists. So, if you have a setting such as
8613 domains = +local_domains
8615 on several of your routers
8616 or in several ACL statements,
8617 the actual test is done only for the first one. However, the caching works only
8618 if there are no expansions within the list itself or any sublists that it
8619 references. In other words, caching happens only for lists that are known to be
8620 the same each time they are referenced.
8622 By default, there may be up to 16 named lists of each type. This limit can be
8623 extended by changing a compile-time variable. The use of domain and host lists
8624 is recommended for concepts such as local domains, relay domains, and relay
8625 hosts. The default configuration is set up like this.
8629 .section "Named lists compared with macros" "SECID78"
8630 .cindex "list" "named compared with macro"
8631 .cindex "macro" "compared with named list"
8632 At first sight, named lists might seem to be no different from macros in the
8633 configuration file. However, macros are just textual substitutions. If you
8636 ALIST = host1 : host2
8637 auth_advertise_hosts = !ALIST
8639 it probably won't do what you want, because that is exactly the same as
8641 auth_advertise_hosts = !host1 : host2
8643 Notice that the second host name is not negated. However, if you use a host
8646 hostlist alist = host1 : host2
8647 auth_advertise_hosts = ! +alist
8649 the negation applies to the whole list, and so that is equivalent to
8651 auth_advertise_hosts = !host1 : !host2
8655 .section "Named list caching" "SECID79"
8656 .cindex "list" "caching of named"
8657 .cindex "caching" "named lists"
8658 While processing a message, Exim caches the result of checking a named list if
8659 it is sure that the list is the same each time. In practice, this means that
8660 the cache operates only if the list contains no $ characters, which guarantees
8661 that it will not change when it is expanded. Sometimes, however, you may have
8662 an expanded list that you know will be the same each time within a given
8663 message. For example:
8665 domainlist special_domains = \
8666 ${lookup{$sender_host_address}cdb{/some/file}}
8668 This provides a list of domains that depends only on the sending host's IP
8669 address. If this domain list is referenced a number of times (for example,
8670 in several ACL lines, or in several routers) the result of the check is not
8671 cached by default, because Exim does not know that it is going to be the
8672 same list each time.
8674 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8675 cache the result anyway. For example:
8677 domainlist_cache special_domains = ${lookup{...
8679 If you do this, you should be absolutely sure that caching is going to do
8680 the right thing in all cases. When in doubt, leave it out.
8684 .section "Domain lists" "SECTdomainlist"
8685 .cindex "domain list" "patterns for"
8686 .cindex "list" "domain list"
8687 Domain lists contain patterns that are to be matched against a mail domain.
8688 The following types of item may appear in domain lists:
8691 .cindex "primary host name"
8692 .cindex "host name" "matched in domain list"
8693 .oindex "&%primary_hostname%&"
8694 .cindex "domain list" "matching primary host name"
8695 .cindex "@ in a domain list"
8696 If a pattern consists of a single @ character, it matches the local host name,
8697 as set by the &%primary_hostname%& option (or defaulted). This makes it
8698 possible to use the same configuration file on several different hosts that
8699 differ only in their names.
8701 The value for a match will be the primary host name.
8705 .cindex "@[] in a domain list"
8706 .cindex "domain list" "matching local IP interfaces"
8707 .cindex "domain literal"
8708 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8709 in square brackets (as in an email address that contains a domain literal), but
8710 only if that IP address is recognized as local for email routing purposes. The
8711 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8712 control which of a host's several IP addresses are treated as local.
8713 In today's Internet, the use of domain literals is controversial;
8714 see the &%allow_domain_literals%& main option.
8716 The value for a match will be the string &`@[]`&.
8721 .cindex "@mx_primary"
8722 .cindex "@mx_secondary"
8723 .cindex "domain list" "matching MX pointers to local host"
8724 If a pattern consists of the string &`@mx_any`& it matches any domain that
8725 has an MX record pointing to the local host or to any host that is listed in
8726 .oindex "&%hosts_treat_as_local%&"
8727 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8728 are similar, except that the first matches only when a primary MX target is the
8729 local host, and the second only when no primary MX target is the local host,
8730 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8731 preference value &-- there may of course be more than one of them.
8733 The MX lookup that takes place when matching a pattern of this type is
8734 performed with the resolver options for widening names turned off. Thus, for
8735 example, a single-component domain will &'not'& be expanded by adding the
8736 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8737 options of the &(dnslookup)& router for a discussion of domain widening.
8739 Sometimes you may want to ignore certain IP addresses when using one of these
8740 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8741 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8742 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8743 on a router). For example:
8745 domains = @mx_any/ignore=127.0.0.1
8747 This example matches any domain that has an MX record pointing to one of
8748 the local host's IP addresses other than 127.0.0.1.
8750 The list of IP addresses is in fact processed by the same code that processes
8751 host lists, so it may contain CIDR-coded network specifications and it may also
8752 contain negative items.
8754 Because the list of IP addresses is a sublist within a domain list, you have to
8755 be careful about delimiters if there is more than one address. Like any other
8756 list, the default delimiter can be changed. Thus, you might have:
8758 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8759 an.other.domain : ...
8761 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8762 involved, it is easiest to change the delimiter for the main list as well:
8764 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8765 an.other.domain ? ...
8767 The value for a match will be the list element string (starting &`@mx_`&).
8771 .cindex "asterisk" "in domain list"
8772 .cindex "domain list" "asterisk in"
8773 .cindex "domain list" "matching &""ends with""&"
8774 If a pattern starts with an asterisk, the remaining characters of the pattern
8775 are compared with the terminating characters of the domain. The use of &"*"& in
8776 domain lists differs from its use in partial matching lookups. In a domain
8777 list, the character following the asterisk need not be a dot, whereas partial
8778 matching works only in terms of dot-separated components. For example, a domain
8779 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8782 The value for a match will be the list element string (starting with the asterisk).
8783 Additionally, &$0$& will be set to the matched string
8784 and &$1$& to the variable portion which the asterisk matched.
8787 .cindex "regular expressions" "in domain list"
8788 .cindex "domain list" "matching regular expression"
8789 If a pattern starts with a circumflex character, it is treated as a regular
8790 expression, and matched against the domain using a regular expression matching
8791 function. The circumflex is treated as part of the regular expression.
8792 Email domains are case-independent, so this regular expression match is by
8793 default case-independent, but you can make it case-dependent by starting it
8794 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8795 are given in chapter &<<CHAPregexp>>&.
8797 &*Warning*&: Because domain lists are expanded before being processed, you
8798 must escape any backslash and dollar characters in the regular expression, or
8799 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8800 it is not to be expanded (unless you really do want to build a regular
8801 expression by expansion, of course).
8803 The value for a match will be the list element string (starting with the circumflex).
8804 Additionally, &$0$& will be set to the string matching the regular expression,
8805 and &$1$& (onwards) to any submatches identified by parentheses.
8810 .cindex "lookup" "in domain list"
8811 .cindex "domain list" "matching by lookup"
8812 If a pattern starts with the name of a single-key lookup type followed by a
8813 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8814 must be a filename in a suitable format for the lookup type. For example, for
8815 &"cdb;"& it must be an absolute path:
8817 domains = cdb;/etc/mail/local_domains.cdb
8819 The appropriate type of lookup is done on the file using the domain name as the
8820 key. In most cases, the value resulting from the lookup is not used; Exim is interested
8821 only in whether or not the key is present in the file. However, when a lookup
8822 is used for the &%domains%& option on a router
8823 or a &%domains%& condition in an ACL statement, the value is preserved in the
8824 &$domain_data$& variable and can be referred to in other router options or
8825 other statements in the same ACL.
8826 .cindex "tainted data" "de-tainting"
8827 The value will be untainted.
8830 &*Note*&: If the data result of the lookup (as opposed to the key)
8831 is empty, then this empty value is stored in &$domain_data$&.
8832 The option to return the key for the lookup, as the value,
8833 may be what is wanted.
8838 Any of the single-key lookup type names may be preceded by
8839 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8841 domains = partial-dbm;/partial/domains
8843 This causes partial matching logic to be invoked; a description of how this
8844 works is given in section &<<SECTpartiallookup>>&.
8847 .cindex "asterisk" "in lookup type"
8848 Any of the single-key lookup types may be followed by an asterisk. This causes
8849 a default lookup for a key consisting of a single asterisk to be done if the
8850 original lookup fails. This is not a useful feature when using a domain list to
8851 select particular domains (because any domain would match), but it might have
8852 value if the result of the lookup is being used via the &$domain_data$&
8856 If the pattern starts with the name of a query-style lookup type followed by a
8857 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8858 pattern must be an appropriate query for the lookup type, as described in
8859 chapter &<<CHAPfdlookup>>&. For example:
8861 hold_domains = mysql;select domain from holdlist \
8862 where domain = '${quote_mysql:$domain}';
8864 In most cases, the value resulting from the lookup is not used (so for an SQL query, for
8865 example, it doesn't matter what field you select). Exim is interested only in
8866 whether or not the query succeeds. However, when a lookup is used for the
8867 &%domains%& option on a router, the value is preserved in the &$domain_data$&
8868 variable and can be referred to in other options.
8869 .cindex "tainted data" "de-tainting"
8870 The value will be untainted.
8873 If the pattern starts with the name of a lookup type
8874 of either kind (single-key or query-style) it may be
8875 followed by a comma and options,
8876 The options are lookup-type specific and consist of a comma-separated list.
8877 Each item starts with a tag and and equals "=" sign.
8880 .cindex "domain list" "matching literal domain name"
8881 If none of the above cases apply, a caseless textual comparison is made
8882 between the pattern and the domain.
8884 The value for a match will be the list element string.
8885 .cindex "tainted data" "de-tainting"
8886 Note that this is commonly untainted
8887 (depending on the way the list was created).
8888 Specifically, explicit text in the configuration file in not tainted.
8889 This is a useful way of obtaining an untainted equivalent to
8890 the domain, for later operations.
8892 However if the list (including one-element lists)
8893 is created by expanding a variable containing tainted data,
8894 it is tainted and so will the match value be.
8898 Here is an example that uses several different kinds of pattern:
8900 domainlist funny_domains = \
8903 *.foundation.fict.example : \
8904 \N^[1-2]\d{3}\.fict\.example$\N : \
8905 partial-dbm;/opt/data/penguin/book : \
8906 nis;domains.byname : \
8907 nisplus;[name=$domain,status=local],domains.org_dir
8909 There are obvious processing trade-offs among the various matching modes. Using
8910 an asterisk is faster than a regular expression, and listing a few names
8911 explicitly probably is too. The use of a file or database lookup is expensive,
8912 but may be the only option if hundreds of names are required. Because the
8913 patterns are tested in order, it makes sense to put the most commonly matched
8918 .section "Host lists" "SECThostlist"
8919 .cindex "host list" "patterns in"
8920 .cindex "list" "host list"
8921 Host lists are used to control what remote hosts are allowed to do. For
8922 example, some hosts may be allowed to use the local host as a relay, and some
8923 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8924 two different ways, by name or by IP address. In a host list, some types of
8925 pattern are matched to a host name, and some are matched to an IP address.
8926 You need to be particularly careful with this when single-key lookups are
8927 involved, to ensure that the right value is being used as the key.
8930 .section "Special host list patterns" "SECID80"
8931 .cindex "empty item in hosts list"
8932 .cindex "host list" "empty string in"
8933 If a host list item is the empty string, it matches only when no remote host is
8934 involved. This is the case when a message is being received from a local
8935 process using SMTP on the standard input, that is, when a TCP/IP connection is
8938 .cindex "asterisk" "in host list"
8939 The special pattern &"*"& in a host list matches any host or no host. Neither
8940 the IP address nor the name is actually inspected.
8944 .section "Host list patterns that match by IP address" "SECThoslispatip"
8945 .cindex "host list" "matching IP addresses"
8946 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8947 the incoming address actually appears in the IPv6 host as
8948 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8949 list, it is converted into a traditional IPv4 address first. (Not all operating
8950 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8953 The following types of pattern in a host list check the remote host by
8954 inspecting its IP address:
8957 If the pattern is a plain domain name (not a regular expression, not starting
8958 with *, not a lookup of any kind), Exim calls the operating system function
8959 to find the associated IP address(es). Exim uses the newer
8960 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8961 This typically causes a forward DNS lookup of the name. The result is compared
8962 with the IP address of the subject host.
8964 If there is a temporary problem (such as a DNS timeout) with the host name
8965 lookup, a temporary error occurs. For example, if the list is being used in an
8966 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8967 temporary SMTP error code. If no IP address can be found for the host name,
8968 what happens is described in section &<<SECTbehipnot>>& below.
8971 .cindex "@ in a host list"
8972 If the pattern is &"@"&, the primary host name is substituted and used as a
8973 domain name, as just described.
8976 If the pattern is an IP address, it is matched against the IP address of the
8977 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8978 IPv6 addresses can be given in colon-separated format, but the colons have to
8979 be doubled so as not to be taken as item separators when the default list
8980 separator is used. IPv6 addresses are recognized even when Exim is compiled
8981 without IPv6 support. This means that if they appear in a host list on an
8982 IPv4-only host, Exim will not treat them as host names. They are just addresses
8983 that can never match a client host.
8986 .cindex "@[] in a host list"
8987 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8988 the local host. For example, if the local host is an IPv4 host with one
8989 interface address 10.45.23.56, these two ACL statements have the same effect:
8991 accept hosts = 127.0.0.1 : 10.45.23.56
8995 .cindex "CIDR notation"
8996 If the pattern is an IP address followed by a slash and a mask length, for
9001 , it is matched against the IP address of the subject
9002 host under the given mask. This allows an entire network of hosts to be
9003 included (or excluded) by a single item. The mask uses CIDR notation; it
9004 specifies the number of address bits that must match, starting from the most
9005 significant end of the address.
9007 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
9008 of a range of addresses. It is the number of bits in the network portion of the
9009 address. The above example specifies a 24-bit netmask, so it matches all 256
9010 addresses in the 10.11.42.0 network. An item such as
9014 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
9015 32 for an IPv4 address is the same as no mask at all; just a single address
9018 Here is another example which shows an IPv4 and an IPv6 network:
9020 recipient_unqualified_hosts = 192.168.0.0/16: \
9021 3ffe::ffff::836f::::/48
9023 The doubling of list separator characters applies only when these items
9024 appear inline in a host list. It is not required when indirecting via a file.
9027 recipient_unqualified_hosts = /opt/exim/unqualnets
9029 could make use of a file containing
9034 to have exactly the same effect as the previous example. When listing IPv6
9035 addresses inline, it is usually more convenient to use the facility for
9036 changing separator characters. This list contains the same two networks:
9038 recipient_unqualified_hosts = <; 172.16.0.0/12; \
9041 The separator is changed to semicolon by the leading &"<;"& at the start of the
9047 .section "Host list patterns for single-key lookups by host address" &&&
9048 "SECThoslispatsikey"
9049 .cindex "host list" "lookup of IP address"
9050 When a host is to be identified by a single-key lookup of its complete IP
9051 address, the pattern takes this form:
9053 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
9057 hosts_lookup = net-cdb;/hosts-by-ip.db
9059 The text form of the IP address of the subject host is used as the lookup key.
9060 IPv6 addresses are converted to an unabbreviated form, using lower case
9061 letters, with dots as separators because colon is the key terminator in
9062 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
9063 quoting the keys, but this is a facility that was added later.] The data
9064 returned by the lookup is not used.
9066 .cindex "IP address" "masking"
9067 .cindex "host list" "masked IP address"
9068 Single-key lookups can also be performed using masked IP addresses, using
9069 patterns of this form:
9071 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
9075 net24-dbm;/networks.db
9077 The IP address of the subject host is masked using <&'number'&> as the mask
9078 length. A textual string is constructed from the masked value, followed by the
9079 mask, and this is used as the lookup key. For example, if the host's IP address
9080 is 192.168.34.6, the key that is looked up for the above example is
9081 &"192.168.34.0/24"&.
9083 When an IPv6 address is converted to a string, dots are normally used instead
9084 of colons, so that keys in &(lsearch)& files need not contain colons (which
9085 terminate &(lsearch)& keys). This was implemented some time before the ability
9086 to quote keys was made available in &(lsearch)& files. However, the more
9087 recently implemented &(iplsearch)& files do require colons in IPv6 keys
9088 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
9089 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
9090 converted using colons and not dots.
9091 In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
9092 addresses are always used.
9093 The latter are converted to IPv4 addresses, in dotted-quad form.
9095 Ideally, it would be nice to tidy up this anomalous situation by changing to
9096 colons in all cases, given that quoting is now available for &(lsearch)&.
9097 However, this would be an incompatible change that might break some existing
9100 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
9101 IPv6 address) is not the same as specifying just &%net-%& without a number. In
9102 the former case the key strings include the mask value, whereas in the latter
9103 case the IP address is used on its own.
9107 .section "Host list patterns that match by host name" "SECThoslispatnam"
9108 .cindex "host" "lookup failures"
9109 .cindex "unknown host name"
9110 .cindex "host list" "matching host name"
9111 There are several types of pattern that require Exim to know the name of the
9112 remote host. These are either wildcard patterns or lookups by name. (If a
9113 complete hostname is given without any wildcarding, it is used to find an IP
9114 address to match against, as described in section &<<SECThoslispatip>>&
9117 If the remote host name is not already known when Exim encounters one of these
9118 patterns, it has to be found from the IP address.
9119 Although many sites on the Internet are conscientious about maintaining reverse
9120 DNS data for their hosts, there are also many that do not do this.
9121 Consequently, a name cannot always be found, and this may lead to unwanted
9122 effects. Take care when configuring host lists with wildcarded name patterns.
9123 Consider what will happen if a name cannot be found.
9125 Because of the problems of determining host names from IP addresses, matching
9126 against host names is not as common as matching against IP addresses.
9128 By default, in order to find a host name, Exim first does a reverse DNS lookup;
9129 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
9130 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
9131 are done can be changed by setting the &%host_lookup_order%& option. For
9132 security, once Exim has found one or more names, it looks up the IP addresses
9133 for these names and compares them with the IP address that it started with.
9134 Only those names whose IP addresses match are accepted. Any other names are
9135 discarded. If no names are left, Exim behaves as if the host name cannot be
9136 found. In the most common case there is only one name and one IP address.
9138 There are some options that control what happens if a host name cannot be
9139 found. These are described in section &<<SECTbehipnot>>& below.
9141 .cindex "host" "alias for"
9142 .cindex "alias for host"
9143 As a result of aliasing, hosts may have more than one name. When processing any
9144 of the following types of pattern, all the host's names are checked:
9147 .cindex "asterisk" "in host list"
9148 If a pattern starts with &"*"& the remainder of the item must match the end of
9149 the host name. For example, &`*.b.c`& matches all hosts whose names end in
9150 &'.b.c'&. This special simple form is provided because this is a very common
9151 requirement. Other kinds of wildcarding require the use of a regular
9154 .cindex "regular expressions" "in host list"
9155 .cindex "host list" "regular expression in"
9156 If the item starts with &"^"& it is taken to be a regular expression which is
9157 matched against the host name. Host names are case-independent, so this regular
9158 expression match is by default case-independent, but you can make it
9159 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
9160 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
9165 is a regular expression that matches either of the two hosts &'a.c.d'& or
9166 &'b.c.d'&. When a regular expression is used in a host list, you must take care
9167 that backslash and dollar characters are not misinterpreted as part of the
9168 string expansion. The simplest way to do this is to use &`\N`& to mark that
9169 part of the string as non-expandable. For example:
9171 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
9173 &*Warning*&: If you want to match a complete host name, you must include the
9174 &`$`& terminating metacharacter in the regular expression, as in the above
9175 example. Without it, a match at the start of the host name is all that is
9182 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
9183 .cindex "host" "lookup failures, permanent"
9184 While processing a host list, Exim may need to look up an IP address from a
9185 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
9186 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
9187 behaviour when it fails to find the information it is seeking is the same.
9189 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
9190 apply to temporary DNS errors, whose handling is described in the next section.
9192 .cindex "&`+include_unknown`&"
9193 .cindex "&`+ignore_unknown`&"
9194 Exim parses a host list from left to right. If it encounters a permanent
9195 lookup failure in any item in the host list before it has found a match,
9196 Exim treats it as a failure and the default behavior is as if the host
9197 does not match the list. This may not always be what you want to happen.
9198 To change Exim's behaviour, the special items &`+include_unknown`& or
9199 &`+ignore_unknown`& may appear in the list (at top level &-- they are
9200 not recognized in an indirected file).
9203 If any item that follows &`+include_unknown`& requires information that
9204 cannot found, Exim behaves as if the host does match the list. For example,
9206 host_reject_connection = +include_unknown:*.enemy.ex
9208 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
9209 any hosts whose name it cannot find.
9212 If any item that follows &`+ignore_unknown`& requires information that cannot
9213 be found, Exim ignores that item and proceeds to the rest of the list. For
9216 accept hosts = +ignore_unknown : friend.example : \
9219 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
9220 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
9221 name can be found for 192.168.4.5, it is rejected.
9224 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
9225 list. The effect of each one lasts until the next, or until the end of the
9228 .section "Mixing wildcarded host names and addresses in host lists" &&&
9230 .cindex "host list" "mixing names and addresses in"
9232 This section explains the host/ip processing logic with the same concepts
9233 as the previous section, but specifically addresses what happens when a
9234 wildcarded hostname is one of the items in the hostlist.
9237 If you have name lookups or wildcarded host names and
9238 IP addresses in the same host list, you should normally put the IP
9239 addresses first. For example, in an ACL you could have:
9241 accept hosts = 10.9.8.7 : *.friend.example
9243 The reason you normally would order it this way lies in the
9244 left-to-right way that Exim processes lists. It can test IP addresses
9245 without doing any DNS lookups, but when it reaches an item that requires
9246 a host name, it fails if it cannot find a host name to compare with the
9247 pattern. If the above list is given in the opposite order, the
9248 &%accept%& statement fails for a host whose name cannot be found, even
9249 if its IP address is 10.9.8.7.
9252 If you really do want to do the name check first, and still recognize the IP
9253 address, you can rewrite the ACL like this:
9255 accept hosts = *.friend.example
9256 accept hosts = 10.9.8.7
9258 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
9259 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
9260 &`+ignore_unknown`&, which was discussed in depth in the first example in
9265 .section "Temporary DNS errors when looking up host information" &&&
9267 .cindex "host" "lookup failures, temporary"
9268 .cindex "&`+include_defer`&"
9269 .cindex "&`+ignore_defer`&"
9270 A temporary DNS lookup failure normally causes a defer action (except when
9271 &%dns_again_means_nonexist%& converts it into a permanent error). However,
9272 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
9273 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
9274 section. These options should be used with care, probably only in non-critical
9275 host lists such as whitelists.
9279 .section "Host list patterns for single-key lookups by host name" &&&
9280 "SECThoslispatnamsk"
9281 .cindex "unknown host name"
9282 .cindex "host list" "matching host name"
9283 If a pattern is of the form
9285 <&'single-key-search-type'&>;<&'search-data'&>
9289 dbm;/host/accept/list
9291 a single-key lookup is performed, using the host name as its key. If the
9292 lookup succeeds, the host matches the item. The actual data that is looked up
9295 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
9296 keys in the file, not IP addresses. If you want to do lookups based on IP
9297 addresses, you must precede the search type with &"net-"& (see section
9298 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
9299 two items in the same list, one doing an address lookup and one doing a name
9300 lookup, both using the same file.
9304 .section "Host list patterns for query-style lookups" "SECID81"
9305 If a pattern is of the form
9307 <&'query-style-search-type'&>;<&'query'&>
9309 the query is obeyed, and if it succeeds, the host matches the item. The actual
9310 data that is looked up is not used. The variables &$sender_host_address$& and
9311 &$sender_host_name$& can be used in the query. For example:
9313 hosts_lookup = pgsql;\
9314 select ip from hostlist where ip='$sender_host_address'
9316 The value of &$sender_host_address$& for an IPv6 address contains colons. You
9317 can use the &%sg%& expansion item to change this if you need to. If you want to
9318 use masked IP addresses in database queries, you can use the &%mask%& expansion
9321 If the query contains a reference to &$sender_host_name$&, Exim automatically
9322 looks up the host name if it has not already done so. (See section
9323 &<<SECThoslispatnam>>& for comments on finding host names.)
9325 Historical note: prior to release 4.30, Exim would always attempt to find a
9326 host name before running the query, unless the search type was preceded by
9327 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
9328 still recognized for query-style lookups, but its presence or absence has no
9329 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
9330 See section &<<SECThoslispatsikey>>&.)
9336 .section "Address lists" "SECTaddresslist"
9337 .cindex "list" "address list"
9338 .cindex "address list" "empty item"
9339 .cindex "address list" "patterns"
9340 Address lists contain patterns that are matched against mail addresses. There
9341 is one special case to be considered: the sender address of a bounce message is
9342 always empty. You can test for this by providing an empty item in an address
9343 list. For example, you can set up a router to process bounce messages by
9344 using this option setting:
9348 The presence of the colon creates an empty item. If you do not provide any
9349 data, the list is empty and matches nothing. The empty sender can also be
9350 detected by a regular expression that matches an empty string,
9351 and by a query-style lookup that succeeds when &$sender_address$& is empty.
9353 Non-empty items in an address list can be straightforward email addresses. For
9356 senders = jbc@askone.example : hs@anacreon.example
9358 A certain amount of wildcarding is permitted. If a pattern contains an @
9359 character, but is not a regular expression and does not begin with a
9360 semicolon-terminated lookup type (described below), the local part of the
9361 subject address is compared with the local part of the pattern, which may start
9362 with an asterisk. If the local parts match, the domain is checked in exactly
9363 the same way as for a pattern in a domain list. For example, the domain can be
9364 wildcarded, refer to a named list, or be a lookup:
9366 deny senders = *@*.spamming.site:\
9367 *@+hostile_domains:\
9368 bozo@partial-lsearch;/list/of/dodgy/sites:\
9369 *@dbm;/bad/domains.db
9371 .cindex "local part" "starting with !"
9372 .cindex "address list" "local part starting with !"
9373 If a local part that begins with an exclamation mark is required, it has to be
9374 specified using a regular expression, because otherwise the exclamation mark is
9375 treated as a sign of negation, as is standard in lists.
9377 If a non-empty pattern that is not a regular expression or a lookup does not
9378 contain an @ character, it is matched against the domain part of the subject
9379 address. The only two formats that are recognized this way are a literal
9380 domain, or a domain pattern that starts with *. In both these cases, the effect
9381 is the same as if &`*@`& preceded the pattern. For example:
9383 deny senders = enemy.domain : *.enemy.domain
9386 The following kinds of more complicated address list pattern can match any
9387 address, including the empty address that is characteristic of bounce message
9391 .cindex "regular expressions" "in address list"
9392 .cindex "address list" "regular expression in"
9393 If (after expansion) a pattern starts with &"^"&, a regular expression match is
9394 done against the complete address, with the pattern as the regular expression.
9395 You must take care that backslash and dollar characters are not misinterpreted
9396 as part of the string expansion. The simplest way to do this is to use &`\N`&
9397 to mark that part of the string as non-expandable. For example:
9399 deny senders = \N^.*this.*@example\.com$\N : \
9400 \N^\d{8}.+@spamhaus.example$\N : ...
9402 The &`\N`& sequences are removed by the expansion, so these items do indeed
9403 start with &"^"& by the time they are being interpreted as address patterns.
9406 .cindex "address list" "lookup for complete address"
9407 Complete addresses can be looked up by using a pattern that starts with a
9408 lookup type terminated by a semicolon, followed by the data for the lookup. For
9411 deny senders = cdb;/etc/blocked.senders : \
9412 mysql;select address from blocked where \
9413 address='${quote_mysql:$sender_address}'
9415 Both query-style and single-key lookup types can be used. For a single-key
9416 lookup type, Exim uses the complete address as the key. However, empty keys are
9417 not supported for single-key lookups, so a match against the empty address
9418 always fails. This restriction does not apply to query-style lookups.
9420 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
9421 cannot be used, and is ignored if specified, with an entry being written to the
9423 .cindex "*@ with single-key lookup"
9424 However, you can configure lookup defaults, as described in section
9425 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
9426 default. For example, with this lookup:
9428 accept senders = lsearch*@;/some/file
9430 the file could contains lines like this:
9432 user1@domain1.example
9435 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
9438 nimrod@jaeger.example
9442 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
9443 would mean that every address matches, thus rendering the test useless.
9445 &*Warning 2*&: Do not confuse these two kinds of item:
9447 deny recipients = dbm*@;/some/file
9448 deny recipients = *@dbm;/some/file
9450 The first does a whole address lookup, with defaulting, as just described,
9451 because it starts with a lookup type. The second matches the local part and
9452 domain independently, as described in a bullet point below.
9456 The following kinds of address list pattern can match only non-empty addresses.
9457 If the subject address is empty, a match against any of these pattern types
9462 .cindex "@@ with single-key lookup"
9463 .cindex "address list" "@@ lookup type"
9464 .cindex "address list" "split local part and domain"
9465 If a pattern starts with &"@@"& followed by a single-key lookup item
9466 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
9467 split into a local part and a domain. The domain is looked up in the file. If
9468 it is not found, there is no match. If it is found, the data that is looked up
9469 from the file is treated as a colon-separated list of local part patterns, each
9470 of which is matched against the subject local part in turn.
9472 .cindex "asterisk" "in address list"
9473 The lookup may be a partial one, and/or one involving a search for a default
9474 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
9475 patterns that are looked up can be regular expressions or begin with &"*"&, or
9476 even be further lookups. They may also be independently negated. For example,
9479 deny senders = @@dbm;/etc/reject-by-domain
9481 the data from which the DBM file is built could contain lines like
9483 baddomain.com: !postmaster : *
9485 to reject all senders except &%postmaster%& from that domain.
9487 .cindex "local part" "starting with !"
9488 If a local part that actually begins with an exclamation mark is required, it
9489 has to be specified using a regular expression. In &(lsearch)& files, an entry
9490 may be split over several lines by indenting the second and subsequent lines,
9491 but the separating colon must still be included at line breaks. White space
9492 surrounding the colons is ignored. For example:
9494 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
9497 As in all colon-separated lists in Exim, a colon can be included in an item by
9500 If the last item in the list starts with a right angle-bracket, the remainder
9501 of the item is taken as a new key to look up in order to obtain a continuation
9502 list of local parts. The new key can be any sequence of characters. Thus one
9503 might have entries like
9505 aol.com: spammer1 : spammer 2 : >*
9506 xyz.com: spammer3 : >*
9509 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
9510 local parts for all domains, in addition to the specific local parts listed for
9511 each domain. Of course, using this feature costs another lookup each time a
9512 chain is followed, but the effort needed to maintain the data is reduced.
9514 .cindex "loop" "in lookups"
9515 It is possible to construct loops using this facility, and in order to catch
9516 them, the chains may be no more than fifty items long.
9519 The @@<&'lookup'&> style of item can also be used with a query-style
9520 lookup, but in this case, the chaining facility is not available. The lookup
9521 can only return a single list of local parts.
9524 &*Warning*&: There is an important difference between the address list items
9525 in these two examples:
9528 senders = *@+my_list
9530 In the first one, &`my_list`& is a named address list, whereas in the second
9531 example it is a named domain list.
9536 .section "Case of letters in address lists" "SECTcasletadd"
9537 .cindex "case of local parts"
9538 .cindex "address list" "case forcing"
9539 .cindex "case forcing in address lists"
9540 Domains in email addresses are always handled caselessly, but for local parts
9541 case may be significant on some systems (see &%caseful_local_part%& for how
9542 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
9543 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
9544 blocking lists should be done in a case-independent manner. Since most address
9545 lists in Exim are used for this kind of control, Exim attempts to do this by
9548 The domain portion of an address is always lowercased before matching it to an
9549 address list. The local part is lowercased by default, and any string
9550 comparisons that take place are done caselessly. This means that the data in
9551 the address list itself, in files included as plain filenames, and in any file
9552 that is looked up using the &"@@"& mechanism, can be in any case. However, the
9553 keys in files that are looked up by a search type other than &(lsearch)& (which
9554 works caselessly) must be in lower case, because these lookups are not
9557 .cindex "&`+caseful`&"
9558 To allow for the possibility of caseful address list matching, if an item in
9559 an address list is the string &"+caseful"&, the original case of the local
9560 part is restored for any comparisons that follow, and string comparisons are no
9561 longer case-independent. This does not affect the domain, which remains in
9562 lower case. However, although independent matches on the domain alone are still
9563 performed caselessly, regular expressions that match against an entire address
9564 become case-sensitive after &"+caseful"& has been seen.
9568 .section "Local part lists" "SECTlocparlis"
9569 .cindex "list" "local part list"
9570 .cindex "local part" "list"
9571 These behave in the same way as domain and host lists, with the following
9574 Case-sensitivity in local part lists is handled in the same way as for address
9575 lists, as just described. The &"+caseful"& item can be used if required. In a
9576 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
9577 set false, the subject is lowercased and the matching is initially
9578 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
9579 matching in the local part list, but not elsewhere in the router. If
9580 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
9581 option is case-sensitive from the start.
9583 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
9584 comments are handled in the same way as address lists &-- they are recognized
9585 only if the # is preceded by white space or the start of the line.
9586 Otherwise, local part lists are matched in the same way as domain lists, except
9587 that the special items that refer to the local host (&`@`&, &`@[]`&,
9588 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
9589 Refer to section &<<SECTdomainlist>>& for details of the other available item
9591 .ecindex IIDdohoadli
9596 . ////////////////////////////////////////////////////////////////////////////
9597 . ////////////////////////////////////////////////////////////////////////////
9599 .chapter "String expansions" "CHAPexpand"
9600 .scindex IIDstrexp "expansion" "of strings"
9601 Many strings in Exim's runtime configuration are expanded before use. Some of
9602 them are expanded every time they are used; others are expanded only once.
9604 When a string is being expanded it is copied verbatim from left to right except
9605 .cindex expansion "string concatenation"
9606 when a dollar or backslash character is encountered. A dollar specifies the
9607 start of a portion of the string that is interpreted and replaced as described
9608 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
9609 escape character, as described in the following section.
9611 Whether a string is expanded depends upon the context. Usually this is solely
9612 dependent upon the option for which a value is sought; in this documentation,
9613 options for which string expansion is performed are marked with † after
9614 the data type. ACL rules always expand strings. A couple of expansion
9615 conditions do not expand some of the brace-delimited branches, for security
9617 .cindex "tainted data" expansion
9618 .cindex "tainted data" definition
9619 .cindex expansion "tainted data"
9620 and expansion of data deriving from the sender (&"tainted data"&)
9622 is not permitted (including acessing a file using a tainted name).
9623 The main config option &%allow_insecure_tainted_data%& can be used as
9624 mitigation during uprades to more secure configurations.
9628 Common ways of obtaining untainted equivalents of variables with
9630 .cindex "tainted data" "de-tainting"
9631 come down to using the tainted value as a lookup key in a trusted database.
9632 This database could be the filesystem structure,
9633 or the password file,
9634 or accessed via a DBMS.
9635 Specific methods are indexed under &"de-tainting"&.
9640 .section "Literal text in expanded strings" "SECTlittext"
9641 .cindex "expansion" "including literal text"
9642 An uninterpreted dollar can be included in an expanded string by putting a
9643 backslash in front of it. A backslash can be used to prevent any special
9644 character being treated specially in an expansion, including backslash itself.
9645 If the string appears in quotes in the configuration file, two backslashes are
9646 required because the quotes themselves cause interpretation of backslashes when
9647 the string is read in (see section &<<SECTstrings>>&).
9649 .cindex "expansion" "non-expandable substrings"
9650 A portion of the string can specified as non-expandable by placing it between
9651 two occurrences of &`\N`&. This is particularly useful for protecting regular
9652 expressions, which often contain backslashes and dollar signs. For example:
9654 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
9656 On encountering the first &`\N`&, the expander copies subsequent characters
9657 without interpretation until it reaches the next &`\N`& or the end of the
9662 .section "Character escape sequences in expanded strings" "SECID82"
9663 .cindex "expansion" "escape sequences"
9664 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9665 expanded string is recognized as an escape sequence for the character newline,
9666 carriage return, or tab, respectively. A backslash followed by up to three
9667 octal digits is recognized as an octal encoding for a single character, and a
9668 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9671 These escape sequences are also recognized in quoted strings when they are read
9672 in. Their interpretation in expansions as well is useful for unquoted strings,
9673 and for other cases such as looked-up strings that are then expanded.
9676 .section "Testing string expansions" "SECID83"
9677 .cindex "expansion" "testing"
9678 .cindex "testing" "string expansion"
9680 Many expansions can be tested by calling Exim with the &%-be%& option. This
9681 takes the command arguments, or lines from the standard input if there are no
9682 arguments, runs them through the string expansion code, and writes the results
9683 to the standard output. Variables based on configuration values are set up, but
9684 since no message is being processed, variables such as &$local_part$& have no
9685 value. Nevertheless the &%-be%& option can be useful for checking out file and
9686 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9689 Exim gives up its root privilege when it is called with the &%-be%& option, and
9690 instead runs under the uid and gid it was called with, to prevent users from
9691 using &%-be%& for reading files to which they do not have access.
9694 If you want to test expansions that include variables whose values are taken
9695 from a message, there are two other options that can be used. The &%-bem%&
9696 option is like &%-be%& except that it is followed by a filename. The file is
9697 read as a message before doing the test expansions. For example:
9699 exim -bem /tmp/test.message '$h_subject:'
9701 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9702 Exim message identifier. For example:
9704 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9706 This loads the message from Exim's spool before doing the test expansions, and
9707 is therefore restricted to admin users.
9710 .section "Forced expansion failure" "SECTforexpfai"
9711 .cindex "expansion" "forced failure"
9712 A number of expansions that are described in the following section have
9713 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9714 (which are sometimes called &"curly brackets"&). Which of the two strings is
9715 used depends on some condition that is evaluated as part of the expansion. If,
9716 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9717 the entire string expansion fails in a way that can be detected by the code
9718 that requested the expansion. This is called &"forced expansion failure"&, and
9719 its consequences depend on the circumstances. In some cases it is no different
9720 from any other expansion failure, but in others a different action may be
9721 taken. Such variations are mentioned in the documentation of the option that is
9727 .section "Expansion items" "SECTexpansionitems"
9728 The following items are recognized in expanded strings. White space may be used
9729 between sub-items that are keywords or substrings enclosed in braces inside an
9730 outer set of braces, to improve readability. &*Warning*&: Within braces,
9731 white space is significant.
9734 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9735 .cindex "expansion" "variables"
9736 Substitute the contents of the named variable, for example:
9741 The second form can be used to separate the name from subsequent alphanumeric
9742 characters. This form (using braces) is available only for variables; it does
9743 &'not'& apply to message headers. The names of the variables are given in
9744 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9745 given, the expansion fails.
9747 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9748 .cindex "expansion" "operators"
9749 The string is first itself expanded, and then the operation specified by
9750 <&'op'&> is applied to it. For example:
9754 The string starts with the first character after the colon, which may be
9755 leading white space. A list of operators is given in section &<<SECTexpop>>&
9756 below. The operator notation is used for simple expansion items that have just
9757 one argument, because it reduces the number of braces and therefore makes the
9758 string easier to understand.
9760 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9761 This item inserts &"basic"& header lines. It is described with the &%header%&
9762 expansion item below.
9765 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9766 .cindex "expansion" "calling an acl"
9767 .cindex "&%acl%&" "call from expansion"
9768 The name and zero to nine argument strings are first expanded separately. The expanded
9769 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9770 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9771 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9772 and may use the variables; if another acl expansion is used the values
9773 are restored after it returns. If the ACL sets
9774 a value using a "message =" modifier and returns accept or deny, the value becomes
9775 the result of the expansion.
9776 If no message is set and the ACL returns accept or deny
9777 the expansion result is an empty string.
9778 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9781 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
9782 .cindex authentication "results header"
9783 .chindex Authentication-Results:
9784 .cindex authentication "expansion item"
9785 This item returns a string suitable for insertion as an
9786 &'Authentication-Results:'&
9788 The given <&'authserv-id'&> is included in the result; typically this
9789 will be a domain name identifying the system performing the authentications.
9790 Methods that might be present in the result include:
9799 Example use (as an ACL modifier):
9801 add_header = :at_start:${authresults {$primary_hostname}}
9803 This is safe even if no authentication results are available.
9806 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9807 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9808 .cindex "expansion" "extracting certificate fields"
9809 .cindex "&%certextract%&" "certificate fields"
9810 .cindex "certificate" "extracting fields"
9811 The <&'certificate'&> must be a variable of type certificate.
9812 The field name is expanded and used to retrieve the relevant field from
9813 the certificate. Supported fields are:
9817 &`subject `& RFC4514 DN
9818 &`issuer `& RFC4514 DN
9823 &`subj_altname `& tagged list
9827 If the field is found,
9828 <&'string2'&> is expanded, and replaces the whole item;
9829 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9830 variable &$value$& contains the value that has been extracted. Afterwards, it
9831 is restored to any previous value it might have had.
9833 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9834 key is not found. If {<&'string2'&>} is also omitted, the value that was
9837 Some field names take optional modifiers, appended and separated by commas.
9839 The field selectors marked as "RFC4514" above
9840 output a Distinguished Name string which is
9842 parseable by Exim as a comma-separated tagged list
9843 (the exceptions being elements containing commas).
9844 RDN elements of a single type may be selected by
9845 a modifier of the type label; if so the expansion
9846 result is a list (newline-separated by default).
9847 The separator may be changed by another modifier of
9848 a right angle-bracket followed immediately by the new separator.
9849 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9851 The field selectors marked as "time" above
9852 take an optional modifier of "int"
9853 for which the result is the number of seconds since epoch.
9854 Otherwise the result is a human-readable string
9855 in the timezone selected by the main "timezone" option.
9857 The field selectors marked as "list" above return a list,
9858 newline-separated by default,
9859 (embedded separator characters in elements are doubled).
9860 The separator may be changed by a modifier of
9861 a right angle-bracket followed immediately by the new separator.
9863 The field selectors marked as "tagged" above
9864 prefix each list element with a type string and an equals sign.
9865 Elements of only one type may be selected by a modifier
9866 which is one of "dns", "uri" or "mail";
9867 if so the element tags are omitted.
9869 If not otherwise noted field values are presented in human-readable form.
9871 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9872 {*&<&'arg'&>&*}...}*&"
9874 This expansion dynamically loads and then calls a locally-written C function.
9875 This functionality is available only if Exim is compiled with
9879 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9880 object so that it doesn't reload the same object file in the same Exim process
9881 (but of course Exim does start new processes frequently).
9883 There may be from zero to eight arguments to the function.
9886 a local function that is to be called in this way,
9887 first &_DLFUNC_IMPL_& should be defined,
9888 and second &_local_scan.h_& should be included.
9889 The Exim variables and functions that are defined by that API
9890 are also available for dynamically loaded functions. The function itself
9891 must have the following type:
9893 int dlfunction(uschar **yield, int argc, uschar *argv[])
9895 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9896 function should return one of the following values:
9898 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9899 into the expanded string that is being built.
9901 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9902 from &'yield'&, if it is set.
9904 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9905 taken from &'yield'& if it is set.
9907 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9909 When compiling a function that is to be used in this way with gcc,
9910 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9911 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9914 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9915 .cindex "expansion" "extracting value from environment"
9916 .cindex "environment" "values from"
9917 The key is first expanded separately, and leading and trailing white space
9919 This is then searched for as a name in the environment.
9920 If a variable is found then its value is placed in &$value$&
9921 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9923 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9924 appear, for example:
9926 ${env{USER}{$value} fail }
9928 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9929 {<&'string1'&>} must be present for &"fail"& to be recognized.
9931 If {<&'string2'&>} is omitted an empty string is substituted on
9933 If {<&'string1'&>} is omitted the search result is substituted on
9936 The environment is adjusted by the &%keep_environment%& and
9937 &%add_environment%& main section options.
9940 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9941 {*&<&'string3'&>&*}}*&"
9942 .cindex "expansion" "extracting substrings by key"
9943 .cindex "&%extract%&" "substrings by key"
9944 The key and <&'string1'&> are first expanded separately. Leading and trailing
9945 white space is removed from the key (but not from any of the strings). The key
9946 must not be empty and must not consist entirely of digits.
9947 The expanded <&'string1'&> must be of the form:
9949 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9952 where the equals signs and spaces (but not both) are optional. If any of the
9953 values contain white space, they must be enclosed in double quotes, and any
9954 values that are enclosed in double quotes are subject to escape processing as
9955 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9956 for the value that corresponds to the key. The search is case-insensitive. If
9957 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9958 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9959 variable &$value$& contains the value that has been extracted. Afterwards, it
9960 is restored to any previous value it might have had.
9962 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9963 key is not found. If {<&'string2'&>} is also omitted, the value that was
9964 extracted is used. Thus, for example, these two expansions are identical, and
9967 ${extract{gid}{uid=1984 gid=2001}}
9968 ${extract{gid}{uid=1984 gid=2001}{$value}}
9970 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9971 appear, for example:
9973 ${extract{Z}{A=... B=...}{$value} fail }
9975 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9976 {<&'string2'&>} must be present for &"fail"& to be recognized.
9978 .vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9979 {*&<&'string3'&>&*}}*&" &&&
9980 "&*${extract jsons{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9981 {*&<&'string3'&>&*}}*&"
9982 .cindex "expansion" "extracting from JSON object"
9983 .cindex JSON expansions
9984 The key and <&'string1'&> are first expanded separately. Leading and trailing
9985 white space is removed from the key (but not from any of the strings). The key
9986 must not be empty and must not consist entirely of digits.
9987 The expanded <&'string1'&> must be of the form:
9989 { <&'"key1"'&> : <&'value1'&> , <&'"key2"'&> , <&'value2'&> ... }
9992 The braces, commas and colons, and the quoting of the member name are required;
9993 the spaces are optional.
9994 Matching of the key against the member names is done case-sensitively.
9995 For the &"json"& variant,
9996 if a returned value is a JSON string, it retains its leading and
9998 For the &"jsons"& variant, which is intended for use with JSON strings, the
9999 leading and trailing quotes are removed from the returned value.
10000 . XXX should be a UTF-8 compare
10002 The results of matching are handled as above.
10005 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
10006 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10007 .cindex "expansion" "extracting substrings by number"
10008 .cindex "&%extract%&" "substrings by number"
10009 The <&'number'&> argument must consist entirely of decimal digits,
10010 apart from leading and trailing white space, which is ignored.
10011 This is what distinguishes this form of &%extract%& from the previous kind. It
10012 behaves in the same way, except that, instead of extracting a named field, it
10013 extracts from <&'string1'&> the field whose number is given as the first
10014 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
10015 <&'string3'&> as before.
10017 The fields in the string are separated by any one of the characters in the
10018 separator string. These may include space or tab characters.
10019 The first field is numbered one. If the number is negative, the fields are
10020 counted from the end of the string, with the rightmost one numbered -1. If the
10021 number given is zero, the entire string is returned. If the modulus of the
10022 number is greater than the number of fields in the string, the result is the
10023 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
10024 provided. For example:
10026 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
10030 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
10032 yields &"99"&. Two successive separators mean that the field between them is
10033 empty (for example, the fifth field above).
10036 .vitem "&*${extract json {*&<&'number'&>&*}}&&&
10037 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" &&&
10038 "&*${extract jsons{*&<&'number'&>&*}}&&&
10039 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10040 .cindex "expansion" "extracting from JSON array"
10041 .cindex JSON expansions
10042 The <&'number'&> argument must consist entirely of decimal digits,
10043 apart from leading and trailing white space, which is ignored.
10045 Field selection and result handling is as above;
10046 there is no choice of field separator.
10047 For the &"json"& variant,
10048 if a returned value is a JSON string, it retains its leading and
10050 For the &"jsons"& variant, which is intended for use with JSON strings, the
10051 leading and trailing quotes are removed from the returned value.
10054 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
10055 .cindex "list" "selecting by condition"
10056 .cindex "expansion" "selecting from list by condition"
10058 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10059 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10061 in this list, its value is place in &$item$&, and then the condition is
10062 evaluated. If the condition is true, &$item$& is added to the output as an
10063 item in a new list; if the condition is false, the item is discarded. The
10064 separator used for the output list is the same as the one used for the
10065 input, but a separator setting is not included in the output. For example:
10067 ${filter{a:b:c}{!eq{$item}{b}}}
10069 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
10070 to what it was before. See also the &%map%& and &%reduce%& expansion items.
10073 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10074 .cindex "hash function" "textual"
10075 .cindex "expansion" "textual hash"
10076 This is a textual hashing function, and was the first to be implemented in
10077 early versions of Exim. In current releases, there are other hashing functions
10078 (numeric, MD5, and SHA-1), which are described below.
10080 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
10081 <&'n'&>. If you are using fixed values for these numbers, that is, if
10082 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
10083 use the simpler operator notation that avoids some of the braces:
10085 ${hash_<n>_<m>:<string>}
10087 The second number is optional (in both notations). If <&'n'&> is greater than
10088 or equal to the length of the string, the expansion item returns the string.
10089 Otherwise it computes a new string of length <&'n'&> by applying a hashing
10090 function to the string. The new string consists of characters taken from the
10091 first <&'m'&> characters of the string
10093 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
10095 If <&'m'&> is not present the value 26 is used, so that only lower case
10096 letters appear. For example:
10098 &`$hash{3}{monty}} `& yields &`jmg`&
10099 &`$hash{5}{monty}} `& yields &`monty`&
10100 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
10103 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
10104 &*$h_*&<&'header&~name'&>&*:*&" &&&
10105 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10106 &*$bh_*&<&'header&~name'&>&*:*&" &&&
10107 "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10108 &*$lh_*&<&'header&~name'&>&*:*&" &&&
10109 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10110 &*$rh_*&<&'header&~name'&>&*:*&"
10111 .cindex "expansion" "header insertion"
10112 .vindex "&$header_$&"
10113 .vindex "&$bheader_$&"
10114 .vindex "&$lheader_$&"
10115 .vindex "&$rheader_$&"
10116 .cindex "header lines" "in expansion strings"
10117 .cindex "header lines" "character sets"
10118 .cindex "header lines" "decoding"
10119 Substitute the contents of the named message header line, for example
10123 The newline that terminates a header line is not included in the expansion, but
10124 internal newlines (caused by splitting the header line over several physical
10125 lines) may be present.
10127 The difference between the four pairs of expansions is in the way
10128 the data in the header line is interpreted.
10131 .cindex "white space" "in header lines"
10132 &%rheader%& gives the original &"raw"& content of the header line, with no
10133 processing at all, and without the removal of leading and trailing white space.
10136 .cindex "list" "of header lines"
10137 &%lheader%& gives a colon-separated list, one element per header when there
10138 are multiple headers with a given name.
10139 Any embedded colon characters within an element are doubled, so normal Exim
10140 list-processing facilities can be used.
10141 The terminating newline of each element is removed; in other respects
10142 the content is &"raw"&.
10145 .cindex "base64 encoding" "in header lines"
10146 &%bheader%& removes leading and trailing white space, and then decodes base64
10147 or quoted-printable MIME &"words"& within the header text, but does no
10148 character set translation. If decoding of what looks superficially like a MIME
10149 &"word"& fails, the raw string is returned. If decoding
10150 .cindex "binary zero" "in header line"
10151 produces a binary zero character, it is replaced by a question mark &-- this is
10152 what Exim does for binary zeros that are actually received in header lines.
10155 &%header%& tries to translate the string as decoded by &%bheader%& to a
10156 standard character set. This is an attempt to produce the same string as would
10157 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
10158 returned. Translation is attempted only on operating systems that support the
10159 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
10160 a system Makefile or in &_Local/Makefile_&.
10163 In a filter file, the target character set for &%header%& can be specified by a
10164 command of the following form:
10166 headers charset "UTF-8"
10168 This command affects all references to &$h_$& (or &$header_$&) expansions in
10169 subsequently obeyed filter commands. In the absence of this command, the target
10170 character set in a filter is taken from the setting of the &%headers_charset%&
10171 option in the runtime configuration. The value of this option defaults to the
10172 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
10175 Header names follow the syntax of RFC 2822, which states that they may contain
10176 any printing characters except space and colon. Consequently, curly brackets
10177 &'do not'& terminate header names, and should not be used to enclose them as
10178 if they were variables. Attempting to do so causes a syntax error.
10180 Only header lines that are common to all copies of a message are visible to
10181 this mechanism. These are the original header lines that are received with the
10182 message, and any that are added by an ACL statement or by a system
10183 filter. Header lines that are added to a particular copy of a message by a
10184 router or transport are not accessible.
10186 For incoming SMTP messages, no header lines are visible in
10187 ACLs that are obeyed before the data phase completes,
10188 because the header structure is not set up until the message is received.
10189 They are visible in DKIM, PRDR and DATA ACLs.
10190 Header lines that are added in a RCPT ACL (for example)
10191 are saved until the message's incoming header lines are available, at which
10192 point they are added.
10193 When any of the above ACLs are
10194 running, however, header lines added by earlier ACLs are visible.
10196 Upper case and lower case letters are synonymous in header names. If the
10197 following character is white space, the terminating colon may be omitted, but
10198 this is not recommended, because you may then forget it when it is needed. When
10199 white space terminates the header name, this white space is included in the
10200 expanded string. If the message does not contain the given header, the
10201 expansion item is replaced by an empty string. (See the &%def%& condition in
10202 section &<<SECTexpcond>>& for a means of testing for the existence of a
10205 If there is more than one header with the same name, they are all concatenated
10206 to form the substitution string, up to a maximum length of 64K. Unless
10207 &%rheader%& is being used, leading and trailing white space is removed from
10208 each header before concatenation, and a completely empty header is ignored. A
10209 newline character is then inserted between non-empty headers, but there is no
10210 newline at the very end. For the &%header%& and &%bheader%& expansion, for
10211 those headers that contain lists of addresses, a comma is also inserted at the
10212 junctions between headers. This does not happen for the &%rheader%& expansion.
10214 .cindex "tainted data" "message headers"
10215 When the headers are from an incoming message,
10216 the result of expanding any of these variables is tainted.
10219 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
10220 .cindex "expansion" "hmac hashing"
10222 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
10223 shared secret and some text into a message authentication code, as specified in
10224 RFC 2104. This differs from &`${md5:secret_text...}`& or
10225 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
10226 cryptographic hash, allowing for authentication that is not possible with MD5
10227 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
10228 present. For example:
10230 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
10232 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
10235 dd97e3ba5d1a61b5006108f8c8252953
10237 As an example of how this might be used, you might put in the main part of
10238 an Exim configuration:
10240 SPAMSCAN_SECRET=cohgheeLei2thahw
10242 In a router or a transport you could then have:
10245 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
10246 ${hmac{md5}{SPAMSCAN_SECRET}\
10247 {${primary_hostname},${message_exim_id},$h_message-id:}}
10249 Then given a message, you can check where it was scanned by looking at the
10250 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
10251 this header line is authentic by recomputing the authentication code from the
10252 host name, message ID and the &'Message-id:'& header line. This can be done
10253 using Exim's &%-be%& option, or by other means, for example, by using the
10254 &'hmac_md5_hex()'& function in Perl.
10257 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10258 .cindex "expansion" "conditional"
10259 .cindex "&%if%&, expansion item"
10260 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
10261 item; otherwise <&'string2'&> is used. The available conditions are described
10262 in section &<<SECTexpcond>>& below. For example:
10264 ${if eq {$local_part}{postmaster} {yes}{no} }
10266 The second string need not be present; if it is not and the condition is not
10267 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
10268 be present instead of the second string (without any curly brackets). In this
10269 case, the expansion is forced to fail if the condition is not true (see section
10270 &<<SECTforexpfai>>&).
10272 If both strings are omitted, the result is the string &`true`& if the condition
10273 is true, and the empty string if the condition is false. This makes it less
10274 cumbersome to write custom ACL and router conditions. For example, instead of
10276 condition = ${if >{$acl_m4}{3}{true}{false}}
10280 condition = ${if >{$acl_m4}{3}}
10285 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
10286 .cindex expansion "imap folder"
10287 .cindex "&%imapfolder%& expansion item"
10288 This item converts a (possibly multilevel, or with non-ASCII characters)
10289 folder specification to a Maildir name for filesystem use.
10290 For information on internationalisation support see &<<SECTi18nMDA>>&.
10294 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10295 .cindex "expansion" "string truncation"
10296 .cindex "&%length%& expansion item"
10297 The &%length%& item is used to extract the initial portion of a string. Both
10298 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
10299 you are using a fixed value for the number, that is, if <&'string1'&> does not
10300 change when expanded, you can use the simpler operator notation that avoids
10301 some of the braces:
10303 ${length_<n>:<string>}
10305 The result of this item is either the first <&'n'&> bytes or the whole
10306 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
10307 &%strlen%&, which gives the length of a string.
10308 All measurement is done in bytes and is not UTF-8 aware.
10311 .vitem "&*${listextract{*&<&'number'&>&*}&&&
10312 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10313 .cindex "expansion" "extracting list elements by number"
10314 .cindex "&%listextract%&" "extract list elements by number"
10315 .cindex "list" "extracting elements by number"
10316 The <&'number'&> argument must consist entirely of decimal digits,
10317 apart from an optional leading minus,
10318 and leading and trailing white space (which is ignored).
10320 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10321 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10323 The first field of the list is numbered one.
10324 If the number is negative, the fields are
10325 counted from the end of the list, with the rightmost one numbered -1.
10326 The numbered element of the list is extracted and placed in &$value$&,
10327 then <&'string2'&> is expanded as the result.
10329 If the modulus of the
10330 number is zero or greater than the number of fields in the string,
10331 the result is the expansion of <&'string3'&>.
10335 ${listextract{2}{x:42:99}}
10339 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
10341 yields &"result: 42"&.
10343 If {<&'string3'&>} is omitted, an empty string is used for string3.
10344 If {<&'string2'&>} is also omitted, the value that was
10346 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
10350 .vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*&
10351 .cindex quoting "for list"
10352 .cindex list quoting
10353 This item doubles any occurrence of the separator character
10354 in the given string.
10355 An empty string is replaced with a single space.
10356 This converts the string into a safe form for use as a list element,
10357 in a list using the given separator.
10361 .vitem "&*${lookup&~{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
10362 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" &&&
10363 "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
10364 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
10365 .cindex "expansion" "lookup in"
10366 .cindex "file" "lookups"
10367 .cindex "lookup" "in expanded string"
10368 The two forms of lookup item specify data lookups in files and databases, as
10369 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
10370 lookups, and the second is used for query-style lookups. The <&'key'&>,
10371 <&'file'&>, and <&'query'&> strings are expanded before use.
10373 If there is any white space in a lookup item which is part of a filter command,
10374 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
10375 other place where white space is significant, the lookup item must be enclosed
10376 in double quotes. The use of data lookups in users' filter files may be locked
10377 out by the system administrator.
10379 .vindex "&$value$&"
10380 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
10381 During its expansion, the variable &$value$& contains the data returned by the
10382 lookup. Afterwards it reverts to the value it had previously (at the outer
10383 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
10384 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
10385 string on failure. If <&'string2'&> is provided, it can itself be a nested
10386 lookup, thus providing a mechanism for looking up a default value when the
10387 original lookup fails.
10389 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
10390 data for the outer lookup while the parameters of the second lookup are
10391 expanded, and also while <&'string2'&> of the second lookup is expanded, should
10392 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
10393 appear, and in this case, if the lookup fails, the entire expansion is forced
10394 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
10395 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
10396 successful lookup, and nothing in the case of failure.
10398 For single-key lookups, the string &"partial"& is permitted to precede the
10399 search type in order to do partial matching, and * or *@ may follow a search
10400 type to request default lookups if the key does not match (see sections
10401 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
10403 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
10404 If a partial search is used, the variables &$1$& and &$2$& contain the wild
10405 and non-wild parts of the key during the expansion of the replacement text.
10406 They return to their previous values at the end of the lookup item.
10408 This example looks up the postmaster alias in the conventional alias file:
10410 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
10412 This example uses NIS+ to look up the full name of the user corresponding to
10413 the local part of an address, forcing the expansion to fail if it is not found:
10415 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
10420 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10421 .cindex "expansion" "list creation"
10423 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10424 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10426 in this list, its value is place in &$item$&, and then <&'string2'&> is
10427 expanded and added to the output as an item in a new list. The separator used
10428 for the output list is the same as the one used for the input, but a separator
10429 setting is not included in the output. For example:
10431 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
10433 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
10434 value of &$item$& is restored to what it was before. See also the &%filter%&
10435 and &%reduce%& expansion items.
10437 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10438 .cindex "expansion" "numeric hash"
10439 .cindex "hash function" "numeric"
10440 The three strings are expanded; the first two must yield numbers. Call them
10441 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10442 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10443 can use the simpler operator notation that avoids some of the braces:
10445 ${nhash_<n>_<m>:<string>}
10447 The second number is optional (in both notations). If there is only one number,
10448 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
10449 processed by a div/mod hash function that returns two numbers, separated by a
10450 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
10453 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
10455 returns the string &"6/33"&.
10459 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
10460 .cindex "Perl" "use in expanded string"
10461 .cindex "expansion" "calling Perl from"
10462 This item is available only if Exim has been built to include an embedded Perl
10463 interpreter. The subroutine name and the arguments are first separately
10464 expanded, and then the Perl subroutine is called with those arguments. No
10465 additional arguments need be given; the maximum number permitted, including the
10466 name of the subroutine, is nine.
10468 The return value of the subroutine is inserted into the expanded string, unless
10469 the return value is &%undef%&. In that case, the entire expansion is
10470 forced to fail, in the same way as an explicit &"fail"& on a lookup item
10471 does (see section &<<SECTforexpfai>>&). Whatever you return is evaluated
10472 in a scalar context, thus the return value is a scalar. For example, if you
10473 return a Perl vector, the return value is the size of the vector,
10476 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
10477 with the error message that was passed to &%die%&. More details of the embedded
10478 Perl facility are given in chapter &<<CHAPperl>>&.
10480 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
10481 out the use of this expansion item in filter files.
10484 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
10485 .cindex "&%prvs%& expansion item"
10486 The first argument is a complete email address and the second is secret
10487 keystring. The third argument, specifying a key number, is optional. If absent,
10488 it defaults to 0. The result of the expansion is a prvs-signed email address,
10489 to be typically used with the &%return_path%& option on an &(smtp)& transport
10490 as part of a bounce address tag validation (BATV) scheme. For more discussion
10491 and an example, see section &<<SECTverifyPRVS>>&.
10493 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
10494 {*&<&'string'&>&*}}*&"
10495 .cindex "&%prvscheck%& expansion item"
10496 This expansion item is the complement of the &%prvs%& item. It is used for
10497 checking prvs-signed addresses. If the expansion of the first argument does not
10498 yield a syntactically valid prvs-signed address, the whole item expands to the
10499 empty string. When the first argument does expand to a syntactically valid
10500 prvs-signed address, the second argument is expanded, with the prvs-decoded
10501 version of the address and the key number extracted from the address in the
10502 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
10504 These two variables can be used in the expansion of the second argument to
10505 retrieve the secret. The validity of the prvs-signed address is then checked
10506 against the secret. The result is stored in the variable &$prvscheck_result$&,
10507 which is empty for failure or &"1"& for success.
10509 The third argument is optional; if it is missing, it defaults to an empty
10510 string. This argument is now expanded. If the result is an empty string, the
10511 result of the expansion is the decoded version of the address. This is the case
10512 whether or not the signature was valid. Otherwise, the result of the expansion
10513 is the expansion of the third argument.
10515 All three variables can be used in the expansion of the third argument.
10516 However, once the expansion is complete, only &$prvscheck_result$& remains set.
10517 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
10519 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
10520 .cindex "expansion" "inserting an entire file"
10521 .cindex "file" "inserting into expansion"
10522 .cindex "&%readfile%& expansion item"
10523 The filename and end-of-line (eol) string are first expanded separately. The file is
10524 then read, and its contents replace the entire item. All newline characters in
10525 the file are replaced by the end-of-line string if it is present. Otherwise,
10526 newlines are left in the string.
10527 String expansion is not applied to the contents of the file. If you want this,
10528 you must wrap the item in an &%expand%& operator. If the file cannot be read,
10529 the string expansion fails.
10531 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
10532 locks out the use of this expansion item in filter files.
10536 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
10537 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
10538 .cindex "expansion" "inserting from a socket"
10539 .cindex "socket, use of in expansion"
10540 .cindex "&%readsocket%& expansion item"
10541 This item inserts data from a Unix domain or TCP socket into the expanded
10542 string. The minimal way of using it uses just two arguments, as in these
10545 ${readsocket{/socket/name}{request string}}
10546 ${readsocket{inet:some.host:1234}{request string}}
10548 For a Unix domain socket, the first substring must be the path to the socket.
10549 For an Internet socket, the first substring must contain &`inet:`& followed by
10550 a host name or IP address, followed by a colon and a port, which can be a
10551 number or the name of a TCP port in &_/etc/services_&. An IP address may
10552 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
10555 ${readsocket{inet:[::1]:1234}{request string}}
10557 Only a single host name may be given, but if looking it up yields more than
10558 one IP address, they are each tried in turn until a connection is made. For
10559 both kinds of socket, Exim makes a connection, writes the request string
10560 (unless it is an empty string; no terminating NUL is ever sent)
10561 and reads from the socket until an end-of-file
10562 is read. A timeout of 5 seconds is applied. Additional, optional arguments
10563 extend what can be done. Firstly, you can vary the timeout. For example:
10565 ${readsocket{/socket/name}{request string}{3s}}
10568 The third argument is a list of options, of which the first element is the timeout
10569 and must be present if any options are given.
10570 Further elements are options of form &'name=value'&.
10573 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
10576 The following option names are recognised:
10579 Defines if the result data can be cached for use by a later identical
10580 request in the same process.
10581 Values are &"yes"& or &"no"& (the default).
10582 If not, all cached results for this connection specification
10583 will be invalidated.
10587 Defines whether or not a write-shutdown is done on the connection after
10588 sending the request. Values are &"yes"& (the default) or &"no"&
10589 (preferred, eg. by some webservers).
10593 Controls the use of TLS on the connection.
10594 Values are &"yes"& or &"no"& (the default).
10595 If it is enabled, a shutdown as descripbed above is never done.
10599 A fourth argument allows you to change any newlines that are in the data
10600 that is read, in the same way as for &%readfile%& (see above). This example
10601 turns them into spaces:
10603 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
10605 As with all expansions, the substrings are expanded before the processing
10606 happens. Errors in these sub-expansions cause the expansion to fail. In
10607 addition, the following errors can occur:
10610 Failure to create a socket file descriptor;
10612 Failure to connect the socket;
10614 Failure to write the request string;
10616 Timeout on reading from the socket.
10619 By default, any of these errors causes the expansion to fail. However, if
10620 you supply a fifth substring, it is expanded and used when any of the above
10621 errors occurs. For example:
10623 ${readsocket{/socket/name}{request string}{3s}{\n}\
10626 You can test for the existence of a Unix domain socket by wrapping this
10627 expansion in &`${if exists`&, but there is a race condition between that test
10628 and the actual opening of the socket, so it is safer to use the fifth argument
10629 if you want to be absolutely sure of avoiding an expansion error for a
10630 non-existent Unix domain socket, or a failure to connect to an Internet socket.
10632 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
10633 locks out the use of this expansion item in filter files.
10636 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10637 .cindex "expansion" "reducing a list to a scalar"
10638 .cindex "list" "reducing to a scalar"
10639 .vindex "&$value$&"
10641 This operation reduces a list to a single, scalar string. After expansion,
10642 <&'string1'&> is interpreted as a list, colon-separated by default, but the
10643 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10644 Then <&'string2'&> is expanded and
10645 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
10646 list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
10647 them. The result of that expansion is assigned to &$value$& before the next
10648 iteration. When the end of the list is reached, the final value of &$value$& is
10649 added to the expansion output. The &%reduce%& expansion item can be used in a
10650 number of ways. For example, to add up a list of numbers:
10652 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
10654 The result of that expansion would be &`6`&. The maximum of a list of numbers
10657 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
10659 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
10660 restored to what they were before. See also the &%filter%& and &%map%&
10663 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
10664 This item inserts &"raw"& header lines. It is described with the &%header%&
10665 expansion item in section &<<SECTexpansionitems>>& above.
10667 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
10668 {*&<&'string2'&>&*}}*&"
10669 .cindex "expansion" "running a command"
10670 .cindex "&%run%& expansion item"
10671 The command and its arguments are first expanded as one string. The string is
10672 split apart into individual arguments by spaces, and then the command is run
10673 in a separate process, but under the same uid and gid. As in other command
10674 executions from Exim, a shell is not used by default. If the command requires
10675 a shell, you must explicitly code it.
10677 Since the arguments are split by spaces, when there is a variable expansion
10678 which has an empty result, it will cause the situation that the argument will
10679 simply be omitted when the program is actually executed by Exim. If the
10680 script/program requires a specific number of arguments and the expanded
10681 variable could possibly result in this empty expansion, the variable must be
10682 quoted. This is more difficult if the expanded variable itself could result
10683 in a string containing quotes, because it would interfere with the quotes
10684 around the command arguments. A possible guard against this is to wrap the
10685 variable in the &%sg%& operator to change any quote marks to some other
10688 The standard input for the command exists, but is empty. The standard output
10689 and standard error are set to the same file descriptor.
10690 .cindex "return code" "from &%run%& expansion"
10691 .vindex "&$value$&"
10692 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
10693 and replaces the entire item; during this expansion, the standard output/error
10694 from the command is in the variable &$value$&. If the command fails,
10695 <&'string2'&>, if present, is expanded and used. Once again, during the
10696 expansion, the standard output/error from the command is in the variable
10699 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
10700 can be the word &"fail"& (not in braces) to force expansion failure if the
10701 command does not succeed. If both strings are omitted, the result is contents
10702 of the standard output/error on success, and nothing on failure.
10704 .vindex "&$run_in_acl$&"
10705 The standard output/error of the command is put in the variable &$value$&.
10706 In this ACL example, the output of a command is logged for the admin to
10709 warn condition = ${run{/usr/bin/id}{yes}{no}}
10710 log_message = Output of id: $value
10712 If the command requires shell idioms, such as the > redirect operator, the
10713 shell must be invoked directly, such as with:
10715 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
10718 .vindex "&$runrc$&"
10719 The return code from the command is put in the variable &$runrc$&, and this
10720 remains set afterwards, so in a filter file you can do things like this:
10722 if "${run{x y z}{}}$runrc" is 1 then ...
10723 elif $runrc is 2 then ...
10727 If execution of the command fails (for example, the command does not exist),
10728 the return code is 127 &-- the same code that shells use for non-existent
10731 &*Warning*&: In a router or transport, you cannot assume the order in which
10732 option values are expanded, except for those preconditions whose order of
10733 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
10734 by the expansion of one option, and use it in another.
10736 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
10737 out the use of this expansion item in filter files.
10740 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
10741 .cindex "expansion" "string substitution"
10742 .cindex "&%sg%& expansion item"
10743 This item works like Perl's substitution operator (s) with the global (/g)
10744 option; hence its name. However, unlike the Perl equivalent, Exim does not
10745 modify the subject string; instead it returns the modified string for insertion
10746 into the overall expansion. The item takes three arguments: the subject string,
10747 a regular expression, and a substitution string. For example:
10749 ${sg{abcdefabcdef}{abc}{xyz}}
10751 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
10752 if any $, } or \ characters are required in the regular expression or in the
10753 substitution string, they have to be escaped. For example:
10755 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
10757 yields &"defabc"&, and
10759 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
10761 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
10762 the regular expression from string expansion.
10764 The regular expression is compiled in 8-bit mode, working against bytes
10765 rather than any Unicode-aware character handling.
10768 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
10769 .cindex sorting "a list"
10770 .cindex list sorting
10771 .cindex expansion "list sorting"
10772 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10773 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10774 The <&'comparator'&> argument is interpreted as the operator
10775 of a two-argument expansion condition.
10776 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
10777 The comparison should return true when applied to two values
10778 if the first value should sort before the second value.
10779 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
10780 the element being placed in &$item$&,
10781 to give values for comparison.
10783 The item result is a sorted list,
10784 with the original list separator,
10785 of the list elements (in full) of the original.
10789 ${sort{3:2:1:4}{<}{$item}}
10791 sorts a list of numbers, and
10793 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10795 will sort an MX lookup into priority order.
10800 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
10801 SRS encoding. See SECT &<<SECTSRS>>& for details.
10806 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10807 .cindex "&%substr%& expansion item"
10808 .cindex "substring extraction"
10809 .cindex "expansion" "substring extraction"
10810 The three strings are expanded; the first two must yield numbers. Call them
10811 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10812 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10813 can use the simpler operator notation that avoids some of the braces:
10815 ${substr_<n>_<m>:<string>}
10817 The second number is optional (in both notations).
10818 If it is absent in the simpler format, the preceding underscore must also be
10821 The &%substr%& item can be used to extract more general substrings than
10822 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10823 length required. For example
10825 ${substr{3}{2}{$local_part}}
10827 If the starting offset is greater than the string length the result is the
10828 null string; if the length plus starting offset is greater than the string
10829 length, the result is the right-hand part of the string, starting from the
10830 given offset. The first byte (character) in the string has offset zero.
10832 The &%substr%& expansion item can take negative offset values to count
10833 from the right-hand end of its operand. The last byte (character) is offset -1,
10834 the second-last is offset -2, and so on. Thus, for example,
10836 ${substr{-5}{2}{1234567}}
10838 yields &"34"&. If the absolute value of a negative offset is greater than the
10839 length of the string, the substring starts at the beginning of the string, and
10840 the length is reduced by the amount of overshoot. Thus, for example,
10842 ${substr{-5}{2}{12}}
10844 yields an empty string, but
10846 ${substr{-3}{2}{12}}
10850 When the second number is omitted from &%substr%&, the remainder of the string
10851 is taken if the offset is positive. If it is negative, all bytes (characters) in the
10852 string preceding the offset point are taken. For example, an offset of -1 and
10853 no length, as in these semantically identical examples:
10856 ${substr{-1}{abcde}}
10858 yields all but the last character of the string, that is, &"abcd"&.
10860 All measurement is done in bytes and is not UTF-8 aware.
10864 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10865 {*&<&'replacements'&>&*}}*&"
10866 .cindex "expansion" "character translation"
10867 .cindex "&%tr%& expansion item"
10868 This item does single-character (in bytes) translation on its subject string. The second
10869 argument is a list of characters to be translated in the subject string. Each
10870 matching character is replaced by the corresponding character from the
10871 replacement list. For example
10873 ${tr{abcdea}{ac}{13}}
10875 yields &`1b3de1`&. If there are duplicates in the second character string, the
10876 last occurrence is used. If the third string is shorter than the second, its
10877 last character is replicated. However, if it is empty, no translation takes
10880 All character handling is done in bytes and is not UTF-8 aware.
10886 .section "Expansion operators" "SECTexpop"
10887 .cindex "expansion" "operators"
10888 For expansion items that perform transformations on a single argument string,
10889 the &"operator"& notation is used because it is simpler and uses fewer braces.
10890 The substring is first expanded before the operation is applied to it. The
10891 following operations can be performed:
10894 .vitem &*${address:*&<&'string'&>&*}*&
10895 .cindex "expansion" "RFC 2822 address handling"
10896 .cindex "&%address%& expansion item"
10897 The string is interpreted as an RFC 2822 address, as it might appear in a
10898 header line, and the effective address is extracted from it. If the string does
10899 not parse successfully, the result is empty.
10901 The parsing correctly handles SMTPUTF8 Unicode in the string.
10904 .vitem &*${addresses:*&<&'string'&>&*}*&
10905 .cindex "expansion" "RFC 2822 address handling"
10906 .cindex "&%addresses%& expansion item"
10907 The string (after expansion) is interpreted as a list of addresses in RFC
10908 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10909 operative address (&'local-part@domain'&) is extracted from each item, and the
10910 result of the expansion is a colon-separated list, with appropriate
10911 doubling of colons should any happen to be present in the email addresses.
10912 Syntactically invalid RFC2822 address items are omitted from the output.
10914 It is possible to specify a character other than colon for the output
10915 separator by starting the string with > followed by the new separator
10916 character. For example:
10918 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10920 expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
10921 first, so if the expanded string starts with >, it may change the output
10922 separator unintentionally. This can be avoided by setting the output
10923 separator explicitly:
10925 ${addresses:>:$h_from:}
10928 Compare the &%address%& (singular)
10929 expansion item, which extracts the working address from a single RFC2822
10930 address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
10933 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10934 a strict interpretation of header line formatting. Exim parses the bare,
10935 unquoted portion of an email address and if it finds a comma, treats it as an
10936 email address separator. For the example header line:
10938 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10940 The first example below demonstrates that Q-encoded email addresses are parsed
10941 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10942 It does not see the comma because it's still encoded as "=2C". The second
10943 example below is passed the contents of &`$header_from:`&, meaning it gets
10944 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10945 The third example shows that the presence of a comma is skipped when it is
10946 quoted. The fourth example shows SMTPUTF8 handling.
10948 # exim -be '${addresses:From: \
10949 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10951 # exim -be '${addresses:From: Last, First <user@example.com>}'
10952 Last:user@example.com
10953 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10955 # exim -be '${addresses:フィル <フィリップ@example.jp>}'
10959 .vitem &*${base32:*&<&'digits'&>&*}*&
10960 .cindex "&%base32%& expansion item"
10961 .cindex "expansion" "conversion to base 32"
10962 The string must consist entirely of decimal digits. The number is converted to
10963 base 32 and output as a (empty, for zero) string of characters.
10964 Only lowercase letters are used.
10966 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10967 .cindex "&%base32d%& expansion item"
10968 .cindex "expansion" "conversion to base 32"
10969 The string must consist entirely of base-32 digits.
10970 The number is converted to decimal and output as a string.
10972 .vitem &*${base62:*&<&'digits'&>&*}*&
10973 .cindex "&%base62%& expansion item"
10974 .cindex "expansion" "conversion to base 62"
10975 The string must consist entirely of decimal digits. The number is converted to
10976 base 62 and output as a string of six characters, including leading zeros. In
10977 the few operating environments where Exim uses base 36 instead of base 62 for
10978 its message identifiers (because those systems do not have case-sensitive
10979 filenames), base 36 is used by this operator, despite its name. &*Note*&: Just
10980 to be absolutely clear: this is &'not'& base64 encoding.
10982 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10983 .cindex "&%base62d%& expansion item"
10984 .cindex "expansion" "conversion to base 62"
10985 The string must consist entirely of base-62 digits, or, in operating
10986 environments where Exim uses base 36 instead of base 62 for its message
10987 identifiers, base-36 digits. The number is converted to decimal and output as a
10990 .vitem &*${base64:*&<&'string'&>&*}*&
10991 .cindex "expansion" "base64 encoding"
10992 .cindex "base64 encoding" "in string expansion"
10993 .cindex "&%base64%& expansion item"
10994 .cindex certificate "base64 of DER"
10995 This operator converts a string into one that is base64 encoded.
10997 If the string is a single variable of type certificate,
10998 returns the base64 encoding of the DER form of the certificate.
11001 .vitem &*${base64d:*&<&'string'&>&*}*&
11002 .cindex "expansion" "base64 decoding"
11003 .cindex "base64 decoding" "in string expansion"
11004 .cindex "&%base64d%& expansion item"
11005 This operator converts a base64-encoded string into the un-coded form.
11008 .vitem &*${domain:*&<&'string'&>&*}*&
11009 .cindex "domain" "extraction"
11010 .cindex "expansion" "domain extraction"
11011 The string is interpreted as an RFC 2822 address and the domain is extracted
11012 from it. If the string does not parse successfully, the result is empty.
11015 .vitem &*${escape:*&<&'string'&>&*}*&
11016 .cindex "expansion" "escaping non-printing characters"
11017 .cindex "&%escape%& expansion item"
11018 If the string contains any non-printing characters, they are converted to
11019 escape sequences starting with a backslash. Whether characters with the most
11020 significant bit set (so-called &"8-bit characters"&) count as printing or not
11021 is controlled by the &%print_topbitchars%& option.
11023 .vitem &*${escape8bit:*&<&'string'&>&*}*&
11024 .cindex "expansion" "escaping 8-bit characters"
11025 .cindex "&%escape8bit%& expansion item"
11026 If the string contains any characters with the most significant bit set,
11027 they are converted to escape sequences starting with a backslash.
11028 Backslashes and DEL characters are also converted.
11031 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
11032 .cindex "expansion" "expression evaluation"
11033 .cindex "expansion" "arithmetic expression"
11034 .cindex "&%eval%& expansion item"
11035 These items supports simple arithmetic and bitwise logical operations in
11036 expansion strings. The string (after expansion) must be a conventional
11037 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
11038 logical operators, and parentheses. All operations are carried out using
11039 integer arithmetic. The operator priorities are as follows (the same as in the
11040 C programming language):
11042 .irow &'highest:'& "not (~), negate (-)"
11043 .irow "" "multiply (*), divide (/), remainder (%)"
11044 .irow "" "plus (+), minus (-)"
11045 .irow "" "shift-left (<<), shift-right (>>)"
11046 .irow "" "and (&&)"
11048 .irow &'lowest:'& "or (|)"
11050 Binary operators with the same priority are evaluated from left to right. White
11051 space is permitted before or after operators.
11053 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
11054 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
11055 decimal, even if they start with a leading zero; hexadecimal numbers are not
11056 permitted. This can be useful when processing numbers extracted from dates or
11057 times, which often do have leading zeros.
11059 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
11061 respectively. Negative numbers are supported. The result of the computation is
11062 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
11065 &`${eval:1+1} `& yields 2
11066 &`${eval:1+2*3} `& yields 7
11067 &`${eval:(1+2)*3} `& yields 9
11068 &`${eval:2+42%5} `& yields 4
11069 &`${eval:0xc&5} `& yields 4
11070 &`${eval:0xc|5} `& yields 13
11071 &`${eval:0xc^5} `& yields 9
11072 &`${eval:0xc>>1} `& yields 6
11073 &`${eval:0xc<<1} `& yields 24
11074 &`${eval:~255&0x1234} `& yields 4608
11075 &`${eval:-(~255&0x1234)} `& yields -4608
11078 As a more realistic example, in an ACL you might have
11082 {>{$rcpt_count}{10}} \
11085 {$recipients_count} \
11086 {${eval:$rcpt_count/2}} \
11089 message = Too many bad recipients
11091 The condition is true if there have been more than 10 RCPT commands and
11092 fewer than half of them have resulted in a valid recipient.
11095 .vitem &*${expand:*&<&'string'&>&*}*&
11096 .cindex "expansion" "re-expansion of substring"
11097 The &%expand%& operator causes a string to be expanded for a second time. For
11100 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
11102 first looks up a string in a file while expanding the operand for &%expand%&,
11103 and then re-expands what it has found.
11106 .vitem &*${from_utf8:*&<&'string'&>&*}*&
11108 .cindex "UTF-8" "conversion from"
11109 .cindex "expansion" "UTF-8 conversion"
11110 .cindex "&%from_utf8%& expansion item"
11111 The world is slowly moving towards Unicode, although there are no standards for
11112 email yet. However, other applications (including some databases) are starting
11113 to store data in Unicode, using UTF-8 encoding. This operator converts from a
11114 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
11115 converted to underscores. The input must be a valid UTF-8 string. If it is not,
11116 the result is an undefined sequence of bytes.
11118 Unicode code points with values less than 256 are compatible with ASCII and
11119 ISO-8859-1 (also known as Latin-1).
11120 For example, character 169 is the copyright symbol in both cases, though the
11121 way it is encoded is different. In UTF-8, more than one byte is needed for
11122 characters with code values greater than 127, whereas ISO-8859-1 is a
11123 single-byte encoding (but thereby limited to 256 characters). This makes
11124 translation from UTF-8 to ISO-8859-1 straightforward.
11127 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11128 .cindex "hash function" "textual"
11129 .cindex "expansion" "textual hash"
11130 The &%hash%& operator is a simpler interface to the hashing function that can
11131 be used when the two parameters are fixed numbers (as opposed to strings that
11132 change when expanded). The effect is the same as
11134 ${hash{<n>}{<m>}{<string>}}
11136 See the description of the general &%hash%& item above for details. The
11137 abbreviation &%h%& can be used when &%hash%& is used as an operator.
11141 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
11142 .cindex "base64 encoding" "conversion from hex"
11143 .cindex "expansion" "hex to base64"
11144 .cindex "&%hex2b64%& expansion item"
11145 This operator converts a hex string into one that is base64 encoded. This can
11146 be useful for processing the output of the various hashing functions.
11150 .vitem &*${hexquote:*&<&'string'&>&*}*&
11151 .cindex "quoting" "hex-encoded unprintable characters"
11152 .cindex "&%hexquote%& expansion item"
11153 This operator converts non-printable characters in a string into a hex
11154 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
11155 as is, and other byte values are converted to &`\xNN`&, for example, a
11156 byte value 127 is converted to &`\x7f`&.
11159 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
11160 .cindex "&%ipv6denorm%& expansion item"
11161 .cindex "IP address" normalisation
11162 This expands an IPv6 address to a full eight-element colon-separated set
11163 of hex digits including leading zeroes.
11164 A trailing ipv4-style dotted-decimal set is converted to hex.
11165 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11167 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
11168 .cindex "&%ipv6norm%& expansion item"
11169 .cindex "IP address" normalisation
11170 .cindex "IP address" "canonical form"
11171 This converts an IPv6 address to canonical form.
11172 Leading zeroes of groups are omitted, and the longest
11173 set of zero-valued groups is replaced with a double colon.
11174 A trailing ipv4-style dotted-decimal set is converted to hex.
11175 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11178 .vitem &*${lc:*&<&'string'&>&*}*&
11179 .cindex "case forcing in strings"
11180 .cindex "string" "case forcing"
11181 .cindex "lower casing"
11182 .cindex "expansion" "case forcing"
11183 .cindex "&%lc%& expansion item"
11184 This forces the letters in the string into lower-case, for example:
11188 Case is defined per the system C locale.
11190 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
11191 .cindex "expansion" "string truncation"
11192 .cindex "&%length%& expansion item"
11193 The &%length%& operator is a simpler interface to the &%length%& function that
11194 can be used when the parameter is a fixed number (as opposed to a string that
11195 changes when expanded). The effect is the same as
11197 ${length{<number>}{<string>}}
11199 See the description of the general &%length%& item above for details. Note that
11200 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
11201 when &%length%& is used as an operator.
11202 All measurement is done in bytes and is not UTF-8 aware.
11205 .vitem &*${listcount:*&<&'string'&>&*}*&
11206 .cindex "expansion" "list item count"
11207 .cindex "list" "item count"
11208 .cindex "list" "count of items"
11209 .cindex "&%listcount%& expansion item"
11210 The string is interpreted as a list and the number of items is returned.
11213 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
11214 .cindex "expansion" "named list"
11215 .cindex "&%listnamed%& expansion item"
11216 The name is interpreted as a named list and the content of the list is returned,
11217 expanding any referenced lists, re-quoting as needed for colon-separation.
11218 If the optional type is given it must be one of "a", "d", "h" or "l"
11219 and selects address-, domain-, host- or localpart- lists to search among respectively.
11220 Otherwise all types are searched in an undefined order and the first
11221 matching list is returned.
11223 &*Note*&: Neither string-expansion of lists referenced by named-list syntax elements,
11224 nor expansion of lookup elements, is done by the &%listnamed%& operator.
11228 .vitem &*${local_part:*&<&'string'&>&*}*&
11229 .cindex "expansion" "local part extraction"
11230 .cindex "&%local_part%& expansion item"
11231 The string is interpreted as an RFC 2822 address and the local part is
11232 extracted from it. If the string does not parse successfully, the result is
11234 The parsing correctly handles SMTPUTF8 Unicode in the string.
11237 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
11238 .cindex "masked IP address"
11239 .cindex "IP address" "masking"
11240 .cindex "CIDR notation"
11241 .cindex "expansion" "IP address masking"
11242 .cindex "&%mask%& expansion item"
11243 If the form of the string to be operated on is not an IP address followed by a
11244 slash and an integer (that is, a network address in CIDR notation), the
11245 expansion fails. Otherwise, this operator converts the IP address to binary,
11246 masks off the least significant bits according to the bit count, and converts
11247 the result back to text, with mask appended. For example,
11249 ${mask:10.111.131.206/28}
11251 returns the string &"10.111.131.192/28"&. Since this operation is expected to
11252 be mostly used for looking up masked addresses in files, the result for an IPv6
11253 address uses dots to separate components instead of colons, because colon
11254 terminates a key string in lsearch files. So, for example,
11256 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
11260 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
11262 Letters in IPv6 addresses are always output in lower case.
11265 .vitem &*${md5:*&<&'string'&>&*}*&
11267 .cindex "expansion" "MD5 hash"
11268 .cindex certificate fingerprint
11269 .cindex "&%md5%& expansion item"
11270 The &%md5%& operator computes the MD5 hash value of the string, and returns it
11271 as a 32-digit hexadecimal number, in which any letters are in lower case.
11273 If the string is a single variable of type certificate,
11274 returns the MD5 hash fingerprint of the certificate.
11277 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11278 .cindex "expansion" "numeric hash"
11279 .cindex "hash function" "numeric"
11280 The &%nhash%& operator is a simpler interface to the numeric hashing function
11281 that can be used when the two parameters are fixed numbers (as opposed to
11282 strings that change when expanded). The effect is the same as
11284 ${nhash{<n>}{<m>}{<string>}}
11286 See the description of the general &%nhash%& item above for details.
11289 .vitem &*${quote:*&<&'string'&>&*}*&
11290 .cindex "quoting" "in string expansions"
11291 .cindex "expansion" "quoting"
11292 .cindex "&%quote%& expansion item"
11293 The &%quote%& operator puts its argument into double quotes if it
11294 is an empty string or
11295 contains anything other than letters, digits, underscores, dots, and hyphens.
11296 Any occurrences of double quotes and backslashes are escaped with a backslash.
11297 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
11298 respectively For example,
11306 The place where this is useful is when the argument is a substitution from a
11307 variable or a message header.
11309 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
11310 .cindex "&%quote_local_part%& expansion item"
11311 This operator is like &%quote%&, except that it quotes the string only if
11312 required to do so by the rules of RFC 2822 for quoting local parts. For
11313 example, a plus sign would not cause quoting (but it would for &%quote%&).
11314 If you are creating a new email address from the contents of &$local_part$&
11315 (or any other unknown data), you should always use this operator.
11317 This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
11318 will likely use the quoting form.
11319 Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
11322 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
11323 .cindex "quoting" "lookup-specific"
11324 This operator applies lookup-specific quoting rules to the string. Each
11325 query-style lookup type has its own quoting rules which are described with
11326 the lookups in chapter &<<CHAPfdlookup>>&. For example,
11328 ${quote_ldap:two * two}
11334 For single-key lookup types, no quoting is ever necessary and this operator
11335 yields an unchanged string.
11338 .vitem &*${randint:*&<&'n'&>&*}*&
11339 .cindex "random number"
11340 This operator returns a somewhat random number which is less than the
11341 supplied number and is at least 0. The quality of this randomness depends
11342 on how Exim was built; the values are not suitable for keying material.
11343 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
11344 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
11345 for versions of GnuTLS with that function.
11346 Otherwise, the implementation may be arc4random(), random() seeded by
11347 srandomdev() or srandom(), or a custom implementation even weaker than
11351 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
11352 .cindex "expansion" "IP address"
11353 This operator reverses an IP address; for IPv4 addresses, the result is in
11354 dotted-quad decimal form, while for IPv6 addresses the result is in
11355 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
11356 for DNS. For example,
11358 ${reverse_ip:192.0.2.4}
11359 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
11364 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
11368 .vitem &*${rfc2047:*&<&'string'&>&*}*&
11369 .cindex "expansion" "RFC 2047"
11370 .cindex "RFC 2047" "expansion operator"
11371 .cindex "&%rfc2047%& expansion item"
11372 This operator encodes text according to the rules of RFC 2047. This is an
11373 encoding that is used in header lines to encode non-ASCII characters. It is
11374 assumed that the input string is in the encoding specified by the
11375 &%headers_charset%& option, which gets its default at build time. If the string
11376 contains only characters in the range 33&--126, and no instances of the
11379 ? = ( ) < > @ , ; : \ " . [ ] _
11381 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
11382 string, using as many &"encoded words"& as necessary to encode all the
11386 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
11387 .cindex "expansion" "RFC 2047"
11388 .cindex "RFC 2047" "decoding"
11389 .cindex "&%rfc2047d%& expansion item"
11390 This operator decodes strings that are encoded as per RFC 2047. Binary zero
11391 bytes are replaced by question marks. Characters are converted into the
11392 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
11393 not recognized unless &%check_rfc2047_length%& is set false.
11395 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
11396 access a header line, RFC 2047 decoding is done automatically. You do not need
11397 to use this operator as well.
11401 .vitem &*${rxquote:*&<&'string'&>&*}*&
11402 .cindex "quoting" "in regular expressions"
11403 .cindex "regular expressions" "quoting"
11404 .cindex "&%rxquote%& expansion item"
11405 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
11406 characters in its argument. This is useful when substituting the values of
11407 variables or headers inside regular expressions.
11410 .vitem &*${sha1:*&<&'string'&>&*}*&
11411 .cindex "SHA-1 hash"
11412 .cindex "expansion" "SHA-1 hashing"
11413 .cindex certificate fingerprint
11414 .cindex "&%sha1%& expansion item"
11415 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
11416 it as a 40-digit hexadecimal number, in which any letters are in upper case.
11418 If the string is a single variable of type certificate,
11419 returns the SHA-1 hash fingerprint of the certificate.
11422 .vitem &*${sha256:*&<&'string'&>&*}*& &&&
11423 &*${sha2:*&<&'string'&>&*}*& &&&
11424 &*${sha2_<n>:*&<&'string'&>&*}*&
11425 .cindex "SHA-256 hash"
11426 .cindex "SHA-2 hash"
11427 .cindex certificate fingerprint
11428 .cindex "expansion" "SHA-256 hashing"
11429 .cindex "&%sha256%& expansion item"
11430 .cindex "&%sha2%& expansion item"
11431 The &%sha256%& operator computes the SHA-256 hash value of the string
11433 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11435 If the string is a single variable of type certificate,
11436 returns the SHA-256 hash fingerprint of the certificate.
11438 The operator can also be spelled &%sha2%& and does the same as &%sha256%&
11439 (except for certificates, which are not supported).
11440 Finally, if an underbar
11441 and a number is appended it specifies the output length, selecting a
11442 member of the SHA-2 family of hash functions.
11443 Values of 256, 384 and 512 are accepted, with 256 being the default.
11446 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
11447 &*${sha3_<n>:*&<&'string'&>&*}*&
11448 .cindex "SHA3 hash"
11449 .cindex "expansion" "SHA3 hashing"
11450 .cindex "&%sha3%& expansion item"
11451 The &%sha3%& operator computes the SHA3-256 hash value of the string
11453 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11455 If a number is appended, separated by an underbar, it specifies
11456 the output length. Values of 224, 256, 384 and 512 are accepted;
11457 with 256 being the default.
11459 The &%sha3%& expansion item is only supported if Exim has been
11460 compiled with GnuTLS 3.5.0 or later,
11461 or OpenSSL 1.1.1 or later.
11462 The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
11465 .vitem &*${stat:*&<&'string'&>&*}*&
11466 .cindex "expansion" "statting a file"
11467 .cindex "file" "extracting characteristics"
11468 .cindex "&%stat%& expansion item"
11469 The string, after expansion, must be a file path. A call to the &[stat()]&
11470 function is made for this path. If &[stat()]& fails, an error occurs and the
11471 expansion fails. If it succeeds, the data from the stat replaces the item, as a
11472 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
11473 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
11474 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
11475 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
11476 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
11477 can extract individual fields using the &%extract%& expansion item.
11479 The use of the &%stat%& expansion in users' filter files can be locked out by
11480 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
11481 systems for files larger than 2GB.
11483 .vitem &*${str2b64:*&<&'string'&>&*}*&
11484 .cindex "&%str2b64%& expansion item"
11485 Now deprecated, a synonym for the &%base64%& expansion operator.
11489 .vitem &*${strlen:*&<&'string'&>&*}*&
11490 .cindex "expansion" "string length"
11491 .cindex "string" "length in expansion"
11492 .cindex "&%strlen%& expansion item"
11493 The item is replaced by the length of the expanded string, expressed as a
11494 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
11495 All measurement is done in bytes and is not UTF-8 aware.
11498 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
11499 .cindex "&%substr%& expansion item"
11500 .cindex "substring extraction"
11501 .cindex "expansion" "substring expansion"
11502 The &%substr%& operator is a simpler interface to the &%substr%& function that
11503 can be used when the two parameters are fixed numbers (as opposed to strings
11504 that change when expanded). The effect is the same as
11506 ${substr{<start>}{<length>}{<string>}}
11508 See the description of the general &%substr%& item above for details. The
11509 abbreviation &%s%& can be used when &%substr%& is used as an operator.
11510 All measurement is done in bytes and is not UTF-8 aware.
11512 .vitem &*${time_eval:*&<&'string'&>&*}*&
11513 .cindex "&%time_eval%& expansion item"
11514 .cindex "time interval" "decoding"
11515 This item converts an Exim time interval such as &`2d4h5m`& into a number of
11518 .vitem &*${time_interval:*&<&'string'&>&*}*&
11519 .cindex "&%time_interval%& expansion item"
11520 .cindex "time interval" "formatting"
11521 The argument (after sub-expansion) must be a sequence of decimal digits that
11522 represents an interval of time as a number of seconds. It is converted into a
11523 number of larger units and output in Exim's normal time format, for example,
11526 .vitem &*${uc:*&<&'string'&>&*}*&
11527 .cindex "case forcing in strings"
11528 .cindex "string" "case forcing"
11529 .cindex "upper casing"
11530 .cindex "expansion" "case forcing"
11531 .cindex "&%uc%& expansion item"
11532 This forces the letters in the string into upper-case.
11533 Case is defined per the system C locale.
11535 .vitem &*${utf8clean:*&<&'string'&>&*}*&
11536 .cindex "correction of invalid utf-8 sequences in strings"
11537 .cindex "utf-8" "utf-8 sequences"
11538 .cindex "incorrect utf-8"
11539 .cindex "expansion" "utf-8 forcing"
11540 .cindex "&%utf8clean%& expansion item"
11541 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
11542 In versions of Exim before 4.92, this did not correctly do so for a truncated
11543 final codepoint's encoding, and the character would be silently dropped.
11544 If you must handle detection of this scenario across both sets of Exim behavior,
11545 the complexity will depend upon the task.
11546 For instance, to detect if the first character is multibyte and a 1-byte
11547 extraction can be successfully used as a path component (as is common for
11548 dividing up delivery folders), you might use:
11550 condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
11552 (which will false-positive if the first character of the local part is a
11553 literal question mark).
11555 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
11556 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
11557 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
11558 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
11559 .cindex expansion UTF-8
11560 .cindex UTF-8 expansion
11562 .cindex internationalisation
11563 .cindex "&%utf8_domain_to_alabel%& expansion item"
11564 .cindex "&%utf8_domain_from_alabel%& expansion item"
11565 .cindex "&%utf8_localpart_to_alabel%& expansion item"
11566 .cindex "&%utf8_localpart_from_alabel%& expansion item"
11567 These convert EAI mail name components between UTF-8 and a-label forms.
11568 For information on internationalisation support see &<<SECTi18nMTA>>&.
11576 .section "Expansion conditions" "SECTexpcond"
11577 .scindex IIDexpcond "expansion" "conditions"
11578 The following conditions are available for testing by the &%${if%& construct
11579 while expanding strings:
11582 .vitem &*!*&<&'condition'&>
11583 .cindex "expansion" "negating a condition"
11584 .cindex "negation" "in expansion condition"
11585 Preceding any condition with an exclamation mark negates the result of the
11588 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11589 .cindex "numeric comparison"
11590 .cindex "expansion" "numeric comparison"
11591 There are a number of symbolic operators for doing numeric comparisons. They
11597 &`>= `& greater or equal
11599 &`<= `& less or equal
11603 ${if >{$message_size}{10M} ...
11605 Note that the general negation operator provides for inequality testing. The
11606 two strings must take the form of optionally signed decimal integers,
11607 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
11608 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
11609 As a special case, the numerical value of an empty string is taken as
11612 In all cases, a relative comparator OP is testing if <&'string1'&> OP
11613 <&'string2'&>; the above example is checking if &$message_size$& is larger than
11614 10M, not if 10M is larger than &$message_size$&.
11617 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
11618 {*&<&'arg2'&>&*}...}*&
11619 .cindex "expansion" "calling an acl"
11620 .cindex "&%acl%&" "expansion condition"
11621 The name and zero to nine argument strings are first expanded separately. The expanded
11622 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
11623 Any unused are made empty. The variable &$acl_narg$& is set to the number of
11624 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
11625 and may use the variables; if another acl expansion is used the values
11626 are restored after it returns. If the ACL sets
11627 a value using a "message =" modifier the variable $value becomes
11628 the result of the expansion, otherwise it is empty.
11629 If the ACL returns accept the condition is true; if deny, false.
11630 If the ACL returns defer the result is a forced-fail.
11632 .vitem &*bool&~{*&<&'string'&>&*}*&
11633 .cindex "expansion" "boolean parsing"
11634 .cindex "&%bool%& expansion condition"
11635 This condition turns a string holding a true or false representation into
11636 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
11637 (case-insensitively); also integer numbers map to true if non-zero,
11639 An empty string is treated as false.
11640 Leading and trailing whitespace is ignored;
11641 thus a string consisting only of whitespace is false.
11642 All other string values will result in expansion failure.
11644 When combined with ACL variables, this expansion condition will let you
11645 make decisions in one place and act on those decisions in another place.
11648 ${if bool{$acl_m_privileged_sender} ...
11652 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
11653 .cindex "expansion" "boolean parsing"
11654 .cindex "&%bool_lax%& expansion condition"
11655 Like &%bool%&, this condition turns a string into a boolean state. But
11656 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
11657 loose definition that the Router &%condition%& option uses. The empty string
11658 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
11659 true. Leading and trailing whitespace is ignored.
11661 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
11663 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11664 .cindex "expansion" "encrypted comparison"
11665 .cindex "encrypted strings, comparing"
11666 .cindex "&%crypteq%& expansion condition"
11667 This condition is included in the Exim binary if it is built to support any
11668 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
11669 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
11670 included in the binary.
11672 The &%crypteq%& condition has two arguments. The first is encrypted and
11673 compared against the second, which is already encrypted. The second string may
11674 be in the LDAP form for storing encrypted strings, which starts with the
11675 encryption type in curly brackets, followed by the data. If the second string
11676 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
11677 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
11678 Typically this will be a field from a password file. An example of an encrypted
11679 string in LDAP form is:
11681 {md5}CY9rzUYh03PK3k6DJie09g==
11683 If such a string appears directly in an expansion, the curly brackets have to
11684 be quoted, because they are part of the expansion syntax. For example:
11686 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
11688 The following encryption types (whose names are matched case-independently) are
11693 .cindex "base64 encoding" "in encrypted password"
11694 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
11695 printable characters to compare with the remainder of the second string. If the
11696 length of the comparison string is 24, Exim assumes that it is base64 encoded
11697 (as in the above example). If the length is 32, Exim assumes that it is a
11698 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
11702 .cindex "SHA-1 hash"
11703 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
11704 printable characters to compare with the remainder of the second string. If the
11705 length of the comparison string is 28, Exim assumes that it is base64 encoded.
11706 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
11707 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
11710 .cindex "&[crypt()]&"
11711 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
11712 only the first eight characters of the password. However, in modern operating
11713 systems this is no longer true, and in many cases the entire password is used,
11714 whatever its length.
11717 .cindex "&[crypt16()]&"
11718 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
11719 use up to 16 characters of the password in some operating systems. Again, in
11720 modern operating systems, more characters may be used.
11722 Exim has its own version of &[crypt16()]&, which is just a double call to
11723 &[crypt()]&. For operating systems that have their own version, setting
11724 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
11725 operating system version instead of its own. This option is set by default in
11726 the OS-dependent &_Makefile_& for those operating systems that are known to
11727 support &[crypt16()]&.
11729 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
11730 it was not using the same algorithm as some operating systems' versions. It
11731 turns out that as well as &[crypt16()]& there is a function called
11732 &[bigcrypt()]& in some operating systems. This may or may not use the same
11733 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
11735 However, since there is now a move away from the traditional &[crypt()]&
11736 functions towards using SHA1 and other algorithms, tidying up this area of
11737 Exim is seen as very low priority.
11739 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
11740 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
11741 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
11742 default is &`{crypt}`&. Whatever the default, you can always use either
11743 function by specifying it explicitly in curly brackets.
11745 .vitem &*def:*&<&'variable&~name'&>
11746 .cindex "expansion" "checking for empty variable"
11747 .cindex "&%def%& expansion condition"
11748 The &%def%& condition must be followed by the name of one of the expansion
11749 variables defined in section &<<SECTexpvar>>&. The condition is true if the
11750 variable does not contain the empty string. For example:
11752 ${if def:sender_ident {from $sender_ident}}
11754 Note that the variable name is given without a leading &%$%& character. If the
11755 variable does not exist, the expansion fails.
11757 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
11758 &~&*def:h_*&<&'header&~name'&>&*:*&"
11759 .cindex "expansion" "checking header line existence"
11760 This condition is true if a message is being processed and the named header
11761 exists in the message. For example,
11763 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
11765 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
11766 the header name must be terminated by a colon if white space does not follow.
11768 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11769 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11770 .cindex "string" "comparison"
11771 .cindex "expansion" "string comparison"
11772 .cindex "&%eq%& expansion condition"
11773 .cindex "&%eqi%& expansion condition"
11774 The two substrings are first expanded. The condition is true if the two
11775 resulting strings are identical. For &%eq%& the comparison includes the case of
11776 letters, whereas for &%eqi%& the comparison is case-independent, where
11777 case is defined per the system C locale.
11779 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
11780 .cindex "expansion" "file existence test"
11781 .cindex "file" "existence test"
11782 .cindex "&%exists%&, expansion condition"
11783 The substring is first expanded and then interpreted as an absolute path. The
11784 condition is true if the named file (or directory) exists. The existence test
11785 is done by calling the &[stat()]& function. The use of the &%exists%& test in
11786 users' filter files may be locked out by the system administrator.
11789 &*Note:*& Testing a path using this condition is not a sufficient way of
11791 Consider using a dsearch lookup.
11794 .vitem &*first_delivery*&
11795 .cindex "delivery" "first"
11796 .cindex "first delivery"
11797 .cindex "expansion" "first delivery test"
11798 .cindex "&%first_delivery%& expansion condition"
11799 This condition, which has no data, is true during a message's first delivery
11800 attempt. It is false during any subsequent delivery attempts.
11803 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
11804 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
11805 .cindex "list" "iterative conditions"
11806 .cindex "expansion" "&*forall*& condition"
11807 .cindex "expansion" "&*forany*& condition"
11809 These conditions iterate over a list. The first argument is expanded to form
11810 the list. By default, the list separator is a colon, but it can be changed by
11811 the normal method (&<<SECTlistsepchange>>&).
11812 The second argument is interpreted as a condition that is to
11813 be applied to each item in the list in turn. During the interpretation of the
11814 condition, the current list item is placed in a variable called &$item$&.
11816 For &*forany*&, interpretation stops if the condition is true for any item, and
11817 the result of the whole condition is true. If the condition is false for all
11818 items in the list, the overall condition is false.
11820 For &*forall*&, interpretation stops if the condition is false for any item,
11821 and the result of the whole condition is false. If the condition is true for
11822 all items in the list, the overall condition is true.
11824 Note that negation of &*forany*& means that the condition must be false for all
11825 items for the overall condition to succeed, and negation of &*forall*& means
11826 that the condition must be false for at least one item. In this example, the
11827 list separator is changed to a comma:
11829 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
11831 The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
11832 being processed, to enable these expansion items to be nested.
11834 To scan a named list, expand it with the &*listnamed*& operator.
11836 .vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11837 "&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11838 "&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11839 "&*forany_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&"
11840 .cindex JSON "iterative conditions"
11841 .cindex JSON expansions
11842 .cindex expansion "&*forall_json*& condition"
11843 .cindex expansion "&*forany_json*& condition"
11844 .cindex expansion "&*forall_jsons*& condition"
11845 .cindex expansion "&*forany_jsons*& condition"
11846 As for the above, except that the first argument must, after expansion,
11848 The array separator is not changeable.
11849 For the &"jsons"& variants the elements are expected to be JSON strings
11850 and have their quotes removed before the evaluation of the condition.
11854 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11855 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11856 .cindex "string" "comparison"
11857 .cindex "expansion" "string comparison"
11858 .cindex "&%ge%& expansion condition"
11859 .cindex "&%gei%& expansion condition"
11860 The two substrings are first expanded. The condition is true if the first
11861 string is lexically greater than or equal to the second string. For &%ge%& the
11862 comparison includes the case of letters, whereas for &%gei%& the comparison is
11864 Case and collation order are defined per the system C locale.
11866 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11867 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11868 .cindex "string" "comparison"
11869 .cindex "expansion" "string comparison"
11870 .cindex "&%gt%& expansion condition"
11871 .cindex "&%gti%& expansion condition"
11872 The two substrings are first expanded. The condition is true if the first
11873 string is lexically greater than the second string. For &%gt%& the comparison
11874 includes the case of letters, whereas for &%gti%& the comparison is
11876 Case and collation order are defined per the system C locale.
11880 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
11881 SRS decode. See SECT &<<SECTSRS>>& for details.
11885 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11886 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11887 .cindex "string" "comparison"
11888 .cindex "list" "iterative conditions"
11889 Both strings are expanded; the second string is treated as a list of simple
11890 strings; if the first string is a member of the second, then the condition
11892 For the case-independent &%inlisti%& condition, case is defined per the system C locale.
11894 These are simpler to use versions of the more powerful &*forany*& condition.
11895 Examples, and the &*forany*& equivalents:
11897 ${if inlist{needle}{foo:needle:bar}}
11898 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11899 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11900 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11903 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11904 &*isip4&~{*&<&'string'&>&*}*& &&&
11905 &*isip6&~{*&<&'string'&>&*}*&
11906 .cindex "IP address" "testing string format"
11907 .cindex "string" "testing for IP address"
11908 .cindex "&%isip%& expansion condition"
11909 .cindex "&%isip4%& expansion condition"
11910 .cindex "&%isip6%& expansion condition"
11911 The substring is first expanded, and then tested to see if it has the form of
11912 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11913 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11915 For an IPv4 address, the test is for four dot-separated components, each of
11916 which consists of from one to three digits. For an IPv6 address, up to eight
11917 colon-separated components are permitted, each containing from one to four
11918 hexadecimal digits. There may be fewer than eight components if an empty
11919 component (adjacent colons) is present. Only one empty component is permitted.
11921 &*Note*&: The checks used to be just on the form of the address; actual numerical
11922 values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
11924 This is no longer the case.
11926 The main use of these tests is to distinguish between IP addresses and
11927 host names, or between IPv4 and IPv6 addresses. For example, you could use
11929 ${if isip4{$sender_host_address}...
11931 to test which IP version an incoming SMTP connection is using.
11933 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11934 .cindex "LDAP" "use for authentication"
11935 .cindex "expansion" "LDAP authentication test"
11936 .cindex "&%ldapauth%& expansion condition"
11937 This condition supports user authentication using LDAP. See section
11938 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11939 queries. For this use, the query must contain a user name and password. The
11940 query itself is not used, and can be empty. The condition is true if the
11941 password is not empty, and the user name and password are accepted by the LDAP
11942 server. An empty password is rejected without calling LDAP because LDAP binds
11943 with an empty password are considered anonymous regardless of the username, and
11944 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11945 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11949 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11950 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11951 .cindex "string" "comparison"
11952 .cindex "expansion" "string comparison"
11953 .cindex "&%le%& expansion condition"
11954 .cindex "&%lei%& expansion condition"
11955 The two substrings are first expanded. The condition is true if the first
11956 string is lexically less than or equal to the second string. For &%le%& the
11957 comparison includes the case of letters, whereas for &%lei%& the comparison is
11959 Case and collation order are defined per the system C locale.
11961 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11962 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11963 .cindex "string" "comparison"
11964 .cindex "expansion" "string comparison"
11965 .cindex "&%lt%& expansion condition"
11966 .cindex "&%lti%& expansion condition"
11967 The two substrings are first expanded. The condition is true if the first
11968 string is lexically less than the second string. For &%lt%& the comparison
11969 includes the case of letters, whereas for &%lti%& the comparison is
11971 Case and collation order are defined per the system C locale.
11974 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11975 .cindex "expansion" "regular expression comparison"
11976 .cindex "regular expressions" "match in expanded string"
11977 .cindex "&%match%& expansion condition"
11978 The two substrings are first expanded. The second is then treated as a regular
11979 expression and applied to the first. Because of the pre-expansion, if the
11980 regular expression contains dollar, or backslash characters, they must be
11981 escaped. Care must also be taken if the regular expression contains braces
11982 (curly brackets). A closing brace must be escaped so that it is not taken as a
11983 premature termination of <&'string2'&>. The easiest approach is to use the
11984 &`\N`& feature to disable expansion of the regular expression.
11987 ${if match {$local_part}{\N^\d{3}\N} ...
11989 If the whole expansion string is in double quotes, further escaping of
11990 backslashes is also required.
11992 The condition is true if the regular expression match succeeds.
11993 The regular expression is not required to begin with a circumflex
11994 metacharacter, but if there is no circumflex, the expression is not anchored,
11995 and it may match anywhere in the subject, not just at the start. If you want
11996 the pattern to match at the end of the subject, you must include the &`$`&
11997 metacharacter at an appropriate point.
11998 All character handling is done in bytes and is not UTF-8 aware,
11999 but we might change this in a future Exim release.
12001 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
12002 At the start of an &%if%& expansion the values of the numeric variable
12003 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
12004 succeeds causes them to be reset to the substrings of that condition and they
12005 will have these values during the expansion of the success string. At the end
12006 of the &%if%& expansion, the previous values are restored. After testing a
12007 combination of conditions using &%or%&, the subsequent values of the numeric
12008 variables are those of the condition that succeeded.
12010 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12011 .cindex "&%match_address%& expansion condition"
12012 See &*match_local_part*&.
12014 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12015 .cindex "&%match_domain%& expansion condition"
12016 See &*match_local_part*&.
12018 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12019 .cindex "&%match_ip%& expansion condition"
12020 This condition matches an IP address to a list of IP address patterns. It must
12021 be followed by two argument strings. The first (after expansion) must be an IP
12022 address or an empty string. The second (not expanded) is a restricted host
12023 list that can match only an IP address, not a host name. For example:
12025 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
12027 The specific types of host list item that are permitted in the list are:
12030 An IP address, optionally with a CIDR mask.
12032 A single asterisk, which matches any IP address.
12034 An empty item, which matches only if the IP address is empty. This could be
12035 useful for testing for a locally submitted message or one from specific hosts
12036 in a single test such as
12037 . ==== As this is a nested list, any displays it contains must be indented
12038 . ==== as otherwise they are too far to the left. This comment applies to
12039 . ==== the use of xmlto plus fop. There's no problem when formatting with
12040 . ==== sdop, with or without the extra indent.
12042 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
12044 where the first item in the list is the empty string.
12046 The item @[] matches any of the local host's interface addresses.
12048 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
12049 even if &`net-`& is not specified. There is never any attempt to turn the IP
12050 address into a host name. The most common type of linear search for
12051 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
12052 masks. For example:
12054 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
12056 It is of course possible to use other kinds of lookup, and in such a case, you
12057 do need to specify the &`net-`& prefix if you want to specify a specific
12058 address mask, for example:
12060 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
12062 However, unless you are combining a &%match_ip%& condition with others, it is
12063 just as easy to use the fact that a lookup is itself a condition, and write:
12065 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
12069 Note that <&'string2'&> is not itself subject to string expansion, unless
12070 Exim was built with the EXPAND_LISTMATCH_RHS option.
12072 Consult section &<<SECThoslispatip>>& for further details of these patterns.
12074 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12075 .cindex "domain list" "in expansion condition"
12076 .cindex "address list" "in expansion condition"
12077 .cindex "local part" "list, in expansion condition"
12078 .cindex "&%match_local_part%& expansion condition"
12079 This condition, together with &%match_address%& and &%match_domain%&, make it
12080 possible to test domain, address, and local part lists within expansions. Each
12081 condition requires two arguments: an item and a list to match. A trivial
12084 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
12086 In each case, the second argument may contain any of the allowable items for a
12087 list of the appropriate type. Also, because the second argument
12088 is a standard form of list, it is possible to refer to a named list.
12089 Thus, you can use conditions like this:
12091 ${if match_domain{$domain}{+local_domains}{...
12093 .cindex "&`+caseful`&"
12094 For address lists, the matching starts off caselessly, but the &`+caseful`&
12095 item can be used, as in all address lists, to cause subsequent items to
12096 have their local parts matched casefully. Domains are always matched
12099 Note that <&'string2'&> is not itself subject to string expansion, unless
12100 Exim was built with the EXPAND_LISTMATCH_RHS option.
12102 &*Note*&: Host lists are &'not'& supported in this way. This is because
12103 hosts have two identities: a name and an IP address, and it is not clear
12104 how to specify cleanly how such a test would work. However, IP addresses can be
12105 matched using &%match_ip%&.
12107 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
12108 .cindex "PAM authentication"
12109 .cindex "AUTH" "with PAM"
12110 .cindex "Solaris" "PAM support"
12111 .cindex "expansion" "PAM authentication test"
12112 .cindex "&%pam%& expansion condition"
12113 &'Pluggable Authentication Modules'&
12114 (&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
12115 available in the latest releases of Solaris and in some GNU/Linux
12116 distributions. The Exim support, which is intended for use in conjunction with
12117 the SMTP AUTH command, is available only if Exim is compiled with
12121 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
12122 in some releases of GNU/Linux &%-ldl%& is also needed.
12124 The argument string is first expanded, and the result must be a
12125 colon-separated list of strings. Leading and trailing white space is ignored.
12126 The PAM module is initialized with the service name &"exim"& and the user name
12127 taken from the first item in the colon-separated data string (<&'string1'&>).
12128 The remaining items in the data string are passed over in response to requests
12129 from the authentication function. In the simple case there will only be one
12130 request, for a password, so the data consists of just two strings.
12132 There can be problems if any of the strings are permitted to contain colon
12133 characters. In the usual way, these have to be doubled to avoid being taken as
12135 The &%listquote%& expansion item can be used for this.
12136 For example, the configuration
12137 of a LOGIN authenticator might contain this setting:
12139 server_condition = ${if pam{$auth1:${listquote{:}{$auth2}}}}
12141 In some operating systems, PAM authentication can be done only from a process
12142 running as root. Since Exim is running as the Exim user when receiving
12143 messages, this means that PAM cannot be used directly in those systems.
12144 . --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that
12147 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
12148 .cindex "&'pwcheck'& daemon"
12150 .cindex "expansion" "&'pwcheck'& authentication test"
12151 .cindex "&%pwcheck%& expansion condition"
12152 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
12153 This is one way of making it possible for passwords to be checked by a process
12154 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
12155 deprecated. Its replacement is &'saslauthd'& (see below).
12157 The pwcheck support is not included in Exim by default. You need to specify
12158 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
12159 building Exim. For example:
12161 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
12163 You do not need to install the full Cyrus software suite in order to use
12164 the pwcheck daemon. You can compile and install just the daemon alone
12165 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
12166 access to the &_/var/pwcheck_& directory.
12168 The &%pwcheck%& condition takes one argument, which must be the user name and
12169 password, separated by a colon. For example, in a LOGIN authenticator
12170 configuration, you might have this:
12172 server_condition = ${if pwcheck{$auth1:$auth2}}
12174 Again, for a PLAIN authenticator configuration, this would be:
12176 server_condition = ${if pwcheck{$auth2:$auth3}}
12178 .vitem &*queue_running*&
12179 .cindex "queue runner" "detecting when delivering from"
12180 .cindex "expansion" "queue runner test"
12181 .cindex "&%queue_running%& expansion condition"
12182 This condition, which has no data, is true during delivery attempts that are
12183 initiated by queue runner processes, and false otherwise.
12186 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
12188 .cindex "expansion" "Radius authentication"
12189 .cindex "&%radius%& expansion condition"
12190 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
12191 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
12192 the Radius client configuration file in order to build Exim with Radius
12195 With just that one setting, Exim expects to be linked with the &%radiusclient%&
12196 library, using the original API. If you are using release 0.4.0 or later of
12197 this library, you need to set
12199 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
12201 in &_Local/Makefile_& when building Exim. You can also link Exim with the
12202 &%libradius%& library that comes with FreeBSD. To do this, set
12204 RADIUS_LIB_TYPE=RADLIB
12206 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
12207 You may also have to supply a suitable setting in EXTRALIBS so that the
12208 Radius library can be found when Exim is linked.
12210 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
12211 Radius client library, which calls the Radius server. The condition is true if
12212 the authentication is successful. For example:
12214 server_condition = ${if radius{<arguments>}}
12218 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
12219 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
12220 .cindex "&'saslauthd'& daemon"
12222 .cindex "expansion" "&'saslauthd'& authentication test"
12223 .cindex "&%saslauthd%& expansion condition"
12224 This condition supports user authentication using the Cyrus &'saslauthd'&
12225 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
12226 Using this daemon is one way of making it possible for passwords to be checked
12227 by a process that is not running as root.
12229 The saslauthd support is not included in Exim by default. You need to specify
12230 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
12231 building Exim. For example:
12233 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
12235 You do not need to install the full Cyrus software suite in order to use
12236 the saslauthd daemon. You can compile and install just the daemon alone
12237 from the Cyrus SASL library.
12239 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
12240 two are mandatory. For example:
12242 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
12244 The service and the realm are optional (which is why the arguments are enclosed
12245 in their own set of braces). For details of the meaning of the service and
12246 realm, and how to run the daemon, consult the Cyrus documentation.
12251 .section "Combining expansion conditions" "SECID84"
12252 .cindex "expansion" "combining conditions"
12253 Several conditions can be tested at once by combining them using the &%and%&
12254 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
12255 conditions on their own, and precede their lists of sub-conditions. Each
12256 sub-condition must be enclosed in braces within the overall braces that contain
12257 the list. No repetition of &%if%& is used.
12261 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12262 .cindex "&""or""& expansion condition"
12263 .cindex "expansion" "&""or""& of conditions"
12264 The sub-conditions are evaluated from left to right. The condition is true if
12265 any one of the sub-conditions is true.
12268 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
12270 When a true sub-condition is found, the following ones are parsed but not
12271 evaluated. If there are several &"match"& sub-conditions the values of the
12272 numeric variables afterwards are taken from the first one that succeeds.
12274 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12275 .cindex "&""and""& expansion condition"
12276 .cindex "expansion" "&""and""& of conditions"
12277 The sub-conditions are evaluated from left to right. The condition is true if
12278 all of the sub-conditions are true. If there are several &"match"&
12279 sub-conditions, the values of the numeric variables afterwards are taken from
12280 the last one. When a false sub-condition is found, the following ones are
12281 parsed but not evaluated.
12283 .ecindex IIDexpcond
12288 .section "Expansion variables" "SECTexpvar"
12289 .cindex "expansion" "variables, list of"
12290 This section contains an alphabetical list of all the expansion variables. Some
12291 of them are available only when Exim is compiled with specific options such as
12292 support for TLS or the content scanning extension.
12295 .vitem "&$0$&, &$1$&, etc"
12296 .cindex "numerical variables (&$1$& &$2$& etc)"
12297 When a &%match%& expansion condition succeeds, these variables contain the
12298 captured substrings identified by the regular expression during subsequent
12299 processing of the success string of the containing &%if%& expansion item.
12300 In the expansion condition case
12301 they do not retain their values afterwards; in fact, their previous
12302 values are restored at the end of processing an &%if%& item. The numerical
12303 variables may also be set externally by some other matching process which
12304 precedes the expansion of the string. For example, the commands available in
12305 Exim filter files include an &%if%& command with its own regular expression
12306 matching condition.
12308 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
12309 Within an acl condition, expansion condition or expansion item
12310 any arguments are copied to these variables,
12311 any unused variables being made empty.
12313 .vitem "&$acl_c...$&"
12314 Values can be placed in these variables by the &%set%& modifier in an ACL. They
12315 can be given any name that starts with &$acl_c$& and is at least six characters
12316 long, but the sixth character must be either a digit or an underscore. For
12317 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
12318 variables persist throughout the lifetime of an SMTP connection. They can be
12319 used to pass information between ACLs and between different invocations of the
12320 same ACL. When a message is received, the values of these variables are saved
12321 with the message, and can be accessed by filters, routers, and transports
12322 during subsequent delivery.
12324 .vitem "&$acl_m...$&"
12325 These variables are like the &$acl_c...$& variables, except that their values
12326 are reset after a message has been received. Thus, if several messages are
12327 received in one SMTP connection, &$acl_m...$& values are not passed on from one
12328 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
12329 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
12330 message is received, the values of these variables are saved with the message,
12331 and can be accessed by filters, routers, and transports during subsequent
12334 .vitem &$acl_narg$&
12335 Within an acl condition, expansion condition or expansion item
12336 this variable has the number of arguments.
12338 .vitem &$acl_verify_message$&
12339 .vindex "&$acl_verify_message$&"
12340 After an address verification has failed, this variable contains the failure
12341 message. It retains its value for use in subsequent modifiers of the verb.
12342 The message can be preserved by coding like this:
12344 warn !verify = sender
12345 set acl_m0 = $acl_verify_message
12347 You can use &$acl_verify_message$& during the expansion of the &%message%& or
12348 &%log_message%& modifiers, to include information about the verification
12351 &*Note*&: The variable is cleared at the end of processing the ACL verb.
12354 .vitem &$address_data$&
12355 .vindex "&$address_data$&"
12356 This variable is set by means of the &%address_data%& option in routers. The
12357 value then remains with the address while it is processed by subsequent routers
12358 and eventually a transport. If the transport is handling multiple addresses,
12359 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
12360 for more details. &*Note*&: The contents of &$address_data$& are visible in
12363 If &$address_data$& is set when the routers are called from an ACL to verify
12364 a recipient address, the final value is still in the variable for subsequent
12365 conditions and modifiers of the ACL statement. If routing the address caused it
12366 to be redirected to just one address, the child address is also routed as part
12367 of the verification, and in this case the final value of &$address_data$& is
12368 from the child's routing.
12370 If &$address_data$& is set when the routers are called from an ACL to verify a
12371 sender address, the final value is also preserved, but this time in
12372 &$sender_address_data$&, to distinguish it from data from a recipient
12375 In both cases (recipient and sender verification), the value does not persist
12376 after the end of the current ACL statement. If you want to preserve
12377 these values for longer, you can save them in ACL variables.
12379 .vitem &$address_file$&
12380 .vindex "&$address_file$&"
12381 When, as a result of aliasing, forwarding, or filtering, a message is directed
12382 to a specific file, this variable holds the name of the file when the transport
12383 is running. At other times, the variable is empty. For example, using the
12384 default configuration, if user &%r2d2%& has a &_.forward_& file containing
12386 /home/r2d2/savemail
12388 then when the &(address_file)& transport is running, &$address_file$&
12389 contains the text string &`/home/r2d2/savemail`&.
12390 .cindex "Sieve filter" "value of &$address_file$&"
12391 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
12392 then up to the transport configuration to generate an appropriate absolute path
12393 to the relevant file.
12395 .vitem &$address_pipe$&
12396 .vindex "&$address_pipe$&"
12397 When, as a result of aliasing or forwarding, a message is directed to a pipe,
12398 this variable holds the pipe command when the transport is running.
12400 .vitem "&$auth1$& &-- &$auth4$&"
12401 .vindex "&$auth1$&, &$auth2$&, etc"
12402 These variables are used in SMTP authenticators (see chapters
12403 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
12405 .vitem &$authenticated_id$&
12406 .cindex "authentication" "id"
12407 .vindex "&$authenticated_id$&"
12408 When a server successfully authenticates a client it may be configured to
12409 preserve some of the authentication information in the variable
12410 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
12411 user/password authenticator configuration might preserve the user name for use
12412 in the routers. Note that this is not the same information that is saved in
12413 &$sender_host_authenticated$&.
12415 When a message is submitted locally (that is, not over a TCP connection)
12416 the value of &$authenticated_id$& is normally the login name of the calling
12417 process. However, a trusted user can override this by means of the &%-oMai%&
12418 command line option.
12419 This second case also sets up information used by the
12420 &$authresults$& expansion item.
12422 .vitem &$authenticated_fail_id$&
12423 .cindex "authentication" "fail" "id"
12424 .vindex "&$authenticated_fail_id$&"
12425 When an authentication attempt fails, the variable &$authenticated_fail_id$&
12426 will contain the failed authentication id. If more than one authentication
12427 id is attempted, it will contain only the last one. The variable is
12428 available for processing in the ACL's, generally the quit or notquit ACL.
12429 A message to a local recipient could still be accepted without requiring
12430 authentication, which means this variable could also be visible in all of
12434 .vitem &$authenticated_sender$&
12435 .cindex "sender" "authenticated"
12436 .cindex "authentication" "sender"
12437 .cindex "AUTH" "on MAIL command"
12438 .vindex "&$authenticated_sender$&"
12439 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
12440 SMTP MAIL command if it believes the sender is sufficiently trusted, as
12441 described in section &<<SECTauthparamail>>&. Unless the data is the string
12442 &"<>"&, it is set as the authenticated sender of the message, and the value is
12443 available during delivery in the &$authenticated_sender$& variable. If the
12444 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
12446 .vindex "&$qualify_domain$&"
12447 When a message is submitted locally (that is, not over a TCP connection), the
12448 value of &$authenticated_sender$& is an address constructed from the login
12449 name of the calling process and &$qualify_domain$&, except that a trusted user
12450 can override this by means of the &%-oMas%& command line option.
12453 .vitem &$authentication_failed$&
12454 .cindex "authentication" "failure"
12455 .vindex "&$authentication_failed$&"
12456 This variable is set to &"1"& in an Exim server if a client issues an AUTH
12457 command that does not succeed. Otherwise it is set to &"0"&. This makes it
12458 possible to distinguish between &"did not try to authenticate"&
12459 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
12460 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
12461 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
12462 negative response to an AUTH command, including (for example) an attempt to use
12463 an undefined mechanism.
12465 .vitem &$av_failed$&
12466 .cindex "content scanning" "AV scanner failure"
12467 This variable is available when Exim is compiled with the content-scanning
12468 extension. It is set to &"0"& by default, but will be set to &"1"& if any
12469 problem occurs with the virus scanner (specified by &%av_scanner%&) during
12470 the ACL malware condition.
12472 .vitem &$body_linecount$&
12473 .cindex "message body" "line count"
12474 .cindex "body of message" "line count"
12475 .vindex "&$body_linecount$&"
12476 When a message is being received or delivered, this variable contains the
12477 number of lines in the message's body. See also &$message_linecount$&.
12479 .vitem &$body_zerocount$&
12480 .cindex "message body" "binary zero count"
12481 .cindex "body of message" "binary zero count"
12482 .cindex "binary zero" "in message body"
12483 .vindex "&$body_zerocount$&"
12484 When a message is being received or delivered, this variable contains the
12485 number of binary zero bytes (ASCII NULs) in the message's body.
12487 .vitem &$bounce_recipient$&
12488 .vindex "&$bounce_recipient$&"
12489 This is set to the recipient address of a bounce message while Exim is creating
12490 it. It is useful if a customized bounce message text file is in use (see
12491 chapter &<<CHAPemsgcust>>&).
12493 .vitem &$bounce_return_size_limit$&
12494 .vindex "&$bounce_return_size_limit$&"
12495 This contains the value set in the &%bounce_return_size_limit%& option, rounded
12496 up to a multiple of 1000. It is useful when a customized error message text
12497 file is in use (see chapter &<<CHAPemsgcust>>&).
12499 .vitem &$caller_gid$&
12500 .cindex "gid (group id)" "caller"
12501 .vindex "&$caller_gid$&"
12502 The real group id under which the process that called Exim was running. This is
12503 not the same as the group id of the originator of a message (see
12504 &$originator_gid$&). If Exim re-execs itself, this variable in the new
12505 incarnation normally contains the Exim gid.
12507 .vitem &$caller_uid$&
12508 .cindex "uid (user id)" "caller"
12509 .vindex "&$caller_uid$&"
12510 The real user id under which the process that called Exim was running. This is
12511 not the same as the user id of the originator of a message (see
12512 &$originator_uid$&). If Exim re-execs itself, this variable in the new
12513 incarnation normally contains the Exim uid.
12515 .vitem &$callout_address$&
12516 .vindex "&$callout_address$&"
12517 After a callout for verification, spamd or malware daemon service, the
12518 address that was connected to.
12520 .vitem &$compile_number$&
12521 .vindex "&$compile_number$&"
12522 The building process for Exim keeps a count of the number
12523 of times it has been compiled. This serves to distinguish different
12524 compilations of the same version of Exim.
12526 .vitem &$config_dir$&
12527 .vindex "&$config_dir$&"
12528 The directory name of the main configuration file. That is, the content of
12529 &$config_file$& with the last component stripped. The value does not
12530 contain the trailing slash. If &$config_file$& does not contain a slash,
12531 &$config_dir$& is ".".
12533 .vitem &$config_file$&
12534 .vindex "&$config_file$&"
12535 The name of the main configuration file Exim is using.
12537 .vitem &$dkim_verify_status$&
12538 Results of DKIM verification.
12539 For details see section &<<SECDKIMVFY>>&.
12541 .vitem &$dkim_cur_signer$& &&&
12542 &$dkim_verify_reason$& &&&
12543 &$dkim_domain$& &&&
12544 &$dkim_identity$& &&&
12545 &$dkim_selector$& &&&
12547 &$dkim_canon_body$& &&&
12548 &$dkim_canon_headers$& &&&
12549 &$dkim_copiedheaders$& &&&
12550 &$dkim_bodylength$& &&&
12551 &$dkim_created$& &&&
12552 &$dkim_expires$& &&&
12553 &$dkim_headernames$& &&&
12554 &$dkim_key_testing$& &&&
12555 &$dkim_key_nosubdomains$& &&&
12556 &$dkim_key_srvtype$& &&&
12557 &$dkim_key_granularity$& &&&
12558 &$dkim_key_notes$& &&&
12559 &$dkim_key_length$&
12560 These variables are only available within the DKIM ACL.
12561 For details see section &<<SECDKIMVFY>>&.
12563 .vitem &$dkim_signers$&
12564 .vindex &$dkim_signers$&
12565 When a message has been received this variable contains
12566 a colon-separated list of signer domains and identities for the message.
12567 For details see section &<<SECDKIMVFY>>&.
12569 .vitem &$dmarc_domain_policy$& &&&
12570 &$dmarc_status$& &&&
12571 &$dmarc_status_text$& &&&
12572 &$dmarc_used_domains$&
12573 Results of DMARC verification.
12574 For details see section &<<SECDMARC>>&.
12576 .vitem &$dnslist_domain$& &&&
12577 &$dnslist_matched$& &&&
12578 &$dnslist_text$& &&&
12580 .vindex "&$dnslist_domain$&"
12581 .vindex "&$dnslist_matched$&"
12582 .vindex "&$dnslist_text$&"
12583 .vindex "&$dnslist_value$&"
12584 .cindex "black list (DNS)"
12585 When a DNS (black) list lookup succeeds, these variables are set to contain
12586 the following data from the lookup: the list's domain name, the key that was
12587 looked up, the contents of any associated TXT record, and the value from the
12588 main A record. See section &<<SECID204>>& for more details.
12591 .vindex "&$domain$&"
12592 When an address is being routed, or delivered on its own, this variable
12593 contains the domain. Uppercase letters in the domain are converted into lower
12594 case for &$domain$&.
12596 Global address rewriting happens when a message is received, so the value of
12597 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
12598 is set during user filtering, but not during system filtering, because a
12599 message may have many recipients and the system filter is called just once.
12601 When more than one address is being delivered at once (for example, several
12602 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
12603 have the same domain. Transports can be restricted to handling only one domain
12604 at a time if the value of &$domain$& is required at transport time &-- this is
12605 the default for local transports. For further details of the environment in
12606 which local transports are run, see chapter &<<CHAPenvironment>>&.
12608 .oindex "&%delay_warning_condition%&"
12609 At the end of a delivery, if all deferred addresses have the same domain, it is
12610 set in &$domain$& during the expansion of &%delay_warning_condition%&.
12612 The &$domain$& variable is also used in some other circumstances:
12615 When an ACL is running for a RCPT command, &$domain$& contains the domain of
12616 the recipient address. The domain of the &'sender'& address is in
12617 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
12618 normally set during the running of the MAIL ACL. However, if the sender address
12619 is verified with a callout during the MAIL ACL, the sender domain is placed in
12620 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
12621 the &(smtp)& transport.
12624 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12625 &$domain$& contains the domain portion of the address that is being rewritten;
12626 it can be used in the expansion of the replacement address, for example, to
12627 rewrite domains by file lookup.
12630 With one important exception, whenever a domain list is being scanned,
12631 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
12632 a &%sender_domains%& condition in an ACL is being processed, the subject domain
12633 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
12634 that, in a RCPT ACL, the sender domain list can be dependent on the
12635 recipient domain (which is what is in &$domain$& at this time).
12638 .cindex "ETRN" "value of &$domain$&"
12639 .oindex "&%smtp_etrn_command%&"
12640 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
12641 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
12644 .cindex "tainted data"
12645 If the origin of the data is an incoming message,
12646 the result of expanding this variable is tainted and may not
12647 be further expanded or used as a filename.
12648 When an untainted version is needed, one should be obtained from
12649 looking up the value in a local (therefore trusted) database.
12650 Often &$domain_data$& is usable in this role.
12653 .vitem &$domain_data$&
12654 .vindex "&$domain_data$&"
12655 When the &%domains%& condition on a router
12659 against a list, the match value is copied to &$domain_data$&.
12660 This is an enhancement over previous versions of Exim, when it only
12661 applied to the data read by a lookup.
12662 For details on match values see section &<<SECTlistresults>>& et. al.
12665 If the router routes the
12666 address to a transport, the value is available in that transport. If the
12667 transport is handling multiple addresses, the value from the first address is
12670 &$domain_data$& set in an ACL is available during
12671 the rest of the ACL statement.
12673 .vitem &$exim_gid$&
12674 .vindex "&$exim_gid$&"
12675 This variable contains the numerical value of the Exim group id.
12677 .vitem &$exim_path$&
12678 .vindex "&$exim_path$&"
12679 This variable contains the path to the Exim binary.
12681 .vitem &$exim_uid$&
12682 .vindex "&$exim_uid$&"
12683 This variable contains the numerical value of the Exim user id.
12685 .vitem &$exim_version$&
12686 .vindex "&$exim_version$&"
12687 This variable contains the version string of the Exim build.
12688 The first character is a major version number, currently 4.
12689 Then after a dot, the next group of digits is a minor version number.
12690 There may be other characters following the minor version.
12691 This value may be overridden by the &%exim_version%& main config option.
12693 .vitem &$header_$&<&'name'&>
12694 This is not strictly an expansion variable. It is expansion syntax for
12695 inserting the message header line with the given name. Note that the name must
12696 be terminated by colon or white space, because it may contain a wide variety of
12697 characters. Note also that braces must &'not'& be used.
12698 See the full description in section &<<SECTexpansionitems>>& above.
12700 .vitem &$headers_added$&
12701 .vindex "&$headers_added$&"
12702 Within an ACL this variable contains the headers added so far by
12703 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
12704 The headers are a newline-separated list.
12708 When the &%check_local_user%& option is set for a router, the user's home
12709 directory is placed in &$home$& when the check succeeds. In particular, this
12710 means it is set during the running of users' filter files. A router may also
12711 explicitly set a home directory for use by a transport; this can be overridden
12712 by a setting on the transport itself.
12714 When running a filter test via the &%-bf%& option, &$home$& is set to the value
12715 of the environment variable HOME, which is subject to the
12716 &%keep_environment%& and &%add_environment%& main config options.
12720 If a router assigns an address to a transport (any transport), and passes a
12721 list of hosts with the address, the value of &$host$& when the transport starts
12722 to run is the name of the first host on the list. Note that this applies both
12723 to local and remote transports.
12725 .cindex "transport" "filter"
12726 .cindex "filter" "transport filter"
12727 For the &(smtp)& transport, if there is more than one host, the value of
12728 &$host$& changes as the transport works its way through the list. In
12729 particular, when the &(smtp)& transport is expanding its options for encryption
12730 using TLS, or for specifying a transport filter (see chapter
12731 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
12734 When used in the client part of an authenticator configuration (see chapter
12735 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
12736 client is connected.
12739 .vitem &$host_address$&
12740 .vindex "&$host_address$&"
12741 This variable is set to the remote host's IP address whenever &$host$& is set
12742 for a remote connection. It is also set to the IP address that is being checked
12743 when the &%ignore_target_hosts%& option is being processed.
12745 .vitem &$host_data$&
12746 .vindex "&$host_data$&"
12747 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
12748 result of the lookup is made available in the &$host_data$& variable. This
12749 allows you, for example, to do things like this:
12751 deny hosts = net-lsearch;/some/file
12752 message = $host_data
12754 .vitem &$host_lookup_deferred$&
12755 .cindex "host name" "lookup, failure of"
12756 .vindex "&$host_lookup_deferred$&"
12757 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
12758 message comes from a remote host and there is an attempt to look up the host's
12759 name from its IP address, and the attempt is not successful, one of these
12760 variables is set to &"1"&.
12763 If the lookup receives a definite negative response (for example, a DNS lookup
12764 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
12767 If there is any kind of problem during the lookup, such that Exim cannot
12768 tell whether or not the host name is defined (for example, a timeout for a DNS
12769 lookup), &$host_lookup_deferred$& is set to &"1"&.
12772 Looking up a host's name from its IP address consists of more than just a
12773 single reverse lookup. Exim checks that a forward lookup of at least one of the
12774 names it receives from a reverse lookup yields the original IP address. If this
12775 is not the case, Exim does not accept the looked up name(s), and
12776 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
12777 IP address (for example, the existence of a PTR record in the DNS) is not
12778 sufficient on its own for the success of a host name lookup. If the reverse
12779 lookup succeeds, but there is a lookup problem such as a timeout when checking
12780 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
12781 &"1"&. See also &$sender_host_name$&.
12783 .cindex authentication "expansion item"
12784 Performing these checks sets up information used by the
12785 &%authresults%& expansion item.
12788 .vitem &$host_lookup_failed$&
12789 .vindex "&$host_lookup_failed$&"
12790 See &$host_lookup_deferred$&.
12792 .vitem &$host_port$&
12793 .vindex "&$host_port$&"
12794 This variable is set to the remote host's TCP port whenever &$host$& is set
12795 for an outbound connection.
12797 .vitem &$initial_cwd$&
12798 .vindex "&$initial_cwd$&
12799 This variable contains the full path name of the initial working
12800 directory of the current Exim process. This may differ from the current
12801 working directory, as Exim changes this to "/" during early startup, and
12802 to &$spool_directory$& later.
12805 .vindex "&$inode$&"
12806 The only time this variable is set is while expanding the &%directory_file%&
12807 option in the &(appendfile)& transport. The variable contains the inode number
12808 of the temporary file which is about to be renamed. It can be used to construct
12809 a unique name for the file.
12811 .vitem &$interface_address$& &&&
12813 .vindex "&$interface_address$&"
12814 .vindex "&$interface_port$&"
12815 These are ebsolete names for &$received_ip_address$& and &$received_port$&.
12819 This variable is used during the expansion of &*forall*& and &*forany*&
12820 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
12821 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
12825 .vindex "&$ldap_dn$&"
12826 This variable, which is available only when Exim is compiled with LDAP support,
12827 contains the DN from the last entry in the most recently successful LDAP
12830 .vitem &$load_average$&
12831 .vindex "&$load_average$&"
12832 This variable contains the system load average, multiplied by 1000 so that it
12833 is an integer. For example, if the load average is 0.21, the value of the
12834 variable is 210. The value is recomputed every time the variable is referenced.
12836 .vitem &$local_part$&
12837 .vindex "&$local_part$&"
12838 When an address is being routed, or delivered on its own, this
12839 variable contains the local part. When a number of addresses are being
12840 delivered together (for example, multiple RCPT commands in an SMTP
12841 session), &$local_part$& is not set.
12843 Global address rewriting happens when a message is received, so the value of
12844 &$local_part$& during routing and delivery is the value after rewriting.
12845 &$local_part$& is set during user filtering, but not during system filtering,
12846 because a message may have many recipients and the system filter is called just
12849 .cindex "tainted data"
12850 If the origin of the data is an incoming message,
12851 the result of expanding this variable is tainted and
12852 may not be further expanded or used as a filename.
12854 &*Warning*&: the content of this variable is usually provided by a potential
12856 Consider carefully the implications of using it unvalidated as a name
12858 This presents issues for users' &_.forward_& and filter files.
12859 For traditional full user accounts, use &%check_local_users%& and the
12860 &$local_part_data$& variable rather than this one.
12861 For virtual users, store a suitable pathname component in the database
12862 which is used for account name validation, and use that retrieved value
12863 rather than this variable.
12864 Often &$local_part_data$& is usable in this role.
12865 If needed, use a router &%address_data%& or &%set%& option for
12866 the retrieved data.
12868 When a message is being delivered to a file, pipe, or autoreply transport as a
12869 result of aliasing or forwarding, &$local_part$& is set to the local part of
12870 the parent address, not to the filename or command (see &$address_file$& and
12873 When an ACL is running for a RCPT command, &$local_part$& contains the
12874 local part of the recipient address.
12876 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12877 &$local_part$& contains the local part of the address that is being rewritten;
12878 it can be used in the expansion of the replacement address, for example.
12880 In all cases, all quoting is removed from the local part. For example, for both
12883 "abc:xyz"@test.example
12884 abc\:xyz@test.example
12886 the value of &$local_part$& is
12890 If you use &$local_part$& to create another address, you should always wrap it
12891 inside a quoting operator. For example, in a &(redirect)& router you could
12894 data = ${quote_local_part:$local_part}@new.domain.example
12896 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
12897 to process local parts in a case-dependent manner in a router, you can set the
12898 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
12900 .vitem &$local_part_data$&
12901 .vindex "&$local_part_data$&"
12902 When the &%local_parts%& condition on a router or ACL
12903 matches a local part list
12905 the match value is copied to &$local_part_data$&.
12906 This is an enhancement over previous versions of Exim, when it only
12907 applied to the data read by a lookup.
12908 For details on match values see section &<<SECTlistresults>>& et. al.
12911 The &%check_local_user%& router option also sets this variable.
12913 .vindex &$local_part_prefix$& &&&
12914 &$local_part_prefix_v$& &&&
12915 &$local_part_suffix$& &&&
12916 &$local_part_suffix_v$&
12917 .cindex affix variables
12918 If a local part prefix or suffix has been recognized, it is not included in the
12919 value of &$local_part$& during routing and subsequent delivery. The values of
12920 any prefix or suffix are in &$local_part_prefix$& and
12921 &$local_part_suffix$&, respectively.
12922 .cindex "tainted data"
12923 If the specification did not include a wildcard then
12924 the affix variable value is not tainted.
12926 If the affix specification included a wildcard then the portion of
12927 the affix matched by the wildcard is in
12928 &$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate,
12929 and both the whole and varying values are tainted.
12931 .vitem &$local_scan_data$&
12932 .vindex "&$local_scan_data$&"
12933 This variable contains the text returned by the &[local_scan()]& function when
12934 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
12936 .vitem &$local_user_gid$&
12937 .vindex "&$local_user_gid$&"
12938 See &$local_user_uid$&.
12940 .vitem &$local_user_uid$&
12941 .vindex "&$local_user_uid$&"
12942 This variable and &$local_user_gid$& are set to the uid and gid after the
12943 &%check_local_user%& router precondition succeeds. This means that their values
12944 are available for the remaining preconditions (&%senders%&, &%require_files%&,
12945 and &%condition%&), for the &%address_data%& expansion, and for any
12946 router-specific expansions. At all other times, the values in these variables
12947 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
12949 .vitem &$localhost_number$&
12950 .vindex "&$localhost_number$&"
12951 This contains the expanded value of the
12952 &%localhost_number%& option. The expansion happens after the main options have
12955 .vitem &$log_inodes$&
12956 .vindex "&$log_inodes$&"
12957 The number of free inodes in the disk partition where Exim's
12958 log files are being written. The value is recalculated whenever the variable is
12959 referenced. If the relevant file system does not have the concept of inodes,
12960 the value of is -1. See also the &%check_log_inodes%& option.
12962 .vitem &$log_space$&
12963 .vindex "&$log_space$&"
12964 The amount of free space (as a number of kilobytes) in the disk
12965 partition where Exim's log files are being written. The value is recalculated
12966 whenever the variable is referenced. If the operating system does not have the
12967 ability to find the amount of free space (only true for experimental systems),
12968 the space value is -1. See also the &%check_log_space%& option.
12971 .vitem &$lookup_dnssec_authenticated$&
12972 .vindex "&$lookup_dnssec_authenticated$&"
12973 This variable is set after a DNS lookup done by
12974 a dnsdb lookup expansion, dnslookup router or smtp transport.
12975 .cindex "DNS" "DNSSEC"
12976 It will be empty if &(DNSSEC)& was not requested,
12977 &"no"& if the result was not labelled as authenticated data
12978 and &"yes"& if it was.
12979 Results that are labelled as authoritative answer that match
12980 the &%dns_trust_aa%& configuration variable count also
12981 as authenticated data.
12983 .vitem &$mailstore_basename$&
12984 .vindex "&$mailstore_basename$&"
12985 This variable is set only when doing deliveries in &"mailstore"& format in the
12986 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
12987 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
12988 contains the basename of the files that are being written, that is, the name
12989 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
12992 .vitem &$malware_name$&
12993 .vindex "&$malware_name$&"
12994 This variable is available when Exim is compiled with the
12995 content-scanning extension. It is set to the name of the virus that was found
12996 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12998 .vitem &$max_received_linelength$&
12999 .vindex "&$max_received_linelength$&"
13000 .cindex "maximum" "line length"
13001 .cindex "line length" "maximum"
13002 This variable contains the number of bytes in the longest line that was
13003 received as part of the message, not counting the line termination
13005 It is not valid if the &%spool_wireformat%& option is used.
13007 .vitem &$message_age$&
13008 .cindex "message" "age of"
13009 .vindex "&$message_age$&"
13010 This variable is set at the start of a delivery attempt to contain the number
13011 of seconds since the message was received. It does not change during a single
13014 .vitem &$message_body$&
13015 .cindex "body of message" "expansion variable"
13016 .cindex "message body" "in expansion"
13017 .cindex "binary zero" "in message body"
13018 .vindex "&$message_body$&"
13019 .oindex "&%message_body_visible%&"
13020 This variable contains the initial portion of a message's body while it is
13021 being delivered, and is intended mainly for use in filter files. The maximum
13022 number of characters of the body that are put into the variable is set by the
13023 &%message_body_visible%& configuration option; the default is 500.
13025 .oindex "&%message_body_newlines%&"
13026 By default, newlines are converted into spaces in &$message_body$&, to make it
13027 easier to search for phrases that might be split over a line break. However,
13028 this can be disabled by setting &%message_body_newlines%& to be true. Binary
13029 zeros are always converted into spaces.
13031 .vitem &$message_body_end$&
13032 .cindex "body of message" "expansion variable"
13033 .cindex "message body" "in expansion"
13034 .vindex "&$message_body_end$&"
13035 This variable contains the final portion of a message's
13036 body while it is being delivered. The format and maximum size are as for
13039 .vitem &$message_body_size$&
13040 .cindex "body of message" "size"
13041 .cindex "message body" "size"
13042 .vindex "&$message_body_size$&"
13043 When a message is being delivered, this variable contains the size of the body
13044 in bytes. The count starts from the character after the blank line that
13045 separates the body from the header. Newlines are included in the count. See
13046 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
13048 If the spool file is wireformat
13049 (see the &%spool_wireformat%& main option)
13050 the CRLF line-terminators are included in the count.
13052 .vitem &$message_exim_id$&
13053 .vindex "&$message_exim_id$&"
13054 When a message is being received or delivered, this variable contains the
13055 unique message id that is generated and used by Exim to identify the message.
13056 An id is not created for a message until after its header has been successfully
13057 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
13058 line; it is the local id that Exim assigns to the message, for example:
13059 &`1BXTIK-0001yO-VA`&.
13061 .vitem &$message_headers$&
13062 .vindex &$message_headers$&
13063 This variable contains a concatenation of all the header lines when a message
13064 is being processed, except for lines added by routers or transports. The header
13065 lines are separated by newline characters. Their contents are decoded in the
13066 same way as a header line that is inserted by &%bheader%&.
