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 "4.95"
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>The Exim Maintainers</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 PCRE2 library, copyright
776 © University of Cambridge. The source to PCRE2 is not longer shipped with
777 Exim, so you will need to use the version of PCRE2 shipped with your system,
778 or obtain and install the full version of the library from
779 &url(https://github.com/PhilipHazel/pcre2/releases).
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.
1424 .cindex "tainted data" "de-tainting"
1425 A match verifies the variable &$domain$& (which carries tainted data)
1426 and assigns an untainted value to the &$domain_data$& variable.
1427 Such an untainted value is often needed in the transport.
1428 For specifics of the matching operation and the resulting untainted value,
1429 refer to section &<<SECTdomainlist>>&.
1431 When an untainted value is wanted, use this option
1432 rather than the generic &%condition%& option.
1435 .vindex "&$local_part_prefix$&"
1436 .vindex "&$local_part_prefix_v$&"
1437 .vindex "&$local_part$&"
1438 .vindex "&$local_part_suffix$&"
1439 .vindex "&$local_part_suffix_v$&"
1440 .cindex affix "router precondition"
1441 If the &%local_parts%& option is set, the local part of the address must be in
1442 the set of local parts that it defines.
1443 A match verifies the variable &$local_part$& (which carries tainted data)
1444 and assigns an untainted value to the &$local_part_data$& variable.
1445 Such an untainted value is often needed in the transport.
1446 For specifics of the matching operation and the resulting untainted value,
1447 refer to section &<<SECTlocparlis>>&.
1449 When an untainted value is wanted, use this option
1450 rather than the generic &%condition%& option.
1452 If &%local_part_prefix%& or
1453 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1454 part before this check. If you want to do precondition tests on local parts
1455 that include affixes, you can do so by using a &%condition%& option (see below)
1456 that uses the variables &$local_part$&, &$local_part_prefix$&,
1457 &$local_part_prefix_v$&, &$local_part_suffix$&
1458 and &$local_part_suffix_v$& as necessary.
1461 .vindex "&$local_user_uid$&"
1462 .vindex "&$local_user_gid$&"
1464 If the &%check_local_user%& option is set, the local part must be the name of
1465 an account on the local host. If this check succeeds, the uid and gid of the
1466 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1467 user's home directory is placed in &$home$&; these values can be used in the
1468 remaining preconditions.
1471 If the &%router_home_directory%& option is set, it is expanded at this point,
1472 because it overrides the value of &$home$&. If this expansion were left till
1473 later, the value of &$home$& as set by &%check_local_user%& would be used in
1474 subsequent tests. Having two different values of &$home$& in the same router
1475 could lead to confusion.
1478 If the &%senders%& option is set, the envelope sender address must be in the
1479 set of addresses that it defines.
1482 If the &%require_files%& option is set, the existence or non-existence of
1483 specified files is tested.
1486 .cindex "customizing" "precondition"
1487 If the &%condition%& option is set, it is evaluated and tested. This option
1488 uses an expanded string to allow you to set up your own custom preconditions.
1489 Expanded strings are described in chapter &<<CHAPexpand>>&.
1491 Note that while using
1492 this option for address matching technically works,
1493 it does not set any de-tainted values.
1494 Such values are often needed, either for router-specific options or
1495 for transport options.
1496 Using the &%domains%& and &%local_parts%& options is usually the most
1497 convenient way to obtain them.
1501 Note that &%require_files%& comes near the end of the list, so you cannot use
1502 it to check for the existence of a file in which to lookup up a domain, local
1503 part, or sender. However, as these options are all expanded, you can use the
1504 &%exists%& expansion condition to make such tests within each condition. The
1505 &%require_files%& option is intended for checking files that the router may be
1506 going to use internally, or which are needed by a specific transport (for
1507 example, &_.procmailrc_&).
1511 .section "Delivery in detail" "SECID18"
1512 .cindex "delivery" "in detail"
1513 When a message is to be delivered, the sequence of events is as follows:
1516 If a system-wide filter file is specified, the message is passed to it. The
1517 filter may add recipients to the message, replace the recipients, discard the
1518 message, cause a new message to be generated, or cause the message delivery to
1519 fail. The format of the system filter file is the same as for Exim user filter
1520 files, described in the separate document entitled &'Exim's interfaces to mail
1522 .cindex "Sieve filter" "not available for system filter"
1523 (&*Note*&: Sieve cannot be used for system filter files.)
1525 Some additional features are available in system filters &-- see chapter
1526 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1527 filter only once per delivery attempt, however many recipients it has. However,
1528 if there are several delivery attempts because one or more addresses could not
1529 be immediately delivered, the system filter is run each time. The filter
1530 condition &%first_delivery%& can be used to detect the first run of the system
1533 Each recipient address is offered to each configured router, in turn, subject to
1534 its preconditions, until one is able to handle it. If no router can handle the
1535 address, that is, if they all decline, the address is failed. Because routers
1536 can be targeted at particular domains, several locally handled domains can be
1537 processed entirely independently of each other.
1539 .cindex "routing" "loops in"
1540 .cindex "loop" "while routing"
1541 A router that accepts an address may assign it to a local or a remote
1542 transport. However, the transport is not run at this time. Instead, the address
1543 is placed on a list for the particular transport, which will be run later.
1544 Alternatively, the router may generate one or more new addresses (typically
1545 from alias, forward, or filter files). New addresses are fed back into this
1546 process from the top, but in order to avoid loops, a router ignores any address
1547 which has an identically-named ancestor that was processed by itself.
1549 When all the routing has been done, addresses that have been successfully
1550 handled are passed to their assigned transports. When local transports are
1551 doing real local deliveries, they handle only one address at a time, but if a
1552 local transport is being used as a pseudo-remote transport (for example, to
1553 collect batched SMTP messages for transmission by some other means) multiple
1554 addresses can be handled. Remote transports can always handle more than one
1555 address at a time, but can be configured not to do so, or to restrict multiple
1556 addresses to the same domain.
1558 Each local delivery to a file or a pipe runs in a separate process under a
1559 non-privileged uid, and these deliveries are run one at a time. Remote
1560 deliveries also run in separate processes, normally under a uid that is private
1561 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1562 run in parallel. The maximum number of simultaneous remote deliveries for any
1563 one message is set by the &%remote_max_parallel%& option.
1564 The order in which deliveries are done is not defined, except that all local
1565 deliveries happen before any remote deliveries.
1567 .cindex "queue runner"
1568 When it encounters a local delivery during a queue run, Exim checks its retry
1569 database to see if there has been a previous temporary delivery failure for the
1570 address before running the local transport. If there was a previous failure,
1571 Exim does not attempt a new delivery until the retry time for the address is
1572 reached. However, this happens only for delivery attempts that are part of a
1573 queue run. Local deliveries are always attempted when delivery immediately
1574 follows message reception, even if retry times are set for them. This makes for
1575 better behaviour if one particular message is causing problems (for example,
1576 causing quota overflow, or provoking an error in a filter file).
1578 .cindex "delivery" "retry in remote transports"
1579 Remote transports do their own retry handling, since an address may be
1580 deliverable to one of a number of hosts, each of which may have a different
1581 retry time. If there have been previous temporary failures and no host has
1582 reached its retry time, no delivery is attempted, whether in a queue run or
1583 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1585 If there were any permanent errors, a bounce message is returned to an
1586 appropriate address (the sender in the common case), with details of the error
1587 for each failing address. Exim can be configured to send copies of bounce
1588 messages to other addresses.
1590 .cindex "delivery" "deferral"
1591 If one or more addresses suffered a temporary failure, the message is left on
1592 the queue, to be tried again later. Delivery of these addresses is said to be
1595 When all the recipient addresses have either been delivered or bounced,
1596 handling of the message is complete. The spool files and message log are
1597 deleted, though the message log can optionally be preserved if required.
1603 .section "Retry mechanism" "SECID19"
1604 .cindex "delivery" "retry mechanism"
1605 .cindex "retry" "description of mechanism"
1606 .cindex "queue runner"
1607 Exim's mechanism for retrying messages that fail to get delivered at the first
1608 attempt is the queue runner process. You must either run an Exim daemon that
1609 uses the &%-q%& option with a time interval to start queue runners at regular
1610 intervals or use some other means (such as &'cron'&) to start them. If you do
1611 not arrange for queue runners to be run, messages that fail temporarily at the
1612 first attempt will remain in your queue forever. A queue runner process works
1613 its way through the queue, one message at a time, trying each delivery that has
1614 passed its retry time.
1615 You can run several queue runners at once.
1617 Exim uses a set of configured rules to determine when next to retry the failing
1618 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1619 should give up trying to deliver to the address, at which point it generates a
1620 bounce message. If no retry rules are set for a particular host, address, and
1621 error combination, no retries are attempted, and temporary errors are treated
1626 .section "Temporary delivery failure" "SECID20"
1627 .cindex "delivery" "temporary failure"
1628 There are many reasons why a message may not be immediately deliverable to a
1629 particular address. Failure to connect to a remote machine (because it, or the
1630 connection to it, is down) is one of the most common. Temporary failures may be
1631 detected during routing as well as during the transport stage of delivery.
1632 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1633 is on a file system where the user is over quota. Exim can be configured to
1634 impose its own quotas on local mailboxes; where system quotas are set they will
1637 If a host is unreachable for a period of time, a number of messages may be
1638 waiting for it by the time it recovers, and sending them in a single SMTP
1639 connection is clearly beneficial. Whenever a delivery to a remote host is
1641 .cindex "hints database" "deferred deliveries"
1642 Exim makes a note in its hints database, and whenever a successful
1643 SMTP delivery has happened, it looks to see if any other messages are waiting
1644 for the same host. If any are found, they are sent over the same SMTP
1645 connection, subject to a configuration limit as to the maximum number in any
1650 .section "Permanent delivery failure" "SECID21"
1651 .cindex "delivery" "permanent failure"
1652 .cindex "bounce message" "when generated"
1653 When a message cannot be delivered to some or all of its intended recipients, a
1654 bounce message is generated. Temporary delivery failures turn into permanent
1655 errors when their timeout expires. All the addresses that fail in a given
1656 delivery attempt are listed in a single message. If the original message has
1657 many recipients, it is possible for some addresses to fail in one delivery
1658 attempt and others to fail subsequently, giving rise to more than one bounce
1659 message. The wording of bounce messages can be customized by the administrator.
1660 See chapter &<<CHAPemsgcust>>& for details.
1662 .cindex "&'X-Failed-Recipients:'& header line"
1663 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1664 failed addresses, for the benefit of programs that try to analyse such messages
1667 .cindex "bounce message" "recipient of"
1668 A bounce message is normally sent to the sender of the original message, as
1669 obtained from the message's envelope. For incoming SMTP messages, this is the
1670 address given in the MAIL command. However, when an address is expanded via a
1671 forward or alias file, an alternative address can be specified for delivery
1672 failures of the generated addresses. For a mailing list expansion (see section
1673 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1678 .section "Failures to deliver bounce messages" "SECID22"
1679 .cindex "bounce message" "failure to deliver"
1680 If a bounce message (either locally generated or received from a remote host)
1681 itself suffers a permanent delivery failure, the message is left in the queue,
1682 but it is frozen, awaiting the attention of an administrator. There are options
1683 that can be used to make Exim discard such failed messages, or to keep them
1684 for only a short time (see &%timeout_frozen_after%& and
1685 &%ignore_bounce_errors_after%&).
1691 . ////////////////////////////////////////////////////////////////////////////
1692 . ////////////////////////////////////////////////////////////////////////////
1694 .chapter "Building and installing Exim" "CHID3"
1695 .scindex IIDbuex "building Exim"
1697 .section "Unpacking" "SECID23"
1698 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1699 creates a directory with the name of the current release (for example,
1700 &_exim-&version()_&) into which the following files are placed:
1703 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1704 .irow &_CHANGES_& "contains a reference to where changes are &&&
1706 .irow &_LICENCE_& "the GNU General Public Licence"
1707 .irow &_Makefile_& "top-level make file"
1708 .irow &_NOTICE_& "conditions for the use of Exim"
1709 .irow &_README_& "list of files, directories and simple build &&&
1713 Other files whose names begin with &_README_& may also be present. The
1714 following subdirectories are created:
1717 .irow &_Local_& "an empty directory for local configuration files"
1718 .irow &_OS_& "OS-specific files"
1719 .irow &_doc_& "documentation files"
1720 .irow &_exim_monitor_& "source files for the Exim monitor"
1721 .irow &_scripts_& "scripts used in the build process"
1722 .irow &_src_& "remaining source files"
1723 .irow &_util_& "independent utilities"
1726 The main utility programs are contained in the &_src_& directory and are built
1727 with the Exim binary. The &_util_& directory contains a few optional scripts
1728 that may be useful to some sites.
1731 .section "Multiple machine architectures and operating systems" "SECID24"
1732 .cindex "building Exim" "multiple OS/architectures"
1733 The building process for Exim is arranged to make it easy to build binaries for
1734 a number of different architectures and operating systems from the same set of
1735 source files. Compilation does not take place in the &_src_& directory.
1736 Instead, a &'build directory'& is created for each architecture and operating
1738 .cindex "symbolic link" "to build directory"
1739 Symbolic links to the sources are installed in this directory, which is where
1740 the actual building takes place. In most cases, Exim can discover the machine
1741 architecture and operating system for itself, but the defaults can be
1742 overridden if necessary.
1743 .cindex compiler requirements
1744 .cindex compiler version
1745 A C99-capable compiler will be required for the build.
1748 .section "PCRE2 library" "SECTpcre"
1749 .cindex "PCRE2 library"
1750 Exim no longer has an embedded regular-expression library as the vast majority of
1751 modern systems include PCRE2 as a system library, although you may need to
1752 install the PCRE2 package or the PCRE2 development package for your operating
1753 system. If your system has a normal PCRE2 installation the Exim build
1754 process will need no further configuration. If the library or the
1755 headers are in an unusual location you will need to either set the PCRE2_LIBS
1756 and INCLUDE directives appropriately,
1757 or set PCRE2_CONFIG=yes to use the installed &(pcre-config)& command.
1758 If your operating system has no
1759 PCRE2 support then you will need to obtain and build the current PCRE
1760 from &url(https://github.com/PhilipHazel/pcre2/releases).
1761 More information on PCRE2 is available at &url(https://www.pcre.org/).
1763 .section "DBM libraries" "SECTdb"
1764 .cindex "DBM libraries" "discussion of"
1765 .cindex "hints database" "DBM files used for"
1766 Even if you do not use any DBM files in your configuration, Exim still needs a
1767 DBM library in order to operate, because it uses indexed files for its hints
1768 databases. Unfortunately, there are a number of DBM libraries in existence, and
1769 different operating systems often have different ones installed.
1771 .cindex "Solaris" "DBM library for"
1772 .cindex "IRIX, DBM library for"
1773 .cindex "BSD, DBM library for"
1774 .cindex "Linux, DBM library for"
1775 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1776 Linux distribution, the DBM configuration should happen automatically, and you
1777 may be able to ignore this section. Otherwise, you may have to learn more than
1778 you would like about DBM libraries from what follows.
1780 .cindex "&'ndbm'& DBM library"
1781 Licensed versions of Unix normally contain a library of DBM functions operating
1782 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1783 versions of Unix seem to vary in what they contain as standard. In particular,
1784 some early versions of Linux have no default DBM library, and different
1785 distributors have chosen to bundle different libraries with their packaged
1786 versions. However, the more recent releases seem to have standardized on the
1787 Berkeley DB library.
1789 Different DBM libraries have different conventions for naming the files they
1790 use. When a program opens a file called &_dbmfile_&, there are several
1794 A traditional &'ndbm'& implementation, such as that supplied as part of
1795 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1797 .cindex "&'gdbm'& DBM library"
1798 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1799 compatibility interface it makes two different hard links to it with names
1800 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1801 filename is used unmodified.
1803 .cindex "Berkeley DB library"
1804 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1805 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1806 programmer exactly the same as the traditional &'ndbm'& implementation.
1808 If the Berkeley package is used in its native mode, it operates on a single
1809 file called &_dbmfile_&; the programmer's interface is somewhat different to
1810 the traditional &'ndbm'& interface.
1812 To complicate things further, there are several very different versions of the
1813 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1814 2.&'x'& and 3.&'x'& were current for a while, but the latest versions when Exim last revamped support were numbered 4.&'x'&.
1815 Maintenance of some of the earlier releases has ceased. All versions of
1816 Berkeley DB could be obtained from
1817 &url(http://www.sleepycat.com/), which is now a redirect to their new owner's
1818 page with far newer versions listed.
1819 It is probably wise to plan to move your storage configurations away from
1820 Berkeley DB format, as today there are smaller and simpler alternatives more
1821 suited to Exim's usage model.
1823 .cindex "&'tdb'& DBM library"
1824 Yet another DBM library, called &'tdb'&, is available from
1825 &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
1826 operates on a single file.
1830 .cindex "DBM libraries" "configuration for building"
1831 Exim and its utilities can be compiled to use any of these interfaces. In order
1832 to use any version of the Berkeley DB package in native mode, you must set
1833 USE_DB in an appropriate configuration file (typically
1834 &_Local/Makefile_&). For example:
1838 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1839 error is diagnosed if you set more than one of these.
1841 At the lowest level, the build-time configuration sets none of these options,
1842 thereby assuming an interface of type (1). However, some operating system
1843 configuration files (for example, those for the BSD operating systems and
1844 Linux) assume type (4) by setting USE_DB as their default, and the
1845 configuration files for Cygwin set USE_GDBM. Anything you set in
1846 &_Local/Makefile_&, however, overrides these system defaults.
1848 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1849 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1850 in one of these lines:
1855 Settings like that will work if the DBM library is installed in the standard
1856 place. Sometimes it is not, and the library's header file may also not be in
1857 the default path. You may need to set INCLUDE to specify where the header
1858 file is, and to specify the path to the library more fully in DBMLIB, as in
1861 INCLUDE=-I/usr/local/include/db-4.1
1862 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1864 There is further detailed discussion about the various DBM libraries in the
1865 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1869 .section "Pre-building configuration" "SECID25"
1870 .cindex "building Exim" "pre-building configuration"
1871 .cindex "configuration for building Exim"
1872 .cindex "&_Local/Makefile_&"
1873 .cindex "&_src/EDITME_&"
1874 Before building Exim, a local configuration file that specifies options
1875 independent of any operating system has to be created with the name
1876 &_Local/Makefile_&. A template for this file is supplied as the file
1877 &_src/EDITME_&, and it contains full descriptions of all the option settings
1878 therein. These descriptions are therefore not repeated here. If you are
1879 building Exim for the first time, the simplest thing to do is to copy
1880 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1882 There are three settings that you must supply, because Exim will not build
1883 without them. They are the location of the runtime configuration file
1884 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1885 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1886 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1887 a colon-separated list of filenames; Exim uses the first of them that exists.
1889 There are a few other parameters that can be specified either at build time or
1890 at runtime, to enable the same binary to be used on a number of different
1891 machines. However, if the locations of Exim's spool directory and log file
1892 directory (if not within the spool directory) are fixed, it is recommended that
1893 you specify them in &_Local/Makefile_& instead of at runtime, so that errors
1894 detected early in Exim's execution (such as a malformed configuration file) can
1897 .cindex "content scanning" "specifying at build time"
1898 Exim's interfaces for calling virus and spam scanning software directly from
1899 access control lists are not compiled by default. If you want to include these
1900 facilities, you need to set
1902 WITH_CONTENT_SCAN=yes
1904 in your &_Local/Makefile_&. For details of the facilities themselves, see
1905 chapter &<<CHAPexiscan>>&.
1908 .cindex "&_Local/eximon.conf_&"
1909 .cindex "&_exim_monitor/EDITME_&"
1910 If you are going to build the Exim monitor, a similar configuration process is
1911 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1912 your installation and saved under the name &_Local/eximon.conf_&. If you are
1913 happy with the default settings described in &_exim_monitor/EDITME_&,
1914 &_Local/eximon.conf_& can be empty, but it must exist.
1916 This is all the configuration that is needed in straightforward cases for known
1917 operating systems. However, the building process is set up so that it is easy
1918 to override options that are set by default or by operating-system-specific
1919 configuration files, for example, to change the C compiler, which
1920 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1925 .section "Support for iconv()" "SECID26"
1926 .cindex "&[iconv()]& support"
1928 The contents of header lines in messages may be encoded according to the rules
1929 described RFC 2047. This makes it possible to transmit characters that are not
1930 in the ASCII character set, and to label them as being in a particular
1931 character set. When Exim is inspecting header lines by means of the &%$h_%&
1932 mechanism, it decodes them, and translates them into a specified character set
1933 (default is set at build time). The translation is possible only if the operating system
1934 supports the &[iconv()]& function.
1936 However, some of the operating systems that supply &[iconv()]& do not support
1937 very many conversions. The GNU &%libiconv%& library (available from
1938 &url(https://www.gnu.org/software/libiconv/)) can be installed on such
1939 systems to remedy this deficiency, as well as on systems that do not supply
1940 &[iconv()]& at all. After installing &%libiconv%&, you should add
1944 to your &_Local/Makefile_& and rebuild Exim.
1948 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1949 .cindex "TLS" "including support for TLS"
1950 .cindex "encryption" "including support for"
1951 .cindex "OpenSSL" "building Exim with"
1952 .cindex "GnuTLS" "building Exim with"
1953 Exim is usually built to support encrypted SMTP connections, using the STARTTLS
1954 command as per RFC 2487. It can also support clients that expect to
1955 start a TLS session immediately on connection to a non-standard port (see the
1956 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1959 If you want to build Exim with TLS support, you must first install either the
1960 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1963 If you do not want TLS support you should set
1967 in &_Local/Makefile_&.
1969 If OpenSSL is installed, you should set
1972 TLS_LIBS=-lssl -lcrypto
1974 in &_Local/Makefile_&. You may also need to specify the locations of the
1975 OpenSSL library and include files. For example:
1978 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1979 TLS_INCLUDE=-I/usr/local/openssl/include/
1981 .cindex "pkg-config" "OpenSSL"
1982 If you have &'pkg-config'& available, then instead you can just use:
1985 USE_OPENSSL_PC=openssl
1987 .cindex "USE_GNUTLS"
1988 If GnuTLS is installed, you should set
1991 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1993 in &_Local/Makefile_&, and again you may need to specify the locations of the
1994 library and include files. For example:
1997 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1998 TLS_INCLUDE=-I/usr/gnu/include
2000 .cindex "pkg-config" "GnuTLS"
2001 If you have &'pkg-config'& available, then instead you can just use:
2004 USE_GNUTLS_PC=gnutls
2007 You do not need to set TLS_INCLUDE if the relevant directory is already
2008 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
2009 given in chapter &<<CHAPTLS>>&.
2014 .section "Use of tcpwrappers" "SECID27"
2016 .cindex "tcpwrappers, building Exim to support"
2017 .cindex "USE_TCP_WRAPPERS"
2018 .cindex "TCP_WRAPPERS_DAEMON_NAME"
2019 .cindex "tcp_wrappers_daemon_name"
2020 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
2021 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
2022 alternative to Exim's own checking facilities for installations that are
2023 already making use of &'tcpwrappers'& for other purposes. To do this, you
2024 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
2025 &_tcpd.h_& to be available at compile time, and also ensure that the library
2026 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
2027 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
2030 USE_TCP_WRAPPERS=yes
2031 CFLAGS=-O -I/usr/local/include
2032 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
2034 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
2035 files is &"exim"&. For example, the line
2037 exim : LOCAL 192.168.1. .friendly.domain.example
2039 in your &_/etc/hosts.allow_& file allows connections from the local host, from
2040 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
2041 All other connections are denied. The daemon name used by &'tcpwrappers'&
2042 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
2043 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
2044 configure file. Consult the &'tcpwrappers'& documentation for
2048 .section "Including support for IPv6" "SECID28"
2049 .cindex "IPv6" "including support for"
2050 Exim contains code for use on systems that have IPv6 support. Setting
2051 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
2052 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
2053 where the IPv6 support is not fully integrated into the normal include and
2056 Two different types of DNS record for handling IPv6 addresses have been
2057 defined. AAAA records (analogous to A records for IPv4) are in use, and are
2058 currently seen as the mainstream. Another record type called A6 was proposed
2059 as better than AAAA because it had more flexibility. However, it was felt to be
2060 over-complex, and its status was reduced to &"experimental"&.
2062 have a compile option for including A6 record support but this has now been
2067 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
2068 .cindex "lookup modules"
2069 .cindex "dynamic modules"
2070 .cindex ".so building"
2071 On some platforms, Exim supports not compiling all lookup types directly into
2072 the main binary, instead putting some into external modules which can be loaded
2074 This permits packagers to build Exim with support for lookups with extensive
2075 library dependencies without requiring all users to install all of those
2077 Most, but not all, lookup types can be built this way.
2079 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2080 installed; Exim will only load modules from that directory, as a security
2081 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2082 for your OS; see &_OS/Makefile-Linux_& for an example.
2083 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2084 see &_src/EDITME_& for details.
2086 Then, for each module to be loaded dynamically, define the relevant
2087 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2088 For example, this will build in lsearch but load sqlite and mysql support
2097 .section "The building process" "SECID29"
2098 .cindex "build directory"
2099 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2100 created, run &'make'& at the top level. It determines the architecture and
2101 operating system types, and creates a build directory if one does not exist.
2102 For example, on a Sun system running Solaris 8, the directory
2103 &_build-SunOS5-5.8-sparc_& is created.
2104 .cindex "symbolic link" "to source files"
2105 Symbolic links to relevant source files are installed in the build directory.
2107 If this is the first time &'make'& has been run, it calls a script that builds
2108 a make file inside the build directory, using the configuration files from the
2109 &_Local_& directory. The new make file is then passed to another instance of
2110 &'make'&. This does the real work, building a number of utility scripts, and
2111 then compiling and linking the binaries for the Exim monitor (if configured), a
2112 number of utility programs, and finally Exim itself. The command &`make
2113 makefile`& can be used to force a rebuild of the make file in the build
2114 directory, should this ever be necessary.
2116 If you have problems building Exim, check for any comments there may be in the
2117 &_README_& file concerning your operating system, and also take a look at the
2118 FAQ, where some common problems are covered.
2122 .section 'Output from &"make"&' "SECID283"
2123 The output produced by the &'make'& process for compile lines is often very
2124 unreadable, because these lines can be very long. For this reason, the normal
2125 output is suppressed by default, and instead output similar to that which
2126 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2127 each module that is being compiled or linked. However, it is still possible to
2128 get the full output, by calling &'make'& like this:
2132 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2133 command reflection in &'make'&. When you ask for the full output, it is
2134 given in addition to the short output.
2138 .section "Overriding build-time options for Exim" "SECToverride"
2139 .cindex "build-time options, overriding"
2140 The main make file that is created at the beginning of the building process
2141 consists of the concatenation of a number of files which set configuration
2142 values, followed by a fixed set of &'make'& instructions. If a value is set
2143 more than once, the last setting overrides any previous ones. This provides a
2144 convenient way of overriding defaults. The files that are concatenated are, in
2147 &_OS/Makefile-Default_&
2148 &_OS/Makefile-_&<&'ostype'&>
2150 &_Local/Makefile-_&<&'ostype'&>
2151 &_Local/Makefile-_&<&'archtype'&>
2152 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2153 &_OS/Makefile-Base_&
2155 .cindex "&_Local/Makefile_&"
2156 .cindex "building Exim" "operating system type"
2157 .cindex "building Exim" "architecture type"
2158 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2159 architecture type. &_Local/Makefile_& is required to exist, and the building
2160 process fails if it is absent. The other three &_Local_& files are optional,
2161 and are often not needed.
2163 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2164 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2165 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2166 values are used, thereby providing a means of forcing particular settings.
2167 Otherwise, the scripts try to get values from the &%uname%& command. If this
2168 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2169 of &'ad hoc'& transformations are then applied, to produce the standard names
2170 that Exim expects. You can run these scripts directly from the shell in order
2171 to find out what values are being used on your system.
2174 &_OS/Makefile-Default_& contains comments about the variables that are set
2175 therein. Some (but not all) are mentioned below. If there is something that
2176 needs changing, review the contents of this file and the contents of the make
2177 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2181 .cindex "building Exim" "overriding default settings"
2182 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2183 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2184 need to change the original files. Instead, you should make the changes by
2185 putting the new values in an appropriate &_Local_& file. For example,
2186 .cindex "Tru64-Unix build-time settings"
2187 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2188 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2189 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2190 called with the option &%-std1%&, to make it recognize some of the features of
2191 Standard C that Exim uses. (Most other compilers recognize Standard C by
2192 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2193 containing the lines
2198 If you are compiling for just one operating system, it may be easier to put
2199 these lines directly into &_Local/Makefile_&.
2201 Keeping all your local configuration settings separate from the distributed
2202 files makes it easy to transfer them to new versions of Exim simply by copying
2203 the contents of the &_Local_& directory.
2206 .cindex "NIS lookup type" "including support for"
2207 .cindex "NIS+ lookup type" "including support for"
2208 .cindex "LDAP" "including support for"
2209 .cindex "lookup" "inclusion in binary"
2210 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2211 lookup, but not all systems have these components installed, so the default is
2212 not to include the relevant code in the binary. All the different kinds of file
2213 and database lookup that Exim supports are implemented as separate code modules
2214 which are included only if the relevant compile-time options are set. In the
2215 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2221 and similar settings apply to the other lookup types. They are all listed in
2222 &_src/EDITME_&. In many cases the relevant include files and interface
2223 libraries need to be installed before compiling Exim.
2224 .cindex "cdb" "including support for"
2225 However, there are some optional lookup types (such as cdb) for which
2226 the code is entirely contained within Exim, and no external include
2227 files or libraries are required. When a lookup type is not included in the
2228 binary, attempts to configure Exim to use it cause runtime configuration
2231 .cindex "pkg-config" "lookups"
2232 .cindex "pkg-config" "authenticators"
2233 Many systems now use a tool called &'pkg-config'& to encapsulate information
2234 about how to compile against a library; Exim has some initial support for
2235 being able to use pkg-config for lookups and authenticators. For any given
2236 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2237 variable with the &`_PC`& suffix in the name and assign as the value the
2238 name of the package to be queried. The results of querying via the
2239 &'pkg-config'& command will be added to the appropriate Makefile variables
2240 with &`+=`& directives, so your version of &'make'& will need to support that
2241 syntax. For instance:
2244 LOOKUP_SQLITE_PC=sqlite3
2246 AUTH_GSASL_PC=libgsasl
2247 AUTH_HEIMDAL_GSSAPI=yes
2248 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2251 .cindex "Perl" "including support for"
2252 Exim can be linked with an embedded Perl interpreter, allowing Perl
2253 subroutines to be called during string expansion. To enable this facility,
2257 must be defined in &_Local/Makefile_&. Details of this facility are given in
2258 chapter &<<CHAPperl>>&.
2260 .cindex "X11 libraries, location of"
2261 The location of the X11 libraries is something that varies a lot between
2262 operating systems, and there may be different versions of X11 to cope
2263 with. Exim itself makes no use of X11, but if you are compiling the Exim
2264 monitor, the X11 libraries must be available.
2265 The following three variables are set in &_OS/Makefile-Default_&:
2268 XINCLUDE=-I$(X11)/include
2269 XLFLAGS=-L$(X11)/lib
2271 These are overridden in some of the operating-system configuration files. For
2272 example, in &_OS/Makefile-SunOS5_& there is
2275 XINCLUDE=-I$(X11)/include
2276 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2278 If you need to override the default setting for your operating system, place a
2279 definition of all three of these variables into your
2280 &_Local/Makefile-<ostype>_& file.
2283 If you need to add any extra libraries to the link steps, these can be put in a
2284 variable called EXTRALIBS, which appears in all the link commands, but by
2285 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2286 command for linking the main Exim binary, and not for any associated utilities.
2288 .cindex "DBM libraries" "configuration for building"
2289 There is also DBMLIB, which appears in the link commands for binaries that
2290 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2291 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2292 binary, and which can be used, for example, to include additional X11
2295 .cindex "configuration file" "editing"
2296 The make file copes with rebuilding Exim correctly if any of the configuration
2297 files are edited. However, if an optional configuration file is deleted, it is
2298 necessary to touch the associated non-optional file (that is,
2299 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2302 .section "OS-specific header files" "SECID30"
2304 .cindex "building Exim" "OS-specific C header files"
2305 The &_OS_& directory contains a number of files with names of the form
2306 &_os.h-<ostype>_&. These are system-specific C header files that should not
2307 normally need to be changed. There is a list of macro settings that are
2308 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2309 are porting Exim to a new operating system.
2313 .section "Overriding build-time options for the monitor" "SECID31"
2314 .cindex "building Eximon"
2315 A similar process is used for overriding things when building the Exim monitor,
2316 where the files that are involved are
2318 &_OS/eximon.conf-Default_&
2319 &_OS/eximon.conf-_&<&'ostype'&>
2320 &_Local/eximon.conf_&
2321 &_Local/eximon.conf-_&<&'ostype'&>
2322 &_Local/eximon.conf-_&<&'archtype'&>
2323 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2325 .cindex "&_Local/eximon.conf_&"
2326 As with Exim itself, the final three files need not exist, and in this case the
2327 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2328 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2329 variables of the same name, preceded by EXIMON_. For example, setting
2330 EXIMON_LOG_DEPTH in the environment overrides the value of
2331 LOG_DEPTH at runtime.
2335 .section "Installing Exim binaries and scripts" "SECID32"
2336 .cindex "installing Exim"
2337 .cindex "BIN_DIRECTORY"
2338 The command &`make install`& runs the &(exim_install)& script with no
2339 arguments. The script copies binaries and utility scripts into the directory
2340 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2341 .cindex "setuid" "installing Exim with"
2342 The install script copies files only if they are newer than the files they are
2343 going to replace. The Exim binary is required to be owned by root and have the
2344 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2345 install`& as root so that it can set up the Exim binary in this way. However, in
2346 some special situations (for example, if a host is doing no local deliveries)
2347 it may be possible to run Exim without making the binary setuid root (see
2348 chapter &<<CHAPsecurity>>& for details).
2350 .cindex "CONFIGURE_FILE"
2351 Exim's runtime configuration file is named by the CONFIGURE_FILE setting
2352 in &_Local/Makefile_&. If this names a single file, and the file does not
2353 exist, the default configuration file &_src/configure.default_& is copied there
2354 by the installation script. If a runtime configuration file already exists, it
2355 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2356 alternative files, no default is installed.
2358 .cindex "system aliases file"
2359 .cindex "&_/etc/aliases_&"
2360 One change is made to the default configuration file when it is installed: the
2361 default configuration contains a router that references a system aliases file.
2362 The path to this file is set to the value specified by
2363 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2364 If the system aliases file does not exist, the installation script creates it,
2365 and outputs a comment to the user.
2367 The created file contains no aliases, but it does contain comments about the
2368 aliases a site should normally have. Mail aliases have traditionally been
2369 kept in &_/etc/aliases_&. However, some operating systems are now using
2370 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2371 Exim's configuration if necessary.
2373 The default configuration uses the local host's name as the only local domain,
2374 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2375 running as the local user. System aliases and &_.forward_& files in users' home
2376 directories are supported, but no NIS or NIS+ support is configured. Domains
2377 other than the name of the local host are routed using the DNS, with delivery
2380 It is possible to install Exim for special purposes (such as building a binary
2381 distribution) in a private part of the file system. You can do this by a
2384 make DESTDIR=/some/directory/ install
2386 This has the effect of pre-pending the specified directory to all the file
2387 paths, except the name of the system aliases file that appears in the default
2388 configuration. (If a default alias file is created, its name &'is'& modified.)
2389 For backwards compatibility, ROOT is used if DESTDIR is not set,
2390 but this usage is deprecated.
2392 .cindex "installing Exim" "what is not installed"
2393 Running &'make install'& does not copy the Exim 4 conversion script
2394 &'convert4r4'&. You will probably run this only once if you are
2395 upgrading from Exim 3. None of the documentation files in the &_doc_&
2396 directory are copied, except for the info files when you have set
2397 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2399 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2400 to their names. The Exim binary itself, however, is handled differently. It is
2401 installed under a name that includes the version number and the compile number,
2402 for example, &_exim-&version()-1_&. The script then arranges for a symbolic link
2403 called &_exim_& to point to the binary. If you are updating a previous version
2404 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2405 from the directory (as seen by other processes).
2407 .cindex "installing Exim" "testing the script"
2408 If you want to see what the &'make install'& will do before running it for
2409 real, you can pass the &%-n%& option to the installation script by this
2412 make INSTALL_ARG=-n install
2414 The contents of the variable INSTALL_ARG are passed to the installation
2415 script. You do not need to be root to run this test. Alternatively, you can run
2416 the installation script directly, but this must be from within the build
2417 directory. For example, from the top-level Exim directory you could use this
2420 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2422 .cindex "installing Exim" "install script options"
2423 There are two other options that can be supplied to the installation script.
2426 &%-no_chown%& bypasses the call to change the owner of the installed binary
2427 to root, and the call to make it a setuid binary.
2429 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2433 INSTALL_ARG can be used to pass these options to the script. For example:
2435 make INSTALL_ARG=-no_symlink install
2437 The installation script can also be given arguments specifying which files are
2438 to be copied. For example, to install just the Exim binary, and nothing else,
2439 without creating the symbolic link, you could use:
2441 make INSTALL_ARG='-no_symlink exim' install
2446 .section "Installing info documentation" "SECTinsinfdoc"
2447 .cindex "installing Exim" "&'info'& documentation"
2448 Not all systems use the GNU &'info'& system for documentation, and for this
2449 reason, the Texinfo source of Exim's documentation is not included in the main
2450 distribution. Instead it is available separately from the FTP site (see section
2453 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2454 source of the documentation is found in the source tree, running &`make
2455 install`& automatically builds the info files and installs them.
2459 .section "Setting up the spool directory" "SECID33"
2460 .cindex "spool directory" "creating"
2461 When it starts up, Exim tries to create its spool directory if it does not
2462 exist. The Exim uid and gid are used for the owner and group of the spool
2463 directory. Sub-directories are automatically created in the spool directory as
2469 .section "Testing" "SECID34"
2470 .cindex "testing" "installation"
2471 Having installed Exim, you can check that the runtime configuration file is
2472 syntactically valid by running the following command, which assumes that the
2473 Exim binary directory is within your PATH environment variable:
2477 If there are any errors in the configuration file, Exim outputs error messages.
2478 Otherwise it outputs the version number and build date,
2479 the DBM library that is being used, and information about which drivers and
2480 other optional code modules are included in the binary.
2481 Some simple routing tests can be done by using the address testing option. For
2484 &`exim -bt`& <&'local username'&>
2486 should verify that it recognizes a local mailbox, and
2488 &`exim -bt`& <&'remote address'&>
2490 a remote one. Then try getting it to deliver mail, both locally and remotely.
2491 This can be done by passing messages directly to Exim, without going through a
2492 user agent. For example:
2494 exim -v postmaster@your.domain.example
2495 From: user@your.domain.example
2496 To: postmaster@your.domain.example
2497 Subject: Testing Exim
2499 This is a test message.
2502 The &%-v%& option causes Exim to output some verification of what it is doing.
2503 In this case you should see copies of three log lines, one for the message's
2504 arrival, one for its delivery, and one containing &"Completed"&.
2506 .cindex "delivery" "problems with"
2507 If you encounter problems, look at Exim's log files (&'mainlog'& and
2508 &'paniclog'&) to see if there is any relevant information there. Another source
2509 of information is running Exim with debugging turned on, by specifying the
2510 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2511 with debugging turned on by a command of the form
2513 &`exim -d -M`& <&'exim-message-id'&>
2515 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2516 produces rather a lot of output, but you can cut this down to specific areas.
2517 For example, if you use &%-d-all+route%& only the debugging information
2518 relevant to routing is included. (See the &%-d%& option in chapter
2519 &<<CHAPcommandline>>& for more details.)
2521 .cindex '&"sticky"& bit'
2522 .cindex "lock files"
2523 One specific problem that has shown up on some sites is the inability to do
2524 local deliveries into a shared mailbox directory, because it does not have the
2525 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2526 writing to a mailbox file, and if it cannot create the lock file, the delivery
2527 is deferred. You can get round this either by setting the &"sticky bit"& on the
2528 directory, or by setting a specific group for local deliveries and allowing
2529 that group to create files in the directory (see the comments above the
2530 &(local_delivery)& transport in the default configuration file). Another
2531 approach is to configure Exim not to use lock files, but just to rely on
2532 &[fcntl()]& locking instead. However, you should do this only if all user
2533 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2534 see chapter &<<CHAPappendfile>>&.
2536 One thing that cannot be tested on a system that is already running an MTA is
2537 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2538 &%-oX%& option can be used to run an Exim daemon that listens on some other
2539 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2540 &'exim_checkaccess'& utility can be used to check out policy controls on
2543 Testing a new version on a system that is already running Exim can most easily
2544 be done by building a binary with a different CONFIGURE_FILE setting. From
2545 within the runtime configuration, all other file and directory names
2546 that Exim uses can be altered, in order to keep it entirely clear of the
2550 .section "Replacing another MTA with Exim" "SECID35"
2551 .cindex "replacing another MTA"
2552 Building and installing Exim for the first time does not of itself put it in
2553 general use. The name by which the system's MTA is called by mail user agents
2554 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2555 operating system), and it is necessary to make this name point to the &'exim'&
2556 binary in order to get the user agents to pass messages to Exim. This is
2557 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2558 or &_/usr/lib/sendmail_&
2559 .cindex "symbolic link" "to &'exim'& binary"
2560 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2561 privilege and executable status from the old MTA. It is then necessary to stop
2562 and restart the mailer daemon, if one is running.
2564 .cindex "FreeBSD, MTA indirection"
2565 .cindex "&_/etc/mail/mailer.conf_&"
2566 Some operating systems have introduced alternative ways of switching MTAs. For
2567 example, if you are running FreeBSD, you need to edit the file
2568 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2569 described. A typical example of the contents of this file for running Exim is
2572 sendmail /usr/exim/bin/exim
2573 send-mail /usr/exim/bin/exim
2574 mailq /usr/exim/bin/exim -bp
2575 newaliases /usr/bin/true
2577 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2578 your Exim installation is &"live"&. Check it by sending a message from your
2579 favourite user agent.
2581 You should consider what to tell your users about the change of MTA. Exim may
2582 have different capabilities to what was previously running, and there are
2583 various operational differences such as the text of messages produced by
2584 command line options and in bounce messages. If you allow your users to make
2585 use of Exim's filtering capabilities, you should make the document entitled
2586 &'Exim's interface to mail filtering'& available to them.
2590 .section "Running the daemon" SECTdaemonLaunch
2591 The most common command line for launching the Exim daemon looks like
2595 This starts a daemon which
2597 listens for incoming smtp connections, launching handler processes for
2600 starts a queue-runner process every five minutes, to inspect queued messages
2601 and run delivery attempts on any that have arrived at their retry time
2603 Should a queue run take longer than the time between queue-runner starts,
2604 they will run in parallel.
2605 Numbers of jobs of the various types are subject to policy controls
2606 defined in the configuration.
2609 .section "Upgrading Exim" "SECID36"
2610 .cindex "upgrading Exim"
2611 If you are already running Exim on your host, building and installing a new
2612 version automatically makes it available to MUAs, or any other programs that
2613 call the MTA directly. However, if you are running an Exim daemon, you do need
2614 .cindex restart "on HUP signal"
2615 .cindex signal "HUP, to restart"
2616 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2617 new binary. You do not need to stop processing mail in order to install a new
2618 version of Exim. The install script does not modify an existing runtime
2624 .section "Stopping the Exim daemon on Solaris" "SECID37"
2625 .cindex "Solaris" "stopping Exim on"
2626 The standard command for stopping the mailer daemon on Solaris is
2628 /etc/init.d/sendmail stop
2630 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2631 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2632 for the text &"sendmail"&; this is not present because the actual program name
2633 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2634 solution is to replace the line that finds the process id with something like
2636 pid=`cat /var/spool/exim/exim-daemon.pid`
2638 to obtain the daemon's pid directly from the file that Exim saves it in.
2640 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2641 still be received from local processes, and if automatic delivery is configured
2642 (the normal case), deliveries will still occur.
2647 . ////////////////////////////////////////////////////////////////////////////
2648 . ////////////////////////////////////////////////////////////////////////////
2650 .chapter "The Exim command line" "CHAPcommandline"
2651 .scindex IIDclo1 "command line" "options"
2652 .scindex IIDclo2 "options" "command line"
2653 Exim's command line takes the standard Unix form of a sequence of options,
2654 each starting with a hyphen character, followed by a number of arguments. The
2655 options are compatible with the main options of Sendmail, and there are also
2656 some additional options, some of which are compatible with Smail 3. Certain
2657 combinations of options do not make sense, and provoke an error if used.
2658 The form of the arguments depends on which options are set.
2661 .section "Setting options by program name" "SECID38"
2663 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2664 were present before any other options.
2665 The &%-bp%& option requests a listing of the contents of the mail queue on the
2667 This feature is for compatibility with some systems that contain a command of
2668 that name in one of the standard libraries, symbolically linked to
2669 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2672 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2673 were present before any other options, for compatibility with Smail. The
2674 &%-bS%& option is used for reading in a number of messages in batched SMTP
2678 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2679 &%-oee%& options were present before any other options, for compatibility with
2680 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2683 .cindex "queue runner"
2684 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2685 were present before any other options, for compatibility with Smail. The &%-q%&
2686 option causes a single queue runner process to be started.
2688 .cindex "&'newaliases'&"
2689 .cindex "alias file" "building"
2690 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2691 If Exim is called under the name &'newaliases'& it behaves as if the option
2692 &%-bi%& were present before any other options, for compatibility with Sendmail.
2693 This option is used for rebuilding Sendmail's alias file. Exim does not have
2694 the concept of a single alias file, but can be configured to run a given
2695 command if called with the &%-bi%& option.
2698 .section "Trusted and admin users" "SECTtrustedadmin"
2699 Some Exim options are available only to &'trusted users'& and others are
2700 available only to &'admin users'&. In the description below, the phrases &"Exim
2701 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2702 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2703 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2706 .cindex "trusted users" "definition of"
2707 .cindex "user" "trusted definition of"
2708 The trusted users are root, the Exim user, any user listed in the
2709 &%trusted_users%& configuration option, and any user whose current group or any
2710 supplementary group is one of those listed in the &%trusted_groups%&
2711 configuration option. Note that the Exim group is not automatically trusted.
2713 .cindex '&"From"& line'
2714 .cindex "envelope from"
2715 .cindex "envelope sender"
2716 Trusted users are always permitted to use the &%-f%& option or a leading
2717 &"From&~"& line to specify the envelope sender of a message that is passed to
2718 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2719 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2720 users to set envelope senders.
2724 For a trusted user, there is never any check on the contents of the &'From:'&
2725 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2726 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2728 Trusted users may also specify a host name, host address, interface address,
2729 protocol name, ident value, and authentication data when submitting a message
2730 locally. Thus, they are able to insert messages into Exim's queue locally that
2731 have the characteristics of messages received from a remote host. Untrusted
2732 users may in some circumstances use &%-f%&, but can never set the other values
2733 that are available to trusted users.
2735 .cindex "user" "admin definition of"
2736 .cindex "admin user" "definition of"
2737 The admin users are root, the Exim user, and any user that is a member of the
2738 Exim group or of any group listed in the &%admin_groups%& configuration option.
2739 The current group does not have to be one of these groups.
2741 Admin users are permitted to list the queue, and to carry out certain
2742 operations on messages, for example, to force delivery failures. It is also
2743 necessary to be an admin user in order to see the full information provided by
2744 the Exim monitor, and full debugging output.
2746 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2747 Exim to attempt delivery of messages on its queue is restricted to admin users.
2748 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2749 option false (that is, specifying &%no_prod_requires_admin%&).
2751 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2752 is restricted to admin users unless &%queue_list_requires_admin%& is set
2757 &*Warning*&: If you configure your system so that admin users are able to
2758 edit Exim's configuration file, you are giving those users an easy way of
2759 getting root. There is further discussion of this issue at the start of chapter
2765 .section "Command line options" "SECID39"
2766 Exim's command line options are described in alphabetical order below. If none
2767 of the options that specifies a specific action (such as starting the daemon or
2768 a queue runner, or testing an address, or receiving a message in a specific
2769 format, or listing the queue) are present, and there is at least one argument
2770 on the command line, &%-bm%& (accept a local message on the standard input,
2771 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2772 outputs a brief message about itself and exits.
2774 . ////////////////////////////////////////////////////////////////////////////
2775 . Insert a stylized XML comment here, to identify the start of the command line
2776 . options. This is for the benefit of the Perl script that automatically
2777 . creates a man page for the options.
2778 . ////////////////////////////////////////////////////////////////////////////
2781 <!-- === Start of command line options === -->
2788 .cindex "options" "command line; terminating"
2789 This is a pseudo-option whose only purpose is to terminate the options and
2790 therefore to cause subsequent command line items to be treated as arguments
2791 rather than options, even if they begin with hyphens.
2794 .oindex "&%--help%&"
2795 This option causes Exim to output a few sentences stating what it is.
2796 The same output is generated if the Exim binary is called with no options and
2799 .vitem &%--version%&
2800 .oindex "&%--version%&"
2801 This option is an alias for &%-bV%& and causes version information to be
2808 These options are used by Sendmail for selecting configuration files and are
2811 .vitem &%-B%&<&'type'&>
2813 .cindex "8-bit characters"
2814 .cindex "Sendmail compatibility" "8-bit characters"
2815 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2816 clean; it ignores this option.
2821 .cindex "SMTP" "listener"
2822 .cindex "queue runner"
2823 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2824 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2825 that the daemon should also initiate periodic queue runs.
2827 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2828 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2829 disconnect from the controlling terminal. When running this way, it can be
2830 stopped by pressing ctrl-C.
2832 By default, Exim listens for incoming connections to the standard SMTP port on
2833 all the host's running interfaces. However, it is possible to listen on other
2834 ports, on multiple ports, and only on specific interfaces. Chapter
2835 &<<CHAPinterfaces>>& contains a description of the options that control this.
2837 When a listening daemon
2838 .cindex "daemon" "process id (pid)"
2839 .cindex "pid (process id)" "of daemon"
2840 is started without the use of &%-oX%& (that is, without overriding the normal
2841 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2842 in Exim's spool directory. This location can be overridden by setting
2843 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2846 When &%-oX%& is used on the command line to start a listening daemon, the
2847 process id is not written to the normal pid file path. However, &%-oP%& can be
2848 used to specify a path on the command line if a pid file is required.
2852 .cindex restart "on HUP signal"
2853 .cindex signal "HUP, to restart"
2854 .cindex "daemon" "restarting"
2855 .cindex signal "to reload configuration"
2856 .cindex daemon "reload configuration"
2857 .cindex reload configuration
2858 can be used to cause the daemon to re-execute itself. This should be done
2859 whenever Exim's configuration file, or any file that is incorporated into it by
2860 means of the &%.include%& facility, is changed, and also whenever a new version
2861 of Exim is installed. It is not necessary to do this when other files that are
2862 referenced from the configuration (for example, alias files) are changed,
2863 because these are reread each time they are used.
2867 This option has the same effect as &%-bd%& except that it never disconnects
2868 from the controlling terminal, even when no debugging is specified.
2872 .cindex "testing" "string expansion"
2873 .cindex "expansion" "testing"
2874 Run Exim in expansion testing mode. Exim discards its root privilege, to
2875 prevent ordinary users from using this mode to read otherwise inaccessible
2876 files. If no arguments are given, Exim runs interactively, prompting for lines
2877 of data. Otherwise, it processes each argument in turn.
2879 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2880 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2881 used without command line arguments. If successful, it uses the &[readline()]&
2882 function, which provides extensive line-editing facilities, for reading the
2883 test data. A line history is supported.
2885 Long expansion expressions can be split over several lines by using backslash
2886 continuations. As in Exim's runtime configuration, white space at the start of
2887 continuation lines is ignored. Each argument or data line is passed through the
2888 string expansion mechanism, and the result is output. Variable values from the
2889 configuration file (for example, &$qualify_domain$&) are available, but no
2890 message-specific values (such as &$message_exim_id$&) are set, because no message
2891 is being processed (but see &%-bem%& and &%-Mset%&).
2893 &*Note*&: If you use this mechanism to test lookups, and you change the data
2894 files or databases you are using, you must exit and restart Exim before trying
2895 the same lookup again. Otherwise, because each Exim process caches the results
2896 of lookups, you will just get the same result as before.
2898 Macro processing is done on lines before string-expansion: new macros can be
2899 defined and macros will be expanded.
2900 Because macros in the config file are often used for secrets, those are only
2901 available to admin users.
2903 .vitem &%-bem%&&~<&'filename'&>
2905 .cindex "testing" "string expansion"
2906 .cindex "expansion" "testing"
2907 This option operates like &%-be%& except that it must be followed by the name
2908 of a file. For example:
2910 exim -bem /tmp/testmessage
2912 The file is read as a message (as if receiving a locally-submitted non-SMTP
2913 message) before any of the test expansions are done. Thus, message-specific
2914 variables such as &$message_size$& and &$header_from:$& are available. However,
2915 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2916 recipients are read from the headers in the normal way, and are shown in the
2917 &$recipients$& variable. Note that recipients cannot be given on the command
2918 line, because further arguments are taken as strings to expand (just like
2921 .vitem &%-bF%&&~<&'filename'&>
2923 .cindex "system filter" "testing"
2924 .cindex "testing" "system filter"
2925 This option is the same as &%-bf%& except that it assumes that the filter being
2926 tested is a system filter. The additional commands that are available only in
2927 system filters are recognized.
2929 .vitem &%-bf%&&~<&'filename'&>
2931 .cindex "filter" "testing"
2932 .cindex "testing" "filter file"
2933 .cindex "forward file" "testing"
2934 .cindex "testing" "forward file"
2935 .cindex "Sieve filter" "testing"
2936 This option runs Exim in user filter testing mode; the file is the filter file
2937 to be tested, and a test message must be supplied on the standard input. If
2938 there are no message-dependent tests in the filter, an empty file can be
2941 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2942 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2943 filter and a user filter in the same run. For example:
2945 exim -bF /system/filter -bf /user/filter </test/message
2947 This is helpful when the system filter adds header lines or sets filter
2948 variables that are used by the user filter.
2950 If the test filter file does not begin with one of the special lines
2955 it is taken to be a normal &_.forward_& file, and is tested for validity under
2956 that interpretation. See sections &<<SECTitenonfilred>>& to
2957 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2960 The result of an Exim command that uses &%-bf%&, provided no errors are
2961 detected, is a list of the actions that Exim would try to take if presented
2962 with the message for real. More details of filter testing are given in the
2963 separate document entitled &'Exim's interfaces to mail filtering'&.
2965 When testing a filter file,
2966 .cindex "&""From""& line"
2967 .cindex "envelope from"
2968 .cindex "envelope sender"
2969 .oindex "&%-f%&" "for filter testing"
2970 the envelope sender can be set by the &%-f%& option,
2971 or by a &"From&~"& line at the start of the test message. Various parameters
2972 that would normally be taken from the envelope recipient address of the message
2973 can be set by means of additional command line options (see the next four
2976 .vitem &%-bfd%&&~<&'domain'&>
2978 .vindex "&$qualify_domain$&"
2979 This sets the domain of the recipient address when a filter file is being
2980 tested by means of the &%-bf%& option. The default is the value of
2983 .vitem &%-bfl%&&~<&'local&~part'&>
2985 This sets the local part of the recipient address when a filter file is being
2986 tested by means of the &%-bf%& option. The default is the username of the
2987 process that calls Exim. A local part should be specified with any prefix or
2988 suffix stripped, because that is how it appears to the filter when a message is
2989 actually being delivered.
2991 .vitem &%-bfp%&&~<&'prefix'&>
2993 .cindex affix "filter testing"
2994 This sets the prefix of the local part of the recipient address when a filter
2995 file is being tested by means of the &%-bf%& option. The default is an empty
2998 .vitem &%-bfs%&&~<&'suffix'&>
3000 .cindex affix "filter testing"
3001 This sets the suffix of the local part of the recipient address when a filter
3002 file is being tested by means of the &%-bf%& option. The default is an empty
3005 .vitem &%-bh%&&~<&'IP&~address'&>
3007 .cindex "testing" "incoming SMTP"
3008 .cindex "SMTP" "testing incoming"
3009 .cindex "testing" "relay control"
3010 .cindex "relaying" "testing configuration"
3011 .cindex "policy control" "testing"
3012 .cindex "debugging" "&%-bh%& option"
3013 This option runs a fake SMTP session as if from the given IP address, using the
3014 standard input and output. The IP address may include a port number at the end,
3015 after a full stop. For example:
3017 exim -bh 10.9.8.7.1234
3018 exim -bh fe80::a00:20ff:fe86:a061.5678
3020 When an IPv6 address is given, it is converted into canonical form. In the case
3021 of the second example above, the value of &$sender_host_address$& after
3022 conversion to the canonical form is
3023 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
3025 Comments as to what is going on are written to the standard error file. These
3026 include lines beginning with &"LOG"& for anything that would have been logged.
3027 This facility is provided for testing configuration options for incoming
3028 messages, to make sure they implement the required policy. For example, you can
3029 test your relay controls using &%-bh%&.
3033 You can test features of the configuration that rely on ident (RFC 1413)
3034 information by using the &%-oMt%& option. However, Exim cannot actually perform
3035 an ident callout when testing using &%-bh%& because there is no incoming SMTP
3038 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
3039 are also skipped when testing using &%-bh%&. If you want these callouts to
3040 occur, use &%-bhc%& instead.
3042 Messages supplied during the testing session are discarded, and nothing is
3043 written to any of the real log files. There may be pauses when DNS (and other)
3044 lookups are taking place, and of course these may time out. The &%-oMi%& option
3045 can be used to specify a specific IP interface and port if this is important,
3046 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
3047 session were authenticated.
3049 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
3050 output just states whether a given recipient address from a given host is
3051 acceptable or not. See section &<<SECTcheckaccess>>&.
3053 Features such as authentication and encryption, where the client input is not
3054 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
3055 specialized SMTP test program such as
3056 &url(https://www.jetmore.org/john/code/swaks/,swaks).
3058 .vitem &%-bhc%&&~<&'IP&~address'&>
3060 This option operates in the same way as &%-bh%&, except that address
3061 verification callouts are performed if required. This includes consulting and
3062 updating the callout cache database.
3066 .cindex "alias file" "building"
3067 .cindex "building alias file"
3068 .cindex "Sendmail compatibility" "&%-bi%& option"
3069 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
3070 Exim does not have the concept of a single alias file, and so it cannot mimic
3071 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
3072 tend to appear in various scripts such as NIS make files, so the option must be
3075 If &%-bi%& is encountered, the command specified by the &%bi_command%&
3076 configuration option is run, under the uid and gid of the caller of Exim. If
3077 the &%-oA%& option is used, its value is passed to the command as an argument.
3078 The command set by &%bi_command%& may not contain arguments. The command can
3079 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
3080 if this is required. If the &%bi_command%& option is not set, calling Exim with
3083 . // Keep :help first, then the rest in alphabetical order
3085 .oindex "&%-bI:help%&"
3086 .cindex "querying exim information"
3087 We shall provide various options starting &`-bI:`& for querying Exim for
3088 information. The output of many of these will be intended for machine
3089 consumption. This one is not. The &%-bI:help%& option asks Exim for a
3090 synopsis of supported options beginning &`-bI:`&. Use of any of these
3091 options shall cause Exim to exit after producing the requested output.
3094 .oindex "&%-bI:dscp%&"
3095 .cindex "DSCP" "values"
3096 This option causes Exim to emit an alphabetically sorted list of all
3097 recognised DSCP names.
3099 .vitem &%-bI:sieve%&
3100 .oindex "&%-bI:sieve%&"
3101 .cindex "Sieve filter" "capabilities"
3102 This option causes Exim to emit an alphabetically sorted list of all supported
3103 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3104 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3105 &`SIEVE`& capability response line. As the precise list may depend upon
3106 compile-time build options, which this option will adapt to, this is the only
3107 way to guarantee a correct response.
3111 .cindex "local message reception"
3112 This option runs an Exim receiving process that accepts an incoming,
3113 locally-generated message on the standard input. The recipients are given as the
3114 command arguments (except when &%-t%& is also present &-- see below). Each
3115 argument can be a comma-separated list of RFC 2822 addresses. This is the
3116 default option for selecting the overall action of an Exim call; it is assumed
3117 if no other conflicting option is present.
3119 If any addresses in the message are unqualified (have no domain), they are
3120 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3121 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3122 suppressing this for special cases.
3124 Policy checks on the contents of local messages can be enforced by means of
3125 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3127 .cindex "return code" "for &%-bm%&"
3128 The return code is zero if the message is successfully accepted. Otherwise, the
3129 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3132 .cindex "message" "format"
3133 .cindex "format" "message"
3134 .cindex "&""From""& line"
3135 .cindex "UUCP" "&""From""& line"
3136 .cindex "Sendmail compatibility" "&""From""& line"
3137 of the message must be as defined in RFC 2822, except that, for
3138 compatibility with Sendmail and Smail, a line in one of the forms
3140 From sender Fri Jan 5 12:55 GMT 1997
3141 From sender Fri, 5 Jan 97 12:55:01
3143 (with the weekday optional, and possibly with additional text after the date)
3144 is permitted to appear at the start of the message. There appears to be no
3145 authoritative specification of the format of this line. Exim recognizes it by
3146 matching against the regular expression defined by the &%uucp_from_pattern%&
3147 option, which can be changed if necessary.
3149 .oindex "&%-f%&" "overriding &""From""& line"
3150 The specified sender is treated as if it were given as the argument to the
3151 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3152 preference to the address taken from the message. The caller of Exim must be a
3153 trusted user for the sender of a message to be set in this way.
3155 .vitem &%-bmalware%&&~<&'filename'&>
3156 .oindex "&%-bmalware%&"
3157 .cindex "testing", "malware"
3158 .cindex "malware scan test"
3159 This debugging option causes Exim to scan the given file or directory
3160 (depending on the used scanner interface),
3161 using the malware scanning framework. The option of &%av_scanner%& influences
3162 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3163 the expansion should have defaults which apply to this invocation. ACLs are
3164 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3165 will never be populated and &%-bmalware%& will fail.
3167 Exim will have changed working directory before resolving the filename, so
3168 using fully qualified pathnames is advisable. Exim will be running as the Exim
3169 user when it tries to open the file, rather than as the invoking user.
3170 This option requires admin privileges.
3172 The &%-bmalware%& option will not be extended to be more generally useful,
3173 there are better tools for file-scanning. This option exists to help
3174 administrators verify their Exim and AV scanner configuration.
3178 .cindex "address qualification, suppressing"
3179 By default, Exim automatically qualifies unqualified addresses (those
3180 without domains) that appear in messages that are submitted locally (that
3181 is, not over TCP/IP). This qualification applies both to addresses in
3182 envelopes, and addresses in header lines. Sender addresses are qualified using
3183 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3184 defaults to the value of &%qualify_domain%&).
3186 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3187 being used to re-submit messages that originally came from remote hosts after
3188 content scanning, you probably do not want to qualify unqualified addresses in
3189 header lines. (Such lines will be present only if you have not enabled a header
3190 syntax check in the appropriate ACL.)
3192 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3193 messages that originate on the local host. When this is used, unqualified
3194 addresses in the envelope provoke errors (causing message rejection) and
3195 unqualified addresses in header lines are left alone.
3200 .cindex "configuration options" "extracting"
3201 .cindex "options" "configuration &-- extracting"
3202 If this option is given with no arguments, it causes the values of all Exim's
3203 main configuration options to be written to the standard output. The values
3204 of one or more specific options can be requested by giving their names as
3205 arguments, for example:
3207 exim -bP qualify_domain hold_domains
3209 .cindex "hiding configuration option values"
3210 .cindex "configuration options" "hiding value of"
3211 .cindex "options" "hiding value of"
3212 However, any option setting that is preceded by the word &"hide"& in the
3213 configuration file is not shown in full, except to an admin user. For other
3214 users, the output is as in this example:
3216 mysql_servers = <value not displayable>
3218 If &%config%& is given as an argument, the config is
3219 output, as it was parsed, any include file resolved, any comment removed.
3221 If &%config_file%& is given as an argument, the name of the runtime
3222 configuration file is output. (&%configure_file%& works too, for
3223 backward compatibility.)
3224 If a list of configuration files was supplied, the value that is output here
3225 is the name of the file that was actually used.
3227 .cindex "options" "hiding name of"
3228 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3229 name will not be output.
3231 .cindex "daemon" "process id (pid)"
3232 .cindex "pid (process id)" "of daemon"
3233 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3234 directories where log files and daemon pid files are written are output,
3235 respectively. If these values are unset, log files are written in a
3236 sub-directory of the spool directory called &%log%&, and the pid file is
3237 written directly into the spool directory.
3239 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3241 exim -bP +local_domains
3243 it searches for a matching named list of any type (domain, host, address, or
3244 local part) and outputs what it finds.
3246 .cindex "options" "router &-- extracting"
3247 .cindex "options" "transport &-- extracting"
3248 .cindex "options" "authenticator &-- extracting"
3249 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3250 followed by the name of an appropriate driver instance, the option settings for
3251 that driver are output. For example:
3253 exim -bP transport local_delivery
3255 The generic driver options are output first, followed by the driver's private
3256 options. A list of the names of drivers of a particular type can be obtained by
3257 using one of the words &%router_list%&, &%transport_list%&, or
3258 &%authenticator_list%&, and a complete list of all drivers with their option
3259 settings can be obtained by using &%routers%&, &%transports%&, or
3262 .cindex "environment"
3263 If &%environment%& is given as an argument, the set of environment
3264 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3267 .cindex "options" "macro &-- extracting"
3268 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3269 are available, similarly to the drivers. Because macros are sometimes used
3270 for storing passwords, this option is restricted.
3271 The output format is one item per line.
3272 For the "-bP macro <name>" form, if no such macro is found
3273 the exit status will be nonzero.
3277 .cindex "queue" "listing messages in"
3278 .cindex "listing" "messages in the queue"
3279 This option requests a listing of the contents of the mail queue on the
3280 standard output. If the &%-bp%& option is followed by a list of message ids,
3281 just those messages are listed. By default, this option can be used only by an
3282 admin user. However, the &%queue_list_requires_admin%& option can be set false
3283 to allow any user to see the queue.
3285 Each message in the queue is displayed as in the following example:
3287 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3288 red.king@looking-glass.fict.example
3291 .cindex "message" "size in queue listing"
3292 .cindex "size" "of message"
3293 The first line contains the length of time the message has been in the queue
3294 (in this case 25 minutes), the size of the message (2.9K), the unique local
3295 identifier for the message, and the message sender, as contained in the
3296 envelope. For bounce messages, the sender address is empty, and appears as
3297 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3298 the default sender address, the user's login name is shown in parentheses
3299 before the sender address.
3301 .cindex "frozen messages" "in queue listing"
3302 If the message is frozen (attempts to deliver it are suspended) then the text
3303 &"*** frozen ***"& is displayed at the end of this line.
3305 The recipients of the message (taken from the envelope, not the headers) are
3306 displayed on subsequent lines. Those addresses to which the message has already
3307 been delivered are marked with the letter D. If an original address gets
3308 expanded into several addresses via an alias or forward file, the original is
3309 displayed with a D only when deliveries for all of its child addresses are
3315 This option operates like &%-bp%&, but in addition it shows delivered addresses
3316 that were generated from the original top level address(es) in each message by
3317 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3323 .cindex "queue" "count of messages on"
3324 This option counts the number of messages in the queue, and writes the total
3325 to the standard output. It is restricted to admin users, unless
3326 &%queue_list_requires_admin%& is set false.
3331 This option operates like &%-bp%&, but the output is not sorted into
3332 chronological order of message arrival. This can speed it up when there are
3333 lots of messages in the queue, and is particularly useful if the output is
3334 going to be post-processed in a way that doesn't need the sorting.
3338 This option is a combination of &%-bpr%& and &%-bpa%&.
3342 This option is a combination of &%-bpr%& and &%-bpu%&.
3347 This option operates like &%-bp%& but shows only undelivered top-level
3348 addresses for each message displayed. Addresses generated by aliasing or
3349 forwarding are not shown, unless the message was deferred after processing by a
3350 router with the &%one_time%& option set.
3355 .cindex "testing" "retry configuration"
3356 .cindex "retry" "configuration testing"
3357 This option is for testing retry rules, and it must be followed by up to three
3358 arguments. It causes Exim to look for a retry rule that matches the values
3359 and to write it to the standard output. For example:
3361 exim -brt bach.comp.mus.example
3362 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3364 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3365 argument, which is required, can be a complete address in the form
3366 &'local_part@domain'&, or it can be just a domain name. If the second argument
3367 contains a dot, it is interpreted as an optional second domain name; if no
3368 retry rule is found for the first argument, the second is tried. This ties in
3369 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3370 rule is found that matches the host, one that matches the mail domain is
3371 sought. Finally, an argument that is the name of a specific delivery error, as
3372 used in setting up retry rules, can be given. For example:
3374 exim -brt haydn.comp.mus.example quota_3d
3375 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3380 .cindex "testing" "rewriting"
3381 .cindex "rewriting" "testing"
3382 This option is for testing address rewriting rules, and it must be followed by
3383 a single argument, consisting of either a local part without a domain, or a
3384 complete address with a fully qualified domain. Exim outputs how this address
3385 would be rewritten for each possible place it might appear. See chapter
3386 &<<CHAPrewrite>>& for further details.
3390 .cindex "SMTP" "batched incoming"
3391 .cindex "batched SMTP input"
3392 This option is used for batched SMTP input, which is an alternative interface
3393 for non-interactive local message submission. A number of messages can be
3394 submitted in a single run. However, despite its name, this is not really SMTP
3395 input. Exim reads each message's envelope from SMTP commands on the standard
3396 input, but generates no responses. If the caller is trusted, or
3397 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3398 believed; otherwise the sender is always the caller of Exim.
3400 The message itself is read from the standard input, in SMTP format (leading
3401 dots doubled), terminated by a line containing just a single dot. An error is
3402 provoked if the terminating dot is missing. A further message may then follow.
3404 As for other local message submissions, the contents of incoming batch SMTP
3405 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3406 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3407 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3409 Some other SMTP commands are recognized in the input. HELO and EHLO act
3410 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3411 QUIT quits, ignoring the rest of the standard input.
3413 .cindex "return code" "for &%-bS%&"
3414 If any error is encountered, reports are written to the standard output and
3415 error streams, and Exim gives up immediately. The return code is 0 if no error
3416 was detected; it is 1 if one or more messages were accepted before the error
3417 was detected; otherwise it is 2.
3419 More details of input using batched SMTP are given in section
3420 &<<SECTincomingbatchedSMTP>>&.
3424 .cindex "SMTP" "local input"
3425 .cindex "local SMTP input"
3426 This option causes Exim to accept one or more messages by reading SMTP commands
3427 on the standard input, and producing SMTP replies on the standard output. SMTP
3428 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3429 Some user agents use this interface as a way of passing locally-generated
3430 messages to the MTA.
3433 .cindex "sender" "source of"
3434 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3435 set, the senders of messages are taken from the SMTP MAIL commands.
3436 Otherwise the content of these commands is ignored and the sender is set up as
3437 the calling user. Unqualified addresses are automatically qualified using
3438 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3439 &%-bnq%& option is used.
3443 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3444 using a listening daemon. Exim can distinguish the two cases by checking
3445 whether the standard input is a TCP/IP socket. When Exim is called from
3446 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3447 above concerning senders and qualification do not apply. In this situation,
3448 Exim behaves in exactly the same way as it does when receiving a message via
3449 the listening daemon.
3453 .cindex "testing" "addresses"
3454 .cindex "address" "testing"
3455 This option runs Exim in address testing mode, in which each argument is taken
3456 as a recipient address to be tested for deliverability. The results are
3457 written to the standard output. If a test fails, and the caller is not an admin
3458 user, no details of the failure are output, because these might contain
3459 sensitive information such as usernames and passwords for database lookups.
3461 If no arguments are given, Exim runs in an interactive manner, prompting with a
3462 right angle bracket for addresses to be tested.
3464 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3465 &[readline()]& function, because it is running as &'root'& and there are
3468 Each address is handled as if it were the recipient address of a message
3469 (compare the &%-bv%& option). It is passed to the routers and the result is
3470 written to the standard output. However, any router that has
3471 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3472 genuine routing tests if your first router passes everything to a scanner
3475 .cindex "return code" "for &%-bt%&"
3476 The return code is 2 if any address failed outright; it is 1 if no address
3477 failed outright but at least one could not be resolved for some reason. Return
3478 code 0 is given only when all addresses succeed.
3480 .cindex "duplicate addresses"
3481 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3482 addresses after routing is complete, so that only one delivery takes place.
3483 This does not happen when testing with &%-bt%&; the full results of routing are
3486 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3487 routers in the configuration makes any tests on the sender address of a
3489 .oindex "&%-f%&" "for address testing"
3490 you can use the &%-f%& option to set an appropriate sender when running
3491 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3492 default qualifying domain. However, if you have set up (for example) routers
3493 whose behaviour depends on the contents of an incoming message, you cannot test
3494 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3499 .cindex "version number of Exim"
3500 This option causes Exim to write the current version number, compilation
3501 number, and compilation date of the &'exim'& binary to the standard output.
3502 It also lists the DBM library that is being used, the optional modules (such as
3503 specific lookup types), the drivers that are included in the binary, and the
3504 name of the runtime configuration file that is in use.
3506 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3507 configuration file. However, this is a static check only. It cannot check
3508 values that are to be expanded. For example, although a misspelt ACL verb is
3509 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3510 alone to discover (for example) all the typos in the configuration; some
3511 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3512 dynamic testing facilities.
3516 .cindex "verifying address" "using &%-bv%&"
3517 .cindex "address" "verification"
3518 This option runs Exim in address verification mode, in which each argument is
3519 taken as a recipient address to be verified by the routers. (This does
3520 not involve any verification callouts). During normal operation, verification
3521 happens mostly as a consequence processing a &%verify%& condition in an ACL
3522 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3523 including callouts, see the &%-bh%& and &%-bhc%& options.
3525 If verification fails, and the caller is not an admin user, no details of the
3526 failure are output, because these might contain sensitive information such as
3527 usernames and passwords for database lookups.
3529 If no arguments are given, Exim runs in an interactive manner, prompting with a
3530 right angle bracket for addresses to be verified.
3532 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3533 &[readline()]& function, because it is running as &'exim'& and there are
3536 Verification differs from address testing (the &%-bt%& option) in that routers
3537 that have &%no_verify%& set are skipped, and if the address is accepted by a
3538 router that has &%fail_verify%& set, verification fails. The address is
3539 verified as a recipient if &%-bv%& is used; to test verification for a sender
3540 address, &%-bvs%& should be used.
3542 If the &%-v%& option is not set, the output consists of a single line for each
3543 address, stating whether it was verified or not, and giving a reason in the
3544 latter case. Without &%-v%&, generating more than one address by redirection
3545 causes verification to end successfully, without considering the generated
3546 addresses. However, if just one address is generated, processing continues,
3547 and the generated address must verify successfully for the overall verification
3550 When &%-v%& is set, more details are given of how the address has been handled,
3551 and in the case of address redirection, all the generated addresses are also
3552 considered. Verification may succeed for some and fail for others.
3555 .cindex "return code" "for &%-bv%&"
3556 return code is 2 if any address failed outright; it is 1 if no address
3557 failed outright but at least one could not be resolved for some reason. Return
3558 code 0 is given only when all addresses succeed.
3560 If any of the routers in the configuration makes any tests on the sender
3561 address of a message, you should use the &%-f%& option to set an appropriate
3562 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3563 calling user at the default qualifying domain.
3567 This option acts like &%-bv%&, but verifies the address as a sender rather
3568 than a recipient address. This affects any rewriting and qualification that
3575 .cindex "inetd" "wait mode"
3576 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3577 similarly to the &%-bd%& option. All port specifications on the command-line
3578 and in the configuration file are ignored. Queue-running may not be specified.
3580 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3581 listening for connections. This permits the system to start up and have
3582 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3583 each port only when the first connection is received.
3585 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3586 which the daemon will exit, which should cause inetd to listen once more.
3588 .vitem &%-C%&&~<&'filelist'&>
3590 .cindex "configuration file" "alternate"
3591 .cindex "CONFIGURE_FILE"
3592 .cindex "alternate configuration file"
3593 This option causes Exim to find the runtime configuration file from the given
3594 list instead of from the list specified by the CONFIGURE_FILE
3595 compile-time setting. Usually, the list will consist of just a single filename,
3596 but it can be a colon-separated list of names. In this case, the first
3597 file that exists is used. Failure to open an existing file stops Exim from
3598 proceeding any further along the list, and an error is generated.
3600 When this option is used by a caller other than root, and the list is different
3601 from the compiled-in list, Exim gives up its root privilege immediately, and
3602 runs with the real and effective uid and gid set to those of the caller.
3603 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3604 file contains a list of full pathnames, one per line, for configuration files
3605 which are trusted. Root privilege is retained for any configuration file so
3606 listed, as long as the caller is the Exim user (or the user specified in the
3607 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3608 not writeable by inappropriate users or groups.
3610 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3611 configuration using &%-C%& right through message reception and delivery,
3612 even if the caller is root. The reception works, but by that time, Exim is
3613 running as the Exim user, so when it re-executes to regain privilege for the
3614 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3615 test reception and delivery using two separate commands (one to put a message
3616 in the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3618 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3619 prefix string with which any file named in a &%-C%& command line option
3620 must start. In addition, the filename must not contain the sequence &`/../`&.
3621 However, if the value of the &%-C%& option is identical to the value of
3622 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3623 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3624 unset, any filename can be used with &%-C%&.
3626 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3627 to a directory to which only root has access. This prevents someone who has
3628 broken into the Exim account from running a privileged Exim with an arbitrary
3631 The &%-C%& facility is useful for ensuring that configuration files are
3632 syntactically correct, but cannot be used for test deliveries, unless the
3633 caller is privileged, or unless it is an exotic configuration that does not
3634 require privilege. No check is made on the owner or group of the files
3635 specified by this option.
3638 .vitem &%-D%&<&'macro'&>=<&'value'&>
3640 .cindex "macro" "setting on command line"
3641 This option can be used to override macro definitions in the configuration file
3642 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3643 unprivileged caller, it causes Exim to give up its root privilege.
3644 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3645 completely disabled, and its use causes an immediate error exit.
3647 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3648 colon-separated list of macros which are considered safe and, if &%-D%& only
3649 supplies macros from this list, and the values are acceptable, then Exim will
3650 not give up root privilege if the caller is root, the Exim run-time user, or
3651 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3652 to be removed in the future. Acceptable values for the macros satisfy the
3653 regexp: &`^[A-Za-z0-9_/.-]*$`&
3655 The entire option (including equals sign if present) must all be within one
3656 command line item. &%-D%& can be used to set the value of a macro to the empty
3657 string, in which case the equals sign is optional. These two commands are
3663 To include spaces in a macro definition item, quotes must be used. If you use
3664 quotes, spaces are permitted around the macro name and the equals sign. For
3667 exim '-D ABC = something' ...
3669 &%-D%& may be repeated up to 10 times on a command line.
3670 Only macro names up to 22 letters long can be set.
3673 .vitem &%-d%&<&'debug&~options'&>
3675 .cindex "debugging" "list of selectors"
3676 .cindex "debugging" "&%-d%& option"
3677 This option causes debugging information to be written to the standard
3678 error stream. It is restricted to admin users because debugging output may show
3679 database queries that contain password information. Also, the details of users'
3680 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3681 writes an error message to the standard error stream and exits with a non-zero
3684 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3685 standard debugging data is output. This can be reduced, or increased to include
3686 some more rarely needed information, by directly following &%-d%& with a string
3687 made up of names preceded by plus or minus characters. These add or remove sets
3688 of debugging data, respectively. For example, &%-d+filter%& adds filter
3689 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3690 no spaces are allowed in the debug setting. The available debugging categories
3693 &`acl `& ACL interpretation
3694 &`auth `& authenticators
3695 &`deliver `& general delivery logic
3696 &`dns `& DNS lookups (see also resolver)
3697 &`dnsbl `& DNS black list (aka RBL) code
3698 &`exec `& arguments for &[execv()]& calls
3699 &`expand `& detailed debugging for string expansions
3700 &`filter `& filter handling
3701 &`hints_lookup `& hints data lookups
3702 &`host_lookup `& all types of name-to-IP address handling
3703 &`ident `& ident lookup
3704 &`interface `& lists of local interfaces
3705 &`lists `& matching things in lists
3706 &`load `& system load checks
3707 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3708 &<<CHAPlocalscan>>&)
3709 &`lookup `& general lookup code and all lookups
3710 &`memory `& memory handling
3711 &`noutf8 `& modifier: avoid UTF-8 line-drawing
3712 &`pid `& modifier: add pid to debug output lines
3713 &`process_info `& setting info for the process log
3714 &`queue_run `& queue runs
3715 &`receive `& general message reception logic
3716 &`resolver `& turn on the DNS resolver's debugging output
3717 &`retry `& retry handling
3718 &`rewrite `& address rewriting
3719 &`route `& address routing
3720 &`timestamp `& modifier: add timestamp to debug output lines
3722 &`transport `& transports
3723 &`uid `& changes of uid/gid and looking up uid/gid
3724 &`verify `& address verification logic
3725 &`all `& almost all of the above (see below), and also &%-v%&
3727 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3728 for &`-all`&. The reason for this is that &`+all`& is something that people
3729 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3730 is included, an awful lot of output that is very rarely of interest is
3731 generated, so it now has to be explicitly requested. However, &`-all`& does
3732 turn everything off.
3734 .cindex "resolver, debugging output"
3735 .cindex "DNS resolver, debugging output"
3736 The &`resolver`& option produces output only if the DNS resolver was compiled
3737 with DEBUG enabled. This is not the case in some operating systems. Also,
3738 unfortunately, debugging output from the DNS resolver is written to stdout
3741 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3742 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3743 However, the &`pid`& selector is forced when debugging is turned on for a
3744 daemon, which then passes it on to any re-executed Exims. Exim also
3745 automatically adds the pid to debug lines when several remote deliveries are
3748 The &`timestamp`& selector causes the current time to be inserted at the start
3749 of all debug output lines. This can be useful when trying to track down delays
3752 .cindex debugging "UTF-8 in"
3753 .cindex UTF-8 "in debug output"
3754 The &`noutf8`& selector disables the use of
3755 UTF-8 line-drawing characters to group related information.
3756 When disabled. ascii-art is used instead.
3757 Using the &`+all`& option does not set this modifier,
3759 If the &%debug_print%& option is set in any driver, it produces output whenever
3760 any debugging is selected, or if &%-v%& is used.
3762 .vitem &%-dd%&<&'debug&~options'&>
3764 This option behaves exactly like &%-d%& except when used on a command that
3765 starts a daemon process. In that case, debugging is turned off for the
3766 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3767 behaviour of the daemon without creating as much output as full debugging does.
3770 .oindex "&%-dropcr%&"
3771 This is an obsolete option that is now a no-op. It used to affect the way Exim
3772 handled CR and LF characters in incoming messages. What happens now is
3773 described in section &<<SECTlineendings>>&.
3777 .cindex "bounce message" "generating"
3778 This option specifies that an incoming message is a locally-generated delivery
3779 failure report. It is used internally by Exim when handling delivery failures
3780 and is not intended for external use. Its only effect is to stop Exim
3781 generating certain messages to the postmaster, as otherwise message cascades
3782 could occur in some situations. As part of the same option, a message id may
3783 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3784 new message contains the id, following &"R="&, as a cross-reference.
3787 .oindex "&%-e%&&'x'&"
3788 There are a number of Sendmail options starting with &%-oe%& which seem to be
3789 called by various programs without the leading &%o%& in the option. For
3790 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3791 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3793 .vitem &%-F%&&~<&'string'&>
3795 .cindex "sender" "name"
3796 .cindex "name" "of sender"
3797 This option sets the sender's full name for use when a locally-generated
3798 message is being accepted. In the absence of this option, the user's &'gecos'&
3799 entry from the password data is used. As users are generally permitted to alter
3800 their &'gecos'& entries, no security considerations are involved. White space
3801 between &%-F%& and the <&'string'&> is optional.
3803 .vitem &%-f%&&~<&'address'&>
3805 .cindex "sender" "address"
3806 .cindex "address" "sender"
3807 .cindex "trusted users"
3808 .cindex "envelope from"
3809 .cindex "envelope sender"
3810 .cindex "user" "trusted"
3811 This option sets the address of the envelope sender of a locally-generated
3812 message (also known as the return path). The option can normally be used only
3813 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3816 Processes running as root or the Exim user are always trusted. Other
3817 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3818 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3819 of a local message is set to the caller's login name at the default qualify
3822 There is one exception to the restriction on the use of &%-f%&: an empty sender
3823 can be specified by any user, trusted or not, to create a message that can
3824 never provoke a bounce. An empty sender can be specified either as an empty
3825 string, or as a pair of angle brackets with nothing between them, as in these
3826 examples of shell commands:
3828 exim -f '<>' user@domain
3829 exim -f "" user@domain
3831 In addition, the use of &%-f%& is not restricted when testing a filter file
3832 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3835 Allowing untrusted users to change the sender address does not of itself make
3836 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3837 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3838 though this can be overridden by setting &%no_local_from_check%&.
3841 .cindex "&""From""& line"
3842 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3843 given as two arguments or one combined argument). The sender of a
3844 locally-generated message can also be set (when permitted) by an initial
3845 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3846 if &%-f%& is also present, it overrides &"From&~"&.
3850 .cindex "submission fixups, suppressing (command-line)"
3851 This option is equivalent to an ACL applying:
3853 control = suppress_local_fixups
3855 for every message received. Note that Sendmail will complain about such
3856 bad formatting, where Exim silently just does not fix it up. This may change
3859 As this affects audit information, the caller must be a trusted user to use
3862 .vitem &%-h%&&~<&'number'&>
3864 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3865 This option is accepted for compatibility with Sendmail, but has no effect. (In
3866 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3871 .cindex "Solaris" "&'mail'& command"
3872 .cindex "dot" "in incoming non-SMTP message"
3873 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3874 line by itself should not terminate an incoming, non-SMTP message.
3875 Solaris 2.4 (SunOS 5.4) Sendmail has a similar &%-i%& processing option
3876 &url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf),
3877 p. 1M-529), and therefore a &%-oi%& command line option, which both are used
3878 by its &'mailx'& command.
3880 .vitem &%-L%&&~<&'tag'&>
3882 .cindex "syslog" "process name; set with flag"
3883 This option is equivalent to setting &%syslog_processname%& in the config
3884 file and setting &%log_file_path%& to &`syslog`&.
3885 Its use is restricted to administrators. The configuration file has to be
3886 read and parsed, to determine access rights, before this is set and takes
3887 effect, so early configuration file errors will not honour this flag.
3889 The tag should not be longer than 32 characters.
3891 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3893 .cindex "forcing delivery"
3894 .cindex "delivery" "forcing attempt"
3895 .cindex "frozen messages" "forcing delivery"
3896 This option requests Exim to run a delivery attempt on each message in turn. If
3897 any of the messages are frozen, they are automatically thawed before the
3898 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3899 and &%hold_domains%& are ignored.
3902 .cindex "hints database" "overriding retry hints"
3903 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3904 the normal retry time has not yet been reached. This option requires the caller
3905 to be an admin user. However, there is an option called &%prod_requires_admin%&
3906 which can be set false to relax this restriction (and also the same requirement
3907 for the &%-q%&, &%-R%&, and &%-S%& options).
3909 The deliveries happen synchronously, that is, the original Exim process does
3910 not terminate until all the delivery attempts have finished. No output is
3911 produced unless there is a serious error. If you want to see what is happening,
3912 use the &%-v%& option as well, or inspect Exim's main log.
3914 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3916 .cindex "message" "adding recipients"
3917 .cindex "recipient" "adding"
3918 This option requests Exim to add the addresses to the list of recipients of the
3919 message (&"ar"& for &"add recipients"&). The first argument must be a message
3920 id, and the remaining ones must be email addresses. However, if the message is
3921 active (in the middle of a delivery attempt), it is not altered. This option
3922 can be used only by an admin user.
3924 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&&&
3926 &~<&'sequence&~number'&>&&&
3927 &~<&'message&~id'&>"
3929 .cindex "SMTP" "passed connection"
3930 .cindex "SMTP" "multiple deliveries"
3931 .cindex "multiple SMTP deliveries"
3932 This option is not intended for use by external callers. It is used internally
3933 by Exim to invoke another instance of itself to deliver a waiting message using
3934 an existing SMTP connection, which is passed as the standard input. Details are
3935 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3936 must be root or the Exim user in order to use it.
3940 This option is not intended for use by external callers. It is used internally
3941 by Exim in conjunction with the &%-MC%& option. It signifies that the
3942 connection to the remote host has been authenticated.
3946 This option is not intended for use by external callers. It is used internally
3947 by Exim in conjunction with the &%-MC%& option. It signifies that the
3948 remote host supports the ESMTP &_DSN_& extension.
3952 This option is not intended for use by external callers. It is used internally
3953 by Exim in conjunction with the &%-d%& option
3954 to pass on an information string on the purpose of the process.
3956 .vitem &%-MCG%&&~<&'queue&~name'&>
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 an
3960 alternate queue is used, named by the following argument.
3964 This option is not intended for use by external callers. It is used internally
3965 by Exim in conjunction with the &%-MC%& option. It signifies that a
3966 remote host supports the ESMTP &_CHUNKING_& extension.
3970 This option is not intended for use by external callers. It is used internally
3971 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3972 which Exim is connected advertised limits on numbers of mails, recipients or
3974 The limits are given by the following three arguments.
3978 This option is not intended for use by external callers. It is used internally
3979 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3980 which Exim is connected supports pipelining.
3984 This option is not intended for use by external callers. It is used internally
3985 by Exim in conjunction with the &%-MC%& option. It signifies that the connection
3986 t a remote server is via a SOCKS proxy, using addresses and ports given by
3987 the following four arguments.
3989 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3991 This option is not intended for use by external callers. It is used internally
3992 by Exim in conjunction with the &%-MC%& option when the original delivery was
3993 started by a queue runner. It passes on the process id of the queue runner,
3994 together with the file descriptor number of an open pipe. Closure of the pipe
3995 signals the final completion of the sequence of processes that are passing
3996 messages through the same SMTP connection.
3998 .vitem &%-MCq%&&~<&'recipient&~address'&>&~<&'size'&>
4000 This option is not intended for use by external callers. It is used internally
4001 by Exim to implement quota checking for local users.
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 ESMTP SIZE option should be used on messages delivered down the existing
4012 This option is not intended for use by external callers. It is used internally
4013 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
4014 host to which Exim is connected supports TLS encryption.
4016 .vitem &%-MCr%&&~<&'SNI'&> &&&
4020 These options are not intended for use by external callers. It is used internally
4021 by Exim in conjunction with the &%-MCt%& option, and passes on the fact that
4022 a TLS Server Name Indication was sent as part of the channel establishment.
4023 The argument gives the SNI string.
4024 The "r" variant indicates a DANE-verified connection.
4026 .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
4028 This option is not intended for use by external callers. It is used internally
4029 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
4030 connection is being proxied by a parent process for handling TLS encryption.
4031 The arguments give the local address and port being proxied, and the TLS cipher.
4033 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4035 .cindex "hints database" "not overridden by &%-Mc%&"
4036 .cindex "delivery" "manually started &-- not forced"
4037 This option requests Exim to run a delivery attempt on each message, in turn,
4038 but unlike the &%-M%& option, it does check for retry hints, and respects any
4039 that are found. This option is not very useful to external callers. It is
4040 provided mainly for internal use by Exim when it needs to re-invoke itself in
4041 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
4042 However, &%-Mc%& can be useful when testing, in order to run a delivery that
4043 respects retry times and other options such as &%hold_domains%& that are
4044 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
4045 If you want to run a specific delivery as if in a queue run, you should use
4046 &%-q%& with a message id argument. A distinction between queue run deliveries
4047 and other deliveries is made in one or two places.
4049 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
4051 .cindex "message" "changing sender"
4052 .cindex "sender" "changing"
4053 This option requests Exim to change the sender address in the message to the
4054 given address, which must be a fully qualified address or &"<>"& (&"es"& for
4055 &"edit sender"&). There must be exactly two arguments. The first argument must
4056 be a message id, and the second one an email address. However, if the message
4057 is active (in the middle of a delivery attempt), its status is not altered.
4058 This option can be used only by an admin user.
4060 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4062 .cindex "freezing messages"
4063 .cindex "message" "manually freezing"
4064 This option requests Exim to mark each listed message as &"frozen"&. This
4065 prevents any delivery attempts taking place until the message is &"thawed"&,
4066 either manually or as a result of the &%auto_thaw%& configuration option.
4067 However, if any of the messages are active (in the middle of a delivery
4068 attempt), their status is not altered. This option can be used only by an admin
4071 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4073 .cindex "giving up on messages"
4074 .cindex "message" "abandoning delivery attempts"
4075 .cindex "delivery" "abandoning further attempts"
4076 This option requests Exim to give up trying to deliver the listed messages,
4077 including any that are frozen. However, if any of the messages are active,
4078 their status is not altered. For non-bounce messages, a delivery error message
4079 is sent to the sender, containing the text &"cancelled by administrator"&.
4080 Bounce messages are just discarded. This option can be used only by an admin
4083 .vitem &%-MG%&&~<&'queue&~name'&>&~<&'message&~id'&>&~<&'message&~id'&>&~...
4086 .cindex "named queues" "moving messages"
4087 .cindex "queue" "moving messages"
4088 This option requests that each listed message be moved from its current
4089 queue to the given named queue.
4090 The destination queue name argument is required, but can be an empty
4091 string to define the default queue.
4092 If the messages are not currently located in the default queue,
4093 a &%-qG<name>%& option will be required to define the source queue.
4095 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4097 .cindex "delivery" "cancelling all"
4098 This option requests Exim to mark all the recipient addresses in the messages
4099 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
4100 message is active (in the middle of a delivery attempt), its status is not
4101 altered. This option can be used only by an admin user.
4103 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
4105 .cindex "delivery" "cancelling by address"
4106 .cindex "recipient" "removing"
4107 .cindex "removing recipients"
4108 This option requests Exim to mark the given addresses as already delivered
4109 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
4110 the remaining ones must be email addresses. These are matched to recipient
4111 addresses in the message in a case-sensitive manner. If the message is active
4112 (in the middle of a delivery attempt), its status is not altered. This option
4113 can be used only by an admin user.
4115 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4117 .cindex "removing messages"
4118 .cindex "abandoning mail"
4119 .cindex "message" "manually discarding"
4120 This option requests Exim to remove the given messages from the queue. No
4121 bounce messages are sent; each message is simply forgotten. However, if any of
4122 the messages are active, their status is not altered. This option can be used
4123 only by an admin user or by the user who originally caused the message to be
4124 placed in the queue.
4129 . .cindex REQUIRETLS
4130 . This option is used to request REQUIRETLS processing on the message.
4131 . It is used internally by Exim in conjunction with -E when generating
4135 .vitem &%-Mset%&&~<&'message&~id'&>
4137 .cindex "testing" "string expansion"
4138 .cindex "expansion" "testing"
4139 This option is useful only in conjunction with &%-be%& (that is, when testing
4140 string expansions). Exim loads the given message from its spool before doing
4141 the test expansions, thus setting message-specific variables such as
4142 &$message_size$& and the header variables. The &$recipients$& variable is made
4143 available. This feature is provided to make it easier to test expansions that
4144 make use of these variables. However, this option can be used only by an admin
4145 user. See also &%-bem%&.
4147 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4149 .cindex "thawing messages"
4150 .cindex "unfreezing messages"
4151 .cindex "frozen messages" "thawing"
4152 .cindex "message" "thawing frozen"
4153 This option requests Exim to &"thaw"& any of the listed messages that are
4154 &"frozen"&, so that delivery attempts can resume. However, if any of the
4155 messages are active, their status is not altered. This option can be used only
4158 .vitem &%-Mvb%&&~<&'message&~id'&>
4160 .cindex "listing" "message body"
4161 .cindex "message" "listing body of"
4162 This option causes the contents of the message body (-D) spool file to be
4163 written to the standard output. This option can be used only by an admin user.
4165 .vitem &%-Mvc%&&~<&'message&~id'&>
4167 .cindex "message" "listing in RFC 2822 format"
4168 .cindex "listing" "message in RFC 2822 format"
4169 This option causes a copy of the complete message (header lines plus body) to
4170 be written to the standard output in RFC 2822 format. This option can be used
4171 only by an admin user.
4173 .vitem &%-Mvh%&&~<&'message&~id'&>
4175 .cindex "listing" "message headers"
4176 .cindex "header lines" "listing"
4177 .cindex "message" "listing header lines"
4178 This option causes the contents of the message headers (-H) spool file to be
4179 written to the standard output. This option can be used only by an admin user.
4181 .vitem &%-Mvl%&&~<&'message&~id'&>
4183 .cindex "listing" "message log"
4184 .cindex "message" "listing message log"
4185 This option causes the contents of the message log spool file to be written to
4186 the standard output. This option can be used only by an admin user.
4190 This is a synonym for &%-om%& that is accepted by Sendmail
4191 (&url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf)
4192 p. 1M-258), so Exim treats it that way too.
4196 .cindex "debugging" "&%-N%& option"
4197 .cindex "debugging" "suppressing delivery"
4198 This is a debugging option that inhibits delivery of a message at the transport
4199 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4200 it just doesn't actually transport the message, but instead behaves as if it
4201 had successfully done so. However, it does not make any updates to the retry
4202 database, and the log entries for deliveries are flagged with &"*>"& rather
4205 Because &%-N%& discards any message to which it applies, only root or the Exim
4206 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4207 words, an ordinary user can use it only when supplying an incoming message to
4208 which it will apply. Although transportation never fails when &%-N%& is set, an
4209 address may be deferred because of a configuration problem on a transport, or a
4210 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4211 the message, and applies to any subsequent delivery attempts that may happen
4216 This option is interpreted by Sendmail to mean &"no aliasing"&.
4217 For normal modes of operation, it is ignored by Exim.
4218 When combined with &%-bP%& it makes the output more terse (suppresses
4219 option names, environment values and config pretty printing).
4221 .vitem &%-O%&&~<&'data'&>
4223 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4226 .vitem &%-oA%&&~<&'file&~name'&>
4228 .cindex "Sendmail compatibility" "&%-oA%& option"
4229 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4230 alternative alias filename. Exim handles &%-bi%& differently; see the
4233 .vitem &%-oB%&&~<&'n'&>
4235 .cindex "SMTP" "passed connection"
4236 .cindex "SMTP" "multiple deliveries"
4237 .cindex "multiple SMTP deliveries"
4238 This is a debugging option which limits the maximum number of messages that can
4239 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4240 transport. If <&'n'&> is omitted, the limit is set to 1.
4244 .cindex "background delivery"
4245 .cindex "delivery" "in the background"
4246 This option applies to all modes in which Exim accepts incoming messages,
4247 including the listening daemon. It requests &"background"& delivery of such
4248 messages, which means that the accepting process automatically starts a
4249 delivery process for each message received, but does not wait for the delivery
4250 processes to finish.
4252 When all the messages have been received, the reception process exits,
4253 leaving the delivery processes to finish in their own time. The standard output
4254 and error streams are closed at the start of each delivery process.
4255 This is the default action if none of the &%-od%& options are present.
4257 If one of the queueing options in the configuration file
4258 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4259 overrides it if &%queue_only_override%& is set true, which is the default
4260 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4264 .cindex "foreground delivery"
4265 .cindex "delivery" "in the foreground"
4266 This option requests &"foreground"& (synchronous) delivery when Exim has
4267 accepted a locally-generated message. (For the daemon it is exactly the same as
4268 &%-odb%&.) A delivery process is automatically started to deliver the message,
4269 and Exim waits for it to complete before proceeding.
4271 The original Exim reception process does not finish until the delivery
4272 process for the final message has ended. The standard error stream is left open
4275 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4276 false and one of the queueing options in the configuration file is in effect.
4278 If there is a temporary delivery error during foreground delivery, the
4279 message is left in the queue for later delivery, and the original reception
4280 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4281 restricted configuration that never queues messages.
4286 This option is synonymous with &%-odf%&. It is provided for compatibility with
4291 .cindex "non-immediate delivery"
4292 .cindex "delivery" "suppressing immediate"
4293 .cindex "queueing incoming messages"
4294 This option applies to all modes in which Exim accepts incoming messages,
4295 including the listening daemon. It specifies that the accepting process should
4296 not automatically start a delivery process for each message received. Messages
4297 are placed in the queue, and remain there until a subsequent queue runner
4298 process encounters them. There are several configuration options (such as
4299 &%queue_only%&) that can be used to queue incoming messages under certain
4300 conditions. This option overrides all of them and also &%-odqs%&. It always
4305 .cindex "SMTP" "delaying delivery"
4306 .cindex "first pass routing"
4307 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4308 However, like &%-odb%& and &%-odi%&, this option has no effect if
4309 &%queue_only_override%& is false and one of the queueing options in the
4310 configuration file is in effect.
4312 When &%-odqs%& does operate, a delivery process is started for each incoming
4313 message, in the background by default, but in the foreground if &%-odi%& is
4314 also present. The recipient addresses are routed, and local deliveries are done
4315 in the normal way. However, if any SMTP deliveries are required, they are not
4316 done at this time, so the message remains in the queue until a subsequent queue
4317 runner process encounters it. Because routing was done, Exim knows which
4318 messages are waiting for which hosts, and so a number of messages for the same
4319 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4320 configuration option has the same effect for specific domains. See also the
4325 .cindex "error" "reporting"
4326 If an error is detected while a non-SMTP message is being received (for
4327 example, a malformed address), the error is reported to the sender in a mail
4330 .cindex "return code" "for &%-oee%&"
4332 this error message is successfully sent, the Exim receiving process
4333 exits with a return code of zero. If not, the return code is 2 if the problem
4334 is that the original message has no recipients, or 1 for any other error.
4335 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4339 .cindex "error" "reporting"
4340 .cindex "return code" "for &%-oem%&"
4341 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4342 return code, whether or not the error message was successfully sent.
4343 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4347 .cindex "error" "reporting"
4348 If an error is detected while a non-SMTP message is being received, the
4349 error is reported by writing a message to the standard error file (stderr).
4350 .cindex "return code" "for &%-oep%&"
4351 The return code is 1 for all errors.
4355 .cindex "error" "reporting"
4356 This option is supported for compatibility with Sendmail, but has the same
4361 .cindex "error" "reporting"
4362 This option is supported for compatibility with Sendmail, but has the same
4367 .cindex "dot" "in incoming non-SMTP message"
4368 This option, which has the same effect as &%-i%&, specifies that a dot on a
4369 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4370 single dot does terminate, though Exim does no special processing for other
4371 lines that start with a dot. This option is set by default if Exim is called as
4372 &'rmail'&. See also &%-ti%&.
4375 .oindex "&%-oitrue%&"
4376 This option is treated as synonymous with &%-oi%&.
4378 .vitem &%-oMa%&&~<&'host&~address'&>
4380 .cindex "sender" "host address, specifying for local message"
4381 A number of options starting with &%-oM%& can be used to set values associated
4382 with remote hosts on locally-submitted messages (that is, messages not received
4383 over TCP/IP). These options can be used by any caller in conjunction with the
4384 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4385 other circumstances, they are ignored unless the caller is trusted.
4387 The &%-oMa%& option sets the sender host address. This may include a port
4388 number at the end, after a full stop (period). For example:
4390 exim -bs -oMa 10.9.8.7.1234
4392 An alternative syntax is to enclose the IP address in square brackets,
4393 followed by a colon and the port number:
4395 exim -bs -oMa [10.9.8.7]:1234
4397 The IP address is placed in the &$sender_host_address$& variable, and the
4398 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4399 are present on the command line, the sender host IP address is taken from
4400 whichever one is last.
4402 .vitem &%-oMaa%&&~<&'name'&>
4404 .cindex "authentication" "name, specifying for local message"
4405 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4406 option sets the value of &$sender_host_authenticated$& (the authenticator
4407 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4408 This option can be used with &%-bh%& and &%-bs%& to set up an
4409 authenticated SMTP session without actually using the SMTP AUTH command.
4411 .vitem &%-oMai%&&~<&'string'&>
4413 .cindex "authentication" "id, specifying for local message"
4414 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4415 option sets the value of &$authenticated_id$& (the id that was authenticated).
4416 This overrides the default value (the caller's login id, except with &%-bh%&,
4417 where there is no default) for messages from local sources. See chapter
4418 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4420 .vitem &%-oMas%&&~<&'address'&>
4422 .cindex "authentication" "sender, specifying for local message"
4423 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4424 option sets the authenticated sender value in &$authenticated_sender$&. It
4425 overrides the sender address that is created from the caller's login id for
4426 messages from local sources, except when &%-bh%& is used, when there is no
4427 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4428 specified on a MAIL command overrides this value. See chapter
4429 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4431 .vitem &%-oMi%&&~<&'interface&~address'&>
4433 .cindex "interface" "address, specifying for local message"
4434 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4435 option sets the IP interface address value. A port number may be included,
4436 using the same syntax as for &%-oMa%&. The interface address is placed in
4437 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4439 .vitem &%-oMm%&&~<&'message&~reference'&>
4441 .cindex "message reference" "message reference, specifying for local message"
4442 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4443 option sets the message reference, e.g. message-id, and is logged during
4444 delivery. This is useful when some kind of audit trail is required to tie
4445 messages together. The format of the message reference is checked and will
4446 abort if the format is invalid. The option will only be accepted if exim is
4447 running in trusted mode, not as any regular user.
4449 The best example of a message reference is when Exim sends a bounce message.
4450 The message reference is the message-id of the original message for which Exim
4451 is sending the bounce.
4453 .vitem &%-oMr%&&~<&'protocol&~name'&>
4455 .cindex "protocol, specifying for local message"
4456 .vindex "&$received_protocol$&"
4457 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4458 option sets the received protocol value that is stored in
4459 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4460 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4461 SMTP protocol names (see the description of &$received_protocol$& in section
4462 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4463 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4464 be set by &%-oMr%&. Repeated use of this option is not supported.
4466 .vitem &%-oMs%&&~<&'host&~name'&>
4468 .cindex "sender" "host name, specifying for local message"
4469 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4470 option sets the sender host name in &$sender_host_name$&. When this option is
4471 present, Exim does not attempt to look up a host name from an IP address; it
4472 uses the name it is given.
4474 .vitem &%-oMt%&&~<&'ident&~string'&>
4476 .cindex "sender" "ident string, specifying for local message"
4477 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4478 option sets the sender ident value in &$sender_ident$&. The default setting for
4479 local callers is the login id of the calling process, except when &%-bh%& is
4480 used, when there is no default.
4484 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4485 In Sendmail, this option means &"me too"&, indicating that the sender of a
4486 message should receive a copy of the message if the sender appears in an alias
4487 expansion. Exim always does this, so the option does nothing.
4491 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4492 This option is ignored. In Sendmail it specifies &"old style headers"&,
4493 whatever that means.
4495 .vitem &%-oP%&&~<&'path'&>
4497 .cindex "pid (process id)" "of daemon"
4498 .cindex "daemon" "process id (pid)"
4499 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4500 value. The option specifies the file to which the process id of the daemon is
4501 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4502 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4503 because in those cases, the normal pid file is not used.
4507 .cindex "pid (process id)" "of daemon"
4508 .cindex "daemon" "process id (pid)"
4509 This option is not intended for general use.
4510 The daemon uses it when terminating due to a SIGTEM, possibly in
4511 combination with &%-oP%&&~<&'path'&>.
4512 It causes the pid file to be removed.
4514 .vitem &%-or%&&~<&'time'&>
4516 .cindex "timeout" "for non-SMTP input"
4517 This option sets a timeout value for incoming non-SMTP messages. If it is not
4518 set, Exim will wait forever for the standard input. The value can also be set
4519 by the &%receive_timeout%& option. The format used for specifying times is
4520 described in section &<<SECTtimeformat>>&.
4522 .vitem &%-os%&&~<&'time'&>
4524 .cindex "timeout" "for SMTP input"
4525 .cindex "SMTP" "input timeout"
4526 This option sets a timeout value for incoming SMTP messages. The timeout
4527 applies to each SMTP command and block of data. The value can also be set by
4528 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4529 for specifying times is described in section &<<SECTtimeformat>>&.
4533 This option has exactly the same effect as &%-v%&.
4535 .vitem &%-oX%&&~<&'number&~or&~string'&>
4537 .cindex "TCP/IP" "setting listening ports"
4538 .cindex "TCP/IP" "setting listening interfaces"
4539 .cindex "port" "receiving TCP/IP"
4540 This option is relevant only when the &%-bd%& (start listening daemon) option
4541 is also given. It controls which ports and interfaces the daemon uses. Details
4542 of the syntax, and how it interacts with configuration file options, are given
4543 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4544 file is written unless &%-oP%& is also present to specify a pid filename.
4548 .cindex "daemon notifier socket"
4549 This option controls the creation of an inter-process communications endpoint
4551 It is only relevant when the &%-bd%& (start listening daemon) option is also
4553 Normally the daemon creates this socket, unless a &%-oX%& and &*no*& &%-oP%&
4554 option is also present.
4555 If this option is given then the socket will not be created. This could be
4556 required if the system is running multiple daemons.
4558 The socket is currently used for
4560 fast ramp-up of queue runner processes
4562 obtaining a current queue size
4567 .cindex "Perl" "starting the interpreter"
4568 This option applies when an embedded Perl interpreter is linked with Exim (see
4569 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4570 option, forcing the starting of the interpreter to be delayed until it is
4575 .cindex "Perl" "starting the interpreter"
4576 This option applies when an embedded Perl interpreter is linked with Exim (see
4577 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4578 option, forcing the starting of the interpreter to occur as soon as Exim is
4581 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4583 For compatibility with Sendmail, this option is equivalent to
4585 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4587 It sets the incoming protocol and host name (for trusted callers). The
4588 host name and its colon can be omitted when only the protocol is to be set.
4589 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4590 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4591 or &`s`& using this option (but that does not seem a real limitation).
4592 Repeated use of this option is not supported.
4596 .cindex "queue runner" "starting manually"
4597 This option is normally restricted to admin users. However, there is a
4598 configuration option called &%prod_requires_admin%& which can be set false to
4599 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4600 and &%-S%& options).
4602 .cindex "queue runner" "description of operation"
4603 If other commandline options do not specify an action,
4604 the &%-q%& option starts one queue runner process. This scans the queue of
4605 waiting messages, and runs a delivery process for each one in turn. It waits
4606 for each delivery process to finish before starting the next one. A delivery
4607 process may not actually do any deliveries if the retry times for the addresses
4608 have not been reached. Use &%-qf%& (see below) if you want to override this.
4611 .cindex "SMTP" "passed connection"
4612 .cindex "SMTP" "multiple deliveries"
4613 .cindex "multiple SMTP deliveries"
4614 the delivery process spawns other processes to deliver other messages down
4615 passed SMTP connections, the queue runner waits for these to finish before
4618 When all the queued messages have been considered, the original queue runner
4619 process terminates. In other words, a single pass is made over the waiting
4620 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4621 this to be repeated periodically.
4623 Exim processes the waiting messages in an unpredictable order. It isn't very
4624 random, but it is likely to be different each time, which is all that matters.
4625 If one particular message screws up a remote MTA, other messages to the same
4626 MTA have a chance of getting through if they get tried first.
4628 It is possible to cause the messages to be processed in lexical message id
4629 order, which is essentially the order in which they arrived, by setting the
4630 &%queue_run_in_order%& option, but this is not recommended for normal use.
4632 .vitem &%-q%&<&'qflags'&>
4633 The &%-q%& option may be followed by one or more flag letters that change its
4634 behaviour. They are all optional, but if more than one is present, they must
4635 appear in the correct order. Each flag is described in a separate item below.
4639 .cindex "queue" "double scanning"
4640 .cindex "queue" "routing"
4641 .cindex "routing" "whole queue before delivery"
4642 .cindex "first pass routing"
4643 .cindex "queue runner" "two phase"
4644 An option starting with &%-qq%& requests a two-stage queue run. In the first
4645 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4646 every domain. Addresses are routed, local deliveries happen, but no remote
4649 Performance will be best if the &%queue_run_in_order%& option is false.
4650 If that is so and the &%queue_fast_ramp%& option is true then
4651 in the first phase of the run,
4652 once a threshold number of messages are routed for a given host,
4653 a delivery process is forked in parallel with the rest of the scan.
4655 .cindex "hints database" "remembering routing"
4656 The hints database that remembers which messages are waiting for specific hosts
4657 is updated, as if delivery to those hosts had been deferred. After this is
4658 complete, a second, normal queue scan happens, with routing and delivery taking
4659 place as normal. Messages that are routed to the same host should mostly be
4660 delivered down a single SMTP
4661 .cindex "SMTP" "passed connection"
4662 .cindex "SMTP" "multiple deliveries"
4663 .cindex "multiple SMTP deliveries"
4664 connection because of the hints that were set up during the first queue scan.
4665 This option may be useful for hosts that are connected to the Internet
4668 .vitem &%-q[q]i...%&
4670 .cindex "queue" "initial delivery"
4671 If the &'i'& flag is present, the queue runner runs delivery processes only for
4672 those messages that haven't previously been tried. (&'i'& stands for &"initial
4673 delivery"&.) This can be helpful if you are putting messages in the queue using
4674 &%-odq%& and want a queue runner just to process the new messages.
4676 .vitem &%-q[q][i]f...%&
4678 .cindex "queue" "forcing delivery"
4679 .cindex "delivery" "forcing in queue run"
4680 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4681 message, whereas without &'f'& only those non-frozen addresses that have passed
4682 their retry times are tried.
4684 .vitem &%-q[q][i]ff...%&
4686 .cindex "frozen messages" "forcing delivery"
4687 If &'ff'& is present, a delivery attempt is forced for every message, whether
4690 .vitem &%-q[q][i][f[f]]l%&
4692 .cindex "queue" "local deliveries only"
4693 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4694 be done. If a message requires any remote deliveries, it remains in the queue
4697 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4700 .cindex "named queues" "deliver from"
4701 .cindex "queue" "delivering specific messages"
4702 If the &'G'& flag and a name is present, the queue runner operates on the
4703 queue with the given name rather than the default queue.
4704 The name should not contain a &'/'& character.
4705 For a periodic queue run (see below)
4706 append to the name a slash and a time value.
4708 If other commandline options specify an action, a &'-qG<name>'& option
4709 will specify a queue to operate on.
4712 exim -bp -qGquarantine
4714 exim -qGoffpeak -Rf @special.domain.example
4717 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4718 When scanning the queue, Exim can be made to skip over messages whose ids are
4719 lexically less than a given value by following the &%-q%& option with a
4720 starting message id. For example:
4722 exim -q 0t5C6f-0000c8-00
4724 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4725 second message id is given, messages whose ids are lexically greater than it
4726 are also skipped. If the same id is given twice, for example,
4728 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4730 just one delivery process is started, for that message. This differs from
4731 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4732 that it counts as a delivery from a queue run. Note that the selection
4733 mechanism does not affect the order in which the messages are scanned. There
4734 are also other ways of selecting specific sets of messages for delivery in a
4735 queue run &-- see &%-R%& and &%-S%&.
4737 .vitem &%-q%&<&'qflags'&><&'time'&>
4738 .cindex "queue runner" "starting periodically"
4739 .cindex "periodic queue running"
4740 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4741 starting a queue runner process at intervals specified by the given time value
4742 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4743 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4744 single daemon process handles both functions. A common way of starting up a
4745 combined daemon at system boot time is to use a command such as
4747 /usr/exim/bin/exim -bd -q30m
4749 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4750 process every 30 minutes.
4752 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4753 pid file is written unless one is explicitly requested by the &%-oP%& option.
4755 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4757 This option is synonymous with &%-R%&. It is provided for Sendmail
4760 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4762 This option is synonymous with &%-S%&.
4764 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4766 .cindex "queue runner" "for specific recipients"
4767 .cindex "delivery" "to given domain"
4768 .cindex "domain" "delivery to"
4769 The <&'rsflags'&> may be empty, in which case the white space before the string
4770 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4771 which are the possible values for <&'rsflags'&>. White space is required if
4772 <&'rsflags'&> is not empty.
4774 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4775 perform a single queue run, except that, when scanning the messages on the
4776 queue, Exim processes only those that have at least one undelivered recipient
4777 address containing the given string, which is checked in a case-independent
4778 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4779 regular expression; otherwise it is a literal string.
4781 If you want to do periodic queue runs for messages with specific recipients,
4782 you can combine &%-R%& with &%-q%& and a time value. For example:
4784 exim -q25m -R @special.domain.example
4786 This example does a queue run for messages with recipients in the given domain
4787 every 25 minutes. Any additional flags that are specified with &%-q%& are
4788 applied to each queue run.
4790 Once a message is selected for delivery by this mechanism, all its addresses
4791 are processed. For the first selected message, Exim overrides any retry
4792 information and forces a delivery attempt for each undelivered address. This
4793 means that if delivery of any address in the first message is successful, any
4794 existing retry information is deleted, and so delivery attempts for that
4795 address in subsequently selected messages (which are processed without forcing)
4796 will run. However, if delivery of any address does not succeed, the retry
4797 information is updated, and in subsequently selected messages, the failing
4798 address will be skipped.
4800 .cindex "frozen messages" "forcing delivery"
4801 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4802 all selected messages, not just the first; frozen messages are included when
4805 The &%-R%& option makes it straightforward to initiate delivery of all messages
4806 to a given domain after a host has been down for some time. When the SMTP
4807 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4808 effect is to run Exim with the &%-R%& option, but it can be configured to run
4809 an arbitrary command instead.
4813 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4815 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4817 .cindex "delivery" "from given sender"
4818 .cindex "queue runner" "for specific senders"
4819 This option acts like &%-R%& except that it checks the string against each
4820 message's sender instead of against the recipients. If &%-R%& is also set, both
4821 conditions must be met for a message to be selected. If either of the options
4822 has &'f'& or &'ff'& in its flags, the associated action is taken.
4824 .vitem &%-Tqt%&&~<&'times'&>
4826 This is an option that is exclusively for use by the Exim testing suite. It is not
4827 recognized when Exim is run normally. It allows for the setting up of explicit
4828 &"queue times"& so that various warning/retry features can be tested.
4832 .cindex "recipient" "extracting from header lines"
4836 When Exim is receiving a locally-generated, non-SMTP message on its standard
4837 input, the &%-t%& option causes the recipients of the message to be obtained
4838 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4839 from the command arguments. The addresses are extracted before any rewriting
4840 takes place and the &'Bcc:'& header line, if present, is then removed.
4842 .cindex "Sendmail compatibility" "&%-t%& option"
4843 If the command has any arguments, they specify addresses to which the message
4844 is &'not'& to be delivered. That is, the argument addresses are removed from
4845 the recipients list obtained from the headers. This is compatible with Smail 3
4846 and in accordance with the documented behaviour of several versions of
4847 Sendmail, as described in man pages on a number of operating systems (e.g.
4848 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4849 argument addresses to those obtained from the headers, and the O'Reilly
4850 Sendmail book documents it that way. Exim can be made to add argument addresses
4851 instead of subtracting them by setting the option
4852 &%extract_addresses_remove_arguments%& false.
4854 .cindex "&%Resent-%& header lines" "with &%-t%&"
4855 If there are any &%Resent-%& header lines in the message, Exim extracts
4856 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4857 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4858 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4859 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4861 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4862 message is resent several times). The RFC also specifies that they should be
4863 added at the front of the message, and separated by &'Received:'& lines. It is
4864 not at all clear how &%-t%& should operate in the present of multiple sets,
4865 nor indeed exactly what constitutes a &"set"&.
4866 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4867 are often added at the end of the header, and if a message is resent more than
4868 once, it is common for the original set of &%Resent-%& headers to be renamed as
4869 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4873 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4874 compatibility with Sendmail.
4876 .vitem &%-tls-on-connect%&
4877 .oindex "&%-tls-on-connect%&"
4878 .cindex "TLS" "use without STARTTLS"
4879 .cindex "TLS" "automatic start"
4880 This option is available when Exim is compiled with TLS support. It forces all
4881 incoming SMTP connections to behave as if the incoming port is listed in the
4882 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4883 &<<CHAPTLS>>& for further details.
4888 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4889 Sendmail uses this option for &"initial message submission"&, and its
4890 documentation states that in future releases, it may complain about
4891 syntactically invalid messages rather than fixing them when this flag is not
4892 set. Exim ignores this option.
4896 This option causes Exim to write information to the standard error stream,
4897 describing what it is doing. In particular, it shows the log lines for
4898 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4899 dialogue is shown. Some of the log lines shown may not actually be written to
4900 the log if the setting of &%log_selector%& discards them. Any relevant
4901 selectors are shown with each log line. If none are shown, the logging is
4906 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4907 National Language Support extended characters in the body of the mail item"&).
4908 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4911 .vitem &%-X%&&~<&'logfile'&>
4913 This option is interpreted by Sendmail to cause debug information to be sent
4914 to the named file. It is ignored by Exim.
4916 .vitem &%-z%&&~<&'log-line'&>
4918 This option writes its argument to Exim's logfile.
4919 Use is restricted to administrators; the intent is for operational notes.
4920 Quotes should be used to maintain a multi-word item as a single argument,
4928 . ////////////////////////////////////////////////////////////////////////////
4929 . Insert a stylized DocBook comment here, to identify the end of the command
4930 . line options. This is for the benefit of the Perl script that automatically
4931 . creates a man page for the options.
4932 . ////////////////////////////////////////////////////////////////////////////
4935 <!-- === End of command line options === -->
4942 . ////////////////////////////////////////////////////////////////////////////
4943 . ////////////////////////////////////////////////////////////////////////////
4946 .chapter "The Exim runtime configuration file" "CHAPconf" &&&
4947 "The runtime configuration file"
4949 .cindex "runtime configuration"
4950 .cindex "configuration file" "general description"
4951 .cindex "CONFIGURE_FILE"
4952 .cindex "configuration file" "errors in"
4953 .cindex "error" "in configuration file"
4954 .cindex "return code" "for bad configuration"
4955 Exim uses a single runtime configuration file that is read whenever an Exim
4956 binary is executed. Note that in normal operation, this happens frequently,
4957 because Exim is designed to operate in a distributed manner, without central
4960 If a syntax error is detected while reading the configuration file, Exim
4961 writes a message on the standard error, and exits with a non-zero return code.
4962 The message is also written to the panic log. &*Note*&: Only simple syntax
4963 errors can be detected at this time. The values of any expanded options are
4964 not checked until the expansion happens, even when the expansion does not
4965 actually alter the string.
4967 The name of the configuration file is compiled into the binary for security
4968 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4969 most configurations, this specifies a single file. However, it is permitted to
4970 give a colon-separated list of filenames, in which case Exim uses the first
4971 existing file in the list.
4974 .cindex "EXIM_GROUP"
4975 .cindex "CONFIGURE_OWNER"
4976 .cindex "CONFIGURE_GROUP"
4977 .cindex "configuration file" "ownership"
4978 .cindex "ownership" "configuration file"
4979 The runtime configuration file must be owned by root or by the user that is
4980 specified at compile time by the CONFIGURE_OWNER option (if set). The
4981 configuration file must not be world-writeable, or group-writeable unless its
4982 group is the root group or the one specified at compile time by the
4983 CONFIGURE_GROUP option.
4985 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4986 to root, anybody who is able to edit the runtime configuration file has an
4987 easy way to run commands as root. If you specify a user or group in the
4988 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4989 who are members of that group will trivially be able to obtain root privileges.
4991 Up to Exim version 4.72, the runtime configuration file was also permitted to
4992 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4993 since it offered a simple privilege escalation for any attacker who managed to
4994 compromise the Exim user account.
4996 A default configuration file, which will work correctly in simple situations,
4997 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4998 defines just one filename, the installation process copies the default
4999 configuration to a new file of that name if it did not previously exist. If
5000 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
5001 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
5006 .section "Using a different configuration file" "SECID40"
5007 .cindex "configuration file" "alternate"
5008 A one-off alternate configuration can be specified by the &%-C%& command line
5009 option, which may specify a single file or a list of files. However, when
5010 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
5011 unless the argument for &%-C%& is identical to the built-in value from
5012 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
5013 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
5014 is useful mainly for checking the syntax of configuration files before
5015 installing them. No owner or group checks are done on a configuration file
5016 specified by &%-C%&, if root privilege has been dropped.
5018 Even the Exim user is not trusted to specify an arbitrary configuration file
5019 with the &%-C%& option to be used with root privileges, unless that file is
5020 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
5021 testing a configuration using &%-C%& right through message reception and
5022 delivery, even if the caller is root. The reception works, but by that time,
5023 Exim is running as the Exim user, so when it re-execs to regain privilege for
5024 the delivery, the use of &%-C%& causes privilege to be lost. However, root
5025 can test reception and delivery using two separate commands (one to put a
5026 message in the queue, using &%-odq%&, and another to do the delivery, using
5029 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
5030 prefix string with which any file named in a &%-C%& command line option must
5031 start. In addition, the filename must not contain the sequence &"&`/../`&"&.
5032 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any
5033 filename can be used with &%-C%&.
5035 One-off changes to a configuration can be specified by the &%-D%& command line
5036 option, which defines and overrides values for macros used inside the
5037 configuration file. However, like &%-C%&, the use of this option by a
5038 non-privileged user causes Exim to discard its root privilege.
5039 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
5040 completely disabled, and its use causes an immediate error exit.
5042 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
5043 to declare certain macro names trusted, such that root privilege will not
5044 necessarily be discarded.
5045 WHITELIST_D_MACROS defines a colon-separated list of macros which are
5046 considered safe and, if &%-D%& only supplies macros from this list, and the
5047 values are acceptable, then Exim will not give up root privilege if the caller
5048 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
5049 transition mechanism and is expected to be removed in the future. Acceptable
5050 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
5052 Some sites may wish to use the same Exim binary on different machines that
5053 share a file system, but to use different configuration files on each machine.
5054 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
5055 looks for a file whose name is the configuration filename followed by a dot
5056 and the machine's node name, as obtained from the &[uname()]& function. If this
5057 file does not exist, the standard name is tried. This processing occurs for
5058 each filename in the list given by CONFIGURE_FILE or &%-C%&.
5060 In some esoteric situations different versions of Exim may be run under
5061 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
5062 help with this. See the comments in &_src/EDITME_& for details.
5066 .section "Configuration file format" "SECTconffilfor"
5067 .cindex "configuration file" "format of"
5068 .cindex "format" "configuration file"
5069 Exim's configuration file is divided into a number of different parts. General
5070 option settings must always appear at the start of the file. The other parts
5071 are all optional, and may appear in any order. Each part other than the first
5072 is introduced by the word &"begin"& followed by at least one literal
5073 space, and the name of the part. The optional parts are:
5076 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
5079 .cindex "AUTH" "configuration"
5080 &'authenticators'&: Configuration settings for the authenticator drivers. These
5081 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
5083 &'routers'&: Configuration settings for the router drivers. Routers process
5084 addresses and determine how the message is to be delivered (see chapters
5085 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
5087 &'transports'&: Configuration settings for the transport drivers. Transports
5088 define mechanisms for copying messages to destinations (see chapters
5089 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
5091 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
5092 If there is no retry section, or if it is empty (that is, no retry rules are
5093 defined), Exim will not retry deliveries. In this situation, temporary errors
5094 are treated the same as permanent errors. Retry rules are discussed in chapter
5097 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
5098 when new addresses are generated during delivery. Rewriting is discussed in
5099 chapter &<<CHAPrewrite>>&.
5101 &'local_scan'&: Private options for the &[local_scan()]& function. If you
5102 want to use this feature, you must set
5104 LOCAL_SCAN_HAS_OPTIONS=yes
5106 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
5107 facility are given in chapter &<<CHAPlocalscan>>&.
5110 .cindex "configuration file" "leading white space in"
5111 .cindex "configuration file" "trailing white space in"
5112 .cindex "white space" "in configuration file"
5113 Leading and trailing white space in configuration lines is always ignored.
5115 Blank lines in the file, and lines starting with a # character (ignoring
5116 leading white space) are treated as comments and are ignored. &*Note*&: A
5117 # character other than at the beginning of a line is not treated specially,
5118 and does not introduce a comment.
5120 Any non-comment line can be continued by ending it with a backslash. Note that
5121 the general rule for white space means that trailing white space after the
5122 backslash and leading white space at the start of continuation
5123 lines is ignored. Comment lines beginning with # (but not empty lines) may
5124 appear in the middle of a sequence of continuation lines.
5126 A convenient way to create a configuration file is to start from the
5127 default, which is supplied in &_src/configure.default_&, and add, delete, or
5128 change settings as required.
5130 The ACLs, retry rules, and rewriting rules have their own syntax which is
5131 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
5132 respectively. The other parts of the configuration file have some syntactic
5133 items in common, and these are described below, from section &<<SECTcos>>&
5134 onwards. Before that, the inclusion, macro, and conditional facilities are
5139 .section "File inclusions in the configuration file" "SECID41"
5140 .cindex "inclusions in configuration file"
5141 .cindex "configuration file" "including other files"
5142 .cindex "&`.include`& in configuration file"
5143 .cindex "&`.include_if_exists`& in configuration file"
5144 You can include other files inside Exim's runtime configuration file by
5147 &`.include`& <&'filename'&>
5148 &`.include_if_exists`& <&'filename'&>
5150 on a line by itself. Double quotes round the filename are optional. If you use
5151 the first form, a configuration error occurs if the file does not exist; the
5152 second form does nothing for non-existent files.
5153 The first form allows a relative name. It is resolved relative to
5154 the directory of the including file. For the second form an absolute filename
5157 Includes may be nested to any depth, but remember that Exim reads its
5158 configuration file often, so it is a good idea to keep them to a minimum.
5159 If you change the contents of an included file, you must HUP the daemon,
5160 because an included file is read only when the configuration itself is read.
5162 The processing of inclusions happens early, at a physical line level, so, like
5163 comment lines, an inclusion can be used in the middle of an option setting,
5166 hosts_lookup = a.b.c \
5169 Include processing happens after macro processing (see below). Its effect is to
5170 process the lines of the included file as if they occurred inline where the
5175 .section "Macros in the configuration file" "SECTmacrodefs"
5176 .cindex "macro" "description of"
5177 .cindex "configuration file" "macros"
5178 If a line in the main part of the configuration (that is, before the first
5179 &"begin"& line) begins with an upper case letter, it is taken as a macro
5180 definition, and must be of the form
5182 <&'name'&> = <&'rest of line'&>
5184 The name must consist of letters, digits, and underscores, and need not all be
5185 in upper case, though that is recommended. The rest of the line, including any
5186 continuations, is the replacement text, and has leading and trailing white
5187 space removed. Quotes are not removed. The replacement text can never end with
5188 a backslash character, but this doesn't seem to be a serious limitation.
5190 Macros may also be defined between router, transport, authenticator, or ACL
5191 definitions. They may not, however, be defined within an individual driver or
5192 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
5194 .section "Macro substitution" "SECID42"
5195 Once a macro is defined, all subsequent lines in the file (and any included
5196 files) are scanned for the macro name; if there are several macros, the line is
5197 scanned for each, in turn, in the order in which the macros are defined. The
5198 replacement text is not re-scanned for the current macro, though it is scanned
5199 for subsequently defined macros. For this reason, a macro name may not contain
5200 the name of a previously defined macro as a substring. You could, for example,
5203 &`ABCD_XYZ = `&<&'something'&>
5204 &`ABCD = `&<&'something else'&>
5206 but putting the definitions in the opposite order would provoke a configuration
5207 error. Macro expansion is applied to individual physical lines from the file,
5208 before checking for line continuation or file inclusion (see above). If a line
5209 consists solely of a macro name, and the expansion of the macro is empty, the
5210 line is ignored. A macro at the start of a line may turn the line into a
5211 comment line or a &`.include`& line.
5214 .section "Redefining macros" "SECID43"
5215 Once defined, the value of a macro can be redefined later in the configuration
5216 (or in an included file). Redefinition is specified by using &'=='& instead of
5221 MAC == updated value
5223 Redefinition does not alter the order in which the macros are applied to the
5224 subsequent lines of the configuration file. It is still the same order in which
5225 the macros were originally defined. All that changes is the macro's value.
5226 Redefinition makes it possible to accumulate values. For example:
5230 MAC == MAC and something added
5232 This can be helpful in situations where the configuration file is built
5233 from a number of other files.
5235 .section "Overriding macro values" "SECID44"
5236 The values set for macros in the configuration file can be overridden by the
5237 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5238 used, unless called by root or the Exim user. A definition on the command line
5239 using the &%-D%& option causes all definitions and redefinitions within the
5244 .section "Example of macro usage" "SECID45"
5245 As an example of macro usage, consider a configuration where aliases are looked
5246 up in a MySQL database. It helps to keep the file less cluttered if long
5247 strings such as SQL statements are defined separately as macros, for example:
5249 ALIAS_QUERY = select mailbox from user where \
5250 login='${quote_mysql:$local_part}';
5252 This can then be used in a &(redirect)& router setting like this:
5254 data = ${lookup mysql{ALIAS_QUERY}}
5256 In earlier versions of Exim macros were sometimes used for domain, host, or
5257 address lists. In Exim 4 these are handled better by named lists &-- see
5258 section &<<SECTnamedlists>>&.
5261 .section "Builtin macros" "SECTbuiltinmacros"
5262 Exim defines some macros depending on facilities available, which may
5263 differ due to build-time definitions and from one release to another.
5264 All of these macros start with an underscore.
5265 They can be used to conditionally include parts of a configuration
5268 The following classes of macros are defined:
5270 &` _HAVE_* `& build-time defines
5271 &` _DRIVER_ROUTER_* `& router drivers
5272 &` _DRIVER_TRANSPORT_* `& transport drivers
5273 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5274 &` _LOG_* `& log_selector values
5275 &` _OPT_MAIN_* `& main config options
5276 &` _OPT_ROUTERS_* `& generic router options
5277 &` _OPT_TRANSPORTS_* `& generic transport options
5278 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5279 &` _OPT_ROUTER_*_* `& private router options
5280 &` _OPT_TRANSPORT_*_* `& private transport options
5281 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5284 Use an &"exim -bP macros"& command to get the list of macros.
5287 .section "Conditional skips in the configuration file" "SECID46"
5288 .cindex "configuration file" "conditional skips"
5289 .cindex "&`.ifdef`&"
5290 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5291 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5292 portions of the configuration file. The processing happens whenever the file is
5293 read (that is, when an Exim binary starts to run).
5295 The implementation is very simple. Instances of the first four directives must
5296 be followed by text that includes the names of one or macros. The condition
5297 that is tested is whether or not any macro substitution has taken place in the
5301 message_size_limit = 50M
5303 message_size_limit = 100M
5306 sets a message size limit of 50M if the macro &`AAA`& is defined
5307 (or &`A`& or &`AA`&), and 100M
5308 otherwise. If there is more than one macro named on the line, the condition
5309 is true if any of them are defined. That is, it is an &"or"& condition. To
5310 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5312 Although you can use a macro expansion to generate one of these directives,
5313 it is not very useful, because the condition &"there was a macro substitution
5314 in this line"& will always be true.
5316 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5317 to clarify complicated nestings.
5321 .section "Common option syntax" "SECTcos"
5322 .cindex "common option syntax"
5323 .cindex "syntax of common options"
5324 .cindex "configuration file" "common option syntax"
5325 For the main set of options, driver options, and &[local_scan()]& options,
5326 each setting is on a line by itself, and starts with a name consisting of
5327 lower-case letters and underscores. Many options require a data value, and in
5328 these cases the name must be followed by an equals sign (with optional white
5329 space) and then the value. For example:
5331 qualify_domain = mydomain.example.com
5333 .cindex "hiding configuration option values"
5334 .cindex "configuration options" "hiding value of"
5335 .cindex "options" "hiding value of"
5336 Some option settings may contain sensitive data, for example, passwords for
5337 accessing databases. To stop non-admin users from using the &%-bP%& command
5338 line option to read these values, you can precede the option settings with the
5339 word &"hide"&. For example:
5341 hide mysql_servers = localhost/users/admin/secret-password
5343 For non-admin users, such options are displayed like this:
5345 mysql_servers = <value not displayable>
5347 If &"hide"& is used on a driver option, it hides the value of that option on
5348 all instances of the same driver.
5350 The following sections describe the syntax used for the different data types
5351 that are found in option settings.
5354 .section "Boolean options" "SECID47"
5355 .cindex "format" "boolean"
5356 .cindex "boolean configuration values"
5357 .oindex "&%no_%&&'xxx'&"
5358 .oindex "&%not_%&&'xxx'&"
5359 Options whose type is given as boolean are on/off switches. There are two
5360 different ways of specifying such options: with and without a data value. If
5361 the option name is specified on its own without data, the switch is turned on;
5362 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5363 boolean options may be followed by an equals sign and one of the words
5364 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5365 the following two settings have exactly the same effect:
5370 The following two lines also have the same (opposite) effect:
5375 You can use whichever syntax you prefer.
5380 .section "Integer values" "SECID48"
5381 .cindex "integer configuration values"
5382 .cindex "format" "integer"
5383 If an option's type is given as &"integer"&, the value can be given in decimal,
5384 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5385 number is assumed. Otherwise, it is treated as an octal number unless it starts
5386 with the characters &"0x"&, in which case the remainder is interpreted as a
5389 If an integer value is followed by the letter K, it is multiplied by 1024; if
5390 it is followed by the letter M, it is multiplied by 1024x1024;
5391 if by the letter G, 1024x1024x1024.
5393 of integer option settings are output, values which are an exact multiple of
5394 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5395 and M. The printing style is independent of the actual input format that was
5399 .section "Octal integer values" "SECID49"
5400 .cindex "integer format"
5401 .cindex "format" "octal integer"
5402 If an option's type is given as &"octal integer"&, its value is always
5403 interpreted as an octal number, whether or not it starts with the digit zero.
5404 Such options are always output in octal.
5407 .section "Fixed point numbers" "SECID50"
5408 .cindex "fixed point configuration values"
5409 .cindex "format" "fixed point"
5410 If an option's type is given as &"fixed-point"&, its value must be a decimal
5411 integer, optionally followed by a decimal point and up to three further digits.
5415 .section "Time intervals" "SECTtimeformat"
5416 .cindex "time interval" "specifying in configuration"
5417 .cindex "format" "time interval"
5418 A time interval is specified as a sequence of numbers, each followed by one of
5419 the following letters, with no intervening white space:
5429 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5430 intervals are output in the same format. Exim does not restrict the values; it
5431 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5435 .section "String values" "SECTstrings"
5436 .cindex "string" "format of configuration values"
5437 .cindex "format" "string"
5438 If an option's type is specified as &"string"&, the value can be specified with
5439 or without double-quotes. If it does not start with a double-quote, the value
5440 consists of the remainder of the line plus any continuation lines, starting at
5441 the first character after any leading white space, with trailing white space
5442 removed, and with no interpretation of the characters in the string. Because
5443 Exim removes comment lines (those beginning with #) at an early stage, they can
5444 appear in the middle of a multi-line string. The following two settings are
5445 therefore equivalent:
5447 trusted_users = uucp:mail
5448 trusted_users = uucp:\
5449 # This comment line is ignored
5452 .cindex "string" "quoted"
5453 .cindex "escape characters in quoted strings"
5454 If a string does start with a double-quote, it must end with a closing
5455 double-quote, and any backslash characters other than those used for line
5456 continuation are interpreted as escape characters, as follows:
5459 .irow &`\\`& "single backslash"
5460 .irow &`\n`& "newline"
5461 .irow &`\r`& "carriage return"
5463 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5464 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5468 If a backslash is followed by some other character, including a double-quote
5469 character, that character replaces the pair.
5471 Quoting is necessary only if you want to make use of the backslash escapes to
5472 insert special characters, or if you need to specify a value with leading or
5473 trailing spaces. These cases are rare, so quoting is almost never needed in
5474 current versions of Exim. In versions of Exim before 3.14, quoting was required
5475 in order to continue lines, so you may come across older configuration files
5476 and examples that apparently quote unnecessarily.
5479 .section "Expanded strings" "SECID51"
5480 .cindex "expansion" "definition of"
5481 Some strings in the configuration file are subjected to &'string expansion'&,
5482 by which means various parts of the string may be changed according to the
5483 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5484 is as just described; in particular, the handling of backslashes in quoted
5485 strings is done as part of the input process, before expansion takes place.
5486 However, backslash is also an escape character for the expander, so any
5487 backslashes that are required for that reason must be doubled if they are
5488 within a quoted configuration string.
5491 .section "User and group names" "SECID52"
5492 .cindex "user name" "format of"
5493 .cindex "format" "user name"
5494 .cindex "groups" "name format"
5495 .cindex "format" "group name"
5496 User and group names are specified as strings, using the syntax described
5497 above, but the strings are interpreted specially. A user or group name must
5498 either consist entirely of digits, or be a name that can be looked up using the
5499 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5502 .section "List construction" "SECTlistconstruct"
5503 .cindex "list" "syntax of in configuration"
5504 .cindex "format" "list item in configuration"
5505 .cindex "string" "list, definition of"
5506 The data for some configuration options is a list of items, with colon as the
5507 default separator. Many of these options are shown with type &"string list"& in
5508 the descriptions later in this document. Others are listed as &"domain list"&,
5509 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5510 are all the same; however, those other than &"string list"& are subject to
5511 particular kinds of interpretation, as described in chapter
5512 &<<CHAPdomhosaddlists>>&.
5514 In all these cases, the entire list is treated as a single string as far as the
5515 input syntax is concerned. The &%trusted_users%& setting in section
5516 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5517 in a list, it must be entered as two colons. Leading and trailing white space
5518 on each item in a list is ignored. This makes it possible to include items that
5519 start with a colon, and in particular, certain forms of IPv6 address. For
5522 local_interfaces = 127.0.0.1 : ::::1
5524 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5526 &*Note*&: Although leading and trailing white space is ignored in individual
5527 list items, it is not ignored when parsing the list. The spaces around the first
5528 colon in the example above are necessary. If they were not there, the list would
5529 be interpreted as the two items 127.0.0.1:: and 1.
5531 .section "Changing list separators" "SECTlistsepchange"
5532 .cindex "list separator" "changing"
5533 .cindex "IPv6" "addresses in lists"
5534 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5535 introduced to allow the separator character to be changed. If a list begins
5536 with a left angle bracket, followed by any punctuation character, that
5537 character is used instead of colon as the list separator. For example, the list
5538 above can be rewritten to use a semicolon separator like this:
5540 local_interfaces = <; 127.0.0.1 ; ::1
5542 This facility applies to all lists, with the exception of the list in
5543 &%log_file_path%&. It is recommended that the use of non-colon separators be
5544 confined to circumstances where they really are needed.
5546 .cindex "list separator" "newline as"
5547 .cindex "newline" "as list separator"
5548 It is also possible to use newline and other control characters (those with
5549 code values less than 32, plus DEL) as separators in lists. Such separators
5550 must be provided literally at the time the list is processed. For options that
5551 are string-expanded, you can write the separator using a normal escape
5552 sequence. This will be processed by the expander before the string is
5553 interpreted as a list. For example, if a newline-separated list of domains is
5554 generated by a lookup, you can process it directly by a line such as this:
5556 domains = <\n ${lookup mysql{.....}}
5558 This avoids having to change the list separator in such data. You are unlikely
5559 to want to use a control character as a separator in an option that is not
5560 expanded, because the value is literal text. However, it can be done by giving
5561 the value in quotes. For example:
5563 local_interfaces = "<\n 127.0.0.1 \n ::1"
5565 Unlike printing character separators, which can be included in list items by
5566 doubling, it is not possible to include a control character as data when it is
5567 set as the separator. Two such characters in succession are interpreted as
5568 enclosing an empty list item.
5572 .section "Empty items in lists" "SECTempitelis"
5573 .cindex "list" "empty item in"
5574 An empty item at the end of a list is always ignored. In other words, trailing
5575 separator characters are ignored. Thus, the list in
5577 senders = user@domain :
5579 contains only a single item. If you want to include an empty string as one item
5580 in a list, it must not be the last item. For example, this list contains three
5581 items, the second of which is empty:
5583 senders = user1@domain : : user2@domain
5585 &*Note*&: There must be white space between the two colons, as otherwise they
5586 are interpreted as representing a single colon data character (and the list
5587 would then contain just one item). If you want to specify a list that contains
5588 just one, empty item, you can do it as in this example:
5592 In this case, the first item is empty, and the second is discarded because it
5593 is at the end of the list.
5598 .section "Format of driver configurations" "SECTfordricon"
5599 .cindex "drivers" "configuration format"
5600 There are separate parts in the configuration for defining routers, transports,
5601 and authenticators. In each part, you are defining a number of driver
5602 instances, each with its own set of options. Each driver instance is defined by
5603 a sequence of lines like this:
5605 <&'instance name'&>:
5610 In the following example, the instance name is &(localuser)&, and it is
5611 followed by three options settings:
5616 transport = local_delivery
5618 For each driver instance, you specify which Exim code module it uses &-- by the
5619 setting of the &%driver%& option &-- and (optionally) some configuration
5620 settings. For example, in the case of transports, if you want a transport to
5621 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5622 a local file you would use the &(appendfile)& driver. Each of the drivers is
5623 described in detail in its own separate chapter later in this manual.
5625 You can have several routers, transports, or authenticators that are based on
5626 the same underlying driver (each must have a different instance name).
5628 The order in which routers are defined is important, because addresses are
5629 passed to individual routers one by one, in order. The order in which
5630 transports are defined does not matter at all. The order in which
5631 authenticators are defined is used only when Exim, as a client, is searching
5632 them to find one that matches an authentication mechanism offered by the
5635 .cindex "generic options"
5636 .cindex "options" "generic &-- definition of"
5637 Within a driver instance definition, there are two kinds of option: &'generic'&
5638 and &'private'&. The generic options are those that apply to all drivers of the
5639 same type (that is, all routers, all transports or all authenticators). The
5640 &%driver%& option is a generic option that must appear in every definition.
5641 .cindex "private options"
5642 The private options are special for each driver, and none need appear, because
5643 they all have default values.
5645 The options may appear in any order, except that the &%driver%& option must
5646 precede any private options, since these depend on the particular driver. For
5647 this reason, it is recommended that &%driver%& always be the first option.
5649 Driver instance names, which are used for reference in log entries and
5650 elsewhere, can be any sequence of letters, digits, and underscores (starting
5651 with a letter) and must be unique among drivers of the same type. A router and
5652 a transport (for example) can each have the same name, but no two router
5653 instances can have the same name. The name of a driver instance should not be
5654 confused with the name of the underlying driver module. For example, the
5655 configuration lines:
5660 create an instance of the &(smtp)& transport driver whose name is
5661 &(remote_smtp)&. The same driver code can be used more than once, with
5662 different instance names and different option settings each time. A second
5663 instance of the &(smtp)& transport, with different options, might be defined
5669 command_timeout = 10s
5671 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5672 these transport instances from routers, and these names would appear in log
5675 Comment lines may be present in the middle of driver specifications. The full
5676 list of option settings for any particular driver instance, including all the
5677 defaulted values, can be extracted by making use of the &%-bP%& command line
5685 . ////////////////////////////////////////////////////////////////////////////
5686 . ////////////////////////////////////////////////////////////////////////////
5688 .chapter "The default configuration file" "CHAPdefconfil"
5689 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5690 .cindex "default" "configuration file &""walk through""&"
5691 The default configuration file supplied with Exim as &_src/configure.default_&
5692 is sufficient for a host with simple mail requirements. As an introduction to
5693 the way Exim is configured, this chapter &"walks through"& the default
5694 configuration, giving brief explanations of the settings. Detailed descriptions
5695 of the options are given in subsequent chapters. The default configuration file
5696 itself contains extensive comments about ways you might want to modify the
5697 initial settings. However, note that there are many options that are not
5698 mentioned at all in the default configuration.
5702 .section "Macros" "SECTdefconfmacros"
5703 All macros should be defined before any options.
5705 One macro is specified, but commented out, in the default configuration:
5707 # ROUTER_SMARTHOST=MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
5709 If all off-site mail is expected to be delivered to a "smarthost", then set the
5710 hostname here and uncomment the macro. This will affect which router is used
5711 later on. If this is left commented out, then Exim will perform direct-to-MX
5712 deliveries using a &(dnslookup)& router.
5714 In addition to macros defined here, Exim includes a number of built-in macros
5715 to enable configuration to be guarded by a binary built with support for a
5716 given feature. See section &<<SECTbuiltinmacros>>& for more details.
5719 .section "Main configuration settings" "SECTdefconfmain"
5720 The main (global) configuration option settings section must always come first
5721 in the file, after the macros.
5722 The first thing you'll see in the file, after some initial comments, is the line
5724 # primary_hostname =
5726 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5727 to know the official, fully qualified name of your host, and this is where you
5728 can specify it. However, in most cases you do not need to set this option. When
5729 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5731 The first three non-comment configuration lines are as follows:
5733 domainlist local_domains = @
5734 domainlist relay_to_domains =
5735 hostlist relay_from_hosts = 127.0.0.1
5737 These are not, in fact, option settings. They are definitions of two named
5738 domain lists and one named host list. Exim allows you to give names to lists of
5739 domains, hosts, and email addresses, in order to make it easier to manage the
5740 configuration file (see section &<<SECTnamedlists>>&).
5742 The first line defines a domain list called &'local_domains'&; this is used
5743 later in the configuration to identify domains that are to be delivered
5746 .cindex "@ in a domain list"
5747 There is just one item in this list, the string &"@"&. This is a special form
5748 of entry which means &"the name of the local host"&. Thus, if the local host is
5749 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5750 be delivered locally. Because the local host's name is referenced indirectly,
5751 the same configuration file can be used on different hosts.
5753 The second line defines a domain list called &'relay_to_domains'&, but the
5754 list itself is empty. Later in the configuration we will come to the part that
5755 controls mail relaying through the local host; it allows relaying to any
5756 domains in this list. By default, therefore, no relaying on the basis of a mail
5757 domain is permitted.
5759 The third line defines a host list called &'relay_from_hosts'&. This list is
5760 used later in the configuration to permit relaying from any host or IP address
5761 that matches the list. The default contains just the IP address of the IPv4
5762 loopback interface, which means that processes on the local host are able to
5763 submit mail for relaying by sending it over TCP/IP to that interface. No other
5764 hosts are permitted to submit messages for relaying.
5766 Just to be sure there's no misunderstanding: at this point in the configuration
5767 we aren't actually setting up any controls. We are just defining some domains
5768 and hosts that will be used in the controls that are specified later.
5770 The next two configuration lines are genuine option settings:
5772 acl_smtp_rcpt = acl_check_rcpt
5773 acl_smtp_data = acl_check_data
5775 These options specify &'Access Control Lists'& (ACLs) that are to be used
5776 during an incoming SMTP session for every recipient of a message (every RCPT
5777 command), and after the contents of the message have been received,
5778 respectively. The names of the lists are &'acl_check_rcpt'& and
5779 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5780 section of the configuration. The RCPT ACL controls which recipients are
5781 accepted for an incoming message &-- if a configuration does not provide an ACL
5782 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5783 contents of a message to be checked.
5785 Two commented-out option settings are next:
5787 # av_scanner = clamd:/tmp/clamd
5788 # spamd_address = 127.0.0.1 783
5790 These are example settings that can be used when Exim is compiled with the
5791 content-scanning extension. The first specifies the interface to the virus
5792 scanner, and the second specifies the interface to SpamAssassin. Further
5793 details are given in chapter &<<CHAPexiscan>>&.
5795 Three more commented-out option settings follow:
5797 # tls_advertise_hosts = *
5798 # tls_certificate = /etc/ssl/exim.crt
5799 # tls_privatekey = /etc/ssl/exim.pem
5801 These are example settings that can be used when Exim is compiled with
5802 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5803 first one specifies the list of clients that are allowed to use TLS when
5804 connecting to this server; in this case, the wildcard means all clients. The
5805 other options specify where Exim should find its TLS certificate and private
5806 key, which together prove the server's identity to any clients that connect.
5807 More details are given in chapter &<<CHAPTLS>>&.
5809 Another two commented-out option settings follow:
5811 # daemon_smtp_ports = 25 : 465 : 587
5812 # tls_on_connect_ports = 465
5814 .cindex "port" "465 and 587"
5815 .cindex "port" "for message submission"
5816 .cindex "message" "submission, ports for"
5817 .cindex "submissions protocol"
5818 .cindex "smtps protocol"
5819 .cindex "ssmtp protocol"
5820 .cindex "SMTP" "submissions protocol"
5821 .cindex "SMTP" "ssmtp protocol"
5822 .cindex "SMTP" "smtps protocol"
5823 These options provide better support for roaming users who wish to use this
5824 server for message submission. They are not much use unless you have turned on
5825 TLS (as described in the previous paragraph) and authentication (about which
5826 more in section &<<SECTdefconfauth>>&).
5827 Mail submission from mail clients (MUAs) should be separate from inbound mail
5828 to your domain (MX delivery) for various good reasons (eg, ability to impose
5829 much saner TLS protocol and ciphersuite requirements without unintended
5831 RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
5832 which uses STARTTLS, so this is the &"submission"& port.
5833 RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
5834 which should be used in preference to 587.
5835 You should also consider deploying SRV records to help clients find
5837 Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
5839 Two more commented-out options settings follow:
5842 # qualify_recipient =
5844 The first of these specifies a domain that Exim uses when it constructs a
5845 complete email address from a local login name. This is often needed when Exim
5846 receives a message from a local process. If you do not set &%qualify_domain%&,
5847 the value of &%primary_hostname%& is used. If you set both of these options,
5848 you can have different qualification domains for sender and recipient
5849 addresses. If you set only the first one, its value is used in both cases.
5851 .cindex "domain literal" "recognizing format"
5852 The following line must be uncommented if you want Exim to recognize
5853 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5854 (an IP address within square brackets) instead of a named domain.
5856 # allow_domain_literals
5858 The RFCs still require this form, but many people think that in the modern
5859 Internet it makes little sense to permit mail to be sent to specific hosts by
5860 quoting their IP addresses. This ancient format has been used by people who
5861 try to abuse hosts by using them for unwanted relaying. However, some
5862 people believe there are circumstances (for example, messages addressed to
5863 &'postmaster'&) where domain literals are still useful.
5865 The next configuration line is a kind of trigger guard:
5869 It specifies that no delivery must ever be run as the root user. The normal
5870 convention is to set up &'root'& as an alias for the system administrator. This
5871 setting is a guard against slips in the configuration.
5872 The list of users specified by &%never_users%& is not, however, the complete
5873 list; the build-time configuration in &_Local/Makefile_& has an option called
5874 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5875 contents of &%never_users%& are added to this list. By default
5876 FIXED_NEVER_USERS also specifies root.
5878 When a remote host connects to Exim in order to send mail, the only information
5879 Exim has about the host's identity is its IP address. The next configuration
5884 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5885 in order to get a host name. This improves the quality of the logging
5886 information, but if you feel it is too expensive, you can remove it entirely,
5887 or restrict the lookup to hosts on &"nearby"& networks.
5888 Note that it is not always possible to find a host name from an IP address,
5889 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5892 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5893 1413 (hence their names):
5896 rfc1413_query_timeout = 0s
5898 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5899 Few hosts offer RFC1413 service these days; calls have to be
5900 terminated by a timeout and this needlessly delays the startup
5901 of an incoming SMTP connection.
5902 If you have hosts for which you trust RFC1413 and need this
5903 information, you can change this.
5905 This line enables an efficiency SMTP option. It is negotiated by clients
5906 and not expected to cause problems but can be disabled if needed.
5911 When Exim receives messages over SMTP connections, it expects all addresses to
5912 be fully qualified with a domain, as required by the SMTP definition. However,
5913 if you are running a server to which simple clients submit messages, you may
5914 find that they send unqualified addresses. The two commented-out options:
5916 # sender_unqualified_hosts =
5917 # recipient_unqualified_hosts =
5919 show how you can specify hosts that are permitted to send unqualified sender
5920 and recipient addresses, respectively.
5922 The &%log_selector%& option is used to increase the detail of logging
5925 log_selector = +smtp_protocol_error +smtp_syntax_error \
5926 +tls_certificate_verified
5929 The &%percent_hack_domains%& option is also commented out:
5931 # percent_hack_domains =
5933 It provides a list of domains for which the &"percent hack"& is to operate.
5934 This is an almost obsolete form of explicit email routing. If you do not know
5935 anything about it, you can safely ignore this topic.
5937 The next two settings in the main part of the default configuration are
5938 concerned with messages that have been &"frozen"& on Exim's queue. When a
5939 message is frozen, Exim no longer continues to try to deliver it. Freezing
5940 occurs when a bounce message encounters a permanent failure because the sender
5941 address of the original message that caused the bounce is invalid, so the
5942 bounce cannot be delivered. This is probably the most common case, but there
5943 are also other conditions that cause freezing, and frozen messages are not
5944 always bounce messages.
5946 ignore_bounce_errors_after = 2d
5947 timeout_frozen_after = 7d
5949 The first of these options specifies that failing bounce messages are to be
5950 discarded after 2 days in the queue. The second specifies that any frozen
5951 message (whether a bounce message or not) is to be timed out (and discarded)
5952 after a week. In this configuration, the first setting ensures that no failing
5953 bounce message ever lasts a week.
5955 Exim queues it's messages in a spool directory. If you expect to have
5956 large queues, you may consider using this option. It splits the spool
5957 directory into subdirectories to avoid file system degradation from
5958 many files in a single directory, resulting in better performance.
5959 Manual manipulation of queued messages becomes more complex (though fortunately
5962 # split_spool_directory = true
5965 In an ideal world everybody follows the standards. For non-ASCII
5966 messages RFC 2047 is a standard, allowing a maximum line length of 76
5967 characters. Exim adheres that standard and won't process messages which
5968 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5969 In particular, the Exim maintainers have had multiple reports of
5970 problems from Russian administrators of issues until they disable this
5971 check, because of some popular, yet buggy, mail composition software.
5973 # check_rfc2047_length = false
5976 If you need to be strictly RFC compliant you may wish to disable the
5977 8BITMIME advertisement. Use this, if you exchange mails with systems
5978 that are not 8-bit clean.
5980 # accept_8bitmime = false
5983 Libraries you use may depend on specific environment settings. This
5984 imposes a security risk (e.g. PATH). There are two lists:
5985 &%keep_environment%& for the variables to import as they are, and
5986 &%add_environment%& for variables we want to set to a fixed value.
5987 Note that TZ is handled separately, by the &%timezone%& runtime
5988 option and by the TIMEZONE_DEFAULT buildtime option.
5990 # keep_environment = ^LDAP
5991 # add_environment = PATH=/usr/bin::/bin
5995 .section "ACL configuration" "SECID54"
5996 .cindex "default" "ACLs"
5997 .cindex "&ACL;" "default configuration"
5998 In the default configuration, the ACL section follows the main configuration.
5999 It starts with the line
6003 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
6004 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
6005 and &%acl_smtp_data%& above.
6007 .cindex "RCPT" "ACL for"
6008 The first ACL is used for every RCPT command in an incoming SMTP message. Each
6009 RCPT command specifies one of the message's recipients. The ACL statements
6010 are considered in order, until the recipient address is either accepted or
6011 rejected. The RCPT command is then accepted or rejected, according to the
6012 result of the ACL processing.
6016 This line, consisting of a name terminated by a colon, marks the start of the
6021 This ACL statement accepts the recipient if the sending host matches the list.
6022 But what does that strange list mean? It doesn't actually contain any host
6023 names or IP addresses. The presence of the colon puts an empty item in the
6024 list; Exim matches this only if the incoming message did not come from a remote
6025 host, because in that case, the remote hostname is empty. The colon is
6026 important. Without it, the list itself is empty, and can never match anything.
6028 What this statement is doing is to accept unconditionally all recipients in
6029 messages that are submitted by SMTP from local processes using the standard
6030 input and output (that is, not using TCP/IP). A number of MUAs operate in this
6033 deny domains = +local_domains
6034 local_parts = ^[.] : ^.*[@%!/|]
6035 message = Restricted characters in address
6037 deny domains = !+local_domains
6038 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
6039 message = Restricted characters in address
6041 These statements are concerned with local parts that contain any of the
6042 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
6043 Although these characters are entirely legal in local parts (in the case of
6044 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
6045 in Internet mail addresses.
6047 The first three have in the past been associated with explicitly routed
6048 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
6049 option). Addresses containing these characters are regularly tried by spammers
6050 in an attempt to bypass relaying restrictions, and also by open relay testing
6051 programs. Unless you really need them it is safest to reject these characters
6052 at this early stage. This configuration is heavy-handed in rejecting these
6053 characters for all messages it accepts from remote hosts. This is a deliberate
6054 policy of being as safe as possible.
6056 The first rule above is stricter, and is applied to messages that are addressed
6057 to one of the local domains handled by this host. This is implemented by the
6058 first condition, which restricts it to domains that are listed in the
6059 &'local_domains'& domain list. The &"+"& character is used to indicate a
6060 reference to a named list. In this configuration, there is just one domain in
6061 &'local_domains'&, but in general there may be many.
6063 The second condition on the first statement uses two regular expressions to
6064 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
6065 or &"|"&. If you have local accounts that include these characters, you will
6066 have to modify this rule.
6068 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
6069 allows them because they have been encountered in practice. (Consider the
6070 common convention of local parts constructed as
6071 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
6072 the author of Exim, who has no second initial.) However, a local part starting
6073 with a dot or containing &"/../"& can cause trouble if it is used as part of a
6074 filename (for example, for a mailing list). This is also true for local parts
6075 that contain slashes. A pipe symbol can also be troublesome if the local part
6076 is incorporated unthinkingly into a shell command line.
6078 The second rule above applies to all other domains, and is less strict. This
6079 allows your own users to send outgoing messages to sites that use slashes
6080 and vertical bars in their local parts. It blocks local parts that begin
6081 with a dot, slash, or vertical bar, but allows these characters within the
6082 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
6083 and &"!"& is blocked, as before. The motivation here is to prevent your users
6084 (or your users' viruses) from mounting certain kinds of attack on remote sites.
6086 accept local_parts = postmaster
6087 domains = +local_domains
6089 This statement, which has two conditions, accepts an incoming address if the
6090 local part is &'postmaster'& and the domain is one of those listed in the
6091 &'local_domains'& domain list. The &"+"& character is used to indicate a
6092 reference to a named list. In this configuration, there is just one domain in
6093 &'local_domains'&, but in general there may be many.
6095 The presence of this statement means that mail to postmaster is never blocked
6096 by any of the subsequent tests. This can be helpful while sorting out problems
6097 in cases where the subsequent tests are incorrectly denying access.
6099 require verify = sender
6101 This statement requires the sender address to be verified before any subsequent
6102 ACL statement can be used. If verification fails, the incoming recipient
6103 address is refused. Verification consists of trying to route the address, to
6104 see if a bounce message could be delivered to it. In the case of remote
6105 addresses, basic verification checks only the domain, but &'callouts'& can be
6106 used for more verification if required. Section &<<SECTaddressverification>>&
6107 discusses the details of address verification.
6109 accept hosts = +relay_from_hosts
6110 control = submission
6112 This statement accepts the address if the message is coming from one of the
6113 hosts that are defined as being allowed to relay through this host. Recipient
6114 verification is omitted here, because in many cases the clients are dumb MUAs
6115 that do not cope well with SMTP error responses. For the same reason, the
6116 second line specifies &"submission mode"& for messages that are accepted. This
6117 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
6118 messages that are deficient in some way, for example, because they lack a
6119 &'Date:'& header line. If you are actually relaying out from MTAs, you should
6120 probably add recipient verification here, and disable submission mode.
6122 accept authenticated = *
6123 control = submission
6125 This statement accepts the address if the client host has authenticated itself.
6126 Submission mode is again specified, on the grounds that such messages are most
6127 likely to come from MUAs. The default configuration does not define any
6128 authenticators, though it does include some nearly complete commented-out
6129 examples described in &<<SECTdefconfauth>>&. This means that no client can in
6130 fact authenticate until you complete the authenticator definitions.
6132 require message = relay not permitted
6133 domains = +local_domains : +relay_to_domains
6135 This statement rejects the address if its domain is neither a local domain nor
6136 one of the domains for which this host is a relay.
6138 require verify = recipient
6140 This statement requires the recipient address to be verified; if verification
6141 fails, the address is rejected.
6143 # deny dnslists = black.list.example
6144 # message = rejected because $sender_host_address \
6145 # is in a black list at $dnslist_domain\n\
6148 # warn dnslists = black.list.example
6149 # add_header = X-Warning: $sender_host_address is in \
6150 # a black list at $dnslist_domain
6151 # log_message = found in $dnslist_domain
6153 These commented-out lines are examples of how you could configure Exim to check
6154 sending hosts against a DNS black list. The first statement rejects messages
6155 from blacklisted hosts, whereas the second just inserts a warning header
6158 # require verify = csa
6160 This commented-out line is an example of how you could turn on client SMTP
6161 authorization (CSA) checking. Such checks do DNS lookups for special SRV
6166 The final statement in the first ACL unconditionally accepts any recipient
6167 address that has successfully passed all the previous tests.
6171 This line marks the start of the second ACL, and names it. Most of the contents
6172 of this ACL are commented out:
6175 # message = This message contains a virus \
6178 These lines are examples of how to arrange for messages to be scanned for
6179 viruses when Exim has been compiled with the content-scanning extension, and a
6180 suitable virus scanner is installed. If the message is found to contain a
6181 virus, it is rejected with the given custom error message.
6183 # warn spam = nobody
6184 # message = X-Spam_score: $spam_score\n\
6185 # X-Spam_score_int: $spam_score_int\n\
6186 # X-Spam_bar: $spam_bar\n\
6187 # X-Spam_report: $spam_report
6189 These lines are an example of how to arrange for messages to be scanned by
6190 SpamAssassin when Exim has been compiled with the content-scanning extension,
6191 and SpamAssassin has been installed. The SpamAssassin check is run with
6192 &`nobody`& as its user parameter, and the results are added to the message as a
6193 series of extra header line. In this case, the message is not rejected,
6194 whatever the spam score.
6198 This final line in the DATA ACL accepts the message unconditionally.
6201 .section "Router configuration" "SECID55"
6202 .cindex "default" "routers"
6203 .cindex "routers" "default"
6204 The router configuration comes next in the default configuration, introduced
6209 Routers are the modules in Exim that make decisions about where to send
6210 messages. An address is passed to each router, in turn, until it is either
6211 accepted, or failed. This means that the order in which you define the routers
6212 matters. Each router is fully described in its own chapter later in this
6213 manual. Here we give only brief overviews.
6216 # driver = ipliteral
6217 # domains = !+local_domains
6218 # transport = remote_smtp
6220 .cindex "domain literal" "default router"
6221 This router is commented out because the majority of sites do not want to
6222 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
6223 you uncomment this router, you also need to uncomment the setting of
6224 &%allow_domain_literals%& in the main part of the configuration.
6226 Which router is used next depends upon whether or not the ROUTER_SMARTHOST
6227 macro has been defined, per
6229 .ifdef ROUTER_SMARTHOST
6238 If ROUTER_SMARTHOST has been defined, either at the top of the file or on the
6239 command-line, then we route all non-local mail to that smarthost; otherwise, we'll
6240 perform DNS lookups for direct-to-MX lookup. Any mail which is to a local domain will
6241 skip these routers because of the &%domains%& option.
6245 driver = manualroute
6246 domains = ! +local_domains
6247 transport = smarthost_smtp
6248 route_data = ROUTER_SMARTHOST
6249 ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
6252 This router only handles mail which is not to any local domains; this is
6253 specified by the line
6255 domains = ! +local_domains
6257 The &%domains%& option lists the domains to which this router applies, but the
6258 exclamation mark is a negation sign, so the router is used only for domains
6259 that are not in the domain list called &'local_domains'& (which was defined at
6260 the start of the configuration). The plus sign before &'local_domains'&
6261 indicates that it is referring to a named list. Addresses in other domains are
6262 passed on to the following routers.
6264 The name of the router driver is &(manualroute)& because we are manually
6265 specifying how mail should be routed onwards, instead of using DNS MX.
6266 While the name of this router instance is arbitrary, the &%driver%& option must
6267 be one of the driver modules that is in the Exim binary.
6269 With no pre-conditions other than &%domains%&, all mail for non-local domains
6270 will be handled by this router, and the &%no_more%& setting will ensure that no
6271 other routers will be used for messages matching the pre-conditions. See
6272 &<<SECTrouprecon>>& for more on how the pre-conditions apply. For messages which
6273 are handled by this router, we provide a hostname to deliver to in &%route_data%&
6274 and the macro supplies the value; the address is then queued for the
6275 &(smarthost_smtp)& transport.
6280 domains = ! +local_domains
6281 transport = remote_smtp
6282 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
6285 The &%domains%& option behaves as per smarthost, above.
6287 The name of the router driver is &(dnslookup)&,
6288 and is specified by the &%driver%& option. Do not be confused by the fact that
6289 the name of this router instance is the same as the name of the driver. The
6290 instance name is arbitrary, but the name set in the &%driver%& option must be
6291 one of the driver modules that is in the Exim binary.
6293 The &(dnslookup)& router routes addresses by looking up their domains in the
6294 DNS in order to obtain a list of hosts to which the address is routed. If the
6295 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6296 specified by the &%transport%& option. If the router does not find the domain
6297 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6298 the address fails and is bounced.
6300 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6301 be entirely ignored. This option is present because a number of cases have been
6302 encountered where MX records in the DNS point to host names
6303 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6304 Completely ignoring these IP addresses causes Exim to fail to route the
6305 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6306 continue to try to deliver the message periodically until the address timed
6313 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6315 file_transport = address_file
6316 pipe_transport = address_pipe
6318 Control reaches this and subsequent routers only for addresses in the local
6319 domains. This router checks to see whether the local part is defined as an
6320 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6321 data that it looks up from that file. If no data is found for the local part,
6322 the value of the &%data%& option is empty, causing the address to be passed to
6325 &_/etc/aliases_& is a conventional name for the system aliases file that is
6326 often used. That is why it is referenced by from the default configuration
6327 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6328 &_Local/Makefile_& before building Exim.
6333 # local_part_suffix = +* : -*
6334 # local_part_suffix_optional
6335 file = $home/.forward
6340 file_transport = address_file
6341 pipe_transport = address_pipe
6342 reply_transport = address_reply
6344 This is the most complicated router in the default configuration. It is another
6345 redirection router, but this time it is looking for forwarding data set up by
6346 individual users. The &%check_local_user%& setting specifies a check that the
6347 local part of the address is the login name of a local user. If it is not, the
6348 router is skipped. The two commented options that follow &%check_local_user%&,
6351 # local_part_suffix = +* : -*
6352 # local_part_suffix_optional
6354 .vindex "&$local_part_suffix$&"
6355 show how you can specify the recognition of local part suffixes. If the first
6356 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6357 by any sequence of characters, is removed from the local part and placed in the
6358 variable &$local_part_suffix$&. The second suffix option specifies that the
6359 presence of a suffix in the local part is optional. When a suffix is present,
6360 the check for a local login uses the local part with the suffix removed.
6362 When a local user account is found, the file called &_.forward_& in the user's
6363 home directory is consulted. If it does not exist, or is empty, the router
6364 declines. Otherwise, the contents of &_.forward_& are interpreted as
6365 redirection data (see chapter &<<CHAPredirect>>& for more details).
6367 .cindex "Sieve filter" "enabling in default router"
6368 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6369 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6370 is commented out by default), the contents of the file are interpreted as a set
6371 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6372 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6373 separate document entitled &'Exim's interfaces to mail filtering'&.
6375 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6376 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6377 There are two reasons for doing this:
6380 Whether or not a local user has a &_.forward_& file is not really relevant when
6381 checking an address for validity; it makes sense not to waste resources doing
6384 More importantly, when Exim is verifying addresses or handling an EXPN
6385 command during an SMTP session, it is running as the Exim user, not as root.
6386 The group is the Exim group, and no additional groups are set up.
6387 It may therefore not be possible for Exim to read users' &_.forward_& files at
6391 The setting of &%check_ancestor%& prevents the router from generating a new
6392 address that is the same as any previous address that was redirected. (This
6393 works round a problem concerning a bad interaction between aliasing and
6394 forwarding &-- see section &<<SECTredlocmai>>&).
6396 The final three option settings specify the transports that are to be used when
6397 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6398 auto-reply, respectively. For example, if a &_.forward_& file contains
6400 a.nother@elsewhere.example, /home/spqr/archive
6402 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6408 # local_part_suffix = +* : -*
6409 # local_part_suffix_optional
6410 transport = local_delivery
6412 The final router sets up delivery into local mailboxes, provided that the local
6413 part is the name of a local login, by accepting the address and assigning it to
6414 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6415 routers, so the address is bounced. The commented suffix settings fulfil the
6416 same purpose as they do for the &(userforward)& router.
6419 .section "Transport configuration" "SECID56"
6420 .cindex "default" "transports"
6421 .cindex "transports" "default"
6422 Transports define mechanisms for actually delivering messages. They operate
6423 only when referenced from routers, so the order in which they are defined does
6424 not matter. The transports section of the configuration starts with
6428 Two remote transports and four local transports are defined.
6432 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6437 This transport is used for delivering messages over SMTP connections.
6438 The list of remote hosts comes from the router.
6439 The &%message_size_limit%& usage is a hack to avoid sending on messages
6440 with over-long lines.
6442 The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
6443 negotiated between client and server and not expected to cause problems
6444 but can be disabled if needed. The built-in macro _HAVE_PRDR guards the
6445 use of the &%hosts_try_prdr%& configuration option.
6447 The other remote transport is used when delivering to a specific smarthost
6448 with whom there must be some kind of existing relationship, instead of the
6449 usual federated system.
6454 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6458 # Comment out any of these which you have to, then file a Support
6459 # request with your smarthost provider to get things fixed:
6460 hosts_require_tls = *
6461 tls_verify_hosts = *
6462 # As long as tls_verify_hosts is enabled, this this will have no effect,
6463 # but if you have to comment it out then this will at least log whether
6464 # you succeed or not:
6465 tls_try_verify_hosts = *
6467 # The SNI name should match the name which we'll expect to verify;
6468 # many mail systems don't use SNI and this doesn't matter, but if it does,
6469 # we need to send a name which the remote site will recognize.
6470 # This _should_ be the name which the smarthost operators specified as
6471 # the hostname for sending your mail to.
6472 tls_sni = ROUTER_SMARTHOST
6474 .ifdef _HAVE_OPENSSL
6475 tls_require_ciphers = HIGH:!aNULL:@STRENGTH
6478 tls_require_ciphers = SECURE192:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1
6485 After the same &%message_size_limit%& hack, we then specify that this Transport
6486 can handle messages to multiple domains in one run. The assumption here is
6487 that you're routing all non-local mail to the same place and that place is
6488 happy to take all messages from you as quickly as possible.
6489 All other options depend upon built-in macros; if Exim was built without TLS support
6490 then no other options are defined.
6491 If TLS is available, then we configure "stronger than default" TLS ciphersuites
6492 and versions using the &%tls_require_ciphers%& option, where the value to be
6493 used depends upon the library providing TLS.
6494 Beyond that, the options adopt the stance that you should have TLS support available
6495 from your smarthost on today's Internet, so we turn on requiring TLS for the
6496 mail to be delivered, and requiring that the certificate be valid, and match
6497 the expected hostname. The &%tls_sni%& option can be used by service providers
6498 to select an appropriate certificate to present to you and here we re-use the
6499 ROUTER_SMARTHOST macro, because that is unaffected by CNAMEs present in DNS.
6500 You want to specify the hostname which you'll expect to validate for, and that
6501 should not be subject to insecure tampering via DNS results.
6503 For the &%hosts_try_prdr%& option see the previous transport.
6505 All other options are defaulted.
6509 file = /var/mail/$local_part_data
6516 This &(appendfile)& transport is used for local delivery to user mailboxes in
6517 traditional BSD mailbox format.
6519 We prefer to avoid using &$local_part$& directly to define the mailbox filename,
6520 as it is provided by a potential bad actor.
6521 Instead we use &$local_part_data$&,
6522 the result of looking up &$local_part$& in the user database
6523 (done by using &%check_local_user%& in the the router).
6525 By default &(appendfile)& runs under the uid and gid of the
6526 local user, which requires the sticky bit to be set on the &_/var/mail_&
6527 directory. Some systems use the alternative approach of running mail deliveries
6528 under a particular group instead of using the sticky bit. The commented options
6529 show how this can be done.
6531 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6532 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6533 similarly-named options above.
6539 This transport is used for handling deliveries to pipes that are generated by
6540 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6541 option specifies that any output on stdout or stderr generated by the pipe is to
6542 be returned to the sender.
6550 This transport is used for handling deliveries to files that are generated by
6551 redirection. The name of the file is not specified in this instance of
6552 &(appendfile)&, because it comes from the &(redirect)& router.
6557 This transport is used for handling automatic replies generated by users'
6562 .section "Default retry rule" "SECID57"
6563 .cindex "retry" "default rule"
6564 .cindex "default" "retry rule"
6565 The retry section of the configuration file contains rules which affect the way
6566 Exim retries deliveries that cannot be completed at the first attempt. It is
6567 introduced by the line
6571 In the default configuration, there is just one rule, which applies to all
6574 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6576 This causes any temporarily failing address to be retried every 15 minutes for
6577 2 hours, then at intervals starting at one hour and increasing by a factor of
6578 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6579 is not delivered after 4 days of temporary failure, it is bounced. The time is
6580 measured from first failure, not from the time the message was received.
6582 If the retry section is removed from the configuration, or is empty (that is,
6583 if no retry rules are defined), Exim will not retry deliveries. This turns
6584 temporary errors into permanent errors.
6587 .section "Rewriting configuration" "SECID58"
6588 The rewriting section of the configuration, introduced by
6592 contains rules for rewriting addresses in messages as they arrive. There are no
6593 rewriting rules in the default configuration file.
6597 .section "Authenticators configuration" "SECTdefconfauth"
6598 .cindex "AUTH" "configuration"
6599 The authenticators section of the configuration, introduced by
6601 begin authenticators
6603 defines mechanisms for the use of the SMTP AUTH command. The default
6604 configuration file contains two commented-out example authenticators
6605 which support plaintext username/password authentication using the
6606 standard PLAIN mechanism and the traditional but non-standard LOGIN
6607 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6608 to support most MUA software.
6610 The example PLAIN authenticator looks like this:
6613 # driver = plaintext
6614 # server_set_id = $auth2
6615 # server_prompts = :
6616 # server_condition = Authentication is not yet configured
6617 # server_advertise_condition = ${if def:tls_in_cipher }
6619 And the example LOGIN authenticator looks like this:
6622 # driver = plaintext
6623 # server_set_id = $auth1
6624 # server_prompts = <| Username: | Password:
6625 # server_condition = Authentication is not yet configured
6626 # server_advertise_condition = ${if def:tls_in_cipher }
6629 The &%server_set_id%& option makes Exim remember the authenticated username
6630 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6631 &%server_prompts%& option configures the &(plaintext)& authenticator so
6632 that it implements the details of the specific authentication mechanism,
6633 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6634 when Exim offers authentication to clients; in the examples, this is only
6635 when TLS or SSL has been started, so to enable the authenticators you also
6636 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6638 The &%server_condition%& setting defines how to verify that the username and
6639 password are correct. In the examples it just produces an error message.
6640 To make the authenticators work, you can use a string expansion
6641 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6643 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6644 usercode and password are in different positions.
6645 Chapter &<<CHAPplaintext>>& covers both.
6647 .ecindex IIDconfiwal
6651 . ////////////////////////////////////////////////////////////////////////////
6652 . ////////////////////////////////////////////////////////////////////////////
6654 .chapter "Regular expressions" "CHAPregexp"
6656 .cindex "regular expressions" "library"
6658 Exim supports the use of regular expressions in many of its options. It
6659 uses the PCRE2 regular expression library; this provides regular expression
6660 matching that is compatible with Perl 5. The syntax and semantics of
6661 regular expressions is discussed in
6662 online Perl manpages, in
6663 many Perl reference books, and also in
6664 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6665 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6666 . --- the http: URL here redirects to another page with the ISBN in the URL
6667 . --- where trying to use https: just redirects back to http:, so sticking
6668 . --- to the old URL for now. 2018-09-07.
6670 The documentation for the syntax and semantics of the regular expressions that
6671 are supported by PCRE2 is included in the PCRE2 distribution, and no further
6672 description is included here. The PCRE2 functions are called from Exim using
6673 the default option settings (that is, with no PCRE2 options set), except that
6674 the PCRE2_CASELESS option is set when the matching is required to be
6677 In most cases, when a regular expression is required in an Exim configuration,
6678 it has to start with a circumflex, in order to distinguish it from plain text
6679 or an &"ends with"& wildcard. In this example of a configuration setting, the
6680 second item in the colon-separated list is a regular expression.
6682 domains = a.b.c : ^\\d{3} : *.y.z : ...
6684 The doubling of the backslash is required because of string expansion that
6685 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6686 of this issue, and a way of avoiding the need for doubling backslashes. The
6687 regular expression that is eventually used in this example contains just one
6688 backslash. The circumflex is included in the regular expression, and has the
6689 normal effect of &"anchoring"& it to the start of the string that is being
6692 There are, however, two cases where a circumflex is not required for the
6693 recognition of a regular expression: these are the &%match%& condition in a
6694 string expansion, and the &%matches%& condition in an Exim filter file. In
6695 these cases, the relevant string is always treated as a regular expression; if
6696 it does not start with a circumflex, the expression is not anchored, and can
6697 match anywhere in the subject string.
6699 In all cases, if you want a regular expression to match at the end of a string,
6700 you must code the $ metacharacter to indicate this. For example:
6702 domains = ^\\d{3}\\.example
6704 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6707 domains = ^\\d{3}\\.example\$
6709 if you want &'example'& to be the top-level domain. The backslash before the
6710 $ is needed because string expansion also interprets dollar characters.
6714 . ////////////////////////////////////////////////////////////////////////////
6715 . ////////////////////////////////////////////////////////////////////////////
6717 .chapter "File and database lookups" "CHAPfdlookup"
6718 .scindex IIDfidalo1 "file" "lookups"
6719 .scindex IIDfidalo2 "database" "lookups"
6720 .cindex "lookup" "description of"
6721 Exim can be configured to look up data in files or databases as it processes
6722 messages. Two different kinds of syntax are used:
6725 A string that is to be expanded may contain explicit lookup requests. These
6726 cause parts of the string to be replaced by data that is obtained from the
6727 lookup. Lookups of this type are conditional expansion items. Different results
6728 can be defined for the cases of lookup success and failure. See chapter
6729 &<<CHAPexpand>>&, where string expansions are described in detail.
6730 The key for the lookup is &*specified*& as part of the string expansion.
6732 Lists of domains, hosts, and email addresses can contain lookup requests as a
6733 way of avoiding excessively long linear lists. In this case, the data that is
6734 returned by the lookup is often (but not always) discarded; whether the lookup
6735 succeeds or fails is what really counts. These kinds of list are described in
6736 chapter &<<CHAPdomhosaddlists>>&.
6737 The key for the lookup is &*implicit*&,
6738 given by the context in which the list is expanded.
6741 String expansions, lists, and lookups interact with each other in such a way
6742 that there is no order in which to describe any one of them that does not
6743 involve references to the others. Each of these three chapters makes more sense
6744 if you have read the other two first. If you are reading this for the first
6745 time, be aware that some of it will make a lot more sense after you have read
6746 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6748 .section "Examples of different lookup syntax" "SECID60"
6749 It is easy to confuse the two different kinds of lookup, especially as the
6750 lists that may contain the second kind are always expanded before being
6751 processed as lists. Therefore, they may also contain lookups of the first kind.