13068 .vitem &$message_headers_raw$&
13069 .vindex &$message_headers_raw$&
13070 This variable is like &$message_headers$& except that no processing of the
13071 contents of header lines is done.
13073 .vitem &$message_id$&
13074 This is an old name for &$message_exim_id$&. It is now deprecated.
13076 .vitem &$message_linecount$&
13077 .vindex "&$message_linecount$&"
13078 This variable contains the total number of lines in the header and body of the
13079 message. Compare &$body_linecount$&, which is the count for the body only.
13080 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
13081 number of lines received. Before delivery happens (that is, before filters,
13082 routers, and transports run) the count is increased to include the
13083 &'Received:'& header line that Exim standardly adds, and also any other header
13084 lines that are added by ACLs. The blank line that separates the message header
13085 from the body is not counted.
13087 As with the special case of &$message_size$&, during the expansion of the
13088 appendfile transport's maildir_tag option in maildir format, the value of
13089 &$message_linecount$& is the precise size of the number of newlines in the
13090 file that has been written (minus one for the blank line between the
13091 header and the body).
13093 Here is an example of the use of this variable in a DATA ACL:
13096 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
13097 message = Too many lines in message header
13099 In the MAIL and RCPT ACLs, the value is zero because at that stage the
13100 message has not yet been received.
13102 This variable is not valid if the &%spool_wireformat%& option is used.
13104 .vitem &$message_size$&
13105 .cindex "size" "of message"
13106 .cindex "message" "size"
13107 .vindex "&$message_size$&"
13108 When a message is being processed, this variable contains its size in bytes. In
13109 most cases, the size includes those headers that were received with the
13110 message, but not those (such as &'Envelope-to:'&) that are added to individual
13111 deliveries as they are written. However, there is one special case: during the
13112 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
13113 doing a delivery in maildir format, the value of &$message_size$& is the
13114 precise size of the file that has been written. See also
13115 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
13117 .cindex "RCPT" "value of &$message_size$&"
13118 While running a per message ACL (mail/rcpt/predata), &$message_size$&
13119 contains the size supplied on the MAIL command, or -1 if no size was given. The
13120 value may not, of course, be truthful.
13122 .vitem &$mime_anomaly_level$& &&&
13123 &$mime_anomaly_text$& &&&
13124 &$mime_boundary$& &&&
13125 &$mime_charset$& &&&
13126 &$mime_content_description$& &&&
13127 &$mime_content_disposition$& &&&
13128 &$mime_content_id$& &&&
13129 &$mime_content_size$& &&&
13130 &$mime_content_transfer_encoding$& &&&
13131 &$mime_content_type$& &&&
13132 &$mime_decoded_filename$& &&&
13133 &$mime_filename$& &&&
13134 &$mime_is_coverletter$& &&&
13135 &$mime_is_multipart$& &&&
13136 &$mime_is_rfc822$& &&&
13137 &$mime_part_count$&
13138 A number of variables whose names start with &$mime$& are
13139 available when Exim is compiled with the content-scanning extension. For
13140 details, see section &<<SECTscanmimepart>>&.
13142 .vitem "&$n0$& &-- &$n9$&"
13143 These variables are counters that can be incremented by means
13144 of the &%add%& command in filter files.
13146 .vitem &$original_domain$&
13147 .vindex "&$domain$&"
13148 .vindex "&$original_domain$&"
13149 When a top-level address is being processed for delivery, this contains the
13150 same value as &$domain$&. However, if a &"child"& address (for example,
13151 generated by an alias, forward, or filter file) is being processed, this
13152 variable contains the domain of the original address (lower cased). This
13153 differs from &$parent_domain$& only when there is more than one level of
13154 aliasing or forwarding. When more than one address is being delivered in a
13155 single transport run, &$original_domain$& is not set.
13157 If a new address is created by means of a &%deliver%& command in a system
13158 filter, it is set up with an artificial &"parent"& address. This has the local
13159 part &'system-filter'& and the default qualify domain.
13161 .vitem &$original_local_part$&
13162 .vindex "&$local_part$&"
13163 .vindex "&$original_local_part$&"
13164 When a top-level address is being processed for delivery, this contains the
13165 same value as &$local_part$&, unless a prefix or suffix was removed from the
13166 local part, because &$original_local_part$& always contains the full local
13167 part. When a &"child"& address (for example, generated by an alias, forward, or
13168 filter file) is being processed, this variable contains the full local part of
13169 the original address.
13171 If the router that did the redirection processed the local part
13172 case-insensitively, the value in &$original_local_part$& is in lower case.
13173 This variable differs from &$parent_local_part$& only when there is more than
13174 one level of aliasing or forwarding. When more than one address is being
13175 delivered in a single transport run, &$original_local_part$& is not set.
13177 If a new address is created by means of a &%deliver%& command in a system
13178 filter, it is set up with an artificial &"parent"& address. This has the local
13179 part &'system-filter'& and the default qualify domain.
13181 .vitem &$originator_gid$&
13182 .cindex "gid (group id)" "of originating user"
13183 .cindex "sender" "gid"
13184 .vindex "&$caller_gid$&"
13185 .vindex "&$originator_gid$&"
13186 This variable contains the value of &$caller_gid$& that was set when the
13187 message was received. For messages received via the command line, this is the
13188 gid of the sending user. For messages received by SMTP over TCP/IP, this is
13189 normally the gid of the Exim user.
13191 .vitem &$originator_uid$&
13192 .cindex "uid (user id)" "of originating user"
13193 .cindex "sender" "uid"
13194 .vindex "&$caller_uid$&"
13195 .vindex "&$originator_uid$&"
13196 The value of &$caller_uid$& that was set when the message was received. For
13197 messages received via the command line, this is the uid of the sending user.
13198 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
13201 .vitem &$parent_domain$&
13202 .vindex "&$parent_domain$&"
13203 This variable is similar to &$original_domain$& (see
13204 above), except that it refers to the immediately preceding parent address.
13206 .vitem &$parent_local_part$&
13207 .vindex "&$parent_local_part$&"
13208 This variable is similar to &$original_local_part$&
13209 (see above), except that it refers to the immediately preceding parent address.
13212 .cindex "pid (process id)" "of current process"
13214 This variable contains the current process id.
13216 .vitem &$pipe_addresses$&
13217 .cindex "filter" "transport filter"
13218 .cindex "transport" "filter"
13219 .vindex "&$pipe_addresses$&"
13220 This is not an expansion variable, but is mentioned here because the string
13221 &`$pipe_addresses`& is handled specially in the command specification for the
13222 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
13223 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
13224 It cannot be used in general expansion strings, and provokes an &"unknown
13225 variable"& error if encountered.
13227 .vitem &$primary_hostname$&
13228 .vindex "&$primary_hostname$&"
13229 This variable contains the value set by &%primary_hostname%& in the
13230 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
13231 a single-component name, Exim calls &[gethostbyname()]& (or
13232 &[getipnodebyname()]& where available) in an attempt to acquire a fully
13233 qualified host name. See also &$smtp_active_hostname$&.
13236 .vitem &$proxy_external_address$& &&&
13237 &$proxy_external_port$& &&&
13238 &$proxy_local_address$& &&&
13239 &$proxy_local_port$& &&&
13241 These variables are only available when built with Proxy Protocol
13243 For details see chapter &<<SECTproxyInbound>>&.
13245 .vitem &$prdr_requested$&
13246 .cindex "PRDR" "variable for"
13247 This variable is set to &"yes"& if PRDR was requested by the client for the
13248 current message, otherwise &"no"&.
13250 .vitem &$prvscheck_address$& &&&
13251 &$prvscheck_keynum$& &&&
13252 &$prvscheck_result$&
13253 These variables are used in conjunction with the &%prvscheck%& expansion item,
13254 which is described in sections &<<SECTexpansionitems>>& and
13255 &<<SECTverifyPRVS>>&.
13257 .vitem &$qualify_domain$&
13258 .vindex "&$qualify_domain$&"
13259 The value set for the &%qualify_domain%& option in the configuration file.
13261 .vitem &$qualify_recipient$&
13262 .vindex "&$qualify_recipient$&"
13263 The value set for the &%qualify_recipient%& option in the configuration file,
13264 or if not set, the value of &$qualify_domain$&.
13266 .vitem &$queue_name$&
13267 .vindex &$queue_name$&
13268 .cindex "named queues" variable
13269 .cindex queues named
13270 The name of the spool queue in use; empty for the default queue.
13272 .vitem &$queue_size$&
13273 .vindex "&$queue_size$&"
13274 .cindex "queue" "size of"
13275 .cindex "spool" "number of messages"
13276 This variable contains the number of messages queued.
13277 It is evaluated on demand, but no more often than once every minute.
13278 If there is no daemon notifier socket open, the value will be
13283 .cindex router variables
13284 Values can be placed in these variables by the &%set%& option of a router.
13285 They can be given any name that starts with &$r_$&.
13286 The values persist for the address being handled through subsequent routers
13287 and the eventual transport.
13289 .vitem &$rcpt_count$&
13290 .vindex "&$rcpt_count$&"
13291 When a message is being received by SMTP, this variable contains the number of
13292 RCPT commands received for the current message. If this variable is used in a
13293 RCPT ACL, its value includes the current command.
13295 .vitem &$rcpt_defer_count$&
13296 .vindex "&$rcpt_defer_count$&"
13297 .cindex "4&'xx'& responses" "count of"
13298 When a message is being received by SMTP, this variable contains the number of
13299 RCPT commands in the current message that have previously been rejected with a
13300 temporary (4&'xx'&) response.
13302 .vitem &$rcpt_fail_count$&
13303 .vindex "&$rcpt_fail_count$&"
13304 When a message is being received by SMTP, this variable contains the number of
13305 RCPT commands in the current message that have previously been rejected with a
13306 permanent (5&'xx'&) response.
13308 .vitem &$received_count$&
13309 .vindex "&$received_count$&"
13310 This variable contains the number of &'Received:'& header lines in the message,
13311 including the one added by Exim (so its value is always greater than zero). It
13312 is available in the DATA ACL, the non-SMTP ACL, and while routing and
13315 .vitem &$received_for$&
13316 .vindex "&$received_for$&"
13317 If there is only a single recipient address in an incoming message, this
13318 variable contains that address when the &'Received:'& header line is being
13319 built. The value is copied after recipient rewriting has happened, but before
13320 the &[local_scan()]& function is run.
13322 .vitem &$received_ip_address$& &&&
13324 .vindex "&$received_ip_address$&"
13325 .vindex "&$received_port$&"
13326 As soon as an Exim server starts processing an incoming TCP/IP connection, these
13327 variables are set to the address and port on the local IP interface.
13328 (The remote IP address and port are in
13329 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
13330 the port value is -1 unless it has been set using the &%-oMi%& command line
13333 As well as being useful in ACLs (including the &"connect"& ACL), these variable
13334 could be used, for example, to make the filename for a TLS certificate depend
13335 on which interface and/or port is being used for the incoming connection. The
13336 values of &$received_ip_address$& and &$received_port$& are saved with any
13337 messages that are received, thus making these variables available at delivery
13339 For outbound connections see &$sending_ip_address$&.
13341 .vitem &$received_protocol$&
13342 .vindex "&$received_protocol$&"
13343 When a message is being processed, this variable contains the name of the
13344 protocol by which it was received. Most of the names used by Exim are defined
13345 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
13346 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
13347 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
13348 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
13349 connection and the client was successfully authenticated.
13351 Exim uses the protocol name &"smtps"& for the case when encryption is
13352 automatically set up on connection without the use of STARTTLS (see
13353 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
13354 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
13355 where the client initially uses EHLO, sets up an encrypted connection using
13356 STARTTLS, and then uses HELO afterwards.
13358 The &%-oMr%& option provides a way of specifying a custom protocol name for
13359 messages that are injected locally by trusted callers. This is commonly used to
13360 identify messages that are being re-injected after some kind of scanning.
13362 .vitem &$received_time$&
13363 .vindex "&$received_time$&"
13364 This variable contains the date and time when the current message was received,
13365 as a number of seconds since the start of the Unix epoch.
13367 .vitem &$recipient_data$&
13368 .vindex "&$recipient_data$&"
13369 This variable is set after an indexing lookup success in an ACL &%recipients%&
13370 condition. It contains the data from the lookup, and the value remains set
13371 until the next &%recipients%& test. Thus, you can do things like this:
13373 &`require recipients = cdb*@;/some/file`&
13374 &`deny `&&'some further test involving'& &`$recipient_data`&
13376 &*Warning*&: This variable is set only when a lookup is used as an indexing
13377 method in the address list, using the semicolon syntax as in the example above.
13378 The variable is not set for a lookup that is used as part of the string
13379 expansion that all such lists undergo before being interpreted.
13381 .vitem &$recipient_verify_failure$&
13382 .vindex "&$recipient_verify_failure$&"
13383 In an ACL, when a recipient verification fails, this variable contains
13384 information about the failure. It is set to one of the following words:
13387 &"qualify"&: The address was unqualified (no domain), and the message
13388 was neither local nor came from an exempted host.
13391 &"route"&: Routing failed.
13394 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
13395 or before the MAIL command (that is, on initial connection, HELO, or
13399 &"recipient"&: The RCPT command in a callout was rejected.
13402 &"postmaster"&: The postmaster check in a callout was rejected.
13405 The main use of this variable is expected to be to distinguish between
13406 rejections of MAIL and rejections of RCPT.
13408 .vitem &$recipients$&
13409 .vindex "&$recipients$&"
13410 This variable contains a list of envelope recipients for a message. A comma and
13411 a space separate the addresses in the replacement text. However, the variable
13412 is not generally available, to prevent exposure of Bcc recipients in
13413 unprivileged users' filter files. You can use &$recipients$& only in these
13417 In a system filter file.
13419 In the ACLs associated with the DATA command and with non-SMTP messages, that
13420 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
13421 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
13422 &%acl_not_smtp_mime%&.
13424 From within a &[local_scan()]& function.
13428 .vitem &$recipients_count$&
13429 .vindex "&$recipients_count$&"
13430 When a message is being processed, this variable contains the number of
13431 envelope recipients that came with the message. Duplicates are not excluded
13432 from the count. While a message is being received over SMTP, the number
13433 increases for each accepted recipient. It can be referenced in an ACL.
13436 .vitem &$regex_match_string$&
13437 .vindex "&$regex_match_string$&"
13438 This variable is set to contain the matching regular expression after a
13439 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
13441 .vitem "&$regex1$&, &$regex2$&, etc"
13442 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
13443 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
13444 these variables contain the
13445 captured substrings identified by the regular expression.
13448 .vitem &$reply_address$&
13449 .vindex "&$reply_address$&"
13450 When a message is being processed, this variable contains the contents of the
13451 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
13452 contents of the &'From:'& header line. Apart from the removal of leading
13453 white space, the value is not processed in any way. In particular, no RFC 2047
13454 decoding or character code translation takes place.
13456 .vitem &$return_path$&
13457 .vindex "&$return_path$&"
13458 When a message is being delivered, this variable contains the return path &--
13459 the sender field that will be sent as part of the envelope. It is not enclosed
13460 in <> characters. At the start of routing an address, &$return_path$& has the
13461 same value as &$sender_address$&, but if, for example, an incoming message to a
13462 mailing list has been expanded by a router which specifies a different address
13463 for bounce messages, &$return_path$& subsequently contains the new bounce
13464 address, whereas &$sender_address$& always contains the original sender address
13465 that was received with the message. In other words, &$sender_address$& contains
13466 the incoming envelope sender, and &$return_path$& contains the outgoing
13469 .vitem &$return_size_limit$&
13470 .vindex "&$return_size_limit$&"
13471 This is an obsolete name for &$bounce_return_size_limit$&.
13473 .vitem &$router_name$&
13474 .cindex "router" "name"
13475 .cindex "name" "of router"
13476 .vindex "&$router_name$&"
13477 During the running of a router this variable contains its name.
13480 .cindex "return code" "from &%run%& expansion"
13481 .vindex "&$runrc$&"
13482 This variable contains the return code from a command that is run by the
13483 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
13484 assume the order in which option values are expanded, except for those
13485 preconditions whose order of testing is documented. Therefore, you cannot
13486 reliably expect to set &$runrc$& by the expansion of one option, and use it in
13489 .vitem &$self_hostname$&
13490 .oindex "&%self%&" "value of host name"
13491 .vindex "&$self_hostname$&"
13492 When an address is routed to a supposedly remote host that turns out to be the
13493 local host, what happens is controlled by the &%self%& generic router option.
13494 One of its values causes the address to be passed to another router. When this
13495 happens, &$self_hostname$& is set to the name of the local host that the
13496 original router encountered. In other circumstances its contents are null.
13498 .vitem &$sender_address$&
13499 .vindex "&$sender_address$&"
13500 When a message is being processed, this variable contains the sender's address
13501 that was received in the message's envelope. The case of letters in the address
13502 is retained, in both the local part and the domain. For bounce messages, the
13503 value of this variable is the empty string. See also &$return_path$&.
13505 .vitem &$sender_address_data$&
13506 .vindex "&$address_data$&"
13507 .vindex "&$sender_address_data$&"
13508 If &$address_data$& is set when the routers are called from an ACL to verify a
13509 sender address, the final value is preserved in &$sender_address_data$&, to
13510 distinguish it from data from a recipient address. The value does not persist
13511 after the end of the current ACL statement. If you want to preserve it for
13512 longer, you can save it in an ACL variable.
13514 .vitem &$sender_address_domain$&
13515 .vindex "&$sender_address_domain$&"
13516 The domain portion of &$sender_address$&.
13518 .vitem &$sender_address_local_part$&
13519 .vindex "&$sender_address_local_part$&"
13520 The local part portion of &$sender_address$&.
13522 .vitem &$sender_data$&
13523 .vindex "&$sender_data$&"
13524 This variable is set after a lookup success in an ACL &%senders%& condition or
13525 in a router &%senders%& option. It contains the data from the lookup, and the
13526 value remains set until the next &%senders%& test. Thus, you can do things like
13529 &`require senders = cdb*@;/some/file`&
13530 &`deny `&&'some further test involving'& &`$sender_data`&
13532 &*Warning*&: This variable is set only when a lookup is used as an indexing
13533 method in the address list, using the semicolon syntax as in the example above.
13534 The variable is not set for a lookup that is used as part of the string
13535 expansion that all such lists undergo before being interpreted.
13537 .vitem &$sender_fullhost$&
13538 .vindex "&$sender_fullhost$&"
13539 When a message is received from a remote host, this variable contains the host
13540 name and IP address in a single string. It ends with the IP address in square
13541 brackets, followed by a colon and a port number if the logging of ports is
13542 enabled. The format of the rest of the string depends on whether the host
13543 issued a HELO or EHLO SMTP command, and whether the host name was verified by
13544 looking up its IP address. (Looking up the IP address can be forced by the
13545 &%host_lookup%& option, independent of verification.) A plain host name at the
13546 start of the string is a verified host name; if this is not present,
13547 verification either failed or was not requested. A host name in parentheses is
13548 the argument of a HELO or EHLO command. This is omitted if it is identical to
13549 the verified host name or to the host's IP address in square brackets.
13551 .vitem &$sender_helo_dnssec$&
13552 .vindex "&$sender_helo_dnssec$&"
13553 This boolean variable is true if a successful HELO verification was
13554 .cindex "DNS" "DNSSEC"
13555 done using DNS information the resolver library stated was authenticated data.
13557 .vitem &$sender_helo_name$&
13558 .vindex "&$sender_helo_name$&"
13559 When a message is received from a remote host that has issued a HELO or EHLO
13560 command, the argument of that command is placed in this variable. It is also
13561 set if HELO or EHLO is used when a message is received using SMTP locally via
13562 the &%-bs%& or &%-bS%& options.
13564 .vitem &$sender_host_address$&
13565 .vindex "&$sender_host_address$&"
13566 When a message is received from a remote host using SMTP,
13567 this variable contains that
13568 host's IP address. For locally non-SMTP submitted messages, it is empty.
13570 .vitem &$sender_host_authenticated$&
13571 .vindex "&$sender_host_authenticated$&"
13572 This variable contains the name (not the public name) of the authenticator
13573 driver that successfully authenticated the client from which the message was
13574 received. It is empty if there was no successful authentication. See also
13575 &$authenticated_id$&.
13577 .vitem &$sender_host_dnssec$&
13578 .vindex "&$sender_host_dnssec$&"
13579 If an attempt to populate &$sender_host_name$& has been made
13580 (by reference, &%hosts_lookup%& or
13581 otherwise) then this boolean will have been set true if, and only if, the
13582 resolver library states that both
13583 the reverse and forward DNS were authenticated data. At all
13584 other times, this variable is false.
13586 .cindex "DNS" "DNSSEC"
13587 It is likely that you will need to coerce DNSSEC support on in the resolver
13588 library, by setting:
13593 In addition, on Linux with glibc 2.31 or newer the resolver library will
13594 default to stripping out a successful validation status.
13595 This will break a previously working Exim installation.
13596 Provided that you do trust the resolver (ie, is on localhost) you can tell
13597 glibc to pass through any successful validation with a new option in
13598 &_/etc/resolv.conf_&:
13603 Exim does not perform DNSSEC validation itself, instead leaving that to a
13604 validating resolver (e.g. unbound, or bind with suitable configuration).
13606 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
13607 mechanism in the list, then this variable will be false.
13609 This requires that your system resolver library support EDNS0 (and that
13610 DNSSEC flags exist in the system headers). If the resolver silently drops
13611 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
13612 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
13615 .vitem &$sender_host_name$&
13616 .vindex "&$sender_host_name$&"
13617 When a message is received from a remote host, this variable contains the
13618 host's name as obtained by looking up its IP address. For messages received by
13619 other means, this variable is empty.
13621 .vindex "&$host_lookup_failed$&"
13622 If the host name has not previously been looked up, a reference to
13623 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
13624 A looked up name is accepted only if it leads back to the original IP address
13625 via a forward lookup. If either the reverse or the forward lookup fails to find
13626 any data, or if the forward lookup does not yield the original IP address,
13627 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
13629 .vindex "&$host_lookup_deferred$&"
13630 However, if either of the lookups cannot be completed (for example, there is a
13631 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
13632 &$host_lookup_failed$& remains set to &"0"&.
13634 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
13635 host name again if there is a subsequent reference to &$sender_host_name$&
13636 in the same Exim process, but it does try again if &$host_lookup_deferred$&
13639 Exim does not automatically look up every calling host's name. If you want
13640 maximum efficiency, you should arrange your configuration so that it avoids
13641 these lookups altogether. The lookup happens only if one or more of the
13642 following are true:
13645 A string containing &$sender_host_name$& is expanded.
13647 The calling host matches the list in &%host_lookup%&. In the default
13648 configuration, this option is set to *, so it must be changed if lookups are
13649 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
13651 Exim needs the host name in order to test an item in a host list. The items
13652 that require this are described in sections &<<SECThoslispatnam>>& and
13653 &<<SECThoslispatnamsk>>&.
13655 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
13656 In this case, the host name is required to compare with the name quoted in any
13657 EHLO or HELO commands that the client issues.
13659 The remote host issues a EHLO or HELO command that quotes one of the
13660 domains in &%helo_lookup_domains%&. The default value of this option is
13661 . ==== As this is a nested list, any displays it contains must be indented
13662 . ==== as otherwise they are too far to the left.
13664 helo_lookup_domains = @ : @[]
13666 which causes a lookup if a remote host (incorrectly) gives the server's name or
13667 IP address in an EHLO or HELO command.
13671 .vitem &$sender_host_port$&
13672 .vindex "&$sender_host_port$&"
13673 When a message is received from a remote host, this variable contains the port
13674 number that was used on the remote host.
13676 .vitem &$sender_ident$&
13677 .vindex "&$sender_ident$&"
13678 When a message is received from a remote host, this variable contains the
13679 identification received in response to an RFC 1413 request. When a message has
13680 been received locally, this variable contains the login name of the user that
13683 .vitem &$sender_rate_$&&'xxx'&
13684 A number of variables whose names begin &$sender_rate_$& are set as part of the
13685 &%ratelimit%& ACL condition. Details are given in section
13686 &<<SECTratelimiting>>&.
13688 .vitem &$sender_rcvhost$&
13689 .cindex "DNS" "reverse lookup"
13690 .cindex "reverse DNS lookup"
13691 .vindex "&$sender_rcvhost$&"
13692 This is provided specifically for use in &'Received:'& headers. It starts with
13693 either the verified host name (as obtained from a reverse DNS lookup) or, if
13694 there is no verified host name, the IP address in square brackets. After that
13695 there may be text in parentheses. When the first item is a verified host name,
13696 the first thing in the parentheses is the IP address in square brackets,
13697 followed by a colon and a port number if port logging is enabled. When the
13698 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
13701 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
13702 was used and its argument was not identical to the real host name or IP
13703 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
13704 all three items are present in the parentheses, a newline and tab are inserted
13705 into the string, to improve the formatting of the &'Received:'& header.
13707 .vitem &$sender_verify_failure$&
13708 .vindex "&$sender_verify_failure$&"
13709 In an ACL, when a sender verification fails, this variable contains information
13710 about the failure. The details are the same as for
13711 &$recipient_verify_failure$&.
13713 .vitem &$sending_ip_address$&
13714 .vindex "&$sending_ip_address$&"
13715 This variable is set whenever an outgoing SMTP connection to another host has
13716 been set up. It contains the IP address of the local interface that is being
13717 used. This is useful if a host that has more than one IP address wants to take
13718 on different personalities depending on which one is being used. For incoming
13719 connections, see &$received_ip_address$&.
13721 .vitem &$sending_port$&
13722 .vindex "&$sending_port$&"
13723 This variable is set whenever an outgoing SMTP connection to another host has
13724 been set up. It contains the local port that is being used. For incoming
13725 connections, see &$received_port$&.
13727 .vitem &$smtp_active_hostname$&
13728 .vindex "&$smtp_active_hostname$&"
13729 During an incoming SMTP session, this variable contains the value of the active
13730 host name, as specified by the &%smtp_active_hostname%& option. The value of
13731 &$smtp_active_hostname$& is saved with any message that is received, so its
13732 value can be consulted during routing and delivery.
13734 .vitem &$smtp_command$&
13735 .vindex "&$smtp_command$&"
13736 During the processing of an incoming SMTP command, this variable contains the
13737 entire command. This makes it possible to distinguish between HELO and EHLO in
13738 the HELO ACL, and also to distinguish between commands such as these:
13743 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
13744 command, the address in &$smtp_command$& is the original address before any
13745 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
13746 the address after SMTP-time rewriting.
13748 .vitem &$smtp_command_argument$&
13749 .cindex "SMTP" "command, argument for"
13750 .vindex "&$smtp_command_argument$&"
13751 While an ACL is running to check an SMTP command, this variable contains the
13752 argument, that is, the text that follows the command name, with leading white
13753 space removed. Following the introduction of &$smtp_command$&, this variable is
13754 somewhat redundant, but is retained for backwards compatibility.
13756 .vitem &$smtp_command_history$&
13757 .cindex SMTP "command history"
13758 .vindex "&$smtp_command_history$&"
13759 A comma-separated list (with no whitespace) of the most-recent SMTP commands
13760 received, in time-order left to right. Only a limited number of commands
13763 .vitem &$smtp_count_at_connection_start$&
13764 .vindex "&$smtp_count_at_connection_start$&"
13765 This variable is set greater than zero only in processes spawned by the Exim
13766 daemon for handling incoming SMTP connections. The name is deliberately long,
13767 in order to emphasize what the contents are. When the daemon accepts a new
13768 connection, it increments this variable. A copy of the variable is passed to
13769 the child process that handles the connection, but its value is fixed, and
13770 never changes. It is only an approximation of how many incoming connections
13771 there actually are, because many other connections may come and go while a
13772 single connection is being processed. When a child process terminates, the
13773 daemon decrements its copy of the variable.
13775 .vitem "&$sn0$& &-- &$sn9$&"
13776 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
13777 that were current at the end of the system filter file. This allows a system
13778 filter file to set values that can be tested in users' filter files. For
13779 example, a system filter could set a value indicating how likely it is that a
13780 message is junk mail.
13782 .vitem &$spam_score$& &&&
13783 &$spam_score_int$& &&&
13785 &$spam_report$& &&&
13787 A number of variables whose names start with &$spam$& are available when Exim
13788 is compiled with the content-scanning extension. For details, see section
13789 &<<SECTscanspamass>>&.
13791 .vitem &$spf_header_comment$& &&&
13792 &$spf_received$& &&&
13794 &$spf_result_guessed$& &&&
13795 &$spf_smtp_comment$&
13796 These variables are only available if Exim is built with SPF support.
13797 For details see section &<<SECSPF>>&.
13799 .vitem &$spool_directory$&
13800 .vindex "&$spool_directory$&"
13801 The name of Exim's spool directory.
13803 .vitem &$spool_inodes$&
13804 .vindex "&$spool_inodes$&"
13805 The number of free inodes in the disk partition where Exim's spool files are
13806 being written. The value is recalculated whenever the variable is referenced.
13807 If the relevant file system does not have the concept of inodes, the value of
13808 is -1. See also the &%check_spool_inodes%& option.
13810 .vitem &$spool_space$&
13811 .vindex "&$spool_space$&"
13812 The amount of free space (as a number of kilobytes) in the disk partition where
13813 Exim's spool files are being written. The value is recalculated whenever the
13814 variable is referenced. If the operating system does not have the ability to
13815 find the amount of free space (only true for experimental systems), the space
13816 value is -1. For example, to check in an ACL that there is at least 50
13817 megabytes free on the spool, you could write:
13819 condition = ${if > {$spool_space}{50000}}
13821 See also the &%check_spool_space%& option.
13824 .vitem &$thisaddress$&
13825 .vindex "&$thisaddress$&"
13826 This variable is set only during the processing of the &%foranyaddress%&
13827 command in a filter file. Its use is explained in the description of that
13828 command, which can be found in the separate document entitled &'Exim's
13829 interfaces to mail filtering'&.
13831 .vitem &$tls_in_bits$&
13832 .vindex "&$tls_in_bits$&"
13833 Contains an approximation of the TLS cipher's bit-strength
13834 on the inbound connection; the meaning of
13835 this depends upon the TLS implementation used.
13836 If TLS has not been negotiated, the value will be 0.
13837 The value of this is automatically fed into the Cyrus SASL authenticator
13838 when acting as a server, to specify the "external SSF" (a SASL term).
13840 The deprecated &$tls_bits$& variable refers to the inbound side
13841 except when used in the context of an outbound SMTP delivery, when it refers to
13844 .vitem &$tls_out_bits$&
13845 .vindex "&$tls_out_bits$&"
13846 Contains an approximation of the TLS cipher's bit-strength
13847 on an outbound SMTP connection; the meaning of
13848 this depends upon the TLS implementation used.
13849 If TLS has not been negotiated, the value will be 0.
13851 .vitem &$tls_in_ourcert$&
13852 .vindex "&$tls_in_ourcert$&"
13853 .cindex certificate variables
13854 This variable refers to the certificate presented to the peer of an
13855 inbound connection when the message was received.
13856 It is only useful as the argument of a
13857 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13858 or a &%def%& condition.
13860 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
13861 when a list of more than one
13862 file is used for &%tls_certificate%&, this variable is not reliable.
13863 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
13865 .vitem &$tls_in_peercert$&
13866 .vindex "&$tls_in_peercert$&"
13867 This variable refers to the certificate presented by the peer of an
13868 inbound connection when the message was received.
13869 It is only useful as the argument of a
13870 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13871 or a &%def%& condition.
13872 If certificate verification fails it may refer to a failing chain element
13873 which is not the leaf.
13875 .vitem &$tls_out_ourcert$&
13876 .vindex "&$tls_out_ourcert$&"
13877 This variable refers to the certificate presented to the peer of an
13878 outbound connection. It is only useful as the argument of a
13879 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13880 or a &%def%& condition.
13882 .vitem &$tls_out_peercert$&
13883 .vindex "&$tls_out_peercert$&"
13884 This variable refers to the certificate presented by the peer of an
13885 outbound connection. It is only useful as the argument of a
13886 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13887 or a &%def%& condition.
13888 If certificate verification fails it may refer to a failing chain element
13889 which is not the leaf.
13891 .vitem &$tls_in_certificate_verified$&
13892 .vindex "&$tls_in_certificate_verified$&"
13893 This variable is set to &"1"& if a TLS certificate was verified when the
13894 message was received, and &"0"& otherwise.
13896 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
13897 except when used in the context of an outbound SMTP delivery, when it refers to
13900 .vitem &$tls_out_certificate_verified$&
13901 .vindex "&$tls_out_certificate_verified$&"
13902 This variable is set to &"1"& if a TLS certificate was verified when an
13903 outbound SMTP connection was made,
13904 and &"0"& otherwise.
13906 .vitem &$tls_in_cipher$&
13907 .vindex "&$tls_in_cipher$&"
13908 .vindex "&$tls_cipher$&"
13909 When a message is received from a remote host over an encrypted SMTP
13910 connection, this variable is set to the cipher suite that was negotiated, for
13911 example DES-CBC3-SHA. In other circumstances, in particular, for message
13912 received over unencrypted connections, the variable is empty. Testing
13913 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
13914 non-encrypted connections during ACL processing.
13916 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
13917 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
13918 becomes the same as &$tls_out_cipher$&.
13920 .vitem &$tls_in_cipher_std$&
13921 .vindex "&$tls_in_cipher_std$&"
13922 As above, but returning the RFC standard name for the cipher suite.
13924 .vitem &$tls_out_cipher$&
13925 .vindex "&$tls_out_cipher$&"
13927 cleared before any outgoing SMTP connection is made,
13928 and then set to the outgoing cipher suite if one is negotiated. See chapter
13929 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
13930 details of the &(smtp)& transport.
13932 .vitem &$tls_out_cipher_std$&
13933 .vindex "&$tls_out_cipher_std$&"
13934 As above, but returning the RFC standard name for the cipher suite.
13936 .vitem &$tls_out_dane$&
13937 .vindex &$tls_out_dane$&
13938 DANE active status. See section &<<SECDANE>>&.
13940 .vitem &$tls_in_ocsp$&
13941 .vindex "&$tls_in_ocsp$&"
13942 When a message is received from a remote client connection
13943 the result of any OCSP request from the client is encoded in this variable:
13945 0 OCSP proof was not requested (default value)
13946 1 No response to request
13947 2 Response not verified
13948 3 Verification failed
13949 4 Verification succeeded
13952 .vitem &$tls_out_ocsp$&
13953 .vindex "&$tls_out_ocsp$&"
13954 When a message is sent to a remote host connection
13955 the result of any OCSP request made is encoded in this variable.
13956 See &$tls_in_ocsp$& for values.
13958 .vitem &$tls_in_peerdn$&
13959 .vindex "&$tls_in_peerdn$&"
13960 .vindex "&$tls_peerdn$&"
13961 .cindex certificate "extracting fields"
13962 When a message is received from a remote host over an encrypted SMTP
13963 connection, and Exim is configured to request a certificate from the client,
13964 the value of the Distinguished Name of the certificate is made available in the
13965 &$tls_in_peerdn$& during subsequent processing.
13966 If certificate verification fails it may refer to a failing chain element
13967 which is not the leaf.
13969 The deprecated &$tls_peerdn$& variable refers to the inbound side
13970 except when used in the context of an outbound SMTP delivery, when it refers to
13973 .vitem &$tls_out_peerdn$&
13974 .vindex "&$tls_out_peerdn$&"
13975 When a message is being delivered to a remote host over an encrypted SMTP
13976 connection, and Exim is configured to request a certificate from the server,
13977 the value of the Distinguished Name of the certificate is made available in the
13978 &$tls_out_peerdn$& during subsequent processing.
13979 If certificate verification fails it may refer to a failing chain element
13980 which is not the leaf.
13984 .vitem &$tls_in_resumption$& &&&
13985 &$tls_out_resumption$&
13986 .vindex &$tls_in_resumption$&
13987 .vindex &$tls_out_resumption$&
13988 .cindex TLS resumption
13989 Observability for TLS session resumption. See &<<SECTresumption>>& for details.
13993 .vitem &$tls_in_sni$&
13994 .vindex "&$tls_in_sni$&"
13995 .vindex "&$tls_sni$&"
13996 .cindex "TLS" "Server Name Indication"
13998 .cindex SNI "observability on server"
13999 When a TLS session is being established, if the client sends the Server
14000 Name Indication extension, the value will be placed in this variable.
14001 If the variable appears in &%tls_certificate%& then this option and
14002 some others, described in &<<SECTtlssni>>&,
14003 will be re-expanded early in the TLS session, to permit
14004 a different certificate to be presented (and optionally a different key to be
14005 used) to the client, based upon the value of the SNI extension.
14007 The deprecated &$tls_sni$& variable refers to the inbound side
14008 except when used in the context of an outbound SMTP delivery, when it refers to
14011 .vitem &$tls_out_sni$&
14012 .vindex "&$tls_out_sni$&"
14013 .cindex "TLS" "Server Name Indication"
14015 .cindex SNI "observability in client"
14017 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
14020 .vitem &$tls_out_tlsa_usage$&
14021 .vindex &$tls_out_tlsa_usage$&
14022 Bitfield of TLSA record types found. See section &<<SECDANE>>&.
14024 .vitem &$tls_in_ver$&
14025 .vindex "&$tls_in_ver$&"
14026 When a message is received from a remote host over an encrypted SMTP connection
14027 this variable is set to the protocol version, eg &'TLS1.2'&.
14029 .vitem &$tls_out_ver$&
14030 .vindex "&$tls_out_ver$&"
14031 When a message is being delivered to a remote host over an encrypted SMTP connection
14032 this variable is set to the protocol version.
14035 .vitem &$tod_bsdinbox$&
14036 .vindex "&$tod_bsdinbox$&"
14037 The time of day and the date, in the format required for BSD-style mailbox
14038 files, for example: Thu Oct 17 17:14:09 1995.
14040 .vitem &$tod_epoch$&
14041 .vindex "&$tod_epoch$&"
14042 The time and date as a number of seconds since the start of the Unix epoch.
14044 .vitem &$tod_epoch_l$&
14045 .vindex "&$tod_epoch_l$&"
14046 The time and date as a number of microseconds since the start of the Unix epoch.
14048 .vitem &$tod_full$&
14049 .vindex "&$tod_full$&"
14050 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
14051 +0100. The timezone is always given as a numerical offset from UTC, with
14052 positive values used for timezones that are ahead (east) of UTC, and negative
14053 values for those that are behind (west).
14056 .vindex "&$tod_log$&"
14057 The time and date in the format used for writing Exim's log files, for example:
14058 1995-10-12 15:32:29, but without a timezone.
14060 .vitem &$tod_logfile$&
14061 .vindex "&$tod_logfile$&"
14062 This variable contains the date in the format yyyymmdd. This is the format that
14063 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
14066 .vitem &$tod_zone$&
14067 .vindex "&$tod_zone$&"
14068 This variable contains the numerical value of the local timezone, for example:
14071 .vitem &$tod_zulu$&
14072 .vindex "&$tod_zulu$&"
14073 This variable contains the UTC date and time in &"Zulu"& format, as specified
14074 by ISO 8601, for example: 20030221154023Z.
14076 .vitem &$transport_name$&
14077 .cindex "transport" "name"
14078 .cindex "name" "of transport"
14079 .vindex "&$transport_name$&"
14080 During the running of a transport, this variable contains its name.
14083 .vindex "&$value$&"
14084 This variable contains the result of an expansion lookup, extraction operation,
14085 or external command, as described above. It is also used during a
14086 &*reduce*& expansion.
14088 .vitem &$verify_mode$&
14089 .vindex "&$verify_mode$&"
14090 While a router or transport is being run in verify mode or for cutthrough delivery,
14091 contains "S" for sender-verification or "R" for recipient-verification.
14094 .vitem &$version_number$&
14095 .vindex "&$version_number$&"
14096 The version number of Exim. Same as &$exim_version$&, may be overridden
14097 by the &%exim_version%& main config option.
14099 .vitem &$warn_message_delay$&
14100 .vindex "&$warn_message_delay$&"
14101 This variable is set only during the creation of a message warning about a
14102 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14104 .vitem &$warn_message_recipients$&
14105 .vindex "&$warn_message_recipients$&"
14106 This variable is set only during the creation of a message warning about a
14107 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14113 . ////////////////////////////////////////////////////////////////////////////
14114 . ////////////////////////////////////////////////////////////////////////////
14116 .chapter "Embedded Perl" "CHAPperl"
14117 .scindex IIDperl "Perl" "calling from Exim"
14118 Exim can be built to include an embedded Perl interpreter. When this is done,
14119 Perl subroutines can be called as part of the string expansion process. To make
14120 use of the Perl support, you need version 5.004 or later of Perl installed on
14121 your system. To include the embedded interpreter in the Exim binary, include
14126 in your &_Local/Makefile_& and then build Exim in the normal way.
14129 .section "Setting up so Perl can be used" "SECID85"
14130 .oindex "&%perl_startup%&"
14131 Access to Perl subroutines is via a global configuration option called
14132 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
14133 no &%perl_startup%& option in the Exim configuration file then no Perl
14134 interpreter is started and there is almost no overhead for Exim (since none of
14135 the Perl library will be paged in unless used). If there is a &%perl_startup%&
14136 option then the associated value is taken to be Perl code which is executed in
14137 a newly created Perl interpreter.
14139 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
14140 need backslashes before any characters to escape special meanings. The option
14141 should usually be something like
14143 perl_startup = do '/etc/exim.pl'
14145 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
14146 use from Exim. Exim can be configured either to start up a Perl interpreter as
14147 soon as it is entered, or to wait until the first time it is needed. Starting
14148 the interpreter at the beginning ensures that it is done while Exim still has
14149 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
14150 fact used in a particular run. Also, note that this does not mean that Exim is
14151 necessarily running as root when Perl is called at a later time. By default,
14152 the interpreter is started only when it is needed, but this can be changed in
14156 .oindex "&%perl_at_start%&"
14157 Setting &%perl_at_start%& (a boolean option) in the configuration requests
14158 a startup when Exim is entered.
14160 The command line option &%-ps%& also requests a startup when Exim is entered,
14161 overriding the setting of &%perl_at_start%&.
14164 There is also a command line option &%-pd%& (for delay) which suppresses the
14165 initial startup, even if &%perl_at_start%& is set.
14168 .oindex "&%perl_taintmode%&"
14169 .cindex "Perl" "taintmode"
14170 To provide more security executing Perl code via the embedded Perl
14171 interpreter, the &%perl_taintmode%& option can be set. This enables the
14172 taint mode of the Perl interpreter. You are encouraged to set this
14173 option to a true value. To avoid breaking existing installations, it
14177 &*Note*&: This is entirely separate from Exim's tainted-data tracking.
14181 .section "Calling Perl subroutines" "SECID86"
14182 When the configuration file includes a &%perl_startup%& option you can make use
14183 of the string expansion item to call the Perl subroutines that are defined
14184 by the &%perl_startup%& code. The operator is used in any of the following
14188 ${perl{foo}{argument}}
14189 ${perl{foo}{argument1}{argument2} ... }
14191 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
14192 arguments may be passed. Passing more than this results in an expansion failure
14193 with an error message of the form
14195 Too many arguments passed to Perl subroutine "foo" (max is 8)
14197 The return value of the Perl subroutine is evaluated in a scalar context before
14198 it is passed back to Exim to be inserted into the expanded string. If the
14199 return value is &'undef'&, the expansion is forced to fail in the same way as
14200 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
14201 by obeying Perl's &%die%& function, the expansion fails with the error message
14202 that was passed to &%die%&.
14205 .section "Calling Exim functions from Perl" "SECID87"
14206 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
14207 is available to call back into Exim's string expansion function. For example,
14210 my $lp = Exim::expand_string('$local_part');
14212 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
14213 Note those are single quotes and not double quotes to protect against
14214 &$local_part$& being interpolated as a Perl variable.
14216 If the string expansion is forced to fail by a &"fail"& item, the result of
14217 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
14218 expansion string, the Perl call from the original expansion string fails with
14219 an appropriate error message, in the same way as if &%die%& were used.
14221 .cindex "debugging" "from embedded Perl"
14222 .cindex "log" "writing from embedded Perl"
14223 Two other Exim functions are available for use from within Perl code.
14224 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
14225 debugging is enabled. If you want a newline at the end, you must supply it.
14226 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
14227 timestamp. In this case, you should not supply a terminating newline.
14230 .section "Use of standard output and error by Perl" "SECID88"
14231 .cindex "Perl" "standard output and error"
14232 You should not write to the standard error or output streams from within your
14233 Perl code, as it is not defined how these are set up. In versions of Exim
14234 before 4.50, it is possible for the standard output or error to refer to the
14235 SMTP connection during message reception via the daemon. Writing to this stream
14236 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
14237 error streams are connected to &_/dev/null_& in the daemon. The chaos is
14238 avoided, but the output is lost.
14240 .cindex "Perl" "use of &%warn%&"
14241 The Perl &%warn%& statement writes to the standard error stream by default.
14242 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
14243 you have no control. When Exim starts up the Perl interpreter, it arranges for
14244 output from the &%warn%& statement to be written to the Exim main log. You can
14245 change this by including appropriate Perl magic somewhere in your Perl code.
14246 For example, to discard &%warn%& output completely, you need this:
14248 $SIG{__WARN__} = sub { };
14250 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
14251 example, the code for the subroutine is empty, so it does nothing, but you can
14252 include any Perl code that you like. The text of the &%warn%& message is passed
14253 as the first subroutine argument.
14257 . ////////////////////////////////////////////////////////////////////////////
14258 . ////////////////////////////////////////////////////////////////////////////
14260 .chapter "Starting the daemon and the use of network interfaces" &&&
14261 "CHAPinterfaces" &&&
14262 "Starting the daemon"
14263 .cindex "daemon" "starting"
14264 .cindex "interface" "listening"
14265 .cindex "network interface"
14266 .cindex "interface" "network"
14267 .cindex "IP address" "for listening"
14268 .cindex "daemon" "listening IP addresses"
14269 .cindex "TCP/IP" "setting listening interfaces"
14270 .cindex "TCP/IP" "setting listening ports"
14271 A host that is connected to a TCP/IP network may have one or more physical
14272 hardware network interfaces. Each of these interfaces may be configured as one
14273 or more &"logical"& interfaces, which are the entities that a program actually
14274 works with. Each of these logical interfaces is associated with an IP address.
14275 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
14276 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
14277 knowledge about the host's interfaces for use in three different circumstances:
14280 When a listening daemon is started, Exim needs to know which interfaces
14281 and ports to listen on.
14283 When Exim is routing an address, it needs to know which IP addresses
14284 are associated with local interfaces. This is required for the correct
14285 processing of MX lists by removing the local host and others with the
14286 same or higher priority values. Also, Exim needs to detect cases
14287 when an address is routed to an IP address that in fact belongs to the
14288 local host. Unless the &%self%& router option or the &%allow_localhost%&
14289 option of the smtp transport is set (as appropriate), this is treated
14290 as an error situation.
14292 When Exim connects to a remote host, it may need to know which interface to use
14293 for the outgoing connection.
14297 Exim's default behaviour is likely to be appropriate in the vast majority
14298 of cases. If your host has only one interface, and you want all its IP
14299 addresses to be treated in the same way, and you are using only the
14300 standard SMTP port, you should not need to take any special action. The
14301 rest of this chapter does not apply to you.
14303 In a more complicated situation you may want to listen only on certain
14304 interfaces, or on different ports, and for this reason there are a number of
14305 options that can be used to influence Exim's behaviour. The rest of this
14306 chapter describes how they operate.
14308 When a message is received over TCP/IP, the interface and port that were
14309 actually used are set in &$received_ip_address$& and &$received_port$&.
14313 .section "Starting a listening daemon" "SECID89"
14314 When a listening daemon is started (by means of the &%-bd%& command line
14315 option), the interfaces and ports on which it listens are controlled by the
14319 &%daemon_smtp_ports%& contains a list of default ports
14321 (For backward compatibility, this option can also be specified in the singular.)
14323 &%local_interfaces%& contains list of interface IP addresses on which to
14324 listen. Each item may optionally also specify a port.
14327 The default list separator in both cases is a colon, but this can be changed as
14328 described in section &<<SECTlistsepchange>>&. When IPv6 addresses are involved,
14329 it is usually best to change the separator to avoid having to double all the
14330 colons. For example:
14332 local_interfaces = <; 127.0.0.1 ; \
14335 3ffe:ffff:836f::fe86:a061
14337 There are two different formats for specifying a port along with an IP address
14338 in &%local_interfaces%&:
14341 The port is added onto the address with a dot separator. For example, to listen
14342 on port 1234 on two different IP addresses:
14344 local_interfaces = <; 192.168.23.65.1234 ; \
14345 3ffe:ffff:836f::fe86:a061.1234
14348 The IP address is enclosed in square brackets, and the port is added
14349 with a colon separator, for example:
14351 local_interfaces = <; [192.168.23.65]:1234 ; \
14352 [3ffe:ffff:836f::fe86:a061]:1234
14356 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
14357 default setting contains just one port:
14359 daemon_smtp_ports = smtp
14361 If more than one port is listed, each interface that does not have its own port
14362 specified listens on all of them. Ports that are listed in
14363 &%daemon_smtp_ports%& can be identified either by name (defined in
14364 &_/etc/services_&) or by number. However, when ports are given with individual
14365 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
14369 .section "Special IP listening addresses" "SECID90"
14370 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
14371 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
14372 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
14373 instead of setting up separate listening sockets for each interface. The
14374 default value of &%local_interfaces%& is
14376 local_interfaces = 0.0.0.0
14378 when Exim is built without IPv6 support; otherwise it is:
14380 local_interfaces = <; ::0 ; 0.0.0.0
14382 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
14386 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
14387 The &%-oX%& command line option can be used to override the values of
14388 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
14389 instance. Another way of doing this would be to use macros and the &%-D%&
14390 option. However, &%-oX%& can be used by any admin user, whereas modification of
14391 the runtime configuration by &%-D%& is allowed only when the caller is root or
14394 The value of &%-oX%& is a list of items. The default colon separator can be
14395 changed in the usual way (&<<SECTlistsepchange>>&) if required.
14396 If there are any items that do not
14397 contain dots or colons (that is, are not IP addresses), the value of
14398 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
14399 items that do contain dots or colons, the value of &%local_interfaces%& is
14400 replaced by those items. Thus, for example,
14404 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
14407 -oX 192.168.34.5.1125
14409 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
14410 (However, since &%local_interfaces%& now contains no items without ports, the
14411 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
14415 .section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
14416 .cindex "submissions protocol"
14417 .cindex "ssmtp protocol"
14418 .cindex "smtps protocol"
14419 .cindex "SMTP" "ssmtp protocol"
14420 .cindex "SMTP" "smtps protocol"
14421 Exim supports the use of TLS-on-connect, used by mail clients in the
14422 &"submissions"& protocol, historically also known as SMTPS or SSMTP.
14423 For some years, IETF Standards Track documents only blessed the
14424 STARTTLS-based Submission service (port 587) while common practice was to support
14425 the same feature set on port 465, but using TLS-on-connect.
14426 If your installation needs to provide service to mail clients
14427 (Mail User Agents, MUAs) then you should provide service on both the 587 and
14430 If the &%tls_on_connect_ports%& option is set to a list of port numbers or
14431 service names, connections to those ports must first establish TLS, before
14432 proceeding to the application layer use of the SMTP protocol.
14434 The common use of this option is expected to be
14436 tls_on_connect_ports = 465
14439 There is also a command line option &%-tls-on-connect%&, which forces all ports
14440 to behave in this way when a daemon is started.
14442 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
14443 daemon to listen on those ports. You must still specify them in
14444 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
14445 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
14446 connections via the daemon.)
14451 .section "IPv6 address scopes" "SECID92"
14452 .cindex "IPv6" "address scopes"
14453 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
14454 can, in principle, have the same link-local IPv6 address on different
14455 interfaces. Thus, additional information is needed, over and above the IP
14456 address, to distinguish individual interfaces. A convention of using a
14457 percent sign followed by something (often the interface name) has been
14458 adopted in some cases, leading to addresses like this:
14460 fe80::202:b3ff:fe03:45c1%eth0
14462 To accommodate this usage, a percent sign followed by an arbitrary string is
14463 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
14464 to convert a textual IPv6 address for actual use. This function recognizes the
14465 percent convention in operating systems that support it, and it processes the
14466 address appropriately. Unfortunately, some older libraries have problems with
14467 &[getaddrinfo()]&. If
14469 IPV6_USE_INET_PTON=yes
14471 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
14472 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
14473 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
14474 function.) Of course, this means that the additional functionality of
14475 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
14477 .section "Disabling IPv6" "SECID93"
14478 .cindex "IPv6" "disabling"
14479 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
14480 run on a host whose kernel does not support IPv6. The binary will fall back to
14481 using IPv4, but it may waste resources looking up AAAA records, and trying to
14482 connect to IPv6 addresses, causing delays to mail delivery. If you set the
14483 .oindex "&%disable_ipv6%&"
14484 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
14485 activities take place. AAAA records are never looked up, and any IPv6 addresses
14486 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
14487 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14488 to handle IPv6 literal addresses.
14490 On the other hand, when IPv6 is in use, there may be times when you want to
14491 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
14492 option to globally suppress the lookup of AAAA records for specified domains,
14493 and you can use the &%ignore_target_hosts%& generic router option to ignore
14494 IPv6 addresses in an individual router.
14498 .section "Examples of starting a listening daemon" "SECID94"
14499 The default case in an IPv6 environment is
14501 daemon_smtp_ports = smtp
14502 local_interfaces = <; ::0 ; 0.0.0.0
14504 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
14505 Either one or two sockets may be used, depending on the characteristics of
14506 the TCP/IP stack. (This is complicated and messy; for more information,
14507 read the comments in the &_daemon.c_& source file.)
14509 To specify listening on ports 25 and 26 on all interfaces:
14511 daemon_smtp_ports = 25 : 26
14513 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
14515 local_interfaces = <; ::0.25 ; ::0.26 \
14516 0.0.0.0.25 ; 0.0.0.0.26
14518 To listen on the default port on all IPv4 interfaces, and on port 26 on the
14519 IPv4 loopback address only:
14521 local_interfaces = 0.0.0.0 : 127.0.0.1.26
14523 To specify listening on the default port on specific interfaces only:
14525 local_interfaces = 10.0.0.67 : 192.168.34.67
14527 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
14531 .section "Recognizing the local host" "SECTreclocipadd"
14532 The &%local_interfaces%& option is also used when Exim needs to determine
14533 whether or not an IP address refers to the local host. That is, the IP
14534 addresses of all the interfaces on which a daemon is listening are always
14537 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
14538 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
14539 available interfaces from the operating system, and extracts the relevant
14540 (that is, IPv4 or IPv6) addresses to use for checking.
14542 Some systems set up large numbers of virtual interfaces in order to provide
14543 many virtual web servers. In this situation, you may want to listen for
14544 email on only a few of the available interfaces, but nevertheless treat all
14545 interfaces as local when routing. You can do this by setting
14546 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
14547 &"all"& wildcard values. These addresses are recognized as local, but are not
14548 used for listening. Consider this example:
14550 local_interfaces = <; 127.0.0.1 ; ::1 ; \
14552 3ffe:2101:12:1:a00:20ff:fe86:a061
14554 extra_local_interfaces = <; ::0 ; 0.0.0.0
14556 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
14557 address, but all available interface addresses are treated as local when
14560 In some environments the local host name may be in an MX list, but with an IP
14561 address that is not assigned to any local interface. In other cases it may be
14562 desirable to treat other host names as if they referred to the local host. Both
14563 these cases can be handled by setting the &%hosts_treat_as_local%& option.
14564 This contains host names rather than IP addresses. When a host is referenced
14565 during routing, either via an MX record or directly, it is treated as the local
14566 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
14567 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
14571 .section "Delivering to a remote host" "SECID95"
14572 Delivery to a remote host is handled by the smtp transport. By default, it
14573 allows the system's TCP/IP functions to choose which interface to use (if
14574 there is more than one) when connecting to a remote host. However, the
14575 &%interface%& option can be set to specify which interface is used. See the
14576 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
14582 . ////////////////////////////////////////////////////////////////////////////
14583 . ////////////////////////////////////////////////////////////////////////////
14585 .chapter "Main configuration" "CHAPmainconfig"
14586 .scindex IIDconfima "configuration file" "main section"
14587 .scindex IIDmaiconf "main configuration"
14588 The first part of the runtime configuration file contains three types of item:
14591 Macro definitions: These lines start with an upper case letter. See section
14592 &<<SECTmacrodefs>>& for details of macro processing.
14594 Named list definitions: These lines start with one of the words &"domainlist"&,
14595 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
14596 section &<<SECTnamedlists>>&.
14598 Main configuration settings: Each setting occupies one line of the file
14599 (with possible continuations). If any setting is preceded by the word
14600 &"hide"&, the &%-bP%& command line option displays its value to admin users
14601 only. See section &<<SECTcos>>& for a description of the syntax of these option
14605 This chapter specifies all the main configuration options, along with their
14606 types and default values. For ease of finding a particular option, they appear
14607 in alphabetical order in section &<<SECTalomo>>& below. However, because there
14608 are now so many options, they are first listed briefly in functional groups, as
14609 an aid to finding the name of the option you are looking for. Some options are
14610 listed in more than one group.
14612 .section "Miscellaneous" "SECID96"
14614 .row &%add_environment%& "environment variables"
14615 .row &%allow_insecure_tainted_data%& "turn taint errors into warnings"
14616 .row &%bi_command%& "to run for &%-bi%& command line option"
14617 .row &%debug_store%& "do extra internal checks"
14618 .row &%disable_ipv6%& "do no IPv6 processing"
14619 .row &%keep_environment%& "environment variables"
14620 .row &%keep_malformed%& "for broken files &-- should not happen"
14621 .row &%localhost_number%& "for unique message ids in clusters"
14622 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
14623 .row &%message_body_visible%& "how much to show in &$message_body$&"
14624 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
14625 .row &%print_topbitchars%& "top-bit characters are printing"
14626 .row &%spool_wireformat%& "use wire-format spool data files when possible"
14627 .row &%timezone%& "force time zone"
14631 .section "Exim parameters" "SECID97"
14633 .row &%exim_group%& "override compiled-in value"
14634 .row &%exim_path%& "override compiled-in value"
14635 .row &%exim_user%& "override compiled-in value"
14636 .row &%primary_hostname%& "default from &[uname()]&"
14637 .row &%split_spool_directory%& "use multiple directories"
14638 .row &%spool_directory%& "override compiled-in value"
14643 .section "Privilege controls" "SECID98"
14645 .row &%admin_groups%& "groups that are Exim admin users"
14646 .row &%commandline_checks_require_admin%& "require admin for various checks"
14647 .row &%deliver_drop_privilege%& "drop root for delivery processes"
14648 .row &%local_from_check%& "insert &'Sender:'& if necessary"
14649 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
14650 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
14651 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
14652 .row &%never_users%& "do not run deliveries as these"
14653 .row &%prod_requires_admin%& "forced delivery requires admin user"
14654 .row &%queue_list_requires_admin%& "queue listing requires admin user"
14655 .row &%trusted_groups%& "groups that are trusted"
14656 .row &%trusted_users%& "users that are trusted"
14661 .section "Logging" "SECID99"
14663 .row &%event_action%& "custom logging"
14664 .row &%hosts_connection_nolog%& "exemption from connect logging"
14665 .row &%log_file_path%& "override compiled-in value"
14666 .row &%log_selector%& "set/unset optional logging"
14667 .row &%log_timezone%& "add timezone to log lines"
14668 .row &%message_logs%& "create per-message logs"
14669 .row &%preserve_message_logs%& "after message completion"
14670 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
14671 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
14672 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
14673 .row &%syslog_facility%& "set syslog &""facility""& field"
14674 .row &%syslog_pid%& "pid in syslog lines"
14675 .row &%syslog_processname%& "set syslog &""ident""& field"
14676 .row &%syslog_timestamp%& "timestamp syslog lines"
14677 .row &%write_rejectlog%& "control use of message log"
14682 .section "Frozen messages" "SECID100"
14684 .row &%auto_thaw%& "sets time for retrying frozen messages"
14685 .row &%freeze_tell%& "send message when freezing"
14686 .row &%move_frozen_messages%& "to another directory"
14687 .row &%timeout_frozen_after%& "keep frozen messages only so long"
14692 .section "Data lookups" "SECID101"
14694 .row &%ibase_servers%& "InterBase servers"
14695 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
14696 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
14697 .row &%ldap_cert_file%& "client cert file for LDAP"
14698 .row &%ldap_cert_key%& "client key file for LDAP"
14699 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
14700 .row &%ldap_default_servers%& "used if no server in query"
14701 .row &%ldap_require_cert%& "action to take without LDAP server cert"
14702 .row &%ldap_start_tls%& "require TLS within LDAP"
14703 .row &%ldap_version%& "set protocol version"
14704 .row &%lookup_open_max%& "lookup files held open"
14705 .row &%mysql_servers%& "default MySQL servers"
14706 .row &%oracle_servers%& "Oracle servers"
14707 .row &%pgsql_servers%& "default PostgreSQL servers"
14708 .row &%sqlite_lock_timeout%& "as it says"
14713 .section "Message ids" "SECID102"
14715 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
14716 .row &%message_id_header_text%& "ditto"
14721 .section "Embedded Perl Startup" "SECID103"
14723 .row &%perl_at_start%& "always start the interpreter"
14724 .row &%perl_startup%& "code to obey when starting Perl"
14725 .row &%perl_taintmode%& "enable taint mode in Perl"
14730 .section "Daemon" "SECID104"
14732 .row &%daemon_smtp_ports%& "default ports"
14733 .row &%daemon_startup_retries%& "number of times to retry"
14734 .row &%daemon_startup_sleep%& "time to sleep between tries"
14735 .row &%extra_local_interfaces%& "not necessarily listened on"
14736 .row &%local_interfaces%& "on which to listen, with optional ports"
14737 .row &%notifier_socket%& "override compiled-in value"
14738 .row &%pid_file_path%& "override compiled-in value"
14739 .row &%queue_run_max%& "maximum simultaneous queue runners"
14740 .row &%smtp_backlog_monitor%& "level to log listen backlog"
14745 .section "Resource control" "SECID105"
14747 .row &%check_log_inodes%& "before accepting a message"
14748 .row &%check_log_space%& "before accepting a message"
14749 .row &%check_spool_inodes%& "before accepting a message"
14750 .row &%check_spool_space%& "before accepting a message"
14751 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
14752 .row &%queue_only_load%& "queue incoming if load high"
14753 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14754 .row &%queue_run_max%& "maximum simultaneous queue runners"
14755 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14756 .row &%smtp_accept_max%& "simultaneous incoming connections"
14757 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14758 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14759 .row &%smtp_accept_max_per_connection%& "messages per connection"
14760 .row &%smtp_accept_max_per_host%& "connections from one host"
14761 .row &%smtp_accept_queue%& "queue mail if more connections"
14762 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14764 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14765 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14766 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14767 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
14768 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14773 .section "Policy controls" "SECID106"
14775 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
14776 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
14777 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
14778 .row &%acl_smtp_auth%& "ACL for AUTH"
14779 .row &%acl_smtp_connect%& "ACL for connection"
14780 .row &%acl_smtp_data%& "ACL for DATA"
14781 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
14782 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
14783 .row &%acl_smtp_etrn%& "ACL for ETRN"
14784 .row &%acl_smtp_expn%& "ACL for EXPN"
14785 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
14786 .row &%acl_smtp_mail%& "ACL for MAIL"
14787 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
14788 .row &%acl_smtp_mime%& "ACL for MIME parts"
14789 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
14790 .row &%acl_smtp_predata%& "ACL for start of data"
14791 .row &%acl_smtp_quit%& "ACL for QUIT"
14792 .row &%acl_smtp_rcpt%& "ACL for RCPT"
14793 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
14794 .row &%acl_smtp_vrfy%& "ACL for VRFY"
14795 .row &%av_scanner%& "specify virus scanner"
14796 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14798 .row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
14799 .row &%dns_csa_search_limit%& "control CSA parent search depth"
14800 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
14801 .row &%header_maxsize%& "total size of message header"
14802 .row &%header_line_maxsize%& "individual header line limit"
14803 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
14804 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
14805 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
14806 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
14807 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
14808 .row &%host_lookup%& "host name looked up for these hosts"
14809 .row &%host_lookup_order%& "order of DNS and local name lookups"
14810 .row &%hosts_proxy%& "use proxy protocol for these hosts"
14811 .row &%host_reject_connection%& "reject connection from these hosts"
14812 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
14813 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
14814 .row &%message_size_limit%& "for all messages"
14815 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14816 .row &%proxy_protocol_timeout%& "timeout for proxy protocol negotiation"
14817 .row &%spamd_address%& "set interface to SpamAssassin"
14818 .row &%strict_acl_vars%& "object to unset ACL variables"
14819 .row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&"
14824 .section "Callout cache" "SECID107"
14826 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
14828 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
14830 .row &%callout_negative_expire%& "timeout for negative address cache item"
14831 .row &%callout_positive_expire%& "timeout for positive address cache item"
14832 .row &%callout_random_local_part%& "string to use for &""random""& testing"
14837 .section "TLS" "SECID108"
14839 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
14840 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
14841 .row &%hosts_require_alpn%& "mandatory ALPN"
14842 .row &%openssl_options%& "adjust OpenSSL compatibility options"
14843 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14844 .row &%tls_alpn%& "acceptable protocol names"
14845 .row &%tls_certificate%& "location of server certificate"
14846 .row &%tls_crl%& "certificate revocation list"
14847 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
14848 .row &%tls_dhparam%& "DH parameters for server"
14849 .row &%tls_eccurve%& "EC curve selection for server"
14850 .row &%tls_ocsp_file%& "location of server certificate status proof"
14851 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
14852 .row &%tls_privatekey%& "location of server private key"
14853 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
14854 .row &%tls_require_ciphers%& "specify acceptable ciphers"
14855 .row &%tls_try_verify_hosts%& "try to verify client certificate"
14856 .row &%tls_verify_certificates%& "expected client certificates"
14857 .row &%tls_verify_hosts%& "insist on client certificate verify"
14862 .section "Local user handling" "SECID109"
14864 .row &%finduser_retries%& "useful in NIS environments"
14865 .row &%gecos_name%& "used when creating &'Sender:'&"
14866 .row &%gecos_pattern%& "ditto"
14867 .row &%max_username_length%& "for systems that truncate"
14868 .row &%unknown_login%& "used when no login name found"
14869 .row &%unknown_username%& "ditto"
14870 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
14871 .row &%uucp_from_sender%& "ditto"
14876 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
14878 .row &%header_maxsize%& "total size of message header"
14879 .row &%header_line_maxsize%& "individual header line limit"
14880 .row &%message_size_limit%& "applies to all messages"
14881 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14882 .row &%received_header_text%& "expanded to make &'Received:'&"
14883 .row &%received_headers_max%& "for mail loop detection"
14884 .row &%recipients_max%& "limit per message"
14885 .row &%recipients_max_reject%& "permanently reject excess recipients"
14891 .section "Non-SMTP incoming messages" "SECID111"
14893 .row &%receive_timeout%& "for non-SMTP messages"
14900 .section "Incoming SMTP messages" "SECID112"
14901 See also the &'Policy controls'& section above.
14904 .row &%dkim_verify_hashes%& "DKIM hash methods accepted for signatures"
14905 .row &%dkim_verify_keytypes%& "DKIM key types accepted for signatures"
14906 .row &%dkim_verify_min_keysizes%& "DKIM key sizes accepted for signatures"
14907 .row &%dkim_verify_signers%& "DKIM domains for which DKIM ACL is run"
14908 .row &%dmarc_forensic_sender%& "DMARC sender for report messages"
14909 .row &%dmarc_history_file%& "DMARC results log"
14910 .row &%dmarc_tld_file%& "DMARC toplevel domains file"
14911 .row &%host_lookup%& "host name looked up for these hosts"
14912 .row &%host_lookup_order%& "order of DNS and local name lookups"
14913 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
14914 .row &%rfc1413_hosts%& "make ident calls to these hosts"
14915 .row &%rfc1413_query_timeout%& "zero disables ident calls"
14916 .row &%sender_unqualified_hosts%& "may send unqualified senders"
14917 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
14918 .row &%smtp_accept_max%& "simultaneous incoming connections"
14919 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14920 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14921 .row &%smtp_accept_max_per_connection%& "messages per connection"
14922 .row &%smtp_accept_max_per_host%& "connections from one host"
14923 .row &%smtp_accept_queue%& "queue mail if more connections"
14924 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14926 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14927 .row &%smtp_active_hostname%& "host name to use in messages"
14928 .row &%smtp_banner%& "text for welcome banner"
14929 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14930 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14931 .row &%smtp_enforce_sync%& "of SMTP command/responses"
14932 .row &%smtp_etrn_command%& "what to run for ETRN"
14933 .row &%smtp_etrn_serialize%& "only one at once"
14934 .row &%smtp_load_reserve%& "only reserve hosts if this load"
14935 .row &%smtp_max_unknown_commands%& "before dropping connection"
14936 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
14937 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
14938 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
14939 .row &%smtp_receive_timeout%& "per command or data line"
14940 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14941 .row &%smtp_return_error_details%& "give detail on rejections"
14946 .section "SMTP extensions" "SECID113"
14948 .row &%accept_8bitmime%& "advertise 8BITMIME"
14949 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
14950 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
14951 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
14952 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
14953 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
14954 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
14955 .row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts"
14956 .row &%prdr_enable%& "advertise PRDR to all hosts"
14957 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
14958 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14963 .section "Processing messages" "SECID114"
14965 .row &%allow_domain_literals%& "recognize domain literal syntax"
14966 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
14967 .row &%allow_utf8_domains%& "in addresses"
14968 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14970 .row &%delivery_date_remove%& "from incoming messages"
14971 .row &%envelope_to_remove%& "from incoming messages"
14972 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
14973 .row &%headers_charset%& "default for translations"
14974 .row &%qualify_domain%& "default for senders"
14975 .row &%qualify_recipient%& "default for recipients"
14976 .row &%return_path_remove%& "from incoming messages"
14977 .row &%strip_excess_angle_brackets%& "in addresses"
14978 .row &%strip_trailing_dot%& "at end of addresses"
14979 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
14984 .section "System filter" "SECID115"
14986 .row &%system_filter%& "locate system filter"
14987 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
14989 .row &%system_filter_file_transport%& "transport for delivery to a file"
14990 .row &%system_filter_group%& "group for filter running"
14991 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
14992 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
14993 .row &%system_filter_user%& "user for filter running"
14998 .section "Routing and delivery" "SECID116"
15000 .row &%disable_ipv6%& "do no IPv6 processing"
15001 .row &%dns_again_means_nonexist%& "for broken domains"
15002 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
15003 .row &%dns_dnssec_ok%& "parameter for resolver"
15004 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
15005 .row &%dns_retrans%& "parameter for resolver"
15006 .row &%dns_retry%& "parameter for resolver"
15007 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
15008 .row &%dns_use_edns0%& "parameter for resolver"
15009 .row &%hold_domains%& "hold delivery for these domains"
15010 .row &%local_interfaces%& "for routing checks"
15011 .row &%queue_domains%& "no immediate delivery for these"
15012 .row &%queue_fast_ramp%& "parallel delivery with 2-phase queue run"
15013 .row &%queue_only%& "no immediate delivery at all"
15014 .row &%queue_only_file%& "no immediate delivery if file exists"
15015 .row &%queue_only_load%& "no immediate delivery if load is high"
15016 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
15017 .row &%queue_only_override%& "allow command line to override"
15018 .row &%queue_run_in_order%& "order of arrival"
15019 .row &%queue_run_max%& "of simultaneous queue runners"
15020 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
15021 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
15022 .row &%remote_sort_domains%& "order of remote deliveries"
15023 .row &%retry_data_expire%& "timeout for retry data"
15024 .row &%retry_interval_max%& "safety net for retry rules"
15029 .section "Bounce and warning messages" "SECID117"
15031 .row &%bounce_message_file%& "content of bounce"
15032 .row &%bounce_message_text%& "content of bounce"
15033 .row &%bounce_return_body%& "include body if returning message"
15034 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
15035 .row &%bounce_return_message%& "include original message in bounce"
15036 .row &%bounce_return_size_limit%& "limit on returned message"
15037 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
15038 .row &%dsn_from%& "set &'From:'& contents in bounces"
15039 .row &%errors_copy%& "copy bounce messages"
15040 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
15041 .row &%delay_warning%& "time schedule"
15042 .row &%delay_warning_condition%& "condition for warning messages"
15043 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
15044 .row &%smtp_return_error_details%& "give detail on rejections"
15045 .row &%warn_message_file%& "content of warning message"
15050 .section "Alphabetical list of main options" "SECTalomo"
15051 Those options that undergo string expansion before use are marked with
15054 .option accept_8bitmime main boolean true
15056 .cindex "8-bit characters"
15057 .cindex "log" "selectors"
15058 .cindex "log" "8BITMIME"
15059 .cindex "ESMTP extensions" 8BITMIME
15060 This option causes Exim to send 8BITMIME in its response to an SMTP
15061 EHLO command, and to accept the BODY= parameter on MAIL commands.
15062 However, though Exim is 8-bit clean, it is not a protocol converter, and it
15063 takes no steps to do anything special with messages received by this route.
15065 Historically Exim kept this option off by default, but the maintainers
15066 feel that in today's Internet, this causes more problems than it solves.
15067 It now defaults to true.
15068 A more detailed analysis of the issues is provided by Dan Bernstein:
15070 &url(https://cr.yp.to/smtp/8bitmime.html)
15073 To log received 8BITMIME status use
15075 log_selector = +8bitmime
15078 .option acl_not_smtp main string&!! unset
15079 .cindex "&ACL;" "for non-SMTP messages"
15080 .cindex "non-SMTP messages" "ACLs for"
15081 This option defines the ACL that is run when a non-SMTP message has been
15082 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
15085 .option acl_not_smtp_mime main string&!! unset
15086 This option defines the ACL that is run for individual MIME parts of non-SMTP
15087 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
15090 .option acl_not_smtp_start main string&!! unset
15091 .cindex "&ACL;" "at start of non-SMTP message"
15092 .cindex "non-SMTP messages" "ACLs for"
15093 This option defines the ACL that is run before Exim starts reading a
15094 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
15096 .option acl_smtp_auth main string&!! unset
15097 .cindex "&ACL;" "setting up for SMTP commands"
15098 .cindex "AUTH" "ACL for"
15099 This option defines the ACL that is run when an SMTP AUTH command is
15100 received. See chapter &<<CHAPACL>>& for further details.
15102 .option acl_smtp_connect main string&!! unset
15103 .cindex "&ACL;" "on SMTP connection"
15104 This option defines the ACL that is run when an SMTP connection is received.
15105 See chapter &<<CHAPACL>>& for further details.
15107 .option acl_smtp_data main string&!! unset
15108 .cindex "DATA" "ACL for"
15109 This option defines the ACL that is run after an SMTP DATA command has been
15110 processed and the message itself has been received, but before the final
15111 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15113 .option acl_smtp_data_prdr main string&!! accept
15114 .cindex "PRDR" "ACL for"
15115 .cindex "DATA" "PRDR ACL for"
15116 .cindex "&ACL;" "PRDR-related"
15117 .cindex "&ACL;" "per-user data processing"
15118 This option defines the ACL that,
15119 if the PRDR feature has been negotiated,
15120 is run for each recipient after an SMTP DATA command has been
15121 processed and the message itself has been received, but before the
15122 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15124 .option acl_smtp_dkim main string&!! unset
15125 .cindex DKIM "ACL for"
15126 This option defines the ACL that is run for each DKIM signature
15127 (by default, or as specified in the dkim_verify_signers option)
15128 of a received message.
15129 See section &<<SECDKIMVFY>>& for further details.
15131 .option acl_smtp_etrn main string&!! unset
15132 .cindex "ETRN" "ACL for"
15133 This option defines the ACL that is run when an SMTP ETRN command is
15134 received. See chapter &<<CHAPACL>>& for further details.
15136 .option acl_smtp_expn main string&!! unset
15137 .cindex "EXPN" "ACL for"
15138 This option defines the ACL that is run when an SMTP EXPN command is
15139 received. See chapter &<<CHAPACL>>& for further details.
15141 .option acl_smtp_helo main string&!! unset
15142 .cindex "EHLO" "ACL for"
15143 .cindex "HELO" "ACL for"
15144 This option defines the ACL that is run when an SMTP EHLO or HELO
15145 command is received. See chapter &<<CHAPACL>>& for further details.
15148 .option acl_smtp_mail main string&!! unset
15149 .cindex "MAIL" "ACL for"
15150 This option defines the ACL that is run when an SMTP MAIL command is
15151 received. See chapter &<<CHAPACL>>& for further details.
15153 .option acl_smtp_mailauth main string&!! unset
15154 .cindex "AUTH" "on MAIL command"
15155 This option defines the ACL that is run when there is an AUTH parameter on
15156 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
15157 &<<CHAPSMTPAUTH>>& for details of authentication.
15159 .option acl_smtp_mime main string&!! unset
15160 .cindex "MIME content scanning" "ACL for"
15161 This option is available when Exim is built with the content-scanning
15162 extension. It defines the ACL that is run for each MIME part in a message. See
15163 section &<<SECTscanmimepart>>& for details.
15165 .option acl_smtp_notquit main string&!! unset
15166 .cindex "not-QUIT, ACL for"
15167 This option defines the ACL that is run when an SMTP session
15168 ends without a QUIT command being received.
15169 See chapter &<<CHAPACL>>& for further details.
15171 .option acl_smtp_predata main string&!! unset
15172 This option defines the ACL that is run when an SMTP DATA command is
15173 received, before the message itself is received. See chapter &<<CHAPACL>>& for
15176 .option acl_smtp_quit main string&!! unset
15177 .cindex "QUIT, ACL for"
15178 This option defines the ACL that is run when an SMTP QUIT command is
15179 received. See chapter &<<CHAPACL>>& for further details.
15181 .option acl_smtp_rcpt main string&!! unset
15182 .cindex "RCPT" "ACL for"
15183 This option defines the ACL that is run when an SMTP RCPT command is
15184 received. See chapter &<<CHAPACL>>& for further details.
15186 .option acl_smtp_starttls main string&!! unset
15187 .cindex "STARTTLS, ACL for"
15188 This option defines the ACL that is run when an SMTP STARTTLS command is
15189 received. See chapter &<<CHAPACL>>& for further details.
15191 .option acl_smtp_vrfy main string&!! unset
15192 .cindex "VRFY" "ACL for"
15193 This option defines the ACL that is run when an SMTP VRFY command is
15194 received. See chapter &<<CHAPACL>>& for further details.
15196 .option add_environment main "string list" empty
15197 .cindex "environment" "set values"
15198 This option adds individual environment variables that the
15199 currently linked libraries and programs in child processes may use.
15200 Each list element should be of the form &"name=value"&.
15202 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
15204 .option admin_groups main "string list&!!" unset
15205 .cindex "admin user"
15206 This option is expanded just once, at the start of Exim's processing. If the
15207 current group or any of the supplementary groups of an Exim caller is in this
15208 colon-separated list, the caller has admin privileges. If all your system
15209 programmers are in a specific group, for example, you can give them all Exim
15210 admin privileges by putting that group in &%admin_groups%&. However, this does
15211 not permit them to read Exim's spool files (whose group owner is the Exim gid).
15212 To permit this, you have to add individuals to the Exim group.
15214 .option allow_domain_literals main boolean false
15215 .cindex "domain literal"
15216 If this option is set, the RFC 2822 domain literal format is permitted in
15217 email addresses. The option is not set by default, because the domain literal
15218 format is not normally required these days, and few people know about it. It
15219 has, however, been exploited by mail abusers.
15221 Unfortunately, it seems that some DNS black list maintainers are using this
15222 format to report black listing to postmasters. If you want to accept messages
15223 addressed to your hosts by IP address, you need to set
15224 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
15225 domains (defined in the named domain list &%local_domains%& in the default
15226 configuration). This &"magic string"& matches the domain literal form of all
15227 the local host's IP addresses.
15230 .option allow_insecure_tainted_data main boolean false
15231 .cindex "de-tainting"
15232 .oindex "allow_insecure_tainted_data"
15233 The handling of tainted data may break older (pre 4.94) configurations.
15234 Setting this option to "true" turns taint errors (which result in a temporary
15235 message rejection) into warnings. This option is meant as mitigation only
15236 and deprecated already today. Future releases of Exim may ignore it.
15237 The &%taint%& log selector can be used to suppress even the warnings.
15242 .option allow_mx_to_ip main boolean false
15243 .cindex "MX record" "pointing to IP address"
15244 It appears that more and more DNS zone administrators are breaking the rules
15245 and putting domain names that look like IP addresses on the right hand side of
15246 MX records. Exim follows the rules and rejects this, giving an error message
15247 that explains the misconfiguration. However, some other MTAs support this
15248 practice, so to avoid &"Why can't Exim do this?"& complaints,
15249 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
15250 recommended, except when you have no other choice.
15252 .option allow_utf8_domains main boolean false
15253 .cindex "domain" "UTF-8 characters in"
15254 .cindex "UTF-8" "in domain name"
15255 Lots of discussion is going on about internationalized domain names. One
15256 camp is strongly in favour of just using UTF-8 characters, and it seems
15257 that at least two other MTAs permit this.
15258 This option allows Exim users to experiment if they wish.
15260 If it is set true, Exim's domain parsing function allows valid
15261 UTF-8 multicharacters to appear in domain name components, in addition to
15262 letters, digits, and hyphens.
15264 If Exim is built with internationalization support
15265 and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
15266 this option can be left as default.
15268 if you want to look up such domain names in the DNS, you must also
15269 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
15270 suitable setting is:
15272 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
15273 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
15275 Alternatively, you can just disable this feature by setting
15277 dns_check_names_pattern =
15279 That is, set the option to an empty string so that no check is done.
15282 .option auth_advertise_hosts main "host list&!!" *
15283 .cindex "authentication" "advertising"
15284 .cindex "AUTH" "advertising"
15285 .cindex "ESMTP extensions" AUTH
15286 If any server authentication mechanisms are configured, Exim advertises them in
15287 response to an EHLO command only if the calling host matches this list.
15288 Otherwise, Exim does not advertise AUTH.
15289 Exim does not accept AUTH commands from clients to which it has not
15290 advertised the availability of AUTH. The advertising of individual
15291 authentication mechanisms can be controlled by the use of the
15292 &%server_advertise_condition%& generic authenticator option on the individual
15293 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
15295 Certain mail clients (for example, Netscape) require the user to provide a name
15296 and password for authentication if AUTH is advertised, even though it may
15297 not be needed (the host may accept messages from hosts on its local LAN without
15298 authentication, for example). The &%auth_advertise_hosts%& option can be used
15299 to make these clients more friendly by excluding them from the set of hosts to
15300 which Exim advertises AUTH.
15302 .cindex "AUTH" "advertising when encrypted"
15303 If you want to advertise the availability of AUTH only when the connection
15304 is encrypted using TLS, you can make use of the fact that the value of this
15305 option is expanded, with a setting like this:
15307 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
15309 .vindex "&$tls_in_cipher$&"
15310 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
15311 the expansion is empty, thus matching no hosts. Otherwise, the result of the
15312 expansion is *, which matches all hosts.
15315 .option auto_thaw main time 0s
15316 .cindex "thawing messages"
15317 .cindex "unfreezing messages"
15318 If this option is set to a time greater than zero, a queue runner will try a
15319 new delivery attempt on any frozen message, other than a bounce message, if
15320 this much time has passed since it was frozen. This may result in the message
15321 being re-frozen if nothing has changed since the last attempt. It is a way of
15322 saying &"keep on trying, even though there are big problems"&.
15324 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
15325 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
15326 thought to be very useful any more, and its use should probably be avoided.
15329 .option av_scanner main string "see below"
15330 This option is available if Exim is built with the content-scanning extension.
15331 It specifies which anti-virus scanner to use. The default value is:
15333 sophie:/var/run/sophie
15335 If the value of &%av_scanner%& starts with a dollar character, it is expanded
15336 before use. See section &<<SECTscanvirus>>& for further details.
15339 .option bi_command main string unset
15341 This option supplies the name of a command that is run when Exim is called with
15342 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
15343 just the command name, it is not a complete command line. If an argument is
15344 required, it must come from the &%-oA%& command line option.
15347 .option bounce_message_file main string&!! unset
15348 .cindex "bounce message" "customizing"
15349 .cindex "customizing" "bounce message"
15350 This option defines a template file containing paragraphs of text to be used
15351 for constructing bounce messages. Details of the file's contents are given in
15352 chapter &<<CHAPemsgcust>>&.
15353 .cindex bounce_message_file "tainted data"
15354 The option is expanded to give the file path, which must be
15355 absolute and untainted.
15356 See also &%warn_message_file%&.
15359 .option bounce_message_text main string unset
15360 When this option is set, its contents are included in the default bounce
15361 message immediately after &"This message was created automatically by mail
15362 delivery software."& It is not used if &%bounce_message_file%& is set.
15364 .option bounce_return_body main boolean true
15365 .cindex "bounce message" "including body"
15366 This option controls whether the body of an incoming message is included in a
15367 bounce message when &%bounce_return_message%& is true. The default setting
15368 causes the entire message, both header and body, to be returned (subject to the
15369 value of &%bounce_return_size_limit%&). If this option is false, only the
15370 message header is included. In the case of a non-SMTP message containing an
15371 error that is detected during reception, only those header lines preceding the
15372 point at which the error was detected are returned.
15373 .cindex "bounce message" "including original"
15375 .option bounce_return_linesize_limit main integer 998
15376 .cindex "size" "of bounce lines, limit"
15377 .cindex "bounce message" "line length limit"
15378 .cindex "limit" "bounce message line length"
15379 This option sets a limit in bytes on the line length of messages
15380 that are returned to senders due to delivery problems,
15381 when &%bounce_return_message%& is true.
15382 The default value corresponds to RFC limits.
15383 If the message being returned has lines longer than this value it is
15384 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
15386 The option also applies to bounces returned when an error is detected
15387 during reception of a message.
15388 In this case lines from the original are truncated.
15390 The option does not apply to messages generated by an &(autoreply)& transport.
15393 .option bounce_return_message main boolean true
15394 If this option is set false, none of the original message is included in
15395 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
15396 &%bounce_return_body%&.
15399 .option bounce_return_size_limit main integer 100K
15400 .cindex "size" "of bounce, limit"
15401 .cindex "bounce message" "size limit"
15402 .cindex "limit" "bounce message size"
15403 This option sets a limit in bytes on the size of messages that are returned to
15404 senders as part of bounce messages when &%bounce_return_message%& is true. The
15405 limit should be less than the value of the global &%message_size_limit%& and of
15406 any &%message_size_limit%& settings on transports, to allow for the bounce text
15407 that Exim generates. If this option is set to zero there is no limit.
15409 When the body of any message that is to be included in a bounce message is
15410 greater than the limit, it is truncated, and a comment pointing this out is
15411 added at the top. The actual cutoff may be greater than the value given, owing
15412 to the use of buffering for transferring the message in chunks (typically 8K in
15413 size). The idea is to save bandwidth on those undeliverable 15-megabyte
15416 .option bounce_sender_authentication main string unset
15417 .cindex "bounce message" "sender authentication"
15418 .cindex "authentication" "bounce message"
15419 .cindex "AUTH" "on bounce message"
15420 This option provides an authenticated sender address that is sent with any
15421 bounce messages generated by Exim that are sent over an authenticated SMTP
15422 connection. A typical setting might be:
15424 bounce_sender_authentication = mailer-daemon@my.domain.example
15426 which would cause bounce messages to be sent using the SMTP command:
15428 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
15430 The value of &%bounce_sender_authentication%& must always be a complete email
15433 .option callout_domain_negative_expire main time 3h
15434 .cindex "caching" "callout timeouts"
15435 .cindex "callout" "caching timeouts"
15436 This option specifies the expiry time for negative callout cache data for a
15437 domain. See section &<<SECTcallver>>& for details of callout verification, and
15438 section &<<SECTcallvercache>>& for details of the caching.
15441 .option callout_domain_positive_expire main time 7d
15442 This option specifies the expiry time for positive callout cache data for a
15443 domain. See section &<<SECTcallver>>& for details of callout verification, and
15444 section &<<SECTcallvercache>>& for details of the caching.
15447 .option callout_negative_expire main time 2h
15448 This option specifies the expiry time for negative callout cache data for an
15449 address. See section &<<SECTcallver>>& for details of callout verification, and
15450 section &<<SECTcallvercache>>& for details of the caching.
15453 .option callout_positive_expire main time 24h
15454 This option specifies the expiry time for positive callout cache data for an
15455 address. See section &<<SECTcallver>>& for details of callout verification, and
15456 section &<<SECTcallvercache>>& for details of the caching.
15459 .option callout_random_local_part main string&!! "see below"
15460 This option defines the &"random"& local part that can be used as part of
15461 callout verification. The default value is
15463 $primary_hostname-$tod_epoch-testing
15465 See section &<<CALLaddparcall>>& for details of how this value is used.
15468 .option check_log_inodes main integer 100
15469 See &%check_spool_space%& below.
15472 .option check_log_space main integer 10M
15473 See &%check_spool_space%& below.
15475 .oindex "&%check_rfc2047_length%&"
15476 .cindex "RFC 2047" "disabling length check"
15477 .option check_rfc2047_length main boolean true
15478 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
15479 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
15480 word; strings to be encoded that exceed this length are supposed to use
15481 multiple encoded words. By default, Exim does not recognize encoded words that
15482 exceed the maximum length. However, it seems that some software, in violation
15483 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
15484 set false, Exim recognizes encoded words of any length.
15487 .option check_spool_inodes main integer 100
15488 See &%check_spool_space%& below.
15491 .option check_spool_space main integer 10M
15492 .cindex "checking disk space"
15493 .cindex "disk space, checking"
15494 .cindex "spool directory" "checking space"
15495 The four &%check_...%& options allow for checking of disk resources before a
15496 message is accepted.
15498 .vindex "&$log_inodes$&"
15499 .vindex "&$log_space$&"
15500 .vindex "&$spool_inodes$&"
15501 .vindex "&$spool_space$&"
15502 When any of these options are nonzero, they apply to all incoming messages. If you
15503 want to apply different checks to different kinds of message, you can do so by
15504 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
15505 &$spool_space$& in an ACL with appropriate additional conditions.
15508 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
15509 either value is greater than zero, for example:
15511 check_spool_space = 100M
15512 check_spool_inodes = 100
15514 The spool partition is the one that contains the directory defined by
15515 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
15518 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
15519 files are written if either is greater than zero. These should be set only if
15520 &%log_file_path%& and &%spool_directory%& refer to different partitions.
15522 If there is less space or fewer inodes than requested, Exim refuses to accept
15523 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
15524 error response to the MAIL command. If ESMTP is in use and there was a
15525 SIZE parameter on the MAIL command, its value is added to the
15526 &%check_spool_space%& value, and the check is performed even if
15527 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
15529 The values for &%check_spool_space%& and &%check_log_space%& are held as a
15530 number of kilobytes (though specified in bytes).
15531 If a non-multiple of 1024 is specified, it is rounded up.
15533 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
15534 failure a message is written to stderr and Exim exits with a non-zero code, as
15535 it obviously cannot send an error message of any kind.
15537 There is a slight performance penalty for these checks.
15538 Versions of Exim preceding 4.88 had these disabled by default;
15539 high-rate installations confident they will never run out of resources
15540 may wish to deliberately disable them.
15542 .option chunking_advertise_hosts main "host list&!!" *
15543 .cindex CHUNKING advertisement
15544 .cindex "RFC 3030" "CHUNKING"
15545 .cindex "ESMTP extensions" CHUNKING
15546 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
15548 Hosts may use the BDAT command as an alternate to DATA.
15550 .option commandline_checks_require_admin main boolean &`false`&
15551 .cindex "restricting access to features"
15552 This option restricts various basic checking features to require an
15553 administrative user.
15554 This affects most of the &%-b*%& options, such as &%-be%&.
15556 .option debug_store main boolean &`false`&
15557 .cindex debugging "memory corruption"
15558 .cindex memory debugging
15559 This option, when true, enables extra checking in Exim's internal memory
15560 management. For use when a memory corruption issue is being investigated,
15561 it should normally be left as default.
15563 .option daemon_smtp_ports main string &`smtp`&
15564 .cindex "port" "for daemon"
15565 .cindex "TCP/IP" "setting listening ports"
15566 This option specifies one or more default SMTP ports on which the Exim daemon
15567 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
15568 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
15570 .option daemon_startup_retries main integer 9
15571 .cindex "daemon startup, retrying"
15572 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
15573 the daemon at startup when it cannot immediately bind a listening socket
15574 (typically because the socket is already in use): &%daemon_startup_retries%&
15575 defines the number of retries after the first failure, and
15576 &%daemon_startup_sleep%& defines the length of time to wait between retries.
15578 .option daemon_startup_sleep main time 30s
15579 See &%daemon_startup_retries%&.
15581 .option delay_warning main "time list" 24h
15582 .cindex "warning of delay"
15583 .cindex "delay warning, specifying"
15584 .cindex "queue" "delay warning"
15585 When a message is delayed, Exim sends a warning message to the sender at
15586 intervals specified by this option. The data is a colon-separated list of times
15587 after which to send warning messages. If the value of the option is an empty
15588 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
15589 message has been in the queue for longer than the last time, the last interval
15590 between the times is used to compute subsequent warning times. For example,
15593 delay_warning = 4h:8h:24h
15595 the first message is sent after 4 hours, the second after 8 hours, and
15596 the third one after 24 hours. After that, messages are sent every 16 hours,
15597 because that is the interval between the last two times on the list. If you set
15598 just one time, it specifies the repeat interval. For example, with:
15602 messages are repeated every six hours. To stop warnings after a given time, set
15603 a very large time at the end of the list. For example:
15605 delay_warning = 2h:12h:99d
15607 Note that the option is only evaluated at the time a delivery attempt fails,
15608 which depends on retry and queue-runner configuration.
15609 Typically retries will be configured more frequently than warning messages.
15611 .option delay_warning_condition main string&!! "see below"
15612 .vindex "&$domain$&"
15613 The string is expanded at the time a warning message might be sent. If all the
15614 deferred addresses have the same domain, it is set in &$domain$& during the
15615 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
15616 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
15617 &"false"& (the comparison being done caselessly) then the warning message is
15618 not sent. The default is:
15620 delay_warning_condition = ${if or {\
15621 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
15622 { match{$h_precedence:}{(?i)bulk|list|junk} }\
15623 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
15626 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
15627 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
15628 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
15629 &"auto-replied"& in an &'Auto-Submitted:'& header.
15631 .option deliver_drop_privilege main boolean false
15632 .cindex "unprivileged delivery"
15633 .cindex "delivery" "unprivileged"
15634 If this option is set true, Exim drops its root privilege at the start of a
15635 delivery process, and runs as the Exim user throughout. This severely restricts
15636 the kinds of local delivery that are possible, but is viable in certain types
15637 of configuration. There is a discussion about the use of root privilege in
15638 chapter &<<CHAPsecurity>>&.
15640 .option deliver_queue_load_max main fixed-point unset
15641 .cindex "load average"
15642 .cindex "queue runner" "abandoning"
15643 When this option is set, a queue run is abandoned if the system load average
15644 becomes greater than the value of the option. The option has no effect on
15645 ancient operating systems on which Exim cannot determine the load average.
15646 See also &%queue_only_load%& and &%smtp_load_reserve%&.
15649 .option delivery_date_remove main boolean true
15650 .cindex "&'Delivery-date:'& header line"
15651 Exim's transports have an option for adding a &'Delivery-date:'& header to a
15652 message when it is delivered, in exactly the same way as &'Return-path:'& is
15653 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
15654 should not be present in incoming messages, and this option causes them to be
15655 removed at the time the message is received, to avoid any problems that might
15656 occur when a delivered message is subsequently sent on to some other recipient.
15658 .option disable_fsync main boolean false
15659 .cindex "&[fsync()]&, disabling"
15660 This option is available only if Exim was built with the compile-time option
15661 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
15662 a runtime configuration generates an &"unknown option"& error. You should not
15663 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
15664 really, really, really understand what you are doing. &'No pre-compiled
15665 distributions of Exim should ever make this option available.'&
15667 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
15668 updated files' data to be written to disc before continuing. Unexpected events
15669 such as crashes and power outages may cause data to be lost or scrambled.
15670 Here be Dragons. &*Beware.*&
15673 .option disable_ipv6 main boolean false
15674 .cindex "IPv6" "disabling"
15675 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
15676 activities take place. AAAA records are never looked up, and any IPv6 addresses
15677 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
15678 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
15679 to handle IPv6 literal addresses.
15682 .option dkim_verify_hashes main "string list" "sha256 : sha512"
15683 .cindex DKIM "selecting signature algorithms"
15684 This option gives a list of hash types which are acceptable in signatures,
15685 and an order of processing.
15686 Signatures with algorithms not in the list will be ignored.
15688 Acceptable values include:
15695 Note that the acceptance of sha1 violates RFC 8301.
15697 .option dkim_verify_keytypes main "string list" "ed25519 : rsa"
15698 This option gives a list of key types which are acceptable in signatures,
15699 and an order of processing.
15700 Signatures with algorithms not in the list will be ignored.
15703 .option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250"
15704 This option gives a list of key sizes which are acceptable in signatures.
15705 The list is keyed by the algorithm type for the key; the values are in bits.
15706 Signatures with keys smaller than given by this option will fail verification.
15708 The default enforces the RFC 8301 minimum key size for RSA signatures.
15710 .option dkim_verify_minimal main boolean false
15711 If set to true, verification of signatures will terminate after the
15714 .option dkim_verify_signers main "domain list&!!" $dkim_signers
15715 .cindex DKIM "controlling calls to the ACL"
15716 This option gives a list of DKIM domains for which the DKIM ACL is run.
15717 It is expanded after the message is received; by default it runs
15718 the ACL once for each signature in the message.
15719 See section &<<SECDKIMVFY>>&.
15722 .option dmarc_forensic_sender main string&!! unset
15723 .option dmarc_history_file main string unset
15724 .option dmarc_tld_file main string unset
15725 .cindex DMARC "main section options"
15726 These options control DMARC processing.
15727 See section &<<SECDMARC>>& for details.
15730 .option dns_again_means_nonexist main "domain list&!!" unset
15731 .cindex "DNS" "&""try again""& response; overriding"
15732 DNS lookups give a &"try again"& response for the DNS errors
15733 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
15734 keep trying to deliver a message, or to give repeated temporary errors to
15735 incoming mail. Sometimes the effect is caused by a badly set up name server and
15736 may persist for a long time. If a domain which exhibits this problem matches
15737 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
15738 This option should be used with care. You can make it apply to reverse lookups
15739 by a setting such as this:
15741 dns_again_means_nonexist = *.in-addr.arpa
15743 This option applies to all DNS lookups that Exim does. It also applies when the
15744 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
15745 since these are most likely to be caused by DNS lookup problems. The
15746 &(dnslookup)& router has some options of its own for controlling what happens
15747 when lookups for MX or SRV records give temporary errors. These more specific
15748 options are applied after this global option.
15750 .option dns_check_names_pattern main string "see below"
15751 .cindex "DNS" "pre-check of name syntax"
15752 When this option is set to a non-empty string, it causes Exim to check domain
15753 names for characters that are not allowed in host names before handing them to
15754 the DNS resolver, because some resolvers give temporary errors for names that
15755 contain unusual characters. If a domain name contains any unwanted characters,
15756 a &"not found"& result is forced, and the resolver is not called. The check is
15757 done by matching the domain name against a regular expression, which is the
15758 value of this option. The default pattern is
15760 dns_check_names_pattern = \
15761 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
15763 which permits only letters, digits, slashes, and hyphens in components, but
15764 they must start and end with a letter or digit. Slashes are not, in fact,
15765 permitted in host names, but they are found in certain NS records (which can be
15766 accessed in Exim by using a &%dnsdb%& lookup). If you set
15767 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
15770 .option dns_csa_search_limit main integer 5
15771 This option controls the depth of parental searching for CSA SRV records in the
15772 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
15774 .option dns_csa_use_reverse main boolean true
15775 This option controls whether or not an IP address, given as a CSA domain, is
15776 reversed and looked up in the reverse DNS, as described in more detail in
15777 section &<<SECTverifyCSA>>&.
15779 .option dns_cname_loops main integer 1
15780 .cindex DNS "CNAME following"
15781 This option controls the following of CNAME chains, needed if the resolver does
15782 not do it internally.
15783 As of 2018 most should, and the default can be left.
15784 If you have an ancient one, a value of 10 is likely needed.
15786 The default value of one CNAME-follow is needed
15787 thanks to the observed return for an MX request,
15788 given no MX presence but a CNAME to an A, of the CNAME.
15791 .option dns_dnssec_ok main integer -1
15792 .cindex "DNS" "resolver options"
15793 .cindex "DNS" "DNSSEC"
15794 If this option is set to a non-negative number then Exim will initialise the
15795 DNS resolver library to either use or not use DNSSEC, overriding the system
15796 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
15798 If the resolver library does not support DNSSEC then this option has no effect.
15800 On Linux with glibc 2.31 or newer this is insufficient, the resolver library
15801 will default to stripping out a successful validation status.
15802 This will break a previously working Exim installation.
15803 Provided that you do trust the resolver (ie, is on localhost) you can tell
15804 glibc to pass through any successful validation with a new option in
15805 &_/etc/resolv.conf_&:
15811 .option dns_ipv4_lookup main "domain list&!!" unset
15812 .cindex "IPv6" "DNS lookup for AAAA records"
15813 .cindex "DNS" "IPv6 lookup for AAAA records"
15814 .cindex DNS "IPv6 disabling"
15815 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
15816 looks for IPv6 address records (AAAA records) as well as IPv4 address records
15817 (A records) when trying to find IP addresses for hosts, unless the host's
15818 domain matches this list.
15820 This is a fudge to help with name servers that give big delays or otherwise do
15821 not work for the AAAA record type. In due course, when the world's name
15822 servers have all been upgraded, there should be no need for this option.
15823 Note that all lookups, including those done for verification, are affected;
15824 this will result in verify failure for IPv6 connections or ones using names
15825 only valid for IPv6 addresses.
15828 .option dns_retrans main time 0s
15829 .cindex "DNS" "resolver options"
15830 .cindex timeout "dns lookup"
15831 .cindex "DNS" timeout
15832 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
15833 retransmission and retry parameters for DNS lookups. Values of zero (the
15834 defaults) leave the system default settings unchanged. The first value is the
15835 time between retries, and the second is the number of retries. It isn't
15836 totally clear exactly how these settings affect the total time a DNS lookup may
15837 take. I haven't found any documentation about timeouts on DNS lookups; these
15838 parameter values are available in the external resolver interface structure,
15839 but nowhere does it seem to describe how they are used or what you might want
15841 See also the &%slow_lookup_log%& option.
15844 .option dns_retry main integer 0
15845 See &%dns_retrans%& above.
15848 .option dns_trust_aa main "domain list&!!" unset
15849 .cindex "DNS" "resolver options"
15850 .cindex "DNS" "DNSSEC"
15851 If this option is set then lookup results marked with the AA bit
15852 (Authoritative Answer) are trusted the same way as if they were
15853 DNSSEC-verified. The authority section's name of the answer must
15854 match with this expanded domain list.
15856 Use this option only if you talk directly to a resolver that is
15857 authoritative for some zones and does not set the AD (Authentic Data)
15858 bit in the answer. Some DNS servers may have an configuration option to
15859 mark the answers from their own zones as verified (they set the AD bit).
15860 Others do not have this option. It is considered as poor practice using
15861 a resolver that is an authoritative server for some zones.
15863 Use this option only if you really have to (e.g. if you want
15864 to use DANE for remote delivery to a server that is listed in the DNS
15865 zones that your resolver is authoritative for).
15867 If the DNS answer packet has the AA bit set and contains resource record
15868 in the answer section, the name of the first NS record appearing in the
15869 authority section is compared against the list. If the answer packet is
15870 authoritative but the answer section is empty, the name of the first SOA
15871 record in the authoritative section is used instead.
15873 .cindex "DNS" "resolver options"
15874 .option dns_use_edns0 main integer -1
15875 .cindex "DNS" "resolver options"
15876 .cindex "DNS" "EDNS0"
15877 .cindex "DNS" "OpenBSD
15878 If this option is set to a non-negative number then Exim will initialise the
15879 DNS resolver library to either use or not use EDNS0 extensions, overriding
15880 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
15883 If the resolver library does not support EDNS0 then this option has no effect.
15885 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
15886 means that DNSSEC will not work with Exim on that platform either, unless Exim
15887 is linked against an alternative DNS client library.
15890 .option drop_cr main boolean false
15891 This is an obsolete option that is now a no-op. It used to affect the way Exim
15892 handled CR and LF characters in incoming messages. What happens now is
15893 described in section &<<SECTlineendings>>&.
15895 .option dsn_advertise_hosts main "host list&!!" unset
15896 .cindex "bounce messages" "success"
15897 .cindex "DSN" "success"
15898 .cindex "Delivery Status Notification" "success"
15899 .cindex "ESMTP extensions" DSN
15900 DSN extensions (RFC3461) will be advertised in the EHLO message to,
15901 and accepted from, these hosts.
15902 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
15903 and RET and ORCPT options on MAIL FROM commands.
15904 A NOTIFY=SUCCESS option requests success-DSN messages.
15905 A NOTIFY= option with no argument requests that no delay or failure DSNs
15907 &*Note*&: Supplying success-DSN messages has been criticised
15908 on privacy grounds; it can leak details of internal forwarding.
15910 .option dsn_from main "string&!!" "see below"
15911 .cindex "&'From:'& header line" "in bounces"
15912 .cindex "bounce messages" "&'From:'& line, specifying"
15913 This option can be used to vary the contents of &'From:'& header lines in
15914 bounces and other automatically generated messages (&"Delivery Status
15915 Notifications"& &-- hence the name of the option). The default setting is:
15917 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
15919 The value is expanded every time it is needed. If the expansion fails, a
15920 panic is logged, and the default value is used.
15922 .option envelope_to_remove main boolean true
15923 .cindex "&'Envelope-to:'& header line"
15924 Exim's transports have an option for adding an &'Envelope-to:'& header to a
15925 message when it is delivered, in exactly the same way as &'Return-path:'& is
15926 handled. &'Envelope-to:'& records the original recipient address from the
15927 message's envelope that caused the delivery to happen. Such headers should not
15928 be present in incoming messages, and this option causes them to be removed at
15929 the time the message is received, to avoid any problems that might occur when a
15930 delivered message is subsequently sent on to some other recipient.
15933 .option errors_copy main "string list&!!" unset
15934 .cindex "bounce message" "copy to other address"
15935 .cindex "copy of bounce message"
15936 Setting this option causes Exim to send bcc copies of bounce messages that it
15937 generates to other addresses. &*Note*&: This does not apply to bounce messages
15938 coming from elsewhere. The value of the option is a colon-separated list of
15939 items. Each item consists of a pattern, terminated by white space, followed by
15940 a comma-separated list of email addresses. If a pattern contains spaces, it
15941 must be enclosed in double quotes.
15943 Each pattern is processed in the same way as a single item in an address list
15944 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
15945 the bounce message, the message is copied to the addresses on the list. The
15946 items are scanned in order, and once a matching one is found, no further items
15947 are examined. For example:
15949 errors_copy = spqr@mydomain postmaster@mydomain.example :\
15950 rqps@mydomain hostmaster@mydomain.example,\
15951 postmaster@mydomain.example
15953 .vindex "&$domain$&"
15954 .vindex "&$local_part$&"
15955 The address list is expanded before use. The expansion variables &$local_part$&
15956 and &$domain$& are set from the original recipient of the error message, and if
15957 there was any wildcard matching in the pattern, the expansion
15958 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
15959 variables &$0$&, &$1$&, etc. are set in the normal way.
15962 .option errors_reply_to main string unset
15963 .cindex "bounce message" "&'Reply-to:'& in"
15964 By default, Exim's bounce and delivery warning messages contain the header line
15966 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
15968 .oindex &%quota_warn_message%&
15969 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
15970 A warning message that is generated by the &%quota_warn_message%& option in an
15971 &(appendfile)& transport may contain its own &'From:'& header line that
15972 overrides the default.
15974 Experience shows that people reply to bounce messages. If the
15975 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
15976 and warning messages. For example:
15978 errors_reply_to = postmaster@my.domain.example
15980 The value of the option is not expanded. It must specify a valid RFC 2822
15981 address. However, if a warning message that is generated by the
15982 &%quota_warn_message%& option in an &(appendfile)& transport contain its
15983 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
15987 .option event_action main string&!! unset
15989 This option declares a string to be expanded for Exim's events mechanism.
15990 For details see chapter &<<CHAPevents>>&.
15993 .option exim_group main string "compile-time configured"
15994 .cindex "gid (group id)" "Exim's own"
15995 .cindex "Exim group"
15996 This option changes the gid under which Exim runs when it gives up root
15997 privilege. The default value is compiled into the binary. The value of this
15998 option is used only when &%exim_user%& is also set. Unless it consists entirely
15999 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
16000 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
16004 .option exim_path main string "see below"
16005 .cindex "Exim binary, path name"
16006 This option specifies the path name of the Exim binary, which is used when Exim
16007 needs to re-exec itself. The default is set up to point to the file &'exim'& in
16008 the directory configured at compile time by the BIN_DIRECTORY setting. It
16009 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
16011 &*Warning*&: Do not use a macro to define the value of this option, because
16012 you will break those Exim utilities that scan the configuration file to find
16013 where the binary is. (They then use the &%-bP%& option to extract option
16014 settings such as the value of &%spool_directory%&.)
16017 .option exim_user main string "compile-time configured"
16018 .cindex "uid (user id)" "Exim's own"
16019 .cindex "Exim user"
16020 This option changes the uid under which Exim runs when it gives up root
16021 privilege. The default value is compiled into the binary. Ownership of the run
16022 time configuration file and the use of the &%-C%& and &%-D%& command line
16023 options is checked against the values in the binary, not what is set here.
16025 Unless it consists entirely of digits, the string is looked up using
16026 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
16027 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
16028 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
16031 .option exim_version main string "current version"
16032 .cindex "Exim version"
16033 .cindex customizing "version number"
16034 .cindex "version number of Exim" override
16035 This option overrides the &$version_number$&/&$exim_version$& that Exim reports in
16036 various places. Use with care; this may fool stupid security scanners.
16039 .option extra_local_interfaces main "string list" unset
16040 This option defines network interfaces that are to be considered local when
16041 routing, but which are not used for listening by the daemon. See section
16042 &<<SECTreclocipadd>>& for details.
16045 . Allow this long option name to split; give it unsplit as a fifth argument
16046 . for the automatic .oindex that is generated by .option.
16048 .option "extract_addresses_remove_arguments" main boolean true &&&
16049 extract_addresses_remove_arguments
16051 .cindex "command line" "addresses with &%-t%&"
16052 .cindex "Sendmail compatibility" "&%-t%& option"
16053 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
16054 are present on the command line when the &%-t%& option is used to build an
16055 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
16056 line addresses are removed from the recipients list. This is also how Smail
16057 behaves. However, other Sendmail documentation (the O'Reilly book) states that
16058 command line addresses are added to those obtained from the header lines. When
16059 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
16060 argument headers. If it is set false, Exim adds rather than removes argument
16064 .option finduser_retries main integer 0
16065 .cindex "NIS, retrying user lookups"
16066 On systems running NIS or other schemes in which user and group information is
16067 distributed from a remote system, there can be times when &[getpwnam()]& and
16068 related functions fail, even when given valid data, because things time out.
16069 Unfortunately these failures cannot be distinguished from genuine &"not found"&
16070 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
16071 many extra times to find a user or a group, waiting for one second between
16074 .cindex "&_/etc/passwd_&" "multiple reading of"
16075 You should not set this option greater than zero if your user information is in
16076 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
16077 search the file multiple times for non-existent users, and also cause delay.
16081 .option freeze_tell main "string list, comma separated" unset
16082 .cindex "freezing messages" "sending a message when freezing"
16083 On encountering certain errors, or when configured to do so in a system filter,
16084 ACL, or special router, Exim freezes a message. This means that no further
16085 delivery attempts take place until an administrator thaws the message, or the
16086 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
16087 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
16088 warning message whenever it freezes something, unless the message it is
16089 freezing is a locally-generated bounce message. (Without this exception there
16090 is the possibility of looping.) The warning message is sent to the addresses
16091 supplied as the comma-separated value of this option. If several of the
16092 message's addresses cause freezing, only a single message is sent. If the
16093 freezing was automatic, the reason(s) for freezing can be found in the message
16094 log. If you configure freezing in a filter or ACL, you must arrange for any
16095 logging that you require.
16098 .option gecos_name main string&!! unset
16100 .cindex "&""gecos""& field, parsing"
16101 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
16102 password file to hold other information in addition to users' real names. Exim
16103 looks up this field for use when it is creating &'Sender:'& or &'From:'&
16104 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
16105 of the field are used unchanged, except that, if an ampersand is encountered,
16106 it is replaced by the user's login name with the first character forced to
16107 upper case, since this is a convention that is observed on many systems.
16109 When these options are set, &%gecos_pattern%& is treated as a regular
16110 expression that is to be applied to the field (again with && replaced by the
16111 login name), and if it matches, &%gecos_name%& is expanded and used as the
16114 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
16115 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
16116 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
16117 name terminates at the first comma, the following can be used:
16119 gecos_pattern = ([^,]*)
16123 .option gecos_pattern main string unset
16124 See &%gecos_name%& above.
16127 .option gnutls_compat_mode main boolean unset
16128 This option controls whether GnuTLS is used in compatibility mode in an Exim
16129 server. This reduces security slightly, but improves interworking with older
16130 implementations of TLS.
16133 .option gnutls_allow_auto_pkcs11 main boolean unset
16134 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
16135 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
16138 &url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
16143 .option headers_charset main string "see below"
16144 This option sets a default character set for translating from encoded MIME
16145 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
16146 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
16147 ultimate default is ISO-8859-1. For more details see the description of header
16148 insertions in section &<<SECTexpansionitems>>&.
16152 .option header_maxsize main integer "see below"
16153 .cindex "header section" "maximum size of"
16154 .cindex "limit" "size of message header section"
16155 This option controls the overall maximum size of a message's header
16156 section. The default is the value of HEADER_MAXSIZE in
16157 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
16158 sections are rejected.
16161 .option header_line_maxsize main integer 0
16162 .cindex "header lines" "maximum size of"
16163 .cindex "limit" "size of one header line"
16164 This option limits the length of any individual header line in a message, after
16165 all the continuations have been joined together. Messages with individual
16166 header lines that are longer than the limit are rejected. The default value of
16167 zero means &"no limit"&.
16172 .option helo_accept_junk_hosts main "host list&!!" unset
16173 .cindex "HELO" "accepting junk data"
16174 .cindex "EHLO" "accepting junk data"
16175 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
16176 mail, and gives an error response for invalid data. Unfortunately, there are
16177 some SMTP clients that send syntactic junk. They can be accommodated by setting
16178 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
16179 if you want to do semantic checking.
16180 See also &%helo_allow_chars%& for a way of extending the permitted character
16184 .option helo_allow_chars main string unset
16185 .cindex "HELO" "underscores in"
16186 .cindex "EHLO" "underscores in"
16187 .cindex "underscore in EHLO/HELO"
16188 This option can be set to a string of rogue characters that are permitted in
16189 all EHLO and HELO names in addition to the standard letters, digits,
16190 hyphens, and dots. If you really must allow underscores, you can set
16192 helo_allow_chars = _
16194 Note that the value is one string, not a list.
16197 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
16198 .cindex "HELO" "forcing reverse lookup"
16199 .cindex "EHLO" "forcing reverse lookup"
16200 If the domain given by a client in a HELO or EHLO command matches this
16201 list, a reverse lookup is done in order to establish the host's true name. The
16202 default forces a lookup if the client host gives the server's name or any of
16203 its IP addresses (in brackets), something that broken clients have been seen to
16207 .option helo_try_verify_hosts main "host list&!!" unset
16208 .cindex "HELO verifying" "optional"
16209 .cindex "EHLO" "verifying, optional"
16210 By default, Exim just checks the syntax of HELO and EHLO commands (see
16211 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
16212 to do more extensive checking of the data supplied by these commands. The ACL
16213 condition &`verify = helo`& is provided to make this possible.
16214 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
16215 to force the check to occur. From release 4.53 onwards, this is no longer
16216 necessary. If the check has not been done before &`verify = helo`& is
16217 encountered, it is done at that time. Consequently, this option is obsolete.
16218 Its specification is retained here for backwards compatibility.
16220 When an EHLO or HELO command is received, if the calling host matches
16221 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
16222 EHLO command either:
16225 is an IP literal matching the calling address of the host, or
16227 .cindex "DNS" "reverse lookup"
16228 .cindex "reverse DNS lookup"
16229 matches the host name that Exim obtains by doing a reverse lookup of the
16230 calling host address, or
16232 when looked up in DNS yields the calling host address.
16235 However, the EHLO or HELO command is not rejected if any of the checks
16236 fail. Processing continues, but the result of the check is remembered, and can
16237 be detected later in an ACL by the &`verify = helo`& condition.
16239 If DNS was used for successful verification, the variable
16240 .cindex "DNS" "DNSSEC"
16241 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
16243 .option helo_verify_hosts main "host list&!!" unset
16244 .cindex "HELO verifying" "mandatory"
16245 .cindex "EHLO" "verifying, mandatory"
16246 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
16247 backwards compatibility. For hosts that match this option, Exim checks the host
16248 name given in the HELO or EHLO in the same way as for
16249 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
16250 rejected with a 550 error, and entries are written to the main and reject logs.
16251 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
16254 .option hold_domains main "domain list&!!" unset
16255 .cindex "domain" "delaying delivery"
16256 .cindex "delivery" "delaying certain domains"
16257 This option allows mail for particular domains to be held in the queue
16258 manually. The option is overridden if a message delivery is forced with the
16259 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
16260 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
16261 item in &%hold_domains%&, no routing or delivery for that address is done, and
16262 it is deferred every time the message is looked at.
16264 This option is intended as a temporary operational measure for delaying the
16265 delivery of mail while some problem is being sorted out, or some new
16266 configuration tested. If you just want to delay the processing of some
16267 domains until a queue run occurs, you should use &%queue_domains%& or
16268 &%queue_smtp_domains%&, not &%hold_domains%&.
16270 A setting of &%hold_domains%& does not override Exim's code for removing
16271 messages from the queue if they have been there longer than the longest retry
16272 time in any retry rule. If you want to hold messages for longer than the normal
16273 retry times, insert a dummy retry rule with a long retry time.
16276 .option host_lookup main "host list&!!" unset
16277 .cindex "host name" "lookup, forcing"
16278 Exim does not look up the name of a calling host from its IP address unless it
16279 is required to compare against some host list, or the host matches
16280 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
16281 option (which normally contains IP addresses rather than host names). The
16282 default configuration file contains
16286 which causes a lookup to happen for all hosts. If the expense of these lookups
16287 is felt to be too great, the setting can be changed or removed.
16289 After a successful reverse lookup, Exim does a forward lookup on the name it
16290 has obtained, to verify that it yields the IP address that it started with. If
16291 this check fails, Exim behaves as if the name lookup failed.
16293 .vindex "&$host_lookup_failed$&"
16294 .vindex "&$sender_host_name$&"
16295 After any kind of failure, the host name (in &$sender_host_name$&) remains
16296 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
16297 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
16298 &`verify = reverse_host_lookup`& in ACLs.
16301 .option host_lookup_order main "string list" &`bydns:byaddr`&
16302 This option specifies the order of different lookup methods when Exim is trying
16303 to find a host name from an IP address. The default is to do a DNS lookup
16304 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
16305 if that fails. You can change the order of these lookups, or omit one entirely,
16308 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
16309 multiple PTR records in the DNS and the IP address is not listed in
16310 &_/etc/hosts_&. Different operating systems give different results in this
16311 case. That is why the default tries a DNS lookup first.
16315 .option host_reject_connection main "host list&!!" unset
16316 .cindex "host" "rejecting connections from"
16317 If this option is set, incoming SMTP calls from the hosts listed are rejected
16318 as soon as the connection is made.
16319 This option is obsolete, and retained only for backward compatibility, because
16320 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
16321 connections immediately.
16323 The ability to give an immediate rejection (either by this option or using an
16324 ACL) is provided for use in unusual cases. Many hosts will just try again,
16325 sometimes without much delay. Normally, it is better to use an ACL to reject
16326 incoming messages at a later stage, such as after RCPT commands. See
16327 chapter &<<CHAPACL>>&.
16330 .option hosts_connection_nolog main "host list&!!" unset
16331 .cindex "host" "not logging connections from"
16332 This option defines a list of hosts for which connection logging does not
16333 happen, even though the &%smtp_connection%& log selector is set. For example,
16334 you might want not to log SMTP connections from local processes, or from
16335 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
16336 the daemon; you should therefore strive to restrict its value to a short inline
16337 list of IP addresses and networks. To disable logging SMTP connections from
16338 local processes, you must create a host list with an empty item. For example:
16340 hosts_connection_nolog = :
16342 If the &%smtp_connection%& log selector is not set, this option has no effect.
16346 .option hosts_require_alpn main "host list&!!" unset
16347 .cindex ALPN "require negotiation in server"
16349 .cindex TLS "Application Layer Protocol Names"
16350 If the TLS library supports ALPN
16351 then a successful negotiation of ALPN will be required for any client
16352 matching the list, for TLS to be used.
16353 See also the &%tls_alpn%& option.
16355 &*Note*&: prevention of fallback to in-clear connection is not
16356 managed by this option, and should be done separately.
16360 .option hosts_proxy main "host list&!!" unset
16361 .cindex proxy "proxy protocol"
16362 This option enables use of Proxy Protocol proxies for incoming
16363 connections. For details see section &<<SECTproxyInbound>>&.
16366 .option hosts_treat_as_local main "domain list&!!" unset
16367 .cindex "local host" "domains treated as"
16368 .cindex "host" "treated as local"
16369 If this option is set, any host names that match the domain list are treated as
16370 if they were the local host when Exim is scanning host lists obtained from MX
16372 or other sources. Note that the value of this option is a domain list, not a
16373 host list, because it is always used to check host names, not IP addresses.
16375 This option also applies when Exim is matching the special items
16376 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
16377 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
16378 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
16379 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
16380 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
16381 interfaces and recognizing the local host.
16384 .option ibase_servers main "string list" unset
16385 .cindex "InterBase" "server list"
16386 This option provides a list of InterBase servers and associated connection data,
16387 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
16388 The option is available only if Exim has been built with InterBase support.
16392 .option ignore_bounce_errors_after main time 10w
16393 .cindex "bounce message" "discarding"
16394 .cindex "discarding bounce message"
16395 This option affects the processing of bounce messages that cannot be delivered,
16396 that is, those that suffer a permanent delivery failure. (Bounce messages that
16397 suffer temporary delivery failures are of course retried in the usual way.)
16399 After a permanent delivery failure, bounce messages are frozen,
16400 because there is no sender to whom they can be returned. When a frozen bounce
16401 message has been in the queue for more than the given time, it is unfrozen at
16402 the next queue run, and a further delivery is attempted. If delivery fails
16403 again, the bounce message is discarded. This makes it possible to keep failed
16404 bounce messages around for a shorter time than the normal maximum retry time
16405 for frozen messages. For example,
16407 ignore_bounce_errors_after = 12h
16409 retries failed bounce message deliveries after 12 hours, discarding any further
16410 failures. If the value of this option is set to a zero time period, bounce
16411 failures are discarded immediately. Setting a very long time (as in the default
16412 value) has the effect of disabling this option. For ways of automatically
16413 dealing with other kinds of frozen message, see &%auto_thaw%& and
16414 &%timeout_frozen_after%&.
16417 .option ignore_fromline_hosts main "host list&!!" unset
16418 .cindex "&""From""& line"
16419 .cindex "UUCP" "&""From""& line"
16420 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
16421 the headers of a message. By default this is treated as the start of the
16422 message's body, which means that any following headers are not recognized as
16423 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
16424 match those hosts that insist on sending it. If the sender is actually a local
16425 process rather than a remote host, and is using &%-bs%& to inject the messages,
16426 &%ignore_fromline_local%& must be set to achieve this effect.
16429 .option ignore_fromline_local main boolean false
16430 See &%ignore_fromline_hosts%& above.
16432 .option keep_environment main "string list" unset
16433 .cindex "environment" "values from"
16434 This option contains a string list of environment variables to keep.
16435 You have to trust these variables or you have to be sure that
16436 these variables do not impose any security risk. Keep in mind that
16437 during the startup phase Exim is running with an effective UID 0 in most
16438 installations. As the default value is an empty list, the default
16439 environment for using libraries, running embedded Perl code, or running
16440 external binaries is empty, and does not not even contain PATH or HOME.
16442 Actually the list is interpreted as a list of patterns
16443 (&<<SECTlistexpand>>&), except that it is not expanded first.
16445 WARNING: Macro substitution is still done first, so having a macro
16446 FOO and having FOO_HOME in your &%keep_environment%& option may have
16447 unexpected results. You may work around this using a regular expression
16448 that does not match the macro name: ^[F]OO_HOME$.
16450 Current versions of Exim issue a warning during startup if you do not mention
16451 &%keep_environment%& in your runtime configuration file and if your
16452 current environment is not empty. Future versions may not issue that warning
16455 See the &%add_environment%& main config option for a way to set
16456 environment variables to a fixed value. The environment for &(pipe)&
16457 transports is handled separately, see section &<<SECTpipeenv>>& for
16461 .option keep_malformed main time 4d
16462 This option specifies the length of time to keep messages whose spool files
16463 have been corrupted in some way. This should, of course, never happen. At the
16464 next attempt to deliver such a message, it gets removed. The incident is
16468 .option ldap_ca_cert_dir main string unset
16469 .cindex "LDAP", "TLS CA certificate directory"
16470 .cindex certificate "directory for LDAP"
16471 This option indicates which directory contains CA certificates for verifying
16472 a TLS certificate presented by an LDAP server.
16473 While Exim does not provide a default value, your SSL library may.
16474 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16475 and constrained to be a directory.
16478 .option ldap_ca_cert_file main string unset
16479 .cindex "LDAP", "TLS CA certificate file"
16480 .cindex certificate "file for LDAP"
16481 This option indicates which file contains CA certificates for verifying
16482 a TLS certificate presented by an LDAP server.
16483 While Exim does not provide a default value, your SSL library may.
16484 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16485 and constrained to be a file.
16488 .option ldap_cert_file main string unset
16489 .cindex "LDAP" "TLS client certificate file"
16490 .cindex certificate "file for LDAP"
16491 This option indicates which file contains an TLS client certificate which
16492 Exim should present to the LDAP server during TLS negotiation.
16493 Should be used together with &%ldap_cert_key%&.
16496 .option ldap_cert_key main string unset
16497 .cindex "LDAP" "TLS client key file"
16498 .cindex certificate "key for LDAP"
16499 This option indicates which file contains the secret/private key to use
16500 to prove identity to the LDAP server during TLS negotiation.
16501 Should be used together with &%ldap_cert_file%&, which contains the
16502 identity to be proven.
16505 .option ldap_cipher_suite main string unset
16506 .cindex "LDAP" "TLS cipher suite"
16507 This controls the TLS cipher-suite negotiation during TLS negotiation with
16508 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
16509 cipher-suite options with OpenSSL (as used by LDAP client libraries).
16512 .option ldap_default_servers main "string list" unset
16513 .cindex "LDAP" "default servers"
16514 This option provides a list of LDAP servers which are tried in turn when an
16515 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
16516 details of LDAP queries. This option is available only when Exim has been built
16520 .option ldap_require_cert main string unset.
16521 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
16522 This should be one of the values "hard", "demand", "allow", "try" or "never".
16523 A value other than one of these is interpreted as "never".
16524 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
16525 Although Exim does not set a default, the LDAP library probably defaults
16529 .option ldap_start_tls main boolean false
16530 .cindex "LDAP" "whether or not to negotiate TLS"
16531 If set, Exim will attempt to negotiate TLS with the LDAP server when
16532 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
16533 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
16535 In the event of failure to negotiate TLS, the action taken is controlled
16536 by &%ldap_require_cert%&.
16537 This option is ignored for &`ldapi`& connections.
16540 .option ldap_version main integer unset
16541 .cindex "LDAP" "protocol version, forcing"
16542 This option can be used to force Exim to set a specific protocol version for
16543 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
16544 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
16545 the LDAP headers; otherwise it is 2. This option is available only when Exim
16546 has been built with LDAP support.
16550 .option local_from_check main boolean true
16551 .cindex "&'Sender:'& header line" "disabling addition of"
16552 .cindex "&'From:'& header line" "disabling checking of"
16553 When a message is submitted locally (that is, not over a TCP/IP connection) by
16554 an untrusted user, Exim removes any existing &'Sender:'& header line, and
16555 checks that the &'From:'& header line matches the login of the calling user and
16556 the domain specified by &%qualify_domain%&.
16558 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
16559 locally submitted message is automatically qualified by Exim, unless the
16560 &%-bnq%& command line option is used.
16562 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
16563 on the local part. If the &'From:'& header line does not match, Exim adds a
16564 &'Sender:'& header with an address constructed from the calling user's login
16565 and the default qualify domain.
16567 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
16568 and no &'Sender:'& header is ever added. If, in addition, you want to retain
16569 &'Sender:'& header lines supplied by untrusted users, you must also set
16570 &%local_sender_retain%& to be true.
16572 .cindex "envelope from"
16573 .cindex "envelope sender"
16574 These options affect only the header lines in the message. The envelope sender
16575 is still forced to be the login id at the qualify domain unless
16576 &%untrusted_set_sender%& permits the user to supply an envelope sender.
16578 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
16579 request similar header line checking. See section &<<SECTthesenhea>>&, which
16580 has more details about &'Sender:'& processing.
16585 .option local_from_prefix main string unset
16586 When Exim checks the &'From:'& header line of locally submitted messages for
16587 matching the login id (see &%local_from_check%& above), it can be configured to
16588 ignore certain prefixes and suffixes in the local part of the address. This is
16589 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
16590 appropriate lists, in the same form as the &%local_part_prefix%& and
16591 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
16594 local_from_prefix = *-
16596 is set, a &'From:'& line containing
16598 From: anything-user@your.domain.example
16600 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
16601 matches the actual sender address that is constructed from the login name and
16605 .option local_from_suffix main string unset
16606 See &%local_from_prefix%& above.
16609 .option local_interfaces main "string list" "see below"
16610 This option controls which network interfaces are used by the daemon for
16611 listening; they are also used to identify the local host when routing. Chapter
16612 &<<CHAPinterfaces>>& contains a full description of this option and the related
16613 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
16614 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
16615 &%local_interfaces%& is
16617 local_interfaces = 0.0.0.0
16619 when Exim is built without IPv6 support; otherwise it is
16621 local_interfaces = <; ::0 ; 0.0.0.0
16624 .option local_scan_timeout main time 5m
16625 .cindex "timeout" "for &[local_scan()]& function"
16626 .cindex "&[local_scan()]& function" "timeout"
16627 This timeout applies to the &[local_scan()]& function (see chapter
16628 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
16629 the incoming message is rejected with a temporary error if it is an SMTP
16630 message. For a non-SMTP message, the message is dropped and Exim ends with a
16631 non-zero code. The incident is logged on the main and reject logs.
16635 .option local_sender_retain main boolean false
16636 .cindex "&'Sender:'& header line" "retaining from local submission"
16637 When a message is submitted locally (that is, not over a TCP/IP connection) by
16638 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
16639 do not want this to happen, you must set &%local_sender_retain%&, and you must
16640 also set &%local_from_check%& to be false (Exim will complain if you do not).
16641 See also the ACL modifier &`control = suppress_local_fixups`&. Section
16642 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
16647 .option localhost_number main string&!! unset
16648 .cindex "host" "locally unique number for"
16649 .cindex "message ids" "with multiple hosts"
16650 .vindex "&$localhost_number$&"
16651 Exim's message ids are normally unique only within the local host. If
16652 uniqueness among a set of hosts is required, each host must set a different
16653 value for the &%localhost_number%& option. The string is expanded immediately
16654 after reading the configuration file (so that a number can be computed from the
16655 host name, for example) and the result of the expansion must be a number in the
16656 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
16657 systems). This is available in subsequent string expansions via the variable
16658 &$localhost_number$&. When &%localhost_number is set%&, the final two
16659 characters of the message id, instead of just being a fractional part of the
16660 time, are computed from the time and the local host number as described in
16661 section &<<SECTmessiden>>&.
16665 .option log_file_path main "string list&!!" "set at compile time"
16666 .cindex "log" "file path for"
16667 This option sets the path which is used to determine the names of Exim's log
16668 files, or indicates that logging is to be to syslog, or both. It is expanded
16669 when Exim is entered, so it can, for example, contain a reference to the host
16670 name. If no specific path is set for the log files at compile or runtime,
16671 or if the option is unset at runtime (i.e. &`log_file_path = `&)
16672 they are written in a sub-directory called &_log_& in Exim's spool directory.
16673 A path must start with a slash.
16674 To send to syslog, use the word &"syslog"&.
16675 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
16676 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
16677 used. If this string is fixed at your installation (contains no expansion
16678 variables) it is recommended that you do not set this option in the
16679 configuration file, but instead supply the path using LOG_FILE_PATH in
16680 &_Local/Makefile_& so that it is available to Exim for logging errors detected
16681 early on &-- in particular, failure to read the configuration file.
16684 .option log_selector main string unset
16685 .cindex "log" "selectors"
16686 This option can be used to reduce or increase the number of things that Exim
16687 writes to its log files. Its argument is made up of names preceded by plus or
16688 minus characters. For example:
16690 log_selector = +arguments -retry_defer
16692 A list of possible names and what they control is given in the chapter on
16693 logging, in section &<<SECTlogselector>>&.
16696 .option log_timezone main boolean false
16697 .cindex "log" "timezone for entries"
16698 .vindex "&$tod_log$&"
16699 .vindex "&$tod_zone$&"
16700 By default, the timestamps on log lines are in local time without the
16701 timezone. This means that if your timezone changes twice a year, the timestamps
16702 in log lines are ambiguous for an hour when the clocks go back. One way of
16703 avoiding this problem is to set the timezone to UTC. An alternative is to set
16704 &%log_timezone%& true. This turns on the addition of the timezone offset to
16705 timestamps in log lines. Turning on this option can add quite a lot to the size
16706 of log files because each line is extended by 6 characters. Note that the
16707 &$tod_log$& variable contains the log timestamp without the zone, but there is
16708 another variable called &$tod_zone$& that contains just the timezone offset.
16711 .option lookup_open_max main integer 25
16712 .cindex "too many open files"
16713 .cindex "open files, too many"
16714 .cindex "file" "too many open"
16715 .cindex "lookup" "maximum open files"
16716 .cindex "limit" "open files for lookups"
16717 This option limits the number of simultaneously open files for single-key
16718 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
16719 Exim normally keeps these files open during routing, because often the same
16720 file is required several times. If the limit is reached, Exim closes the least
16721 recently used file. Note that if you are using the &'ndbm'& library, it
16722 actually opens two files for each logical DBM database, though it still counts
16723 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
16724 open files"& errors with NDBM, you need to reduce the value of
16725 &%lookup_open_max%&.
16728 .option max_username_length main integer 0
16729 .cindex "length of login name"
16730 .cindex "user name" "maximum length"
16731 .cindex "limit" "user name length"
16732 Some operating systems are broken in that they truncate long arguments to
16733 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
16734 this option is set greater than zero, any attempt to call &[getpwnam()]& with
16735 an argument that is longer behaves as if &[getpwnam()]& failed.
16738 .option message_body_newlines main bool false
16739 .cindex "message body" "newlines in variables"
16740 .cindex "newline" "in message body variables"
16741 .vindex "&$message_body$&"
16742 .vindex "&$message_body_end$&"
16743 By default, newlines in the message body are replaced by spaces when setting
16744 the &$message_body$& and &$message_body_end$& expansion variables. If this
16745 option is set true, this no longer happens.
16748 .option message_body_visible main integer 500
16749 .cindex "body of message" "visible size"
16750 .cindex "message body" "visible size"
16751 .vindex "&$message_body$&"
16752 .vindex "&$message_body_end$&"
16753 This option specifies how much of a message's body is to be included in the
16754 &$message_body$& and &$message_body_end$& expansion variables.
16757 .option message_id_header_domain main string&!! unset
16758 .cindex "&'Message-ID:'& header line"
16759 If this option is set, the string is expanded and used as the right hand side
16760 (domain) of the &'Message-ID:'& header that Exim creates if a
16761 locally-originated incoming message does not have one. &"Locally-originated"&
16762 means &"not received over TCP/IP."&
16763 Otherwise, the primary host name is used.
16764 Only letters, digits, dot and hyphen are accepted; any other characters are
16765 replaced by hyphens. If the expansion is forced to fail, or if the result is an
16766 empty string, the option is ignored.
16769 .option message_id_header_text main string&!! unset
16770 If this variable is set, the string is expanded and used to augment the text of
16771 the &'Message-id:'& header that Exim creates if a locally-originated incoming
16772 message does not have one. The text of this header is required by RFC 2822 to
16773 take the form of an address. By default, Exim uses its internal message id as
16774 the local part, and the primary host name as the domain. If this option is set,
16775 it is expanded, and provided the expansion is not forced to fail, and does not
16776 yield an empty string, the result is inserted into the header immediately
16777 before the @, separated from the internal message id by a dot. Any characters
16778 that are illegal in an address are automatically converted into hyphens. This
16779 means that variables such as &$tod_log$& can be used, because the spaces and
16780 colons will become hyphens.
16783 .option message_logs main boolean true
16784 .cindex "message logs" "disabling"
16785 .cindex "log" "message log; disabling"
16786 If this option is turned off, per-message log files are not created in the
16787 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
16788 Exim, by reducing the number of files involved in handling a message from a
16789 minimum of four (header spool file, body spool file, delivery journal, and
16790 per-message log) to three. The other major I/O activity is Exim's main log,
16791 which is not affected by this option.
16794 .option message_size_limit main string&!! 50M
16795 .cindex "message" "size limit"
16796 .cindex "limit" "message size"
16797 .cindex "size" "of message, limit"
16798 This option limits the maximum size of message that Exim will process. The
16799 value is expanded for each incoming connection so, for example, it can be made
16800 to depend on the IP address of the remote host for messages arriving via
16801 TCP/IP. After expansion, the value must be a sequence of decimal digits,
16802 optionally followed by K or M.
16804 .cindex "SIZE" "ESMTP extension, advertising"
16805 .cindex "ESMTP extensions" SIZE
16806 If nonzero the value will be advertised as a parameter to the ESMTP SIZE
16807 service extension keyword.
16809 &*Note*&: This limit cannot be made to depend on a message's sender or any
16810 other properties of an individual message, because it has to be advertised in
16811 the server's response to EHLO. String expansion failure causes a temporary
16812 error. A value of zero means no limit, but its use is not recommended. See also
16813 &%bounce_return_size_limit%&.
16815 Incoming SMTP messages are failed with a 552 error if the limit is
16816 exceeded; locally-generated messages either get a stderr message or a delivery
16817 failure message to the sender, depending on the &%-oe%& setting. Rejection of
16818 an oversized message is logged in both the main and the reject logs. See also
16819 the generic transport option &%message_size_limit%&, which limits the size of
16820 message that an individual transport can process.
16822 If you use a virus-scanner and set this option to to a value larger than the
16823 maximum size that your virus-scanner is configured to support, you may get
16824 failures triggered by large mails. The right size to configure for the
16825 virus-scanner depends upon what data is passed and the options in use but it's
16826 probably safest to just set it to a little larger than this value. E.g., with a
16827 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
16828 some problems may result.
16830 A value of 0 will disable size limit checking; Exim will still advertise the
16831 SIZE extension in an EHLO response, but without a limit, so as to permit
16832 SMTP clients to still indicate the message size along with the MAIL verb.
16835 .option move_frozen_messages main boolean false
16836 .cindex "frozen messages" "moving"
16837 This option, which is available only if Exim has been built with the setting
16839 SUPPORT_MOVE_FROZEN_MESSAGES=yes
16841 in &_Local/Makefile_&, causes frozen messages and their message logs to be
16842 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
16843 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
16844 standard utilities for handling such moved messages, and they do not show up in
16845 lists generated by &%-bp%& or by the Exim monitor.
16848 .option mua_wrapper main boolean false
16849 Setting this option true causes Exim to run in a very restrictive mode in which
16850 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
16851 contains a full description of this facility.
16855 .option mysql_servers main "string list" unset
16856 .cindex "MySQL" "server list"
16857 This option provides a list of MySQL servers and associated connection data, to
16858 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
16859 option is available only if Exim has been built with MySQL support.
16862 .option never_users main "string list&!!" unset
16863 This option is expanded just once, at the start of Exim's processing. Local
16864 message deliveries are normally run in processes that are setuid to the
16865 recipient, and remote deliveries are normally run under Exim's own uid and gid.
16866 It is usually desirable to prevent any deliveries from running as root, as a
16869 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
16870 list of users that must not be used for local deliveries. This list is fixed in
16871 the binary and cannot be overridden by the configuration file. By default, it
16872 contains just the single user name &"root"&. The &%never_users%& runtime option
16873 can be used to add more users to the fixed list.
16875 If a message is to be delivered as one of the users on the fixed list or the
16876 &%never_users%& list, an error occurs, and delivery is deferred. A common
16879 never_users = root:daemon:bin
16881 Including root is redundant if it is also on the fixed list, but it does no
16882 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
16886 .option notifier_socket main string "$spool_directory/exim_daemon_notify"
16887 This option gives the name for a unix-domain socket on which the daemon
16888 listens for work and information-requests.
16889 Only installations running multiple daemons sharing a spool directory
16890 should need to modify the default.
16892 The option is expanded before use.
16893 If the platform supports Linux-style abstract socket names, the result
16894 is used with a nul byte prefixed.
16896 .new "if nonempty,"
16897 it should be a full path name and use a directory accessible
16901 If this option is set as empty,
16902 or the command line &%-oY%& option is used, or
16904 the command line uses a &%-oX%& option and does not use &%-oP%&,
16905 then a notifier socket is not created.
16908 .option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation"
16909 .cindex "OpenSSL "compatibility options"
16910 This option allows an administrator to adjust the SSL options applied
16911 by OpenSSL to connections. It is given as a space-separated list of items,
16912 each one to be +added or -subtracted from the current value.
16914 This option is only available if Exim is built against OpenSSL. The values
16915 available for this option vary according to the age of your OpenSSL install.
16916 The &"all"& value controls a subset of flags which are available, typically
16917 the bug workaround options. The &'SSL_CTX_set_options'& man page will
16918 list the values known on your system and Exim should support all the
16919 &"bug workaround"& options and many of the &"modifying"& options. The Exim
16920 names lose the leading &"SSL_OP_"& and are lower-cased.
16922 Note that adjusting the options can have severe impact upon the security of
16923 SSL as used by Exim. It is possible to disable safety checks and shoot
16924 yourself in the foot in various unpleasant ways. This option should not be
16925 adjusted lightly. An unrecognised item will be detected at startup, by
16926 invoking Exim with the &%-bV%& flag.
16928 The option affects Exim operating both as a server and as a client.
16930 Historical note: prior to release 4.80, Exim defaulted this value to
16931 "+dont_insert_empty_fragments", which may still be needed for compatibility
16932 with some clients, but which lowers security by increasing exposure to
16933 some now infamous attacks.
16937 # Make both old MS and old Eudora happy:
16938 openssl_options = -all +microsoft_big_sslv3_buffer \
16939 +dont_insert_empty_fragments
16941 # Disable older protocol versions:
16942 openssl_options = +no_sslv2 +no_sslv3
16945 Possible options may include:
16949 &`allow_unsafe_legacy_renegotiation`&
16951 &`cipher_server_preference`&
16953 &`dont_insert_empty_fragments`&
16957 &`legacy_server_connect`&
16959 &`microsoft_big_sslv3_buffer`&
16961 &`microsoft_sess_id_bug`&
16963 &`msie_sslv2_rsa_padding`&
16965 &`netscape_challenge_bug`&
16967 &`netscape_reuse_cipher_change_bug`&
16971 &`no_session_resumption_on_renegotiation`&
16985 &`safari_ecdhe_ecdsa_bug`&
16989 &`single_ecdh_use`&
16991 &`ssleay_080_client_dh_bug`&
16993 &`sslref2_reuse_cert_type_bug`&
16995 &`tls_block_padding_bug`&
16999 &`tls_rollback_bug`&
17002 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
17003 all clients connecting using the MacOS SecureTransport TLS facility prior
17004 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
17005 to negotiate TLS then this option value might help, provided that your OpenSSL
17006 release is new enough to contain this work-around. This may be a situation
17007 where you have to upgrade OpenSSL to get buggy clients working.
17010 .option oracle_servers main "string list" unset
17011 .cindex "Oracle" "server list"
17012 This option provides a list of Oracle servers and associated connection data,
17013 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
17014 The option is available only if Exim has been built with Oracle support.
17017 .option percent_hack_domains main "domain list&!!" unset
17018 .cindex "&""percent hack""&"
17019 .cindex "source routing" "in email address"
17020 .cindex "address" "source-routed"
17021 The &"percent hack"& is the convention whereby a local part containing a
17022 percent sign is re-interpreted as a new email address, with the percent
17023 replaced by @. This is sometimes called &"source routing"&, though that term is
17024 also applied to RFC 2822 addresses that begin with an @ character. If this
17025 option is set, Exim implements the percent facility for those domains listed,
17026 but no others. This happens before an incoming SMTP address is tested against
17029 &*Warning*&: The &"percent hack"& has often been abused by people who are
17030 trying to get round relaying restrictions. For this reason, it is best avoided
17031 if at all possible. Unfortunately, a number of less security-conscious MTAs
17032 implement it unconditionally. If you are running Exim on a gateway host, and
17033 routing mail through to internal MTAs without processing the local parts, it is
17034 a good idea to reject recipient addresses with percent characters in their
17035 local parts. Exim's default configuration does this.
17038 .option perl_at_start main boolean false
17040 This option is available only when Exim is built with an embedded Perl
17041 interpreter. See chapter &<<CHAPperl>>& for details of its use.
17044 .option perl_startup main string unset
17046 This option is available only when Exim is built with an embedded Perl
17047 interpreter. See chapter &<<CHAPperl>>& for details of its use.
17049 .option perl_taintmode main boolean false
17051 This option enables the taint mode of the embedded Perl interpreter.
17054 .option pgsql_servers main "string list" unset
17055 .cindex "PostgreSQL lookup type" "server list"
17056 This option provides a list of PostgreSQL servers and associated connection
17057 data, to be used in conjunction with &(pgsql)& lookups (see section
17058 &<<SECID72>>&). The option is available only if Exim has been built with
17059 PostgreSQL support.
17062 .option pid_file_path main string&!! "set at compile time"
17063 .cindex "daemon" "pid file path"
17064 .cindex "pid file, path for"
17065 This option sets the name of the file to which the Exim daemon writes its
17066 process id. The string is expanded, so it can contain, for example, references
17069 pid_file_path = /var/log/$primary_hostname/exim.pid
17071 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
17073 The value set by the option can be overridden by the &%-oP%& command line
17074 option. A pid file is not written if a &"non-standard"& daemon is run by means
17075 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
17078 .option pipelining_advertise_hosts main "host list&!!" *
17079 .cindex "PIPELINING" "suppressing advertising"
17080 .cindex "ESMTP extensions" PIPELINING
17081 This option can be used to suppress the advertisement of the SMTP
17082 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
17083 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
17084 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
17085 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
17086 that clients will use it; &"out of order"& commands that are &"expected"& do
17087 not count as protocol errors (see &%smtp_max_synprot_errors%&).
17089 .option pipelining_connect_advertise_hosts main "host list&!!" *
17090 .cindex "pipelining" "early connection"
17091 .cindex "pipelining" PIPE_CONNECT
17092 .cindex "ESMTP extensions" PIPE_CONNECT
17093 If Exim is built with the SUPPORT_PIPE_CONNECT build option
17094 this option controls which hosts the facility is advertised to
17095 and from which pipeline early-connection (before MAIL) SMTP
17096 commands are acceptable.
17097 When used, the pipelining saves on roundtrip times.
17099 See also the &%hosts_pipe_connect%& smtp transport option.
17102 The SMTP service extension keyword advertised is &"PIPE_CONNECT"&.
17106 .option prdr_enable main boolean false
17107 .cindex "PRDR" "enabling on server"
17108 .cindex "ESMTP extensions" PRDR
17109 This option can be used to enable the Per-Recipient Data Response extension
17110 to SMTP, defined by Eric Hall.
17111 If the option is set, PRDR is advertised by Exim when operating as a server.
17112 If the client requests PRDR, and more than one recipient, for a message
17113 an additional ACL is called for each recipient after the message content
17114 is received. See section &<<SECTPRDRACL>>&.
17116 .option preserve_message_logs main boolean false
17117 .cindex "message logs" "preserving"
17118 If this option is set, message log files are not deleted when messages are
17119 completed. Instead, they are moved to a sub-directory of the spool directory
17120 called &_msglog.OLD_&, where they remain available for statistical or debugging
17121 purposes. This is a dangerous option to set on systems with any appreciable
17122 volume of mail. Use with care!
17125 .option primary_hostname main string "see below"
17126 .cindex "name" "of local host"
17127 .cindex "host" "name of local"
17128 .cindex "local host" "name of"
17129 .vindex "&$primary_hostname$&"
17130 This specifies the name of the current host. It is used in the default EHLO or
17131 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
17132 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
17133 The value is also used by default in some SMTP response messages from an Exim
17134 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
17136 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
17137 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
17138 contains only one component, Exim passes it to &[gethostbyname()]& (or
17139 &[getipnodebyname()]& when available) in order to obtain the fully qualified
17140 version. The variable &$primary_hostname$& contains the host name, whether set
17141 explicitly by this option, or defaulted.
17144 .option print_topbitchars main boolean false
17145 .cindex "printing characters"
17146 .cindex "8-bit characters"
17147 By default, Exim considers only those characters whose codes lie in the range
17148 32&--126 to be printing characters. In a number of circumstances (for example,
17149 when writing log entries) non-printing characters are converted into escape
17150 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
17151 is set, code values of 128 and above are also considered to be printing
17154 This option also affects the header syntax checks performed by the
17155 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
17156 the user's full name when constructing From: and Sender: addresses (as
17157 described in section &<<SECTconstr>>&). Setting this option can cause
17158 Exim to generate eight bit message headers that do not conform to the
17162 .option process_log_path main string unset
17163 .cindex "process log path"
17164 .cindex "log" "process log"
17165 .cindex "&'exiwhat'&"
17166 This option sets the name of the file to which an Exim process writes its
17167 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
17168 utility script. If this option is unset, the file called &_exim-process.info_&
17169 in Exim's spool directory is used. The ability to specify the name explicitly
17170 can be useful in environments where two different Exims are running, using
17171 different spool directories.
17174 .option prod_requires_admin main boolean true
17175 .cindex "restricting access to features"
17179 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
17180 admin user unless &%prod_requires_admin%& is set false. See also
17181 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
17185 .option proxy_protocol_timeout main time 3s
17186 .cindex proxy "proxy protocol"
17187 This option sets the timeout for proxy protocol negotiation.
17188 For details see section &<<SECTproxyInbound>>&.
17192 .option qualify_domain main string "see below"
17193 .cindex "domain" "for qualifying addresses"
17194 .cindex "address" "qualification"
17195 This option specifies the domain name that is added to any envelope sender
17196 addresses that do not have a domain qualification. It also applies to
17197 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
17198 are accepted by default only for locally-generated messages. Qualification is
17199 also applied to addresses in header lines such as &'From:'& and &'To:'& for
17200 locally-generated messages, unless the &%-bnq%& command line option is used.
17202 Messages from external sources must always contain fully qualified addresses,
17203 unless the sending host matches &%sender_unqualified_hosts%& or
17204 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
17205 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
17206 necessary. Internally, Exim always works with fully qualified envelope
17207 addresses. If &%qualify_domain%& is not set, it defaults to the
17208 &%primary_hostname%& value.
17211 .option qualify_recipient main string "see below"
17212 This option allows you to specify a different domain for qualifying recipient
17213 addresses to the one that is used for senders. See &%qualify_domain%& above.
17217 .option queue_domains main "domain list&!!" unset
17218 .cindex "domain" "specifying non-immediate delivery"
17219 .cindex "queueing incoming messages"
17220 .cindex "message" "queueing certain domains"
17221 This option lists domains for which immediate delivery is not required.
17222 A delivery process is started whenever a message is received, but only those
17223 domains that do not match are processed. All other deliveries wait until the
17224 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
17228 .option queue_fast_ramp main boolean false
17229 .cindex "queue runner" "two phase"
17230 .cindex "queue" "double scanning"
17231 If set to true, two-phase queue runs, initiated using &%-qq%& on the
17232 command line, may start parallel delivery processes during their first
17233 phase. This will be done when a threshold number of messages have been
17234 routed for a single host.
17238 .option queue_list_requires_admin main boolean true
17239 .cindex "restricting access to features"
17241 The &%-bp%& command-line option, which lists the messages that are on the
17242 queue, requires the caller to be an admin user unless
17243 &%queue_list_requires_admin%& is set false.
17244 See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
17247 .option queue_only main boolean false
17248 .cindex "queueing incoming messages"
17249 .cindex "message" "queueing unconditionally"
17250 If &%queue_only%& is set, a delivery process is not automatically started
17251 whenever a message is received. Instead, the message waits in the queue for the
17252 next queue run. Even if &%queue_only%& is false, incoming messages may not get
17253 delivered immediately when certain conditions (such as heavy load) occur.
17255 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
17256 and &%-odi%& command line options override &%queue_only%& unless
17257 &%queue_only_override%& is set false. See also &%queue_only_file%&,
17258 &%queue_only_load%&, and &%smtp_accept_queue%&.
17261 .option queue_only_file main string unset
17262 .cindex "queueing incoming messages"
17263 .cindex "message" "queueing by file existence"
17264 This option can be set to a colon-separated list of absolute path names, each
17265 one optionally preceded by &"smtp"&. When Exim is receiving a message,
17266 it tests for the existence of each listed path using a call to &[stat()]&. For
17267 each path that exists, the corresponding queueing option is set.
17268 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
17269 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
17271 queue_only_file = smtp/some/file
17273 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
17274 &_/some/file_& exists.
17277 .option queue_only_load main fixed-point unset
17278 .cindex "load average"
17279 .cindex "queueing incoming messages"
17280 .cindex "message" "queueing by load"
17281 If the system load average is higher than this value, incoming messages from
17282 all sources are queued, and no automatic deliveries are started. If this
17283 happens during local or remote SMTP input, all subsequent messages received on
17284 the same SMTP connection are queued by default, whatever happens to the load in
17285 the meantime, but this can be changed by setting &%queue_only_load_latch%&
17288 Deliveries will subsequently be performed by queue runner processes. This
17289 option has no effect on ancient operating systems on which Exim cannot
17290 determine the load average. See also &%deliver_queue_load_max%& and
17291 &%smtp_load_reserve%&.
17294 .option queue_only_load_latch main boolean true
17295 .cindex "load average" "re-evaluating per message"
17296 When this option is true (the default), once one message has been queued
17297 because the load average is higher than the value set by &%queue_only_load%&,
17298 all subsequent messages received on the same SMTP connection are also queued.
17299 This is a deliberate choice; even though the load average may fall below the
17300 threshold, it doesn't seem right to deliver later messages on the same
17301 connection when not delivering earlier ones. However, there are special
17302 circumstances such as very long-lived connections from scanning appliances
17303 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
17304 should be set false. This causes the value of the load average to be
17305 re-evaluated for each message.
17308 .option queue_only_override main boolean true
17309 .cindex "queueing incoming messages"
17310 When this option is true, the &%-od%&&'x'& command line options override the
17311 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
17312 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
17313 to override; they are accepted, but ignored.
17316 .option queue_run_in_order main boolean false
17317 .cindex "queue runner" "processing messages in order"
17318 If this option is set, queue runs happen in order of message arrival instead of
17319 in an arbitrary order. For this to happen, a complete list of the entire queue
17320 must be set up before the deliveries start. When the queue is all held in a
17321 single directory (the default), a single list is created for both the ordered
17322 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
17323 single list is not created when &%queue_run_in_order%& is false. In this case,
17324 the sub-directories are processed one at a time (in a random order), and this
17325 avoids setting up one huge list for the whole queue. Thus, setting
17326 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
17327 when the queue is large, because of the extra work in setting up the single,
17328 large list. In most situations, &%queue_run_in_order%& should not be set.
17332 .option queue_run_max main integer&!! 5
17333 .cindex "queue runner" "maximum number of"
17334 This controls the maximum number of queue runner processes that an Exim daemon
17335 can run simultaneously. This does not mean that it starts them all at once,
17336 but rather that if the maximum number are still running when the time comes to
17337 start another one, it refrains from starting another one. This can happen with
17338 very large queues and/or very sluggish deliveries. This option does not,
17339 however, interlock with other processes, so additional queue runners can be
17340 started by other means, or by killing and restarting the daemon.
17342 Setting this option to zero does not suppress queue runs; rather, it disables
17343 the limit, allowing any number of simultaneous queue runner processes to be
17344 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
17345 the daemon's command line.
17347 .cindex queues named
17348 .cindex "named queues" "resource limit"
17349 To set limits for different named queues use
17350 an expansion depending on the &$queue_name$& variable.
17352 .option queue_smtp_domains main "domain list&!!" unset
17353 .cindex "queueing incoming messages"
17354 .cindex "message" "queueing remote deliveries"
17355 .cindex "first pass routing"
17356 When this option is set, a delivery process is started whenever a message is
17357 received, routing is performed, and local deliveries take place.
17358 However, if any SMTP deliveries are required for domains that match
17359 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
17360 message waits in the queue for the next queue run. Since routing of the message
17361 has taken place, Exim knows to which remote hosts it must be delivered, and so
17362 when the queue run happens, multiple messages for the same host are delivered
17363 over a single SMTP connection. The &%-odqs%& command line option causes all
17364 SMTP deliveries to be queued in this way, and is equivalent to setting
17365 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
17369 .option receive_timeout main time 0s
17370 .cindex "timeout" "for non-SMTP input"
17371 This option sets the timeout for accepting a non-SMTP message, that is, the
17372 maximum time that Exim waits when reading a message on the standard input. If
17373 the value is zero, it will wait forever. This setting is overridden by the
17374 &%-or%& command line option. The timeout for incoming SMTP messages is
17375 controlled by &%smtp_receive_timeout%&.
17377 .option received_header_text main string&!! "see below"
17378 .cindex "customizing" "&'Received:'& header"
17379 .cindex "&'Received:'& header line" "customizing"
17380 This string defines the contents of the &'Received:'& message header that is
17381 added to each message, except for the timestamp, which is automatically added
17382 on at the end (preceded by a semicolon). The string is expanded each time it is
17383 used. If the expansion yields an empty string, no &'Received:'& header line is
17384 added to the message. Otherwise, the string should start with the text
17385 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
17387 The default setting is:
17390 received_header_text = Received: \
17391 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
17392 {${if def:sender_ident \
17393 {from ${quote_local_part:$sender_ident} }}\
17394 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
17395 by $primary_hostname \
17396 ${if def:received_protocol {with $received_protocol }}\
17397 ${if def:tls_in_ver { ($tls_in_ver)}}\
17398 ${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\
17399 (Exim $version_number)\n\t\
17400 ${if def:sender_address \
17401 {(envelope-from <$sender_address>)\n\t}}\
17402 id $message_exim_id\
17403 ${if def:received_for {\n\tfor $received_for}}
17406 The references to the TLS version and cipher are
17407 omitted when Exim is built without TLS
17408 support. The use of conditional expansions ensures that this works for both
17409 locally generated messages and messages received from remote hosts, giving
17410 header lines such as the following:
17412 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
17413 by marley.carol.example with esmtp (Exim 4.00)
17414 (envelope-from <bob@carol.example>)
17415 id 16IOWa-00019l-00
17416 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
17417 Received: by scrooge.carol.example with local (Exim 4.00)
17418 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
17420 Until the body of the message has been received, the timestamp is the time when
17421 the message started to be received. Once the body has arrived, and all policy
17422 checks have taken place, the timestamp is updated to the time at which the
17423 message was accepted.
17426 .option received_headers_max main integer 30
17427 .cindex "loop" "prevention"
17428 .cindex "mail loop prevention"
17429 .cindex "&'Received:'& header line" "counting"
17430 When a message is to be delivered, the number of &'Received:'& headers is
17431 counted, and if it is greater than this parameter, a mail loop is assumed to
17432 have occurred, the delivery is abandoned, and an error message is generated.
17433 This applies to both local and remote deliveries.
17436 .option recipient_unqualified_hosts main "host list&!!" unset
17437 .cindex "unqualified addresses"
17438 .cindex "host" "unqualified addresses from"
17439 This option lists those hosts from which Exim is prepared to accept unqualified
17440 recipient addresses in message envelopes. The addresses are made fully
17441 qualified by the addition of the &%qualify_recipient%& value. This option also
17442 affects message header lines. Exim does not reject unqualified recipient
17443 addresses in headers, but it qualifies them only if the message came from a
17444 host that matches &%recipient_unqualified_hosts%&,
17445 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
17446 option was not set.
17449 .option recipients_max main integer 50000
17450 .cindex "limit" "number of recipients"
17451 .cindex "recipient" "maximum number"
17452 If this option is set greater than zero, it specifies the maximum number of
17453 original recipients for any message. Additional recipients that are generated
17454 by aliasing or forwarding do not count. SMTP messages get a 452 response for
17455 all recipients over the limit; earlier recipients are delivered as normal.
17456 Non-SMTP messages with too many recipients are failed, and no deliveries are
17459 .cindex "RCPT" "maximum number of incoming"
17460 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
17461 RCPT commands in a single message.
17464 .option recipients_max_reject main boolean false
17465 If this option is set true, Exim rejects SMTP messages containing too many
17466 recipients by giving 552 errors to the surplus RCPT commands, and a 554
17467 error to the eventual DATA command. Otherwise (the default) it gives a 452
17468 error to the surplus RCPT commands and accepts the message on behalf of the
17469 initial set of recipients. The remote server should then re-send the message
17470 for the remaining recipients at a later time.
17473 .option remote_max_parallel main integer 2
17474 .cindex "delivery" "parallelism for remote"
17475 This option controls parallel delivery of one message to a number of remote
17476 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
17477 does all the remote deliveries for a message one by one. Otherwise, if a single
17478 message has to be delivered to more than one remote host, or if several copies
17479 have to be sent to the same remote host, up to &%remote_max_parallel%&
17480 deliveries are done simultaneously. If more than &%remote_max_parallel%&
17481 deliveries are required, the maximum number of processes are started, and as
17482 each one finishes, another is begun. The order of starting processes is the
17483 same as if sequential delivery were being done, and can be controlled by the
17484 &%remote_sort_domains%& option. If parallel delivery takes place while running
17485 with debugging turned on, the debugging output from each delivery process is
17486 tagged with its process id.
17488 This option controls only the maximum number of parallel deliveries for one
17489 message in one Exim delivery process. Because Exim has no central queue
17490 manager, there is no way of controlling the total number of simultaneous
17491 deliveries if the configuration allows a delivery attempt as soon as a message
17494 See also the &%max_parallel%& generic transport option,
17495 and the &%serialize_hosts%& smtp transport option.
17497 .cindex "number of deliveries"
17498 .cindex "delivery" "maximum number of"
17499 If you want to control the total number of deliveries on the system, you
17500 need to set the &%queue_only%& option. This ensures that all incoming messages
17501 are added to the queue without starting a delivery process. Then set up an Exim
17502 daemon to start queue runner processes at appropriate intervals (probably
17503 fairly often, for example, every minute), and limit the total number of queue
17504 runners by setting the &%queue_run_max%& parameter. Because each queue runner
17505 delivers only one message at a time, the maximum number of deliveries that can
17506 then take place at once is &%queue_run_max%& multiplied by
17507 &%remote_max_parallel%&.
17509 If it is purely remote deliveries you want to control, use
17510 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
17511 doing the SMTP routing before queueing, so that several messages for the same
17512 host will eventually get delivered down the same connection.
17515 .option remote_sort_domains main "domain list&!!" unset
17516 .cindex "sorting remote deliveries"
17517 .cindex "delivery" "sorting remote"
17518 When there are a number of remote deliveries for a message, they are sorted by
17519 domain into the order given by this list. For example,
17521 remote_sort_domains = *.cam.ac.uk:*.uk
17523 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
17524 then to those in the &%uk%& domain, then to any others.
17527 .option retry_data_expire main time 7d
17528 .cindex "hints database" "data expiry"
17529 This option sets a &"use before"& time on retry information in Exim's hints
17530 database. Any older retry data is ignored. This means that, for example, once a
17531 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
17535 .option retry_interval_max main time 24h
17536 .cindex "retry" "limit on interval"
17537 .cindex "limit" "on retry interval"
17538 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
17539 intervals between delivery attempts for messages that cannot be delivered
17540 straight away. This option sets an overall limit to the length of time between
17541 retries. It cannot be set greater than 24 hours; any attempt to do so forces
17545 .option return_path_remove main boolean true
17546 .cindex "&'Return-path:'& header line" "removing"
17547 RFC 2821, section 4.4, states that an SMTP server must insert a
17548 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
17549 The &'Return-path:'& header preserves the sender address as received in the
17550 MAIL command. This description implies that this header should not be present
17551 in an incoming message. If &%return_path_remove%& is true, any existing
17552 &'Return-path:'& headers are removed from messages at the time they are
17553 received. Exim's transports have options for adding &'Return-path:'& headers at
17554 the time of delivery. They are normally used only for final local deliveries.
17557 .option return_size_limit main integer 100K
17558 This option is an obsolete synonym for &%bounce_return_size_limit%&.
17561 .option rfc1413_hosts main "host list&!!" @[]
17563 .cindex "host" "for RFC 1413 calls"
17564 RFC 1413 identification calls are made to any client host which matches
17565 an item in the list.
17566 The default value specifies just this host, being any local interface
17569 .option rfc1413_query_timeout main time 0s
17570 .cindex "RFC 1413" "query timeout"
17571 .cindex "timeout" "for RFC 1413 call"
17572 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
17573 no RFC 1413 calls are ever made.
17576 .option sender_unqualified_hosts main "host list&!!" unset
17577 .cindex "unqualified addresses"
17578 .cindex "host" "unqualified addresses from"
17579 This option lists those hosts from which Exim is prepared to accept unqualified
17580 sender addresses. The addresses are made fully qualified by the addition of
17581 &%qualify_domain%&. This option also affects message header lines. Exim does
17582 not reject unqualified addresses in headers that contain sender addresses, but
17583 it qualifies them only if the message came from a host that matches
17584 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
17585 using TCP/IP), and the &%-bnq%& option was not set.
17588 .option slow_lookup_log main integer 0
17589 .cindex "logging" "slow lookups"
17590 .cindex "dns" "logging slow lookups"
17591 This option controls logging of slow lookups.
17592 If the value is nonzero it is taken as a number of milliseconds
17593 and lookups taking longer than this are logged.
17594 Currently this applies only to DNS lookups.
17598 .option smtp_accept_keepalive main boolean true
17599 .cindex "keepalive" "on incoming connection"
17600 This option controls the setting of the SO_KEEPALIVE option on incoming
17601 TCP/IP socket connections. When set, it causes the kernel to probe idle
17602 connections periodically, by sending packets with &"old"& sequence numbers. The
17603 other end of the connection should send an acknowledgment if the connection is
17604 still okay or a reset if the connection has been aborted. The reason for doing
17605 this is that it has the beneficial effect of freeing up certain types of
17606 connection that can get stuck when the remote host is disconnected without
17607 tidying up the TCP/IP call properly. The keepalive mechanism takes several
17608 hours to detect unreachable hosts.
17612 .option smtp_accept_max main integer 20
17613 .cindex "limit" "incoming SMTP connections"
17614 .cindex "SMTP" "incoming connection count"
17616 This option specifies the maximum number of simultaneous incoming SMTP calls
17617 that Exim will accept. It applies only to the listening daemon; there is no
17618 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
17619 value is set to zero, no limit is applied. However, it is required to be
17620 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
17621 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
17623 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
17624 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
17625 that limit has not been reached for the client host, &%smtp_accept_reserve%&
17626 and &%smtp_load_reserve%& are then checked before accepting the connection.
17629 .option smtp_accept_max_nonmail main integer 10
17630 .cindex "limit" "non-mail SMTP commands"
17631 .cindex "SMTP" "limiting non-mail commands"
17632 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
17633 the connection if there are too many. This option defines &"too many"&. The
17634 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
17635 client looping sending EHLO, for example. The check is applied only if the
17636 client host matches &%smtp_accept_max_nonmail_hosts%&.
17638 When a new message is expected, one occurrence of RSET is not counted. This
17639 allows a client to send one RSET between messages (this is not necessary,
17640 but some clients do it). Exim also allows one uncounted occurrence of HELO
17641 or EHLO, and one occurrence of STARTTLS between messages. After
17642 starting up a TLS session, another EHLO is expected, and so it too is not
17643 counted. The first occurrence of AUTH in a connection, or immediately
17644 following STARTTLS is not counted. Otherwise, all commands other than
17645 MAIL, RCPT, DATA, and QUIT are counted.
17648 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
17649 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
17650 check by setting this option. The default value makes it apply to all hosts. By
17651 changing the value, you can exclude any badly-behaved hosts that you have to
17655 . Allow this long option name to split; give it unsplit as a fifth argument
17656 . for the automatic .oindex that is generated by .option.
17657 . We insert " &~&~" which is both pretty nasty visually and results in
17658 . non-searchable text. HowItWorks.txt mentions an option for inserting
17659 . zero-width-space, which would be nicer visually and results in (at least)
17660 . html that Firefox will split on when it's forced to reflow (rather than
17661 . inserting a horizontal scrollbar). However, the text is still not
17662 . searchable. NM changed this occurrence for bug 1197 to no longer allow
17663 . the option name to split.
17665 .option "smtp_accept_max_per_connection" main integer&!! 1000 &&&
17666 smtp_accept_max_per_connection
17667 .cindex "SMTP" "limiting incoming message count"
17668 .cindex "limit" "messages per SMTP connection"
17669 The value of this option limits the number of MAIL commands that Exim is
17670 prepared to accept over a single SMTP connection, whether or not each command
17671 results in the transfer of a message. After the limit is reached, a 421
17672 response is given to subsequent MAIL commands. This limit is a safety
17673 precaution against a client that goes mad (incidents of this type have been
17676 The option is expanded after the HELO or EHLO is received
17677 and may depend on values available at that time.
17678 An empty or zero value after expansion removes the limit.
17682 .option smtp_accept_max_per_host main string&!! unset
17683 .cindex "limit" "SMTP connections from one host"
17684 .cindex "host" "limiting SMTP connections from"
17685 This option restricts the number of simultaneous IP connections from a single
17686 host (strictly, from a single IP address) to the Exim daemon. The option is
17687 expanded, to enable different limits to be applied to different hosts by
17688 reference to &$sender_host_address$&. Once the limit is reached, additional
17689 connection attempts from the same host are rejected with error code 421. This
17690 is entirely independent of &%smtp_accept_reserve%&. The option's default value
17691 of zero imposes no limit. If this option is set greater than zero, it is
17692 required that &%smtp_accept_max%& be non-zero.
17694 &*Warning*&: When setting this option you should not use any expansion
17695 constructions that take an appreciable amount of time. The expansion and test
17696 happen in the main daemon loop, in order to reject additional connections
17697 without forking additional processes (otherwise a denial-of-service attack
17698 could cause a vast number or processes to be created). While the daemon is
17699 doing this processing, it cannot accept any other incoming connections.
17703 .option smtp_accept_queue main integer 0
17704 .cindex "SMTP" "incoming connection count"
17705 .cindex "queueing incoming messages"
17706 .cindex "message" "queueing by SMTP connection count"
17707 If the number of simultaneous incoming SMTP connections being handled via the
17708 listening daemon exceeds this value, messages received by SMTP are just placed
17709 in the queue; no delivery processes are started automatically. The count is
17710 fixed at the start of an SMTP connection. It cannot be updated in the
17711 subprocess that receives messages, and so the queueing or not queueing applies
17712 to all messages received in the same connection.
17714 A value of zero implies no limit, and clearly any non-zero value is useful only
17715 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
17716 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
17717 various &%-od%&&'x'& command line options.
17720 . See the comment on smtp_accept_max_per_connection
17722 .option "smtp_accept_queue_per_connection" main integer 10 &&&
17723 smtp_accept_queue_per_connection
17724 .cindex "queueing incoming messages"
17725 .cindex "message" "queueing by message count"
17726 This option limits the number of delivery processes that Exim starts
17727 automatically when receiving messages via SMTP, whether via the daemon or by
17728 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
17729 and the number of messages received in a single SMTP session exceeds this
17730 number, subsequent messages are placed in the queue, but no delivery processes
17731 are started. This helps to limit the number of Exim processes when a server
17732 restarts after downtime and there is a lot of mail waiting for it on other
17733 systems. On large systems, the default should probably be increased, and on
17734 dial-in client systems it should probably be set to zero (that is, disabled).
17737 .option smtp_accept_reserve main integer 0
17738 .cindex "SMTP" "incoming call count"
17739 .cindex "host" "reserved"
17740 When &%smtp_accept_max%& is set greater than zero, this option specifies a
17741 number of SMTP connections that are reserved for connections from the hosts
17742 that are specified in &%smtp_reserve_hosts%&. The value set in
17743 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
17744 restricted to this number of connections; the option specifies a minimum number
17745 of connection slots for them, not a maximum. It is a guarantee that this group
17746 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
17747 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
17750 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
17751 set to 5, once there are 45 active connections (from any hosts), new
17752 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
17753 provided the other criteria for acceptance are met.
17756 .option smtp_active_hostname main string&!! unset
17757 .cindex "host" "name in SMTP responses"
17758 .cindex "SMTP" "host name in responses"
17759 .vindex "&$primary_hostname$&"
17760 This option is provided for multi-homed servers that want to masquerade as
17761 several different hosts. At the start of an incoming SMTP connection, its value
17762 is expanded and used instead of the value of &$primary_hostname$& in SMTP
17763 responses. For example, it is used as domain name in the response to an
17764 incoming HELO or EHLO command.
17766 .vindex "&$smtp_active_hostname$&"
17767 The active hostname is placed in the &$smtp_active_hostname$& variable, which
17768 is saved with any messages that are received. It is therefore available for use
17769 in routers and transports when the message is later delivered.
17771 If this option is unset, or if its expansion is forced to fail, or if the
17772 expansion results in an empty string, the value of &$primary_hostname$& is
17773 used. Other expansion failures cause a message to be written to the main and
17774 panic logs, and the SMTP command receives a temporary error. Typically, the
17775 value of &%smtp_active_hostname%& depends on the incoming interface address.
17778 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
17779 {cox.mydomain}{box.mydomain}}
17782 Although &$smtp_active_hostname$& is primarily concerned with incoming
17783 messages, it is also used as the default for HELO commands in callout
17784 verification if there is no remote transport from which to obtain a
17785 &%helo_data%& value.
17787 .option smtp_backlog_monitor main integer 0
17788 .cindex "connection backlog" monitoring
17789 If this option is set to greater than zero, and the backlog of available
17790 TCP connections on a socket listening for SMTP is larger than it, a line
17791 is logged giving the value and the socket address and port.
17792 The value is retrived jsut before an accept call.
17793 This facility is only available on Linux.
17795 .option smtp_banner main string&!! "see below"
17796 .cindex "SMTP" "welcome banner"
17797 .cindex "banner for SMTP"
17798 .cindex "welcome banner for SMTP"
17799 .cindex "customizing" "SMTP banner"
17800 This string, which is expanded every time it is used, is output as the initial
17801 positive response to an SMTP connection. The default setting is:
17803 smtp_banner = $smtp_active_hostname ESMTP Exim \
17804 $version_number $tod_full
17806 Failure to expand the string causes a panic error. If you want to create a
17807 multiline response to the initial SMTP connection, use &"\n"& in the string at
17808 appropriate points, but not at the end. Note that the 220 code is not included
17809 in this string. Exim adds it automatically (several times in the case of a
17810 multiline response).
17813 .option smtp_check_spool_space main boolean true
17814 .cindex "checking disk space"
17815 .cindex "disk space, checking"
17816 .cindex "spool directory" "checking space"
17817 When this option is set, if an incoming SMTP session encounters the SIZE
17818 option on a MAIL command, it checks that there is enough space in the
17819 spool directory's partition to accept a message of that size, while still
17820 leaving free the amount specified by &%check_spool_space%& (even if that value
17821 is zero). If there isn't enough space, a temporary error code is returned.
17824 .option smtp_connect_backlog main integer 20
17825 .cindex "connection backlog" "set maximum"
17826 .cindex "SMTP" "connection backlog"
17827 .cindex "backlog of connections"
17828 This option specifies a maximum number of waiting SMTP connections. Exim passes
17829 this value to the TCP/IP system when it sets up its listener. Once this number
17830 of connections are waiting for the daemon's attention, subsequent connection
17831 attempts are refused at the TCP/IP level. At least, that is what the manuals
17832 say; in some circumstances such connection attempts have been observed to time
17833 out instead. For large systems it is probably a good idea to increase the
17834 value (to 50, say). It also gives some protection against denial-of-service
17835 attacks by SYN flooding.
17838 .option smtp_enforce_sync main boolean true
17839 .cindex "SMTP" "synchronization checking"
17840 .cindex "synchronization checking in SMTP"
17841 The SMTP protocol specification requires the client to wait for a response from
17842 the server at certain points in the dialogue. Without PIPELINING these
17843 synchronization points are after every command; with PIPELINING they are
17844 fewer, but they still exist.
17846 Some spamming sites send out a complete set of SMTP commands without waiting
17847 for any response. Exim protects against this by rejecting a message if the
17848 client has sent further input when it should not have. The error response &"554
17849 SMTP synchronization error"& is sent, and the connection is dropped. Testing
17850 for this error cannot be perfect because of transmission delays (unexpected
17851 input may be on its way but not yet received when Exim checks). However, it
17852 does detect many instances.
17854 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
17855 If you want to disable the check selectively (for example, only for certain
17856 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
17857 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
17861 .option smtp_etrn_command main string&!! unset
17862 .cindex "ETRN" "command to be run"
17863 .cindex "ESMTP extensions" ETRN
17864 .vindex "&$domain$&"
17865 If this option is set, the given command is run whenever an SMTP ETRN
17866 command is received from a host that is permitted to issue such commands (see
17867 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
17868 are independently expanded. The expansion variable &$domain$& is set to the
17869 argument of the ETRN command, and no syntax checking is done on it. For
17872 smtp_etrn_command = /etc/etrn_command $domain \
17873 $sender_host_address
17875 If the option is not set, the argument for the ETRN command must
17876 be a &'#'& followed by an address string.
17877 In this case an &'exim -R <string>'& command is used;
17878 if the ETRN ACL has set up a named-queue then &'-MCG <queue>'& is appended.
17880 A new process is created to run the command, but Exim does not wait for it to
17881 complete. Consequently, its status cannot be checked. If the command cannot be
17882 run, a line is written to the panic log, but the ETRN caller still receives
17883 a 250 success response. Exim is normally running under its own uid when
17884 receiving SMTP, so it is not possible for it to change the uid before running
17888 .option smtp_etrn_serialize main boolean true
17889 .cindex "ETRN" "serializing"
17890 When this option is set, it prevents the simultaneous execution of more than
17891 one identical command as a result of ETRN in an SMTP connection. See
17892 section &<<SECTETRN>>& for details.
17895 .option smtp_load_reserve main fixed-point unset
17896 .cindex "load average"
17897 If the system load average ever gets higher than this, incoming SMTP calls are
17898 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
17899 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
17900 the load is over the limit. The option has no effect on ancient operating
17901 systems on which Exim cannot determine the load average. See also
17902 &%deliver_queue_load_max%& and &%queue_only_load%&.
17906 .option smtp_max_synprot_errors main integer 3
17907 .cindex "SMTP" "limiting syntax and protocol errors"
17908 .cindex "limit" "SMTP syntax and protocol errors"
17909 Exim rejects SMTP commands that contain syntax or protocol errors. In
17910 particular, a syntactically invalid email address, as in this command:
17912 RCPT TO:<abc xyz@a.b.c>
17914 causes immediate rejection of the command, before any other tests are done.
17915 (The ACL cannot be run if there is no valid address to set up for it.) An
17916 example of a protocol error is receiving RCPT before MAIL. If there are
17917 too many syntax or protocol errors in one SMTP session, the connection is
17918 dropped. The limit is set by this option.
17920 .cindex "PIPELINING" "expected errors"
17921 When the PIPELINING extension to SMTP is in use, some protocol errors are
17922 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
17923 Exim assumes that PIPELINING will be used if it advertises it (see
17924 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
17925 not count towards the limit.
17929 .option smtp_max_unknown_commands main integer 3
17930 .cindex "SMTP" "limiting unknown commands"
17931 .cindex "limit" "unknown SMTP commands"
17932 If there are too many unrecognized commands in an incoming SMTP session, an
17933 Exim server drops the connection. This is a defence against some kinds of abuse
17936 into making connections to SMTP ports; in these circumstances, a number of
17937 non-SMTP command lines are sent first.
17941 .option smtp_ratelimit_hosts main "host list&!!" unset
17942 .cindex "SMTP" "rate limiting"
17943 .cindex "limit" "rate of message arrival"
17944 .cindex "RCPT" "rate limiting"
17945 Some sites find it helpful to be able to limit the rate at which certain hosts
17946 can send them messages, and the rate at which an individual message can specify
17949 Exim has two rate-limiting facilities. This section describes the older
17950 facility, which can limit rates within a single connection. The newer
17951 &%ratelimit%& ACL condition can limit rates across all connections. See section
17952 &<<SECTratelimiting>>& for details of the newer facility.
17954 When a host matches &%smtp_ratelimit_hosts%&, the values of
17955 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
17956 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
17957 respectively. Each option, if set, must contain a set of four comma-separated
17961 A threshold, before which there is no rate limiting.
17963 An initial time delay. Unlike other times in Exim, numbers with decimal
17964 fractional parts are allowed here.
17966 A factor by which to increase the delay each time.
17968 A maximum value for the delay. This should normally be less than 5 minutes,
17969 because after that time, the client is liable to timeout the SMTP command.
17972 For example, these settings have been used successfully at the site which
17973 first suggested this feature, for controlling mail from their customers:
17975 smtp_ratelimit_mail = 2,0.5s,1.05,4m
17976 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
17978 The first setting specifies delays that are applied to MAIL commands after
17979 two have been received over a single connection. The initial delay is 0.5
17980 seconds, increasing by a factor of 1.05 each time. The second setting applies
17981 delays to RCPT commands when more than four occur in a single message.
17984 .option smtp_ratelimit_mail main string unset
17985 See &%smtp_ratelimit_hosts%& above.
17988 .option smtp_ratelimit_rcpt main string unset
17989 See &%smtp_ratelimit_hosts%& above.
17992 .option smtp_receive_timeout main time&!! 5m
17993 .cindex "timeout" "for SMTP input"
17994 .cindex "SMTP" "input timeout"
17995 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
17996 input, including batch SMTP. If a line of input (either an SMTP command or a
17997 data line) is not received within this time, the SMTP connection is dropped and
17998 the message is abandoned.
17999 A line is written to the log containing one of the following messages:
18001 SMTP command timeout on connection from...
18002 SMTP data timeout on connection from...
18004 The former means that Exim was expecting to read an SMTP command; the latter
18005 means that it was in the DATA phase, reading the contents of a message.
18007 If the first character of the option is a &"$"& the option is
18008 expanded before use and may depend on
18009 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
18013 The value set by this option can be overridden by the
18014 &%-os%& command-line option. A setting of zero time disables the timeout, but
18015 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
18016 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
18017 timeout is controlled by &%receive_timeout%& and &%-or%&.
18020 .option smtp_reserve_hosts main "host list&!!" unset
18021 This option defines hosts for which SMTP connections are reserved; see
18022 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
18025 .option smtp_return_error_details main boolean false
18026 .cindex "SMTP" "details policy failures"
18027 .cindex "policy control" "rejection, returning details"
18028 In the default state, Exim uses bland messages such as
18029 &"Administrative prohibition"& when it rejects SMTP commands for policy
18030 reasons. Many sysadmins like this because it gives away little information
18031 to spammers. However, some other sysadmins who are applying strict checking
18032 policies want to give out much fuller information about failures. Setting
18033 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
18034 example, instead of &"Administrative prohibition"&, it might give:
18036 550-Rejected after DATA: '>' missing at end of address:
18037 550 failing address in "From" header is: <user@dom.ain
18041 .option smtputf8_advertise_hosts main "host list&!!" *
18042 .cindex "SMTPUTF8" "ESMTP extension, advertising"
18043 .cindex "ESMTP extensions" SMTPUTF8
18044 When Exim is built with support for internationalised mail names,
18045 the availability thereof is advertised in
18046 response to EHLO only to those client hosts that match this option. See
18047 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
18050 .option spamd_address main string "127.0.0.1 783"
18051 This option is available when Exim is compiled with the content-scanning
18052 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
18053 See section &<<SECTscanspamass>>& for more details.
18057 .option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
18058 This option is available when Exim is compiled with SPF support.
18059 See section &<<SECSPF>>& for more details.
18061 .option spf_smtp_comment_template main string&!! "Please%_see%_http://www.open-spf.org/Why"
18062 This option is available when Exim is compiled with SPF support. It
18063 allows the customisation of the SMTP comment that the SPF library
18064 generates. You are strongly encouraged to link to your own explanative
18065 site. The template must not contain spaces. If you need spaces in the
18066 output, use the proper placeholder. If libspf2 can not parse the
18067 template, it uses a built-in default broken link. The following placeholders
18068 (along with Exim variables (but see below)) are allowed in the template:
18072 &*%{L}*&: Envelope sender's local part.
18074 &*%{S}*&: Envelope sender.
18076 &*%{O}*&: Envelope sender's domain.
18078 &*%{D}*&: Current(?) domain.
18080 &*%{I}*&: SMTP client Ip.
18082 &*%{C}*&: SMTP client pretty IP.
18084 &*%{T}*&: Epoch time (UTC).
18086 &*%{P}*&: SMTP client domain name.
18088 &*%{V}*&: IP version.
18090 &*%{H}*&: EHLO/HELO domain.
18092 &*%{R}*&: Receiving domain.
18094 The capitalized placeholders do proper URL encoding, if you use them
18095 lowercased, no encoding takes place. This list was compiled from the
18098 A note on using Exim variables: As
18099 currently the SPF library is initialized before the SMTP EHLO phase,
18100 the variables useful for expansion are quite limited.
18103 .option split_spool_directory main boolean false
18104 .cindex "multiple spool directories"
18105 .cindex "spool directory" "split"
18106 .cindex "directories, multiple"
18107 If this option is set, it causes Exim to split its input directory into 62
18108 subdirectories, each with a single alphanumeric character as its name. The
18109 sixth character of the message id is used to allocate messages to
18110 subdirectories; this is the least significant base-62 digit of the time of
18111 arrival of the message.
18113 Splitting up the spool in this way may provide better performance on systems
18114 where there are long mail queues, by reducing the number of files in any one
18115 directory. The msglog directory is also split up in a similar way to the input
18116 directory; however, if &%preserve_message_logs%& is set, all old msglog files
18117 are still placed in the single directory &_msglog.OLD_&.
18119 It is not necessary to take any special action for existing messages when
18120 changing &%split_spool_directory%&. Exim notices messages that are in the
18121 &"wrong"& place, and continues to process them. If the option is turned off
18122 after a period of being on, the subdirectories will eventually empty and be
18123 automatically deleted.
18125 When &%split_spool_directory%& is set, the behaviour of queue runner processes
18126 changes. Instead of creating a list of all messages in the queue, and then
18127 trying to deliver each one, in turn, it constructs a list of those in one
18128 sub-directory and tries to deliver them, before moving on to the next
18129 sub-directory. The sub-directories are processed in a random order. This
18130 spreads out the scanning of the input directories, and uses less memory. It is
18131 particularly beneficial when there are lots of messages in the queue. However,
18132 if &%queue_run_in_order%& is set, none of this new processing happens. The
18133 entire queue has to be scanned and sorted before any deliveries can start.
18136 .option spool_directory main string&!! "set at compile time"
18137 .cindex "spool directory" "path to"
18138 This defines the directory in which Exim keeps its spool, that is, the messages
18139 it is waiting to deliver. The default value is taken from the compile-time
18140 configuration setting, if there is one. If not, this option must be set. The
18141 string is expanded, so it can contain, for example, a reference to
18142 &$primary_hostname$&.
18144 If the spool directory name is fixed on your installation, it is recommended
18145 that you set it at build time rather than from this option, particularly if the
18146 log files are being written to the spool directory (see &%log_file_path%&).
18147 Otherwise log files cannot be used for errors that are detected early on, such
18148 as failures in the configuration file.
18150 By using this option to override the compiled-in path, it is possible to run
18151 tests of Exim without using the standard spool.
18153 .option spool_wireformat main boolean false
18154 .cindex "spool directory" "file formats"
18155 If this option is set, Exim may for some messages use an alternative format
18156 for data-files in the spool which matches the wire format.
18157 Doing this permits more efficient message reception and transmission.
18158 Currently it is only done for messages received using the ESMTP CHUNKING
18161 The following variables will not have useful values:
18163 $max_received_linelength
18168 Users of the local_scan() API (see &<<CHAPlocalscan>>&),
18169 and any external programs which are passed a reference to a message data file
18170 (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
18171 will need to be aware of the different formats potentially available.
18173 Using any of the ACL conditions noted will negate the reception benefit
18174 (as a Unix-mbox-format file is constructed for them).
18175 The transmission benefit is maintained.
18177 .option sqlite_lock_timeout main time 5s
18178 .cindex "sqlite lookup type" "lock timeout"
18179 This option controls the timeout that the &(sqlite)& lookup uses when trying to
18180 access an SQLite database. See section &<<SECTsqlite>>& for more details.
18182 .option strict_acl_vars main boolean false
18183 .cindex "&ACL;" "variables, handling unset"
18184 This option controls what happens if a syntactically valid but undefined ACL
18185 variable is referenced. If it is false (the default), an empty string
18186 is substituted; if it is true, an error is generated. See section
18187 &<<SECTaclvariables>>& for details of ACL variables.
18189 .option strip_excess_angle_brackets main boolean false
18190 .cindex "angle brackets, excess"
18191 If this option is set, redundant pairs of angle brackets round &"route-addr"&
18192 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
18193 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
18194 passed on to another MTA, the excess angle brackets are not passed on. If this
18195 option is not set, multiple pairs of angle brackets cause a syntax error.
18198 .option strip_trailing_dot main boolean false
18199 .cindex "trailing dot on domain"
18200 .cindex "dot" "trailing on domain"
18201 If this option is set, a trailing dot at the end of a domain in an address is
18202 ignored. If this is in the envelope and the message is passed on to another
18203 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
18204 domain causes a syntax error.
18205 However, addresses in header lines are checked only when an ACL requests header
18209 .option syslog_duplication main boolean true
18210 .cindex "syslog" "duplicate log lines; suppressing"
18211 When Exim is logging to syslog, it writes the log lines for its three
18212 separate logs at different syslog priorities so that they can in principle
18213 be separated on the logging hosts. Some installations do not require this
18214 separation, and in those cases, the duplication of certain log lines is a
18215 nuisance. If &%syslog_duplication%& is set false, only one copy of any
18216 particular log line is written to syslog. For lines that normally go to
18217 both the main log and the reject log, the reject log version (possibly
18218 containing message header lines) is written, at LOG_NOTICE priority.
18219 Lines that normally go to both the main and the panic log are written at
18220 the LOG_ALERT priority.
18223 .option syslog_facility main string unset
18224 .cindex "syslog" "facility; setting"
18225 This option sets the syslog &"facility"& name, used when Exim is logging to
18226 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
18227 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
18228 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
18229 details of Exim's logging.
18232 .option syslog_pid main boolean true
18233 .cindex "syslog" "pid"
18234 If &%syslog_pid%& is set false, the PID on Exim's log lines are
18235 omitted when these lines are sent to syslog. (Syslog normally prefixes
18236 the log lines with the PID of the logging process automatically.) You need
18237 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
18238 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
18242 .option syslog_processname main string &`exim`&
18243 .cindex "syslog" "process name; setting"
18244 This option sets the syslog &"ident"& name, used when Exim is logging to
18245 syslog. The value must be no longer than 32 characters. See chapter
18246 &<<CHAPlog>>& for details of Exim's logging.
18250 .option syslog_timestamp main boolean true
18251 .cindex "syslog" "timestamps"
18252 .cindex timestamps syslog
18253 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
18254 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
18255 details of Exim's logging.
18258 .option system_filter main string&!! unset
18259 .cindex "filter" "system filter"
18260 .cindex "system filter" "specifying"
18261 .cindex "Sieve filter" "not available for system filter"
18262 This option specifies an Exim filter file that is applied to all messages at
18263 the start of each delivery attempt, before any routing is done. System filters
18264 must be Exim filters; they cannot be Sieve filters. If the system filter
18265 generates any deliveries to files or pipes, or any new mail messages, the
18266 appropriate &%system_filter_..._transport%& option(s) must be set, to define
18267 which transports are to be used. Details of this facility are given in chapter
18268 &<<CHAPsystemfilter>>&.
18269 A forced expansion failure results in no filter operation.
18272 .option system_filter_directory_transport main string&!! unset
18273 .vindex "&$address_file$&"
18274 This sets the name of the transport driver that is to be used when the
18275 &%save%& command in a system message filter specifies a path ending in &"/"&,
18276 implying delivery of each message into a separate file in some directory.
18277 During the delivery, the variable &$address_file$& contains the path name.
18280 .option system_filter_file_transport main string&!! unset
18281 .cindex "file" "transport for system filter"
18282 This sets the name of the transport driver that is to be used when the &%save%&
18283 command in a system message filter specifies a path not ending in &"/"&. During
18284 the delivery, the variable &$address_file$& contains the path name.
18286 .option system_filter_group main string unset
18287 .cindex "gid (group id)" "system filter"
18288 This option is used only when &%system_filter_user%& is also set. It sets the
18289 gid under which the system filter is run, overriding any gid that is associated
18290 with the user. The value may be numerical or symbolic.
18292 .option system_filter_pipe_transport main string&!! unset
18293 .cindex "&(pipe)& transport" "for system filter"
18294 .vindex "&$address_pipe$&"
18295 This specifies the transport driver that is to be used when a &%pipe%& command
18296 is used in a system filter. During the delivery, the variable &$address_pipe$&
18297 contains the pipe command.
18300 .option system_filter_reply_transport main string&!! unset
18301 .cindex "&(autoreply)& transport" "for system filter"
18302 This specifies the transport driver that is to be used when a &%mail%& command
18303 is used in a system filter.
18306 .option system_filter_user main string unset
18307 .cindex "uid (user id)" "system filter"
18308 If this option is set to root, the system filter is run in the main Exim
18309 delivery process, as root. Otherwise, the system filter runs in a separate
18310 process, as the given user, defaulting to the Exim run-time user.
18311 Unless the string consists entirely of digits, it
18312 is looked up in the password data. Failure to find the named user causes a
18313 configuration error. The gid is either taken from the password data, or
18314 specified by &%system_filter_group%&. When the uid is specified numerically,
18315 &%system_filter_group%& is required to be set.
18317 If the system filter generates any pipe, file, or reply deliveries, the uid
18318 under which the filter is run is used when transporting them, unless a
18319 transport option overrides.
18322 .option tcp_nodelay main boolean true
18323 .cindex "daemon" "TCP_NODELAY on sockets"
18324 .cindex "Nagle algorithm"
18325 .cindex "TCP_NODELAY on listening sockets"
18326 If this option is set false, it stops the Exim daemon setting the
18327 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
18328 turns off the &"Nagle algorithm"&, which is a way of improving network
18329 performance in interactive (character-by-character) situations. Turning it off
18330 should improve Exim's performance a bit, so that is what happens by default.
18331 However, it appears that some broken clients cannot cope, and time out. Hence
18332 this option. It affects only those sockets that are set up for listening by the
18333 daemon. Sockets created by the smtp transport for delivering mail always set
18337 .option timeout_frozen_after main time 0s
18338 .cindex "frozen messages" "timing out"
18339 .cindex "timeout" "frozen messages"
18340 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
18341 message of any kind that has been in the queue for longer than the given time
18342 is automatically cancelled at the next queue run. If the frozen message is a
18343 bounce message, it is just discarded; otherwise, a bounce is sent to the
18344 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
18345 If you want to timeout frozen bounce messages earlier than other kinds of
18346 frozen message, see &%ignore_bounce_errors_after%&.
18348 &*Note:*& the default value of zero means no timeouts; with this setting,
18349 frozen messages remain in the queue forever (except for any frozen bounce
18350 messages that are released by &%ignore_bounce_errors_after%&).
18353 .option timezone main string unset
18354 .cindex "timezone, setting"
18355 .cindex "environment" "values from"
18356 The value of &%timezone%& is used to set the environment variable TZ while
18357 running Exim (if it is different on entry). This ensures that all timestamps
18358 created by Exim are in the required timezone. If you want all your timestamps
18359 to be in UTC (aka GMT) you should set
18363 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
18364 or, if that is not set, from the value of the TZ environment variable when Exim
18365 is built. If &%timezone%& is set to the empty string, either at build or run
18366 time, any existing TZ variable is removed from the environment when Exim
18367 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
18368 unfortunately not all, operating systems.
18371 .option tls_advertise_hosts main "host list&!!" *
18372 .cindex "TLS" "advertising"
18373 .cindex "encryption" "on SMTP connection"
18374 .cindex "SMTP" "encrypted connection"
18375 .cindex "ESMTP extensions" STARTTLS
18376 When Exim is built with support for TLS encrypted connections, the availability
18377 of the STARTTLS command to set up an encrypted session is advertised in
18378 response to EHLO only to those client hosts that match this option. See
18379 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
18380 Note that the default value requires that a certificate be supplied
18381 using the &%tls_certificate%& option. If TLS support for incoming connections
18382 is not required the &%tls_advertise_hosts%& option should be set empty.
18386 .option tls_alpn main "string list&!!" "smtp : esmtp"
18387 .cindex TLS "Application Layer Protocol Names"
18389 .cindex ALPN "set acceptable names for server"
18390 If this option is set,
18391 the TLS library supports ALPN,
18392 and the client offers either more than
18393 ALPN name or a name which does not match the list,
18394 the TLS connection is declined.
18398 .option tls_certificate main "string list&!!" unset
18399 .cindex "TLS" "server certificate; location of"
18400 .cindex "certificate" "server, location of"
18401 The value of this option is expanded, and must then be a list of absolute paths to
18402 files which contain the server's certificates (in PEM format).
18403 Commonly only one file is needed.
18404 The server's private key is also
18405 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
18406 &<<CHAPTLS>>& for further details.
18408 &*Note*&: The certificates defined by this option are used only when Exim is
18409 receiving incoming messages as a server. If you want to supply certificates for
18410 use when sending messages as a client, you must set the &%tls_certificate%&
18411 option in the relevant &(smtp)& transport.
18413 &*Note*&: If you use filenames based on IP addresses, change the list
18414 separator in the usual way (&<<SECTlistsepchange>>&) to avoid confusion under IPv6.
18416 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
18417 when a list of more than one
18418 file is used, the &$tls_in_ourcert$& variable is unreliable.
18419 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
18421 .cindex SNI "selecting server certificate based on"
18422 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
18423 if the OpenSSL build supports TLS extensions and the TLS client sends the
18424 Server Name Indication extension, then this option and others documented in
18425 &<<SECTtlssni>>& will be re-expanded.
18427 If this option is unset or empty a self-signed certificate will be
18430 Under Linux this is generated at daemon startup; on other platforms it will be
18431 generated fresh for every connection.
18434 .option tls_crl main string&!! unset
18435 .cindex "TLS" "server certificate revocation list"
18436 .cindex "certificate" "revocation list for server"
18437 This option specifies a certificate revocation list. The expanded value must
18438 be the name of a file that contains CRLs in PEM format.
18440 Under OpenSSL the option can specify a directory with CRL files.
18442 &*Note:*& Under OpenSSL the option must, if given, supply a CRL
18443 for each signing element of the certificate chain (i.e. all but the leaf).
18444 For the file variant this can be multiple PEM blocks in the one file.
18446 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18449 .option tls_dh_max_bits main integer 2236
18450 .cindex "TLS" "D-H bit count"
18451 The number of bits used for Diffie-Hellman key-exchange may be suggested by
18452 the chosen TLS library. That value might prove to be too high for
18453 interoperability. This option provides a maximum clamp on the value
18454 suggested, trading off security for interoperability.
18456 The value must be at least 1024.
18458 The value 2236 was chosen because, at time of adding the option, it was the
18459 hard-coded maximum value supported by the NSS cryptographic library, as used
18460 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
18462 If you prefer more security and are willing to break some clients, raise this
18465 Note that the value passed to GnuTLS for *generating* a new prime may be a
18466 little less than this figure, because GnuTLS is inexact and may produce a
18467 larger prime than requested.
18470 .option tls_dhparam main string&!! unset
18471 .cindex "TLS" "D-H parameters for server"
18472 The value of this option is expanded and indicates the source of DH parameters
18473 to be used by Exim.
18475 This option is ignored for GnuTLS version 3.6.0 and later.
18476 The library manages parameter negotiation internally.
18478 &*Note: The Exim Maintainers strongly recommend,
18479 for other TLS library versions,
18480 using a filename with site-generated
18481 local DH parameters*&, which has been supported across all versions of Exim. The
18482 other specific constants available are a fallback so that even when
18483 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
18485 If &%tls_dhparam%& is a filename starting with a &`/`&,
18486 then it names a file from which DH
18487 parameters should be loaded. If the file exists, it should hold a PEM-encoded
18488 PKCS#3 representation of the DH prime. If the file does not exist, for
18489 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
18490 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
18491 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
18492 and treated as though the &%tls_dhparam%& were set to "none".
18494 If this option expands to the string "none", then no DH parameters will be
18497 If this option expands to the string "historic" and Exim is using GnuTLS, then
18498 Exim will attempt to load a file from inside the spool directory. If the file
18499 does not exist, Exim will attempt to create it.
18500 See section &<<SECTgnutlsparam>>& for further details.
18502 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
18503 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
18505 In older versions of Exim the default was the 2048 bit prime described in section
18506 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
18507 in IKE is assigned number 23.
18509 Otherwise, the option must expand to the name used by Exim for any of a number
18510 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
18511 sources. As names, Exim uses a standard specified name, else "ike" followed by
18512 the number used by IKE, or "default" which corresponds to
18513 &`exim.dev.20160529.3`&.
18515 The available standard primes are:
18516 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
18517 &`ike1`&, &`ike2`&, &`ike5`&,
18518 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
18519 &`ike22`&, &`ike23`& and &`ike24`&.
18521 The available additional primes are:
18522 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
18524 Some of these will be too small to be accepted by clients.
18525 Some may be too large to be accepted by clients.
18526 The open cryptographic community has suspicions about the integrity of some
18527 of the later IKE values, which led into RFC7919 providing new fixed constants
18528 (the "ffdhe" identifiers).
18530 At this point, all of the "ike" values should be considered obsolete;
18531 they're still in Exim to avoid breaking unusual configurations, but are
18532 candidates for removal the next time we have backwards-incompatible changes.
18534 The TLS protocol does not negotiate an acceptable size for this; clients tend
18535 to hard-drop connections if what is offered by the server is unacceptable,
18536 whether too large or too small, and there's no provision for the client to
18537 tell the server what these constraints are. Thus, as a server operator, you
18538 need to make an educated guess as to what is most likely to work for your
18541 Some known size constraints suggest that a bit-size in the range 2048 to 2236
18542 is most likely to maximise interoperability. The upper bound comes from
18543 applications using the Mozilla Network Security Services (NSS) library, which
18544 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
18545 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
18546 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
18547 acceptable bound from 1024 to 2048.
18550 .option tls_eccurve main string&!! &`auto`&
18551 .cindex TLS "EC cryptography"
18552 This option selects a EC curve for use by Exim when used with OpenSSL.
18553 It has no effect when Exim is used with GnuTLS.
18555 After expansion it must contain a valid EC curve parameter, such as
18556 &`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
18557 for valid selections.
18559 For OpenSSL versions before (and not including) 1.0.2, the string
18560 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
18561 &`auto`& tells the library to choose.
18563 If the option expands to an empty string, no EC curves will be enabled.
18566 .option tls_ocsp_file main string&!! unset
18567 .cindex TLS "certificate status"
18568 .cindex TLS "OCSP proof file"
18570 must if set expand to the absolute path to a file which contains a current
18571 status proof for the server's certificate, as obtained from the
18572 Certificate Authority.
18574 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
18575 The macro "_HAVE_TLS_OCSP" will be defined for those versions.
18577 For OpenSSL 1.1.0 or later, and
18578 for GnuTLS 3.5.6 or later the expanded value of this option can be a list
18579 of files, to match a list given for the &%tls_certificate%& option.
18580 The ordering of the two lists must match.
18581 The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
18583 The file(s) should be in DER format,
18584 except for GnuTLS 3.6.3 or later
18586 when an optional filetype prefix can be used.
18587 The prefix must be one of "DER" or "PEM", followed by
18588 a single space. If one is used it sets the format for subsequent
18589 files in the list; the initial format is DER.
18590 If multiple proofs are wanted, for multiple chain elements
18591 (this only works under TLS1.3)
18592 they must be coded as a combined OCSP response.
18594 Although GnuTLS will accept PEM files with multiple separate
18595 PEM blobs (ie. separate OCSP responses), it sends them in the
18596 TLS Certificate record interleaved with the certificates of the chain;
18597 although a GnuTLS client is happy with that, an OpenSSL client is not.
18599 .option tls_on_connect_ports main "string list" unset
18602 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
18603 operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
18604 set up without waiting for the client to issue a STARTTLS command. For
18605 further details, see section &<<SECTsupobssmt>>&.
18609 .option tls_privatekey main "string list&!!" unset
18610 .cindex "TLS" "server private key; location of"
18611 The value of this option is expanded, and must then be a list of absolute paths to
18612 files which contains the server's private keys.
18613 If this option is unset, or if
18614 the expansion is forced to fail, or the result is an empty string, the private
18615 key is assumed to be in the same file as the server's certificates. See chapter
18616 &<<CHAPTLS>>& for further details.
18618 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18621 .option tls_remember_esmtp main boolean false
18622 .cindex "TLS" "esmtp state; remembering"
18623 .cindex "TLS" "broken clients"
18624 If this option is set true, Exim violates the RFCs by remembering that it is in
18625 &"esmtp"& state after successfully negotiating a TLS session. This provides
18626 support for broken clients that fail to send a new EHLO after starting a
18630 .option tls_require_ciphers main string&!! unset
18631 .cindex "TLS" "requiring specific ciphers"
18632 .cindex "cipher" "requiring specific"
18633 This option controls which ciphers can be used for incoming TLS connections.
18634 The &(smtp)& transport has an option of the same name for controlling outgoing
18635 connections. This option is expanded for each connection, so can be varied for
18636 different clients if required. The value of this option must be a list of
18637 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
18638 in somewhat different ways. If GnuTLS is being used, the client controls the
18639 preference order of the available ciphers. Details are given in sections
18640 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
18644 .option tls_resumption_hosts main "host list&!!" unset
18645 .cindex TLS resumption
18646 This option controls which connections to offer the TLS resumption feature.
18647 See &<<SECTresumption>>& for details.
18651 .option tls_try_verify_hosts main "host list&!!" unset
18652 .cindex "TLS" "client certificate verification"
18653 .cindex "certificate" "verification of client"
18654 See &%tls_verify_hosts%& below.
18657 .option tls_verify_certificates main string&!! system
18658 .cindex "TLS" "client certificate verification"
18659 .cindex "certificate" "verification of client"
18660 The value of this option is expanded, and must then be either the
18662 or the absolute path to
18663 a file or directory containing permitted certificates for clients that
18664 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
18666 The "system" value for the option will use a
18667 system default location compiled into the SSL library.
18668 This is not available for GnuTLS versions preceding 3.0.20,
18669 and will be taken as empty; an explicit location
18672 The use of a directory for the option value is not available for GnuTLS versions
18673 preceding 3.3.6 and a single file must be used.
18675 With OpenSSL the certificates specified
18677 either by file or directory
18678 are added to those given by the system default location.
18680 These certificates should be for the certificate authorities trusted, rather
18681 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
18682 the value is a file then the certificates are sent by Exim as a server to
18683 connecting clients, defining the list of accepted certificate authorities.
18684 Thus the values defined should be considered public data. To avoid this,
18685 use the explicit directory version. (If your peer is Exim up to 4.85,
18686 using GnuTLS, you may need to send the CAs (thus using the file
18687 variant). Otherwise the peer doesn't send its certificate.)
18689 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18691 A forced expansion failure or setting to an empty string is equivalent to
18695 .option tls_verify_hosts main "host list&!!" unset
18696 .cindex "TLS" "client certificate verification"
18697 .cindex "certificate" "verification of client"
18698 This option, along with &%tls_try_verify_hosts%&, controls the checking of
18699 certificates from clients. The expected certificates are defined by
18700 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
18701 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
18702 &%tls_verify_certificates%& is not set.
18704 Any client that matches &%tls_verify_hosts%& is constrained by
18705 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
18706 present one of the listed certificates. If it does not, the connection is
18707 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
18708 the host to use TLS. It can still send SMTP commands through unencrypted
18709 connections. Forcing a client to use TLS has to be done separately using an
18710 ACL to reject inappropriate commands when the connection is not encrypted.
18712 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
18713 matches this option (but not &%tls_verify_hosts%&), Exim requests a
18714 certificate and checks it against &%tls_verify_certificates%&, but does not
18715 abort the connection if there is no certificate or if it does not match. This
18716 state can be detected in an ACL, which makes it possible to implement policies
18717 such as &"accept for relay only if a verified certificate has been received,
18718 but accept for local delivery if encrypted, even without a verified
18721 Client hosts that match neither of these lists are not asked to present
18725 .option trusted_groups main "string list&!!" unset
18726 .cindex "trusted groups"
18727 .cindex "groups" "trusted"
18728 This option is expanded just once, at the start of Exim's processing. If this
18729 option is set, any process that is running in one of the listed groups, or
18730 which has one of them as a supplementary group, is trusted. The groups can be
18731 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
18732 details of what trusted callers are permitted to do. If neither
18733 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
18736 .option trusted_users main "string list&!!" unset
18737 .cindex "trusted users"
18738 .cindex "user" "trusted"
18739 This option is expanded just once, at the start of Exim's processing. If this
18740 option is set, any process that is running as one of the listed users is
18741 trusted. The users can be specified numerically or by name. See section
18742 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
18743 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
18744 Exim user are trusted.
18746 .option unknown_login main string&!! unset
18747 .cindex "uid (user id)" "unknown caller"
18748 .vindex "&$caller_uid$&"
18749 This is a specialized feature for use in unusual configurations. By default, if
18750 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
18751 gives up. The &%unknown_login%& option can be used to set a login name to be
18752 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
18753 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
18754 is used for the user's real name (gecos field), unless this has been set by the
18757 .option unknown_username main string unset
18758 See &%unknown_login%&.
18760 .option untrusted_set_sender main "address list&!!" unset
18761 .cindex "trusted users"
18762 .cindex "sender" "setting by untrusted user"
18763 .cindex "untrusted user setting sender"
18764 .cindex "user" "untrusted setting sender"
18765 .cindex "envelope from"
18766 .cindex "envelope sender"
18767 When an untrusted user submits a message to Exim using the standard input, Exim
18768 normally creates an envelope sender address from the user's login and the
18769 default qualification domain. Data from the &%-f%& option (for setting envelope
18770 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
18771 is used) is ignored.
18773 However, untrusted users are permitted to set an empty envelope sender address,
18774 to declare that a message should never generate any bounces. For example:
18776 exim -f '<>' user@domain.example
18778 .vindex "&$sender_ident$&"
18779 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
18780 other envelope sender addresses in a controlled way. When it is set, untrusted
18781 users are allowed to set envelope sender addresses that match any of the
18782 patterns in the list. Like all address lists, the string is expanded. The
18783 identity of the user is in &$sender_ident$&, so you can, for example, restrict
18784 users to setting senders that start with their login ids
18785 followed by a hyphen
18786 by a setting like this:
18788 untrusted_set_sender = ^$sender_ident-
18790 If you want to allow untrusted users to set envelope sender addresses without
18791 restriction, you can use
18793 untrusted_set_sender = *
18795 The &%untrusted_set_sender%& option applies to all forms of local input, but
18796 only to the setting of the envelope sender. It does not permit untrusted users
18797 to use the other options which trusted user can use to override message
18798 parameters. Furthermore, it does not stop Exim from removing an existing
18799 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
18800 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
18801 overriding these actions. The handling of the &'Sender:'& header is also
18802 described in section &<<SECTthesenhea>>&.
18804 The log line for a message's arrival shows the envelope sender following
18805 &"<="&. For local messages, the user's login always follows, after &"U="&. In
18806 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
18807 envelope sender address, the user's login is shown in parentheses after the
18811 .option uucp_from_pattern main string "see below"
18812 .cindex "&""From""& line"
18813 .cindex "UUCP" "&""From""& line"
18814 Some applications that pass messages to an MTA via a command line interface use
18815 an initial line starting with &"From&~"& to pass the envelope sender. In
18816 particular, this is used by UUCP software. Exim recognizes such a line by means
18817 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
18818 matches, the sender address is constructed by expanding the contents of
18819 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
18820 default pattern recognizes lines in the following two forms:
18822 From ph10 Fri Jan 5 12:35 GMT 1996
18823 From ph10 Fri, 7 Jan 97 14:00:00 GMT
18825 The pattern can be seen by running
18827 exim -bP uucp_from_pattern
18829 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
18830 year in the second case. The first word after &"From&~"& is matched in the
18831 regular expression by a parenthesized subpattern. The default value for
18832 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
18833 (&"ph10"& in the example above) as the message's sender. See also
18834 &%ignore_fromline_hosts%&.
18837 .option uucp_from_sender main string&!! &`$1`&
18838 See &%uucp_from_pattern%& above.
18841 .option warn_message_file main string&!! unset
18842 .cindex "warning of delay" "customizing the message"
18843 .cindex "customizing" "warning message"
18844 This option defines a template file containing paragraphs of text to be used
18845 for constructing the warning message which is sent by Exim when a message has
18846 been in the queue for a specified amount of time, as specified by
18847 &%delay_warning%&. Details of the file's contents are given in chapter
18848 &<<CHAPemsgcust>>&.
18849 .cindex warn_message_file "tainted data"
18850 The option is expanded to give the file path, which must be
18851 absolute and untainted.
18852 See also &%bounce_message_file%&.
18855 .option write_rejectlog main boolean true
18856 .cindex "reject log" "disabling"
18857 If this option is set false, Exim no longer writes anything to the reject log.
18858 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
18859 .ecindex IIDconfima
18860 .ecindex IIDmaiconf
18865 . ////////////////////////////////////////////////////////////////////////////
18866 . ////////////////////////////////////////////////////////////////////////////
18868 .chapter "Generic options for routers" "CHAProutergeneric"
18869 .scindex IIDgenoprou1 "options" "generic; for routers"
18870 .scindex IIDgenoprou2 "generic options" "router"
18871 This chapter describes the generic options that apply to all routers.
18872 Those that are preconditions are marked with ‡ in the &"use"& field.
18874 For a general description of how a router operates, see sections
18875 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
18876 which the preconditions are tested. The order of expansion of the options that
18877 provide data for a transport is: &%errors_to%&, &%headers_add%&,
18878 &%headers_remove%&, &%transport%&.
18881 The name of a router is limited to be &drivernamemax; ASCII characters long;
18882 prior to Exim 4.95 names would be silently truncated at this length, but now
18887 .option address_data routers string&!! unset
18888 .cindex "router" "data attached to address"
18889 The string is expanded just before the router is run, that is, after all the
18890 precondition tests have succeeded. If the expansion is forced to fail, the
18891 router declines, the value of &%address_data%& remains unchanged, and the
18892 &%more%& option controls what happens next. Other expansion failures cause
18893 delivery of the address to be deferred.
18895 .vindex "&$address_data$&"
18896 When the expansion succeeds, the value is retained with the address, and can be
18897 accessed using the variable &$address_data$& in the current router, subsequent
18898 routers, and the eventual transport.
18900 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
18901 that runs a user's filter file, the contents of &$address_data$& are accessible
18902 in the filter. This is not normally a problem, because such data is usually
18903 either not confidential or it &"belongs"& to the current user, but if you do
18904 put confidential data into &$address_data$& you need to remember this point.
18906 Even if the router declines or passes, the value of &$address_data$& remains
18907 with the address, though it can be changed by another &%address_data%& setting
18908 on a subsequent router. If a router generates child addresses, the value of
18909 &$address_data$& propagates to them. This also applies to the special kind of
18910 &"child"& that is generated by a router with the &%unseen%& option.
18912 The idea of &%address_data%& is that you can use it to look up a lot of data
18913 for the address once, and then pick out parts of the data later. For example,
18914 you could use a single LDAP lookup to return a string of the form
18916 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
18918 In the transport you could pick out the mailbox by a setting such as
18920 file = ${extract{mailbox}{$address_data}}
18922 This makes the configuration file less messy, and also reduces the number of
18923 lookups (though Exim does cache lookups).
18925 See also the &%set%& option below.
18927 .vindex "&$sender_address_data$&"
18928 .vindex "&$address_data$&"
18929 The &%address_data%& facility is also useful as a means of passing information
18930 from one router to another, and from a router to a transport. In addition, if
18931 &$address_data$& is set by a router when verifying a recipient address from an
18932 ACL, it remains available for use in the rest of the ACL statement. After
18933 verifying a sender, the value is transferred to &$sender_address_data$&.
18937 .option address_test routers&!? boolean true
18939 .cindex "router" "skipping when address testing"
18940 If this option is set false, the router is skipped when routing is being tested
18941 by means of the &%-bt%& command line option. This can be a convenience when
18942 your first router sends messages to an external scanner, because it saves you
18943 having to set the &"already scanned"& indicator when testing real address
18948 .option cannot_route_message routers string&!! unset
18949 .cindex "router" "customizing &""cannot route""& message"
18950 .cindex "customizing" "&""cannot route""& message"
18951 This option specifies a text message that is used when an address cannot be
18952 routed because Exim has run out of routers. The default message is
18953 &"Unrouteable address"&. This option is useful only on routers that have
18954 &%more%& set false, or on the very last router in a configuration, because the
18955 value that is used is taken from the last router that is considered. This
18956 includes a router that is skipped because its preconditions are not met, as
18957 well as a router that declines. For example, using the default configuration,
18960 cannot_route_message = Remote domain not found in DNS
18962 on the first router, which is a &(dnslookup)& router with &%more%& set false,
18965 cannot_route_message = Unknown local user
18967 on the final router that checks for local users. If string expansion fails for
18968 this option, the default message is used. Unless the expansion failure was
18969 explicitly forced, a message about the failure is written to the main and panic
18970 logs, in addition to the normal message about the routing failure.
18973 .option caseful_local_part routers boolean false
18974 .cindex "case of local parts"
18975 .cindex "router" "case of local parts"
18976 By default, routers handle the local parts of addresses in a case-insensitive
18977 manner, though the actual case is preserved for transmission with the message.
18978 If you want the case of letters to be significant in a router, you must set
18979 this option true. For individual router options that contain address or local
18980 part lists (for example, &%local_parts%&), case-sensitive matching can be
18981 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
18984 .vindex "&$local_part$&"
18985 .vindex "&$original_local_part$&"
18986 .vindex "&$parent_local_part$&"
18987 The value of the &$local_part$& variable is forced to lower case while a
18988 router is running unless &%caseful_local_part%& is set. When a router assigns
18989 an address to a transport, the value of &$local_part$& when the transport runs
18990 is the same as it was in the router. Similarly, when a router generates child
18991 addresses by aliasing or forwarding, the values of &$original_local_part$&
18992 and &$parent_local_part$& are those that were used by the redirecting router.
18994 This option applies to the processing of an address by a router. When a
18995 recipient address is being processed in an ACL, there is a separate &%control%&
18996 modifier that can be used to specify case-sensitive processing within the ACL
18997 (see section &<<SECTcontrols>>&).
19001 .option check_local_user routers&!? boolean false
19002 .cindex "local user, checking in router"
19003 .cindex "router" "checking for local user"
19004 .cindex "&_/etc/passwd_&"
19006 When this option is true, Exim checks that the local part of the recipient
19007 address (with affixes removed if relevant) is the name of an account on the
19008 local system. The check is done by calling the &[getpwnam()]& function rather
19009 than trying to read &_/etc/passwd_& directly. This means that other methods of
19010 holding password data (such as NIS) are supported. If the local part is a local
19012 .cindex "tainted data" "de-tainting"
19013 &$local_part_data$& is set to an untainted version of the local part and
19014 &$home$& is set from the password data. The latter can be tested in other
19015 preconditions that are evaluated after this one (the order of evaluation is
19016 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
19017 overridden by &%router_home_directory%&. If the local part is not a local user,
19018 the router is skipped.
19020 If you want to check that the local part is either the name of a local user
19021 or matches something else, you cannot combine &%check_local_user%& with a
19022 setting of &%local_parts%&, because that specifies the logical &'and'& of the
19023 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
19024 setting to achieve this. For example:
19026 local_parts = passwd;$local_part : lsearch;/etc/other/users
19028 Note, however, that the side effects of &%check_local_user%& (such as setting
19029 up a home directory) do not occur when a &(passwd)& lookup is used in a
19030 &%local_parts%& (or any other) precondition.
19034 .option condition routers&!? string&!! unset
19035 .cindex "router" "customized precondition"
19036 This option specifies a general precondition test that has to succeed for the
19037 router to be called. The &%condition%& option is the last precondition to be
19038 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
19039 result is a forced failure, or an empty string, or one of the strings &"0"& or
19040 &"no"& or &"false"& (checked without regard to the case of the letters), the
19041 router is skipped, and the address is offered to the next one.
19043 If the result is any other value, the router is run (as this is the last
19044 precondition to be evaluated, all the other preconditions must be true).
19046 This option is unusual in that multiple &%condition%& options may be present.
19047 All &%condition%& options must succeed.
19049 The &%condition%& option provides a means of applying custom conditions to the
19050 running of routers. Note that in the case of a simple conditional expansion,
19051 the default expansion values are exactly what is wanted. For example:
19053 condition = ${if >{$message_age}{600}}
19055 Because of the default behaviour of the string expansion, this is equivalent to
19057 condition = ${if >{$message_age}{600}{true}{}}
19060 A multiple condition example, which succeeds:
19062 condition = ${if >{$message_age}{600}}
19063 condition = ${if !eq{${lc:$local_part}}{postmaster}}
19067 If the expansion fails (other than forced failure) delivery is deferred. Some
19068 of the other precondition options are common special cases that could in fact
19069 be specified using &%condition%&.
19071 Historical note: We have &%condition%& on ACLs and on Routers. Routers
19072 are far older, and use one set of semantics. ACLs are newer and when
19073 they were created, the ACL &%condition%& process was given far stricter
19074 parse semantics. The &%bool{}%& expansion condition uses the same rules as
19075 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
19076 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
19077 Router rules processing behavior.
19079 This is best illustrated in an example:
19081 # If used in an ACL condition will fail with a syntax error, but
19082 # in a router condition any extra characters are treated as a string
19084 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
19087 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
19090 In each example above, the &%if%& statement actually ends after
19091 &"{google.com}}"&. Since no true or false braces were defined, the
19092 default &%if%& behavior is to return a boolean true or a null answer
19093 (which evaluates to false). The rest of the line is then treated as a
19094 string. So the first example resulted in the boolean answer &"true"&
19095 with the string &" {yes} {no}}"& appended to it. The second example
19096 resulted in the null output (indicating false) with the string
19097 &" {yes} {no}}"& appended to it.
19099 In fact you can put excess forward braces in too. In the router
19100 &%condition%&, Exim's parser only looks for &"{"& symbols when they
19101 mean something, like after a &"$"& or when required as part of a
19102 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
19105 Thus, in a Router, the above expansion strings will both always evaluate
19106 true, as the result of expansion is a non-empty string which doesn't
19107 match an explicit false value. This can be tricky to debug. By
19108 contrast, in an ACL either of those strings will always result in an
19109 expansion error because the result doesn't look sufficiently boolean.
19112 .option debug_print routers string&!! unset
19113 .cindex "testing" "variables in drivers"
19114 If this option is set and debugging is enabled (see the &%-d%& command line
19115 option) or in address-testing mode (see the &%-bt%& command line option),
19116 the string is expanded and included in the debugging output.
19117 If expansion of the string fails, the error message is written to the debugging
19118 output, and Exim carries on processing.
19119 This option is provided to help with checking out the values of variables and
19120 so on when debugging router configurations. For example, if a &%condition%&
19121 option appears not to be working, &%debug_print%& can be used to output the
19122 variables it references. The output happens after checks for &%domains%&,
19123 &%local_parts%&, and &%check_local_user%& but before any other preconditions
19124 are tested. A newline is added to the text if it does not end with one.
19125 The variable &$router_name$& contains the name of the router.
19129 .option disable_logging routers boolean false
19130 If this option is set true, nothing is logged for any routing errors
19131 or for any deliveries caused by this router. You should not set this option
19132 unless you really, really know what you are doing. See also the generic
19133 transport option of the same name.
19135 .option dnssec_request_domains routers "domain list&!!" *
19136 .cindex "MX record" "security"
19137 .cindex "DNSSEC" "MX lookup"
19138 .cindex "security" "MX lookup"
19139 .cindex "DNS" "DNSSEC"
19140 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
19141 the DNSSEC request bit set.
19142 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19144 .option dnssec_require_domains routers "domain list&!!" unset
19145 .cindex "MX record" "security"
19146 .cindex "DNSSEC" "MX lookup"
19147 .cindex "security" "MX lookup"
19148 .cindex "DNS" "DNSSEC"
19149 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
19150 the DNSSEC request bit set. Any returns not having the Authenticated Data bit
19151 (AD bit) set will be ignored and logged as a host-lookup failure.
19152 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19155 .option domains routers&!? "domain list&!!" unset
19156 .cindex "router" "restricting to specific domains"
19157 .vindex "&$domain_data$&"
19158 If this option is set, the router is skipped unless the current domain matches
19159 the list. If the match is achieved by means of a file lookup, the data that the
19160 lookup returned for the domain is placed in &$domain_data$& for use in string
19161 expansions of the driver's private options and in the transport.
19162 See section &<<SECTrouprecon>>& for
19163 a list of the order in which preconditions are evaluated.
19167 .option driver routers string unset
19168 This option must always be set. It specifies which of the available routers is
19172 .option dsn_lasthop routers boolean false
19173 .cindex "DSN" "success"
19174 .cindex "Delivery Status Notification" "success"
19175 If this option is set true, and extended DSN (RFC3461) processing is in effect,
19176 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
19177 instead send a success DSN as if the next hop does not support DSN.
19178 Not effective on redirect routers.
19182 .option errors_to routers string&!! unset
19183 .cindex "envelope from"
19184 .cindex "envelope sender"
19185 .cindex "router" "changing address for errors"
19186 If a router successfully handles an address, it may assign the address to a
19187 transport for delivery or it may generate child addresses. In both cases, if
19188 there is a delivery problem during later processing, the resulting bounce
19189 message is sent to the address that results from expanding this string,
19190 provided that the address verifies successfully. The &%errors_to%& option is
19191 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
19193 The &%errors_to%& setting associated with an address can be overridden if it
19194 subsequently passes through other routers that have their own &%errors_to%&
19195 settings, or if the message is delivered by a transport with a &%return_path%&
19198 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
19199 the expansion fails to verify, the errors address associated with the incoming
19200 address is used. At top level, this is the envelope sender. A non-forced
19201 expansion failure causes delivery to be deferred.
19203 If an address for which &%errors_to%& has been set ends up being delivered over
19204 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
19205 any bounces that are generated by other MTAs on the delivery route are also
19206 sent there. You can set &%errors_to%& to the empty string by either of these
19212 An expansion item that yields an empty string has the same effect. If you do
19213 this, a locally detected delivery error for addresses processed by this router
19214 no longer gives rise to a bounce message; the error is discarded. If the
19215 address is delivered to a remote host, the return path is set to &`<>`&, unless
19216 overridden by the &%return_path%& option on the transport.
19218 .vindex "&$address_data$&"
19219 If for some reason you want to discard local errors, but use a non-empty
19220 MAIL command for remote delivery, you can preserve the original return
19221 path in &$address_data$& in the router, and reinstate it in the transport by
19222 setting &%return_path%&.
19224 The most common use of &%errors_to%& is to direct mailing list bounces to the
19225 manager of the list, as described in section &<<SECTmailinglists>>&, or to
19226 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
19230 .option expn routers&!? boolean true
19231 .cindex "address" "testing"
19232 .cindex "testing" "addresses"
19233 .cindex "EXPN" "router skipping"
19234 .cindex "router" "skipping for EXPN"
19235 If this option is turned off, the router is skipped when testing an address
19236 as a result of processing an SMTP EXPN command. You might, for example,
19237 want to turn it off on a router for users' &_.forward_& files, while leaving it
19238 on for the system alias file.
19239 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19242 The use of the SMTP EXPN command is controlled by an ACL (see chapter
19243 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
19244 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
19248 .option fail_verify routers boolean false
19249 .cindex "router" "forcing verification failure"
19250 Setting this option has the effect of setting both &%fail_verify_sender%& and
19251 &%fail_verify_recipient%& to the same value.
19255 .option fail_verify_recipient routers boolean false
19256 If this option is true and an address is accepted by this router when
19257 verifying a recipient, verification fails.
19261 .option fail_verify_sender routers boolean false
19262 If this option is true and an address is accepted by this router when
19263 verifying a sender, verification fails.
19267 .option fallback_hosts routers "string list" unset
19268 .cindex "router" "fallback hosts"
19269 .cindex "fallback" "hosts specified on router"
19270 String expansion is not applied to this option. The argument must be a
19271 colon-separated list of host names or IP addresses. The list separator can be
19272 changed (see section &<<SECTlistsepchange>>&), and a port can be specified with
19273 each name or address. In fact, the format of each item is exactly the same as
19274 defined for the list of hosts in a &(manualroute)& router (see section
19275 &<<SECTformatonehostitem>>&).
19277 If a router queues an address for a remote transport, this host list is
19278 associated with the address, and used instead of the transport's fallback host
19279 list. If &%hosts_randomize%& is set on the transport, the order of the list is
19280 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
19281 transport for further details.
19284 .option group routers string&!! "see below"
19285 .cindex "gid (group id)" "local delivery"
19286 .cindex "local transports" "uid and gid"
19287 .cindex "transport" "local"
19288 .cindex "router" "setting group"
19289 When a router queues an address for a transport, and the transport does not
19290 specify a group, the group given here is used when running the delivery
19292 The group may be specified numerically or by name. If expansion fails, the
19293 error is logged and delivery is deferred.
19294 The default is unset, unless &%check_local_user%& is set, when the default
19295 is taken from the password information. See also &%initgroups%& and &%user%&
19296 and the discussion in chapter &<<CHAPenvironment>>&.
19300 .option headers_add routers list&!! unset
19301 .cindex "header lines" "adding"
19302 .cindex "router" "adding header lines"
19303 This option specifies a list of text headers,
19304 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19305 that is associated with any addresses that are accepted by the router.
19306 Each item is separately expanded, at routing time. However, this
19307 option has no effect when an address is just being verified. The way in which
19308 the text is used to add header lines at transport time is described in section
19309 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
19310 message is in the process of being transported. This means that references to
19311 header lines in string expansions in the transport's configuration do not
19312 &"see"& the added header lines.
19314 The &%headers_add%& option is expanded after &%errors_to%&, but before
19315 &%headers_remove%& and &%transport%&. If an item is empty, or if
19316 an item expansion is forced to fail, the item has no effect. Other expansion
19317 failures are treated as configuration errors.
19319 Unlike most options, &%headers_add%& can be specified multiple times
19320 for a router; all listed headers are added.
19322 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
19323 router that has the &%one_time%& option set.
19325 .cindex "duplicate addresses"
19326 .oindex "&%unseen%&"
19327 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19328 additions are deleted when the address is passed on to subsequent routers.
19329 For a &%redirect%& router, if a generated address is the same as the incoming
19330 address, this can lead to duplicate addresses with different header
19331 modifications. Exim does not do duplicate deliveries (except, in certain
19332 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
19333 which of the duplicates is discarded, so this ambiguous situation should be
19334 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
19338 .option headers_remove routers list&!! unset
19339 .cindex "header lines" "removing"
19340 .cindex "router" "removing header lines"
19341 This option specifies a list of text headers,
19342 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19343 that is associated with any addresses that are accepted by the router.
19344 However, the option has no effect when an address is just being verified.
19345 Each list item is separately expanded, at transport time.
19346 If an item ends in *, it will match any header with the given prefix.
19348 the text is used to remove header lines at transport time is described in
19349 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
19350 the message is in the process of being transported. This means that references
19351 to header lines in string expansions in the transport's configuration still
19352 &"see"& the original header lines.
19354 The &%headers_remove%& option is handled after &%errors_to%& and
19355 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
19356 the item has no effect. Other expansion failures are treated as configuration
19359 Unlike most options, &%headers_remove%& can be specified multiple times
19360 for a router; all listed headers are removed.
19362 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
19363 router that has the &%one_time%& option set.
19365 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19366 removal requests are deleted when the address is passed on to subsequent
19367 routers, and this can lead to problems with duplicates -- see the similar
19368 warning for &%headers_add%& above.
19370 &*Warning 3*&: Because of the separate expansion of the list items,
19371 items that contain a list separator must have it doubled.
19372 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
19376 .option ignore_target_hosts routers "host list&!!" unset
19377 .cindex "IP address" "discarding"
19378 .cindex "router" "discarding IP addresses"
19379 Although this option is a host list, it should normally contain IP address
19380 entries rather than names. If any host that is looked up by the router has an
19381 IP address that matches an item in this list, Exim behaves as if that IP
19382 address did not exist. This option allows you to cope with rogue DNS entries
19385 remote.domain.example. A 127.0.0.1
19389 ignore_target_hosts = 127.0.0.1
19391 on the relevant router. If all the hosts found by a &(dnslookup)& router are
19392 discarded in this way, the router declines. In a conventional configuration, an
19393 attempt to mail to such a domain would normally provoke the &"unrouteable
19394 domain"& error, and an attempt to verify an address in the domain would fail.
19395 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
19396 router declines if presented with one of the listed addresses.
19398 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
19399 means of the first or the second of the following settings, respectively:
19401 ignore_target_hosts = 0.0.0.0/0
19402 ignore_target_hosts = <; 0::0/0
19404 The pattern in the first line matches all IPv4 addresses, whereas the pattern
19405 in the second line matches all IPv6 addresses.
19407 This option may also be useful for ignoring link-local and site-local IPv6
19408 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
19409 is expanded before use as a list, it is possible to make it dependent on the
19410 domain that is being routed.
19412 .vindex "&$host_address$&"
19413 During its expansion, &$host_address$& is set to the IP address that is being
19416 .option initgroups routers boolean false
19417 .cindex "additional groups"
19418 .cindex "groups" "additional"
19419 .cindex "local transports" "uid and gid"
19420 .cindex "transport" "local"
19421 If the router queues an address for a transport, and this option is true, and
19422 the uid supplied by the router is not overridden by the transport, the
19423 &[initgroups()]& function is called when running the transport to ensure that
19424 any additional groups associated with the uid are set up. See also &%group%&
19425 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
19429 .option local_part_prefix routers&!? "string list" unset
19430 .cindex affix "router precondition"
19431 .cindex "router" "prefix for local part"
19432 .cindex "prefix" "for local part, used in router"
19433 If this option is set, the router is skipped unless the local part starts with
19434 one of the given strings, or &%local_part_prefix_optional%& is true. See
19435 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
19438 The list is scanned from left to right, and the first prefix that matches is
19439 used. A limited form of wildcard is available; if the prefix begins with an
19440 asterisk, it matches the longest possible sequence of arbitrary characters at
19441 the start of the local part. An asterisk should therefore always be followed by
19442 some character that does not occur in normal local parts.
19443 .cindex "multiple mailboxes"
19444 .cindex "mailbox" "multiple"
19445 Wildcarding can be used to set up multiple user mailboxes, as described in
19446 section &<<SECTmulbox>>&.
19448 .vindex "&$local_part$&"
19449 .vindex "&$local_part_prefix$&"
19450 During the testing of the &%local_parts%& option, and while the router is
19451 running, the prefix is removed from the local part, and is available in the
19452 expansion variable &$local_part_prefix$&. When a message is being delivered, if
19453 the router accepts the address, this remains true during subsequent delivery by
19454 a transport. In particular, the local part that is transmitted in the RCPT
19455 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
19456 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
19457 the relevant transport.
19459 .vindex &$local_part_prefix_v$&
19460 If wildcarding (above) was used then the part of the prefix matching the
19461 wildcard is available in &$local_part_prefix_v$&.
19463 When an address is being verified, &%local_part_prefix%& affects only the
19464 behaviour of the router. If the callout feature of verification is in use, this
19465 means that the full address, including the prefix, will be used during the
19468 The prefix facility is commonly used to handle local parts of the form
19469 &%owner-something%&. Another common use is to support local parts of the form
19470 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
19471 to tell a user their forwarding is broken &-- by placing a router like this one
19472 immediately before the router that handles &_.forward_& files:
19476 local_part_prefix = real-
19478 transport = local_delivery
19480 For security, it would probably be a good idea to restrict the use of this
19481 router to locally-generated messages, using a condition such as this:
19483 condition = ${if match {$sender_host_address}\
19484 {\N^(|127\.0\.0\.1)$\N}}
19487 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
19488 both conditions must be met if not optional. Care must be taken if wildcards
19489 are used in both a prefix and a suffix on the same router. Different
19490 separator characters must be used to avoid ambiguity.
19493 .option local_part_prefix_optional routers boolean false
19494 See &%local_part_prefix%& above.
19498 .option local_part_suffix routers&!? "string list" unset
19499 .cindex "router" "suffix for local part"
19500 .cindex "suffix for local part" "used in router"
19501 This option operates in the same way as &%local_part_prefix%&, except that the
19502 local part must end (rather than start) with the given string, the
19503 &%local_part_suffix_optional%& option determines whether the suffix is
19504 mandatory, and the wildcard * character, if present, must be the last
19505 character of the suffix. This option facility is commonly used to handle local
19506 parts of the form &%something-request%& and multiple user mailboxes of the form
19510 .option local_part_suffix_optional routers boolean false
19511 See &%local_part_suffix%& above.
19515 .option local_parts routers&!? "local part list&!!" unset
19516 .cindex "router" "restricting to specific local parts"
19517 .cindex "local part" "checking in router"
19518 The router is run only if the local part of the address matches the list.
19519 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19521 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
19522 string is expanded, it is possible to make it depend on the domain, for
19525 local_parts = dbm;/usr/local/specials/$domain_data
19527 .vindex "&$local_part_data$&"
19528 If the match is achieved by a lookup, the data that the lookup returned
19529 for the local part is placed in the variable &$local_part_data$& for use in
19530 expansions of the router's private options or in the transport.
19531 You might use this option, for
19532 example, if you have a large number of local virtual domains, and you want to
19533 send all postmaster mail to the same place without having to set up an alias in
19534 each virtual domain:
19538 local_parts = postmaster
19539 data = postmaster@real.domain.example
19543 .option log_as_local routers boolean "see below"
19544 .cindex "log" "delivery line"
19545 .cindex "delivery" "log line format"
19546 Exim has two logging styles for delivery, the idea being to make local
19547 deliveries stand out more visibly from remote ones. In the &"local"& style, the
19548 recipient address is given just as the local part, without a domain. The use of
19549 this style is controlled by this option. It defaults to true for the &(accept)&
19550 router, and false for all the others. This option applies only when a
19551 router assigns an address to a transport. It has no effect on routers that
19552 redirect addresses.
19556 .option more routers boolean&!! true
19557 The result of string expansion for this option must be a valid boolean value,
19558 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19559 result causes an error, and delivery is deferred. If the expansion is forced to
19560 fail, the default value for the option (true) is used. Other failures cause
19561 delivery to be deferred.
19563 If this option is set false, and the router declines to handle the address, no
19564 further routers are tried, routing fails, and the address is bounced.
19566 However, if the router explicitly passes an address to the following router by
19567 means of the setting
19571 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
19572 does not affect the behaviour if one of the precondition tests fails. In that
19573 case, the address is always passed to the next router.
19575 Note that &%address_data%& is not considered to be a precondition. If its
19576 expansion is forced to fail, the router declines, and the value of &%more%&
19577 controls what happens next.
19580 .option pass_on_timeout routers boolean false
19581 .cindex "timeout" "of router"
19582 .cindex "router" "timeout"
19583 If a router times out during a host lookup, it normally causes deferral of the
19584 address. If &%pass_on_timeout%& is set, the address is passed on to the next
19585 router, overriding &%no_more%&. This may be helpful for systems that are
19586 intermittently connected to the Internet, or those that want to pass to a smart
19587 host any messages that cannot immediately be delivered.
19589 There are occasional other temporary errors that can occur while doing DNS
19590 lookups. They are treated in the same way as a timeout, and this option
19591 applies to all of them.
19595 .option pass_router routers string unset
19596 .cindex "router" "go to after &""pass""&"
19597 Routers that recognize the generic &%self%& option (&(dnslookup)&,
19598 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
19599 routing to continue, and overriding a false setting of &%more%&. When one of
19600 these routers returns &"pass"&, the address is normally handed on to the next
19601 router in sequence. This can be changed by setting &%pass_router%& to the name
19602 of another router. However (unlike &%redirect_router%&) the named router must
19603 be below the current router, to avoid loops. Note that this option applies only
19604 to the special case of &"pass"&. It does not apply when a router returns
19605 &"decline"& because it cannot handle an address.
19609 .option redirect_router routers string unset
19610 .cindex "router" "start at after redirection"
19611 Sometimes an administrator knows that it is pointless to reprocess addresses
19612 generated from alias or forward files with the same router again. For
19613 example, if an alias file translates real names into login ids there is no
19614 point searching the alias file a second time, especially if it is a large file.
19616 The &%redirect_router%& option can be set to the name of any router instance.
19617 It causes the routing of any generated addresses to start at the named router
19618 instead of at the first router. This option has no effect if the router in
19619 which it is set does not generate new addresses.
19623 .option require_files routers&!? "string list&!!" unset
19624 .cindex "file" "requiring for router"
19625 .cindex "router" "requiring file existence"
19626 This option provides a general mechanism for predicating the running of a
19627 router on the existence or non-existence of certain files or directories.
19628 Before running a router, as one of its precondition tests, Exim works its way
19629 through the &%require_files%& list, expanding each item separately.
19631 Because the list is split before expansion, any colons in expansion items must
19632 be doubled, or the facility for using a different list separator must be used
19633 (&<<SECTlistsepchange>>&).
19634 If any expansion is forced to fail, the item is ignored. Other expansion
19635 failures cause routing of the address to be deferred.
19637 If any expanded string is empty, it is ignored. Otherwise, except as described
19638 below, each string must be a fully qualified file path, optionally preceded by
19639 &"!"&. The paths are passed to the &[stat()]& function to test for the
19640 existence of the files or directories. The router is skipped if any paths not
19641 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
19644 If &[stat()]& cannot determine whether a file exists or not, delivery of
19645 the message is deferred. This can happen when NFS-mounted filesystems are
19648 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
19649 options, so you cannot use it to check for the existence of a file in which to
19650 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
19651 full list of the order in which preconditions are evaluated.) However, as
19652 these options are all expanded, you can use the &%exists%& expansion condition
19653 to make such tests. The &%require_files%& option is intended for checking files
19654 that the router may be going to use internally, or which are needed by a
19655 transport (e.g., &_.procmailrc_&).
19657 During delivery, the &[stat()]& function is run as root, but there is a
19658 facility for some checking of the accessibility of a file by another user.
19659 This is not a proper permissions check, but just a &"rough"& check that
19660 operates as follows:
19662 If an item in a &%require_files%& list does not contain any forward slash
19663 characters, it is taken to be the user (and optional group, separated by a
19664 comma) to be checked for subsequent files in the list. If no group is specified
19665 but the user is specified symbolically, the gid associated with the uid is
19668 require_files = mail:/some/file
19669 require_files = $local_part_data:$home/.procmailrc
19671 If a user or group name in a &%require_files%& list does not exist, the
19672 &%require_files%& condition fails.
19674 Exim performs the check by scanning along the components of the file path, and
19675 checking the access for the given uid and gid. It checks for &"x"& access on
19676 directories, and &"r"& access on the final file. Note that this means that file
19677 access control lists, if the operating system has them, are ignored.
19679 &*Warning 1*&: When the router is being run to verify addresses for an
19680 incoming SMTP message, Exim is not running as root, but under its own uid. This
19681 may affect the result of a &%require_files%& check. In particular, &[stat()]&
19682 may yield the error EACCES (&"Permission denied"&). This means that the Exim
19683 user is not permitted to read one of the directories on the file's path.
19685 &*Warning 2*&: Even when Exim is running as root while delivering a message,
19686 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
19687 without root access. In this case, if a check for access by a particular user
19688 is requested, Exim creates a subprocess that runs as that user, and tries the
19689 check again in that process.
19691 The default action for handling an unresolved EACCES is to consider it to
19692 be caused by a configuration error, and routing is deferred because the
19693 existence or non-existence of the file cannot be determined. However, in some
19694 circumstances it may be desirable to treat this condition as if the file did
19695 not exist. If the filename (or the exclamation mark that precedes the filename
19696 for non-existence) is preceded by a plus sign, the EACCES error is treated
19697 as if the file did not exist. For example:
19699 require_files = +/some/file
19701 If the router is not an essential part of verification (for example, it
19702 handles users' &_.forward_& files), another solution is to set the &%verify%&
19703 option false so that the router is skipped when verifying.
19707 .option retry_use_local_part routers boolean "see below"
19708 .cindex "hints database" "retry keys"
19709 .cindex "local part" "in retry keys"
19710 When a delivery suffers a temporary routing failure, a retry record is created
19711 in Exim's hints database. For addresses whose routing depends only on the
19712 domain, the key for the retry record should not involve the local part, but for
19713 other addresses, both the domain and the local part should be included.
19714 Usually, remote routing is of the former kind, and local routing is of the
19717 This option controls whether the local part is used to form the key for retry
19718 hints for addresses that suffer temporary errors while being handled by this
19719 router. The default value is true for any router that has any of
19720 &%check_local_user%&,
19723 &%local_part_prefix%&,
19724 &%local_part_suffix%&,
19727 set, and false otherwise. Note that this option does not apply to hints keys
19728 for transport delays; they are controlled by a generic transport option of the
19731 Failing to set this option when it is needed
19732 (because a remote router handles only some of the local-parts for a domain)
19733 can result in incorrect error messages being generated.
19735 The setting of &%retry_use_local_part%& applies only to the router on which it
19736 appears. If the router generates child addresses, they are routed
19737 independently; this setting does not become attached to them.
19741 .option router_home_directory routers string&!! unset
19742 .cindex "router" "home directory for"
19743 .cindex "home directory" "for router"
19745 This option sets a home directory for use while the router is running. (Compare
19746 &%transport_home_directory%&, which sets a home directory for later
19747 transporting.) In particular, if used on a &(redirect)& router, this option
19748 sets a value for &$home$& while a filter is running. The value is expanded;
19749 forced expansion failure causes the option to be ignored &-- other failures
19750 cause the router to defer.
19752 Expansion of &%router_home_directory%& happens immediately after the
19753 &%check_local_user%& test (if configured), before any further expansions take
19755 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19757 While the router is running, &%router_home_directory%& overrides the value of
19758 &$home$& that came from &%check_local_user%&.
19760 When a router accepts an address and assigns it to a local transport (including
19761 the cases when a &(redirect)& router generates a pipe, file, or autoreply
19762 delivery), the home directory setting for the transport is taken from the first
19763 of these values that is set:
19766 The &%home_directory%& option on the transport;
19768 The &%transport_home_directory%& option on the router;
19770 The password data if &%check_local_user%& is set on the router;
19772 The &%router_home_directory%& option on the router.
19775 In other words, &%router_home_directory%& overrides the password data for the
19776 router, but not for the transport.
19780 .option self routers string freeze
19781 .cindex "MX record" "pointing to local host"
19782 .cindex "local host" "MX pointing to"
19783 This option applies to those routers that use a recipient address to find a
19784 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
19785 and &(manualroute)& routers.
19786 Certain configurations of the &(queryprogram)& router can also specify a list
19788 Usually such routers are configured to send the message to a remote host via an
19789 &(smtp)& transport. The &%self%& option specifies what happens when the first
19790 host on the list turns out to be the local host.
19791 The way in which Exim checks for the local host is described in section
19792 &<<SECTreclocipadd>>&.
19794 Normally this situation indicates either an error in Exim's configuration (for
19795 example, the router should be configured not to process this domain), or an
19796 error in the DNS (for example, the MX should not point to this host). For this
19797 reason, the default action is to log the incident, defer the address, and
19798 freeze the message. The following alternatives are provided for use in special
19803 Delivery of the message is tried again later, but the message is not frozen.
19805 .vitem "&%reroute%&: <&'domain'&>"
19806 The domain is changed to the given domain, and the address is passed back to
19807 be reprocessed by the routers. No rewriting of headers takes place. This
19808 behaviour is essentially a redirection.
19810 .vitem "&%reroute: rewrite:%& <&'domain'&>"
19811 The domain is changed to the given domain, and the address is passed back to be
19812 reprocessed by the routers. Any headers that contain the original domain are
19817 .vindex "&$self_hostname$&"
19818 The router passes the address to the next router, or to the router named in the
19819 &%pass_router%& option if it is set. This overrides &%no_more%&. During
19820 subsequent routing and delivery, the variable &$self_hostname$& contains the
19821 name of the local host that the router encountered. This can be used to
19822 distinguish between different cases for hosts with multiple names. The
19828 ensures that only those addresses that routed to the local host are passed on.
19829 Without &%no_more%&, addresses that were declined for other reasons would also
19830 be passed to the next router.
19833 Delivery fails and an error report is generated.
19836 .cindex "local host" "sending to"
19837 The anomaly is ignored and the address is queued for the transport. This
19838 setting should be used with extreme caution. For an &(smtp)& transport, it
19839 makes sense only in cases where the program that is listening on the SMTP port
19840 is not this version of Exim. That is, it must be some other MTA, or Exim with a
19841 different configuration file that handles the domain in another way.
19846 .option senders routers&!? "address list&!!" unset
19847 .cindex "router" "checking senders"
19848 If this option is set, the router is skipped unless the message's sender
19849 address matches something on the list.
19850 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19853 There are issues concerning verification when the running of routers is
19854 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
19855 setting, it sets the sender to the null string. When using the &%-bt%& option
19856 to check a configuration file, it is necessary also to use the &%-f%& option to
19857 set an appropriate sender. For incoming mail, the sender is unset when
19858 verifying the sender, but is available when verifying any recipients. If the
19859 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
19863 .option set routers "string list" unset
19864 .cindex router variables
19865 This option may be used multiple times on a router;
19866 because of this the list aspect is mostly irrelevant.
19867 The list separator is a semicolon but can be changed in the
19870 Each list-element given must be of the form &"name = value"&
19871 and the names used must start with the string &"r_"&.
19872 Values containing a list-separator should have them doubled.
19873 When a router runs, the strings are evaluated in order,
19874 to create variables which are added to the set associated with
19877 This is done immediately after all the preconditions, before the
19878 evaluation of the &%address_data%& option.
19880 The variable is set with the expansion of the value.
19881 The variables can be used by the router options
19882 (not including any preconditions)
19883 and by the transport.
19884 Later definitions of a given named variable will override former ones.
19885 Variable use is via the usual &$r_...$& syntax.
19887 This is similar to the &%address_data%& option, except that
19888 many independent variables can be used, with choice of naming.
19891 .option translate_ip_address routers string&!! unset
19892 .cindex "IP address" "translating"
19893 .cindex "packet radio"
19894 .cindex "router" "IP address translation"
19895 There exist some rare networking situations (for example, packet radio) where
19896 it is helpful to be able to translate IP addresses generated by normal routing
19897 mechanisms into other IP addresses, thus performing a kind of manual IP
19898 routing. This should be done only if the normal IP routing of the TCP/IP stack
19899 is inadequate or broken. Because this is an extremely uncommon requirement, the
19900 code to support this option is not included in the Exim binary unless
19901 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
19903 .vindex "&$host_address$&"
19904 The &%translate_ip_address%& string is expanded for every IP address generated
19905 by the router, with the generated address set in &$host_address$&. If the
19906 expansion is forced to fail, no action is taken.
19907 For any other expansion error, delivery of the message is deferred.
19908 If the result of the expansion is an IP address, that replaces the original
19909 address; otherwise the result is assumed to be a host name &-- this is looked
19910 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
19911 produce one or more replacement IP addresses. For example, to subvert all IP
19912 addresses in some specific networks, this could be added to a router:
19914 translate_ip_address = \
19915 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
19918 The file would contain lines like
19920 10.2.3.128/26 some.host
19921 10.8.4.34/26 10.44.8.15
19923 You should not make use of this facility unless you really understand what you
19928 .option transport routers string&!! unset
19929 This option specifies the transport to be used when a router accepts an address
19930 and sets it up for delivery. A transport is never needed if a router is used
19931 only for verification. The value of the option is expanded at routing time,
19932 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
19933 and result must be the name of one of the configured transports. If it is not,
19934 delivery is deferred.
19936 The &%transport%& option is not used by the &(redirect)& router, but it does
19937 have some private options that set up transports for pipe and file deliveries
19938 (see chapter &<<CHAPredirect>>&).
19942 .option transport_current_directory routers string&!! unset
19943 .cindex "current directory for local transport"
19944 This option associates a current directory with any address that is routed
19945 to a local transport. This can happen either because a transport is
19946 explicitly configured for the router, or because it generates a delivery to a
19947 file or a pipe. During the delivery process (that is, at transport time), this
19948 option string is expanded and is set as the current directory, unless
19949 overridden by a setting on the transport.
19950 If the expansion fails for any reason, including forced failure, an error is
19951 logged, and delivery is deferred.
19952 See chapter &<<CHAPenvironment>>& for details of the local delivery
19958 .option transport_home_directory routers string&!! "see below"
19959 .cindex "home directory" "for local transport"
19960 This option associates a home directory with any address that is routed to a
19961 local transport. This can happen either because a transport is explicitly
19962 configured for the router, or because it generates a delivery to a file or a
19963 pipe. During the delivery process (that is, at transport time), the option
19964 string is expanded and is set as the home directory, unless overridden by a
19965 setting of &%home_directory%& on the transport.
19966 If the expansion fails for any reason, including forced failure, an error is
19967 logged, and delivery is deferred.
19969 If the transport does not specify a home directory, and
19970 &%transport_home_directory%& is not set for the router, the home directory for
19971 the transport is taken from the password data if &%check_local_user%& is set for
19972 the router. Otherwise it is taken from &%router_home_directory%& if that option
19973 is set; if not, no home directory is set for the transport.
19975 See chapter &<<CHAPenvironment>>& for further details of the local delivery
19981 .option unseen routers boolean&!! false
19982 .cindex "router" "carrying on after success"
19983 The result of string expansion for this option must be a valid boolean value,
19984 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19985 result causes an error, and delivery is deferred. If the expansion is forced to
19986 fail, the default value for the option (false) is used. Other failures cause
19987 delivery to be deferred.
19989 When this option is set true, routing does not cease if the router accepts the
19990 address. Instead, a copy of the incoming address is passed to the next router,
19991 overriding a false setting of &%more%&. There is little point in setting
19992 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
19993 the value of &%unseen%& contains expansion items (and therefore, presumably, is
19994 sometimes true and sometimes false).
19996 .cindex "copy of message (&%unseen%& option)"
19997 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
19998 qualifier in filter files. It can be used to cause copies of messages to be
19999 delivered to some other destination, while also carrying out a normal delivery.
20000 In effect, the current address is made into a &"parent"& that has two children
20001 &-- one that is delivered as specified by this router, and a clone that goes on
20002 to be routed further. For this reason, &%unseen%& may not be combined with the
20003 &%one_time%& option in a &(redirect)& router.
20005 &*Warning*&: Header lines added to the address (or specified for removal) by
20006 this router or by previous routers affect the &"unseen"& copy of the message
20007 only. The clone that continues to be processed by further routers starts with
20008 no added headers and none specified for removal. For a &%redirect%& router, if
20009 a generated address is the same as the incoming address, this can lead to
20010 duplicate addresses with different header modifications. Exim does not do
20011 duplicate deliveries (except, in certain circumstances, to pipes -- see section
20012 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
20013 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
20014 &%redirect%& router may be of help.
20016 Unlike the handling of header modifications, any data that was set by the
20017 &%address_data%& option in the current or previous routers &'is'& passed on to
20018 subsequent routers.
20021 .option user routers string&!! "see below"
20022 .cindex "uid (user id)" "local delivery"
20023 .cindex "local transports" "uid and gid"
20024 .cindex "transport" "local"
20025 .cindex "router" "user for filter processing"
20026 .cindex "filter" "user for processing"
20027 When a router queues an address for a transport, and the transport does not
20028 specify a user, the user given here is used when running the delivery process.
20029 The user may be specified numerically or by name. If expansion fails, the
20030 error is logged and delivery is deferred.
20031 This user is also used by the &(redirect)& router when running a filter file.
20032 The default is unset, except when &%check_local_user%& is set. In this case,
20033 the default is taken from the password information. If the user is specified as
20034 a name, and &%group%& is not set, the group associated with the user is used.
20035 See also &%initgroups%& and &%group%& and the discussion in chapter
20036 &<<CHAPenvironment>>&.
20040 .option verify routers&!? boolean true
20041 Setting this option has the effect of setting &%verify_sender%& and
20042 &%verify_recipient%& to the same value.
20045 .option verify_only routers&!? boolean false
20046 .cindex "EXPN" "with &%verify_only%&"
20048 .cindex "router" "used only when verifying"
20049 If this option is set, the router is used only when verifying an address,
20050 delivering in cutthrough mode or
20051 testing with the &%-bv%& option, not when actually doing a delivery, testing
20052 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
20053 restricted to verifying only senders or recipients by means of
20054 &%verify_sender%& and &%verify_recipient%&.
20056 &*Warning*&: When the router is being run to verify addresses for an incoming
20057 SMTP message, Exim is not running as root, but under its own uid. If the router
20058 accesses any files, you need to make sure that they are accessible to the Exim
20062 .option verify_recipient routers&!? boolean true
20063 If this option is false, the router is skipped when verifying recipient
20065 delivering in cutthrough mode
20066 or testing recipient verification using &%-bv%&.
20067 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
20069 See also the &$verify_mode$& variable.
20072 .option verify_sender routers&!? boolean true
20073 If this option is false, the router is skipped when verifying sender addresses
20074 or testing sender verification using &%-bvs%&.
20075 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
20077 See also the &$verify_mode$& variable.
20078 .ecindex IIDgenoprou1
20079 .ecindex IIDgenoprou2
20086 . ////////////////////////////////////////////////////////////////////////////
20087 . ////////////////////////////////////////////////////////////////////////////
20089 .chapter "The accept router" "CHID4"
20090 .cindex "&(accept)& router"
20091 .cindex "routers" "&(accept)&"
20092 The &(accept)& router has no private options of its own. Unless it is being
20093 used purely for verification (see &%verify_only%&) a transport is required to
20094 be defined by the generic &%transport%& option. If the preconditions that are
20095 specified by generic options are met, the router accepts the address and queues
20096 it for the given transport. The most common use of this router is for setting
20097 up deliveries to local mailboxes. For example:
20101 domains = mydomain.example
20103 transport = local_delivery
20105 The &%domains%& condition in this example checks the domain of the address, and
20106 &%check_local_user%& checks that the local part is the login of a local user.
20107 When both preconditions are met, the &(accept)& router runs, and queues the
20108 address for the &(local_delivery)& transport.
20115 . ////////////////////////////////////////////////////////////////////////////
20116 . ////////////////////////////////////////////////////////////////////////////
20118 .chapter "The dnslookup router" "CHAPdnslookup"
20119 .scindex IIDdnsrou1 "&(dnslookup)& router"
20120 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
20121 The &(dnslookup)& router looks up the hosts that handle mail for the
20122 recipient's domain in the DNS. A transport must always be set for this router,
20123 unless &%verify_only%& is set.
20125 If SRV support is configured (see &%check_srv%& below), Exim first searches for
20126 SRV records. If none are found, or if SRV support is not configured,
20127 MX records are looked up. If no MX records exist, address records are sought.
20128 However, &%mx_domains%& can be set to disable the direct use of address
20131 MX records of equal priority are sorted by Exim into a random order. Exim then
20132 looks for address records for the host names obtained from MX or SRV records.
20133 When a host has more than one IP address, they are sorted into a random order,
20134 except that IPv6 addresses are sorted before IPv4 addresses. If all the
20135 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
20136 generic option, the router declines.
20138 Unless they have the highest priority (lowest MX value), MX records that point
20139 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
20140 are discarded, together with any other MX records of equal or lower priority.
20142 .cindex "MX record" "pointing to local host"
20143 .cindex "local host" "MX pointing to"
20144 .oindex "&%self%&" "in &(dnslookup)& router"
20145 If the host pointed to by the highest priority MX record, or looked up as an
20146 address record, is the local host, or matches &%hosts_treat_as_local%&, what
20147 happens is controlled by the generic &%self%& option.
20150 .section "Problems with DNS lookups" "SECTprowitdnsloo"
20151 There have been problems with DNS servers when SRV records are looked up.
20152 Some misbehaving servers return a DNS error or timeout when a non-existent
20153 SRV record is sought. Similar problems have in the past been reported for
20154 MX records. The global &%dns_again_means_nonexist%& option can help with this
20155 problem, but it is heavy-handed because it is a global option.
20157 For this reason, there are two options, &%srv_fail_domains%& and
20158 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
20159 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
20160 an attempt to look up an SRV or MX record causes one of these results, and the
20161 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
20162 such record"&. In the case of an SRV lookup, this means that the router
20163 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
20164 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
20165 case routing fails.
20168 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
20169 .cindex "&(dnslookup)& router" "declines"
20170 There are a few cases where a &(dnslookup)& router will decline to accept
20171 an address; if such a router is expected to handle "all remaining non-local
20172 domains", then it is important to set &%no_more%&.
20174 The router will defer rather than decline if the domain
20175 is found in the &%fail_defer_domains%& router option.
20177 Reasons for a &(dnslookup)& router to decline currently include:
20179 The domain does not exist in DNS
20181 The domain exists but the MX record's host part is just "."; this is a common
20182 convention (borrowed from SRV) used to indicate that there is no such service
20183 for this domain and to not fall back to trying A/AAAA records.
20185 Ditto, but for SRV records, when &%check_srv%& is set on this router.
20187 MX record points to a non-existent host.
20189 MX record points to an IP address and the main section option
20190 &%allow_mx_to_ip%& is not set.
20192 MX records exist and point to valid hosts, but all hosts resolve only to
20193 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
20195 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
20196 &%dns_check_names_pattern%& for handling one variant of this)
20198 &%check_secondary_mx%& is set on this router but the local host can
20199 not be found in the MX records (see below)
20205 .section "Private options for dnslookup" "SECID118"
20206 .cindex "options" "&(dnslookup)& router"
20207 The private options for the &(dnslookup)& router are as follows:
20209 .option check_secondary_mx dnslookup boolean false
20210 .cindex "MX record" "checking for secondary"
20211 If this option is set, the router declines unless the local host is found in
20212 (and removed from) the list of hosts obtained by MX lookup. This can be used to
20213 process domains for which the local host is a secondary mail exchanger
20214 differently to other domains. The way in which Exim decides whether a host is
20215 the local host is described in section &<<SECTreclocipadd>>&.
20218 .option check_srv dnslookup string&!! unset
20219 .cindex "SRV record" "enabling use of"
20220 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
20221 addition to MX and address records. The support is disabled by default. To
20222 enable SRV support, set the &%check_srv%& option to the name of the service
20223 required. For example,
20227 looks for SRV records that refer to the normal smtp service. The option is
20228 expanded, so the service name can vary from message to message or address
20229 to address. This might be helpful if SRV records are being used for a
20230 submission service. If the expansion is forced to fail, the &%check_srv%&
20231 option is ignored, and the router proceeds to look for MX records in the
20234 When the expansion succeeds, the router searches first for SRV records for
20235 the given service (it assumes TCP protocol). A single SRV record with a
20236 host name that consists of just a single dot indicates &"no such service for
20237 this domain"&; if this is encountered, the router declines. If other kinds of
20238 SRV record are found, they are used to construct a host list for delivery
20239 according to the rules of RFC 2782. MX records are not sought in this case.
20241 When no SRV records are found, MX records (and address records) are sought in
20242 the traditional way. In other words, SRV records take precedence over MX
20243 records, just as MX records take precedence over address records. Note that
20244 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
20245 defined it. It is apparently believed that MX records are sufficient for email
20246 and that SRV records should not be used for this purpose. However, SRV records
20247 have an additional &"weight"& feature which some people might find useful when
20248 trying to split an SMTP load between hosts of different power.
20250 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
20251 when there is a DNS lookup error.
20256 .option fail_defer_domains dnslookup "domain list&!!" unset
20257 .cindex "MX record" "not found"
20258 DNS lookups for domains matching &%fail_defer_domains%&
20259 which find no matching record will cause the router to defer
20260 rather than the default behaviour of decline.
20261 This maybe be useful for queueing messages for a newly created
20262 domain while the DNS configuration is not ready.
20263 However, it will result in any message with mistyped domains
20267 .option ipv4_only "string&!!" unset
20268 .cindex IPv6 disabling
20269 .cindex DNS "IPv6 disabling"
20270 The string is expanded, and if the result is anything but a forced failure,
20271 or an empty string, or one of the strings “0” or “no” or “false”
20272 (checked without regard to the case of the letters),
20273 only A records are used.
20275 .option ipv4_prefer "string&!!" unset
20276 .cindex IPv4 preference
20277 .cindex DNS "IPv4 preference"
20278 The string is expanded, and if the result is anything but a forced failure,
20279 or an empty string, or one of the strings “0” or “no” or “false”
20280 (checked without regard to the case of the letters),
20281 A records are sorted before AAAA records (inverting the default).
20283 .option mx_domains dnslookup "domain list&!!" unset
20284 .cindex "MX record" "required to exist"
20285 .cindex "SRV record" "required to exist"
20286 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
20287 record in order to be recognized. (The name of this option could be improved.)
20288 For example, if all the mail hosts in &'fict.example'& are known to have MX
20289 records, except for those in &'discworld.fict.example'&, you could use this
20292 mx_domains = ! *.discworld.fict.example : *.fict.example
20294 This specifies that messages addressed to a domain that matches the list but
20295 has no MX record should be bounced immediately instead of being routed using
20296 the address record.
20299 .option mx_fail_domains dnslookup "domain list&!!" unset
20300 If the DNS lookup for MX records for one of the domains in this list causes a
20301 DNS lookup error, Exim behaves as if no MX records were found. See section
20302 &<<SECTprowitdnsloo>>& for more discussion.
20307 .option qualify_single dnslookup boolean true
20308 .cindex "DNS" "resolver options"
20309 .cindex "DNS" "qualifying single-component names"
20310 When this option is true, the resolver option RES_DEFNAMES is set for DNS
20311 lookups. Typically, but not standardly, this causes the resolver to qualify
20312 single-component names with the default domain. For example, on a machine
20313 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
20314 &'thesaurus.ref.example'& inside the resolver. For details of what your
20315 resolver actually does, consult your man pages for &'resolver'& and
20320 .option rewrite_headers dnslookup boolean true
20321 .cindex "rewriting" "header lines"
20322 .cindex "header lines" "rewriting"
20323 If the domain name in the address that is being processed is not fully
20324 qualified, it may be expanded to its full form by a DNS lookup. For example, if
20325 an address is specified as &'dormouse@teaparty'&, the domain might be
20326 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
20327 occur as a result of setting the &%widen_domains%& option. If
20328 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
20329 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
20330 header lines of the message are rewritten with the full domain name.
20332 This option should be turned off only when it is known that no message is
20333 ever going to be sent outside an environment where the abbreviation makes
20336 When an MX record is looked up in the DNS and matches a wildcard record, name
20337 servers normally return a record containing the name that has been looked up,
20338 making it impossible to detect whether a wildcard was present or not. However,
20339 some name servers have recently been seen to return the wildcard entry. If the
20340 name returned by a DNS lookup begins with an asterisk, it is not used for
20344 .option same_domain_copy_routing dnslookup boolean false
20345 .cindex "address" "copying routing"
20346 Addresses with the same domain are normally routed by the &(dnslookup)& router
20347 to the same list of hosts. However, this cannot be presumed, because the router
20348 options and preconditions may refer to the local part of the address. By
20349 default, therefore, Exim routes each address in a message independently. DNS
20350 servers run caches, so repeated DNS lookups are not normally expensive, and in
20351 any case, personal messages rarely have more than a few recipients.
20353 If you are running mailing lists with large numbers of subscribers at the same
20354 domain, and you are using a &(dnslookup)& router which is independent of the
20355 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20356 lookups for identical domains in one message. In this case, when &(dnslookup)&
20357 routes an address to a remote transport, any other unrouted addresses in the
20358 message that have the same domain are automatically given the same routing
20359 without processing them independently,
20360 provided the following conditions are met:
20363 No router that processed the address specified &%headers_add%& or
20364 &%headers_remove%&.
20366 The router did not change the address in any way, for example, by &"widening"&
20373 .option search_parents dnslookup boolean false
20374 .cindex "DNS" "resolver options"
20375 When this option is true, the resolver option RES_DNSRCH is set for DNS
20376 lookups. This is different from the &%qualify_single%& option in that it
20377 applies to domains containing dots. Typically, but not standardly, it causes
20378 the resolver to search for the name in the current domain and in parent
20379 domains. For example, on a machine in the &'fict.example'& domain, if looking
20380 up &'teaparty.wonderland'& failed, the resolver would try
20381 &'teaparty.wonderland.fict.example'&. For details of what your resolver
20382 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
20384 Setting this option true can cause problems in domains that have a wildcard MX
20385 record, because any domain that does not have its own MX record matches the
20390 .option srv_fail_domains dnslookup "domain list&!!" unset
20391 If the DNS lookup for SRV records for one of the domains in this list causes a
20392 DNS lookup error, Exim behaves as if no SRV records were found. See section
20393 &<<SECTprowitdnsloo>>& for more discussion.
20398 .option widen_domains dnslookup "string list" unset
20399 .cindex "domain" "partial; widening"
20400 If a DNS lookup fails and this option is set, each of its strings in turn is
20401 added onto the end of the domain, and the lookup is tried again. For example,
20404 widen_domains = fict.example:ref.example
20406 is set and a lookup of &'klingon.dictionary'& fails,
20407 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
20408 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
20409 and &%search_parents%& options can cause some widening to be undertaken inside
20410 the DNS resolver. &%widen_domains%& is not applied to sender addresses
20411 when verifying, unless &%rewrite_headers%& is false (not the default).
20414 .section "Effect of qualify_single and search_parents" "SECID119"
20415 When a domain from an envelope recipient is changed by the resolver as a result
20416 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
20417 corresponding address in the message's header lines unless &%rewrite_headers%&
20418 is set false. Exim then re-routes the address, using the full domain.
20420 These two options affect only the DNS lookup that takes place inside the router
20421 for the domain of the address that is being routed. They do not affect lookups
20422 such as that implied by
20426 that may happen while processing a router precondition before the router is
20427 entered. No widening ever takes place for these lookups.
20428 .ecindex IIDdnsrou1
20429 .ecindex IIDdnsrou2
20439 . ////////////////////////////////////////////////////////////////////////////
20440 . ////////////////////////////////////////////////////////////////////////////
20442 .chapter "The ipliteral router" "CHID5"
20443 .cindex "&(ipliteral)& router"
20444 .cindex "domain literal" "routing"
20445 .cindex "routers" "&(ipliteral)&"
20446 This router has no private options. Unless it is being used purely for
20447 verification (see &%verify_only%&) a transport is required to be defined by the
20448 generic &%transport%& option. The router accepts the address if its domain part
20449 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
20450 router handles the address
20454 by setting up delivery to the host with that IP address. IPv4 domain literals
20455 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
20456 are similar, but the address is preceded by &`ipv6:`&. For example:
20458 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
20460 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
20461 grounds that sooner or later somebody will try it.
20463 .oindex "&%self%&" "in &(ipliteral)& router"
20464 If the IP address matches something in &%ignore_target_hosts%&, the router
20465 declines. If an IP literal turns out to refer to the local host, the generic
20466 &%self%& option determines what happens.
20468 The RFCs require support for domain literals; however, their use is
20469 controversial in today's Internet. If you want to use this router, you must
20470 also set the main configuration option &%allow_domain_literals%&. Otherwise,
20471 Exim will not recognize the domain literal syntax in addresses.
20475 . ////////////////////////////////////////////////////////////////////////////
20476 . ////////////////////////////////////////////////////////////////////////////
20478 .chapter "The iplookup router" "CHID6"
20479 .cindex "&(iplookup)& router"
20480 .cindex "routers" "&(iplookup)&"
20481 The &(iplookup)& router was written to fulfil a specific requirement in
20482 Cambridge University (which in fact no longer exists). For this reason, it is
20483 not included in the binary of Exim by default. If you want to include it, you
20486 ROUTER_IPLOOKUP=yes
20488 in your &_Local/Makefile_& configuration file.
20490 The &(iplookup)& router routes an address by sending it over a TCP or UDP
20491 connection to one or more specific hosts. The host can then return the same or
20492 a different address &-- in effect rewriting the recipient address in the
20493 message's envelope. The new address is then passed on to subsequent routers. If
20494 this process fails, the address can be passed on to other routers, or delivery
20495 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
20496 must not be specified for it.
20498 .cindex "options" "&(iplookup)& router"
20499 .option hosts iplookup string unset
20500 This option must be supplied. Its value is a colon-separated list of host
20501 names. The hosts are looked up using &[gethostbyname()]&
20502 (or &[getipnodebyname()]& when available)
20503 and are tried in order until one responds to the query. If none respond, what
20504 happens is controlled by &%optional%&.
20507 .option optional iplookup boolean false
20508 If &%optional%& is true, if no response is obtained from any host, the address
20509 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
20510 delivery to the address is deferred.
20513 .option port iplookup integer 0
20514 .cindex "port" "&(iplookup)& router"
20515 This option must be supplied. It specifies the port number for the TCP or UDP
20519 .option protocol iplookup string udp
20520 This option can be set to &"udp"& or &"tcp"& to specify which of the two
20521 protocols is to be used.
20524 .option query iplookup string&!! "see below"
20525 This defines the content of the query that is sent to the remote hosts. The
20528 $local_part@$domain $local_part@$domain
20530 The repetition serves as a way of checking that a response is to the correct
20531 query in the default case (see &%response_pattern%& below).
20534 .option reroute iplookup string&!! unset
20535 If this option is not set, the rerouted address is precisely the byte string
20536 returned by the remote host, up to the first white space, if any. If set, the
20537 string is expanded to form the rerouted address. It can include parts matched
20538 in the response by &%response_pattern%& by means of numeric variables such as
20539 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
20540 whether or not a pattern is in use. In all cases, the rerouted address must end
20541 up in the form &'local_part@domain'&.
20544 .option response_pattern iplookup string unset
20545 This option can be set to a regular expression that is applied to the string
20546 returned from the remote host. If the pattern does not match the response, the
20547 router declines. If &%response_pattern%& is not set, no checking of the
20548 response is done, unless the query was defaulted, in which case there is a
20549 check that the text returned after the first white space is the original
20550 address. This checks that the answer that has been received is in response to
20551 the correct question. For example, if the response is just a new domain, the
20552 following could be used:
20554 response_pattern = ^([^@]+)$
20555 reroute = $local_part@$1
20558 .option timeout iplookup time 5s
20559 This specifies the amount of time to wait for a response from the remote
20560 machine. The same timeout is used for the &[connect()]& function for a TCP
20561 call. It does not apply to UDP.
20566 . ////////////////////////////////////////////////////////////////////////////
20567 . ////////////////////////////////////////////////////////////////////////////
20569 .chapter "The manualroute router" "CHID7"
20570 .scindex IIDmanrou1 "&(manualroute)& router"
20571 .scindex IIDmanrou2 "routers" "&(manualroute)&"
20572 .cindex "domain" "manually routing"
20573 The &(manualroute)& router is so-called because it provides a way of manually
20574 routing an address according to its domain. It is mainly used when you want to
20575 route addresses to remote hosts according to your own rules, bypassing the
20576 normal DNS routing that looks up MX records. However, &(manualroute)& can also
20577 route to local transports, a facility that may be useful if you want to save
20578 messages for dial-in hosts in local files.
20580 The &(manualroute)& router compares a list of domain patterns with the domain
20581 it is trying to route. If there is no match, the router declines. Each pattern
20582 has associated with it a list of hosts and some other optional data, which may
20583 include a transport. The combination of a pattern and its data is called a
20584 &"routing rule"&. For patterns that do not have an associated transport, the
20585 generic &%transport%& option must specify a transport, unless the router is
20586 being used purely for verification (see &%verify_only%&).
20589 In the case of verification, matching the domain pattern is sufficient for the
20590 router to accept the address. When actually routing an address for delivery,
20591 an address that matches a domain pattern is queued for the associated
20592 transport. If the transport is not a local one, a host list must be associated
20593 with the pattern; IP addresses are looked up for the hosts, and these are
20594 passed to the transport along with the mail address. For local transports, a
20595 host list is optional. If it is present, it is passed in &$host$& as a single
20598 The list of routing rules can be provided as an inline string in
20599 &%route_list%&, or the data can be obtained by looking up the domain in a file
20600 or database by setting &%route_data%&. Only one of these settings may appear in
20601 any one instance of &(manualroute)&. The format of routing rules is described
20602 below, following the list of private options.
20605 .section "Private options for manualroute" "SECTprioptman"
20607 .cindex "options" "&(manualroute)& router"
20608 The private options for the &(manualroute)& router are as follows:
20610 .option host_all_ignored manualroute string defer
20611 See &%host_find_failed%&.
20613 .option host_find_failed manualroute string freeze
20614 This option controls what happens when &(manualroute)& tries to find an IP
20615 address for a host, and the host does not exist. The option can be set to one
20616 of the following values:
20625 The default (&"freeze"&) assumes that this state is a serious configuration
20626 error. The difference between &"pass"& and &"decline"& is that the former
20627 forces the address to be passed to the next router (or the router defined by
20630 overriding &%no_more%&, whereas the latter passes the address to the next
20631 router only if &%more%& is true.
20633 The value &"ignore"& causes Exim to completely ignore a host whose IP address
20634 cannot be found. If all the hosts in the list are ignored, the behaviour is
20635 controlled by the &%host_all_ignored%& option. This takes the same values
20636 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
20638 The &%host_find_failed%& option applies only to a definite &"does not exist"&
20639 state; if a host lookup gets a temporary error, delivery is deferred unless the
20640 generic &%pass_on_timeout%& option is set.
20643 .option hosts_randomize manualroute boolean false
20644 .cindex "randomized host list"
20645 .cindex "host" "list of; randomized"
20646 If this option is set, the order of the items in a host list in a routing rule
20647 is randomized each time the list is used, unless an option in the routing rule
20648 overrides (see below). Randomizing the order of a host list can be used to do
20649 crude load sharing. However, if more than one mail address is routed by the
20650 same router to the same host list, the host lists are considered to be the same
20651 (even though they may be randomized into different orders) for the purpose of
20652 deciding whether to batch the deliveries into a single SMTP transaction.
20654 When &%hosts_randomize%& is true, a host list may be split
20655 into groups whose order is separately randomized. This makes it possible to
20656 set up MX-like behaviour. The boundaries between groups are indicated by an
20657 item that is just &`+`& in the host list. For example:
20659 route_list = * host1:host2:host3:+:host4:host5
20661 The order of the first three hosts and the order of the last two hosts is
20662 randomized for each use, but the first three always end up before the last two.
20663 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
20664 randomized host list is passed to an &(smtp)& transport that also has
20665 &%hosts_randomize set%&, the list is not re-randomized.
20668 .option route_data manualroute string&!! unset
20669 If this option is set, it must expand to yield the data part of a routing rule.
20670 Typically, the expansion string includes a lookup based on the domain. For
20673 route_data = ${lookup{$domain}dbm{/etc/routes}}
20675 If the expansion is forced to fail, or the result is an empty string, the
20676 router declines. Other kinds of expansion failure cause delivery to be
20680 .option route_list manualroute "string list" unset
20681 This string is a list of routing rules, in the form defined below. Note that,
20682 unlike most string lists, the items are separated by semicolons. This is so
20683 that they may contain colon-separated host lists.
20686 .option same_domain_copy_routing manualroute boolean false
20687 .cindex "address" "copying routing"
20688 Addresses with the same domain are normally routed by the &(manualroute)&
20689 router to the same list of hosts. However, this cannot be presumed, because the
20690 router options and preconditions may refer to the local part of the address. By
20691 default, therefore, Exim routes each address in a message independently. DNS
20692 servers run caches, so repeated DNS lookups are not normally expensive, and in
20693 any case, personal messages rarely have more than a few recipients.
20695 If you are running mailing lists with large numbers of subscribers at the same
20696 domain, and you are using a &(manualroute)& router which is independent of the
20697 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20698 lookups for identical domains in one message. In this case, when
20699 &(manualroute)& routes an address to a remote transport, any other unrouted
20700 addresses in the message that have the same domain are automatically given the
20701 same routing without processing them independently. However, this is only done
20702 if &%headers_add%& and &%headers_remove%& are unset.
20707 .section "Routing rules in route_list" "SECID120"
20708 The value of &%route_list%& is a string consisting of a sequence of routing
20709 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
20710 entered as two semicolons. Alternatively, the list separator can be changed as
20711 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
20712 Empty rules are ignored. The format of each rule is
20714 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
20716 The following example contains two rules, each with a simple domain pattern and
20720 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
20721 thes.ref.example mail-3.ref.example:mail-4.ref.example
20723 The three parts of a rule are separated by white space. The pattern and the
20724 list of hosts can be enclosed in quotes if necessary, and if they are, the
20725 usual quoting rules apply. Each rule in a &%route_list%& must start with a
20726 single domain pattern, which is the only mandatory item in the rule. The
20727 pattern is in the same format as one item in a domain list (see section
20728 &<<SECTdomainlist>>&),
20729 except that it may not be the name of an interpolated file.
20730 That is, it may be wildcarded, or a regular expression, or a file or database
20731 lookup (with semicolons doubled, because of the use of semicolon as a separator
20732 in a &%route_list%&).
20734 The rules in &%route_list%& are searched in order until one of the patterns
20735 matches the domain that is being routed. The list of hosts and then options are
20736 then used as described below. If there is no match, the router declines. When
20737 &%route_list%& is set, &%route_data%& must not be set.
20741 .section "Routing rules in route_data" "SECID121"
20742 The use of &%route_list%& is convenient when there are only a small number of
20743 routing rules. For larger numbers, it is easier to use a file or database to
20744 hold the routing information, and use the &%route_data%& option instead.
20745 The value of &%route_data%& is a list of hosts, followed by (optional) options.
20746 Most commonly, &%route_data%& is set as a string that contains an
20747 expansion lookup. For example, suppose we place two routing rules in a file
20750 dict.ref.example: mail-1.ref.example:mail-2.ref.example
20751 thes.ref.example: mail-3.ref.example:mail-4.ref.example
20753 This data can be accessed by setting
20755 route_data = ${lookup{$domain}lsearch{/the/file/name}}
20757 Failure of the lookup results in an empty string, causing the router to
20758 decline. However, you do not have to use a lookup in &%route_data%&. The only
20759 requirement is that the result of expanding the string is a list of hosts,
20760 possibly followed by options, separated by white space. The list of hosts must
20761 be enclosed in quotes if it contains white space.
20766 .section "Format of the list of hosts" "SECID122"
20767 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
20768 always separately expanded before use. If the expansion fails, the router
20769 declines. The result of the expansion must be a colon-separated list of names
20770 and/or IP addresses, optionally also including ports.
20771 If the list is written with spaces, it must be protected with quotes.
20772 The format of each item
20773 in the list is described in the next section. The list separator can be changed
20774 as described in section &<<SECTlistsepchange>>&.
20776 If the list of hosts was obtained from a &%route_list%& item, the following
20777 variables are set during its expansion:
20780 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
20781 If the domain was matched against a regular expression, the numeric variables
20782 &$1$&, &$2$&, etc. may be set. For example:
20784 route_list = ^domain(\d+) host-$1.text.example
20787 &$0$& is always set to the entire domain.
20789 &$1$& is also set when partial matching is done in a file lookup.
20792 .vindex "&$value$&"
20793 If the pattern that matched the domain was a lookup item, the data that was
20794 looked up is available in the expansion variable &$value$&. For example:
20796 route_list = lsearch;;/some/file.routes $value
20800 Note the doubling of the semicolon in the pattern that is necessary because
20801 semicolon is the default route list separator.
20805 .section "Format of one host item" "SECTformatonehostitem"
20806 Each item in the list of hosts can be either a host name or an IP address,
20807 optionally with an attached port number, or it can be a single "+"
20808 (see &%hosts_randomize%&).
20809 When no port is given, an IP address
20810 is not enclosed in brackets. When a port is specified, it overrides the port
20811 specification on the transport. The port is separated from the name or address
20812 by a colon. This leads to some complications:
20815 Because colon is the default separator for the list of hosts, either
20816 the colon that specifies a port must be doubled, or the list separator must
20817 be changed. The following two examples have the same effect:
20819 route_list = * "host1.tld::1225 : host2.tld::1226"
20820 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
20823 When IPv6 addresses are involved, it gets worse, because they contain
20824 colons of their own. To make this case easier, it is permitted to
20825 enclose an IP address (either v4 or v6) in square brackets if a port
20826 number follows. For example:
20828 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
20832 .section "How the list of hosts is used" "SECThostshowused"
20833 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
20834 the hosts is tried, in the order specified, when carrying out the SMTP
20835 delivery. However, the order can be changed by setting the &%hosts_randomize%&
20836 option, either on the router (see section &<<SECTprioptman>>& above), or on the
20839 Hosts may be listed by name or by IP address. An unadorned name in the list of
20840 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
20841 interpreted as an indirection to a sublist of hosts obtained by looking up MX
20842 records in the DNS. For example:
20844 route_list = * x.y.z:p.q.r/MX:e.f.g
20846 If this feature is used with a port specifier, the port must come last. For
20849 route_list = * dom1.tld/mx::1225
20851 If the &%hosts_randomize%& option is set, the order of the items in the list is
20852 randomized before any lookups are done. Exim then scans the list; for any name
20853 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
20854 be an interface on the local host and the item is not the first in the list,
20855 Exim discards it and any subsequent items. If it is the first item, what
20856 happens is controlled by the
20857 .oindex "&%self%&" "in &(manualroute)& router"
20858 &%self%& option of the router.
20860 A name on the list that is followed by &`/MX`& is replaced with the list of
20861 hosts obtained by looking up MX records for the name. This is always a DNS
20862 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
20863 below) are not relevant here. The order of these hosts is determined by the
20864 preference values in the MX records, according to the usual rules. Because
20865 randomizing happens before the MX lookup, it does not affect the order that is
20866 defined by MX preferences.
20868 If the local host is present in the sublist obtained from MX records, but is
20869 not the most preferred host in that list, it and any equally or less
20870 preferred hosts are removed before the sublist is inserted into the main list.
20872 If the local host is the most preferred host in the MX list, what happens
20873 depends on where in the original list of hosts the &`/MX`& item appears. If it
20874 is not the first item (that is, there are previous hosts in the main list),
20875 Exim discards this name and any subsequent items in the main list.
20877 If the MX item is first in the list of hosts, and the local host is the
20878 most preferred host, what happens is controlled by the &%self%& option of the
20881 DNS failures when lookup up the MX records are treated in the same way as DNS
20882 failures when looking up IP addresses: &%pass_on_timeout%& and
20883 &%host_find_failed%& are used when relevant.
20885 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
20886 whether obtained from an MX lookup or not.
20890 .section "How the options are used" "SECThowoptused"
20891 The options are a sequence of words, space-separated.
20892 One of the words can be the name of a transport; this overrides the
20893 &%transport%& option on the router for this particular routing rule only. The
20894 other words (if present) control randomization of the list of hosts on a
20895 per-rule basis, and how the IP addresses of the hosts are to be found when
20896 routing to a remote transport. These options are as follows:
20899 &%randomize%&: randomize the order of the hosts in this list, overriding the
20900 setting of &%hosts_randomize%& for this routing rule only.
20902 &%no_randomize%&: do not randomize the order of the hosts in this list,
20903 overriding the setting of &%hosts_randomize%& for this routing rule only.
20905 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
20906 find IP addresses. This function may ultimately cause a DNS lookup, but it may
20907 also look in &_/etc/hosts_& or other sources of information.
20909 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
20910 no address records are found. If there is a temporary DNS error (such as a
20911 timeout), delivery is deferred.
20913 &%ipv4_only%&: in direct DNS lookups, look up only A records.
20915 &%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
20920 route_list = domain1 host1:host2:host3 randomize bydns;\
20921 domain2 host4:host5
20923 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
20924 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
20925 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
20926 or &[gethostbyname()]&, and the result of the lookup is the result of that
20929 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
20930 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
20931 instead of TRY_AGAIN. That is why the default action is to try a DNS
20932 lookup first. Only if that gives a definite &"no such host"& is the local
20935 &*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
20936 inadvertent constraint that a transport name as an option had to be the last
20941 If no IP address for a host can be found, what happens is controlled by the
20942 &%host_find_failed%& option.
20945 When an address is routed to a local transport, IP addresses are not looked up.
20946 The host list is passed to the transport in the &$host$& variable.
20950 .section "Manualroute examples" "SECID123"
20951 In some of the examples that follow, the presence of the &%remote_smtp%&
20952 transport, as defined in the default configuration file, is assumed:
20955 .cindex "smart host" "example router"
20956 The &(manualroute)& router can be used to forward all external mail to a
20957 &'smart host'&. If you have set up, in the main part of the configuration, a
20958 named domain list that contains your local domains, for example:
20960 domainlist local_domains = my.domain.example
20962 You can arrange for all other domains to be routed to a smart host by making
20963 your first router something like this:
20966 driver = manualroute
20967 domains = !+local_domains
20968 transport = remote_smtp
20969 route_list = * smarthost.ref.example
20971 This causes all non-local addresses to be sent to the single host
20972 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
20973 they are tried in order
20974 (but you can use &%hosts_randomize%& to vary the order each time).
20975 Another way of configuring the same thing is this:
20978 driver = manualroute
20979 transport = remote_smtp
20980 route_list = !+local_domains smarthost.ref.example
20982 There is no difference in behaviour between these two routers as they stand.
20983 However, they behave differently if &%no_more%& is added to them. In the first
20984 example, the router is skipped if the domain does not match the &%domains%&
20985 precondition; the following router is always tried. If the router runs, it
20986 always matches the domain and so can never decline. Therefore, &%no_more%&
20987 would have no effect. In the second case, the router is never skipped; it
20988 always runs. However, if it doesn't match the domain, it declines. In this case
20989 &%no_more%& would prevent subsequent routers from running.
20992 .cindex "mail hub example"
20993 A &'mail hub'& is a host which receives mail for a number of domains via MX
20994 records in the DNS and delivers it via its own private routing mechanism. Often
20995 the final destinations are behind a firewall, with the mail hub being the one
20996 machine that can connect to machines both inside and outside the firewall. The
20997 &(manualroute)& router is usually used on a mail hub to route incoming messages
20998 to the correct hosts. For a small number of domains, the routing can be inline,
20999 using the &%route_list%& option, but for a larger number a file or database
21000 lookup is easier to manage.
21002 If the domain names are in fact the names of the machines to which the mail is
21003 to be sent by the mail hub, the configuration can be quite simple. For
21007 driver = manualroute
21008 transport = remote_smtp
21009 route_list = *.rhodes.tvs.example $domain
21011 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
21012 whose names are the same as the mail domains. A similar approach can be taken
21013 if the host name can be obtained from the domain name by a string manipulation
21014 that the expansion facilities can handle. Otherwise, a lookup based on the
21015 domain can be used to find the host:
21018 driver = manualroute
21019 transport = remote_smtp
21020 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
21022 The result of the lookup must be the name or IP address of the host (or
21023 hosts) to which the address is to be routed. If the lookup fails, the route
21024 data is empty, causing the router to decline. The address then passes to the
21028 .cindex "batched SMTP output example"
21029 .cindex "SMTP" "batched outgoing; example"
21030 You can use &(manualroute)& to deliver messages to pipes or files in batched
21031 SMTP format for onward transportation by some other means. This is one way of
21032 storing mail for a dial-up host when it is not connected. The route list entry
21033 can be as simple as a single domain name in a configuration like this:
21036 driver = manualroute
21037 transport = batchsmtp_appendfile
21038 route_list = saved.domain.example
21040 though often a pattern is used to pick up more than one domain. If there are
21041 several domains or groups of domains with different transport requirements,
21042 different transports can be listed in the routing information:
21045 driver = manualroute
21047 *.saved.domain1.example $domain batch_appendfile; \
21048 *.saved.domain2.example \
21049 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
21052 .vindex "&$domain$&"
21054 The first of these just passes the domain in the &$host$& variable, which
21055 doesn't achieve much (since it is also in &$domain$&), but the second does a
21056 file lookup to find a value to pass, causing the router to decline to handle
21057 the address if the lookup fails.
21060 .cindex "UUCP" "example of router for"
21061 Routing mail directly to UUCP software is a specific case of the use of
21062 &(manualroute)& in a gateway to another mail environment. This is an example of
21063 one way it can be done:
21069 command = /usr/local/bin/uux -r - \
21070 ${substr_-5:$host}!rmail ${local_part}
21071 return_fail_output = true
21076 driver = manualroute
21078 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
21080 The file &_/usr/local/exim/uucphosts_& contains entries like
21082 darksite.ethereal.example: darksite.UUCP
21084 It can be set up more simply without adding and removing &".UUCP"& but this way
21085 makes clear the distinction between the domain name
21086 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
21088 .ecindex IIDmanrou1
21089 .ecindex IIDmanrou2
21098 . ////////////////////////////////////////////////////////////////////////////
21099 . ////////////////////////////////////////////////////////////////////////////
21101 .chapter "The queryprogram router" "CHAPdriverlast"
21102 .scindex IIDquerou1 "&(queryprogram)& router"
21103 .scindex IIDquerou2 "routers" "&(queryprogram)&"
21104 .cindex "routing" "by external program"
21105 The &(queryprogram)& router routes an address by running an external command
21106 and acting on its output. This is an expensive way to route, and is intended
21107 mainly for use in lightly-loaded systems, or for performing experiments.
21108 However, if it is possible to use the precondition options (&%domains%&,
21109 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
21110 be used in special cases, even on a busy host. There are the following private
21112 .cindex "options" "&(queryprogram)& router"
21114 .option command queryprogram string&!! unset
21115 This option must be set. It specifies the command that is to be run. The
21116 command is split up into a command name and arguments, and then each is
21117 expanded separately (exactly as for a &(pipe)& transport, described in chapter
21118 &<<CHAPpipetransport>>&).
21121 .option command_group queryprogram string unset
21122 .cindex "gid (group id)" "in &(queryprogram)& router"
21123 This option specifies a gid to be set when running the command while routing an
21124 address for deliver. It must be set if &%command_user%& specifies a numerical
21125 uid. If it begins with a digit, it is interpreted as the numerical value of the
21126 gid. Otherwise it is looked up using &[getgrnam()]&.
21129 .option command_user queryprogram string unset
21130 .cindex "uid (user id)" "for &(queryprogram)&"
21131 This option must be set. It specifies the uid which is set when running the
21132 command while routing an address for delivery. If the value begins with a digit,
21133 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
21134 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
21135 not set, a value for the gid also.
21137 &*Warning:*& Changing uid and gid is possible only when Exim is running as
21138 root, which it does during a normal delivery in a conventional configuration.
21139 However, when an address is being verified during message reception, Exim is
21140 usually running as the Exim user, not as root. If the &(queryprogram)& router
21141 is called from a non-root process, Exim cannot change uid or gid before running
21142 the command. In this circumstance the command runs under the current uid and
21146 .option current_directory queryprogram string /
21147 This option specifies an absolute path which is made the current directory
21148 before running the command.
21151 .option timeout queryprogram time 1h
21152 If the command does not complete within the timeout period, its process group
21153 is killed and the message is frozen. A value of zero time specifies no
21157 The standard output of the command is connected to a pipe, which is read when
21158 the command terminates. It should consist of a single line of output,
21159 containing up to five fields, separated by white space. The maximum length of
21160 the line is 1023 characters. Longer lines are silently truncated. The first
21161 field is one of the following words (case-insensitive):
21164 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
21167 &'Decline'&: the router declines; pass the address to the next router, unless
21168 &%no_more%& is set.
21170 &'Fail'&: routing failed; do not pass the address to any more routers. Any
21171 subsequent text on the line is an error message. If the router is run as part
21172 of address verification during an incoming SMTP message, the message is
21173 included in the SMTP response.
21175 &'Defer'&: routing could not be completed at this time; try again later. Any
21176 subsequent text on the line is an error message which is logged. It is not
21177 included in any SMTP response.
21179 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
21181 &'Pass'&: pass the address to the next router (or the router specified by
21182 &%pass_router%&), overriding &%no_more%&.
21184 &'Redirect'&: the message is redirected. The remainder of the line is a list of
21185 new addresses, which are routed independently, starting with the first router,
21186 or the router specified by &%redirect_router%&, if set.
21189 When the first word is &'accept'&, the remainder of the line consists of a
21190 number of keyed data values, as follows (split into two lines here, to fit on
21193 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
21194 LOOKUP=byname|bydns DATA=<text>
21196 The data items can be given in any order, and all are optional. If no transport
21197 is included, the transport specified by the generic &%transport%& option is
21198 used. The list of hosts and the lookup type are needed only if the transport is
21199 an &(smtp)& transport that does not itself supply a list of hosts.
21201 The format of the list of hosts is the same as for the &(manualroute)& router.
21202 As well as host names and IP addresses with optional port numbers, as described
21203 in section &<<SECTformatonehostitem>>&, it may contain names followed by
21204 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
21205 (see section &<<SECThostshowused>>&).
21207 If the lookup type is not specified, Exim behaves as follows when trying to
21208 find an IP address for each host: First, a DNS lookup is done. If this yields
21209 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
21210 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
21211 result of the lookup is the result of that call.
21213 .vindex "&$address_data$&"
21214 If the DATA field is set, its value is placed in the &$address_data$&
21215 variable. For example, this return line
21217 accept hosts=x1.y.example:x2.y.example data="rule1"
21219 routes the address to the default transport, passing a list of two hosts. When
21220 the transport runs, the string &"rule1"& is in &$address_data$&.
21221 .ecindex IIDquerou1
21222 .ecindex IIDquerou2
21227 . ////////////////////////////////////////////////////////////////////////////
21228 . ////////////////////////////////////////////////////////////////////////////
21230 .chapter "The redirect router" "CHAPredirect"
21231 .scindex IIDredrou1 "&(redirect)& router"
21232 .scindex IIDredrou2 "routers" "&(redirect)&"
21233 .cindex "alias file" "in a &(redirect)& router"
21234 .cindex "address redirection" "&(redirect)& router"
21235 The &(redirect)& router handles several kinds of address redirection. Its most
21236 common uses are for resolving local part aliases from a central alias file
21237 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
21238 files, but it has many other potential uses. The incoming address can be
21239 redirected in several different ways:
21242 It can be replaced by one or more new addresses which are themselves routed
21245 It can be routed to be delivered to a given file or directory.
21247 It can be routed to be delivered to a specified pipe command.
21249 It can cause an automatic reply to be generated.
21251 It can be forced to fail, optionally with a custom error message.
21253 It can be temporarily deferred, optionally with a custom message.
21255 It can be discarded.
21258 The generic &%transport%& option must not be set for &(redirect)& routers.
21259 However, there are some private options which define transports for delivery to
21260 files and pipes, and for generating autoreplies. See the &%file_transport%&,
21261 &%pipe_transport%& and &%reply_transport%& descriptions below.
21263 If success DSNs have been requested
21264 .cindex "DSN" "success"
21265 .cindex "Delivery Status Notification" "success"
21266 redirection triggers one and the DSN options are not passed any further.
21270 .section "Redirection data" "SECID124"
21271 The router operates by interpreting a text string which it obtains either by
21272 expanding the contents of the &%data%& option, or by reading the entire
21273 contents of a file whose name is given in the &%file%& option. These two
21274 options are mutually exclusive. The first is commonly used for handling system
21275 aliases, in a configuration like this:
21279 data = ${lookup{$local_part}lsearch{/etc/aliases}}
21281 If the lookup fails, the expanded string in this example is empty. When the
21282 expansion of &%data%& results in an empty string, the router declines. A forced
21283 expansion failure also causes the router to decline; other expansion failures
21284 cause delivery to be deferred.
21286 A configuration using &%file%& is commonly used for handling users'
21287 &_.forward_& files, like this:
21292 file = $home/.forward
21295 If the file does not exist, or causes no action to be taken (for example, it is
21296 empty or consists only of comments), the router declines. &*Warning*&: This
21297 is not the case when the file contains syntactically valid items that happen to
21298 yield empty addresses, for example, items containing only RFC 2822 address
21301 .cindex "tainted data" "in filenames"
21302 .cindex redirect "tainted data"
21303 Tainted data may not be used for a filename.
21305 &*Warning*&: It is unwise to use &$local_part$& or &$domain$&
21306 directly for redirection,
21307 as they are provided by a potential attacker.
21308 In the examples above, &$local_part$& is used for looking up data held locally
21309 on the system, and not used directly (the second example derives &$home$& via
21310 the passsword file or database, using &$local_part$&).
21314 .section "Forward files and address verification" "SECID125"
21315 .cindex "address redirection" "while verifying"
21316 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
21317 &_.forward_& files, as in the example above. There are two reasons for this:
21320 When Exim is receiving an incoming SMTP message from a remote host, it is
21321 running under the Exim uid, not as root. Exim is unable to change uid to read
21322 the file as the user, and it may not be able to read it as the Exim user. So in
21323 practice the router may not be able to operate.
21325 However, even when the router can operate, the existence of a &_.forward_& file
21326 is unimportant when verifying an address. What should be checked is whether the
21327 local part is a valid user name or not. Cutting out the redirection processing
21328 saves some resources.
21336 .section "Interpreting redirection data" "SECID126"
21337 .cindex "Sieve filter" "specifying in redirection data"
21338 .cindex "filter" "specifying in redirection data"
21339 The contents of the data string, whether obtained from &%data%& or &%file%&,
21340 can be interpreted in two different ways:
21343 If the &%allow_filter%& option is set true, and the data begins with the text
21344 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
21345 &'filtering'& instructions in the form of an Exim or Sieve filter file,
21346 respectively. Details of the syntax and semantics of filter files are described
21347 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
21348 document is intended for use by end users.
21350 Otherwise, the data must be a comma-separated list of redirection items, as
21351 described in the next section.
21354 When a message is redirected to a file (a &"mail folder"&), the filename given
21355 in a non-filter redirection list must always be an absolute path. A filter may
21356 generate a relative path &-- how this is handled depends on the transport's
21357 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
21358 for the &(appendfile)& transport.
21362 .section "Items in a non-filter redirection list" "SECTitenonfilred"
21363 .cindex "address redirection" "non-filter list items"
21364 When the redirection data is not an Exim or Sieve filter, for example, if it
21365 comes from a conventional alias or forward file, it consists of a list of
21366 addresses, filenames, pipe commands, or certain special items (see section
21367 &<<SECTspecitredli>>& below). The special items can be individually enabled or
21368 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
21369 depending on their default values. The items in the list are separated by
21370 commas or newlines.
21371 If a comma is required in an item, the entire item must be enclosed in double
21374 Lines starting with a # character are comments, and are ignored, and # may
21375 also appear following a comma, in which case everything between the # and the
21376 next newline character is ignored.
21378 If an item is entirely enclosed in double quotes, these are removed. Otherwise
21379 double quotes are retained because some forms of mail address require their use
21380 (but never to enclose the entire address). In the following description,
21381 &"item"& refers to what remains after any surrounding double quotes have been
21384 .vindex "&$local_part$&"
21385 &*Warning*&: If you use an Exim expansion to construct a redirection address,
21386 and the expansion contains a reference to &$local_part$&, you should make use
21387 of the &%quote_local_part%& expansion operator, in case the local part contains
21388 special characters. For example, to redirect all mail for the domain
21389 &'obsolete.example'&, retaining the existing local part, you could use this
21392 data = ${quote_local_part:$local_part}@newdomain.example
21396 .section "Redirecting to a local mailbox" "SECTredlocmai"
21397 .cindex "routing" "loops in"
21398 .cindex "loop" "while routing, avoidance of"
21399 .cindex "address redirection" "to local mailbox"
21400 A redirection item may safely be the same as the address currently under
21401 consideration. This does not cause a routing loop, because a router is
21402 automatically skipped if any ancestor of the address that is being processed
21403 is the same as the current address and was processed by the current router.