6752 Be careful to distinguish between the following two examples:
6754 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6755 domains = lsearch;/some/file
6757 The first uses a string expansion, the result of which must be a domain list.
6758 No strings have been specified for a successful or a failing lookup; the
6759 defaults in this case are the looked-up data and an empty string, respectively.
6760 The expansion takes place before the string is processed as a list, and the
6761 file that is searched could contain lines like this:
6763 192.168.3.4: domain1:domain2:...
6764 192.168.1.9: domain3:domain4:...
6766 When the lookup succeeds, the result of the expansion is a list of domains (and
6767 possibly other types of item that are allowed in domain lists).
6768 .cindex "tainted data" "de-tainting"
6769 The result of the expansion is not tainted.
6771 In the second example, the lookup is a single item in a domain list. It causes
6772 Exim to use a lookup to see if the domain that is being processed can be found
6774 The file could contains lines like this:
6779 Any data that follows the keys is not relevant when checking that the domain
6780 matches the list item.
6782 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6783 Consider a file containing lines like this:
6785 192.168.5.6: lsearch;/another/file
6787 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6788 first &%domains%& setting above generates the second setting, which therefore
6789 causes a second lookup to occur.
6791 The lookup type may optionally be followed by a comma
6792 and a comma-separated list of options.
6793 Each option is a &"name=value"& pair.
6794 Whether an option is meaningful depends on the lookup type.
6796 All lookups support the option &"cache=no_rd"&.
6797 If this is given then the cache that Exim manages for lookup results
6798 is not checked before doing the lookup.
6799 The result of the lookup is still written to the cache.
6801 The rest of this chapter describes the different lookup types that are
6802 available. Any of them can be used in any part of the configuration where a
6803 lookup is permitted.
6806 .section "Lookup types" "SECID61"
6807 .cindex "lookup" "types of"
6808 .cindex "single-key lookup" "definition of"
6809 Two different types of data lookup are implemented:
6812 The &'single-key'& type requires the specification of a file in which to look,
6813 and a single key to search for. The key must be a non-empty string for the
6814 lookup to succeed. The lookup type determines how the file is searched.
6815 .cindex "tainted data" "single-key lookups"
6816 The file string may not be tainted
6818 .cindex "tainted data" "de-tainting"
6819 All single-key lookups support the option &"ret=key"&.
6820 If this is given and the lookup
6821 (either underlying implementation or cached value)
6822 returns data, the result is replaced with a non-tainted
6823 version of the lookup key.
6824 .cindex "tainted data" "de-tainting"
6826 .cindex "query-style lookup" "definition of"
6827 The &'query-style'& type accepts a generalized database query. No particular
6828 key value is assumed by Exim for query-style lookups. You can use whichever
6829 Exim variables you need to construct the database query.
6832 The code for each lookup type is in a separate source file that is included in
6833 the binary of Exim only if the corresponding compile-time option is set. The
6834 default settings in &_src/EDITME_& are:
6839 which means that only linear searching and DBM lookups are included by default.
6840 For some types of lookup (e.g. SQL databases), you need to install appropriate
6841 libraries and header files before building Exim.
6846 .section "Single-key lookup types" "SECTsinglekeylookups"
6847 .cindex "lookup" "single-key types"
6848 .cindex "single-key lookup" "list of types"
6849 The following single-key lookup types are implemented:
6852 .cindex "cdb" "description of"
6853 .cindex "lookup" "cdb"
6854 .cindex "binary zero" "in lookup key"
6855 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6856 string without a terminating binary zero. The cdb format is designed for
6857 indexed files that are read frequently and never updated, except by total
6858 re-creation. As such, it is particularly suitable for large files containing
6859 aliases or other indexed data referenced by an MTA. Information about cdb and
6860 tools for building the files can be found in several places:
6862 &url(https://cr.yp.to/cdb.html)
6863 &url(https://www.corpit.ru/mjt/tinycdb.html)
6864 &url(https://packages.debian.org/stable/utils/freecdb)
6865 &url(https://github.com/philpennock/cdbtools) (in Go)
6867 A cdb distribution is not needed in order to build Exim with cdb support,
6868 because the code for reading cdb files is included directly in Exim itself.
6869 However, no means of building or testing cdb files is provided with Exim, so
6870 you need to obtain a cdb distribution in order to do this.
6872 .cindex "DBM" "lookup type"
6873 .cindex "lookup" "dbm"
6874 .cindex "binary zero" "in lookup key"
6875 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6876 DBM file by looking up the record with the given key. A terminating binary
6877 zero is included in the key that is passed to the DBM library. See section
6878 &<<SECTdb>>& for a discussion of DBM libraries.
6880 .cindex "Berkeley DB library" "file format"
6881 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6882 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6883 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6884 the DB_UNKNOWN option. This enables it to handle any of the types of database
6885 that the library supports, and can be useful for accessing DBM files created by
6886 other applications. (For earlier DB versions, DB_HASH is always used.)
6888 .cindex "lookup" "dbmjz"
6889 .cindex "lookup" "dbm &-- embedded NULs"
6891 .cindex "dbmjz lookup type"
6892 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6893 interpreted as an Exim list; the elements of the list are joined together with
6894 ASCII NUL characters to form the lookup key. An example usage would be to
6895 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6896 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6897 &(cram_md5)& authenticator.
6899 .cindex "lookup" "dbmnz"
6900 .cindex "lookup" "dbm &-- terminating zero"
6901 .cindex "binary zero" "in lookup key"
6903 .cindex "&_/etc/userdbshadow.dat_&"
6904 .cindex "dbmnz lookup type"
6905 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6906 is not included in the key that is passed to the DBM library. You may need this
6907 if you want to look up data in files that are created by or shared with some
6908 other application that does not use terminating zeros. For example, you need to
6909 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6910 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6911 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6912 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6914 .cindex "lookup" "dsearch"
6915 .cindex "dsearch lookup type"
6916 &(dsearch)&: The given file must be an
6918 directory path; this is searched for an entry
6919 whose name is the key by calling the &[lstat()]& function.
6921 contain any forward slash characters.
6922 If &[lstat()]& succeeds then so does the lookup.
6923 .cindex "tainted data" "dsearch result"
6924 The result is regarded as untainted.
6926 Options for the lookup can be given by appending them after the word "dsearch",
6927 separated by a comma. Options, if present, are a comma-separated list having
6928 each element starting with a tag name and an equals.
6930 Two options are supported, for the return value and for filtering match
6932 The "ret" option requests an alternate result value of
6933 the entire path for the entry. Example:
6935 ${lookup {passwd} dsearch,ret=full {/etc}}
6937 The default result is just the requested entry.
6938 The "filter" option requests that only directory entries of a given type
6939 are matched. The match value is one of "file", "dir" or "subdir" (the latter
6940 not matching "." or ".."). Example:
6942 ${lookup {passwd} dsearch,filter=file {/etc}}
6944 The default matching is for any entry type, including directories
6947 An example of how this
6948 lookup can be used to support virtual domains is given in section
6949 &<<SECTvirtualdomains>>&.
6951 .cindex "lookup" "iplsearch"
6952 .cindex "iplsearch lookup type"
6953 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6954 terminated by a colon or white space or the end of the line. The keys in the
6955 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6956 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6957 being interpreted as a key terminator. For example:
6959 1.2.3.4: data for 1.2.3.4
6960 192.168.0.0/16: data for 192.168.0.0/16
6961 "abcd::cdab": data for abcd::cdab
6962 "abcd:abcd::/32" data for abcd:abcd::/32
6964 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6965 file is searched linearly, using the CIDR masks where present, until a matching
6966 key is found. The first key that matches is used; there is no attempt to find a
6967 &"best"& match. Apart from the way the keys are matched, the processing for
6968 &(iplsearch)& is the same as for &(lsearch)&.
6970 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6971 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6972 lookup types support only literal keys.
6974 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6975 the implicit key is the host's IP address rather than its name (see section
6976 &<<SECThoslispatsikey>>&).
6978 &*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
6979 IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
6980 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.
6988 .cindex json "lookup type"
6989 .cindex JSON expansions
6990 &(json)&: The given file is a text file with a JSON structure.
6991 An element of the structure is extracted, defined by the search key.
6992 The key is a list of subelement selectors
6993 (colon-separated by default but changeable in the usual way)
6994 which are applied in turn to select smaller and smaller portions
6995 of the JSON structure.
6996 If a selector is numeric, it must apply to a JSON array; the (zero-based)
6997 nunbered array element is selected.
6998 Otherwise it must apply to a JSON object; the named element is selected.
6999 The final resulting element can be a simple JSON type or a JSON object
7000 or array; for the latter two a string-representation of the JSON
7002 For elements of type string, the returned value is de-quoted.
7008 .cindex database lmdb
7009 &(lmdb)&: The given file is an LMDB database.
7010 LMDB is a memory-mapped key-value store,
7011 with API modeled loosely on that of BerkeleyDB.
7012 See &url(https://symas.com/products/lightning-memory-mapped-database/)
7013 for the feature set and operation modes.
7015 Exim provides read-only access via the LMDB C library.
7016 The library can be obtained from &url(https://github.com/LMDB/lmdb)
7017 or your operating system package repository.
7018 To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&.
7020 You will need to separately create the LMDB database file,
7021 possibly using the &"mdb_load"& utility.
7025 .cindex "linear search"
7026 .cindex "lookup" "lsearch"
7027 .cindex "lsearch lookup type"
7028 .cindex "case sensitivity" "in lsearch lookup"
7029 &(lsearch)&: The given file is a text file that is searched linearly for a
7030 line beginning with the search key, terminated by a colon or white space or the
7031 end of the line. The search is case-insensitive; that is, upper and lower case
7032 letters are treated as the same. The first occurrence of the key that is found
7033 in the file is used.
7035 White space between the key and the colon is permitted. The remainder of the
7036 line, with leading and trailing white space removed, is the data. This can be
7037 continued onto subsequent lines by starting them with any amount of white
7038 space, but only a single space character is included in the data at such a
7039 junction. If the data begins with a colon, the key must be terminated by a
7044 Empty lines and lines beginning with # are ignored, even if they occur in the
7045 middle of an item. This is the traditional textual format of alias files. Note
7046 that the keys in an &(lsearch)& file are literal strings. There is no
7047 wildcarding of any kind.
7049 .cindex "lookup" "lsearch &-- colons in keys"
7050 .cindex "white space" "in lsearch key"
7051 In most &(lsearch)& files, keys are not required to contain colons or #
7052 characters, or white space. However, if you need this feature, it is available.
7053 If a key begins with a doublequote character, it is terminated only by a
7054 matching quote (or end of line), and the normal escaping rules apply to its
7055 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
7056 quoted keys (exactly as for unquoted keys). There is no special handling of
7057 quotes for the data part of an &(lsearch)& line.
7060 .cindex "NIS lookup type"
7061 .cindex "lookup" "NIS"
7062 .cindex "binary zero" "in lookup key"
7063 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
7064 the given key, without a terminating binary zero. There is a variant called
7065 &(nis0)& which does include the terminating binary zero in the key. This is
7066 reportedly needed for Sun-style alias files. Exim does not recognize NIS
7067 aliases; the full map names must be used.
7070 .cindex "wildlsearch lookup type"
7071 .cindex "lookup" "wildlsearch"
7072 .cindex "nwildlsearch lookup type"
7073 .cindex "lookup" "nwildlsearch"
7074 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
7075 &(lsearch)&, but instead of being interpreted as a literal string, each key in
7076 the file may be wildcarded. The difference between these two lookup types is
7077 that for &(wildlsearch)&, each key in the file is string-expanded before being
7078 used, whereas for &(nwildlsearch)&, no expansion takes place.
7080 .cindex "case sensitivity" "in (n)wildlsearch lookup"
7081 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
7082 file that are regular expressions can be made case-sensitive by the use of
7083 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
7085 . ==== As this is a nested list, any displays it contains must be indented
7086 . ==== as otherwise they are too far to the left.
7089 The string may begin with an asterisk to mean &"ends with"&. For example:
7091 *.a.b.c data for anything.a.b.c
7092 *fish data for anythingfish
7095 The string may begin with a circumflex to indicate a regular expression. For
7096 example, for &(wildlsearch)&:
7098 ^\N\d+\.a\.b\N data for <digits>.a.b
7100 Note the use of &`\N`& to disable expansion of the contents of the regular
7101 expression. If you are using &(nwildlsearch)&, where the keys are not
7102 string-expanded, the equivalent entry is:
7104 ^\d+\.a\.b data for <digits>.a.b
7106 The case-insensitive flag is set at the start of compiling the regular
7107 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
7108 For example, to make the entire pattern case-sensitive:
7110 ^(?-i)\d+\.a\.b data for <digits>.a.b
7113 If the regular expression contains white space or colon characters, you must
7114 either quote it (see &(lsearch)& above), or represent these characters in other
7115 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
7116 colon. This may be easier than quoting, because if you quote, you have to
7117 escape all the backslashes inside the quotes.
7119 &*Note*&: It is not possible to capture substrings in a regular expression
7120 match for later use, because the results of all lookups are cached. If a lookup
7121 is repeated, the result is taken from the cache, and no actual pattern matching
7122 takes place. The values of all the numeric variables are unset after a
7123 &((n)wildlsearch)& match.
7126 Although I cannot see it being of much use, the general matching function that
7127 is used to implement &((n)wildlsearch)& means that the string may begin with a
7128 lookup name terminated by a semicolon, and followed by lookup data. For
7131 cdb;/some/file data for keys that match the file
7133 The data that is obtained from the nested lookup is discarded.
7136 Keys that do not match any of these patterns are interpreted literally. The
7137 continuation rules for the data are the same as for &(lsearch)&, and keys may
7138 be followed by optional colons.
7140 &*Warning*&: Unlike most other single-key lookup types, a file of data for
7141 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
7142 lookup types support only literal keys.
7145 .cindex "spf lookup type"
7146 .cindex "lookup" "spf"
7147 &(spf)&: If Exim is built with SPF support, manual lookups can be done
7148 (as opposed to the standard ACL condition method).
7149 For details see section &<<SECSPF>>&.
7153 .section "Query-style lookup types" "SECTquerystylelookups"
7154 .cindex "lookup" "query-style types"
7155 .cindex "query-style lookup" "list of types"
7156 The supported query-style lookup types are listed below. Further details about
7157 many of them are given in later sections.
7160 .cindex "DNS" "as a lookup type"
7161 .cindex "lookup" "DNS"
7162 &(dnsdb)&: This does a DNS search for one or more records whose domain names
7163 are given in the supplied query. The resulting data is the contents of the
7164 records. See section &<<SECTdnsdb>>&.
7166 .cindex "InterBase lookup type"
7167 .cindex "lookup" "InterBase"
7168 &(ibase)&: This does a lookup in an InterBase database.
7170 .cindex "LDAP" "lookup type"
7171 .cindex "lookup" "LDAP"
7172 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
7173 returns attributes from a single entry. There is a variant called &(ldapm)&
7174 that permits values from multiple entries to be returned. A third variant
7175 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
7176 any attribute values. See section &<<SECTldap>>&.
7178 .cindex "MySQL" "lookup type"
7179 .cindex "lookup" "MySQL"
7180 &(mysql)&: The format of the query is an SQL statement that is passed to a
7181 MySQL database. See section &<<SECTsql>>&.
7183 .cindex "NIS+ lookup type"
7184 .cindex "lookup" "NIS+"
7185 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
7186 the field to be returned. See section &<<SECTnisplus>>&.
7188 .cindex "Oracle" "lookup type"
7189 .cindex "lookup" "Oracle"
7190 &(oracle)&: The format of the query is an SQL statement that is passed to an
7191 Oracle database. See section &<<SECTsql>>&.
7193 .cindex "lookup" "passwd"
7194 .cindex "passwd lookup type"
7195 .cindex "&_/etc/passwd_&"
7196 &(passwd)& is a query-style lookup with queries that are just user names. The
7197 lookup calls &[getpwnam()]& to interrogate the system password data, and on
7198 success, the result string is the same as you would get from an &(lsearch)&
7199 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
7200 password value. For example:
7202 *:42:42:King Rat:/home/kr:/bin/bash
7205 .cindex "PostgreSQL lookup type"
7206 .cindex "lookup" "PostgreSQL"
7207 &(pgsql)&: The format of the query is an SQL statement that is passed to a
7208 PostgreSQL database. See section &<<SECTsql>>&.
7211 .cindex "Redis lookup type"
7212 .cindex lookup Redis
7213 &(redis)&: The format of the query is either a simple get or simple set,
7214 passed to a Redis database. See section &<<SECTsql>>&.
7217 .cindex "sqlite lookup type"
7218 .cindex "lookup" "sqlite"
7219 &(sqlite)&: The format of the query is
7220 an SQL statement that is passed to an SQLite database. See section &<<SECTsqlite>>&.
7223 &(testdb)&: This is a lookup type that is used for testing Exim. It is
7224 not likely to be useful in normal operation.
7226 .cindex "whoson lookup type"
7227 .cindex "lookup" "whoson"
7228 . --- still http:-only, 2018-09-07
7229 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
7230 allows a server to check whether a particular (dynamically allocated) IP
7231 address is currently allocated to a known (trusted) user and, optionally, to
7232 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
7233 at one time for &"POP before SMTP"& authentication, but that approach has been
7234 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
7235 &"POP before SMTP"& checking using ACL statements such as
7237 require condition = \
7238 ${lookup whoson {$sender_host_address}{yes}{no}}
7240 The query consists of a single IP address. The value returned is the name of
7241 the authenticated user, which is stored in the variable &$value$&. However, in
7242 this example, the data in &$value$& is not used; the result of the lookup is
7243 one of the fixed strings &"yes"& or &"no"&.
7248 .section "Temporary errors in lookups" "SECID63"
7249 .cindex "lookup" "temporary error in"
7250 Lookup functions can return temporary error codes if the lookup cannot be
7251 completed. For example, an SQL or LDAP database might be unavailable. For this
7252 reason, it is not advisable to use a lookup that might do this for critical
7253 options such as a list of local domains.
7255 When a lookup cannot be completed in a router or transport, delivery
7256 of the message (to the relevant address) is deferred, as for any other
7257 temporary error. In other circumstances Exim may assume the lookup has failed,
7258 or may give up altogether.
7262 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
7263 .cindex "wildcard lookups"
7264 .cindex "lookup" "default values"
7265 .cindex "lookup" "wildcard"
7266 .cindex "lookup" "* added to type"
7267 .cindex "default" "in single-key lookups"
7268 In this context, a &"default value"& is a value specified by the administrator
7269 that is to be used if a lookup fails.
7271 &*Note:*& This section applies only to single-key lookups. For query-style
7272 lookups, the facilities of the query language must be used. An attempt to
7273 specify a default for a query-style lookup provokes an error.
7275 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
7276 and the initial lookup fails, the key &"*"& is looked up in the file to
7277 provide a default value. See also the section on partial matching below.
7279 .cindex "*@ with single-key lookup"
7280 .cindex "lookup" "*@ added to type"
7281 .cindex "alias file" "per-domain default"
7282 Alternatively, if &"*@"& is added to a single-key lookup type (for example
7283 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
7284 character, a second lookup is done with everything before the last @ replaced
7285 by *. This makes it possible to provide per-domain defaults in alias files
7286 that include the domains in the keys. If the second lookup fails (or doesn't
7287 take place because there is no @ in the key), &"*"& is looked up.
7288 For example, a &(redirect)& router might contain:
7290 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
7292 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
7293 looks up these keys, in this order:
7299 The data is taken from whichever key it finds first. &*Note*&: In an
7300 &(lsearch)& file, this does not mean the first of these keys in the file. A
7301 complete scan is done for each key, and only if it is not found at all does
7302 Exim move on to try the next key.
7306 .section "Partial matching in single-key lookups" "SECTpartiallookup"
7307 .cindex "partial matching"
7308 .cindex "wildcard lookups"
7309 .cindex "lookup" "partial matching"
7310 .cindex "lookup" "wildcard"
7311 .cindex "asterisk" "in search type"
7312 The normal operation of a single-key lookup is to search the file for an exact
7313 match with the given key. However, in a number of situations where domains are
7314 being looked up, it is useful to be able to do partial matching. In this case,
7315 information in the file that has a key starting with &"*."& is matched by any
7316 domain that ends with the components that follow the full stop. For example, if
7317 a key in a DBM file is
7319 *.dates.fict.example
7321 then when partial matching is enabled this is matched by (amongst others)
7322 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
7323 by &'dates.fict.example'&, if that does not appear as a separate key in the
7326 &*Note*&: Partial matching is not available for query-style lookups. It is
7327 also not available for any lookup items in address lists (see section
7328 &<<SECTaddresslist>>&).
7330 Partial matching is implemented by doing a series of separate lookups using
7331 keys constructed by modifying the original subject key. This means that it can
7332 be used with any of the single-key lookup types, provided that
7333 partial matching keys
7334 beginning with a special prefix (default &"*."&) are included in the data file.
7335 Keys in the file that do not begin with the prefix are matched only by
7336 unmodified subject keys when partial matching is in use.
7338 Partial matching is requested by adding the string &"partial-"& to the front of
7339 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
7340 is done, the subject key is first looked up unmodified; if that fails, &"*."&
7341 is added at the start of the subject key, and it is looked up again. If that
7342 fails, further lookups are tried with dot-separated components removed from the
7343 start of the subject key, one-by-one, and &"*."& added on the front of what
7346 A minimum number of two non-* components are required. This can be adjusted
7347 by including a number before the hyphen in the search type. For example,
7348 &%partial3-lsearch%& specifies a minimum of three non-* components in the
7349 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
7350 subject key is &'2250.dates.fict.example'& then the following keys are looked
7351 up when the minimum number of non-* components is two:
7353 2250.dates.fict.example
7354 *.2250.dates.fict.example
7355 *.dates.fict.example
7358 As soon as one key in the sequence is successfully looked up, the lookup
7361 .cindex "lookup" "partial matching &-- changing prefix"
7362 .cindex "prefix" "for partial matching"
7363 The use of &"*."& as the partial matching prefix is a default that can be
7364 changed. The motivation for this feature is to allow Exim to operate with file
7365 formats that are used by other MTAs. A different prefix can be supplied in
7366 parentheses instead of the hyphen after &"partial"&. For example:
7368 domains = partial(.)lsearch;/some/file
7370 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
7371 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
7372 components is unchanged). The prefix may consist of any punctuation characters
7373 other than a closing parenthesis. It may be empty, for example:
7375 domains = partial1()cdb;/some/file
7377 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
7378 &`a.b.c`&, &`b.c`&, and &`c`&.
7380 If &"partial0"& is specified, what happens at the end (when the lookup with
7381 just one non-wild component has failed, and the original key is shortened right
7382 down to the null string) depends on the prefix:
7385 If the prefix has zero length, the whole lookup fails.
7387 If the prefix has length 1, a lookup for just the prefix is done. For
7388 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
7390 Otherwise, if the prefix ends in a dot, the dot is removed, and the
7391 remainder is looked up. With the default prefix, therefore, the final lookup is
7392 for &"*"& on its own.
7394 Otherwise, the whole prefix is looked up.
7398 If the search type ends in &"*"& or &"*@"& (see section
7399 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
7400 this implies happens after all partial lookups have failed. If &"partial0"& is
7401 specified, adding &"*"& to the search type has no effect with the default
7402 prefix, because the &"*"& key is already included in the sequence of partial
7403 lookups. However, there might be a use for lookup types such as
7404 &"partial0(.)lsearch*"&.
7406 The use of &"*"& in lookup partial matching differs from its use as a wildcard
7407 in domain lists and the like. Partial matching works only in terms of
7408 dot-separated components; a key such as &`*fict.example`&
7409 in a database file is useless, because the asterisk in a partial matching
7410 subject key is always followed by a dot.
7415 .section "Lookup caching" "SECID64"
7416 .cindex "lookup" "caching"
7417 .cindex "caching" "lookup data"
7418 Exim caches all lookup results in order to avoid needless repetition of
7419 lookups. However, because (apart from the daemon) Exim operates as a collection
7420 of independent, short-lived processes, this caching applies only within a
7421 single Exim process. There is no inter-process lookup caching facility.
7423 If an option &"cache=no_rd"& is used on the lookup then
7424 the cache is only written to, cached data is not used for the operation
7425 and a real lookup is done.
7427 For single-key lookups, Exim keeps the relevant files open in case there is
7428 another lookup that needs them. In some types of configuration this can lead to
7429 many files being kept open for messages with many recipients. To avoid hitting
7430 the operating system limit on the number of simultaneously open files, Exim
7431 closes the least recently used file when it needs to open more files than its
7432 own internal limit, which can be changed via the &%lookup_open_max%& option.
7434 The single-key lookup files are closed and the lookup caches are flushed at
7435 strategic points during delivery &-- for example, after all routing is
7441 .section "Quoting lookup data" "SECID65"
7442 .cindex "lookup" "quoting"
7443 .cindex "quoting" "in lookups"
7444 When data from an incoming message is included in a query-style lookup, there
7445 is the possibility of special characters in the data messing up the syntax of
7446 the query. For example, a NIS+ query that contains
7450 will be broken if the local part happens to contain a closing square bracket.
7451 For NIS+, data can be enclosed in double quotes like this:
7453 [name="$local_part"]
7455 but this still leaves the problem of a double quote in the data. The rule for
7456 NIS+ is that double quotes must be doubled. Other lookup types have different
7457 rules, and to cope with the differing requirements, an expansion operator
7458 of the following form is provided:
7460 ${quote_<lookup-type>:<string>}
7462 For example, the safest way to write the NIS+ query is
7464 [name="${quote_nisplus:$local_part}"]
7466 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
7467 operator can be used for all lookup types, but has no effect for single-key
7468 lookups, since no quoting is ever needed in their key strings.
7473 .section "More about dnsdb" "SECTdnsdb"
7474 .cindex "dnsdb lookup"
7475 .cindex "lookup" "dnsdb"
7476 .cindex "DNS" "as a lookup type"
7477 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7478 of a record type and a domain name, separated by an equals sign. For example,
7479 an expansion string could contain:
7481 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7483 If the lookup succeeds, the result is placed in &$value$&, which in this case
7484 is used on its own as the result. If the lookup does not succeed, the
7485 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7486 &<<SECTforexpfai>>& for an explanation of what this means.
7488 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7489 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7490 If no type is given, TXT is assumed.
7492 For any record type, if multiple records are found, the data is returned as a
7493 concatenation, with newline as the default separator. The order, of course,
7494 depends on the DNS resolver. You can specify a different separator character
7495 between multiple records by putting a right angle-bracket followed immediately
7496 by the new separator at the start of the query. For example:
7498 ${lookup dnsdb{>: a=host1.example}}
7500 It is permitted to specify a space as the separator character. Further
7501 white space is ignored.
7502 For lookup types that return multiple fields per record,
7503 an alternate field separator can be specified using a comma after the main
7504 separator character, followed immediately by the field separator.
7506 .cindex "PTR record" "in &(dnsdb)& lookup"
7507 When the type is PTR,
7508 the data can be an IP address, written as normal; inversion and the addition of
7509 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7511 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7513 If the data for a PTR record is not a syntactically valid IP address, it is not
7514 altered and nothing is added.
7516 .cindex "MX record" "in &(dnsdb)& lookup"
7517 .cindex "SRV record" "in &(dnsdb)& lookup"
7518 For an MX lookup, both the preference value and the host name are returned for
7519 each record, separated by a space. For an SRV lookup, the priority, weight,
7520 port, and host name are returned for each record, separated by spaces.
7521 The field separator can be modified as above.
7523 .cindex "TXT record" "in &(dnsdb)& lookup"
7524 .cindex "SPF record" "in &(dnsdb)& lookup"
7525 For TXT records with multiple items of data, only the first item is returned,
7526 unless a field separator is specified.
7527 To concatenate items without a separator, use a semicolon instead.
7529 default behaviour is to concatenate multiple items without using a separator.
7531 ${lookup dnsdb{>\n,: txt=a.b.example}}
7532 ${lookup dnsdb{>\n; txt=a.b.example}}
7533 ${lookup dnsdb{spf=example.org}}
7535 It is permitted to specify a space as the separator character. Further
7536 white space is ignored.
7538 .cindex "SOA record" "in &(dnsdb)& lookup"
7539 For an SOA lookup, while no result is obtained the lookup is redone with
7540 successively more leading components dropped from the given domain.
7541 Only the primary-nameserver field is returned unless a field separator is
7544 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7547 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7548 .cindex "dnsdb modifiers"
7549 .cindex "modifiers" "dnsdb"
7550 .cindex "options" "dnsdb"
7551 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7552 each followed by a comma,
7553 that may appear before the record type.
7555 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7556 temporary DNS error for any of them, the behaviour is controlled by
7557 a defer-option modifier.
7558 The possible keywords are
7559 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7560 With &"strict"& behaviour, any temporary DNS error causes the
7561 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7562 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7563 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7564 error causes the whole lookup to defer only if none of the other lookups
7565 succeed. The default is &"lax"&, so the following lookups are equivalent:
7567 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7568 ${lookup dnsdb{a=one.host.com:two.host.com}}
7570 Thus, in the default case, as long as at least one of the DNS lookups
7571 yields some data, the lookup succeeds.
7573 .cindex "DNSSEC" "dns lookup"
7574 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7575 The possible keywords are
7576 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7577 With &"strict"& or &"lax"& DNSSEC information is requested
7579 With &"strict"& a response from the DNS resolver that
7580 is not labelled as authenticated data
7581 is treated as equivalent to a temporary DNS error.
7582 The default is &"lax"&.
7584 See also the &$lookup_dnssec_authenticated$& variable.
7586 .cindex timeout "dns lookup"
7587 .cindex "DNS" timeout
7588 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7589 The form is &"retrans_VAL"& where VAL is an Exim time specification
7591 The default value is set by the main configuration option &%dns_retrans%&.
7593 Retries for the dnsdb lookup can be controlled by a retry modifier.
7594 The form if &"retry_VAL"& where VAL is an integer.
7595 The default count is set by the main configuration option &%dns_retry%&.
7597 .cindex caching "of dns lookup"
7598 .cindex TTL "of dns lookup"
7600 Dnsdb lookup results are cached within a single process (and its children).
7601 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7602 value of the set of returned DNS records.
7605 .section "Pseudo dnsdb record types" "SECID66"
7606 .cindex "MX record" "in &(dnsdb)& lookup"
7607 By default, both the preference value and the host name are returned for
7608 each MX record, separated by a space. If you want only host names, you can use
7609 the pseudo-type MXH:
7611 ${lookup dnsdb{mxh=a.b.example}}
7613 In this case, the preference values are omitted, and just the host names are
7616 .cindex "name server for enclosing domain"
7617 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7618 records on the given domain, but if none are found, it removes the first
7619 component of the domain name, and tries again. This process continues until NS
7620 records are found or there are no more components left (or there is a DNS
7621 error). In other words, it may return the name servers for a top-level domain,
7622 but it never returns the root name servers. If there are no NS records for the
7623 top-level domain, the lookup fails. Consider these examples:
7625 ${lookup dnsdb{zns=xxx.quercite.com}}
7626 ${lookup dnsdb{zns=xxx.edu}}
7628 Assuming that in each case there are no NS records for the full domain name,
7629 the first returns the name servers for &%quercite.com%&, and the second returns
7630 the name servers for &%edu%&.
7632 You should be careful about how you use this lookup because, unless the
7633 top-level domain does not exist, the lookup always returns some host names. The
7634 sort of use to which this might be put is for seeing if the name servers for a
7635 given domain are on a blacklist. You can probably assume that the name servers
7636 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7639 .cindex "CSA" "in &(dnsdb)& lookup"
7640 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7641 records according to the CSA rules, which are described in section
7642 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7643 not sufficient because of the extra parent domain search behaviour of CSA. The
7644 result of a successful lookup such as:
7646 ${lookup dnsdb {csa=$sender_helo_name}}
7648 has two space-separated fields: an authorization code and a target host name.
7649 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7650 authorization required but absent, or &"?"& for unknown.
7652 .cindex "A+" "in &(dnsdb)& lookup"
7653 The pseudo-type A+ performs an AAAA
7654 and then an A lookup. All results are returned; defer processing
7655 (see below) is handled separately for each lookup. Example:
7657 ${lookup dnsdb {>; a+=$sender_helo_name}}
7661 .section "Multiple dnsdb lookups" "SECID67"
7662 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7663 However, you can specify a list of domains or IP addresses in a single
7664 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7665 the default separator, but with the ability to change this. For example:
7667 ${lookup dnsdb{one.domain.com:two.domain.com}}
7668 ${lookup dnsdb{a=one.host.com:two.host.com}}
7669 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7671 In order to retain backwards compatibility, there is one special case: if
7672 the lookup type is PTR and no change of separator is specified, Exim looks
7673 to see if the rest of the string is precisely one IPv6 address. In this
7674 case, it does not treat it as a list.
7676 The data from each lookup is concatenated, with newline separators by default,
7677 in the same way that multiple DNS records for a single item are handled. A
7678 different separator can be specified, as described above.
7683 .section "More about LDAP" "SECTldap"
7684 .cindex "LDAP" "lookup, more about"
7685 .cindex "lookup" "LDAP"
7686 .cindex "Solaris" "LDAP"
7687 The original LDAP implementation came from the University of Michigan; this has
7688 become &"Open LDAP"&, and there are now two different releases. Another
7689 implementation comes from Netscape, and Solaris 7 and subsequent releases
7690 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7691 the lookup function level, their error handling is different. For this reason
7692 it is necessary to set a compile-time variable when building Exim with LDAP, to
7693 indicate which LDAP library is in use. One of the following should appear in
7694 your &_Local/Makefile_&:
7696 LDAP_LIB_TYPE=UMICHIGAN
7697 LDAP_LIB_TYPE=OPENLDAP1
7698 LDAP_LIB_TYPE=OPENLDAP2
7699 LDAP_LIB_TYPE=NETSCAPE
7700 LDAP_LIB_TYPE=SOLARIS
7702 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7703 same interface as the University of Michigan version.
7705 There are three LDAP lookup types in Exim. These behave slightly differently in
7706 the way they handle the results of a query:
7709 &(ldap)& requires the result to contain just one entry; if there are more, it
7712 &(ldapdn)& also requires the result to contain just one entry, but it is the
7713 Distinguished Name that is returned rather than any attribute values.
7715 &(ldapm)& permits the result to contain more than one entry; the attributes
7716 from all of them are returned.
7720 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7721 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7722 the data returned by a successful lookup is described in the next section.
7723 First we explain how LDAP queries are coded.
7726 .section "Format of LDAP queries" "SECTforldaque"
7727 .cindex "LDAP" "query format"
7728 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7729 the configuration of a &(redirect)& router one might have this setting:
7731 data = ${lookup ldap \
7732 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7733 c=UK?mailbox?base?}}
7735 .cindex "LDAP" "with TLS"
7736 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7737 secure (encrypted) LDAP connections. The second of these ensures that an
7738 encrypted TLS connection is used.
7740 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7741 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7742 See the &%ldap_start_tls%& option.
7744 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7745 controlled. Every part of the TLS configuration can be configured by settings in
7746 &_exim.conf_&. Depending on the version of the client libraries installed on
7747 your system, some of the initialization may have required setting options in
7748 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7749 certificates. This revealed a nuance where the current UID that exim was
7750 running as could affect which config files it read. With Exim 4.83, these
7751 methods become optional, only taking effect if not specifically set in
7755 .section "LDAP quoting" "SECID68"
7756 .cindex "LDAP" "quoting"
7757 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7758 and the second because the LDAP query is represented as a URL. Furthermore,
7759 within an LDAP query, two different kinds of quoting are required. For this
7760 reason, there are two different LDAP-specific quoting operators.
7762 The &%quote_ldap%& operator is designed for use on strings that are part of
7763 filter specifications. Conceptually, it first does the following conversions on
7771 in accordance with RFC 2254. The resulting string is then quoted according
7772 to the rules for URLs, that is, all non-alphanumeric characters except
7776 are converted to their hex values, preceded by a percent sign. For example:
7778 ${quote_ldap: a(bc)*, a<yz>; }
7782 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7784 Removing the URL quoting, this is (with a leading and a trailing space):
7786 a\28bc\29\2A, a<yz>;
7788 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7789 base DN specifications in queries. Conceptually, it first converts the string
7790 by inserting a backslash in front of any of the following characters:
7794 It also inserts a backslash before any leading spaces or # characters, and
7795 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7796 is then quoted according to the rules for URLs. For example:
7798 ${quote_ldap_dn: a(bc)*, a<yz>; }
7802 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7804 Removing the URL quoting, this is (with a trailing space):
7806 \ a(bc)*\, a\<yz\>\;\
7808 There are some further comments about quoting in the section on LDAP
7809 authentication below.
7812 .section "LDAP connections" "SECID69"
7813 .cindex "LDAP" "connections"
7814 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7815 is in use, via a Unix domain socket. The example given above does not specify
7816 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7819 ldap://<hostname>:<port>/...
7821 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7822 used. When no server is specified in a query, a list of default servers is
7823 taken from the &%ldap_default_servers%& configuration option. This supplies a
7824 colon-separated list of servers which are tried in turn until one successfully
7825 handles a query, or there is a serious error. Successful handling either
7826 returns the requested data, or indicates that it does not exist. Serious errors
7827 are syntactical, or multiple values when only a single value is expected.
7828 Errors which cause the next server to be tried are connection failures, bind
7829 failures, and timeouts.
7831 For each server name in the list, a port number can be given. The standard way
7832 of specifying a host and port is to use a colon separator (RFC 1738). Because
7833 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7834 doubled. For example
7836 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7838 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7839 to the LDAP library with no server name, and the library's default (normally
7840 the local host) is used.
7842 If you are using the OpenLDAP library, you can connect to an LDAP server using
7843 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7844 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7845 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7848 For this type of connection, instead of a host name for the server, a pathname
7849 for the socket is required, and the port number is not relevant. The pathname
7850 can be specified either as an item in &%ldap_default_servers%&, or inline in
7851 the query. In the former case, you can have settings such as
7853 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7855 When the pathname is given in the query, you have to escape the slashes as
7856 &`%2F`& to fit in with the LDAP URL syntax. For example:
7858 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7860 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7861 a pathname, it uses the Unix domain socket code, even if the query actually
7862 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7863 socket connection. This behaviour means that you can use a setting of
7864 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7865 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7866 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7869 If an explicit &`ldapi`& type is given in a query when a host name is
7870 specified, an error is diagnosed. However, if there are more items in
7871 &%ldap_default_servers%&, they are tried. In other words:
7874 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7877 Using &`ldapi`& with a host name causes an error.
7881 Using &`ldapi`& with no host or path in the query, and no setting of
7882 &%ldap_default_servers%&, does whatever the library does by default.
7886 .section "LDAP authentication and control information" "SECID70"
7887 .cindex "LDAP" "authentication"
7888 The LDAP URL syntax provides no way of passing authentication and other control
7889 information to the server. To make this possible, the URL in an LDAP query may
7890 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7891 spaces. If a value contains spaces it must be enclosed in double quotes, and
7892 when double quotes are used, backslash is interpreted in the usual way inside
7893 them. The following names are recognized:
7895 &`DEREFERENCE`& set the dereferencing parameter
7896 &`NETTIME `& set a timeout for a network operation
7897 &`USER `& set the DN, for authenticating the LDAP bind
7898 &`PASS `& set the password, likewise
7899 &`REFERRALS `& set the referrals parameter
7900 &`SERVERS `& set alternate server list for this query only
7901 &`SIZE `& set the limit for the number of entries returned
7902 &`TIME `& set the maximum waiting time for a query
7904 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7905 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7906 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7907 library from trying to follow referrals issued by the LDAP server.
7909 .cindex LDAP timeout
7910 .cindex timeout "LDAP lookup"
7911 The name CONNECT is an obsolete name for NETTIME, retained for
7912 backwards compatibility. This timeout (specified as a number of seconds) is
7913 enforced from the client end for operations that can be carried out over a
7914 network. Specifically, it applies to network connections and calls to the
7915 &'ldap_result()'& function. If the value is greater than zero, it is used if
7916 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7917 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7918 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7919 Netscape SDK; for OpenLDAP no action is taken.
7921 The TIME parameter (also a number of seconds) is passed to the server to
7922 set a server-side limit on the time taken to complete a search.
7924 The SERVERS parameter allows you to specify an alternate list of ldap servers
7925 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7926 default list of ldap servers, and a single lookup can specify a single ldap
7927 server to use. But when you need to do a lookup with a list of servers that is
7928 different than the default list (maybe different order, maybe a completely
7929 different set of servers), the SERVERS parameter allows you to specify this
7930 alternate list (colon-separated).
7932 Here is an example of an LDAP query in an Exim lookup that uses some of these
7933 values. This is a single line, folded to fit on the page:
7936 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7937 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7940 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7941 any of the auxiliary data. Exim configuration settings that include lookups
7942 which contain password information should be preceded by &"hide"& to prevent
7943 non-admin users from using the &%-bP%& option to see their values.
7945 The auxiliary data items may be given in any order. The default is no
7946 connection timeout (the system timeout is used), no user or password, no limit
7947 on the number of entries returned, and no time limit on queries.
7949 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7950 removes any URL quoting that it may contain before passing it LDAP. Apparently
7951 some libraries do this for themselves, but some do not. Removing the URL
7952 quoting has two advantages:
7955 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7956 DNs as with DNs inside actual queries.
7958 It permits spaces inside USER= DNs.
7961 For example, a setting such as
7963 USER=cn=${quote_ldap_dn:$1}
7965 should work even if &$1$& contains spaces.
7967 Expanded data for the PASS= value should be quoted using the &%quote%&
7968 expansion operator, rather than the LDAP quote operators. The only reason this
7969 field needs quoting is to ensure that it conforms to the Exim syntax, which
7970 does not allow unquoted spaces. For example:
7974 The LDAP authentication mechanism can be used to check passwords as part of
7975 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7980 .section "Format of data returned by LDAP" "SECID71"
7981 .cindex "LDAP" "returned data formats"
7982 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7983 as a sequence of values, for example
7985 cn=manager,o=University of Cambridge,c=UK
7987 The &(ldap)& lookup type generates an error if more than one entry matches the
7988 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7989 the result between the data from different entries. It is possible for multiple
7990 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7991 you know that whatever values are returned all came from a single entry in the
7994 In the common case where you specify a single attribute in your LDAP query, the
7995 result is not quoted, and does not contain the attribute name. If the attribute
7996 has multiple values, they are separated by commas. Any comma that is
7997 part of an attribute's value is doubled.
7999 If you specify multiple attributes, the result contains space-separated, quoted
8000 strings, each preceded by the attribute name and an equals sign. Within the
8001 quotes, the quote character, backslash, and newline are escaped with
8002 backslashes, and commas are used to separate multiple values for the attribute.
8003 Any commas in attribute values are doubled
8004 (permitting treatment of the values as a comma-separated list).
8005 Apart from the escaping, the string within quotes takes the same form as the
8006 output when a single attribute is requested. Specifying no attributes is the
8007 same as specifying all of an entry's attributes.
8009 Here are some examples of the output format. The first line of each pair is an
8010 LDAP query, and the second is the data that is returned. The attribute called
8011 &%attr1%& has two values, one of them with an embedded comma, whereas
8012 &%attr2%& has only one value. Both attributes are derived from &%attr%&
8013 (they have SUP &%attr%& in their schema definitions).
8016 ldap:///o=base?attr1?sub?(uid=fred)
8019 ldap:///o=base?attr2?sub?(uid=fred)
8022 ldap:///o=base?attr?sub?(uid=fred)
8023 value1.1,value1,,2,value two
8025 ldap:///o=base?attr1,attr2?sub?(uid=fred)
8026 attr1="value1.1,value1,,2" attr2="value two"
8028 ldap:///o=base??sub?(uid=fred)
8029 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
8032 make use of Exim's &%-be%& option to run expansion tests and thereby check the
8033 results of LDAP lookups.
8034 The &%extract%& operator in string expansions can be used to pick out
8035 individual fields from data that consists of &'key'&=&'value'& pairs.
8036 The &%listextract%& operator should be used to pick out individual values
8037 of attributes, even when only a single value is expected.
8038 The doubling of embedded commas allows you to use the returned data as a
8039 comma separated list (using the "<," syntax for changing the input list separator).
8044 .section "More about NIS+" "SECTnisplus"
8045 .cindex "NIS+ lookup type"
8046 .cindex "lookup" "NIS+"
8047 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
8048 and field name. If this is given, the result of a successful query is the
8049 contents of the named field; otherwise the result consists of a concatenation
8050 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
8051 values containing spaces are quoted. For example, the query
8053 [name=mg1456],passwd.org_dir
8055 might return the string
8057 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
8058 home=/home/mg1456 shell=/bin/bash shadow=""
8060 (split over two lines here to fit on the page), whereas
8062 [name=mg1456],passwd.org_dir:gcos
8068 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
8069 for the given indexed key. The effect of the &%quote_nisplus%& expansion
8070 operator is to double any quote characters within the text.
8074 .section "SQL lookups" "SECTsql"
8075 .cindex "SQL lookup types"
8076 .cindex "MySQL" "lookup type"
8077 .cindex "PostgreSQL lookup type"
8078 .cindex "lookup" "MySQL"
8079 .cindex "lookup" "PostgreSQL"
8080 .cindex "Oracle" "lookup type"
8081 .cindex "lookup" "Oracle"
8082 .cindex "InterBase lookup type"
8083 .cindex "lookup" "InterBase"
8084 .cindex "Redis lookup type"
8085 .cindex lookup Redis
8086 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
8088 databases. Queries for these databases contain SQL statements, so an example
8091 ${lookup mysql{select mailbox from users where id='userx'}\
8094 If the result of the query contains more than one field, the data for each
8095 field in the row is returned, preceded by its name, so the result of
8097 ${lookup pgsql{select home,name from users where id='userx'}\
8102 home=/home/userx name="Mister X"
8104 Empty values and values containing spaces are double quoted, with embedded
8105 quotes escaped by a backslash. If the result of the query contains just one
8106 field, the value is passed back verbatim, without a field name, for example:
8110 If the result of the query yields more than one row, it is all concatenated,
8111 with a newline between the data for each row.
8114 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
8115 .cindex "MySQL" "lookup type"
8116 .cindex "PostgreSQL lookup type"
8117 .cindex "lookup" "MySQL"
8118 .cindex "lookup" "PostgreSQL"
8119 .cindex "Oracle" "lookup type"
8120 .cindex "lookup" "Oracle"
8121 .cindex "InterBase lookup type"
8122 .cindex "lookup" "InterBase"
8123 .cindex "Redis lookup type"
8124 .cindex lookup Redis
8125 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
8126 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
8127 or &%redis_servers%&
8128 option (as appropriate) must be set to a colon-separated list of server
8130 .oindex &%mysql_servers%&
8131 .oindex &%pgsql_servers%&
8132 .oindex &%oracle_servers%&
8133 .oindex &%ibase_servers%&
8134 .oindex &%redis_servers%&
8135 (For MySQL and PostgreSQL, the global option need not be set if all
8136 queries contain their own server information &-- see section
8137 &<<SECTspeserque>>&.)
8139 each item in the list is a slash-separated list of four
8140 items: host name, database name, user name, and password. In the case of
8141 Oracle, the host name field is used for the &"service name"&, and the database
8142 name field is not used and should be empty. For example:
8144 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
8146 Because password data is sensitive, you should always precede the setting with
8147 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
8148 option. Here is an example where two MySQL servers are listed:
8150 hide mysql_servers = localhost/users/root/secret:\
8151 otherhost/users/root/othersecret
8153 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
8154 because this is a colon-separated list, the colon has to be doubled. For each
8155 query, these parameter groups are tried in order until a connection is made and
8156 a query is successfully processed. The result of a query may be that no data is
8157 found, but that is still a successful query. In other words, the list of
8158 servers provides a backup facility, not a list of different places to look.
8160 For Redis the global option need not be specified if all queries contain their
8161 own server information &-- see section &<<SECTspeserque>>&.
8162 If specified, the option must be set to a colon-separated list of server
8164 Each item in the list is a slash-separated list of three items:
8165 host, database number, and password.
8167 The host is required and may be either an IPv4 address and optional
8168 port number (separated by a colon, which needs doubling due to the
8169 higher-level list), or a Unix socket pathname enclosed in parentheses
8171 The database number is optional; if present that number is selected in the backend
8173 The password is optional; if present it is used to authenticate to the backend
8176 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
8177 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
8178 respectively, and the characters single-quote, double-quote, and backslash
8179 itself are escaped with backslashes.
8181 The &%quote_redis%& expansion operator
8182 escapes whitespace and backslash characters with a backslash.
8184 .section "Specifying the server in the query" "SECTspeserque"
8185 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
8186 it is possible to specify a list of servers with an individual query. This is
8187 done by appending a comma-separated option to the query type:
8189 &`,servers=`&&'server1:server2:server3:...'&
8191 Each item in the list may take one of two forms:
8193 If it contains no slashes it is assumed to be just a host name. The appropriate
8194 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
8195 of the same name, and the remaining parameters (database, user, password) are
8198 If it contains any slashes, it is taken as a complete parameter set.
8200 The list of servers is used in exactly the same way as the global list.
8201 Once a connection to a server has happened and a query has been
8202 successfully executed, processing of the lookup ceases.
8204 This feature is intended for use in master/slave situations where updates
8205 are occurring and you want to update the master rather than a slave. If the
8206 master is in the list as a backup for reading, you might have a global setting
8209 mysql_servers = slave1/db/name/pw:\
8213 In an updating lookup, you could then write:
8215 ${lookup mysql,servers=master {UPDATE ...} }
8217 That query would then be sent only to the master server. If, on the other hand,
8218 the master is not to be used for reading, and so is not present in the global
8219 option, you can still update it by a query of this form:
8221 ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
8224 An older syntax places the servers specification before the query,
8225 semicolon separated:
8227 ${lookup mysql{servers=master; UPDATE ...} }
8229 The new version avoids potential issues with tainted
8230 arguments in the query, for explicit expansion.
8231 &*Note*&: server specifications in list-style lookups are still problematic.
8234 .section "Special MySQL features" "SECID73"
8235 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
8236 causes a connection to the server on the local host by means of a Unix domain
8237 socket. An alternate socket can be specified in parentheses.
8238 An option group name for MySQL option files can be specified in square brackets;
8239 the default value is &"exim"&.
8240 The full syntax of each item in &%mysql_servers%& is:
8242 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
8243 <&'database'&>/<&'user'&>/<&'password'&>
8245 Any of the four sub-parts of the first field can be omitted. For normal use on
8246 the local host it can be left blank or set to just &"localhost"&.
8248 No database need be supplied &-- but if it is absent here, it must be given in
8251 If a MySQL query is issued that does not request any data (an insert, update,
8252 or delete command), the result of the lookup is the number of rows affected.
8254 &*Warning*&: This can be misleading. If an update does not actually change
8255 anything (for example, setting a field to the value it already has), the result
8256 is zero because no rows are affected.
8259 .section "Special PostgreSQL features" "SECID74"
8260 PostgreSQL lookups can also use Unix domain socket connections to the database.
8261 This is usually faster and costs less CPU time than a TCP/IP connection.
8262 However it can be used only if the mail server runs on the same machine as the
8263 database server. A configuration line for PostgreSQL via Unix domain sockets
8266 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
8268 In other words, instead of supplying a host name, a path to the socket is
8269 given. The path name is enclosed in parentheses so that its slashes aren't
8270 visually confused with the delimiters for the other server parameters.
8272 If a PostgreSQL query is issued that does not request any data (an insert,
8273 update, or delete command), the result of the lookup is the number of rows
8276 .section "More about SQLite" "SECTsqlite"
8277 .cindex "lookup" "SQLite"
8278 .cindex "sqlite lookup type"
8279 SQLite is different to the other SQL lookups because a filename is required in
8280 addition to the SQL query. An SQLite database is a single file, and there is no
8281 daemon as in the other SQL databases.
8283 .oindex &%sqlite_dbfile%&
8284 There are two ways of
8285 specifying the file.
8286 The first is is by using the &%sqlite_dbfile%& main option.
8287 The second, which allows separate files for each query,
8288 is to use an option appended, comma-separated, to the &"sqlite"&
8289 lookup type word. The option is the word &"file"&, then an equals,
8291 The filename in this case cannot contain whitespace or open-brace charachters.
8293 A deprecated method is available, prefixing the query with the filename
8294 separated by white space.
8296 .cindex "tainted data" "sqlite file"
8297 the query cannot use any tainted values, as that taints
8298 the entire query including the filename - resulting in a refusal to open
8301 In all the above cases the filename must be an absolute path.
8303 Here is a lookup expansion example:
8305 sqlite_dbfile = /some/thing/sqlitedb
8307 ${lookup sqlite {select name from aliases where id='userx';}}
8309 In a list, the syntax is similar. For example:
8311 domainlist relay_to_domains = sqlite;\
8312 select * from relays where ip='$sender_host_address';
8314 The only character affected by the &%quote_sqlite%& operator is a single
8315 quote, which it doubles.
8317 .cindex timeout SQLite
8318 .cindex sqlite "lookup timeout"
8319 The SQLite library handles multiple simultaneous accesses to the database
8320 internally. Multiple readers are permitted, but only one process can
8321 update at once. Attempts to access the database while it is being updated
8322 are rejected after a timeout period, during which the SQLite library
8323 waits for the lock to be released. In Exim, the default timeout is set
8324 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
8327 .section "More about Redis" "SECTredis"
8328 .cindex "lookup" "Redis"
8329 .cindex "redis lookup type"
8330 Redis is a non-SQL database. Commands are simple get and set.
8333 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
8334 ${lookup redis{get keyname}}
8337 As of release 4.91, "lightweight" support for Redis Cluster is available.
8338 Requires &%redis_servers%& list to contain all the servers in the cluster, all
8339 of which must be reachable from the running exim instance. If the cluster has
8340 master/slave replication, the list must contain all the master and slave
8343 When the Redis Cluster returns a "MOVED" response to a query, Exim does not
8344 immediately follow the redirection but treats the response as a DEFER, moving on
8345 to the next server in the &%redis_servers%& list until the correct server is
8352 . ////////////////////////////////////////////////////////////////////////////
8353 . ////////////////////////////////////////////////////////////////////////////
8355 .chapter "Domain, host, address, and local part lists" &&&
8356 "CHAPdomhosaddlists" &&&
8357 "Domain, host, and address lists"
8358 .scindex IIDdohoadli "lists of domains; hosts; etc."
8359 A number of Exim configuration options contain lists of domains, hosts,
8360 email addresses, or local parts. For example, the &%hold_domains%& option
8361 contains a list of domains whose delivery is currently suspended. These lists
8362 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
8363 arguments to expansion conditions such as &%match_domain%&.
8365 Each item in one of these lists is a pattern to be matched against a domain,
8366 host, email address, or local part, respectively. In the sections below, the
8367 different types of pattern for each case are described, but first we cover some
8368 general facilities that apply to all four kinds of list.
8370 Note that other parts of Exim use a &'string list'& which does not
8371 support all the complexity available in
8372 domain, host, address and local part lists.
8376 .section "Expansion of lists" "SECTlistexpand"
8377 .cindex "expansion" "of lists"
8378 Each list is expanded as a single string before it is used.
8380 &'Exception: the router headers_remove option, where list-item
8381 splitting is done before string-expansion.'&
8384 expansion must be a list, possibly containing empty items, which is split up
8385 into separate items for matching. By default, colon is the separator character,
8386 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
8387 &<<SECTempitelis>>& for details of the list syntax; the second of these
8388 discusses the way to specify empty list items.
8391 If the string expansion is forced to fail, Exim behaves as if the item it is
8392 testing (domain, host, address, or local part) is not in the list. Other
8393 expansion failures cause temporary errors.
8395 If an item in a list is a regular expression, backslashes, dollars and possibly
8396 other special characters in the expression must be protected against
8397 misinterpretation by the string expander. The easiest way to do this is to use
8398 the &`\N`& expansion feature to indicate that the contents of the regular
8399 expression should not be expanded. For example, in an ACL you might have:
8401 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
8402 ${lookup{$domain}lsearch{/badsenders/bydomain}}
8404 The first item is a regular expression that is protected from expansion by
8405 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
8406 senders based on the receiving domain.
8411 .section "Negated items in lists" "SECID76"
8412 .cindex "list" "negation"
8413 .cindex "negation" "in lists"
8414 Items in a list may be positive or negative. Negative items are indicated by a
8415 leading exclamation mark, which may be followed by optional white space. A list
8416 defines a set of items (domains, etc). When Exim processes one of these lists,
8417 it is trying to find out whether a domain, host, address, or local part
8418 (respectively) is in the set that is defined by the list. It works like this:
8420 The list is scanned from left to right. If a positive item is matched, the
8421 subject that is being checked is in the set; if a negative item is matched, the
8422 subject is not in the set. If the end of the list is reached without the
8423 subject having matched any of the patterns, it is in the set if the last item
8424 was a negative one, but not if it was a positive one. For example, the list in
8426 domainlist relay_to_domains = !a.b.c : *.b.c
8428 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
8429 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
8430 list is positive. However, if the setting were
8432 domainlist relay_to_domains = !a.b.c
8434 then all domains other than &'a.b.c'& would match because the last item in the
8435 list is negative. In other words, a list that ends with a negative item behaves
8436 as if it had an extra item &`:*`& on the end.
8438 Another way of thinking about positive and negative items in lists is to read
8439 the connector as &"or"& after a positive item and as &"and"& after a negative
8444 .section "File names in lists" "SECTfilnamlis"
8445 .cindex "list" "filename in"
8446 If an item in a domain, host, address, or local part list is an absolute
8447 filename (beginning with a slash character), each line of the file is read and
8448 processed as if it were an independent item in the list, except that further
8449 filenames are not allowed,
8450 and no expansion of the data from the file takes place.
8451 Empty lines in the file are ignored, and the file may also contain comment
8455 For domain and host lists, if a # character appears anywhere in a line of the
8456 file, it and all following characters are ignored.
8458 Because local parts may legitimately contain # characters, a comment in an
8459 address list or local part list file is recognized only if # is preceded by
8460 white space or the start of the line. For example:
8462 not#comment@x.y.z # but this is a comment
8466 Putting a filename in a list has the same effect as inserting each line of the
8467 file as an item in the list (blank lines and comments excepted). However, there
8468 is one important difference: the file is read each time the list is processed,
8469 so if its contents vary over time, Exim's behaviour changes.
8471 If a filename is preceded by an exclamation mark, the sense of any match
8472 within the file is inverted. For example, if
8474 hold_domains = !/etc/nohold-domains
8476 and the file contains the lines
8481 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
8482 any domain matching &`*.b.c`& is not.
8486 .section "An lsearch file is not an out-of-line list" "SECID77"
8487 As will be described in the sections that follow, lookups can be used in lists
8488 to provide indexed methods of checking list membership. There has been some
8489 confusion about the way &(lsearch)& lookups work in lists. Because
8490 an &(lsearch)& file contains plain text and is scanned sequentially, it is
8491 sometimes thought that it is allowed to contain wild cards and other kinds of
8492 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
8493 always fixed strings, just as for any other single-key lookup type.
8495 If you want to use a file to contain wild-card patterns that form part of a
8496 list, just give the filename on its own, without a search type, as described
8497 in the previous section. You could also use the &(wildlsearch)& or
8498 &(nwildlsearch)&, but there is no advantage in doing this.
8503 .section "Results of list checking" SECTlistresults
8504 The primary result of doing a list check is a truth value.
8505 In some contexts additional information is stored
8506 about the list element that matched:
8509 A &%hosts%& ACL condition
8510 will store a result in the &$host_data$& variable.
8512 A &%local_parts%& router option or &%local_parts%& ACL condition
8513 will store a result in the &$local_part_data$& variable.
8515 A &%domains%& router option or &%domains%& ACL condition
8516 will store a result in the &$domain_data$& variable.
8518 A &%senders%& router option or &%senders%& ACL condition
8519 will store a result in the &$sender_data$& variable.
8521 A &%recipients%& ACL condition
8522 will store a result in the &$recipient_data$& variable.
8525 The detail of the additional information depends on the
8526 type of match and is given below as the &*value*& information.
8531 .section "Named lists" "SECTnamedlists"
8532 .cindex "named lists"
8533 .cindex "list" "named"
8534 A list of domains, hosts, email addresses, or local parts can be given a name
8535 which is then used to refer to the list elsewhere in the configuration. This is
8536 particularly convenient if the same list is required in several different
8537 places. It also allows lists to be given meaningful names, which can improve
8538 the readability of the configuration. For example, it is conventional to define
8539 a domain list called &'local_domains'& for all the domains that are handled
8540 locally on a host, using a configuration line such as
8542 domainlist local_domains = localhost:my.dom.example
8544 Named lists are referenced by giving their name preceded by a plus sign, so,
8545 for example, a router that is intended to handle local domains would be
8546 configured with the line
8548 domains = +local_domains
8550 The first router in a configuration is often one that handles all domains
8551 except the local ones, using a configuration with a negated item like this:
8555 domains = ! +local_domains
8556 transport = remote_smtp
8559 The four kinds of named list are created by configuration lines starting with
8560 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8561 respectively. Then there follows the name that you are defining, followed by an
8562 equals sign and the list itself. For example:
8564 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8565 addresslist bad_senders = cdb;/etc/badsenders
8567 A named list may refer to other named lists:
8569 domainlist dom1 = first.example : second.example
8570 domainlist dom2 = +dom1 : third.example
8571 domainlist dom3 = fourth.example : +dom2 : fifth.example
8573 &*Warning*&: If the last item in a referenced list is a negative one, the
8574 effect may not be what you intended, because the negation does not propagate
8575 out to the higher level. For example, consider:
8577 domainlist dom1 = !a.b
8578 domainlist dom2 = +dom1 : *.b
8580 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8581 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8582 means it matches the second list as well. The effect is not the same as
8584 domainlist dom2 = !a.b : *.b
8586 where &'x.y'& does not match. It's best to avoid negation altogether in
8587 referenced lists if you can.
8589 .cindex "hiding named list values"
8590 .cindex "named lists" "hiding value of"
8591 Some named list definitions may contain sensitive data, for example, passwords for
8592 accessing databases. To stop non-admin users from using the &%-bP%& command
8593 line option to read these values, you can precede the definition with the
8594 word &"hide"&. For example:
8596 hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
8600 Named lists may have a performance advantage. When Exim is routing an
8601 address or checking an incoming message, it caches the result of tests on named
8602 lists. So, if you have a setting such as
8604 domains = +local_domains
8606 on several of your routers
8607 or in several ACL statements,
8608 the actual test is done only for the first one. However, the caching works only
8609 if there are no expansions within the list itself or any sublists that it
8610 references. In other words, caching happens only for lists that are known to be
8611 the same each time they are referenced.
8613 By default, there may be up to 16 named lists of each type. This limit can be
8614 extended by changing a compile-time variable. The use of domain and host lists
8615 is recommended for concepts such as local domains, relay domains, and relay
8616 hosts. The default configuration is set up like this.
8620 .section "Named lists compared with macros" "SECID78"
8621 .cindex "list" "named compared with macro"
8622 .cindex "macro" "compared with named list"
8623 At first sight, named lists might seem to be no different from macros in the
8624 configuration file. However, macros are just textual substitutions. If you
8627 ALIST = host1 : host2
8628 auth_advertise_hosts = !ALIST
8630 it probably won't do what you want, because that is exactly the same as
8632 auth_advertise_hosts = !host1 : host2
8634 Notice that the second host name is not negated. However, if you use a host
8637 hostlist alist = host1 : host2
8638 auth_advertise_hosts = ! +alist
8640 the negation applies to the whole list, and so that is equivalent to
8642 auth_advertise_hosts = !host1 : !host2
8646 .section "Named list caching" "SECID79"
8647 .cindex "list" "caching of named"
8648 .cindex "caching" "named lists"
8649 While processing a message, Exim caches the result of checking a named list if
8650 it is sure that the list is the same each time. In practice, this means that
8651 the cache operates only if the list contains no $ characters, which guarantees
8652 that it will not change when it is expanded. Sometimes, however, you may have
8653 an expanded list that you know will be the same each time within a given
8654 message. For example:
8656 domainlist special_domains = \
8657 ${lookup{$sender_host_address}cdb{/some/file}}
8659 This provides a list of domains that depends only on the sending host's IP
8660 address. If this domain list is referenced a number of times (for example,
8661 in several ACL lines, or in several routers) the result of the check is not
8662 cached by default, because Exim does not know that it is going to be the
8663 same list each time.
8665 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8666 cache the result anyway. For example:
8668 domainlist_cache special_domains = ${lookup{...
8670 If you do this, you should be absolutely sure that caching is going to do
8671 the right thing in all cases. When in doubt, leave it out.
8675 .section "Domain lists" "SECTdomainlist"
8676 .cindex "domain list" "patterns for"
8677 .cindex "list" "domain list"
8678 Domain lists contain patterns that are to be matched against a mail domain.
8679 The following types of item may appear in domain lists:
8682 .cindex "primary host name"
8683 .cindex "host name" "matched in domain list"
8684 .oindex "&%primary_hostname%&"
8685 .cindex "domain list" "matching primary host name"
8686 .cindex "@ in a domain list"
8687 If a pattern consists of a single @ character, it matches the local host name,
8688 as set by the &%primary_hostname%& option (or defaulted). This makes it
8689 possible to use the same configuration file on several different hosts that
8690 differ only in their names.
8692 The value for a match will be the primary host name.
8696 .cindex "@[] in a domain list"
8697 .cindex "domain list" "matching local IP interfaces"
8698 .cindex "domain literal"
8699 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8700 in square brackets (as in an email address that contains a domain literal), but
8701 only if that IP address is recognized as local for email routing purposes. The
8702 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8703 control which of a host's several IP addresses are treated as local.
8704 In today's Internet, the use of domain literals is controversial;
8705 see the &%allow_domain_literals%& main option.
8707 The value for a match will be the string &`@[]`&.
8712 .cindex "@mx_primary"
8713 .cindex "@mx_secondary"
8714 .cindex "domain list" "matching MX pointers to local host"
8715 If a pattern consists of the string &`@mx_any`& it matches any domain that
8716 has an MX record pointing to the local host or to any host that is listed in
8717 .oindex "&%hosts_treat_as_local%&"
8718 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8719 are similar, except that the first matches only when a primary MX target is the
8720 local host, and the second only when no primary MX target is the local host,
8721 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8722 preference value &-- there may of course be more than one of them.
8724 The MX lookup that takes place when matching a pattern of this type is
8725 performed with the resolver options for widening names turned off. Thus, for
8726 example, a single-component domain will &'not'& be expanded by adding the
8727 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8728 options of the &(dnslookup)& router for a discussion of domain widening.
8730 Sometimes you may want to ignore certain IP addresses when using one of these
8731 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8732 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8733 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8734 on a router). For example:
8736 domains = @mx_any/ignore=127.0.0.1
8738 This example matches any domain that has an MX record pointing to one of
8739 the local host's IP addresses other than 127.0.0.1.
8741 The list of IP addresses is in fact processed by the same code that processes
8742 host lists, so it may contain CIDR-coded network specifications and it may also
8743 contain negative items.
8745 Because the list of IP addresses is a sublist within a domain list, you have to
8746 be careful about delimiters if there is more than one address. Like any other
8747 list, the default delimiter can be changed. Thus, you might have:
8749 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8750 an.other.domain : ...
8752 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8753 involved, it is easiest to change the delimiter for the main list as well:
8755 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8756 an.other.domain ? ...
8758 The value for a match will be the list element string (starting &`@mx_`&).
8762 .cindex "asterisk" "in domain list"
8763 .cindex "domain list" "asterisk in"
8764 .cindex "domain list" "matching &""ends with""&"
8765 If a pattern starts with an asterisk, the remaining characters of the pattern
8766 are compared with the terminating characters of the domain. The use of &"*"& in
8767 domain lists differs from its use in partial matching lookups. In a domain
8768 list, the character following the asterisk need not be a dot, whereas partial
8769 matching works only in terms of dot-separated components. For example, a domain
8770 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8773 The value for a match will be the list element string (starting with the asterisk).
8774 Additionally, &$0$& will be set to the matched string
8775 and &$1$& to the variable portion which the asterisk matched.
8778 .cindex "regular expressions" "in domain list"
8779 .cindex "domain list" "matching regular expression"
8780 If a pattern starts with a circumflex character, it is treated as a regular
8781 expression, and matched against the domain using a regular expression matching
8782 function. The circumflex is treated as part of the regular expression.
8783 Email domains are case-independent, so this regular expression match is by
8784 default case-independent, but you can make it case-dependent by starting it
8785 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8786 are given in chapter &<<CHAPregexp>>&.
8788 &*Warning*&: Because domain lists are expanded before being processed, you
8789 must escape any backslash and dollar characters in the regular expression, or
8790 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8791 it is not to be expanded (unless you really do want to build a regular
8792 expression by expansion, of course).
8794 The value for a match will be the list element string (starting with the circumflex).
8795 Additionally, &$0$& will be set to the string matching the regular expression,
8796 and &$1$& (onwards) to any submatches identified by parentheses.
8801 .cindex "lookup" "in domain list"
8802 .cindex "domain list" "matching by lookup"
8803 If a pattern starts with the name of a single-key lookup type followed by a
8804 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8805 must be a filename in a suitable format for the lookup type. For example, for
8806 &"cdb;"& it must be an absolute path:
8808 domains = cdb;/etc/mail/local_domains.cdb
8810 The appropriate type of lookup is done on the file using the domain name as the
8811 key. In most cases, the value resulting from the lookup is not used; Exim is interested
8812 only in whether or not the key is present in the file. However, when a lookup
8813 is used for the &%domains%& option on a router
8814 or a &%domains%& condition in an ACL statement, the value is preserved in the
8815 &$domain_data$& variable and can be referred to in other router options or
8816 other statements in the same ACL.
8817 .cindex "tainted data" "de-tainting"
8818 The value will be untainted.
8820 &*Note*&: If the data result of the lookup (as opposed to the key)
8821 is empty, then this empty value is stored in &$domain_data$&.
8822 The option to return the key for the lookup, as the value,
8823 may be what is wanted.
8827 Any of the single-key lookup type names may be preceded by
8828 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8830 domains = partial-dbm;/partial/domains
8832 This causes partial matching logic to be invoked; a description of how this
8833 works is given in section &<<SECTpartiallookup>>&.
8836 .cindex "asterisk" "in lookup type"
8837 Any of the single-key lookup types may be followed by an asterisk. This causes
8838 a default lookup for a key consisting of a single asterisk to be done if the
8839 original lookup fails. This is not a useful feature when using a domain list to
8840 select particular domains (because any domain would match), but it might have
8841 value if the result of the lookup is being used via the &$domain_data$&
8845 If the pattern starts with the name of a query-style lookup type followed by a
8846 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8847 pattern must be an appropriate query for the lookup type, as described in
8848 chapter &<<CHAPfdlookup>>&. For example:
8850 hold_domains = mysql;select domain from holdlist \
8851 where domain = '${quote_mysql:$domain}';
8853 In most cases, the value resulting from the lookup is not used (so for an SQL query, for
8854 example, it doesn't matter what field you select). Exim is interested only in
8855 whether or not the query succeeds. However, when a lookup is used for the
8856 &%domains%& option on a router, the value is preserved in the &$domain_data$&
8857 variable and can be referred to in other options.
8858 .cindex "tainted data" "de-tainting"
8859 The value will be untainted.
8862 If the pattern starts with the name of a lookup type
8863 of either kind (single-key or query-style) it may be
8864 followed by a comma and options,
8865 The options are lookup-type specific and consist of a comma-separated list.
8866 Each item starts with a tag and and equals "=" sign.
8869 .cindex "domain list" "matching literal domain name"
8870 If none of the above cases apply, a caseless textual comparison is made
8871 between the pattern and the domain.
8873 The value for a match will be the list element string.
8874 .cindex "tainted data" "de-tainting"
8875 Note that this is commonly untainted
8876 (depending on the way the list was created).
8877 Specifically, explicit text in the configuration file in not tainted.
8878 This is a useful way of obtaining an untainted equivalent to
8879 the domain, for later operations.
8881 However if the list (including one-element lists)
8882 is created by expanding a variable containing tainted data,
8883 it is tainted and so will the match value be.
8887 Here is an example that uses several different kinds of pattern:
8889 domainlist funny_domains = \
8892 *.foundation.fict.example : \
8893 \N^[1-2]\d{3}\.fict\.example$\N : \
8894 partial-dbm;/opt/data/penguin/book : \
8895 nis;domains.byname : \
8896 nisplus;[name=$domain,status=local],domains.org_dir
8898 There are obvious processing trade-offs among the various matching modes. Using
8899 an asterisk is faster than a regular expression, and listing a few names
8900 explicitly probably is too. The use of a file or database lookup is expensive,
8901 but may be the only option if hundreds of names are required. Because the
8902 patterns are tested in order, it makes sense to put the most commonly matched
8907 .section "Host lists" "SECThostlist"
8908 .cindex "host list" "patterns in"
8909 .cindex "list" "host list"
8910 Host lists are used to control what remote hosts are allowed to do. For
8911 example, some hosts may be allowed to use the local host as a relay, and some
8912 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8913 two different ways, by name or by IP address. In a host list, some types of
8914 pattern are matched to a host name, and some are matched to an IP address.
8915 You need to be particularly careful with this when single-key lookups are
8916 involved, to ensure that the right value is being used as the key.
8919 .section "Special host list patterns" "SECID80"
8920 .cindex "empty item in hosts list"
8921 .cindex "host list" "empty string in"
8922 If a host list item is the empty string, it matches only when no remote host is
8923 involved. This is the case when a message is being received from a local
8924 process using SMTP on the standard input, that is, when a TCP/IP connection is
8927 .cindex "asterisk" "in host list"
8928 The special pattern &"*"& in a host list matches any host or no host. Neither
8929 the IP address nor the name is actually inspected.
8933 .section "Host list patterns that match by IP address" "SECThoslispatip"
8934 .cindex "host list" "matching IP addresses"
8935 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8936 the incoming address actually appears in the IPv6 host as
8937 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8938 list, it is converted into a traditional IPv4 address first. (Not all operating
8939 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8942 The following types of pattern in a host list check the remote host by
8943 inspecting its IP address:
8946 If the pattern is a plain domain name (not a regular expression, not starting
8947 with *, not a lookup of any kind), Exim calls the operating system function
8948 to find the associated IP address(es). Exim uses the newer
8949 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8950 This typically causes a forward DNS lookup of the name. The result is compared
8951 with the IP address of the subject host.
8953 If there is a temporary problem (such as a DNS timeout) with the host name
8954 lookup, a temporary error occurs. For example, if the list is being used in an
8955 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8956 temporary SMTP error code. If no IP address can be found for the host name,
8957 what happens is described in section &<<SECTbehipnot>>& below.
8960 .cindex "@ in a host list"
8961 If the pattern is &"@"&, the primary host name is substituted and used as a
8962 domain name, as just described.
8965 If the pattern is an IP address, it is matched against the IP address of the
8966 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8967 IPv6 addresses can be given in colon-separated format, but the colons have to
8968 be doubled so as not to be taken as item separators when the default list
8969 separator is used. IPv6 addresses are recognized even when Exim is compiled
8970 without IPv6 support. This means that if they appear in a host list on an
8971 IPv4-only host, Exim will not treat them as host names. They are just addresses
8972 that can never match a client host.
8975 .cindex "@[] in a host list"
8976 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8977 the local host. For example, if the local host is an IPv4 host with one
8978 interface address 10.45.23.56, these two ACL statements have the same effect:
8980 accept hosts = 127.0.0.1 : 10.45.23.56
8984 .cindex "CIDR notation"
8985 If the pattern is an IP address followed by a slash and a mask length, for
8990 , it is matched against the IP address of the subject
8991 host under the given mask. This allows an entire network of hosts to be
8992 included (or excluded) by a single item. The mask uses CIDR notation; it
8993 specifies the number of address bits that must match, starting from the most
8994 significant end of the address.
8996 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8997 of a range of addresses. It is the number of bits in the network portion of the
8998 address. The above example specifies a 24-bit netmask, so it matches all 256
8999 addresses in the 10.11.42.0 network. An item such as
9003 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
9004 32 for an IPv4 address is the same as no mask at all; just a single address
9007 Here is another example which shows an IPv4 and an IPv6 network:
9009 recipient_unqualified_hosts = 192.168.0.0/16: \
9010 3ffe::ffff::836f::::/48
9012 The doubling of list separator characters applies only when these items
9013 appear inline in a host list. It is not required when indirecting via a file.
9016 recipient_unqualified_hosts = /opt/exim/unqualnets
9018 could make use of a file containing
9023 to have exactly the same effect as the previous example. When listing IPv6
9024 addresses inline, it is usually more convenient to use the facility for
9025 changing separator characters. This list contains the same two networks:
9027 recipient_unqualified_hosts = <; 172.16.0.0/12; \
9030 The separator is changed to semicolon by the leading &"<;"& at the start of the
9036 .section "Host list patterns for single-key lookups by host address" &&&
9037 "SECThoslispatsikey"
9038 .cindex "host list" "lookup of IP address"
9039 When a host is to be identified by a single-key lookup of its complete IP
9040 address, the pattern takes this form:
9042 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
9046 hosts_lookup = net-cdb;/hosts-by-ip.db
9048 The text form of the IP address of the subject host is used as the lookup key.
9049 IPv6 addresses are converted to an unabbreviated form, using lower case
9050 letters, with dots as separators because colon is the key terminator in
9051 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
9052 quoting the keys, but this is a facility that was added later.] The data
9053 returned by the lookup is not used.
9055 .cindex "IP address" "masking"
9056 .cindex "host list" "masked IP address"
9057 Single-key lookups can also be performed using masked IP addresses, using
9058 patterns of this form:
9060 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
9064 net24-dbm;/networks.db
9066 The IP address of the subject host is masked using <&'number'&> as the mask
9067 length. A textual string is constructed from the masked value, followed by the
9068 mask, and this is used as the lookup key. For example, if the host's IP address
9069 is 192.168.34.6, the key that is looked up for the above example is
9070 &"192.168.34.0/24"&.
9072 When an IPv6 address is converted to a string, dots are normally used instead
9073 of colons, so that keys in &(lsearch)& files need not contain colons (which
9074 terminate &(lsearch)& keys). This was implemented some time before the ability
9075 to quote keys was made available in &(lsearch)& files. However, the more
9076 recently implemented &(iplsearch)& files do require colons in IPv6 keys
9077 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
9078 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
9079 converted using colons and not dots.
9080 In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
9081 addresses are always used.
9082 The latter are converted to IPv4 addresses, in dotted-quad form.
9084 Ideally, it would be nice to tidy up this anomalous situation by changing to
9085 colons in all cases, given that quoting is now available for &(lsearch)&.
9086 However, this would be an incompatible change that might break some existing
9089 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
9090 IPv6 address) is not the same as specifying just &%net-%& without a number. In
9091 the former case the key strings include the mask value, whereas in the latter
9092 case the IP address is used on its own.
9096 .section "Host list patterns that match by host name" "SECThoslispatnam"
9097 .cindex "host" "lookup failures"
9098 .cindex "unknown host name"
9099 .cindex "host list" "matching host name"
9100 There are several types of pattern that require Exim to know the name of the
9101 remote host. These are either wildcard patterns or lookups by name. (If a
9102 complete hostname is given without any wildcarding, it is used to find an IP
9103 address to match against, as described in section &<<SECThoslispatip>>&
9106 If the remote host name is not already known when Exim encounters one of these
9107 patterns, it has to be found from the IP address.
9108 Although many sites on the Internet are conscientious about maintaining reverse
9109 DNS data for their hosts, there are also many that do not do this.
9110 Consequently, a name cannot always be found, and this may lead to unwanted
9111 effects. Take care when configuring host lists with wildcarded name patterns.
9112 Consider what will happen if a name cannot be found.
9114 Because of the problems of determining host names from IP addresses, matching
9115 against host names is not as common as matching against IP addresses.
9117 By default, in order to find a host name, Exim first does a reverse DNS lookup;
9118 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
9119 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
9120 are done can be changed by setting the &%host_lookup_order%& option. For
9121 security, once Exim has found one or more names, it looks up the IP addresses
9122 for these names and compares them with the IP address that it started with.
9123 Only those names whose IP addresses match are accepted. Any other names are
9124 discarded. If no names are left, Exim behaves as if the host name cannot be
9125 found. In the most common case there is only one name and one IP address.
9127 There are some options that control what happens if a host name cannot be
9128 found. These are described in section &<<SECTbehipnot>>& below.
9130 .cindex "host" "alias for"
9131 .cindex "alias for host"
9132 As a result of aliasing, hosts may have more than one name. When processing any
9133 of the following types of pattern, all the host's names are checked:
9136 .cindex "asterisk" "in host list"
9137 If a pattern starts with &"*"& the remainder of the item must match the end of
9138 the host name. For example, &`*.b.c`& matches all hosts whose names end in
9139 &'.b.c'&. This special simple form is provided because this is a very common
9140 requirement. Other kinds of wildcarding require the use of a regular
9143 .cindex "regular expressions" "in host list"
9144 .cindex "host list" "regular expression in"
9145 If the item starts with &"^"& it is taken to be a regular expression which is
9146 matched against the host name. Host names are case-independent, so this regular
9147 expression match is by default case-independent, but you can make it
9148 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
9149 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
9154 is a regular expression that matches either of the two hosts &'a.c.d'& or
9155 &'b.c.d'&. When a regular expression is used in a host list, you must take care
9156 that backslash and dollar characters are not misinterpreted as part of the
9157 string expansion. The simplest way to do this is to use &`\N`& to mark that
9158 part of the string as non-expandable. For example:
9160 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
9162 &*Warning*&: If you want to match a complete host name, you must include the
9163 &`$`& terminating metacharacter in the regular expression, as in the above
9164 example. Without it, a match at the start of the host name is all that is
9171 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
9172 .cindex "host" "lookup failures, permanent"
9173 While processing a host list, Exim may need to look up an IP address from a
9174 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
9175 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
9176 behaviour when it fails to find the information it is seeking is the same.
9178 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
9179 apply to temporary DNS errors, whose handling is described in the next section.
9181 .cindex "&`+include_unknown`&"
9182 .cindex "&`+ignore_unknown`&"
9183 Exim parses a host list from left to right. If it encounters a permanent
9184 lookup failure in any item in the host list before it has found a match,
9185 Exim treats it as a failure and the default behavior is as if the host
9186 does not match the list. This may not always be what you want to happen.
9187 To change Exim's behaviour, the special items &`+include_unknown`& or
9188 &`+ignore_unknown`& may appear in the list (at top level &-- they are
9189 not recognized in an indirected file).
9192 If any item that follows &`+include_unknown`& requires information that
9193 cannot found, Exim behaves as if the host does match the list. For example,
9195 host_reject_connection = +include_unknown:*.enemy.ex
9197 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
9198 any hosts whose name it cannot find.
9201 If any item that follows &`+ignore_unknown`& requires information that cannot
9202 be found, Exim ignores that item and proceeds to the rest of the list. For
9205 accept hosts = +ignore_unknown : friend.example : \
9208 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
9209 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
9210 name can be found for 192.168.4.5, it is rejected.
9213 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
9214 list. The effect of each one lasts until the next, or until the end of the
9217 .section "Mixing wildcarded host names and addresses in host lists" &&&
9219 .cindex "host list" "mixing names and addresses in"
9221 This section explains the host/ip processing logic with the same concepts
9222 as the previous section, but specifically addresses what happens when a
9223 wildcarded hostname is one of the items in the hostlist.
9226 If you have name lookups or wildcarded host names and
9227 IP addresses in the same host list, you should normally put the IP
9228 addresses first. For example, in an ACL you could have:
9230 accept hosts = 10.9.8.7 : *.friend.example
9232 The reason you normally would order it this way lies in the
9233 left-to-right way that Exim processes lists. It can test IP addresses
9234 without doing any DNS lookups, but when it reaches an item that requires
9235 a host name, it fails if it cannot find a host name to compare with the
9236 pattern. If the above list is given in the opposite order, the
9237 &%accept%& statement fails for a host whose name cannot be found, even
9238 if its IP address is 10.9.8.7.
9241 If you really do want to do the name check first, and still recognize the IP
9242 address, you can rewrite the ACL like this:
9244 accept hosts = *.friend.example
9245 accept hosts = 10.9.8.7
9247 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
9248 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
9249 &`+ignore_unknown`&, which was discussed in depth in the first example in
9254 .section "Temporary DNS errors when looking up host information" &&&
9256 .cindex "host" "lookup failures, temporary"
9257 .cindex "&`+include_defer`&"
9258 .cindex "&`+ignore_defer`&"
9259 A temporary DNS lookup failure normally causes a defer action (except when
9260 &%dns_again_means_nonexist%& converts it into a permanent error). However,
9261 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
9262 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
9263 section. These options should be used with care, probably only in non-critical
9264 host lists such as whitelists.
9268 .section "Host list patterns for single-key lookups by host name" &&&
9269 "SECThoslispatnamsk"
9270 .cindex "unknown host name"
9271 .cindex "host list" "matching host name"
9272 If a pattern is of the form
9274 <&'single-key-search-type'&>;<&'search-data'&>
9278 dbm;/host/accept/list
9280 a single-key lookup is performed, using the host name as its key. If the
9281 lookup succeeds, the host matches the item. The actual data that is looked up
9284 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
9285 keys in the file, not IP addresses. If you want to do lookups based on IP
9286 addresses, you must precede the search type with &"net-"& (see section
9287 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
9288 two items in the same list, one doing an address lookup and one doing a name
9289 lookup, both using the same file.
9293 .section "Host list patterns for query-style lookups" "SECID81"
9294 If a pattern is of the form
9296 <&'query-style-search-type'&>;<&'query'&>
9298 the query is obeyed, and if it succeeds, the host matches the item. The actual
9299 data that is looked up is not used. The variables &$sender_host_address$& and
9300 &$sender_host_name$& can be used in the query. For example:
9302 hosts_lookup = pgsql;\
9303 select ip from hostlist where ip='$sender_host_address'
9305 The value of &$sender_host_address$& for an IPv6 address contains colons. You
9306 can use the &%sg%& expansion item to change this if you need to. If you want to
9307 use masked IP addresses in database queries, you can use the &%mask%& expansion
9310 If the query contains a reference to &$sender_host_name$&, Exim automatically
9311 looks up the host name if it has not already done so. (See section
9312 &<<SECThoslispatnam>>& for comments on finding host names.)
9314 Historical note: prior to release 4.30, Exim would always attempt to find a
9315 host name before running the query, unless the search type was preceded by
9316 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
9317 still recognized for query-style lookups, but its presence or absence has no
9318 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
9319 See section &<<SECThoslispatsikey>>&.)
9325 .section "Address lists" "SECTaddresslist"
9326 .cindex "list" "address list"
9327 .cindex "address list" "empty item"
9328 .cindex "address list" "patterns"
9329 Address lists contain patterns that are matched against mail addresses. There
9330 is one special case to be considered: the sender address of a bounce message is
9331 always empty. You can test for this by providing an empty item in an address
9332 list. For example, you can set up a router to process bounce messages by
9333 using this option setting:
9337 The presence of the colon creates an empty item. If you do not provide any
9338 data, the list is empty and matches nothing. The empty sender can also be
9339 detected by a regular expression that matches an empty string,
9340 and by a query-style lookup that succeeds when &$sender_address$& is empty.
9342 Non-empty items in an address list can be straightforward email addresses. For
9345 senders = jbc@askone.example : hs@anacreon.example
9347 A certain amount of wildcarding is permitted. If a pattern contains an @
9348 character, but is not a regular expression and does not begin with a
9349 semicolon-terminated lookup type (described below), the local part of the
9350 subject address is compared with the local part of the pattern, which may start
9351 with an asterisk. If the local parts match, the domain is checked in exactly
9352 the same way as for a pattern in a domain list. For example, the domain can be
9353 wildcarded, refer to a named list, or be a lookup:
9355 deny senders = *@*.spamming.site:\
9356 *@+hostile_domains:\
9357 bozo@partial-lsearch;/list/of/dodgy/sites:\
9358 *@dbm;/bad/domains.db
9360 .cindex "local part" "starting with !"
9361 .cindex "address list" "local part starting with !"
9362 If a local part that begins with an exclamation mark is required, it has to be
9363 specified using a regular expression, because otherwise the exclamation mark is
9364 treated as a sign of negation, as is standard in lists.
9366 If a non-empty pattern that is not a regular expression or a lookup does not
9367 contain an @ character, it is matched against the domain part of the subject
9368 address. The only two formats that are recognized this way are a literal
9369 domain, or a domain pattern that starts with *. In both these cases, the effect
9370 is the same as if &`*@`& preceded the pattern. For example:
9372 deny senders = enemy.domain : *.enemy.domain
9375 The following kinds of more complicated address list pattern can match any
9376 address, including the empty address that is characteristic of bounce message
9380 .cindex "regular expressions" "in address list"
9381 .cindex "address list" "regular expression in"
9382 If (after expansion) a pattern starts with &"^"&, a regular expression match is
9383 done against the complete address, with the pattern as the regular expression.
9384 You must take care that backslash and dollar characters are not misinterpreted
9385 as part of the string expansion. The simplest way to do this is to use &`\N`&
9386 to mark that part of the string as non-expandable. For example:
9388 deny senders = \N^.*this.*@example\.com$\N : \
9389 \N^\d{8}.+@spamhaus.example$\N : ...
9391 The &`\N`& sequences are removed by the expansion, so these items do indeed
9392 start with &"^"& by the time they are being interpreted as address patterns.
9395 .cindex "address list" "lookup for complete address"
9396 Complete addresses can be looked up by using a pattern that starts with a
9397 lookup type terminated by a semicolon, followed by the data for the lookup. For
9400 deny senders = cdb;/etc/blocked.senders : \
9401 mysql;select address from blocked where \
9402 address='${quote_mysql:$sender_address}'
9404 Both query-style and single-key lookup types can be used. For a single-key
9405 lookup type, Exim uses the complete address as the key. However, empty keys are
9406 not supported for single-key lookups, so a match against the empty address
9407 always fails. This restriction does not apply to query-style lookups.
9409 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
9410 cannot be used, and is ignored if specified, with an entry being written to the
9412 .cindex "*@ with single-key lookup"
9413 However, you can configure lookup defaults, as described in section
9414 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
9415 default. For example, with this lookup:
9417 accept senders = lsearch*@;/some/file
9419 the file could contains lines like this:
9421 user1@domain1.example
9424 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
9427 nimrod@jaeger.example
9431 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
9432 would mean that every address matches, thus rendering the test useless.
9434 &*Warning 2*&: Do not confuse these two kinds of item:
9436 deny recipients = dbm*@;/some/file
9437 deny recipients = *@dbm;/some/file
9439 The first does a whole address lookup, with defaulting, as just described,
9440 because it starts with a lookup type. The second matches the local part and
9441 domain independently, as described in a bullet point below.
9445 The following kinds of address list pattern can match only non-empty addresses.
9446 If the subject address is empty, a match against any of these pattern types
9451 .cindex "@@ with single-key lookup"
9452 .cindex "address list" "@@ lookup type"
9453 .cindex "address list" "split local part and domain"
9454 If a pattern starts with &"@@"& followed by a single-key lookup item
9455 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
9456 split into a local part and a domain. The domain is looked up in the file. If
9457 it is not found, there is no match. If it is found, the data that is looked up
9458 from the file is treated as a colon-separated list of local part patterns, each
9459 of which is matched against the subject local part in turn.
9461 .cindex "asterisk" "in address list"
9462 The lookup may be a partial one, and/or one involving a search for a default
9463 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
9464 patterns that are looked up can be regular expressions or begin with &"*"&, or
9465 even be further lookups. They may also be independently negated. For example,
9468 deny senders = @@dbm;/etc/reject-by-domain
9470 the data from which the DBM file is built could contain lines like
9472 baddomain.com: !postmaster : *
9474 to reject all senders except &%postmaster%& from that domain.
9476 .cindex "local part" "starting with !"
9477 If a local part that actually begins with an exclamation mark is required, it
9478 has to be specified using a regular expression. In &(lsearch)& files, an entry
9479 may be split over several lines by indenting the second and subsequent lines,
9480 but the separating colon must still be included at line breaks. White space
9481 surrounding the colons is ignored. For example:
9483 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
9486 As in all colon-separated lists in Exim, a colon can be included in an item by
9489 If the last item in the list starts with a right angle-bracket, the remainder
9490 of the item is taken as a new key to look up in order to obtain a continuation
9491 list of local parts. The new key can be any sequence of characters. Thus one
9492 might have entries like
9494 aol.com: spammer1 : spammer 2 : >*
9495 xyz.com: spammer3 : >*
9498 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
9499 local parts for all domains, in addition to the specific local parts listed for
9500 each domain. Of course, using this feature costs another lookup each time a
9501 chain is followed, but the effort needed to maintain the data is reduced.
9503 .cindex "loop" "in lookups"
9504 It is possible to construct loops using this facility, and in order to catch
9505 them, the chains may be no more than fifty items long.
9508 The @@<&'lookup'&> style of item can also be used with a query-style
9509 lookup, but in this case, the chaining facility is not available. The lookup
9510 can only return a single list of local parts.
9513 &*Warning*&: There is an important difference between the address list items
9514 in these two examples:
9517 senders = *@+my_list
9519 In the first one, &`my_list`& is a named address list, whereas in the second
9520 example it is a named domain list.
9525 .section "Case of letters in address lists" "SECTcasletadd"
9526 .cindex "case of local parts"
9527 .cindex "address list" "case forcing"
9528 .cindex "case forcing in address lists"
9529 Domains in email addresses are always handled caselessly, but for local parts
9530 case may be significant on some systems (see &%caseful_local_part%& for how
9531 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
9532 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
9533 blocking lists should be done in a case-independent manner. Since most address
9534 lists in Exim are used for this kind of control, Exim attempts to do this by
9537 The domain portion of an address is always lowercased before matching it to an
9538 address list. The local part is lowercased by default, and any string
9539 comparisons that take place are done caselessly. This means that the data in
9540 the address list itself, in files included as plain filenames, and in any file
9541 that is looked up using the &"@@"& mechanism, can be in any case. However, the
9542 keys in files that are looked up by a search type other than &(lsearch)& (which
9543 works caselessly) must be in lower case, because these lookups are not
9546 .cindex "&`+caseful`&"
9547 To allow for the possibility of caseful address list matching, if an item in
9548 an address list is the string &"+caseful"&, the original case of the local
9549 part is restored for any comparisons that follow, and string comparisons are no
9550 longer case-independent. This does not affect the domain, which remains in
9551 lower case. However, although independent matches on the domain alone are still
9552 performed caselessly, regular expressions that match against an entire address
9553 become case-sensitive after &"+caseful"& has been seen.
9557 .section "Local part lists" "SECTlocparlis"
9558 .cindex "list" "local part list"
9559 .cindex "local part" "list"
9560 These behave in the same way as domain and host lists, with the following
9563 Case-sensitivity in local part lists is handled in the same way as for address
9564 lists, as just described. The &"+caseful"& item can be used if required. In a
9565 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
9566 set false, the subject is lowercased and the matching is initially
9567 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
9568 matching in the local part list, but not elsewhere in the router. If
9569 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
9570 option is case-sensitive from the start.
9572 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
9573 comments are handled in the same way as address lists &-- they are recognized
9574 only if the # is preceded by white space or the start of the line.
9575 Otherwise, local part lists are matched in the same way as domain lists, except
9576 that the special items that refer to the local host (&`@`&, &`@[]`&,
9577 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
9578 Refer to section &<<SECTdomainlist>>& for details of the other available item
9580 .ecindex IIDdohoadli
9585 . ////////////////////////////////////////////////////////////////////////////
9586 . ////////////////////////////////////////////////////////////////////////////
9588 .chapter "String expansions" "CHAPexpand"
9589 .scindex IIDstrexp "expansion" "of strings"
9590 Many strings in Exim's runtime configuration are expanded before use. Some of
9591 them are expanded every time they are used; others are expanded only once.
9593 When a string is being expanded it is copied verbatim from left to right except
9594 .cindex expansion "string concatenation"
9595 when a dollar or backslash character is encountered. A dollar specifies the
9596 start of a portion of the string that is interpreted and replaced as described
9597 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
9598 escape character, as described in the following section.
9600 Whether a string is expanded depends upon the context. Usually this is solely
9601 dependent upon the option for which a value is sought; in this documentation,
9602 options for which string expansion is performed are marked with † after
9603 the data type. ACL rules always expand strings. A couple of expansion
9604 conditions do not expand some of the brace-delimited branches, for security
9606 .cindex "tainted data" expansion
9607 .cindex "tainted data" definition
9608 .cindex expansion "tainted data"
9609 and expansion of data deriving from the sender (&"tainted data"&)
9610 is not permitted (including acessing a file using a tainted name).
9611 The main config option &%allow_insecure_tainted_data%& can be used as
9612 mitigation during uprades to more secure configurations.
9614 Common ways of obtaining untainted equivalents of variables with
9616 .cindex "tainted data" "de-tainting"
9617 come down to using the tainted value as a lookup key in a trusted database.
9618 This database could be the filesystem structure,
9619 or the password file,
9620 or accessed via a DBMS.
9621 Specific methods are indexed under &"de-tainting"&.
9625 .section "Literal text in expanded strings" "SECTlittext"
9626 .cindex "expansion" "including literal text"
9627 An uninterpreted dollar can be included in an expanded string by putting a
9628 backslash in front of it. A backslash can be used to prevent any special
9629 character being treated specially in an expansion, including backslash itself.
9630 If the string appears in quotes in the configuration file, two backslashes are
9631 required because the quotes themselves cause interpretation of backslashes when
9632 the string is read in (see section &<<SECTstrings>>&).
9634 .cindex "expansion" "non-expandable substrings"
9635 A portion of the string can specified as non-expandable by placing it between
9636 two occurrences of &`\N`&. This is particularly useful for protecting regular
9637 expressions, which often contain backslashes and dollar signs. For example:
9639 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
9641 On encountering the first &`\N`&, the expander copies subsequent characters
9642 without interpretation until it reaches the next &`\N`& or the end of the
9647 .section "Character escape sequences in expanded strings" "SECID82"
9648 .cindex "expansion" "escape sequences"
9649 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9650 expanded string is recognized as an escape sequence for the character newline,
9651 carriage return, or tab, respectively. A backslash followed by up to three
9652 octal digits is recognized as an octal encoding for a single character, and a
9653 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9656 These escape sequences are also recognized in quoted strings when they are read
9657 in. Their interpretation in expansions as well is useful for unquoted strings,
9658 and for other cases such as looked-up strings that are then expanded.
9661 .section "Testing string expansions" "SECID83"
9662 .cindex "expansion" "testing"
9663 .cindex "testing" "string expansion"
9665 Many expansions can be tested by calling Exim with the &%-be%& option. This
9666 takes the command arguments, or lines from the standard input if there are no
9667 arguments, runs them through the string expansion code, and writes the results
9668 to the standard output. Variables based on configuration values are set up, but
9669 since no message is being processed, variables such as &$local_part$& have no
9670 value. Nevertheless the &%-be%& option can be useful for checking out file and
9671 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9674 Exim gives up its root privilege when it is called with the &%-be%& option, and
9675 instead runs under the uid and gid it was called with, to prevent users from
9676 using &%-be%& for reading files to which they do not have access.
9679 If you want to test expansions that include variables whose values are taken
9680 from a message, there are two other options that can be used. The &%-bem%&
9681 option is like &%-be%& except that it is followed by a filename. The file is
9682 read as a message before doing the test expansions. For example:
9684 exim -bem /tmp/test.message '$h_subject:'
9686 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9687 Exim message identifier. For example:
9689 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9691 This loads the message from Exim's spool before doing the test expansions, and
9692 is therefore restricted to admin users.
9695 .section "Forced expansion failure" "SECTforexpfai"
9696 .cindex "expansion" "forced failure"
9697 A number of expansions that are described in the following section have
9698 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9699 (which are sometimes called &"curly brackets"&). Which of the two strings is
9700 used depends on some condition that is evaluated as part of the expansion. If,
9701 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9702 the entire string expansion fails in a way that can be detected by the code
9703 that requested the expansion. This is called &"forced expansion failure"&, and
9704 its consequences depend on the circumstances. In some cases it is no different
9705 from any other expansion failure, but in others a different action may be
9706 taken. Such variations are mentioned in the documentation of the option that is
9712 .section "Expansion items" "SECTexpansionitems"
9713 The following items are recognized in expanded strings. White space may be used
9714 between sub-items that are keywords or substrings enclosed in braces inside an
9715 outer set of braces, to improve readability. &*Warning*&: Within braces,
9716 white space is significant.
9719 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9720 .cindex "expansion" "variables"
9721 Substitute the contents of the named variable, for example:
9726 The second form can be used to separate the name from subsequent alphanumeric
9727 characters. This form (using braces) is available only for variables; it does
9728 &'not'& apply to message headers. The names of the variables are given in
9729 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9730 given, the expansion fails.
9732 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9733 .cindex "expansion" "operators"
9734 The string is first itself expanded, and then the operation specified by
9735 <&'op'&> is applied to it. For example:
9739 The string starts with the first character after the colon, which may be
9740 leading white space. A list of operators is given in section &<<SECTexpop>>&
9741 below. The operator notation is used for simple expansion items that have just
9742 one argument, because it reduces the number of braces and therefore makes the
9743 string easier to understand.
9745 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9746 This item inserts &"basic"& header lines. It is described with the &%header%&
9747 expansion item below.
9750 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9751 .cindex "expansion" "calling an acl"
9752 .cindex "&%acl%&" "call from expansion"
9753 The name and zero to nine argument strings are first expanded separately. The expanded
9754 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9755 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9756 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9757 and may use the variables; if another acl expansion is used the values
9758 are restored after it returns. If the ACL sets
9759 a value using a "message =" modifier and returns accept or deny, the value becomes
9760 the result of the expansion.
9761 If no message is set and the ACL returns accept or deny
9762 the expansion result is an empty string.
9763 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9766 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
9767 .cindex authentication "results header"
9768 .chindex Authentication-Results:
9769 .cindex authentication "expansion item"
9770 This item returns a string suitable for insertion as an
9771 &'Authentication-Results:'&
9773 The given <&'authserv-id'&> is included in the result; typically this
9774 will be a domain name identifying the system performing the authentications.
9775 Methods that might be present in the result include:
9784 Example use (as an ACL modifier):
9786 add_header = :at_start:${authresults {$primary_hostname}}
9788 This is safe even if no authentication results are available.
9791 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9792 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9793 .cindex "expansion" "extracting certificate fields"
9794 .cindex "&%certextract%&" "certificate fields"
9795 .cindex "certificate" "extracting fields"
9796 The <&'certificate'&> must be a variable of type certificate.
9797 The field name is expanded and used to retrieve the relevant field from
9798 the certificate. Supported fields are:
9802 &`subject `& RFC4514 DN
9803 &`issuer `& RFC4514 DN
9808 &`subj_altname `& tagged list
9812 If the field is found,
9813 <&'string2'&> is expanded, and replaces the whole item;
9814 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9815 variable &$value$& contains the value that has been extracted. Afterwards, it
9816 is restored to any previous value it might have had.
9818 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9819 key is not found. If {<&'string2'&>} is also omitted, the value that was
9822 Some field names take optional modifiers, appended and separated by commas.
9824 The field selectors marked as "RFC4514" above
9825 output a Distinguished Name string which is
9827 parseable by Exim as a comma-separated tagged list
9828 (the exceptions being elements containing commas).
9829 RDN elements of a single type may be selected by
9830 a modifier of the type label; if so the expansion
9831 result is a list (newline-separated by default).
9832 The separator may be changed by another modifier of
9833 a right angle-bracket followed immediately by the new separator.
9834 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9836 The field selectors marked as "time" above
9837 take an optional modifier of "int"
9838 for which the result is the number of seconds since epoch.
9839 Otherwise the result is a human-readable string
9840 in the timezone selected by the main "timezone" option.
9842 The field selectors marked as "list" above return a list,
9843 newline-separated by default,
9844 (embedded separator characters in elements are doubled).
9845 The separator may be changed by a modifier of
9846 a right angle-bracket followed immediately by the new separator.
9848 The field selectors marked as "tagged" above
9849 prefix each list element with a type string and an equals sign.
9850 Elements of only one type may be selected by a modifier
9851 which is one of "dns", "uri" or "mail";
9852 if so the element tags are omitted.
9854 If not otherwise noted field values are presented in human-readable form.
9856 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9857 {*&<&'arg'&>&*}...}*&"
9859 This expansion dynamically loads and then calls a locally-written C function.
9860 This functionality is available only if Exim is compiled with
9864 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9865 object so that it doesn't reload the same object file in the same Exim process
9866 (but of course Exim does start new processes frequently).
9868 There may be from zero to eight arguments to the function.
9871 a local function that is to be called in this way,
9872 first &_DLFUNC_IMPL_& should be defined,
9873 and second &_local_scan.h_& should be included.
9874 The Exim variables and functions that are defined by that API
9875 are also available for dynamically loaded functions. The function itself
9876 must have the following type:
9878 int dlfunction(uschar **yield, int argc, uschar *argv[])
9880 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9881 function should return one of the following values:
9883 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9884 into the expanded string that is being built.
9886 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9887 from &'yield'&, if it is set.
9889 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9890 taken from &'yield'& if it is set.
9892 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9894 When compiling a function that is to be used in this way with gcc,
9895 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9896 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9899 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9900 .cindex "expansion" "extracting value from environment"
9901 .cindex "environment" "values from"
9902 The key is first expanded separately, and leading and trailing white space
9904 This is then searched for as a name in the environment.
9905 If a variable is found then its value is placed in &$value$&
9906 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9908 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9909 appear, for example:
9911 ${env{USER}{$value} fail }
9913 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9914 {<&'string1'&>} must be present for &"fail"& to be recognized.
9916 If {<&'string2'&>} is omitted an empty string is substituted on
9918 If {<&'string1'&>} is omitted the search result is substituted on
9921 The environment is adjusted by the &%keep_environment%& and
9922 &%add_environment%& main section options.
9925 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9926 {*&<&'string3'&>&*}}*&"
9927 .cindex "expansion" "extracting substrings by key"
9928 .cindex "&%extract%&" "substrings by key"
9929 The key and <&'string1'&> are first expanded separately. Leading and trailing
9930 white space is removed from the key (but not from any of the strings). The key
9931 must not be empty and must not consist entirely of digits.
9932 The expanded <&'string1'&> must be of the form:
9934 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9937 where the equals signs and spaces (but not both) are optional. If any of the
9938 values contain white space, they must be enclosed in double quotes, and any
9939 values that are enclosed in double quotes are subject to escape processing as
9940 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9941 for the value that corresponds to the key. The search is case-insensitive. If
9942 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9943 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9944 variable &$value$& contains the value that has been extracted. Afterwards, it
9945 is restored to any previous value it might have had.
9947 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9948 key is not found. If {<&'string2'&>} is also omitted, the value that was
9949 extracted is used. Thus, for example, these two expansions are identical, and
9952 ${extract{gid}{uid=1984 gid=2001}}
9953 ${extract{gid}{uid=1984 gid=2001}{$value}}
9955 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9956 appear, for example:
9958 ${extract{Z}{A=... B=...}{$value} fail }
9960 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9961 {<&'string2'&>} must be present for &"fail"& to be recognized.
9963 .vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9964 {*&<&'string3'&>&*}}*&" &&&
9965 "&*${extract jsons{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9966 {*&<&'string3'&>&*}}*&"
9967 .cindex "expansion" "extracting from JSON object"
9968 .cindex JSON expansions
9969 The key and <&'string1'&> are first expanded separately. Leading and trailing
9970 white space is removed from the key (but not from any of the strings). The key
9971 must not be empty and must not consist entirely of digits.
9972 The expanded <&'string1'&> must be of the form:
9974 { <&'"key1"'&> : <&'value1'&> , <&'"key2"'&> , <&'value2'&> ... }
9977 The braces, commas and colons, and the quoting of the member name are required;
9978 the spaces are optional.
9979 Matching of the key against the member names is done case-sensitively.
9980 For the &"json"& variant,
9981 if a returned value is a JSON string, it retains its leading and
9983 For the &"jsons"& variant, which is intended for use with JSON strings, the
9984 leading and trailing quotes are removed from the returned value.
9985 . XXX should be a UTF-8 compare
9987 The results of matching are handled as above.
9990 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9991 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9992 .cindex "expansion" "extracting substrings by number"
9993 .cindex "&%extract%&" "substrings by number"
9994 The <&'number'&> argument must consist entirely of decimal digits,
9995 apart from leading and trailing white space, which is ignored.
9996 This is what distinguishes this form of &%extract%& from the previous kind. It
9997 behaves in the same way, except that, instead of extracting a named field, it
9998 extracts from <&'string1'&> the field whose number is given as the first
9999 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
10000 <&'string3'&> as before.
10002 The fields in the string are separated by any one of the characters in the
10003 separator string. These may include space or tab characters.
10004 The first field is numbered one. If the number is negative, the fields are
10005 counted from the end of the string, with the rightmost one numbered -1. If the
10006 number given is zero, the entire string is returned. If the modulus of the
10007 number is greater than the number of fields in the string, the result is the
10008 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
10009 provided. For example:
10011 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
10015 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
10017 yields &"99"&. Two successive separators mean that the field between them is
10018 empty (for example, the fifth field above).
10021 .vitem "&*${extract json {*&<&'number'&>&*}}&&&
10022 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" &&&
10023 "&*${extract jsons{*&<&'number'&>&*}}&&&
10024 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10025 .cindex "expansion" "extracting from JSON array"
10026 .cindex JSON expansions
10027 The <&'number'&> argument must consist entirely of decimal digits,
10028 apart from leading and trailing white space, which is ignored.
10030 Field selection and result handling is as above;
10031 there is no choice of field separator.
10032 For the &"json"& variant,
10033 if a returned value is a JSON string, it retains its leading and
10035 For the &"jsons"& variant, which is intended for use with JSON strings, the
10036 leading and trailing quotes are removed from the returned value.
10039 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
10040 .cindex "list" "selecting by condition"
10041 .cindex "expansion" "selecting from list by condition"
10043 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10044 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10046 in this list, its value is place in &$item$&, and then the condition is
10047 evaluated. If the condition is true, &$item$& is added to the output as an
10048 item in a new list; if the condition is false, the item is discarded. The
10049 separator used for the output list is the same as the one used for the
10050 input, but a separator setting is not included in the output. For example:
10052 ${filter{a:b:c}{!eq{$item}{b}}}
10054 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
10055 to what it was before. See also the &%map%& and &%reduce%& expansion items.
10058 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10059 .cindex "hash function" "textual"
10060 .cindex "expansion" "textual hash"
10061 This is a textual hashing function, and was the first to be implemented in
10062 early versions of Exim. In current releases, there are other hashing functions
10063 (numeric, MD5, and SHA-1), which are described below.
10065 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
10066 <&'n'&>. If you are using fixed values for these numbers, that is, if
10067 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
10068 use the simpler operator notation that avoids some of the braces:
10070 ${hash_<n>_<m>:<string>}
10072 The second number is optional (in both notations). If <&'n'&> is greater than
10073 or equal to the length of the string, the expansion item returns the string.
10074 Otherwise it computes a new string of length <&'n'&> by applying a hashing
10075 function to the string. The new string consists of characters taken from the
10076 first <&'m'&> characters of the string
10078 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
10080 If <&'m'&> is not present the value 26 is used, so that only lower case
10081 letters appear. For example:
10083 &`$hash{3}{monty}} `& yields &`jmg`&
10084 &`$hash{5}{monty}} `& yields &`monty`&
10085 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
10088 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
10089 &*$h_*&<&'header&~name'&>&*:*&" &&&
10090 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10091 &*$bh_*&<&'header&~name'&>&*:*&" &&&
10092 "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10093 &*$lh_*&<&'header&~name'&>&*:*&" &&&
10094 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10095 &*$rh_*&<&'header&~name'&>&*:*&"
10096 .cindex "expansion" "header insertion"
10097 .vindex "&$header_$&"
10098 .vindex "&$bheader_$&"
10099 .vindex "&$lheader_$&"
10100 .vindex "&$rheader_$&"
10101 .cindex "header lines" "in expansion strings"
10102 .cindex "header lines" "character sets"
10103 .cindex "header lines" "decoding"
10104 Substitute the contents of the named message header line, for example
10108 The newline that terminates a header line is not included in the expansion, but
10109 internal newlines (caused by splitting the header line over several physical
10110 lines) may be present.
10112 The difference between the four pairs of expansions is in the way
10113 the data in the header line is interpreted.
10116 .cindex "white space" "in header lines"
10117 &%rheader%& gives the original &"raw"& content of the header line, with no
10118 processing at all, and without the removal of leading and trailing white space.
10121 .cindex "list" "of header lines"
10122 &%lheader%& gives a colon-separated list, one element per header when there
10123 are multiple headers with a given name.
10124 Any embedded colon characters within an element are doubled, so normal Exim
10125 list-processing facilities can be used.
10126 The terminating newline of each element is removed; in other respects
10127 the content is &"raw"&.
10130 .cindex "base64 encoding" "in header lines"
10131 &%bheader%& removes leading and trailing white space, and then decodes base64
10132 or quoted-printable MIME &"words"& within the header text, but does no
10133 character set translation. If decoding of what looks superficially like a MIME
10134 &"word"& fails, the raw string is returned. If decoding
10135 .cindex "binary zero" "in header line"
10136 produces a binary zero character, it is replaced by a question mark &-- this is
10137 what Exim does for binary zeros that are actually received in header lines.
10140 &%header%& tries to translate the string as decoded by &%bheader%& to a
10141 standard character set. This is an attempt to produce the same string as would
10142 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
10143 returned. Translation is attempted only on operating systems that support the
10144 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
10145 a system Makefile or in &_Local/Makefile_&.
10148 In a filter file, the target character set for &%header%& can be specified by a
10149 command of the following form:
10151 headers charset "UTF-8"
10153 This command affects all references to &$h_$& (or &$header_$&) expansions in
10154 subsequently obeyed filter commands. In the absence of this command, the target
10155 character set in a filter is taken from the setting of the &%headers_charset%&
10156 option in the runtime configuration. The value of this option defaults to the
10157 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
10160 Header names follow the syntax of RFC 2822, which states that they may contain
10161 any printing characters except space and colon. Consequently, curly brackets
10162 &'do not'& terminate header names, and should not be used to enclose them as
10163 if they were variables. Attempting to do so causes a syntax error.
10165 Only header lines that are common to all copies of a message are visible to
10166 this mechanism. These are the original header lines that are received with the
10167 message, and any that are added by an ACL statement or by a system
10168 filter. Header lines that are added to a particular copy of a message by a
10169 router or transport are not accessible.
10171 For incoming SMTP messages, no header lines are visible in
10172 ACLs that are obeyed before the data phase completes,
10173 because the header structure is not set up until the message is received.
10174 They are visible in DKIM, PRDR and DATA ACLs.
10175 Header lines that are added in a RCPT ACL (for example)
10176 are saved until the message's incoming header lines are available, at which
10177 point they are added.
10178 When any of the above ACLs are
10179 running, however, header lines added by earlier ACLs are visible.
10181 Upper case and lower case letters are synonymous in header names. If the
10182 following character is white space, the terminating colon may be omitted, but
10183 this is not recommended, because you may then forget it when it is needed. When
10184 white space terminates the header name, this white space is included in the
10185 expanded string. If the message does not contain the given header, the
10186 expansion item is replaced by an empty string. (See the &%def%& condition in
10187 section &<<SECTexpcond>>& for a means of testing for the existence of a
10190 If there is more than one header with the same name, they are all concatenated
10191 to form the substitution string, up to a maximum length of 64K. Unless
10192 &%rheader%& is being used, leading and trailing white space is removed from
10193 each header before concatenation, and a completely empty header is ignored. A
10194 newline character is then inserted between non-empty headers, but there is no
10195 newline at the very end. For the &%header%& and &%bheader%& expansion, for
10196 those headers that contain lists of addresses, a comma is also inserted at the
10197 junctions between headers. This does not happen for the &%rheader%& expansion.
10199 .cindex "tainted data" "message headers"
10200 When the headers are from an incoming message,
10201 the result of expanding any of these variables is tainted.
10204 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
10205 .cindex "expansion" "hmac hashing"
10207 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
10208 shared secret and some text into a message authentication code, as specified in
10209 RFC 2104. This differs from &`${md5:secret_text...}`& or
10210 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
10211 cryptographic hash, allowing for authentication that is not possible with MD5
10212 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
10213 present. For example:
10215 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
10217 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
10220 dd97e3ba5d1a61b5006108f8c8252953
10222 As an example of how this might be used, you might put in the main part of
10223 an Exim configuration:
10225 SPAMSCAN_SECRET=cohgheeLei2thahw
10227 In a router or a transport you could then have:
10230 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
10231 ${hmac{md5}{SPAMSCAN_SECRET}\
10232 {${primary_hostname},${message_exim_id},$h_message-id:}}
10234 Then given a message, you can check where it was scanned by looking at the
10235 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
10236 this header line is authentic by recomputing the authentication code from the
10237 host name, message ID and the &'Message-id:'& header line. This can be done
10238 using Exim's &%-be%& option, or by other means, for example, by using the
10239 &'hmac_md5_hex()'& function in Perl.
10242 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10243 .cindex "expansion" "conditional"
10244 .cindex "&%if%&, expansion item"
10245 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
10246 item; otherwise <&'string2'&> is used. The available conditions are described
10247 in section &<<SECTexpcond>>& below. For example:
10249 ${if eq {$local_part}{postmaster} {yes}{no} }
10251 The second string need not be present; if it is not and the condition is not
10252 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
10253 be present instead of the second string (without any curly brackets). In this
10254 case, the expansion is forced to fail if the condition is not true (see section
10255 &<<SECTforexpfai>>&).
10257 If both strings are omitted, the result is the string &`true`& if the condition
10258 is true, and the empty string if the condition is false. This makes it less
10259 cumbersome to write custom ACL and router conditions. For example, instead of
10261 condition = ${if >{$acl_m4}{3}{true}{false}}
10265 condition = ${if >{$acl_m4}{3}}
10270 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
10271 .cindex expansion "imap folder"
10272 .cindex "&%imapfolder%& expansion item"
10273 This item converts a (possibly multilevel, or with non-ASCII characters)
10274 folder specification to a Maildir name for filesystem use.
10275 For information on internationalisation support see &<<SECTi18nMDA>>&.
10279 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10280 .cindex "expansion" "string truncation"
10281 .cindex "&%length%& expansion item"
10282 The &%length%& item is used to extract the initial portion of a string. Both
10283 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
10284 you are using a fixed value for the number, that is, if <&'string1'&> does not
10285 change when expanded, you can use the simpler operator notation that avoids
10286 some of the braces:
10288 ${length_<n>:<string>}
10290 The result of this item is either the first <&'n'&> bytes or the whole
10291 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
10292 &%strlen%&, which gives the length of a string.
10293 All measurement is done in bytes and is not UTF-8 aware.
10296 .vitem "&*${listextract{*&<&'number'&>&*}&&&
10297 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10298 .cindex "expansion" "extracting list elements by number"
10299 .cindex "&%listextract%&" "extract list elements by number"
10300 .cindex "list" "extracting elements by number"
10301 The <&'number'&> argument must consist entirely of decimal digits,
10302 apart from an optional leading minus,
10303 and leading and trailing white space (which is ignored).
10305 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10306 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10308 The first field of the list is numbered one.
10309 If the number is negative, the fields are
10310 counted from the end of the list, with the rightmost one numbered -1.
10311 The numbered element of the list is extracted and placed in &$value$&,
10312 then <&'string2'&> is expanded as the result.
10314 If the modulus of the
10315 number is zero or greater than the number of fields in the string,
10316 the result is the expansion of <&'string3'&>.
10320 ${listextract{2}{x:42:99}}
10324 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
10326 yields &"result: 42"&.
10328 If {<&'string3'&>} is omitted, an empty string is used for string3.
10329 If {<&'string2'&>} is also omitted, the value that was
10331 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
10334 .vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*&
10335 .cindex quoting "for list"
10336 .cindex list quoting
10337 This item doubles any occurrence of the separator character
10338 in the given string.
10339 An empty string is replaced with a single space.
10340 This converts the string into a safe form for use as a list element,
10341 in a list using the given separator.
10344 .vitem "&*${lookup&~{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
10345 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" &&&
10346 "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
10347 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
10348 .cindex "expansion" "lookup in"
10349 .cindex "file" "lookups"
10350 .cindex "lookup" "in expanded string"
10351 The two forms of lookup item specify data lookups in files and databases, as
10352 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
10353 lookups, and the second is used for query-style lookups. The <&'key'&>,
10354 <&'file'&>, and <&'query'&> strings are expanded before use.
10356 If there is any white space in a lookup item which is part of a filter command,
10357 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
10358 other place where white space is significant, the lookup item must be enclosed
10359 in double quotes. The use of data lookups in users' filter files may be locked
10360 out by the system administrator.
10362 .vindex "&$value$&"
10363 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
10364 During its expansion, the variable &$value$& contains the data returned by the
10365 lookup. Afterwards it reverts to the value it had previously (at the outer
10366 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
10367 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
10368 string on failure. If <&'string2'&> is provided, it can itself be a nested
10369 lookup, thus providing a mechanism for looking up a default value when the
10370 original lookup fails.
10372 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
10373 data for the outer lookup while the parameters of the second lookup are
10374 expanded, and also while <&'string2'&> of the second lookup is expanded, should
10375 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
10376 appear, and in this case, if the lookup fails, the entire expansion is forced
10377 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
10378 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
10379 successful lookup, and nothing in the case of failure.
10381 For single-key lookups, the string &"partial"& is permitted to precede the
10382 search type in order to do partial matching, and * or *@ may follow a search
10383 type to request default lookups if the key does not match (see sections
10384 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
10386 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
10387 If a partial search is used, the variables &$1$& and &$2$& contain the wild
10388 and non-wild parts of the key during the expansion of the replacement text.
10389 They return to their previous values at the end of the lookup item.
10391 This example looks up the postmaster alias in the conventional alias file:
10393 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
10395 This example uses NIS+ to look up the full name of the user corresponding to
10396 the local part of an address, forcing the expansion to fail if it is not found:
10398 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
10403 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10404 .cindex "expansion" "list creation"
10406 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10407 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10409 in this list, its value is place in &$item$&, and then <&'string2'&> is
10410 expanded and added to the output as an item in a new list. The separator used
10411 for the output list is the same as the one used for the input, but a separator
10412 setting is not included in the output. For example:
10414 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
10416 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
10417 value of &$item$& is restored to what it was before. See also the &%filter%&
10418 and &%reduce%& expansion items.
10420 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10421 .cindex "expansion" "numeric hash"
10422 .cindex "hash function" "numeric"
10423 The three strings are expanded; the first two must yield numbers. Call them
10424 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10425 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10426 can use the simpler operator notation that avoids some of the braces:
10428 ${nhash_<n>_<m>:<string>}
10430 The second number is optional (in both notations). If there is only one number,
10431 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
10432 processed by a div/mod hash function that returns two numbers, separated by a
10433 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
10436 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
10438 returns the string &"6/33"&.
10442 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
10443 .cindex "Perl" "use in expanded string"
10444 .cindex "expansion" "calling Perl from"
10445 This item is available only if Exim has been built to include an embedded Perl
10446 interpreter. The subroutine name and the arguments are first separately
10447 expanded, and then the Perl subroutine is called with those arguments. No
10448 additional arguments need be given; the maximum number permitted, including the
10449 name of the subroutine, is nine.
10451 The return value of the subroutine is inserted into the expanded string, unless
10452 the return value is &%undef%&. In that case, the entire expansion is
10453 forced to fail, in the same way as an explicit &"fail"& on a lookup item
10454 does (see section &<<SECTforexpfai>>&). Whatever you return is evaluated
10455 in a scalar context, thus the return value is a scalar. For example, if you
10456 return a Perl vector, the return value is the size of the vector,
10459 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
10460 with the error message that was passed to &%die%&. More details of the embedded
10461 Perl facility are given in chapter &<<CHAPperl>>&.
10463 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
10464 out the use of this expansion item in filter files.
10467 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
10468 .cindex "&%prvs%& expansion item"
10469 The first argument is a complete email address and the second is secret
10470 keystring. The third argument, specifying a key number, is optional. If absent,
10471 it defaults to 0. The result of the expansion is a prvs-signed email address,
10472 to be typically used with the &%return_path%& option on an &(smtp)& transport
10473 as part of a bounce address tag validation (BATV) scheme. For more discussion
10474 and an example, see section &<<SECTverifyPRVS>>&.
10476 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
10477 {*&<&'string'&>&*}}*&"
10478 .cindex "&%prvscheck%& expansion item"
10479 This expansion item is the complement of the &%prvs%& item. It is used for
10480 checking prvs-signed addresses. If the expansion of the first argument does not
10481 yield a syntactically valid prvs-signed address, the whole item expands to the
10482 empty string. When the first argument does expand to a syntactically valid
10483 prvs-signed address, the second argument is expanded, with the prvs-decoded
10484 version of the address and the key number extracted from the address in the
10485 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
10487 These two variables can be used in the expansion of the second argument to
10488 retrieve the secret. The validity of the prvs-signed address is then checked
10489 against the secret. The result is stored in the variable &$prvscheck_result$&,
10490 which is empty for failure or &"1"& for success.
10492 The third argument is optional; if it is missing, it defaults to an empty
10493 string. This argument is now expanded. If the result is an empty string, the
10494 result of the expansion is the decoded version of the address. This is the case
10495 whether or not the signature was valid. Otherwise, the result of the expansion
10496 is the expansion of the third argument.
10498 All three variables can be used in the expansion of the third argument.
10499 However, once the expansion is complete, only &$prvscheck_result$& remains set.
10500 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
10502 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
10503 .cindex "expansion" "inserting an entire file"
10504 .cindex "file" "inserting into expansion"
10505 .cindex "&%readfile%& expansion item"
10506 The filename and end-of-line (eol) string are first expanded separately. The file is
10507 then read, and its contents replace the entire item. All newline characters in
10508 the file are replaced by the end-of-line string if it is present. Otherwise,
10509 newlines are left in the string.
10510 String expansion is not applied to the contents of the file. If you want this,
10511 you must wrap the item in an &%expand%& operator. If the file cannot be read,
10512 the string expansion fails.
10514 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
10515 locks out the use of this expansion item in filter files.
10519 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
10520 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
10521 .cindex "expansion" "inserting from a socket"
10522 .cindex "socket, use of in expansion"
10523 .cindex "&%readsocket%& expansion item"
10524 This item inserts data from a Unix domain or TCP socket into the expanded
10525 string. The minimal way of using it uses just two arguments, as in these
10528 ${readsocket{/socket/name}{request string}}
10529 ${readsocket{inet:some.host:1234}{request string}}
10531 For a Unix domain socket, the first substring must be the path to the socket.
10532 For an Internet socket, the first substring must contain &`inet:`& followed by
10533 a host name or IP address, followed by a colon and a port, which can be a
10534 number or the name of a TCP port in &_/etc/services_&. An IP address may
10535 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
10538 ${readsocket{inet:[::1]:1234}{request string}}
10540 Only a single host name may be given, but if looking it up yields more than
10541 one IP address, they are each tried in turn until a connection is made. For
10542 both kinds of socket, Exim makes a connection, writes the request string
10543 (unless it is an empty string; no terminating NUL is ever sent)
10544 and reads from the socket until an end-of-file
10545 is read. A timeout of 5 seconds is applied. Additional, optional arguments
10546 extend what can be done. Firstly, you can vary the timeout. For example:
10548 ${readsocket{/socket/name}{request string}{3s}}
10551 The third argument is a list of options, of which the first element is the timeout
10552 and must be present if any options are given.
10553 Further elements are options of form &'name=value'&.
10556 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
10559 The following option names are recognised:
10562 Defines if the result data can be cached for use by a later identical
10563 request in the same process.
10564 Values are &"yes"& or &"no"& (the default).
10565 If not, all cached results for this connection specification
10566 will be invalidated.
10570 Defines whether or not a write-shutdown is done on the connection after
10571 sending the request. Values are &"yes"& (the default) or &"no"&
10572 (preferred, eg. by some webservers).
10576 Controls the use of TLS on the connection.
10577 Values are &"yes"& or &"no"& (the default).
10578 If it is enabled, a shutdown as descripbed above is never done.
10582 A fourth argument allows you to change any newlines that are in the data
10583 that is read, in the same way as for &%readfile%& (see above). This example
10584 turns them into spaces:
10586 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
10588 As with all expansions, the substrings are expanded before the processing
10589 happens. Errors in these sub-expansions cause the expansion to fail. In
10590 addition, the following errors can occur:
10593 Failure to create a socket file descriptor;
10595 Failure to connect the socket;
10597 Failure to write the request string;
10599 Timeout on reading from the socket.
10602 By default, any of these errors causes the expansion to fail. However, if
10603 you supply a fifth substring, it is expanded and used when any of the above
10604 errors occurs. For example:
10606 ${readsocket{/socket/name}{request string}{3s}{\n}\
10609 You can test for the existence of a Unix domain socket by wrapping this
10610 expansion in &`${if exists`&, but there is a race condition between that test
10611 and the actual opening of the socket, so it is safer to use the fifth argument
10612 if you want to be absolutely sure of avoiding an expansion error for a
10613 non-existent Unix domain socket, or a failure to connect to an Internet socket.
10615 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
10616 locks out the use of this expansion item in filter files.
10619 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10620 .cindex "expansion" "reducing a list to a scalar"
10621 .cindex "list" "reducing to a scalar"
10622 .vindex "&$value$&"
10624 This operation reduces a list to a single, scalar string. After expansion,
10625 <&'string1'&> is interpreted as a list, colon-separated by default, but the
10626 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10627 Then <&'string2'&> is expanded and
10628 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
10629 list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
10630 them. The result of that expansion is assigned to &$value$& before the next
10631 iteration. When the end of the list is reached, the final value of &$value$& is
10632 added to the expansion output. The &%reduce%& expansion item can be used in a
10633 number of ways. For example, to add up a list of numbers:
10635 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
10637 The result of that expansion would be &`6`&. The maximum of a list of numbers
10640 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
10642 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
10643 restored to what they were before. See also the &%filter%& and &%map%&
10646 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
10647 This item inserts &"raw"& header lines. It is described with the &%header%&
10648 expansion item in section &<<SECTexpansionitems>>& above.
10650 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
10651 {*&<&'string2'&>&*}}*&"
10652 .cindex "expansion" "running a command"
10653 .cindex "&%run%& expansion item"
10654 The command and its arguments are first expanded as one string. The string is
10655 split apart into individual arguments by spaces, and then the command is run
10656 in a separate process, but under the same uid and gid. As in other command
10657 executions from Exim, a shell is not used by default. If the command requires
10658 a shell, you must explicitly code it.
10660 Since the arguments are split by spaces, when there is a variable expansion
10661 which has an empty result, it will cause the situation that the argument will
10662 simply be omitted when the program is actually executed by Exim. If the
10663 script/program requires a specific number of arguments and the expanded
10664 variable could possibly result in this empty expansion, the variable must be
10665 quoted. This is more difficult if the expanded variable itself could result
10666 in a string containing quotes, because it would interfere with the quotes
10667 around the command arguments. A possible guard against this is to wrap the
10668 variable in the &%sg%& operator to change any quote marks to some other
10671 The standard input for the command exists, but is empty. The standard output
10672 and standard error are set to the same file descriptor.
10673 .cindex "return code" "from &%run%& expansion"
10674 .vindex "&$value$&"
10675 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
10676 and replaces the entire item; during this expansion, the standard output/error
10677 from the command is in the variable &$value$&. If the command fails,
10678 <&'string2'&>, if present, is expanded and used. Once again, during the
10679 expansion, the standard output/error from the command is in the variable
10682 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
10683 can be the word &"fail"& (not in braces) to force expansion failure if the
10684 command does not succeed. If both strings are omitted, the result is contents
10685 of the standard output/error on success, and nothing on failure.
10687 .vindex "&$run_in_acl$&"
10688 The standard output/error of the command is put in the variable &$value$&.
10689 In this ACL example, the output of a command is logged for the admin to
10692 warn condition = ${run{/usr/bin/id}{yes}{no}}
10693 log_message = Output of id: $value
10695 If the command requires shell idioms, such as the > redirect operator, the
10696 shell must be invoked directly, such as with:
10698 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
10701 .vindex "&$runrc$&"
10702 The return code from the command is put in the variable &$runrc$&, and this
10703 remains set afterwards, so in a filter file you can do things like this:
10705 if "${run{x y z}{}}$runrc" is 1 then ...
10706 elif $runrc is 2 then ...
10710 If execution of the command fails (for example, the command does not exist),
10711 the return code is 127 &-- the same code that shells use for non-existent
10714 &*Warning*&: In a router or transport, you cannot assume the order in which
10715 option values are expanded, except for those preconditions whose order of
10716 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
10717 by the expansion of one option, and use it in another.
10719 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
10720 out the use of this expansion item in filter files.
10723 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
10724 .cindex "expansion" "string substitution"
10725 .cindex "&%sg%& expansion item"
10726 This item works like Perl's substitution operator (s) with the global (/g)
10727 option; hence its name. However, unlike the Perl equivalent, Exim does not
10728 modify the subject string; instead it returns the modified string for insertion
10729 into the overall expansion. The item takes three arguments: the subject string,
10730 a regular expression, and a substitution string. For example:
10732 ${sg{abcdefabcdef}{abc}{xyz}}
10734 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
10735 if any $, } or \ characters are required in the regular expression or in the
10736 substitution string, they have to be escaped. For example:
10738 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
10740 yields &"defabc"&, and
10742 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
10744 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
10745 the regular expression from string expansion.
10747 The regular expression is compiled in 8-bit mode, working against bytes
10748 rather than any Unicode-aware character handling.
10751 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
10752 .cindex sorting "a list"
10753 .cindex list sorting
10754 .cindex expansion "list sorting"
10755 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10756 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10757 The <&'comparator'&> argument is interpreted as the operator
10758 of a two-argument expansion condition.
10759 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
10760 The comparison should return true when applied to two values
10761 if the first value should sort before the second value.
10762 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
10763 the element being placed in &$item$&,
10764 to give values for comparison.
10766 The item result is a sorted list,
10767 with the original list separator,
10768 of the list elements (in full) of the original.
10772 ${sort{3:2:1:4}{<}{$item}}
10774 sorts a list of numbers, and
10776 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10778 will sort an MX lookup into priority order.
10782 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
10783 SRS encoding. See SECT &<<SECTSRS>>& for details.
10787 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10788 .cindex "&%substr%& expansion item"
10789 .cindex "substring extraction"
10790 .cindex "expansion" "substring extraction"
10791 The three strings are expanded; the first two must yield numbers. Call them
10792 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10793 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10794 can use the simpler operator notation that avoids some of the braces:
10796 ${substr_<n>_<m>:<string>}
10798 The second number is optional (in both notations).
10799 If it is absent in the simpler format, the preceding underscore must also be
10802 The &%substr%& item can be used to extract more general substrings than
10803 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10804 length required. For example
10806 ${substr{3}{2}{$local_part}}
10808 If the starting offset is greater than the string length the result is the
10809 null string; if the length plus starting offset is greater than the string
10810 length, the result is the right-hand part of the string, starting from the
10811 given offset. The first byte (character) in the string has offset zero.
10813 The &%substr%& expansion item can take negative offset values to count
10814 from the right-hand end of its operand. The last byte (character) is offset -1,
10815 the second-last is offset -2, and so on. Thus, for example,
10817 ${substr{-5}{2}{1234567}}
10819 yields &"34"&. If the absolute value of a negative offset is greater than the
10820 length of the string, the substring starts at the beginning of the string, and
10821 the length is reduced by the amount of overshoot. Thus, for example,
10823 ${substr{-5}{2}{12}}
10825 yields an empty string, but
10827 ${substr{-3}{2}{12}}
10831 When the second number is omitted from &%substr%&, the remainder of the string
10832 is taken if the offset is positive. If it is negative, all bytes (characters) in the
10833 string preceding the offset point are taken. For example, an offset of -1 and
10834 no length, as in these semantically identical examples:
10837 ${substr{-1}{abcde}}
10839 yields all but the last character of the string, that is, &"abcd"&.
10841 All measurement is done in bytes and is not UTF-8 aware.
10845 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10846 {*&<&'replacements'&>&*}}*&"
10847 .cindex "expansion" "character translation"
10848 .cindex "&%tr%& expansion item"
10849 This item does single-character (in bytes) translation on its subject string. The second
10850 argument is a list of characters to be translated in the subject string. Each
10851 matching character is replaced by the corresponding character from the
10852 replacement list. For example
10854 ${tr{abcdea}{ac}{13}}
10856 yields &`1b3de1`&. If there are duplicates in the second character string, the
10857 last occurrence is used. If the third string is shorter than the second, its
10858 last character is replicated. However, if it is empty, no translation takes
10861 All character handling is done in bytes and is not UTF-8 aware.
10867 .section "Expansion operators" "SECTexpop"
10868 .cindex "expansion" "operators"
10869 For expansion items that perform transformations on a single argument string,
10870 the &"operator"& notation is used because it is simpler and uses fewer braces.
10871 The substring is first expanded before the operation is applied to it. The
10872 following operations can be performed:
10875 .vitem &*${address:*&<&'string'&>&*}*&
10876 .cindex "expansion" "RFC 2822 address handling"
10877 .cindex "&%address%& expansion item"
10878 The string is interpreted as an RFC 2822 address, as it might appear in a
10879 header line, and the effective address is extracted from it. If the string does
10880 not parse successfully, the result is empty.
10882 The parsing correctly handles SMTPUTF8 Unicode in the string.
10885 .vitem &*${addresses:*&<&'string'&>&*}*&
10886 .cindex "expansion" "RFC 2822 address handling"
10887 .cindex "&%addresses%& expansion item"
10888 The string (after expansion) is interpreted as a list of addresses in RFC
10889 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10890 operative address (&'local-part@domain'&) is extracted from each item, and the
10891 result of the expansion is a colon-separated list, with appropriate
10892 doubling of colons should any happen to be present in the email addresses.
10893 Syntactically invalid RFC2822 address items are omitted from the output.
10895 It is possible to specify a character other than colon for the output
10896 separator by starting the string with > followed by the new separator
10897 character. For example:
10899 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10901 expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
10902 first, so if the expanded string starts with >, it may change the output
10903 separator unintentionally. This can be avoided by setting the output
10904 separator explicitly:
10906 ${addresses:>:$h_from:}
10909 Compare the &%address%& (singular)
10910 expansion item, which extracts the working address from a single RFC2822
10911 address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
10914 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10915 a strict interpretation of header line formatting. Exim parses the bare,
10916 unquoted portion of an email address and if it finds a comma, treats it as an
10917 email address separator. For the example header line:
10919 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10921 The first example below demonstrates that Q-encoded email addresses are parsed
10922 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10923 It does not see the comma because it's still encoded as "=2C". The second
10924 example below is passed the contents of &`$header_from:`&, meaning it gets
10925 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10926 The third example shows that the presence of a comma is skipped when it is
10927 quoted. The fourth example shows SMTPUTF8 handling.
10929 # exim -be '${addresses:From: \
10930 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10932 # exim -be '${addresses:From: Last, First <user@example.com>}'
10933 Last:user@example.com
10934 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10936 # exim -be '${addresses:フィル <フィリップ@example.jp>}'
10940 .vitem &*${base32:*&<&'digits'&>&*}*&
10941 .cindex "&%base32%& expansion item"
10942 .cindex "expansion" "conversion to base 32"
10943 The string must consist entirely of decimal digits. The number is converted to
10944 base 32 and output as a (empty, for zero) string of characters.
10945 Only lowercase letters are used.
10947 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10948 .cindex "&%base32d%& expansion item"
10949 .cindex "expansion" "conversion to base 32"
10950 The string must consist entirely of base-32 digits.
10951 The number is converted to decimal and output as a string.
10953 .vitem &*${base62:*&<&'digits'&>&*}*&
10954 .cindex "&%base62%& expansion item"
10955 .cindex "expansion" "conversion to base 62"
10956 The string must consist entirely of decimal digits. The number is converted to
10957 base 62 and output as a string of six characters, including leading zeros. In
10958 the few operating environments where Exim uses base 36 instead of base 62 for
10959 its message identifiers (because those systems do not have case-sensitive
10960 filenames), base 36 is used by this operator, despite its name. &*Note*&: Just
10961 to be absolutely clear: this is &'not'& base64 encoding.
10963 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10964 .cindex "&%base62d%& expansion item"
10965 .cindex "expansion" "conversion to base 62"
10966 The string must consist entirely of base-62 digits, or, in operating
10967 environments where Exim uses base 36 instead of base 62 for its message
10968 identifiers, base-36 digits. The number is converted to decimal and output as a
10971 .vitem &*${base64:*&<&'string'&>&*}*&
10972 .cindex "expansion" "base64 encoding"
10973 .cindex "base64 encoding" "in string expansion"
10974 .cindex "&%base64%& expansion item"
10975 .cindex certificate "base64 of DER"
10976 This operator converts a string into one that is base64 encoded.
10978 If the string is a single variable of type certificate,
10979 returns the base64 encoding of the DER form of the certificate.
10982 .vitem &*${base64d:*&<&'string'&>&*}*&
10983 .cindex "expansion" "base64 decoding"
10984 .cindex "base64 decoding" "in string expansion"
10985 .cindex "&%base64d%& expansion item"
10986 This operator converts a base64-encoded string into the un-coded form.
10989 .vitem &*${domain:*&<&'string'&>&*}*&
10990 .cindex "domain" "extraction"
10991 .cindex "expansion" "domain extraction"
10992 The string is interpreted as an RFC 2822 address and the domain is extracted
10993 from it. If the string does not parse successfully, the result is empty.
10996 .vitem &*${escape:*&<&'string'&>&*}*&
10997 .cindex "expansion" "escaping non-printing characters"
10998 .cindex "&%escape%& expansion item"
10999 If the string contains any non-printing characters, they are converted to
11000 escape sequences starting with a backslash. Whether characters with the most
11001 significant bit set (so-called &"8-bit characters"&) count as printing or not
11002 is controlled by the &%print_topbitchars%& option.
11004 .vitem &*${escape8bit:*&<&'string'&>&*}*&
11005 .cindex "expansion" "escaping 8-bit characters"
11006 .cindex "&%escape8bit%& expansion item"
11007 If the string contains any characters with the most significant bit set,
11008 they are converted to escape sequences starting with a backslash.
11009 Backslashes and DEL characters are also converted.
11012 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
11013 .cindex "expansion" "expression evaluation"
11014 .cindex "expansion" "arithmetic expression"
11015 .cindex "&%eval%& expansion item"
11016 These items supports simple arithmetic and bitwise logical operations in
11017 expansion strings. The string (after expansion) must be a conventional
11018 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
11019 logical operators, and parentheses. All operations are carried out using
11020 integer arithmetic. The operator priorities are as follows (the same as in the
11021 C programming language):
11023 .irow &'highest:'& "not (~), negate (-)"
11024 .irow "" "multiply (*), divide (/), remainder (%)"
11025 .irow "" "plus (+), minus (-)"
11026 .irow "" "shift-left (<<), shift-right (>>)"
11027 .irow "" "and (&&)"
11029 .irow &'lowest:'& "or (|)"
11031 Binary operators with the same priority are evaluated from left to right. White
11032 space is permitted before or after operators.
11034 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
11035 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
11036 decimal, even if they start with a leading zero; hexadecimal numbers are not
11037 permitted. This can be useful when processing numbers extracted from dates or
11038 times, which often do have leading zeros.
11040 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
11042 respectively. Negative numbers are supported. The result of the computation is
11043 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
11046 &`${eval:1+1} `& yields 2
11047 &`${eval:1+2*3} `& yields 7
11048 &`${eval:(1+2)*3} `& yields 9
11049 &`${eval:2+42%5} `& yields 4
11050 &`${eval:0xc&5} `& yields 4
11051 &`${eval:0xc|5} `& yields 13
11052 &`${eval:0xc^5} `& yields 9
11053 &`${eval:0xc>>1} `& yields 6
11054 &`${eval:0xc<<1} `& yields 24
11055 &`${eval:~255&0x1234} `& yields 4608
11056 &`${eval:-(~255&0x1234)} `& yields -4608
11059 As a more realistic example, in an ACL you might have
11063 {>{$rcpt_count}{10}} \
11066 {$recipients_count} \
11067 {${eval:$rcpt_count/2}} \
11070 message = Too many bad recipients
11072 The condition is true if there have been more than 10 RCPT commands and
11073 fewer than half of them have resulted in a valid recipient.
11076 .vitem &*${expand:*&<&'string'&>&*}*&
11077 .cindex "expansion" "re-expansion of substring"
11078 The &%expand%& operator causes a string to be expanded for a second time. For
11081 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
11083 first looks up a string in a file while expanding the operand for &%expand%&,
11084 and then re-expands what it has found.
11087 .vitem &*${from_utf8:*&<&'string'&>&*}*&
11089 .cindex "UTF-8" "conversion from"
11090 .cindex "expansion" "UTF-8 conversion"
11091 .cindex "&%from_utf8%& expansion item"
11092 The world is slowly moving towards Unicode, although there are no standards for
11093 email yet. However, other applications (including some databases) are starting
11094 to store data in Unicode, using UTF-8 encoding. This operator converts from a
11095 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
11096 converted to underscores. The input must be a valid UTF-8 string. If it is not,
11097 the result is an undefined sequence of bytes.
11099 Unicode code points with values less than 256 are compatible with ASCII and
11100 ISO-8859-1 (also known as Latin-1).
11101 For example, character 169 is the copyright symbol in both cases, though the
11102 way it is encoded is different. In UTF-8, more than one byte is needed for
11103 characters with code values greater than 127, whereas ISO-8859-1 is a
11104 single-byte encoding (but thereby limited to 256 characters). This makes
11105 translation from UTF-8 to ISO-8859-1 straightforward.
11108 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11109 .cindex "hash function" "textual"
11110 .cindex "expansion" "textual hash"
11111 The &%hash%& operator is a simpler interface to the hashing function that can
11112 be used when the two parameters are fixed numbers (as opposed to strings that
11113 change when expanded). The effect is the same as
11115 ${hash{<n>}{<m>}{<string>}}
11117 See the description of the general &%hash%& item above for details. The
11118 abbreviation &%h%& can be used when &%hash%& is used as an operator.
11122 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
11123 .cindex "base64 encoding" "conversion from hex"
11124 .cindex "expansion" "hex to base64"
11125 .cindex "&%hex2b64%& expansion item"
11126 This operator converts a hex string into one that is base64 encoded. This can
11127 be useful for processing the output of the various hashing functions.
11131 .vitem &*${hexquote:*&<&'string'&>&*}*&
11132 .cindex "quoting" "hex-encoded unprintable characters"
11133 .cindex "&%hexquote%& expansion item"
11134 This operator converts non-printable characters in a string into a hex
11135 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
11136 as is, and other byte values are converted to &`\xNN`&, for example, a
11137 byte value 127 is converted to &`\x7f`&.
11140 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
11141 .cindex "&%ipv6denorm%& expansion item"
11142 .cindex "IP address" normalisation
11143 This expands an IPv6 address to a full eight-element colon-separated set
11144 of hex digits including leading zeroes.
11145 A trailing ipv4-style dotted-decimal set is converted to hex.
11146 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11148 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
11149 .cindex "&%ipv6norm%& expansion item"
11150 .cindex "IP address" normalisation
11151 .cindex "IP address" "canonical form"
11152 This converts an IPv6 address to canonical form.
11153 Leading zeroes of groups are omitted, and the longest
11154 set of zero-valued groups is replaced with a double colon.
11155 A trailing ipv4-style dotted-decimal set is converted to hex.
11156 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11159 .vitem &*${lc:*&<&'string'&>&*}*&
11160 .cindex "case forcing in strings"
11161 .cindex "string" "case forcing"
11162 .cindex "lower casing"
11163 .cindex "expansion" "case forcing"
11164 .cindex "&%lc%& expansion item"
11165 This forces the letters in the string into lower-case, for example:
11169 Case is defined per the system C locale.
11171 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
11172 .cindex "expansion" "string truncation"
11173 .cindex "&%length%& expansion item"
11174 The &%length%& operator is a simpler interface to the &%length%& function that
11175 can be used when the parameter is a fixed number (as opposed to a string that
11176 changes when expanded). The effect is the same as
11178 ${length{<number>}{<string>}}
11180 See the description of the general &%length%& item above for details. Note that
11181 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
11182 when &%length%& is used as an operator.
11183 All measurement is done in bytes and is not UTF-8 aware.
11186 .vitem &*${listcount:*&<&'string'&>&*}*&
11187 .cindex "expansion" "list item count"
11188 .cindex "list" "item count"
11189 .cindex "list" "count of items"
11190 .cindex "&%listcount%& expansion item"
11191 The string is interpreted as a list and the number of items is returned.
11194 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
11195 .cindex "expansion" "named list"
11196 .cindex "&%listnamed%& expansion item"
11197 The name is interpreted as a named list and the content of the list is returned,
11198 expanding any referenced lists, re-quoting as needed for colon-separation.
11199 If the optional type is given it must be one of "a", "d", "h" or "l"
11200 and selects address-, domain-, host- or localpart- lists to search among respectively.
11201 Otherwise all types are searched in an undefined order and the first
11202 matching list is returned.
11203 &*Note*&: Neither string-expansion of lists referenced by named-list syntax elements,
11204 nor expansion of lookup elements, is done by the &%listnamed%& operator.
11207 .vitem &*${local_part:*&<&'string'&>&*}*&
11208 .cindex "expansion" "local part extraction"
11209 .cindex "&%local_part%& expansion item"
11210 The string is interpreted as an RFC 2822 address and the local part is
11211 extracted from it. If the string does not parse successfully, the result is
11213 The parsing correctly handles SMTPUTF8 Unicode in the string.
11216 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*& &&&
11217 &*${mask_n:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
11218 .cindex "masked IP address"
11219 .cindex "IP address" "masking"
11220 .cindex "CIDR notation"
11221 .cindex "expansion" "IP address masking"
11222 .cindex "&%mask%& expansion item"
11223 If the form of the string to be operated on is not an IP address followed by a
11224 slash and an integer (that is, a network address in CIDR notation), the
11225 expansion fails. Otherwise, this operator converts the IP address to binary,
11226 masks off the least significant bits according to the bit count, and converts
11227 the result back to text, with mask appended. For example,
11229 ${mask:10.111.131.206/28}
11231 returns the string &"10.111.131.192/28"&.
11233 Since this operation is expected to
11234 be mostly used for looking up masked addresses in files, the
11239 address uses dots to separate components instead of colons, because colon
11240 terminates a key string in lsearch files. So, for example,
11242 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
11246 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
11249 If the optional form &*mask_n*& is used, IPv6 address result are instead
11250 returned in normailsed form, using colons and with zero-compression.
11252 Letters in IPv6 addresses are always output in lower case.
11255 .vitem &*${md5:*&<&'string'&>&*}*&
11257 .cindex "expansion" "MD5 hash"
11258 .cindex certificate fingerprint
11259 .cindex "&%md5%& expansion item"
11260 The &%md5%& operator computes the MD5 hash value of the string, and returns it
11261 as a 32-digit hexadecimal number, in which any letters are in lower case.
11263 If the string is a single variable of type certificate,
11264 returns the MD5 hash fingerprint of the certificate.
11267 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11268 .cindex "expansion" "numeric hash"
11269 .cindex "hash function" "numeric"
11270 The &%nhash%& operator is a simpler interface to the numeric hashing function
11271 that can be used when the two parameters are fixed numbers (as opposed to
11272 strings that change when expanded). The effect is the same as
11274 ${nhash{<n>}{<m>}{<string>}}
11276 See the description of the general &%nhash%& item above for details.
11279 .vitem &*${quote:*&<&'string'&>&*}*&
11280 .cindex "quoting" "in string expansions"
11281 .cindex "expansion" "quoting"
11282 .cindex "&%quote%& expansion item"
11283 The &%quote%& operator puts its argument into double quotes if it
11284 is an empty string or
11285 contains anything other than letters, digits, underscores, dots, and hyphens.
11286 Any occurrences of double quotes and backslashes are escaped with a backslash.
11287 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
11288 respectively For example,
11296 The place where this is useful is when the argument is a substitution from a
11297 variable or a message header.
11299 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
11300 .cindex "&%quote_local_part%& expansion item"
11301 This operator is like &%quote%&, except that it quotes the string only if
11302 required to do so by the rules of RFC 2822 for quoting local parts. For
11303 example, a plus sign would not cause quoting (but it would for &%quote%&).
11304 If you are creating a new email address from the contents of &$local_part$&
11305 (or any other unknown data), you should always use this operator.
11307 This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
11308 will likely use the quoting form.
11309 Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
11312 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
11313 .cindex "quoting" "lookup-specific"
11314 This operator applies lookup-specific quoting rules to the string. Each
11315 query-style lookup type has its own quoting rules which are described with
11316 the lookups in chapter &<<CHAPfdlookup>>&. For example,
11318 ${quote_ldap:two * two}
11324 For single-key lookup types, no quoting is ever necessary and this operator
11325 yields an unchanged string.
11328 .vitem &*${randint:*&<&'n'&>&*}*&
11329 .cindex "random number"
11330 This operator returns a somewhat random number which is less than the
11331 supplied number and is at least 0. The quality of this randomness depends
11332 on how Exim was built; the values are not suitable for keying material.
11333 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
11334 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
11335 for versions of GnuTLS with that function.
11336 Otherwise, the implementation may be arc4random(), random() seeded by
11337 srandomdev() or srandom(), or a custom implementation even weaker than
11341 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
11342 .cindex "expansion" "IP address"
11343 This operator reverses an IP address; for IPv4 addresses, the result is in
11344 dotted-quad decimal form, while for IPv6 addresses the result is in
11345 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
11346 for DNS. For example,
11348 ${reverse_ip:192.0.2.4}
11349 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
11354 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
11358 .vitem &*${rfc2047:*&<&'string'&>&*}*&
11359 .cindex "expansion" "RFC 2047"
11360 .cindex "RFC 2047" "expansion operator"
11361 .cindex "&%rfc2047%& expansion item"
11362 This operator encodes text according to the rules of RFC 2047. This is an
11363 encoding that is used in header lines to encode non-ASCII characters. It is
11364 assumed that the input string is in the encoding specified by the
11365 &%headers_charset%& option, which gets its default at build time. If the string
11366 contains only characters in the range 33&--126, and no instances of the
11369 ? = ( ) < > @ , ; : \ " . [ ] _
11371 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
11372 string, using as many &"encoded words"& as necessary to encode all the
11376 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
11377 .cindex "expansion" "RFC 2047"
11378 .cindex "RFC 2047" "decoding"
11379 .cindex "&%rfc2047d%& expansion item"
11380 This operator decodes strings that are encoded as per RFC 2047. Binary zero
11381 bytes are replaced by question marks. Characters are converted into the
11382 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
11383 not recognized unless &%check_rfc2047_length%& is set false.
11385 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
11386 access a header line, RFC 2047 decoding is done automatically. You do not need
11387 to use this operator as well.
11391 .vitem &*${rxquote:*&<&'string'&>&*}*&
11392 .cindex "quoting" "in regular expressions"
11393 .cindex "regular expressions" "quoting"
11394 .cindex "&%rxquote%& expansion item"
11395 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
11396 characters in its argument. This is useful when substituting the values of
11397 variables or headers inside regular expressions.
11400 .vitem &*${sha1:*&<&'string'&>&*}*&
11401 .cindex "SHA-1 hash"
11402 .cindex "expansion" "SHA-1 hashing"
11403 .cindex certificate fingerprint
11404 .cindex "&%sha1%& expansion item"
11405 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
11406 it as a 40-digit hexadecimal number, in which any letters are in upper case.
11408 If the string is a single variable of type certificate,
11409 returns the SHA-1 hash fingerprint of the certificate.
11412 .vitem &*${sha256:*&<&'string'&>&*}*& &&&
11413 &*${sha2:*&<&'string'&>&*}*& &&&
11414 &*${sha2_<n>:*&<&'string'&>&*}*&
11415 .cindex "SHA-256 hash"
11416 .cindex "SHA-2 hash"
11417 .cindex certificate fingerprint
11418 .cindex "expansion" "SHA-256 hashing"
11419 .cindex "&%sha256%& expansion item"
11420 .cindex "&%sha2%& expansion item"
11421 The &%sha256%& operator computes the SHA-256 hash value of the string
11423 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11425 If the string is a single variable of type certificate,
11426 returns the SHA-256 hash fingerprint of the certificate.
11428 The operator can also be spelled &%sha2%& and does the same as &%sha256%&
11429 (except for certificates, which are not supported).
11430 Finally, if an underbar
11431 and a number is appended it specifies the output length, selecting a
11432 member of the SHA-2 family of hash functions.
11433 Values of 256, 384 and 512 are accepted, with 256 being the default.
11436 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
11437 &*${sha3_<n>:*&<&'string'&>&*}*&
11438 .cindex "SHA3 hash"
11439 .cindex "expansion" "SHA3 hashing"
11440 .cindex "&%sha3%& expansion item"
11441 The &%sha3%& operator computes the SHA3-256 hash value of the string
11443 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11445 If a number is appended, separated by an underbar, it specifies
11446 the output length. Values of 224, 256, 384 and 512 are accepted;
11447 with 256 being the default.
11449 The &%sha3%& expansion item is only supported if Exim has been
11450 compiled with GnuTLS 3.5.0 or later,
11451 or OpenSSL 1.1.1 or later.
11452 The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
11455 .vitem &*${stat:*&<&'string'&>&*}*&
11456 .cindex "expansion" "statting a file"
11457 .cindex "file" "extracting characteristics"
11458 .cindex "&%stat%& expansion item"
11459 The string, after expansion, must be a file path. A call to the &[stat()]&
11460 function is made for this path. If &[stat()]& fails, an error occurs and the
11461 expansion fails. If it succeeds, the data from the stat replaces the item, as a
11462 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
11463 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
11464 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
11465 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
11466 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
11467 can extract individual fields using the &%extract%& expansion item.
11469 The use of the &%stat%& expansion in users' filter files can be locked out by
11470 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
11471 systems for files larger than 2GB.
11473 .vitem &*${str2b64:*&<&'string'&>&*}*&
11474 .cindex "&%str2b64%& expansion item"
11475 Now deprecated, a synonym for the &%base64%& expansion operator.
11479 .vitem &*${strlen:*&<&'string'&>&*}*&
11480 .cindex "expansion" "string length"
11481 .cindex "string" "length in expansion"
11482 .cindex "&%strlen%& expansion item"
11483 The item is replaced by the length of the expanded string, expressed as a
11484 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
11485 All measurement is done in bytes and is not UTF-8 aware.
11488 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
11489 .cindex "&%substr%& expansion item"
11490 .cindex "substring extraction"
11491 .cindex "expansion" "substring expansion"
11492 The &%substr%& operator is a simpler interface to the &%substr%& function that
11493 can be used when the two parameters are fixed numbers (as opposed to strings
11494 that change when expanded). The effect is the same as
11496 ${substr{<start>}{<length>}{<string>}}
11498 See the description of the general &%substr%& item above for details. The
11499 abbreviation &%s%& can be used when &%substr%& is used as an operator.
11500 All measurement is done in bytes and is not UTF-8 aware.
11502 .vitem &*${time_eval:*&<&'string'&>&*}*&
11503 .cindex "&%time_eval%& expansion item"
11504 .cindex "time interval" "decoding"
11505 This item converts an Exim time interval such as &`2d4h5m`& into a number of
11508 .vitem &*${time_interval:*&<&'string'&>&*}*&
11509 .cindex "&%time_interval%& expansion item"
11510 .cindex "time interval" "formatting"
11511 The argument (after sub-expansion) must be a sequence of decimal digits that
11512 represents an interval of time as a number of seconds. It is converted into a
11513 number of larger units and output in Exim's normal time format, for example,
11516 .vitem &*${uc:*&<&'string'&>&*}*&
11517 .cindex "case forcing in strings"
11518 .cindex "string" "case forcing"
11519 .cindex "upper casing"
11520 .cindex "expansion" "case forcing"
11521 .cindex "&%uc%& expansion item"
11522 This forces the letters in the string into upper-case.
11523 Case is defined per the system C locale.
11525 .vitem &*${utf8clean:*&<&'string'&>&*}*&
11526 .cindex "correction of invalid utf-8 sequences in strings"
11527 .cindex "utf-8" "utf-8 sequences"
11528 .cindex "incorrect utf-8"
11529 .cindex "expansion" "utf-8 forcing"
11530 .cindex "&%utf8clean%& expansion item"
11531 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
11532 In versions of Exim before 4.92, this did not correctly do so for a truncated
11533 final codepoint's encoding, and the character would be silently dropped.
11534 If you must handle detection of this scenario across both sets of Exim behavior,
11535 the complexity will depend upon the task.
11536 For instance, to detect if the first character is multibyte and a 1-byte
11537 extraction can be successfully used as a path component (as is common for
11538 dividing up delivery folders), you might use:
11540 condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
11542 (which will false-positive if the first character of the local part is a
11543 literal question mark).
11545 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
11546 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
11547 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
11548 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
11549 .cindex expansion UTF-8
11550 .cindex UTF-8 expansion
11552 .cindex internationalisation
11553 .cindex "&%utf8_domain_to_alabel%& expansion item"
11554 .cindex "&%utf8_domain_from_alabel%& expansion item"
11555 .cindex "&%utf8_localpart_to_alabel%& expansion item"
11556 .cindex "&%utf8_localpart_from_alabel%& expansion item"
11557 These convert EAI mail name components between UTF-8 and a-label forms.
11558 For information on internationalisation support see &<<SECTi18nMTA>>&.
11566 .section "Expansion conditions" "SECTexpcond"
11567 .scindex IIDexpcond "expansion" "conditions"
11568 The following conditions are available for testing by the &%${if%& construct
11569 while expanding strings:
11572 .vitem &*!*&<&'condition'&>
11573 .cindex "expansion" "negating a condition"
11574 .cindex "negation" "in expansion condition"
11575 Preceding any condition with an exclamation mark negates the result of the
11578 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11579 .cindex "numeric comparison"
11580 .cindex "expansion" "numeric comparison"
11581 There are a number of symbolic operators for doing numeric comparisons. They
11587 &`>= `& greater or equal
11589 &`<= `& less or equal
11593 ${if >{$message_size}{10M} ...
11595 Note that the general negation operator provides for inequality testing. The
11596 two strings must take the form of optionally signed decimal integers,
11597 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
11598 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
11599 As a special case, the numerical value of an empty string is taken as
11602 In all cases, a relative comparator OP is testing if <&'string1'&> OP
11603 <&'string2'&>; the above example is checking if &$message_size$& is larger than
11604 10M, not if 10M is larger than &$message_size$&.
11607 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
11608 {*&<&'arg2'&>&*}...}*&
11609 .cindex "expansion" "calling an acl"
11610 .cindex "&%acl%&" "expansion condition"
11611 The name and zero to nine argument strings are first expanded separately. The expanded
11612 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
11613 Any unused are made empty. The variable &$acl_narg$& is set to the number of
11614 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
11615 and may use the variables; if another acl expansion is used the values
11616 are restored after it returns. If the ACL sets
11617 a value using a "message =" modifier the variable $value becomes
11618 the result of the expansion, otherwise it is empty.
11619 If the ACL returns accept the condition is true; if deny, false.
11620 If the ACL returns defer the result is a forced-fail.
11622 .vitem &*bool&~{*&<&'string'&>&*}*&
11623 .cindex "expansion" "boolean parsing"
11624 .cindex "&%bool%& expansion condition"
11625 This condition turns a string holding a true or false representation into
11626 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
11627 (case-insensitively); also integer numbers map to true if non-zero,
11629 An empty string is treated as false.
11630 Leading and trailing whitespace is ignored;
11631 thus a string consisting only of whitespace is false.
11632 All other string values will result in expansion failure.
11634 When combined with ACL variables, this expansion condition will let you
11635 make decisions in one place and act on those decisions in another place.
11638 ${if bool{$acl_m_privileged_sender} ...
11642 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
11643 .cindex "expansion" "boolean parsing"
11644 .cindex "&%bool_lax%& expansion condition"
11645 Like &%bool%&, this condition turns a string into a boolean state. But
11646 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
11647 loose definition that the Router &%condition%& option uses. The empty string
11648 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
11649 true. Leading and trailing whitespace is ignored.
11651 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
11653 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11654 .cindex "expansion" "encrypted comparison"
11655 .cindex "encrypted strings, comparing"
11656 .cindex "&%crypteq%& expansion condition"
11657 This condition is included in the Exim binary if it is built to support any
11658 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
11659 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
11660 included in the binary.
11662 The &%crypteq%& condition has two arguments. The first is encrypted and
11663 compared against the second, which is already encrypted. The second string may
11664 be in the LDAP form for storing encrypted strings, which starts with the
11665 encryption type in curly brackets, followed by the data. If the second string
11666 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
11667 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
11668 Typically this will be a field from a password file. An example of an encrypted
11669 string in LDAP form is:
11671 {md5}CY9rzUYh03PK3k6DJie09g==
11673 If such a string appears directly in an expansion, the curly brackets have to
11674 be quoted, because they are part of the expansion syntax. For example:
11676 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
11678 The following encryption types (whose names are matched case-independently) are
11683 .cindex "base64 encoding" "in encrypted password"
11684 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
11685 printable characters to compare with the remainder of the second string. If the
11686 length of the comparison string is 24, Exim assumes that it is base64 encoded
11687 (as in the above example). If the length is 32, Exim assumes that it is a
11688 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
11692 .cindex "SHA-1 hash"
11693 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
11694 printable characters to compare with the remainder of the second string. If the
11695 length of the comparison string is 28, Exim assumes that it is base64 encoded.
11696 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
11697 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
11700 .cindex "&[crypt()]&"
11701 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
11702 only the first eight characters of the password. However, in modern operating
11703 systems this is no longer true, and in many cases the entire password is used,
11704 whatever its length.
11707 .cindex "&[crypt16()]&"
11708 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
11709 use up to 16 characters of the password in some operating systems. Again, in
11710 modern operating systems, more characters may be used.
11712 Exim has its own version of &[crypt16()]&, which is just a double call to
11713 &[crypt()]&. For operating systems that have their own version, setting
11714 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
11715 operating system version instead of its own. This option is set by default in
11716 the OS-dependent &_Makefile_& for those operating systems that are known to
11717 support &[crypt16()]&.
11719 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
11720 it was not using the same algorithm as some operating systems' versions. It
11721 turns out that as well as &[crypt16()]& there is a function called
11722 &[bigcrypt()]& in some operating systems. This may or may not use the same
11723 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
11725 However, since there is now a move away from the traditional &[crypt()]&
11726 functions towards using SHA1 and other algorithms, tidying up this area of
11727 Exim is seen as very low priority.
11729 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
11730 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
11731 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
11732 default is &`{crypt}`&. Whatever the default, you can always use either
11733 function by specifying it explicitly in curly brackets.
11735 .vitem &*def:*&<&'variable&~name'&>
11736 .cindex "expansion" "checking for empty variable"
11737 .cindex "&%def%& expansion condition"
11738 The &%def%& condition must be followed by the name of one of the expansion
11739 variables defined in section &<<SECTexpvar>>&. The condition is true if the
11740 variable does not contain the empty string. For example:
11742 ${if def:sender_ident {from $sender_ident}}
11744 Note that the variable name is given without a leading &%$%& character. If the
11745 variable does not exist, the expansion fails.
11747 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
11748 &~&*def:h_*&<&'header&~name'&>&*:*&"
11749 .cindex "expansion" "checking header line existence"
11750 This condition is true if a message is being processed and the named header
11751 exists in the message. For example,
11753 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
11755 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
11756 the header name must be terminated by a colon if white space does not follow.
11758 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11759 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11760 .cindex "string" "comparison"
11761 .cindex "expansion" "string comparison"
11762 .cindex "&%eq%& expansion condition"
11763 .cindex "&%eqi%& expansion condition"
11764 The two substrings are first expanded. The condition is true if the two
11765 resulting strings are identical. For &%eq%& the comparison includes the case of
11766 letters, whereas for &%eqi%& the comparison is case-independent, where
11767 case is defined per the system C locale.
11769 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
11770 .cindex "expansion" "file existence test"
11771 .cindex "file" "existence test"
11772 .cindex "&%exists%&, expansion condition"
11773 The substring is first expanded and then interpreted as an absolute path. The
11774 condition is true if the named file (or directory) exists. The existence test
11775 is done by calling the &[stat()]& function. The use of the &%exists%& test in
11776 users' filter files may be locked out by the system administrator.
11778 &*Note:*& Testing a path using this condition is not a sufficient way of
11780 Consider using a dsearch lookup.
11782 .vitem &*first_delivery*&
11783 .cindex "delivery" "first"
11784 .cindex "first delivery"
11785 .cindex "expansion" "first delivery test"
11786 .cindex "&%first_delivery%& expansion condition"
11787 This condition, which has no data, is true during a message's first delivery
11788 attempt. It is false during any subsequent delivery attempts.
11791 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
11792 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
11793 .cindex "list" "iterative conditions"
11794 .cindex "expansion" "&*forall*& condition"
11795 .cindex "expansion" "&*forany*& condition"
11797 These conditions iterate over a list. The first argument is expanded to form
11798 the list. By default, the list separator is a colon, but it can be changed by
11799 the normal method (&<<SECTlistsepchange>>&).
11800 The second argument is interpreted as a condition that is to
11801 be applied to each item in the list in turn. During the interpretation of the
11802 condition, the current list item is placed in a variable called &$item$&.
11804 For &*forany*&, interpretation stops if the condition is true for any item, and
11805 the result of the whole condition is true. If the condition is false for all
11806 items in the list, the overall condition is false.
11808 For &*forall*&, interpretation stops if the condition is false for any item,
11809 and the result of the whole condition is false. If the condition is true for
11810 all items in the list, the overall condition is true.
11812 Note that negation of &*forany*& means that the condition must be false for all
11813 items for the overall condition to succeed, and negation of &*forall*& means
11814 that the condition must be false for at least one item. In this example, the
11815 list separator is changed to a comma:
11817 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
11819 The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
11820 being processed, to enable these expansion items to be nested.
11822 To scan a named list, expand it with the &*listnamed*& operator.
11824 .vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11825 "&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11826 "&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11827 "&*forany_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&"
11828 .cindex JSON "iterative conditions"
11829 .cindex JSON expansions
11830 .cindex expansion "&*forall_json*& condition"
11831 .cindex expansion "&*forany_json*& condition"
11832 .cindex expansion "&*forall_jsons*& condition"
11833 .cindex expansion "&*forany_jsons*& condition"
11834 As for the above, except that the first argument must, after expansion,
11836 The array separator is not changeable.
11837 For the &"jsons"& variants the elements are expected to be JSON strings
11838 and have their quotes removed before the evaluation of the condition.
11842 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11843 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11844 .cindex "string" "comparison"
11845 .cindex "expansion" "string comparison"
11846 .cindex "&%ge%& expansion condition"
11847 .cindex "&%gei%& expansion condition"
11848 The two substrings are first expanded. The condition is true if the first
11849 string is lexically greater than or equal to the second string. For &%ge%& the
11850 comparison includes the case of letters, whereas for &%gei%& the comparison is
11852 Case and collation order are defined per the system C locale.
11854 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11855 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11856 .cindex "string" "comparison"
11857 .cindex "expansion" "string comparison"
11858 .cindex "&%gt%& expansion condition"
11859 .cindex "&%gti%& expansion condition"
11860 The two substrings are first expanded. The condition is true if the first
11861 string is lexically greater than the second string. For &%gt%& the comparison
11862 includes the case of letters, whereas for &%gti%& the comparison is
11864 Case and collation order are defined per the system C locale.
11867 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
11868 SRS decode. See SECT &<<SECTSRS>>& for details.
11871 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11872 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11873 .cindex "string" "comparison"
11874 .cindex "list" "iterative conditions"
11875 Both strings are expanded; the second string is treated as a list of simple
11876 strings; if the first string is a member of the second, then the condition
11878 For the case-independent &%inlisti%& condition, case is defined per the system C locale.
11880 These are simpler to use versions of the more powerful &*forany*& condition.
11881 Examples, and the &*forany*& equivalents:
11883 ${if inlist{needle}{foo:needle:bar}}
11884 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11885 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11886 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11889 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11890 &*isip4&~{*&<&'string'&>&*}*& &&&
11891 &*isip6&~{*&<&'string'&>&*}*&
11892 .cindex "IP address" "testing string format"
11893 .cindex "string" "testing for IP address"
11894 .cindex "&%isip%& expansion condition"
11895 .cindex "&%isip4%& expansion condition"
11896 .cindex "&%isip6%& expansion condition"
11897 The substring is first expanded, and then tested to see if it has the form of
11898 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11899 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11901 For an IPv4 address, the test is for four dot-separated components, each of
11902 which consists of from one to three digits. For an IPv6 address, up to eight
11903 colon-separated components are permitted, each containing from one to four
11904 hexadecimal digits. There may be fewer than eight components if an empty
11905 component (adjacent colons) is present. Only one empty component is permitted.
11907 &*Note*&: The checks used to be just on the form of the address; actual numerical
11908 values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
11910 This is no longer the case.
11912 The main use of these tests is to distinguish between IP addresses and
11913 host names, or between IPv4 and IPv6 addresses. For example, you could use
11915 ${if isip4{$sender_host_address}...
11917 to test which IP version an incoming SMTP connection is using.
11919 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11920 .cindex "LDAP" "use for authentication"
11921 .cindex "expansion" "LDAP authentication test"
11922 .cindex "&%ldapauth%& expansion condition"
11923 This condition supports user authentication using LDAP. See section
11924 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11925 queries. For this use, the query must contain a user name and password. The
11926 query itself is not used, and can be empty. The condition is true if the
11927 password is not empty, and the user name and password are accepted by the LDAP
11928 server. An empty password is rejected without calling LDAP because LDAP binds
11929 with an empty password are considered anonymous regardless of the username, and
11930 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11931 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11935 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11936 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11937 .cindex "string" "comparison"
11938 .cindex "expansion" "string comparison"
11939 .cindex "&%le%& expansion condition"
11940 .cindex "&%lei%& expansion condition"
11941 The two substrings are first expanded. The condition is true if the first
11942 string is lexically less than or equal to the second string. For &%le%& the
11943 comparison includes the case of letters, whereas for &%lei%& the comparison is
11945 Case and collation order are defined per the system C locale.
11947 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11948 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11949 .cindex "string" "comparison"
11950 .cindex "expansion" "string comparison"
11951 .cindex "&%lt%& expansion condition"
11952 .cindex "&%lti%& expansion condition"
11953 The two substrings are first expanded. The condition is true if the first
11954 string is lexically less than the second string. For &%lt%& the comparison
11955 includes the case of letters, whereas for &%lti%& the comparison is
11957 Case and collation order are defined per the system C locale.
11960 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11961 .cindex "expansion" "regular expression comparison"
11962 .cindex "regular expressions" "match in expanded string"
11963 .cindex "&%match%& expansion condition"
11964 The two substrings are first expanded. The second is then treated as a regular
11965 expression and applied to the first. Because of the pre-expansion, if the
11966 regular expression contains dollar, or backslash characters, they must be
11967 escaped. Care must also be taken if the regular expression contains braces
11968 (curly brackets). A closing brace must be escaped so that it is not taken as a
11969 premature termination of <&'string2'&>. The easiest approach is to use the
11970 &`\N`& feature to disable expansion of the regular expression.
11973 ${if match {$local_part}{\N^\d{3}\N} ...
11975 If the whole expansion string is in double quotes, further escaping of
11976 backslashes is also required.
11978 The condition is true if the regular expression match succeeds.
11979 The regular expression is not required to begin with a circumflex
11980 metacharacter, but if there is no circumflex, the expression is not anchored,
11981 and it may match anywhere in the subject, not just at the start. If you want
11982 the pattern to match at the end of the subject, you must include the &`$`&
11983 metacharacter at an appropriate point.
11984 All character handling is done in bytes and is not UTF-8 aware,
11985 but we might change this in a future Exim release.
11987 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11988 At the start of an &%if%& expansion the values of the numeric variable
11989 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11990 succeeds causes them to be reset to the substrings of that condition and they
11991 will have these values during the expansion of the success string. At the end
11992 of the &%if%& expansion, the previous values are restored. After testing a
11993 combination of conditions using &%or%&, the subsequent values of the numeric
11994 variables are those of the condition that succeeded.
11996 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11997 .cindex "&%match_address%& expansion condition"
11998 See &*match_local_part*&.
12000 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12001 .cindex "&%match_domain%& expansion condition"
12002 See &*match_local_part*&.
12004 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12005 .cindex "&%match_ip%& expansion condition"
12006 This condition matches an IP address to a list of IP address patterns. It must
12007 be followed by two argument strings. The first (after expansion) must be an IP
12008 address or an empty string. The second (not expanded) is a restricted host
12009 list that can match only an IP address, not a host name. For example:
12011 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
12013 The specific types of host list item that are permitted in the list are:
12016 An IP address, optionally with a CIDR mask.
12018 A single asterisk, which matches any IP address.
12020 An empty item, which matches only if the IP address is empty. This could be
12021 useful for testing for a locally submitted message or one from specific hosts
12022 in a single test such as
12023 . ==== As this is a nested list, any displays it contains must be indented
12024 . ==== as otherwise they are too far to the left. This comment applies to
12025 . ==== the use of xmlto plus fop. There's no problem when formatting with
12026 . ==== sdop, with or without the extra indent.
12028 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
12030 where the first item in the list is the empty string.
12032 The item @[] matches any of the local host's interface addresses.
12034 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
12035 even if &`net-`& is not specified. There is never any attempt to turn the IP
12036 address into a host name. The most common type of linear search for
12037 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
12038 masks. For example:
12040 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
12042 It is of course possible to use other kinds of lookup, and in such a case, you
12043 do need to specify the &`net-`& prefix if you want to specify a specific
12044 address mask, for example:
12046 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
12048 However, unless you are combining a &%match_ip%& condition with others, it is
12049 just as easy to use the fact that a lookup is itself a condition, and write:
12051 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
12055 Note that <&'string2'&> is not itself subject to string expansion, unless
12056 Exim was built with the EXPAND_LISTMATCH_RHS option.
12058 Consult section &<<SECThoslispatip>>& for further details of these patterns.
12060 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12061 .cindex "domain list" "in expansion condition"
12062 .cindex "address list" "in expansion condition"
12063 .cindex "local part" "list, in expansion condition"
12064 .cindex "&%match_local_part%& expansion condition"
12065 This condition, together with &%match_address%& and &%match_domain%&, make it
12066 possible to test domain, address, and local part lists within expansions. Each
12067 condition requires two arguments: an item and a list to match. A trivial
12070 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
12072 In each case, the second argument may contain any of the allowable items for a
12073 list of the appropriate type. Also, because the second argument
12074 is a standard form of list, it is possible to refer to a named list.
12075 Thus, you can use conditions like this:
12077 ${if match_domain{$domain}{+local_domains}{...
12079 .cindex "&`+caseful`&"
12080 For address lists, the matching starts off caselessly, but the &`+caseful`&
12081 item can be used, as in all address lists, to cause subsequent items to
12082 have their local parts matched casefully. Domains are always matched
12085 Note that <&'string2'&> is not itself subject to string expansion, unless
12086 Exim was built with the EXPAND_LISTMATCH_RHS option.
12088 &*Note*&: Host lists are &'not'& supported in this way. This is because
12089 hosts have two identities: a name and an IP address, and it is not clear
12090 how to specify cleanly how such a test would work. However, IP addresses can be
12091 matched using &%match_ip%&.
12093 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
12094 .cindex "PAM authentication"
12095 .cindex "AUTH" "with PAM"
12096 .cindex "Solaris" "PAM support"
12097 .cindex "expansion" "PAM authentication test"
12098 .cindex "&%pam%& expansion condition"
12099 &'Pluggable Authentication Modules'&
12100 (&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
12101 available in the latest releases of Solaris and in some GNU/Linux
12102 distributions. The Exim support, which is intended for use in conjunction with
12103 the SMTP AUTH command, is available only if Exim is compiled with
12107 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
12108 in some releases of GNU/Linux &%-ldl%& is also needed.
12110 The argument string is first expanded, and the result must be a
12111 colon-separated list of strings. Leading and trailing white space is ignored.
12112 The PAM module is initialized with the service name &"exim"& and the user name
12113 taken from the first item in the colon-separated data string (<&'string1'&>).
12114 The remaining items in the data string are passed over in response to requests
12115 from the authentication function. In the simple case there will only be one
12116 request, for a password, so the data consists of just two strings.
12118 There can be problems if any of the strings are permitted to contain colon
12119 characters. In the usual way, these have to be doubled to avoid being taken as
12121 The &%listquote%& expansion item can be used for this.
12122 For example, the configuration
12123 of a LOGIN authenticator might contain this setting:
12125 server_condition = ${if pam{$auth1:${listquote{:}{$auth2}}}}
12127 In some operating systems, PAM authentication can be done only from a process
12128 running as root. Since Exim is running as the Exim user when receiving
12129 messages, this means that PAM cannot be used directly in those systems.
12130 . --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that
12133 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
12134 .cindex "&'pwcheck'& daemon"
12136 .cindex "expansion" "&'pwcheck'& authentication test"
12137 .cindex "&%pwcheck%& expansion condition"
12138 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
12139 This is one way of making it possible for passwords to be checked by a process
12140 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
12141 deprecated. Its replacement is &'saslauthd'& (see below).
12143 The pwcheck support is not included in Exim by default. You need to specify
12144 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
12145 building Exim. For example:
12147 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
12149 You do not need to install the full Cyrus software suite in order to use
12150 the pwcheck daemon. You can compile and install just the daemon alone
12151 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
12152 access to the &_/var/pwcheck_& directory.
12154 The &%pwcheck%& condition takes one argument, which must be the user name and
12155 password, separated by a colon. For example, in a LOGIN authenticator
12156 configuration, you might have this:
12158 server_condition = ${if pwcheck{$auth1:$auth2}}
12160 Again, for a PLAIN authenticator configuration, this would be:
12162 server_condition = ${if pwcheck{$auth2:$auth3}}
12164 .vitem &*queue_running*&
12165 .cindex "queue runner" "detecting when delivering from"
12166 .cindex "expansion" "queue runner test"
12167 .cindex "&%queue_running%& expansion condition"
12168 This condition, which has no data, is true during delivery attempts that are
12169 initiated by queue runner processes, and false otherwise.
12172 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
12174 .cindex "expansion" "Radius authentication"
12175 .cindex "&%radius%& expansion condition"
12176 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
12177 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
12178 the Radius client configuration file in order to build Exim with Radius
12181 With just that one setting, Exim expects to be linked with the &%radiusclient%&
12182 library, using the original API. If you are using release 0.4.0 or later of
12183 this library, you need to set
12185 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
12187 in &_Local/Makefile_& when building Exim. You can also link Exim with the
12188 &%libradius%& library that comes with FreeBSD. To do this, set
12190 RADIUS_LIB_TYPE=RADLIB
12192 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
12193 You may also have to supply a suitable setting in EXTRALIBS so that the
12194 Radius library can be found when Exim is linked.
12196 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
12197 Radius client library, which calls the Radius server. The condition is true if
12198 the authentication is successful. For example:
12200 server_condition = ${if radius{<arguments>}}
12204 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
12205 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
12206 .cindex "&'saslauthd'& daemon"
12208 .cindex "expansion" "&'saslauthd'& authentication test"
12209 .cindex "&%saslauthd%& expansion condition"
12210 This condition supports user authentication using the Cyrus &'saslauthd'&
12211 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
12212 Using this daemon is one way of making it possible for passwords to be checked
12213 by a process that is not running as root.