21404 Such an address is therefore passed to the following routers, so it is handled
21405 as if there were no redirection. When making this loop-avoidance test, the
21406 complete local part, including any prefix or suffix, is used.
21408 .cindex "address redirection" "local part without domain"
21409 Specifying the same local part without a domain is a common usage in personal
21410 filter files when the user wants to have messages delivered to the local
21411 mailbox and also forwarded elsewhere. For example, the user whose login is
21412 &'cleo'& might have a &_.forward_& file containing this:
21414 cleo, cleopatra@egypt.example
21416 .cindex "backslash in alias file"
21417 .cindex "alias file" "backslash in"
21418 For compatibility with other MTAs, such unqualified local parts may be
21419 preceded by &"\"&, but this is not a requirement for loop prevention. However,
21420 it does make a difference if more than one domain is being handled
21423 If an item begins with &"\"& and the rest of the item parses as a valid RFC
21424 2822 address that does not include a domain, the item is qualified using the
21425 domain of the incoming address. In the absence of a leading &"\"&, unqualified
21426 addresses are qualified using the value in &%qualify_recipient%&, but you can
21427 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
21429 Care must be taken if there are alias names for local users.
21430 Consider an MTA handling a single local domain where the system alias file
21435 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
21436 messages in the local mailbox, and also forward copies elsewhere. He creates
21439 Sam.Reman, spqr@reme.elsewhere.example
21441 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
21442 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
21443 second time round, because it has previously routed it,
21444 and the following routers presumably cannot handle the alias. The forward file
21445 should really contain
21447 spqr, spqr@reme.elsewhere.example
21449 but because this is such a common error, the &%check_ancestor%& option (see
21450 below) exists to provide a way to get round it. This is normally set on a
21451 &(redirect)& router that is handling users' &_.forward_& files.
21455 .section "Special items in redirection lists" "SECTspecitredli"
21456 In addition to addresses, the following types of item may appear in redirection
21457 lists (that is, in non-filter redirection data):
21460 .cindex "pipe" "in redirection list"
21461 .cindex "address redirection" "to pipe"
21462 An item is treated as a pipe command if it begins with &"|"& and does not parse
21463 as a valid RFC 2822 address that includes a domain. A transport for running the
21464 command must be specified by the &%pipe_transport%& option.
21465 Normally, either the router or the transport specifies a user and a group under
21466 which to run the delivery. The default is to use the Exim user and group.
21468 Single or double quotes can be used for enclosing the individual arguments of
21469 the pipe command; no interpretation of escapes is done for single quotes. If
21470 the command contains a comma character, it is necessary to put the whole item
21471 in double quotes, for example:
21473 "|/some/command ready,steady,go"
21475 since items in redirection lists are terminated by commas. Do not, however,
21476 quote just the command. An item such as
21478 |"/some/command ready,steady,go"
21480 is interpreted as a pipe with a rather strange command name, and no arguments.
21482 Note that the above example assumes that the text comes from a lookup source
21483 of some sort, so that the quotes are part of the data. If composing a
21484 redirect router with a &%data%& option directly specifying this command, the
21485 quotes will be used by the configuration parser to define the extent of one
21486 string, but will not be passed down into the redirect router itself. There
21487 are two main approaches to get around this: escape quotes to be part of the
21488 data itself, or avoid using this mechanism and instead create a custom
21489 transport with the &%command%& option set and reference that transport from
21490 an &%accept%& router.
21493 .cindex "file" "in redirection list"
21494 .cindex "address redirection" "to file"
21495 An item is interpreted as a path name if it begins with &"/"& and does not
21496 parse as a valid RFC 2822 address that includes a domain. For example,
21498 /home/world/minbari
21500 is treated as a filename, but
21502 /s=molari/o=babylon/@x400gate.way
21504 is treated as an address. For a filename, a transport must be specified using
21505 the &%file_transport%& option. However, if the generated path name ends with a
21506 forward slash character, it is interpreted as a directory name rather than a
21507 filename, and &%directory_transport%& is used instead.
21509 Normally, either the router or the transport specifies a user and a group under
21510 which to run the delivery. The default is to use the Exim user and group.
21512 .cindex "&_/dev/null_&"
21513 However, if a redirection item is the path &_/dev/null_&, delivery to it is
21514 bypassed at a high level, and the log entry shows &"**bypassed**"&
21515 instead of a transport name. In this case the user and group are not used.
21518 .cindex "included address list"
21519 .cindex "address redirection" "included external list"
21520 If an item is of the form
21522 :include:<path name>
21524 a list of further items is taken from the given file and included at that
21525 point. &*Note*&: Such a file can not be a filter file; it is just an
21526 out-of-line addition to the list. The items in the included list are separated
21527 by commas or newlines and are not subject to expansion. If this is the first
21528 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
21529 the alias name. This example is incorrect:
21531 list1 :include:/opt/lists/list1
21533 It must be given as
21535 list1: :include:/opt/lists/list1
21537 .cindex "tainted data" "in filenames"
21538 .cindex redirect "tainted data"
21539 Tainted data may not be used for a filename.
21541 .cindex "address redirection" "to black hole"
21542 .cindex "delivery" "discard"
21543 .cindex "delivery" "blackhole"
21544 .cindex "black hole"
21545 .cindex "abandoning mail"
21546 Sometimes you want to throw away mail to a particular local part. Making the
21547 &%data%& option expand to an empty string does not work, because that causes
21548 the router to decline. Instead, the alias item
21552 can be used. It does what its name implies. No delivery is
21553 done, and no error message is generated. This has the same effect as specifying
21554 &_/dev/null_& as a destination, but it can be independently disabled.
21556 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
21557 delivery is done for the original local part, even if other redirection items
21558 are present. If you are generating a multi-item list (for example, by reading a
21559 database) and need the ability to provide a no-op item, you must use
21563 .cindex "delivery" "forcing failure"
21564 .cindex "delivery" "forcing deferral"
21565 .cindex "failing delivery" "forcing"
21566 .cindex "deferred delivery, forcing"
21567 .cindex "customizing" "failure message"
21568 An attempt to deliver a particular address can be deferred or forced to fail by
21569 redirection items of the form
21574 respectively. When a redirection list contains such an item, it applies
21575 to the entire redirection; any other items in the list are ignored. Any
21576 text following &':fail:'& or &':defer:'& is placed in the error text
21577 associated with the failure. For example, an alias file might contain:
21579 X.Employee: :fail: Gone away, no forwarding address
21581 In the case of an address that is being verified from an ACL or as the subject
21583 .cindex "VRFY" "error text, display of"
21584 VRFY command, the text is included in the SMTP error response by
21586 .cindex "EXPN" "error text, display of"
21587 The text is not included in the response to an EXPN command. In non-SMTP cases
21588 the text is included in the error message that Exim generates.
21590 .cindex "SMTP" "error codes"
21591 By default for verify, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
21592 &':fail:'&. However, if the message starts with three digits followed by a
21593 space, optionally followed by an extended code of the form &'n.n.n'&, also
21594 followed by a space, and the very first digit is the same as the default error
21595 code, the code from the message is used instead. If the very first digit is
21596 incorrect, a panic error is logged, and the default code is used. You can
21597 suppress the use of the supplied code in a redirect router by setting the
21598 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
21601 .vindex "&$acl_verify_message$&"
21602 In an ACL, an explicitly provided message overrides the default, but the
21603 default message is available in the variable &$acl_verify_message$& and can
21604 therefore be included in a custom message if this is desired.
21606 Normally the error text is the rest of the redirection list &-- a comma does
21607 not terminate it &-- but a newline does act as a terminator. Newlines are not
21608 normally present in alias expansions. In &(lsearch)& lookups they are removed
21609 as part of the continuation process, but they may exist in other kinds of
21610 lookup and in &':include:'& files.
21612 During routing for message delivery (as opposed to verification), a redirection
21613 containing &':fail:'& causes an immediate failure of the incoming address,
21614 whereas &':defer:'& causes the message to remain in the queue so that a
21615 subsequent delivery attempt can happen at a later time. If an address is
21616 deferred for too long, it will ultimately fail, because the normal retry
21620 .cindex "alias file" "exception to default"
21621 Sometimes it is useful to use a single-key search type with a default (see
21622 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
21623 for exceptions to the default. These can be handled by aliasing them to
21624 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
21625 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
21626 results in an empty redirection list has the same effect.
21630 .section "Duplicate addresses" "SECTdupaddr"
21631 .cindex "duplicate addresses"
21632 .cindex "address duplicate, discarding"
21633 .cindex "pipe" "duplicated"
21634 Exim removes duplicate addresses from the list to which it is delivering, so as
21635 to deliver just one copy to each address. This does not apply to deliveries
21636 routed to pipes by different immediate parent addresses, but an indirect
21637 aliasing scheme of the type
21639 pipe: |/some/command $local_part
21643 does not work with a message that is addressed to both local parts, because
21644 when the second is aliased to the intermediate local part &"pipe"& it gets
21645 discarded as being the same as a previously handled address. However, a scheme
21648 localpart1: |/some/command $local_part
21649 localpart2: |/some/command $local_part
21651 does result in two different pipe deliveries, because the immediate parents of
21652 the pipes are distinct.
21656 .section "Repeated redirection expansion" "SECID128"
21657 .cindex "repeated redirection expansion"
21658 .cindex "address redirection" "repeated for each delivery attempt"
21659 When a message cannot be delivered to all of its recipients immediately,
21660 leading to two or more delivery attempts, redirection expansion is carried out
21661 afresh each time for those addresses whose children were not all previously
21662 delivered. If redirection is being used as a mailing list, this can lead to new
21663 members of the list receiving copies of old messages. The &%one_time%& option
21664 can be used to avoid this.
21667 .section "Errors in redirection lists" "SECID129"
21668 .cindex "address redirection" "errors"
21669 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
21670 error is skipped, and an entry is written to the main log. This may be useful
21671 for mailing lists that are automatically managed. Otherwise, if an error is
21672 detected while generating the list of new addresses, the original address is
21673 deferred. See also &%syntax_errors_to%&.
21677 .section "Private options for the redirect router" "SECID130"
21679 .cindex "options" "&(redirect)& router"
21680 The private options for the &(redirect)& router are as follows:
21683 .option allow_defer redirect boolean false
21684 Setting this option allows the use of &':defer:'& in non-filter redirection
21685 data, or the &%defer%& command in an Exim filter file.
21688 .option allow_fail redirect boolean false
21689 .cindex "failing delivery" "from filter"
21690 If this option is true, the &':fail:'& item can be used in a redirection list,
21691 and the &%fail%& command may be used in an Exim filter file.
21694 .option allow_filter redirect boolean false
21695 .cindex "filter" "enabling use of"
21696 .cindex "Sieve filter" "enabling use of"
21697 Setting this option allows Exim to interpret redirection data that starts with
21698 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
21699 are some features of Exim filter files that some administrators may wish to
21700 lock out; see the &%forbid_filter_%&&'xxx'& options below.
21702 It is also possible to lock out Exim filters or Sieve filters while allowing
21703 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
21706 The filter is run using the uid and gid set by the generic &%user%& and
21707 &%group%& options. These take their defaults from the password data if
21708 &%check_local_user%& is set, so in the normal case of users' personal filter
21709 files, the filter is run as the relevant user. When &%allow_filter%& is set
21710 true, Exim insists that either &%check_local_user%& or &%user%& is set.
21714 .option allow_freeze redirect boolean false
21715 .cindex "freezing messages" "allowing in filter"
21716 Setting this option allows the use of the &%freeze%& command in an Exim filter.
21717 This command is more normally encountered in system filters, and is disabled by
21718 default for redirection filters because it isn't something you usually want to
21719 let ordinary users do.
21723 .option check_ancestor redirect boolean false
21724 This option is concerned with handling generated addresses that are the same
21725 as some address in the list of redirection ancestors of the current address.
21726 Although it is turned off by default in the code, it is set in the default
21727 configuration file for handling users' &_.forward_& files. It is recommended
21728 for this use of the &(redirect)& router.
21730 When &%check_ancestor%& is set, if a generated address (including the domain)
21731 is the same as any ancestor of the current address, it is replaced by a copy of
21732 the current address. This helps in the case where local part A is aliased to B,
21733 and B has a &_.forward_& file pointing back to A. For example, within a single
21734 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
21735 &_&~jb/.forward_& contains:
21737 \Joe.Bloggs, <other item(s)>
21739 Without the &%check_ancestor%& setting, either local part (&"jb"& or
21740 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
21741 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
21742 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
21743 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
21744 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
21745 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
21746 original address. See also the &%repeat_use%& option below.
21749 .option check_group redirect boolean "see below"
21750 When the &%file%& option is used, the group owner of the file is checked only
21751 when this option is set. The permitted groups are those listed in the
21752 &%owngroups%& option, together with the user's default group if
21753 &%check_local_user%& is set. If the file has the wrong group, routing is
21754 deferred. The default setting for this option is true if &%check_local_user%&
21755 is set and the &%modemask%& option permits the group write bit, or if the
21756 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
21760 .option check_owner redirect boolean "see below"
21761 When the &%file%& option is used, the owner of the file is checked only when
21762 this option is set. If &%check_local_user%& is set, the local user is
21763 permitted; otherwise the owner must be one of those listed in the &%owners%&
21764 option. The default value for this option is true if &%check_local_user%& or
21765 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
21768 .option data redirect string&!! unset
21769 This option is mutually exclusive with &%file%&. One or other of them must be
21770 set, but not both. The contents of &%data%& are expanded, and then used as the
21771 list of forwarding items, or as a set of filtering instructions. If the
21772 expansion is forced to fail, or the result is an empty string or a string that
21773 has no effect (consists entirely of comments), the router declines.
21775 When filtering instructions are used, the string must begin with &"#Exim
21776 filter"&, and all comments in the string, including this initial one, must be
21777 terminated with newline characters. For example:
21779 data = #Exim filter\n\
21780 if $h_to: contains Exim then save $home/mail/exim endif
21782 If you are reading the data from a database where newlines cannot be included,
21783 you can use the &${sg}$& expansion item to turn the escape string of your
21784 choice into a newline.
21787 .option directory_transport redirect string&!! unset
21788 A &(redirect)& router sets up a direct delivery to a directory when a path name
21789 ending with a slash is specified as a new &"address"&. The transport used is
21790 specified by this option, which, after expansion, must be the name of a
21791 configured transport. This should normally be an &(appendfile)& transport.
21794 .option file redirect string&!! unset
21795 This option specifies the name of a file that contains the redirection data. It
21796 is mutually exclusive with the &%data%& option. The string is expanded before
21797 use; if the expansion is forced to fail, the router declines. Other expansion
21798 failures cause delivery to be deferred. The result of a successful expansion
21799 must be an absolute path. The entire file is read and used as the redirection
21800 data. If the data is an empty string or a string that has no effect (consists
21801 entirely of comments), the router declines.
21803 .cindex "NFS" "checking for file existence"
21804 If the attempt to open the file fails with a &"does not exist"& error, Exim
21805 runs a check on the containing directory,
21806 unless &%ignore_enotdir%& is true (see below).
21807 If the directory does not appear to exist, delivery is deferred. This can
21808 happen when users' &_.forward_& files are in NFS-mounted directories, and there
21809 is a mount problem. If the containing directory does exist, but the file does
21810 not, the router declines.
21813 .option file_transport redirect string&!! unset
21814 .vindex "&$address_file$&"
21815 A &(redirect)& router sets up a direct delivery to a file when a path name not
21816 ending in a slash is specified as a new &"address"&. The transport used is
21817 specified by this option, which, after expansion, must be the name of a
21818 configured transport. This should normally be an &(appendfile)& transport. When
21819 it is running, the filename is in &$address_file$&.
21822 .option filter_prepend_home redirect boolean true
21823 When this option is true, if a &(save)& command in an Exim filter specifies a
21824 relative path, and &$home$& is defined, it is automatically prepended to the
21825 relative path. If this option is set false, this action does not happen. The
21826 relative path is then passed to the transport unmodified.
21829 .option forbid_blackhole redirect boolean false
21830 .cindex "restricting access to features"
21831 .cindex "filter" "locking out certain features"
21832 If this option is true, the &':blackhole:'& item may not appear in a
21836 .option forbid_exim_filter redirect boolean false
21837 .cindex "restricting access to features"
21838 .cindex "filter" "locking out certain features"
21839 If this option is set true, only Sieve filters are permitted when
21840 &%allow_filter%& is true.
21845 .option forbid_file redirect boolean false
21846 .cindex "restricting access to features"
21847 .cindex "delivery" "to file; forbidding"
21848 .cindex "filter" "locking out certain features"
21849 .cindex "Sieve filter" "forbidding delivery to a file"
21850 .cindex "Sieve filter" "&""keep""& facility; disabling"
21851 If this option is true, this router may not generate a new address that
21852 specifies delivery to a local file or directory, either from a filter or from a
21853 conventional forward file. This option is forced to be true if &%one_time%& is
21854 set. It applies to Sieve filters as well as to Exim filters, but if true, it
21855 locks out the Sieve's &"keep"& facility.
21858 .option forbid_filter_dlfunc redirect boolean false
21859 .cindex "restricting access to features"
21860 .cindex "filter" "locking out certain features"
21861 If this option is true, string expansions in Exim filters are not allowed to
21862 make use of the &%dlfunc%& expansion facility to run dynamically loaded
21865 .option forbid_filter_existstest redirect boolean false
21866 .cindex "restricting access to features"
21867 .cindex "filter" "locking out certain features"
21868 .cindex "expansion" "statting a file"
21869 If this option is true, string expansions in Exim filters are not allowed to
21870 make use of the &%exists%& condition or the &%stat%& expansion item.
21872 .option forbid_filter_logwrite redirect boolean false
21873 .cindex "restricting access to features"
21874 .cindex "filter" "locking out certain features"
21875 If this option is true, use of the logging facility in Exim filters is not
21876 permitted. Logging is in any case available only if the filter is being run
21877 under some unprivileged uid (which is normally the case for ordinary users'
21878 &_.forward_& files).
21881 .option forbid_filter_lookup redirect boolean false
21882 .cindex "restricting access to features"
21883 .cindex "filter" "locking out certain features"
21884 If this option is true, string expansions in Exim filter files are not allowed
21885 to make use of &%lookup%& items.
21888 .option forbid_filter_perl redirect boolean false
21889 .cindex "restricting access to features"
21890 .cindex "filter" "locking out certain features"
21891 This option has an effect only if Exim is built with embedded Perl support. If
21892 it is true, string expansions in Exim filter files are not allowed to make use
21893 of the embedded Perl support.
21896 .option forbid_filter_readfile redirect boolean false
21897 .cindex "restricting access to features"
21898 .cindex "filter" "locking out certain features"
21899 If this option is true, string expansions in Exim filter files are not allowed
21900 to make use of &%readfile%& items.
21903 .option forbid_filter_readsocket redirect boolean false
21904 .cindex "restricting access to features"
21905 .cindex "filter" "locking out certain features"
21906 If this option is true, string expansions in Exim filter files are not allowed
21907 to make use of &%readsocket%& items.
21910 .option forbid_filter_reply redirect boolean false
21911 .cindex "restricting access to features"
21912 .cindex "filter" "locking out certain features"
21913 If this option is true, this router may not generate an automatic reply
21914 message. Automatic replies can be generated only from Exim or Sieve filter
21915 files, not from traditional forward files. This option is forced to be true if
21916 &%one_time%& is set.
21919 .option forbid_filter_run redirect boolean false
21920 .cindex "restricting access to features"
21921 .cindex "filter" "locking out certain features"
21922 If this option is true, string expansions in Exim filter files are not allowed
21923 to make use of &%run%& items.
21926 .option forbid_include redirect boolean false
21927 .cindex "restricting access to features"
21928 .cindex "filter" "locking out certain features"
21929 If this option is true, items of the form
21931 :include:<path name>
21933 are not permitted in non-filter redirection lists.
21936 .option forbid_pipe redirect boolean false
21937 .cindex "restricting access to features"
21938 .cindex "filter" "locking out certain features"
21939 .cindex "delivery" "to pipe; forbidding"
21940 If this option is true, this router may not generate a new address which
21941 specifies delivery to a pipe, either from an Exim filter or from a conventional
21942 forward file. This option is forced to be true if &%one_time%& is set.
21945 .option forbid_sieve_filter redirect boolean false
21946 .cindex "restricting access to features"
21947 .cindex "filter" "locking out certain features"
21948 If this option is set true, only Exim filters are permitted when
21949 &%allow_filter%& is true.
21952 .cindex "SMTP" "error codes"
21953 .option forbid_smtp_code redirect boolean false
21954 If this option is set true, any SMTP error codes that are present at the start
21955 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
21956 the default codes (451 and 550, respectively) are always used.
21961 .option hide_child_in_errmsg redirect boolean false
21962 .cindex "bounce message" "redirection details; suppressing"
21963 If this option is true, it prevents Exim from quoting a child address if it
21964 generates a bounce or delay message for it. Instead it says &"an address
21965 generated from <&'the top level address'&>"&. Of course, this applies only to
21966 bounces generated locally. If a message is forwarded to another host, &'its'&
21967 bounce may well quote the generated address.
21970 .option ignore_eacces redirect boolean false
21972 If this option is set and an attempt to open a redirection file yields the
21973 EACCES error (permission denied), the &(redirect)& router behaves as if the
21974 file did not exist.
21977 .option ignore_enotdir redirect boolean false
21979 If this option is set and an attempt to open a redirection file yields the
21980 ENOTDIR error (something on the path is not a directory), the &(redirect)&
21981 router behaves as if the file did not exist.
21983 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
21984 router that has the &%file%& option set discovers that the file does not exist
21985 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
21986 against unmounted NFS directories. If the parent can not be statted, delivery
21987 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
21988 is set, because that option tells Exim to ignore &"something on the path is not
21989 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
21990 that some operating systems give ENOENT where others give ENOTDIR.
21994 .option include_directory redirect string unset
21995 If this option is set, the path names of any &':include:'& items in a
21996 redirection list must start with this directory.
21999 .option modemask redirect "octal integer" 022
22000 This specifies mode bits which must not be set for a file specified by the
22001 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
22004 .option one_time redirect boolean false
22005 .cindex "one-time aliasing/forwarding expansion"
22006 .cindex "alias file" "one-time expansion"
22007 .cindex "forward file" "one-time expansion"
22008 .cindex "mailing lists" "one-time expansion"
22009 .cindex "address redirection" "one-time expansion"
22010 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
22011 files each time it tries to deliver a message causes a problem when one or more
22012 of the generated addresses fails be delivered at the first attempt. The problem
22013 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
22014 but of what happens when the redirection list changes during the time that the
22015 message is on Exim's queue. This is particularly true in the case of mailing
22016 lists, where new subscribers might receive copies of messages that were posted
22017 before they subscribed.
22019 If &%one_time%& is set and any addresses generated by the router fail to
22020 deliver at the first attempt, the failing addresses are added to the message as
22021 &"top level"& addresses, and the parent address that generated them is marked
22022 &"delivered"&. Thus, redirection does not happen again at the next delivery
22025 &*Warning 1*&: Any header line addition or removal that is specified by this
22026 router would be lost if delivery did not succeed at the first attempt. For this
22027 reason, the &%headers_add%& and &%headers_remove%& generic options are not
22028 permitted when &%one_time%& is set.
22030 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
22031 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
22032 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
22034 &*Warning 3*&: The &%unseen%& generic router option may not be set with
22037 The original top-level address is remembered with each of the generated
22038 addresses, and is output in any log messages. However, any intermediate parent
22039 addresses are not recorded. This makes a difference to the log only if
22040 &%all_parents%& log selector is set. It is expected that &%one_time%& will
22041 typically be used for mailing lists, where there is normally just one level of
22045 .option owners redirect "string list" unset
22046 .cindex "ownership" "alias file"
22047 .cindex "ownership" "forward file"
22048 .cindex "alias file" "ownership"
22049 .cindex "forward file" "ownership"
22050 This specifies a list of permitted owners for the file specified by &%file%&.
22051 This list is in addition to the local user when &%check_local_user%& is set.
22052 See &%check_owner%& above.
22055 .option owngroups redirect "string list" unset
22056 This specifies a list of permitted groups for the file specified by &%file%&.
22057 The list is in addition to the local user's primary group when
22058 &%check_local_user%& is set. See &%check_group%& above.
22061 .option pipe_transport redirect string&!! unset
22062 .vindex "&$address_pipe$&"
22063 A &(redirect)& router sets up a direct delivery to a pipe when a string
22064 starting with a vertical bar character is specified as a new &"address"&. The
22065 transport used is specified by this option, which, after expansion, must be the
22066 name of a configured transport. This should normally be a &(pipe)& transport.
22067 When the transport is run, the pipe command is in &$address_pipe$&.
22070 .option qualify_domain redirect string&!! unset
22071 .vindex "&$qualify_recipient$&"
22072 If this option is set, and an unqualified address (one without a domain) is
22073 generated, and that address would normally be qualified by the global setting
22074 in &%qualify_recipient%&, it is instead qualified with the domain specified by
22075 expanding this string. If the expansion fails, the router declines. If you want
22076 to revert to the default, you can have the expansion generate
22077 &$qualify_recipient$&.
22079 This option applies to all unqualified addresses generated by Exim filters,
22080 but for traditional &_.forward_& files, it applies only to addresses that are
22081 not preceded by a backslash. Sieve filters cannot generate unqualified
22084 .option qualify_preserve_domain redirect boolean false
22085 .cindex "domain" "in redirection; preserving"
22086 .cindex "preserving domain in redirection"
22087 .cindex "address redirection" "domain; preserving"
22088 If this option is set, the router's local &%qualify_domain%& option must not be
22089 set (a configuration error occurs if it is). If an unqualified address (one
22090 without a domain) is generated, it is qualified with the domain of the parent
22091 address (the immediately preceding ancestor) instead of the global
22092 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
22093 this applies whether or not the address is preceded by a backslash.
22096 .option repeat_use redirect boolean true
22097 If this option is set false, the router is skipped for a child address that has
22098 any ancestor that was routed by this router. This test happens before any of
22099 the other preconditions are tested. Exim's default anti-looping rules skip
22100 only when the ancestor is the same as the current address. See also
22101 &%check_ancestor%& above and the generic &%redirect_router%& option.
22104 .option reply_transport redirect string&!! unset
22105 A &(redirect)& router sets up an automatic reply when a &%mail%& or
22106 &%vacation%& command is used in a filter file. The transport used is specified
22107 by this option, which, after expansion, must be the name of a configured
22108 transport. This should normally be an &(autoreply)& transport. Other transports
22109 are unlikely to do anything sensible or useful.
22112 .option rewrite redirect boolean true
22113 .cindex "address redirection" "disabling rewriting"
22114 If this option is set false, addresses generated by the router are not
22115 subject to address rewriting. Otherwise, they are treated like new addresses
22116 and are rewritten according to the global rewriting rules.
22119 .option sieve_subaddress redirect string&!! unset
22120 The value of this option is passed to a Sieve filter to specify the
22121 :subaddress part of an address.
22123 .option sieve_useraddress redirect string&!! unset
22124 The value of this option is passed to a Sieve filter to specify the :user part
22125 of an address. However, if it is unset, the entire original local part
22126 (including any prefix or suffix) is used for :user.
22129 .option sieve_vacation_directory redirect string&!! unset
22130 .cindex "Sieve filter" "vacation directory"
22131 To enable the &"vacation"& extension for Sieve filters, you must set
22132 &%sieve_vacation_directory%& to the directory where vacation databases are held
22133 (do not put anything else in that directory), and ensure that the
22134 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
22135 needs their own directory; Exim will create it if necessary.
22139 .option skip_syntax_errors redirect boolean false
22140 .cindex "forward file" "broken"
22141 .cindex "address redirection" "broken files"
22142 .cindex "alias file" "broken"
22143 .cindex "broken alias or forward files"
22144 .cindex "ignoring faulty addresses"
22145 .cindex "skipping faulty addresses"
22146 .cindex "error" "skipping bad syntax"
22147 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
22148 non-filter redirection data are skipped, and each failing address is logged. If
22149 &%syntax_errors_to%& is set, a message is sent to the address it defines,
22150 giving details of the failures. If &%syntax_errors_text%& is set, its contents
22151 are expanded and placed at the head of the error message generated by
22152 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
22153 be the same address as the generic &%errors_to%& option. The
22154 &%skip_syntax_errors%& option is often used when handling mailing lists.
22156 If all the addresses in a redirection list are skipped because of syntax
22157 errors, the router declines to handle the original address, and it is passed to
22158 the following routers.
22160 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
22161 error in the filter causes filtering to be abandoned without any action being
22162 taken. The incident is logged, and the router declines to handle the address,
22163 so it is passed to the following routers.
22165 .cindex "Sieve filter" "syntax errors in"
22166 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
22167 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
22168 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
22170 &%skip_syntax_errors%& can be used to specify that errors in users' forward
22171 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
22172 option, used with an address that does not get redirected, can be used to
22173 notify users of these errors, by means of a router like this:
22179 file = $home/.forward
22180 file_transport = address_file
22181 pipe_transport = address_pipe
22182 reply_transport = address_reply
22185 syntax_errors_to = real-$local_part@$domain
22186 syntax_errors_text = \
22187 This is an automatically generated message. An error has\n\
22188 been found in your .forward file. Details of the error are\n\
22189 reported below. While this error persists, you will receive\n\
22190 a copy of this message for every message that is addressed\n\
22191 to you. If your .forward file is a filter file, or if it is\n\
22192 a non-filter file containing no valid forwarding addresses,\n\
22193 a copy of each incoming message will be put in your normal\n\
22194 mailbox. If a non-filter file contains at least one valid\n\
22195 forwarding address, forwarding to the valid addresses will\n\
22196 happen, and those will be the only deliveries that occur.
22198 You also need a router to ensure that local addresses that are prefixed by
22199 &`real-`& are recognized, but not forwarded or filtered. For example, you could
22200 put this immediately before the &(userforward)& router:
22205 local_part_prefix = real-
22206 transport = local_delivery
22208 For security, it would probably be a good idea to restrict the use of this
22209 router to locally-generated messages, using a condition such as this:
22211 condition = ${if match {$sender_host_address}\
22212 {\N^(|127\.0\.0\.1)$\N}}
22216 .option syntax_errors_text redirect string&!! unset
22217 See &%skip_syntax_errors%& above.
22220 .option syntax_errors_to redirect string unset
22221 See &%skip_syntax_errors%& above.
22222 .ecindex IIDredrou1
22223 .ecindex IIDredrou2
22230 . ////////////////////////////////////////////////////////////////////////////
22231 . ////////////////////////////////////////////////////////////////////////////
22233 .chapter "Environment for running local transports" "CHAPenvironment" &&&
22234 "Environment for local transports"
22235 .scindex IIDenvlotra1 "local transports" "environment for"
22236 .scindex IIDenvlotra2 "environment" "local transports"
22237 .scindex IIDenvlotra3 "transport" "local; environment for"
22238 Local transports handle deliveries to files and pipes. (The &(autoreply)&
22239 transport can be thought of as similar to a pipe.) Exim always runs transports
22240 in subprocesses, under specified uids and gids. Typical deliveries to local
22241 mailboxes run under the uid and gid of the local user.
22243 Exim also sets a specific current directory while running the transport; for
22244 some transports a home directory setting is also relevant. The &(pipe)&
22245 transport is the only one that sets up environment variables; see section
22246 &<<SECTpipeenv>>& for details.
22248 The values used for the uid, gid, and the directories may come from several
22249 different places. In many cases, the router that handles the address associates
22250 settings with that address as a result of its &%check_local_user%&, &%group%&,
22251 or &%user%& options. However, values may also be given in the transport's own
22252 configuration, and these override anything that comes from the router.
22256 .section "Concurrent deliveries" "SECID131"
22257 .cindex "concurrent deliveries"
22258 .cindex "simultaneous deliveries"
22259 If two different messages for the same local recipient arrive more or less
22260 simultaneously, the two delivery processes are likely to run concurrently. When
22261 the &(appendfile)& transport is used to write to a file, Exim applies locking
22262 rules to stop concurrent processes from writing to the same file at the same
22265 However, when you use a &(pipe)& transport, it is up to you to arrange any
22266 locking that is needed. Here is a silly example:
22270 command = /bin/sh -c 'cat >>/some/file'
22272 This is supposed to write the message at the end of the file. However, if two
22273 messages arrive at the same time, the file will be scrambled. You can use the
22274 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
22275 file using the same algorithm that Exim itself uses.
22280 .section "Uids and gids" "SECTenvuidgid"
22281 .cindex "local transports" "uid and gid"
22282 .cindex "transport" "local; uid and gid"
22283 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
22284 overrides any group that the router set in the address, even if &%user%& is not
22285 set for the transport. This makes it possible, for example, to run local mail
22286 delivery under the uid of the recipient (set by the router), but in a special
22287 group (set by the transport). For example:
22290 # User/group are set by check_local_user in this router
22294 transport = group_delivery
22297 # This transport overrides the group
22299 driver = appendfile
22300 file = /var/spool/mail/$local_part_data
22303 If &%user%& is set for a transport, its value overrides what is set in the
22304 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
22305 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
22308 .oindex "&%initgroups%&"
22309 When the uid is taken from the transport's configuration, the &[initgroups()]&
22310 function is called for the groups associated with that uid if the
22311 &%initgroups%& option is set for the transport. When the uid is not specified
22312 by the transport, but is associated with the address by a router, the option
22313 for calling &[initgroups()]& is taken from the router configuration.
22315 .cindex "&(pipe)& transport" "uid for"
22316 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
22317 is set and &%user%& is not set, the uid of the process that called Exim to
22318 receive the message is used, and if &%group%& is not set, the corresponding
22319 original gid is also used.
22321 This is the detailed preference order for obtaining a gid; the first of the
22322 following that is set is used:
22325 A &%group%& setting of the transport;
22327 A &%group%& setting of the router;
22329 A gid associated with a user setting of the router, either as a result of
22330 &%check_local_user%& or an explicit non-numeric &%user%& setting;
22332 The group associated with a non-numeric &%user%& setting of the transport;
22334 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
22335 the uid is the creator's uid;
22337 The Exim gid if the Exim uid is being used as a default.
22340 If, for example, the user is specified numerically on the router and there are
22341 no group settings, no gid is available. In this situation, an error occurs.
22342 This is different for the uid, for which there always is an ultimate default.
22343 The first of the following that is set is used:
22346 A &%user%& setting of the transport;
22348 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
22350 A &%user%& setting of the router;
22352 A &%check_local_user%& setting of the router;
22357 Of course, an error will still occur if the uid that is chosen is on the
22358 &%never_users%& list.
22364 .section "Current and home directories" "SECID132"
22365 .cindex "current directory for local transport"
22366 .cindex "home directory" "for local transport"
22367 .cindex "transport" "local; home directory for"
22368 .cindex "transport" "local; current directory for"
22369 Routers may set current and home directories for local transports by means of
22370 the &%transport_current_directory%& and &%transport_home_directory%& options.
22371 However, if the transport's &%current_directory%& or &%home_directory%& options
22372 are set, they override the router's values. In detail, the home directory
22373 for a local transport is taken from the first of these values that is set:
22376 The &%home_directory%& option on the transport;
22378 The &%transport_home_directory%& option on the router;
22380 The password data if &%check_local_user%& is set on the router;
22382 The &%router_home_directory%& option on the router.
22385 The current directory is taken from the first of these values that is set:
22388 The &%current_directory%& option on the transport;
22390 The &%transport_current_directory%& option on the router.
22394 If neither the router nor the transport sets a current directory, Exim uses the
22395 value of the home directory, if it is set. Otherwise it sets the current
22396 directory to &_/_& before running a local transport.
22400 .section "Expansion variables derived from the address" "SECID133"
22401 .vindex "&$domain$&"
22402 .vindex "&$local_part$&"
22403 .vindex "&$original_domain$&"
22404 Normally a local delivery is handling a single address, and in that case the
22405 variables such as &$domain$& and &$local_part$& are set during local
22406 deliveries. However, in some circumstances more than one address may be handled
22407 at once (for example, while writing batch SMTP for onward transmission by some
22408 other means). In this case, the variables associated with the local part are
22409 never set, &$domain$& is set only if all the addresses have the same domain,
22410 and &$original_domain$& is never set.
22411 .ecindex IIDenvlotra1
22412 .ecindex IIDenvlotra2
22413 .ecindex IIDenvlotra3
22421 . ////////////////////////////////////////////////////////////////////////////
22422 . ////////////////////////////////////////////////////////////////////////////
22424 .chapter "Generic options for transports" "CHAPtransportgeneric"
22425 .scindex IIDgenoptra1 "generic options" "transport"
22426 .scindex IIDgenoptra2 "options" "generic; for transports"
22427 .scindex IIDgenoptra3 "transport" "generic options for"
22429 The name of a transport is limited to be &drivernamemax; ASCII characters long;
22430 prior to Exim 4.95 names would be silently truncated at this length, but now
22434 The following generic options apply to all transports:
22437 .option body_only transports boolean false
22438 .cindex "transport" "body only"
22439 .cindex "message" "transporting body only"
22440 .cindex "body of message" "transporting"
22441 If this option is set, the message's headers are not transported. It is
22442 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
22443 or &(pipe)& transports, the settings of &%message_prefix%& and
22444 &%message_suffix%& should be checked, because this option does not
22445 automatically suppress them.
22448 .option current_directory transports string&!! unset
22449 .cindex "transport" "current directory for"
22450 This specifies the current directory that is to be set while running the
22451 transport, overriding any value that may have been set by the router.
22452 If the expansion fails for any reason, including forced failure, an error is
22453 logged, and delivery is deferred.
22456 .option disable_logging transports boolean false
22457 If this option is set true, nothing is logged for any
22458 deliveries by the transport or for any
22459 transport errors. You should not set this option unless you really, really know
22460 what you are doing.
22463 .option debug_print transports string&!! unset
22464 .cindex "testing" "variables in drivers"
22465 If this option is set and debugging is enabled (see the &%-d%& command line
22466 option), the string is expanded and included in the debugging output when the
22468 If expansion of the string fails, the error message is written to the debugging
22469 output, and Exim carries on processing.
22470 This facility is provided to help with checking out the values of variables and
22471 so on when debugging driver configurations. For example, if a &%headers_add%&
22472 option is not working properly, &%debug_print%& could be used to output the
22473 variables it references. A newline is added to the text if it does not end with
22475 The variables &$transport_name$& and &$router_name$& contain the name of the
22476 transport and the router that called it.
22478 .option delivery_date_add transports boolean false
22479 .cindex "&'Delivery-date:'& header line"
22480 If this option is true, a &'Delivery-date:'& header is added to the message.
22481 This gives the actual time the delivery was made. As this is not a standard
22482 header, Exim has a configuration option (&%delivery_date_remove%&) which
22483 requests its removal from incoming messages, so that delivered messages can
22484 safely be resent to other recipients.
22487 .option driver transports string unset
22488 This specifies which of the available transport drivers is to be used.
22489 There is no default, and this option must be set for every transport.
22492 .option envelope_to_add transports boolean false
22493 .cindex "&'Envelope-to:'& header line"
22494 If this option is true, an &'Envelope-to:'& header is added to the message.
22495 This gives the original address(es) in the incoming envelope that caused this
22496 delivery to happen. More than one address may be present if the transport is
22497 configured to handle several addresses at once, or if more than one original
22498 address was redirected to the same final address. As this is not a standard
22499 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
22500 its removal from incoming messages, so that delivered messages can safely be
22501 resent to other recipients.
22504 &*Note:*& If used on a transport handling multiple recipients
22505 (the smtp transport unless &%rcpt_max%& is 1, the appendfile, pipe or lmtp
22506 transport if &%batch_max%& is greater than 1)
22507 then information about Bcc recipients will be leaked.
22508 Doing so is generally not advised.
22512 .option event_action transports string&!! unset
22514 This option declares a string to be expanded for Exim's events mechanism.
22515 For details see chapter &<<CHAPevents>>&.
22518 .option group transports string&!! "Exim group"
22519 .cindex "transport" "group; specifying"
22520 This option specifies a gid for running the transport process, overriding any
22521 value that the router supplies, and also overriding any value associated with
22522 &%user%& (see below).
22525 .option headers_add transports list&!! unset
22526 .cindex "header lines" "adding in transport"
22527 .cindex "transport" "header lines; adding"
22528 This option specifies a list of text headers,
22529 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22530 which are (separately) expanded and added to the header
22531 portion of a message as it is transported, as described in section
22532 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
22533 routers. If the result of the expansion is an empty string, or if the expansion
22534 is forced to fail, no action is taken. Other expansion failures are treated as
22535 errors and cause the delivery to be deferred.
22537 Unlike most options, &%headers_add%& can be specified multiple times
22538 for a transport; all listed headers are added.
22541 .option headers_only transports boolean false
22542 .cindex "transport" "header lines only"
22543 .cindex "message" "transporting headers only"
22544 .cindex "header lines" "transporting"
22545 If this option is set, the message's body is not transported. It is mutually
22546 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
22547 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
22548 checked, since this option does not automatically suppress them.
22551 .option headers_remove transports list&!! unset
22552 .cindex "header lines" "removing"
22553 .cindex "transport" "header lines; removing"
22554 This option specifies a list of text headers,
22555 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22556 to be removed from the message.
22557 However, the option has no effect when an address is just being verified.
22558 Each list item is separately expanded.
22559 If the result of the expansion is an empty string, or if the expansion
22560 is forced to fail, no action is taken. Other expansion failures are treated as
22561 errors and cause the delivery to be deferred.
22562 If an item ends in *, it will match any header with the given prefix.
22564 Matching headers are omitted from the message as it is transported, as described
22565 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
22568 Unlike most options, &%headers_remove%& can be specified multiple times
22569 for a transport; all listed headers are removed.
22571 &*Warning*&: Because of the separate expansion of the list items,
22572 items that contain a list separator must have it doubled.
22573 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
22577 .option headers_rewrite transports string unset
22578 .cindex "transport" "header lines; rewriting"
22579 .cindex "rewriting" "at transport time"
22580 This option allows addresses in header lines to be rewritten at transport time,
22581 that is, as the message is being copied to its destination. The contents of the
22582 option are a colon-separated list of rewriting rules. Each rule is in exactly
22583 the same form as one of the general rewriting rules that are applied when a
22584 message is received. These are described in chapter &<<CHAPrewrite>>&. For
22587 headers_rewrite = a@b c@d f : \
22590 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
22591 &'w@z'& in all address-bearing header lines. The rules are applied to the
22592 header lines just before they are written out at transport time, so they affect
22593 only those copies of the message that pass through the transport. However, only
22594 the message's original header lines, and any that were added by a system
22595 filter, are rewritten. If a router or transport adds header lines, they are not
22596 affected by this option. These rewriting rules are &'not'& applied to the
22597 envelope. You can change the return path using &%return_path%&, but you cannot
22598 change envelope recipients at this time.
22601 .option home_directory transports string&!! unset
22602 .cindex "transport" "home directory for"
22604 This option specifies a home directory setting for a local transport,
22605 overriding any value that may be set by the router. The home directory is
22606 placed in &$home$& while expanding the transport's private options. It is also
22607 used as the current directory if no current directory is set by the
22608 &%current_directory%& option on the transport or the
22609 &%transport_current_directory%& option on the router. If the expansion fails
22610 for any reason, including forced failure, an error is logged, and delivery is
22614 .option initgroups transports boolean false
22615 .cindex "additional groups"
22616 .cindex "groups" "additional"
22617 .cindex "transport" "group; additional"
22618 If this option is true and the uid for the delivery process is provided by the
22619 transport, the &[initgroups()]& function is called when running the transport
22620 to ensure that any additional groups associated with the uid are set up.
22623 .option max_parallel transports integer&!! unset
22624 .cindex limit "transport parallelism"
22625 .cindex transport "parallel processes"
22626 .cindex transport "concurrency limit"
22627 .cindex "delivery" "parallelism for transport"
22628 If this option is set and expands to an integer greater than zero
22629 it limits the number of concurrent runs of the transport.
22630 The control does not apply to shadow transports.
22632 .cindex "hints database" "transport concurrency control"
22633 Exim implements this control by means of a hints database in which a record is
22634 incremented whenever a transport process is being created. The record
22635 is decremented and possibly removed when the process terminates.
22636 Obviously there is scope for
22637 records to get left lying around if there is a system or program crash. To
22638 guard against this, Exim ignores any records that are more than six hours old.
22640 If you use this option, you should also arrange to delete the
22641 relevant hints database whenever your system reboots. The names of the files
22642 start with &_misc_& and they are kept in the &_spool/db_& directory. There
22643 may be one or two files, depending on the type of DBM in use. The same files
22644 are used for ETRN and smtp transport serialization.
22647 .option message_size_limit transports string&!! 0
22648 .cindex "limit" "message size per transport"
22649 .cindex "size" "of message, limit"
22650 .cindex "transport" "message size; limiting"
22651 This option controls the size of messages passed through the transport. It is
22652 expanded before use; the result of the expansion must be a sequence of decimal
22653 digits, optionally followed by K or M. If the expansion fails for any reason,
22654 including forced failure, or if the result is not of the required form,
22655 delivery is deferred. If the value is greater than zero and the size of a
22656 message exceeds this limit, the address is failed. If there is any chance that
22657 the resulting bounce message could be routed to the same transport, you should
22658 ensure that &%return_size_limit%& is less than the transport's
22659 &%message_size_limit%&, as otherwise the bounce message will fail to get
22664 .option rcpt_include_affixes transports boolean false
22665 .cindex "prefix" "for local part, including in envelope"
22666 .cindex "suffix for local part" "including in envelope"
22667 .cindex "local part" "prefix"
22668 .cindex "local part" "suffix"
22669 When this option is false (the default), and an address that has had any
22670 affixes (prefixes or suffixes) removed from the local part is delivered by any
22671 form of SMTP or LMTP, the affixes are not included. For example, if a router
22674 local_part_prefix = *-
22676 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
22679 RCPT TO:<xyz@some.domain>
22681 This is also the case when an ACL-time callout is being used to verify a
22682 recipient address. However, if &%rcpt_include_affixes%& is set true, the
22683 whole local part is included in the RCPT command. This option applies to BSMTP
22684 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
22685 &(lmtp)& and &(smtp)& transports.
22688 .option retry_use_local_part transports boolean "see below"
22689 .cindex "hints database" "retry keys"
22690 When a delivery suffers a temporary failure, a retry record is created
22691 in Exim's hints database. For remote deliveries, the key for the retry record
22692 is based on the name and/or IP address of the failing remote host. For local
22693 deliveries, the key is normally the entire address, including both the local
22694 part and the domain. This is suitable for most common cases of local delivery
22695 temporary failure &-- for example, exceeding a mailbox quota should delay only
22696 deliveries to that mailbox, not to the whole domain.
22698 However, in some special cases you may want to treat a temporary local delivery
22699 as a failure associated with the domain, and not with a particular local part.
22700 (For example, if you are storing all mail for some domain in files.) You can do
22701 this by setting &%retry_use_local_part%& false.
22703 For all the local transports, its default value is true. For remote transports,
22704 the default value is false for tidiness, but changing the value has no effect
22705 on a remote transport in the current implementation.
22708 .option return_path transports string&!! unset
22709 .cindex "envelope sender"
22710 .cindex "envelope from"
22711 .cindex "transport" "return path; changing"
22712 .cindex "return path" "changing in transport"
22713 If this option is set, the string is expanded at transport time and replaces
22714 the existing return path (envelope sender) value in the copy of the message
22715 that is being delivered. An empty return path is permitted. This feature is
22716 designed for remote deliveries, where the value of this option is used in the
22717 SMTP MAIL command. If you set &%return_path%& for a local transport, the
22718 only effect is to change the address that is placed in the &'Return-path:'&
22719 header line, if one is added to the message (see the next option).
22721 &*Note:*& A changed return path is not logged unless you add
22722 &%return_path_on_delivery%& to the log selector.
22724 .vindex "&$return_path$&"
22725 The expansion can refer to the existing value via &$return_path$&. This is
22726 either the message's envelope sender, or an address set by the
22727 &%errors_to%& option on a router. If the expansion is forced to fail, no
22728 replacement occurs; if it fails for another reason, delivery is deferred. This
22729 option can be used to support VERP (Variable Envelope Return Paths) &-- see
22730 section &<<SECTverp>>&.
22732 &*Note*&: If a delivery error is detected locally, including the case when a
22733 remote server rejects a message at SMTP time, the bounce message is not sent to
22734 the value of this option. It is sent to the previously set errors address.
22735 This defaults to the incoming sender address, but can be changed by setting
22736 &%errors_to%& in a router.
22740 .option return_path_add transports boolean false
22741 .chindex Return-path:
22742 If this option is true, a &'Return-path:'& header is added to the message.
22743 Although the return path is normally available in the prefix line of BSD
22744 mailboxes, this is commonly not displayed by MUAs, and so the user does not
22745 have easy access to it.
22747 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
22748 the delivery SMTP server makes the final delivery"&. This implies that this
22749 header should not be present in incoming messages. Exim has a configuration
22750 option, &%return_path_remove%&, which requests removal of this header from
22751 incoming messages, so that delivered messages can safely be resent to other
22755 .option shadow_condition transports string&!! unset
22756 See &%shadow_transport%& below.
22759 .option shadow_transport transports string unset
22760 .cindex "shadow transport"
22761 .cindex "transport" "shadow"
22762 A local transport may set the &%shadow_transport%& option to the name of
22763 another local transport. Shadow remote transports are not supported.
22765 Whenever a delivery to the main transport succeeds, and either
22766 &%shadow_condition%& is unset, or its expansion does not result in the empty
22767 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
22768 passed to the shadow transport, with the same delivery address or addresses. If
22769 expansion fails, no action is taken except that non-forced expansion failures
22770 cause a log line to be written.
22772 The result of the shadow transport is discarded and does not affect the
22773 subsequent processing of the message. Only a single level of shadowing is
22774 provided; the &%shadow_transport%& option is ignored on any transport when it
22775 is running as a shadow. Options concerned with output from pipes are also
22776 ignored. The log line for the successful delivery has an item added on the end,
22779 ST=<shadow transport name>
22781 If the shadow transport did not succeed, the error message is put in
22782 parentheses afterwards. Shadow transports can be used for a number of different
22783 purposes, including keeping more detailed log information than Exim normally
22784 provides, and implementing automatic acknowledgment policies based on message
22785 headers that some sites insist on.
22788 .option transport_filter transports string&!! unset
22789 .cindex "transport" "filter"
22790 .cindex "filter" "transport filter"
22791 This option sets up a filtering (in the Unix shell sense) process for messages
22792 at transport time. It should not be confused with mail filtering as set up by
22793 individual users or via a system filter.
22794 If unset, or expanding to an empty string, no filtering is done.
22796 When the message is about to be written out, the command specified by
22797 &%transport_filter%& is started up in a separate, parallel process, and
22798 the entire message, including the header lines, is passed to it on its standard
22799 input (this in fact is done from a third process, to avoid deadlock). The
22800 command must be specified as an absolute path.
22802 The lines of the message that are written to the transport filter are
22803 terminated by newline (&"\n"&). The message is passed to the filter before any
22804 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
22805 lines beginning with a dot, and also before any processing implied by the
22806 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
22807 &(pipe)& transports.
22809 The standard error for the filter process is set to the same destination as its
22810 standard output; this is read and written to the message's ultimate
22811 destination. The process that writes the message to the filter, the
22812 filter itself, and the original process that reads the result and delivers it
22813 are all run in parallel, like a shell pipeline.
22815 The filter can perform any transformations it likes, but of course should take
22816 care not to break RFC 2822 syntax. Exim does not check the result, except to
22817 test for a final newline when SMTP is in use. All messages transmitted over
22818 SMTP must end with a newline, so Exim supplies one if it is missing.
22820 .cindex "content scanning" "per user"
22821 A transport filter can be used to provide content-scanning on a per-user basis
22822 at delivery time if the only required effect of the scan is to modify the
22823 message. For example, a content scan could insert a new header line containing
22824 a spam score. This could be interpreted by a filter in the user's MUA. It is
22825 not possible to discard a message at this stage.
22827 .cindex "SIZE" "ESMTP extension"
22828 A problem might arise if the filter increases the size of a message that is
22829 being sent down an SMTP connection. If the receiving SMTP server has indicated
22830 support for the SIZE parameter, Exim will have sent the size of the message
22831 at the start of the SMTP session. If what is actually sent is substantially
22832 more, the server might reject the message. This can be worked round by setting
22833 the &%size_addition%& option on the &(smtp)& transport, either to allow for
22834 additions to the message, or to disable the use of SIZE altogether.
22836 .vindex "&$pipe_addresses$&"
22837 The value of the &%transport_filter%& option is the command string for starting
22838 the filter, which is run directly from Exim, not under a shell. The string is
22839 parsed by Exim in the same way as a command string for the &(pipe)& transport:
22840 Exim breaks it up into arguments and then expands each argument separately (see
22841 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
22842 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
22843 of arguments, one for each address that applies to this delivery. (This isn't
22844 an ideal name for this feature here, but as it was already implemented for the
22845 &(pipe)& transport, it seemed sensible not to change it.)
22848 .vindex "&$host_address$&"
22849 The expansion variables &$host$& and &$host_address$& are available when the
22850 transport is a remote one. They contain the name and IP address of the host to
22851 which the message is being sent. For example:
22853 transport_filter = /some/directory/transport-filter.pl \
22854 $host $host_address $sender_address $pipe_addresses
22857 Two problems arise if you want to use more complicated expansion items to
22858 generate transport filter commands, both of which due to the fact that the
22859 command is split up &'before'& expansion.
22861 If an expansion item contains white space, you must quote it, so that it is all
22862 part of the same command item. If the entire option setting is one such
22863 expansion item, you have to take care what kind of quoting you use. For
22866 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
22868 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
22869 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
22870 stripped by Exim when it read the option's value. When the value is used, if
22871 the single quotes were missing, the line would be split into two items,
22872 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
22873 Exim tried to expand the first one.
22875 Except for the special case of &$pipe_addresses$& that is mentioned above, an
22876 expansion cannot generate multiple arguments, or a command name followed by
22877 arguments. Consider this example:
22879 transport_filter = ${lookup{$host}lsearch{/a/file}\
22880 {$value}{/bin/cat}}
22882 The result of the lookup is interpreted as the name of the command, even
22883 if it contains white space. The simplest way round this is to use a shell:
22885 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
22886 {$value}{/bin/cat}}
22890 The filter process is run under the same uid and gid as the normal delivery.
22891 For remote deliveries this is the Exim uid/gid by default. The command should
22892 normally yield a zero return code. Transport filters are not supposed to fail.
22893 A non-zero code is taken to mean that the transport filter encountered some
22894 serious problem. Delivery of the message is deferred; the message remains on
22895 the queue and is tried again later. It is not possible to cause a message to be
22896 bounced from a transport filter.
22898 If a transport filter is set on an autoreply transport, the original message is
22899 passed through the filter as it is being copied into the newly generated
22900 message, which happens if the &%return_message%& option is set.
22903 .option transport_filter_timeout transports time 5m
22904 .cindex "transport" "filter, timeout"
22905 When Exim is reading the output of a transport filter, it applies a timeout
22906 that can be set by this option. Exceeding the timeout is normally treated as a
22907 temporary delivery failure. However, if a transport filter is used with a
22908 &(pipe)& transport, a timeout in the transport filter is treated in the same
22909 way as a timeout in the pipe command itself. By default, a timeout is a hard
22910 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
22911 becomes a temporary error.
22914 .option user transports string&!! "Exim user"
22915 .cindex "uid (user id)" "local delivery"
22916 .cindex "transport" "user, specifying"
22917 This option specifies the user under whose uid the delivery process is to be
22918 run, overriding any uid that may have been set by the router. If the user is
22919 given as a name, the uid is looked up from the password data, and the
22920 associated group is taken as the value of the gid to be used if the &%group%&
22923 For deliveries that use local transports, a user and group are normally
22924 specified explicitly or implicitly (for example, as a result of
22925 &%check_local_user%&) by the router or transport.
22927 .cindex "hints database" "access by remote transport"
22928 For remote transports, you should leave this option unset unless you really are
22929 sure you know what you are doing. When a remote transport is running, it needs
22930 to be able to access Exim's hints databases, because each host may have its own
22932 .ecindex IIDgenoptra1
22933 .ecindex IIDgenoptra2
22934 .ecindex IIDgenoptra3
22941 . ////////////////////////////////////////////////////////////////////////////
22942 . ////////////////////////////////////////////////////////////////////////////
22944 .chapter "Address batching in local transports" "CHAPbatching" &&&
22946 .cindex "transport" "local; address batching in"
22947 The only remote transport (&(smtp)&) is normally configured to handle more than
22948 one address at a time, so that when several addresses are routed to the same
22949 remote host, just one copy of the message is sent. Local transports, however,
22950 normally handle one address at a time. That is, a separate instance of the
22951 transport is run for each address that is routed to the transport. A separate
22952 copy of the message is delivered each time.
22954 .cindex "batched local delivery"
22955 .oindex "&%batch_max%&"
22956 .oindex "&%batch_id%&"
22957 In special cases, it may be desirable to handle several addresses at once in a
22958 local transport, for example:
22961 In an &(appendfile)& transport, when storing messages in files for later
22962 delivery by some other means, a single copy of the message with multiple
22963 recipients saves space.
22965 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
22966 a single copy saves time, and is the normal way LMTP is expected to work.
22968 In a &(pipe)& transport, when passing the message
22969 to a scanner program or
22970 to some other delivery mechanism such as UUCP, multiple recipients may be
22974 These three local transports all have the same options for controlling multiple
22975 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
22976 repeating the information for each transport, these options are described here.
22978 The &%batch_max%& option specifies the maximum number of addresses that can be
22979 delivered together in a single run of the transport. Its default value is one
22980 (no batching). When more than one address is routed to a transport that has a
22981 &%batch_max%& value greater than one, the addresses are delivered in a batch
22982 (that is, in a single run of the transport with multiple recipients), subject
22983 to certain conditions:
22986 .vindex "&$local_part$&"
22987 If any of the transport's options contain a reference to &$local_part$&, no
22988 batching is possible.
22990 .vindex "&$domain$&"
22991 If any of the transport's options contain a reference to &$domain$&, only
22992 addresses with the same domain are batched.
22994 .cindex "customizing" "batching condition"
22995 If &%batch_id%& is set, it is expanded for each address, and only those
22996 addresses with the same expanded value are batched. This allows you to specify
22997 customized batching conditions. Failure of the expansion for any reason,
22998 including forced failure, disables batching, but it does not stop the delivery
23001 Batched addresses must also have the same errors address (where to send
23002 delivery errors), the same header additions and removals, the same user and
23003 group for the transport, and if a host list is present, the first host must
23007 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
23008 both when the file or pipe command is specified in the transport, and when it
23009 is specified by a &(redirect)& router, but all the batched addresses must of
23010 course be routed to the same file or pipe command. These two transports have an
23011 option called &%use_bsmtp%&, which causes them to deliver the message in
23012 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
23013 &%check_string%& and &%escape_string%& options are forced to the values
23016 escape_string = ".."
23018 when batched SMTP is in use. A full description of the batch SMTP mechanism is
23019 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
23020 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
23022 .cindex "&'Envelope-to:'& header line"
23023 If the generic &%envelope_to_add%& option is set for a batching transport, the
23024 &'Envelope-to:'& header that is added to the message contains all the addresses
23025 that are being processed together. If you are using a batching &(appendfile)&
23026 transport without &%use_bsmtp%&, the only way to preserve the recipient
23027 addresses is to set the &%envelope_to_add%& option.
23029 .cindex "&(pipe)& transport" "with multiple addresses"
23030 .vindex "&$pipe_addresses$&"
23031 If you are using a &(pipe)& transport without BSMTP, and setting the
23032 transport's &%command%& option, you can include &$pipe_addresses$& as part of
23033 the command. This is not a true variable; it is a bit of magic that causes each
23034 of the recipient addresses to be inserted into the command as a separate
23035 argument. This provides a way of accessing all the addresses that are being
23036 delivered in the batch. &*Note:*& This is not possible for pipe commands that
23037 are specified by a &(redirect)& router.
23042 . ////////////////////////////////////////////////////////////////////////////
23043 . ////////////////////////////////////////////////////////////////////////////
23045 .chapter "The appendfile transport" "CHAPappendfile"
23046 .scindex IIDapptra1 "&(appendfile)& transport"
23047 .scindex IIDapptra2 "transports" "&(appendfile)&"
23048 .cindex "directory creation"
23049 .cindex "creating directories"
23050 The &(appendfile)& transport delivers a message by appending it to an existing
23051 file, or by creating an entirely new file in a specified directory. Single
23052 files to which messages are appended can be in the traditional Unix mailbox
23053 format, or optionally in the MBX format supported by the Pine MUA and
23054 University of Washington IMAP daemon, &'inter alia'&. When each message is
23055 being delivered as a separate file, &"maildir"& format can optionally be used
23056 to give added protection against failures that happen part-way through the
23057 delivery. A third form of separate-file delivery known as &"mailstore"& is also
23058 supported. For all file formats, Exim attempts to create as many levels of
23059 directory as necessary, provided that &%create_directory%& is set.
23061 The code for the optional formats is not included in the Exim binary by
23062 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
23063 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
23066 .cindex "quota" "system"
23067 Exim recognizes system quota errors, and generates an appropriate message. Exim
23068 also supports its own quota control within the transport, for use when the
23069 system facility is unavailable or cannot be used for some reason.
23071 If there is an error while appending to a file (for example, quota exceeded or
23072 partition filled), Exim attempts to reset the file's length and last
23073 modification time back to what they were before. If there is an error while
23074 creating an entirely new file, the new file is removed.
23076 Before appending to a file, a number of security checks are made, and the
23077 file is locked. A detailed description is given below, after the list of
23080 The &(appendfile)& transport is most commonly used for local deliveries to
23081 users' mailboxes. However, it can also be used as a pseudo-remote transport for
23082 putting messages into files for remote delivery by some means other than Exim.
23083 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
23088 .section "The file and directory options" "SECTfildiropt"
23089 The &%file%& option specifies a single file, to which the message is appended;
23090 the &%directory%& option specifies a directory, in which a new file containing
23091 the message is created. Only one of these two options can be set, and for
23092 normal deliveries to mailboxes, one of them &'must'& be set.
23094 .vindex "&$address_file$&"
23095 .vindex "&$local_part$&"
23096 However, &(appendfile)& is also used for delivering messages to files or
23097 directories whose names (or parts of names) are obtained from alias,
23098 forwarding, or filtering operations (for example, a &%save%& command in a
23099 user's Exim filter). When such a transport is running, &$local_part$& contains
23100 the local part that was aliased or forwarded, and &$address_file$& contains the
23101 name (or partial name) of the file or directory generated by the redirection
23102 operation. There are two cases:
23105 If neither &%file%& nor &%directory%& is set, the redirection operation
23106 must specify an absolute path (one that begins with &`/`&). This is the most
23107 common case when users with local accounts use filtering to sort mail into
23108 different folders. See for example, the &(address_file)& transport in the
23109 default configuration. If the path ends with a slash, it is assumed to be the
23110 name of a directory. A delivery to a directory can also be forced by setting
23111 &%maildir_format%& or &%mailstore_format%&.
23113 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
23114 used to determine the file or directory name for the delivery. Normally, the
23115 contents of &$address_file$& are used in some way in the string expansion.
23117 If the &%create_file%& option is set to a path which
23118 matches (see the option definition below for details)
23119 a file or directory name
23120 for the delivery, that name becomes de-tainted.
23122 .cindex "tainted data" "in filenames"
23123 .cindex appendfile "tainted data"
23124 Tainted data may not be used for a file or directory name.
23125 This means that, for instance, &$local_part$& cannot be used directly
23126 as a component of a path. It can however be used as the key for a lookup
23127 which returns a path (or component).
23130 .cindex "Sieve filter" "configuring &(appendfile)&"
23131 .cindex "Sieve filter" "relative mailbox path handling"
23132 As an example of the second case, consider an environment where users do not
23133 have home directories. They may be permitted to use Exim filter commands of the
23138 or Sieve filter commands of the form:
23140 require "fileinto";
23141 fileinto "folder23";
23143 In this situation, the expansion of &%file%& or &%directory%& in the transport
23144 must transform the relative path into an appropriate absolute filename. In the
23145 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
23146 is used as a result of a &"keep"& action in the filter. This example shows one
23147 way of handling this requirement:
23149 file = ${if eq{$address_file}{inbox} \
23150 {/var/mail/$local_part_data} \
23151 {${if eq{${substr_0_1:$address_file}}{/} \
23153 {$home/mail/$address_file} \
23157 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
23158 location, absolute paths are used without change, and other folders are in the
23159 &_mail_& directory within the home directory.
23161 &*Note 1*&: While processing an Exim filter, a relative path such as
23162 &_folder23_& is turned into an absolute path if a home directory is known to
23163 the router. In particular, this is the case if &%check_local_user%& is set. If
23164 you want to prevent this happening at routing time, you can set
23165 &%router_home_directory%& empty. This forces the router to pass the relative
23166 path to the transport.
23168 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
23169 the &%file%& or &%directory%& option is still used if it is set.
23174 .section "Private options for appendfile" "SECID134"
23175 .cindex "options" "&(appendfile)& transport"
23179 .option allow_fifo appendfile boolean false
23180 .cindex "fifo (named pipe)"
23181 .cindex "named pipe (fifo)"
23182 .cindex "pipe" "named (fifo)"
23183 Setting this option permits delivery to named pipes (FIFOs) as well as to
23184 regular files. If no process is reading the named pipe at delivery time, the
23185 delivery is deferred.
23188 .option allow_symlink appendfile boolean false
23189 .cindex "symbolic link" "to mailbox"
23190 .cindex "mailbox" "symbolic link"
23191 By default, &(appendfile)& will not deliver if the path name for the file is
23192 that of a symbolic link. Setting this option relaxes that constraint, but there
23193 are security issues involved in the use of symbolic links. Be sure you know
23194 what you are doing if you set this. Details of exactly what this option affects
23195 are included in the discussion which follows this list of options.
23198 .option batch_id appendfile string&!! unset
23199 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23200 However, batching is automatically disabled for &(appendfile)& deliveries that
23201 happen as a result of forwarding or aliasing or other redirection directly to a
23205 .option batch_max appendfile integer 1
23206 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23209 .option check_group appendfile boolean false
23210 When this option is set, the group owner of the file defined by the &%file%&
23211 option is checked to see that it is the same as the group under which the
23212 delivery process is running. The default setting is false because the default
23213 file mode is 0600, which means that the group is irrelevant.
23216 .option check_owner appendfile boolean true
23217 When this option is set, the owner of the file defined by the &%file%& option
23218 is checked to ensure that it is the same as the user under which the delivery
23219 process is running.
23222 .option check_string appendfile string "see below"
23223 .cindex "&""From""& line"
23224 As &(appendfile)& writes the message, the start of each line is tested for
23225 matching &%check_string%&, and if it does, the initial matching characters are
23226 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
23227 a literal string, not a regular expression, and the case of any letters it
23228 contains is significant.
23230 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
23231 are forced to &"."& and &".."& respectively, and any settings in the
23232 configuration are ignored. Otherwise, they default to &"From&~"& and
23233 &">From&~"& when the &%file%& option is set, and unset when any of the
23234 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
23236 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
23237 suitable for traditional &"BSD"& mailboxes, where a line beginning with
23238 &"From&~"& indicates the start of a new message. All four options need changing
23239 if another format is used. For example, to deliver to mailboxes in MMDF format:
23240 .cindex "MMDF format mailbox"
23241 .cindex "mailbox" "MMDF format"
23243 check_string = "\1\1\1\1\n"
23244 escape_string = "\1\1\1\1 \n"
23245 message_prefix = "\1\1\1\1\n"
23246 message_suffix = "\1\1\1\1\n"
23248 .option create_directory appendfile boolean true
23249 .cindex "directory creation"
23250 When this option is true, Exim attempts to create any missing superior
23251 directories for the file that it is about to write. A created directory's mode
23252 is given by the &%directory_mode%& option.
23254 The group ownership of a newly created directory is highly dependent on the
23255 operating system (and possibly the file system) that is being used. For
23256 example, in Solaris, if the parent directory has the setgid bit set, its group
23257 is propagated to the child; if not, the currently set group is used. However,
23258 in FreeBSD, the parent's group is always used.
23262 .option create_file appendfile string anywhere
23263 This option constrains the location of files and directories that are created
23264 by this transport. It applies to files defined by the &%file%& option and
23265 directories defined by the &%directory%& option. In the case of maildir
23266 delivery, it applies to the top level directory, not the maildir directories
23270 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
23271 &"belowhome"&, or to an absolute path.
23274 In the second and third cases, a home directory must have been
23275 set for the transport, and the file or directory being created must
23277 The "belowhome" checking additionally checks for attempts to use "../"
23278 to evade the testing.
23279 This option is not useful when an explicit filename is
23280 given for normal mailbox deliveries. It is intended for the case when filenames
23281 are generated from users' &_.forward_& files. These are usually handled
23282 by an &(appendfile)& transport called &%address_file%&. See also
23283 &%file_must_exist%&.
23286 In the fourth case,
23287 the value given for this option must be an absolute path for an
23288 existing directory.
23289 The value is used for checking instead of a home directory;
23290 checking is done in "belowhome" mode.
23292 .cindex "tainted data" "de-tainting"
23293 If "belowhome" checking is used, the file or directory path
23294 becomes de-tainted.
23298 .option directory appendfile string&!! unset
23299 This option is mutually exclusive with the &%file%& option, but one of &%file%&
23300 or &%directory%& must be set, unless the delivery is the direct result of a
23301 redirection (see section &<<SECTfildiropt>>&).
23303 When &%directory%& is set, the string is expanded, and the message is delivered
23304 into a new file or files in or below the given directory, instead of being
23305 appended to a single mailbox file. A number of different formats are provided
23306 (see &%maildir_format%& and &%mailstore_format%&), and see section
23307 &<<SECTopdir>>& for further details of this form of delivery.
23310 The result of expansion must not be tainted, unless the &%create_file%& option
23315 .option directory_file appendfile string&!! "see below"
23317 .vindex "&$inode$&"
23318 When &%directory%& is set, but neither &%maildir_format%& nor
23319 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
23320 whose name is obtained by expanding this string. The default value is:
23322 q${base62:$tod_epoch}-$inode
23324 This generates a unique name from the current time, in base 62 form, and the
23325 inode of the file. The variable &$inode$& is available only when expanding this
23329 .option directory_mode appendfile "octal integer" 0700
23330 If &(appendfile)& creates any directories as a result of the
23331 &%create_directory%& option, their mode is specified by this option.
23334 .option escape_string appendfile string "see description"
23335 See &%check_string%& above.
23338 .option file appendfile string&!! unset
23339 This option is mutually exclusive with the &%directory%& option, but one of
23340 &%file%& or &%directory%& must be set, unless the delivery is the direct result
23341 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
23342 specifies a single file, to which the message is appended. One or more of
23343 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
23347 The result of expansion must not be tainted, unless the &%create_file%& option
23351 .cindex "NFS" "lock file"
23352 .cindex "locking files"
23353 .cindex "lock files"
23354 If you are using more than one host to deliver over NFS into the same
23355 mailboxes, you should always use lock files.
23357 The string value is expanded for each delivery, and must yield an absolute
23358 path. The most common settings of this option are variations on one of these
23361 file = /var/spool/mail/$local_part_data
23362 file = /home/$local_part_data/inbox
23365 .cindex "&""sticky""& bit"
23366 In the first example, all deliveries are done into the same directory. If Exim
23367 is configured to use lock files (see &%use_lockfile%& below) it must be able to
23368 create a file in the directory, so the &"sticky"& bit must be turned on for
23369 deliveries to be possible, or alternatively the &%group%& option can be used to
23370 run the delivery under a group id which has write access to the directory.
23374 .option file_format appendfile string unset
23375 .cindex "file" "mailbox; checking existing format"
23376 This option requests the transport to check the format of an existing file
23377 before adding to it. The check consists of matching a specific string at the
23378 start of the file. The value of the option consists of an even number of
23379 colon-separated strings. The first of each pair is the test string, and the
23380 second is the name of a transport. If the transport associated with a matched
23381 string is not the current transport, control is passed over to the other
23382 transport. For example, suppose the standard &(local_delivery)& transport has
23385 file_format = "From : local_delivery :\
23386 \1\1\1\1\n : local_mmdf_delivery"
23388 Mailboxes that begin with &"From"& are still handled by this transport, but if
23389 a mailbox begins with four binary ones followed by a newline, control is passed
23390 to a transport called &%local_mmdf_delivery%&, which presumably is configured
23391 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
23392 is assumed to match the current transport. If the start of a mailbox doesn't
23393 match any string, or if the transport named for a given string is not defined,
23394 delivery is deferred.
23397 .option file_must_exist appendfile boolean false
23398 If this option is true, the file specified by the &%file%& option must exist.
23399 A temporary error occurs if it does not, causing delivery to be deferred.
23400 If this option is false, the file is created if it does not exist.
23403 .option lock_fcntl_timeout appendfile time 0s
23404 .cindex "timeout" "mailbox locking"
23405 .cindex "mailbox" "locking, blocking and non-blocking"
23406 .cindex "locking files"
23407 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
23408 when locking an open mailbox file. If the call fails, the delivery process
23409 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
23410 Non-blocking calls are used so that the file is not kept open during the wait
23411 for the lock; the reason for this is to make it as safe as possible for
23412 deliveries over NFS in the case when processes might be accessing an NFS
23413 mailbox without using a lock file. This should not be done, but
23414 misunderstandings and hence misconfigurations are not unknown.
23416 On a busy system, however, the performance of a non-blocking lock approach is
23417 not as good as using a blocking lock with a timeout. In this case, the waiting
23418 is done inside the system call, and Exim's delivery process acquires the lock
23419 and can proceed as soon as the previous lock holder releases it.
23421 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
23422 timeout, are used. There may still be some retrying: the maximum number of
23425 (lock_retries * lock_interval) / lock_fcntl_timeout
23427 rounded up to the next whole number. In other words, the total time during
23428 which &(appendfile)& is trying to get a lock is roughly the same, unless
23429 &%lock_fcntl_timeout%& is set very large.
23431 You should consider setting this option if you are getting a lot of delayed
23432 local deliveries because of errors of the form
23434 failed to lock mailbox /some/file (fcntl)
23437 .option lock_flock_timeout appendfile time 0s
23438 This timeout applies to file locking when using &[flock()]& (see
23439 &%use_flock%&); the timeout operates in a similar manner to
23440 &%lock_fcntl_timeout%&.
23443 .option lock_interval appendfile time 3s
23444 This specifies the time to wait between attempts to lock the file. See below
23445 for details of locking.
23448 .option lock_retries appendfile integer 10
23449 This specifies the maximum number of attempts to lock the file. A value of zero
23450 is treated as 1. See below for details of locking.
23453 .option lockfile_mode appendfile "octal integer" 0600
23454 This specifies the mode of the created lock file, when a lock file is being
23455 used (see &%use_lockfile%& and &%use_mbx_lock%&).
23458 .option lockfile_timeout appendfile time 30m
23459 .cindex "timeout" "mailbox locking"
23460 When a lock file is being used (see &%use_lockfile%&), if a lock file already
23461 exists and is older than this value, it is assumed to have been left behind by
23462 accident, and Exim attempts to remove it.
23465 .option mailbox_filecount appendfile string&!! unset
23466 .cindex "mailbox" "specifying size of"
23467 .cindex "size" "of mailbox"
23468 If this option is set, it is expanded, and the result is taken as the current
23469 number of files in the mailbox. It must be a decimal number, optionally
23470 followed by K or M. This provides a way of obtaining this information from an
23471 external source that maintains the data.
23474 .option mailbox_size appendfile string&!! unset
23475 .cindex "mailbox" "specifying size of"
23476 .cindex "size" "of mailbox"
23477 If this option is set, it is expanded, and the result is taken as the current
23478 size the mailbox. It must be a decimal number, optionally followed by K or M.
23479 This provides a way of obtaining this information from an external source that
23480 maintains the data. This is likely to be helpful for maildir deliveries where
23481 it is computationally expensive to compute the size of a mailbox.
23485 .option maildir_format appendfile boolean false
23486 .cindex "maildir format" "specifying"
23487 If this option is set with the &%directory%& option, the delivery is into a new
23488 file, in the &"maildir"& format that is used by other mail software. When the
23489 transport is activated directly from a &(redirect)& router (for example, the
23490 &(address_file)& transport in the default configuration), setting
23491 &%maildir_format%& causes the path received from the router to be treated as a
23492 directory, whether or not it ends with &`/`&. This option is available only if
23493 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
23494 &<<SECTmaildirdelivery>>& below for further details.
23497 .option maildir_quota_directory_regex appendfile string "See below"
23498 .cindex "maildir format" "quota; directories included in"
23499 .cindex "quota" "maildir; directories included in"
23500 This option is relevant only when &%maildir_use_size_file%& is set. It defines
23501 a regular expression for specifying directories, relative to the quota
23502 directory (see &%quota_directory%&), that should be included in the quota
23503 calculation. The default value is:
23505 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
23507 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
23508 (directories whose names begin with a dot). If you want to exclude the
23510 folder from the count (as some sites do), you need to change this setting to
23512 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
23514 This uses a negative lookahead in the regular expression to exclude the
23515 directory whose name is &_.Trash_&. When a directory is excluded from quota
23516 calculations, quota processing is bypassed for any messages that are delivered
23517 directly into that directory.
23520 .option maildir_retries appendfile integer 10
23521 This option specifies the number of times to retry when writing a file in
23522 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
23525 .option maildir_tag appendfile string&!! unset
23526 This option applies only to deliveries in maildir format, and is described in
23527 section &<<SECTmaildirdelivery>>& below.
23530 .option maildir_use_size_file appendfile&!! boolean false
23531 .cindex "maildir format" "&_maildirsize_& file"
23532 The result of string expansion for this option must be a valid boolean value.
23533 If it is true, it enables support for &_maildirsize_& files. Exim
23534 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
23535 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
23536 value is zero. See &%maildir_quota_directory_regex%& above and section
23537 &<<SECTmaildirdelivery>>& below for further details.
23539 .option maildirfolder_create_regex appendfile string unset
23540 .cindex "maildir format" "&_maildirfolder_& file"
23541 .cindex "&_maildirfolder_&, creating"
23542 The value of this option is a regular expression. If it is unset, it has no
23543 effect. Otherwise, before a maildir delivery takes place, the pattern is
23544 matched against the name of the maildir directory, that is, the directory
23545 containing the &_new_& and &_tmp_& subdirectories that will be used for the
23546 delivery. If there is a match, Exim checks for the existence of a file called
23547 &_maildirfolder_& in the directory, and creates it if it does not exist.
23548 See section &<<SECTmaildirdelivery>>& for more details.
23551 .option mailstore_format appendfile boolean false
23552 .cindex "mailstore format" "specifying"
23553 If this option is set with the &%directory%& option, the delivery is into two
23554 new files in &"mailstore"& format. The option is available only if
23555 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
23556 below for further details.
23559 .option mailstore_prefix appendfile string&!! unset
23560 This option applies only to deliveries in mailstore format, and is described in
23561 section &<<SECTopdir>>& below.
23564 .option mailstore_suffix appendfile string&!! unset
23565 This option applies only to deliveries in mailstore format, and is described in
23566 section &<<SECTopdir>>& below.
23569 .option mbx_format appendfile boolean false
23570 .cindex "locking files"
23571 .cindex "file" "locking"
23572 .cindex "file" "MBX format"
23573 .cindex "MBX format, specifying"
23574 This option is available only if Exim has been compiled with SUPPORT_MBX
23575 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
23576 the message is appended to the mailbox file in MBX format instead of
23577 traditional Unix format. This format is supported by Pine4 and its associated
23578 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
23580 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
23581 automatically changed by the use of &%mbx_format%&. They should normally be set
23582 empty when using MBX format, so this option almost always appears in this
23589 If none of the locking options are mentioned in the configuration,
23590 &%use_mbx_lock%& is assumed and the other locking options default to false. It
23591 is possible to specify the other kinds of locking with &%mbx_format%&, but
23592 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
23593 interworks with &'c-client'&, providing for shared access to the mailbox. It
23594 should not be used if any program that does not use this form of locking is
23595 going to access the mailbox, nor should it be used if the mailbox file is NFS
23596 mounted, because it works only when the mailbox is accessed from a single host.
23598 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
23599 the standard version of &'c-client'&, because as long as it has a mailbox open
23600 (this means for the whole of a Pine or IMAP session), Exim will not be able to
23601 append messages to it.
23604 .option message_prefix appendfile string&!! "see below"
23605 .cindex "&""From""& line"
23606 The string specified here is expanded and output at the start of every message.
23607 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23608 in which case it is:
23610 message_prefix = "From ${if def:return_path{$return_path}\
23611 {MAILER-DAEMON}} $tod_bsdinbox\n"
23613 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23614 &`\n`& to &`\r\n`& in &%message_prefix%&.
23616 .option message_suffix appendfile string&!! "see below"
23617 The string specified here is expanded and output at the end of every message.
23618 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23619 in which case it is a single newline character. The suffix can be suppressed by
23624 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23625 &`\n`& to &`\r\n`& in &%message_suffix%&.
23627 .option mode appendfile "octal integer" 0600
23628 If the output file is created, it is given this mode. If it already exists and
23629 has wider permissions, they are reduced to this mode. If it has narrower
23630 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
23631 if the delivery is the result of a &%save%& command in a filter file specifying
23632 a particular mode, the mode of the output file is always forced to take that
23633 value, and this option is ignored.
23636 .option mode_fail_narrower appendfile boolean true
23637 This option applies in the case when an existing mailbox file has a narrower
23638 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
23639 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
23640 continues with the delivery attempt, using the existing mode of the file.
23643 .option notify_comsat appendfile boolean false
23644 If this option is true, the &'comsat'& daemon is notified after every
23645 successful delivery to a user mailbox. This is the daemon that notifies logged
23646 on users about incoming mail.
23649 .option quota appendfile string&!! unset
23650 .cindex "quota" "imposed by Exim"
23651 This option imposes a limit on the size of the file to which Exim is appending,
23652 or to the total space used in the directory tree when the &%directory%& option
23653 is set. In the latter case, computation of the space used is expensive, because
23654 all the files in the directory (and any sub-directories) have to be
23655 individually inspected and their sizes summed. (See &%quota_size_regex%& and
23656 &%maildir_use_size_file%& for ways to avoid this in environments where users
23657 have no shell access to their mailboxes).
23659 As there is no interlock against two simultaneous deliveries into a
23660 multi-file mailbox, it is possible for the quota to be overrun in this case.
23661 For single-file mailboxes, of course, an interlock is a necessity.
23663 A file's size is taken as its &'used'& value. Because of blocking effects, this
23664 may be a lot less than the actual amount of disk space allocated to the file.
23665 If the sizes of a number of files are being added up, the rounding effect can
23666 become quite noticeable, especially on systems that have large block sizes.
23667 Nevertheless, it seems best to stick to the &'used'& figure, because this is
23668 the obvious value which users understand most easily.
23670 The value of the option is expanded, and must then be a numerical value
23671 (decimal point allowed), optionally followed by one of the letters K, M, or G,
23672 for kilobytes, megabytes, or gigabytes, optionally followed by a slash
23673 and further option modifiers. If Exim is running on a system with
23674 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
23677 The option modifier &%no_check%& can be used to force delivery even if the over
23678 quota condition is met. The quota gets updated as usual.
23680 &*Note*&: A value of zero is interpreted as &"no quota"&.
23682 The expansion happens while Exim is running as root, before it changes uid for
23683 the delivery. This means that files that are inaccessible to the end user can
23684 be used to hold quota values that are looked up in the expansion. When delivery
23685 fails because this quota is exceeded, the handling of the error is as for
23686 system quota failures.
23688 By default, Exim's quota checking mimics system quotas, and restricts the
23689 mailbox to the specified maximum size, though the value is not accurate to the
23690 last byte, owing to separator lines and additional headers that may get added
23691 during message delivery. When a mailbox is nearly full, large messages may get
23692 refused even though small ones are accepted, because the size of the current
23693 message is added to the quota when the check is made. This behaviour can be
23694 changed by setting &%quota_is_inclusive%& false. When this is done, the check
23695 for exceeding the quota does not include the current message. Thus, deliveries
23696 continue until the quota has been exceeded; thereafter, no further messages are
23697 delivered. See also &%quota_warn_threshold%&.
23700 .option quota_directory appendfile string&!! unset
23701 This option defines the directory to check for quota purposes when delivering
23702 into individual files. The default is the delivery directory, or, if a file
23703 called &_maildirfolder_& exists in a maildir directory, the parent of the
23704 delivery directory.
23707 .option quota_filecount appendfile string&!! 0
23708 This option applies when the &%directory%& option is set. It limits the total
23709 number of files in the directory (compare the inode limit in system quotas). It
23710 can only be used if &%quota%& is also set. The value is expanded; an expansion
23711 failure causes delivery to be deferred. A value of zero is interpreted as
23714 The option modifier &%no_check%& can be used to force delivery even if the over
23715 quota condition is met. The quota gets updated as usual.
23717 .option quota_is_inclusive appendfile boolean true
23718 See &%quota%& above.
23721 .option quota_size_regex appendfile string unset
23722 This option applies when one of the delivery modes that writes a separate file
23723 for each message is being used. When Exim wants to find the size of one of
23724 these files in order to test the quota, it first checks &%quota_size_regex%&.
23725 If this is set to a regular expression that matches the filename, and it
23726 captures one string, that string is interpreted as a representation of the
23727 file's size. The value of &%quota_size_regex%& is not expanded.
23729 This feature is useful only when users have no shell access to their mailboxes
23730 &-- otherwise they could defeat the quota simply by renaming the files. This
23731 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
23732 the file length to the filename. For example:
23734 maildir_tag = ,S=$message_size
23735 quota_size_regex = ,S=(\d+)
23737 An alternative to &$message_size$& is &$message_linecount$&, which contains the
23738 number of lines in the message.
23740 The regular expression should not assume that the length is at the end of the
23741 filename (even though &%maildir_tag%& puts it there) because maildir MUAs
23742 sometimes add other information onto the ends of message filenames.
23744 Section &<<SECID136>>& contains further information.
23746 This option should not be used when other message-handling software
23747 may duplicate messages by making hardlinks to the files. When that is done Exim
23748 will count the message size once for each filename, in contrast with the actual
23749 disk usage. When the option is not set, calculating total usage requires
23750 a system-call per file to get the size; the number of links is then available also
23751 as is used to adjust the effective size.
23754 .option quota_warn_message appendfile string&!! "see below"
23755 See below for the use of this option. If it is not set when
23756 &%quota_warn_threshold%& is set, it defaults to
23758 quota_warn_message = "\
23759 To: $local_part@$domain\n\
23760 Subject: Your mailbox\n\n\
23761 This message is automatically created \
23762 by mail delivery software.\n\n\
23763 The size of your mailbox has exceeded \
23764 a warning threshold that is\n\
23765 set by the system administrator.\n"
23769 .option quota_warn_threshold appendfile string&!! 0
23770 .cindex "quota" "warning threshold"
23771 .cindex "mailbox" "size warning"
23772 .cindex "size" "of mailbox"
23773 This option is expanded in the same way as &%quota%& (see above). If the
23774 resulting value is greater than zero, and delivery of the message causes the
23775 size of the file or total space in the directory tree to cross the given
23776 threshold, a warning message is sent. If &%quota%& is also set, the threshold
23777 may be specified as a percentage of it by following the value with a percent
23781 quota_warn_threshold = 75%
23783 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
23784 percent sign is ignored.
23786 The warning message itself is specified by the &%quota_warn_message%& option,
23787 and it must start with a &'To:'& header line containing the recipient(s) of the
23788 warning message. These do not necessarily have to include the recipient(s) of
23789 the original message. A &'Subject:'& line should also normally be supplied. You
23790 can include any other header lines that you want. If you do not include a
23791 &'From:'& line, the default is:
23793 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
23795 .oindex &%errors_reply_to%&
23796 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
23799 The &%quota%& option does not have to be set in order to use this option; they
23800 are independent of one another except when the threshold is specified as a
23804 .option use_bsmtp appendfile boolean false
23805 .cindex "envelope from"
23806 .cindex "envelope sender"
23807 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
23808 format, with the envelope sender and recipient(s) included as SMTP commands. If
23809 you want to include a leading HELO command with such messages, you can do
23810 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
23811 for details of batch SMTP.
23814 .option use_crlf appendfile boolean false
23815 .cindex "carriage return"
23817 This option causes lines to be terminated with the two-character CRLF sequence
23818 (carriage return, linefeed) instead of just a linefeed character. In the case
23819 of batched SMTP, the byte sequence written to the file is then an exact image
23820 of what would be sent down a real SMTP connection.
23822 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
23823 (which are used to supply the traditional &"From&~"& and blank line separators
23824 in Berkeley-style mailboxes) are written verbatim, so must contain their own
23825 carriage return characters if these are needed. In cases where these options
23826 have non-empty defaults, the values end with a single linefeed, so they must be
23827 changed to end with &`\r\n`& if &%use_crlf%& is set.
23830 .option use_fcntl_lock appendfile boolean "see below"
23831 This option controls the use of the &[fcntl()]& function to lock a file for
23832 exclusive use when a message is being appended. It is set by default unless
23833 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
23834 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
23835 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
23838 .option use_flock_lock appendfile boolean false
23839 This option is provided to support the use of &[flock()]& for file locking, for
23840 the few situations where it is needed. Most modern operating systems support
23841 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
23842 each other. Exim uses &[fcntl()]& locking by default.
23844 This option is required only if you are using an operating system where
23845 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
23846 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
23847 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
23849 .cindex "Solaris" "&[flock()]& support"
23850 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
23851 have it (and some, I think, provide a not quite right version built on top of
23852 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
23853 the ability to use it, and any attempt to do so will cause a configuration
23856 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
23857 is just being mapped onto &[fcntl()]& by the OS).
23860 .option use_lockfile appendfile boolean "see below"
23861 If this option is turned off, Exim does not attempt to create a lock file when
23862 appending to a mailbox file. In this situation, the only locking is by
23863 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
23864 sure that every MUA that is ever going to look at your users' mailboxes uses
23865 &[fcntl()]& rather than a lock file, and even then only when you are not
23866 delivering over NFS from more than one host.
23868 .cindex "NFS" "lock file"
23869 In order to append to an NFS file safely from more than one host, it is
23870 necessary to take out a lock &'before'& opening the file, and the lock file
23871 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
23874 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
23875 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
23876 except when &%mbx_format%& is set.
23879 .option use_mbx_lock appendfile boolean "see below"
23880 This option is available only if Exim has been compiled with SUPPORT_MBX
23881 set in &_Local/Makefile_&. Setting the option specifies that special MBX
23882 locking rules be used. It is set by default if &%mbx_format%& is set and none
23883 of the locking options are mentioned in the configuration. The locking rules
23884 are the same as are used by the &'c-client'& library that underlies Pine and
23885 the IMAP4 and POP daemons that come with it (see the discussion below). The
23886 rules allow for shared access to the mailbox. However, this kind of locking
23887 does not work when the mailbox is NFS mounted.
23889 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
23890 &%use_flock_lock%& to control what kind of locking is used in implementing the
23891 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
23892 without &%use_fcntl_lock%& or &%use_flock_lock%&.
23897 .section "Operational details for appending" "SECTopappend"
23898 .cindex "appending to a file"
23899 .cindex "file" "appending"
23900 Before appending to a file, the following preparations are made:
23903 If the name of the file is &_/dev/null_&, no action is taken, and a success
23907 .cindex "directory creation"
23908 If any directories on the file's path are missing, Exim creates them if the
23909 &%create_directory%& option is set. A created directory's mode is given by the
23910 &%directory_mode%& option.
23913 If &%file_format%& is set, the format of an existing file is checked. If this
23914 indicates that a different transport should be used, control is passed to that
23918 .cindex "file" "locking"
23919 .cindex "locking files"
23920 .cindex "NFS" "lock file"
23921 If &%use_lockfile%& is set, a lock file is built in a way that will work
23922 reliably over NFS, as follows:
23925 Create a &"hitching post"& file whose name is that of the lock file with the
23926 current time, primary host name, and process id added, by opening for writing
23927 as a new file. If this fails with an access error, delivery is deferred.
23929 Close the hitching post file, and hard link it to the lock filename.
23931 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
23932 Unlink the hitching post name.
23934 Otherwise, use &[stat()]& to get information about the hitching post file, and
23935 then unlink hitching post name. If the number of links is exactly two, creation
23936 of the lock file succeeded but something (for example, an NFS server crash and
23937 restart) caused this fact not to be communicated to the &[link()]& call.
23939 If creation of the lock file failed, wait for &%lock_interval%& and try again,
23940 up to &%lock_retries%& times. However, since any program that writes to a
23941 mailbox should complete its task very quickly, it is reasonable to time out old
23942 lock files that are normally the result of user agent and system crashes. If an
23943 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
23944 it before trying again.
23948 A call is made to &[lstat()]& to discover whether the main file exists, and if
23949 so, what its characteristics are. If &[lstat()]& fails for any reason other
23950 than non-existence, delivery is deferred.
23953 .cindex "symbolic link" "to mailbox"
23954 .cindex "mailbox" "symbolic link"
23955 If the file does exist and is a symbolic link, delivery is deferred, unless the
23956 &%allow_symlink%& option is set, in which case the ownership of the link is
23957 checked, and then &[stat()]& is called to find out about the real file, which
23958 is then subjected to the checks below. The check on the top-level link
23959 ownership prevents one user creating a link for another's mailbox in a sticky
23960 directory, though allowing symbolic links in this case is definitely not a good
23961 idea. If there is a chain of symbolic links, the intermediate ones are not
23965 If the file already exists but is not a regular file, or if the file's owner
23966 and group (if the group is being checked &-- see &%check_group%& above) are
23967 different from the user and group under which the delivery is running,
23968 delivery is deferred.
23971 If the file's permissions are more generous than specified, they are reduced.
23972 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
23973 is set false, in which case the delivery is tried using the existing
23977 The file's inode number is saved, and the file is then opened for appending.
23978 If this fails because the file has vanished, &(appendfile)& behaves as if it
23979 hadn't existed (see below). For any other failures, delivery is deferred.
23982 If the file is opened successfully, check that the inode number hasn't
23983 changed, that it is still a regular file, and that the owner and permissions
23984 have not changed. If anything is wrong, defer delivery and freeze the message.
23987 If the file did not exist originally, defer delivery if the &%file_must_exist%&
23988 option is set. Otherwise, check that the file is being created in a permitted
23989 directory if the &%create_file%& option is set (deferring on failure), and then
23990 open for writing as a new file, with the O_EXCL and O_CREAT options,
23991 except when dealing with a symbolic link (the &%allow_symlink%& option must be
23992 set). In this case, which can happen if the link points to a non-existent file,
23993 the file is opened for writing using O_CREAT but not O_EXCL, because
23994 that prevents link following.
23997 .cindex "loop" "while file testing"
23998 If opening fails because the file exists, obey the tests given above for
23999 existing files. However, to avoid looping in a situation where the file is
24000 being continuously created and destroyed, the exists/not-exists loop is broken
24001 after 10 repetitions, and the message is then frozen.
24004 If opening fails with any other error, defer delivery.
24007 .cindex "file" "locking"
24008 .cindex "locking files"
24009 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
24010 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
24011 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
24012 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
24013 file, and an exclusive lock on the file whose name is
24015 /tmp/.<device-number>.<inode-number>
24017 using the device and inode numbers of the open mailbox file, in accordance with
24018 the MBX locking rules. This file is created with a mode that is specified by
24019 the &%lockfile_mode%& option.
24021 If Exim fails to lock the file, there are two possible courses of action,
24022 depending on the value of the locking timeout. This is obtained from
24023 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
24025 If the timeout value is zero, the file is closed, Exim waits for
24026 &%lock_interval%&, and then goes back and re-opens the file as above and tries
24027 to lock it again. This happens up to &%lock_retries%& times, after which the
24028 delivery is deferred.
24030 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
24031 &[flock()]& are used (with the given timeout), so there has already been some
24032 waiting involved by the time locking fails. Nevertheless, Exim does not give up
24033 immediately. It retries up to
24035 (lock_retries * lock_interval) / <timeout>
24037 times (rounded up).
24040 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
24041 and/or &[flock()]& locks) and then deletes the lock file if one was created.
24044 .section "Operational details for delivery to a new file" "SECTopdir"
24045 .cindex "delivery" "to single file"
24046 .cindex "&""From""& line"
24047 When the &%directory%& option is set instead of &%file%&, each message is
24048 delivered into a newly-created file or set of files. When &(appendfile)& is
24049 activated directly from a &(redirect)& router, neither &%file%& nor
24050 &%directory%& is normally set, because the path for delivery is supplied by the
24051 router. (See for example, the &(address_file)& transport in the default
24052 configuration.) In this case, delivery is to a new file if either the path name
24053 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
24055 No locking is required while writing the message to a new file, so the various
24056 locking options of the transport are ignored. The &"From"& line that by default
24057 separates messages in a single file is not normally needed, nor is the escaping
24058 of message lines that start with &"From"&, and there is no need to ensure a
24059 newline at the end of each message. Consequently, the default values for
24060 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
24061 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
24063 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
24064 the files in the delivery directory by default. However, you can specify a
24065 different directory by setting &%quota_directory%&. Also, for maildir
24066 deliveries (see below) the &_maildirfolder_& convention is honoured.
24069 .cindex "maildir format"
24070 .cindex "mailstore format"
24071 There are three different ways in which delivery to individual files can be
24072 done, controlled by the settings of the &%maildir_format%& and
24073 &%mailstore_format%& options. Note that code to support maildir or mailstore
24074 formats is not included in the binary unless SUPPORT_MAILDIR or
24075 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
24077 .cindex "directory creation"
24078 In all three cases an attempt is made to create the directory and any necessary
24079 sub-directories if they do not exist, provided that the &%create_directory%&
24080 option is set (the default). The location of a created directory can be
24081 constrained by setting &%create_file%&. A created directory's mode is given by
24082 the &%directory_mode%& option. If creation fails, or if the
24083 &%create_directory%& option is not set when creation is required, delivery is
24088 .section "Maildir delivery" "SECTmaildirdelivery"
24089 .cindex "maildir format" "description of"
24090 If the &%maildir_format%& option is true, Exim delivers each message by writing
24091 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
24092 directory that is defined by the &%directory%& option (the &"delivery
24093 directory"&). If the delivery is successful, the file is renamed into the
24094 &_new_& subdirectory.
24096 In the filename, <&'stime'&> is the current time of day in seconds, and
24097 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
24098 Exim checks that the time-of-day clock has moved on by at least one microsecond
24099 before terminating the delivery process. This guarantees uniqueness for the
24100 filename. However, as a precaution, Exim calls &[stat()]& for the file before
24101 opening it. If any response other than ENOENT (does not exist) is given,
24102 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
24104 Before Exim carries out a maildir delivery, it ensures that subdirectories
24105 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
24106 do not exist, Exim tries to create them and any superior directories in their
24107 path, subject to the &%create_directory%& and &%create_file%& options. If the
24108 &%maildirfolder_create_regex%& option is set, and the regular expression it
24109 contains matches the delivery directory, Exim also ensures that a file called
24110 &_maildirfolder_& exists in the delivery directory. If a missing directory or
24111 &_maildirfolder_& file cannot be created, delivery is deferred.
24113 These features make it possible to use Exim to create all the necessary files
24114 and directories in a maildir mailbox, including subdirectories for maildir++
24115 folders. Consider this example:
24117 maildir_format = true
24118 directory = /var/mail/$local_part_data\
24119 ${if eq{$local_part_suffix}{}{}\
24120 {/.${substr_1:$local_part_suffix}}}
24121 maildirfolder_create_regex = /\.[^/]+$
24123 If &$local_part_suffix$& is empty (there was no suffix for the local part),
24124 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
24125 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
24126 not match this name, so Exim will not look for or create the file
24127 &_/var/mail/pimbo/maildirfolder_&, though it will create
24128 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
24130 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
24131 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
24132 does match &%maildirfolder_create_regex%&. In this case, Exim will create
24133 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
24134 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
24136 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
24137 not inadvertently match the toplevel maildir directory, because a
24138 &_maildirfolder_& file at top level would completely break quota calculations.
24140 .cindex "quota" "in maildir delivery"
24141 .cindex "maildir++"
24142 If Exim is required to check a &%quota%& setting before a maildir delivery, and
24143 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
24144 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
24145 Exim assumes the directory is a maildir++ folder directory, which is one level
24146 down from the user's top level mailbox directory. This causes it to start at
24147 the parent directory instead of the current directory when calculating the
24148 amount of space used.
24150 One problem with delivering into a multi-file mailbox is that it is
24151 computationally expensive to compute the size of the mailbox for quota
24152 checking. Various approaches have been taken to reduce the amount of work
24153 needed. The next two sections describe two of them. A third alternative is to
24154 use some external process for maintaining the size data, and use the expansion
24155 of the &%mailbox_size%& option as a way of importing it into Exim.
24160 .section "Using tags to record message sizes" "SECID135"
24161 If &%maildir_tag%& is set, the string is expanded for each delivery.
24162 When the maildir file is renamed into the &_new_& sub-directory, the
24163 tag is added to its name. However, if adding the tag takes the length of the
24164 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
24165 the tag is dropped and the maildir file is created with no tag.
24168 .vindex "&$message_size$&"
24169 Tags can be used to encode the size of files in their names; see
24170 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
24171 happens after the message has been written. The value of the &$message_size$&
24172 variable is set to the number of bytes actually written. If the expansion is
24173 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
24174 be deferred. The expanded tag may contain any printing characters except &"/"&.
24175 Non-printing characters in the string are ignored; if the resulting string is
24176 empty, it is ignored. If it starts with an alphanumeric character, a leading
24177 colon is inserted; this default has not proven to be the path that popular
24178 maildir implementations have chosen (but changing it in Exim would break
24179 backwards compatibility).
24181 For one common implementation, you might set:
24183 maildir_tag = ,S=${message_size}
24185 but you should check the documentation of the other software to be sure.
24187 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
24188 as this allows Exim to extract the size from your tag, instead of having to
24189 &[stat()]& each message file.
24192 .section "Using a maildirsize file" "SECID136"
24193 .cindex "quota" "in maildir delivery"
24194 .cindex "maildir format" "&_maildirsize_& file"
24195 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
24196 storing quota and message size information in a file called &_maildirsize_&
24197 within the toplevel maildir directory. If this file does not exist, Exim
24198 creates it, setting the quota from the &%quota%& option of the transport. If
24199 the maildir directory itself does not exist, it is created before any attempt
24200 to write a &_maildirsize_& file.
24202 The &_maildirsize_& file is used to hold information about the sizes of
24203 messages in the maildir, thus speeding up quota calculations. The quota value
24204 in the file is just a cache; if the quota is changed in the transport, the new
24205 value overrides the cached value when the next message is delivered. The cache
24206 is maintained for the benefit of other programs that access the maildir and
24207 need to know the quota.
24209 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
24210 file is maintained (with a zero quota setting), but no quota is imposed.
24212 A regular expression is available for controlling which directories in the
24213 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
24214 See the description of the &%maildir_quota_directory_regex%& option above for
24218 .section "Mailstore delivery" "SECID137"
24219 .cindex "mailstore format" "description of"
24220 If the &%mailstore_format%& option is true, each message is written as two
24221 files in the given directory. A unique base name is constructed from the
24222 message id and the current delivery process, and the files that are written use
24223 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
24224 contains the message's envelope, and the &_.msg_& file contains the message
24225 itself. The base name is placed in the variable &$mailstore_basename$&.
24227 During delivery, the envelope is first written to a file with the suffix
24228 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
24229 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
24230 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
24231 file before accessing either of them. An alternative approach is to wait for
24232 the absence of a &_.tmp_& file.
24234 The envelope file starts with any text defined by the &%mailstore_prefix%&
24235 option, expanded and terminated by a newline if there isn't one. Then follows
24236 the sender address on one line, then all the recipient addresses, one per line.
24237 There can be more than one recipient only if the &%batch_max%& option is set
24238 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
24239 appended to the file, followed by a newline if it does not end with one.
24241 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
24242 failure, it is ignored. Other expansion errors are treated as serious
24243 configuration errors, and delivery is deferred. The variable
24244 &$mailstore_basename$& is available for use during these expansions.
24247 .section "Non-special new file delivery" "SECID138"
24248 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
24249 file is created directly in the named directory. For example, when delivering
24250 messages into files in batched SMTP format for later delivery to some host (see
24251 section &<<SECTbatchSMTP>>&), a setting such as
24253 directory = /var/bsmtp/$host
24255 might be used. A message is written to a file with a temporary name, which is
24256 then renamed when the delivery is complete. The final name is obtained by
24257 expanding the contents of the &%directory_file%& option.
24258 .ecindex IIDapptra1
24259 .ecindex IIDapptra2
24266 . ////////////////////////////////////////////////////////////////////////////
24267 . ////////////////////////////////////////////////////////////////////////////
24269 .chapter "The autoreply transport" "CHID8"
24270 .scindex IIDauttra1 "transports" "&(autoreply)&"
24271 .scindex IIDauttra2 "&(autoreply)& transport"
24272 The &(autoreply)& transport is not a true transport in that it does not cause
24273 the message to be transmitted. Instead, it generates a new mail message as an
24274 automatic reply to the incoming message. &'References:'& and
24275 &'Auto-Submitted:'& header lines are included. These are constructed according
24276 to the rules in RFCs 2822 and 3834, respectively.
24278 If the router that passes the message to this transport does not have the
24279 &%unseen%& option set, the original message (for the current recipient) is not
24280 delivered anywhere. However, when the &%unseen%& option is set on the router
24281 that passes the message to this transport, routing of the address continues, so
24282 another router can set up a normal message delivery.
24285 The &(autoreply)& transport is usually run as the result of mail filtering, a
24286 &"vacation"& message being the standard example. However, it can also be run
24287 directly from a router like any other transport. To reduce the possibility of
24288 message cascades, messages created by the &(autoreply)& transport always have
24289 empty envelope sender addresses, like bounce messages.
24291 The parameters of the message to be sent can be specified in the configuration
24292 by options described below. However, these are used only when the address
24293 passed to the transport does not contain its own reply information. When the
24294 transport is run as a consequence of a
24296 or &%vacation%& command in a filter file, the parameters of the message are
24297 supplied by the filter, and passed with the address. The transport's options
24298 that define the message are then ignored (so they are not usually set in this
24299 case). The message is specified entirely by the filter or by the transport; it
24300 is never built from a mixture of options. However, the &%file_optional%&,
24301 &%mode%&, and &%return_message%& options apply in all cases.
24303 &(Autoreply)& is implemented as a local transport. When used as a result of a
24304 command in a user's filter file, &(autoreply)& normally runs under the uid and
24305 gid of the user, and with appropriate current and home directories (see chapter
24306 &<<CHAPenvironment>>&).
24308 There is a subtle difference between routing a message to a &(pipe)& transport
24309 that generates some text to be returned to the sender, and routing it to an
24310 &(autoreply)& transport. This difference is noticeable only if more than one
24311 address from the same message is so handled. In the case of a pipe, the
24312 separate outputs from the different addresses are gathered up and returned to
24313 the sender in a single message, whereas if &(autoreply)& is used, a separate
24314 message is generated for each address that is passed to it.
24316 Non-printing characters are not permitted in the header lines generated for the
24317 message that &(autoreply)& creates, with the exception of newlines that are
24318 immediately followed by white space. If any non-printing characters are found,
24319 the transport defers.
24320 Whether characters with the top bit set count as printing characters or not is
24321 controlled by the &%print_topbitchars%& global option.
24323 If any of the generic options for manipulating headers (for example,
24324 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
24325 of the original message that is included in the generated message when
24326 &%return_message%& is set. They do not apply to the generated message itself.
24328 .vindex "&$sender_address$&"
24329 If the &(autoreply)& transport receives return code 2 from Exim when it submits
24330 the message, indicating that there were no recipients, it does not treat this
24331 as an error. This means that autoreplies sent to &$sender_address$& when this
24332 is empty (because the incoming message is a bounce message) do not cause
24333 problems. They are just discarded.
24337 .section "Private options for autoreply" "SECID139"
24338 .cindex "options" "&(autoreply)& transport"
24340 .option bcc autoreply string&!! unset
24341 This specifies the addresses that are to receive &"blind carbon copies"& of the
24342 message when the message is specified by the transport.
24345 .option cc autoreply string&!! unset
24346 This specifies recipients of the message and the contents of the &'Cc:'& header
24347 when the message is specified by the transport.
24350 .option file autoreply string&!! unset
24351 The contents of the file are sent as the body of the message when the message
24352 is specified by the transport. If both &%file%& and &%text%& are set, the text
24353 string comes first.
24356 .option file_expand autoreply boolean false
24357 If this is set, the contents of the file named by the &%file%& option are
24358 subjected to string expansion as they are added to the message.
24361 .option file_optional autoreply boolean false
24362 If this option is true, no error is generated if the file named by the &%file%&
24363 option or passed with the address does not exist or cannot be read.
24366 .option from autoreply string&!! unset
24367 This specifies the contents of the &'From:'& header when the message is
24368 specified by the transport.
24371 .option headers autoreply string&!! unset
24372 This specifies additional RFC 2822 headers that are to be added to the message
24373 when the message is specified by the transport. Several can be given by using
24374 &"\n"& to separate them. There is no check on the format.
24377 .option log autoreply string&!! unset
24378 This option names a file in which a record of every message sent is logged when
24379 the message is specified by the transport.
24382 .option mode autoreply "octal integer" 0600
24383 If either the log file or the &"once"& file has to be created, this mode is
24387 .option never_mail autoreply "address list&!!" unset
24388 If any run of the transport creates a message with a recipient that matches any
24389 item in the list, that recipient is quietly discarded. If all recipients are
24390 discarded, no message is created. This applies both when the recipients are
24391 generated by a filter and when they are specified in the transport.
24395 .option once autoreply string&!! unset
24396 This option names a file or DBM database in which a record of each &'To:'&
24397 recipient is kept when the message is specified by the transport. &*Note*&:
24398 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
24400 If &%once%& is unset, or is set to an empty string, the message is always sent.
24401 By default, if &%once%& is set to a non-empty filename, the message
24402 is not sent if a potential recipient is already listed in the database.
24403 However, if the &%once_repeat%& option specifies a time greater than zero, the
24404 message is sent if that much time has elapsed since a message was last sent to
24405 this recipient. A setting of zero time for &%once_repeat%& (the default)
24406 prevents a message from being sent a second time &-- in this case, zero means
24409 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
24410 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
24411 greater than zero, it changes the way Exim implements the &%once%& option.
24412 Instead of using a DBM file to record every recipient it sends to, it uses a
24413 regular file, whose size will never get larger than the given value.
24415 In the file, Exim keeps a linear list of recipient addresses and the times at
24416 which they were sent messages. If the file is full when a new address needs to
24417 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
24418 means that a given recipient may receive multiple messages, but at
24419 unpredictable intervals that depend on the rate of turnover of addresses in the
24420 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
24423 .option once_file_size autoreply integer 0
24424 See &%once%& above.
24427 .option once_repeat autoreply time&!! 0s
24428 See &%once%& above.
24429 After expansion, the value of this option must be a valid time value.
24432 .option reply_to autoreply string&!! unset
24433 This specifies the contents of the &'Reply-To:'& header when the message is
24434 specified by the transport.
24437 .option return_message autoreply boolean false
24438 If this is set, a copy of the original message is returned with the new
24439 message, subject to the maximum size set in the &%return_size_limit%& global
24440 configuration option.
24443 .option subject autoreply string&!! unset
24444 This specifies the contents of the &'Subject:'& header when the message is
24445 specified by the transport. It is tempting to quote the original subject in
24446 automatic responses. For example:
24448 subject = Re: $h_subject:
24450 There is a danger in doing this, however. It may allow a third party to
24451 subscribe your users to an opt-in mailing list, provided that the list accepts
24452 bounce messages as subscription confirmations. Well-managed lists require a
24453 non-bounce message to confirm a subscription, so the danger is relatively
24458 .option text autoreply string&!! unset
24459 This specifies a single string to be used as the body of the message when the
24460 message is specified by the transport. If both &%text%& and &%file%& are set,
24461 the text comes first.
24464 .option to autoreply string&!! unset
24465 This specifies recipients of the message and the contents of the &'To:'& header
24466 when the message is specified by the transport.
24467 .ecindex IIDauttra1
24468 .ecindex IIDauttra2
24473 . ////////////////////////////////////////////////////////////////////////////
24474 . ////////////////////////////////////////////////////////////////////////////
24476 .chapter "The lmtp transport" "CHAPLMTP"
24477 .cindex "transports" "&(lmtp)&"
24478 .cindex "&(lmtp)& transport"
24479 .cindex "LMTP" "over a pipe"
24480 .cindex "LMTP" "over a socket"
24481 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
24483 or by interacting with a Unix domain socket.
24484 This transport is something of a cross between the &(pipe)& and &(smtp)&
24485 transports. Exim also has support for using LMTP over TCP/IP; this is
24486 implemented as an option for the &(smtp)& transport. Because LMTP is expected
24487 to be of minority interest, the default build-time configure in &_src/EDITME_&
24488 has it commented out. You need to ensure that
24492 .cindex "options" "&(lmtp)& transport"
24493 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
24494 included in the Exim binary. The private options of the &(lmtp)& transport are
24497 .option batch_id lmtp string&!! unset
24498 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24501 .option batch_max lmtp integer 1
24502 This limits the number of addresses that can be handled in a single delivery.
24503 Most LMTP servers can handle several addresses at once, so it is normally a
24504 good idea to increase this value. See the description of local delivery
24505 batching in chapter &<<CHAPbatching>>&.
24508 .option command lmtp string&!! unset
24509 This option must be set if &%socket%& is not set. The string is a command which
24510 is run in a separate process. It is split up into a command name and list of
24511 arguments, each of which is separately expanded (so expansion cannot change the
24512 number of arguments). The command is run directly, not via a shell. The message
24513 is passed to the new process using the standard input and output to operate the
24516 .option ignore_quota lmtp boolean false
24517 .cindex "LMTP" "ignoring quota errors"
24518 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
24519 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
24520 in its response to the LHLO command.
24522 .option socket lmtp string&!! unset
24523 This option must be set if &%command%& is not set. The result of expansion must
24524 be the name of a Unix domain socket. The transport connects to the socket and
24525 delivers the message to it using the LMTP protocol.
24528 .option timeout lmtp time 5m
24529 The transport is aborted if the created process or Unix domain socket does not
24530 respond to LMTP commands or message input within this timeout. Delivery
24531 is deferred, and will be tried again later. Here is an example of a typical
24536 command = /some/local/lmtp/delivery/program
24540 This delivers up to 20 addresses at a time, in a mixture of domains if
24541 necessary, running as the user &'exim'&.
24545 . ////////////////////////////////////////////////////////////////////////////
24546 . ////////////////////////////////////////////////////////////////////////////
24548 .chapter "The pipe transport" "CHAPpipetransport"
24549 .scindex IIDpiptra1 "transports" "&(pipe)&"
24550 .scindex IIDpiptra2 "&(pipe)& transport"
24551 The &(pipe)& transport is used to deliver messages via a pipe to a command
24552 running in another process. One example is the use of &(pipe)& as a
24553 pseudo-remote transport for passing messages to some other delivery mechanism
24554 (such as UUCP). Another is the use by individual users to automatically process
24555 their incoming messages. The &(pipe)& transport can be used in one of the
24559 .vindex "&$local_part$&"
24560 A router routes one address to a transport in the normal way, and the
24561 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
24562 contains the local part of the address (as usual), and the command that is run
24563 is specified by the &%command%& option on the transport.
24565 .vindex "&$pipe_addresses$&"
24566 If the &%batch_max%& option is set greater than 1 (the default is 1), the
24567 transport can handle more than one address in a single run. In this case, when
24568 more than one address is routed to the transport, &$local_part$& is not set
24569 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
24570 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
24571 that are routed to the transport.
24573 .vindex "&$address_pipe$&"
24574 A router redirects an address directly to a pipe command (for example, from an
24575 alias or forward file). In this case, &$address_pipe$& contains the text of the
24576 pipe command, and the &%command%& option on the transport is ignored unless
24577 &%force_command%& is set. If only one address is being transported
24578 (&%batch_max%& is not greater than one, or only one address was redirected to
24579 this pipe command), &$local_part$& contains the local part that was redirected.
24583 The &(pipe)& transport is a non-interactive delivery method. Exim can also
24584 deliver messages over pipes using the LMTP interactive protocol. This is
24585 implemented by the &(lmtp)& transport.
24587 In the case when &(pipe)& is run as a consequence of an entry in a local user's
24588 &_.forward_& file, the command runs under the uid and gid of that user. In
24589 other cases, the uid and gid have to be specified explicitly, either on the
24590 transport or on the router that handles the address. Current and &"home"&
24591 directories are also controllable. See chapter &<<CHAPenvironment>>& for
24592 details of the local delivery environment and chapter &<<CHAPbatching>>&
24593 for a discussion of local delivery batching.
24595 .cindex "tainted data" "in pipe command"
24596 .cindex pipe "tainted data"
24597 Tainted data may not be used for the command name.
24600 .section "Concurrent delivery" "SECID140"
24601 If two messages arrive at almost the same time, and both are routed to a pipe
24602 delivery, the two pipe transports may be run concurrently. You must ensure that
24603 any pipe commands you set up are robust against this happening. If the commands
24604 write to a file, the &%exim_lock%& utility might be of use.
24605 Alternatively the &%max_parallel%& option could be used with a value
24606 of "1" to enforce serialization.
24611 .section "Returned status and data" "SECID141"
24612 .cindex "&(pipe)& transport" "returned data"
24613 If the command exits with a non-zero return code, the delivery is deemed to
24614 have failed, unless either the &%ignore_status%& option is set (in which case
24615 the return code is treated as zero), or the return code is one of those listed
24616 in the &%temp_errors%& option, which are interpreted as meaning &"try again
24617 later"&. In this case, delivery is deferred. Details of a permanent failure are
24618 logged, but are not included in the bounce message, which merely contains
24619 &"local delivery failed"&.
24621 If the command exits on a signal and the &%freeze_signal%& option is set then
24622 the message will be frozen in the queue. If that option is not set, a bounce
24623 will be sent as normal.
24625 If the return code is greater than 128 and the command being run is a shell
24626 script, it normally means that the script was terminated by a signal whose
24627 value is the return code minus 128. The &%freeze_signal%& option does not
24628 apply in this case.
24630 If Exim is unable to run the command (that is, if &[execve()]& fails), the
24631 return code is set to 127. This is the value that a shell returns if it is
24632 asked to run a non-existent command. The wording for the log line suggests that
24633 a non-existent command may be the problem.
24635 The &%return_output%& option can affect the result of a pipe delivery. If it is
24636 set and the command produces any output on its standard output or standard
24637 error streams, the command is considered to have failed, even if it gave a zero
24638 return code or if &%ignore_status%& is set. The output from the command is
24639 included as part of the bounce message. The &%return_fail_output%& option is
24640 similar, except that output is returned only when the command exits with a
24641 failure return code, that is, a value other than zero or a code that matches
24646 .section "How the command is run" "SECThowcommandrun"
24647 .cindex "&(pipe)& transport" "path for command"
24648 The command line is (by default) broken down into a command name and arguments
24649 by the &(pipe)& transport itself. The &%allow_commands%& and
24650 &%restrict_to_path%& options can be used to restrict the commands that may be
24653 .cindex "quoting" "in pipe command"
24654 Unquoted arguments are delimited by white space. If an argument appears in
24655 double quotes, backslash is interpreted as an escape character in the usual
24656 way. If an argument appears in single quotes, no escaping is done.
24658 String expansion is applied to the command line except when it comes from a
24659 traditional &_.forward_& file (commands from a filter file are expanded). The
24660 expansion is applied to each argument in turn rather than to the whole line.
24661 For this reason, any string expansion item that contains white space must be
24662 quoted so as to be contained within a single argument. A setting such as
24664 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
24666 will not work, because the expansion item gets split between several
24667 arguments. You have to write
24669 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
24671 to ensure that it is all in one argument. The expansion is done in this way,
24672 argument by argument, so that the number of arguments cannot be changed as a
24673 result of expansion, and quotes or backslashes in inserted variables do not
24674 interact with external quoting. However, this leads to problems if you want to
24675 generate multiple arguments (or the command name plus arguments) from a single
24676 expansion. In this situation, the simplest solution is to use a shell. For
24679 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
24682 .cindex "transport" "filter"
24683 .cindex "filter" "transport filter"
24684 .vindex "&$pipe_addresses$&"
24685 Special handling takes place when an argument consists of precisely the text
24686 &`$pipe_addresses`& (no quotes).
24687 This is not a general expansion variable; the only
24688 place this string is recognized is when it appears as an argument for a pipe or
24689 transport filter command. It causes each address that is being handled to be
24690 inserted in the argument list at that point &'as a separate argument'&. This
24691 avoids any problems with spaces or shell metacharacters, and is of use when a
24692 &(pipe)& transport is handling groups of addresses in a batch.
24694 If &%force_command%& is enabled on the transport, special handling takes place
24695 for an argument that consists of precisely the text &`$address_pipe`&. It
24696 is handled similarly to &$pipe_addresses$& above. It is expanded and each
24697 argument is inserted in the argument list at that point
24698 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
24699 the only item in the argument; in fact, if it were then &%force_command%&
24700 should behave as a no-op. Rather, it should be used to adjust the command
24701 run while preserving the argument vector separation.
24703 After splitting up into arguments and expansion, the resulting command is run
24704 in a subprocess directly from the transport, &'not'& under a shell. The
24705 message that is being delivered is supplied on the standard input, and the
24706 standard output and standard error are both connected to a single pipe that is
24707 read by Exim. The &%max_output%& option controls how much output the command
24708 may produce, and the &%return_output%& and &%return_fail_output%& options
24709 control what is done with it.
24711 Not running the command under a shell (by default) lessens the security risks
24712 in cases when a command from a user's filter file is built out of data that was
24713 taken from an incoming message. If a shell is required, it can of course be
24714 explicitly specified as the command to be run. However, there are circumstances
24715 where existing commands (for example, in &_.forward_& files) expect to be run
24716 under a shell and cannot easily be modified. To allow for these cases, there is
24717 an option called &%use_shell%&, which changes the way the &(pipe)& transport
24718 works. Instead of breaking up the command line as just described, it expands it
24719 as a single string and passes the result to &_/bin/sh_&. The
24720 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
24721 with &%use_shell%&, and the whole mechanism is inherently less secure.
24725 .section "Environment variables" "SECTpipeenv"
24726 .cindex "&(pipe)& transport" "environment for command"
24727 .cindex "environment" "&(pipe)& transport"
24728 The environment variables listed below are set up when the command is invoked.
24729 This list is a compromise for maximum compatibility with other MTAs. Note that
24730 the &%environment%& option can be used to add additional variables to this
24731 environment. The environment for the &(pipe)& transport is not subject
24732 to the &%add_environment%& and &%keep_environment%& main config options.
24734 &`DOMAIN `& the domain of the address
24735 &`HOME `& the home directory, if set
24736 &`HOST `& the host name when called from a router (see below)
24737 &`LOCAL_PART `& see below
24738 &`LOCAL_PART_PREFIX `& see below
24739 &`LOCAL_PART_SUFFIX `& see below
24740 &`LOGNAME `& see below
24741 &`MESSAGE_ID `& Exim's local ID for the message
24742 &`PATH `& as specified by the &%path%& option below
24743 &`QUALIFY_DOMAIN `& the sender qualification domain
24744 &`RECIPIENT `& the complete recipient address
24745 &`SENDER `& the sender of the message (empty if a bounce)
24746 &`SHELL `& &`/bin/sh`&
24747 &`TZ `& the value of the &%timezone%& option, if set
24748 &`USER `& see below
24750 When a &(pipe)& transport is called directly from (for example) an &(accept)&
24751 router, LOCAL_PART is set to the local part of the address. When it is
24752 called as a result of a forward or alias expansion, LOCAL_PART is set to
24753 the local part of the address that was expanded. In both cases, any affixes are
24754 removed from the local part, and made available in LOCAL_PART_PREFIX and
24755 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
24756 same value as LOCAL_PART for compatibility with other MTAs.
24759 HOST is set only when a &(pipe)& transport is called from a router that
24760 associates hosts with an address, typically when using &(pipe)& as a
24761 pseudo-remote transport. HOST is set to the first host name specified by
24765 If the transport's generic &%home_directory%& option is set, its value is used
24766 for the HOME environment variable. Otherwise, a home directory may be set
24767 by the router's &%transport_home_directory%& option, which defaults to the
24768 user's home directory if &%check_local_user%& is set.
24771 .section "Private options for pipe" "SECID142"
24772 .cindex "options" "&(pipe)& transport"
24776 .option allow_commands pipe "string list&!!" unset
24777 .cindex "&(pipe)& transport" "permitted commands"
24778 The string is expanded, and is then interpreted as a colon-separated list of
24779 permitted commands. If &%restrict_to_path%& is not set, the only commands
24780 permitted are those in the &%allow_commands%& list. They need not be absolute
24781 paths; the &%path%& option is still used for relative paths. If
24782 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
24783 in the &%allow_commands%& list, or a name without any slashes that is found on
24784 the path. In other words, if neither &%allow_commands%& nor
24785 &%restrict_to_path%& is set, there is no restriction on the command, but
24786 otherwise only commands that are permitted by one or the other are allowed. For
24789 allow_commands = /usr/bin/vacation
24791 and &%restrict_to_path%& is not set, the only permitted command is
24792 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
24793 &%use_shell%& is set.
24796 .option batch_id pipe string&!! unset
24797 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24800 .option batch_max pipe integer 1
24801 This limits the number of addresses that can be handled in a single delivery.
24802 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24805 .option check_string pipe string unset
24806 As &(pipe)& writes the message, the start of each line is tested for matching
24807 &%check_string%&, and if it does, the initial matching characters are replaced
24808 by the contents of &%escape_string%&, provided both are set. The value of
24809 &%check_string%& is a literal string, not a regular expression, and the case of
24810 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
24811 of &%check_string%& and &%escape_string%& are forced to values that implement
24812 the SMTP escaping protocol. Any settings made in the configuration file are
24816 .option command pipe string&!! unset
24817 This option need not be set when &(pipe)& is being used to deliver to pipes
24818 obtained directly from address redirections. In other cases, the option must be
24819 set, to provide a command to be run. It need not yield an absolute path (see
24820 the &%path%& option below). The command is split up into separate arguments by
24821 Exim, and each argument is separately expanded, as described in section
24822 &<<SECThowcommandrun>>& above.
24825 .option environment pipe string&!! unset
24826 .cindex "&(pipe)& transport" "environment for command"
24827 .cindex "environment" "&(pipe)& transport"
24828 This option is used to add additional variables to the environment in which the
24829 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
24830 a string which is expanded, and then interpreted as a colon-separated list of
24831 environment settings of the form <&'name'&>=<&'value'&>.
24834 .option escape_string pipe string unset
24835 See &%check_string%& above.
24838 .option freeze_exec_fail pipe boolean false
24839 .cindex "exec failure"
24840 .cindex "failure of exec"
24841 .cindex "&(pipe)& transport" "failure of exec"
24842 Failure to exec the command in a pipe transport is by default treated like
24843 any other failure while running the command. However, if &%freeze_exec_fail%&
24844 is set, failure to exec is treated specially, and causes the message to be
24845 frozen, whatever the setting of &%ignore_status%&.
24848 .option freeze_signal pipe boolean false
24849 .cindex "signal exit"
24850 .cindex "&(pipe)& transport", "signal exit"
24851 Normally if the process run by a command in a pipe transport exits on a signal,
24852 a bounce message is sent. If &%freeze_signal%& is set, the message will be
24853 frozen in Exim's queue instead.
24856 .option force_command pipe boolean false
24857 .cindex "force command"
24858 .cindex "&(pipe)& transport", "force command"
24859 Normally when a router redirects an address directly to a pipe command
24860 the &%command%& option on the transport is ignored. If &%force_command%&
24861 is set, the &%command%& option will used. This is especially
24862 useful for forcing a wrapper or additional argument to be added to the
24863 command. For example:
24865 command = /usr/bin/remote_exec myhost -- $address_pipe
24869 Note that &$address_pipe$& is handled specially in &%command%& when
24870 &%force_command%& is set, expanding out to the original argument vector as
24871 separate items, similarly to a Unix shell &`"$@"`& construct.
24874 .option ignore_status pipe boolean false
24875 If this option is true, the status returned by the subprocess that is set up to
24876 run the command is ignored, and Exim behaves as if zero had been returned.
24877 Otherwise, a non-zero status or termination by signal causes an error return
24878 from the transport unless the status value is one of those listed in
24879 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
24881 &*Note*&: This option does not apply to timeouts, which do not return a status.
24882 See the &%timeout_defer%& option for how timeouts are handled.
24885 .option log_defer_output pipe boolean false
24886 .cindex "&(pipe)& transport" "logging output"
24887 If this option is set, and the status returned by the command is
24888 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
24889 and any output was produced on stdout or stderr, the first line of it is
24890 written to the main log.
24893 .option log_fail_output pipe boolean false
24894 If this option is set, and the command returns any output on stdout or
24895 stderr, and also ends with a return code that is neither zero nor one of
24896 the return codes listed in &%temp_errors%& (that is, the delivery
24897 failed), the first line of output is written to the main log. This
24898 option and &%log_output%& are mutually exclusive. Only one of them may
24902 .option log_output pipe boolean false
24903 If this option is set and the command returns any output on stdout or
24904 stderr, the first line of output is written to the main log, whatever
24905 the return code. This option and &%log_fail_output%& are mutually
24906 exclusive. Only one of them may be set.
24909 .option max_output pipe integer 20K
24910 This specifies the maximum amount of output that the command may produce on its
24911 standard output and standard error file combined. If the limit is exceeded, the
24912 process running the command is killed. This is intended as a safety measure to
24913 catch runaway processes. The limit is applied independently of the settings of
24914 the options that control what is done with such output (for example,
24915 &%return_output%&). Because of buffering effects, the amount of output may
24916 exceed the limit by a small amount before Exim notices.
24919 .option message_prefix pipe string&!! "see below"
24920 The string specified here is expanded and output at the start of every message.
24921 The default is unset if &%use_bsmtp%& is set. Otherwise it is
24924 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
24928 .cindex "&%tmail%&"
24929 .cindex "&""From""& line"
24930 This is required by the commonly used &_/usr/bin/vacation_& program.
24931 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
24932 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
24937 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24938 &`\n`& to &`\r\n`& in &%message_prefix%&.
24941 .option message_suffix pipe string&!! "see below"
24942 The string specified here is expanded and output at the end of every message.
24943 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
24944 The suffix can be suppressed by setting
24948 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24949 &`\n`& to &`\r\n`& in &%message_suffix%&.
24952 .option path pipe string&!! "/bin:/usr/bin"
24953 This option is expanded and
24954 specifies the string that is set up in the PATH environment
24955 variable of the subprocess.
24956 If the &%command%& option does not yield an absolute path name, the command is
24957 sought in the PATH directories, in the usual way. &*Warning*&: This does not
24958 apply to a command specified as a transport filter.
24961 .option permit_coredump pipe boolean false
24962 Normally Exim inhibits core-dumps during delivery. If you have a need to get
24963 a core-dump of a pipe command, enable this command. This enables core-dumps
24964 during delivery and affects both the Exim binary and the pipe command run.
24965 It is recommended that this option remain off unless and until you have a need
24966 for it and that this only be enabled when needed, as the risk of excessive
24967 resource consumption can be quite high. Note also that Exim is typically
24968 installed as a setuid binary and most operating systems will inhibit coredumps
24969 of these by default, so further OS-specific action may be required.
24972 .option pipe_as_creator pipe boolean false
24973 .cindex "uid (user id)" "local delivery"
24974 If the generic &%user%& option is not set and this option is true, the delivery
24975 process is run under the uid that was in force when Exim was originally called
24976 to accept the message. If the group id is not otherwise set (via the generic
24977 &%group%& option), the gid that was in force when Exim was originally called to
24978 accept the message is used.
24981 .option restrict_to_path pipe boolean false
24982 When this option is set, any command name not listed in &%allow_commands%& must
24983 contain no slashes. The command is searched for only in the directories listed
24984 in the &%path%& option. This option is intended for use in the case when a pipe
24985 command has been generated from a user's &_.forward_& file. This is usually
24986 handled by a &(pipe)& transport called &%address_pipe%&.
24989 .option return_fail_output pipe boolean false
24990 If this option is true, and the command produced any output and ended with a
24991 return code other than zero or one of the codes listed in &%temp_errors%& (that
24992 is, the delivery failed), the output is returned in the bounce message.
24993 However, if the message has a null sender (that is, it is itself a bounce
24994 message), output from the command is discarded. This option and
24995 &%return_output%& are mutually exclusive. Only one of them may be set.
24999 .option return_output pipe boolean false
25000 If this option is true, and the command produced any output, the delivery is
25001 deemed to have failed whatever the return code from the command, and the output
25002 is returned in the bounce message. Otherwise, the output is just discarded.
25003 However, if the message has a null sender (that is, it is a bounce message),
25004 output from the command is always discarded, whatever the setting of this
25005 option. This option and &%return_fail_output%& are mutually exclusive. Only one
25006 of them may be set.
25010 .option temp_errors pipe "string list" "see below"
25011 .cindex "&(pipe)& transport" "temporary failure"
25012 This option contains either a colon-separated list of numbers, or a single
25013 asterisk. If &%ignore_status%& is false
25014 and &%return_output%& is not set,
25015 and the command exits with a non-zero return code, the failure is treated as
25016 temporary and the delivery is deferred if the return code matches one of the
25017 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
25018 codes are treated as permanent errors. The default setting contains the codes
25019 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
25020 compiled on a system that does not define these macros, it assumes values of 75
25021 and 73, respectively.
25024 .option timeout pipe time 1h
25025 If the command fails to complete within this time, it is killed. This normally
25026 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
25027 specifies no timeout. In order to ensure that any subprocesses created by the
25028 command are also killed, Exim makes the initial process a process group leader,
25029 and kills the whole process group on a timeout. However, this can be defeated
25030 if one of the processes starts a new process group.
25032 .option timeout_defer pipe boolean false
25033 A timeout in a &(pipe)& transport, either in the command that the transport
25034 runs, or in a transport filter that is associated with it, is by default
25035 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
25036 is set true, both kinds of timeout become temporary errors, causing the
25037 delivery to be deferred.
25039 .option umask pipe "octal integer" 022
25040 This specifies the umask setting for the subprocess that runs the command.
25043 .option use_bsmtp pipe boolean false
25044 .cindex "envelope sender"
25045 If this option is set true, the &(pipe)& transport writes messages in &"batch
25046 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
25047 commands. If you want to include a leading HELO command with such messages,
25048 you can do so by setting the &%message_prefix%& option. See section
25049 &<<SECTbatchSMTP>>& for details of batch SMTP.
25051 .option use_classresources pipe boolean false
25052 .cindex "class resources (BSD)"
25053 This option is available only when Exim is running on FreeBSD, NetBSD, or
25054 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
25055 resource limits when a &(pipe)& transport is run to perform a delivery. The
25056 limits for the uid under which the pipe is to run are obtained from the login
25060 .option use_crlf pipe boolean false
25061 .cindex "carriage return"
25063 This option causes lines to be terminated with the two-character CRLF sequence
25064 (carriage return, linefeed) instead of just a linefeed character. In the case
25065 of batched SMTP, the byte sequence written to the pipe is then an exact image
25066 of what would be sent down a real SMTP connection.
25068 The contents of the &%message_prefix%& and &%message_suffix%& options are
25069 written verbatim, so must contain their own carriage return characters if these
25070 are needed. When &%use_bsmtp%& is not set, the default values for both
25071 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
25072 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
25075 .option use_shell pipe boolean false
25076 .vindex "&$pipe_addresses$&"
25077 If this option is set, it causes the command to be passed to &_/bin/sh_&
25078 instead of being run directly from the transport, as described in section
25079 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
25080 where the command is expected to be run under a shell and cannot easily be
25081 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
25082 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
25083 command is expanded as a single string, and handed to &_/bin/sh_& as data for
25088 .section "Using an external local delivery agent" "SECID143"
25089 .cindex "local delivery" "using an external agent"
25090 .cindex "&'procmail'&"
25091 .cindex "external local delivery"
25092 .cindex "delivery" "&'procmail'&"
25093 .cindex "delivery" "by external agent"
25094 The &(pipe)& transport can be used to pass all messages that require local
25095 delivery to a separate local delivery agent such as &%procmail%&. When doing
25096 this, care must be taken to ensure that the pipe is run under an appropriate
25097 uid and gid. In some configurations one wants this to be a uid that is trusted
25098 by the delivery agent to supply the correct sender of the message. It may be
25099 necessary to recompile or reconfigure the delivery agent so that it trusts an
25100 appropriate user. The following is an example transport and router
25101 configuration for &%procmail%&:
25106 command = /usr/local/bin/procmail -d $local_part_data
25110 check_string = "From "
25111 escape_string = ">From "
25113 user = $local_part_data
25120 transport = procmail_pipe
25122 In this example, the pipe is run as the local user, but with the group set to
25123 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
25124 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
25125 user to supply a correct sender address. If you do not specify either a
25126 &%group%& or a &%user%& option, the pipe command is run as the local user. The
25127 home directory is the user's home directory by default.
25129 &*Note*&: The command that the pipe transport runs does &'not'& begin with
25133 as shown in some &%procmail%& documentation, because Exim does not by default
25134 use a shell to run pipe commands.
25137 The next example shows a transport and a router for a system where local
25138 deliveries are handled by the Cyrus IMAP server.
25141 local_delivery_cyrus:
25143 command = /usr/cyrus/bin/deliver \
25144 -m ${substr_1:$local_part_suffix} -- $local_part
25156 local_part_suffix = .*
25157 transport = local_delivery_cyrus
25159 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
25160 &%return_output%& to cause any text written by Cyrus to be returned to the
25162 .ecindex IIDpiptra1
25163 .ecindex IIDpiptra2
25166 . ////////////////////////////////////////////////////////////////////////////
25167 . ////////////////////////////////////////////////////////////////////////////
25169 .chapter "The smtp transport" "CHAPsmtptrans"
25170 .scindex IIDsmttra1 "transports" "&(smtp)&"
25171 .scindex IIDsmttra2 "&(smtp)& transport"
25172 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
25173 or LMTP protocol. The list of hosts to try can either be taken from the address
25174 that is being processed (having been set up by the router), or specified
25175 explicitly for the transport. Timeout and retry processing (see chapter
25176 &<<CHAPretry>>&) is applied to each IP address independently.
25179 .section "Multiple messages on a single connection" "SECID144"
25180 The sending of multiple messages over a single TCP/IP connection can arise in
25184 If a message contains more than &%max_rcpt%& (see below) addresses that are
25185 routed to the same host, more than one copy of the message has to be sent to
25186 that host. In this situation, multiple copies may be sent in a single run of
25187 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
25188 does when it has too many addresses to send in one message also depends on the
25189 value of the global &%remote_max_parallel%& option. Details are given in
25190 section &<<SECToutSMTPTCP>>&.)
25192 .cindex "hints database" "remembering routing"
25193 When a message has been successfully delivered over a TCP/IP connection, Exim
25194 looks in its hints database to see if there are any other messages awaiting a
25195 connection to the same host. If there are, a new delivery process is started
25196 for one of them, and the current TCP/IP connection is passed on to it. The new
25197 process may in turn send multiple copies and possibly create yet another
25202 For each copy sent over the same TCP/IP connection, a sequence counter is
25203 incremented, and if it ever gets to the value of &%connection_max_messages%&,
25204 no further messages are sent over that connection.
25208 .section "Use of the $host and $host_address variables" "SECID145"
25210 .vindex "&$host_address$&"
25211 At the start of a run of the &(smtp)& transport, the values of &$host$& and
25212 &$host_address$& are the name and IP address of the first host on the host list
25213 passed by the router. However, when the transport is about to connect to a
25214 specific host, and while it is connected to that host, &$host$& and
25215 &$host_address$& are set to the values for that host. These are the values
25216 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
25217 &%serialize_hosts%&, and the various TLS options are expanded.
25220 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
25221 .vindex &$tls_bits$&
25222 .vindex &$tls_cipher$&
25223 .vindex &$tls_peerdn$&
25224 .vindex &$tls_sni$&
25225 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
25226 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
25227 are the values that were set when the message was received.
25228 These are the values that are used for options that are expanded before any
25229 SMTP connections are made. Just before each connection is made, these four
25230 variables are emptied. If TLS is subsequently started, they are set to the
25231 appropriate values for the outgoing connection, and these are the values that
25232 are in force when any authenticators are run and when the
25233 &%authenticated_sender%& option is expanded.
25235 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
25236 and will be removed in a future release.
25239 .section "Private options for smtp" "SECID146"
25240 .cindex "options" "&(smtp)& transport"
25241 The private options of the &(smtp)& transport are as follows:
25244 .option address_retry_include_sender smtp boolean true
25245 .cindex "4&'xx'& responses" "retrying after"
25246 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
25247 is the combination of sender and recipient that is delayed in subsequent queue
25248 runs until the retry time is reached. You can delay the recipient without
25249 reference to the sender (which is what earlier versions of Exim did), by
25250 setting &%address_retry_include_sender%& false. However, this can lead to
25251 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
25253 .option allow_localhost smtp boolean false
25254 .cindex "local host" "sending to"
25255 .cindex "fallback" "hosts specified on transport"
25256 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
25257 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
25258 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
25259 the delivery anyway. This should be used only in special cases when the
25260 configuration ensures that no looping will result (for example, a differently
25261 configured Exim is listening on the port to which the message is sent).
25264 .option authenticated_sender smtp string&!! unset
25266 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
25267 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
25268 overriding any existing authenticated sender value. If the string expansion is
25269 forced to fail, the option is ignored. Other expansion failures cause delivery
25270 to be deferred. If the result of expansion is an empty string, that is also
25273 The expansion happens after the outgoing connection has been made and TLS
25274 started, if required. This means that the &$host$&, &$host_address$&,
25275 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
25276 particular connection.
25278 If the SMTP session is not authenticated, the expansion of
25279 &%authenticated_sender%& still happens (and can cause the delivery to be
25280 deferred if it fails), but no AUTH= item is added to MAIL commands
25281 unless &%authenticated_sender_force%& is true.
25283 This option allows you to use the &(smtp)& transport in LMTP mode to
25284 deliver mail to Cyrus IMAP and provide the proper local part as the
25285 &"authenticated sender"&, via a setting such as:
25287 authenticated_sender = $local_part
25289 This removes the need for IMAP subfolders to be assigned special ACLs to
25290 allow direct delivery to those subfolders.
25292 Because of expected uses such as that just described for Cyrus (when no
25293 domain is involved), there is no checking on the syntax of the provided
25297 .option authenticated_sender_force smtp boolean false
25298 If this option is set true, the &%authenticated_sender%& option's value
25299 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
25300 authenticated as a client.
25303 .option command_timeout smtp time 5m
25304 .cindex timeout "smtp transport command"
25305 This sets a timeout for receiving a response to an SMTP command that has been
25306 sent out. It is also used when waiting for the initial banner line from the
25307 remote host. Its value must not be zero.
25310 .option connect_timeout smtp time 5m
25311 .cindex timeout "smtp transport connect"
25312 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
25313 to a remote host. A setting of zero allows the system timeout (typically
25314 several minutes) to act. To have any effect, the value of this option must be
25315 less than the system timeout. However, it has been observed that on some
25316 systems there is no system timeout, which is why the default value for this
25317 option is 5 minutes, a value recommended by RFC 1123.
25320 .option connection_max_messages smtp integer 500
25321 .cindex "SMTP" "passed connection"
25322 .cindex "SMTP" "multiple deliveries"
25323 .cindex "multiple SMTP deliveries"
25324 This controls the maximum number of separate message deliveries that are sent
25325 over a single TCP/IP connection. If the value is zero, there is no limit.
25326 For testing purposes, this value can be overridden by the &%-oB%& command line
25330 .option dane_require_tls_ciphers smtp string&!! unset
25331 .cindex "TLS" "requiring specific ciphers for DANE"
25332 .cindex "cipher" "requiring specific"
25333 .cindex DANE "TLS ciphers"
25334 This option may be used to override &%tls_require_ciphers%& for connections
25335 where DANE has been determined to be in effect.
25336 If not set, then &%tls_require_ciphers%& will be used.
25337 Normal SMTP delivery is not able to make strong demands of TLS cipher
25338 configuration, because delivery will fall back to plaintext. Once DANE has
25339 been determined to be in effect, there is no plaintext fallback and making the
25340 TLS cipherlist configuration stronger will increase security, rather than
25341 counter-intuitively decreasing it.
25342 If the option expands to be empty or is forced to fail, then it will
25343 be treated as unset and &%tls_require_ciphers%& will be used instead.
25346 .option data_timeout smtp time 5m
25347 .cindex timeout "for transmitted SMTP data blocks"
25348 This sets a timeout for the transmission of each block in the data portion of
25349 the message. As a result, the overall timeout for a message depends on the size
25350 of the message. Its value must not be zero. See also &%final_timeout%&.
25353 .option dkim_canon smtp string&!! unset
25354 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25355 .option dkim_domain smtp "string list&!!" unset
25356 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25357 .option dkim_hash smtp string&!! sha256
25358 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25359 .option dkim_identity smtp string&!! unset
25360 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25361 .option dkim_private_key smtp string&!! unset
25362 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25363 .option dkim_selector smtp string&!! unset
25364 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25365 .option dkim_strict smtp string&!! unset
25366 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25367 .option dkim_sign_headers smtp string&!! "per RFC"
25368 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25369 .option dkim_timestamps smtp string&!! unset
25370 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25373 .option delay_after_cutoff smtp boolean true
25374 .cindex "final cutoff" "retries, controlling"
25375 .cindex retry "final cutoff"
25376 This option controls what happens when all remote IP addresses for a given
25377 domain have been inaccessible for so long that they have passed their retry
25380 In the default state, if the next retry time has not been reached for any of
25381 them, the address is bounced without trying any deliveries. In other words,
25382 Exim delays retrying an IP address after the final cutoff time until a new
25383 retry time is reached, and can therefore bounce an address without ever trying
25384 a delivery, when machines have been down for a long time. Some people are
25385 unhappy at this prospect, so...
25387 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25388 addresses are past their final cutoff time, Exim tries to deliver to those
25389 IP addresses that have not been tried since the message arrived. If there are
25390 none, of if they all fail, the address is bounced. In other words, it does not
25391 delay when a new message arrives, but immediately tries those expired IP
25392 addresses that haven't been tried since the message arrived. If there is a
25393 continuous stream of messages for the dead hosts, unsetting
25394 &%delay_after_cutoff%& means that there will be many more attempts to deliver
25398 .option dns_qualify_single smtp boolean true
25399 If the &%hosts%& or &%fallback_hosts%& option is being used,
25400 and the &%gethostbyname%& option is false,
25401 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
25402 in chapter &<<CHAPdnslookup>>& for more details.
25405 .option dns_search_parents smtp boolean false
25406 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
25407 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
25408 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
25412 .option dnssec_request_domains smtp "domain list&!!" *
25413 .cindex "MX record" "security"
25414 .cindex "DNSSEC" "MX lookup"
25415 .cindex "security" "MX lookup"
25416 .cindex "DNS" "DNSSEC"
25417 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
25418 the DNSSEC request bit set. Setting this transport option is only useful if the
25419 transport overrides or sets the host names. See the &%dnssec_request_domains%&
25424 .option dnssec_require_domains smtp "domain list&!!" unset
25425 .cindex "MX record" "security"
25426 .cindex "DNSSEC" "MX lookup"
25427 .cindex "security" "MX lookup"
25428 .cindex "DNS" "DNSSEC"
25429 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
25430 the DNSSEC request bit set. Setting this transport option is only
25431 useful if the transport overrides or sets the host names. See the
25432 &%dnssec_require_domains%& router option.
25436 .option dscp smtp string&!! unset
25437 .cindex "DCSP" "outbound"
25438 This option causes the DSCP value associated with a socket to be set to one
25439 of a number of fixed strings or to numeric value.
25440 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
25441 Common values include &`throughput`&, &`mincost`&, and on newer systems
25442 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
25444 The outbound packets from Exim will be marked with this value in the header
25445 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
25446 that these values will have any effect, not be stripped by networking
25447 equipment, or do much of anything without cooperation with your Network
25448 Engineer and those of all network operators between the source and destination.
25451 .option fallback_hosts smtp "string list" unset
25452 .cindex "fallback" "hosts specified on transport"
25453 String expansion is not applied to this option. The argument must be a
25454 colon-separated list of host names or IP addresses, optionally also including
25455 port numbers, though the separator can be changed, as described in section
25456 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25457 item in a &%route_list%& setting for the &(manualroute)& router, as described
25458 in section &<<SECTformatonehostitem>>&.
25460 Fallback hosts can also be specified on routers, which associate them with the
25461 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
25462 &%fallback_hosts%& specified on the transport is used only if the address does
25463 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
25464 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
25465 However, &%hosts_randomize%& does apply to fallback host lists.
25467 If Exim is unable to deliver to any of the hosts for a particular address, and
25468 the errors are not permanent rejections, the address is put on a separate
25469 transport queue with its host list replaced by the fallback hosts, unless the
25470 address was routed via MX records and the current host was in the original MX
25471 list. In that situation, the fallback host list is not used.
25473 Once normal deliveries are complete, the fallback queue is delivered by
25474 re-running the same transports with the new host lists. If several failing
25475 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
25476 copy of the message is sent.
25478 The resolution of the host names on the fallback list is controlled by the
25479 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
25480 both to cases when the host list comes with the address and when it is taken
25481 from &%hosts%&. This option provides a &"use a smart host only if delivery
25485 .option final_timeout smtp time 10m
25486 .cindex timeout "for transmitted SMTP data accept"
25487 This is the timeout that applies while waiting for the response to the final
25488 line containing just &"."& that terminates a message. Its value must not be
25491 .option gethostbyname smtp boolean false
25492 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
25493 being used, names are looked up using &[gethostbyname()]&
25494 (or &[getipnodebyname()]& when available)
25495 instead of using the DNS. Of course, that function may in fact use the DNS, but
25496 it may also consult other sources of information such as &_/etc/hosts_&.
25498 .option gnutls_compat_mode smtp boolean unset
25499 This option controls whether GnuTLS is used in compatibility mode in an Exim
25500 server. This reduces security slightly, but improves interworking with older
25501 implementations of TLS.
25503 .option helo_data smtp string&!! "see below"
25504 .cindex "HELO" "argument, setting"
25505 .cindex "EHLO" "argument, setting"
25506 .cindex "LHLO argument setting"
25507 The value of this option is expanded after a connection to a another host has
25508 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
25509 command that starts the outgoing SMTP or LMTP session. The default value of the
25514 During the expansion, the variables &$host$& and &$host_address$& are set to
25515 the identity of the remote host, and the variables &$sending_ip_address$& and
25516 &$sending_port$& are set to the local IP address and port number that are being
25517 used. These variables can be used to generate different values for different
25518 servers or different local IP addresses. For example, if you want the string
25519 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
25520 interface address, you could use this:
25522 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
25523 {$primary_hostname}}
25525 The use of &%helo_data%& applies both to sending messages and when doing
25528 .option hosts smtp "string list&!!" unset
25529 Hosts are associated with an address by a router such as &(dnslookup)&, which
25530 finds the hosts by looking up the address domain in the DNS, or by
25531 &(manualroute)&, which has lists of hosts in its configuration. However,
25532 email addresses can be passed to the &(smtp)& transport by any router, and not
25533 all of them can provide an associated list of hosts.
25535 The &%hosts%& option specifies a list of hosts to be used if the address being
25536 processed does not have any hosts associated with it. The hosts specified by
25537 &%hosts%& are also used, whether or not the address has its own hosts, if
25538 &%hosts_override%& is set.
25540 The string is first expanded, before being interpreted as a colon-separated
25541 list of host names or IP addresses, possibly including port numbers. The
25542 separator may be changed to something other than colon, as described in section
25543 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25544 item in a &%route_list%& setting for the &(manualroute)& router, as described
25545 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
25546 of the &(manualroute)& router is not available here.
25548 If the expansion fails, delivery is deferred. Unless the failure was caused by
25549 the inability to complete a lookup, the error is logged to the panic log as
25550 well as the main log. Host names are looked up either by searching directly for
25551 address records in the DNS or by calling &[gethostbyname()]& (or
25552 &[getipnodebyname()]& when available), depending on the setting of the
25553 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
25554 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
25557 During delivery, the hosts are tried in order, subject to their retry status,
25558 unless &%hosts_randomize%& is set.
25561 .option hosts_avoid_esmtp smtp "host list&!!" unset
25562 .cindex "ESMTP, avoiding use of"
25563 .cindex "HELO" "forcing use of"
25564 .cindex "EHLO" "avoiding use of"
25565 .cindex "PIPELINING" "avoiding the use of"
25566 This option is for use with broken hosts that announce ESMTP facilities (for
25567 example, PIPELINING) and then fail to implement them properly. When a host
25568 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
25569 start of the SMTP session. This means that it cannot use any of the ESMTP
25570 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
25573 .option hosts_avoid_pipelining smtp "host list&!!" unset
25574 .cindex "PIPELINING" "avoiding the use of"
25575 .cindex "ESMTP extensions" PIPELINING
25576 Exim will not use the ESMTP PIPELINING extension when delivering to any host
25577 that matches this list, even if the server host advertises PIPELINING support.
25579 .option hosts_pipe_connect smtp "host list&!!" unset
25580 .cindex "pipelining" "early connection"
25581 .cindex "pipelining" PIPE_CONNECT
25582 If Exim is built with the SUPPORT_PIPE_CONNECT build option
25583 this option controls which to hosts the facility watched for
25584 and recorded, and used for subsequent connections.
25586 The retry hints database is used for the record,
25587 and records are subject to the &%retry_data_expire%& option.
25588 When used, the pipelining saves on roundtrip times.
25589 It also turns SMTP into a client-first protocol
25590 so combines well with TCP Fast Open.
25592 See also the &%pipelining_connect_advertise_hosts%& main option.
25595 When the facility is used, the transport &%helo_data%& option
25596 will be expanded before the &$sending_ip_address$& variable
25598 A check is made for the use of that variable, without the
25599 presence of a &"def:"& test on it, but suitably complex coding
25600 can avoid the check and produce unexpected results.
25601 You have been warned.
25604 .option hosts_avoid_tls smtp "host list&!!" unset
25605 .cindex "TLS" "avoiding for certain hosts"
25606 Exim will not try to start a TLS session when delivering to any host that
25607 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25609 .option hosts_verify_avoid_tls smtp "host list&!!" unset
25610 .cindex "TLS" "avoiding for certain hosts"
25611 Exim will not try to start a TLS session for a verify callout,
25612 or when delivering in cutthrough mode,
25613 to any host that matches this list.
25616 .option hosts_max_try smtp integer 5
25617 .cindex "host" "maximum number to try"
25618 .cindex "limit" "number of hosts tried"
25619 .cindex "limit" "number of MX tried"
25620 .cindex "MX record" "maximum tried"
25621 This option limits the number of IP addresses that are tried for any one
25622 delivery in cases where there are temporary delivery errors. Section
25623 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
25626 .option hosts_max_try_hardlimit smtp integer 50
25627 This is an additional check on the maximum number of IP addresses that Exim
25628 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
25633 .option hosts_nopass_tls smtp "host list&!!" unset
25634 .cindex "TLS" "passing connection"
25635 .cindex "multiple SMTP deliveries"
25636 .cindex "TLS" "multiple message deliveries"
25637 For any host that matches this list, a connection on which a TLS session has
25638 been started will not be passed to a new delivery process for sending another
25639 message on the same connection. See section &<<SECTmulmessam>>& for an
25640 explanation of when this might be needed.
25642 .option hosts_noproxy_tls smtp "host list&!!" unset
25643 .cindex "TLS" "passing connection"
25644 .cindex "multiple SMTP deliveries"
25645 .cindex "TLS" "multiple message deliveries"
25646 For any host that matches this list, a TLS session which has
25647 been started will not be passed to a new delivery process for sending another
25648 message on the same session.
25650 The traditional implementation closes down TLS and re-starts it in the new
25651 process, on the same open TCP connection, for each successive message
25652 sent. If permitted by this option a pipe to to the new process is set up
25653 instead, and the original process maintains the TLS connection and proxies
25654 the SMTP connection from and to the new process and any subsequents.
25655 The new process has no access to TLS information, so cannot include it in
25660 .option hosts_override smtp boolean false
25661 If this option is set and the &%hosts%& option is also set, any hosts that are
25662 attached to the address are ignored, and instead the hosts specified by the
25663 &%hosts%& option are always used. This option does not apply to
25664 &%fallback_hosts%&.
25667 .option hosts_randomize smtp boolean false
25668 .cindex "randomized host list"
25669 .cindex "host" "list of; randomized"
25670 .cindex "fallback" "randomized hosts"
25671 If this option is set, and either the list of hosts is taken from the
25672 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
25673 were not obtained from MX records (this includes fallback hosts from the
25674 router), and were not randomized by the router, the order of trying the hosts
25675 is randomized each time the transport runs. Randomizing the order of a host
25676 list can be used to do crude load sharing.
25678 When &%hosts_randomize%& is true, a host list may be split into groups whose
25679 order is separately randomized. This makes it possible to set up MX-like
25680 behaviour. The boundaries between groups are indicated by an item that is just
25681 &`+`& in the host list. For example:
25683 hosts = host1:host2:host3:+:host4:host5
25685 The order of the first three hosts and the order of the last two hosts is
25686 randomized for each use, but the first three always end up before the last two.
25687 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
25689 .option hosts_require_auth smtp "host list&!!" unset
25690 .cindex "authentication" "required by client"
25691 This option provides a list of servers for which authentication must succeed
25692 before Exim will try to transfer a message. If authentication fails for
25693 servers which are not in this list, Exim tries to send unauthenticated. If
25694 authentication fails for one of these servers, delivery is deferred. This
25695 temporary error is detectable in the retry rules, so it can be turned into a
25696 hard failure if required. See also &%hosts_try_auth%&, and chapter
25697 &<<CHAPSMTPAUTH>>& for details of authentication.
25700 .option hosts_request_ocsp smtp "host list&!!" *
25701 .cindex "TLS" "requiring for certain servers"
25702 Exim will request a Certificate Status on a
25703 TLS session for any host that matches this list.
25704 &%tls_verify_certificates%& should also be set for the transport.
25707 .option hosts_require_alpn smtp "host list&!!" unset
25708 .cindex ALPN "require negotiation in client"
25710 .cindex TLS "Application Layer Protocol Names"
25711 If the TLS library supports ALPN
25712 then a successful negotiation of ALPN will be required for any host
25713 matching the list, for TLS to be used.
25714 See also the &%tls_alpn%& option.
25716 &*Note*&: prevention of fallback to in-clear connection is not
25717 managed by this option; see &%hosts_require_tls%&.
25720 .option hosts_require_dane smtp "host list&!!" unset
25721 .cindex DANE "transport options"
25722 .cindex DANE "requiring for certain servers"
25723 If built with DANE support, Exim will require that a DNSSEC-validated
25724 TLSA record is present for any host matching the list,
25725 and that a DANE-verified TLS connection is made.
25726 There will be no fallback to in-clear communication.
25727 See the &%dnssec_request_domains%& router and transport options.
25728 See section &<<SECDANE>>&.
25730 .option hosts_require_helo smtp "host list&!!" *
25731 .cindex "HELO/EHLO" requiring
25732 Exim will require an accepted HELO or EHLO command from a host matching
25733 this list, before accepting a MAIL command.
25735 .option hosts_require_ocsp smtp "host list&!!" unset
25736 .cindex "TLS" "requiring for certain servers"
25737 Exim will request, and check for a valid Certificate Status being given, on a
25738 TLS session for any host that matches this list.
25739 &%tls_verify_certificates%& should also be set for the transport.
25741 .option hosts_require_tls smtp "host list&!!" unset
25742 .cindex "TLS" "requiring for certain servers"
25743 Exim will insist on using a TLS session when delivering to any host that
25744 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25745 &*Note*&: This option affects outgoing mail only. To insist on TLS for
25746 incoming messages, use an appropriate ACL.
25748 .option hosts_try_auth smtp "host list&!!" unset
25749 .cindex "authentication" "optional in client"
25750 This option provides a list of servers to which, provided they announce
25751 authentication support, Exim will attempt to authenticate as a client when it
25752 connects. If authentication fails
25754 and &%hosts_require_auth%& permits,
25756 Exim will try to transfer the message unauthenticated.
25757 See also chapter &<<CHAPSMTPAUTH>>& for details of authentication.
25759 .option hosts_try_chunking smtp "host list&!!" *
25760 .cindex CHUNKING "enabling, in client"
25761 .cindex BDAT "SMTP command"
25762 .cindex "RFC 3030" "CHUNKING"
25763 This option provides a list of servers to which, provided they announce
25764 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
25765 Unless DKIM signing is being done,
25766 BDAT will not be used in conjunction with a transport filter.
25768 .option hosts_try_dane smtp "host list&!!" *
25769 .cindex DANE "transport options"
25770 .cindex DANE "attempting for certain servers"
25772 If built with DANE support, Exim will look up a
25773 TLSA record for any host matching the list,
25774 If one is found and that lookup was DNSSEC-validated,
25775 then Exim requires that a DANE-verified TLS connection is made for that host;
25776 there will be no fallback to in-clear communication.
25778 See the &%dnssec_request_domains%& router and transport options.
25779 See section &<<SECDANE>>&.
25781 .option hosts_try_fastopen smtp "host list&!!" *
25782 .cindex "fast open, TCP" "enabling, in client"
25783 .cindex "TCP Fast Open" "enabling, in client"
25784 .cindex "RFC 7413" "TCP Fast Open"
25785 This option provides a list of servers to which, provided
25786 the facility is supported by this system, Exim will attempt to
25787 perform a TCP Fast Open.
25788 No data is sent on the SYN segment but, if the remote server also
25789 supports the facility, it can send its SMTP banner immediately after
25790 the SYN,ACK segment. This can save up to one round-trip time.
25792 The facility is only active for previously-contacted servers,
25793 as the initiator must present a cookie in the SYN segment.
25795 On (at least some) current Linux distributions the facility must be enabled
25796 in the kernel by the sysadmin before the support is usable.
25797 There is no option for control of the server side; if the system supports
25798 it it is always enabled. Note that lengthy operations in the connect ACL,
25799 such as DNSBL lookups, will still delay the emission of the SMTP banner.
25801 .option hosts_try_prdr smtp "host list&!!" *
25802 .cindex "PRDR" "enabling, optional in client"
25803 .cindex "ESMTP extensions" PRDR
25804 This option provides a list of servers to which, provided they announce
25805 PRDR support, Exim will attempt to negotiate PRDR
25806 for multi-recipient messages.
25807 The option can usually be left as default.
25809 .option interface smtp "string list&!!" unset
25810 .cindex "bind IP address"
25811 .cindex "IP address" "binding"
25813 .vindex "&$host_address$&"
25814 This option specifies which interface to bind to when making an outgoing SMTP
25815 call. The value is an IP address, not an interface name such as
25816 &`eth0`&. Do not confuse this with the interface address that was used when a
25817 message was received, which is in &$received_ip_address$&, formerly known as
25818 &$interface_address$&. The name was changed to minimize confusion with the
25819 outgoing interface address. There is no variable that contains an outgoing
25820 interface address because, unless it is set by this option, its value is
25823 During the expansion of the &%interface%& option the variables &$host$& and
25824 &$host_address$& refer to the host to which a connection is about to be made
25825 during the expansion of the string. Forced expansion failure, or an empty
25826 string result causes the option to be ignored. Otherwise, after expansion, the
25827 string must be a list of IP addresses, colon-separated by default, but the
25828 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
25831 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
25833 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
25834 connection. If none of them are the correct type, the option is ignored. If
25835 &%interface%& is not set, or is ignored, the system's IP functions choose which
25836 interface to use if the host has more than one.
25839 .option keepalive smtp boolean true
25840 .cindex "keepalive" "on outgoing connection"
25841 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
25842 connections. When set, it causes the kernel to probe idle connections
25843 periodically, by sending packets with &"old"& sequence numbers. The other end
25844 of the connection should send a acknowledgment if the connection is still okay
25845 or a reset if the connection has been aborted. The reason for doing this is
25846 that it has the beneficial effect of freeing up certain types of connection
25847 that can get stuck when the remote host is disconnected without tidying up the
25848 TCP/IP call properly. The keepalive mechanism takes several hours to detect
25852 .option lmtp_ignore_quota smtp boolean false
25853 .cindex "LMTP" "ignoring quota errors"
25854 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
25855 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
25856 has advertised support for IGNOREQUOTA in its response to the LHLO command.
25858 .option max_rcpt smtp integer 100
25859 .cindex "RCPT" "maximum number of outgoing"
25860 This option limits the number of RCPT commands that are sent in a single
25861 SMTP message transaction. Each set of addresses is treated independently, and
25862 so can cause parallel connections to the same host if &%remote_max_parallel%&
25863 permits this. A value setting of zero disables the limit.
25867 .option message_linelength_limit smtp integer 998
25868 .cindex "line length" limit
25869 This option sets the maximum line length, in bytes, that the transport
25870 will send. Any messages with lines exceeding the given value
25871 will fail and a failure-DSN ("bounce") message will if possible be returned
25873 The default value is that defined by the SMTP standards.
25875 It is generally wise to also check in the data ACL so that messages
25876 received via SMTP can be refused without producing a bounce.
25880 .option multi_domain smtp boolean&!! true
25881 .vindex "&$domain$&"
25882 When this option is set, the &(smtp)& transport can handle a number of
25883 addresses containing a mixture of different domains provided they all resolve
25884 to the same list of hosts. Turning the option off restricts the transport to
25885 handling only one domain at a time. This is useful if you want to use
25886 &$domain$& in an expansion for the transport, because it is set only when there
25887 is a single domain involved in a remote delivery.
25889 It is expanded per-address and can depend on any of
25890 &$address_data$&, &$domain_data$&, &$local_part_data$&,
25891 &$host$&, &$host_address$& and &$host_port$&.
25894 If the connection is DANE-enabled then this option is ignored;
25895 only messages having the domain used for the DANE TLSA lookup are
25896 sent on the connection.
25899 .option port smtp string&!! "see below"
25900 .cindex "port" "sending TCP/IP"
25901 .cindex "TCP/IP" "setting outgoing port"
25902 This option specifies the TCP/IP port on the server to which Exim connects.
25903 &*Note:*& Do not confuse this with the port that was used when a message was
25904 received, which is in &$received_port$&, formerly known as &$interface_port$&.
25905 The name was changed to minimize confusion with the outgoing port. There is no
25906 variable that contains an outgoing port.
25908 If the value of this option begins with a digit it is taken as a port number;
25909 otherwise it is looked up using &[getservbyname()]&. The default value is
25911 but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"&
25912 and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
25913 If the expansion fails, or if a port number cannot be found, delivery
25916 Note that at least one Linux distribution has been seen failing
25917 to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
25921 .option protocol smtp string smtp
25922 .cindex "LMTP" "over TCP/IP"
25923 .cindex "ssmtp protocol" "outbound"
25924 .cindex "TLS" "SSL-on-connect outbound"
25926 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
25927 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
25928 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
25929 deliveries into closed message stores. Exim also has support for running LMTP
25930 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
25932 If this option is set to &"smtps"&, the default value for the &%port%& option
25933 changes to &"smtps"&, and the transport initiates TLS immediately after
25934 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
25935 The Internet standards bodies used to strongly discourage use of this mode,
25936 but as of RFC 8314 it is preferred over STARTTLS for message submission
25937 (as distinct from MTA-MTA communication).
25940 .option retry_include_ip_address smtp boolean&!! true
25941 Exim normally includes both the host name and the IP address in the key it
25942 constructs for indexing retry data after a temporary delivery failure. This
25943 means that when one of several IP addresses for a host is failing, it gets
25944 tried periodically (controlled by the retry rules), but use of the other IP
25945 addresses is not affected.
25947 However, in some dialup environments hosts are assigned a different IP address
25948 each time they connect. In this situation the use of the IP address as part of
25949 the retry key leads to undesirable behaviour. Setting this option false causes
25950 Exim to use only the host name.
25951 Since it is expanded it can be made to depend on the host or domain.
25954 .option serialize_hosts smtp "host list&!!" unset
25955 .cindex "serializing connections"
25956 .cindex "host" "serializing connections"
25957 Because Exim operates in a distributed manner, if several messages for the same
25958 host arrive at around the same time, more than one simultaneous connection to
25959 the remote host can occur. This is not usually a problem except when there is a
25960 slow link between the hosts. In that situation it may be helpful to restrict
25961 Exim to one connection at a time. This can be done by setting
25962 &%serialize_hosts%& to match the relevant hosts.
25964 .cindex "hints database" "serializing deliveries to a host"
25965 Exim implements serialization by means of a hints database in which a record is
25966 written whenever a process connects to one of the restricted hosts. The record
25967 is deleted when the connection is completed. Obviously there is scope for
25968 records to get left lying around if there is a system or program crash. To
25969 guard against this, Exim ignores any records that are more than six hours old.
25971 If you set up this kind of serialization, you should also arrange to delete the
25972 relevant hints database whenever your system reboots. The names of the files
25973 start with &_misc_& and they are kept in the &_spool/db_& directory. There
25974 may be one or two files, depending on the type of DBM in use. The same files
25975 are used for ETRN serialization.
25977 See also the &%max_parallel%& generic transport option.
25980 .option size_addition smtp integer 1024
25981 .cindex "SIZE" "ESMTP extension"
25982 .cindex "message" "size issue for transport filter"
25983 .cindex "size" "of message"
25984 .cindex "transport" "filter"
25985 .cindex "filter" "transport filter"
25986 If a remote SMTP server indicates that it supports the SIZE option of the
25987 MAIL command, Exim uses this to pass over the message size at the start of
25988 an SMTP transaction. It adds the value of &%size_addition%& to the value it
25989 sends, to allow for headers and other text that may be added during delivery by
25990 configuration options or in a transport filter. It may be necessary to increase
25991 this if a lot of text is added to messages.
25993 Alternatively, if the value of &%size_addition%& is set negative, it disables
25994 the use of the SIZE option altogether.
25997 .option socks_proxy smtp string&!! unset
25998 .cindex proxy SOCKS
25999 This option enables use of SOCKS proxies for connections made by the
26000 transport. For details see section &<<SECTproxySOCKS>>&.
26004 .option tls_alpn smtp string&!! unset
26005 .cindex TLS "Application Layer Protocol Names"
26007 .cindex ALPN "set name in client"
26008 If this option is set
26009 and the TLS library supports ALPN,
26010 the value given is used.
26012 As of writing no value has been standardised for email use.
26013 The authors suggest using &"smtp"&.
26018 .option tls_certificate smtp string&!! unset
26019 .cindex "TLS" "client certificate, location of"
26020 .cindex "certificate" "client, location of"
26022 .vindex "&$host_address$&"
26023 The value of this option must be the absolute path to a file which contains the
26024 client's certificate, for possible use when sending a message over an encrypted
26025 connection. The values of &$host$& and &$host_address$& are set to the name and
26026 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
26029 &*Note*&: This option must be set if you want Exim to be able to use a TLS
26030 certificate when sending messages as a client. The global option of the same
26031 name specifies the certificate for Exim as a server; it is not automatically
26032 assumed that the same certificate should be used when Exim is operating as a
26036 .option tls_crl smtp string&!! unset
26037 .cindex "TLS" "client certificate revocation list"
26038 .cindex "certificate" "revocation list for client"
26039 This option specifies a certificate revocation list. The expanded value must
26040 be the name of a file that contains a CRL in PEM format.
26043 .option tls_dh_min_bits smtp integer 1024
26044 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
26045 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
26046 key agreement is negotiated, the server will provide a large prime number
26047 for use. This option establishes the minimum acceptable size of that number.
26048 If the parameter offered by the server is too small, then the TLS handshake
26051 Only supported when using GnuTLS.
26054 .option tls_privatekey smtp string&!! unset
26055 .cindex "TLS" "client private key, location of"
26057 .vindex "&$host_address$&"
26058 The value of this option must be the absolute path to a file which contains the
26059 client's private key. This is used when sending a message over an encrypted
26060 connection using a client certificate. The values of &$host$& and
26061 &$host_address$& are set to the name and address of the server during the
26062 expansion. If this option is unset, or the expansion is forced to fail, or the
26063 result is an empty string, the private key is assumed to be in the same file as
26064 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
26067 .option tls_require_ciphers smtp string&!! unset
26068 .cindex "TLS" "requiring specific ciphers"
26069 .cindex "cipher" "requiring specific"
26071 .vindex "&$host_address$&"
26072 The value of this option must be a list of permitted cipher suites, for use
26073 when setting up an outgoing encrypted connection. (There is a global option of
26074 the same name for controlling incoming connections.) The values of &$host$& and
26075 &$host_address$& are set to the name and address of the server during the
26076 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
26077 is used in different ways by OpenSSL and GnuTLS (see sections
26078 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
26079 ciphers is a preference order.
26083 .option tls_resumption_hosts smtp "host list&!!" unset
26084 .cindex TLS resumption
26085 This option controls which connections to use the TLS resumption feature.
26086 See &<<SECTresumption>>& for details.
26091 .option tls_sni smtp string&!! unset
26092 .cindex "TLS" "Server Name Indication"
26094 .cindex SNI "setting in client"
26095 .vindex "&$tls_sni$&"
26096 If this option is set
26098 and the connection is not DANE-validated
26100 then it sets the $tls_out_sni variable and causes any
26101 TLS session to pass this value as the Server Name Indication extension to
26102 the remote side, which can be used by the remote side to select an appropriate
26103 certificate and private key for the session.
26105 See &<<SECTtlssni>>& for more information.
26107 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
26113 .option tls_tempfail_tryclear smtp boolean true
26114 .cindex "4&'xx'& responses" "to STARTTLS"
26115 When the server host is not in &%hosts_require_tls%&, and there is a problem in
26116 setting up a TLS session, this option determines whether or not Exim should try
26117 to deliver the message unencrypted. If it is set false, delivery to the
26118 current host is deferred; if there are other hosts, they are tried. If this
26119 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
26120 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
26121 TLS negotiation fails, Exim closes the current connection (because it is in an
26122 unknown state), opens a new one to the same host, and then tries the delivery
26126 .option tls_try_verify_hosts smtp "host list&!!" *
26127 .cindex "TLS" "server certificate verification"
26128 .cindex "certificate" "verification of server"
26129 This option gives a list of hosts for which, on encrypted connections,
26130 certificate verification will be tried but need not succeed.
26131 The &%tls_verify_certificates%& option must also be set.
26132 Note that unless the host is in this list
26133 TLS connections will be denied to hosts using self-signed certificates
26134 when &%tls_verify_certificates%& is matched.
26135 The &$tls_out_certificate_verified$& variable is set when
26136 certificate verification succeeds.
26139 .option tls_verify_cert_hostnames smtp "host list&!!" *
26140 .cindex "TLS" "server certificate hostname verification"
26141 .cindex "certificate" "verification of server"
26142 This option give a list of hosts for which,
26143 while verifying the server certificate,
26144 checks will be included on the host name
26145 (note that this will generally be the result of a DNS MX lookup)
26146 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
26147 limited to being the initial component of a 3-or-more component FQDN.
26149 There is no equivalent checking on client certificates.
26152 .option tls_verify_certificates smtp string&!! system
26153 .cindex "TLS" "server certificate verification"
26154 .cindex "certificate" "verification of server"
26156 .vindex "&$host_address$&"
26157 The value of this option must be either the
26159 or the absolute path to
26160 a file or directory containing permitted certificates for servers,
26161 for use when setting up an encrypted connection.
26163 The "system" value for the option will use a location compiled into the SSL library.
26164 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
26165 is taken as empty and an explicit location
26168 The use of a directory for the option value is not available for GnuTLS versions
26169 preceding 3.3.6 and a single file must be used.
26171 With OpenSSL the certificates specified
26173 either by file or directory
26174 are added to those given by the system default location.
26176 The values of &$host$& and
26177 &$host_address$& are set to the name and address of the server during the
26178 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
26180 For back-compatibility,
26181 if neither tls_verify_hosts nor tls_try_verify_hosts are set
26182 (a single-colon empty list counts as being set)
26183 and certificate verification fails the TLS connection is closed.
26186 .option tls_verify_hosts smtp "host list&!!" unset
26187 .cindex "TLS" "server certificate verification"
26188 .cindex "certificate" "verification of server"
26189 This option gives a list of hosts for which, on encrypted connections,
26190 certificate verification must succeed.
26191 The &%tls_verify_certificates%& option must also be set.
26192 If both this option and &%tls_try_verify_hosts%& are unset
26193 operation is as if this option selected all hosts.
26195 .option utf8_downconvert smtp integer&!! -1
26196 .cindex utf8 "address downconversion"
26197 .cindex i18n "utf8 address downconversion"
26198 If built with internationalization support,
26199 this option controls conversion of UTF-8 in message envelope addresses
26201 If, after expansion, the value is 1, 0, or -1 then this value overrides
26202 any value previously set for the message. Otherwise, any previously
26203 set value is used. To permit use of a previous value,
26204 set this option to an empty string.
26205 For details on the values see section &<<SECTi18nMTA>>&.
26210 .section "How the limits for the number of hosts to try are used" &&&
26212 .cindex "host" "maximum number to try"
26213 .cindex "limit" "hosts; maximum number tried"
26214 There are two options that are concerned with the number of hosts that are
26215 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
26216 &%hosts_max_try_hardlimit%&.
26219 The &%hosts_max_try%& option limits the number of hosts that are tried
26220 for a single delivery. However, despite the term &"host"& in its name, the
26221 option actually applies to each IP address independently. In other words, a
26222 multihomed host is treated as several independent hosts, just as it is for
26225 Many of the larger ISPs have multiple MX records which often point to
26226 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
26227 created as a result of routing one of these domains.
26229 Trying every single IP address on such a long list does not seem sensible; if
26230 several at the top of the list fail, it is reasonable to assume there is some
26231 problem that is likely to affect all of them. Roughly speaking, the value of
26232 &%hosts_max_try%& is the maximum number that are tried before deferring the
26233 delivery. However, the logic cannot be quite that simple.
26235 Firstly, IP addresses that are skipped because their retry times have not
26236 arrived do not count, and in addition, addresses that are past their retry
26237 limits are also not counted, even when they are tried. This means that when
26238 some IP addresses are past their retry limits, more than the value of
26239 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
26240 that all IP addresses are considered before timing out an email address (but
26241 see below for an exception).
26243 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
26244 list to see if there is a subsequent host with a different (higher valued) MX.
26245 If there is, that host is considered next, and the current IP address is used
26246 but not counted. This behaviour helps in the case of a domain with a retry rule
26247 that hardly ever delays any hosts, as is now explained:
26249 Consider the case of a long list of hosts with one MX value, and a few with a
26250 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
26251 hosts at the top of the list are tried at first. With the default retry rule,
26252 which specifies increasing retry times, the higher MX hosts are eventually
26253 tried when those at the top of the list are skipped because they have not
26254 reached their retry times.
26256 However, it is common practice to put a fixed short retry time on domains for
26257 large ISPs, on the grounds that their servers are rarely down for very long.
26258 Unfortunately, these are exactly the domains that tend to resolve to long lists
26259 of hosts. The short retry time means that the lowest MX hosts are tried every
26260 time. The attempts may be in a different order because of random sorting, but
26261 without the special MX check, the higher MX hosts would never be tried until
26262 all the lower MX hosts had timed out (which might be several days), because
26263 there are always some lower MX hosts that have reached their retry times. With
26264 the special check, Exim considers at least one IP address from each MX value at
26265 every delivery attempt, even if the &%hosts_max_try%& limit has already been
26268 The above logic means that &%hosts_max_try%& is not a hard limit, and in
26269 particular, Exim normally eventually tries all the IP addresses before timing
26270 out an email address. When &%hosts_max_try%& was implemented, this seemed a
26271 reasonable thing to do. Recently, however, some lunatic DNS configurations have
26272 been set up with hundreds of IP addresses for some domains. It can
26273 take a very long time indeed for an address to time out in these cases.
26275 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
26276 Exim never tries more than this number of IP addresses; if it hits this limit
26277 and they are all timed out, the email address is bounced, even though not all
26278 possible IP addresses have been tried.
26279 .ecindex IIDsmttra1
26280 .ecindex IIDsmttra2
26286 . ////////////////////////////////////////////////////////////////////////////
26287 . ////////////////////////////////////////////////////////////////////////////
26289 .chapter "Address rewriting" "CHAPrewrite"
26290 .scindex IIDaddrew "rewriting" "addresses"
26291 There are some circumstances in which Exim automatically rewrites domains in
26292 addresses. The two most common are when an address is given without a domain
26293 (referred to as an &"unqualified address"&) or when an address contains an
26294 abbreviated domain that is expanded by DNS lookup.
26296 Unqualified envelope addresses are accepted only for locally submitted
26297 messages, or for messages that are received from hosts matching
26298 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
26299 appropriate. Unqualified addresses in header lines are qualified if they are in
26300 locally submitted messages, or messages from hosts that are permitted to send
26301 unqualified envelope addresses. Otherwise, unqualified addresses in header
26302 lines are neither qualified nor rewritten.
26304 One situation in which Exim does &'not'& automatically rewrite a domain is
26305 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
26306 such a domain should be rewritten using the &"canonical"& name, and some MTAs
26307 do this. The new RFCs do not contain this suggestion.
26310 .section "Explicitly configured address rewriting" "SECID147"
26311 This chapter describes the rewriting rules that can be used in the
26312 main rewrite section of the configuration file, and also in the generic
26313 &%headers_rewrite%& option that can be set on any transport.
26315 Some people believe that configured address rewriting is a Mortal Sin.
26316 Others believe that life is not possible without it. Exim provides the
26317 facility; you do not have to use it.
26319 The main rewriting rules that appear in the &"rewrite"& section of the
26320 configuration file are applied to addresses in incoming messages, both envelope
26321 addresses and addresses in header lines. Each rule specifies the types of
26322 address to which it applies.
26324 Whether or not addresses in header lines are rewritten depends on the origin of
26325 the headers and the type of rewriting. Global rewriting, that is, rewriting
26326 rules from the rewrite section of the configuration file, is applied only to
26327 those headers that were received with the message. Header lines that are added
26328 by ACLs or by a system filter or by individual routers or transports (which
26329 are specific to individual recipient addresses) are not rewritten by the global
26332 Rewriting at transport time, by means of the &%headers_rewrite%& option,
26333 applies all headers except those added by routers and transports. That is, as
26334 well as the headers that were received with the message, it also applies to
26335 headers that were added by an ACL or a system filter.
26338 In general, rewriting addresses from your own system or domain has some
26339 legitimacy. Rewriting other addresses should be done only with great care and
26340 in special circumstances. The author of Exim believes that rewriting should be
26341 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
26342 Although it can sometimes be used as a routing tool, this is very strongly
26345 There are two commonly encountered circumstances where rewriting is used, as
26346 illustrated by these examples:
26349 The company whose domain is &'hitch.fict.example'& has a number of hosts that
26350 exchange mail with each other behind a firewall, but there is only a single
26351 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
26352 &'hitch.fict.example'& when sending mail off-site.
26354 A host rewrites the local parts of its own users so that, for example,
26355 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
26360 .section "When does rewriting happen?" "SECID148"
26361 .cindex "rewriting" "timing of"
26362 .cindex "&ACL;" "rewriting addresses in"
26363 Configured address rewriting can take place at several different stages of a
26364 message's processing.
26366 .vindex "&$sender_address$&"
26367 At the start of an ACL for MAIL, the sender address may have been rewritten
26368 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
26369 ordinary rewrite rules have yet been applied. If, however, the sender address
26370 is verified in the ACL, it is rewritten before verification, and remains
26371 rewritten thereafter. The subsequent value of &$sender_address$& is the
26372 rewritten address. This also applies if sender verification happens in a
26373 RCPT ACL. Otherwise, when the sender address is not verified, it is
26374 rewritten as soon as a message's header lines have been received.
26376 .vindex "&$domain$&"
26377 .vindex "&$local_part$&"
26378 Similarly, at the start of an ACL for RCPT, the current recipient's address
26379 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
26380 rewrite rules have yet been applied to it. However, the behaviour is different
26381 from the sender address when a recipient is verified. The address is rewritten
26382 for the verification, but the rewriting is not remembered at this stage. The
26383 value of &$local_part$& and &$domain$& after verification are always the same
26384 as they were before (that is, they contain the unrewritten &-- except for
26385 SMTP-time rewriting &-- address).
26387 As soon as a message's header lines have been received, all the envelope
26388 recipient addresses are permanently rewritten, and rewriting is also applied to
26389 the addresses in the header lines (if configured). This happens before adding
26390 any header lines that were specified in MAIL or RCPT ACLs, and
26391 .cindex "&[local_scan()]& function" "address rewriting; timing of"
26392 before the DATA ACL and &[local_scan()]& functions are run.
26394 When an address is being routed, either for delivery or for verification,
26395 rewriting is applied immediately to child addresses that are generated by
26396 redirection, unless &%no_rewrite%& is set on the router.
26398 .cindex "envelope from"
26399 .cindex "envelope sender" "rewriting at transport time"
26400 .cindex "rewriting" "at transport time"
26401 .cindex "header lines" "rewriting at transport time"
26402 At transport time, additional rewriting of addresses in header lines can be
26403 specified by setting the generic &%headers_rewrite%& option on a transport.
26404 This option contains rules that are identical in form to those in the rewrite
26405 section of the configuration file. They are applied to the original message
26406 header lines and any that were added by ACLs or a system filter. They are not
26407 applied to header lines that are added by routers or the transport.
26409 The outgoing envelope sender can be rewritten by means of the &%return_path%&
26410 transport option. However, it is not possible to rewrite envelope recipients at
26416 .section "Testing the rewriting rules that apply on input" "SECID149"
26417 .cindex "rewriting" "testing"
26418 .cindex "testing" "rewriting"
26419 Exim's input rewriting configuration appears in a part of the runtime
26420 configuration file headed by &"begin rewrite"&. It can be tested by the
26421 &%-brw%& command line option. This takes an address (which can be a full RFC
26422 2822 address) as its argument. The output is a list of how the address would be
26423 transformed by the rewriting rules for each of the different places it might
26424 appear in an incoming message, that is, for each different header and for the
26425 envelope sender and recipient fields. For example,
26427 exim -brw ph10@exim.workshop.example
26429 might produce the output
26431 sender: Philip.Hazel@exim.workshop.example
26432 from: Philip.Hazel@exim.workshop.example
26433 to: ph10@exim.workshop.example
26434 cc: ph10@exim.workshop.example
26435 bcc: ph10@exim.workshop.example
26436 reply-to: Philip.Hazel@exim.workshop.example
26437 env-from: Philip.Hazel@exim.workshop.example
26438 env-to: ph10@exim.workshop.example
26440 which shows that rewriting has been set up for that address when used in any of
26441 the source fields, but not when it appears as a recipient address. At the
26442 present time, there is no equivalent way of testing rewriting rules that are
26443 set for a particular transport.
26446 .section "Rewriting rules" "SECID150"
26447 .cindex "rewriting" "rules"
26448 The rewrite section of the configuration file consists of lines of rewriting
26451 <&'source pattern'&> <&'replacement'&> <&'flags'&>
26453 Rewriting rules that are specified for the &%headers_rewrite%& generic
26454 transport option are given as a colon-separated list. Each item in the list
26455 takes the same form as a line in the main rewriting configuration (except that
26456 any colons must be doubled, of course).
26458 The formats of source patterns and replacement strings are described below.
26459 Each is terminated by white space, unless enclosed in double quotes, in which
26460 case normal quoting conventions apply inside the quotes. The flags are single
26461 characters which may appear in any order. Spaces and tabs between them are
26464 For each address that could potentially be rewritten, the rules are scanned in
26465 order, and replacements for the address from earlier rules can themselves be
26466 replaced by later rules (but see the &"q"& and &"R"& flags).
26468 The order in which addresses are rewritten is undefined, may change between
26469 releases, and must not be relied on, with one exception: when a message is
26470 received, the envelope sender is always rewritten first, before any header
26471 lines are rewritten. For example, the replacement string for a rewrite of an
26472 address in &'To:'& must not assume that the message's address in &'From:'& has
26473 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
26474 that the envelope sender has already been rewritten.
26476 .vindex "&$domain$&"
26477 .vindex "&$local_part$&"
26478 The variables &$local_part$& and &$domain$& can be used in the replacement
26479 string to refer to the address that is being rewritten. Note that lookup-driven
26480 rewriting can be done by a rule of the form
26484 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
26485 refer to the address that is being rewritten.
26488 .section "Rewriting patterns" "SECID151"
26489 .cindex "rewriting" "patterns"
26490 .cindex "address list" "in a rewriting pattern"
26491 The source pattern in a rewriting rule is any item which may appear in an
26492 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
26493 single-item address list, which means that it is expanded before being tested
26494 against the address. As always, if you use a regular expression as a pattern,
26495 you must take care to escape dollar and backslash characters, or use the &`\N`&
26496 facility to suppress string expansion within the regular expression.
26498 Domains in patterns should be given in lower case. Local parts in patterns are
26499 case-sensitive. If you want to do case-insensitive matching of local parts, you
26500 can use a regular expression that starts with &`^(?i)`&.
26502 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
26503 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
26504 depending on the type of match which occurred. These can be used in the
26505 replacement string to insert portions of the incoming address. &$0$& always
26506 refers to the complete incoming address. When a regular expression is used, the
26507 numerical variables are set from its capturing subexpressions. For other types
26508 of pattern they are set as follows:
26511 If a local part or domain starts with an asterisk, the numerical variables
26512 refer to the character strings matched by asterisks, with &$1$& associated with
26513 the first asterisk, and &$2$& with the second, if present. For example, if the
26516 *queen@*.fict.example
26518 is matched against the address &'hearts-queen@wonderland.fict.example'& then
26520 $0 = hearts-queen@wonderland.fict.example
26524 Note that if the local part does not start with an asterisk, but the domain
26525 does, it is &$1$& that contains the wild part of the domain.
26528 If the domain part of the pattern is a partial lookup, the wild and fixed parts
26529 of the domain are placed in the next available numerical variables. Suppose,
26530 for example, that the address &'foo@bar.baz.example'& is processed by a
26531 rewriting rule of the form
26533 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
26535 and the key in the file that matches the domain is &`*.baz.example`&. Then
26541 If the address &'foo@baz.example'& is looked up, this matches the same
26542 wildcard file entry, and in this case &$2$& is set to the empty string, but
26543 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
26544 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
26545 whole domain. For non-partial domain lookups, no numerical variables are set.
26549 .section "Rewriting replacements" "SECID152"
26550 .cindex "rewriting" "replacements"
26551 If the replacement string for a rule is a single asterisk, addresses that
26552 match the pattern and the flags are &'not'& rewritten, and no subsequent
26553 rewriting rules are scanned. For example,
26555 hatta@lookingglass.fict.example * f
26557 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
26560 .vindex "&$domain$&"
26561 .vindex "&$local_part$&"
26562 If the replacement string is not a single asterisk, it is expanded, and must
26563 yield a fully qualified address. Within the expansion, the variables
26564 &$local_part$& and &$domain$& refer to the address that is being rewritten.
26565 Any letters they contain retain their original case &-- they are not lower
26566 cased. The numerical variables are set up according to the type of pattern that
26567 matched the address, as described above. If the expansion is forced to fail by
26568 the presence of &"fail"& in a conditional or lookup item, rewriting by the
26569 current rule is abandoned, but subsequent rules may take effect. Any other
26570 expansion failure causes the entire rewriting operation to be abandoned, and an
26571 entry written to the panic log.
26575 .section "Rewriting flags" "SECID153"
26576 There are three different kinds of flag that may appear on rewriting rules:
26579 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
26582 A flag that specifies rewriting at SMTP time: S.
26584 Flags that control the rewriting process: Q, q, R, w.
26587 For rules that are part of the &%headers_rewrite%& generic transport option,
26588 E, F, T, and S are not permitted.
26592 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
26594 .cindex "rewriting" "flags"
26595 If none of the following flag letters, nor the &"S"& flag (see section
26596 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
26597 and to both the sender and recipient fields of the envelope, whereas a
26598 transport-time rewriting rule just applies to all headers. Otherwise, the
26599 rewriting rule is skipped unless the relevant addresses are being processed.
26601 &`E`& rewrite all envelope fields
26602 &`F`& rewrite the envelope From field
26603 &`T`& rewrite the envelope To field
26604 &`b`& rewrite the &'Bcc:'& header
26605 &`c`& rewrite the &'Cc:'& header
26606 &`f`& rewrite the &'From:'& header
26607 &`h`& rewrite all headers
26608 &`r`& rewrite the &'Reply-To:'& header
26609 &`s`& rewrite the &'Sender:'& header
26610 &`t`& rewrite the &'To:'& header
26612 "All headers" means all of the headers listed above that can be selected
26613 individually, plus their &'Resent-'& versions. It does not include
26614 other headers such as &'Subject:'& etc.
26616 You should be particularly careful about rewriting &'Sender:'& headers, and
26617 restrict this to special known cases in your own domains.
26620 .section "The SMTP-time rewriting flag" "SECTrewriteS"
26621 .cindex "SMTP" "rewriting malformed addresses"
26622 .cindex "RCPT" "rewriting argument of"
26623 .cindex "MAIL" "rewriting argument of"
26624 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
26625 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
26626 before any other processing; even before syntax checking. The pattern is
26627 required to be a regular expression, and it is matched against the whole of the
26628 data for the command, including any surrounding angle brackets.
26630 .vindex "&$domain$&"
26631 .vindex "&$local_part$&"
26632 This form of rewrite rule allows for the handling of addresses that are not
26633 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
26634 input). Because the input is not required to be a syntactically valid address,
26635 the variables &$local_part$& and &$domain$& are not available during the
26636 expansion of the replacement string. The result of rewriting replaces the
26637 original address in the MAIL or RCPT command.
26640 .section "Flags controlling the rewriting process" "SECID155"
26641 There are four flags which control the way the rewriting process works. These
26642 take effect only when a rule is invoked, that is, when the address is of the
26643 correct type (matches the flags) and matches the pattern:
26646 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
26647 unqualified local part. It is qualified with &%qualify_recipient%&. In the
26648 absence of &"Q"& the rewritten address must always include a domain.
26650 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
26651 even if no rewriting actually takes place because of a &"fail"& in the
26652 expansion. The &"q"& flag is not effective if the address is of the wrong type
26653 (does not match the flags) or does not match the pattern.
26655 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
26656 address, up to ten times. It can be combined with the &"q"& flag, to stop
26657 rewriting once it fails to match (after at least one successful rewrite).
26659 .cindex "rewriting" "whole addresses"
26660 When an address in a header is rewritten, the rewriting normally applies only
26661 to the working part of the address, with any comments and RFC 2822 &"phrase"&
26662 left unchanged. For example, rewriting might change
26664 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
26668 From: Ford Prefect <prefectf@hitch.fict.example>
26671 Sometimes there is a need to replace the whole address item, and this can be
26672 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
26673 causes an address in a header line to be rewritten, the entire address is
26674 replaced, not just the working part. The replacement must be a complete RFC
26675 2822 address, including the angle brackets if necessary. If text outside angle
26676 brackets contains a character whose value is greater than 126 or less than 32
26677 (except for tab), the text is encoded according to RFC 2047. The character set
26678 is taken from &%headers_charset%&, which gets its default at build time.
26680 When the &"w"& flag is set on a rule that causes an envelope address to be
26681 rewritten, all but the working part of the replacement address is discarded.
26685 .section "Rewriting examples" "SECID156"
26686 Here is an example of the two common rewriting paradigms:
26688 *@*.hitch.fict.example $1@hitch.fict.example
26689 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
26690 {$value}fail}@hitch.fict.example bctfrF
26692 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
26693 the string expansion to fail if the lookup does not succeed. In this context it
26694 has the effect of leaving the original address unchanged, but Exim goes on to
26695 consider subsequent rewriting rules, if any, because the &"q"& flag is not
26696 present in that rule. An alternative to &"fail"& would be to supply &$1$&
26697 explicitly, which would cause the rewritten address to be the same as before,
26698 at the cost of a small bit of processing. Not supplying either of these is an
26699 error, since the rewritten address would then contain no local part.
26701 The first example above replaces the domain with a superior, more general
26702 domain. This may not be desirable for certain local parts. If the rule
26704 root@*.hitch.fict.example *
26706 were inserted before the first rule, rewriting would be suppressed for the
26707 local part &'root'& at any domain ending in &'hitch.fict.example'&.
26709 Rewriting can be made conditional on a number of tests, by making use of
26710 &${if$& in the expansion item. For example, to apply a rewriting rule only to
26711 messages that originate outside the local host:
26713 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
26714 {$1@hitch.fict.example}fail}"
26716 The replacement string is quoted in this example because it contains white
26719 .cindex "rewriting" "bang paths"
26720 .cindex "bang paths" "rewriting"
26721 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
26722 an address it treats it as an unqualified local part which it qualifies with
26723 the local qualification domain (if the source of the message is local or if the
26724 remote host is permitted to send unqualified addresses). Rewriting can
26725 sometimes be used to handle simple bang paths with a fixed number of
26726 components. For example, the rule
26728 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
26730 rewrites a two-component bang path &'host.name!user'& as the domain address
26731 &'user@host.name'&. However, there is a security implication in using this as
26732 a global rewriting rule for envelope addresses. It can provide a backdoor
26733 method for using your system as a relay, because the incoming addresses appear
26734 to be local. If the bang path addresses are received via SMTP, it is safer to
26735 use the &"S"& flag to rewrite them as they are received, so that relay checking
26736 can be done on the rewritten addresses.
26743 . ////////////////////////////////////////////////////////////////////////////
26744 . ////////////////////////////////////////////////////////////////////////////
26746 .chapter "Retry configuration" "CHAPretry"
26747 .scindex IIDretconf1 "retry" "configuration, description of"
26748 .scindex IIDregconf2 "configuration file" "retry section"
26749 The &"retry"& section of the runtime configuration file contains a list of
26750 retry rules that control how often Exim tries to deliver messages that cannot
26751 be delivered at the first attempt. If there are no retry rules (the section is
26752 empty or not present), there are no retries. In this situation, temporary
26753 errors are treated as permanent. The default configuration contains a single,
26754 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
26755 line option can be used to test which retry rule will be used for a given
26756 address, domain and error.
26758 The most common cause of retries is temporary failure to deliver to a remote
26759 host because the host is down, or inaccessible because of a network problem.
26760 Exim's retry processing in this case is applied on a per-host (strictly, per IP
26761 address) basis, not on a per-message basis. Thus, if one message has recently
26762 been delayed, delivery of a new message to the same host is not immediately
26763 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
26764 log selector is set, the message
26765 .cindex "retry" "time not reached"
26766 &"retry time not reached"& is written to the main log whenever a delivery is
26767 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
26768 the handling of errors during remote deliveries.
26770 Retry processing applies to routing as well as to delivering, except as covered
26771 in the next paragraph. The retry rules do not distinguish between these
26772 actions. It is not possible, for example, to specify different behaviour for
26773 failures to route the domain &'snark.fict.example'& and failures to deliver to
26774 the host &'snark.fict.example'&. I didn't think anyone would ever need this
26775 added complication, so did not implement it. However, although they share the
26776 same retry rule, the actual retry times for routing and transporting a given
26777 domain are maintained independently.
26779 When a delivery is not part of a queue run (typically an immediate delivery on
26780 receipt of a message), the routers are always run, and local deliveries are
26781 always attempted, even if retry times are set for them. This makes for better
26782 behaviour if one particular message is causing problems (for example, causing
26783 quota overflow, or provoking an error in a filter file). If such a delivery
26784 suffers a temporary failure, the retry data is updated as normal, and
26785 subsequent delivery attempts from queue runs occur only when the retry time for
26786 the local address is reached.
26788 .section "Changing retry rules" "SECID157"
26789 If you change the retry rules in your configuration, you should consider
26790 whether or not to delete the retry data that is stored in Exim's spool area in
26791 files with names like &_db/retry_&. Deleting any of Exim's hints files is
26792 always safe; that is why they are called &"hints"&.
26794 The hints retry data contains suggested retry times based on the previous
26795 rules. In the case of a long-running problem with a remote host, it might
26796 record the fact that the host has timed out. If your new rules increase the
26797 timeout time for such a host, you should definitely remove the old retry data
26798 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
26799 messages that it should now be retaining.
26803 .section "Format of retry rules" "SECID158"
26804 .cindex "retry" "rules"
26805 Each retry rule occupies one line and consists of three or four parts,
26806 separated by white space: a pattern, an error name, an optional list of sender
26807 addresses, and a list of retry parameters. The pattern and sender lists must be
26808 enclosed in double quotes if they contain white space. The rules are searched
26809 in order until one is found where the pattern, error name, and sender list (if
26810 present) match the failing host or address, the error that occurred, and the
26811 message's sender, respectively.
26814 The pattern is any single item that may appear in an address list (see section
26815 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
26816 which means that it is expanded before being tested against the address that
26817 has been delayed. A negated address list item is permitted. Address
26818 list processing treats a plain domain name as if it were preceded by &"*@"&,
26819 which makes it possible for many retry rules to start with just a domain. For
26822 lookingglass.fict.example * F,24h,30m;
26824 provides a rule for any address in the &'lookingglass.fict.example'& domain,
26827 alice@lookingglass.fict.example * F,24h,30m;
26829 applies only to temporary failures involving the local part &%alice%&.
26830 In practice, almost all rules start with a domain name pattern without a local
26833 .cindex "regular expressions" "in retry rules"
26834 &*Warning*&: If you use a regular expression in a retry rule pattern, it
26835 must match a complete address, not just a domain, because that is how regular
26836 expressions work in address lists.
26838 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
26839 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
26843 .section "Choosing which retry rule to use for address errors" "SECID159"
26844 When Exim is looking for a retry rule after a routing attempt has failed (for
26845 example, after a DNS timeout), each line in the retry configuration is tested
26846 against the complete address only if &%retry_use_local_part%& is set for the
26847 router. Otherwise, only the domain is used, except when matching against a
26848 regular expression, when the local part of the address is replaced with &"*"&.
26849 A domain on its own can match a domain pattern, or a pattern that starts with
26850 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
26851 &%check_local_user%& is true, and false for other routers.
26853 Similarly, when Exim is looking for a retry rule after a local delivery has
26854 failed (for example, after a mailbox full error), each line in the retry
26855 configuration is tested against the complete address only if
26856 &%retry_use_local_part%& is set for the transport (it defaults true for all
26859 .cindex "4&'xx'& responses" "retry rules for"
26860 However, when Exim is looking for a retry rule after a remote delivery attempt
26861 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
26862 whole address is always used as the key when searching the retry rules. The
26863 rule that is found is used to create a retry time for the combination of the
26864 failing address and the message's sender. It is the combination of sender and
26865 recipient that is delayed in subsequent queue runs until its retry time is
26866 reached. You can delay the recipient without regard to the sender by setting
26867 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
26868 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
26873 .section "Choosing which retry rule to use for host and message errors" &&&
26875 For a temporary error that is not related to an individual address (for
26876 example, a connection timeout), each line in the retry configuration is checked
26877 twice. First, the name of the remote host is used as a domain name (preceded by
26878 &"*@"& when matching a regular expression). If this does not match the line,
26879 the domain from the email address is tried in a similar fashion. For example,
26880 suppose the MX records for &'a.b.c.example'& are
26882 a.b.c.example MX 5 x.y.z.example
26886 and the retry rules are
26888 p.q.r.example * F,24h,30m;
26889 a.b.c.example * F,4d,45m;
26891 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
26892 first rule matches neither the host nor the domain, so Exim looks at the second
26893 rule. This does not match the host, but it does match the domain, so it is used
26894 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
26895 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
26896 first retry rule is used, because it matches the host.
26898 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
26899 first rule to determine retry times, but for all the other hosts for the domain
26900 &'a.b.c.example'&, the second rule is used. The second rule is also used if
26901 routing to &'a.b.c.example'& suffers a temporary failure.
26903 &*Note*&: The host name is used when matching the patterns, not its IP address.
26904 However, if a message is routed directly to an IP address without the use of a
26905 host name, for example, if a &(manualroute)& router contains a setting such as:
26907 route_list = *.a.example 192.168.34.23
26909 then the &"host name"& that is used when searching for a retry rule is the
26910 textual form of the IP address.
26912 .section "Retry rules for specific errors" "SECID161"
26913 .cindex "retry" "specific errors; specifying"
26914 The second field in a retry rule is the name of a particular error, or an
26915 asterisk, which matches any error. The errors that can be tested for are:
26918 .vitem &%auth_failed%&
26919 Authentication failed when trying to send to a host in the
26920 &%hosts_require_auth%& list in an &(smtp)& transport.
26922 .vitem &%data_4xx%&
26923 A 4&'xx'& error was received for an outgoing DATA command, either immediately
26924 after the command, or after sending the message's data.
26926 .vitem &%mail_4xx%&
26927 A 4&'xx'& error was received for an outgoing MAIL command.
26929 .vitem &%rcpt_4xx%&
26930 A 4&'xx'& error was received for an outgoing RCPT command.
26933 For the three 4&'xx'& errors, either the first or both of the x's can be given
26934 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
26935 recognize 452 errors given to RCPT commands for addresses in a certain domain,
26936 and have retries every ten minutes with a one-hour timeout, you could set up a
26937 retry rule of this form:
26939 the.domain.name rcpt_452 F,1h,10m
26941 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
26942 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
26945 .vitem &%lost_connection%&
26946 A server unexpectedly closed the SMTP connection. There may, of course,
26947 legitimate reasons for this (host died, network died), but if it repeats a lot
26948 for the same host, it indicates something odd.
26951 A DNS lookup for a host failed.
26952 Note that a &%dnslookup%& router will need to have matched
26953 its &%fail_defer_domains%& option for this retry type to be usable.
26954 Also note that a &%manualroute%& router will probably need
26955 its &%host_find_failed%& option set to &%defer%&.
26957 .vitem &%refused_MX%&
26958 A connection to a host obtained from an MX record was refused.
26960 .vitem &%refused_A%&
26961 A connection to a host not obtained from an MX record was refused.
26964 A connection was refused.
26966 .vitem &%timeout_connect_MX%&
26967 A connection attempt to a host obtained from an MX record timed out.
26969 .vitem &%timeout_connect_A%&
26970 A connection attempt to a host not obtained from an MX record timed out.
26972 .vitem &%timeout_connect%&
26973 A connection attempt timed out.
26975 .vitem &%timeout_MX%&
26976 There was a timeout while connecting or during an SMTP session with a host
26977 obtained from an MX record.
26979 .vitem &%timeout_A%&
26980 There was a timeout while connecting or during an SMTP session with a host not
26981 obtained from an MX record.
26984 There was a timeout while connecting or during an SMTP session.
26986 .vitem &%tls_required%&
26987 The server was required to use TLS (it matched &%hosts_require_tls%& in the
26988 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
26989 to STARTTLS, or there was a problem setting up the TLS connection.
26992 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26995 .vitem &%quota_%&<&'time'&>
26996 .cindex "quota" "error testing in retry rule"
26997 .cindex "retry" "quota error testing"
26998 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26999 transport, and the mailbox has not been accessed for <&'time'&>. For example,
27000 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
27004 .cindex "mailbox" "time of last read"
27005 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
27006 timeouts when the mailbox is full and is not being read by its owner. Ideally,
27007 it should be based on the last time that the user accessed the mailbox.
27008 However, it is not always possible to determine this. Exim uses the following
27012 If the mailbox is a single file, the time of last access (the &"atime"&) is
27013 used. As no new messages are being delivered (because the mailbox is over
27014 quota), Exim does not access the file, so this is the time of last user access.
27016 .cindex "maildir format" "time of last read"
27017 For a maildir delivery, the time of last modification of the &_new_&
27018 subdirectory is used. As the mailbox is over quota, no new files are created in
27019 the &_new_& subdirectory, because no new messages are being delivered. Any
27020 change to the &_new_& subdirectory is therefore assumed to be the result of an
27021 MUA moving a new message to the &_cur_& directory when it is first read. The
27022 time that is used is therefore the last time that the user read a new message.
27024 For other kinds of multi-file mailbox, the time of last access cannot be
27025 obtained, so a retry rule that uses this type of error field is never matched.
27028 The quota errors apply both to system-enforced quotas and to Exim's own quota
27029 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
27030 when a local delivery is deferred because a partition is full (the ENOSPC
27035 .section "Retry rules for specified senders" "SECID162"
27036 .cindex "retry" "rules; sender-specific"
27037 You can specify retry rules that apply only when the failing message has a
27038 specific sender. In particular, this can be used to define retry rules that
27039 apply only to bounce messages. The third item in a retry rule can be of this
27042 &`senders=`&<&'address list'&>
27044 The retry timings themselves are then the fourth item. For example:
27046 * rcpt_4xx senders=: F,1h,30m
27048 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
27049 host. If the address list contains white space, it must be enclosed in quotes.
27052 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
27054 &*Warning*&: This facility can be unhelpful if it is used for host errors
27055 (which do not depend on the recipient). The reason is that the sender is used
27056 only to match the retry rule. Once the rule has been found for a host error,
27057 its contents are used to set a retry time for the host, and this will apply to
27058 all messages, not just those with specific senders.
27060 When testing retry rules using &%-brt%&, you can supply a sender using the
27061 &%-f%& command line option, like this:
27063 exim -f "" -brt user@dom.ain
27065 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
27066 list is never matched.
27072 .section "Retry parameters" "SECID163"
27073 .cindex "retry" "parameters in rules"
27074 The third (or fourth, if a senders list is present) field in a retry rule is a
27075 sequence of retry parameter sets, separated by semicolons. Each set consists of
27077 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
27079 The letter identifies the algorithm for computing a new retry time; the cutoff
27080 time is the time beyond which this algorithm no longer applies, and the
27081 arguments vary the algorithm's action. The cutoff time is measured from the
27082 time that the first failure for the domain (combined with the local part if
27083 relevant) was detected, not from the time the message was received.
27085 .cindex "retry" "algorithms"
27086 .cindex "retry" "fixed intervals"
27087 .cindex "retry" "increasing intervals"
27088 .cindex "retry" "random intervals"
27089 The available algorithms are:
27092 &'F'&: retry at fixed intervals. There is a single time parameter specifying
27095 &'G'&: retry at geometrically increasing intervals. The first argument
27096 specifies a starting value for the interval, and the second a multiplier, which
27097 is used to increase the size of the interval at each retry.
27099 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
27100 retry, the previous interval is multiplied by the factor in order to get a
27101 maximum for the next interval. The minimum interval is the first argument of
27102 the parameter, and an actual interval is chosen randomly between them. Such a
27103 rule has been found to be helpful in cluster configurations when all the
27104 members of the cluster restart at once, and may therefore synchronize their
27105 queue processing times.
27108 When computing the next retry time, the algorithm definitions are scanned in
27109 order until one whose cutoff time has not yet passed is reached. This is then
27110 used to compute a new retry time that is later than the current time. In the
27111 case of fixed interval retries, this simply means adding the interval to the
27112 current time. For geometrically increasing intervals, retry intervals are
27113 computed from the rule's parameters until one that is greater than the previous
27114 interval is found. The main configuration variable
27115 .cindex "limit" "retry interval"
27116 .cindex "retry" "interval, maximum"
27117 .oindex "&%retry_interval_max%&"
27118 &%retry_interval_max%& limits the maximum interval between retries. It
27119 cannot be set greater than &`24h`&, which is its default value.
27121 A single remote domain may have a number of hosts associated with it, and each
27122 host may have more than one IP address. Retry algorithms are selected on the
27123 basis of the domain name, but are applied to each IP address independently. If,
27124 for example, a host has two IP addresses and one is unusable, Exim will
27125 generate retry times for it and will not try to use it until its next retry
27126 time comes. Thus the good IP address is likely to be tried first most of the
27129 .cindex "hints database" "use for retrying"
27130 Retry times are hints rather than promises. Exim does not make any attempt to
27131 run deliveries exactly at the computed times. Instead, a queue runner process
27132 starts delivery processes for delayed messages periodically, and these attempt
27133 new deliveries only for those addresses that have passed their next retry time.
27134 If a new message arrives for a deferred address, an immediate delivery attempt
27135 occurs only if the address has passed its retry time. In the absence of new
27136 messages, the minimum time between retries is the interval between queue runner
27137 processes. There is not much point in setting retry times of five minutes if
27138 your queue runners happen only once an hour, unless there are a significant
27139 number of incoming messages (which might be the case on a system that is
27140 sending everything to a smart host, for example).
27142 The data in the retry hints database can be inspected by using the
27143 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
27144 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
27145 &'exinext'& utility script can be used to find out what the next retry times
27146 are for the hosts associated with a particular mail domain, and also for local
27147 deliveries that have been deferred.
27150 .section "Retry rule examples" "SECID164"
27151 Here are some example retry rules:
27153 alice@wonderland.fict.example quota_5d F,7d,3h
27154 wonderland.fict.example quota_5d
27155 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
27156 lookingglass.fict.example * F,24h,30m;
27157 * refused_A F,2h,20m;
27158 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
27160 The first rule sets up special handling for mail to
27161 &'alice@wonderland.fict.example'& when there is an over-quota error and the
27162 mailbox has not been read for at least 5 days. Retries continue every three
27163 hours for 7 days. The second rule handles over-quota errors for all other local
27164 parts at &'wonderland.fict.example'&; the absence of a local part has the same
27165 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
27166 fail are bounced immediately if the mailbox has not been read for at least 5
27169 The third rule handles all other errors at &'wonderland.fict.example'&; retries
27170 happen every 15 minutes for an hour, then with geometrically increasing
27171 intervals until two days have passed since a delivery first failed. After the
27172 first hour there is a delay of one hour, then two hours, then four hours, and
27173 so on (this is a rather extreme example).
27175 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
27176 They happen every 30 minutes for 24 hours only. The remaining two rules handle
27177 all other domains, with special action for connection refusal from hosts that
27178 were not obtained from an MX record.
27180 The final rule in a retry configuration should always have asterisks in the
27181 first two fields so as to provide a general catch-all for any addresses that do
27182 not have their own special handling. This example tries every 15 minutes for 2
27183 hours, then with intervals starting at one hour and increasing by a factor of
27184 1.5 up to 16 hours, then every 8 hours up to 5 days.
27188 .section "Timeout of retry data" "SECID165"
27189 .cindex "timeout" "of retry data"
27190 .oindex "&%retry_data_expire%&"
27191 .cindex "hints database" "data expiry"
27192 .cindex "retry" "timeout of data"
27193 Exim timestamps the data that it writes to its retry hints database. When it
27194 consults the data during a delivery it ignores any that is older than the value
27195 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
27196 been tried for 7 days, Exim will try to deliver to it immediately a message
27197 arrives, and if that fails, it will calculate a retry time as if it were
27198 failing for the first time.
27200 This improves the behaviour for messages routed to rarely-used hosts such as MX
27201 backups. If such a host was down at one time, and happens to be down again when
27202 Exim tries a month later, using the old retry data would imply that it had been
27203 down all the time, which is not a justified assumption.
27205 If a host really is permanently dead, this behaviour causes a burst of retries
27206 every now and again, but only if messages routed to it are rare. If there is a
27207 message at least once every 7 days the retry data never expires.
27212 .section "Long-term failures" "SECID166"
27213 .cindex "delivery failure, long-term"
27214 .cindex "retry" "after long-term failure"
27215 Special processing happens when an email address has been failing for so long
27216 that the cutoff time for the last algorithm is reached. For example, using the
27217 default retry rule:
27219 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
27221 the cutoff time is four days. Reaching the retry cutoff is independent of how
27222 long any specific message has been failing; it is the length of continuous
27223 failure for the recipient address that counts.
27225 When the cutoff time is reached for a local delivery, or for all the IP
27226 addresses associated with a remote delivery, a subsequent delivery failure
27227 causes Exim to give up on the address, and a bounce message is generated.
27228 In order to cater for new messages that use the failing address, a next retry
27229 time is still computed from the final algorithm, and is used as follows:
27231 For local deliveries, one delivery attempt is always made for any subsequent
27232 messages. If this delivery fails, the address fails immediately. The
27233 post-cutoff retry time is not used.
27235 .cindex "final cutoff" "retries, controlling"
27236 .cindex retry "final cutoff"
27237 If the delivery is remote, there are two possibilities, controlled by the
27238 .oindex "&%delay_after_cutoff%&"
27239 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
27240 default. Until the post-cutoff retry time for one of the IP addresses,
27241 as set by the &%retry_data_expire%& option, is
27242 reached, the failing email address is bounced immediately, without a delivery
27243 attempt taking place. After that time, one new delivery attempt is made to
27244 those IP addresses that are past their retry times, and if that still fails,
27245 the address is bounced and new retry times are computed.
27247 In other words, when all the hosts for a given email address have been failing
27248 for a long time, Exim bounces rather then defers until one of the hosts' retry
27249 times is reached. Then it tries once, and bounces if that attempt fails. This
27250 behaviour ensures that few resources are wasted in repeatedly trying to deliver
27251 to a broken destination, but if the host does recover, Exim will eventually
27254 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
27255 addresses are past their final cutoff time, Exim tries to deliver to those IP
27256 addresses that have not been tried since the message arrived. If there are
27257 no suitable IP addresses, or if they all fail, the address is bounced. In other
27258 words, it does not delay when a new message arrives, but tries the expired
27259 addresses immediately, unless they have been tried since the message arrived.
27260 If there is a continuous stream of messages for the failing domains, setting
27261 &%delay_after_cutoff%& false means that there will be many more attempts to
27262 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
27265 .section "Deliveries that work intermittently" "SECID167"
27266 .cindex "retry" "intermittently working deliveries"
27267 Some additional logic is needed to cope with cases where a host is
27268 intermittently available, or when a message has some attribute that prevents
27269 its delivery when others to the same address get through. In this situation,
27270 because some messages are successfully delivered, the &"retry clock"& for the
27271 host or address keeps getting reset by the successful deliveries, and so
27272 failing messages remain in the queue for ever because the cutoff time is never
27275 Two exceptional actions are applied to prevent this happening. The first
27276 applies to errors that are related to a message rather than a remote host.
27277 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
27278 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
27279 commands, and quota failures. For this type of error, if a message's arrival
27280 time is earlier than the &"first failed"& time for the error, the earlier time
27281 is used when scanning the retry rules to decide when to try next and when to
27282 time out the address.
27284 The exceptional second action applies in all cases. If a message has been on
27285 the queue for longer than the cutoff time of any applicable retry rule for a
27286 given address, a delivery is attempted for that address, even if it is not yet
27287 time, and if this delivery fails, the address is timed out. A new retry time is
27288 not computed in this case, so that other messages for the same address are
27289 considered immediately.
27290 .ecindex IIDretconf1
27291 .ecindex IIDregconf2
27298 . ////////////////////////////////////////////////////////////////////////////
27299 . ////////////////////////////////////////////////////////////////////////////
27301 .chapter "SMTP authentication" "CHAPSMTPAUTH"
27302 .scindex IIDauthconf1 "SMTP" "authentication configuration"
27303 .scindex IIDauthconf2 "authentication"
27304 The &"authenticators"& section of Exim's runtime configuration is concerned
27305 with SMTP authentication. This facility is an extension to the SMTP protocol,
27306 described in RFC 2554, which allows a client SMTP host to authenticate itself
27307 to a server. This is a common way for a server to recognize clients that are
27308 permitted to use it as a relay. SMTP authentication is not of relevance to the
27309 transfer of mail between servers that have no managerial connection with each
27313 The name of an authenticator is limited to be &drivernamemax; ASCII characters long;
27314 prior to Exim 4.95 names would be silently truncated at this length, but now
27318 .cindex "AUTH" "description of"
27319 .cindex "ESMTP extensions" AUTH
27320 Very briefly, the way SMTP authentication works is as follows:
27323 The server advertises a number of authentication &'mechanisms'& in response to
27324 the client's EHLO command.
27326 The client issues an AUTH command, naming a specific mechanism. The command
27327 may, optionally, contain some authentication data.
27329 The server may issue one or more &'challenges'&, to which the client must send
27330 appropriate responses. In simple authentication mechanisms, the challenges are
27331 just prompts for user names and passwords. The server does not have to issue
27332 any challenges &-- in some mechanisms the relevant data may all be transmitted
27333 with the AUTH command.
27335 The server either accepts or denies authentication.
27337 If authentication succeeds, the client may optionally make use of the AUTH
27338 option on the MAIL command to pass an authenticated sender in subsequent
27339 mail transactions. Authentication lasts for the remainder of the SMTP
27342 If authentication fails, the client may give up, or it may try a different
27343 authentication mechanism, or it may try transferring mail over the
27344 unauthenticated connection.
27347 If you are setting up a client, and want to know which authentication
27348 mechanisms the server supports, you can use Telnet to connect to port 25 (the
27349 SMTP port) on the server, and issue an EHLO command. The response to this
27350 includes the list of supported mechanisms. For example:
27352 &`$ `&&*&`telnet server.example 25`&*&
27353 &`Trying 192.168.34.25...`&
27354 &`Connected to server.example.`&
27355 &`Escape character is '^]'.`&
27356 &`220 server.example ESMTP Exim 4.20 ...`&
27357 &*&`ehlo client.example`&*&
27358 &`250-server.example Hello client.example [10.8.4.5]`&
27359 &`250-SIZE 52428800`&
27364 The second-last line of this example output shows that the server supports
27365 authentication using the PLAIN mechanism. In Exim, the different authentication
27366 mechanisms are configured by specifying &'authenticator'& drivers. Like the
27367 routers and transports, which authenticators are included in the binary is
27368 controlled by build-time definitions. The following are currently available,
27369 included by setting
27372 AUTH_CYRUS_SASL=yes
27376 AUTH_HEIMDAL_GSSAPI=yes
27381 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
27382 authentication mechanism (RFC 2195), and the second provides an interface to
27383 the Cyrus SASL authentication library.
27384 The third is an interface to Dovecot's authentication system, delegating the
27385 work via a socket interface.
27386 The fourth provides for negotiation of authentication done via non-SMTP means,
27387 as defined by RFC 4422 Appendix A.
27388 The fifth provides an interface to the GNU SASL authentication library, which
27389 provides mechanisms but typically not data sources.
27390 The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
27391 supporting setting a server keytab.
27392 The seventh can be configured to support
27393 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
27394 not formally documented, but used by several MUAs.
27395 The eighth authenticator
27396 supports Microsoft's &'Secure Password Authentication'& mechanism.
27397 The last is an Exim authenticator but not an SMTP one;
27398 instead it can use information from a TLS negotiation.
27400 The authenticators are configured using the same syntax as other drivers (see
27401 section &<<SECTfordricon>>&). If no authenticators are required, no
27402 authentication section need be present in the configuration file. Each
27403 authenticator can in principle have both server and client functions. When Exim
27404 is receiving SMTP mail, it is acting as a server; when it is sending out
27405 messages over SMTP, it is acting as a client. Authenticator configuration
27406 options are provided for use in both these circumstances.
27408 To make it clear which options apply to which situation, the prefixes
27409 &%server_%& and &%client_%& are used on option names that are specific to
27410 either the server or the client function, respectively. Server and client
27411 functions are disabled if none of their options are set. If an authenticator is
27412 to be used for both server and client functions, a single definition, using
27413 both sets of options, is required. For example:
27417 public_name = CRAM-MD5
27418 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
27420 client_secret = secret2
27422 The &%server_%& option is used when Exim is acting as a server, and the
27423 &%client_%& options when it is acting as a client.
27425 Descriptions of the individual authenticators are given in subsequent chapters.
27426 The remainder of this chapter covers the generic options for the
27427 authenticators, followed by general discussion of the way authentication works
27430 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
27431 per-mechanism basis. Please read carefully to determine which variables hold
27432 account labels such as usercodes and which hold passwords or other
27433 authenticating data.
27435 Note that some mechanisms support two different identifiers for accounts: the
27436 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
27437 and &'authz'& are commonly encountered. The American spelling is standard here.
27438 Conceptually, authentication data such as passwords are tied to the identifier
27439 used to authenticate; servers may have rules to permit one user to act as a
27440 second user, so that after login the session is treated as though that second
27441 user had logged in. That second user is the &'authorization id'&. A robust
27442 configuration might confirm that the &'authz'& field is empty or matches the
27443 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
27444 as verified data, the &'authz'& as an unverified request which the server might
27447 A &'realm'& is a text string, typically a domain name, presented by a server
27448 to a client to help it select an account and credentials to use. In some
27449 mechanisms, the client and server provably agree on the realm, but clients
27450 typically can not treat the realm as secure data to be blindly trusted.
27454 .section "Generic options for authenticators" "SECID168"
27455 .cindex "authentication" "generic options"
27456 .cindex "options" "generic; for authenticators"
27458 .option client_condition authenticators string&!! unset
27459 When Exim is authenticating as a client, it skips any authenticator whose
27460 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
27461 used, for example, to skip plain text authenticators when the connection is not
27462 encrypted by a setting such as:
27464 client_condition = ${if !eq{$tls_out_cipher}{}}
27468 .option client_set_id authenticators string&!! unset
27469 When client authentication succeeds, this condition is expanded; the
27470 result is used in the log lines for outbound messages.
27471 Typically it will be the user name used for authentication.
27474 .option driver authenticators string unset
27475 This option must always be set. It specifies which of the available
27476 authenticators is to be used.
27479 .option public_name authenticators string unset
27480 This option specifies the name of the authentication mechanism that the driver
27481 implements, and by which it is known to the outside world. These names should
27482 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
27483 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
27484 defaults to the driver's instance name.
27487 .option server_advertise_condition authenticators string&!! unset
27488 When a server is about to advertise an authentication mechanism, the condition
27489 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
27490 mechanism is not advertised.
27491 If the expansion fails, the mechanism is not advertised. If the failure was not
27492 forced, and was not caused by a lookup defer, the incident is logged.
27493 See section &<<SECTauthexiser>>& below for further discussion.
27496 .option server_condition authenticators string&!! unset
27497 This option must be set for a &%plaintext%& server authenticator, where it
27498 is used directly to control authentication. See section &<<SECTplainserver>>&
27501 For the &(gsasl)& authenticator, this option is required for various
27502 mechanisms; see chapter &<<CHAPgsasl>>& for details.
27504 For the other authenticators, &%server_condition%& can be used as an additional
27505 authentication or authorization mechanism that is applied after the other
27506 authenticator conditions succeed. If it is set, it is expanded when the
27507 authenticator would otherwise return a success code. If the expansion is forced
27508 to fail, authentication fails. Any other expansion failure causes a temporary
27509 error code to be returned. If the result of a successful expansion is an empty
27510 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27511 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
27512 other result, a temporary error code is returned, with the expanded string as
27516 .option server_debug_print authenticators string&!! unset
27517 If this option is set and authentication debugging is enabled (see the &%-d%&
27518 command line option), the string is expanded and included in the debugging
27519 output when the authenticator is run as a server. This can help with checking
27520 out the values of variables.
27521 If expansion of the string fails, the error message is written to the debugging
27522 output, and Exim carries on processing.
27525 .option server_set_id authenticators string&!! unset
27526 .vindex "&$authenticated_id$&"
27527 .vindex "&$authenticated_fail_id$&"
27528 When an Exim server successfully authenticates a client, this string is
27529 expanded using data from the authentication, and preserved for any incoming
27530 messages in the variable &$authenticated_id$&. It is also included in the log
27531 lines for incoming messages. For example, a user/password authenticator
27532 configuration might preserve the user name that was used to authenticate, and
27533 refer to it subsequently during delivery of the message.
27534 On a failing authentication the expansion result is instead saved in
27535 the &$authenticated_fail_id$& variable.
27536 If expansion fails, the option is ignored.
27539 .option server_mail_auth_condition authenticators string&!! unset
27540 This option allows a server to discard authenticated sender addresses supplied
27541 as part of MAIL commands in SMTP connections that are authenticated by the
27542 driver on which &%server_mail_auth_condition%& is set. The option is not used
27543 as part of the authentication process; instead its (unexpanded) value is
27544 remembered for later use.
27545 How it is used is described in the following section.
27551 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
27552 .cindex "authentication" "sender; authenticated"
27553 .cindex "AUTH" "on MAIL command"
27554 When a client supplied an AUTH= item on a MAIL command, Exim applies
27555 the following checks before accepting it as the authenticated sender of the
27559 If the connection is not using extended SMTP (that is, HELO was used rather
27560 than EHLO), the use of AUTH= is a syntax error.
27562 If the value of the AUTH= parameter is &"<>"&, it is ignored.
27564 .vindex "&$authenticated_sender$&"
27565 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
27566 running, the value of &$authenticated_sender$& is set to the value obtained
27567 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
27568 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
27569 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
27570 given for the MAIL command.
27572 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
27573 is accepted and placed in &$authenticated_sender$& only if the client has
27576 If the AUTH= value was accepted by either of the two previous rules, and
27577 the client has authenticated, and the authenticator has a setting for the
27578 &%server_mail_auth_condition%&, the condition is checked at this point. The
27579 valued that was saved from the authenticator is expanded. If the expansion
27580 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
27581 &$authenticated_sender$& is deleted. If the expansion yields any other value,
27582 the value of &$authenticated_sender$& is retained and passed on with the
27587 When &$authenticated_sender$& is set for a message, it is passed on to other
27588 hosts to which Exim authenticates as a client. Do not confuse this value with
27589 &$authenticated_id$&, which is a string obtained from the authentication
27590 process, and which is not usually a complete email address.
27592 .vindex "&$sender_address$&"
27593 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
27594 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
27595 therefore make use of &$authenticated_sender$&. The converse is not true: the
27596 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
27601 .section "Authentication on an Exim server" "SECTauthexiser"
27602 .cindex "authentication" "on an Exim server"
27603 When Exim receives an EHLO command, it advertises the public names of those
27604 authenticators that are configured as servers, subject to the following
27608 The client host must match &%auth_advertise_hosts%& (default *).
27610 If the &%server_advertise_condition%& option is set, its expansion must not
27611 yield the empty string, &"0"&, &"no"&, or &"false"&.
27614 The order in which the authenticators are defined controls the order in which
27615 the mechanisms are advertised.
27617 Some mail clients (for example, some versions of Netscape) require the user to
27618 provide a name and password for authentication whenever AUTH is advertised,
27619 even though authentication may not in fact be needed (for example, Exim may be
27620 set up to allow unconditional relaying from the client by an IP address check).
27621 You can make such clients more friendly by not advertising AUTH to them.
27622 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
27623 that runs for RCPT) to relay without authentication, you should set
27625 auth_advertise_hosts = ! 10.9.8.0/24
27627 so that no authentication mechanisms are advertised to them.
27629 The &%server_advertise_condition%& controls the advertisement of individual
27630 authentication mechanisms. For example, it can be used to restrict the
27631 advertisement of a particular mechanism to encrypted connections, by a setting
27634 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
27636 .vindex "&$tls_in_cipher$&"
27637 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
27638 yields &"yes"&, which allows the advertisement to happen.
27640 When an Exim server receives an AUTH command from a client, it rejects it
27641 immediately if AUTH was not advertised in response to an earlier EHLO
27642 command. This is the case if
27645 The client host does not match &%auth_advertise_hosts%&; or
27647 No authenticators are configured with server options; or
27649 Expansion of &%server_advertise_condition%& blocked the advertising of all the
27650 server authenticators.
27654 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
27655 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
27656 AUTH is accepted from any client host.
27658 If AUTH is not rejected by the ACL, Exim searches its configuration for a
27659 server authentication mechanism that was advertised in response to EHLO and
27660 that matches the one named in the AUTH command. If it finds one, it runs
27661 the appropriate authentication protocol, and authentication either succeeds or
27662 fails. If there is no matching advertised mechanism, the AUTH command is
27663 rejected with a 504 error.
27665 .vindex "&$received_protocol$&"
27666 .vindex "&$sender_host_authenticated$&"
27667 When a message is received from an authenticated host, the value of
27668 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
27669 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
27670 public name) of the authenticator driver that successfully authenticated the
27671 client from which the message was received. This variable is empty if there was
27672 no successful authentication.
27674 .cindex authentication "expansion item"
27675 Successful authentication sets up information used by the
27676 &%authresults%& expansion item.
27681 .section "Testing server authentication" "SECID169"
27682 .cindex "authentication" "testing a server"
27683 .cindex "AUTH" "testing a server"
27684 .cindex "base64 encoding" "creating authentication test data"
27685 Exim's &%-bh%& option can be useful for testing server authentication
27686 configurations. The data for the AUTH command has to be sent using base64
27687 encoding. A quick way to produce such data for testing is the following Perl
27691 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
27693 .cindex "binary zero" "in authentication data"
27694 This interprets its argument as a Perl string, and then encodes it. The
27695 interpretation as a Perl string allows binary zeros, which are required for
27696 some kinds of authentication, to be included in the data. For example, a
27697 command line to run this script on such data might be
27699 encode '\0user\0password'
27701 Note the use of single quotes to prevent the shell interpreting the
27702 backslashes, so that they can be interpreted by Perl to specify characters
27703 whose code value is zero.
27705 &*Warning 1*&: If either of the user or password strings starts with an octal
27706 digit, you must use three zeros instead of one after the leading backslash. If
27707 you do not, the octal digit that starts your string will be incorrectly
27708 interpreted as part of the code for the first character.
27710 &*Warning 2*&: If there are characters in the strings that Perl interprets
27711 specially, you must use a Perl escape to prevent them being misinterpreted. For
27712 example, a command such as
27714 encode '\0user@domain.com\0pas$$word'
27716 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
27718 If you have the &%mimencode%& command installed, another way to produce
27719 base64-encoded strings is to run the command
27721 echo -e -n `\0user\0password' | mimencode
27723 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
27724 in the argument, and the &%-n%& option specifies no newline at the end of its
27725 output. However, not all versions of &%echo%& recognize these options, so you
27726 should check your version before relying on this suggestion.
27730 .section "Authentication by an Exim client" "SECID170"
27731 .cindex "authentication" "on an Exim client"
27732 The &(smtp)& transport has two options called &%hosts_require_auth%& and
27733 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
27734 announces support for authentication, and the host matches an entry in either
27735 of these options, Exim (as a client) tries to authenticate as follows:
27738 For each authenticator that is configured as a client, in the order in which
27739 they are defined in the configuration, it searches the authentication
27740 mechanisms announced by the server for one whose name matches the public name
27741 of the authenticator.
27744 .vindex "&$host_address$&"
27745 When it finds one that matches, it runs the authenticator's client code. The
27746 variables &$host$& and &$host_address$& are available for any string expansions
27747 that the client might do. They are set to the server's name and IP address. If
27748 any expansion is forced to fail, the authentication attempt is abandoned, and
27749 Exim moves on to the next authenticator. Otherwise an expansion failure causes
27750 delivery to be deferred.
27752 If the result of the authentication attempt is a temporary error or a timeout,
27753 Exim abandons trying to send the message to the host for the moment. It will
27754 try again later. If there are any backup hosts available, they are tried in the
27757 If the response to authentication is a permanent error (5&'xx'& code), Exim
27758 carries on searching the list of authenticators and tries another one if
27759 possible. If all authentication attempts give permanent errors, or if there are
27760 no attempts because no mechanisms match (or option expansions force failure),
27761 what happens depends on whether the host matches &%hosts_require_auth%& or
27762 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
27763 delivery is deferred. The error can be detected in the retry rules, and thereby
27764 turned into a permanent error if you wish. In the second case, Exim tries to
27765 deliver the message unauthenticated.
27768 Note that the hostlist test for whether to do authentication can be
27769 confused if name-IP lookups change between the time the peer is decided
27770 upon and the time that the transport runs. For example, with a manualroute
27771 router given a host name, and with DNS "round-robin" used by that name: if
27772 the local resolver cache times out between the router and the transport
27773 running, the transport may get an IP for the name for its authentication
27774 check which does not match the connection peer IP.
27775 No authentication will then be done, despite the names being identical.
27777 For such cases use a separate transport which always authenticates.
27779 .cindex "AUTH" "on MAIL command"
27780 When Exim has authenticated itself to a remote server, it adds the AUTH
27781 parameter to the MAIL commands it sends, if it has an authenticated sender for
27782 the message. If the message came from a remote host, the authenticated sender
27783 is the one that was receiving on an incoming MAIL command, provided that the
27784 incoming connection was authenticated and the &%server_mail_auth%& condition
27785 allowed the authenticated sender to be retained. If a local process calls Exim
27786 to send a message, the sender address that is built from the login name and
27787 &%qualify_domain%& is treated as authenticated. However, if the
27788 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
27789 the authenticated sender that was received with the message.
27790 .ecindex IIDauthconf1
27791 .ecindex IIDauthconf2
27798 . ////////////////////////////////////////////////////////////////////////////
27799 . ////////////////////////////////////////////////////////////////////////////
27801 .chapter "The plaintext authenticator" "CHAPplaintext"
27802 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
27803 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
27804 The &(plaintext)& authenticator can be configured to support the PLAIN and
27805 LOGIN authentication mechanisms, both of which transfer authentication data as
27806 plain (unencrypted) text (though base64 encoded). The use of plain text is a
27807 security risk; you are strongly advised to insist on the use of SMTP encryption
27808 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
27809 use unencrypted plain text, you should not use the same passwords for SMTP
27810 connections as you do for login accounts.
27812 .section "Avoiding cleartext use" "SECTplain_TLS"
27813 The following generic option settings will disable &(plaintext)& authenticators when
27814 TLS is not being used:
27816 server_advertise_condition = ${if def:tls_in_cipher }
27817 client_condition = ${if def:tls_out_cipher}
27820 &*Note*&: a plaintext SMTP AUTH done inside TLS is not vulnerable to casual snooping,
27821 but is still vulnerable to a Man In The Middle attack unless certificates
27822 (including their names) have been properly verified.
27824 .section "Plaintext server options" "SECID171"
27825 .cindex "options" "&(plaintext)& authenticator (server)"
27826 When configured as a server, &(plaintext)& uses the following options:
27828 .option server_condition authenticators string&!! unset
27829 This is actually a global authentication option, but it must be set in order to
27830 configure the &(plaintext)& driver as a server. Its use is described below.
27832 .option server_prompts plaintext "string list&!!" unset
27833 The contents of this option, after expansion, must be a colon-separated list of
27834 prompt strings. If expansion fails, a temporary authentication rejection is
27837 .section "Using plaintext in a server" "SECTplainserver"
27838 .cindex "AUTH" "in &(plaintext)& authenticator"
27839 .cindex "binary zero" "in &(plaintext)& authenticator"
27840 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
27841 "in &(plaintext)& authenticator"
27842 .vindex "&$auth1$&, &$auth2$&, etc"
27843 .cindex "base64 encoding" "in &(plaintext)& authenticator"
27845 When running as a server, &(plaintext)& performs the authentication test by
27846 expanding a string. The data sent by the client with the AUTH command, or in
27847 response to subsequent prompts, is base64 encoded, and so may contain any byte
27848 values when decoded. If any data is supplied with the command, it is treated as
27849 a list of strings, separated by NULs (binary zeros), the first three of which
27850 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
27851 (neither LOGIN nor PLAIN uses more than three strings).
27853 For compatibility with previous releases of Exim, the values are also placed in
27854 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
27855 variables for this purpose is now deprecated, as it can lead to confusion in
27856 string expansions that also use them for other things.
27858 If there are more strings in &%server_prompts%& than the number of strings
27859 supplied with the AUTH command, the remaining prompts are used to obtain more
27860 data. Each response from the client may be a list of NUL-separated strings.
27862 .vindex "&$authenticated_id$&"
27863 Once a sufficient number of data strings have been received,
27864 &%server_condition%& is expanded. If the expansion is forced to fail,
27865 authentication fails. Any other expansion failure causes a temporary error code
27866 to be returned. If the result of a successful expansion is an empty string,
27867 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27868 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
27869 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
27870 For any other result, a temporary error code is returned, with the expanded
27871 string as the error text.
27873 &*Warning*&: If you use a lookup in the expansion to find the user's
27874 password, be sure to make the authentication fail if the user is unknown.
27875 There are good and bad examples at the end of the next section.
27879 .section "The PLAIN authentication mechanism" "SECID172"
27880 .cindex "PLAIN authentication mechanism"
27881 .cindex authentication PLAIN
27882 .cindex "binary zero" "in &(plaintext)& authenticator"
27883 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
27884 sent as one item of data (that is, one combined string containing two NUL
27885 separators). The data is sent either as part of the AUTH command, or
27886 subsequently in response to an empty prompt from the server.
27888 The second and third strings are a user name and a corresponding password.
27889 Using a single fixed user name and password as an example, this could be
27890 configured as follows:
27894 public_name = PLAIN
27896 server_condition = \
27897 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
27898 server_set_id = $auth2
27900 Note that the default result strings from &%if%& (&"true"& or an empty string)
27901 are exactly what we want here, so they need not be specified. Obviously, if the
27902 password contains expansion-significant characters such as dollar, backslash,
27903 or closing brace, they have to be escaped.
27905 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
27906 the end of a string list are ignored). If all the data comes as part of the
27907 AUTH command, as is commonly the case, the prompt is not used. This
27908 authenticator is advertised in the response to EHLO as
27912 and a client host can authenticate itself by sending the command
27914 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
27916 As this contains three strings (more than the number of prompts), no further
27917 data is required from the client. Alternatively, the client may just send
27921 to initiate authentication, in which case the server replies with an empty
27922 prompt. The client must respond with the combined data string.
27924 The data string is base64 encoded, as required by the RFC. This example,
27925 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
27926 represents a zero byte. This is split up into three strings, the first of which
27927 is empty. The &%server_condition%& option in the authenticator checks that the
27928 second two are &`username`& and &`mysecret`& respectively.
27930 Having just one fixed user name and password, as in this example, is not very
27931 realistic, though for a small organization with only a handful of
27932 authenticating clients it could make sense.
27934 A more sophisticated instance of this authenticator could use the user name in
27935 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
27936 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
27937 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
27938 This is an incorrect example:
27940 server_condition = \
27941 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
27943 The expansion uses the user name (&$auth2$&) as the key to look up a password,
27944 which it then compares to the supplied password (&$auth3$&). Why is this example
27945 incorrect? It works fine for existing users, but consider what happens if a
27946 non-existent user name is given. The lookup fails, but as no success/failure
27947 strings are given for the lookup, it yields an empty string. Thus, to defeat
27948 the authentication, all a client has to do is to supply a non-existent user
27949 name and an empty password. The correct way of writing this test is:
27951 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
27952 {${if eq{$value}{$auth3}}} {false}}
27954 In this case, if the lookup succeeds, the result is checked; if the lookup
27955 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
27956 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
27957 always fails if its second argument is empty. However, the second way of
27958 writing the test makes the logic clearer.
27961 .section "The LOGIN authentication mechanism" "SECID173"
27962 .cindex "LOGIN authentication mechanism"
27963 .cindex authentication LOGIN
27964 The LOGIN authentication mechanism is not documented in any RFC, but is in use
27965 in a number of programs. No data is sent with the AUTH command. Instead, a
27966 user name and password are supplied separately, in response to prompts. The
27967 plaintext authenticator can be configured to support this as in this example:
27971 public_name = LOGIN
27972 server_prompts = User Name : Password
27973 server_condition = \
27974 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
27975 server_set_id = $auth1
27977 Because of the way plaintext operates, this authenticator accepts data supplied
27978 with the AUTH command (in contravention of the specification of LOGIN), but
27979 if the client does not supply it (as is the case for LOGIN clients), the prompt
27980 strings are used to obtain two data items.
27982 Some clients are very particular about the precise text of the prompts. For
27983 example, Outlook Express is reported to recognize only &"Username:"& and
27984 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
27985 strings. It uses the &%ldapauth%& expansion condition to check the user
27986 name and password by binding to an LDAP server:
27990 public_name = LOGIN
27991 server_prompts = Username:: : Password::
27992 server_condition = ${if and{{ \
27995 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
27996 pass=${quote:$auth2} \
27997 ldap://ldap.example.org/} }} }
27998 server_set_id = uid=$auth1,ou=people,o=example.org
28000 We have to check that the username is not empty before using it, because LDAP
28001 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
28002 operator to correctly quote the DN for authentication. However, the basic
28003 &%quote%& operator, rather than any of the LDAP quoting operators, is the
28004 correct one to use for the password, because quoting is needed only to make
28005 the password conform to the Exim syntax. At the LDAP level, the password is an
28006 uninterpreted string.
28009 .section "Support for different kinds of authentication" "SECID174"
28010 A number of string expansion features are provided for the purpose of
28011 interfacing to different ways of user authentication. These include checking
28012 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
28013 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
28019 .section "Using plaintext in a client" "SECID175"
28020 .cindex "options" "&(plaintext)& authenticator (client)"
28021 The &(plaintext)& authenticator has two client options:
28023 .option client_ignore_invalid_base64 plaintext boolean false
28024 If the client receives a server prompt that is not a valid base64 string,
28025 authentication is abandoned by default. However, if this option is set true,
28026 the error in the challenge is ignored and the client sends the response as
28029 .option client_send plaintext string&!! unset
28030 The string is a colon-separated list of authentication data strings. Each
28031 string is independently expanded before being sent to the server. The first
28032 string is sent with the AUTH command; any more strings are sent in response
28033 to prompts from the server. Before each string is expanded, the value of the
28034 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
28035 with &$auth1$& for the first prompt. Up to three prompts are stored in this
28036 way. Thus, the prompt that is received in response to sending the first string
28037 (with the AUTH command) can be used in the expansion of the second string, and
28038 so on. If an invalid base64 string is received when
28039 &%client_ignore_invalid_base64%& is set, an empty string is put in the
28040 &$auth$&<&'n'&> variable.
28042 &*Note*&: You cannot use expansion to create multiple strings, because
28043 splitting takes priority and happens first.
28045 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
28046 the data, further processing is applied to each string before it is sent. If
28047 there are any single circumflex characters in the string, they are converted to
28048 NULs. Should an actual circumflex be required as data, it must be doubled in
28051 This is an example of a client configuration that implements the PLAIN
28052 authentication mechanism with a fixed user name and password:
28056 public_name = PLAIN
28057 client_send = ^username^mysecret
28059 The lack of colons means that the entire text is sent with the AUTH
28060 command, with the circumflex characters converted to NULs.
28062 Note that due to the ambiguity of parsing three consectutive circumflex characters
28063 there is no way to provide a password having a leading circumflex.
28068 that uses the LOGIN mechanism is:
28072 public_name = LOGIN
28073 client_send = : username : mysecret
28075 The initial colon means that the first string is empty, so no data is sent with
28076 the AUTH command itself. The remaining strings are sent in response to
28078 .ecindex IIDplaiauth1
28079 .ecindex IIDplaiauth2
28084 . ////////////////////////////////////////////////////////////////////////////
28085 . ////////////////////////////////////////////////////////////////////////////
28087 .chapter "The cram_md5 authenticator" "CHID9"
28088 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
28089 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
28090 .cindex "CRAM-MD5 authentication mechanism"
28091 .cindex authentication CRAM-MD5
28092 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
28093 sends a challenge string to the client, and the response consists of a user
28094 name and the CRAM-MD5 digest of the challenge string combined with a secret
28095 string (password) which is known to both server and client. Thus, the secret
28096 is not sent over the network as plain text, which makes this authenticator more
28097 secure than &(plaintext)&. However, the downside is that the secret has to be
28098 available in plain text at either end.
28101 .section "Using cram_md5 as a server" "SECID176"
28102 .cindex "options" "&(cram_md5)& authenticator (server)"
28103 This authenticator has one server option, which must be set to configure the
28104 authenticator as a server:
28106 .option server_secret cram_md5 string&!! unset
28107 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
28108 When the server receives the client's response, the user name is placed in
28109 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
28110 obtain the password for that user. The server then computes the CRAM-MD5 digest
28111 that the client should have sent, and checks that it received the correct
28112 string. If the expansion of &%server_secret%& is forced to fail, authentication
28113 fails. If the expansion fails for some other reason, a temporary error code is
28114 returned to the client.
28116 For compatibility with previous releases of Exim, the user name is also placed
28117 in &$1$&. However, the use of this variables for this purpose is now
28118 deprecated, as it can lead to confusion in string expansions that also use
28119 numeric variables for other things.
28121 For example, the following authenticator checks that the user name given by the
28122 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
28123 user name, authentication fails.
28127 public_name = CRAM-MD5
28128 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
28129 server_set_id = $auth1
28131 .vindex "&$authenticated_id$&"
28132 If authentication succeeds, the setting of &%server_set_id%& preserves the user
28133 name in &$authenticated_id$&. A more typical configuration might look up the
28134 secret string in a file, using the user name as the key. For example:
28138 public_name = CRAM-MD5
28139 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
28141 server_set_id = $auth1
28143 Note that this expansion explicitly forces failure if the lookup fails
28144 because &$auth1$& contains an unknown user name.
28146 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
28147 using the relevant libraries, you need to know the realm to specify in the
28148 lookup and then ask for the &"userPassword"& attribute for that user in that
28153 public_name = CRAM-MD5
28154 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
28155 dbmjz{/etc/sasldb2}{$value}fail}
28156 server_set_id = $auth1
28159 .section "Using cram_md5 as a client" "SECID177"
28160 .cindex "options" "&(cram_md5)& authenticator (client)"
28161 When used as a client, the &(cram_md5)& authenticator has two options:
28165 .option client_name cram_md5 string&!! "the primary host name"
28166 This string is expanded, and the result used as the user name data when
28167 computing the response to the server's challenge.
28170 .option client_secret cram_md5 string&!! unset
28171 This option must be set for the authenticator to work as a client. Its value is
28172 expanded and the result used as the secret string when computing the response.
28176 .vindex "&$host_address$&"
28177 Different user names and secrets can be used for different servers by referring
28178 to &$host$& or &$host_address$& in the options. Forced failure of either
28179 expansion string is treated as an indication that this authenticator is not
28180 prepared to handle this case. Exim moves on to the next configured client
28181 authenticator. Any other expansion failure causes Exim to give up trying to
28182 send the message to the current server.
28184 A simple example configuration of a &(cram_md5)& authenticator, using fixed
28189 public_name = CRAM-MD5
28191 client_secret = secret
28193 .ecindex IIDcramauth1
28194 .ecindex IIDcramauth2
28198 . ////////////////////////////////////////////////////////////////////////////
28199 . ////////////////////////////////////////////////////////////////////////////
28201 .chapter "The cyrus_sasl authenticator" "CHID10"
28202 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
28203 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
28204 .cindex "Cyrus" "SASL library"
28206 The code for this authenticator was provided by Matthew Byng-Maddick while
28207 at A L Digital Ltd.
28209 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
28210 library implementation of the RFC 2222 (&"Simple Authentication and Security
28211 Layer"&). This library supports a number of authentication mechanisms,
28212 including PLAIN and LOGIN, but also several others that Exim does not support
28213 directly. In particular, there is support for Kerberos authentication.
28215 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
28216 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
28217 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
28218 name of the driver to determine which mechanism to support.
28220 Where access to some kind of secret file is required, for example, in GSSAPI
28221 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
28222 user, and that the Cyrus SASL library has no way of escalating privileges
28223 by default. You may also find you need to set environment variables,
28224 depending on the driver you are using.
28226 The application name provided by Exim is &"exim"&, so various SASL options may
28227 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
28228 Kerberos, note that because of limitations in the GSSAPI interface,
28229 changing the server keytab might need to be communicated down to the Kerberos
28230 layer independently. The mechanism for doing so is dependent upon the Kerberos
28233 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
28234 may be set to point to an alternative keytab file. Exim will pass this
28235 variable through from its own inherited environment when started as root or the
28236 Exim user. The keytab file needs to be readable by the Exim user.
28237 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
28238 environment variable. In practice, for those releases, the Cyrus authenticator
28239 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
28240 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
28243 .section "Using cyrus_sasl as a server" "SECID178"
28244 The &(cyrus_sasl)& authenticator has four private options. It puts the username
28245 (on a successful authentication) into &$auth1$&. For compatibility with
28246 previous releases of Exim, the username is also placed in &$1$&. However, the
28247 use of this variable for this purpose is now deprecated, as it can lead to
28248 confusion in string expansions that also use numeric variables for other
28252 .option server_hostname cyrus_sasl string&!! "see below"
28253 This option selects the hostname that is used when communicating with the
28254 library. The default value is &`$primary_hostname`&. It is up to the underlying
28255 SASL plug-in what it does with this data.
28258 .option server_mech cyrus_sasl string "see below"
28259 This option selects the authentication mechanism this driver should use. The
28260 default is the value of the generic &%public_name%& option. This option allows
28261 you to use a different underlying mechanism from the advertised name. For
28265 driver = cyrus_sasl
28266 public_name = X-ANYTHING
28267 server_mech = CRAM-MD5
28268 server_set_id = $auth1
28271 .option server_realm cyrus_sasl string&!! unset
28272 This specifies the SASL realm that the server claims to be in.
28275 .option server_service cyrus_sasl string &`smtp`&
28276 This is the SASL service that the server claims to implement.
28279 For straightforward cases, you do not need to set any of the authenticator's
28280 private options. All you need to do is to specify an appropriate mechanism as
28281 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
28282 PLAIN, you could have two authenticators as follows:
28285 driver = cyrus_sasl
28286 public_name = CRAM-MD5
28287 server_set_id = $auth1
28290 driver = cyrus_sasl
28291 public_name = PLAIN
28292 server_set_id = $auth2
28294 Cyrus SASL does implement the LOGIN authentication method, even though it is
28295 not a standard method. It is disabled by default in the source distribution,
28296 but it is present in many binary distributions.
28297 .ecindex IIDcyrauth1
28298 .ecindex IIDcyrauth2
28303 . ////////////////////////////////////////////////////////////////////////////
28304 . ////////////////////////////////////////////////////////////////////////////
28305 .chapter "The dovecot authenticator" "CHAPdovecot"
28306 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
28307 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
28308 This authenticator is an interface to the authentication facility of the
28309 Dovecot 2 POP/IMAP server, which can support a number of authentication methods.
28310 Note that Dovecot must be configured to use auth-client not auth-userdb.
28311 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
28312 to use the same mechanisms for SMTP authentication. This is a server
28313 authenticator only. There is only one option:
28315 .option server_socket dovecot string unset
28317 This option must specify the UNIX socket that is the interface to Dovecot
28318 authentication. The &%public_name%& option must specify an authentication
28319 mechanism that Dovecot is configured to support. You can have several
28320 authenticators for different mechanisms. For example:
28324 public_name = PLAIN
28325 server_socket = /var/run/dovecot/auth-client
28326 server_set_id = $auth1
28331 server_socket = /var/run/dovecot/auth-client
28332 server_set_id = $auth1
28334 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
28335 &$received_ip_address$& (that is, the connection is local), the &"secured"&
28336 option is passed in the Dovecot authentication command. If, for a TLS
28337 connection, a client certificate has been verified, the &"valid-client-cert"&
28338 option is passed. When authentication succeeds, the identity of the user
28339 who authenticated is placed in &$auth1$&.
28341 The Dovecot configuration to match the above will look
28344 conf.d/10-master.conf :-
28349 unix_listener auth-client {
28356 conf.d/10-auth.conf :-
28358 auth_mechanisms = plain login ntlm
28361 .ecindex IIDdcotauth1
28362 .ecindex IIDdcotauth2
28365 . ////////////////////////////////////////////////////////////////////////////
28366 . ////////////////////////////////////////////////////////////////////////////
28367 .chapter "The gsasl authenticator" "CHAPgsasl"
28368 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
28369 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
28370 .cindex "authentication" "GNU SASL"
28371 .cindex "authentication" "SASL"
28372 .cindex "authentication" "EXTERNAL"
28373 .cindex "authentication" "ANONYMOUS"
28374 .cindex "authentication" "PLAIN"
28375 .cindex "authentication" "LOGIN"
28376 .cindex "authentication" "DIGEST-MD5"
28377 .cindex "authentication" "CRAM-MD5"
28378 .cindex "authentication" "SCRAM family"
28379 The &(gsasl)& authenticator provides integration for the GNU SASL
28380 library and the mechanisms it provides. This is new as of the 4.80 release
28381 and there are a few areas where the library does not let Exim smoothly
28382 scale to handle future authentication mechanisms, so no guarantee can be
28383 made that any particular new authentication mechanism will be supported
28384 without code changes in Exim.
28386 The library is expected to add support in an upcoming
28387 realease for the SCRAM-SHA-256 method.
28388 The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
28392 To see the list of mechanisms supported by the library run Exim with "auth" debug
28393 enabled and look for a line containing "GNU SASL supports".
28394 Note however that some may not have been tested from Exim.
28398 .option client_authz gsasl string&!! unset
28399 This option can be used to supply an &'authorization id'&
28400 which is different to the &'authentication_id'& provided
28401 by &%client_username%& option.
28402 If unset or (after expansion) empty it is not used,
28403 which is the common case.
28405 .option client_channelbinding gsasl boolean false
28406 See &%server_channelbinding%& below.
28408 .option client_password gsasl string&!! unset
28409 This option is exapanded before use, and should result in
28410 the password to be used, in clear.
28412 .option client_username gsasl string&!! unset
28413 This option is exapanded before use, and should result in
28414 the account name to be used.
28417 .option client_spassword gsasl string&!! unset
28419 This option is only supported for library versions 1.9.1 and greater.
28420 The macro _HAVE_AUTH_GSASL_SCRAM_S_KEY will be defined when this is so.
28423 If a SCRAM mechanism is being used and this option is set
28424 and correctly sized
28425 it is used in preference to &%client_password%&.
28426 The value after expansion should be
28427 a 40 (for SHA-1) or 64 (for SHA-256) character string
28428 with the PBKDF2-prepared password, hex-encoded.
28430 Note that this value will depend on the salt and iteration-count
28431 supplied by the server.
28432 The option is expanded before use.
28434 During the expansion &$auth1$& is set with the client username,
28435 &$auth2$& with the iteration count, and
28436 &$auth3$& with the salt.
28438 The intent of this option
28439 is to support clients that can cache thes salted password
28440 to save on recalculation costs.
28441 The cache lookup should return an unusable value
28442 (eg. an empty string)
28443 if the salt or iteration count has changed
28445 If the authentication succeeds then the above variables are set,
28446 .vindex "&$auth4$&"
28447 plus the calculated salted password value value in &$auth4$&,
28448 during the expansion of the &%client_set_id%& option.
28449 A side-effect of this expansion can be used to prime the cache.
28453 .option server_channelbinding gsasl boolean false
28454 Some authentication mechanisms are able to use external context at both ends
28455 of the session to bind the authentication to that context, and fail the
28456 authentication process if that context differs. Specifically, some TLS
28457 ciphersuites can provide identifying information about the cryptographic
28460 This should have meant that certificate identity and verification becomes a
28461 non-issue, as a man-in-the-middle attack will cause the correct client and
28462 server to see different identifiers and authentication will fail.
28465 only usable by mechanisms which support "channel binding"; at time of
28466 writing, that's the SCRAM family.
28467 When using this feature the "-PLUS" variants of the method names need to be used.
28469 This defaults off to ensure smooth upgrade across Exim releases, in case
28470 this option causes some clients to start failing. Some future release
28471 of Exim might have switched the default to be true.
28473 . However, Channel Binding in TLS has proven to be vulnerable in current versions.
28474 . Do not plan to rely upon this feature for security, ever, without consulting
28475 . with a subject matter expert (a cryptographic engineer).
28478 This option was deprecated in previous releases due to doubts over
28479 the "Triple Handshake" vulnerability.
28480 Exim takes suitable precausions (requiring Extended Master Secret if TLS
28481 Session Resumption was used) for safety.
28485 .option server_hostname gsasl string&!! "see below"
28486 This option selects the hostname that is used when communicating with the
28487 library. The default value is &`$primary_hostname`&.
28488 Some mechanisms will use this data.
28491 .option server_mech gsasl string "see below"
28492 This option selects the authentication mechanism this driver should use. The
28493 default is the value of the generic &%public_name%& option. This option allows
28494 you to use a different underlying mechanism from the advertised name. For
28499 public_name = X-ANYTHING
28500 server_mech = CRAM-MD5
28501 server_set_id = $auth1
28505 .option server_password gsasl string&!! unset
28506 Various mechanisms need access to the cleartext password on the server, so
28507 that proof-of-possession can be demonstrated on the wire, without sending
28508 the password itself.
28510 The data available for lookup varies per mechanism.
28511 In all cases, &$auth1$& is set to the &'authentication id'&.
28512 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
28513 if available, else the empty string.
28514 The &$auth3$& variable will always be the &'realm'& if available,
28515 else the empty string.
28517 A forced failure will cause authentication to defer.
28519 If using this option, it may make sense to set the &%server_condition%&
28520 option to be simply "true".
28523 .option server_realm gsasl string&!! unset
28524 This specifies the SASL realm that the server claims to be in.
28525 Some mechanisms will use this data.
28528 .option server_scram_iter gsasl string&!! 4096
28529 This option provides data for the SCRAM family of mechanisms.
28530 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28531 when this option is expanded.
28533 The result of expansion should be a decimal number,
28534 and represents both a lower-bound on the security, and
28535 a compute cost factor imposed on the client
28536 (if it does not cache results, or the server changes
28537 either the iteration count or the salt).
28538 A minimum value of 4096 is required by the standards
28539 for all current SCRAM mechanism variants.
28541 .option server_scram_salt gsasl string&!! unset
28542 This option provides data for the SCRAM family of mechanisms.
28543 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28544 when this option is expanded.
28545 The value should be a base64-encoded string,
28546 of random data typically 4-to-16 bytes long.
28547 If unset or empty after expansion the library will provides a value for the
28548 protocol conversation.
28551 .option server_key gsasl string&!! unset
28552 .option server_skey gsasl string&!! unset
28553 These options can be used for the SCRAM family of mechanisms
28554 to provide stored information related to a password,
28555 the storage of which is preferable to plaintext.
28557 &%server_key%& is the value defined in the SCRAM standards as ServerKey;
28558 &%server_skey%& is StoredKey.
28560 They are only available for version 1.9.0 (or later) of the gsasl library.
28561 When this is so, the macros
28562 _OPT_AUTHENTICATOR_GSASL_SERVER_KEY
28563 and _HAVE_AUTH_GSASL_SCRAM_S_KEY
28566 The &$authN$& variables are available when these options are expanded.
28568 If set, the results of expansion should for each
28569 should be a 28 (for SHA-1) or 44 (for SHA-256) character string
28570 of base64-coded data, and will be used in preference to the
28571 &%server_password%& option.
28572 If unset or not of the right length, &%server_password%& will be used.
28574 The libgsasl library release includes a utility &'gsasl'& which can be used
28575 to generate these values.
28578 .option server_service gsasl string &`smtp`&
28579 This is the SASL service that the server claims to implement.
28580 Some mechanisms will use this data.
28583 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
28584 .vindex "&$auth1$&, &$auth2$&, etc"
28585 These may be set when evaluating specific options, as detailed above.
28586 They will also be set when evaluating &%server_condition%&.
28588 Unless otherwise stated below, the &(gsasl)& integration will use the following
28589 meanings for these variables:
28592 .vindex "&$auth1$&"
28593 &$auth1$&: the &'authentication id'&
28595 .vindex "&$auth2$&"
28596 &$auth2$&: the &'authorization id'&
28598 .vindex "&$auth3$&"
28599 &$auth3$&: the &'realm'&
28602 On a per-mechanism basis:
28605 .cindex "authentication" "EXTERNAL"
28606 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
28607 the &%server_condition%& option must be present.
28609 .cindex "authentication" "ANONYMOUS"
28610 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
28611 the &%server_condition%& option must be present.
28613 .cindex "authentication" "GSSAPI"
28614 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
28615 &$auth2$& will be set to the &'authorization id'&,
28616 the &%server_condition%& option must be present.
28619 An &'anonymous token'& is something passed along as an unauthenticated
28620 identifier; this is analogous to FTP anonymous authentication passing an
28621 email address, or software-identifier@, as the "password".
28624 An example showing the password having the realm specified in the callback
28625 and demonstrating a Cyrus SASL to GSASL migration approach is:
28627 gsasl_cyrusless_crammd5:
28629 public_name = CRAM-MD5
28630 server_realm = imap.example.org
28631 server_password = ${lookup{$auth1:$auth3:userPassword}\
28632 dbmjz{/etc/sasldb2}{$value}fail}
28633 server_set_id = ${quote:$auth1}
28634 server_condition = yes
28638 . ////////////////////////////////////////////////////////////////////////////
28639 . ////////////////////////////////////////////////////////////////////////////
28641 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
28642 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
28643 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
28644 .cindex "authentication" "GSSAPI"
28645 .cindex "authentication" "Kerberos"
28646 The &(heimdal_gssapi)& authenticator provides server integration for the
28647 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
28650 .option server_hostname heimdal_gssapi string&!! "see below"
28651 This option selects the hostname that is used, with &%server_service%&,
28652 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
28653 identifier. The default value is &`$primary_hostname`&.
28655 .option server_keytab heimdal_gssapi string&!! unset
28656 If set, then Heimdal will not use the system default keytab (typically
28657 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
28658 The value should be a pathname, with no &"file:"& prefix.
28660 .option server_service heimdal_gssapi string&!! "smtp"
28661 This option specifies the service identifier used, in conjunction with
28662 &%server_hostname%&, for building the identifier for finding credentials
28666 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
28667 Beware that these variables will typically include a realm, thus will appear
28668 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
28669 not verified, so a malicious client can set it to anything.
28671 The &$auth1$& field should be safely trustable as a value from the Key
28672 Distribution Center. Note that these are not quite email addresses.
28673 Each identifier is for a role, and so the left-hand-side may include a
28674 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
28676 .vindex "&$auth1$&, &$auth2$&, etc"
28678 .vindex "&$auth1$&"
28679 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
28681 .vindex "&$auth2$&"
28682 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
28683 authentication. If that was empty, this will also be set to the
28688 . ////////////////////////////////////////////////////////////////////////////
28689 . ////////////////////////////////////////////////////////////////////////////
28691 .chapter "The spa authenticator" "CHAPspa"
28692 .scindex IIDspaauth1 "&(spa)& authenticator"
28693 .scindex IIDspaauth2 "authenticators" "&(spa)&"
28694 .cindex "authentication" "Microsoft Secure Password"
28695 .cindex "authentication" "NTLM"
28696 .cindex "Microsoft Secure Password Authentication"
28697 .cindex "NTLM authentication"
28698 The &(spa)& authenticator provides client support for Microsoft's &'Secure
28699 Password Authentication'& mechanism,
28700 which is also sometimes known as NTLM (NT LanMan). The code for client side of
28701 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
28702 taken from the Samba project (&url(https://www.samba.org/)). The code for the
28703 server side was subsequently contributed by Tom Kistner. The mechanism works as
28707 After the AUTH command has been accepted, the client sends an SPA
28708 authentication request based on the user name and optional domain.
28710 The server sends back a challenge.
28712 The client builds a challenge response which makes use of the user's password
28713 and sends it to the server, which then accepts or rejects it.
28716 Encryption is used to protect the password in transit.
28720 .section "Using spa as a server" "SECID179"
28721 .cindex "options" "&(spa)& authenticator (server)"
28722 The &(spa)& authenticator has just one server option:
28724 .option server_password spa string&!! unset
28725 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
28726 This option is expanded, and the result must be the cleartext password for the
28727 authenticating user, whose name is at this point in &$auth1$&. For
28728 compatibility with previous releases of Exim, the user name is also placed in
28729 &$1$&. However, the use of this variable for this purpose is now deprecated, as
28730 it can lead to confusion in string expansions that also use numeric variables
28731 for other things. For example:
28736 server_password = \
28737 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
28739 If the expansion is forced to fail, authentication fails. Any other expansion
28740 failure causes a temporary error code to be returned.
28746 .section "Using spa as a client" "SECID180"
28747 .cindex "options" "&(spa)& authenticator (client)"
28748 The &(spa)& authenticator has the following client options:
28752 .option client_domain spa string&!! unset
28753 This option specifies an optional domain for the authentication.
28756 .option client_password spa string&!! unset
28757 This option specifies the user's password, and must be set.
28760 .option client_username spa string&!! unset
28761 This option specifies the user name, and must be set. Here is an example of a
28762 configuration of this authenticator for use with the mail servers at
28768 client_username = msn/msn_username
28769 client_password = msn_plaintext_password
28770 client_domain = DOMAIN_OR_UNSET
28772 .ecindex IIDspaauth1
28773 .ecindex IIDspaauth2
28779 . ////////////////////////////////////////////////////////////////////////////
28780 . ////////////////////////////////////////////////////////////////////////////
28782 .chapter "The external authenticator" "CHAPexternauth"
28783 .scindex IIDexternauth1 "&(external)& authenticator"
28784 .scindex IIDexternauth2 "authenticators" "&(external)&"
28785 .cindex "authentication" "Client Certificate"
28786 .cindex "authentication" "X509"
28787 .cindex "Certificate-based authentication"
28788 The &(external)& authenticator provides support for
28789 authentication based on non-SMTP information.
28790 The specification is in RFC 4422 Appendix A
28791 (&url(https://tools.ietf.org/html/rfc4422)).
28792 It is only a transport and negotiation mechanism;
28793 the process of authentication is entirely controlled
28794 by the server configuration.
28796 The client presents an identity in-clear.
28797 It is probably wise for a server to only advertise,
28798 and for clients to only attempt,
28799 this authentication method on a secure (eg. under TLS) connection.
28801 One possible use, compatible with the
28802 K-9 Mail Android client (&url(https://k9mail.github.io/)),
28803 is for using X509 client certificates.
28805 It thus overlaps in function with the TLS authenticator
28806 (see &<<CHAPtlsauth>>&)
28807 but is a full SMTP SASL authenticator
28808 rather than being implicit for TLS-connection carried
28809 client certificates only.
28811 The examples and discussion in this chapter assume that
28812 client-certificate authentication is being done.
28814 The client must present a certificate,
28815 for which it must have been requested via the
28816 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28817 (see &<<CHAPTLS>>&).
28818 For authentication to be effective the certificate should be
28819 verifiable against a trust-anchor certificate known to the server.
28821 .section "External options" "SECTexternsoptions"
28822 .cindex "options" "&(external)& authenticator (server)"
28823 The &(external)& authenticator has two server options:
28825 .option server_param2 external string&!! unset
28826 .option server_param3 external string&!! unset
28827 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(external)& authenticator"
28828 These options are expanded before the &%server_condition%& option
28829 and the result are placed in &$auth2$& and &$auth3$& resectively.
28830 If the expansion is forced to fail, authentication fails. Any other expansion
28831 failure causes a temporary error code to be returned.
28833 They can be used to clarify the coding of a complex &%server_condition%&.
28835 .section "Using external in a server" "SECTexternserver"
28836 .cindex "AUTH" "in &(external)& authenticator"
28837 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
28838 "in &(external)& authenticator"
28839 .vindex "&$auth1$&, &$auth2$&, etc"
28840 .cindex "base64 encoding" "in &(external)& authenticator"
28842 When running as a server, &(external)& performs the authentication test by
28843 expanding a string. The data sent by the client with the AUTH command, or in
28844 response to subsequent prompts, is base64 encoded, and so may contain any byte
28845 values when decoded. The decoded value is treated as
28846 an identity for authentication and
28847 placed in the expansion variable &$auth1$&.
28849 For compatibility with previous releases of Exim, the value is also placed in
28850 the expansion variable &$1$&. However, the use of this
28851 variable for this purpose is now deprecated, as it can lead to confusion in
28852 string expansions that also use them for other things.
28854 .vindex "&$authenticated_id$&"
28855 Once an identity has been received,
28856 &%server_condition%& is expanded. If the expansion is forced to fail,
28857 authentication fails. Any other expansion failure causes a temporary error code
28858 to be returned. If the result of a successful expansion is an empty string,
28859 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
28860 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
28861 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
28862 For any other result, a temporary error code is returned, with the expanded
28863 string as the error text.
28867 ext_ccert_san_mail:
28869 public_name = EXTERNAL
28871 server_advertise_condition = $tls_in_certificate_verified
28872 server_param2 = ${certextract {subj_altname,mail,>:} \
28873 {$tls_in_peercert}}
28874 server_condition = ${if forany {$auth2} \
28875 {eq {$item}{$auth1}}}
28876 server_set_id = $auth1
28878 This accepts a client certificate that is verifiable against any
28879 of your configured trust-anchors
28880 (which usually means the full set of public CAs)
28881 and which has a mail-SAN matching the claimed identity sent by the client.
28883 &*Note*&: up to TLS1.2, the client cert is on the wire in-clear, including the SAN.
28884 The account name is therefore guessable by an opponent.
28885 TLS 1.3 protects both server and client certificates, and is not vulnerable
28889 .section "Using external in a client" "SECTexternclient"
28890 .cindex "options" "&(external)& authenticator (client)"
28891 The &(external)& authenticator has one client option:
28893 .option client_send external string&!! unset
28894 This option is expanded and sent with the AUTH command as the
28895 identity being asserted.
28901 public_name = EXTERNAL
28903 client_condition = ${if !eq{$tls_out_cipher}{}}
28904 client_send = myaccount@smarthost.example.net
28908 .ecindex IIDexternauth1
28909 .ecindex IIDexternauth2
28915 . ////////////////////////////////////////////////////////////////////////////
28916 . ////////////////////////////////////////////////////////////////////////////
28918 .chapter "The tls authenticator" "CHAPtlsauth"
28919 .scindex IIDtlsauth1 "&(tls)& authenticator"
28920 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
28921 .cindex "authentication" "Client Certificate"
28922 .cindex "authentication" "X509"
28923 .cindex "Certificate-based authentication"
28924 The &(tls)& authenticator provides server support for
28925 authentication based on client certificates.
28927 It is not an SMTP authentication mechanism and is not
28928 advertised by the server as part of the SMTP EHLO response.
28929 It is an Exim authenticator in the sense that it affects
28930 the protocol element of the log line, can be tested for
28931 by the &%authenticated%& ACL condition, and can set
28932 the &$authenticated_id$& variable.
28934 The client must present a verifiable certificate,
28935 for which it must have been requested via the
28936 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28937 (see &<<CHAPTLS>>&).
28939 If an authenticator of this type is configured it is
28940 run before any SMTP-level communication is done,
28941 and can authenticate the connection.
28942 If it does, SMTP authentication is not offered.
28944 A maximum of one authenticator of this type may be present.
28947 .cindex "options" "&(tls)& authenticator (server)"
28948 The &(tls)& authenticator has three server options:
28950 .option server_param1 tls string&!! unset
28951 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
28952 This option is expanded after the TLS negotiation and
28953 the result is placed in &$auth1$&.
28954 If the expansion is forced to fail, authentication fails. Any other expansion
28955 failure causes a temporary error code to be returned.
28957 .option server_param2 tls string&!! unset
28958 .option server_param3 tls string&!! unset
28959 As above, for &$auth2$& and &$auth3$&.
28961 &%server_param1%& may also be spelled &%server_param%&.
28968 server_param1 = ${certextract {subj_altname,mail,>:} \
28969 {$tls_in_peercert}}
28970 server_condition = ${if and { {eq{$tls_in_certificate_verified}{1}} \
28973 {${lookup ldap{ldap:///\
28974 mailname=${quote_ldap_dn:${lc:$item}},\
28975 ou=users,LDAP_DC?mailid} {$value}{0} \
28977 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
28979 This accepts a client certificate that is verifiable against any
28980 of your configured trust-anchors
28981 (which usually means the full set of public CAs)
28982 and which has a SAN with a good account name.
28984 Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
28985 The account name is therefore guessable by an opponent.
28986 TLS 1.3 protects both server and client certificates, and is not vulnerable
28988 Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
28990 . An alternative might use
28992 . server_param1 = ${sha256:$tls_in_peercert}
28994 . to require one of a set of specific certs that define a given account
28995 . (the verification is still required, but mostly irrelevant).
28996 . This would help for per-device use.
28998 . However, for the future we really need support for checking a
28999 . user cert in LDAP - which probably wants a base-64 DER.
29001 .ecindex IIDtlsauth1
29002 .ecindex IIDtlsauth2
29005 Note that because authentication is traditionally an SMTP operation,
29006 the &%authenticated%& ACL condition cannot be used in
29007 a connect- or helo-ACL.
29011 . ////////////////////////////////////////////////////////////////////////////
29012 . ////////////////////////////////////////////////////////////////////////////
29014 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
29015 "Encrypted SMTP connections"
29016 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
29017 .scindex IIDencsmtp2 "SMTP" "encryption"
29018 .cindex "TLS" "on SMTP connection"
29021 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
29022 Sockets Layer), is implemented by making use of the OpenSSL library or the
29023 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
29024 cryptographic code in the Exim distribution itself for implementing TLS. In
29025 order to use this feature you must install OpenSSL or GnuTLS, and then build a
29026 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
29027 You also need to understand the basic concepts of encryption at a managerial
29028 level, and in particular, the way that public keys, private keys, and
29029 certificates are used.
29031 RFC 3207 defines how SMTP connections can make use of encryption. Once a
29032 connection is established, the client issues a STARTTLS command. If the
29033 server accepts this, the client and the server negotiate an encryption
29034 mechanism. If the negotiation succeeds, the data that subsequently passes
29035 between them is encrypted.
29037 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
29038 and if so, what cipher suite is in use, whether the client supplied a
29039 certificate, and whether or not that certificate was verified. This makes it
29040 possible for an Exim server to deny or accept certain commands based on the
29043 &*Warning*&: Certain types of firewall and certain anti-virus products can
29044 disrupt TLS connections. You need to turn off SMTP scanning for these products
29045 in order to get TLS to work.
29049 .section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
29051 .cindex "submissions protocol"
29052 .cindex "ssmtp protocol"
29053 .cindex "smtps protocol"
29054 .cindex "SMTP" "submissions protocol"
29055 .cindex "SMTP" "ssmtp protocol"
29056 .cindex "SMTP" "smtps protocol"
29057 The history of port numbers for TLS in SMTP is a little messy and has been
29058 contentious. As of RFC 8314, the common practice of using the historically
29059 allocated port 465 for "email submission but with TLS immediately upon connect
29060 instead of using STARTTLS" is officially blessed by the IETF, and recommended
29061 by them in preference to STARTTLS.
29063 The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
29064 clarity emerged over the dual roles of SMTP, for MX delivery and Email
29065 Submission, nomenclature has shifted. The modern name is now &"submissions"&.
29067 This approach was, for a while, officially abandoned when encrypted SMTP was
29068 standardized, but many clients kept using it, even as the TCP port number was
29069 reassigned for other use.
29070 Thus you may encounter guidance claiming that you shouldn't enable use of
29072 In practice, a number of mail-clients have only ever supported submissions,
29073 not submission with STARTTLS upgrade.
29074 Ideally, offer both submission (587) and submissions (465) service.
29076 Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
29077 global option. Its value must be a list of port numbers;
29078 the most common use is expected to be:
29080 tls_on_connect_ports = 465
29082 The port numbers specified by this option apply to all SMTP connections, both
29083 via the daemon and via &'inetd'&. You still need to specify all the ports that
29084 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
29085 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
29086 an extra port &-- rather, it specifies different behaviour on a port that is
29089 There is also a &%-tls-on-connect%& command line option. This overrides
29090 &%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
29097 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
29098 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
29099 TLS is supported in Exim using either the OpenSSL or GnuTLS library.
29100 To build Exim to use OpenSSL you need to set
29106 To build Exim to use GnuTLS, you need to set
29112 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
29113 include files and libraries for GnuTLS can be found.
29115 There are some differences in usage when using GnuTLS instead of OpenSSL:
29118 The &%tls_verify_certificates%& option
29119 cannot be the path of a directory
29120 for GnuTLS versions before 3.3.6
29121 (for later versions, or OpenSSL, it can be either).
29123 The default value for &%tls_dhparam%& differs for historical reasons.
29125 .vindex "&$tls_in_peerdn$&"
29126 .vindex "&$tls_out_peerdn$&"
29127 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
29128 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
29129 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
29131 OpenSSL identifies cipher suites using hyphens as separators, for example:
29132 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
29133 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
29134 in a cipher list. To make life simpler, Exim changes underscores to hyphens
29135 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
29136 to handle its own older variants) when processing lists of cipher suites in the
29137 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
29140 The &%tls_require_ciphers%& options operate differently, as described in the
29141 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
29143 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
29144 When using OpenSSL, this option is ignored.
29145 (If an API is found to let OpenSSL be configured in this way,
29146 let the Exim Maintainers know and we'll likely use it).
29148 With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
29149 main option, it must be ordered to match the &%tls_certificate%& list.
29151 Some other recently added features may only be available in one or the other.
29152 This should be documented with the feature. If the documentation does not
29153 explicitly state that the feature is infeasible in the other TLS
29154 implementation, then patches are welcome.
29157 The output from "exim -bV" will show which (if any) support was included
29159 Also, the macro "_HAVE_OPENSSL" or "_HAVE_GNUTLS" will be defined.
29164 .section "GnuTLS parameter computation" "SECTgnutlsparam"
29165 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
29166 an explicit path; if the latter, then the text about generation still applies,
29167 but not the chosen filename.
29168 By default, as of Exim 4.80 a hard-coded D-H prime is used.
29169 See the documentation of &%tls_dhparam%& for more information.
29171 GnuTLS uses D-H parameters that may take a substantial amount of time
29172 to compute. It is unreasonable to re-compute them for every TLS session.
29173 Therefore, Exim keeps this data in a file in its spool directory, called
29174 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
29176 The file is owned by the Exim user and is readable only by
29177 its owner. Every Exim process that start up GnuTLS reads the D-H
29178 parameters from this file. If the file does not exist, the first Exim process
29179 that needs it computes the data and writes it to a temporary file which is
29180 renamed once it is complete. It does not matter if several Exim processes do
29181 this simultaneously (apart from wasting a few resources). Once a file is in
29182 place, new Exim processes immediately start using it.
29184 For maximum security, the parameters that are stored in this file should be
29185 recalculated periodically, the frequency depending on your paranoia level.
29186 If you are avoiding using the fixed D-H primes published in RFCs, then you
29187 are concerned about some advanced attacks and will wish to do this; if you do
29188 not regenerate then you might as well stick to the standard primes.
29190 Arranging this is easy in principle; just delete the file when you want new
29191 values to be computed. However, there may be a problem. The calculation of new
29192 parameters needs random numbers, and these are obtained from &_/dev/random_&.
29193 If the system is not very active, &_/dev/random_& may delay returning data
29194 until enough randomness (entropy) is available. This may cause Exim to hang for
29195 a substantial amount of time, causing timeouts on incoming connections.
29197 The solution is to generate the parameters externally to Exim. They are stored
29198 in &_gnutls-params-N_& in PEM format, which means that they can be
29199 generated externally using the &(certtool)& command that is part of GnuTLS.
29201 To replace the parameters with new ones, instead of deleting the file
29202 and letting Exim re-create it, you can generate new parameters using
29203 &(certtool)& and, when this has been done, replace Exim's cache file by
29204 renaming. The relevant commands are something like this:
29207 [ look for file; assume gnutls-params-2236 is the most recent ]
29210 # chown exim:exim new-params
29211 # chmod 0600 new-params
29212 # certtool --generate-dh-params --bits 2236 >>new-params
29213 # openssl dhparam -noout -text -in new-params | head
29214 [ check the first line, make sure it's not more than 2236;
29215 if it is, then go back to the start ("rm") and repeat
29216 until the size generated is at most the size requested ]
29217 # chmod 0400 new-params
29218 # mv new-params gnutls-params-2236
29220 If Exim never has to generate the parameters itself, the possibility of
29221 stalling is removed.
29223 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
29224 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
29225 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
29226 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
29227 and Exim does so. This attempt to remove Exim from TLS policy decisions
29228 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
29229 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
29230 which applies to all D-H usage, client or server. If the value returned by
29231 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
29232 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
29233 limit, which is still much higher than Exim historically used.
29235 The filename and bits used will change as the GnuTLS maintainers change the
29236 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
29237 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
29238 2432 bits, while NSS is limited to 2236 bits.
29240 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
29241 increase the chance of the generated prime actually being within acceptable
29242 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
29243 procedure above. There is no sane procedure available to Exim to double-check
29244 the size of the generated prime, so it might still be too large.
29247 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
29248 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
29249 .oindex "&%tls_require_ciphers%&" "OpenSSL"
29250 There is a function in the OpenSSL library that can be passed a list of cipher
29251 suites before the cipher negotiation takes place. This specifies which ciphers
29252 are acceptable for TLS versions prior to 1.3.
29253 The list is colon separated and may contain names like
29254 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
29255 directly to this function call.
29256 Many systems will install the OpenSSL manual-pages, so you may have
29257 &'ciphers(1)'& available to you.
29258 The following quotation from the OpenSSL
29259 documentation specifies what forms of item are allowed in the cipher string:
29262 It can consist of a single cipher suite such as RC4-SHA.
29264 It can represent a list of cipher suites containing a certain algorithm,
29265 or cipher suites of a certain type. For example SHA1 represents all
29266 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
29269 Lists of cipher suites can be combined in a single cipher string using
29270 the + character. This is used as a logical and operation. For example
29271 SHA1+DES represents all cipher suites containing the SHA1 and the DES
29275 Each cipher string can be optionally preceded by one of the characters &`!`&,
29278 If &`!`& is used, the ciphers are permanently deleted from the list. The
29279 ciphers deleted can never reappear in the list even if they are explicitly
29282 If &`-`& is used, the ciphers are deleted from the list, but some or all
29283 of the ciphers can be added again by later options.
29285 If &`+`& is used, the ciphers are moved to the end of the list. This
29286 option does not add any new ciphers; it just moves matching existing ones.
29289 If none of these characters is present, the string is interpreted as
29290 a list of ciphers to be appended to the current preference list. If the list
29291 includes any ciphers already present they will be ignored: that is, they will
29292 not be moved to the end of the list.
29295 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
29298 # note single-quotes to get ! past any shell history expansion
29299 $ openssl ciphers 'HIGH:!MD5:!SHA1'
29302 This example will let the library defaults be permitted on the MX port, where
29303 there's probably no identity verification anyway, but ups the ante on the
29304 submission ports where the administrator might have some influence on the
29305 choice of clients used:
29307 # OpenSSL variant; see man ciphers(1)
29308 tls_require_ciphers = ${if =={$received_port}{25}\
29313 This example will prefer ECDSA-authenticated ciphers over RSA ones:
29315 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
29318 For TLS version 1.3 the control available is less fine-grained
29319 and Exim does not provide access to it at present.
29320 The value of the &%tls_require_ciphers%& option is ignored when
29321 TLS version 1.3 is negotiated.
29323 As of writing the library default cipher suite list for TLSv1.3 is
29325 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
29329 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
29331 .cindex "GnuTLS" "specifying parameters for"
29332 .cindex "TLS" "specifying ciphers (GnuTLS)"
29333 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
29334 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
29335 .cindex "TLS" "specifying protocols (GnuTLS)"
29336 .cindex "TLS" "specifying priority string (GnuTLS)"
29337 .oindex "&%tls_require_ciphers%&" "GnuTLS"
29338 The GnuTLS library allows the caller to provide a "priority string", documented
29339 as part of the &[gnutls_priority_init]& function. This is very similar to the
29340 ciphersuite specification in OpenSSL.
29342 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
29343 and controls both protocols and ciphers.
29345 The &%tls_require_ciphers%& option is available both as an global option,
29346 controlling how Exim behaves as a server, and also as an option of the
29347 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
29348 the value is string expanded. The resulting string is not an Exim list and
29349 the string is given to the GnuTLS library, so that Exim does not need to be
29350 aware of future feature enhancements of GnuTLS.
29352 Documentation of the strings accepted may be found in the GnuTLS manual, under
29353 "Priority strings". This is online as
29354 &url(https://www.gnutls.org/manual/html_node/Priority-Strings.html),
29355 but beware that this relates to GnuTLS 3, which may be newer than the version
29356 installed on your system. If you are using GnuTLS 3,
29357 then the example code
29358 &url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
29359 on that site can be used to test a given string.
29363 # Disable older versions of protocols
29364 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
29367 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
29368 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
29369 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
29371 This example will let the library defaults be permitted on the MX port, where
29372 there's probably no identity verification anyway, and lowers security further
29373 by increasing compatibility; but this ups the ante on the submission ports
29374 where the administrator might have some influence on the choice of clients
29378 tls_require_ciphers = ${if =={$received_port}{25}\
29384 .section "Configuring an Exim server to use TLS" "SECID182"
29385 .cindex "TLS" "configuring an Exim server"
29386 .cindex "ESMTP extensions" STARTTLS
29387 When Exim has been built with TLS support, it advertises the availability of
29388 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
29389 but not to any others. The default value of this option is *, which means
29390 that STARTTLS is always advertised. Set it to blank to never advertise;
29391 this is reasonable for systems that want to use TLS only as a client.
29393 If STARTTLS is to be used you
29394 need to set some other options in order to make TLS available.
29396 If a client issues a STARTTLS command and there is some configuration
29397 problem in the server, the command is rejected with a 454 error. If the client
29398 persists in trying to issue SMTP commands, all except QUIT are rejected
29401 554 Security failure
29403 If a STARTTLS command is issued within an existing TLS session, it is
29404 rejected with a 554 error code.
29406 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
29407 must be set to match some hosts. The default is * which matches all hosts.
29409 If this is all you do, TLS encryption will be enabled but not authentication -
29410 meaning that the peer has no assurance it is actually you he is talking to.
29411 You gain protection from a passive sniffer listening on the wire but not
29412 from someone able to intercept the communication.
29414 Further protection requires some further configuration at the server end.
29416 To make TLS work you need to set, in the server,
29418 tls_certificate = /some/file/name
29419 tls_privatekey = /some/file/name
29421 These options are, in fact, expanded strings, so you can make them depend on
29422 the identity of the client that is connected if you wish. The first file
29423 contains the server's X509 certificate, and the second contains the private key
29424 that goes with it. These files need to be
29425 PEM format and readable by the Exim user, and must
29426 always be given as full path names.
29427 The key must not be password-protected.
29428 They can be the same file if both the
29429 certificate and the key are contained within it. If &%tls_privatekey%& is not
29430 set, or if its expansion is forced to fail or results in an empty string, this
29431 is assumed to be the case. The certificate file may also contain intermediate
29432 certificates that need to be sent to the client to enable it to authenticate
29433 the server's certificate.
29435 For dual-stack (eg. RSA and ECDSA) configurations, these options can be
29436 colon-separated lists of file paths. Ciphers using given authentication
29437 algorithms require the presence of a suitable certificate to supply the
29438 public-key. The server selects among the certificates to present to the
29439 client depending on the selected cipher, hence the priority ordering for
29440 ciphers will affect which certificate is used.
29442 If you do not understand about certificates and keys, please try to find a
29443 source of this background information, which is not Exim-specific. (There are a
29444 few comments below in section &<<SECTcerandall>>&.)
29446 &*Note*&: These options do not apply when Exim is operating as a client &--
29447 they apply only in the case of a server. If you need to use a certificate in an
29448 Exim client, you must set the options of the same names in an &(smtp)&
29451 With just these options, an Exim server will be able to use TLS. It does not
29452 require the client to have a certificate (but see below for how to insist on
29453 this). There is one other option that may be needed in other situations. If
29455 tls_dhparam = /some/file/name
29457 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
29458 with the parameters contained in the file.
29459 Set this to &`none`& to disable use of DH entirely, by making no prime
29464 This may also be set to a string identifying a standard prime to be used for
29465 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
29466 used is &`ike23`&. There are a few standard primes available, see the
29467 documentation for &%tls_dhparam%& for the complete list.
29473 for a way of generating file data.
29475 The strings supplied for these three options are expanded every time a client
29476 host connects. It is therefore possible to use different certificates and keys
29477 for different hosts, if you so wish, by making use of the client's IP address
29478 in &$sender_host_address$& to control the expansion. If a string expansion is
29479 forced to fail, Exim behaves as if the option is not set.
29481 .cindex "cipher" "logging"
29482 .cindex "log" "TLS cipher"
29483 .vindex "&$tls_in_cipher$&"
29484 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
29485 an incoming TLS connection. It is included in the &'Received:'& header of an
29486 incoming message (by default &-- you can, of course, change this), and it is
29487 also included in the log line that records a message's arrival, keyed by
29488 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
29489 condition can be used to test for specific cipher suites in ACLs.
29491 Once TLS has been established, the ACLs that run for subsequent SMTP commands
29492 can check the name of the cipher suite and vary their actions accordingly. The
29493 cipher suite names vary, depending on which TLS library is being used. For
29494 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
29495 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
29496 documentation for more details.
29498 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
29499 (again depending on the &%tls_cipher%& log selector).
29502 .section "Requesting and verifying client certificates" "SECID183"
29503 .cindex "certificate" "verification of client"
29504 .cindex "TLS" "client certificate verification"
29505 If you want an Exim server to request a certificate when negotiating a TLS
29506 session with a client, you must set either &%tls_verify_hosts%& or
29507 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
29508 apply to all TLS connections. For any host that matches one of these options,
29509 Exim requests a certificate as part of the setup of the TLS session. The
29510 contents of the certificate are verified by comparing it with a list of
29511 expected trust-anchors or certificates.
29512 These may be the system default set (depending on library version),
29513 an explicit file or,
29514 depending on library version, a directory, identified by
29515 &%tls_verify_certificates%&.
29517 A file can contain multiple certificates, concatenated end to end. If a
29520 each certificate must be in a separate file, with a name (or a symbolic link)
29521 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
29522 certificate. You can compute the relevant hash by running the command
29524 openssl x509 -hash -noout -in /cert/file
29526 where &_/cert/file_& contains a single certificate.
29528 There is no checking of names of the client against the certificate
29529 Subject Name or Subject Alternate Names.
29531 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
29532 what happens if the client does not supply a certificate, or if the certificate
29533 does not match any of the certificates in the collection named by
29534 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
29535 attempt to set up a TLS session is aborted, and the incoming connection is
29536 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
29537 session continues. ACLs that run for subsequent SMTP commands can detect the
29538 fact that no certificate was verified, and vary their actions accordingly. For
29539 example, you can insist on a certificate before accepting a message for
29540 relaying, but not when the message is destined for local delivery.
29542 .vindex "&$tls_in_peerdn$&"
29543 When a client supplies a certificate (whether it verifies or not), the value of
29544 the Distinguished Name of the certificate is made available in the variable
29545 &$tls_in_peerdn$& during subsequent processing of the message.
29547 .cindex "log" "distinguished name"
29548 Because it is often a long text string, it is not included in the log line or
29549 &'Received:'& header by default. You can arrange for it to be logged, keyed by
29550 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
29551 &%received_header_text%& to change the &'Received:'& header. When no
29552 certificate is supplied, &$tls_in_peerdn$& is empty.
29555 .section "Revoked certificates" "SECID184"
29556 .cindex "TLS" "revoked certificates"
29557 .cindex "revocation list"
29558 .cindex "certificate" "revocation list"
29559 .cindex "OCSP" "stapling"
29560 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
29561 certificates are revoked. If you have such a list, you can pass it to an Exim
29562 server using the global option called &%tls_crl%& and to an Exim client using
29563 an identically named option for the &(smtp)& transport. In each case, the value
29564 of the option is expanded and must then be the name of a file that contains a
29566 The downside is that clients have to periodically re-download a potentially huge
29567 file from every certificate authority they know of.
29569 The way with most moving parts at query time is Online Certificate
29570 Status Protocol (OCSP), where the client verifies the certificate
29571 against an OCSP server run by the CA. This lets the CA track all
29572 usage of the certs. It requires running software with access to the
29573 private key of the CA, to sign the responses to the OCSP queries. OCSP
29574 is based on HTTP and can be proxied accordingly.
29576 The only widespread OCSP server implementation (known to this writer)
29577 comes as part of OpenSSL and aborts on an invalid request, such as
29578 connecting to the port and then disconnecting. This requires
29579 re-entering the passphrase each time some random client does this.
29581 The third way is OCSP Stapling; in this, the server using a certificate
29582 issued by the CA periodically requests an OCSP proof of validity from
29583 the OCSP server, then serves it up inline as part of the TLS
29584 negotiation. This approach adds no extra round trips, does not let the
29585 CA track users, scales well with number of certs issued by the CA and is
29586 resilient to temporary OCSP server failures, as long as the server
29587 starts retrying to fetch an OCSP proof some time before its current
29588 proof expires. The downside is that it requires server support.
29590 Unless Exim is built with the support disabled,
29591 or with GnuTLS earlier than version 3.3.16 / 3.4.8
29592 support for OCSP stapling is included.
29594 There is a global option called &%tls_ocsp_file%&.
29595 The file specified therein is expected to be in DER format, and contain
29596 an OCSP proof. Exim will serve it as part of the TLS handshake. This
29597 option will be re-expanded for SNI, if the &%tls_certificate%& option
29598 contains &`tls_in_sni`&, as per other TLS options.
29600 Exim does not at this time implement any support for fetching a new OCSP
29601 proof. The burden is on the administrator to handle this, outside of
29602 Exim. The file specified should be replaced atomically, so that the
29603 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
29604 on each connection, so a new file will be handled transparently on the
29607 When built with OpenSSL Exim will check for a valid next update timestamp
29608 in the OCSP proof; if not present, or if the proof has expired, it will be
29611 For the client to be able to verify the stapled OCSP the server must
29612 also supply, in its stapled information, any intermediate
29613 certificates for the chain leading to the OCSP proof from the signer
29614 of the server certificate. There may be zero or one such. These
29615 intermediate certificates should be added to the server OCSP stapling
29616 file named by &%tls_ocsp_file%&.
29618 Note that the proof only covers the terminal server certificate,
29619 not any of the chain from CA to it.
29621 There is no current way to staple a proof for a client certificate.
29624 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
29625 OCSP server is supplied. The server URL may be included in the
29626 server certificate, if the CA is helpful.
29628 One failure mode seen was the OCSP Signer cert expiring before the end
29629 of validity of the OCSP proof. The checking done by Exim/OpenSSL
29630 noted this as invalid overall, but the re-fetch script did not.
29635 .section "Caching of static server configuration items" "SECTserverTLScache"
29636 .cindex certificate caching
29637 .cindex privatekey caching
29638 .cindex crl caching
29639 .cindex ocsp caching
29640 .cindex ciphers caching
29641 .cindex "CA bundle" caching
29642 .cindex "certificate authorities" caching
29643 .cindex tls_certificate caching
29644 .cindex tls_privatekey caching
29645 .cindex tls_crl caching
29646 .cindex tls_ocsp_file caching
29647 .cindex tls_require_ciphers caching
29648 .cindex tls_verify_certificate caching
29649 .cindex caching certificate
29650 .cindex caching privatekey
29651 .cindex caching crl
29652 .cindex caching ocsp
29653 .cindex caching ciphers
29654 .cindex caching "certificate authorities
29655 If any of the main configuration options &%tls_certificate%&, &%tls_privatekey%&,
29656 &%tls_crl%& and &%tls_ocsp_file%& have values with no
29657 expandable elements,
29658 then the associated information is loaded at daemon startup.
29659 It is made available
29660 to child processes forked for handling received SMTP connections.
29662 This caching is currently only supported under Linux and FreeBSD.
29664 If caching is not possible, for example if an item has to be dependent
29665 on the peer host so contains a &$sender_host_name$& expansion, the load
29666 of the associated information is done at the startup of the TLS connection.
29668 The cache is invalidated and reloaded after any changes to the directories
29669 containing files specified by these options.
29671 The information specified by the main option &%tls_verify_certificates%&
29672 is similarly cached so long as it specifies files explicitly
29673 or (under GnuTLS) is the string &"system,cache"&.
29674 The latter case is not automatically invalidated;
29675 it is the operator's responsibility to arrange for a daemon restart
29676 any time the system certificate authority bundle is updated.
29677 A HUP signal is sufficient for this.
29678 The value &"system"& results in no caching under GnuTLS.
29680 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29681 is acceptable in configurations for the Exim executavble.
29683 Caching of the system Certificate Authorities bundle can
29684 save siginificant time and processing on every TLS connection
29691 .section "Configuring an Exim client to use TLS" "SECTclientTLS"
29692 .cindex "cipher" "logging"
29693 .cindex "log" "TLS cipher"
29694 .cindex "log" "distinguished name"
29695 .cindex "TLS" "configuring an Exim client"
29696 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
29697 deliveries as well as to incoming, the latter one causing logging of the
29698 server certificate's DN. The remaining client configuration for TLS is all
29699 within the &(smtp)& transport.
29701 .cindex "ESMTP extensions" STARTTLS
29702 It is not necessary to set any options to have TLS work in the &(smtp)&
29703 transport. If Exim is built with TLS support, and TLS is advertised by a
29704 server, the &(smtp)& transport always tries to start a TLS session. However,
29705 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
29706 transport) to a list of server hosts for which TLS should not be used.
29708 If you do not want Exim to attempt to send messages unencrypted when an attempt
29709 to set up an encrypted connection fails in any way, you can set
29710 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
29711 those hosts, delivery is always deferred if an encrypted connection cannot be
29712 set up. If there are any other hosts for the address, they are tried in the
29715 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
29716 the message unencrypted. It always does this if the response to STARTTLS is
29717 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
29718 session after a success response code, what happens is controlled by the
29719 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
29720 delivery to this host is deferred, and other hosts (if available) are tried. If
29721 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
29722 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
29723 negotiation fails, Exim closes the current connection (because it is in an
29724 unknown state), opens a new one to the same host, and then tries the delivery
29727 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
29728 transport provide the client with a certificate, which is passed to the server
29730 This is an optional thing for TLS connections, although either end
29732 If the server is Exim, it will request a certificate only if
29733 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
29735 &*Note*&: Do not use a certificate which has the OCSP-must-staple extension,
29736 for client use (they are usable for server use).
29737 As the TLS protocol has no means for the client to staple before TLS 1.3 it will result
29738 in failed connections.
29740 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
29741 specifies a collection of expected server certificates.
29743 the system default set (depending on library version),
29745 or (depending on library version) a directory.
29746 The client verifies the server's certificate
29747 against this collection, taking into account any revoked certificates that are
29748 in the list defined by &%tls_crl%&.
29749 Failure to verify fails the TLS connection unless either of the
29750 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
29752 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
29753 certificate verification to the listed servers. Verification either must
29754 or need not succeed respectively.
29756 The &%tls_verify_cert_hostnames%& option lists hosts for which additional
29757 name checks are made on the server certificate.
29759 The match against this list is, as per other Exim usage, the
29760 IP for the host. That is most closely associated with the
29761 name on the DNS A (or AAAA) record for the host.
29762 However, the name that needs to be in the certificate
29763 is the one at the head of any CNAME chain leading to the A record.
29765 The option defaults to always checking.
29767 The &(smtp)& transport has two OCSP-related options:
29768 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
29769 is requested and required for the connection to proceed. The default
29771 &%hosts_request_ocsp%&; a host-list for which (additionally)
29772 a Certificate Status is requested (but not necessarily verified). The default
29773 value is "*" meaning that requests are made unless configured
29776 The host(s) should also be in &%hosts_require_tls%&, and
29777 &%tls_verify_certificates%& configured for the transport,
29778 for OCSP to be relevant.
29781 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
29782 list of permitted cipher suites. If either of these checks fails, delivery to
29783 the current host is abandoned, and the &(smtp)& transport tries to deliver to
29784 alternative hosts, if any.
29787 These options must be set in the &(smtp)& transport for Exim to use TLS when it
29788 is operating as a client. Exim does not assume that a server certificate (set
29789 by the global options of the same name) should also be used when operating as a
29793 .vindex "&$host_address$&"
29794 All the TLS options in the &(smtp)& transport are expanded before use, with
29795 &$host$& and &$host_address$& containing the name and address of the server to
29796 which the client is connected. Forced failure of an expansion causes Exim to
29797 behave as if the relevant option were unset.
29799 .vindex &$tls_out_bits$&
29800 .vindex &$tls_out_cipher$&
29801 .vindex &$tls_out_peerdn$&
29802 .vindex &$tls_out_sni$&
29803 Before an SMTP connection is established, the
29804 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
29805 variables are emptied. (Until the first connection, they contain the values
29806 that were set when the message was received.) If STARTTLS is subsequently
29807 successfully obeyed, these variables are set to the relevant values for the
29808 outgoing connection.
29813 .section "Caching of static client configuration items" "SECTclientTLScache"
29814 .cindex certificate caching
29815 .cindex privatekey caching
29816 .cindex crl caching
29817 .cindex ciphers caching
29818 .cindex "CA bundle" caching
29819 .cindex "certificate authorities" caching
29820 .cindex tls_certificate caching
29821 .cindex tls_privatekey caching
29822 .cindex tls_crl caching
29823 .cindex tls_require_ciphers caching
29824 .cindex tls_verify_certificate caching
29825 .cindex caching certificate
29826 .cindex caching privatekey
29827 .cindex caching crl
29828 .cindex caching ciphers
29829 .cindex caching "certificate authorities
29830 If any of the transport configuration options &%tls_certificate%&, &%tls_privatekey%&
29831 and &%tls_crl%& have values with no
29832 expandable elements,
29833 then the associated information is loaded per smtp transport
29834 at daemon startup, at the start of a queue run, or on a
29835 command-line specified message delivery.