12215 The saslauthd support is not included in Exim by default. You need to specify
12216 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
12217 building Exim. For example:
12219 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
12221 You do not need to install the full Cyrus software suite in order to use
12222 the saslauthd daemon. You can compile and install just the daemon alone
12223 from the Cyrus SASL library.
12225 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
12226 two are mandatory. For example:
12228 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
12230 The service and the realm are optional (which is why the arguments are enclosed
12231 in their own set of braces). For details of the meaning of the service and
12232 realm, and how to run the daemon, consult the Cyrus documentation.
12237 .section "Combining expansion conditions" "SECID84"
12238 .cindex "expansion" "combining conditions"
12239 Several conditions can be tested at once by combining them using the &%and%&
12240 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
12241 conditions on their own, and precede their lists of sub-conditions. Each
12242 sub-condition must be enclosed in braces within the overall braces that contain
12243 the list. No repetition of &%if%& is used.
12247 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12248 .cindex "&""or""& expansion condition"
12249 .cindex "expansion" "&""or""& of conditions"
12250 The sub-conditions are evaluated from left to right. The condition is true if
12251 any one of the sub-conditions is true.
12254 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
12256 When a true sub-condition is found, the following ones are parsed but not
12257 evaluated. If there are several &"match"& sub-conditions the values of the
12258 numeric variables afterwards are taken from the first one that succeeds.
12260 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12261 .cindex "&""and""& expansion condition"
12262 .cindex "expansion" "&""and""& of conditions"
12263 The sub-conditions are evaluated from left to right. The condition is true if
12264 all of the sub-conditions are true. If there are several &"match"&
12265 sub-conditions, the values of the numeric variables afterwards are taken from
12266 the last one. When a false sub-condition is found, the following ones are
12267 parsed but not evaluated.
12269 .ecindex IIDexpcond
12274 .section "Expansion variables" "SECTexpvar"
12275 .cindex "expansion" "variables, list of"
12276 This section contains an alphabetical list of all the expansion variables. Some
12277 of them are available only when Exim is compiled with specific options such as
12278 support for TLS or the content scanning extension.
12281 .vitem "&$0$&, &$1$&, etc"
12282 .cindex "numerical variables (&$1$& &$2$& etc)"
12283 When a &%match%& expansion condition succeeds, these variables contain the
12284 captured substrings identified by the regular expression during subsequent
12285 processing of the success string of the containing &%if%& expansion item.
12286 In the expansion condition case
12287 they do not retain their values afterwards; in fact, their previous
12288 values are restored at the end of processing an &%if%& item. The numerical
12289 variables may also be set externally by some other matching process which
12290 precedes the expansion of the string. For example, the commands available in
12291 Exim filter files include an &%if%& command with its own regular expression
12292 matching condition.
12294 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
12295 Within an acl condition, expansion condition or expansion item
12296 any arguments are copied to these variables,
12297 any unused variables being made empty.
12299 .vitem "&$acl_c...$&"
12300 Values can be placed in these variables by the &%set%& modifier in an ACL. They
12301 can be given any name that starts with &$acl_c$& and is at least six characters
12302 long, but the sixth character must be either a digit or an underscore. For
12303 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
12304 variables persist throughout the lifetime of an SMTP connection. They can be
12305 used to pass information between ACLs and between different invocations of the
12306 same ACL. When a message is received, the values of these variables are saved
12307 with the message, and can be accessed by filters, routers, and transports
12308 during subsequent delivery.
12310 .vitem "&$acl_m...$&"
12311 These variables are like the &$acl_c...$& variables, except that their values
12312 are reset after a message has been received. Thus, if several messages are
12313 received in one SMTP connection, &$acl_m...$& values are not passed on from one
12314 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
12315 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
12316 message is received, the values of these variables are saved with the message,
12317 and can be accessed by filters, routers, and transports during subsequent
12320 .vitem &$acl_narg$&
12321 Within an acl condition, expansion condition or expansion item
12322 this variable has the number of arguments.
12324 .vitem &$acl_verify_message$&
12325 .vindex "&$acl_verify_message$&"
12326 After an address verification has failed, this variable contains the failure
12327 message. It retains its value for use in subsequent modifiers of the verb.
12328 The message can be preserved by coding like this:
12330 warn !verify = sender
12331 set acl_m0 = $acl_verify_message
12333 You can use &$acl_verify_message$& during the expansion of the &%message%& or
12334 &%log_message%& modifiers, to include information about the verification
12336 &*Note*&: The variable is cleared at the end of processing the ACL verb.
12338 .vitem &$address_data$&
12339 .vindex "&$address_data$&"
12340 This variable is set by means of the &%address_data%& option in routers. The
12341 value then remains with the address while it is processed by subsequent routers
12342 and eventually a transport. If the transport is handling multiple addresses,
12343 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
12344 for more details. &*Note*&: The contents of &$address_data$& are visible in
12347 If &$address_data$& is set when the routers are called from an ACL to verify
12348 a recipient address, the final value is still in the variable for subsequent
12349 conditions and modifiers of the ACL statement. If routing the address caused it
12350 to be redirected to just one address, the child address is also routed as part
12351 of the verification, and in this case the final value of &$address_data$& is
12352 from the child's routing.
12354 If &$address_data$& is set when the routers are called from an ACL to verify a
12355 sender address, the final value is also preserved, but this time in
12356 &$sender_address_data$&, to distinguish it from data from a recipient
12359 In both cases (recipient and sender verification), the value does not persist
12360 after the end of the current ACL statement. If you want to preserve
12361 these values for longer, you can save them in ACL variables.
12363 .vitem &$address_file$&
12364 .vindex "&$address_file$&"
12365 When, as a result of aliasing, forwarding, or filtering, a message is directed
12366 to a specific file, this variable holds the name of the file when the transport
12367 is running. At other times, the variable is empty. For example, using the
12368 default configuration, if user &%r2d2%& has a &_.forward_& file containing
12370 /home/r2d2/savemail
12372 then when the &(address_file)& transport is running, &$address_file$&
12373 contains the text string &`/home/r2d2/savemail`&.
12374 .cindex "Sieve filter" "value of &$address_file$&"
12375 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
12376 then up to the transport configuration to generate an appropriate absolute path
12377 to the relevant file.
12379 .vitem &$address_pipe$&
12380 .vindex "&$address_pipe$&"
12381 When, as a result of aliasing or forwarding, a message is directed to a pipe,
12382 this variable holds the pipe command when the transport is running.
12384 .vitem "&$auth1$& &-- &$auth4$&"
12385 .vindex "&$auth1$&, &$auth2$&, etc"
12386 These variables are used in SMTP authenticators (see chapters
12387 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
12389 .vitem &$authenticated_id$&
12390 .cindex "authentication" "id"
12391 .vindex "&$authenticated_id$&"
12392 When a server successfully authenticates a client it may be configured to
12393 preserve some of the authentication information in the variable
12394 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
12395 user/password authenticator configuration might preserve the user name for use
12396 in the routers. Note that this is not the same information that is saved in
12397 &$sender_host_authenticated$&.
12399 When a message is submitted locally (that is, not over a TCP connection)
12400 the value of &$authenticated_id$& is normally the login name of the calling
12401 process. However, a trusted user can override this by means of the &%-oMai%&
12402 command line option.
12403 This second case also sets up information used by the
12404 &$authresults$& expansion item.
12406 .vitem &$authenticated_fail_id$&
12407 .cindex "authentication" "fail" "id"
12408 .vindex "&$authenticated_fail_id$&"
12409 When an authentication attempt fails, the variable &$authenticated_fail_id$&
12410 will contain the failed authentication id. If more than one authentication
12411 id is attempted, it will contain only the last one. The variable is
12412 available for processing in the ACL's, generally the quit or notquit ACL.
12413 A message to a local recipient could still be accepted without requiring
12414 authentication, which means this variable could also be visible in all of
12418 .vitem &$authenticated_sender$&
12419 .cindex "sender" "authenticated"
12420 .cindex "authentication" "sender"
12421 .cindex "AUTH" "on MAIL command"
12422 .vindex "&$authenticated_sender$&"
12423 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
12424 SMTP MAIL command if it believes the sender is sufficiently trusted, as
12425 described in section &<<SECTauthparamail>>&. Unless the data is the string
12426 &"<>"&, it is set as the authenticated sender of the message, and the value is
12427 available during delivery in the &$authenticated_sender$& variable. If the
12428 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
12430 .vindex "&$qualify_domain$&"
12431 When a message is submitted locally (that is, not over a TCP connection), the
12432 value of &$authenticated_sender$& is an address constructed from the login
12433 name of the calling process and &$qualify_domain$&, except that a trusted user
12434 can override this by means of the &%-oMas%& command line option.
12437 .vitem &$authentication_failed$&
12438 .cindex "authentication" "failure"
12439 .vindex "&$authentication_failed$&"
12440 This variable is set to &"1"& in an Exim server if a client issues an AUTH
12441 command that does not succeed. Otherwise it is set to &"0"&. This makes it
12442 possible to distinguish between &"did not try to authenticate"&
12443 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
12444 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
12445 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
12446 negative response to an AUTH command, including (for example) an attempt to use
12447 an undefined mechanism.
12449 .vitem &$av_failed$&
12450 .cindex "content scanning" "AV scanner failure"
12451 This variable is available when Exim is compiled with the content-scanning
12452 extension. It is set to &"0"& by default, but will be set to &"1"& if any
12453 problem occurs with the virus scanner (specified by &%av_scanner%&) during
12454 the ACL malware condition.
12456 .vitem &$body_linecount$&
12457 .cindex "message body" "line count"
12458 .cindex "body of message" "line count"
12459 .vindex "&$body_linecount$&"
12460 When a message is being received or delivered, this variable contains the
12461 number of lines in the message's body. See also &$message_linecount$&.
12463 .vitem &$body_zerocount$&
12464 .cindex "message body" "binary zero count"
12465 .cindex "body of message" "binary zero count"
12466 .cindex "binary zero" "in message body"
12467 .vindex "&$body_zerocount$&"
12468 When a message is being received or delivered, this variable contains the
12469 number of binary zero bytes (ASCII NULs) in the message's body.
12471 .vitem &$bounce_recipient$&
12472 .vindex "&$bounce_recipient$&"
12473 This is set to the recipient address of a bounce message while Exim is creating
12474 it. It is useful if a customized bounce message text file is in use (see
12475 chapter &<<CHAPemsgcust>>&).
12477 .vitem &$bounce_return_size_limit$&
12478 .vindex "&$bounce_return_size_limit$&"
12479 This contains the value set in the &%bounce_return_size_limit%& option, rounded
12480 up to a multiple of 1000. It is useful when a customized error message text
12481 file is in use (see chapter &<<CHAPemsgcust>>&).
12483 .vitem &$caller_gid$&
12484 .cindex "gid (group id)" "caller"
12485 .vindex "&$caller_gid$&"
12486 The real group id under which the process that called Exim was running. This is
12487 not the same as the group id of the originator of a message (see
12488 &$originator_gid$&). If Exim re-execs itself, this variable in the new
12489 incarnation normally contains the Exim gid.
12491 .vitem &$caller_uid$&
12492 .cindex "uid (user id)" "caller"
12493 .vindex "&$caller_uid$&"
12494 The real user id under which the process that called Exim was running. This is
12495 not the same as the user id of the originator of a message (see
12496 &$originator_uid$&). If Exim re-execs itself, this variable in the new
12497 incarnation normally contains the Exim uid.
12499 .vitem &$callout_address$&
12500 .vindex "&$callout_address$&"
12501 After a callout for verification, spamd or malware daemon service, the
12502 address that was connected to.
12504 .vitem &$compile_number$&
12505 .vindex "&$compile_number$&"
12506 The building process for Exim keeps a count of the number
12507 of times it has been compiled. This serves to distinguish different
12508 compilations of the same version of Exim.
12510 .vitem &$config_dir$&
12511 .vindex "&$config_dir$&"
12512 The directory name of the main configuration file. That is, the content of
12513 &$config_file$& with the last component stripped. The value does not
12514 contain the trailing slash. If &$config_file$& does not contain a slash,
12515 &$config_dir$& is ".".
12517 .vitem &$config_file$&
12518 .vindex "&$config_file$&"
12519 The name of the main configuration file Exim is using.
12521 .vitem &$dkim_verify_status$&
12522 Results of DKIM verification.
12523 For details see section &<<SECDKIMVFY>>&.
12525 .vitem &$dkim_cur_signer$& &&&
12526 &$dkim_verify_reason$& &&&
12527 &$dkim_domain$& &&&
12528 &$dkim_identity$& &&&
12529 &$dkim_selector$& &&&
12531 &$dkim_canon_body$& &&&
12532 &$dkim_canon_headers$& &&&
12533 &$dkim_copiedheaders$& &&&
12534 &$dkim_bodylength$& &&&
12535 &$dkim_created$& &&&
12536 &$dkim_expires$& &&&
12537 &$dkim_headernames$& &&&
12538 &$dkim_key_testing$& &&&
12539 &$dkim_key_nosubdomains$& &&&
12540 &$dkim_key_srvtype$& &&&
12541 &$dkim_key_granularity$& &&&
12542 &$dkim_key_notes$& &&&
12543 &$dkim_key_length$&
12544 These variables are only available within the DKIM ACL.
12545 For details see section &<<SECDKIMVFY>>&.
12547 .vitem &$dkim_signers$&
12548 .vindex &$dkim_signers$&
12549 When a message has been received this variable contains
12550 a colon-separated list of signer domains and identities for the message.
12551 For details see section &<<SECDKIMVFY>>&.
12553 .vitem &$dmarc_domain_policy$& &&&
12554 &$dmarc_status$& &&&
12555 &$dmarc_status_text$& &&&
12556 &$dmarc_used_domains$&
12557 Results of DMARC verification.
12558 For details see section &<<SECDMARC>>&.
12560 .vitem &$dnslist_domain$& &&&
12561 &$dnslist_matched$& &&&
12562 &$dnslist_text$& &&&
12564 .vindex "&$dnslist_domain$&"
12565 .vindex "&$dnslist_matched$&"
12566 .vindex "&$dnslist_text$&"
12567 .vindex "&$dnslist_value$&"
12568 .cindex "black list (DNS)"
12569 When a DNS (black) list lookup succeeds, these variables are set to contain
12570 the following data from the lookup: the list's domain name, the key that was
12571 looked up, the contents of any associated TXT record, and the value from the
12572 main A record. See section &<<SECID204>>& for more details.
12575 .vindex "&$domain$&"
12576 When an address is being routed, or delivered on its own, this variable
12577 contains the domain. Uppercase letters in the domain are converted into lower
12578 case for &$domain$&.
12580 Global address rewriting happens when a message is received, so the value of
12581 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
12582 is set during user filtering, but not during system filtering, because a
12583 message may have many recipients and the system filter is called just once.
12585 When more than one address is being delivered at once (for example, several
12586 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
12587 have the same domain. Transports can be restricted to handling only one domain
12588 at a time if the value of &$domain$& is required at transport time &-- this is
12589 the default for local transports. For further details of the environment in
12590 which local transports are run, see chapter &<<CHAPenvironment>>&.
12592 .oindex "&%delay_warning_condition%&"
12593 At the end of a delivery, if all deferred addresses have the same domain, it is
12594 set in &$domain$& during the expansion of &%delay_warning_condition%&.
12596 The &$domain$& variable is also used in some other circumstances:
12599 When an ACL is running for a RCPT command, &$domain$& contains the domain of
12600 the recipient address. The domain of the &'sender'& address is in
12601 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
12602 normally set during the running of the MAIL ACL. However, if the sender address
12603 is verified with a callout during the MAIL ACL, the sender domain is placed in
12604 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
12605 the &(smtp)& transport.
12608 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12609 &$domain$& contains the domain portion of the address that is being rewritten;
12610 it can be used in the expansion of the replacement address, for example, to
12611 rewrite domains by file lookup.
12614 With one important exception, whenever a domain list is being scanned,
12615 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
12616 a &%sender_domains%& condition in an ACL is being processed, the subject domain
12617 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
12618 that, in a RCPT ACL, the sender domain list can be dependent on the
12619 recipient domain (which is what is in &$domain$& at this time).
12622 .cindex "ETRN" "value of &$domain$&"
12623 .oindex "&%smtp_etrn_command%&"
12624 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
12625 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
12628 .cindex "tainted data"
12629 If the origin of the data is an incoming message,
12630 the result of expanding this variable is tainted and may not
12631 be further expanded or used as a filename.
12632 When an untainted version is needed, one should be obtained from
12633 looking up the value in a local (therefore trusted) database.
12634 Often &$domain_data$& is usable in this role.
12637 .vitem &$domain_data$&
12638 .vindex "&$domain_data$&"
12639 When the &%domains%& condition on a router
12642 against a list, the match value is copied to &$domain_data$&.
12643 This is an enhancement over previous versions of Exim, when it only
12644 applied to the data read by a lookup.
12645 For details on match values see section &<<SECTlistresults>>& et. al.
12647 If the router routes the
12648 address to a transport, the value is available in that transport. If the
12649 transport is handling multiple addresses, the value from the first address is
12652 &$domain_data$& set in an ACL is available during
12653 the rest of the ACL statement.
12655 .vitem &$exim_gid$&
12656 .vindex "&$exim_gid$&"
12657 This variable contains the numerical value of the Exim group id.
12659 .vitem &$exim_path$&
12660 .vindex "&$exim_path$&"
12661 This variable contains the path to the Exim binary.
12663 .vitem &$exim_uid$&
12664 .vindex "&$exim_uid$&"
12665 This variable contains the numerical value of the Exim user id.
12667 .vitem &$exim_version$&
12668 .vindex "&$exim_version$&"
12669 This variable contains the version string of the Exim build.
12670 The first character is a major version number, currently 4.
12671 Then after a dot, the next group of digits is a minor version number.
12672 There may be other characters following the minor version.
12673 This value may be overridden by the &%exim_version%& main config option.
12675 .vitem &$header_$&<&'name'&>
12676 This is not strictly an expansion variable. It is expansion syntax for
12677 inserting the message header line with the given name. Note that the name must
12678 be terminated by colon or white space, because it may contain a wide variety of
12679 characters. Note also that braces must &'not'& be used.
12680 See the full description in section &<<SECTexpansionitems>>& above.
12682 .vitem &$headers_added$&
12683 .vindex "&$headers_added$&"
12684 Within an ACL this variable contains the headers added so far by
12685 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
12686 The headers are a newline-separated list.
12690 When the &%check_local_user%& option is set for a router, the user's home
12691 directory is placed in &$home$& when the check succeeds. In particular, this
12692 means it is set during the running of users' filter files. A router may also
12693 explicitly set a home directory for use by a transport; this can be overridden
12694 by a setting on the transport itself.
12696 When running a filter test via the &%-bf%& option, &$home$& is set to the value
12697 of the environment variable HOME, which is subject to the
12698 &%keep_environment%& and &%add_environment%& main config options.
12702 If a router assigns an address to a transport (any transport), and passes a
12703 list of hosts with the address, the value of &$host$& when the transport starts
12704 to run is the name of the first host on the list. Note that this applies both
12705 to local and remote transports.
12707 .cindex "transport" "filter"
12708 .cindex "filter" "transport filter"
12709 For the &(smtp)& transport, if there is more than one host, the value of
12710 &$host$& changes as the transport works its way through the list. In
12711 particular, when the &(smtp)& transport is expanding its options for encryption
12712 using TLS, or for specifying a transport filter (see chapter
12713 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
12716 When used in the client part of an authenticator configuration (see chapter
12717 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
12718 client is connected.
12721 .vitem &$host_address$&
12722 .vindex "&$host_address$&"
12723 This variable is set to the remote host's IP address whenever &$host$& is set
12724 for a remote connection. It is also set to the IP address that is being checked
12725 when the &%ignore_target_hosts%& option is being processed.
12727 .vitem &$host_data$&
12728 .vindex "&$host_data$&"
12729 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
12730 result of the lookup is made available in the &$host_data$& variable. This
12731 allows you, for example, to do things like this:
12733 deny hosts = net-lsearch;/some/file
12734 message = $host_data
12736 .vitem &$host_lookup_deferred$&
12737 .cindex "host name" "lookup, failure of"
12738 .vindex "&$host_lookup_deferred$&"
12739 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
12740 message comes from a remote host and there is an attempt to look up the host's
12741 name from its IP address, and the attempt is not successful, one of these
12742 variables is set to &"1"&.
12745 If the lookup receives a definite negative response (for example, a DNS lookup
12746 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
12749 If there is any kind of problem during the lookup, such that Exim cannot
12750 tell whether or not the host name is defined (for example, a timeout for a DNS
12751 lookup), &$host_lookup_deferred$& is set to &"1"&.
12754 Looking up a host's name from its IP address consists of more than just a
12755 single reverse lookup. Exim checks that a forward lookup of at least one of the
12756 names it receives from a reverse lookup yields the original IP address. If this
12757 is not the case, Exim does not accept the looked up name(s), and
12758 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
12759 IP address (for example, the existence of a PTR record in the DNS) is not
12760 sufficient on its own for the success of a host name lookup. If the reverse
12761 lookup succeeds, but there is a lookup problem such as a timeout when checking
12762 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
12763 &"1"&. See also &$sender_host_name$&.
12765 .cindex authentication "expansion item"
12766 Performing these checks sets up information used by the
12767 &%authresults%& expansion item.
12770 .vitem &$host_lookup_failed$&
12771 .vindex "&$host_lookup_failed$&"
12772 See &$host_lookup_deferred$&.
12774 .vitem &$host_port$&
12775 .vindex "&$host_port$&"
12776 This variable is set to the remote host's TCP port whenever &$host$& is set
12777 for an outbound connection.
12779 .vitem &$initial_cwd$&
12780 .vindex "&$initial_cwd$&
12781 This variable contains the full path name of the initial working
12782 directory of the current Exim process. This may differ from the current
12783 working directory, as Exim changes this to "/" during early startup, and
12784 to &$spool_directory$& later.
12787 .vindex "&$inode$&"
12788 The only time this variable is set is while expanding the &%directory_file%&
12789 option in the &(appendfile)& transport. The variable contains the inode number
12790 of the temporary file which is about to be renamed. It can be used to construct
12791 a unique name for the file.
12793 .vitem &$interface_address$& &&&
12795 .vindex "&$interface_address$&"
12796 .vindex "&$interface_port$&"
12797 These are obsolete names for &$received_ip_address$& and &$received_port$&.
12801 This variable is used during the expansion of &*forall*& and &*forany*&
12802 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
12803 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
12807 .vindex "&$ldap_dn$&"
12808 This variable, which is available only when Exim is compiled with LDAP support,
12809 contains the DN from the last entry in the most recently successful LDAP
12812 .vitem &$load_average$&
12813 .vindex "&$load_average$&"
12814 This variable contains the system load average, multiplied by 1000 so that it
12815 is an integer. For example, if the load average is 0.21, the value of the
12816 variable is 210. The value is recomputed every time the variable is referenced.
12818 .vitem &$local_part$&
12819 .vindex "&$local_part$&"
12820 When an address is being routed, or delivered on its own, this
12821 variable contains the local part. When a number of addresses are being
12822 delivered together (for example, multiple RCPT commands in an SMTP
12823 session), &$local_part$& is not set.
12825 Global address rewriting happens when a message is received, so the value of
12826 &$local_part$& during routing and delivery is the value after rewriting.
12827 &$local_part$& is set during user filtering, but not during system filtering,
12828 because a message may have many recipients and the system filter is called just
12831 .cindex "tainted data"
12832 If the origin of the data is an incoming message,
12833 the result of expanding this variable is tainted and
12834 may not be further expanded or used as a filename.
12836 &*Warning*&: the content of this variable is usually provided by a potential
12838 Consider carefully the implications of using it unvalidated as a name
12840 This presents issues for users' &_.forward_& and filter files.
12841 For traditional full user accounts, use &%check_local_users%& and the
12842 &$local_part_data$& variable rather than this one.
12843 For virtual users, store a suitable pathname component in the database
12844 which is used for account name validation, and use that retrieved value
12845 rather than this variable.
12846 Often &$local_part_data$& is usable in this role.
12847 If needed, use a router &%address_data%& or &%set%& option for
12848 the retrieved data.
12850 When a message is being delivered to a file, pipe, or autoreply transport as a
12851 result of aliasing or forwarding, &$local_part$& is set to the local part of
12852 the parent address, not to the filename or command (see &$address_file$& and
12855 When an ACL is running for a RCPT command, &$local_part$& contains the
12856 local part of the recipient address.
12858 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12859 &$local_part$& contains the local part of the address that is being rewritten;
12860 it can be used in the expansion of the replacement address, for example.
12862 In all cases, all quoting is removed from the local part. For example, for both
12865 "abc:xyz"@test.example
12866 abc\:xyz@test.example
12868 the value of &$local_part$& is
12872 If you use &$local_part$& to create another address, you should always wrap it
12873 inside a quoting operator. For example, in a &(redirect)& router you could
12876 data = ${quote_local_part:$local_part}@new.domain.example
12878 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
12879 to process local parts in a case-dependent manner in a router, you can set the
12880 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
12882 .vitem &$local_part_data$&
12883 .vindex "&$local_part_data$&"
12884 When the &%local_parts%& condition on a router or ACL
12885 matches a local part list
12886 the match value is copied to &$local_part_data$&.
12887 This is an enhancement over previous versions of Exim, when it only
12888 applied to the data read by a lookup.
12889 For details on match values see section &<<SECTlistresults>>& et. al.
12891 The &%check_local_user%& router option also sets this variable.
12893 .vindex &$local_part_prefix$& &&&
12894 &$local_part_prefix_v$& &&&
12895 &$local_part_suffix$& &&&
12896 &$local_part_suffix_v$&
12897 .cindex affix variables
12898 If a local part prefix or suffix has been recognized, it is not included in the
12899 value of &$local_part$& during routing and subsequent delivery. The values of
12900 any prefix or suffix are in &$local_part_prefix$& and
12901 &$local_part_suffix$&, respectively.
12902 .cindex "tainted data"
12903 If the specification did not include a wildcard then
12904 the affix variable value is not tainted.
12906 If the affix specification included a wildcard then the portion of
12907 the affix matched by the wildcard is in
12908 &$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate,
12909 and both the whole and varying values are tainted.
12911 .vitem &$local_scan_data$&
12912 .vindex "&$local_scan_data$&"
12913 This variable contains the text returned by the &[local_scan()]& function when
12914 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
12916 .vitem &$local_user_gid$&
12917 .vindex "&$local_user_gid$&"
12918 See &$local_user_uid$&.
12920 .vitem &$local_user_uid$&
12921 .vindex "&$local_user_uid$&"
12922 This variable and &$local_user_gid$& are set to the uid and gid after the
12923 &%check_local_user%& router precondition succeeds. This means that their values
12924 are available for the remaining preconditions (&%senders%&, &%require_files%&,
12925 and &%condition%&), for the &%address_data%& expansion, and for any
12926 router-specific expansions. At all other times, the values in these variables
12927 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
12929 .vitem &$localhost_number$&
12930 .vindex "&$localhost_number$&"
12931 This contains the expanded value of the
12932 &%localhost_number%& option. The expansion happens after the main options have
12935 .vitem &$log_inodes$&
12936 .vindex "&$log_inodes$&"
12937 The number of free inodes in the disk partition where Exim's
12938 log files are being written. The value is recalculated whenever the variable is
12939 referenced. If the relevant file system does not have the concept of inodes,
12940 the value of is -1. See also the &%check_log_inodes%& option.
12942 .vitem &$log_space$&
12943 .vindex "&$log_space$&"
12944 The amount of free space (as a number of kilobytes) in the disk
12945 partition where Exim's log files are being written. The value is recalculated
12946 whenever the variable is referenced. If the operating system does not have the
12947 ability to find the amount of free space (only true for experimental systems),
12948 the space value is -1. See also the &%check_log_space%& option.
12951 .vitem &$lookup_dnssec_authenticated$&
12952 .vindex "&$lookup_dnssec_authenticated$&"
12953 This variable is set after a DNS lookup done by
12954 a dnsdb lookup expansion, dnslookup router or smtp transport.
12955 .cindex "DNS" "DNSSEC"
12956 It will be empty if &(DNSSEC)& was not requested,
12957 &"no"& if the result was not labelled as authenticated data
12958 and &"yes"& if it was.
12959 Results that are labelled as authoritative answer that match
12960 the &%dns_trust_aa%& configuration variable count also
12961 as authenticated data.
12963 .vitem &$mailstore_basename$&
12964 .vindex "&$mailstore_basename$&"
12965 This variable is set only when doing deliveries in &"mailstore"& format in the
12966 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
12967 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
12968 contains the basename of the files that are being written, that is, the name
12969 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
12972 .vitem &$malware_name$&
12973 .vindex "&$malware_name$&"
12974 This variable is available when Exim is compiled with the
12975 content-scanning extension. It is set to the name of the virus that was found
12976 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12978 .vitem &$max_received_linelength$&
12979 .vindex "&$max_received_linelength$&"
12980 .cindex "maximum" "line length"
12981 .cindex "line length" "maximum"
12982 This variable contains the number of bytes in the longest line that was
12983 received as part of the message, not counting the line termination
12985 It is not valid if the &%spool_wireformat%& option is used.
12987 .vitem &$message_age$&
12988 .cindex "message" "age of"
12989 .vindex "&$message_age$&"
12990 This variable is set at the start of a delivery attempt to contain the number
12991 of seconds since the message was received. It does not change during a single
12994 .vitem &$message_body$&
12995 .cindex "body of message" "expansion variable"
12996 .cindex "message body" "in expansion"
12997 .cindex "binary zero" "in message body"
12998 .vindex "&$message_body$&"
12999 .oindex "&%message_body_visible%&"
13000 This variable contains the initial portion of a message's body while it is
13001 being delivered, and is intended mainly for use in filter files. The maximum
13002 number of characters of the body that are put into the variable is set by the
13003 &%message_body_visible%& configuration option; the default is 500.
13005 .oindex "&%message_body_newlines%&"
13006 By default, newlines are converted into spaces in &$message_body$&, to make it
13007 easier to search for phrases that might be split over a line break. However,
13008 this can be disabled by setting &%message_body_newlines%& to be true. Binary
13009 zeros are always converted into spaces.
13011 .vitem &$message_body_end$&
13012 .cindex "body of message" "expansion variable"
13013 .cindex "message body" "in expansion"
13014 .vindex "&$message_body_end$&"
13015 This variable contains the final portion of a message's
13016 body while it is being delivered. The format and maximum size are as for
13019 .vitem &$message_body_size$&
13020 .cindex "body of message" "size"
13021 .cindex "message body" "size"
13022 .vindex "&$message_body_size$&"
13023 When a message is being delivered, this variable contains the size of the body
13024 in bytes. The count starts from the character after the blank line that
13025 separates the body from the header. Newlines are included in the count. See
13026 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
13028 If the spool file is wireformat
13029 (see the &%spool_wireformat%& main option)
13030 the CRLF line-terminators are included in the count.
13032 .vitem &$message_exim_id$&
13033 .vindex "&$message_exim_id$&"
13034 When a message is being received or delivered, this variable contains the
13035 unique message id that is generated and used by Exim to identify the message.
13036 An id is not created for a message until after its header has been successfully
13037 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
13038 line; it is the local id that Exim assigns to the message, for example:
13039 &`1BXTIK-0001yO-VA`&.
13041 .vitem &$message_headers$&
13042 .vindex &$message_headers$&
13043 This variable contains a concatenation of all the header lines when a message
13044 is being processed, except for lines added by routers or transports. The header
13045 lines are separated by newline characters. Their contents are decoded in the
13046 same way as a header line that is inserted by &%bheader%&.
13048 .vitem &$message_headers_raw$&
13049 .vindex &$message_headers_raw$&
13050 This variable is like &$message_headers$& except that no processing of the
13051 contents of header lines is done.
13053 .vitem &$message_id$&
13054 This is an old name for &$message_exim_id$&. It is now deprecated.
13056 .vitem &$message_linecount$&
13057 .vindex "&$message_linecount$&"
13058 This variable contains the total number of lines in the header and body of the
13059 message. Compare &$body_linecount$&, which is the count for the body only.
13060 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
13061 number of lines received. Before delivery happens (that is, before filters,
13062 routers, and transports run) the count is increased to include the
13063 &'Received:'& header line that Exim standardly adds, and also any other header
13064 lines that are added by ACLs. The blank line that separates the message header
13065 from the body is not counted.
13067 As with the special case of &$message_size$&, during the expansion of the
13068 appendfile transport's maildir_tag option in maildir format, the value of
13069 &$message_linecount$& is the precise size of the number of newlines in the
13070 file that has been written (minus one for the blank line between the
13071 header and the body).
13073 Here is an example of the use of this variable in a DATA ACL:
13076 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
13077 message = Too many lines in message header
13079 In the MAIL and RCPT ACLs, the value is zero because at that stage the
13080 message has not yet been received.
13082 This variable is not valid if the &%spool_wireformat%& option is used.
13084 .vitem &$message_size$&
13085 .cindex "size" "of message"
13086 .cindex "message" "size"
13087 .vindex "&$message_size$&"
13088 When a message is being processed, this variable contains its size in bytes. In
13089 most cases, the size includes those headers that were received with the
13090 message, but not those (such as &'Envelope-to:'&) that are added to individual
13091 deliveries as they are written. However, there is one special case: during the
13092 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
13093 doing a delivery in maildir format, the value of &$message_size$& is the
13094 precise size of the file that has been written. See also
13095 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
13097 .cindex "RCPT" "value of &$message_size$&"
13098 While running a per message ACL (mail/rcpt/predata), &$message_size$&
13099 contains the size supplied on the MAIL command, or -1 if no size was given. The
13100 value may not, of course, be truthful.
13102 .vitem &$mime_anomaly_level$& &&&
13103 &$mime_anomaly_text$& &&&
13104 &$mime_boundary$& &&&
13105 &$mime_charset$& &&&
13106 &$mime_content_description$& &&&
13107 &$mime_content_disposition$& &&&
13108 &$mime_content_id$& &&&
13109 &$mime_content_size$& &&&
13110 &$mime_content_transfer_encoding$& &&&
13111 &$mime_content_type$& &&&
13112 &$mime_decoded_filename$& &&&
13113 &$mime_filename$& &&&
13114 &$mime_is_coverletter$& &&&
13115 &$mime_is_multipart$& &&&
13116 &$mime_is_rfc822$& &&&
13117 &$mime_part_count$&
13118 A number of variables whose names start with &$mime$& are
13119 available when Exim is compiled with the content-scanning extension. For
13120 details, see section &<<SECTscanmimepart>>&.
13122 .vitem "&$n0$& &-- &$n9$&"
13123 These variables are counters that can be incremented by means
13124 of the &%add%& command in filter files.
13126 .vitem &$original_domain$&
13127 .vindex "&$domain$&"
13128 .vindex "&$original_domain$&"
13129 When a top-level address is being processed for delivery, this contains the
13130 same value as &$domain$&. However, if a &"child"& address (for example,
13131 generated by an alias, forward, or filter file) is being processed, this
13132 variable contains the domain of the original address (lower cased). This
13133 differs from &$parent_domain$& only when there is more than one level of
13134 aliasing or forwarding. When more than one address is being delivered in a
13135 single transport run, &$original_domain$& is not set.
13137 If a new address is created by means of a &%deliver%& command in a system
13138 filter, it is set up with an artificial &"parent"& address. This has the local
13139 part &'system-filter'& and the default qualify domain.
13141 .vitem &$original_local_part$&
13142 .vindex "&$local_part$&"
13143 .vindex "&$original_local_part$&"
13144 When a top-level address is being processed for delivery, this contains the
13145 same value as &$local_part$&, unless a prefix or suffix was removed from the
13146 local part, because &$original_local_part$& always contains the full local
13147 part. When a &"child"& address (for example, generated by an alias, forward, or
13148 filter file) is being processed, this variable contains the full local part of
13149 the original address.
13151 If the router that did the redirection processed the local part
13152 case-insensitively, the value in &$original_local_part$& is in lower case.
13153 This variable differs from &$parent_local_part$& only when there is more than
13154 one level of aliasing or forwarding. When more than one address is being
13155 delivered in a single transport run, &$original_local_part$& is not set.
13157 If a new address is created by means of a &%deliver%& command in a system
13158 filter, it is set up with an artificial &"parent"& address. This has the local
13159 part &'system-filter'& and the default qualify domain.
13161 .vitem &$originator_gid$&
13162 .cindex "gid (group id)" "of originating user"
13163 .cindex "sender" "gid"
13164 .vindex "&$caller_gid$&"
13165 .vindex "&$originator_gid$&"
13166 This variable contains the value of &$caller_gid$& that was set when the
13167 message was received. For messages received via the command line, this is the
13168 gid of the sending user. For messages received by SMTP over TCP/IP, this is
13169 normally the gid of the Exim user.
13171 .vitem &$originator_uid$&
13172 .cindex "uid (user id)" "of originating user"
13173 .cindex "sender" "uid"
13174 .vindex "&$caller_uid$&"
13175 .vindex "&$originator_uid$&"
13176 The value of &$caller_uid$& that was set when the message was received. For
13177 messages received via the command line, this is the uid of the sending user.
13178 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
13181 .vitem &$parent_domain$&
13182 .vindex "&$parent_domain$&"
13183 This variable is similar to &$original_domain$& (see
13184 above), except that it refers to the immediately preceding parent address.
13186 .vitem &$parent_local_part$&
13187 .vindex "&$parent_local_part$&"
13188 This variable is similar to &$original_local_part$&
13189 (see above), except that it refers to the immediately preceding parent address.
13192 .cindex "pid (process id)" "of current process"
13194 This variable contains the current process id.
13196 .vitem &$pipe_addresses$&
13197 .cindex "filter" "transport filter"
13198 .cindex "transport" "filter"
13199 .vindex "&$pipe_addresses$&"
13200 This is not an expansion variable, but is mentioned here because the string
13201 &`$pipe_addresses`& is handled specially in the command specification for the
13202 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
13203 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
13204 It cannot be used in general expansion strings, and provokes an &"unknown
13205 variable"& error if encountered.
13207 .vitem &$primary_hostname$&
13208 .vindex "&$primary_hostname$&"
13209 This variable contains the value set by &%primary_hostname%& in the
13210 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
13211 a single-component name, Exim calls &[gethostbyname()]& (or
13212 &[getipnodebyname()]& where available) in an attempt to acquire a fully
13213 qualified host name. See also &$smtp_active_hostname$&.
13216 .vitem &$proxy_external_address$& &&&
13217 &$proxy_external_port$& &&&
13218 &$proxy_local_address$& &&&
13219 &$proxy_local_port$& &&&
13221 These variables are only available when built with Proxy Protocol
13223 For details see chapter &<<SECTproxyInbound>>&.
13225 .vitem &$prdr_requested$&
13226 .cindex "PRDR" "variable for"
13227 This variable is set to &"yes"& if PRDR was requested by the client for the
13228 current message, otherwise &"no"&.
13230 .vitem &$prvscheck_address$& &&&
13231 &$prvscheck_keynum$& &&&
13232 &$prvscheck_result$&
13233 These variables are used in conjunction with the &%prvscheck%& expansion item,
13234 which is described in sections &<<SECTexpansionitems>>& and
13235 &<<SECTverifyPRVS>>&.
13237 .vitem &$qualify_domain$&
13238 .vindex "&$qualify_domain$&"
13239 The value set for the &%qualify_domain%& option in the configuration file.
13241 .vitem &$qualify_recipient$&
13242 .vindex "&$qualify_recipient$&"
13243 The value set for the &%qualify_recipient%& option in the configuration file,
13244 or if not set, the value of &$qualify_domain$&.
13246 .vitem &$queue_name$&
13247 .vindex &$queue_name$&
13248 .cindex "named queues" variable
13249 .cindex queues named
13250 The name of the spool queue in use; empty for the default queue.
13252 .vitem &$queue_size$&
13253 .vindex "&$queue_size$&"
13254 .cindex "queue" "size of"
13255 .cindex "spool" "number of messages"
13256 This variable contains the number of messages queued.
13257 It is evaluated on demand, but no more often than once every minute.
13258 If there is no daemon notifier socket open, the value will be
13263 .cindex router variables
13264 Values can be placed in these variables by the &%set%& option of a router.
13265 They can be given any name that starts with &$r_$&.
13266 The values persist for the address being handled through subsequent routers
13267 and the eventual transport.
13269 .vitem &$rcpt_count$&
13270 .vindex "&$rcpt_count$&"
13271 When a message is being received by SMTP, this variable contains the number of
13272 RCPT commands received for the current message. If this variable is used in a
13273 RCPT ACL, its value includes the current command.
13275 .vitem &$rcpt_defer_count$&
13276 .vindex "&$rcpt_defer_count$&"
13277 .cindex "4&'xx'& responses" "count of"
13278 When a message is being received by SMTP, this variable contains the number of
13279 RCPT commands in the current message that have previously been rejected with a
13280 temporary (4&'xx'&) response.
13282 .vitem &$rcpt_fail_count$&
13283 .vindex "&$rcpt_fail_count$&"
13284 When a message is being received by SMTP, this variable contains the number of
13285 RCPT commands in the current message that have previously been rejected with a
13286 permanent (5&'xx'&) response.
13288 .vitem &$received_count$&
13289 .vindex "&$received_count$&"
13290 This variable contains the number of &'Received:'& header lines in the message,
13291 including the one added by Exim (so its value is always greater than zero). It
13292 is available in the DATA ACL, the non-SMTP ACL, and while routing and
13295 .vitem &$received_for$&
13296 .vindex "&$received_for$&"
13297 If there is only a single recipient address in an incoming message, this
13298 variable contains that address when the &'Received:'& header line is being
13299 built. The value is copied after recipient rewriting has happened, but before
13300 the &[local_scan()]& function is run.
13302 .vitem &$received_ip_address$& &&&
13304 .vindex "&$received_ip_address$&"
13305 .vindex "&$received_port$&"
13306 As soon as an Exim server starts processing an incoming TCP/IP connection, these
13307 variables are set to the address and port on the local IP interface.
13308 (The remote IP address and port are in
13309 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
13310 the port value is -1 unless it has been set using the &%-oMi%& command line
13313 As well as being useful in ACLs (including the &"connect"& ACL), these variable
13314 could be used, for example, to make the filename for a TLS certificate depend
13315 on which interface and/or port is being used for the incoming connection. The
13316 values of &$received_ip_address$& and &$received_port$& are saved with any
13317 messages that are received, thus making these variables available at delivery
13319 For outbound connections see &$sending_ip_address$&.
13321 .vitem &$received_protocol$&
13322 .vindex "&$received_protocol$&"
13323 When a message is being processed, this variable contains the name of the
13324 protocol by which it was received. Most of the names used by Exim are defined
13325 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
13326 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
13327 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
13328 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
13329 connection and the client was successfully authenticated.
13331 Exim uses the protocol name &"smtps"& for the case when encryption is
13332 automatically set up on connection without the use of STARTTLS (see
13333 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
13334 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
13335 where the client initially uses EHLO, sets up an encrypted connection using
13336 STARTTLS, and then uses HELO afterwards.
13338 The &%-oMr%& option provides a way of specifying a custom protocol name for
13339 messages that are injected locally by trusted callers. This is commonly used to
13340 identify messages that are being re-injected after some kind of scanning.
13342 .vitem &$received_time$&
13343 .vindex "&$received_time$&"
13344 This variable contains the date and time when the current message was received,
13345 as a number of seconds since the start of the Unix epoch.
13347 .vitem &$recipient_data$&
13348 .vindex "&$recipient_data$&"
13349 This variable is set after an indexing lookup success in an ACL &%recipients%&
13350 condition. It contains the data from the lookup, and the value remains set
13351 until the next &%recipients%& test. Thus, you can do things like this:
13353 &`require recipients = cdb*@;/some/file`&
13354 &`deny `&&'some further test involving'& &`$recipient_data`&
13356 &*Warning*&: This variable is set only when a lookup is used as an indexing
13357 method in the address list, using the semicolon syntax as in the example above.
13358 The variable is not set for a lookup that is used as part of the string
13359 expansion that all such lists undergo before being interpreted.
13361 .vitem &$recipient_verify_failure$&
13362 .vindex "&$recipient_verify_failure$&"
13363 In an ACL, when a recipient verification fails, this variable contains
13364 information about the failure. It is set to one of the following words:
13367 &"qualify"&: The address was unqualified (no domain), and the message
13368 was neither local nor came from an exempted host.
13371 &"route"&: Routing failed.
13374 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
13375 or before the MAIL command (that is, on initial connection, HELO, or
13379 &"recipient"&: The RCPT command in a callout was rejected.
13382 &"postmaster"&: The postmaster check in a callout was rejected.
13385 The main use of this variable is expected to be to distinguish between
13386 rejections of MAIL and rejections of RCPT.
13388 .vitem &$recipients$&
13389 .vindex "&$recipients$&"
13390 This variable contains a list of envelope recipients for a message. A comma and
13391 a space separate the addresses in the replacement text. However, the variable
13392 is not generally available, to prevent exposure of Bcc recipients in
13393 unprivileged users' filter files. You can use &$recipients$& only in these
13397 In a system filter file.
13399 In the ACLs associated with the DATA command and with non-SMTP messages, that
13400 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
13401 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
13402 &%acl_not_smtp_mime%&.
13404 From within a &[local_scan()]& function.
13408 .vitem &$recipients_count$&
13409 .vindex "&$recipients_count$&"
13410 When a message is being processed, this variable contains the number of
13411 envelope recipients that came with the message. Duplicates are not excluded
13412 from the count. While a message is being received over SMTP, the number
13413 increases for each accepted recipient. It can be referenced in an ACL.
13416 .vitem &$regex_match_string$&
13417 .vindex "&$regex_match_string$&"
13418 This variable is set to contain the matching regular expression after a
13419 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
13421 .vitem "&$regex1$&, &$regex2$&, etc"
13422 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
13423 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
13424 these variables contain the
13425 captured substrings identified by the regular expression.
13428 .vitem &$reply_address$&
13429 .vindex "&$reply_address$&"
13430 When a message is being processed, this variable contains the contents of the
13431 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
13432 contents of the &'From:'& header line. Apart from the removal of leading
13433 white space, the value is not processed in any way. In particular, no RFC 2047
13434 decoding or character code translation takes place.
13436 .vitem &$return_path$&
13437 .vindex "&$return_path$&"
13438 When a message is being delivered, this variable contains the return path &--
13439 the sender field that will be sent as part of the envelope. It is not enclosed
13440 in <> characters. At the start of routing an address, &$return_path$& has the
13441 same value as &$sender_address$&, but if, for example, an incoming message to a
13442 mailing list has been expanded by a router which specifies a different address
13443 for bounce messages, &$return_path$& subsequently contains the new bounce
13444 address, whereas &$sender_address$& always contains the original sender address
13445 that was received with the message. In other words, &$sender_address$& contains
13446 the incoming envelope sender, and &$return_path$& contains the outgoing
13449 .vitem &$return_size_limit$&
13450 .vindex "&$return_size_limit$&"
13451 This is an obsolete name for &$bounce_return_size_limit$&.
13453 .vitem &$router_name$&
13454 .cindex "router" "name"
13455 .cindex "name" "of router"
13456 .vindex "&$router_name$&"
13457 During the running of a router this variable contains its name.
13460 .cindex "return code" "from &%run%& expansion"
13461 .vindex "&$runrc$&"
13462 This variable contains the return code from a command that is run by the
13463 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
13464 assume the order in which option values are expanded, except for those
13465 preconditions whose order of testing is documented. Therefore, you cannot
13466 reliably expect to set &$runrc$& by the expansion of one option, and use it in
13469 .vitem &$self_hostname$&
13470 .oindex "&%self%&" "value of host name"
13471 .vindex "&$self_hostname$&"
13472 When an address is routed to a supposedly remote host that turns out to be the
13473 local host, what happens is controlled by the &%self%& generic router option.
13474 One of its values causes the address to be passed to another router. When this
13475 happens, &$self_hostname$& is set to the name of the local host that the
13476 original router encountered. In other circumstances its contents are null.
13478 .vitem &$sender_address$&
13479 .vindex "&$sender_address$&"
13480 When a message is being processed, this variable contains the sender's address
13481 that was received in the message's envelope. The case of letters in the address
13482 is retained, in both the local part and the domain. For bounce messages, the
13483 value of this variable is the empty string. See also &$return_path$&.
13485 .vitem &$sender_address_data$&
13486 .vindex "&$address_data$&"
13487 .vindex "&$sender_address_data$&"
13488 If &$address_data$& is set when the routers are called from an ACL to verify a
13489 sender address, the final value is preserved in &$sender_address_data$&, to
13490 distinguish it from data from a recipient address. The value does not persist
13491 after the end of the current ACL statement. If you want to preserve it for
13492 longer, you can save it in an ACL variable.
13494 .vitem &$sender_address_domain$&
13495 .vindex "&$sender_address_domain$&"
13496 The domain portion of &$sender_address$&.
13498 .vitem &$sender_address_local_part$&
13499 .vindex "&$sender_address_local_part$&"
13500 The local part portion of &$sender_address$&.
13502 .vitem &$sender_data$&
13503 .vindex "&$sender_data$&"
13504 This variable is set after a lookup success in an ACL &%senders%& condition or
13505 in a router &%senders%& option. It contains the data from the lookup, and the
13506 value remains set until the next &%senders%& test. Thus, you can do things like
13509 &`require senders = cdb*@;/some/file`&
13510 &`deny `&&'some further test involving'& &`$sender_data`&
13512 &*Warning*&: This variable is set only when a lookup is used as an indexing
13513 method in the address list, using the semicolon syntax as in the example above.
13514 The variable is not set for a lookup that is used as part of the string
13515 expansion that all such lists undergo before being interpreted.
13517 .vitem &$sender_fullhost$&
13518 .vindex "&$sender_fullhost$&"
13519 When a message is received from a remote host, this variable contains the host
13520 name and IP address in a single string. It ends with the IP address in square
13521 brackets, followed by a colon and a port number if the logging of ports is
13522 enabled. The format of the rest of the string depends on whether the host
13523 issued a HELO or EHLO SMTP command, and whether the host name was verified by
13524 looking up its IP address. (Looking up the IP address can be forced by the
13525 &%host_lookup%& option, independent of verification.) A plain host name at the
13526 start of the string is a verified host name; if this is not present,
13527 verification either failed or was not requested. A host name in parentheses is
13528 the argument of a HELO or EHLO command. This is omitted if it is identical to
13529 the verified host name or to the host's IP address in square brackets.
13531 .vitem &$sender_helo_dnssec$&
13532 .vindex "&$sender_helo_dnssec$&"
13533 This boolean variable is true if a successful HELO verification was
13534 .cindex "DNS" "DNSSEC"
13535 done using DNS information the resolver library stated was authenticated data.
13537 .vitem &$sender_helo_name$&
13538 .vindex "&$sender_helo_name$&"
13539 When a message is received from a remote host that has issued a HELO or EHLO
13540 command, the argument of that command is placed in this variable. It is also
13541 set if HELO or EHLO is used when a message is received using SMTP locally via
13542 the &%-bs%& or &%-bS%& options.
13544 .vitem &$sender_host_address$&
13545 .vindex "&$sender_host_address$&"
13546 When a message is received from a remote host using SMTP,
13547 this variable contains that
13548 host's IP address. For locally non-SMTP submitted messages, it is empty.
13550 .vitem &$sender_host_authenticated$&
13551 .vindex "&$sender_host_authenticated$&"
13552 This variable contains the name (not the public name) of the authenticator
13553 driver that successfully authenticated the client from which the message was
13554 received. It is empty if there was no successful authentication. See also
13555 &$authenticated_id$&.
13557 .vitem &$sender_host_dnssec$&
13558 .vindex "&$sender_host_dnssec$&"
13559 If an attempt to populate &$sender_host_name$& has been made
13560 (by reference, &%hosts_lookup%& or
13561 otherwise) then this boolean will have been set true if, and only if, the
13562 resolver library states that both
13563 the reverse and forward DNS were authenticated data. At all
13564 other times, this variable is false.
13566 .cindex "DNS" "DNSSEC"
13567 It is likely that you will need to coerce DNSSEC support on in the resolver
13568 library, by setting:
13573 In addition, on Linux with glibc 2.31 or newer the resolver library will
13574 default to stripping out a successful validation status.
13575 This will break a previously working Exim installation.
13576 Provided that you do trust the resolver (ie, is on localhost) you can tell
13577 glibc to pass through any successful validation with a new option in
13578 &_/etc/resolv.conf_&:
13583 Exim does not perform DNSSEC validation itself, instead leaving that to a
13584 validating resolver (e.g. unbound, or bind with suitable configuration).
13586 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
13587 mechanism in the list, then this variable will be false.
13589 This requires that your system resolver library support EDNS0 (and that
13590 DNSSEC flags exist in the system headers). If the resolver silently drops
13591 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
13592 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
13595 .vitem &$sender_host_name$&
13596 .vindex "&$sender_host_name$&"
13597 When a message is received from a remote host, this variable contains the
13598 host's name as obtained by looking up its IP address. For messages received by
13599 other means, this variable is empty.
13601 .vindex "&$host_lookup_failed$&"
13602 If the host name has not previously been looked up, a reference to
13603 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
13604 A looked up name is accepted only if it leads back to the original IP address
13605 via a forward lookup. If either the reverse or the forward lookup fails to find
13606 any data, or if the forward lookup does not yield the original IP address,
13607 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
13609 .vindex "&$host_lookup_deferred$&"
13610 However, if either of the lookups cannot be completed (for example, there is a
13611 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
13612 &$host_lookup_failed$& remains set to &"0"&.
13614 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
13615 host name again if there is a subsequent reference to &$sender_host_name$&
13616 in the same Exim process, but it does try again if &$host_lookup_deferred$&
13619 Exim does not automatically look up every calling host's name. If you want
13620 maximum efficiency, you should arrange your configuration so that it avoids
13621 these lookups altogether. The lookup happens only if one or more of the
13622 following are true:
13625 A string containing &$sender_host_name$& is expanded.
13627 The calling host matches the list in &%host_lookup%&. In the default
13628 configuration, this option is set to *, so it must be changed if lookups are
13629 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
13631 Exim needs the host name in order to test an item in a host list. The items
13632 that require this are described in sections &<<SECThoslispatnam>>& and
13633 &<<SECThoslispatnamsk>>&.
13635 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
13636 In this case, the host name is required to compare with the name quoted in any
13637 EHLO or HELO commands that the client issues.
13639 The remote host issues a EHLO or HELO command that quotes one of the
13640 domains in &%helo_lookup_domains%&. The default value of this option is
13641 . ==== As this is a nested list, any displays it contains must be indented
13642 . ==== as otherwise they are too far to the left.
13644 helo_lookup_domains = @ : @[]
13646 which causes a lookup if a remote host (incorrectly) gives the server's name or
13647 IP address in an EHLO or HELO command.
13651 .vitem &$sender_host_port$&
13652 .vindex "&$sender_host_port$&"
13653 When a message is received from a remote host, this variable contains the port
13654 number that was used on the remote host.
13656 .vitem &$sender_ident$&
13657 .vindex "&$sender_ident$&"
13658 When a message is received from a remote host, this variable contains the
13659 identification received in response to an RFC 1413 request. When a message has
13660 been received locally, this variable contains the login name of the user that
13663 .vitem &$sender_rate_$&&'xxx'&
13664 A number of variables whose names begin &$sender_rate_$& are set as part of the
13665 &%ratelimit%& ACL condition. Details are given in section
13666 &<<SECTratelimiting>>&.
13668 .vitem &$sender_rcvhost$&
13669 .cindex "DNS" "reverse lookup"
13670 .cindex "reverse DNS lookup"
13671 .vindex "&$sender_rcvhost$&"
13672 This is provided specifically for use in &'Received:'& headers. It starts with
13673 either the verified host name (as obtained from a reverse DNS lookup) or, if
13674 there is no verified host name, the IP address in square brackets. After that
13675 there may be text in parentheses. When the first item is a verified host name,
13676 the first thing in the parentheses is the IP address in square brackets,
13677 followed by a colon and a port number if port logging is enabled. When the
13678 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
13681 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
13682 was used and its argument was not identical to the real host name or IP
13683 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
13684 all three items are present in the parentheses, a newline and tab are inserted
13685 into the string, to improve the formatting of the &'Received:'& header.
13687 .vitem &$sender_verify_failure$&
13688 .vindex "&$sender_verify_failure$&"
13689 In an ACL, when a sender verification fails, this variable contains information
13690 about the failure. The details are the same as for
13691 &$recipient_verify_failure$&.
13693 .vitem &$sending_ip_address$&
13694 .vindex "&$sending_ip_address$&"
13695 This variable is set whenever an outgoing SMTP connection to another host has
13696 been set up. It contains the IP address of the local interface that is being
13697 used. This is useful if a host that has more than one IP address wants to take
13698 on different personalities depending on which one is being used. For incoming
13699 connections, see &$received_ip_address$&.
13701 .vitem &$sending_port$&
13702 .vindex "&$sending_port$&"
13703 This variable is set whenever an outgoing SMTP connection to another host has
13704 been set up. It contains the local port that is being used. For incoming
13705 connections, see &$received_port$&.
13707 .vitem &$smtp_active_hostname$&
13708 .vindex "&$smtp_active_hostname$&"
13709 During an incoming SMTP session, this variable contains the value of the active
13710 host name, as specified by the &%smtp_active_hostname%& option. The value of
13711 &$smtp_active_hostname$& is saved with any message that is received, so its
13712 value can be consulted during routing and delivery.
13714 .vitem &$smtp_command$&
13715 .vindex "&$smtp_command$&"
13716 During the processing of an incoming SMTP command, this variable contains the
13717 entire command. This makes it possible to distinguish between HELO and EHLO in
13718 the HELO ACL, and also to distinguish between commands such as these:
13723 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
13724 command, the address in &$smtp_command$& is the original address before any
13725 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
13726 the address after SMTP-time rewriting.
13728 .vitem &$smtp_command_argument$&
13729 .cindex "SMTP" "command, argument for"
13730 .vindex "&$smtp_command_argument$&"
13731 While an ACL is running to check an SMTP command, this variable contains the
13732 argument, that is, the text that follows the command name, with leading white
13733 space removed. Following the introduction of &$smtp_command$&, this variable is
13734 somewhat redundant, but is retained for backwards compatibility.
13736 .vitem &$smtp_command_history$&
13737 .cindex SMTP "command history"
13738 .vindex "&$smtp_command_history$&"
13739 A comma-separated list (with no whitespace) of the most-recent SMTP commands
13740 received, in time-order left to right. Only a limited number of commands
13743 .vitem &$smtp_count_at_connection_start$&
13744 .vindex "&$smtp_count_at_connection_start$&"
13745 This variable is set greater than zero only in processes spawned by the Exim
13746 daemon for handling incoming SMTP connections. The name is deliberately long,
13747 in order to emphasize what the contents are. When the daemon accepts a new
13748 connection, it increments this variable. A copy of the variable is passed to
13749 the child process that handles the connection, but its value is fixed, and
13750 never changes. It is only an approximation of how many incoming connections
13751 there actually are, because many other connections may come and go while a
13752 single connection is being processed. When a child process terminates, the
13753 daemon decrements its copy of the variable.
13755 .vitem "&$sn0$& &-- &$sn9$&"
13756 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
13757 that were current at the end of the system filter file. This allows a system
13758 filter file to set values that can be tested in users' filter files. For
13759 example, a system filter could set a value indicating how likely it is that a
13760 message is junk mail.
13762 .vitem &$spam_score$& &&&
13763 &$spam_score_int$& &&&
13765 &$spam_report$& &&&
13767 A number of variables whose names start with &$spam$& are available when Exim
13768 is compiled with the content-scanning extension. For details, see section
13769 &<<SECTscanspamass>>&.
13771 .vitem &$spf_header_comment$& &&&
13772 &$spf_received$& &&&
13774 &$spf_result_guessed$& &&&
13775 &$spf_smtp_comment$&
13776 These variables are only available if Exim is built with SPF support.
13777 For details see section &<<SECSPF>>&.
13779 .vitem &$spool_directory$&
13780 .vindex "&$spool_directory$&"
13781 The name of Exim's spool directory.
13783 .vitem &$spool_inodes$&
13784 .vindex "&$spool_inodes$&"
13785 The number of free inodes in the disk partition where Exim's spool files are
13786 being written. The value is recalculated whenever the variable is referenced.
13787 If the relevant file system does not have the concept of inodes, the value of
13788 is -1. See also the &%check_spool_inodes%& option.
13790 .vitem &$spool_space$&
13791 .vindex "&$spool_space$&"
13792 The amount of free space (as a number of kilobytes) in the disk partition where
13793 Exim's spool files are being written. The value is recalculated whenever the
13794 variable is referenced. If the operating system does not have the ability to
13795 find the amount of free space (only true for experimental systems), the space
13796 value is -1. For example, to check in an ACL that there is at least 50
13797 megabytes free on the spool, you could write:
13799 condition = ${if > {$spool_space}{50000}}
13801 See also the &%check_spool_space%& option.
13804 .vitem &$thisaddress$&
13805 .vindex "&$thisaddress$&"
13806 This variable is set only during the processing of the &%foranyaddress%&
13807 command in a filter file. Its use is explained in the description of that
13808 command, which can be found in the separate document entitled &'Exim's
13809 interfaces to mail filtering'&.
13811 .vitem &$tls_in_bits$&
13812 .vindex "&$tls_in_bits$&"
13813 Contains an approximation of the TLS cipher's bit-strength
13814 on the inbound connection; the meaning of
13815 this depends upon the TLS implementation used.
13816 If TLS has not been negotiated, the value will be 0.
13817 The value of this is automatically fed into the Cyrus SASL authenticator
13818 when acting as a server, to specify the "external SSF" (a SASL term).
13820 The deprecated &$tls_bits$& variable refers to the inbound side
13821 except when used in the context of an outbound SMTP delivery, when it refers to
13824 .vitem &$tls_out_bits$&
13825 .vindex "&$tls_out_bits$&"
13826 Contains an approximation of the TLS cipher's bit-strength
13827 on an outbound SMTP connection; the meaning of
13828 this depends upon the TLS implementation used.
13829 If TLS has not been negotiated, the value will be 0.
13831 .vitem &$tls_in_ourcert$&
13832 .vindex "&$tls_in_ourcert$&"
13833 .cindex certificate variables
13834 This variable refers to the certificate presented to the peer of an
13835 inbound connection when the message was received.
13836 It is only useful as the argument of a
13837 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13838 or a &%def%& condition.
13840 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
13841 when a list of more than one
13842 file is used for &%tls_certificate%&, this variable is not reliable.
13843 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
13845 .vitem &$tls_in_peercert$&
13846 .vindex "&$tls_in_peercert$&"
13847 This variable refers to the certificate presented by the peer of an
13848 inbound connection when the message was received.
13849 It is only useful as the argument of a
13850 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13851 or a &%def%& condition.
13852 If certificate verification fails it may refer to a failing chain element
13853 which is not the leaf.
13855 .vitem &$tls_out_ourcert$&
13856 .vindex "&$tls_out_ourcert$&"
13857 This variable refers to the certificate presented to the peer of an
13858 outbound connection. It is only useful as the argument of a
13859 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13860 or a &%def%& condition.
13862 .vitem &$tls_out_peercert$&
13863 .vindex "&$tls_out_peercert$&"
13864 This variable refers to the certificate presented by the peer of an
13865 outbound connection. It is only useful as the argument of a
13866 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13867 or a &%def%& condition.
13868 If certificate verification fails it may refer to a failing chain element
13869 which is not the leaf.
13871 .vitem &$tls_in_certificate_verified$&
13872 .vindex "&$tls_in_certificate_verified$&"
13873 This variable is set to &"1"& if a TLS certificate was verified when the
13874 message was received, and &"0"& otherwise.
13876 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
13877 except when used in the context of an outbound SMTP delivery, when it refers to
13880 .vitem &$tls_out_certificate_verified$&
13881 .vindex "&$tls_out_certificate_verified$&"
13882 This variable is set to &"1"& if a TLS certificate was verified when an
13883 outbound SMTP connection was made,
13884 and &"0"& otherwise.
13886 .vitem &$tls_in_cipher$&
13887 .vindex "&$tls_in_cipher$&"
13888 .vindex "&$tls_cipher$&"
13889 When a message is received from a remote host over an encrypted SMTP
13890 connection, this variable is set to the cipher suite that was negotiated, for
13891 example DES-CBC3-SHA. In other circumstances, in particular, for message
13892 received over unencrypted connections, the variable is empty. Testing
13893 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
13894 non-encrypted connections during ACL processing.
13896 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
13897 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
13898 becomes the same as &$tls_out_cipher$&.
13900 .vitem &$tls_in_cipher_std$&
13901 .vindex "&$tls_in_cipher_std$&"
13902 As above, but returning the RFC standard name for the cipher suite.
13904 .vitem &$tls_out_cipher$&
13905 .vindex "&$tls_out_cipher$&"
13907 cleared before any outgoing SMTP connection is made,
13908 and then set to the outgoing cipher suite if one is negotiated. See chapter
13909 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
13910 details of the &(smtp)& transport.
13912 .vitem &$tls_out_cipher_std$&
13913 .vindex "&$tls_out_cipher_std$&"
13914 As above, but returning the RFC standard name for the cipher suite.
13916 .vitem &$tls_out_dane$&
13917 .vindex &$tls_out_dane$&
13918 DANE active status. See section &<<SECDANE>>&.
13920 .vitem &$tls_in_ocsp$&
13921 .vindex "&$tls_in_ocsp$&"
13922 When a message is received from a remote client connection
13923 the result of any OCSP request from the client is encoded in this variable:
13925 0 OCSP proof was not requested (default value)
13926 1 No response to request
13927 2 Response not verified
13928 3 Verification failed
13929 4 Verification succeeded
13932 .vitem &$tls_out_ocsp$&
13933 .vindex "&$tls_out_ocsp$&"
13934 When a message is sent to a remote host connection
13935 the result of any OCSP request made is encoded in this variable.
13936 See &$tls_in_ocsp$& for values.
13938 .vitem &$tls_in_peerdn$&
13939 .vindex "&$tls_in_peerdn$&"
13940 .vindex "&$tls_peerdn$&"
13941 .cindex certificate "extracting fields"
13942 When a message is received from a remote host over an encrypted SMTP
13943 connection, and Exim is configured to request a certificate from the client,
13944 the value of the Distinguished Name of the certificate is made available in the
13945 &$tls_in_peerdn$& during subsequent processing.
13946 If certificate verification fails it may refer to a failing chain element
13947 which is not the leaf.
13949 The deprecated &$tls_peerdn$& variable refers to the inbound side
13950 except when used in the context of an outbound SMTP delivery, when it refers to
13953 .vitem &$tls_out_peerdn$&
13954 .vindex "&$tls_out_peerdn$&"
13955 When a message is being delivered to a remote host over an encrypted SMTP
13956 connection, and Exim is configured to request a certificate from the server,
13957 the value of the Distinguished Name of the certificate is made available in the
13958 &$tls_out_peerdn$& during subsequent processing.
13959 If certificate verification fails it may refer to a failing chain element
13960 which is not the leaf.
13963 .vitem &$tls_in_resumption$& &&&
13964 &$tls_out_resumption$&
13965 .vindex &$tls_in_resumption$&
13966 .vindex &$tls_out_resumption$&
13967 .cindex TLS resumption
13968 Observability for TLS session resumption. See &<<SECTresumption>>& for details.
13971 .vitem &$tls_in_sni$&
13972 .vindex "&$tls_in_sni$&"
13973 .vindex "&$tls_sni$&"
13974 .cindex "TLS" "Server Name Indication"
13976 .cindex SNI "observability on server"
13977 When a TLS session is being established, if the client sends the Server
13978 Name Indication extension, the value will be placed in this variable.
13979 If the variable appears in &%tls_certificate%& then this option and
13980 some others, described in &<<SECTtlssni>>&,
13981 will be re-expanded early in the TLS session, to permit
13982 a different certificate to be presented (and optionally a different key to be
13983 used) to the client, based upon the value of the SNI extension.
13985 The deprecated &$tls_sni$& variable refers to the inbound side
13986 except when used in the context of an outbound SMTP delivery, when it refers to
13989 .vitem &$tls_out_sni$&
13990 .vindex "&$tls_out_sni$&"
13991 .cindex "TLS" "Server Name Indication"
13993 .cindex SNI "observability in client"
13995 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
13998 .vitem &$tls_out_tlsa_usage$&
13999 .vindex &$tls_out_tlsa_usage$&
14000 Bitfield of TLSA record types found. See section &<<SECDANE>>&.
14002 .vitem &$tls_in_ver$&
14003 .vindex "&$tls_in_ver$&"
14004 When a message is received from a remote host over an encrypted SMTP connection
14005 this variable is set to the protocol version, eg &'TLS1.2'&.
14007 .vitem &$tls_out_ver$&
14008 .vindex "&$tls_out_ver$&"
14009 When a message is being delivered to a remote host over an encrypted SMTP connection
14010 this variable is set to the protocol version.
14013 .vitem &$tod_bsdinbox$&
14014 .vindex "&$tod_bsdinbox$&"
14015 The time of day and the date, in the format required for BSD-style mailbox
14016 files, for example: Thu Oct 17 17:14:09 1995.
14018 .vitem &$tod_epoch$&
14019 .vindex "&$tod_epoch$&"
14020 The time and date as a number of seconds since the start of the Unix epoch.
14022 .vitem &$tod_epoch_l$&
14023 .vindex "&$tod_epoch_l$&"
14024 The time and date as a number of microseconds since the start of the Unix epoch.
14026 .vitem &$tod_full$&
14027 .vindex "&$tod_full$&"
14028 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
14029 +0100. The timezone is always given as a numerical offset from UTC, with
14030 positive values used for timezones that are ahead (east) of UTC, and negative
14031 values for those that are behind (west).
14034 .vindex "&$tod_log$&"
14035 The time and date in the format used for writing Exim's log files, for example:
14036 1995-10-12 15:32:29, but without a timezone.
14038 .vitem &$tod_logfile$&
14039 .vindex "&$tod_logfile$&"
14040 This variable contains the date in the format yyyymmdd. This is the format that
14041 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
14044 .vitem &$tod_zone$&
14045 .vindex "&$tod_zone$&"
14046 This variable contains the numerical value of the local timezone, for example:
14049 .vitem &$tod_zulu$&
14050 .vindex "&$tod_zulu$&"
14051 This variable contains the UTC date and time in &"Zulu"& format, as specified
14052 by ISO 8601, for example: 20030221154023Z.
14054 .vitem &$transport_name$&
14055 .cindex "transport" "name"
14056 .cindex "name" "of transport"
14057 .vindex "&$transport_name$&"
14058 During the running of a transport, this variable contains its name.
14061 .vindex "&$value$&"
14062 This variable contains the result of an expansion lookup, extraction operation,
14063 or external command, as described above. It is also used during a
14064 &*reduce*& expansion.
14066 .vitem &$verify_mode$&
14067 .vindex "&$verify_mode$&"
14068 While a router or transport is being run in verify mode or for cutthrough delivery,
14069 contains "S" for sender-verification or "R" for recipient-verification.
14072 .vitem &$version_number$&
14073 .vindex "&$version_number$&"
14074 The version number of Exim. Same as &$exim_version$&, may be overridden
14075 by the &%exim_version%& main config option.
14077 .vitem &$warn_message_delay$&
14078 .vindex "&$warn_message_delay$&"
14079 This variable is set only during the creation of a message warning about a
14080 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14082 .vitem &$warn_message_recipients$&
14083 .vindex "&$warn_message_recipients$&"
14084 This variable is set only during the creation of a message warning about a
14085 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14091 . ////////////////////////////////////////////////////////////////////////////
14092 . ////////////////////////////////////////////////////////////////////////////
14094 .chapter "Embedded Perl" "CHAPperl"
14095 .scindex IIDperl "Perl" "calling from Exim"
14096 Exim can be built to include an embedded Perl interpreter. When this is done,
14097 Perl subroutines can be called as part of the string expansion process. To make
14098 use of the Perl support, you need version 5.004 or later of Perl installed on
14099 your system. To include the embedded interpreter in the Exim binary, include
14104 in your &_Local/Makefile_& and then build Exim in the normal way.
14107 .section "Setting up so Perl can be used" "SECID85"
14108 .oindex "&%perl_startup%&"
14109 Access to Perl subroutines is via a global configuration option called
14110 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
14111 no &%perl_startup%& option in the Exim configuration file then no Perl
14112 interpreter is started and there is almost no overhead for Exim (since none of
14113 the Perl library will be paged in unless used). If there is a &%perl_startup%&
14114 option then the associated value is taken to be Perl code which is executed in
14115 a newly created Perl interpreter.
14117 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
14118 need backslashes before any characters to escape special meanings. The option
14119 should usually be something like
14121 perl_startup = do '/etc/exim.pl'
14123 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
14124 use from Exim. Exim can be configured either to start up a Perl interpreter as
14125 soon as it is entered, or to wait until the first time it is needed. Starting
14126 the interpreter at the beginning ensures that it is done while Exim still has
14127 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
14128 fact used in a particular run. Also, note that this does not mean that Exim is
14129 necessarily running as root when Perl is called at a later time. By default,
14130 the interpreter is started only when it is needed, but this can be changed in
14134 .oindex "&%perl_at_start%&"
14135 Setting &%perl_at_start%& (a boolean option) in the configuration requests
14136 a startup when Exim is entered.
14138 The command line option &%-ps%& also requests a startup when Exim is entered,
14139 overriding the setting of &%perl_at_start%&.
14142 There is also a command line option &%-pd%& (for delay) which suppresses the
14143 initial startup, even if &%perl_at_start%& is set.
14146 .oindex "&%perl_taintmode%&"
14147 .cindex "Perl" "taintmode"
14148 To provide more security executing Perl code via the embedded Perl
14149 interpreter, the &%perl_taintmode%& option can be set. This enables the
14150 taint mode of the Perl interpreter. You are encouraged to set this
14151 option to a true value. To avoid breaking existing installations, it
14154 &*Note*&: This is entirely separate from Exim's tainted-data tracking.
14157 .section "Calling Perl subroutines" "SECID86"
14158 When the configuration file includes a &%perl_startup%& option you can make use
14159 of the string expansion item to call the Perl subroutines that are defined
14160 by the &%perl_startup%& code. The operator is used in any of the following
14164 ${perl{foo}{argument}}
14165 ${perl{foo}{argument1}{argument2} ... }
14167 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
14168 arguments may be passed. Passing more than this results in an expansion failure
14169 with an error message of the form
14171 Too many arguments passed to Perl subroutine "foo" (max is 8)
14173 The return value of the Perl subroutine is evaluated in a scalar context before
14174 it is passed back to Exim to be inserted into the expanded string. If the
14175 return value is &'undef'&, the expansion is forced to fail in the same way as
14176 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
14177 by obeying Perl's &%die%& function, the expansion fails with the error message
14178 that was passed to &%die%&.
14181 .section "Calling Exim functions from Perl" "SECID87"
14182 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
14183 is available to call back into Exim's string expansion function. For example,
14186 my $lp = Exim::expand_string('$local_part');
14188 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
14189 Note those are single quotes and not double quotes to protect against
14190 &$local_part$& being interpolated as a Perl variable.
14192 If the string expansion is forced to fail by a &"fail"& item, the result of
14193 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
14194 expansion string, the Perl call from the original expansion string fails with
14195 an appropriate error message, in the same way as if &%die%& were used.
14197 .cindex "debugging" "from embedded Perl"
14198 .cindex "log" "writing from embedded Perl"
14199 Two other Exim functions are available for use from within Perl code.
14200 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
14201 debugging is enabled. If you want a newline at the end, you must supply it.
14202 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
14203 timestamp. In this case, you should not supply a terminating newline.
14206 .section "Use of standard output and error by Perl" "SECID88"
14207 .cindex "Perl" "standard output and error"
14208 You should not write to the standard error or output streams from within your
14209 Perl code, as it is not defined how these are set up. In versions of Exim
14210 before 4.50, it is possible for the standard output or error to refer to the
14211 SMTP connection during message reception via the daemon. Writing to this stream
14212 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
14213 error streams are connected to &_/dev/null_& in the daemon. The chaos is
14214 avoided, but the output is lost.
14216 .cindex "Perl" "use of &%warn%&"
14217 The Perl &%warn%& statement writes to the standard error stream by default.
14218 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
14219 you have no control. When Exim starts up the Perl interpreter, it arranges for
14220 output from the &%warn%& statement to be written to the Exim main log. You can
14221 change this by including appropriate Perl magic somewhere in your Perl code.
14222 For example, to discard &%warn%& output completely, you need this:
14224 $SIG{__WARN__} = sub { };
14226 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
14227 example, the code for the subroutine is empty, so it does nothing, but you can
14228 include any Perl code that you like. The text of the &%warn%& message is passed
14229 as the first subroutine argument.
14233 . ////////////////////////////////////////////////////////////////////////////
14234 . ////////////////////////////////////////////////////////////////////////////
14236 .chapter "Starting the daemon and the use of network interfaces" &&&
14237 "CHAPinterfaces" &&&
14238 "Starting the daemon"
14239 .cindex "daemon" "starting"
14240 .cindex "interface" "listening"
14241 .cindex "network interface"
14242 .cindex "interface" "network"
14243 .cindex "IP address" "for listening"
14244 .cindex "daemon" "listening IP addresses"
14245 .cindex "TCP/IP" "setting listening interfaces"
14246 .cindex "TCP/IP" "setting listening ports"
14247 A host that is connected to a TCP/IP network may have one or more physical
14248 hardware network interfaces. Each of these interfaces may be configured as one
14249 or more &"logical"& interfaces, which are the entities that a program actually
14250 works with. Each of these logical interfaces is associated with an IP address.
14251 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
14252 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
14253 knowledge about the host's interfaces for use in three different circumstances:
14256 When a listening daemon is started, Exim needs to know which interfaces
14257 and ports to listen on.
14259 When Exim is routing an address, it needs to know which IP addresses
14260 are associated with local interfaces. This is required for the correct
14261 processing of MX lists by removing the local host and others with the
14262 same or higher priority values. Also, Exim needs to detect cases
14263 when an address is routed to an IP address that in fact belongs to the
14264 local host. Unless the &%self%& router option or the &%allow_localhost%&
14265 option of the smtp transport is set (as appropriate), this is treated
14266 as an error situation.
14268 When Exim connects to a remote host, it may need to know which interface to use
14269 for the outgoing connection.
14273 Exim's default behaviour is likely to be appropriate in the vast majority
14274 of cases. If your host has only one interface, and you want all its IP
14275 addresses to be treated in the same way, and you are using only the
14276 standard SMTP port, you should not need to take any special action. The
14277 rest of this chapter does not apply to you.
14279 In a more complicated situation you may want to listen only on certain
14280 interfaces, or on different ports, and for this reason there are a number of
14281 options that can be used to influence Exim's behaviour. The rest of this
14282 chapter describes how they operate.
14284 When a message is received over TCP/IP, the interface and port that were
14285 actually used are set in &$received_ip_address$& and &$received_port$&.
14289 .section "Starting a listening daemon" "SECID89"
14290 When a listening daemon is started (by means of the &%-bd%& command line
14291 option), the interfaces and ports on which it listens are controlled by the
14295 &%daemon_smtp_ports%& contains a list of default ports
14297 (For backward compatibility, this option can also be specified in the singular.)
14299 &%local_interfaces%& contains list of interface IP addresses on which to
14300 listen. Each item may optionally also specify a port.
14303 The default list separator in both cases is a colon, but this can be changed as
14304 described in section &<<SECTlistsepchange>>&. When IPv6 addresses are involved,
14305 it is usually best to change the separator to avoid having to double all the
14306 colons. For example:
14308 local_interfaces = <; 127.0.0.1 ; \
14311 3ffe:ffff:836f::fe86:a061
14313 There are two different formats for specifying a port along with an IP address
14314 in &%local_interfaces%&:
14317 The port is added onto the address with a dot separator. For example, to listen
14318 on port 1234 on two different IP addresses:
14320 local_interfaces = <; 192.168.23.65.1234 ; \
14321 3ffe:ffff:836f::fe86:a061.1234
14324 The IP address is enclosed in square brackets, and the port is added
14325 with a colon separator, for example:
14327 local_interfaces = <; [192.168.23.65]:1234 ; \
14328 [3ffe:ffff:836f::fe86:a061]:1234
14332 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
14333 default setting contains just one port:
14335 daemon_smtp_ports = smtp
14337 If more than one port is listed, each interface that does not have its own port
14338 specified listens on all of them. Ports that are listed in
14339 &%daemon_smtp_ports%& can be identified either by name (defined in
14340 &_/etc/services_&) or by number. However, when ports are given with individual
14341 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
14345 .section "Special IP listening addresses" "SECID90"
14346 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
14347 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
14348 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
14349 instead of setting up separate listening sockets for each interface. The
14350 default value of &%local_interfaces%& is
14352 local_interfaces = 0.0.0.0
14354 when Exim is built without IPv6 support; otherwise it is:
14356 local_interfaces = <; ::0 ; 0.0.0.0
14358 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
14362 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
14363 The &%-oX%& command line option can be used to override the values of
14364 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
14365 instance. Another way of doing this would be to use macros and the &%-D%&
14366 option. However, &%-oX%& can be used by any admin user, whereas modification of
14367 the runtime configuration by &%-D%& is allowed only when the caller is root or
14370 The value of &%-oX%& is a list of items. The default colon separator can be
14371 changed in the usual way (&<<SECTlistsepchange>>&) if required.
14372 If there are any items that do not
14373 contain dots or colons (that is, are not IP addresses), the value of
14374 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
14375 items that do contain dots or colons, the value of &%local_interfaces%& is
14376 replaced by those items. Thus, for example,
14380 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
14383 -oX 192.168.34.5.1125
14385 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
14386 (However, since &%local_interfaces%& now contains no items without ports, the
14387 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
14391 .section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
14392 .cindex "submissions protocol"
14393 .cindex "ssmtp protocol"
14394 .cindex "smtps protocol"
14395 .cindex "SMTP" "ssmtp protocol"
14396 .cindex "SMTP" "smtps protocol"
14397 Exim supports the use of TLS-on-connect, used by mail clients in the
14398 &"submissions"& protocol, historically also known as SMTPS or SSMTP.
14399 For some years, IETF Standards Track documents only blessed the
14400 STARTTLS-based Submission service (port 587) while common practice was to support
14401 the same feature set on port 465, but using TLS-on-connect.
14402 If your installation needs to provide service to mail clients
14403 (Mail User Agents, MUAs) then you should provide service on both the 587 and
14406 If the &%tls_on_connect_ports%& option is set to a list of port numbers or
14407 service names, connections to those ports must first establish TLS, before
14408 proceeding to the application layer use of the SMTP protocol.
14410 The common use of this option is expected to be
14412 tls_on_connect_ports = 465
14415 There is also a command line option &%-tls-on-connect%&, which forces all ports
14416 to behave in this way when a daemon is started.
14418 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
14419 daemon to listen on those ports. You must still specify them in
14420 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
14421 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
14422 connections via the daemon.)
14427 .section "IPv6 address scopes" "SECID92"
14428 .cindex "IPv6" "address scopes"
14429 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
14430 can, in principle, have the same link-local IPv6 address on different
14431 interfaces. Thus, additional information is needed, over and above the IP
14432 address, to distinguish individual interfaces. A convention of using a
14433 percent sign followed by something (often the interface name) has been
14434 adopted in some cases, leading to addresses like this:
14436 fe80::202:b3ff:fe03:45c1%eth0
14438 To accommodate this usage, a percent sign followed by an arbitrary string is
14439 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
14440 to convert a textual IPv6 address for actual use. This function recognizes the
14441 percent convention in operating systems that support it, and it processes the
14442 address appropriately. Unfortunately, some older libraries have problems with
14443 &[getaddrinfo()]&. If
14445 IPV6_USE_INET_PTON=yes
14447 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
14448 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
14449 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
14450 function.) Of course, this means that the additional functionality of
14451 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
14453 .section "Disabling IPv6" "SECID93"
14454 .cindex "IPv6" "disabling"
14455 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
14456 run on a host whose kernel does not support IPv6. The binary will fall back to
14457 using IPv4, but it may waste resources looking up AAAA records, and trying to
14458 connect to IPv6 addresses, causing delays to mail delivery. If you set the
14459 .oindex "&%disable_ipv6%&"
14460 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
14461 activities take place. AAAA records are never looked up, and any IPv6 addresses
14462 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
14463 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14464 to handle IPv6 literal addresses.
14466 On the other hand, when IPv6 is in use, there may be times when you want to
14467 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
14468 option to globally suppress the lookup of AAAA records for specified domains,
14469 and you can use the &%ignore_target_hosts%& generic router option to ignore
14470 IPv6 addresses in an individual router.
14474 .section "Examples of starting a listening daemon" "SECID94"
14475 The default case in an IPv6 environment is
14477 daemon_smtp_ports = smtp
14478 local_interfaces = <; ::0 ; 0.0.0.0
14480 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
14481 Either one or two sockets may be used, depending on the characteristics of
14482 the TCP/IP stack. (This is complicated and messy; for more information,
14483 read the comments in the &_daemon.c_& source file.)
14485 To specify listening on ports 25 and 26 on all interfaces:
14487 daemon_smtp_ports = 25 : 26
14489 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
14491 local_interfaces = <; ::0.25 ; ::0.26 \
14492 0.0.0.0.25 ; 0.0.0.0.26
14494 To listen on the default port on all IPv4 interfaces, and on port 26 on the
14495 IPv4 loopback address only:
14497 local_interfaces = 0.0.0.0 : 127.0.0.1.26
14499 To specify listening on the default port on specific interfaces only:
14501 local_interfaces = 10.0.0.67 : 192.168.34.67
14503 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
14507 .section "Recognizing the local host" "SECTreclocipadd"
14508 The &%local_interfaces%& option is also used when Exim needs to determine
14509 whether or not an IP address refers to the local host. That is, the IP
14510 addresses of all the interfaces on which a daemon is listening are always
14513 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
14514 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
14515 available interfaces from the operating system, and extracts the relevant
14516 (that is, IPv4 or IPv6) addresses to use for checking.
14518 Some systems set up large numbers of virtual interfaces in order to provide
14519 many virtual web servers. In this situation, you may want to listen for
14520 email on only a few of the available interfaces, but nevertheless treat all
14521 interfaces as local when routing. You can do this by setting
14522 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
14523 &"all"& wildcard values. These addresses are recognized as local, but are not
14524 used for listening. Consider this example:
14526 local_interfaces = <; 127.0.0.1 ; ::1 ; \
14528 3ffe:2101:12:1:a00:20ff:fe86:a061
14530 extra_local_interfaces = <; ::0 ; 0.0.0.0
14532 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
14533 address, but all available interface addresses are treated as local when
14536 In some environments the local host name may be in an MX list, but with an IP
14537 address that is not assigned to any local interface. In other cases it may be
14538 desirable to treat other host names as if they referred to the local host. Both
14539 these cases can be handled by setting the &%hosts_treat_as_local%& option.
14540 This contains host names rather than IP addresses. When a host is referenced
14541 during routing, either via an MX record or directly, it is treated as the local
14542 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
14543 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
14547 .section "Delivering to a remote host" "SECID95"
14548 Delivery to a remote host is handled by the smtp transport. By default, it
14549 allows the system's TCP/IP functions to choose which interface to use (if
14550 there is more than one) when connecting to a remote host. However, the
14551 &%interface%& option can be set to specify which interface is used. See the
14552 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
14558 . ////////////////////////////////////////////////////////////////////////////
14559 . ////////////////////////////////////////////////////////////////////////////
14561 .chapter "Main configuration" "CHAPmainconfig"
14562 .scindex IIDconfima "configuration file" "main section"
14563 .scindex IIDmaiconf "main configuration"
14564 The first part of the runtime configuration file contains three types of item:
14567 Macro definitions: These lines start with an upper case letter. See section
14568 &<<SECTmacrodefs>>& for details of macro processing.
14570 Named list definitions: These lines start with one of the words &"domainlist"&,
14571 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
14572 section &<<SECTnamedlists>>&.
14574 Main configuration settings: Each setting occupies one line of the file
14575 (with possible continuations). If any setting is preceded by the word
14576 &"hide"&, the &%-bP%& command line option displays its value to admin users
14577 only. See section &<<SECTcos>>& for a description of the syntax of these option
14581 This chapter specifies all the main configuration options, along with their
14582 types and default values. For ease of finding a particular option, they appear
14583 in alphabetical order in section &<<SECTalomo>>& below. However, because there
14584 are now so many options, they are first listed briefly in functional groups, as
14585 an aid to finding the name of the option you are looking for. Some options are
14586 listed in more than one group.
14588 .section "Miscellaneous" "SECID96"
14590 .row &%add_environment%& "environment variables"
14591 .row &%allow_insecure_tainted_data%& "turn taint errors into warnings"
14592 .row &%bi_command%& "to run for &%-bi%& command line option"
14593 .row &%debug_store%& "do extra internal checks"
14594 .row &%disable_ipv6%& "do no IPv6 processing"
14595 .row &%keep_environment%& "environment variables"
14596 .row &%keep_malformed%& "for broken files &-- should not happen"
14597 .row &%localhost_number%& "for unique message ids in clusters"
14598 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
14599 .row &%message_body_visible%& "how much to show in &$message_body$&"
14600 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
14601 .row &%print_topbitchars%& "top-bit characters are printing"
14602 .row &%spool_wireformat%& "use wire-format spool data files when possible"
14603 .row &%timezone%& "force time zone"
14607 .section "Exim parameters" "SECID97"
14609 .row &%exim_group%& "override compiled-in value"
14610 .row &%exim_path%& "override compiled-in value"
14611 .row &%exim_user%& "override compiled-in value"
14612 .row &%primary_hostname%& "default from &[uname()]&"
14613 .row &%split_spool_directory%& "use multiple directories"
14614 .row &%spool_directory%& "override compiled-in value"
14619 .section "Privilege controls" "SECID98"
14621 .row &%admin_groups%& "groups that are Exim admin users"
14622 .row &%commandline_checks_require_admin%& "require admin for various checks"
14623 .row &%deliver_drop_privilege%& "drop root for delivery processes"
14624 .row &%local_from_check%& "insert &'Sender:'& if necessary"
14625 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
14626 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
14627 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
14628 .row &%never_users%& "do not run deliveries as these"
14629 .row &%prod_requires_admin%& "forced delivery requires admin user"
14630 .row &%queue_list_requires_admin%& "queue listing requires admin user"
14631 .row &%trusted_groups%& "groups that are trusted"
14632 .row &%trusted_users%& "users that are trusted"
14637 .section "Logging" "SECID99"
14639 .row &%event_action%& "custom logging"
14640 .row &%hosts_connection_nolog%& "exemption from connect logging"
14641 .row &%log_file_path%& "override compiled-in value"
14642 .row &%log_selector%& "set/unset optional logging"
14643 .row &%log_timezone%& "add timezone to log lines"
14644 .row &%message_logs%& "create per-message logs"
14645 .row &%preserve_message_logs%& "after message completion"
14646 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
14647 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
14648 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
14649 .row &%syslog_facility%& "set syslog &""facility""& field"
14650 .row &%syslog_pid%& "pid in syslog lines"
14651 .row &%syslog_processname%& "set syslog &""ident""& field"
14652 .row &%syslog_timestamp%& "timestamp syslog lines"
14653 .row &%write_rejectlog%& "control use of message log"
14658 .section "Frozen messages" "SECID100"
14660 .row &%auto_thaw%& "sets time for retrying frozen messages"
14661 .row &%freeze_tell%& "send message when freezing"
14662 .row &%move_frozen_messages%& "to another directory"
14663 .row &%timeout_frozen_after%& "keep frozen messages only so long"
14668 .section "Data lookups" "SECID101"
14670 .row &%ibase_servers%& "InterBase servers"
14671 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
14672 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
14673 .row &%ldap_cert_file%& "client cert file for LDAP"
14674 .row &%ldap_cert_key%& "client key file for LDAP"
14675 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
14676 .row &%ldap_default_servers%& "used if no server in query"
14677 .row &%ldap_require_cert%& "action to take without LDAP server cert"
14678 .row &%ldap_start_tls%& "require TLS within LDAP"
14679 .row &%ldap_version%& "set protocol version"
14680 .row &%lookup_open_max%& "lookup files held open"
14681 .row &%mysql_servers%& "default MySQL servers"
14682 .row &%oracle_servers%& "Oracle servers"
14683 .row &%pgsql_servers%& "default PostgreSQL servers"
14684 .row &%sqlite_lock_timeout%& "as it says"
14689 .section "Message ids" "SECID102"
14691 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
14692 .row &%message_id_header_text%& "ditto"
14697 .section "Embedded Perl Startup" "SECID103"
14699 .row &%perl_at_start%& "always start the interpreter"
14700 .row &%perl_startup%& "code to obey when starting Perl"
14701 .row &%perl_taintmode%& "enable taint mode in Perl"
14706 .section "Daemon" "SECID104"
14708 .row &%daemon_smtp_ports%& "default ports"
14709 .row &%daemon_startup_retries%& "number of times to retry"
14710 .row &%daemon_startup_sleep%& "time to sleep between tries"
14711 .row &%extra_local_interfaces%& "not necessarily listened on"
14712 .row &%local_interfaces%& "on which to listen, with optional ports"
14713 .row &%notifier_socket%& "override compiled-in value"
14714 .row &%pid_file_path%& "override compiled-in value"
14715 .row &%queue_run_max%& "maximum simultaneous queue runners"
14716 .row &%smtp_backlog_monitor%& "level to log listen backlog"
14721 .section "Resource control" "SECID105"
14723 .row &%check_log_inodes%& "before accepting a message"
14724 .row &%check_log_space%& "before accepting a message"
14725 .row &%check_spool_inodes%& "before accepting a message"
14726 .row &%check_spool_space%& "before accepting a message"
14727 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
14728 .row &%queue_only_load%& "queue incoming if load high"
14729 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14730 .row &%queue_run_max%& "maximum simultaneous queue runners"
14731 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14732 .row &%smtp_accept_max%& "simultaneous incoming connections"
14733 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14734 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14735 .row &%smtp_accept_max_per_connection%& "messages per connection"
14736 .row &%smtp_accept_max_per_host%& "connections from one host"
14737 .row &%smtp_accept_queue%& "queue mail if more connections"
14738 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14740 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14741 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14742 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14743 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
14744 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14749 .section "Policy controls" "SECID106"
14751 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
14752 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
14753 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
14754 .row &%acl_smtp_auth%& "ACL for AUTH"
14755 .row &%acl_smtp_connect%& "ACL for connection"
14756 .row &%acl_smtp_data%& "ACL for DATA"
14757 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
14758 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
14759 .row &%acl_smtp_etrn%& "ACL for ETRN"
14760 .row &%acl_smtp_expn%& "ACL for EXPN"
14761 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
14762 .row &%acl_smtp_mail%& "ACL for MAIL"
14763 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
14764 .row &%acl_smtp_mime%& "ACL for MIME parts"
14765 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
14766 .row &%acl_smtp_predata%& "ACL for start of data"
14767 .row &%acl_smtp_quit%& "ACL for QUIT"
14768 .row &%acl_smtp_rcpt%& "ACL for RCPT"
14769 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
14770 .row &%acl_smtp_vrfy%& "ACL for VRFY"
14771 .row &%av_scanner%& "specify virus scanner"
14772 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14774 .row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
14775 .row &%dns_csa_search_limit%& "control CSA parent search depth"
14776 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
14777 .row &%header_maxsize%& "total size of message header"
14778 .row &%header_line_maxsize%& "individual header line limit"
14779 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
14780 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
14781 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
14782 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
14783 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
14784 .row &%host_lookup%& "host name looked up for these hosts"
14785 .row &%host_lookup_order%& "order of DNS and local name lookups"
14786 .row &%hosts_proxy%& "use proxy protocol for these hosts"
14787 .row &%host_reject_connection%& "reject connection from these hosts"
14788 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
14789 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
14790 .row &%message_size_limit%& "for all messages"
14791 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14792 .row &%proxy_protocol_timeout%& "timeout for proxy protocol negotiation"
14793 .row &%spamd_address%& "set interface to SpamAssassin"
14794 .row &%strict_acl_vars%& "object to unset ACL variables"
14795 .row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&"
14800 .section "Callout cache" "SECID107"
14802 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
14804 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
14806 .row &%callout_negative_expire%& "timeout for negative address cache item"
14807 .row &%callout_positive_expire%& "timeout for positive address cache item"
14808 .row &%callout_random_local_part%& "string to use for &""random""& testing"
14813 .section "TLS" "SECID108"
14815 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
14816 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
14817 .row &%hosts_require_alpn%& "mandatory ALPN"
14818 .row &%openssl_options%& "adjust OpenSSL compatibility options"
14819 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14820 .row &%tls_alpn%& "acceptable protocol names"
14821 .row &%tls_certificate%& "location of server certificate"
14822 .row &%tls_crl%& "certificate revocation list"
14823 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
14824 .row &%tls_dhparam%& "DH parameters for server"
14825 .row &%tls_eccurve%& "EC curve selection for server"
14826 .row &%tls_ocsp_file%& "location of server certificate status proof"
14827 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
14828 .row &%tls_privatekey%& "location of server private key"
14829 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
14830 .row &%tls_require_ciphers%& "specify acceptable ciphers"
14831 .row &%tls_try_verify_hosts%& "try to verify client certificate"
14832 .row &%tls_verify_certificates%& "expected client certificates"
14833 .row &%tls_verify_hosts%& "insist on client certificate verify"
14838 .section "Local user handling" "SECID109"
14840 .row &%finduser_retries%& "useful in NIS environments"
14841 .row &%gecos_name%& "used when creating &'Sender:'&"
14842 .row &%gecos_pattern%& "ditto"
14843 .row &%max_username_length%& "for systems that truncate"
14844 .row &%unknown_login%& "used when no login name found"
14845 .row &%unknown_username%& "ditto"
14846 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
14847 .row &%uucp_from_sender%& "ditto"
14852 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
14854 .row &%header_maxsize%& "total size of message header"
14855 .row &%header_line_maxsize%& "individual header line limit"
14856 .row &%message_size_limit%& "applies to all messages"
14857 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14858 .row &%received_header_text%& "expanded to make &'Received:'&"
14859 .row &%received_headers_max%& "for mail loop detection"
14860 .row &%recipients_max%& "limit per message"
14861 .row &%recipients_max_reject%& "permanently reject excess recipients"
14867 .section "Non-SMTP incoming messages" "SECID111"
14869 .row &%receive_timeout%& "for non-SMTP messages"
14876 .section "Incoming SMTP messages" "SECID112"
14877 See also the &'Policy controls'& section above.
14880 .row &%dkim_verify_hashes%& "DKIM hash methods accepted for signatures"
14881 .row &%dkim_verify_keytypes%& "DKIM key types accepted for signatures"
14882 .row &%dkim_verify_min_keysizes%& "DKIM key sizes accepted for signatures"
14883 .row &%dkim_verify_signers%& "DKIM domains for which DKIM ACL is run"
14884 .row &%dmarc_forensic_sender%& "DMARC sender for report messages"
14885 .row &%dmarc_history_file%& "DMARC results log"
14886 .row &%dmarc_tld_file%& "DMARC toplevel domains file"
14887 .row &%host_lookup%& "host name looked up for these hosts"
14888 .row &%host_lookup_order%& "order of DNS and local name lookups"
14889 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
14890 .row &%rfc1413_hosts%& "make ident calls to these hosts"
14891 .row &%rfc1413_query_timeout%& "zero disables ident calls"
14892 .row &%sender_unqualified_hosts%& "may send unqualified senders"
14893 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
14894 .row &%smtp_accept_max%& "simultaneous incoming connections"
14895 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14896 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14897 .row &%smtp_accept_max_per_connection%& "messages per connection"
14898 .row &%smtp_accept_max_per_host%& "connections from one host"
14899 .row &%smtp_accept_queue%& "queue mail if more connections"
14900 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14902 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14903 .row &%smtp_active_hostname%& "host name to use in messages"
14904 .row &%smtp_banner%& "text for welcome banner"
14905 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14906 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14907 .row &%smtp_enforce_sync%& "of SMTP command/responses"
14908 .row &%smtp_etrn_command%& "what to run for ETRN"
14909 .row &%smtp_etrn_serialize%& "only one at once"
14910 .row &%smtp_load_reserve%& "only reserve hosts if this load"
14911 .row &%smtp_max_unknown_commands%& "before dropping connection"
14912 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
14913 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
14914 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
14915 .row &%smtp_receive_timeout%& "per command or data line"
14916 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14917 .row &%smtp_return_error_details%& "give detail on rejections"
14922 .section "SMTP extensions" "SECID113"
14924 .row &%accept_8bitmime%& "advertise 8BITMIME"
14925 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
14926 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
14927 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
14928 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
14929 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
14930 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
14931 .row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts"
14932 .row &%prdr_enable%& "advertise PRDR to all hosts"
14933 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
14934 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14939 .section "Processing messages" "SECID114"
14941 .row &%allow_domain_literals%& "recognize domain literal syntax"
14942 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
14943 .row &%allow_utf8_domains%& "in addresses"
14944 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14946 .row &%delivery_date_remove%& "from incoming messages"
14947 .row &%envelope_to_remove%& "from incoming messages"
14948 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
14949 .row &%headers_charset%& "default for translations"
14950 .row &%qualify_domain%& "default for senders"
14951 .row &%qualify_recipient%& "default for recipients"
14952 .row &%return_path_remove%& "from incoming messages"
14953 .row &%strip_excess_angle_brackets%& "in addresses"
14954 .row &%strip_trailing_dot%& "at end of addresses"
14955 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
14960 .section "System filter" "SECID115"
14962 .row &%system_filter%& "locate system filter"
14963 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
14965 .row &%system_filter_file_transport%& "transport for delivery to a file"
14966 .row &%system_filter_group%& "group for filter running"
14967 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
14968 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
14969 .row &%system_filter_user%& "user for filter running"
14974 .section "Routing and delivery" "SECID116"
14976 .row &%disable_ipv6%& "do no IPv6 processing"
14977 .row &%dns_again_means_nonexist%& "for broken domains"
14978 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
14979 .row &%dns_dnssec_ok%& "parameter for resolver"
14980 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
14981 .row &%dns_retrans%& "parameter for resolver"
14982 .row &%dns_retry%& "parameter for resolver"
14983 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
14984 .row &%dns_use_edns0%& "parameter for resolver"
14985 .row &%hold_domains%& "hold delivery for these domains"
14986 .row &%local_interfaces%& "for routing checks"
14987 .row &%queue_domains%& "no immediate delivery for these"
14988 .row &%queue_fast_ramp%& "parallel delivery with 2-phase queue run"
14989 .row &%queue_only%& "no immediate delivery at all"
14990 .row &%queue_only_file%& "no immediate delivery if file exists"
14991 .row &%queue_only_load%& "no immediate delivery if load is high"
14992 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14993 .row &%queue_only_override%& "allow command line to override"
14994 .row &%queue_run_in_order%& "order of arrival"
14995 .row &%queue_run_max%& "of simultaneous queue runners"
14996 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
14997 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14998 .row &%remote_sort_domains%& "order of remote deliveries"
14999 .row &%retry_data_expire%& "timeout for retry data"
15000 .row &%retry_interval_max%& "safety net for retry rules"
15005 .section "Bounce and warning messages" "SECID117"
15007 .row &%bounce_message_file%& "content of bounce"
15008 .row &%bounce_message_text%& "content of bounce"
15009 .row &%bounce_return_body%& "include body if returning message"
15010 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
15011 .row &%bounce_return_message%& "include original message in bounce"
15012 .row &%bounce_return_size_limit%& "limit on returned message"
15013 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
15014 .row &%dsn_from%& "set &'From:'& contents in bounces"
15015 .row &%errors_copy%& "copy bounce messages"
15016 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
15017 .row &%delay_warning%& "time schedule"
15018 .row &%delay_warning_condition%& "condition for warning messages"
15019 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
15020 .row &%smtp_return_error_details%& "give detail on rejections"
15021 .row &%warn_message_file%& "content of warning message"
15026 .section "Alphabetical list of main options" "SECTalomo"
15027 Those options that undergo string expansion before use are marked with
15030 .option accept_8bitmime main boolean true
15032 .cindex "8-bit characters"
15033 .cindex "log" "selectors"
15034 .cindex "log" "8BITMIME"
15035 .cindex "ESMTP extensions" 8BITMIME
15036 This option causes Exim to send 8BITMIME in its response to an SMTP
15037 EHLO command, and to accept the BODY= parameter on MAIL commands.
15038 However, though Exim is 8-bit clean, it is not a protocol converter, and it
15039 takes no steps to do anything special with messages received by this route.
15041 Historically Exim kept this option off by default, but the maintainers
15042 feel that in today's Internet, this causes more problems than it solves.
15043 It now defaults to true.
15044 A more detailed analysis of the issues is provided by Dan Bernstein:
15046 &url(https://cr.yp.to/smtp/8bitmime.html)
15049 To log received 8BITMIME status use
15051 log_selector = +8bitmime
15054 .option acl_not_smtp main string&!! unset
15055 .cindex "&ACL;" "for non-SMTP messages"
15056 .cindex "non-SMTP messages" "ACLs for"
15057 This option defines the ACL that is run when a non-SMTP message has been
15058 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
15061 .option acl_not_smtp_mime main string&!! unset
15062 This option defines the ACL that is run for individual MIME parts of non-SMTP
15063 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
15066 .option acl_not_smtp_start main string&!! unset
15067 .cindex "&ACL;" "at start of non-SMTP message"
15068 .cindex "non-SMTP messages" "ACLs for"
15069 This option defines the ACL that is run before Exim starts reading a
15070 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
15072 .option acl_smtp_auth main string&!! unset
15073 .cindex "&ACL;" "setting up for SMTP commands"
15074 .cindex "AUTH" "ACL for"
15075 This option defines the ACL that is run when an SMTP AUTH command is
15076 received. See chapter &<<CHAPACL>>& for further details.
15078 .option acl_smtp_connect main string&!! unset
15079 .cindex "&ACL;" "on SMTP connection"
15080 This option defines the ACL that is run when an SMTP connection is received.
15081 See chapter &<<CHAPACL>>& for further details.
15083 .option acl_smtp_data main string&!! unset
15084 .cindex "DATA" "ACL for"
15085 This option defines the ACL that is run after an SMTP DATA command has been
15086 processed and the message itself has been received, but before the final
15087 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15089 .option acl_smtp_data_prdr main string&!! accept
15090 .cindex "PRDR" "ACL for"
15091 .cindex "DATA" "PRDR ACL for"
15092 .cindex "&ACL;" "PRDR-related"
15093 .cindex "&ACL;" "per-user data processing"
15094 This option defines the ACL that,
15095 if the PRDR feature has been negotiated,
15096 is run for each recipient after an SMTP DATA command has been
15097 processed and the message itself has been received, but before the
15098 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15100 .option acl_smtp_dkim main string&!! unset
15101 .cindex DKIM "ACL for"
15102 This option defines the ACL that is run for each DKIM signature
15103 (by default, or as specified in the dkim_verify_signers option)
15104 of a received message.
15105 See section &<<SECDKIMVFY>>& for further details.
15107 .option acl_smtp_etrn main string&!! unset
15108 .cindex "ETRN" "ACL for"
15109 This option defines the ACL that is run when an SMTP ETRN command is
15110 received. See chapter &<<CHAPACL>>& for further details.
15112 .option acl_smtp_expn main string&!! unset
15113 .cindex "EXPN" "ACL for"
15114 This option defines the ACL that is run when an SMTP EXPN command is
15115 received. See chapter &<<CHAPACL>>& for further details.
15117 .option acl_smtp_helo main string&!! unset
15118 .cindex "EHLO" "ACL for"
15119 .cindex "HELO" "ACL for"
15120 This option defines the ACL that is run when an SMTP EHLO or HELO
15121 command is received. See chapter &<<CHAPACL>>& for further details.
15124 .option acl_smtp_mail main string&!! unset
15125 .cindex "MAIL" "ACL for"
15126 This option defines the ACL that is run when an SMTP MAIL command is
15127 received. See chapter &<<CHAPACL>>& for further details.
15129 .option acl_smtp_mailauth main string&!! unset
15130 .cindex "AUTH" "on MAIL command"
15131 This option defines the ACL that is run when there is an AUTH parameter on
15132 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
15133 &<<CHAPSMTPAUTH>>& for details of authentication.
15135 .option acl_smtp_mime main string&!! unset
15136 .cindex "MIME content scanning" "ACL for"
15137 This option is available when Exim is built with the content-scanning
15138 extension. It defines the ACL that is run for each MIME part in a message. See
15139 section &<<SECTscanmimepart>>& for details.
15141 .option acl_smtp_notquit main string&!! unset
15142 .cindex "not-QUIT, ACL for"
15143 This option defines the ACL that is run when an SMTP session
15144 ends without a QUIT command being received.
15145 See chapter &<<CHAPACL>>& for further details.
15147 .option acl_smtp_predata main string&!! unset
15148 This option defines the ACL that is run when an SMTP DATA command is
15149 received, before the message itself is received. See chapter &<<CHAPACL>>& for
15152 .option acl_smtp_quit main string&!! unset
15153 .cindex "QUIT, ACL for"
15154 This option defines the ACL that is run when an SMTP QUIT command is
15155 received. See chapter &<<CHAPACL>>& for further details.
15157 .option acl_smtp_rcpt main string&!! unset
15158 .cindex "RCPT" "ACL for"
15159 This option defines the ACL that is run when an SMTP RCPT command is
15160 received. See chapter &<<CHAPACL>>& for further details.
15162 .option acl_smtp_starttls main string&!! unset
15163 .cindex "STARTTLS, ACL for"
15164 This option defines the ACL that is run when an SMTP STARTTLS command is
15165 received. See chapter &<<CHAPACL>>& for further details.
15167 .option acl_smtp_vrfy main string&!! unset
15168 .cindex "VRFY" "ACL for"
15169 This option defines the ACL that is run when an SMTP VRFY command is
15170 received. See chapter &<<CHAPACL>>& for further details.
15172 .option add_environment main "string list" empty
15173 .cindex "environment" "set values"
15174 This option adds individual environment variables that the
15175 currently linked libraries and programs in child processes may use.
15176 Each list element should be of the form &"name=value"&.
15178 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
15180 .option admin_groups main "string list&!!" unset
15181 .cindex "admin user"
15182 This option is expanded just once, at the start of Exim's processing. If the
15183 current group or any of the supplementary groups of an Exim caller is in this
15184 colon-separated list, the caller has admin privileges. If all your system
15185 programmers are in a specific group, for example, you can give them all Exim
15186 admin privileges by putting that group in &%admin_groups%&. However, this does
15187 not permit them to read Exim's spool files (whose group owner is the Exim gid).
15188 To permit this, you have to add individuals to the Exim group.
15190 .option allow_domain_literals main boolean false
15191 .cindex "domain literal"
15192 If this option is set, the RFC 2822 domain literal format is permitted in
15193 email addresses. The option is not set by default, because the domain literal
15194 format is not normally required these days, and few people know about it. It
15195 has, however, been exploited by mail abusers.
15197 Unfortunately, it seems that some DNS black list maintainers are using this
15198 format to report black listing to postmasters. If you want to accept messages
15199 addressed to your hosts by IP address, you need to set
15200 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
15201 domains (defined in the named domain list &%local_domains%& in the default
15202 configuration). This &"magic string"& matches the domain literal form of all
15203 the local host's IP addresses.
15205 .option allow_insecure_tainted_data main boolean false
15206 .cindex "de-tainting"
15207 .oindex "allow_insecure_tainted_data"
15208 The handling of tainted data may break older (pre 4.94) configurations.
15209 Setting this option to "true" turns taint errors (which result in a temporary
15210 message rejection) into warnings. This option is meant as mitigation only
15211 and deprecated already today. Future releases of Exim may ignore it.
15212 The &%taint%& log selector can be used to suppress even the warnings.
15216 .option allow_mx_to_ip main boolean false
15217 .cindex "MX record" "pointing to IP address"
15218 It appears that more and more DNS zone administrators are breaking the rules
15219 and putting domain names that look like IP addresses on the right hand side of
15220 MX records. Exim follows the rules and rejects this, giving an error message
15221 that explains the misconfiguration. However, some other MTAs support this
15222 practice, so to avoid &"Why can't Exim do this?"& complaints,
15223 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
15224 recommended, except when you have no other choice.
15226 .option allow_utf8_domains main boolean false
15227 .cindex "domain" "UTF-8 characters in"
15228 .cindex "UTF-8" "in domain name"
15229 Lots of discussion is going on about internationalized domain names. One
15230 camp is strongly in favour of just using UTF-8 characters, and it seems
15231 that at least two other MTAs permit this.
15232 This option allows Exim users to experiment if they wish.
15234 If it is set true, Exim's domain parsing function allows valid
15235 UTF-8 multicharacters to appear in domain name components, in addition to
15236 letters, digits, and hyphens.
15238 If Exim is built with internationalization support
15239 and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
15240 this option can be left as default.
15242 if you want to look up such domain names in the DNS, you must also
15243 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
15244 suitable setting is:
15246 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
15247 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
15249 Alternatively, you can just disable this feature by setting
15251 dns_check_names_pattern =
15253 That is, set the option to an empty string so that no check is done.
15256 .option auth_advertise_hosts main "host list&!!" *
15257 .cindex "authentication" "advertising"
15258 .cindex "AUTH" "advertising"
15259 .cindex "ESMTP extensions" AUTH
15260 If any server authentication mechanisms are configured, Exim advertises them in
15261 response to an EHLO command only if the calling host matches this list.
15262 Otherwise, Exim does not advertise AUTH.
15263 Exim does not accept AUTH commands from clients to which it has not
15264 advertised the availability of AUTH. The advertising of individual
15265 authentication mechanisms can be controlled by the use of the
15266 &%server_advertise_condition%& generic authenticator option on the individual
15267 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
15269 Certain mail clients (for example, Netscape) require the user to provide a name
15270 and password for authentication if AUTH is advertised, even though it may
15271 not be needed (the host may accept messages from hosts on its local LAN without
15272 authentication, for example). The &%auth_advertise_hosts%& option can be used
15273 to make these clients more friendly by excluding them from the set of hosts to
15274 which Exim advertises AUTH.
15276 .cindex "AUTH" "advertising when encrypted"
15277 If you want to advertise the availability of AUTH only when the connection
15278 is encrypted using TLS, you can make use of the fact that the value of this
15279 option is expanded, with a setting like this:
15281 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
15283 .vindex "&$tls_in_cipher$&"
15284 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
15285 the expansion is empty, thus matching no hosts. Otherwise, the result of the
15286 expansion is *, which matches all hosts.
15289 .option auto_thaw main time 0s
15290 .cindex "thawing messages"
15291 .cindex "unfreezing messages"
15292 If this option is set to a time greater than zero, a queue runner will try a
15293 new delivery attempt on any frozen message, other than a bounce message, if
15294 this much time has passed since it was frozen. This may result in the message
15295 being re-frozen if nothing has changed since the last attempt. It is a way of
15296 saying &"keep on trying, even though there are big problems"&.
15298 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
15299 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
15300 thought to be very useful any more, and its use should probably be avoided.
15303 .option av_scanner main string "see below"
15304 This option is available if Exim is built with the content-scanning extension.
15305 It specifies which anti-virus scanner to use. The default value is:
15307 sophie:/var/run/sophie
15309 If the value of &%av_scanner%& starts with a dollar character, it is expanded
15310 before use. See section &<<SECTscanvirus>>& for further details.
15313 .option bi_command main string unset
15315 This option supplies the name of a command that is run when Exim is called with
15316 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
15317 just the command name, it is not a complete command line. If an argument is
15318 required, it must come from the &%-oA%& command line option.
15321 .option bounce_message_file main string&!! unset
15322 .cindex "bounce message" "customizing"
15323 .cindex "customizing" "bounce message"
15324 This option defines a template file containing paragraphs of text to be used
15325 for constructing bounce messages. Details of the file's contents are given in
15326 chapter &<<CHAPemsgcust>>&.
15327 .cindex bounce_message_file "tainted data"
15328 The option is expanded to give the file path, which must be
15329 absolute and untainted.
15330 See also &%warn_message_file%&.
15333 .option bounce_message_text main string unset
15334 When this option is set, its contents are included in the default bounce
15335 message immediately after &"This message was created automatically by mail
15336 delivery software."& It is not used if &%bounce_message_file%& is set.
15338 .option bounce_return_body main boolean true
15339 .cindex "bounce message" "including body"
15340 This option controls whether the body of an incoming message is included in a
15341 bounce message when &%bounce_return_message%& is true. The default setting
15342 causes the entire message, both header and body, to be returned (subject to the
15343 value of &%bounce_return_size_limit%&). If this option is false, only the
15344 message header is included. In the case of a non-SMTP message containing an
15345 error that is detected during reception, only those header lines preceding the
15346 point at which the error was detected are returned.
15347 .cindex "bounce message" "including original"
15349 .option bounce_return_linesize_limit main integer 998
15350 .cindex "size" "of bounce lines, limit"
15351 .cindex "bounce message" "line length limit"
15352 .cindex "limit" "bounce message line length"
15353 This option sets a limit in bytes on the line length of messages
15354 that are returned to senders due to delivery problems,
15355 when &%bounce_return_message%& is true.
15356 The default value corresponds to RFC limits.
15357 If the message being returned has lines longer than this value it is
15358 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
15360 The option also applies to bounces returned when an error is detected
15361 during reception of a message.
15362 In this case lines from the original are truncated.
15364 The option does not apply to messages generated by an &(autoreply)& transport.
15367 .option bounce_return_message main boolean true
15368 If this option is set false, none of the original message is included in
15369 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
15370 &%bounce_return_body%&.
15373 .option bounce_return_size_limit main integer 100K
15374 .cindex "size" "of bounce, limit"
15375 .cindex "bounce message" "size limit"
15376 .cindex "limit" "bounce message size"
15377 This option sets a limit in bytes on the size of messages that are returned to
15378 senders as part of bounce messages when &%bounce_return_message%& is true. The
15379 limit should be less than the value of the global &%message_size_limit%& and of
15380 any &%message_size_limit%& settings on transports, to allow for the bounce text
15381 that Exim generates. If this option is set to zero there is no limit.
15383 When the body of any message that is to be included in a bounce message is
15384 greater than the limit, it is truncated, and a comment pointing this out is
15385 added at the top. The actual cutoff may be greater than the value given, owing
15386 to the use of buffering for transferring the message in chunks (typically 8K in
15387 size). The idea is to save bandwidth on those undeliverable 15-megabyte
15390 .option bounce_sender_authentication main string unset
15391 .cindex "bounce message" "sender authentication"
15392 .cindex "authentication" "bounce message"
15393 .cindex "AUTH" "on bounce message"
15394 This option provides an authenticated sender address that is sent with any
15395 bounce messages generated by Exim that are sent over an authenticated SMTP
15396 connection. A typical setting might be:
15398 bounce_sender_authentication = mailer-daemon@my.domain.example
15400 which would cause bounce messages to be sent using the SMTP command:
15402 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
15404 The value of &%bounce_sender_authentication%& must always be a complete email
15407 .option callout_domain_negative_expire main time 3h
15408 .cindex "caching" "callout timeouts"
15409 .cindex "callout" "caching timeouts"
15410 This option specifies the expiry time for negative callout cache data for a
15411 domain. See section &<<SECTcallver>>& for details of callout verification, and
15412 section &<<SECTcallvercache>>& for details of the caching.
15415 .option callout_domain_positive_expire main time 7d
15416 This option specifies the expiry time for positive callout cache data for a
15417 domain. See section &<<SECTcallver>>& for details of callout verification, and
15418 section &<<SECTcallvercache>>& for details of the caching.
15421 .option callout_negative_expire main time 2h
15422 This option specifies the expiry time for negative callout cache data for an
15423 address. See section &<<SECTcallver>>& for details of callout verification, and
15424 section &<<SECTcallvercache>>& for details of the caching.
15427 .option callout_positive_expire main time 24h
15428 This option specifies the expiry time for positive callout cache data for an
15429 address. See section &<<SECTcallver>>& for details of callout verification, and
15430 section &<<SECTcallvercache>>& for details of the caching.
15433 .option callout_random_local_part main string&!! "see below"
15434 This option defines the &"random"& local part that can be used as part of
15435 callout verification. The default value is
15437 $primary_hostname-$tod_epoch-testing
15439 See section &<<CALLaddparcall>>& for details of how this value is used.
15442 .option check_log_inodes main integer 100
15443 See &%check_spool_space%& below.
15446 .option check_log_space main integer 10M
15447 See &%check_spool_space%& below.
15449 .oindex "&%check_rfc2047_length%&"
15450 .cindex "RFC 2047" "disabling length check"
15451 .option check_rfc2047_length main boolean true
15452 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
15453 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
15454 word; strings to be encoded that exceed this length are supposed to use
15455 multiple encoded words. By default, Exim does not recognize encoded words that
15456 exceed the maximum length. However, it seems that some software, in violation
15457 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
15458 set false, Exim recognizes encoded words of any length.
15461 .option check_spool_inodes main integer 100
15462 See &%check_spool_space%& below.
15465 .option check_spool_space main integer 10M
15466 .cindex "checking disk space"
15467 .cindex "disk space, checking"
15468 .cindex "spool directory" "checking space"
15469 The four &%check_...%& options allow for checking of disk resources before a
15470 message is accepted.
15472 .vindex "&$log_inodes$&"
15473 .vindex "&$log_space$&"
15474 .vindex "&$spool_inodes$&"
15475 .vindex "&$spool_space$&"
15476 When any of these options are nonzero, they apply to all incoming messages. If you
15477 want to apply different checks to different kinds of message, you can do so by
15478 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
15479 &$spool_space$& in an ACL with appropriate additional conditions.
15482 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
15483 either value is greater than zero, for example:
15485 check_spool_space = 100M
15486 check_spool_inodes = 100
15488 The spool partition is the one that contains the directory defined by
15489 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
15492 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
15493 files are written if either is greater than zero. These should be set only if
15494 &%log_file_path%& and &%spool_directory%& refer to different partitions.
15496 If there is less space or fewer inodes than requested, Exim refuses to accept
15497 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
15498 error response to the MAIL command. If ESMTP is in use and there was a
15499 SIZE parameter on the MAIL command, its value is added to the
15500 &%check_spool_space%& value, and the check is performed even if
15501 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
15503 The values for &%check_spool_space%& and &%check_log_space%& are held as a
15504 number of kilobytes (though specified in bytes).
15505 If a non-multiple of 1024 is specified, it is rounded up.
15507 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
15508 failure a message is written to stderr and Exim exits with a non-zero code, as
15509 it obviously cannot send an error message of any kind.
15511 There is a slight performance penalty for these checks.
15512 Versions of Exim preceding 4.88 had these disabled by default;
15513 high-rate installations confident they will never run out of resources
15514 may wish to deliberately disable them.
15516 .option chunking_advertise_hosts main "host list&!!" *
15517 .cindex CHUNKING advertisement
15518 .cindex "RFC 3030" "CHUNKING"
15519 .cindex "ESMTP extensions" CHUNKING
15520 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
15522 Hosts may use the BDAT command as an alternate to DATA.
15524 .option commandline_checks_require_admin main boolean &`false`&
15525 .cindex "restricting access to features"
15526 This option restricts various basic checking features to require an
15527 administrative user.
15528 This affects most of the &%-b*%& options, such as &%-be%&.
15530 .option debug_store main boolean &`false`&
15531 .cindex debugging "memory corruption"
15532 .cindex memory debugging
15533 This option, when true, enables extra checking in Exim's internal memory
15534 management. For use when a memory corruption issue is being investigated,
15535 it should normally be left as default.
15537 .option daemon_smtp_ports main string &`smtp`&
15538 .cindex "port" "for daemon"
15539 .cindex "TCP/IP" "setting listening ports"
15540 This option specifies one or more default SMTP ports on which the Exim daemon
15541 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
15542 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
15544 .option daemon_startup_retries main integer 9
15545 .cindex "daemon startup, retrying"
15546 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
15547 the daemon at startup when it cannot immediately bind a listening socket
15548 (typically because the socket is already in use): &%daemon_startup_retries%&
15549 defines the number of retries after the first failure, and
15550 &%daemon_startup_sleep%& defines the length of time to wait between retries.
15552 .option daemon_startup_sleep main time 30s
15553 See &%daemon_startup_retries%&.
15555 .option delay_warning main "time list" 24h
15556 .cindex "warning of delay"
15557 .cindex "delay warning, specifying"
15558 .cindex "queue" "delay warning"
15559 When a message is delayed, Exim sends a warning message to the sender at
15560 intervals specified by this option. The data is a colon-separated list of times
15561 after which to send warning messages. If the value of the option is an empty
15562 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
15563 message has been in the queue for longer than the last time, the last interval
15564 between the times is used to compute subsequent warning times. For example,
15567 delay_warning = 4h:8h:24h
15569 the first message is sent after 4 hours, the second after 8 hours, and
15570 the third one after 24 hours. After that, messages are sent every 16 hours,
15571 because that is the interval between the last two times on the list. If you set
15572 just one time, it specifies the repeat interval. For example, with:
15576 messages are repeated every six hours. To stop warnings after a given time, set
15577 a very large time at the end of the list. For example:
15579 delay_warning = 2h:12h:99d
15581 Note that the option is only evaluated at the time a delivery attempt fails,
15582 which depends on retry and queue-runner configuration.
15583 Typically retries will be configured more frequently than warning messages.
15585 .option delay_warning_condition main string&!! "see below"
15586 .vindex "&$domain$&"
15587 The string is expanded at the time a warning message might be sent. If all the
15588 deferred addresses have the same domain, it is set in &$domain$& during the
15589 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
15590 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
15591 &"false"& (the comparison being done caselessly) then the warning message is
15592 not sent. The default is:
15594 delay_warning_condition = ${if or {\
15595 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
15596 { match{$h_precedence:}{(?i)bulk|list|junk} }\
15597 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
15600 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
15601 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
15602 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
15603 &"auto-replied"& in an &'Auto-Submitted:'& header.
15605 .option deliver_drop_privilege main boolean false
15606 .cindex "unprivileged delivery"
15607 .cindex "delivery" "unprivileged"
15608 If this option is set true, Exim drops its root privilege at the start of a
15609 delivery process, and runs as the Exim user throughout. This severely restricts
15610 the kinds of local delivery that are possible, but is viable in certain types
15611 of configuration. There is a discussion about the use of root privilege in
15612 chapter &<<CHAPsecurity>>&.
15614 .option deliver_queue_load_max main fixed-point unset
15615 .cindex "load average"
15616 .cindex "queue runner" "abandoning"
15617 When this option is set, a queue run is abandoned if the system load average
15618 becomes greater than the value of the option. The option has no effect on
15619 ancient operating systems on which Exim cannot determine the load average.
15620 See also &%queue_only_load%& and &%smtp_load_reserve%&.
15623 .option delivery_date_remove main boolean true
15624 .cindex "&'Delivery-date:'& header line"
15625 Exim's transports have an option for adding a &'Delivery-date:'& header to a
15626 message when it is delivered, in exactly the same way as &'Return-path:'& is
15627 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
15628 should not be present in incoming messages, and this option causes them to be
15629 removed at the time the message is received, to avoid any problems that might
15630 occur when a delivered message is subsequently sent on to some other recipient.
15632 .option disable_fsync main boolean false
15633 .cindex "&[fsync()]&, disabling"
15634 This option is available only if Exim was built with the compile-time option
15635 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
15636 a runtime configuration generates an &"unknown option"& error. You should not
15637 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
15638 really, really, really understand what you are doing. &'No pre-compiled
15639 distributions of Exim should ever make this option available.'&
15641 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
15642 updated files' data to be written to disc before continuing. Unexpected events
15643 such as crashes and power outages may cause data to be lost or scrambled.
15644 Here be Dragons. &*Beware.*&
15647 .option disable_ipv6 main boolean false
15648 .cindex "IPv6" "disabling"
15649 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
15650 activities take place. AAAA records are never looked up, and any IPv6 addresses
15651 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
15652 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
15653 to handle IPv6 literal addresses.
15656 .option dkim_verify_hashes main "string list" "sha256 : sha512"
15657 .cindex DKIM "selecting signature algorithms"
15658 This option gives a list of hash types which are acceptable in signatures,
15659 and an order of processing.
15660 Signatures with algorithms not in the list will be ignored.
15662 Acceptable values include:
15669 Note that the acceptance of sha1 violates RFC 8301.
15671 .option dkim_verify_keytypes main "string list" "ed25519 : rsa"
15672 This option gives a list of key types which are acceptable in signatures,
15673 and an order of processing.
15674 Signatures with algorithms not in the list will be ignored.
15677 .option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250"
15678 This option gives a list of key sizes which are acceptable in signatures.
15679 The list is keyed by the algorithm type for the key; the values are in bits.
15680 Signatures with keys smaller than given by this option will fail verification.
15682 The default enforces the RFC 8301 minimum key size for RSA signatures.
15684 .option dkim_verify_minimal main boolean false
15685 If set to true, verification of signatures will terminate after the
15688 .option dkim_verify_signers main "domain list&!!" $dkim_signers
15689 .cindex DKIM "controlling calls to the ACL"
15690 This option gives a list of DKIM domains for which the DKIM ACL is run.
15691 It is expanded after the message is received; by default it runs
15692 the ACL once for each signature in the message.
15693 See section &<<SECDKIMVFY>>&.
15696 .option dmarc_forensic_sender main string&!! unset
15697 .option dmarc_history_file main string unset
15698 .option dmarc_tld_file main string unset
15699 .cindex DMARC "main section options"
15700 These options control DMARC processing.
15701 See section &<<SECDMARC>>& for details.
15704 .option dns_again_means_nonexist main "domain list&!!" unset
15705 .cindex "DNS" "&""try again""& response; overriding"
15706 DNS lookups give a &"try again"& response for the DNS errors
15707 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
15708 keep trying to deliver a message, or to give repeated temporary errors to
15709 incoming mail. Sometimes the effect is caused by a badly set up name server and
15710 may persist for a long time. If a domain which exhibits this problem matches
15711 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
15712 This option should be used with care. You can make it apply to reverse lookups
15713 by a setting such as this:
15715 dns_again_means_nonexist = *.in-addr.arpa
15717 This option applies to all DNS lookups that Exim does. It also applies when the
15718 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
15719 since these are most likely to be caused by DNS lookup problems. The
15720 &(dnslookup)& router has some options of its own for controlling what happens
15721 when lookups for MX or SRV records give temporary errors. These more specific
15722 options are applied after this global option.
15724 .option dns_check_names_pattern main string "see below"
15725 .cindex "DNS" "pre-check of name syntax"
15726 When this option is set to a non-empty string, it causes Exim to check domain
15727 names for characters that are not allowed in host names before handing them to
15728 the DNS resolver, because some resolvers give temporary errors for names that
15729 contain unusual characters. If a domain name contains any unwanted characters,
15730 a &"not found"& result is forced, and the resolver is not called. The check is
15731 done by matching the domain name against a regular expression, which is the
15732 value of this option. The default pattern is
15734 dns_check_names_pattern = \
15735 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
15737 which permits only letters, digits, slashes, and hyphens in components, but
15738 they must start and end with a letter or digit. Slashes are not, in fact,
15739 permitted in host names, but they are found in certain NS records (which can be
15740 accessed in Exim by using a &%dnsdb%& lookup). If you set
15741 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
15744 .option dns_csa_search_limit main integer 5
15745 This option controls the depth of parental searching for CSA SRV records in the
15746 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
15748 .option dns_csa_use_reverse main boolean true
15749 This option controls whether or not an IP address, given as a CSA domain, is
15750 reversed and looked up in the reverse DNS, as described in more detail in
15751 section &<<SECTverifyCSA>>&.
15753 .option dns_cname_loops main integer 1
15754 .cindex DNS "CNAME following"
15755 This option controls the following of CNAME chains, needed if the resolver does
15756 not do it internally.
15757 As of 2018 most should, and the default can be left.
15758 If you have an ancient one, a value of 10 is likely needed.
15760 The default value of one CNAME-follow is needed
15761 thanks to the observed return for an MX request,
15762 given no MX presence but a CNAME to an A, of the CNAME.
15765 .option dns_dnssec_ok main integer -1
15766 .cindex "DNS" "resolver options"
15767 .cindex "DNS" "DNSSEC"
15768 If this option is set to a non-negative number then Exim will initialise the
15769 DNS resolver library to either use or not use DNSSEC, overriding the system
15770 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
15772 If the resolver library does not support DNSSEC then this option has no effect.
15774 On Linux with glibc 2.31 or newer this is insufficient, the resolver library
15775 will default to stripping out a successful validation status.
15776 This will break a previously working Exim installation.
15777 Provided that you do trust the resolver (ie, is on localhost) you can tell
15778 glibc to pass through any successful validation with a new option in
15779 &_/etc/resolv.conf_&:
15785 .option dns_ipv4_lookup main "domain list&!!" unset
15786 .cindex "IPv6" "DNS lookup for AAAA records"
15787 .cindex "DNS" "IPv6 lookup for AAAA records"
15788 .cindex DNS "IPv6 disabling"
15789 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
15790 looks for IPv6 address records (AAAA records) as well as IPv4 address records
15791 (A records) when trying to find IP addresses for hosts, unless the host's
15792 domain matches this list.
15794 This is a fudge to help with name servers that give big delays or otherwise do
15795 not work for the AAAA record type. In due course, when the world's name
15796 servers have all been upgraded, there should be no need for this option.
15797 Note that all lookups, including those done for verification, are affected;
15798 this will result in verify failure for IPv6 connections or ones using names
15799 only valid for IPv6 addresses.
15802 .option dns_retrans main time 0s
15803 .cindex "DNS" "resolver options"
15804 .cindex timeout "dns lookup"
15805 .cindex "DNS" timeout
15806 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
15807 retransmission and retry parameters for DNS lookups. Values of zero (the
15808 defaults) leave the system default settings unchanged. The first value is the
15809 time between retries, and the second is the number of retries. It isn't
15810 totally clear exactly how these settings affect the total time a DNS lookup may
15811 take. I haven't found any documentation about timeouts on DNS lookups; these
15812 parameter values are available in the external resolver interface structure,
15813 but nowhere does it seem to describe how they are used or what you might want
15815 See also the &%slow_lookup_log%& option.
15818 .option dns_retry main integer 0
15819 See &%dns_retrans%& above.
15822 .option dns_trust_aa main "domain list&!!" unset
15823 .cindex "DNS" "resolver options"
15824 .cindex "DNS" "DNSSEC"
15825 If this option is set then lookup results marked with the AA bit
15826 (Authoritative Answer) are trusted the same way as if they were
15827 DNSSEC-verified. The authority section's name of the answer must
15828 match with this expanded domain list.
15830 Use this option only if you talk directly to a resolver that is
15831 authoritative for some zones and does not set the AD (Authentic Data)
15832 bit in the answer. Some DNS servers may have an configuration option to
15833 mark the answers from their own zones as verified (they set the AD bit).
15834 Others do not have this option. It is considered as poor practice using
15835 a resolver that is an authoritative server for some zones.
15837 Use this option only if you really have to (e.g. if you want
15838 to use DANE for remote delivery to a server that is listed in the DNS
15839 zones that your resolver is authoritative for).
15841 If the DNS answer packet has the AA bit set and contains resource record
15842 in the answer section, the name of the first NS record appearing in the
15843 authority section is compared against the list. If the answer packet is
15844 authoritative but the answer section is empty, the name of the first SOA
15845 record in the authoritative section is used instead.
15847 .cindex "DNS" "resolver options"
15848 .option dns_use_edns0 main integer -1
15849 .cindex "DNS" "resolver options"
15850 .cindex "DNS" "EDNS0"
15851 .cindex "DNS" "OpenBSD
15852 If this option is set to a non-negative number then Exim will initialise the
15853 DNS resolver library to either use or not use EDNS0 extensions, overriding
15854 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
15857 If the resolver library does not support EDNS0 then this option has no effect.
15859 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
15860 means that DNSSEC will not work with Exim on that platform either, unless Exim
15861 is linked against an alternative DNS client library.
15864 .option drop_cr main boolean false
15865 This is an obsolete option that is now a no-op. It used to affect the way Exim
15866 handled CR and LF characters in incoming messages. What happens now is
15867 described in section &<<SECTlineendings>>&.
15869 .option dsn_advertise_hosts main "host list&!!" unset
15870 .cindex "bounce messages" "success"
15871 .cindex "DSN" "success"
15872 .cindex "Delivery Status Notification" "success"
15873 .cindex "ESMTP extensions" DSN
15874 DSN extensions (RFC3461) will be advertised in the EHLO message to,
15875 and accepted from, these hosts.
15876 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
15877 and RET and ORCPT options on MAIL FROM commands.
15878 A NOTIFY=SUCCESS option requests success-DSN messages.
15879 A NOTIFY= option with no argument requests that no delay or failure DSNs
15881 &*Note*&: Supplying success-DSN messages has been criticised
15882 on privacy grounds; it can leak details of internal forwarding.
15884 .option dsn_from main "string&!!" "see below"
15885 .cindex "&'From:'& header line" "in bounces"
15886 .cindex "bounce messages" "&'From:'& line, specifying"
15887 This option can be used to vary the contents of &'From:'& header lines in
15888 bounces and other automatically generated messages (&"Delivery Status
15889 Notifications"& &-- hence the name of the option). The default setting is:
15891 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
15893 The value is expanded every time it is needed. If the expansion fails, a
15894 panic is logged, and the default value is used.
15896 .option envelope_to_remove main boolean true
15897 .cindex "&'Envelope-to:'& header line"
15898 Exim's transports have an option for adding an &'Envelope-to:'& header to a
15899 message when it is delivered, in exactly the same way as &'Return-path:'& is
15900 handled. &'Envelope-to:'& records the original recipient address from the
15901 message's envelope that caused the delivery to happen. Such headers should not
15902 be present in incoming messages, and this option causes them to be removed at
15903 the time the message is received, to avoid any problems that might occur when a
15904 delivered message is subsequently sent on to some other recipient.
15907 .option errors_copy main "string list&!!" unset
15908 .cindex "bounce message" "copy to other address"
15909 .cindex "copy of bounce message"
15910 Setting this option causes Exim to send bcc copies of bounce messages that it
15911 generates to other addresses. &*Note*&: This does not apply to bounce messages
15912 coming from elsewhere. The value of the option is a colon-separated list of
15913 items. Each item consists of a pattern, terminated by white space, followed by
15914 a comma-separated list of email addresses. If a pattern contains spaces, it
15915 must be enclosed in double quotes.
15917 Each pattern is processed in the same way as a single item in an address list
15918 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
15919 the bounce message, the message is copied to the addresses on the list. The
15920 items are scanned in order, and once a matching one is found, no further items
15921 are examined. For example:
15923 errors_copy = spqr@mydomain postmaster@mydomain.example :\
15924 rqps@mydomain hostmaster@mydomain.example,\
15925 postmaster@mydomain.example
15927 .vindex "&$domain$&"
15928 .vindex "&$local_part$&"
15929 The address list is expanded before use. The expansion variables &$local_part$&
15930 and &$domain$& are set from the original recipient of the error message, and if
15931 there was any wildcard matching in the pattern, the expansion
15932 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
15933 variables &$0$&, &$1$&, etc. are set in the normal way.
15936 .option errors_reply_to main string unset
15937 .cindex "bounce message" "&'Reply-to:'& in"
15938 By default, Exim's bounce and delivery warning messages contain the header line
15940 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
15942 .oindex &%quota_warn_message%&
15943 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
15944 A warning message that is generated by the &%quota_warn_message%& option in an
15945 &(appendfile)& transport may contain its own &'From:'& header line that
15946 overrides the default.
15948 Experience shows that people reply to bounce messages. If the
15949 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
15950 and warning messages. For example:
15952 errors_reply_to = postmaster@my.domain.example
15954 The value of the option is not expanded. It must specify a valid RFC 2822
15955 address. However, if a warning message that is generated by the
15956 &%quota_warn_message%& option in an &(appendfile)& transport contain its
15957 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
15961 .option event_action main string&!! unset
15963 This option declares a string to be expanded for Exim's events mechanism.
15964 For details see chapter &<<CHAPevents>>&.
15967 .option exim_group main string "compile-time configured"
15968 .cindex "gid (group id)" "Exim's own"
15969 .cindex "Exim group"
15970 This option changes the gid under which Exim runs when it gives up root
15971 privilege. The default value is compiled into the binary. The value of this
15972 option is used only when &%exim_user%& is also set. Unless it consists entirely
15973 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
15974 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
15978 .option exim_path main string "see below"
15979 .cindex "Exim binary, path name"
15980 This option specifies the path name of the Exim binary, which is used when Exim
15981 needs to re-exec itself. The default is set up to point to the file &'exim'& in
15982 the directory configured at compile time by the BIN_DIRECTORY setting. It
15983 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
15985 &*Warning*&: Do not use a macro to define the value of this option, because
15986 you will break those Exim utilities that scan the configuration file to find
15987 where the binary is. (They then use the &%-bP%& option to extract option
15988 settings such as the value of &%spool_directory%&.)
15991 .option exim_user main string "compile-time configured"
15992 .cindex "uid (user id)" "Exim's own"
15993 .cindex "Exim user"
15994 This option changes the uid under which Exim runs when it gives up root
15995 privilege. The default value is compiled into the binary. Ownership of the run
15996 time configuration file and the use of the &%-C%& and &%-D%& command line
15997 options is checked against the values in the binary, not what is set here.
15999 Unless it consists entirely of digits, the string is looked up using
16000 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
16001 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
16002 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
16005 .option exim_version main string "current version"
16006 .cindex "Exim version"
16007 .cindex customizing "version number"
16008 .cindex "version number of Exim" override
16009 This option overrides the &$version_number$&/&$exim_version$& that Exim reports in
16010 various places. Use with care; this may fool stupid security scanners.
16013 .option extra_local_interfaces main "string list" unset
16014 This option defines network interfaces that are to be considered local when
16015 routing, but which are not used for listening by the daemon. See section
16016 &<<SECTreclocipadd>>& for details.
16019 . Allow this long option name to split; give it unsplit as a fifth argument
16020 . for the automatic .oindex that is generated by .option.
16022 .option "extract_addresses_remove_arguments" main boolean true &&&
16023 extract_addresses_remove_arguments
16025 .cindex "command line" "addresses with &%-t%&"
16026 .cindex "Sendmail compatibility" "&%-t%& option"
16027 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
16028 are present on the command line when the &%-t%& option is used to build an
16029 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
16030 line addresses are removed from the recipients list. This is also how Smail
16031 behaves. However, other Sendmail documentation (the O'Reilly book) states that
16032 command line addresses are added to those obtained from the header lines. When
16033 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
16034 argument headers. If it is set false, Exim adds rather than removes argument
16038 .option finduser_retries main integer 0
16039 .cindex "NIS, retrying user lookups"
16040 On systems running NIS or other schemes in which user and group information is
16041 distributed from a remote system, there can be times when &[getpwnam()]& and
16042 related functions fail, even when given valid data, because things time out.
16043 Unfortunately these failures cannot be distinguished from genuine &"not found"&
16044 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
16045 many extra times to find a user or a group, waiting for one second between
16048 .cindex "&_/etc/passwd_&" "multiple reading of"
16049 You should not set this option greater than zero if your user information is in
16050 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
16051 search the file multiple times for non-existent users, and also cause delay.
16055 .option freeze_tell main "string list, comma separated" unset
16056 .cindex "freezing messages" "sending a message when freezing"
16057 On encountering certain errors, or when configured to do so in a system filter,
16058 ACL, or special router, Exim freezes a message. This means that no further
16059 delivery attempts take place until an administrator thaws the message, or the
16060 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
16061 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
16062 warning message whenever it freezes something, unless the message it is
16063 freezing is a locally-generated bounce message. (Without this exception there
16064 is the possibility of looping.) The warning message is sent to the addresses
16065 supplied as the comma-separated value of this option. If several of the
16066 message's addresses cause freezing, only a single message is sent. If the
16067 freezing was automatic, the reason(s) for freezing can be found in the message
16068 log. If you configure freezing in a filter or ACL, you must arrange for any
16069 logging that you require.
16072 .option gecos_name main string&!! unset
16074 .cindex "&""gecos""& field, parsing"
16075 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
16076 password file to hold other information in addition to users' real names. Exim
16077 looks up this field for use when it is creating &'Sender:'& or &'From:'&
16078 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
16079 of the field are used unchanged, except that, if an ampersand is encountered,
16080 it is replaced by the user's login name with the first character forced to
16081 upper case, since this is a convention that is observed on many systems.
16083 When these options are set, &%gecos_pattern%& is treated as a regular
16084 expression that is to be applied to the field (again with && replaced by the
16085 login name), and if it matches, &%gecos_name%& is expanded and used as the
16088 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
16089 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
16090 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
16091 name terminates at the first comma, the following can be used:
16093 gecos_pattern = ([^,]*)
16097 .option gecos_pattern main string unset
16098 See &%gecos_name%& above.
16101 .option gnutls_compat_mode main boolean unset
16102 This option controls whether GnuTLS is used in compatibility mode in an Exim
16103 server. This reduces security slightly, but improves interworking with older
16104 implementations of TLS.
16107 .option gnutls_allow_auto_pkcs11 main boolean unset
16108 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
16109 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
16112 &url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
16117 .option headers_charset main string "see below"
16118 This option sets a default character set for translating from encoded MIME
16119 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
16120 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
16121 ultimate default is ISO-8859-1. For more details see the description of header
16122 insertions in section &<<SECTexpansionitems>>&.
16126 .option header_maxsize main integer "see below"
16127 .cindex "header section" "maximum size of"
16128 .cindex "limit" "size of message header section"
16129 This option controls the overall maximum size of a message's header
16130 section. The default is the value of HEADER_MAXSIZE in
16131 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
16132 sections are rejected.
16135 .option header_line_maxsize main integer 0
16136 .cindex "header lines" "maximum size of"
16137 .cindex "limit" "size of one header line"
16138 This option limits the length of any individual header line in a message, after
16139 all the continuations have been joined together. Messages with individual
16140 header lines that are longer than the limit are rejected. The default value of
16141 zero means &"no limit"&.
16146 .option helo_accept_junk_hosts main "host list&!!" unset
16147 .cindex "HELO" "accepting junk data"
16148 .cindex "EHLO" "accepting junk data"
16149 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
16150 mail, and gives an error response for invalid data. Unfortunately, there are
16151 some SMTP clients that send syntactic junk. They can be accommodated by setting
16152 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
16153 if you want to do semantic checking.
16154 See also &%helo_allow_chars%& for a way of extending the permitted character
16158 .option helo_allow_chars main string unset
16159 .cindex "HELO" "underscores in"
16160 .cindex "EHLO" "underscores in"
16161 .cindex "underscore in EHLO/HELO"
16162 This option can be set to a string of rogue characters that are permitted in
16163 all EHLO and HELO names in addition to the standard letters, digits,
16164 hyphens, and dots. If you really must allow underscores, you can set
16166 helo_allow_chars = _
16168 Note that the value is one string, not a list.
16171 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
16172 .cindex "HELO" "forcing reverse lookup"
16173 .cindex "EHLO" "forcing reverse lookup"
16174 If the domain given by a client in a HELO or EHLO command matches this
16175 list, a reverse lookup is done in order to establish the host's true name. The
16176 default forces a lookup if the client host gives the server's name or any of
16177 its IP addresses (in brackets), something that broken clients have been seen to
16181 .option helo_try_verify_hosts main "host list&!!" unset
16182 .cindex "HELO verifying" "optional"
16183 .cindex "EHLO" "verifying, optional"
16184 By default, Exim just checks the syntax of HELO and EHLO commands (see
16185 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
16186 to do more extensive checking of the data supplied by these commands. The ACL
16187 condition &`verify = helo`& is provided to make this possible.
16188 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
16189 to force the check to occur. From release 4.53 onwards, this is no longer
16190 necessary. If the check has not been done before &`verify = helo`& is
16191 encountered, it is done at that time. Consequently, this option is obsolete.
16192 Its specification is retained here for backwards compatibility.
16194 When an EHLO or HELO command is received, if the calling host matches
16195 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
16196 EHLO command either:
16199 is an IP literal matching the calling address of the host, or
16201 .cindex "DNS" "reverse lookup"
16202 .cindex "reverse DNS lookup"
16203 matches the host name that Exim obtains by doing a reverse lookup of the
16204 calling host address, or
16206 when looked up in DNS yields the calling host address.
16209 However, the EHLO or HELO command is not rejected if any of the checks
16210 fail. Processing continues, but the result of the check is remembered, and can
16211 be detected later in an ACL by the &`verify = helo`& condition.
16213 If DNS was used for successful verification, the variable
16214 .cindex "DNS" "DNSSEC"
16215 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
16217 .option helo_verify_hosts main "host list&!!" unset
16218 .cindex "HELO verifying" "mandatory"
16219 .cindex "EHLO" "verifying, mandatory"
16220 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
16221 backwards compatibility. For hosts that match this option, Exim checks the host
16222 name given in the HELO or EHLO in the same way as for
16223 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
16224 rejected with a 550 error, and entries are written to the main and reject logs.
16225 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
16228 .option hold_domains main "domain list&!!" unset
16229 .cindex "domain" "delaying delivery"
16230 .cindex "delivery" "delaying certain domains"
16231 This option allows mail for particular domains to be held in the queue
16232 manually. The option is overridden if a message delivery is forced with the
16233 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
16234 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
16235 item in &%hold_domains%&, no routing or delivery for that address is done, and
16236 it is deferred every time the message is looked at.
16238 This option is intended as a temporary operational measure for delaying the
16239 delivery of mail while some problem is being sorted out, or some new
16240 configuration tested. If you just want to delay the processing of some
16241 domains until a queue run occurs, you should use &%queue_domains%& or
16242 &%queue_smtp_domains%&, not &%hold_domains%&.
16244 A setting of &%hold_domains%& does not override Exim's code for removing
16245 messages from the queue if they have been there longer than the longest retry
16246 time in any retry rule. If you want to hold messages for longer than the normal
16247 retry times, insert a dummy retry rule with a long retry time.
16250 .option host_lookup main "host list&!!" unset
16251 .cindex "host name" "lookup, forcing"
16252 Exim does not look up the name of a calling host from its IP address unless it
16253 is required to compare against some host list, or the host matches
16254 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
16255 option (which normally contains IP addresses rather than host names). The
16256 default configuration file contains
16260 which causes a lookup to happen for all hosts. If the expense of these lookups
16261 is felt to be too great, the setting can be changed or removed.
16263 After a successful reverse lookup, Exim does a forward lookup on the name it
16264 has obtained, to verify that it yields the IP address that it started with. If
16265 this check fails, Exim behaves as if the name lookup failed.
16267 .vindex "&$host_lookup_failed$&"
16268 .vindex "&$sender_host_name$&"
16269 After any kind of failure, the host name (in &$sender_host_name$&) remains
16270 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
16271 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
16272 &`verify = reverse_host_lookup`& in ACLs.
16275 .option host_lookup_order main "string list" &`bydns:byaddr`&
16276 This option specifies the order of different lookup methods when Exim is trying
16277 to find a host name from an IP address. The default is to do a DNS lookup
16278 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
16279 if that fails. You can change the order of these lookups, or omit one entirely,
16282 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
16283 multiple PTR records in the DNS and the IP address is not listed in
16284 &_/etc/hosts_&. Different operating systems give different results in this
16285 case. That is why the default tries a DNS lookup first.
16289 .option host_reject_connection main "host list&!!" unset
16290 .cindex "host" "rejecting connections from"
16291 If this option is set, incoming SMTP calls from the hosts listed are rejected
16292 as soon as the connection is made.
16293 This option is obsolete, and retained only for backward compatibility, because
16294 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
16295 connections immediately.
16297 The ability to give an immediate rejection (either by this option or using an
16298 ACL) is provided for use in unusual cases. Many hosts will just try again,
16299 sometimes without much delay. Normally, it is better to use an ACL to reject
16300 incoming messages at a later stage, such as after RCPT commands. See
16301 chapter &<<CHAPACL>>&.
16304 .option hosts_connection_nolog main "host list&!!" unset
16305 .cindex "host" "not logging connections from"
16306 This option defines a list of hosts for which connection logging does not
16307 happen, even though the &%smtp_connection%& log selector is set. For example,
16308 you might want not to log SMTP connections from local processes, or from
16309 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
16310 the daemon; you should therefore strive to restrict its value to a short inline
16311 list of IP addresses and networks. To disable logging SMTP connections from
16312 local processes, you must create a host list with an empty item. For example:
16314 hosts_connection_nolog = :
16316 If the &%smtp_connection%& log selector is not set, this option has no effect.
16319 .option hosts_require_alpn main "host list&!!" unset
16320 .cindex ALPN "require negotiation in server"
16322 .cindex TLS "Application Layer Protocol Names"
16323 If the TLS library supports ALPN
16324 then a successful negotiation of ALPN will be required for any client
16325 matching the list, for TLS to be used.
16326 See also the &%tls_alpn%& option.
16328 &*Note*&: prevention of fallback to in-clear connection is not
16329 managed by this option, and should be done separately.
16332 .option hosts_proxy main "host list&!!" unset
16333 .cindex proxy "proxy protocol"
16334 This option enables use of Proxy Protocol proxies for incoming
16335 connections. For details see section &<<SECTproxyInbound>>&.
16338 .option hosts_treat_as_local main "domain list&!!" unset
16339 .cindex "local host" "domains treated as"
16340 .cindex "host" "treated as local"
16341 If this option is set, any host names that match the domain list are treated as
16342 if they were the local host when Exim is scanning host lists obtained from MX
16344 or other sources. Note that the value of this option is a domain list, not a
16345 host list, because it is always used to check host names, not IP addresses.
16347 This option also applies when Exim is matching the special items
16348 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
16349 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
16350 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
16351 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
16352 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
16353 interfaces and recognizing the local host.
16356 .option ibase_servers main "string list" unset
16357 .cindex "InterBase" "server list"
16358 This option provides a list of InterBase servers and associated connection data,
16359 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
16360 The option is available only if Exim has been built with InterBase support.
16364 .option ignore_bounce_errors_after main time 10w
16365 .cindex "bounce message" "discarding"
16366 .cindex "discarding bounce message"
16367 This option affects the processing of bounce messages that cannot be delivered,
16368 that is, those that suffer a permanent delivery failure. (Bounce messages that
16369 suffer temporary delivery failures are of course retried in the usual way.)
16371 After a permanent delivery failure, bounce messages are frozen,
16372 because there is no sender to whom they can be returned. When a frozen bounce
16373 message has been in the queue for more than the given time, it is unfrozen at
16374 the next queue run, and a further delivery is attempted. If delivery fails
16375 again, the bounce message is discarded. This makes it possible to keep failed
16376 bounce messages around for a shorter time than the normal maximum retry time
16377 for frozen messages. For example,
16379 ignore_bounce_errors_after = 12h
16381 retries failed bounce message deliveries after 12 hours, discarding any further
16382 failures. If the value of this option is set to a zero time period, bounce
16383 failures are discarded immediately. Setting a very long time (as in the default
16384 value) has the effect of disabling this option. For ways of automatically
16385 dealing with other kinds of frozen message, see &%auto_thaw%& and
16386 &%timeout_frozen_after%&.
16389 .option ignore_fromline_hosts main "host list&!!" unset
16390 .cindex "&""From""& line"
16391 .cindex "UUCP" "&""From""& line"
16392 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
16393 the headers of a message. By default this is treated as the start of the
16394 message's body, which means that any following headers are not recognized as
16395 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
16396 match those hosts that insist on sending it. If the sender is actually a local
16397 process rather than a remote host, and is using &%-bs%& to inject the messages,
16398 &%ignore_fromline_local%& must be set to achieve this effect.
16401 .option ignore_fromline_local main boolean false
16402 See &%ignore_fromline_hosts%& above.
16404 .option keep_environment main "string list" unset
16405 .cindex "environment" "values from"
16406 This option contains a string list of environment variables to keep.
16407 You have to trust these variables or you have to be sure that
16408 these variables do not impose any security risk. Keep in mind that
16409 during the startup phase Exim is running with an effective UID 0 in most
16410 installations. As the default value is an empty list, the default
16411 environment for using libraries, running embedded Perl code, or running
16412 external binaries is empty, and does not not even contain PATH or HOME.
16414 Actually the list is interpreted as a list of patterns
16415 (&<<SECTlistexpand>>&), except that it is not expanded first.
16417 WARNING: Macro substitution is still done first, so having a macro
16418 FOO and having FOO_HOME in your &%keep_environment%& option may have
16419 unexpected results. You may work around this using a regular expression
16420 that does not match the macro name: ^[F]OO_HOME$.
16422 Current versions of Exim issue a warning during startup if you do not mention
16423 &%keep_environment%& in your runtime configuration file and if your
16424 current environment is not empty. Future versions may not issue that warning
16427 See the &%add_environment%& main config option for a way to set
16428 environment variables to a fixed value. The environment for &(pipe)&
16429 transports is handled separately, see section &<<SECTpipeenv>>& for
16433 .option keep_malformed main time 4d
16434 This option specifies the length of time to keep messages whose spool files
16435 have been corrupted in some way. This should, of course, never happen. At the
16436 next attempt to deliver such a message, it gets removed. The incident is
16440 .option ldap_ca_cert_dir main string unset
16441 .cindex "LDAP", "TLS CA certificate directory"
16442 .cindex certificate "directory for LDAP"
16443 This option indicates which directory contains CA certificates for verifying
16444 a TLS certificate presented by an LDAP server.
16445 While Exim does not provide a default value, your SSL library may.
16446 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16447 and constrained to be a directory.
16450 .option ldap_ca_cert_file main string unset
16451 .cindex "LDAP", "TLS CA certificate file"
16452 .cindex certificate "file for LDAP"
16453 This option indicates which file contains CA certificates for verifying
16454 a TLS certificate presented by an LDAP server.
16455 While Exim does not provide a default value, your SSL library may.
16456 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16457 and constrained to be a file.
16460 .option ldap_cert_file main string unset
16461 .cindex "LDAP" "TLS client certificate file"
16462 .cindex certificate "file for LDAP"
16463 This option indicates which file contains an TLS client certificate which
16464 Exim should present to the LDAP server during TLS negotiation.
16465 Should be used together with &%ldap_cert_key%&.
16468 .option ldap_cert_key main string unset
16469 .cindex "LDAP" "TLS client key file"
16470 .cindex certificate "key for LDAP"
16471 This option indicates which file contains the secret/private key to use
16472 to prove identity to the LDAP server during TLS negotiation.
16473 Should be used together with &%ldap_cert_file%&, which contains the
16474 identity to be proven.
16477 .option ldap_cipher_suite main string unset
16478 .cindex "LDAP" "TLS cipher suite"
16479 This controls the TLS cipher-suite negotiation during TLS negotiation with
16480 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
16481 cipher-suite options with OpenSSL (as used by LDAP client libraries).
16484 .option ldap_default_servers main "string list" unset
16485 .cindex "LDAP" "default servers"
16486 This option provides a list of LDAP servers which are tried in turn when an
16487 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
16488 details of LDAP queries. This option is available only when Exim has been built
16492 .option ldap_require_cert main string unset.
16493 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
16494 This should be one of the values "hard", "demand", "allow", "try" or "never".
16495 A value other than one of these is interpreted as "never".
16496 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
16497 Although Exim does not set a default, the LDAP library probably defaults
16501 .option ldap_start_tls main boolean false
16502 .cindex "LDAP" "whether or not to negotiate TLS"
16503 If set, Exim will attempt to negotiate TLS with the LDAP server when
16504 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
16505 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
16507 In the event of failure to negotiate TLS, the action taken is controlled
16508 by &%ldap_require_cert%&.
16509 This option is ignored for &`ldapi`& connections.
16512 .option ldap_version main integer unset
16513 .cindex "LDAP" "protocol version, forcing"
16514 This option can be used to force Exim to set a specific protocol version for
16515 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
16516 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
16517 the LDAP headers; otherwise it is 2. This option is available only when Exim
16518 has been built with LDAP support.
16522 .option local_from_check main boolean true
16523 .cindex "&'Sender:'& header line" "disabling addition of"
16524 .cindex "&'From:'& header line" "disabling checking of"
16525 When a message is submitted locally (that is, not over a TCP/IP connection) by
16526 an untrusted user, Exim removes any existing &'Sender:'& header line, and
16527 checks that the &'From:'& header line matches the login of the calling user and
16528 the domain specified by &%qualify_domain%&.
16530 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
16531 locally submitted message is automatically qualified by Exim, unless the
16532 &%-bnq%& command line option is used.
16534 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
16535 on the local part. If the &'From:'& header line does not match, Exim adds a
16536 &'Sender:'& header with an address constructed from the calling user's login
16537 and the default qualify domain.
16539 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
16540 and no &'Sender:'& header is ever added. If, in addition, you want to retain
16541 &'Sender:'& header lines supplied by untrusted users, you must also set
16542 &%local_sender_retain%& to be true.
16544 .cindex "envelope from"
16545 .cindex "envelope sender"
16546 These options affect only the header lines in the message. The envelope sender
16547 is still forced to be the login id at the qualify domain unless
16548 &%untrusted_set_sender%& permits the user to supply an envelope sender.
16550 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
16551 request similar header line checking. See section &<<SECTthesenhea>>&, which
16552 has more details about &'Sender:'& processing.
16557 .option local_from_prefix main string unset
16558 When Exim checks the &'From:'& header line of locally submitted messages for
16559 matching the login id (see &%local_from_check%& above), it can be configured to
16560 ignore certain prefixes and suffixes in the local part of the address. This is
16561 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
16562 appropriate lists, in the same form as the &%local_part_prefix%& and
16563 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
16566 local_from_prefix = *-
16568 is set, a &'From:'& line containing
16570 From: anything-user@your.domain.example
16572 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
16573 matches the actual sender address that is constructed from the login name and
16577 .option local_from_suffix main string unset
16578 See &%local_from_prefix%& above.
16581 .option local_interfaces main "string list" "see below"
16582 This option controls which network interfaces are used by the daemon for
16583 listening; they are also used to identify the local host when routing. Chapter
16584 &<<CHAPinterfaces>>& contains a full description of this option and the related
16585 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
16586 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
16587 &%local_interfaces%& is
16589 local_interfaces = 0.0.0.0
16591 when Exim is built without IPv6 support; otherwise it is
16593 local_interfaces = <; ::0 ; 0.0.0.0
16596 .option local_scan_timeout main time 5m
16597 .cindex "timeout" "for &[local_scan()]& function"
16598 .cindex "&[local_scan()]& function" "timeout"
16599 This timeout applies to the &[local_scan()]& function (see chapter
16600 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
16601 the incoming message is rejected with a temporary error if it is an SMTP
16602 message. For a non-SMTP message, the message is dropped and Exim ends with a
16603 non-zero code. The incident is logged on the main and reject logs.
16607 .option local_sender_retain main boolean false
16608 .cindex "&'Sender:'& header line" "retaining from local submission"
16609 When a message is submitted locally (that is, not over a TCP/IP connection) by
16610 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
16611 do not want this to happen, you must set &%local_sender_retain%&, and you must
16612 also set &%local_from_check%& to be false (Exim will complain if you do not).
16613 See also the ACL modifier &`control = suppress_local_fixups`&. Section
16614 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
16619 .option localhost_number main string&!! unset
16620 .cindex "host" "locally unique number for"
16621 .cindex "message ids" "with multiple hosts"
16622 .vindex "&$localhost_number$&"
16623 Exim's message ids are normally unique only within the local host. If
16624 uniqueness among a set of hosts is required, each host must set a different
16625 value for the &%localhost_number%& option. The string is expanded immediately
16626 after reading the configuration file (so that a number can be computed from the
16627 host name, for example) and the result of the expansion must be a number in the
16628 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
16629 systems). This is available in subsequent string expansions via the variable
16630 &$localhost_number$&. When &%localhost_number is set%&, the final two
16631 characters of the message id, instead of just being a fractional part of the
16632 time, are computed from the time and the local host number as described in
16633 section &<<SECTmessiden>>&.
16637 .option log_file_path main "string list&!!" "set at compile time"
16638 .cindex "log" "file path for"
16639 This option sets the path which is used to determine the names of Exim's log
16640 files, or indicates that logging is to be to syslog, or both. It is expanded
16641 when Exim is entered, so it can, for example, contain a reference to the host
16642 name. If no specific path is set for the log files at compile or runtime,
16643 or if the option is unset at runtime (i.e. &`log_file_path = `&)
16644 they are written in a sub-directory called &_log_& in Exim's spool directory.
16645 A path must start with a slash.
16646 To send to syslog, use the word &"syslog"&.
16647 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
16648 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
16649 used. If this string is fixed at your installation (contains no expansion
16650 variables) it is recommended that you do not set this option in the
16651 configuration file, but instead supply the path using LOG_FILE_PATH in
16652 &_Local/Makefile_& so that it is available to Exim for logging errors detected
16653 early on &-- in particular, failure to read the configuration file.
16656 .option log_selector main string unset
16657 .cindex "log" "selectors"
16658 This option can be used to reduce or increase the number of things that Exim
16659 writes to its log files. Its argument is made up of names preceded by plus or
16660 minus characters. For example:
16662 log_selector = +arguments -retry_defer
16664 A list of possible names and what they control is given in the chapter on
16665 logging, in section &<<SECTlogselector>>&.
16668 .option log_timezone main boolean false
16669 .cindex "log" "timezone for entries"
16670 .vindex "&$tod_log$&"
16671 .vindex "&$tod_zone$&"
16672 By default, the timestamps on log lines are in local time without the
16673 timezone. This means that if your timezone changes twice a year, the timestamps
16674 in log lines are ambiguous for an hour when the clocks go back. One way of
16675 avoiding this problem is to set the timezone to UTC. An alternative is to set
16676 &%log_timezone%& true. This turns on the addition of the timezone offset to
16677 timestamps in log lines. Turning on this option can add quite a lot to the size
16678 of log files because each line is extended by 6 characters. Note that the
16679 &$tod_log$& variable contains the log timestamp without the zone, but there is
16680 another variable called &$tod_zone$& that contains just the timezone offset.
16683 .option lookup_open_max main integer 25
16684 .cindex "too many open files"
16685 .cindex "open files, too many"
16686 .cindex "file" "too many open"
16687 .cindex "lookup" "maximum open files"
16688 .cindex "limit" "open files for lookups"
16689 This option limits the number of simultaneously open files for single-key
16690 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
16691 Exim normally keeps these files open during routing, because often the same
16692 file is required several times. If the limit is reached, Exim closes the least
16693 recently used file. Note that if you are using the &'ndbm'& library, it
16694 actually opens two files for each logical DBM database, though it still counts
16695 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
16696 open files"& errors with NDBM, you need to reduce the value of
16697 &%lookup_open_max%&.
16700 .option max_username_length main integer 0
16701 .cindex "length of login name"
16702 .cindex "user name" "maximum length"
16703 .cindex "limit" "user name length"
16704 Some operating systems are broken in that they truncate long arguments to
16705 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
16706 this option is set greater than zero, any attempt to call &[getpwnam()]& with
16707 an argument that is longer behaves as if &[getpwnam()]& failed.
16710 .option message_body_newlines main bool false
16711 .cindex "message body" "newlines in variables"
16712 .cindex "newline" "in message body variables"
16713 .vindex "&$message_body$&"
16714 .vindex "&$message_body_end$&"
16715 By default, newlines in the message body are replaced by spaces when setting
16716 the &$message_body$& and &$message_body_end$& expansion variables. If this
16717 option is set true, this no longer happens.
16720 .option message_body_visible main integer 500
16721 .cindex "body of message" "visible size"
16722 .cindex "message body" "visible size"
16723 .vindex "&$message_body$&"
16724 .vindex "&$message_body_end$&"
16725 This option specifies how much of a message's body is to be included in the
16726 &$message_body$& and &$message_body_end$& expansion variables.
16729 .option message_id_header_domain main string&!! unset
16730 .cindex "&'Message-ID:'& header line"
16731 If this option is set, the string is expanded and used as the right hand side
16732 (domain) of the &'Message-ID:'& header that Exim creates if a
16733 locally-originated incoming message does not have one. &"Locally-originated"&
16734 means &"not received over TCP/IP."&
16735 Otherwise, the primary host name is used.
16736 Only letters, digits, dot and hyphen are accepted; any other characters are
16737 replaced by hyphens. If the expansion is forced to fail, or if the result is an
16738 empty string, the option is ignored.
16741 .option message_id_header_text main string&!! unset
16742 If this variable is set, the string is expanded and used to augment the text of
16743 the &'Message-id:'& header that Exim creates if a locally-originated incoming
16744 message does not have one. The text of this header is required by RFC 2822 to
16745 take the form of an address. By default, Exim uses its internal message id as
16746 the local part, and the primary host name as the domain. If this option is set,
16747 it is expanded, and provided the expansion is not forced to fail, and does not
16748 yield an empty string, the result is inserted into the header immediately
16749 before the @, separated from the internal message id by a dot. Any characters
16750 that are illegal in an address are automatically converted into hyphens. This
16751 means that variables such as &$tod_log$& can be used, because the spaces and
16752 colons will become hyphens.
16755 .option message_logs main boolean true
16756 .cindex "message logs" "disabling"
16757 .cindex "log" "message log; disabling"
16758 If this option is turned off, per-message log files are not created in the
16759 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
16760 Exim, by reducing the number of files involved in handling a message from a
16761 minimum of four (header spool file, body spool file, delivery journal, and
16762 per-message log) to three. The other major I/O activity is Exim's main log,
16763 which is not affected by this option.
16766 .option message_size_limit main string&!! 50M
16767 .cindex "message" "size limit"
16768 .cindex "limit" "message size"
16769 .cindex "size" "of message, limit"
16770 This option limits the maximum size of message that Exim will process. The
16771 value is expanded for each incoming connection so, for example, it can be made
16772 to depend on the IP address of the remote host for messages arriving via
16773 TCP/IP. After expansion, the value must be a sequence of decimal digits,
16774 optionally followed by K or M.
16776 .cindex "SIZE" "ESMTP extension, advertising"
16777 .cindex "ESMTP extensions" SIZE
16778 If nonzero the value will be advertised as a parameter to the ESMTP SIZE
16779 service extension keyword.
16781 &*Note*&: This limit cannot be made to depend on a message's sender or any
16782 other properties of an individual message, because it has to be advertised in
16783 the server's response to EHLO. String expansion failure causes a temporary
16784 error. A value of zero means no limit, but its use is not recommended. See also
16785 &%bounce_return_size_limit%&.
16787 Incoming SMTP messages are failed with a 552 error if the limit is
16788 exceeded; locally-generated messages either get a stderr message or a delivery
16789 failure message to the sender, depending on the &%-oe%& setting. Rejection of
16790 an oversized message is logged in both the main and the reject logs. See also
16791 the generic transport option &%message_size_limit%&, which limits the size of
16792 message that an individual transport can process.
16794 If you use a virus-scanner and set this option to to a value larger than the
16795 maximum size that your virus-scanner is configured to support, you may get
16796 failures triggered by large mails. The right size to configure for the
16797 virus-scanner depends upon what data is passed and the options in use but it's
16798 probably safest to just set it to a little larger than this value. E.g., with a
16799 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
16800 some problems may result.
16802 A value of 0 will disable size limit checking; Exim will still advertise the
16803 SIZE extension in an EHLO response, but without a limit, so as to permit
16804 SMTP clients to still indicate the message size along with the MAIL verb.
16807 .option move_frozen_messages main boolean false
16808 .cindex "frozen messages" "moving"
16809 This option, which is available only if Exim has been built with the setting
16811 SUPPORT_MOVE_FROZEN_MESSAGES=yes
16813 in &_Local/Makefile_&, causes frozen messages and their message logs to be
16814 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
16815 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
16816 standard utilities for handling such moved messages, and they do not show up in
16817 lists generated by &%-bp%& or by the Exim monitor.
16820 .option mua_wrapper main boolean false
16821 Setting this option true causes Exim to run in a very restrictive mode in which
16822 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
16823 contains a full description of this facility.
16827 .option mysql_servers main "string list" unset
16828 .cindex "MySQL" "server list"
16829 This option provides a list of MySQL servers and associated connection data, to
16830 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
16831 option is available only if Exim has been built with MySQL support.
16834 .option never_users main "string list&!!" unset
16835 This option is expanded just once, at the start of Exim's processing. Local
16836 message deliveries are normally run in processes that are setuid to the
16837 recipient, and remote deliveries are normally run under Exim's own uid and gid.
16838 It is usually desirable to prevent any deliveries from running as root, as a
16841 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
16842 list of users that must not be used for local deliveries. This list is fixed in
16843 the binary and cannot be overridden by the configuration file. By default, it
16844 contains just the single user name &"root"&. The &%never_users%& runtime option
16845 can be used to add more users to the fixed list.
16847 If a message is to be delivered as one of the users on the fixed list or the
16848 &%never_users%& list, an error occurs, and delivery is deferred. A common
16851 never_users = root:daemon:bin
16853 Including root is redundant if it is also on the fixed list, but it does no
16854 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
16858 .option notifier_socket main string "$spool_directory/exim_daemon_notify"
16859 This option gives the name for a unix-domain socket on which the daemon
16860 listens for work and information-requests.
16861 Only installations running multiple daemons sharing a spool directory
16862 should need to modify the default.
16864 The option is expanded before use.
16865 If the platform supports Linux-style abstract socket names, the result
16866 is used with a nul byte prefixed.
16868 it should be a full path name and use a directory accessible
16871 If this option is set as empty,
16872 or the command line &%-oY%& option is used, or
16873 the command line uses a &%-oX%& option and does not use &%-oP%&,
16874 then a notifier socket is not created.
16877 .option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation"
16878 .cindex "OpenSSL "compatibility options"
16879 This option allows an administrator to adjust the SSL options applied
16880 by OpenSSL to connections. It is given as a space-separated list of items,
16881 each one to be +added or -subtracted from the current value.
16883 This option is only available if Exim is built against OpenSSL. The values
16884 available for this option vary according to the age of your OpenSSL install.
16885 The &"all"& value controls a subset of flags which are available, typically
16886 the bug workaround options. The &'SSL_CTX_set_options'& man page will
16887 list the values known on your system and Exim should support all the
16888 &"bug workaround"& options and many of the &"modifying"& options. The Exim
16889 names lose the leading &"SSL_OP_"& and are lower-cased.
16891 Note that adjusting the options can have severe impact upon the security of
16892 SSL as used by Exim. It is possible to disable safety checks and shoot
16893 yourself in the foot in various unpleasant ways. This option should not be
16894 adjusted lightly. An unrecognised item will be detected at startup, by
16895 invoking Exim with the &%-bV%& flag.
16897 The option affects Exim operating both as a server and as a client.
16899 Historical note: prior to release 4.80, Exim defaulted this value to
16900 "+dont_insert_empty_fragments", which may still be needed for compatibility
16901 with some clients, but which lowers security by increasing exposure to
16902 some now infamous attacks.
16906 # Make both old MS and old Eudora happy:
16907 openssl_options = -all +microsoft_big_sslv3_buffer \
16908 +dont_insert_empty_fragments
16910 # Disable older protocol versions:
16911 openssl_options = +no_sslv2 +no_sslv3
16914 Possible options may include:
16918 &`allow_unsafe_legacy_renegotiation`&
16920 &`cipher_server_preference`&
16922 &`dont_insert_empty_fragments`&
16926 &`legacy_server_connect`&
16928 &`microsoft_big_sslv3_buffer`&
16930 &`microsoft_sess_id_bug`&
16932 &`msie_sslv2_rsa_padding`&
16934 &`netscape_challenge_bug`&
16936 &`netscape_reuse_cipher_change_bug`&
16940 &`no_session_resumption_on_renegotiation`&
16954 &`safari_ecdhe_ecdsa_bug`&
16958 &`single_ecdh_use`&
16960 &`ssleay_080_client_dh_bug`&
16962 &`sslref2_reuse_cert_type_bug`&
16964 &`tls_block_padding_bug`&
16968 &`tls_rollback_bug`&
16971 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
16972 all clients connecting using the MacOS SecureTransport TLS facility prior
16973 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
16974 to negotiate TLS then this option value might help, provided that your OpenSSL
16975 release is new enough to contain this work-around. This may be a situation
16976 where you have to upgrade OpenSSL to get buggy clients working.
16979 .option oracle_servers main "string list" unset
16980 .cindex "Oracle" "server list"
16981 This option provides a list of Oracle servers and associated connection data,
16982 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
16983 The option is available only if Exim has been built with Oracle support.
16986 .option percent_hack_domains main "domain list&!!" unset
16987 .cindex "&""percent hack""&"
16988 .cindex "source routing" "in email address"
16989 .cindex "address" "source-routed"
16990 The &"percent hack"& is the convention whereby a local part containing a
16991 percent sign is re-interpreted as a new email address, with the percent
16992 replaced by @. This is sometimes called &"source routing"&, though that term is
16993 also applied to RFC 2822 addresses that begin with an @ character. If this
16994 option is set, Exim implements the percent facility for those domains listed,
16995 but no others. This happens before an incoming SMTP address is tested against
16998 &*Warning*&: The &"percent hack"& has often been abused by people who are
16999 trying to get round relaying restrictions. For this reason, it is best avoided
17000 if at all possible. Unfortunately, a number of less security-conscious MTAs
17001 implement it unconditionally. If you are running Exim on a gateway host, and
17002 routing mail through to internal MTAs without processing the local parts, it is
17003 a good idea to reject recipient addresses with percent characters in their
17004 local parts. Exim's default configuration does this.
17007 .option perl_at_start main boolean false
17009 This option is available only when Exim is built with an embedded Perl
17010 interpreter. See chapter &<<CHAPperl>>& for details of its use.
17013 .option perl_startup main string unset
17015 This option is available only when Exim is built with an embedded Perl
17016 interpreter. See chapter &<<CHAPperl>>& for details of its use.
17018 .option perl_taintmode main boolean false
17020 This option enables the taint mode of the embedded Perl interpreter.
17023 .option pgsql_servers main "string list" unset
17024 .cindex "PostgreSQL lookup type" "server list"
17025 This option provides a list of PostgreSQL servers and associated connection
17026 data, to be used in conjunction with &(pgsql)& lookups (see section
17027 &<<SECID72>>&). The option is available only if Exim has been built with
17028 PostgreSQL support.
17031 .option pid_file_path main string&!! "set at compile time"
17032 .cindex "daemon" "pid file path"
17033 .cindex "pid file, path for"
17034 This option sets the name of the file to which the Exim daemon writes its
17035 process id. The string is expanded, so it can contain, for example, references
17038 pid_file_path = /var/log/$primary_hostname/exim.pid
17040 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
17042 The value set by the option can be overridden by the &%-oP%& command line
17043 option. A pid file is not written if a &"non-standard"& daemon is run by means
17044 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
17047 .option pipelining_advertise_hosts main "host list&!!" *
17048 .cindex "PIPELINING" "suppressing advertising"
17049 .cindex "ESMTP extensions" PIPELINING
17050 This option can be used to suppress the advertisement of the SMTP
17051 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
17052 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
17053 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
17054 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
17055 that clients will use it; &"out of order"& commands that are &"expected"& do
17056 not count as protocol errors (see &%smtp_max_synprot_errors%&).
17058 .option pipelining_connect_advertise_hosts main "host list&!!" *
17059 .cindex "pipelining" "early connection"
17060 .cindex "pipelining" PIPE_CONNECT
17061 .cindex "ESMTP extensions" PIPE_CONNECT
17062 If Exim is built with the SUPPORT_PIPE_CONNECT build option
17063 this option controls which hosts the facility is advertised to
17064 and from which pipeline early-connection (before MAIL) SMTP
17065 commands are acceptable.
17066 When used, the pipelining saves on roundtrip times.
17068 See also the &%hosts_pipe_connect%& smtp transport option.
17070 The SMTP service extension keyword advertised is &"PIPE_CONNECT"&.
17073 .option prdr_enable main boolean false
17074 .cindex "PRDR" "enabling on server"
17075 .cindex "ESMTP extensions" PRDR
17076 This option can be used to enable the Per-Recipient Data Response extension
17077 to SMTP, defined by Eric Hall.
17078 If the option is set, PRDR is advertised by Exim when operating as a server.
17079 If the client requests PRDR, and more than one recipient, for a message
17080 an additional ACL is called for each recipient after the message content
17081 is received. See section &<<SECTPRDRACL>>&.
17083 .option preserve_message_logs main boolean false
17084 .cindex "message logs" "preserving"
17085 If this option is set, message log files are not deleted when messages are
17086 completed. Instead, they are moved to a sub-directory of the spool directory
17087 called &_msglog.OLD_&, where they remain available for statistical or debugging
17088 purposes. This is a dangerous option to set on systems with any appreciable
17089 volume of mail. Use with care!
17092 .option primary_hostname main string "see below"
17093 .cindex "name" "of local host"
17094 .cindex "host" "name of local"
17095 .cindex "local host" "name of"
17096 .vindex "&$primary_hostname$&"
17097 This specifies the name of the current host. It is used in the default EHLO or
17098 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
17099 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
17100 The value is also used by default in some SMTP response messages from an Exim
17101 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
17103 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
17104 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
17105 contains only one component, Exim passes it to &[gethostbyname()]& (or
17106 &[getipnodebyname()]& when available) in order to obtain the fully qualified
17107 version. The variable &$primary_hostname$& contains the host name, whether set
17108 explicitly by this option, or defaulted.
17111 .option print_topbitchars main boolean false
17112 .cindex "printing characters"
17113 .cindex "8-bit characters"
17114 By default, Exim considers only those characters whose codes lie in the range
17115 32&--126 to be printing characters. In a number of circumstances (for example,
17116 when writing log entries) non-printing characters are converted into escape
17117 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
17118 is set, code values of 128 and above are also considered to be printing
17121 This option also affects the header syntax checks performed by the
17122 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
17123 the user's full name when constructing From: and Sender: addresses (as
17124 described in section &<<SECTconstr>>&). Setting this option can cause
17125 Exim to generate eight bit message headers that do not conform to the
17129 .option process_log_path main string unset
17130 .cindex "process log path"
17131 .cindex "log" "process log"
17132 .cindex "&'exiwhat'&"
17133 This option sets the name of the file to which an Exim process writes its
17134 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
17135 utility script. If this option is unset, the file called &_exim-process.info_&
17136 in Exim's spool directory is used. The ability to specify the name explicitly
17137 can be useful in environments where two different Exims are running, using
17138 different spool directories.
17141 .option prod_requires_admin main boolean true
17142 .cindex "restricting access to features"
17146 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
17147 admin user unless &%prod_requires_admin%& is set false. See also
17148 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
17151 .option proxy_protocol_timeout main time 3s
17152 .cindex proxy "proxy protocol"
17153 This option sets the timeout for proxy protocol negotiation.
17154 For details see section &<<SECTproxyInbound>>&.
17157 .option qualify_domain main string "see below"
17158 .cindex "domain" "for qualifying addresses"
17159 .cindex "address" "qualification"
17160 This option specifies the domain name that is added to any envelope sender
17161 addresses that do not have a domain qualification. It also applies to
17162 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
17163 are accepted by default only for locally-generated messages. Qualification is
17164 also applied to addresses in header lines such as &'From:'& and &'To:'& for
17165 locally-generated messages, unless the &%-bnq%& command line option is used.
17167 Messages from external sources must always contain fully qualified addresses,
17168 unless the sending host matches &%sender_unqualified_hosts%& or
17169 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
17170 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
17171 necessary. Internally, Exim always works with fully qualified envelope
17172 addresses. If &%qualify_domain%& is not set, it defaults to the
17173 &%primary_hostname%& value.
17176 .option qualify_recipient main string "see below"
17177 This option allows you to specify a different domain for qualifying recipient
17178 addresses to the one that is used for senders. See &%qualify_domain%& above.