29836 It is made available
29837 to child processes forked for handling making SMTP connections.
29839 This caching is currently only supported under Linux.
29841 If caching is not possible, the load
29842 of the associated information is done at the startup of the TLS connection.
29844 The cache is invalidated in the daemon
29845 and reloaded after any changes to the directories
29846 containing files specified by these options.
29848 The information specified by the main option &%tls_verify_certificates%&
29849 is similarly cached so long as it specifies files explicitly
29850 or (under GnuTLS) is the string &"system,cache"&.
29851 The latter case is not automatically invaludated;
29852 it is the operator's responsibility to arrange for a daemon restart
29853 any time the system certificate authority bundle is updated.
29854 A HUP signal is sufficient for this.
29855 The value &"system"& results in no caching under GnuTLS.
29857 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29858 is acceptable in configurations for the Exim executavble.
29860 Caching of the system Certificate Authorities bundle can
29861 save siginificant time and processing on every TLS connection
29868 .section "Use of TLS Server Name Indication" "SECTtlssni"
29869 .cindex "TLS" "Server Name Indication"
29872 .vindex "&$tls_in_sni$&"
29873 .oindex "&%tls_in_sni%&"
29874 With TLS1.0 or above, there is an extension mechanism by which extra
29875 information can be included at various points in the protocol. One of these
29876 extensions, documented in RFC 6066 (and before that RFC 4366) is
29877 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
29878 client in the initial handshake, so that the server can examine the servername
29879 within and possibly choose to use different certificates and keys (and more)
29882 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
29883 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
29886 With SMTP to MX, there are the same problems here as in choosing the identity
29887 against which to validate a certificate: you can't rely on insecure DNS to
29888 provide the identity which you then cryptographically verify. So this will
29889 be of limited use in that environment.
29891 With SMTP to Submission, there is a well-defined hostname which clients are
29892 connecting to and can validate certificates against. Thus clients &*can*&
29893 choose to include this information in the TLS negotiation. If this becomes
29894 wide-spread, then hosters can choose to present different certificates to
29895 different clients. Or even negotiate different cipher suites.
29897 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
29898 if not empty, will be sent on a TLS session as part of the handshake. There's
29899 nothing more to it. Choosing a sensible value not derived insecurely is the
29900 only point of caution. The &$tls_out_sni$& variable will be set to this string
29901 for the lifetime of the client connection (including during authentication).
29904 If DANE validated the connection attempt then the value of the &%tls_sni%& option
29905 is forced to the domain part of the recipient address.
29908 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
29909 received from a client.
29910 It can be logged with the &%log_selector%& item &`+tls_sni`&.
29912 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
29913 option (prior to expansion) then the following options will be re-expanded
29914 during TLS session handshake, to permit alternative values to be chosen:
29917 &%tls_certificate%&
29923 &%tls_verify_certificates%&
29928 Great care should be taken to deal with matters of case, various injection
29929 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
29930 can always be referenced; it is important to remember that &$tls_in_sni$& is
29931 arbitrary unverified data provided prior to authentication.
29932 Further, the initial certificate is loaded before SNI has arrived, so
29933 an expansion for &%tls_certificate%& must have a default which is used
29934 when &$tls_in_sni$& is empty.
29936 The Exim developers are proceeding cautiously and so far no other TLS options
29939 When Exim is built against OpenSSL, OpenSSL must have been built with support
29940 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
29941 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
29942 see &`-servername`& in the output, then OpenSSL has support.
29944 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
29945 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
29946 built, then you have SNI support).
29950 .cindex ALPN "general information"
29951 .cindex TLS "Application Layer Protocol Names"
29952 There is a TLS feature related to SNI
29953 called Application Layer Protocol Name (ALPN).
29954 This is intended to declare, or select, what protocol layer will be using a TLS
29956 The client for the connection proposes a set of protocol names, and
29957 the server responds with a selected one.
29958 It is not, as of 2021, commonly used for SMTP connections.
29959 However, to guard against misirected or malicious use of web clients
29960 (which often do use ALPN) against MTA ports, Exim by default check that
29961 there is no incompatible ALPN specified by a client for a TLS connection.
29962 If there is, the connection is rejected.
29964 As a client Exim does not supply ALPN by default.
29965 The behaviour of both client and server can be configured using the options
29966 &%tls_alpn%& and &%hosts_require_alpn%&.
29967 There are no variables providing observability.
29968 Some feature-specific logging may appear on denied connections, but this
29969 depends on the behavious of the peer
29970 (not all peers can send a feature-specific TLS Alert).
29972 This feature is available when Exim is built with
29973 OpenSSL 1.1.0 or later or GnuTLS 3.2.0 or later;
29974 the macro _HAVE_TLS_ALPN will be defined when this is so.
29979 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
29981 .cindex "multiple SMTP deliveries with TLS"
29982 .cindex "TLS" "multiple message deliveries"
29983 Exim sends multiple messages down the same TCP/IP connection by starting up
29984 an entirely new delivery process for each message, passing the socket from
29985 one process to the next. This implementation does not fit well with the use
29986 of TLS, because there is quite a lot of state information associated with a TLS
29987 connection, not just a socket identification. Passing all the state information
29988 to a new process is not feasible. Consequently, for sending using TLS Exim
29989 starts an additional proxy process for handling the encryption, piping the
29990 unencrypted data stream from and to the delivery processes.
29992 An older mode of operation can be enabled on a per-host basis by the
29993 &%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
29994 this list the proxy process described above is not used; instead Exim
29995 shuts down an existing TLS session being run by the delivery process
29996 before passing the socket to a new process. The new process may then
29997 try to start a new TLS session, and if successful, may try to re-authenticate
29998 if AUTH is in use, before sending the next message.
30000 The RFC is not clear as to whether or not an SMTP session continues in clear
30001 after TLS has been shut down, or whether TLS may be restarted again later, as
30002 just described. However, if the server is Exim, this shutdown and
30003 reinitialization works. It is not known which (if any) other servers operate
30004 successfully if the client closes a TLS session and continues with unencrypted
30005 SMTP, but there are certainly some that do not work. For such servers, Exim
30006 should not pass the socket to another process, because the failure of the
30007 subsequent attempt to use it would cause Exim to record a temporary host error,
30008 and delay other deliveries to that host.
30010 To test for this case, Exim sends an EHLO command to the server after
30011 closing down the TLS session. If this fails in any way, the connection is
30012 closed instead of being passed to a new delivery process, but no retry
30013 information is recorded.
30015 There is also a manual override; you can set &%hosts_nopass_tls%& on the
30016 &(smtp)& transport to match those hosts for which Exim should not pass
30017 connections to new processes if TLS has been used.
30022 .section "Certificates and all that" "SECTcerandall"
30023 .cindex "certificate" "references to discussion"
30024 In order to understand fully how TLS works, you need to know about
30025 certificates, certificate signing, and certificate authorities.
30026 This is a large topic and an introductory guide is unsuitable for the Exim
30027 reference manual, so instead we provide pointers to existing documentation.
30029 The Apache web-server was for a long time the canonical guide, so their
30030 documentation is a good place to start; their SSL module's Introduction
30031 document is currently at
30033 &url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html)
30035 and their FAQ is at
30037 &url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html)
30040 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
30041 0-201-61598-3) in 2001, contains both introductory and more in-depth
30043 More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&,
30044 published by Feisty Duck (ISBN 978-1907117046) in 2013 is good.
30045 Ivan is the author of the popular TLS testing tools at
30046 &url(https://www.ssllabs.com/).
30049 .section "Certificate chains" "SECID186"
30050 A file named by &%tls_certificate%& may contain more than one
30051 certificate. This is useful in the case where the certificate that is being
30052 sent is validated by an intermediate certificate which the other end does
30053 not have. Multiple certificates must be in the correct order in the file.
30054 First the host's certificate itself, then the first intermediate
30055 certificate to validate the issuer of the host certificate, then the next
30056 intermediate certificate to validate the issuer of the first intermediate
30057 certificate, and so on, until finally (optionally) the root certificate.
30058 The root certificate must already be trusted by the recipient for
30059 validation to succeed, of course, but if it's not preinstalled, sending the
30060 root certificate along with the rest makes it available for the user to
30061 install if the receiving end is a client MUA that can interact with a user.
30063 Note that certificates using MD5 are unlikely to work on today's Internet;
30064 even if your libraries allow loading them for use in Exim when acting as a
30065 server, increasingly clients will not accept such certificates. The error
30066 diagnostics in such a case can be frustratingly vague.
30070 .section "Self-signed certificates" "SECID187"
30071 .cindex "certificate" "self-signed"
30072 You can create a self-signed certificate using the &'req'& command provided
30073 with OpenSSL, like this:
30074 . ==== Do not shorten the duration here without reading and considering
30075 . ==== the text below. Please leave it at 9999 days.
30077 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
30080 &_file1_& and &_file2_& can be the same file; the key and the certificate are
30081 delimited and so can be identified independently. The &%-days%& option
30082 specifies a period for which the certificate is valid. The &%-nodes%& option is
30083 important: if you do not set it, the key is encrypted with a passphrase
30084 that you are prompted for, and any use that is made of the key causes more
30085 prompting for the passphrase. This is not helpful if you are going to use
30086 this certificate and key in an MTA, where prompting is not possible.
30088 . ==== I expect to still be working 26 years from now. The less technical
30089 . ==== debt I create, in terms of storing up trouble for my later years, the
30090 . ==== happier I will be then. We really have reached the point where we
30091 . ==== should start, at the very least, provoking thought and making folks
30092 . ==== pause before proceeding, instead of leaving all the fixes until two
30093 . ==== years before 2^31 seconds after the 1970 Unix epoch.
30095 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
30096 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
30097 the above command might produce a date in the past. Think carefully about
30098 the lifetime of the systems you're deploying, and either reduce the duration
30099 of the certificate or reconsider your platform deployment. (At time of
30100 writing, reducing the duration is the most likely choice, but the inexorable
30101 progression of time takes us steadily towards an era where this will not
30102 be a sensible resolution).
30104 A self-signed certificate made in this way is sufficient for testing, and
30105 may be adequate for all your requirements if you are mainly interested in
30106 encrypting transfers, and not in secure identification.
30108 However, many clients require that the certificate presented by the server be a
30109 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
30110 certificate. In this situation, the self-signed certificate described above
30111 must be installed on the client host as a trusted root &'certification
30112 authority'& (CA), and the certificate used by Exim must be a user certificate
30113 signed with that self-signed certificate.
30115 For information on creating self-signed CA certificates and using them to sign
30116 user certificates, see the &'General implementation overview'& chapter of the
30117 Open-source PKI book, available online at
30118 &url(https://sourceforge.net/projects/ospkibook/).
30119 .ecindex IIDencsmtp1
30120 .ecindex IIDencsmtp2
30124 .section "TLS Resumption" "SECTresumption"
30125 .cindex TLS resumption
30126 TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
30127 in RFC 5077 for 1.2). The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1
30130 Session resumption (this is the "stateless" variant) involves the server sending
30131 a "session ticket" to the client on one connection, which can be stored by the
30132 client and used for a later session. The ticket contains sufficient state for
30133 the server to reconstruct the TLS session, avoiding some expensive crypto
30134 calculation and (on TLS1.2) one full packet roundtrip time.
30137 Operational cost/benefit:
30139 The extra data being transmitted costs a minor amount, and the client has
30140 extra costs in storing and retrieving the data.
30142 In the Exim/Gnutls implementation the extra cost on an initial connection
30143 which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware.
30144 The saved cost on a subsequent connection is about 4ms; three or more
30145 connections become a net win. On longer network paths, two or more
30146 connections will have an average lower startup time thanks to the one
30147 saved packet roundtrip. TLS1.3 will save the crypto cpu costs but not any
30150 .cindex "hints database" tls
30151 Since a new hints DB is used on the TLS client,
30152 the hints DB maintenance should be updated to additionally handle "tls".
30157 The session ticket is encrypted, but is obviously an additional security
30158 vulnarability surface. An attacker able to decrypt it would have access
30159 all connections using the resumed session.
30160 The session ticket encryption key is not committed to storage by the server
30161 and is rotated regularly (OpenSSL: 1hr, and one previous key is used for
30162 overlap; GnuTLS 6hr but does not specify any overlap).
30163 Tickets have limited lifetime (2hr, and new ones issued after 1hr under
30164 OpenSSL. GnuTLS 2hr, appears to not do overlap).
30166 There is a question-mark over the security of the Diffie-Helman parameters
30167 used for session negotiation.
30172 The &%log_selector%& "tls_resumption" appends an asterisk to the tls_cipher "X="
30175 The variables &$tls_in_resumption$& and &$tls_out_resumption$&
30176 have bits 0-4 indicating respectively
30177 support built, client requested ticket, client offered session,
30178 server issued ticket, resume used. A suitable decode list is provided
30179 in the builtin macro _RESUME_DECODE for in &%listextract%& expansions.
30184 The &%tls_resumption_hosts%& main option specifies a hostlist for which
30185 exim, operating as a server, will offer resumption to clients.
30186 Current best practice is to not offer the feature to MUA connection.
30187 Commonly this can be done like this:
30189 tls_resumption_hosts = ${if inlist {$received_port}{587:465} {:}{*}}
30191 If the peer host matches the list after expansion then resumption
30192 is offered and/or accepted.
30194 The &%tls_resumption_hosts%& smtp transport option performs the
30195 equivalent function for operation as a client.
30196 If the peer host matches the list after expansion then resumption
30197 is attempted (if a stored session is available) or the information
30198 stored (if supplied by the peer).
30204 In a resumed session:
30206 The variables &$tls_{in,out}_cipher$& will have values different
30207 to the original (under GnuTLS).
30209 The variables &$tls_{in,out}_ocsp$& will be "not requested" or "no response",
30210 and the &%hosts_require_ocsp%& smtp trasnport option will fail.
30211 . XXX need to do something with that hosts_require_ocsp
30218 .section DANE "SECDANE"
30220 DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
30221 it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
30222 operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
30223 you and the server still think you have an encrypted connection) and, if one of the "well known" set of
30224 Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
30225 certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
30227 What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
30228 that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
30229 by (a) is thought to be smaller than that of the set of root CAs.
30231 It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
30232 fail to pass on a server's STARTTLS.
30234 DANE scales better than having to maintain (and communicate via side-channel) copies of server certificates
30235 for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
30236 client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
30238 DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
30239 that DNS lookups they do for the server have not been tampered with. The domain MX record applying
30240 to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
30242 2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
30243 3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
30245 There are no changes to Exim specific to server-side operation of DANE.
30246 Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
30247 in &_Local/Makefile_&.
30248 If it has been included, the macro "_HAVE_DANE" will be defined.
30250 A TLSA record consist of 4 fields, the "Certificate Usage", the
30251 "Selector", the "Matching type", and the "Certificate Association Data".
30252 For a detailed description of the TLSA record see
30253 &url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671).
30255 The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3).
30256 These are the "Trust Anchor" and "End Entity" variants.
30257 The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
30258 (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
30259 this is appropriate for a single system, using a self-signed certificate.
30260 DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
30262 A private CA at simplest is just a self-signed certificate (with certain
30263 attributes) which is used to sign server certificates, but running one securely
30264 does require careful arrangement.
30265 With DANE-TA, as implemented in Exim and commonly in other MTAs,
30266 the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
30267 DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
30268 all of which point to a single TLSA record.
30269 DANE-TA and DANE-EE can both be used together.
30271 Our recommendation is to use DANE with a certificate from a public CA,
30272 because this enables a variety of strategies for remote clients to verify
30274 You can then publish information both via DANE and another technology,
30275 "MTA-STS", described below.
30277 When you use DANE-TA to publish trust anchor information, you ask entities
30278 outside your administrative control to trust the Certificate Authority for
30279 connections to you.
30280 If using a private CA then you should expect others to still apply the
30281 technical criteria they'd use for a public CA to your certificates.
30282 In particular, you should probably try to follow current best practices for CA
30283 operation around hash algorithms and key sizes.
30284 Do not expect other organizations to lower their security expectations just
30285 because a particular profile might be reasonable for your own internal use.
30287 When this text was last updated, this in practice means to avoid use of SHA-1
30288 and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
30289 than 4096, for interoperability); to use keyUsage fields correctly; to use
30290 random serial numbers.
30291 The list of requirements is subject to change as best practices evolve.
30292 If you're not already using a private CA, or it doesn't meet these
30293 requirements, then we encourage you to avoid all these issues and use a public
30294 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
30296 The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
30297 a "Matching Type" (3rd) field of SHA2-512(2).
30299 For the "Certificate Authority Data" (4th) field, commands like
30302 openssl x509 -pubkey -noout <certificate.pem \
30303 | openssl rsa -outform der -pubin 2>/dev/null \
30308 are workable to create a hash of the certificate's public key.
30310 An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like
30313 _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E...
30316 At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
30317 is useful for quickly generating TLSA records.
30320 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
30322 The Certificate issued by the CA published in the DANE-TA model should be
30323 issued using a strong hash algorithm.
30324 Exim, and importantly various other MTAs sending to you, will not
30325 re-enable hash algorithms which have been disabled by default in TLS
30327 This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
30328 interoperability (and probably the maximum too, in 2018).
30330 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
30331 be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
30332 default of requesting OCSP for all hosts is modified iff DANE is in use, to:
30335 hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
30336 {= {4}{$tls_out_tlsa_usage}} } \
30340 The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
30341 The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
30342 found. If the definition of &%hosts_request_ocsp%& includes the
30343 string "tls_out_tlsa_usage", they are re-expanded in time to
30344 control the OCSP request.
30346 This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
30347 those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
30350 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
30351 and &%dane_require_tls_ciphers%&.
30352 The &"require"& variant will result in failure if the target host is not
30353 DNSSEC-secured. To get DNSSEC-secured hostname resolution, use
30354 the &%dnssec_request_domains%& router or transport option.
30356 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
30358 A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using DNSSEC.
30359 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
30360 will be required for the host. If it does not, the host will not
30361 be used; there is no fallback to non-DANE or non-TLS.
30363 If DANE is requested and usable, then the TLS cipher list configuration
30364 prefers to use the option &%dane_require_tls_ciphers%& and falls
30365 back to &%tls_require_ciphers%& only if that is unset.
30366 This lets you configure "decent crypto" for DANE and "better than nothing
30367 crypto" as the default. Note though that while GnuTLS lets the string control
30368 which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
30369 limited to ciphersuite constraints.
30371 If DANE is requested and useable (see above) the following transport options are ignored:
30375 tls_try_verify_hosts
30376 tls_verify_certificates
30378 tls_verify_cert_hostnames
30382 If DANE is not usable, whether requested or not, and CA-anchored
30383 verification evaluation is wanted, the above variables should be set appropriately.
30385 The router and transport option &%dnssec_request_domains%& must not be
30386 set to &"never"&, and &%dnssec_require_domains%& is ignored.
30388 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
30390 There is a new variable &$tls_out_dane$& which will have "yes" if
30391 verification succeeded using DANE and "no" otherwise (only useful
30392 in combination with events; see &<<CHAPevents>>&),
30393 and a new variable &$tls_out_tlsa_usage$& (detailed above).
30395 .cindex DANE reporting
30396 An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
30397 to achieve DANE-verified connection, if one was either requested and offered, or
30398 required. This is intended to support TLS-reporting as defined in
30399 &url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
30400 The &$event_data$& will be one of the Result Types defined in
30401 Section 4.3 of that document.
30403 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
30405 DANE is specified in published RFCs and decouples certificate authority trust
30406 selection from a "race to the bottom" of "you must trust everything for mail
30407 to get through". There is an alternative technology called MTA-STS, which
30408 instead publishes MX trust anchor information on an HTTPS website. At the
30409 time this text was last updated, MTA-STS was still a draft, not yet an RFC.
30410 Exim has no support for MTA-STS as a client, but Exim mail server operators
30411 can choose to publish information describing their TLS configuration using
30412 MTA-STS to let those clients who do use that protocol derive trust
30415 The MTA-STS design requires a certificate from a public Certificate Authority
30416 which is recognized by clients sending to you.
30417 That selection of which CAs are trusted by others is outside your control.
30419 The most interoperable course of action is probably to use
30420 &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
30421 renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
30422 records for DANE clients (such as Exim and Postfix) and to publish anchor
30423 information for MTA-STS as well. This is what is done for the &'exim.org'&
30424 domain itself (with caveats around occasionally broken MTA-STS because of
30425 incompatible specification changes prior to reaching RFC status).
30429 . ////////////////////////////////////////////////////////////////////////////
30430 . ////////////////////////////////////////////////////////////////////////////
30432 .chapter "Access control lists" "CHAPACL"
30433 .scindex IIDacl "&ACL;" "description"
30434 .cindex "control of incoming mail"
30435 .cindex "message" "controlling incoming"
30436 .cindex "policy control" "access control lists"
30437 Access Control Lists (ACLs) are defined in a separate section of the runtime
30438 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
30439 name, terminated by a colon. Here is a complete ACL section that contains just
30440 one very small ACL:
30444 accept hosts = one.host.only
30446 You can have as many lists as you like in the ACL section, and the order in
30447 which they appear does not matter. The lists are self-terminating.
30449 The majority of ACLs are used to control Exim's behaviour when it receives
30450 certain SMTP commands. This applies both to incoming TCP/IP connections, and
30451 when a local process submits a message using SMTP by specifying the &%-bs%&
30452 option. The most common use is for controlling which recipients are accepted
30453 in incoming messages. In addition, you can define an ACL that is used to check
30454 local non-SMTP messages. The default configuration file contains an example of
30455 a realistic ACL for checking RCPT commands. This is discussed in chapter
30456 &<<CHAPdefconfil>>&.
30459 .section "Testing ACLs" "SECID188"
30460 The &%-bh%& command line option provides a way of testing your ACL
30461 configuration locally by running a fake SMTP session with which you interact.
30464 .section "Specifying when ACLs are used" "SECID189"
30465 .cindex "&ACL;" "options for specifying"
30466 In order to cause an ACL to be used, you have to name it in one of the relevant
30467 options in the main part of the configuration. These options are:
30468 .cindex "AUTH" "ACL for"
30469 .cindex "DATA" "ACLs for"
30470 .cindex "ETRN" "ACL for"
30471 .cindex "EXPN" "ACL for"
30472 .cindex "HELO" "ACL for"
30473 .cindex "EHLO" "ACL for"
30474 .cindex "DKIM" "ACL for"
30475 .cindex "MAIL" "ACL for"
30476 .cindex "QUIT, ACL for"
30477 .cindex "RCPT" "ACL for"
30478 .cindex "STARTTLS, ACL for"
30479 .cindex "VRFY" "ACL for"
30480 .cindex "SMTP" "connection, ACL for"
30481 .cindex "non-SMTP messages" "ACLs for"
30482 .cindex "MIME content scanning" "ACL for"
30483 .cindex "PRDR" "ACL for"
30486 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
30487 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
30488 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
30489 .irow &%acl_smtp_auth%& "ACL for AUTH"
30490 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
30491 .irow &%acl_smtp_data%& "ACL after DATA is complete"
30492 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
30493 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
30494 .irow &%acl_smtp_etrn%& "ACL for ETRN"
30495 .irow &%acl_smtp_expn%& "ACL for EXPN"
30496 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
30497 .irow &%acl_smtp_mail%& "ACL for MAIL"
30498 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
30499 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
30500 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
30501 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
30502 .irow &%acl_smtp_quit%& "ACL for QUIT"
30503 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
30504 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
30505 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
30508 For example, if you set
30510 acl_smtp_rcpt = small_acl
30512 the little ACL defined above is used whenever Exim receives a RCPT command
30513 in an SMTP dialogue. The majority of policy tests on incoming messages can be
30514 done when RCPT commands arrive. A rejection of RCPT should cause the
30515 sending MTA to give up on the recipient address contained in the RCPT
30516 command, whereas rejection at other times may cause the client MTA to keep on
30517 trying to deliver the message. It is therefore recommended that you do as much
30518 testing as possible at RCPT time.
30521 .section "The non-SMTP ACLs" "SECID190"
30522 .cindex "non-SMTP messages" "ACLs for"
30523 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
30524 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
30525 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
30526 the state of the SMTP connection such as encryption and authentication) are not
30527 relevant and are forbidden in these ACLs. However, the sender and recipients
30528 are known, so the &%senders%& and &%sender_domains%& conditions and the
30529 &$sender_address$& and &$recipients$& variables can be used. Variables such as
30530 &$authenticated_sender$& are also available. You can specify added header lines
30531 in any of these ACLs.
30533 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
30534 non-SMTP message, before any of the message has been read. (This is the
30535 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
30536 batched SMTP input, it runs after the DATA command has been reached. The
30537 result of this ACL is ignored; it cannot be used to reject a message. If you
30538 really need to, you could set a value in an ACL variable here and reject based
30539 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
30540 controls, and in particular, it can be used to set
30542 control = suppress_local_fixups
30544 This cannot be used in the other non-SMTP ACLs because by the time they are
30545 run, it is too late.
30547 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
30548 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30550 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
30551 kind of rejection is treated as permanent, because there is no way of sending a
30552 temporary error for these kinds of message.
30555 .section "The SMTP connect ACL" "SECID191"
30556 .cindex "SMTP" "connection, ACL for"
30557 .oindex &%smtp_banner%&
30558 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
30559 session, after the test specified by &%host_reject_connection%& (which is now
30560 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
30561 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
30562 the message override the banner message that is otherwise specified by the
30563 &%smtp_banner%& option.
30566 .section "The EHLO/HELO ACL" "SECID192"
30567 .cindex "EHLO" "ACL for"
30568 .cindex "HELO" "ACL for"
30569 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
30570 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
30571 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
30572 Note that a client may issue more than one EHLO or HELO command in an SMTP
30573 session, and indeed is required to issue a new EHLO or HELO after successfully
30574 setting up encryption following a STARTTLS command.
30576 Note also that a deny neither forces the client to go away nor means that
30577 mail will be refused on the connection. Consider checking for
30578 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
30580 If the command is accepted by an &%accept%& verb that has a &%message%&
30581 modifier, the message may not contain more than one line (it will be truncated
30582 at the first newline and a panic logged if it does). Such a message cannot
30583 affect the EHLO options that are listed on the second and subsequent lines of
30587 .section "The DATA ACLs" "SECID193"
30588 .cindex "DATA" "ACLs for"
30589 Two ACLs are associated with the DATA command, because it is two-stage
30590 command, with two responses being sent to the client.
30591 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
30592 is obeyed. This gives you control after all the RCPT commands, but before
30593 the message itself is received. It offers the opportunity to give a negative
30594 response to the DATA command before the data is transmitted. Header lines
30595 added by MAIL or RCPT ACLs are not visible at this time, but any that
30596 are defined here are visible when the &%acl_smtp_data%& ACL is run.
30598 You cannot test the contents of the message, for example, to verify addresses
30599 in the headers, at RCPT time or when the DATA command is received. Such
30600 tests have to appear in the ACL that is run after the message itself has been
30601 received, before the final response to the DATA command is sent. This is
30602 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
30603 associated with the DATA command.
30605 .cindex CHUNKING "BDAT command"
30606 .cindex BDAT "SMTP command"
30607 .cindex "RFC 3030" CHUNKING
30608 If CHUNKING was advertised and a BDAT command sequence is received,
30609 the &%acl_smtp_predata%& ACL is not run.
30610 . XXX why not? It should be possible, for the first BDAT.
30611 The &%acl_smtp_data%& is run after the last BDAT command and all of
30612 the data specified is received.
30614 For both of these ACLs, it is not possible to reject individual recipients. An
30615 error response rejects the entire message. Unfortunately, it is known that some
30616 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
30617 before or after the data) correctly &-- they keep the message on their queues
30618 and try again later, but that is their problem, though it does waste some of
30621 The &%acl_smtp_data%& ACL is run after
30622 the &%acl_smtp_data_prdr%&,
30623 the &%acl_smtp_dkim%&
30624 and the &%acl_smtp_mime%& ACLs.
30626 .section "The SMTP DKIM ACL" "SECTDKIMACL"
30627 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
30628 enabled (which is the default).
30630 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
30631 received, and is executed for each DKIM signature found in a message. If not
30632 otherwise specified, the default action is to accept.
30634 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
30636 For details on the operation of DKIM, see section &<<SECDKIM>>&.
30639 .section "The SMTP MIME ACL" "SECID194"
30640 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
30641 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30643 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30646 .section "The SMTP PRDR ACL" "SECTPRDRACL"
30647 .cindex "PRDR" "ACL for"
30648 .oindex "&%prdr_enable%&"
30649 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
30650 with PRDR support enabled (which is the default).
30651 It becomes active only when the PRDR feature is negotiated between
30652 client and server for a message, and more than one recipient
30655 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
30656 has been received, and is executed once for each recipient of the message
30657 with &$local_part$& and &$domain$& valid.
30658 The test may accept, defer or deny for individual recipients.
30659 The &%acl_smtp_data%& will still be called after this ACL and
30660 can reject the message overall, even if this ACL has accepted it
30661 for some or all recipients.
30663 PRDR may be used to support per-user content filtering. Without it
30664 one must defer any recipient after the first that has a different
30665 content-filter configuration. With PRDR, the RCPT-time check
30666 .cindex "PRDR" "variable for"
30667 for this can be disabled when the variable &$prdr_requested$&
30669 Any required difference in behaviour of the main DATA-time
30670 ACL should however depend on the PRDR-time ACL having run, as Exim
30671 will avoid doing so in some situations (e.g. single-recipient mails).
30673 See also the &%prdr_enable%& global option
30674 and the &%hosts_try_prdr%& smtp transport option.
30676 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30677 If the ACL is not defined, processing completes as if
30678 the feature was not requested by the client.
30680 .section "The QUIT ACL" "SECTQUITACL"
30681 .cindex "QUIT, ACL for"
30682 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
30683 does not affect the response code to QUIT, which is always 221. Thus, the ACL
30684 does not in fact control any access.
30685 For this reason, it may only accept
30686 or warn as its final result.
30688 This ACL can be used for tasks such as custom logging at the end of an SMTP
30689 session. For example, you can use ACL variables in other ACLs to count
30690 messages, recipients, etc., and log the totals at QUIT time using one or
30691 more &%logwrite%& modifiers on a &%warn%& verb.
30693 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
30694 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
30696 You do not need to have a final &%accept%&, but if you do, you can use a
30697 &%message%& modifier to specify custom text that is sent as part of the 221
30700 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
30701 failure (for example, failure to open a log file, or when Exim is bombing out
30702 because it has detected an unrecoverable error), all SMTP commands from the
30703 client are given temporary error responses until QUIT is received or the
30704 connection is closed. In these special cases, the QUIT ACL does not run.
30707 .section "The not-QUIT ACL" "SECTNOTQUITACL"
30708 .vindex &$acl_smtp_notquit$&
30709 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
30710 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
30711 trouble, such as being unable to write to its log files, this ACL is not run,
30712 because it might try to do things (such as write to log files) that make the
30713 situation even worse.
30715 Like the QUIT ACL, this ACL is provided to make it possible to do customized
30716 logging or to gather statistics, and its outcome is ignored. The &%delay%&
30717 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
30720 .vindex &$smtp_notquit_reason$&
30721 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
30722 to a string that indicates the reason for the termination of the SMTP
30723 connection. The possible values are:
30725 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
30726 .irow &`bad-commands`& "Too many unknown or non-mail commands"
30727 .irow &`command-timeout`& "Timeout while reading SMTP commands"
30728 .irow &`connection-lost`& "The SMTP connection has been lost"
30729 .irow &`data-timeout`& "Timeout while reading message data"
30730 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
30731 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
30732 .irow &`signal-exit`& "SIGTERM or SIGINT"
30733 .irow &`synchronization-error`& "SMTP synchronization error"
30734 .irow &`tls-failed`& "TLS failed to start"
30736 In most cases when an SMTP connection is closed without having received QUIT,
30737 Exim sends an SMTP response message before actually closing the connection.
30738 With the exception of the &`acl-drop`& case, the default message can be
30739 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
30740 &%drop%& verb in another ACL, it is the message from the other ACL that is
30744 .section "Finding an ACL to use" "SECID195"
30745 .cindex "&ACL;" "finding which to use"
30746 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
30747 you can use different ACLs in different circumstances. For example,
30749 acl_smtp_rcpt = ${if ={25}{$interface_port} \
30750 {acl_check_rcpt} {acl_check_rcpt_submit} }
30752 In the default configuration file there are some example settings for
30753 providing an RFC 4409 message &"submission"& service on port 587 and
30754 an RFC 8314 &"submissions"& service on port 465. You can use a string
30755 expansion like this to choose an ACL for MUAs on these ports which is
30756 more appropriate for this purpose than the default ACL on port 25.
30758 The expanded string does not have to be the name of an ACL in the
30759 configuration file; there are other possibilities. Having expanded the
30760 string, Exim searches for an ACL as follows:
30763 If the string begins with a slash, Exim uses it as a filename, and reads its
30764 contents as an ACL. The lines are processed in the same way as lines in the
30765 Exim configuration file. In particular, continuation lines are supported, blank
30766 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
30767 If the file does not exist or cannot be read, an error occurs (typically
30768 causing a temporary failure of whatever caused the ACL to be run). For example:
30770 acl_smtp_data = /etc/acls/\
30771 ${lookup{$sender_host_address}lsearch\
30772 {/etc/acllist}{$value}{default}}
30774 This looks up an ACL file to use on the basis of the host's IP address, falling
30775 back to a default if the lookup fails. If an ACL is successfully read from a
30776 file, it is retained in memory for the duration of the Exim process, so that it
30777 can be re-used without having to re-read the file.
30779 If the string does not start with a slash, and does not contain any spaces,
30780 Exim searches the ACL section of the configuration for an ACL whose name
30781 matches the string.
30783 If no named ACL is found, or if the string contains spaces, Exim parses
30784 the string as an inline ACL. This can save typing in cases where you just
30785 want to have something like
30787 acl_smtp_vrfy = accept
30789 in order to allow free use of the VRFY command. Such a string may contain
30790 newlines; it is processed in the same way as an ACL that is read from a file.
30796 .section "ACL return codes" "SECID196"
30797 .cindex "&ACL;" "return codes"
30798 Except for the QUIT ACL, which does not affect the SMTP return code (see
30799 section &<<SECTQUITACL>>& above), the result of running an ACL is either
30800 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
30801 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
30802 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
30803 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
30804 This also causes a 4&'xx'& return code.
30806 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
30807 &"deny"&, because there is no mechanism for passing temporary errors to the
30808 submitters of non-SMTP messages.
30811 ACLs that are relevant to message reception may also return &"discard"&. This
30812 has the effect of &"accept"&, but causes either the entire message or an
30813 individual recipient address to be discarded. In other words, it is a
30814 blackholing facility. Use it with care.
30816 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
30817 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
30818 RCPT ACL is to discard just the one recipient address. If there are no
30819 recipients left when the message's data is received, the DATA ACL is not
30820 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
30821 remaining recipients. The &"discard"& return is not permitted for the
30822 &%acl_smtp_predata%& ACL.
30824 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
30825 is done on the address and the result determines the SMTP response.
30828 .cindex "&[local_scan()]& function" "when all recipients discarded"
30829 The &[local_scan()]& function is always run, even if there are no remaining
30830 recipients; it may create new recipients.
30834 .section "Unset ACL options" "SECID197"
30835 .cindex "&ACL;" "unset options"
30836 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
30837 all the same. &*Note*&: These defaults apply only when the relevant ACL is
30838 not defined at all. For any defined ACL, the default action when control
30839 reaches the end of the ACL statements is &"deny"&.
30841 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
30842 these two are ACLs that are used only for their side effects. They cannot be
30843 used to accept or reject anything.
30845 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
30846 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
30847 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
30848 when the ACL is not defined is &"accept"&.
30850 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
30851 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
30852 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
30853 messages over an SMTP connection. For an example, see the ACL in the default
30854 configuration file.
30859 .section "Data for message ACLs" "SECID198"
30860 .cindex "&ACL;" "data for message ACL"
30862 .vindex &$local_part$&
30863 .vindex &$sender_address$&
30864 .vindex &$sender_host_address$&
30865 .vindex &$smtp_command$&
30866 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
30867 that contain information about the host and the message's sender (for example,
30868 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
30869 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
30870 &$local_part$& are set from the argument address. The entire SMTP command
30871 is available in &$smtp_command$&.
30873 When an ACL for the AUTH parameter of MAIL is running, the variables that
30874 contain information about the host are set, but &$sender_address$& is not yet
30875 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
30878 .vindex "&$message_size$&"
30879 The &$message_size$& variable is set to the value of the SIZE parameter on
30880 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
30881 that parameter is not given. The value is updated to the true message size by
30882 the time the final DATA ACL is run (after the message data has been
30885 .vindex "&$rcpt_count$&"
30886 .vindex "&$recipients_count$&"
30887 The &$rcpt_count$& variable increases by one for each RCPT command received.
30888 The &$recipients_count$& variable increases by one each time a RCPT command is
30889 accepted, so while an ACL for RCPT is being processed, it contains the number
30890 of previously accepted recipients. At DATA time (for both the DATA ACLs),
30891 &$rcpt_count$& contains the total number of RCPT commands, and
30892 &$recipients_count$& contains the total number of accepted recipients.
30898 .section "Data for non-message ACLs" "SECTdatfornon"
30899 .cindex "&ACL;" "data for non-message ACL"
30900 .vindex &$smtp_command_argument$&
30901 .vindex &$smtp_command$&
30902 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
30903 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
30904 and the entire SMTP command is available in &$smtp_command$&.
30905 These variables can be tested using a &%condition%& condition. For example,
30906 here is an ACL for use with AUTH, which insists that either the session is
30907 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
30908 does not permit authentication methods that use cleartext passwords on
30909 unencrypted connections.
30912 accept encrypted = *
30913 accept condition = ${if eq{${uc:$smtp_command_argument}}\
30915 deny message = TLS encryption or CRAM-MD5 required
30917 (Another way of applying this restriction is to arrange for the authenticators
30918 that use cleartext passwords not to be advertised when the connection is not
30919 encrypted. You can use the generic &%server_advertise_condition%& authenticator
30920 option to do this.)
30924 .section "Format of an ACL" "SECID199"
30925 .cindex "&ACL;" "format of"
30926 .cindex "&ACL;" "verbs, definition of"
30927 An individual ACL consists of a number of statements. Each statement starts
30928 with a verb, optionally followed by a number of conditions and &"modifiers"&.
30929 Modifiers can change the way the verb operates, define error and log messages,
30930 set variables, insert delays, and vary the processing of accepted messages.
30932 If all the conditions are met, the verb is obeyed. The same condition may be
30933 used (with different arguments) more than once in the same statement. This
30934 provides a means of specifying an &"and"& conjunction between conditions. For
30937 deny dnslists = list1.example
30938 dnslists = list2.example
30940 If there are no conditions, the verb is always obeyed. Exim stops evaluating
30941 the conditions and modifiers when it reaches a condition that fails. What
30942 happens then depends on the verb (and in one case, on a special modifier). Not
30943 all the conditions make sense at every testing point. For example, you cannot
30944 test a sender address in the ACL that is run for a VRFY command.
30947 .section "ACL verbs" "SECID200"
30948 The ACL verbs are as follows:
30951 .cindex "&%accept%& ACL verb"
30952 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
30953 of the conditions are not met, what happens depends on whether &%endpass%&
30954 appears among the conditions (for syntax see below). If the failing condition
30955 is before &%endpass%&, control is passed to the next ACL statement; if it is
30956 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
30957 check a RCPT command:
30959 accept domains = +local_domains
30963 If the recipient domain does not match the &%domains%& condition, control
30964 passes to the next statement. If it does match, the recipient is verified, and
30965 the command is accepted if verification succeeds. However, if verification
30966 fails, the ACL yields &"deny"&, because the failing condition is after
30969 The &%endpass%& feature has turned out to be confusing to many people, so its
30970 use is not recommended nowadays. It is always possible to rewrite an ACL so
30971 that &%endpass%& is not needed, and it is no longer used in the default
30974 .cindex "&%message%& ACL modifier" "with &%accept%&"
30975 If a &%message%& modifier appears on an &%accept%& statement, its action
30976 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
30977 (when an &%accept%& verb either accepts or passes control to the next
30978 statement), &%message%& can be used to vary the message that is sent when an
30979 SMTP command is accepted. For example, in a RCPT ACL you could have:
30981 &`accept `&<&'some conditions'&>
30982 &` message = OK, I will allow you through today`&
30984 You can specify an SMTP response code, optionally followed by an &"extended
30985 response code"& at the start of the message, but the first digit must be the
30986 same as would be sent by default, which is 2 for an &%accept%& verb.
30988 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
30989 an error message that is used when access is denied. This behaviour is retained
30990 for backward compatibility, but current &"best practice"& is to avoid the use
30995 .cindex "&%defer%& ACL verb"
30996 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
30997 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
30998 &%defer%& is the same as &%deny%&, because there is no way of sending a
30999 temporary error. For a RCPT command, &%defer%& is much the same as using a
31000 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
31001 be used in any ACL, and even for a recipient it might be a simpler approach.
31005 .cindex "&%deny%& ACL verb"
31006 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
31007 the conditions are not met, control is passed to the next ACL statement. For
31010 deny dnslists = blackholes.mail-abuse.org
31012 rejects commands from hosts that are on a DNS black list.
31016 .cindex "&%discard%& ACL verb"
31017 &%discard%&: This verb behaves like &%accept%&, except that it returns
31018 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
31019 that are concerned with receiving messages. When all the conditions are true,
31020 the sending entity receives a &"success"& response. However, &%discard%& causes
31021 recipients to be discarded. If it is used in an ACL for RCPT, just the one
31022 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
31023 message's recipients are discarded. Recipients that are discarded before DATA
31024 do not appear in the log line when the &%received_recipients%& log selector is set.
31026 If the &%log_message%& modifier is set when &%discard%& operates,
31027 its contents are added to the line that is automatically written to the log.
31028 The &%message%& modifier operates exactly as it does for &%accept%&.
31032 .cindex "&%drop%& ACL verb"
31033 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
31034 forcibly closed after the 5&'xx'& error message has been sent. For example:
31036 drop condition = ${if > {$rcpt_count}{20}}
31037 message = I don't take more than 20 RCPTs
31039 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
31040 The connection is always dropped after sending a 550 response.
31043 .cindex "&%require%& ACL verb"
31044 &%require%&: If all the conditions are met, control is passed to the next ACL
31045 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
31046 example, when checking a RCPT command,
31048 require message = Sender did not verify
31051 passes control to subsequent statements only if the message's sender can be
31052 verified. Otherwise, it rejects the command. Note the positioning of the
31053 &%message%& modifier, before the &%verify%& condition. The reason for this is
31054 discussed in section &<<SECTcondmodproc>>&.
31057 .cindex "&%warn%& ACL verb"
31058 &%warn%&: If all the conditions are true, a line specified by the
31059 &%log_message%& modifier is written to Exim's main log. Control always passes
31060 to the next ACL statement. If any condition is false, the log line is not
31061 written. If an identical log line is requested several times in the same
31062 message, only one copy is actually written to the log. If you want to force
31063 duplicates to be written, use the &%logwrite%& modifier instead.
31065 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
31066 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
31067 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
31068 first failing condition. There is more about adding header lines in section
31069 &<<SECTaddheadacl>>&.
31071 If any condition on a &%warn%& statement cannot be completed (that is, there is
31072 some sort of defer), the log line specified by &%log_message%& is not written.
31073 This does not include the case of a forced failure from a lookup, which
31074 is considered to be a successful completion. After a defer, no further
31075 conditions or modifiers in the &%warn%& statement are processed. The incident
31076 is logged, and the ACL continues to be processed, from the next statement
31080 .vindex "&$acl_verify_message$&"
31081 When one of the &%warn%& conditions is an address verification that fails, the
31082 text of the verification failure message is in &$acl_verify_message$&. If you
31083 want this logged, you must set it up explicitly. For example:
31085 warn !verify = sender
31086 log_message = sender verify failed: $acl_verify_message
31090 At the end of each ACL there is an implicit unconditional &%deny%&.
31092 As you can see from the examples above, the conditions and modifiers are
31093 written one to a line, with the first one on the same line as the verb, and
31094 subsequent ones on following lines. If you have a very long condition, you can
31095 continue it onto several physical lines by the usual backslash continuation
31096 mechanism. It is conventional to align the conditions vertically.
31100 .section "ACL variables" "SECTaclvariables"
31101 .cindex "&ACL;" "variables"
31102 There are some special variables that can be set during ACL processing. They
31103 can be used to pass information between different ACLs, different invocations
31104 of the same ACL in the same SMTP connection, and between ACLs and the routers,
31105 transports, and filters that are used to deliver a message. The names of these
31106 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
31107 an underscore, but the remainder of the name can be any sequence of
31108 alphanumeric characters and underscores that you choose. There is no limit on
31109 the number of ACL variables. The two sets act as follows:
31111 The values of those variables whose names begin with &$acl_c$& persist
31112 throughout an SMTP connection. They are never reset. Thus, a value that is set
31113 while receiving one message is still available when receiving the next message
31114 on the same SMTP connection.
31116 The values of those variables whose names begin with &$acl_m$& persist only
31117 while a message is being received. They are reset afterwards. They are also
31118 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
31121 When a message is accepted, the current values of all the ACL variables are
31122 preserved with the message and are subsequently made available at delivery
31123 time. The ACL variables are set by a modifier called &%set%&. For example:
31125 accept hosts = whatever
31126 set acl_m4 = some value
31127 accept authenticated = *
31128 set acl_c_auth = yes
31130 &*Note*&: A leading dollar sign is not used when naming a variable that is to
31131 be set. If you want to set a variable without taking any action, you can use a
31132 &%warn%& verb without any other modifiers or conditions.
31134 .oindex &%strict_acl_vars%&
31135 What happens if a syntactically valid but undefined ACL variable is
31136 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
31137 false (the default), an empty string is substituted; if it is true, an
31138 error is generated.
31140 Versions of Exim before 4.64 have a limited set of numbered variables, but
31141 their names are compatible, so there is no problem with upgrading.
31144 .section "Condition and modifier processing" "SECTcondmodproc"
31145 .cindex "&ACL;" "conditions; processing"
31146 .cindex "&ACL;" "modifiers; processing"
31147 An exclamation mark preceding a condition negates its result. For example:
31149 deny domains = *.dom.example
31150 !verify = recipient
31152 causes the ACL to return &"deny"& if the recipient domain ends in
31153 &'dom.example'& and the recipient address cannot be verified. Sometimes
31154 negation can be used on the right-hand side of a condition. For example, these
31155 two statements are equivalent:
31157 deny hosts = !192.168.3.4
31158 deny !hosts = 192.168.3.4
31160 However, for many conditions (&%verify%& being a good example), only left-hand
31161 side negation of the whole condition is possible.
31163 The arguments of conditions and modifiers are expanded. A forced failure
31164 of an expansion causes a condition to be ignored, that is, it behaves as if the
31165 condition is true. Consider these two statements:
31167 accept senders = ${lookup{$host_name}lsearch\
31168 {/some/file}{$value}fail}
31169 accept senders = ${lookup{$host_name}lsearch\
31170 {/some/file}{$value}{}}
31172 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
31173 the returned list is searched, but if the lookup fails the behaviour is
31174 different in the two cases. The &%fail%& in the first statement causes the
31175 condition to be ignored, leaving no further conditions. The &%accept%& verb
31176 therefore succeeds. The second statement, however, generates an empty list when
31177 the lookup fails. No sender can match an empty list, so the condition fails,
31178 and therefore the &%accept%& also fails.
31180 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
31181 specify actions that are taken as the conditions for a statement are checked;
31182 others specify text for messages that are used when access is denied or a
31183 warning is generated. The &%control%& modifier affects the way an incoming
31184 message is handled.
31186 The positioning of the modifiers in an ACL statement is important, because the
31187 processing of a verb ceases as soon as its outcome is known. Only those
31188 modifiers that have already been encountered will take effect. For example,
31189 consider this use of the &%message%& modifier:
31191 require message = Can't verify sender
31193 message = Can't verify recipient
31195 message = This message cannot be used
31197 If sender verification fails, Exim knows that the result of the statement is
31198 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
31199 so its text is used as the error message. If sender verification succeeds, but
31200 recipient verification fails, the second message is used. If recipient
31201 verification succeeds, the third message becomes &"current"&, but is never used
31202 because there are no more conditions to cause failure.
31204 For the &%deny%& verb, on the other hand, it is always the last &%message%&
31205 modifier that is used, because all the conditions must be true for rejection to
31206 happen. Specifying more than one &%message%& modifier does not make sense, and
31207 the message can even be specified after all the conditions. For example:
31210 !senders = *@my.domain.example
31211 message = Invalid sender from client host
31213 The &"deny"& result does not happen until the end of the statement is reached,
31214 by which time Exim has set up the message.
31218 .section "ACL modifiers" "SECTACLmodi"
31219 .cindex "&ACL;" "modifiers; list of"
31220 The ACL modifiers are as follows:
31223 .vitem &*add_header*&&~=&~<&'text'&>
31224 This modifier specifies one or more header lines that are to be added to an
31225 incoming message, assuming, of course, that the message is ultimately
31226 accepted. For details, see section &<<SECTaddheadacl>>&.
31228 .vitem &*continue*&&~=&~<&'text'&>
31229 .cindex "&%continue%& ACL modifier"
31230 .cindex "database" "updating in ACL"
31231 This modifier does nothing of itself, and processing of the ACL always
31232 continues with the next condition or modifier. The value of &%continue%& is in
31233 the side effects of expanding its argument. Typically this could be used to
31234 update a database. It is really just a syntactic tidiness, to avoid having to
31235 write rather ugly lines like this:
31237 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
31239 Instead, all you need is
31241 &`continue = `&<&'some expansion'&>
31244 .vitem &*control*&&~=&~<&'text'&>
31245 .cindex "&%control%& ACL modifier"
31246 This modifier affects the subsequent processing of the SMTP connection or of an
31247 incoming message that is accepted. The effect of the first type of control
31248 lasts for the duration of the connection, whereas the effect of the second type
31249 lasts only until the current message has been received. The message-specific
31250 controls always apply to the whole message, not to individual recipients,
31251 even if the &%control%& modifier appears in a RCPT ACL.
31253 As there are now quite a few controls that can be applied, they are described
31254 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
31255 in several different ways. For example:
31257 . ==== As this is a nested list, any displays it contains must be indented
31258 . ==== as otherwise they are too far to the left. That comment applies only
31259 . ==== when xmlto and fop are used; formatting with sdop gets it right either
31263 It can be at the end of an &%accept%& statement:
31265 accept ...some conditions
31268 In this case, the control is applied when this statement yields &"accept"&, in
31269 other words, when the conditions are all true.
31272 It can be in the middle of an &%accept%& statement:
31274 accept ...some conditions...
31276 ...some more conditions...
31278 If the first set of conditions are true, the control is applied, even if the
31279 statement does not accept because one of the second set of conditions is false.
31280 In this case, some subsequent statement must yield &"accept"& for the control
31284 It can be used with &%warn%& to apply the control, leaving the
31285 decision about accepting or denying to a subsequent verb. For
31288 warn ...some conditions...
31292 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
31293 &%logwrite%&, so it does not add anything to the message and does not write a
31297 If you want to apply a control unconditionally, you can use it with a
31298 &%require%& verb. For example:
31300 require control = no_multiline_responses
31304 .vitem &*delay*&&~=&~<&'time'&>
31305 .cindex "&%delay%& ACL modifier"
31307 This modifier may appear in any ACL except notquit. It causes Exim to wait for
31308 the time interval before proceeding. However, when testing Exim using the
31309 &%-bh%& option, the delay is not actually imposed (an appropriate message is
31310 output instead). The time is given in the usual Exim notation, and the delay
31311 happens as soon as the modifier is processed. In an SMTP session, pending
31312 output is flushed before the delay is imposed.
31314 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
31317 deny ...some conditions...
31320 The delay happens if all the conditions are true, before the statement returns
31321 &"deny"&. Compare this with:
31324 ...some conditions...
31326 which waits for 30s before processing the conditions. The &%delay%& modifier
31327 can also be used with &%warn%& and together with &%control%&:
31329 warn ...some conditions...
31335 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
31336 responses to several commands are no longer buffered and sent in one packet (as
31337 they would normally be) because all output is flushed before imposing the
31338 delay. This optimization is disabled so that a number of small delays do not
31339 appear to the client as one large aggregated delay that might provoke an
31340 unwanted timeout. You can, however, disable output flushing for &%delay%& by
31341 using a &%control%& modifier to set &%no_delay_flush%&.
31345 .cindex "&%endpass%& ACL modifier"
31346 This modifier, which has no argument, is recognized only in &%accept%& and
31347 &%discard%& statements. It marks the boundary between the conditions whose
31348 failure causes control to pass to the next statement, and the conditions whose
31349 failure causes the ACL to return &"deny"&. This concept has proved to be
31350 confusing to some people, so the use of &%endpass%& is no longer recommended as
31351 &"best practice"&. See the description of &%accept%& above for more details.
31354 .vitem &*log_message*&&~=&~<&'text'&>
31355 .cindex "&%log_message%& ACL modifier"
31356 This modifier sets up a message that is used as part of the log message if the
31357 ACL denies access or a &%warn%& statement's conditions are true. For example:
31359 require log_message = wrong cipher suite $tls_in_cipher
31360 encrypted = DES-CBC3-SHA
31362 &%log_message%& is also used when recipients are discarded by &%discard%&. For
31365 &`discard `&<&'some conditions'&>
31366 &` log_message = Discarded $local_part@$domain because...`&
31368 When access is denied, &%log_message%& adds to any underlying error message
31369 that may exist because of a condition failure. For example, while verifying a
31370 recipient address, a &':fail:'& redirection might have already set up a
31373 The message may be defined before the conditions to which it applies, because
31374 the string expansion does not happen until Exim decides that access is to be
31375 denied. This means that any variables that are set by the condition are
31376 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
31377 variables are set after a DNS black list lookup succeeds. If the expansion of
31378 &%log_message%& fails, or if the result is an empty string, the modifier is
31381 .vindex "&$acl_verify_message$&"
31382 If you want to use a &%warn%& statement to log the result of an address
31383 verification, you can use &$acl_verify_message$& to include the verification
31386 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
31387 the start of the logged message. If the same warning log message is requested
31388 more than once while receiving a single email message, only one copy is
31389 actually logged. If you want to log multiple copies, use &%logwrite%& instead
31390 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
31391 is logged for a successful &%warn%& statement.
31393 If &%log_message%& is not present and there is no underlying error message (for
31394 example, from the failure of address verification), but &%message%& is present,
31395 the &%message%& text is used for logging rejections. However, if any text for
31396 logging contains newlines, only the first line is logged. In the absence of
31397 both &%log_message%& and &%message%&, a default built-in message is used for
31398 logging rejections.
31401 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
31402 .cindex "&%log_reject_target%& ACL modifier"
31403 .cindex "logging in ACL" "specifying which log"
31404 This modifier makes it possible to specify which logs are used for messages
31405 about ACL rejections. Its argument is a colon-separated list of words that can
31406 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
31407 may be empty, in which case a rejection is not logged at all. For example, this
31408 ACL fragment writes no logging information when access is denied:
31410 &`deny `&<&'some conditions'&>
31411 &` log_reject_target =`&
31413 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
31414 permanent and temporary rejections. Its effect lasts for the rest of the
31418 .vitem &*logwrite*&&~=&~<&'text'&>
31419 .cindex "&%logwrite%& ACL modifier"
31420 .cindex "logging in ACL" "immediate"
31421 This modifier writes a message to a log file as soon as it is encountered when
31422 processing an ACL. (Compare &%log_message%&, which, except in the case of
31423 &%warn%& and &%discard%&, is used only if the ACL statement denies
31424 access.) The &%logwrite%& modifier can be used to log special incidents in
31427 &`accept `&<&'some special conditions'&>
31428 &` control = freeze`&
31429 &` logwrite = froze message because ...`&
31431 By default, the message is written to the main log. However, it may begin
31432 with a colon, followed by a comma-separated list of log names, and then
31433 another colon, to specify exactly which logs are to be written. For
31436 logwrite = :main,reject: text for main and reject logs
31437 logwrite = :panic: text for panic log only
31441 .vitem &*message*&&~=&~<&'text'&>
31442 .cindex "&%message%& ACL modifier"
31443 This modifier sets up a text string that is expanded and used as a response
31444 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
31445 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
31446 there is some complication if &%endpass%& is involved; see the description of
31447 &%accept%& for details.)
31449 The expansion of the message happens at the time Exim decides that the ACL is
31450 to end, not at the time it processes &%message%&. If the expansion fails, or
31451 generates an empty string, the modifier is ignored. Here is an example where
31452 &%message%& must be specified first, because the ACL ends with a rejection if
31453 the &%hosts%& condition fails:
31455 require message = Host not recognized
31458 (Once a condition has failed, no further conditions or modifiers are
31461 .cindex "SMTP" "error codes"
31462 .oindex "&%smtp_banner%&
31463 For ACLs that are triggered by SMTP commands, the message is returned as part
31464 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
31465 is meaningful only for SMTP, as no message is returned when a non-SMTP message
31466 is accepted. In the case of the connect ACL, accepting with a message modifier
31467 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
31468 accept message may not contain more than one line (otherwise it will be
31469 truncated at the first newline and a panic logged), and it cannot affect the
31472 When SMTP is involved, the message may begin with an overriding response code,
31473 consisting of three digits optionally followed by an &"extended response code"&
31474 of the form &'n.n.n'&, each code being followed by a space. For example:
31476 deny message = 599 1.2.3 Host not welcome
31477 hosts = 192.168.34.0/24
31479 The first digit of the supplied response code must be the same as would be sent
31480 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
31481 access, but for the predata ACL, note that the default success code is 354, not
31484 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
31485 the message modifier cannot override the 221 response code.
31487 The text in a &%message%& modifier is literal; any quotes are taken as
31488 literals, but because the string is expanded, backslash escapes are processed
31489 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
31492 .vindex "&$acl_verify_message$&"
31494 While the text is being expanded, the &$acl_verify_message$& variable
31495 contains any message previously set.
31496 Afterwards, &$acl_verify_message$& is cleared.
31499 If &%message%& is used on a statement that verifies an address, the message
31500 specified overrides any message that is generated by the verification process.
31501 However, the original message is available in the variable
31502 &$acl_verify_message$&, so you can incorporate it into your message if you
31503 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
31504 routers to be passed back as part of the SMTP response, you should either not
31505 use a &%message%& modifier, or make use of &$acl_verify_message$&.
31507 For compatibility with previous releases of Exim, a &%message%& modifier that
31508 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
31509 modifier, but this usage is now deprecated. However, &%message%& acts only when
31510 all the conditions are true, wherever it appears in an ACL command, whereas
31511 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
31512 &%warn%& in an ACL that is not concerned with receiving a message, it has no
31516 .vitem &*queue*&&~=&~<&'text'&>
31517 .cindex "&%queue%& ACL modifier"
31518 .cindex "named queues" "selecting in ACL"
31519 This modifier specifies the use of a named queue for spool files
31521 It can only be used before the message is received (i.e. not in
31523 This could be used, for example, for known high-volume burst sources
31524 of traffic, or for quarantine of messages.
31525 Separate queue-runner processes will be needed for named queues.
31526 If the text after expansion is empty, the default queue is used.
31529 .vitem &*remove_header*&&~=&~<&'text'&>
31530 This modifier specifies one or more header names in a colon-separated list
31531 that are to be removed from an incoming message, assuming, of course, that
31532 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
31535 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
31536 .cindex "&%set%& ACL modifier"
31537 This modifier puts a value into one of the ACL variables (see section
31538 &<<SECTaclvariables>>&).
31541 .vitem &*udpsend*&&~=&~<&'parameters'&>
31542 .cindex "UDP communications"
31543 This modifier sends a UDP packet, for purposes such as statistics
31544 collection or behaviour monitoring. The parameters are expanded, and
31545 the result of the expansion must be a colon-separated list consisting
31546 of a destination server, port number, and the packet contents. The
31547 server can be specified as a host name or IPv4 or IPv6 address. The
31548 separator can be changed with the usual angle bracket syntax. For
31549 example, you might want to collect information on which hosts connect
31552 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
31553 $tod_zulu $sender_host_address
31560 .section "Use of the control modifier" "SECTcontrols"
31561 .cindex "&%control%& ACL modifier"
31562 The &%control%& modifier supports the following settings:
31565 .vitem &*control&~=&~allow_auth_unadvertised*&
31566 This modifier allows a client host to use the SMTP AUTH command even when it
31567 has not been advertised in response to EHLO. Furthermore, because there are
31568 apparently some really broken clients that do this, Exim will accept AUTH after
31569 HELO (rather than EHLO) when this control is set. It should be used only if you
31570 really need it, and you should limit its use to those broken clients that do
31571 not work without it. For example:
31573 warn hosts = 192.168.34.25
31574 control = allow_auth_unadvertised
31576 Normally, when an Exim server receives an AUTH command, it checks the name of
31577 the authentication mechanism that is given in the command to ensure that it
31578 matches an advertised mechanism. When this control is set, the check that a
31579 mechanism has been advertised is bypassed. Any configured mechanism can be used
31580 by the client. This control is permitted only in the connection and HELO ACLs.
31583 .vitem &*control&~=&~caseful_local_part*& &&&
31584 &*control&~=&~caselower_local_part*&
31585 .cindex "&ACL;" "case of local part in"
31586 .cindex "case of local parts"
31587 .vindex "&$local_part$&"
31588 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
31589 (that is, during RCPT processing). By default, the contents of &$local_part$&
31590 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
31591 any uppercase letters in the original local part are restored in &$local_part$&
31592 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
31595 These controls affect only the current recipient. Moreover, they apply only to
31596 local part handling that takes place directly in the ACL (for example, as a key
31597 in lookups). If a test to verify the recipient is obeyed, the case-related
31598 handling of the local part during the verification is controlled by the router
31599 configuration (see the &%caseful_local_part%& generic router option).
31601 This facility could be used, for example, to add a spam score to local parts
31602 containing upper case letters. For example, using &$acl_m4$& to accumulate the
31605 warn control = caseful_local_part
31606 set acl_m4 = ${eval:\
31608 ${if match{$local_part}{[A-Z]}{1}{0}}\
31610 control = caselower_local_part
31612 Notice that we put back the lower cased version afterwards, assuming that
31613 is what is wanted for subsequent tests.
31616 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
31617 .cindex "&ACL;" "cutthrough routing"
31618 .cindex "cutthrough" "requesting"
31619 This option requests delivery be attempted while the item is being received.
31621 The option is usable in the RCPT ACL.
31622 If enabled for a message received via smtp and routed to an smtp transport,
31623 and only one transport, interface, destination host and port combination
31624 is used for all recipients of the message,
31625 then the delivery connection is made while the receiving connection is open
31626 and data is copied from one to the other.
31628 An attempt to set this option for any recipient but the first
31629 for a mail will be quietly ignored.
31630 If a recipient-verify callout
31632 connection is subsequently
31633 requested in the same ACL it is held open and used for
31634 any subsequent recipients and the data,
31635 otherwise one is made after the initial RCPT ACL completes.
31637 Note that routers are used in verify mode,
31638 and cannot depend on content of received headers.
31639 Note also that headers cannot be
31640 modified by any of the post-data ACLs (DATA, MIME and DKIM).
31641 Headers may be modified by routers (subject to the above) and transports.
31642 The &'Received-By:'& header is generated as soon as the body reception starts,
31643 rather than the traditional time after the full message is received;
31644 this will affect the timestamp.
31646 All the usual ACLs are called; if one results in the message being
31647 rejected, all effort spent in delivery (including the costs on
31648 the ultimate destination) will be wasted.
31649 Note that in the case of data-time ACLs this includes the entire
31652 Cutthrough delivery is not supported via transport-filters or when DKIM signing
31653 of outgoing messages is done, because it sends data to the ultimate destination
31654 before the entire message has been received from the source.
31655 It is not supported for messages received with the SMTP PRDR
31659 Should the ultimate destination system positively accept or reject the mail,
31660 a corresponding indication is given to the source system and nothing is queued.
31661 If the item is successfully delivered in cutthrough mode
31662 the delivery log lines are tagged with ">>" rather than "=>" and appear
31663 before the acceptance "<=" line.
31665 If there is a temporary error the item is queued for later delivery in the
31667 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
31668 to the control; the default value is &"spool"& and the alternate value
31669 &"pass"& copies an SMTP defer response from the target back to the initiator
31670 and does not queue the message.
31671 Note that this is independent of any recipient verify conditions in the ACL.
31673 Delivery in this mode avoids the generation of a bounce mail to a
31675 sender when the destination system is doing content-scan based rejection.
31678 .vitem &*control&~=&~debug/*&<&'options'&>
31679 .cindex "&ACL;" "enabling debug logging"
31680 .cindex "debugging" "enabling from an ACL"
31681 This control turns on debug logging, almost as though Exim had been invoked
31682 with &`-d`&, with the output going to a new logfile in the usual logs directory,
31683 by default called &'debuglog'&.
31684 The filename can be adjusted with the &'tag'& option, which
31685 may access any variables already defined. The logging may be adjusted with
31686 the &'opts'& option, which takes the same values as the &`-d`& command-line
31688 Logging started this way may be stopped, and the file removed,
31689 with the &'kill'& option.
31690 Some examples (which depend on variables that don't exist in all
31694 control = debug/tag=.$sender_host_address
31695 control = debug/opts=+expand+acl
31696 control = debug/tag=.$message_exim_id/opts=+expand
31697 control = debug/kill
31701 .vitem &*control&~=&~dkim_disable_verify*&
31702 .cindex "disable DKIM verify"
31703 .cindex "DKIM" "disable verify"
31704 This control turns off DKIM verification processing entirely. For details on
31705 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
31708 .vitem &*control&~=&~dmarc_disable_verify*&
31709 .cindex "disable DMARC verify"
31710 .cindex "DMARC" "disable verify"
31711 This control turns off DMARC verification processing entirely. For details on
31712 the operation and configuration of DMARC, see section &<<SECDMARC>>&.
31715 .vitem &*control&~=&~dscp/*&<&'value'&>
31716 .cindex "&ACL;" "setting DSCP value"
31717 .cindex "DSCP" "inbound"
31718 This option causes the DSCP value associated with the socket for the inbound
31719 connection to be adjusted to a given value, given as one of a number of fixed
31720 strings or to numeric value.
31721 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
31722 Common values include &`throughput`&, &`mincost`&, and on newer systems
31723 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
31725 The outbound packets from Exim will be marked with this value in the header
31726 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
31727 that these values will have any effect, not be stripped by networking
31728 equipment, or do much of anything without cooperation with your Network
31729 Engineer and those of all network operators between the source and destination.
31732 .vitem &*control&~=&~enforce_sync*& &&&
31733 &*control&~=&~no_enforce_sync*&
31734 .cindex "SMTP" "synchronization checking"
31735 .cindex "synchronization checking in SMTP"
31736 These controls make it possible to be selective about when SMTP synchronization
31737 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
31738 state of the switch (it is true by default). See the description of this option
31739 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
31741 The effect of these two controls lasts for the remainder of the SMTP
31742 connection. They can appear in any ACL except the one for the non-SMTP
31743 messages. The most straightforward place to put them is in the ACL defined by
31744 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
31745 before the first synchronization check. The expected use is to turn off the
31746 synchronization checks for badly-behaved hosts that you nevertheless need to
31750 .vitem &*control&~=&~fakedefer/*&<&'message'&>
31751 .cindex "fake defer"
31752 .cindex "defer, fake"
31753 This control works in exactly the same way as &%fakereject%& (described below)
31754 except that it causes an SMTP 450 response after the message data instead of a
31755 550 response. You must take care when using &%fakedefer%& because it causes the
31756 messages to be duplicated when the sender retries. Therefore, you should not
31757 use &%fakedefer%& if the message is to be delivered normally.
31759 .vitem &*control&~=&~fakereject/*&<&'message'&>
31760 .cindex "fake rejection"
31761 .cindex "rejection, fake"
31762 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
31763 words, only when an SMTP message is being received. If Exim accepts the
31764 message, instead the final 250 response, a 550 rejection message is sent.
31765 However, Exim proceeds to deliver the message as normal. The control applies
31766 only to the current message, not to any subsequent ones that may be received in
31767 the same SMTP connection.
31769 The text for the 550 response is taken from the &%control%& modifier. If no
31770 message is supplied, the following is used:
31772 550-Your message has been rejected but is being
31773 550-kept for evaluation.
31774 550-If it was a legitimate message, it may still be
31775 550 delivered to the target recipient(s).
31777 This facility should be used with extreme caution.
31779 .vitem &*control&~=&~freeze*&
31780 .cindex "frozen messages" "forcing in ACL"
31781 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31782 other words, only when a message is being received. If the message is accepted,
31783 it is placed on Exim's queue and frozen. The control applies only to the
31784 current message, not to any subsequent ones that may be received in the same
31787 This modifier can optionally be followed by &`/no_tell`&. If the global option
31788 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
31789 is told about the freezing), provided all the &*control=freeze*& modifiers that
31790 are obeyed for the current message have the &`/no_tell`& option.
31792 .vitem &*control&~=&~no_delay_flush*&
31793 .cindex "SMTP" "output flushing, disabling for delay"
31794 Exim normally flushes SMTP output before implementing a delay in an ACL, to
31795 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31796 use. This control, as long as it is encountered before the &%delay%& modifier,
31797 disables such output flushing.
31799 .vitem &*control&~=&~no_callout_flush*&
31800 .cindex "SMTP" "output flushing, disabling for callout"
31801 Exim normally flushes SMTP output before performing a callout in an ACL, to
31802 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31803 use. This control, as long as it is encountered before the &%verify%& condition
31804 that causes the callout, disables such output flushing.
31806 .vitem &*control&~=&~no_mbox_unspool*&
31807 This control is available when Exim is compiled with the content scanning
31808 extension. Content scanning may require a copy of the current message, or parts
31809 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
31810 or spam scanner. Normally, such copies are deleted when they are no longer
31811 needed. If this control is set, the copies are not deleted. The control applies
31812 only to the current message, not to any subsequent ones that may be received in
31813 the same SMTP connection. It is provided for debugging purposes and is unlikely
31814 to be useful in production.
31816 .vitem &*control&~=&~no_multiline_responses*&
31817 .cindex "multiline responses, suppressing"
31818 This control is permitted for any ACL except the one for non-SMTP messages.
31819 It seems that there are broken clients in use that cannot handle multiline
31820 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
31822 If this control is set, multiline SMTP responses from ACL rejections are
31823 suppressed. One way of doing this would have been to put out these responses as
31824 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
31825 (&"use multiline responses for more"& it says &-- ha!), and some of the
31826 responses might get close to that. So this facility, which is after all only a
31827 sop to broken clients, is implemented by doing two very easy things:
31830 Extra information that is normally output as part of a rejection caused by
31831 sender verification failure is omitted. Only the final line (typically &"sender
31832 verification failed"&) is sent.
31834 If a &%message%& modifier supplies a multiline response, only the first
31838 The setting of the switch can, of course, be made conditional on the
31839 calling host. Its effect lasts until the end of the SMTP connection.
31841 .vitem &*control&~=&~no_pipelining*&
31842 .cindex "PIPELINING" "suppressing advertising"
31843 .cindex "ESMTP extensions" PIPELINING
31844 This control turns off the advertising of the PIPELINING extension to SMTP in
31845 the current session. To be useful, it must be obeyed before Exim sends its
31846 response to an EHLO command. Therefore, it should normally appear in an ACL
31847 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
31848 &%pipelining_advertise_hosts%&.
31850 .vitem &*control&~=&~queue/*&<&'options'&>* &&&
31851 &*control&~=&~queue_only*&
31852 .oindex "&%queue%&"
31853 .oindex "&%queue_only%&"
31854 .cindex "queueing incoming messages"
31855 .cindex queueing "forcing in ACL"
31856 .cindex "first pass routing"
31857 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31858 other words, only when a message is being received. If the message is accepted,
31859 it is placed on Exim's queue and left there for delivery by a subsequent queue
31861 If used with no options set,
31862 no immediate delivery process is started. In other words, it has the
31863 effect as the &%queue_only%& global option or &'-odq'& command-line option.
31865 If the &'first_pass_route'& option is given then
31866 the behaviour is like the command-line &'-oqds'& option;
31867 a delivery process is started which stops short of making
31868 any SMTP delivery. The benefit is that the hints database will be updated for
31869 the message being waiting for a specific host, and a later queue run will be
31870 able to send all such messages on a single connection.
31872 The control only applies to the current message, not to any subsequent ones that
31873 may be received in the same SMTP connection.
31875 .vitem &*control&~=&~submission/*&<&'options'&>
31876 .cindex "message" "submission"
31877 .cindex "submission mode"
31878 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
31879 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
31880 the current message is a submission from a local MUA. In this case, Exim
31881 operates in &"submission mode"&, and applies certain fixups to the message if
31882 necessary. For example, it adds a &'Date:'& header line if one is not present.
31883 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
31884 late (the message has already been created).
31886 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
31887 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
31888 submission mode; the available options for this control are described there.
31889 The control applies only to the current message, not to any subsequent ones
31890 that may be received in the same SMTP connection.
31892 .vitem &*control&~=&~suppress_local_fixups*&
31893 .cindex "submission fixups, suppressing"
31894 This control applies to locally submitted (non TCP/IP) messages, and is the
31895 complement of &`control = submission`&. It disables the fixups that are
31896 normally applied to locally-submitted messages. Specifically:
31899 Any &'Sender:'& header line is left alone (in this respect, it is a
31900 dynamic version of &%local_sender_retain%&).
31902 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
31904 There is no check that &'From:'& corresponds to the actual sender.
31907 This control may be useful when a remotely-originated message is accepted,
31908 passed to some scanning program, and then re-submitted for delivery. It can be
31909 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
31910 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
31913 &*Note:*& This control applies only to the current message, not to any others
31914 that are being submitted at the same time using &%-bs%& or &%-bS%&.
31916 .vitem &*control&~=&~utf8_downconvert*&
31917 This control enables conversion of UTF-8 in message envelope addresses
31919 For details see section &<<SECTi18nMTA>>&.
31923 .section "Summary of message fixup control" "SECTsummesfix"
31924 All four possibilities for message fixups can be specified:
31927 Locally submitted, fixups applied: the default.
31929 Locally submitted, no fixups applied: use
31930 &`control = suppress_local_fixups`&.
31932 Remotely submitted, no fixups applied: the default.
31934 Remotely submitted, fixups applied: use &`control = submission`&.
31939 .section "Adding header lines in ACLs" "SECTaddheadacl"
31940 .cindex "header lines" "adding in an ACL"
31941 .cindex "header lines" "position of added lines"
31942 .cindex "&%add_header%& ACL modifier"
31943 The &%add_header%& modifier can be used to add one or more extra header lines
31944 to an incoming message, as in this example:
31946 warn dnslists = sbl.spamhaus.org : \
31947 dialup.mail-abuse.org
31948 add_header = X-blacklisted-at: $dnslist_domain
31950 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31951 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31952 receiving a message). The message must ultimately be accepted for
31953 &%add_header%& to have any significant effect. You can use &%add_header%& with
31954 any ACL verb, including &%deny%& (though this is potentially useful only in a
31957 Headers will not be added to the message if the modifier is used in
31958 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31960 Leading and trailing newlines are removed from
31961 the data for the &%add_header%& modifier; if it then
31962 contains one or more newlines that
31963 are not followed by a space or a tab, it is assumed to contain multiple header
31964 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
31965 front of any line that is not a valid header line.
31967 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
31968 They are added to the message before processing the DATA and MIME ACLs.
31969 However, if an identical header line is requested more than once, only one copy
31970 is actually added to the message. Further header lines may be accumulated
31971 during the DATA and MIME ACLs, after which they are added to the message, again
31972 with duplicates suppressed. Thus, it is possible to add two identical header
31973 lines to an SMTP message, but only if one is added before DATA and one after.
31974 In the case of non-SMTP messages, new headers are accumulated during the
31975 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
31976 message is rejected after DATA or by the non-SMTP ACL, all added header lines
31977 are included in the entry that is written to the reject log.
31979 .cindex "header lines" "added; visibility of"
31980 Header lines are not visible in string expansions
31982 until they are added to the
31983 message. It follows that header lines defined in the MAIL, RCPT, and predata
31984 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
31985 header lines that are added by the DATA or MIME ACLs are not visible in those
31986 ACLs. Because of this restriction, you cannot use header lines as a way of
31987 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
31988 this, you can use ACL variables, as described in section
31989 &<<SECTaclvariables>>&.
31991 The list of headers yet to be added is given by the &%$headers_added%& variable.
31993 The &%add_header%& modifier acts immediately as it is encountered during the
31994 processing of an ACL. Notice the difference between these two cases:
31996 &`accept add_header = ADDED: some text`&
31997 &` `&<&'some condition'&>
31999 &`accept `&<&'some condition'&>
32000 &` add_header = ADDED: some text`&
32002 In the first case, the header line is always added, whether or not the
32003 condition is true. In the second case, the header line is added only if the
32004 condition is true. Multiple occurrences of &%add_header%& may occur in the same
32005 ACL statement. All those that are encountered before a condition fails are
32008 .cindex "&%warn%& ACL verb"
32009 For compatibility with previous versions of Exim, a &%message%& modifier for a
32010 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
32011 effect only if all the conditions are true, even if it appears before some of
32012 them. Furthermore, only the last occurrence of &%message%& is honoured. This
32013 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
32014 are present on a &%warn%& verb, both are processed according to their
32017 By default, new header lines are added to a message at the end of the existing
32018 header lines. However, you can specify that any particular header line should
32019 be added right at the start (before all the &'Received:'& lines), immediately
32020 after the first block of &'Received:'& lines, or immediately before any line
32021 that is not a &'Received:'& or &'Resent-something:'& header.
32023 This is done by specifying &":at_start:"&, &":after_received:"&, or
32024 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
32025 header line, respectively. (Header text cannot start with a colon, as there has
32026 to be a header name first.) For example:
32028 warn add_header = \
32029 :after_received:X-My-Header: something or other...
32031 If more than one header line is supplied in a single &%add_header%& modifier,
32032 each one is treated independently and can therefore be placed differently. If
32033 you add more than one line at the start, or after the Received: block, they end
32034 up in reverse order.
32036 &*Warning*&: This facility currently applies only to header lines that are
32037 added in an ACL. It does NOT work for header lines that are added in a
32038 system filter or in a router or transport.
32042 .section "Removing header lines in ACLs" "SECTremoveheadacl"
32043 .cindex "header lines" "removing in an ACL"
32044 .cindex "header lines" "position of removed lines"
32045 .cindex "&%remove_header%& ACL modifier"
32046 The &%remove_header%& modifier can be used to remove one or more header lines
32047 from an incoming message, as in this example:
32049 warn message = Remove internal headers
32050 remove_header = x-route-mail1 : x-route-mail2
32052 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
32053 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
32054 receiving a message). The message must ultimately be accepted for
32055 &%remove_header%& to have any significant effect. You can use &%remove_header%&
32056 with any ACL verb, including &%deny%&, though this is really not useful for
32057 any verb that doesn't result in a delivered message.
32059 Headers will not be removed from the message if the modifier is used in
32060 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
32062 More than one header can be removed at the same time by using a colon separated
32063 list of header names. The header matching is case insensitive. Wildcards are
32064 not permitted, nor is list expansion performed, so you cannot use hostlists to
32065 create a list of headers, however both connection and message variable expansion
32066 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
32068 warn hosts = +internal_hosts
32069 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
32070 warn message = Remove internal headers
32071 remove_header = $acl_c_ihdrs
32073 Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
32074 Matching header lines are removed from the message before processing the DATA and MIME ACLs.
32075 If multiple header lines match, all are removed.
32076 There is no harm in attempting to remove the same header twice nor in removing
32077 a non-existent header. Further header lines to be removed may be accumulated
32078 during the DATA and MIME ACLs, after which they are removed from the message,
32079 if present. In the case of non-SMTP messages, headers to be removed are
32080 accumulated during the non-SMTP ACLs, and are removed from the message after
32081 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
32082 ACL, there really is no effect because there is no logging of what headers
32083 would have been removed.
32085 .cindex "header lines" "removed; visibility of"
32086 Header lines are not visible in string expansions until the DATA phase when it
32087 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
32088 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
32089 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
32090 this restriction, you cannot use header lines as a way of controlling data
32091 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
32092 you should instead use ACL variables, as described in section
32093 &<<SECTaclvariables>>&.
32095 The &%remove_header%& modifier acts immediately as it is encountered during the
32096 processing of an ACL. Notice the difference between these two cases:
32098 &`accept remove_header = X-Internal`&
32099 &` `&<&'some condition'&>
32101 &`accept `&<&'some condition'&>
32102 &` remove_header = X-Internal`&
32104 In the first case, the header line is always removed, whether or not the
32105 condition is true. In the second case, the header line is removed only if the
32106 condition is true. Multiple occurrences of &%remove_header%& may occur in the
32107 same ACL statement. All those that are encountered before a condition fails
32110 &*Warning*&: This facility currently applies only to header lines that are
32111 present during ACL processing. It does NOT remove header lines that are added
32112 in a system filter or in a router or transport.
32117 .section "ACL conditions" "SECTaclconditions"
32118 .cindex "&ACL;" "conditions; list of"
32119 Some of the conditions listed in this section are available only when Exim is
32120 compiled with the content-scanning extension. They are included here briefly
32121 for completeness. More detailed descriptions can be found in the discussion on
32122 content scanning in chapter &<<CHAPexiscan>>&.
32124 Not all conditions are relevant in all circumstances. For example, testing
32125 senders and recipients does not make sense in an ACL that is being run as the
32126 result of the arrival of an ETRN command, and checks on message headers can be
32127 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
32128 can use the same condition (with different parameters) more than once in the
32129 same ACL statement. This provides a way of specifying an &"and"& conjunction.
32130 The conditions are as follows:
32134 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
32135 .cindex "&ACL;" "nested"
32136 .cindex "&ACL;" "indirect"
32137 .cindex "&ACL;" "arguments"
32138 .cindex "&%acl%& ACL condition"
32139 The possible values of the argument are the same as for the
32140 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
32141 &"accept"& the condition is true; if it returns &"deny"& the condition is
32142 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
32143 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
32144 condition false. This means that further processing of the &%warn%& verb
32145 ceases, but processing of the ACL continues.
32147 If the argument is a named ACL, up to nine space-separated optional values
32148 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
32149 and $acl_narg is set to the count of values.
32150 Previous values of these variables are restored after the call returns.
32151 The name and values are expanded separately.
32152 Note that spaces in complex expansions which are used as arguments
32153 will act as argument separators.
32155 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
32156 the connection is dropped. If it returns &"discard"&, the verb must be
32157 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
32158 conditions are tested.
32160 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
32161 loops. This condition allows you to use different ACLs in different
32162 circumstances. For example, different ACLs can be used to handle RCPT commands
32163 for different local users or different local domains.
32165 .vitem &*authenticated&~=&~*&<&'string&~list'&>
32166 .cindex "&%authenticated%& ACL condition"
32167 .cindex "authentication" "ACL checking"
32168 .cindex "&ACL;" "testing for authentication"
32169 If the SMTP connection is not authenticated, the condition is false. Otherwise,
32170 the name of the authenticator is tested against the list. To test for
32171 authentication by any authenticator, you can set
32176 .vitem &*condition&~=&~*&<&'string'&>
32177 .cindex "&%condition%& ACL condition"
32178 .cindex "customizing" "ACL condition"
32179 .cindex "&ACL;" "customized test"
32180 .cindex "&ACL;" "testing, customized"
32181 This feature allows you to make up custom conditions. If the result of
32182 expanding the string is an empty string, the number zero, or one of the strings
32183 &"no"& or &"false"&, the condition is false. If the result is any non-zero
32184 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
32185 any other value, some error is assumed to have occurred, and the ACL returns
32186 &"defer"&. However, if the expansion is forced to fail, the condition is
32187 ignored. The effect is to treat it as true, whether it is positive or
32190 .vitem &*decode&~=&~*&<&'location'&>
32191 .cindex "&%decode%& ACL condition"
32192 This condition is available only when Exim is compiled with the
32193 content-scanning extension, and it is allowed only in the ACL defined by
32194 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
32195 If all goes well, the condition is true. It is false only if there are
32196 problems such as a syntax error or a memory shortage. For more details, see
32197 chapter &<<CHAPexiscan>>&.
32199 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
32200 .cindex "&%dnslists%& ACL condition"
32201 .cindex "DNS list" "in ACL"
32202 .cindex "black list (DNS)"
32203 .cindex "&ACL;" "testing a DNS list"
32204 This condition checks for entries in DNS black lists. These are also known as
32205 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
32206 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
32207 different variants of this condition to describe briefly here. See sections
32208 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
32210 .vitem &*domains&~=&~*&<&'domain&~list'&>
32211 .cindex "&%domains%& ACL condition"
32212 .cindex "domain" "ACL checking"
32213 .cindex "&ACL;" "testing a recipient domain"
32214 .vindex "&$domain_data$&"
32215 This condition is relevant only after a RCPT command. It checks that the domain
32216 of the recipient address is in the domain list. If percent-hack processing is
32217 enabled, it is done before this test is done. If the check succeeds with a
32218 lookup, the result of the lookup is placed in &$domain_data$& until the next
32221 &*Note carefully*& (because many people seem to fall foul of this): you cannot
32222 use &%domains%& in a DATA ACL.
32225 .vitem &*encrypted&~=&~*&<&'string&~list'&>
32226 .cindex "&%encrypted%& ACL condition"
32227 .cindex "encryption" "checking in an ACL"
32228 .cindex "&ACL;" "testing for encryption"
32229 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
32230 name of the cipher suite in use is tested against the list. To test for
32231 encryption without testing for any specific cipher suite(s), set
32237 .vitem &*hosts&~=&~*&<&'host&~list'&>
32238 .cindex "&%hosts%& ACL condition"
32239 .cindex "host" "ACL checking"
32240 .cindex "&ACL;" "testing the client host"
32241 This condition tests that the calling host matches the host list. If you have
32242 name lookups or wildcarded host names and IP addresses in the same host list,
32243 you should normally put the IP addresses first. For example, you could have:
32245 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
32247 The lookup in this example uses the host name for its key. This is implied by
32248 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
32249 and it wouldn't matter which way round you had these two items.)
32251 The reason for the problem with host names lies in the left-to-right way that
32252 Exim processes lists. It can test IP addresses without doing any DNS lookups,
32253 but when it reaches an item that requires a host name, it fails if it cannot
32254 find a host name to compare with the pattern. If the above list is given in the
32255 opposite order, the &%accept%& statement fails for a host whose name cannot be
32256 found, even if its IP address is 10.9.8.7.
32258 If you really do want to do the name check first, and still recognize the IP
32259 address even if the name lookup fails, you can rewrite the ACL like this:
32261 accept hosts = dbm;/etc/friendly/hosts
32262 accept hosts = 10.9.8.7
32264 The default action on failing to find the host name is to assume that the host
32265 is not in the list, so the first &%accept%& statement fails. The second
32266 statement can then check the IP address.
32268 .vindex "&$host_data$&"
32269 If a &%hosts%& condition is satisfied by means of a lookup, the result
32270 of the lookup is made available in the &$host_data$& variable. This
32271 allows you, for example, to set up a statement like this:
32273 deny hosts = net-lsearch;/some/file
32274 message = $host_data
32276 which gives a custom error message for each denied host.
32278 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
32279 .cindex "&%local_parts%& ACL condition"
32280 .cindex "local part" "ACL checking"
32281 .cindex "&ACL;" "testing a local part"
32282 .vindex "&$local_part_data$&"
32283 This condition is relevant only after a RCPT command. It checks that the local
32284 part of the recipient address is in the list. If percent-hack processing is
32285 enabled, it is done before this test. If the check succeeds with a lookup, the
32286 result of the lookup is placed in &$local_part_data$&, which remains set until
32287 the next &%local_parts%& test.
32289 .vitem &*malware&~=&~*&<&'option'&>
32290 .cindex "&%malware%& ACL condition"
32291 .cindex "&ACL;" "virus scanning"
32292 .cindex "&ACL;" "scanning for viruses"
32293 This condition is available only when Exim is compiled with the
32294 content-scanning extension
32295 and only after a DATA command.
32296 It causes the incoming message to be scanned for
32297 viruses. For details, see chapter &<<CHAPexiscan>>&.
32299 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32300 .cindex "&%mime_regex%& ACL condition"
32301 .cindex "&ACL;" "testing by regex matching"
32302 This condition is available only when Exim is compiled with the
32303 content-scanning extension, and it is allowed only in the ACL defined by
32304 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
32305 with any of the regular expressions. For details, see chapter
32308 .vitem &*ratelimit&~=&~*&<&'parameters'&>
32309 .cindex "rate limiting"
32310 This condition can be used to limit the rate at which a user or host submits
32311 messages. Details are given in section &<<SECTratelimiting>>&.
32313 .vitem &*recipients&~=&~*&<&'address&~list'&>
32314 .cindex "&%recipients%& ACL condition"
32315 .cindex "recipient" "ACL checking"
32316 .cindex "&ACL;" "testing a recipient"
32317 This condition is relevant only after a RCPT command. It checks the entire
32318 recipient address against a list of recipients.
32320 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32321 .cindex "&%regex%& ACL condition"
32322 .cindex "&ACL;" "testing by regex matching"
32323 This condition is available only when Exim is compiled with the
32324 content-scanning extension, and is available only in the DATA, MIME, and
32325 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
32326 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
32328 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
32329 .cindex "&%sender_domains%& ACL condition"
32330 .cindex "sender" "ACL checking"
32331 .cindex "&ACL;" "testing a sender domain"
32332 .vindex "&$domain$&"
32333 .vindex "&$sender_address_domain$&"
32334 This condition tests the domain of the sender of the message against the given
32335 domain list. &*Note*&: The domain of the sender address is in
32336 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
32337 of this condition. This is an exception to the general rule for testing domain
32338 lists. It is done this way so that, if this condition is used in an ACL for a
32339 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
32340 influence the sender checking.
32342 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32343 relaying, because sender addresses are easily, and commonly, forged.
32345 .vitem &*senders&~=&~*&<&'address&~list'&>
32346 .cindex "&%senders%& ACL condition"
32347 .cindex "sender" "ACL checking"
32348 .cindex "&ACL;" "testing a sender"
32349 This condition tests the sender of the message against the given list. To test
32350 for a bounce message, which has an empty sender, set
32354 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32355 relaying, because sender addresses are easily, and commonly, forged.
32357 .vitem &*spam&~=&~*&<&'username'&>
32358 .cindex "&%spam%& ACL condition"
32359 .cindex "&ACL;" "scanning for spam"
32360 This condition is available only when Exim is compiled with the
32361 content-scanning extension. It causes the incoming message to be scanned by
32362 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
32364 .vitem &*verify&~=&~certificate*&
32365 .cindex "&%verify%& ACL condition"
32366 .cindex "TLS" "client certificate verification"
32367 .cindex "certificate" "verification of client"
32368 .cindex "&ACL;" "certificate verification"
32369 .cindex "&ACL;" "testing a TLS certificate"
32370 This condition is true in an SMTP session if the session is encrypted, and a
32371 certificate was received from the client, and the certificate was verified. The
32372 server requests a certificate only if the client matches &%tls_verify_hosts%&
32373 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
32375 .vitem &*verify&~=&~csa*&
32376 .cindex "CSA verification"
32377 This condition checks whether the sending host (the client) is authorized to
32378 send email. Details of how this works are given in section
32379 &<<SECTverifyCSA>>&.
32381 .vitem &*verify&~=&~header_names_ascii*&
32382 .cindex "&%verify%& ACL condition"
32383 .cindex "&ACL;" "verifying header names only ASCII"
32384 .cindex "header lines" "verifying header names only ASCII"
32385 .cindex "verifying" "header names only ASCII"
32386 This condition is relevant only in an ACL that is run after a message has been
32388 This usually means an ACL specified by &%acl_smtp_data%& or &%acl_not_smtp%&.
32389 It checks all header names (not the content) to make sure
32390 there are no non-ASCII characters, also excluding control characters. The
32391 allowable characters are decimal ASCII values 33 through 126.
32393 Exim itself will handle headers with non-ASCII characters, but it can cause
32394 problems for downstream applications, so this option will allow their
32395 detection and rejection in the DATA ACL's.
32397 .vitem &*verify&~=&~header_sender/*&<&'options'&>
32398 .cindex "&%verify%& ACL condition"
32399 .cindex "&ACL;" "verifying sender in the header"
32400 .cindex "header lines" "verifying the sender in"
32401 .cindex "sender" "verifying in header"
32402 .cindex "verifying" "sender in header"
32403 This condition is relevant only in an ACL that is run after a message has been
32404 received, that is, in an ACL specified by &%acl_smtp_data%& or
32405 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
32406 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
32407 is loosely thought of as a &"sender"& address (hence the name of the test).
32408 However, an address that appears in one of these headers need not be an address
32409 that accepts bounce messages; only sender addresses in envelopes are required
32410 to accept bounces. Therefore, if you use the callout option on this check, you
32411 might want to arrange for a non-empty address in the MAIL command.
32413 Details of address verification and the options are given later, starting at
32414 section &<<SECTaddressverification>>& (callouts are described in section
32415 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
32416 condition to restrict it to bounce messages only:
32419 !verify = header_sender
32420 message = A valid sender header is required for bounces
32423 .vitem &*verify&~=&~header_syntax*&
32424 .cindex "&%verify%& ACL condition"
32425 .cindex "&ACL;" "verifying header syntax"
32426 .cindex "header lines" "verifying syntax"
32427 .cindex "verifying" "header syntax"
32428 This condition is relevant only in an ACL that is run after a message has been
32429 received, that is, in an ACL specified by &%acl_smtp_data%& or
32430 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
32431 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
32432 and &'Bcc:'&), returning true if there are no problems.
32433 Unqualified addresses (local parts without domains) are
32434 permitted only in locally generated messages and from hosts that match
32435 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
32438 Note that this condition is a syntax check only. However, a common spamming
32439 ploy used to be to send syntactically invalid headers such as
32443 and this condition can be used to reject such messages, though they are not as
32444 common as they used to be.
32446 .vitem &*verify&~=&~helo*&
32447 .cindex "&%verify%& ACL condition"
32448 .cindex "&ACL;" "verifying HELO/EHLO"
32449 .cindex "HELO" "verifying"
32450 .cindex "EHLO" "verifying"
32451 .cindex "verifying" "EHLO"
32452 .cindex "verifying" "HELO"
32453 This condition is true if a HELO or EHLO command has been received from the
32454 client host, and its contents have been verified. If there has been no previous
32455 attempt to verify the HELO/EHLO contents, it is carried out when this
32456 condition is encountered. See the description of the &%helo_verify_hosts%& and
32457 &%helo_try_verify_hosts%& options for details of how to request verification
32458 independently of this condition, and for detail of the verification.
32460 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
32461 option), this condition is always true.
32464 .vitem &*verify&~=&~not_blind/*&<&'options'&>
32465 .cindex "verifying" "not blind"
32466 .cindex "bcc recipients, verifying none"
32467 This condition checks that there are no blind (bcc) recipients in the message.
32468 Every envelope recipient must appear either in a &'To:'& header line or in a
32469 &'Cc:'& header line for this condition to be true. Local parts are checked
32470 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
32471 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
32472 used only in a DATA or non-SMTP ACL.
32474 There is one possible option, &`case_insensitive`&. If this is present then
32475 local parts are checked case-insensitively.
32477 There are, of course, many legitimate messages that make use of blind (bcc)
32478 recipients. This check should not be used on its own for blocking messages.
32481 .vitem &*verify&~=&~recipient/*&<&'options'&>
32482 .cindex "&%verify%& ACL condition"
32483 .cindex "&ACL;" "verifying recipient"
32484 .cindex "recipient" "verifying"
32485 .cindex "verifying" "recipient"
32486 .vindex "&$address_data$&"
32487 This condition is relevant only after a RCPT command. It verifies the current
32488 recipient. Details of address verification are given later, starting at section
32489 &<<SECTaddressverification>>&. After a recipient has been verified, the value
32490 of &$address_data$& is the last value that was set while routing the address.
32491 This applies even if the verification fails. When an address that is being
32492 verified is redirected to a single address, verification continues with the new
32493 address, and in that case, the subsequent value of &$address_data$& is the
32494 value for the child address.
32496 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
32497 .cindex "&%verify%& ACL condition"
32498 .cindex "&ACL;" "verifying host reverse lookup"
32499 .cindex "host" "verifying reverse lookup"
32500 This condition ensures that a verified host name has been looked up from the IP
32501 address of the client host. (This may have happened already if the host name
32502 was needed for checking a host list, or if the host matched &%host_lookup%&.)
32503 Verification ensures that the host name obtained from a reverse DNS lookup, or
32504 one of its aliases, does, when it is itself looked up in the DNS, yield the
32505 original IP address.
32507 There is one possible option, &`defer_ok`&. If this is present and a
32508 DNS operation returns a temporary error, the verify condition succeeds.
32510 If this condition is used for a locally generated message (that is, when there
32511 is no client host involved), it always succeeds.
32513 .vitem &*verify&~=&~sender/*&<&'options'&>
32514 .cindex "&%verify%& ACL condition"
32515 .cindex "&ACL;" "verifying sender"
32516 .cindex "sender" "verifying"
32517 .cindex "verifying" "sender"
32518 This condition is relevant only after a MAIL or RCPT command, or after a
32519 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
32520 the message's sender is empty (that is, this is a bounce message), the
32521 condition is true. Otherwise, the sender address is verified.
32523 .vindex "&$address_data$&"
32524 .vindex "&$sender_address_data$&"
32525 If there is data in the &$address_data$& variable at the end of routing, its
32526 value is placed in &$sender_address_data$& at the end of verification. This
32527 value can be used in subsequent conditions and modifiers in the same ACL
32528 statement. It does not persist after the end of the current statement. If you
32529 want to preserve the value for longer, you can save it in an ACL variable.
32531 Details of verification are given later, starting at section
32532 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
32533 to avoid doing it more than once per message.
32535 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
32536 .cindex "&%verify%& ACL condition"
32537 This is a variation of the previous option, in which a modified address is
32538 verified as a sender.
32540 Note that '/' is legal in local-parts; if the address may have such
32541 (eg. is generated from the received message)
32542 they must be protected from the options parsing by doubling:
32544 verify = sender=${listquote{/}{${address:$h_sender:}}}
32550 .section "Using DNS lists" "SECTmorednslists"
32551 .cindex "DNS list" "in ACL"
32552 .cindex "black list (DNS)"
32553 .cindex "&ACL;" "testing a DNS list"
32554 In its simplest form, the &%dnslists%& condition tests whether the calling host
32555 is on at least one of a number of DNS lists by looking up the inverted IP
32556 address in one or more DNS domains. (Note that DNS list domains are not mail
32557 domains, so the &`+`& syntax for named lists doesn't work - it is used for
32558 special options instead.) For example, if the calling host's IP
32559 address is 192.168.62.43, and the ACL statement is
32561 deny dnslists = blackholes.mail-abuse.org : \
32562 dialups.mail-abuse.org
32564 the following records are looked up:
32566 43.62.168.192.blackholes.mail-abuse.org
32567 43.62.168.192.dialups.mail-abuse.org
32569 As soon as Exim finds an existing DNS record, processing of the list stops.
32570 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
32571 to test that a host is on more than one list (an &"and"& conjunction), you can
32572 use two separate conditions:
32574 deny dnslists = blackholes.mail-abuse.org
32575 dnslists = dialups.mail-abuse.org
32577 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
32578 behaves as if the host does not match the list item, that is, as if the DNS
32579 record does not exist. If there are further items in the DNS list, they are
32582 This is usually the required action when &%dnslists%& is used with &%deny%&
32583 (which is the most common usage), because it prevents a DNS failure from
32584 blocking mail. However, you can change this behaviour by putting one of the
32585 following special items in the list:
32587 &`+include_unknown `& behave as if the item is on the list
32588 &`+exclude_unknown `& behave as if the item is not on the list (default)
32589 &`+defer_unknown `& give a temporary error
32591 .cindex "&`+include_unknown`&"
32592 .cindex "&`+exclude_unknown`&"
32593 .cindex "&`+defer_unknown`&"
32594 Each of these applies to any subsequent items on the list. For example:
32596 deny dnslists = +defer_unknown : foo.bar.example
32598 Testing the list of domains stops as soon as a match is found. If you want to
32599 warn for one list and block for another, you can use two different statements:
32601 deny dnslists = blackholes.mail-abuse.org
32602 warn dnslists = dialups.mail-abuse.org
32603 message = X-Warn: sending host is on dialups list
32605 .cindex caching "of dns lookup"
32607 DNS list lookups are cached by Exim for the duration of the SMTP session
32608 (but limited by the DNS return TTL value),
32609 so a lookup based on the IP address is done at most once for any incoming
32610 connection (assuming long-enough TTL).
32611 Exim does not share information between multiple incoming
32612 connections (but your local name server cache should be active).
32614 There are a number of DNS lists to choose from, some commercial, some free,
32615 or free for small deployments. An overview can be found at
32616 &url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists).
32620 .section "Specifying the IP address for a DNS list lookup" "SECID201"
32621 .cindex "DNS list" "keyed by explicit IP address"
32622 By default, the IP address that is used in a DNS list lookup is the IP address
32623 of the calling host. However, you can specify another IP address by listing it
32624 after the domain name, introduced by a slash. For example:
32626 deny dnslists = black.list.tld/192.168.1.2
32628 This feature is not very helpful with explicit IP addresses; it is intended for
32629 use with IP addresses that are looked up, for example, the IP addresses of the
32630 MX hosts or nameservers of an email sender address. For an example, see section
32631 &<<SECTmulkeyfor>>& below.
32636 .section "DNS lists keyed on domain names" "SECID202"
32637 .cindex "DNS list" "keyed by domain name"
32638 There are some lists that are keyed on domain names rather than inverted IP
32639 addresses (see, e.g., the &'domain based zones'& link at
32640 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
32641 with these lists. You can change the name that is looked up in a DNS list by
32642 listing it after the domain name, introduced by a slash. For example,
32644 deny dnslists = dsn.rfc-ignorant.org/$sender_address_domain
32645 message = Sender's domain is listed at $dnslist_domain
32647 This particular example is useful only in ACLs that are obeyed after the
32648 RCPT or DATA commands, when a sender address is available. If (for
32649 example) the message's sender is &'user@tld.example'& the name that is looked
32650 up by this example is
32652 tld.example.dsn.rfc-ignorant.org
32654 A single &%dnslists%& condition can contain entries for both names and IP
32655 addresses. For example:
32657 deny dnslists = sbl.spamhaus.org : \
32658 dsn.rfc-ignorant.org/$sender_address_domain
32660 The first item checks the sending host's IP address; the second checks a domain
32661 name. The whole condition is true if either of the DNS lookups succeeds.
32666 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
32667 .cindex "DNS list" "multiple keys for"
32668 The syntax described above for looking up explicitly-defined values (either
32669 names or IP addresses) in a DNS blacklist is a simplification. After the domain
32670 name for the DNS list, what follows the slash can in fact be a list of items.
32671 As with all lists in Exim, the default separator is a colon. However, because
32672 this is a sublist within the list of DNS blacklist domains, it is necessary
32673 either to double the separators like this:
32675 dnslists = black.list.tld/name.1::name.2
32677 or to change the separator character, like this:
32679 dnslists = black.list.tld/<;name.1;name.2
32681 If an item in the list is an IP address, it is inverted before the DNS
32682 blacklist domain is appended. If it is not an IP address, no inversion
32683 occurs. Consider this condition:
32685 dnslists = black.list.tld/<;192.168.1.2;a.domain
32687 The DNS lookups that occur are:
32689 2.1.168.192.black.list.tld
32690 a.domain.black.list.tld
32692 Once a DNS record has been found (that matches a specific IP return
32693 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
32694 are done. If there is a temporary DNS error, the rest of the sublist of domains
32695 or IP addresses is tried. A temporary error for the whole dnslists item occurs
32696 only if no other DNS lookup in this sublist succeeds. In other words, a
32697 successful lookup for any of the items in the sublist overrides a temporary
32698 error for a previous item.
32700 The ability to supply a list of items after the slash is in some sense just a
32701 syntactic convenience. These two examples have the same effect:
32703 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
32704 dnslists = black.list.tld/a.domain::b.domain
32706 However, when the data for the list is obtained from a lookup, the second form
32707 is usually much more convenient. Consider this example:
32709 deny dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
32710 ${lookup dnsdb {>|mxh=\
32711 $sender_address_domain} }} }
32712 message = The mail servers for the domain \
32713 $sender_address_domain \
32714 are listed at $dnslist_domain ($dnslist_value); \
32717 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
32718 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
32719 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
32720 of expanding the condition might be something like this:
32722 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
32724 Thus, this example checks whether or not the IP addresses of the sender
32725 domain's mail servers are on the Spamhaus black list.
32727 The key that was used for a successful DNS list lookup is put into the variable
32728 &$dnslist_matched$& (see section &<<SECID204>>&).
32733 .section "Data returned by DNS lists" "SECID203"
32734 .cindex "DNS list" "data returned from"
32735 DNS lists are constructed using address records in the DNS. The original RBL
32736 just used the address 127.0.0.1 on the right hand side of each record, but the
32737 RBL+ list and some other lists use a number of values with different meanings.
32738 The values used on the RBL+ list are:
32742 127.1.0.3 DUL and RBL
32744 127.1.0.5 RSS and RBL
32745 127.1.0.6 RSS and DUL
32746 127.1.0.7 RSS and DUL and RBL
32748 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
32749 different values. Some DNS lists may return more than one address record;
32750 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
32753 Values returned by a properly running DBSBL should be in the 127.0.0.0/8
32754 range. If a DNSBL operator loses control of the domain, lookups on it
32755 may start returning other addresses. Because of this, Exim now ignores
32756 returned values outside the 127/8 region.
32760 .section "Variables set from DNS lists" "SECID204"
32761 .cindex "expansion" "variables, set from DNS list"
32762 .cindex "DNS list" "variables set from"
32763 .vindex "&$dnslist_domain$&"
32764 .vindex "&$dnslist_matched$&"
32765 .vindex "&$dnslist_text$&"
32766 .vindex "&$dnslist_value$&"
32767 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
32768 the name of the overall domain that matched (for example,
32769 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
32770 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
32771 the DNS record. When the key is an IP address, it is not reversed in
32772 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
32773 cases, for example:
32775 deny dnslists = spamhaus.example
32777 the key is also available in another variable (in this case,
32778 &$sender_host_address$&). In more complicated cases, however, this is not true.
32779 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
32780 might generate a dnslists lookup like this:
32782 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
32784 If this condition succeeds, the value in &$dnslist_matched$& might be
32785 &`192.168.6.7`& (for example).
32787 If more than one address record is returned by the DNS lookup, all the IP
32788 addresses are included in &$dnslist_value$&, separated by commas and spaces.
32789 The variable &$dnslist_text$& contains the contents of any associated TXT
32790 record. For lists such as RBL+ the TXT record for a merged entry is often not
32791 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
32794 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
32795 &-- even if these appear before the condition in the ACL, they are not
32796 expanded until after it has failed. For example:
32798 deny hosts = !+local_networks
32799 message = $sender_host_address is listed \
32801 dnslists = rbl-plus.mail-abuse.example
32806 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
32807 .cindex "DNS list" "matching specific returned data"
32808 You can add an equals sign and an IP address after a &%dnslists%& domain name
32809 in order to restrict its action to DNS records with a matching right hand side.
32812 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
32814 rejects only those hosts that yield 127.0.0.2. Without this additional data,
32815 any address record is considered to be a match. For the moment, we assume
32816 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
32817 describes how multiple records are handled.
32819 More than one IP address may be given for checking, using a comma as a
32820 separator. These are alternatives &-- if any one of them matches, the
32821 &%dnslists%& condition is true. For example:
32823 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32825 If you want to specify a constraining address list and also specify names or IP
32826 addresses to be looked up, the constraining address list must be specified
32827 first. For example:
32829 deny dnslists = dsn.rfc-ignorant.org\
32830 =127.0.0.2/$sender_address_domain
32833 If the character &`&&`& is used instead of &`=`&, the comparison for each
32834 listed IP address is done by a bitwise &"and"& instead of by an equality test.
32835 In other words, the listed addresses are used as bit masks. The comparison is
32836 true if all the bits in the mask are present in the address that is being
32837 tested. For example:
32839 dnslists = a.b.c&0.0.0.3
32841 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
32842 want to test whether one bit or another bit is present (as opposed to both
32843 being present), you must use multiple values. For example:
32845 dnslists = a.b.c&0.0.0.1,0.0.0.2
32847 matches if the final component of the address is an odd number or two times
32852 .section "Negated DNS matching conditions" "SECID205"
32853 You can supply a negative list of IP addresses as part of a &%dnslists%&
32856 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32858 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32859 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
32861 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
32863 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32864 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
32865 words, the result of the test is inverted if an exclamation mark appears before
32866 the &`=`& (or the &`&&`&) sign.
32868 &*Note*&: This kind of negation is not the same as negation in a domain,
32869 host, or address list (which is why the syntax is different).
32871 If you are using just one list, the negation syntax does not gain you much. The
32872 previous example is precisely equivalent to
32874 deny dnslists = a.b.c
32875 !dnslists = a.b.c=127.0.0.2,127.0.0.3
32877 However, if you are using multiple lists, the negation syntax is clearer.
32878 Consider this example:
32880 deny dnslists = sbl.spamhaus.org : \
32882 dnsbl.njabl.org!=127.0.0.3 : \
32885 Using only positive lists, this would have to be:
32887 deny dnslists = sbl.spamhaus.org : \
32889 deny dnslists = dnsbl.njabl.org
32890 !dnslists = dnsbl.njabl.org=127.0.0.3
32891 deny dnslists = relays.ordb.org
32893 which is less clear, and harder to maintain.
32895 Negation can also be used with a bitwise-and restriction.
32896 The dnslists condition with only be trus if a result is returned
32897 by the lookup which, anded with the restriction, is all zeroes.
32900 deny dnslists = zen.spamhaus.org!&0.255.255.0
32906 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
32907 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
32908 thereby providing more than one IP address. When an item in a &%dnslists%& list
32909 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
32910 the match to specific results from the DNS lookup, there are two ways in which
32911 the checking can be handled. For example, consider the condition:
32913 dnslists = a.b.c=127.0.0.1
32915 What happens if the DNS lookup for the incoming IP address yields both
32916 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
32917 condition true because at least one given value was found, or is it false
32918 because at least one of the found values was not listed? And how does this
32919 affect negated conditions? Both possibilities are provided for with the help of
32920 additional separators &`==`& and &`=&&`&.
32923 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
32924 IP addresses matches one of the listed addresses. For the example above, the
32925 condition is true because 127.0.0.1 matches.
32927 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
32928 looked up IP addresses matches one of the listed addresses. If the condition is
32931 dnslists = a.b.c==127.0.0.1
32933 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32934 false because 127.0.0.2 is not listed. You would need to have:
32936 dnslists = a.b.c==127.0.0.1,127.0.0.2
32938 for the condition to be true.
32941 When &`!`& is used to negate IP address matching, it inverts the result, giving
32942 the precise opposite of the behaviour above. Thus:
32944 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
32945 addresses matches one of the listed addresses. Consider:
32947 dnslists = a.b.c!&0.0.0.1
32949 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32950 false because 127.0.0.1 matches.
32952 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
32953 looked up IP address that does not match. Consider:
32955 dnslists = a.b.c!=&0.0.0.1
32957 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32958 true, because 127.0.0.2 does not match. You would need to have:
32960 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
32962 for the condition to be false.
32964 When the DNS lookup yields only a single IP address, there is no difference
32965 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
32970 .section "Detailed information from merged DNS lists" "SECTmordetinf"
32971 .cindex "DNS list" "information from merged"
32972 When the facility for restricting the matching IP values in a DNS list is used,
32973 the text from the TXT record that is set in &$dnslist_text$& may not reflect
32974 the true reason for rejection. This happens when lists are merged and the IP
32975 address in the A record is used to distinguish them; unfortunately there is
32976 only one TXT record. One way round this is not to use merged lists, but that
32977 can be inefficient because it requires multiple DNS lookups where one would do
32978 in the vast majority of cases when the host of interest is not on any of the
32981 A less inefficient way of solving this problem is available. If
32982 two domain names, comma-separated, are given, the second is used first to
32983 do an initial check, making use of any IP value restrictions that are set.
32984 If there is a match, the first domain is used, without any IP value
32985 restrictions, to get the TXT record. As a byproduct of this, there is also
32986 a check that the IP being tested is indeed on the first list. The first
32987 domain is the one that is put in &$dnslist_domain$&. For example:
32990 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
32991 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32993 rejected because $sender_host_address is blacklisted \
32994 at $dnslist_domain\n$dnslist_text
32996 For the first blacklist item, this starts by doing a lookup in
32997 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
32998 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
32999 value, and as long as something is found, it looks for the corresponding TXT
33000 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
33001 The second blacklist item is processed similarly.
33003 If you are interested in more than one merged list, the same list must be
33004 given several times, but because the results of the DNS lookups are cached,
33005 the DNS calls themselves are not repeated. For example:
33008 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
33009 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
33010 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
33011 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
33013 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
33014 values matches (or if no record is found), this is the only lookup that is
33015 done. Only if there is a match is one of the more specific lists consulted.
33019 .section "DNS lists and IPv6" "SECTmorednslistslast"
33020 .cindex "IPv6" "DNS black lists"
33021 .cindex "DNS list" "IPv6 usage"
33022 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
33023 nibble by nibble. For example, if the calling host's IP address is
33024 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
33026 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
33027 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
33029 (split over two lines here to fit on the page). Unfortunately, some of the DNS
33030 lists contain wildcard records, intended for IPv4, that interact badly with
33031 IPv6. For example, the DNS entry
33033 *.3.some.list.example. A 127.0.0.1
33035 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
33036 Unfortunately, it also matches the entire 3::/4 IPv6 network.
33038 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
33039 &%condition%& condition, as in this example:
33041 deny condition = ${if isip4{$sender_host_address}}
33042 dnslists = some.list.example
33045 If an explicit key is being used for a DNS lookup and it may be an IPv6
33046 address you should specify alternate list separators for both the outer
33047 (DNS list name) list and inner (lookup keys) list:
33049 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
33052 .section "Rate limiting incoming messages" "SECTratelimiting"
33053 .cindex "rate limiting" "client sending"
33054 .cindex "limiting client sending rates"
33055 .oindex "&%smtp_ratelimit_*%&"
33056 The &%ratelimit%& ACL condition can be used to measure and control the rate at
33057 which clients can send email. This is more powerful than the
33058 &%smtp_ratelimit_*%& options, because those options control the rate of
33059 commands in a single SMTP session only, whereas the &%ratelimit%& condition
33060 works across all connections (concurrent and sequential) from the same client
33061 host. The syntax of the &%ratelimit%& condition is:
33063 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
33065 If the average client sending rate is less than &'m'& messages per time
33066 period &'p'& then the condition is false; otherwise it is true.
33068 As a side-effect, the &%ratelimit%& condition sets the expansion variable
33069 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
33070 configured value of &'m'&, and &$sender_rate_period$& to the configured value
33073 The parameter &'p'& is the smoothing time constant, in the form of an Exim
33074 time interval, for example, &`8h`& for eight hours. A larger time constant
33075 means that it takes Exim longer to forget a client's past behaviour. The
33076 parameter &'m'& is the maximum number of messages that a client is permitted to
33077 send in each time interval. It also specifies the number of messages permitted
33078 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
33079 constant, you can allow a client to send more messages in a burst without
33080 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
33081 both small, messages must be sent at an even rate.
33083 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
33084 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
33085 when deploying the &%ratelimit%& ACL condition. The script prints usage
33086 instructions when it is run with no arguments.
33088 The key is used to look up the data for calculating the client's average
33089 sending rate. This data is stored in Exim's spool directory, alongside the
33090 retry and other hints databases. The default key is &$sender_host_address$&,
33091 which means Exim computes the sending rate of each client host IP address.
33092 By changing the key you can change how Exim identifies clients for the purpose
33093 of ratelimiting. For example, to limit the sending rate of each authenticated
33094 user, independent of the computer they are sending from, set the key to
33095 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
33096 example, &$authenticated_id$& is only meaningful if the client has
33097 authenticated (which you can check with the &%authenticated%& ACL condition).
33099 The lookup key does not have to identify clients: If you want to limit the
33100 rate at which a recipient receives messages, you can use the key
33101 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
33104 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
33105 specifies what Exim measures the rate of, for example, messages or recipients
33106 or bytes. You can adjust the measurement using the &%unique=%& and/or
33107 &%count=%& options. You can also control when Exim updates the recorded rate
33108 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
33109 separated by a slash, like the other parameters. They may appear in any order.
33111 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
33112 any options that alter the meaning of the stored data. The limit &'m'& is not
33113 stored, so you can alter the configured maximum rate and Exim will still
33114 remember clients' past behaviour. If you change the &%per_*%& mode or add or
33115 remove the &%unique=%& option, the lookup key changes so Exim will forget past
33116 behaviour. The lookup key is not affected by changes to the update mode and
33117 the &%count=%& option.
33120 .section "Ratelimit options for what is being measured" "ratoptmea"
33121 .cindex "rate limiting" "per_* options"
33122 The &%per_conn%& option limits the client's connection rate. It is not
33123 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
33124 &%acl_not_smtp_start%& ACLs.
33126 The &%per_mail%& option limits the client's rate of sending messages. This is
33127 the default if none of the &%per_*%& options is specified. It can be used in
33128 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
33129 &%acl_smtp_data%&, or &%acl_not_smtp%&.
33131 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
33132 the same ACLs as the &%per_mail%& option, though it is best to use this option
33133 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
33134 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
33135 in its MAIL command, which may be inaccurate or completely missing. You can
33136 follow the limit &'m'& in the configuration with K, M, or G to specify limits
33137 in kilobytes, megabytes, or gigabytes, respectively.
33139 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
33140 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
33141 &%acl_smtp_mime%&, or &%acl_smtp_data%& ACLs. In
33142 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
33143 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
33144 in either case the rate limiting engine will see a message with many
33145 recipients as a large high-speed burst.
33147 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
33148 number of different recipients that the client has sent messages to in the
33149 last time period. That is, if the client repeatedly sends messages to the same
33150 recipient, its measured rate is not increased. This option can only be used in
33153 The &%per_cmd%& option causes Exim to recompute the rate every time the
33154 condition is processed. This can be used to limit the rate of any SMTP
33155 command. If it is used in multiple ACLs it can limit the aggregate rate of
33156 multiple different commands.
33158 The &%count=%& option can be used to alter how much Exim adds to the client's
33159 measured rate. For example, the &%per_byte%& option is equivalent to
33160 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
33161 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
33162 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
33164 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
33167 .section "Ratelimit update modes" "ratoptupd"
33168 .cindex "rate limiting" "reading data without updating"
33169 You can specify one of three options with the &%ratelimit%& condition to
33170 control when its database is updated. This section describes the &%readonly%&
33171 mode, and the next section describes the &%strict%& and &%leaky%& modes.
33173 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
33174 previously-computed rate to check against the limit.
33176 For example, you can test the client's sending rate and deny it access (when
33177 it is too fast) in the connect ACL. If the client passes this check then it
33178 can go on to send a message, in which case its recorded rate will be updated
33179 in the MAIL ACL. Subsequent connections from the same client will check this
33183 deny ratelimit = 100 / 5m / readonly
33184 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
33185 (max $sender_rate_limit)
33188 warn ratelimit = 100 / 5m / strict
33189 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
33190 (max $sender_rate_limit)
33193 If Exim encounters multiple &%ratelimit%& conditions with the same key when
33194 processing a message then it may increase the client's measured rate more than
33195 it should. For example, this will happen if you check the &%per_rcpt%& option
33196 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
33197 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
33198 multiple update problems by using the &%readonly%& option on later ratelimit
33201 The &%per_*%& options described above do not make sense in some ACLs. If you
33202 use a &%per_*%& option in an ACL where it is not normally permitted then the
33203 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
33204 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
33205 next section) so you must specify the &%readonly%& option explicitly.
33208 .section "Ratelimit options for handling fast clients" "ratoptfast"
33209 .cindex "rate limiting" "strict and leaky modes"
33210 If a client's average rate is greater than the maximum, the rate limiting
33211 engine can react in two possible ways, depending on the presence of the
33212 &%strict%& or &%leaky%& update modes. This is independent of the other
33213 counter-measures (such as rejecting the message) that may be specified by the
33216 The &%leaky%& (default) option means that the client's recorded rate is not
33217 updated if it is above the limit. The effect of this is that Exim measures the
33218 client's average rate of successfully sent email,
33219 up to the given limit.
33220 This is appropriate if the countermeasure when the condition is true
33221 consists of refusing the message, and
33222 is generally the better choice if you have clients that retry automatically.
33223 If the action when true is anything more complex then this option is
33224 likely not what is wanted.
33226 The &%strict%& option means that the client's recorded rate is always
33227 updated. The effect of this is that Exim measures the client's average rate
33228 of attempts to send email, which can be much higher than the maximum it is
33229 actually allowed. If the client is over the limit it may be subjected to
33230 counter-measures by the ACL. It must slow down and allow sufficient time to
33231 pass that its computed rate falls below the maximum before it can send email
33232 again. The time (the number of smoothing periods) it must wait and not
33233 attempt to send mail can be calculated with this formula:
33235 ln(peakrate/maxrate)
33239 .section "Limiting the rate of different events" "ratoptuniq"
33240 .cindex "rate limiting" "counting unique events"
33241 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
33242 rate of different events. For example, the &%per_addr%& option uses this
33243 mechanism to count the number of different recipients that the client has
33244 sent messages to in the last time period; it is equivalent to
33245 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
33246 measure the rate that a client uses different sender addresses with the
33247 options &`per_mail/unique=$sender_address`&.
33249 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
33250 has seen for that key. The whole set is thrown away when it is older than the
33251 rate smoothing period &'p'&, so each different event is counted at most once
33252 per period. In the &%leaky%& update mode, an event that causes the client to
33253 go over the limit is not added to the set, in the same way that the client's
33254 recorded rate is not updated in the same situation.
33256 When you combine the &%unique=%& and &%readonly%& options, the specific
33257 &%unique=%& value is ignored, and Exim just retrieves the client's stored
33260 The &%unique=%& mechanism needs more space in the ratelimit database than the
33261 other &%ratelimit%& options in order to store the event set. The number of
33262 unique values is potentially as large as the rate limit, so the extra space
33263 required increases with larger limits.
33265 The uniqueification is not perfect: there is a small probability that Exim
33266 will think a new event has happened before. If the sender's rate is less than
33267 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
33268 the measured rate can go above the limit, in which case Exim may under-count
33269 events by a significant margin. Fortunately, if the rate is high enough (2.7
33270 times the limit) that the false positive rate goes above 9%, then Exim will
33271 throw away the over-full event set before the measured rate falls below the
33272 limit. Therefore the only harm should be that exceptionally high sending rates
33273 are logged incorrectly; any countermeasures you configure will be as effective
33277 .section "Using rate limiting" "useratlim"
33278 Exim's other ACL facilities are used to define what counter-measures are taken
33279 when the rate limit is exceeded. This might be anything from logging a warning
33280 (for example, while measuring existing sending rates in order to define
33281 policy), through time delays to slow down fast senders, up to rejecting the
33282 message. For example:
33284 # Log all senders' rates
33285 warn ratelimit = 0 / 1h / strict
33286 log_message = Sender rate $sender_rate / $sender_rate_period
33288 # Slow down fast senders; note the need to truncate $sender_rate
33289 # at the decimal point.
33290 warn ratelimit = 100 / 1h / per_rcpt / strict
33291 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
33292 $sender_rate_limit }s
33294 # Keep authenticated users under control
33295 deny authenticated = *
33296 ratelimit = 100 / 1d / strict / $authenticated_id
33298 # System-wide rate limit
33299 defer ratelimit = 10 / 1s / $primary_hostname
33300 message = Sorry, too busy. Try again later.
33302 # Restrict incoming rate from each host, with a default
33303 # set using a macro and special cases looked up in a table.
33304 defer ratelimit = ${lookup {$sender_host_address} \
33305 cdb {DB/ratelimits.cdb} \
33306 {$value} {RATELIMIT} }
33307 message = Sender rate exceeds $sender_rate_limit \
33308 messages per $sender_rate_period
33310 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
33311 especially with the &%per_rcpt%& option, you may suffer from a performance
33312 bottleneck caused by locking on the ratelimit hints database. Apart from
33313 making your ACLs less complicated, you can reduce the problem by using a
33314 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
33315 this means that Exim will lose its hints data after a reboot (including retry
33316 hints, the callout cache, and ratelimit data).
33320 .section "Address verification" "SECTaddressverification"
33321 .cindex "verifying address" "options for"
33322 .cindex "policy control" "address verification"
33323 Several of the &%verify%& conditions described in section
33324 &<<SECTaclconditions>>& cause addresses to be verified. Section
33325 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
33326 The verification conditions can be followed by options that modify the
33327 verification process. The options are separated from the keyword and from each
33328 other by slashes, and some of them contain parameters. For example:
33330 verify = sender/callout
33331 verify = recipient/defer_ok/callout=10s,defer_ok
33333 The first stage of address verification, which always happens, is to run the
33334 address through the routers, in &"verify mode"&. Routers can detect the
33335 difference between verification and routing for delivery, and their actions can
33336 be varied by a number of generic options such as &%verify%& and &%verify_only%&
33337 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
33338 The available options are as follows:
33341 If the &%callout%& option is specified, successful routing to one or more
33342 remote hosts is followed by a &"callout"& to those hosts as an additional
33343 check. Callouts and their sub-options are discussed in the next section.
33345 If there is a defer error while doing verification routing, the ACL
33346 normally returns &"defer"&. However, if you include &%defer_ok%& in the
33347 options, the condition is forced to be true instead. Note that this is a main
33348 verification option as well as a suboption for callouts.
33350 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
33351 discusses the reporting of sender address verification failures.
33353 The &%success_on_redirect%& option causes verification always to succeed
33354 immediately after a successful redirection. By default, if a redirection
33355 generates just one address, that address is also verified. See further
33356 discussion in section &<<SECTredirwhilveri>>&.
33359 If the &%quota%& option is specified for recipient verify,
33360 successful routing to an appendfile transport is followed by a call into
33361 the transport to evaluate the quota status for the recipient.
33362 No actual delivery is done, but verification will succeed if the quota
33363 is sufficient for the message (if the sender gave a message size) or
33364 not already exceeded (otherwise).
33368 .cindex "verifying address" "differentiating failures"
33369 .vindex "&$recipient_verify_failure$&"
33370 .vindex "&$sender_verify_failure$&"
33371 .vindex "&$acl_verify_message$&"
33372 After an address verification failure, &$acl_verify_message$& contains the
33373 error message that is associated with the failure. It can be preserved by
33376 warn !verify = sender
33377 set acl_m0 = $acl_verify_message
33379 If you are writing your own custom rejection message or log message when
33380 denying access, you can use this variable to include information about the
33381 verification failure.
33382 This variable is cleared at the end of processing the ACL verb.
33384 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
33385 appropriate) contains one of the following words:
33388 &%qualify%&: The address was unqualified (no domain), and the message
33389 was neither local nor came from an exempted host.
33391 &%route%&: Routing failed.
33393 &%mail%&: Routing succeeded, and a callout was attempted; rejection
33394 occurred at or before the MAIL command (that is, on initial
33395 connection, HELO, or MAIL).
33397 &%recipient%&: The RCPT command in a callout was rejected.
33399 &%postmaster%&: The postmaster check in a callout was rejected.
33402 &%quota%&: The quota check for a local recipient did non pass.
33405 The main use of these variables is expected to be to distinguish between
33406 rejections of MAIL and rejections of RCPT in callouts.
33408 The above variables may also be set after a &*successful*&
33409 address verification to:
33412 &%random%&: A random local-part callout succeeded
33418 .section "Callout verification" "SECTcallver"
33419 .cindex "verifying address" "by callout"
33420 .cindex "callout" "verification"
33421 .cindex "SMTP" "callout verification"
33422 For non-local addresses, routing verifies the domain, but is unable to do any
33423 checking of the local part. There are situations where some means of verifying
33424 the local part is desirable. One way this can be done is to make an SMTP
33425 &'callback'& to a delivery host for the sender address or a &'callforward'& to
33426 a subsequent host for a recipient address, to see if the host accepts the
33427 address. We use the term &'callout'& to cover both cases. Note that for a
33428 sender address, the callback is not to the client host that is trying to
33429 deliver the message, but to one of the hosts that accepts incoming mail for the
33432 Exim does not do callouts by default. If you want them to happen, you must
33433 request them by setting appropriate options on the &%verify%& condition, as
33434 described below. This facility should be used with care, because it can add a
33435 lot of resource usage to the cost of verifying an address. However, Exim does
33436 cache the results of callouts, which helps to reduce the cost. Details of
33437 caching are in section &<<SECTcallvercache>>&.
33439 Recipient callouts are usually used only between hosts that are controlled by
33440 the same administration. For example, a corporate gateway host could use
33441 callouts to check for valid recipients on an internal mailserver. A successful
33442 callout does not guarantee that a real delivery to the address would succeed;
33443 on the other hand, a failing callout does guarantee that a delivery would fail.
33445 If the &%callout%& option is present on a condition that verifies an address, a
33446 second stage of verification occurs if the address is successfully routed to
33447 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
33448 &(manualroute)& router, where the router specifies the hosts. However, if a
33449 router that does not set up hosts routes to an &(smtp)& transport with a
33450 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
33451 &%hosts_override%& set, its hosts are always used, whether or not the router
33452 supplies a host list.
33453 Callouts are only supported on &(smtp)& transports.
33455 The port that is used is taken from the transport, if it is specified and is a
33456 remote transport. (For routers that do verification only, no transport need be
33457 specified.) Otherwise, the default SMTP port is used. If a remote transport
33458 specifies an outgoing interface, this is used; otherwise the interface is not
33459 specified. Likewise, the text that is used for the HELO command is taken from
33460 the transport's &%helo_data%& option; if there is no transport, the value of
33461 &$smtp_active_hostname$& is used.
33463 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
33464 test whether a bounce message could be delivered to the sender address. The
33465 following SMTP commands are sent:
33467 &`HELO `&<&'local host name'&>
33469 &`RCPT TO:`&<&'the address to be tested'&>
33472 LHLO is used instead of HELO if the transport's &%protocol%& option is
33475 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
33478 A recipient callout check is similar. By default, it also uses an empty address
33479 for the sender. This default is chosen because most hosts do not make use of
33480 the sender address when verifying a recipient. Using the same address means
33481 that a single cache entry can be used for each recipient. Some sites, however,
33482 do make use of the sender address when verifying. These are catered for by the
33483 &%use_sender%& and &%use_postmaster%& options, described in the next section.
33485 If the response to the RCPT command is a 2&'xx'& code, the verification
33486 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
33487 Exim tries the next host, if any. If there is a problem with all the remote
33488 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
33489 &%callout%& option is given, in which case the condition is forced to succeed.
33491 .cindex "SMTP" "output flushing, disabling for callout"
33492 A callout may take a little time. For this reason, Exim normally flushes SMTP
33493 output before performing a callout in an ACL, to avoid unexpected timeouts in
33494 clients when the SMTP PIPELINING extension is in use. The flushing can be
33495 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
33500 .section "Additional parameters for callouts" "CALLaddparcall"
33501 .cindex "callout" "additional parameters for"
33502 The &%callout%& option can be followed by an equals sign and a number of
33503 optional parameters, separated by commas. For example:
33505 verify = recipient/callout=10s,defer_ok
33507 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
33508 separate verify options, is retained for backwards compatibility, but is now
33509 deprecated. The additional parameters for &%callout%& are as follows:
33513 .vitem <&'a&~time&~interval'&>
33514 .cindex "callout" "timeout, specifying"
33515 This specifies the timeout that applies for the callout attempt to each host.
33518 verify = sender/callout=5s
33520 The default is 30 seconds. The timeout is used for each response from the
33521 remote host. It is also used for the initial connection, unless overridden by
33522 the &%connect%& parameter.
33525 .vitem &*connect&~=&~*&<&'time&~interval'&>
33526 .cindex "callout" "connection timeout, specifying"
33527 This parameter makes it possible to set a different (usually smaller) timeout
33528 for making the SMTP connection. For example:
33530 verify = sender/callout=5s,connect=1s
33532 If not specified, this timeout defaults to the general timeout value.
33534 .vitem &*defer_ok*&
33535 .cindex "callout" "defer, action on"
33536 When this parameter is present, failure to contact any host, or any other kind
33537 of temporary error, is treated as success by the ACL. However, the cache is not
33538 updated in this circumstance.
33540 .vitem &*fullpostmaster*&
33541 .cindex "callout" "full postmaster check"
33542 This operates like the &%postmaster%& option (see below), but if the check for
33543 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
33544 accordance with the specification in RFC 2821. The RFC states that the
33545 unqualified address &'postmaster'& should be accepted.
33548 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
33549 .cindex "callout" "sender when verifying header"
33550 When verifying addresses in header lines using the &%header_sender%&
33551 verification option, Exim behaves by default as if the addresses are envelope
33552 sender addresses from a message. Callout verification therefore tests to see
33553 whether a bounce message could be delivered, by using an empty address in the
33554 MAIL command. However, it is arguable that these addresses might never be used
33555 as envelope senders, and could therefore justifiably reject bounce messages
33556 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
33557 address to use in the MAIL command. For example:
33559 require verify = header_sender/callout=mailfrom=abcd@x.y.z
33561 This parameter is available only for the &%header_sender%& verification option.
33564 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
33565 .cindex "callout" "overall timeout, specifying"
33566 This parameter sets an overall timeout for performing a callout verification.
33569 verify = sender/callout=5s,maxwait=30s
33571 This timeout defaults to four times the callout timeout for individual SMTP
33572 commands. The overall timeout applies when there is more than one host that can
33573 be tried. The timeout is checked before trying the next host. This prevents
33574 very long delays if there are a large number of hosts and all are timing out
33575 (for example, when network connections are timing out).
33578 .vitem &*no_cache*&
33579 .cindex "callout" "cache, suppressing"
33580 .cindex "caching callout, suppressing"
33581 When this parameter is given, the callout cache is neither read nor updated.
33583 .vitem &*postmaster*&
33584 .cindex "callout" "postmaster; checking"
33585 When this parameter is set, a successful callout check is followed by a similar
33586 check for the local part &'postmaster'& at the same domain. If this address is
33587 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
33588 the postmaster check is recorded in a cache record; if it is a failure, this is
33589 used to fail subsequent callouts for the domain without a connection being
33590 made, until the cache record expires.
33592 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
33593 The postmaster check uses an empty sender in the MAIL command by default.
33594 You can use this parameter to do a postmaster check using a different address.
33597 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
33599 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
33600 one overrides. The &%postmaster%& parameter is equivalent to this example:
33602 require verify = sender/callout=postmaster_mailfrom=
33604 &*Warning*&: The caching arrangements for postmaster checking do not take
33605 account of the sender address. It is assumed that either the empty address or
33606 a fixed non-empty address will be used. All that Exim remembers is that the
33607 postmaster check for the domain succeeded or failed.
33611 .cindex "callout" "&""random""& check"
33612 When this parameter is set, before doing the normal callout check, Exim does a
33613 check for a &"random"& local part at the same domain. The local part is not
33614 really random &-- it is defined by the expansion of the option
33615 &%callout_random_local_part%&, which defaults to
33617 $primary_hostname-$tod_epoch-testing
33619 The idea here is to try to determine whether the remote host accepts all local
33620 parts without checking. If it does, there is no point in doing callouts for
33621 specific local parts. If the &"random"& check succeeds, the result is saved in
33622 a cache record, and used to force the current and subsequent callout checks to
33623 succeed without a connection being made, until the cache record expires.
33625 .vitem &*use_postmaster*&
33626 .cindex "callout" "sender for recipient check"
33627 This parameter applies to recipient callouts only. For example:
33629 deny !verify = recipient/callout=use_postmaster
33631 .vindex "&$qualify_domain$&"
33632 It causes a non-empty postmaster address to be used in the MAIL command when
33633 performing the callout for the recipient, and also for a &"random"& check if
33634 that is configured. The local part of the address is &`postmaster`& and the
33635 domain is the contents of &$qualify_domain$&.
33637 .vitem &*use_sender*&
33638 This option applies to recipient callouts only. For example:
33640 require verify = recipient/callout=use_sender
33642 It causes the message's actual sender address to be used in the MAIL
33643 command when performing the callout, instead of an empty address. There is no
33644 need to use this option unless you know that the called hosts make use of the
33645 sender when checking recipients. If used indiscriminately, it reduces the
33646 usefulness of callout caching.
33649 This option applies to recipient callouts only. For example:
33651 require verify = recipient/callout=use_sender,hold
33653 It causes the connection to be held open and used for any further recipients
33654 and for eventual delivery (should that be done quickly).
33655 Doing this saves on TCP and SMTP startup costs, and TLS costs also
33656 when that is used for the connections.
33657 The advantage is only gained if there are no callout cache hits
33658 (which could be enforced by the no_cache option),
33659 if the use_sender option is used,
33660 if neither the random nor the use_postmaster option is used,
33661 and if no other callouts intervene.
33664 If you use any of the parameters that set a non-empty sender for the MAIL
33665 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
33666 &%use_sender%&), you should think about possible loops. Recipient checking is
33667 usually done between two hosts that are under the same management, and the host
33668 that receives the callouts is not normally configured to do callouts itself.
33669 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
33670 these circumstances.
33672 However, if you use a non-empty sender address for a callout to an arbitrary
33673 host, there is the likelihood that the remote host will itself initiate a
33674 callout check back to your host. As it is checking what appears to be a message
33675 sender, it is likely to use an empty address in MAIL, thus avoiding a
33676 callout loop. However, to be on the safe side it would be best to set up your
33677 own ACLs so that they do not do sender verification checks when the recipient
33678 is the address you use for header sender or postmaster callout checking.
33680 Another issue to think about when using non-empty senders for callouts is
33681 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
33682 by the sender/recipient combination; thus, for any given recipient, many more
33683 actual callouts are performed than when an empty sender or postmaster is used.
33688 .section "Callout caching" "SECTcallvercache"
33689 .cindex "hints database" "callout cache"
33690 .cindex "callout" "cache, description of"
33691 .cindex "caching" "callout"
33692 Exim caches the results of callouts in order to reduce the amount of resources
33693 used, unless you specify the &%no_cache%& parameter with the &%callout%&
33694 option. A hints database called &"callout"& is used for the cache. Two
33695 different record types are used: one records the result of a callout check for
33696 a specific address, and the other records information that applies to the
33697 entire domain (for example, that it accepts the local part &'postmaster'&).
33699 When an original callout fails, a detailed SMTP error message is given about
33700 the failure. However, for subsequent failures use the cache data, this message
33703 The expiry times for negative and positive address cache records are
33704 independent, and can be set by the global options &%callout_negative_expire%&
33705 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
33707 If a host gives a negative response to an SMTP connection, or rejects any
33708 commands up to and including
33712 (but not including the MAIL command with a non-empty address),
33713 any callout attempt is bound to fail. Exim remembers such failures in a
33714 domain cache record, which it uses to fail callouts for the domain without
33715 making new connections, until the domain record times out. There are two
33716 separate expiry times for domain cache records:
33717 &%callout_domain_negative_expire%& (default 3h) and
33718 &%callout_domain_positive_expire%& (default 7d).
33720 Domain records expire when the negative expiry time is reached if callouts
33721 cannot be made for the domain, or if the postmaster check failed.
33722 Otherwise, they expire when the positive expiry time is reached. This
33723 ensures that, for example, a host that stops accepting &"random"& local parts
33724 will eventually be noticed.
33726 The callout caching mechanism is based on the domain of the address that is
33727 being tested. If the domain routes to several hosts, it is assumed that their
33728 behaviour will be the same.
33733 .section "Quota caching" "SECTquotacache"
33734 .cindex "hints database" "quota cache"
33735 .cindex "quota" "cache, description of"
33736 .cindex "caching" "quota"
33737 Exim caches the results of quota verification
33738 in order to reduce the amount of resources used.
33739 The &"callout"& hints database is used.
33741 The default cache periods are five minutes for a positive (good) result
33742 and one hour for a negative result.
33743 To change the periods the &%quota%& option can be followed by an equals sign
33744 and a number of optional paramemters, separated by commas.
33747 verify = recipient/quota=cachepos=1h,cacheneg=1d
33749 Possible parameters are:
33751 .vitem &*cachepos&~=&~*&<&'time&~interval'&>
33752 .cindex "quota cache" "positive entry expiry, specifying"
33753 Set the lifetime for a positive cache entry.
33754 A value of zero seconds is legitimate.
33756 .vitem &*cacheneg&~=&~*&<&'time&~interval'&>
33757 .cindex "quota cache" "negative entry expiry, specifying"
33758 As above, for a negative entry.
33760 .vitem &*no_cache*&
33761 Set both positive and negative lifetimes to zero.
33764 .section "Sender address verification reporting" "SECTsenaddver"
33765 .cindex "verifying" "suppressing error details"
33766 See section &<<SECTaddressverification>>& for a general discussion of
33767 verification. When sender verification fails in an ACL, the details of the
33768 failure are given as additional output lines before the 550 response to the
33769 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
33772 MAIL FROM:<xyz@abc.example>
33774 RCPT TO:<pqr@def.example>
33775 550-Verification failed for <xyz@abc.example>
33776 550-Called: 192.168.34.43
33777 550-Sent: RCPT TO:<xyz@abc.example>
33778 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
33779 550 Sender verification failed
33781 If more than one RCPT command fails in the same way, the details are given
33782 only for the first of them. However, some administrators do not want to send
33783 out this much information. You can suppress the details by adding
33784 &`/no_details`& to the ACL statement that requests sender verification. For
33787 verify = sender/no_details
33790 .section "Redirection while verifying" "SECTredirwhilveri"
33791 .cindex "verifying" "redirection while"
33792 .cindex "address redirection" "while verifying"
33793 A dilemma arises when a local address is redirected by aliasing or forwarding
33794 during verification: should the generated addresses themselves be verified,
33795 or should the successful expansion of the original address be enough to verify
33796 it? By default, Exim takes the following pragmatic approach:
33799 When an incoming address is redirected to just one child address, verification
33800 continues with the child address, and if that fails to verify, the original
33801 verification also fails.
33803 When an incoming address is redirected to more than one child address,
33804 verification does not continue. A success result is returned.
33807 This seems the most reasonable behaviour for the common use of aliasing as a
33808 way of redirecting different local parts to the same mailbox. It means, for
33809 example, that a pair of alias entries of the form
33812 aw123: :fail: Gone away, no forwarding address
33814 work as expected, with both local parts causing verification failure. When a
33815 redirection generates more than one address, the behaviour is more like a
33816 mailing list, where the existence of the alias itself is sufficient for
33817 verification to succeed.
33819 It is possible, however, to change the default behaviour so that all successful
33820 redirections count as successful verifications, however many new addresses are
33821 generated. This is specified by the &%success_on_redirect%& verification
33822 option. For example:
33824 require verify = recipient/success_on_redirect/callout=10s
33826 In this example, verification succeeds if a router generates a new address, and
33827 the callout does not occur, because no address was routed to a remote host.
33829 When verification is being tested via the &%-bv%& option, the treatment of
33830 redirections is as just described, unless the &%-v%& or any debugging option is
33831 also specified. In that case, full verification is done for every generated
33832 address and a report is output for each of them.
33836 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
33837 .cindex "CSA" "verifying"
33838 Client SMTP Authorization is a system that allows a site to advertise
33839 which machines are and are not permitted to send email. This is done by placing
33840 special SRV records in the DNS; these are looked up using the client's HELO
33841 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
33842 Authorization checks in Exim are performed by the ACL condition:
33846 This fails if the client is not authorized. If there is a DNS problem, or if no
33847 valid CSA SRV record is found, or if the client is authorized, the condition
33848 succeeds. These three cases can be distinguished using the expansion variable
33849 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
33850 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
33851 be likely to cause problems for legitimate email.
33853 The error messages produced by the CSA code include slightly more
33854 detail. If &$csa_status$& is &"defer"&, this may be because of problems
33855 looking up the CSA SRV record, or problems looking up the CSA target
33856 address record. There are four reasons for &$csa_status$& being &"fail"&:
33859 The client's host name is explicitly not authorized.
33861 The client's IP address does not match any of the CSA target IP addresses.
33863 The client's host name is authorized but it has no valid target IP addresses
33864 (for example, the target's addresses are IPv6 and the client is using IPv4).
33866 The client's host name has no CSA SRV record but a parent domain has asserted
33867 that all subdomains must be explicitly authorized.
33870 The &%csa%& verification condition can take an argument which is the domain to
33871 use for the DNS query. The default is:
33873 verify = csa/$sender_helo_name
33875 This implementation includes an extension to CSA. If the query domain
33876 is an address literal such as [192.0.2.95], or if it is a bare IP
33877 address, Exim searches for CSA SRV records in the reverse DNS as if
33878 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
33881 verify = csa/$sender_host_address
33883 In fact, this is the check that Exim performs if the client does not say HELO.
33884 This extension can be turned off by setting the main configuration option
33885 &%dns_csa_use_reverse%& to be false.
33887 If a CSA SRV record is not found for the domain itself, a search
33888 is performed through its parent domains for a record which might be
33889 making assertions about subdomains. The maximum depth of this search is limited
33890 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
33891 default. Exim does not look for CSA SRV records in a top level domain, so the
33892 default settings handle HELO domains as long as seven
33893 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
33894 of legitimate HELO domains.
33896 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
33897 direct SRV lookups, this is not sufficient because of the extra parent domain
33898 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
33899 addresses into lookups in the reverse DNS space. The result of a successful
33902 ${lookup dnsdb {csa=$sender_helo_name}}
33904 has two space-separated fields: an authorization code and a target host name.
33905 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
33906 authorization required but absent, or &"?"& for unknown.
33911 .section "Bounce address tag validation" "SECTverifyPRVS"
33912 .cindex "BATV, verifying"
33913 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
33914 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
33915 Genuine incoming bounce messages should therefore always be addressed to
33916 recipients that have a valid tag. This scheme is a way of detecting unwanted
33917 bounce messages caused by sender address forgeries (often called &"collateral
33918 spam"&), because the recipients of such messages do not include valid tags.
33920 There are two expansion items to help with the implementation of the BATV
33921 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
33922 the original envelope sender address by using a simple key to add a hash of the
33923 address and some time-based randomizing information. The &%prvs%& expansion
33924 item creates a signed address, and the &%prvscheck%& expansion item checks one.
33925 The syntax of these expansion items is described in section
33926 &<<SECTexpansionitems>>&.
33927 The validity period on signed addresses is seven days.
33929 As an example, suppose the secret per-address keys are stored in an MySQL
33930 database. A query to look up the key for an address could be defined as a macro
33933 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
33934 WHERE sender='${quote_mysql:$prvscheck_address}'\
33937 Suppose also that the senders who make use of BATV are defined by an address
33938 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
33941 # Bounces: drop unsigned addresses for BATV senders
33943 recipients = +batv_senders
33944 message = This address does not send an unsigned reverse path
33946 # Bounces: In case of prvs-signed address, check signature.
33948 condition = ${prvscheck {$local_part@$domain}\
33949 {PRVSCHECK_SQL}{1}}
33950 !condition = $prvscheck_result
33951 message = Invalid reverse path signature.
33953 The first statement rejects recipients for bounce messages that are addressed
33954 to plain BATV sender addresses, because it is known that BATV senders do not
33955 send out messages with plain sender addresses. The second statement rejects
33956 recipients that are prvs-signed, but with invalid signatures (either because
33957 the key is wrong, or the signature has timed out).
33959 A non-prvs-signed address is not rejected by the second statement, because the
33960 &%prvscheck%& expansion yields an empty string if its first argument is not a
33961 prvs-signed address, thus causing the &%condition%& condition to be false. If
33962 the first argument is a syntactically valid prvs-signed address, the yield is
33963 the third string (in this case &"1"&), whether or not the cryptographic and
33964 timeout checks succeed. The &$prvscheck_result$& variable contains the result
33965 of the checks (empty for failure, &"1"& for success).
33967 There is one more issue you must consider when implementing prvs-signing:
33968 you have to ensure that the routers accept prvs-signed addresses and
33969 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
33970 router to remove the signature with a configuration along these lines:
33974 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
33976 This works because, if the third argument of &%prvscheck%& is empty, the result
33977 of the expansion of a prvs-signed address is the decoded value of the original
33978 address. This router should probably be the first of your routers that handles
33981 To create BATV-signed addresses in the first place, a transport of this form
33984 external_smtp_batv:
33986 return_path = ${prvs {$return_path} \
33987 {${lookup mysql{SELECT \
33988 secret FROM batv_prvs WHERE \
33989 sender='${quote_mysql:$sender_address}'} \
33992 If no key can be found for the existing return path, no signing takes place.
33996 .section "Using an ACL to control relaying" "SECTrelaycontrol"
33997 .cindex "&ACL;" "relay control"
33998 .cindex "relaying" "control by ACL"
33999 .cindex "policy control" "relay control"
34000 An MTA is said to &'relay'& a message if it receives it from some host and
34001 delivers it directly to another host as a result of a remote address contained
34002 within it. Redirecting a local address via an alias or forward file and then
34003 passing the message on to another host is not relaying,
34004 .cindex "&""percent hack""&"
34005 but a redirection as a result of the &"percent hack"& is.
34007 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
34008 A host which is acting as a gateway or an MX backup is concerned with incoming
34009 relaying from arbitrary hosts to a specific set of domains. On the other hand,
34010 a host which is acting as a smart host for a number of clients is concerned
34011 with outgoing relaying from those clients to the Internet at large. Often the
34012 same host is fulfilling both functions,
34014 . as illustrated in the diagram below,
34016 but in principle these two kinds of relaying are entirely independent. What is
34017 not wanted is the transmission of mail from arbitrary remote hosts through your
34018 system to arbitrary domains.
34021 You can implement relay control by means of suitable statements in the ACL that
34022 runs for each RCPT command. For convenience, it is often easiest to use
34023 Exim's named list facility to define the domains and hosts involved. For
34024 example, suppose you want to do the following:
34027 Deliver a number of domains to mailboxes on the local host (or process them
34028 locally in some other way). Let's say these are &'my.dom1.example'& and
34029 &'my.dom2.example'&.
34031 Relay mail for a number of other domains for which you are the secondary MX.
34032 These might be &'friend1.example'& and &'friend2.example'&.
34034 Relay mail from the hosts on your local LAN, to whatever domains are involved.
34035 Suppose your LAN is 192.168.45.0/24.
34039 In the main part of the configuration, you put the following definitions:
34041 domainlist local_domains = my.dom1.example : my.dom2.example
34042 domainlist relay_to_domains = friend1.example : friend2.example
34043 hostlist relay_from_hosts = 192.168.45.0/24
34045 Now you can use these definitions in the ACL that is run for every RCPT
34049 accept domains = +local_domains : +relay_to_domains
34050 accept hosts = +relay_from_hosts
34052 The first statement accepts any RCPT command that contains an address in
34053 the local or relay domains. For any other domain, control passes to the second
34054 statement, which accepts the command only if it comes from one of the relay
34055 hosts. In practice, you will probably want to make your ACL more sophisticated
34056 than this, for example, by including sender and recipient verification. The
34057 default configuration includes a more comprehensive example, which is described
34058 in chapter &<<CHAPdefconfil>>&.
34062 .section "Checking a relay configuration" "SECTcheralcon"
34063 .cindex "relaying" "checking control of"
34064 You can check the relay characteristics of your configuration in the same way
34065 that you can test any ACL behaviour for an incoming SMTP connection, by using
34066 the &%-bh%& option to run a fake SMTP session with which you interact.
34071 . ////////////////////////////////////////////////////////////////////////////
34072 . ////////////////////////////////////////////////////////////////////////////
34074 .chapter "Content scanning at ACL time" "CHAPexiscan"
34075 .scindex IIDcosca "content scanning" "at ACL time"
34076 The extension of Exim to include content scanning at ACL time, formerly known
34077 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
34078 was integrated into the main source for Exim release 4.50, and Tom continues to
34079 maintain it. Most of the wording of this chapter is taken from Tom's
34082 It is also possible to scan the content of messages at other times. The
34083 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
34084 scanning after all the ACLs have run. A transport filter can be used to scan
34085 messages at delivery time (see the &%transport_filter%& option, described in
34086 chapter &<<CHAPtransportgeneric>>&).