17182 .option queue_domains main "domain list&!!" unset
17183 .cindex "domain" "specifying non-immediate delivery"
17184 .cindex "queueing incoming messages"
17185 .cindex "message" "queueing certain domains"
17186 This option lists domains for which immediate delivery is not required.
17187 A delivery process is started whenever a message is received, but only those
17188 domains that do not match are processed. All other deliveries wait until the
17189 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
17192 .option queue_fast_ramp main boolean false
17193 .cindex "queue runner" "two phase"
17194 .cindex "queue" "double scanning"
17195 If set to true, two-phase queue runs, initiated using &%-qq%& on the
17196 command line, may start parallel delivery processes during their first
17197 phase. This will be done when a threshold number of messages have been
17198 routed for a single host.
17201 .option queue_list_requires_admin main boolean true
17202 .cindex "restricting access to features"
17204 The &%-bp%& command-line option, which lists the messages that are on the
17205 queue, requires the caller to be an admin user unless
17206 &%queue_list_requires_admin%& is set false.
17207 See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
17210 .option queue_only main boolean false
17211 .cindex "queueing incoming messages"
17212 .cindex "message" "queueing unconditionally"
17213 If &%queue_only%& is set, a delivery process is not automatically started
17214 whenever a message is received. Instead, the message waits in the queue for the
17215 next queue run. Even if &%queue_only%& is false, incoming messages may not get
17216 delivered immediately when certain conditions (such as heavy load) occur.
17218 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
17219 and &%-odi%& command line options override &%queue_only%& unless
17220 &%queue_only_override%& is set false. See also &%queue_only_file%&,
17221 &%queue_only_load%&, and &%smtp_accept_queue%&.
17224 .option queue_only_file main string unset
17225 .cindex "queueing incoming messages"
17226 .cindex "message" "queueing by file existence"
17227 This option can be set to a colon-separated list of absolute path names, each
17228 one optionally preceded by &"smtp"&. When Exim is receiving a message,
17229 it tests for the existence of each listed path using a call to &[stat()]&. For
17230 each path that exists, the corresponding queueing option is set.
17231 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
17232 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
17234 queue_only_file = smtp/some/file
17236 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
17237 &_/some/file_& exists.
17240 .option queue_only_load main fixed-point unset
17241 .cindex "load average"
17242 .cindex "queueing incoming messages"
17243 .cindex "message" "queueing by load"
17244 If the system load average is higher than this value, incoming messages from
17245 all sources are queued, and no automatic deliveries are started. If this
17246 happens during local or remote SMTP input, all subsequent messages received on
17247 the same SMTP connection are queued by default, whatever happens to the load in
17248 the meantime, but this can be changed by setting &%queue_only_load_latch%&
17251 Deliveries will subsequently be performed by queue runner processes. This
17252 option has no effect on ancient operating systems on which Exim cannot
17253 determine the load average. See also &%deliver_queue_load_max%& and
17254 &%smtp_load_reserve%&.
17257 .option queue_only_load_latch main boolean true
17258 .cindex "load average" "re-evaluating per message"
17259 When this option is true (the default), once one message has been queued
17260 because the load average is higher than the value set by &%queue_only_load%&,
17261 all subsequent messages received on the same SMTP connection are also queued.
17262 This is a deliberate choice; even though the load average may fall below the
17263 threshold, it doesn't seem right to deliver later messages on the same
17264 connection when not delivering earlier ones. However, there are special
17265 circumstances such as very long-lived connections from scanning appliances
17266 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
17267 should be set false. This causes the value of the load average to be
17268 re-evaluated for each message.
17271 .option queue_only_override main boolean true
17272 .cindex "queueing incoming messages"
17273 When this option is true, the &%-od%&&'x'& command line options override the
17274 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
17275 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
17276 to override; they are accepted, but ignored.
17279 .option queue_run_in_order main boolean false
17280 .cindex "queue runner" "processing messages in order"
17281 If this option is set, queue runs happen in order of message arrival instead of
17282 in an arbitrary order. For this to happen, a complete list of the entire queue
17283 must be set up before the deliveries start. When the queue is all held in a
17284 single directory (the default), a single list is created for both the ordered
17285 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
17286 single list is not created when &%queue_run_in_order%& is false. In this case,
17287 the sub-directories are processed one at a time (in a random order), and this
17288 avoids setting up one huge list for the whole queue. Thus, setting
17289 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
17290 when the queue is large, because of the extra work in setting up the single,
17291 large list. In most situations, &%queue_run_in_order%& should not be set.
17295 .option queue_run_max main integer&!! 5
17296 .cindex "queue runner" "maximum number of"
17297 This controls the maximum number of queue runner processes that an Exim daemon
17298 can run simultaneously. This does not mean that it starts them all at once,
17299 but rather that if the maximum number are still running when the time comes to
17300 start another one, it refrains from starting another one. This can happen with
17301 very large queues and/or very sluggish deliveries. This option does not,
17302 however, interlock with other processes, so additional queue runners can be
17303 started by other means, or by killing and restarting the daemon.
17305 Setting this option to zero does not suppress queue runs; rather, it disables
17306 the limit, allowing any number of simultaneous queue runner processes to be
17307 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
17308 the daemon's command line.
17310 .cindex queues named
17311 .cindex "named queues" "resource limit"
17312 To set limits for different named queues use
17313 an expansion depending on the &$queue_name$& variable.
17315 .option queue_smtp_domains main "domain list&!!" unset
17316 .cindex "queueing incoming messages"
17317 .cindex "message" "queueing remote deliveries"
17318 .cindex "first pass routing"
17319 When this option is set, a delivery process is started whenever a message is
17320 received, routing is performed, and local deliveries take place.
17321 However, if any SMTP deliveries are required for domains that match
17322 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
17323 message waits in the queue for the next queue run. Since routing of the message
17324 has taken place, Exim knows to which remote hosts it must be delivered, and so
17325 when the queue run happens, multiple messages for the same host are delivered
17326 over a single SMTP connection. The &%-odqs%& command line option causes all
17327 SMTP deliveries to be queued in this way, and is equivalent to setting
17328 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
17332 .option receive_timeout main time 0s
17333 .cindex "timeout" "for non-SMTP input"
17334 This option sets the timeout for accepting a non-SMTP message, that is, the
17335 maximum time that Exim waits when reading a message on the standard input. If
17336 the value is zero, it will wait forever. This setting is overridden by the
17337 &%-or%& command line option. The timeout for incoming SMTP messages is
17338 controlled by &%smtp_receive_timeout%&.
17340 .option received_header_text main string&!! "see below"
17341 .cindex "customizing" "&'Received:'& header"
17342 .cindex "&'Received:'& header line" "customizing"
17343 This string defines the contents of the &'Received:'& message header that is
17344 added to each message, except for the timestamp, which is automatically added
17345 on at the end (preceded by a semicolon). The string is expanded each time it is
17346 used. If the expansion yields an empty string, no &'Received:'& header line is
17347 added to the message. Otherwise, the string should start with the text
17348 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
17350 The default setting is:
17353 received_header_text = Received: \
17354 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
17355 {${if def:sender_ident \
17356 {from ${quote_local_part:$sender_ident} }}\
17357 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
17358 by $primary_hostname \
17359 ${if def:received_protocol {with $received_protocol }}\
17360 ${if def:tls_in_ver { ($tls_in_ver)}}\
17361 ${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\
17362 (Exim $version_number)\n\t\
17363 ${if def:sender_address \
17364 {(envelope-from <$sender_address>)\n\t}}\
17365 id $message_exim_id\
17366 ${if def:received_for {\n\tfor $received_for}}
17369 The references to the TLS version and cipher are
17370 omitted when Exim is built without TLS
17371 support. The use of conditional expansions ensures that this works for both
17372 locally generated messages and messages received from remote hosts, giving
17373 header lines such as the following:
17375 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
17376 by marley.carol.example with esmtp (Exim 4.00)
17377 (envelope-from <bob@carol.example>)
17378 id 16IOWa-00019l-00
17379 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
17380 Received: by scrooge.carol.example with local (Exim 4.00)
17381 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
17383 Until the body of the message has been received, the timestamp is the time when
17384 the message started to be received. Once the body has arrived, and all policy
17385 checks have taken place, the timestamp is updated to the time at which the
17386 message was accepted.
17389 .option received_headers_max main integer 30
17390 .cindex "loop" "prevention"
17391 .cindex "mail loop prevention"
17392 .cindex "&'Received:'& header line" "counting"
17393 When a message is to be delivered, the number of &'Received:'& headers is
17394 counted, and if it is greater than this parameter, a mail loop is assumed to
17395 have occurred, the delivery is abandoned, and an error message is generated.
17396 This applies to both local and remote deliveries.
17399 .option recipient_unqualified_hosts main "host list&!!" unset
17400 .cindex "unqualified addresses"
17401 .cindex "host" "unqualified addresses from"
17402 This option lists those hosts from which Exim is prepared to accept unqualified
17403 recipient addresses in message envelopes. The addresses are made fully
17404 qualified by the addition of the &%qualify_recipient%& value. This option also
17405 affects message header lines. Exim does not reject unqualified recipient
17406 addresses in headers, but it qualifies them only if the message came from a
17407 host that matches &%recipient_unqualified_hosts%&,
17408 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
17409 option was not set.
17412 .option recipients_max main integer 50000
17413 .cindex "limit" "number of recipients"
17414 .cindex "recipient" "maximum number"
17415 If this option is set greater than zero, it specifies the maximum number of
17416 original recipients for any message. Additional recipients that are generated
17417 by aliasing or forwarding do not count. SMTP messages get a 452 response for
17418 all recipients over the limit; earlier recipients are delivered as normal.
17419 Non-SMTP messages with too many recipients are failed, and no deliveries are
17422 .cindex "RCPT" "maximum number of incoming"
17423 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
17424 RCPT commands in a single message.
17427 .option recipients_max_reject main boolean false
17428 If this option is set true, Exim rejects SMTP messages containing too many
17429 recipients by giving 552 errors to the surplus RCPT commands, and a 554
17430 error to the eventual DATA command. Otherwise (the default) it gives a 452
17431 error to the surplus RCPT commands and accepts the message on behalf of the
17432 initial set of recipients. The remote server should then re-send the message
17433 for the remaining recipients at a later time.
17436 .option remote_max_parallel main integer 2
17437 .cindex "delivery" "parallelism for remote"
17438 This option controls parallel delivery of one message to a number of remote
17439 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
17440 does all the remote deliveries for a message one by one. Otherwise, if a single
17441 message has to be delivered to more than one remote host, or if several copies
17442 have to be sent to the same remote host, up to &%remote_max_parallel%&
17443 deliveries are done simultaneously. If more than &%remote_max_parallel%&
17444 deliveries are required, the maximum number of processes are started, and as
17445 each one finishes, another is begun. The order of starting processes is the
17446 same as if sequential delivery were being done, and can be controlled by the
17447 &%remote_sort_domains%& option. If parallel delivery takes place while running
17448 with debugging turned on, the debugging output from each delivery process is
17449 tagged with its process id.
17451 This option controls only the maximum number of parallel deliveries for one
17452 message in one Exim delivery process. Because Exim has no central queue
17453 manager, there is no way of controlling the total number of simultaneous
17454 deliveries if the configuration allows a delivery attempt as soon as a message
17457 See also the &%max_parallel%& generic transport option,
17458 and the &%serialize_hosts%& smtp transport option.
17460 .cindex "number of deliveries"
17461 .cindex "delivery" "maximum number of"
17462 If you want to control the total number of deliveries on the system, you
17463 need to set the &%queue_only%& option. This ensures that all incoming messages
17464 are added to the queue without starting a delivery process. Then set up an Exim
17465 daemon to start queue runner processes at appropriate intervals (probably
17466 fairly often, for example, every minute), and limit the total number of queue
17467 runners by setting the &%queue_run_max%& parameter. Because each queue runner
17468 delivers only one message at a time, the maximum number of deliveries that can
17469 then take place at once is &%queue_run_max%& multiplied by
17470 &%remote_max_parallel%&.
17472 If it is purely remote deliveries you want to control, use
17473 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
17474 doing the SMTP routing before queueing, so that several messages for the same
17475 host will eventually get delivered down the same connection.
17478 .option remote_sort_domains main "domain list&!!" unset
17479 .cindex "sorting remote deliveries"
17480 .cindex "delivery" "sorting remote"
17481 When there are a number of remote deliveries for a message, they are sorted by
17482 domain into the order given by this list. For example,
17484 remote_sort_domains = *.cam.ac.uk:*.uk
17486 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
17487 then to those in the &%uk%& domain, then to any others.
17490 .option retry_data_expire main time 7d
17491 .cindex "hints database" "data expiry"
17492 This option sets a &"use before"& time on retry information in Exim's hints
17493 database. Any older retry data is ignored. This means that, for example, once a
17494 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
17498 .option retry_interval_max main time 24h
17499 .cindex "retry" "limit on interval"
17500 .cindex "limit" "on retry interval"
17501 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
17502 intervals between delivery attempts for messages that cannot be delivered
17503 straight away. This option sets an overall limit to the length of time between
17504 retries. It cannot be set greater than 24 hours; any attempt to do so forces
17508 .option return_path_remove main boolean true
17509 .cindex "&'Return-path:'& header line" "removing"
17510 RFC 2821, section 4.4, states that an SMTP server must insert a
17511 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
17512 The &'Return-path:'& header preserves the sender address as received in the
17513 MAIL command. This description implies that this header should not be present
17514 in an incoming message. If &%return_path_remove%& is true, any existing
17515 &'Return-path:'& headers are removed from messages at the time they are
17516 received. Exim's transports have options for adding &'Return-path:'& headers at
17517 the time of delivery. They are normally used only for final local deliveries.
17520 .option return_size_limit main integer 100K
17521 This option is an obsolete synonym for &%bounce_return_size_limit%&.
17524 .option rfc1413_hosts main "host list&!!" @[]
17526 .cindex "host" "for RFC 1413 calls"
17527 RFC 1413 identification calls are made to any client host which matches
17528 an item in the list.
17529 The default value specifies just this host, being any local interface
17532 .option rfc1413_query_timeout main time 0s
17533 .cindex "RFC 1413" "query timeout"
17534 .cindex "timeout" "for RFC 1413 call"
17535 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
17536 no RFC 1413 calls are ever made.
17539 .option sender_unqualified_hosts main "host list&!!" unset
17540 .cindex "unqualified addresses"
17541 .cindex "host" "unqualified addresses from"
17542 This option lists those hosts from which Exim is prepared to accept unqualified
17543 sender addresses. The addresses are made fully qualified by the addition of
17544 &%qualify_domain%&. This option also affects message header lines. Exim does
17545 not reject unqualified addresses in headers that contain sender addresses, but
17546 it qualifies them only if the message came from a host that matches
17547 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
17548 using TCP/IP), and the &%-bnq%& option was not set.
17551 .option slow_lookup_log main integer 0
17552 .cindex "logging" "slow lookups"
17553 .cindex "dns" "logging slow lookups"
17554 This option controls logging of slow lookups.
17555 If the value is nonzero it is taken as a number of milliseconds
17556 and lookups taking longer than this are logged.
17557 Currently this applies only to DNS lookups.
17561 .option smtp_accept_keepalive main boolean true
17562 .cindex "keepalive" "on incoming connection"
17563 This option controls the setting of the SO_KEEPALIVE option on incoming
17564 TCP/IP socket connections. When set, it causes the kernel to probe idle
17565 connections periodically, by sending packets with &"old"& sequence numbers. The
17566 other end of the connection should send an acknowledgment if the connection is
17567 still okay or a reset if the connection has been aborted. The reason for doing
17568 this is that it has the beneficial effect of freeing up certain types of
17569 connection that can get stuck when the remote host is disconnected without
17570 tidying up the TCP/IP call properly. The keepalive mechanism takes several
17571 hours to detect unreachable hosts.
17575 .option smtp_accept_max main integer 20
17576 .cindex "limit" "incoming SMTP connections"
17577 .cindex "SMTP" "incoming connection count"
17579 This option specifies the maximum number of simultaneous incoming SMTP calls
17580 that Exim will accept. It applies only to the listening daemon; there is no
17581 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
17582 value is set to zero, no limit is applied. However, it is required to be
17583 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
17584 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
17586 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
17587 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
17588 that limit has not been reached for the client host, &%smtp_accept_reserve%&
17589 and &%smtp_load_reserve%& are then checked before accepting the connection.
17592 .option smtp_accept_max_nonmail main integer 10
17593 .cindex "limit" "non-mail SMTP commands"
17594 .cindex "SMTP" "limiting non-mail commands"
17595 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
17596 the connection if there are too many. This option defines &"too many"&. The
17597 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
17598 client looping sending EHLO, for example. The check is applied only if the
17599 client host matches &%smtp_accept_max_nonmail_hosts%&.
17601 When a new message is expected, one occurrence of RSET is not counted. This
17602 allows a client to send one RSET between messages (this is not necessary,
17603 but some clients do it). Exim also allows one uncounted occurrence of HELO
17604 or EHLO, and one occurrence of STARTTLS between messages. After
17605 starting up a TLS session, another EHLO is expected, and so it too is not
17606 counted. The first occurrence of AUTH in a connection, or immediately
17607 following STARTTLS is not counted. Otherwise, all commands other than
17608 MAIL, RCPT, DATA, and QUIT are counted.
17611 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
17612 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
17613 check by setting this option. The default value makes it apply to all hosts. By
17614 changing the value, you can exclude any badly-behaved hosts that you have to
17618 . Allow this long option name to split; give it unsplit as a fifth argument
17619 . for the automatic .oindex that is generated by .option.
17620 . We insert " &~&~" which is both pretty nasty visually and results in
17621 . non-searchable text. HowItWorks.txt mentions an option for inserting
17622 . zero-width-space, which would be nicer visually and results in (at least)
17623 . html that Firefox will split on when it's forced to reflow (rather than
17624 . inserting a horizontal scrollbar). However, the text is still not
17625 . searchable. NM changed this occurrence for bug 1197 to no longer allow
17626 . the option name to split.
17628 .option "smtp_accept_max_per_connection" main integer&!! 1000 &&&
17629 smtp_accept_max_per_connection
17630 .cindex "SMTP" "limiting incoming message count"
17631 .cindex "limit" "messages per SMTP connection"
17632 The value of this option limits the number of MAIL commands that Exim is
17633 prepared to accept over a single SMTP connection, whether or not each command
17634 results in the transfer of a message. After the limit is reached, a 421
17635 response is given to subsequent MAIL commands. This limit is a safety
17636 precaution against a client that goes mad (incidents of this type have been
17638 The option is expanded after the HELO or EHLO is received
17639 and may depend on values available at that time.
17640 An empty or zero value after expansion removes the limit.
17643 .option smtp_accept_max_per_host main string&!! unset
17644 .cindex "limit" "SMTP connections from one host"
17645 .cindex "host" "limiting SMTP connections from"
17646 This option restricts the number of simultaneous IP connections from a single
17647 host (strictly, from a single IP address) to the Exim daemon. The option is
17648 expanded, to enable different limits to be applied to different hosts by
17649 reference to &$sender_host_address$&. Once the limit is reached, additional
17650 connection attempts from the same host are rejected with error code 421. This
17651 is entirely independent of &%smtp_accept_reserve%&. The option's default value
17652 of zero imposes no limit. If this option is set greater than zero, it is
17653 required that &%smtp_accept_max%& be non-zero.
17655 &*Warning*&: When setting this option you should not use any expansion
17656 constructions that take an appreciable amount of time. The expansion and test
17657 happen in the main daemon loop, in order to reject additional connections
17658 without forking additional processes (otherwise a denial-of-service attack
17659 could cause a vast number or processes to be created). While the daemon is
17660 doing this processing, it cannot accept any other incoming connections.
17664 .option smtp_accept_queue main integer 0
17665 .cindex "SMTP" "incoming connection count"
17666 .cindex "queueing incoming messages"
17667 .cindex "message" "queueing by SMTP connection count"
17668 If the number of simultaneous incoming SMTP connections being handled via the
17669 listening daemon exceeds this value, messages received by SMTP are just placed
17670 in the queue; no delivery processes are started automatically. The count is
17671 fixed at the start of an SMTP connection. It cannot be updated in the
17672 subprocess that receives messages, and so the queueing or not queueing applies
17673 to all messages received in the same connection.
17675 A value of zero implies no limit, and clearly any non-zero value is useful only
17676 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
17677 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
17678 various &%-od%&&'x'& command line options.
17681 . See the comment on smtp_accept_max_per_connection
17683 .option "smtp_accept_queue_per_connection" main integer 10 &&&
17684 smtp_accept_queue_per_connection
17685 .cindex "queueing incoming messages"
17686 .cindex "message" "queueing by message count"
17687 This option limits the number of delivery processes that Exim starts
17688 automatically when receiving messages via SMTP, whether via the daemon or by
17689 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
17690 and the number of messages received in a single SMTP session exceeds this
17691 number, subsequent messages are placed in the queue, but no delivery processes
17692 are started. This helps to limit the number of Exim processes when a server
17693 restarts after downtime and there is a lot of mail waiting for it on other
17694 systems. On large systems, the default should probably be increased, and on
17695 dial-in client systems it should probably be set to zero (that is, disabled).
17698 .option smtp_accept_reserve main integer 0
17699 .cindex "SMTP" "incoming call count"
17700 .cindex "host" "reserved"
17701 When &%smtp_accept_max%& is set greater than zero, this option specifies a
17702 number of SMTP connections that are reserved for connections from the hosts
17703 that are specified in &%smtp_reserve_hosts%&. The value set in
17704 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
17705 restricted to this number of connections; the option specifies a minimum number
17706 of connection slots for them, not a maximum. It is a guarantee that this group
17707 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
17708 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
17711 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
17712 set to 5, once there are 45 active connections (from any hosts), new
17713 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
17714 provided the other criteria for acceptance are met.
17717 .option smtp_active_hostname main string&!! unset
17718 .cindex "host" "name in SMTP responses"
17719 .cindex "SMTP" "host name in responses"
17720 .vindex "&$primary_hostname$&"
17721 This option is provided for multi-homed servers that want to masquerade as
17722 several different hosts. At the start of an incoming SMTP connection, its value
17723 is expanded and used instead of the value of &$primary_hostname$& in SMTP
17724 responses. For example, it is used as domain name in the response to an
17725 incoming HELO or EHLO command.
17727 .vindex "&$smtp_active_hostname$&"
17728 The active hostname is placed in the &$smtp_active_hostname$& variable, which
17729 is saved with any messages that are received. It is therefore available for use
17730 in routers and transports when the message is later delivered.
17732 If this option is unset, or if its expansion is forced to fail, or if the
17733 expansion results in an empty string, the value of &$primary_hostname$& is
17734 used. Other expansion failures cause a message to be written to the main and
17735 panic logs, and the SMTP command receives a temporary error. Typically, the
17736 value of &%smtp_active_hostname%& depends on the incoming interface address.
17739 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
17740 {cox.mydomain}{box.mydomain}}
17743 Although &$smtp_active_hostname$& is primarily concerned with incoming
17744 messages, it is also used as the default for HELO commands in callout
17745 verification if there is no remote transport from which to obtain a
17746 &%helo_data%& value.
17748 .option smtp_backlog_monitor main integer 0
17749 .cindex "connection backlog" monitoring
17750 If this option is set to greater than zero, and the backlog of available
17751 TCP connections on a socket listening for SMTP is larger than it, a line
17752 is logged giving the value and the socket address and port.
17753 The value is retrived jsut before an accept call.
17754 This facility is only available on Linux.
17756 .option smtp_banner main string&!! "see below"
17757 .cindex "SMTP" "welcome banner"
17758 .cindex "banner for SMTP"
17759 .cindex "welcome banner for SMTP"
17760 .cindex "customizing" "SMTP banner"
17761 This string, which is expanded every time it is used, is output as the initial
17762 positive response to an SMTP connection. The default setting is:
17764 smtp_banner = $smtp_active_hostname ESMTP Exim \
17765 $version_number $tod_full
17767 Failure to expand the string causes a panic error. If you want to create a
17768 multiline response to the initial SMTP connection, use &"\n"& in the string at
17769 appropriate points, but not at the end. Note that the 220 code is not included
17770 in this string. Exim adds it automatically (several times in the case of a
17771 multiline response).
17774 .option smtp_check_spool_space main boolean true
17775 .cindex "checking disk space"
17776 .cindex "disk space, checking"
17777 .cindex "spool directory" "checking space"
17778 When this option is set, if an incoming SMTP session encounters the SIZE
17779 option on a MAIL command, it checks that there is enough space in the
17780 spool directory's partition to accept a message of that size, while still
17781 leaving free the amount specified by &%check_spool_space%& (even if that value
17782 is zero). If there isn't enough space, a temporary error code is returned.
17785 .option smtp_connect_backlog main integer 20
17786 .cindex "connection backlog" "set maximum"
17787 .cindex "SMTP" "connection backlog"
17788 .cindex "backlog of connections"
17789 This option specifies a maximum number of waiting SMTP connections. Exim passes
17790 this value to the TCP/IP system when it sets up its listener. Once this number
17791 of connections are waiting for the daemon's attention, subsequent connection
17792 attempts are refused at the TCP/IP level. At least, that is what the manuals
17793 say; in some circumstances such connection attempts have been observed to time
17794 out instead. For large systems it is probably a good idea to increase the
17795 value (to 50, say). It also gives some protection against denial-of-service
17796 attacks by SYN flooding.
17799 .option smtp_enforce_sync main boolean true
17800 .cindex "SMTP" "synchronization checking"
17801 .cindex "synchronization checking in SMTP"
17802 The SMTP protocol specification requires the client to wait for a response from
17803 the server at certain points in the dialogue. Without PIPELINING these
17804 synchronization points are after every command; with PIPELINING they are
17805 fewer, but they still exist.
17807 Some spamming sites send out a complete set of SMTP commands without waiting
17808 for any response. Exim protects against this by rejecting a message if the
17809 client has sent further input when it should not have. The error response &"554
17810 SMTP synchronization error"& is sent, and the connection is dropped. Testing
17811 for this error cannot be perfect because of transmission delays (unexpected
17812 input may be on its way but not yet received when Exim checks). However, it
17813 does detect many instances.
17815 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
17816 If you want to disable the check selectively (for example, only for certain
17817 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
17818 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
17822 .option smtp_etrn_command main string&!! unset
17823 .cindex "ETRN" "command to be run"
17824 .cindex "ESMTP extensions" ETRN
17825 .vindex "&$domain$&"
17826 If this option is set, the given command is run whenever an SMTP ETRN
17827 command is received from a host that is permitted to issue such commands (see
17828 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
17829 are independently expanded. The expansion variable &$domain$& is set to the
17830 argument of the ETRN command, and no syntax checking is done on it. For
17833 smtp_etrn_command = /etc/etrn_command $domain \
17834 $sender_host_address
17836 If the option is not set, the argument for the ETRN command must
17837 be a &'#'& followed by an address string.
17838 In this case an &'exim -R <string>'& command is used;
17839 if the ETRN ACL has set up a named-queue then &'-MCG <queue>'& is appended.
17841 A new process is created to run the command, but Exim does not wait for it to
17842 complete. Consequently, its status cannot be checked. If the command cannot be
17843 run, a line is written to the panic log, but the ETRN caller still receives
17844 a 250 success response. Exim is normally running under its own uid when
17845 receiving SMTP, so it is not possible for it to change the uid before running
17849 .option smtp_etrn_serialize main boolean true
17850 .cindex "ETRN" "serializing"
17851 When this option is set, it prevents the simultaneous execution of more than
17852 one identical command as a result of ETRN in an SMTP connection. See
17853 section &<<SECTETRN>>& for details.
17856 .option smtp_load_reserve main fixed-point unset
17857 .cindex "load average"
17858 If the system load average ever gets higher than this, incoming SMTP calls are
17859 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
17860 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
17861 the load is over the limit. The option has no effect on ancient operating
17862 systems on which Exim cannot determine the load average. See also
17863 &%deliver_queue_load_max%& and &%queue_only_load%&.
17867 .option smtp_max_synprot_errors main integer 3
17868 .cindex "SMTP" "limiting syntax and protocol errors"
17869 .cindex "limit" "SMTP syntax and protocol errors"
17870 Exim rejects SMTP commands that contain syntax or protocol errors. In
17871 particular, a syntactically invalid email address, as in this command:
17873 RCPT TO:<abc xyz@a.b.c>
17875 causes immediate rejection of the command, before any other tests are done.
17876 (The ACL cannot be run if there is no valid address to set up for it.) An
17877 example of a protocol error is receiving RCPT before MAIL. If there are
17878 too many syntax or protocol errors in one SMTP session, the connection is
17879 dropped. The limit is set by this option.
17881 .cindex "PIPELINING" "expected errors"
17882 When the PIPELINING extension to SMTP is in use, some protocol errors are
17883 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
17884 Exim assumes that PIPELINING will be used if it advertises it (see
17885 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
17886 not count towards the limit.
17890 .option smtp_max_unknown_commands main integer 3
17891 .cindex "SMTP" "limiting unknown commands"
17892 .cindex "limit" "unknown SMTP commands"
17893 If there are too many unrecognized commands in an incoming SMTP session, an
17894 Exim server drops the connection. This is a defence against some kinds of abuse
17897 into making connections to SMTP ports; in these circumstances, a number of
17898 non-SMTP command lines are sent first.
17902 .option smtp_ratelimit_hosts main "host list&!!" unset
17903 .cindex "SMTP" "rate limiting"
17904 .cindex "limit" "rate of message arrival"
17905 .cindex "RCPT" "rate limiting"
17906 Some sites find it helpful to be able to limit the rate at which certain hosts
17907 can send them messages, and the rate at which an individual message can specify
17910 Exim has two rate-limiting facilities. This section describes the older
17911 facility, which can limit rates within a single connection. The newer
17912 &%ratelimit%& ACL condition can limit rates across all connections. See section
17913 &<<SECTratelimiting>>& for details of the newer facility.
17915 When a host matches &%smtp_ratelimit_hosts%&, the values of
17916 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
17917 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
17918 respectively. Each option, if set, must contain a set of four comma-separated
17922 A threshold, before which there is no rate limiting.
17924 An initial time delay. Unlike other times in Exim, numbers with decimal
17925 fractional parts are allowed here.
17927 A factor by which to increase the delay each time.
17929 A maximum value for the delay. This should normally be less than 5 minutes,
17930 because after that time, the client is liable to timeout the SMTP command.
17933 For example, these settings have been used successfully at the site which
17934 first suggested this feature, for controlling mail from their customers:
17936 smtp_ratelimit_mail = 2,0.5s,1.05,4m
17937 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
17939 The first setting specifies delays that are applied to MAIL commands after
17940 two have been received over a single connection. The initial delay is 0.5
17941 seconds, increasing by a factor of 1.05 each time. The second setting applies
17942 delays to RCPT commands when more than four occur in a single message.
17945 .option smtp_ratelimit_mail main string unset
17946 See &%smtp_ratelimit_hosts%& above.
17949 .option smtp_ratelimit_rcpt main string unset
17950 See &%smtp_ratelimit_hosts%& above.
17953 .option smtp_receive_timeout main time&!! 5m
17954 .cindex "timeout" "for SMTP input"
17955 .cindex "SMTP" "input timeout"
17956 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
17957 input, including batch SMTP. If a line of input (either an SMTP command or a
17958 data line) is not received within this time, the SMTP connection is dropped and
17959 the message is abandoned.
17960 A line is written to the log containing one of the following messages:
17962 SMTP command timeout on connection from...
17963 SMTP data timeout on connection from...
17965 The former means that Exim was expecting to read an SMTP command; the latter
17966 means that it was in the DATA phase, reading the contents of a message.
17968 If the first character of the option is a &"$"& the option is
17969 expanded before use and may depend on
17970 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
17974 The value set by this option can be overridden by the
17975 &%-os%& command-line option. A setting of zero time disables the timeout, but
17976 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
17977 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
17978 timeout is controlled by &%receive_timeout%& and &%-or%&.
17981 .option smtp_reserve_hosts main "host list&!!" unset
17982 This option defines hosts for which SMTP connections are reserved; see
17983 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
17986 .option smtp_return_error_details main boolean false
17987 .cindex "SMTP" "details policy failures"
17988 .cindex "policy control" "rejection, returning details"
17989 In the default state, Exim uses bland messages such as
17990 &"Administrative prohibition"& when it rejects SMTP commands for policy
17991 reasons. Many sysadmins like this because it gives away little information
17992 to spammers. However, some other sysadmins who are applying strict checking
17993 policies want to give out much fuller information about failures. Setting
17994 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
17995 example, instead of &"Administrative prohibition"&, it might give:
17997 550-Rejected after DATA: '>' missing at end of address:
17998 550 failing address in "From" header is: <user@dom.ain
18002 .option smtputf8_advertise_hosts main "host list&!!" *
18003 .cindex "SMTPUTF8" "ESMTP extension, advertising"
18004 .cindex "ESMTP extensions" SMTPUTF8
18005 When Exim is built with support for internationalised mail names,
18006 the availability thereof is advertised in
18007 response to EHLO only to those client hosts that match this option. See
18008 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
18011 .option spamd_address main string "127.0.0.1 783"
18012 This option is available when Exim is compiled with the content-scanning
18013 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
18014 See section &<<SECTscanspamass>>& for more details.
18018 .option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
18019 This option is available when Exim is compiled with SPF support.
18020 See section &<<SECSPF>>& for more details.
18022 .option spf_smtp_comment_template main string&!! "Please%_see%_http://www.open-spf.org/Why"
18023 This option is available when Exim is compiled with SPF support. It
18024 allows the customisation of the SMTP comment that the SPF library
18025 generates. You are strongly encouraged to link to your own explanative
18026 site. The template must not contain spaces. If you need spaces in the
18027 output, use the proper placeholder. If libspf2 can not parse the
18028 template, it uses a built-in default broken link. The following placeholders
18029 (along with Exim variables (but see below)) are allowed in the template:
18033 &*%{L}*&: Envelope sender's local part.
18035 &*%{S}*&: Envelope sender.
18037 &*%{O}*&: Envelope sender's domain.
18039 &*%{D}*&: Current(?) domain.
18041 &*%{I}*&: SMTP client Ip.
18043 &*%{C}*&: SMTP client pretty IP.
18045 &*%{T}*&: Epoch time (UTC).
18047 &*%{P}*&: SMTP client domain name.
18049 &*%{V}*&: IP version.
18051 &*%{H}*&: EHLO/HELO domain.
18053 &*%{R}*&: Receiving domain.
18055 The capitalized placeholders do proper URL encoding, if you use them
18056 lowercased, no encoding takes place. This list was compiled from the
18059 A note on using Exim variables: As
18060 currently the SPF library is initialized before the SMTP EHLO phase,
18061 the variables useful for expansion are quite limited.
18064 .option split_spool_directory main boolean false
18065 .cindex "multiple spool directories"
18066 .cindex "spool directory" "split"
18067 .cindex "directories, multiple"
18068 If this option is set, it causes Exim to split its input directory into 62
18069 subdirectories, each with a single alphanumeric character as its name. The
18070 sixth character of the message id is used to allocate messages to
18071 subdirectories; this is the least significant base-62 digit of the time of
18072 arrival of the message.
18074 Splitting up the spool in this way may provide better performance on systems
18075 where there are long mail queues, by reducing the number of files in any one
18076 directory. The msglog directory is also split up in a similar way to the input
18077 directory; however, if &%preserve_message_logs%& is set, all old msglog files
18078 are still placed in the single directory &_msglog.OLD_&.
18080 It is not necessary to take any special action for existing messages when
18081 changing &%split_spool_directory%&. Exim notices messages that are in the
18082 &"wrong"& place, and continues to process them. If the option is turned off
18083 after a period of being on, the subdirectories will eventually empty and be
18084 automatically deleted.
18086 When &%split_spool_directory%& is set, the behaviour of queue runner processes
18087 changes. Instead of creating a list of all messages in the queue, and then
18088 trying to deliver each one, in turn, it constructs a list of those in one
18089 sub-directory and tries to deliver them, before moving on to the next
18090 sub-directory. The sub-directories are processed in a random order. This
18091 spreads out the scanning of the input directories, and uses less memory. It is
18092 particularly beneficial when there are lots of messages in the queue. However,
18093 if &%queue_run_in_order%& is set, none of this new processing happens. The
18094 entire queue has to be scanned and sorted before any deliveries can start.
18097 .option spool_directory main string&!! "set at compile time"
18098 .cindex "spool directory" "path to"
18099 This defines the directory in which Exim keeps its spool, that is, the messages
18100 it is waiting to deliver. The default value is taken from the compile-time
18101 configuration setting, if there is one. If not, this option must be set. The
18102 string is expanded, so it can contain, for example, a reference to
18103 &$primary_hostname$&.
18105 If the spool directory name is fixed on your installation, it is recommended
18106 that you set it at build time rather than from this option, particularly if the
18107 log files are being written to the spool directory (see &%log_file_path%&).
18108 Otherwise log files cannot be used for errors that are detected early on, such
18109 as failures in the configuration file.
18111 By using this option to override the compiled-in path, it is possible to run
18112 tests of Exim without using the standard spool.
18114 .option spool_wireformat main boolean false
18115 .cindex "spool directory" "file formats"
18116 If this option is set, Exim may for some messages use an alternative format
18117 for data-files in the spool which matches the wire format.
18118 Doing this permits more efficient message reception and transmission.
18119 Currently it is only done for messages received using the ESMTP CHUNKING
18122 The following variables will not have useful values:
18124 $max_received_linelength
18129 Users of the local_scan() API (see &<<CHAPlocalscan>>&),
18130 and any external programs which are passed a reference to a message data file
18131 (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
18132 will need to be aware of the different formats potentially available.
18134 Using any of the ACL conditions noted will negate the reception benefit
18135 (as a Unix-mbox-format file is constructed for them).
18136 The transmission benefit is maintained.
18138 .option sqlite_lock_timeout main time 5s
18139 .cindex "sqlite lookup type" "lock timeout"
18140 This option controls the timeout that the &(sqlite)& lookup uses when trying to
18141 access an SQLite database. See section &<<SECTsqlite>>& for more details.
18143 .option strict_acl_vars main boolean false
18144 .cindex "&ACL;" "variables, handling unset"
18145 This option controls what happens if a syntactically valid but undefined ACL
18146 variable is referenced. If it is false (the default), an empty string
18147 is substituted; if it is true, an error is generated. See section
18148 &<<SECTaclvariables>>& for details of ACL variables.
18150 .option strip_excess_angle_brackets main boolean false
18151 .cindex "angle brackets, excess"
18152 If this option is set, redundant pairs of angle brackets round &"route-addr"&
18153 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
18154 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
18155 passed on to another MTA, the excess angle brackets are not passed on. If this
18156 option is not set, multiple pairs of angle brackets cause a syntax error.
18159 .option strip_trailing_dot main boolean false
18160 .cindex "trailing dot on domain"
18161 .cindex "dot" "trailing on domain"
18162 If this option is set, a trailing dot at the end of a domain in an address is
18163 ignored. If this is in the envelope and the message is passed on to another
18164 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
18165 domain causes a syntax error.
18166 However, addresses in header lines are checked only when an ACL requests header
18170 .option syslog_duplication main boolean true
18171 .cindex "syslog" "duplicate log lines; suppressing"
18172 When Exim is logging to syslog, it writes the log lines for its three
18173 separate logs at different syslog priorities so that they can in principle
18174 be separated on the logging hosts. Some installations do not require this
18175 separation, and in those cases, the duplication of certain log lines is a
18176 nuisance. If &%syslog_duplication%& is set false, only one copy of any
18177 particular log line is written to syslog. For lines that normally go to
18178 both the main log and the reject log, the reject log version (possibly
18179 containing message header lines) is written, at LOG_NOTICE priority.
18180 Lines that normally go to both the main and the panic log are written at
18181 the LOG_ALERT priority.
18184 .option syslog_facility main string unset
18185 .cindex "syslog" "facility; setting"
18186 This option sets the syslog &"facility"& name, used when Exim is logging to
18187 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
18188 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
18189 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
18190 details of Exim's logging.
18193 .option syslog_pid main boolean true
18194 .cindex "syslog" "pid"
18195 If &%syslog_pid%& is set false, the PID on Exim's log lines are
18196 omitted when these lines are sent to syslog. (Syslog normally prefixes
18197 the log lines with the PID of the logging process automatically.) You need
18198 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
18199 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
18203 .option syslog_processname main string &`exim`&
18204 .cindex "syslog" "process name; setting"
18205 This option sets the syslog &"ident"& name, used when Exim is logging to
18206 syslog. The value must be no longer than 32 characters. See chapter
18207 &<<CHAPlog>>& for details of Exim's logging.
18211 .option syslog_timestamp main boolean true
18212 .cindex "syslog" "timestamps"
18213 .cindex timestamps syslog
18214 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
18215 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
18216 details of Exim's logging.
18219 .option system_filter main string&!! unset
18220 .cindex "filter" "system filter"
18221 .cindex "system filter" "specifying"
18222 .cindex "Sieve filter" "not available for system filter"
18223 This option specifies an Exim filter file that is applied to all messages at
18224 the start of each delivery attempt, before any routing is done. System filters
18225 must be Exim filters; they cannot be Sieve filters. If the system filter
18226 generates any deliveries to files or pipes, or any new mail messages, the
18227 appropriate &%system_filter_..._transport%& option(s) must be set, to define
18228 which transports are to be used. Details of this facility are given in chapter
18229 &<<CHAPsystemfilter>>&.
18230 A forced expansion failure results in no filter operation.
18233 .option system_filter_directory_transport main string&!! unset
18234 .vindex "&$address_file$&"
18235 This sets the name of the transport driver that is to be used when the
18236 &%save%& command in a system message filter specifies a path ending in &"/"&,
18237 implying delivery of each message into a separate file in some directory.
18238 During the delivery, the variable &$address_file$& contains the path name.
18241 .option system_filter_file_transport main string&!! unset
18242 .cindex "file" "transport for system filter"
18243 This sets the name of the transport driver that is to be used when the &%save%&
18244 command in a system message filter specifies a path not ending in &"/"&. During
18245 the delivery, the variable &$address_file$& contains the path name.
18247 .option system_filter_group main string unset
18248 .cindex "gid (group id)" "system filter"
18249 This option is used only when &%system_filter_user%& is also set. It sets the
18250 gid under which the system filter is run, overriding any gid that is associated
18251 with the user. The value may be numerical or symbolic.
18253 .option system_filter_pipe_transport main string&!! unset
18254 .cindex "&(pipe)& transport" "for system filter"
18255 .vindex "&$address_pipe$&"
18256 This specifies the transport driver that is to be used when a &%pipe%& command
18257 is used in a system filter. During the delivery, the variable &$address_pipe$&
18258 contains the pipe command.
18261 .option system_filter_reply_transport main string&!! unset
18262 .cindex "&(autoreply)& transport" "for system filter"
18263 This specifies the transport driver that is to be used when a &%mail%& command
18264 is used in a system filter.
18267 .option system_filter_user main string unset
18268 .cindex "uid (user id)" "system filter"
18269 If this option is set to root, the system filter is run in the main Exim
18270 delivery process, as root. Otherwise, the system filter runs in a separate
18271 process, as the given user, defaulting to the Exim run-time user.
18272 Unless the string consists entirely of digits, it
18273 is looked up in the password data. Failure to find the named user causes a
18274 configuration error. The gid is either taken from the password data, or
18275 specified by &%system_filter_group%&. When the uid is specified numerically,
18276 &%system_filter_group%& is required to be set.
18278 If the system filter generates any pipe, file, or reply deliveries, the uid
18279 under which the filter is run is used when transporting them, unless a
18280 transport option overrides.
18283 .option tcp_nodelay main boolean true
18284 .cindex "daemon" "TCP_NODELAY on sockets"
18285 .cindex "Nagle algorithm"
18286 .cindex "TCP_NODELAY on listening sockets"
18287 If this option is set false, it stops the Exim daemon setting the
18288 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
18289 turns off the &"Nagle algorithm"&, which is a way of improving network
18290 performance in interactive (character-by-character) situations. Turning it off
18291 should improve Exim's performance a bit, so that is what happens by default.
18292 However, it appears that some broken clients cannot cope, and time out. Hence
18293 this option. It affects only those sockets that are set up for listening by the
18294 daemon. Sockets created by the smtp transport for delivering mail always set
18298 .option timeout_frozen_after main time 0s
18299 .cindex "frozen messages" "timing out"
18300 .cindex "timeout" "frozen messages"
18301 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
18302 message of any kind that has been in the queue for longer than the given time
18303 is automatically cancelled at the next queue run. If the frozen message is a
18304 bounce message, it is just discarded; otherwise, a bounce is sent to the
18305 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
18306 If you want to timeout frozen bounce messages earlier than other kinds of
18307 frozen message, see &%ignore_bounce_errors_after%&.
18309 &*Note:*& the default value of zero means no timeouts; with this setting,
18310 frozen messages remain in the queue forever (except for any frozen bounce
18311 messages that are released by &%ignore_bounce_errors_after%&).
18314 .option timezone main string unset
18315 .cindex "timezone, setting"
18316 .cindex "environment" "values from"
18317 The value of &%timezone%& is used to set the environment variable TZ while
18318 running Exim (if it is different on entry). This ensures that all timestamps
18319 created by Exim are in the required timezone. If you want all your timestamps
18320 to be in UTC (aka GMT) you should set
18324 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
18325 or, if that is not set, from the value of the TZ environment variable when Exim
18326 is built. If &%timezone%& is set to the empty string, either at build or run
18327 time, any existing TZ variable is removed from the environment when Exim
18328 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
18329 unfortunately not all, operating systems.
18332 .option tls_advertise_hosts main "host list&!!" *
18333 .cindex "TLS" "advertising"
18334 .cindex "encryption" "on SMTP connection"
18335 .cindex "SMTP" "encrypted connection"
18336 .cindex "ESMTP extensions" STARTTLS
18337 When Exim is built with support for TLS encrypted connections, the availability
18338 of the STARTTLS command to set up an encrypted session is advertised in
18339 response to EHLO only to those client hosts that match this option. See
18340 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
18341 Note that the default value requires that a certificate be supplied
18342 using the &%tls_certificate%& option. If TLS support for incoming connections
18343 is not required the &%tls_advertise_hosts%& option should be set empty.
18346 .option tls_alpn main "string list&!!" "smtp : esmtp"
18347 .cindex TLS "Application Layer Protocol Names"
18349 .cindex ALPN "set acceptable names for server"
18350 If this option is set,
18351 the TLS library supports ALPN,
18352 and the client offers either more than
18353 ALPN name or a name which does not match the list,
18354 the TLS connection is declined.
18357 .option tls_certificate main "string list&!!" unset
18358 .cindex "TLS" "server certificate; location of"
18359 .cindex "certificate" "server, location of"
18360 The value of this option is expanded, and must then be a list of absolute paths to
18361 files which contain the server's certificates (in PEM format).
18362 Commonly only one file is needed.
18363 The server's private key is also
18364 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
18365 &<<CHAPTLS>>& for further details.
18367 &*Note*&: The certificates defined by this option are used only when Exim is
18368 receiving incoming messages as a server. If you want to supply certificates for
18369 use when sending messages as a client, you must set the &%tls_certificate%&
18370 option in the relevant &(smtp)& transport.
18372 &*Note*&: If you use filenames based on IP addresses, change the list
18373 separator in the usual way (&<<SECTlistsepchange>>&) to avoid confusion under IPv6.
18375 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
18376 when a list of more than one
18377 file is used, the &$tls_in_ourcert$& variable is unreliable.
18378 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
18380 .cindex SNI "selecting server certificate based on"
18381 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
18382 if the OpenSSL build supports TLS extensions and the TLS client sends the
18383 Server Name Indication extension, then this option and others documented in
18384 &<<SECTtlssni>>& will be re-expanded.
18386 If this option is unset or empty a self-signed certificate will be
18388 Under Linux this is generated at daemon startup; on other platforms it will be
18389 generated fresh for every connection.
18391 .option tls_crl main string&!! unset
18392 .cindex "TLS" "server certificate revocation list"
18393 .cindex "certificate" "revocation list for server"
18394 This option specifies a certificate revocation list. The expanded value must
18395 be the name of a file that contains CRLs in PEM format.
18397 Under OpenSSL the option can specify a directory with CRL files.
18399 &*Note:*& Under OpenSSL the option must, if given, supply a CRL
18400 for each signing element of the certificate chain (i.e. all but the leaf).
18401 For the file variant this can be multiple PEM blocks in the one file.
18403 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18406 .option tls_dh_max_bits main integer 2236
18407 .cindex "TLS" "D-H bit count"
18408 The number of bits used for Diffie-Hellman key-exchange may be suggested by
18409 the chosen TLS library. That value might prove to be too high for
18410 interoperability. This option provides a maximum clamp on the value
18411 suggested, trading off security for interoperability.
18413 The value must be at least 1024.
18415 The value 2236 was chosen because, at time of adding the option, it was the
18416 hard-coded maximum value supported by the NSS cryptographic library, as used
18417 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
18419 If you prefer more security and are willing to break some clients, raise this
18422 Note that the value passed to GnuTLS for *generating* a new prime may be a
18423 little less than this figure, because GnuTLS is inexact and may produce a
18424 larger prime than requested.
18427 .option tls_dhparam main string&!! unset
18428 .cindex "TLS" "D-H parameters for server"
18429 The value of this option is expanded and indicates the source of DH parameters
18430 to be used by Exim.
18432 This option is ignored for GnuTLS version 3.6.0 and later.
18433 The library manages parameter negotiation internally.
18435 &*Note: The Exim Maintainers strongly recommend,
18436 for other TLS library versions,
18437 using a filename with site-generated
18438 local DH parameters*&, which has been supported across all versions of Exim. The
18439 other specific constants available are a fallback so that even when
18440 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
18442 If &%tls_dhparam%& is a filename starting with a &`/`&,
18443 then it names a file from which DH
18444 parameters should be loaded. If the file exists, it should hold a PEM-encoded
18445 PKCS#3 representation of the DH prime. If the file does not exist, for
18446 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
18447 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
18448 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
18449 and treated as though the &%tls_dhparam%& were set to "none".
18451 If this option expands to the string "none", then no DH parameters will be
18454 If this option expands to the string "historic" and Exim is using GnuTLS, then
18455 Exim will attempt to load a file from inside the spool directory. If the file
18456 does not exist, Exim will attempt to create it.
18457 See section &<<SECTgnutlsparam>>& for further details.
18459 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
18460 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
18462 In older versions of Exim the default was the 2048 bit prime described in section
18463 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
18464 in IKE is assigned number 23.
18466 Otherwise, the option must expand to the name used by Exim for any of a number
18467 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
18468 sources. As names, Exim uses a standard specified name, else "ike" followed by
18469 the number used by IKE, or "default" which corresponds to
18470 &`exim.dev.20160529.3`&.
18472 The available standard primes are:
18473 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
18474 &`ike1`&, &`ike2`&, &`ike5`&,
18475 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
18476 &`ike22`&, &`ike23`& and &`ike24`&.
18478 The available additional primes are:
18479 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
18481 Some of these will be too small to be accepted by clients.
18482 Some may be too large to be accepted by clients.
18483 The open cryptographic community has suspicions about the integrity of some
18484 of the later IKE values, which led into RFC7919 providing new fixed constants
18485 (the "ffdhe" identifiers).
18487 At this point, all of the "ike" values should be considered obsolete;
18488 they're still in Exim to avoid breaking unusual configurations, but are
18489 candidates for removal the next time we have backwards-incompatible changes.
18491 The TLS protocol does not negotiate an acceptable size for this; clients tend
18492 to hard-drop connections if what is offered by the server is unacceptable,
18493 whether too large or too small, and there's no provision for the client to
18494 tell the server what these constraints are. Thus, as a server operator, you
18495 need to make an educated guess as to what is most likely to work for your
18498 Some known size constraints suggest that a bit-size in the range 2048 to 2236
18499 is most likely to maximise interoperability. The upper bound comes from
18500 applications using the Mozilla Network Security Services (NSS) library, which
18501 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
18502 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
18503 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
18504 acceptable bound from 1024 to 2048.
18507 .option tls_eccurve main string&!! &`auto`&
18508 .cindex TLS "EC cryptography"
18509 This option selects a EC curve for use by Exim when used with OpenSSL.
18510 It has no effect when Exim is used with GnuTLS.
18512 After expansion it must contain a valid EC curve parameter, such as
18513 &`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
18514 for valid selections.
18516 For OpenSSL versions before (and not including) 1.0.2, the string
18517 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
18518 &`auto`& tells the library to choose.
18520 If the option expands to an empty string, no EC curves will be enabled.
18523 .option tls_ocsp_file main string&!! unset
18524 .cindex TLS "certificate status"
18525 .cindex TLS "OCSP proof file"
18527 must if set expand to the absolute path to a file which contains a current
18528 status proof for the server's certificate, as obtained from the
18529 Certificate Authority.
18531 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
18532 The macro "_HAVE_TLS_OCSP" will be defined for those versions.
18534 For OpenSSL 1.1.0 or later, and
18535 for GnuTLS 3.5.6 or later the expanded value of this option can be a list
18536 of files, to match a list given for the &%tls_certificate%& option.
18537 The ordering of the two lists must match.
18538 The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
18540 The file(s) should be in DER format,
18541 except for GnuTLS 3.6.3 or later
18543 when an optional filetype prefix can be used.
18544 The prefix must be one of "DER" or "PEM", followed by
18545 a single space. If one is used it sets the format for subsequent
18546 files in the list; the initial format is DER.
18547 If multiple proofs are wanted, for multiple chain elements
18548 (this only works under TLS1.3)
18549 they must be coded as a combined OCSP response.
18551 Although GnuTLS will accept PEM files with multiple separate
18552 PEM blobs (ie. separate OCSP responses), it sends them in the
18553 TLS Certificate record interleaved with the certificates of the chain;
18554 although a GnuTLS client is happy with that, an OpenSSL client is not.
18556 .option tls_on_connect_ports main "string list" unset
18559 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
18560 operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
18561 set up without waiting for the client to issue a STARTTLS command. For
18562 further details, see section &<<SECTsupobssmt>>&.
18566 .option tls_privatekey main "string list&!!" unset
18567 .cindex "TLS" "server private key; location of"
18568 The value of this option is expanded, and must then be a list of absolute paths to
18569 files which contains the server's private keys.
18570 If this option is unset, or if
18571 the expansion is forced to fail, or the result is an empty string, the private
18572 key is assumed to be in the same file as the server's certificates. See chapter
18573 &<<CHAPTLS>>& for further details.
18575 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18578 .option tls_remember_esmtp main boolean false
18579 .cindex "TLS" "esmtp state; remembering"
18580 .cindex "TLS" "broken clients"
18581 If this option is set true, Exim violates the RFCs by remembering that it is in
18582 &"esmtp"& state after successfully negotiating a TLS session. This provides
18583 support for broken clients that fail to send a new EHLO after starting a
18587 .option tls_require_ciphers main string&!! unset
18588 .cindex "TLS" "requiring specific ciphers"
18589 .cindex "cipher" "requiring specific"
18590 This option controls which ciphers can be used for incoming TLS connections.
18591 The &(smtp)& transport has an option of the same name for controlling outgoing
18592 connections. This option is expanded for each connection, so can be varied for
18593 different clients if required. The value of this option must be a list of
18594 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
18595 in somewhat different ways. If GnuTLS is being used, the client controls the
18596 preference order of the available ciphers. Details are given in sections
18597 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
18600 .option tls_resumption_hosts main "host list&!!" unset
18601 .cindex TLS resumption
18602 This option controls which connections to offer the TLS resumption feature.
18603 See &<<SECTresumption>>& for details.
18606 .option tls_try_verify_hosts main "host list&!!" unset
18607 .cindex "TLS" "client certificate verification"
18608 .cindex "certificate" "verification of client"
18609 See &%tls_verify_hosts%& below.
18612 .option tls_verify_certificates main string&!! system
18613 .cindex "TLS" "client certificate verification"
18614 .cindex "certificate" "verification of client"
18615 The value of this option is expanded, and must then be either the
18617 or the absolute path to
18618 a file or directory containing permitted certificates for clients that
18619 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
18621 The "system" value for the option will use a
18622 system default location compiled into the SSL library.
18623 This is not available for GnuTLS versions preceding 3.0.20,
18624 and will be taken as empty; an explicit location
18627 The use of a directory for the option value is not available for GnuTLS versions
18628 preceding 3.3.6 and a single file must be used.
18630 With OpenSSL the certificates specified
18632 either by file or directory
18633 are added to those given by the system default location.
18635 These certificates should be for the certificate authorities trusted, rather
18636 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
18637 the value is a file then the certificates are sent by Exim as a server to
18638 connecting clients, defining the list of accepted certificate authorities.
18639 Thus the values defined should be considered public data. To avoid this,
18640 use the explicit directory version. (If your peer is Exim up to 4.85,
18641 using GnuTLS, you may need to send the CAs (thus using the file
18642 variant). Otherwise the peer doesn't send its certificate.)
18644 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18646 A forced expansion failure or setting to an empty string is equivalent to
18650 .option tls_verify_hosts main "host list&!!" unset
18651 .cindex "TLS" "client certificate verification"
18652 .cindex "certificate" "verification of client"
18653 This option, along with &%tls_try_verify_hosts%&, controls the checking of
18654 certificates from clients. The expected certificates are defined by
18655 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
18656 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
18657 &%tls_verify_certificates%& is not set.
18659 Any client that matches &%tls_verify_hosts%& is constrained by
18660 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
18661 present one of the listed certificates. If it does not, the connection is
18663 &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
18664 the host to use TLS. It can still send SMTP commands through unencrypted
18665 connections. Forcing a client to use TLS has to be done separately using an
18666 ACL to reject inappropriate commands when the connection is not encrypted.
18668 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
18669 matches this option (but not &%tls_verify_hosts%&), Exim requests a
18670 certificate and checks it against &%tls_verify_certificates%&, but does not
18671 abort the connection if there is no certificate or if it does not match. This
18672 state can be detected in an ACL, which makes it possible to implement policies
18673 such as &"accept for relay only if a verified certificate has been received,
18674 but accept for local delivery if encrypted, even without a verified
18677 Client hosts that match neither of these lists are not asked to present
18681 .option trusted_groups main "string list&!!" unset
18682 .cindex "trusted groups"
18683 .cindex "groups" "trusted"
18684 This option is expanded just once, at the start of Exim's processing. If this
18685 option is set, any process that is running in one of the listed groups, or
18686 which has one of them as a supplementary group, is trusted. The groups can be
18687 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
18688 details of what trusted callers are permitted to do. If neither
18689 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
18692 .option trusted_users main "string list&!!" unset
18693 .cindex "trusted users"
18694 .cindex "user" "trusted"
18695 This option is expanded just once, at the start of Exim's processing. If this
18696 option is set, any process that is running as one of the listed users is
18697 trusted. The users can be specified numerically or by name. See section
18698 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
18699 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
18700 Exim user are trusted.
18702 .option unknown_login main string&!! unset
18703 .cindex "uid (user id)" "unknown caller"
18704 .vindex "&$caller_uid$&"
18705 This is a specialized feature for use in unusual configurations. By default, if
18706 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
18707 gives up. The &%unknown_login%& option can be used to set a login name to be
18708 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
18709 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
18710 is used for the user's real name (gecos field), unless this has been set by the
18713 .option unknown_username main string unset
18714 See &%unknown_login%&.
18716 .option untrusted_set_sender main "address list&!!" unset
18717 .cindex "trusted users"
18718 .cindex "sender" "setting by untrusted user"
18719 .cindex "untrusted user setting sender"
18720 .cindex "user" "untrusted setting sender"
18721 .cindex "envelope from"
18722 .cindex "envelope sender"
18723 When an untrusted user submits a message to Exim using the standard input, Exim
18724 normally creates an envelope sender address from the user's login and the
18725 default qualification domain. Data from the &%-f%& option (for setting envelope
18726 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
18727 is used) is ignored.
18729 However, untrusted users are permitted to set an empty envelope sender address,
18730 to declare that a message should never generate any bounces. For example:
18732 exim -f '<>' user@domain.example
18734 .vindex "&$sender_ident$&"
18735 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
18736 other envelope sender addresses in a controlled way. When it is set, untrusted
18737 users are allowed to set envelope sender addresses that match any of the
18738 patterns in the list. Like all address lists, the string is expanded. The
18739 identity of the user is in &$sender_ident$&, so you can, for example, restrict
18740 users to setting senders that start with their login ids
18741 followed by a hyphen
18742 by a setting like this:
18744 untrusted_set_sender = ^$sender_ident-
18746 If you want to allow untrusted users to set envelope sender addresses without
18747 restriction, you can use
18749 untrusted_set_sender = *
18751 The &%untrusted_set_sender%& option applies to all forms of local input, but
18752 only to the setting of the envelope sender. It does not permit untrusted users
18753 to use the other options which trusted user can use to override message
18754 parameters. Furthermore, it does not stop Exim from removing an existing
18755 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
18756 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
18757 overriding these actions. The handling of the &'Sender:'& header is also
18758 described in section &<<SECTthesenhea>>&.
18760 The log line for a message's arrival shows the envelope sender following
18761 &"<="&. For local messages, the user's login always follows, after &"U="&. In
18762 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
18763 envelope sender address, the user's login is shown in parentheses after the
18767 .option uucp_from_pattern main string "see below"
18768 .cindex "&""From""& line"
18769 .cindex "UUCP" "&""From""& line"
18770 Some applications that pass messages to an MTA via a command line interface use
18771 an initial line starting with &"From&~"& to pass the envelope sender. In
18772 particular, this is used by UUCP software. Exim recognizes such a line by means
18773 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
18774 matches, the sender address is constructed by expanding the contents of
18775 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
18776 default pattern recognizes lines in the following two forms:
18778 From ph10 Fri Jan 5 12:35 GMT 1996
18779 From ph10 Fri, 7 Jan 97 14:00:00 GMT
18781 The pattern can be seen by running
18783 exim -bP uucp_from_pattern
18785 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
18786 year in the second case. The first word after &"From&~"& is matched in the
18787 regular expression by a parenthesized subpattern. The default value for
18788 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
18789 (&"ph10"& in the example above) as the message's sender. See also
18790 &%ignore_fromline_hosts%&.
18793 .option uucp_from_sender main string&!! &`$1`&
18794 See &%uucp_from_pattern%& above.
18797 .option warn_message_file main string&!! unset
18798 .cindex "warning of delay" "customizing the message"
18799 .cindex "customizing" "warning message"
18800 This option defines a template file containing paragraphs of text to be used
18801 for constructing the warning message which is sent by Exim when a message has
18802 been in the queue for a specified amount of time, as specified by
18803 &%delay_warning%&. Details of the file's contents are given in chapter
18804 &<<CHAPemsgcust>>&.
18805 .cindex warn_message_file "tainted data"
18806 The option is expanded to give the file path, which must be
18807 absolute and untainted.
18808 See also &%bounce_message_file%&.
18811 .option write_rejectlog main boolean true
18812 .cindex "reject log" "disabling"
18813 If this option is set false, Exim no longer writes anything to the reject log.
18814 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
18815 .ecindex IIDconfima
18816 .ecindex IIDmaiconf
18821 . ////////////////////////////////////////////////////////////////////////////
18822 . ////////////////////////////////////////////////////////////////////////////
18824 .chapter "Generic options for routers" "CHAProutergeneric"
18825 .scindex IIDgenoprou1 "options" "generic; for routers"
18826 .scindex IIDgenoprou2 "generic options" "router"
18827 This chapter describes the generic options that apply to all routers.
18828 Those that are preconditions are marked with ‡ in the &"use"& field.
18830 For a general description of how a router operates, see sections
18831 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
18832 which the preconditions are tested. The order of expansion of the options that
18833 provide data for a transport is: &%errors_to%&, &%headers_add%&,
18834 &%headers_remove%&, &%transport%&.
18836 The name of a router is limited to be &drivernamemax; ASCII characters long;
18837 prior to Exim 4.95 names would be silently truncated at this length, but now
18841 .option address_data routers string&!! unset
18842 .cindex "router" "data attached to address"
18843 The string is expanded just before the router is run, that is, after all the
18844 precondition tests have succeeded. If the expansion is forced to fail, the
18845 router declines, the value of &%address_data%& remains unchanged, and the
18846 &%more%& option controls what happens next. Other expansion failures cause
18847 delivery of the address to be deferred.
18849 .vindex "&$address_data$&"
18850 When the expansion succeeds, the value is retained with the address, and can be
18851 accessed using the variable &$address_data$& in the current router, subsequent
18852 routers, and the eventual transport.
18854 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
18855 that runs a user's filter file, the contents of &$address_data$& are accessible
18856 in the filter. This is not normally a problem, because such data is usually
18857 either not confidential or it &"belongs"& to the current user, but if you do
18858 put confidential data into &$address_data$& you need to remember this point.
18860 Even if the router declines or passes, the value of &$address_data$& remains
18861 with the address, though it can be changed by another &%address_data%& setting
18862 on a subsequent router. If a router generates child addresses, the value of
18863 &$address_data$& propagates to them. This also applies to the special kind of
18864 &"child"& that is generated by a router with the &%unseen%& option.
18866 The idea of &%address_data%& is that you can use it to look up a lot of data
18867 for the address once, and then pick out parts of the data later. For example,
18868 you could use a single LDAP lookup to return a string of the form
18870 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
18872 In the transport you could pick out the mailbox by a setting such as
18874 file = ${extract{mailbox}{$address_data}}
18876 This makes the configuration file less messy, and also reduces the number of
18877 lookups (though Exim does cache lookups).
18879 See also the &%set%& option below.
18881 .vindex "&$sender_address_data$&"
18882 .vindex "&$address_data$&"
18883 The &%address_data%& facility is also useful as a means of passing information
18884 from one router to another, and from a router to a transport. In addition, if
18885 &$address_data$& is set by a router when verifying a recipient address from an
18886 ACL, it remains available for use in the rest of the ACL statement. After
18887 verifying a sender, the value is transferred to &$sender_address_data$&.
18891 .option address_test routers&!? boolean true
18893 .cindex "router" "skipping when address testing"
18894 If this option is set false, the router is skipped when routing is being tested
18895 by means of the &%-bt%& command line option. This can be a convenience when
18896 your first router sends messages to an external scanner, because it saves you
18897 having to set the &"already scanned"& indicator when testing real address
18902 .option cannot_route_message routers string&!! unset
18903 .cindex "router" "customizing &""cannot route""& message"
18904 .cindex "customizing" "&""cannot route""& message"
18905 This option specifies a text message that is used when an address cannot be
18906 routed because Exim has run out of routers. The default message is
18907 &"Unrouteable address"&. This option is useful only on routers that have
18908 &%more%& set false, or on the very last router in a configuration, because the
18909 value that is used is taken from the last router that is considered. This
18910 includes a router that is skipped because its preconditions are not met, as
18911 well as a router that declines. For example, using the default configuration,
18914 cannot_route_message = Remote domain not found in DNS
18916 on the first router, which is a &(dnslookup)& router with &%more%& set false,
18919 cannot_route_message = Unknown local user
18921 on the final router that checks for local users. If string expansion fails for
18922 this option, the default message is used. Unless the expansion failure was
18923 explicitly forced, a message about the failure is written to the main and panic
18924 logs, in addition to the normal message about the routing failure.
18927 .option caseful_local_part routers boolean false
18928 .cindex "case of local parts"
18929 .cindex "router" "case of local parts"
18930 By default, routers handle the local parts of addresses in a case-insensitive
18931 manner, though the actual case is preserved for transmission with the message.
18932 If you want the case of letters to be significant in a router, you must set
18933 this option true. For individual router options that contain address or local
18934 part lists (for example, &%local_parts%&), case-sensitive matching can be
18935 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
18938 .vindex "&$local_part$&"
18939 .vindex "&$original_local_part$&"
18940 .vindex "&$parent_local_part$&"
18941 The value of the &$local_part$& variable is forced to lower case while a
18942 router is running unless &%caseful_local_part%& is set. When a router assigns
18943 an address to a transport, the value of &$local_part$& when the transport runs
18944 is the same as it was in the router. Similarly, when a router generates child
18945 addresses by aliasing or forwarding, the values of &$original_local_part$&
18946 and &$parent_local_part$& are those that were used by the redirecting router.
18948 This option applies to the processing of an address by a router. When a
18949 recipient address is being processed in an ACL, there is a separate &%control%&
18950 modifier that can be used to specify case-sensitive processing within the ACL
18951 (see section &<<SECTcontrols>>&).
18955 .option check_local_user routers&!? boolean false
18956 .cindex "local user, checking in router"
18957 .cindex "router" "checking for local user"
18958 .cindex "&_/etc/passwd_&"
18960 When this option is true, Exim checks that the local part of the recipient
18961 address (with affixes removed if relevant) is the name of an account on the
18962 local system. The check is done by calling the &[getpwnam()]& function rather
18963 than trying to read &_/etc/passwd_& directly. This means that other methods of
18964 holding password data (such as NIS) are supported. If the local part is a local
18966 .cindex "tainted data" "de-tainting"
18967 &$local_part_data$& is set to an untainted version of the local part and
18968 &$home$& is set from the password data. The latter can be tested in other
18969 preconditions that are evaluated after this one (the order of evaluation is
18970 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
18971 overridden by &%router_home_directory%&. If the local part is not a local user,
18972 the router is skipped.
18974 If you want to check that the local part is either the name of a local user
18975 or matches something else, you cannot combine &%check_local_user%& with a
18976 setting of &%local_parts%&, because that specifies the logical &'and'& of the
18977 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
18978 setting to achieve this. For example:
18980 local_parts = passwd;$local_part : lsearch;/etc/other/users
18982 Note, however, that the side effects of &%check_local_user%& (such as setting
18983 up a home directory) do not occur when a &(passwd)& lookup is used in a
18984 &%local_parts%& (or any other) precondition.
18988 .option condition routers&!? string&!! unset
18989 .cindex "router" "customized precondition"
18990 This option specifies a general precondition test that has to succeed for the
18991 router to be called. The &%condition%& option is the last precondition to be
18992 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
18993 result is a forced failure, or an empty string, or one of the strings &"0"& or
18994 &"no"& or &"false"& (checked without regard to the case of the letters), the
18995 router is skipped, and the address is offered to the next one.
18997 If the result is any other value, the router is run (as this is the last
18998 precondition to be evaluated, all the other preconditions must be true).
19000 This option is unusual in that multiple &%condition%& options may be present.
19001 All &%condition%& options must succeed.
19003 The &%condition%& option provides a means of applying custom conditions to the
19004 running of routers. Note that in the case of a simple conditional expansion,
19005 the default expansion values are exactly what is wanted. For example:
19007 condition = ${if >{$message_age}{600}}
19009 Because of the default behaviour of the string expansion, this is equivalent to
19011 condition = ${if >{$message_age}{600}{true}{}}
19014 A multiple condition example, which succeeds:
19016 condition = ${if >{$message_age}{600}}
19017 condition = ${if !eq{${lc:$local_part}}{postmaster}}
19021 If the expansion fails (other than forced failure) delivery is deferred. Some
19022 of the other precondition options are common special cases that could in fact
19023 be specified using &%condition%&.
19025 Historical note: We have &%condition%& on ACLs and on Routers. Routers
19026 are far older, and use one set of semantics. ACLs are newer and when
19027 they were created, the ACL &%condition%& process was given far stricter
19028 parse semantics. The &%bool{}%& expansion condition uses the same rules as
19029 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
19030 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
19031 Router rules processing behavior.
19033 This is best illustrated in an example:
19035 # If used in an ACL condition will fail with a syntax error, but
19036 # in a router condition any extra characters are treated as a string
19038 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
19041 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
19044 In each example above, the &%if%& statement actually ends after
19045 &"{google.com}}"&. Since no true or false braces were defined, the
19046 default &%if%& behavior is to return a boolean true or a null answer
19047 (which evaluates to false). The rest of the line is then treated as a
19048 string. So the first example resulted in the boolean answer &"true"&
19049 with the string &" {yes} {no}}"& appended to it. The second example
19050 resulted in the null output (indicating false) with the string
19051 &" {yes} {no}}"& appended to it.
19053 In fact you can put excess forward braces in too. In the router
19054 &%condition%&, Exim's parser only looks for &"{"& symbols when they
19055 mean something, like after a &"$"& or when required as part of a
19056 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
19059 Thus, in a Router, the above expansion strings will both always evaluate
19060 true, as the result of expansion is a non-empty string which doesn't
19061 match an explicit false value. This can be tricky to debug. By
19062 contrast, in an ACL either of those strings will always result in an
19063 expansion error because the result doesn't look sufficiently boolean.
19066 .option debug_print routers string&!! unset
19067 .cindex "testing" "variables in drivers"
19068 If this option is set and debugging is enabled (see the &%-d%& command line
19069 option) or in address-testing mode (see the &%-bt%& command line option),
19070 the string is expanded and included in the debugging output.
19071 If expansion of the string fails, the error message is written to the debugging
19072 output, and Exim carries on processing.
19073 This option is provided to help with checking out the values of variables and
19074 so on when debugging router configurations. For example, if a &%condition%&
19075 option appears not to be working, &%debug_print%& can be used to output the
19076 variables it references. The output happens after checks for &%domains%&,
19077 &%local_parts%&, and &%check_local_user%& but before any other preconditions
19078 are tested. A newline is added to the text if it does not end with one.
19079 The variable &$router_name$& contains the name of the router.
19083 .option disable_logging routers boolean false
19084 If this option is set true, nothing is logged for any routing errors
19085 or for any deliveries caused by this router. You should not set this option
19086 unless you really, really know what you are doing. See also the generic
19087 transport option of the same name.
19089 .option dnssec_request_domains routers "domain list&!!" *
19090 .cindex "MX record" "security"
19091 .cindex "DNSSEC" "MX lookup"
19092 .cindex "security" "MX lookup"
19093 .cindex "DNS" "DNSSEC"
19094 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
19095 the DNSSEC request bit set.
19096 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19098 .option dnssec_require_domains routers "domain list&!!" unset
19099 .cindex "MX record" "security"
19100 .cindex "DNSSEC" "MX lookup"
19101 .cindex "security" "MX lookup"
19102 .cindex "DNS" "DNSSEC"
19103 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
19104 the DNSSEC request bit set. Any returns not having the Authenticated Data bit
19105 (AD bit) set will be ignored and logged as a host-lookup failure.
19106 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19109 .option domains routers&!? "domain list&!!" unset
19110 .cindex "router" "restricting to specific domains"
19111 .vindex "&$domain_data$&"
19112 If this option is set, the router is skipped unless the current domain matches
19113 the list. If the match is achieved by means of a file lookup, the data that the
19114 lookup returned for the domain is placed in &$domain_data$& for use in string
19115 expansions of the driver's private options and in the transport.
19116 See section &<<SECTrouprecon>>& for
19117 a list of the order in which preconditions are evaluated.
19121 .option driver routers string unset
19122 This option must always be set. It specifies which of the available routers is
19126 .option dsn_lasthop routers boolean false
19127 .cindex "DSN" "success"
19128 .cindex "Delivery Status Notification" "success"
19129 If this option is set true, and extended DSN (RFC3461) processing is in effect,
19130 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
19131 instead send a success DSN as if the next hop does not support DSN.
19132 Not effective on redirect routers.
19136 .option errors_to routers string&!! unset
19137 .cindex "envelope from"
19138 .cindex "envelope sender"
19139 .cindex "router" "changing address for errors"
19140 If a router successfully handles an address, it may assign the address to a
19141 transport for delivery or it may generate child addresses. In both cases, if
19142 there is a delivery problem during later processing, the resulting bounce
19143 message is sent to the address that results from expanding this string,
19144 provided that the address verifies successfully. The &%errors_to%& option is
19145 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
19147 The &%errors_to%& setting associated with an address can be overridden if it
19148 subsequently passes through other routers that have their own &%errors_to%&
19149 settings, or if the message is delivered by a transport with a &%return_path%&
19152 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
19153 the expansion fails to verify, the errors address associated with the incoming
19154 address is used. At top level, this is the envelope sender. A non-forced
19155 expansion failure causes delivery to be deferred.
19157 If an address for which &%errors_to%& has been set ends up being delivered over
19158 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
19159 any bounces that are generated by other MTAs on the delivery route are also
19160 sent there. You can set &%errors_to%& to the empty string by either of these
19166 An expansion item that yields an empty string has the same effect. If you do
19167 this, a locally detected delivery error for addresses processed by this router
19168 no longer gives rise to a bounce message; the error is discarded. If the
19169 address is delivered to a remote host, the return path is set to &`<>`&, unless
19170 overridden by the &%return_path%& option on the transport.
19172 .vindex "&$address_data$&"
19173 If for some reason you want to discard local errors, but use a non-empty
19174 MAIL command for remote delivery, you can preserve the original return
19175 path in &$address_data$& in the router, and reinstate it in the transport by
19176 setting &%return_path%&.
19178 The most common use of &%errors_to%& is to direct mailing list bounces to the
19179 manager of the list, as described in section &<<SECTmailinglists>>&, or to
19180 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
19184 .option expn routers&!? boolean true
19185 .cindex "address" "testing"
19186 .cindex "testing" "addresses"
19187 .cindex "EXPN" "router skipping"
19188 .cindex "router" "skipping for EXPN"
19189 If this option is turned off, the router is skipped when testing an address
19190 as a result of processing an SMTP EXPN command. You might, for example,
19191 want to turn it off on a router for users' &_.forward_& files, while leaving it
19192 on for the system alias file.
19193 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19196 The use of the SMTP EXPN command is controlled by an ACL (see chapter
19197 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
19198 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
19202 .option fail_verify routers boolean false
19203 .cindex "router" "forcing verification failure"
19204 Setting this option has the effect of setting both &%fail_verify_sender%& and
19205 &%fail_verify_recipient%& to the same value.
19209 .option fail_verify_recipient routers boolean false
19210 If this option is true and an address is accepted by this router when
19211 verifying a recipient, verification fails.
19215 .option fail_verify_sender routers boolean false
19216 If this option is true and an address is accepted by this router when
19217 verifying a sender, verification fails.
19221 .option fallback_hosts routers "string list" unset
19222 .cindex "router" "fallback hosts"
19223 .cindex "fallback" "hosts specified on router"
19224 String expansion is not applied to this option. The argument must be a
19225 colon-separated list of host names or IP addresses. The list separator can be
19226 changed (see section &<<SECTlistsepchange>>&), and a port can be specified with
19227 each name or address. In fact, the format of each item is exactly the same as
19228 defined for the list of hosts in a &(manualroute)& router (see section
19229 &<<SECTformatonehostitem>>&).
19231 If a router queues an address for a remote transport, this host list is
19232 associated with the address, and used instead of the transport's fallback host
19233 list. If &%hosts_randomize%& is set on the transport, the order of the list is
19234 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
19235 transport for further details.
19238 .option group routers string&!! "see below"
19239 .cindex "gid (group id)" "local delivery"
19240 .cindex "local transports" "uid and gid"
19241 .cindex "transport" "local"
19242 .cindex "router" "setting group"
19243 When a router queues an address for a transport, and the transport does not
19244 specify a group, the group given here is used when running the delivery
19246 The group may be specified numerically or by name. If expansion fails, the
19247 error is logged and delivery is deferred.
19248 The default is unset, unless &%check_local_user%& is set, when the default
19249 is taken from the password information. See also &%initgroups%& and &%user%&
19250 and the discussion in chapter &<<CHAPenvironment>>&.
19254 .option headers_add routers list&!! unset
19255 .cindex "header lines" "adding"
19256 .cindex "router" "adding header lines"
19257 This option specifies a list of text headers,
19258 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19259 that is associated with any addresses that are accepted by the router.
19260 Each item is separately expanded, at routing time. However, this
19261 option has no effect when an address is just being verified. The way in which
19262 the text is used to add header lines at transport time is described in section
19263 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
19264 message is in the process of being transported. This means that references to
19265 header lines in string expansions in the transport's configuration do not
19266 &"see"& the added header lines.
19268 The &%headers_add%& option is expanded after &%errors_to%&, but before
19269 &%headers_remove%& and &%transport%&. If an item is empty, or if
19270 an item expansion is forced to fail, the item has no effect. Other expansion
19271 failures are treated as configuration errors.
19273 Unlike most options, &%headers_add%& can be specified multiple times
19274 for a router; all listed headers are added.
19276 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
19277 router that has the &%one_time%& option set.
19279 .cindex "duplicate addresses"
19280 .oindex "&%unseen%&"
19281 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19282 additions are deleted when the address is passed on to subsequent routers.
19283 For a &%redirect%& router, if a generated address is the same as the incoming
19284 address, this can lead to duplicate addresses with different header
19285 modifications. Exim does not do duplicate deliveries (except, in certain
19286 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
19287 which of the duplicates is discarded, so this ambiguous situation should be
19288 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
19292 .option headers_remove routers list&!! unset
19293 .cindex "header lines" "removing"
19294 .cindex "router" "removing header lines"
19295 This option specifies a list of text headers,
19296 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19297 that is associated with any addresses that are accepted by the router.
19298 However, the option has no effect when an address is just being verified.
19299 Each list item is separately expanded, at transport time.
19300 If an item ends in *, it will match any header with the given prefix.
19302 the text is used to remove header lines at transport time is described in
19303 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
19304 the message is in the process of being transported. This means that references
19305 to header lines in string expansions in the transport's configuration still
19306 &"see"& the original header lines.
19308 The &%headers_remove%& option is handled after &%errors_to%& and
19309 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
19310 the item has no effect. Other expansion failures are treated as configuration
19313 Unlike most options, &%headers_remove%& can be specified multiple times
19314 for a router; all listed headers are removed.
19316 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
19317 router that has the &%one_time%& option set.
19319 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19320 removal requests are deleted when the address is passed on to subsequent
19321 routers, and this can lead to problems with duplicates -- see the similar
19322 warning for &%headers_add%& above.
19324 &*Warning 3*&: Because of the separate expansion of the list items,
19325 items that contain a list separator must have it doubled.
19326 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
19330 .option ignore_target_hosts routers "host list&!!" unset
19331 .cindex "IP address" "discarding"
19332 .cindex "router" "discarding IP addresses"
19333 Although this option is a host list, it should normally contain IP address
19334 entries rather than names. If any host that is looked up by the router has an
19335 IP address that matches an item in this list, Exim behaves as if that IP
19336 address did not exist. This option allows you to cope with rogue DNS entries
19339 remote.domain.example. A 127.0.0.1
19343 ignore_target_hosts = 127.0.0.1
19345 on the relevant router. If all the hosts found by a &(dnslookup)& router are
19346 discarded in this way, the router declines. In a conventional configuration, an
19347 attempt to mail to such a domain would normally provoke the &"unrouteable
19348 domain"& error, and an attempt to verify an address in the domain would fail.
19349 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
19350 router declines if presented with one of the listed addresses.
19352 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
19353 means of the first or the second of the following settings, respectively:
19355 ignore_target_hosts = 0.0.0.0/0
19356 ignore_target_hosts = <; 0::0/0
19358 The pattern in the first line matches all IPv4 addresses, whereas the pattern
19359 in the second line matches all IPv6 addresses.
19361 This option may also be useful for ignoring link-local and site-local IPv6
19362 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
19363 is expanded before use as a list, it is possible to make it dependent on the
19364 domain that is being routed.
19366 .vindex "&$host_address$&"
19367 During its expansion, &$host_address$& is set to the IP address that is being
19370 .option initgroups routers boolean false
19371 .cindex "additional groups"
19372 .cindex "groups" "additional"
19373 .cindex "local transports" "uid and gid"
19374 .cindex "transport" "local"
19375 If the router queues an address for a transport, and this option is true, and
19376 the uid supplied by the router is not overridden by the transport, the
19377 &[initgroups()]& function is called when running the transport to ensure that
19378 any additional groups associated with the uid are set up. See also &%group%&
19379 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
19383 .option local_part_prefix routers&!? "string list" unset
19384 .cindex affix "router precondition"
19385 .cindex "router" "prefix for local part"
19386 .cindex "prefix" "for local part, used in router"
19387 If this option is set, the router is skipped unless the local part starts with
19388 one of the given strings, or &%local_part_prefix_optional%& is true. See
19389 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
19392 The list is scanned from left to right, and the first prefix that matches is
19393 used. A limited form of wildcard is available; if the prefix begins with an
19394 asterisk, it matches the longest possible sequence of arbitrary characters at
19395 the start of the local part. An asterisk should therefore always be followed by
19396 some character that does not occur in normal local parts.
19397 .cindex "multiple mailboxes"
19398 .cindex "mailbox" "multiple"
19399 Wildcarding can be used to set up multiple user mailboxes, as described in
19400 section &<<SECTmulbox>>&.
19402 .vindex "&$local_part$&"
19403 .vindex "&$local_part_prefix$&"
19404 During the testing of the &%local_parts%& option, and while the router is
19405 running, the prefix is removed from the local part, and is available in the
19406 expansion variable &$local_part_prefix$&. When a message is being delivered, if
19407 the router accepts the address, this remains true during subsequent delivery by
19408 a transport. In particular, the local part that is transmitted in the RCPT
19409 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
19410 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
19411 the relevant transport.
19413 .vindex &$local_part_prefix_v$&
19414 If wildcarding (above) was used then the part of the prefix matching the
19415 wildcard is available in &$local_part_prefix_v$&.
19417 When an address is being verified, &%local_part_prefix%& affects only the
19418 behaviour of the router. If the callout feature of verification is in use, this
19419 means that the full address, including the prefix, will be used during the
19422 The prefix facility is commonly used to handle local parts of the form
19423 &%owner-something%&. Another common use is to support local parts of the form
19424 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
19425 to tell a user their forwarding is broken &-- by placing a router like this one
19426 immediately before the router that handles &_.forward_& files:
19430 local_part_prefix = real-
19432 transport = local_delivery
19434 For security, it would probably be a good idea to restrict the use of this
19435 router to locally-generated messages, using a condition such as this:
19437 condition = ${if match {$sender_host_address}\
19438 {\N^(|127\.0\.0\.1)$\N}}
19441 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
19442 both conditions must be met if not optional. Care must be taken if wildcards
19443 are used in both a prefix and a suffix on the same router. Different
19444 separator characters must be used to avoid ambiguity.
19447 .option local_part_prefix_optional routers boolean false
19448 See &%local_part_prefix%& above.
19452 .option local_part_suffix routers&!? "string list" unset
19453 .cindex "router" "suffix for local part"
19454 .cindex "suffix for local part" "used in router"
19455 This option operates in the same way as &%local_part_prefix%&, except that the
19456 local part must end (rather than start) with the given string, the
19457 &%local_part_suffix_optional%& option determines whether the suffix is
19458 mandatory, and the wildcard * character, if present, must be the last
19459 character of the suffix. This option facility is commonly used to handle local
19460 parts of the form &%something-request%& and multiple user mailboxes of the form
19464 .option local_part_suffix_optional routers boolean false
19465 See &%local_part_suffix%& above.
19469 .option local_parts routers&!? "local part list&!!" unset
19470 .cindex "router" "restricting to specific local parts"
19471 .cindex "local part" "checking in router"
19472 The router is run only if the local part of the address matches the list.
19473 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19475 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
19476 string is expanded, it is possible to make it depend on the domain, for
19479 local_parts = dbm;/usr/local/specials/$domain_data
19481 .vindex "&$local_part_data$&"
19482 If the match is achieved by a lookup, the data that the lookup returned
19483 for the local part is placed in the variable &$local_part_data$& for use in
19484 expansions of the router's private options or in the transport.
19485 You might use this option, for
19486 example, if you have a large number of local virtual domains, and you want to
19487 send all postmaster mail to the same place without having to set up an alias in
19488 each virtual domain:
19492 local_parts = postmaster
19493 data = postmaster@real.domain.example
19497 .option log_as_local routers boolean "see below"
19498 .cindex "log" "delivery line"
19499 .cindex "delivery" "log line format"
19500 Exim has two logging styles for delivery, the idea being to make local
19501 deliveries stand out more visibly from remote ones. In the &"local"& style, the
19502 recipient address is given just as the local part, without a domain. The use of
19503 this style is controlled by this option. It defaults to true for the &(accept)&
19504 router, and false for all the others. This option applies only when a
19505 router assigns an address to a transport. It has no effect on routers that
19506 redirect addresses.
19510 .option more routers boolean&!! true
19511 The result of string expansion for this option must be a valid boolean value,
19512 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19513 result causes an error, and delivery is deferred. If the expansion is forced to
19514 fail, the default value for the option (true) is used. Other failures cause
19515 delivery to be deferred.
19517 If this option is set false, and the router declines to handle the address, no
19518 further routers are tried, routing fails, and the address is bounced.
19520 However, if the router explicitly passes an address to the following router by
19521 means of the setting
19525 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
19526 does not affect the behaviour if one of the precondition tests fails. In that
19527 case, the address is always passed to the next router.
19529 Note that &%address_data%& is not considered to be a precondition. If its
19530 expansion is forced to fail, the router declines, and the value of &%more%&
19531 controls what happens next.
19534 .option pass_on_timeout routers boolean false
19535 .cindex "timeout" "of router"
19536 .cindex "router" "timeout"
19537 If a router times out during a host lookup, it normally causes deferral of the
19538 address. If &%pass_on_timeout%& is set, the address is passed on to the next
19539 router, overriding &%no_more%&. This may be helpful for systems that are
19540 intermittently connected to the Internet, or those that want to pass to a smart
19541 host any messages that cannot immediately be delivered.
19543 There are occasional other temporary errors that can occur while doing DNS
19544 lookups. They are treated in the same way as a timeout, and this option
19545 applies to all of them.
19549 .option pass_router routers string unset
19550 .cindex "router" "go to after &""pass""&"
19551 Routers that recognize the generic &%self%& option (&(dnslookup)&,
19552 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
19553 routing to continue, and overriding a false setting of &%more%&. When one of
19554 these routers returns &"pass"&, the address is normally handed on to the next
19555 router in sequence. This can be changed by setting &%pass_router%& to the name
19556 of another router. However (unlike &%redirect_router%&) the named router must
19557 be below the current router, to avoid loops. Note that this option applies only
19558 to the special case of &"pass"&. It does not apply when a router returns
19559 &"decline"& because it cannot handle an address.
19563 .option redirect_router routers string unset
19564 .cindex "router" "start at after redirection"
19565 Sometimes an administrator knows that it is pointless to reprocess addresses
19566 generated from alias or forward files with the same router again. For
19567 example, if an alias file translates real names into login ids there is no
19568 point searching the alias file a second time, especially if it is a large file.
19570 The &%redirect_router%& option can be set to the name of any router instance.
19571 It causes the routing of any generated addresses to start at the named router
19572 instead of at the first router. This option has no effect if the router in
19573 which it is set does not generate new addresses.
19577 .option require_files routers&!? "string list&!!" unset
19578 .cindex "file" "requiring for router"
19579 .cindex "router" "requiring file existence"
19580 This option provides a general mechanism for predicating the running of a
19581 router on the existence or non-existence of certain files or directories.
19582 Before running a router, as one of its precondition tests, Exim works its way
19583 through the &%require_files%& list, expanding each item separately.
19585 Because the list is split before expansion, any colons in expansion items must
19586 be doubled, or the facility for using a different list separator must be used
19587 (&<<SECTlistsepchange>>&).
19588 If any expansion is forced to fail, the item is ignored. Other expansion
19589 failures cause routing of the address to be deferred.
19591 If any expanded string is empty, it is ignored. Otherwise, except as described
19592 below, each string must be a fully qualified file path, optionally preceded by
19593 &"!"&. The paths are passed to the &[stat()]& function to test for the
19594 existence of the files or directories. The router is skipped if any paths not
19595 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
19598 If &[stat()]& cannot determine whether a file exists or not, delivery of
19599 the message is deferred. This can happen when NFS-mounted filesystems are
19602 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
19603 options, so you cannot use it to check for the existence of a file in which to
19604 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
19605 full list of the order in which preconditions are evaluated.) However, as
19606 these options are all expanded, you can use the &%exists%& expansion condition
19607 to make such tests. The &%require_files%& option is intended for checking files
19608 that the router may be going to use internally, or which are needed by a
19609 transport (e.g., &_.procmailrc_&).
19611 During delivery, the &[stat()]& function is run as root, but there is a
19612 facility for some checking of the accessibility of a file by another user.
19613 This is not a proper permissions check, but just a &"rough"& check that
19614 operates as follows:
19616 If an item in a &%require_files%& list does not contain any forward slash
19617 characters, it is taken to be the user (and optional group, separated by a
19618 comma) to be checked for subsequent files in the list. If no group is specified
19619 but the user is specified symbolically, the gid associated with the uid is
19622 require_files = mail:/some/file
19623 require_files = $local_part_data:$home/.procmailrc
19625 If a user or group name in a &%require_files%& list does not exist, the
19626 &%require_files%& condition fails.
19628 Exim performs the check by scanning along the components of the file path, and
19629 checking the access for the given uid and gid. It checks for &"x"& access on
19630 directories, and &"r"& access on the final file. Note that this means that file
19631 access control lists, if the operating system has them, are ignored.
19633 &*Warning 1*&: When the router is being run to verify addresses for an
19634 incoming SMTP message, Exim is not running as root, but under its own uid. This
19635 may affect the result of a &%require_files%& check. In particular, &[stat()]&
19636 may yield the error EACCES (&"Permission denied"&). This means that the Exim
19637 user is not permitted to read one of the directories on the file's path.
19639 &*Warning 2*&: Even when Exim is running as root while delivering a message,
19640 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
19641 without root access. In this case, if a check for access by a particular user
19642 is requested, Exim creates a subprocess that runs as that user, and tries the
19643 check again in that process.
19645 The default action for handling an unresolved EACCES is to consider it to
19646 be caused by a configuration error, and routing is deferred because the
19647 existence or non-existence of the file cannot be determined. However, in some
19648 circumstances it may be desirable to treat this condition as if the file did
19649 not exist. If the filename (or the exclamation mark that precedes the filename
19650 for non-existence) is preceded by a plus sign, the EACCES error is treated
19651 as if the file did not exist. For example:
19653 require_files = +/some/file
19655 If the router is not an essential part of verification (for example, it
19656 handles users' &_.forward_& files), another solution is to set the &%verify%&
19657 option false so that the router is skipped when verifying.
19661 .option retry_use_local_part routers boolean "see below"
19662 .cindex "hints database" "retry keys"
19663 .cindex "local part" "in retry keys"
19664 When a delivery suffers a temporary routing failure, a retry record is created
19665 in Exim's hints database. For addresses whose routing depends only on the
19666 domain, the key for the retry record should not involve the local part, but for
19667 other addresses, both the domain and the local part should be included.
19668 Usually, remote routing is of the former kind, and local routing is of the
19671 This option controls whether the local part is used to form the key for retry
19672 hints for addresses that suffer temporary errors while being handled by this
19673 router. The default value is true for any router that has any of
19674 &%check_local_user%&,
19677 &%local_part_prefix%&,
19678 &%local_part_suffix%&,
19681 set, and false otherwise. Note that this option does not apply to hints keys
19682 for transport delays; they are controlled by a generic transport option of the
19685 Failing to set this option when it is needed
19686 (because a remote router handles only some of the local-parts for a domain)
19687 can result in incorrect error messages being generated.
19689 The setting of &%retry_use_local_part%& applies only to the router on which it
19690 appears. If the router generates child addresses, they are routed
19691 independently; this setting does not become attached to them.
19695 .option router_home_directory routers string&!! unset
19696 .cindex "router" "home directory for"
19697 .cindex "home directory" "for router"
19699 This option sets a home directory for use while the router is running. (Compare
19700 &%transport_home_directory%&, which sets a home directory for later
19701 transporting.) In particular, if used on a &(redirect)& router, this option
19702 sets a value for &$home$& while a filter is running. The value is expanded;
19703 forced expansion failure causes the option to be ignored &-- other failures
19704 cause the router to defer.
19706 Expansion of &%router_home_directory%& happens immediately after the
19707 &%check_local_user%& test (if configured), before any further expansions take
19709 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19711 While the router is running, &%router_home_directory%& overrides the value of
19712 &$home$& that came from &%check_local_user%&.
19714 When a router accepts an address and assigns it to a local transport (including
19715 the cases when a &(redirect)& router generates a pipe, file, or autoreply
19716 delivery), the home directory setting for the transport is taken from the first
19717 of these values that is set:
19720 The &%home_directory%& option on the transport;
19722 The &%transport_home_directory%& option on the router;
19724 The password data if &%check_local_user%& is set on the router;
19726 The &%router_home_directory%& option on the router.
19729 In other words, &%router_home_directory%& overrides the password data for the
19730 router, but not for the transport.
19734 .option self routers string freeze
19735 .cindex "MX record" "pointing to local host"
19736 .cindex "local host" "MX pointing to"
19737 This option applies to those routers that use a recipient address to find a
19738 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
19739 and &(manualroute)& routers.
19740 Certain configurations of the &(queryprogram)& router can also specify a list
19742 Usually such routers are configured to send the message to a remote host via an
19743 &(smtp)& transport. The &%self%& option specifies what happens when the first
19744 host on the list turns out to be the local host.
19745 The way in which Exim checks for the local host is described in section
19746 &<<SECTreclocipadd>>&.
19748 Normally this situation indicates either an error in Exim's configuration (for
19749 example, the router should be configured not to process this domain), or an
19750 error in the DNS (for example, the MX should not point to this host). For this
19751 reason, the default action is to log the incident, defer the address, and
19752 freeze the message. The following alternatives are provided for use in special
19757 Delivery of the message is tried again later, but the message is not frozen.
19759 .vitem "&%reroute%&: <&'domain'&>"
19760 The domain is changed to the given domain, and the address is passed back to
19761 be reprocessed by the routers. No rewriting of headers takes place. This
19762 behaviour is essentially a redirection.
19764 .vitem "&%reroute: rewrite:%& <&'domain'&>"
19765 The domain is changed to the given domain, and the address is passed back to be
19766 reprocessed by the routers. Any headers that contain the original domain are
19771 .vindex "&$self_hostname$&"
19772 The router passes the address to the next router, or to the router named in the
19773 &%pass_router%& option if it is set. This overrides &%no_more%&. During
19774 subsequent routing and delivery, the variable &$self_hostname$& contains the
19775 name of the local host that the router encountered. This can be used to
19776 distinguish between different cases for hosts with multiple names. The
19782 ensures that only those addresses that routed to the local host are passed on.
19783 Without &%no_more%&, addresses that were declined for other reasons would also
19784 be passed to the next router.
19787 Delivery fails and an error report is generated.
19790 .cindex "local host" "sending to"
19791 The anomaly is ignored and the address is queued for the transport. This
19792 setting should be used with extreme caution. For an &(smtp)& transport, it
19793 makes sense only in cases where the program that is listening on the SMTP port
19794 is not this version of Exim. That is, it must be some other MTA, or Exim with a
19795 different configuration file that handles the domain in another way.
19800 .option senders routers&!? "address list&!!" unset
19801 .cindex "router" "checking senders"
19802 If this option is set, the router is skipped unless the message's sender
19803 address matches something on the list.
19804 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19807 There are issues concerning verification when the running of routers is
19808 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
19809 setting, it sets the sender to the null string. When using the &%-bt%& option
19810 to check a configuration file, it is necessary also to use the &%-f%& option to
19811 set an appropriate sender. For incoming mail, the sender is unset when
19812 verifying the sender, but is available when verifying any recipients. If the
19813 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
19817 .option set routers "string list" unset
19818 .cindex router variables
19819 This option may be used multiple times on a router;
19820 because of this the list aspect is mostly irrelevant.
19821 The list separator is a semicolon but can be changed in the
19824 Each list-element given must be of the form &"name = value"&
19825 and the names used must start with the string &"r_"&.
19826 Values containing a list-separator should have them doubled.
19827 When a router runs, the strings are evaluated in order,
19828 to create variables which are added to the set associated with
19830 This is done immediately after all the preconditions, before the
19831 evaluation of the &%address_data%& option.
19832 The variable is set with the expansion of the value.
19833 The variables can be used by the router options
19834 (not including any preconditions)
19835 and by the transport.
19836 Later definitions of a given named variable will override former ones.
19837 Variable use is via the usual &$r_...$& syntax.
19839 This is similar to the &%address_data%& option, except that
19840 many independent variables can be used, with choice of naming.
19843 .option translate_ip_address routers string&!! unset
19844 .cindex "IP address" "translating"
19845 .cindex "packet radio"
19846 .cindex "router" "IP address translation"
19847 There exist some rare networking situations (for example, packet radio) where
19848 it is helpful to be able to translate IP addresses generated by normal routing
19849 mechanisms into other IP addresses, thus performing a kind of manual IP
19850 routing. This should be done only if the normal IP routing of the TCP/IP stack
19851 is inadequate or broken. Because this is an extremely uncommon requirement, the
19852 code to support this option is not included in the Exim binary unless
19853 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
19855 .vindex "&$host_address$&"
19856 The &%translate_ip_address%& string is expanded for every IP address generated
19857 by the router, with the generated address set in &$host_address$&. If the
19858 expansion is forced to fail, no action is taken.
19859 For any other expansion error, delivery of the message is deferred.
19860 If the result of the expansion is an IP address, that replaces the original
19861 address; otherwise the result is assumed to be a host name &-- this is looked
19862 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
19863 produce one or more replacement IP addresses. For example, to subvert all IP
19864 addresses in some specific networks, this could be added to a router:
19866 translate_ip_address = \
19867 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
19870 The file would contain lines like
19872 10.2.3.128/26 some.host
19873 10.8.4.34/26 10.44.8.15
19875 You should not make use of this facility unless you really understand what you
19880 .option transport routers string&!! unset
19881 This option specifies the transport to be used when a router accepts an address
19882 and sets it up for delivery. A transport is never needed if a router is used
19883 only for verification. The value of the option is expanded at routing time,
19884 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
19885 and result must be the name of one of the configured transports. If it is not,
19886 delivery is deferred.
19888 The &%transport%& option is not used by the &(redirect)& router, but it does
19889 have some private options that set up transports for pipe and file deliveries
19890 (see chapter &<<CHAPredirect>>&).
19894 .option transport_current_directory routers string&!! unset
19895 .cindex "current directory for local transport"
19896 This option associates a current directory with any address that is routed
19897 to a local transport. This can happen either because a transport is
19898 explicitly configured for the router, or because it generates a delivery to a
19899 file or a pipe. During the delivery process (that is, at transport time), this
19900 option string is expanded and is set as the current directory, unless
19901 overridden by a setting on the transport.
19902 If the expansion fails for any reason, including forced failure, an error is
19903 logged, and delivery is deferred.
19904 See chapter &<<CHAPenvironment>>& for details of the local delivery
19910 .option transport_home_directory routers string&!! "see below"
19911 .cindex "home directory" "for local transport"
19912 This option associates a home directory with any address that is routed to a
19913 local transport. This can happen either because a transport is explicitly
19914 configured for the router, or because it generates a delivery to a file or a
19915 pipe. During the delivery process (that is, at transport time), the option
19916 string is expanded and is set as the home directory, unless overridden by a
19917 setting of &%home_directory%& on the transport.
19918 If the expansion fails for any reason, including forced failure, an error is
19919 logged, and delivery is deferred.
19921 If the transport does not specify a home directory, and
19922 &%transport_home_directory%& is not set for the router, the home directory for
19923 the transport is taken from the password data if &%check_local_user%& is set for
19924 the router. Otherwise it is taken from &%router_home_directory%& if that option
19925 is set; if not, no home directory is set for the transport.
19927 See chapter &<<CHAPenvironment>>& for further details of the local delivery
19933 .option unseen routers boolean&!! false
19934 .cindex "router" "carrying on after success"
19935 The result of string expansion for this option must be a valid boolean value,
19936 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19937 result causes an error, and delivery is deferred. If the expansion is forced to
19938 fail, the default value for the option (false) is used. Other failures cause
19939 delivery to be deferred.
19941 When this option is set true, routing does not cease if the router accepts the
19942 address. Instead, a copy of the incoming address is passed to the next router,
19943 overriding a false setting of &%more%&. There is little point in setting
19944 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
19945 the value of &%unseen%& contains expansion items (and therefore, presumably, is
19946 sometimes true and sometimes false).
19948 .cindex "copy of message (&%unseen%& option)"
19949 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
19950 qualifier in filter files. It can be used to cause copies of messages to be
19951 delivered to some other destination, while also carrying out a normal delivery.
19952 In effect, the current address is made into a &"parent"& that has two children
19953 &-- one that is delivered as specified by this router, and a clone that goes on
19954 to be routed further. For this reason, &%unseen%& may not be combined with the
19955 &%one_time%& option in a &(redirect)& router.
19957 &*Warning*&: Header lines added to the address (or specified for removal) by
19958 this router or by previous routers affect the &"unseen"& copy of the message
19959 only. The clone that continues to be processed by further routers starts with
19960 no added headers and none specified for removal. For a &%redirect%& router, if
19961 a generated address is the same as the incoming address, this can lead to
19962 duplicate addresses with different header modifications. Exim does not do
19963 duplicate deliveries (except, in certain circumstances, to pipes -- see section
19964 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
19965 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
19966 &%redirect%& router may be of help.
19968 Unlike the handling of header modifications, any data that was set by the
19969 &%address_data%& option in the current or previous routers &'is'& passed on to
19970 subsequent routers.
19973 .option user routers string&!! "see below"
19974 .cindex "uid (user id)" "local delivery"
19975 .cindex "local transports" "uid and gid"
19976 .cindex "transport" "local"
19977 .cindex "router" "user for filter processing"
19978 .cindex "filter" "user for processing"
19979 When a router queues an address for a transport, and the transport does not
19980 specify a user, the user given here is used when running the delivery process.
19981 The user may be specified numerically or by name. If expansion fails, the
19982 error is logged and delivery is deferred.
19983 This user is also used by the &(redirect)& router when running a filter file.
19984 The default is unset, except when &%check_local_user%& is set. In this case,
19985 the default is taken from the password information. If the user is specified as
19986 a name, and &%group%& is not set, the group associated with the user is used.
19987 See also &%initgroups%& and &%group%& and the discussion in chapter
19988 &<<CHAPenvironment>>&.
19992 .option verify routers&!? boolean true
19993 Setting this option has the effect of setting &%verify_sender%& and
19994 &%verify_recipient%& to the same value.
19997 .option verify_only routers&!? boolean false
19998 .cindex "EXPN" "with &%verify_only%&"
20000 .cindex "router" "used only when verifying"
20001 If this option is set, the router is used only when verifying an address,
20002 delivering in cutthrough mode or
20003 testing with the &%-bv%& option, not when actually doing a delivery, testing
20004 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
20005 restricted to verifying only senders or recipients by means of
20006 &%verify_sender%& and &%verify_recipient%&.
20008 &*Warning*&: When the router is being run to verify addresses for an incoming
20009 SMTP message, Exim is not running as root, but under its own uid. If the router
20010 accesses any files, you need to make sure that they are accessible to the Exim
20014 .option verify_recipient routers&!? boolean true
20015 If this option is false, the router is skipped when verifying recipient
20017 delivering in cutthrough mode
20018 or testing recipient verification using &%-bv%&.
20019 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
20021 See also the &$verify_mode$& variable.
20024 .option verify_sender routers&!? boolean true
20025 If this option is false, the router is skipped when verifying sender addresses
20026 or testing sender verification using &%-bvs%&.
20027 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
20029 See also the &$verify_mode$& variable.
20030 .ecindex IIDgenoprou1
20031 .ecindex IIDgenoprou2
20038 . ////////////////////////////////////////////////////////////////////////////
20039 . ////////////////////////////////////////////////////////////////////////////
20041 .chapter "The accept router" "CHID4"
20042 .cindex "&(accept)& router"
20043 .cindex "routers" "&(accept)&"
20044 The &(accept)& router has no private options of its own. Unless it is being
20045 used purely for verification (see &%verify_only%&) a transport is required to
20046 be defined by the generic &%transport%& option. If the preconditions that are
20047 specified by generic options are met, the router accepts the address and queues
20048 it for the given transport. The most common use of this router is for setting
20049 up deliveries to local mailboxes. For example:
20053 domains = mydomain.example
20055 transport = local_delivery
20057 The &%domains%& condition in this example checks the domain of the address, and
20058 &%check_local_user%& checks that the local part is the login of a local user.
20059 When both preconditions are met, the &(accept)& router runs, and queues the
20060 address for the &(local_delivery)& transport.
20067 . ////////////////////////////////////////////////////////////////////////////
20068 . ////////////////////////////////////////////////////////////////////////////
20070 .chapter "The dnslookup router" "CHAPdnslookup"
20071 .scindex IIDdnsrou1 "&(dnslookup)& router"
20072 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
20073 The &(dnslookup)& router looks up the hosts that handle mail for the
20074 recipient's domain in the DNS. A transport must always be set for this router,
20075 unless &%verify_only%& is set.
20077 If SRV support is configured (see &%check_srv%& below), Exim first searches for
20078 SRV records. If none are found, or if SRV support is not configured,
20079 MX records are looked up. If no MX records exist, address records are sought.
20080 However, &%mx_domains%& can be set to disable the direct use of address
20083 MX records of equal priority are sorted by Exim into a random order. Exim then
20084 looks for address records for the host names obtained from MX or SRV records.
20085 When a host has more than one IP address, they are sorted into a random order,
20086 except that IPv6 addresses are sorted before IPv4 addresses. If all the
20087 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
20088 generic option, the router declines.
20090 Unless they have the highest priority (lowest MX value), MX records that point
20091 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
20092 are discarded, together with any other MX records of equal or lower priority.
20094 .cindex "MX record" "pointing to local host"
20095 .cindex "local host" "MX pointing to"
20096 .oindex "&%self%&" "in &(dnslookup)& router"
20097 If the host pointed to by the highest priority MX record, or looked up as an
20098 address record, is the local host, or matches &%hosts_treat_as_local%&, what
20099 happens is controlled by the generic &%self%& option.
20102 .section "Problems with DNS lookups" "SECTprowitdnsloo"
20103 There have been problems with DNS servers when SRV records are looked up.
20104 Some misbehaving servers return a DNS error or timeout when a non-existent
20105 SRV record is sought. Similar problems have in the past been reported for
20106 MX records. The global &%dns_again_means_nonexist%& option can help with this
20107 problem, but it is heavy-handed because it is a global option.
20109 For this reason, there are two options, &%srv_fail_domains%& and
20110 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
20111 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
20112 an attempt to look up an SRV or MX record causes one of these results, and the
20113 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
20114 such record"&. In the case of an SRV lookup, this means that the router
20115 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
20116 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
20117 case routing fails.
20120 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
20121 .cindex "&(dnslookup)& router" "declines"
20122 There are a few cases where a &(dnslookup)& router will decline to accept
20123 an address; if such a router is expected to handle "all remaining non-local
20124 domains", then it is important to set &%no_more%&.
20126 The router will defer rather than decline if the domain
20127 is found in the &%fail_defer_domains%& router option.
20129 Reasons for a &(dnslookup)& router to decline currently include:
20131 The domain does not exist in DNS
20133 The domain exists but the MX record's host part is just "."; this is a common
20134 convention (borrowed from SRV) used to indicate that there is no such service
20135 for this domain and to not fall back to trying A/AAAA records.
20137 Ditto, but for SRV records, when &%check_srv%& is set on this router.
20139 MX record points to a non-existent host.
20141 MX record points to an IP address and the main section option
20142 &%allow_mx_to_ip%& is not set.
20144 MX records exist and point to valid hosts, but all hosts resolve only to
20145 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
20147 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
20148 &%dns_check_names_pattern%& for handling one variant of this)
20150 &%check_secondary_mx%& is set on this router but the local host can
20151 not be found in the MX records (see below)
20157 .section "Private options for dnslookup" "SECID118"
20158 .cindex "options" "&(dnslookup)& router"
20159 The private options for the &(dnslookup)& router are as follows:
20161 .option check_secondary_mx dnslookup boolean false
20162 .cindex "MX record" "checking for secondary"
20163 If this option is set, the router declines unless the local host is found in
20164 (and removed from) the list of hosts obtained by MX lookup. This can be used to
20165 process domains for which the local host is a secondary mail exchanger
20166 differently to other domains. The way in which Exim decides whether a host is
20167 the local host is described in section &<<SECTreclocipadd>>&.
20170 .option check_srv dnslookup string&!! unset
20171 .cindex "SRV record" "enabling use of"
20172 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
20173 addition to MX and address records. The support is disabled by default. To
20174 enable SRV support, set the &%check_srv%& option to the name of the service
20175 required. For example,
20179 looks for SRV records that refer to the normal smtp service. The option is
20180 expanded, so the service name can vary from message to message or address
20181 to address. This might be helpful if SRV records are being used for a
20182 submission service. If the expansion is forced to fail, the &%check_srv%&
20183 option is ignored, and the router proceeds to look for MX records in the
20186 When the expansion succeeds, the router searches first for SRV records for
20187 the given service (it assumes TCP protocol). A single SRV record with a
20188 host name that consists of just a single dot indicates &"no such service for
20189 this domain"&; if this is encountered, the router declines. If other kinds of
20190 SRV record are found, they are used to construct a host list for delivery
20191 according to the rules of RFC 2782. MX records are not sought in this case.
20193 When no SRV records are found, MX records (and address records) are sought in
20194 the traditional way. In other words, SRV records take precedence over MX
20195 records, just as MX records take precedence over address records. Note that
20196 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
20197 defined it. It is apparently believed that MX records are sufficient for email
20198 and that SRV records should not be used for this purpose. However, SRV records
20199 have an additional &"weight"& feature which some people might find useful when
20200 trying to split an SMTP load between hosts of different power.
20202 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
20203 when there is a DNS lookup error.
20208 .option fail_defer_domains dnslookup "domain list&!!" unset
20209 .cindex "MX record" "not found"
20210 DNS lookups for domains matching &%fail_defer_domains%&
20211 which find no matching record will cause the router to defer
20212 rather than the default behaviour of decline.
20213 This maybe be useful for queueing messages for a newly created
20214 domain while the DNS configuration is not ready.
20215 However, it will result in any message with mistyped domains
20219 .option ipv4_only "string&!!" unset
20220 .cindex IPv6 disabling
20221 .cindex DNS "IPv6 disabling"
20222 The string is expanded, and if the result is anything but a forced failure,
20223 or an empty string, or one of the strings “0” or “no” or “false”
20224 (checked without regard to the case of the letters),
20225 only A records are used.
20227 .option ipv4_prefer "string&!!" unset
20228 .cindex IPv4 preference
20229 .cindex DNS "IPv4 preference"
20230 The string is expanded, and if the result is anything but a forced failure,
20231 or an empty string, or one of the strings “0” or “no” or “false”
20232 (checked without regard to the case of the letters),
20233 A records are sorted before AAAA records (inverting the default).
20235 .option mx_domains dnslookup "domain list&!!" unset
20236 .cindex "MX record" "required to exist"
20237 .cindex "SRV record" "required to exist"
20238 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
20239 record in order to be recognized. (The name of this option could be improved.)
20240 For example, if all the mail hosts in &'fict.example'& are known to have MX
20241 records, except for those in &'discworld.fict.example'&, you could use this
20244 mx_domains = ! *.discworld.fict.example : *.fict.example
20246 This specifies that messages addressed to a domain that matches the list but
20247 has no MX record should be bounced immediately instead of being routed using
20248 the address record.
20251 .option mx_fail_domains dnslookup "domain list&!!" unset
20252 If the DNS lookup for MX records for one of the domains in this list causes a
20253 DNS lookup error, Exim behaves as if no MX records were found. See section
20254 &<<SECTprowitdnsloo>>& for more discussion.
20259 .option qualify_single dnslookup boolean true
20260 .cindex "DNS" "resolver options"
20261 .cindex "DNS" "qualifying single-component names"
20262 When this option is true, the resolver option RES_DEFNAMES is set for DNS
20263 lookups. Typically, but not standardly, this causes the resolver to qualify
20264 single-component names with the default domain. For example, on a machine
20265 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
20266 &'thesaurus.ref.example'& inside the resolver. For details of what your
20267 resolver actually does, consult your man pages for &'resolver'& and
20272 .option rewrite_headers dnslookup boolean true
20273 .cindex "rewriting" "header lines"
20274 .cindex "header lines" "rewriting"
20275 If the domain name in the address that is being processed is not fully
20276 qualified, it may be expanded to its full form by a DNS lookup. For example, if
20277 an address is specified as &'dormouse@teaparty'&, the domain might be
20278 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
20279 occur as a result of setting the &%widen_domains%& option. If
20280 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
20281 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
20282 header lines of the message are rewritten with the full domain name.
20284 This option should be turned off only when it is known that no message is
20285 ever going to be sent outside an environment where the abbreviation makes
20288 When an MX record is looked up in the DNS and matches a wildcard record, name
20289 servers normally return a record containing the name that has been looked up,
20290 making it impossible to detect whether a wildcard was present or not. However,
20291 some name servers have recently been seen to return the wildcard entry. If the
20292 name returned by a DNS lookup begins with an asterisk, it is not used for
20296 .option same_domain_copy_routing dnslookup boolean false
20297 .cindex "address" "copying routing"
20298 Addresses with the same domain are normally routed by the &(dnslookup)& router
20299 to the same list of hosts. However, this cannot be presumed, because the router
20300 options and preconditions may refer to the local part of the address. By
20301 default, therefore, Exim routes each address in a message independently. DNS
20302 servers run caches, so repeated DNS lookups are not normally expensive, and in
20303 any case, personal messages rarely have more than a few recipients.
20305 If you are running mailing lists with large numbers of subscribers at the same
20306 domain, and you are using a &(dnslookup)& router which is independent of the
20307 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20308 lookups for identical domains in one message. In this case, when &(dnslookup)&
20309 routes an address to a remote transport, any other unrouted addresses in the
20310 message that have the same domain are automatically given the same routing
20311 without processing them independently,
20312 provided the following conditions are met:
20315 No router that processed the address specified &%headers_add%& or
20316 &%headers_remove%&.
20318 The router did not change the address in any way, for example, by &"widening"&
20325 .option search_parents dnslookup boolean false
20326 .cindex "DNS" "resolver options"
20327 When this option is true, the resolver option RES_DNSRCH is set for DNS
20328 lookups. This is different from the &%qualify_single%& option in that it
20329 applies to domains containing dots. Typically, but not standardly, it causes
20330 the resolver to search for the name in the current domain and in parent
20331 domains. For example, on a machine in the &'fict.example'& domain, if looking
20332 up &'teaparty.wonderland'& failed, the resolver would try
20333 &'teaparty.wonderland.fict.example'&. For details of what your resolver
20334 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
20336 Setting this option true can cause problems in domains that have a wildcard MX
20337 record, because any domain that does not have its own MX record matches the
20342 .option srv_fail_domains dnslookup "domain list&!!" unset
20343 If the DNS lookup for SRV records for one of the domains in this list causes a
20344 DNS lookup error, Exim behaves as if no SRV records were found. See section
20345 &<<SECTprowitdnsloo>>& for more discussion.
20350 .option widen_domains dnslookup "string list" unset
20351 .cindex "domain" "partial; widening"
20352 If a DNS lookup fails and this option is set, each of its strings in turn is
20353 added onto the end of the domain, and the lookup is tried again. For example,
20356 widen_domains = fict.example:ref.example
20358 is set and a lookup of &'klingon.dictionary'& fails,
20359 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
20360 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
20361 and &%search_parents%& options can cause some widening to be undertaken inside
20362 the DNS resolver. &%widen_domains%& is not applied to sender addresses
20363 when verifying, unless &%rewrite_headers%& is false (not the default).
20366 .section "Effect of qualify_single and search_parents" "SECID119"
20367 When a domain from an envelope recipient is changed by the resolver as a result
20368 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
20369 corresponding address in the message's header lines unless &%rewrite_headers%&
20370 is set false. Exim then re-routes the address, using the full domain.
20372 These two options affect only the DNS lookup that takes place inside the router
20373 for the domain of the address that is being routed. They do not affect lookups
20374 such as that implied by
20378 that may happen while processing a router precondition before the router is
20379 entered. No widening ever takes place for these lookups.
20380 .ecindex IIDdnsrou1
20381 .ecindex IIDdnsrou2
20391 . ////////////////////////////////////////////////////////////////////////////
20392 . ////////////////////////////////////////////////////////////////////////////
20394 .chapter "The ipliteral router" "CHID5"
20395 .cindex "&(ipliteral)& router"
20396 .cindex "domain literal" "routing"
20397 .cindex "routers" "&(ipliteral)&"
20398 This router has no private options. Unless it is being used purely for
20399 verification (see &%verify_only%&) a transport is required to be defined by the
20400 generic &%transport%& option. The router accepts the address if its domain part
20401 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
20402 router handles the address
20406 by setting up delivery to the host with that IP address. IPv4 domain literals
20407 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
20408 are similar, but the address is preceded by &`ipv6:`&. For example:
20410 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
20412 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
20413 grounds that sooner or later somebody will try it.
20415 .oindex "&%self%&" "in &(ipliteral)& router"
20416 If the IP address matches something in &%ignore_target_hosts%&, the router
20417 declines. If an IP literal turns out to refer to the local host, the generic
20418 &%self%& option determines what happens.
20420 The RFCs require support for domain literals; however, their use is
20421 controversial in today's Internet. If you want to use this router, you must
20422 also set the main configuration option &%allow_domain_literals%&. Otherwise,
20423 Exim will not recognize the domain literal syntax in addresses.
20427 . ////////////////////////////////////////////////////////////////////////////
20428 . ////////////////////////////////////////////////////////////////////////////
20430 .chapter "The iplookup router" "CHID6"
20431 .cindex "&(iplookup)& router"
20432 .cindex "routers" "&(iplookup)&"
20433 The &(iplookup)& router was written to fulfil a specific requirement in
20434 Cambridge University (which in fact no longer exists). For this reason, it is
20435 not included in the binary of Exim by default. If you want to include it, you
20438 ROUTER_IPLOOKUP=yes
20440 in your &_Local/Makefile_& configuration file.
20442 The &(iplookup)& router routes an address by sending it over a TCP or UDP
20443 connection to one or more specific hosts. The host can then return the same or
20444 a different address &-- in effect rewriting the recipient address in the
20445 message's envelope. The new address is then passed on to subsequent routers. If
20446 this process fails, the address can be passed on to other routers, or delivery
20447 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
20448 must not be specified for it.
20450 .cindex "options" "&(iplookup)& router"
20451 .option hosts iplookup string unset
20452 This option must be supplied. Its value is a colon-separated list of host
20453 names. The hosts are looked up using &[gethostbyname()]&
20454 (or &[getipnodebyname()]& when available)
20455 and are tried in order until one responds to the query. If none respond, what
20456 happens is controlled by &%optional%&.
20459 .option optional iplookup boolean false
20460 If &%optional%& is true, if no response is obtained from any host, the address
20461 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
20462 delivery to the address is deferred.
20465 .option port iplookup integer 0
20466 .cindex "port" "&(iplookup)& router"
20467 This option must be supplied. It specifies the port number for the TCP or UDP
20471 .option protocol iplookup string udp
20472 This option can be set to &"udp"& or &"tcp"& to specify which of the two
20473 protocols is to be used.
20476 .option query iplookup string&!! "see below"
20477 This defines the content of the query that is sent to the remote hosts. The
20480 $local_part@$domain $local_part@$domain
20482 The repetition serves as a way of checking that a response is to the correct
20483 query in the default case (see &%response_pattern%& below).
20486 .option reroute iplookup string&!! unset
20487 If this option is not set, the rerouted address is precisely the byte string
20488 returned by the remote host, up to the first white space, if any. If set, the
20489 string is expanded to form the rerouted address. It can include parts matched
20490 in the response by &%response_pattern%& by means of numeric variables such as
20491 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
20492 whether or not a pattern is in use. In all cases, the rerouted address must end
20493 up in the form &'local_part@domain'&.
20496 .option response_pattern iplookup string unset
20497 This option can be set to a regular expression that is applied to the string
20498 returned from the remote host. If the pattern does not match the response, the
20499 router declines. If &%response_pattern%& is not set, no checking of the
20500 response is done, unless the query was defaulted, in which case there is a
20501 check that the text returned after the first white space is the original
20502 address. This checks that the answer that has been received is in response to
20503 the correct question. For example, if the response is just a new domain, the
20504 following could be used:
20506 response_pattern = ^([^@]+)$
20507 reroute = $local_part@$1
20510 .option timeout iplookup time 5s
20511 This specifies the amount of time to wait for a response from the remote
20512 machine. The same timeout is used for the &[connect()]& function for a TCP
20513 call. It does not apply to UDP.
20518 . ////////////////////////////////////////////////////////////////////////////
20519 . ////////////////////////////////////////////////////////////////////////////
20521 .chapter "The manualroute router" "CHID7"
20522 .scindex IIDmanrou1 "&(manualroute)& router"
20523 .scindex IIDmanrou2 "routers" "&(manualroute)&"
20524 .cindex "domain" "manually routing"
20525 The &(manualroute)& router is so-called because it provides a way of manually
20526 routing an address according to its domain. It is mainly used when you want to
20527 route addresses to remote hosts according to your own rules, bypassing the
20528 normal DNS routing that looks up MX records. However, &(manualroute)& can also
20529 route to local transports, a facility that may be useful if you want to save
20530 messages for dial-in hosts in local files.
20532 The &(manualroute)& router compares a list of domain patterns with the domain
20533 it is trying to route. If there is no match, the router declines. Each pattern
20534 has associated with it a list of hosts and some other optional data, which may
20535 include a transport. The combination of a pattern and its data is called a
20536 &"routing rule"&. For patterns that do not have an associated transport, the
20537 generic &%transport%& option must specify a transport, unless the router is
20538 being used purely for verification (see &%verify_only%&).
20541 In the case of verification, matching the domain pattern is sufficient for the
20542 router to accept the address. When actually routing an address for delivery,
20543 an address that matches a domain pattern is queued for the associated
20544 transport. If the transport is not a local one, a host list must be associated
20545 with the pattern; IP addresses are looked up for the hosts, and these are
20546 passed to the transport along with the mail address. For local transports, a
20547 host list is optional. If it is present, it is passed in &$host$& as a single
20550 The list of routing rules can be provided as an inline string in
20551 &%route_list%&, or the data can be obtained by looking up the domain in a file
20552 or database by setting &%route_data%&. Only one of these settings may appear in
20553 any one instance of &(manualroute)&. The format of routing rules is described
20554 below, following the list of private options.
20557 .section "Private options for manualroute" "SECTprioptman"
20559 .cindex "options" "&(manualroute)& router"
20560 The private options for the &(manualroute)& router are as follows:
20562 .option host_all_ignored manualroute string defer
20563 See &%host_find_failed%&.
20565 .option host_find_failed manualroute string freeze
20566 This option controls what happens when &(manualroute)& tries to find an IP
20567 address for a host, and the host does not exist. The option can be set to one
20568 of the following values:
20577 The default (&"freeze"&) assumes that this state is a serious configuration
20578 error. The difference between &"pass"& and &"decline"& is that the former
20579 forces the address to be passed to the next router (or the router defined by
20582 overriding &%no_more%&, whereas the latter passes the address to the next
20583 router only if &%more%& is true.
20585 The value &"ignore"& causes Exim to completely ignore a host whose IP address
20586 cannot be found. If all the hosts in the list are ignored, the behaviour is
20587 controlled by the &%host_all_ignored%& option. This takes the same values
20588 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
20590 The &%host_find_failed%& option applies only to a definite &"does not exist"&
20591 state; if a host lookup gets a temporary error, delivery is deferred unless the
20592 generic &%pass_on_timeout%& option is set.
20595 .option hosts_randomize manualroute boolean false
20596 .cindex "randomized host list"
20597 .cindex "host" "list of; randomized"
20598 If this option is set, the order of the items in a host list in a routing rule
20599 is randomized each time the list is used, unless an option in the routing rule
20600 overrides (see below). Randomizing the order of a host list can be used to do
20601 crude load sharing. However, if more than one mail address is routed by the
20602 same router to the same host list, the host lists are considered to be the same
20603 (even though they may be randomized into different orders) for the purpose of
20604 deciding whether to batch the deliveries into a single SMTP transaction.
20606 When &%hosts_randomize%& is true, a host list may be split
20607 into groups whose order is separately randomized. This makes it possible to
20608 set up MX-like behaviour. The boundaries between groups are indicated by an
20609 item that is just &`+`& in the host list. For example:
20611 route_list = * host1:host2:host3:+:host4:host5
20613 The order of the first three hosts and the order of the last two hosts is
20614 randomized for each use, but the first three always end up before the last two.
20615 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
20616 randomized host list is passed to an &(smtp)& transport that also has
20617 &%hosts_randomize set%&, the list is not re-randomized.
20620 .option route_data manualroute string&!! unset
20621 If this option is set, it must expand to yield the data part of a routing rule.
20622 Typically, the expansion string includes a lookup based on the domain. For
20625 route_data = ${lookup{$domain}dbm{/etc/routes}}
20627 If the expansion is forced to fail, or the result is an empty string, the
20628 router declines. Other kinds of expansion failure cause delivery to be
20632 .option route_list manualroute "string list" unset
20633 This string is a list of routing rules, in the form defined below. Note that,
20634 unlike most string lists, the items are separated by semicolons. This is so
20635 that they may contain colon-separated host lists.
20638 .option same_domain_copy_routing manualroute boolean false
20639 .cindex "address" "copying routing"
20640 Addresses with the same domain are normally routed by the &(manualroute)&
20641 router to the same list of hosts. However, this cannot be presumed, because the
20642 router options and preconditions may refer to the local part of the address. By
20643 default, therefore, Exim routes each address in a message independently. DNS
20644 servers run caches, so repeated DNS lookups are not normally expensive, and in
20645 any case, personal messages rarely have more than a few recipients.
20647 If you are running mailing lists with large numbers of subscribers at the same
20648 domain, and you are using a &(manualroute)& router which is independent of the
20649 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20650 lookups for identical domains in one message. In this case, when
20651 &(manualroute)& routes an address to a remote transport, any other unrouted
20652 addresses in the message that have the same domain are automatically given the
20653 same routing without processing them independently. However, this is only done
20654 if &%headers_add%& and &%headers_remove%& are unset.
20659 .section "Routing rules in route_list" "SECID120"
20660 The value of &%route_list%& is a string consisting of a sequence of routing
20661 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
20662 entered as two semicolons. Alternatively, the list separator can be changed as
20663 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
20664 Empty rules are ignored. The format of each rule is
20666 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
20668 The following example contains two rules, each with a simple domain pattern and
20672 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
20673 thes.ref.example mail-3.ref.example:mail-4.ref.example
20675 The three parts of a rule are separated by white space. The pattern and the
20676 list of hosts can be enclosed in quotes if necessary, and if they are, the
20677 usual quoting rules apply. Each rule in a &%route_list%& must start with a
20678 single domain pattern, which is the only mandatory item in the rule. The
20679 pattern is in the same format as one item in a domain list (see section
20680 &<<SECTdomainlist>>&),
20681 except that it may not be the name of an interpolated file.
20682 That is, it may be wildcarded, or a regular expression, or a file or database
20683 lookup (with semicolons doubled, because of the use of semicolon as a separator
20684 in a &%route_list%&).
20686 The rules in &%route_list%& are searched in order until one of the patterns
20687 matches the domain that is being routed. The list of hosts and then options are
20688 then used as described below. If there is no match, the router declines. When
20689 &%route_list%& is set, &%route_data%& must not be set.
20693 .section "Routing rules in route_data" "SECID121"
20694 The use of &%route_list%& is convenient when there are only a small number of
20695 routing rules. For larger numbers, it is easier to use a file or database to
20696 hold the routing information, and use the &%route_data%& option instead.
20697 The value of &%route_data%& is a list of hosts, followed by (optional) options.
20698 Most commonly, &%route_data%& is set as a string that contains an
20699 expansion lookup. For example, suppose we place two routing rules in a file
20702 dict.ref.example: mail-1.ref.example:mail-2.ref.example
20703 thes.ref.example: mail-3.ref.example:mail-4.ref.example
20705 This data can be accessed by setting
20707 route_data = ${lookup{$domain}lsearch{/the/file/name}}
20709 Failure of the lookup results in an empty string, causing the router to
20710 decline. However, you do not have to use a lookup in &%route_data%&. The only
20711 requirement is that the result of expanding the string is a list of hosts,
20712 possibly followed by options, separated by white space. The list of hosts must
20713 be enclosed in quotes if it contains white space.
20718 .section "Format of the list of hosts" "SECID122"
20719 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
20720 always separately expanded before use. If the expansion fails, the router
20721 declines. The result of the expansion must be a colon-separated list of names
20722 and/or IP addresses, optionally also including ports.
20723 If the list is written with spaces, it must be protected with quotes.
20724 The format of each item
20725 in the list is described in the next section. The list separator can be changed
20726 as described in section &<<SECTlistsepchange>>&.
20728 If the list of hosts was obtained from a &%route_list%& item, the following
20729 variables are set during its expansion:
20732 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
20733 If the domain was matched against a regular expression, the numeric variables
20734 &$1$&, &$2$&, etc. may be set. For example:
20736 route_list = ^domain(\d+) host-$1.text.example
20739 &$0$& is always set to the entire domain.
20741 &$1$& is also set when partial matching is done in a file lookup.
20744 .vindex "&$value$&"
20745 If the pattern that matched the domain was a lookup item, the data that was
20746 looked up is available in the expansion variable &$value$&. For example:
20748 route_list = lsearch;;/some/file.routes $value
20752 Note the doubling of the semicolon in the pattern that is necessary because
20753 semicolon is the default route list separator.
20757 .section "Format of one host item" "SECTformatonehostitem"
20758 Each item in the list of hosts can be either a host name or an IP address,
20759 optionally with an attached port number, or it can be a single "+"
20760 (see &%hosts_randomize%&).
20761 When no port is given, an IP address
20762 is not enclosed in brackets. When a port is specified, it overrides the port
20763 specification on the transport. The port is separated from the name or address
20764 by a colon. This leads to some complications:
20767 Because colon is the default separator for the list of hosts, either
20768 the colon that specifies a port must be doubled, or the list separator must
20769 be changed. The following two examples have the same effect:
20771 route_list = * "host1.tld::1225 : host2.tld::1226"
20772 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
20775 When IPv6 addresses are involved, it gets worse, because they contain
20776 colons of their own. To make this case easier, it is permitted to
20777 enclose an IP address (either v4 or v6) in square brackets if a port
20778 number follows. For example:
20780 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
20784 .section "How the list of hosts is used" "SECThostshowused"
20785 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
20786 the hosts is tried, in the order specified, when carrying out the SMTP
20787 delivery. However, the order can be changed by setting the &%hosts_randomize%&
20788 option, either on the router (see section &<<SECTprioptman>>& above), or on the
20791 Hosts may be listed by name or by IP address. An unadorned name in the list of
20792 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
20793 interpreted as an indirection to a sublist of hosts obtained by looking up MX
20794 records in the DNS. For example:
20796 route_list = * x.y.z:p.q.r/MX:e.f.g
20798 If this feature is used with a port specifier, the port must come last. For
20801 route_list = * dom1.tld/mx::1225
20803 If the &%hosts_randomize%& option is set, the order of the items in the list is
20804 randomized before any lookups are done. Exim then scans the list; for any name
20805 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
20806 be an interface on the local host and the item is not the first in the list,
20807 Exim discards it and any subsequent items. If it is the first item, what
20808 happens is controlled by the
20809 .oindex "&%self%&" "in &(manualroute)& router"
20810 &%self%& option of the router.
20812 A name on the list that is followed by &`/MX`& is replaced with the list of
20813 hosts obtained by looking up MX records for the name. This is always a DNS
20814 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
20815 below) are not relevant here. The order of these hosts is determined by the
20816 preference values in the MX records, according to the usual rules. Because
20817 randomizing happens before the MX lookup, it does not affect the order that is
20818 defined by MX preferences.
20820 If the local host is present in the sublist obtained from MX records, but is
20821 not the most preferred host in that list, it and any equally or less
20822 preferred hosts are removed before the sublist is inserted into the main list.
20824 If the local host is the most preferred host in the MX list, what happens
20825 depends on where in the original list of hosts the &`/MX`& item appears. If it
20826 is not the first item (that is, there are previous hosts in the main list),
20827 Exim discards this name and any subsequent items in the main list.
20829 If the MX item is first in the list of hosts, and the local host is the
20830 most preferred host, what happens is controlled by the &%self%& option of the
20833 DNS failures when lookup up the MX records are treated in the same way as DNS
20834 failures when looking up IP addresses: &%pass_on_timeout%& and
20835 &%host_find_failed%& are used when relevant.
20837 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
20838 whether obtained from an MX lookup or not.
20842 .section "How the options are used" "SECThowoptused"
20843 The options are a sequence of words, space-separated.
20844 One of the words can be the name of a transport; this overrides the
20845 &%transport%& option on the router for this particular routing rule only. The
20846 other words (if present) control randomization of the list of hosts on a
20847 per-rule basis, and how the IP addresses of the hosts are to be found when
20848 routing to a remote transport. These options are as follows:
20851 &%randomize%&: randomize the order of the hosts in this list, overriding the
20852 setting of &%hosts_randomize%& for this routing rule only.
20854 &%no_randomize%&: do not randomize the order of the hosts in this list,
20855 overriding the setting of &%hosts_randomize%& for this routing rule only.
20857 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
20858 find IP addresses. This function may ultimately cause a DNS lookup, but it may
20859 also look in &_/etc/hosts_& or other sources of information.
20861 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
20862 no address records are found. If there is a temporary DNS error (such as a
20863 timeout), delivery is deferred.
20865 &%ipv4_only%&: in direct DNS lookups, look up only A records.
20867 &%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
20872 route_list = domain1 host1:host2:host3 randomize bydns;\
20873 domain2 host4:host5
20875 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
20876 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
20877 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
20878 or &[gethostbyname()]&, and the result of the lookup is the result of that
20881 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
20882 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
20883 instead of TRY_AGAIN. That is why the default action is to try a DNS
20884 lookup first. Only if that gives a definite &"no such host"& is the local
20887 &*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
20888 inadvertent constraint that a transport name as an option had to be the last
20893 If no IP address for a host can be found, what happens is controlled by the
20894 &%host_find_failed%& option.
20897 When an address is routed to a local transport, IP addresses are not looked up.
20898 The host list is passed to the transport in the &$host$& variable.
20902 .section "Manualroute examples" "SECID123"
20903 In some of the examples that follow, the presence of the &%remote_smtp%&
20904 transport, as defined in the default configuration file, is assumed:
20907 .cindex "smart host" "example router"
20908 The &(manualroute)& router can be used to forward all external mail to a
20909 &'smart host'&. If you have set up, in the main part of the configuration, a
20910 named domain list that contains your local domains, for example:
20912 domainlist local_domains = my.domain.example
20914 You can arrange for all other domains to be routed to a smart host by making
20915 your first router something like this:
20918 driver = manualroute
20919 domains = !+local_domains
20920 transport = remote_smtp
20921 route_list = * smarthost.ref.example
20923 This causes all non-local addresses to be sent to the single host
20924 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
20925 they are tried in order
20926 (but you can use &%hosts_randomize%& to vary the order each time).
20927 Another way of configuring the same thing is this:
20930 driver = manualroute
20931 transport = remote_smtp
20932 route_list = !+local_domains smarthost.ref.example
20934 There is no difference in behaviour between these two routers as they stand.
20935 However, they behave differently if &%no_more%& is added to them. In the first
20936 example, the router is skipped if the domain does not match the &%domains%&
20937 precondition; the following router is always tried. If the router runs, it
20938 always matches the domain and so can never decline. Therefore, &%no_more%&
20939 would have no effect. In the second case, the router is never skipped; it
20940 always runs. However, if it doesn't match the domain, it declines. In this case
20941 &%no_more%& would prevent subsequent routers from running.
20944 .cindex "mail hub example"
20945 A &'mail hub'& is a host which receives mail for a number of domains via MX
20946 records in the DNS and delivers it via its own private routing mechanism. Often
20947 the final destinations are behind a firewall, with the mail hub being the one
20948 machine that can connect to machines both inside and outside the firewall. The
20949 &(manualroute)& router is usually used on a mail hub to route incoming messages
20950 to the correct hosts. For a small number of domains, the routing can be inline,
20951 using the &%route_list%& option, but for a larger number a file or database
20952 lookup is easier to manage.
20954 If the domain names are in fact the names of the machines to which the mail is
20955 to be sent by the mail hub, the configuration can be quite simple. For
20959 driver = manualroute
20960 transport = remote_smtp
20961 route_list = *.rhodes.tvs.example $domain
20963 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
20964 whose names are the same as the mail domains. A similar approach can be taken
20965 if the host name can be obtained from the domain name by a string manipulation
20966 that the expansion facilities can handle. Otherwise, a lookup based on the
20967 domain can be used to find the host:
20970 driver = manualroute
20971 transport = remote_smtp
20972 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
20974 The result of the lookup must be the name or IP address of the host (or
20975 hosts) to which the address is to be routed. If the lookup fails, the route
20976 data is empty, causing the router to decline. The address then passes to the
20980 .cindex "batched SMTP output example"
20981 .cindex "SMTP" "batched outgoing; example"
20982 You can use &(manualroute)& to deliver messages to pipes or files in batched
20983 SMTP format for onward transportation by some other means. This is one way of
20984 storing mail for a dial-up host when it is not connected. The route list entry
20985 can be as simple as a single domain name in a configuration like this:
20988 driver = manualroute
20989 transport = batchsmtp_appendfile
20990 route_list = saved.domain.example
20992 though often a pattern is used to pick up more than one domain. If there are
20993 several domains or groups of domains with different transport requirements,
20994 different transports can be listed in the routing information:
20997 driver = manualroute
20999 *.saved.domain1.example $domain batch_appendfile; \
21000 *.saved.domain2.example \
21001 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
21004 .vindex "&$domain$&"
21006 The first of these just passes the domain in the &$host$& variable, which
21007 doesn't achieve much (since it is also in &$domain$&), but the second does a
21008 file lookup to find a value to pass, causing the router to decline to handle
21009 the address if the lookup fails.
21012 .cindex "UUCP" "example of router for"
21013 Routing mail directly to UUCP software is a specific case of the use of
21014 &(manualroute)& in a gateway to another mail environment. This is an example of
21015 one way it can be done:
21021 command = /usr/local/bin/uux -r - \
21022 ${substr_-5:$host}!rmail ${local_part}
21023 return_fail_output = true
21028 driver = manualroute
21030 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
21032 The file &_/usr/local/exim/uucphosts_& contains entries like
21034 darksite.ethereal.example: darksite.UUCP
21036 It can be set up more simply without adding and removing &".UUCP"& but this way
21037 makes clear the distinction between the domain name
21038 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
21040 .ecindex IIDmanrou1
21041 .ecindex IIDmanrou2
21050 . ////////////////////////////////////////////////////////////////////////////
21051 . ////////////////////////////////////////////////////////////////////////////
21053 .chapter "The queryprogram router" "CHAPdriverlast"
21054 .scindex IIDquerou1 "&(queryprogram)& router"
21055 .scindex IIDquerou2 "routers" "&(queryprogram)&"
21056 .cindex "routing" "by external program"
21057 The &(queryprogram)& router routes an address by running an external command
21058 and acting on its output. This is an expensive way to route, and is intended
21059 mainly for use in lightly-loaded systems, or for performing experiments.
21060 However, if it is possible to use the precondition options (&%domains%&,
21061 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
21062 be used in special cases, even on a busy host. There are the following private
21064 .cindex "options" "&(queryprogram)& router"
21066 .option command queryprogram string&!! unset
21067 This option must be set. It specifies the command that is to be run. The
21068 command is split up into a command name and arguments, and then each is
21069 expanded separately (exactly as for a &(pipe)& transport, described in chapter
21070 &<<CHAPpipetransport>>&).
21073 .option command_group queryprogram string unset
21074 .cindex "gid (group id)" "in &(queryprogram)& router"
21075 This option specifies a gid to be set when running the command while routing an
21076 address for deliver. It must be set if &%command_user%& specifies a numerical
21077 uid. If it begins with a digit, it is interpreted as the numerical value of the
21078 gid. Otherwise it is looked up using &[getgrnam()]&.
21081 .option command_user queryprogram string unset
21082 .cindex "uid (user id)" "for &(queryprogram)&"
21083 This option must be set. It specifies the uid which is set when running the
21084 command while routing an address for delivery. If the value begins with a digit,
21085 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
21086 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
21087 not set, a value for the gid also.
21089 &*Warning:*& Changing uid and gid is possible only when Exim is running as
21090 root, which it does during a normal delivery in a conventional configuration.
21091 However, when an address is being verified during message reception, Exim is
21092 usually running as the Exim user, not as root. If the &(queryprogram)& router
21093 is called from a non-root process, Exim cannot change uid or gid before running
21094 the command. In this circumstance the command runs under the current uid and
21098 .option current_directory queryprogram string /
21099 This option specifies an absolute path which is made the current directory
21100 before running the command.
21103 .option timeout queryprogram time 1h
21104 If the command does not complete within the timeout period, its process group
21105 is killed and the message is frozen. A value of zero time specifies no
21109 The standard output of the command is connected to a pipe, which is read when
21110 the command terminates. It should consist of a single line of output,
21111 containing up to five fields, separated by white space. The maximum length of
21112 the line is 1023 characters. Longer lines are silently truncated. The first
21113 field is one of the following words (case-insensitive):
21116 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
21119 &'Decline'&: the router declines; pass the address to the next router, unless
21120 &%no_more%& is set.
21122 &'Fail'&: routing failed; do not pass the address to any more routers. Any
21123 subsequent text on the line is an error message. If the router is run as part
21124 of address verification during an incoming SMTP message, the message is
21125 included in the SMTP response.
21127 &'Defer'&: routing could not be completed at this time; try again later. Any
21128 subsequent text on the line is an error message which is logged. It is not
21129 included in any SMTP response.
21131 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
21133 &'Pass'&: pass the address to the next router (or the router specified by
21134 &%pass_router%&), overriding &%no_more%&.
21136 &'Redirect'&: the message is redirected. The remainder of the line is a list of
21137 new addresses, which are routed independently, starting with the first router,
21138 or the router specified by &%redirect_router%&, if set.
21141 When the first word is &'accept'&, the remainder of the line consists of a
21142 number of keyed data values, as follows (split into two lines here, to fit on
21145 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
21146 LOOKUP=byname|bydns DATA=<text>
21148 The data items can be given in any order, and all are optional. If no transport
21149 is included, the transport specified by the generic &%transport%& option is
21150 used. The list of hosts and the lookup type are needed only if the transport is
21151 an &(smtp)& transport that does not itself supply a list of hosts.
21153 The format of the list of hosts is the same as for the &(manualroute)& router.
21154 As well as host names and IP addresses with optional port numbers, as described
21155 in section &<<SECTformatonehostitem>>&, it may contain names followed by
21156 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
21157 (see section &<<SECThostshowused>>&).
21159 If the lookup type is not specified, Exim behaves as follows when trying to
21160 find an IP address for each host: First, a DNS lookup is done. If this yields
21161 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
21162 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
21163 result of the lookup is the result of that call.
21165 .vindex "&$address_data$&"
21166 If the DATA field is set, its value is placed in the &$address_data$&
21167 variable. For example, this return line
21169 accept hosts=x1.y.example:x2.y.example data="rule1"
21171 routes the address to the default transport, passing a list of two hosts. When
21172 the transport runs, the string &"rule1"& is in &$address_data$&.
21173 .ecindex IIDquerou1
21174 .ecindex IIDquerou2
21179 . ////////////////////////////////////////////////////////////////////////////
21180 . ////////////////////////////////////////////////////////////////////////////
21182 .chapter "The redirect router" "CHAPredirect"
21183 .scindex IIDredrou1 "&(redirect)& router"
21184 .scindex IIDredrou2 "routers" "&(redirect)&"
21185 .cindex "alias file" "in a &(redirect)& router"
21186 .cindex "address redirection" "&(redirect)& router"
21187 The &(redirect)& router handles several kinds of address redirection. Its most
21188 common uses are for resolving local part aliases from a central alias file
21189 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
21190 files, but it has many other potential uses. The incoming address can be
21191 redirected in several different ways:
21194 It can be replaced by one or more new addresses which are themselves routed
21197 It can be routed to be delivered to a given file or directory.
21199 It can be routed to be delivered to a specified pipe command.
21201 It can cause an automatic reply to be generated.
21203 It can be forced to fail, optionally with a custom error message.
21205 It can be temporarily deferred, optionally with a custom message.
21207 It can be discarded.
21210 The generic &%transport%& option must not be set for &(redirect)& routers.
21211 However, there are some private options which define transports for delivery to
21212 files and pipes, and for generating autoreplies. See the &%file_transport%&,
21213 &%pipe_transport%& and &%reply_transport%& descriptions below.
21215 If success DSNs have been requested
21216 .cindex "DSN" "success"
21217 .cindex "Delivery Status Notification" "success"
21218 redirection triggers one and the DSN options are not passed any further.
21222 .section "Redirection data" "SECID124"
21223 The router operates by interpreting a text string which it obtains either by
21224 expanding the contents of the &%data%& option, or by reading the entire
21225 contents of a file whose name is given in the &%file%& option. These two
21226 options are mutually exclusive. The first is commonly used for handling system
21227 aliases, in a configuration like this:
21231 data = ${lookup{$local_part}lsearch{/etc/aliases}}
21233 If the lookup fails, the expanded string in this example is empty. When the
21234 expansion of &%data%& results in an empty string, the router declines. A forced
21235 expansion failure also causes the router to decline; other expansion failures
21236 cause delivery to be deferred.
21238 A configuration using &%file%& is commonly used for handling users'
21239 &_.forward_& files, like this:
21244 file = $home/.forward
21247 If the file does not exist, or causes no action to be taken (for example, it is
21248 empty or consists only of comments), the router declines. &*Warning*&: This
21249 is not the case when the file contains syntactically valid items that happen to
21250 yield empty addresses, for example, items containing only RFC 2822 address
21253 .cindex "tainted data" "in filenames"
21254 .cindex redirect "tainted data"
21255 Tainted data may not be used for a filename.
21257 &*Warning*&: It is unwise to use &$local_part$& or &$domain$&
21258 directly for redirection,
21259 as they are provided by a potential attacker.
21260 In the examples above, &$local_part$& is used for looking up data held locally
21261 on the system, and not used directly (the second example derives &$home$& via
21262 the passsword file or database, using &$local_part$&).
21266 .section "Forward files and address verification" "SECID125"
21267 .cindex "address redirection" "while verifying"
21268 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
21269 &_.forward_& files, as in the example above. There are two reasons for this:
21272 When Exim is receiving an incoming SMTP message from a remote host, it is
21273 running under the Exim uid, not as root. Exim is unable to change uid to read
21274 the file as the user, and it may not be able to read it as the Exim user. So in
21275 practice the router may not be able to operate.
21277 However, even when the router can operate, the existence of a &_.forward_& file
21278 is unimportant when verifying an address. What should be checked is whether the
21279 local part is a valid user name or not. Cutting out the redirection processing
21280 saves some resources.
21288 .section "Interpreting redirection data" "SECID126"
21289 .cindex "Sieve filter" "specifying in redirection data"
21290 .cindex "filter" "specifying in redirection data"
21291 The contents of the data string, whether obtained from &%data%& or &%file%&,
21292 can be interpreted in two different ways:
21295 If the &%allow_filter%& option is set true, and the data begins with the text
21296 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
21297 &'filtering'& instructions in the form of an Exim or Sieve filter file,
21298 respectively. Details of the syntax and semantics of filter files are described
21299 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
21300 document is intended for use by end users.
21302 Otherwise, the data must be a comma-separated list of redirection items, as
21303 described in the next section.
21306 When a message is redirected to a file (a &"mail folder"&), the filename given
21307 in a non-filter redirection list must always be an absolute path. A filter may
21308 generate a relative path &-- how this is handled depends on the transport's
21309 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
21310 for the &(appendfile)& transport.
21314 .section "Items in a non-filter redirection list" "SECTitenonfilred"
21315 .cindex "address redirection" "non-filter list items"
21316 When the redirection data is not an Exim or Sieve filter, for example, if it
21317 comes from a conventional alias or forward file, it consists of a list of
21318 addresses, filenames, pipe commands, or certain special items (see section
21319 &<<SECTspecitredli>>& below). The special items can be individually enabled or
21320 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
21321 depending on their default values. The items in the list are separated by
21322 commas or newlines.
21323 If a comma is required in an item, the entire item must be enclosed in double
21326 Lines starting with a # character are comments, and are ignored, and # may
21327 also appear following a comma, in which case everything between the # and the
21328 next newline character is ignored.
21330 If an item is entirely enclosed in double quotes, these are removed. Otherwise
21331 double quotes are retained because some forms of mail address require their use
21332 (but never to enclose the entire address). In the following description,
21333 &"item"& refers to what remains after any surrounding double quotes have been
21336 .vindex "&$local_part$&"
21337 &*Warning*&: If you use an Exim expansion to construct a redirection address,
21338 and the expansion contains a reference to &$local_part$&, you should make use
21339 of the &%quote_local_part%& expansion operator, in case the local part contains
21340 special characters. For example, to redirect all mail for the domain
21341 &'obsolete.example'&, retaining the existing local part, you could use this
21344 data = ${quote_local_part:$local_part}@newdomain.example
21348 .section "Redirecting to a local mailbox" "SECTredlocmai"
21349 .cindex "routing" "loops in"
21350 .cindex "loop" "while routing, avoidance of"
21351 .cindex "address redirection" "to local mailbox"
21352 A redirection item may safely be the same as the address currently under
21353 consideration. This does not cause a routing loop, because a router is
21354 automatically skipped if any ancestor of the address that is being processed
21355 is the same as the current address and was processed by the current router.
21356 Such an address is therefore passed to the following routers, so it is handled
21357 as if there were no redirection. When making this loop-avoidance test, the
21358 complete local part, including any prefix or suffix, is used.
21360 .cindex "address redirection" "local part without domain"
21361 Specifying the same local part without a domain is a common usage in personal
21362 filter files when the user wants to have messages delivered to the local
21363 mailbox and also forwarded elsewhere. For example, the user whose login is
21364 &'cleo'& might have a &_.forward_& file containing this:
21366 cleo, cleopatra@egypt.example
21368 .cindex "backslash in alias file"
21369 .cindex "alias file" "backslash in"
21370 For compatibility with other MTAs, such unqualified local parts may be
21371 preceded by &"\"&, but this is not a requirement for loop prevention. However,
21372 it does make a difference if more than one domain is being handled
21375 If an item begins with &"\"& and the rest of the item parses as a valid RFC
21376 2822 address that does not include a domain, the item is qualified using the
21377 domain of the incoming address. In the absence of a leading &"\"&, unqualified
21378 addresses are qualified using the value in &%qualify_recipient%&, but you can
21379 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
21381 Care must be taken if there are alias names for local users.
21382 Consider an MTA handling a single local domain where the system alias file
21387 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
21388 messages in the local mailbox, and also forward copies elsewhere. He creates
21391 Sam.Reman, spqr@reme.elsewhere.example
21393 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
21394 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
21395 second time round, because it has previously routed it,
21396 and the following routers presumably cannot handle the alias. The forward file
21397 should really contain
21399 spqr, spqr@reme.elsewhere.example
21401 but because this is such a common error, the &%check_ancestor%& option (see
21402 below) exists to provide a way to get round it. This is normally set on a
21403 &(redirect)& router that is handling users' &_.forward_& files.
21407 .section "Special items in redirection lists" "SECTspecitredli"
21408 In addition to addresses, the following types of item may appear in redirection
21409 lists (that is, in non-filter redirection data):
21412 .cindex "pipe" "in redirection list"
21413 .cindex "address redirection" "to pipe"
21414 An item is treated as a pipe command if it begins with &"|"& and does not parse
21415 as a valid RFC 2822 address that includes a domain. A transport for running the
21416 command must be specified by the &%pipe_transport%& option.
21417 Normally, either the router or the transport specifies a user and a group under
21418 which to run the delivery. The default is to use the Exim user and group.
21420 Single or double quotes can be used for enclosing the individual arguments of
21421 the pipe command; no interpretation of escapes is done for single quotes. If
21422 the command contains a comma character, it is necessary to put the whole item
21423 in double quotes, for example:
21425 "|/some/command ready,steady,go"
21427 since items in redirection lists are terminated by commas. Do not, however,
21428 quote just the command. An item such as
21430 |"/some/command ready,steady,go"
21432 is interpreted as a pipe with a rather strange command name, and no arguments.
21434 Note that the above example assumes that the text comes from a lookup source
21435 of some sort, so that the quotes are part of the data. If composing a
21436 redirect router with a &%data%& option directly specifying this command, the
21437 quotes will be used by the configuration parser to define the extent of one
21438 string, but will not be passed down into the redirect router itself. There
21439 are two main approaches to get around this: escape quotes to be part of the
21440 data itself, or avoid using this mechanism and instead create a custom
21441 transport with the &%command%& option set and reference that transport from
21442 an &%accept%& router.
21445 .cindex "file" "in redirection list"
21446 .cindex "address redirection" "to file"
21447 An item is interpreted as a path name if it begins with &"/"& and does not
21448 parse as a valid RFC 2822 address that includes a domain. For example,
21450 /home/world/minbari
21452 is treated as a filename, but
21454 /s=molari/o=babylon/@x400gate.way
21456 is treated as an address. For a filename, a transport must be specified using
21457 the &%file_transport%& option. However, if the generated path name ends with a
21458 forward slash character, it is interpreted as a directory name rather than a
21459 filename, and &%directory_transport%& is used instead.
21461 Normally, either the router or the transport specifies a user and a group under
21462 which to run the delivery. The default is to use the Exim user and group.
21464 .cindex "&_/dev/null_&"
21465 However, if a redirection item is the path &_/dev/null_&, delivery to it is
21466 bypassed at a high level, and the log entry shows &"**bypassed**"&
21467 instead of a transport name. In this case the user and group are not used.
21470 .cindex "included address list"
21471 .cindex "address redirection" "included external list"
21472 If an item is of the form
21474 :include:<path name>
21476 a list of further items is taken from the given file and included at that
21477 point. &*Note*&: Such a file can not be a filter file; it is just an
21478 out-of-line addition to the list. The items in the included list are separated
21479 by commas or newlines and are not subject to expansion. If this is the first
21480 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
21481 the alias name. This example is incorrect:
21483 list1 :include:/opt/lists/list1
21485 It must be given as
21487 list1: :include:/opt/lists/list1
21489 .cindex "tainted data" "in filenames"
21490 .cindex redirect "tainted data"
21491 Tainted data may not be used for a filename.
21493 .cindex "address redirection" "to black hole"
21494 .cindex "delivery" "discard"
21495 .cindex "delivery" "blackhole"
21496 .cindex "black hole"
21497 .cindex "abandoning mail"
21498 Sometimes you want to throw away mail to a particular local part. Making the
21499 &%data%& option expand to an empty string does not work, because that causes
21500 the router to decline. Instead, the alias item
21504 can be used. It does what its name implies. No delivery is
21505 done, and no error message is generated. This has the same effect as specifying
21506 &_/dev/null_& as a destination, but it can be independently disabled.
21508 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
21509 delivery is done for the original local part, even if other redirection items
21510 are present. If you are generating a multi-item list (for example, by reading a
21511 database) and need the ability to provide a no-op item, you must use
21515 .cindex "delivery" "forcing failure"
21516 .cindex "delivery" "forcing deferral"
21517 .cindex "failing delivery" "forcing"
21518 .cindex "deferred delivery, forcing"
21519 .cindex "customizing" "failure message"
21520 An attempt to deliver a particular address can be deferred or forced to fail by
21521 redirection items of the form
21526 respectively. When a redirection list contains such an item, it applies
21527 to the entire redirection; any other items in the list are ignored. Any
21528 text following &':fail:'& or &':defer:'& is placed in the error text
21529 associated with the failure. For example, an alias file might contain:
21531 X.Employee: :fail: Gone away, no forwarding address
21533 In the case of an address that is being verified from an ACL or as the subject
21535 .cindex "VRFY" "error text, display of"
21536 VRFY command, the text is included in the SMTP error response by
21538 .cindex "EXPN" "error text, display of"
21539 The text is not included in the response to an EXPN command. In non-SMTP cases
21540 the text is included in the error message that Exim generates.
21542 .cindex "SMTP" "error codes"
21543 By default for verify, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
21544 &':fail:'&. However, if the message starts with three digits followed by a
21545 space, optionally followed by an extended code of the form &'n.n.n'&, also
21546 followed by a space, and the very first digit is the same as the default error
21547 code, the code from the message is used instead. If the very first digit is
21548 incorrect, a panic error is logged, and the default code is used. You can
21549 suppress the use of the supplied code in a redirect router by setting the
21550 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
21553 .vindex "&$acl_verify_message$&"
21554 In an ACL, an explicitly provided message overrides the default, but the
21555 default message is available in the variable &$acl_verify_message$& and can
21556 therefore be included in a custom message if this is desired.
21558 Normally the error text is the rest of the redirection list &-- a comma does
21559 not terminate it &-- but a newline does act as a terminator. Newlines are not
21560 normally present in alias expansions. In &(lsearch)& lookups they are removed
21561 as part of the continuation process, but they may exist in other kinds of
21562 lookup and in &':include:'& files.
21564 During routing for message delivery (as opposed to verification), a redirection
21565 containing &':fail:'& causes an immediate failure of the incoming address,
21566 whereas &':defer:'& causes the message to remain in the queue so that a
21567 subsequent delivery attempt can happen at a later time. If an address is
21568 deferred for too long, it will ultimately fail, because the normal retry
21572 .cindex "alias file" "exception to default"
21573 Sometimes it is useful to use a single-key search type with a default (see
21574 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
21575 for exceptions to the default. These can be handled by aliasing them to
21576 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
21577 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
21578 results in an empty redirection list has the same effect.
21582 .section "Duplicate addresses" "SECTdupaddr"
21583 .cindex "duplicate addresses"
21584 .cindex "address duplicate, discarding"
21585 .cindex "pipe" "duplicated"
21586 Exim removes duplicate addresses from the list to which it is delivering, so as
21587 to deliver just one copy to each address. This does not apply to deliveries
21588 routed to pipes by different immediate parent addresses, but an indirect
21589 aliasing scheme of the type
21591 pipe: |/some/command $local_part
21595 does not work with a message that is addressed to both local parts, because
21596 when the second is aliased to the intermediate local part &"pipe"& it gets
21597 discarded as being the same as a previously handled address. However, a scheme
21600 localpart1: |/some/command $local_part
21601 localpart2: |/some/command $local_part
21603 does result in two different pipe deliveries, because the immediate parents of
21604 the pipes are distinct.
21608 .section "Repeated redirection expansion" "SECID128"
21609 .cindex "repeated redirection expansion"
21610 .cindex "address redirection" "repeated for each delivery attempt"
21611 When a message cannot be delivered to all of its recipients immediately,
21612 leading to two or more delivery attempts, redirection expansion is carried out
21613 afresh each time for those addresses whose children were not all previously
21614 delivered. If redirection is being used as a mailing list, this can lead to new
21615 members of the list receiving copies of old messages. The &%one_time%& option
21616 can be used to avoid this.
21619 .section "Errors in redirection lists" "SECID129"
21620 .cindex "address redirection" "errors"
21621 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
21622 error is skipped, and an entry is written to the main log. This may be useful
21623 for mailing lists that are automatically managed. Otherwise, if an error is
21624 detected while generating the list of new addresses, the original address is
21625 deferred. See also &%syntax_errors_to%&.
21629 .section "Private options for the redirect router" "SECID130"
21631 .cindex "options" "&(redirect)& router"
21632 The private options for the &(redirect)& router are as follows:
21635 .option allow_defer redirect boolean false
21636 Setting this option allows the use of &':defer:'& in non-filter redirection
21637 data, or the &%defer%& command in an Exim filter file.
21640 .option allow_fail redirect boolean false
21641 .cindex "failing delivery" "from filter"
21642 If this option is true, the &':fail:'& item can be used in a redirection list,
21643 and the &%fail%& command may be used in an Exim filter file.
21646 .option allow_filter redirect boolean false
21647 .cindex "filter" "enabling use of"
21648 .cindex "Sieve filter" "enabling use of"
21649 Setting this option allows Exim to interpret redirection data that starts with
21650 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
21651 are some features of Exim filter files that some administrators may wish to
21652 lock out; see the &%forbid_filter_%&&'xxx'& options below.
21654 It is also possible to lock out Exim filters or Sieve filters while allowing
21655 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
21658 The filter is run using the uid and gid set by the generic &%user%& and
21659 &%group%& options. These take their defaults from the password data if
21660 &%check_local_user%& is set, so in the normal case of users' personal filter
21661 files, the filter is run as the relevant user. When &%allow_filter%& is set
21662 true, Exim insists that either &%check_local_user%& or &%user%& is set.
21666 .option allow_freeze redirect boolean false
21667 .cindex "freezing messages" "allowing in filter"
21668 Setting this option allows the use of the &%freeze%& command in an Exim filter.
21669 This command is more normally encountered in system filters, and is disabled by
21670 default for redirection filters because it isn't something you usually want to
21671 let ordinary users do.
21675 .option check_ancestor redirect boolean false
21676 This option is concerned with handling generated addresses that are the same
21677 as some address in the list of redirection ancestors of the current address.
21678 Although it is turned off by default in the code, it is set in the default
21679 configuration file for handling users' &_.forward_& files. It is recommended
21680 for this use of the &(redirect)& router.
21682 When &%check_ancestor%& is set, if a generated address (including the domain)
21683 is the same as any ancestor of the current address, it is replaced by a copy of
21684 the current address. This helps in the case where local part A is aliased to B,
21685 and B has a &_.forward_& file pointing back to A. For example, within a single
21686 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
21687 &_&~jb/.forward_& contains:
21689 \Joe.Bloggs, <other item(s)>
21691 Without the &%check_ancestor%& setting, either local part (&"jb"& or
21692 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
21693 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
21694 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
21695 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
21696 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
21697 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
21698 original address. See also the &%repeat_use%& option below.
21701 .option check_group redirect boolean "see below"
21702 When the &%file%& option is used, the group owner of the file is checked only
21703 when this option is set. The permitted groups are those listed in the
21704 &%owngroups%& option, together with the user's default group if
21705 &%check_local_user%& is set. If the file has the wrong group, routing is
21706 deferred. The default setting for this option is true if &%check_local_user%&
21707 is set and the &%modemask%& option permits the group write bit, or if the
21708 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
21712 .option check_owner redirect boolean "see below"
21713 When the &%file%& option is used, the owner of the file is checked only when
21714 this option is set. If &%check_local_user%& is set, the local user is
21715 permitted; otherwise the owner must be one of those listed in the &%owners%&
21716 option. The default value for this option is true if &%check_local_user%& or
21717 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
21720 .option data redirect string&!! unset
21721 This option is mutually exclusive with &%file%&. One or other of them must be
21722 set, but not both. The contents of &%data%& are expanded, and then used as the
21723 list of forwarding items, or as a set of filtering instructions. If the
21724 expansion is forced to fail, or the result is an empty string or a string that
21725 has no effect (consists entirely of comments), the router declines.
21727 When filtering instructions are used, the string must begin with &"#Exim
21728 filter"&, and all comments in the string, including this initial one, must be
21729 terminated with newline characters. For example:
21731 data = #Exim filter\n\
21732 if $h_to: contains Exim then save $home/mail/exim endif
21734 If you are reading the data from a database where newlines cannot be included,
21735 you can use the &${sg}$& expansion item to turn the escape string of your
21736 choice into a newline.
21739 .option directory_transport redirect string&!! unset
21740 A &(redirect)& router sets up a direct delivery to a directory when a path name
21741 ending with a slash is specified as a new &"address"&. The transport used is
21742 specified by this option, which, after expansion, must be the name of a
21743 configured transport. This should normally be an &(appendfile)& transport.
21746 .option file redirect string&!! unset
21747 This option specifies the name of a file that contains the redirection data. It
21748 is mutually exclusive with the &%data%& option. The string is expanded before
21749 use; if the expansion is forced to fail, the router declines. Other expansion
21750 failures cause delivery to be deferred. The result of a successful expansion
21751 must be an absolute path. The entire file is read and used as the redirection
21752 data. If the data is an empty string or a string that has no effect (consists
21753 entirely of comments), the router declines.
21755 .cindex "NFS" "checking for file existence"
21756 If the attempt to open the file fails with a &"does not exist"& error, Exim
21757 runs a check on the containing directory,
21758 unless &%ignore_enotdir%& is true (see below).
21759 If the directory does not appear to exist, delivery is deferred. This can
21760 happen when users' &_.forward_& files are in NFS-mounted directories, and there
21761 is a mount problem. If the containing directory does exist, but the file does
21762 not, the router declines.
21765 .option file_transport redirect string&!! unset
21766 .vindex "&$address_file$&"
21767 A &(redirect)& router sets up a direct delivery to a file when a path name not
21768 ending in a slash is specified as a new &"address"&. The transport used is
21769 specified by this option, which, after expansion, must be the name of a
21770 configured transport. This should normally be an &(appendfile)& transport. When
21771 it is running, the filename is in &$address_file$&.
21774 .option filter_prepend_home redirect boolean true
21775 When this option is true, if a &(save)& command in an Exim filter specifies a
21776 relative path, and &$home$& is defined, it is automatically prepended to the
21777 relative path. If this option is set false, this action does not happen. The
21778 relative path is then passed to the transport unmodified.
21781 .option forbid_blackhole redirect boolean false
21782 .cindex "restricting access to features"
21783 .cindex "filter" "locking out certain features"
21784 If this option is true, the &':blackhole:'& item may not appear in a
21788 .option forbid_exim_filter redirect boolean false
21789 .cindex "restricting access to features"
21790 .cindex "filter" "locking out certain features"
21791 If this option is set true, only Sieve filters are permitted when
21792 &%allow_filter%& is true.
21797 .option forbid_file redirect boolean false
21798 .cindex "restricting access to features"
21799 .cindex "delivery" "to file; forbidding"
21800 .cindex "filter" "locking out certain features"
21801 .cindex "Sieve filter" "forbidding delivery to a file"
21802 .cindex "Sieve filter" "&""keep""& facility; disabling"
21803 If this option is true, this router may not generate a new address that
21804 specifies delivery to a local file or directory, either from a filter or from a
21805 conventional forward file. This option is forced to be true if &%one_time%& is
21806 set. It applies to Sieve filters as well as to Exim filters, but if true, it
21807 locks out the Sieve's &"keep"& facility.
21810 .option forbid_filter_dlfunc redirect boolean false
21811 .cindex "restricting access to features"
21812 .cindex "filter" "locking out certain features"
21813 If this option is true, string expansions in Exim filters are not allowed to
21814 make use of the &%dlfunc%& expansion facility to run dynamically loaded
21817 .option forbid_filter_existstest redirect boolean false
21818 .cindex "restricting access to features"
21819 .cindex "filter" "locking out certain features"
21820 .cindex "expansion" "statting a file"
21821 If this option is true, string expansions in Exim filters are not allowed to
21822 make use of the &%exists%& condition or the &%stat%& expansion item.
21824 .option forbid_filter_logwrite redirect boolean false
21825 .cindex "restricting access to features"
21826 .cindex "filter" "locking out certain features"
21827 If this option is true, use of the logging facility in Exim filters is not
21828 permitted. Logging is in any case available only if the filter is being run
21829 under some unprivileged uid (which is normally the case for ordinary users'
21830 &_.forward_& files).
21833 .option forbid_filter_lookup redirect boolean false
21834 .cindex "restricting access to features"
21835 .cindex "filter" "locking out certain features"
21836 If this option is true, string expansions in Exim filter files are not allowed
21837 to make use of &%lookup%& items.
21840 .option forbid_filter_perl redirect boolean false
21841 .cindex "restricting access to features"
21842 .cindex "filter" "locking out certain features"
21843 This option has an effect only if Exim is built with embedded Perl support. If
21844 it is true, string expansions in Exim filter files are not allowed to make use
21845 of the embedded Perl support.
21848 .option forbid_filter_readfile redirect boolean false
21849 .cindex "restricting access to features"
21850 .cindex "filter" "locking out certain features"
21851 If this option is true, string expansions in Exim filter files are not allowed
21852 to make use of &%readfile%& items.
21855 .option forbid_filter_readsocket redirect boolean false
21856 .cindex "restricting access to features"
21857 .cindex "filter" "locking out certain features"
21858 If this option is true, string expansions in Exim filter files are not allowed
21859 to make use of &%readsocket%& items.
21862 .option forbid_filter_reply redirect boolean false
21863 .cindex "restricting access to features"
21864 .cindex "filter" "locking out certain features"
21865 If this option is true, this router may not generate an automatic reply
21866 message. Automatic replies can be generated only from Exim or Sieve filter
21867 files, not from traditional forward files. This option is forced to be true if
21868 &%one_time%& is set.
21871 .option forbid_filter_run redirect boolean false
21872 .cindex "restricting access to features"
21873 .cindex "filter" "locking out certain features"
21874 If this option is true, string expansions in Exim filter files are not allowed
21875 to make use of &%run%& items.
21878 .option forbid_include redirect boolean false
21879 .cindex "restricting access to features"
21880 .cindex "filter" "locking out certain features"
21881 If this option is true, items of the form
21883 :include:<path name>
21885 are not permitted in non-filter redirection lists.
21888 .option forbid_pipe redirect boolean false
21889 .cindex "restricting access to features"
21890 .cindex "filter" "locking out certain features"
21891 .cindex "delivery" "to pipe; forbidding"
21892 If this option is true, this router may not generate a new address which
21893 specifies delivery to a pipe, either from an Exim filter or from a conventional
21894 forward file. This option is forced to be true if &%one_time%& is set.
21897 .option forbid_sieve_filter redirect boolean false
21898 .cindex "restricting access to features"
21899 .cindex "filter" "locking out certain features"
21900 If this option is set true, only Exim filters are permitted when
21901 &%allow_filter%& is true.
21904 .cindex "SMTP" "error codes"
21905 .option forbid_smtp_code redirect boolean false
21906 If this option is set true, any SMTP error codes that are present at the start
21907 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
21908 the default codes (451 and 550, respectively) are always used.
21913 .option hide_child_in_errmsg redirect boolean false
21914 .cindex "bounce message" "redirection details; suppressing"
21915 If this option is true, it prevents Exim from quoting a child address if it
21916 generates a bounce or delay message for it. Instead it says &"an address
21917 generated from <&'the top level address'&>"&. Of course, this applies only to
21918 bounces generated locally. If a message is forwarded to another host, &'its'&
21919 bounce may well quote the generated address.
21922 .option ignore_eacces redirect boolean false
21924 If this option is set and an attempt to open a redirection file yields the
21925 EACCES error (permission denied), the &(redirect)& router behaves as if the
21926 file did not exist.
21929 .option ignore_enotdir redirect boolean false
21931 If this option is set and an attempt to open a redirection file yields the
21932 ENOTDIR error (something on the path is not a directory), the &(redirect)&
21933 router behaves as if the file did not exist.
21935 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
21936 router that has the &%file%& option set discovers that the file does not exist
21937 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
21938 against unmounted NFS directories. If the parent can not be statted, delivery
21939 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
21940 is set, because that option tells Exim to ignore &"something on the path is not
21941 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
21942 that some operating systems give ENOENT where others give ENOTDIR.
21946 .option include_directory redirect string unset
21947 If this option is set, the path names of any &':include:'& items in a
21948 redirection list must start with this directory.
21951 .option modemask redirect "octal integer" 022
21952 This specifies mode bits which must not be set for a file specified by the
21953 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
21956 .option one_time redirect boolean false
21957 .cindex "one-time aliasing/forwarding expansion"
21958 .cindex "alias file" "one-time expansion"
21959 .cindex "forward file" "one-time expansion"
21960 .cindex "mailing lists" "one-time expansion"
21961 .cindex "address redirection" "one-time expansion"
21962 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
21963 files each time it tries to deliver a message causes a problem when one or more
21964 of the generated addresses fails be delivered at the first attempt. The problem
21965 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
21966 but of what happens when the redirection list changes during the time that the
21967 message is on Exim's queue. This is particularly true in the case of mailing
21968 lists, where new subscribers might receive copies of messages that were posted
21969 before they subscribed.
21971 If &%one_time%& is set and any addresses generated by the router fail to
21972 deliver at the first attempt, the failing addresses are added to the message as
21973 &"top level"& addresses, and the parent address that generated them is marked
21974 &"delivered"&. Thus, redirection does not happen again at the next delivery
21977 &*Warning 1*&: Any header line addition or removal that is specified by this
21978 router would be lost if delivery did not succeed at the first attempt. For this
21979 reason, the &%headers_add%& and &%headers_remove%& generic options are not
21980 permitted when &%one_time%& is set.
21982 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
21983 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
21984 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
21986 &*Warning 3*&: The &%unseen%& generic router option may not be set with
21989 The original top-level address is remembered with each of the generated
21990 addresses, and is output in any log messages. However, any intermediate parent
21991 addresses are not recorded. This makes a difference to the log only if
21992 &%all_parents%& log selector is set. It is expected that &%one_time%& will
21993 typically be used for mailing lists, where there is normally just one level of
21997 .option owners redirect "string list" unset
21998 .cindex "ownership" "alias file"
21999 .cindex "ownership" "forward file"
22000 .cindex "alias file" "ownership"
22001 .cindex "forward file" "ownership"
22002 This specifies a list of permitted owners for the file specified by &%file%&.
22003 This list is in addition to the local user when &%check_local_user%& is set.
22004 See &%check_owner%& above.
22007 .option owngroups redirect "string list" unset
22008 This specifies a list of permitted groups for the file specified by &%file%&.
22009 The list is in addition to the local user's primary group when
22010 &%check_local_user%& is set. See &%check_group%& above.
22013 .option pipe_transport redirect string&!! unset
22014 .vindex "&$address_pipe$&"
22015 A &(redirect)& router sets up a direct delivery to a pipe when a string
22016 starting with a vertical bar character is specified as a new &"address"&. The
22017 transport used is specified by this option, which, after expansion, must be the
22018 name of a configured transport. This should normally be a &(pipe)& transport.
22019 When the transport is run, the pipe command is in &$address_pipe$&.
22022 .option qualify_domain redirect string&!! unset
22023 .vindex "&$qualify_recipient$&"
22024 If this option is set, and an unqualified address (one without a domain) is
22025 generated, and that address would normally be qualified by the global setting
22026 in &%qualify_recipient%&, it is instead qualified with the domain specified by
22027 expanding this string. If the expansion fails, the router declines. If you want
22028 to revert to the default, you can have the expansion generate
22029 &$qualify_recipient$&.
22031 This option applies to all unqualified addresses generated by Exim filters,
22032 but for traditional &_.forward_& files, it applies only to addresses that are
22033 not preceded by a backslash. Sieve filters cannot generate unqualified
22036 .option qualify_preserve_domain redirect boolean false
22037 .cindex "domain" "in redirection; preserving"
22038 .cindex "preserving domain in redirection"
22039 .cindex "address redirection" "domain; preserving"
22040 If this option is set, the router's local &%qualify_domain%& option must not be
22041 set (a configuration error occurs if it is). If an unqualified address (one
22042 without a domain) is generated, it is qualified with the domain of the parent
22043 address (the immediately preceding ancestor) instead of the global
22044 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
22045 this applies whether or not the address is preceded by a backslash.
22048 .option repeat_use redirect boolean true
22049 If this option is set false, the router is skipped for a child address that has
22050 any ancestor that was routed by this router. This test happens before any of
22051 the other preconditions are tested. Exim's default anti-looping rules skip
22052 only when the ancestor is the same as the current address. See also
22053 &%check_ancestor%& above and the generic &%redirect_router%& option.
22056 .option reply_transport redirect string&!! unset
22057 A &(redirect)& router sets up an automatic reply when a &%mail%& or
22058 &%vacation%& command is used in a filter file. The transport used is specified
22059 by this option, which, after expansion, must be the name of a configured
22060 transport. This should normally be an &(autoreply)& transport. Other transports
22061 are unlikely to do anything sensible or useful.
22064 .option rewrite redirect boolean true
22065 .cindex "address redirection" "disabling rewriting"
22066 If this option is set false, addresses generated by the router are not
22067 subject to address rewriting. Otherwise, they are treated like new addresses
22068 and are rewritten according to the global rewriting rules.
22071 .option sieve_subaddress redirect string&!! unset
22072 The value of this option is passed to a Sieve filter to specify the
22073 :subaddress part of an address.
22075 .option sieve_useraddress redirect string&!! unset
22076 The value of this option is passed to a Sieve filter to specify the :user part
22077 of an address. However, if it is unset, the entire original local part
22078 (including any prefix or suffix) is used for :user.
22081 .option sieve_vacation_directory redirect string&!! unset
22082 .cindex "Sieve filter" "vacation directory"
22083 To enable the &"vacation"& extension for Sieve filters, you must set
22084 &%sieve_vacation_directory%& to the directory where vacation databases are held
22085 (do not put anything else in that directory), and ensure that the
22086 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
22087 needs their own directory; Exim will create it if necessary.
22091 .option skip_syntax_errors redirect boolean false
22092 .cindex "forward file" "broken"
22093 .cindex "address redirection" "broken files"
22094 .cindex "alias file" "broken"
22095 .cindex "broken alias or forward files"
22096 .cindex "ignoring faulty addresses"
22097 .cindex "skipping faulty addresses"
22098 .cindex "error" "skipping bad syntax"
22099 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
22100 non-filter redirection data are skipped, and each failing address is logged. If
22101 &%syntax_errors_to%& is set, a message is sent to the address it defines,
22102 giving details of the failures. If &%syntax_errors_text%& is set, its contents
22103 are expanded and placed at the head of the error message generated by
22104 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
22105 be the same address as the generic &%errors_to%& option. The
22106 &%skip_syntax_errors%& option is often used when handling mailing lists.
22108 If all the addresses in a redirection list are skipped because of syntax
22109 errors, the router declines to handle the original address, and it is passed to
22110 the following routers.
22112 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
22113 error in the filter causes filtering to be abandoned without any action being
22114 taken. The incident is logged, and the router declines to handle the address,
22115 so it is passed to the following routers.
22117 .cindex "Sieve filter" "syntax errors in"
22118 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
22119 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
22120 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
22122 &%skip_syntax_errors%& can be used to specify that errors in users' forward
22123 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
22124 option, used with an address that does not get redirected, can be used to
22125 notify users of these errors, by means of a router like this:
22131 file = $home/.forward
22132 file_transport = address_file
22133 pipe_transport = address_pipe
22134 reply_transport = address_reply
22137 syntax_errors_to = real-$local_part@$domain
22138 syntax_errors_text = \
22139 This is an automatically generated message. An error has\n\
22140 been found in your .forward file. Details of the error are\n\
22141 reported below. While this error persists, you will receive\n\
22142 a copy of this message for every message that is addressed\n\
22143 to you. If your .forward file is a filter file, or if it is\n\
22144 a non-filter file containing no valid forwarding addresses,\n\
22145 a copy of each incoming message will be put in your normal\n\
22146 mailbox. If a non-filter file contains at least one valid\n\
22147 forwarding address, forwarding to the valid addresses will\n\
22148 happen, and those will be the only deliveries that occur.
22150 You also need a router to ensure that local addresses that are prefixed by
22151 &`real-`& are recognized, but not forwarded or filtered. For example, you could
22152 put this immediately before the &(userforward)& router:
22157 local_part_prefix = real-
22158 transport = local_delivery
22160 For security, it would probably be a good idea to restrict the use of this
22161 router to locally-generated messages, using a condition such as this:
22163 condition = ${if match {$sender_host_address}\
22164 {\N^(|127\.0\.0\.1)$\N}}
22168 .option syntax_errors_text redirect string&!! unset
22169 See &%skip_syntax_errors%& above.
22172 .option syntax_errors_to redirect string unset
22173 See &%skip_syntax_errors%& above.
22174 .ecindex IIDredrou1
22175 .ecindex IIDredrou2
22182 . ////////////////////////////////////////////////////////////////////////////
22183 . ////////////////////////////////////////////////////////////////////////////
22185 .chapter "Environment for running local transports" "CHAPenvironment" &&&
22186 "Environment for local transports"
22187 .scindex IIDenvlotra1 "local transports" "environment for"
22188 .scindex IIDenvlotra2 "environment" "local transports"
22189 .scindex IIDenvlotra3 "transport" "local; environment for"
22190 Local transports handle deliveries to files and pipes. (The &(autoreply)&
22191 transport can be thought of as similar to a pipe.) Exim always runs transports
22192 in subprocesses, under specified uids and gids. Typical deliveries to local
22193 mailboxes run under the uid and gid of the local user.