34088 If you want to include the ACL-time content-scanning features when you compile
34089 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
34090 &_Local/Makefile_&. When you do that, the Exim binary is built with:
34093 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
34094 for all MIME parts for SMTP and non-SMTP messages, respectively.
34096 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
34097 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
34098 run at the end of message reception (the &%acl_smtp_data%& ACL).
34100 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
34101 of messages, or parts of messages, for debugging purposes.
34103 Additional expansion variables that are set in the new ACL and by the new
34106 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
34109 Content-scanning is continually evolving, and new features are still being
34110 added. While such features are still unstable and liable to incompatible
34111 changes, they are made available in Exim by setting options whose names begin
34112 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
34113 this manual. You can find out about them by reading the file called
34114 &_doc/experimental.txt_&.
34116 All the content-scanning facilities work on a MBOX copy of the message that is
34117 temporarily created in a file called:
34119 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
34121 The &_.eml_& extension is a friendly hint to virus scanners that they can
34122 expect an MBOX-like structure inside that file. The file is created when the
34123 first content scanning facility is called. Subsequent calls to content
34124 scanning conditions open the same file again. The directory is recursively
34125 removed when the &%acl_smtp_data%& ACL has finished running, unless
34127 control = no_mbox_unspool
34129 has been encountered. When the MIME ACL decodes files, they are put into the
34130 same directory by default.
34134 .section "Scanning for viruses" "SECTscanvirus"
34135 .cindex "virus scanning"
34136 .cindex "content scanning" "for viruses"
34137 .cindex "content scanning" "the &%malware%& condition"
34138 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
34139 It supports a &"generic"& interface to scanners called via the shell, and
34140 specialized interfaces for &"daemon"& type virus scanners, which are resident
34141 in memory and thus are much faster.
34143 Since message data needs to have arrived,
34144 the condition may be only called in ACL defined by
34146 &%acl_smtp_data_prdr%&,
34147 &%acl_smtp_mime%& or
34150 A timeout of 2 minutes is applied to a scanner call (by default);
34151 if it expires then a defer action is taken.
34153 .oindex "&%av_scanner%&"
34154 You can set the &%av_scanner%& option in the main part of the configuration
34155 to specify which scanner to use, together with any additional options that
34156 are needed. The basic syntax is as follows:
34158 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
34160 If you do not set &%av_scanner%&, it defaults to
34162 av_scanner = sophie:/var/run/sophie
34164 If the value of &%av_scanner%& starts with a dollar character, it is expanded
34166 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
34167 The following scanner types are supported in this release,
34168 though individual ones can be included or not at build time:
34172 .cindex "virus scanners" "avast"
34173 This is the scanner daemon of Avast. It has been tested with Avast Core
34174 Security (currently at version 2.2.0).
34175 You can get a trial version at &url(https://www.avast.com) or for Linux
34176 at &url(https://www.avast.com/linux-server-antivirus).
34177 This scanner type takes one option,
34178 which can be either a full path to a UNIX socket,
34179 or host and port specifiers separated by white space.
34180 The host may be a name or an IP address; the port is either a
34181 single number or a pair of numbers with a dash between.
34182 A list of options may follow. These options are interpreted on the
34183 Exim's side of the malware scanner, or are given on separate lines to
34184 the daemon as options before the main scan command.
34186 .cindex &`pass_unscanned`& "avast"
34187 If &`pass_unscanned`&
34188 is set, any files the Avast scanner can't scan (e.g.
34189 decompression bombs, or invalid archives) are considered clean. Use with
34194 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
34195 av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
34196 av_scanner = avast:192.168.2.22 5036
34198 If you omit the argument, the default path
34199 &_/var/run/avast/scan.sock_&
34201 If you use a remote host,
34202 you need to make Exim's spool directory available to it,
34203 as the scanner is passed a file path, not file contents.
34204 For information about available commands and their options you may use
34206 $ socat UNIX:/var/run/avast/scan.sock STDIO:
34212 If the scanner returns a temporary failure (e.g. license issues, or
34213 permission problems), the message is deferred and a paniclog entry is
34214 written. The usual &`defer_ok`& option is available.
34216 .vitem &%aveserver%&
34217 .cindex "virus scanners" "Kaspersky"
34218 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
34219 at &url(https://www.kaspersky.com/). This scanner type takes one option,
34220 which is the path to the daemon's UNIX socket. The default is shown in this
34223 av_scanner = aveserver:/var/run/aveserver
34228 .cindex "virus scanners" "clamd"
34229 This daemon-type scanner is GPL and free. You can get it at
34230 &url(https://www.clamav.net/). Some older versions of clamd do not seem to
34231 unpack MIME containers, so it used to be recommended to unpack MIME attachments
34232 in the MIME ACL. This is no longer believed to be necessary.
34234 The options are a list of server specifiers, which may be
34235 a UNIX socket specification,
34236 a TCP socket specification,
34237 or a (global) option.
34239 A socket specification consists of a space-separated list.
34240 For a Unix socket the first element is a full path for the socket,
34241 for a TCP socket the first element is the IP address
34242 and the second a port number,
34243 Any further elements are per-server (non-global) options.
34244 These per-server options are supported:
34246 retry=<timespec> Retry on connect fail
34249 The &`retry`& option specifies a time after which a single retry for
34250 a failed connect is made. The default is to not retry.
34252 If a Unix socket file is specified, only one server is supported.
34256 av_scanner = clamd:/opt/clamd/socket
34257 av_scanner = clamd:192.0.2.3 1234
34258 av_scanner = clamd:192.0.2.3 1234:local
34259 av_scanner = clamd:192.0.2.3 1234 retry=10s
34260 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
34262 If the value of av_scanner points to a UNIX socket file or contains the
34264 option, then the ClamAV interface will pass a filename containing the data
34265 to be scanned, which should normally result in less I/O happening and be
34266 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
34267 Exim does not assume that there is a common filesystem with the remote host.
34269 The final example shows that multiple TCP targets can be specified. Exim will
34270 randomly use one for each incoming email (i.e. it load balances them). Note
34271 that only TCP targets may be used if specifying a list of scanners; a UNIX
34272 socket cannot be mixed in with TCP targets. If one of the servers becomes
34273 unavailable, Exim will try the remaining one(s) until it finds one that works.
34274 When a clamd server becomes unreachable, Exim will log a message. Exim does
34275 not keep track of scanner state between multiple messages, and the scanner
34276 selection is random, so the message will get logged in the mainlog for each
34277 email that the down scanner gets chosen first (message wrapped to be readable):
34279 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
34280 clamd: connection to localhost, port 3310 failed
34281 (Connection refused)
34284 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
34285 contributing the code for this scanner.
34288 .cindex "virus scanners" "command line interface"
34289 This is the keyword for the generic command line scanner interface. It can be
34290 used to attach virus scanners that are invoked from the shell. This scanner
34291 type takes 3 mandatory options:
34294 The full path and name of the scanner binary, with all command line options,
34295 and a placeholder (&`%s`&) for the directory to scan.
34298 A regular expression to match against the STDOUT and STDERR output of the
34299 virus scanner. If the expression matches, a virus was found. You must make
34300 absolutely sure that this expression matches on &"virus found"&. This is called
34301 the &"trigger"& expression.
34304 Another regular expression, containing exactly one pair of parentheses, to
34305 match the name of the virus found in the scanners output. This is called the
34306 &"name"& expression.
34309 For example, Sophos Sweep reports a virus on a line like this:
34311 Virus 'W32/Magistr-B' found in file ./those.bat
34313 For the trigger expression, we can match the phrase &"found in file"&. For the
34314 name expression, we want to extract the W32/Magistr-B string, so we can match
34315 for the single quotes left and right of it. Altogether, this makes the
34316 configuration setting:
34318 av_scanner = cmdline:\
34319 /path/to/sweep -ss -all -rec -archive %s:\
34320 found in file:'(.+)'
34323 .cindex "virus scanners" "DrWeb"
34324 The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface
34326 either a full path to a UNIX socket,
34327 or host and port specifiers separated by white space.
34328 The host may be a name or an IP address; the port is either a
34329 single number or a pair of numbers with a dash between.
34332 av_scanner = drweb:/var/run/drwebd.sock
34333 av_scanner = drweb:192.168.2.20 31337
34335 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
34336 is used. Thanks to Alex Miller for contributing the code for this scanner.
34339 .cindex "virus scanners" "f-protd"
34340 The f-protd scanner is accessed via HTTP over TCP.
34341 One argument is taken, being a space-separated hostname and port number
34345 av_scanner = f-protd:localhost 10200-10204
34347 If you omit the argument, the default values shown above are used.
34349 .vitem &%f-prot6d%&
34350 .cindex "virus scanners" "f-prot6d"
34351 The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
34352 One argument is taken, being a space-separated hostname and port number.
34355 av_scanner = f-prot6d:localhost 10200
34357 If you omit the argument, the default values show above are used.
34360 .cindex "virus scanners" "F-Secure"
34361 The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one
34362 argument which is the path to a UNIX socket. For example:
34364 av_scanner = fsecure:/path/to/.fsav
34366 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
34367 Thelmen for contributing the code for this scanner.
34369 .vitem &%kavdaemon%&
34370 .cindex "virus scanners" "Kaspersky"
34371 This is the scanner daemon of Kaspersky Version 4. This version of the
34372 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
34373 scanner type takes one option, which is the path to the daemon's UNIX socket.
34376 av_scanner = kavdaemon:/opt/AVP/AvpCtl
34378 The default path is &_/var/run/AvpCtl_&.
34381 .cindex "virus scanners" "mksd"
34382 This was a daemon type scanner that is aimed mainly at Polish users,
34383 though some documentation was available in English.
34384 The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir)
34385 and this appears to be a candidate for removal from Exim, unless
34386 we are informed of other virus scanners which use the same protocol
34388 The only option for this scanner type is
34389 the maximum number of processes used simultaneously to scan the attachments,
34390 provided that mksd has
34391 been run with at least the same number of child processes. For example:
34393 av_scanner = mksd:2
34395 You can safely omit this option (the default value is 1).
34398 .cindex "virus scanners" "simple socket-connected"
34399 This is a general-purpose way of talking to simple scanner daemons
34400 running on the local machine.
34401 There are four options:
34402 an address (which may be an IP address and port, or the path of a Unix socket),
34403 a commandline to send (may include a single %s which will be replaced with
34404 the path to the mail file to be scanned),
34405 an RE to trigger on from the returned data,
34406 and an RE to extract malware_name from the returned data.
34409 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
34411 Note that surrounding whitespace is stripped from each option, meaning
34412 there is no way to specify a trailing newline.
34413 The socket specifier and both regular-expressions are required.
34414 Default for the commandline is &_%s\n_& (note this does have a trailing newline);
34415 specify an empty element to get this.
34418 .cindex "virus scanners" "Sophos and Sophie"
34419 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
34420 You can get Sophie at &url(http://sophie.sourceforge.net/). The only option
34421 for this scanner type is the path to the UNIX socket that Sophie uses for
34422 client communication. For example:
34424 av_scanner = sophie:/tmp/sophie
34426 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
34430 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
34431 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
34434 The &%av_scanner%& option is expanded each time &%malware%& is called. This
34435 makes it possible to use different scanners. See further below for an example.
34436 The &%malware%& condition caches its results, so when you use it multiple times
34437 for the same message, the actual scanning process is only carried out once.
34438 However, using expandable items in &%av_scanner%& disables this caching, in
34439 which case each use of the &%malware%& condition causes a new scan of the
34442 The &%malware%& condition takes a right-hand argument that is expanded before
34443 use and taken as a list, slash-separated by default.
34444 The first element can then be one of
34447 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
34448 The condition succeeds if a virus was found, and fail otherwise. This is the
34451 &"false"& or &"0"& or an empty string, in which case no scanning is done and
34452 the condition fails immediately.
34454 A regular expression, in which case the message is scanned for viruses. The
34455 condition succeeds if a virus is found and its name matches the regular
34456 expression. This allows you to take special actions on certain types of virus.
34457 Note that &"/"& characters in the RE must be doubled due to the list-processing,
34458 unless the separator is changed (in the usual way &<<SECTlistsepchange>>&).
34461 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
34462 messages even if there is a problem with the virus scanner.
34463 Otherwise, such a problem causes the ACL to defer.
34465 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
34466 specify a non-default timeout. The default is two minutes.
34469 malware = * / defer_ok / tmo=10s
34471 A timeout causes the ACL to defer.
34473 .vindex "&$callout_address$&"
34474 When a connection is made to the scanner the expansion variable &$callout_address$&
34475 is set to record the actual address used.
34477 .vindex "&$malware_name$&"
34478 When a virus is found, the condition sets up an expansion variable called
34479 &$malware_name$& that contains the name of the virus. You can use it in a
34480 &%message%& modifier that specifies the error returned to the sender, and/or in
34483 Beware the interaction of Exim's &%message_size_limit%& with any size limits
34484 imposed by your anti-virus scanner.
34486 Here is a very simple scanning example:
34489 message = This message contains malware ($malware_name)
34491 The next example accepts messages when there is a problem with the scanner:
34493 deny malware = */defer_ok
34494 message = This message contains malware ($malware_name)
34496 The next example shows how to use an ACL variable to scan with both sophie and
34497 aveserver. It assumes you have set:
34499 av_scanner = $acl_m0
34501 in the main Exim configuration.
34503 deny set acl_m0 = sophie
34505 message = This message contains malware ($malware_name)
34507 deny set acl_m0 = aveserver
34509 message = This message contains malware ($malware_name)
34513 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
34514 .cindex "content scanning" "for spam"
34515 .cindex "spam scanning"
34516 .cindex "SpamAssassin"
34518 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
34519 score and a report for the message.
34520 Support is also provided for Rspamd.
34522 For more information about installation and configuration of SpamAssassin or
34523 Rspamd refer to their respective websites at
34524 &url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/)
34526 SpamAssassin can be installed with CPAN by running:
34528 perl -MCPAN -e 'install Mail::SpamAssassin'
34530 SpamAssassin has its own set of configuration files. Please review its
34531 documentation to see how you can tweak it. The default installation should work
34534 .oindex "&%spamd_address%&"
34535 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
34536 intend to use an instance running on the local host you do not need to set
34537 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
34538 you must set the &%spamd_address%& option in the global part of the Exim
34539 configuration as follows (example):
34541 spamd_address = 192.168.99.45 783
34543 The SpamAssassin protocol relies on a TCP half-close from the client.
34544 If your SpamAssassin client side is running a Linux system with an
34545 iptables firewall, consider setting
34546 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
34547 timeout, Exim uses when waiting for a response from the SpamAssassin
34548 server (currently defaulting to 120s). With a lower value the Linux
34549 connection tracking may consider your half-closed connection as dead too
34553 To use Rspamd (which by default listens on all local addresses
34555 you should add &%variant=rspamd%& after the address/port pair, for example:
34557 spamd_address = 127.0.0.1 11333 variant=rspamd
34560 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
34561 sockets. If you want to us these, supply &%spamd_address%& with an absolute
34562 filename instead of an address/port pair:
34564 spamd_address = /var/run/spamd_socket
34566 You can have multiple &%spamd%& servers to improve scalability. These can
34567 reside on other hardware reachable over the network. To specify multiple
34568 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
34569 option, separated with colons (the separator can be changed in the usual way &<<SECTlistsepchange>>&):
34571 spamd_address = 192.168.2.10 783 : \
34572 192.168.2.11 783 : \
34575 Up to 32 &%spamd%& servers are supported.
34576 When a server fails to respond to the connection attempt, all other
34577 servers are tried until one succeeds. If no server responds, the &%spam%&
34580 Unix and TCP socket specifications may be mixed in any order.
34581 Each element of the list is a list itself, space-separated by default
34582 and changeable in the usual way (&<<SECTlistsepchange>>&);
34583 take care to not double the separator.
34585 For TCP socket specifications a host name or IP (v4 or v6, but
34586 subject to list-separator quoting rules) address can be used,
34587 and the port can be one or a dash-separated pair.
34588 In the latter case, the range is tried in strict order.
34590 Elements after the first for Unix sockets, or second for TCP socket,
34592 The supported options are:
34594 pri=<priority> Selection priority
34595 weight=<value> Selection bias
34596 time=<start>-<end> Use only between these times of day
34597 retry=<timespec> Retry on connect fail
34598 tmo=<timespec> Connection time limit
34599 variant=rspamd Use Rspamd rather than SpamAssassin protocol
34602 The &`pri`& option specifies a priority for the server within the list,
34603 higher values being tried first.
34604 The default priority is 1.
34606 The &`weight`& option specifies a selection bias.
34607 Within a priority set
34608 servers are queried in a random fashion, weighted by this value.
34609 The default value for selection bias is 1.
34611 Time specifications for the &`time`& option are <hour>.<minute>.<second>
34612 in the local time zone; each element being one or more digits.
34613 Either the seconds or both minutes and seconds, plus the leading &`.`&
34614 characters, may be omitted and will be taken as zero.
34616 Timeout specifications for the &`retry`& and &`tmo`& options
34617 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
34619 The &`tmo`& option specifies an overall timeout for communication.
34620 The default value is two minutes.
34622 The &`retry`& option specifies a time after which a single retry for
34623 a failed connect is made.
34624 The default is to not retry.
34626 The &%spamd_address%& variable is expanded before use if it starts with
34627 a dollar sign. In this case, the expansion may return a string that is
34628 used as the list so that multiple spamd servers can be the result of an
34631 .vindex "&$callout_address$&"
34632 When a connection is made to the server the expansion variable &$callout_address$&
34633 is set to record the actual address used.
34635 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
34636 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
34639 message = This message was classified as SPAM
34641 The right-hand side of the &%spam%& condition specifies a name. This is
34642 relevant if you have set up multiple SpamAssassin profiles. If you do not want
34643 to scan using a specific profile, but rather use the SpamAssassin system-wide
34644 default profile, you can scan for an unknown name, or simply use &"nobody"&.
34645 Rspamd does not use this setting. However, you must put something on the
34648 The name allows you to use per-domain or per-user antispam profiles in
34649 principle, but this is not straightforward in practice, because a message may
34650 have multiple recipients, not necessarily all in the same domain. Because the
34651 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
34652 read the contents of the message, the variables &$local_part$& and &$domain$&
34654 Careful enforcement of single-recipient messages
34655 (e.g. by responding with defer in the recipient ACL for all recipients
34657 or the use of PRDR,
34658 .cindex "PRDR" "use for per-user SpamAssassin profiles"
34659 are needed to use this feature.
34661 The right-hand side of the &%spam%& condition is expanded before being used, so
34662 you can put lookups or conditions there. When the right-hand side evaluates to
34663 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
34666 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
34667 large ones may cause significant performance degradation. As most spam messages
34668 are quite small, it is recommended that you do not scan the big ones. For
34671 deny condition = ${if < {$message_size}{10K}}
34673 message = This message was classified as SPAM
34676 The &%spam%& condition returns true if the threshold specified in the user's
34677 SpamAssassin profile has been matched or exceeded. If you want to use the
34678 &%spam%& condition for its side effects (see the variables below), you can make
34679 it always return &"true"& by appending &`:true`& to the username.
34681 .cindex "spam scanning" "returned variables"
34682 When the &%spam%& condition is run, it sets up a number of expansion
34684 Except for &$spam_report$&,
34685 these variables are saved with the received message so are
34686 available for use at delivery time.
34689 .vitem &$spam_score$&
34690 The spam score of the message, for example, &"3.4"& or &"30.5"&. This is useful
34691 for inclusion in log or reject messages.
34693 .vitem &$spam_score_int$&
34694 The spam score of the message, multiplied by ten, as an integer value. For
34695 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
34696 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
34697 The integer value is useful for numeric comparisons in conditions.
34699 .vitem &$spam_bar$&
34700 A string consisting of a number of &"+"& or &"-"& characters, representing the
34701 integer part of the spam score value. A spam score of 4.4 would have a
34702 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
34703 headers, since MUAs can match on such strings. The maximum length of the
34704 spam bar is 50 characters.
34706 .vitem &$spam_report$&
34707 A multiline text table, containing the full SpamAssassin report for the
34708 message. Useful for inclusion in headers or reject messages.
34709 This variable is only usable in a DATA-time ACL.
34710 Beware that SpamAssassin may return non-ASCII characters, especially
34711 when running in country-specific locales, which are not legal
34712 unencoded in headers.
34714 .vitem &$spam_action$&
34715 For SpamAssassin either 'reject' or 'no action' depending on the
34716 spam score versus threshold.
34717 For Rspamd, the recommended action.
34721 The &%spam%& condition caches its results unless expansion in
34722 spamd_address was used. If you call it again with the same user name, it
34723 does not scan again, but rather returns the same values as before.
34725 The &%spam%& condition returns DEFER if there is any error while running
34726 the message through SpamAssassin or if the expansion of spamd_address
34727 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
34728 statement block), append &`/defer_ok`& to the right-hand side of the
34729 spam condition, like this:
34731 deny spam = joe/defer_ok
34732 message = This message was classified as SPAM
34734 This causes messages to be accepted even if there is a problem with &%spamd%&.
34736 Here is a longer, commented example of the use of the &%spam%&
34739 # put headers in all messages (no matter if spam or not)
34740 warn spam = nobody:true
34741 add_header = X-Spam-Score: $spam_score ($spam_bar)
34742 add_header = X-Spam-Report: $spam_report
34744 # add second subject line with *SPAM* marker when message
34745 # is over threshold
34747 add_header = Subject: *SPAM* $h_Subject:
34749 # reject spam at high scores (> 12)
34750 deny spam = nobody:true
34751 condition = ${if >{$spam_score_int}{120}{1}{0}}
34752 message = This message scored $spam_score spam points.
34757 .section "Scanning MIME parts" "SECTscanmimepart"
34758 .cindex "content scanning" "MIME parts"
34759 .cindex "MIME content scanning"
34760 .oindex "&%acl_smtp_mime%&"
34761 .oindex "&%acl_not_smtp_mime%&"
34762 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
34763 each MIME part of an SMTP message, including multipart types, in the sequence
34764 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
34765 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
34766 options may both refer to the same ACL if you want the same processing in both
34769 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
34770 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
34771 the case of a non-SMTP message. However, a MIME ACL is called only if the
34772 message contains a &'Content-Type:'& header line. When a call to a MIME
34773 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
34774 result code is sent to the client. In the case of an SMTP message, the
34775 &%acl_smtp_data%& ACL is not called when this happens.
34777 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
34778 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
34779 condition to match against the raw MIME part. You can also use the
34780 &%mime_regex%& condition to match against the decoded MIME part (see section
34781 &<<SECTscanregex>>&).
34783 At the start of a MIME ACL, a number of variables are set from the header
34784 information for the relevant MIME part. These are described below. The contents
34785 of the MIME part are not by default decoded into a disk file except for MIME
34786 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
34787 part into a disk file, you can use the &%decode%& condition. The general
34790 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
34792 The right hand side is expanded before use. After expansion,
34796 &"0"& or &"false"&, in which case no decoding is done.
34798 The string &"default"&. In that case, the file is put in the temporary
34799 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
34800 a sequential filename consisting of the message id and a sequence number. The
34801 full path and name is available in &$mime_decoded_filename$& after decoding.
34803 A full path name starting with a slash. If the full name is an existing
34804 directory, it is used as a replacement for the default directory. The filename
34805 is then sequentially assigned. If the path does not exist, it is used as
34806 the full path and filename.
34808 If the string does not start with a slash, it is used as the
34809 filename, and the default path is then used.
34811 The &%decode%& condition normally succeeds. It is only false for syntax
34812 errors or unusual circumstances such as memory shortages. You can easily decode
34813 a file with its original, proposed filename using
34815 decode = $mime_filename
34817 However, you should keep in mind that &$mime_filename$& might contain
34818 anything. If you place files outside of the default path, they are not
34819 automatically unlinked.
34821 For RFC822 attachments (these are messages attached to messages, with a
34822 content-type of &"message/rfc822"&), the ACL is called again in the same manner
34823 as for the primary message, only that the &$mime_is_rfc822$& expansion
34824 variable is set (see below). Attached messages are always decoded to disk
34825 before being checked, and the files are unlinked once the check is done.
34827 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
34828 used to match regular expressions against raw and decoded MIME parts,
34829 respectively. They are described in section &<<SECTscanregex>>&.
34831 .cindex "MIME content scanning" "returned variables"
34832 The following list describes all expansion variables that are
34833 available in the MIME ACL:
34836 .vitem &$mime_anomaly_level$& &&&
34837 &$mime_anomaly_text$&
34838 .vindex &$mime_anomaly_level$&
34839 .vindex &$mime_anomaly_text$&
34840 If there are problems decoding, these variables contain information on
34841 the detected issue.
34843 .vitem &$mime_boundary$&
34844 .vindex &$mime_boundary$&
34845 If the current part is a multipart (see &$mime_is_multipart$& below), it should
34846 have a boundary string, which is stored in this variable. If the current part
34847 has no boundary parameter in the &'Content-Type:'& header, this variable
34848 contains the empty string.
34850 .vitem &$mime_charset$&
34851 .vindex &$mime_charset$&
34852 This variable contains the character set identifier, if one was found in the
34853 &'Content-Type:'& header. Examples for charset identifiers are:
34859 Please note that this value is not normalized, so you should do matches
34860 case-insensitively.
34862 .vitem &$mime_content_description$&
34863 .vindex &$mime_content_description$&
34864 This variable contains the normalized content of the &'Content-Description:'&
34865 header. It can contain a human-readable description of the parts content. Some
34866 implementations repeat the filename for attachments here, but they are usually
34867 only used for display purposes.
34869 .vitem &$mime_content_disposition$&
34870 .vindex &$mime_content_disposition$&
34871 This variable contains the normalized content of the &'Content-Disposition:'&
34872 header. You can expect strings like &"attachment"& or &"inline"& here.
34874 .vitem &$mime_content_id$&
34875 .vindex &$mime_content_id$&
34876 This variable contains the normalized content of the &'Content-ID:'& header.
34877 This is a unique ID that can be used to reference a part from another part.
34879 .vitem &$mime_content_size$&
34880 .vindex &$mime_content_size$&
34881 This variable is set only after the &%decode%& modifier (see above) has been
34882 successfully run. It contains the size of the decoded part in kilobytes. The
34883 size is always rounded up to full kilobytes, so only a completely empty part
34884 has a &$mime_content_size$& of zero.
34886 .vitem &$mime_content_transfer_encoding$&
34887 .vindex &$mime_content_transfer_encoding$&
34888 This variable contains the normalized content of the
34889 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
34890 type. Typical values are &"base64"& and &"quoted-printable"&.
34892 .vitem &$mime_content_type$&
34893 .vindex &$mime_content_type$&
34894 If the MIME part has a &'Content-Type:'& header, this variable contains its
34895 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
34896 are some examples of popular MIME types, as they may appear in this variable:
34900 application/octet-stream
34904 If the MIME part has no &'Content-Type:'& header, this variable contains the
34907 .vitem &$mime_decoded_filename$&
34908 .vindex &$mime_decoded_filename$&
34909 This variable is set only after the &%decode%& modifier (see above) has been
34910 successfully run. It contains the full path and filename of the file
34911 containing the decoded data.
34916 .vitem &$mime_filename$&
34917 .vindex &$mime_filename$&
34918 This is perhaps the most important of the MIME variables. It contains a
34919 proposed filename for an attachment, if one was found in either the
34920 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
34923 decoded, but no additional sanity checks are done.
34925 found, this variable contains the empty string.
34927 .vitem &$mime_is_coverletter$&
34928 .vindex &$mime_is_coverletter$&
34929 This variable attempts to differentiate the &"cover letter"& of an e-mail from
34930 attached data. It can be used to clamp down on flashy or unnecessarily encoded
34931 content in the cover letter, while not restricting attachments at all.
34933 The variable contains 1 (true) for a MIME part believed to be part of the
34934 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
34938 The outermost MIME part of a message is always a cover letter.
34941 If a multipart/alternative or multipart/related MIME part is a cover letter,
34942 so are all MIME subparts within that multipart.
34945 If any other multipart is a cover letter, the first subpart is a cover letter,
34946 and the rest are attachments.
34949 All parts contained within an attachment multipart are attachments.
34952 As an example, the following will ban &"HTML mail"& (including that sent with
34953 alternative plain text), while allowing HTML files to be attached. HTML
34954 coverletter mail attached to non-HTML coverletter mail will also be allowed:
34956 deny !condition = $mime_is_rfc822
34957 condition = $mime_is_coverletter
34958 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
34959 message = HTML mail is not accepted here
34962 .vitem &$mime_is_multipart$&
34963 .vindex &$mime_is_multipart$&
34964 This variable has the value 1 (true) when the current part has the main type
34965 &"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
34966 Since multipart entities only serve as containers for other parts, you may not
34967 want to carry out specific actions on them.
34969 .vitem &$mime_is_rfc822$&
34970 .vindex &$mime_is_rfc822$&
34971 This variable has the value 1 (true) if the current part is not a part of the
34972 checked message itself, but part of an attached message. Attached message
34973 decoding is fully recursive.
34975 .vitem &$mime_part_count$&
34976 .vindex &$mime_part_count$&
34977 This variable is a counter that is raised for each processed MIME part. It
34978 starts at zero for the very first part (which is usually a multipart). The
34979 counter is per-message, so it is reset when processing RFC822 attachments (see
34980 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
34981 complete, so you can use it in the DATA ACL to determine the number of MIME
34982 parts of a message. For non-MIME messages, this variable contains the value -1.
34987 .section "Scanning with regular expressions" "SECTscanregex"
34988 .cindex "content scanning" "with regular expressions"
34989 .cindex "regular expressions" "content scanning with"
34990 You can specify your own custom regular expression matches on the full body of
34991 the message, or on individual MIME parts.
34993 The &%regex%& condition takes one or more regular expressions as arguments and
34994 matches them against the full message (when called in the DATA ACL) or a raw
34995 MIME part (when called in the MIME ACL). The &%regex%& condition matches
34996 linewise, with a maximum line length of 32K characters. That means you cannot
34997 have multiline matches with the &%regex%& condition.
34999 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
35000 to 32K of decoded content (the whole content at once, not linewise). If the
35001 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
35002 is decoded automatically when &%mime_regex%& is executed (using default path
35003 and filename values). If the decoded data is larger than 32K, only the first
35004 32K characters are checked.
35006 The regular expressions are passed as a colon-separated list. To include a
35007 literal colon, you must double it. Since the whole right-hand side string is
35008 expanded before being used, you must also escape dollar signs and backslashes
35009 with more backslashes, or use the &`\N`& facility to disable expansion.
35010 Here is a simple example that contains two regular expressions:
35012 deny regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
35013 message = contains blacklisted regex ($regex_match_string)
35015 The conditions returns true if any one of the regular expressions matches. The
35016 &$regex_match_string$& expansion variable is then set up and contains the
35017 matching regular expression.
35018 The expansion variables &$regex1$& &$regex2$& etc
35019 are set to any substrings captured by the regular expression.
35021 &*Warning*&: With large messages, these conditions can be fairly
35029 . ////////////////////////////////////////////////////////////////////////////
35030 . ////////////////////////////////////////////////////////////////////////////
35032 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
35033 "Local scan function"
35034 .scindex IIDlosca "&[local_scan()]& function" "description of"
35035 .cindex "customizing" "input scan using C function"
35036 .cindex "policy control" "by local scan function"
35037 In these days of email worms, viruses, and ever-increasing spam, some sites
35038 want to apply a lot of checking to messages before accepting them.
35040 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
35041 passing messages to external virus and spam scanning software. You can also do
35042 a certain amount in Exim itself through string expansions and the &%condition%&
35043 condition in the ACL that runs after the SMTP DATA command or the ACL for
35044 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
35046 To allow for further customization to a site's own requirements, there is the
35047 possibility of linking Exim with a private message scanning function, written
35048 in C. If you want to run code that is written in something other than C, you
35049 can of course use a little C stub to call it.
35051 The local scan function is run once for every incoming message, at the point
35052 when Exim is just about to accept the message.
35053 It can therefore be used to control non-SMTP messages from local processes as
35054 well as messages arriving via SMTP.
35056 Exim applies a timeout to calls of the local scan function, and there is an
35057 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
35058 Zero means &"no timeout"&.
35059 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
35060 before calling the local scan function, so that the most common types of crash
35061 are caught. If the timeout is exceeded or one of those signals is caught, the
35062 incoming message is rejected with a temporary error if it is an SMTP message.
35063 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
35064 code. The incident is logged on the main and reject logs.
35068 .section "Building Exim to use a local scan function" "SECID207"
35069 .cindex "&[local_scan()]& function" "building Exim to use"
35070 To make use of the local scan function feature, you must tell Exim where your
35071 function is before building Exim, by setting
35072 both HAVE_LOCAL_SCAN and
35073 LOCAL_SCAN_SOURCE in your
35074 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
35075 directory, so you might set
35077 HAVE_LOCAL_SCAN=yes
35078 LOCAL_SCAN_SOURCE=Local/local_scan.c
35080 for example. The function must be called &[local_scan()]&;
35081 the source file(s) for it should first #define LOCAL_SCAN
35082 and then #include "local_scan.h".
35084 Exim after it has received a message, when the success return code is about to
35085 be sent. This is after all the ACLs have been run. The return code from your
35086 function controls whether the message is actually accepted or not. There is a
35087 commented template function (that just accepts the message) in the file
35088 _src/local_scan.c_.
35090 If you want to make use of Exim's runtime configuration file to set options
35091 for your &[local_scan()]& function, you must also set
35093 LOCAL_SCAN_HAS_OPTIONS=yes
35095 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
35100 .section "API for local_scan()" "SECTapiforloc"
35101 .cindex "&[local_scan()]& function" "API description"
35102 .cindex &%dlfunc%& "API description"
35103 You must include this line near the start of your code:
35106 #include "local_scan.h"
35108 This header file defines a number of variables and other values, and the
35109 prototype for the function itself. Exim is coded to use unsigned char values
35110 almost exclusively, and one of the things this header defines is a shorthand
35111 for &`unsigned char`& called &`uschar`&.
35112 It also makes available the following macro definitions, to simplify casting character
35113 strings and pointers to character strings:
35115 #define CS (char *)
35116 #define CCS (const char *)
35117 #define CSS (char **)
35118 #define US (unsigned char *)
35119 #define CUS (const unsigned char *)
35120 #define USS (unsigned char **)
35122 The function prototype for &[local_scan()]& is:
35124 extern int local_scan(int fd, uschar **return_text);
35126 The arguments are as follows:
35129 &%fd%& is a file descriptor for the file that contains the body of the message
35130 (the -D file). The file is open for reading and writing, but updating it is not
35131 recommended. &*Warning*&: You must &'not'& close this file descriptor.
35133 The descriptor is positioned at character 19 of the file, which is the first
35134 character of the body itself, because the first 19 characters are the message
35135 id followed by &`-D`& and a newline. If you rewind the file, you should use the
35136 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
35137 case this changes in some future version.
35139 &%return_text%& is an address which you can use to return a pointer to a text
35140 string at the end of the function. The value it points to on entry is NULL.
35143 The function must return an &%int%& value which is one of the following macros:
35146 .vitem &`LOCAL_SCAN_ACCEPT`&
35147 .vindex "&$local_scan_data$&"
35148 The message is accepted. If you pass back a string of text, it is saved with
35149 the message, and made available in the variable &$local_scan_data$&. No
35150 newlines are permitted (if there are any, they are turned into spaces) and the
35151 maximum length of text is 1000 characters.
35153 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
35154 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
35155 queued without immediate delivery, and is frozen.
35157 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
35158 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
35159 queued without immediate delivery.
35161 .vitem &`LOCAL_SCAN_REJECT`&
35162 The message is rejected; the returned text is used as an error message which is
35163 passed back to the sender and which is also logged. Newlines are permitted &--
35164 they cause a multiline response for SMTP rejections, but are converted to
35165 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
35168 .vitem &`LOCAL_SCAN_TEMPREJECT`&
35169 The message is temporarily rejected; the returned text is used as an error
35170 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
35173 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
35174 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
35175 message is not written to the reject log. It has the effect of unsetting the
35176 &%rejected_header%& log selector for just this rejection. If
35177 &%rejected_header%& is already unset (see the discussion of the
35178 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
35179 same as LOCAL_SCAN_REJECT.
35181 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
35182 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
35183 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
35186 If the message is not being received by interactive SMTP, rejections are
35187 reported by writing to &%stderr%& or by sending an email, as configured by the
35188 &%-oe%& command line options.
35192 .section "Configuration options for local_scan()" "SECTconoptloc"
35193 .cindex "&[local_scan()]& function" "configuration options"
35194 It is possible to have option settings in the main configuration file
35195 that set values in static variables in the &[local_scan()]& module. If you
35196 want to do this, you must have the line
35198 LOCAL_SCAN_HAS_OPTIONS=yes
35200 in your &_Local/Makefile_& when you build Exim. (This line is in
35201 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
35202 file, you must define static variables to hold the option values, and a table
35205 The table must be a vector called &%local_scan_options%&, of type
35206 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
35207 and a pointer to the variable that holds the value. The entries must appear in
35208 alphabetical order. Following &%local_scan_options%& you must also define a
35209 variable called &%local_scan_options_count%& that contains the number of
35210 entries in the table. Here is a short example, showing two kinds of option:
35212 static int my_integer_option = 42;
35213 static uschar *my_string_option = US"a default string";
35215 optionlist local_scan_options[] = {
35216 { "my_integer", opt_int, &my_integer_option },
35217 { "my_string", opt_stringptr, &my_string_option }
35220 int local_scan_options_count =
35221 sizeof(local_scan_options)/sizeof(optionlist);
35223 The values of the variables can now be changed from Exim's runtime
35224 configuration file by including a local scan section as in this example:
35228 my_string = some string of text...
35230 The available types of option data are as follows:
35233 .vitem &*opt_bool*&
35234 This specifies a boolean (true/false) option. The address should point to a
35235 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
35236 that are defined as &"1"& and &"0"&, respectively. If you want to detect
35237 whether such a variable has been set at all, you can initialize it to
35238 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
35241 .vitem &*opt_fixed*&
35242 This specifies a fixed point number, such as is used for load averages.
35243 The address should point to a variable of type &`int`&. The value is stored
35244 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
35247 This specifies an integer; the address should point to a variable of type
35248 &`int`&. The value may be specified in any of the integer formats accepted by
35251 .vitem &*opt_mkint*&
35252 This is the same as &%opt_int%&, except that when such a value is output in a
35253 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
35254 printed with the suffix K or M.
35256 .vitem &*opt_octint*&
35257 This also specifies an integer, but the value is always interpreted as an
35258 octal integer, whether or not it starts with the digit zero, and it is
35259 always output in octal.
35261 .vitem &*opt_stringptr*&
35262 This specifies a string value; the address must be a pointer to a
35263 variable that points to a string (for example, of type &`uschar *`&).
35265 .vitem &*opt_time*&
35266 This specifies a time interval value. The address must point to a variable of
35267 type &`int`&. The value that is placed there is a number of seconds.
35270 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
35271 out the values of all the &[local_scan()]& options.
35275 .section "Available Exim variables" "SECID208"
35276 .cindex "&[local_scan()]& function" "available Exim variables"
35277 The header &_local_scan.h_& gives you access to a number of C variables. These
35278 are the only ones that are guaranteed to be maintained from release to release.
35279 Note, however, that you can obtain the value of any Exim expansion variable,
35280 including &$recipients$&, by calling &'expand_string()'&. The exported
35281 C variables are as follows:
35284 .vitem &*int&~body_linecount*&
35285 This variable contains the number of lines in the message's body.
35286 It is not valid if the &%spool_wireformat%& option is used.
35288 .vitem &*int&~body_zerocount*&
35289 This variable contains the number of binary zero bytes in the message's body.
35290 It is not valid if the &%spool_wireformat%& option is used.
35292 .vitem &*unsigned&~int&~debug_selector*&
35293 This variable is set to zero when no debugging is taking place. Otherwise, it
35294 is a bitmap of debugging selectors. Two bits are identified for use in
35295 &[local_scan()]&; they are defined as macros:
35298 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
35299 testing option that is not privileged &-- any caller may set it. All the
35300 other selector bits can be set only by admin users.
35303 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
35304 by the &`+local_scan`& debug selector. It is not included in the default set
35308 Thus, to write to the debugging output only when &`+local_scan`& has been
35309 selected, you should use code like this:
35311 if ((debug_selector & D_local_scan) != 0)
35312 debug_printf("xxx", ...);
35314 .vitem &*uschar&~*expand_string_message*&
35315 After a failing call to &'expand_string()'& (returned value NULL), the
35316 variable &%expand_string_message%& contains the error message, zero-terminated.
35318 .vitem &*header_line&~*header_list*&
35319 A pointer to a chain of header lines. The &%header_line%& structure is
35322 .vitem &*header_line&~*header_last*&
35323 A pointer to the last of the header lines.
35325 .vitem &*uschar&~*headers_charset*&
35326 The value of the &%headers_charset%& configuration option.
35328 .vitem &*BOOL&~host_checking*&
35329 This variable is TRUE during a host checking session that is initiated by the
35330 &%-bh%& command line option.
35332 .vitem &*uschar&~*interface_address*&
35333 The IP address of the interface that received the message, as a string. This
35334 is NULL for locally submitted messages.
35336 .vitem &*int&~interface_port*&
35337 The port on which this message was received. When testing with the &%-bh%&
35338 command line option, the value of this variable is -1 unless a port has been
35339 specified via the &%-oMi%& option.
35341 .vitem &*uschar&~*message_id*&
35342 This variable contains Exim's message id for the incoming message (the value of
35343 &$message_exim_id$&) as a zero-terminated string.
35345 .vitem &*uschar&~*received_protocol*&
35346 The name of the protocol by which the message was received.
35348 .vitem &*int&~recipients_count*&
35349 The number of accepted recipients.
35351 .vitem &*recipient_item&~*recipients_list*&
35352 .cindex "recipient" "adding in local scan"
35353 .cindex "recipient" "removing in local scan"
35354 The list of accepted recipients, held in a vector of length
35355 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
35356 can add additional recipients by calling &'receive_add_recipient()'& (see
35357 below). You can delete recipients by removing them from the vector and
35358 adjusting the value in &%recipients_count%&. In particular, by setting
35359 &%recipients_count%& to zero you remove all recipients. If you then return the
35360 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
35361 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
35362 and then call &'receive_add_recipient()'& as often as needed.
35364 .vitem &*uschar&~*sender_address*&
35365 The envelope sender address. For bounce messages this is the empty string.
35367 .vitem &*uschar&~*sender_host_address*&
35368 The IP address of the sending host, as a string. This is NULL for
35369 locally-submitted messages.
35371 .vitem &*uschar&~*sender_host_authenticated*&
35372 The name of the authentication mechanism that was used, or NULL if the message
35373 was not received over an authenticated SMTP connection.
35375 .vitem &*uschar&~*sender_host_name*&
35376 The name of the sending host, if known.
35378 .vitem &*int&~sender_host_port*&
35379 The port on the sending host.
35381 .vitem &*BOOL&~smtp_input*&
35382 This variable is TRUE for all SMTP input, including BSMTP.
35384 .vitem &*BOOL&~smtp_batched_input*&
35385 This variable is TRUE for BSMTP input.
35387 .vitem &*int&~store_pool*&
35388 The contents of this variable control which pool of memory is used for new
35389 requests. See section &<<SECTmemhanloc>>& for details.
35393 .section "Structure of header lines" "SECID209"
35394 The &%header_line%& structure contains the members listed below.
35395 You can add additional header lines by calling the &'header_add()'& function
35396 (see below). You can cause header lines to be ignored (deleted) by setting
35401 .vitem &*struct&~header_line&~*next*&
35402 A pointer to the next header line, or NULL for the last line.
35404 .vitem &*int&~type*&
35405 A code identifying certain headers that Exim recognizes. The codes are printing
35406 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
35407 Notice in particular that any header line whose type is * is not transmitted
35408 with the message. This flagging is used for header lines that have been
35409 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
35410 lines.) Effectively, * means &"deleted"&.
35412 .vitem &*int&~slen*&
35413 The number of characters in the header line, including the terminating and any
35416 .vitem &*uschar&~*text*&
35417 A pointer to the text of the header. It always ends with a newline, followed by
35418 a zero byte. Internal newlines are preserved.
35423 .section "Structure of recipient items" "SECID210"
35424 The &%recipient_item%& structure contains these members:
35427 .vitem &*uschar&~*address*&
35428 This is a pointer to the recipient address as it was received.
35430 .vitem &*int&~pno*&
35431 This is used in later Exim processing when top level addresses are created by
35432 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
35433 and must always contain -1 at this stage.
35435 .vitem &*uschar&~*errors_to*&
35436 If this value is not NULL, bounce messages caused by failing to deliver to the
35437 recipient are sent to the address it contains. In other words, it overrides the
35438 envelope sender for this one recipient. (Compare the &%errors_to%& generic
35439 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
35440 an unqualified address, Exim qualifies it using the domain from
35441 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
35442 is NULL for all recipients.
35447 .section "Available Exim functions" "SECID211"
35448 .cindex "&[local_scan()]& function" "available Exim functions"
35449 The header &_local_scan.h_& gives you access to a number of Exim functions.
35450 These are the only ones that are guaranteed to be maintained from release to
35454 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
35455 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
35457 This function creates a child process that runs the command specified by
35458 &%argv%&. The environment for the process is specified by &%envp%&, which can
35459 be NULL if no environment variables are to be passed. A new umask is supplied
35460 for the process in &%newumask%&.
35462 Pipes to the standard input and output of the new process are set up
35463 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
35464 standard error is cloned to the standard output. If there are any file
35465 descriptors &"in the way"& in the new process, they are closed. If the final
35466 argument is TRUE, the new process is made into a process group leader.
35468 The function returns the pid of the new process, or -1 if things go wrong.
35470 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
35471 This function waits for a child process to terminate, or for a timeout (in
35472 seconds) to expire. A timeout value of zero means wait as long as it takes. The
35473 return value is as follows:
35478 The process terminated by a normal exit and the value is the process
35484 The process was terminated by a signal and the value is the negation of the
35490 The process timed out.
35494 The was some other error in wait(); &%errno%& is still set.
35497 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
35498 This function provide you with a means of submitting a new message to
35499 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
35500 want, but this packages it all up for you.) The function creates a pipe,
35501 forks a subprocess that is running
35503 exim -t -oem -oi -f <>
35505 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
35506 that is connected to the standard input. The yield of the function is the PID
35507 of the subprocess. You can then write a message to the file descriptor, with
35508 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
35510 When you have finished, call &'child_close()'& to wait for the process to
35511 finish and to collect its ending status. A timeout value of zero is usually
35512 fine in this circumstance. Unless you have made a mistake with the recipient
35513 addresses, you should get a return code of zero.
35516 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
35517 *sender_authentication)*&
35518 This function is a more sophisticated version of &'child_open()'&. The command
35521 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
35523 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
35526 .vitem &*void&~debug_printf(char&~*,&~...)*&
35527 This is Exim's debugging function, with arguments as for &'(printf()'&. The
35528 output is written to the standard error stream. If no debugging is selected,
35529 calls to &'debug_printf()'& have no effect. Normally, you should make calls
35530 conditional on the &`local_scan`& debug selector by coding like this:
35532 if ((debug_selector & D_local_scan) != 0)
35533 debug_printf("xxx", ...);
35536 .vitem &*uschar&~*expand_string(uschar&~*string)*&
35537 This is an interface to Exim's string expansion code. The return value is the
35538 expanded string, or NULL if there was an expansion failure.
35539 The C variable &%expand_string_message%& contains an error message after an
35540 expansion failure. If expansion does not change the string, the return value is
35541 the pointer to the input string. Otherwise, the return value points to a new
35542 block of memory that was obtained by a call to &'store_get()'&. See section
35543 &<<SECTmemhanloc>>& below for a discussion of memory handling.
35545 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
35546 This function allows you to an add additional header line at the end of the
35547 existing ones. The first argument is the type, and should normally be a space
35548 character. The second argument is a format string and any number of
35549 substitution arguments as for &[sprintf()]&. You may include internal newlines
35550 if you want, and you must ensure that the string ends with a newline.
35552 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
35553 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
35554 This function adds a new header line at a specified point in the header
35555 chain. The header itself is specified as for &'header_add()'&.
35557 If &%name%& is NULL, the new header is added at the end of the chain if
35558 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
35559 NULL, the header lines are searched for the first non-deleted header that
35560 matches the name. If one is found, the new header is added before it if
35561 &%after%& is false. If &%after%& is true, the new header is added after the
35562 found header and any adjacent subsequent ones with the same name (even if
35563 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
35564 option controls where the header is added. If it is true, addition is at the
35565 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
35566 headers, or at the top if there are no &'Received:'& headers, you could use
35568 header_add_at_position(TRUE, US"Received", TRUE,
35569 ' ', "X-xxx: ...");
35571 Normally, there is always at least one non-deleted &'Received:'& header, but
35572 there may not be if &%received_header_text%& expands to an empty string.
35575 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
35576 This function removes header lines. If &%occurrence%& is zero or negative, all
35577 occurrences of the header are removed. If occurrence is greater than zero, that
35578 particular instance of the header is removed. If no header(s) can be found that
35579 match the specification, the function does nothing.
35582 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
35583 int&~length,&~BOOL&~notdel)*&"
35584 This function tests whether the given header has the given name. It is not just
35585 a string comparison, because white space is permitted between the name and the
35586 colon. If the &%notdel%& argument is true, a false return is forced for all
35587 &"deleted"& headers; otherwise they are not treated specially. For example:
35589 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
35591 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
35592 .cindex "base64 encoding" "functions for &[local_scan()]& use"
35593 This function base64-encodes a string, which is passed by address and length.
35594 The text may contain bytes of any value, including zero. The result is passed
35595 back in dynamic memory that is obtained by calling &'store_get()'&. It is
35598 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
35599 This function decodes a base64-encoded string. Its arguments are a
35600 zero-terminated base64-encoded string and the address of a variable that is set
35601 to point to the result, which is in dynamic memory. The length of the decoded
35602 string is the yield of the function. If the input is invalid base64 data, the
35603 yield is -1. A zero byte is added to the end of the output string to make it
35604 easy to interpret as a C string (assuming it contains no zeros of its own). The
35605 added zero byte is not included in the returned count.
35607 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
35608 This function checks for a match in a domain list. Domains are always
35609 matched caselessly. The return value is one of the following:
35611 &`OK `& match succeeded
35612 &`FAIL `& match failed
35613 &`DEFER `& match deferred
35615 DEFER is usually caused by some kind of lookup defer, such as the
35616 inability to contact a database.
35618 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
35620 This function checks for a match in a local part list. The third argument
35621 controls case-sensitivity. The return values are as for
35622 &'lss_match_domain()'&.
35624 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
35626 This function checks for a match in an address list. The third argument
35627 controls the case-sensitivity of the local part match. The domain is always
35628 matched caselessly. The return values are as for &'lss_match_domain()'&.
35630 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
35632 This function checks for a match in a host list. The most common usage is
35635 lss_match_host(sender_host_name, sender_host_address, ...)
35637 .vindex "&$sender_host_address$&"
35638 An empty address field matches an empty item in the host list. If the host name
35639 is NULL, the name corresponding to &$sender_host_address$& is automatically
35640 looked up if a host name is required to match an item in the list. The return
35641 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
35642 returns ERROR in the case when it had to look up a host name, but the lookup
35645 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
35647 This function writes to Exim's log files. The first argument should be zero (it
35648 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
35649 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
35650 them. It specifies to which log or logs the message is written. The remaining
35651 arguments are a format and relevant insertion arguments. The string should not
35652 contain any newlines, not even at the end.
35655 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
35656 This function adds an additional recipient to the message. The first argument
35657 is the recipient address. If it is unqualified (has no domain), it is qualified
35658 with the &%qualify_recipient%& domain. The second argument must always be -1.
35660 This function does not allow you to specify a private &%errors_to%& address (as
35661 described with the structure of &%recipient_item%& above), because it pre-dates
35662 the addition of that field to the structure. However, it is easy to add such a
35663 value afterwards. For example:
35665 receive_add_recipient(US"monitor@mydom.example", -1);
35666 recipients_list[recipients_count-1].errors_to =
35667 US"postmaster@mydom.example";
35670 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
35671 This is a convenience function to remove a named recipient from the list of
35672 recipients. It returns true if a recipient was removed, and false if no
35673 matching recipient could be found. The argument must be a complete email
35680 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
35681 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
35682 This function decodes strings that are encoded according to RFC 2047. Typically
35683 these are the contents of header lines. First, each &"encoded word"& is decoded
35684 from the Q or B encoding into a byte-string. Then, if provided with the name of
35685 a charset encoding, and if the &[iconv()]& function is available, an attempt is
35686 made to translate the result to the named character set. If this fails, the
35687 binary string is returned with an error message.
35689 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
35690 maximum MIME word length is enforced. The third argument is the target
35691 encoding, or NULL if no translation is wanted.
35693 .cindex "binary zero" "in RFC 2047 decoding"
35694 .cindex "RFC 2047" "binary zero in"
35695 If a binary zero is encountered in the decoded string, it is replaced by the
35696 contents of the &%zeroval%& argument. For use with Exim headers, the value must
35697 not be 0 because header lines are handled as zero-terminated strings.
35699 The function returns the result of processing the string, zero-terminated; if
35700 &%lenptr%& is not NULL, the length of the result is set in the variable to
35701 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
35703 If an error is encountered, the function returns NULL and uses the &%error%&
35704 argument to return an error message. The variable pointed to by &%error%& is
35705 set to NULL if there is no error; it may be set non-NULL even when the function
35706 returns a non-NULL value if decoding was successful, but there was a problem
35710 .vitem &*int&~smtp_fflush(void)*&
35711 This function is used in conjunction with &'smtp_printf()'&, as described
35714 .vitem &*void&~smtp_printf(char&~*,BOOL,&~...)*&
35715 The arguments of this function are almost like &[printf()]&; it writes to the SMTP
35716 output stream. You should use this function only when there is an SMTP output
35717 stream, that is, when the incoming message is being received via interactive
35718 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
35719 is FALSE. If you want to test for an incoming message from another host (as
35720 opposed to a local process that used the &%-bs%& command line option), you can
35721 test the value of &%sender_host_address%&, which is non-NULL when a remote host
35724 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
35725 output function, so it can be used for all forms of SMTP connection.
35727 The second argument is used to request that the data be buffered
35728 (when TRUE) or flushed (along with any previously buffered, when FALSE).
35729 This is advisory only, but likely to save on system-calls and packets
35730 sent when a sequence of calls to the function are made.
35732 The argument was added in Exim version 4.90 - changing the API/ABI.
35733 Nobody noticed until 4.93 was imminent, at which point the
35734 ABI version number was incremented.
35736 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
35737 must start with an appropriate response code: 550 if you are going to return
35738 LOCAL_SCAN_REJECT, 451 if you are going to return
35739 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
35740 initial lines of a multi-line response, the code must be followed by a hyphen
35741 to indicate that the line is not the final response line. You must also ensure
35742 that the lines you write terminate with CRLF. For example:
35744 smtp_printf("550-this is some extra info\r\n");
35745 return LOCAL_SCAN_REJECT;
35747 Note that you can also create multi-line responses by including newlines in
35748 the data returned via the &%return_text%& argument. The added value of using
35749 &'smtp_printf()'& is that, for instance, you could introduce delays between
35750 multiple output lines.
35752 The &'smtp_printf()'& function does not return any error indication, because it
35754 guarantee a flush of
35755 pending output, and therefore does not test
35756 the state of the stream. (In the main code of Exim, flushing and error
35757 detection is done when Exim is ready for the next SMTP input command.) If
35758 you want to flush the output and check for an error (for example, the
35759 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
35760 arguments. It flushes the output stream, and returns a non-zero value if there
35763 .vitem &*void&~*store_get(int,BOOL)*&
35764 This function accesses Exim's internal store (memory) manager. It gets a new
35765 chunk of memory whose size is given by the first argument.
35766 The second argument should be given as TRUE if the memory will be used for
35767 data possibly coming from an attacker (eg. the message content),
35768 FALSE if it is locally-sourced.
35769 Exim bombs out if it ever
35770 runs out of memory. See the next section for a discussion of memory handling.
35772 .vitem &*void&~*store_get_perm(int,BOOL)*&
35773 This function is like &'store_get()'&, but it always gets memory from the
35774 permanent pool. See the next section for a discussion of memory handling.
35776 .vitem &*uschar&~*string_copy(uschar&~*string)*&
35779 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
35782 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
35783 These three functions create strings using Exim's dynamic memory facilities.
35784 The first makes a copy of an entire string. The second copies up to a maximum
35785 number of characters, indicated by the second argument. The third uses a format
35786 and insertion arguments to create a new string. In each case, the result is a
35787 pointer to a new string in the current memory pool. See the next section for
35793 .section "More about Exim's memory handling" "SECTmemhanloc"
35794 .cindex "&[local_scan()]& function" "memory handling"
35795 No function is provided for freeing memory, because that is never needed.
35796 The dynamic memory that Exim uses when receiving a message is automatically
35797 recycled if another message is received by the same process (this applies only
35798 to incoming SMTP connections &-- other input methods can supply only one
35799 message at a time). After receiving the last message, a reception process
35802 Because it is recycled, the normal dynamic memory cannot be used for holding
35803 data that must be preserved over a number of incoming messages on the same SMTP
35804 connection. However, Exim in fact uses two pools of dynamic memory; the second
35805 one is not recycled, and can be used for this purpose.
35807 If you want to allocate memory that remains available for subsequent messages
35808 in the same SMTP connection, you should set
35810 store_pool = POOL_PERM
35812 before calling the function that does the allocation. There is no need to
35813 restore the value if you do not need to; however, if you do want to revert to
35814 the normal pool, you can either restore the previous value of &%store_pool%& or
35815 set it explicitly to POOL_MAIN.
35817 The pool setting applies to all functions that get dynamic memory, including
35818 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
35819 There is also a convenience function called &'store_get_perm()'& that gets a
35820 block of memory from the permanent pool while preserving the value of
35827 . ////////////////////////////////////////////////////////////////////////////
35828 . ////////////////////////////////////////////////////////////////////////////
35830 .chapter "System-wide message filtering" "CHAPsystemfilter"
35831 .scindex IIDsysfil1 "filter" "system filter"
35832 .scindex IIDsysfil2 "filtering all mail"
35833 .scindex IIDsysfil3 "system filter"
35834 The previous chapters (on ACLs and the local scan function) describe checks
35835 that can be applied to messages before they are accepted by a host. There is
35836 also a mechanism for checking messages once they have been received, but before
35837 they are delivered. This is called the &'system filter'&.
35839 The system filter operates in a similar manner to users' filter files, but it
35840 is run just once per message (however many recipients the message has).
35841 It should not normally be used as a substitute for routing, because &%deliver%&
35842 commands in a system router provide new envelope recipient addresses.
35843 The system filter must be an Exim filter. It cannot be a Sieve filter.
35845 The system filter is run at the start of a delivery attempt, before any routing
35846 is done. If a message fails to be completely delivered at the first attempt,
35847 the system filter is run again at the start of every retry.
35848 If you want your filter to do something only once per message, you can make use
35849 of the &%first_delivery%& condition in an &%if%& command in the filter to
35850 prevent it happening on retries.
35852 .vindex "&$domain$&"
35853 .vindex "&$local_part$&"
35854 &*Warning*&: Because the system filter runs just once, variables that are
35855 specific to individual recipient addresses, such as &$local_part$& and
35856 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
35857 you want to run a centrally-specified filter for each recipient address
35858 independently, you can do so by setting up a suitable &(redirect)& router, as
35859 described in section &<<SECTperaddfil>>& below.
35862 .section "Specifying a system filter" "SECID212"
35863 .cindex "uid (user id)" "system filter"
35864 .cindex "gid (group id)" "system filter"
35865 The name of the file that contains the system filter must be specified by
35866 setting &%system_filter%&. If you want the filter to run under a uid and gid
35867 other than root, you must also set &%system_filter_user%& and
35868 &%system_filter_group%& as appropriate. For example:
35870 system_filter = /etc/mail/exim.filter
35871 system_filter_user = exim
35873 If a system filter generates any deliveries directly to files or pipes (via the
35874 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
35875 specified by setting &%system_filter_file_transport%& and
35876 &%system_filter_pipe_transport%&, respectively. Similarly,
35877 &%system_filter_reply_transport%& must be set to handle any messages generated
35878 by the &%reply%& command.
35881 .section "Testing a system filter" "SECID213"
35882 You can run simple tests of a system filter in the same way as for a user
35883 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
35884 are permitted only in system filters are recognized.
35886 If you want to test the combined effect of a system filter and a user filter,
35887 you can use both &%-bF%& and &%-bf%& on the same command line.
35891 .section "Contents of a system filter" "SECID214"
35892 The language used to specify system filters is the same as for users' filter
35893 files. It is described in the separate end-user document &'Exim's interface to
35894 mail filtering'&. However, there are some additional features that are
35895 available only in system filters; these are described in subsequent sections.
35896 If they are encountered in a user's filter file or when testing with &%-bf%&,
35899 .cindex "frozen messages" "manual thaw; testing in filter"
35900 There are two special conditions which, though available in users' filter
35901 files, are designed for use in system filters. The condition &%first_delivery%&
35902 is true only for the first attempt at delivering a message, and
35903 &%manually_thawed%& is true only if the message has been frozen, and
35904 subsequently thawed by an admin user. An explicit forced delivery counts as a
35905 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
35907 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
35908 specify an &"unseen"& (non-significant) delivery, and that delivery does not
35909 succeed, it will not be tried again.
35910 If you want Exim to retry an unseen delivery until it succeeds, you should
35911 arrange to set it up every time the filter runs.
35913 When a system filter finishes running, the values of the variables &$n0$& &--
35914 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
35915 users' filter files. Thus a system filter can, for example, set up &"scores"&
35916 to which users' filter files can refer.
35920 .section "Additional variable for system filters" "SECID215"
35921 .vindex "&$recipients$&"
35922 The expansion variable &$recipients$&, containing a list of all the recipients
35923 of the message (separated by commas and white space), is available in system
35924 filters. It is not available in users' filters for privacy reasons.
35928 .section "Defer, freeze, and fail commands for system filters" "SECID216"
35929 .cindex "freezing messages"
35930 .cindex "message" "freezing"
35931 .cindex "message" "forced failure"
35932 .cindex "&%fail%&" "in system filter"
35933 .cindex "&%freeze%& in system filter"
35934 .cindex "&%defer%& in system filter"
35935 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
35936 always available in system filters, but are not normally enabled in users'
35937 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
35938 for the &(redirect)& router.) These commands can optionally be followed by the
35939 word &%text%& and a string containing an error message, for example:
35941 fail text "this message looks like spam to me"
35943 The keyword &%text%& is optional if the next character is a double quote.
35945 The &%defer%& command defers delivery of the original recipients of the
35946 message. The &%fail%& command causes all the original recipients to be failed,
35947 and a bounce message to be created. The &%freeze%& command suspends all
35948 delivery attempts for the original recipients. In all cases, any new deliveries
35949 that are specified by the filter are attempted as normal after the filter has
35952 The &%freeze%& command is ignored if the message has been manually unfrozen and
35953 not manually frozen since. This means that automatic freezing by a system
35954 filter can be used as a way of checking out suspicious messages. If a message
35955 is found to be all right, manually unfreezing it allows it to be delivered.
35957 .cindex "log" "&%fail%& command log line"
35958 .cindex "&%fail%&" "log line; reducing"
35959 The text given with a fail command is used as part of the bounce message as
35960 well as being written to the log. If the message is quite long, this can fill
35961 up a lot of log space when such failures are common. To reduce the size of the
35962 log message, Exim interprets the text in a special way if it starts with the
35963 two characters &`<<`& and contains &`>>`& later. The text between these two
35964 strings is written to the log, and the rest of the text is used in the bounce
35965 message. For example:
35967 fail "<<filter test 1>>Your message is rejected \
35968 because it contains attachments that we are \
35969 not prepared to receive."
35972 .cindex "loop" "caused by &%fail%&"
35973 Take great care with the &%fail%& command when basing the decision to fail on
35974 the contents of the message, because the bounce message will of course include
35975 the contents of the original message and will therefore trigger the &%fail%&
35976 command again (causing a mail loop) unless steps are taken to prevent this.
35977 Testing the &%error_message%& condition is one way to prevent this. You could
35980 if $message_body contains "this is spam" and not error_message
35981 then fail text "spam is not wanted here" endif
35983 though of course that might let through unwanted bounce messages. The
35984 alternative is clever checking of the body and/or headers to detect bounces
35985 generated by the filter.
35987 The interpretation of a system filter file ceases after a
35989 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
35990 set up earlier in the filter file are honoured, so you can use a sequence such
35996 to send a specified message when the system filter is freezing (or deferring or
35997 failing) a message. The normal deliveries for the message do not, of course,
36002 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
36003 .cindex "header lines" "adding; in system filter"
36004 .cindex "header lines" "removing; in system filter"
36005 .cindex "filter" "header lines; adding/removing"
36006 Two filter commands that are available only in system filters are:
36008 headers add <string>
36009 headers remove <string>
36011 The argument for the &%headers add%& is a string that is expanded and then
36012 added to the end of the message's headers. It is the responsibility of the
36013 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
36014 space is ignored, and if the string is otherwise empty, or if the expansion is
36015 forced to fail, the command has no effect.
36017 You can use &"\n"& within the string, followed by white space, to specify
36018 continued header lines. More than one header may be added in one command by
36019 including &"\n"& within the string without any following white space. For
36022 headers add "X-header-1: ....\n \
36023 continuation of X-header-1 ...\n\
36026 Note that the header line continuation white space after the first newline must
36027 be placed before the backslash that continues the input string, because white
36028 space after input continuations is ignored.
36030 The argument for &%headers remove%& is a colon-separated list of header names.
36031 This command applies only to those headers that are stored with the message;
36032 those that are added at delivery time (such as &'Envelope-To:'& and
36033 &'Return-Path:'&) cannot be removed by this means. If there is more than one
36034 header with the same name, they are all removed.
36036 The &%headers%& command in a system filter makes an immediate change to the set
36037 of header lines that was received with the message (with possible additions
36038 from ACL processing). Subsequent commands in the system filter operate on the
36039 modified set, which also forms the basis for subsequent message delivery.
36040 Unless further modified during routing or transporting, this set of headers is
36041 used for all recipients of the message.
36043 During routing and transporting, the variables that refer to the contents of
36044 header lines refer only to those lines that are in this set. Thus, header lines
36045 that are added by a system filter are visible to users' filter files and to all
36046 routers and transports. This contrasts with the manipulation of header lines by
36047 routers and transports, which is not immediate, but which instead is saved up
36048 until the message is actually being written (see section
36049 &<<SECTheadersaddrem>>&).
36051 If the message is not delivered at the first attempt, header lines that were
36052 added by the system filter are stored with the message, and so are still
36053 present at the next delivery attempt. Header lines that were removed are still
36054 present, but marked &"deleted"& so that they are not transported with the
36055 message. For this reason, it is usual to make the &%headers%& command
36056 conditional on &%first_delivery%& so that the set of header lines is not
36057 modified more than once.
36059 Because header modification in a system filter acts immediately, you have to
36060 use an indirect approach if you want to modify the contents of a header line.
36063 headers add "Old-Subject: $h_subject:"
36064 headers remove "Subject"
36065 headers add "Subject: new subject (was: $h_old-subject:)"
36066 headers remove "Old-Subject"
36071 .section "Setting an errors address in a system filter" "SECID217"
36072 .cindex "envelope from"
36073 .cindex "envelope sender"
36074 In a system filter, if a &%deliver%& command is followed by
36076 errors_to <some address>
36078 in order to change the envelope sender (and hence the error reporting) for that
36079 delivery, any address may be specified. (In a user filter, only the current
36080 user's address can be set.) For example, if some mail is being monitored, you
36083 unseen deliver monitor@spying.example errors_to root@local.example
36085 to take a copy which would not be sent back to the normal error reporting
36086 address if its delivery failed.
36090 .section "Per-address filtering" "SECTperaddfil"
36091 .vindex "&$domain_data$&"
36092 .vindex "&$local_part_data$&"
36093 In contrast to the system filter, which is run just once per message for each
36094 delivery attempt, it is also possible to set up a system-wide filtering
36095 operation that runs once for each recipient address. In this case, variables
36096 such as &$local_part_data$& and &$domain_data$& can be used,
36097 and indeed, the choice of filter file could be made dependent on them.
36098 This is an example of a router which implements such a filter:
36103 domains = +local_domains
36104 file = /central/filters/$local_part_data
36109 The filter is run in a separate process under its own uid. Therefore, either
36110 &%check_local_user%& must be set (as above), in which case the filter is run as
36111 the local user, or the &%user%& option must be used to specify which user to
36112 use. If both are set, &%user%& overrides.
36114 Care should be taken to ensure that none of the commands in the filter file
36115 specify a significant delivery if the message is to go on to be delivered to
36116 its intended recipient. The router will not then claim to have dealt with the
36117 address, so it will be passed on to subsequent routers to be delivered in the
36119 .ecindex IIDsysfil1
36120 .ecindex IIDsysfil2
36121 .ecindex IIDsysfil3
36128 . ////////////////////////////////////////////////////////////////////////////
36129 . ////////////////////////////////////////////////////////////////////////////
36131 .chapter "Message processing" "CHAPmsgproc"
36132 .scindex IIDmesproc "message" "general processing"
36133 Exim performs various transformations on the sender and recipient addresses of
36134 all messages that it handles, and also on the messages' header lines. Some of
36135 these are optional and configurable, while others always take place. All of
36136 this processing, except rewriting as a result of routing, and the addition or
36137 removal of header lines while delivering, happens when a message is received,
36138 before it is placed on Exim's queue.
36140 Some of the automatic processing takes place by default only for
36141 &"locally-originated"& messages. This adjective is used to describe messages
36142 that are not received over TCP/IP, but instead are passed to an Exim process on
36143 its standard input. This includes the interactive &"local SMTP"& case that is
36144 set up by the &%-bs%& command line option.
36146 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
36147 or ::1) are not considered to be locally-originated. Exim does not treat the
36148 loopback interface specially in any way.
36150 If you want the loopback interface to be treated specially, you must ensure
36151 that there are appropriate entries in your ACLs.
36156 .section "Submission mode for non-local messages" "SECTsubmodnon"
36157 .cindex "message" "submission"
36158 .cindex "submission mode"
36159 Processing that happens automatically for locally-originated messages (unless
36160 &%suppress_local_fixups%& is set) can also be requested for messages that are
36161 received over TCP/IP. The term &"submission mode"& is used to describe this
36162 state. Submission mode is set by the modifier
36164 control = submission
36166 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
36167 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
36168 a local submission, and is normally used when the source of the message is
36169 known to be an MUA running on a client host (as opposed to an MTA). For
36170 example, to set submission mode for messages originating on the IPv4 loopback
36171 interface, you could include the following in the MAIL ACL:
36173 warn hosts = 127.0.0.1
36174 control = submission
36176 .cindex "&%sender_retain%& submission option"
36177 There are some options that can be used when setting submission mode. A slash
36178 is used to separate options. For example:
36180 control = submission/sender_retain
36182 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
36183 true and &%local_from_check%& false for the current incoming message. The first
36184 of these allows an existing &'Sender:'& header in the message to remain, and
36185 the second suppresses the check to ensure that &'From:'& matches the
36186 authenticated sender. With this setting, Exim still fixes up messages by adding
36187 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
36188 attempt to check sender authenticity in header lines.
36190 When &%sender_retain%& is not set, a submission mode setting may specify a
36191 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
36194 control = submission/domain=some.domain
36196 The domain may be empty. How this value is used is described in sections
36197 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
36198 that allows you to specify the user's full name for inclusion in a created
36199 &'Sender:'& or &'From:'& header line. For example:
36201 accept authenticated = *
36202 control = submission/domain=wonderland.example/\
36203 name=${lookup {$authenticated_id} \
36204 lsearch {/etc/exim/namelist}}
36206 Because the name may contain any characters, including slashes, the &%name%&
36207 option must be given last. The remainder of the string is used as the name. For
36208 the example above, if &_/etc/exim/namelist_& contains:
36210 bigegg: Humpty Dumpty
36212 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
36215 Sender: Humpty Dumpty <bigegg@wonderland.example>
36217 .cindex "return path" "in submission mode"
36218 By default, submission mode forces the return path to the same address as is
36219 used to create the &'Sender:'& header. However, if &%sender_retain%& is
36220 specified, the return path is also left unchanged.
36222 &*Note*&: The changes caused by submission mode take effect after the predata
36223 ACL. This means that any sender checks performed before the fix-ups use the
36224 untrusted sender address specified by the user, not the trusted sender address
36225 specified by submission mode. Although this might be slightly unexpected, it
36226 does mean that you can configure ACL checks to spot that a user is trying to
36227 spoof another's address.
36229 .section "Line endings" "SECTlineendings"
36230 .cindex "line endings"
36231 .cindex "carriage return"
36233 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
36234 linefeed) is the line ending for messages transmitted over the Internet using
36235 SMTP over TCP/IP. However, within individual operating systems, different
36236 conventions are used. For example, Unix-like systems use just LF, but others
36237 use CRLF or just CR.
36239 Exim was designed for Unix-like systems, and internally, it stores messages
36240 using the system's convention of a single LF as a line terminator. When
36241 receiving a message, all line endings are translated to this standard format.
36242 Originally, it was thought that programs that passed messages directly to an
36243 MTA within an operating system would use that system's convention. Experience
36244 has shown that this is not the case; for example, there are Unix applications
36245 that use CRLF in this circumstance. For this reason, and for compatibility with
36246 other MTAs, the way Exim handles line endings for all messages is now as
36250 LF not preceded by CR is treated as a line ending.
36252 CR is treated as a line ending; if it is immediately followed by LF, the LF
36255 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
36256 nor a local message in the state where a line containing only a dot is a
36259 If a bare CR is encountered within a header line, an extra space is added after
36260 the line terminator so as not to end the header line. The reasoning behind this
36261 is that bare CRs in header lines are most likely either to be mistakes, or
36262 people trying to play silly games.
36264 If the first header line received in a message ends with CRLF, a subsequent
36265 bare LF in a header line is treated in the same way as a bare CR in a header
36273 .section "Unqualified addresses" "SECID218"
36274 .cindex "unqualified addresses"
36275 .cindex "address" "qualification"
36276 By default, Exim expects every envelope address it receives from an external
36277 host to be fully qualified. Unqualified addresses cause negative responses to
36278 SMTP commands. However, because SMTP is used as a means of transporting
36279 messages from MUAs running on personal workstations, there is sometimes a
36280 requirement to accept unqualified addresses from specific hosts or IP networks.
36282 Exim has two options that separately control which hosts may send unqualified
36283 sender or recipient addresses in SMTP commands, namely
36284 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
36285 cases, if an unqualified address is accepted, it is qualified by adding the
36286 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
36288 .oindex "&%qualify_domain%&"
36289 .oindex "&%qualify_recipient%&"
36290 Unqualified addresses in header lines are automatically qualified for messages
36291 that are locally originated, unless the &%-bnq%& option is given on the command
36292 line. For messages received over SMTP, unqualified addresses in header lines
36293 are qualified only if unqualified addresses are permitted in SMTP commands. In
36294 other words, such qualification is also controlled by
36295 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
36300 .section "The UUCP From line" "SECID219"
36301 .cindex "&""From""& line"
36302 .cindex "UUCP" "&""From""& line"
36303 .cindex "sender" "address"
36304 .oindex "&%uucp_from_pattern%&"
36305 .oindex "&%uucp_from_sender%&"
36306 .cindex "envelope from"
36307 .cindex "envelope sender"
36308 .cindex "Sendmail compatibility" "&""From""& line"
36309 Messages that have come from UUCP (and some other applications) often begin
36310 with a line containing the envelope sender and a timestamp, following the word
36311 &"From"&. Examples of two common formats are:
36313 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
36314 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
36316 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
36317 Exim recognizes such lines at the start of messages that are submitted to it
36318 via the command line (that is, on the standard input). It does not recognize
36319 such lines in incoming SMTP messages, unless the sending host matches
36320 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
36321 and &%ignore_fromline_local%& is set. The recognition is controlled by a
36322 regular expression that is defined by the &%uucp_from_pattern%& option, whose
36323 default value matches the two common cases shown above and puts the address
36324 that follows &"From"& into &$1$&.
36326 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
36327 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
36328 a trusted user, the message's sender address is constructed by expanding the
36329 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
36330 then parsed as an RFC 2822 address. If there is no domain, the local part is
36331 qualified with &%qualify_domain%& unless it is the empty string. However, if
36332 the command line &%-f%& option is used, it overrides the &"From"& line.
36334 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
36335 sender address is not changed. This is also the case for incoming SMTP messages
36336 that are permitted to contain &"From"& lines.
36338 Only one &"From"& line is recognized. If there is more than one, the second is
36339 treated as a data line that starts the body of the message, as it is not valid
36340 as a header line. This also happens if a &"From"& line is present in an
36341 incoming SMTP message from a source that is not permitted to send them.
36345 .section "Resent- header lines" "SECID220"
36347 RFC 2822 makes provision for sets of header lines starting with the string
36348 &`Resent-`& to be added to a message when it is resent by the original
36349 recipient to somebody else. These headers are &'Resent-Date:'&,
36350 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
36351 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
36354 &'Resent fields are strictly informational. They MUST NOT be used in the normal
36355 processing of replies or other such automatic actions on messages.'&
36358 This leaves things a bit vague as far as other processing actions such as
36359 address rewriting are concerned. Exim treats &%Resent-%& header lines as
36363 A &'Resent-From:'& line that just contains the login id of the submitting user
36364 is automatically rewritten in the same way as &'From:'& (see below).
36366 If there's a rewriting rule for a particular header line, it is also applied to
36367 &%Resent-%& header lines of the same type. For example, a rule that rewrites
36368 &'From:'& also rewrites &'Resent-From:'&.
36370 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
36373 For a locally-submitted message,
36374 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
36375 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
36376 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
36377 included in log lines in this case.
36379 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
36380 &%Resent-%& header lines are present.
36386 .section "The Auto-Submitted: header line" "SECID221"
36387 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
36388 includes the header line:
36390 Auto-Submitted: auto-replied
36393 .section "The Bcc: header line" "SECID222"
36394 .cindex "&'Bcc:'& header line"
36395 If Exim is called with the &%-t%& option, to take recipient addresses from a
36396 message's header, it removes any &'Bcc:'& header line that may exist (after
36397 extracting its addresses). If &%-t%& is not present on the command line, any
36398 existing &'Bcc:'& is not removed.
36401 .section "The Date: header line" "SECID223"
36403 If a locally-generated or submission-mode message has no &'Date:'& header line,
36404 Exim adds one, using the current date and time, unless the
36405 &%suppress_local_fixups%& control has been specified.
36407 .section "The Delivery-date: header line" "SECID224"
36408 .cindex "&'Delivery-date:'& header line"
36409 .oindex "&%delivery_date_remove%&"
36410 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
36411 set. Exim can be configured to add them to the final delivery of messages. (See
36412 the generic &%delivery_date_add%& transport option.) They should not be present
36413 in messages in transit. If the &%delivery_date_remove%& configuration option is
36414 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
36418 .section "The Envelope-to: header line" "SECID225"
36419 .chindex Envelope-to:
36420 .oindex "&%envelope_to_remove%&"
36421 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
36422 Exim can be configured to add them to the final delivery of messages. (See the
36423 generic &%envelope_to_add%& transport option.) They should not be present in
36424 messages in transit. If the &%envelope_to_remove%& configuration option is set
36425 (the default), Exim removes &'Envelope-to:'& header lines from incoming
36429 .section "The From: header line" "SECTthefrohea"
36431 .cindex "Sendmail compatibility" "&""From""& line"
36432 .cindex "message" "submission"
36433 .cindex "submission mode"
36434 If a submission-mode message does not contain a &'From:'& header line, Exim
36435 adds one if either of the following conditions is true:
36438 The envelope sender address is not empty (that is, this is not a bounce
36439 message). The added header line copies the envelope sender address.
36441 .vindex "&$authenticated_id$&"
36442 The SMTP session is authenticated and &$authenticated_id$& is not empty.
36444 .vindex "&$qualify_domain$&"
36445 If no domain is specified by the submission control, the local part is
36446 &$authenticated_id$& and the domain is &$qualify_domain$&.
36448 If a non-empty domain is specified by the submission control, the local
36449 part is &$authenticated_id$&, and the domain is the specified domain.
36451 If an empty domain is specified by the submission control,
36452 &$authenticated_id$& is assumed to be the complete address.
36456 A non-empty envelope sender takes precedence.
36458 If a locally-generated incoming message does not contain a &'From:'& header
36459 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
36460 containing the sender's address. The calling user's login name and full name
36461 are used to construct the address, as described in section &<<SECTconstr>>&.
36462 They are obtained from the password data by calling &[getpwuid()]& (but see the
36463 &%unknown_login%& configuration option). The address is qualified with
36464 &%qualify_domain%&.
36466 For compatibility with Sendmail, if an incoming, non-SMTP message has a
36467 &'From:'& header line containing just the unqualified login name of the calling
36468 user, this is replaced by an address containing the user's login name and full
36469 name as described in section &<<SECTconstr>>&.
36472 .section "The Message-ID: header line" "SECID226"
36473 .chindex Message-ID:
36474 .cindex "message" "submission"
36475 .oindex "&%message_id_header_text%&"
36476 If a locally-generated or submission-mode incoming message does not contain a
36477 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
36478 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
36479 to the message. If there are any &'Resent-:'& headers in the message, it
36480 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
36481 message id, preceded by the letter E to ensure it starts with a letter, and
36482 followed by @ and the primary host name. Additional information can be included
36483 in this header line by setting the &%message_id_header_text%& and/or
36484 &%message_id_header_domain%& options.
36487 .section "The Received: header line" "SECID227"
36489 A &'Received:'& header line is added at the start of every message. The
36490 contents are defined by the &%received_header_text%& configuration option, and
36491 Exim automatically adds a semicolon and a timestamp to the configured string.
36493 The &'Received:'& header is generated as soon as the message's header lines
36494 have been received. At this stage, the timestamp in the &'Received:'& header
36495 line is the time that the message started to be received. This is the value
36496 that is seen by the DATA ACL and by the &[local_scan()]& function.
36498 Once a message is accepted, the timestamp in the &'Received:'& header line is
36499 changed to the time of acceptance, which is (apart from a small delay while the
36500 -H spool file is written) the earliest time at which delivery could start.
36503 .section "The References: header line" "SECID228"
36504 .chindex References:
36505 Messages created by the &(autoreply)& transport include a &'References:'&
36506 header line. This is constructed according to the rules that are described in
36507 section 3.64 of RFC 2822 (which states that replies should contain such a
36508 header line), and section 3.14 of RFC 3834 (which states that automatic
36509 responses are not different in this respect). However, because some mail
36510 processing software does not cope well with very long header lines, no more
36511 than 12 message IDs are copied from the &'References:'& header line in the
36512 incoming message. If there are more than 12, the first one and then the final
36513 11 are copied, before adding the message ID of the incoming message.
36517 .section "The Return-path: header line" "SECID229"
36518 .chindex Return-path:
36519 .oindex "&%return_path_remove%&"
36520 &'Return-path:'& header lines are defined as something an MTA may insert when
36521 it does the final delivery of messages. (See the generic &%return_path_add%&
36522 transport option.) Therefore, they should not be present in messages in
36523 transit. If the &%return_path_remove%& configuration option is set (the
36524 default), Exim removes &'Return-path:'& header lines from incoming messages.
36528 .section "The Sender: header line" "SECTthesenhea"
36529 .cindex "&'Sender:'& header line"
36530 .cindex "message" "submission"
36532 For a locally-originated message from an untrusted user, Exim may remove an
36533 existing &'Sender:'& header line, and it may add a new one. You can modify
36534 these actions by setting the &%local_sender_retain%& option true, the
36535 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
36538 When a local message is received from an untrusted user and
36539 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
36540 control has not been set, a check is made to see if the address given in the
36541 &'From:'& header line is the correct (local) sender of the message. The address
36542 that is expected has the login name as the local part and the value of
36543 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
36544 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
36545 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
36546 line is added to the message.
36548 If you set &%local_from_check%& false, this checking does not occur. However,
36549 the removal of an existing &'Sender:'& line still happens, unless you also set
36550 &%local_sender_retain%& to be true. It is not possible to set both of these
36551 options true at the same time.
36553 .cindex "submission mode"
36554 By default, no processing of &'Sender:'& header lines is done for messages
36555 received over TCP/IP or for messages submitted by trusted users. However, when
36556 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
36557 not specified on the submission control, the following processing takes place:
36559 .vindex "&$authenticated_id$&"
36560 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
36561 authenticated, and &$authenticated_id$& is not empty, a sender address is
36562 created as follows:
36565 .vindex "&$qualify_domain$&"
36566 If no domain is specified by the submission control, the local part is
36567 &$authenticated_id$& and the domain is &$qualify_domain$&.
36569 If a non-empty domain is specified by the submission control, the local part
36570 is &$authenticated_id$&, and the domain is the specified domain.
36572 If an empty domain is specified by the submission control,
36573 &$authenticated_id$& is assumed to be the complete address.
36576 This address is compared with the address in the &'From:'& header line. If they
36577 are different, a &'Sender:'& header line containing the created address is
36578 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
36579 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
36581 .cindex "return path" "created from &'Sender:'&"
36582 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
36583 the message (the envelope sender address) is changed to be the same address,
36584 except in the case of submission mode when &%sender_retain%& is specified.
36588 .section "Adding and removing header lines in routers and transports" &&&
36589 "SECTheadersaddrem"
36590 .cindex "header lines" "adding; in router or transport"
36591 .cindex "header lines" "removing; in router or transport"
36592 When a message is delivered, the addition and removal of header lines can be
36593 specified in a system filter, or on any of the routers and transports that
36594 process the message. Section &<<SECTaddremheasys>>& contains details about
36595 modifying headers in a system filter. Header lines can also be added in an ACL
36596 as a message is received (see section &<<SECTaddheadacl>>&).
36598 In contrast to what happens in a system filter, header modifications that are
36599 specified on routers and transports apply only to the particular recipient
36600 addresses that are being processed by those routers and transports. These
36601 changes do not actually take place until a copy of the message is being
36602 transported. Therefore, they do not affect the basic set of header lines, and
36603 they do not affect the values of the variables that refer to header lines.
36605 &*Note*&: In particular, this means that any expansions in the configuration of
36606 the transport cannot refer to the modified header lines, because such
36607 expansions all occur before the message is actually transported.
36609 For both routers and transports, the argument of a &%headers_add%&
36610 option must be in the form of one or more RFC 2822 header lines, separated by
36611 newlines (coded as &"\n"&). For example:
36613 headers_add = X-added-header: added by $primary_hostname\n\
36614 X-added-second: another added header line
36616 Exim does not check the syntax of these added header lines.
36618 Multiple &%headers_add%& options for a single router or transport can be
36619 specified; the values will append to a single list of header lines.
36620 Each header-line is separately expanded.
36622 The argument of a &%headers_remove%& option must consist of a colon-separated
36623 list of header names. This is confusing, because header names themselves are
36624 often terminated by colons. In this case, the colons are the list separators,
36625 not part of the names. For example:
36627 headers_remove = return-receipt-to:acknowledge-to
36630 Multiple &%headers_remove%& options for a single router or transport can be
36631 specified; the arguments will append to a single header-names list.
36632 Each item is separately expanded.
36633 Note that colons in complex expansions which are used to
36634 form all or part of a &%headers_remove%& list
36635 will act as list separators.
36637 When &%headers_add%& or &%headers_remove%& is specified on a router,
36638 items are expanded at routing time,
36639 and then associated with all addresses that are
36640 accepted by that router, and also with any new addresses that it generates. If
36641 an address passes through several routers as a result of aliasing or
36642 forwarding, the changes are cumulative.
36644 .oindex "&%unseen%&"
36645 However, this does not apply to multiple routers that result from the use of
36646 the &%unseen%& option. Any header modifications that were specified by the
36647 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
36649 Addresses that end up with different &%headers_add%& or &%headers_remove%&
36650 settings cannot be delivered together in a batch, so a transport is always
36651 dealing with a set of addresses that have the same header-processing
36654 The transport starts by writing the original set of header lines that arrived
36655 with the message, possibly modified by the system filter. As it writes out
36656 these lines, it consults the list of header names that were attached to the
36657 recipient address(es) by &%headers_remove%& options in routers, and it also
36658 consults the transport's own &%headers_remove%& option. Header lines whose
36659 names are on either of these lists are not written out. If there are multiple
36660 instances of any listed header, they are all skipped.
36662 After the remaining original header lines have been written, new header
36663 lines that were specified by routers' &%headers_add%& options are written, in
36664 the order in which they were attached to the address. These are followed by any
36665 header lines specified by the transport's &%headers_add%& option.
36667 This way of handling header line modifications in routers and transports has
36668 the following consequences:
36671 The original set of header lines, possibly modified by the system filter,
36672 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
36673 to it, at all times.
36675 Header lines that are added by a router's
36676 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
36677 expansion syntax in subsequent routers or the transport.
36679 Conversely, header lines that are specified for removal by &%headers_remove%&
36680 in a router remain visible to subsequent routers and the transport.
36682 Headers added to an address by &%headers_add%& in a router cannot be removed by
36683 a later router or by a transport.
36685 An added header can refer to the contents of an original header that is to be
36686 removed, even it has the same name as the added header. For example:
36688 headers_remove = subject
36689 headers_add = Subject: new subject (was: $h_subject:)
36693 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
36694 for a &(redirect)& router that has the &%one_time%& option set.
36700 .section "Constructed addresses" "SECTconstr"
36701 .cindex "address" "constructed"
36702 .cindex "constructed address"
36703 When Exim constructs a sender address for a locally-generated message, it uses
36706 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
36710 Zaphod Beeblebrox <zaphod@end.univ.example>
36712 The user name is obtained from the &%-F%& command line option if set, or
36713 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
36714 &"gecos"& field from the password entry. If the &"gecos"& field contains an
36715 ampersand character, this is replaced by the login name with the first letter
36716 upper cased, as is conventional in a number of operating systems. See the
36717 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
36718 The &%unknown_username%& option can be used to specify user names in cases when
36719 there is no password file entry.
36722 In all cases, the user name is made to conform to RFC 2822 by quoting all or
36723 parts of it if necessary. In addition, if it contains any non-printing
36724 characters, it is encoded as described in RFC 2047, which defines a way of
36725 including non-ASCII characters in header lines. The value of the
36726 &%headers_charset%& option specifies the name of the encoding that is used (the
36727 characters are assumed to be in this encoding). The setting of
36728 &%print_topbitchars%& controls whether characters with the top bit set (that
36729 is, with codes greater than 127) count as printing characters or not.
36733 .section "Case of local parts" "SECID230"
36734 .cindex "case of local parts"
36735 .cindex "local part" "case of"
36736 RFC 2822 states that the case of letters in the local parts of addresses cannot
36737 be assumed to be non-significant. Exim preserves the case of local parts of
36738 addresses, but by default it uses a lower-cased form when it is routing,
36739 because on most Unix systems, usernames are in lower case and case-insensitive
36740 routing is required. However, any particular router can be made to use the
36741 original case for local parts by setting the &%caseful_local_part%& generic
36744 .cindex "mixed-case login names"
36745 If you must have mixed-case user names on your system, the best way to proceed,
36746 assuming you want case-independent handling of incoming email, is to set up
36747 your first router to convert incoming local parts in your domains to the
36748 correct case by means of a file lookup. For example:
36752 domains = +local_domains
36753 data = ${lookup{$local_part}cdb\
36754 {/etc/usercased.cdb}{$value}fail}\
36757 For this router, the local part is forced to lower case by the default action
36758 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
36759 up a new local part in the correct case. If you then set &%caseful_local_part%&
36760 on any subsequent routers which process your domains, they will operate on
36761 local parts with the correct case in a case-sensitive manner.
36765 .section "Dots in local parts" "SECID231"
36766 .cindex "dot" "in local part"
36767 .cindex "local part" "dots in"
36768 RFC 2822 forbids empty components in local parts. That is, an unquoted local
36769 part may not begin or end with a dot, nor have two consecutive dots in the
36770 middle. However, it seems that many MTAs do not enforce this, so Exim permits
36771 empty components for compatibility.
36775 .section "Rewriting addresses" "SECID232"
36776 .cindex "rewriting" "addresses"
36777 Rewriting of sender and recipient addresses, and addresses in headers, can
36778 happen automatically, or as the result of configuration options, as described
36779 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
36780 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
36782 Automatic rewriting includes qualification, as mentioned above. The other case
36783 in which it can happen is when an incomplete non-local domain is given. The
36784 routing process may cause this to be expanded into the full domain name. For
36785 example, a header such as
36789 might get rewritten as
36791 To: hare@teaparty.wonderland.fict.example
36793 Rewriting as a result of routing is the one kind of message processing that
36794 does not happen at input time, as it cannot be done until the address has
36797 Strictly, one should not do &'any'& deliveries of a message until all its
36798 addresses have been routed, in case any of the headers get changed as a
36799 result of routing. However, doing this in practice would hold up many
36800 deliveries for unreasonable amounts of time, just because one address could not
36801 immediately be routed. Exim therefore does not delay other deliveries when
36802 routing of one or more addresses is deferred.
36803 .ecindex IIDmesproc
36807 . ////////////////////////////////////////////////////////////////////////////
36808 . ////////////////////////////////////////////////////////////////////////////
36810 .chapter "SMTP processing" "CHAPSMTP"
36811 .scindex IIDsmtpproc1 "SMTP" "processing details"
36812 .scindex IIDsmtpproc2 "LMTP" "processing details"
36813 Exim supports a number of different ways of using the SMTP protocol, and its
36814 LMTP variant, which is an interactive protocol for transferring messages into a
36815 closed mail store application. This chapter contains details of how SMTP is
36816 processed. For incoming mail, the following are available:
36819 SMTP over TCP/IP (Exim daemon or &'inetd'&);
36821 SMTP over the standard input and output (the &%-bs%& option);
36823 Batched SMTP on the standard input (the &%-bS%& option).
36826 For mail delivery, the following are available:
36829 SMTP over TCP/IP (the &(smtp)& transport);
36831 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
36834 LMTP over a pipe to a process running in the local host (the &(lmtp)&
36837 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
36838 the &%use_bsmtp%& option set).
36841 &'Batched SMTP'& is the name for a process in which batches of messages are
36842 stored in or read from files (or pipes), in a format in which SMTP commands are
36843 used to contain the envelope information.
36847 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
36848 .cindex "SMTP" "outgoing over TCP/IP"
36849 .cindex "outgoing SMTP over TCP/IP"
36850 .cindex "LMTP" "over TCP/IP"
36851 .cindex "outgoing LMTP over TCP/IP"
36854 .cindex "SIZE" "option on MAIL command"
36855 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
36856 The &%protocol%& option selects which protocol is to be used, but the actual
36857 processing is the same in both cases.
36859 .cindex "ESMTP extensions" SIZE
36860 If, in response to its EHLO command, Exim is told that the SIZE
36861 extension is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
36862 command. The value of <&'n'&> is the message size plus the value of the
36863 &%size_addition%& option (default 1024) to allow for additions to the message
36864 such as per-transport header lines, or changes made in a
36865 .cindex "transport" "filter"
36866 .cindex "filter" "transport filter"
36867 transport filter. If &%size_addition%& is set negative, the use of SIZE is
36870 If the remote server advertises support for PIPELINING, Exim uses the
36871 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
36872 required for the transaction.
36874 If the remote server advertises support for the STARTTLS command, and Exim
36875 was built to support TLS encryption, it tries to start a TLS session unless the
36876 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
36877 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
36878 is called for verification.
36880 If the remote server advertises support for the AUTH command, Exim scans
36881 the authenticators configuration for any suitable client settings, as described
36882 in chapter &<<CHAPSMTPAUTH>>&.
36884 .cindex "carriage return"
36886 Responses from the remote host are supposed to be terminated by CR followed by
36887 LF. However, there are known to be hosts that do not send CR characters, so in
36888 order to be able to interwork with such hosts, Exim treats LF on its own as a
36891 If a message contains a number of different addresses, all those with the same
36892 characteristics (for example, the same envelope sender) that resolve to the
36893 same set of hosts, in the same order, are sent in a single SMTP transaction,
36894 even if they are for different domains, unless there are more than the setting
36895 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
36896 they are split into groups containing no more than &%max_rcpt%&s addresses
36897 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
36898 in parallel sessions. The order of hosts with identical MX values is not
36899 significant when checking whether addresses can be batched in this way.
36901 When the &(smtp)& transport suffers a temporary failure that is not
36902 message-related, Exim updates its transport-specific database, which contains
36903 records indexed by host name that remember which messages are waiting for each
36904 particular host. It also updates the retry database with new retry times.
36906 .cindex "hints database" "retry keys"
36907 Exim's retry hints are based on host name plus IP address, so if one address of
36908 a multi-homed host is broken, it will soon be skipped most of the time.
36909 See the next section for more detail about error handling.
36911 .cindex "SMTP" "passed connection"
36912 .cindex "SMTP" "batching over TCP/IP"
36913 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
36914 looks in the hints database for the transport to see if there are any queued
36915 messages waiting for the host to which it is connected. If it finds one, it
36916 creates a new Exim process using the &%-MC%& option (which can only be used by
36917 a process running as root or the Exim user) and passes the TCP/IP socket to it
36918 so that it can deliver another message using the same socket. The new process
36919 does only those deliveries that are routed to the connected host, and may in
36920 turn pass the socket on to a third process, and so on.
36922 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
36923 limit the number of messages sent down a single TCP/IP connection.
36925 .cindex "asterisk" "after IP address"
36926 The second and subsequent messages delivered down an existing connection are
36927 identified in the main log by the addition of an asterisk after the closing
36928 square bracket of the IP address.
36933 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
36934 .cindex "error" "in outgoing SMTP"
36935 .cindex "SMTP" "errors in outgoing"
36936 .cindex "host" "error"
36937 Three different kinds of error are recognized for outgoing SMTP: host errors,
36938 message errors, and recipient errors.
36941 .vitem "&*Host errors*&"
36942 A host error is not associated with a particular message or with a
36943 particular recipient of a message. The host errors are:
36946 Connection refused or timed out,
36948 Any error response code on connection,
36950 Any error response code to EHLO or HELO,
36952 Loss of connection at any time, except after &"."&,
36954 I/O errors at any time,
36956 Timeouts during the session, other than in response to MAIL, RCPT or
36957 the &"."& at the end of the data.
36960 For a host error, a permanent error response on connection, or in response to
36961 EHLO, causes all addresses routed to the host to be failed. Any other host
36962 error causes all addresses to be deferred, and retry data to be created for the
36963 host. It is not tried again, for any message, until its retry time arrives. If
36964 the current set of addresses are not all delivered in this run (to some
36965 alternative host), the message is added to the list of those waiting for this
36966 host, so if it is still undelivered when a subsequent successful delivery is
36967 made to the host, it will be sent down the same SMTP connection.
36969 .vitem "&*Message errors*&"
36970 .cindex "message" "error"
36971 A message error is associated with a particular message when sent to a
36972 particular host, but not with a particular recipient of the message. The
36973 message errors are:
36976 Any error response code to MAIL, DATA, or the &"."& that terminates
36979 Timeout after MAIL,
36981 Timeout or loss of connection after the &"."& that terminates the data. A
36982 timeout after the DATA command itself is treated as a host error, as is loss of
36983 connection at any other time.
36986 For a message error, a permanent error response (5&'xx'&) causes all addresses
36987 to be failed, and a delivery error report to be returned to the sender. A
36988 temporary error response (4&'xx'&), or one of the timeouts, causes all
36989 addresses to be deferred. Retry data is not created for the host, but instead,
36990 a retry record for the combination of host plus message id is created. The
36991 message is not added to the list of those waiting for this host. This ensures
36992 that the failing message will not be sent to this host again until the retry
36993 time arrives. However, other messages that are routed to the host are not
36994 affected, so if it is some property of the message that is causing the error,
36995 it will not stop the delivery of other mail.
36997 If the remote host specified support for the SIZE parameter in its response
36998 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
36999 over-large message will cause a message error because the error arrives as a
37002 .vitem "&*Recipient errors*&"
37003 .cindex "recipient" "error"
37004 A recipient error is associated with a particular recipient of a message. The
37005 recipient errors are:
37008 Any error response to RCPT,
37010 Timeout after RCPT.
37013 For a recipient error, a permanent error response (5&'xx'&) causes the
37014 recipient address to be failed, and a bounce message to be returned to the
37015 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
37016 address to be deferred, and routing retry data to be created for it. This is
37017 used to delay processing of the address in subsequent queue runs, until its
37018 routing retry time arrives. This applies to all messages, but because it
37019 operates only in queue runs, one attempt will be made to deliver a new message
37020 to the failing address before the delay starts to operate. This ensures that,
37021 if the failure is really related to the message rather than the recipient
37022 (&"message too big for this recipient"& is a possible example), other messages
37023 have a chance of getting delivered. If a delivery to the address does succeed,
37024 the retry information gets cleared, so all stuck messages get tried again, and
37025 the retry clock is reset.
37027 The message is not added to the list of those waiting for this host. Use of the
37028 host for other messages is unaffected, and except in the case of a timeout,
37029 other recipients are processed independently, and may be successfully delivered
37030 in the current SMTP session. After a timeout it is of course impossible to
37031 proceed with the session, so all addresses get deferred. However, those other
37032 than the one that failed do not suffer any subsequent retry delays. Therefore,
37033 if one recipient is causing trouble, the others have a chance of getting
37034 through when a subsequent delivery attempt occurs before the failing
37035 recipient's retry time.
37038 In all cases, if there are other hosts (or IP addresses) available for the
37039 current set of addresses (for example, from multiple MX records), they are
37040 tried in this run for any undelivered addresses, subject of course to their
37041 own retry data. In other words, recipient error retry data does not take effect
37042 until the next delivery attempt.
37044 Some hosts have been observed to give temporary error responses to every
37045 MAIL command at certain times (&"insufficient space"& has been seen). It
37046 would be nice if such circumstances could be recognized, and defer data for the
37047 host itself created, but this is not possible within the current Exim design.
37048 What actually happens is that retry data for every (host, message) combination
37051 The reason that timeouts after MAIL and RCPT are treated specially is that
37052 these can sometimes arise as a result of the remote host's verification
37053 procedures. Exim makes this assumption, and treats them as if a temporary error
37054 response had been received. A timeout after &"."& is treated specially because
37055 it is known that some broken implementations fail to recognize the end of the
37056 message if the last character of the last line is a binary zero. Thus, it is
37057 helpful to treat this case as a message error.
37059 Timeouts at other times are treated as host errors, assuming a problem with the
37060 host, or the connection to it. If a timeout after MAIL, RCPT,
37061 or &"."& is really a connection problem, the assumption is that at the next try
37062 the timeout is likely to occur at some other point in the dialogue, causing it
37063 then to be treated as a host error.
37065 There is experimental evidence that some MTAs drop the connection after the
37066 terminating &"."& if they do not like the contents of the message for some
37067 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
37068 should be given. That is why Exim treats this case as a message rather than a
37069 host error, in order not to delay other messages to the same host.
37074 .section "Incoming SMTP messages over TCP/IP" "SECID233"
37075 .cindex "SMTP" "incoming over TCP/IP"
37076 .cindex "incoming SMTP over TCP/IP"
37079 Incoming SMTP messages can be accepted in one of two ways: by running a
37080 listening daemon, or by using &'inetd'&. In the latter case, the entry in
37081 &_/etc/inetd.conf_& should be like this:
37083 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
37085 Exim distinguishes between this case and the case of a locally running user
37086 agent using the &%-bs%& option by checking whether or not the standard input is
37087 a socket. When it is, either the port must be privileged (less than 1024), or
37088 the caller must be root or the Exim user. If any other user passes a socket
37089 with an unprivileged port number, Exim prints a message on the standard error
37090 stream and exits with an error code.
37092 By default, Exim does not make a log entry when a remote host connects or
37093 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
37094 unexpected. It can be made to write such log entries by setting the
37095 &%smtp_connection%& log selector.
37097 .cindex "carriage return"
37099 Commands from the remote host are supposed to be terminated by CR followed by
37100 LF. However, there are known to be hosts that do not send CR characters. In
37101 order to be able to interwork with such hosts, Exim treats LF on its own as a
37103 Furthermore, because common code is used for receiving messages from all
37104 sources, a CR on its own is also interpreted as a line terminator. However, the
37105 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
37107 .cindex "EHLO" "invalid data"
37108 .cindex "HELO" "invalid data"
37109 One area that sometimes gives rise to problems concerns the EHLO or
37110 HELO commands. Some clients send syntactically invalid versions of these
37111 commands, which Exim rejects by default. (This is nothing to do with verifying
37112 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
37113 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
37114 match the broken hosts that send invalid commands.
37116 .cindex "SIZE option on MAIL command"
37117 .cindex "MAIL" "SIZE option"
37118 The amount of disk space available is checked whenever SIZE is received on
37119 a MAIL command, independently of whether &%message_size_limit%& or
37120 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
37121 false. A temporary error is given if there is not enough space. If
37122 &%check_spool_space%& is set, the check is for that amount of space plus the
37123 value given with SIZE, that is, it checks that the addition of the incoming
37124 message will not reduce the space below the threshold.
37126 When a message is successfully received, Exim includes the local message id in
37127 its response to the final &"."& that terminates the data. If the remote host
37128 logs this text it can help with tracing what has happened to a message.
37130 The Exim daemon can limit the number of simultaneous incoming connections it is
37131 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
37132 number of simultaneous incoming connections from a single remote host (see the
37133 &%smtp_accept_max_per_host%& option). Additional connection attempts are
37134 rejected using the SMTP temporary error code 421.
37136 The Exim daemon does not rely on the SIGCHLD signal to detect when a
37137 subprocess has finished, as this can get lost at busy times. Instead, it looks
37138 for completed subprocesses every time it wakes up. Provided there are other
37139 things happening (new incoming calls, starts of queue runs), completed
37140 processes will be noticed and tidied away. On very quiet systems you may
37141 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
37142 it will be noticed when the daemon next wakes up.
37144 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
37145 and can also be set up to reject SMTP calls from non-reserved hosts at times of
37146 high system load &-- for details see the &%smtp_accept_reserve%&,
37147 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
37148 applies in both the daemon and &'inetd'& cases.
37150 Exim normally starts a delivery process for each message received, though this
37151 can be varied by means of the &%-odq%& command line option and the
37152 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
37153 number of simultaneously running delivery processes started in this way from
37154 SMTP input can be limited by the &%smtp_accept_queue%& and
37155 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
37156 subsequently received messages are just put on the input queue without starting
37157 a delivery process.
37159 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
37160 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
37161 started up from the &'inetd'& daemon, because in that case each connection is
37162 handled by an entirely independent Exim process. Control by load average is,
37163 however, available with &'inetd'&.
37165 Exim can be configured to verify addresses in incoming SMTP commands as they
37166 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
37167 to rewrite addresses at this time &-- before any syntax checking is done. See
37168 section &<<SECTrewriteS>>&.
37170 Exim can also be configured to limit the rate at which a client host submits
37171 MAIL and RCPT commands in a single SMTP session. See the
37172 &%smtp_ratelimit_hosts%& option.
37176 .section "Unrecognized SMTP commands" "SECID234"
37177 .cindex "SMTP" "unrecognized commands"
37178 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
37179 commands during a single SMTP connection, it drops the connection after sending
37180 the error response to the last command. The default value for
37181 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
37182 abuse that subvert web servers into making connections to SMTP ports; in these
37183 circumstances, a number of non-SMTP lines are sent first.
37186 .section "Syntax and protocol errors in SMTP commands" "SECID235"
37187 .cindex "SMTP" "syntax errors"
37188 .cindex "SMTP" "protocol errors"
37189 A syntax error is detected if an SMTP command is recognized, but there is
37190 something syntactically wrong with its data, for example, a malformed email
37191 address in a RCPT command. Protocol errors include invalid command
37192 sequencing such as RCPT before MAIL. If Exim receives more than
37193 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
37194 drops the connection after sending the error response to the last command. The
37195 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
37196 broken clients that loop sending bad commands (yes, it has been seen).
37200 .section "Use of non-mail SMTP commands" "SECID236"
37201 .cindex "SMTP" "non-mail commands"
37202 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
37203 DATA. Exim counts such commands, and drops the connection if there are too
37204 many of them in a single SMTP session. This action catches some
37205 denial-of-service attempts and things like repeated failing AUTHs, or a mad
37206 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
37207 defines what &"too many"& means. Its default value is 10.
37209 When a new message is expected, one occurrence of RSET is not counted. This
37210 allows a client to send one RSET between messages (this is not necessary,
37211 but some clients do it). Exim also allows one uncounted occurrence of HELO
37212 or EHLO, and one occurrence of STARTTLS between messages. After
37213 starting up a TLS session, another EHLO is expected, and so it too is not
37216 The first occurrence of AUTH in a connection, or immediately following
37217 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
37218 RCPT, DATA, and QUIT are counted.
37220 You can control which hosts are subject to the limit set by
37221 &%smtp_accept_max_nonmail%& by setting
37222 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
37223 the limit apply to all hosts. This option means that you can exclude any
37224 specific badly-behaved hosts that you have to live with.
37229 .section "The VRFY and EXPN commands" "SECID237"
37230 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
37231 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
37232 appropriate) in order to decide whether the command should be accepted or not.
37234 .cindex "VRFY" "processing"
37235 When no ACL is defined for VRFY, or if it rejects without
37236 setting an explicit response code, the command is accepted
37237 (with a 252 SMTP response code)
37238 in order to support awkward clients that do a VRFY before every RCPT.
37239 When VRFY is accepted, it runs exactly the same code as when Exim is
37240 called with the &%-bv%& option, and returns 250/451/550
37241 SMTP response codes.
37243 .cindex "EXPN" "processing"
37244 If no ACL for EXPN is defined, the command is rejected.
37245 When EXPN is accepted, a single-level expansion of the address is done.
37246 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
37247 than a verification (the &%-bv%& option). If an unqualified local part is given
37248 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
37249 of VRFY and EXPN commands are logged on the main and reject logs, and
37250 VRFY verification failures are logged on the main log for consistency with
37255 .section "The ETRN command" "SECTETRN"
37256 .cindex "ETRN" "processing"
37257 .cindex "ESMTP extensions" ETRN
37258 RFC 1985 describes an ESMTP command called ETRN that is designed to
37259 overcome the security problems of the TURN command (which has fallen into
37260 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
37261 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
37262 should be accepted or not. If no ACL is defined, the command is rejected.
37264 The ETRN command is concerned with &"releasing"& messages that are awaiting
37265 delivery to certain hosts. As Exim does not organize its message queue by host,
37266 the only form of ETRN that is supported by default is the one where the
37267 text starts with the &"#"& prefix, in which case the remainder of the text is
37268 specific to the SMTP server. A valid ETRN command causes a run of Exim with
37269 the &%-R%& option to happen, with the remainder of the ETRN text as its
37270 argument. For example,
37278 which causes a delivery attempt on all messages with undelivered addresses
37279 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
37280 default), Exim prevents the simultaneous execution of more than one queue run
37281 for the same argument string as a result of an ETRN command. This stops
37282 a misbehaving client from starting more than one queue runner at once.
37284 .cindex "hints database" "ETRN serialization"
37285 Exim implements the serialization by means of a hints database in which a
37286 record is written whenever a process is started by ETRN, and deleted when
37287 the process completes. However, Exim does not keep the SMTP session waiting for
37288 the ETRN process to complete. Once ETRN is accepted, the client is sent
37289 a &"success"& return code. Obviously there is scope for hints records to get
37290 left lying around if there is a system or program crash. To guard against this,
37291 Exim ignores any records that are more than six hours old.
37293 .oindex "&%smtp_etrn_command%&"
37294 For more control over what ETRN does, the &%smtp_etrn_command%& option can
37295 used. This specifies a command that is run whenever ETRN is received,
37296 whatever the form of its argument. For
37299 smtp_etrn_command = /etc/etrn_command $domain \
37300 $sender_host_address
37302 .vindex "&$domain$&"
37303 The string is split up into arguments which are independently expanded. The
37304 expansion variable &$domain$& is set to the argument of the ETRN command,
37305 and no syntax checking is done on the contents of this argument. Exim does not
37306 wait for the command to complete, so its status code is not checked. Exim runs
37307 under its own uid and gid when receiving incoming SMTP, so it is not possible
37308 for it to change them before running the command.
37312 .section "Incoming local SMTP" "SECID238"
37313 .cindex "SMTP" "local incoming"
37314 Some user agents use SMTP to pass messages to their local MTA using the
37315 standard input and output, as opposed to passing the envelope on the command
37316 line and writing the message to the standard input. This is supported by the
37317 &%-bs%& option. This form of SMTP is handled in the same way as incoming
37318 messages over TCP/IP (including the use of ACLs), except that the envelope
37319 sender given in a MAIL command is ignored unless the caller is trusted. In
37320 an ACL you can detect this form of SMTP input by testing for an empty host
37321 identification. It is common to have this as the first line in the ACL that
37322 runs for RCPT commands:
37326 This accepts SMTP messages from local processes without doing any other tests.
37330 .section "Outgoing batched SMTP" "SECTbatchSMTP"
37331 .cindex "SMTP" "batched outgoing"
37332 .cindex "batched SMTP output"
37333 Both the &(appendfile)& and &(pipe)& transports can be used for handling
37334 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
37335 be output in BSMTP format. No SMTP responses are possible for this form of
37336 delivery. All it is doing is using SMTP commands as a way of transmitting the
37337 envelope along with the message.
37339 The message is written to the file or pipe preceded by the SMTP commands
37340 MAIL and RCPT, and followed by a line containing a single dot. Lines in
37341 the message that start with a dot have an extra dot added. The SMTP command
37342 HELO is not normally used. If it is required, the &%message_prefix%& option
37343 can be used to specify it.
37345 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
37346 one recipient address at a time by default. However, you can arrange for them
37347 to handle several addresses at once by setting the &%batch_max%& option. When
37348 this is done for BSMTP, messages may contain multiple RCPT commands. See
37349 chapter &<<CHAPbatching>>& for more details.
37352 When one or more addresses are routed to a BSMTP transport by a router that
37353 sets up a host list, the name of the first host on the list is available to the
37354 transport in the variable &$host$&. Here is an example of such a transport and
37359 driver = manualroute
37360 transport = smtp_appendfile
37361 route_list = domain.example batch.host.example
37365 driver = appendfile
37366 directory = /var/bsmtp/$host
37371 This causes messages addressed to &'domain.example'& to be written in BSMTP
37372 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
37373 message (unless there are more than 1000 recipients).
37377 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
37378 .cindex "SMTP" "batched incoming"
37379 .cindex "batched SMTP input"
37380 The &%-bS%& command line option causes Exim to accept one or more messages by
37381 reading SMTP on the standard input, but to generate no responses. If the caller
37382 is trusted, the senders in the MAIL commands are believed; otherwise the
37383 sender is always the caller of Exim. Unqualified senders and receivers are not
37384 rejected (there seems little point) but instead just get qualified. HELO
37385 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
37386 as NOOP; QUIT quits.
37388 Minimal policy checking is done for BSMTP input. Only the non-SMTP
37389 ACL is run in the same way as for non-SMTP local input.
37391 If an error is detected while reading a message, including a missing &"."& at
37392 the end, Exim gives up immediately. It writes details of the error to the
37393 standard output in a stylized way that the calling program should be able to
37394 make some use of automatically, for example:
37396 554 Unexpected end of file
37397 Transaction started in line 10
37398 Error detected in line 14
37400 It writes a more verbose version, for human consumption, to the standard error
37403 An error was detected while processing a file of BSMTP input.
37404 The error message was:
37406 501 '>' missing at end of address
37408 The SMTP transaction started in line 10.
37409 The error was detected in line 12.
37410 The SMTP command at fault was:
37412 rcpt to:<malformed@in.com.plete
37414 1 previous message was successfully processed.
37415 The rest of the batch was abandoned.
37417 The return code from Exim is zero only if there were no errors. It is 1 if some
37418 messages were accepted before an error was detected, and 2 if no messages were
37420 .ecindex IIDsmtpproc1
37421 .ecindex IIDsmtpproc2
37425 . ////////////////////////////////////////////////////////////////////////////
37426 . ////////////////////////////////////////////////////////////////////////////
37428 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
37429 "Customizing messages"
37430 When a message fails to be delivered, or remains in the queue for more than a
37431 configured amount of time, Exim sends a message to the original sender, or
37432 to an alternative configured address. The text of these messages is built into
37433 the code of Exim, but it is possible to change it, either by adding a single
37434 string, or by replacing each of the paragraphs by text supplied in a file.
37436 The &'From:'& and &'To:'& header lines are automatically generated; you can
37437 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
37438 option. Exim also adds the line
37440 Auto-Submitted: auto-generated
37442 to all warning and bounce messages,
37445 .section "Customizing bounce messages" "SECID239"
37446 .cindex "customizing" "bounce message"
37447 .cindex "bounce message" "customizing"
37448 If &%bounce_message_text%& is set, its contents are included in the default
37449 message immediately after &"This message was created automatically by mail
37450 delivery software."& The string is not expanded. It is not used if
37451 &%bounce_message_file%& is set.
37453 When &%bounce_message_file%& is set, it must point to a template file for
37454 constructing error messages. The file consists of a series of text items,
37455 separated by lines consisting of exactly four asterisks. If the file cannot be
37456 opened, default text is used and a message is written to the main and panic
37457 logs. If any text item in the file is empty, default text is used for that
37460 .vindex "&$bounce_recipient$&"
37461 .vindex "&$bounce_return_size_limit$&"
37462 Each item of text that is read from the file is expanded, and there are two
37463 expansion variables which can be of use here: &$bounce_recipient$& is set to
37464 the recipient of an error message while it is being created, and
37465 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
37466 option, rounded to a whole number.
37468 The items must appear in the file in the following order:
37471 The first item is included in the headers, and should include at least a
37472 &'Subject:'& header. Exim does not check the syntax of these headers.
37474 The second item forms the start of the error message. After it, Exim lists the
37475 failing addresses with their error messages.
37477 The third item is used to introduce any text from pipe transports that is to be
37478 returned to the sender. It is omitted if there is no such text.
37480 The fourth, fifth and sixth items will be ignored and may be empty.
37481 The fields exist for back-compatibility
37484 The default state (&%bounce_message_file%& unset) is equivalent to the
37485 following file, in which the sixth item is empty. The &'Subject:'& and some
37486 other lines have been split in order to fit them on the page:
37488 Subject: Mail delivery failed
37489 ${if eq{$sender_address}{$bounce_recipient}
37490 {: returning message to sender}}
37492 This message was created automatically by mail delivery software.
37494 A message ${if eq{$sender_address}{$bounce_recipient}
37495 {that you sent }{sent by
37499 }}could not be delivered to all of its recipients.
37500 This is a permanent error. The following address(es) failed:
37502 The following text was generated during the delivery attempt(s):
37504 ------ This is a copy of the message, including all the headers.
37507 ------ The body of the message is $message_size characters long;
37509 ------ $bounce_return_size_limit or so are included here.
37512 .section "Customizing warning messages" "SECTcustwarn"
37513 .cindex "customizing" "warning message"
37514 .cindex "warning of delay" "customizing the message"
37515 The option &%warn_message_file%& can be pointed at a template file for use when
37516 warnings about message delays are created. In this case there are only three
37520 The first item is included in the headers, and should include at least a
37521 &'Subject:'& header. Exim does not check the syntax of these headers.
37523 The second item forms the start of the warning message. After it, Exim lists
37524 the delayed addresses.
37526 The third item then ends the message.
37529 The default state is equivalent to the following file, except that some lines
37530 have been split here, in order to fit them on the page:
37532 Subject: Warning: message $message_exim_id delayed
37533 $warn_message_delay
37535 This message was created automatically by mail delivery software.
37537 A message ${if eq{$sender_address}{$warn_message_recipients}
37538 {that you sent }{sent by
37542 }}has not been delivered to all of its recipients after
37543 more than $warn_message_delay in the queue on $primary_hostname.
37545 The message identifier is: $message_exim_id
37546 The subject of the message is: $h_subject
37547 The date of the message is: $h_date
37549 The following address(es) have not yet been delivered:
37551 No action is required on your part. Delivery attempts will
37552 continue for some time, and this warning may be repeated at
37553 intervals if the message remains undelivered. Eventually the
37554 mail delivery software will give up, and when that happens,
37555 the message will be returned to you.
37557 .vindex "&$warn_message_delay$&"
37558 .vindex "&$warn_message_recipients$&"
37559 However, in the default state the subject and date lines are omitted if no
37560 appropriate headers exist. During the expansion of this file,
37561 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
37562 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
37563 of recipients for the warning message. There may be more than one if there are
37564 multiple addresses with different &%errors_to%& settings on the routers that
37570 . ////////////////////////////////////////////////////////////////////////////
37571 . ////////////////////////////////////////////////////////////////////////////
37573 .chapter "Some common configuration settings" "CHAPcomconreq"
37574 This chapter discusses some configuration settings that seem to be fairly
37575 common. More examples and discussion can be found in the Exim book.
37579 .section "Sending mail to a smart host" "SECID240"
37580 .cindex "smart host" "example router"
37581 If you want to send all mail for non-local domains to a &"smart host"&, you
37582 should replace the default &(dnslookup)& router with a router which does the
37583 routing explicitly:
37585 send_to_smart_host:
37586 driver = manualroute
37587 route_list = !+local_domains smart.host.name
37588 transport = remote_smtp
37590 You can use the smart host's IP address instead of the name if you wish.
37591 If you are using Exim only to submit messages to a smart host, and not for
37592 receiving incoming messages, you can arrange for it to do the submission
37593 synchronously by setting the &%mua_wrapper%& option (see chapter
37594 &<<CHAPnonqueueing>>&).
37599 .section "Using Exim to handle mailing lists" "SECTmailinglists"
37600 .cindex "mailing lists"
37601 Exim can be used to run simple mailing lists, but for large and/or complicated
37602 requirements, the use of additional specialized mailing list software such as
37603 Majordomo or Mailman is recommended.
37605 The &(redirect)& router can be used to handle mailing lists where each list
37606 is maintained in a separate file, which can therefore be managed by an
37607 independent manager. The &%domains%& router option can be used to run these
37608 lists in a separate domain from normal mail. For example:
37612 domains = lists.example
37613 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37616 errors_to = ${quote_local_part:$local_part-request}@lists.example
37619 This router is skipped for domains other than &'lists.example'&. For addresses
37620 in that domain, it looks for a file that matches the local part. If there is no
37621 such file, the router declines, but because &%no_more%& is set, no subsequent
37622 routers are tried, and so the whole delivery fails.
37624 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
37625 expanded into a filename or a pipe delivery, which is usually inappropriate in
37628 .oindex "&%errors_to%&"
37629 The &%errors_to%& option specifies that any delivery errors caused by addresses
37630 taken from a mailing list are to be sent to the given address rather than the
37631 original sender of the message. However, before acting on this, Exim verifies
37632 the error address, and ignores it if verification fails.
37634 For example, using the configuration above, mail sent to
37635 &'dicts@lists.example'& is passed on to those addresses contained in
37636 &_/usr/lists/dicts_&, with error reports directed to
37637 &'dicts-request@lists.example'&, provided that this address can be verified.
37638 There could be a file called &_/usr/lists/dicts-request_& containing
37639 the address(es) of this particular list's manager(s), but other approaches,
37640 such as setting up an earlier router (possibly using the &%local_part_prefix%&
37641 or &%local_part_suffix%& options) to handle addresses of the form
37642 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
37646 .section "Syntax errors in mailing lists" "SECID241"
37647 .cindex "mailing lists" "syntax errors in"
37648 If an entry in redirection data contains a syntax error, Exim normally defers
37649 delivery of the original address. That means that a syntax error in a mailing
37650 list holds up all deliveries to the list. This may not be appropriate when a
37651 list is being maintained automatically from data supplied by users, and the
37652 addresses are not rigorously checked.
37654 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
37655 entries that fail to parse, noting the incident in the log. If in addition
37656 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
37657 whenever a broken address is skipped. It is usually appropriate to set
37658 &%syntax_errors_to%& to the same address as &%errors_to%&.
37662 .section "Re-expansion of mailing lists" "SECID242"
37663 .cindex "mailing lists" "re-expansion of"
37664 Exim remembers every individual address to which a message has been delivered,
37665 in order to avoid duplication, but it normally stores only the original
37666 recipient addresses with a message. If all the deliveries to a mailing list
37667 cannot be done at the first attempt, the mailing list is re-expanded when the
37668 delivery is next tried. This means that alterations to the list are taken into
37669 account at each delivery attempt, so addresses that have been added to
37670 the list since the message arrived will therefore receive a copy of the
37671 message, even though it pre-dates their subscription.
37673 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
37674 on the &(redirect)& router. If this is done, any addresses generated by the
37675 router that fail to deliver at the first attempt are added to the message as
37676 &"top level"& addresses, and the parent address that generated them is marked
37677 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
37678 subsequent delivery attempts. The disadvantage of this is that if any of the
37679 failing addresses are incorrect, correcting them in the file has no effect on
37680 pre-existing messages.
37682 The original top-level address is remembered with each of the generated
37683 addresses, and is output in any log messages. However, any intermediate parent
37684 addresses are not recorded. This makes a difference to the log only if the
37685 &%all_parents%& selector is set, but for mailing lists there is normally only
37686 one level of expansion anyway.
37690 .section "Closed mailing lists" "SECID243"
37691 .cindex "mailing lists" "closed"
37692 The examples so far have assumed open mailing lists, to which anybody may
37693 send mail. It is also possible to set up closed lists, where mail is accepted
37694 from specified senders only. This is done by making use of the generic
37695 &%senders%& option to restrict the router that handles the list.
37697 The following example uses the same file as a list of recipients and as a list
37698 of permitted senders. It requires three routers:
37702 domains = lists.example
37703 local_part_suffix = -request
37704 local_parts = ${lookup {$local_part} dsearch,filter=file {/usr/lists}}
37705 file = /usr/lists/${local_part_data}-request
37710 domains = lists.example
37711 local_parts = ${lookup {$local_part} dsearch,filter=file,ret=full {/usr/lists}}
37712 senders = ${if exists {$local_part_data} {lsearch;$local_part_data}{*}}
37713 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37716 errors_to = ${quote_local_part:$local_part-request}@lists.example
37721 domains = lists.example
37723 data = :fail: $local_part@lists.example is a closed mailing list
37725 All three routers have the same &%domains%& setting, so for any other domains,
37726 they are all skipped. The first router runs only if the local part ends in
37727 &%-request%&. It handles messages to the list manager(s) by means of an open
37730 The second router runs only if the &%senders%& precondition is satisfied. It
37731 checks for the existence of a list that corresponds to the local part, and then
37732 checks that the sender is on the list by means of a linear search. It is
37733 necessary to check for the existence of the file before trying to search it,
37734 because otherwise Exim thinks there is a configuration error. If the file does
37735 not exist, the expansion of &%senders%& is *, which matches all senders. This
37736 means that the router runs, but because there is no list, declines, and
37737 &%no_more%& ensures that no further routers are run. The address fails with an
37738 &"unrouteable address"& error.
37740 The third router runs only if the second router is skipped, which happens when
37741 a mailing list exists, but the sender is not on it. This router forcibly fails
37742 the address, giving a suitable error message.
37747 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
37749 .cindex "Variable Envelope Return Paths"
37750 .cindex "envelope from"
37751 .cindex "envelope sender"
37752 Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
37753 are a way of helping mailing list administrators discover which subscription
37754 address is the cause of a particular delivery failure. The idea is to encode
37755 the original recipient address in the outgoing envelope sender address, so that
37756 if the message is forwarded by another host and then subsequently bounces, the
37757 original recipient can be extracted from the recipient address of the bounce.
37759 .oindex &%errors_to%&
37760 .oindex &%return_path%&
37761 Envelope sender addresses can be modified by Exim using two different
37762 facilities: the &%errors_to%& option on a router (as shown in previous mailing
37763 list examples), or the &%return_path%& option on a transport. The second of
37764 these is effective only if the message is successfully delivered to another
37765 host; it is not used for errors detected on the local host (see the description
37766 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
37767 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
37773 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37774 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37776 This has the effect of rewriting the return path (envelope sender) on outgoing
37777 SMTP messages, if the local part of the original return path ends in
37778 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
37779 local part and domain of the recipient into the return path. Suppose, for
37780 example, that a message whose return path has been set to
37781 &'somelist-request@your.dom.example'& is sent to
37782 &'subscriber@other.dom.example'&. In the transport, the return path is
37785 somelist-request+subscriber=other.dom.example@your.dom.example
37787 .vindex "&$local_part$&"
37788 For this to work, you must tell Exim to send multiple copies of messages that
37789 have more than one recipient, so that each copy has just one recipient. This is
37790 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
37791 might be sent to several different recipients in the same domain, in which case
37792 &$local_part$& is not available in the transport, because it is not unique.
37794 Unless your host is doing nothing but mailing list deliveries, you should
37795 probably use a separate transport for the VERP deliveries, so as not to use
37796 extra resources in making one-per-recipient copies for other deliveries. This
37797 can easily be done by expanding the &%transport%& option in the router:
37801 domains = ! +local_domains
37803 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37804 {verp_smtp}{remote_smtp}}
37807 If you want to change the return path using &%errors_to%& in a router instead
37808 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
37809 routers that handle mailing list addresses. This will ensure that all delivery
37810 errors, including those detected on the local host, are sent to the VERP
37813 On a host that does no local deliveries and has no manual routing, only the
37814 &(dnslookup)& router needs to be changed. A special transport is not needed for
37815 SMTP deliveries. Every mailing list recipient has its own return path value,
37816 and so Exim must hand them to the transport one at a time. Here is an example
37817 of a &(dnslookup)& router that implements VERP:
37821 domains = ! +local_domains
37822 transport = remote_smtp
37824 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
37825 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37828 Before you start sending out messages with VERPed return paths, you must also
37829 configure Exim to accept the bounce messages that come back to those paths.
37830 Typically this is done by setting a &%local_part_suffix%& option for a
37831 router, and using this to route the messages to wherever you want to handle
37834 The overhead incurred in using VERP depends very much on the size of the
37835 message, the number of recipient addresses that resolve to the same remote
37836 host, and the speed of the connection over which the message is being sent. If
37837 a lot of addresses resolve to the same host and the connection is slow, sending
37838 a separate copy of the message for each address may take substantially longer
37839 than sending a single copy with many recipients (for which VERP cannot be
37847 .section "Virtual domains" "SECTvirtualdomains"
37848 .cindex "virtual domains"
37849 .cindex "domain" "virtual"
37850 The phrase &'virtual domain'& is unfortunately used with two rather different
37854 A domain for which there are no real mailboxes; all valid local parts are
37855 aliases for other email addresses. Common examples are organizational
37856 top-level domains and &"vanity"& domains.
37858 One of a number of independent domains that are all handled by the same host,
37859 with mailboxes on that host, but where the mailbox owners do not necessarily
37860 have login accounts on that host.
37863 The first usage is probably more common, and does seem more &"virtual"& than
37864 the second. This kind of domain can be handled in Exim with a straightforward
37865 aliasing router. One approach is to create a separate alias file for each
37866 virtual domain. Exim can test for the existence of the alias file to determine
37867 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
37868 to a router of this form:
37872 domains = dsearch;/etc/mail/virtual
37873 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
37876 The &%domains%& option specifies that the router is to be skipped, unless there
37877 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
37878 domain that is being processed.
37879 The &(dsearch)& lookup used results in an untainted version of &$domain$&
37880 being placed into the &$domain_data$& variable.
37882 When the router runs, it looks up the local
37883 part in the file to find a new address (or list of addresses). The &%no_more%&
37884 setting ensures that if the lookup fails (leading to &%data%& being an empty
37885 string), Exim gives up on the address without trying any subsequent routers.
37887 This one router can handle all the virtual domains because the alias filenames
37888 follow a fixed pattern. Permissions can be arranged so that appropriate people
37889 can edit the different alias files. A successful aliasing operation results in
37890 a new envelope recipient address, which is then routed from scratch.
37892 The other kind of &"virtual"& domain can also be handled in a straightforward
37893 way. One approach is to create a file for each domain containing a list of
37894 valid local parts, and use it in a router like this:
37898 domains = dsearch;/etc/mail/domains
37899 local_parts = lsearch;/etc/mail/domains/$domain
37900 transport = my_mailboxes
37902 The address is accepted if there is a file for the domain, and the local part
37903 can be found in the file. The &%domains%& option is used to check for the
37904 file's existence because &%domains%& is tested before the &%local_parts%&
37905 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
37906 because that option is tested after &%local_parts%&. The transport is as
37910 driver = appendfile
37911 file = /var/mail/$domain_data/$local_part_data
37914 This uses a directory of mailboxes for each domain. The &%user%& setting is
37915 required, to specify which uid is to be used for writing to the mailboxes.
37917 The configuration shown here is just one example of how you might support this
37918 requirement. There are many other ways this kind of configuration can be set
37919 up, for example, by using a database instead of separate files to hold all the
37920 information about the domains.
37924 .section "Multiple user mailboxes" "SECTmulbox"
37925 .cindex "multiple mailboxes"
37926 .cindex "mailbox" "multiple"
37927 .cindex "local part" "prefix"
37928 .cindex "local part" "suffix"
37929 Heavy email users often want to operate with multiple mailboxes, into which
37930 incoming mail is automatically sorted. A popular way of handling this is to
37931 allow users to use multiple sender addresses, so that replies can easily be
37932 identified. Users are permitted to add prefixes or suffixes to their local
37933 parts for this purpose. The wildcard facility of the generic router options
37934 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
37935 example, consider this router:
37940 file = $home/.forward
37941 local_part_suffix = -*
37942 local_part_suffix_optional
37945 .vindex "&$local_part_suffix$&"
37946 It runs a user's &_.forward_& file for all local parts of the form
37947 &'username-*'&. Within the filter file the user can distinguish different
37948 cases by testing the variable &$local_part_suffix$&. For example:
37950 if $local_part_suffix contains -special then
37951 save /home/$local_part_data/Mail/special
37954 If the filter file does not exist, or does not deal with such addresses, they
37955 fall through to subsequent routers, and, assuming no subsequent use of the
37956 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
37957 control over which suffixes are valid.
37959 Alternatively, a suffix can be used to trigger the use of a different
37960 &_.forward_& file &-- which is the way a similar facility is implemented in
37966 local_part_suffix = -*
37967 local_part_suffix_optional
37968 file = ${lookup {.forward$local_part_suffix} dsearch,ret=full {$home} {$value}fail}
37971 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
37972 example, &_.forward-special_& is used. Once again, if the appropriate file
37973 does not exist, or does not deal with the address, it is passed on to
37974 subsequent routers, which could, if required, look for an unqualified
37975 &_.forward_& file to use as a default.
37979 .section "Simplified vacation processing" "SECID244"
37980 .cindex "vacation processing"
37981 The traditional way of running the &'vacation'& program is for a user to set up
37982 a pipe command in a &_.forward_& file
37983 (see section &<<SECTspecitredli>>& for syntax details).
37984 This is prone to error by inexperienced users. There are two features of Exim
37985 that can be used to make this process simpler for users:
37988 A local part prefix such as &"vacation-"& can be specified on a router which
37989 can cause the message to be delivered directly to the &'vacation'& program, or
37990 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
37991 &_.forward_& file are then much simpler. For example:
37993 spqr, vacation-spqr
37996 The &%require_files%& generic router option can be used to trigger a
37997 vacation delivery by checking for the existence of a certain file in the
37998 user's home directory. The &%unseen%& generic option should also be used, to
37999 ensure that the original delivery also proceeds. In this case, all the user has
38000 to do is to create a file called, say, &_.vacation_&, containing a vacation
38004 Another advantage of both these methods is that they both work even when the
38005 use of arbitrary pipes by users is locked out.
38009 .section "Taking copies of mail" "SECID245"
38010 .cindex "message" "copying every"
38011 Some installations have policies that require archive copies of all messages to
38012 be made. A single copy of each message can easily be taken by an appropriate
38013 command in a system filter, which could, for example, use a different file for
38014 each day's messages.
38016 There is also a shadow transport mechanism that can be used to take copies of
38017 messages that are successfully delivered by local transports, one copy per
38018 delivery. This could be used, &'inter alia'&, to implement automatic
38019 notification of delivery by sites that insist on doing such things.
38023 .section "Intermittently connected hosts" "SECID246"
38024 .cindex "intermittently connected hosts"
38025 It has become quite common (because it is cheaper) for hosts to connect to the
38026 Internet periodically rather than remain connected all the time. The normal
38027 arrangement is that mail for such hosts accumulates on a system that is
38028 permanently connected.
38030 Exim was designed for use on permanently connected hosts, and so it is not
38031 particularly well-suited to use in an intermittently connected environment.
38032 Nevertheless there are some features that can be used.
38035 .section "Exim on the upstream server host" "SECID247"
38036 It is tempting to arrange for incoming mail for the intermittently connected
38037 host to remain in Exim's queue until the client connects. However, this
38038 approach does not scale very well. Two different kinds of waiting message are
38039 being mixed up in the same queue &-- those that cannot be delivered because of
38040 some temporary problem, and those that are waiting for their destination host
38041 to connect. This makes it hard to manage the queue, as well as wasting
38042 resources, because each queue runner scans the entire queue.
38044 A better approach is to separate off those messages that are waiting for an
38045 intermittently connected host. This can be done by delivering these messages
38046 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
38047 format, from where they are transmitted by other software when their
38048 destination connects. This makes it easy to collect all the mail for one host
38049 in a single directory, and to apply local timeout rules on a per-message basis
38052 On a very small scale, leaving the mail on Exim's queue can be made to work. If
38053 you are doing this, you should configure Exim with a long retry period for the
38054 intermittent host. For example:
38056 cheshire.wonderland.fict.example * F,5d,24h
38058 This stops a lot of failed delivery attempts from occurring, but Exim remembers
38059 which messages it has queued up for that host. Once the intermittent host comes
38060 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
38061 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
38062 causes all the queued up messages to be delivered, often down a single SMTP
38063 connection. While the host remains connected, any new messages get delivered
38066 If the connecting hosts do not have fixed IP addresses, that is, if a host is
38067 issued with a different IP address each time it connects, Exim's retry
38068 mechanisms on the holding host get confused, because the IP address is normally
38069 used as part of the key string for holding retry information. This can be
38070 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
38071 Since this has disadvantages for permanently connected hosts, it is best to
38072 arrange a separate transport for the intermittently connected ones.
38076 .section "Exim on the intermittently connected client host" "SECID248"
38077 The value of &%smtp_accept_queue_per_connection%& should probably be
38078 increased, or even set to zero (that is, disabled) on the intermittently
38079 connected host, so that all incoming messages down a single connection get
38080 delivered immediately.
38082 .cindex "SMTP" "passed connection"
38083 .cindex "SMTP" "multiple deliveries"
38084 .cindex "multiple SMTP deliveries"
38085 .cindex "first pass routing"
38086 Mail waiting to be sent from an intermittently connected host will probably
38087 not have been routed, because without a connection DNS lookups are not
38088 possible. This means that if a normal queue run is done at connection time,
38089 each message is likely to be sent in a separate SMTP session. This can be
38090 avoided by starting the queue run with a command line option beginning with
38091 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
38092 first pass, routing is done but no deliveries take place. The second pass is a
38093 normal queue run; since all the messages have been previously routed, those
38094 destined for the same host are likely to get sent as multiple deliveries in a
38095 single SMTP connection.
38099 . ////////////////////////////////////////////////////////////////////////////
38100 . ////////////////////////////////////////////////////////////////////////////
38102 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
38103 "Exim as a non-queueing client"
38104 .cindex "client, non-queueing"
38105 .cindex "smart host" "suppressing queueing"
38106 On a personal computer, it is a common requirement for all
38107 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
38108 configured to operate that way, for all the popular operating systems.
38109 However, there are some MUAs for Unix-like systems that cannot be so
38110 configured: they submit messages using the command line interface of
38111 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
38114 If the personal computer runs continuously, there is no problem, because it can
38115 run a conventional MTA that handles delivery to the smart host, and deal with
38116 any delays via its queueing mechanism. However, if the computer does not run
38117 continuously or runs different operating systems at different times, queueing
38118 email is not desirable.
38120 There is therefore a requirement for something that can provide the
38121 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
38122 any queueing or retrying facilities. Furthermore, the delivery to the smart
38123 host should be synchronous, so that if it fails, the sending MUA is immediately
38124 informed. In other words, we want something that extends an MUA that submits
38125 to a local MTA via the command line so that it behaves like one that submits
38126 to a remote smart host using TCP/SMTP.
38128 There are a number of applications (for example, there is one called &'ssmtp'&)
38129 that do this job. However, people have found them to be lacking in various
38130 ways. For instance, you might want to allow aliasing and forwarding to be done
38131 before sending a message to the smart host.
38133 Exim already had the necessary infrastructure for doing this job. Just a few
38134 tweaks were needed to make it behave as required, though it is somewhat of an
38135 overkill to use a fully-featured MTA for this purpose.
38137 .oindex "&%mua_wrapper%&"
38138 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
38139 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
38140 assumes that it is being used to &"wrap"& a command-line MUA in the manner
38141 just described. As well as setting &%mua_wrapper%&, you also need to provide a
38142 compatible router and transport configuration. Typically there will be just one
38143 router and one transport, sending everything to a smart host.
38145 When run in MUA wrapping mode, the behaviour of Exim changes in the
38149 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
38150 In other words, the only way to submit messages is via the command line.
38152 Each message is synchronously delivered as soon as it is received (&%-odi%& is
38153 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
38154 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
38155 does not finish until the delivery attempt is complete. If the delivery is
38156 successful, a zero return code is given.
38158 Address redirection is permitted, but the final routing for all addresses must
38159 be to the same remote transport, and to the same list of hosts. Furthermore,
38160 the return address (envelope sender) must be the same for all recipients, as
38161 must any added or deleted header lines. In other words, it must be possible to
38162 deliver the message in a single SMTP transaction, however many recipients there
38165 If these conditions are not met, or if routing any address results in a
38166 failure or defer status, or if Exim is unable to deliver all the recipients
38167 successfully to one of the smart hosts, delivery of the entire message fails.
38169 Because no queueing is allowed, all failures are treated as permanent; there
38170 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
38171 smart host. Furthermore, because only a single yes/no response can be given to
38172 the caller, it is not possible to deliver to some recipients and not others. If
38173 there is an error (temporary or permanent) for any recipient, all are failed.
38175 If more than one smart host is listed, Exim will try another host after a
38176 connection failure or a timeout, in the normal way. However, if this kind of
38177 failure happens for all the hosts, the delivery fails.
38179 When delivery fails, an error message is written to the standard error stream
38180 (as well as to Exim's log), and Exim exits to the caller with a return code
38181 value 1. The message is expunged from Exim's spool files. No bounce messages
38182 are ever generated.
38184 No retry data is maintained, and any retry rules are ignored.
38186 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
38187 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
38188 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
38191 The overall effect is that Exim makes a single synchronous attempt to deliver
38192 the message, failing if there is any kind of problem. Because no local
38193 deliveries are done and no daemon can be run, Exim does not need root
38194 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
38195 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
38196 the advantages and disadvantages of running without root privilege.
38201 . ////////////////////////////////////////////////////////////////////////////
38202 . ////////////////////////////////////////////////////////////////////////////
38204 .chapter "Log files" "CHAPlog"
38205 .scindex IIDloggen "log" "general description"
38206 .cindex "log" "types of"
38207 Exim writes three different logs, referred to as the main log, the reject log,
38212 The main log records the arrival of each message and each delivery in a single
38213 line in each case. The format is as compact as possible, in an attempt to keep
38214 down the size of log files. Two-character flag sequences make it easy to pick
38215 out these lines. A number of other events are recorded in the main log. Some of
38216 them are optional, in which case the &%log_selector%& option controls whether
38217 they are included or not. A Perl script called &'eximstats'&, which does simple
38218 analysis of main log files, is provided in the Exim distribution (see section
38219 &<<SECTmailstat>>&).
38221 .cindex "reject log"
38222 The reject log records information from messages that are rejected as a result
38223 of a configuration option (that is, for policy reasons).
38224 The first line of each rejection is a copy of the line that is also written to
38225 the main log. Then, if the message's header has been read at the time the log
38226 is written, its contents are written to this log. Only the original header
38227 lines are available; header lines added by ACLs are not logged. You can use the
38228 reject log to check that your policy controls are working correctly; on a busy
38229 host this may be easier than scanning the main log for rejection messages. You
38230 can suppress the writing of the reject log by setting &%write_rejectlog%&
38233 .cindex "panic log"
38234 .cindex "system log"
38235 When certain serious errors occur, Exim writes entries to its panic log. If the
38236 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
38237 are usually written to the main log as well, but can get lost amid the mass of
38238 other entries. The panic log should be empty under normal circumstances. It is
38239 therefore a good idea to check it (or to have a &'cron'& script check it)
38240 regularly, in order to become aware of any problems. When Exim cannot open its
38241 panic log, it tries as a last resort to write to the system log (syslog). This
38242 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
38243 message itself is written at priority LOG_CRIT.
38246 Every log line starts with a timestamp, in the format shown in the following
38247 example. Note that many of the examples shown in this chapter are line-wrapped.
38248 In the log file, this would be all on one line:
38250 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
38253 By default, the timestamps are in the local timezone. There are two
38254 ways of changing this:
38257 You can set the &%timezone%& option to a different time zone; in particular, if
38262 the timestamps will be in UTC (aka GMT).
38264 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
38267 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
38271 .cindex "log" "process ids in"
38272 .cindex "pid (process id)" "in log lines"
38273 Exim does not include its process id in log lines by default, but you can
38274 request that it does so by specifying the &`pid`& log selector (see section
38275 &<<SECTlogselector>>&). When this is set, the process id is output, in square
38276 brackets, immediately after the time and date.
38281 .section "Where the logs are written" "SECTwhelogwri"
38282 .cindex "log" "destination"
38283 .cindex "log" "to file"
38284 .cindex "log" "to syslog"
38286 The logs may be written to local files, or to syslog, or both. However, it
38287 should be noted that many syslog implementations use UDP as a transport, and
38288 are therefore unreliable in the sense that messages are not guaranteed to
38289 arrive at the loghost, nor is the ordering of messages necessarily maintained.
38290 It has also been reported that on large log files (tens of megabytes) you may
38291 need to tweak syslog to prevent it syncing the file with each write &-- on
38292 Linux this has been seen to make syslog take 90% plus of CPU time.
38294 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
38295 &_Local/Makefile_& or by setting &%log_file_path%& in the runtime
38296 configuration. This latter string is expanded, so it can contain, for example,
38297 references to the host name:
38299 log_file_path = /var/log/$primary_hostname/exim_%slog
38301 It is generally advisable, however, to set the string in &_Local/Makefile_&
38302 rather than at runtime, because then the setting is available right from the
38303 start of Exim's execution. Otherwise, if there's something it wants to log
38304 before it has read the configuration file (for example, an error in the
38305 configuration file) it will not use the path you want, and may not be able to
38308 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
38309 list, currently limited to at most two items. This is one option where the
38310 facility for changing a list separator may not be used. The list must always be
38311 colon-separated. If an item in the list is &"syslog"& then syslog is used;
38312 otherwise the item must either be an absolute path, containing &`%s`& at the
38313 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
38314 implying the use of a default path.
38316 When Exim encounters an empty item in the list, it searches the list defined by
38317 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
38318 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
38319 mean &"use the path specified at build time"&. If no such item exists, log
38320 files are written in the &_log_& subdirectory of the spool directory. This is
38321 equivalent to the setting:
38323 log_file_path = $spool_directory/log/%slog
38325 If you do not specify anything at build time or runtime,
38326 or if you unset the option at runtime (i.e. &`log_file_path = `&),
38327 that is where the logs are written.
38329 A log file path may also contain &`%D`& or &`%M`& if datestamped log filenames
38330 are in use &-- see section &<<SECTdatlogfil>>& below.
38332 Here are some examples of possible settings:
38334 &`LOG_FILE_PATH=syslog `& syslog only
38335 &`LOG_FILE_PATH=:syslog `& syslog and default path
38336 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
38337 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
38339 If there are more than two paths in the list, the first is used and a panic
38344 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
38345 .cindex "log" "cycling local files"
38346 .cindex "cycling logs"
38347 .cindex "&'exicyclog'&"
38348 .cindex "log" "local files; writing to"
38349 Some operating systems provide centralized and standardized methods for cycling
38350 log files. For those that do not, a utility script called &'exicyclog'& is
38351 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
38352 main and reject logs each time it is called. The maximum number of old logs to
38353 keep can be set. It is suggested this script is run as a daily &'cron'& job.
38355 An Exim delivery process opens the main log when it first needs to write to it,
38356 and it keeps the file open in case subsequent entries are required &-- for
38357 example, if a number of different deliveries are being done for the same
38358 message. However, remote SMTP deliveries can take a long time, and this means
38359 that the file may be kept open long after it is renamed if &'exicyclog'& or
38360 something similar is being used to rename log files on a regular basis. To
38361 ensure that a switch of log files is noticed as soon as possible, Exim calls
38362 &[stat()]& on the main log's name before reusing an open file, and if the file
38363 does not exist, or its inode has changed, the old file is closed and Exim
38364 tries to open the main log from scratch. Thus, an old log file may remain open
38365 for quite some time, but no Exim processes should write to it once it has been
38370 .section "Datestamped log files" "SECTdatlogfil"
38371 .cindex "log" "datestamped files"
38372 Instead of cycling the main and reject log files by renaming them
38373 periodically, some sites like to use files whose names contain a datestamp,
38374 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
38375 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
38376 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
38377 point where the datestamp is required. For example:
38379 log_file_path = /var/spool/exim/log/%slog-%D
38380 log_file_path = /var/log/exim-%s-%D.log
38381 log_file_path = /var/spool/exim/log/%D-%slog
38382 log_file_path = /var/log/exim/%s.%M
38384 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
38385 examples of names generated by the above examples:
38387 /var/spool/exim/log/mainlog-20021225
38388 /var/log/exim-reject-20021225.log
38389 /var/spool/exim/log/20021225-mainlog
38390 /var/log/exim/main.200212
38392 When this form of log file is specified, Exim automatically switches to new
38393 files at midnight. It does not make any attempt to compress old logs; you
38394 will need to write your own script if you require this. You should not
38395 run &'exicyclog'& with this form of logging.
38397 The location of the panic log is also determined by &%log_file_path%&, but it
38398 is not datestamped, because rotation of the panic log does not make sense.
38399 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
38400 the string. In addition, if it immediately follows a slash, a following
38401 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
38402 character is removed. Thus, the four examples above would give these panic
38405 /var/spool/exim/log/paniclog
38406 /var/log/exim-panic.log
38407 /var/spool/exim/log/paniclog
38408 /var/log/exim/panic
38412 .section "Logging to syslog" "SECID249"
38413 .cindex "log" "syslog; writing to"
38414 The use of syslog does not change what Exim logs or the format of its messages,
38415 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
38416 Exim's log lines are omitted when these lines are sent to syslog. Apart from
38417 that, the same strings are written to syslog as to log files. The syslog
38418 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
38419 by default, but you can change these by setting the &%syslog_facility%& and
38420 &%syslog_processname%& options, respectively. If Exim was compiled with
38421 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
38422 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
38423 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
38424 the time and host name to each line.
38425 The three log streams are mapped onto syslog priorities as follows:
38428 &'mainlog'& is mapped to LOG_INFO
38430 &'rejectlog'& is mapped to LOG_NOTICE
38432 &'paniclog'& is mapped to LOG_ALERT
38435 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
38436 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
38437 these are routed by syslog to the same place. You can suppress this duplication
38438 by setting &%syslog_duplication%& false.
38440 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
38441 entries contain multiple lines when headers are included. To cope with both
38442 these cases, entries written to syslog are split into separate &[syslog()]&
38443 calls at each internal newline, and also after a maximum of
38444 870 data characters. (This allows for a total syslog line length of 1024, when
38445 additions such as timestamps are added.) If you are running a syslog
38446 replacement that can handle lines longer than the 1024 characters allowed by
38447 RFC 3164, you should set
38449 SYSLOG_LONG_LINES=yes
38451 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
38452 lines, but it still splits at internal newlines in &'reject'& log entries.