22195 Exim also sets a specific current directory while running the transport; for
22196 some transports a home directory setting is also relevant. The &(pipe)&
22197 transport is the only one that sets up environment variables; see section
22198 &<<SECTpipeenv>>& for details.
22200 The values used for the uid, gid, and the directories may come from several
22201 different places. In many cases, the router that handles the address associates
22202 settings with that address as a result of its &%check_local_user%&, &%group%&,
22203 or &%user%& options. However, values may also be given in the transport's own
22204 configuration, and these override anything that comes from the router.
22208 .section "Concurrent deliveries" "SECID131"
22209 .cindex "concurrent deliveries"
22210 .cindex "simultaneous deliveries"
22211 If two different messages for the same local recipient arrive more or less
22212 simultaneously, the two delivery processes are likely to run concurrently. When
22213 the &(appendfile)& transport is used to write to a file, Exim applies locking
22214 rules to stop concurrent processes from writing to the same file at the same
22217 However, when you use a &(pipe)& transport, it is up to you to arrange any
22218 locking that is needed. Here is a silly example:
22222 command = /bin/sh -c 'cat >>/some/file'
22224 This is supposed to write the message at the end of the file. However, if two
22225 messages arrive at the same time, the file will be scrambled. You can use the
22226 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
22227 file using the same algorithm that Exim itself uses.
22232 .section "Uids and gids" "SECTenvuidgid"
22233 .cindex "local transports" "uid and gid"
22234 .cindex "transport" "local; uid and gid"
22235 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
22236 overrides any group that the router set in the address, even if &%user%& is not
22237 set for the transport. This makes it possible, for example, to run local mail
22238 delivery under the uid of the recipient (set by the router), but in a special
22239 group (set by the transport). For example:
22242 # User/group are set by check_local_user in this router
22246 transport = group_delivery
22249 # This transport overrides the group
22251 driver = appendfile
22252 file = /var/spool/mail/$local_part_data
22255 If &%user%& is set for a transport, its value overrides what is set in the
22256 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
22257 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
22260 .oindex "&%initgroups%&"
22261 When the uid is taken from the transport's configuration, the &[initgroups()]&
22262 function is called for the groups associated with that uid if the
22263 &%initgroups%& option is set for the transport. When the uid is not specified
22264 by the transport, but is associated with the address by a router, the option
22265 for calling &[initgroups()]& is taken from the router configuration.
22267 .cindex "&(pipe)& transport" "uid for"
22268 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
22269 is set and &%user%& is not set, the uid of the process that called Exim to
22270 receive the message is used, and if &%group%& is not set, the corresponding
22271 original gid is also used.
22273 This is the detailed preference order for obtaining a gid; the first of the
22274 following that is set is used:
22277 A &%group%& setting of the transport;
22279 A &%group%& setting of the router;
22281 A gid associated with a user setting of the router, either as a result of
22282 &%check_local_user%& or an explicit non-numeric &%user%& setting;
22284 The group associated with a non-numeric &%user%& setting of the transport;
22286 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
22287 the uid is the creator's uid;
22289 The Exim gid if the Exim uid is being used as a default.
22292 If, for example, the user is specified numerically on the router and there are
22293 no group settings, no gid is available. In this situation, an error occurs.
22294 This is different for the uid, for which there always is an ultimate default.
22295 The first of the following that is set is used:
22298 A &%user%& setting of the transport;
22300 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
22302 A &%user%& setting of the router;
22304 A &%check_local_user%& setting of the router;
22309 Of course, an error will still occur if the uid that is chosen is on the
22310 &%never_users%& list.
22316 .section "Current and home directories" "SECID132"
22317 .cindex "current directory for local transport"
22318 .cindex "home directory" "for local transport"
22319 .cindex "transport" "local; home directory for"
22320 .cindex "transport" "local; current directory for"
22321 Routers may set current and home directories for local transports by means of
22322 the &%transport_current_directory%& and &%transport_home_directory%& options.
22323 However, if the transport's &%current_directory%& or &%home_directory%& options
22324 are set, they override the router's values. In detail, the home directory
22325 for a local transport is taken from the first of these values that is set:
22328 The &%home_directory%& option on the transport;
22330 The &%transport_home_directory%& option on the router;
22332 The password data if &%check_local_user%& is set on the router;
22334 The &%router_home_directory%& option on the router.
22337 The current directory is taken from the first of these values that is set:
22340 The &%current_directory%& option on the transport;
22342 The &%transport_current_directory%& option on the router.
22346 If neither the router nor the transport sets a current directory, Exim uses the
22347 value of the home directory, if it is set. Otherwise it sets the current
22348 directory to &_/_& before running a local transport.
22352 .section "Expansion variables derived from the address" "SECID133"
22353 .vindex "&$domain$&"
22354 .vindex "&$local_part$&"
22355 .vindex "&$original_domain$&"
22356 Normally a local delivery is handling a single address, and in that case the
22357 variables such as &$domain$& and &$local_part$& are set during local
22358 deliveries. However, in some circumstances more than one address may be handled
22359 at once (for example, while writing batch SMTP for onward transmission by some
22360 other means). In this case, the variables associated with the local part are
22361 never set, &$domain$& is set only if all the addresses have the same domain,
22362 and &$original_domain$& is never set.
22363 .ecindex IIDenvlotra1
22364 .ecindex IIDenvlotra2
22365 .ecindex IIDenvlotra3
22373 . ////////////////////////////////////////////////////////////////////////////
22374 . ////////////////////////////////////////////////////////////////////////////
22376 .chapter "Generic options for transports" "CHAPtransportgeneric"
22377 .scindex IIDgenoptra1 "generic options" "transport"
22378 .scindex IIDgenoptra2 "options" "generic; for transports"
22379 .scindex IIDgenoptra3 "transport" "generic options for"
22380 The name of a transport is limited to be &drivernamemax; ASCII characters long;
22381 prior to Exim 4.95 names would be silently truncated at this length, but now
22384 The following generic options apply to all transports:
22387 .option body_only transports boolean false
22388 .cindex "transport" "body only"
22389 .cindex "message" "transporting body only"
22390 .cindex "body of message" "transporting"
22391 If this option is set, the message's headers are not transported. It is
22392 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
22393 or &(pipe)& transports, the settings of &%message_prefix%& and
22394 &%message_suffix%& should be checked, because this option does not
22395 automatically suppress them.
22398 .option current_directory transports string&!! unset
22399 .cindex "transport" "current directory for"
22400 This specifies the current directory that is to be set while running the
22401 transport, overriding any value that may have been set by the router.
22402 If the expansion fails for any reason, including forced failure, an error is
22403 logged, and delivery is deferred.
22406 .option disable_logging transports boolean false
22407 If this option is set true, nothing is logged for any
22408 deliveries by the transport or for any
22409 transport errors. You should not set this option unless you really, really know
22410 what you are doing.
22413 .option debug_print transports string&!! unset
22414 .cindex "testing" "variables in drivers"
22415 If this option is set and debugging is enabled (see the &%-d%& command line
22416 option), the string is expanded and included in the debugging output when the
22418 If expansion of the string fails, the error message is written to the debugging
22419 output, and Exim carries on processing.
22420 This facility is provided to help with checking out the values of variables and
22421 so on when debugging driver configurations. For example, if a &%headers_add%&
22422 option is not working properly, &%debug_print%& could be used to output the
22423 variables it references. A newline is added to the text if it does not end with
22425 The variables &$transport_name$& and &$router_name$& contain the name of the
22426 transport and the router that called it.
22428 .option delivery_date_add transports boolean false
22429 .cindex "&'Delivery-date:'& header line"
22430 If this option is true, a &'Delivery-date:'& header is added to the message.
22431 This gives the actual time the delivery was made. As this is not a standard
22432 header, Exim has a configuration option (&%delivery_date_remove%&) which
22433 requests its removal from incoming messages, so that delivered messages can
22434 safely be resent to other recipients.
22437 .option driver transports string unset
22438 This specifies which of the available transport drivers is to be used.
22439 There is no default, and this option must be set for every transport.
22442 .option envelope_to_add transports boolean false
22443 .cindex "&'Envelope-to:'& header line"
22444 If this option is true, an &'Envelope-to:'& header is added to the message.
22445 This gives the original address(es) in the incoming envelope that caused this
22446 delivery to happen. More than one address may be present if the transport is
22447 configured to handle several addresses at once, or if more than one original
22448 address was redirected to the same final address. As this is not a standard
22449 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
22450 its removal from incoming messages, so that delivered messages can safely be
22451 resent to other recipients.
22453 &*Note:*& If used on a transport handling multiple recipients
22454 (the smtp transport unless &%rcpt_max%& is 1, the appendfile, pipe or lmtp
22455 transport if &%batch_max%& is greater than 1)
22456 then information about Bcc recipients will be leaked.
22457 Doing so is generally not advised.
22460 .option event_action transports string&!! unset
22462 This option declares a string to be expanded for Exim's events mechanism.
22463 For details see chapter &<<CHAPevents>>&.
22466 .option group transports string&!! "Exim group"
22467 .cindex "transport" "group; specifying"
22468 This option specifies a gid for running the transport process, overriding any
22469 value that the router supplies, and also overriding any value associated with
22470 &%user%& (see below).
22473 .option headers_add transports list&!! unset
22474 .cindex "header lines" "adding in transport"
22475 .cindex "transport" "header lines; adding"
22476 This option specifies a list of text headers,
22477 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22478 which are (separately) expanded and added to the header
22479 portion of a message as it is transported, as described in section
22480 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
22481 routers. If the result of the expansion is an empty string, or if the expansion
22482 is forced to fail, no action is taken. Other expansion failures are treated as
22483 errors and cause the delivery to be deferred.
22485 Unlike most options, &%headers_add%& can be specified multiple times
22486 for a transport; all listed headers are added.
22489 .option headers_only transports boolean false
22490 .cindex "transport" "header lines only"
22491 .cindex "message" "transporting headers only"
22492 .cindex "header lines" "transporting"
22493 If this option is set, the message's body is not transported. It is mutually
22494 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
22495 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
22496 checked, since this option does not automatically suppress them.
22499 .option headers_remove transports list&!! unset
22500 .cindex "header lines" "removing"
22501 .cindex "transport" "header lines; removing"
22502 This option specifies a list of text headers,
22503 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22504 to be removed from the message.
22505 However, the option has no effect when an address is just being verified.
22506 Each list item is separately expanded.
22507 If the result of the expansion is an empty string, or if the expansion
22508 is forced to fail, no action is taken. Other expansion failures are treated as
22509 errors and cause the delivery to be deferred.
22510 If an item ends in *, it will match any header with the given prefix.
22512 Matching headers are omitted from the message as it is transported, as described
22513 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
22516 Unlike most options, &%headers_remove%& can be specified multiple times
22517 for a transport; all listed headers are removed.
22519 &*Warning*&: Because of the separate expansion of the list items,
22520 items that contain a list separator must have it doubled.
22521 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
22525 .option headers_rewrite transports string unset
22526 .cindex "transport" "header lines; rewriting"
22527 .cindex "rewriting" "at transport time"
22528 This option allows addresses in header lines to be rewritten at transport time,
22529 that is, as the message is being copied to its destination. The contents of the
22530 option are a colon-separated list of rewriting rules. Each rule is in exactly
22531 the same form as one of the general rewriting rules that are applied when a
22532 message is received. These are described in chapter &<<CHAPrewrite>>&. For
22535 headers_rewrite = a@b c@d f : \
22538 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
22539 &'w@z'& in all address-bearing header lines. The rules are applied to the
22540 header lines just before they are written out at transport time, so they affect
22541 only those copies of the message that pass through the transport. However, only
22542 the message's original header lines, and any that were added by a system
22543 filter, are rewritten. If a router or transport adds header lines, they are not
22544 affected by this option. These rewriting rules are &'not'& applied to the
22545 envelope. You can change the return path using &%return_path%&, but you cannot
22546 change envelope recipients at this time.
22549 .option home_directory transports string&!! unset
22550 .cindex "transport" "home directory for"
22552 This option specifies a home directory setting for a local transport,
22553 overriding any value that may be set by the router. The home directory is
22554 placed in &$home$& while expanding the transport's private options. It is also
22555 used as the current directory if no current directory is set by the
22556 &%current_directory%& option on the transport or the
22557 &%transport_current_directory%& option on the router. If the expansion fails
22558 for any reason, including forced failure, an error is logged, and delivery is
22562 .option initgroups transports boolean false
22563 .cindex "additional groups"
22564 .cindex "groups" "additional"
22565 .cindex "transport" "group; additional"
22566 If this option is true and the uid for the delivery process is provided by the
22567 transport, the &[initgroups()]& function is called when running the transport
22568 to ensure that any additional groups associated with the uid are set up.
22571 .option max_parallel transports integer&!! unset
22572 .cindex limit "transport parallelism"
22573 .cindex transport "parallel processes"
22574 .cindex transport "concurrency limit"
22575 .cindex "delivery" "parallelism for transport"
22576 If this option is set and expands to an integer greater than zero
22577 it limits the number of concurrent runs of the transport.
22578 The control does not apply to shadow transports.
22580 .cindex "hints database" "transport concurrency control"
22581 Exim implements this control by means of a hints database in which a record is
22582 incremented whenever a transport process is being created. The record
22583 is decremented and possibly removed when the process terminates.
22584 Obviously there is scope for
22585 records to get left lying around if there is a system or program crash. To
22586 guard against this, Exim ignores any records that are more than six hours old.
22588 If you use this option, you should also arrange to delete the
22589 relevant hints database whenever your system reboots. The names of the files
22590 start with &_misc_& and they are kept in the &_spool/db_& directory. There
22591 may be one or two files, depending on the type of DBM in use. The same files
22592 are used for ETRN and smtp transport serialization.
22595 .option message_size_limit transports string&!! 0
22596 .cindex "limit" "message size per transport"
22597 .cindex "size" "of message, limit"
22598 .cindex "transport" "message size; limiting"
22599 This option controls the size of messages passed through the transport. It is
22600 expanded before use; the result of the expansion must be a sequence of decimal
22601 digits, optionally followed by K or M. If the expansion fails for any reason,
22602 including forced failure, or if the result is not of the required form,
22603 delivery is deferred. If the value is greater than zero and the size of a
22604 message exceeds this limit, the address is failed. If there is any chance that
22605 the resulting bounce message could be routed to the same transport, you should
22606 ensure that &%return_size_limit%& is less than the transport's
22607 &%message_size_limit%&, as otherwise the bounce message will fail to get
22612 .option rcpt_include_affixes transports boolean false
22613 .cindex "prefix" "for local part, including in envelope"
22614 .cindex "suffix for local part" "including in envelope"
22615 .cindex "local part" "prefix"
22616 .cindex "local part" "suffix"
22617 When this option is false (the default), and an address that has had any
22618 affixes (prefixes or suffixes) removed from the local part is delivered by any
22619 form of SMTP or LMTP, the affixes are not included. For example, if a router
22622 local_part_prefix = *-
22624 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
22627 RCPT TO:<xyz@some.domain>
22629 This is also the case when an ACL-time callout is being used to verify a
22630 recipient address. However, if &%rcpt_include_affixes%& is set true, the
22631 whole local part is included in the RCPT command. This option applies to BSMTP
22632 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
22633 &(lmtp)& and &(smtp)& transports.
22636 .option retry_use_local_part transports boolean "see below"
22637 .cindex "hints database" "retry keys"
22638 When a delivery suffers a temporary failure, a retry record is created
22639 in Exim's hints database. For remote deliveries, the key for the retry record
22640 is based on the name and/or IP address of the failing remote host. For local
22641 deliveries, the key is normally the entire address, including both the local
22642 part and the domain. This is suitable for most common cases of local delivery
22643 temporary failure &-- for example, exceeding a mailbox quota should delay only
22644 deliveries to that mailbox, not to the whole domain.
22646 However, in some special cases you may want to treat a temporary local delivery
22647 as a failure associated with the domain, and not with a particular local part.
22648 (For example, if you are storing all mail for some domain in files.) You can do
22649 this by setting &%retry_use_local_part%& false.
22651 For all the local transports, its default value is true. For remote transports,
22652 the default value is false for tidiness, but changing the value has no effect
22653 on a remote transport in the current implementation.
22656 .option return_path transports string&!! unset
22657 .cindex "envelope sender"
22658 .cindex "envelope from"
22659 .cindex "transport" "return path; changing"
22660 .cindex "return path" "changing in transport"
22661 If this option is set, the string is expanded at transport time and replaces
22662 the existing return path (envelope sender) value in the copy of the message
22663 that is being delivered. An empty return path is permitted. This feature is
22664 designed for remote deliveries, where the value of this option is used in the
22665 SMTP MAIL command. If you set &%return_path%& for a local transport, the
22666 only effect is to change the address that is placed in the &'Return-path:'&
22667 header line, if one is added to the message (see the next option).
22669 &*Note:*& A changed return path is not logged unless you add
22670 &%return_path_on_delivery%& to the log selector.
22672 .vindex "&$return_path$&"
22673 The expansion can refer to the existing value via &$return_path$&. This is
22674 either the message's envelope sender, or an address set by the
22675 &%errors_to%& option on a router. If the expansion is forced to fail, no
22676 replacement occurs; if it fails for another reason, delivery is deferred. This
22677 option can be used to support VERP (Variable Envelope Return Paths) &-- see
22678 section &<<SECTverp>>&.
22680 &*Note*&: If a delivery error is detected locally, including the case when a
22681 remote server rejects a message at SMTP time, the bounce message is not sent to
22682 the value of this option. It is sent to the previously set errors address.
22683 This defaults to the incoming sender address, but can be changed by setting
22684 &%errors_to%& in a router.
22688 .option return_path_add transports boolean false
22689 .chindex Return-path:
22690 If this option is true, a &'Return-path:'& header is added to the message.
22691 Although the return path is normally available in the prefix line of BSD
22692 mailboxes, this is commonly not displayed by MUAs, and so the user does not
22693 have easy access to it.
22695 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
22696 the delivery SMTP server makes the final delivery"&. This implies that this
22697 header should not be present in incoming messages. Exim has a configuration
22698 option, &%return_path_remove%&, which requests removal of this header from
22699 incoming messages, so that delivered messages can safely be resent to other
22703 .option shadow_condition transports string&!! unset
22704 See &%shadow_transport%& below.
22707 .option shadow_transport transports string unset
22708 .cindex "shadow transport"
22709 .cindex "transport" "shadow"
22710 A local transport may set the &%shadow_transport%& option to the name of
22711 another local transport. Shadow remote transports are not supported.
22713 Whenever a delivery to the main transport succeeds, and either
22714 &%shadow_condition%& is unset, or its expansion does not result in the empty
22715 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
22716 passed to the shadow transport, with the same delivery address or addresses. If
22717 expansion fails, no action is taken except that non-forced expansion failures
22718 cause a log line to be written.
22720 The result of the shadow transport is discarded and does not affect the
22721 subsequent processing of the message. Only a single level of shadowing is
22722 provided; the &%shadow_transport%& option is ignored on any transport when it
22723 is running as a shadow. Options concerned with output from pipes are also
22724 ignored. The log line for the successful delivery has an item added on the end,
22727 ST=<shadow transport name>
22729 If the shadow transport did not succeed, the error message is put in
22730 parentheses afterwards. Shadow transports can be used for a number of different
22731 purposes, including keeping more detailed log information than Exim normally
22732 provides, and implementing automatic acknowledgment policies based on message
22733 headers that some sites insist on.
22736 .option transport_filter transports string&!! unset
22737 .cindex "transport" "filter"
22738 .cindex "filter" "transport filter"
22739 This option sets up a filtering (in the Unix shell sense) process for messages
22740 at transport time. It should not be confused with mail filtering as set up by
22741 individual users or via a system filter.
22742 If unset, or expanding to an empty string, no filtering is done.
22744 When the message is about to be written out, the command specified by
22745 &%transport_filter%& is started up in a separate, parallel process, and
22746 the entire message, including the header lines, is passed to it on its standard
22747 input (this in fact is done from a third process, to avoid deadlock). The
22748 command must be specified as an absolute path.
22750 The lines of the message that are written to the transport filter are
22751 terminated by newline (&"\n"&). The message is passed to the filter before any
22752 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
22753 lines beginning with a dot, and also before any processing implied by the
22754 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
22755 &(pipe)& transports.
22757 The standard error for the filter process is set to the same destination as its
22758 standard output; this is read and written to the message's ultimate
22759 destination. The process that writes the message to the filter, the
22760 filter itself, and the original process that reads the result and delivers it
22761 are all run in parallel, like a shell pipeline.
22763 The filter can perform any transformations it likes, but of course should take
22764 care not to break RFC 2822 syntax. Exim does not check the result, except to
22765 test for a final newline when SMTP is in use. All messages transmitted over
22766 SMTP must end with a newline, so Exim supplies one if it is missing.
22768 .cindex "content scanning" "per user"
22769 A transport filter can be used to provide content-scanning on a per-user basis
22770 at delivery time if the only required effect of the scan is to modify the
22771 message. For example, a content scan could insert a new header line containing
22772 a spam score. This could be interpreted by a filter in the user's MUA. It is
22773 not possible to discard a message at this stage.
22775 .cindex "SIZE" "ESMTP extension"
22776 A problem might arise if the filter increases the size of a message that is
22777 being sent down an SMTP connection. If the receiving SMTP server has indicated
22778 support for the SIZE parameter, Exim will have sent the size of the message
22779 at the start of the SMTP session. If what is actually sent is substantially
22780 more, the server might reject the message. This can be worked round by setting
22781 the &%size_addition%& option on the &(smtp)& transport, either to allow for
22782 additions to the message, or to disable the use of SIZE altogether.
22784 .vindex "&$pipe_addresses$&"
22785 The value of the &%transport_filter%& option is the command string for starting
22786 the filter, which is run directly from Exim, not under a shell. The string is
22787 parsed by Exim in the same way as a command string for the &(pipe)& transport:
22788 Exim breaks it up into arguments and then expands each argument separately (see
22789 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
22790 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
22791 of arguments, one for each address that applies to this delivery. (This isn't
22792 an ideal name for this feature here, but as it was already implemented for the
22793 &(pipe)& transport, it seemed sensible not to change it.)
22796 .vindex "&$host_address$&"
22797 The expansion variables &$host$& and &$host_address$& are available when the
22798 transport is a remote one. They contain the name and IP address of the host to
22799 which the message is being sent. For example:
22801 transport_filter = /some/directory/transport-filter.pl \
22802 $host $host_address $sender_address $pipe_addresses
22805 Two problems arise if you want to use more complicated expansion items to
22806 generate transport filter commands, both of which due to the fact that the
22807 command is split up &'before'& expansion.
22809 If an expansion item contains white space, you must quote it, so that it is all
22810 part of the same command item. If the entire option setting is one such
22811 expansion item, you have to take care what kind of quoting you use. For
22814 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
22816 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
22817 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
22818 stripped by Exim when it read the option's value. When the value is used, if
22819 the single quotes were missing, the line would be split into two items,
22820 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
22821 Exim tried to expand the first one.
22823 Except for the special case of &$pipe_addresses$& that is mentioned above, an
22824 expansion cannot generate multiple arguments, or a command name followed by
22825 arguments. Consider this example:
22827 transport_filter = ${lookup{$host}lsearch{/a/file}\
22828 {$value}{/bin/cat}}
22830 The result of the lookup is interpreted as the name of the command, even
22831 if it contains white space. The simplest way round this is to use a shell:
22833 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
22834 {$value}{/bin/cat}}
22838 The filter process is run under the same uid and gid as the normal delivery.
22839 For remote deliveries this is the Exim uid/gid by default. The command should
22840 normally yield a zero return code. Transport filters are not supposed to fail.
22841 A non-zero code is taken to mean that the transport filter encountered some
22842 serious problem. Delivery of the message is deferred; the message remains on
22843 the queue and is tried again later. It is not possible to cause a message to be
22844 bounced from a transport filter.
22846 If a transport filter is set on an autoreply transport, the original message is
22847 passed through the filter as it is being copied into the newly generated
22848 message, which happens if the &%return_message%& option is set.
22851 .option transport_filter_timeout transports time 5m
22852 .cindex "transport" "filter, timeout"
22853 When Exim is reading the output of a transport filter, it applies a timeout
22854 that can be set by this option. Exceeding the timeout is normally treated as a
22855 temporary delivery failure. However, if a transport filter is used with a
22856 &(pipe)& transport, a timeout in the transport filter is treated in the same
22857 way as a timeout in the pipe command itself. By default, a timeout is a hard
22858 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
22859 becomes a temporary error.
22862 .option user transports string&!! "Exim user"
22863 .cindex "uid (user id)" "local delivery"
22864 .cindex "transport" "user, specifying"
22865 This option specifies the user under whose uid the delivery process is to be
22866 run, overriding any uid that may have been set by the router. If the user is
22867 given as a name, the uid is looked up from the password data, and the
22868 associated group is taken as the value of the gid to be used if the &%group%&
22871 For deliveries that use local transports, a user and group are normally
22872 specified explicitly or implicitly (for example, as a result of
22873 &%check_local_user%&) by the router or transport.
22875 .cindex "hints database" "access by remote transport"
22876 For remote transports, you should leave this option unset unless you really are
22877 sure you know what you are doing. When a remote transport is running, it needs
22878 to be able to access Exim's hints databases, because each host may have its own
22880 .ecindex IIDgenoptra1
22881 .ecindex IIDgenoptra2
22882 .ecindex IIDgenoptra3
22889 . ////////////////////////////////////////////////////////////////////////////
22890 . ////////////////////////////////////////////////////////////////////////////
22892 .chapter "Address batching in local transports" "CHAPbatching" &&&
22894 .cindex "transport" "local; address batching in"
22895 The only remote transport (&(smtp)&) is normally configured to handle more than
22896 one address at a time, so that when several addresses are routed to the same
22897 remote host, just one copy of the message is sent. Local transports, however,
22898 normally handle one address at a time. That is, a separate instance of the
22899 transport is run for each address that is routed to the transport. A separate
22900 copy of the message is delivered each time.
22902 .cindex "batched local delivery"
22903 .oindex "&%batch_max%&"
22904 .oindex "&%batch_id%&"
22905 In special cases, it may be desirable to handle several addresses at once in a
22906 local transport, for example:
22909 In an &(appendfile)& transport, when storing messages in files for later
22910 delivery by some other means, a single copy of the message with multiple
22911 recipients saves space.
22913 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
22914 a single copy saves time, and is the normal way LMTP is expected to work.
22916 In a &(pipe)& transport, when passing the message
22917 to a scanner program or
22918 to some other delivery mechanism such as UUCP, multiple recipients may be
22922 These three local transports all have the same options for controlling multiple
22923 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
22924 repeating the information for each transport, these options are described here.
22926 The &%batch_max%& option specifies the maximum number of addresses that can be
22927 delivered together in a single run of the transport. Its default value is one
22928 (no batching). When more than one address is routed to a transport that has a
22929 &%batch_max%& value greater than one, the addresses are delivered in a batch
22930 (that is, in a single run of the transport with multiple recipients), subject
22931 to certain conditions:
22934 .vindex "&$local_part$&"
22935 If any of the transport's options contain a reference to &$local_part$&, no
22936 batching is possible.
22938 .vindex "&$domain$&"
22939 If any of the transport's options contain a reference to &$domain$&, only
22940 addresses with the same domain are batched.
22942 .cindex "customizing" "batching condition"
22943 If &%batch_id%& is set, it is expanded for each address, and only those
22944 addresses with the same expanded value are batched. This allows you to specify
22945 customized batching conditions. Failure of the expansion for any reason,
22946 including forced failure, disables batching, but it does not stop the delivery
22949 Batched addresses must also have the same errors address (where to send
22950 delivery errors), the same header additions and removals, the same user and
22951 group for the transport, and if a host list is present, the first host must
22955 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
22956 both when the file or pipe command is specified in the transport, and when it
22957 is specified by a &(redirect)& router, but all the batched addresses must of
22958 course be routed to the same file or pipe command. These two transports have an
22959 option called &%use_bsmtp%&, which causes them to deliver the message in
22960 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
22961 &%check_string%& and &%escape_string%& options are forced to the values
22964 escape_string = ".."
22966 when batched SMTP is in use. A full description of the batch SMTP mechanism is
22967 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
22968 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
22970 .cindex "&'Envelope-to:'& header line"
22971 If the generic &%envelope_to_add%& option is set for a batching transport, the
22972 &'Envelope-to:'& header that is added to the message contains all the addresses
22973 that are being processed together. If you are using a batching &(appendfile)&
22974 transport without &%use_bsmtp%&, the only way to preserve the recipient
22975 addresses is to set the &%envelope_to_add%& option.
22977 .cindex "&(pipe)& transport" "with multiple addresses"
22978 .vindex "&$pipe_addresses$&"
22979 If you are using a &(pipe)& transport without BSMTP, and setting the
22980 transport's &%command%& option, you can include &$pipe_addresses$& as part of
22981 the command. This is not a true variable; it is a bit of magic that causes each
22982 of the recipient addresses to be inserted into the command as a separate
22983 argument. This provides a way of accessing all the addresses that are being
22984 delivered in the batch. &*Note:*& This is not possible for pipe commands that
22985 are specified by a &(redirect)& router.
22990 . ////////////////////////////////////////////////////////////////////////////
22991 . ////////////////////////////////////////////////////////////////////////////
22993 .chapter "The appendfile transport" "CHAPappendfile"
22994 .scindex IIDapptra1 "&(appendfile)& transport"
22995 .scindex IIDapptra2 "transports" "&(appendfile)&"
22996 .cindex "directory creation"
22997 .cindex "creating directories"
22998 The &(appendfile)& transport delivers a message by appending it to an existing
22999 file, or by creating an entirely new file in a specified directory. Single
23000 files to which messages are appended can be in the traditional Unix mailbox
23001 format, or optionally in the MBX format supported by the Pine MUA and
23002 University of Washington IMAP daemon, &'inter alia'&. When each message is
23003 being delivered as a separate file, &"maildir"& format can optionally be used
23004 to give added protection against failures that happen part-way through the
23005 delivery. A third form of separate-file delivery known as &"mailstore"& is also
23006 supported. For all file formats, Exim attempts to create as many levels of
23007 directory as necessary, provided that &%create_directory%& is set.
23009 The code for the optional formats is not included in the Exim binary by
23010 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
23011 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
23014 .cindex "quota" "system"
23015 Exim recognizes system quota errors, and generates an appropriate message. Exim
23016 also supports its own quota control within the transport, for use when the
23017 system facility is unavailable or cannot be used for some reason.
23019 If there is an error while appending to a file (for example, quota exceeded or
23020 partition filled), Exim attempts to reset the file's length and last
23021 modification time back to what they were before. If there is an error while
23022 creating an entirely new file, the new file is removed.
23024 Before appending to a file, a number of security checks are made, and the
23025 file is locked. A detailed description is given below, after the list of
23028 The &(appendfile)& transport is most commonly used for local deliveries to
23029 users' mailboxes. However, it can also be used as a pseudo-remote transport for
23030 putting messages into files for remote delivery by some means other than Exim.
23031 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
23036 .section "The file and directory options" "SECTfildiropt"
23037 The &%file%& option specifies a single file, to which the message is appended;
23038 the &%directory%& option specifies a directory, in which a new file containing
23039 the message is created. Only one of these two options can be set, and for
23040 normal deliveries to mailboxes, one of them &'must'& be set.
23042 .vindex "&$address_file$&"
23043 .vindex "&$local_part$&"
23044 However, &(appendfile)& is also used for delivering messages to files or
23045 directories whose names (or parts of names) are obtained from alias,
23046 forwarding, or filtering operations (for example, a &%save%& command in a
23047 user's Exim filter). When such a transport is running, &$local_part$& contains
23048 the local part that was aliased or forwarded, and &$address_file$& contains the
23049 name (or partial name) of the file or directory generated by the redirection
23050 operation. There are two cases:
23053 If neither &%file%& nor &%directory%& is set, the redirection operation
23054 must specify an absolute path (one that begins with &`/`&). This is the most
23055 common case when users with local accounts use filtering to sort mail into
23056 different folders. See for example, the &(address_file)& transport in the
23057 default configuration. If the path ends with a slash, it is assumed to be the
23058 name of a directory. A delivery to a directory can also be forced by setting
23059 &%maildir_format%& or &%mailstore_format%&.
23061 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
23062 used to determine the file or directory name for the delivery. Normally, the
23063 contents of &$address_file$& are used in some way in the string expansion.
23065 If the &%create_file%& option is set to a path which
23066 matches (see the option definition below for details)
23067 a file or directory name
23068 for the delivery, that name becomes de-tainted.
23070 .cindex "tainted data" "in filenames"
23071 .cindex appendfile "tainted data"
23072 Tainted data may not be used for a file or directory name.
23073 This means that, for instance, &$local_part$& cannot be used directly
23074 as a component of a path. It can however be used as the key for a lookup
23075 which returns a path (or component).
23078 .cindex "Sieve filter" "configuring &(appendfile)&"
23079 .cindex "Sieve filter" "relative mailbox path handling"
23080 As an example of the second case, consider an environment where users do not
23081 have home directories. They may be permitted to use Exim filter commands of the
23086 or Sieve filter commands of the form:
23088 require "fileinto";
23089 fileinto "folder23";
23091 In this situation, the expansion of &%file%& or &%directory%& in the transport
23092 must transform the relative path into an appropriate absolute filename. In the
23093 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
23094 is used as a result of a &"keep"& action in the filter. This example shows one
23095 way of handling this requirement:
23097 file = ${if eq{$address_file}{inbox} \
23098 {/var/mail/$local_part_data} \
23099 {${if eq{${substr_0_1:$address_file}}{/} \
23101 {$home/mail/$address_file} \
23105 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
23106 location, absolute paths are used without change, and other folders are in the
23107 &_mail_& directory within the home directory.
23109 &*Note 1*&: While processing an Exim filter, a relative path such as
23110 &_folder23_& is turned into an absolute path if a home directory is known to
23111 the router. In particular, this is the case if &%check_local_user%& is set. If
23112 you want to prevent this happening at routing time, you can set
23113 &%router_home_directory%& empty. This forces the router to pass the relative
23114 path to the transport.
23116 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
23117 the &%file%& or &%directory%& option is still used if it is set.
23122 .section "Private options for appendfile" "SECID134"
23123 .cindex "options" "&(appendfile)& transport"
23127 .option allow_fifo appendfile boolean false
23128 .cindex "fifo (named pipe)"
23129 .cindex "named pipe (fifo)"
23130 .cindex "pipe" "named (fifo)"
23131 Setting this option permits delivery to named pipes (FIFOs) as well as to
23132 regular files. If no process is reading the named pipe at delivery time, the
23133 delivery is deferred.
23136 .option allow_symlink appendfile boolean false
23137 .cindex "symbolic link" "to mailbox"
23138 .cindex "mailbox" "symbolic link"
23139 By default, &(appendfile)& will not deliver if the path name for the file is
23140 that of a symbolic link. Setting this option relaxes that constraint, but there
23141 are security issues involved in the use of symbolic links. Be sure you know
23142 what you are doing if you set this. Details of exactly what this option affects
23143 are included in the discussion which follows this list of options.
23146 .option batch_id appendfile string&!! unset
23147 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23148 However, batching is automatically disabled for &(appendfile)& deliveries that
23149 happen as a result of forwarding or aliasing or other redirection directly to a
23153 .option batch_max appendfile integer 1
23154 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23157 .option check_group appendfile boolean false
23158 When this option is set, the group owner of the file defined by the &%file%&
23159 option is checked to see that it is the same as the group under which the
23160 delivery process is running. The default setting is false because the default
23161 file mode is 0600, which means that the group is irrelevant.
23164 .option check_owner appendfile boolean true
23165 When this option is set, the owner of the file defined by the &%file%& option
23166 is checked to ensure that it is the same as the user under which the delivery
23167 process is running.
23170 .option check_string appendfile string "see below"
23171 .cindex "&""From""& line"
23172 As &(appendfile)& writes the message, the start of each line is tested for
23173 matching &%check_string%&, and if it does, the initial matching characters are
23174 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
23175 a literal string, not a regular expression, and the case of any letters it
23176 contains is significant.
23178 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
23179 are forced to &"."& and &".."& respectively, and any settings in the
23180 configuration are ignored. Otherwise, they default to &"From&~"& and
23181 &">From&~"& when the &%file%& option is set, and unset when any of the
23182 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
23184 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
23185 suitable for traditional &"BSD"& mailboxes, where a line beginning with
23186 &"From&~"& indicates the start of a new message. All four options need changing
23187 if another format is used. For example, to deliver to mailboxes in MMDF format:
23188 .cindex "MMDF format mailbox"
23189 .cindex "mailbox" "MMDF format"
23191 check_string = "\1\1\1\1\n"
23192 escape_string = "\1\1\1\1 \n"
23193 message_prefix = "\1\1\1\1\n"
23194 message_suffix = "\1\1\1\1\n"
23196 .option create_directory appendfile boolean true
23197 .cindex "directory creation"
23198 When this option is true, Exim attempts to create any missing superior
23199 directories for the file that it is about to write. A created directory's mode
23200 is given by the &%directory_mode%& option.
23202 The group ownership of a newly created directory is highly dependent on the
23203 operating system (and possibly the file system) that is being used. For
23204 example, in Solaris, if the parent directory has the setgid bit set, its group
23205 is propagated to the child; if not, the currently set group is used. However,
23206 in FreeBSD, the parent's group is always used.
23210 .option create_file appendfile string anywhere
23211 This option constrains the location of files and directories that are created
23212 by this transport. It applies to files defined by the &%file%& option and
23213 directories defined by the &%directory%& option. In the case of maildir
23214 delivery, it applies to the top level directory, not the maildir directories
23217 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
23218 &"belowhome"&, or to an absolute path.
23220 In the second and third cases, a home directory must have been
23221 set for the transport, and the file or directory being created must
23223 The "belowhome" checking additionally checks for attempts to use "../"
23224 to evade the testing.
23225 This option is not useful when an explicit filename is
23226 given for normal mailbox deliveries. It is intended for the case when filenames
23227 are generated from users' &_.forward_& files. These are usually handled
23228 by an &(appendfile)& transport called &%address_file%&. See also
23229 &%file_must_exist%&.
23231 In the fourth case,
23232 the value given for this option must be an absolute path for an
23233 existing directory.
23234 The value is used for checking instead of a home directory;
23235 checking is done in "belowhome" mode.
23237 .cindex "tainted data" "de-tainting"
23238 If "belowhome" checking is used, the file or directory path
23239 becomes de-tainted.
23242 .option directory appendfile string&!! unset
23243 This option is mutually exclusive with the &%file%& option, but one of &%file%&
23244 or &%directory%& must be set, unless the delivery is the direct result of a
23245 redirection (see section &<<SECTfildiropt>>&).
23247 When &%directory%& is set, the string is expanded, and the message is delivered
23248 into a new file or files in or below the given directory, instead of being
23249 appended to a single mailbox file. A number of different formats are provided
23250 (see &%maildir_format%& and &%mailstore_format%&), and see section
23251 &<<SECTopdir>>& for further details of this form of delivery.
23253 The result of expansion must not be tainted, unless the &%create_file%& option
23257 .option directory_file appendfile string&!! "see below"
23259 .vindex "&$inode$&"
23260 When &%directory%& is set, but neither &%maildir_format%& nor
23261 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
23262 whose name is obtained by expanding this string. The default value is:
23264 q${base62:$tod_epoch}-$inode
23266 This generates a unique name from the current time, in base 62 form, and the
23267 inode of the file. The variable &$inode$& is available only when expanding this
23271 .option directory_mode appendfile "octal integer" 0700
23272 If &(appendfile)& creates any directories as a result of the
23273 &%create_directory%& option, their mode is specified by this option.
23276 .option escape_string appendfile string "see description"
23277 See &%check_string%& above.
23280 .option file appendfile string&!! unset
23281 This option is mutually exclusive with the &%directory%& option, but one of
23282 &%file%& or &%directory%& must be set, unless the delivery is the direct result
23283 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
23284 specifies a single file, to which the message is appended. One or more of
23285 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
23288 The result of expansion must not be tainted, unless the &%create_file%& option
23291 .cindex "NFS" "lock file"
23292 .cindex "locking files"
23293 .cindex "lock files"
23294 If you are using more than one host to deliver over NFS into the same
23295 mailboxes, you should always use lock files.
23297 The string value is expanded for each delivery, and must yield an absolute
23298 path. The most common settings of this option are variations on one of these
23301 file = /var/spool/mail/$local_part_data
23302 file = /home/$local_part_data/inbox
23305 .cindex "&""sticky""& bit"
23306 In the first example, all deliveries are done into the same directory. If Exim
23307 is configured to use lock files (see &%use_lockfile%& below) it must be able to
23308 create a file in the directory, so the &"sticky"& bit must be turned on for
23309 deliveries to be possible, or alternatively the &%group%& option can be used to
23310 run the delivery under a group id which has write access to the directory.
23314 .option file_format appendfile string unset
23315 .cindex "file" "mailbox; checking existing format"
23316 This option requests the transport to check the format of an existing file
23317 before adding to it. The check consists of matching a specific string at the
23318 start of the file. The value of the option consists of an even number of
23319 colon-separated strings. The first of each pair is the test string, and the
23320 second is the name of a transport. If the transport associated with a matched
23321 string is not the current transport, control is passed over to the other
23322 transport. For example, suppose the standard &(local_delivery)& transport has
23325 file_format = "From : local_delivery :\
23326 \1\1\1\1\n : local_mmdf_delivery"
23328 Mailboxes that begin with &"From"& are still handled by this transport, but if
23329 a mailbox begins with four binary ones followed by a newline, control is passed
23330 to a transport called &%local_mmdf_delivery%&, which presumably is configured
23331 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
23332 is assumed to match the current transport. If the start of a mailbox doesn't
23333 match any string, or if the transport named for a given string is not defined,
23334 delivery is deferred.
23337 .option file_must_exist appendfile boolean false
23338 If this option is true, the file specified by the &%file%& option must exist.
23339 A temporary error occurs if it does not, causing delivery to be deferred.
23340 If this option is false, the file is created if it does not exist.
23343 .option lock_fcntl_timeout appendfile time 0s
23344 .cindex "timeout" "mailbox locking"
23345 .cindex "mailbox" "locking, blocking and non-blocking"
23346 .cindex "locking files"
23347 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
23348 when locking an open mailbox file. If the call fails, the delivery process
23349 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
23350 Non-blocking calls are used so that the file is not kept open during the wait
23351 for the lock; the reason for this is to make it as safe as possible for
23352 deliveries over NFS in the case when processes might be accessing an NFS
23353 mailbox without using a lock file. This should not be done, but
23354 misunderstandings and hence misconfigurations are not unknown.
23356 On a busy system, however, the performance of a non-blocking lock approach is
23357 not as good as using a blocking lock with a timeout. In this case, the waiting
23358 is done inside the system call, and Exim's delivery process acquires the lock
23359 and can proceed as soon as the previous lock holder releases it.
23361 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
23362 timeout, are used. There may still be some retrying: the maximum number of
23365 (lock_retries * lock_interval) / lock_fcntl_timeout
23367 rounded up to the next whole number. In other words, the total time during
23368 which &(appendfile)& is trying to get a lock is roughly the same, unless
23369 &%lock_fcntl_timeout%& is set very large.
23371 You should consider setting this option if you are getting a lot of delayed
23372 local deliveries because of errors of the form
23374 failed to lock mailbox /some/file (fcntl)
23377 .option lock_flock_timeout appendfile time 0s
23378 This timeout applies to file locking when using &[flock()]& (see
23379 &%use_flock%&); the timeout operates in a similar manner to
23380 &%lock_fcntl_timeout%&.
23383 .option lock_interval appendfile time 3s
23384 This specifies the time to wait between attempts to lock the file. See below
23385 for details of locking.
23388 .option lock_retries appendfile integer 10
23389 This specifies the maximum number of attempts to lock the file. A value of zero
23390 is treated as 1. See below for details of locking.
23393 .option lockfile_mode appendfile "octal integer" 0600
23394 This specifies the mode of the created lock file, when a lock file is being
23395 used (see &%use_lockfile%& and &%use_mbx_lock%&).
23398 .option lockfile_timeout appendfile time 30m
23399 .cindex "timeout" "mailbox locking"
23400 When a lock file is being used (see &%use_lockfile%&), if a lock file already
23401 exists and is older than this value, it is assumed to have been left behind by
23402 accident, and Exim attempts to remove it.
23405 .option mailbox_filecount appendfile string&!! unset
23406 .cindex "mailbox" "specifying size of"
23407 .cindex "size" "of mailbox"
23408 If this option is set, it is expanded, and the result is taken as the current
23409 number of files in the mailbox. It must be a decimal number, optionally
23410 followed by K or M. This provides a way of obtaining this information from an
23411 external source that maintains the data.
23414 .option mailbox_size appendfile string&!! unset
23415 .cindex "mailbox" "specifying size of"
23416 .cindex "size" "of mailbox"
23417 If this option is set, it is expanded, and the result is taken as the current
23418 size the mailbox. It must be a decimal number, optionally followed by K or M.
23419 This provides a way of obtaining this information from an external source that
23420 maintains the data. This is likely to be helpful for maildir deliveries where
23421 it is computationally expensive to compute the size of a mailbox.
23425 .option maildir_format appendfile boolean false
23426 .cindex "maildir format" "specifying"
23427 If this option is set with the &%directory%& option, the delivery is into a new
23428 file, in the &"maildir"& format that is used by other mail software. When the
23429 transport is activated directly from a &(redirect)& router (for example, the
23430 &(address_file)& transport in the default configuration), setting
23431 &%maildir_format%& causes the path received from the router to be treated as a
23432 directory, whether or not it ends with &`/`&. This option is available only if
23433 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
23434 &<<SECTmaildirdelivery>>& below for further details.
23437 .option maildir_quota_directory_regex appendfile string "See below"
23438 .cindex "maildir format" "quota; directories included in"
23439 .cindex "quota" "maildir; directories included in"
23440 This option is relevant only when &%maildir_use_size_file%& is set. It defines
23441 a regular expression for specifying directories, relative to the quota
23442 directory (see &%quota_directory%&), that should be included in the quota
23443 calculation. The default value is:
23445 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
23447 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
23448 (directories whose names begin with a dot). If you want to exclude the
23450 folder from the count (as some sites do), you need to change this setting to
23452 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
23454 This uses a negative lookahead in the regular expression to exclude the
23455 directory whose name is &_.Trash_&. When a directory is excluded from quota
23456 calculations, quota processing is bypassed for any messages that are delivered
23457 directly into that directory.
23460 .option maildir_retries appendfile integer 10
23461 This option specifies the number of times to retry when writing a file in
23462 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
23465 .option maildir_tag appendfile string&!! unset
23466 This option applies only to deliveries in maildir format, and is described in
23467 section &<<SECTmaildirdelivery>>& below.
23470 .option maildir_use_size_file appendfile&!! boolean false
23471 .cindex "maildir format" "&_maildirsize_& file"
23472 The result of string expansion for this option must be a valid boolean value.
23473 If it is true, it enables support for &_maildirsize_& files. Exim
23474 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
23475 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
23476 value is zero. See &%maildir_quota_directory_regex%& above and section
23477 &<<SECTmaildirdelivery>>& below for further details.
23479 .option maildirfolder_create_regex appendfile string unset
23480 .cindex "maildir format" "&_maildirfolder_& file"
23481 .cindex "&_maildirfolder_&, creating"
23482 The value of this option is a regular expression. If it is unset, it has no
23483 effect. Otherwise, before a maildir delivery takes place, the pattern is
23484 matched against the name of the maildir directory, that is, the directory
23485 containing the &_new_& and &_tmp_& subdirectories that will be used for the
23486 delivery. If there is a match, Exim checks for the existence of a file called
23487 &_maildirfolder_& in the directory, and creates it if it does not exist.
23488 See section &<<SECTmaildirdelivery>>& for more details.
23491 .option mailstore_format appendfile boolean false
23492 .cindex "mailstore format" "specifying"
23493 If this option is set with the &%directory%& option, the delivery is into two
23494 new files in &"mailstore"& format. The option is available only if
23495 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
23496 below for further details.
23499 .option mailstore_prefix appendfile string&!! unset
23500 This option applies only to deliveries in mailstore format, and is described in
23501 section &<<SECTopdir>>& below.
23504 .option mailstore_suffix appendfile string&!! unset
23505 This option applies only to deliveries in mailstore format, and is described in
23506 section &<<SECTopdir>>& below.
23509 .option mbx_format appendfile boolean false
23510 .cindex "locking files"
23511 .cindex "file" "locking"
23512 .cindex "file" "MBX format"
23513 .cindex "MBX format, specifying"
23514 This option is available only if Exim has been compiled with SUPPORT_MBX
23515 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
23516 the message is appended to the mailbox file in MBX format instead of
23517 traditional Unix format. This format is supported by Pine4 and its associated
23518 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
23520 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
23521 automatically changed by the use of &%mbx_format%&. They should normally be set
23522 empty when using MBX format, so this option almost always appears in this
23529 If none of the locking options are mentioned in the configuration,
23530 &%use_mbx_lock%& is assumed and the other locking options default to false. It
23531 is possible to specify the other kinds of locking with &%mbx_format%&, but
23532 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
23533 interworks with &'c-client'&, providing for shared access to the mailbox. It
23534 should not be used if any program that does not use this form of locking is
23535 going to access the mailbox, nor should it be used if the mailbox file is NFS
23536 mounted, because it works only when the mailbox is accessed from a single host.
23538 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
23539 the standard version of &'c-client'&, because as long as it has a mailbox open
23540 (this means for the whole of a Pine or IMAP session), Exim will not be able to
23541 append messages to it.
23544 .option message_prefix appendfile string&!! "see below"
23545 .cindex "&""From""& line"
23546 The string specified here is expanded and output at the start of every message.
23547 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23548 in which case it is:
23550 message_prefix = "From ${if def:return_path{$return_path}\
23551 {MAILER-DAEMON}} $tod_bsdinbox\n"
23553 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23554 &`\n`& to &`\r\n`& in &%message_prefix%&.
23556 .option message_suffix appendfile string&!! "see below"
23557 The string specified here is expanded and output at the end of every message.
23558 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23559 in which case it is a single newline character. The suffix can be suppressed by
23564 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23565 &`\n`& to &`\r\n`& in &%message_suffix%&.
23567 .option mode appendfile "octal integer" 0600
23568 If the output file is created, it is given this mode. If it already exists and
23569 has wider permissions, they are reduced to this mode. If it has narrower
23570 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
23571 if the delivery is the result of a &%save%& command in a filter file specifying
23572 a particular mode, the mode of the output file is always forced to take that
23573 value, and this option is ignored.
23576 .option mode_fail_narrower appendfile boolean true
23577 This option applies in the case when an existing mailbox file has a narrower
23578 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
23579 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
23580 continues with the delivery attempt, using the existing mode of the file.
23583 .option notify_comsat appendfile boolean false
23584 If this option is true, the &'comsat'& daemon is notified after every
23585 successful delivery to a user mailbox. This is the daemon that notifies logged
23586 on users about incoming mail.
23589 .option quota appendfile string&!! unset
23590 .cindex "quota" "imposed by Exim"
23591 This option imposes a limit on the size of the file to which Exim is appending,
23592 or to the total space used in the directory tree when the &%directory%& option
23593 is set. In the latter case, computation of the space used is expensive, because
23594 all the files in the directory (and any sub-directories) have to be
23595 individually inspected and their sizes summed. (See &%quota_size_regex%& and
23596 &%maildir_use_size_file%& for ways to avoid this in environments where users
23597 have no shell access to their mailboxes).
23599 As there is no interlock against two simultaneous deliveries into a
23600 multi-file mailbox, it is possible for the quota to be overrun in this case.
23601 For single-file mailboxes, of course, an interlock is a necessity.
23603 A file's size is taken as its &'used'& value. Because of blocking effects, this
23604 may be a lot less than the actual amount of disk space allocated to the file.
23605 If the sizes of a number of files are being added up, the rounding effect can
23606 become quite noticeable, especially on systems that have large block sizes.
23607 Nevertheless, it seems best to stick to the &'used'& figure, because this is
23608 the obvious value which users understand most easily.
23610 The value of the option is expanded, and must then be a numerical value
23611 (decimal point allowed), optionally followed by one of the letters K, M, or G,
23612 for kilobytes, megabytes, or gigabytes, optionally followed by a slash
23613 and further option modifiers. If Exim is running on a system with
23614 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
23617 The option modifier &%no_check%& can be used to force delivery even if the over
23618 quota condition is met. The quota gets updated as usual.
23620 &*Note*&: A value of zero is interpreted as &"no quota"&.
23622 The expansion happens while Exim is running as root, before it changes uid for
23623 the delivery. This means that files that are inaccessible to the end user can
23624 be used to hold quota values that are looked up in the expansion. When delivery
23625 fails because this quota is exceeded, the handling of the error is as for
23626 system quota failures.
23628 By default, Exim's quota checking mimics system quotas, and restricts the
23629 mailbox to the specified maximum size, though the value is not accurate to the
23630 last byte, owing to separator lines and additional headers that may get added
23631 during message delivery. When a mailbox is nearly full, large messages may get
23632 refused even though small ones are accepted, because the size of the current
23633 message is added to the quota when the check is made. This behaviour can be
23634 changed by setting &%quota_is_inclusive%& false. When this is done, the check
23635 for exceeding the quota does not include the current message. Thus, deliveries
23636 continue until the quota has been exceeded; thereafter, no further messages are
23637 delivered. See also &%quota_warn_threshold%&.
23640 .option quota_directory appendfile string&!! unset
23641 This option defines the directory to check for quota purposes when delivering
23642 into individual files. The default is the delivery directory, or, if a file
23643 called &_maildirfolder_& exists in a maildir directory, the parent of the
23644 delivery directory.
23647 .option quota_filecount appendfile string&!! 0
23648 This option applies when the &%directory%& option is set. It limits the total
23649 number of files in the directory (compare the inode limit in system quotas). It
23650 can only be used if &%quota%& is also set. The value is expanded; an expansion
23651 failure causes delivery to be deferred. A value of zero is interpreted as
23654 The option modifier &%no_check%& can be used to force delivery even if the over
23655 quota condition is met. The quota gets updated as usual.
23657 .option quota_is_inclusive appendfile boolean true
23658 See &%quota%& above.
23661 .option quota_size_regex appendfile string unset
23662 This option applies when one of the delivery modes that writes a separate file
23663 for each message is being used. When Exim wants to find the size of one of
23664 these files in order to test the quota, it first checks &%quota_size_regex%&.
23665 If this is set to a regular expression that matches the filename, and it
23666 captures one string, that string is interpreted as a representation of the
23667 file's size. The value of &%quota_size_regex%& is not expanded.
23669 This feature is useful only when users have no shell access to their mailboxes
23670 &-- otherwise they could defeat the quota simply by renaming the files. This
23671 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
23672 the file length to the filename. For example:
23674 maildir_tag = ,S=$message_size
23675 quota_size_regex = ,S=(\d+)
23677 An alternative to &$message_size$& is &$message_linecount$&, which contains the
23678 number of lines in the message.
23680 The regular expression should not assume that the length is at the end of the
23681 filename (even though &%maildir_tag%& puts it there) because maildir MUAs
23682 sometimes add other information onto the ends of message filenames.
23684 Section &<<SECID136>>& contains further information.
23686 This option should not be used when other message-handling software
23687 may duplicate messages by making hardlinks to the files. When that is done Exim
23688 will count the message size once for each filename, in contrast with the actual
23689 disk usage. When the option is not set, calculating total usage requires
23690 a system-call per file to get the size; the number of links is then available also
23691 as is used to adjust the effective size.
23694 .option quota_warn_message appendfile string&!! "see below"
23695 See below for the use of this option. If it is not set when
23696 &%quota_warn_threshold%& is set, it defaults to
23698 quota_warn_message = "\
23699 To: $local_part@$domain\n\
23700 Subject: Your mailbox\n\n\
23701 This message is automatically created \
23702 by mail delivery software.\n\n\
23703 The size of your mailbox has exceeded \
23704 a warning threshold that is\n\
23705 set by the system administrator.\n"
23709 .option quota_warn_threshold appendfile string&!! 0
23710 .cindex "quota" "warning threshold"
23711 .cindex "mailbox" "size warning"
23712 .cindex "size" "of mailbox"
23713 This option is expanded in the same way as &%quota%& (see above). If the
23714 resulting value is greater than zero, and delivery of the message causes the
23715 size of the file or total space in the directory tree to cross the given
23716 threshold, a warning message is sent. If &%quota%& is also set, the threshold
23717 may be specified as a percentage of it by following the value with a percent
23721 quota_warn_threshold = 75%
23723 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
23724 percent sign is ignored.
23726 The warning message itself is specified by the &%quota_warn_message%& option,
23727 and it must start with a &'To:'& header line containing the recipient(s) of the
23728 warning message. These do not necessarily have to include the recipient(s) of
23729 the original message. A &'Subject:'& line should also normally be supplied. You
23730 can include any other header lines that you want. If you do not include a
23731 &'From:'& line, the default is:
23733 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
23735 .oindex &%errors_reply_to%&
23736 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
23739 The &%quota%& option does not have to be set in order to use this option; they
23740 are independent of one another except when the threshold is specified as a
23744 .option use_bsmtp appendfile boolean false
23745 .cindex "envelope from"
23746 .cindex "envelope sender"
23747 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
23748 format, with the envelope sender and recipient(s) included as SMTP commands. If
23749 you want to include a leading HELO command with such messages, you can do
23750 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
23751 for details of batch SMTP.
23754 .option use_crlf appendfile boolean false
23755 .cindex "carriage return"
23757 This option causes lines to be terminated with the two-character CRLF sequence
23758 (carriage return, linefeed) instead of just a linefeed character. In the case
23759 of batched SMTP, the byte sequence written to the file is then an exact image
23760 of what would be sent down a real SMTP connection.
23762 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
23763 (which are used to supply the traditional &"From&~"& and blank line separators
23764 in Berkeley-style mailboxes) are written verbatim, so must contain their own
23765 carriage return characters if these are needed. In cases where these options
23766 have non-empty defaults, the values end with a single linefeed, so they must be
23767 changed to end with &`\r\n`& if &%use_crlf%& is set.
23770 .option use_fcntl_lock appendfile boolean "see below"
23771 This option controls the use of the &[fcntl()]& function to lock a file for
23772 exclusive use when a message is being appended. It is set by default unless
23773 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
23774 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
23775 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
23778 .option use_flock_lock appendfile boolean false
23779 This option is provided to support the use of &[flock()]& for file locking, for
23780 the few situations where it is needed. Most modern operating systems support
23781 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
23782 each other. Exim uses &[fcntl()]& locking by default.
23784 This option is required only if you are using an operating system where
23785 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
23786 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
23787 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
23789 .cindex "Solaris" "&[flock()]& support"
23790 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
23791 have it (and some, I think, provide a not quite right version built on top of
23792 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
23793 the ability to use it, and any attempt to do so will cause a configuration
23796 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
23797 is just being mapped onto &[fcntl()]& by the OS).
23800 .option use_lockfile appendfile boolean "see below"
23801 If this option is turned off, Exim does not attempt to create a lock file when
23802 appending to a mailbox file. In this situation, the only locking is by
23803 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
23804 sure that every MUA that is ever going to look at your users' mailboxes uses
23805 &[fcntl()]& rather than a lock file, and even then only when you are not
23806 delivering over NFS from more than one host.
23808 .cindex "NFS" "lock file"
23809 In order to append to an NFS file safely from more than one host, it is
23810 necessary to take out a lock &'before'& opening the file, and the lock file
23811 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
23814 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
23815 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
23816 except when &%mbx_format%& is set.
23819 .option use_mbx_lock appendfile boolean "see below"
23820 This option is available only if Exim has been compiled with SUPPORT_MBX
23821 set in &_Local/Makefile_&. Setting the option specifies that special MBX
23822 locking rules be used. It is set by default if &%mbx_format%& is set and none
23823 of the locking options are mentioned in the configuration. The locking rules
23824 are the same as are used by the &'c-client'& library that underlies Pine and
23825 the IMAP4 and POP daemons that come with it (see the discussion below). The
23826 rules allow for shared access to the mailbox. However, this kind of locking
23827 does not work when the mailbox is NFS mounted.
23829 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
23830 &%use_flock_lock%& to control what kind of locking is used in implementing the
23831 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
23832 without &%use_fcntl_lock%& or &%use_flock_lock%&.
23837 .section "Operational details for appending" "SECTopappend"
23838 .cindex "appending to a file"
23839 .cindex "file" "appending"
23840 Before appending to a file, the following preparations are made:
23843 If the name of the file is &_/dev/null_&, no action is taken, and a success
23847 .cindex "directory creation"
23848 If any directories on the file's path are missing, Exim creates them if the
23849 &%create_directory%& option is set. A created directory's mode is given by the
23850 &%directory_mode%& option.
23853 If &%file_format%& is set, the format of an existing file is checked. If this
23854 indicates that a different transport should be used, control is passed to that
23858 .cindex "file" "locking"
23859 .cindex "locking files"
23860 .cindex "NFS" "lock file"
23861 If &%use_lockfile%& is set, a lock file is built in a way that will work
23862 reliably over NFS, as follows:
23865 Create a &"hitching post"& file whose name is that of the lock file with the
23866 current time, primary host name, and process id added, by opening for writing
23867 as a new file. If this fails with an access error, delivery is deferred.
23869 Close the hitching post file, and hard link it to the lock filename.
23871 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
23872 Unlink the hitching post name.
23874 Otherwise, use &[stat()]& to get information about the hitching post file, and
23875 then unlink hitching post name. If the number of links is exactly two, creation
23876 of the lock file succeeded but something (for example, an NFS server crash and
23877 restart) caused this fact not to be communicated to the &[link()]& call.
23879 If creation of the lock file failed, wait for &%lock_interval%& and try again,
23880 up to &%lock_retries%& times. However, since any program that writes to a
23881 mailbox should complete its task very quickly, it is reasonable to time out old
23882 lock files that are normally the result of user agent and system crashes. If an
23883 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
23884 it before trying again.
23888 A call is made to &[lstat()]& to discover whether the main file exists, and if
23889 so, what its characteristics are. If &[lstat()]& fails for any reason other
23890 than non-existence, delivery is deferred.
23893 .cindex "symbolic link" "to mailbox"
23894 .cindex "mailbox" "symbolic link"
23895 If the file does exist and is a symbolic link, delivery is deferred, unless the
23896 &%allow_symlink%& option is set, in which case the ownership of the link is
23897 checked, and then &[stat()]& is called to find out about the real file, which
23898 is then subjected to the checks below. The check on the top-level link
23899 ownership prevents one user creating a link for another's mailbox in a sticky
23900 directory, though allowing symbolic links in this case is definitely not a good
23901 idea. If there is a chain of symbolic links, the intermediate ones are not
23905 If the file already exists but is not a regular file, or if the file's owner
23906 and group (if the group is being checked &-- see &%check_group%& above) are
23907 different from the user and group under which the delivery is running,
23908 delivery is deferred.
23911 If the file's permissions are more generous than specified, they are reduced.
23912 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
23913 is set false, in which case the delivery is tried using the existing
23917 The file's inode number is saved, and the file is then opened for appending.
23918 If this fails because the file has vanished, &(appendfile)& behaves as if it
23919 hadn't existed (see below). For any other failures, delivery is deferred.
23922 If the file is opened successfully, check that the inode number hasn't
23923 changed, that it is still a regular file, and that the owner and permissions
23924 have not changed. If anything is wrong, defer delivery and freeze the message.
23927 If the file did not exist originally, defer delivery if the &%file_must_exist%&
23928 option is set. Otherwise, check that the file is being created in a permitted
23929 directory if the &%create_file%& option is set (deferring on failure), and then
23930 open for writing as a new file, with the O_EXCL and O_CREAT options,
23931 except when dealing with a symbolic link (the &%allow_symlink%& option must be
23932 set). In this case, which can happen if the link points to a non-existent file,
23933 the file is opened for writing using O_CREAT but not O_EXCL, because
23934 that prevents link following.
23937 .cindex "loop" "while file testing"
23938 If opening fails because the file exists, obey the tests given above for
23939 existing files. However, to avoid looping in a situation where the file is
23940 being continuously created and destroyed, the exists/not-exists loop is broken
23941 after 10 repetitions, and the message is then frozen.
23944 If opening fails with any other error, defer delivery.
23947 .cindex "file" "locking"
23948 .cindex "locking files"
23949 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
23950 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
23951 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
23952 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
23953 file, and an exclusive lock on the file whose name is
23955 /tmp/.<device-number>.<inode-number>
23957 using the device and inode numbers of the open mailbox file, in accordance with
23958 the MBX locking rules. This file is created with a mode that is specified by
23959 the &%lockfile_mode%& option.
23961 If Exim fails to lock the file, there are two possible courses of action,
23962 depending on the value of the locking timeout. This is obtained from
23963 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
23965 If the timeout value is zero, the file is closed, Exim waits for
23966 &%lock_interval%&, and then goes back and re-opens the file as above and tries
23967 to lock it again. This happens up to &%lock_retries%& times, after which the
23968 delivery is deferred.
23970 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
23971 &[flock()]& are used (with the given timeout), so there has already been some
23972 waiting involved by the time locking fails. Nevertheless, Exim does not give up
23973 immediately. It retries up to
23975 (lock_retries * lock_interval) / <timeout>
23977 times (rounded up).
23980 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
23981 and/or &[flock()]& locks) and then deletes the lock file if one was created.
23984 .section "Operational details for delivery to a new file" "SECTopdir"
23985 .cindex "delivery" "to single file"
23986 .cindex "&""From""& line"
23987 When the &%directory%& option is set instead of &%file%&, each message is
23988 delivered into a newly-created file or set of files. When &(appendfile)& is
23989 activated directly from a &(redirect)& router, neither &%file%& nor
23990 &%directory%& is normally set, because the path for delivery is supplied by the
23991 router. (See for example, the &(address_file)& transport in the default
23992 configuration.) In this case, delivery is to a new file if either the path name
23993 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
23995 No locking is required while writing the message to a new file, so the various
23996 locking options of the transport are ignored. The &"From"& line that by default
23997 separates messages in a single file is not normally needed, nor is the escaping
23998 of message lines that start with &"From"&, and there is no need to ensure a
23999 newline at the end of each message. Consequently, the default values for
24000 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
24001 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
24003 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
24004 the files in the delivery directory by default. However, you can specify a
24005 different directory by setting &%quota_directory%&. Also, for maildir
24006 deliveries (see below) the &_maildirfolder_& convention is honoured.
24009 .cindex "maildir format"
24010 .cindex "mailstore format"
24011 There are three different ways in which delivery to individual files can be
24012 done, controlled by the settings of the &%maildir_format%& and
24013 &%mailstore_format%& options. Note that code to support maildir or mailstore
24014 formats is not included in the binary unless SUPPORT_MAILDIR or
24015 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
24017 .cindex "directory creation"
24018 In all three cases an attempt is made to create the directory and any necessary
24019 sub-directories if they do not exist, provided that the &%create_directory%&
24020 option is set (the default). The location of a created directory can be
24021 constrained by setting &%create_file%&. A created directory's mode is given by
24022 the &%directory_mode%& option. If creation fails, or if the
24023 &%create_directory%& option is not set when creation is required, delivery is
24028 .section "Maildir delivery" "SECTmaildirdelivery"
24029 .cindex "maildir format" "description of"
24030 If the &%maildir_format%& option is true, Exim delivers each message by writing
24031 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
24032 directory that is defined by the &%directory%& option (the &"delivery
24033 directory"&). If the delivery is successful, the file is renamed into the
24034 &_new_& subdirectory.
24036 In the filename, <&'stime'&> is the current time of day in seconds, and
24037 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
24038 Exim checks that the time-of-day clock has moved on by at least one microsecond
24039 before terminating the delivery process. This guarantees uniqueness for the
24040 filename. However, as a precaution, Exim calls &[stat()]& for the file before
24041 opening it. If any response other than ENOENT (does not exist) is given,
24042 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
24044 Before Exim carries out a maildir delivery, it ensures that subdirectories
24045 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
24046 do not exist, Exim tries to create them and any superior directories in their
24047 path, subject to the &%create_directory%& and &%create_file%& options. If the
24048 &%maildirfolder_create_regex%& option is set, and the regular expression it
24049 contains matches the delivery directory, Exim also ensures that a file called
24050 &_maildirfolder_& exists in the delivery directory. If a missing directory or
24051 &_maildirfolder_& file cannot be created, delivery is deferred.
24053 These features make it possible to use Exim to create all the necessary files
24054 and directories in a maildir mailbox, including subdirectories for maildir++
24055 folders. Consider this example:
24057 maildir_format = true
24058 directory = /var/mail/$local_part_data\
24059 ${if eq{$local_part_suffix}{}{}\
24060 {/.${substr_1:$local_part_suffix}}}
24061 maildirfolder_create_regex = /\.[^/]+$
24063 If &$local_part_suffix$& is empty (there was no suffix for the local part),
24064 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
24065 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
24066 not match this name, so Exim will not look for or create the file
24067 &_/var/mail/pimbo/maildirfolder_&, though it will create
24068 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
24070 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
24071 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
24072 does match &%maildirfolder_create_regex%&. In this case, Exim will create
24073 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
24074 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
24076 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
24077 not inadvertently match the toplevel maildir directory, because a
24078 &_maildirfolder_& file at top level would completely break quota calculations.
24080 .cindex "quota" "in maildir delivery"
24081 .cindex "maildir++"
24082 If Exim is required to check a &%quota%& setting before a maildir delivery, and
24083 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
24084 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
24085 Exim assumes the directory is a maildir++ folder directory, which is one level
24086 down from the user's top level mailbox directory. This causes it to start at
24087 the parent directory instead of the current directory when calculating the
24088 amount of space used.
24090 One problem with delivering into a multi-file mailbox is that it is
24091 computationally expensive to compute the size of the mailbox for quota
24092 checking. Various approaches have been taken to reduce the amount of work
24093 needed. The next two sections describe two of them. A third alternative is to
24094 use some external process for maintaining the size data, and use the expansion
24095 of the &%mailbox_size%& option as a way of importing it into Exim.
24100 .section "Using tags to record message sizes" "SECID135"
24101 If &%maildir_tag%& is set, the string is expanded for each delivery.
24102 When the maildir file is renamed into the &_new_& sub-directory, the
24103 tag is added to its name. However, if adding the tag takes the length of the
24104 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
24105 the tag is dropped and the maildir file is created with no tag.
24108 .vindex "&$message_size$&"
24109 Tags can be used to encode the size of files in their names; see
24110 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
24111 happens after the message has been written. The value of the &$message_size$&
24112 variable is set to the number of bytes actually written. If the expansion is
24113 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
24114 be deferred. The expanded tag may contain any printing characters except &"/"&.
24115 Non-printing characters in the string are ignored; if the resulting string is
24116 empty, it is ignored. If it starts with an alphanumeric character, a leading
24117 colon is inserted; this default has not proven to be the path that popular
24118 maildir implementations have chosen (but changing it in Exim would break
24119 backwards compatibility).
24121 For one common implementation, you might set:
24123 maildir_tag = ,S=${message_size}
24125 but you should check the documentation of the other software to be sure.
24127 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
24128 as this allows Exim to extract the size from your tag, instead of having to
24129 &[stat()]& each message file.
24132 .section "Using a maildirsize file" "SECID136"
24133 .cindex "quota" "in maildir delivery"
24134 .cindex "maildir format" "&_maildirsize_& file"
24135 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
24136 storing quota and message size information in a file called &_maildirsize_&
24137 within the toplevel maildir directory. If this file does not exist, Exim
24138 creates it, setting the quota from the &%quota%& option of the transport. If
24139 the maildir directory itself does not exist, it is created before any attempt
24140 to write a &_maildirsize_& file.
24142 The &_maildirsize_& file is used to hold information about the sizes of
24143 messages in the maildir, thus speeding up quota calculations. The quota value
24144 in the file is just a cache; if the quota is changed in the transport, the new
24145 value overrides the cached value when the next message is delivered. The cache
24146 is maintained for the benefit of other programs that access the maildir and
24147 need to know the quota.
24149 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
24150 file is maintained (with a zero quota setting), but no quota is imposed.
24152 A regular expression is available for controlling which directories in the
24153 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
24154 See the description of the &%maildir_quota_directory_regex%& option above for
24158 .section "Mailstore delivery" "SECID137"
24159 .cindex "mailstore format" "description of"
24160 If the &%mailstore_format%& option is true, each message is written as two
24161 files in the given directory. A unique base name is constructed from the
24162 message id and the current delivery process, and the files that are written use
24163 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
24164 contains the message's envelope, and the &_.msg_& file contains the message
24165 itself. The base name is placed in the variable &$mailstore_basename$&.
24167 During delivery, the envelope is first written to a file with the suffix
24168 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
24169 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
24170 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
24171 file before accessing either of them. An alternative approach is to wait for
24172 the absence of a &_.tmp_& file.
24174 The envelope file starts with any text defined by the &%mailstore_prefix%&
24175 option, expanded and terminated by a newline if there isn't one. Then follows
24176 the sender address on one line, then all the recipient addresses, one per line.
24177 There can be more than one recipient only if the &%batch_max%& option is set
24178 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
24179 appended to the file, followed by a newline if it does not end with one.
24181 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
24182 failure, it is ignored. Other expansion errors are treated as serious
24183 configuration errors, and delivery is deferred. The variable
24184 &$mailstore_basename$& is available for use during these expansions.
24187 .section "Non-special new file delivery" "SECID138"
24188 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
24189 file is created directly in the named directory. For example, when delivering
24190 messages into files in batched SMTP format for later delivery to some host (see
24191 section &<<SECTbatchSMTP>>&), a setting such as
24193 directory = /var/bsmtp/$host
24195 might be used. A message is written to a file with a temporary name, which is
24196 then renamed when the delivery is complete. The final name is obtained by
24197 expanding the contents of the &%directory_file%& option.
24198 .ecindex IIDapptra1
24199 .ecindex IIDapptra2
24206 . ////////////////////////////////////////////////////////////////////////////
24207 . ////////////////////////////////////////////////////////////////////////////
24209 .chapter "The autoreply transport" "CHID8"
24210 .scindex IIDauttra1 "transports" "&(autoreply)&"
24211 .scindex IIDauttra2 "&(autoreply)& transport"
24212 The &(autoreply)& transport is not a true transport in that it does not cause
24213 the message to be transmitted. Instead, it generates a new mail message as an
24214 automatic reply to the incoming message. &'References:'& and
24215 &'Auto-Submitted:'& header lines are included. These are constructed according
24216 to the rules in RFCs 2822 and 3834, respectively.
24218 If the router that passes the message to this transport does not have the
24219 &%unseen%& option set, the original message (for the current recipient) is not
24220 delivered anywhere. However, when the &%unseen%& option is set on the router
24221 that passes the message to this transport, routing of the address continues, so
24222 another router can set up a normal message delivery.
24225 The &(autoreply)& transport is usually run as the result of mail filtering, a
24226 &"vacation"& message being the standard example. However, it can also be run
24227 directly from a router like any other transport. To reduce the possibility of
24228 message cascades, messages created by the &(autoreply)& transport always have
24229 empty envelope sender addresses, like bounce messages.
24231 The parameters of the message to be sent can be specified in the configuration
24232 by options described below. However, these are used only when the address
24233 passed to the transport does not contain its own reply information. When the
24234 transport is run as a consequence of a
24236 or &%vacation%& command in a filter file, the parameters of the message are
24237 supplied by the filter, and passed with the address. The transport's options
24238 that define the message are then ignored (so they are not usually set in this
24239 case). The message is specified entirely by the filter or by the transport; it
24240 is never built from a mixture of options. However, the &%file_optional%&,
24241 &%mode%&, and &%return_message%& options apply in all cases.
24243 &(Autoreply)& is implemented as a local transport. When used as a result of a
24244 command in a user's filter file, &(autoreply)& normally runs under the uid and
24245 gid of the user, and with appropriate current and home directories (see chapter
24246 &<<CHAPenvironment>>&).
24248 There is a subtle difference between routing a message to a &(pipe)& transport
24249 that generates some text to be returned to the sender, and routing it to an
24250 &(autoreply)& transport. This difference is noticeable only if more than one
24251 address from the same message is so handled. In the case of a pipe, the
24252 separate outputs from the different addresses are gathered up and returned to
24253 the sender in a single message, whereas if &(autoreply)& is used, a separate
24254 message is generated for each address that is passed to it.
24256 Non-printing characters are not permitted in the header lines generated for the
24257 message that &(autoreply)& creates, with the exception of newlines that are
24258 immediately followed by white space. If any non-printing characters are found,
24259 the transport defers.
24260 Whether characters with the top bit set count as printing characters or not is
24261 controlled by the &%print_topbitchars%& global option.
24263 If any of the generic options for manipulating headers (for example,
24264 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
24265 of the original message that is included in the generated message when
24266 &%return_message%& is set. They do not apply to the generated message itself.
24268 .vindex "&$sender_address$&"
24269 If the &(autoreply)& transport receives return code 2 from Exim when it submits
24270 the message, indicating that there were no recipients, it does not treat this
24271 as an error. This means that autoreplies sent to &$sender_address$& when this
24272 is empty (because the incoming message is a bounce message) do not cause
24273 problems. They are just discarded.
24277 .section "Private options for autoreply" "SECID139"
24278 .cindex "options" "&(autoreply)& transport"
24280 .option bcc autoreply string&!! unset
24281 This specifies the addresses that are to receive &"blind carbon copies"& of the
24282 message when the message is specified by the transport.
24285 .option cc autoreply string&!! unset
24286 This specifies recipients of the message and the contents of the &'Cc:'& header
24287 when the message is specified by the transport.
24290 .option file autoreply string&!! unset
24291 The contents of the file are sent as the body of the message when the message
24292 is specified by the transport. If both &%file%& and &%text%& are set, the text
24293 string comes first.
24296 .option file_expand autoreply boolean false
24297 If this is set, the contents of the file named by the &%file%& option are
24298 subjected to string expansion as they are added to the message.
24301 .option file_optional autoreply boolean false
24302 If this option is true, no error is generated if the file named by the &%file%&
24303 option or passed with the address does not exist or cannot be read.
24306 .option from autoreply string&!! unset
24307 This specifies the contents of the &'From:'& header when the message is
24308 specified by the transport.
24311 .option headers autoreply string&!! unset
24312 This specifies additional RFC 2822 headers that are to be added to the message
24313 when the message is specified by the transport. Several can be given by using
24314 &"\n"& to separate them. There is no check on the format.
24317 .option log autoreply string&!! unset
24318 This option names a file in which a record of every message sent is logged when
24319 the message is specified by the transport.
24322 .option mode autoreply "octal integer" 0600
24323 If either the log file or the &"once"& file has to be created, this mode is
24327 .option never_mail autoreply "address list&!!" unset
24328 If any run of the transport creates a message with a recipient that matches any
24329 item in the list, that recipient is quietly discarded. If all recipients are
24330 discarded, no message is created. This applies both when the recipients are
24331 generated by a filter and when they are specified in the transport.
24335 .option once autoreply string&!! unset
24336 This option names a file or DBM database in which a record of each &'To:'&
24337 recipient is kept when the message is specified by the transport. &*Note*&:
24338 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
24340 If &%once%& is unset, or is set to an empty string, the message is always sent.
24341 By default, if &%once%& is set to a non-empty filename, the message
24342 is not sent if a potential recipient is already listed in the database.
24343 However, if the &%once_repeat%& option specifies a time greater than zero, the
24344 message is sent if that much time has elapsed since a message was last sent to
24345 this recipient. A setting of zero time for &%once_repeat%& (the default)
24346 prevents a message from being sent a second time &-- in this case, zero means
24349 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
24350 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
24351 greater than zero, it changes the way Exim implements the &%once%& option.
24352 Instead of using a DBM file to record every recipient it sends to, it uses a
24353 regular file, whose size will never get larger than the given value.
24355 In the file, Exim keeps a linear list of recipient addresses and the times at
24356 which they were sent messages. If the file is full when a new address needs to
24357 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
24358 means that a given recipient may receive multiple messages, but at
24359 unpredictable intervals that depend on the rate of turnover of addresses in the
24360 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
24363 .option once_file_size autoreply integer 0
24364 See &%once%& above.
24367 .option once_repeat autoreply time&!! 0s
24368 See &%once%& above.
24369 After expansion, the value of this option must be a valid time value.
24372 .option reply_to autoreply string&!! unset
24373 This specifies the contents of the &'Reply-To:'& header when the message is
24374 specified by the transport.
24377 .option return_message autoreply boolean false
24378 If this is set, a copy of the original message is returned with the new
24379 message, subject to the maximum size set in the &%return_size_limit%& global
24380 configuration option.
24383 .option subject autoreply string&!! unset
24384 This specifies the contents of the &'Subject:'& header when the message is
24385 specified by the transport. It is tempting to quote the original subject in
24386 automatic responses. For example:
24388 subject = Re: $h_subject:
24390 There is a danger in doing this, however. It may allow a third party to
24391 subscribe your users to an opt-in mailing list, provided that the list accepts
24392 bounce messages as subscription confirmations. Well-managed lists require a
24393 non-bounce message to confirm a subscription, so the danger is relatively
24398 .option text autoreply string&!! unset
24399 This specifies a single string to be used as the body of the message when the
24400 message is specified by the transport. If both &%text%& and &%file%& are set,
24401 the text comes first.
24404 .option to autoreply string&!! unset
24405 This specifies recipients of the message and the contents of the &'To:'& header
24406 when the message is specified by the transport.
24407 .ecindex IIDauttra1
24408 .ecindex IIDauttra2
24413 . ////////////////////////////////////////////////////////////////////////////
24414 . ////////////////////////////////////////////////////////////////////////////
24416 .chapter "The lmtp transport" "CHAPLMTP"
24417 .cindex "transports" "&(lmtp)&"
24418 .cindex "&(lmtp)& transport"
24419 .cindex "LMTP" "over a pipe"
24420 .cindex "LMTP" "over a socket"
24421 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
24423 or by interacting with a Unix domain socket.
24424 This transport is something of a cross between the &(pipe)& and &(smtp)&
24425 transports. Exim also has support for using LMTP over TCP/IP; this is
24426 implemented as an option for the &(smtp)& transport. Because LMTP is expected
24427 to be of minority interest, the default build-time configure in &_src/EDITME_&
24428 has it commented out. You need to ensure that
24432 .cindex "options" "&(lmtp)& transport"
24433 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
24434 included in the Exim binary. The private options of the &(lmtp)& transport are
24437 .option batch_id lmtp string&!! unset
24438 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24441 .option batch_max lmtp integer 1
24442 This limits the number of addresses that can be handled in a single delivery.
24443 Most LMTP servers can handle several addresses at once, so it is normally a
24444 good idea to increase this value. See the description of local delivery
24445 batching in chapter &<<CHAPbatching>>&.
24448 .option command lmtp string&!! unset
24449 This option must be set if &%socket%& is not set. The string is a command which
24450 is run in a separate process. It is split up into a command name and list of
24451 arguments, each of which is separately expanded (so expansion cannot change the
24452 number of arguments). The command is run directly, not via a shell. The message
24453 is passed to the new process using the standard input and output to operate the
24456 .option ignore_quota lmtp boolean false
24457 .cindex "LMTP" "ignoring quota errors"
24458 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
24459 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
24460 in its response to the LHLO command.
24462 .option socket lmtp string&!! unset
24463 This option must be set if &%command%& is not set. The result of expansion must
24464 be the name of a Unix domain socket. The transport connects to the socket and
24465 delivers the message to it using the LMTP protocol.
24468 .option timeout lmtp time 5m
24469 The transport is aborted if the created process or Unix domain socket does not
24470 respond to LMTP commands or message input within this timeout. Delivery
24471 is deferred, and will be tried again later. Here is an example of a typical
24476 command = /some/local/lmtp/delivery/program
24480 This delivers up to 20 addresses at a time, in a mixture of domains if
24481 necessary, running as the user &'exim'&.
24485 . ////////////////////////////////////////////////////////////////////////////
24486 . ////////////////////////////////////////////////////////////////////////////
24488 .chapter "The pipe transport" "CHAPpipetransport"
24489 .scindex IIDpiptra1 "transports" "&(pipe)&"
24490 .scindex IIDpiptra2 "&(pipe)& transport"
24491 The &(pipe)& transport is used to deliver messages via a pipe to a command
24492 running in another process. One example is the use of &(pipe)& as a
24493 pseudo-remote transport for passing messages to some other delivery mechanism
24494 (such as UUCP). Another is the use by individual users to automatically process
24495 their incoming messages. The &(pipe)& transport can be used in one of the
24499 .vindex "&$local_part$&"
24500 A router routes one address to a transport in the normal way, and the
24501 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
24502 contains the local part of the address (as usual), and the command that is run
24503 is specified by the &%command%& option on the transport.
24505 .vindex "&$pipe_addresses$&"
24506 If the &%batch_max%& option is set greater than 1 (the default is 1), the
24507 transport can handle more than one address in a single run. In this case, when
24508 more than one address is routed to the transport, &$local_part$& is not set
24509 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
24510 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
24511 that are routed to the transport.
24513 .vindex "&$address_pipe$&"
24514 A router redirects an address directly to a pipe command (for example, from an
24515 alias or forward file). In this case, &$address_pipe$& contains the text of the
24516 pipe command, and the &%command%& option on the transport is ignored unless
24517 &%force_command%& is set. If only one address is being transported
24518 (&%batch_max%& is not greater than one, or only one address was redirected to
24519 this pipe command), &$local_part$& contains the local part that was redirected.
24523 The &(pipe)& transport is a non-interactive delivery method. Exim can also
24524 deliver messages over pipes using the LMTP interactive protocol. This is
24525 implemented by the &(lmtp)& transport.
24527 In the case when &(pipe)& is run as a consequence of an entry in a local user's
24528 &_.forward_& file, the command runs under the uid and gid of that user. In
24529 other cases, the uid and gid have to be specified explicitly, either on the
24530 transport or on the router that handles the address. Current and &"home"&
24531 directories are also controllable. See chapter &<<CHAPenvironment>>& for
24532 details of the local delivery environment and chapter &<<CHAPbatching>>&
24533 for a discussion of local delivery batching.
24535 .cindex "tainted data" "in pipe command"
24536 .cindex pipe "tainted data"
24537 Tainted data may not be used for the command name.
24540 .section "Concurrent delivery" "SECID140"
24541 If two messages arrive at almost the same time, and both are routed to a pipe
24542 delivery, the two pipe transports may be run concurrently. You must ensure that
24543 any pipe commands you set up are robust against this happening. If the commands
24544 write to a file, the &%exim_lock%& utility might be of use.
24545 Alternatively the &%max_parallel%& option could be used with a value
24546 of "1" to enforce serialization.
24551 .section "Returned status and data" "SECID141"
24552 .cindex "&(pipe)& transport" "returned data"
24553 If the command exits with a non-zero return code, the delivery is deemed to
24554 have failed, unless either the &%ignore_status%& option is set (in which case
24555 the return code is treated as zero), or the return code is one of those listed
24556 in the &%temp_errors%& option, which are interpreted as meaning &"try again
24557 later"&. In this case, delivery is deferred. Details of a permanent failure are
24558 logged, but are not included in the bounce message, which merely contains
24559 &"local delivery failed"&.
24561 If the command exits on a signal and the &%freeze_signal%& option is set then
24562 the message will be frozen in the queue. If that option is not set, a bounce
24563 will be sent as normal.
24565 If the return code is greater than 128 and the command being run is a shell
24566 script, it normally means that the script was terminated by a signal whose
24567 value is the return code minus 128. The &%freeze_signal%& option does not
24568 apply in this case.
24570 If Exim is unable to run the command (that is, if &[execve()]& fails), the
24571 return code is set to 127. This is the value that a shell returns if it is
24572 asked to run a non-existent command. The wording for the log line suggests that
24573 a non-existent command may be the problem.
24575 The &%return_output%& option can affect the result of a pipe delivery. If it is
24576 set and the command produces any output on its standard output or standard
24577 error streams, the command is considered to have failed, even if it gave a zero
24578 return code or if &%ignore_status%& is set. The output from the command is
24579 included as part of the bounce message. The &%return_fail_output%& option is
24580 similar, except that output is returned only when the command exits with a
24581 failure return code, that is, a value other than zero or a code that matches
24586 .section "How the command is run" "SECThowcommandrun"
24587 .cindex "&(pipe)& transport" "path for command"
24588 The command line is (by default) broken down into a command name and arguments
24589 by the &(pipe)& transport itself. The &%allow_commands%& and
24590 &%restrict_to_path%& options can be used to restrict the commands that may be
24593 .cindex "quoting" "in pipe command"
24594 Unquoted arguments are delimited by white space. If an argument appears in
24595 double quotes, backslash is interpreted as an escape character in the usual
24596 way. If an argument appears in single quotes, no escaping is done.
24598 String expansion is applied to the command line except when it comes from a
24599 traditional &_.forward_& file (commands from a filter file are expanded). The
24600 expansion is applied to each argument in turn rather than to the whole line.
24601 For this reason, any string expansion item that contains white space must be
24602 quoted so as to be contained within a single argument. A setting such as
24604 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
24606 will not work, because the expansion item gets split between several
24607 arguments. You have to write
24609 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
24611 to ensure that it is all in one argument. The expansion is done in this way,
24612 argument by argument, so that the number of arguments cannot be changed as a
24613 result of expansion, and quotes or backslashes in inserted variables do not
24614 interact with external quoting. However, this leads to problems if you want to
24615 generate multiple arguments (or the command name plus arguments) from a single
24616 expansion. In this situation, the simplest solution is to use a shell. For
24619 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
24622 .cindex "transport" "filter"
24623 .cindex "filter" "transport filter"
24624 .vindex "&$pipe_addresses$&"
24625 Special handling takes place when an argument consists of precisely the text
24626 &`$pipe_addresses`& (no quotes).
24627 This is not a general expansion variable; the only
24628 place this string is recognized is when it appears as an argument for a pipe or
24629 transport filter command. It causes each address that is being handled to be
24630 inserted in the argument list at that point &'as a separate argument'&. This
24631 avoids any problems with spaces or shell metacharacters, and is of use when a
24632 &(pipe)& transport is handling groups of addresses in a batch.
24634 If &%force_command%& is enabled on the transport, special handling takes place
24635 for an argument that consists of precisely the text &`$address_pipe`&. It
24636 is handled similarly to &$pipe_addresses$& above. It is expanded and each
24637 argument is inserted in the argument list at that point
24638 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
24639 the only item in the argument; in fact, if it were then &%force_command%&
24640 should behave as a no-op. Rather, it should be used to adjust the command
24641 run while preserving the argument vector separation.
24643 After splitting up into arguments and expansion, the resulting command is run
24644 in a subprocess directly from the transport, &'not'& under a shell. The
24645 message that is being delivered is supplied on the standard input, and the
24646 standard output and standard error are both connected to a single pipe that is
24647 read by Exim. The &%max_output%& option controls how much output the command
24648 may produce, and the &%return_output%& and &%return_fail_output%& options
24649 control what is done with it.
24651 Not running the command under a shell (by default) lessens the security risks
24652 in cases when a command from a user's filter file is built out of data that was
24653 taken from an incoming message. If a shell is required, it can of course be
24654 explicitly specified as the command to be run. However, there are circumstances
24655 where existing commands (for example, in &_.forward_& files) expect to be run
24656 under a shell and cannot easily be modified. To allow for these cases, there is
24657 an option called &%use_shell%&, which changes the way the &(pipe)& transport
24658 works. Instead of breaking up the command line as just described, it expands it
24659 as a single string and passes the result to &_/bin/sh_&. The
24660 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
24661 with &%use_shell%&, and the whole mechanism is inherently less secure.
24665 .section "Environment variables" "SECTpipeenv"
24666 .cindex "&(pipe)& transport" "environment for command"
24667 .cindex "environment" "&(pipe)& transport"
24668 The environment variables listed below are set up when the command is invoked.
24669 This list is a compromise for maximum compatibility with other MTAs. Note that
24670 the &%environment%& option can be used to add additional variables to this
24671 environment. The environment for the &(pipe)& transport is not subject
24672 to the &%add_environment%& and &%keep_environment%& main config options.
24674 &`DOMAIN `& the domain of the address
24675 &`HOME `& the home directory, if set
24676 &`HOST `& the host name when called from a router (see below)
24677 &`LOCAL_PART `& see below
24678 &`LOCAL_PART_PREFIX `& see below
24679 &`LOCAL_PART_SUFFIX `& see below
24680 &`LOGNAME `& see below
24681 &`MESSAGE_ID `& Exim's local ID for the message
24682 &`PATH `& as specified by the &%path%& option below
24683 &`QUALIFY_DOMAIN `& the sender qualification domain
24684 &`RECIPIENT `& the complete recipient address
24685 &`SENDER `& the sender of the message (empty if a bounce)
24686 &`SHELL `& &`/bin/sh`&
24687 &`TZ `& the value of the &%timezone%& option, if set
24688 &`USER `& see below
24690 When a &(pipe)& transport is called directly from (for example) an &(accept)&
24691 router, LOCAL_PART is set to the local part of the address. When it is
24692 called as a result of a forward or alias expansion, LOCAL_PART is set to
24693 the local part of the address that was expanded. In both cases, any affixes are
24694 removed from the local part, and made available in LOCAL_PART_PREFIX and
24695 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
24696 same value as LOCAL_PART for compatibility with other MTAs.
24699 HOST is set only when a &(pipe)& transport is called from a router that
24700 associates hosts with an address, typically when using &(pipe)& as a
24701 pseudo-remote transport. HOST is set to the first host name specified by
24705 If the transport's generic &%home_directory%& option is set, its value is used
24706 for the HOME environment variable. Otherwise, a home directory may be set
24707 by the router's &%transport_home_directory%& option, which defaults to the
24708 user's home directory if &%check_local_user%& is set.
24711 .section "Private options for pipe" "SECID142"
24712 .cindex "options" "&(pipe)& transport"
24716 .option allow_commands pipe "string list&!!" unset
24717 .cindex "&(pipe)& transport" "permitted commands"
24718 The string is expanded, and is then interpreted as a colon-separated list of
24719 permitted commands. If &%restrict_to_path%& is not set, the only commands
24720 permitted are those in the &%allow_commands%& list. They need not be absolute
24721 paths; the &%path%& option is still used for relative paths. If
24722 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
24723 in the &%allow_commands%& list, or a name without any slashes that is found on
24724 the path. In other words, if neither &%allow_commands%& nor
24725 &%restrict_to_path%& is set, there is no restriction on the command, but
24726 otherwise only commands that are permitted by one or the other are allowed. For
24729 allow_commands = /usr/bin/vacation
24731 and &%restrict_to_path%& is not set, the only permitted command is
24732 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
24733 &%use_shell%& is set.
24736 .option batch_id pipe string&!! unset
24737 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24740 .option batch_max pipe integer 1
24741 This limits the number of addresses that can be handled in a single delivery.
24742 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24745 .option check_string pipe string unset
24746 As &(pipe)& writes the message, the start of each line is tested for matching
24747 &%check_string%&, and if it does, the initial matching characters are replaced
24748 by the contents of &%escape_string%&, provided both are set. The value of
24749 &%check_string%& is a literal string, not a regular expression, and the case of
24750 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
24751 of &%check_string%& and &%escape_string%& are forced to values that implement
24752 the SMTP escaping protocol. Any settings made in the configuration file are
24756 .option command pipe string&!! unset
24757 This option need not be set when &(pipe)& is being used to deliver to pipes
24758 obtained directly from address redirections. In other cases, the option must be
24759 set, to provide a command to be run. It need not yield an absolute path (see
24760 the &%path%& option below). The command is split up into separate arguments by
24761 Exim, and each argument is separately expanded, as described in section
24762 &<<SECThowcommandrun>>& above.
24765 .option environment pipe string&!! unset
24766 .cindex "&(pipe)& transport" "environment for command"
24767 .cindex "environment" "&(pipe)& transport"
24768 This option is used to add additional variables to the environment in which the
24769 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
24770 a string which is expanded, and then interpreted as a colon-separated list of
24771 environment settings of the form <&'name'&>=<&'value'&>.
24774 .option escape_string pipe string unset
24775 See &%check_string%& above.
24778 .option freeze_exec_fail pipe boolean false
24779 .cindex "exec failure"
24780 .cindex "failure of exec"
24781 .cindex "&(pipe)& transport" "failure of exec"
24782 Failure to exec the command in a pipe transport is by default treated like
24783 any other failure while running the command. However, if &%freeze_exec_fail%&
24784 is set, failure to exec is treated specially, and causes the message to be
24785 frozen, whatever the setting of &%ignore_status%&.
24788 .option freeze_signal pipe boolean false
24789 .cindex "signal exit"
24790 .cindex "&(pipe)& transport", "signal exit"
24791 Normally if the process run by a command in a pipe transport exits on a signal,
24792 a bounce message is sent. If &%freeze_signal%& is set, the message will be
24793 frozen in Exim's queue instead.
24796 .option force_command pipe boolean false
24797 .cindex "force command"
24798 .cindex "&(pipe)& transport", "force command"
24799 Normally when a router redirects an address directly to a pipe command
24800 the &%command%& option on the transport is ignored. If &%force_command%&
24801 is set, the &%command%& option will used. This is especially
24802 useful for forcing a wrapper or additional argument to be added to the
24803 command. For example:
24805 command = /usr/bin/remote_exec myhost -- $address_pipe
24809 Note that &$address_pipe$& is handled specially in &%command%& when
24810 &%force_command%& is set, expanding out to the original argument vector as
24811 separate items, similarly to a Unix shell &`"$@"`& construct.
24814 .option ignore_status pipe boolean false
24815 If this option is true, the status returned by the subprocess that is set up to
24816 run the command is ignored, and Exim behaves as if zero had been returned.
24817 Otherwise, a non-zero status or termination by signal causes an error return
24818 from the transport unless the status value is one of those listed in
24819 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
24821 &*Note*&: This option does not apply to timeouts, which do not return a status.
24822 See the &%timeout_defer%& option for how timeouts are handled.
24825 .option log_defer_output pipe boolean false
24826 .cindex "&(pipe)& transport" "logging output"
24827 If this option is set, and the status returned by the command is
24828 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
24829 and any output was produced on stdout or stderr, the first line of it is
24830 written to the main log.
24833 .option log_fail_output pipe boolean false
24834 If this option is set, and the command returns any output on stdout or
24835 stderr, and also ends with a return code that is neither zero nor one of
24836 the return codes listed in &%temp_errors%& (that is, the delivery
24837 failed), the first line of output is written to the main log. This
24838 option and &%log_output%& are mutually exclusive. Only one of them may
24842 .option log_output pipe boolean false
24843 If this option is set and the command returns any output on stdout or
24844 stderr, the first line of output is written to the main log, whatever
24845 the return code. This option and &%log_fail_output%& are mutually
24846 exclusive. Only one of them may be set.
24849 .option max_output pipe integer 20K
24850 This specifies the maximum amount of output that the command may produce on its
24851 standard output and standard error file combined. If the limit is exceeded, the
24852 process running the command is killed. This is intended as a safety measure to
24853 catch runaway processes. The limit is applied independently of the settings of
24854 the options that control what is done with such output (for example,
24855 &%return_output%&). Because of buffering effects, the amount of output may
24856 exceed the limit by a small amount before Exim notices.
24859 .option message_prefix pipe string&!! "see below"
24860 The string specified here is expanded and output at the start of every message.
24861 The default is unset if &%use_bsmtp%& is set. Otherwise it is
24864 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
24868 .cindex "&%tmail%&"
24869 .cindex "&""From""& line"
24870 This is required by the commonly used &_/usr/bin/vacation_& program.
24871 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
24872 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
24877 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24878 &`\n`& to &`\r\n`& in &%message_prefix%&.
24881 .option message_suffix pipe string&!! "see below"
24882 The string specified here is expanded and output at the end of every message.
24883 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
24884 The suffix can be suppressed by setting
24888 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24889 &`\n`& to &`\r\n`& in &%message_suffix%&.
24892 .option path pipe string&!! "/bin:/usr/bin"
24893 This option is expanded and
24894 specifies the string that is set up in the PATH environment
24895 variable of the subprocess.
24896 If the &%command%& option does not yield an absolute path name, the command is
24897 sought in the PATH directories, in the usual way. &*Warning*&: This does not
24898 apply to a command specified as a transport filter.
24901 .option permit_coredump pipe boolean false
24902 Normally Exim inhibits core-dumps during delivery. If you have a need to get
24903 a core-dump of a pipe command, enable this command. This enables core-dumps
24904 during delivery and affects both the Exim binary and the pipe command run.
24905 It is recommended that this option remain off unless and until you have a need
24906 for it and that this only be enabled when needed, as the risk of excessive
24907 resource consumption can be quite high. Note also that Exim is typically
24908 installed as a setuid binary and most operating systems will inhibit coredumps
24909 of these by default, so further OS-specific action may be required.
24912 .option pipe_as_creator pipe boolean false
24913 .cindex "uid (user id)" "local delivery"
24914 If the generic &%user%& option is not set and this option is true, the delivery
24915 process is run under the uid that was in force when Exim was originally called
24916 to accept the message. If the group id is not otherwise set (via the generic
24917 &%group%& option), the gid that was in force when Exim was originally called to
24918 accept the message is used.
24921 .option restrict_to_path pipe boolean false
24922 When this option is set, any command name not listed in &%allow_commands%& must
24923 contain no slashes. The command is searched for only in the directories listed
24924 in the &%path%& option. This option is intended for use in the case when a pipe
24925 command has been generated from a user's &_.forward_& file. This is usually
24926 handled by a &(pipe)& transport called &%address_pipe%&.
24929 .option return_fail_output pipe boolean false
24930 If this option is true, and the command produced any output and ended with a
24931 return code other than zero or one of the codes listed in &%temp_errors%& (that
24932 is, the delivery failed), the output is returned in the bounce message.
24933 However, if the message has a null sender (that is, it is itself a bounce
24934 message), output from the command is discarded. This option and
24935 &%return_output%& are mutually exclusive. Only one of them may be set.
24939 .option return_output pipe boolean false
24940 If this option is true, and the command produced any output, the delivery is
24941 deemed to have failed whatever the return code from the command, and the output
24942 is returned in the bounce message. Otherwise, the output is just discarded.
24943 However, if the message has a null sender (that is, it is a bounce message),
24944 output from the command is always discarded, whatever the setting of this
24945 option. This option and &%return_fail_output%& are mutually exclusive. Only one
24946 of them may be set.
24950 .option temp_errors pipe "string list" "see below"
24951 .cindex "&(pipe)& transport" "temporary failure"
24952 This option contains either a colon-separated list of numbers, or a single
24953 asterisk. If &%ignore_status%& is false
24954 and &%return_output%& is not set,
24955 and the command exits with a non-zero return code, the failure is treated as
24956 temporary and the delivery is deferred if the return code matches one of the
24957 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
24958 codes are treated as permanent errors. The default setting contains the codes
24959 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
24960 compiled on a system that does not define these macros, it assumes values of 75
24961 and 73, respectively.
24964 .option timeout pipe time 1h
24965 If the command fails to complete within this time, it is killed. This normally
24966 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
24967 specifies no timeout. In order to ensure that any subprocesses created by the
24968 command are also killed, Exim makes the initial process a process group leader,
24969 and kills the whole process group on a timeout. However, this can be defeated
24970 if one of the processes starts a new process group.
24972 .option timeout_defer pipe boolean false
24973 A timeout in a &(pipe)& transport, either in the command that the transport
24974 runs, or in a transport filter that is associated with it, is by default
24975 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
24976 is set true, both kinds of timeout become temporary errors, causing the
24977 delivery to be deferred.
24979 .option umask pipe "octal integer" 022
24980 This specifies the umask setting for the subprocess that runs the command.
24983 .option use_bsmtp pipe boolean false
24984 .cindex "envelope sender"
24985 If this option is set true, the &(pipe)& transport writes messages in &"batch
24986 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
24987 commands. If you want to include a leading HELO command with such messages,
24988 you can do so by setting the &%message_prefix%& option. See section
24989 &<<SECTbatchSMTP>>& for details of batch SMTP.
24991 .option use_classresources pipe boolean false
24992 .cindex "class resources (BSD)"
24993 This option is available only when Exim is running on FreeBSD, NetBSD, or
24994 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
24995 resource limits when a &(pipe)& transport is run to perform a delivery. The
24996 limits for the uid under which the pipe is to run are obtained from the login
25000 .option use_crlf pipe boolean false
25001 .cindex "carriage return"
25003 This option causes lines to be terminated with the two-character CRLF sequence
25004 (carriage return, linefeed) instead of just a linefeed character. In the case
25005 of batched SMTP, the byte sequence written to the pipe is then an exact image
25006 of what would be sent down a real SMTP connection.
25008 The contents of the &%message_prefix%& and &%message_suffix%& options are
25009 written verbatim, so must contain their own carriage return characters if these
25010 are needed. When &%use_bsmtp%& is not set, the default values for both
25011 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
25012 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
25015 .option use_shell pipe boolean false
25016 .vindex "&$pipe_addresses$&"
25017 If this option is set, it causes the command to be passed to &_/bin/sh_&
25018 instead of being run directly from the transport, as described in section
25019 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
25020 where the command is expected to be run under a shell and cannot easily be
25021 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
25022 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
25023 command is expanded as a single string, and handed to &_/bin/sh_& as data for
25028 .section "Using an external local delivery agent" "SECID143"
25029 .cindex "local delivery" "using an external agent"
25030 .cindex "&'procmail'&"
25031 .cindex "external local delivery"
25032 .cindex "delivery" "&'procmail'&"
25033 .cindex "delivery" "by external agent"
25034 The &(pipe)& transport can be used to pass all messages that require local
25035 delivery to a separate local delivery agent such as &%procmail%&. When doing
25036 this, care must be taken to ensure that the pipe is run under an appropriate
25037 uid and gid. In some configurations one wants this to be a uid that is trusted
25038 by the delivery agent to supply the correct sender of the message. It may be
25039 necessary to recompile or reconfigure the delivery agent so that it trusts an
25040 appropriate user. The following is an example transport and router
25041 configuration for &%procmail%&:
25046 command = /usr/local/bin/procmail -d $local_part_data
25050 check_string = "From "
25051 escape_string = ">From "
25053 user = $local_part_data
25060 transport = procmail_pipe
25062 In this example, the pipe is run as the local user, but with the group set to
25063 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
25064 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
25065 user to supply a correct sender address. If you do not specify either a
25066 &%group%& or a &%user%& option, the pipe command is run as the local user. The
25067 home directory is the user's home directory by default.
25069 &*Note*&: The command that the pipe transport runs does &'not'& begin with
25073 as shown in some &%procmail%& documentation, because Exim does not by default
25074 use a shell to run pipe commands.
25077 The next example shows a transport and a router for a system where local
25078 deliveries are handled by the Cyrus IMAP server.
25081 local_delivery_cyrus:
25083 command = /usr/cyrus/bin/deliver \
25084 -m ${substr_1:$local_part_suffix} -- $local_part
25096 local_part_suffix = .*
25097 transport = local_delivery_cyrus
25099 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
25100 &%return_output%& to cause any text written by Cyrus to be returned to the
25102 .ecindex IIDpiptra1
25103 .ecindex IIDpiptra2
25106 . ////////////////////////////////////////////////////////////////////////////
25107 . ////////////////////////////////////////////////////////////////////////////
25109 .chapter "The smtp transport" "CHAPsmtptrans"
25110 .scindex IIDsmttra1 "transports" "&(smtp)&"
25111 .scindex IIDsmttra2 "&(smtp)& transport"
25112 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
25113 or LMTP protocol. The list of hosts to try can either be taken from the address
25114 that is being processed (having been set up by the router), or specified
25115 explicitly for the transport. Timeout and retry processing (see chapter
25116 &<<CHAPretry>>&) is applied to each IP address independently.
25119 .section "Multiple messages on a single connection" "SECID144"
25120 The sending of multiple messages over a single TCP/IP connection can arise in
25124 If a message contains more than &%max_rcpt%& (see below) addresses that are
25125 routed to the same host, more than one copy of the message has to be sent to
25126 that host. In this situation, multiple copies may be sent in a single run of
25127 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
25128 does when it has too many addresses to send in one message also depends on the
25129 value of the global &%remote_max_parallel%& option. Details are given in
25130 section &<<SECToutSMTPTCP>>&.)
25132 .cindex "hints database" "remembering routing"
25133 When a message has been successfully delivered over a TCP/IP connection, Exim
25134 looks in its hints database to see if there are any other messages awaiting a
25135 connection to the same host. If there are, a new delivery process is started
25136 for one of them, and the current TCP/IP connection is passed on to it. The new
25137 process may in turn send multiple copies and possibly create yet another
25142 For each copy sent over the same TCP/IP connection, a sequence counter is
25143 incremented, and if it ever gets to the value of &%connection_max_messages%&,
25144 no further messages are sent over that connection.
25148 .section "Use of the $host and $host_address variables" "SECID145"
25150 .vindex "&$host_address$&"
25151 At the start of a run of the &(smtp)& transport, the values of &$host$& and
25152 &$host_address$& are the name and IP address of the first host on the host list
25153 passed by the router. However, when the transport is about to connect to a
25154 specific host, and while it is connected to that host, &$host$& and
25155 &$host_address$& are set to the values for that host. These are the values
25156 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
25157 &%serialize_hosts%&, and the various TLS options are expanded.
25160 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
25161 .vindex &$tls_bits$&
25162 .vindex &$tls_cipher$&
25163 .vindex &$tls_peerdn$&
25164 .vindex &$tls_sni$&
25165 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
25166 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
25167 are the values that were set when the message was received.
25168 These are the values that are used for options that are expanded before any
25169 SMTP connections are made. Just before each connection is made, these four
25170 variables are emptied. If TLS is subsequently started, they are set to the
25171 appropriate values for the outgoing connection, and these are the values that
25172 are in force when any authenticators are run and when the
25173 &%authenticated_sender%& option is expanded.
25175 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
25176 and will be removed in a future release.
25179 .section "Private options for smtp" "SECID146"
25180 .cindex "options" "&(smtp)& transport"
25181 The private options of the &(smtp)& transport are as follows:
25184 .option address_retry_include_sender smtp boolean true
25185 .cindex "4&'xx'& responses" "retrying after"
25186 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
25187 is the combination of sender and recipient that is delayed in subsequent queue
25188 runs until the retry time is reached. You can delay the recipient without
25189 reference to the sender (which is what earlier versions of Exim did), by
25190 setting &%address_retry_include_sender%& false. However, this can lead to
25191 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
25193 .option allow_localhost smtp boolean false
25194 .cindex "local host" "sending to"
25195 .cindex "fallback" "hosts specified on transport"
25196 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
25197 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
25198 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
25199 the delivery anyway. This should be used only in special cases when the
25200 configuration ensures that no looping will result (for example, a differently
25201 configured Exim is listening on the port to which the message is sent).
25204 .option authenticated_sender smtp string&!! unset
25206 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
25207 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
25208 overriding any existing authenticated sender value. If the string expansion is
25209 forced to fail, the option is ignored. Other expansion failures cause delivery
25210 to be deferred. If the result of expansion is an empty string, that is also
25213 The expansion happens after the outgoing connection has been made and TLS
25214 started, if required. This means that the &$host$&, &$host_address$&,
25215 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
25216 particular connection.
25218 If the SMTP session is not authenticated, the expansion of
25219 &%authenticated_sender%& still happens (and can cause the delivery to be
25220 deferred if it fails), but no AUTH= item is added to MAIL commands
25221 unless &%authenticated_sender_force%& is true.
25223 This option allows you to use the &(smtp)& transport in LMTP mode to
25224 deliver mail to Cyrus IMAP and provide the proper local part as the
25225 &"authenticated sender"&, via a setting such as:
25227 authenticated_sender = $local_part
25229 This removes the need for IMAP subfolders to be assigned special ACLs to
25230 allow direct delivery to those subfolders.
25232 Because of expected uses such as that just described for Cyrus (when no
25233 domain is involved), there is no checking on the syntax of the provided
25237 .option authenticated_sender_force smtp boolean false
25238 If this option is set true, the &%authenticated_sender%& option's value
25239 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
25240 authenticated as a client.
25243 .option command_timeout smtp time 5m
25244 .cindex timeout "smtp transport command"
25245 This sets a timeout for receiving a response to an SMTP command that has been
25246 sent out. It is also used when waiting for the initial banner line from the
25247 remote host. Its value must not be zero.
25250 .option connect_timeout smtp time 5m
25251 .cindex timeout "smtp transport connect"
25252 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
25253 to a remote host. A setting of zero allows the system timeout (typically
25254 several minutes) to act. To have any effect, the value of this option must be
25255 less than the system timeout. However, it has been observed that on some
25256 systems there is no system timeout, which is why the default value for this
25257 option is 5 minutes, a value recommended by RFC 1123.
25260 .option connection_max_messages smtp integer 500
25261 .cindex "SMTP" "passed connection"
25262 .cindex "SMTP" "multiple deliveries"
25263 .cindex "multiple SMTP deliveries"
25264 This controls the maximum number of separate message deliveries that are sent
25265 over a single TCP/IP connection. If the value is zero, there is no limit.
25266 For testing purposes, this value can be overridden by the &%-oB%& command line
25270 .option dane_require_tls_ciphers smtp string&!! unset
25271 .cindex "TLS" "requiring specific ciphers for DANE"
25272 .cindex "cipher" "requiring specific"
25273 .cindex DANE "TLS ciphers"
25274 This option may be used to override &%tls_require_ciphers%& for connections
25275 where DANE has been determined to be in effect.
25276 If not set, then &%tls_require_ciphers%& will be used.
25277 Normal SMTP delivery is not able to make strong demands of TLS cipher
25278 configuration, because delivery will fall back to plaintext. Once DANE has
25279 been determined to be in effect, there is no plaintext fallback and making the
25280 TLS cipherlist configuration stronger will increase security, rather than
25281 counter-intuitively decreasing it.
25282 If the option expands to be empty or is forced to fail, then it will
25283 be treated as unset and &%tls_require_ciphers%& will be used instead.
25286 .option data_timeout smtp time 5m
25287 .cindex timeout "for transmitted SMTP data blocks"
25288 This sets a timeout for the transmission of each block in the data portion of
25289 the message. As a result, the overall timeout for a message depends on the size
25290 of the message. Its value must not be zero. See also &%final_timeout%&.
25293 .option dkim_canon smtp string&!! unset
25294 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25295 .option dkim_domain smtp "string list&!!" unset
25296 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25297 .option dkim_hash smtp string&!! sha256
25298 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25299 .option dkim_identity smtp string&!! unset
25300 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25301 .option dkim_private_key smtp string&!! unset
25302 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25303 .option dkim_selector smtp string&!! unset
25304 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25305 .option dkim_strict smtp string&!! unset
25306 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25307 .option dkim_sign_headers smtp string&!! "per RFC"
25308 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25309 .option dkim_timestamps smtp string&!! unset
25310 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25313 .option delay_after_cutoff smtp boolean true
25314 .cindex "final cutoff" "retries, controlling"
25315 .cindex retry "final cutoff"
25316 This option controls what happens when all remote IP addresses for a given
25317 domain have been inaccessible for so long that they have passed their retry
25320 In the default state, if the next retry time has not been reached for any of
25321 them, the address is bounced without trying any deliveries. In other words,
25322 Exim delays retrying an IP address after the final cutoff time until a new
25323 retry time is reached, and can therefore bounce an address without ever trying
25324 a delivery, when machines have been down for a long time. Some people are
25325 unhappy at this prospect, so...
25327 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25328 addresses are past their final cutoff time, Exim tries to deliver to those
25329 IP addresses that have not been tried since the message arrived. If there are
25330 none, of if they all fail, the address is bounced. In other words, it does not
25331 delay when a new message arrives, but immediately tries those expired IP
25332 addresses that haven't been tried since the message arrived. If there is a
25333 continuous stream of messages for the dead hosts, unsetting
25334 &%delay_after_cutoff%& means that there will be many more attempts to deliver
25338 .option dns_qualify_single smtp boolean true
25339 If the &%hosts%& or &%fallback_hosts%& option is being used,
25340 and the &%gethostbyname%& option is false,
25341 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
25342 in chapter &<<CHAPdnslookup>>& for more details.
25345 .option dns_search_parents smtp boolean false
25346 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
25347 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
25348 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
25352 .option dnssec_request_domains smtp "domain list&!!" *
25353 .cindex "MX record" "security"
25354 .cindex "DNSSEC" "MX lookup"
25355 .cindex "security" "MX lookup"
25356 .cindex "DNS" "DNSSEC"
25357 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
25358 the DNSSEC request bit set. Setting this transport option is only useful if the
25359 transport overrides or sets the host names. See the &%dnssec_request_domains%&
25364 .option dnssec_require_domains smtp "domain list&!!" unset
25365 .cindex "MX record" "security"
25366 .cindex "DNSSEC" "MX lookup"
25367 .cindex "security" "MX lookup"
25368 .cindex "DNS" "DNSSEC"
25369 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
25370 the DNSSEC request bit set. Setting this transport option is only
25371 useful if the transport overrides or sets the host names. See the
25372 &%dnssec_require_domains%& router option.
25376 .option dscp smtp string&!! unset
25377 .cindex "DCSP" "outbound"
25378 This option causes the DSCP value associated with a socket to be set to one
25379 of a number of fixed strings or to numeric value.
25380 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
25381 Common values include &`throughput`&, &`mincost`&, and on newer systems
25382 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
25384 The outbound packets from Exim will be marked with this value in the header
25385 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
25386 that these values will have any effect, not be stripped by networking
25387 equipment, or do much of anything without cooperation with your Network
25388 Engineer and those of all network operators between the source and destination.
25391 .option fallback_hosts smtp "string list" unset
25392 .cindex "fallback" "hosts specified on transport"
25393 String expansion is not applied to this option. The argument must be a
25394 colon-separated list of host names or IP addresses, optionally also including
25395 port numbers, though the separator can be changed, as described in section
25396 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25397 item in a &%route_list%& setting for the &(manualroute)& router, as described
25398 in section &<<SECTformatonehostitem>>&.
25400 Fallback hosts can also be specified on routers, which associate them with the
25401 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
25402 &%fallback_hosts%& specified on the transport is used only if the address does
25403 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
25404 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
25405 However, &%hosts_randomize%& does apply to fallback host lists.
25407 If Exim is unable to deliver to any of the hosts for a particular address, and
25408 the errors are not permanent rejections, the address is put on a separate
25409 transport queue with its host list replaced by the fallback hosts, unless the
25410 address was routed via MX records and the current host was in the original MX
25411 list. In that situation, the fallback host list is not used.
25413 Once normal deliveries are complete, the fallback queue is delivered by
25414 re-running the same transports with the new host lists. If several failing
25415 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
25416 copy of the message is sent.
25418 The resolution of the host names on the fallback list is controlled by the
25419 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
25420 both to cases when the host list comes with the address and when it is taken
25421 from &%hosts%&. This option provides a &"use a smart host only if delivery
25425 .option final_timeout smtp time 10m
25426 .cindex timeout "for transmitted SMTP data accept"
25427 This is the timeout that applies while waiting for the response to the final
25428 line containing just &"."& that terminates a message. Its value must not be
25431 .option gethostbyname smtp boolean false
25432 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
25433 being used, names are looked up using &[gethostbyname()]&
25434 (or &[getipnodebyname()]& when available)
25435 instead of using the DNS. Of course, that function may in fact use the DNS, but
25436 it may also consult other sources of information such as &_/etc/hosts_&.
25438 .option gnutls_compat_mode smtp boolean unset
25439 This option controls whether GnuTLS is used in compatibility mode in an Exim
25440 server. This reduces security slightly, but improves interworking with older
25441 implementations of TLS.
25443 .option helo_data smtp string&!! "see below"
25444 .cindex "HELO" "argument, setting"
25445 .cindex "EHLO" "argument, setting"
25446 .cindex "LHLO argument setting"
25447 The value of this option is expanded after a connection to a another host has
25448 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
25449 command that starts the outgoing SMTP or LMTP session. The default value of the
25454 During the expansion, the variables &$host$& and &$host_address$& are set to
25455 the identity of the remote host, and the variables &$sending_ip_address$& and
25456 &$sending_port$& are set to the local IP address and port number that are being
25457 used. These variables can be used to generate different values for different
25458 servers or different local IP addresses. For example, if you want the string
25459 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
25460 interface address, you could use this:
25462 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
25463 {$primary_hostname}}
25465 The use of &%helo_data%& applies both to sending messages and when doing
25468 .option hosts smtp "string list&!!" unset
25469 Hosts are associated with an address by a router such as &(dnslookup)&, which
25470 finds the hosts by looking up the address domain in the DNS, or by
25471 &(manualroute)&, which has lists of hosts in its configuration. However,
25472 email addresses can be passed to the &(smtp)& transport by any router, and not
25473 all of them can provide an associated list of hosts.
25475 The &%hosts%& option specifies a list of hosts to be used if the address being
25476 processed does not have any hosts associated with it. The hosts specified by
25477 &%hosts%& are also used, whether or not the address has its own hosts, if
25478 &%hosts_override%& is set.
25480 The string is first expanded, before being interpreted as a colon-separated
25481 list of host names or IP addresses, possibly including port numbers. The
25482 separator may be changed to something other than colon, as described in section
25483 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25484 item in a &%route_list%& setting for the &(manualroute)& router, as described
25485 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
25486 of the &(manualroute)& router is not available here.
25488 If the expansion fails, delivery is deferred. Unless the failure was caused by
25489 the inability to complete a lookup, the error is logged to the panic log as
25490 well as the main log. Host names are looked up either by searching directly for
25491 address records in the DNS or by calling &[gethostbyname()]& (or
25492 &[getipnodebyname()]& when available), depending on the setting of the
25493 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
25494 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
25497 During delivery, the hosts are tried in order, subject to their retry status,
25498 unless &%hosts_randomize%& is set.
25501 .option hosts_avoid_esmtp smtp "host list&!!" unset
25502 .cindex "ESMTP, avoiding use of"
25503 .cindex "HELO" "forcing use of"
25504 .cindex "EHLO" "avoiding use of"
25505 .cindex "PIPELINING" "avoiding the use of"
25506 This option is for use with broken hosts that announce ESMTP facilities (for
25507 example, PIPELINING) and then fail to implement them properly. When a host
25508 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
25509 start of the SMTP session. This means that it cannot use any of the ESMTP
25510 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
25513 .option hosts_avoid_pipelining smtp "host list&!!" unset
25514 .cindex "PIPELINING" "avoiding the use of"
25515 .cindex "ESMTP extensions" PIPELINING
25516 Exim will not use the ESMTP PIPELINING extension when delivering to any host
25517 that matches this list, even if the server host advertises PIPELINING support.
25519 .option hosts_pipe_connect smtp "host list&!!" unset
25520 .cindex "pipelining" "early connection"
25521 .cindex "pipelining" PIPE_CONNECT
25522 If Exim is built with the SUPPORT_PIPE_CONNECT build option
25523 this option controls which to hosts the facility watched for
25524 and recorded, and used for subsequent connections.
25526 The retry hints database is used for the record,
25527 and records are subject to the &%retry_data_expire%& option.
25528 When used, the pipelining saves on roundtrip times.
25529 It also turns SMTP into a client-first protocol
25530 so combines well with TCP Fast Open.
25532 See also the &%pipelining_connect_advertise_hosts%& main option.
25535 When the facility is used, the transport &%helo_data%& option
25536 will be expanded before the &$sending_ip_address$& variable
25538 A check is made for the use of that variable, without the
25539 presence of a &"def:"& test on it, but suitably complex coding
25540 can avoid the check and produce unexpected results.
25541 You have been warned.
25544 .option hosts_avoid_tls smtp "host list&!!" unset
25545 .cindex "TLS" "avoiding for certain hosts"
25546 Exim will not try to start a TLS session when delivering to any host that
25547 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25549 .option hosts_verify_avoid_tls smtp "host list&!!" unset
25550 .cindex "TLS" "avoiding for certain hosts"
25551 Exim will not try to start a TLS session for a verify callout,
25552 or when delivering in cutthrough mode,
25553 to any host that matches this list.
25556 .option hosts_max_try smtp integer 5
25557 .cindex "host" "maximum number to try"
25558 .cindex "limit" "number of hosts tried"
25559 .cindex "limit" "number of MX tried"
25560 .cindex "MX record" "maximum tried"
25561 This option limits the number of IP addresses that are tried for any one
25562 delivery in cases where there are temporary delivery errors. Section
25563 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
25566 .option hosts_max_try_hardlimit smtp integer 50
25567 This is an additional check on the maximum number of IP addresses that Exim
25568 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
25573 .option hosts_nopass_tls smtp "host list&!!" unset
25574 .cindex "TLS" "passing connection"
25575 .cindex "multiple SMTP deliveries"
25576 .cindex "TLS" "multiple message deliveries"
25577 For any host that matches this list, a connection on which a TLS session has
25578 been started will not be passed to a new delivery process for sending another
25579 message on the same connection. See section &<<SECTmulmessam>>& for an
25580 explanation of when this might be needed.
25582 .option hosts_noproxy_tls smtp "host list&!!" unset
25583 .cindex "TLS" "passing connection"
25584 .cindex "multiple SMTP deliveries"
25585 .cindex "TLS" "multiple message deliveries"
25586 For any host that matches this list, a TLS session which has
25587 been started will not be passed to a new delivery process for sending another
25588 message on the same session.
25590 The traditional implementation closes down TLS and re-starts it in the new
25591 process, on the same open TCP connection, for each successive message
25592 sent. If permitted by this option a pipe to to the new process is set up
25593 instead, and the original process maintains the TLS connection and proxies
25594 the SMTP connection from and to the new process and any subsequents.
25595 The new process has no access to TLS information, so cannot include it in
25600 .option hosts_override smtp boolean false
25601 If this option is set and the &%hosts%& option is also set, any hosts that are
25602 attached to the address are ignored, and instead the hosts specified by the
25603 &%hosts%& option are always used. This option does not apply to
25604 &%fallback_hosts%&.
25607 .option hosts_randomize smtp boolean false
25608 .cindex "randomized host list"
25609 .cindex "host" "list of; randomized"
25610 .cindex "fallback" "randomized hosts"
25611 If this option is set, and either the list of hosts is taken from the
25612 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
25613 were not obtained from MX records (this includes fallback hosts from the
25614 router), and were not randomized by the router, the order of trying the hosts
25615 is randomized each time the transport runs. Randomizing the order of a host
25616 list can be used to do crude load sharing.
25618 When &%hosts_randomize%& is true, a host list may be split into groups whose
25619 order is separately randomized. This makes it possible to set up MX-like
25620 behaviour. The boundaries between groups are indicated by an item that is just
25621 &`+`& in the host list. For example:
25623 hosts = host1:host2:host3:+:host4:host5
25625 The order of the first three hosts and the order of the last two hosts is
25626 randomized for each use, but the first three always end up before the last two.
25627 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
25629 .option hosts_require_auth smtp "host list&!!" unset
25630 .cindex "authentication" "required by client"
25631 This option provides a list of servers for which authentication must succeed
25632 before Exim will try to transfer a message. If authentication fails for
25633 servers which are not in this list, Exim tries to send unauthenticated. If
25634 authentication fails for one of these servers, delivery is deferred. This
25635 temporary error is detectable in the retry rules, so it can be turned into a
25636 hard failure if required. See also &%hosts_try_auth%&, and chapter
25637 &<<CHAPSMTPAUTH>>& for details of authentication.
25640 .option hosts_request_ocsp smtp "host list&!!" *
25641 .cindex "TLS" "requiring for certain servers"
25642 Exim will request a Certificate Status on a
25643 TLS session for any host that matches this list.
25644 &%tls_verify_certificates%& should also be set for the transport.
25646 .option hosts_require_alpn smtp "host list&!!" unset
25647 .cindex ALPN "require negotiation in client"
25649 .cindex TLS "Application Layer Protocol Names"
25650 If the TLS library supports ALPN
25651 then a successful negotiation of ALPN will be required for any host
25652 matching the list, for TLS to be used.
25653 See also the &%tls_alpn%& option.
25655 &*Note*&: prevention of fallback to in-clear connection is not
25656 managed by this option; see &%hosts_require_tls%&.
25658 .option hosts_require_dane smtp "host list&!!" unset
25659 .cindex DANE "transport options"
25660 .cindex DANE "requiring for certain servers"
25661 If built with DANE support, Exim will require that a DNSSEC-validated
25662 TLSA record is present for any host matching the list,
25663 and that a DANE-verified TLS connection is made.
25664 There will be no fallback to in-clear communication.
25665 See the &%dnssec_request_domains%& router and transport options.
25666 See section &<<SECDANE>>&.
25668 .option hosts_require_helo smtp "host list&!!" *
25669 .cindex "HELO/EHLO" requiring
25670 Exim will require an accepted HELO or EHLO command from a host matching
25671 this list, before accepting a MAIL command.
25673 .option hosts_require_ocsp smtp "host list&!!" unset
25674 .cindex "TLS" "requiring for certain servers"
25675 Exim will request, and check for a valid Certificate Status being given, on a
25676 TLS session for any host that matches this list.
25677 &%tls_verify_certificates%& should also be set for the transport.
25679 .option hosts_require_tls smtp "host list&!!" unset
25680 .cindex "TLS" "requiring for certain servers"
25681 Exim will insist on using a TLS session when delivering to any host that
25682 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25683 &*Note*&: This option affects outgoing mail only. To insist on TLS for
25684 incoming messages, use an appropriate ACL.
25686 .option hosts_try_auth smtp "host list&!!" unset
25687 .cindex "authentication" "optional in client"
25688 This option provides a list of servers to which, provided they announce
25689 authentication support, Exim will attempt to authenticate as a client when it
25690 connects. If authentication fails
25691 and &%hosts_require_auth%& permits,
25692 Exim will try to transfer the message unauthenticated.
25693 See also chapter &<<CHAPSMTPAUTH>>& for details of authentication.
25695 .option hosts_try_chunking smtp "host list&!!" *
25696 .cindex CHUNKING "enabling, in client"
25697 .cindex BDAT "SMTP command"
25698 .cindex "RFC 3030" "CHUNKING"
25699 This option provides a list of servers to which, provided they announce
25700 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
25701 Unless DKIM signing is being done,
25702 BDAT will not be used in conjunction with a transport filter.
25704 .option hosts_try_dane smtp "host list&!!" *
25705 .cindex DANE "transport options"
25706 .cindex DANE "attempting for certain servers"
25707 If built with DANE support, Exim will look up a
25708 TLSA record for any host matching the list,
25709 If one is found and that lookup was DNSSEC-validated,
25710 then Exim requires that a DANE-verified TLS connection is made for that host;
25711 there will be no fallback to in-clear communication.
25712 See the &%dnssec_request_domains%& router and transport options.
25713 See section &<<SECDANE>>&.
25715 .option hosts_try_fastopen smtp "host list&!!" *
25716 .cindex "fast open, TCP" "enabling, in client"
25717 .cindex "TCP Fast Open" "enabling, in client"
25718 .cindex "RFC 7413" "TCP Fast Open"
25719 This option provides a list of servers to which, provided
25720 the facility is supported by this system, Exim will attempt to
25721 perform a TCP Fast Open.
25722 No data is sent on the SYN segment but, if the remote server also
25723 supports the facility, it can send its SMTP banner immediately after
25724 the SYN,ACK segment. This can save up to one round-trip time.
25726 The facility is only active for previously-contacted servers,
25727 as the initiator must present a cookie in the SYN segment.
25729 On (at least some) current Linux distributions the facility must be enabled
25730 in the kernel by the sysadmin before the support is usable.
25731 There is no option for control of the server side; if the system supports
25732 it it is always enabled. Note that lengthy operations in the connect ACL,
25733 such as DNSBL lookups, will still delay the emission of the SMTP banner.
25735 .option hosts_try_prdr smtp "host list&!!" *
25736 .cindex "PRDR" "enabling, optional in client"
25737 .cindex "ESMTP extensions" PRDR
25738 This option provides a list of servers to which, provided they announce
25739 PRDR support, Exim will attempt to negotiate PRDR
25740 for multi-recipient messages.
25741 The option can usually be left as default.
25743 .option interface smtp "string list&!!" unset
25744 .cindex "bind IP address"
25745 .cindex "IP address" "binding"
25747 .vindex "&$host_address$&"
25748 This option specifies which interface to bind to when making an outgoing SMTP
25749 call. The value is an IP address, not an interface name such as
25750 &`eth0`&. Do not confuse this with the interface address that was used when a
25751 message was received, which is in &$received_ip_address$&, formerly known as
25752 &$interface_address$&. The name was changed to minimize confusion with the
25753 outgoing interface address. There is no variable that contains an outgoing
25754 interface address because, unless it is set by this option, its value is
25757 During the expansion of the &%interface%& option the variables &$host$& and
25758 &$host_address$& refer to the host to which a connection is about to be made
25759 during the expansion of the string. Forced expansion failure, or an empty
25760 string result causes the option to be ignored. Otherwise, after expansion, the
25761 string must be a list of IP addresses, colon-separated by default, but the
25762 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
25765 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
25767 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
25768 connection. If none of them are the correct type, the option is ignored. If
25769 &%interface%& is not set, or is ignored, the system's IP functions choose which
25770 interface to use if the host has more than one.
25773 .option keepalive smtp boolean true
25774 .cindex "keepalive" "on outgoing connection"
25775 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
25776 connections. When set, it causes the kernel to probe idle connections
25777 periodically, by sending packets with &"old"& sequence numbers. The other end
25778 of the connection should send a acknowledgment if the connection is still okay
25779 or a reset if the connection has been aborted. The reason for doing this is
25780 that it has the beneficial effect of freeing up certain types of connection
25781 that can get stuck when the remote host is disconnected without tidying up the
25782 TCP/IP call properly. The keepalive mechanism takes several hours to detect
25786 .option lmtp_ignore_quota smtp boolean false
25787 .cindex "LMTP" "ignoring quota errors"
25788 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
25789 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
25790 has advertised support for IGNOREQUOTA in its response to the LHLO command.
25792 .option max_rcpt smtp integer 100
25793 .cindex "RCPT" "maximum number of outgoing"
25794 This option limits the number of RCPT commands that are sent in a single
25795 SMTP message transaction. Each set of addresses is treated independently, and
25796 so can cause parallel connections to the same host if &%remote_max_parallel%&
25797 permits this. A value setting of zero disables the limit.
25800 .option message_linelength_limit smtp integer 998
25801 .cindex "line length" limit
25802 This option sets the maximum line length, in bytes, that the transport
25803 will send. Any messages with lines exceeding the given value
25804 will fail and a failure-DSN ("bounce") message will if possible be returned
25806 The default value is that defined by the SMTP standards.
25808 It is generally wise to also check in the data ACL so that messages
25809 received via SMTP can be refused without producing a bounce.
25812 .option multi_domain smtp boolean&!! true
25813 .vindex "&$domain$&"
25814 When this option is set, the &(smtp)& transport can handle a number of
25815 addresses containing a mixture of different domains provided they all resolve
25816 to the same list of hosts. Turning the option off restricts the transport to
25817 handling only one domain at a time. This is useful if you want to use
25818 &$domain$& in an expansion for the transport, because it is set only when there
25819 is a single domain involved in a remote delivery.
25821 It is expanded per-address and can depend on any of
25822 &$address_data$&, &$domain_data$&, &$local_part_data$&,
25823 &$host$&, &$host_address$& and &$host_port$&.
25825 If the connection is DANE-enabled then this option is ignored;
25826 only messages having the domain used for the DANE TLSA lookup are
25827 sent on the connection.
25829 .option port smtp string&!! "see below"
25830 .cindex "port" "sending TCP/IP"
25831 .cindex "TCP/IP" "setting outgoing port"
25832 This option specifies the TCP/IP port on the server to which Exim connects.
25833 &*Note:*& Do not confuse this with the port that was used when a message was
25834 received, which is in &$received_port$&, formerly known as &$interface_port$&.
25835 The name was changed to minimize confusion with the outgoing port. There is no
25836 variable that contains an outgoing port.
25838 If the value of this option begins with a digit it is taken as a port number;
25839 otherwise it is looked up using &[getservbyname()]&. The default value is
25841 but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"&
25842 and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
25843 If the expansion fails, or if a port number cannot be found, delivery
25846 Note that at least one Linux distribution has been seen failing
25847 to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
25851 .option protocol smtp string smtp
25852 .cindex "LMTP" "over TCP/IP"
25853 .cindex "ssmtp protocol" "outbound"
25854 .cindex "TLS" "SSL-on-connect outbound"
25856 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
25857 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
25858 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
25859 deliveries into closed message stores. Exim also has support for running LMTP
25860 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
25862 If this option is set to &"smtps"&, the default value for the &%port%& option
25863 changes to &"smtps"&, and the transport initiates TLS immediately after
25864 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
25865 The Internet standards bodies used to strongly discourage use of this mode,
25866 but as of RFC 8314 it is preferred over STARTTLS for message submission
25867 (as distinct from MTA-MTA communication).
25870 .option retry_include_ip_address smtp boolean&!! true
25871 Exim normally includes both the host name and the IP address in the key it
25872 constructs for indexing retry data after a temporary delivery failure. This
25873 means that when one of several IP addresses for a host is failing, it gets
25874 tried periodically (controlled by the retry rules), but use of the other IP
25875 addresses is not affected.
25877 However, in some dialup environments hosts are assigned a different IP address
25878 each time they connect. In this situation the use of the IP address as part of
25879 the retry key leads to undesirable behaviour. Setting this option false causes
25880 Exim to use only the host name.
25881 Since it is expanded it can be made to depend on the host or domain.
25884 .option serialize_hosts smtp "host list&!!" unset
25885 .cindex "serializing connections"
25886 .cindex "host" "serializing connections"
25887 Because Exim operates in a distributed manner, if several messages for the same
25888 host arrive at around the same time, more than one simultaneous connection to
25889 the remote host can occur. This is not usually a problem except when there is a
25890 slow link between the hosts. In that situation it may be helpful to restrict
25891 Exim to one connection at a time. This can be done by setting
25892 &%serialize_hosts%& to match the relevant hosts.
25894 .cindex "hints database" "serializing deliveries to a host"
25895 Exim implements serialization by means of a hints database in which a record is
25896 written whenever a process connects to one of the restricted hosts. The record
25897 is deleted when the connection is completed. Obviously there is scope for
25898 records to get left lying around if there is a system or program crash. To
25899 guard against this, Exim ignores any records that are more than six hours old.
25901 If you set up this kind of serialization, you should also arrange to delete the
25902 relevant hints database whenever your system reboots. The names of the files
25903 start with &_misc_& and they are kept in the &_spool/db_& directory. There
25904 may be one or two files, depending on the type of DBM in use. The same files
25905 are used for ETRN serialization.
25907 See also the &%max_parallel%& generic transport option.
25910 .option size_addition smtp integer 1024
25911 .cindex "SIZE" "ESMTP extension"
25912 .cindex "message" "size issue for transport filter"
25913 .cindex "size" "of message"
25914 .cindex "transport" "filter"
25915 .cindex "filter" "transport filter"
25916 If a remote SMTP server indicates that it supports the SIZE option of the
25917 MAIL command, Exim uses this to pass over the message size at the start of
25918 an SMTP transaction. It adds the value of &%size_addition%& to the value it
25919 sends, to allow for headers and other text that may be added during delivery by
25920 configuration options or in a transport filter. It may be necessary to increase
25921 this if a lot of text is added to messages.
25923 Alternatively, if the value of &%size_addition%& is set negative, it disables
25924 the use of the SIZE option altogether.
25927 .option socks_proxy smtp string&!! unset
25928 .cindex proxy SOCKS
25929 This option enables use of SOCKS proxies for connections made by the
25930 transport. For details see section &<<SECTproxySOCKS>>&.
25933 .option tls_alpn smtp string&!! unset
25934 .cindex TLS "Application Layer Protocol Names"
25936 .cindex ALPN "set name in client"
25937 If this option is set
25938 and the TLS library supports ALPN,
25939 the value given is used.
25941 As of writing no value has been standardised for email use.
25942 The authors suggest using &"smtp"&.
25946 .option tls_certificate smtp string&!! unset
25947 .cindex "TLS" "client certificate, location of"
25948 .cindex "certificate" "client, location of"
25950 .vindex "&$host_address$&"
25951 The value of this option must be the absolute path to a file which contains the
25952 client's certificate, for possible use when sending a message over an encrypted
25953 connection. The values of &$host$& and &$host_address$& are set to the name and
25954 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
25957 &*Note*&: This option must be set if you want Exim to be able to use a TLS
25958 certificate when sending messages as a client. The global option of the same
25959 name specifies the certificate for Exim as a server; it is not automatically
25960 assumed that the same certificate should be used when Exim is operating as a
25964 .option tls_crl smtp string&!! unset
25965 .cindex "TLS" "client certificate revocation list"
25966 .cindex "certificate" "revocation list for client"
25967 This option specifies a certificate revocation list. The expanded value must
25968 be the name of a file that contains a CRL in PEM format.
25971 .option tls_dh_min_bits smtp integer 1024
25972 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
25973 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
25974 key agreement is negotiated, the server will provide a large prime number
25975 for use. This option establishes the minimum acceptable size of that number.
25976 If the parameter offered by the server is too small, then the TLS handshake
25979 Only supported when using GnuTLS.
25982 .option tls_privatekey smtp string&!! unset
25983 .cindex "TLS" "client private key, location of"
25985 .vindex "&$host_address$&"
25986 The value of this option must be the absolute path to a file which contains the
25987 client's private key. This is used when sending a message over an encrypted
25988 connection using a client certificate. The values of &$host$& and
25989 &$host_address$& are set to the name and address of the server during the
25990 expansion. If this option is unset, or the expansion is forced to fail, or the
25991 result is an empty string, the private key is assumed to be in the same file as
25992 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
25995 .option tls_require_ciphers smtp string&!! unset
25996 .cindex "TLS" "requiring specific ciphers"
25997 .cindex "cipher" "requiring specific"
25999 .vindex "&$host_address$&"
26000 The value of this option must be a list of permitted cipher suites, for use
26001 when setting up an outgoing encrypted connection. (There is a global option of
26002 the same name for controlling incoming connections.) The values of &$host$& and
26003 &$host_address$& are set to the name and address of the server during the
26004 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
26005 is used in different ways by OpenSSL and GnuTLS (see sections
26006 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
26007 ciphers is a preference order.
26010 .option tls_resumption_hosts smtp "host list&!!" unset
26011 .cindex TLS resumption
26012 This option controls which connections to use the TLS resumption feature.
26013 See &<<SECTresumption>>& for details.
26017 .option tls_sni smtp string&!! unset
26018 .cindex "TLS" "Server Name Indication"
26020 .cindex SNI "setting in client"
26021 .vindex "&$tls_sni$&"
26022 If this option is set
26023 and the connection is not DANE-validated
26024 then it sets the $tls_out_sni variable and causes any
26025 TLS session to pass this value as the Server Name Indication extension to
26026 the remote side, which can be used by the remote side to select an appropriate
26027 certificate and private key for the session.
26029 See &<<SECTtlssni>>& for more information.
26031 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
26037 .option tls_tempfail_tryclear smtp boolean true
26038 .cindex "4&'xx'& responses" "to STARTTLS"
26039 When the server host is not in &%hosts_require_tls%&, and there is a problem in
26040 setting up a TLS session, this option determines whether or not Exim should try
26041 to deliver the message unencrypted. If it is set false, delivery to the
26042 current host is deferred; if there are other hosts, they are tried. If this
26043 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
26044 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
26045 TLS negotiation fails, Exim closes the current connection (because it is in an
26046 unknown state), opens a new one to the same host, and then tries the delivery
26050 .option tls_try_verify_hosts smtp "host list&!!" *
26051 .cindex "TLS" "server certificate verification"
26052 .cindex "certificate" "verification of server"
26053 This option gives a list of hosts for which, on encrypted connections,
26054 certificate verification will be tried but need not succeed.
26055 The &%tls_verify_certificates%& option must also be set.
26056 Note that unless the host is in this list
26057 TLS connections will be denied to hosts using self-signed certificates
26058 when &%tls_verify_certificates%& is matched.
26059 The &$tls_out_certificate_verified$& variable is set when
26060 certificate verification succeeds.
26063 .option tls_verify_cert_hostnames smtp "host list&!!" *
26064 .cindex "TLS" "server certificate hostname verification"
26065 .cindex "certificate" "verification of server"
26066 This option give a list of hosts for which,
26067 while verifying the server certificate,
26068 checks will be included on the host name
26069 (note that this will generally be the result of a DNS MX lookup)
26070 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
26071 limited to being the initial component of a 3-or-more component FQDN.
26073 There is no equivalent checking on client certificates.
26076 .option tls_verify_certificates smtp string&!! system
26077 .cindex "TLS" "server certificate verification"
26078 .cindex "certificate" "verification of server"
26080 .vindex "&$host_address$&"
26081 The value of this option must be either the
26083 or the absolute path to
26084 a file or directory containing permitted certificates for servers,
26085 for use when setting up an encrypted connection.
26087 The "system" value for the option will use a location compiled into the SSL library.
26088 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
26089 is taken as empty and an explicit location
26092 The use of a directory for the option value is not available for GnuTLS versions
26093 preceding 3.3.6 and a single file must be used.
26095 With OpenSSL the certificates specified
26097 either by file or directory
26098 are added to those given by the system default location.
26100 The values of &$host$& and
26101 &$host_address$& are set to the name and address of the server during the
26102 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
26104 For back-compatibility,
26105 if neither tls_verify_hosts nor tls_try_verify_hosts are set
26106 (a single-colon empty list counts as being set)
26107 and certificate verification fails the TLS connection is closed.
26110 .option tls_verify_hosts smtp "host list&!!" unset
26111 .cindex "TLS" "server certificate verification"
26112 .cindex "certificate" "verification of server"
26113 This option gives a list of hosts for which, on encrypted connections,
26114 certificate verification must succeed.
26115 The &%tls_verify_certificates%& option must also be set.
26116 If both this option and &%tls_try_verify_hosts%& are unset
26117 operation is as if this option selected all hosts.
26118 &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
26119 that connections use TLS.
26120 Fallback to in-clear communication will be done unless restricted by
26121 the &%hosts_require_tls%& option.
26123 .option utf8_downconvert smtp integer&!! -1
26124 .cindex utf8 "address downconversion"
26125 .cindex i18n "utf8 address downconversion"
26126 If built with internationalization support,
26127 this option controls conversion of UTF-8 in message envelope addresses
26129 If, after expansion, the value is 1, 0, or -1 then this value overrides
26130 any value previously set for the message. Otherwise, any previously
26131 set value is used. To permit use of a previous value,
26132 set this option to an empty string.
26133 For details on the values see section &<<SECTi18nMTA>>&.
26138 .section "How the limits for the number of hosts to try are used" &&&
26140 .cindex "host" "maximum number to try"
26141 .cindex "limit" "hosts; maximum number tried"
26142 There are two options that are concerned with the number of hosts that are
26143 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
26144 &%hosts_max_try_hardlimit%&.
26147 The &%hosts_max_try%& option limits the number of hosts that are tried
26148 for a single delivery. However, despite the term &"host"& in its name, the
26149 option actually applies to each IP address independently. In other words, a
26150 multihomed host is treated as several independent hosts, just as it is for
26153 Many of the larger ISPs have multiple MX records which often point to
26154 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
26155 created as a result of routing one of these domains.
26157 Trying every single IP address on such a long list does not seem sensible; if
26158 several at the top of the list fail, it is reasonable to assume there is some
26159 problem that is likely to affect all of them. Roughly speaking, the value of
26160 &%hosts_max_try%& is the maximum number that are tried before deferring the
26161 delivery. However, the logic cannot be quite that simple.
26163 Firstly, IP addresses that are skipped because their retry times have not
26164 arrived do not count, and in addition, addresses that are past their retry
26165 limits are also not counted, even when they are tried. This means that when
26166 some IP addresses are past their retry limits, more than the value of
26167 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
26168 that all IP addresses are considered before timing out an email address (but
26169 see below for an exception).
26171 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
26172 list to see if there is a subsequent host with a different (higher valued) MX.
26173 If there is, that host is considered next, and the current IP address is used
26174 but not counted. This behaviour helps in the case of a domain with a retry rule
26175 that hardly ever delays any hosts, as is now explained:
26177 Consider the case of a long list of hosts with one MX value, and a few with a
26178 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
26179 hosts at the top of the list are tried at first. With the default retry rule,
26180 which specifies increasing retry times, the higher MX hosts are eventually
26181 tried when those at the top of the list are skipped because they have not
26182 reached their retry times.
26184 However, it is common practice to put a fixed short retry time on domains for
26185 large ISPs, on the grounds that their servers are rarely down for very long.
26186 Unfortunately, these are exactly the domains that tend to resolve to long lists
26187 of hosts. The short retry time means that the lowest MX hosts are tried every
26188 time. The attempts may be in a different order because of random sorting, but
26189 without the special MX check, the higher MX hosts would never be tried until
26190 all the lower MX hosts had timed out (which might be several days), because
26191 there are always some lower MX hosts that have reached their retry times. With
26192 the special check, Exim considers at least one IP address from each MX value at
26193 every delivery attempt, even if the &%hosts_max_try%& limit has already been
26196 The above logic means that &%hosts_max_try%& is not a hard limit, and in
26197 particular, Exim normally eventually tries all the IP addresses before timing
26198 out an email address. When &%hosts_max_try%& was implemented, this seemed a
26199 reasonable thing to do. Recently, however, some lunatic DNS configurations have
26200 been set up with hundreds of IP addresses for some domains. It can
26201 take a very long time indeed for an address to time out in these cases.
26203 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
26204 Exim never tries more than this number of IP addresses; if it hits this limit
26205 and they are all timed out, the email address is bounced, even though not all
26206 possible IP addresses have been tried.
26207 .ecindex IIDsmttra1
26208 .ecindex IIDsmttra2
26214 . ////////////////////////////////////////////////////////////////////////////
26215 . ////////////////////////////////////////////////////////////////////////////
26217 .chapter "Address rewriting" "CHAPrewrite"
26218 .scindex IIDaddrew "rewriting" "addresses"
26219 There are some circumstances in which Exim automatically rewrites domains in
26220 addresses. The two most common are when an address is given without a domain
26221 (referred to as an &"unqualified address"&) or when an address contains an
26222 abbreviated domain that is expanded by DNS lookup.
26224 Unqualified envelope addresses are accepted only for locally submitted
26225 messages, or for messages that are received from hosts matching
26226 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
26227 appropriate. Unqualified addresses in header lines are qualified if they are in
26228 locally submitted messages, or messages from hosts that are permitted to send
26229 unqualified envelope addresses. Otherwise, unqualified addresses in header
26230 lines are neither qualified nor rewritten.
26232 One situation in which Exim does &'not'& automatically rewrite a domain is
26233 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
26234 such a domain should be rewritten using the &"canonical"& name, and some MTAs
26235 do this. The new RFCs do not contain this suggestion.
26238 .section "Explicitly configured address rewriting" "SECID147"
26239 This chapter describes the rewriting rules that can be used in the
26240 main rewrite section of the configuration file, and also in the generic
26241 &%headers_rewrite%& option that can be set on any transport.
26243 Some people believe that configured address rewriting is a Mortal Sin.
26244 Others believe that life is not possible without it. Exim provides the
26245 facility; you do not have to use it.
26247 The main rewriting rules that appear in the &"rewrite"& section of the
26248 configuration file are applied to addresses in incoming messages, both envelope
26249 addresses and addresses in header lines. Each rule specifies the types of
26250 address to which it applies.
26252 Whether or not addresses in header lines are rewritten depends on the origin of
26253 the headers and the type of rewriting. Global rewriting, that is, rewriting
26254 rules from the rewrite section of the configuration file, is applied only to
26255 those headers that were received with the message. Header lines that are added
26256 by ACLs or by a system filter or by individual routers or transports (which
26257 are specific to individual recipient addresses) are not rewritten by the global
26260 Rewriting at transport time, by means of the &%headers_rewrite%& option,
26261 applies all headers except those added by routers and transports. That is, as
26262 well as the headers that were received with the message, it also applies to
26263 headers that were added by an ACL or a system filter.
26266 In general, rewriting addresses from your own system or domain has some
26267 legitimacy. Rewriting other addresses should be done only with great care and
26268 in special circumstances. The author of Exim believes that rewriting should be
26269 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
26270 Although it can sometimes be used as a routing tool, this is very strongly
26273 There are two commonly encountered circumstances where rewriting is used, as
26274 illustrated by these examples:
26277 The company whose domain is &'hitch.fict.example'& has a number of hosts that
26278 exchange mail with each other behind a firewall, but there is only a single
26279 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
26280 &'hitch.fict.example'& when sending mail off-site.
26282 A host rewrites the local parts of its own users so that, for example,
26283 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
26288 .section "When does rewriting happen?" "SECID148"
26289 .cindex "rewriting" "timing of"
26290 .cindex "&ACL;" "rewriting addresses in"
26291 Configured address rewriting can take place at several different stages of a
26292 message's processing.
26294 .vindex "&$sender_address$&"
26295 At the start of an ACL for MAIL, the sender address may have been rewritten
26296 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
26297 ordinary rewrite rules have yet been applied. If, however, the sender address
26298 is verified in the ACL, it is rewritten before verification, and remains
26299 rewritten thereafter. The subsequent value of &$sender_address$& is the
26300 rewritten address. This also applies if sender verification happens in a
26301 RCPT ACL. Otherwise, when the sender address is not verified, it is
26302 rewritten as soon as a message's header lines have been received.
26304 .vindex "&$domain$&"
26305 .vindex "&$local_part$&"
26306 Similarly, at the start of an ACL for RCPT, the current recipient's address
26307 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
26308 rewrite rules have yet been applied to it. However, the behaviour is different
26309 from the sender address when a recipient is verified. The address is rewritten
26310 for the verification, but the rewriting is not remembered at this stage. The
26311 value of &$local_part$& and &$domain$& after verification are always the same
26312 as they were before (that is, they contain the unrewritten &-- except for
26313 SMTP-time rewriting &-- address).
26315 As soon as a message's header lines have been received, all the envelope
26316 recipient addresses are permanently rewritten, and rewriting is also applied to
26317 the addresses in the header lines (if configured). This happens before adding
26318 any header lines that were specified in MAIL or RCPT ACLs, and
26319 .cindex "&[local_scan()]& function" "address rewriting; timing of"
26320 before the DATA ACL and &[local_scan()]& functions are run.
26322 When an address is being routed, either for delivery or for verification,
26323 rewriting is applied immediately to child addresses that are generated by
26324 redirection, unless &%no_rewrite%& is set on the router.
26326 .cindex "envelope from"
26327 .cindex "envelope sender" "rewriting at transport time"
26328 .cindex "rewriting" "at transport time"
26329 .cindex "header lines" "rewriting at transport time"
26330 At transport time, additional rewriting of addresses in header lines can be
26331 specified by setting the generic &%headers_rewrite%& option on a transport.
26332 This option contains rules that are identical in form to those in the rewrite
26333 section of the configuration file. They are applied to the original message
26334 header lines and any that were added by ACLs or a system filter. They are not
26335 applied to header lines that are added by routers or the transport.
26337 The outgoing envelope sender can be rewritten by means of the &%return_path%&
26338 transport option. However, it is not possible to rewrite envelope recipients at
26344 .section "Testing the rewriting rules that apply on input" "SECID149"
26345 .cindex "rewriting" "testing"
26346 .cindex "testing" "rewriting"
26347 Exim's input rewriting configuration appears in a part of the runtime
26348 configuration file headed by &"begin rewrite"&. It can be tested by the
26349 &%-brw%& command line option. This takes an address (which can be a full RFC
26350 2822 address) as its argument. The output is a list of how the address would be
26351 transformed by the rewriting rules for each of the different places it might
26352 appear in an incoming message, that is, for each different header and for the
26353 envelope sender and recipient fields. For example,
26355 exim -brw ph10@exim.workshop.example
26357 might produce the output
26359 sender: Philip.Hazel@exim.workshop.example
26360 from: Philip.Hazel@exim.workshop.example
26361 to: ph10@exim.workshop.example
26362 cc: ph10@exim.workshop.example
26363 bcc: ph10@exim.workshop.example
26364 reply-to: Philip.Hazel@exim.workshop.example
26365 env-from: Philip.Hazel@exim.workshop.example
26366 env-to: ph10@exim.workshop.example
26368 which shows that rewriting has been set up for that address when used in any of
26369 the source fields, but not when it appears as a recipient address. At the
26370 present time, there is no equivalent way of testing rewriting rules that are
26371 set for a particular transport.
26374 .section "Rewriting rules" "SECID150"
26375 .cindex "rewriting" "rules"
26376 The rewrite section of the configuration file consists of lines of rewriting
26379 <&'source pattern'&> <&'replacement'&> <&'flags'&>
26381 Rewriting rules that are specified for the &%headers_rewrite%& generic
26382 transport option are given as a colon-separated list. Each item in the list
26383 takes the same form as a line in the main rewriting configuration (except that
26384 any colons must be doubled, of course).
26386 The formats of source patterns and replacement strings are described below.
26387 Each is terminated by white space, unless enclosed in double quotes, in which
26388 case normal quoting conventions apply inside the quotes. The flags are single
26389 characters which may appear in any order. Spaces and tabs between them are
26392 For each address that could potentially be rewritten, the rules are scanned in
26393 order, and replacements for the address from earlier rules can themselves be
26394 replaced by later rules (but see the &"q"& and &"R"& flags).
26396 The order in which addresses are rewritten is undefined, may change between
26397 releases, and must not be relied on, with one exception: when a message is
26398 received, the envelope sender is always rewritten first, before any header
26399 lines are rewritten. For example, the replacement string for a rewrite of an
26400 address in &'To:'& must not assume that the message's address in &'From:'& has
26401 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
26402 that the envelope sender has already been rewritten.
26404 .vindex "&$domain$&"
26405 .vindex "&$local_part$&"
26406 The variables &$local_part$& and &$domain$& can be used in the replacement
26407 string to refer to the address that is being rewritten. Note that lookup-driven
26408 rewriting can be done by a rule of the form
26412 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
26413 refer to the address that is being rewritten.
26416 .section "Rewriting patterns" "SECID151"
26417 .cindex "rewriting" "patterns"
26418 .cindex "address list" "in a rewriting pattern"
26419 The source pattern in a rewriting rule is any item which may appear in an
26420 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
26421 single-item address list, which means that it is expanded before being tested
26422 against the address. As always, if you use a regular expression as a pattern,
26423 you must take care to escape dollar and backslash characters, or use the &`\N`&
26424 facility to suppress string expansion within the regular expression.
26426 Domains in patterns should be given in lower case. Local parts in patterns are
26427 case-sensitive. If you want to do case-insensitive matching of local parts, you
26428 can use a regular expression that starts with &`^(?i)`&.
26430 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
26431 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
26432 depending on the type of match which occurred. These can be used in the
26433 replacement string to insert portions of the incoming address. &$0$& always
26434 refers to the complete incoming address. When a regular expression is used, the
26435 numerical variables are set from its capturing subexpressions. For other types
26436 of pattern they are set as follows:
26439 If a local part or domain starts with an asterisk, the numerical variables
26440 refer to the character strings matched by asterisks, with &$1$& associated with
26441 the first asterisk, and &$2$& with the second, if present. For example, if the
26444 *queen@*.fict.example
26446 is matched against the address &'hearts-queen@wonderland.fict.example'& then
26448 $0 = hearts-queen@wonderland.fict.example
26452 Note that if the local part does not start with an asterisk, but the domain
26453 does, it is &$1$& that contains the wild part of the domain.
26456 If the domain part of the pattern is a partial lookup, the wild and fixed parts
26457 of the domain are placed in the next available numerical variables. Suppose,
26458 for example, that the address &'foo@bar.baz.example'& is processed by a
26459 rewriting rule of the form
26461 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
26463 and the key in the file that matches the domain is &`*.baz.example`&. Then
26469 If the address &'foo@baz.example'& is looked up, this matches the same
26470 wildcard file entry, and in this case &$2$& is set to the empty string, but
26471 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
26472 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
26473 whole domain. For non-partial domain lookups, no numerical variables are set.
26477 .section "Rewriting replacements" "SECID152"
26478 .cindex "rewriting" "replacements"
26479 If the replacement string for a rule is a single asterisk, addresses that
26480 match the pattern and the flags are &'not'& rewritten, and no subsequent
26481 rewriting rules are scanned. For example,
26483 hatta@lookingglass.fict.example * f
26485 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
26488 .vindex "&$domain$&"
26489 .vindex "&$local_part$&"
26490 If the replacement string is not a single asterisk, it is expanded, and must
26491 yield a fully qualified address. Within the expansion, the variables
26492 &$local_part$& and &$domain$& refer to the address that is being rewritten.
26493 Any letters they contain retain their original case &-- they are not lower
26494 cased. The numerical variables are set up according to the type of pattern that
26495 matched the address, as described above. If the expansion is forced to fail by
26496 the presence of &"fail"& in a conditional or lookup item, rewriting by the
26497 current rule is abandoned, but subsequent rules may take effect. Any other
26498 expansion failure causes the entire rewriting operation to be abandoned, and an
26499 entry written to the panic log.
26503 .section "Rewriting flags" "SECID153"
26504 There are three different kinds of flag that may appear on rewriting rules:
26507 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
26510 A flag that specifies rewriting at SMTP time: S.
26512 Flags that control the rewriting process: Q, q, R, w.
26515 For rules that are part of the &%headers_rewrite%& generic transport option,
26516 E, F, T, and S are not permitted.
26520 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
26522 .cindex "rewriting" "flags"
26523 If none of the following flag letters, nor the &"S"& flag (see section
26524 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
26525 and to both the sender and recipient fields of the envelope, whereas a
26526 transport-time rewriting rule just applies to all headers. Otherwise, the
26527 rewriting rule is skipped unless the relevant addresses are being processed.
26529 &`E`& rewrite all envelope fields
26530 &`F`& rewrite the envelope From field
26531 &`T`& rewrite the envelope To field
26532 &`b`& rewrite the &'Bcc:'& header
26533 &`c`& rewrite the &'Cc:'& header
26534 &`f`& rewrite the &'From:'& header
26535 &`h`& rewrite all headers
26536 &`r`& rewrite the &'Reply-To:'& header
26537 &`s`& rewrite the &'Sender:'& header
26538 &`t`& rewrite the &'To:'& header
26540 "All headers" means all of the headers listed above that can be selected
26541 individually, plus their &'Resent-'& versions. It does not include
26542 other headers such as &'Subject:'& etc.
26544 You should be particularly careful about rewriting &'Sender:'& headers, and
26545 restrict this to special known cases in your own domains.
26548 .section "The SMTP-time rewriting flag" "SECTrewriteS"
26549 .cindex "SMTP" "rewriting malformed addresses"
26550 .cindex "RCPT" "rewriting argument of"
26551 .cindex "MAIL" "rewriting argument of"
26552 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
26553 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
26554 before any other processing; even before syntax checking. The pattern is
26555 required to be a regular expression, and it is matched against the whole of the
26556 data for the command, including any surrounding angle brackets.
26558 .vindex "&$domain$&"
26559 .vindex "&$local_part$&"
26560 This form of rewrite rule allows for the handling of addresses that are not
26561 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
26562 input). Because the input is not required to be a syntactically valid address,
26563 the variables &$local_part$& and &$domain$& are not available during the
26564 expansion of the replacement string. The result of rewriting replaces the
26565 original address in the MAIL or RCPT command.
26568 .section "Flags controlling the rewriting process" "SECID155"
26569 There are four flags which control the way the rewriting process works. These
26570 take effect only when a rule is invoked, that is, when the address is of the
26571 correct type (matches the flags) and matches the pattern:
26574 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
26575 unqualified local part. It is qualified with &%qualify_recipient%&. In the
26576 absence of &"Q"& the rewritten address must always include a domain.
26578 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
26579 even if no rewriting actually takes place because of a &"fail"& in the
26580 expansion. The &"q"& flag is not effective if the address is of the wrong type
26581 (does not match the flags) or does not match the pattern.
26583 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
26584 address, up to ten times. It can be combined with the &"q"& flag, to stop
26585 rewriting once it fails to match (after at least one successful rewrite).
26587 .cindex "rewriting" "whole addresses"
26588 When an address in a header is rewritten, the rewriting normally applies only
26589 to the working part of the address, with any comments and RFC 2822 &"phrase"&
26590 left unchanged. For example, rewriting might change
26592 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
26596 From: Ford Prefect <prefectf@hitch.fict.example>
26599 Sometimes there is a need to replace the whole address item, and this can be
26600 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
26601 causes an address in a header line to be rewritten, the entire address is
26602 replaced, not just the working part. The replacement must be a complete RFC
26603 2822 address, including the angle brackets if necessary. If text outside angle
26604 brackets contains a character whose value is greater than 126 or less than 32
26605 (except for tab), the text is encoded according to RFC 2047. The character set
26606 is taken from &%headers_charset%&, which gets its default at build time.
26608 When the &"w"& flag is set on a rule that causes an envelope address to be
26609 rewritten, all but the working part of the replacement address is discarded.
26613 .section "Rewriting examples" "SECID156"
26614 Here is an example of the two common rewriting paradigms:
26616 *@*.hitch.fict.example $1@hitch.fict.example
26617 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
26618 {$value}fail}@hitch.fict.example bctfrF
26620 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
26621 the string expansion to fail if the lookup does not succeed. In this context it
26622 has the effect of leaving the original address unchanged, but Exim goes on to
26623 consider subsequent rewriting rules, if any, because the &"q"& flag is not
26624 present in that rule. An alternative to &"fail"& would be to supply &$1$&
26625 explicitly, which would cause the rewritten address to be the same as before,
26626 at the cost of a small bit of processing. Not supplying either of these is an
26627 error, since the rewritten address would then contain no local part.
26629 The first example above replaces the domain with a superior, more general
26630 domain. This may not be desirable for certain local parts. If the rule
26632 root@*.hitch.fict.example *
26634 were inserted before the first rule, rewriting would be suppressed for the
26635 local part &'root'& at any domain ending in &'hitch.fict.example'&.
26637 Rewriting can be made conditional on a number of tests, by making use of
26638 &${if$& in the expansion item. For example, to apply a rewriting rule only to
26639 messages that originate outside the local host:
26641 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
26642 {$1@hitch.fict.example}fail}"
26644 The replacement string is quoted in this example because it contains white
26647 .cindex "rewriting" "bang paths"
26648 .cindex "bang paths" "rewriting"
26649 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
26650 an address it treats it as an unqualified local part which it qualifies with
26651 the local qualification domain (if the source of the message is local or if the
26652 remote host is permitted to send unqualified addresses). Rewriting can
26653 sometimes be used to handle simple bang paths with a fixed number of
26654 components. For example, the rule
26656 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
26658 rewrites a two-component bang path &'host.name!user'& as the domain address
26659 &'user@host.name'&. However, there is a security implication in using this as
26660 a global rewriting rule for envelope addresses. It can provide a backdoor
26661 method for using your system as a relay, because the incoming addresses appear
26662 to be local. If the bang path addresses are received via SMTP, it is safer to
26663 use the &"S"& flag to rewrite them as they are received, so that relay checking
26664 can be done on the rewritten addresses.
26671 . ////////////////////////////////////////////////////////////////////////////
26672 . ////////////////////////////////////////////////////////////////////////////
26674 .chapter "Retry configuration" "CHAPretry"
26675 .scindex IIDretconf1 "retry" "configuration, description of"
26676 .scindex IIDregconf2 "configuration file" "retry section"
26677 The &"retry"& section of the runtime configuration file contains a list of
26678 retry rules that control how often Exim tries to deliver messages that cannot
26679 be delivered at the first attempt. If there are no retry rules (the section is
26680 empty or not present), there are no retries. In this situation, temporary
26681 errors are treated as permanent. The default configuration contains a single,
26682 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
26683 line option can be used to test which retry rule will be used for a given
26684 address, domain and error.
26686 The most common cause of retries is temporary failure to deliver to a remote
26687 host because the host is down, or inaccessible because of a network problem.
26688 Exim's retry processing in this case is applied on a per-host (strictly, per IP
26689 address) basis, not on a per-message basis. Thus, if one message has recently
26690 been delayed, delivery of a new message to the same host is not immediately
26691 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
26692 log selector is set, the message
26693 .cindex "retry" "time not reached"
26694 &"retry time not reached"& is written to the main log whenever a delivery is
26695 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
26696 the handling of errors during remote deliveries.
26698 Retry processing applies to routing as well as to delivering, except as covered
26699 in the next paragraph. The retry rules do not distinguish between these
26700 actions. It is not possible, for example, to specify different behaviour for
26701 failures to route the domain &'snark.fict.example'& and failures to deliver to
26702 the host &'snark.fict.example'&. I didn't think anyone would ever need this
26703 added complication, so did not implement it. However, although they share the
26704 same retry rule, the actual retry times for routing and transporting a given
26705 domain are maintained independently.
26707 When a delivery is not part of a queue run (typically an immediate delivery on
26708 receipt of a message), the routers are always run, and local deliveries are
26709 always attempted, even if retry times are set for them. This makes for better
26710 behaviour if one particular message is causing problems (for example, causing
26711 quota overflow, or provoking an error in a filter file). If such a delivery
26712 suffers a temporary failure, the retry data is updated as normal, and
26713 subsequent delivery attempts from queue runs occur only when the retry time for
26714 the local address is reached.
26716 .section "Changing retry rules" "SECID157"
26717 If you change the retry rules in your configuration, you should consider
26718 whether or not to delete the retry data that is stored in Exim's spool area in
26719 files with names like &_db/retry_&. Deleting any of Exim's hints files is
26720 always safe; that is why they are called &"hints"&.
26722 The hints retry data contains suggested retry times based on the previous
26723 rules. In the case of a long-running problem with a remote host, it might
26724 record the fact that the host has timed out. If your new rules increase the
26725 timeout time for such a host, you should definitely remove the old retry data
26726 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
26727 messages that it should now be retaining.
26731 .section "Format of retry rules" "SECID158"
26732 .cindex "retry" "rules"
26733 Each retry rule occupies one line and consists of three or four parts,
26734 separated by white space: a pattern, an error name, an optional list of sender
26735 addresses, and a list of retry parameters. The pattern and sender lists must be
26736 enclosed in double quotes if they contain white space. The rules are searched
26737 in order until one is found where the pattern, error name, and sender list (if
26738 present) match the failing host or address, the error that occurred, and the
26739 message's sender, respectively.
26742 The pattern is any single item that may appear in an address list (see section
26743 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
26744 which means that it is expanded before being tested against the address that
26745 has been delayed. A negated address list item is permitted. Address
26746 list processing treats a plain domain name as if it were preceded by &"*@"&,
26747 which makes it possible for many retry rules to start with just a domain. For
26750 lookingglass.fict.example * F,24h,30m;
26752 provides a rule for any address in the &'lookingglass.fict.example'& domain,
26755 alice@lookingglass.fict.example * F,24h,30m;
26757 applies only to temporary failures involving the local part &%alice%&.
26758 In practice, almost all rules start with a domain name pattern without a local
26761 .cindex "regular expressions" "in retry rules"
26762 &*Warning*&: If you use a regular expression in a retry rule pattern, it
26763 must match a complete address, not just a domain, because that is how regular
26764 expressions work in address lists.
26766 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
26767 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
26771 .section "Choosing which retry rule to use for address errors" "SECID159"
26772 When Exim is looking for a retry rule after a routing attempt has failed (for
26773 example, after a DNS timeout), each line in the retry configuration is tested
26774 against the complete address only if &%retry_use_local_part%& is set for the
26775 router. Otherwise, only the domain is used, except when matching against a
26776 regular expression, when the local part of the address is replaced with &"*"&.
26777 A domain on its own can match a domain pattern, or a pattern that starts with
26778 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
26779 &%check_local_user%& is true, and false for other routers.
26781 Similarly, when Exim is looking for a retry rule after a local delivery has
26782 failed (for example, after a mailbox full error), each line in the retry
26783 configuration is tested against the complete address only if
26784 &%retry_use_local_part%& is set for the transport (it defaults true for all
26787 .cindex "4&'xx'& responses" "retry rules for"
26788 However, when Exim is looking for a retry rule after a remote delivery attempt
26789 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
26790 whole address is always used as the key when searching the retry rules. The
26791 rule that is found is used to create a retry time for the combination of the
26792 failing address and the message's sender. It is the combination of sender and
26793 recipient that is delayed in subsequent queue runs until its retry time is
26794 reached. You can delay the recipient without regard to the sender by setting
26795 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
26796 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
26801 .section "Choosing which retry rule to use for host and message errors" &&&
26803 For a temporary error that is not related to an individual address (for
26804 example, a connection timeout), each line in the retry configuration is checked
26805 twice. First, the name of the remote host is used as a domain name (preceded by
26806 &"*@"& when matching a regular expression). If this does not match the line,
26807 the domain from the email address is tried in a similar fashion. For example,
26808 suppose the MX records for &'a.b.c.example'& are
26810 a.b.c.example MX 5 x.y.z.example
26814 and the retry rules are
26816 p.q.r.example * F,24h,30m;
26817 a.b.c.example * F,4d,45m;
26819 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
26820 first rule matches neither the host nor the domain, so Exim looks at the second
26821 rule. This does not match the host, but it does match the domain, so it is used
26822 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
26823 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
26824 first retry rule is used, because it matches the host.
26826 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
26827 first rule to determine retry times, but for all the other hosts for the domain
26828 &'a.b.c.example'&, the second rule is used. The second rule is also used if
26829 routing to &'a.b.c.example'& suffers a temporary failure.
26831 &*Note*&: The host name is used when matching the patterns, not its IP address.
26832 However, if a message is routed directly to an IP address without the use of a
26833 host name, for example, if a &(manualroute)& router contains a setting such as:
26835 route_list = *.a.example 192.168.34.23
26837 then the &"host name"& that is used when searching for a retry rule is the
26838 textual form of the IP address.
26840 .section "Retry rules for specific errors" "SECID161"
26841 .cindex "retry" "specific errors; specifying"
26842 The second field in a retry rule is the name of a particular error, or an
26843 asterisk, which matches any error. The errors that can be tested for are:
26846 .vitem &%auth_failed%&
26847 Authentication failed when trying to send to a host in the
26848 &%hosts_require_auth%& list in an &(smtp)& transport.
26850 .vitem &%data_4xx%&
26851 A 4&'xx'& error was received for an outgoing DATA command, either immediately
26852 after the command, or after sending the message's data.
26854 .vitem &%mail_4xx%&
26855 A 4&'xx'& error was received for an outgoing MAIL command.
26857 .vitem &%rcpt_4xx%&
26858 A 4&'xx'& error was received for an outgoing RCPT command.
26861 For the three 4&'xx'& errors, either the first or both of the x's can be given
26862 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
26863 recognize 452 errors given to RCPT commands for addresses in a certain domain,
26864 and have retries every ten minutes with a one-hour timeout, you could set up a
26865 retry rule of this form:
26867 the.domain.name rcpt_452 F,1h,10m
26869 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
26870 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
26873 .vitem &%lost_connection%&
26874 A server unexpectedly closed the SMTP connection. There may, of course,
26875 legitimate reasons for this (host died, network died), but if it repeats a lot
26876 for the same host, it indicates something odd.
26879 A DNS lookup for a host failed.
26880 Note that a &%dnslookup%& router will need to have matched
26881 its &%fail_defer_domains%& option for this retry type to be usable.
26882 Also note that a &%manualroute%& router will probably need
26883 its &%host_find_failed%& option set to &%defer%&.
26885 .vitem &%refused_MX%&
26886 A connection to a host obtained from an MX record was refused.
26888 .vitem &%refused_A%&
26889 A connection to a host not obtained from an MX record was refused.
26892 A connection was refused.
26894 .vitem &%timeout_connect_MX%&
26895 A connection attempt to a host obtained from an MX record timed out.
26897 .vitem &%timeout_connect_A%&
26898 A connection attempt to a host not obtained from an MX record timed out.
26900 .vitem &%timeout_connect%&
26901 A connection attempt timed out.
26903 .vitem &%timeout_MX%&
26904 There was a timeout while connecting or during an SMTP session with a host
26905 obtained from an MX record.
26907 .vitem &%timeout_A%&
26908 There was a timeout while connecting or during an SMTP session with a host not
26909 obtained from an MX record.
26912 There was a timeout while connecting or during an SMTP session.
26914 .vitem &%tls_required%&
26915 The server was required to use TLS (it matched &%hosts_require_tls%& in the
26916 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
26917 to STARTTLS, or there was a problem setting up the TLS connection.
26920 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26923 .vitem &%quota_%&<&'time'&>
26924 .cindex "quota" "error testing in retry rule"
26925 .cindex "retry" "quota error testing"
26926 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26927 transport, and the mailbox has not been accessed for <&'time'&>. For example,
26928 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
26932 .cindex "mailbox" "time of last read"
26933 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
26934 timeouts when the mailbox is full and is not being read by its owner. Ideally,
26935 it should be based on the last time that the user accessed the mailbox.
26936 However, it is not always possible to determine this. Exim uses the following
26940 If the mailbox is a single file, the time of last access (the &"atime"&) is
26941 used. As no new messages are being delivered (because the mailbox is over
26942 quota), Exim does not access the file, so this is the time of last user access.
26944 .cindex "maildir format" "time of last read"
26945 For a maildir delivery, the time of last modification of the &_new_&
26946 subdirectory is used. As the mailbox is over quota, no new files are created in
26947 the &_new_& subdirectory, because no new messages are being delivered. Any
26948 change to the &_new_& subdirectory is therefore assumed to be the result of an
26949 MUA moving a new message to the &_cur_& directory when it is first read. The
26950 time that is used is therefore the last time that the user read a new message.
26952 For other kinds of multi-file mailbox, the time of last access cannot be
26953 obtained, so a retry rule that uses this type of error field is never matched.
26956 The quota errors apply both to system-enforced quotas and to Exim's own quota
26957 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
26958 when a local delivery is deferred because a partition is full (the ENOSPC
26963 .section "Retry rules for specified senders" "SECID162"
26964 .cindex "retry" "rules; sender-specific"
26965 You can specify retry rules that apply only when the failing message has a
26966 specific sender. In particular, this can be used to define retry rules that
26967 apply only to bounce messages. The third item in a retry rule can be of this
26970 &`senders=`&<&'address list'&>
26972 The retry timings themselves are then the fourth item. For example:
26974 * rcpt_4xx senders=: F,1h,30m
26976 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
26977 host. If the address list contains white space, it must be enclosed in quotes.
26980 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
26982 &*Warning*&: This facility can be unhelpful if it is used for host errors
26983 (which do not depend on the recipient). The reason is that the sender is used
26984 only to match the retry rule. Once the rule has been found for a host error,
26985 its contents are used to set a retry time for the host, and this will apply to
26986 all messages, not just those with specific senders.
26988 When testing retry rules using &%-brt%&, you can supply a sender using the
26989 &%-f%& command line option, like this:
26991 exim -f "" -brt user@dom.ain
26993 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
26994 list is never matched.
27000 .section "Retry parameters" "SECID163"
27001 .cindex "retry" "parameters in rules"
27002 The third (or fourth, if a senders list is present) field in a retry rule is a
27003 sequence of retry parameter sets, separated by semicolons. Each set consists of
27005 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
27007 The letter identifies the algorithm for computing a new retry time; the cutoff
27008 time is the time beyond which this algorithm no longer applies, and the
27009 arguments vary the algorithm's action. The cutoff time is measured from the
27010 time that the first failure for the domain (combined with the local part if
27011 relevant) was detected, not from the time the message was received.
27013 .cindex "retry" "algorithms"
27014 .cindex "retry" "fixed intervals"
27015 .cindex "retry" "increasing intervals"
27016 .cindex "retry" "random intervals"
27017 The available algorithms are:
27020 &'F'&: retry at fixed intervals. There is a single time parameter specifying
27023 &'G'&: retry at geometrically increasing intervals. The first argument
27024 specifies a starting value for the interval, and the second a multiplier, which
27025 is used to increase the size of the interval at each retry.
27027 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
27028 retry, the previous interval is multiplied by the factor in order to get a
27029 maximum for the next interval. The minimum interval is the first argument of
27030 the parameter, and an actual interval is chosen randomly between them. Such a
27031 rule has been found to be helpful in cluster configurations when all the
27032 members of the cluster restart at once, and may therefore synchronize their
27033 queue processing times.
27036 When computing the next retry time, the algorithm definitions are scanned in
27037 order until one whose cutoff time has not yet passed is reached. This is then
27038 used to compute a new retry time that is later than the current time. In the
27039 case of fixed interval retries, this simply means adding the interval to the
27040 current time. For geometrically increasing intervals, retry intervals are
27041 computed from the rule's parameters until one that is greater than the previous
27042 interval is found. The main configuration variable
27043 .cindex "limit" "retry interval"
27044 .cindex "retry" "interval, maximum"
27045 .oindex "&%retry_interval_max%&"
27046 &%retry_interval_max%& limits the maximum interval between retries. It
27047 cannot be set greater than &`24h`&, which is its default value.
27049 A single remote domain may have a number of hosts associated with it, and each
27050 host may have more than one IP address. Retry algorithms are selected on the
27051 basis of the domain name, but are applied to each IP address independently. If,
27052 for example, a host has two IP addresses and one is unusable, Exim will
27053 generate retry times for it and will not try to use it until its next retry
27054 time comes. Thus the good IP address is likely to be tried first most of the
27057 .cindex "hints database" "use for retrying"
27058 Retry times are hints rather than promises. Exim does not make any attempt to
27059 run deliveries exactly at the computed times. Instead, a queue runner process
27060 starts delivery processes for delayed messages periodically, and these attempt
27061 new deliveries only for those addresses that have passed their next retry time.
27062 If a new message arrives for a deferred address, an immediate delivery attempt
27063 occurs only if the address has passed its retry time. In the absence of new
27064 messages, the minimum time between retries is the interval between queue runner
27065 processes. There is not much point in setting retry times of five minutes if
27066 your queue runners happen only once an hour, unless there are a significant
27067 number of incoming messages (which might be the case on a system that is
27068 sending everything to a smart host, for example).
27070 The data in the retry hints database can be inspected by using the
27071 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
27072 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
27073 &'exinext'& utility script can be used to find out what the next retry times
27074 are for the hosts associated with a particular mail domain, and also for local
27075 deliveries that have been deferred.
27078 .section "Retry rule examples" "SECID164"
27079 Here are some example retry rules:
27081 alice@wonderland.fict.example quota_5d F,7d,3h
27082 wonderland.fict.example quota_5d
27083 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
27084 lookingglass.fict.example * F,24h,30m;
27085 * refused_A F,2h,20m;
27086 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
27088 The first rule sets up special handling for mail to
27089 &'alice@wonderland.fict.example'& when there is an over-quota error and the
27090 mailbox has not been read for at least 5 days. Retries continue every three
27091 hours for 7 days. The second rule handles over-quota errors for all other local
27092 parts at &'wonderland.fict.example'&; the absence of a local part has the same
27093 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
27094 fail are bounced immediately if the mailbox has not been read for at least 5
27097 The third rule handles all other errors at &'wonderland.fict.example'&; retries
27098 happen every 15 minutes for an hour, then with geometrically increasing
27099 intervals until two days have passed since a delivery first failed. After the
27100 first hour there is a delay of one hour, then two hours, then four hours, and
27101 so on (this is a rather extreme example).
27103 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
27104 They happen every 30 minutes for 24 hours only. The remaining two rules handle
27105 all other domains, with special action for connection refusal from hosts that
27106 were not obtained from an MX record.
27108 The final rule in a retry configuration should always have asterisks in the
27109 first two fields so as to provide a general catch-all for any addresses that do
27110 not have their own special handling. This example tries every 15 minutes for 2
27111 hours, then with intervals starting at one hour and increasing by a factor of
27112 1.5 up to 16 hours, then every 8 hours up to 5 days.
27116 .section "Timeout of retry data" "SECID165"
27117 .cindex "timeout" "of retry data"
27118 .oindex "&%retry_data_expire%&"
27119 .cindex "hints database" "data expiry"
27120 .cindex "retry" "timeout of data"
27121 Exim timestamps the data that it writes to its retry hints database. When it
27122 consults the data during a delivery it ignores any that is older than the value
27123 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
27124 been tried for 7 days, Exim will try to deliver to it immediately a message
27125 arrives, and if that fails, it will calculate a retry time as if it were
27126 failing for the first time.
27128 This improves the behaviour for messages routed to rarely-used hosts such as MX
27129 backups. If such a host was down at one time, and happens to be down again when
27130 Exim tries a month later, using the old retry data would imply that it had been
27131 down all the time, which is not a justified assumption.
27133 If a host really is permanently dead, this behaviour causes a burst of retries
27134 every now and again, but only if messages routed to it are rare. If there is a
27135 message at least once every 7 days the retry data never expires.
27140 .section "Long-term failures" "SECID166"
27141 .cindex "delivery failure, long-term"
27142 .cindex "retry" "after long-term failure"
27143 Special processing happens when an email address has been failing for so long
27144 that the cutoff time for the last algorithm is reached. For example, using the
27145 default retry rule:
27147 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
27149 the cutoff time is four days. Reaching the retry cutoff is independent of how
27150 long any specific message has been failing; it is the length of continuous
27151 failure for the recipient address that counts.
27153 When the cutoff time is reached for a local delivery, or for all the IP
27154 addresses associated with a remote delivery, a subsequent delivery failure
27155 causes Exim to give up on the address, and a bounce message is generated.
27156 In order to cater for new messages that use the failing address, a next retry
27157 time is still computed from the final algorithm, and is used as follows:
27159 For local deliveries, one delivery attempt is always made for any subsequent
27160 messages. If this delivery fails, the address fails immediately. The
27161 post-cutoff retry time is not used.
27163 .cindex "final cutoff" "retries, controlling"
27164 .cindex retry "final cutoff"
27165 If the delivery is remote, there are two possibilities, controlled by the
27166 .oindex "&%delay_after_cutoff%&"
27167 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
27168 default. Until the post-cutoff retry time for one of the IP addresses,
27169 as set by the &%retry_data_expire%& option, is
27170 reached, the failing email address is bounced immediately, without a delivery
27171 attempt taking place. After that time, one new delivery attempt is made to
27172 those IP addresses that are past their retry times, and if that still fails,
27173 the address is bounced and new retry times are computed.
27175 In other words, when all the hosts for a given email address have been failing
27176 for a long time, Exim bounces rather then defers until one of the hosts' retry
27177 times is reached. Then it tries once, and bounces if that attempt fails. This
27178 behaviour ensures that few resources are wasted in repeatedly trying to deliver
27179 to a broken destination, but if the host does recover, Exim will eventually
27182 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
27183 addresses are past their final cutoff time, Exim tries to deliver to those IP
27184 addresses that have not been tried since the message arrived. If there are
27185 no suitable IP addresses, or if they all fail, the address is bounced. In other
27186 words, it does not delay when a new message arrives, but tries the expired
27187 addresses immediately, unless they have been tried since the message arrived.
27188 If there is a continuous stream of messages for the failing domains, setting
27189 &%delay_after_cutoff%& false means that there will be many more attempts to
27190 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
27193 .section "Deliveries that work intermittently" "SECID167"
27194 .cindex "retry" "intermittently working deliveries"
27195 Some additional logic is needed to cope with cases where a host is
27196 intermittently available, or when a message has some attribute that prevents
27197 its delivery when others to the same address get through. In this situation,
27198 because some messages are successfully delivered, the &"retry clock"& for the
27199 host or address keeps getting reset by the successful deliveries, and so
27200 failing messages remain in the queue for ever because the cutoff time is never
27203 Two exceptional actions are applied to prevent this happening. The first
27204 applies to errors that are related to a message rather than a remote host.
27205 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
27206 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
27207 commands, and quota failures. For this type of error, if a message's arrival
27208 time is earlier than the &"first failed"& time for the error, the earlier time
27209 is used when scanning the retry rules to decide when to try next and when to
27210 time out the address.
27212 The exceptional second action applies in all cases. If a message has been on
27213 the queue for longer than the cutoff time of any applicable retry rule for a
27214 given address, a delivery is attempted for that address, even if it is not yet
27215 time, and if this delivery fails, the address is timed out. A new retry time is
27216 not computed in this case, so that other messages for the same address are
27217 considered immediately.
27218 .ecindex IIDretconf1
27219 .ecindex IIDregconf2
27226 . ////////////////////////////////////////////////////////////////////////////
27227 . ////////////////////////////////////////////////////////////////////////////
27229 .chapter "SMTP authentication" "CHAPSMTPAUTH"
27230 .scindex IIDauthconf1 "SMTP" "authentication configuration"
27231 .scindex IIDauthconf2 "authentication"
27232 The &"authenticators"& section of Exim's runtime configuration is concerned
27233 with SMTP authentication. This facility is an extension to the SMTP protocol,
27234 described in RFC 2554, which allows a client SMTP host to authenticate itself
27235 to a server. This is a common way for a server to recognize clients that are
27236 permitted to use it as a relay. SMTP authentication is not of relevance to the
27237 transfer of mail between servers that have no managerial connection with each
27240 The name of an authenticator is limited to be &drivernamemax; ASCII characters long;
27241 prior to Exim 4.95 names would be silently truncated at this length, but now
27244 .cindex "AUTH" "description of"
27245 .cindex "ESMTP extensions" AUTH
27246 Very briefly, the way SMTP authentication works is as follows:
27249 The server advertises a number of authentication &'mechanisms'& in response to
27250 the client's EHLO command.
27252 The client issues an AUTH command, naming a specific mechanism. The command
27253 may, optionally, contain some authentication data.
27255 The server may issue one or more &'challenges'&, to which the client must send
27256 appropriate responses. In simple authentication mechanisms, the challenges are
27257 just prompts for user names and passwords. The server does not have to issue
27258 any challenges &-- in some mechanisms the relevant data may all be transmitted
27259 with the AUTH command.
27261 The server either accepts or denies authentication.
27263 If authentication succeeds, the client may optionally make use of the AUTH
27264 option on the MAIL command to pass an authenticated sender in subsequent
27265 mail transactions. Authentication lasts for the remainder of the SMTP
27268 If authentication fails, the client may give up, or it may try a different
27269 authentication mechanism, or it may try transferring mail over the
27270 unauthenticated connection.
27273 If you are setting up a client, and want to know which authentication
27274 mechanisms the server supports, you can use Telnet to connect to port 25 (the
27275 SMTP port) on the server, and issue an EHLO command. The response to this
27276 includes the list of supported mechanisms. For example:
27278 &`$ `&&*&`telnet server.example 25`&*&
27279 &`Trying 192.168.34.25...`&
27280 &`Connected to server.example.`&
27281 &`Escape character is '^]'.`&
27282 &`220 server.example ESMTP Exim 4.20 ...`&
27283 &*&`ehlo client.example`&*&
27284 &`250-server.example Hello client.example [10.8.4.5]`&
27285 &`250-SIZE 52428800`&
27290 The second-last line of this example output shows that the server supports
27291 authentication using the PLAIN mechanism. In Exim, the different authentication
27292 mechanisms are configured by specifying &'authenticator'& drivers. Like the
27293 routers and transports, which authenticators are included in the binary is
27294 controlled by build-time definitions. The following are currently available,
27295 included by setting
27298 AUTH_CYRUS_SASL=yes
27302 AUTH_HEIMDAL_GSSAPI=yes
27307 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
27308 authentication mechanism (RFC 2195), and the second provides an interface to
27309 the Cyrus SASL authentication library.
27310 The third is an interface to Dovecot's authentication system, delegating the
27311 work via a socket interface.
27312 The fourth provides for negotiation of authentication done via non-SMTP means,
27313 as defined by RFC 4422 Appendix A.
27314 The fifth provides an interface to the GNU SASL authentication library, which
27315 provides mechanisms but typically not data sources.
27316 The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
27317 supporting setting a server keytab.
27318 The seventh can be configured to support
27319 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
27320 not formally documented, but used by several MUAs.
27321 The eighth authenticator
27322 supports Microsoft's &'Secure Password Authentication'& mechanism.
27323 The last is an Exim authenticator but not an SMTP one;
27324 instead it can use information from a TLS negotiation.
27326 The authenticators are configured using the same syntax as other drivers (see
27327 section &<<SECTfordricon>>&). If no authenticators are required, no
27328 authentication section need be present in the configuration file. Each
27329 authenticator can in principle have both server and client functions. When Exim
27330 is receiving SMTP mail, it is acting as a server; when it is sending out
27331 messages over SMTP, it is acting as a client. Authenticator configuration
27332 options are provided for use in both these circumstances.
27334 To make it clear which options apply to which situation, the prefixes
27335 &%server_%& and &%client_%& are used on option names that are specific to
27336 either the server or the client function, respectively. Server and client
27337 functions are disabled if none of their options are set. If an authenticator is
27338 to be used for both server and client functions, a single definition, using
27339 both sets of options, is required. For example:
27343 public_name = CRAM-MD5
27344 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
27346 client_secret = secret2
27348 The &%server_%& option is used when Exim is acting as a server, and the
27349 &%client_%& options when it is acting as a client.
27351 Descriptions of the individual authenticators are given in subsequent chapters.
27352 The remainder of this chapter covers the generic options for the
27353 authenticators, followed by general discussion of the way authentication works
27356 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
27357 per-mechanism basis. Please read carefully to determine which variables hold
27358 account labels such as usercodes and which hold passwords or other
27359 authenticating data.
27361 Note that some mechanisms support two different identifiers for accounts: the
27362 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
27363 and &'authz'& are commonly encountered. The American spelling is standard here.
27364 Conceptually, authentication data such as passwords are tied to the identifier
27365 used to authenticate; servers may have rules to permit one user to act as a
27366 second user, so that after login the session is treated as though that second
27367 user had logged in. That second user is the &'authorization id'&. A robust
27368 configuration might confirm that the &'authz'& field is empty or matches the
27369 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
27370 as verified data, the &'authz'& as an unverified request which the server might
27373 A &'realm'& is a text string, typically a domain name, presented by a server
27374 to a client to help it select an account and credentials to use. In some
27375 mechanisms, the client and server provably agree on the realm, but clients
27376 typically can not treat the realm as secure data to be blindly trusted.
27380 .section "Generic options for authenticators" "SECID168"
27381 .cindex "authentication" "generic options"
27382 .cindex "options" "generic; for authenticators"
27384 .option client_condition authenticators string&!! unset
27385 When Exim is authenticating as a client, it skips any authenticator whose
27386 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
27387 used, for example, to skip plain text authenticators when the connection is not
27388 encrypted by a setting such as:
27390 client_condition = ${if !eq{$tls_out_cipher}{}}
27394 .option client_set_id authenticators string&!! unset
27395 When client authentication succeeds, this condition is expanded; the
27396 result is used in the log lines for outbound messages.
27397 Typically it will be the user name used for authentication.
27400 .option driver authenticators string unset
27401 This option must always be set. It specifies which of the available
27402 authenticators is to be used.
27405 .option public_name authenticators string unset
27406 This option specifies the name of the authentication mechanism that the driver
27407 implements, and by which it is known to the outside world. These names should
27408 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
27409 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
27410 defaults to the driver's instance name.
27413 .option server_advertise_condition authenticators string&!! unset
27414 When a server is about to advertise an authentication mechanism, the condition
27415 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
27416 mechanism is not advertised.
27417 If the expansion fails, the mechanism is not advertised. If the failure was not
27418 forced, and was not caused by a lookup defer, the incident is logged.
27419 See section &<<SECTauthexiser>>& below for further discussion.
27422 .option server_condition authenticators string&!! unset
27423 This option must be set for a &%plaintext%& server authenticator, where it
27424 is used directly to control authentication. See section &<<SECTplainserver>>&
27427 For the &(gsasl)& authenticator, this option is required for various
27428 mechanisms; see chapter &<<CHAPgsasl>>& for details.
27430 For the other authenticators, &%server_condition%& can be used as an additional
27431 authentication or authorization mechanism that is applied after the other
27432 authenticator conditions succeed. If it is set, it is expanded when the
27433 authenticator would otherwise return a success code. If the expansion is forced
27434 to fail, authentication fails. Any other expansion failure causes a temporary
27435 error code to be returned. If the result of a successful expansion is an empty
27436 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27437 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
27438 other result, a temporary error code is returned, with the expanded string as
27442 .option server_debug_print authenticators string&!! unset
27443 If this option is set and authentication debugging is enabled (see the &%-d%&
27444 command line option), the string is expanded and included in the debugging
27445 output when the authenticator is run as a server. This can help with checking
27446 out the values of variables.
27447 If expansion of the string fails, the error message is written to the debugging
27448 output, and Exim carries on processing.
27451 .option server_set_id authenticators string&!! unset
27452 .vindex "&$authenticated_id$&"
27453 .vindex "&$authenticated_fail_id$&"
27454 When an Exim server successfully authenticates a client, this string is
27455 expanded using data from the authentication, and preserved for any incoming
27456 messages in the variable &$authenticated_id$&. It is also included in the log
27457 lines for incoming messages. For example, a user/password authenticator
27458 configuration might preserve the user name that was used to authenticate, and
27459 refer to it subsequently during delivery of the message.
27460 On a failing authentication the expansion result is instead saved in
27461 the &$authenticated_fail_id$& variable.
27462 If expansion fails, the option is ignored.
27465 .option server_mail_auth_condition authenticators string&!! unset
27466 This option allows a server to discard authenticated sender addresses supplied
27467 as part of MAIL commands in SMTP connections that are authenticated by the
27468 driver on which &%server_mail_auth_condition%& is set. The option is not used
27469 as part of the authentication process; instead its (unexpanded) value is
27470 remembered for later use.
27471 How it is used is described in the following section.
27477 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
27478 .cindex "authentication" "sender; authenticated"
27479 .cindex "AUTH" "on MAIL command"
27480 When a client supplied an AUTH= item on a MAIL command, Exim applies
27481 the following checks before accepting it as the authenticated sender of the
27485 If the connection is not using extended SMTP (that is, HELO was used rather
27486 than EHLO), the use of AUTH= is a syntax error.
27488 If the value of the AUTH= parameter is &"<>"&, it is ignored.
27490 .vindex "&$authenticated_sender$&"
27491 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
27492 running, the value of &$authenticated_sender$& is set to the value obtained
27493 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
27494 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
27495 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
27496 given for the MAIL command.
27498 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
27499 is accepted and placed in &$authenticated_sender$& only if the client has
27502 If the AUTH= value was accepted by either of the two previous rules, and
27503 the client has authenticated, and the authenticator has a setting for the
27504 &%server_mail_auth_condition%&, the condition is checked at this point. The
27505 valued that was saved from the authenticator is expanded. If the expansion
27506 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
27507 &$authenticated_sender$& is deleted. If the expansion yields any other value,
27508 the value of &$authenticated_sender$& is retained and passed on with the
27513 When &$authenticated_sender$& is set for a message, it is passed on to other
27514 hosts to which Exim authenticates as a client. Do not confuse this value with
27515 &$authenticated_id$&, which is a string obtained from the authentication
27516 process, and which is not usually a complete email address.
27518 .vindex "&$sender_address$&"
27519 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
27520 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
27521 therefore make use of &$authenticated_sender$&. The converse is not true: the
27522 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
27527 .section "Authentication on an Exim server" "SECTauthexiser"
27528 .cindex "authentication" "on an Exim server"
27529 When Exim receives an EHLO command, it advertises the public names of those
27530 authenticators that are configured as servers, subject to the following
27534 The client host must match &%auth_advertise_hosts%& (default *).
27536 If the &%server_advertise_condition%& option is set, its expansion must not
27537 yield the empty string, &"0"&, &"no"&, or &"false"&.
27540 The order in which the authenticators are defined controls the order in which
27541 the mechanisms are advertised.
27543 Some mail clients (for example, some versions of Netscape) require the user to
27544 provide a name and password for authentication whenever AUTH is advertised,
27545 even though authentication may not in fact be needed (for example, Exim may be
27546 set up to allow unconditional relaying from the client by an IP address check).
27547 You can make such clients more friendly by not advertising AUTH to them.
27548 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
27549 that runs for RCPT) to relay without authentication, you should set
27551 auth_advertise_hosts = ! 10.9.8.0/24
27553 so that no authentication mechanisms are advertised to them.
27555 The &%server_advertise_condition%& controls the advertisement of individual
27556 authentication mechanisms. For example, it can be used to restrict the
27557 advertisement of a particular mechanism to encrypted connections, by a setting
27560 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
27562 .vindex "&$tls_in_cipher$&"
27563 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
27564 yields &"yes"&, which allows the advertisement to happen.
27566 When an Exim server receives an AUTH command from a client, it rejects it
27567 immediately if AUTH was not advertised in response to an earlier EHLO
27568 command. This is the case if
27571 The client host does not match &%auth_advertise_hosts%&; or
27573 No authenticators are configured with server options; or
27575 Expansion of &%server_advertise_condition%& blocked the advertising of all the
27576 server authenticators.
27580 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
27581 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
27582 AUTH is accepted from any client host.
27584 If AUTH is not rejected by the ACL, Exim searches its configuration for a
27585 server authentication mechanism that was advertised in response to EHLO and
27586 that matches the one named in the AUTH command. If it finds one, it runs
27587 the appropriate authentication protocol, and authentication either succeeds or
27588 fails. If there is no matching advertised mechanism, the AUTH command is
27589 rejected with a 504 error.
27591 .vindex "&$received_protocol$&"
27592 .vindex "&$sender_host_authenticated$&"
27593 When a message is received from an authenticated host, the value of
27594 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
27595 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
27596 public name) of the authenticator driver that successfully authenticated the
27597 client from which the message was received. This variable is empty if there was
27598 no successful authentication.
27600 .cindex authentication "expansion item"
27601 Successful authentication sets up information used by the
27602 &%authresults%& expansion item.
27607 .section "Testing server authentication" "SECID169"
27608 .cindex "authentication" "testing a server"
27609 .cindex "AUTH" "testing a server"
27610 .cindex "base64 encoding" "creating authentication test data"
27611 Exim's &%-bh%& option can be useful for testing server authentication
27612 configurations. The data for the AUTH command has to be sent using base64
27613 encoding. A quick way to produce such data for testing is the following Perl
27617 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
27619 .cindex "binary zero" "in authentication data"
27620 This interprets its argument as a Perl string, and then encodes it. The
27621 interpretation as a Perl string allows binary zeros, which are required for
27622 some kinds of authentication, to be included in the data. For example, a
27623 command line to run this script on such data might be
27625 encode '\0user\0password'
27627 Note the use of single quotes to prevent the shell interpreting the
27628 backslashes, so that they can be interpreted by Perl to specify characters
27629 whose code value is zero.
27631 &*Warning 1*&: If either of the user or password strings starts with an octal
27632 digit, you must use three zeros instead of one after the leading backslash. If
27633 you do not, the octal digit that starts your string will be incorrectly
27634 interpreted as part of the code for the first character.
27636 &*Warning 2*&: If there are characters in the strings that Perl interprets
27637 specially, you must use a Perl escape to prevent them being misinterpreted. For
27638 example, a command such as
27640 encode '\0user@domain.com\0pas$$word'
27642 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
27644 If you have the &%mimencode%& command installed, another way to produce
27645 base64-encoded strings is to run the command
27647 echo -e -n `\0user\0password' | mimencode
27649 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
27650 in the argument, and the &%-n%& option specifies no newline at the end of its
27651 output. However, not all versions of &%echo%& recognize these options, so you
27652 should check your version before relying on this suggestion.
27656 .section "Authentication by an Exim client" "SECID170"
27657 .cindex "authentication" "on an Exim client"
27658 The &(smtp)& transport has two options called &%hosts_require_auth%& and
27659 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
27660 announces support for authentication, and the host matches an entry in either
27661 of these options, Exim (as a client) tries to authenticate as follows:
27664 For each authenticator that is configured as a client, in the order in which
27665 they are defined in the configuration, it searches the authentication
27666 mechanisms announced by the server for one whose name matches the public name
27667 of the authenticator.
27670 .vindex "&$host_address$&"
27671 When it finds one that matches, it runs the authenticator's client code. The
27672 variables &$host$& and &$host_address$& are available for any string expansions
27673 that the client might do. They are set to the server's name and IP address. If
27674 any expansion is forced to fail, the authentication attempt is abandoned, and
27675 Exim moves on to the next authenticator. Otherwise an expansion failure causes
27676 delivery to be deferred.
27678 If the result of the authentication attempt is a temporary error or a timeout,
27679 Exim abandons trying to send the message to the host for the moment. It will
27680 try again later. If there are any backup hosts available, they are tried in the
27683 If the response to authentication is a permanent error (5&'xx'& code), Exim
27684 carries on searching the list of authenticators and tries another one if
27685 possible. If all authentication attempts give permanent errors, or if there are
27686 no attempts because no mechanisms match (or option expansions force failure),
27687 what happens depends on whether the host matches &%hosts_require_auth%& or
27688 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
27689 delivery is deferred. The error can be detected in the retry rules, and thereby
27690 turned into a permanent error if you wish. In the second case, Exim tries to
27691 deliver the message unauthenticated.
27694 Note that the hostlist test for whether to do authentication can be
27695 confused if name-IP lookups change between the time the peer is decided
27696 upon and the time that the transport runs. For example, with a manualroute
27697 router given a host name, and with DNS "round-robin" used by that name: if
27698 the local resolver cache times out between the router and the transport
27699 running, the transport may get an IP for the name for its authentication
27700 check which does not match the connection peer IP.
27701 No authentication will then be done, despite the names being identical.
27703 For such cases use a separate transport which always authenticates.
27705 .cindex "AUTH" "on MAIL command"
27706 When Exim has authenticated itself to a remote server, it adds the AUTH
27707 parameter to the MAIL commands it sends, if it has an authenticated sender for
27708 the message. If the message came from a remote host, the authenticated sender
27709 is the one that was receiving on an incoming MAIL command, provided that the
27710 incoming connection was authenticated and the &%server_mail_auth%& condition
27711 allowed the authenticated sender to be retained. If a local process calls Exim
27712 to send a message, the sender address that is built from the login name and
27713 &%qualify_domain%& is treated as authenticated. However, if the
27714 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
27715 the authenticated sender that was received with the message.
27716 .ecindex IIDauthconf1
27717 .ecindex IIDauthconf2
27724 . ////////////////////////////////////////////////////////////////////////////
27725 . ////////////////////////////////////////////////////////////////////////////
27727 .chapter "The plaintext authenticator" "CHAPplaintext"
27728 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
27729 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
27730 The &(plaintext)& authenticator can be configured to support the PLAIN and
27731 LOGIN authentication mechanisms, both of which transfer authentication data as
27732 plain (unencrypted) text (though base64 encoded). The use of plain text is a
27733 security risk; you are strongly advised to insist on the use of SMTP encryption
27734 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
27735 use unencrypted plain text, you should not use the same passwords for SMTP
27736 connections as you do for login accounts.
27738 .section "Avoiding cleartext use" "SECTplain_TLS"
27739 The following generic option settings will disable &(plaintext)& authenticators when
27740 TLS is not being used:
27742 server_advertise_condition = ${if def:tls_in_cipher }
27743 client_condition = ${if def:tls_out_cipher}
27746 &*Note*&: a plaintext SMTP AUTH done inside TLS is not vulnerable to casual snooping,
27747 but is still vulnerable to a Man In The Middle attack unless certificates
27748 (including their names) have been properly verified.
27750 .section "Plaintext server options" "SECID171"
27751 .cindex "options" "&(plaintext)& authenticator (server)"
27752 When configured as a server, &(plaintext)& uses the following options:
27754 .option server_condition authenticators string&!! unset
27755 This is actually a global authentication option, but it must be set in order to
27756 configure the &(plaintext)& driver as a server. Its use is described below.
27758 .option server_prompts plaintext "string list&!!" unset
27759 The contents of this option, after expansion, must be a colon-separated list of
27760 prompt strings. If expansion fails, a temporary authentication rejection is
27763 .section "Using plaintext in a server" "SECTplainserver"
27764 .cindex "AUTH" "in &(plaintext)& authenticator"
27765 .cindex "binary zero" "in &(plaintext)& authenticator"
27766 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
27767 "in &(plaintext)& authenticator"
27768 .vindex "&$auth1$&, &$auth2$&, etc"
27769 .cindex "base64 encoding" "in &(plaintext)& authenticator"
27771 When running as a server, &(plaintext)& performs the authentication test by
27772 expanding a string. The data sent by the client with the AUTH command, or in
27773 response to subsequent prompts, is base64 encoded, and so may contain any byte
27774 values when decoded. If any data is supplied with the command, it is treated as
27775 a list of strings, separated by NULs (binary zeros), the first three of which
27776 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
27777 (neither LOGIN nor PLAIN uses more than three strings).
27779 For compatibility with previous releases of Exim, the values are also placed in
27780 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
27781 variables for this purpose is now deprecated, as it can lead to confusion in
27782 string expansions that also use them for other things.
27784 If there are more strings in &%server_prompts%& than the number of strings
27785 supplied with the AUTH command, the remaining prompts are used to obtain more
27786 data. Each response from the client may be a list of NUL-separated strings.
27788 .vindex "&$authenticated_id$&"
27789 Once a sufficient number of data strings have been received,
27790 &%server_condition%& is expanded. If the expansion is forced to fail,
27791 authentication fails. Any other expansion failure causes a temporary error code
27792 to be returned. If the result of a successful expansion is an empty string,
27793 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27794 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
27795 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
27796 For any other result, a temporary error code is returned, with the expanded
27797 string as the error text.
27799 &*Warning*&: If you use a lookup in the expansion to find the user's
27800 password, be sure to make the authentication fail if the user is unknown.
27801 There are good and bad examples at the end of the next section.
27805 .section "The PLAIN authentication mechanism" "SECID172"
27806 .cindex "PLAIN authentication mechanism"
27807 .cindex authentication PLAIN
27808 .cindex "binary zero" "in &(plaintext)& authenticator"
27809 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
27810 sent as one item of data (that is, one combined string containing two NUL
27811 separators). The data is sent either as part of the AUTH command, or
27812 subsequently in response to an empty prompt from the server.
27814 The second and third strings are a user name and a corresponding password.
27815 Using a single fixed user name and password as an example, this could be
27816 configured as follows:
27820 public_name = PLAIN
27822 server_condition = \
27823 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
27824 server_set_id = $auth2
27826 Note that the default result strings from &%if%& (&"true"& or an empty string)
27827 are exactly what we want here, so they need not be specified. Obviously, if the
27828 password contains expansion-significant characters such as dollar, backslash,
27829 or closing brace, they have to be escaped.
27831 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
27832 the end of a string list are ignored). If all the data comes as part of the
27833 AUTH command, as is commonly the case, the prompt is not used. This
27834 authenticator is advertised in the response to EHLO as
27838 and a client host can authenticate itself by sending the command
27840 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
27842 As this contains three strings (more than the number of prompts), no further
27843 data is required from the client. Alternatively, the client may just send
27847 to initiate authentication, in which case the server replies with an empty
27848 prompt. The client must respond with the combined data string.
27850 The data string is base64 encoded, as required by the RFC. This example,
27851 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
27852 represents a zero byte. This is split up into three strings, the first of which
27853 is empty. The &%server_condition%& option in the authenticator checks that the
27854 second two are &`username`& and &`mysecret`& respectively.
27856 Having just one fixed user name and password, as in this example, is not very
27857 realistic, though for a small organization with only a handful of
27858 authenticating clients it could make sense.
27860 A more sophisticated instance of this authenticator could use the user name in
27861 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
27862 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
27863 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
27864 This is an incorrect example:
27866 server_condition = \
27867 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
27869 The expansion uses the user name (&$auth2$&) as the key to look up a password,
27870 which it then compares to the supplied password (&$auth3$&). Why is this example
27871 incorrect? It works fine for existing users, but consider what happens if a
27872 non-existent user name is given. The lookup fails, but as no success/failure
27873 strings are given for the lookup, it yields an empty string. Thus, to defeat
27874 the authentication, all a client has to do is to supply a non-existent user
27875 name and an empty password. The correct way of writing this test is:
27877 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
27878 {${if eq{$value}{$auth3}}} {false}}
27880 In this case, if the lookup succeeds, the result is checked; if the lookup
27881 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
27882 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
27883 always fails if its second argument is empty. However, the second way of
27884 writing the test makes the logic clearer.
27887 .section "The LOGIN authentication mechanism" "SECID173"
27888 .cindex "LOGIN authentication mechanism"
27889 .cindex authentication LOGIN
27890 The LOGIN authentication mechanism is not documented in any RFC, but is in use
27891 in a number of programs. No data is sent with the AUTH command. Instead, a
27892 user name and password are supplied separately, in response to prompts. The
27893 plaintext authenticator can be configured to support this as in this example:
27897 public_name = LOGIN
27898 server_prompts = User Name : Password
27899 server_condition = \
27900 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
27901 server_set_id = $auth1
27903 Because of the way plaintext operates, this authenticator accepts data supplied
27904 with the AUTH command (in contravention of the specification of LOGIN), but
27905 if the client does not supply it (as is the case for LOGIN clients), the prompt
27906 strings are used to obtain two data items.
27908 Some clients are very particular about the precise text of the prompts. For
27909 example, Outlook Express is reported to recognize only &"Username:"& and
27910 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
27911 strings. It uses the &%ldapauth%& expansion condition to check the user
27912 name and password by binding to an LDAP server:
27916 public_name = LOGIN
27917 server_prompts = Username:: : Password::
27918 server_condition = ${if and{{ \
27921 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
27922 pass=${quote:$auth2} \
27923 ldap://ldap.example.org/} }} }
27924 server_set_id = uid=$auth1,ou=people,o=example.org
27926 We have to check that the username is not empty before using it, because LDAP
27927 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
27928 operator to correctly quote the DN for authentication. However, the basic
27929 &%quote%& operator, rather than any of the LDAP quoting operators, is the
27930 correct one to use for the password, because quoting is needed only to make
27931 the password conform to the Exim syntax. At the LDAP level, the password is an
27932 uninterpreted string.
27935 .section "Support for different kinds of authentication" "SECID174"
27936 A number of string expansion features are provided for the purpose of
27937 interfacing to different ways of user authentication. These include checking
27938 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
27939 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
27945 .section "Using plaintext in a client" "SECID175"
27946 .cindex "options" "&(plaintext)& authenticator (client)"
27947 The &(plaintext)& authenticator has two client options:
27949 .option client_ignore_invalid_base64 plaintext boolean false
27950 If the client receives a server prompt that is not a valid base64 string,
27951 authentication is abandoned by default. However, if this option is set true,
27952 the error in the challenge is ignored and the client sends the response as
27955 .option client_send plaintext string&!! unset
27956 The string is a colon-separated list of authentication data strings. Each
27957 string is independently expanded before being sent to the server. The first
27958 string is sent with the AUTH command; any more strings are sent in response
27959 to prompts from the server. Before each string is expanded, the value of the
27960 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
27961 with &$auth1$& for the first prompt. Up to three prompts are stored in this
27962 way. Thus, the prompt that is received in response to sending the first string
27963 (with the AUTH command) can be used in the expansion of the second string, and
27964 so on. If an invalid base64 string is received when
27965 &%client_ignore_invalid_base64%& is set, an empty string is put in the
27966 &$auth$&<&'n'&> variable.
27968 &*Note*&: You cannot use expansion to create multiple strings, because
27969 splitting takes priority and happens first.
27971 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
27972 the data, further processing is applied to each string before it is sent. If
27973 there are any single circumflex characters in the string, they are converted to
27974 NULs. Should an actual circumflex be required as data, it must be doubled in
27977 This is an example of a client configuration that implements the PLAIN
27978 authentication mechanism with a fixed user name and password:
27982 public_name = PLAIN
27983 client_send = ^username^mysecret
27985 The lack of colons means that the entire text is sent with the AUTH
27986 command, with the circumflex characters converted to NULs.
27987 Note that due to the ambiguity of parsing three consectutive circumflex characters
27988 there is no way to provide a password having a leading circumflex.
27992 that uses the LOGIN mechanism is:
27996 public_name = LOGIN
27997 client_send = : username : mysecret
27999 The initial colon means that the first string is empty, so no data is sent with
28000 the AUTH command itself. The remaining strings are sent in response to
28002 .ecindex IIDplaiauth1
28003 .ecindex IIDplaiauth2
28008 . ////////////////////////////////////////////////////////////////////////////
28009 . ////////////////////////////////////////////////////////////////////////////
28011 .chapter "The cram_md5 authenticator" "CHID9"
28012 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
28013 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
28014 .cindex "CRAM-MD5 authentication mechanism"
28015 .cindex authentication CRAM-MD5
28016 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
28017 sends a challenge string to the client, and the response consists of a user
28018 name and the CRAM-MD5 digest of the challenge string combined with a secret
28019 string (password) which is known to both server and client. Thus, the secret
28020 is not sent over the network as plain text, which makes this authenticator more
28021 secure than &(plaintext)&. However, the downside is that the secret has to be
28022 available in plain text at either end.
28025 .section "Using cram_md5 as a server" "SECID176"
28026 .cindex "options" "&(cram_md5)& authenticator (server)"
28027 This authenticator has one server option, which must be set to configure the
28028 authenticator as a server:
28030 .option server_secret cram_md5 string&!! unset
28031 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
28032 When the server receives the client's response, the user name is placed in
28033 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
28034 obtain the password for that user. The server then computes the CRAM-MD5 digest
28035 that the client should have sent, and checks that it received the correct
28036 string. If the expansion of &%server_secret%& is forced to fail, authentication
28037 fails. If the expansion fails for some other reason, a temporary error code is
28038 returned to the client.
28040 For compatibility with previous releases of Exim, the user name is also placed
28041 in &$1$&. However, the use of this variables for this purpose is now
28042 deprecated, as it can lead to confusion in string expansions that also use
28043 numeric variables for other things.
28045 For example, the following authenticator checks that the user name given by the
28046 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
28047 user name, authentication fails.
28051 public_name = CRAM-MD5
28052 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
28053 server_set_id = $auth1
28055 .vindex "&$authenticated_id$&"
28056 If authentication succeeds, the setting of &%server_set_id%& preserves the user
28057 name in &$authenticated_id$&. A more typical configuration might look up the
28058 secret string in a file, using the user name as the key. For example:
28062 public_name = CRAM-MD5
28063 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
28065 server_set_id = $auth1
28067 Note that this expansion explicitly forces failure if the lookup fails
28068 because &$auth1$& contains an unknown user name.
28070 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
28071 using the relevant libraries, you need to know the realm to specify in the
28072 lookup and then ask for the &"userPassword"& attribute for that user in that
28077 public_name = CRAM-MD5
28078 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
28079 dbmjz{/etc/sasldb2}{$value}fail}
28080 server_set_id = $auth1
28083 .section "Using cram_md5 as a client" "SECID177"
28084 .cindex "options" "&(cram_md5)& authenticator (client)"
28085 When used as a client, the &(cram_md5)& authenticator has two options:
28089 .option client_name cram_md5 string&!! "the primary host name"
28090 This string is expanded, and the result used as the user name data when
28091 computing the response to the server's challenge.
28094 .option client_secret cram_md5 string&!! unset
28095 This option must be set for the authenticator to work as a client. Its value is
28096 expanded and the result used as the secret string when computing the response.
28100 .vindex "&$host_address$&"
28101 Different user names and secrets can be used for different servers by referring
28102 to &$host$& or &$host_address$& in the options. Forced failure of either
28103 expansion string is treated as an indication that this authenticator is not
28104 prepared to handle this case. Exim moves on to the next configured client
28105 authenticator. Any other expansion failure causes Exim to give up trying to
28106 send the message to the current server.
28108 A simple example configuration of a &(cram_md5)& authenticator, using fixed
28113 public_name = CRAM-MD5
28115 client_secret = secret
28117 .ecindex IIDcramauth1
28118 .ecindex IIDcramauth2
28122 . ////////////////////////////////////////////////////////////////////////////
28123 . ////////////////////////////////////////////////////////////////////////////
28125 .chapter "The cyrus_sasl authenticator" "CHID10"
28126 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
28127 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
28128 .cindex "Cyrus" "SASL library"
28130 The code for this authenticator was provided by Matthew Byng-Maddick while
28131 at A L Digital Ltd.
28133 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
28134 library implementation of the RFC 2222 (&"Simple Authentication and Security
28135 Layer"&). This library supports a number of authentication mechanisms,
28136 including PLAIN and LOGIN, but also several others that Exim does not support
28137 directly. In particular, there is support for Kerberos authentication.
28139 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
28140 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
28141 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
28142 name of the driver to determine which mechanism to support.
28144 Where access to some kind of secret file is required, for example, in GSSAPI
28145 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
28146 user, and that the Cyrus SASL library has no way of escalating privileges
28147 by default. You may also find you need to set environment variables,
28148 depending on the driver you are using.
28150 The application name provided by Exim is &"exim"&, so various SASL options may
28151 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
28152 Kerberos, note that because of limitations in the GSSAPI interface,
28153 changing the server keytab might need to be communicated down to the Kerberos
28154 layer independently. The mechanism for doing so is dependent upon the Kerberos
28157 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
28158 may be set to point to an alternative keytab file. Exim will pass this
28159 variable through from its own inherited environment when started as root or the
28160 Exim user. The keytab file needs to be readable by the Exim user.
28161 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
28162 environment variable. In practice, for those releases, the Cyrus authenticator
28163 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
28164 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
28167 .section "Using cyrus_sasl as a server" "SECID178"
28168 The &(cyrus_sasl)& authenticator has four private options. It puts the username
28169 (on a successful authentication) into &$auth1$&. For compatibility with
28170 previous releases of Exim, the username is also placed in &$1$&. However, the
28171 use of this variable for this purpose is now deprecated, as it can lead to
28172 confusion in string expansions that also use numeric variables for other
28176 .option server_hostname cyrus_sasl string&!! "see below"
28177 This option selects the hostname that is used when communicating with the
28178 library. The default value is &`$primary_hostname`&. It is up to the underlying
28179 SASL plug-in what it does with this data.
28182 .option server_mech cyrus_sasl string "see below"
28183 This option selects the authentication mechanism this driver should use. The
28184 default is the value of the generic &%public_name%& option. This option allows
28185 you to use a different underlying mechanism from the advertised name. For
28189 driver = cyrus_sasl
28190 public_name = X-ANYTHING
28191 server_mech = CRAM-MD5
28192 server_set_id = $auth1
28195 .option server_realm cyrus_sasl string&!! unset
28196 This specifies the SASL realm that the server claims to be in.
28199 .option server_service cyrus_sasl string &`smtp`&
28200 This is the SASL service that the server claims to implement.
28203 For straightforward cases, you do not need to set any of the authenticator's
28204 private options. All you need to do is to specify an appropriate mechanism as
28205 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
28206 PLAIN, you could have two authenticators as follows:
28209 driver = cyrus_sasl
28210 public_name = CRAM-MD5
28211 server_set_id = $auth1
28214 driver = cyrus_sasl
28215 public_name = PLAIN
28216 server_set_id = $auth2
28218 Cyrus SASL does implement the LOGIN authentication method, even though it is
28219 not a standard method. It is disabled by default in the source distribution,
28220 but it is present in many binary distributions.
28221 .ecindex IIDcyrauth1
28222 .ecindex IIDcyrauth2
28227 . ////////////////////////////////////////////////////////////////////////////
28228 . ////////////////////////////////////////////////////////////////////////////
28229 .chapter "The dovecot authenticator" "CHAPdovecot"
28230 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
28231 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
28232 This authenticator is an interface to the authentication facility of the
28233 Dovecot 2 POP/IMAP server, which can support a number of authentication methods.
28234 Note that Dovecot must be configured to use auth-client not auth-userdb.
28235 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
28236 to use the same mechanisms for SMTP authentication. This is a server
28237 authenticator only. There is only one option:
28239 .option server_socket dovecot string unset
28241 This option must specify the UNIX socket that is the interface to Dovecot
28242 authentication. The &%public_name%& option must specify an authentication
28243 mechanism that Dovecot is configured to support. You can have several
28244 authenticators for different mechanisms. For example:
28248 public_name = PLAIN
28249 server_socket = /var/run/dovecot/auth-client
28250 server_set_id = $auth1
28255 server_socket = /var/run/dovecot/auth-client
28256 server_set_id = $auth1
28258 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
28259 &$received_ip_address$& (that is, the connection is local), the &"secured"&
28260 option is passed in the Dovecot authentication command. If, for a TLS
28261 connection, a client certificate has been verified, the &"valid-client-cert"&
28262 option is passed. When authentication succeeds, the identity of the user
28263 who authenticated is placed in &$auth1$&.
28265 The Dovecot configuration to match the above will look
28268 conf.d/10-master.conf :-
28273 unix_listener auth-client {
28280 conf.d/10-auth.conf :-
28282 auth_mechanisms = plain login ntlm
28285 .ecindex IIDdcotauth1
28286 .ecindex IIDdcotauth2
28289 . ////////////////////////////////////////////////////////////////////////////
28290 . ////////////////////////////////////////////////////////////////////////////
28291 .chapter "The gsasl authenticator" "CHAPgsasl"
28292 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
28293 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
28294 .cindex "authentication" "GNU SASL"
28295 .cindex "authentication" "SASL"
28296 .cindex "authentication" "EXTERNAL"
28297 .cindex "authentication" "ANONYMOUS"
28298 .cindex "authentication" "PLAIN"
28299 .cindex "authentication" "LOGIN"
28300 .cindex "authentication" "DIGEST-MD5"
28301 .cindex "authentication" "CRAM-MD5"
28302 .cindex "authentication" "SCRAM family"
28303 The &(gsasl)& authenticator provides integration for the GNU SASL
28304 library and the mechanisms it provides. This is new as of the 4.80 release
28305 and there are a few areas where the library does not let Exim smoothly
28306 scale to handle future authentication mechanisms, so no guarantee can be
28307 made that any particular new authentication mechanism will be supported
28308 without code changes in Exim.
28310 The library is expected to add support in an upcoming
28311 realease for the SCRAM-SHA-256 method.
28312 The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
28315 To see the list of mechanisms supported by the library run Exim with "auth" debug
28316 enabled and look for a line containing "GNU SASL supports".
28317 Note however that some may not have been tested from Exim.
28320 .option client_authz gsasl string&!! unset
28321 This option can be used to supply an &'authorization id'&
28322 which is different to the &'authentication_id'& provided
28323 by &%client_username%& option.
28324 If unset or (after expansion) empty it is not used,
28325 which is the common case.
28327 .option client_channelbinding gsasl boolean false
28328 See &%server_channelbinding%& below.
28330 .option client_password gsasl string&!! unset
28331 This option is exapanded before use, and should result in
28332 the password to be used, in clear.
28334 .option client_username gsasl string&!! unset
28335 This option is exapanded before use, and should result in
28336 the account name to be used.
28339 .option client_spassword gsasl string&!! unset
28340 This option is only supported for library versions 1.9.1 and greater.
28341 The macro _HAVE_AUTH_GSASL_SCRAM_S_KEY will be defined when this is so.
28343 If a SCRAM mechanism is being used and this option is set
28344 and correctly sized
28345 it is used in preference to &%client_password%&.
28346 The value after expansion should be
28347 a 40 (for SHA-1) or 64 (for SHA-256) character string
28348 with the PBKDF2-prepared password, hex-encoded.
28350 Note that this value will depend on the salt and iteration-count
28351 supplied by the server.
28352 The option is expanded before use.
28353 During the expansion &$auth1$& is set with the client username,
28354 &$auth2$& with the iteration count, and
28355 &$auth3$& with the salt.
28357 The intent of this option
28358 is to support clients that can cache thes salted password
28359 to save on recalculation costs.
28360 The cache lookup should return an unusable value
28361 (eg. an empty string)
28362 if the salt or iteration count has changed
28364 If the authentication succeeds then the above variables are set,
28365 .vindex "&$auth4$&"
28366 plus the calculated salted password value value in &$auth4$&,
28367 during the expansion of the &%client_set_id%& option.
28368 A side-effect of this expansion can be used to prime the cache.
28371 .option server_channelbinding gsasl boolean false
28372 Some authentication mechanisms are able to use external context at both ends
28373 of the session to bind the authentication to that context, and fail the
28374 authentication process if that context differs. Specifically, some TLS
28375 ciphersuites can provide identifying information about the cryptographic
28378 This should have meant that certificate identity and verification becomes a
28379 non-issue, as a man-in-the-middle attack will cause the correct client and
28380 server to see different identifiers and authentication will fail.
28383 only usable by mechanisms which support "channel binding"; at time of
28384 writing, that's the SCRAM family.
28385 When using this feature the "-PLUS" variants of the method names need to be used.
28387 This defaults off to ensure smooth upgrade across Exim releases, in case
28388 this option causes some clients to start failing. Some future release
28389 of Exim might have switched the default to be true.
28391 . However, Channel Binding in TLS has proven to be vulnerable in current versions.
28392 . Do not plan to rely upon this feature for security, ever, without consulting
28393 . with a subject matter expert (a cryptographic engineer).
28395 This option was deprecated in previous releases due to doubts over
28396 the "Triple Handshake" vulnerability.
28397 Exim takes suitable precausions (requiring Extended Master Secret if TLS
28398 Session Resumption was used) for safety.
28401 .option server_hostname gsasl string&!! "see below"
28402 This option selects the hostname that is used when communicating with the
28403 library. The default value is &`$primary_hostname`&.
28404 Some mechanisms will use this data.
28407 .option server_mech gsasl string "see below"
28408 This option selects the authentication mechanism this driver should use. The
28409 default is the value of the generic &%public_name%& option. This option allows
28410 you to use a different underlying mechanism from the advertised name. For
28415 public_name = X-ANYTHING
28416 server_mech = CRAM-MD5
28417 server_set_id = $auth1
28421 .option server_password gsasl string&!! unset
28422 Various mechanisms need access to the cleartext password on the server, so
28423 that proof-of-possession can be demonstrated on the wire, without sending
28424 the password itself.
28426 The data available for lookup varies per mechanism.
28427 In all cases, &$auth1$& is set to the &'authentication id'&.
28428 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
28429 if available, else the empty string.
28430 The &$auth3$& variable will always be the &'realm'& if available,
28431 else the empty string.
28433 A forced failure will cause authentication to defer.
28435 If using this option, it may make sense to set the &%server_condition%&
28436 option to be simply "true".
28439 .option server_realm gsasl string&!! unset
28440 This specifies the SASL realm that the server claims to be in.
28441 Some mechanisms will use this data.
28444 .option server_scram_iter gsasl string&!! 4096
28445 This option provides data for the SCRAM family of mechanisms.
28446 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28447 when this option is expanded.
28449 The result of expansion should be a decimal number,
28450 and represents both a lower-bound on the security, and
28451 a compute cost factor imposed on the client
28452 (if it does not cache results, or the server changes
28453 either the iteration count or the salt).
28454 A minimum value of 4096 is required by the standards
28455 for all current SCRAM mechanism variants.
28457 .option server_scram_salt gsasl string&!! unset
28458 This option provides data for the SCRAM family of mechanisms.
28459 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28460 when this option is expanded.
28461 The value should be a base64-encoded string,
28462 of random data typically 4-to-16 bytes long.
28463 If unset or empty after expansion the library will provides a value for the
28464 protocol conversation.
28467 .option server_key gsasl string&!! unset
28468 .option server_skey gsasl string&!! unset
28469 These options can be used for the SCRAM family of mechanisms
28470 to provide stored information related to a password,
28471 the storage of which is preferable to plaintext.
28473 &%server_key%& is the value defined in the SCRAM standards as ServerKey;
28474 &%server_skey%& is StoredKey.
28476 They are only available for version 1.9.0 (or later) of the gsasl library.
28477 When this is so, the macros
28478 _OPT_AUTHENTICATOR_GSASL_SERVER_KEY
28479 and _HAVE_AUTH_GSASL_SCRAM_S_KEY
28482 The &$authN$& variables are available when these options are expanded.
28484 If set, the results of expansion should for each
28485 should be a 28 (for SHA-1) or 44 (for SHA-256) character string
28486 of base64-coded data, and will be used in preference to the
28487 &%server_password%& option.
28488 If unset or not of the right length, &%server_password%& will be used.
28490 The libgsasl library release includes a utility &'gsasl'& which can be used
28491 to generate these values.
28494 .option server_service gsasl string &`smtp`&
28495 This is the SASL service that the server claims to implement.
28496 Some mechanisms will use this data.
28499 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
28500 .vindex "&$auth1$&, &$auth2$&, etc"
28501 These may be set when evaluating specific options, as detailed above.
28502 They will also be set when evaluating &%server_condition%&.
28504 Unless otherwise stated below, the &(gsasl)& integration will use the following
28505 meanings for these variables:
28508 .vindex "&$auth1$&"
28509 &$auth1$&: the &'authentication id'&
28511 .vindex "&$auth2$&"
28512 &$auth2$&: the &'authorization id'&
28514 .vindex "&$auth3$&"
28515 &$auth3$&: the &'realm'&
28518 On a per-mechanism basis:
28521 .cindex "authentication" "EXTERNAL"
28522 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
28523 the &%server_condition%& option must be present.
28525 .cindex "authentication" "ANONYMOUS"
28526 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
28527 the &%server_condition%& option must be present.
28529 .cindex "authentication" "GSSAPI"
28530 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
28531 &$auth2$& will be set to the &'authorization id'&,
28532 the &%server_condition%& option must be present.
28535 An &'anonymous token'& is something passed along as an unauthenticated
28536 identifier; this is analogous to FTP anonymous authentication passing an
28537 email address, or software-identifier@, as the "password".
28540 An example showing the password having the realm specified in the callback
28541 and demonstrating a Cyrus SASL to GSASL migration approach is:
28543 gsasl_cyrusless_crammd5:
28545 public_name = CRAM-MD5
28546 server_realm = imap.example.org
28547 server_password = ${lookup{$auth1:$auth3:userPassword}\
28548 dbmjz{/etc/sasldb2}{$value}fail}
28549 server_set_id = ${quote:$auth1}
28550 server_condition = yes
28554 . ////////////////////////////////////////////////////////////////////////////
28555 . ////////////////////////////////////////////////////////////////////////////
28557 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
28558 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
28559 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
28560 .cindex "authentication" "GSSAPI"
28561 .cindex "authentication" "Kerberos"
28562 The &(heimdal_gssapi)& authenticator provides server integration for the
28563 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
28566 .option server_hostname heimdal_gssapi string&!! "see below"
28567 This option selects the hostname that is used, with &%server_service%&,
28568 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
28569 identifier. The default value is &`$primary_hostname`&.
28571 .option server_keytab heimdal_gssapi string&!! unset
28572 If set, then Heimdal will not use the system default keytab (typically
28573 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
28574 The value should be a pathname, with no &"file:"& prefix.
28576 .option server_service heimdal_gssapi string&!! "smtp"
28577 This option specifies the service identifier used, in conjunction with
28578 &%server_hostname%&, for building the identifier for finding credentials
28582 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
28583 Beware that these variables will typically include a realm, thus will appear
28584 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
28585 not verified, so a malicious client can set it to anything.
28587 The &$auth1$& field should be safely trustable as a value from the Key
28588 Distribution Center. Note that these are not quite email addresses.
28589 Each identifier is for a role, and so the left-hand-side may include a
28590 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
28592 .vindex "&$auth1$&, &$auth2$&, etc"
28594 .vindex "&$auth1$&"
28595 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
28597 .vindex "&$auth2$&"
28598 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
28599 authentication. If that was empty, this will also be set to the
28604 . ////////////////////////////////////////////////////////////////////////////
28605 . ////////////////////////////////////////////////////////////////////////////
28607 .chapter "The spa authenticator" "CHAPspa"
28608 .scindex IIDspaauth1 "&(spa)& authenticator"
28609 .scindex IIDspaauth2 "authenticators" "&(spa)&"
28610 .cindex "authentication" "Microsoft Secure Password"
28611 .cindex "authentication" "NTLM"
28612 .cindex "Microsoft Secure Password Authentication"
28613 .cindex "NTLM authentication"
28614 The &(spa)& authenticator provides client support for Microsoft's &'Secure
28615 Password Authentication'& mechanism,
28616 which is also sometimes known as NTLM (NT LanMan). The code for client side of
28617 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
28618 taken from the Samba project (&url(https://www.samba.org/)). The code for the
28619 server side was subsequently contributed by Tom Kistner. The mechanism works as
28623 After the AUTH command has been accepted, the client sends an SPA
28624 authentication request based on the user name and optional domain.
28626 The server sends back a challenge.
28628 The client builds a challenge response which makes use of the user's password
28629 and sends it to the server, which then accepts or rejects it.
28632 Encryption is used to protect the password in transit.
28636 .section "Using spa as a server" "SECID179"
28637 .cindex "options" "&(spa)& authenticator (server)"
28638 The &(spa)& authenticator has just one server option:
28640 .option server_password spa string&!! unset
28641 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
28642 This option is expanded, and the result must be the cleartext password for the
28643 authenticating user, whose name is at this point in &$auth1$&. For
28644 compatibility with previous releases of Exim, the user name is also placed in
28645 &$1$&. However, the use of this variable for this purpose is now deprecated, as
28646 it can lead to confusion in string expansions that also use numeric variables
28647 for other things. For example:
28652 server_password = \
28653 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
28655 If the expansion is forced to fail, authentication fails. Any other expansion
28656 failure causes a temporary error code to be returned.
28662 .section "Using spa as a client" "SECID180"
28663 .cindex "options" "&(spa)& authenticator (client)"
28664 The &(spa)& authenticator has the following client options:
28668 .option client_domain spa string&!! unset
28669 This option specifies an optional domain for the authentication.
28672 .option client_password spa string&!! unset
28673 This option specifies the user's password, and must be set.
28676 .option client_username spa string&!! unset
28677 This option specifies the user name, and must be set. Here is an example of a
28678 configuration of this authenticator for use with the mail servers at
28684 client_username = msn/msn_username
28685 client_password = msn_plaintext_password
28686 client_domain = DOMAIN_OR_UNSET
28688 .ecindex IIDspaauth1
28689 .ecindex IIDspaauth2
28695 . ////////////////////////////////////////////////////////////////////////////
28696 . ////////////////////////////////////////////////////////////////////////////
28698 .chapter "The external authenticator" "CHAPexternauth"
28699 .scindex IIDexternauth1 "&(external)& authenticator"
28700 .scindex IIDexternauth2 "authenticators" "&(external)&"
28701 .cindex "authentication" "Client Certificate"
28702 .cindex "authentication" "X509"
28703 .cindex "Certificate-based authentication"
28704 The &(external)& authenticator provides support for
28705 authentication based on non-SMTP information.
28706 The specification is in RFC 4422 Appendix A
28707 (&url(https://tools.ietf.org/html/rfc4422)).
28708 It is only a transport and negotiation mechanism;
28709 the process of authentication is entirely controlled
28710 by the server configuration.
28712 The client presents an identity in-clear.
28713 It is probably wise for a server to only advertise,
28714 and for clients to only attempt,
28715 this authentication method on a secure (eg. under TLS) connection.
28717 One possible use, compatible with the
28718 K-9 Mail Android client (&url(https://k9mail.github.io/)),
28719 is for using X509 client certificates.
28721 It thus overlaps in function with the TLS authenticator
28722 (see &<<CHAPtlsauth>>&)
28723 but is a full SMTP SASL authenticator
28724 rather than being implicit for TLS-connection carried
28725 client certificates only.
28727 The examples and discussion in this chapter assume that
28728 client-certificate authentication is being done.
28730 The client must present a certificate,
28731 for which it must have been requested via the
28732 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28733 (see &<<CHAPTLS>>&).
28734 For authentication to be effective the certificate should be
28735 verifiable against a trust-anchor certificate known to the server.
28737 .section "External options" "SECTexternsoptions"
28738 .cindex "options" "&(external)& authenticator (server)"
28739 The &(external)& authenticator has two server options:
28741 .option server_param2 external string&!! unset
28742 .option server_param3 external string&!! unset
28743 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(external)& authenticator"
28744 These options are expanded before the &%server_condition%& option
28745 and the result are placed in &$auth2$& and &$auth3$& resectively.
28746 If the expansion is forced to fail, authentication fails. Any other expansion
28747 failure causes a temporary error code to be returned.
28749 They can be used to clarify the coding of a complex &%server_condition%&.
28751 .section "Using external in a server" "SECTexternserver"
28752 .cindex "AUTH" "in &(external)& authenticator"
28753 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
28754 "in &(external)& authenticator"
28755 .vindex "&$auth1$&, &$auth2$&, etc"
28756 .cindex "base64 encoding" "in &(external)& authenticator"
28758 When running as a server, &(external)& performs the authentication test by
28759 expanding a string. The data sent by the client with the AUTH command, or in
28760 response to subsequent prompts, is base64 encoded, and so may contain any byte
28761 values when decoded. The decoded value is treated as
28762 an identity for authentication and
28763 placed in the expansion variable &$auth1$&.
28765 For compatibility with previous releases of Exim, the value is also placed in
28766 the expansion variable &$1$&. However, the use of this
28767 variable for this purpose is now deprecated, as it can lead to confusion in
28768 string expansions that also use them for other things.
28770 .vindex "&$authenticated_id$&"
28771 Once an identity has been received,
28772 &%server_condition%& is expanded. If the expansion is forced to fail,
28773 authentication fails. Any other expansion failure causes a temporary error code
28774 to be returned. If the result of a successful expansion is an empty string,
28775 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
28776 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
28777 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
28778 For any other result, a temporary error code is returned, with the expanded
28779 string as the error text.
28783 ext_ccert_san_mail:
28785 public_name = EXTERNAL
28787 server_advertise_condition = $tls_in_certificate_verified
28788 server_param2 = ${certextract {subj_altname,mail,>:} \
28789 {$tls_in_peercert}}
28790 server_condition = ${if forany {$auth2} \
28791 {eq {$item}{$auth1}}}
28792 server_set_id = $auth1
28794 This accepts a client certificate that is verifiable against any
28795 of your configured trust-anchors
28796 (which usually means the full set of public CAs)
28797 and which has a mail-SAN matching the claimed identity sent by the client.
28799 &*Note*&: up to TLS1.2, the client cert is on the wire in-clear, including the SAN.
28800 The account name is therefore guessable by an opponent.
28801 TLS 1.3 protects both server and client certificates, and is not vulnerable
28805 .section "Using external in a client" "SECTexternclient"
28806 .cindex "options" "&(external)& authenticator (client)"
28807 The &(external)& authenticator has one client option:
28809 .option client_send external string&!! unset
28810 This option is expanded and sent with the AUTH command as the
28811 identity being asserted.
28817 public_name = EXTERNAL
28819 client_condition = ${if !eq{$tls_out_cipher}{}}
28820 client_send = myaccount@smarthost.example.net
28824 .ecindex IIDexternauth1
28825 .ecindex IIDexternauth2
28831 . ////////////////////////////////////////////////////////////////////////////
28832 . ////////////////////////////////////////////////////////////////////////////
28834 .chapter "The tls authenticator" "CHAPtlsauth"
28835 .scindex IIDtlsauth1 "&(tls)& authenticator"
28836 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
28837 .cindex "authentication" "Client Certificate"
28838 .cindex "authentication" "X509"
28839 .cindex "Certificate-based authentication"
28840 The &(tls)& authenticator provides server support for
28841 authentication based on client certificates.
28843 It is not an SMTP authentication mechanism and is not
28844 advertised by the server as part of the SMTP EHLO response.
28845 It is an Exim authenticator in the sense that it affects
28846 the protocol element of the log line, can be tested for
28847 by the &%authenticated%& ACL condition, and can set
28848 the &$authenticated_id$& variable.
28850 The client must present a verifiable certificate,
28851 for which it must have been requested via the
28852 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28853 (see &<<CHAPTLS>>&).
28855 If an authenticator of this type is configured it is
28856 run before any SMTP-level communication is done,
28857 and can authenticate the connection.
28858 If it does, SMTP authentication is not offered.
28860 A maximum of one authenticator of this type may be present.
28863 .cindex "options" "&(tls)& authenticator (server)"
28864 The &(tls)& authenticator has three server options:
28866 .option server_param1 tls string&!! unset
28867 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
28868 This option is expanded after the TLS negotiation and
28869 the result is placed in &$auth1$&.
28870 If the expansion is forced to fail, authentication fails. Any other expansion
28871 failure causes a temporary error code to be returned.
28873 .option server_param2 tls string&!! unset
28874 .option server_param3 tls string&!! unset
28875 As above, for &$auth2$& and &$auth3$&.
28877 &%server_param1%& may also be spelled &%server_param%&.
28884 server_param1 = ${certextract {subj_altname,mail,>:} \
28885 {$tls_in_peercert}}
28886 server_condition = ${if and { {eq{$tls_in_certificate_verified}{1}} \
28889 {${lookup ldap{ldap:///\
28890 mailname=${quote_ldap_dn:${lc:$item}},\
28891 ou=users,LDAP_DC?mailid} {$value}{0} \
28893 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
28895 This accepts a client certificate that is verifiable against any
28896 of your configured trust-anchors
28897 (which usually means the full set of public CAs)
28898 and which has a SAN with a good account name.
28900 Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
28901 The account name is therefore guessable by an opponent.
28902 TLS 1.3 protects both server and client certificates, and is not vulnerable
28904 Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
28906 . An alternative might use
28908 . server_param1 = ${sha256:$tls_in_peercert}
28910 . to require one of a set of specific certs that define a given account
28911 . (the verification is still required, but mostly irrelevant).
28912 . This would help for per-device use.
28914 . However, for the future we really need support for checking a
28915 . user cert in LDAP - which probably wants a base-64 DER.
28917 .ecindex IIDtlsauth1
28918 .ecindex IIDtlsauth2
28921 Note that because authentication is traditionally an SMTP operation,
28922 the &%authenticated%& ACL condition cannot be used in
28923 a connect- or helo-ACL.
28927 . ////////////////////////////////////////////////////////////////////////////
28928 . ////////////////////////////////////////////////////////////////////////////
28930 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
28931 "Encrypted SMTP connections"
28932 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
28933 .scindex IIDencsmtp2 "SMTP" "encryption"
28934 .cindex "TLS" "on SMTP connection"
28937 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
28938 Sockets Layer), is implemented by making use of the OpenSSL library or the
28939 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
28940 cryptographic code in the Exim distribution itself for implementing TLS. In
28941 order to use this feature you must install OpenSSL or GnuTLS, and then build a
28942 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
28943 You also need to understand the basic concepts of encryption at a managerial
28944 level, and in particular, the way that public keys, private keys, and
28945 certificates are used.
28947 RFC 3207 defines how SMTP connections can make use of encryption. Once a
28948 connection is established, the client issues a STARTTLS command. If the
28949 server accepts this, the client and the server negotiate an encryption
28950 mechanism. If the negotiation succeeds, the data that subsequently passes
28951 between them is encrypted.
28953 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
28954 and if so, what cipher suite is in use, whether the client supplied a
28955 certificate, and whether or not that certificate was verified. This makes it
28956 possible for an Exim server to deny or accept certain commands based on the
28959 &*Warning*&: Certain types of firewall and certain anti-virus products can
28960 disrupt TLS connections. You need to turn off SMTP scanning for these products
28961 in order to get TLS to work.
28965 .section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
28967 .cindex "submissions protocol"
28968 .cindex "ssmtp protocol"
28969 .cindex "smtps protocol"
28970 .cindex "SMTP" "submissions protocol"
28971 .cindex "SMTP" "ssmtp protocol"
28972 .cindex "SMTP" "smtps protocol"
28973 The history of port numbers for TLS in SMTP is a little messy and has been
28974 contentious. As of RFC 8314, the common practice of using the historically
28975 allocated port 465 for "email submission but with TLS immediately upon connect
28976 instead of using STARTTLS" is officially blessed by the IETF, and recommended
28977 by them in preference to STARTTLS.
28979 The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
28980 clarity emerged over the dual roles of SMTP, for MX delivery and Email
28981 Submission, nomenclature has shifted. The modern name is now &"submissions"&.
28983 This approach was, for a while, officially abandoned when encrypted SMTP was
28984 standardized, but many clients kept using it, even as the TCP port number was
28985 reassigned for other use.
28986 Thus you may encounter guidance claiming that you shouldn't enable use of
28988 In practice, a number of mail-clients have only ever supported submissions,
28989 not submission with STARTTLS upgrade.
28990 Ideally, offer both submission (587) and submissions (465) service.
28992 Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
28993 global option. Its value must be a list of port numbers;
28994 the most common use is expected to be:
28996 tls_on_connect_ports = 465
28998 The port numbers specified by this option apply to all SMTP connections, both
28999 via the daemon and via &'inetd'&. You still need to specify all the ports that
29000 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
29001 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
29002 an extra port &-- rather, it specifies different behaviour on a port that is
29005 There is also a &%-tls-on-connect%& command line option. This overrides
29006 &%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
29013 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
29014 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
29015 TLS is supported in Exim using either the OpenSSL or GnuTLS library.
29016 To build Exim to use OpenSSL you need to set
29022 To build Exim to use GnuTLS, you need to set
29028 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
29029 include files and libraries for GnuTLS can be found.
29031 There are some differences in usage when using GnuTLS instead of OpenSSL:
29034 The &%tls_verify_certificates%& option
29035 cannot be the path of a directory
29036 for GnuTLS versions before 3.3.6
29037 (for later versions, or OpenSSL, it can be either).
29039 The default value for &%tls_dhparam%& differs for historical reasons.
29041 .vindex "&$tls_in_peerdn$&"
29042 .vindex "&$tls_out_peerdn$&"
29043 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
29044 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
29045 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
29047 OpenSSL identifies cipher suites using hyphens as separators, for example:
29048 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
29049 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
29050 in a cipher list. To make life simpler, Exim changes underscores to hyphens
29051 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
29052 to handle its own older variants) when processing lists of cipher suites in the
29053 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
29056 The &%tls_require_ciphers%& options operate differently, as described in the
29057 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
29059 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
29060 When using OpenSSL, this option is ignored.
29061 (If an API is found to let OpenSSL be configured in this way,
29062 let the Exim Maintainers know and we'll likely use it).
29064 With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
29065 main option, it must be ordered to match the &%tls_certificate%& list.
29067 Some other recently added features may only be available in one or the other.
29068 This should be documented with the feature. If the documentation does not
29069 explicitly state that the feature is infeasible in the other TLS
29070 implementation, then patches are welcome.
29072 The output from "exim -bV" will show which (if any) support was included
29074 Also, the macro "_HAVE_OPENSSL" or "_HAVE_GNUTLS" will be defined.
29078 .section "GnuTLS parameter computation" "SECTgnutlsparam"
29079 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
29080 an explicit path; if the latter, then the text about generation still applies,
29081 but not the chosen filename.
29082 By default, as of Exim 4.80 a hard-coded D-H prime is used.
29083 See the documentation of &%tls_dhparam%& for more information.
29085 GnuTLS uses D-H parameters that may take a substantial amount of time
29086 to compute. It is unreasonable to re-compute them for every TLS session.
29087 Therefore, Exim keeps this data in a file in its spool directory, called
29088 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
29090 The file is owned by the Exim user and is readable only by
29091 its owner. Every Exim process that start up GnuTLS reads the D-H
29092 parameters from this file. If the file does not exist, the first Exim process
29093 that needs it computes the data and writes it to a temporary file which is
29094 renamed once it is complete. It does not matter if several Exim processes do
29095 this simultaneously (apart from wasting a few resources). Once a file is in
29096 place, new Exim processes immediately start using it.
29098 For maximum security, the parameters that are stored in this file should be
29099 recalculated periodically, the frequency depending on your paranoia level.
29100 If you are avoiding using the fixed D-H primes published in RFCs, then you
29101 are concerned about some advanced attacks and will wish to do this; if you do
29102 not regenerate then you might as well stick to the standard primes.
29104 Arranging this is easy in principle; just delete the file when you want new
29105 values to be computed. However, there may be a problem. The calculation of new
29106 parameters needs random numbers, and these are obtained from &_/dev/random_&.
29107 If the system is not very active, &_/dev/random_& may delay returning data
29108 until enough randomness (entropy) is available. This may cause Exim to hang for
29109 a substantial amount of time, causing timeouts on incoming connections.
29111 The solution is to generate the parameters externally to Exim. They are stored
29112 in &_gnutls-params-N_& in PEM format, which means that they can be
29113 generated externally using the &(certtool)& command that is part of GnuTLS.
29115 To replace the parameters with new ones, instead of deleting the file
29116 and letting Exim re-create it, you can generate new parameters using
29117 &(certtool)& and, when this has been done, replace Exim's cache file by
29118 renaming. The relevant commands are something like this:
29121 [ look for file; assume gnutls-params-2236 is the most recent ]
29124 # chown exim:exim new-params
29125 # chmod 0600 new-params
29126 # certtool --generate-dh-params --bits 2236 >>new-params
29127 # openssl dhparam -noout -text -in new-params | head
29128 [ check the first line, make sure it's not more than 2236;
29129 if it is, then go back to the start ("rm") and repeat
29130 until the size generated is at most the size requested ]
29131 # chmod 0400 new-params
29132 # mv new-params gnutls-params-2236
29134 If Exim never has to generate the parameters itself, the possibility of
29135 stalling is removed.
29137 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
29138 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
29139 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
29140 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
29141 and Exim does so. This attempt to remove Exim from TLS policy decisions
29142 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
29143 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
29144 which applies to all D-H usage, client or server. If the value returned by
29145 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
29146 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
29147 limit, which is still much higher than Exim historically used.
29149 The filename and bits used will change as the GnuTLS maintainers change the
29150 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
29151 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
29152 2432 bits, while NSS is limited to 2236 bits.
29154 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
29155 increase the chance of the generated prime actually being within acceptable
29156 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
29157 procedure above. There is no sane procedure available to Exim to double-check
29158 the size of the generated prime, so it might still be too large.
29161 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
29162 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
29163 .oindex "&%tls_require_ciphers%&" "OpenSSL"
29164 There is a function in the OpenSSL library that can be passed a list of cipher
29165 suites before the cipher negotiation takes place. This specifies which ciphers
29166 are acceptable for TLS versions prior to 1.3.
29167 The list is colon separated and may contain names like
29168 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
29169 directly to this function call.
29170 Many systems will install the OpenSSL manual-pages, so you may have
29171 &'ciphers(1)'& available to you.
29172 The following quotation from the OpenSSL
29173 documentation specifies what forms of item are allowed in the cipher string:
29176 It can consist of a single cipher suite such as RC4-SHA.
29178 It can represent a list of cipher suites containing a certain algorithm,
29179 or cipher suites of a certain type. For example SHA1 represents all
29180 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
29183 Lists of cipher suites can be combined in a single cipher string using
29184 the + character. This is used as a logical and operation. For example
29185 SHA1+DES represents all cipher suites containing the SHA1 and the DES
29189 Each cipher string can be optionally preceded by one of the characters &`!`&,
29192 If &`!`& is used, the ciphers are permanently deleted from the list. The
29193 ciphers deleted can never reappear in the list even if they are explicitly
29196 If &`-`& is used, the ciphers are deleted from the list, but some or all
29197 of the ciphers can be added again by later options.
29199 If &`+`& is used, the ciphers are moved to the end of the list. This
29200 option does not add any new ciphers; it just moves matching existing ones.
29203 If none of these characters is present, the string is interpreted as
29204 a list of ciphers to be appended to the current preference list. If the list
29205 includes any ciphers already present they will be ignored: that is, they will
29206 not be moved to the end of the list.
29209 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
29212 # note single-quotes to get ! past any shell history expansion
29213 $ openssl ciphers 'HIGH:!MD5:!SHA1'
29216 This example will let the library defaults be permitted on the MX port, where
29217 there's probably no identity verification anyway, but ups the ante on the
29218 submission ports where the administrator might have some influence on the
29219 choice of clients used:
29221 # OpenSSL variant; see man ciphers(1)
29222 tls_require_ciphers = ${if =={$received_port}{25}\
29227 This example will prefer ECDSA-authenticated ciphers over RSA ones:
29229 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
29232 For TLS version 1.3 the control available is less fine-grained
29233 and Exim does not provide access to it at present.
29234 The value of the &%tls_require_ciphers%& option is ignored when
29235 TLS version 1.3 is negotiated.
29237 As of writing the library default cipher suite list for TLSv1.3 is
29239 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
29243 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
29245 .cindex "GnuTLS" "specifying parameters for"
29246 .cindex "TLS" "specifying ciphers (GnuTLS)"
29247 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
29248 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
29249 .cindex "TLS" "specifying protocols (GnuTLS)"
29250 .cindex "TLS" "specifying priority string (GnuTLS)"
29251 .oindex "&%tls_require_ciphers%&" "GnuTLS"
29252 The GnuTLS library allows the caller to provide a "priority string", documented
29253 as part of the &[gnutls_priority_init]& function. This is very similar to the
29254 ciphersuite specification in OpenSSL.
29256 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
29257 and controls both protocols and ciphers.
29259 The &%tls_require_ciphers%& option is available both as an global option,
29260 controlling how Exim behaves as a server, and also as an option of the
29261 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
29262 the value is string expanded. The resulting string is not an Exim list and
29263 the string is given to the GnuTLS library, so that Exim does not need to be
29264 aware of future feature enhancements of GnuTLS.
29266 Documentation of the strings accepted may be found in the GnuTLS manual, under
29267 "Priority strings". This is online as
29268 &url(https://www.gnutls.org/manual/html_node/Priority-Strings.html),
29269 but beware that this relates to GnuTLS 3, which may be newer than the version
29270 installed on your system. If you are using GnuTLS 3,
29271 then the example code
29272 &url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
29273 on that site can be used to test a given string.
29277 # Disable older versions of protocols
29278 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
29281 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
29282 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
29283 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
29285 This example will let the library defaults be permitted on the MX port, where
29286 there's probably no identity verification anyway, and lowers security further
29287 by increasing compatibility; but this ups the ante on the submission ports
29288 where the administrator might have some influence on the choice of clients
29292 tls_require_ciphers = ${if =={$received_port}{25}\
29298 .section "Configuring an Exim server to use TLS" "SECID182"
29299 .cindex "TLS" "configuring an Exim server"
29300 .cindex "ESMTP extensions" STARTTLS
29301 When Exim has been built with TLS support, it advertises the availability of
29302 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
29303 but not to any others. The default value of this option is *, which means
29304 that STARTTLS is always advertised. Set it to blank to never advertise;
29305 this is reasonable for systems that want to use TLS only as a client.
29307 If STARTTLS is to be used you
29308 need to set some other options in order to make TLS available.
29310 If a client issues a STARTTLS command and there is some configuration
29311 problem in the server, the command is rejected with a 454 error. If the client
29312 persists in trying to issue SMTP commands, all except QUIT are rejected
29315 554 Security failure
29317 If a STARTTLS command is issued within an existing TLS session, it is
29318 rejected with a 554 error code.
29320 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
29321 must be set to match some hosts. The default is * which matches all hosts.
29323 If this is all you do, TLS encryption will be enabled but not authentication -
29324 meaning that the peer has no assurance it is actually you he is talking to.
29325 You gain protection from a passive sniffer listening on the wire but not
29326 from someone able to intercept the communication.
29328 Further protection requires some further configuration at the server end.
29330 To make TLS work you need to set, in the server,
29332 tls_certificate = /some/file/name
29333 tls_privatekey = /some/file/name
29335 These options are, in fact, expanded strings, so you can make them depend on
29336 the identity of the client that is connected if you wish. The first file
29337 contains the server's X509 certificate, and the second contains the private key
29338 that goes with it. These files need to be
29339 PEM format and readable by the Exim user, and must
29340 always be given as full path names.
29341 The key must not be password-protected.
29342 They can be the same file if both the
29343 certificate and the key are contained within it. If &%tls_privatekey%& is not
29344 set, or if its expansion is forced to fail or results in an empty string, this
29345 is assumed to be the case. The certificate file may also contain intermediate
29346 certificates that need to be sent to the client to enable it to authenticate
29347 the server's certificate.
29349 For dual-stack (eg. RSA and ECDSA) configurations, these options can be
29350 colon-separated lists of file paths. Ciphers using given authentication
29351 algorithms require the presence of a suitable certificate to supply the
29352 public-key. The server selects among the certificates to present to the
29353 client depending on the selected cipher, hence the priority ordering for
29354 ciphers will affect which certificate is used.
29356 If you do not understand about certificates and keys, please try to find a
29357 source of this background information, which is not Exim-specific. (There are a
29358 few comments below in section &<<SECTcerandall>>&.)
29360 &*Note*&: These options do not apply when Exim is operating as a client &--
29361 they apply only in the case of a server. If you need to use a certificate in an
29362 Exim client, you must set the options of the same names in an &(smtp)&
29365 With just these options, an Exim server will be able to use TLS. It does not
29366 require the client to have a certificate (but see below for how to insist on
29367 this). There is one other option that may be needed in other situations. If
29369 tls_dhparam = /some/file/name
29371 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
29372 with the parameters contained in the file.
29373 Set this to &`none`& to disable use of DH entirely, by making no prime
29378 This may also be set to a string identifying a standard prime to be used for
29379 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
29380 used is &`ike23`&. There are a few standard primes available, see the
29381 documentation for &%tls_dhparam%& for the complete list.
29387 for a way of generating file data.
29389 The strings supplied for these three options are expanded every time a client
29390 host connects. It is therefore possible to use different certificates and keys
29391 for different hosts, if you so wish, by making use of the client's IP address
29392 in &$sender_host_address$& to control the expansion. If a string expansion is
29393 forced to fail, Exim behaves as if the option is not set.
29395 .cindex "cipher" "logging"
29396 .cindex "log" "TLS cipher"
29397 .vindex "&$tls_in_cipher$&"
29398 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
29399 an incoming TLS connection. It is included in the &'Received:'& header of an
29400 incoming message (by default &-- you can, of course, change this), and it is
29401 also included in the log line that records a message's arrival, keyed by
29402 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
29403 condition can be used to test for specific cipher suites in ACLs.
29405 Once TLS has been established, the ACLs that run for subsequent SMTP commands
29406 can check the name of the cipher suite and vary their actions accordingly. The
29407 cipher suite names vary, depending on which TLS library is being used. For
29408 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
29409 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
29410 documentation for more details.
29412 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
29413 (again depending on the &%tls_cipher%& log selector).
29416 .section "Requesting and verifying client certificates" "SECID183"
29417 .cindex "certificate" "verification of client"
29418 .cindex "TLS" "client certificate verification"
29419 If you want an Exim server to request a certificate when negotiating a TLS
29420 session with a client, you must set either &%tls_verify_hosts%& or
29421 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
29422 apply to all TLS connections. For any host that matches one of these options,
29423 Exim requests a certificate as part of the setup of the TLS session. The
29424 contents of the certificate are verified by comparing it with a list of
29425 expected trust-anchors or certificates.
29426 These may be the system default set (depending on library version),
29427 an explicit file or,
29428 depending on library version, a directory, identified by
29429 &%tls_verify_certificates%&.
29431 A file can contain multiple certificates, concatenated end to end. If a
29434 each certificate must be in a separate file, with a name (or a symbolic link)
29435 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
29436 certificate. You can compute the relevant hash by running the command
29438 openssl x509 -hash -noout -in /cert/file
29440 where &_/cert/file_& contains a single certificate.
29442 There is no checking of names of the client against the certificate
29443 Subject Name or Subject Alternate Names.
29445 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
29446 what happens if the client does not supply a certificate, or if the certificate
29447 does not match any of the certificates in the collection named by
29448 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
29449 attempt to set up a TLS session is aborted, and the incoming connection is
29450 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
29451 session continues. ACLs that run for subsequent SMTP commands can detect the
29452 fact that no certificate was verified, and vary their actions accordingly. For
29453 example, you can insist on a certificate before accepting a message for
29454 relaying, but not when the message is destined for local delivery.
29456 .vindex "&$tls_in_peerdn$&"
29457 When a client supplies a certificate (whether it verifies or not), the value of
29458 the Distinguished Name of the certificate is made available in the variable
29459 &$tls_in_peerdn$& during subsequent processing of the message.
29461 .cindex "log" "distinguished name"
29462 Because it is often a long text string, it is not included in the log line or
29463 &'Received:'& header by default. You can arrange for it to be logged, keyed by
29464 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
29465 &%received_header_text%& to change the &'Received:'& header. When no
29466 certificate is supplied, &$tls_in_peerdn$& is empty.
29469 .section "Revoked certificates" "SECID184"
29470 .cindex "TLS" "revoked certificates"
29471 .cindex "revocation list"
29472 .cindex "certificate" "revocation list"
29473 .cindex "OCSP" "stapling"
29474 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
29475 certificates are revoked. If you have such a list, you can pass it to an Exim
29476 server using the global option called &%tls_crl%& and to an Exim client using
29477 an identically named option for the &(smtp)& transport. In each case, the value
29478 of the option is expanded and must then be the name of a file that contains a
29480 The downside is that clients have to periodically re-download a potentially huge
29481 file from every certificate authority they know of.
29483 The way with most moving parts at query time is Online Certificate
29484 Status Protocol (OCSP), where the client verifies the certificate
29485 against an OCSP server run by the CA. This lets the CA track all
29486 usage of the certs. It requires running software with access to the
29487 private key of the CA, to sign the responses to the OCSP queries. OCSP
29488 is based on HTTP and can be proxied accordingly.
29490 The only widespread OCSP server implementation (known to this writer)
29491 comes as part of OpenSSL and aborts on an invalid request, such as
29492 connecting to the port and then disconnecting. This requires
29493 re-entering the passphrase each time some random client does this.
29495 The third way is OCSP Stapling; in this, the server using a certificate
29496 issued by the CA periodically requests an OCSP proof of validity from
29497 the OCSP server, then serves it up inline as part of the TLS
29498 negotiation. This approach adds no extra round trips, does not let the
29499 CA track users, scales well with number of certs issued by the CA and is
29500 resilient to temporary OCSP server failures, as long as the server
29501 starts retrying to fetch an OCSP proof some time before its current
29502 proof expires. The downside is that it requires server support.
29504 Unless Exim is built with the support disabled,
29505 or with GnuTLS earlier than version 3.3.16 / 3.4.8
29506 support for OCSP stapling is included.
29508 There is a global option called &%tls_ocsp_file%&.
29509 The file specified therein is expected to be in DER format, and contain
29510 an OCSP proof. Exim will serve it as part of the TLS handshake. This
29511 option will be re-expanded for SNI, if the &%tls_certificate%& option
29512 contains &`tls_in_sni`&, as per other TLS options.
29514 Exim does not at this time implement any support for fetching a new OCSP
29515 proof. The burden is on the administrator to handle this, outside of
29516 Exim. The file specified should be replaced atomically, so that the
29517 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
29518 on each connection, so a new file will be handled transparently on the
29521 When built with OpenSSL Exim will check for a valid next update timestamp
29522 in the OCSP proof; if not present, or if the proof has expired, it will be
29525 For the client to be able to verify the stapled OCSP the server must
29526 also supply, in its stapled information, any intermediate
29527 certificates for the chain leading to the OCSP proof from the signer
29528 of the server certificate. There may be zero or one such. These
29529 intermediate certificates should be added to the server OCSP stapling
29530 file named by &%tls_ocsp_file%&.
29532 Note that the proof only covers the terminal server certificate,
29533 not any of the chain from CA to it.
29535 There is no current way to staple a proof for a client certificate.
29538 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
29539 OCSP server is supplied. The server URL may be included in the
29540 server certificate, if the CA is helpful.
29542 One failure mode seen was the OCSP Signer cert expiring before the end
29543 of validity of the OCSP proof. The checking done by Exim/OpenSSL
29544 noted this as invalid overall, but the re-fetch script did not.
29548 .section "Caching of static server configuration items" "SECTserverTLScache"
29549 .cindex certificate caching
29550 .cindex privatekey caching
29551 .cindex crl caching
29552 .cindex ocsp caching
29553 .cindex ciphers caching
29554 .cindex "CA bundle" caching
29555 .cindex "certificate authorities" caching
29556 .cindex tls_certificate caching
29557 .cindex tls_privatekey caching
29558 .cindex tls_crl caching
29559 .cindex tls_ocsp_file caching
29560 .cindex tls_require_ciphers caching
29561 .cindex tls_verify_certificate caching
29562 .cindex caching certificate
29563 .cindex caching privatekey
29564 .cindex caching crl
29565 .cindex caching ocsp
29566 .cindex caching ciphers
29567 .cindex caching "certificate authorities
29568 If any of the main configuration options &%tls_certificate%&, &%tls_privatekey%&,
29569 &%tls_crl%& and &%tls_ocsp_file%& have values with no
29570 expandable elements,
29571 then the associated information is loaded at daemon startup.
29572 It is made available
29573 to child processes forked for handling received SMTP connections.
29575 This caching is currently only supported under Linux and FreeBSD.
29577 If caching is not possible, for example if an item has to be dependent
29578 on the peer host so contains a &$sender_host_name$& expansion, the load
29579 of the associated information is done at the startup of the TLS connection.
29581 The cache is invalidated and reloaded after any changes to the directories
29582 containing files specified by these options.
29584 The information specified by the main option &%tls_verify_certificates%&
29585 is similarly cached so long as it specifies files explicitly
29586 or (under GnuTLS) is the string &"system,cache"&.
29587 The latter case is not automatically invalidated;
29588 it is the operator's responsibility to arrange for a daemon restart
29589 any time the system certificate authority bundle is updated.
29590 A HUP signal is sufficient for this.
29591 The value &"system"& results in no caching under GnuTLS.
29593 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29594 is acceptable in configurations for the Exim executavble.
29596 Caching of the system Certificate Authorities bundle can
29597 save siginificant time and processing on every TLS connection
29603 .section "Configuring an Exim client to use TLS" "SECTclientTLS"
29604 .cindex "cipher" "logging"
29605 .cindex "log" "TLS cipher"
29606 .cindex "log" "distinguished name"
29607 .cindex "TLS" "configuring an Exim client"
29608 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
29609 deliveries as well as to incoming, the latter one causing logging of the
29610 server certificate's DN. The remaining client configuration for TLS is all
29611 within the &(smtp)& transport.
29613 .cindex "ESMTP extensions" STARTTLS
29614 It is not necessary to set any options to have TLS work in the &(smtp)&
29615 transport. If Exim is built with TLS support, and TLS is advertised by a
29616 server, the &(smtp)& transport always tries to start a TLS session. However,
29617 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
29618 transport) to a list of server hosts for which TLS should not be used.
29620 If you do not want Exim to attempt to send messages unencrypted when an attempt
29621 to set up an encrypted connection fails in any way, you can set
29622 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
29623 those hosts, delivery is always deferred if an encrypted connection cannot be
29624 set up. If there are any other hosts for the address, they are tried in the
29627 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
29628 the message unencrypted. It always does this if the response to STARTTLS is
29629 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
29630 session after a success response code, what happens is controlled by the
29631 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
29632 delivery to this host is deferred, and other hosts (if available) are tried. If
29633 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
29634 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
29635 negotiation fails, Exim closes the current connection (because it is in an
29636 unknown state), opens a new one to the same host, and then tries the delivery
29639 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
29640 transport provide the client with a certificate, which is passed to the server
29642 This is an optional thing for TLS connections, although either end
29644 If the server is Exim, it will request a certificate only if
29645 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
29647 &*Note*&: Do not use a certificate which has the OCSP-must-staple extension,
29648 for client use (they are usable for server use).
29649 As the TLS protocol has no means for the client to staple before TLS 1.3 it will result
29650 in failed connections.
29652 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
29653 specifies a collection of expected server certificates.
29655 the system default set (depending on library version),
29657 or (depending on library version) a directory.
29658 The client verifies the server's certificate
29659 against this collection, taking into account any revoked certificates that are
29660 in the list defined by &%tls_crl%&.
29661 Failure to verify fails the TLS connection unless either of the
29662 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
29664 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
29665 certificate verification to the listed servers. Verification either must
29666 or need not succeed respectively.
29668 The &%tls_verify_cert_hostnames%& option lists hosts for which additional
29669 name checks are made on the server certificate.
29670 The match against this list is, as per other Exim usage, the
29671 IP for the host. That is most closely associated with the
29672 name on the DNS A (or AAAA) record for the host.
29673 However, the name that needs to be in the certificate
29674 is the one at the head of any CNAME chain leading to the A record.
29675 The option defaults to always checking.
29677 The &(smtp)& transport has two OCSP-related options:
29678 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
29679 is requested and required for the connection to proceed. The default
29681 &%hosts_request_ocsp%&; a host-list for which (additionally)
29682 a Certificate Status is requested (but not necessarily verified). The default
29683 value is "*" meaning that requests are made unless configured
29686 The host(s) should also be in &%hosts_require_tls%&, and
29687 &%tls_verify_certificates%& configured for the transport,
29688 for OCSP to be relevant.
29691 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
29692 list of permitted cipher suites. If either of these checks fails, delivery to
29693 the current host is abandoned, and the &(smtp)& transport tries to deliver to
29694 alternative hosts, if any.
29697 These options must be set in the &(smtp)& transport for Exim to use TLS when it
29698 is operating as a client. Exim does not assume that a server certificate (set
29699 by the global options of the same name) should also be used when operating as a
29703 .vindex "&$host_address$&"
29704 All the TLS options in the &(smtp)& transport are expanded before use, with
29705 &$host$& and &$host_address$& containing the name and address of the server to
29706 which the client is connected. Forced failure of an expansion causes Exim to
29707 behave as if the relevant option were unset.
29709 .vindex &$tls_out_bits$&
29710 .vindex &$tls_out_cipher$&
29711 .vindex &$tls_out_peerdn$&
29712 .vindex &$tls_out_sni$&
29713 Before an SMTP connection is established, the
29714 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
29715 variables are emptied. (Until the first connection, they contain the values
29716 that were set when the message was received.) If STARTTLS is subsequently
29717 successfully obeyed, these variables are set to the relevant values for the
29718 outgoing connection.
29722 .section "Caching of static client configuration items" "SECTclientTLScache"
29723 .cindex certificate caching
29724 .cindex privatekey caching
29725 .cindex crl caching
29726 .cindex ciphers caching
29727 .cindex "CA bundle" caching
29728 .cindex "certificate authorities" caching
29729 .cindex tls_certificate caching
29730 .cindex tls_privatekey caching
29731 .cindex tls_crl caching
29732 .cindex tls_require_ciphers caching
29733 .cindex tls_verify_certificate caching
29734 .cindex caching certificate
29735 .cindex caching privatekey
29736 .cindex caching crl
29737 .cindex caching ciphers
29738 .cindex caching "certificate authorities
29739 If any of the transport configuration options &%tls_certificate%&, &%tls_privatekey%&
29740 and &%tls_crl%& have values with no
29741 expandable elements,
29742 then the associated information is loaded per smtp transport
29743 at daemon startup, at the start of a queue run, or on a
29744 command-line specified message delivery.
29745 It is made available
29746 to child processes forked for handling making SMTP connections.
29748 This caching is currently only supported under Linux.
29750 If caching is not possible, the load
29751 of the associated information is done at the startup of the TLS connection.
29753 The cache is invalidated in the daemon
29754 and reloaded after any changes to the directories
29755 containing files specified by these options.
29757 The information specified by the main option &%tls_verify_certificates%&
29758 is similarly cached so long as it specifies files explicitly
29759 or (under GnuTLS) is the string &"system,cache"&.
29760 The latter case is not automatically invaludated;
29761 it is the operator's responsibility to arrange for a daemon restart
29762 any time the system certificate authority bundle is updated.
29763 A HUP signal is sufficient for this.
29764 The value &"system"& results in no caching under GnuTLS.
29766 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29767 is acceptable in configurations for the Exim executavble.
29769 Caching of the system Certificate Authorities bundle can
29770 save siginificant time and processing on every TLS connection
29776 .section "Use of TLS Server Name Indication" "SECTtlssni"
29777 .cindex "TLS" "Server Name Indication"
29780 .vindex "&$tls_in_sni$&"
29781 .oindex "&%tls_in_sni%&"
29782 With TLS1.0 or above, there is an extension mechanism by which extra
29783 information can be included at various points in the protocol. One of these
29784 extensions, documented in RFC 6066 (and before that RFC 4366) is
29785 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
29786 client in the initial handshake, so that the server can examine the servername
29787 within and possibly choose to use different certificates and keys (and more)
29790 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
29791 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
29794 With SMTP to MX, there are the same problems here as in choosing the identity
29795 against which to validate a certificate: you can't rely on insecure DNS to
29796 provide the identity which you then cryptographically verify. So this will
29797 be of limited use in that environment.
29799 With SMTP to Submission, there is a well-defined hostname which clients are
29800 connecting to and can validate certificates against. Thus clients &*can*&
29801 choose to include this information in the TLS negotiation. If this becomes
29802 wide-spread, then hosters can choose to present different certificates to
29803 different clients. Or even negotiate different cipher suites.
29805 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
29806 if not empty, will be sent on a TLS session as part of the handshake. There's
29807 nothing more to it. Choosing a sensible value not derived insecurely is the
29808 only point of caution. The &$tls_out_sni$& variable will be set to this string
29809 for the lifetime of the client connection (including during authentication).
29811 If DANE validated the connection attempt then the value of the &%tls_sni%& option
29812 is forced to the domain part of the recipient address.
29814 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
29815 received from a client.
29816 It can be logged with the &%log_selector%& item &`+tls_sni`&.
29818 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
29819 option (prior to expansion) then the following options will be re-expanded
29820 during TLS session handshake, to permit alternative values to be chosen:
29823 &%tls_certificate%&
29829 &%tls_verify_certificates%&
29834 Great care should be taken to deal with matters of case, various injection
29835 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
29836 can always be referenced; it is important to remember that &$tls_in_sni$& is
29837 arbitrary unverified data provided prior to authentication.
29838 Further, the initial certificate is loaded before SNI has arrived, so
29839 an expansion for &%tls_certificate%& must have a default which is used
29840 when &$tls_in_sni$& is empty.
29842 The Exim developers are proceeding cautiously and so far no other TLS options
29845 When Exim is built against OpenSSL, OpenSSL must have been built with support
29846 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
29847 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
29848 see &`-servername`& in the output, then OpenSSL has support.
29850 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
29851 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
29852 built, then you have SNI support).
29855 .cindex ALPN "general information"
29856 .cindex TLS "Application Layer Protocol Names"
29857 There is a TLS feature related to SNI
29858 called Application Layer Protocol Name (ALPN).
29859 This is intended to declare, or select, what protocol layer will be using a TLS
29861 The client for the connection proposes a set of protocol names, and
29862 the server responds with a selected one.
29863 It is not, as of 2021, commonly used for SMTP connections.
29864 However, to guard against misirected or malicious use of web clients
29865 (which often do use ALPN) against MTA ports, Exim by default check that
29866 there is no incompatible ALPN specified by a client for a TLS connection.
29867 If there is, the connection is rejected.
29869 As a client Exim does not supply ALPN by default.
29870 The behaviour of both client and server can be configured using the options
29871 &%tls_alpn%& and &%hosts_require_alpn%&.
29872 There are no variables providing observability.
29873 Some feature-specific logging may appear on denied connections, but this
29874 depends on the behavious of the peer
29875 (not all peers can send a feature-specific TLS Alert).
29877 This feature is available when Exim is built with
29878 OpenSSL 1.1.0 or later or GnuTLS 3.2.0 or later;
29879 the macro _HAVE_TLS_ALPN will be defined when this is so.
29883 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
29885 .cindex "multiple SMTP deliveries with TLS"
29886 .cindex "TLS" "multiple message deliveries"
29887 Exim sends multiple messages down the same TCP/IP connection by starting up
29888 an entirely new delivery process for each message, passing the socket from
29889 one process to the next. This implementation does not fit well with the use
29890 of TLS, because there is quite a lot of state information associated with a TLS
29891 connection, not just a socket identification. Passing all the state information
29892 to a new process is not feasible. Consequently, for sending using TLS Exim
29893 starts an additional proxy process for handling the encryption, piping the
29894 unencrypted data stream from and to the delivery processes.
29896 An older mode of operation can be enabled on a per-host basis by the
29897 &%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
29898 this list the proxy process described above is not used; instead Exim
29899 shuts down an existing TLS session being run by the delivery process
29900 before passing the socket to a new process. The new process may then
29901 try to start a new TLS session, and if successful, may try to re-authenticate
29902 if AUTH is in use, before sending the next message.
29904 The RFC is not clear as to whether or not an SMTP session continues in clear
29905 after TLS has been shut down, or whether TLS may be restarted again later, as
29906 just described. However, if the server is Exim, this shutdown and
29907 reinitialization works. It is not known which (if any) other servers operate
29908 successfully if the client closes a TLS session and continues with unencrypted
29909 SMTP, but there are certainly some that do not work. For such servers, Exim
29910 should not pass the socket to another process, because the failure of the
29911 subsequent attempt to use it would cause Exim to record a temporary host error,
29912 and delay other deliveries to that host.
29914 To test for this case, Exim sends an EHLO command to the server after
29915 closing down the TLS session. If this fails in any way, the connection is
29916 closed instead of being passed to a new delivery process, but no retry
29917 information is recorded.
29919 There is also a manual override; you can set &%hosts_nopass_tls%& on the
29920 &(smtp)& transport to match those hosts for which Exim should not pass
29921 connections to new processes if TLS has been used.
29926 .section "Certificates and all that" "SECTcerandall"
29927 .cindex "certificate" "references to discussion"
29928 In order to understand fully how TLS works, you need to know about
29929 certificates, certificate signing, and certificate authorities.
29930 This is a large topic and an introductory guide is unsuitable for the Exim
29931 reference manual, so instead we provide pointers to existing documentation.
29933 The Apache web-server was for a long time the canonical guide, so their
29934 documentation is a good place to start; their SSL module's Introduction
29935 document is currently at
29937 &url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html)
29939 and their FAQ is at
29941 &url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html)
29944 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
29945 0-201-61598-3) in 2001, contains both introductory and more in-depth
29947 More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&,
29948 published by Feisty Duck (ISBN 978-1907117046) in 2013 is good.
29949 Ivan is the author of the popular TLS testing tools at
29950 &url(https://www.ssllabs.com/).
29953 .section "Certificate chains" "SECID186"
29954 A file named by &%tls_certificate%& may contain more than one
29955 certificate. This is useful in the case where the certificate that is being
29956 sent is validated by an intermediate certificate which the other end does
29957 not have. Multiple certificates must be in the correct order in the file.
29958 First the host's certificate itself, then the first intermediate
29959 certificate to validate the issuer of the host certificate, then the next
29960 intermediate certificate to validate the issuer of the first intermediate
29961 certificate, and so on, until finally (optionally) the root certificate.
29962 The root certificate must already be trusted by the recipient for
29963 validation to succeed, of course, but if it's not preinstalled, sending the
29964 root certificate along with the rest makes it available for the user to
29965 install if the receiving end is a client MUA that can interact with a user.
29967 Note that certificates using MD5 are unlikely to work on today's Internet;
29968 even if your libraries allow loading them for use in Exim when acting as a
29969 server, increasingly clients will not accept such certificates. The error
29970 diagnostics in such a case can be frustratingly vague.
29974 .section "Self-signed certificates" "SECID187"
29975 .cindex "certificate" "self-signed"
29976 You can create a self-signed certificate using the &'req'& command provided
29977 with OpenSSL, like this:
29978 . ==== Do not shorten the duration here without reading and considering
29979 . ==== the text below. Please leave it at 9999 days.
29981 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
29984 &_file1_& and &_file2_& can be the same file; the key and the certificate are
29985 delimited and so can be identified independently. The &%-days%& option
29986 specifies a period for which the certificate is valid. The &%-nodes%& option is
29987 important: if you do not set it, the key is encrypted with a passphrase
29988 that you are prompted for, and any use that is made of the key causes more
29989 prompting for the passphrase. This is not helpful if you are going to use
29990 this certificate and key in an MTA, where prompting is not possible.
29992 . ==== I expect to still be working 26 years from now. The less technical
29993 . ==== debt I create, in terms of storing up trouble for my later years, the
29994 . ==== happier I will be then. We really have reached the point where we
29995 . ==== should start, at the very least, provoking thought and making folks
29996 . ==== pause before proceeding, instead of leaving all the fixes until two
29997 . ==== years before 2^31 seconds after the 1970 Unix epoch.
29999 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
30000 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
30001 the above command might produce a date in the past. Think carefully about
30002 the lifetime of the systems you're deploying, and either reduce the duration
30003 of the certificate or reconsider your platform deployment. (At time of
30004 writing, reducing the duration is the most likely choice, but the inexorable
30005 progression of time takes us steadily towards an era where this will not
30006 be a sensible resolution).
30008 A self-signed certificate made in this way is sufficient for testing, and
30009 may be adequate for all your requirements if you are mainly interested in
30010 encrypting transfers, and not in secure identification.
30012 However, many clients require that the certificate presented by the server be a
30013 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
30014 certificate. In this situation, the self-signed certificate described above
30015 must be installed on the client host as a trusted root &'certification
30016 authority'& (CA), and the certificate used by Exim must be a user certificate
30017 signed with that self-signed certificate.
30019 For information on creating self-signed CA certificates and using them to sign
30020 user certificates, see the &'General implementation overview'& chapter of the
30021 Open-source PKI book, available online at
30022 &url(https://sourceforge.net/projects/ospkibook/).
30023 .ecindex IIDencsmtp1
30024 .ecindex IIDencsmtp2
30027 .section "TLS Resumption" "SECTresumption"
30028 .cindex TLS resumption
30029 TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
30030 in RFC 5077 for 1.2). The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1
30033 Session resumption (this is the "stateless" variant) involves the server sending
30034 a "session ticket" to the client on one connection, which can be stored by the
30035 client and used for a later session. The ticket contains sufficient state for
30036 the server to reconstruct the TLS session, avoiding some expensive crypto
30037 calculation and (on TLS1.2) one full packet roundtrip time.
30040 Operational cost/benefit:
30042 The extra data being transmitted costs a minor amount, and the client has
30043 extra costs in storing and retrieving the data.
30045 In the Exim/Gnutls implementation the extra cost on an initial connection
30046 which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware.
30047 The saved cost on a subsequent connection is about 4ms; three or more
30048 connections become a net win. On longer network paths, two or more
30049 connections will have an average lower startup time thanks to the one
30050 saved packet roundtrip. TLS1.3 will save the crypto cpu costs but not any
30053 .cindex "hints database" tls
30054 Since a new hints DB is used on the TLS client,
30055 the hints DB maintenance should be updated to additionally handle "tls".
30060 The session ticket is encrypted, but is obviously an additional security
30061 vulnarability surface. An attacker able to decrypt it would have access
30062 all connections using the resumed session.
30063 The session ticket encryption key is not committed to storage by the server
30064 and is rotated regularly (OpenSSL: 1hr, and one previous key is used for
30065 overlap; GnuTLS 6hr but does not specify any overlap).
30066 Tickets have limited lifetime (2hr, and new ones issued after 1hr under
30067 OpenSSL. GnuTLS 2hr, appears to not do overlap).
30069 There is a question-mark over the security of the Diffie-Helman parameters
30070 used for session negotiation.
30075 The &%log_selector%& "tls_resumption" appends an asterisk to the tls_cipher "X="
30078 The variables &$tls_in_resumption$& and &$tls_out_resumption$&
30079 have bits 0-4 indicating respectively
30080 support built, client requested ticket, client offered session,
30081 server issued ticket, resume used. A suitable decode list is provided
30082 in the builtin macro _RESUME_DECODE for in &%listextract%& expansions.
30087 The &%tls_resumption_hosts%& main option specifies a hostlist for which
30088 exim, operating as a server, will offer resumption to clients.
30089 Current best practice is to not offer the feature to MUA connection.
30090 Commonly this can be done like this:
30092 tls_resumption_hosts = ${if inlist {$received_port}{587:465} {:}{*}}
30094 If the peer host matches the list after expansion then resumption
30095 is offered and/or accepted.
30097 The &%tls_resumption_hosts%& smtp transport option performs the
30098 equivalent function for operation as a client.
30099 If the peer host matches the list after expansion then resumption
30100 is attempted (if a stored session is available) or the information
30101 stored (if supplied by the peer).
30107 In a resumed session:
30109 The variables &$tls_{in,out}_cipher$& will have values different
30110 to the original (under GnuTLS).
30112 The variables &$tls_{in,out}_ocsp$& will be "not requested" or "no response",
30113 and the &%hosts_require_ocsp%& smtp trasnport option will fail.
30114 . XXX need to do something with that hosts_require_ocsp
30120 .section DANE "SECDANE"
30122 DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
30123 it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
30124 operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
30125 you and the server still think you have an encrypted connection) and, if one of the "well known" set of
30126 Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
30127 certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
30129 What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
30130 that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
30131 by (a) is thought to be smaller than that of the set of root CAs.
30133 It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
30134 fail to pass on a server's STARTTLS.
30136 DANE scales better than having to maintain (and communicate via side-channel) copies of server certificates
30137 for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
30138 client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
30140 DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
30141 that DNS lookups they do for the server have not been tampered with. The domain MX record applying
30142 to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
30144 2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
30145 3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
30147 There are no changes to Exim specific to server-side operation of DANE.
30148 Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
30149 in &_Local/Makefile_&.
30150 If it has been included, the macro "_HAVE_DANE" will be defined.
30152 A TLSA record consist of 4 fields, the "Certificate Usage", the
30153 "Selector", the "Matching type", and the "Certificate Association Data".
30154 For a detailed description of the TLSA record see
30155 &url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671).
30157 The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3).
30158 These are the "Trust Anchor" and "End Entity" variants.
30159 The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
30160 (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
30161 this is appropriate for a single system, using a self-signed certificate.
30162 DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
30164 A private CA at simplest is just a self-signed certificate (with certain
30165 attributes) which is used to sign server certificates, but running one securely
30166 does require careful arrangement.
30167 With DANE-TA, as implemented in Exim and commonly in other MTAs,
30168 the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
30169 DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
30170 all of which point to a single TLSA record.
30171 DANE-TA and DANE-EE can both be used together.
30173 Our recommendation is to use DANE with a certificate from a public CA,
30174 because this enables a variety of strategies for remote clients to verify
30176 You can then publish information both via DANE and another technology,
30177 "MTA-STS", described below.
30179 When you use DANE-TA to publish trust anchor information, you ask entities
30180 outside your administrative control to trust the Certificate Authority for
30181 connections to you.
30182 If using a private CA then you should expect others to still apply the
30183 technical criteria they'd use for a public CA to your certificates.
30184 In particular, you should probably try to follow current best practices for CA
30185 operation around hash algorithms and key sizes.
30186 Do not expect other organizations to lower their security expectations just
30187 because a particular profile might be reasonable for your own internal use.
30189 When this text was last updated, this in practice means to avoid use of SHA-1
30190 and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
30191 than 4096, for interoperability); to use keyUsage fields correctly; to use
30192 random serial numbers.
30193 The list of requirements is subject to change as best practices evolve.
30194 If you're not already using a private CA, or it doesn't meet these
30195 requirements, then we encourage you to avoid all these issues and use a public
30196 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
30198 The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
30199 a "Matching Type" (3rd) field of SHA2-512(2).
30201 For the "Certificate Authority Data" (4th) field, commands like
30204 openssl x509 -pubkey -noout <certificate.pem \
30205 | openssl rsa -outform der -pubin 2>/dev/null \
30210 are workable to create a hash of the certificate's public key.
30212 An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like
30215 _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E...
30218 At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
30219 is useful for quickly generating TLSA records.
30222 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
30224 The Certificate issued by the CA published in the DANE-TA model should be
30225 issued using a strong hash algorithm.
30226 Exim, and importantly various other MTAs sending to you, will not
30227 re-enable hash algorithms which have been disabled by default in TLS
30229 This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
30230 interoperability (and probably the maximum too, in 2018).
30232 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
30233 be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
30234 default of requesting OCSP for all hosts is modified iff DANE is in use, to:
30237 hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
30238 {= {4}{$tls_out_tlsa_usage}} } \
30242 The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
30243 The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
30244 found. If the definition of &%hosts_request_ocsp%& includes the
30245 string "tls_out_tlsa_usage", they are re-expanded in time to
30246 control the OCSP request.
30248 This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
30249 those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
30252 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
30253 and &%dane_require_tls_ciphers%&.
30254 The &"require"& variant will result in failure if the target host is not
30255 DNSSEC-secured. To get DNSSEC-secured hostname resolution, use
30256 the &%dnssec_request_domains%& router or transport option.
30258 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
30260 A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using DNSSEC.
30261 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
30262 will be required for the host. If it does not, the host will not
30263 be used; there is no fallback to non-DANE or non-TLS.
30265 If DANE is requested and usable, then the TLS cipher list configuration
30266 prefers to use the option &%dane_require_tls_ciphers%& and falls
30267 back to &%tls_require_ciphers%& only if that is unset.
30268 This lets you configure "decent crypto" for DANE and "better than nothing
30269 crypto" as the default. Note though that while GnuTLS lets the string control
30270 which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
30271 limited to ciphersuite constraints.
30273 If DANE is requested and useable (see above) the following transport options are ignored:
30277 tls_try_verify_hosts
30278 tls_verify_certificates
30280 tls_verify_cert_hostnames
30284 If DANE is not usable, whether requested or not, and CA-anchored
30285 verification evaluation is wanted, the above variables should be set appropriately.
30287 The router and transport option &%dnssec_request_domains%& must not be
30288 set to &"never"&, and &%dnssec_require_domains%& is ignored.
30290 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
30292 There is a new variable &$tls_out_dane$& which will have "yes" if
30293 verification succeeded using DANE and "no" otherwise (only useful
30294 in combination with events; see &<<CHAPevents>>&),
30295 and a new variable &$tls_out_tlsa_usage$& (detailed above).
30297 .cindex DANE reporting
30298 An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
30299 to achieve DANE-verified connection, if one was either requested and offered, or
30300 required. This is intended to support TLS-reporting as defined in
30301 &url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
30302 The &$event_data$& will be one of the Result Types defined in
30303 Section 4.3 of that document.
30305 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
30307 DANE is specified in published RFCs and decouples certificate authority trust
30308 selection from a "race to the bottom" of "you must trust everything for mail
30309 to get through". There is an alternative technology called MTA-STS, which
30310 instead publishes MX trust anchor information on an HTTPS website. At the
30311 time this text was last updated, MTA-STS was still a draft, not yet an RFC.
30312 Exim has no support for MTA-STS as a client, but Exim mail server operators
30313 can choose to publish information describing their TLS configuration using
30314 MTA-STS to let those clients who do use that protocol derive trust
30317 The MTA-STS design requires a certificate from a public Certificate Authority
30318 which is recognized by clients sending to you.
30319 That selection of which CAs are trusted by others is outside your control.
30321 The most interoperable course of action is probably to use
30322 &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
30323 renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
30324 records for DANE clients (such as Exim and Postfix) and to publish anchor
30325 information for MTA-STS as well. This is what is done for the &'exim.org'&
30326 domain itself (with caveats around occasionally broken MTA-STS because of
30327 incompatible specification changes prior to reaching RFC status).
30331 . ////////////////////////////////////////////////////////////////////////////
30332 . ////////////////////////////////////////////////////////////////////////////
30334 .chapter "Access control lists" "CHAPACL"
30335 .scindex IIDacl "&ACL;" "description"
30336 .cindex "control of incoming mail"
30337 .cindex "message" "controlling incoming"
30338 .cindex "policy control" "access control lists"
30339 Access Control Lists (ACLs) are defined in a separate section of the runtime
30340 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
30341 name, terminated by a colon. Here is a complete ACL section that contains just
30342 one very small ACL:
30346 accept hosts = one.host.only
30348 You can have as many lists as you like in the ACL section, and the order in
30349 which they appear does not matter. The lists are self-terminating.
30351 The majority of ACLs are used to control Exim's behaviour when it receives
30352 certain SMTP commands. This applies both to incoming TCP/IP connections, and
30353 when a local process submits a message using SMTP by specifying the &%-bs%&
30354 option. The most common use is for controlling which recipients are accepted
30355 in incoming messages. In addition, you can define an ACL that is used to check
30356 local non-SMTP messages. The default configuration file contains an example of
30357 a realistic ACL for checking RCPT commands. This is discussed in chapter
30358 &<<CHAPdefconfil>>&.
30361 .section "Testing ACLs" "SECID188"
30362 The &%-bh%& command line option provides a way of testing your ACL
30363 configuration locally by running a fake SMTP session with which you interact.
30366 .section "Specifying when ACLs are used" "SECID189"
30367 .cindex "&ACL;" "options for specifying"
30368 In order to cause an ACL to be used, you have to name it in one of the relevant
30369 options in the main part of the configuration. These options are:
30370 .cindex "AUTH" "ACL for"
30371 .cindex "DATA" "ACLs for"
30372 .cindex "ETRN" "ACL for"
30373 .cindex "EXPN" "ACL for"
30374 .cindex "HELO" "ACL for"
30375 .cindex "EHLO" "ACL for"
30376 .cindex "DKIM" "ACL for"
30377 .cindex "MAIL" "ACL for"
30378 .cindex "QUIT, ACL for"
30379 .cindex "RCPT" "ACL for"
30380 .cindex "STARTTLS, ACL for"
30381 .cindex "VRFY" "ACL for"
30382 .cindex "SMTP" "connection, ACL for"
30383 .cindex "non-SMTP messages" "ACLs for"
30384 .cindex "MIME content scanning" "ACL for"
30385 .cindex "PRDR" "ACL for"
30388 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
30389 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
30390 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
30391 .irow &%acl_smtp_auth%& "ACL for AUTH"
30392 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
30393 .irow &%acl_smtp_data%& "ACL after DATA is complete"
30394 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
30395 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
30396 .irow &%acl_smtp_etrn%& "ACL for ETRN"
30397 .irow &%acl_smtp_expn%& "ACL for EXPN"
30398 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
30399 .irow &%acl_smtp_mail%& "ACL for MAIL"
30400 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
30401 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
30402 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
30403 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
30404 .irow &%acl_smtp_quit%& "ACL for QUIT"
30405 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
30406 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
30407 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
30410 For example, if you set
30412 acl_smtp_rcpt = small_acl
30414 the little ACL defined above is used whenever Exim receives a RCPT command
30415 in an SMTP dialogue. The majority of policy tests on incoming messages can be
30416 done when RCPT commands arrive. A rejection of RCPT should cause the
30417 sending MTA to give up on the recipient address contained in the RCPT
30418 command, whereas rejection at other times may cause the client MTA to keep on
30419 trying to deliver the message. It is therefore recommended that you do as much
30420 testing as possible at RCPT time.
30423 .section "The non-SMTP ACLs" "SECID190"
30424 .cindex "non-SMTP messages" "ACLs for"
30425 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
30426 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
30427 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
30428 the state of the SMTP connection such as encryption and authentication) are not
30429 relevant and are forbidden in these ACLs. However, the sender and recipients
30430 are known, so the &%senders%& and &%sender_domains%& conditions and the
30431 &$sender_address$& and &$recipients$& variables can be used. Variables such as
30432 &$authenticated_sender$& are also available. You can specify added header lines
30433 in any of these ACLs.
30435 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
30436 non-SMTP message, before any of the message has been read. (This is the
30437 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
30438 batched SMTP input, it runs after the DATA command has been reached. The
30439 result of this ACL is ignored; it cannot be used to reject a message. If you
30440 really need to, you could set a value in an ACL variable here and reject based
30441 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
30442 controls, and in particular, it can be used to set
30444 control = suppress_local_fixups
30446 This cannot be used in the other non-SMTP ACLs because by the time they are
30447 run, it is too late.
30449 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
30450 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30452 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
30453 kind of rejection is treated as permanent, because there is no way of sending a
30454 temporary error for these kinds of message.
30457 .section "The SMTP connect ACL" "SECID191"
30458 .cindex "SMTP" "connection, ACL for"
30459 .oindex &%smtp_banner%&
30460 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
30461 session, after the test specified by &%host_reject_connection%& (which is now
30462 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
30463 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
30464 the message override the banner message that is otherwise specified by the
30465 &%smtp_banner%& option.
30468 .section "The EHLO/HELO ACL" "SECID192"
30469 .cindex "EHLO" "ACL for"
30470 .cindex "HELO" "ACL for"
30471 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
30472 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
30473 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
30474 Note that a client may issue more than one EHLO or HELO command in an SMTP
30475 session, and indeed is required to issue a new EHLO or HELO after successfully
30476 setting up encryption following a STARTTLS command.
30478 Note also that a deny neither forces the client to go away nor means that
30479 mail will be refused on the connection. Consider checking for
30480 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
30482 If the command is accepted by an &%accept%& verb that has a &%message%&
30483 modifier, the message may not contain more than one line (it will be truncated
30484 at the first newline and a panic logged if it does). Such a message cannot
30485 affect the EHLO options that are listed on the second and subsequent lines of
30489 .section "The DATA ACLs" "SECID193"
30490 .cindex "DATA" "ACLs for"
30491 Two ACLs are associated with the DATA command, because it is two-stage
30492 command, with two responses being sent to the client.
30493 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
30494 is obeyed. This gives you control after all the RCPT commands, but before
30495 the message itself is received. It offers the opportunity to give a negative
30496 response to the DATA command before the data is transmitted. Header lines
30497 added by MAIL or RCPT ACLs are not visible at this time, but any that
30498 are defined here are visible when the &%acl_smtp_data%& ACL is run.
30500 You cannot test the contents of the message, for example, to verify addresses
30501 in the headers, at RCPT time or when the DATA command is received. Such
30502 tests have to appear in the ACL that is run after the message itself has been
30503 received, before the final response to the DATA command is sent. This is
30504 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
30505 associated with the DATA command.
30507 .cindex CHUNKING "BDAT command"
30508 .cindex BDAT "SMTP command"
30509 .cindex "RFC 3030" CHUNKING
30510 If CHUNKING was advertised and a BDAT command sequence is received,
30511 the &%acl_smtp_predata%& ACL is not run.
30512 . XXX why not? It should be possible, for the first BDAT.
30513 The &%acl_smtp_data%& is run after the last BDAT command and all of
30514 the data specified is received.
30516 For both of these ACLs, it is not possible to reject individual recipients. An
30517 error response rejects the entire message. Unfortunately, it is known that some
30518 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
30519 before or after the data) correctly &-- they keep the message on their queues
30520 and try again later, but that is their problem, though it does waste some of
30523 The &%acl_smtp_data%& ACL is run after
30524 the &%acl_smtp_data_prdr%&,
30525 the &%acl_smtp_dkim%&
30526 and the &%acl_smtp_mime%& ACLs.
30528 .section "The SMTP DKIM ACL" "SECTDKIMACL"
30529 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
30530 enabled (which is the default).
30532 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
30533 received, and is executed for each DKIM signature found in a message. If not
30534 otherwise specified, the default action is to accept.
30536 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
30538 For details on the operation of DKIM, see section &<<SECDKIM>>&.
30541 .section "The SMTP MIME ACL" "SECID194"
30542 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
30543 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30545 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30548 .section "The SMTP PRDR ACL" "SECTPRDRACL"
30549 .cindex "PRDR" "ACL for"
30550 .oindex "&%prdr_enable%&"
30551 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
30552 with PRDR support enabled (which is the default).
30553 It becomes active only when the PRDR feature is negotiated between
30554 client and server for a message, and more than one recipient
30557 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
30558 has been received, and is executed once for each recipient of the message
30559 with &$local_part$& and &$domain$& valid.
30560 The test may accept, defer or deny for individual recipients.
30561 The &%acl_smtp_data%& will still be called after this ACL and
30562 can reject the message overall, even if this ACL has accepted it
30563 for some or all recipients.
30565 PRDR may be used to support per-user content filtering. Without it
30566 one must defer any recipient after the first that has a different
30567 content-filter configuration. With PRDR, the RCPT-time check
30568 .cindex "PRDR" "variable for"
30569 for this can be disabled when the variable &$prdr_requested$&
30571 Any required difference in behaviour of the main DATA-time
30572 ACL should however depend on the PRDR-time ACL having run, as Exim
30573 will avoid doing so in some situations (e.g. single-recipient mails).
30575 See also the &%prdr_enable%& global option
30576 and the &%hosts_try_prdr%& smtp transport option.
30578 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30579 If the ACL is not defined, processing completes as if
30580 the feature was not requested by the client.
30582 .section "The QUIT ACL" "SECTQUITACL"
30583 .cindex "QUIT, ACL for"
30584 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
30585 does not affect the response code to QUIT, which is always 221. Thus, the ACL
30586 does not in fact control any access.
30587 For this reason, it may only accept
30588 or warn as its final result.
30590 This ACL can be used for tasks such as custom logging at the end of an SMTP
30591 session. For example, you can use ACL variables in other ACLs to count
30592 messages, recipients, etc., and log the totals at QUIT time using one or
30593 more &%logwrite%& modifiers on a &%warn%& verb.
30595 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
30596 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
30598 You do not need to have a final &%accept%&, but if you do, you can use a
30599 &%message%& modifier to specify custom text that is sent as part of the 221
30602 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
30603 failure (for example, failure to open a log file, or when Exim is bombing out
30604 because it has detected an unrecoverable error), all SMTP commands from the
30605 client are given temporary error responses until QUIT is received or the
30606 connection is closed. In these special cases, the QUIT ACL does not run.
30609 .section "The not-QUIT ACL" "SECTNOTQUITACL"
30610 .vindex &$acl_smtp_notquit$&
30611 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
30612 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
30613 trouble, such as being unable to write to its log files, this ACL is not run,
30614 because it might try to do things (such as write to log files) that make the
30615 situation even worse.
30617 Like the QUIT ACL, this ACL is provided to make it possible to do customized
30618 logging or to gather statistics, and its outcome is ignored. The &%delay%&
30619 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
30622 .vindex &$smtp_notquit_reason$&
30623 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
30624 to a string that indicates the reason for the termination of the SMTP
30625 connection. The possible values are:
30627 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
30628 .irow &`bad-commands`& "Too many unknown or non-mail commands"
30629 .irow &`command-timeout`& "Timeout while reading SMTP commands"
30630 .irow &`connection-lost`& "The SMTP connection has been lost"
30631 .irow &`data-timeout`& "Timeout while reading message data"
30632 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
30633 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
30634 .irow &`signal-exit`& "SIGTERM or SIGINT"
30635 .irow &`synchronization-error`& "SMTP synchronization error"
30636 .irow &`tls-failed`& "TLS failed to start"
30638 In most cases when an SMTP connection is closed without having received QUIT,
30639 Exim sends an SMTP response message before actually closing the connection.
30640 With the exception of the &`acl-drop`& case, the default message can be
30641 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
30642 &%drop%& verb in another ACL, it is the message from the other ACL that is
30646 .section "Finding an ACL to use" "SECID195"
30647 .cindex "&ACL;" "finding which to use"
30648 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
30649 you can use different ACLs in different circumstances. For example,
30651 acl_smtp_rcpt = ${if ={25}{$interface_port} \
30652 {acl_check_rcpt} {acl_check_rcpt_submit} }
30654 In the default configuration file there are some example settings for
30655 providing an RFC 4409 message &"submission"& service on port 587 and
30656 an RFC 8314 &"submissions"& service on port 465. You can use a string
30657 expansion like this to choose an ACL for MUAs on these ports which is
30658 more appropriate for this purpose than the default ACL on port 25.
30660 The expanded string does not have to be the name of an ACL in the
30661 configuration file; there are other possibilities. Having expanded the
30662 string, Exim searches for an ACL as follows:
30665 If the string begins with a slash, Exim uses it as a filename, and reads its
30666 contents as an ACL. The lines are processed in the same way as lines in the
30667 Exim configuration file. In particular, continuation lines are supported, blank
30668 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
30669 If the file does not exist or cannot be read, an error occurs (typically
30670 causing a temporary failure of whatever caused the ACL to be run). For example:
30672 acl_smtp_data = /etc/acls/\
30673 ${lookup{$sender_host_address}lsearch\
30674 {/etc/acllist}{$value}{default}}
30676 This looks up an ACL file to use on the basis of the host's IP address, falling
30677 back to a default if the lookup fails. If an ACL is successfully read from a
30678 file, it is retained in memory for the duration of the Exim process, so that it
30679 can be re-used without having to re-read the file.
30681 If the string does not start with a slash, and does not contain any spaces,
30682 Exim searches the ACL section of the configuration for an ACL whose name
30683 matches the string.
30685 If no named ACL is found, or if the string contains spaces, Exim parses
30686 the string as an inline ACL. This can save typing in cases where you just
30687 want to have something like
30689 acl_smtp_vrfy = accept
30691 in order to allow free use of the VRFY command. Such a string may contain
30692 newlines; it is processed in the same way as an ACL that is read from a file.
30698 .section "ACL return codes" "SECID196"
30699 .cindex "&ACL;" "return codes"
30700 Except for the QUIT ACL, which does not affect the SMTP return code (see
30701 section &<<SECTQUITACL>>& above), the result of running an ACL is either
30702 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
30703 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
30704 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
30705 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
30706 This also causes a 4&'xx'& return code.
30708 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
30709 &"deny"&, because there is no mechanism for passing temporary errors to the
30710 submitters of non-SMTP messages.
30713 ACLs that are relevant to message reception may also return &"discard"&. This
30714 has the effect of &"accept"&, but causes either the entire message or an
30715 individual recipient address to be discarded. In other words, it is a
30716 blackholing facility. Use it with care.
30718 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
30719 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
30720 RCPT ACL is to discard just the one recipient address. If there are no
30721 recipients left when the message's data is received, the DATA ACL is not
30722 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
30723 remaining recipients. The &"discard"& return is not permitted for the
30724 &%acl_smtp_predata%& ACL.
30726 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
30727 is done on the address and the result determines the SMTP response.
30730 .cindex "&[local_scan()]& function" "when all recipients discarded"
30731 The &[local_scan()]& function is always run, even if there are no remaining
30732 recipients; it may create new recipients.
30736 .section "Unset ACL options" "SECID197"
30737 .cindex "&ACL;" "unset options"
30738 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
30739 all the same. &*Note*&: These defaults apply only when the relevant ACL is
30740 not defined at all. For any defined ACL, the default action when control
30741 reaches the end of the ACL statements is &"deny"&.
30743 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
30744 these two are ACLs that are used only for their side effects. They cannot be
30745 used to accept or reject anything.
30747 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
30748 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
30749 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
30750 when the ACL is not defined is &"accept"&.
30752 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
30753 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
30754 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
30755 messages over an SMTP connection. For an example, see the ACL in the default
30756 configuration file.
30761 .section "Data for message ACLs" "SECID198"
30762 .cindex "&ACL;" "data for message ACL"
30764 .vindex &$local_part$&
30765 .vindex &$sender_address$&
30766 .vindex &$sender_host_address$&
30767 .vindex &$smtp_command$&
30768 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
30769 that contain information about the host and the message's sender (for example,
30770 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
30771 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
30772 &$local_part$& are set from the argument address. The entire SMTP command
30773 is available in &$smtp_command$&.
30775 When an ACL for the AUTH parameter of MAIL is running, the variables that
30776 contain information about the host are set, but &$sender_address$& is not yet
30777 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
30780 .vindex "&$message_size$&"
30781 The &$message_size$& variable is set to the value of the SIZE parameter on
30782 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
30783 that parameter is not given. The value is updated to the true message size by
30784 the time the final DATA ACL is run (after the message data has been
30787 .vindex "&$rcpt_count$&"
30788 .vindex "&$recipients_count$&"
30789 The &$rcpt_count$& variable increases by one for each RCPT command received.
30790 The &$recipients_count$& variable increases by one each time a RCPT command is
30791 accepted, so while an ACL for RCPT is being processed, it contains the number
30792 of previously accepted recipients. At DATA time (for both the DATA ACLs),
30793 &$rcpt_count$& contains the total number of RCPT commands, and
30794 &$recipients_count$& contains the total number of accepted recipients.
30800 .section "Data for non-message ACLs" "SECTdatfornon"
30801 .cindex "&ACL;" "data for non-message ACL"
30802 .vindex &$smtp_command_argument$&
30803 .vindex &$smtp_command$&
30804 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
30805 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
30806 and the entire SMTP command is available in &$smtp_command$&.
30807 These variables can be tested using a &%condition%& condition. For example,
30808 here is an ACL for use with AUTH, which insists that either the session is
30809 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
30810 does not permit authentication methods that use cleartext passwords on
30811 unencrypted connections.
30814 accept encrypted = *
30815 accept condition = ${if eq{${uc:$smtp_command_argument}}\
30817 deny message = TLS encryption or CRAM-MD5 required
30819 (Another way of applying this restriction is to arrange for the authenticators
30820 that use cleartext passwords not to be advertised when the connection is not
30821 encrypted. You can use the generic &%server_advertise_condition%& authenticator
30822 option to do this.)
30826 .section "Format of an ACL" "SECID199"
30827 .cindex "&ACL;" "format of"
30828 .cindex "&ACL;" "verbs, definition of"
30829 An individual ACL consists of a number of statements. Each statement starts
30830 with a verb, optionally followed by a number of conditions and &"modifiers"&.
30831 Modifiers can change the way the verb operates, define error and log messages,
30832 set variables, insert delays, and vary the processing of accepted messages.
30834 If all the conditions are met, the verb is obeyed. The same condition may be
30835 used (with different arguments) more than once in the same statement. This
30836 provides a means of specifying an &"and"& conjunction between conditions. For
30839 deny dnslists = list1.example
30840 dnslists = list2.example
30842 If there are no conditions, the verb is always obeyed. Exim stops evaluating
30843 the conditions and modifiers when it reaches a condition that fails. What
30844 happens then depends on the verb (and in one case, on a special modifier). Not
30845 all the conditions make sense at every testing point. For example, you cannot
30846 test a sender address in the ACL that is run for a VRFY command.
30849 .section "ACL verbs" "SECID200"
30850 The ACL verbs are as follows:
30853 .cindex "&%accept%& ACL verb"
30854 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
30855 of the conditions are not met, what happens depends on whether &%endpass%&
30856 appears among the conditions (for syntax see below). If the failing condition
30857 is before &%endpass%&, control is passed to the next ACL statement; if it is
30858 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
30859 check a RCPT command:
30861 accept domains = +local_domains
30865 If the recipient domain does not match the &%domains%& condition, control
30866 passes to the next statement. If it does match, the recipient is verified, and
30867 the command is accepted if verification succeeds. However, if verification
30868 fails, the ACL yields &"deny"&, because the failing condition is after
30871 The &%endpass%& feature has turned out to be confusing to many people, so its
30872 use is not recommended nowadays. It is always possible to rewrite an ACL so
30873 that &%endpass%& is not needed, and it is no longer used in the default
30876 .cindex "&%message%& ACL modifier" "with &%accept%&"
30877 If a &%message%& modifier appears on an &%accept%& statement, its action
30878 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
30879 (when an &%accept%& verb either accepts or passes control to the next
30880 statement), &%message%& can be used to vary the message that is sent when an
30881 SMTP command is accepted. For example, in a RCPT ACL you could have:
30883 &`accept `&<&'some conditions'&>
30884 &` message = OK, I will allow you through today`&
30886 You can specify an SMTP response code, optionally followed by an &"extended
30887 response code"& at the start of the message, but the first digit must be the
30888 same as would be sent by default, which is 2 for an &%accept%& verb.
30890 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
30891 an error message that is used when access is denied. This behaviour is retained
30892 for backward compatibility, but current &"best practice"& is to avoid the use
30897 .cindex "&%defer%& ACL verb"
30898 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
30899 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
30900 &%defer%& is the same as &%deny%&, because there is no way of sending a
30901 temporary error. For a RCPT command, &%defer%& is much the same as using a
30902 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
30903 be used in any ACL, and even for a recipient it might be a simpler approach.
30907 .cindex "&%deny%& ACL verb"
30908 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
30909 the conditions are not met, control is passed to the next ACL statement. For
30912 deny dnslists = blackholes.mail-abuse.org
30914 rejects commands from hosts that are on a DNS black list.
30918 .cindex "&%discard%& ACL verb"
30919 &%discard%&: This verb behaves like &%accept%&, except that it returns
30920 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
30921 that are concerned with receiving messages. When all the conditions are true,
30922 the sending entity receives a &"success"& response. However, &%discard%& causes
30923 recipients to be discarded. If it is used in an ACL for RCPT, just the one
30924 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
30925 message's recipients are discarded. Recipients that are discarded before DATA
30926 do not appear in the log line when the &%received_recipients%& log selector is set.
30928 If the &%log_message%& modifier is set when &%discard%& operates,
30929 its contents are added to the line that is automatically written to the log.
30930 The &%message%& modifier operates exactly as it does for &%accept%&.
30934 .cindex "&%drop%& ACL verb"
30935 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
30936 forcibly closed after the 5&'xx'& error message has been sent. For example:
30938 drop condition = ${if > {$rcpt_count}{20}}
30939 message = I don't take more than 20 RCPTs
30941 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
30942 The connection is always dropped after sending a 550 response.
30945 .cindex "&%require%& ACL verb"
30946 &%require%&: If all the conditions are met, control is passed to the next ACL
30947 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
30948 example, when checking a RCPT command,
30950 require message = Sender did not verify
30953 passes control to subsequent statements only if the message's sender can be
30954 verified. Otherwise, it rejects the command. Note the positioning of the
30955 &%message%& modifier, before the &%verify%& condition. The reason for this is
30956 discussed in section &<<SECTcondmodproc>>&.
30959 .cindex "&%warn%& ACL verb"
30960 &%warn%&: If all the conditions are true, a line specified by the
30961 &%log_message%& modifier is written to Exim's main log. Control always passes
30962 to the next ACL statement. If any condition is false, the log line is not
30963 written. If an identical log line is requested several times in the same
30964 message, only one copy is actually written to the log. If you want to force
30965 duplicates to be written, use the &%logwrite%& modifier instead.
30967 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
30968 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
30969 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
30970 first failing condition. There is more about adding header lines in section
30971 &<<SECTaddheadacl>>&.
30973 If any condition on a &%warn%& statement cannot be completed (that is, there is
30974 some sort of defer), the log line specified by &%log_message%& is not written.
30975 This does not include the case of a forced failure from a lookup, which
30976 is considered to be a successful completion. After a defer, no further
30977 conditions or modifiers in the &%warn%& statement are processed. The incident
30978 is logged, and the ACL continues to be processed, from the next statement
30982 .vindex "&$acl_verify_message$&"
30983 When one of the &%warn%& conditions is an address verification that fails, the
30984 text of the verification failure message is in &$acl_verify_message$&. If you
30985 want this logged, you must set it up explicitly. For example:
30987 warn !verify = sender
30988 log_message = sender verify failed: $acl_verify_message
30992 At the end of each ACL there is an implicit unconditional &%deny%&.
30994 As you can see from the examples above, the conditions and modifiers are
30995 written one to a line, with the first one on the same line as the verb, and
30996 subsequent ones on following lines. If you have a very long condition, you can
30997 continue it onto several physical lines by the usual backslash continuation
30998 mechanism. It is conventional to align the conditions vertically.
31002 .section "ACL variables" "SECTaclvariables"
31003 .cindex "&ACL;" "variables"
31004 There are some special variables that can be set during ACL processing. They
31005 can be used to pass information between different ACLs, different invocations
31006 of the same ACL in the same SMTP connection, and between ACLs and the routers,
31007 transports, and filters that are used to deliver a message. The names of these
31008 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
31009 an underscore, but the remainder of the name can be any sequence of
31010 alphanumeric characters and underscores that you choose. There is no limit on
31011 the number of ACL variables. The two sets act as follows:
31013 The values of those variables whose names begin with &$acl_c$& persist
31014 throughout an SMTP connection. They are never reset. Thus, a value that is set
31015 while receiving one message is still available when receiving the next message
31016 on the same SMTP connection.
31018 The values of those variables whose names begin with &$acl_m$& persist only
31019 while a message is being received. They are reset afterwards. They are also
31020 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
31023 When a message is accepted, the current values of all the ACL variables are
31024 preserved with the message and are subsequently made available at delivery
31025 time. The ACL variables are set by a modifier called &%set%&. For example:
31027 accept hosts = whatever
31028 set acl_m4 = some value
31029 accept authenticated = *
31030 set acl_c_auth = yes
31032 &*Note*&: A leading dollar sign is not used when naming a variable that is to
31033 be set. If you want to set a variable without taking any action, you can use a
31034 &%warn%& verb without any other modifiers or conditions.
31036 .oindex &%strict_acl_vars%&
31037 What happens if a syntactically valid but undefined ACL variable is
31038 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
31039 false (the default), an empty string is substituted; if it is true, an
31040 error is generated.
31042 Versions of Exim before 4.64 have a limited set of numbered variables, but
31043 their names are compatible, so there is no problem with upgrading.
31046 .section "Condition and modifier processing" "SECTcondmodproc"
31047 .cindex "&ACL;" "conditions; processing"
31048 .cindex "&ACL;" "modifiers; processing"
31049 An exclamation mark preceding a condition negates its result. For example:
31051 deny domains = *.dom.example
31052 !verify = recipient
31054 causes the ACL to return &"deny"& if the recipient domain ends in
31055 &'dom.example'& and the recipient address cannot be verified. Sometimes
31056 negation can be used on the right-hand side of a condition. For example, these
31057 two statements are equivalent:
31059 deny hosts = !192.168.3.4
31060 deny !hosts = 192.168.3.4
31062 However, for many conditions (&%verify%& being a good example), only left-hand
31063 side negation of the whole condition is possible.
31065 The arguments of conditions and modifiers are expanded. A forced failure
31066 of an expansion causes a condition to be ignored, that is, it behaves as if the
31067 condition is true. Consider these two statements:
31069 accept senders = ${lookup{$host_name}lsearch\
31070 {/some/file}{$value}fail}
31071 accept senders = ${lookup{$host_name}lsearch\
31072 {/some/file}{$value}{}}
31074 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
31075 the returned list is searched, but if the lookup fails the behaviour is
31076 different in the two cases. The &%fail%& in the first statement causes the
31077 condition to be ignored, leaving no further conditions. The &%accept%& verb
31078 therefore succeeds. The second statement, however, generates an empty list when
31079 the lookup fails. No sender can match an empty list, so the condition fails,
31080 and therefore the &%accept%& also fails.
31082 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
31083 specify actions that are taken as the conditions for a statement are checked;
31084 others specify text for messages that are used when access is denied or a
31085 warning is generated. The &%control%& modifier affects the way an incoming
31086 message is handled.
31088 The positioning of the modifiers in an ACL statement is important, because the
31089 processing of a verb ceases as soon as its outcome is known. Only those
31090 modifiers that have already been encountered will take effect. For example,
31091 consider this use of the &%message%& modifier:
31093 require message = Can't verify sender
31095 message = Can't verify recipient
31097 message = This message cannot be used
31099 If sender verification fails, Exim knows that the result of the statement is
31100 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
31101 so its text is used as the error message. If sender verification succeeds, but
31102 recipient verification fails, the second message is used. If recipient
31103 verification succeeds, the third message becomes &"current"&, but is never used
31104 because there are no more conditions to cause failure.
31106 For the &%deny%& verb, on the other hand, it is always the last &%message%&
31107 modifier that is used, because all the conditions must be true for rejection to
31108 happen. Specifying more than one &%message%& modifier does not make sense, and
31109 the message can even be specified after all the conditions. For example:
31112 !senders = *@my.domain.example
31113 message = Invalid sender from client host
31115 The &"deny"& result does not happen until the end of the statement is reached,
31116 by which time Exim has set up the message.
31120 .section "ACL modifiers" "SECTACLmodi"
31121 .cindex "&ACL;" "modifiers; list of"
31122 The ACL modifiers are as follows:
31125 .vitem &*add_header*&&~=&~<&'text'&>
31126 This modifier specifies one or more header lines that are to be added to an
31127 incoming message, assuming, of course, that the message is ultimately
31128 accepted. For details, see section &<<SECTaddheadacl>>&.
31130 .vitem &*continue*&&~=&~<&'text'&>
31131 .cindex "&%continue%& ACL modifier"
31132 .cindex "database" "updating in ACL"
31133 This modifier does nothing of itself, and processing of the ACL always
31134 continues with the next condition or modifier. The value of &%continue%& is in
31135 the side effects of expanding its argument. Typically this could be used to
31136 update a database. It is really just a syntactic tidiness, to avoid having to
31137 write rather ugly lines like this:
31139 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
31141 Instead, all you need is
31143 &`continue = `&<&'some expansion'&>
31146 .vitem &*control*&&~=&~<&'text'&>
31147 .cindex "&%control%& ACL modifier"
31148 This modifier affects the subsequent processing of the SMTP connection or of an
31149 incoming message that is accepted. The effect of the first type of control
31150 lasts for the duration of the connection, whereas the effect of the second type
31151 lasts only until the current message has been received. The message-specific
31152 controls always apply to the whole message, not to individual recipients,
31153 even if the &%control%& modifier appears in a RCPT ACL.
31155 As there are now quite a few controls that can be applied, they are described
31156 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
31157 in several different ways. For example:
31159 . ==== As this is a nested list, any displays it contains must be indented
31160 . ==== as otherwise they are too far to the left. That comment applies only
31161 . ==== when xmlto and fop are used; formatting with sdop gets it right either
31165 It can be at the end of an &%accept%& statement:
31167 accept ...some conditions
31170 In this case, the control is applied when this statement yields &"accept"&, in
31171 other words, when the conditions are all true.
31174 It can be in the middle of an &%accept%& statement:
31176 accept ...some conditions...
31178 ...some more conditions...
31180 If the first set of conditions are true, the control is applied, even if the
31181 statement does not accept because one of the second set of conditions is false.
31182 In this case, some subsequent statement must yield &"accept"& for the control
31186 It can be used with &%warn%& to apply the control, leaving the
31187 decision about accepting or denying to a subsequent verb. For
31190 warn ...some conditions...
31194 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
31195 &%logwrite%&, so it does not add anything to the message and does not write a
31199 If you want to apply a control unconditionally, you can use it with a
31200 &%require%& verb. For example:
31202 require control = no_multiline_responses
31206 .vitem &*delay*&&~=&~<&'time'&>
31207 .cindex "&%delay%& ACL modifier"
31209 This modifier may appear in any ACL except notquit. It causes Exim to wait for
31210 the time interval before proceeding. However, when testing Exim using the
31211 &%-bh%& option, the delay is not actually imposed (an appropriate message is
31212 output instead). The time is given in the usual Exim notation, and the delay
31213 happens as soon as the modifier is processed. In an SMTP session, pending
31214 output is flushed before the delay is imposed.
31216 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
31219 deny ...some conditions...
31222 The delay happens if all the conditions are true, before the statement returns
31223 &"deny"&. Compare this with:
31226 ...some conditions...
31228 which waits for 30s before processing the conditions. The &%delay%& modifier
31229 can also be used with &%warn%& and together with &%control%&:
31231 warn ...some conditions...
31237 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
31238 responses to several commands are no longer buffered and sent in one packet (as
31239 they would normally be) because all output is flushed before imposing the
31240 delay. This optimization is disabled so that a number of small delays do not
31241 appear to the client as one large aggregated delay that might provoke an
31242 unwanted timeout. You can, however, disable output flushing for &%delay%& by
31243 using a &%control%& modifier to set &%no_delay_flush%&.
31247 .cindex "&%endpass%& ACL modifier"
31248 This modifier, which has no argument, is recognized only in &%accept%& and
31249 &%discard%& statements. It marks the boundary between the conditions whose
31250 failure causes control to pass to the next statement, and the conditions whose
31251 failure causes the ACL to return &"deny"&. This concept has proved to be
31252 confusing to some people, so the use of &%endpass%& is no longer recommended as
31253 &"best practice"&. See the description of &%accept%& above for more details.
31256 .vitem &*log_message*&&~=&~<&'text'&>
31257 .cindex "&%log_message%& ACL modifier"
31258 This modifier sets up a message that is used as part of the log message if the
31259 ACL denies access or a &%warn%& statement's conditions are true. For example:
31261 require log_message = wrong cipher suite $tls_in_cipher
31262 encrypted = DES-CBC3-SHA
31264 &%log_message%& is also used when recipients are discarded by &%discard%&. For
31267 &`discard `&<&'some conditions'&>
31268 &` log_message = Discarded $local_part@$domain because...`&
31270 When access is denied, &%log_message%& adds to any underlying error message
31271 that may exist because of a condition failure. For example, while verifying a
31272 recipient address, a &':fail:'& redirection might have already set up a
31275 The message may be defined before the conditions to which it applies, because
31276 the string expansion does not happen until Exim decides that access is to be
31277 denied. This means that any variables that are set by the condition are
31278 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
31279 variables are set after a DNS black list lookup succeeds. If the expansion of
31280 &%log_message%& fails, or if the result is an empty string, the modifier is
31283 .vindex "&$acl_verify_message$&"
31284 If you want to use a &%warn%& statement to log the result of an address
31285 verification, you can use &$acl_verify_message$& to include the verification
31288 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
31289 the start of the logged message. If the same warning log message is requested
31290 more than once while receiving a single email message, only one copy is
31291 actually logged. If you want to log multiple copies, use &%logwrite%& instead
31292 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
31293 is logged for a successful &%warn%& statement.
31295 If &%log_message%& is not present and there is no underlying error message (for
31296 example, from the failure of address verification), but &%message%& is present,
31297 the &%message%& text is used for logging rejections. However, if any text for
31298 logging contains newlines, only the first line is logged. In the absence of
31299 both &%log_message%& and &%message%&, a default built-in message is used for
31300 logging rejections.
31303 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
31304 .cindex "&%log_reject_target%& ACL modifier"
31305 .cindex "logging in ACL" "specifying which log"
31306 This modifier makes it possible to specify which logs are used for messages
31307 about ACL rejections. Its argument is a colon-separated list of words that can
31308 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
31309 may be empty, in which case a rejection is not logged at all. For example, this
31310 ACL fragment writes no logging information when access is denied:
31312 &`deny `&<&'some conditions'&>
31313 &` log_reject_target =`&
31315 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
31316 permanent and temporary rejections. Its effect lasts for the rest of the
31320 .vitem &*logwrite*&&~=&~<&'text'&>
31321 .cindex "&%logwrite%& ACL modifier"
31322 .cindex "logging in ACL" "immediate"
31323 This modifier writes a message to a log file as soon as it is encountered when
31324 processing an ACL. (Compare &%log_message%&, which, except in the case of
31325 &%warn%& and &%discard%&, is used only if the ACL statement denies
31326 access.) The &%logwrite%& modifier can be used to log special incidents in
31329 &`accept `&<&'some special conditions'&>
31330 &` control = freeze`&
31331 &` logwrite = froze message because ...`&
31333 By default, the message is written to the main log. However, it may begin
31334 with a colon, followed by a comma-separated list of log names, and then
31335 another colon, to specify exactly which logs are to be written. For
31338 logwrite = :main,reject: text for main and reject logs
31339 logwrite = :panic: text for panic log only
31343 .vitem &*message*&&~=&~<&'text'&>
31344 .cindex "&%message%& ACL modifier"
31345 This modifier sets up a text string that is expanded and used as a response
31346 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
31347 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
31348 there is some complication if &%endpass%& is involved; see the description of
31349 &%accept%& for details.)
31351 The expansion of the message happens at the time Exim decides that the ACL is
31352 to end, not at the time it processes &%message%&. If the expansion fails, or
31353 generates an empty string, the modifier is ignored. Here is an example where
31354 &%message%& must be specified first, because the ACL ends with a rejection if
31355 the &%hosts%& condition fails:
31357 require message = Host not recognized
31360 (Once a condition has failed, no further conditions or modifiers are
31363 .cindex "SMTP" "error codes"
31364 .oindex "&%smtp_banner%&
31365 For ACLs that are triggered by SMTP commands, the message is returned as part
31366 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
31367 is meaningful only for SMTP, as no message is returned when a non-SMTP message
31368 is accepted. In the case of the connect ACL, accepting with a message modifier
31369 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
31370 accept message may not contain more than one line (otherwise it will be
31371 truncated at the first newline and a panic logged), and it cannot affect the
31374 When SMTP is involved, the message may begin with an overriding response code,
31375 consisting of three digits optionally followed by an &"extended response code"&
31376 of the form &'n.n.n'&, each code being followed by a space. For example:
31378 deny message = 599 1.2.3 Host not welcome
31379 hosts = 192.168.34.0/24
31381 The first digit of the supplied response code must be the same as would be sent
31382 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
31383 access, but for the predata ACL, note that the default success code is 354, not
31386 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
31387 the message modifier cannot override the 221 response code.
31389 The text in a &%message%& modifier is literal; any quotes are taken as
31390 literals, but because the string is expanded, backslash escapes are processed
31391 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
31394 .vindex "&$acl_verify_message$&"
31395 While the text is being expanded, the &$acl_verify_message$& variable
31396 contains any message previously set.
31397 Afterwards, &$acl_verify_message$& is cleared.
31399 If &%message%& is used on a statement that verifies an address, the message
31400 specified overrides any message that is generated by the verification process.
31401 However, the original message is available in the variable
31402 &$acl_verify_message$&, so you can incorporate it into your message if you
31403 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
31404 routers to be passed back as part of the SMTP response, you should either not
31405 use a &%message%& modifier, or make use of &$acl_verify_message$&.
31407 For compatibility with previous releases of Exim, a &%message%& modifier that
31408 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
31409 modifier, but this usage is now deprecated. However, &%message%& acts only when
31410 all the conditions are true, wherever it appears in an ACL command, whereas
31411 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
31412 &%warn%& in an ACL that is not concerned with receiving a message, it has no
31416 .vitem &*queue*&&~=&~<&'text'&>
31417 .cindex "&%queue%& ACL modifier"
31418 .cindex "named queues" "selecting in ACL"
31419 This modifier specifies the use of a named queue for spool files
31421 It can only be used before the message is received (i.e. not in
31423 This could be used, for example, for known high-volume burst sources
31424 of traffic, or for quarantine of messages.
31425 Separate queue-runner processes will be needed for named queues.
31426 If the text after expansion is empty, the default queue is used.
31429 .vitem &*remove_header*&&~=&~<&'text'&>
31430 This modifier specifies one or more header names in a colon-separated list
31431 that are to be removed from an incoming message, assuming, of course, that
31432 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
31435 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
31436 .cindex "&%set%& ACL modifier"
31437 This modifier puts a value into one of the ACL variables (see section
31438 &<<SECTaclvariables>>&).
31441 .vitem &*udpsend*&&~=&~<&'parameters'&>
31442 .cindex "UDP communications"
31443 This modifier sends a UDP packet, for purposes such as statistics
31444 collection or behaviour monitoring. The parameters are expanded, and
31445 the result of the expansion must be a colon-separated list consisting
31446 of a destination server, port number, and the packet contents. The
31447 server can be specified as a host name or IPv4 or IPv6 address. The
31448 separator can be changed with the usual angle bracket syntax. For
31449 example, you might want to collect information on which hosts connect
31452 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
31453 $tod_zulu $sender_host_address
31460 .section "Use of the control modifier" "SECTcontrols"
31461 .cindex "&%control%& ACL modifier"
31462 The &%control%& modifier supports the following settings:
31465 .vitem &*control&~=&~allow_auth_unadvertised*&
31466 This modifier allows a client host to use the SMTP AUTH command even when it
31467 has not been advertised in response to EHLO. Furthermore, because there are
31468 apparently some really broken clients that do this, Exim will accept AUTH after
31469 HELO (rather than EHLO) when this control is set. It should be used only if you
31470 really need it, and you should limit its use to those broken clients that do
31471 not work without it. For example:
31473 warn hosts = 192.168.34.25
31474 control = allow_auth_unadvertised
31476 Normally, when an Exim server receives an AUTH command, it checks the name of
31477 the authentication mechanism that is given in the command to ensure that it
31478 matches an advertised mechanism. When this control is set, the check that a
31479 mechanism has been advertised is bypassed. Any configured mechanism can be used
31480 by the client. This control is permitted only in the connection and HELO ACLs.
31483 .vitem &*control&~=&~caseful_local_part*& &&&
31484 &*control&~=&~caselower_local_part*&
31485 .cindex "&ACL;" "case of local part in"
31486 .cindex "case of local parts"
31487 .vindex "&$local_part$&"
31488 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
31489 (that is, during RCPT processing). By default, the contents of &$local_part$&
31490 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
31491 any uppercase letters in the original local part are restored in &$local_part$&
31492 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
31495 These controls affect only the current recipient. Moreover, they apply only to
31496 local part handling that takes place directly in the ACL (for example, as a key
31497 in lookups). If a test to verify the recipient is obeyed, the case-related
31498 handling of the local part during the verification is controlled by the router
31499 configuration (see the &%caseful_local_part%& generic router option).
31501 This facility could be used, for example, to add a spam score to local parts
31502 containing upper case letters. For example, using &$acl_m4$& to accumulate the
31505 warn control = caseful_local_part
31506 set acl_m4 = ${eval:\
31508 ${if match{$local_part}{[A-Z]}{1}{0}}\
31510 control = caselower_local_part
31512 Notice that we put back the lower cased version afterwards, assuming that
31513 is what is wanted for subsequent tests.
31516 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
31517 .cindex "&ACL;" "cutthrough routing"
31518 .cindex "cutthrough" "requesting"
31519 This option requests delivery be attempted while the item is being received.
31521 The option is usable in the RCPT ACL.
31522 If enabled for a message received via smtp and routed to an smtp transport,
31523 and only one transport, interface, destination host and port combination
31524 is used for all recipients of the message,
31525 then the delivery connection is made while the receiving connection is open
31526 and data is copied from one to the other.
31528 An attempt to set this option for any recipient but the first
31529 for a mail will be quietly ignored.
31530 If a recipient-verify callout
31532 connection is subsequently
31533 requested in the same ACL it is held open and used for
31534 any subsequent recipients and the data,
31535 otherwise one is made after the initial RCPT ACL completes.
31537 Note that routers are used in verify mode,
31538 and cannot depend on content of received headers.
31539 Note also that headers cannot be
31540 modified by any of the post-data ACLs (DATA, MIME and DKIM).
31541 Headers may be modified by routers (subject to the above) and transports.
31542 The &'Received-By:'& header is generated as soon as the body reception starts,
31543 rather than the traditional time after the full message is received;
31544 this will affect the timestamp.
31546 All the usual ACLs are called; if one results in the message being
31547 rejected, all effort spent in delivery (including the costs on
31548 the ultimate destination) will be wasted.
31549 Note that in the case of data-time ACLs this includes the entire
31552 Cutthrough delivery is not supported via transport-filters or when DKIM signing
31553 of outgoing messages is done, because it sends data to the ultimate destination
31554 before the entire message has been received from the source.
31555 It is not supported for messages received with the SMTP PRDR
31559 Should the ultimate destination system positively accept or reject the mail,
31560 a corresponding indication is given to the source system and nothing is queued.
31561 If the item is successfully delivered in cutthrough mode
31562 the delivery log lines are tagged with ">>" rather than "=>" and appear
31563 before the acceptance "<=" line.
31565 If there is a temporary error the item is queued for later delivery in the
31567 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
31568 to the control; the default value is &"spool"& and the alternate value
31569 &"pass"& copies an SMTP defer response from the target back to the initiator
31570 and does not queue the message.
31571 Note that this is independent of any recipient verify conditions in the ACL.
31573 Delivery in this mode avoids the generation of a bounce mail to a
31575 sender when the destination system is doing content-scan based rejection.
31578 .vitem &*control&~=&~debug/*&<&'options'&>
31579 .cindex "&ACL;" "enabling debug logging"
31580 .cindex "debugging" "enabling from an ACL"
31581 This control turns on debug logging, almost as though Exim had been invoked
31582 with &`-d`&, with the output going to a new logfile in the usual logs directory,
31583 by default called &'debuglog'&.
31584 The filename can be adjusted with the &'tag'& option, which
31585 may access any variables already defined. The logging may be adjusted with
31586 the &'opts'& option, which takes the same values as the &`-d`& command-line
31588 Logging started this way may be stopped, and the file removed,
31589 with the &'kill'& option.
31590 Some examples (which depend on variables that don't exist in all
31594 control = debug/tag=.$sender_host_address
31595 control = debug/opts=+expand+acl
31596 control = debug/tag=.$message_exim_id/opts=+expand
31597 control = debug/kill
31601 .vitem &*control&~=&~dkim_disable_verify*&
31602 .cindex "disable DKIM verify"
31603 .cindex "DKIM" "disable verify"
31604 This control turns off DKIM verification processing entirely. For details on
31605 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
31608 .vitem &*control&~=&~dmarc_disable_verify*&
31609 .cindex "disable DMARC verify"
31610 .cindex "DMARC" "disable verify"
31611 This control turns off DMARC verification processing entirely. For details on
31612 the operation and configuration of DMARC, see section &<<SECDMARC>>&.
31615 .vitem &*control&~=&~dscp/*&<&'value'&>
31616 .cindex "&ACL;" "setting DSCP value"
31617 .cindex "DSCP" "inbound"
31618 This option causes the DSCP value associated with the socket for the inbound
31619 connection to be adjusted to a given value, given as one of a number of fixed
31620 strings or to numeric value.
31621 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
31622 Common values include &`throughput`&, &`mincost`&, and on newer systems
31623 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
31625 The outbound packets from Exim will be marked with this value in the header
31626 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
31627 that these values will have any effect, not be stripped by networking
31628 equipment, or do much of anything without cooperation with your Network
31629 Engineer and those of all network operators between the source and destination.
31632 .vitem &*control&~=&~enforce_sync*& &&&
31633 &*control&~=&~no_enforce_sync*&
31634 .cindex "SMTP" "synchronization checking"
31635 .cindex "synchronization checking in SMTP"
31636 These controls make it possible to be selective about when SMTP synchronization
31637 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
31638 state of the switch (it is true by default). See the description of this option
31639 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
31641 The effect of these two controls lasts for the remainder of the SMTP
31642 connection. They can appear in any ACL except the one for the non-SMTP
31643 messages. The most straightforward place to put them is in the ACL defined by
31644 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
31645 before the first synchronization check. The expected use is to turn off the
31646 synchronization checks for badly-behaved hosts that you nevertheless need to
31650 .vitem &*control&~=&~fakedefer/*&<&'message'&>
31651 .cindex "fake defer"
31652 .cindex "defer, fake"
31653 This control works in exactly the same way as &%fakereject%& (described below)
31654 except that it causes an SMTP 450 response after the message data instead of a
31655 550 response. You must take care when using &%fakedefer%& because it causes the
31656 messages to be duplicated when the sender retries. Therefore, you should not
31657 use &%fakedefer%& if the message is to be delivered normally.
31659 .vitem &*control&~=&~fakereject/*&<&'message'&>
31660 .cindex "fake rejection"
31661 .cindex "rejection, fake"
31662 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
31663 words, only when an SMTP message is being received. If Exim accepts the
31664 message, instead the final 250 response, a 550 rejection message is sent.
31665 However, Exim proceeds to deliver the message as normal. The control applies
31666 only to the current message, not to any subsequent ones that may be received in
31667 the same SMTP connection.
31669 The text for the 550 response is taken from the &%control%& modifier. If no
31670 message is supplied, the following is used:
31672 550-Your message has been rejected but is being
31673 550-kept for evaluation.
31674 550-If it was a legitimate message, it may still be
31675 550 delivered to the target recipient(s).
31677 This facility should be used with extreme caution.
31679 .vitem &*control&~=&~freeze*&
31680 .cindex "frozen messages" "forcing in ACL"
31681 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31682 other words, only when a message is being received. If the message is accepted,
31683 it is placed on Exim's queue and frozen. The control applies only to the
31684 current message, not to any subsequent ones that may be received in the same
31687 This modifier can optionally be followed by &`/no_tell`&. If the global option
31688 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
31689 is told about the freezing), provided all the &*control=freeze*& modifiers that
31690 are obeyed for the current message have the &`/no_tell`& option.
31692 .vitem &*control&~=&~no_delay_flush*&
31693 .cindex "SMTP" "output flushing, disabling for delay"
31694 Exim normally flushes SMTP output before implementing a delay in an ACL, to
31695 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31696 use. This control, as long as it is encountered before the &%delay%& modifier,
31697 disables such output flushing.
31699 .vitem &*control&~=&~no_callout_flush*&
31700 .cindex "SMTP" "output flushing, disabling for callout"
31701 Exim normally flushes SMTP output before performing a callout in an ACL, to
31702 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31703 use. This control, as long as it is encountered before the &%verify%& condition
31704 that causes the callout, disables such output flushing.
31706 .vitem &*control&~=&~no_mbox_unspool*&
31707 This control is available when Exim is compiled with the content scanning
31708 extension. Content scanning may require a copy of the current message, or parts
31709 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
31710 or spam scanner. Normally, such copies are deleted when they are no longer
31711 needed. If this control is set, the copies are not deleted. The control applies
31712 only to the current message, not to any subsequent ones that may be received in
31713 the same SMTP connection. It is provided for debugging purposes and is unlikely
31714 to be useful in production.
31716 .vitem &*control&~=&~no_multiline_responses*&
31717 .cindex "multiline responses, suppressing"
31718 This control is permitted for any ACL except the one for non-SMTP messages.
31719 It seems that there are broken clients in use that cannot handle multiline
31720 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
31722 If this control is set, multiline SMTP responses from ACL rejections are
31723 suppressed. One way of doing this would have been to put out these responses as
31724 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
31725 (&"use multiline responses for more"& it says &-- ha!), and some of the
31726 responses might get close to that. So this facility, which is after all only a
31727 sop to broken clients, is implemented by doing two very easy things:
31730 Extra information that is normally output as part of a rejection caused by
31731 sender verification failure is omitted. Only the final line (typically &"sender
31732 verification failed"&) is sent.
31734 If a &%message%& modifier supplies a multiline response, only the first
31738 The setting of the switch can, of course, be made conditional on the
31739 calling host. Its effect lasts until the end of the SMTP connection.
31741 .vitem &*control&~=&~no_pipelining*&
31742 .cindex "PIPELINING" "suppressing advertising"
31743 .cindex "ESMTP extensions" PIPELINING
31744 This control turns off the advertising of the PIPELINING extension to SMTP in
31745 the current session. To be useful, it must be obeyed before Exim sends its
31746 response to an EHLO command. Therefore, it should normally appear in an ACL
31747 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
31748 &%pipelining_advertise_hosts%&.
31750 .vitem &*control&~=&~queue/*&<&'options'&>* &&&
31751 &*control&~=&~queue_only*&
31752 .oindex "&%queue%&"
31753 .oindex "&%queue_only%&"
31754 .cindex "queueing incoming messages"
31755 .cindex queueing "forcing in ACL"
31756 .cindex "first pass routing"
31757 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31758 other words, only when a message is being received. If the message is accepted,
31759 it is placed on Exim's queue and left there for delivery by a subsequent queue
31761 If used with no options set,
31762 no immediate delivery process is started. In other words, it has the
31763 effect as the &%queue_only%& global option or &'-odq'& command-line option.
31765 If the &'first_pass_route'& option is given then
31766 the behaviour is like the command-line &'-oqds'& option;
31767 a delivery process is started which stops short of making
31768 any SMTP delivery. The benefit is that the hints database will be updated for
31769 the message being waiting for a specific host, and a later queue run will be
31770 able to send all such messages on a single connection.
31772 The control only applies to the current message, not to any subsequent ones that
31773 may be received in the same SMTP connection.
31775 .vitem &*control&~=&~submission/*&<&'options'&>
31776 .cindex "message" "submission"
31777 .cindex "submission mode"
31778 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
31779 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
31780 the current message is a submission from a local MUA. In this case, Exim
31781 operates in &"submission mode"&, and applies certain fixups to the message if
31782 necessary. For example, it adds a &'Date:'& header line if one is not present.
31783 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
31784 late (the message has already been created).
31786 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
31787 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
31788 submission mode; the available options for this control are described there.
31789 The control applies only to the current message, not to any subsequent ones
31790 that may be received in the same SMTP connection.
31792 .vitem &*control&~=&~suppress_local_fixups*&
31793 .cindex "submission fixups, suppressing"
31794 This control applies to locally submitted (non TCP/IP) messages, and is the
31795 complement of &`control = submission`&. It disables the fixups that are
31796 normally applied to locally-submitted messages. Specifically:
31799 Any &'Sender:'& header line is left alone (in this respect, it is a
31800 dynamic version of &%local_sender_retain%&).
31802 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
31804 There is no check that &'From:'& corresponds to the actual sender.
31807 This control may be useful when a remotely-originated message is accepted,
31808 passed to some scanning program, and then re-submitted for delivery. It can be
31809 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
31810 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
31813 &*Note:*& This control applies only to the current message, not to any others
31814 that are being submitted at the same time using &%-bs%& or &%-bS%&.
31816 .vitem &*control&~=&~utf8_downconvert*&
31817 This control enables conversion of UTF-8 in message envelope addresses
31819 For details see section &<<SECTi18nMTA>>&.
31823 .section "Summary of message fixup control" "SECTsummesfix"
31824 All four possibilities for message fixups can be specified:
31827 Locally submitted, fixups applied: the default.
31829 Locally submitted, no fixups applied: use
31830 &`control = suppress_local_fixups`&.
31832 Remotely submitted, no fixups applied: the default.
31834 Remotely submitted, fixups applied: use &`control = submission`&.
31839 .section "Adding header lines in ACLs" "SECTaddheadacl"
31840 .cindex "header lines" "adding in an ACL"
31841 .cindex "header lines" "position of added lines"
31842 .cindex "&%add_header%& ACL modifier"
31843 The &%add_header%& modifier can be used to add one or more extra header lines
31844 to an incoming message, as in this example:
31846 warn dnslists = sbl.spamhaus.org : \
31847 dialup.mail-abuse.org
31848 add_header = X-blacklisted-at: $dnslist_domain
31850 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31851 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31852 receiving a message). The message must ultimately be accepted for
31853 &%add_header%& to have any significant effect. You can use &%add_header%& with
31854 any ACL verb, including &%deny%& (though this is potentially useful only in a
31857 Headers will not be added to the message if the modifier is used in
31858 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31860 Leading and trailing newlines are removed from
31861 the data for the &%add_header%& modifier; if it then
31862 contains one or more newlines that
31863 are not followed by a space or a tab, it is assumed to contain multiple header
31864 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
31865 front of any line that is not a valid header line.
31867 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
31868 They are added to the message before processing the DATA and MIME ACLs.
31869 However, if an identical header line is requested more than once, only one copy
31870 is actually added to the message. Further header lines may be accumulated
31871 during the DATA and MIME ACLs, after which they are added to the message, again
31872 with duplicates suppressed. Thus, it is possible to add two identical header
31873 lines to an SMTP message, but only if one is added before DATA and one after.
31874 In the case of non-SMTP messages, new headers are accumulated during the
31875 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
31876 message is rejected after DATA or by the non-SMTP ACL, all added header lines
31877 are included in the entry that is written to the reject log.
31879 .cindex "header lines" "added; visibility of"
31880 Header lines are not visible in string expansions
31882 until they are added to the
31883 message. It follows that header lines defined in the MAIL, RCPT, and predata
31884 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
31885 header lines that are added by the DATA or MIME ACLs are not visible in those
31886 ACLs. Because of this restriction, you cannot use header lines as a way of
31887 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
31888 this, you can use ACL variables, as described in section
31889 &<<SECTaclvariables>>&.
31891 The list of headers yet to be added is given by the &%$headers_added%& variable.
31893 The &%add_header%& modifier acts immediately as it is encountered during the
31894 processing of an ACL. Notice the difference between these two cases:
31896 &`accept add_header = ADDED: some text`&
31897 &` `&<&'some condition'&>
31899 &`accept `&<&'some condition'&>
31900 &` add_header = ADDED: some text`&
31902 In the first case, the header line is always added, whether or not the
31903 condition is true. In the second case, the header line is added only if the
31904 condition is true. Multiple occurrences of &%add_header%& may occur in the same
31905 ACL statement. All those that are encountered before a condition fails are
31908 .cindex "&%warn%& ACL verb"
31909 For compatibility with previous versions of Exim, a &%message%& modifier for a
31910 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
31911 effect only if all the conditions are true, even if it appears before some of
31912 them. Furthermore, only the last occurrence of &%message%& is honoured. This
31913 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
31914 are present on a &%warn%& verb, both are processed according to their
31917 By default, new header lines are added to a message at the end of the existing
31918 header lines. However, you can specify that any particular header line should
31919 be added right at the start (before all the &'Received:'& lines), immediately
31920 after the first block of &'Received:'& lines, or immediately before any line
31921 that is not a &'Received:'& or &'Resent-something:'& header.
31923 This is done by specifying &":at_start:"&, &":after_received:"&, or
31924 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
31925 header line, respectively. (Header text cannot start with a colon, as there has
31926 to be a header name first.) For example:
31928 warn add_header = \
31929 :after_received:X-My-Header: something or other...
31931 If more than one header line is supplied in a single &%add_header%& modifier,
31932 each one is treated independently and can therefore be placed differently. If
31933 you add more than one line at the start, or after the Received: block, they end
31934 up in reverse order.
31936 &*Warning*&: This facility currently applies only to header lines that are
31937 added in an ACL. It does NOT work for header lines that are added in a
31938 system filter or in a router or transport.
31942 .section "Removing header lines in ACLs" "SECTremoveheadacl"
31943 .cindex "header lines" "removing in an ACL"
31944 .cindex "header lines" "position of removed lines"
31945 .cindex "&%remove_header%& ACL modifier"
31946 The &%remove_header%& modifier can be used to remove one or more header lines
31947 from an incoming message, as in this example:
31949 warn message = Remove internal headers
31950 remove_header = x-route-mail1 : x-route-mail2
31952 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31953 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31954 receiving a message). The message must ultimately be accepted for
31955 &%remove_header%& to have any significant effect. You can use &%remove_header%&
31956 with any ACL verb, including &%deny%&, though this is really not useful for
31957 any verb that doesn't result in a delivered message.
31959 Headers will not be removed from the message if the modifier is used in
31960 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31962 More than one header can be removed at the same time by using a colon separated
31963 list of header names. The header matching is case insensitive. Wildcards are
31964 not permitted, nor is list expansion performed, so you cannot use hostlists to
31965 create a list of headers, however both connection and message variable expansion
31966 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
31968 warn hosts = +internal_hosts
31969 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
31970 warn message = Remove internal headers
31971 remove_header = $acl_c_ihdrs
31973 Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
31974 Matching header lines are removed from the message before processing the DATA and MIME ACLs.
31975 If multiple header lines match, all are removed.
31976 There is no harm in attempting to remove the same header twice nor in removing
31977 a non-existent header. Further header lines to be removed may be accumulated
31978 during the DATA and MIME ACLs, after which they are removed from the message,
31979 if present. In the case of non-SMTP messages, headers to be removed are
31980 accumulated during the non-SMTP ACLs, and are removed from the message after
31981 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
31982 ACL, there really is no effect because there is no logging of what headers
31983 would have been removed.
31985 .cindex "header lines" "removed; visibility of"
31986 Header lines are not visible in string expansions until the DATA phase when it
31987 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
31988 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
31989 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
31990 this restriction, you cannot use header lines as a way of controlling data
31991 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
31992 you should instead use ACL variables, as described in section
31993 &<<SECTaclvariables>>&.
31995 The &%remove_header%& modifier acts immediately as it is encountered during the
31996 processing of an ACL. Notice the difference between these two cases:
31998 &`accept remove_header = X-Internal`&
31999 &` `&<&'some condition'&>
32001 &`accept `&<&'some condition'&>
32002 &` remove_header = X-Internal`&
32004 In the first case, the header line is always removed, whether or not the
32005 condition is true. In the second case, the header line is removed only if the
32006 condition is true. Multiple occurrences of &%remove_header%& may occur in the
32007 same ACL statement. All those that are encountered before a condition fails
32010 &*Warning*&: This facility currently applies only to header lines that are
32011 present during ACL processing. It does NOT remove header lines that are added
32012 in a system filter or in a router or transport.
32017 .section "ACL conditions" "SECTaclconditions"
32018 .cindex "&ACL;" "conditions; list of"
32019 Some of the conditions listed in this section are available only when Exim is
32020 compiled with the content-scanning extension. They are included here briefly
32021 for completeness. More detailed descriptions can be found in the discussion on
32022 content scanning in chapter &<<CHAPexiscan>>&.
32024 Not all conditions are relevant in all circumstances. For example, testing
32025 senders and recipients does not make sense in an ACL that is being run as the
32026 result of the arrival of an ETRN command, and checks on message headers can be
32027 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
32028 can use the same condition (with different parameters) more than once in the
32029 same ACL statement. This provides a way of specifying an &"and"& conjunction.
32030 The conditions are as follows:
32034 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
32035 .cindex "&ACL;" "nested"
32036 .cindex "&ACL;" "indirect"
32037 .cindex "&ACL;" "arguments"
32038 .cindex "&%acl%& ACL condition"
32039 The possible values of the argument are the same as for the
32040 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
32041 &"accept"& the condition is true; if it returns &"deny"& the condition is
32042 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
32043 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
32044 condition false. This means that further processing of the &%warn%& verb
32045 ceases, but processing of the ACL continues.
32047 If the argument is a named ACL, up to nine space-separated optional values
32048 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
32049 and $acl_narg is set to the count of values.
32050 Previous values of these variables are restored after the call returns.
32051 The name and values are expanded separately.
32052 Note that spaces in complex expansions which are used as arguments
32053 will act as argument separators.
32055 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
32056 the connection is dropped. If it returns &"discard"&, the verb must be
32057 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
32058 conditions are tested.
32060 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
32061 loops. This condition allows you to use different ACLs in different
32062 circumstances. For example, different ACLs can be used to handle RCPT commands
32063 for different local users or different local domains.
32065 .vitem &*authenticated&~=&~*&<&'string&~list'&>
32066 .cindex "&%authenticated%& ACL condition"
32067 .cindex "authentication" "ACL checking"
32068 .cindex "&ACL;" "testing for authentication"
32069 If the SMTP connection is not authenticated, the condition is false. Otherwise,
32070 the name of the authenticator is tested against the list. To test for
32071 authentication by any authenticator, you can set
32076 .vitem &*condition&~=&~*&<&'string'&>
32077 .cindex "&%condition%& ACL condition"
32078 .cindex "customizing" "ACL condition"
32079 .cindex "&ACL;" "customized test"
32080 .cindex "&ACL;" "testing, customized"
32081 This feature allows you to make up custom conditions. If the result of
32082 expanding the string is an empty string, the number zero, or one of the strings
32083 &"no"& or &"false"&, the condition is false. If the result is any non-zero
32084 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
32085 any other value, some error is assumed to have occurred, and the ACL returns
32086 &"defer"&. However, if the expansion is forced to fail, the condition is
32087 ignored. The effect is to treat it as true, whether it is positive or
32090 .vitem &*decode&~=&~*&<&'location'&>
32091 .cindex "&%decode%& ACL condition"
32092 This condition is available only when Exim is compiled with the
32093 content-scanning extension, and it is allowed only in the ACL defined by
32094 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
32095 If all goes well, the condition is true. It is false only if there are
32096 problems such as a syntax error or a memory shortage. For more details, see
32097 chapter &<<CHAPexiscan>>&.
32099 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
32100 .cindex "&%dnslists%& ACL condition"
32101 .cindex "DNS list" "in ACL"
32102 .cindex "black list (DNS)"
32103 .cindex "&ACL;" "testing a DNS list"
32104 This condition checks for entries in DNS black lists. These are also known as
32105 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
32106 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
32107 different variants of this condition to describe briefly here. See sections
32108 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
32110 .vitem &*domains&~=&~*&<&'domain&~list'&>
32111 .cindex "&%domains%& ACL condition"
32112 .cindex "domain" "ACL checking"
32113 .cindex "&ACL;" "testing a recipient domain"
32114 .vindex "&$domain_data$&"
32115 This condition is relevant only after a RCPT command. It checks that the domain
32116 of the recipient address is in the domain list. If percent-hack processing is
32117 enabled, it is done before this test is done. If the check succeeds with a
32118 lookup, the result of the lookup is placed in &$domain_data$& until the next
32121 &*Note carefully*& (because many people seem to fall foul of this): you cannot
32122 use &%domains%& in a DATA ACL.
32125 .vitem &*encrypted&~=&~*&<&'string&~list'&>
32126 .cindex "&%encrypted%& ACL condition"
32127 .cindex "encryption" "checking in an ACL"
32128 .cindex "&ACL;" "testing for encryption"
32129 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
32130 name of the cipher suite in use is tested against the list. To test for
32131 encryption without testing for any specific cipher suite(s), set
32137 .vitem &*hosts&~=&~*&<&'host&~list'&>
32138 .cindex "&%hosts%& ACL condition"
32139 .cindex "host" "ACL checking"
32140 .cindex "&ACL;" "testing the client host"
32141 This condition tests that the calling host matches the host list. If you have
32142 name lookups or wildcarded host names and IP addresses in the same host list,
32143 you should normally put the IP addresses first. For example, you could have:
32145 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
32147 The lookup in this example uses the host name for its key. This is implied by
32148 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
32149 and it wouldn't matter which way round you had these two items.)
32151 The reason for the problem with host names lies in the left-to-right way that
32152 Exim processes lists. It can test IP addresses without doing any DNS lookups,
32153 but when it reaches an item that requires a host name, it fails if it cannot
32154 find a host name to compare with the pattern. If the above list is given in the
32155 opposite order, the &%accept%& statement fails for a host whose name cannot be
32156 found, even if its IP address is 10.9.8.7.
32158 If you really do want to do the name check first, and still recognize the IP
32159 address even if the name lookup fails, you can rewrite the ACL like this:
32161 accept hosts = dbm;/etc/friendly/hosts
32162 accept hosts = 10.9.8.7
32164 The default action on failing to find the host name is to assume that the host
32165 is not in the list, so the first &%accept%& statement fails. The second
32166 statement can then check the IP address.
32168 .vindex "&$host_data$&"
32169 If a &%hosts%& condition is satisfied by means of a lookup, the result
32170 of the lookup is made available in the &$host_data$& variable. This
32171 allows you, for example, to set up a statement like this:
32173 deny hosts = net-lsearch;/some/file
32174 message = $host_data
32176 which gives a custom error message for each denied host.
32178 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
32179 .cindex "&%local_parts%& ACL condition"
32180 .cindex "local part" "ACL checking"
32181 .cindex "&ACL;" "testing a local part"
32182 .vindex "&$local_part_data$&"
32183 This condition is relevant only after a RCPT command. It checks that the local
32184 part of the recipient address is in the list. If percent-hack processing is
32185 enabled, it is done before this test. If the check succeeds with a lookup, the
32186 result of the lookup is placed in &$local_part_data$&, which remains set until
32187 the next &%local_parts%& test.
32189 .vitem &*malware&~=&~*&<&'option'&>
32190 .cindex "&%malware%& ACL condition"
32191 .cindex "&ACL;" "virus scanning"
32192 .cindex "&ACL;" "scanning for viruses"
32193 This condition is available only when Exim is compiled with the
32194 content-scanning extension
32195 and only after a DATA command.
32196 It causes the incoming message to be scanned for
32197 viruses. For details, see chapter &<<CHAPexiscan>>&.
32199 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32200 .cindex "&%mime_regex%& ACL condition"
32201 .cindex "&ACL;" "testing by regex matching"
32202 This condition is available only when Exim is compiled with the
32203 content-scanning extension, and it is allowed only in the ACL defined by
32204 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
32205 with any of the regular expressions. For details, see chapter
32208 .vitem &*ratelimit&~=&~*&<&'parameters'&>
32209 .cindex "rate limiting"
32210 This condition can be used to limit the rate at which a user or host submits
32211 messages. Details are given in section &<<SECTratelimiting>>&.
32213 .vitem &*recipients&~=&~*&<&'address&~list'&>
32214 .cindex "&%recipients%& ACL condition"
32215 .cindex "recipient" "ACL checking"
32216 .cindex "&ACL;" "testing a recipient"
32217 This condition is relevant only after a RCPT command. It checks the entire
32218 recipient address against a list of recipients.
32220 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32221 .cindex "&%regex%& ACL condition"
32222 .cindex "&ACL;" "testing by regex matching"
32223 This condition is available only when Exim is compiled with the
32224 content-scanning extension, and is available only in the DATA, MIME, and
32225 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
32226 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
32229 .vitem &*seen&~=&~*&<&'parameters'&>
32230 .cindex "&%sseen%& ACL condition"
32231 This condition can be used to test if a situation has been previously met,
32232 for example for greylisting.
32233 Details are given in section &<<SECTseen>>&.
32236 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
32237 .cindex "&%sender_domains%& ACL condition"
32238 .cindex "sender" "ACL checking"
32239 .cindex "&ACL;" "testing a sender domain"
32240 .vindex "&$domain$&"
32241 .vindex "&$sender_address_domain$&"
32242 This condition tests the domain of the sender of the message against the given
32243 domain list. &*Note*&: The domain of the sender address is in
32244 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
32245 of this condition. This is an exception to the general rule for testing domain
32246 lists. It is done this way so that, if this condition is used in an ACL for a
32247 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
32248 influence the sender checking.
32250 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32251 relaying, because sender addresses are easily, and commonly, forged.
32253 .vitem &*senders&~=&~*&<&'address&~list'&>
32254 .cindex "&%senders%& ACL condition"
32255 .cindex "sender" "ACL checking"
32256 .cindex "&ACL;" "testing a sender"
32257 This condition tests the sender of the message against the given list. To test
32258 for a bounce message, which has an empty sender, set
32262 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32263 relaying, because sender addresses are easily, and commonly, forged.
32265 .vitem &*spam&~=&~*&<&'username'&>
32266 .cindex "&%spam%& ACL condition"
32267 .cindex "&ACL;" "scanning for spam"
32268 This condition is available only when Exim is compiled with the
32269 content-scanning extension. It causes the incoming message to be scanned by
32270 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
32272 .vitem &*verify&~=&~certificate*&
32273 .cindex "&%verify%& ACL condition"
32274 .cindex "TLS" "client certificate verification"
32275 .cindex "certificate" "verification of client"
32276 .cindex "&ACL;" "certificate verification"
32277 .cindex "&ACL;" "testing a TLS certificate"
32278 This condition is true in an SMTP session if the session is encrypted, and a
32279 certificate was received from the client, and the certificate was verified. The
32280 server requests a certificate only if the client matches &%tls_verify_hosts%&
32281 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
32283 .vitem &*verify&~=&~csa*&
32284 .cindex "CSA verification"
32285 This condition checks whether the sending host (the client) is authorized to
32286 send email. Details of how this works are given in section
32287 &<<SECTverifyCSA>>&.
32289 .vitem &*verify&~=&~header_names_ascii*&
32290 .cindex "&%verify%& ACL condition"
32291 .cindex "&ACL;" "verifying header names only ASCII"
32292 .cindex "header lines" "verifying header names only ASCII"
32293 .cindex "verifying" "header names only ASCII"
32294 This condition is relevant only in an ACL that is run after a message has been
32296 This usually means an ACL specified by &%acl_smtp_data%& or &%acl_not_smtp%&.
32297 It checks all header names (not the content) to make sure
32298 there are no non-ASCII characters, also excluding control characters. The
32299 allowable characters are decimal ASCII values 33 through 126.
32301 Exim itself will handle headers with non-ASCII characters, but it can cause
32302 problems for downstream applications, so this option will allow their
32303 detection and rejection in the DATA ACL's.