38454 To make it easy to re-assemble split lines later, each component of a split
38455 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
38456 where <&'n'&> is the component number and <&'m'&> is the total number of
38457 components in the entry. The / delimiter is used when the line was split
38458 because it was too long; if it was split because of an internal newline, the \
38459 delimiter is used. For example, supposing the length limit to be 50 instead of
38460 870, the following would be the result of a typical rejection message to
38461 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
38462 name, and pid as added by syslog:
38464 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
38465 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
38466 [3/5] when scanning for sender: missing or malformed lo
38467 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
38470 The same error might cause the following lines to be written to &"rejectlog"&
38473 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
38474 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
38475 [3/18] er when scanning for sender: missing or malformed
38476 [4/18] local part in "<>" (envelope sender is <ph10@cam
38478 [6\18] Recipients: ph10@some.domain.cam.example
38479 [7\18] P Received: from [127.0.0.1] (ident=ph10)
38480 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
38481 [9\18] id 16RdAL-0006pc-00
38482 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
38483 [11\18] 09:43 +0100
38485 [13\18] Subject: this is a test header
38486 [18\18] X-something: this is another header
38487 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
38490 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
38492 Log lines that are neither too long nor contain newlines are written to syslog
38493 without modification.
38495 If only syslog is being used, the Exim monitor is unable to provide a log tail
38496 display, unless syslog is routing &'mainlog'& to a file on the local host and
38497 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
38502 .section "Log line flags" "SECID250"
38503 One line is written to the main log for each message received, and for each
38504 successful, unsuccessful, and delayed delivery. These lines can readily be
38505 picked out by the distinctive two-character flags that immediately follow the
38506 timestamp. The flags are:
38508 &`<=`& message arrival
38509 &`(=`& message fakereject
38510 &`=>`& normal message delivery
38511 &`->`& additional address in same delivery
38512 &`>>`& cutthrough message delivery
38513 &`*>`& delivery suppressed by &%-N%&
38514 &`**`& delivery failed; address bounced
38515 &`==`& delivery deferred; temporary problem
38519 .section "Logging message reception" "SECID251"
38520 .cindex "log" "reception line"
38521 The format of the single-line entry in the main log that is written for every
38522 message received is shown in the basic example below, which is split over
38523 several lines in order to fit it on the page:
38525 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
38526 H=mailer.fict.example [192.168.123.123] U=exim
38527 P=smtp S=5678 id=<incoming message id>
38529 The address immediately following &"<="& is the envelope sender address. A
38530 bounce message is shown with the sender address &"<>"&, and if it is locally
38531 generated, this is followed by an item of the form
38535 which is a reference to the message that caused the bounce to be sent.
38539 For messages from other hosts, the H and U fields identify the remote host and
38540 record the RFC 1413 identity of the user that sent the message, if one was
38541 received. The number given in square brackets is the IP address of the sending
38542 host. If there is a single, unparenthesized host name in the H field, as
38543 above, it has been verified to correspond to the IP address (see the
38544 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
38545 by the remote host in the SMTP HELO or EHLO command, and has not been
38546 verified. If verification yields a different name to that given for HELO or
38547 EHLO, the verified name appears first, followed by the HELO or EHLO
38548 name in parentheses.
38550 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
38551 without brackets, in the HELO or EHLO command, leading to entries in
38552 the log containing text like these examples:
38554 H=(10.21.32.43) [192.168.8.34]
38555 H=([10.21.32.43]) [192.168.8.34]
38557 This can be confusing. Only the final address in square brackets can be relied
38560 For locally generated messages (that is, messages not received over TCP/IP),
38561 the H field is omitted, and the U field contains the login name of the caller
38564 .cindex "authentication" "logging"
38565 .cindex "AUTH" "logging"
38566 For all messages, the P field specifies the protocol used to receive the
38567 message. This is the value that is stored in &$received_protocol$&. In the case
38568 of incoming SMTP messages, the value indicates whether or not any SMTP
38569 extensions (ESMTP), encryption, or authentication were used. If the SMTP
38570 session was encrypted, there is an additional X field that records the cipher
38571 suite that was used.
38573 .cindex log protocol
38574 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
38575 hosts that have authenticated themselves using the SMTP AUTH command. The first
38576 value is used when the SMTP connection was encrypted (&"secure"&). In this case
38577 there is an additional item A= followed by the name of the authenticator that
38578 was used. If an authenticated identification was set up by the authenticator's
38579 &%server_set_id%& option, this is logged too, separated by a colon from the
38580 authenticator name.
38582 .cindex "size" "of message"
38583 The id field records the existing message id, if present. The size of the
38584 received message is given by the S field. When the message is delivered,
38585 headers may be removed or added, so that the size of delivered copies of the
38586 message may not correspond with this value (and indeed may be different to each
38589 The &%log_selector%& option can be used to request the logging of additional
38590 data when a message is received. See section &<<SECTlogselector>>& below.
38594 .section "Logging deliveries" "SECID252"
38595 .cindex "log" "delivery line"
38596 The format of the single-line entry in the main log that is written for every
38597 delivery is shown in one of the examples below, for local and remote
38598 deliveries, respectively. Each example has been split into multiple lines in order
38599 to fit it on the page:
38601 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
38602 <marv@hitch.fict.example> R=localuser T=local_delivery
38603 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
38604 monk@holistic.fict.example R=dnslookup T=remote_smtp
38605 H=holistic.fict.example [192.168.234.234]
38607 For ordinary local deliveries, the original address is given in angle brackets
38608 after the final delivery address, which might be a pipe or a file. If
38609 intermediate address(es) exist between the original and the final address, the
38610 last of these is given in parentheses after the final address. The R and T
38611 fields record the router and transport that were used to process the address.
38613 If SMTP AUTH was used for the delivery there is an additional item A=
38614 followed by the name of the authenticator that was used.
38615 If an authenticated identification was set up by the authenticator's &%client_set_id%&
38616 option, this is logged too, as a second colon-separated list item.
38617 Optionally (see the &%smtp_mailauth%& &%log_selector%&) there may be a third list item.
38619 If a shadow transport was run after a successful local delivery, the log line
38620 for the successful delivery has an item added on the end, of the form
38622 &`ST=<`&&'shadow transport name'&&`>`&
38624 If the shadow transport did not succeed, the error message is put in
38625 parentheses afterwards.
38627 .cindex "asterisk" "after IP address"
38628 When more than one address is included in a single delivery (for example, two
38629 SMTP RCPT commands in one transaction) the second and subsequent addresses are
38630 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
38631 down a single SMTP connection, an asterisk follows the
38633 remote IP address (and port if enabled)
38635 in the log lines for the second and subsequent messages.
38636 When two or more messages are delivered down a single TLS connection, the
38637 DNS and some TLS-related information logged for the first message delivered
38638 will not be present in the log lines for the second and subsequent messages.
38639 TLS cipher information is still available.
38641 .cindex "delivery" "cutthrough; logging"
38642 .cindex "cutthrough" "logging"
38643 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
38644 line precedes the reception line, since cutthrough waits for a possible
38645 rejection from the destination in case it can reject the sourced item.
38647 The generation of a reply message by a filter file gets logged as a
38648 &"delivery"& to the addressee, preceded by &">"&.
38650 The &%log_selector%& option can be used to request the logging of additional
38651 data when a message is delivered. See section &<<SECTlogselector>>& below.
38654 .section "Discarded deliveries" "SECID253"
38655 .cindex "discarded messages"
38656 .cindex "message" "discarded"
38657 .cindex "delivery" "discarded; logging"
38658 When a message is discarded as a result of the command &"seen finish"& being
38659 obeyed in a filter file which generates no deliveries, a log entry of the form
38661 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
38662 <low.club@bridge.example> R=userforward
38664 is written, to record why no deliveries are logged. When a message is discarded
38665 because it is aliased to &":blackhole:"& the log line is like this:
38667 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
38668 <hole@nowhere.example> R=blackhole_router
38672 .section "Deferred deliveries" "SECID254"
38673 When a delivery is deferred, a line of the following form is logged:
38675 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
38676 R=dnslookup T=smtp defer (146): Connection refused
38678 In the case of remote deliveries, the error is the one that was given for the
38679 last IP address that was tried. Details of individual SMTP failures are also
38680 written to the log, so the above line would be preceded by something like
38682 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
38683 mail1.endrest.example [192.168.239.239]: Connection refused
38685 When a deferred address is skipped because its retry time has not been reached,
38686 a message is written to the log, but this can be suppressed by setting an
38687 appropriate value in &%log_selector%&.
38691 .section "Delivery failures" "SECID255"
38692 .cindex "delivery" "failure; logging"
38693 If a delivery fails because an address cannot be routed, a line of the
38694 following form is logged:
38696 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
38697 <jim@trek99.example>: unknown mail domain
38699 If a delivery fails at transport time, the router and transport are shown, and
38700 the response from the remote host is included, as in this example:
38702 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
38703 R=dnslookup T=remote_smtp: SMTP error from remote mailer
38704 after pipelined RCPT TO:<ace400@pb.example>: host
38705 pbmail3.py.example [192.168.63.111]: 553 5.3.0
38706 <ace400@pb.example>...Addressee unknown
38708 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
38709 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
38710 disabling PIPELINING. The log lines for all forms of delivery failure are
38711 flagged with &`**`&.
38715 .section "Fake deliveries" "SECID256"
38716 .cindex "delivery" "fake; logging"
38717 If a delivery does not actually take place because the &%-N%& option has been
38718 used to suppress it, a normal delivery line is written to the log, except that
38719 &"=>"& is replaced by &"*>"&.
38723 .section "Completion" "SECID257"
38726 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
38728 is written to the main log when a message is about to be removed from the spool
38729 at the end of its processing.
38734 .section "Summary of Fields in Log Lines" "SECID258"
38735 .cindex "log" "summary of fields"
38736 A summary of the field identifiers that are used in log lines is shown in
38737 the following table:
38739 &`A `& authenticator name (and optional id and sender)
38740 &`C `& SMTP confirmation on delivery
38741 &` `& command list for &"no mail in SMTP session"&
38742 &`CV `& certificate verification status
38743 &`D `& duration of &"no mail in SMTP session"&
38744 &`DKIM`& domain verified in incoming message
38745 &`DN `& distinguished name from peer certificate
38746 &`DS `& DNSSEC secured lookups
38747 &`DT `& on &`=>`&, &'=='& and &'**'& lines: time taken for, or to attempt, a delivery
38748 &`F `& sender address (on delivery lines)
38749 &`H `& host name and IP address
38750 &`I `& local interface used
38751 &`id `& message id (from header) for incoming message
38752 &`K `& CHUNKING extension used
38753 &`L `& on &`<=`& and &`=>`& lines: PIPELINING extension used
38754 &`M8S `& 8BITMIME status for incoming message
38755 &`P `& on &`<=`& lines: protocol used
38756 &` `& on &`=>`& and &`**`& lines: return path
38757 &`PRDR`& PRDR extension used
38758 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
38759 &`Q `& alternate queue name
38760 &`QT `& on &`=>`& lines: time spent on queue so far
38761 &` `& on &"Completed"& lines: time spent on queue
38762 &`R `& on &`<=`& lines: reference for local bounce
38763 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
38764 &`RT `& on &`<=`& lines: time taken for reception
38765 &`S `& size of message in bytes
38766 &`SNI `& server name indication from TLS client hello
38767 &`ST `& shadow transport name
38768 &`T `& on &`<=`& lines: message subject (topic)
38769 &`TFO `& connection took advantage of TCP Fast Open
38770 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
38771 &`U `& local user or RFC 1413 identity
38772 &`X `& TLS cipher suite
38776 .section "Other log entries" "SECID259"
38777 Various other types of log entry are written from time to time. Most should be
38778 self-explanatory. Among the more common are:
38781 .cindex "retry" "time not reached"
38782 &'retry time not reached'&&~&~An address previously suffered a temporary error
38783 during routing or local delivery, and the time to retry has not yet arrived.
38784 This message is not written to an individual message log file unless it happens
38785 during the first delivery attempt.
38787 &'retry time not reached for any host'&&~&~An address previously suffered
38788 temporary errors during remote delivery, and the retry time has not yet arrived
38789 for any of the hosts to which it is routed.
38791 .cindex "spool directory" "file locked"
38792 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
38793 some other Exim process is already working on the message. This can be quite
38794 common if queue running processes are started at frequent intervals. The
38795 &'exiwhat'& utility script can be used to find out what Exim processes are
38798 .cindex "error" "ignored"
38799 &'error ignored'&&~&~There are several circumstances that give rise to this
38802 Exim failed to deliver a bounce message whose age was greater than
38803 &%ignore_bounce_errors_after%&. The bounce was discarded.
38805 A filter file set up a delivery using the &"noerror"& option, and the delivery
38806 failed. The delivery was discarded.
38808 A delivery set up by a router configured with
38809 . ==== As this is a nested list, any displays it contains must be indented
38810 . ==== as otherwise they are too far to the left.
38814 failed. The delivery was discarded.
38817 .cindex DKIM "log line"
38818 &'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
38819 logging and the message has a DKIM signature header.
38826 .section "Reducing or increasing what is logged" "SECTlogselector"
38827 .cindex "log" "selectors"
38828 By setting the &%log_selector%& global option, you can disable some of Exim's
38829 default logging, or you can request additional logging. The value of
38830 &%log_selector%& is made up of names preceded by plus or minus characters. For
38833 log_selector = +arguments -retry_defer
38835 The list of optional log items is in the following table, with the default
38836 selection marked by asterisks:
38838 &` 8bitmime `& received 8BITMIME status
38839 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
38840 &` address_rewrite `& address rewriting
38841 &` all_parents `& all parents in => lines
38842 &` arguments `& command line arguments
38843 &`*connection_reject `& connection rejections
38844 &`*delay_delivery `& immediate delivery delayed
38845 &` deliver_time `& time taken to attempt delivery
38846 &` delivery_size `& add &`S=`&&'nnn'& to => lines
38847 &`*dkim `& DKIM verified domain on <= lines
38848 &` dkim_verbose `& separate full DKIM verification result line, per signature
38849 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
38850 &` dnssec `& DNSSEC secured lookups
38851 &`*etrn `& ETRN commands
38852 &`*host_lookup_failed `& as it says
38853 &` ident_timeout `& timeout for ident connection
38854 &` incoming_interface `& local interface on <= and => lines
38855 &` incoming_port `& remote port on <= lines
38856 &`*lost_incoming_connection `& as it says (includes timeouts)
38857 &` millisec `& millisecond timestamps and RT,QT,DT,D times
38858 &`*msg_id `& on <= lines, Message-ID: header value
38859 &` msg_id_created `& on <= lines, Message-ID: header value when one had to be added
38860 &` outgoing_interface `& local interface on => lines
38861 &` outgoing_port `& add remote port to => lines
38862 &`*queue_run `& start and end queue runs
38863 &` queue_time `& time on queue for one recipient
38864 &`*queue_time_exclusive `& exclude recieve time from QT times
38865 &` queue_time_overall `& time on queue for whole message
38866 &` pid `& Exim process id
38867 &` pipelining `& PIPELINING use, on <= and => lines
38868 &` proxy `& proxy address on <= and => lines
38869 &` receive_time `& time taken to receive message
38870 &` received_recipients `& recipients on <= lines
38871 &` received_sender `& sender on <= lines
38872 &`*rejected_header `& header contents on reject log
38873 &`*retry_defer `& &"retry time not reached"&
38874 &` return_path_on_delivery `& put return path on => and ** lines
38875 &` sender_on_delivery `& add sender to => lines
38876 &`*sender_verify_fail `& sender verification failures
38877 &`*size_reject `& rejection because too big
38878 &`*skip_delivery `& delivery skipped in a queue run
38879 &`*smtp_confirmation `& SMTP confirmation on => lines
38880 &` smtp_connection `& incoming SMTP connections
38881 &` smtp_incomplete_transaction`& incomplete SMTP transactions
38882 &` smtp_mailauth `& AUTH argument to MAIL commands
38883 &` smtp_no_mail `& session with no MAIL commands
38884 &` smtp_protocol_error `& SMTP protocol errors
38885 &` smtp_syntax_error `& SMTP syntax errors
38886 &` subject `& contents of &'Subject:'& on <= lines
38887 &`*taint `& taint errors or warnings
38888 &`*tls_certificate_verified `& certificate verification status
38889 &`*tls_cipher `& TLS cipher suite on <= and => lines
38890 &` tls_peerdn `& TLS peer DN on <= and => lines
38891 &` tls_resumption `& append * to cipher field
38892 &` tls_sni `& TLS SNI on <= lines
38893 &` unknown_in_list `& DNS lookup failed in list match
38895 &` all `& all of the above
38897 See also the &%slow_lookup_log%& main configuration option,
38898 section &<<SECID99>>&
38900 More details on each of these items follows:
38904 .cindex "log" "8BITMIME"
38905 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
38906 which may help in tracking down interoperability issues with ancient MTAs
38907 that are not 8bit clean. This is added to the &"<="& line, tagged with
38908 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
38909 &`7BIT`& and &`8BITMIME`& respectively.
38911 .cindex "&%warn%& ACL verb" "log when skipping"
38912 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
38913 its conditions cannot be evaluated, a log line to this effect is written if
38914 this log selector is set.
38916 .cindex "log" "rewriting"
38917 .cindex "rewriting" "logging"
38918 &%address_rewrite%&: This applies both to global rewrites and per-transport
38919 rewrites, but not to rewrites in filters run as an unprivileged user (because
38920 such users cannot access the log).
38922 .cindex "log" "full parentage"
38923 &%all_parents%&: Normally only the original and final addresses are logged on
38924 delivery lines; with this selector, intermediate parents are given in
38925 parentheses between them.
38927 .cindex "log" "Exim arguments"
38928 .cindex "Exim arguments, logging"
38929 &%arguments%&: This causes Exim to write the arguments with which it was called
38930 to the main log, preceded by the current working directory. This is a debugging
38931 feature, added to make it easier to find out how certain MUAs call
38932 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
38933 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
38934 that are empty or that contain white space are quoted. Non-printing characters
38935 are shown as escape sequences. This facility cannot log unrecognized arguments,
38936 because the arguments are checked before the configuration file is read. The
38937 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
38938 between the caller and Exim.
38940 .cindex "log" "connection rejections"
38941 &%connection_reject%&: A log entry is written whenever an incoming SMTP
38942 connection is rejected, for whatever reason.
38944 .cindex "log" "delayed delivery"
38945 .cindex "delayed delivery, logging"
38946 &%delay_delivery%&: A log entry is written whenever a delivery process is not
38947 started for an incoming message because the load is too high or too many
38948 messages were received on one connection. Logging does not occur if no delivery
38949 process is started because &%queue_only%& is set or &%-odq%& was used.
38951 .cindex "log" "delivery duration"
38952 &%deliver_time%&: For each delivery, the amount of real time it has taken to
38953 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
38954 If millisecond logging is enabled, short times will be shown with greater
38955 precision, eg. &`DT=0.304s`&.
38957 .cindex "log" "message size on delivery"
38958 .cindex "size" "of message"
38959 &%delivery_size%&: For each delivery, the size of message delivered is added to
38960 the &"=>"& line, tagged with S=.
38962 .cindex log "DKIM verification"
38963 .cindex DKIM "verification logging"
38964 &%dkim%&: For message acceptance log lines, when an DKIM signature in the header
38965 verifies successfully a tag of DKIM is added, with one of the verified domains.
38967 .cindex log "DKIM verification"
38968 .cindex DKIM "verification logging"
38969 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
38971 .cindex "log" "dnslist defer"
38972 .cindex "DNS list" "logging defer"
38973 .cindex "black list (DNS)"
38974 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
38975 DNS black list suffers a temporary error.
38978 .cindex dnssec logging
38979 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
38980 dns lookups gave secure results a tag of DS is added.
38981 For acceptance this covers the reverse and forward lookups for host name verification.
38982 It does not cover helo-name verification.
38983 For delivery this covers the SRV, MX, A and/or AAAA lookups.
38985 .cindex "log" "ETRN commands"
38986 .cindex "ETRN" "logging"
38987 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
38988 is run to determine whether or not it is actually accepted. An invalid ETRN
38989 command, or one received within a message transaction is not logged by this
38990 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
38992 .cindex "log" "host lookup failure"
38993 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
38994 any addresses, or when a lookup of an IP address fails to find a host name, a
38995 log line is written. This logging does not apply to direct DNS lookups when
38996 routing email addresses, but it does apply to &"byname"& lookups.
38998 .cindex "log" "ident timeout"
38999 .cindex "RFC 1413" "logging timeout"
39000 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
39001 client's ident port times out.
39003 .cindex "log" "incoming interface"
39004 .cindex "log" "outgoing interface"
39005 .cindex "log" "local interface"
39006 .cindex "log" "local address and port"
39007 .cindex "TCP/IP" "logging local address and port"
39008 .cindex "interface" "logging"
39009 &%incoming_interface%&: The interface on which a message was received is added
39010 to the &"<="& line as an IP address in square brackets, tagged by I= and
39011 followed by a colon and the port number. The local interface and port are also
39012 added to other SMTP log lines, for example, &"SMTP connection from"&, to
39013 rejection lines, and (despite the name) to outgoing
39015 &"=>"&, &"->"&, &"=="& and &"**"& lines.
39017 The latter can be disabled by turning off the &%outgoing_interface%& option.
39019 .cindex log "incoming proxy address"
39020 .cindex proxy "logging proxy address"
39021 .cindex "TCP/IP" "logging proxy address"
39022 &%proxy%&: The internal (closest to the system running Exim) IP address
39023 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
39024 on a proxied connection
39025 or the &"=>"& line for a message delivered on a proxied connection.
39026 See &<<SECTproxyInbound>>& for more information.
39028 .cindex "log" "incoming remote port"
39029 .cindex "port" "logging remote"
39030 .cindex "TCP/IP" "logging incoming remote port"
39031 .vindex "&$sender_fullhost$&"
39032 .vindex "&$sender_rcvhost$&"
39033 &%incoming_port%&: The remote port number from which a message was received is
39034 added to log entries and &'Received:'& header lines, following the IP address
39035 in square brackets, and separated from it by a colon. This is implemented by
39036 changing the value that is put in the &$sender_fullhost$& and
39037 &$sender_rcvhost$& variables. Recording the remote port number has become more
39038 important with the widening use of NAT (see RFC 2505).
39040 .cindex "log" "dropped connection"
39041 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
39042 connection is unexpectedly dropped.
39044 .cindex "log" "millisecond timestamps"
39045 .cindex millisecond logging
39046 .cindex timestamps "millisecond, in logs"
39047 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
39048 appended to the seconds value.
39050 .cindex "log" "message id"
39051 &%msg_id%&: The value of the Message-ID: header.
39053 &%msg_id_created%&: The value of the Message-ID: header, when one had to be created.
39054 This will be either because the message is a bounce, or was submitted locally
39055 (submission mode) without one.
39056 The field identifier will have an asterix appended: &"id*="&.
39058 .cindex "log" "outgoing interface"
39059 .cindex "log" "local interface"
39060 .cindex "log" "local address and port"
39061 .cindex "TCP/IP" "logging local address and port"
39062 .cindex "interface" "logging"
39063 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
39064 interface on which a message was sent is added to delivery lines as an I= tag
39065 followed by IP address in square brackets. You can disable this by turning
39066 off the &%outgoing_interface%& option.
39068 .cindex "log" "outgoing remote port"
39069 .cindex "port" "logging outgoing remote"
39070 .cindex "TCP/IP" "logging outgoing remote port"
39071 &%outgoing_port%&: The remote port number is added to delivery log lines (those
39072 containing => tags) following the IP address.
39073 The local port is also added if &%incoming_interface%& and
39074 &%outgoing_interface%& are both enabled.
39075 This option is not included in the default setting, because for most ordinary
39076 configurations, the remote port number is always 25 (the SMTP port), and the
39077 local port is a random ephemeral port.
39079 .cindex "log" "process ids in"
39080 .cindex "pid (process id)" "in log lines"
39081 &%pid%&: The current process id is added to every log line, in square brackets,
39082 immediately after the time and date.
39084 .cindex log pipelining
39085 .cindex pipelining "logging outgoing"
39086 &%pipelining%&: A field is added to delivery and accept
39087 log lines when the ESMTP PIPELINING extension was used.
39088 The field is a single "L".
39090 On accept lines, where PIPELINING was offered but not used by the client,
39091 the field has a minus appended.
39093 .cindex "pipelining" "early connection"
39094 If Exim is built with the SUPPORT_PIPE_CONNECT build option
39095 accept "L" fields have a period appended if the feature was
39096 offered but not used, or an asterisk appended if used.
39097 Delivery "L" fields have an asterisk appended if used.
39100 .cindex "log" "queue run"
39101 .cindex "queue runner" "logging"
39102 &%queue_run%&: The start and end of every queue run are logged.
39104 .cindex "log" "queue time"
39105 &%queue_time%&: The amount of time the message has been in the queue on the
39106 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
39108 If millisecond logging is enabled, short times will be shown with greater
39109 precision, eg. &`QT=1.578s`&.
39111 &%queue_time_overall%&: The amount of time the message has been in the queue on
39112 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
39113 example, &`QT=3m45s`&.
39115 .cindex "log" "receive duration"
39116 &%receive_time%&: For each message, the amount of real time it has taken to
39117 perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
39118 If millisecond logging is enabled, short times will be shown with greater
39119 precision, eg. &`RT=0.204s`&.
39121 .cindex "log" "recipients"
39122 &%received_recipients%&: The recipients of a message are listed in the main log
39123 as soon as the message is received. The list appears at the end of the log line
39124 that is written when a message is received, preceded by the word &"for"&. The
39125 addresses are listed after they have been qualified, but before any rewriting
39127 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
39130 .cindex "log" "sender reception"
39131 &%received_sender%&: The unrewritten original sender of a message is added to
39132 the end of the log line that records the message's arrival, after the word
39133 &"from"& (before the recipients if &%received_recipients%& is also set).
39135 .cindex "log" "header lines for rejection"
39136 &%rejected_header%&: If a message's header has been received at the time a
39137 rejection is written to the reject log, the complete header is added to the
39138 log. Header logging can be turned off individually for messages that are
39139 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
39141 .cindex "log" "retry defer"
39142 &%retry_defer%&: A log line is written if a delivery is deferred because a
39143 retry time has not yet been reached. However, this &"retry time not reached"&
39144 message is always omitted from individual message logs after the first delivery
39147 .cindex "log" "return path"
39148 &%return_path_on_delivery%&: The return path that is being transmitted with
39149 the message is included in delivery and bounce lines, using the tag P=.
39150 This is omitted if no delivery actually happens, for example, if routing fails,
39151 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
39153 .cindex "log" "sender on delivery"
39154 &%sender_on_delivery%&: The message's sender address is added to every delivery
39155 and bounce line, tagged by F= (for &"from"&).
39156 This is the original sender that was received with the message; it is not
39157 necessarily the same as the outgoing return path.
39159 .cindex "log" "sender verify failure"
39160 &%sender_verify_fail%&: If this selector is unset, the separate log line that
39161 gives details of a sender verification failure is not written. Log lines for
39162 the rejection of SMTP commands contain just &"sender verify failed"&, so some
39165 .cindex "log" "size rejection"
39166 &%size_reject%&: A log line is written whenever a message is rejected because
39169 .cindex "log" "frozen messages; skipped"
39170 .cindex "frozen messages" "logging skipping"
39171 &%skip_delivery%&: A log line is written whenever a message is skipped during a
39172 queue run because it another process is already delivering it or because
39174 .cindex "&""spool file is locked""&"
39175 .cindex "&""message is frozen""&"
39176 The message that is written is either &"spool file is locked"& or
39177 &"message is frozen"&.
39179 .cindex "log" "smtp confirmation"
39180 .cindex "SMTP" "logging confirmation"
39181 .cindex "LMTP" "logging confirmation"
39182 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
39183 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
39184 A number of MTAs (including Exim) return an identifying string in this
39187 .cindex "log" "SMTP connections"
39188 .cindex "SMTP" "logging connections"
39189 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
39190 established or closed, unless the connection is from a host that matches
39191 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
39192 only when the closure is unexpected.) This applies to connections from local
39193 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
39194 dropped in the middle of a message, a log line is always written, whether or
39195 not this selector is set, but otherwise nothing is written at the start and end
39196 of connections unless this selector is enabled.
39198 For TCP/IP connections to an Exim daemon, the current number of connections is
39199 included in the log message for each new connection, but note that the count is
39200 reset if the daemon is restarted.
39201 Also, because connections are closed (and the closure is logged) in
39202 subprocesses, the count may not include connections that have been closed but
39203 whose termination the daemon has not yet noticed. Thus, while it is possible to
39204 match up the opening and closing of connections in the log, the value of the
39205 logged counts may not be entirely accurate.
39207 .cindex "log" "SMTP transaction; incomplete"
39208 .cindex "SMTP" "logging incomplete transactions"
39209 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
39210 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
39211 and the message sender plus any accepted recipients are included in the log
39212 line. This can provide evidence of dictionary attacks.
39214 .cindex "log" "non-MAIL SMTP sessions"
39215 .cindex "MAIL" "logging session without"
39216 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
39217 connection terminates without having issued a MAIL command. This includes both
39218 the case when the connection is dropped, and the case when QUIT is used. It
39219 does not include cases where the connection is rejected right at the start (by
39220 an ACL, or because there are too many connections, or whatever). These cases
39221 already have their own log lines.
39223 The log line that is written contains the identity of the client in the usual
39224 way, followed by D= and a time, which records the duration of the connection.
39225 If the connection was authenticated, this fact is logged exactly as it is for
39226 an incoming message, with an A= item. If the connection was encrypted, CV=,
39227 DN=, and X= items may appear as they do for an incoming message, controlled by
39228 the same logging options.
39230 Finally, if any SMTP commands were issued during the connection, a C= item
39231 is added to the line, listing the commands that were used. For example,
39235 shows that the client issued QUIT straight after EHLO. If there were fewer
39236 than 20 commands, they are all listed. If there were more than 20 commands,
39237 the last 20 are listed, preceded by &"..."&. However, with the default
39238 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
39239 have been aborted before 20 non-mail commands are processed.
39241 &%smtp_mailauth%&: A third subfield with the authenticated sender,
39242 colon-separated, is appended to the A= item for a message arrival or delivery
39243 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
39244 was accepted or used.
39246 .cindex "log" "SMTP protocol error"
39247 .cindex "SMTP" "logging protocol error"
39248 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
39249 encountered. Exim does not have perfect detection of all protocol errors
39250 because of transmission delays and the use of pipelining. If PIPELINING has
39251 been advertised to a client, an Exim server assumes that the client will use
39252 it, and therefore it does not count &"expected"& errors (for example, RCPT
39253 received after rejecting MAIL) as protocol errors.
39255 .cindex "SMTP" "logging syntax errors"
39256 .cindex "SMTP" "syntax errors; logging"
39257 .cindex "SMTP" "unknown command; logging"
39258 .cindex "log" "unknown SMTP command"
39259 .cindex "log" "SMTP syntax error"
39260 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
39261 encountered. An unrecognized command is treated as a syntax error. For an
39262 external connection, the host identity is given; for an internal connection
39263 using &%-bs%& the sender identification (normally the calling user) is given.
39265 .cindex "log" "subject"
39266 .cindex "subject, logging"
39267 &%subject%&: The subject of the message is added to the arrival log line,
39268 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
39269 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
39270 specifies whether characters with values greater than 127 should be logged
39271 unchanged, or whether they should be rendered as escape sequences.
39273 .cindex "log" "certificate verification"
39275 .cindex DANE logging
39276 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
39277 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
39279 using a CA trust anchor,
39280 &`CV=dane`& if using a DNS trust anchor,
39281 and &`CV=no`& if not.
39283 .cindex "log" "Taint warnings"
39284 &%taint%&: Log warnings about tainted data. This selector can't be
39285 turned of if &%allow_insecure_tainted_data%& is false (which is the
39288 .cindex "log" "TLS cipher"
39289 .cindex "TLS" "logging cipher"
39290 &%tls_cipher%&: When a message is sent or received over an encrypted
39291 connection, the cipher suite used is added to the log line, preceded by X=.
39293 .cindex "log" "TLS peer DN"
39294 .cindex "TLS" "logging peer DN"
39295 &%tls_peerdn%&: When a message is sent or received over an encrypted
39296 connection, and a certificate is supplied by the remote host, the peer DN is
39297 added to the log line, preceded by DN=.
39299 .cindex "log" "TLS resumption"
39300 .cindex "TLS" "logging session resumption"
39302 &%tls_resumption%&: When a message is sent or received over an encrypted
39303 connection and the TLS session resumed one used on a previous TCP connection,
39304 an asterisk is appended to the X= cipher field in the log line.
39307 .cindex "log" "TLS SNI"
39308 .cindex "TLS" "logging SNI"
39309 .cindex SNI logging
39310 &%tls_sni%&: When a message is received over an encrypted connection, and
39311 the remote host provided the Server Name Indication extension, the SNI is
39312 added to the log line, preceded by SNI=.
39314 .cindex "log" "DNS failure in list"
39315 &%unknown_in_list%&: This setting causes a log entry to be written when the
39316 result of a list match is failure because a DNS lookup failed.
39320 .section "Message log" "SECID260"
39321 .cindex "message" "log file for"
39322 .cindex "log" "message log; description of"
39323 .cindex "&_msglog_& directory"
39324 .oindex "&%preserve_message_logs%&"
39325 In addition to the general log files, Exim writes a log file for each message
39326 that it handles. The names of these per-message logs are the message ids, and
39327 they are kept in the &_msglog_& sub-directory of the spool directory. Each
39328 message log contains copies of the log lines that apply to the message. This
39329 makes it easier to inspect the status of an individual message without having
39330 to search the main log. A message log is deleted when processing of the message
39331 is complete, unless &%preserve_message_logs%& is set, but this should be used
39332 only with great care because they can fill up your disk very quickly.
39334 On a heavily loaded system, it may be desirable to disable the use of
39335 per-message logs, in order to reduce disk I/O. This can be done by setting the
39336 &%message_logs%& option false.
39342 . ////////////////////////////////////////////////////////////////////////////
39343 . ////////////////////////////////////////////////////////////////////////////
39345 .chapter "Exim utilities" "CHAPutils"
39346 .scindex IIDutils "utilities"
39347 A number of utility scripts and programs are supplied with Exim and are
39348 described in this chapter. There is also the Exim Monitor, which is covered in
39349 the next chapter. The utilities described here are:
39351 .itable none 0 0 3 7* left 15* left 40* left
39352 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
39353 "list what Exim processes are doing"
39354 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
39355 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
39356 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
39357 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
39359 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
39360 .irow &<<SECTmailstat>>& &'eximstats'& &&&
39361 "extract statistics from the log"
39362 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
39363 "check address acceptance from given IP"
39364 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
39365 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
39366 .irow &<<SECTdumpdb>>& &'exim_dumpdb'& "dump a hints database"
39367 .irow &<<SECTtidydb>>& &'exim_tidydb'& "clean up a hints database"
39368 .irow &<<SECTfixdb>>& &'exim_fixdb'& "patch a hints database"
39369 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
39372 Another utility that might be of use to sites with many MTAs is Tom Kistner's
39373 &'exilog'&. It provides log visualizations across multiple Exim servers. See
39374 &url(https://duncanthrax.net/exilog/) for details.
39379 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
39380 .cindex "&'exiwhat'&"
39381 .cindex "process, querying"
39383 On operating systems that can restart a system call after receiving a signal
39384 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
39385 a line describing what it is doing to the file &_exim-process.info_& in the
39386 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
39387 processes it can find, having first emptied the file. It then waits for one
39388 second to allow the Exim processes to react before displaying the results. In
39389 order to run &'exiwhat'& successfully you have to have sufficient privilege to
39390 send the signal to the Exim processes, so it is normally run as root.
39392 &*Warning*&: This is not an efficient process. It is intended for occasional
39393 use by system administrators. It is not sensible, for example, to set up a
39394 script that sends SIGUSR1 signals to Exim processes at short intervals.
39397 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
39398 varies in different operating systems. Not only are different options used,
39399 but the format of the output is different. For this reason, there are some
39400 system configuration options that configure exactly how &'exiwhat'& works. If
39401 it doesn't seem to be working for you, check the following compile-time
39404 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
39405 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
39406 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
39407 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
39409 An example of typical output from &'exiwhat'& is
39411 164 daemon: -q1h, listening on port 25
39412 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
39413 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
39414 [10.19.42.42] (editor@ref.example)
39415 10592 handling incoming call from [192.168.243.242]
39416 10628 accepting a local non-SMTP message
39418 The first number in the output line is the process number. The third line has
39419 been split here, in order to fit it on the page.
39423 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
39424 .cindex "&'exiqgrep'&"
39425 .cindex "queue" "grepping"
39426 This utility is a Perl script contributed by Matt Hubbard. It runs
39430 or (in case &*-a*& switch is specified)
39434 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
39435 contain alternate exim configuration the queue management might be using.
39437 to obtain a queue listing, and then greps the output to select messages
39438 that match given criteria. The following selection options are available:
39441 .vitem &*-f*&&~<&'regex'&>
39442 Match the sender address using a case-insensitive search. The field that is
39443 tested is enclosed in angle brackets, so you can test for bounce messages with
39447 .vitem &*-r*&&~<&'regex'&>
39448 Match a recipient address using a case-insensitive search. The field that is
39449 tested is not enclosed in angle brackets.
39451 .vitem &*-s*&&~<&'regex'&>
39452 Match against the size field.
39454 .vitem &*-y*&&~<&'seconds'&>
39455 Match messages that are younger than the given time.
39457 .vitem &*-o*&&~<&'seconds'&>
39458 Match messages that are older than the given time.
39461 Match only frozen messages.
39464 Match only non-frozen messages.
39466 .vitem &*-G*&&~<&'queuename'&>
39467 Match only messages in the given queue. Without this, the default queue is searched.
39470 The following options control the format of the output:
39474 Display only the count of matching messages.
39477 Long format &-- display the full message information as output by Exim. This is
39481 Display message ids only.
39484 Brief format &-- one line per message.
39487 Display messages in reverse order.
39490 Include delivered recipients in queue listing.
39493 There is one more option, &%-h%&, which outputs a list of options.
39497 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
39498 .cindex "&'exiqsumm'&"
39499 .cindex "queue" "summary"
39500 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
39501 -bp`& and produces a summary of the messages in the queue. Thus, you use it by
39502 running a command such as
39504 exim -bp | exiqsumm
39506 The output consists of one line for each domain that has messages waiting for
39507 it, as in the following example:
39509 3 2322 74m 66m msn.com.example
39511 Each line lists the number of pending deliveries for a domain, their total
39512 volume, and the length of time that the oldest and the newest messages have
39513 been waiting. Note that the number of pending deliveries is greater than the
39514 number of messages when messages have more than one recipient.
39516 A summary line is output at the end. By default the output is sorted on the
39517 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
39518 the output to be sorted by oldest message and by count of messages,
39519 respectively. There are also three options that split the messages for each
39520 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
39521 separates frozen messages, and &%-s%& separates messages according to their
39524 The output of &'exim -bp'& contains the original addresses in the message, so
39525 this also applies to the output from &'exiqsumm'&. No domains from addresses
39526 generated by aliasing or forwarding are included (unless the &%one_time%&
39527 option of the &(redirect)& router has been used to convert them into &"top
39528 level"& addresses).
39533 .section "Extracting specific information from the log (exigrep)" &&&
39535 .cindex "&'exigrep'&"
39536 .cindex "log" "extracts; grepping for"
39537 The &'exigrep'& utility is a Perl script that searches one or more main log
39538 files for entries that match a given pattern. When it finds a match, it
39539 extracts all the log entries for the relevant message, not just those that
39540 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
39541 given message, or all mail for a given user, or for a given host, for example.
39542 The input files can be in Exim log format or syslog format.
39543 If a matching log line is not associated with a specific message, it is
39544 included in &'exigrep'&'s output without any additional lines. The usage is:
39546 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
39548 If no log filenames are given on the command line, the standard input is read.
39550 The &%-t%& argument specifies a number of seconds. It adds an additional
39551 condition for message selection. Messages that are complete are shown only if
39552 they spent more than <&'n'&> seconds in the queue.
39554 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
39555 makes it case-sensitive. This may give a performance improvement when searching
39556 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
39557 option; with &%-I%& they do not. In both cases it is possible to change the
39558 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
39560 The &%-l%& option means &"literal"&, that is, treat all characters in the
39561 pattern as standing for themselves. Otherwise the pattern must be a Perl
39562 regular expression.
39564 The &%-v%& option inverts the matching condition. That is, a line is selected
39565 if it does &'not'& match the pattern.
39567 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
39568 that are generated as a result/response to a message that &'exigrep'& matched
39572 user_a sends a message to user_b, which generates a bounce back to user_b. If
39573 &'exigrep'& is used to search for &"user_a"&, only the first message will be
39574 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
39575 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
39576 when searching for &"user_a"& will show both messages since the bounce is
39577 &"related"& to or a &"result"& of the first message that was found by the
39580 If the location of a &'zcat'& command is known from the definition of
39581 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
39582 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
39583 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
39584 autodetection of some well known compression extensions.
39587 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
39588 .cindex "&'exipick'&"
39589 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
39590 lists messages from the queue according to a variety of criteria. For details
39591 of &'exipick'&'s facilities, run &'exipick'& with
39592 the &%--help%& option.
39595 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
39596 .cindex "log" "cycling local files"
39597 .cindex "cycling logs"
39598 .cindex "&'exicyclog'&"
39599 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
39600 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
39601 you are using log files with datestamps in their names (see section
39602 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
39603 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
39604 There are two command line options for &'exicyclog'&:
39606 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
39607 default that is set when Exim is built. The default default is 10.
39609 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
39610 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
39611 overriding the script's default, which is to find the setting from Exim's
39615 Each time &'exicyclog'& is run the filenames get &"shuffled down"& by one. If
39616 the main log filename is &_mainlog_& (the default) then when &'exicyclog'& is
39617 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
39618 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
39619 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
39620 logs are handled similarly.
39622 If the limit is greater than 99, the script uses 3-digit numbers such as
39623 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
39624 to one that is greater, or &'vice versa'&, you will have to fix the names of
39625 any existing log files.
39627 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
39628 the end are deleted. All files with numbers greater than 01 are compressed,
39629 using a compression command which is configured by the COMPRESS_COMMAND
39630 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
39631 root &%crontab%& entry of the form
39633 1 0 * * * su exim -c /usr/exim/bin/exicyclog
39635 assuming you have used the name &"exim"& for the Exim user. You can run
39636 &'exicyclog'& as root if you wish, but there is no need.
39640 .section "Mail statistics (eximstats)" "SECTmailstat"
39641 .cindex "statistics"
39642 .cindex "&'eximstats'&"
39643 A Perl script called &'eximstats'& is provided for extracting statistical
39644 information from log files. The output is either plain text, or HTML.
39645 . --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan
39646 . --- 404 error and everything else points to that.
39648 The &'eximstats'& script has been hacked about quite a bit over time. The
39649 latest version is the result of some extensive revision by Steve Campbell. A
39650 lot of information is given by default, but there are options for suppressing
39651 various parts of it. Following any options, the arguments to the script are a
39652 list of files, which should be main log files. For example:
39654 eximstats -nr /var/spool/exim/log/mainlog.01
39656 By default, &'eximstats'& extracts information about the number and volume of
39657 messages received from or delivered to various hosts. The information is sorted
39658 both by message count and by volume, and the top fifty hosts in each category
39659 are listed on the standard output. Similar information, based on email
39660 addresses or domains instead of hosts can be requested by means of various
39661 options. For messages delivered and received locally, similar statistics are
39662 also produced per user.
39664 The output also includes total counts and statistics about delivery errors, and
39665 histograms showing the number of messages received and deliveries made in each
39666 hour of the day. A delivery with more than one address in its envelope (for
39667 example, an SMTP transaction with more than one RCPT command) is counted
39668 as a single delivery by &'eximstats'&.
39670 Though normally more deliveries than receipts are reported (as messages may
39671 have multiple recipients), it is possible for &'eximstats'& to report more
39672 messages received than delivered, even though the queue is empty at the start
39673 and end of the period in question. If an incoming message contains no valid
39674 recipients, no deliveries are recorded for it. A bounce message is handled as
39675 an entirely separate message.
39677 &'eximstats'& always outputs a grand total summary giving the volume and number
39678 of messages received and deliveries made, and the number of hosts involved in
39679 each case. It also outputs the number of messages that were delayed (that is,
39680 not completely delivered at the first attempt), and the number that had at
39681 least one address that failed.
39683 The remainder of the output is in sections that can be independently disabled
39684 or modified by various options. It consists of a summary of deliveries by
39685 transport, histograms of messages received and delivered per time interval
39686 (default per hour), information about the time messages spent in the queue,
39687 a list of relayed messages, lists of the top fifty sending hosts, local
39688 senders, destination hosts, and destination local users by count and by volume,
39689 and a list of delivery errors that occurred.
39691 The relay information lists messages that were actually relayed, that is, they
39692 came from a remote host and were directly delivered to some other remote host,
39693 without being processed (for example, for aliasing or forwarding) locally.
39695 There are quite a few options for &'eximstats'& to control exactly what it
39696 outputs. These are documented in the Perl script itself, and can be extracted
39697 by running the command &(perldoc)& on the script. For example:
39699 perldoc /usr/exim/bin/eximstats
39702 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
39703 .cindex "&'exim_checkaccess'&"
39704 .cindex "policy control" "checking access"
39705 .cindex "checking access"
39706 The &%-bh%& command line argument allows you to run a fake SMTP session with
39707 debugging output, in order to check what Exim is doing when it is applying
39708 policy controls to incoming SMTP mail. However, not everybody is sufficiently
39709 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
39710 sometimes you just want to answer the question &"Does this address have
39711 access?"& without bothering with any further details.
39713 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
39714 two arguments, an IP address and an email address:
39716 exim_checkaccess 10.9.8.7 A.User@a.domain.example
39718 The utility runs a call to Exim with the &%-bh%& option, to test whether the
39719 given email address would be accepted in a RCPT command in a TCP/IP
39720 connection from the host with the given IP address. The output of the utility
39721 is either the word &"accepted"&, or the SMTP error response, for example:
39724 550 Relay not permitted
39726 When running this test, the utility uses &`<>`& as the envelope sender address
39727 for the MAIL command, but you can change this by providing additional
39728 options. These are passed directly to the Exim command. For example, to specify
39729 that the test is to be run with the sender address &'himself@there.example'&
39732 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
39733 -f himself@there.example
39735 Note that these additional Exim command line items must be given after the two
39736 mandatory arguments.
39738 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
39739 while running its checks. You can run checks that include callouts by using
39740 &%-bhc%&, but this is not yet available in a &"packaged"& form.
39744 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
39745 .cindex "DBM" "building dbm files"
39746 .cindex "building DBM files"
39747 .cindex "&'exim_dbmbuild'&"
39748 .cindex "lower casing"
39749 .cindex "binary zero" "in lookup key"
39750 The &'exim_dbmbuild'& program reads an input file containing keys and data in
39751 the format used by the &(lsearch)& lookup (see section
39752 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
39753 names as keys and the remainder of the information as data. The lower-casing
39754 can be prevented by calling the program with the &%-nolc%& option.
39756 A terminating zero is included as part of the key string. This is expected by
39757 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
39758 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
39759 strings or the data strings. The &(dbmnz)& lookup type can be used with such
39762 The program requires two arguments: the name of the input file (which can be a
39763 single hyphen to indicate the standard input), and the name of the output file.
39764 It creates the output under a temporary name, and then renames it if all went
39768 If the native DB interface is in use (USE_DB is set in a compile-time
39769 configuration file &-- this is common in free versions of Unix) the two
39770 filenames must be different, because in this mode the Berkeley DB functions
39771 create a single output file using exactly the name given. For example,
39773 exim_dbmbuild /etc/aliases /etc/aliases.db
39775 reads the system alias file and creates a DBM version of it in
39776 &_/etc/aliases.db_&.
39778 In systems that use the &'ndbm'& routines (mostly proprietary versions of
39779 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
39780 environment, the suffixes are added to the second argument of
39781 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
39782 when the Berkeley functions are used in compatibility mode (though this is not
39783 recommended), because in that case it adds a &_.db_& suffix to the filename.
39785 If a duplicate key is encountered, the program outputs a warning, and when it
39786 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
39787 option is used. By default, only the first of a set of duplicates is used &--
39788 this makes it compatible with &(lsearch)& lookups. There is an option
39789 &%-lastdup%& which causes it to use the data for the last duplicate instead.
39790 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
39791 &%stderr%&. For other errors, where it doesn't actually make a new file, the
39797 .section "Finding individual retry times (exinext)" "SECTfinindret"
39798 .cindex "retry" "times"
39799 .cindex "&'exinext'&"
39800 A utility called &'exinext'& (mostly a Perl script) provides the ability to
39801 fish specific information out of the retry database. Given a mail domain (or a
39802 complete address), it looks up the hosts for that domain, and outputs any retry
39803 information for the hosts or for the domain. At present, the retry information
39804 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
39805 output. For example:
39807 $ exinext piglet@milne.fict.example
39808 kanga.milne.example:192.168.8.1 error 146: Connection refused
39809 first failed: 21-Feb-1996 14:57:34
39810 last tried: 21-Feb-1996 14:57:34
39811 next try at: 21-Feb-1996 15:02:34
39812 roo.milne.example:192.168.8.3 error 146: Connection refused
39813 first failed: 20-Jan-1996 13:12:08
39814 last tried: 21-Feb-1996 11:42:03
39815 next try at: 21-Feb-1996 19:42:03
39816 past final cutoff time
39818 You can also give &'exinext'& a local part, without a domain, and it
39819 will give any retry information for that local part in your default domain.
39820 A message id can be used to obtain retry information pertaining to a specific
39821 message. This exists only when an attempt to deliver a message to a remote host
39822 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
39823 &'exinext'& is not particularly efficient, but then it is not expected to be
39826 The &'exinext'& utility calls Exim to find out information such as the location
39827 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
39828 passed on to the &'exim'& commands. The first specifies an alternate Exim
39829 configuration file, and the second sets macros for use within the configuration
39830 file. These features are mainly to help in testing, but might also be useful in
39831 environments where more than one configuration file is in use.
39835 .section "Hints database maintenance" "SECThindatmai"
39836 .cindex "hints database" "maintenance"
39837 .cindex "maintaining Exim's hints database"
39838 Three utility programs are provided for maintaining the DBM files that Exim
39839 uses to contain its delivery hint information. Each program requires two
39840 arguments. The first specifies the name of Exim's spool directory, and the
39841 second is the name of the database it is to operate on. These are as follows:
39844 &'retry'&: the database of retry information
39846 &'wait-'&<&'transport name'&>: databases of information about messages waiting
39849 &'callout'&: the callout cache
39851 &'ratelimit'&: the data for implementing the ratelimit ACL condition
39854 &'tls'&: TLS session resumption data
39857 &'misc'&: other hints data
39860 The &'misc'& database is used for
39863 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
39865 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
39866 &(smtp)& transport)
39868 Limiting the concurrency of specific transports (when &%max_parallel%& is set
39874 .section "exim_dumpdb" "SECTdumpdb"
39875 .cindex "&'exim_dumpdb'&"
39876 The entire contents of a database are written to the standard output by the
39877 &'exim_dumpdb'& program, which has no options or arguments other than the
39878 spool and database names. For example, to dump the retry database:
39880 exim_dumpdb /var/spool/exim retry
39882 Two lines of output are produced for each entry:
39884 T:mail.ref.example:192.168.242.242 146 77 Connection refused
39885 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
39887 The first item on the first line is the key of the record. It starts with one
39888 of the letters R, or T, depending on whether it refers to a routing or
39889 transport retry. For a local delivery, the next part is the local address; for
39890 a remote delivery it is the name of the remote host, followed by its failing IP
39891 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
39892 transport). If the remote port is not the standard one (port 25), it is added
39893 to the IP address. Then there follows an error code, an additional error code,
39894 and a textual description of the error.
39896 The three times on the second line are the time of first failure, the time of
39897 the last delivery attempt, and the computed time for the next attempt. The line
39898 ends with an asterisk if the cutoff time for the last retry rule has been
39901 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
39902 consists of a host name followed by a list of ids for messages that are or were
39903 waiting to be delivered to that host. If there are a very large number for any
39904 one host, continuation records, with a sequence number added to the host name,
39905 may be seen. The data in these records is often out of date, because a message
39906 may be routed to several alternative hosts, and Exim makes no effort to keep
39911 .section "exim_tidydb" "SECTtidydb"
39912 .cindex "&'exim_tidydb'&"
39913 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
39914 database. If run with no options, it removes all records that are more than 30
39915 days old. The age is calculated from the date and time that the record was last
39916 updated. Note that, in the case of the retry database, it is &'not'& the time
39917 since the first delivery failure. Information about a host that has been down
39918 for more than 30 days will remain in the database, provided that the record is
39919 updated sufficiently often.
39921 The cutoff date can be altered by means of the &%-t%& option, which must be
39922 followed by a time. For example, to remove all records older than a week from
39923 the retry database:
39925 exim_tidydb -t 7d /var/spool/exim retry
39927 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
39928 message ids. In the former these appear as data in records keyed by host &--
39929 they were messages that were waiting for that host &-- and in the latter they
39930 are the keys for retry information for messages that have suffered certain
39931 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
39932 message ids in database records are those of messages that are still on the
39933 queue. Message ids for messages that no longer exist are removed from
39934 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
39935 For the &'retry'& database, records whose keys are non-existent message ids are
39936 removed. The &'exim_tidydb'& utility outputs comments on the standard output
39937 whenever it removes information from the database.
39939 Certain records are automatically removed by Exim when they are no longer
39940 needed, but others are not. For example, if all the MX hosts for a domain are
39941 down, a retry record is created for each one. If the primary MX host comes back
39942 first, its record is removed when Exim successfully delivers to it, but the
39943 records for the others remain because Exim has not tried to use those hosts.
39945 It is important, therefore, to run &'exim_tidydb'& periodically on all the
39946 hints databases. You should do this at a quiet time of day, because it requires
39947 a database to be locked (and therefore inaccessible to Exim) while it does its
39948 work. Removing records from a DBM file does not normally make the file smaller,
39949 but all the common DBM libraries are able to re-use the space that is released.
39950 After an initial phase of increasing in size, the databases normally reach a
39951 point at which they no longer get any bigger, as long as they are regularly
39954 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
39955 databases is likely to keep on increasing.
39960 .section "exim_fixdb" "SECTfixdb"
39961 .cindex "&'exim_fixdb'&"
39962 The &'exim_fixdb'& program is a utility for interactively modifying databases.
39963 Its main use is for testing Exim, but it might also be occasionally useful for
39964 getting round problems in a live system. It has no options, and its interface
39965 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
39966 key of a database record can then be entered, and the data for that record is
39969 If &"d"& is typed at the next prompt, the entire record is deleted. For all
39970 except the &'retry'& database, that is the only operation that can be carried
39971 out. For the &'retry'& database, each field is output preceded by a number, and
39972 data for individual fields can be changed by typing the field number followed
39973 by new data, for example:
39977 resets the time of the next delivery attempt. Time values are given as a
39978 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
39979 used as optional separators.
39984 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
39985 .cindex "mailbox" "maintenance"
39986 .cindex "&'exim_lock'&"
39987 .cindex "locking mailboxes"
39988 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
39989 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
39990 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
39991 a user agent while investigating a problem. The utility requires the name of
39992 the file as its first argument. If the locking is successful, the second
39993 argument is run as a command (using C's &[system()]& function); if there is no
39994 second argument, the value of the SHELL environment variable is used; if this
39995 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
39996 is unlocked and the utility ends. The following options are available:
40000 Use &[fcntl()]& locking on the open mailbox.
40003 Use &[flock()]& locking on the open mailbox, provided the operating system
40006 .vitem &%-interval%&
40007 This must be followed by a number, which is a number of seconds; it sets the
40008 interval to sleep between retries (default 3).
40010 .vitem &%-lockfile%&
40011 Create a lock file before opening the mailbox.
40014 Lock the mailbox using MBX rules.
40017 Suppress verification output.
40019 .vitem &%-retries%&
40020 This must be followed by a number; it sets the number of times to try to get
40021 the lock (default 10).
40023 .vitem &%-restore_time%&
40024 This option causes &%exim_lock%& to restore the modified and read times to the
40025 locked file before exiting. This allows you to access a locked mailbox (for
40026 example, to take a backup copy) without disturbing the times that the user
40029 .vitem &%-timeout%&
40030 This must be followed by a number, which is a number of seconds; it sets a
40031 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
40032 default), a non-blocking call is used.
40035 Generate verbose output.
40038 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
40039 default is to create a lock file and also to use &[fcntl()]& locking on the
40040 mailbox, which is the same as Exim's default. The use of &%-flock%& or
40041 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
40042 requires that the directory containing the file be writeable. Locking by lock
40043 file does not last forever; Exim assumes that a lock file is expired if it is
40044 more than 30 minutes old.
40046 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
40047 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
40048 to be taken out on the open mailbox, and an exclusive lock on the file
40049 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
40050 number of the mailbox file. When the locking is released, if an exclusive lock
40051 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
40053 The default output contains verification of the locking that takes place. The
40054 &%-v%& option causes some additional information to be given. The &%-q%& option
40055 suppresses all output except error messages.
40059 exim_lock /var/spool/mail/spqr
40061 runs an interactive shell while the file is locked, whereas
40063 &`exim_lock -q /var/spool/mail/spqr <<End`&
40064 <&'some commands'&>
40067 runs a specific non-interactive sequence of commands while the file is locked,
40068 suppressing all verification output. A single command can be run by a command
40071 exim_lock -q /var/spool/mail/spqr \
40072 "cp /var/spool/mail/spqr /some/where"
40074 Note that if a command is supplied, it must be entirely contained within the
40075 second argument &-- hence the quotes.
40079 . ////////////////////////////////////////////////////////////////////////////
40080 . ////////////////////////////////////////////////////////////////////////////
40082 .chapter "The Exim monitor" "CHAPeximon"
40083 .scindex IIDeximon "Exim monitor" "description"
40084 .cindex "X-windows"
40085 .cindex "&'eximon'&"
40086 .cindex "Local/eximon.conf"
40087 .cindex "&_exim_monitor/EDITME_&"
40088 The Exim monitor is an application which displays in an X window information
40089 about the state of Exim's queue and what Exim is doing. An admin user can
40090 perform certain operations on messages from this GUI interface; however all
40091 such facilities are also available from the command line, and indeed, the
40092 monitor itself makes use of the command line to perform any actions requested.
40096 .section "Running the monitor" "SECID264"
40097 The monitor is started by running the script called &'eximon'&. This is a shell
40098 script that sets up a number of environment variables, and then runs the
40099 binary called &_eximon.bin_&. The default appearance of the monitor window can
40100 be changed by editing the &_Local/eximon.conf_& file created by editing
40101 &_exim_monitor/EDITME_&. Comments in that file describe what the various
40102 parameters are for.
40104 The parameters that get built into the &'eximon'& script can be overridden for
40105 a particular invocation by setting up environment variables of the same names,
40106 preceded by &`EXIMON_`&. For example, a shell command such as
40108 EXIMON_LOG_DEPTH=400 eximon
40110 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
40111 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
40112 overrides the Exim log file configuration. This makes it possible to have
40113 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
40114 syslog messages are routed to a file on the local host.
40116 X resources can be used to change the appearance of the window in the normal
40117 way. For example, a resource setting of the form
40119 Eximon*background: gray94
40121 changes the colour of the background to light grey rather than white. The
40122 stripcharts are drawn with both the data lines and the reference lines in
40123 black. This means that the reference lines are not visible when on top of the
40124 data. However, their colour can be changed by setting a resource called
40125 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
40126 For example, if your X server is running Unix, you could set up lighter
40127 reference lines in the stripcharts by obeying
40130 Eximon*highlight: gray
40133 .cindex "admin user"
40134 In order to see the contents of messages in the queue, and to operate on them,
40135 &'eximon'& must either be run as root or by an admin user.
40137 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
40138 contain X11 resource parameters interpreted by the X11 library. In addition,
40139 if the first parameter starts with the string "gdb" then it is removed and the
40140 binary is invoked under gdb (the parameter is used as the gdb command-name, so
40141 versioned variants of gdb can be invoked).
40143 The monitor's window is divided into three parts. The first contains one or
40144 more stripcharts and two action buttons, the second contains a &"tail"& of the
40145 main log file, and the third is a display of the queue of messages awaiting
40146 delivery, with two more action buttons. The following sections describe these
40147 different parts of the display.
40152 .section "The stripcharts" "SECID265"
40153 .cindex "stripchart"
40154 The first stripchart is always a count of messages in the queue. Its name can
40155 be configured by setting QUEUE_STRIPCHART_NAME in the
40156 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
40157 configuration script by regular expression matches on log file entries, making
40158 it possible to display, for example, counts of messages delivered to certain
40159 hosts or using certain transports. The supplied defaults display counts of
40160 received and delivered messages, and of local and SMTP deliveries. The default
40161 period between stripchart updates is one minute; this can be adjusted by a
40162 parameter in the &_Local/eximon.conf_& file.
40164 The stripchart displays rescale themselves automatically as the value they are
40165 displaying changes. There are always 10 horizontal lines in each chart; the
40166 title string indicates the value of each division when it is greater than one.
40167 For example, &"x2"& means that each division represents a value of 2.
40169 It is also possible to have a stripchart which shows the percentage fullness of
40170 a particular disk partition, which is useful when local deliveries are confined
40171 to a single partition.
40173 .cindex "&%statvfs%& function"
40174 This relies on the availability of the &[statvfs()]& function or equivalent in
40175 the operating system. Most, but not all versions of Unix that support Exim have
40176 this. For this particular stripchart, the top of the chart always represents
40177 100%, and the scale is given as &"x10%"&. This chart is configured by setting
40178 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
40179 &_Local/eximon.conf_& file.
40184 .section "Main action buttons" "SECID266"
40185 .cindex "size" "of monitor window"
40186 .cindex "Exim monitor" "window size"
40187 .cindex "window size"
40188 Below the stripcharts there is an action button for quitting the monitor. Next
40189 to this is another button marked &"Size"&. They are placed here so that
40190 shrinking the window to its default minimum size leaves just the queue count
40191 stripchart and these two buttons visible. Pressing the &"Size"& button causes
40192 the window to expand to its maximum size, unless it is already at the maximum,
40193 in which case it is reduced to its minimum.
40195 When expanding to the maximum, if the window cannot be fully seen where it
40196 currently is, it is moved back to where it was the last time it was at full
40197 size. When it is expanding from its minimum size, the old position is
40198 remembered, and next time it is reduced to the minimum it is moved back there.
40200 The idea is that you can keep a reduced window just showing one or two
40201 stripcharts at a convenient place on your screen, easily expand it to show
40202 the full window when required, and just as easily put it back to what it was.
40203 The idea is copied from what the &'twm'& window manager does for its
40204 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
40205 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
40207 Normally, the monitor starts up with the window at its full size, but it can be
40208 built so that it starts up with the window at its smallest size, by setting
40209 START_SMALL=yes in &_Local/eximon.conf_&.
40213 .section "The log display" "SECID267"
40214 .cindex "log" "tail of; in monitor"
40215 The second section of the window is an area in which a display of the tail of
40216 the main log is maintained.
40217 To save space on the screen, the timestamp on each log line is shortened by
40218 removing the date and, if &%log_timezone%& is set, the timezone.
40219 The log tail is not available when the only destination for logging data is
40220 syslog, unless the syslog lines are routed to a local file whose name is passed
40221 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
40223 The log sub-window has a scroll bar at its lefthand side which can be used to
40224 move back to look at earlier text, and the up and down arrow keys also have a
40225 scrolling effect. The amount of log that is kept depends on the setting of
40226 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
40227 to use. When this is full, the earlier 50% of data is discarded &-- this is
40228 much more efficient than throwing it away line by line. The sub-window also has
40229 a horizontal scroll bar for accessing the ends of long log lines. This is the
40230 only means of horizontal scrolling; the right and left arrow keys are not
40231 available. Text can be cut from this part of the window using the mouse in the
40232 normal way. The size of this subwindow is controlled by parameters in the
40233 configuration file &_Local/eximon.conf_&.
40235 Searches of the text in the log window can be carried out by means of the ^R
40236 and ^S keystrokes, which default to a reverse and a forward search,
40237 respectively. The search covers only the text that is displayed in the window.
40238 It cannot go further back up the log.
40240 The point from which the search starts is indicated by a caret marker. This is
40241 normally at the end of the text in the window, but can be positioned explicitly
40242 by pointing and clicking with the left mouse button, and is moved automatically
40243 by a successful search. If new text arrives in the window when it is scrolled
40244 back, the caret remains where it is, but if the window is not scrolled back,
40245 the caret is moved to the end of the new text.
40247 Pressing ^R or ^S pops up a window into which the search text can be typed.
40248 There are buttons for selecting forward or reverse searching, for carrying out
40249 the search, and for cancelling. If the &"Search"& button is pressed, the search
40250 happens and the window remains so that further searches can be done. If the
40251 &"Return"& key is pressed, a single search is done and the window is closed. If
40252 ^C is typed the search is cancelled.
40254 The searching facility is implemented using the facilities of the Athena text
40255 widget. By default this pops up a window containing both &"search"& and
40256 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
40257 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
40258 However, the linkers in BSDI and HP-UX seem unable to handle an externally
40259 provided version of &%TextPop%& when the remaining parts of the text widget
40260 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
40261 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
40262 on these systems, at the expense of having unwanted items in the search popup
40267 .section "The queue display" "SECID268"
40268 .cindex "queue" "display in monitor"
40269 The bottom section of the monitor window contains a list of all messages that
40270 are in the queue, which includes those currently being received or delivered,
40271 as well as those awaiting delivery. The size of this subwindow is controlled by
40272 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
40273 at which it is updated is controlled by another parameter in the same file &--
40274 the default is 5 minutes, since queue scans can be quite expensive. However,
40275 there is an &"Update"& action button just above the display which can be used
40276 to force an update of the queue display at any time.
40278 When a host is down for some time, a lot of pending mail can build up for it,
40279 and this can make it hard to deal with other messages in the queue. To help
40280 with this situation there is a button next to &"Update"& called &"Hide"&. If
40281 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
40282 type anything in here and press &"Return"&, the text is added to a chain of
40283 such texts, and if every undelivered address in a message matches at least one
40284 of the texts, the message is not displayed.
40286 If there is an address that does not match any of the texts, all the addresses
40287 are displayed as normal. The matching happens on the ends of addresses so, for
40288 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
40289 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
40290 has been set up, a button called &"Unhide"& is displayed. If pressed, it
40291 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
40292 a hide request is automatically cancelled after one hour.
40294 While the dialogue box is displayed, you can't press any buttons or do anything
40295 else to the monitor window. For this reason, if you want to cut text from the
40296 queue display to use in the dialogue box, you have to do the cutting before
40297 pressing the &"Hide"& button.
40299 The queue display contains, for each unhidden queued message, the length of
40300 time it has been in the queue, the size of the message, the message id, the
40301 message sender, and the first undelivered recipient, all on one line. If it is
40302 a bounce message, the sender is shown as &"<>"&. If there is more than one
40303 recipient to which the message has not yet been delivered, subsequent ones are
40304 listed on additional lines, up to a maximum configured number, following which
40305 an ellipsis is displayed. Recipients that have already received the message are
40308 .cindex "frozen messages" "display"
40309 If a message is frozen, an asterisk is displayed at the left-hand side.
40311 The queue display has a vertical scroll bar, and can also be scrolled by means
40312 of the arrow keys. Text can be cut from it using the mouse in the normal way.
40313 The text searching facilities, as described above for the log window, are also
40314 available, but the caret is always moved to the end of the text when the queue
40315 display is updated.
40319 .section "The queue menu" "SECID269"
40320 .cindex "queue" "menu in monitor"
40321 If the &%shift%& key is held down and the left button is clicked when the mouse
40322 pointer is over the text for any message, an action menu pops up, and the first
40323 line of the queue display for the message is highlighted. This does not affect
40326 If you want to use some other event for popping up the menu, you can set the
40327 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
40328 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
40329 value set in this parameter is a standard X event description. For example, to
40330 run eximon using &%ctrl%& rather than &%shift%& you could use
40332 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
40334 The title of the menu is the message id, and it contains entries which act as
40338 &'message log'&: The contents of the message log for the message are displayed
40339 in a new text window.
40341 &'headers'&: Information from the spool file that contains the envelope
40342 information and headers is displayed in a new text window. See chapter
40343 &<<CHAPspool>>& for a description of the format of spool files.
40345 &'body'&: The contents of the spool file containing the body of the message are
40346 displayed in a new text window. There is a default limit of 20,000 bytes to the
40347 amount of data displayed. This can be changed by setting the BODY_MAX
40348 option at compile time, or the EXIMON_BODY_MAX option at runtime.
40350 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
40351 delivery of the message. This causes an automatic thaw if the message is
40352 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
40353 a new text window. The delivery is run in a separate process, to avoid holding
40354 up the monitor while the delivery proceeds.
40356 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
40357 that the message be frozen.
40359 .cindex "thawing messages"
40360 .cindex "unfreezing messages"
40361 .cindex "frozen messages" "thawing"
40362 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
40363 that the message be thawed.
40365 .cindex "delivery" "forcing failure"
40366 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
40367 that Exim gives up trying to deliver the message. A bounce message is generated
40368 for any remaining undelivered addresses.
40370 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
40371 that the message be deleted from the system without generating a bounce
40374 &'add recipient'&: A dialog box is displayed into which a recipient address can
40375 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40376 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40377 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40378 causes a call to Exim to be made using the &%-Mar%& option to request that an
40379 additional recipient be added to the message, unless the entry box is empty, in
40380 which case no action is taken.
40382 &'mark delivered'&: A dialog box is displayed into which a recipient address
40383 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40384 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40385 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40386 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
40387 recipient address as already delivered, unless the entry box is empty, in which
40388 case no action is taken.
40390 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
40391 mark all recipient addresses as already delivered.
40393 &'edit sender'&: A dialog box is displayed initialized with the current
40394 sender's address. Pressing RETURN causes a call to Exim to be made using the
40395 &%-Mes%& option to replace the sender address, unless the entry box is empty,
40396 in which case no action is taken. If you want to set an empty sender (as in
40397 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
40398 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
40399 the address is qualified with that domain.
40402 When a delivery is forced, a window showing the &%-v%& output is displayed. In
40403 other cases when a call to Exim is made, if there is any output from Exim (in
40404 particular, if the command fails) a window containing the command and the
40405 output is displayed. Otherwise, the results of the action are normally apparent
40406 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
40407 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
40408 if no output is generated.
40410 The queue display is automatically updated for actions such as freezing and
40411 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
40412 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
40413 force an update of the display after one of these actions.
40415 In any text window that is displayed as result of a menu action, the normal
40416 cut-and-paste facility is available, and searching can be carried out using ^R
40417 and ^S, as described above for the log tail window.
40424 . ////////////////////////////////////////////////////////////////////////////
40425 . ////////////////////////////////////////////////////////////////////////////
40427 .chapter "Security considerations" "CHAPsecurity"
40428 .scindex IIDsecurcon "security" "discussion of"
40429 This chapter discusses a number of issues concerned with security, some of
40430 which are also covered in other parts of this manual.
40432 For reasons that this author does not understand, some people have promoted
40433 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
40434 existence of this chapter in the documentation. However, the intent of the
40435 chapter is simply to describe the way Exim works in relation to certain
40436 security concerns, not to make any specific claims about the effectiveness of
40437 its security as compared with other MTAs.
40439 What follows is a description of the way Exim is supposed to be. Best efforts
40440 have been made to try to ensure that the code agrees with the theory, but an
40441 absence of bugs can never be guaranteed. Any that are reported will get fixed
40442 as soon as possible.
40445 .section "Building a more &""hardened""& Exim" "SECID286"
40446 .cindex "security" "build-time features"
40447 There are a number of build-time options that can be set in &_Local/Makefile_&
40448 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
40449 Exim administrator who does not have the root password, or by someone who has
40450 penetrated the Exim (but not the root) account. These options are as follows:
40453 ALT_CONFIG_PREFIX can be set to a string that is required to match the
40454 start of any filenames used with the &%-C%& option. When it is set, these
40455 filenames are also not allowed to contain the sequence &"/../"&. (However, if
40456 the value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
40457 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
40458 default setting for &%ALT_CONFIG_PREFIX%&.
40460 If the permitted configuration files are confined to a directory to
40461 which only root has access, this guards against someone who has broken
40462 into the Exim account from running a privileged Exim with an arbitrary
40463 configuration file, and using it to break into other accounts.
40466 If a non-trusted configuration file (i.e. not the default configuration file
40467 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
40468 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
40469 the next item), then root privilege is retained only if the caller of Exim is
40470 root. This locks out the possibility of testing a configuration using &%-C%&
40471 right through message reception and delivery, even if the caller is root. The
40472 reception works, but by that time, Exim is running as the Exim user, so when
40473 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
40474 privilege to be lost. However, root can test reception and delivery using two
40478 The WHITELIST_D_MACROS build option declares some macros to be safe to override
40479 with &%-D%& if the real uid is one of root, the Exim run-time user or the
40480 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
40481 requiring the run-time value supplied to &%-D%& to match a regex that errs on
40482 the restrictive side. Requiring build-time selection of safe macros is onerous
40483 but this option is intended solely as a transition mechanism to permit
40484 previously-working configurations to continue to work after release 4.73.
40486 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
40489 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
40490 never to be used for any deliveries. This is like the &%never_users%& runtime
40491 option, but it cannot be overridden; the runtime option adds additional users
40492 to the list. The default setting is &"root"&; this prevents a non-root user who
40493 is permitted to modify the runtime file from using Exim as a way to get root.
40498 .section "Root privilege" "SECID270"
40500 .cindex "root privilege"
40501 The Exim binary is normally setuid to root, which means that it gains root
40502 privilege (runs as root) when it starts execution. In some special cases (for
40503 example, when the daemon is not in use and there are no local deliveries), it
40504 may be possible to run Exim setuid to some user other than root. This is
40505 discussed in the next section. However, in most installations, root privilege
40506 is required for two things:
40509 To set up a socket connected to the standard SMTP port (25) when initialising
40510 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
40513 To be able to change uid and gid in order to read users' &_.forward_& files and
40514 perform local deliveries as the receiving user or as specified in the
40518 It is not necessary to be root to do any of the other things Exim does, such as
40519 receiving messages and delivering them externally over SMTP, and it is
40520 obviously more secure if Exim does not run as root except when necessary.
40521 For this reason, a user and group for Exim to use must be defined in
40522 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
40523 group"&. Their values can be changed by the runtime configuration, though this
40524 is not recommended. Often a user called &'exim'& is used, but some sites use
40525 &'mail'& or another user name altogether.
40527 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
40528 abdication; the process cannot regain root afterwards. Prior to release 4.00,
40529 &[seteuid()]& was used in some circumstances, but this is no longer the case.
40531 After a new Exim process has interpreted its command line options, it changes
40532 uid and gid in the following cases:
40537 If the &%-C%& option is used to specify an alternate configuration file, or if
40538 the &%-D%& option is used to define macro values for the configuration, and the
40539 calling process is not running as root, the uid and gid are changed to those of
40540 the calling process.
40541 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
40542 option may not be used at all.
40543 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
40544 can be supplied if the calling process is running as root, the Exim run-time
40545 user or CONFIGURE_OWNER, if defined.
40550 If the expansion test option (&%-be%&) or one of the filter testing options
40551 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
40554 If the process is not a daemon process or a queue runner process or a delivery
40555 process or a process for testing address routing (started with &%-bt%&), the
40556 uid and gid are changed to the Exim user and group. This means that Exim always
40557 runs under its own uid and gid when receiving messages. This also applies when
40558 testing address verification
40561 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
40564 For a daemon, queue runner, delivery, or address testing process, the uid
40565 remains as root at this stage, but the gid is changed to the Exim group.
40568 The processes that initially retain root privilege behave as follows:
40571 A daemon process changes the gid to the Exim group and the uid to the Exim
40572 user after setting up one or more listening sockets. The &[initgroups()]&
40573 function is called, so that if the Exim user is in any additional groups, they
40574 will be used during message reception.
40576 A queue runner process retains root privilege throughout its execution. Its
40577 job is to fork a controlled sequence of delivery processes.
40579 A delivery process retains root privilege throughout most of its execution,
40580 but any actual deliveries (that is, the transports themselves) are run in
40581 subprocesses which always change to a non-root uid and gid. For local
40582 deliveries this is typically the uid and gid of the owner of the mailbox; for
40583 remote deliveries, the Exim uid and gid are used. Once all the delivery
40584 subprocesses have been run, a delivery process changes to the Exim uid and gid
40585 while doing post-delivery tidying up such as updating the retry database and
40586 generating bounce and warning messages.
40588 While the recipient addresses in a message are being routed, the delivery
40589 process runs as root. However, if a user's filter file has to be processed,
40590 this is done in a subprocess that runs under the individual user's uid and
40591 gid. A system filter is run as root unless &%system_filter_user%& is set.
40593 A process that is testing addresses (the &%-bt%& option) runs as root so that
40594 the routing is done in the same environment as a message delivery.
40600 .section "Running Exim without privilege" "SECTrunexiwitpri"
40601 .cindex "privilege, running without"
40602 .cindex "unprivileged running"
40603 .cindex "root privilege" "running without"
40604 Some installations like to run Exim in an unprivileged state for more of its
40605 operation, for added security. Support for this mode of operation is provided
40606 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
40607 gid are changed to the Exim user and group at the start of a delivery process
40608 (and also queue runner and address testing processes). This means that address
40609 routing is no longer run as root, and the deliveries themselves cannot change
40613 .cindex "daemon" "restarting"
40614 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
40615 that the daemon can still be started in the usual way, and it can respond
40616 correctly to SIGHUP because the re-invocation regains root privilege.
40618 An alternative approach is to make Exim setuid to the Exim user and also setgid
40619 to the Exim group. If you do this, the daemon must be started from a root
40620 process. (Calling Exim from a root process makes it behave in the way it does
40621 when it is setuid root.) However, the daemon cannot restart itself after a
40622 SIGHUP signal because it cannot regain privilege.
40624 It is still useful to set &%deliver_drop_privilege%& in this case, because it
40625 stops Exim from trying to re-invoke itself to do a delivery after a message has
40626 been received. Such a re-invocation is a waste of resources because it has no
40629 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
40630 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
40631 to the Exim user seems a clean approach, but there is one complication:
40633 In this style of operation, Exim is running with the real uid and gid set to
40634 those of the calling process, and the effective uid/gid set to Exim's values.
40635 Ideally, any association with the calling process' uid/gid should be dropped,
40636 that is, the real uid/gid should be reset to the effective values so as to
40637 discard any privileges that the caller may have. While some operating systems
40638 have a function that permits this action for a non-root effective uid, quite a
40639 number of them do not. Because of this lack of standardization, Exim does not
40640 address this problem at this time.
40642 For this reason, the recommended approach for &"mostly unprivileged"& running
40643 is to keep the Exim binary setuid to root, and to set
40644 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
40645 be used in the most straightforward way.
40647 If you configure Exim not to run delivery processes as root, there are a
40648 number of restrictions on what you can do:
40651 You can deliver only as the Exim user/group. You should explicitly use the
40652 &%user%& and &%group%& options to override routers or local transports that
40653 normally deliver as the recipient. This makes sure that configurations that
40654 work in this mode function the same way in normal mode. Any implicit or
40655 explicit specification of another user causes an error.
40657 Use of &_.forward_& files is severely restricted, such that it is usually
40658 not worthwhile to include them in the configuration.
40660 Users who wish to use &_.forward_& would have to make their home directory and
40661 the file itself accessible to the Exim user. Pipe and append-to-file entries,
40662 and their equivalents in Exim filters, cannot be used. While they could be
40663 enabled in the Exim user's name, that would be insecure and not very useful.
40665 Unless the local user mailboxes are all owned by the Exim user (possible in
40666 some POP3 or IMAP-only environments):
40669 They must be owned by the Exim group and be writeable by that group. This
40670 implies you must set &%mode%& in the appendfile configuration, as well as the
40671 mode of the mailbox files themselves.
40673 You must set &%no_check_owner%&, since most or all of the files will not be
40674 owned by the Exim user.
40676 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
40677 on a newly created mailbox when unprivileged. This also implies that new
40678 mailboxes need to be created manually.
40683 These restrictions severely restrict what can be done in local deliveries.
40684 However, there are no restrictions on remote deliveries. If you are running a
40685 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
40686 gives more security at essentially no cost.
40688 If you are using the &%mua_wrapper%& facility (see chapter
40689 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
40694 .section "Delivering to local files" "SECID271"
40695 Full details of the checks applied by &(appendfile)& before it writes to a file
40696 are given in chapter &<<CHAPappendfile>>&.
40700 .section "Running local commands" "SECTsecconslocalcmds"
40701 .cindex "security" "local commands"
40702 .cindex "security" "command injection attacks"
40703 There are a number of ways in which an administrator can configure Exim to run
40704 commands based upon received, untrustworthy, data. Further, in some
40705 configurations a user who can control a &_.forward_& file can also arrange to
40706 run commands. Configuration to check includes, but is not limited to:
40709 Use of &%use_shell%& in the pipe transport: various forms of shell command
40710 injection may be possible with this option present. It is dangerous and should
40711 be used only with considerable caution. Consider constraints which whitelist
40712 allowed characters in a variable which is to be used in a pipe transport that
40713 has &%use_shell%& enabled.
40715 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
40716 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
40717 &_.forward_& files in a redirect router. If Exim is running on a central mail
40718 hub to which ordinary users do not have shell access, but home directories are
40719 NFS mounted (for instance) then administrators should review the list of these
40720 forbid options available, and should bear in mind that the options that may
40721 need forbidding can change as new features are added between releases.
40723 The &%${run...}%& expansion item does not use a shell by default, but
40724 administrators can configure use of &_/bin/sh_& as part of the command.
40725 Such invocations should be viewed with prejudicial suspicion.
40727 Administrators who use embedded Perl are advised to explore how Perl's
40728 taint checking might apply to their usage.
40730 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
40731 administrators are well advised to view its use with suspicion, in case (for
40732 instance) it allows a local-part to contain embedded Exim directives.
40734 Use of &%${match_local_part...}%& and friends becomes more dangerous if
40735 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
40736 each can reference arbitrary lists and files, rather than just being a list
40738 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
40739 real-world security vulnerabilities caused by its use with untrustworthy data
40740 injected in, for SQL injection attacks.
40741 Consider the use of the &%inlisti%& expansion condition instead.
40747 .section "Trust in configuration data" "SECTsecconfdata"
40748 .cindex "security" "data sources"
40749 .cindex "security" "regular expressions"
40750 .cindex "regular expressions" "security"
40751 .cindex "PCRE" "security"
40752 If configuration data for Exim can come from untrustworthy sources, there
40753 are some issues to be aware of:
40756 Use of &%${expand...}%& may provide a path for shell injection attacks.
40758 Letting untrusted data provide a regular expression is unwise.
40760 Using &%${match...}%& to apply a fixed regular expression against untrusted
40761 data may result in pathological behaviour within PCRE. Be aware of what
40762 "backtracking" means and consider options for being more strict with a regular
40763 expression. Avenues to explore include limiting what can match (avoiding &`.`&
40764 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
40765 possessive quantifiers or just not using regular expressions against untrusted
40768 It can be important to correctly use &%${quote:...}%&,
40769 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
40770 items to ensure that data is correctly constructed.
40772 Some lookups might return multiple results, even though normal usage is only
40773 expected to yield one result.
40779 .section "IPv4 source routing" "SECID272"
40780 .cindex "source routing" "in IP packets"
40781 .cindex "IP source routing"
40782 Many operating systems suppress IP source-routed packets in the kernel, but
40783 some cannot be made to do this, so Exim does its own check. It logs incoming
40784 IPv4 source-routed TCP calls, and then drops them. Things are all different in
40785 IPv6. No special checking is currently done.
40789 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
40790 Support for these SMTP commands is disabled by default. If required, they can
40791 be enabled by defining suitable ACLs.
40796 .section "Privileged users" "SECID274"
40797 .cindex "trusted users"
40798 .cindex "admin user"
40799 .cindex "privileged user"
40800 .cindex "user" "trusted"
40801 .cindex "user" "admin"
40802 Exim recognizes two sets of users with special privileges. Trusted users are
40803 able to submit new messages to Exim locally, but supply their own sender
40804 addresses and information about a sending host. For other users submitting
40805 local messages, Exim sets up the sender address from the uid, and doesn't
40806 permit a remote host to be specified.
40809 However, an untrusted user is permitted to use the &%-f%& command line option
40810 in the special form &%-f <>%& to indicate that a delivery failure for the
40811 message should not cause an error report. This affects the message's envelope,
40812 but it does not affect the &'Sender:'& header. Untrusted users may also be
40813 permitted to use specific forms of address with the &%-f%& option by setting
40814 the &%untrusted_set_sender%& option.
40816 Trusted users are used to run processes that receive mail messages from some
40817 other mail domain and pass them on to Exim for delivery either locally, or over
40818 the Internet. Exim trusts a caller that is running as root, as the Exim user,
40819 as any user listed in the &%trusted_users%& configuration option, or under any
40820 group listed in the &%trusted_groups%& option.
40822 Admin users are permitted to do things to the messages on Exim's queue. They
40823 can freeze or thaw messages, cause them to be returned to their senders, remove
40824 them entirely, or modify them in various ways. In addition, admin users can run
40825 the Exim monitor and see all the information it is capable of providing, which
40826 includes the contents of files on the spool.
40830 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
40831 delivery of messages on its queue is restricted to admin users. This
40832 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
40833 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
40834 queue is also restricted to admin users. This restriction can be relaxed by
40835 setting &%no_queue_list_requires_admin%&.
40837 Exim recognizes an admin user if the calling process is running as root or as
40838 the Exim user or if any of the groups associated with the calling process is
40839 the Exim group. It is not necessary actually to be running under the Exim
40840 group. However, if admin users who are not root or the Exim user are to access
40841 the contents of files on the spool via the Exim monitor (which runs
40842 unprivileged), Exim must be built to allow group read access to its spool
40845 By default, regular users are trusted to perform basic testing and
40846 introspection commands, as themselves. This setting can be tightened by
40847 setting the &%commandline_checks_require_admin%& option.
40848 This affects most of the checking options,
40849 such as &%-be%& and anything else &%-b*%&.
40852 .section "Spool files" "SECID275"
40853 .cindex "spool directory" "files"
40854 Exim's spool directory and everything it contains is owned by the Exim user and
40855 set to the Exim group. The mode for spool files is defined in the
40856 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
40857 any user who is a member of the Exim group can access these files.
40861 .section "Use of argv[0]" "SECID276"
40862 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
40863 of specific strings, Exim assumes certain options. For example, calling Exim
40864 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
40865 to calling it with the option &%-bS%&. There are no security implications in
40870 .section "Use of %f formatting" "SECID277"
40871 The only use made of &"%f"& by Exim is in formatting load average values. These
40872 are actually stored in integer variables as 1000 times the load average.
40873 Consequently, their range is limited and so therefore is the length of the
40878 .section "Embedded Exim path" "SECID278"
40879 Exim uses its own path name, which is embedded in the code, only when it needs
40880 to re-exec in order to regain root privilege. Therefore, it is not root when it
40881 does so. If some bug allowed the path to get overwritten, it would lead to an
40882 arbitrary program's being run as exim, not as root.
40886 .section "Dynamic module directory" "SECTdynmoddir"
40887 Any dynamically loadable modules must be installed into the directory
40888 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
40892 .section "Use of sprintf()" "SECID279"
40893 .cindex "&[sprintf()]&"
40894 A large number of occurrences of &"sprintf"& in the code are actually calls to
40895 &'string_sprintf()'&, a function that returns the result in malloc'd store.
40896 The intermediate formatting is done into a large fixed buffer by a function
40897 that runs through the format string itself, and checks the length of each
40898 conversion before performing it, thus preventing buffer overruns.
40900 The remaining uses of &[sprintf()]& happen in controlled circumstances where
40901 the output buffer is known to be sufficiently long to contain the converted
40906 .section "Use of debug_printf() and log_write()" "SECID280"
40907 Arbitrary strings are passed to both these functions, but they do their
40908 formatting by calling the function &'string_vformat()'&, which runs through
40909 the format string itself, and checks the length of each conversion.
40913 .section "Use of strcat() and strcpy()" "SECID281"
40914 These are used only in cases where the output buffer is known to be large
40915 enough to hold the result.
40916 .ecindex IIDsecurcon
40921 . ////////////////////////////////////////////////////////////////////////////
40922 . ////////////////////////////////////////////////////////////////////////////
40924 .chapter "Format of spool files" "CHAPspool"
40925 .scindex IIDforspo1 "format" "spool files"
40926 .scindex IIDforspo2 "spool directory" "format of files"
40927 .scindex IIDforspo3 "spool files" "format of"
40928 .cindex "spool files" "editing"
40929 A message on Exim's queue consists of two files, whose names are the message id
40930 followed by -D and -H, respectively. The data portion of the message is kept in
40931 the -D file on its own. The message's envelope, status, and headers are all
40932 kept in the -H file, whose format is described in this chapter. Each of these
40933 two files contains the final component of its own name as its first line. This
40934 is insurance against disk crashes where the directory is lost but the files
40935 themselves are recoverable.
40937 The file formats may be changed, or new formats added, at any release.
40938 Spool files are not intended as an interface to other programs
40939 and should not be used as such.
40941 Some people are tempted into editing -D files in order to modify messages. You
40942 need to be extremely careful if you do this; it is not recommended and you are
40943 on your own if you do it. Here are some of the pitfalls:
40946 You must ensure that Exim does not try to deliver the message while you are
40947 fiddling with it. The safest way is to take out a write lock on the -D file,
40948 which is what Exim itself does, using &[fcntl()]&. If you update the file in
40949 place, the lock will be retained. If you write a new file and rename it, the
40950 lock will be lost at the instant of rename.
40952 .vindex "&$body_linecount$&"
40953 If you change the number of lines in the file, the value of
40954 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
40955 cause incomplete transmission of messages or undeliverable messages.
40957 If the message is in MIME format, you must take care not to break it.
40959 If the message is cryptographically signed, any change will invalidate the
40962 All in all, modifying -D files is fraught with danger.
40964 Files whose names end with -J may also be seen in the &_input_& directory (or
40965 its subdirectories when &%split_spool_directory%& is set). These are journal
40966 files, used to record addresses to which the message has been delivered during
40967 the course of a delivery attempt. If there are still undelivered recipients at
40968 the end, the -H file is updated, and the -J file is deleted. If, however, there
40969 is some kind of crash (for example, a power outage) before this happens, the -J
40970 file remains in existence. When Exim next processes the message, it notices the
40971 -J file and uses it to update the -H file before starting the next delivery
40974 Files whose names end with -K or .eml may also be seen in the spool.
40975 These are temporaries used for DKIM or malware processing, when that is used.
40976 They should be tidied up by normal operations; any old ones are probably
40977 relics of crashes and can be removed.
40979 .section "Format of the -H file" "SECID282"
40980 .cindex "uid (user id)" "in spool file"
40981 .cindex "gid (group id)" "in spool file"
40982 The second line of the -H file contains the login name for the uid of the
40983 process that called Exim to read the message, followed by the numerical uid and
40984 gid. For a locally generated message, this is normally the user who sent the
40985 message. For a message received over TCP/IP via the daemon, it is
40986 normally the Exim user.
40988 The third line of the file contains the address of the message's sender as
40989 transmitted in the envelope, contained in angle brackets. The sender address is
40990 empty for bounce messages. For incoming SMTP mail, the sender address is given
40991 in the MAIL command. For locally generated mail, the sender address is
40992 created by Exim from the login name of the current user and the configured
40993 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
40994 leading &"From&~"& line if the caller is trusted, or if the supplied address is
40995 &"<>"& or an address that matches &%untrusted_set_senders%&.
40997 The fourth line contains two numbers. The first is the time that the message
40998 was received, in the conventional Unix form &-- the number of seconds since the
40999 start of the epoch. The second number is a count of the number of messages
41000 warning of delayed delivery that have been sent to the sender.
41002 There follow a number of lines starting with a hyphen. These can appear in any
41003 order, and are omitted when not relevant:
41006 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
41007 This item is obsolete, and is not generated from Exim release 4.61 onwards;
41008 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
41009 recognized, to provide backward compatibility. In the old format, a line of
41010 this form is present for every ACL variable that is not empty. The number
41011 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
41012 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
41013 the data string for the variable. The string itself starts at the beginning of
41014 the next line, and is followed by a newline character. It may contain internal
41017 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
41018 A line of this form is present for every ACL connection variable that is
41019 defined. Note that there is a space between &%-aclc%& and the rest of the name.
41020 The length is the length of the data string for the variable. The string itself
41021 starts at the beginning of the next line, and is followed by a newline
41022 character. It may contain internal newlines.
41024 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
41025 A line of this form is present for every ACL message variable that is defined.
41026 Note that there is a space between &%-aclm%& and the rest of the name. The
41027 length is the length of the data string for the variable. The string itself
41028 starts at the beginning of the next line, and is followed by a newline
41029 character. It may contain internal newlines.
41031 .vitem "&%-active_hostname%&&~<&'hostname'&>"
41032 This is present if, when the message was received over SMTP, the value of
41033 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
41035 .vitem &%-allow_unqualified_recipient%&
41036 This is present if unqualified recipient addresses are permitted in header
41037 lines (to stop such addresses from being qualified if rewriting occurs at
41038 transport time). Local messages that were input using &%-bnq%& and remote
41039 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
41041 .vitem &%-allow_unqualified_sender%&
41042 This is present if unqualified sender addresses are permitted in header lines
41043 (to stop such addresses from being qualified if rewriting occurs at transport
41044 time). Local messages that were input using &%-bnq%& and remote messages from
41045 hosts that match &%sender_unqualified_hosts%& set this flag.
41047 .vitem "&%-auth_id%&&~<&'text'&>"
41048 The id information for a message received on an authenticated SMTP connection
41049 &-- the value of the &$authenticated_id$& variable.
41051 .vitem "&%-auth_sender%&&~<&'address'&>"
41052 The address of an authenticated sender &-- the value of the
41053 &$authenticated_sender$& variable.
41055 .vitem "&%-body_linecount%&&~<&'number'&>"
41056 This records the number of lines in the body of the message, and is
41057 present unless &%-spool_file_wireformat%& is.
41059 .vitem "&%-body_zerocount%&&~<&'number'&>"
41060 This records the number of binary zero bytes in the body of the message, and is
41061 present if the number is greater than zero.
41063 .vitem &%-deliver_firsttime%&
41064 This is written when a new message is first added to the spool. When the spool
41065 file is updated after a deferral, it is omitted.
41067 .vitem "&%-frozen%&&~<&'time'&>"
41068 .cindex "frozen messages" "spool data"
41069 The message is frozen, and the freezing happened at <&'time'&>.
41071 .vitem "&%-helo_name%&&~<&'text'&>"
41072 This records the host name as specified by a remote host in a HELO or EHLO
41075 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
41076 This records the IP address of the host from which the message was received and
41077 the remote port number that was used. It is omitted for locally generated
41080 .vitem "&%-host_auth%&&~<&'text'&>"
41081 If the message was received on an authenticated SMTP connection, this records
41082 the name of the authenticator &-- the value of the
41083 &$sender_host_authenticated$& variable.
41085 .vitem &%-host_lookup_failed%&
41086 This is present if an attempt to look up the sending host's name from its IP
41087 address failed. It corresponds to the &$host_lookup_failed$& variable.
41089 .vitem "&%-host_name%&&~<&'text'&>"
41090 .cindex "reverse DNS lookup"
41091 .cindex "DNS" "reverse lookup"
41092 This records the name of the remote host from which the message was received,
41093 if the host name was looked up from the IP address when the message was being
41094 received. It is not present if no reverse lookup was done.
41096 .vitem "&%-ident%&&~<&'text'&>"
41097 For locally submitted messages, this records the login of the originating user,
41098 unless it was a trusted user and the &%-oMt%& option was used to specify an
41099 ident value. For messages received over TCP/IP, this records the ident string
41100 supplied by the remote host, if any.
41102 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
41103 This records the IP address of the local interface and the port number through
41104 which a message was received from a remote host. It is omitted for locally
41105 generated messages.
41108 The message is from a local sender.
41110 .vitem &%-localerror%&
41111 The message is a locally-generated bounce message.
41113 .vitem "&%-local_scan%&&~<&'string'&>"
41114 This records the data string that was returned by the &[local_scan()]& function
41115 when the message was received &-- the value of the &$local_scan_data$&
41116 variable. It is omitted if no data was returned.
41118 .vitem &%-manual_thaw%&
41119 The message was frozen but has been thawed manually, that is, by an explicit
41120 Exim command rather than via the auto-thaw process.
41123 A testing delivery process was started using the &%-N%& option to suppress any
41124 actual deliveries, but delivery was deferred. At any further delivery attempts,
41127 .vitem &%-received_protocol%&
41128 This records the value of the &$received_protocol$& variable, which contains
41129 the name of the protocol by which the message was received.
41131 .vitem &%-sender_set_untrusted%&
41132 The envelope sender of this message was set by an untrusted local caller (used
41133 to ensure that the caller is displayed in queue listings).
41135 .vitem "&%-spam_score_int%&&~<&'number'&>"
41136 If a message was scanned by SpamAssassin, this is present. It records the value
41137 of &$spam_score_int$&.
41139 .vitem &%-spool_file_wireformat%&
41140 The -D file for this message is in wire-format (for ESMTP CHUNKING)
41141 rather than Unix-format.
41142 The line-ending is CRLF rather than newline.
41143 There is still, however, no leading-dot-stuffing.
41145 .vitem &%-tls_certificate_verified%&
41146 A TLS certificate was received from the client that sent this message, and the
41147 certificate was verified by the server.
41149 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
41150 When the message was received over an encrypted connection, this records the
41151 name of the cipher suite that was used.
41153 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
41154 When the message was received over an encrypted connection, and a certificate
41155 was received from the client, this records the Distinguished Name from that
41159 Any of the above may have an extra hyphen prepended, to indicate the the
41160 corresponding data is untrusted.
41162 Following the options there is a list of those addresses to which the message
41163 is not to be delivered. This set of addresses is initialized from the command
41164 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
41165 is set; otherwise it starts out empty. Whenever a successful delivery is made,
41166 the address is added to this set. The addresses are kept internally as a
41167 balanced binary tree, and it is a representation of that tree which is written
41168 to the spool file. If an address is expanded via an alias or forward file, the
41169 original address is added to the tree when deliveries to all its child
41170 addresses are complete.
41172 If the tree is empty, there is a single line in the spool file containing just
41173 the text &"XX"&. Otherwise, each line consists of two letters, which are either
41174 Y or N, followed by an address. The address is the value for the node of the
41175 tree, and the letters indicate whether the node has a left branch and/or a
41176 right branch attached to it, respectively. If branches exist, they immediately
41177 follow. Here is an example of a three-node tree:
41179 YY darcy@austen.fict.example
41180 NN alice@wonderland.fict.example
41181 NN editor@thesaurus.ref.example
41183 After the non-recipients tree, there is a list of the message's recipients.
41184 This is a simple list, preceded by a count. It includes all the original
41185 recipients of the message, including those to whom the message has already been
41186 delivered. In the simplest case, the list contains one address per line. For
41190 editor@thesaurus.ref.example
41191 darcy@austen.fict.example
41193 alice@wonderland.fict.example
41195 However, when a child address has been added to the top-level addresses as a
41196 result of the use of the &%one_time%& option on a &(redirect)& router, each
41197 line is of the following form:
41199 <&'top-level address'&> <&'errors_to address'&> &&&
41200 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
41202 The 01 flag bit indicates the presence of the three other fields that follow
41203 the top-level address. Other bits may be used in future to support additional
41204 fields. The <&'parent number'&> is the offset in the recipients list of the
41205 original parent of the &"one time"& address. The first two fields are the
41206 envelope sender that is associated with this address and its length. If the
41207 length is zero, there is no special envelope sender (there are then two space
41208 characters in the line). A non-empty field can arise from a &(redirect)& router
41209 that has an &%errors_to%& setting.
41212 A blank line separates the envelope and status information from the headers
41213 which follow. A header may occupy several lines of the file, and to save effort
41214 when reading it in, each header is preceded by a number and an identifying
41215 character. The number is the number of characters in the header, including any
41216 embedded newlines and the terminating newline. The character is one of the
41220 .row <&'blank'&> "header in which Exim has no special interest"
41221 .row &`B`& "&'Bcc:'& header"
41222 .row &`C`& "&'Cc:'& header"
41223 .row &`F`& "&'From:'& header"
41224 .row &`I`& "&'Message-id:'& header"
41225 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
41226 .row &`R`& "&'Reply-To:'& header"
41227 .row &`S`& "&'Sender:'& header"
41228 .row &`T`& "&'To:'& header"
41229 .row &`*`& "replaced or deleted header"
41232 Deleted or replaced (rewritten) headers remain in the spool file for debugging
41233 purposes. They are not transmitted when the message is delivered. Here is a
41234 typical set of headers:
41236 111P Received: by hobbit.fict.example with local (Exim 4.00)
41237 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
41238 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
41239 038* X-rewrote-sender: bb@hobbit.fict.example
41240 042* From: Bilbo Baggins <bb@hobbit.fict.example>
41241 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
41242 099* To: alice@wonderland.fict.example, rdo@foundation,
41243 darcy@austen.fict.example, editor@thesaurus.ref.example
41244 104T To: alice@wonderland.fict.example, rdo@foundation.example,
41245 darcy@austen.fict.example, editor@thesaurus.ref.example
41246 038 Date: Fri, 11 May 2001 10:28:59 +0100
41248 The asterisked headers indicate that the envelope sender, &'From:'& header, and
41249 &'To:'& header have been rewritten, the last one because routing expanded the
41250 unqualified domain &'foundation'&.
41251 .ecindex IIDforspo1
41252 .ecindex IIDforspo2
41253 .ecindex IIDforspo3
41255 .section "Format of the -D file" "SECID282a"
41256 The data file is traditionally in Unix-standard format: lines are ended with
41257 an ASCII newline character.
41258 However, when the &%spool_wireformat%& main option is used some -D files
41259 can have an alternate format.
41260 This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
41261 The -D file lines (not including the first name-component line) are
41262 suitable for direct copying to the wire when transmitting using the
41263 ESMTP CHUNKING option, meaning lower processing overhead.
41264 Lines are terminated with an ASCII CRLF pair.
41265 There is no dot-stuffing (and no dot-termination).
41267 . ////////////////////////////////////////////////////////////////////////////
41268 . ////////////////////////////////////////////////////////////////////////////
41270 .chapter "DKIM, SPF, SRS and DMARC" "CHAPdkim" &&&
41271 "DKIM, SPF, SRS and DMARC Support"
41273 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
41276 DKIM is a mechanism by which messages sent by some entity can be provably
41277 linked to a domain which that entity controls. It permits reputation to
41278 be tracked on a per-domain basis, rather than merely upon source IP address.
41279 DKIM is documented in RFC 6376.
41281 As DKIM relies on the message being unchanged in transit, messages handled
41282 by a mailing-list (which traditionally adds to the message) will not match
41283 any original DKIM signature.
41285 DKIM support is compiled into Exim by default if TLS support is present.
41286 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
41288 Exim's DKIM implementation allows for
41290 Signing outgoing messages: This function is implemented in the SMTP transport.
41291 It can co-exist with all other Exim features
41292 (including transport filters)
41293 except cutthrough delivery.
41295 Verifying signatures in incoming messages: This is implemented by an additional
41296 ACL (acl_smtp_dkim), which can be called several times per message, with
41297 different signature contexts.
41300 In typical Exim style, the verification implementation does not include any
41301 default "policy". Instead it enables you to build your own policy using
41302 Exim's standard controls.
41304 Please note that verification of DKIM signatures in incoming mail is turned
41305 on by default for logging (in the <= line) purposes.
41307 Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
41308 When set, for each signature in incoming email,
41309 exim will log a line displaying the most important signature details, and the
41310 signature status. Here is an example (with line-breaks added for clarity):
41312 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
41313 d=facebookmail.com s=q1-2009b
41314 c=relaxed/relaxed a=rsa-sha1
41315 i=@facebookmail.com t=1252484542 [verification succeeded]
41318 You might want to turn off DKIM verification processing entirely for internal
41319 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
41320 control modifier. This should typically be done in the RCPT ACL, at points
41321 where you accept mail from relay sources (internal hosts or authenticated
41325 .section "Signing outgoing messages" "SECDKIMSIGN"
41326 .cindex "DKIM" "signing"
41328 For signing to be usable you must have published a DKIM record in DNS.
41329 Note that RFC 8301 (which does not cover EC keys) says:
41331 rsa-sha1 MUST NOT be used for signing or verifying.
41333 Signers MUST use RSA keys of at least 1024 bits for all keys.
41334 Signers SHOULD use RSA keys of at least 2048 bits.
41337 Note also that the key content (the 'p=' field)
41338 in the DNS record is different between RSA and EC keys;
41339 for the former it is the base64 of the ASN.1 for the RSA public key
41340 (equivalent to the private-key .pem with the header/trailer stripped)
41341 but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
41343 Signing is enabled by setting private options on the SMTP transport.
41344 These options take (expandable) strings as arguments.
41346 .option dkim_domain smtp "string list&!!" unset
41347 The domain(s) you want to sign with.
41348 After expansion, this can be a list.
41349 Each element in turn,
41351 is put into the &%$dkim_domain%& expansion variable
41352 while expanding the remaining signing options.
41353 If it is empty after expansion, DKIM signing is not done,
41354 and no error will result even if &%dkim_strict%& is set.
41356 .option dkim_selector smtp "string list&!!" unset
41357 This sets the key selector string.
41358 After expansion, which can use &$dkim_domain$&, this can be a list.
41359 Each element in turn is put in the expansion
41360 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
41361 option along with &%$dkim_domain%&.
41362 If the option is empty after expansion, DKIM signing is not done for this domain,
41363 and no error will result even if &%dkim_strict%& is set.
41366 To do, for example, dual-signing with RSA and EC keys
41367 this could be be used:
41369 dkim_selector = ec_sel : rsa_sel
41370 dkim_private_key = KEYS_DIR/$dkim_selector
41374 .option dkim_private_key smtp string&!! unset
41375 This sets the private key to use.
41376 You can use the &%$dkim_domain%& and
41377 &%$dkim_selector%& expansion variables to determine the private key to use.
41378 The result can either
41380 be a valid RSA private key in ASCII armor (.pem file), including line breaks
41382 with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41383 be a valid Ed25519 private key (same format as above)
41385 start with a slash, in which case it is treated as a file that contains
41388 be "0", "false" or the empty string, in which case the message will not
41389 be signed. This case will not result in an error, even if &%dkim_strict%&
41393 To generate keys under OpenSSL:
41395 openssl genrsa -out dkim_rsa.private 2048
41396 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
41398 The result file from the first command should be retained, and
41399 this option set to use it.
41400 Take the base-64 lines from the output of the second command, concatenated,
41401 for the DNS TXT record.
41402 See section 3.6 of RFC6376 for the record specification.
41406 certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
41407 certtool --load-privkey=dkim_rsa.private --pubkey-info
41410 Note that RFC 8301 says:
41412 Signers MUST use RSA keys of at least 1024 bits for all keys.
41413 Signers SHOULD use RSA keys of at least 2048 bits.
41416 EC keys for DKIM are defined by RFC 8463.
41417 They are considerably smaller than RSA keys for equivalent protection.
41418 As they are a recent development, users should consider dual-signing
41419 (by setting a list of selectors, and an expansion for this option)
41420 for some transition period.
41421 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41424 OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
41426 openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
41427 certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
41430 To produce the required public key value for a DNS record:
41432 openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
41433 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
41436 Exim also supports an alternate format
41437 of Ed25519 keys in DNS which was a candidate during development
41438 of the standard, but not adopted.
41439 A future release will probably drop that support.
41441 .option dkim_hash smtp string&!! sha256
41442 Can be set to any one of the supported hash methods, which are:
41444 &`sha1`& &-- should not be used, is old and insecure
41446 &`sha256`& &-- the default
41448 &`sha512`& &-- possibly more secure but less well supported
41451 Note that RFC 8301 says:
41453 rsa-sha1 MUST NOT be used for signing or verifying.
41456 .option dkim_identity smtp string&!! unset
41457 If set after expansion, the value is used to set an "i=" tag in
41458 the signing header. The DKIM standards restrict the permissible
41459 syntax of this optional tag to a mail address, with possibly-empty
41460 local part, an @, and a domain identical to or subdomain of the "d="
41461 tag value. Note that Exim does not check the value.
41463 .option dkim_canon smtp string&!! unset
41464 This option sets the canonicalization method used when signing a message.
41465 The DKIM RFC currently supports two methods: "simple" and "relaxed".
41466 The option defaults to "relaxed" when unset. Note: the current implementation
41467 only supports signing with the same canonicalization method for both headers and body.
41469 .option dkim_strict smtp string&!! unset
41470 This option defines how Exim behaves when signing a message that
41471 should be signed fails for some reason. When the expansion evaluates to
41472 either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message
41473 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
41476 .option dkim_sign_headers smtp string&!! "see below"
41477 If set, this option must expand to a colon-separated
41478 list of header names.
41479 Headers with these names, or the absence or such a header, will be included
41480 in the message signature.
41481 When unspecified, the header names listed in RFC4871 will be used,
41482 whether or not each header is present in the message.
41483 The default list is available for the expansion in the macro
41484 &"_DKIM_SIGN_HEADERS"&
41485 and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
41487 If a name is repeated, multiple headers by that name (or the absence thereof)
41488 will be signed. The textually later headers in the headers part of the
41489 message are signed first, if there are multiples.
41491 A name can be prefixed with either an &"="& or a &"+"& character.
41492 If an &"="& prefix is used, all headers that are present with this name
41494 If a &"+"& prefix if used, all headers that are present with this name
41495 will be signed, and one signature added for a missing header with the
41496 name will be appended.
41498 .option dkim_timestamps smtp integer&!! unset
41499 This option controls the inclusion of timestamp information in the signature.
41500 If not set, no such information will be included.
41501 Otherwise, must be an unsigned number giving an offset in seconds from the current time
41503 (eg. 1209600 for two weeks);
41504 both creation (t=) and expiry (x=) tags will be included.
41506 RFC 6376 lists these tags as RECOMMENDED.
41509 .section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
41510 .cindex "DKIM" "verification"
41512 Verification of DKIM signatures in SMTP incoming email is done for all
41513 messages for which an ACL control &%dkim_disable_verify%& has not been set.
41514 .cindex DKIM "selecting signature algorithms"
41515 Individual classes of signature algorithm can be ignored by changing
41516 the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
41517 The &%dkim_verify_minimal%& option can be set to cease verification
41518 processing for a message once the first passing signature is found.
41520 .cindex authentication "expansion item"
41521 Performing verification sets up information used by the
41522 &%authresults%& expansion item.
41524 For most purposes the default option settings suffice and the remainder
41525 of this section can be ignored.
41527 The results of verification are made available to the
41528 &%acl_smtp_dkim%& ACL, which can examine and modify them.
41529 A missing ACL definition defaults to accept.
41530 By default, the ACL is called once for each
41531 syntactically(!) correct signature in the incoming message.
41532 If any ACL call does not accept, the message is not accepted.
41533 If a cutthrough delivery was in progress for the message, that is
41534 summarily dropped (having wasted the transmission effort).
41536 To evaluate the verification result in the ACL
41537 a large number of expansion variables
41538 containing the signature status and its details are set up during the
41539 runtime of the ACL.
41541 Calling the ACL only for existing signatures is not sufficient to build
41542 more advanced policies. For that reason, the main option
41543 &%dkim_verify_signers%&, and an expansion variable
41544 &%$dkim_signers%& exist.
41546 The main option &%dkim_verify_signers%& can be set to a colon-separated
41547 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
41548 called. It is expanded when the message has been received. At this point,
41549 the expansion variable &%$dkim_signers%& already contains a colon-separated
41550 list of signer domains and identities for the message. When
41551 &%dkim_verify_signers%& is not specified in the main configuration,
41554 dkim_verify_signers = $dkim_signers
41556 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
41557 DKIM signature in the message. Current DKIM verifiers may want to explicitly
41558 call the ACL for known domains or identities. This would be achieved as follows:
41560 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
41562 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
41563 and "ebay.com", plus all domains and identities that have signatures in the message.
41564 You can also be more creative in constructing your policy. For example:
41566 dkim_verify_signers = $sender_address_domain:$dkim_signers
41569 If a domain or identity is listed several times in the (expanded) value of
41570 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
41572 Note that if the option is set using untrustworthy data
41573 (such as the From: header)
41574 care should be taken to force lowercase for domains
41575 and for the domain part if identities.
41576 The default setting can be regarded as trustworthy in this respect.
41578 If multiple signatures match a domain (or identity), the ACL is called once
41579 for each matching signature.
41582 Inside the DKIM ACL, the following expansion variables are
41583 available (from most to least important):
41587 .vitem &%$dkim_cur_signer%&
41588 The signer that is being evaluated in this ACL run. This can be a domain or
41589 an identity. This is one of the list items from the expanded main option
41590 &%dkim_verify_signers%& (see above).
41592 .vitem &%$dkim_verify_status%&
41593 Within the DKIM ACL,
41594 a string describing the general status of the signature. One of
41596 &%none%&: There is no signature in the message for the current domain or
41597 identity (as reflected by &%$dkim_cur_signer%&).
41599 &%invalid%&: The signature could not be verified due to a processing error.
41600 More detail is available in &%$dkim_verify_reason%&.
41602 &%fail%&: Verification of the signature failed. More detail is
41603 available in &%$dkim_verify_reason%&.
41605 &%pass%&: The signature passed verification. It is valid.
41608 This variable can be overwritten using an ACL 'set' modifier.
41609 This might, for instance, be done to enforce a policy restriction on
41610 hash-method or key-size:
41612 warn condition = ${if eq {$dkim_verify_status}{pass}}
41613 condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
41614 condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
41615 {< {$dkim_key_length}{1024}}}}
41616 logwrite = NOTE: forcing DKIM verify fail (was pass)
41617 set dkim_verify_status = fail
41618 set dkim_verify_reason = hash too weak or key too short
41621 So long as a DKIM ACL is defined (it need do no more than accept),
41622 after all the DKIM ACL runs have completed, the value becomes a
41623 colon-separated list of the values after each run.
41624 This is maintained for the mime, prdr and data ACLs.
41626 .vitem &%$dkim_verify_reason%&
41627 A string giving a little bit more detail when &%$dkim_verify_status%& is either
41628 "fail" or "invalid". One of
41630 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
41631 key for the domain could not be retrieved. This may be a temporary problem.
41633 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
41634 record for the domain is syntactically invalid.
41636 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
41637 body hash does not match the one specified in the signature header. This
41638 means that the message body was modified in transit.
41640 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
41641 could not be verified. This may mean that headers were modified,
41642 re-written or otherwise changed in a way which is incompatible with
41643 DKIM verification. It may of course also mean that the signature is forged.
41646 This variable can be overwritten, with any value, using an ACL 'set' modifier.
41648 .vitem &%$dkim_domain%&
41649 The signing domain. IMPORTANT: This variable is only populated if there is
41650 an actual signature in the message for the current domain or identity (as
41651 reflected by &%$dkim_cur_signer%&).
41653 .vitem &%$dkim_identity%&
41654 The signing identity, if present. IMPORTANT: This variable is only populated
41655 if there is an actual signature in the message for the current domain or
41656 identity (as reflected by &%$dkim_cur_signer%&).
41658 .vitem &%$dkim_selector%&
41659 The key record selector string.
41661 .vitem &%$dkim_algo%&
41662 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
41663 If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41664 may also be 'ed25519-sha256'.
41665 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41668 Note that RFC 8301 says:
41670 rsa-sha1 MUST NOT be used for signing or verifying.
41672 DKIM signatures identified as having been signed with historic
41673 algorithms (currently, rsa-sha1) have permanently failed evaluation
41676 To enforce this you must either have a DKIM ACL which checks this variable
41677 and overwrites the &$dkim_verify_status$& variable as discussed above,
41678 or have set the main option &%dkim_verify_hashes%& to exclude
41679 processing of such signatures.
41681 .vitem &%$dkim_canon_body%&
41682 The body canonicalization method. One of 'relaxed' or 'simple'.
41684 .vitem &%$dkim_canon_headers%&
41685 The header canonicalization method. One of 'relaxed' or 'simple'.
41687 .vitem &%$dkim_copiedheaders%&
41688 A transcript of headers and their values which are included in the signature
41689 (copied from the 'z=' tag of the signature).
41690 Note that RFC6376 requires that verification fail if the From: header is
41691 not included in the signature. Exim does not enforce this; sites wishing
41692 strict enforcement should code the check explicitly.
41694 .vitem &%$dkim_bodylength%&
41695 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
41696 limit was set by the signer, "9999999999999" is returned. This makes sure
41697 that this variable always expands to an integer value.
41698 &*Note:*& The presence of the signature tag specifying a signing body length
41699 is one possible route to spoofing of valid DKIM signatures.
41700 A paranoid implementation might wish to regard signature where this variable
41701 shows less than the "no limit" return as being invalid.
41703 .vitem &%$dkim_created%&
41704 UNIX timestamp reflecting the date and time when the signature was created.
41705 When this was not specified by the signer, "0" is returned.
41707 .vitem &%$dkim_expires%&
41708 UNIX timestamp reflecting the date and time when the signer wants the
41709 signature to be treated as "expired". When this was not specified by the
41710 signer, "9999999999999" is returned. This makes it possible to do useful
41711 integer size comparisons against this value.
41712 Note that Exim does not check this value.
41714 .vitem &%$dkim_headernames%&
41715 A colon-separated list of names of headers included in the signature.
41717 .vitem &%$dkim_key_testing%&
41718 "1" if the key record has the "testing" flag set, "0" if not.
41720 .vitem &%$dkim_key_nosubdomains%&
41721 "1" if the key record forbids subdomaining, "0" otherwise.
41723 .vitem &%$dkim_key_srvtype%&
41724 Service type (tag s=) from the key record. Defaults to "*" if not specified
41727 .vitem &%$dkim_key_granularity%&
41728 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
41731 .vitem &%$dkim_key_notes%&
41732 Notes from the key record (tag n=).
41734 .vitem &%$dkim_key_length%&
41735 Number of bits in the key.
41736 Valid only once the key is loaded, which is at the time the header signature
41737 is verified, which is after the body hash is.
41739 Note that RFC 8301 says:
41741 Verifiers MUST NOT consider signatures using RSA keys of
41742 less than 1024 bits as valid signatures.
41745 This is enforced by the default setting for the &%dkim_verify_min_keysizes%&
41750 In addition, two ACL conditions are provided:
41753 .vitem &%dkim_signers%&
41754 ACL condition that checks a colon-separated list of domains or identities
41755 for a match against the domain or identity that the ACL is currently verifying
41756 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
41757 verb to a group of domains or identities. For example:
41760 # Warn when Mail purportedly from GMail has no gmail signature
41761 warn sender_domains = gmail.com
41762 dkim_signers = gmail.com
41764 log_message = GMail sender without gmail.com DKIM signature
41767 Note that the above does not check for a total lack of DKIM signing;
41768 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
41770 .vitem &%dkim_status%&
41771 ACL condition that checks a colon-separated list of possible DKIM verification
41772 results against the actual result of verification. This is typically used
41773 to restrict an ACL verb to a list of verification outcomes, for example:
41776 deny sender_domains = paypal.com:paypal.de
41777 dkim_signers = paypal.com:paypal.de
41778 dkim_status = none:invalid:fail
41779 message = Mail from Paypal with invalid/missing signature
41782 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
41783 see the documentation of the &%$dkim_verify_status%& expansion variable above
41784 for more information of what they mean.
41790 .section "SPF (Sender Policy Framework)" SECSPF
41791 .cindex SPF verification
41793 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
41794 messages with its domain in the envelope from, documented by RFC 7208.
41795 For more information on SPF see &url(http://www.open-spf.org), a static copy of
41796 the &url(http://openspf.org).
41797 . --- 2019-10-28: still not https, open-spf.org is told to be a
41798 . --- web-archive copy of the now dead openspf.org site
41799 . --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a
41802 Messages sent by a system not authorised will fail checking of such assertions.
41803 This includes retransmissions done by traditional forwarders.
41805 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
41806 &_Local/Makefile_&. The support uses the &_libspf2_& library
41807 &url(https://www.libspf2.org/).
41808 There is no Exim involvement in the transmission of messages;
41809 publishing certain DNS records is all that is required.
41811 For verification, an ACL condition and an expansion lookup are provided.
41812 .cindex authentication "expansion item"
41813 Performing verification sets up information used by the
41814 &%authresults%& expansion item.
41817 .cindex SPF "ACL condition"
41818 .cindex ACL "spf condition"
41819 The ACL condition "spf" can be used at or after the MAIL ACL.
41820 It takes as an argument a list of strings giving the outcome of the SPF check,
41821 and will succeed for any matching outcome.
41825 The SPF check passed, the sending host is positively verified by SPF.
41828 The SPF check failed, the sending host is NOT allowed to send mail for the
41829 domain in the envelope-from address.
41831 .vitem &%softfail%&
41832 The SPF check failed, but the queried domain can't absolutely confirm that this
41836 The queried domain does not publish SPF records.
41839 The SPF check returned a "neutral" state. This means the queried domain has
41840 published a SPF record, but wants to allow outside servers to send mail under
41841 its domain as well. This should be treated like "none".
41843 .vitem &%permerror%&
41844 This indicates a syntax error in the SPF record of the queried domain.
41845 You may deny messages when this occurs.
41847 .vitem &%temperror%&
41848 This indicates a temporary error during all processing, including Exim's
41849 SPF processing. You may defer messages when this occurs.
41852 There was an error during processing of the SPF lookup
41855 You can prefix each string with an exclamation mark to invert
41856 its meaning, for example "!fail" will match all results but
41857 "fail". The string list is evaluated left-to-right, in a
41858 short-circuit fashion.
41863 message = $sender_host_address is not allowed to send mail from \
41864 ${if def:sender_address_domain \
41865 {$sender_address_domain}{$sender_helo_name}}. \
41866 Please see http://www.open-spf.org/Why;\
41867 identity=${if def:sender_address_domain \
41868 {$sender_address}{$sender_helo_name}};\
41869 ip=$sender_host_address
41872 Note: The above mentioned URL may not be as helpful as expected. You are
41873 encouraged to replace the link with a link to a site with more
41876 When the spf condition has run, it sets up several expansion
41879 .cindex SPF "verification variables"
41881 .vitem &$spf_header_comment$&
41882 .vindex &$spf_header_comment$&
41883 This contains a human-readable string describing the outcome
41884 of the SPF check. You can add it to a custom header or use
41885 it for logging purposes.
41887 .vitem &$spf_received$&
41888 .vindex &$spf_received$&
41889 This contains a complete Received-SPF: header (name and
41890 content) that can be added to the message. Please note that
41891 according to the SPF draft, this header must be added at the
41892 top of the header list, i.e. with
41894 add_header = :at_start:$spf_received
41896 See section &<<SECTaddheadacl>>& for further details.
41898 Note: in case of "Best-guess" (see below), the convention is
41899 to put this string in a header called X-SPF-Guess: instead.
41901 .vitem &$spf_result$&
41902 .vindex &$spf_result$&
41903 This contains the outcome of the SPF check in string form,
41904 currently one of pass, fail, softfail, none, neutral, permerror,
41905 temperror, or &"(invalid)"&.
41907 .vitem &$spf_result_guessed$&
41908 .vindex &$spf_result_guessed$&
41909 This boolean is true only if a best-guess operation was used
41910 and required in order to obtain a result.
41912 .vitem &$spf_smtp_comment$&
41913 .vindex &$spf_smtp_comment$&
41914 .vindex &%spf_smtp_comment_template%&
41915 This contains a string that can be used in a SMTP response
41916 to the calling party. Useful for "fail".
41917 The string is generated by the SPF library from the template configured in the main config
41918 option &%spf_smtp_comment_template%&.
41922 .cindex SPF "ACL condition"
41923 .cindex ACL "spf_guess condition"
41924 .cindex SPF "best guess"
41925 In addition to SPF, you can also perform checks for so-called
41926 "Best-guess". Strictly speaking, "Best-guess" is not standard
41927 SPF, but it is supported by the same framework that enables SPF
41929 Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record)
41930 for a description of what it means.
41931 . --- 2019-10-28: still not https:
41933 To access this feature, simply use the spf_guess condition in place
41934 of the spf one. For example:
41937 deny spf_guess = fail
41938 message = $sender_host_address doesn't look trustworthy to me
41941 In case you decide to reject messages based on this check, you
41942 should note that although it uses the same framework, "Best-guess"
41943 is not SPF, and therefore you should not mention SPF at all in your
41946 When the spf_guess condition has run, it sets up the same expansion
41947 variables as when spf condition is run, described above.
41949 Additionally, since Best-guess is not standardized, you may redefine
41950 what "Best-guess" means to you by redefining the main configuration
41951 &%spf_guess%& option.
41952 For example, the following:
41955 spf_guess = v=spf1 a/16 mx/16 ptr ?all
41958 would relax host matching rules to a broader network range.
41961 .cindex SPF "lookup expansion"
41963 A lookup expansion is also available. It takes an email
41964 address as the key and an IP address
41969 ${lookup {username@domain} spf {ip.ip.ip.ip}}
41972 The lookup will return the same result strings as can appear in
41973 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
41979 .section "SRS (Sender Rewriting Scheme)" SECTSRS
41980 .cindex SRS "sender rewriting scheme"
41983 SRS can be used to modify sender addresses when forwarding so that
41984 SPF verification does not object to them.
41985 It operates by encoding the original envelope sender in a new
41986 sender local part and using a domain run by the forwarding site
41987 as the new domain for the sender. Any DSN message should be returned
41988 to this new sender at the forwarding site, which can extract the
41989 original sender from the coded local part and forward the DSN to
41992 This is a way of avoiding the breakage that SPF does to forwarding.
41993 The constructed local-part will be longer than the original,
41994 leading to possible problems with very long addresses.
41995 The changing of the sender address also hinders the tracing of mail
41998 Exim can be built to include native SRS support. To do this
41999 SUPPORT_SRS=yes must be defined in &_Local/Makefile_&.
42000 If this has been done, the macros _HAVE_SRS and _HAVE_NATIVE_SRS
42002 The support is limited to SRS0-encoding; SRS1 is not supported.
42004 .cindex SRS excoding
42005 To encode an address use this expansion item:
42007 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
42008 .cindex "&%srs_encode%& expansion item"
42009 .cindex SRS "expansion item"
42010 The first argument should be a secret known and used by all systems
42011 handling the recipient domain for the original message.
42012 There is no need to periodically change this key; a timestamp is also
42014 The second argument should be given as the envelope sender address before this
42015 encoding operation.
42016 The third argument should be the recipient domain of the message when
42017 it arrived at this system.
42020 .cindex SRS decoding
42021 To decode an address use this expansion condition:
42023 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
42024 The first argument should be the recipient local prt as is was received.
42025 The second argument is the site secret.
42027 If the messages is not for an SRS-encoded recipient the condition will
42028 return false. If it is, the condition will return true and the variable
42029 &$srs_recipient$& will be set to the decoded (original) value.
42035 SRS_SECRET = <pick something unique for your site for this. Use on all MXs.>
42041 # if outbound, and forwarding has been done, use an alternate transport
42042 domains = ! +my_domains
42043 transport = ${if eq {$local_part@$domain} \
42044 {$original_local_part@$original_domain} \
42045 {remote_smtp} {remote_forwarded_smtp}}
42050 domains = +my_domains
42051 # detect inbound bounces which are SRS'd, and decode them
42052 condition = ${if inbound_srs {$local_part} {SRS_SECRET}}
42053 data = $srs_recipient
42055 inbound_srs_failure:
42058 domains = +my_domains
42059 # detect inbound bounces which look SRS'd but are invalid
42060 condition = ${if inbound_srs {$local_part} {}}
42062 data = :fail: Invalid SRS recipient address
42064 #... further routers here
42067 # transport; should look like the non-forward outbound
42068 # one, plus the max_rcpt and return_path options
42069 remote_forwarded_smtp:
42071 # modify the envelope from, for mails that we forward
42073 return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}}
42081 .section DMARC SECDMARC
42082 .cindex DMARC verification
42084 DMARC combines feedback from SPF, DKIM, and header From: in order
42085 to attempt to provide better indicators of the authenticity of an
42086 email. This document does not explain the fundamentals; you
42087 should read and understand how it works by visiting the website at
42088 &url(http://www.dmarc.org/).
42090 If Exim is built with DMARC support,
42091 the libopendmarc library is used.
42093 For building Exim yourself, obtain the library from
42094 &url(http://sourceforge.net/projects/opendmarc/)
42095 to obtain a copy, or find it in your favorite package
42096 repository. You will need to attend to the local/Makefile feature
42097 SUPPORT_DMARC and the associated LDFLAGS addition.
42098 This description assumes
42099 that headers will be in /usr/local/include, and that the libraries
42100 are in /usr/local/lib.
42104 There are three main-configuration options:
42105 .cindex DMARC "configuration options"
42107 The &%dmarc_tld_file%& option
42108 .oindex &%dmarc_tld_file%&
42109 defines the location of a text file of valid
42110 top level domains the opendmarc library uses
42111 during domain parsing. Maintained by Mozilla,
42112 the most current version can be downloaded
42113 from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat).
42114 See also the util/renew-opendmarc-tlds.sh script.
42115 The default for the option is unset.
42116 If not set, DMARC processing is disabled.
42119 The &%dmarc_history_file%& option, if set
42120 .oindex &%dmarc_history_file%&
42121 defines the location of a file to log results
42122 of dmarc verification on inbound emails. The
42123 contents are importable by the opendmarc tools
42124 which will manage the data, send out DMARC
42125 reports, and expire the data. Make sure the
42126 directory of this file is writable by the user
42128 The default is unset.
42130 The &%dmarc_forensic_sender%& option
42131 .oindex &%dmarc_forensic_sender%&
42132 defines an alternate email address to use when sending a
42133 forensic report detailing alignment failures
42134 if a sender domain's dmarc record specifies it
42135 and you have configured Exim to send them.
42136 If set, this is expanded and used for the
42137 From: header line; the address is extracted
42138 from it and used for the envelope from.
42139 If not set (the default), the From: header is expanded from
42140 the dsn_from option, and <> is used for the
42143 . I wish we had subsections...
42145 .cindex DMARC controls
42146 By default, the DMARC processing will run for any remote,
42147 non-authenticated user. It makes sense to only verify DMARC
42148 status of messages coming from remote, untrusted sources. You can
42149 use standard conditions such as hosts, senders, etc, to decide that
42150 DMARC verification should *not* be performed for them and disable
42151 DMARC with an ACL control modifier:
42153 control = dmarc_disable_verify
42155 A DMARC record can also specify a "forensic address", which gives
42156 exim an email address to submit reports about failed alignment.
42157 Exim does not do this by default because in certain conditions it
42158 results in unintended information leakage (what lists a user might
42159 be subscribed to, etc). You must configure exim to submit forensic
42160 reports to the owner of the domain. If the DMARC record contains a
42161 forensic address and you specify the control statement below, then
42162 exim will send these forensic emails. It is also advised that you
42163 configure a &%dmarc_forensic_sender%& because the default sender address
42164 construction might be inadequate.
42166 control = dmarc_enable_forensic
42168 (AGAIN: You can choose not to send these forensic reports by simply
42169 not putting the dmarc_enable_forensic control line at any point in
42170 your exim config. If you don't tell exim to send them, it will not
42173 There are no options to either control. Both must appear before
42178 DMARC checks cam be run on incoming SMTP messages by using the
42179 &"dmarc_status"& ACL condition in the DATA ACL. You are required to
42180 call the &"spf"& condition first in the ACLs, then the &"dmarc_status"&
42181 condition. Putting this condition in the ACLs is required in order
42182 for a DMARC check to actually occur. All of the variables are set
42183 up before the DATA ACL, but there is no actual DMARC check that
42184 occurs until a &"dmarc_status"& condition is encountered in the ACLs.
42186 The &"dmarc_status"& condition takes a list of strings on its
42187 right-hand side. These strings describe recommended action based
42188 on the DMARC check. To understand what the policy recommendations
42189 mean, refer to the DMARC website above. Valid strings are:
42191 &'accept '& The DMARC check passed and the library recommends accepting the email.
42192 &'reject '& The DMARC check failed and the library recommends rejecting the email.
42193 &'quarantine '& The DMARC check failed and the library recommends keeping it for further inspection.
42194 &'none '& The DMARC check passed and the library recommends no specific action, neutral.
42195 &'norecord '& No policy section in the DMARC record for this RFC5322.From field
42196 &'nofrom '& Unable to determine the domain of the sender.
42197 &'temperror '& Library error or dns error.
42198 &'off '& The DMARC check was disabled for this email.
42200 You can prefix each string with an exclamation mark to invert its
42201 meaning, for example "!accept" will match all results but
42202 "accept". The string list is evaluated left-to-right in a
42203 short-circuit fashion. When a string matches the outcome of the
42204 DMARC check, the condition succeeds. If none of the listed
42205 strings matches the outcome of the DMARC check, the condition
42208 Of course, you can also use any other lookup method that Exim
42209 supports, including LDAP, Postgres, MySQL, etc, as long as the
42210 result is a list of colon-separated strings.
42212 Performing the check sets up information used by the
42213 &%authresults%& expansion item.
42215 Several expansion variables are set before the DATA ACL is
42216 processed, and you can use them in this ACL. The following
42217 expansion variables are available:
42220 .vitem &$dmarc_status$&
42221 .vindex &$dmarc_status$&
42222 .cindex DMARC result
42223 A one word status indicating what the DMARC library
42224 thinks of the email. It is a combination of the results of
42225 DMARC record lookup and the SPF/DKIM/DMARC processing results
42226 (if a DMARC record was found). The actual policy declared
42227 in the DMARC record is in a separate expansion variable.
42229 .vitem &$dmarc_status_text$&
42230 .vindex &$dmarc_status_text$&
42231 Slightly longer, human readable status.
42233 .vitem &$dmarc_used_domain$&
42234 .vindex &$dmarc_used_domain$&
42235 The domain which DMARC used to look up the DMARC policy record.
42237 .vitem &$dmarc_domain_policy$&
42238 .vindex &$dmarc_domain_policy$&
42239 The policy declared in the DMARC record. Valid values
42240 are "none", "reject" and "quarantine". It is blank when there
42241 is any error, including no DMARC record.
42246 By default, Exim's DMARC configuration is intended to be
42247 non-intrusive and conservative. To facilitate this, Exim will not
42248 create any type of logging files without explicit configuration by
42249 you, the admin. Nor will Exim send out any emails/reports about
42250 DMARC issues without explicit configuration by you, the admin (other
42251 than typical bounce messages that may come about due to ACL
42252 processing or failure delivery issues).
42254 In order to log statistics suitable to be imported by the opendmarc
42255 tools, you need to:
42257 Configure the global option &%dmarc_history_file%&
42259 Configure cron jobs to call the appropriate opendmarc history
42260 import scripts and truncating the dmarc_history_file
42263 In order to send forensic reports, you need to:
42265 Configure the global option &%dmarc_forensic_sender%&
42267 Configure, somewhere before the DATA ACL, the control option to
42268 enable sending DMARC forensic reports
42276 warn domains = +local_domains
42277 hosts = +local_hosts
42278 control = dmarc_disable_verify
42280 warn !domains = +screwed_up_dmarc_records
42281 control = dmarc_enable_forensic
42283 warn condition = (lookup if destined to mailing list)
42284 set acl_m_mailing_list = 1
42287 warn dmarc_status = accept : none : off
42289 log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
42291 warn dmarc_status = !accept
42293 log_message = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
42295 warn dmarc_status = quarantine
42297 set $acl_m_quarantine = 1
42298 # Do something in a transport with this flag variable
42300 deny condition = ${if eq{$dmarc_domain_policy}{reject}}
42301 condition = ${if eq{$acl_m_mailing_list}{1}}
42302 message = Messages from $dmarc_used_domain break mailing lists
42304 deny dmarc_status = reject
42306 message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
42308 warn add_header = :at_start:${authresults {$primary_hostname}}
42315 . ////////////////////////////////////////////////////////////////////////////
42316 . ////////////////////////////////////////////////////////////////////////////
42318 .chapter "Proxies" "CHAPproxies" &&&
42320 .cindex "proxy support"
42321 .cindex "proxy" "access via"
42323 A proxy is an intermediate system through which communication is passed.
42324 Proxies may provide a security, availability or load-distribution function.
42327 .section "Inbound proxies" SECTproxyInbound
42328 .cindex proxy inbound
42329 .cindex proxy "server side"
42330 .cindex proxy "Proxy protocol"
42331 .cindex "Proxy protocol" proxy
42333 Exim has support for receiving inbound SMTP connections via a proxy
42334 that uses &"Proxy Protocol"& to speak to it.
42335 To include this support, include &"SUPPORT_PROXY=yes"&
42338 It was built on the HAProxy specification, found at
42339 &url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt).
42341 The purpose of this facility is so that an application load balancer,
42342 such as HAProxy, can sit in front of several Exim servers
42343 to distribute load.
42344 Exim uses the local protocol communication with the proxy to obtain
42345 the remote SMTP system IP address and port information.
42346 There is no logging if a host passes or
42347 fails Proxy Protocol negotiation, but it can easily be determined and
42348 recorded in an ACL (example is below).
42350 Use of a proxy is enabled by setting the &%hosts_proxy%&
42351 main configuration option to a hostlist; connections from these
42352 hosts will use Proxy Protocol.
42353 Exim supports both version 1 and version 2 of the Proxy Protocol and
42354 automatically determines which version is in use.
42356 The Proxy Protocol header is the first data received on a TCP connection
42357 and is inserted before any TLS-on-connect handshake from the client; Exim
42358 negotiates TLS between Exim-as-server and the remote client, not between
42359 Exim and the proxy server. The Proxy Protocol header must be received
42360 within &%proxy_protocol_timeout%&, which defaults to 3s.
42362 The following expansion variables are usable
42363 (&"internal"& and &"external"& here refer to the interfaces
42366 &'proxy_external_address '& IP of host being proxied or IP of remote interface of proxy
42367 &'proxy_external_port '& Port of host being proxied or Port on remote interface of proxy
42368 &'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
42369 &'proxy_local_port '& Port of proxy server inbound or Port on local interface of proxy
42370 &'proxy_session '& boolean: SMTP connection via proxy
42372 If &$proxy_session$& is set but &$proxy_external_address$& is empty
42373 there was a protocol error.
42374 The variables &$sender_host_address$& and &$sender_host_port$&
42375 will have values for the actual client system, not the proxy.
42377 Since the real connections are all coming from the proxy, and the
42378 per host connection tracking is done before Proxy Protocol is
42379 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
42380 handle all of the parallel volume you expect per inbound proxy.
42381 With the option set so high, you lose the ability
42382 to protect your server from many connections from one IP.
42383 In order to prevent your server from overload, you
42384 need to add a per connection ratelimit to your connect ACL.
42385 A possible solution is:
42387 # Set max number of connections per host
42389 # Or do some kind of IP lookup in a flat file or database
42390 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
42392 defer ratelimit = LIMIT / 5s / per_conn / strict
42393 message = Too many connections from this IP right now
42398 .section "Outbound proxies" SECTproxySOCKS
42399 .cindex proxy outbound
42400 .cindex proxy "client side"
42401 .cindex proxy SOCKS
42402 .cindex SOCKS proxy
42403 Exim has support for sending outbound SMTP via a proxy
42404 using a protocol called SOCKS5 (defined by RFC1928).
42405 The support can be optionally included by defining SUPPORT_SOCKS=yes in
42408 Use of a proxy is enabled by setting the &%socks_proxy%& option
42409 on an smtp transport.
42410 The option value is expanded and should then be a list
42411 (colon-separated by default) of proxy specifiers.
42412 Each proxy specifier is a list
42413 (space-separated by default) where the initial element
42414 is an IP address and any subsequent elements are options.
42416 Options are a string <name>=<value>.
42417 The list of options is in the following table:
42419 &'auth '& authentication method
42420 &'name '& authentication username
42421 &'pass '& authentication password
42423 &'tmo '& connection timeout
42425 &'weight '& selection bias
42428 More details on each of these options follows:
42431 .cindex authentication "to proxy"
42432 .cindex proxy authentication
42433 &%auth%&: Either &"none"& (default) or &"name"&.
42434 Using &"name"& selects username/password authentication per RFC 1929
42435 for access to the proxy.
42436 Default is &"none"&.
42438 &%name%&: sets the username for the &"name"& authentication method.
42441 &%pass%&: sets the password for the &"name"& authentication method.
42444 &%port%&: the TCP port number to use for the connection to the proxy.
42447 &%tmo%&: sets a connection timeout in seconds for this proxy.
42450 &%pri%&: specifies a priority for the proxy within the list,
42451 higher values being tried first.
42452 The default priority is 1.
42454 &%weight%&: specifies a selection bias.
42455 Within a priority set servers are queried in a random fashion,
42456 weighted by this value.
42457 The default value for selection bias is 1.
42460 Proxies from the list are tried according to their priority
42461 and weight settings until one responds. The timeout for the
42462 overall connection applies to the set of proxied attempts.
42464 .section Logging SECTproxyLog
42465 To log the (local) IP of a proxy in the incoming or delivery logline,
42466 add &"+proxy"& to the &%log_selector%& option.
42467 This will add a component tagged with &"PRX="& to the line.
42469 . ////////////////////////////////////////////////////////////////////////////
42470 . ////////////////////////////////////////////////////////////////////////////
42472 .chapter "Internationalisation" "CHAPi18n" &&&
42473 "Internationalisation""
42474 .cindex internationalisation "email address"
42477 .cindex utf8 "mail name handling"
42479 Exim has support for Internationalised mail names.
42480 To include this it must be built with SUPPORT_I18N and the libidn library.
42481 Standards supported are RFCs 2060, 5890, 6530 and 6533.
42483 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
42484 instead of it) then IDNA2008 is supported; this adds an extra library
42485 requirement, upon libidn2.
42487 .section "MTA operations" SECTi18nMTA
42488 .cindex SMTPUTF8 "ESMTP option"
42489 .cindex "ESMTP extensions" SMTPUTF8
42490 The main configuration option &%smtputf8_advertise_hosts%& specifies
42491 a host list. If this matches the sending host and
42492 accept_8bitmime is true (the default) then the ESMTP option
42493 SMTPUTF8 will be advertised.
42495 If the sender specifies the SMTPUTF8 option on a MAIL command
42496 international handling for the message is enabled and
42497 the expansion variable &$message_smtputf8$& will have value TRUE.
42499 The option &%allow_utf8_domains%& is set to true for this
42500 message. All DNS lookups are converted to a-label form
42501 whatever the setting of &%allow_utf8_domains%&
42502 when Exim is built with SUPPORT_I18N.
42504 Both localparts and domain are maintained as the original
42505 UTF-8 form internally; any comparison or regular-expression use will
42506 require appropriate care. Filenames created, eg. by
42507 the appendfile transport, will have UTF-8 names.
42509 HELO names sent by the smtp transport will have any UTF-8
42510 components expanded to a-label form,
42511 and any certificate name checks will be done using the a-label
42514 .cindex log protocol
42515 .cindex SMTPUTF8 logging
42516 .cindex i18n logging
42517 Log lines and Received-by: header lines will acquire a "utf8"
42518 prefix on the protocol element, eg. utf8esmtp.
42520 The following expansion operators can be used:
42522 ${utf8_domain_to_alabel:str}
42523 ${utf8_domain_from_alabel:str}
42524 ${utf8_localpart_to_alabel:str}
42525 ${utf8_localpart_from_alabel:str}
42528 .cindex utf8 "address downconversion"
42529 .cindex i18n "utf8 address downconversion"
42531 may use the following modifier:
42533 control = utf8_downconvert
42534 control = utf8_downconvert/<value>
42536 This sets a flag requiring that envelope addresses are converted to
42537 a-label form before smtp delivery.
42538 This is usually for use in a Message Submission Agent context,
42539 but could be used for any message.
42541 If a value is appended it may be:
42543 &`1 `& mandatory downconversion
42544 &`0 `& no downconversion
42545 &`-1 `& if SMTPUTF8 not supported by destination host
42547 If no value is given, 1 is used.
42549 If mua_wrapper is set, the utf8_downconvert control
42550 is initially set to -1.
42552 The smtp transport has an option &%utf8_downconvert%&.
42553 If set it must expand to one of the three values described above,
42554 or an empty string.
42555 If non-empty it overrides value previously set
42556 (due to mua_wrapper or by an ACL control).
42559 There is no explicit support for VRFY and EXPN.
42560 Configurations supporting these should inspect
42561 &$smtp_command_argument$& for an SMTPUTF8 argument.
42563 There is no support for LMTP on Unix sockets.
42564 Using the "lmtp" protocol option on an smtp transport,
42565 for LMTP over TCP, should work as expected.
42567 There is no support for DSN unitext handling,
42568 and no provision for converting logging from or to UTF-8.
42572 .section "MDA operations" SECTi18nMDA
42573 To aid in constructing names suitable for IMAP folders
42574 the following expansion operator can be used:
42576 ${imapfolder {<string>} {<sep>} {<specials>}}
42579 The string is converted from the charset specified by
42580 the "headers charset" command (in a filter file)
42581 or &%headers_charset%& main configuration option (otherwise),
42583 modified UTF-7 encoding specified by RFC 2060,
42584 with the following exception: All occurrences of <sep>
42585 (which has to be a single character)
42586 are replaced with periods ("."), and all periods and slashes that are not
42587 <sep> and are not in the <specials> string are BASE64 encoded.
42589 The third argument can be omitted, defaulting to an empty string.
42590 The second argument can be omitted, defaulting to "/".
42592 This is the encoding used by Courier for Maildir names on disk, and followed
42593 by many other IMAP servers.
42597 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
42598 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
42599 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
42602 Note that the source charset setting is vital, and also that characters
42603 must be representable in UTF-16.
42606 . ////////////////////////////////////////////////////////////////////////////
42607 . ////////////////////////////////////////////////////////////////////////////
42609 .chapter "Events" "CHAPevents" &&&
42613 The events mechanism in Exim can be used to intercept processing at a number
42614 of points. It was originally invented to give a way to do customised logging
42615 actions (for example, to a database) but can also be used to modify some
42616 processing actions.
42618 Most installations will never need to use Events.
42619 The support can be left out of a build by defining DISABLE_EVENT=yes
42620 in &_Local/Makefile_&.
42622 There are two major classes of events: main and transport.
42623 The main configuration option &%event_action%& controls reception events;
42624 a transport option &%event_action%& controls delivery events.
42626 Both options are a string which is expanded when the event fires.
42627 An example might look like:
42628 .cindex logging custom
42630 event_action = ${if eq {msg:delivery}{$event_name} \
42631 {${lookup pgsql {SELECT * FROM record_Delivery( \
42632 '${quote_pgsql:$sender_address_domain}',\
42633 '${quote_pgsql:${lc:$sender_address_local_part}}', \
42634 '${quote_pgsql:$domain}', \
42635 '${quote_pgsql:${lc:$local_part}}', \
42636 '${quote_pgsql:$host_address}', \
42637 '${quote_pgsql:${lc:$host}}', \
42638 '${quote_pgsql:$message_exim_id}')}} \
42642 Events have names which correspond to the point in process at which they fire.
42643 The name is placed in the variable &$event_name$& and the event action
42644 expansion must check this, as it will be called for every possible event type.
42646 The current list of events is:
42648 &`dane:fail after transport `& per connection
42649 &`msg:complete after main `& per message
42650 &`msg:defer after transport `& per message per delivery try
42651 &`msg:delivery after transport `& per recipient
42652 &`msg:rcpt:host:defer after transport `& per recipient per host
42653 &`msg:rcpt:defer after transport `& per recipient
42654 &`msg:host:defer after transport `& per host per delivery try; host errors
42655 &`msg:fail:delivery after transport `& per recipient
42656 &`msg:fail:internal after main `& per recipient
42657 &`tcp:connect before transport `& per connection
42658 &`tcp:close after transport `& per connection
42659 &`tls:cert before both `& per certificate in verification chain
42660 &`smtp:connect after transport `& per connection
42661 &`smtp:ehlo after transport `& per connection
42663 New event types may be added in future.
42665 The event name is a colon-separated list, defining the type of
42666 event in a tree of possibilities. It may be used as a list
42667 or just matched on as a whole. There will be no spaces in the name.
42669 The second column in the table above describes whether the event fires
42670 before or after the action is associates with. Those which fire before
42671 can be used to affect that action (more on this below).
42673 The third column in the table above says what section of the configuration
42674 should define the event action.
42676 An additional variable, &$event_data$&, is filled with information varying
42677 with the event type:
42679 &`dane:fail `& failure reason
42680 &`msg:defer `& error string
42681 &`msg:delivery `& smtp confirmation message
42682 &`msg:fail:internal `& failure reason
42683 &`msg:fail:delivery `& smtp error message
42684 &`msg:host:defer `& error string
42685 &`msg:rcpt:host:defer `& error string
42686 &`msg:rcpt:defer `& error string
42687 &`tls:cert `& verification chain depth
42688 &`smtp:connect `& smtp banner
42689 &`smtp:ehlo `& smtp ehlo response
42692 The :defer events populate one extra variable: &$event_defer_errno$&.
42694 For complex operations an ACL expansion can be used in &%event_action%&
42695 however due to the multiple contexts that Exim operates in during
42696 the course of its processing:
42698 variables set in transport events will not be visible outside that
42701 acl_m variables in a server context are lost on a new connection,
42702 and after smtp helo/ehlo/mail/starttls/rset commands
42704 Using an ACL expansion with the logwrite modifier can be
42705 a useful way of writing to the main log.
42707 The expansion of the event_action option should normally
42708 return an empty string. Should it return anything else the
42709 following will be forced:
42711 &`tcp:connect `& do not connect
42712 &`tls:cert `& refuse verification
42713 &`smtp:connect `& close connection
42715 All other message types ignore the result string, and
42716 no other use is made of it.
42718 For a tcp:connect event, if the connection is being made to a proxy
42719 then the address and port variables will be that of the proxy and not
42722 For tls:cert events, if GnuTLS is in use this will trigger only per
42723 chain element received on the connection.
42724 For OpenSSL it will trigger for every chain element including those
42727 . ////////////////////////////////////////////////////////////////////////////
42728 . ////////////////////////////////////////////////////////////////////////////
42730 .chapter "Adding new drivers or lookup types" "CHID13" &&&
42731 "Adding drivers or lookups"
42732 .cindex "adding drivers"
42733 .cindex "new drivers, adding"
42734 .cindex "drivers" "adding new"
42735 The following actions have to be taken in order to add a new router, transport,
42736 authenticator, or lookup type to Exim:
42739 Choose a name for the driver or lookup type that does not conflict with any
42740 existing name; I will use &"newdriver"& in what follows.
42742 Add to &_src/EDITME_& the line:
42744 <&'type'&>&`_NEWDRIVER=yes`&
42746 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
42747 code is not to be included in the binary by default, comment this line out. You
42748 should also add any relevant comments about the driver or lookup type.
42750 Add to &_src/config.h.defaults_& the line:
42752 #define <type>_NEWDRIVER
42755 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
42756 and create a table entry as is done for all the other drivers and lookup types.
42758 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
42759 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
42760 Add your &`NEWDRIVER`& to that list.
42761 As long as the dynamic module would be named &_newdriver.so_&, you can use the
42762 simple form that most lookups have.
42764 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
42765 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
42766 driver or lookup type and add it to the definition of OBJ.
42768 Edit &_OS/Makefile-Base_& adding a &_.o_& file for the predefined-macros, to the
42769 definition of OBJ_MACRO. Add a set of line to do the compile also.
42771 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
42774 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
42775 as for other drivers and lookups.
42778 Then all you need to do is write the code! A good way to start is to make a
42779 proforma by copying an existing module of the same type, globally changing all
42780 occurrences of the name, and cutting out most of the code. Note that any
42781 options you create must be listed in alphabetical order, because the tables are
42782 searched using a binary chop procedure.
42784 There is a &_README_& file in each of the sub-directories of &_src_& describing
42785 the interface that is expected.
42790 . ////////////////////////////////////////////////////////////////////////////
42791 . ////////////////////////////////////////////////////////////////////////////
42793 . /////////////////////////////////////////////////////////////////////////////
42794 . These lines are processing instructions for the Simple DocBook Processor that
42795 . Philip Hazel has developed as a less cumbersome way of making PostScript and
42796 . PDFs than using xmlto and fop. They will be ignored by all other XML
42798 . /////////////////////////////////////////////////////////////////////////////
42803 foot_right_recto="&chaptertitle;"
42804 foot_right_verso="&chaptertitle;"
42808 .makeindex "Options index" "option"
42809 .makeindex "Variables index" "variable"
42810 .makeindex "Concept index" "concept"
42813 . /////////////////////////////////////////////////////////////////////////////
42814 . /////////////////////////////////////////////////////////////////////////////