32305 .vitem &*verify&~=&~header_sender/*&<&'options'&>
32306 .cindex "&%verify%& ACL condition"
32307 .cindex "&ACL;" "verifying sender in the header"
32308 .cindex "header lines" "verifying the sender in"
32309 .cindex "sender" "verifying in header"
32310 .cindex "verifying" "sender in header"
32311 This condition is relevant only in an ACL that is run after a message has been
32312 received, that is, in an ACL specified by &%acl_smtp_data%& or
32313 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
32314 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
32315 is loosely thought of as a &"sender"& address (hence the name of the test).
32316 However, an address that appears in one of these headers need not be an address
32317 that accepts bounce messages; only sender addresses in envelopes are required
32318 to accept bounces. Therefore, if you use the callout option on this check, you
32319 might want to arrange for a non-empty address in the MAIL command.
32321 Details of address verification and the options are given later, starting at
32322 section &<<SECTaddressverification>>& (callouts are described in section
32323 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
32324 condition to restrict it to bounce messages only:
32327 !verify = header_sender
32328 message = A valid sender header is required for bounces
32331 .vitem &*verify&~=&~header_syntax*&
32332 .cindex "&%verify%& ACL condition"
32333 .cindex "&ACL;" "verifying header syntax"
32334 .cindex "header lines" "verifying syntax"
32335 .cindex "verifying" "header syntax"
32336 This condition is relevant only in an ACL that is run after a message has been
32337 received, that is, in an ACL specified by &%acl_smtp_data%& or
32338 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
32339 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
32340 and &'Bcc:'&), returning true if there are no problems.
32341 Unqualified addresses (local parts without domains) are
32342 permitted only in locally generated messages and from hosts that match
32343 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
32346 Note that this condition is a syntax check only. However, a common spamming
32347 ploy used to be to send syntactically invalid headers such as
32351 and this condition can be used to reject such messages, though they are not as
32352 common as they used to be.
32354 .vitem &*verify&~=&~helo*&
32355 .cindex "&%verify%& ACL condition"
32356 .cindex "&ACL;" "verifying HELO/EHLO"
32357 .cindex "HELO" "verifying"
32358 .cindex "EHLO" "verifying"
32359 .cindex "verifying" "EHLO"
32360 .cindex "verifying" "HELO"
32361 This condition is true if a HELO or EHLO command has been received from the
32362 client host, and its contents have been verified. If there has been no previous
32363 attempt to verify the HELO/EHLO contents, it is carried out when this
32364 condition is encountered. See the description of the &%helo_verify_hosts%& and
32365 &%helo_try_verify_hosts%& options for details of how to request verification
32366 independently of this condition, and for detail of the verification.
32368 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
32369 option), this condition is always true.
32372 .vitem &*verify&~=&~not_blind/*&<&'options'&>
32373 .cindex "verifying" "not blind"
32374 .cindex "bcc recipients, verifying none"
32375 This condition checks that there are no blind (bcc) recipients in the message.
32376 Every envelope recipient must appear either in a &'To:'& header line or in a
32377 &'Cc:'& header line for this condition to be true. Local parts are checked
32378 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
32379 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
32380 used only in a DATA or non-SMTP ACL.
32382 There is one possible option, &`case_insensitive`&. If this is present then
32383 local parts are checked case-insensitively.
32385 There are, of course, many legitimate messages that make use of blind (bcc)
32386 recipients. This check should not be used on its own for blocking messages.
32389 .vitem &*verify&~=&~recipient/*&<&'options'&>
32390 .cindex "&%verify%& ACL condition"
32391 .cindex "&ACL;" "verifying recipient"
32392 .cindex "recipient" "verifying"
32393 .cindex "verifying" "recipient"
32394 .vindex "&$address_data$&"
32395 This condition is relevant only after a RCPT command. It verifies the current
32396 recipient. Details of address verification are given later, starting at section
32397 &<<SECTaddressverification>>&. After a recipient has been verified, the value
32398 of &$address_data$& is the last value that was set while routing the address.
32399 This applies even if the verification fails. When an address that is being
32400 verified is redirected to a single address, verification continues with the new
32401 address, and in that case, the subsequent value of &$address_data$& is the
32402 value for the child address.
32404 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
32405 .cindex "&%verify%& ACL condition"
32406 .cindex "&ACL;" "verifying host reverse lookup"
32407 .cindex "host" "verifying reverse lookup"
32408 This condition ensures that a verified host name has been looked up from the IP
32409 address of the client host. (This may have happened already if the host name
32410 was needed for checking a host list, or if the host matched &%host_lookup%&.)
32411 Verification ensures that the host name obtained from a reverse DNS lookup, or
32412 one of its aliases, does, when it is itself looked up in the DNS, yield the
32413 original IP address.
32415 There is one possible option, &`defer_ok`&. If this is present and a
32416 DNS operation returns a temporary error, the verify condition succeeds.
32418 If this condition is used for a locally generated message (that is, when there
32419 is no client host involved), it always succeeds.
32421 .vitem &*verify&~=&~sender/*&<&'options'&>
32422 .cindex "&%verify%& ACL condition"
32423 .cindex "&ACL;" "verifying sender"
32424 .cindex "sender" "verifying"
32425 .cindex "verifying" "sender"
32426 This condition is relevant only after a MAIL or RCPT command, or after a
32427 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
32428 the message's sender is empty (that is, this is a bounce message), the
32429 condition is true. Otherwise, the sender address is verified.
32431 .vindex "&$address_data$&"
32432 .vindex "&$sender_address_data$&"
32433 If there is data in the &$address_data$& variable at the end of routing, its
32434 value is placed in &$sender_address_data$& at the end of verification. This
32435 value can be used in subsequent conditions and modifiers in the same ACL
32436 statement. It does not persist after the end of the current statement. If you
32437 want to preserve the value for longer, you can save it in an ACL variable.
32439 Details of verification are given later, starting at section
32440 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
32441 to avoid doing it more than once per message.
32443 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
32444 .cindex "&%verify%& ACL condition"
32445 This is a variation of the previous option, in which a modified address is
32446 verified as a sender.
32448 Note that '/' is legal in local-parts; if the address may have such
32449 (eg. is generated from the received message)
32450 they must be protected from the options parsing by doubling:
32452 verify = sender=${listquote{/}{${address:$h_sender:}}}
32458 .section "Using DNS lists" "SECTmorednslists"
32459 .cindex "DNS list" "in ACL"
32460 .cindex "black list (DNS)"
32461 .cindex "&ACL;" "testing a DNS list"
32462 In its simplest form, the &%dnslists%& condition tests whether the calling host
32463 is on at least one of a number of DNS lists by looking up the inverted IP
32464 address in one or more DNS domains. (Note that DNS list domains are not mail
32465 domains, so the &`+`& syntax for named lists doesn't work - it is used for
32466 special options instead.) For example, if the calling host's IP
32467 address is 192.168.62.43, and the ACL statement is
32469 deny dnslists = blackholes.mail-abuse.org : \
32470 dialups.mail-abuse.org
32472 the following records are looked up:
32474 43.62.168.192.blackholes.mail-abuse.org
32475 43.62.168.192.dialups.mail-abuse.org
32477 As soon as Exim finds an existing DNS record, processing of the list stops.
32478 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
32479 to test that a host is on more than one list (an &"and"& conjunction), you can
32480 use two separate conditions:
32482 deny dnslists = blackholes.mail-abuse.org
32483 dnslists = dialups.mail-abuse.org
32485 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
32486 behaves as if the host does not match the list item, that is, as if the DNS
32487 record does not exist. If there are further items in the DNS list, they are
32490 This is usually the required action when &%dnslists%& is used with &%deny%&
32491 (which is the most common usage), because it prevents a DNS failure from
32492 blocking mail. However, you can change this behaviour by putting one of the
32493 following special items in the list:
32495 &`+include_unknown `& behave as if the item is on the list
32496 &`+exclude_unknown `& behave as if the item is not on the list (default)
32497 &`+defer_unknown `& give a temporary error
32499 .cindex "&`+include_unknown`&"
32500 .cindex "&`+exclude_unknown`&"
32501 .cindex "&`+defer_unknown`&"
32502 Each of these applies to any subsequent items on the list. For example:
32504 deny dnslists = +defer_unknown : foo.bar.example
32506 Testing the list of domains stops as soon as a match is found. If you want to
32507 warn for one list and block for another, you can use two different statements:
32509 deny dnslists = blackholes.mail-abuse.org
32510 warn dnslists = dialups.mail-abuse.org
32511 message = X-Warn: sending host is on dialups list
32513 .cindex caching "of dns lookup"
32515 DNS list lookups are cached by Exim for the duration of the SMTP session
32516 (but limited by the DNS return TTL value),
32517 so a lookup based on the IP address is done at most once for any incoming
32518 connection (assuming long-enough TTL).
32519 Exim does not share information between multiple incoming
32520 connections (but your local name server cache should be active).
32522 There are a number of DNS lists to choose from, some commercial, some free,
32523 or free for small deployments. An overview can be found at
32524 &url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists).
32528 .section "Specifying the IP address for a DNS list lookup" "SECID201"
32529 .cindex "DNS list" "keyed by explicit IP address"
32530 By default, the IP address that is used in a DNS list lookup is the IP address
32531 of the calling host. However, you can specify another IP address by listing it
32532 after the domain name, introduced by a slash. For example:
32534 deny dnslists = black.list.tld/192.168.1.2
32536 This feature is not very helpful with explicit IP addresses; it is intended for
32537 use with IP addresses that are looked up, for example, the IP addresses of the
32538 MX hosts or nameservers of an email sender address. For an example, see section
32539 &<<SECTmulkeyfor>>& below.
32544 .section "DNS lists keyed on domain names" "SECID202"
32545 .cindex "DNS list" "keyed by domain name"
32546 There are some lists that are keyed on domain names rather than inverted IP
32547 addresses (see, e.g., the &'domain based zones'& link at
32548 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
32549 with these lists. You can change the name that is looked up in a DNS list by
32550 listing it after the domain name, introduced by a slash. For example,
32552 deny dnslists = dsn.rfc-ignorant.org/$sender_address_domain
32553 message = Sender's domain is listed at $dnslist_domain
32555 This particular example is useful only in ACLs that are obeyed after the
32556 RCPT or DATA commands, when a sender address is available. If (for
32557 example) the message's sender is &'user@tld.example'& the name that is looked
32558 up by this example is
32560 tld.example.dsn.rfc-ignorant.org
32562 A single &%dnslists%& condition can contain entries for both names and IP
32563 addresses. For example:
32565 deny dnslists = sbl.spamhaus.org : \
32566 dsn.rfc-ignorant.org/$sender_address_domain
32568 The first item checks the sending host's IP address; the second checks a domain
32569 name. The whole condition is true if either of the DNS lookups succeeds.
32574 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
32575 .cindex "DNS list" "multiple keys for"
32576 The syntax described above for looking up explicitly-defined values (either
32577 names or IP addresses) in a DNS blacklist is a simplification. After the domain
32578 name for the DNS list, what follows the slash can in fact be a list of items.
32579 As with all lists in Exim, the default separator is a colon. However, because
32580 this is a sublist within the list of DNS blacklist domains, it is necessary
32581 either to double the separators like this:
32583 dnslists = black.list.tld/name.1::name.2
32585 or to change the separator character, like this:
32587 dnslists = black.list.tld/<;name.1;name.2
32589 If an item in the list is an IP address, it is inverted before the DNS
32590 blacklist domain is appended. If it is not an IP address, no inversion
32591 occurs. Consider this condition:
32593 dnslists = black.list.tld/<;192.168.1.2;a.domain
32595 The DNS lookups that occur are:
32597 2.1.168.192.black.list.tld
32598 a.domain.black.list.tld
32600 Once a DNS record has been found (that matches a specific IP return
32601 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
32602 are done. If there is a temporary DNS error, the rest of the sublist of domains
32603 or IP addresses is tried. A temporary error for the whole dnslists item occurs
32604 only if no other DNS lookup in this sublist succeeds. In other words, a
32605 successful lookup for any of the items in the sublist overrides a temporary
32606 error for a previous item.
32608 The ability to supply a list of items after the slash is in some sense just a
32609 syntactic convenience. These two examples have the same effect:
32611 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
32612 dnslists = black.list.tld/a.domain::b.domain
32614 However, when the data for the list is obtained from a lookup, the second form
32615 is usually much more convenient. Consider this example:
32617 deny dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
32618 ${lookup dnsdb {>|mxh=\
32619 $sender_address_domain} }} }
32620 message = The mail servers for the domain \
32621 $sender_address_domain \
32622 are listed at $dnslist_domain ($dnslist_value); \
32625 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
32626 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
32627 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
32628 of expanding the condition might be something like this:
32630 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
32632 Thus, this example checks whether or not the IP addresses of the sender
32633 domain's mail servers are on the Spamhaus black list.
32635 The key that was used for a successful DNS list lookup is put into the variable
32636 &$dnslist_matched$& (see section &<<SECID204>>&).
32641 .section "Data returned by DNS lists" "SECID203"
32642 .cindex "DNS list" "data returned from"
32643 DNS lists are constructed using address records in the DNS. The original RBL
32644 just used the address 127.0.0.1 on the right hand side of each record, but the
32645 RBL+ list and some other lists use a number of values with different meanings.
32646 The values used on the RBL+ list are:
32650 127.1.0.3 DUL and RBL
32652 127.1.0.5 RSS and RBL
32653 127.1.0.6 RSS and DUL
32654 127.1.0.7 RSS and DUL and RBL
32656 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
32657 different values. Some DNS lists may return more than one address record;
32658 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
32660 Values returned by a properly running DBSBL should be in the 127.0.0.0/8
32661 range. If a DNSBL operator loses control of the domain, lookups on it
32662 may start returning other addresses. Because of this, Exim now ignores
32663 returned values outside the 127/8 region.
32666 .section "Variables set from DNS lists" "SECID204"
32667 .cindex "expansion" "variables, set from DNS list"
32668 .cindex "DNS list" "variables set from"
32669 .vindex "&$dnslist_domain$&"
32670 .vindex "&$dnslist_matched$&"
32671 .vindex "&$dnslist_text$&"
32672 .vindex "&$dnslist_value$&"
32673 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
32674 the name of the overall domain that matched (for example,
32675 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
32676 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
32677 the DNS record. When the key is an IP address, it is not reversed in
32678 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
32679 cases, for example:
32681 deny dnslists = spamhaus.example
32683 the key is also available in another variable (in this case,
32684 &$sender_host_address$&). In more complicated cases, however, this is not true.
32685 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
32686 might generate a dnslists lookup like this:
32688 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
32690 If this condition succeeds, the value in &$dnslist_matched$& might be
32691 &`192.168.6.7`& (for example).
32693 If more than one address record is returned by the DNS lookup, all the IP
32694 addresses are included in &$dnslist_value$&, separated by commas and spaces.
32695 The variable &$dnslist_text$& contains the contents of any associated TXT
32696 record. For lists such as RBL+ the TXT record for a merged entry is often not
32697 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
32700 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
32701 &-- even if these appear before the condition in the ACL, they are not
32702 expanded until after it has failed. For example:
32704 deny hosts = !+local_networks
32705 message = $sender_host_address is listed \
32707 dnslists = rbl-plus.mail-abuse.example
32712 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
32713 .cindex "DNS list" "matching specific returned data"
32714 You can add an equals sign and an IP address after a &%dnslists%& domain name
32715 in order to restrict its action to DNS records with a matching right hand side.
32718 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
32720 rejects only those hosts that yield 127.0.0.2. Without this additional data,
32721 any address record is considered to be a match. For the moment, we assume
32722 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
32723 describes how multiple records are handled.
32725 More than one IP address may be given for checking, using a comma as a
32726 separator. These are alternatives &-- if any one of them matches, the
32727 &%dnslists%& condition is true. For example:
32729 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32731 If you want to specify a constraining address list and also specify names or IP
32732 addresses to be looked up, the constraining address list must be specified
32733 first. For example:
32735 deny dnslists = dsn.rfc-ignorant.org\
32736 =127.0.0.2/$sender_address_domain
32739 If the character &`&&`& is used instead of &`=`&, the comparison for each
32740 listed IP address is done by a bitwise &"and"& instead of by an equality test.
32741 In other words, the listed addresses are used as bit masks. The comparison is
32742 true if all the bits in the mask are present in the address that is being
32743 tested. For example:
32745 dnslists = a.b.c&0.0.0.3
32747 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
32748 want to test whether one bit or another bit is present (as opposed to both
32749 being present), you must use multiple values. For example:
32751 dnslists = a.b.c&0.0.0.1,0.0.0.2
32753 matches if the final component of the address is an odd number or two times
32758 .section "Negated DNS matching conditions" "SECID205"
32759 You can supply a negative list of IP addresses as part of a &%dnslists%&
32762 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32764 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32765 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
32767 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
32769 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32770 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
32771 words, the result of the test is inverted if an exclamation mark appears before
32772 the &`=`& (or the &`&&`&) sign.
32774 &*Note*&: This kind of negation is not the same as negation in a domain,
32775 host, or address list (which is why the syntax is different).
32777 If you are using just one list, the negation syntax does not gain you much. The
32778 previous example is precisely equivalent to
32780 deny dnslists = a.b.c
32781 !dnslists = a.b.c=127.0.0.2,127.0.0.3
32783 However, if you are using multiple lists, the negation syntax is clearer.
32784 Consider this example:
32786 deny dnslists = sbl.spamhaus.org : \
32788 dnsbl.njabl.org!=127.0.0.3 : \
32791 Using only positive lists, this would have to be:
32793 deny dnslists = sbl.spamhaus.org : \
32795 deny dnslists = dnsbl.njabl.org
32796 !dnslists = dnsbl.njabl.org=127.0.0.3
32797 deny dnslists = relays.ordb.org
32799 which is less clear, and harder to maintain.
32801 Negation can also be used with a bitwise-and restriction.
32802 The dnslists condition with only be trus if a result is returned
32803 by the lookup which, anded with the restriction, is all zeroes.
32806 deny dnslists = zen.spamhaus.org!&0.255.255.0
32812 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
32813 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
32814 thereby providing more than one IP address. When an item in a &%dnslists%& list
32815 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
32816 the match to specific results from the DNS lookup, there are two ways in which
32817 the checking can be handled. For example, consider the condition:
32819 dnslists = a.b.c=127.0.0.1
32821 What happens if the DNS lookup for the incoming IP address yields both
32822 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
32823 condition true because at least one given value was found, or is it false
32824 because at least one of the found values was not listed? And how does this
32825 affect negated conditions? Both possibilities are provided for with the help of
32826 additional separators &`==`& and &`=&&`&.
32829 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
32830 IP addresses matches one of the listed addresses. For the example above, the
32831 condition is true because 127.0.0.1 matches.
32833 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
32834 looked up IP addresses matches one of the listed addresses. If the condition is
32837 dnslists = a.b.c==127.0.0.1
32839 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32840 false because 127.0.0.2 is not listed. You would need to have:
32842 dnslists = a.b.c==127.0.0.1,127.0.0.2
32844 for the condition to be true.
32847 When &`!`& is used to negate IP address matching, it inverts the result, giving
32848 the precise opposite of the behaviour above. Thus:
32850 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
32851 addresses matches one of the listed addresses. Consider:
32853 dnslists = a.b.c!&0.0.0.1
32855 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32856 false because 127.0.0.1 matches.
32858 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
32859 looked up IP address that does not match. Consider:
32861 dnslists = a.b.c!=&0.0.0.1
32863 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32864 true, because 127.0.0.2 does not match. You would need to have:
32866 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
32868 for the condition to be false.
32870 When the DNS lookup yields only a single IP address, there is no difference
32871 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
32876 .section "Detailed information from merged DNS lists" "SECTmordetinf"
32877 .cindex "DNS list" "information from merged"
32878 When the facility for restricting the matching IP values in a DNS list is used,
32879 the text from the TXT record that is set in &$dnslist_text$& may not reflect
32880 the true reason for rejection. This happens when lists are merged and the IP
32881 address in the A record is used to distinguish them; unfortunately there is
32882 only one TXT record. One way round this is not to use merged lists, but that
32883 can be inefficient because it requires multiple DNS lookups where one would do
32884 in the vast majority of cases when the host of interest is not on any of the
32887 A less inefficient way of solving this problem is available. If
32888 two domain names, comma-separated, are given, the second is used first to
32889 do an initial check, making use of any IP value restrictions that are set.
32890 If there is a match, the first domain is used, without any IP value
32891 restrictions, to get the TXT record. As a byproduct of this, there is also
32892 a check that the IP being tested is indeed on the first list. The first
32893 domain is the one that is put in &$dnslist_domain$&. For example:
32896 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
32897 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32899 rejected because $sender_host_address is blacklisted \
32900 at $dnslist_domain\n$dnslist_text
32902 For the first blacklist item, this starts by doing a lookup in
32903 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
32904 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
32905 value, and as long as something is found, it looks for the corresponding TXT
32906 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
32907 The second blacklist item is processed similarly.
32909 If you are interested in more than one merged list, the same list must be
32910 given several times, but because the results of the DNS lookups are cached,
32911 the DNS calls themselves are not repeated. For example:
32914 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
32915 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
32916 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
32917 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32919 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
32920 values matches (or if no record is found), this is the only lookup that is
32921 done. Only if there is a match is one of the more specific lists consulted.
32925 .section "DNS lists and IPv6" "SECTmorednslistslast"
32926 .cindex "IPv6" "DNS black lists"
32927 .cindex "DNS list" "IPv6 usage"
32928 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
32929 nibble by nibble. For example, if the calling host's IP address is
32930 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
32932 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
32933 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
32935 (split over two lines here to fit on the page). Unfortunately, some of the DNS
32936 lists contain wildcard records, intended for IPv4, that interact badly with
32937 IPv6. For example, the DNS entry
32939 *.3.some.list.example. A 127.0.0.1
32941 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
32942 Unfortunately, it also matches the entire 3::/4 IPv6 network.
32944 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
32945 &%condition%& condition, as in this example:
32947 deny condition = ${if isip4{$sender_host_address}}
32948 dnslists = some.list.example
32951 If an explicit key is being used for a DNS lookup and it may be an IPv6
32952 address you should specify alternate list separators for both the outer
32953 (DNS list name) list and inner (lookup keys) list:
32955 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
32960 .section "Previously seen user and hosts" "SECTseen"
32961 .cindex "&%sseen%& ACL condition"
32962 .cindex greylisting
32963 The &%seen%& ACL condition can be used to test whether a
32964 situation has been previously met.
32965 It uses a hints database to record a timestamp against a key.
32966 host. The syntax of the condition is:
32968 &`seen =`& <&'time interval'&> &`/`& <&'options'&>
32973 defer seen = -5m / key=${sender_host_address}_$local_part@$domain
32975 in a RCPT ACL will implement simple greylisting.
32977 The parameters for the condition
32978 are an interval followed, slash-separated, by a list of options.
32979 The interval is taken as an offset before the current time,
32980 and used for the test.
32981 If the interval is preceded by a minus sign then the condition returns
32982 whether a record is found which is before the test time.
32983 Otherwise, the condition returns whether one is found which is since the
32986 Options are read in order with later ones overriding earlier ones.
32988 The default key is &$sender_host_address$&.
32989 An explicit key can be set using a &%key=value%& option.
32991 If a &%readonly%& option is given then
32992 no record create or update is done.
32993 If a &%write%& option is given then
32994 a record create or update is always done.
32995 An update is done if the test is for &"since"&.
32997 Creates and updates are marked with the current time.
32999 Finally, a &"before"& test which succeeds, and for which the record
33000 is old enough, will be refreshed with a timestamp of the test time.
33001 This can prevent tidying of the database from removing the entry.
33002 The interval for this is, by default, 10 days.
33003 An explicit interval can be set using a
33004 &%refresh=value%& option.
33006 Note that &"seen"& should be added to the list of hints databases
33007 for maintenance if this ACL condition is used.
33011 .section "Rate limiting incoming messages" "SECTratelimiting"
33012 .cindex "rate limiting" "client sending"
33013 .cindex "limiting client sending rates"
33014 .oindex "&%smtp_ratelimit_*%&"
33015 The &%ratelimit%& ACL condition can be used to measure and control the rate at
33016 which clients can send email. This is more powerful than the
33017 &%smtp_ratelimit_*%& options, because those options control the rate of
33018 commands in a single SMTP session only, whereas the &%ratelimit%& condition
33019 works across all connections (concurrent and sequential) from the same client
33020 host. The syntax of the &%ratelimit%& condition is:
33022 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
33024 If the average client sending rate is less than &'m'& messages per time
33025 period &'p'& then the condition is false; otherwise it is true.
33027 As a side-effect, the &%ratelimit%& condition sets the expansion variable
33028 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
33029 configured value of &'m'&, and &$sender_rate_period$& to the configured value
33032 The parameter &'p'& is the smoothing time constant, in the form of an Exim
33033 time interval, for example, &`8h`& for eight hours. A larger time constant
33034 means that it takes Exim longer to forget a client's past behaviour. The
33035 parameter &'m'& is the maximum number of messages that a client is permitted to
33036 send in each time interval. It also specifies the number of messages permitted
33037 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
33038 constant, you can allow a client to send more messages in a burst without
33039 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
33040 both small, messages must be sent at an even rate.
33042 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
33043 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
33044 when deploying the &%ratelimit%& ACL condition. The script prints usage
33045 instructions when it is run with no arguments.
33047 The key is used to look up the data for calculating the client's average
33048 sending rate. This data is stored in Exim's spool directory, alongside the
33049 retry and other hints databases. The default key is &$sender_host_address$&,
33050 which means Exim computes the sending rate of each client host IP address.
33051 By changing the key you can change how Exim identifies clients for the purpose
33052 of ratelimiting. For example, to limit the sending rate of each authenticated
33053 user, independent of the computer they are sending from, set the key to
33054 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
33055 example, &$authenticated_id$& is only meaningful if the client has
33056 authenticated (which you can check with the &%authenticated%& ACL condition).
33058 The lookup key does not have to identify clients: If you want to limit the
33059 rate at which a recipient receives messages, you can use the key
33060 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
33063 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
33064 specifies what Exim measures the rate of, for example, messages or recipients
33065 or bytes. You can adjust the measurement using the &%unique=%& and/or
33066 &%count=%& options. You can also control when Exim updates the recorded rate
33067 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
33068 separated by a slash, like the other parameters. They may appear in any order.
33070 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
33071 any options that alter the meaning of the stored data. The limit &'m'& is not
33072 stored, so you can alter the configured maximum rate and Exim will still
33073 remember clients' past behaviour. If you change the &%per_*%& mode or add or
33074 remove the &%unique=%& option, the lookup key changes so Exim will forget past
33075 behaviour. The lookup key is not affected by changes to the update mode and
33076 the &%count=%& option.
33079 .section "Ratelimit options for what is being measured" "ratoptmea"
33080 .cindex "rate limiting" "per_* options"
33081 The &%per_conn%& option limits the client's connection rate. It is not
33082 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
33083 &%acl_not_smtp_start%& ACLs.
33085 The &%per_mail%& option limits the client's rate of sending messages. This is
33086 the default if none of the &%per_*%& options is specified. It can be used in
33087 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
33088 &%acl_smtp_data%&, or &%acl_not_smtp%&.
33090 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
33091 the same ACLs as the &%per_mail%& option, though it is best to use this option
33092 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
33093 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
33094 in its MAIL command, which may be inaccurate or completely missing. You can
33095 follow the limit &'m'& in the configuration with K, M, or G to specify limits
33096 in kilobytes, megabytes, or gigabytes, respectively.
33098 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
33099 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
33100 &%acl_smtp_mime%&, or &%acl_smtp_data%& ACLs. In
33101 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
33102 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
33103 in either case the rate limiting engine will see a message with many
33104 recipients as a large high-speed burst.
33106 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
33107 number of different recipients that the client has sent messages to in the
33108 last time period. That is, if the client repeatedly sends messages to the same
33109 recipient, its measured rate is not increased. This option can only be used in
33112 The &%per_cmd%& option causes Exim to recompute the rate every time the
33113 condition is processed. This can be used to limit the rate of any SMTP
33114 command. If it is used in multiple ACLs it can limit the aggregate rate of
33115 multiple different commands.
33117 The &%count=%& option can be used to alter how much Exim adds to the client's
33118 measured rate. For example, the &%per_byte%& option is equivalent to
33119 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
33120 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
33121 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
33123 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
33126 .section "Ratelimit update modes" "ratoptupd"
33127 .cindex "rate limiting" "reading data without updating"
33128 You can specify one of three options with the &%ratelimit%& condition to
33129 control when its database is updated. This section describes the &%readonly%&
33130 mode, and the next section describes the &%strict%& and &%leaky%& modes.
33132 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
33133 previously-computed rate to check against the limit.
33135 For example, you can test the client's sending rate and deny it access (when
33136 it is too fast) in the connect ACL. If the client passes this check then it
33137 can go on to send a message, in which case its recorded rate will be updated
33138 in the MAIL ACL. Subsequent connections from the same client will check this
33142 deny ratelimit = 100 / 5m / readonly
33143 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
33144 (max $sender_rate_limit)
33147 warn ratelimit = 100 / 5m / strict
33148 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
33149 (max $sender_rate_limit)
33152 If Exim encounters multiple &%ratelimit%& conditions with the same key when
33153 processing a message then it may increase the client's measured rate more than
33154 it should. For example, this will happen if you check the &%per_rcpt%& option
33155 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
33156 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
33157 multiple update problems by using the &%readonly%& option on later ratelimit
33160 The &%per_*%& options described above do not make sense in some ACLs. If you
33161 use a &%per_*%& option in an ACL where it is not normally permitted then the
33162 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
33163 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
33164 next section) so you must specify the &%readonly%& option explicitly.
33167 .section "Ratelimit options for handling fast clients" "ratoptfast"
33168 .cindex "rate limiting" "strict and leaky modes"
33169 If a client's average rate is greater than the maximum, the rate limiting
33170 engine can react in two possible ways, depending on the presence of the
33171 &%strict%& or &%leaky%& update modes. This is independent of the other
33172 counter-measures (such as rejecting the message) that may be specified by the
33175 The &%leaky%& (default) option means that the client's recorded rate is not
33176 updated if it is above the limit. The effect of this is that Exim measures the
33177 client's average rate of successfully sent email,
33178 up to the given limit.
33179 This is appropriate if the countermeasure when the condition is true
33180 consists of refusing the message, and
33181 is generally the better choice if you have clients that retry automatically.
33182 If the action when true is anything more complex then this option is
33183 likely not what is wanted.
33185 The &%strict%& option means that the client's recorded rate is always
33186 updated. The effect of this is that Exim measures the client's average rate
33187 of attempts to send email, which can be much higher than the maximum it is
33188 actually allowed. If the client is over the limit it may be subjected to
33189 counter-measures by the ACL. It must slow down and allow sufficient time to
33190 pass that its computed rate falls below the maximum before it can send email
33191 again. The time (the number of smoothing periods) it must wait and not
33192 attempt to send mail can be calculated with this formula:
33194 ln(peakrate/maxrate)
33198 .section "Limiting the rate of different events" "ratoptuniq"
33199 .cindex "rate limiting" "counting unique events"
33200 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
33201 rate of different events. For example, the &%per_addr%& option uses this
33202 mechanism to count the number of different recipients that the client has
33203 sent messages to in the last time period; it is equivalent to
33204 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
33205 measure the rate that a client uses different sender addresses with the
33206 options &`per_mail/unique=$sender_address`&.
33208 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
33209 has seen for that key. The whole set is thrown away when it is older than the
33210 rate smoothing period &'p'&, so each different event is counted at most once
33211 per period. In the &%leaky%& update mode, an event that causes the client to
33212 go over the limit is not added to the set, in the same way that the client's
33213 recorded rate is not updated in the same situation.
33215 When you combine the &%unique=%& and &%readonly%& options, the specific
33216 &%unique=%& value is ignored, and Exim just retrieves the client's stored
33219 The &%unique=%& mechanism needs more space in the ratelimit database than the
33220 other &%ratelimit%& options in order to store the event set. The number of
33221 unique values is potentially as large as the rate limit, so the extra space
33222 required increases with larger limits.
33224 The uniqueification is not perfect: there is a small probability that Exim
33225 will think a new event has happened before. If the sender's rate is less than
33226 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
33227 the measured rate can go above the limit, in which case Exim may under-count
33228 events by a significant margin. Fortunately, if the rate is high enough (2.7
33229 times the limit) that the false positive rate goes above 9%, then Exim will
33230 throw away the over-full event set before the measured rate falls below the
33231 limit. Therefore the only harm should be that exceptionally high sending rates
33232 are logged incorrectly; any countermeasures you configure will be as effective
33236 .section "Using rate limiting" "useratlim"
33237 Exim's other ACL facilities are used to define what counter-measures are taken
33238 when the rate limit is exceeded. This might be anything from logging a warning
33239 (for example, while measuring existing sending rates in order to define
33240 policy), through time delays to slow down fast senders, up to rejecting the
33241 message. For example:
33243 # Log all senders' rates
33244 warn ratelimit = 0 / 1h / strict
33245 log_message = Sender rate $sender_rate / $sender_rate_period
33247 # Slow down fast senders; note the need to truncate $sender_rate
33248 # at the decimal point.
33249 warn ratelimit = 100 / 1h / per_rcpt / strict
33250 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
33251 $sender_rate_limit }s
33253 # Keep authenticated users under control
33254 deny authenticated = *
33255 ratelimit = 100 / 1d / strict / $authenticated_id
33257 # System-wide rate limit
33258 defer ratelimit = 10 / 1s / $primary_hostname
33259 message = Sorry, too busy. Try again later.
33261 # Restrict incoming rate from each host, with a default
33262 # set using a macro and special cases looked up in a table.
33263 defer ratelimit = ${lookup {$sender_host_address} \
33264 cdb {DB/ratelimits.cdb} \
33265 {$value} {RATELIMIT} }
33266 message = Sender rate exceeds $sender_rate_limit \
33267 messages per $sender_rate_period
33269 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
33270 especially with the &%per_rcpt%& option, you may suffer from a performance
33271 bottleneck caused by locking on the ratelimit hints database. Apart from
33272 making your ACLs less complicated, you can reduce the problem by using a
33273 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
33274 this means that Exim will lose its hints data after a reboot (including retry
33275 hints, the callout cache, and ratelimit data).
33279 .section "Address verification" "SECTaddressverification"
33280 .cindex "verifying address" "options for"
33281 .cindex "policy control" "address verification"
33282 Several of the &%verify%& conditions described in section
33283 &<<SECTaclconditions>>& cause addresses to be verified. Section
33284 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
33285 The verification conditions can be followed by options that modify the
33286 verification process. The options are separated from the keyword and from each
33287 other by slashes, and some of them contain parameters. For example:
33289 verify = sender/callout
33290 verify = recipient/defer_ok/callout=10s,defer_ok
33292 The first stage of address verification, which always happens, is to run the
33293 address through the routers, in &"verify mode"&. Routers can detect the
33294 difference between verification and routing for delivery, and their actions can
33295 be varied by a number of generic options such as &%verify%& and &%verify_only%&
33296 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
33297 The available options are as follows:
33300 If the &%callout%& option is specified, successful routing to one or more
33301 remote hosts is followed by a &"callout"& to those hosts as an additional
33302 check. Callouts and their sub-options are discussed in the next section.
33304 If there is a defer error while doing verification routing, the ACL
33305 normally returns &"defer"&. However, if you include &%defer_ok%& in the
33306 options, the condition is forced to be true instead. Note that this is a main
33307 verification option as well as a suboption for callouts.
33309 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
33310 discusses the reporting of sender address verification failures.
33312 The &%success_on_redirect%& option causes verification always to succeed
33313 immediately after a successful redirection. By default, if a redirection
33314 generates just one address, that address is also verified. See further
33315 discussion in section &<<SECTredirwhilveri>>&.
33317 If the &%quota%& option is specified for recipient verify,
33318 successful routing to an appendfile transport is followed by a call into
33319 the transport to evaluate the quota status for the recipient.
33320 No actual delivery is done, but verification will succeed if the quota
33321 is sufficient for the message (if the sender gave a message size) or
33322 not already exceeded (otherwise).
33325 .cindex "verifying address" "differentiating failures"
33326 .vindex "&$recipient_verify_failure$&"
33327 .vindex "&$sender_verify_failure$&"
33328 .vindex "&$acl_verify_message$&"
33329 After an address verification failure, &$acl_verify_message$& contains the
33330 error message that is associated with the failure. It can be preserved by
33333 warn !verify = sender
33334 set acl_m0 = $acl_verify_message
33336 If you are writing your own custom rejection message or log message when
33337 denying access, you can use this variable to include information about the
33338 verification failure.
33339 This variable is cleared at the end of processing the ACL verb.
33341 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
33342 appropriate) contains one of the following words:
33345 &%qualify%&: The address was unqualified (no domain), and the message
33346 was neither local nor came from an exempted host.
33348 &%route%&: Routing failed.
33350 &%mail%&: Routing succeeded, and a callout was attempted; rejection
33351 occurred at or before the MAIL command (that is, on initial
33352 connection, HELO, or MAIL).
33354 &%recipient%&: The RCPT command in a callout was rejected.
33356 &%postmaster%&: The postmaster check in a callout was rejected.
33358 &%quota%&: The quota check for a local recipient did non pass.
33361 The main use of these variables is expected to be to distinguish between
33362 rejections of MAIL and rejections of RCPT in callouts.
33364 The above variables may also be set after a &*successful*&
33365 address verification to:
33368 &%random%&: A random local-part callout succeeded
33374 .section "Callout verification" "SECTcallver"
33375 .cindex "verifying address" "by callout"
33376 .cindex "callout" "verification"
33377 .cindex "SMTP" "callout verification"
33378 For non-local addresses, routing verifies the domain, but is unable to do any
33379 checking of the local part. There are situations where some means of verifying
33380 the local part is desirable. One way this can be done is to make an SMTP
33381 &'callback'& to a delivery host for the sender address or a &'callforward'& to
33382 a subsequent host for a recipient address, to see if the host accepts the
33383 address. We use the term &'callout'& to cover both cases. Note that for a
33384 sender address, the callback is not to the client host that is trying to
33385 deliver the message, but to one of the hosts that accepts incoming mail for the
33388 Exim does not do callouts by default. If you want them to happen, you must
33389 request them by setting appropriate options on the &%verify%& condition, as
33390 described below. This facility should be used with care, because it can add a
33391 lot of resource usage to the cost of verifying an address. However, Exim does
33392 cache the results of callouts, which helps to reduce the cost. Details of
33393 caching are in section &<<SECTcallvercache>>&.
33395 Recipient callouts are usually used only between hosts that are controlled by
33396 the same administration. For example, a corporate gateway host could use
33397 callouts to check for valid recipients on an internal mailserver. A successful
33398 callout does not guarantee that a real delivery to the address would succeed;
33399 on the other hand, a failing callout does guarantee that a delivery would fail.
33401 If the &%callout%& option is present on a condition that verifies an address, a
33402 second stage of verification occurs if the address is successfully routed to
33403 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
33404 &(manualroute)& router, where the router specifies the hosts. However, if a
33405 router that does not set up hosts routes to an &(smtp)& transport with a
33406 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
33407 &%hosts_override%& set, its hosts are always used, whether or not the router
33408 supplies a host list.
33409 Callouts are only supported on &(smtp)& transports.
33411 The port that is used is taken from the transport, if it is specified and is a
33412 remote transport. (For routers that do verification only, no transport need be
33413 specified.) Otherwise, the default SMTP port is used. If a remote transport
33414 specifies an outgoing interface, this is used; otherwise the interface is not
33415 specified. Likewise, the text that is used for the HELO command is taken from
33416 the transport's &%helo_data%& option; if there is no transport, the value of
33417 &$smtp_active_hostname$& is used.
33419 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
33420 test whether a bounce message could be delivered to the sender address. The
33421 following SMTP commands are sent:
33423 &`HELO `&<&'local host name'&>
33425 &`RCPT TO:`&<&'the address to be tested'&>
33428 LHLO is used instead of HELO if the transport's &%protocol%& option is
33431 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
33434 A recipient callout check is similar. By default, it also uses an empty address
33435 for the sender. This default is chosen because most hosts do not make use of
33436 the sender address when verifying a recipient. Using the same address means
33437 that a single cache entry can be used for each recipient. Some sites, however,
33438 do make use of the sender address when verifying. These are catered for by the
33439 &%use_sender%& and &%use_postmaster%& options, described in the next section.
33441 If the response to the RCPT command is a 2&'xx'& code, the verification
33442 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
33443 Exim tries the next host, if any. If there is a problem with all the remote
33444 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
33445 &%callout%& option is given, in which case the condition is forced to succeed.
33447 .cindex "SMTP" "output flushing, disabling for callout"
33448 A callout may take a little time. For this reason, Exim normally flushes SMTP
33449 output before performing a callout in an ACL, to avoid unexpected timeouts in
33450 clients when the SMTP PIPELINING extension is in use. The flushing can be
33451 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
33456 .section "Additional parameters for callouts" "CALLaddparcall"
33457 .cindex "callout" "additional parameters for"
33458 The &%callout%& option can be followed by an equals sign and a number of
33459 optional parameters, separated by commas. For example:
33461 verify = recipient/callout=10s,defer_ok
33463 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
33464 separate verify options, is retained for backwards compatibility, but is now
33465 deprecated. The additional parameters for &%callout%& are as follows:
33469 .vitem <&'a&~time&~interval'&>
33470 .cindex "callout" "timeout, specifying"
33471 This specifies the timeout that applies for the callout attempt to each host.
33474 verify = sender/callout=5s
33476 The default is 30 seconds. The timeout is used for each response from the
33477 remote host. It is also used for the initial connection, unless overridden by
33478 the &%connect%& parameter.
33481 .vitem &*connect&~=&~*&<&'time&~interval'&>
33482 .cindex "callout" "connection timeout, specifying"
33483 This parameter makes it possible to set a different (usually smaller) timeout
33484 for making the SMTP connection. For example:
33486 verify = sender/callout=5s,connect=1s
33488 If not specified, this timeout defaults to the general timeout value.
33490 .vitem &*defer_ok*&
33491 .cindex "callout" "defer, action on"
33492 When this parameter is present, failure to contact any host, or any other kind
33493 of temporary error, is treated as success by the ACL. However, the cache is not
33494 updated in this circumstance.
33496 .vitem &*fullpostmaster*&
33497 .cindex "callout" "full postmaster check"
33498 This operates like the &%postmaster%& option (see below), but if the check for
33499 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
33500 accordance with the specification in RFC 2821. The RFC states that the
33501 unqualified address &'postmaster'& should be accepted.
33504 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
33505 .cindex "callout" "sender when verifying header"
33506 When verifying addresses in header lines using the &%header_sender%&
33507 verification option, Exim behaves by default as if the addresses are envelope
33508 sender addresses from a message. Callout verification therefore tests to see
33509 whether a bounce message could be delivered, by using an empty address in the
33510 MAIL command. However, it is arguable that these addresses might never be used
33511 as envelope senders, and could therefore justifiably reject bounce messages
33512 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
33513 address to use in the MAIL command. For example:
33515 require verify = header_sender/callout=mailfrom=abcd@x.y.z
33517 This parameter is available only for the &%header_sender%& verification option.
33520 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
33521 .cindex "callout" "overall timeout, specifying"
33522 This parameter sets an overall timeout for performing a callout verification.
33525 verify = sender/callout=5s,maxwait=30s
33527 This timeout defaults to four times the callout timeout for individual SMTP
33528 commands. The overall timeout applies when there is more than one host that can
33529 be tried. The timeout is checked before trying the next host. This prevents
33530 very long delays if there are a large number of hosts and all are timing out
33531 (for example, when network connections are timing out).
33534 .vitem &*no_cache*&
33535 .cindex "callout" "cache, suppressing"
33536 .cindex "caching callout, suppressing"
33537 When this parameter is given, the callout cache is neither read nor updated.
33539 .vitem &*postmaster*&
33540 .cindex "callout" "postmaster; checking"
33541 When this parameter is set, a successful callout check is followed by a similar
33542 check for the local part &'postmaster'& at the same domain. If this address is
33543 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
33544 the postmaster check is recorded in a cache record; if it is a failure, this is
33545 used to fail subsequent callouts for the domain without a connection being
33546 made, until the cache record expires.
33548 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
33549 The postmaster check uses an empty sender in the MAIL command by default.
33550 You can use this parameter to do a postmaster check using a different address.
33553 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
33555 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
33556 one overrides. The &%postmaster%& parameter is equivalent to this example:
33558 require verify = sender/callout=postmaster_mailfrom=
33560 &*Warning*&: The caching arrangements for postmaster checking do not take
33561 account of the sender address. It is assumed that either the empty address or
33562 a fixed non-empty address will be used. All that Exim remembers is that the
33563 postmaster check for the domain succeeded or failed.
33567 .cindex "callout" "&""random""& check"
33568 When this parameter is set, before doing the normal callout check, Exim does a
33569 check for a &"random"& local part at the same domain. The local part is not
33570 really random &-- it is defined by the expansion of the option
33571 &%callout_random_local_part%&, which defaults to
33573 $primary_hostname-$tod_epoch-testing
33575 The idea here is to try to determine whether the remote host accepts all local
33576 parts without checking. If it does, there is no point in doing callouts for
33577 specific local parts. If the &"random"& check succeeds, the result is saved in
33578 a cache record, and used to force the current and subsequent callout checks to
33579 succeed without a connection being made, until the cache record expires.
33581 .vitem &*use_postmaster*&
33582 .cindex "callout" "sender for recipient check"
33583 This parameter applies to recipient callouts only. For example:
33585 deny !verify = recipient/callout=use_postmaster
33587 .vindex "&$qualify_domain$&"
33588 It causes a non-empty postmaster address to be used in the MAIL command when
33589 performing the callout for the recipient, and also for a &"random"& check if
33590 that is configured. The local part of the address is &`postmaster`& and the
33591 domain is the contents of &$qualify_domain$&.
33593 .vitem &*use_sender*&
33594 This option applies to recipient callouts only. For example:
33596 require verify = recipient/callout=use_sender
33598 It causes the message's actual sender address to be used in the MAIL
33599 command when performing the callout, instead of an empty address. There is no
33600 need to use this option unless you know that the called hosts make use of the
33601 sender when checking recipients. If used indiscriminately, it reduces the
33602 usefulness of callout caching.
33605 This option applies to recipient callouts only. For example:
33607 require verify = recipient/callout=use_sender,hold
33609 It causes the connection to be held open and used for any further recipients
33610 and for eventual delivery (should that be done quickly).
33611 Doing this saves on TCP and SMTP startup costs, and TLS costs also
33612 when that is used for the connections.
33613 The advantage is only gained if there are no callout cache hits
33614 (which could be enforced by the no_cache option),
33615 if the use_sender option is used,
33616 if neither the random nor the use_postmaster option is used,
33617 and if no other callouts intervene.
33620 If you use any of the parameters that set a non-empty sender for the MAIL
33621 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
33622 &%use_sender%&), you should think about possible loops. Recipient checking is
33623 usually done between two hosts that are under the same management, and the host
33624 that receives the callouts is not normally configured to do callouts itself.
33625 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
33626 these circumstances.
33628 However, if you use a non-empty sender address for a callout to an arbitrary
33629 host, there is the likelihood that the remote host will itself initiate a
33630 callout check back to your host. As it is checking what appears to be a message
33631 sender, it is likely to use an empty address in MAIL, thus avoiding a
33632 callout loop. However, to be on the safe side it would be best to set up your
33633 own ACLs so that they do not do sender verification checks when the recipient
33634 is the address you use for header sender or postmaster callout checking.
33636 Another issue to think about when using non-empty senders for callouts is
33637 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
33638 by the sender/recipient combination; thus, for any given recipient, many more
33639 actual callouts are performed than when an empty sender or postmaster is used.
33644 .section "Callout caching" "SECTcallvercache"
33645 .cindex "hints database" "callout cache"
33646 .cindex "callout" "cache, description of"
33647 .cindex "caching" "callout"
33648 Exim caches the results of callouts in order to reduce the amount of resources
33649 used, unless you specify the &%no_cache%& parameter with the &%callout%&
33650 option. A hints database called &"callout"& is used for the cache. Two
33651 different record types are used: one records the result of a callout check for
33652 a specific address, and the other records information that applies to the
33653 entire domain (for example, that it accepts the local part &'postmaster'&).
33655 When an original callout fails, a detailed SMTP error message is given about
33656 the failure. However, for subsequent failures use the cache data, this message
33659 The expiry times for negative and positive address cache records are
33660 independent, and can be set by the global options &%callout_negative_expire%&
33661 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
33663 If a host gives a negative response to an SMTP connection, or rejects any
33664 commands up to and including
33668 (but not including the MAIL command with a non-empty address),
33669 any callout attempt is bound to fail. Exim remembers such failures in a
33670 domain cache record, which it uses to fail callouts for the domain without
33671 making new connections, until the domain record times out. There are two
33672 separate expiry times for domain cache records:
33673 &%callout_domain_negative_expire%& (default 3h) and
33674 &%callout_domain_positive_expire%& (default 7d).
33676 Domain records expire when the negative expiry time is reached if callouts
33677 cannot be made for the domain, or if the postmaster check failed.
33678 Otherwise, they expire when the positive expiry time is reached. This
33679 ensures that, for example, a host that stops accepting &"random"& local parts
33680 will eventually be noticed.
33682 The callout caching mechanism is based on the domain of the address that is
33683 being tested. If the domain routes to several hosts, it is assumed that their
33684 behaviour will be the same.
33688 .section "Quota caching" "SECTquotacache"
33689 .cindex "hints database" "quota cache"
33690 .cindex "quota" "cache, description of"
33691 .cindex "caching" "quota"
33692 Exim caches the results of quota verification
33693 in order to reduce the amount of resources used.
33694 The &"callout"& hints database is used.
33696 The default cache periods are five minutes for a positive (good) result
33697 and one hour for a negative result.
33698 To change the periods the &%quota%& option can be followed by an equals sign
33699 and a number of optional paramemters, separated by commas.
33702 verify = recipient/quota=cachepos=1h,cacheneg=1d
33704 Possible parameters are:
33706 .vitem &*cachepos&~=&~*&<&'time&~interval'&>
33707 .cindex "quota cache" "positive entry expiry, specifying"
33708 Set the lifetime for a positive cache entry.
33709 A value of zero seconds is legitimate.
33711 .vitem &*cacheneg&~=&~*&<&'time&~interval'&>
33712 .cindex "quota cache" "negative entry expiry, specifying"
33713 As above, for a negative entry.
33715 .vitem &*no_cache*&
33716 Set both positive and negative lifetimes to zero.
33718 .section "Sender address verification reporting" "SECTsenaddver"
33719 .cindex "verifying" "suppressing error details"
33720 See section &<<SECTaddressverification>>& for a general discussion of
33721 verification. When sender verification fails in an ACL, the details of the
33722 failure are given as additional output lines before the 550 response to the
33723 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
33726 MAIL FROM:<xyz@abc.example>
33728 RCPT TO:<pqr@def.example>
33729 550-Verification failed for <xyz@abc.example>
33730 550-Called: 192.168.34.43
33731 550-Sent: RCPT TO:<xyz@abc.example>
33732 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
33733 550 Sender verification failed
33735 If more than one RCPT command fails in the same way, the details are given
33736 only for the first of them. However, some administrators do not want to send
33737 out this much information. You can suppress the details by adding
33738 &`/no_details`& to the ACL statement that requests sender verification. For
33741 verify = sender/no_details
33744 .section "Redirection while verifying" "SECTredirwhilveri"
33745 .cindex "verifying" "redirection while"
33746 .cindex "address redirection" "while verifying"
33747 A dilemma arises when a local address is redirected by aliasing or forwarding
33748 during verification: should the generated addresses themselves be verified,
33749 or should the successful expansion of the original address be enough to verify
33750 it? By default, Exim takes the following pragmatic approach:
33753 When an incoming address is redirected to just one child address, verification
33754 continues with the child address, and if that fails to verify, the original
33755 verification also fails.
33757 When an incoming address is redirected to more than one child address,
33758 verification does not continue. A success result is returned.
33761 This seems the most reasonable behaviour for the common use of aliasing as a
33762 way of redirecting different local parts to the same mailbox. It means, for
33763 example, that a pair of alias entries of the form
33766 aw123: :fail: Gone away, no forwarding address
33768 work as expected, with both local parts causing verification failure. When a
33769 redirection generates more than one address, the behaviour is more like a
33770 mailing list, where the existence of the alias itself is sufficient for
33771 verification to succeed.
33773 It is possible, however, to change the default behaviour so that all successful
33774 redirections count as successful verifications, however many new addresses are
33775 generated. This is specified by the &%success_on_redirect%& verification
33776 option. For example:
33778 require verify = recipient/success_on_redirect/callout=10s
33780 In this example, verification succeeds if a router generates a new address, and
33781 the callout does not occur, because no address was routed to a remote host.
33783 When verification is being tested via the &%-bv%& option, the treatment of
33784 redirections is as just described, unless the &%-v%& or any debugging option is
33785 also specified. In that case, full verification is done for every generated
33786 address and a report is output for each of them.
33790 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
33791 .cindex "CSA" "verifying"
33792 Client SMTP Authorization is a system that allows a site to advertise
33793 which machines are and are not permitted to send email. This is done by placing
33794 special SRV records in the DNS; these are looked up using the client's HELO
33795 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
33796 Authorization checks in Exim are performed by the ACL condition:
33800 This fails if the client is not authorized. If there is a DNS problem, or if no
33801 valid CSA SRV record is found, or if the client is authorized, the condition
33802 succeeds. These three cases can be distinguished using the expansion variable
33803 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
33804 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
33805 be likely to cause problems for legitimate email.
33807 The error messages produced by the CSA code include slightly more
33808 detail. If &$csa_status$& is &"defer"&, this may be because of problems
33809 looking up the CSA SRV record, or problems looking up the CSA target
33810 address record. There are four reasons for &$csa_status$& being &"fail"&:
33813 The client's host name is explicitly not authorized.
33815 The client's IP address does not match any of the CSA target IP addresses.
33817 The client's host name is authorized but it has no valid target IP addresses
33818 (for example, the target's addresses are IPv6 and the client is using IPv4).
33820 The client's host name has no CSA SRV record but a parent domain has asserted
33821 that all subdomains must be explicitly authorized.
33824 The &%csa%& verification condition can take an argument which is the domain to
33825 use for the DNS query. The default is:
33827 verify = csa/$sender_helo_name
33829 This implementation includes an extension to CSA. If the query domain
33830 is an address literal such as [192.0.2.95], or if it is a bare IP
33831 address, Exim searches for CSA SRV records in the reverse DNS as if
33832 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
33835 verify = csa/$sender_host_address
33837 In fact, this is the check that Exim performs if the client does not say HELO.
33838 This extension can be turned off by setting the main configuration option
33839 &%dns_csa_use_reverse%& to be false.
33841 If a CSA SRV record is not found for the domain itself, a search
33842 is performed through its parent domains for a record which might be
33843 making assertions about subdomains. The maximum depth of this search is limited
33844 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
33845 default. Exim does not look for CSA SRV records in a top level domain, so the
33846 default settings handle HELO domains as long as seven
33847 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
33848 of legitimate HELO domains.
33850 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
33851 direct SRV lookups, this is not sufficient because of the extra parent domain
33852 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
33853 addresses into lookups in the reverse DNS space. The result of a successful
33856 ${lookup dnsdb {csa=$sender_helo_name}}
33858 has two space-separated fields: an authorization code and a target host name.
33859 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
33860 authorization required but absent, or &"?"& for unknown.
33865 .section "Bounce address tag validation" "SECTverifyPRVS"
33866 .cindex "BATV, verifying"
33867 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
33868 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
33869 Genuine incoming bounce messages should therefore always be addressed to
33870 recipients that have a valid tag. This scheme is a way of detecting unwanted
33871 bounce messages caused by sender address forgeries (often called &"collateral
33872 spam"&), because the recipients of such messages do not include valid tags.
33874 There are two expansion items to help with the implementation of the BATV
33875 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
33876 the original envelope sender address by using a simple key to add a hash of the
33877 address and some time-based randomizing information. The &%prvs%& expansion
33878 item creates a signed address, and the &%prvscheck%& expansion item checks one.
33879 The syntax of these expansion items is described in section
33880 &<<SECTexpansionitems>>&.
33881 The validity period on signed addresses is seven days.
33883 As an example, suppose the secret per-address keys are stored in an MySQL
33884 database. A query to look up the key for an address could be defined as a macro
33887 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
33888 WHERE sender='${quote_mysql:$prvscheck_address}'\
33891 Suppose also that the senders who make use of BATV are defined by an address
33892 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
33895 # Bounces: drop unsigned addresses for BATV senders
33897 recipients = +batv_senders
33898 message = This address does not send an unsigned reverse path
33900 # Bounces: In case of prvs-signed address, check signature.
33902 condition = ${prvscheck {$local_part@$domain}\
33903 {PRVSCHECK_SQL}{1}}
33904 !condition = $prvscheck_result
33905 message = Invalid reverse path signature.
33907 The first statement rejects recipients for bounce messages that are addressed
33908 to plain BATV sender addresses, because it is known that BATV senders do not
33909 send out messages with plain sender addresses. The second statement rejects
33910 recipients that are prvs-signed, but with invalid signatures (either because
33911 the key is wrong, or the signature has timed out).
33913 A non-prvs-signed address is not rejected by the second statement, because the
33914 &%prvscheck%& expansion yields an empty string if its first argument is not a
33915 prvs-signed address, thus causing the &%condition%& condition to be false. If
33916 the first argument is a syntactically valid prvs-signed address, the yield is
33917 the third string (in this case &"1"&), whether or not the cryptographic and
33918 timeout checks succeed. The &$prvscheck_result$& variable contains the result
33919 of the checks (empty for failure, &"1"& for success).
33921 There is one more issue you must consider when implementing prvs-signing:
33922 you have to ensure that the routers accept prvs-signed addresses and
33923 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
33924 router to remove the signature with a configuration along these lines:
33928 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
33930 This works because, if the third argument of &%prvscheck%& is empty, the result
33931 of the expansion of a prvs-signed address is the decoded value of the original
33932 address. This router should probably be the first of your routers that handles
33935 To create BATV-signed addresses in the first place, a transport of this form
33938 external_smtp_batv:
33940 return_path = ${prvs {$return_path} \
33941 {${lookup mysql{SELECT \
33942 secret FROM batv_prvs WHERE \
33943 sender='${quote_mysql:$sender_address}'} \
33946 If no key can be found for the existing return path, no signing takes place.
33950 .section "Using an ACL to control relaying" "SECTrelaycontrol"
33951 .cindex "&ACL;" "relay control"
33952 .cindex "relaying" "control by ACL"
33953 .cindex "policy control" "relay control"
33954 An MTA is said to &'relay'& a message if it receives it from some host and
33955 delivers it directly to another host as a result of a remote address contained
33956 within it. Redirecting a local address via an alias or forward file and then
33957 passing the message on to another host is not relaying,
33958 .cindex "&""percent hack""&"
33959 but a redirection as a result of the &"percent hack"& is.
33961 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
33962 A host which is acting as a gateway or an MX backup is concerned with incoming
33963 relaying from arbitrary hosts to a specific set of domains. On the other hand,
33964 a host which is acting as a smart host for a number of clients is concerned
33965 with outgoing relaying from those clients to the Internet at large. Often the
33966 same host is fulfilling both functions,
33968 . as illustrated in the diagram below,
33970 but in principle these two kinds of relaying are entirely independent. What is
33971 not wanted is the transmission of mail from arbitrary remote hosts through your
33972 system to arbitrary domains.
33975 You can implement relay control by means of suitable statements in the ACL that
33976 runs for each RCPT command. For convenience, it is often easiest to use
33977 Exim's named list facility to define the domains and hosts involved. For
33978 example, suppose you want to do the following:
33981 Deliver a number of domains to mailboxes on the local host (or process them
33982 locally in some other way). Let's say these are &'my.dom1.example'& and
33983 &'my.dom2.example'&.
33985 Relay mail for a number of other domains for which you are the secondary MX.
33986 These might be &'friend1.example'& and &'friend2.example'&.
33988 Relay mail from the hosts on your local LAN, to whatever domains are involved.
33989 Suppose your LAN is 192.168.45.0/24.
33993 In the main part of the configuration, you put the following definitions:
33995 domainlist local_domains = my.dom1.example : my.dom2.example
33996 domainlist relay_to_domains = friend1.example : friend2.example
33997 hostlist relay_from_hosts = 192.168.45.0/24
33999 Now you can use these definitions in the ACL that is run for every RCPT
34003 accept domains = +local_domains : +relay_to_domains
34004 accept hosts = +relay_from_hosts
34006 The first statement accepts any RCPT command that contains an address in
34007 the local or relay domains. For any other domain, control passes to the second
34008 statement, which accepts the command only if it comes from one of the relay
34009 hosts. In practice, you will probably want to make your ACL more sophisticated
34010 than this, for example, by including sender and recipient verification. The
34011 default configuration includes a more comprehensive example, which is described
34012 in chapter &<<CHAPdefconfil>>&.
34016 .section "Checking a relay configuration" "SECTcheralcon"
34017 .cindex "relaying" "checking control of"
34018 You can check the relay characteristics of your configuration in the same way
34019 that you can test any ACL behaviour for an incoming SMTP connection, by using
34020 the &%-bh%& option to run a fake SMTP session with which you interact.
34025 . ////////////////////////////////////////////////////////////////////////////
34026 . ////////////////////////////////////////////////////////////////////////////
34028 .chapter "Content scanning at ACL time" "CHAPexiscan"
34029 .scindex IIDcosca "content scanning" "at ACL time"
34030 The extension of Exim to include content scanning at ACL time, formerly known
34031 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
34032 was integrated into the main source for Exim release 4.50, and Tom continues to
34033 maintain it. Most of the wording of this chapter is taken from Tom's
34036 It is also possible to scan the content of messages at other times. The
34037 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
34038 scanning after all the ACLs have run. A transport filter can be used to scan
34039 messages at delivery time (see the &%transport_filter%& option, described in
34040 chapter &<<CHAPtransportgeneric>>&).
34042 If you want to include the ACL-time content-scanning features when you compile
34043 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
34044 &_Local/Makefile_&. When you do that, the Exim binary is built with:
34047 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
34048 for all MIME parts for SMTP and non-SMTP messages, respectively.
34050 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
34051 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
34052 run at the end of message reception (the &%acl_smtp_data%& ACL).
34054 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
34055 of messages, or parts of messages, for debugging purposes.
34057 Additional expansion variables that are set in the new ACL and by the new
34060 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
34063 Content-scanning is continually evolving, and new features are still being
34064 added. While such features are still unstable and liable to incompatible
34065 changes, they are made available in Exim by setting options whose names begin
34066 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
34067 this manual. You can find out about them by reading the file called
34068 &_doc/experimental.txt_&.
34070 All the content-scanning facilities work on a MBOX copy of the message that is
34071 temporarily created in a file called:
34073 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
34075 The &_.eml_& extension is a friendly hint to virus scanners that they can
34076 expect an MBOX-like structure inside that file. The file is created when the
34077 first content scanning facility is called. Subsequent calls to content
34078 scanning conditions open the same file again. The directory is recursively
34079 removed when the &%acl_smtp_data%& ACL has finished running, unless
34081 control = no_mbox_unspool
34083 has been encountered. When the MIME ACL decodes files, they are put into the
34084 same directory by default.
34088 .section "Scanning for viruses" "SECTscanvirus"
34089 .cindex "virus scanning"
34090 .cindex "content scanning" "for viruses"
34091 .cindex "content scanning" "the &%malware%& condition"
34092 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
34093 It supports a &"generic"& interface to scanners called via the shell, and
34094 specialized interfaces for &"daemon"& type virus scanners, which are resident
34095 in memory and thus are much faster.
34097 Since message data needs to have arrived,
34098 the condition may be only called in ACL defined by
34100 &%acl_smtp_data_prdr%&,
34101 &%acl_smtp_mime%& or
34104 A timeout of 2 minutes is applied to a scanner call (by default);
34105 if it expires then a defer action is taken.
34107 .oindex "&%av_scanner%&"
34108 You can set the &%av_scanner%& option in the main part of the configuration
34109 to specify which scanner to use, together with any additional options that
34110 are needed. The basic syntax is as follows:
34112 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
34114 If you do not set &%av_scanner%&, it defaults to
34116 av_scanner = sophie:/var/run/sophie
34118 If the value of &%av_scanner%& starts with a dollar character, it is expanded
34120 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
34121 The following scanner types are supported in this release,
34122 though individual ones can be included or not at build time:
34126 .cindex "virus scanners" "avast"
34127 This is the scanner daemon of Avast. It has been tested with Avast Core
34128 Security (currently at version 2.2.0).
34129 You can get a trial version at &url(https://www.avast.com) or for Linux
34130 at &url(https://www.avast.com/linux-server-antivirus).
34131 This scanner type takes one option,
34132 which can be either a full path to a UNIX socket,
34133 or host and port specifiers separated by white space.
34134 The host may be a name or an IP address; the port is either a
34135 single number or a pair of numbers with a dash between.
34136 A list of options may follow. These options are interpreted on the
34137 Exim's side of the malware scanner, or are given on separate lines to
34138 the daemon as options before the main scan command.
34140 .cindex &`pass_unscanned`& "avast"
34141 If &`pass_unscanned`&
34142 is set, any files the Avast scanner can't scan (e.g.
34143 decompression bombs, or invalid archives) are considered clean. Use with
34148 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
34149 av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
34150 av_scanner = avast:192.168.2.22 5036
34152 If you omit the argument, the default path
34153 &_/var/run/avast/scan.sock_&
34155 If you use a remote host,
34156 you need to make Exim's spool directory available to it,
34157 as the scanner is passed a file path, not file contents.
34158 For information about available commands and their options you may use
34160 $ socat UNIX:/var/run/avast/scan.sock STDIO:
34166 If the scanner returns a temporary failure (e.g. license issues, or
34167 permission problems), the message is deferred and a paniclog entry is
34168 written. The usual &`defer_ok`& option is available.
34170 .vitem &%aveserver%&
34171 .cindex "virus scanners" "Kaspersky"
34172 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
34173 at &url(https://www.kaspersky.com/). This scanner type takes one option,
34174 which is the path to the daemon's UNIX socket. The default is shown in this
34177 av_scanner = aveserver:/var/run/aveserver
34182 .cindex "virus scanners" "clamd"
34183 This daemon-type scanner is GPL and free. You can get it at
34184 &url(https://www.clamav.net/). Some older versions of clamd do not seem to
34185 unpack MIME containers, so it used to be recommended to unpack MIME attachments
34186 in the MIME ACL. This is no longer believed to be necessary.
34188 The options are a list of server specifiers, which may be
34189 a UNIX socket specification,
34190 a TCP socket specification,
34191 or a (global) option.
34193 A socket specification consists of a space-separated list.
34194 For a Unix socket the first element is a full path for the socket,
34195 for a TCP socket the first element is the IP address
34196 and the second a port number,
34197 Any further elements are per-server (non-global) options.
34198 These per-server options are supported:
34200 retry=<timespec> Retry on connect fail
34203 The &`retry`& option specifies a time after which a single retry for
34204 a failed connect is made. The default is to not retry.
34206 If a Unix socket file is specified, only one server is supported.
34210 av_scanner = clamd:/opt/clamd/socket
34211 av_scanner = clamd:192.0.2.3 1234
34212 av_scanner = clamd:192.0.2.3 1234:local
34213 av_scanner = clamd:192.0.2.3 1234 retry=10s
34214 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
34216 If the value of av_scanner points to a UNIX socket file or contains the
34218 option, then the ClamAV interface will pass a filename containing the data
34219 to be scanned, which should normally result in less I/O happening and be
34220 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
34221 Exim does not assume that there is a common filesystem with the remote host.
34223 The final example shows that multiple TCP targets can be specified. Exim will
34224 randomly use one for each incoming email (i.e. it load balances them). Note
34225 that only TCP targets may be used if specifying a list of scanners; a UNIX
34226 socket cannot be mixed in with TCP targets. If one of the servers becomes
34227 unavailable, Exim will try the remaining one(s) until it finds one that works.
34228 When a clamd server becomes unreachable, Exim will log a message. Exim does
34229 not keep track of scanner state between multiple messages, and the scanner
34230 selection is random, so the message will get logged in the mainlog for each
34231 email that the down scanner gets chosen first (message wrapped to be readable):
34233 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
34234 clamd: connection to localhost, port 3310 failed
34235 (Connection refused)
34238 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
34239 contributing the code for this scanner.
34242 .cindex "virus scanners" "command line interface"
34243 This is the keyword for the generic command line scanner interface. It can be
34244 used to attach virus scanners that are invoked from the shell. This scanner
34245 type takes 3 mandatory options:
34248 The full path and name of the scanner binary, with all command line options,
34249 and a placeholder (&`%s`&) for the directory to scan.
34252 A regular expression to match against the STDOUT and STDERR output of the
34253 virus scanner. If the expression matches, a virus was found. You must make
34254 absolutely sure that this expression matches on &"virus found"&. This is called
34255 the &"trigger"& expression.
34258 Another regular expression, containing exactly one pair of parentheses, to
34259 match the name of the virus found in the scanners output. This is called the
34260 &"name"& expression.
34263 For example, Sophos Sweep reports a virus on a line like this:
34265 Virus 'W32/Magistr-B' found in file ./those.bat
34267 For the trigger expression, we can match the phrase &"found in file"&. For the
34268 name expression, we want to extract the W32/Magistr-B string, so we can match
34269 for the single quotes left and right of it. Altogether, this makes the
34270 configuration setting:
34272 av_scanner = cmdline:\
34273 /path/to/sweep -ss -all -rec -archive %s:\
34274 found in file:'(.+)'
34277 .cindex "virus scanners" "DrWeb"
34278 The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface
34280 either a full path to a UNIX socket,
34281 or host and port specifiers separated by white space.
34282 The host may be a name or an IP address; the port is either a
34283 single number or a pair of numbers with a dash between.
34286 av_scanner = drweb:/var/run/drwebd.sock
34287 av_scanner = drweb:192.168.2.20 31337
34289 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
34290 is used. Thanks to Alex Miller for contributing the code for this scanner.
34293 .cindex "virus scanners" "f-protd"
34294 The f-protd scanner is accessed via HTTP over TCP.
34295 One argument is taken, being a space-separated hostname and port number
34299 av_scanner = f-protd:localhost 10200-10204
34301 If you omit the argument, the default values shown above are used.
34303 .vitem &%f-prot6d%&
34304 .cindex "virus scanners" "f-prot6d"
34305 The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
34306 One argument is taken, being a space-separated hostname and port number.
34309 av_scanner = f-prot6d:localhost 10200
34311 If you omit the argument, the default values show above are used.
34314 .cindex "virus scanners" "F-Secure"
34315 The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one
34316 argument which is the path to a UNIX socket. For example:
34318 av_scanner = fsecure:/path/to/.fsav
34320 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
34321 Thelmen for contributing the code for this scanner.
34323 .vitem &%kavdaemon%&
34324 .cindex "virus scanners" "Kaspersky"
34325 This is the scanner daemon of Kaspersky Version 4. This version of the
34326 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
34327 scanner type takes one option, which is the path to the daemon's UNIX socket.
34330 av_scanner = kavdaemon:/opt/AVP/AvpCtl
34332 The default path is &_/var/run/AvpCtl_&.
34335 .cindex "virus scanners" "mksd"
34336 This was a daemon type scanner that is aimed mainly at Polish users,
34337 though some documentation was available in English.
34338 The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir)
34339 and this appears to be a candidate for removal from Exim, unless
34340 we are informed of other virus scanners which use the same protocol
34342 The only option for this scanner type is
34343 the maximum number of processes used simultaneously to scan the attachments,
34344 provided that mksd has
34345 been run with at least the same number of child processes. For example:
34347 av_scanner = mksd:2
34349 You can safely omit this option (the default value is 1).
34352 .cindex "virus scanners" "simple socket-connected"
34353 This is a general-purpose way of talking to simple scanner daemons
34354 running on the local machine.
34355 There are four options:
34356 an address (which may be an IP address and port, or the path of a Unix socket),
34357 a commandline to send (may include a single %s which will be replaced with
34358 the path to the mail file to be scanned),
34359 an RE to trigger on from the returned data,
34360 and an RE to extract malware_name from the returned data.
34363 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
34365 Note that surrounding whitespace is stripped from each option, meaning
34366 there is no way to specify a trailing newline.
34367 The socket specifier and both regular-expressions are required.
34368 Default for the commandline is &_%s\n_& (note this does have a trailing newline);
34369 specify an empty element to get this.
34372 .cindex "virus scanners" "Sophos and Sophie"
34373 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
34374 You can get Sophie at &url(http://sophie.sourceforge.net/). The only option
34375 for this scanner type is the path to the UNIX socket that Sophie uses for
34376 client communication. For example:
34378 av_scanner = sophie:/tmp/sophie
34380 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
34384 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
34385 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
34388 The &%av_scanner%& option is expanded each time &%malware%& is called. This
34389 makes it possible to use different scanners. See further below for an example.
34390 The &%malware%& condition caches its results, so when you use it multiple times
34391 for the same message, the actual scanning process is only carried out once.
34392 However, using expandable items in &%av_scanner%& disables this caching, in
34393 which case each use of the &%malware%& condition causes a new scan of the
34396 The &%malware%& condition takes a right-hand argument that is expanded before
34397 use and taken as a list, slash-separated by default.
34398 The first element can then be one of
34401 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
34402 The condition succeeds if a virus was found, and fail otherwise. This is the
34405 &"false"& or &"0"& or an empty string, in which case no scanning is done and
34406 the condition fails immediately.
34408 A regular expression, in which case the message is scanned for viruses. The
34409 condition succeeds if a virus is found and its name matches the regular
34410 expression. This allows you to take special actions on certain types of virus.
34411 Note that &"/"& characters in the RE must be doubled due to the list-processing,
34412 unless the separator is changed (in the usual way &<<SECTlistsepchange>>&).
34415 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
34416 messages even if there is a problem with the virus scanner.
34417 Otherwise, such a problem causes the ACL to defer.
34419 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
34420 specify a non-default timeout. The default is two minutes.
34423 malware = * / defer_ok / tmo=10s
34425 A timeout causes the ACL to defer.
34427 .vindex "&$callout_address$&"
34428 When a connection is made to the scanner the expansion variable &$callout_address$&
34429 is set to record the actual address used.
34431 .vindex "&$malware_name$&"
34432 When a virus is found, the condition sets up an expansion variable called
34433 &$malware_name$& that contains the name of the virus. You can use it in a
34434 &%message%& modifier that specifies the error returned to the sender, and/or in
34437 Beware the interaction of Exim's &%message_size_limit%& with any size limits
34438 imposed by your anti-virus scanner.
34440 Here is a very simple scanning example:
34443 message = This message contains malware ($malware_name)
34445 The next example accepts messages when there is a problem with the scanner:
34447 deny malware = */defer_ok
34448 message = This message contains malware ($malware_name)
34450 The next example shows how to use an ACL variable to scan with both sophie and
34451 aveserver. It assumes you have set:
34453 av_scanner = $acl_m0
34455 in the main Exim configuration.
34457 deny set acl_m0 = sophie
34459 message = This message contains malware ($malware_name)
34461 deny set acl_m0 = aveserver
34463 message = This message contains malware ($malware_name)
34467 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
34468 .cindex "content scanning" "for spam"
34469 .cindex "spam scanning"
34470 .cindex "SpamAssassin"
34472 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
34473 score and a report for the message.
34474 Support is also provided for Rspamd.
34476 For more information about installation and configuration of SpamAssassin or
34477 Rspamd refer to their respective websites at
34478 &url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/)
34480 SpamAssassin can be installed with CPAN by running:
34482 perl -MCPAN -e 'install Mail::SpamAssassin'
34484 SpamAssassin has its own set of configuration files. Please review its
34485 documentation to see how you can tweak it. The default installation should work
34488 .oindex "&%spamd_address%&"
34489 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
34490 intend to use an instance running on the local host you do not need to set
34491 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
34492 you must set the &%spamd_address%& option in the global part of the Exim
34493 configuration as follows (example):
34495 spamd_address = 192.168.99.45 783
34497 The SpamAssassin protocol relies on a TCP half-close from the client.
34498 If your SpamAssassin client side is running a Linux system with an
34499 iptables firewall, consider setting
34500 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
34501 timeout, Exim uses when waiting for a response from the SpamAssassin
34502 server (currently defaulting to 120s). With a lower value the Linux
34503 connection tracking may consider your half-closed connection as dead too
34507 To use Rspamd (which by default listens on all local addresses
34509 you should add &%variant=rspamd%& after the address/port pair, for example:
34511 spamd_address = 127.0.0.1 11333 variant=rspamd
34514 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
34515 sockets. If you want to us these, supply &%spamd_address%& with an absolute
34516 filename instead of an address/port pair:
34518 spamd_address = /var/run/spamd_socket
34520 You can have multiple &%spamd%& servers to improve scalability. These can
34521 reside on other hardware reachable over the network. To specify multiple
34522 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
34523 option, separated with colons (the separator can be changed in the usual way &<<SECTlistsepchange>>&):
34525 spamd_address = 192.168.2.10 783 : \
34526 192.168.2.11 783 : \
34529 Up to 32 &%spamd%& servers are supported.
34530 When a server fails to respond to the connection attempt, all other
34531 servers are tried until one succeeds. If no server responds, the &%spam%&
34534 Unix and TCP socket specifications may be mixed in any order.
34535 Each element of the list is a list itself, space-separated by default
34536 and changeable in the usual way (&<<SECTlistsepchange>>&);
34537 take care to not double the separator.
34539 For TCP socket specifications a host name or IP (v4 or v6, but
34540 subject to list-separator quoting rules) address can be used,
34541 and the port can be one or a dash-separated pair.
34542 In the latter case, the range is tried in strict order.
34544 Elements after the first for Unix sockets, or second for TCP socket,
34546 The supported options are:
34548 pri=<priority> Selection priority
34549 weight=<value> Selection bias
34550 time=<start>-<end> Use only between these times of day
34551 retry=<timespec> Retry on connect fail
34552 tmo=<timespec> Connection time limit
34553 variant=rspamd Use Rspamd rather than SpamAssassin protocol
34556 The &`pri`& option specifies a priority for the server within the list,
34557 higher values being tried first.
34558 The default priority is 1.
34560 The &`weight`& option specifies a selection bias.
34561 Within a priority set
34562 servers are queried in a random fashion, weighted by this value.
34563 The default value for selection bias is 1.
34565 Time specifications for the &`time`& option are <hour>.<minute>.<second>
34566 in the local time zone; each element being one or more digits.
34567 Either the seconds or both minutes and seconds, plus the leading &`.`&
34568 characters, may be omitted and will be taken as zero.
34570 Timeout specifications for the &`retry`& and &`tmo`& options
34571 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
34573 The &`tmo`& option specifies an overall timeout for communication.
34574 The default value is two minutes.
34576 The &`retry`& option specifies a time after which a single retry for
34577 a failed connect is made.
34578 The default is to not retry.
34580 The &%spamd_address%& variable is expanded before use if it starts with
34581 a dollar sign. In this case, the expansion may return a string that is
34582 used as the list so that multiple spamd servers can be the result of an
34585 .vindex "&$callout_address$&"
34586 When a connection is made to the server the expansion variable &$callout_address$&
34587 is set to record the actual address used.
34589 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
34590 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
34593 message = This message was classified as SPAM
34595 The right-hand side of the &%spam%& condition specifies a name. This is
34596 relevant if you have set up multiple SpamAssassin profiles. If you do not want
34597 to scan using a specific profile, but rather use the SpamAssassin system-wide
34598 default profile, you can scan for an unknown name, or simply use &"nobody"&.
34599 Rspamd does not use this setting. However, you must put something on the
34602 The name allows you to use per-domain or per-user antispam profiles in
34603 principle, but this is not straightforward in practice, because a message may
34604 have multiple recipients, not necessarily all in the same domain. Because the
34605 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
34606 read the contents of the message, the variables &$local_part$& and &$domain$&
34608 Careful enforcement of single-recipient messages
34609 (e.g. by responding with defer in the recipient ACL for all recipients
34611 or the use of PRDR,
34612 .cindex "PRDR" "use for per-user SpamAssassin profiles"
34613 are needed to use this feature.
34615 The right-hand side of the &%spam%& condition is expanded before being used, so
34616 you can put lookups or conditions there. When the right-hand side evaluates to
34617 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
34620 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
34621 large ones may cause significant performance degradation. As most spam messages
34622 are quite small, it is recommended that you do not scan the big ones. For
34625 deny condition = ${if < {$message_size}{10K}}
34627 message = This message was classified as SPAM
34630 The &%spam%& condition returns true if the threshold specified in the user's
34631 SpamAssassin profile has been matched or exceeded. If you want to use the
34632 &%spam%& condition for its side effects (see the variables below), you can make
34633 it always return &"true"& by appending &`:true`& to the username.
34635 .cindex "spam scanning" "returned variables"
34636 When the &%spam%& condition is run, it sets up a number of expansion
34638 Except for &$spam_report$&,
34639 these variables are saved with the received message so are
34640 available for use at delivery time.
34643 .vitem &$spam_score$&
34644 The spam score of the message, for example, &"3.4"& or &"30.5"&. This is useful
34645 for inclusion in log or reject messages.
34647 .vitem &$spam_score_int$&
34648 The spam score of the message, multiplied by ten, as an integer value. For
34649 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
34650 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
34651 The integer value is useful for numeric comparisons in conditions.
34653 .vitem &$spam_bar$&
34654 A string consisting of a number of &"+"& or &"-"& characters, representing the
34655 integer part of the spam score value. A spam score of 4.4 would have a
34656 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
34657 headers, since MUAs can match on such strings. The maximum length of the
34658 spam bar is 50 characters.
34660 .vitem &$spam_report$&
34661 A multiline text table, containing the full SpamAssassin report for the
34662 message. Useful for inclusion in headers or reject messages.
34663 This variable is only usable in a DATA-time ACL.
34664 Beware that SpamAssassin may return non-ASCII characters, especially
34665 when running in country-specific locales, which are not legal
34666 unencoded in headers.
34668 .vitem &$spam_action$&
34669 For SpamAssassin either 'reject' or 'no action' depending on the
34670 spam score versus threshold.
34671 For Rspamd, the recommended action.
34675 The &%spam%& condition caches its results unless expansion in
34676 spamd_address was used. If you call it again with the same user name, it
34677 does not scan again, but rather returns the same values as before.
34679 The &%spam%& condition returns DEFER if there is any error while running
34680 the message through SpamAssassin or if the expansion of spamd_address
34681 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
34682 statement block), append &`/defer_ok`& to the right-hand side of the
34683 spam condition, like this:
34685 deny spam = joe/defer_ok
34686 message = This message was classified as SPAM
34688 This causes messages to be accepted even if there is a problem with &%spamd%&.
34690 Here is a longer, commented example of the use of the &%spam%&
34693 # put headers in all messages (no matter if spam or not)
34694 warn spam = nobody:true
34695 add_header = X-Spam-Score: $spam_score ($spam_bar)
34696 add_header = X-Spam-Report: $spam_report
34698 # add second subject line with *SPAM* marker when message
34699 # is over threshold
34701 add_header = Subject: *SPAM* $h_Subject:
34703 # reject spam at high scores (> 12)
34704 deny spam = nobody:true
34705 condition = ${if >{$spam_score_int}{120}{1}{0}}
34706 message = This message scored $spam_score spam points.
34711 .section "Scanning MIME parts" "SECTscanmimepart"
34712 .cindex "content scanning" "MIME parts"
34713 .cindex "MIME content scanning"
34714 .oindex "&%acl_smtp_mime%&"
34715 .oindex "&%acl_not_smtp_mime%&"
34716 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
34717 each MIME part of an SMTP message, including multipart types, in the sequence
34718 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
34719 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
34720 options may both refer to the same ACL if you want the same processing in both
34723 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
34724 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
34725 the case of a non-SMTP message. However, a MIME ACL is called only if the
34726 message contains a &'Content-Type:'& header line. When a call to a MIME
34727 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
34728 result code is sent to the client. In the case of an SMTP message, the
34729 &%acl_smtp_data%& ACL is not called when this happens.
34731 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
34732 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
34733 condition to match against the raw MIME part. You can also use the
34734 &%mime_regex%& condition to match against the decoded MIME part (see section
34735 &<<SECTscanregex>>&).
34737 At the start of a MIME ACL, a number of variables are set from the header
34738 information for the relevant MIME part. These are described below. The contents
34739 of the MIME part are not by default decoded into a disk file except for MIME
34740 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
34741 part into a disk file, you can use the &%decode%& condition. The general
34744 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
34746 The right hand side is expanded before use. After expansion,
34750 &"0"& or &"false"&, in which case no decoding is done.
34752 The string &"default"&. In that case, the file is put in the temporary
34753 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
34754 a sequential filename consisting of the message id and a sequence number. The
34755 full path and name is available in &$mime_decoded_filename$& after decoding.
34757 A full path name starting with a slash. If the full name is an existing
34758 directory, it is used as a replacement for the default directory. The filename
34759 is then sequentially assigned. If the path does not exist, it is used as
34760 the full path and filename.
34762 If the string does not start with a slash, it is used as the
34763 filename, and the default path is then used.
34765 The &%decode%& condition normally succeeds. It is only false for syntax
34766 errors or unusual circumstances such as memory shortages. You can easily decode
34767 a file with its original, proposed filename using
34769 decode = $mime_filename
34771 However, you should keep in mind that &$mime_filename$& might contain
34772 anything. If you place files outside of the default path, they are not
34773 automatically unlinked.
34775 For RFC822 attachments (these are messages attached to messages, with a
34776 content-type of &"message/rfc822"&), the ACL is called again in the same manner
34777 as for the primary message, only that the &$mime_is_rfc822$& expansion
34778 variable is set (see below). Attached messages are always decoded to disk
34779 before being checked, and the files are unlinked once the check is done.
34781 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
34782 used to match regular expressions against raw and decoded MIME parts,
34783 respectively. They are described in section &<<SECTscanregex>>&.
34785 .cindex "MIME content scanning" "returned variables"
34786 The following list describes all expansion variables that are
34787 available in the MIME ACL:
34790 .vitem &$mime_anomaly_level$& &&&
34791 &$mime_anomaly_text$&
34792 .vindex &$mime_anomaly_level$&
34793 .vindex &$mime_anomaly_text$&
34794 If there are problems decoding, these variables contain information on
34795 the detected issue.
34797 .vitem &$mime_boundary$&
34798 .vindex &$mime_boundary$&
34799 If the current part is a multipart (see &$mime_is_multipart$& below), it should
34800 have a boundary string, which is stored in this variable. If the current part
34801 has no boundary parameter in the &'Content-Type:'& header, this variable
34802 contains the empty string.
34804 .vitem &$mime_charset$&
34805 .vindex &$mime_charset$&
34806 This variable contains the character set identifier, if one was found in the
34807 &'Content-Type:'& header. Examples for charset identifiers are:
34813 Please note that this value is not normalized, so you should do matches
34814 case-insensitively.
34816 .vitem &$mime_content_description$&
34817 .vindex &$mime_content_description$&
34818 This variable contains the normalized content of the &'Content-Description:'&
34819 header. It can contain a human-readable description of the parts content. Some
34820 implementations repeat the filename for attachments here, but they are usually
34821 only used for display purposes.
34823 .vitem &$mime_content_disposition$&
34824 .vindex &$mime_content_disposition$&
34825 This variable contains the normalized content of the &'Content-Disposition:'&
34826 header. You can expect strings like &"attachment"& or &"inline"& here.
34828 .vitem &$mime_content_id$&
34829 .vindex &$mime_content_id$&
34830 This variable contains the normalized content of the &'Content-ID:'& header.
34831 This is a unique ID that can be used to reference a part from another part.
34833 .vitem &$mime_content_size$&
34834 .vindex &$mime_content_size$&
34835 This variable is set only after the &%decode%& modifier (see above) has been
34836 successfully run. It contains the size of the decoded part in kilobytes. The
34837 size is always rounded up to full kilobytes, so only a completely empty part
34838 has a &$mime_content_size$& of zero.
34840 .vitem &$mime_content_transfer_encoding$&
34841 .vindex &$mime_content_transfer_encoding$&
34842 This variable contains the normalized content of the
34843 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
34844 type. Typical values are &"base64"& and &"quoted-printable"&.
34846 .vitem &$mime_content_type$&
34847 .vindex &$mime_content_type$&
34848 If the MIME part has a &'Content-Type:'& header, this variable contains its
34849 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
34850 are some examples of popular MIME types, as they may appear in this variable:
34854 application/octet-stream
34858 If the MIME part has no &'Content-Type:'& header, this variable contains the
34861 .vitem &$mime_decoded_filename$&
34862 .vindex &$mime_decoded_filename$&
34863 This variable is set only after the &%decode%& modifier (see above) has been
34864 successfully run. It contains the full path and filename of the file
34865 containing the decoded data.
34870 .vitem &$mime_filename$&
34871 .vindex &$mime_filename$&
34872 This is perhaps the most important of the MIME variables. It contains a
34873 proposed filename for an attachment, if one was found in either the
34874 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
34877 decoded, but no additional sanity checks are done.
34879 found, this variable contains the empty string.
34881 .vitem &$mime_is_coverletter$&
34882 .vindex &$mime_is_coverletter$&
34883 This variable attempts to differentiate the &"cover letter"& of an e-mail from
34884 attached data. It can be used to clamp down on flashy or unnecessarily encoded
34885 content in the cover letter, while not restricting attachments at all.
34887 The variable contains 1 (true) for a MIME part believed to be part of the
34888 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
34892 The outermost MIME part of a message is always a cover letter.
34895 If a multipart/alternative or multipart/related MIME part is a cover letter,
34896 so are all MIME subparts within that multipart.
34899 If any other multipart is a cover letter, the first subpart is a cover letter,
34900 and the rest are attachments.
34903 All parts contained within an attachment multipart are attachments.
34906 As an example, the following will ban &"HTML mail"& (including that sent with
34907 alternative plain text), while allowing HTML files to be attached. HTML
34908 coverletter mail attached to non-HTML coverletter mail will also be allowed:
34910 deny !condition = $mime_is_rfc822
34911 condition = $mime_is_coverletter
34912 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
34913 message = HTML mail is not accepted here
34916 .vitem &$mime_is_multipart$&
34917 .vindex &$mime_is_multipart$&
34918 This variable has the value 1 (true) when the current part has the main type
34919 &"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
34920 Since multipart entities only serve as containers for other parts, you may not
34921 want to carry out specific actions on them.
34923 .vitem &$mime_is_rfc822$&
34924 .vindex &$mime_is_rfc822$&
34925 This variable has the value 1 (true) if the current part is not a part of the
34926 checked message itself, but part of an attached message. Attached message
34927 decoding is fully recursive.
34929 .vitem &$mime_part_count$&
34930 .vindex &$mime_part_count$&
34931 This variable is a counter that is raised for each processed MIME part. It
34932 starts at zero for the very first part (which is usually a multipart). The
34933 counter is per-message, so it is reset when processing RFC822 attachments (see
34934 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
34935 complete, so you can use it in the DATA ACL to determine the number of MIME
34936 parts of a message. For non-MIME messages, this variable contains the value -1.
34941 .section "Scanning with regular expressions" "SECTscanregex"
34942 .cindex "content scanning" "with regular expressions"
34943 .cindex "regular expressions" "content scanning with"
34944 You can specify your own custom regular expression matches on the full body of
34945 the message, or on individual MIME parts.
34947 The &%regex%& condition takes one or more regular expressions as arguments and
34948 matches them against the full message (when called in the DATA ACL) or a raw
34949 MIME part (when called in the MIME ACL). The &%regex%& condition matches
34950 linewise, with a maximum line length of 32K characters. That means you cannot
34951 have multiline matches with the &%regex%& condition.
34953 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
34954 to 32K of decoded content (the whole content at once, not linewise). If the
34955 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
34956 is decoded automatically when &%mime_regex%& is executed (using default path
34957 and filename values). If the decoded data is larger than 32K, only the first
34958 32K characters are checked.
34960 The regular expressions are passed as a colon-separated list. To include a
34961 literal colon, you must double it. Since the whole right-hand side string is
34962 expanded before being used, you must also escape dollar signs and backslashes
34963 with more backslashes, or use the &`\N`& facility to disable expansion.
34964 Here is a simple example that contains two regular expressions:
34966 deny regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
34967 message = contains blacklisted regex ($regex_match_string)
34969 The conditions returns true if any one of the regular expressions matches. The
34970 &$regex_match_string$& expansion variable is then set up and contains the
34971 matching regular expression.
34972 The expansion variables &$regex1$& &$regex2$& etc
34973 are set to any substrings captured by the regular expression.
34975 &*Warning*&: With large messages, these conditions can be fairly
34983 . ////////////////////////////////////////////////////////////////////////////
34984 . ////////////////////////////////////////////////////////////////////////////
34986 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
34987 "Local scan function"
34988 .scindex IIDlosca "&[local_scan()]& function" "description of"
34989 .cindex "customizing" "input scan using C function"
34990 .cindex "policy control" "by local scan function"
34991 In these days of email worms, viruses, and ever-increasing spam, some sites
34992 want to apply a lot of checking to messages before accepting them.
34994 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
34995 passing messages to external virus and spam scanning software. You can also do
34996 a certain amount in Exim itself through string expansions and the &%condition%&
34997 condition in the ACL that runs after the SMTP DATA command or the ACL for
34998 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
35000 To allow for further customization to a site's own requirements, there is the
35001 possibility of linking Exim with a private message scanning function, written
35002 in C. If you want to run code that is written in something other than C, you
35003 can of course use a little C stub to call it.
35005 The local scan function is run once for every incoming message, at the point
35006 when Exim is just about to accept the message.
35007 It can therefore be used to control non-SMTP messages from local processes as
35008 well as messages arriving via SMTP.
35010 Exim applies a timeout to calls of the local scan function, and there is an
35011 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
35012 Zero means &"no timeout"&.
35013 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
35014 before calling the local scan function, so that the most common types of crash
35015 are caught. If the timeout is exceeded or one of those signals is caught, the
35016 incoming message is rejected with a temporary error if it is an SMTP message.
35017 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
35018 code. The incident is logged on the main and reject logs.
35022 .section "Building Exim to use a local scan function" "SECID207"
35023 .cindex "&[local_scan()]& function" "building Exim to use"
35024 To make use of the local scan function feature, you must tell Exim where your
35025 function is before building Exim, by setting
35026 both HAVE_LOCAL_SCAN and
35027 LOCAL_SCAN_SOURCE in your
35028 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
35029 directory, so you might set
35031 HAVE_LOCAL_SCAN=yes
35032 LOCAL_SCAN_SOURCE=Local/local_scan.c
35034 for example. The function must be called &[local_scan()]&;
35035 the source file(s) for it should first #define LOCAL_SCAN
35036 and then #include "local_scan.h".
35038 Exim after it has received a message, when the success return code is about to
35039 be sent. This is after all the ACLs have been run. The return code from your
35040 function controls whether the message is actually accepted or not. There is a
35041 commented template function (that just accepts the message) in the file
35042 _src/local_scan.c_.
35044 If you want to make use of Exim's runtime configuration file to set options
35045 for your &[local_scan()]& function, you must also set
35047 LOCAL_SCAN_HAS_OPTIONS=yes
35049 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
35054 .section "API for local_scan()" "SECTapiforloc"
35055 .cindex "&[local_scan()]& function" "API description"
35056 .cindex &%dlfunc%& "API description"
35057 You must include this line near the start of your code:
35060 #include "local_scan.h"
35062 This header file defines a number of variables and other values, and the
35063 prototype for the function itself. Exim is coded to use unsigned char values
35064 almost exclusively, and one of the things this header defines is a shorthand
35065 for &`unsigned char`& called &`uschar`&.
35066 It also makes available the following macro definitions, to simplify casting character
35067 strings and pointers to character strings:
35069 #define CS (char *)
35070 #define CCS (const char *)
35071 #define CSS (char **)
35072 #define US (unsigned char *)
35073 #define CUS (const unsigned char *)
35074 #define USS (unsigned char **)
35076 The function prototype for &[local_scan()]& is:
35078 extern int local_scan(int fd, uschar **return_text);
35080 The arguments are as follows:
35083 &%fd%& is a file descriptor for the file that contains the body of the message
35084 (the -D file). The file is open for reading and writing, but updating it is not
35085 recommended. &*Warning*&: You must &'not'& close this file descriptor.
35087 The descriptor is positioned at character 19 of the file, which is the first
35088 character of the body itself, because the first 19 characters are the message
35089 id followed by &`-D`& and a newline. If you rewind the file, you should use the
35090 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
35091 case this changes in some future version.
35093 &%return_text%& is an address which you can use to return a pointer to a text
35094 string at the end of the function. The value it points to on entry is NULL.
35097 The function must return an &%int%& value which is one of the following macros:
35100 .vitem &`LOCAL_SCAN_ACCEPT`&
35101 .vindex "&$local_scan_data$&"
35102 The message is accepted. If you pass back a string of text, it is saved with
35103 the message, and made available in the variable &$local_scan_data$&. No
35104 newlines are permitted (if there are any, they are turned into spaces) and the
35105 maximum length of text is 1000 characters.
35107 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
35108 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
35109 queued without immediate delivery, and is frozen.
35111 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
35112 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
35113 queued without immediate delivery.
35115 .vitem &`LOCAL_SCAN_REJECT`&
35116 The message is rejected; the returned text is used as an error message which is
35117 passed back to the sender and which is also logged. Newlines are permitted &--
35118 they cause a multiline response for SMTP rejections, but are converted to
35119 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
35122 .vitem &`LOCAL_SCAN_TEMPREJECT`&
35123 The message is temporarily rejected; the returned text is used as an error
35124 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
35127 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
35128 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
35129 message is not written to the reject log. It has the effect of unsetting the
35130 &%rejected_header%& log selector for just this rejection. If
35131 &%rejected_header%& is already unset (see the discussion of the
35132 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
35133 same as LOCAL_SCAN_REJECT.
35135 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
35136 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
35137 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
35140 If the message is not being received by interactive SMTP, rejections are
35141 reported by writing to &%stderr%& or by sending an email, as configured by the
35142 &%-oe%& command line options.
35146 .section "Configuration options for local_scan()" "SECTconoptloc"
35147 .cindex "&[local_scan()]& function" "configuration options"
35148 It is possible to have option settings in the main configuration file
35149 that set values in static variables in the &[local_scan()]& module. If you
35150 want to do this, you must have the line
35152 LOCAL_SCAN_HAS_OPTIONS=yes
35154 in your &_Local/Makefile_& when you build Exim. (This line is in
35155 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
35156 file, you must define static variables to hold the option values, and a table
35159 The table must be a vector called &%local_scan_options%&, of type
35160 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
35161 and a pointer to the variable that holds the value. The entries must appear in
35162 alphabetical order. Following &%local_scan_options%& you must also define a
35163 variable called &%local_scan_options_count%& that contains the number of
35164 entries in the table. Here is a short example, showing two kinds of option:
35166 static int my_integer_option = 42;
35167 static uschar *my_string_option = US"a default string";
35169 optionlist local_scan_options[] = {
35170 { "my_integer", opt_int, &my_integer_option },
35171 { "my_string", opt_stringptr, &my_string_option }
35174 int local_scan_options_count =
35175 sizeof(local_scan_options)/sizeof(optionlist);
35177 The values of the variables can now be changed from Exim's runtime
35178 configuration file by including a local scan section as in this example:
35182 my_string = some string of text...
35184 The available types of option data are as follows:
35187 .vitem &*opt_bool*&
35188 This specifies a boolean (true/false) option. The address should point to a
35189 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
35190 that are defined as &"1"& and &"0"&, respectively. If you want to detect
35191 whether such a variable has been set at all, you can initialize it to
35192 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
35195 .vitem &*opt_fixed*&
35196 This specifies a fixed point number, such as is used for load averages.
35197 The address should point to a variable of type &`int`&. The value is stored
35198 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
35201 This specifies an integer; the address should point to a variable of type
35202 &`int`&. The value may be specified in any of the integer formats accepted by
35205 .vitem &*opt_mkint*&
35206 This is the same as &%opt_int%&, except that when such a value is output in a
35207 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
35208 printed with the suffix K or M.
35210 .vitem &*opt_octint*&
35211 This also specifies an integer, but the value is always interpreted as an
35212 octal integer, whether or not it starts with the digit zero, and it is
35213 always output in octal.
35215 .vitem &*opt_stringptr*&
35216 This specifies a string value; the address must be a pointer to a
35217 variable that points to a string (for example, of type &`uschar *`&).
35219 .vitem &*opt_time*&
35220 This specifies a time interval value. The address must point to a variable of
35221 type &`int`&. The value that is placed there is a number of seconds.
35224 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
35225 out the values of all the &[local_scan()]& options.
35229 .section "Available Exim variables" "SECID208"
35230 .cindex "&[local_scan()]& function" "available Exim variables"
35231 The header &_local_scan.h_& gives you access to a number of C variables. These
35232 are the only ones that are guaranteed to be maintained from release to release.
35233 Note, however, that you can obtain the value of any Exim expansion variable,
35234 including &$recipients$&, by calling &'expand_string()'&. The exported
35235 C variables are as follows:
35238 .vitem &*int&~body_linecount*&
35239 This variable contains the number of lines in the message's body.
35240 It is not valid if the &%spool_wireformat%& option is used.
35242 .vitem &*int&~body_zerocount*&
35243 This variable contains the number of binary zero bytes in the message's body.
35244 It is not valid if the &%spool_wireformat%& option is used.
35246 .vitem &*unsigned&~int&~debug_selector*&
35247 This variable is set to zero when no debugging is taking place. Otherwise, it
35248 is a bitmap of debugging selectors. Two bits are identified for use in
35249 &[local_scan()]&; they are defined as macros:
35252 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
35253 testing option that is not privileged &-- any caller may set it. All the
35254 other selector bits can be set only by admin users.
35257 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
35258 by the &`+local_scan`& debug selector. It is not included in the default set
35262 Thus, to write to the debugging output only when &`+local_scan`& has been
35263 selected, you should use code like this:
35265 if ((debug_selector & D_local_scan) != 0)
35266 debug_printf("xxx", ...);
35268 .vitem &*uschar&~*expand_string_message*&
35269 After a failing call to &'expand_string()'& (returned value NULL), the
35270 variable &%expand_string_message%& contains the error message, zero-terminated.
35272 .vitem &*header_line&~*header_list*&
35273 A pointer to a chain of header lines. The &%header_line%& structure is
35276 .vitem &*header_line&~*header_last*&
35277 A pointer to the last of the header lines.
35280 .vitem &*const&~uschar&~*headers_charset*&
35281 The value of the &%headers_charset%& configuration option.
35284 .vitem &*BOOL&~host_checking*&
35285 This variable is TRUE during a host checking session that is initiated by the
35286 &%-bh%& command line option.
35288 .vitem &*uschar&~*interface_address*&
35289 The IP address of the interface that received the message, as a string. This
35290 is NULL for locally submitted messages.
35292 .vitem &*int&~interface_port*&
35293 The port on which this message was received. When testing with the &%-bh%&
35294 command line option, the value of this variable is -1 unless a port has been
35295 specified via the &%-oMi%& option.
35297 .vitem &*uschar&~*message_id*&
35298 This variable contains Exim's message id for the incoming message (the value of
35299 &$message_exim_id$&) as a zero-terminated string.
35301 .vitem &*uschar&~*received_protocol*&
35302 The name of the protocol by which the message was received.
35304 .vitem &*int&~recipients_count*&
35305 The number of accepted recipients.
35307 .vitem &*recipient_item&~*recipients_list*&
35308 .cindex "recipient" "adding in local scan"
35309 .cindex "recipient" "removing in local scan"
35310 The list of accepted recipients, held in a vector of length
35311 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
35312 can add additional recipients by calling &'receive_add_recipient()'& (see
35313 below). You can delete recipients by removing them from the vector and
35314 adjusting the value in &%recipients_count%&. In particular, by setting
35315 &%recipients_count%& to zero you remove all recipients. If you then return the
35316 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
35317 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
35318 and then call &'receive_add_recipient()'& as often as needed.
35320 .vitem &*uschar&~*sender_address*&
35321 The envelope sender address. For bounce messages this is the empty string.
35323 .vitem &*uschar&~*sender_host_address*&
35324 The IP address of the sending host, as a string. This is NULL for
35325 locally-submitted messages.
35327 .vitem &*uschar&~*sender_host_authenticated*&
35328 The name of the authentication mechanism that was used, or NULL if the message
35329 was not received over an authenticated SMTP connection.
35331 .vitem &*uschar&~*sender_host_name*&
35332 The name of the sending host, if known.
35334 .vitem &*int&~sender_host_port*&
35335 The port on the sending host.
35337 .vitem &*BOOL&~smtp_input*&
35338 This variable is TRUE for all SMTP input, including BSMTP.
35340 .vitem &*BOOL&~smtp_batched_input*&
35341 This variable is TRUE for BSMTP input.
35343 .vitem &*int&~store_pool*&
35344 The contents of this variable control which pool of memory is used for new
35345 requests. See section &<<SECTmemhanloc>>& for details.
35349 .section "Structure of header lines" "SECID209"
35350 The &%header_line%& structure contains the members listed below.
35351 You can add additional header lines by calling the &'header_add()'& function
35352 (see below). You can cause header lines to be ignored (deleted) by setting
35357 .vitem &*struct&~header_line&~*next*&
35358 A pointer to the next header line, or NULL for the last line.
35360 .vitem &*int&~type*&
35361 A code identifying certain headers that Exim recognizes. The codes are printing
35362 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
35363 Notice in particular that any header line whose type is * is not transmitted
35364 with the message. This flagging is used for header lines that have been
35365 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
35366 lines.) Effectively, * means &"deleted"&.
35368 .vitem &*int&~slen*&
35369 The number of characters in the header line, including the terminating and any
35372 .vitem &*uschar&~*text*&
35373 A pointer to the text of the header. It always ends with a newline, followed by
35374 a zero byte. Internal newlines are preserved.
35379 .section "Structure of recipient items" "SECID210"
35380 The &%recipient_item%& structure contains these members:
35383 .vitem &*uschar&~*address*&
35384 This is a pointer to the recipient address as it was received.
35386 .vitem &*int&~pno*&
35387 This is used in later Exim processing when top level addresses are created by
35388 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
35389 and must always contain -1 at this stage.
35391 .vitem &*uschar&~*errors_to*&
35392 If this value is not NULL, bounce messages caused by failing to deliver to the
35393 recipient are sent to the address it contains. In other words, it overrides the
35394 envelope sender for this one recipient. (Compare the &%errors_to%& generic
35395 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
35396 an unqualified address, Exim qualifies it using the domain from
35397 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
35398 is NULL for all recipients.
35403 .section "Available Exim functions" "SECID211"
35404 .cindex "&[local_scan()]& function" "available Exim functions"
35405 The header &_local_scan.h_& gives you access to a number of Exim functions.
35406 These are the only ones that are guaranteed to be maintained from release to
35410 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
35411 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
35413 This function creates a child process that runs the command specified by
35414 &%argv%&. The environment for the process is specified by &%envp%&, which can
35415 be NULL if no environment variables are to be passed. A new umask is supplied
35416 for the process in &%newumask%&.
35418 Pipes to the standard input and output of the new process are set up
35419 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
35420 standard error is cloned to the standard output. If there are any file
35421 descriptors &"in the way"& in the new process, they are closed. If the final
35422 argument is TRUE, the new process is made into a process group leader.
35424 The function returns the pid of the new process, or -1 if things go wrong.
35426 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
35427 This function waits for a child process to terminate, or for a timeout (in
35428 seconds) to expire. A timeout value of zero means wait as long as it takes. The
35429 return value is as follows:
35434 The process terminated by a normal exit and the value is the process
35440 The process was terminated by a signal and the value is the negation of the
35446 The process timed out.
35450 The was some other error in wait(); &%errno%& is still set.
35453 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
35454 This function provide you with a means of submitting a new message to
35455 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
35456 want, but this packages it all up for you.) The function creates a pipe,
35457 forks a subprocess that is running
35459 exim -t -oem -oi -f <>
35461 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
35462 that is connected to the standard input. The yield of the function is the PID
35463 of the subprocess. You can then write a message to the file descriptor, with
35464 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
35466 When you have finished, call &'child_close()'& to wait for the process to
35467 finish and to collect its ending status. A timeout value of zero is usually
35468 fine in this circumstance. Unless you have made a mistake with the recipient
35469 addresses, you should get a return code of zero.
35472 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
35473 *sender_authentication)*&
35474 This function is a more sophisticated version of &'child_open()'&. The command
35477 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
35479 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
35482 .vitem &*void&~debug_printf(char&~*,&~...)*&
35483 This is Exim's debugging function, with arguments as for &'(printf()'&. The
35484 output is written to the standard error stream. If no debugging is selected,
35485 calls to &'debug_printf()'& have no effect. Normally, you should make calls
35486 conditional on the &`local_scan`& debug selector by coding like this:
35488 if ((debug_selector & D_local_scan) != 0)
35489 debug_printf("xxx", ...);
35492 .vitem &*uschar&~*expand_string(uschar&~*string)*&
35493 This is an interface to Exim's string expansion code. The return value is the
35494 expanded string, or NULL if there was an expansion failure.
35495 The C variable &%expand_string_message%& contains an error message after an
35496 expansion failure. If expansion does not change the string, the return value is
35497 the pointer to the input string. Otherwise, the return value points to a new
35498 block of memory that was obtained by a call to &'store_get()'&. See section
35499 &<<SECTmemhanloc>>& below for a discussion of memory handling.
35501 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
35502 This function allows you to an add additional header line at the end of the
35503 existing ones. The first argument is the type, and should normally be a space
35504 character. The second argument is a format string and any number of
35505 substitution arguments as for &[sprintf()]&. You may include internal newlines
35506 if you want, and you must ensure that the string ends with a newline.
35508 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
35509 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
35510 This function adds a new header line at a specified point in the header
35511 chain. The header itself is specified as for &'header_add()'&.
35513 If &%name%& is NULL, the new header is added at the end of the chain if
35514 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
35515 NULL, the header lines are searched for the first non-deleted header that
35516 matches the name. If one is found, the new header is added before it if
35517 &%after%& is false. If &%after%& is true, the new header is added after the
35518 found header and any adjacent subsequent ones with the same name (even if
35519 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
35520 option controls where the header is added. If it is true, addition is at the
35521 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
35522 headers, or at the top if there are no &'Received:'& headers, you could use
35524 header_add_at_position(TRUE, US"Received", TRUE,
35525 ' ', "X-xxx: ...");
35527 Normally, there is always at least one non-deleted &'Received:'& header, but
35528 there may not be if &%received_header_text%& expands to an empty string.
35531 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
35532 This function removes header lines. If &%occurrence%& is zero or negative, all
35533 occurrences of the header are removed. If occurrence is greater than zero, that
35534 particular instance of the header is removed. If no header(s) can be found that
35535 match the specification, the function does nothing.
35538 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
35539 int&~length,&~BOOL&~notdel)*&"
35540 This function tests whether the given header has the given name. It is not just
35541 a string comparison, because white space is permitted between the name and the
35542 colon. If the &%notdel%& argument is true, a false return is forced for all
35543 &"deleted"& headers; otherwise they are not treated specially. For example:
35545 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
35547 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
35548 .cindex "base64 encoding" "functions for &[local_scan()]& use"
35549 This function base64-encodes a string, which is passed by address and length.
35550 The text may contain bytes of any value, including zero. The result is passed
35551 back in dynamic memory that is obtained by calling &'store_get()'&. It is
35554 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
35555 This function decodes a base64-encoded string. Its arguments are a
35556 zero-terminated base64-encoded string and the address of a variable that is set
35557 to point to the result, which is in dynamic memory. The length of the decoded
35558 string is the yield of the function. If the input is invalid base64 data, the
35559 yield is -1. A zero byte is added to the end of the output string to make it
35560 easy to interpret as a C string (assuming it contains no zeros of its own). The
35561 added zero byte is not included in the returned count.
35563 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
35564 This function checks for a match in a domain list. Domains are always
35565 matched caselessly. The return value is one of the following:
35567 &`OK `& match succeeded
35568 &`FAIL `& match failed
35569 &`DEFER `& match deferred
35571 DEFER is usually caused by some kind of lookup defer, such as the
35572 inability to contact a database.
35574 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
35576 This function checks for a match in a local part list. The third argument
35577 controls case-sensitivity. The return values are as for
35578 &'lss_match_domain()'&.
35580 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
35582 This function checks for a match in an address list. The third argument
35583 controls the case-sensitivity of the local part match. The domain is always
35584 matched caselessly. The return values are as for &'lss_match_domain()'&.
35586 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
35588 This function checks for a match in a host list. The most common usage is
35591 lss_match_host(sender_host_name, sender_host_address, ...)
35593 .vindex "&$sender_host_address$&"
35594 An empty address field matches an empty item in the host list. If the host name
35595 is NULL, the name corresponding to &$sender_host_address$& is automatically
35596 looked up if a host name is required to match an item in the list. The return
35597 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
35598 returns ERROR in the case when it had to look up a host name, but the lookup
35601 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
35603 This function writes to Exim's log files. The first argument should be zero (it
35604 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
35605 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
35606 them. It specifies to which log or logs the message is written. The remaining
35607 arguments are a format and relevant insertion arguments. The string should not
35608 contain any newlines, not even at the end.
35611 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
35612 This function adds an additional recipient to the message. The first argument
35613 is the recipient address. If it is unqualified (has no domain), it is qualified
35614 with the &%qualify_recipient%& domain. The second argument must always be -1.
35616 This function does not allow you to specify a private &%errors_to%& address (as
35617 described with the structure of &%recipient_item%& above), because it pre-dates
35618 the addition of that field to the structure. However, it is easy to add such a
35619 value afterwards. For example:
35621 receive_add_recipient(US"monitor@mydom.example", -1);
35622 recipients_list[recipients_count-1].errors_to =
35623 US"postmaster@mydom.example";
35626 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
35627 This is a convenience function to remove a named recipient from the list of
35628 recipients. It returns true if a recipient was removed, and false if no
35629 matching recipient could be found. The argument must be a complete email
35636 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
35637 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
35638 This function decodes strings that are encoded according to RFC 2047. Typically
35639 these are the contents of header lines. First, each &"encoded word"& is decoded
35640 from the Q or B encoding into a byte-string. Then, if provided with the name of
35641 a charset encoding, and if the &[iconv()]& function is available, an attempt is
35642 made to translate the result to the named character set. If this fails, the
35643 binary string is returned with an error message.
35645 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
35646 maximum MIME word length is enforced. The third argument is the target
35647 encoding, or NULL if no translation is wanted.
35649 .cindex "binary zero" "in RFC 2047 decoding"
35650 .cindex "RFC 2047" "binary zero in"
35651 If a binary zero is encountered in the decoded string, it is replaced by the
35652 contents of the &%zeroval%& argument. For use with Exim headers, the value must
35653 not be 0 because header lines are handled as zero-terminated strings.
35655 The function returns the result of processing the string, zero-terminated; if
35656 &%lenptr%& is not NULL, the length of the result is set in the variable to
35657 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
35659 If an error is encountered, the function returns NULL and uses the &%error%&
35660 argument to return an error message. The variable pointed to by &%error%& is
35661 set to NULL if there is no error; it may be set non-NULL even when the function
35662 returns a non-NULL value if decoding was successful, but there was a problem
35666 .vitem &*int&~smtp_fflush(void)*&
35667 This function is used in conjunction with &'smtp_printf()'&, as described
35670 .vitem &*void&~smtp_printf(char&~*,BOOL,&~...)*&
35671 The arguments of this function are almost like &[printf()]&; it writes to the SMTP
35672 output stream. You should use this function only when there is an SMTP output
35673 stream, that is, when the incoming message is being received via interactive
35674 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
35675 is FALSE. If you want to test for an incoming message from another host (as
35676 opposed to a local process that used the &%-bs%& command line option), you can
35677 test the value of &%sender_host_address%&, which is non-NULL when a remote host
35680 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
35681 output function, so it can be used for all forms of SMTP connection.
35683 The second argument is used to request that the data be buffered
35684 (when TRUE) or flushed (along with any previously buffered, when FALSE).
35685 This is advisory only, but likely to save on system-calls and packets
35686 sent when a sequence of calls to the function are made.
35688 The argument was added in Exim version 4.90 - changing the API/ABI.
35689 Nobody noticed until 4.93 was imminent, at which point the
35690 ABI version number was incremented.
35692 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
35693 must start with an appropriate response code: 550 if you are going to return
35694 LOCAL_SCAN_REJECT, 451 if you are going to return
35695 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
35696 initial lines of a multi-line response, the code must be followed by a hyphen
35697 to indicate that the line is not the final response line. You must also ensure
35698 that the lines you write terminate with CRLF. For example:
35700 smtp_printf("550-this is some extra info\r\n");
35701 return LOCAL_SCAN_REJECT;
35703 Note that you can also create multi-line responses by including newlines in
35704 the data returned via the &%return_text%& argument. The added value of using
35705 &'smtp_printf()'& is that, for instance, you could introduce delays between
35706 multiple output lines.
35708 The &'smtp_printf()'& function does not return any error indication, because it
35710 guarantee a flush of
35711 pending output, and therefore does not test
35712 the state of the stream. (In the main code of Exim, flushing and error
35713 detection is done when Exim is ready for the next SMTP input command.) If
35714 you want to flush the output and check for an error (for example, the
35715 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
35716 arguments. It flushes the output stream, and returns a non-zero value if there
35719 .vitem &*void&~*store_get(int,BOOL)*&
35720 This function accesses Exim's internal store (memory) manager. It gets a new
35721 chunk of memory whose size is given by the first argument.
35722 The second argument should be given as TRUE if the memory will be used for
35723 data possibly coming from an attacker (eg. the message content),
35724 FALSE if it is locally-sourced.
35725 Exim bombs out if it ever
35726 runs out of memory. See the next section for a discussion of memory handling.
35728 .vitem &*void&~*store_get_perm(int,BOOL)*&
35729 This function is like &'store_get()'&, but it always gets memory from the
35730 permanent pool. See the next section for a discussion of memory handling.
35732 .vitem &*uschar&~*string_copy(uschar&~*string)*&
35735 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
35738 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
35739 These three functions create strings using Exim's dynamic memory facilities.
35740 The first makes a copy of an entire string. The second copies up to a maximum
35741 number of characters, indicated by the second argument. The third uses a format
35742 and insertion arguments to create a new string. In each case, the result is a
35743 pointer to a new string in the current memory pool. See the next section for
35749 .section "More about Exim's memory handling" "SECTmemhanloc"
35750 .cindex "&[local_scan()]& function" "memory handling"
35751 No function is provided for freeing memory, because that is never needed.
35752 The dynamic memory that Exim uses when receiving a message is automatically
35753 recycled if another message is received by the same process (this applies only
35754 to incoming SMTP connections &-- other input methods can supply only one
35755 message at a time). After receiving the last message, a reception process
35758 Because it is recycled, the normal dynamic memory cannot be used for holding
35759 data that must be preserved over a number of incoming messages on the same SMTP
35760 connection. However, Exim in fact uses two pools of dynamic memory; the second
35761 one is not recycled, and can be used for this purpose.
35763 If you want to allocate memory that remains available for subsequent messages
35764 in the same SMTP connection, you should set
35766 store_pool = POOL_PERM
35768 before calling the function that does the allocation. There is no need to
35769 restore the value if you do not need to; however, if you do want to revert to
35770 the normal pool, you can either restore the previous value of &%store_pool%& or
35771 set it explicitly to POOL_MAIN.
35773 The pool setting applies to all functions that get dynamic memory, including
35774 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
35775 There is also a convenience function called &'store_get_perm()'& that gets a
35776 block of memory from the permanent pool while preserving the value of
35783 . ////////////////////////////////////////////////////////////////////////////
35784 . ////////////////////////////////////////////////////////////////////////////
35786 .chapter "System-wide message filtering" "CHAPsystemfilter"
35787 .scindex IIDsysfil1 "filter" "system filter"
35788 .scindex IIDsysfil2 "filtering all mail"
35789 .scindex IIDsysfil3 "system filter"
35790 The previous chapters (on ACLs and the local scan function) describe checks
35791 that can be applied to messages before they are accepted by a host. There is
35792 also a mechanism for checking messages once they have been received, but before
35793 they are delivered. This is called the &'system filter'&.
35795 The system filter operates in a similar manner to users' filter files, but it
35796 is run just once per message (however many recipients the message has).
35797 It should not normally be used as a substitute for routing, because &%deliver%&
35798 commands in a system router provide new envelope recipient addresses.
35799 The system filter must be an Exim filter. It cannot be a Sieve filter.
35801 The system filter is run at the start of a delivery attempt, before any routing
35802 is done. If a message fails to be completely delivered at the first attempt,
35803 the system filter is run again at the start of every retry.
35804 If you want your filter to do something only once per message, you can make use
35805 of the &%first_delivery%& condition in an &%if%& command in the filter to
35806 prevent it happening on retries.
35808 .vindex "&$domain$&"
35809 .vindex "&$local_part$&"
35810 &*Warning*&: Because the system filter runs just once, variables that are
35811 specific to individual recipient addresses, such as &$local_part$& and
35812 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
35813 you want to run a centrally-specified filter for each recipient address
35814 independently, you can do so by setting up a suitable &(redirect)& router, as
35815 described in section &<<SECTperaddfil>>& below.
35818 .section "Specifying a system filter" "SECID212"
35819 .cindex "uid (user id)" "system filter"
35820 .cindex "gid (group id)" "system filter"
35821 The name of the file that contains the system filter must be specified by
35822 setting &%system_filter%&. If you want the filter to run under a uid and gid
35823 other than root, you must also set &%system_filter_user%& and
35824 &%system_filter_group%& as appropriate. For example:
35826 system_filter = /etc/mail/exim.filter
35827 system_filter_user = exim
35829 If a system filter generates any deliveries directly to files or pipes (via the
35830 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
35831 specified by setting &%system_filter_file_transport%& and
35832 &%system_filter_pipe_transport%&, respectively. Similarly,
35833 &%system_filter_reply_transport%& must be set to handle any messages generated
35834 by the &%reply%& command.
35837 .section "Testing a system filter" "SECID213"
35838 You can run simple tests of a system filter in the same way as for a user
35839 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
35840 are permitted only in system filters are recognized.
35842 If you want to test the combined effect of a system filter and a user filter,
35843 you can use both &%-bF%& and &%-bf%& on the same command line.
35847 .section "Contents of a system filter" "SECID214"
35848 The language used to specify system filters is the same as for users' filter
35849 files. It is described in the separate end-user document &'Exim's interface to
35850 mail filtering'&. However, there are some additional features that are
35851 available only in system filters; these are described in subsequent sections.
35852 If they are encountered in a user's filter file or when testing with &%-bf%&,
35855 .cindex "frozen messages" "manual thaw; testing in filter"
35856 There are two special conditions which, though available in users' filter
35857 files, are designed for use in system filters. The condition &%first_delivery%&
35858 is true only for the first attempt at delivering a message, and
35859 &%manually_thawed%& is true only if the message has been frozen, and
35860 subsequently thawed by an admin user. An explicit forced delivery counts as a
35861 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
35863 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
35864 specify an &"unseen"& (non-significant) delivery, and that delivery does not
35865 succeed, it will not be tried again.
35866 If you want Exim to retry an unseen delivery until it succeeds, you should
35867 arrange to set it up every time the filter runs.
35869 When a system filter finishes running, the values of the variables &$n0$& &--
35870 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
35871 users' filter files. Thus a system filter can, for example, set up &"scores"&
35872 to which users' filter files can refer.
35876 .section "Additional variable for system filters" "SECID215"
35877 .vindex "&$recipients$&"
35878 The expansion variable &$recipients$&, containing a list of all the recipients
35879 of the message (separated by commas and white space), is available in system
35880 filters. It is not available in users' filters for privacy reasons.
35884 .section "Defer, freeze, and fail commands for system filters" "SECID216"
35885 .cindex "freezing messages"
35886 .cindex "message" "freezing"
35887 .cindex "message" "forced failure"
35888 .cindex "&%fail%&" "in system filter"
35889 .cindex "&%freeze%& in system filter"
35890 .cindex "&%defer%& in system filter"
35891 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
35892 always available in system filters, but are not normally enabled in users'
35893 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
35894 for the &(redirect)& router.) These commands can optionally be followed by the
35895 word &%text%& and a string containing an error message, for example:
35897 fail text "this message looks like spam to me"
35899 The keyword &%text%& is optional if the next character is a double quote.
35901 The &%defer%& command defers delivery of the original recipients of the
35902 message. The &%fail%& command causes all the original recipients to be failed,
35903 and a bounce message to be created. The &%freeze%& command suspends all
35904 delivery attempts for the original recipients. In all cases, any new deliveries
35905 that are specified by the filter are attempted as normal after the filter has
35908 The &%freeze%& command is ignored if the message has been manually unfrozen and
35909 not manually frozen since. This means that automatic freezing by a system
35910 filter can be used as a way of checking out suspicious messages. If a message
35911 is found to be all right, manually unfreezing it allows it to be delivered.
35913 .cindex "log" "&%fail%& command log line"
35914 .cindex "&%fail%&" "log line; reducing"
35915 The text given with a fail command is used as part of the bounce message as
35916 well as being written to the log. If the message is quite long, this can fill
35917 up a lot of log space when such failures are common. To reduce the size of the
35918 log message, Exim interprets the text in a special way if it starts with the
35919 two characters &`<<`& and contains &`>>`& later. The text between these two
35920 strings is written to the log, and the rest of the text is used in the bounce
35921 message. For example:
35923 fail "<<filter test 1>>Your message is rejected \
35924 because it contains attachments that we are \
35925 not prepared to receive."
35928 .cindex "loop" "caused by &%fail%&"
35929 Take great care with the &%fail%& command when basing the decision to fail on
35930 the contents of the message, because the bounce message will of course include
35931 the contents of the original message and will therefore trigger the &%fail%&
35932 command again (causing a mail loop) unless steps are taken to prevent this.
35933 Testing the &%error_message%& condition is one way to prevent this. You could
35936 if $message_body contains "this is spam" and not error_message
35937 then fail text "spam is not wanted here" endif
35939 though of course that might let through unwanted bounce messages. The
35940 alternative is clever checking of the body and/or headers to detect bounces
35941 generated by the filter.
35943 The interpretation of a system filter file ceases after a
35945 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
35946 set up earlier in the filter file are honoured, so you can use a sequence such
35952 to send a specified message when the system filter is freezing (or deferring or
35953 failing) a message. The normal deliveries for the message do not, of course,
35958 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
35959 .cindex "header lines" "adding; in system filter"
35960 .cindex "header lines" "removing; in system filter"
35961 .cindex "filter" "header lines; adding/removing"
35962 Two filter commands that are available only in system filters are:
35964 headers add <string>
35965 headers remove <string>
35967 The argument for the &%headers add%& is a string that is expanded and then
35968 added to the end of the message's headers. It is the responsibility of the
35969 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
35970 space is ignored, and if the string is otherwise empty, or if the expansion is
35971 forced to fail, the command has no effect.
35973 You can use &"\n"& within the string, followed by white space, to specify
35974 continued header lines. More than one header may be added in one command by
35975 including &"\n"& within the string without any following white space. For
35978 headers add "X-header-1: ....\n \
35979 continuation of X-header-1 ...\n\
35982 Note that the header line continuation white space after the first newline must
35983 be placed before the backslash that continues the input string, because white
35984 space after input continuations is ignored.
35986 The argument for &%headers remove%& is a colon-separated list of header names.
35987 This command applies only to those headers that are stored with the message;
35988 those that are added at delivery time (such as &'Envelope-To:'& and
35989 &'Return-Path:'&) cannot be removed by this means. If there is more than one
35990 header with the same name, they are all removed.
35992 The &%headers%& command in a system filter makes an immediate change to the set
35993 of header lines that was received with the message (with possible additions
35994 from ACL processing). Subsequent commands in the system filter operate on the
35995 modified set, which also forms the basis for subsequent message delivery.
35996 Unless further modified during routing or transporting, this set of headers is
35997 used for all recipients of the message.
35999 During routing and transporting, the variables that refer to the contents of
36000 header lines refer only to those lines that are in this set. Thus, header lines
36001 that are added by a system filter are visible to users' filter files and to all
36002 routers and transports. This contrasts with the manipulation of header lines by
36003 routers and transports, which is not immediate, but which instead is saved up
36004 until the message is actually being written (see section
36005 &<<SECTheadersaddrem>>&).
36007 If the message is not delivered at the first attempt, header lines that were
36008 added by the system filter are stored with the message, and so are still
36009 present at the next delivery attempt. Header lines that were removed are still
36010 present, but marked &"deleted"& so that they are not transported with the
36011 message. For this reason, it is usual to make the &%headers%& command
36012 conditional on &%first_delivery%& so that the set of header lines is not
36013 modified more than once.
36015 Because header modification in a system filter acts immediately, you have to
36016 use an indirect approach if you want to modify the contents of a header line.
36019 headers add "Old-Subject: $h_subject:"
36020 headers remove "Subject"
36021 headers add "Subject: new subject (was: $h_old-subject:)"
36022 headers remove "Old-Subject"
36027 .section "Setting an errors address in a system filter" "SECID217"
36028 .cindex "envelope from"
36029 .cindex "envelope sender"
36030 In a system filter, if a &%deliver%& command is followed by
36032 errors_to <some address>
36034 in order to change the envelope sender (and hence the error reporting) for that
36035 delivery, any address may be specified. (In a user filter, only the current
36036 user's address can be set.) For example, if some mail is being monitored, you
36039 unseen deliver monitor@spying.example errors_to root@local.example
36041 to take a copy which would not be sent back to the normal error reporting
36042 address if its delivery failed.
36046 .section "Per-address filtering" "SECTperaddfil"
36047 .vindex "&$domain_data$&"
36048 .vindex "&$local_part_data$&"
36049 In contrast to the system filter, which is run just once per message for each
36050 delivery attempt, it is also possible to set up a system-wide filtering
36051 operation that runs once for each recipient address. In this case, variables
36052 such as &$local_part_data$& and &$domain_data$& can be used,
36053 and indeed, the choice of filter file could be made dependent on them.
36054 This is an example of a router which implements such a filter:
36059 domains = +local_domains
36060 file = /central/filters/$local_part_data
36065 The filter is run in a separate process under its own uid. Therefore, either
36066 &%check_local_user%& must be set (as above), in which case the filter is run as
36067 the local user, or the &%user%& option must be used to specify which user to
36068 use. If both are set, &%user%& overrides.
36070 Care should be taken to ensure that none of the commands in the filter file
36071 specify a significant delivery if the message is to go on to be delivered to
36072 its intended recipient. The router will not then claim to have dealt with the
36073 address, so it will be passed on to subsequent routers to be delivered in the
36075 .ecindex IIDsysfil1
36076 .ecindex IIDsysfil2
36077 .ecindex IIDsysfil3
36084 . ////////////////////////////////////////////////////////////////////////////
36085 . ////////////////////////////////////////////////////////////////////////////
36087 .chapter "Message processing" "CHAPmsgproc"
36088 .scindex IIDmesproc "message" "general processing"
36089 Exim performs various transformations on the sender and recipient addresses of
36090 all messages that it handles, and also on the messages' header lines. Some of
36091 these are optional and configurable, while others always take place. All of
36092 this processing, except rewriting as a result of routing, and the addition or
36093 removal of header lines while delivering, happens when a message is received,
36094 before it is placed on Exim's queue.
36096 Some of the automatic processing takes place by default only for
36097 &"locally-originated"& messages. This adjective is used to describe messages
36098 that are not received over TCP/IP, but instead are passed to an Exim process on
36099 its standard input. This includes the interactive &"local SMTP"& case that is
36100 set up by the &%-bs%& command line option.
36102 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
36103 or ::1) are not considered to be locally-originated. Exim does not treat the
36104 loopback interface specially in any way.
36106 If you want the loopback interface to be treated specially, you must ensure
36107 that there are appropriate entries in your ACLs.
36112 .section "Submission mode for non-local messages" "SECTsubmodnon"
36113 .cindex "message" "submission"
36114 .cindex "submission mode"
36115 Processing that happens automatically for locally-originated messages (unless
36116 &%suppress_local_fixups%& is set) can also be requested for messages that are
36117 received over TCP/IP. The term &"submission mode"& is used to describe this
36118 state. Submission mode is set by the modifier
36120 control = submission
36122 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
36123 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
36124 a local submission, and is normally used when the source of the message is
36125 known to be an MUA running on a client host (as opposed to an MTA). For
36126 example, to set submission mode for messages originating on the IPv4 loopback
36127 interface, you could include the following in the MAIL ACL:
36129 warn hosts = 127.0.0.1
36130 control = submission
36132 .cindex "&%sender_retain%& submission option"
36133 There are some options that can be used when setting submission mode. A slash
36134 is used to separate options. For example:
36136 control = submission/sender_retain
36138 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
36139 true and &%local_from_check%& false for the current incoming message. The first
36140 of these allows an existing &'Sender:'& header in the message to remain, and
36141 the second suppresses the check to ensure that &'From:'& matches the
36142 authenticated sender. With this setting, Exim still fixes up messages by adding
36143 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
36144 attempt to check sender authenticity in header lines.
36146 When &%sender_retain%& is not set, a submission mode setting may specify a
36147 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
36150 control = submission/domain=some.domain
36152 The domain may be empty. How this value is used is described in sections
36153 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
36154 that allows you to specify the user's full name for inclusion in a created
36155 &'Sender:'& or &'From:'& header line. For example:
36157 accept authenticated = *
36158 control = submission/domain=wonderland.example/\
36159 name=${lookup {$authenticated_id} \
36160 lsearch {/etc/exim/namelist}}
36162 Because the name may contain any characters, including slashes, the &%name%&
36163 option must be given last. The remainder of the string is used as the name. For
36164 the example above, if &_/etc/exim/namelist_& contains:
36166 bigegg: Humpty Dumpty
36168 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
36171 Sender: Humpty Dumpty <bigegg@wonderland.example>
36173 .cindex "return path" "in submission mode"
36174 By default, submission mode forces the return path to the same address as is
36175 used to create the &'Sender:'& header. However, if &%sender_retain%& is
36176 specified, the return path is also left unchanged.
36178 &*Note*&: The changes caused by submission mode take effect after the predata
36179 ACL. This means that any sender checks performed before the fix-ups use the
36180 untrusted sender address specified by the user, not the trusted sender address
36181 specified by submission mode. Although this might be slightly unexpected, it
36182 does mean that you can configure ACL checks to spot that a user is trying to
36183 spoof another's address.
36185 .section "Line endings" "SECTlineendings"
36186 .cindex "line endings"
36187 .cindex "carriage return"
36189 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
36190 linefeed) is the line ending for messages transmitted over the Internet using
36191 SMTP over TCP/IP. However, within individual operating systems, different
36192 conventions are used. For example, Unix-like systems use just LF, but others
36193 use CRLF or just CR.
36195 Exim was designed for Unix-like systems, and internally, it stores messages
36196 using the system's convention of a single LF as a line terminator. When
36197 receiving a message, all line endings are translated to this standard format.
36198 Originally, it was thought that programs that passed messages directly to an
36199 MTA within an operating system would use that system's convention. Experience
36200 has shown that this is not the case; for example, there are Unix applications
36201 that use CRLF in this circumstance. For this reason, and for compatibility with
36202 other MTAs, the way Exim handles line endings for all messages is now as
36206 LF not preceded by CR is treated as a line ending.
36208 CR is treated as a line ending; if it is immediately followed by LF, the LF
36211 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
36212 nor a local message in the state where a line containing only a dot is a
36215 If a bare CR is encountered within a header line, an extra space is added after
36216 the line terminator so as not to end the header line. The reasoning behind this
36217 is that bare CRs in header lines are most likely either to be mistakes, or
36218 people trying to play silly games.
36220 If the first header line received in a message ends with CRLF, a subsequent
36221 bare LF in a header line is treated in the same way as a bare CR in a header
36229 .section "Unqualified addresses" "SECID218"
36230 .cindex "unqualified addresses"
36231 .cindex "address" "qualification"
36232 By default, Exim expects every envelope address it receives from an external
36233 host to be fully qualified. Unqualified addresses cause negative responses to
36234 SMTP commands. However, because SMTP is used as a means of transporting
36235 messages from MUAs running on personal workstations, there is sometimes a
36236 requirement to accept unqualified addresses from specific hosts or IP networks.
36238 Exim has two options that separately control which hosts may send unqualified
36239 sender or recipient addresses in SMTP commands, namely
36240 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
36241 cases, if an unqualified address is accepted, it is qualified by adding the
36242 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
36244 .oindex "&%qualify_domain%&"
36245 .oindex "&%qualify_recipient%&"
36246 Unqualified addresses in header lines are automatically qualified for messages
36247 that are locally originated, unless the &%-bnq%& option is given on the command
36248 line. For messages received over SMTP, unqualified addresses in header lines
36249 are qualified only if unqualified addresses are permitted in SMTP commands. In
36250 other words, such qualification is also controlled by
36251 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
36256 .section "The UUCP From line" "SECID219"
36257 .cindex "&""From""& line"
36258 .cindex "UUCP" "&""From""& line"
36259 .cindex "sender" "address"
36260 .oindex "&%uucp_from_pattern%&"
36261 .oindex "&%uucp_from_sender%&"
36262 .cindex "envelope from"
36263 .cindex "envelope sender"
36264 .cindex "Sendmail compatibility" "&""From""& line"
36265 Messages that have come from UUCP (and some other applications) often begin
36266 with a line containing the envelope sender and a timestamp, following the word
36267 &"From"&. Examples of two common formats are:
36269 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
36270 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
36272 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
36273 Exim recognizes such lines at the start of messages that are submitted to it
36274 via the command line (that is, on the standard input). It does not recognize
36275 such lines in incoming SMTP messages, unless the sending host matches
36276 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
36277 and &%ignore_fromline_local%& is set. The recognition is controlled by a
36278 regular expression that is defined by the &%uucp_from_pattern%& option, whose
36279 default value matches the two common cases shown above and puts the address
36280 that follows &"From"& into &$1$&.
36282 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
36283 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
36284 a trusted user, the message's sender address is constructed by expanding the
36285 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
36286 then parsed as an RFC 2822 address. If there is no domain, the local part is
36287 qualified with &%qualify_domain%& unless it is the empty string. However, if
36288 the command line &%-f%& option is used, it overrides the &"From"& line.
36290 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
36291 sender address is not changed. This is also the case for incoming SMTP messages
36292 that are permitted to contain &"From"& lines.
36294 Only one &"From"& line is recognized. If there is more than one, the second is
36295 treated as a data line that starts the body of the message, as it is not valid
36296 as a header line. This also happens if a &"From"& line is present in an
36297 incoming SMTP message from a source that is not permitted to send them.
36301 .section "Resent- header lines" "SECID220"
36303 RFC 2822 makes provision for sets of header lines starting with the string
36304 &`Resent-`& to be added to a message when it is resent by the original
36305 recipient to somebody else. These headers are &'Resent-Date:'&,
36306 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
36307 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
36310 &'Resent fields are strictly informational. They MUST NOT be used in the normal
36311 processing of replies or other such automatic actions on messages.'&
36314 This leaves things a bit vague as far as other processing actions such as
36315 address rewriting are concerned. Exim treats &%Resent-%& header lines as
36319 A &'Resent-From:'& line that just contains the login id of the submitting user
36320 is automatically rewritten in the same way as &'From:'& (see below).
36322 If there's a rewriting rule for a particular header line, it is also applied to
36323 &%Resent-%& header lines of the same type. For example, a rule that rewrites
36324 &'From:'& also rewrites &'Resent-From:'&.
36326 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
36329 For a locally-submitted message,
36330 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
36331 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
36332 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
36333 included in log lines in this case.
36335 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
36336 &%Resent-%& header lines are present.
36342 .section "The Auto-Submitted: header line" "SECID221"
36343 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
36344 includes the header line:
36346 Auto-Submitted: auto-replied
36349 .section "The Bcc: header line" "SECID222"
36350 .cindex "&'Bcc:'& header line"
36351 If Exim is called with the &%-t%& option, to take recipient addresses from a
36352 message's header, it removes any &'Bcc:'& header line that may exist (after
36353 extracting its addresses). If &%-t%& is not present on the command line, any
36354 existing &'Bcc:'& is not removed.
36357 .section "The Date: header line" "SECID223"
36359 If a locally-generated or submission-mode message has no &'Date:'& header line,
36360 Exim adds one, using the current date and time, unless the
36361 &%suppress_local_fixups%& control has been specified.
36363 .section "The Delivery-date: header line" "SECID224"
36364 .cindex "&'Delivery-date:'& header line"
36365 .oindex "&%delivery_date_remove%&"
36366 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
36367 set. Exim can be configured to add them to the final delivery of messages. (See
36368 the generic &%delivery_date_add%& transport option.) They should not be present
36369 in messages in transit. If the &%delivery_date_remove%& configuration option is
36370 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
36374 .section "The Envelope-to: header line" "SECID225"
36375 .chindex Envelope-to:
36376 .oindex "&%envelope_to_remove%&"
36377 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
36378 Exim can be configured to add them to the final delivery of messages. (See the
36379 generic &%envelope_to_add%& transport option.) They should not be present in
36380 messages in transit. If the &%envelope_to_remove%& configuration option is set
36381 (the default), Exim removes &'Envelope-to:'& header lines from incoming
36385 .section "The From: header line" "SECTthefrohea"
36387 .cindex "Sendmail compatibility" "&""From""& line"
36388 .cindex "message" "submission"
36389 .cindex "submission mode"
36390 If a submission-mode message does not contain a &'From:'& header line, Exim
36391 adds one if either of the following conditions is true:
36394 The envelope sender address is not empty (that is, this is not a bounce
36395 message). The added header line copies the envelope sender address.
36397 .vindex "&$authenticated_id$&"
36398 The SMTP session is authenticated and &$authenticated_id$& is not empty.
36400 .vindex "&$qualify_domain$&"
36401 If no domain is specified by the submission control, the local part is
36402 &$authenticated_id$& and the domain is &$qualify_domain$&.
36404 If a non-empty domain is specified by the submission control, the local
36405 part is &$authenticated_id$&, and the domain is the specified domain.
36407 If an empty domain is specified by the submission control,
36408 &$authenticated_id$& is assumed to be the complete address.
36412 A non-empty envelope sender takes precedence.
36414 If a locally-generated incoming message does not contain a &'From:'& header
36415 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
36416 containing the sender's address. The calling user's login name and full name
36417 are used to construct the address, as described in section &<<SECTconstr>>&.
36418 They are obtained from the password data by calling &[getpwuid()]& (but see the
36419 &%unknown_login%& configuration option). The address is qualified with
36420 &%qualify_domain%&.
36422 For compatibility with Sendmail, if an incoming, non-SMTP message has a
36423 &'From:'& header line containing just the unqualified login name of the calling
36424 user, this is replaced by an address containing the user's login name and full
36425 name as described in section &<<SECTconstr>>&.
36428 .section "The Message-ID: header line" "SECID226"
36429 .chindex Message-ID:
36430 .cindex "message" "submission"
36431 .oindex "&%message_id_header_text%&"
36432 If a locally-generated or submission-mode incoming message does not contain a
36433 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
36434 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
36435 to the message. If there are any &'Resent-:'& headers in the message, it
36436 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
36437 message id, preceded by the letter E to ensure it starts with a letter, and
36438 followed by @ and the primary host name. Additional information can be included
36439 in this header line by setting the &%message_id_header_text%& and/or
36440 &%message_id_header_domain%& options.
36443 .section "The Received: header line" "SECID227"
36445 A &'Received:'& header line is added at the start of every message. The
36446 contents are defined by the &%received_header_text%& configuration option, and
36447 Exim automatically adds a semicolon and a timestamp to the configured string.
36449 The &'Received:'& header is generated as soon as the message's header lines
36450 have been received. At this stage, the timestamp in the &'Received:'& header
36451 line is the time that the message started to be received. This is the value
36452 that is seen by the DATA ACL and by the &[local_scan()]& function.
36454 Once a message is accepted, the timestamp in the &'Received:'& header line is
36455 changed to the time of acceptance, which is (apart from a small delay while the
36456 -H spool file is written) the earliest time at which delivery could start.
36459 .section "The References: header line" "SECID228"
36460 .chindex References:
36461 Messages created by the &(autoreply)& transport include a &'References:'&
36462 header line. This is constructed according to the rules that are described in
36463 section 3.64 of RFC 2822 (which states that replies should contain such a
36464 header line), and section 3.14 of RFC 3834 (which states that automatic
36465 responses are not different in this respect). However, because some mail
36466 processing software does not cope well with very long header lines, no more
36467 than 12 message IDs are copied from the &'References:'& header line in the
36468 incoming message. If there are more than 12, the first one and then the final
36469 11 are copied, before adding the message ID of the incoming message.
36473 .section "The Return-path: header line" "SECID229"
36474 .chindex Return-path:
36475 .oindex "&%return_path_remove%&"
36476 &'Return-path:'& header lines are defined as something an MTA may insert when
36477 it does the final delivery of messages. (See the generic &%return_path_add%&
36478 transport option.) Therefore, they should not be present in messages in
36479 transit. If the &%return_path_remove%& configuration option is set (the
36480 default), Exim removes &'Return-path:'& header lines from incoming messages.
36484 .section "The Sender: header line" "SECTthesenhea"
36485 .cindex "&'Sender:'& header line"
36486 .cindex "message" "submission"
36488 For a locally-originated message from an untrusted user, Exim may remove an
36489 existing &'Sender:'& header line, and it may add a new one. You can modify
36490 these actions by setting the &%local_sender_retain%& option true, the
36491 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
36494 When a local message is received from an untrusted user and
36495 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
36496 control has not been set, a check is made to see if the address given in the
36497 &'From:'& header line is the correct (local) sender of the message. The address
36498 that is expected has the login name as the local part and the value of
36499 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
36500 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
36501 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
36502 line is added to the message.
36504 If you set &%local_from_check%& false, this checking does not occur. However,
36505 the removal of an existing &'Sender:'& line still happens, unless you also set
36506 &%local_sender_retain%& to be true. It is not possible to set both of these
36507 options true at the same time.
36509 .cindex "submission mode"
36510 By default, no processing of &'Sender:'& header lines is done for messages
36511 received over TCP/IP or for messages submitted by trusted users. However, when
36512 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
36513 not specified on the submission control, the following processing takes place:
36515 .vindex "&$authenticated_id$&"
36516 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
36517 authenticated, and &$authenticated_id$& is not empty, a sender address is
36518 created as follows:
36521 .vindex "&$qualify_domain$&"
36522 If no domain is specified by the submission control, the local part is
36523 &$authenticated_id$& and the domain is &$qualify_domain$&.
36525 If a non-empty domain is specified by the submission control, the local part
36526 is &$authenticated_id$&, and the domain is the specified domain.
36528 If an empty domain is specified by the submission control,
36529 &$authenticated_id$& is assumed to be the complete address.
36532 This address is compared with the address in the &'From:'& header line. If they
36533 are different, a &'Sender:'& header line containing the created address is
36534 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
36535 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
36537 .cindex "return path" "created from &'Sender:'&"
36538 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
36539 the message (the envelope sender address) is changed to be the same address,
36540 except in the case of submission mode when &%sender_retain%& is specified.
36544 .section "Adding and removing header lines in routers and transports" &&&
36545 "SECTheadersaddrem"
36546 .cindex "header lines" "adding; in router or transport"
36547 .cindex "header lines" "removing; in router or transport"
36548 When a message is delivered, the addition and removal of header lines can be
36549 specified in a system filter, or on any of the routers and transports that
36550 process the message. Section &<<SECTaddremheasys>>& contains details about
36551 modifying headers in a system filter. Header lines can also be added in an ACL
36552 as a message is received (see section &<<SECTaddheadacl>>&).
36554 In contrast to what happens in a system filter, header modifications that are
36555 specified on routers and transports apply only to the particular recipient
36556 addresses that are being processed by those routers and transports. These
36557 changes do not actually take place until a copy of the message is being
36558 transported. Therefore, they do not affect the basic set of header lines, and
36559 they do not affect the values of the variables that refer to header lines.
36561 &*Note*&: In particular, this means that any expansions in the configuration of
36562 the transport cannot refer to the modified header lines, because such
36563 expansions all occur before the message is actually transported.
36565 For both routers and transports, the argument of a &%headers_add%&
36566 option must be in the form of one or more RFC 2822 header lines, separated by
36567 newlines (coded as &"\n"&). For example:
36569 headers_add = X-added-header: added by $primary_hostname\n\
36570 X-added-second: another added header line
36572 Exim does not check the syntax of these added header lines.
36574 Multiple &%headers_add%& options for a single router or transport can be
36575 specified; the values will append to a single list of header lines.
36576 Each header-line is separately expanded.
36578 The argument of a &%headers_remove%& option must consist of a colon-separated
36579 list of header names. This is confusing, because header names themselves are
36580 often terminated by colons. In this case, the colons are the list separators,
36581 not part of the names. For example:
36583 headers_remove = return-receipt-to:acknowledge-to
36586 Multiple &%headers_remove%& options for a single router or transport can be
36587 specified; the arguments will append to a single header-names list.
36588 Each item is separately expanded.
36589 Note that colons in complex expansions which are used to
36590 form all or part of a &%headers_remove%& list
36591 will act as list separators.
36593 When &%headers_add%& or &%headers_remove%& is specified on a router,
36594 items are expanded at routing time,
36595 and then associated with all addresses that are
36596 accepted by that router, and also with any new addresses that it generates. If
36597 an address passes through several routers as a result of aliasing or
36598 forwarding, the changes are cumulative.
36600 .oindex "&%unseen%&"
36601 However, this does not apply to multiple routers that result from the use of
36602 the &%unseen%& option. Any header modifications that were specified by the
36603 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
36605 Addresses that end up with different &%headers_add%& or &%headers_remove%&
36606 settings cannot be delivered together in a batch, so a transport is always
36607 dealing with a set of addresses that have the same header-processing
36610 The transport starts by writing the original set of header lines that arrived
36611 with the message, possibly modified by the system filter. As it writes out
36612 these lines, it consults the list of header names that were attached to the
36613 recipient address(es) by &%headers_remove%& options in routers, and it also
36614 consults the transport's own &%headers_remove%& option. Header lines whose
36615 names are on either of these lists are not written out. If there are multiple
36616 instances of any listed header, they are all skipped.
36618 After the remaining original header lines have been written, new header
36619 lines that were specified by routers' &%headers_add%& options are written, in
36620 the order in which they were attached to the address. These are followed by any
36621 header lines specified by the transport's &%headers_add%& option.
36623 This way of handling header line modifications in routers and transports has
36624 the following consequences:
36627 The original set of header lines, possibly modified by the system filter,
36628 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
36629 to it, at all times.
36631 Header lines that are added by a router's
36632 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
36633 expansion syntax in subsequent routers or the transport.
36635 Conversely, header lines that are specified for removal by &%headers_remove%&
36636 in a router remain visible to subsequent routers and the transport.
36638 Headers added to an address by &%headers_add%& in a router cannot be removed by
36639 a later router or by a transport.
36641 An added header can refer to the contents of an original header that is to be
36642 removed, even it has the same name as the added header. For example:
36644 headers_remove = subject
36645 headers_add = Subject: new subject (was: $h_subject:)
36649 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
36650 for a &(redirect)& router that has the &%one_time%& option set.
36656 .section "Constructed addresses" "SECTconstr"
36657 .cindex "address" "constructed"
36658 .cindex "constructed address"
36659 When Exim constructs a sender address for a locally-generated message, it uses
36662 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
36666 Zaphod Beeblebrox <zaphod@end.univ.example>
36668 The user name is obtained from the &%-F%& command line option if set, or
36669 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
36670 &"gecos"& field from the password entry. If the &"gecos"& field contains an
36671 ampersand character, this is replaced by the login name with the first letter
36672 upper cased, as is conventional in a number of operating systems. See the
36673 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
36674 The &%unknown_username%& option can be used to specify user names in cases when
36675 there is no password file entry.
36678 In all cases, the user name is made to conform to RFC 2822 by quoting all or
36679 parts of it if necessary. In addition, if it contains any non-printing
36680 characters, it is encoded as described in RFC 2047, which defines a way of
36681 including non-ASCII characters in header lines. The value of the
36682 &%headers_charset%& option specifies the name of the encoding that is used (the
36683 characters are assumed to be in this encoding). The setting of
36684 &%print_topbitchars%& controls whether characters with the top bit set (that
36685 is, with codes greater than 127) count as printing characters or not.
36689 .section "Case of local parts" "SECID230"
36690 .cindex "case of local parts"
36691 .cindex "local part" "case of"
36692 RFC 2822 states that the case of letters in the local parts of addresses cannot
36693 be assumed to be non-significant. Exim preserves the case of local parts of
36694 addresses, but by default it uses a lower-cased form when it is routing,
36695 because on most Unix systems, usernames are in lower case and case-insensitive
36696 routing is required. However, any particular router can be made to use the
36697 original case for local parts by setting the &%caseful_local_part%& generic
36700 .cindex "mixed-case login names"
36701 If you must have mixed-case user names on your system, the best way to proceed,
36702 assuming you want case-independent handling of incoming email, is to set up
36703 your first router to convert incoming local parts in your domains to the
36704 correct case by means of a file lookup. For example:
36708 domains = +local_domains
36709 data = ${lookup{$local_part}cdb\
36710 {/etc/usercased.cdb}{$value}fail}\
36713 For this router, the local part is forced to lower case by the default action
36714 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
36715 up a new local part in the correct case. If you then set &%caseful_local_part%&
36716 on any subsequent routers which process your domains, they will operate on
36717 local parts with the correct case in a case-sensitive manner.
36721 .section "Dots in local parts" "SECID231"
36722 .cindex "dot" "in local part"
36723 .cindex "local part" "dots in"
36724 RFC 2822 forbids empty components in local parts. That is, an unquoted local
36725 part may not begin or end with a dot, nor have two consecutive dots in the
36726 middle. However, it seems that many MTAs do not enforce this, so Exim permits
36727 empty components for compatibility.
36731 .section "Rewriting addresses" "SECID232"
36732 .cindex "rewriting" "addresses"
36733 Rewriting of sender and recipient addresses, and addresses in headers, can
36734 happen automatically, or as the result of configuration options, as described
36735 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
36736 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
36738 Automatic rewriting includes qualification, as mentioned above. The other case
36739 in which it can happen is when an incomplete non-local domain is given. The
36740 routing process may cause this to be expanded into the full domain name. For
36741 example, a header such as
36745 might get rewritten as
36747 To: hare@teaparty.wonderland.fict.example
36749 Rewriting as a result of routing is the one kind of message processing that
36750 does not happen at input time, as it cannot be done until the address has
36753 Strictly, one should not do &'any'& deliveries of a message until all its
36754 addresses have been routed, in case any of the headers get changed as a
36755 result of routing. However, doing this in practice would hold up many
36756 deliveries for unreasonable amounts of time, just because one address could not
36757 immediately be routed. Exim therefore does not delay other deliveries when
36758 routing of one or more addresses is deferred.
36759 .ecindex IIDmesproc
36763 . ////////////////////////////////////////////////////////////////////////////
36764 . ////////////////////////////////////////////////////////////////////////////
36766 .chapter "SMTP processing" "CHAPSMTP"
36767 .scindex IIDsmtpproc1 "SMTP" "processing details"
36768 .scindex IIDsmtpproc2 "LMTP" "processing details"
36769 Exim supports a number of different ways of using the SMTP protocol, and its
36770 LMTP variant, which is an interactive protocol for transferring messages into a
36771 closed mail store application. This chapter contains details of how SMTP is
36772 processed. For incoming mail, the following are available:
36775 SMTP over TCP/IP (Exim daemon or &'inetd'&);
36777 SMTP over the standard input and output (the &%-bs%& option);
36779 Batched SMTP on the standard input (the &%-bS%& option).
36782 For mail delivery, the following are available:
36785 SMTP over TCP/IP (the &(smtp)& transport);
36787 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
36790 LMTP over a pipe to a process running in the local host (the &(lmtp)&
36793 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
36794 the &%use_bsmtp%& option set).
36797 &'Batched SMTP'& is the name for a process in which batches of messages are
36798 stored in or read from files (or pipes), in a format in which SMTP commands are
36799 used to contain the envelope information.
36803 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
36804 .cindex "SMTP" "outgoing over TCP/IP"
36805 .cindex "outgoing SMTP over TCP/IP"
36806 .cindex "LMTP" "over TCP/IP"
36807 .cindex "outgoing LMTP over TCP/IP"
36810 .cindex "SIZE" "option on MAIL command"
36811 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
36812 The &%protocol%& option selects which protocol is to be used, but the actual
36813 processing is the same in both cases.
36815 .cindex "ESMTP extensions" SIZE
36816 If, in response to its EHLO command, Exim is told that the SIZE
36817 extension is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
36818 command. The value of <&'n'&> is the message size plus the value of the
36819 &%size_addition%& option (default 1024) to allow for additions to the message
36820 such as per-transport header lines, or changes made in a
36821 .cindex "transport" "filter"
36822 .cindex "filter" "transport filter"
36823 transport filter. If &%size_addition%& is set negative, the use of SIZE is
36826 If the remote server advertises support for PIPELINING, Exim uses the
36827 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
36828 required for the transaction.
36830 If the remote server advertises support for the STARTTLS command, and Exim
36831 was built to support TLS encryption, it tries to start a TLS session unless the
36832 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
36833 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
36834 is called for verification.
36836 If the remote server advertises support for the AUTH command, Exim scans
36837 the authenticators configuration for any suitable client settings, as described
36838 in chapter &<<CHAPSMTPAUTH>>&.
36840 .cindex "carriage return"
36842 Responses from the remote host are supposed to be terminated by CR followed by
36843 LF. However, there are known to be hosts that do not send CR characters, so in
36844 order to be able to interwork with such hosts, Exim treats LF on its own as a
36847 If a message contains a number of different addresses, all those with the same
36848 characteristics (for example, the same envelope sender) that resolve to the
36849 same set of hosts, in the same order, are sent in a single SMTP transaction,
36850 even if they are for different domains, unless there are more than the setting
36851 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
36852 they are split into groups containing no more than &%max_rcpt%&s addresses
36853 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
36854 in parallel sessions. The order of hosts with identical MX values is not
36855 significant when checking whether addresses can be batched in this way.
36857 When the &(smtp)& transport suffers a temporary failure that is not
36858 message-related, Exim updates its transport-specific database, which contains
36859 records indexed by host name that remember which messages are waiting for each
36860 particular host. It also updates the retry database with new retry times.
36862 .cindex "hints database" "retry keys"
36863 Exim's retry hints are based on host name plus IP address, so if one address of
36864 a multi-homed host is broken, it will soon be skipped most of the time.
36865 See the next section for more detail about error handling.
36867 .cindex "SMTP" "passed connection"
36868 .cindex "SMTP" "batching over TCP/IP"
36869 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
36870 looks in the hints database for the transport to see if there are any queued
36871 messages waiting for the host to which it is connected. If it finds one, it
36872 creates a new Exim process using the &%-MC%& option (which can only be used by
36873 a process running as root or the Exim user) and passes the TCP/IP socket to it
36874 so that it can deliver another message using the same socket. The new process
36875 does only those deliveries that are routed to the connected host, and may in
36876 turn pass the socket on to a third process, and so on.
36878 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
36879 limit the number of messages sent down a single TCP/IP connection.
36881 .cindex "asterisk" "after IP address"
36882 The second and subsequent messages delivered down an existing connection are
36883 identified in the main log by the addition of an asterisk after the closing
36884 square bracket of the IP address.
36889 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
36890 .cindex "error" "in outgoing SMTP"
36891 .cindex "SMTP" "errors in outgoing"
36892 .cindex "host" "error"
36893 Three different kinds of error are recognized for outgoing SMTP: host errors,
36894 message errors, and recipient errors.
36897 .vitem "&*Host errors*&"
36898 A host error is not associated with a particular message or with a
36899 particular recipient of a message. The host errors are:
36902 Connection refused or timed out,
36904 Any error response code on connection,
36906 Any error response code to EHLO or HELO,
36908 Loss of connection at any time, except after &"."&,
36910 I/O errors at any time,
36912 Timeouts during the session, other than in response to MAIL, RCPT or
36913 the &"."& at the end of the data.
36916 For a host error, a permanent error response on connection, or in response to
36917 EHLO, causes all addresses routed to the host to be failed. Any other host
36918 error causes all addresses to be deferred, and retry data to be created for the
36919 host. It is not tried again, for any message, until its retry time arrives. If
36920 the current set of addresses are not all delivered in this run (to some
36921 alternative host), the message is added to the list of those waiting for this
36922 host, so if it is still undelivered when a subsequent successful delivery is
36923 made to the host, it will be sent down the same SMTP connection.
36925 .vitem "&*Message errors*&"
36926 .cindex "message" "error"
36927 A message error is associated with a particular message when sent to a
36928 particular host, but not with a particular recipient of the message. The
36929 message errors are:
36932 Any error response code to MAIL, DATA, or the &"."& that terminates
36935 Timeout after MAIL,
36937 Timeout or loss of connection after the &"."& that terminates the data. A
36938 timeout after the DATA command itself is treated as a host error, as is loss of
36939 connection at any other time.
36942 For a message error, a permanent error response (5&'xx'&) causes all addresses
36943 to be failed, and a delivery error report to be returned to the sender. A
36944 temporary error response (4&'xx'&), or one of the timeouts, causes all
36945 addresses to be deferred. Retry data is not created for the host, but instead,
36946 a retry record for the combination of host plus message id is created. The
36947 message is not added to the list of those waiting for this host. This ensures
36948 that the failing message will not be sent to this host again until the retry
36949 time arrives. However, other messages that are routed to the host are not
36950 affected, so if it is some property of the message that is causing the error,
36951 it will not stop the delivery of other mail.
36953 If the remote host specified support for the SIZE parameter in its response
36954 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
36955 over-large message will cause a message error because the error arrives as a
36958 .vitem "&*Recipient errors*&"
36959 .cindex "recipient" "error"
36960 A recipient error is associated with a particular recipient of a message. The
36961 recipient errors are:
36964 Any error response to RCPT,
36966 Timeout after RCPT.
36969 For a recipient error, a permanent error response (5&'xx'&) causes the
36970 recipient address to be failed, and a bounce message to be returned to the
36971 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
36972 address to be deferred, and routing retry data to be created for it. This is
36973 used to delay processing of the address in subsequent queue runs, until its
36974 routing retry time arrives. This applies to all messages, but because it
36975 operates only in queue runs, one attempt will be made to deliver a new message
36976 to the failing address before the delay starts to operate. This ensures that,
36977 if the failure is really related to the message rather than the recipient
36978 (&"message too big for this recipient"& is a possible example), other messages
36979 have a chance of getting delivered. If a delivery to the address does succeed,
36980 the retry information gets cleared, so all stuck messages get tried again, and
36981 the retry clock is reset.
36983 The message is not added to the list of those waiting for this host. Use of the
36984 host for other messages is unaffected, and except in the case of a timeout,
36985 other recipients are processed independently, and may be successfully delivered
36986 in the current SMTP session. After a timeout it is of course impossible to
36987 proceed with the session, so all addresses get deferred. However, those other
36988 than the one that failed do not suffer any subsequent retry delays. Therefore,
36989 if one recipient is causing trouble, the others have a chance of getting
36990 through when a subsequent delivery attempt occurs before the failing
36991 recipient's retry time.
36994 In all cases, if there are other hosts (or IP addresses) available for the
36995 current set of addresses (for example, from multiple MX records), they are
36996 tried in this run for any undelivered addresses, subject of course to their
36997 own retry data. In other words, recipient error retry data does not take effect
36998 until the next delivery attempt.
37000 Some hosts have been observed to give temporary error responses to every
37001 MAIL command at certain times (&"insufficient space"& has been seen). It
37002 would be nice if such circumstances could be recognized, and defer data for the
37003 host itself created, but this is not possible within the current Exim design.
37004 What actually happens is that retry data for every (host, message) combination
37007 The reason that timeouts after MAIL and RCPT are treated specially is that
37008 these can sometimes arise as a result of the remote host's verification
37009 procedures. Exim makes this assumption, and treats them as if a temporary error
37010 response had been received. A timeout after &"."& is treated specially because
37011 it is known that some broken implementations fail to recognize the end of the
37012 message if the last character of the last line is a binary zero. Thus, it is
37013 helpful to treat this case as a message error.
37015 Timeouts at other times are treated as host errors, assuming a problem with the
37016 host, or the connection to it. If a timeout after MAIL, RCPT,
37017 or &"."& is really a connection problem, the assumption is that at the next try
37018 the timeout is likely to occur at some other point in the dialogue, causing it
37019 then to be treated as a host error.
37021 There is experimental evidence that some MTAs drop the connection after the
37022 terminating &"."& if they do not like the contents of the message for some
37023 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
37024 should be given. That is why Exim treats this case as a message rather than a
37025 host error, in order not to delay other messages to the same host.
37030 .section "Incoming SMTP messages over TCP/IP" "SECID233"
37031 .cindex "SMTP" "incoming over TCP/IP"
37032 .cindex "incoming SMTP over TCP/IP"
37035 Incoming SMTP messages can be accepted in one of two ways: by running a
37036 listening daemon, or by using &'inetd'&. In the latter case, the entry in
37037 &_/etc/inetd.conf_& should be like this:
37039 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
37041 Exim distinguishes between this case and the case of a locally running user
37042 agent using the &%-bs%& option by checking whether or not the standard input is
37043 a socket. When it is, either the port must be privileged (less than 1024), or
37044 the caller must be root or the Exim user. If any other user passes a socket
37045 with an unprivileged port number, Exim prints a message on the standard error
37046 stream and exits with an error code.
37048 By default, Exim does not make a log entry when a remote host connects or
37049 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
37050 unexpected. It can be made to write such log entries by setting the
37051 &%smtp_connection%& log selector.
37053 .cindex "carriage return"
37055 Commands from the remote host are supposed to be terminated by CR followed by
37056 LF. However, there are known to be hosts that do not send CR characters. In
37057 order to be able to interwork with such hosts, Exim treats LF on its own as a
37059 Furthermore, because common code is used for receiving messages from all
37060 sources, a CR on its own is also interpreted as a line terminator. However, the
37061 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
37063 .cindex "EHLO" "invalid data"
37064 .cindex "HELO" "invalid data"
37065 One area that sometimes gives rise to problems concerns the EHLO or
37066 HELO commands. Some clients send syntactically invalid versions of these
37067 commands, which Exim rejects by default. (This is nothing to do with verifying
37068 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
37069 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
37070 match the broken hosts that send invalid commands.
37072 .cindex "SIZE option on MAIL command"
37073 .cindex "MAIL" "SIZE option"
37074 The amount of disk space available is checked whenever SIZE is received on
37075 a MAIL command, independently of whether &%message_size_limit%& or
37076 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
37077 false. A temporary error is given if there is not enough space. If
37078 &%check_spool_space%& is set, the check is for that amount of space plus the
37079 value given with SIZE, that is, it checks that the addition of the incoming
37080 message will not reduce the space below the threshold.
37082 When a message is successfully received, Exim includes the local message id in
37083 its response to the final &"."& that terminates the data. If the remote host
37084 logs this text it can help with tracing what has happened to a message.
37086 The Exim daemon can limit the number of simultaneous incoming connections it is
37087 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
37088 number of simultaneous incoming connections from a single remote host (see the
37089 &%smtp_accept_max_per_host%& option). Additional connection attempts are
37090 rejected using the SMTP temporary error code 421.
37092 The Exim daemon does not rely on the SIGCHLD signal to detect when a
37093 subprocess has finished, as this can get lost at busy times. Instead, it looks
37094 for completed subprocesses every time it wakes up. Provided there are other
37095 things happening (new incoming calls, starts of queue runs), completed
37096 processes will be noticed and tidied away. On very quiet systems you may
37097 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
37098 it will be noticed when the daemon next wakes up.
37100 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
37101 and can also be set up to reject SMTP calls from non-reserved hosts at times of
37102 high system load &-- for details see the &%smtp_accept_reserve%&,
37103 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
37104 applies in both the daemon and &'inetd'& cases.
37106 Exim normally starts a delivery process for each message received, though this
37107 can be varied by means of the &%-odq%& command line option and the
37108 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
37109 number of simultaneously running delivery processes started in this way from
37110 SMTP input can be limited by the &%smtp_accept_queue%& and
37111 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
37112 subsequently received messages are just put on the input queue without starting
37113 a delivery process.
37115 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
37116 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
37117 started up from the &'inetd'& daemon, because in that case each connection is
37118 handled by an entirely independent Exim process. Control by load average is,
37119 however, available with &'inetd'&.
37121 Exim can be configured to verify addresses in incoming SMTP commands as they
37122 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
37123 to rewrite addresses at this time &-- before any syntax checking is done. See
37124 section &<<SECTrewriteS>>&.
37126 Exim can also be configured to limit the rate at which a client host submits
37127 MAIL and RCPT commands in a single SMTP session. See the
37128 &%smtp_ratelimit_hosts%& option.
37132 .section "Unrecognized SMTP commands" "SECID234"
37133 .cindex "SMTP" "unrecognized commands"
37134 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
37135 commands during a single SMTP connection, it drops the connection after sending
37136 the error response to the last command. The default value for
37137 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
37138 abuse that subvert web servers into making connections to SMTP ports; in these
37139 circumstances, a number of non-SMTP lines are sent first.
37142 .section "Syntax and protocol errors in SMTP commands" "SECID235"
37143 .cindex "SMTP" "syntax errors"
37144 .cindex "SMTP" "protocol errors"
37145 A syntax error is detected if an SMTP command is recognized, but there is
37146 something syntactically wrong with its data, for example, a malformed email
37147 address in a RCPT command. Protocol errors include invalid command
37148 sequencing such as RCPT before MAIL. If Exim receives more than
37149 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
37150 drops the connection after sending the error response to the last command. The
37151 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
37152 broken clients that loop sending bad commands (yes, it has been seen).
37156 .section "Use of non-mail SMTP commands" "SECID236"
37157 .cindex "SMTP" "non-mail commands"
37158 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
37159 DATA. Exim counts such commands, and drops the connection if there are too
37160 many of them in a single SMTP session. This action catches some
37161 denial-of-service attempts and things like repeated failing AUTHs, or a mad
37162 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
37163 defines what &"too many"& means. Its default value is 10.
37165 When a new message is expected, one occurrence of RSET is not counted. This
37166 allows a client to send one RSET between messages (this is not necessary,
37167 but some clients do it). Exim also allows one uncounted occurrence of HELO
37168 or EHLO, and one occurrence of STARTTLS between messages. After
37169 starting up a TLS session, another EHLO is expected, and so it too is not
37172 The first occurrence of AUTH in a connection, or immediately following
37173 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
37174 RCPT, DATA, and QUIT are counted.
37176 You can control which hosts are subject to the limit set by
37177 &%smtp_accept_max_nonmail%& by setting
37178 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
37179 the limit apply to all hosts. This option means that you can exclude any
37180 specific badly-behaved hosts that you have to live with.
37185 .section "The VRFY and EXPN commands" "SECID237"
37186 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
37187 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
37188 appropriate) in order to decide whether the command should be accepted or not.
37190 .cindex "VRFY" "processing"
37191 When no ACL is defined for VRFY, or if it rejects without
37192 setting an explicit response code, the command is accepted
37193 (with a 252 SMTP response code)
37194 in order to support awkward clients that do a VRFY before every RCPT.
37195 When VRFY is accepted, it runs exactly the same code as when Exim is
37196 called with the &%-bv%& option, and returns 250/451/550
37197 SMTP response codes.
37199 .cindex "EXPN" "processing"
37200 If no ACL for EXPN is defined, the command is rejected.
37201 When EXPN is accepted, a single-level expansion of the address is done.
37202 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
37203 than a verification (the &%-bv%& option). If an unqualified local part is given
37204 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
37205 of VRFY and EXPN commands are logged on the main and reject logs, and
37206 VRFY verification failures are logged on the main log for consistency with
37211 .section "The ETRN command" "SECTETRN"
37212 .cindex "ETRN" "processing"
37213 .cindex "ESMTP extensions" ETRN
37214 RFC 1985 describes an ESMTP command called ETRN that is designed to
37215 overcome the security problems of the TURN command (which has fallen into
37216 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
37217 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
37218 should be accepted or not. If no ACL is defined, the command is rejected.
37220 The ETRN command is concerned with &"releasing"& messages that are awaiting
37221 delivery to certain hosts. As Exim does not organize its message queue by host,
37222 the only form of ETRN that is supported by default is the one where the
37223 text starts with the &"#"& prefix, in which case the remainder of the text is
37224 specific to the SMTP server. A valid ETRN command causes a run of Exim with
37225 the &%-R%& option to happen, with the remainder of the ETRN text as its
37226 argument. For example,
37234 which causes a delivery attempt on all messages with undelivered addresses
37235 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
37236 default), Exim prevents the simultaneous execution of more than one queue run
37237 for the same argument string as a result of an ETRN command. This stops
37238 a misbehaving client from starting more than one queue runner at once.
37240 .cindex "hints database" "ETRN serialization"
37241 Exim implements the serialization by means of a hints database in which a
37242 record is written whenever a process is started by ETRN, and deleted when
37243 the process completes. However, Exim does not keep the SMTP session waiting for
37244 the ETRN process to complete. Once ETRN is accepted, the client is sent
37245 a &"success"& return code. Obviously there is scope for hints records to get
37246 left lying around if there is a system or program crash. To guard against this,
37247 Exim ignores any records that are more than six hours old.
37249 .oindex "&%smtp_etrn_command%&"
37250 For more control over what ETRN does, the &%smtp_etrn_command%& option can
37251 used. This specifies a command that is run whenever ETRN is received,
37252 whatever the form of its argument. For
37255 smtp_etrn_command = /etc/etrn_command $domain \
37256 $sender_host_address
37258 .vindex "&$domain$&"
37259 The string is split up into arguments which are independently expanded. The
37260 expansion variable &$domain$& is set to the argument of the ETRN command,
37261 and no syntax checking is done on the contents of this argument. Exim does not
37262 wait for the command to complete, so its status code is not checked. Exim runs
37263 under its own uid and gid when receiving incoming SMTP, so it is not possible
37264 for it to change them before running the command.
37268 .section "Incoming local SMTP" "SECID238"
37269 .cindex "SMTP" "local incoming"
37270 Some user agents use SMTP to pass messages to their local MTA using the
37271 standard input and output, as opposed to passing the envelope on the command
37272 line and writing the message to the standard input. This is supported by the
37273 &%-bs%& option. This form of SMTP is handled in the same way as incoming
37274 messages over TCP/IP (including the use of ACLs), except that the envelope
37275 sender given in a MAIL command is ignored unless the caller is trusted. In
37276 an ACL you can detect this form of SMTP input by testing for an empty host
37277 identification. It is common to have this as the first line in the ACL that
37278 runs for RCPT commands:
37282 This accepts SMTP messages from local processes without doing any other tests.
37286 .section "Outgoing batched SMTP" "SECTbatchSMTP"
37287 .cindex "SMTP" "batched outgoing"
37288 .cindex "batched SMTP output"
37289 Both the &(appendfile)& and &(pipe)& transports can be used for handling
37290 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
37291 be output in BSMTP format. No SMTP responses are possible for this form of
37292 delivery. All it is doing is using SMTP commands as a way of transmitting the
37293 envelope along with the message.
37295 The message is written to the file or pipe preceded by the SMTP commands
37296 MAIL and RCPT, and followed by a line containing a single dot. Lines in
37297 the message that start with a dot have an extra dot added. The SMTP command
37298 HELO is not normally used. If it is required, the &%message_prefix%& option
37299 can be used to specify it.
37301 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
37302 one recipient address at a time by default. However, you can arrange for them
37303 to handle several addresses at once by setting the &%batch_max%& option. When
37304 this is done for BSMTP, messages may contain multiple RCPT commands. See
37305 chapter &<<CHAPbatching>>& for more details.
37308 When one or more addresses are routed to a BSMTP transport by a router that
37309 sets up a host list, the name of the first host on the list is available to the
37310 transport in the variable &$host$&. Here is an example of such a transport and
37315 driver = manualroute
37316 transport = smtp_appendfile
37317 route_list = domain.example batch.host.example
37321 driver = appendfile
37322 directory = /var/bsmtp/$host
37327 This causes messages addressed to &'domain.example'& to be written in BSMTP
37328 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
37329 message (unless there are more than 1000 recipients).
37333 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
37334 .cindex "SMTP" "batched incoming"
37335 .cindex "batched SMTP input"
37336 The &%-bS%& command line option causes Exim to accept one or more messages by
37337 reading SMTP on the standard input, but to generate no responses. If the caller
37338 is trusted, the senders in the MAIL commands are believed; otherwise the
37339 sender is always the caller of Exim. Unqualified senders and receivers are not
37340 rejected (there seems little point) but instead just get qualified. HELO
37341 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
37342 as NOOP; QUIT quits.
37344 Minimal policy checking is done for BSMTP input. Only the non-SMTP
37345 ACL is run in the same way as for non-SMTP local input.
37347 If an error is detected while reading a message, including a missing &"."& at
37348 the end, Exim gives up immediately. It writes details of the error to the
37349 standard output in a stylized way that the calling program should be able to
37350 make some use of automatically, for example:
37352 554 Unexpected end of file
37353 Transaction started in line 10
37354 Error detected in line 14
37356 It writes a more verbose version, for human consumption, to the standard error
37359 An error was detected while processing a file of BSMTP input.
37360 The error message was:
37362 501 '>' missing at end of address
37364 The SMTP transaction started in line 10.
37365 The error was detected in line 12.
37366 The SMTP command at fault was:
37368 rcpt to:<malformed@in.com.plete
37370 1 previous message was successfully processed.
37371 The rest of the batch was abandoned.
37373 The return code from Exim is zero only if there were no errors. It is 1 if some
37374 messages were accepted before an error was detected, and 2 if no messages were
37376 .ecindex IIDsmtpproc1
37377 .ecindex IIDsmtpproc2
37381 . ////////////////////////////////////////////////////////////////////////////
37382 . ////////////////////////////////////////////////////////////////////////////
37384 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
37385 "Customizing messages"
37386 When a message fails to be delivered, or remains in the queue for more than a
37387 configured amount of time, Exim sends a message to the original sender, or
37388 to an alternative configured address. The text of these messages is built into
37389 the code of Exim, but it is possible to change it, either by adding a single
37390 string, or by replacing each of the paragraphs by text supplied in a file.
37392 The &'From:'& and &'To:'& header lines are automatically generated; you can
37393 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
37394 option. Exim also adds the line
37396 Auto-Submitted: auto-generated
37398 to all warning and bounce messages,
37401 .section "Customizing bounce messages" "SECID239"
37402 .cindex "customizing" "bounce message"
37403 .cindex "bounce message" "customizing"
37404 If &%bounce_message_text%& is set, its contents are included in the default
37405 message immediately after &"This message was created automatically by mail
37406 delivery software."& The string is not expanded. It is not used if
37407 &%bounce_message_file%& is set.
37409 When &%bounce_message_file%& is set, it must point to a template file for
37410 constructing error messages. The file consists of a series of text items,
37411 separated by lines consisting of exactly four asterisks. If the file cannot be
37412 opened, default text is used and a message is written to the main and panic
37413 logs. If any text item in the file is empty, default text is used for that
37416 .vindex "&$bounce_recipient$&"
37417 .vindex "&$bounce_return_size_limit$&"
37418 Each item of text that is read from the file is expanded, and there are two
37419 expansion variables which can be of use here: &$bounce_recipient$& is set to
37420 the recipient of an error message while it is being created, and
37421 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
37422 option, rounded to a whole number.
37424 The items must appear in the file in the following order:
37427 The first item is included in the headers, and should include at least a
37428 &'Subject:'& header. Exim does not check the syntax of these headers.
37430 The second item forms the start of the error message. After it, Exim lists the
37431 failing addresses with their error messages.
37433 The third item is used to introduce any text from pipe transports that is to be
37434 returned to the sender. It is omitted if there is no such text.
37436 The fourth, fifth and sixth items will be ignored and may be empty.
37437 The fields exist for back-compatibility
37440 The default state (&%bounce_message_file%& unset) is equivalent to the
37441 following file, in which the sixth item is empty. The &'Subject:'& and some
37442 other lines have been split in order to fit them on the page:
37444 Subject: Mail delivery failed
37445 ${if eq{$sender_address}{$bounce_recipient}
37446 {: returning message to sender}}
37448 This message was created automatically by mail delivery software.
37450 A message ${if eq{$sender_address}{$bounce_recipient}
37451 {that you sent }{sent by
37455 }}could not be delivered to all of its recipients.
37456 This is a permanent error. The following address(es) failed:
37458 The following text was generated during the delivery attempt(s):
37460 ------ This is a copy of the message, including all the headers.
37463 ------ The body of the message is $message_size characters long;
37465 ------ $bounce_return_size_limit or so are included here.
37468 .section "Customizing warning messages" "SECTcustwarn"
37469 .cindex "customizing" "warning message"
37470 .cindex "warning of delay" "customizing the message"
37471 The option &%warn_message_file%& can be pointed at a template file for use when
37472 warnings about message delays are created. In this case there are only three
37476 The first item is included in the headers, and should include at least a
37477 &'Subject:'& header. Exim does not check the syntax of these headers.
37479 The second item forms the start of the warning message. After it, Exim lists
37480 the delayed addresses.
37482 The third item then ends the message.
37485 The default state is equivalent to the following file, except that some lines
37486 have been split here, in order to fit them on the page:
37488 Subject: Warning: message $message_exim_id delayed
37489 $warn_message_delay
37491 This message was created automatically by mail delivery software.
37493 A message ${if eq{$sender_address}{$warn_message_recipients}
37494 {that you sent }{sent by
37498 }}has not been delivered to all of its recipients after
37499 more than $warn_message_delay in the queue on $primary_hostname.
37501 The message identifier is: $message_exim_id
37502 The subject of the message is: $h_subject
37503 The date of the message is: $h_date
37505 The following address(es) have not yet been delivered:
37507 No action is required on your part. Delivery attempts will
37508 continue for some time, and this warning may be repeated at
37509 intervals if the message remains undelivered. Eventually the
37510 mail delivery software will give up, and when that happens,
37511 the message will be returned to you.
37513 .vindex "&$warn_message_delay$&"
37514 .vindex "&$warn_message_recipients$&"
37515 However, in the default state the subject and date lines are omitted if no
37516 appropriate headers exist. During the expansion of this file,
37517 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
37518 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
37519 of recipients for the warning message. There may be more than one if there are
37520 multiple addresses with different &%errors_to%& settings on the routers that
37526 . ////////////////////////////////////////////////////////////////////////////
37527 . ////////////////////////////////////////////////////////////////////////////
37529 .chapter "Some common configuration settings" "CHAPcomconreq"
37530 This chapter discusses some configuration settings that seem to be fairly
37531 common. More examples and discussion can be found in the Exim book.
37535 .section "Sending mail to a smart host" "SECID240"
37536 .cindex "smart host" "example router"
37537 If you want to send all mail for non-local domains to a &"smart host"&, you
37538 should replace the default &(dnslookup)& router with a router which does the
37539 routing explicitly:
37541 send_to_smart_host:
37542 driver = manualroute
37543 route_list = !+local_domains smart.host.name
37544 transport = remote_smtp
37546 You can use the smart host's IP address instead of the name if you wish.
37547 If you are using Exim only to submit messages to a smart host, and not for
37548 receiving incoming messages, you can arrange for it to do the submission
37549 synchronously by setting the &%mua_wrapper%& option (see chapter
37550 &<<CHAPnonqueueing>>&).
37555 .section "Using Exim to handle mailing lists" "SECTmailinglists"
37556 .cindex "mailing lists"
37557 Exim can be used to run simple mailing lists, but for large and/or complicated
37558 requirements, the use of additional specialized mailing list software such as
37559 Majordomo or Mailman is recommended.
37561 The &(redirect)& router can be used to handle mailing lists where each list
37562 is maintained in a separate file, which can therefore be managed by an
37563 independent manager. The &%domains%& router option can be used to run these
37564 lists in a separate domain from normal mail. For example:
37568 domains = lists.example
37569 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37572 errors_to = ${quote_local_part:$local_part-request}@lists.example
37575 This router is skipped for domains other than &'lists.example'&. For addresses
37576 in that domain, it looks for a file that matches the local part. If there is no
37577 such file, the router declines, but because &%no_more%& is set, no subsequent
37578 routers are tried, and so the whole delivery fails.
37580 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
37581 expanded into a filename or a pipe delivery, which is usually inappropriate in
37584 .oindex "&%errors_to%&"
37585 The &%errors_to%& option specifies that any delivery errors caused by addresses
37586 taken from a mailing list are to be sent to the given address rather than the
37587 original sender of the message. However, before acting on this, Exim verifies
37588 the error address, and ignores it if verification fails.
37590 For example, using the configuration above, mail sent to
37591 &'dicts@lists.example'& is passed on to those addresses contained in
37592 &_/usr/lists/dicts_&, with error reports directed to
37593 &'dicts-request@lists.example'&, provided that this address can be verified.
37594 There could be a file called &_/usr/lists/dicts-request_& containing
37595 the address(es) of this particular list's manager(s), but other approaches,
37596 such as setting up an earlier router (possibly using the &%local_part_prefix%&
37597 or &%local_part_suffix%& options) to handle addresses of the form
37598 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
37602 .section "Syntax errors in mailing lists" "SECID241"
37603 .cindex "mailing lists" "syntax errors in"
37604 If an entry in redirection data contains a syntax error, Exim normally defers
37605 delivery of the original address. That means that a syntax error in a mailing
37606 list holds up all deliveries to the list. This may not be appropriate when a
37607 list is being maintained automatically from data supplied by users, and the
37608 addresses are not rigorously checked.
37610 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
37611 entries that fail to parse, noting the incident in the log. If in addition
37612 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
37613 whenever a broken address is skipped. It is usually appropriate to set
37614 &%syntax_errors_to%& to the same address as &%errors_to%&.
37618 .section "Re-expansion of mailing lists" "SECID242"
37619 .cindex "mailing lists" "re-expansion of"
37620 Exim remembers every individual address to which a message has been delivered,
37621 in order to avoid duplication, but it normally stores only the original
37622 recipient addresses with a message. If all the deliveries to a mailing list
37623 cannot be done at the first attempt, the mailing list is re-expanded when the
37624 delivery is next tried. This means that alterations to the list are taken into
37625 account at each delivery attempt, so addresses that have been added to
37626 the list since the message arrived will therefore receive a copy of the
37627 message, even though it pre-dates their subscription.
37629 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
37630 on the &(redirect)& router. If this is done, any addresses generated by the
37631 router that fail to deliver at the first attempt are added to the message as
37632 &"top level"& addresses, and the parent address that generated them is marked
37633 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
37634 subsequent delivery attempts. The disadvantage of this is that if any of the
37635 failing addresses are incorrect, correcting them in the file has no effect on
37636 pre-existing messages.
37638 The original top-level address is remembered with each of the generated
37639 addresses, and is output in any log messages. However, any intermediate parent
37640 addresses are not recorded. This makes a difference to the log only if the
37641 &%all_parents%& selector is set, but for mailing lists there is normally only
37642 one level of expansion anyway.
37646 .section "Closed mailing lists" "SECID243"
37647 .cindex "mailing lists" "closed"
37648 The examples so far have assumed open mailing lists, to which anybody may
37649 send mail. It is also possible to set up closed lists, where mail is accepted
37650 from specified senders only. This is done by making use of the generic
37651 &%senders%& option to restrict the router that handles the list.
37653 The following example uses the same file as a list of recipients and as a list
37654 of permitted senders. It requires three routers:
37658 domains = lists.example
37659 local_part_suffix = -request
37660 local_parts = ${lookup {$local_part} dsearch,filter=file {/usr/lists}}
37661 file = /usr/lists/${local_part_data}-request
37666 domains = lists.example
37667 local_parts = ${lookup {$local_part} dsearch,filter=file,ret=full {/usr/lists}}
37668 senders = ${if exists {$local_part_data} {lsearch;$local_part_data}{*}}
37669 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37672 errors_to = ${quote_local_part:$local_part-request}@lists.example
37677 domains = lists.example
37679 data = :fail: $local_part@lists.example is a closed mailing list
37681 All three routers have the same &%domains%& setting, so for any other domains,
37682 they are all skipped. The first router runs only if the local part ends in
37683 &%-request%&. It handles messages to the list manager(s) by means of an open
37686 The second router runs only if the &%senders%& precondition is satisfied. It
37687 checks for the existence of a list that corresponds to the local part, and then
37688 checks that the sender is on the list by means of a linear search. It is
37689 necessary to check for the existence of the file before trying to search it,
37690 because otherwise Exim thinks there is a configuration error. If the file does
37691 not exist, the expansion of &%senders%& is *, which matches all senders. This
37692 means that the router runs, but because there is no list, declines, and
37693 &%no_more%& ensures that no further routers are run. The address fails with an
37694 &"unrouteable address"& error.
37696 The third router runs only if the second router is skipped, which happens when
37697 a mailing list exists, but the sender is not on it. This router forcibly fails
37698 the address, giving a suitable error message.
37703 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
37705 .cindex "Variable Envelope Return Paths"
37706 .cindex "envelope from"
37707 .cindex "envelope sender"
37708 Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
37709 are a way of helping mailing list administrators discover which subscription
37710 address is the cause of a particular delivery failure. The idea is to encode
37711 the original recipient address in the outgoing envelope sender address, so that
37712 if the message is forwarded by another host and then subsequently bounces, the
37713 original recipient can be extracted from the recipient address of the bounce.
37715 .oindex &%errors_to%&
37716 .oindex &%return_path%&
37717 Envelope sender addresses can be modified by Exim using two different
37718 facilities: the &%errors_to%& option on a router (as shown in previous mailing
37719 list examples), or the &%return_path%& option on a transport. The second of
37720 these is effective only if the message is successfully delivered to another
37721 host; it is not used for errors detected on the local host (see the description
37722 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
37723 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
37729 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37730 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37732 This has the effect of rewriting the return path (envelope sender) on outgoing
37733 SMTP messages, if the local part of the original return path ends in
37734 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
37735 local part and domain of the recipient into the return path. Suppose, for
37736 example, that a message whose return path has been set to
37737 &'somelist-request@your.dom.example'& is sent to
37738 &'subscriber@other.dom.example'&. In the transport, the return path is
37741 somelist-request+subscriber=other.dom.example@your.dom.example
37743 .vindex "&$local_part$&"
37744 For this to work, you must tell Exim to send multiple copies of messages that
37745 have more than one recipient, so that each copy has just one recipient. This is
37746 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
37747 might be sent to several different recipients in the same domain, in which case
37748 &$local_part$& is not available in the transport, because it is not unique.
37750 Unless your host is doing nothing but mailing list deliveries, you should
37751 probably use a separate transport for the VERP deliveries, so as not to use
37752 extra resources in making one-per-recipient copies for other deliveries. This
37753 can easily be done by expanding the &%transport%& option in the router:
37757 domains = ! +local_domains
37759 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37760 {verp_smtp}{remote_smtp}}
37763 If you want to change the return path using &%errors_to%& in a router instead
37764 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
37765 routers that handle mailing list addresses. This will ensure that all delivery
37766 errors, including those detected on the local host, are sent to the VERP
37769 On a host that does no local deliveries and has no manual routing, only the
37770 &(dnslookup)& router needs to be changed. A special transport is not needed for
37771 SMTP deliveries. Every mailing list recipient has its own return path value,
37772 and so Exim must hand them to the transport one at a time. Here is an example
37773 of a &(dnslookup)& router that implements VERP:
37777 domains = ! +local_domains
37778 transport = remote_smtp
37780 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
37781 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37784 Before you start sending out messages with VERPed return paths, you must also
37785 configure Exim to accept the bounce messages that come back to those paths.
37786 Typically this is done by setting a &%local_part_suffix%& option for a
37787 router, and using this to route the messages to wherever you want to handle
37790 The overhead incurred in using VERP depends very much on the size of the
37791 message, the number of recipient addresses that resolve to the same remote
37792 host, and the speed of the connection over which the message is being sent. If
37793 a lot of addresses resolve to the same host and the connection is slow, sending
37794 a separate copy of the message for each address may take substantially longer
37795 than sending a single copy with many recipients (for which VERP cannot be
37803 .section "Virtual domains" "SECTvirtualdomains"
37804 .cindex "virtual domains"
37805 .cindex "domain" "virtual"
37806 The phrase &'virtual domain'& is unfortunately used with two rather different
37810 A domain for which there are no real mailboxes; all valid local parts are
37811 aliases for other email addresses. Common examples are organizational
37812 top-level domains and &"vanity"& domains.
37814 One of a number of independent domains that are all handled by the same host,
37815 with mailboxes on that host, but where the mailbox owners do not necessarily
37816 have login accounts on that host.
37819 The first usage is probably more common, and does seem more &"virtual"& than
37820 the second. This kind of domain can be handled in Exim with a straightforward
37821 aliasing router. One approach is to create a separate alias file for each
37822 virtual domain. Exim can test for the existence of the alias file to determine
37823 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
37824 to a router of this form:
37828 domains = dsearch;/etc/mail/virtual
37829 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
37832 The &%domains%& option specifies that the router is to be skipped, unless there
37833 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
37834 domain that is being processed.
37835 The &(dsearch)& lookup used results in an untainted version of &$domain$&
37836 being placed into the &$domain_data$& variable.
37838 When the router runs, it looks up the local
37839 part in the file to find a new address (or list of addresses). The &%no_more%&
37840 setting ensures that if the lookup fails (leading to &%data%& being an empty
37841 string), Exim gives up on the address without trying any subsequent routers.
37843 This one router can handle all the virtual domains because the alias filenames
37844 follow a fixed pattern. Permissions can be arranged so that appropriate people
37845 can edit the different alias files. A successful aliasing operation results in
37846 a new envelope recipient address, which is then routed from scratch.
37848 The other kind of &"virtual"& domain can also be handled in a straightforward
37849 way. One approach is to create a file for each domain containing a list of
37850 valid local parts, and use it in a router like this:
37854 domains = dsearch;/etc/mail/domains
37855 local_parts = lsearch;/etc/mail/domains/$domain
37856 transport = my_mailboxes
37858 The address is accepted if there is a file for the domain, and the local part
37859 can be found in the file. The &%domains%& option is used to check for the
37860 file's existence because &%domains%& is tested before the &%local_parts%&
37861 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
37862 because that option is tested after &%local_parts%&. The transport is as
37866 driver = appendfile
37867 file = /var/mail/$domain_data/$local_part_data
37870 This uses a directory of mailboxes for each domain. The &%user%& setting is
37871 required, to specify which uid is to be used for writing to the mailboxes.
37873 The configuration shown here is just one example of how you might support this
37874 requirement. There are many other ways this kind of configuration can be set
37875 up, for example, by using a database instead of separate files to hold all the
37876 information about the domains.
37880 .section "Multiple user mailboxes" "SECTmulbox"
37881 .cindex "multiple mailboxes"
37882 .cindex "mailbox" "multiple"
37883 .cindex "local part" "prefix"
37884 .cindex "local part" "suffix"
37885 Heavy email users often want to operate with multiple mailboxes, into which
37886 incoming mail is automatically sorted. A popular way of handling this is to
37887 allow users to use multiple sender addresses, so that replies can easily be
37888 identified. Users are permitted to add prefixes or suffixes to their local
37889 parts for this purpose. The wildcard facility of the generic router options
37890 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
37891 example, consider this router:
37896 file = $home/.forward
37897 local_part_suffix = -*
37898 local_part_suffix_optional
37901 .vindex "&$local_part_suffix$&"
37902 It runs a user's &_.forward_& file for all local parts of the form
37903 &'username-*'&. Within the filter file the user can distinguish different
37904 cases by testing the variable &$local_part_suffix$&. For example:
37906 if $local_part_suffix contains -special then
37907 save /home/$local_part_data/Mail/special
37910 If the filter file does not exist, or does not deal with such addresses, they
37911 fall through to subsequent routers, and, assuming no subsequent use of the
37912 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
37913 control over which suffixes are valid.
37915 Alternatively, a suffix can be used to trigger the use of a different
37916 &_.forward_& file &-- which is the way a similar facility is implemented in
37922 local_part_suffix = -*
37923 local_part_suffix_optional
37924 file = ${lookup {.forward$local_part_suffix} dsearch,ret=full {$home} {$value}fail}
37927 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
37928 example, &_.forward-special_& is used. Once again, if the appropriate file
37929 does not exist, or does not deal with the address, it is passed on to
37930 subsequent routers, which could, if required, look for an unqualified
37931 &_.forward_& file to use as a default.
37935 .section "Simplified vacation processing" "SECID244"
37936 .cindex "vacation processing"
37937 The traditional way of running the &'vacation'& program is for a user to set up
37938 a pipe command in a &_.forward_& file
37939 (see section &<<SECTspecitredli>>& for syntax details).
37940 This is prone to error by inexperienced users. There are two features of Exim
37941 that can be used to make this process simpler for users:
37944 A local part prefix such as &"vacation-"& can be specified on a router which
37945 can cause the message to be delivered directly to the &'vacation'& program, or
37946 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
37947 &_.forward_& file are then much simpler. For example:
37949 spqr, vacation-spqr
37952 The &%require_files%& generic router option can be used to trigger a
37953 vacation delivery by checking for the existence of a certain file in the
37954 user's home directory. The &%unseen%& generic option should also be used, to
37955 ensure that the original delivery also proceeds. In this case, all the user has
37956 to do is to create a file called, say, &_.vacation_&, containing a vacation
37960 Another advantage of both these methods is that they both work even when the
37961 use of arbitrary pipes by users is locked out.
37965 .section "Taking copies of mail" "SECID245"
37966 .cindex "message" "copying every"
37967 Some installations have policies that require archive copies of all messages to
37968 be made. A single copy of each message can easily be taken by an appropriate
37969 command in a system filter, which could, for example, use a different file for
37970 each day's messages.
37972 There is also a shadow transport mechanism that can be used to take copies of
37973 messages that are successfully delivered by local transports, one copy per
37974 delivery. This could be used, &'inter alia'&, to implement automatic
37975 notification of delivery by sites that insist on doing such things.
37979 .section "Intermittently connected hosts" "SECID246"
37980 .cindex "intermittently connected hosts"
37981 It has become quite common (because it is cheaper) for hosts to connect to the
37982 Internet periodically rather than remain connected all the time. The normal
37983 arrangement is that mail for such hosts accumulates on a system that is
37984 permanently connected.
37986 Exim was designed for use on permanently connected hosts, and so it is not
37987 particularly well-suited to use in an intermittently connected environment.
37988 Nevertheless there are some features that can be used.
37991 .section "Exim on the upstream server host" "SECID247"
37992 It is tempting to arrange for incoming mail for the intermittently connected
37993 host to remain in Exim's queue until the client connects. However, this
37994 approach does not scale very well. Two different kinds of waiting message are
37995 being mixed up in the same queue &-- those that cannot be delivered because of
37996 some temporary problem, and those that are waiting for their destination host
37997 to connect. This makes it hard to manage the queue, as well as wasting
37998 resources, because each queue runner scans the entire queue.
38000 A better approach is to separate off those messages that are waiting for an
38001 intermittently connected host. This can be done by delivering these messages
38002 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
38003 format, from where they are transmitted by other software when their
38004 destination connects. This makes it easy to collect all the mail for one host
38005 in a single directory, and to apply local timeout rules on a per-message basis
38008 On a very small scale, leaving the mail on Exim's queue can be made to work. If
38009 you are doing this, you should configure Exim with a long retry period for the
38010 intermittent host. For example:
38012 cheshire.wonderland.fict.example * F,5d,24h
38014 This stops a lot of failed delivery attempts from occurring, but Exim remembers
38015 which messages it has queued up for that host. Once the intermittent host comes
38016 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
38017 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
38018 causes all the queued up messages to be delivered, often down a single SMTP
38019 connection. While the host remains connected, any new messages get delivered
38022 If the connecting hosts do not have fixed IP addresses, that is, if a host is
38023 issued with a different IP address each time it connects, Exim's retry
38024 mechanisms on the holding host get confused, because the IP address is normally
38025 used as part of the key string for holding retry information. This can be
38026 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
38027 Since this has disadvantages for permanently connected hosts, it is best to
38028 arrange a separate transport for the intermittently connected ones.
38032 .section "Exim on the intermittently connected client host" "SECID248"
38033 The value of &%smtp_accept_queue_per_connection%& should probably be
38034 increased, or even set to zero (that is, disabled) on the intermittently
38035 connected host, so that all incoming messages down a single connection get
38036 delivered immediately.
38038 .cindex "SMTP" "passed connection"
38039 .cindex "SMTP" "multiple deliveries"
38040 .cindex "multiple SMTP deliveries"
38041 .cindex "first pass routing"
38042 Mail waiting to be sent from an intermittently connected host will probably
38043 not have been routed, because without a connection DNS lookups are not
38044 possible. This means that if a normal queue run is done at connection time,
38045 each message is likely to be sent in a separate SMTP session. This can be
38046 avoided by starting the queue run with a command line option beginning with
38047 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
38048 first pass, routing is done but no deliveries take place. The second pass is a
38049 normal queue run; since all the messages have been previously routed, those
38050 destined for the same host are likely to get sent as multiple deliveries in a
38051 single SMTP connection.
38055 . ////////////////////////////////////////////////////////////////////////////
38056 . ////////////////////////////////////////////////////////////////////////////
38058 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
38059 "Exim as a non-queueing client"
38060 .cindex "client, non-queueing"
38061 .cindex "smart host" "suppressing queueing"
38062 On a personal computer, it is a common requirement for all
38063 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
38064 configured to operate that way, for all the popular operating systems.
38065 However, there are some MUAs for Unix-like systems that cannot be so
38066 configured: they submit messages using the command line interface of
38067 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
38070 If the personal computer runs continuously, there is no problem, because it can
38071 run a conventional MTA that handles delivery to the smart host, and deal with
38072 any delays via its queueing mechanism. However, if the computer does not run
38073 continuously or runs different operating systems at different times, queueing
38074 email is not desirable.
38076 There is therefore a requirement for something that can provide the
38077 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
38078 any queueing or retrying facilities. Furthermore, the delivery to the smart
38079 host should be synchronous, so that if it fails, the sending MUA is immediately
38080 informed. In other words, we want something that extends an MUA that submits
38081 to a local MTA via the command line so that it behaves like one that submits
38082 to a remote smart host using TCP/SMTP.
38084 There are a number of applications (for example, there is one called &'ssmtp'&)
38085 that do this job. However, people have found them to be lacking in various
38086 ways. For instance, you might want to allow aliasing and forwarding to be done
38087 before sending a message to the smart host.
38089 Exim already had the necessary infrastructure for doing this job. Just a few
38090 tweaks were needed to make it behave as required, though it is somewhat of an
38091 overkill to use a fully-featured MTA for this purpose.
38093 .oindex "&%mua_wrapper%&"
38094 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
38095 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
38096 assumes that it is being used to &"wrap"& a command-line MUA in the manner
38097 just described. As well as setting &%mua_wrapper%&, you also need to provide a
38098 compatible router and transport configuration. Typically there will be just one
38099 router and one transport, sending everything to a smart host.
38101 When run in MUA wrapping mode, the behaviour of Exim changes in the
38105 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
38106 In other words, the only way to submit messages is via the command line.
38108 Each message is synchronously delivered as soon as it is received (&%-odi%& is
38109 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
38110 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
38111 does not finish until the delivery attempt is complete. If the delivery is
38112 successful, a zero return code is given.
38114 Address redirection is permitted, but the final routing for all addresses must
38115 be to the same remote transport, and to the same list of hosts. Furthermore,
38116 the return address (envelope sender) must be the same for all recipients, as
38117 must any added or deleted header lines. In other words, it must be possible to
38118 deliver the message in a single SMTP transaction, however many recipients there
38121 If these conditions are not met, or if routing any address results in a
38122 failure or defer status, or if Exim is unable to deliver all the recipients
38123 successfully to one of the smart hosts, delivery of the entire message fails.
38125 Because no queueing is allowed, all failures are treated as permanent; there
38126 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
38127 smart host. Furthermore, because only a single yes/no response can be given to
38128 the caller, it is not possible to deliver to some recipients and not others. If
38129 there is an error (temporary or permanent) for any recipient, all are failed.
38131 If more than one smart host is listed, Exim will try another host after a
38132 connection failure or a timeout, in the normal way. However, if this kind of
38133 failure happens for all the hosts, the delivery fails.
38135 When delivery fails, an error message is written to the standard error stream
38136 (as well as to Exim's log), and Exim exits to the caller with a return code
38137 value 1. The message is expunged from Exim's spool files. No bounce messages
38138 are ever generated.
38140 No retry data is maintained, and any retry rules are ignored.
38142 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
38143 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
38144 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
38147 The overall effect is that Exim makes a single synchronous attempt to deliver
38148 the message, failing if there is any kind of problem. Because no local
38149 deliveries are done and no daemon can be run, Exim does not need root
38150 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
38151 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
38152 the advantages and disadvantages of running without root privilege.
38157 . ////////////////////////////////////////////////////////////////////////////
38158 . ////////////////////////////////////////////////////////////////////////////
38160 .chapter "Log files" "CHAPlog"
38161 .scindex IIDloggen "log" "general description"
38162 .cindex "log" "types of"
38163 Exim writes three different logs, referred to as the main log, the reject log,
38168 The main log records the arrival of each message and each delivery in a single
38169 line in each case. The format is as compact as possible, in an attempt to keep
38170 down the size of log files. Two-character flag sequences make it easy to pick
38171 out these lines. A number of other events are recorded in the main log. Some of
38172 them are optional, in which case the &%log_selector%& option controls whether
38173 they are included or not. A Perl script called &'eximstats'&, which does simple
38174 analysis of main log files, is provided in the Exim distribution (see section
38175 &<<SECTmailstat>>&).
38177 .cindex "reject log"
38178 The reject log records information from messages that are rejected as a result
38179 of a configuration option (that is, for policy reasons).
38180 The first line of each rejection is a copy of the line that is also written to
38181 the main log. Then, if the message's header has been read at the time the log
38182 is written, its contents are written to this log. Only the original header
38183 lines are available; header lines added by ACLs are not logged. You can use the
38184 reject log to check that your policy controls are working correctly; on a busy
38185 host this may be easier than scanning the main log for rejection messages. You
38186 can suppress the writing of the reject log by setting &%write_rejectlog%&
38189 .cindex "panic log"
38190 .cindex "system log"
38191 When certain serious errors occur, Exim writes entries to its panic log. If the
38192 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
38193 are usually written to the main log as well, but can get lost amid the mass of
38194 other entries. The panic log should be empty under normal circumstances. It is
38195 therefore a good idea to check it (or to have a &'cron'& script check it)
38196 regularly, in order to become aware of any problems. When Exim cannot open its
38197 panic log, it tries as a last resort to write to the system log (syslog). This
38198 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
38199 message itself is written at priority LOG_CRIT.
38202 Every log line starts with a timestamp, in the format shown in the following
38203 example. Note that many of the examples shown in this chapter are line-wrapped.
38204 In the log file, this would be all on one line:
38206 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
38209 By default, the timestamps are in the local timezone. There are two
38210 ways of changing this:
38213 You can set the &%timezone%& option to a different time zone; in particular, if
38218 the timestamps will be in UTC (aka GMT).
38220 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
38223 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
38227 .cindex "log" "process ids in"
38228 .cindex "pid (process id)" "in log lines"
38229 Exim does not include its process id in log lines by default, but you can
38230 request that it does so by specifying the &`pid`& log selector (see section
38231 &<<SECTlogselector>>&). When this is set, the process id is output, in square
38232 brackets, immediately after the time and date.
38237 .section "Where the logs are written" "SECTwhelogwri"
38238 .cindex "log" "destination"
38239 .cindex "log" "to file"
38240 .cindex "log" "to syslog"
38242 The logs may be written to local files, or to syslog, or both. However, it
38243 should be noted that many syslog implementations use UDP as a transport, and
38244 are therefore unreliable in the sense that messages are not guaranteed to
38245 arrive at the loghost, nor is the ordering of messages necessarily maintained.
38246 It has also been reported that on large log files (tens of megabytes) you may
38247 need to tweak syslog to prevent it syncing the file with each write &-- on
38248 Linux this has been seen to make syslog take 90% plus of CPU time.
38250 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
38251 &_Local/Makefile_& or by setting &%log_file_path%& in the runtime
38252 configuration. This latter string is expanded, so it can contain, for example,
38253 references to the host name:
38255 log_file_path = /var/log/$primary_hostname/exim_%slog
38257 It is generally advisable, however, to set the string in &_Local/Makefile_&
38258 rather than at runtime, because then the setting is available right from the
38259 start of Exim's execution. Otherwise, if there's something it wants to log
38260 before it has read the configuration file (for example, an error in the
38261 configuration file) it will not use the path you want, and may not be able to
38264 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
38265 list, currently limited to at most two items. This is one option where the
38266 facility for changing a list separator may not be used. The list must always be
38267 colon-separated. If an item in the list is &"syslog"& then syslog is used;
38268 otherwise the item must either be an absolute path, containing &`%s`& at the
38269 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
38270 implying the use of a default path.
38272 When Exim encounters an empty item in the list, it searches the list defined by
38273 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
38274 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
38275 mean &"use the path specified at build time"&. If no such item exists, log
38276 files are written in the &_log_& subdirectory of the spool directory. This is
38277 equivalent to the setting:
38279 log_file_path = $spool_directory/log/%slog
38281 If you do not specify anything at build time or runtime,
38282 or if you unset the option at runtime (i.e. &`log_file_path = `&),
38283 that is where the logs are written.
38285 A log file path may also contain &`%D`& or &`%M`& if datestamped log filenames
38286 are in use &-- see section &<<SECTdatlogfil>>& below.
38288 Here are some examples of possible settings:
38290 &`LOG_FILE_PATH=syslog `& syslog only
38291 &`LOG_FILE_PATH=:syslog `& syslog and default path
38292 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
38293 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
38295 If there are more than two paths in the list, the first is used and a panic
38300 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
38301 .cindex "log" "cycling local files"
38302 .cindex "cycling logs"
38303 .cindex "&'exicyclog'&"
38304 .cindex "log" "local files; writing to"
38305 Some operating systems provide centralized and standardized methods for cycling
38306 log files. For those that do not, a utility script called &'exicyclog'& is
38307 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
38308 main and reject logs each time it is called. The maximum number of old logs to
38309 keep can be set. It is suggested this script is run as a daily &'cron'& job.
38311 An Exim delivery process opens the main log when it first needs to write to it,
38312 and it keeps the file open in case subsequent entries are required &-- for
38313 example, if a number of different deliveries are being done for the same
38314 message. However, remote SMTP deliveries can take a long time, and this means
38315 that the file may be kept open long after it is renamed if &'exicyclog'& or
38316 something similar is being used to rename log files on a regular basis. To
38317 ensure that a switch of log files is noticed as soon as possible, Exim calls
38318 &[stat()]& on the main log's name before reusing an open file, and if the file
38319 does not exist, or its inode has changed, the old file is closed and Exim
38320 tries to open the main log from scratch. Thus, an old log file may remain open
38321 for quite some time, but no Exim processes should write to it once it has been
38326 .section "Datestamped log files" "SECTdatlogfil"
38327 .cindex "log" "datestamped files"
38328 Instead of cycling the main and reject log files by renaming them
38329 periodically, some sites like to use files whose names contain a datestamp,
38330 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
38331 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
38332 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
38333 point where the datestamp is required. For example:
38335 log_file_path = /var/spool/exim/log/%slog-%D
38336 log_file_path = /var/log/exim-%s-%D.log
38337 log_file_path = /var/spool/exim/log/%D-%slog
38338 log_file_path = /var/log/exim/%s.%M
38340 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
38341 examples of names generated by the above examples:
38343 /var/spool/exim/log/mainlog-20021225
38344 /var/log/exim-reject-20021225.log
38345 /var/spool/exim/log/20021225-mainlog
38346 /var/log/exim/main.200212
38348 When this form of log file is specified, Exim automatically switches to new
38349 files at midnight. It does not make any attempt to compress old logs; you
38350 will need to write your own script if you require this. You should not
38351 run &'exicyclog'& with this form of logging.
38353 The location of the panic log is also determined by &%log_file_path%&, but it
38354 is not datestamped, because rotation of the panic log does not make sense.
38355 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
38356 the string. In addition, if it immediately follows a slash, a following
38357 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
38358 character is removed. Thus, the four examples above would give these panic
38361 /var/spool/exim/log/paniclog
38362 /var/log/exim-panic.log
38363 /var/spool/exim/log/paniclog
38364 /var/log/exim/panic
38368 .section "Logging to syslog" "SECID249"
38369 .cindex "log" "syslog; writing to"
38370 The use of syslog does not change what Exim logs or the format of its messages,
38371 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
38372 Exim's log lines are omitted when these lines are sent to syslog. Apart from
38373 that, the same strings are written to syslog as to log files. The syslog
38374 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
38375 by default, but you can change these by setting the &%syslog_facility%& and
38376 &%syslog_processname%& options, respectively. If Exim was compiled with
38377 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
38378 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
38379 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
38380 the time and host name to each line.
38381 The three log streams are mapped onto syslog priorities as follows:
38384 &'mainlog'& is mapped to LOG_INFO
38386 &'rejectlog'& is mapped to LOG_NOTICE
38388 &'paniclog'& is mapped to LOG_ALERT
38391 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
38392 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
38393 these are routed by syslog to the same place. You can suppress this duplication
38394 by setting &%syslog_duplication%& false.
38396 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
38397 entries contain multiple lines when headers are included. To cope with both
38398 these cases, entries written to syslog are split into separate &[syslog()]&
38399 calls at each internal newline, and also after a maximum of
38400 870 data characters. (This allows for a total syslog line length of 1024, when
38401 additions such as timestamps are added.) If you are running a syslog
38402 replacement that can handle lines longer than the 1024 characters allowed by
38403 RFC 3164, you should set
38405 SYSLOG_LONG_LINES=yes
38407 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
38408 lines, but it still splits at internal newlines in &'reject'& log entries.
38410 To make it easy to re-assemble split lines later, each component of a split
38411 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
38412 where <&'n'&> is the component number and <&'m'&> is the total number of
38413 components in the entry. The / delimiter is used when the line was split
38414 because it was too long; if it was split because of an internal newline, the \
38415 delimiter is used. For example, supposing the length limit to be 50 instead of
38416 870, the following would be the result of a typical rejection message to
38417 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
38418 name, and pid as added by syslog:
38420 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
38421 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
38422 [3/5] when scanning for sender: missing or malformed lo
38423 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
38426 The same error might cause the following lines to be written to &"rejectlog"&
38429 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
38430 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
38431 [3/18] er when scanning for sender: missing or malformed
38432 [4/18] local part in "<>" (envelope sender is <ph10@cam
38434 [6\18] Recipients: ph10@some.domain.cam.example
38435 [7\18] P Received: from [127.0.0.1] (ident=ph10)
38436 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
38437 [9\18] id 16RdAL-0006pc-00
38438 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
38439 [11\18] 09:43 +0100
38441 [13\18] Subject: this is a test header
38442 [18\18] X-something: this is another header
38443 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
38446 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
38448 Log lines that are neither too long nor contain newlines are written to syslog
38449 without modification.
38451 If only syslog is being used, the Exim monitor is unable to provide a log tail
38452 display, unless syslog is routing &'mainlog'& to a file on the local host and
38453 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
38458 .section "Log line flags" "SECID250"
38459 One line is written to the main log for each message received, and for each
38460 successful, unsuccessful, and delayed delivery. These lines can readily be
38461 picked out by the distinctive two-character flags that immediately follow the
38462 timestamp. The flags are:
38464 &`<=`& message arrival
38465 &`(=`& message fakereject
38466 &`=>`& normal message delivery
38467 &`->`& additional address in same delivery
38468 &`>>`& cutthrough message delivery
38469 &`*>`& delivery suppressed by &%-N%&
38470 &`**`& delivery failed; address bounced
38471 &`==`& delivery deferred; temporary problem
38475 .section "Logging message reception" "SECID251"
38476 .cindex "log" "reception line"
38477 The format of the single-line entry in the main log that is written for every
38478 message received is shown in the basic example below, which is split over
38479 several lines in order to fit it on the page:
38481 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
38482 H=mailer.fict.example [192.168.123.123] U=exim
38483 P=smtp S=5678 id=<incoming message id>
38485 The address immediately following &"<="& is the envelope sender address. A
38486 bounce message is shown with the sender address &"<>"&, and if it is locally
38487 generated, this is followed by an item of the form
38491 which is a reference to the message that caused the bounce to be sent.
38495 For messages from other hosts, the H and U fields identify the remote host and
38496 record the RFC 1413 identity of the user that sent the message, if one was
38497 received. The number given in square brackets is the IP address of the sending
38498 host. If there is a single, unparenthesized host name in the H field, as
38499 above, it has been verified to correspond to the IP address (see the
38500 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
38501 by the remote host in the SMTP HELO or EHLO command, and has not been
38502 verified. If verification yields a different name to that given for HELO or
38503 EHLO, the verified name appears first, followed by the HELO or EHLO
38504 name in parentheses.
38506 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
38507 without brackets, in the HELO or EHLO command, leading to entries in
38508 the log containing text like these examples:
38510 H=(10.21.32.43) [192.168.8.34]
38511 H=([10.21.32.43]) [192.168.8.34]
38513 This can be confusing. Only the final address in square brackets can be relied
38516 For locally generated messages (that is, messages not received over TCP/IP),
38517 the H field is omitted, and the U field contains the login name of the caller
38520 .cindex "authentication" "logging"
38521 .cindex "AUTH" "logging"
38522 For all messages, the P field specifies the protocol used to receive the
38523 message. This is the value that is stored in &$received_protocol$&. In the case
38524 of incoming SMTP messages, the value indicates whether or not any SMTP
38525 extensions (ESMTP), encryption, or authentication were used. If the SMTP
38526 session was encrypted, there is an additional X field that records the cipher
38527 suite that was used.
38529 .cindex log protocol
38530 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
38531 hosts that have authenticated themselves using the SMTP AUTH command. The first
38532 value is used when the SMTP connection was encrypted (&"secure"&). In this case
38533 there is an additional item A= followed by the name of the authenticator that
38534 was used. If an authenticated identification was set up by the authenticator's
38535 &%server_set_id%& option, this is logged too, separated by a colon from the
38536 authenticator name.
38538 .cindex "size" "of message"
38539 The id field records the existing message id, if present. The size of the
38540 received message is given by the S field. When the message is delivered,
38541 headers may be removed or added, so that the size of delivered copies of the
38542 message may not correspond with this value (and indeed may be different to each
38545 The &%log_selector%& option can be used to request the logging of additional
38546 data when a message is received. See section &<<SECTlogselector>>& below.
38550 .section "Logging deliveries" "SECID252"
38551 .cindex "log" "delivery line"
38552 The format of the single-line entry in the main log that is written for every
38553 delivery is shown in one of the examples below, for local and remote
38554 deliveries, respectively. Each example has been split into multiple lines in order
38555 to fit it on the page:
38557 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
38558 <marv@hitch.fict.example> R=localuser T=local_delivery
38559 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
38560 monk@holistic.fict.example R=dnslookup T=remote_smtp
38561 H=holistic.fict.example [192.168.234.234]
38563 For ordinary local deliveries, the original address is given in angle brackets
38564 after the final delivery address, which might be a pipe or a file. If
38565 intermediate address(es) exist between the original and the final address, the
38566 last of these is given in parentheses after the final address. The R and T
38567 fields record the router and transport that were used to process the address.
38569 If SMTP AUTH was used for the delivery there is an additional item A=
38570 followed by the name of the authenticator that was used.
38571 If an authenticated identification was set up by the authenticator's &%client_set_id%&
38572 option, this is logged too, as a second colon-separated list item.
38573 Optionally (see the &%smtp_mailauth%& &%log_selector%&) there may be a third list item.
38575 If a shadow transport was run after a successful local delivery, the log line
38576 for the successful delivery has an item added on the end, of the form
38578 &`ST=<`&&'shadow transport name'&&`>`&
38580 If the shadow transport did not succeed, the error message is put in
38581 parentheses afterwards.
38583 .cindex "asterisk" "after IP address"
38584 When more than one address is included in a single delivery (for example, two
38585 SMTP RCPT commands in one transaction) the second and subsequent addresses are
38586 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
38587 down a single SMTP connection, an asterisk follows the
38588 remote IP address (and port if enabled)
38589 in the log lines for the second and subsequent messages.
38590 When two or more messages are delivered down a single TLS connection, the
38591 DNS and some TLS-related information logged for the first message delivered
38592 will not be present in the log lines for the second and subsequent messages.
38593 TLS cipher information is still available.
38595 .cindex "delivery" "cutthrough; logging"
38596 .cindex "cutthrough" "logging"
38597 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
38598 line precedes the reception line, since cutthrough waits for a possible
38599 rejection from the destination in case it can reject the sourced item.
38601 The generation of a reply message by a filter file gets logged as a
38602 &"delivery"& to the addressee, preceded by &">"&.
38604 The &%log_selector%& option can be used to request the logging of additional
38605 data when a message is delivered. See section &<<SECTlogselector>>& below.
38608 .section "Discarded deliveries" "SECID253"
38609 .cindex "discarded messages"
38610 .cindex "message" "discarded"
38611 .cindex "delivery" "discarded; logging"
38612 When a message is discarded as a result of the command &"seen finish"& being
38613 obeyed in a filter file which generates no deliveries, a log entry of the form
38615 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
38616 <low.club@bridge.example> R=userforward
38618 is written, to record why no deliveries are logged. When a message is discarded
38619 because it is aliased to &":blackhole:"& the log line is like this:
38621 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
38622 <hole@nowhere.example> R=blackhole_router
38626 .section "Deferred deliveries" "SECID254"
38627 When a delivery is deferred, a line of the following form is logged:
38629 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
38630 R=dnslookup T=smtp defer (146): Connection refused
38632 In the case of remote deliveries, the error is the one that was given for the
38633 last IP address that was tried. Details of individual SMTP failures are also
38634 written to the log, so the above line would be preceded by something like
38636 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
38637 mail1.endrest.example [192.168.239.239]: Connection refused
38639 When a deferred address is skipped because its retry time has not been reached,
38640 a message is written to the log, but this can be suppressed by setting an
38641 appropriate value in &%log_selector%&.
38645 .section "Delivery failures" "SECID255"
38646 .cindex "delivery" "failure; logging"
38647 If a delivery fails because an address cannot be routed, a line of the
38648 following form is logged:
38650 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
38651 <jim@trek99.example>: unknown mail domain
38653 If a delivery fails at transport time, the router and transport are shown, and
38654 the response from the remote host is included, as in this example:
38656 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
38657 R=dnslookup T=remote_smtp: SMTP error from remote mailer
38658 after pipelined RCPT TO:<ace400@pb.example>: host
38659 pbmail3.py.example [192.168.63.111]: 553 5.3.0
38660 <ace400@pb.example>...Addressee unknown
38662 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
38663 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
38664 disabling PIPELINING. The log lines for all forms of delivery failure are
38665 flagged with &`**`&.
38669 .section "Fake deliveries" "SECID256"
38670 .cindex "delivery" "fake; logging"
38671 If a delivery does not actually take place because the &%-N%& option has been
38672 used to suppress it, a normal delivery line is written to the log, except that
38673 &"=>"& is replaced by &"*>"&.
38677 .section "Completion" "SECID257"
38680 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
38682 is written to the main log when a message is about to be removed from the spool
38683 at the end of its processing.
38688 .section "Summary of Fields in Log Lines" "SECID258"
38689 .cindex "log" "summary of fields"
38690 A summary of the field identifiers that are used in log lines is shown in
38691 the following table:
38693 &`A `& authenticator name (and optional id and sender)
38694 &`C `& SMTP confirmation on delivery
38695 &` `& command list for &"no mail in SMTP session"&
38696 &`CV `& certificate verification status
38697 &`D `& duration of &"no mail in SMTP session"&
38698 &`DKIM`& domain verified in incoming message
38699 &`DN `& distinguished name from peer certificate
38700 &`DS `& DNSSEC secured lookups
38701 &`DT `& on &`=>`&, &'=='& and &'**'& lines: time taken for, or to attempt, a delivery
38702 &`F `& sender address (on delivery lines)
38703 &`H `& host name and IP address
38704 &`I `& local interface used
38705 &`id `& message id (from header) for incoming message
38706 &`K `& CHUNKING extension used
38707 &`L `& on &`<=`& and &`=>`& lines: PIPELINING extension used
38708 &`M8S `& 8BITMIME status for incoming message
38709 &`P `& on &`<=`& lines: protocol used
38710 &` `& on &`=>`& and &`**`& lines: return path
38711 &`PRDR`& PRDR extension used
38712 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
38713 &`Q `& alternate queue name
38714 &`QT `& on &`=>`& lines: time spent on queue so far
38715 &` `& on &"Completed"& lines: time spent on queue
38716 &`R `& on &`<=`& lines: reference for local bounce
38717 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
38718 &`RT `& on &`<=`& lines: time taken for reception
38719 &`S `& size of message in bytes
38720 &`SNI `& server name indication from TLS client hello
38721 &`ST `& shadow transport name
38722 &`T `& on &`<=`& lines: message subject (topic)
38723 &`TFO `& connection took advantage of TCP Fast Open
38724 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
38725 &`U `& local user or RFC 1413 identity
38726 &`X `& TLS cipher suite
38730 .section "Other log entries" "SECID259"
38731 Various other types of log entry are written from time to time. Most should be
38732 self-explanatory. Among the more common are:
38735 .cindex "retry" "time not reached"
38736 &'retry time not reached'&&~&~An address previously suffered a temporary error
38737 during routing or local delivery, and the time to retry has not yet arrived.
38738 This message is not written to an individual message log file unless it happens
38739 during the first delivery attempt.
38741 &'retry time not reached for any host'&&~&~An address previously suffered
38742 temporary errors during remote delivery, and the retry time has not yet arrived
38743 for any of the hosts to which it is routed.
38745 .cindex "spool directory" "file locked"
38746 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
38747 some other Exim process is already working on the message. This can be quite
38748 common if queue running processes are started at frequent intervals. The
38749 &'exiwhat'& utility script can be used to find out what Exim processes are
38752 .cindex "error" "ignored"
38753 &'error ignored'&&~&~There are several circumstances that give rise to this
38756 Exim failed to deliver a bounce message whose age was greater than
38757 &%ignore_bounce_errors_after%&. The bounce was discarded.
38759 A filter file set up a delivery using the &"noerror"& option, and the delivery
38760 failed. The delivery was discarded.
38762 A delivery set up by a router configured with
38763 . ==== As this is a nested list, any displays it contains must be indented
38764 . ==== as otherwise they are too far to the left.
38768 failed. The delivery was discarded.
38771 .cindex DKIM "log line"
38772 &'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
38773 logging and the message has a DKIM signature header.
38780 .section "Reducing or increasing what is logged" "SECTlogselector"
38781 .cindex "log" "selectors"
38782 By setting the &%log_selector%& global option, you can disable some of Exim's
38783 default logging, or you can request additional logging. The value of
38784 &%log_selector%& is made up of names preceded by plus or minus characters. For
38787 log_selector = +arguments -retry_defer
38789 The list of optional log items is in the following table, with the default
38790 selection marked by asterisks:
38792 &` 8bitmime `& received 8BITMIME status
38793 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
38794 &` address_rewrite `& address rewriting
38795 &` all_parents `& all parents in => lines
38796 &` arguments `& command line arguments
38797 &`*connection_reject `& connection rejections
38798 &`*delay_delivery `& immediate delivery delayed
38799 &` deliver_time `& time taken to attempt delivery
38800 &` delivery_size `& add &`S=`&&'nnn'& to => lines
38801 &`*dkim `& DKIM verified domain on <= lines
38802 &` dkim_verbose `& separate full DKIM verification result line, per signature
38803 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
38804 &` dnssec `& DNSSEC secured lookups
38805 &`*etrn `& ETRN commands
38806 &`*host_lookup_failed `& as it says
38807 &` ident_timeout `& timeout for ident connection
38808 &` incoming_interface `& local interface on <= and => lines
38809 &` incoming_port `& remote port on <= lines
38810 &`*lost_incoming_connection `& as it says (includes timeouts)
38811 &` millisec `& millisecond timestamps and RT,QT,DT,D times
38812 &`*msg_id `& on <= lines, Message-ID: header value
38813 &` msg_id_created `& on <= lines, Message-ID: header value when one had to be added
38814 &` outgoing_interface `& local interface on => lines
38815 &` outgoing_port `& add remote port to => lines
38816 &`*queue_run `& start and end queue runs
38817 &` queue_time `& time on queue for one recipient
38818 &`*queue_time_exclusive `& exclude recieve time from QT times
38819 &` queue_time_overall `& time on queue for whole message
38820 &` pid `& Exim process id
38821 &` pipelining `& PIPELINING use, on <= and => lines
38822 &` proxy `& proxy address on <= and => lines
38823 &` receive_time `& time taken to receive message
38824 &` received_recipients `& recipients on <= lines
38825 &` received_sender `& sender on <= lines
38826 &`*rejected_header `& header contents on reject log
38827 &`*retry_defer `& &"retry time not reached"&
38828 &` return_path_on_delivery `& put return path on => and ** lines
38829 &` sender_on_delivery `& add sender to => lines
38830 &`*sender_verify_fail `& sender verification failures
38831 &`*size_reject `& rejection because too big
38832 &`*skip_delivery `& delivery skipped in a queue run
38833 &`*smtp_confirmation `& SMTP confirmation on => lines
38834 &` smtp_connection `& incoming SMTP connections
38835 &` smtp_incomplete_transaction`& incomplete SMTP transactions
38836 &` smtp_mailauth `& AUTH argument to MAIL commands
38837 &` smtp_no_mail `& session with no MAIL commands
38838 &` smtp_protocol_error `& SMTP protocol errors
38839 &` smtp_syntax_error `& SMTP syntax errors
38840 &` subject `& contents of &'Subject:'& on <= lines
38841 &`*taint `& taint errors or warnings
38842 &`*tls_certificate_verified `& certificate verification status
38843 &`*tls_cipher `& TLS cipher suite on <= and => lines
38844 &` tls_peerdn `& TLS peer DN on <= and => lines
38845 &` tls_resumption `& append * to cipher field
38846 &` tls_sni `& TLS SNI on <= lines
38847 &` unknown_in_list `& DNS lookup failed in list match
38849 &` all `& all of the above
38851 See also the &%slow_lookup_log%& main configuration option,
38852 section &<<SECID99>>&
38854 More details on each of these items follows:
38858 .cindex "log" "8BITMIME"
38859 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
38860 which may help in tracking down interoperability issues with ancient MTAs
38861 that are not 8bit clean. This is added to the &"<="& line, tagged with
38862 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
38863 &`7BIT`& and &`8BITMIME`& respectively.
38865 .cindex "&%warn%& ACL verb" "log when skipping"
38866 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
38867 its conditions cannot be evaluated, a log line to this effect is written if
38868 this log selector is set.
38870 .cindex "log" "rewriting"
38871 .cindex "rewriting" "logging"
38872 &%address_rewrite%&: This applies both to global rewrites and per-transport
38873 rewrites, but not to rewrites in filters run as an unprivileged user (because
38874 such users cannot access the log).
38876 .cindex "log" "full parentage"
38877 &%all_parents%&: Normally only the original and final addresses are logged on
38878 delivery lines; with this selector, intermediate parents are given in
38879 parentheses between them.
38881 .cindex "log" "Exim arguments"
38882 .cindex "Exim arguments, logging"
38883 &%arguments%&: This causes Exim to write the arguments with which it was called
38884 to the main log, preceded by the current working directory. This is a debugging
38885 feature, added to make it easier to find out how certain MUAs call
38886 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
38887 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
38888 that are empty or that contain white space are quoted. Non-printing characters
38889 are shown as escape sequences. This facility cannot log unrecognized arguments,
38890 because the arguments are checked before the configuration file is read. The
38891 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
38892 between the caller and Exim.
38894 .cindex "log" "connection rejections"
38895 &%connection_reject%&: A log entry is written whenever an incoming SMTP
38896 connection is rejected, for whatever reason.
38898 .cindex "log" "delayed delivery"
38899 .cindex "delayed delivery, logging"
38900 &%delay_delivery%&: A log entry is written whenever a delivery process is not
38901 started for an incoming message because the load is too high or too many
38902 messages were received on one connection. Logging does not occur if no delivery
38903 process is started because &%queue_only%& is set or &%-odq%& was used.
38905 .cindex "log" "delivery duration"
38906 &%deliver_time%&: For each delivery, the amount of real time it has taken to
38907 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
38908 If millisecond logging is enabled, short times will be shown with greater
38909 precision, eg. &`DT=0.304s`&.
38911 .cindex "log" "message size on delivery"
38912 .cindex "size" "of message"
38913 &%delivery_size%&: For each delivery, the size of message delivered is added to
38914 the &"=>"& line, tagged with S=.
38916 .cindex log "DKIM verification"
38917 .cindex DKIM "verification logging"
38918 &%dkim%&: For message acceptance log lines, when an DKIM signature in the header
38919 verifies successfully a tag of DKIM is added, with one of the verified domains.
38921 .cindex log "DKIM verification"
38922 .cindex DKIM "verification logging"
38923 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
38925 .cindex "log" "dnslist defer"
38926 .cindex "DNS list" "logging defer"
38927 .cindex "black list (DNS)"
38928 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
38929 DNS black list suffers a temporary error.
38932 .cindex dnssec logging
38933 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
38934 dns lookups gave secure results a tag of DS is added.
38935 For acceptance this covers the reverse and forward lookups for host name verification.
38936 It does not cover helo-name verification.
38937 For delivery this covers the SRV, MX, A and/or AAAA lookups.
38939 .cindex "log" "ETRN commands"
38940 .cindex "ETRN" "logging"
38941 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
38942 is run to determine whether or not it is actually accepted. An invalid ETRN
38943 command, or one received within a message transaction is not logged by this
38944 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
38946 .cindex "log" "host lookup failure"
38947 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
38948 any addresses, or when a lookup of an IP address fails to find a host name, a
38949 log line is written. This logging does not apply to direct DNS lookups when
38950 routing email addresses, but it does apply to &"byname"& lookups.
38952 .cindex "log" "ident timeout"
38953 .cindex "RFC 1413" "logging timeout"
38954 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
38955 client's ident port times out.
38957 .cindex "log" "incoming interface"
38958 .cindex "log" "outgoing interface"
38959 .cindex "log" "local interface"
38960 .cindex "log" "local address and port"
38961 .cindex "TCP/IP" "logging local address and port"
38962 .cindex "interface" "logging"
38963 &%incoming_interface%&: The interface on which a message was received is added
38964 to the &"<="& line as an IP address in square brackets, tagged by I= and
38965 followed by a colon and the port number. The local interface and port are also
38966 added to other SMTP log lines, for example, &"SMTP connection from"&, to
38967 rejection lines, and (despite the name) to outgoing
38968 &"=>"&, &"->"&, &"=="& and &"**"& lines.
38969 The latter can be disabled by turning off the &%outgoing_interface%& option.
38971 .cindex log "incoming proxy address"
38972 .cindex proxy "logging proxy address"
38973 .cindex "TCP/IP" "logging proxy address"
38974 &%proxy%&: The internal (closest to the system running Exim) IP address
38975 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
38976 on a proxied connection
38977 or the &"=>"& line for a message delivered on a proxied connection.
38978 See &<<SECTproxyInbound>>& for more information.
38980 .cindex "log" "incoming remote port"
38981 .cindex "port" "logging remote"
38982 .cindex "TCP/IP" "logging incoming remote port"
38983 .vindex "&$sender_fullhost$&"
38984 .vindex "&$sender_rcvhost$&"
38985 &%incoming_port%&: The remote port number from which a message was received is
38986 added to log entries and &'Received:'& header lines, following the IP address
38987 in square brackets, and separated from it by a colon. This is implemented by
38988 changing the value that is put in the &$sender_fullhost$& and
38989 &$sender_rcvhost$& variables. Recording the remote port number has become more
38990 important with the widening use of NAT (see RFC 2505).
38992 .cindex "log" "dropped connection"
38993 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
38994 connection is unexpectedly dropped.
38996 .cindex "log" "millisecond timestamps"
38997 .cindex millisecond logging
38998 .cindex timestamps "millisecond, in logs"
38999 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
39000 appended to the seconds value.
39002 .cindex "log" "message id"
39003 &%msg_id%&: The value of the Message-ID: header.
39005 &%msg_id_created%&: The value of the Message-ID: header, when one had to be created.
39006 This will be either because the message is a bounce, or was submitted locally
39007 (submission mode) without one.
39008 The field identifier will have an asterix appended: &"id*="&.
39010 .cindex "log" "outgoing interface"
39011 .cindex "log" "local interface"
39012 .cindex "log" "local address and port"
39013 .cindex "TCP/IP" "logging local address and port"
39014 .cindex "interface" "logging"
39015 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
39016 interface on which a message was sent is added to delivery lines as an I= tag
39017 followed by IP address in square brackets. You can disable this by turning
39018 off the &%outgoing_interface%& option.
39020 .cindex "log" "outgoing remote port"
39021 .cindex "port" "logging outgoing remote"
39022 .cindex "TCP/IP" "logging outgoing remote port"
39023 &%outgoing_port%&: The remote port number is added to delivery log lines (those
39024 containing => tags) following the IP address.
39025 The local port is also added if &%incoming_interface%& and
39026 &%outgoing_interface%& are both enabled.
39027 This option is not included in the default setting, because for most ordinary
39028 configurations, the remote port number is always 25 (the SMTP port), and the
39029 local port is a random ephemeral port.
39031 .cindex "log" "process ids in"
39032 .cindex "pid (process id)" "in log lines"
39033 &%pid%&: The current process id is added to every log line, in square brackets,
39034 immediately after the time and date.
39036 .cindex log pipelining
39037 .cindex pipelining "logging outgoing"
39038 &%pipelining%&: A field is added to delivery and accept
39039 log lines when the ESMTP PIPELINING extension was used.
39040 The field is a single "L".
39042 On accept lines, where PIPELINING was offered but not used by the client,
39043 the field has a minus appended.
39045 .cindex "pipelining" "early connection"
39046 If Exim is built with the SUPPORT_PIPE_CONNECT build option
39047 accept "L" fields have a period appended if the feature was
39048 offered but not used, or an asterisk appended if used.
39049 Delivery "L" fields have an asterisk appended if used.
39052 .cindex "log" "queue run"
39053 .cindex "queue runner" "logging"
39054 &%queue_run%&: The start and end of every queue run are logged.
39056 .cindex "log" "queue time"
39057 &%queue_time%&: The amount of time the message has been in the queue on the
39058 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
39060 If millisecond logging is enabled, short times will be shown with greater
39061 precision, eg. &`QT=1.578s`&.
39063 &%queue_time_overall%&: The amount of time the message has been in the queue on
39064 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
39065 example, &`QT=3m45s`&.
39067 .cindex "log" "receive duration"
39068 &%receive_time%&: For each message, the amount of real time it has taken to
39069 perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
39070 If millisecond logging is enabled, short times will be shown with greater
39071 precision, eg. &`RT=0.204s`&.
39073 .cindex "log" "recipients"
39074 &%received_recipients%&: The recipients of a message are listed in the main log
39075 as soon as the message is received. The list appears at the end of the log line
39076 that is written when a message is received, preceded by the word &"for"&. The
39077 addresses are listed after they have been qualified, but before any rewriting
39079 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
39082 .cindex "log" "sender reception"
39083 &%received_sender%&: The unrewritten original sender of a message is added to
39084 the end of the log line that records the message's arrival, after the word
39085 &"from"& (before the recipients if &%received_recipients%& is also set).
39087 .cindex "log" "header lines for rejection"
39088 &%rejected_header%&: If a message's header has been received at the time a
39089 rejection is written to the reject log, the complete header is added to the
39090 log. Header logging can be turned off individually for messages that are
39091 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
39093 .cindex "log" "retry defer"
39094 &%retry_defer%&: A log line is written if a delivery is deferred because a
39095 retry time has not yet been reached. However, this &"retry time not reached"&
39096 message is always omitted from individual message logs after the first delivery
39099 .cindex "log" "return path"
39100 &%return_path_on_delivery%&: The return path that is being transmitted with
39101 the message is included in delivery and bounce lines, using the tag P=.
39102 This is omitted if no delivery actually happens, for example, if routing fails,
39103 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
39105 .cindex "log" "sender on delivery"
39106 &%sender_on_delivery%&: The message's sender address is added to every delivery
39107 and bounce line, tagged by F= (for &"from"&).
39108 This is the original sender that was received with the message; it is not
39109 necessarily the same as the outgoing return path.
39111 .cindex "log" "sender verify failure"
39112 &%sender_verify_fail%&: If this selector is unset, the separate log line that
39113 gives details of a sender verification failure is not written. Log lines for
39114 the rejection of SMTP commands contain just &"sender verify failed"&, so some
39117 .cindex "log" "size rejection"
39118 &%size_reject%&: A log line is written whenever a message is rejected because
39121 .cindex "log" "frozen messages; skipped"
39122 .cindex "frozen messages" "logging skipping"
39123 &%skip_delivery%&: A log line is written whenever a message is skipped during a
39124 queue run because it another process is already delivering it or because
39126 .cindex "&""spool file is locked""&"
39127 .cindex "&""message is frozen""&"
39128 The message that is written is either &"spool file is locked"& or
39129 &"message is frozen"&.
39131 .cindex "log" "smtp confirmation"
39132 .cindex "SMTP" "logging confirmation"
39133 .cindex "LMTP" "logging confirmation"
39134 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
39135 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
39136 A number of MTAs (including Exim) return an identifying string in this
39139 .cindex "log" "SMTP connections"
39140 .cindex "SMTP" "logging connections"
39141 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
39142 established or closed, unless the connection is from a host that matches
39143 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
39144 only when the closure is unexpected.) This applies to connections from local
39145 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
39146 dropped in the middle of a message, a log line is always written, whether or
39147 not this selector is set, but otherwise nothing is written at the start and end
39148 of connections unless this selector is enabled.
39150 For TCP/IP connections to an Exim daemon, the current number of connections is
39151 included in the log message for each new connection, but note that the count is
39152 reset if the daemon is restarted.
39153 Also, because connections are closed (and the closure is logged) in
39154 subprocesses, the count may not include connections that have been closed but
39155 whose termination the daemon has not yet noticed. Thus, while it is possible to
39156 match up the opening and closing of connections in the log, the value of the
39157 logged counts may not be entirely accurate.
39159 .cindex "log" "SMTP transaction; incomplete"
39160 .cindex "SMTP" "logging incomplete transactions"
39161 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
39162 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
39163 and the message sender plus any accepted recipients are included in the log
39164 line. This can provide evidence of dictionary attacks.
39166 .cindex "log" "non-MAIL SMTP sessions"
39167 .cindex "MAIL" "logging session without"
39168 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
39169 connection terminates without having issued a MAIL command. This includes both
39170 the case when the connection is dropped, and the case when QUIT is used. It
39171 does not include cases where the connection is rejected right at the start (by
39172 an ACL, or because there are too many connections, or whatever). These cases
39173 already have their own log lines.
39175 The log line that is written contains the identity of the client in the usual
39176 way, followed by D= and a time, which records the duration of the connection.
39177 If the connection was authenticated, this fact is logged exactly as it is for
39178 an incoming message, with an A= item. If the connection was encrypted, CV=,
39179 DN=, and X= items may appear as they do for an incoming message, controlled by
39180 the same logging options.
39182 Finally, if any SMTP commands were issued during the connection, a C= item
39183 is added to the line, listing the commands that were used. For example,
39187 shows that the client issued QUIT straight after EHLO. If there were fewer
39188 than 20 commands, they are all listed. If there were more than 20 commands,
39189 the last 20 are listed, preceded by &"..."&. However, with the default
39190 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
39191 have been aborted before 20 non-mail commands are processed.
39193 &%smtp_mailauth%&: A third subfield with the authenticated sender,
39194 colon-separated, is appended to the A= item for a message arrival or delivery
39195 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
39196 was accepted or used.
39198 .cindex "log" "SMTP protocol error"
39199 .cindex "SMTP" "logging protocol error"
39200 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
39201 encountered. Exim does not have perfect detection of all protocol errors
39202 because of transmission delays and the use of pipelining. If PIPELINING has
39203 been advertised to a client, an Exim server assumes that the client will use
39204 it, and therefore it does not count &"expected"& errors (for example, RCPT
39205 received after rejecting MAIL) as protocol errors.
39207 .cindex "SMTP" "logging syntax errors"
39208 .cindex "SMTP" "syntax errors; logging"
39209 .cindex "SMTP" "unknown command; logging"
39210 .cindex "log" "unknown SMTP command"
39211 .cindex "log" "SMTP syntax error"
39212 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
39213 encountered. An unrecognized command is treated as a syntax error. For an
39214 external connection, the host identity is given; for an internal connection
39215 using &%-bs%& the sender identification (normally the calling user) is given.
39217 .cindex "log" "subject"
39218 .cindex "subject, logging"
39219 &%subject%&: The subject of the message is added to the arrival log line,
39220 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
39221 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
39222 specifies whether characters with values greater than 127 should be logged
39223 unchanged, or whether they should be rendered as escape sequences.
39225 .cindex "log" "certificate verification"
39227 .cindex DANE logging
39228 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
39229 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
39231 using a CA trust anchor,
39232 &`CV=dane`& if using a DNS trust anchor,
39233 and &`CV=no`& if not.
39235 .cindex "log" "Taint warnings"
39236 &%taint%&: Log warnings about tainted data. This selector can't be
39237 turned of if &%allow_insecure_tainted_data%& is false (which is the
39240 .cindex "log" "TLS cipher"
39241 .cindex "TLS" "logging cipher"
39242 &%tls_cipher%&: When a message is sent or received over an encrypted
39243 connection, the cipher suite used is added to the log line, preceded by X=.
39245 .cindex "log" "TLS peer DN"
39246 .cindex "TLS" "logging peer DN"
39247 &%tls_peerdn%&: When a message is sent or received over an encrypted
39248 connection, and a certificate is supplied by the remote host, the peer DN is
39249 added to the log line, preceded by DN=.
39251 .cindex "log" "TLS resumption"
39252 .cindex "TLS" "logging session resumption"
39253 &%tls_resumption%&: When a message is sent or received over an encrypted
39254 connection and the TLS session resumed one used on a previous TCP connection,
39255 an asterisk is appended to the X= cipher field in the log line.
39257 .cindex "log" "TLS SNI"
39258 .cindex "TLS" "logging SNI"
39259 .cindex SNI logging
39260 &%tls_sni%&: When a message is received over an encrypted connection, and
39261 the remote host provided the Server Name Indication extension, the SNI is
39262 added to the log line, preceded by SNI=.
39264 .cindex "log" "DNS failure in list"
39265 &%unknown_in_list%&: This setting causes a log entry to be written when the
39266 result of a list match is failure because a DNS lookup failed.
39270 .section "Message log" "SECID260"
39271 .cindex "message" "log file for"
39272 .cindex "log" "message log; description of"
39273 .cindex "&_msglog_& directory"
39274 .oindex "&%preserve_message_logs%&"
39275 In addition to the general log files, Exim writes a log file for each message
39276 that it handles. The names of these per-message logs are the message ids, and
39277 they are kept in the &_msglog_& sub-directory of the spool directory. Each
39278 message log contains copies of the log lines that apply to the message. This
39279 makes it easier to inspect the status of an individual message without having
39280 to search the main log. A message log is deleted when processing of the message
39281 is complete, unless &%preserve_message_logs%& is set, but this should be used
39282 only with great care because they can fill up your disk very quickly.
39284 On a heavily loaded system, it may be desirable to disable the use of
39285 per-message logs, in order to reduce disk I/O. This can be done by setting the
39286 &%message_logs%& option false.
39292 . ////////////////////////////////////////////////////////////////////////////
39293 . ////////////////////////////////////////////////////////////////////////////
39295 .chapter "Exim utilities" "CHAPutils"
39296 .scindex IIDutils "utilities"
39297 A number of utility scripts and programs are supplied with Exim and are
39298 described in this chapter. There is also the Exim Monitor, which is covered in
39299 the next chapter. The utilities described here are:
39301 .itable none 0 0 3 7* left 15* left 40* left
39302 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
39303 "list what Exim processes are doing"
39304 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
39305 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
39306 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
39307 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
39309 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
39310 .irow &<<SECTmailstat>>& &'eximstats'& &&&
39311 "extract statistics from the log"
39312 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
39313 "check address acceptance from given IP"
39314 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
39315 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
39316 .irow &<<SECTdumpdb>>& &'exim_dumpdb'& "dump a hints database"
39317 .irow &<<SECTtidydb>>& &'exim_tidydb'& "clean up a hints database"
39318 .irow &<<SECTfixdb>>& &'exim_fixdb'& "patch a hints database"
39319 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
39322 Another utility that might be of use to sites with many MTAs is Tom Kistner's
39323 &'exilog'&. It provides log visualizations across multiple Exim servers. See
39324 &url(https://duncanthrax.net/exilog/) for details.
39329 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
39330 .cindex "&'exiwhat'&"
39331 .cindex "process, querying"
39333 On operating systems that can restart a system call after receiving a signal
39334 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
39335 a line describing what it is doing to the file &_exim-process.info_& in the
39336 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
39337 processes it can find, having first emptied the file. It then waits for one
39338 second to allow the Exim processes to react before displaying the results. In
39339 order to run &'exiwhat'& successfully you have to have sufficient privilege to
39340 send the signal to the Exim processes, so it is normally run as root.
39342 &*Warning*&: This is not an efficient process. It is intended for occasional
39343 use by system administrators. It is not sensible, for example, to set up a
39344 script that sends SIGUSR1 signals to Exim processes at short intervals.
39347 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
39348 varies in different operating systems. Not only are different options used,
39349 but the format of the output is different. For this reason, there are some
39350 system configuration options that configure exactly how &'exiwhat'& works. If
39351 it doesn't seem to be working for you, check the following compile-time
39354 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
39355 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
39356 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
39357 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
39359 An example of typical output from &'exiwhat'& is
39361 164 daemon: -q1h, listening on port 25
39362 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
39363 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
39364 [10.19.42.42] (editor@ref.example)
39365 10592 handling incoming call from [192.168.243.242]
39366 10628 accepting a local non-SMTP message
39368 The first number in the output line is the process number. The third line has
39369 been split here, in order to fit it on the page.
39373 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
39374 .cindex "&'exiqgrep'&"
39375 .cindex "queue" "grepping"
39376 This utility is a Perl script contributed by Matt Hubbard. It runs
39380 or (in case &*-a*& switch is specified)
39384 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
39385 contain alternate exim configuration the queue management might be using.
39387 to obtain a queue listing, and then greps the output to select messages
39388 that match given criteria. The following selection options are available:
39391 .vitem &*-f*&&~<&'regex'&>
39392 Match the sender address using a case-insensitive search. The field that is
39393 tested is enclosed in angle brackets, so you can test for bounce messages with
39397 .vitem &*-r*&&~<&'regex'&>
39398 Match a recipient address using a case-insensitive search. The field that is
39399 tested is not enclosed in angle brackets.
39401 .vitem &*-s*&&~<&'regex'&>
39402 Match against the size field.
39404 .vitem &*-y*&&~<&'seconds'&>
39405 Match messages that are younger than the given time.
39407 .vitem &*-o*&&~<&'seconds'&>
39408 Match messages that are older than the given time.
39411 Match only frozen messages.
39414 Match only non-frozen messages.
39416 .vitem &*-G*&&~<&'queuename'&>
39417 Match only messages in the given queue. Without this, the default queue is searched.
39420 The following options control the format of the output:
39424 Display only the count of matching messages.
39427 Long format &-- display the full message information as output by Exim. This is
39431 Display message ids only.
39434 Brief format &-- one line per message.
39437 Display messages in reverse order.
39440 Include delivered recipients in queue listing.
39443 There is one more option, &%-h%&, which outputs a list of options.
39447 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
39448 .cindex "&'exiqsumm'&"
39449 .cindex "queue" "summary"
39450 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
39451 -bp`& and produces a summary of the messages in the queue. Thus, you use it by
39452 running a command such as
39454 exim -bp | exiqsumm
39456 The output consists of one line for each domain that has messages waiting for
39457 it, as in the following example:
39459 3 2322 74m 66m msn.com.example
39461 Each line lists the number of pending deliveries for a domain, their total
39462 volume, and the length of time that the oldest and the newest messages have
39463 been waiting. Note that the number of pending deliveries is greater than the
39464 number of messages when messages have more than one recipient.
39466 A summary line is output at the end. By default the output is sorted on the
39467 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
39468 the output to be sorted by oldest message and by count of messages,
39469 respectively. There are also three options that split the messages for each
39470 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
39471 separates frozen messages, and &%-s%& separates messages according to their
39474 The output of &'exim -bp'& contains the original addresses in the message, so
39475 this also applies to the output from &'exiqsumm'&. No domains from addresses
39476 generated by aliasing or forwarding are included (unless the &%one_time%&
39477 option of the &(redirect)& router has been used to convert them into &"top
39478 level"& addresses).
39483 .section "Extracting specific information from the log (exigrep)" &&&
39485 .cindex "&'exigrep'&"
39486 .cindex "log" "extracts; grepping for"
39487 The &'exigrep'& utility is a Perl script that searches one or more main log
39488 files for entries that match a given pattern. When it finds a match, it
39489 extracts all the log entries for the relevant message, not just those that
39490 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
39491 given message, or all mail for a given user, or for a given host, for example.
39492 The input files can be in Exim log format or syslog format.
39493 If a matching log line is not associated with a specific message, it is
39494 included in &'exigrep'&'s output without any additional lines. The usage is:
39496 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
39498 If no log filenames are given on the command line, the standard input is read.
39500 The &%-t%& argument specifies a number of seconds. It adds an additional
39501 condition for message selection. Messages that are complete are shown only if
39502 they spent more than <&'n'&> seconds in the queue.
39504 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
39505 makes it case-sensitive. This may give a performance improvement when searching
39506 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
39507 option; with &%-I%& they do not. In both cases it is possible to change the
39508 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
39510 The &%-l%& option means &"literal"&, that is, treat all characters in the
39511 pattern as standing for themselves. Otherwise the pattern must be a Perl
39512 regular expression.
39514 The &%-v%& option inverts the matching condition. That is, a line is selected
39515 if it does &'not'& match the pattern.
39517 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
39518 that are generated as a result/response to a message that &'exigrep'& matched
39522 user_a sends a message to user_b, which generates a bounce back to user_b. If
39523 &'exigrep'& is used to search for &"user_a"&, only the first message will be
39524 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
39525 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
39526 when searching for &"user_a"& will show both messages since the bounce is
39527 &"related"& to or a &"result"& of the first message that was found by the
39530 If the location of a &'zcat'& command is known from the definition of
39531 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
39532 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
39533 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
39534 autodetection of some well known compression extensions.
39537 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
39538 .cindex "&'exipick'&"
39539 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
39540 lists messages from the queue according to a variety of criteria. For details
39541 of &'exipick'&'s facilities, run &'exipick'& with
39542 the &%--help%& option.
39545 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
39546 .cindex "log" "cycling local files"
39547 .cindex "cycling logs"
39548 .cindex "&'exicyclog'&"
39549 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
39550 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
39551 you are using log files with datestamps in their names (see section
39552 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
39553 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
39554 There are two command line options for &'exicyclog'&:
39556 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
39557 default that is set when Exim is built. The default default is 10.
39559 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
39560 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
39561 overriding the script's default, which is to find the setting from Exim's
39565 Each time &'exicyclog'& is run the filenames get &"shuffled down"& by one. If
39566 the main log filename is &_mainlog_& (the default) then when &'exicyclog'& is
39567 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
39568 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
39569 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
39570 logs are handled similarly.
39572 If the limit is greater than 99, the script uses 3-digit numbers such as
39573 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
39574 to one that is greater, or &'vice versa'&, you will have to fix the names of
39575 any existing log files.
39577 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
39578 the end are deleted. All files with numbers greater than 01 are compressed,
39579 using a compression command which is configured by the COMPRESS_COMMAND
39580 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
39581 root &%crontab%& entry of the form
39583 1 0 * * * su exim -c /usr/exim/bin/exicyclog
39585 assuming you have used the name &"exim"& for the Exim user. You can run
39586 &'exicyclog'& as root if you wish, but there is no need.
39590 .section "Mail statistics (eximstats)" "SECTmailstat"
39591 .cindex "statistics"
39592 .cindex "&'eximstats'&"
39593 A Perl script called &'eximstats'& is provided for extracting statistical
39594 information from log files. The output is either plain text, or HTML.
39595 . --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan
39596 . --- 404 error and everything else points to that.
39598 The &'eximstats'& script has been hacked about quite a bit over time. The
39599 latest version is the result of some extensive revision by Steve Campbell. A
39600 lot of information is given by default, but there are options for suppressing
39601 various parts of it. Following any options, the arguments to the script are a
39602 list of files, which should be main log files. For example:
39604 eximstats -nr /var/spool/exim/log/mainlog.01
39606 By default, &'eximstats'& extracts information about the number and volume of
39607 messages received from or delivered to various hosts. The information is sorted
39608 both by message count and by volume, and the top fifty hosts in each category
39609 are listed on the standard output. Similar information, based on email
39610 addresses or domains instead of hosts can be requested by means of various
39611 options. For messages delivered and received locally, similar statistics are
39612 also produced per user.
39614 The output also includes total counts and statistics about delivery errors, and
39615 histograms showing the number of messages received and deliveries made in each
39616 hour of the day. A delivery with more than one address in its envelope (for
39617 example, an SMTP transaction with more than one RCPT command) is counted
39618 as a single delivery by &'eximstats'&.
39620 Though normally more deliveries than receipts are reported (as messages may
39621 have multiple recipients), it is possible for &'eximstats'& to report more
39622 messages received than delivered, even though the queue is empty at the start
39623 and end of the period in question. If an incoming message contains no valid
39624 recipients, no deliveries are recorded for it. A bounce message is handled as
39625 an entirely separate message.
39627 &'eximstats'& always outputs a grand total summary giving the volume and number
39628 of messages received and deliveries made, and the number of hosts involved in
39629 each case. It also outputs the number of messages that were delayed (that is,
39630 not completely delivered at the first attempt), and the number that had at
39631 least one address that failed.
39633 The remainder of the output is in sections that can be independently disabled
39634 or modified by various options. It consists of a summary of deliveries by
39635 transport, histograms of messages received and delivered per time interval
39636 (default per hour), information about the time messages spent in the queue,
39637 a list of relayed messages, lists of the top fifty sending hosts, local
39638 senders, destination hosts, and destination local users by count and by volume,
39639 and a list of delivery errors that occurred.
39641 The relay information lists messages that were actually relayed, that is, they
39642 came from a remote host and were directly delivered to some other remote host,
39643 without being processed (for example, for aliasing or forwarding) locally.
39645 There are quite a few options for &'eximstats'& to control exactly what it
39646 outputs. These are documented in the Perl script itself, and can be extracted
39647 by running the command &(perldoc)& on the script. For example:
39649 perldoc /usr/exim/bin/eximstats
39652 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
39653 .cindex "&'exim_checkaccess'&"
39654 .cindex "policy control" "checking access"
39655 .cindex "checking access"
39656 The &%-bh%& command line argument allows you to run a fake SMTP session with
39657 debugging output, in order to check what Exim is doing when it is applying
39658 policy controls to incoming SMTP mail. However, not everybody is sufficiently
39659 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
39660 sometimes you just want to answer the question &"Does this address have
39661 access?"& without bothering with any further details.
39663 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
39664 two arguments, an IP address and an email address:
39666 exim_checkaccess 10.9.8.7 A.User@a.domain.example
39668 The utility runs a call to Exim with the &%-bh%& option, to test whether the
39669 given email address would be accepted in a RCPT command in a TCP/IP
39670 connection from the host with the given IP address. The output of the utility
39671 is either the word &"accepted"&, or the SMTP error response, for example:
39674 550 Relay not permitted
39676 When running this test, the utility uses &`<>`& as the envelope sender address
39677 for the MAIL command, but you can change this by providing additional
39678 options. These are passed directly to the Exim command. For example, to specify
39679 that the test is to be run with the sender address &'himself@there.example'&
39682 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
39683 -f himself@there.example
39685 Note that these additional Exim command line items must be given after the two
39686 mandatory arguments.
39688 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
39689 while running its checks. You can run checks that include callouts by using
39690 &%-bhc%&, but this is not yet available in a &"packaged"& form.
39694 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
39695 .cindex "DBM" "building dbm files"
39696 .cindex "building DBM files"
39697 .cindex "&'exim_dbmbuild'&"
39698 .cindex "lower casing"
39699 .cindex "binary zero" "in lookup key"
39700 The &'exim_dbmbuild'& program reads an input file containing keys and data in
39701 the format used by the &(lsearch)& lookup (see section
39702 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
39703 names as keys and the remainder of the information as data. The lower-casing
39704 can be prevented by calling the program with the &%-nolc%& option.
39706 A terminating zero is included as part of the key string. This is expected by
39707 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
39708 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
39709 strings or the data strings. The &(dbmnz)& lookup type can be used with such
39712 The program requires two arguments: the name of the input file (which can be a
39713 single hyphen to indicate the standard input), and the name of the output file.
39714 It creates the output under a temporary name, and then renames it if all went
39718 If the native DB interface is in use (USE_DB is set in a compile-time
39719 configuration file &-- this is common in free versions of Unix) the two
39720 filenames must be different, because in this mode the Berkeley DB functions
39721 create a single output file using exactly the name given. For example,
39723 exim_dbmbuild /etc/aliases /etc/aliases.db
39725 reads the system alias file and creates a DBM version of it in
39726 &_/etc/aliases.db_&.
39728 In systems that use the &'ndbm'& routines (mostly proprietary versions of
39729 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
39730 environment, the suffixes are added to the second argument of
39731 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
39732 when the Berkeley functions are used in compatibility mode (though this is not
39733 recommended), because in that case it adds a &_.db_& suffix to the filename.
39735 If a duplicate key is encountered, the program outputs a warning, and when it
39736 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
39737 option is used. By default, only the first of a set of duplicates is used &--
39738 this makes it compatible with &(lsearch)& lookups. There is an option
39739 &%-lastdup%& which causes it to use the data for the last duplicate instead.
39740 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
39741 &%stderr%&. For other errors, where it doesn't actually make a new file, the
39747 .section "Finding individual retry times (exinext)" "SECTfinindret"
39748 .cindex "retry" "times"
39749 .cindex "&'exinext'&"
39750 A utility called &'exinext'& (mostly a Perl script) provides the ability to
39751 fish specific information out of the retry database. Given a mail domain (or a
39752 complete address), it looks up the hosts for that domain, and outputs any retry
39753 information for the hosts or for the domain. At present, the retry information
39754 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
39755 output. For example:
39757 $ exinext piglet@milne.fict.example
39758 kanga.milne.example:192.168.8.1 error 146: Connection refused
39759 first failed: 21-Feb-1996 14:57:34
39760 last tried: 21-Feb-1996 14:57:34
39761 next try at: 21-Feb-1996 15:02:34
39762 roo.milne.example:192.168.8.3 error 146: Connection refused
39763 first failed: 20-Jan-1996 13:12:08
39764 last tried: 21-Feb-1996 11:42:03
39765 next try at: 21-Feb-1996 19:42:03
39766 past final cutoff time
39768 You can also give &'exinext'& a local part, without a domain, and it
39769 will give any retry information for that local part in your default domain.
39770 A message id can be used to obtain retry information pertaining to a specific
39771 message. This exists only when an attempt to deliver a message to a remote host
39772 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
39773 &'exinext'& is not particularly efficient, but then it is not expected to be
39776 The &'exinext'& utility calls Exim to find out information such as the location
39777 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
39778 passed on to the &'exim'& commands. The first specifies an alternate Exim
39779 configuration file, and the second sets macros for use within the configuration
39780 file. These features are mainly to help in testing, but might also be useful in
39781 environments where more than one configuration file is in use.
39785 .section "Hints database maintenance" "SECThindatmai"
39786 .cindex "hints database" "maintenance"
39787 .cindex "maintaining Exim's hints database"
39788 Three utility programs are provided for maintaining the DBM files that Exim
39789 uses to contain its delivery hint information. Each program requires two
39790 arguments. The first specifies the name of Exim's spool directory, and the
39791 second is the name of the database it is to operate on. These are as follows:
39794 &'retry'&: the database of retry information
39796 &'wait-'&<&'transport name'&>: databases of information about messages waiting
39799 &'callout'&: the callout cache
39801 &'ratelimit'&: the data for implementing the ratelimit ACL condition
39803 &'tls'&: TLS session resumption data
39805 &'misc'&: other hints data
39808 The &'misc'& database is used for
39811 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
39813 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
39814 &(smtp)& transport)
39816 Limiting the concurrency of specific transports (when &%max_parallel%& is set
39822 .section "exim_dumpdb" "SECTdumpdb"
39823 .cindex "&'exim_dumpdb'&"
39824 The entire contents of a database are written to the standard output by the
39825 &'exim_dumpdb'& program,
39827 taking as arguments the spool and database names.
39828 An option &'-z'& may be given to regest times in UTC;
39829 otherwise times are in the local timezone.
39831 For example, to dump the retry database:
39833 exim_dumpdb /var/spool/exim retry
39835 Two lines of output are produced for each entry:
39837 T:mail.ref.example:192.168.242.242 146 77 Connection refused
39838 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
39840 The first item on the first line is the key of the record. It starts with one
39841 of the letters R, or T, depending on whether it refers to a routing or
39842 transport retry. For a local delivery, the next part is the local address; for
39843 a remote delivery it is the name of the remote host, followed by its failing IP
39844 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
39845 transport). If the remote port is not the standard one (port 25), it is added
39846 to the IP address. Then there follows an error code, an additional error code,
39847 and a textual description of the error.
39849 The three times on the second line are the time of first failure, the time of
39850 the last delivery attempt, and the computed time for the next attempt. The line
39851 ends with an asterisk if the cutoff time for the last retry rule has been
39854 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
39855 consists of a host name followed by a list of ids for messages that are or were
39856 waiting to be delivered to that host. If there are a very large number for any
39857 one host, continuation records, with a sequence number added to the host name,
39858 may be seen. The data in these records is often out of date, because a message
39859 may be routed to several alternative hosts, and Exim makes no effort to keep
39864 .section "exim_tidydb" "SECTtidydb"
39865 .cindex "&'exim_tidydb'&"
39866 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
39867 database. If run with no options, it removes all records that are more than 30
39868 days old. The age is calculated from the date and time that the record was last
39869 updated. Note that, in the case of the retry database, it is &'not'& the time
39870 since the first delivery failure. Information about a host that has been down
39871 for more than 30 days will remain in the database, provided that the record is
39872 updated sufficiently often.
39874 The cutoff date can be altered by means of the &%-t%& option, which must be
39875 followed by a time. For example, to remove all records older than a week from
39876 the retry database:
39878 exim_tidydb -t 7d /var/spool/exim retry
39880 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
39881 message ids. In the former these appear as data in records keyed by host &--
39882 they were messages that were waiting for that host &-- and in the latter they
39883 are the keys for retry information for messages that have suffered certain
39884 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
39885 message ids in database records are those of messages that are still on the
39886 queue. Message ids for messages that no longer exist are removed from
39887 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
39888 For the &'retry'& database, records whose keys are non-existent message ids are
39889 removed. The &'exim_tidydb'& utility outputs comments on the standard output
39890 whenever it removes information from the database.
39892 Certain records are automatically removed by Exim when they are no longer
39893 needed, but others are not. For example, if all the MX hosts for a domain are
39894 down, a retry record is created for each one. If the primary MX host comes back
39895 first, its record is removed when Exim successfully delivers to it, but the
39896 records for the others remain because Exim has not tried to use those hosts.
39898 It is important, therefore, to run &'exim_tidydb'& periodically on all the
39899 hints databases. You should do this at a quiet time of day, because it requires
39900 a database to be locked (and therefore inaccessible to Exim) while it does its
39901 work. Removing records from a DBM file does not normally make the file smaller,
39902 but all the common DBM libraries are able to re-use the space that is released.
39903 After an initial phase of increasing in size, the databases normally reach a
39904 point at which they no longer get any bigger, as long as they are regularly
39907 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
39908 databases is likely to keep on increasing.
39913 .section "exim_fixdb" "SECTfixdb"
39914 .cindex "&'exim_fixdb'&"
39915 The &'exim_fixdb'& program is a utility for interactively modifying databases.
39916 Its main use is for testing Exim, but it might also be occasionally useful for
39917 getting round problems in a live system. Its interface
39918 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
39919 key of a database record can then be entered, and the data for that record is
39922 If &"d"& is typed at the next prompt, the entire record is deleted. For all
39923 except the &'retry'& database, that is the only operation that can be carried
39924 out. For the &'retry'& database, each field is output preceded by a number, and
39925 data for individual fields can be changed by typing the field number followed
39926 by new data, for example:
39930 resets the time of the next delivery attempt. Time values are given as a
39931 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
39932 used as optional separators.
39935 Both displayed and input times are in the local timezone by default.
39936 If an option &'-z'& is used on the command line, displayed times
39943 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
39944 .cindex "mailbox" "maintenance"
39945 .cindex "&'exim_lock'&"
39946 .cindex "locking mailboxes"
39947 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
39948 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
39949 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
39950 a user agent while investigating a problem. The utility requires the name of
39951 the file as its first argument. If the locking is successful, the second
39952 argument is run as a command (using C's &[system()]& function); if there is no
39953 second argument, the value of the SHELL environment variable is used; if this
39954 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
39955 is unlocked and the utility ends. The following options are available:
39959 Use &[fcntl()]& locking on the open mailbox.
39962 Use &[flock()]& locking on the open mailbox, provided the operating system
39965 .vitem &%-interval%&
39966 This must be followed by a number, which is a number of seconds; it sets the
39967 interval to sleep between retries (default 3).
39969 .vitem &%-lockfile%&
39970 Create a lock file before opening the mailbox.
39973 Lock the mailbox using MBX rules.
39976 Suppress verification output.
39978 .vitem &%-retries%&
39979 This must be followed by a number; it sets the number of times to try to get
39980 the lock (default 10).
39982 .vitem &%-restore_time%&
39983 This option causes &%exim_lock%& to restore the modified and read times to the
39984 locked file before exiting. This allows you to access a locked mailbox (for
39985 example, to take a backup copy) without disturbing the times that the user
39988 .vitem &%-timeout%&
39989 This must be followed by a number, which is a number of seconds; it sets a
39990 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
39991 default), a non-blocking call is used.
39994 Generate verbose output.
39997 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
39998 default is to create a lock file and also to use &[fcntl()]& locking on the
39999 mailbox, which is the same as Exim's default. The use of &%-flock%& or
40000 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
40001 requires that the directory containing the file be writeable. Locking by lock
40002 file does not last forever; Exim assumes that a lock file is expired if it is
40003 more than 30 minutes old.
40005 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
40006 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
40007 to be taken out on the open mailbox, and an exclusive lock on the file
40008 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
40009 number of the mailbox file. When the locking is released, if an exclusive lock
40010 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
40012 The default output contains verification of the locking that takes place. The
40013 &%-v%& option causes some additional information to be given. The &%-q%& option
40014 suppresses all output except error messages.
40018 exim_lock /var/spool/mail/spqr
40020 runs an interactive shell while the file is locked, whereas
40022 &`exim_lock -q /var/spool/mail/spqr <<End`&
40023 <&'some commands'&>
40026 runs a specific non-interactive sequence of commands while the file is locked,
40027 suppressing all verification output. A single command can be run by a command
40030 exim_lock -q /var/spool/mail/spqr \
40031 "cp /var/spool/mail/spqr /some/where"
40033 Note that if a command is supplied, it must be entirely contained within the
40034 second argument &-- hence the quotes.
40038 . ////////////////////////////////////////////////////////////////////////////
40039 . ////////////////////////////////////////////////////////////////////////////
40041 .chapter "The Exim monitor" "CHAPeximon"
40042 .scindex IIDeximon "Exim monitor" "description"
40043 .cindex "X-windows"
40044 .cindex "&'eximon'&"
40045 .cindex "Local/eximon.conf"
40046 .cindex "&_exim_monitor/EDITME_&"
40047 The Exim monitor is an application which displays in an X window information
40048 about the state of Exim's queue and what Exim is doing. An admin user can
40049 perform certain operations on messages from this GUI interface; however all
40050 such facilities are also available from the command line, and indeed, the
40051 monitor itself makes use of the command line to perform any actions requested.
40055 .section "Running the monitor" "SECID264"
40056 The monitor is started by running the script called &'eximon'&. This is a shell
40057 script that sets up a number of environment variables, and then runs the
40058 binary called &_eximon.bin_&. The default appearance of the monitor window can
40059 be changed by editing the &_Local/eximon.conf_& file created by editing
40060 &_exim_monitor/EDITME_&. Comments in that file describe what the various
40061 parameters are for.
40063 The parameters that get built into the &'eximon'& script can be overridden for
40064 a particular invocation by setting up environment variables of the same names,
40065 preceded by &`EXIMON_`&. For example, a shell command such as
40067 EXIMON_LOG_DEPTH=400 eximon
40069 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
40070 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
40071 overrides the Exim log file configuration. This makes it possible to have
40072 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
40073 syslog messages are routed to a file on the local host.
40075 X resources can be used to change the appearance of the window in the normal
40076 way. For example, a resource setting of the form
40078 Eximon*background: gray94
40080 changes the colour of the background to light grey rather than white. The
40081 stripcharts are drawn with both the data lines and the reference lines in
40082 black. This means that the reference lines are not visible when on top of the
40083 data. However, their colour can be changed by setting a resource called
40084 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
40085 For example, if your X server is running Unix, you could set up lighter
40086 reference lines in the stripcharts by obeying
40089 Eximon*highlight: gray
40092 .cindex "admin user"
40093 In order to see the contents of messages in the queue, and to operate on them,
40094 &'eximon'& must either be run as root or by an admin user.
40096 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
40097 contain X11 resource parameters interpreted by the X11 library. In addition,
40098 if the first parameter starts with the string "gdb" then it is removed and the
40099 binary is invoked under gdb (the parameter is used as the gdb command-name, so
40100 versioned variants of gdb can be invoked).
40102 The monitor's window is divided into three parts. The first contains one or
40103 more stripcharts and two action buttons, the second contains a &"tail"& of the
40104 main log file, and the third is a display of the queue of messages awaiting
40105 delivery, with two more action buttons. The following sections describe these
40106 different parts of the display.
40111 .section "The stripcharts" "SECID265"
40112 .cindex "stripchart"
40113 The first stripchart is always a count of messages in the queue. Its name can
40114 be configured by setting QUEUE_STRIPCHART_NAME in the
40115 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
40116 configuration script by regular expression matches on log file entries, making
40117 it possible to display, for example, counts of messages delivered to certain
40118 hosts or using certain transports. The supplied defaults display counts of
40119 received and delivered messages, and of local and SMTP deliveries. The default
40120 period between stripchart updates is one minute; this can be adjusted by a
40121 parameter in the &_Local/eximon.conf_& file.
40123 The stripchart displays rescale themselves automatically as the value they are
40124 displaying changes. There are always 10 horizontal lines in each chart; the
40125 title string indicates the value of each division when it is greater than one.
40126 For example, &"x2"& means that each division represents a value of 2.
40128 It is also possible to have a stripchart which shows the percentage fullness of
40129 a particular disk partition, which is useful when local deliveries are confined
40130 to a single partition.
40132 .cindex "&%statvfs%& function"
40133 This relies on the availability of the &[statvfs()]& function or equivalent in
40134 the operating system. Most, but not all versions of Unix that support Exim have
40135 this. For this particular stripchart, the top of the chart always represents
40136 100%, and the scale is given as &"x10%"&. This chart is configured by setting
40137 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
40138 &_Local/eximon.conf_& file.
40143 .section "Main action buttons" "SECID266"
40144 .cindex "size" "of monitor window"
40145 .cindex "Exim monitor" "window size"
40146 .cindex "window size"
40147 Below the stripcharts there is an action button for quitting the monitor. Next
40148 to this is another button marked &"Size"&. They are placed here so that
40149 shrinking the window to its default minimum size leaves just the queue count
40150 stripchart and these two buttons visible. Pressing the &"Size"& button causes
40151 the window to expand to its maximum size, unless it is already at the maximum,
40152 in which case it is reduced to its minimum.
40154 When expanding to the maximum, if the window cannot be fully seen where it
40155 currently is, it is moved back to where it was the last time it was at full
40156 size. When it is expanding from its minimum size, the old position is
40157 remembered, and next time it is reduced to the minimum it is moved back there.
40159 The idea is that you can keep a reduced window just showing one or two
40160 stripcharts at a convenient place on your screen, easily expand it to show
40161 the full window when required, and just as easily put it back to what it was.
40162 The idea is copied from what the &'twm'& window manager does for its
40163 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
40164 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
40166 Normally, the monitor starts up with the window at its full size, but it can be
40167 built so that it starts up with the window at its smallest size, by setting
40168 START_SMALL=yes in &_Local/eximon.conf_&.
40172 .section "The log display" "SECID267"
40173 .cindex "log" "tail of; in monitor"
40174 The second section of the window is an area in which a display of the tail of
40175 the main log is maintained.
40176 To save space on the screen, the timestamp on each log line is shortened by
40177 removing the date and, if &%log_timezone%& is set, the timezone.
40178 The log tail is not available when the only destination for logging data is
40179 syslog, unless the syslog lines are routed to a local file whose name is passed
40180 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
40182 The log sub-window has a scroll bar at its lefthand side which can be used to
40183 move back to look at earlier text, and the up and down arrow keys also have a
40184 scrolling effect. The amount of log that is kept depends on the setting of
40185 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
40186 to use. When this is full, the earlier 50% of data is discarded &-- this is
40187 much more efficient than throwing it away line by line. The sub-window also has
40188 a horizontal scroll bar for accessing the ends of long log lines. This is the
40189 only means of horizontal scrolling; the right and left arrow keys are not
40190 available. Text can be cut from this part of the window using the mouse in the
40191 normal way. The size of this subwindow is controlled by parameters in the
40192 configuration file &_Local/eximon.conf_&.
40194 Searches of the text in the log window can be carried out by means of the ^R
40195 and ^S keystrokes, which default to a reverse and a forward search,
40196 respectively. The search covers only the text that is displayed in the window.
40197 It cannot go further back up the log.
40199 The point from which the search starts is indicated by a caret marker. This is
40200 normally at the end of the text in the window, but can be positioned explicitly
40201 by pointing and clicking with the left mouse button, and is moved automatically
40202 by a successful search. If new text arrives in the window when it is scrolled
40203 back, the caret remains where it is, but if the window is not scrolled back,
40204 the caret is moved to the end of the new text.
40206 Pressing ^R or ^S pops up a window into which the search text can be typed.
40207 There are buttons for selecting forward or reverse searching, for carrying out
40208 the search, and for cancelling. If the &"Search"& button is pressed, the search
40209 happens and the window remains so that further searches can be done. If the
40210 &"Return"& key is pressed, a single search is done and the window is closed. If
40211 ^C is typed the search is cancelled.
40213 The searching facility is implemented using the facilities of the Athena text
40214 widget. By default this pops up a window containing both &"search"& and
40215 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
40216 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
40217 However, the linkers in BSDI and HP-UX seem unable to handle an externally
40218 provided version of &%TextPop%& when the remaining parts of the text widget
40219 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
40220 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
40221 on these systems, at the expense of having unwanted items in the search popup
40226 .section "The queue display" "SECID268"
40227 .cindex "queue" "display in monitor"
40228 The bottom section of the monitor window contains a list of all messages that
40229 are in the queue, which includes those currently being received or delivered,
40230 as well as those awaiting delivery. The size of this subwindow is controlled by
40231 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
40232 at which it is updated is controlled by another parameter in the same file &--
40233 the default is 5 minutes, since queue scans can be quite expensive. However,
40234 there is an &"Update"& action button just above the display which can be used
40235 to force an update of the queue display at any time.
40237 When a host is down for some time, a lot of pending mail can build up for it,
40238 and this can make it hard to deal with other messages in the queue. To help
40239 with this situation there is a button next to &"Update"& called &"Hide"&. If
40240 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
40241 type anything in here and press &"Return"&, the text is added to a chain of
40242 such texts, and if every undelivered address in a message matches at least one
40243 of the texts, the message is not displayed.
40245 If there is an address that does not match any of the texts, all the addresses
40246 are displayed as normal. The matching happens on the ends of addresses so, for
40247 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
40248 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
40249 has been set up, a button called &"Unhide"& is displayed. If pressed, it
40250 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
40251 a hide request is automatically cancelled after one hour.
40253 While the dialogue box is displayed, you can't press any buttons or do anything
40254 else to the monitor window. For this reason, if you want to cut text from the
40255 queue display to use in the dialogue box, you have to do the cutting before
40256 pressing the &"Hide"& button.
40258 The queue display contains, for each unhidden queued message, the length of
40259 time it has been in the queue, the size of the message, the message id, the
40260 message sender, and the first undelivered recipient, all on one line. If it is
40261 a bounce message, the sender is shown as &"<>"&. If there is more than one
40262 recipient to which the message has not yet been delivered, subsequent ones are
40263 listed on additional lines, up to a maximum configured number, following which
40264 an ellipsis is displayed. Recipients that have already received the message are
40267 .cindex "frozen messages" "display"
40268 If a message is frozen, an asterisk is displayed at the left-hand side.
40270 The queue display has a vertical scroll bar, and can also be scrolled by means
40271 of the arrow keys. Text can be cut from it using the mouse in the normal way.
40272 The text searching facilities, as described above for the log window, are also
40273 available, but the caret is always moved to the end of the text when the queue
40274 display is updated.
40278 .section "The queue menu" "SECID269"
40279 .cindex "queue" "menu in monitor"
40280 If the &%shift%& key is held down and the left button is clicked when the mouse
40281 pointer is over the text for any message, an action menu pops up, and the first
40282 line of the queue display for the message is highlighted. This does not affect
40285 If you want to use some other event for popping up the menu, you can set the
40286 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
40287 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
40288 value set in this parameter is a standard X event description. For example, to
40289 run eximon using &%ctrl%& rather than &%shift%& you could use
40291 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
40293 The title of the menu is the message id, and it contains entries which act as
40297 &'message log'&: The contents of the message log for the message are displayed
40298 in a new text window.
40300 &'headers'&: Information from the spool file that contains the envelope
40301 information and headers is displayed in a new text window. See chapter
40302 &<<CHAPspool>>& for a description of the format of spool files.
40304 &'body'&: The contents of the spool file containing the body of the message are
40305 displayed in a new text window. There is a default limit of 20,000 bytes to the
40306 amount of data displayed. This can be changed by setting the BODY_MAX
40307 option at compile time, or the EXIMON_BODY_MAX option at runtime.
40309 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
40310 delivery of the message. This causes an automatic thaw if the message is
40311 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
40312 a new text window. The delivery is run in a separate process, to avoid holding
40313 up the monitor while the delivery proceeds.
40315 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
40316 that the message be frozen.
40318 .cindex "thawing messages"
40319 .cindex "unfreezing messages"
40320 .cindex "frozen messages" "thawing"
40321 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
40322 that the message be thawed.
40324 .cindex "delivery" "forcing failure"
40325 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
40326 that Exim gives up trying to deliver the message. A bounce message is generated
40327 for any remaining undelivered addresses.
40329 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
40330 that the message be deleted from the system without generating a bounce
40333 &'add recipient'&: A dialog box is displayed into which a recipient address can
40334 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40335 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40336 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40337 causes a call to Exim to be made using the &%-Mar%& option to request that an
40338 additional recipient be added to the message, unless the entry box is empty, in
40339 which case no action is taken.
40341 &'mark delivered'&: A dialog box is displayed into which a recipient address
40342 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40343 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40344 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40345 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
40346 recipient address as already delivered, unless the entry box is empty, in which
40347 case no action is taken.
40349 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
40350 mark all recipient addresses as already delivered.
40352 &'edit sender'&: A dialog box is displayed initialized with the current
40353 sender's address. Pressing RETURN causes a call to Exim to be made using the
40354 &%-Mes%& option to replace the sender address, unless the entry box is empty,
40355 in which case no action is taken. If you want to set an empty sender (as in
40356 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
40357 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
40358 the address is qualified with that domain.
40361 When a delivery is forced, a window showing the &%-v%& output is displayed. In
40362 other cases when a call to Exim is made, if there is any output from Exim (in
40363 particular, if the command fails) a window containing the command and the
40364 output is displayed. Otherwise, the results of the action are normally apparent
40365 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
40366 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
40367 if no output is generated.
40369 The queue display is automatically updated for actions such as freezing and
40370 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
40371 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
40372 force an update of the display after one of these actions.
40374 In any text window that is displayed as result of a menu action, the normal
40375 cut-and-paste facility is available, and searching can be carried out using ^R
40376 and ^S, as described above for the log tail window.
40383 . ////////////////////////////////////////////////////////////////////////////
40384 . ////////////////////////////////////////////////////////////////////////////
40386 .chapter "Security considerations" "CHAPsecurity"
40387 .scindex IIDsecurcon "security" "discussion of"
40388 This chapter discusses a number of issues concerned with security, some of
40389 which are also covered in other parts of this manual.
40391 For reasons that this author does not understand, some people have promoted
40392 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
40393 existence of this chapter in the documentation. However, the intent of the
40394 chapter is simply to describe the way Exim works in relation to certain
40395 security concerns, not to make any specific claims about the effectiveness of
40396 its security as compared with other MTAs.
40398 What follows is a description of the way Exim is supposed to be. Best efforts
40399 have been made to try to ensure that the code agrees with the theory, but an
40400 absence of bugs can never be guaranteed. Any that are reported will get fixed
40401 as soon as possible.
40404 .section "Building a more &""hardened""& Exim" "SECID286"
40405 .cindex "security" "build-time features"
40406 There are a number of build-time options that can be set in &_Local/Makefile_&
40407 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
40408 Exim administrator who does not have the root password, or by someone who has
40409 penetrated the Exim (but not the root) account. These options are as follows:
40412 ALT_CONFIG_PREFIX can be set to a string that is required to match the
40413 start of any filenames used with the &%-C%& option. When it is set, these
40414 filenames are also not allowed to contain the sequence &"/../"&. (However, if
40415 the value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
40416 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
40417 default setting for &%ALT_CONFIG_PREFIX%&.
40419 If the permitted configuration files are confined to a directory to
40420 which only root has access, this guards against someone who has broken
40421 into the Exim account from running a privileged Exim with an arbitrary
40422 configuration file, and using it to break into other accounts.
40425 If a non-trusted configuration file (i.e. not the default configuration file
40426 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
40427 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
40428 the next item), then root privilege is retained only if the caller of Exim is
40429 root. This locks out the possibility of testing a configuration using &%-C%&
40430 right through message reception and delivery, even if the caller is root. The
40431 reception works, but by that time, Exim is running as the Exim user, so when
40432 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
40433 privilege to be lost. However, root can test reception and delivery using two
40437 The WHITELIST_D_MACROS build option declares some macros to be safe to override
40438 with &%-D%& if the real uid is one of root, the Exim run-time user or the
40439 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
40440 requiring the run-time value supplied to &%-D%& to match a regex that errs on
40441 the restrictive side. Requiring build-time selection of safe macros is onerous
40442 but this option is intended solely as a transition mechanism to permit
40443 previously-working configurations to continue to work after release 4.73.
40445 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
40448 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
40449 never to be used for any deliveries. This is like the &%never_users%& runtime
40450 option, but it cannot be overridden; the runtime option adds additional users
40451 to the list. The default setting is &"root"&; this prevents a non-root user who
40452 is permitted to modify the runtime file from using Exim as a way to get root.
40457 .section "Root privilege" "SECID270"
40459 .cindex "root privilege"
40460 The Exim binary is normally setuid to root, which means that it gains root
40461 privilege (runs as root) when it starts execution. In some special cases (for
40462 example, when the daemon is not in use and there are no local deliveries), it
40463 may be possible to run Exim setuid to some user other than root. This is
40464 discussed in the next section. However, in most installations, root privilege
40465 is required for two things:
40468 To set up a socket connected to the standard SMTP port (25) when initialising
40469 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
40472 To be able to change uid and gid in order to read users' &_.forward_& files and
40473 perform local deliveries as the receiving user or as specified in the
40477 It is not necessary to be root to do any of the other things Exim does, such as
40478 receiving messages and delivering them externally over SMTP, and it is
40479 obviously more secure if Exim does not run as root except when necessary.
40480 For this reason, a user and group for Exim to use must be defined in
40481 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
40482 group"&. Their values can be changed by the runtime configuration, though this
40483 is not recommended. Often a user called &'exim'& is used, but some sites use
40484 &'mail'& or another user name altogether.
40486 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
40487 abdication; the process cannot regain root afterwards. Prior to release 4.00,
40488 &[seteuid()]& was used in some circumstances, but this is no longer the case.
40490 After a new Exim process has interpreted its command line options, it changes
40491 uid and gid in the following cases:
40496 If the &%-C%& option is used to specify an alternate configuration file, or if
40497 the &%-D%& option is used to define macro values for the configuration, and the
40498 calling process is not running as root, the uid and gid are changed to those of
40499 the calling process.
40500 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
40501 option may not be used at all.
40502 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
40503 can be supplied if the calling process is running as root, the Exim run-time
40504 user or CONFIGURE_OWNER, if defined.
40509 If the expansion test option (&%-be%&) or one of the filter testing options
40510 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
40513 If the process is not a daemon process or a queue runner process or a delivery
40514 process or a process for testing address routing (started with &%-bt%&), the
40515 uid and gid are changed to the Exim user and group. This means that Exim always
40516 runs under its own uid and gid when receiving messages. This also applies when
40517 testing address verification
40520 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
40523 For a daemon, queue runner, delivery, or address testing process, the uid
40524 remains as root at this stage, but the gid is changed to the Exim group.
40527 The processes that initially retain root privilege behave as follows:
40530 A daemon process changes the gid to the Exim group and the uid to the Exim
40531 user after setting up one or more listening sockets. The &[initgroups()]&
40532 function is called, so that if the Exim user is in any additional groups, they
40533 will be used during message reception.
40535 A queue runner process retains root privilege throughout its execution. Its
40536 job is to fork a controlled sequence of delivery processes.
40538 A delivery process retains root privilege throughout most of its execution,
40539 but any actual deliveries (that is, the transports themselves) are run in
40540 subprocesses which always change to a non-root uid and gid. For local
40541 deliveries this is typically the uid and gid of the owner of the mailbox; for
40542 remote deliveries, the Exim uid and gid are used. Once all the delivery
40543 subprocesses have been run, a delivery process changes to the Exim uid and gid
40544 while doing post-delivery tidying up such as updating the retry database and
40545 generating bounce and warning messages.
40547 While the recipient addresses in a message are being routed, the delivery
40548 process runs as root. However, if a user's filter file has to be processed,
40549 this is done in a subprocess that runs under the individual user's uid and
40550 gid. A system filter is run as root unless &%system_filter_user%& is set.
40552 A process that is testing addresses (the &%-bt%& option) runs as root so that
40553 the routing is done in the same environment as a message delivery.
40559 .section "Running Exim without privilege" "SECTrunexiwitpri"
40560 .cindex "privilege, running without"
40561 .cindex "unprivileged running"
40562 .cindex "root privilege" "running without"
40563 Some installations like to run Exim in an unprivileged state for more of its
40564 operation, for added security. Support for this mode of operation is provided
40565 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
40566 gid are changed to the Exim user and group at the start of a delivery process
40567 (and also queue runner and address testing processes). This means that address
40568 routing is no longer run as root, and the deliveries themselves cannot change
40572 .cindex "daemon" "restarting"
40573 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
40574 that the daemon can still be started in the usual way, and it can respond
40575 correctly to SIGHUP because the re-invocation regains root privilege.
40577 An alternative approach is to make Exim setuid to the Exim user and also setgid
40578 to the Exim group. If you do this, the daemon must be started from a root
40579 process. (Calling Exim from a root process makes it behave in the way it does
40580 when it is setuid root.) However, the daemon cannot restart itself after a
40581 SIGHUP signal because it cannot regain privilege.
40583 It is still useful to set &%deliver_drop_privilege%& in this case, because it
40584 stops Exim from trying to re-invoke itself to do a delivery after a message has
40585 been received. Such a re-invocation is a waste of resources because it has no
40588 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
40589 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
40590 to the Exim user seems a clean approach, but there is one complication:
40592 In this style of operation, Exim is running with the real uid and gid set to
40593 those of the calling process, and the effective uid/gid set to Exim's values.
40594 Ideally, any association with the calling process' uid/gid should be dropped,
40595 that is, the real uid/gid should be reset to the effective values so as to
40596 discard any privileges that the caller may have. While some operating systems
40597 have a function that permits this action for a non-root effective uid, quite a
40598 number of them do not. Because of this lack of standardization, Exim does not
40599 address this problem at this time.
40601 For this reason, the recommended approach for &"mostly unprivileged"& running
40602 is to keep the Exim binary setuid to root, and to set
40603 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
40604 be used in the most straightforward way.
40606 If you configure Exim not to run delivery processes as root, there are a
40607 number of restrictions on what you can do:
40610 You can deliver only as the Exim user/group. You should explicitly use the
40611 &%user%& and &%group%& options to override routers or local transports that
40612 normally deliver as the recipient. This makes sure that configurations that
40613 work in this mode function the same way in normal mode. Any implicit or
40614 explicit specification of another user causes an error.
40616 Use of &_.forward_& files is severely restricted, such that it is usually
40617 not worthwhile to include them in the configuration.
40619 Users who wish to use &_.forward_& would have to make their home directory and
40620 the file itself accessible to the Exim user. Pipe and append-to-file entries,
40621 and their equivalents in Exim filters, cannot be used. While they could be
40622 enabled in the Exim user's name, that would be insecure and not very useful.
40624 Unless the local user mailboxes are all owned by the Exim user (possible in
40625 some POP3 or IMAP-only environments):
40628 They must be owned by the Exim group and be writeable by that group. This
40629 implies you must set &%mode%& in the appendfile configuration, as well as the
40630 mode of the mailbox files themselves.
40632 You must set &%no_check_owner%&, since most or all of the files will not be
40633 owned by the Exim user.
40635 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
40636 on a newly created mailbox when unprivileged. This also implies that new
40637 mailboxes need to be created manually.
40642 These restrictions severely restrict what can be done in local deliveries.
40643 However, there are no restrictions on remote deliveries. If you are running a
40644 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
40645 gives more security at essentially no cost.
40647 If you are using the &%mua_wrapper%& facility (see chapter
40648 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
40653 .section "Delivering to local files" "SECID271"
40654 Full details of the checks applied by &(appendfile)& before it writes to a file
40655 are given in chapter &<<CHAPappendfile>>&.
40659 .section "Running local commands" "SECTsecconslocalcmds"
40660 .cindex "security" "local commands"
40661 .cindex "security" "command injection attacks"
40662 There are a number of ways in which an administrator can configure Exim to run
40663 commands based upon received, untrustworthy, data. Further, in some
40664 configurations a user who can control a &_.forward_& file can also arrange to
40665 run commands. Configuration to check includes, but is not limited to:
40668 Use of &%use_shell%& in the pipe transport: various forms of shell command
40669 injection may be possible with this option present. It is dangerous and should
40670 be used only with considerable caution. Consider constraints which whitelist
40671 allowed characters in a variable which is to be used in a pipe transport that
40672 has &%use_shell%& enabled.
40674 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
40675 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
40676 &_.forward_& files in a redirect router. If Exim is running on a central mail
40677 hub to which ordinary users do not have shell access, but home directories are
40678 NFS mounted (for instance) then administrators should review the list of these
40679 forbid options available, and should bear in mind that the options that may
40680 need forbidding can change as new features are added between releases.
40682 The &%${run...}%& expansion item does not use a shell by default, but
40683 administrators can configure use of &_/bin/sh_& as part of the command.
40684 Such invocations should be viewed with prejudicial suspicion.
40686 Administrators who use embedded Perl are advised to explore how Perl's
40687 taint checking might apply to their usage.
40689 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
40690 administrators are well advised to view its use with suspicion, in case (for
40691 instance) it allows a local-part to contain embedded Exim directives.
40693 Use of &%${match_local_part...}%& and friends becomes more dangerous if
40694 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
40695 each can reference arbitrary lists and files, rather than just being a list
40697 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
40698 real-world security vulnerabilities caused by its use with untrustworthy data
40699 injected in, for SQL injection attacks.
40700 Consider the use of the &%inlisti%& expansion condition instead.
40706 .section "Trust in configuration data" "SECTsecconfdata"
40707 .cindex "security" "data sources"
40708 .cindex "security" "regular expressions"
40709 .cindex "regular expressions" "security"
40710 .cindex "PCRE2" "security"
40711 If configuration data for Exim can come from untrustworthy sources, there
40712 are some issues to be aware of:
40715 Use of &%${expand...}%& may provide a path for shell injection attacks.
40717 Letting untrusted data provide a regular expression is unwise.
40719 Using &%${match...}%& to apply a fixed regular expression against untrusted
40720 data may result in pathological behaviour within PCRE2. Be aware of what
40721 "backtracking" means and consider options for being more strict with a regular
40722 expression. Avenues to explore include limiting what can match (avoiding &`.`&
40723 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
40724 possessive quantifiers or just not using regular expressions against untrusted
40727 It can be important to correctly use &%${quote:...}%&,
40728 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
40729 items to ensure that data is correctly constructed.
40731 Some lookups might return multiple results, even though normal usage is only
40732 expected to yield one result.
40738 .section "IPv4 source routing" "SECID272"
40739 .cindex "source routing" "in IP packets"
40740 .cindex "IP source routing"
40741 Many operating systems suppress IP source-routed packets in the kernel, but
40742 some cannot be made to do this, so Exim does its own check. It logs incoming
40743 IPv4 source-routed TCP calls, and then drops them. Things are all different in
40744 IPv6. No special checking is currently done.
40748 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
40749 Support for these SMTP commands is disabled by default. If required, they can
40750 be enabled by defining suitable ACLs.
40755 .section "Privileged users" "SECID274"
40756 .cindex "trusted users"
40757 .cindex "admin user"
40758 .cindex "privileged user"
40759 .cindex "user" "trusted"
40760 .cindex "user" "admin"
40761 Exim recognizes two sets of users with special privileges. Trusted users are
40762 able to submit new messages to Exim locally, but supply their own sender
40763 addresses and information about a sending host. For other users submitting
40764 local messages, Exim sets up the sender address from the uid, and doesn't
40765 permit a remote host to be specified.
40768 However, an untrusted user is permitted to use the &%-f%& command line option
40769 in the special form &%-f <>%& to indicate that a delivery failure for the
40770 message should not cause an error report. This affects the message's envelope,
40771 but it does not affect the &'Sender:'& header. Untrusted users may also be
40772 permitted to use specific forms of address with the &%-f%& option by setting
40773 the &%untrusted_set_sender%& option.
40775 Trusted users are used to run processes that receive mail messages from some
40776 other mail domain and pass them on to Exim for delivery either locally, or over
40777 the Internet. Exim trusts a caller that is running as root, as the Exim user,
40778 as any user listed in the &%trusted_users%& configuration option, or under any
40779 group listed in the &%trusted_groups%& option.
40781 Admin users are permitted to do things to the messages on Exim's queue. They
40782 can freeze or thaw messages, cause them to be returned to their senders, remove
40783 them entirely, or modify them in various ways. In addition, admin users can run
40784 the Exim monitor and see all the information it is capable of providing, which
40785 includes the contents of files on the spool.
40789 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
40790 delivery of messages on its queue is restricted to admin users. This
40791 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
40792 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
40793 queue is also restricted to admin users. This restriction can be relaxed by
40794 setting &%no_queue_list_requires_admin%&.
40796 Exim recognizes an admin user if the calling process is running as root or as
40797 the Exim user or if any of the groups associated with the calling process is
40798 the Exim group. It is not necessary actually to be running under the Exim
40799 group. However, if admin users who are not root or the Exim user are to access
40800 the contents of files on the spool via the Exim monitor (which runs
40801 unprivileged), Exim must be built to allow group read access to its spool
40804 By default, regular users are trusted to perform basic testing and
40805 introspection commands, as themselves. This setting can be tightened by
40806 setting the &%commandline_checks_require_admin%& option.
40807 This affects most of the checking options,
40808 such as &%-be%& and anything else &%-b*%&.
40811 .section "Spool files" "SECID275"
40812 .cindex "spool directory" "files"
40813 Exim's spool directory and everything it contains is owned by the Exim user and
40814 set to the Exim group. The mode for spool files is defined in the
40815 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
40816 any user who is a member of the Exim group can access these files.
40820 .section "Use of argv[0]" "SECID276"
40821 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
40822 of specific strings, Exim assumes certain options. For example, calling Exim
40823 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
40824 to calling it with the option &%-bS%&. There are no security implications in
40829 .section "Use of %f formatting" "SECID277"
40830 The only use made of &"%f"& by Exim is in formatting load average values. These
40831 are actually stored in integer variables as 1000 times the load average.
40832 Consequently, their range is limited and so therefore is the length of the
40837 .section "Embedded Exim path" "SECID278"
40838 Exim uses its own path name, which is embedded in the code, only when it needs
40839 to re-exec in order to regain root privilege. Therefore, it is not root when it
40840 does so. If some bug allowed the path to get overwritten, it would lead to an
40841 arbitrary program's being run as exim, not as root.
40845 .section "Dynamic module directory" "SECTdynmoddir"
40846 Any dynamically loadable modules must be installed into the directory
40847 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
40851 .section "Use of sprintf()" "SECID279"
40852 .cindex "&[sprintf()]&"
40853 A large number of occurrences of &"sprintf"& in the code are actually calls to
40854 &'string_sprintf()'&, a function that returns the result in malloc'd store.
40855 The intermediate formatting is done into a large fixed buffer by a function
40856 that runs through the format string itself, and checks the length of each
40857 conversion before performing it, thus preventing buffer overruns.
40859 The remaining uses of &[sprintf()]& happen in controlled circumstances where
40860 the output buffer is known to be sufficiently long to contain the converted
40865 .section "Use of debug_printf() and log_write()" "SECID280"
40866 Arbitrary strings are passed to both these functions, but they do their
40867 formatting by calling the function &'string_vformat()'&, which runs through
40868 the format string itself, and checks the length of each conversion.
40872 .section "Use of strcat() and strcpy()" "SECID281"
40873 These are used only in cases where the output buffer is known to be large
40874 enough to hold the result.
40875 .ecindex IIDsecurcon
40880 . ////////////////////////////////////////////////////////////////////////////
40881 . ////////////////////////////////////////////////////////////////////////////
40883 .chapter "Format of spool files" "CHAPspool"
40884 .scindex IIDforspo1 "format" "spool files"
40885 .scindex IIDforspo2 "spool directory" "format of files"
40886 .scindex IIDforspo3 "spool files" "format of"
40887 .cindex "spool files" "editing"
40888 A message on Exim's queue consists of two files, whose names are the message id
40889 followed by -D and -H, respectively. The data portion of the message is kept in
40890 the -D file on its own. The message's envelope, status, and headers are all
40891 kept in the -H file, whose format is described in this chapter. Each of these
40892 two files contains the final component of its own name as its first line. This
40893 is insurance against disk crashes where the directory is lost but the files
40894 themselves are recoverable.
40896 The file formats may be changed, or new formats added, at any release.
40897 Spool files are not intended as an interface to other programs
40898 and should not be used as such.
40900 Some people are tempted into editing -D files in order to modify messages. You
40901 need to be extremely careful if you do this; it is not recommended and you are
40902 on your own if you do it. Here are some of the pitfalls:
40905 You must ensure that Exim does not try to deliver the message while you are
40906 fiddling with it. The safest way is to take out a write lock on the -D file,
40907 which is what Exim itself does, using &[fcntl()]&. If you update the file in
40908 place, the lock will be retained. If you write a new file and rename it, the
40909 lock will be lost at the instant of rename.
40911 .vindex "&$body_linecount$&"
40912 If you change the number of lines in the file, the value of
40913 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
40914 cause incomplete transmission of messages or undeliverable messages.
40916 If the message is in MIME format, you must take care not to break it.
40918 If the message is cryptographically signed, any change will invalidate the
40921 All in all, modifying -D files is fraught with danger.
40923 Files whose names end with -J may also be seen in the &_input_& directory (or
40924 its subdirectories when &%split_spool_directory%& is set). These are journal
40925 files, used to record addresses to which the message has been delivered during
40926 the course of a delivery attempt. If there are still undelivered recipients at
40927 the end, the -H file is updated, and the -J file is deleted. If, however, there
40928 is some kind of crash (for example, a power outage) before this happens, the -J
40929 file remains in existence. When Exim next processes the message, it notices the
40930 -J file and uses it to update the -H file before starting the next delivery
40933 Files whose names end with -K or .eml may also be seen in the spool.
40934 These are temporaries used for DKIM or malware processing, when that is used.
40935 They should be tidied up by normal operations; any old ones are probably
40936 relics of crashes and can be removed.
40938 .section "Format of the -H file" "SECID282"
40939 .cindex "uid (user id)" "in spool file"
40940 .cindex "gid (group id)" "in spool file"
40941 The second line of the -H file contains the login name for the uid of the
40942 process that called Exim to read the message, followed by the numerical uid and
40943 gid. For a locally generated message, this is normally the user who sent the
40944 message. For a message received over TCP/IP via the daemon, it is
40945 normally the Exim user.
40947 The third line of the file contains the address of the message's sender as
40948 transmitted in the envelope, contained in angle brackets. The sender address is
40949 empty for bounce messages. For incoming SMTP mail, the sender address is given
40950 in the MAIL command. For locally generated mail, the sender address is
40951 created by Exim from the login name of the current user and the configured
40952 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
40953 leading &"From&~"& line if the caller is trusted, or if the supplied address is
40954 &"<>"& or an address that matches &%untrusted_set_senders%&.
40956 The fourth line contains two numbers. The first is the time that the message
40957 was received, in the conventional Unix form &-- the number of seconds since the
40958 start of the epoch. The second number is a count of the number of messages
40959 warning of delayed delivery that have been sent to the sender.
40961 There follow a number of lines starting with a hyphen. These can appear in any
40962 order, and are omitted when not relevant:
40965 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
40966 This item is obsolete, and is not generated from Exim release 4.61 onwards;
40967 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
40968 recognized, to provide backward compatibility. In the old format, a line of
40969 this form is present for every ACL variable that is not empty. The number
40970 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
40971 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
40972 the data string for the variable. The string itself starts at the beginning of
40973 the next line, and is followed by a newline character. It may contain internal
40976 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
40977 A line of this form is present for every ACL connection variable that is
40978 defined. Note that there is a space between &%-aclc%& and the rest of the name.
40979 The length is the length of the data string for the variable. The string itself
40980 starts at the beginning of the next line, and is followed by a newline
40981 character. It may contain internal newlines.
40983 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
40984 A line of this form is present for every ACL message variable that is defined.
40985 Note that there is a space between &%-aclm%& and the rest of the name. The
40986 length is the length of the data string for the variable. The string itself
40987 starts at the beginning of the next line, and is followed by a newline
40988 character. It may contain internal newlines.
40990 .vitem "&%-active_hostname%&&~<&'hostname'&>"
40991 This is present if, when the message was received over SMTP, the value of
40992 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
40994 .vitem &%-allow_unqualified_recipient%&
40995 This is present if unqualified recipient addresses are permitted in header
40996 lines (to stop such addresses from being qualified if rewriting occurs at
40997 transport time). Local messages that were input using &%-bnq%& and remote
40998 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
41000 .vitem &%-allow_unqualified_sender%&
41001 This is present if unqualified sender addresses are permitted in header lines
41002 (to stop such addresses from being qualified if rewriting occurs at transport
41003 time). Local messages that were input using &%-bnq%& and remote messages from
41004 hosts that match &%sender_unqualified_hosts%& set this flag.
41006 .vitem "&%-auth_id%&&~<&'text'&>"
41007 The id information for a message received on an authenticated SMTP connection
41008 &-- the value of the &$authenticated_id$& variable.
41010 .vitem "&%-auth_sender%&&~<&'address'&>"
41011 The address of an authenticated sender &-- the value of the
41012 &$authenticated_sender$& variable.
41014 .vitem "&%-body_linecount%&&~<&'number'&>"
41015 This records the number of lines in the body of the message, and is
41016 present unless &%-spool_file_wireformat%& is.
41018 .vitem "&%-body_zerocount%&&~<&'number'&>"
41019 This records the number of binary zero bytes in the body of the message, and is
41020 present if the number is greater than zero.
41022 .vitem &%-deliver_firsttime%&
41023 This is written when a new message is first added to the spool. When the spool
41024 file is updated after a deferral, it is omitted.
41026 .vitem "&%-frozen%&&~<&'time'&>"
41027 .cindex "frozen messages" "spool data"
41028 The message is frozen, and the freezing happened at <&'time'&>.
41030 .vitem "&%-helo_name%&&~<&'text'&>"
41031 This records the host name as specified by a remote host in a HELO or EHLO
41034 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
41035 This records the IP address of the host from which the message was received and
41036 the remote port number that was used. It is omitted for locally generated
41039 .vitem "&%-host_auth%&&~<&'text'&>"
41040 If the message was received on an authenticated SMTP connection, this records
41041 the name of the authenticator &-- the value of the
41042 &$sender_host_authenticated$& variable.
41044 .vitem &%-host_lookup_failed%&
41045 This is present if an attempt to look up the sending host's name from its IP
41046 address failed. It corresponds to the &$host_lookup_failed$& variable.
41048 .vitem "&%-host_name%&&~<&'text'&>"
41049 .cindex "reverse DNS lookup"
41050 .cindex "DNS" "reverse lookup"
41051 This records the name of the remote host from which the message was received,
41052 if the host name was looked up from the IP address when the message was being
41053 received. It is not present if no reverse lookup was done.
41055 .vitem "&%-ident%&&~<&'text'&>"
41056 For locally submitted messages, this records the login of the originating user,
41057 unless it was a trusted user and the &%-oMt%& option was used to specify an
41058 ident value. For messages received over TCP/IP, this records the ident string
41059 supplied by the remote host, if any.
41061 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
41062 This records the IP address of the local interface and the port number through
41063 which a message was received from a remote host. It is omitted for locally
41064 generated messages.
41067 The message is from a local sender.
41069 .vitem &%-localerror%&
41070 The message is a locally-generated bounce message.
41072 .vitem "&%-local_scan%&&~<&'string'&>"
41073 This records the data string that was returned by the &[local_scan()]& function
41074 when the message was received &-- the value of the &$local_scan_data$&
41075 variable. It is omitted if no data was returned.
41077 .vitem &%-manual_thaw%&
41078 The message was frozen but has been thawed manually, that is, by an explicit
41079 Exim command rather than via the auto-thaw process.
41082 A testing delivery process was started using the &%-N%& option to suppress any
41083 actual deliveries, but delivery was deferred. At any further delivery attempts,
41086 .vitem &%-received_protocol%&
41087 This records the value of the &$received_protocol$& variable, which contains
41088 the name of the protocol by which the message was received.
41090 .vitem &%-sender_set_untrusted%&
41091 The envelope sender of this message was set by an untrusted local caller (used
41092 to ensure that the caller is displayed in queue listings).
41094 .vitem "&%-spam_score_int%&&~<&'number'&>"
41095 If a message was scanned by SpamAssassin, this is present. It records the value
41096 of &$spam_score_int$&.
41098 .vitem &%-spool_file_wireformat%&
41099 The -D file for this message is in wire-format (for ESMTP CHUNKING)
41100 rather than Unix-format.
41101 The line-ending is CRLF rather than newline.
41102 There is still, however, no leading-dot-stuffing.
41104 .vitem &%-tls_certificate_verified%&
41105 A TLS certificate was received from the client that sent this message, and the
41106 certificate was verified by the server.
41108 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
41109 When the message was received over an encrypted connection, this records the
41110 name of the cipher suite that was used.
41112 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
41113 When the message was received over an encrypted connection, and a certificate
41114 was received from the client, this records the Distinguished Name from that
41118 Any of the above may have an extra hyphen prepended, to indicate the the
41119 corresponding data is untrusted.
41121 Following the options there is a list of those addresses to which the message
41122 is not to be delivered. This set of addresses is initialized from the command
41123 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
41124 is set; otherwise it starts out empty. Whenever a successful delivery is made,
41125 the address is added to this set. The addresses are kept internally as a
41126 balanced binary tree, and it is a representation of that tree which is written
41127 to the spool file. If an address is expanded via an alias or forward file, the
41128 original address is added to the tree when deliveries to all its child
41129 addresses are complete.
41131 If the tree is empty, there is a single line in the spool file containing just
41132 the text &"XX"&. Otherwise, each line consists of two letters, which are either
41133 Y or N, followed by an address. The address is the value for the node of the
41134 tree, and the letters indicate whether the node has a left branch and/or a
41135 right branch attached to it, respectively. If branches exist, they immediately
41136 follow. Here is an example of a three-node tree:
41138 YY darcy@austen.fict.example
41139 NN alice@wonderland.fict.example
41140 NN editor@thesaurus.ref.example
41142 After the non-recipients tree, there is a list of the message's recipients.
41143 This is a simple list, preceded by a count. It includes all the original
41144 recipients of the message, including those to whom the message has already been
41145 delivered. In the simplest case, the list contains one address per line. For
41149 editor@thesaurus.ref.example
41150 darcy@austen.fict.example
41152 alice@wonderland.fict.example
41154 However, when a child address has been added to the top-level addresses as a
41155 result of the use of the &%one_time%& option on a &(redirect)& router, each
41156 line is of the following form:
41158 <&'top-level address'&> <&'errors_to address'&> &&&
41159 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
41161 The 01 flag bit indicates the presence of the three other fields that follow
41162 the top-level address. Other bits may be used in future to support additional
41163 fields. The <&'parent number'&> is the offset in the recipients list of the
41164 original parent of the &"one time"& address. The first two fields are the
41165 envelope sender that is associated with this address and its length. If the
41166 length is zero, there is no special envelope sender (there are then two space
41167 characters in the line). A non-empty field can arise from a &(redirect)& router
41168 that has an &%errors_to%& setting.
41171 A blank line separates the envelope and status information from the headers
41172 which follow. A header may occupy several lines of the file, and to save effort
41173 when reading it in, each header is preceded by a number and an identifying
41174 character. The number is the number of characters in the header, including any
41175 embedded newlines and the terminating newline. The character is one of the
41179 .row <&'blank'&> "header in which Exim has no special interest"
41180 .row &`B`& "&'Bcc:'& header"
41181 .row &`C`& "&'Cc:'& header"
41182 .row &`F`& "&'From:'& header"
41183 .row &`I`& "&'Message-id:'& header"
41184 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
41185 .row &`R`& "&'Reply-To:'& header"
41186 .row &`S`& "&'Sender:'& header"
41187 .row &`T`& "&'To:'& header"
41188 .row &`*`& "replaced or deleted header"
41191 Deleted or replaced (rewritten) headers remain in the spool file for debugging
41192 purposes. They are not transmitted when the message is delivered. Here is a
41193 typical set of headers:
41195 111P Received: by hobbit.fict.example with local (Exim 4.00)
41196 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
41197 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
41198 038* X-rewrote-sender: bb@hobbit.fict.example
41199 042* From: Bilbo Baggins <bb@hobbit.fict.example>
41200 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
41201 099* To: alice@wonderland.fict.example, rdo@foundation,
41202 darcy@austen.fict.example, editor@thesaurus.ref.example
41203 104T To: alice@wonderland.fict.example, rdo@foundation.example,
41204 darcy@austen.fict.example, editor@thesaurus.ref.example
41205 038 Date: Fri, 11 May 2001 10:28:59 +0100
41207 The asterisked headers indicate that the envelope sender, &'From:'& header, and
41208 &'To:'& header have been rewritten, the last one because routing expanded the
41209 unqualified domain &'foundation'&.
41210 .ecindex IIDforspo1
41211 .ecindex IIDforspo2
41212 .ecindex IIDforspo3
41214 .section "Format of the -D file" "SECID282a"
41215 The data file is traditionally in Unix-standard format: lines are ended with
41216 an ASCII newline character.
41217 However, when the &%spool_wireformat%& main option is used some -D files
41218 can have an alternate format.
41219 This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
41220 The -D file lines (not including the first name-component line) are
41221 suitable for direct copying to the wire when transmitting using the
41222 ESMTP CHUNKING option, meaning lower processing overhead.
41223 Lines are terminated with an ASCII CRLF pair.
41224 There is no dot-stuffing (and no dot-termination).
41226 . ////////////////////////////////////////////////////////////////////////////
41227 . ////////////////////////////////////////////////////////////////////////////
41229 .chapter "DKIM, SPF, SRS and DMARC" "CHAPdkim" &&&
41230 "DKIM, SPF, SRS and DMARC Support"
41232 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
41235 DKIM is a mechanism by which messages sent by some entity can be provably
41236 linked to a domain which that entity controls. It permits reputation to
41237 be tracked on a per-domain basis, rather than merely upon source IP address.
41238 DKIM is documented in RFC 6376.
41240 As DKIM relies on the message being unchanged in transit, messages handled
41241 by a mailing-list (which traditionally adds to the message) will not match
41242 any original DKIM signature.
41244 DKIM support is compiled into Exim by default if TLS support is present.
41245 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
41247 Exim's DKIM implementation allows for
41249 Signing outgoing messages: This function is implemented in the SMTP transport.
41250 It can co-exist with all other Exim features
41251 (including transport filters)
41252 except cutthrough delivery.
41254 Verifying signatures in incoming messages: This is implemented by an additional
41255 ACL (acl_smtp_dkim), which can be called several times per message, with
41256 different signature contexts.
41259 In typical Exim style, the verification implementation does not include any
41260 default "policy". Instead it enables you to build your own policy using
41261 Exim's standard controls.
41263 Please note that verification of DKIM signatures in incoming mail is turned
41264 on by default for logging (in the <= line) purposes.
41266 Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
41267 When set, for each signature in incoming email,
41268 exim will log a line displaying the most important signature details, and the
41269 signature status. Here is an example (with line-breaks added for clarity):
41271 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
41272 d=facebookmail.com s=q1-2009b
41273 c=relaxed/relaxed a=rsa-sha1
41274 i=@facebookmail.com t=1252484542 [verification succeeded]
41277 You might want to turn off DKIM verification processing entirely for internal
41278 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
41279 control modifier. This should typically be done in the RCPT ACL, at points
41280 where you accept mail from relay sources (internal hosts or authenticated
41284 .section "Signing outgoing messages" "SECDKIMSIGN"
41285 .cindex "DKIM" "signing"
41287 For signing to be usable you must have published a DKIM record in DNS.
41288 Note that RFC 8301 (which does not cover EC keys) says:
41290 rsa-sha1 MUST NOT be used for signing or verifying.
41292 Signers MUST use RSA keys of at least 1024 bits for all keys.
41293 Signers SHOULD use RSA keys of at least 2048 bits.
41296 Note also that the key content (the 'p=' field)
41297 in the DNS record is different between RSA and EC keys;
41298 for the former it is the base64 of the ASN.1 for the RSA public key
41299 (equivalent to the private-key .pem with the header/trailer stripped)
41300 but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
41302 Signing is enabled by setting private options on the SMTP transport.
41303 These options take (expandable) strings as arguments.
41305 .option dkim_domain smtp "string list&!!" unset
41306 The domain(s) you want to sign with.
41307 After expansion, this can be a list.
41308 Each element in turn,
41310 is put into the &%$dkim_domain%& expansion variable
41311 while expanding the remaining signing options.
41312 If it is empty after expansion, DKIM signing is not done,
41313 and no error will result even if &%dkim_strict%& is set.
41315 .option dkim_selector smtp "string list&!!" unset
41316 This sets the key selector string.
41317 After expansion, which can use &$dkim_domain$&, this can be a list.
41318 Each element in turn is put in the expansion
41319 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
41320 option along with &%$dkim_domain%&.
41321 If the option is empty after expansion, DKIM signing is not done for this domain,
41322 and no error will result even if &%dkim_strict%& is set.
41324 To do, for example, dual-signing with RSA and EC keys
41325 this could be be used:
41327 dkim_selector = ec_sel : rsa_sel
41328 dkim_private_key = KEYS_DIR/$dkim_selector
41331 .option dkim_private_key smtp string&!! unset
41332 This sets the private key to use.
41333 You can use the &%$dkim_domain%& and
41334 &%$dkim_selector%& expansion variables to determine the private key to use.
41335 The result can either
41337 be a valid RSA private key in ASCII armor (.pem file), including line breaks
41339 with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41340 be a valid Ed25519 private key (same format as above)
41342 start with a slash, in which case it is treated as a file that contains
41345 be "0", "false" or the empty string, in which case the message will not
41346 be signed. This case will not result in an error, even if &%dkim_strict%&
41350 To generate keys under OpenSSL:
41352 openssl genrsa -out dkim_rsa.private 2048
41353 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
41355 The result file from the first command should be retained, and
41356 this option set to use it.
41357 Take the base-64 lines from the output of the second command, concatenated,
41358 for the DNS TXT record.
41359 See section 3.6 of RFC6376 for the record specification.
41363 certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
41364 certtool --load-privkey=dkim_rsa.private --pubkey-info
41367 Note that RFC 8301 says:
41369 Signers MUST use RSA keys of at least 1024 bits for all keys.
41370 Signers SHOULD use RSA keys of at least 2048 bits.
41373 EC keys for DKIM are defined by RFC 8463.
41374 They are considerably smaller than RSA keys for equivalent protection.
41375 As they are a recent development, users should consider dual-signing
41376 (by setting a list of selectors, and an expansion for this option)
41377 for some transition period.
41378 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41381 OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
41383 openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
41384 certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
41387 To produce the required public key value for a DNS record:
41389 openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
41390 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
41393 Exim also supports an alternate format
41394 of Ed25519 keys in DNS which was a candidate during development
41395 of the standard, but not adopted.
41396 A future release will probably drop that support.
41398 .option dkim_hash smtp string&!! sha256
41399 Can be set to any one of the supported hash methods, which are:
41401 &`sha1`& &-- should not be used, is old and insecure
41403 &`sha256`& &-- the default
41405 &`sha512`& &-- possibly more secure but less well supported
41408 Note that RFC 8301 says:
41410 rsa-sha1 MUST NOT be used for signing or verifying.
41413 .option dkim_identity smtp string&!! unset
41414 If set after expansion, the value is used to set an "i=" tag in
41415 the signing header. The DKIM standards restrict the permissible
41416 syntax of this optional tag to a mail address, with possibly-empty
41417 local part, an @, and a domain identical to or subdomain of the "d="
41418 tag value. Note that Exim does not check the value.
41420 .option dkim_canon smtp string&!! unset
41421 This option sets the canonicalization method used when signing a message.
41422 The DKIM RFC currently supports two methods: "simple" and "relaxed".
41423 The option defaults to "relaxed" when unset. Note: the current implementation
41424 only supports signing with the same canonicalization method for both headers and body.
41426 .option dkim_strict smtp string&!! unset
41427 This option defines how Exim behaves when signing a message that
41428 should be signed fails for some reason. When the expansion evaluates to
41429 either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message
41430 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
41433 .option dkim_sign_headers smtp string&!! "see below"
41434 If set, this option must expand to a colon-separated
41435 list of header names.
41436 Headers with these names, or the absence or such a header, will be included
41437 in the message signature.
41438 When unspecified, the header names listed in RFC4871 will be used,
41439 whether or not each header is present in the message.
41440 The default list is available for the expansion in the macro
41441 &"_DKIM_SIGN_HEADERS"&
41442 and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
41444 If a name is repeated, multiple headers by that name (or the absence thereof)
41445 will be signed. The textually later headers in the headers part of the
41446 message are signed first, if there are multiples.
41448 A name can be prefixed with either an &"="& or a &"+"& character.
41449 If an &"="& prefix is used, all headers that are present with this name
41451 If a &"+"& prefix if used, all headers that are present with this name
41452 will be signed, and one signature added for a missing header with the
41453 name will be appended.
41455 .option dkim_timestamps smtp integer&!! unset
41456 This option controls the inclusion of timestamp information in the signature.
41457 If not set, no such information will be included.
41458 Otherwise, must be an unsigned number giving an offset in seconds from the current time
41460 (eg. 1209600 for two weeks);
41461 both creation (t=) and expiry (x=) tags will be included.
41463 RFC 6376 lists these tags as RECOMMENDED.
41466 .section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
41467 .cindex "DKIM" "verification"
41469 Verification of DKIM signatures in SMTP incoming email is done for all
41470 messages for which an ACL control &%dkim_disable_verify%& has not been set.
41471 .cindex DKIM "selecting signature algorithms"
41472 Individual classes of signature algorithm can be ignored by changing
41473 the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
41474 The &%dkim_verify_minimal%& option can be set to cease verification
41475 processing for a message once the first passing signature is found.
41477 .cindex authentication "expansion item"
41478 Performing verification sets up information used by the
41479 &%authresults%& expansion item.
41481 For most purposes the default option settings suffice and the remainder
41482 of this section can be ignored.
41484 The results of verification are made available to the
41485 &%acl_smtp_dkim%& ACL, which can examine and modify them.
41486 A missing ACL definition defaults to accept.
41487 By default, the ACL is called once for each
41488 syntactically(!) correct signature in the incoming message.
41489 If any ACL call does not accept, the message is not accepted.
41490 If a cutthrough delivery was in progress for the message, that is
41491 summarily dropped (having wasted the transmission effort).
41493 To evaluate the verification result in the ACL
41494 a large number of expansion variables
41495 containing the signature status and its details are set up during the
41496 runtime of the ACL.
41498 Calling the ACL only for existing signatures is not sufficient to build
41499 more advanced policies. For that reason, the main option
41500 &%dkim_verify_signers%&, and an expansion variable
41501 &%$dkim_signers%& exist.
41503 The main option &%dkim_verify_signers%& can be set to a colon-separated
41504 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
41505 called. It is expanded when the message has been received. At this point,
41506 the expansion variable &%$dkim_signers%& already contains a colon-separated
41507 list of signer domains and identities for the message. When
41508 &%dkim_verify_signers%& is not specified in the main configuration,
41511 dkim_verify_signers = $dkim_signers
41513 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
41514 DKIM signature in the message. Current DKIM verifiers may want to explicitly
41515 call the ACL for known domains or identities. This would be achieved as follows:
41517 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
41519 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
41520 and "ebay.com", plus all domains and identities that have signatures in the message.
41521 You can also be more creative in constructing your policy. For example:
41523 dkim_verify_signers = $sender_address_domain:$dkim_signers
41526 If a domain or identity is listed several times in the (expanded) value of
41527 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
41529 Note that if the option is set using untrustworthy data
41530 (such as the From: header)
41531 care should be taken to force lowercase for domains
41532 and for the domain part if identities.
41533 The default setting can be regarded as trustworthy in this respect.
41535 If multiple signatures match a domain (or identity), the ACL is called once
41536 for each matching signature.
41539 Inside the DKIM ACL, the following expansion variables are
41540 available (from most to least important):
41544 .vitem &%$dkim_cur_signer%&
41545 The signer that is being evaluated in this ACL run. This can be a domain or
41546 an identity. This is one of the list items from the expanded main option
41547 &%dkim_verify_signers%& (see above).
41549 .vitem &%$dkim_verify_status%&
41550 Within the DKIM ACL,
41551 a string describing the general status of the signature. One of
41553 &%none%&: There is no signature in the message for the current domain or
41554 identity (as reflected by &%$dkim_cur_signer%&).
41556 &%invalid%&: The signature could not be verified due to a processing error.
41557 More detail is available in &%$dkim_verify_reason%&.
41559 &%fail%&: Verification of the signature failed. More detail is
41560 available in &%$dkim_verify_reason%&.
41562 &%pass%&: The signature passed verification. It is valid.
41565 This variable can be overwritten using an ACL 'set' modifier.
41566 This might, for instance, be done to enforce a policy restriction on
41567 hash-method or key-size:
41569 warn condition = ${if eq {$dkim_verify_status}{pass}}
41570 condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
41571 condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
41572 {< {$dkim_key_length}{1024}}}}
41573 logwrite = NOTE: forcing DKIM verify fail (was pass)
41574 set dkim_verify_status = fail
41575 set dkim_verify_reason = hash too weak or key too short
41578 So long as a DKIM ACL is defined (it need do no more than accept),
41579 after all the DKIM ACL runs have completed, the value becomes a
41580 colon-separated list of the values after each run.
41581 This is maintained for the mime, prdr and data ACLs.
41583 .vitem &%$dkim_verify_reason%&
41584 A string giving a little bit more detail when &%$dkim_verify_status%& is either
41585 "fail" or "invalid". One of
41587 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
41588 key for the domain could not be retrieved. This may be a temporary problem.
41590 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
41591 record for the domain is syntactically invalid.
41593 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
41594 body hash does not match the one specified in the signature header. This
41595 means that the message body was modified in transit.
41597 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
41598 could not be verified. This may mean that headers were modified,
41599 re-written or otherwise changed in a way which is incompatible with
41600 DKIM verification. It may of course also mean that the signature is forged.
41603 This variable can be overwritten, with any value, using an ACL 'set' modifier.
41605 .vitem &%$dkim_domain%&
41606 The signing domain. IMPORTANT: This variable is only populated if there is
41607 an actual signature in the message for the current domain or identity (as
41608 reflected by &%$dkim_cur_signer%&).
41610 .vitem &%$dkim_identity%&
41611 The signing identity, if present. IMPORTANT: This variable is only populated
41612 if there is an actual signature in the message for the current domain or
41613 identity (as reflected by &%$dkim_cur_signer%&).
41615 .vitem &%$dkim_selector%&
41616 The key record selector string.
41618 .vitem &%$dkim_algo%&
41619 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
41620 If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41621 may also be 'ed25519-sha256'.
41622 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41625 Note that RFC 8301 says:
41627 rsa-sha1 MUST NOT be used for signing or verifying.
41629 DKIM signatures identified as having been signed with historic
41630 algorithms (currently, rsa-sha1) have permanently failed evaluation
41633 To enforce this you must either have a DKIM ACL which checks this variable
41634 and overwrites the &$dkim_verify_status$& variable as discussed above,
41635 or have set the main option &%dkim_verify_hashes%& to exclude
41636 processing of such signatures.
41638 .vitem &%$dkim_canon_body%&
41639 The body canonicalization method. One of 'relaxed' or 'simple'.
41641 .vitem &%$dkim_canon_headers%&
41642 The header canonicalization method. One of 'relaxed' or 'simple'.
41644 .vitem &%$dkim_copiedheaders%&
41645 A transcript of headers and their values which are included in the signature
41646 (copied from the 'z=' tag of the signature).
41647 Note that RFC6376 requires that verification fail if the From: header is
41648 not included in the signature. Exim does not enforce this; sites wishing
41649 strict enforcement should code the check explicitly.
41651 .vitem &%$dkim_bodylength%&
41652 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
41653 limit was set by the signer, "9999999999999" is returned. This makes sure
41654 that this variable always expands to an integer value.
41655 &*Note:*& The presence of the signature tag specifying a signing body length
41656 is one possible route to spoofing of valid DKIM signatures.
41657 A paranoid implementation might wish to regard signature where this variable
41658 shows less than the "no limit" return as being invalid.
41660 .vitem &%$dkim_created%&
41661 UNIX timestamp reflecting the date and time when the signature was created.
41662 When this was not specified by the signer, "0" is returned.
41664 .vitem &%$dkim_expires%&
41665 UNIX timestamp reflecting the date and time when the signer wants the
41666 signature to be treated as "expired". When this was not specified by the
41667 signer, "9999999999999" is returned. This makes it possible to do useful
41668 integer size comparisons against this value.
41669 Note that Exim does not check this value.
41671 .vitem &%$dkim_headernames%&
41672 A colon-separated list of names of headers included in the signature.
41674 .vitem &%$dkim_key_testing%&
41675 "1" if the key record has the "testing" flag set, "0" if not.
41677 .vitem &%$dkim_key_nosubdomains%&
41678 "1" if the key record forbids subdomaining, "0" otherwise.
41680 .vitem &%$dkim_key_srvtype%&
41681 Service type (tag s=) from the key record. Defaults to "*" if not specified
41684 .vitem &%$dkim_key_granularity%&
41685 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
41688 .vitem &%$dkim_key_notes%&
41689 Notes from the key record (tag n=).
41691 .vitem &%$dkim_key_length%&
41692 Number of bits in the key.
41693 Valid only once the key is loaded, which is at the time the header signature
41694 is verified, which is after the body hash is.
41696 Note that RFC 8301 says:
41698 Verifiers MUST NOT consider signatures using RSA keys of
41699 less than 1024 bits as valid signatures.
41702 This is enforced by the default setting for the &%dkim_verify_min_keysizes%&
41707 In addition, two ACL conditions are provided:
41710 .vitem &%dkim_signers%&
41711 ACL condition that checks a colon-separated list of domains or identities
41712 for a match against the domain or identity that the ACL is currently verifying
41713 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
41714 verb to a group of domains or identities. For example:
41717 # Warn when Mail purportedly from GMail has no gmail signature
41718 warn sender_domains = gmail.com
41719 dkim_signers = gmail.com
41721 log_message = GMail sender without gmail.com DKIM signature
41724 Note that the above does not check for a total lack of DKIM signing;
41725 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
41727 .vitem &%dkim_status%&
41728 ACL condition that checks a colon-separated list of possible DKIM verification
41729 results against the actual result of verification. This is typically used
41730 to restrict an ACL verb to a list of verification outcomes, for example:
41733 deny sender_domains = paypal.com:paypal.de
41734 dkim_signers = paypal.com:paypal.de
41735 dkim_status = none:invalid:fail
41736 message = Mail from Paypal with invalid/missing signature
41739 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
41740 see the documentation of the &%$dkim_verify_status%& expansion variable above
41741 for more information of what they mean.
41747 .section "SPF (Sender Policy Framework)" SECSPF
41748 .cindex SPF verification
41750 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
41751 messages with its domain in the envelope from, documented by RFC 7208.
41752 For more information on SPF see &url(http://www.open-spf.org), a static copy of
41753 the &url(http://openspf.org).
41754 . --- 2019-10-28: still not https, open-spf.org is told to be a
41755 . --- web-archive copy of the now dead openspf.org site
41756 . --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a
41759 Messages sent by a system not authorised will fail checking of such assertions.
41760 This includes retransmissions done by traditional forwarders.
41762 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
41763 &_Local/Makefile_&. The support uses the &_libspf2_& library
41764 &url(https://www.libspf2.org/).
41765 There is no Exim involvement in the transmission of messages;
41766 publishing certain DNS records is all that is required.
41768 For verification, an ACL condition and an expansion lookup are provided.
41769 .cindex authentication "expansion item"
41770 Performing verification sets up information used by the
41771 &%authresults%& expansion item.
41774 .cindex SPF "ACL condition"
41775 .cindex ACL "spf condition"
41776 The ACL condition "spf" can be used at or after the MAIL ACL.
41777 It takes as an argument a list of strings giving the outcome of the SPF check,
41778 and will succeed for any matching outcome.
41782 The SPF check passed, the sending host is positively verified by SPF.
41785 The SPF check failed, the sending host is NOT allowed to send mail for the
41786 domain in the envelope-from address.
41788 .vitem &%softfail%&
41789 The SPF check failed, but the queried domain can't absolutely confirm that this
41793 The queried domain does not publish SPF records.
41796 The SPF check returned a "neutral" state. This means the queried domain has
41797 published a SPF record, but wants to allow outside servers to send mail under
41798 its domain as well. This should be treated like "none".
41800 .vitem &%permerror%&
41801 This indicates a syntax error in the SPF record of the queried domain.
41802 You may deny messages when this occurs.
41804 .vitem &%temperror%&
41805 This indicates a temporary error during all processing, including Exim's
41806 SPF processing. You may defer messages when this occurs.
41809 There was an error during processing of the SPF lookup
41812 You can prefix each string with an exclamation mark to invert
41813 its meaning, for example "!fail" will match all results but
41814 "fail". The string list is evaluated left-to-right, in a
41815 short-circuit fashion.
41820 message = $sender_host_address is not allowed to send mail from \
41821 ${if def:sender_address_domain \
41822 {$sender_address_domain}{$sender_helo_name}}. \
41823 Please see http://www.open-spf.org/Why;\
41824 identity=${if def:sender_address_domain \
41825 {$sender_address}{$sender_helo_name}};\
41826 ip=$sender_host_address
41829 Note: The above mentioned URL may not be as helpful as expected. You are
41830 encouraged to replace the link with a link to a site with more
41833 When the spf condition has run, it sets up several expansion
41836 .cindex SPF "verification variables"
41838 .vitem &$spf_header_comment$&
41839 .vindex &$spf_header_comment$&
41840 This contains a human-readable string describing the outcome
41841 of the SPF check. You can add it to a custom header or use
41842 it for logging purposes.
41844 .vitem &$spf_received$&
41845 .vindex &$spf_received$&
41846 This contains a complete Received-SPF: header (name and
41847 content) that can be added to the message. Please note that
41848 according to the SPF draft, this header must be added at the
41849 top of the header list, i.e. with
41851 add_header = :at_start:$spf_received
41853 See section &<<SECTaddheadacl>>& for further details.
41855 Note: in case of "Best-guess" (see below), the convention is
41856 to put this string in a header called X-SPF-Guess: instead.
41858 .vitem &$spf_result$&
41859 .vindex &$spf_result$&
41860 This contains the outcome of the SPF check in string form,
41861 currently one of pass, fail, softfail, none, neutral, permerror,
41862 temperror, or &"(invalid)"&.
41864 .vitem &$spf_result_guessed$&
41865 .vindex &$spf_result_guessed$&
41866 This boolean is true only if a best-guess operation was used
41867 and required in order to obtain a result.
41869 .vitem &$spf_smtp_comment$&
41870 .vindex &$spf_smtp_comment$&
41871 .vindex &%spf_smtp_comment_template%&
41872 This contains a string that can be used in a SMTP response
41873 to the calling party. Useful for "fail".
41874 The string is generated by the SPF library from the template configured in the main config
41875 option &%spf_smtp_comment_template%&.
41879 .cindex SPF "ACL condition"
41880 .cindex ACL "spf_guess condition"
41881 .cindex SPF "best guess"
41882 In addition to SPF, you can also perform checks for so-called
41883 "Best-guess". Strictly speaking, "Best-guess" is not standard
41884 SPF, but it is supported by the same framework that enables SPF
41886 Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record)
41887 for a description of what it means.
41888 . --- 2019-10-28: still not https:
41890 To access this feature, simply use the spf_guess condition in place
41891 of the spf one. For example:
41894 deny spf_guess = fail
41895 message = $sender_host_address doesn't look trustworthy to me
41898 In case you decide to reject messages based on this check, you
41899 should note that although it uses the same framework, "Best-guess"
41900 is not SPF, and therefore you should not mention SPF at all in your
41903 When the spf_guess condition has run, it sets up the same expansion
41904 variables as when spf condition is run, described above.
41906 Additionally, since Best-guess is not standardized, you may redefine
41907 what "Best-guess" means to you by redefining the main configuration
41908 &%spf_guess%& option.
41909 For example, the following:
41912 spf_guess = v=spf1 a/16 mx/16 ptr ?all
41915 would relax host matching rules to a broader network range.
41918 .cindex SPF "lookup expansion"
41920 A lookup expansion is also available. It takes an email
41921 address as the key and an IP address
41926 ${lookup {username@domain} spf {ip.ip.ip.ip}}
41929 The lookup will return the same result strings as can appear in
41930 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
41936 .section "SRS (Sender Rewriting Scheme)" SECTSRS
41937 .cindex SRS "sender rewriting scheme"
41939 SRS can be used to modify sender addresses when forwarding so that
41940 SPF verification does not object to them.
41941 It operates by encoding the original envelope sender in a new
41942 sender local part and using a domain run by the forwarding site
41943 as the new domain for the sender. Any DSN message should be returned
41944 to this new sender at the forwarding site, which can extract the
41945 original sender from the coded local part and forward the DSN to
41948 This is a way of avoiding the breakage that SPF does to forwarding.
41949 The constructed local-part will be longer than the original,
41950 leading to possible problems with very long addresses.
41951 The changing of the sender address also hinders the tracing of mail
41954 Exim can be built to include native SRS support. To do this
41955 SUPPORT_SRS=yes must be defined in &_Local/Makefile_&.
41956 If this has been done, the macros _HAVE_SRS and _HAVE_NATIVE_SRS
41958 The support is limited to SRS0-encoding; SRS1 is not supported.
41960 .cindex SRS excoding
41961 To encode an address use this expansion item:
41963 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
41964 .cindex "&%srs_encode%& expansion item"
41965 .cindex SRS "expansion item"
41966 The first argument should be a secret known and used by all systems
41967 handling the recipient domain for the original message.
41968 There is no need to periodically change this key; a timestamp is also
41970 The second argument should be given as the envelope sender address before this
41971 encoding operation.
41972 The third argument should be the recipient domain of the message when
41973 it arrived at this system.
41976 .cindex SRS decoding
41977 To decode an address use this expansion condition:
41979 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
41980 The first argument should be the recipient local prt as is was received.
41981 The second argument is the site secret.
41983 If the messages is not for an SRS-encoded recipient the condition will
41984 return false. If it is, the condition will return true and the variable
41985 &$srs_recipient$& will be set to the decoded (original) value.
41991 SRS_SECRET = <pick something unique for your site for this. Use on all MXs.>
41997 # if outbound, and forwarding has been done, use an alternate transport
41998 domains = ! +my_domains
41999 transport = ${if eq {$local_part@$domain} \
42000 {$original_local_part@$original_domain} \
42001 {remote_smtp} {remote_forwarded_smtp}}
42006 domains = +my_domains
42007 # detect inbound bounces which are SRS'd, and decode them
42008 condition = ${if inbound_srs {$local_part} {SRS_SECRET}}
42009 data = $srs_recipient
42011 inbound_srs_failure:
42014 domains = +my_domains
42015 # detect inbound bounces which look SRS'd but are invalid
42016 condition = ${if inbound_srs {$local_part} {}}
42018 data = :fail: Invalid SRS recipient address
42020 #... further routers here
42023 # transport; should look like the non-forward outbound
42024 # one, plus the max_rcpt and return_path options
42025 remote_forwarded_smtp:
42027 # modify the envelope from, for mails that we forward
42029 return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}}
42036 .section DMARC SECDMARC
42037 .cindex DMARC verification
42039 DMARC combines feedback from SPF, DKIM, and header From: in order
42040 to attempt to provide better indicators of the authenticity of an
42041 email. This document does not explain the fundamentals; you
42042 should read and understand how it works by visiting the website at
42043 &url(http://www.dmarc.org/).
42045 If Exim is built with DMARC support,
42046 the libopendmarc library is used.
42048 For building Exim yourself, obtain the library from
42049 &url(http://sourceforge.net/projects/opendmarc/)
42050 to obtain a copy, or find it in your favorite package
42051 repository. You will need to attend to the local/Makefile feature
42052 SUPPORT_DMARC and the associated LDFLAGS addition.
42053 This description assumes
42054 that headers will be in /usr/local/include, and that the libraries
42055 are in /usr/local/lib.
42059 There are three main-configuration options:
42060 .cindex DMARC "configuration options"
42062 The &%dmarc_tld_file%& option
42063 .oindex &%dmarc_tld_file%&
42064 defines the location of a text file of valid
42065 top level domains the opendmarc library uses
42066 during domain parsing. Maintained by Mozilla,
42067 the most current version can be downloaded
42068 from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat).
42069 See also the util/renew-opendmarc-tlds.sh script.
42070 The default for the option is unset.
42071 If not set, DMARC processing is disabled.
42074 The &%dmarc_history_file%& option, if set
42075 .oindex &%dmarc_history_file%&
42076 defines the location of a file to log results
42077 of dmarc verification on inbound emails. The
42078 contents are importable by the opendmarc tools
42079 which will manage the data, send out DMARC
42080 reports, and expire the data. Make sure the
42081 directory of this file is writable by the user
42083 The default is unset.
42085 The &%dmarc_forensic_sender%& option
42086 .oindex &%dmarc_forensic_sender%&
42087 defines an alternate email address to use when sending a
42088 forensic report detailing alignment failures
42089 if a sender domain's dmarc record specifies it
42090 and you have configured Exim to send them.
42091 If set, this is expanded and used for the
42092 From: header line; the address is extracted
42093 from it and used for the envelope from.
42094 If not set (the default), the From: header is expanded from
42095 the dsn_from option, and <> is used for the
42098 . I wish we had subsections...
42100 .cindex DMARC controls
42101 By default, the DMARC processing will run for any remote,
42102 non-authenticated user. It makes sense to only verify DMARC
42103 status of messages coming from remote, untrusted sources. You can
42104 use standard conditions such as hosts, senders, etc, to decide that
42105 DMARC verification should *not* be performed for them and disable
42106 DMARC with an ACL control modifier:
42108 control = dmarc_disable_verify
42110 A DMARC record can also specify a "forensic address", which gives
42111 exim an email address to submit reports about failed alignment.
42112 Exim does not do this by default because in certain conditions it
42113 results in unintended information leakage (what lists a user might
42114 be subscribed to, etc). You must configure exim to submit forensic
42115 reports to the owner of the domain. If the DMARC record contains a
42116 forensic address and you specify the control statement below, then
42117 exim will send these forensic emails. It is also advised that you
42118 configure a &%dmarc_forensic_sender%& because the default sender address
42119 construction might be inadequate.
42121 control = dmarc_enable_forensic
42123 (AGAIN: You can choose not to send these forensic reports by simply
42124 not putting the dmarc_enable_forensic control line at any point in
42125 your exim config. If you don't tell exim to send them, it will not
42128 There are no options to either control. Both must appear before
42133 DMARC checks cam be run on incoming SMTP messages by using the
42134 &"dmarc_status"& ACL condition in the DATA ACL. You are required to
42135 call the &"spf"& condition first in the ACLs, then the &"dmarc_status"&
42136 condition. Putting this condition in the ACLs is required in order
42137 for a DMARC check to actually occur. All of the variables are set
42138 up before the DATA ACL, but there is no actual DMARC check that
42139 occurs until a &"dmarc_status"& condition is encountered in the ACLs.
42141 The &"dmarc_status"& condition takes a list of strings on its
42142 right-hand side. These strings describe recommended action based
42143 on the DMARC check. To understand what the policy recommendations
42144 mean, refer to the DMARC website above. Valid strings are:
42146 &'accept '& The DMARC check passed and the library recommends accepting the email.
42147 &'reject '& The DMARC check failed and the library recommends rejecting the email.
42148 &'quarantine '& The DMARC check failed and the library recommends keeping it for further inspection.
42149 &'none '& The DMARC check passed and the library recommends no specific action, neutral.
42150 &'norecord '& No policy section in the DMARC record for this RFC5322.From field
42151 &'nofrom '& Unable to determine the domain of the sender.
42152 &'temperror '& Library error or dns error.
42153 &'off '& The DMARC check was disabled for this email.
42155 You can prefix each string with an exclamation mark to invert its
42156 meaning, for example "!accept" will match all results but
42157 "accept". The string list is evaluated left-to-right in a
42158 short-circuit fashion. When a string matches the outcome of the
42159 DMARC check, the condition succeeds. If none of the listed
42160 strings matches the outcome of the DMARC check, the condition
42163 Of course, you can also use any other lookup method that Exim
42164 supports, including LDAP, Postgres, MySQL, etc, as long as the
42165 result is a list of colon-separated strings.
42167 Performing the check sets up information used by the
42168 &%authresults%& expansion item.
42170 Several expansion variables are set before the DATA ACL is
42171 processed, and you can use them in this ACL. The following
42172 expansion variables are available:
42175 .vitem &$dmarc_status$&
42176 .vindex &$dmarc_status$&
42177 .cindex DMARC result
42178 A one word status indicating what the DMARC library
42179 thinks of the email. It is a combination of the results of
42180 DMARC record lookup and the SPF/DKIM/DMARC processing results
42181 (if a DMARC record was found). The actual policy declared
42182 in the DMARC record is in a separate expansion variable.
42184 .vitem &$dmarc_status_text$&
42185 .vindex &$dmarc_status_text$&
42186 Slightly longer, human readable status.
42188 .vitem &$dmarc_used_domain$&
42189 .vindex &$dmarc_used_domain$&
42190 The domain which DMARC used to look up the DMARC policy record.
42192 .vitem &$dmarc_domain_policy$&
42193 .vindex &$dmarc_domain_policy$&
42194 The policy declared in the DMARC record. Valid values
42195 are "none", "reject" and "quarantine". It is blank when there
42196 is any error, including no DMARC record.
42201 By default, Exim's DMARC configuration is intended to be
42202 non-intrusive and conservative. To facilitate this, Exim will not
42203 create any type of logging files without explicit configuration by
42204 you, the admin. Nor will Exim send out any emails/reports about
42205 DMARC issues without explicit configuration by you, the admin (other
42206 than typical bounce messages that may come about due to ACL
42207 processing or failure delivery issues).
42209 In order to log statistics suitable to be imported by the opendmarc
42210 tools, you need to:
42212 Configure the global option &%dmarc_history_file%&
42214 Configure cron jobs to call the appropriate opendmarc history
42215 import scripts and truncating the dmarc_history_file
42218 In order to send forensic reports, you need to:
42220 Configure the global option &%dmarc_forensic_sender%&
42222 Configure, somewhere before the DATA ACL, the control option to
42223 enable sending DMARC forensic reports
42231 warn domains = +local_domains
42232 hosts = +local_hosts
42233 control = dmarc_disable_verify
42235 warn !domains = +screwed_up_dmarc_records
42236 control = dmarc_enable_forensic
42238 warn condition = (lookup if destined to mailing list)
42239 set acl_m_mailing_list = 1
42242 warn dmarc_status = accept : none : off
42244 log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
42246 warn dmarc_status = !accept
42248 log_message = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
42250 warn dmarc_status = quarantine
42252 set $acl_m_quarantine = 1
42253 # Do something in a transport with this flag variable
42255 deny condition = ${if eq{$dmarc_domain_policy}{reject}}
42256 condition = ${if eq{$acl_m_mailing_list}{1}}
42257 message = Messages from $dmarc_used_domain break mailing lists
42259 deny dmarc_status = reject
42261 message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
42263 warn add_header = :at_start:${authresults {$primary_hostname}}
42270 . ////////////////////////////////////////////////////////////////////////////
42271 . ////////////////////////////////////////////////////////////////////////////
42273 .chapter "Proxies" "CHAPproxies" &&&
42275 .cindex "proxy support"
42276 .cindex "proxy" "access via"
42278 A proxy is an intermediate system through which communication is passed.
42279 Proxies may provide a security, availability or load-distribution function.
42282 .section "Inbound proxies" SECTproxyInbound
42283 .cindex proxy inbound
42284 .cindex proxy "server side"
42285 .cindex proxy "Proxy protocol"
42286 .cindex "Proxy protocol" proxy
42288 Exim has support for receiving inbound SMTP connections via a proxy
42289 that uses &"Proxy Protocol"& to speak to it.
42290 To include this support, include &"SUPPORT_PROXY=yes"&
42293 It was built on the HAProxy specification, found at
42294 &url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt).
42296 The purpose of this facility is so that an application load balancer,
42297 such as HAProxy, can sit in front of several Exim servers
42298 to distribute load.
42299 Exim uses the local protocol communication with the proxy to obtain
42300 the remote SMTP system IP address and port information.
42301 There is no logging if a host passes or
42302 fails Proxy Protocol negotiation, but it can easily be determined and
42303 recorded in an ACL (example is below).
42305 Use of a proxy is enabled by setting the &%hosts_proxy%&
42306 main configuration option to a hostlist; connections from these
42307 hosts will use Proxy Protocol.
42308 Exim supports both version 1 and version 2 of the Proxy Protocol and
42309 automatically determines which version is in use.
42311 The Proxy Protocol header is the first data received on a TCP connection
42312 and is inserted before any TLS-on-connect handshake from the client; Exim
42313 negotiates TLS between Exim-as-server and the remote client, not between
42314 Exim and the proxy server. The Proxy Protocol header must be received
42315 within &%proxy_protocol_timeout%&, which defaults to 3s.
42317 The following expansion variables are usable
42318 (&"internal"& and &"external"& here refer to the interfaces
42321 &'proxy_external_address '& IP of host being proxied or IP of remote interface of proxy
42322 &'proxy_external_port '& Port of host being proxied or Port on remote interface of proxy
42323 &'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
42324 &'proxy_local_port '& Port of proxy server inbound or Port on local interface of proxy
42325 &'proxy_session '& boolean: SMTP connection via proxy
42327 If &$proxy_session$& is set but &$proxy_external_address$& is empty
42328 there was a protocol error.
42329 The variables &$sender_host_address$& and &$sender_host_port$&
42330 will have values for the actual client system, not the proxy.
42332 Since the real connections are all coming from the proxy, and the
42333 per host connection tracking is done before Proxy Protocol is
42334 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
42335 handle all of the parallel volume you expect per inbound proxy.
42336 With the option set so high, you lose the ability
42337 to protect your server from many connections from one IP.
42338 In order to prevent your server from overload, you
42339 need to add a per connection ratelimit to your connect ACL.
42340 A possible solution is:
42342 # Set max number of connections per host
42344 # Or do some kind of IP lookup in a flat file or database
42345 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
42347 defer ratelimit = LIMIT / 5s / per_conn / strict
42348 message = Too many connections from this IP right now
42353 .section "Outbound proxies" SECTproxySOCKS
42354 .cindex proxy outbound
42355 .cindex proxy "client side"
42356 .cindex proxy SOCKS
42357 .cindex SOCKS proxy
42358 Exim has support for sending outbound SMTP via a proxy
42359 using a protocol called SOCKS5 (defined by RFC1928).
42360 The support can be optionally included by defining SUPPORT_SOCKS=yes in
42363 Use of a proxy is enabled by setting the &%socks_proxy%& option
42364 on an smtp transport.
42365 The option value is expanded and should then be a list
42366 (colon-separated by default) of proxy specifiers.
42367 Each proxy specifier is a list
42368 (space-separated by default) where the initial element
42369 is an IP address and any subsequent elements are options.
42371 Options are a string <name>=<value>.
42372 The list of options is in the following table:
42374 &'auth '& authentication method
42375 &'name '& authentication username
42376 &'pass '& authentication password
42378 &'tmo '& connection timeout
42380 &'weight '& selection bias
42383 More details on each of these options follows:
42386 .cindex authentication "to proxy"
42387 .cindex proxy authentication
42388 &%auth%&: Either &"none"& (default) or &"name"&.
42389 Using &"name"& selects username/password authentication per RFC 1929
42390 for access to the proxy.
42391 Default is &"none"&.
42393 &%name%&: sets the username for the &"name"& authentication method.
42396 &%pass%&: sets the password for the &"name"& authentication method.
42399 &%port%&: the TCP port number to use for the connection to the proxy.
42402 &%tmo%&: sets a connection timeout in seconds for this proxy.
42405 &%pri%&: specifies a priority for the proxy within the list,
42406 higher values being tried first.
42407 The default priority is 1.
42409 &%weight%&: specifies a selection bias.
42410 Within a priority set servers are queried in a random fashion,
42411 weighted by this value.
42412 The default value for selection bias is 1.
42415 Proxies from the list are tried according to their priority
42416 and weight settings until one responds. The timeout for the
42417 overall connection applies to the set of proxied attempts.
42419 .section Logging SECTproxyLog
42420 To log the (local) IP of a proxy in the incoming or delivery logline,
42421 add &"+proxy"& to the &%log_selector%& option.
42422 This will add a component tagged with &"PRX="& to the line.
42424 . ////////////////////////////////////////////////////////////////////////////
42425 . ////////////////////////////////////////////////////////////////////////////
42427 .chapter "Internationalisation" "CHAPi18n" &&&
42428 "Internationalisation""
42429 .cindex internationalisation "email address"
42432 .cindex utf8 "mail name handling"
42434 Exim has support for Internationalised mail names.
42435 To include this it must be built with SUPPORT_I18N and the libidn library.
42436 Standards supported are RFCs 2060, 5890, 6530 and 6533.
42438 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
42439 instead of it) then IDNA2008 is supported; this adds an extra library
42440 requirement, upon libidn2.
42442 .section "MTA operations" SECTi18nMTA
42443 .cindex SMTPUTF8 "ESMTP option"
42444 .cindex "ESMTP extensions" SMTPUTF8
42445 The main configuration option &%smtputf8_advertise_hosts%& specifies
42446 a host list. If this matches the sending host and
42447 accept_8bitmime is true (the default) then the ESMTP option
42448 SMTPUTF8 will be advertised.
42450 If the sender specifies the SMTPUTF8 option on a MAIL command
42451 international handling for the message is enabled and
42452 the expansion variable &$message_smtputf8$& will have value TRUE.
42454 The option &%allow_utf8_domains%& is set to true for this
42455 message. All DNS lookups are converted to a-label form
42456 whatever the setting of &%allow_utf8_domains%&
42457 when Exim is built with SUPPORT_I18N.
42459 Both localparts and domain are maintained as the original
42460 UTF-8 form internally; any comparison or regular-expression use will
42461 require appropriate care. Filenames created, eg. by
42462 the appendfile transport, will have UTF-8 names.
42464 HELO names sent by the smtp transport will have any UTF-8
42465 components expanded to a-label form,
42466 and any certificate name checks will be done using the a-label
42469 .cindex log protocol
42470 .cindex SMTPUTF8 logging
42471 .cindex i18n logging
42472 Log lines and Received-by: header lines will acquire a "utf8"
42473 prefix on the protocol element, eg. utf8esmtp.
42475 The following expansion operators can be used:
42477 ${utf8_domain_to_alabel:str}
42478 ${utf8_domain_from_alabel:str}
42479 ${utf8_localpart_to_alabel:str}
42480 ${utf8_localpart_from_alabel:str}
42483 .cindex utf8 "address downconversion"
42484 .cindex i18n "utf8 address downconversion"
42486 may use the following modifier:
42488 control = utf8_downconvert
42489 control = utf8_downconvert/<value>
42491 This sets a flag requiring that envelope addresses are converted to
42492 a-label form before smtp delivery.
42493 This is usually for use in a Message Submission Agent context,
42494 but could be used for any message.
42496 If a value is appended it may be:
42498 &`1 `& mandatory downconversion
42499 &`0 `& no downconversion
42500 &`-1 `& if SMTPUTF8 not supported by destination host
42502 If no value is given, 1 is used.
42504 If mua_wrapper is set, the utf8_downconvert control
42505 is initially set to -1.
42507 The smtp transport has an option &%utf8_downconvert%&.
42508 If set it must expand to one of the three values described above,
42509 or an empty string.
42510 If non-empty it overrides value previously set
42511 (due to mua_wrapper or by an ACL control).
42514 There is no explicit support for VRFY and EXPN.
42515 Configurations supporting these should inspect
42516 &$smtp_command_argument$& for an SMTPUTF8 argument.
42518 There is no support for LMTP on Unix sockets.
42519 Using the "lmtp" protocol option on an smtp transport,
42520 for LMTP over TCP, should work as expected.
42522 There is no support for DSN unitext handling,
42523 and no provision for converting logging from or to UTF-8.
42527 .section "MDA operations" SECTi18nMDA
42528 To aid in constructing names suitable for IMAP folders
42529 the following expansion operator can be used:
42531 ${imapfolder {<string>} {<sep>} {<specials>}}
42534 The string is converted from the charset specified by
42535 the "headers charset" command (in a filter file)
42536 or &%headers_charset%& main configuration option (otherwise),
42538 modified UTF-7 encoding specified by RFC 2060,
42539 with the following exception: All occurrences of <sep>
42540 (which has to be a single character)
42541 are replaced with periods ("."), and all periods and slashes that are not
42542 <sep> and are not in the <specials> string are BASE64 encoded.
42544 The third argument can be omitted, defaulting to an empty string.
42545 The second argument can be omitted, defaulting to "/".
42547 This is the encoding used by Courier for Maildir names on disk, and followed
42548 by many other IMAP servers.
42552 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
42553 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
42554 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
42557 Note that the source charset setting is vital, and also that characters
42558 must be representable in UTF-16.
42561 . ////////////////////////////////////////////////////////////////////////////
42562 . ////////////////////////////////////////////////////////////////////////////
42564 .chapter "Events" "CHAPevents" &&&
42568 The events mechanism in Exim can be used to intercept processing at a number
42569 of points. It was originally invented to give a way to do customised logging
42570 actions (for example, to a database) but can also be used to modify some
42571 processing actions.
42573 Most installations will never need to use Events.
42574 The support can be left out of a build by defining DISABLE_EVENT=yes
42575 in &_Local/Makefile_&.
42577 There are two major classes of events: main and transport.
42578 The main configuration option &%event_action%& controls reception events;
42579 a transport option &%event_action%& controls delivery events.
42581 Both options are a string which is expanded when the event fires.
42582 An example might look like:
42583 .cindex logging custom
42585 event_action = ${if eq {msg:delivery}{$event_name} \
42586 {${lookup pgsql {SELECT * FROM record_Delivery( \
42587 '${quote_pgsql:$sender_address_domain}',\
42588 '${quote_pgsql:${lc:$sender_address_local_part}}', \
42589 '${quote_pgsql:$domain}', \
42590 '${quote_pgsql:${lc:$local_part}}', \
42591 '${quote_pgsql:$host_address}', \
42592 '${quote_pgsql:${lc:$host}}', \
42593 '${quote_pgsql:$message_exim_id}')}} \
42597 Events have names which correspond to the point in process at which they fire.
42598 The name is placed in the variable &$event_name$& and the event action
42599 expansion must check this, as it will be called for every possible event type.
42601 The current list of events is:
42603 &`dane:fail after transport `& per connection
42604 &`msg:complete after main `& per message
42605 &`msg:defer after transport `& per message per delivery try
42606 &`msg:delivery after transport `& per recipient
42607 &`msg:rcpt:host:defer after transport `& per recipient per host
42608 &`msg:rcpt:defer after transport `& per recipient
42609 &`msg:host:defer after transport `& per host per delivery try; host errors
42610 &`msg:fail:delivery after transport `& per recipient
42611 &`msg:fail:internal after main `& per recipient
42612 &`tcp:connect before transport `& per connection
42613 &`tcp:close after transport `& per connection
42614 &`tls:cert before both `& per certificate in verification chain
42615 &`smtp:connect after transport `& per connection
42616 &`smtp:ehlo after transport `& per connection
42618 New event types may be added in future.
42620 The event name is a colon-separated list, defining the type of
42621 event in a tree of possibilities. It may be used as a list
42622 or just matched on as a whole. There will be no spaces in the name.
42624 The second column in the table above describes whether the event fires
42625 before or after the action is associates with. Those which fire before
42626 can be used to affect that action (more on this below).
42628 The third column in the table above says what section of the configuration
42629 should define the event action.
42631 An additional variable, &$event_data$&, is filled with information varying
42632 with the event type:
42634 &`dane:fail `& failure reason
42635 &`msg:defer `& error string
42636 &`msg:delivery `& smtp confirmation message
42637 &`msg:fail:internal `& failure reason
42638 &`msg:fail:delivery `& smtp error message
42639 &`msg:host:defer `& error string
42640 &`msg:rcpt:host:defer `& error string
42641 &`msg:rcpt:defer `& error string
42642 &`tls:cert `& verification chain depth
42643 &`smtp:connect `& smtp banner
42644 &`smtp:ehlo `& smtp ehlo response
42647 The :defer events populate one extra variable: &$event_defer_errno$&.
42649 For complex operations an ACL expansion can be used in &%event_action%&
42650 however due to the multiple contexts that Exim operates in during
42651 the course of its processing:
42653 variables set in transport events will not be visible outside that
42656 acl_m variables in a server context are lost on a new connection,
42657 and after smtp helo/ehlo/mail/starttls/rset commands
42659 Using an ACL expansion with the logwrite modifier can be
42660 a useful way of writing to the main log.
42662 The expansion of the event_action option should normally
42663 return an empty string. Should it return anything else the
42664 following will be forced:
42666 &`tcp:connect `& do not connect
42667 &`tls:cert `& refuse verification
42668 &`smtp:connect `& close connection
42670 All other message types ignore the result string, and
42671 no other use is made of it.
42673 For a tcp:connect event, if the connection is being made to a proxy
42674 then the address and port variables will be that of the proxy and not
42677 For tls:cert events, if GnuTLS is in use this will trigger only per
42678 chain element received on the connection.
42679 For OpenSSL it will trigger for every chain element including those
42682 . ////////////////////////////////////////////////////////////////////////////
42683 . ////////////////////////////////////////////////////////////////////////////
42685 .chapter "Adding new drivers or lookup types" "CHID13" &&&
42686 "Adding drivers or lookups"
42687 .cindex "adding drivers"
42688 .cindex "new drivers, adding"
42689 .cindex "drivers" "adding new"
42690 The following actions have to be taken in order to add a new router, transport,
42691 authenticator, or lookup type to Exim:
42694 Choose a name for the driver or lookup type that does not conflict with any
42695 existing name; I will use &"newdriver"& in what follows.
42697 Add to &_src/EDITME_& the line:
42699 <&'type'&>&`_NEWDRIVER=yes`&
42701 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
42702 code is not to be included in the binary by default, comment this line out. You
42703 should also add any relevant comments about the driver or lookup type.
42705 Add to &_src/config.h.defaults_& the line:
42707 #define <type>_NEWDRIVER
42710 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
42711 and create a table entry as is done for all the other drivers and lookup types.
42713 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
42714 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
42715 Add your &`NEWDRIVER`& to that list.
42716 As long as the dynamic module would be named &_newdriver.so_&, you can use the
42717 simple form that most lookups have.
42719 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
42720 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
42721 driver or lookup type and add it to the definition of OBJ.
42723 Edit &_OS/Makefile-Base_& adding a &_.o_& file for the predefined-macros, to the
42724 definition of OBJ_MACRO. Add a set of line to do the compile also.
42726 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
42729 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
42730 as for other drivers and lookups.
42733 Then all you need to do is write the code! A good way to start is to make a
42734 proforma by copying an existing module of the same type, globally changing all
42735 occurrences of the name, and cutting out most of the code. Note that any
42736 options you create must be listed in alphabetical order, because the tables are
42737 searched using a binary chop procedure.
42739 There is a &_README_& file in each of the sub-directories of &_src_& describing
42740 the interface that is expected.
42745 . ////////////////////////////////////////////////////////////////////////////
42746 . ////////////////////////////////////////////////////////////////////////////
42748 . /////////////////////////////////////////////////////////////////////////////
42749 . These lines are processing instructions for the Simple DocBook Processor that
42750 . Philip Hazel has developed as a less cumbersome way of making PostScript and
42751 . PDFs than using xmlto and fop. They will be ignored by all other XML
42753 . /////////////////////////////////////////////////////////////////////////////
42758 foot_right_recto="&chaptertitle;"
42759 foot_right_verso="&chaptertitle;"
42763 .makeindex "Options index" "option"
42764 .makeindex "Variables index" "variable"
42765 .makeindex "Concept index" "concept"
42768 . /////////////////////////////////////////////////////////////////////////////
42769 . /////////////////////////////////////////////////////////////////////////////